Shindengen MR4040 Partial resonance power supply icmodule Datasheet

Provision for standby mode operation
Partial Resonance Power Supply IC Module
MR4000 Series
Application Note
Version 1.4
Shindengen Electric Manufacturing Co., Ltd.
MR4000 Series
Application Note
Precautions
Thank you for purchasing this product.
When using this IC, please follow the warnings and cautions given below to ensure safety.
Warning
!
Improper handling may result in death, serious injury, or major property damage.
Caution
!
Improper handling may result in minor injury or property damage.
!
!
We strive at all times to improve the quality and reliability of our products. However, a certain
risk of malfunctions is inevitable with semiconductor products. You are responsible for producing
a design that meets safety requirements (whether a redundant design, a design that prevents
the spread of fire, or designs that minimize the possibility of malfunctions) necessary to avoid
injury, fire, or damage to social credibility that may result should any of our products
malfunction.
The semiconductor product described in this document is not designed or manufactured for use
in a device or a system required to demonstrate mission-critical reliability or safety, or whose
malfunction may directly cause injuries or endanger human life. Contact us before using the
product for any of the following special or specific applications:
Warning
Special applications
Transport equipment (e.g., automobiles and ships), communications equipment for a
backbone network, traffic signal equipment, disaster or crime prevention equipment, medical
devices, various types of safety equipment, and other applications
Specific applications
Nuclear power control systems, aircraft equipment, aerospace equipment, submarine
repeaters, medical equipment used in life-support, and other applications
Even if the equipment is not designed for a special or specific application, please consult with
us before using any of our IC products in equipment required to run continuously for extended
periods.
Caution
!
Never attempt to repair or modify the product. Doing so may lead to serious accidents.
<<Electric shock, destruction of property, fire, or malfunctions may result.>>
!
In the event of a problem, an excessive voltage may arise at an output terminal, or the voltage
may drop. Anticipate these fluctuations and any consequential malfunctions or destruction and
provide adequate protection for equipment, such as overvoltage or overcurrent protection.
!
Check the polarity of the input and output terminals. Make sure they are properly connected
before turning on power.
<<Failure to do so may lead to failure of the protective element or generate smoke or fire.>>
!
Use only the specified input voltage. Deploy a protective element on the input line.
<<Problems may result in smoke or fire.>>
In the event of a malfunction or other anomaly, shut power off and contact us immediately.
!





The contents of this document are subject to change without notice.
Use of this product constitutes acceptance of the formal specifications.
We have taken every possible measure to ensure the accuracy of the information in this document. However, we will
not be held liable for any losses or damages incurred or infringements of patents or other rights resulting from use of
this information.
This document does not guarantee or license the execution of patent rights, intellectual property rights or any other rights
of Shindengen or third parties.
No part of this document may be reproduced in any form without prior consent from Shindengen.
Shindengen Electric MFG.CO.,LTD
-2-
MR4000 Series
Application Note
1. Overview
1.1 Introduction
1.2 Characteristics
1.3 Applications
1.14 Absolute maximum ratings
and reference output
capacities
1.5 Dimensions and equivalent
circuit
1.6 Basic circuit
2. Block diagram
2.1 Block diagram
2.2 Pin function description
3. Operating principles
3.1 Startup circuit
3.2
3.3
3.4
On-trigger circuit
Partial resonance
Standby mode control
(patent pending)
3.5 Output voltage control
(normal operation)
3.6 Soft drive circuit (patent
pending)
3.7 Circuit for load shorts
3.8 Collector pin (MR40XX
Series)
3.9 Thermal shutdown circuit
(TSD)
3.10 Overvoltage protection
circuit (OVP)
3.11 Leading edge blank (LEB)
3.12 Malfunction prevention
circuit (patent pending)
3.13 Overcurrent protection
circuit
4. Design procedure
4.1 Design flow chart
4.2 Reference conditions for
main transformer design
4.3 Reference formulas for main
transformer design
4.4 Selecting constants for
peripheral components
4.5 Selecting constants for
droop circuit
4.6 Cooling design
Contents
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6.5
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11
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6. Supplementary design information
6.1 Supplementary notes on
design
6.2 Noise reduction
6.3 Supplemental information on
surface mounting
6.4 Precautions for waveform
measurements
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51
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60
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61
Notes on pattern design
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62
6.6
Application circuit examples
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11
6.7
Troubleshooting list
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6.8
Glossary
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Shindengen Electric MFG.CO.,LTD
-3-
MR4000 Series
Application Note
1. Overview
1.1 Introduction
The MR4000 Series IC modules incorporate a burst-mode switching function at micro-loads. These are partial
resonance modules consisting of a switching device optimized for 100 V, 200 V, and auto-sensing power supply input
and a control IC. The IC modules are designed to provide the following power supply characteristics:
1.2 Characteristics
1.
2.
3.
4.
5.
6.
7.
8.
High efficiency and low noise through partial resonance
Second-generation high-speed IGBT with 900-V resistance simplifies design for auto-sensing power supply
input. (MR40XX series)
Burst mode helps reduce power consumption at micro-loads.
Onboard startup circuit eliminates the need for startup resistors.
Soft-drive circuit achieves low noise levels.
Overcurrent protection function (ton limit and primary current limit), overvoltage protection, and thermal
shutdown function
Allow configuration of a power supply circuit with fewer external components.
Full-mold package facilitates insulation design.
1.3 Applications
Televisions, displays, printers, video recorders, DVD, STB, refrigerators, and other appliances; various automated
business machines
1.4 Absolute maximum ratings and reference output capacities
Main switching device
型 名
VDS/VCE
[V]
MR4500
MR4510
MR4520
MR4530
500
MOSFET
MR4710
700
MR4720
MR4010
MR4020
MR4030
MR4040
Second–
generation
high-speed
IGBT
900
Maximum output capacity Po[W]
Input voltage range
AC90 - 132V
AC180 - 276V
AC90 - 276V
12 (20)
―
―
25 (40)
―
―
50 (80)
―
―
80 (100)
―
―
―
25 (40)
12 (20)
―
50 (80)
25 (40)
―
65
45
―
105
70
―
135
90
―
180
120
Maximum output capacity and input voltage range vary with design parameters.
Output capacities in parentheses are peak values.
Shindengen Electric MFG.CO.,LTD
-4-
1. Overview
1.5 Dimensions and equivalent circuit
±0.20
+0.2
4.50
φ 3.2 -0.1
Equivalent Circuit
±0.20
±0.2
2.70
10.0
Marking area
±0.20
2.70
+0.20
0.50 -0.10
+0.20
0.97±0.25
0.50 -0.10
1.94±0.30
3.88±0.30
1.94±0.30
(4.1)
±0.50
7.05
Terminal number
1.6 Basic circuit
Shindengen Electric MFG.CO.,LTD
-5-
MR4000 Series
Application Note
2. Block diagram
2.1 Block diagram
2.2 Pin function description
Pin number
Abbreviation
Description
1
2
3
4
Z/C
F/B
GND
Vcc
Zero current detection pin
Feedback signal input pin
GND pin
Vcc (IC power supply) pin
MR45XX series
Main switching device source and OCL
(current detection) pin
MR47XX series
Main switching device emitter and OCL
MR40XX series
(current detection) pin
―
Vin (startup) pin
―
MR45XX series
Main switching device drain pin
MR47XX series
MR40XX series
Main switching device collector pin
Source/OCL
5
Emitter/OCL
6
7
8
9
Vin
Drain
Collector
Shindengen Electric MFG.CO.,LTD
-6-
MR4000 Series
Application Note
3. Operating principles
3.1 Startup circuit
[Conventional startup circuit]
In a conventional startup circuit employing a startup resistor,
an electric current continues to flow after the power supply
starts, wasting power and reducing efficiency, especially
during standby.
See [Conventional startup circuit] in Fig. 3.1 Comparison of
startup circuits.
In the MR4000 Series startup circuit, the startup current is
supplied from the input voltage and shut off when the power
supply starts up.
Startup current
IC
The startup current flows even
during steady-state operation,
resulting in losses.
[MR4000 startup circuit]
The startup circuit supplies the Istartup current from the
The startup current switches off
after startup, eliminating the
constant current source in the IC until the voltage at the VCC
need for a startup resistor.
Vin pin
pin reaches VCC(start) = VCC(startup off). This current is consumed
7
internally in the IC and also used as the charging current for
the capacitor connected externally between the VCC pin and
GND. This design allows stable startup with minimal
dependence on the input voltage.
VCC pin
When the voltage at the VCC pin reaches VCC(startup off) =
4
VCC(start), the startup circuit disconnects, and the startup
Vcc (startup off)/Vcc (startup on)
current is halted. As soon as it stops, oscillation begins.
The current to be consumed in the IC is then supplied from
Control coil
the control coil.
See [MR4000 startup circuit] in Fig. 3.1 Comparison of
startup circuits.
Fig. 3.1 Comparison of startup circuits
In the case of an instantaneous power failure or a load short,
oscillation stops when the voltage at the VCC pin reaches VCC(stop). When this voltage drops still further to VCC(startup on),
the startup circuit begins to operate once again, and the voltage at the VCC pin begins to rise. See Fig. 3.2.
Incorporating the functions above improves efficiency, particularly during standby, and eliminates the need for a startup
resistor, thereby reducing the overall number of components.
VCC (startup off)
=VCC (Start)
[Vin]
VCC (stop)
VCC (startup on)
[VCC]
[VDS(VCE)]
[VOUT]
Instantaneous
power failure
Load short
Fig. 3.2 Startup circuit operation sequence
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-7-
3. Operating principles
3.2 On-trigger circuit
Approx.
0.3 V
The MR4000 Series employs a current-critical
operation system. When an energy burst to the
secondary side of the main transformer is detected,
the main switching device is turned on.
[VZ/C]
Energy discharge timing is detected at a negative
edge of the control coil voltage waveform. The main
switching device is turned on upon detection of the
discharge to perform current-critical operations.
See the point with approx. 0.3 V in Fig. 3.3 On-trigger
operation sequence.
[ID(IC)]
[Secondary rectification diode current]
The on-trigger detection voltage (approx. 0.3 V)
features 50 mV hysteresis for improved noise
resistance.
[VDS(VCE)]
[Control coil voltage]
Fig. 3.3 On-trigger operation sequence
3.3 Partial resonance
LP
In a current-critical switching power supply (RCC),
when the secondary current in the circuit with a
resonating capacitor connected between the drain
(collector) and GND of the main switching device as
shown on the right reaches 0 A, damping begins at
the resonance frequency determined by the primary
inductance LP of the main transformer and the
resonating capacitor Cq.
Cq
Drain (collector) pin
Resonating
capacitor
9
Z/C pin
5
Source/OCL
(emitter/OCL)
pin
1
R
3
GND pin
C
On-timing is delayed with
CR time constant.
The discharge current of the resonating capacitor Cq
flows through the primary coil and returns energy to
the input. Adjusting the CR time constant applied to
the Z/C pin (see the diagram on the right) allows the
main switching device to be turned on at the trough of
the damping voltage waveform, reducing turn-on
losses.
Turn-on delay
[VDS (VCE)]
In a partial resonance circuit, the energy stored in the
resonating capacitor Cq during the OFF period of the
main switching device is returned to the input,
reducing turn-on losses. This allows the connection of
a high-capacity capacitor between the drain
(collector) and GND of the main switching device,
thereby reducing noise.
Damping begins at the
resonance frequency
determined by LP and Cq.
[ID (IC)]
[Secondary rectification diode current]
The use of partial resonance improves efficiency and
reduces noise with simple circuit configurations.
Fig. 3.4 Partial resonance
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-8-
3. Operating principles
3.4 Standby mode control (patent pending)
The MR4000 Series is capable of switching between
two methods of output voltage control, normal
operation mode and standby mode, in a single power
supply. This IC uses the burst method for standby
mode. Intermittent operation is performed under light
loads to reduce the oscillation frequency and reduce
switching losses. The burst method effectively
reduces the standby input voltage under micro-loads.
This IC uses a burst mode that performs intermittent
operation without stopping IC control, thereby
minimizing the output ripple. The Z/C pin is clamped
to a voltage of VZ/C(burst) or less by an external signal
to switch to standby mode control. To exit standby
mode— i.e., to return to normal mode— the clamp of the
Z/C pin voltage is released, and the VZ/C(burst) or
higher voltage is applied to the pin.
Fig. 3.5 Standby mode control
In normal operation, the ON range of the main switching
device is linearly controlled by voltage variations at the
F/B pin. In standby mode, the current detection
threshold of the Source/OCL (Emitter/OCL) pin switches
from Vth(OCL) for normal mode to Vth(burst OCL) for standby
mode, and the drain (collector) current is limited.
The peak value of the drain (collector) current is set
by the current detection threshold, and the burst
mode is selected.
In standby mode, oscillation occurs when the voltage
Fig. 3.6 Standby mode control sequence
at the F/B pin is VF/B(burst start) or higher. Oscillation
stops when this voltage is VF/B(burst stop) or lower.
Since the output voltage control in standby mode sets the peak value of the drain (collector) current for each oscillation
cycle, the duty ratio of the oscillating and non-oscillating intervals varies to ensure a constant voltage.
Fig. 3.7 Standby signal receiving sequence
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3.5 Output voltage control (normal operation)
5Vref
The MR4000 Series controls output voltage with an
ON range proportional to voltage at the F/B pin.
IF/B
Controlled linearly, the ON range is ton(min) when the
voltage at the F/B pin is 1.5 V and becomes ton(max)
when the voltage is 4.5 V. A current of IF/B flows at
the F/B pin. The impedance of the photocoupler
transistor connected externally between the F/B pin
and GND varies depending on the control signal from
the secondary output detection circuits, which
controls the ON range of the main switching device to
produce a constant voltage.
The output voltage is controlled
by varying the impedance of the
photocoupler.
2
F/B pin
Output voltage
error detection
feedback
signal
Droop
resistor
ton
(max)
The maximum ON range is limited by setting the
maximum value for the voltage at the F/B pin using a
resistor connected externally between the F/B pin
and GND. Thus, the droop point is determined.
ton
(min)
1.5
4.5
Feedback voltage
VF/B [V]
Fig. 3.8 Output voltage control
3.6 Soft drive circuit (patent pending)
The MR4000 Series supplies the main switching
device gate drive voltage from two separate drive
circuits.
A voltage exceeding the threshold for the main
switching device is supplied from the first drive circuit
at the leading edge of the drive voltage waveform to
turn the main switching device on at the optimal
timing.
The drive voltage is then gradually supplied from the
second drive circuit (see Fig. 3.9).
The gradual supply of the drive voltage reduces drive
losses and reduces noise due to the gate charge
current and the current discharged when the
resonating capacitor switches on.
Fig. 3.9 Comparison of drive circuits
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- 10 -
3. Operating principles
3.7 Circuit for load shorts
The MR4000 Series is designed so that voltage droop occurs under excessive load, causing the output voltage to drop, and
so that the control coil voltage drops proportionally. When the control coil voltage falls below VZ/C(burst), the control switches to
standby mode, and the Source/OCL (Emitter/OCL) pin threshold changes from Vth(OCL) to Vth(burst OCL), thereby limiting the
drain (collector) current to approximately 1/10 of its previous value. This design reduces the stress on the MR4000 Series IC
in the case of a load short and controls the short-circuit current to the secondary diode and the load circuit.
Fig. 3.10 Circuit for load shorts
3.8 Collector pin (MR40XX Series)
The collector pin on the main switching device (Pin 7)
The transformer must be designed and the resonating capacitor must be set to ensure that VCE(max) is less than 900 V.
Depending on input conditions, the collector pin may be subject to reverse bias for a certain period during partial resonance.
This IC uses the second-generation high-speed IGBT as the main switching device. Unlike MOSFETs, this device has
no body diode structure and thus requires the connection of an external high-speed diode between the Collector and
Emitter/OCL pins (see Fig. 3.12).
3.9 Thermal shutdown circuit (TSD)
The MR4000 Series incorporates a thermal shutdown circuit. The onboard IC is latched at 150°C (typical), after which
oscillation is halted. Unlatching is achieved by momentarily dropping the voltage at the VCC pin to VUL (unlatch
voltage) or lower.
3.10 Overvoltage protection circuit (OVP)
The MR4000 Series incorporates an overvoltage protection circuit (OVP). Latching occurs when the control coil
voltage exceeds VOVP, providing indirect overvoltage protection for the secondary output. Unlatching is achieved in the
same manner as for the overheat protection circuit.
3.11 Leading edge blank (LEB)
The MR4000 Series has the leading edge blank function. This function improves the margin of noise by rejecting
trigger signals from the drain current detection circuit for a certain time after the main switching device is turned on.
This function prevents false detections due to the gate drive current produced the moment the main switching device is
turned on or due to the discharge current of a resonating capacitor.
Shindengen Electric MFG.CO.,LTD
- 11 -
3. Operating principles
3.12 Malfunction prevention circuit (patent pending)
On-trigger is disabled during this period.
tondead
The current-critical operation of the MR4000
Series ensures that the main transformer does not
become saturated as long as the droop setting is
optimized.
At startup and in the event of a load short, the
output voltage is significantly lower than the set
voltage. Since the control coil voltage is
proportional to the output voltage, it also drops
significantly, and the on-trigger timing may be
incorrectly detected due to the ringing voltage
generated while the main switching device is OFF.
The device may then be turned on before the
current-critical point.
To counter this problem, the MR4000 Series
incorporates a circuit to prevent on-trigger error at
startup or in the event of a load short. This
function disables the on-trigger for a period, tondead,
after the main switching device in the IC is turned
off (On-dead time). This prevents false detection
due to the ringing voltage while the device is OFF.
This design permits detection of the transformer
secondary current of 0 A to turn on the main
switching device even at startup or in the event of
a load short. This prevents the magnetic
saturation of the transformer.
Approx.
0.3 V
[VZ/C]
[IC(ID)]
Enlarged
view
[Secondary rectification diode]
[VZ/C]
[ID(IC)]
[Secondary rectification diode]
[VDS(VCE)]
[VOUT]
Fig. 3.11 Malfunction prevention circuit
3.13 Overcurrent protection circuit
A current detection resistor is connected between
the Source/OCL (Emitter/OCL) pin and GND to
detect currents between the source (emitter) of
the main switching device and the source
(emitter) current detection pin.
During stable operation, the main switching
device current is limited by pulse-by-pulse
operation with the Vth(OCL) threshold.
During standby, the threshold changes to Vth(burst
OCL), and the oscillation noise from the transformer
due to burst oscillation is reduced.
Fig. 3.12 Current detection resistor
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- 12 -
MR4000 Series
Application Note
4. Design procedure
This design procedure provides an example of an electrical design procedure. Confirm that insulation materials,
insulation configurations, and structures meet the safety standards specified by the relevant authorities.
4.1 Design flow chart
Specifications determined
Main transformer design
Reexamination
Selecting primary circuit
components
Cooling design
Refer to:
[4.2 Reference conditions for main transformer design]
Refer to:
[4.3 Reference formulas for main transformer design]
P.13
P.14
Refer to:
[4.4 Selecting constants for peripheral components]
P.16
Refer to: [4.5 Selecting constants for droop circuit]
P.17
Refer to: [4.6 Cooling design]
P.18
Trial manufacture
Operational checks
Problem
found
No
problems
Completion
4.2 Reference conditions for main transformer design
The values given below are provided for reference only. They should be adjusted to suit specific load conditions.
Symbol
Unit
VAC(min)
Vo
Io
Io(max)
η
V
V
A
A
Minimum oscillation frequency
f(min)
kHz
ON duty ratio
Control coil voltage
Effective cross-sectional area of transformer core
Magnetic flux density variation
Coil current density
D
VNC
Ae
ΔB
α
V
2
mm
mT
2
A/mm
Minimum input voltage
Rated output voltage
Rated output current
Maximum output current
Efficiency
Reference value
MR47XX
MR40XX
Series
Series
―
―
―
―
0.80 - 0.85
30k 25k 25k 50kHz
40kHz
50kHz
0.40～0.55 0.28～0.55 0.50～0.70
15 - 17V
―
250 - 320mT
2
4 - 6A/mm
MR45XX
Series
Shindengen Electric MFG.CO.,LTD
- 13 -
4. Design procedure
4.3 Reference formulas for main transformer design
1
Minimum DC input
voltage
VDC(min)  1.2  VAC(min)
[V]
2
Maximum DC input
voltage
VDC(max)  2 VAC(max)
[V]
3
Oscillation cycle
T(max) 
4
Maximum ON Period
ton(max)1 
D
f(min)
[s]
5
Maximum OFF period
toff(max) 
N S1 VDC(min)  ton(max)1
 tq
N P  (VO1 VF1)
[s]
6
Resonance period
tq
1
[s]
f(min)
2π LP  C q

2
Resonance
( 共振周期

cycle
1
)
2
[s]
7
Maximum load power
PO(max)  VO  I O(max)
[W]
8
Maximum output power
(reference value)
PL  1.3  PO(max)
[W]
9
Peak drain (collector)
current
I DP(I CP) 
10
Primary coil inductance
LP 
11
Number of turns in
primary coil
NP 
12
Core gap
lg  4π 10
2  PL
η VDC(min)  D
VDC(min)  ton(max)1
I DP(I CP)
VDC(min)  ton(max)1 10 9
ΔB  A e
 Ae  N P 2
LP
[A]
[H]
[Turn]
10
[mm]
The gap Ig is the center gap value.
Review the transformer core size and oscillation frequency and redesign if Ig is 1 mm or greater.
Shindengen Electric MFG.CO.,LTD
- 14 -
4. Design procedure
(VO1  VF1 )  N P  ( 1 - ton(max)1 - tq )
f(min)

VDC(min)  ton(max)1
13
Number of turns in
control output coil
N S1
14
Number of turns in noncontrol output coil
N S2  N S1  VO2 VF2
VO1 VF1
[Turn]
15
Number of turns in
control coil
N C  N S1  VNC VFNC
VO1 VF1
[Turn]
[Turn]
Consider the secondary diode forward voltage VF for each output when determining the number of
turns in an output coil.
VFNC is the control coil voltage rectification diode forward voltage.
The reference value for determining the control coil voltage VNC(min) is 15 V to 17 V.
If the VNC(min) is too small, startup characteristics may degrade, making startup difficult.
If the VNC(min) is too large, the overvoltage latch stop voltage VOP may be reached relatively easily.
Check the VNC(min) voltage within an actual circuit at the design stage to determine the optimal value.
16
Primary coil size
ANP 
17
Secondary coil size
A NS 
2  D  PO
2
α  3 ηVDC(min)  ton(max)1  f(min)
2  1  D  (tq  f(min) )  I O
α  3  (toff(max)  tq )  f(min)
[mm ]
2
[mm ]
ANC = 0.2 mm dia. is recommended for the NC coil to simplify calculations.
Shindengen Electric MFG.CO.,LTD
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4. Design procedure
4.4 Selecting constants for peripheral components
The table below gives constants for MR4000 peripheral components.
Reference value
MR45XX
MR47XX
MR40XX
Series
Series
Series
Component
C112
C113
C114
C115
R113
R114
R115
R116
R117
R151
D111
DZ151
This capacitor determines the resonance frequency. Select the
value based on noise, efficiency, and other factors.
This is the power supply voltage rectification capacitor. If the
value is small, operation at startup easily becomes intermittent. If
this is too large, startup time will lengthen.
This is the partial resonance adjustment capacitor. Adjust this
capacitor with R115 so that turn-on occurs at the resonance
trough.
This capacitor is used to reduce noise at Pin 2. It is also
beneficial for gain phase adjustments. If the value is too large,
the frequency response may degrade.
This is the current limiting damper resistor for C108. Select the
value after considering noise, efficiency, and other factors.
This is the overcurrent detection resistor. It determines the droop
point.
This resistor limits the Z/C pin current.
This resistor limits the Z/C pin current.
Adjust the value according to the droop characteristics. Set to a
value slightly higher than the droop point set with R114.
This resistor compensates for droop based on the input voltage.
Adjust the value based on droop characteristics.
1200p
- 3300pF
- 330pF
820pF
- 2200pF
47 - 100μF
10p - 330pF
4700pF
100p - 2200pF
0 to several ohms
See [4.5 Selecting constants for droop
circuit].
Approximately 20 kΩ
Approximately 10 kΩ
Select a high-speed diode in the 900 V and 1A class.
This zener diode compensates for droop based on the input
voltage.
Tens of kΩ
Not
required
Not
required
Not
required
Approximately 50 kΩ
High-speed diode, 900 V
and 1 A class
See Section 4.5.
L101
R101
C103
F101
T101
L201
Vin
C101
D201
C104
C201
C106
D101
C204
VO
R266
C105
C112
R114
C262
D111
R113
9
7
5
C115
PH111
PH111
C113
R201
D112
4
IC111
2
R261
R116 R115
1
R202
R262
C261
3
PH141
D151
Q241
DZ151
IC261
R117
SW241
R248
D141
R265
R151
R241
PH141
R247
R263
C114
Fig. 4.1 MR4000 Series reference power supply circuit
R151, D151 and DZ151 are additional components for auto-sensing input specifications.
Shindengen Electric MFG.CO.,LTD
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4. Design procedure
4.5 Selecting constants for droop circuit
The following are methods of determining the constant of a droop circuit. They are recommended for the MR4000
Series standard power supplies.
4.5.1 MR45XX Series
The following is the method recommended for the MR45XX Series standard circuit.
(1) Apply the following formula to calculate the overcurrent
detection resistance R114:
R114 
Vth(OCL)
[Ω]
I DP (I CP)
5
MR4000
3
Vth(OCL)
Overcurrent limit threshold voltage
IDP(ICP)
Drain (Collector) peak current at
maximum output power
2
D112
4
R117
R114
C115
(2) Adjust R117 on an actual board.
Set a droop point slightly higher than that set with R114.
This value will be on the order of several tens of kΩ.
PH111
Fig. 4.2 MR45XX Series droop circuit
4.5.2 MR40XX Series
The following method is recommended for the MR40XX Series standard circuit.
(1) Apply the following formula to calculate the overcurrent
detection resistance R114:
R114 
Vth(OCL)
[Ω]
I DP (I CP)
5
MR4000
3
Vth(OCL)
Overcurrent limit threshold voltage
IDP(ICP)
Drain (Collector) peak current at
maximum output power
2
D112
4
DZ151
R117
R151 D151
R114
C115
(2) Adjust R117 on an actual board.
Set a droop point slightly higher than that set with R114.
This value will be on the order of several tens of kΩ.
PH111
Fig. 4.3 MR40XX Series droop circuit
(3) Select the voltage for DZ151, a zener diode that
compensates for droop based on the input voltage.
Apply the following formula to calculate the zener voltage:
The compensation beginning voltage is assumed to be 150 V.
Zener
ツェナ電圧
 1.3 150 
voltage
NC
[V]
NP
(4) Adjust R151, a resistor that compensates for droop based on the input voltage, on an actual board.
The value of R151 is approximately 50 Ω.
(5) Set C115 at about 2200 pF.
Shindengen Electric MFG.CO.,LTD
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4. Design procedure
4.6 Cooling design
Tj(max) for the MR4000 Series is 150°C. Since the operation of the MR4000 Series is accompanied by an increase in
temperature associated with power losses, you must carefully consider the type of heat sink needed. Additionally, if the
design must ensure that Tj(max) is not exceeded, you must also consider the thermal shutdown function (TSD = 150°C
(typical)). The extent to which Tj is derated in a design is critical for improving reliability.
4.6.1 Junction temperature and power losses
Most power losses that occur while the devices in the MR Series operate are associated with the internal
MOSFET. If most power losses are considered ON losses, they may be expressed as follows:
PD =VDS ×ID
The temperature increase ΔTj attributable to power losses PD is expressed as follows:
ΔTj +Ta ≦Tj(max)
If TSD(min) is assumed to be 120°C, considering TSD = 150°C (typical), PD is constrained to satisfy the following
equation:
ΔTj+Ta≦TSD(min)
4.6.2 Junction temperature and thermal resistance
Tj may be calculated as follows using thermal resistance θja.
Tj =( PD ×θja) +Ta
Junction-to-ambient thermal
resistance
Junction-to-case thermal
resistance
Case-to-fin thermal resistance
(contact thermal resistance)
Fin-to-ambient thermal resistance
(fin thermal resistance)
θja, the junction-to-ambient thermal resistance, is
expressed as follows:
θja =θjc +θcf +θfa
Symbol
Unit
θja
°C /W
θjc
°C /W
θcf
°C /W
θfa
°C /W
4.6.3 Cautions for cooling design
The thermal shutdown (TSD) protective function stops and latches operation at 150°C in the event of abnormal
heat buildup in the MR Series. This means circuit design must incorporate a cooling design whereby the
temperature is sufficiently derated. Shindengen recommends setting a cooling design target so that the case
temperature will not exceed 100°C.
Shindengen Electric MFG.CO.,LTD
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MR4000 Series
Application Note
6. Supplementary design information
This chapter provides supplementary information for MR4000 Series power supply circuits. Use this information when
designing or evaluating MR4000 Series power supply circuits.
Supplementary design information: Contents
6. Supplementary design information
51
6.1.1 VCC control
51
(1) Increasing the damper resistance
51
(2) NC coil winding method
(3) Adding a dummy resistor
6.1.2 Ringing voltage at turn-off of main switching device
52
(1) Transformer leakage inductance
52
(2) Clamp circuit
6.1.3 Resonating capacitor
54
Selecting the resonating capacitor
54
(2) Capacity of resonating capacitor
6.1.4 Constants of components around Z/C pin in the circuit
55
(1) Partial resonance capacitor C114
55
(2) Partial resonance resistor R115
(3) Z/C pin current limiting resistor R116
6.1.5 Enhancing the peak surge current of VCC pin
56
6.1.6 Phase correction
57
(1) Insert C and R between the cathode and REF of the shunt
regulator.
(2) Insert C and R between the front of the secondary LC filter and
REF of the shunt regulator.
(3) Insert C and R between the rear of the secondary LC filter and
REF of the shunt regulator.
(4) Place the power supply side of the photocoupler in front of the
LC filter.
6.2 Noise reduction
57
58
6.2.1 Redesigning the transformer
58
6.2.2 Changing Y capacitor
58
6.2.3 Using a snubber circuit
58
6.2.4 Connecting a capacitor to a secondary diode in parallel
59
6.2.5 Capacitive coupling
59
6.2.6 Other measures
59
6.3 Supplemental information on surface mounting
60
6.3.1 Greasing
60
6.3.2 Screws
60
6.3.3 Radiation fin
60
Shindengen Electric MFG.CO.,LTD
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6. Supplementary design information
6.4 Precautions for waveform measurements
61
6.4.1 Isolating the AC line
61
6.4.2 Simultaneous measurement of primary and secondary sides
61
61
6.5 Notes on pattern design
62
6.5.1 Pattern design for primary side
62
6.5.2 Pattern design around Nc coil
62
6.5.3 Pattern design for secondary side
62
6.5.4 Pattern design around GND pin
62
6.5.5 Connecting a capacitor
62
6.5.6 Pattern of C114
62
6.5.7 Pattern of R116
63
6.5.8 Location of OCL resistor
63
6.6 Application circuit examples
64
6.6.1 Indirect control
64
6.6.2 Oscillation stop circuit in case of low voltage input
65
6.6.3 Remote ON/OFF circuit for MR4000 Series
65
6.6.4 OVP latch circuit by secondary side detection using auxiliary coil
66
6.7 Troubleshooting list
67
6.8 Glossary
69
6.8.1 Power supply operation
69
6.8.2 Transformer design
70
6.8.3 IC functions
70
6.8.4 Other
72
Shindengen Electric MFG.CO.,LTD
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6. Supplementary design information
6.1 Supplementary notes on design
6.1.1 VCC control
Since the IC control current is very low, VCC can be significantly affected by the ringing voltage caused by
transformer leakage inductance. This will increase the VCC voltage of the MR4000 Series beyond the design value.
Under certain load conditions, the IC may be latched and stopped or the VCC may become too low. The ringing
voltage caused by the transformer leakage inductance is reduced with a DCR snubber circuit. Several other
solutions are also available, as shown below.
(1) Increasing the damper resistance
Increasing this resistance reduces voltage variations. Increasing the
resistance will affect VCC. Make sure the design accounts for possible
stoppage of MR4000 Series products due to a fall in VCC. Set the
resistance on an actual board between several ohms and tens of ohms.
Note that a light load may decrease efficiency under certain
circumstances.
4
MR4000
3
Increase this
resistance.
Fig. 6.1 Damper resistance
(2) NC coil winding method
Bring the NC coil into closer contact with a
secondary coil that has limited contact with
the primary coil. Doing so will reduce the
ringing generated in the NC coil. This is our
recommended winding method.
Fig. 6.2 Transformer winding to improve contact
(3) Adding a dummy resistor
If using a dummy resistor increases power consumption and
decreases efficiency, this circuit will improve these performance
somewhat.
If the VCC voltage exceeds the level determined by the zener diode,
the dummy resistor will control the voltage increase. We recommend
a zener diode for 16 V or higher.
Fig. 6.3 Adding a dummy resistor
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6. Supplementary design information
6.1.2 Ringing voltage at turn-off of main switching device
A significant voltage surge component is generated in the main switch if the transformer leakage inductance is too
large or if a relatively high current is output. The most effective way to reduce the voltage surge component is to
reduce the leakage inductance. The voltage surge component can be also reduced by a clamp circuit. Reducing
the voltage surge component protects the main switch. In the case of a multi-output power supply, it also improves
cross regulation in the outputs.
(1) Transformer leakage inductance
When the main switching device is turned off, a ringing
voltage is added to the voltage, as shown in Fig. 6.4, due to
the leakage inductance of the transformer primary coil.
The voltage applied to the main switching device must be
designed to accommodate the ringing voltage. The leakage
inductance of the primary coil is measured as shown in Fig.
6.4.
Fig. 6.4 Leakage inductance
(2) Clamp circuit
A clamp circuit may be required if the withstand voltage limit of the main switching device is exceeded due to load or
other conditions or if the design margin is insufficient due to a ringing voltage caused by the leakage inductance.
We recommend a DCR snubber circuit as a clamp circuit. See the next
page for DCR snubber circuit design procedures.
3
5
9
MR4000
Fig. 6.5 DCR snubber circuit
Shindengen Electric MFG.CO.,LTD
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6. Supplementary design information
Design of DCR snubber circuit
Use the following formulas to estimate the constants for a DCR snubber circuit:
If all the energy of the leakage inductance LI is assumed to be consumed in the snubber circuit, the following
formula holds true:

1
1
2
 L l  I DP (I CP ) 
 C S  1.2V NP  VNP
2
2

2
…(1)
Energy of leakage inductance LI = Energy of snubber capacitor CS R S  I S  1.2 VNP …(2)
Voltage of snubber resistor RS = Charging voltage of snubber capacitor CS R S  I S 2 
1
 L l 2  I DP (I CP ) 2  f …(3)
2
Power consumption of snubber resistor RS = Power of leakage inductance LI
If we assume that LI is 2.5% of the primary inductance LP and that the charging voltage of snubber capacitor CS
is 1.2 times VNP, CS is given as follows:
From formula (1), C S  0.625  L P 
I DP (I CP ) 2
VNP 2
[F]
From formulas (1) and (3), we obtain formula (4). R S  I S
Formula (2) is equivalent to formula (5). I S  1.2 
2

1
2
2
RS
2
f
…(4)
…(5)
We substitute CS into formula (6) to obtain RS. R S  115.2 
2

VNP
When we substitute formula (5) into formula (4), we obtain formula (6).
PRS, power consumption in RS is: PRS  R S  I S

 C S  1.2V NP  V NP
1
RS
VNP 2
f  L P  I DP (I CP ) 2

1
72
 CS  f
…(6)
[Ω]
[W]
These values assume that LI is 2.5% of the primary inductance LP and that the charging voltage of snubber
capacitor CS is 1.2 times the value of VNP. Adjustments must be made on an actual board.
Ll
IDP(ICP)
CS
LP
VNP
RS
IS
f
Leakage inductance
Peak current of main switching device
Snubber capacitor
Primary inductance of transformer
Flyback voltage generated with primary
inductance LP
Snubber resistor
Current flowing to snubber resistor
Oscillation frequency of power supply
* Calculation example
When oscillation frequency f = 25 kHz, LP = 0.5 mH,
IDP = 5 A and VNP = 200V;
CS = 0.2 uF, RS = 14.7 kΩ and PRS = 3.9 W.
Fig. 6.6 Design of DCR snubber circuit
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6. Supplementary design information
6.1.3 Resonating capacitor
(1) Selecting the resonating capacitor
The resonating capacitor must have the following characteristics:
1) The withstand voltage is significantly greater than that of the main switching device.
2) Tangent of loss angle tan δ is small.
3) The upper temperature limit is high.
Ideally, use a mica or polypropylene capacitor. A low-loss ceramic capacitor should also be adequate. Consult with
the manufacturer before using this capacitor type.
(2) Capacity of resonating capacitor
Noise is reduced by the resonance determined by the resonating capacitor and the primary coil inductance. This
has both favorable and adverse effects, as shown in the table below. Consider these effects when setting the
capacity of the capacitor.
Item
Efficiency during standby
Heat buildup in the transformer
Ringing voltage at turn-off of main switching device
Noise
Operating frequency
Small ← Capacitor capacity → Large
Increases
Decreases
Decreases
Increases
Increases
Decreases
Increases
Decreases
Increases
Decreases
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6. Supplementary design information
6.1.4 Constants of components around Z/C pin in the circuit
D112
MR4000 4
At the design stage, keep in mind the following aspects of the
constants for the components around the Z/C pin (Pin 1) in the
circuit.
3
1
R115
C114
PH141
Fig. 6.7 Circuit around Z/C pin
(1) Partial resonance capacitor C114
The capacity of C114 capacitor should be around 100 pF. Since the Z/C pin (Pin 1) is susceptible to noise, the
capacity should not be lower.
(2) Partial resonance resistor R115
Keep in mind the following when determining the value for R115:
Trough
1)
VCC
Vin  N C
 5mA and
 5mA
R 115
R 115  N P
The absolute maximum rating for the Z/C pin (Pin 1) is ±5 mA.
Current flowing to the pin cannot exceed this level. (Vin represents
the input capacitor voltage when the maximum input voltage is
applied.)
Small
Large
R115
Fig. 6.8 Adjusting the resonance trough
2)
Determine R115 so that the main switching device is turned on at
the trough of its partial resonance.
(3) Z/C pin current limiting resistor R116
If requirements 1) and 2) of Section (2) above cannot be met
simultaneously, add R116 as shown in Fig. 6.9. R116 should be
around 10 kΩ.
D112
MR4000 4
3
1
R115 is used to set the partial resonance trough of the main switching
device. Set in the same way as described in Section (2) above.
R115
R116
C114
PH141
Fig. 6.9 Addition of R116
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6. Supplementary design information
6.1.5 Enhancing the peak surge current of VCC pin
This measure helps enhance resistance against surge currents applied from external sources.
Add a capacitor between the VCC pin (Pin 4) and GND pin
(Pin 3).
Use a capacitor with good frequency characteristics. Place
the capacitor as close as possible to the VCC and GND pins
(Pins 4 and 3).
Fig. 6.10 Capacitor between VCC pin and GND pin
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6. Supplementary design information
6.1.6 Phase correction
In an RCC circuit, delays in the phase of the photocoupler, capacitor, or coil may result in hunting. If so, oscillations
may become audible or output voltage ripples may become very large. The following countermeasures are
available:
(1)
Insert C and R between the cathode and
REF of the shunt regulator.
(2)
Output
(3)
Insert C and R between the front of the
secondary LC filter and REF of the shunt
regulator.
Output
Insert C and R between the rear of the
secondary LC filter and REF of the shunt
regulator.
(4)
Output
Place the power supply side of the
photocoupler in front of the LC filter.
Output
If the oscillation tends to be intermittent under light load, one solution is to lower the feedback gain. Insert a
resistor as shown in Fig. 6.11. Set the resistor to 2.2 kΩ or less.
D112
MR4000 4
3
2
R117
C115
PH111
Fig. 6.11 Lowering feedback gain
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6. Supplementary design information
6.2 Noise reduction
This section describes noise reduction methods for the MR4000. Check these methods on an actual board to
determine the best combination of methods.
6.2.1 Redesigning the transformer
Redesign the transformer to reduce noise, considering the following factors. Proceed carefully with respect to the
withstand voltage, operating frequency, and other relevant parameters of the main switching device.
(1) Improve coil contact.
That will reduce ringing at turn-off and reduce noise.
(2) Increase the ON duty ratio.
Taking full advantage of the partial resonance function will reduce surge currents at turn-on and reduce noise.
(3) Decrease the operating frequency.
That will reduce noise attributable to fundamental waves or harmonics thereof.
6.2.2 Changing Y capacitor
We can reduce noise not only by changing the
location of a Y capacitor or adding a Y capacitor, but
by also changing the capacity. The effect varies with
PCB patterns. Check carefully with an actual board.
(1) Try changing the location of the Y capacitor at
the filter.
(2) Connect to ground from the negative side of the
input capacitor.
(3) Connect to ground from the positive side of the
input capacitor.
①
AC in
③
②
Fig. 6.12 Considerations for Y capacitor
6.2.3 Using a snubber circuit
(1) Add a DCR snubber.
That will lower the peak of a ringing voltage at turn-off and reduce noise.
(2) Add a damping resistor.
Connect to the resonating capacitor in series. This will advance the damping of
a ringing voltage at turn-off and reduce noise.
(3) Connect a capacitor in parallel to the DCR snubber diode.
This will reduce noise from the diode handling switching.
Ideally, use a mica or polypropylene capacitor as the capacitors in (2) and (3). A lowloss ceramic capacitor should also prove adequate. Consult with the manufacturer
before using this type of capacitor.
①
③
②
3
5
MR4000
9
Fig. 6.13 Snubber circuit
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6. Supplementary design information
6.2.4 Connecting a capacitor to a secondary diode in parallel
The secondary diode handles switching. Add a capacitor to reduce noise.
Try the diodes on an actual board to determine which is most effective. It may
help to connect a damping resistor to this capacitor in series.
NS1
Ideally, use a mica or polypropylene capacitor. A low-loss ceramic capacitor
should also prove adequate. Consult with the manufacturer before using this type
of capacitor.
NS2
Fig. 6.14 Adding a capacitor to
the secondary side
6.2.5 Capacitive coupling
You can also couple the primary GND and the secondary GND with a capacitor.
Take great care to consider the leakage current between the primary and
secondary and the safety standards.
NP
NS1
NC
NS2
Fig. 6.15 Capacitive coupling
6.2.6 Other measures
(1) Place bead cores around the drain (collector) pin (Pin 9).
(2) Place bead cores around the secondary diode.
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6. Supplementary design information
6.3 Supplemental information on surface mounting
6.3.1 Greasing
When using a radiation fin (heat sink), apply a thin uniform film of silicon grease between the MR4000 Series and
the fin. This will reduce contact thermal resistance and enhance the heat radiation effect.
6.3.2 Screws
Use M3 round head, pan head, binding head, or fillister head screws. Avoid countersunk head screws. Use plain
washers and spring washers to keep the screws tight. Use small, plain 3-mm washers. Do not use washers that are
3.5 mm or larger or washers with one polished side.
6.3.3 Radiation fin
The mounting surface of the radiation fin for the MR4000 series must be flat and free of any unevenness, torsion, or
warping to protect the device from excessive stress and to avoid impairing radiation effects. Make sure the edge of
the mounting hole is free of burrs. Use a long fin positioned laterally. This shape results in more effective radiation
than other shapes.
Fig. 6.16 Mounting the radiation fin
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6. Supplementary design information
6.4 Precautions for waveform measurements
6.4.1 Isolating the AC line
When measuring the MR4000 Series or a peripheral
circuit using an oscilloscope or other such instrument,
isolate the AC line between the circuit to be measured
and the measuring instrument to prevent electric shock
and leakage.
Fig. 6.17 Isolating the AC line
6.4.2 Simultaneous measurement of primary and secondary sides
In the case of a power supply using the MR4000 Series, the AC input (primary) side and the DC output (secondary)
side are isolated from each other by a transformer. Do not use a measuring instrument on the primary and
secondary sides simultaneously. Otherwise, GNDs of different potentials may be connected; this can affect the
operation of the power supply or measurement results. (Example of method to avoid: Measure the primary and
secondary waveforms simultaneously using the voltage probe of an oscilloscope.)
To check both the primary and secondary waveforms simultaneously, use a differential probe for one of the two.
MR
Do not measure
simultaneously.
Measurement GND
Fig. 6.18 Simultaneous measurement of primary and
secondary sides
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6. Supplementary design information
6.5 Notes on pattern design
Patterns must be as short as possible to make the loops as small as possible. Keep the following in mind at the design
stage:
6.5.1 Pattern design for primary side
C106
6.5.2 Pattern design around Nc coil
D112
C112
4
R114
3
MR4000
5
9
3
MR4000
C113
A high-speed switching current flows through the
loop. Reducing the loop area will reduce noise.
Make the loop connecting the transformer, D112,
and C113 thick and short.
6.5.3 Pattern design for secondary side
6.5.4 Pattern design around GND pin
Short
D201
L201
C201
C202
Short
Place as close to the
output pin as possible.
Make the loop connecting the transformer,
rectification diode, and output capacitor thick and
short. Place the capacitor at the rear of the output
choke coil as close to the output pin as possible.
Connect the GND pin (Pin 3) directly to the
negative side of C106. Do not connect any other
component. Do not place the end of the control
circuit inside R114 (closer to GND pin).
6.5.5 Connecting a capacitor
6.5.6 Pattern of C114
Make sure the pattern passes through the
capacitor pads.
The Z/C pin (Pin 1) is susceptible to noise.
Connect the pattern near the Z/C pin (Pin 1) and
GND pin (Pin 3).
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6. Supplementary design information
6.5.7 Pattern of R116
6.5.8 Location of OCL resistor
9
MR4000
5
3
C112
R114
Place close to
Pins 3 and 5.
For patterns incorporating R116, make the pattern
short as shown in the diagram above.
Place the current detection resistor as close as
possible to the OCL pin (Pin 5) and GND pin (Pin 3).
The OCL detection level is low and readily affected
by the inductance or resistance component of the
current detection loop wire. Placing R114 close to
Pins 3 and 5 will help prevent errors due to noise
and increase detection accuracy.
Shindengen Electric MFG.CO.,LTD
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6. Supplementary design information
6.6 Application circuit examples
6.6.1 Indirect control
If output voltage precision is not an issue, a constant voltage control can be provided at the primary side without
using a photocoupler. Figure 6.19 shows an example of 12 V output design.
(1) Circuit configuration
The circuit consists of a transistor and a current control resistor that control the F/B pin (Pin 2) and a zener
diode that detects voltage. In cases where an increase in voltage under light load is an issue, add a dummy
resistor on the secondary side.
(2) Circuit operation
The zener diode in the additional component for indirect control surrounded in a frame in the diagram detects
the output voltage of the control coil. The detection signal controls the F/B pin (Pin 2) directly via the transistor.
(3) Problem
A ringing voltage attributable to transformer leakage inductance can result in significant variations in voltage
precision. This can also increase the output voltage under a light load.
Fig. 6.19 Indirect control
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6. Supplementary design information
6.6.2 Oscillation stop circuit in case of low voltage input
This protection circuit prevents input from a 100 V group
power source to a 200 V group power supply. The circuit
monitors input voltages. On detecting an input of 100 V, the
circuit stops the oscillation of the MR4000 series. On
detecting an input of 200 V, the circuit allows regular
oscillation.
C106
9
NP
IC111
C113
4
D112
(1) Circuit configuration
The circuit consists of a transistor Q1 that short-circuits
NC
R1
2SC945
the input voltage detection resistor and the F/B pin (Pin 2),
2
62kΩ
360kΩ
a transistor Q2 that turns Q1 off, and a zener diode that
3
Q1
2SC945
corrects for variations in VBE of Q2 and temperature
360kΩ
Q2
characteristics.
8.2V
(2) Circuit operation
The transistor Q1 short-circuits the F/B pin (Pin 2) of the
39kΩ
MR4000 Series until the input voltage Vin exceeds 138
0.033μ F 10kΩ
V (a maximum voltage in the 100 V group), thereby
Fig. 6.20 Oscillation stop circuit in case of low
keeping the MR from oscillating. When Vin reaches 170
voltage input
V (a minimum voltage in the 200 V group), Q2 is turned
on, turning Q1 off. The MR4000 Series begins
oscillating.
(3) Problem
Efficiency is reduced during standby. Standby characteristics are decreased due to the current required for the
input voltage detection circuit and the current flowing to Q1 and Q2. If the resistor R1 is set to 56 kΩ or less, the
IC can not start up.
(4) Precautions
If resistor R1 is set to 56 kΩ or less, the IC may not start up.
Carefully consider the startup characteristics if a resistor or any other component is connected to the VCC pin
(Pin 4) of the MR4000 Series for other purposes.
6.6.3 Remote ON/OFF circuit for MR4000 Series
The oscillation of MR4000 Series devices can be turned on and off with
an external ON/OFF signal.
(1) Circuit configuration
The circuit consists of a transistor that short-circuits the F/B pin (Pin 2)
and an external ON/OFF signal on the primary side. The external
signal can be input from the secondary side using a photocoupler
instead of the transistor.
(2) Circuit operation
Fig. 6.21 MR4000 Series ON/OFF
Upon receipt of the external signal, the transistor is turned on, shortcircuit
circuiting the F/B pin (Pin 2) and halting the power supply. When a
low external signal is input, the transistor is turned off, and
oscillation resumes.
(3) Problem
If the power supply has been turned off by the external signal, the built-in startup circuit will continue charging
and discharging the VCC, resulting in losses.
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6. Supplementary design information
6.6.4 OVP latch circuit by secondary side detection using auxiliary coil
R1
100Ω
PC1
PS2501
4
3
C113
35V
100μF
D1
D1NL20U
C1
0.047μF
D201
L201
+12V
Nc2
D112
Nc1
D1NL20U
Ns1
C201
C202
C205
ZD2
15V,B2
470Ω
GND
PC1
PS2501
Fig. 6.22 OVP circuit using auxiliary coil
(1) Circuit configuration
This circuit consists of NC2, an auxiliary coil; PC1, a photocoupler for OVP; R1; C1; D1; and ZD2, a zener diode
for secondary output detection.
(2) Circuit operation
Set the NC2 coil voltage to 22 V (VCC(OVP) x 1.1) or greater. If the output voltage exceeds the zener voltage, as
the F/B pin is opened, the photocoupler will activate. As a result, the NC2 coil voltage is applied to the VCC pin
(Pin 4) of the MR4000 Series, the VCC voltage exceeds 20 V, and the IC is latched and stopped for OVP.
(3) Precautions
Take steps to ensure the circuit does not exceed 21 V, the absolute maximum rating for the withstand voltage of
the IC. Proceed carefully while referring to the constants of the components in the diagram above.
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6. Supplementary design information
6.7 Troubleshooting list
The table below shows common problems with power supply designs using the MR4000 Series, possible causes, and
solutions.
Problem
Possible cause
The polarity of the transformer is
incorrect.
Solution
Check winding directions for NP, NS, and NC.
The droop compensation circuit is
inadequate.
Adjust the droop compensation circuit.
The ON range setting (resistance between the F/B pin and
GND pin) is small.
A constant current load or constant
power load is used.
Change to a constant resistance load.
Adjust the number of turns in the NC coil.
Review the transformer coil structure.
The overvoltage latch is on.
Combine a zener diode and a resistor to clamp VCC.
Insert a resistor between the NC coil and rectification
diode.
The input to the Z/C pin is incorrect. Review the circuit around the Z/C pin.
The IC is activated under a heavy
Startup under a light load is recommended for the MR4000
load.
Series.
Ton(max) has reached the limit value.
Review the transformer design.
There are too few turns in the NC coil. Adjust the number of turns in the NC coil.
The transformer is causing magnetic Review the core ΔB.
saturation.
Adjust the resistance between the F/B pin and GND pin.
The droop compensation circuit is
Adjust the droop compensation circuit.
MR4000 Series is
2
inadequate.
Adjust the resistance between the F/B pin and GND pin.
defective.
Provide a snubber circuit.
The voltage exceeded the withstand
Review the transformer design.
level of the main switching device.
Review the transformer coil structure.
Adjust
the
current
limiting
resistance
Adjust the current limiting resistance of the photodiode.
A control output
3
voltage rises.
of the photodiode.
1 Does not start up.
A non-control
4 output voltage
rises.
Add a dummy resistor or damper resistor at the output
Peak charging to the output capacitor
end.
due to a surge voltage
Review the transformer design.
The constants for the output voltage
Reexamine the output voltage detection resistance.
The output voltage detection circuit are inappropriate.
or current does not The droop compensation circuit is
Adjust the resistance between the F/B pin and GND pin.
5
reach the desired inadequate.
Adjust the OCL resistance.
level.
Increase the oscillation frequency.
Ton(max) has reached the limit value.
Set the ON duty ratio lower.
The heat sink is too small or missing. Provide a heat sink or replace with a larger one.
Reduce the oscillation frequency.
The switching loss is large.
Use a smaller resonating capacitor.
MR4000 Series
The tightening torque is insufficient. Tighten at the torque recommended by Shindengen.
6 generate
Apply silicone grease.
Contact with the heat sink is poor.
excessive heat.
Insert a radiation sheet.
Timing for partial resonance is
Adjust the delay setting for partial resonance.
incorrect.
The partial resonance trough is high. Increase the ON duty ratio.
The oscillation frequency is high.
Reduce the oscillation frequency.
The phase compensation circuit is
Adjust the circuit around the shunt regulator.
Intermittent
inadequate.
7 oscillation occurs
Increase the current limiting resistance on the diode side of
under a light load.
the photocoupler.
The feedback gain is high.
Connect a resistor in series with the transistor side of the
photocoupler.
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6. Supplementary design information
Problem
Possible cause
Abnormal oscillation
8 during steady-state
The phase has shifted.
operation
This results in hunting.
9
10
11
12
13
14
15
16
Solution
Place the secondary F/B pin in front of L.
Adjust the circuit around the shunt regulator.
Adjust the circuit around the photocoupler.
The droop operation is
The droop circuit is inadequate.
ineffective.
Adjust the OCL resistance.
Adjust the resistance between the F/B pin and GND
pin.
Redesign ON duty ratio.
Review the transformer coil structure.
The ON duty ratio is large.
The transformer coupling is poor.
The ratio of numbers of turns in coils is
Review the transformer design.
inappropriate.
VDS or VCE exceeds the
Adjust the resonating capacitor.
withstand level.
Provide a snubber circuit.
The surge is large.
Add a power clamper.
Connect a resistor in series with the resonating
capacitor.
Adjust the current-limiting resistance of the
The current to the photodiode is too low.
photodiode.
The IC cannot enter
Increase the capacity of the capacitor between the
standby mode.
Noise is superimposed on the Z/C pin. Z/C pin and GND pin.
Improve the PCB pattern.
Adjust the number of turns in the NC coil.
The oscillation halts
Review the transformer coil structure.
when the output load is The overvoltage latch is on.
Combine a zener diode and a resistor to clamp VCC.
increased.
Add a damper resistor for VCC.
The transformer
Reinforce impregnation (e.g., double impregnation,
generates an oscillating Transformer vibrations
use of adhesive)
tone in standby mode.
Optimize the load.
Increase the capacity of the capacitor between the
Noise is superimposed on the Z/C pin.
Z/C pin and GND pin.
The input power is large
in the case of a load
Increase the current rating of the diode.
The VF of the secondary diode is large.
short.
Use a Schottky diode.
The transformer coupling is poor.
Review the transformer coil structure.
The resistor between the F/B pin and
Make sure the voltage droops only with the OCL pin
The droop point varies.
GND pin is operating.
resistance.
The tan δ of the resonating capacitor is
Use a capacitor with a smaller tan δ.
large.
The standby power is
Adjust the resonating capacitor (carefully monitor
large.
The capacity of the resonating capacitor
VDS or VCE to ensure that the withstand level is not
is large.
exceeded.)
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6. Supplementary design information
6.8 Glossary
This section provides a glossary of terms used in the MR Series Application Note, power supply reference data, and
other technical materials. It provides various definitions for technical use, such as power supply design and IC
functions.
6.8.1 Power supply operation
[Resonating capacitor]
A capacitor for a damper snubber circuit in a power supply circuit using partial resonance
→ Damper snubber
[Clamper snubber]
A snubber circuit consisting of diode, capacitor, and resistor at the primary coil end (DCR snubber) or a snubber
circuit using a power zener diode
→ Snubber circuit
[Gain and phase]
Important parameters for a feedback control circuit.
[Conducted emissions]
Conducted noise fed back to the input side; also called input feedback noise
[Output ripple voltage]
Output voltage is not completely DC and has various superimposed frequency components.
General ripple voltage components result from commercial and switching frequencies.
[Droop characteristics]
Output characteristics when an overcurrent protection function activates
[Droop compensation circuit]
A compensation circuit used to minimize the dependence of the droop function on input voltage
[Snubber circuit]
A circuit used to reduce stress on a switching device. Snubber circuits are divided into clamper snubber and
damper snubber.
[Damper snubber]
A CR snubber circuit consisting of a resistor and a capacitor between the drain and the source or between the
collector and the emitter of a main switching device. In a partial resonance power supply circuit, C represents a
resonating capacitor and R a damper resistor.
→ Snubber circuit
[Current-critical system]
A power supply control system for an isolated flyback transformer in which the main switching device activates
when the secondary diode is turned off
[Input feedback noise]
Conducted noise fed back to the input side; also called conducted emissions
[Burst mode]
Control mode for a switching power supply using intermittent oscillation
With the MR Series, the drain current peak value during intermittent oscillation is limited to IDP(burst limit).
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6. Supplementary design information
[Hunting]
A situation in which the gain or phase in a feedback control system is not adequate, resulting in abnormal
oscillations
[Feedback]
Signal fed back to the primary control circuit upon detection of the output voltage
Feedback is used for constant voltage control.
[Radiated emissions]
Disturbance field strengths released into the air; also called radiated noise
[Partial resonance]
A soft-switching method or technology used in a circuit that reduces switching losses at startup of the main
switching device in a switching power supply
[Radiated noise]
Disturbance field strengths broadcast into the air; also called radiated emissions
[Ringing voltage]
In this application note, it refers in particular to the oscillation voltage immediately after the main switching
device is turned off.
6.8.2 Transformer design
[Duty ratio]
A ratio of the ON range to the oscillation period; sometimes referred to as D.
[TON-T ratio]
The same as duty ratio
[ON duty ratio]
The same as duty ratio
[Core gap]
A gap in a transformer core
In a flyback power supply, this gap is used to adjust inductance.
[Control coil]
A coil used to supply the source voltage to the internal IC of the MR Series and to output the Z/C signal.
[Magnetic saturation]
State in which the maximum magnetic flux density of a transformer is exceeded
If magnetic saturation occurs, the inductor will not function; a sudden excessive current may flow and damage
the power supply.
[Magnetic flux density]
The magnetic flux per unit area generated at the core by an excitation current
6.8.3 IC functions
【LEB】
See Leading edge blank.
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6. Supplementary design information
[OCP]
See overcurrent protection.
[OVP]
See overvoltage protection.
[TSD]
See thermal shutdown.
[Under voltage lock out]
A function that incorporates several volts of hysteresis into startup characteristics. This function stabilizes
startup characteristics; sometimes referred to as UVLO.
[UVLO]
See Under voltage lock out.
[On-dead timer]
A function that disables the main switching device for a certain period to prevent unintended operation due to
the ringing voltage when turned off
[On-trigger]
With the MR Series, the Z/C pin (Pin 2) detects a falling edge of the control coil signal and uses it as a trigger
signal to turn on the main switching device.
[On-trigger disabled period]
In switching operations, this refers to a period during which the turn-on signal is not accepted to prevent
unintended operations due to ringing voltage when turned off.
[Overvoltage protection]
A function that limits the output voltage to prevent damage to the power supply sometimes referred to as OVP
[Overcurrent protection]
A function that limits the output current to prevent damage to the power supply; sometimes referred to as OCP
[Thermal shutdown]
A function that limits the IC junction temperature to prevent damage to the IC. If the temperature exceeds a
certain level, the IC is latched and stopped; sometimes referred to as TSD; also referred to as overheat
protection.
→ Latch stop
[Soft drive]
A drive system of the main switching device of a switching power supply that reduces noise and enhances
efficiency under a light load. Shindengen has applied for a patent on this technology.
[Negative edge]
A falling edge of a rectangular wave
[Latch stop]
One of IC’s stop modes following activation of a protection function; in this mode, the IC will not restart unless
power is applied again.
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6. Supplementary design information
[Leading edge blank]
A function that prevents the main switching device from being turned off for a certain period to prevent
unintended operations due to a surge voltage at turn-on; sometimes referred to as LEB
[Restart timer]
The MR Series re-oscillates in standby mode or at startup if it does not receive a trigger signal for a certain
period of time. The restart timer determines this duration.
6.8.4 Other
[Ultra fast IGBT]
A switching device developed by Shindengen that offers sufficient speed characteristics for switching power
supplies; employed as the main switching device in the MR2900 Series, MR40XX Series, and MR5000 Series.
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MR4000 Series
Application Note
Guides for MR Series Applications
We offer various applications that make it easier to design power supply circuits using the MR Series. We will
continue to update and add new data and know-how. Please contact our sales department to order reference
materials or to inquire about the latest editions.
Selection guide
Lists the line-up of MR Series and provides product overviews. (We are currently working to include the
MR4000 Series.)
Application note
MR1000 Series
MR2000 Series
MR4000 Series
MR5000 Series
Presents MR1000 Series operating principles, design procedures for power supply
circuits, and supplemental design information.
Presents MR2000 Series operating principles, design procedures for power supply
circuits, and supplemental design information.
Presents MR4000 Series operating principles, design procedures for power supply
circuits, and supplemental design information.
Presents MR5000 Series operating principles, design procedures for power supply
circuits, and supplemental design information.
Power supply reference data
MR1000 Series
MR2000 Series
MR4000 Series
MR5000 Series
Provides power supply reference data for MR1000 Series and abnormal test tables.
Provides power supply reference data for MR2000 Series and abnormal test tables.
In preparation
In preparation
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