Application Note: STR-W6000S Series PWM Off-Line Switching Regulator ICs

Application Information
STR-W6000S Series PWM Off-Line Switching Regulator ICs
General Description
The STR-W6000S series are power ICs for switching power
supplies, incorporating a power MOSFET and a current
mode PWM controller IC in one package. To achieve low
power consumption, the product includes a startup circuit
and a standby function in the controller.
The switching modes are automatically changed according to load conditions so that the PWM mode is in normal
operation and the burst mode is in light load condition. The
rich set of protection features helps to realize low component counts, and high performance-to-cost power supply.
Not to scale
Features and Benefits
TO-220F-6L package
▪ Current mode PWM control
▪ Brown-In and Brown-Out function: auto-restart, prevents
excess input current and heat rise at low input voltage
▪ Auto Standby function: improves efficiency by burst mode
operation in light load
▫ Normal load operation: PWM mode
▫ Light load operation: Burst mode
▪ No load power consumption < 30 mW
▪ Random Switching function: reduces EMI noise, and
simplifies EMI filters
▪ Slope Compensation function: avoids subharmonic
oscillation
▪ Leading Edge Blanking function
▪ Audible Noise Suppression function during Standby mode
▪ Protection features
▫ Overcurrent Protection function (OCP): pulse-by-pulse,
with input compensation function
▫ Overvoltage Protection function (OVP): auto-restart
▫ Overload Protection function (OLP): auto-restart, with
timer
▫ Thermal shutdown protection (TSD): auto-restart
Applications
Switching power supplies for electronic devices such as:
• Home appliances
• Digital appliances
• Office automation (OA) equipment
• Industrial apparatus
• Communication facilities
The product lineup for the STR-W6000S series provides the following options
Output Power*, POUT
Power MOSFET
(W)
fOSC
Part Number
(kHz)
VDSS(min)
RDS(ON)(max)
85 to
230 VAC
(V)
(Ω)
265 VAC
STR-W6051S
STR-W6052S
STR-W6053S
67
650
3.95
2.8
1.9
45
60
90
30
40
60
*The listed output power is based on the thermal ratings, and the peak output power can be 120% to 140% of the value
stated here. At low output voltage and short duty cycle, the output power may be less than the value stated here.
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
http://www.sanken-ele.co.jp/en/
Table of Contents
General Description
1
Absolute Maximum Ratings
2
Electrical Characteristics
3
Functional Block Diagram
5
Pin List Table
5
Typical Application Circuit
6
Package Diagram
7
Marking Diagram
7
Functional Description
8
Startup Operation
Undervoltage Lockout (UVLO) Circuit
Bias Assist Function
Constant Voltage Control Operation
Auto Standby Mode Function
Random Switching Function
Brown-In and Brown-Out Function
10
11
11
Overcurrent Protection Function (OCP)
13
Overvoltage Protection Function (OVP)
13
Overload Protection Function (OLP)
14
Thermal Shutdown Function (TSD)
15
Design Notes
15
Peripheral Components
15
PCB Trace Layout and Component Placement 17
8
8
9
9
Reference Design of Power Supply
18
Important Notes
20
Absolute Maximum Ratings
• Refer to the datasheet of each product for these details.
• The polarity value for current specifies a sink as "+," and a source as
"−," referencing the IC.
Absolute Maximum Ratings Unless otherwise specified, TA = 25°C
Characteristic
Symbol
Conditions
Pins
STR-W6051S
Drain Peak Current
Drain Peak
Current1
IDPEAK
IDMAX
Rating
Unit
5.0
A
7.0
A
STR-W6053S
9.5
A
STR-W6051S
5.0
A
7.0
A
9.5
A
STR-W6052S
STR-W6052S
Single pulse
Single pulse,
TA= –20°C to 125°C
1−3
1−3
STR-W6053S
47
mJ
1−3
62
mJ
86
mJ
VOCP
3−5
−2 to 6
V
Control Part Input Voltage
VCC
4−5
32
V
FB/OLP Pin Voltage
VFB
6−5
−0.3 to 14
V
FB/OLP Pin Sink Current
IFB
6−5
1.0
mA
BR Pin Voltage
VBR
7−5
−0.3 to 7
V
BR Pin Sink Current
IBR
7−5
1.0
mA
Avalanche Energy2
EAS
S/OCP Pin Voltage
STR-W6051S
ILPEAK = 2.0 A
STR-W6052S
ILPEAK = 2.3 A
STR-W6053S
ILPEAK = 2.7 A
STR-W6051S
Power Dissipation of MOSFET
PD1
STR-W6052S
With infinite heatsink
STR-W6053S
1−3
Without heatsink
22.3
W
23.6
W
26.5
W
1.3
W
Power Dissipation of Control Part
PD2
4−5
0.13
W
Internal Frame Temperature in Operation3
TF
–
−20 to 115
°C
Operating Ambient Temperature
TOP
–
−20 to 125
°C
Storage Temperature
Tstg
–
−40 to 125
°C
Channel Temperature
Tch
–
150
°C
VCC × ICC
1The
maximum switching current is the drain current determined by the drive voltage of the IC and threshold voltage (Vth) of the MOSFET.
pulse, VDD = 99 V, L = 20 mH.
3The recommended internal frame temperature in operation, T , is 105°C (max).
F
2Single
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
2
Electrical Characteristics
• Refer to the datasheet of each product for these details.
• The polarity value for current specifies a sink as "+," and a source as
"−," referencing the IC.
Electrical Characteristics of Control Part Unless otherwise specified, TA = 25°C, VCC = 18 V
Characteristic
Symbol
Conditions
Pins
Min.
Typ.
Max.
Unit
Operation Start Voltage
VCC(ON)
4–5
13.8
15.3
16.8
V
Operation Stop Voltage*
VCC(OFF)
4–5
7.3
8.1
8.9
V
mA
Circuit Current in Operation
ICC(ON)
Minimum Start Voltage
VST(ON)
Startup Current
ISTARTUP
VCC = 13.5 V
Startup Current Threshold Biasing Voltage*
VCC(BIAS)
ICC = −100 μA
Average Operation Frequency
fOSC(AVG)
Frequency Modulation Deviation
Maximum Duty Cycle
Leading Edge Blanking Time
OCP Compensation Coefficient
OCP Compensation Duty Cycle Limit
VCC = 12 V
4–5
–
–
2.5
4–5
–
40
–
V
4–5
−3.9
−2.5
−1.1
mA
4–5
8.5
9.5
10.5
V
1–5
60
67
74
kHz
Δf
1–5
–
5
–
kHz
DMAX
1–5
63
71
79
%
tBW
–
–
390
–
ns
DPC
–
–
18
–
mV/μs
DDPC
–
–
36
–
%
OCP Threshold Voltage at Zero Duty Cycle
VOCP(L)
3–5
0.70
0.78
0.86
V
OCP Threshold Voltage at 36% Duty Cycle
VOCP(H)
VCC = 32 V
3–5
0.79
0.88
0.97
V
Maximum Feedback Current
IFB(MAX)
VCC = 12 V
6–5
−340
−230
−150
μA
Minimum Feedback Current
IFB(MIN)
6–5
−30
−15
−7
μA
FB/OLP Pin Oscillation Stop Threshold
Voltage
VFB(STB)
6–5
0.85
0.95
1.05
V
OLP Threshold Voltage
VFB(OLP)
6–5
7.3
8.1
8.9
V
tOLP
6–5
54
68
82
ms
OLP Delay Time
OLP Operation Current
FB/OLP Pin Clamp Voltage
Brown-In Threshold Voltage
Brown-Out Threshold Voltage
BR Pin Clamp Voltage
ICC(OLP)
VCC = 12 V
VFB(CLAMP)
4–5
–
300
–
μA
6–5
11
12.8
14
V
VBR(IN)
VCC = 32 V
7–5
5.2
5.6
6
V
VBR(OUT)
VCC = 32 V
7–5
4.45
4.8
5.15
V
VBR(CLAMP) VCC = 32 V
7–5
6
6.4
7
V
7–5
0.3
0.48
0.7
V
BR Function Disabling Threshold Voltage
VBR(DIS)
VCC Pin OVP Threshold Voltage
VCC(OVP)
4–5
26
29
32
V
Thermal Shutdown Temperature
Tj(TSD)
–
130
–
–
°C
VCC = 32 V
*VCC(BIAS) > VCC(OFF) always.
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
3
Electrical Characteristics of MOSFET Unless otherwise specified, TA is 25°C
Pins
Min.
Typ.
Max.
Unit
Drain-to-Source Breakdown Voltage
Characteristic
Symbol
VDSS
Conditions
1–3
650
–
–
V
Drain Leakage Current
IDSS
1–3
–
–
300
μA
–
–
3.95
Ω
1–3
–
–
2.8
Ω
–
–
1.9
Ω
STR-W6051S
On-Resistance
RDS(ON)
STR-W6052S
STR-W6053S
Switching Time
tf
1–3
STR-W6051S
Thermal Resistance
STR-W6000S-AN, Rev. 1.0
Rθch-C
The thermal resistance between the
STR-W6052S channels of the MOSFET and the
internal frame.
STR-W6053S
SANKEN ELECTRIC CO., LTD.
–
–
–
250
ns
–
–
2.63
°C/W
–
–
2.26
°C/W
–
–
1.95
°C/W
4
Functional Block Diagram
4
VCC
Startup
UVLO
7
BR
REG
VREG
OVP
D/ST
1
TSD
Brown-In/
Brown-Out
6.4 V
DRV
PWM OSC
SQ
R
OCP
7V
VCC
Drain Peak Current
Compe nsa tion
OLP
Fe edback
Control
FB/OLP
6
S/OCP
GND
Slope
Compensation
12.8 V
3
LEB
5
Pin List Table
D/ST
S/OCP
1
3
VCC
GND
Name
1
D/ST
2
–
3
S/OCP
4
VCC
Power supply voltage input for Control Part, and input of Overvoltage
Protection (OVP) signal
5
GND
Ground
6
FB/OLP
7
BR
4
5
FB/OLP
BR
Number
6
7
(LF2003)
STR-W6000S-AN, Rev. 1.0
Function
MOSFET drain, and input of the startup current
(Pin removed)
MOSFET source, and input of Overcurrent Protection (OCP) signal
Feedback signal input for constant voltage control signal, and input of
Overload Protection (OLP) signal
Input of Brown-In and Brown-Out detection voltage
SANKEN ELECTRIC CO., LTD.
5
Typical Application Circuit
The following drawings show circuits enabled and disabled the
Brown-In/Brown-Out function.
• In applications having a power supply specified such that VDS
has large transient surge voltages, a clamp snubber circuit of a
capacitor-resistor-diode (CRD) combination should be added
on the primary-side winding P, or a damper snubber circuit of
a capacitor (C) or a resistor-capacitor (RC) combination should
be added between the D/ST pin and the S/OCP pin.
The following design features should be observed:
• The PCB traces from the D/ST pins should be as wide as possible, in order to enhance thermal dissipation.
VAC
CRD clamp snubber
BR1
L51
T1 D51
C5 R1
C1
PC1
P
D1
C51
R52
S
R51
C52
VOUT
R54
R55
C53
R53
U51
R56
RA
U1
GND
C(CR) damper
snubber
D/ST
S/ OCP
V CC
GND
FB/OLP
BR
S TR-W6000S
1
3 4 5 6 7
C4
RB
D2 R2
C2
C10
ROCP
C3
D
RC
C9
PC1
Typical application circuit example, enabled Brown-In/Brown-Out function (DC line detection)
VAC
CRD clamp snubber
BR1
C5 R1
C1
L51
T1 D51
PC1
P
D1
C51
S
R52
R51
C52
R55
VOUT
R54
C53
R53
U51
U1
R56
GND
C(CR) damper
snubber
D/ST
S/ OCP
V CC
GND
FB/OLP
BR
S TR-W6000S
1
3 4 5 6 7
C4
ROCP
D2 R2
C2
D
C3
PC1
C9
Typical application circuit example, disabled Brown-In/Brown-Out function
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
6
Package Diagram
• TO-220F-6L package
• The pin 2 is removed to provide greater creepage and clearance isolation between
the high voltage pin (pin 1: D/ST) and the low voltage pin (pin 3: S/OCP).
10.0±0.2
4.2±0.2
Gate burr
φ3.2±0.2
7.9±0.2
16.9±0.3
4±0.2
0.5
2.8±0.2
R-end
(5.4)
)
-R1
(2
6-0.65 +0.2
-0.1
6×P1.27±0.15=7.62±0.15
Dimensions between roots
10.4±0.5
6-0.74±0.15
5.0±0.5
2.8
2.6±0.1
Dimensions from root
0.45 +0.2
-0.1
5.08±0.6
Dimensions between tips
0.5
1 2 3 4 5 6 7
0.5
Front view
0.5
0.5
Side view
Unit: mm
Leadform: LF No.2003
Gate burr indicates protrusion of 0.3 mm (max).
Pin treatment Pb-free. Device composition compliant with the RoHS directive.
Marking Diagram
STR
W60xxS
YMDD X
STR-W6000S-AN, Rev. 1.0
Part Number
Lot Number
Y is the last digit of the year (0 to 9)
M is the month (1 to 9, O, N, or D)
DD is the day (01 to 31)
X is the Sanken Control Symbol
SANKEN ELECTRIC CO., LTD.
7
Functional Description
• All of the parameter values used in these descriptions are typical
values, unless they are specified as minimum or maximum.
• With regard to current direction, "+" indicates sink current (toward the IC) and "–" indicates source current (from the IC).
BR1
Startup Operation
T1
VAC
C1
Figure 1 shows the VCC pin peripheral circuit, disabled the
Brown-In/Brown-Out function by connecting the BR pin trace to
the GND pin trace.
The built-in startup circuit is connected to the D/ST pin. When the
D/ST pin voltage increases to VST(ON) = 40 V, the startup circuit
starts operation.
In figure 1, the Startup Current, ISTARTUP , which is a constant
current of –2.5 mA, is provided from the IC to capacitor C2 connected to the VCC pin, and it charges C2. When the VCC pin
voltage increases to VCC(ON) = 15.3 V, the IC starts operation. After
that, the startup circuit stops automatically, in order to eliminate its
own power consumption.
1
D/ST
VCC
4
UI
BR
7
D2
C2
GND
P
R2
VD
D
5
Figure 1. VCC pin peripheral circuit
During the IC operation, the rectified voltage from the auxiliary
winding voltage, VD , of figure 1 becomes a power source to the
VCC pin.
VCC(BIAS)(max) < VCC < VCC(OVP)(min)
(1)
⇒ 10.5 (V) < VCC < 26.0 (V)
ICC
ICC(ON)
= 2.5 mA (max)
tSTART
z
C2 ×
VCC(ON) – VCC(INT)
where:
|ISTARTUP|
Stop
The startup time, tSTART , is determined by the value of C2, and it is
approximately given as below:
Start
The winding turns of winding D should be adjusted so that the
VCC pin voltage is applied to equation (1) within the specifications of the input voltage range and output load range of the power
supply. The target voltage of the winding D is about 15 to 20 V.
8.5 V
VCC(OFF)
15.3 V VCC pin voltage
VCC(ON)
(2)
tSTART is the startup time in s, and
VCC(INT) is the initial voltage of the VCC pin in V.
Undervoltage Lockout (UVLO) Circuit
Figure 2. VCC versus ICC
Figure 2 shows the relationship of VCC and ICC . After the IC starts
operation, when the VCC pin voltage decreases to VCC(OFF) =
8.1 V, the IC stops switching operation by the UVLO (Undervoltage Lockout) circuit and reverts to the state before startup again.
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
8
Bias Assist Function
Figure 3 shows the VCC pin voltage behavior during the startup
period. When the VCC pin voltage increases to VCC(ON) = 15.3 V,
the IC starts operation. Thus, the circuit current, ICC , increases,
and the VCC pin voltage begins dropping. At the same time, the
auxiliary winding voltage, VD , increases in proportion to the
output voltage rise.
Thus, the VCC pin voltage is set by the balance between dropping
due to the increase of ICC and rising due to the increase of the
auxiliary winding voltage, VD .
Just at the turning-off of the power MOSFET, a surge voltage
occurs at the output winding. If the feedback control is activated
by the surge voltage on light load condition at startup, the output
power is restricted and the output voltage decreases.
VCC
pin voltage
Startup success
IC startup
Target
Operating
Voltage
Increasing by
output voltage rising
Bias Assist period
VCC(ON)
VCC(BIAS)
VCC(OFF)
Startup failure
Time
Figure 3. VCC pin voltage during startup period
When the VCC pin voltage decreases to VCC(OFF) = 8.1 V, the IC
stops switching operation and a startup failure occurs.
In order to prevent this, the Bias Assist function is activated when
the VCC pin voltage decreases to the Startup Current Threshold
Biasing Voltage, VCC(BIAS) = 9.5 V, during a state of operating
feedback control. While the Bias Assist function is activated, any
decrease of the VCC pin voltage is counteracted by providing the
Startup Current, ISTARTUP , from the startup circuit. Thus, the VCC
pin voltage is kept almost constant.
By the Bias Assist function, the value of C2 is allowed to be small
and the startup time becomes shorter. Furthermore, because the
increase of VCC pin voltage becomes faster when the output
runs with excess voltage, the response time of the OVP function
becomes shorter.
UI
S/OCP
3
GND
5
VROCP
C3
IFB
Figure 4. FB/OLP pin peripheral circuit
Target voltage including
Slope Compensation
Constant Voltage Control Operation
–
The constant output voltage control function uses current mode
control (peak current mode), which enhances response speed and
provides stable operation.
+
STR-W6000S-AN, Rev. 1.0
6
PC1
ROCP
It is necessary to check and adjust the startup process based on
actual operation in the application, so that the startup failure does
not occur.
The FB/OLP pin voltage is internally added the slope compensation at the feedback control (refer to Function Block Diagram
section), and the target voltage, VSC , is generated. The IC compares the voltage, VROCP , of a current detection resistor with the
target voltage, VSC , by the internal FB comparator, and controls
the peak value of VROCP so that it gets close to VSC , as shown in
figures 4 and 5.
FB/OLP
VSC
VROCP
FB Comparator
OCP pin voltage
Drain current ID
Figure 5. Drain current, ID , and FB comparator in steady operation
SANKEN ELECTRIC CO., LTD.
9
• Light load conditions
When load conditions become lighter, the output voltage, VOUT ,
increases. Thus, the feedback current from the error amplifier
on the secondary-side also increases. The feedback current is
sunk at the FB/OLP pin, transferred through a photocoupler,
PC1, and the FB/OLP pin voltage decreases. Thus, VSC
decreases, and the peak value of VROCP is controlled to be low,
and the peak drain current of ID decreases. This control prevents
the output voltage from increasing.
• Heavy load conditions
When load conditions become greater, the IC performs the
inverse operation to that described above. Thus, VSC increases
and the peak drain current of ID increases. This control prevents
the output voltage from decreasing.
In the current mode control method, when the drain current waveform becomes trapezoidal in continuous operating mode, even
if the peak current level set by the target voltage is constant, the
on-time fluctuates based on the initial value of the drain current.
This results in the on-time fluctuating in multiples of the fundamental operating frequency as shown in figure 6. This is called
the subharmonics phenomenon.
Target voltage
without Slope Compensation
tON1
t
Even if subharmonic oscillations occur when the IC has some
excess supply being out of feedback control, such as during
startup and load shorted, this does not affect performance of
normal operation.
In the current mode control method, the FB comparator and/or
the OCP comparator may respond to the surge voltage resulting
from the drain surge current in turning-on the power MOSFET.
As a result, the power MOSFET may turn off irregularly. In order
to prevent this response to the surge voltage in turning-on the
power MOSFET, Leading Edge Blanking, tBW = 390 ns, is builtin.
Auto Standby Mode Function
Auto Standby mode is activated automatically when the drain
current, ID , reduces under light load conditions, at which ID is
less than 15% to 20% of the maximum drain current (it is in the
Overcurrent Protection state).
The operation mode becomes burst oscillation, as shown in figure 7. Burst mode reduces switching losses and improves power
supply efficiency because of periodic non-switching intervals.
Generally, to improve efficiency under light load conditions,
the frequency of the burst mode becomes just a few kilohertz.
Because the IC suppresses the peak drain current well during
burst mode, audible noises can be reduced.
tON2
t
In order to avoid this, the IC incorporates the Slope Compensation function. Because the target voltage is added a down-slope
compensation signal, which reduces the peak drain current as the
on-duty gets wider relative to the FB/OLP pin signal to compensate VSC, the subharmonics phenomenon is suppressed.
t
Figure 6. Drain current, ID , waveform in subharmonic oscillation
If the VCC pin voltage decreases to VCC(BIAS) = 9.5 V during the
transition to the burst mode, the Bias Assist function is activated
and stabilizes the standby mode operation, because ISTARTUP is
Burst oscillation
Output
current, IOUT
Drain
current, ID
Below several kHz
Normal operation
Standby operation
Normal operation
Figure 7. Auto Standby mode timing
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
10
provided to the VCC pin so that the VCC pin voltage does not
decrease to VCC(OFF).
However, if the Bias Assist function is always activated during
steady-state operation including standby mode, the power loss
increases. Therefore, the VCC pin voltage should be more than
VCC(BIAS), for example, by adjusting the turns ratio of the auxiliary winding and secondary-side winding and/or reducing the
value of R2 in figure 16 (refer to Peripheral Components section
for a detail of R2).
Random Switching Function
The IC modulates its switching frequency randomly within Δf =
5 kHz superposed on the average operation frequency, fOSC(AVG)
= 67 kHz. The conduction noise with this function is smaller than
that without this function, and this function can simplify noise
filtering of the input lines of power supply.
Brown-In and Brown-Out Function by DC Line
Detection
The BR pin detects a voltage proportional to the DC input voltage
(C1 voltage), with the resistive voltage divider RA, RB, and RC
connected between the DC input and GND, plus C10 connected
to the BR pin, as shown in figure 8-9.
This method detects peaks of the ripple voltage of the rectified
AC input voltage, and thus it minimizes the influence of load
conditions on the detecting voltage.
During the input voltage rising from the stopped state of power
supply, when the BR pin voltage increases to VBR(DIS) = 0.48 V or
more, this function is enabled. After that, when the BR pin voltage increases to VBR(IN) = 5.6 V or more and the VCC pin voltage
VAC
BR1
C1
1
3
BR
S/OCP
D/ST
This function stops switching operation when it detects low input
line voltage, and thus prevents excessive input current and overheating. During Auto Standby mode, this function is disabled.
GND
UI
Brown-In and Brown-Out Function
5
7
C4
R OCP
Disabled Brown-In and Brown-Out Function
When the Brown-In and Brown-Out function is unnecessary,
connect the BR pin trace to the GND pin trace so that the BR pin
voltage is VBR(DIS) = 0.48 V or less, as shown in figure 8.
BR pin is connected to GND
Figure 8. The circuit used to disable the Brown-In and Brown-Out function
EIN
ID
C1
VCC pin voltage
EIN
VCC(ON)
VCC(OFF)
UI
RA
1
3
5
BR
GND
D /ST
S/OCP
BR pin voltage
RB
7
C10
Drain current, ID
RC
Figure 9. Brown-In and Brown-Out function controlled by DC line detection
STR-W6000S-AN, Rev. 1.0
VBR(OUT)= 4.8 V
VBR(DIS)= 0.48 V
C4
ROCP
VBR(IN)= 5.6 V
SANKEN ELECTRIC CO., LTD.
68 ms
11
increases to VCC(ON) or more, the IC starts switching operation.
During the input voltage falling from the operated state of power
supply, when the BR pin voltage decreases to VBR(OUT) = 4.8 V or
less for about 68 ms, the IC stops switching operation.
• Component values of the BR pin peripheral circuit:
▫ RA, RB: A few megohms. Because of high DC voltage applied
and high resistance, it is recommended to select a resistor
designed against electromigration or use a combination of
resistors in series for that to reduce each applied voltage,
according to the requirement of the application.
▫ RC: A few hundred kilohms
▫ C10: 100 to 1000 pF for high frequency noise rejection
Brown-In and Brown-Out Function by AC Line
Detection
The BR pin detects a voltage proportional to the AC input voltage, with the resistive voltage divider RA, RB, and RC connected
between one side of the AC line and GND, plus C10 connected to
the BR pin and R9 connected between the BR pin and the VCC
pin, as shown in figure 10.This method detects the AC input voltage, and thus it minimizes the influence from C1 charging and
discharging time, or load conditions, on the detecting voltage.
During the input voltage rising from the stopped state of power
supply, when the BR pin voltage increases to VBR(DIS) = 0.48 V or
more, this function is enabled. After that, when the BR pin voltage increases to VBR(IN) = 5.6 V or more and the VCC pin voltage
increases to VCC(ON) or more, the IC starts switching operation.
During the input voltage falling from the operated state of power
supply, when the BR pin voltage decreases to VBR(OUT) = 4.8 V or
less for about 68 ms, the IC stops switching operation.
• Component values of the BR pin peripheral circuit:
▫ RA, RB: A few megohms. Because of high DC voltage applied
and high resistance, it is recommended to select a resistor
designed against electromigration or use a combination of
resistors in series for that to reduce each applied voltage,
according to the requirement of the application.
▫ RC: A few hundred kilohms
▫ C10: 0.047 to 0.47 μF for AC ripple rejection. This should be
adjusted according to values of RA, RB, and RC.
▫ R9: To enable the Brown-In and Brown-Out function, this
value must be adjusted so that the BR pin voltage is more
than VBR(DIS) = 0.48 V when the VCC pin voltage decreases to
VCC(OFF) = 8.1 V.
BR1
VAC
VAC
ID
C1
NC
UI
VCC
RA
3
BR pin voltage
R9
5
BR
GND
S/OCP
D /ST
1
VCC pin voltage
VCC(ON)
V CC(OFF)
RB
7
C10
Drain current, I D
RC
Figure 10. Brown-In and Brown-Out function controlled by AC line detection
STR-W6000S-AN, Rev. 1.0
V BR(OUT)= 4.8 V
V BR(DIS)= 0.48 V
C4
ROCP
VBR(IN)= 5.6 V
SANKEN ELECTRIC CO., LTD.
68 ms
12
Overcurrent Protection Function (OCP)
The OCP function detects each peak drain current level of the
power MOSFET by the current detection resistor, ROCP . When
the OCP pin voltage increases to the internal OCP threshold voltage, the IC turns off the power MOSFET on pulse-by-pulse basis,
and limits the output power.
ICs with PWM control usually have some detection delay time on
OCP detection. The steeper the slope of the actual drain current at
a high AC input voltage is, the later the actual detection point is,
compared to the internal OCP threshold voltage. Thus, the actual
OCP point limiting the output current usually has some variation
depending on the AC input voltage, as shown in figure 11.
Variance resulting
from propagation delay
Lo
w
AC
in p
ut
A
gh
Hi
np
Ci
VOCP(ONTime) (V) = VOCP(L)(V) + DPC (mV/μs)
× On Time (μs).
ut
VOCP(L) is the OCP threshold voltage at zero duty cycle (V),
0.78 V
DPC is the OCP compensation coefficient (mV/μs), 18 mV/μs,
and
On Time is the the on-time of the duty cycle (μs):
On Time = On Duty / fOSC(AVG)
Overvoltage Protection Function (OVP)
When the voltage between the VCC pin and the GND pin is
applied to the OVP threshold voltage, VCC(OVP) = 29 V or more,
the Overvoltage Protection function (OVP) is activated and the
IC stops switching operation.
265 VAC (as an example)
1.0
85VAC (as an example)
VOCP(H)
About 0.82
VOCP(L)
0.5
0
0
Output Current , IOUT(A)
Figure 11. Output current at OCP without input compensation
STR-W6000S-AN, Rev. 1.0
(3)
where:
VOCP(ONTime) , Typical (V)
Output Voltage, VOUT (V)
The IC incorporates a built-in Input Compensation function that
superposes a signal with a defined slope into the detection signal
on the OCP pin as shown in figure 12. When AC input voltage is
lower and the duty cycle is longer, the OCP compensation level
increases more than that in high AC input voltage. Thus, the OCP
point in low AC input voltage increases to minimize the difference of OCP points between low AC input voltage and high AC
input voltage, without any additional components.
Because the compensation signal level is designed to depend
upon the on-time of the duty cycle, the OCP threshold voltage
after compensation, VOCP(ONTime), is given as below. However,
when the duty cycle becomes 36% or more, the OCP threshold
voltage after compensation remains at VOCP(H) = 0.88 V, constantly
15
36
50
Duty Cycle, D (%)
80
Figure 12. Relationship of duty cycle and OCP threshold voltage after
compensation
SANKEN ELECTRIC CO., LTD.
13
When the OVP function is activated, the Bias Assist function is
disabled and the VCC pin voltage decreases to VCC(OFF) = 8.1 V.
Thus, the IC stops switching operation by the UVLO (Undervoltage Lockout) circuit and reverts to the state before startup. After
that, the startup circuit is activated, the VCC pin voltage increases
to VCC(ON) = 15.3 V, and the IC starts switching operation again.
In this way, the intermittent operation by UVLO is repeated during OVP state.
This operation reduces power stress on the power MOSFET and
secondary-side rectifier diode. Furthermore, this reduces power
consumption, because the switching period in this intermittent
operation is shorter than non-switching interval. When the fault
condition is removed, the IC returns to normal operation automatically.
When the auxiliary winding supplies the VCC pin voltage, the
OVP function is able to detect an excessive output voltage, such
as when the detection circuit for output control is open on the
secondary-side, because the VCC pin voltage is proportional to
the output voltage.
UI
VCC
4
FB /OLP
GND
6
5 I
FB
D2
PC1
C3
R2
C2
D
Figure 13. FB/OLP pin peripheral circuit
The output voltage of the secondary-side at OVP operation,
VOUT(OVP), is approximately given as below:
VOUT(OVP) =
VOUT(normal operation)
× 29 (V)
VCC(normal operation)
(4)
Overload Protection Function (OLP)
Figure 13 shows the FB/OLP pin peripheral circuit, and figure 14
shows each waveform for OLP operation.
When the peak drain current of ID is limited by OCP operation,
the output voltage, VOUT , decreases and the feedback current
flowing to the photocoupler becomes zero. Thus, the feedback
current, IFB , charges C3 connected to the FB/OLP pin, and the
FB/OLP pin voltage increases. When the FB/OLP pin voltage
increases to VFB(OLP) = 8.1 V or more for the OLP Delay Time,
tOLP = 68 ms or more, the OLP function is activated and the IC
stops switching operation.
When the OLP function is activated, the Bias Assist function is
disabled and the intermittent operation by UVLO is repeated in
the same way as described in the Overvoltage Protection Function (OVP) section. When the fault condition is removed, the IC
returns to normal operation automatically.
STR-W6000S-AN, Rev. 1.0
VCC pin
voltage
VCC(ON)
Non-switching interval
V CC(OFF)
FB/OLP pin
voltage
VFB(OLP)
t OLP
t OLP
Drain
current,
ID
Figure 14. OLP operation waveforms
SANKEN ELECTRIC CO., LTD.
14
Thermal Shutdown Function (TSD)
C1
U1
1
3 4 5 6 7
C4
RA
RB
C3
D2 R2
C2
C10
ROCP
Apply proper design margin to accommodate ripple current,
voltage, and temperature rise.
P
D1
Peripheral Components
Take care to use the proper rating and proper type of components.
• Input and output electrolytic capacitors
C5 R1
S/ OCP
V CC
GND
FB/OLP
BR
Design Notes
T1
BR1
VAC
D/ST
If the temperature of the control part in the IC increases to more
than Tj(TSD) = 135°C (min), the Thermal Shutdown function
(TSD) is activated and the IC stops switching operation. When the
TSD function is activated, the Bias Assist function is disabled and
the intermittent operation by UVLO is repeated in the same way
as described in the Overvoltage Protection Function (OVP) section. If the factor causing the overheating condition is removed,
and the temperature of the Control Part decreases to Tj(TSD), the
IC returns to normal operation automatically.
D
RC
PC1
Figure 15. IC peripheral circuit
A low ESR type for output smoothing capacitor, designed for
switch-mode power supplies, is recommended to reduce output
ripple voltage.
• Current detection resistor, ROCP
D2
Choose a low inductance and high surge-tolerant type. Because
a high frequency switching current flows to ROCP in figure 15 , a
high inductance resistor may cause poor operation.
4
VCC
• BR pin peripheral circuit
UI
The Brown-In and Brown-Out function has two types of detection method: AC line or DC line. Refer to Brown-In and BrownOut Function section for more details.
R2
Added
D
C2
GND
5
• FB/OLP pin peripheral circuit
C3, located between the FB/OLP pin and the GND pin in
figure 15, performs high frequency noise rejection and phase
compensation, C3 should be connected close to these pins.
The reference value of C3 is about 2200 pF to 0.01 μF, and
should be selected based on actual operation in the application.
• VCC pin peripheral circuit
Figure 16 shows the VCC pin peripheral circuit. The reference
value of C2 is generally 10 to 47 μF (refer to Startup Operation
section, because the startup time is determined by the value of
C2).
In actual power supply circuits, there are cases in which the
VCC pin voltage fluctuates in proportion to the output current,
IOUT (see figure 17), and the Overvoltage Protection function
(OVP) on the VCC pin may be activated. This happens because
C2 is charged to a peak voltage on the auxiliary winding D,
which is caused by the transient surge voltage coupled from the
primary-side winding when the power MOSFET turns off.
Figure 16. VCC pin peripheral circuit
VCC
pin voltage
Without R2
With R2
Output Current, I OUT
Figure 17. VCC versus IOUT with and without resistor R2
For alleviating C2 peak charging, it is effective to add some
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
15
value R2, of several tenths of ohms to several ohms, in series
with D2 (see figure 16). The optimal value of R2 should be determined using a transformer matching what will be used in the
actual application, because the variation of the auxiliary winding
voltage is affected by the transformer structural design.
• Phase Compensation
L51
D51
T1
VOUT
A typical phase compensation circuit with a secondary-side
shunt regulator (U51) is shown in figure 18.
The reference value of C52 for phase compensation is about
0.047 to 0.47 μF, and should be adjusted based on actual operation in the application.
R54
PC1
R51
R55
C51
C53
R52
S
• Transformer
C52 R53
Apply proper design margin to core temperature rise due to core
loss and copper loss.
U51
Because the switching currents contain high frequency currents,
the skin effect may become a consideration.
Choose a suitable wire gauge in consideration of the RMS current and a current density of about 3 to 4 A/mm2.
R56
GND
Figure 18. Peripheral circuit around secondary-side shunt regulator (U51)
If measures to further reduce temperature are still necessary, the
following should be considered to increase the total surface area
of the wiring:
▫ Increase the number of wires in parallel.
Margin tape
Fluctuation of the VCC pin voltage by IOUT worsens in the
following cases, requiring a transformer designer to pay close
attention to the placement of the auxiliary winding D:
▫ Poor coupling between the primary-side and secondary-side
windings (this causes high surge voltage and is seen in a design with low output voltage and high output current)
▫ Poor coupling between the auxiliary winding D and the
secondary-side stabilized output winding where the output line
voltage is controlled constant by the output voltage feedback
(this is susceptible to surge voltage)
In order to reduce the influence of surge voltage on the VCC
pin, figure 19 shows winding structural examples which take
into consideration the placement of the auxiliary winding D:
▫ Winding structural example (a): Separating the auxiliary winding D from the primary-side windings P1 and P2. P1 and P2
are windings divided the primary-side winding into two.
▫ Winding structural example (b): Placing the auxiliary winding
D within the secondary-side stabilized output winding, S1, in
order to improve the coupling of those windings. S1 is a stabilized output winding of secondary-side windings, controlled to
constant voltage.
STR-W6000S-AN, Rev. 1.0
P1 S1 P2 S2 D
Margin tape
Winding structural example (a)
Margin tape
Bobbin
▫ Thicken the wire gauge.
Bobbin
▫ Use litz wire.
P1 S1
D S2 S1 P2
Margin tape
Winding structural example (b)
P1, P2㧦 Primary main winding
D㧦 Primary auxiliary winding
S1㧦 Secondary stabilized output winding
S2㧦 Secondary output winding
Figure 19. Winding structural examples
SANKEN ELECTRIC CO., LTD.
16
PCB Trace Layout and Component Placement
PCB circuit trace design and component layout significantly
affect operation, EMI noise, and power dissipation. Therefore,
pay extra attention to these designs. In general, trace loops shown
in figure 20 where high frequency currents flow should be wide,
short, and small to reduce line impedance. In addition, earth
ground traces affect radiated EMI noise, and wide, short traces
should be taken into account.
Switch -mode power supplies consist of current traces with high
frequency and high voltage, and thus trace design and component layouts should be done to comply with all safety guidelines.
Furthermore, because the power MOSFET has a positive thermal coefficient of RDS(ON) , consider it when preparing a thermal
design.
Figure 21 shows a circuit layout design example for the IC
peripheral circuit and secondary-side rectifier-smoothing circuit.
• IC Peripheral Circuit
(1) S/OCP pin Trace Layout: S/OCP pin to ROCP to C1 to T1
(winding P) to D/ST pin
This is the main trace containing switching currents, and thus
it should be as wide and short as possible. If the IC and C1
are distant from each other, placing a capacitor such as a film
or ceramic capacitor (about 0.1 μF and with proper voltage
rating) close to the transformer or the IC is recommended to
reduce impedance of the high frequency current loop.
(2) GND Trace Layout: GND pin to C2 (negative pin) to T1
(winding D) to R2 to D2 to C2 (positive pin) to VCC pin
This is the trace for supplying power to the IC, and thus it
should be as wide and short as possible. If the IC and C2 are
distant from each other, placing a capacitor such as a film or
ceramic capacitor (about 0.1 to 1.0 μF) close to the VCC pin
and the GND pin is recommended.
(3) ROCP Trace Layout
ROCP should be placed as close as possible to the S/OCP pin.
The connection between the power ground of the main trace
and the IC ground should be at a single point ground (point A
in figure 21) which is close to the base of ROCP , to reduce
common impedance, and to avoid interference from switching currents to the control part in the IC.
• Secondary-side Rectifier-Smoothing Circuit Trace Layout: T1
(winding S) to D51 to C51
This is the trace of the rectifier-smoothing loop, carrying the
switching current, and thus it should be as wide and short as
possible. If this trace is thin and long, inductance resulting from
the loop may increase surge voltage at turning off the power
MOSFET. Proper rectifier-smoothing trace layout helps to increase margin against the power MOSFET breakdown voltage,
and reduces stress on the clamp snubber circuit and losses in it.
Figure 20. High frequency current loops (hatched areas)
D51
T11
C5 R1
C1
P
D1
C51
S
RA
D/ST
S/ OCP
V CC
GND
FB/OLP
BR
U1
1
3 4 5 6 7
D2 R2
C2
C10
C4
ROCP
RB
C3
Main power circuit trace
GND trace for the IC
D
RC
PC1
C9
Figure 21. Peripheral circuit example around the IC
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
17
Power Supply Specification
Reference Design of Power Supply
As an example, the following show a power supply specification,
circuit schematic, bill of materials, and transformer specification.
VAC
IC
STR-W6053S
Input Voltage
85 to 265 VAC
Maximum Output Power
56 W (70.4 WPEAK)
Output Voltage / Current
8 V / 2.5 A,
12 V / 3 A (4.2 APEAK)
F1
L1
BR1
C1
T1
C2
D52
12 V/4.2A
TH 1
C4
C3
t°
R1 P1
S1
C55
R57
C56
D1
C57
S2
P2
GND
L51
D51
8V/2.5A
S/ OCP
GND
FB/OLP
BR
1
3
4
5
6
7
R54
C51
R4
V CC
D/ST
STR-W6053S
R51
PC1
R55
R5
C5
D2
S3
R3
R52
C53
C7
R2
PC1
C8
R6
C6
C54
C52
R53
U51
D
R56
GND
C9
Figure 22. Circuit schematic
Bill of Materials
Symbol
Part type
Ratingsa
F1
Recommended
Sanken Parts
Symbol
Part type
Ratingsa
Photo-coupler
PC123 or equiv.
Recommended
Sanken Parts
Fuse
250 VAC, 6 A
PC1
L1b
CM inductor
2.2 mH
U1
IC
TH1b
NTC thermistor
Short
T1
Transformer
See the specification
BR1
General
600 V, 6 A
L51
Inductor
5 μH
D1
Fast recovery
1000 V, 0.5 A
EG01C
D51
Schottky
100 V, 10 A
FMEN-210A
D2
Fast recovery
200 V, 1 A
AL01Z
D52
Fast recovery
150 V, 10 A
FMEN-210B
C1b
Film, X2
0.1 μF, 275 V
C51b
Ceramic
470 pF, 1 kV
C2b
Film, X2
0.1 μF, 275 V
C52
Electrolytic
1000 μF, 16 V
C3
Electrolytic
220 μF, 400 V
C53b
Ceramic
0.15 μF, 50 V
C4
Ceramic
3300 pF, 2 kV
C54
Electrolytic
1000 μF, 16 V
C5
Ceramic
Open
C55
Ceramic
470 pF, 1 kV
C6
Electrolytic
22 μF, 50 V
C56
Electrolytic
1500 μF, 25 V
C7b
Ceramic
0.01 μF
C57
Electrolytic
1500 μF, 25 V
STR-W6053S
C8b
Ceramic
1000 pF
R51
General
1.5 kΩ
C9
Ceramic, Y1
2200 pF, 250 V
R52
General
1 kΩ
R1c
Metal oxide
56 kΩ, 2 W
R53b
General
33 kΩ
R2
General
0.27 Ω, 1 W
R54b
General, 1%
3.9 kΩ
R3
General
5.6 Ω
R55
General, 1%
22 kΩ
R4c
General
2.2 MΩ
R56
General, 1%
6.8 kΩ
R5c
General
2.2 MΩ
R57
General
Open
R6
General
330 kΩ
U51
Shunt
regulator
VREF = 2.5 V
TL431 or equiv.
aUnless
otherwise specified, the voltage rating of capacitor is 50 V or less, and the power rating of resistor is 1/8 W or less.
is necessary to be adjusted based on actual operation in the application.
cResistors applied high DC voltage and of high resistance are recommended to select resistors designed against electromigration or use combinations of
resistors in series for that to reduce each applied voltage, according to the requirement of the application.
bIt
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
18
Transformer specification
▫ Primary inductance, LP : 315 μH
▫ Core size: EER28L
▫ AL-value: 163 nH/N2 (Center gap of about 0.8 mm)
▫ Winding specification
Location
Symbol
Number of Turns
(T)
Wire
(mm)
Configuration
Primary winding
P1
26
TEX-Ø0.35×2
1.5 layers, solenoid winding
Primary winding
P2
18
TEX-Ø0.35×2
Solenoid winding
Auxiliary winding
D
10
TEX-Ø0.23×2
Space winding
Output winding 1
S1
7
Ø0.4×4
Space winding
Output winding 2
S2
7
Ø0.4×4
Space winding
Output winding 3
S3
5
Ø0.4×4
Space winding
VDC
P1
S2
D
S3
S1
P2
Bobbin
Cross-section view
STR-W6000S-AN, Rev. 1.0
P1
P2
12V
S1
GND
D/ST
S2
VCC
D
GND
8V
S3
GND
٨ mark shows the start point of winding
SANKEN ELECTRIC CO., LTD.
19
IMPORTANT NOTES
• The contents in this document are subject to changes, for improvement and other purposes, without notice. Make sure that this is the
latest revision of the document before use.
• Application and operation examples described in this document are quoted for the sole purpose of reference for the use of the products herein and Sanken can assume no responsibility for any infringement of industrial property rights, intellectual property rights or
any other rights of Sanken or any third party which may result from its use. Unless otherwise agreed in writing by Sanken, Sanken
makes no warranties of any kind, whether express or implied, as to the products, including product merchantability, and fitness for a
particular purpose and special environment, and the information, including its accuracy, usefulness, and reliability, included in this
document.
• Although Sanken undertakes to enhance the quality and reliability of its products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. Users of Sanken products are requested to take, at their own risk, preventative measures
including safety design of the equipment or systems against any possible injury, death, fires or damages to the society due to device
failure or malfunction.
• Sanken products listed in this document are designed and intended for the use as components in general purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.).
When considering the use of Sanken products in the applications where higher reliability is required (transportation equipment and
its control systems, traffic signal control systems or equipment, fire/crime alarm systems, various safety devices, etc.), and whenever
long life expectancy is required even in general purpose electronic equipment or apparatus, please contact your nearest Sanken sales
representative to discuss, prior to the use of the products herein.
The use of Sanken products without the written consent of Sanken in the applications where extremely high reliability is required
(aerospace equipment, nuclear power control systems, life support systems, etc.) is strictly prohibited.
• When using the products specified herein by either (i) combining other products or materials therewith or (ii) physically, chemically
or otherwise processing or treating the products, please duly consider all possible risks that may result from all such uses in advance
and proceed therewith at your own responsibility.
• Anti radioactive ray design is not considered for the products listed herein.
• Sanken assumes no responsibility for any troubles, such as dropping products caused during transportation out of Sanken’s distribution network.
• The contents in this document must not be transcribed or copied without Sanken’s written consent.
STR-W6000S-AN, Rev. 1.0
SANKEN ELECTRIC CO., LTD.
20
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