Shindengen MR2940 Provision for standby mode operation partial resonance power supply ic module Datasheet

Input voltage autosensing
Provision for Standby mode operation
Partial Resonance Power Supply IC Module
MR2900 Series
2002/03/01
Tentative
Application Note
MR2900
Application Note
Cautions When Using This Document
1. The circuit diagrams and parts tables provided for reference purposes in this document are for the
use of persons with basic circuit design knowledge to aid in understanding the product.
As such they do not constitute a guarantee of output, temperature, or other characteristics, or
characteristics or safety as determined by the relevant authorities.
2. The products noted in this document are semiconductor components for use in general electronic
equipment and for general industrial use. Consideration has been given to ensure safety and
reliability as appropriate for the importance of the systems used by the customer. Please contact
Shindengen's sales section if any points are unclear.
3. Fail-safe design and safety requirements must be considered in applications in which particularly
high levels of reliability and safety are required (eg nuclear power control, aerospace, traffic
equipment, medical equipment used in life-support, combustion control equipment, various types
of safety equipment).
Please contact our sales department if anything is unclear.
4. Shindengen takes no responsibility for losses or damage incurred, or infringements of patents or
other rights, as a result of the use of the circuit diagrams and parts tables provided for reference
purposes in this document.
5. The circuit diagrams and parts tables provided for reference purposes in this document do not
guarantee or authorize execution of intellectual property rights, or any other rights, of Shindengen
or third parties.
6. Systems using Shindengen products noted in this document and which are strategic materials as
defined in the Foreign Exchange and Foreign Trade Control Law or the Export and Trade Control
Law require export permission under the relevant legislation prior to export.
Inquiries: Functional Devices Division, Device Sales Department, Device Sales Section
Ph
Fax
03-5951-8131
03-5951-8089
Thank you
July 1st, 1995
Shindengen Electric MFG.CO.,LTD
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MR2900
Application Note
Contents
1. Outline
1.1 Introduction
…
4
1.2 Characteristics
…
4
1.3 Applications
1.4 Absolute Maximum Ratings
and Reference Output Capacities
1.5 Equivalent Circuit and Dimensions
…
4
…
4
…
4
2.1 Block Diagram
…
5
2.2 Pin Function Description
…
5
3.1 Start-up Circuit
…
6
3.2 On-trigger Circuit
…
7
3.3 Partial Resonance
…
7
3.4 Standby Mode Control
…
8
3.5 Output Voltage Control
…
9
3.6 Soft Drive Circuit
…
9
3.7 Circuit for Load Shorts
…
10
3.8 Collector Pin (pin 7)
…
10
3.9 Thermal Shut-down Circuit (TSD)
…
10
3.10 Over-voltage Protection Circuit (OVP)
…
10
…
11
…
11
…
12
5.1 Design Flow Chart
…
13
5.2 Main Transformer Design Procedure
…
13
5.3 Main Transformer Design Examples
5.4 Selection of Constants for
Peripheral Components
…
15
…
18
…
19
…
19
…
19
2. Block Diagram
3. Operation Description
3.11 Malfunction Prevention Circuit
(patent applied for)
3.12 Over-current Protection Circuit
4. Standard Circuit
5. Design Procedures
6. Cooling Design
6.1 Junction Temperature and Power Losses
6.2 Junction Temperature
and Thermal Resistance
6.3 Cautions for Cooling Design
The values presented in this document are based on tentative specifications as of June 29th, 2001, and may change in future
Shindengen Electric MFG.CO.,LTD
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MR2900
Application Note
1. Outline
1.1 Introduction
The MR2900 Series IC modules are designed for both 200V and autosensing input with a burst-mode switching function at microloads. These modules are of the partial resonance type, and are comprised of a switching device optimized for both 200V and
autosensing power supply input, and a control IC. They are designed to provide the following power supply characteristics.
1.2 Characteristics
1. An ultra high-speed IGBT with 900V resistance ensures high efficiency and low noise at partial resonance.
2. An ultra high-speed IGBT with 900V resistance simplifies design for autosensing power supply input.
3. Very low power consumption at micro-loads (in burst mode).
4. Onboard start-up circuit eliminates the need for start-up resistors.
5. Soft drive circuit achieves low noise levels.
6. Excess current protection function (ton limit, primary current limit).
7. Excess voltage protection and thermal shut-down function.
8. Power supply circuits may be constructed with a minimum of external components.
9. The use of a full mold package provides benefits in insulation design.
1.3 Applications
TVs, displays, printers, VTR, DVD, STB, air-conditioners, refrigerators, and other electrical appliances, and office equipment.
1.4 Absolute Maximum Ratings and Reference Output Capacities
Maximum output capacity Po[W]
Absolute maximum ratings
Model
Peak input voltage
Peak input current
Vin[V]
Iin[A]
90V to 276VAC
180V to 276VAC
7
100
150
10
150
225
MR2920
900
MR2940
Input voltage range
Maximum output capacity and input voltage range differ with design conditions.
1.5 Equivalent Circuit and Dimensions
φ3.2
20.0±0.2
5.0±0.2
12.0
4.2
Collector Z/C
4
Vcc
5
Vin
2.4±0.2
6
Emitter/OCL
2.54±0.2
6×1.7±0.3=15.24±0.3
4.2±0.5 7.6±0.5
GND
IC1
11.8
3
3.0±0.2
F/B
±0.5
Q1
2
16.7±0.3
1
8.0
7
+0.2
-0.1
0.7 +0.3
-0.1
2.7±0.2
0.7±0.2
4.5±0.5
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MR2900
Application Note
2. Block Diagram
2.1 Block Diagram
Vcc
4
Unlatch
comparator
UVLO comp
Vin Collector
5
7
Start-up circuit
UVLO
comparator
Start-up
circuit
OVP
comparator
VUL
VCC(start)
/VCC(stop)
VCC(startup off)
/VCC(startup on)
R
VOVP
Z/C 1
Q
Thermal
Shutdown
circuit
Zero current
detection
circuit
S
Q1
Soft drive
circuit
S
Q
On-dead
timer
R
Excess current
detection
comparator
Standby
circuit
VTH(OCL)
Vref
IF/B
F/B 2
Restart
timer
Burst current
limit
comparator
ON range
timer
VTH(burst limit)
3
6
GND
Emitter/OCL
2.2 Pin Function Description
Pin number
Abbreviation
1
Z/C
Trigger input pin
2
F/B
Feedback signal input pin
3
GND
4
Vcc
IC power supply pin
5
Vin
Start pin
6
7
Emitter
/OCL
Collecter
Description
Zero detection voltage: 0.35V
Standby: Up to 4.5V in standby mode.
ton(min) to ton(max): 1.5V to 4.5V/0μs to 25μs
Standby: Oscillation stopped at up to 0.8V.
Standby: Oscillation started at 1.8V or higher.
GND pin
Main switching device emitter and
current detection pin
Main switching device collector pin
Oscillation start voltage: Vcc≧14V
Oscillation stop voltage: Vcc≦8.5V
Excess voltage latching voltage:Vcc=20V
Current supplied Vin→Vcc at start-up
Start-up circuit OFF:Vcc≧14V
Start-up circuit ON: Vcc≦7.6V
Excess current detection threshold:0.6V
Excess current detection threshold at standby: 50mV
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MR2900
Application Note
3. Operation Description
3.1 Start-up Circuit
【Conventional Start-up Circuit】
In conventional start-up circuits employing a start-up
resistor, current continues to flow following power supply
start-up, thus wasting power and reducing efficiency,
particularly during standby.
See Fig.3.1 Comparison of Start-up Circuits - Conventional
Start-up Circuit.
Start-up
current
IC
Start-up current flows even
during steady-state operation,
resulting in losses.
In the MR2000 Series start-up circuit the start-up current is
supplied from the input voltage at power supply start-up,
and is shut-off when the power supply is in operation.
【MR2000 Start-up Circuit】
The start-up circuit supplies a current of 12mA (typical) from
the IC internal constant current source until the voltage at
the Vcc pin reaches 14V (typical). This current is consumed
internally in the IC as well as being used as the charging
current for the condenser connected externally between the
Vcc pin and GND.
This design allows a stable start-up only minimally
dependent upon input voltage.
When the voltage at the Vcc pin reaches 14V (typical) the
start-up circuit is disconnected, the start-up current no
longer flows and oscillation begins simultaneously.
The current consumed in the IC is then supplied from the
control coil. See Fig.3.1 Comparison of Start-up Circuits MR2000 Start-up Circuit.
Start-up current switched off
following start-up, thus
eliminating the need for start-up
resistors.
5
Vin pin
Control coil
Vcc(startup off)
/Vcc(startup on)
14.5V/7.2V
4
Vcc pin
Fig.3.1 Comparison of Start-up Circuits
In the case of an instantaneous power failure or a load
short, oscillation is stopped when the voltage at the Vcc pin reaches 8.5V, and when this voltage drops to 7.6V the start-up circuit
operates again and the voltage at the Vcc pin then begins rising. See Fig.3.2.
Incorporation of the functions described above improve efficiency, particularly during standby, and reduces the number of start-up
resistors required, thus reducing the overall number of components.
VCC(startup off)
=VCC(Start)
=14.0V
【Vin】
VCC(stop)
=8.5V
VCC(startup on)
=7.6V
【VCC】
【VCE】
【VOUT】
Instantaneous power failure
Load short
Fig.3.2 Start-up Circuit Operation Sequence
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3.2 On-trigger Circuit
0.2V
The MR2000 Series employs current-critical operation to
detect energy bursts at the secondary side of the main
transformer and switch on the main switching device.
【VZ/C】
Energy discharge timing is detected at the negative edge
of the control coil voltage waveform (0.2V in the diagram at
right), and the main switching device switched on for
current-critical operation.
【IC】
The on-trigger detection voltage (0.2V) incorporates a
50mV hystersis to increase noise resistance.
【Secondary rectification diode current】
【VCE】
【Control coil voltage】
Fig.3.3 On-trigger Operation Sequence
3.3 Partial Resonance
In current-critical switching power supplies (RCC), damping
begins at the resonance frequency (determined by the
primary inductance LP of the main transformer and the
resonating condenser C) when the secondary current in the
circuit formed by connecting the resonating condenser
between the collector and GND of the main switching
device reaches 0A.
On timing delayed with
CR time constant.
Emitter/OCL
pin
Resonating
condenser
The discharge current of the resonating condenser flows
through the primary coil and returns energy to the input.
Adjustment of the CR time constant applied to the Z/C pin
(see diagram at right) allows the main switching device to
be turned on at the trough of the damping voltage
waveform, thus permitting a reduction in turn-on losses.
7
6
Collector
pin
1
Z/C pin
R
3
GND pin
C
Turn-on delay
Damping begins at the
resonance frequency
determined by LP and C.
In a circuit using partial resonance, the energy stored in the
resonating condenser during the OFF period of the main
switching device is returned to the input, thus permitting a
reduction in turn-on losses. This allows the connection of a
large-capacity condenser between the collector and GND
of the main switching device, and thus permits a reduction
in noise.
【VCE】
The use of partial resonance is effective in permitting a
simple circuit configuration with improved efficiency and
noise reduction.
【Secondary rectification diode current】
【IC】
Fig.3.4 Partial Resonance
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3.4 Standby Mode Control (patent applied for)
The MR2000 Series is able to switch between two methods
of output voltage control - normal operation and the standby
mode, in a single power supply.
The standby mode supported by this IC employs the burst
method for intermittent operation under light loads to
reduce oscillation frequency and switching losses, and is
effective in reducing the standby input voltage under
micro-loads.
Drain pin
7
Z/C pin
Emitter/OCL
pin
6
1
F/B pin
2
4.5V
(TYP)
Switched from
0.6V to 0.05V
A unique characteristic of this IC is the use of the burst
mode for intermittent operation without stopping IC control,
and thus minimizing output ripple.
The Z/C pin is clamped to a voltage of 4.5V (typical) or less
by an external signal to allow selection of standby mode
control. The standby mode is cleared (ie restored to the
normal mode) by clearing the clamp voltage on the Z/C pin,
and applying a voltage of 4.5V (typical) or higher.
3
Output voltage error
detection feedback
signal
Standby signal
(external signal)
Fig.3.5 Standby Mode Control
VF/B(burst stop)
=0.8V
In normal operation the ON range of the main switching
device is controlled in a linear manner in relation to voltage
variation at the F/B pin, while in standby mode operation the
Emitter/OCL pin current detection threshold value is
switched from 0.6V for the normal mode to 0.05V for the
standby mode.
The collector current is fixed at a peak value by the current
detection threshold value, and the burst mode is selected.
VF/B(burst start)
=1.8V
【VF/B】
【IC】
Burst mode control is such that oscillation occurs when the
voltage at the F/B pin is 1.8V (typical) or higher, and is
stopped when this voltage is 0.8V (typical) or lower.
【VOUT ripple】
As output voltage control in the standby mode fixes the
Fig.3.6 Standby Mode Control Sequence
drain current peak value for each oscillation cycle, the duty
ratio of the oscillating and non-oscillating intervals is varied to ensure a constant voltage.
Standby mode start
0.2V
4.5V(TYP)
Standby mode clear
【VZ/C】
【IC】
【IOUT】
Normal operation
Standby mode
Normal
operation
Fig.3.7 Standby Signal Receive Sequence
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3.5 Output Voltage Control (normal operation)
5Vref
The MR2000 Series controls output voltage with the ON
range proportional to the voltage at the F/B pin.
200μA
When the voltage at the F/B pin is 1.5V the ON range is
0µs, and is controlled in a linear manner so that when the
voltage is 4.5V the ON range is 25µs. A current of
200µA=IF/B (typical) flows at the F/B pin, and the
impedance of the photocoupler transistor connected
externally between the F/B pin and GND is varied with the
control signal from the secondary output detection circuit,
thus controlling the ON range of the main switching device
to produce a constant voltage.
F/B pin
2
Output voltage controlled
by varying impedance of
photocoupler.
ON range ton[μs]
Droop
resistor
The maximum ON range is adjusted 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.
Output voltage
error detection
feedback signal
25
0
1.5
4.5
Feedback voltage
VF/B[V]
Fig.3.8 Output Voltage Control
3.6 Soft Drive Circuit (patent applied for)
Gate voltage supply
matched to collector
current.
The MR2000 Series supplies the main switching device
gate drive voltage from two separate drive circuits.
A voltage exceeding the threshold value for the main
switching device is supplied from the first drive circuit at the
leading edge of the drive voltage waveform to switch on the
main switching device with the optimum timing.
The drive voltage is then supplied gradually by the second
drive circuit (see Fig.3.9).
【VGE】
Gate charge remains
unchanged even when
collector current is small.
Gate charge spikes
reduced.
【IG】
Supply of drive voltage in this manner reduces drive losses,
as well as reducing noise due to gate charge current and
discharge current when the resonating condenser is
switched on.
Reactive charge
reduced under
light load.
Large resonating
condenser discharge
current.
Damping of resonating
condenser discharge
current.
【IC】
【Conventional drive circuit】
【MR2000 drive circuit】
Fig.3.9 Comparison of Drive Circuits
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3.7 Circuit for Load Shorts
The MR2000 Series is designed so that when droop occurs under excessive load, output voltage drops, and control coil voltage
drops in proportion.
When the control coil voltage falls below 4.5V (typical) the standby mode is selected and the Emitter/OCL pin threshold voltage
changes from 0.6V to 0.05V, thus limiting the collector current to approximately 1/10th of its previous value.
This design permits a reduction in the stress on the MR2000 Series IC in the case of a load short, and control of the short-circuit
current in the secondary diode and load circuit.
4.5V(TYP)
【VZ/C】
ICP limited when VZ/C falls
below 4.5V (typical).
【IC】
Load short
【VOUT】
【VCC】
Fig.3.10 Circuit for Load Shorts
3.8 Collector Pin (pin 7)
The collector pin on the main switching device.
The transformer is designed, and the resonating condenser adjusted, to ensure that VCE(max) is less than 900V.
Depending upon input conditions, the collector pin may be subjected to reverse bias for a period during partial resonance.
This IC employs an ultra high-speed IGBT in the main switching device. This device differs from MOSFET devices in that it has no
body diode structure, thus requiring connection of an external high-speed diode between the Collector and Emitter/OCL pins.
3.9 Thermal Shut-down Circuit (TSD)
The MR2000 Series incorporates a thermal shut-down circuit.
The onboard IC is latched at 150°C (typical) and oscillation is then stopped.
Unlatch is achieved by momentarily dropping the voltage at the Vcc pin to VUL (unlatch voltage) or lower.
3.10 Over-voltage Protection Circuit (OVP)
The MR2000 Series incorporates an over-voltage protection circuit (OVP).
Latching occurs when the control coil voltage exceeds 20V (typical), and secondary output over-voltage protection then operates
indirectly.
Unlatch is achieved in the same manner as for the overheat protection circuit.
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3.11 Malfunction Prevention Circuit (patent applied for)
On-trigger disabled during
this period.
2.5μs
0.2V
The use of current-critical operation in the MR2000
Series ensures that the main transformer does not
become saturated provided the droop setting is
optimized.
On the other hand, at start-up, and in the case of a
load short, the output voltage is very much less than
the set voltage.
As the control coil voltage is proportional to the output
voltage it also reaches an extremely small value, and
the on-trigger timing may be incorrectly detected due
to the ringing voltage while the device is OFF and
switched on before the current-critical point.
To counter this problem, the MR2000 Series
incorporates a circuit to prevent on-trigger malfunction
at start-up, and in the case of a load short. This function
disables the on-trigger for a period of 2.7μs (typical)
after the main switching device in the IC is switched
OFF (on-dead time). This prevents incorrect detection
due to the ringing voltage while the device is OFF.
This design permits detection of the point at which the
transformer secondary current is 0A at start-up, and in
the case of a load short. The main switching device is
then switched on at this point, allowing abnormal
oscillation to be controlled.
【VZ/C】
Enlarged
view
【IC】
【Secondary rectification diode】
【VZ/C】
【IC】
【Secondary rectification diode】
【VCE】
【VOUT】
Fig.3.11 Comparison of Drive Circuits
3.12 Over-current Protection Circuit
Body diode
A current detection resistor is connected between the
Emitter/OCL pin and GND to detect current between
the emitter of the main switching device and the emitter
current detection pin.
7
Resonating
condenser
6
Collector pin
Emitter/OCL
pin
During stable operation the main switching device
Current detection
current is limited by pulse-by-pulse operation with the
resistor
0.6V threshold value.
The leading edge clamp function prevents
malfunctioning and thus prevents incorrect detection at
Fig.3.12 Current Detection Resistor
turn-on.
During standby, the 50mV threshold value is selected and the oscillation noise from the transformer due to burst oscillation is
reduced.
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Standard circuit/Parts list
MR2900
Application Note
4. Standard Circuit
L101
L
T101
R101
C103
F101
C102
C104
L201
VO
D201
C101
N
C201-2
R205
C201-1
C106
D101
C202
GND
C105
C108
C203
D102
R102
R103
PC101
7
5
6
C109
PC101
D103
R202
4
IC101
2
C107
R206
R106
1
3
R105
R201
R203
C204
D105 D106
D104
PC102
R207
IC201
R208
TR201
SW201
R209
R210
R204
C111
R104
PC102
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MR2900
Application Note
5. Design Procedures
5.1 Design Flow Chart
Specifications determined
Main transformer design
Selection of primary circuit
components
Reexamination
Refer to:
5.2 Main Transformer Design Procedure
5.3 Main Transformer Design Examples
Refer to:
5.4 Selection of Constants for Peripheral Components
Cooling design
Trial manufacture
Operational checks
Problems found
No problems
Completion
5.2 Main Transformer Design Procedure
This design procedure provides an example of an electrical design procedure.
Ensure that design of insulation materials, insulation configuration, and structure are in accordance with the necessary safety
standards as determined by the relevant authorities.
5.2.1 Standard Design Conditions
Minimum input voltage
Rated output voltage
Rated output current
Maximum output current
Efficiency
Abbreviation
Unit
Reference value
VAC(min)
V
Vo
V
―
―
Io
A
―
Io(max)
A
―
kHz
25k~50kHz
0.80~0.85
η
Minimum oscillation frequency
f(min)
Duty ratio
0.50~0.70
D
Control coil voltage
VNC
15~17V
V
2
Effective cross-sectional area of transformer core
Ae
Magnetic flux density variation
ΔB
mT
α
A/mm
Coil current density
―
mm
250~320mT
2
2
4~6A/mm
Note that the above values are for reference only, and should be adjusted to suit load conditions.
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5.2.2 Standard Design Calculations
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) =
1
[s]
f(min)
4
Maximum ON period
ton(max) = D
f(min)
[s]
5
Maximum OFF period
toff(max) = NS1 ×VDC(min) × tON(max) + tq
NP × (VO1 +VF1)
[s]
6
Resonance period
tq =
7
Maximum load power
PO(max) = VO × IO(max)
[W]
8
Maximum output power
(reference value)
PL = 1.3 × PO(max)
[W]
9
Peak collector current
ICP =
2 × PL
η×VDC(min) × D
[A]
10
Primary coil inductance
LP = VDC(min) × ton(max)
ICP
[H]
11
Number of turns in primary coil
9
NP = VDC(min) × ton(max) ×10
ΔB × Ae
12
Core gap
2π LP × Cq
2
lg = 4π ×10
−10
[s]
[Turn]
× Ae × NP 2
[mm]
LP
The gap Ig is the center gap value.
Review transformer core size and oscillation frequency and redesign if Ig is 1mm or greater.
13
Number of turns
in control output coil
(VO1 +VF1) × NP × ( 1 - ton(max) - tq)
f(min)
NS1 =
VDC(min) × ton(max)
[Turn]
14
Number of turns
in non-control output coil
NS2 = NS1 × VO2 +VF2
VO1 +VF1
[Turn]
15
Number of turns in control coil
NC = NS1 × VNC +VFNC
VO1 +VF1
[Turn]
Consider the secondary diode forward voltage 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 15V to 17V.
If the VNC(min) value is too small, start-up characteristics may deteriorate and start-up may become difficult.
If the VNC(min) value is too large, the over-voltage latch stop voltage VOP is able to be reached easily.
Check the VNC(min) voltage in an actual circuit during the design process to determine its optimum value.
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- 14 -
16
Primary coil size
ANP =
2 × D × PO
α× 3 ×η×VDC(min) × ton(max) × f(min)
[mm ]
17
Secondary coil size
ANS =
2 × 1 − D − (tq × f(min)) × IO
α × 3 × (toff(max) − tq) × f(min)
[mm ]
2
2
ANC=0.2mm dia. is recommended for the NC coil for ease of calculation.
5.3 Main Transformer Design Examples
5.3.1 Initial Setup
Input voltage
Efficiency
AC90~276V
85%
Oscillation
frequency at droop
29.6kHz
Duty ratio
TON/T=0.655
Rated output
VO1:DC135V, 0.45A
VO2:DC35V,0.40A
Total output
81.2W
VO3:DC16V,0.40A
Droop output
110.36W (rated output x 1.36)
5.3.2 Primary Inductance (LP) Calculations
Primary inductance (LP) calculated using equations 1, 4, 9, and 10 in 5.2.2.
VDC(min) =1.2 ×VAC(min) =1.2 × 90 =108 [V]
Ensure that ton(max) is
29μs or less.
ton(max) = D = 0.655 3 = 22.13 [μs]
f(min) 29.6 ×10
ICP =
2 × PL
2 ×110.36
=
= 3.67 [A]
η×VDC(min) × D 0.85 ×108 × 0.655
Droop output (rated total
output x 1.36) calculated
as PL
Substitute
-6
×
LP = VDC(min) ton(max) = 108 × 22.13 ×10 = 651.24 [μH]
ICP
3.67
Primary inductance LP =0.65mH.
5.3.3 Calculation of Number of Turns in Primary Coil (NP), and Gap (Ig)
The number of turns in the primary coil is calculated using equation 11 in 5.2.2.
Specifications require the use of PC40 EER39L steel in the transformer core.
2
Substitute Ae=130mm and ΔB=310mT in equation 11.
The maximum rating for
ΔB for PC40 at 100°C is
390mT.
ΔB has been derated to
310mT in this example.
9
-6
9
NP = VDC(min) × ton(max) ×10 = 108 × 22.13 ×10 ×10 = 59.3 ≅ 59 [Turn]
ΔB × Ae
310 ×130
The gap (Ig) is calculated using equation 12 in 5.2.2.
lg = 4π ×10
× Ae × NP 2 = 4 × 3.14 ×10 −10 ×130 × 59 2 = 0.87 [mm]
LP
0.65 ×10 - 3
-10
The number of turns in the primary coil is NP=59, and the gap Ig=0.87mm.
The gap (Ig) calculated above is a reference value.
During trial manufacture, adjust the gap (Ig) in relation to the value found in the calculations,
and ensure that it is appropriate to the primary inductance value.
The number of turns has
been rounded to the
nearest integer, however
this value may be
adjusted as necessary.
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5.3.4 Calculation of Number of Turns in Secondary Coil (NS1)
The number of turns in the secondary coil is calculated using equation 13 in 5.2.2.
(VO1 +VF1) × NP × ( 1 - ton(max) - tq)
f(min)
NS1 =
VDC(min) × ton(max)
(135 +1) × 59 × (
=
Calculation assumes tq
=2.5μs.
1
− 22.13 ×10 −6 − 2.5 ×10 −6 )
29.6 ×10 3
= 30.73 ≅ 31 [Turn]
108 × 22.13 ×10 −6
The number of turns in the secondary coil is therefore NS1=31.
5.3.5 Verification of Resonance Time (tq)
The calculation above assumes a resonance period (tq) of 2.5μs.
This calculation verifies the effectiveness of this value in terms of LP and the resonance
condenser Cq (C108) as previously calculated.
tq =
2π LP × Cg 2π 0.65 ×10 −3 ×1000 ×10 −12
=
= 2.53 [μs]
2
2
If the calculated value
differs, change tq and
recalculate.
Conditions are therefore satisfied.
Note that the calculation assumes a resonance condenser Cq of 1000pF.
5.3.6 Calculation of Number of Turns in Secondary Coils (NS2, NS3)
The numbers of turns NS2 and NS3 in the secondary coils are calculated using equation 14 in
5.2.2.
NS2 = NS1 × VO2 +VF2 = 31 × 35 +1 = 8.20 ≅ 8 [Turn]
VO1 +VF1
135 +1
NS3 = NS1 × VO3 +VF3 = 31 × 16 + 0.6 = 3.78 ≅ 4 [Turn]
VO1 +VF1
135 +1
The numbers of turns in the secondary coils are NS2=8 and NS3=4.
5.3.7 Calculation of Number of Turns in Control Coil (NC)
A value of between 15V and 17V is optimum for Vcc.
This design assumes Vcc=16V, and the number of turns in the control coil is calculated using
equation 15 in 5.2.2.
NC = NS1 × VNC +VFNC = 31 × 16 +1 = 3.88 ≅ 4 [Turn]
VO1 +VF1
135 +1
For ease of handling, a
0.2mm dia. wire is
recommended for the
control coil.
Shindengen Electric MFG.CO.,LTD
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5.3.8 Calculation of Wire Size for Primary Coil (NP)
Coil size is calculated using the rated output power.
Cross-sectional area of the primary coil is calculated using equation 16 in 5.2.2.
2
With current density(α)set at 6A/mm ,
ANP =
=
Adjust current density in
accordance with
conditions of use and
structure of the
transformer.
2 × D × PO
α × 3 ×η ×VDC(min) × ton(max) × f(min)
2
2 × 0.655 × 81.2
= 0.210 [mm ]
6 × 3 × 0.85 ×108 × 22.13 ×10 −6 × 29.6 ×10 3
A diameter of 0.50mm is therefore appropriate for the wire size of the primary coil.
5.3.9 Calculation of Wire Size for Secondary Coils (NS1, NS2, NS3)
Cross-sectional area of the secondary coil is calculated in the same manner as in 5.3.8 using equation 17 in 5.2.2.
toff(max) is first calculated using equation 5 in 5.2.2.
-6
toff(max) = NS1 ×VDC(min) × tON(max) + tq = 31 ×108 × 22.13 ×10 + 2.5 ×10 −6 = 11.73 [μs]
NP × (VO1 +VF1)
59 × (135 +1)
ANS1 =
2 × 1 − D − (tq × f(min)) × IO1 2 × 1 − 0.655 − (2.5 ×10 −6 × 29.6 ×10 3 ) × 0.45
2
=
= 0.165 [mm ]
α × 3 × (toff(max) − tq) × f(min) 6 × 3 × (11.73 ×10 −6 − 2.5 ×10 −6 ) × 29.6 ×10 3
ANS2 =
2 × 1 − D − (tq × f(min)) × IO2 2 × 1 − 0.655 − (2.5 ×10 −6 × 29.6 ×10 3 ) × 0.40
2
=
= 0.146 [mm ]
α × 3 × (toff(max) − tq) × f(min) 6 × 3 × (11.73 ×10 −6 − 2.5 ×10 −6 ) × 29.6 ×10 3
ANS3 =
2 × 1 − D − (tq × f(min)) × IO3 2 × 1 − 0.655 − (2.5 ×10 −6 × 29.6 ×10 3 ) × 0.40
2
=
= 0.146 [mm ]
α × 3 × (toff(max) − tq) × f(min) 6 × 3 × (11.73 ×10 −6 − 2.5 ×10 −6 ) × 29.6 ×10 3
The wire sizes for the secondary coils are therefore as follows.
NS1: 0.32mm dia. x 2 wires
NS2: 0.29mm dia. x 2 wires
NS3: 0.29mm dia. x 2 wires
NP1=37[Turn]
0.50mmφ
NP2=22[Turn]
0.50mmφ
1
12
NP1
2
NS2
3
11
NS3
10
5
8
NP2
NS2=8[Turn]
0.30mmφ×2wires
NC
NS3=4[Turn]
0.30mmφ×2wires
NP2
NS2 NS3
NS1
NC=4[Turn]
0.20mmφ
NC
6
NS1
7
NP1
NS1=31[Turn]
0.30mmφ×2wires
Spacer
Spacer
Primary inductance (LP): 0.65mH (between transformer pins ① and ③)
Gap Ig: 0.87mm
The structure of the transformer requires that all turns in coil NS1 be in a single layer.
Fig.5.1 Transformer Specifications and Coil Structure
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5.4 Selection of Constants for Peripheral Components
5.4.1 Values of Constants for MR2900 Peripheral Components (see 4. Standard Circuit on P12)
Component
C107
C108
Constant
This is the power supply voltage rectification condenser.
If this value is small operation at start-up readily becomes intermittent, and if it is too large start-up time
becomes excessive.
A value of between 47μF and 100μF is appropriate.
This condenser determines the resonance frequency. Select the value on the basis of noise and efficiency etc.
A value of between 820pF and 2200pF is appropriate for autosensing power supplies of between 75W and
150W capacity.
C109
This condenser is incorporated to deal with noise at pin 2. A value of approximately 4700pF is appropriate.
Also beneficial in gain phase adjustment, however frequency response deteriorates if the value is too large.
C111
This is the partial resonance adjustment condenser. Adjust so that turn-on occurs at the resonance trough.
Turn-on occurs earlier if this value is small, and later if it is large.
A value of between 10pF and 33pF is appropriate.
R102
This is the current limiting damper resistor for C108. A value up to a few ohms is appropriate.
Select the value on the basis of noise and efficiency etc.
R103
This is the over-current detection resistor. It determines the droop point.
Calculate the resistance value as follows.
[0.60 (over-current threshold voltage) / Droop point collector current at minimum input]
R104
Adjust on the basis of droop characteristics. Set to a value slightly higher than the droop point set with R103.
A value of a few tens of kohms is appropriate.
R105
This resistor compensates for droop due to input voltage. Adjust on the basis of droop characteristics.
A value of approximately 50kohms is appropriate.
R106
This resistor limits current at the Z/C pin. A value of approximately 20kohms is appropriate.
D102
This corresponds to the body diode for the main switching device (ultra high-speed IGBT).
Select a high-speed diode in the 900V, 1A class.
D106
This is a Zener diode to compensate for droop due to input voltage.
Select a diode for a Zener voltage at least equal to that found with the following equation.
Zener voltage =1.3 ×150 × NC
NP
(assume an initial compensation voltage of 150V)
R105 and D106 are additional components for autosensing input specifications.
Shindengen Electric MFG.CO.,LTD
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MR2900
Application Note
6. Cooling Design
Tj(max) for the MR Series is 150°C.
As operation of the MR Series is accompanied by an increase in temperature associated with power losses, it is necessary to
consider the type of heat sink to be used. While a design which ensures that Tj(max) is not exceeded is of absolute importance, the
overheat protection function (TSD=150°C (typical)) must be also considered in any design. The extent to which Tj is derated in a
design is therefore extremely important in improving reliability.
6.1 Junction Temperature and Power Losses
The majority of power losses during operation of the MR Series are associated with the internal MOSFET.
If the majority of power losses are considered as ON losses, they may be expressed by the following equation.
PD =VDS ×ID
The temperature increase (ΔTj) due to power losses (PD) is expressed as,
ΔTj +Ta ≦Tj(max)
and if TSD=150°C (typical) and TSD(min)=120°C are assumed, PD is limited so that the following equation is satisfied.
ΔTj+Ta≦TSD(min)
6.2 Junction Temperature and Thermal Resistance
Tj may be calculated as follows using the thermal resistance θja.
Tj =( PD ×θja) +Ta
θja is the thermal resistance in the vicinity of the junction, and is expressed as follows.
θja =θjc +θcf +θfa
Thermal resistance between junction and vicinity.
Thermal resistance between junction and case.
Thermal resistance between case and fins
(contact thermal resistance).
Thermal resistance between case and fins
(contact thermal resistance).
Abbreviation
Unit
θja
θjc
℃/W
℃/W
θcf
℃/W
θfa
℃/W
6.3 Cautions for Cooling Design
Thermal shutdown (TSD) is a protective function which stops and latches operation at 150°C in the event of abnormal heating of the
MR1520. Circuit design therefore requires a cooling design in which temperature has been sufficiently derated.
Shindengen recommends that cooling design be such that case temperature does not exceed 100°C.
Shindengen Electric MFG.CO.,LTD
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