STR-A6059H - Allegro MicroSystems Europe Ltd.

SANKEN ELECTRIC CO., LTD.

http://www.sanken-ele.co.jp/en/

STR-A6000 Series PWM Of f-Line Switching Regulator ICs

Application Information

STR-A6000-AN, Rev. 4.1

General Description

The STR-A6000 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 accord-

ing 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 compo-

nent counts, and high performance-to-cost power supply.

Features and Benefits

 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 < 25 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

DIP8 package

Applications

Switching power supplies for electronic devices such as:

• Battery charger for mobile phone, digital camera, cam-

corder, electric shaver, emergency/guide light, and so forth

• Standby power supply for LCD/PDP television, desktop

PC, multi-function printer, audio equipment, and so forth

• Small switch-mode power supply (SMPS) for printer,

BD/DVD player, CD player, set-top-box, and so forth

• Auxiliary power supply for air conditioner, refrigerator,

washer, dishwasher, and so forth

 Protection features

 Overcurrent Protection function (OCP): pulse-by-pulse,

with input compensation function

 Overvoltage Protection function (OVP): latched shutdown

 Overload Protection function (OLP): auto-restart, with timer

 Thermal shutdown protection (TSD): latched shutdown

Not to scale

The product lineup for the STR-A6000 series provides the following options

Part Number Features

Power MOSFET Output Power1, POUT (W)

VDSS(min)

(V)

RDS(ON)(max)

(Ω)

Open Frame Adaptor

230 VAC 85 to

265 VAC 230 VAC 85 to

265 VAC

STR-A6051M

fOSC = 67 kHz 650

3.95 30 21 20 16

STR-A6052M 2.8 35 25 23 19

STR-A6053M 1.9 41 29 26 22

STR-A6079M 800 19.2 13 9 8 6

STR-A6059H

fOSC = 100 kHz

650 6 30 19 17 11

STR-A6061H

700

3.95 35 24 21 15

STR-A6062H 2.8 38 26 23 18

STR-A6069H 6 30 19 17 11

STR-A6061HD

fOSC = 100 kHz,

two types of OCP2700

3.95 35 24 21 15

STR-A6062HD 2.8 38 26 23 18

STR-A6063HD 2.3 40 27 25 20

STR-A6069HD 6 30 19 17 11

1The 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 volt-

age and short duty cycle, the output power may be less than the value stated here.

2The products suffixed D have an additional OCP function which operates during leading edge blanking period, to operate as protection at the condi-

tion such as output windings shorted or unusual withstand voltage of secondary-side diodes.

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Absolute Maximum Ratings

• The STR-A6059H is used as an example for the STR-A6000 series.

• 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 Rating Unit

Drain Peak Current1IDPEAK Single pulse 8  1 1.8 A

Avalanche Energy1EAS Single pulse, VDD = 99 V, L = 20 mH 8  124mJ

ILPEAK 8  1 1.8 A

S/OCP Pin Voltage VOCP 1  3 2 to 6 V

Control Part Input Voltage VCC 5  332V

FB/OLP Pin Voltage VFB 4  3 0.3 to 14 V

FB/OLP Pin Sink Current IFB 4  3 1.0 mA

BR Pin Voltage VBR 2  3 0.3 to 7 V

BR Pin Sink Current IBR 2  3 1.0 mA

Power Dissipation of MOSFET PD1 Mounted on 15 mm × 15 mm printed circuit board 8  1 1.35 W

Power Dissipation of Control Part PD2 5  3 1.2 W

Operating Ambient Temperature2TOP –20 to 125 °C

Storage Temperature Tstg –40 to 125 °C

Channel Temperature Tch – 150 °C

1Refer to individual product datasheet for details; value differs among products.

2The recommended internal frame temperature, TF

, is 115°C (max).

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 8

Undervoltage Lockout (UVLO) Circuit 8

Bias Assist Function 9

Constant Voltage Control Operation 9

Auto Standby Mode Function 10

Random Switching Function 11

Brown-In and Brown-Out Function 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

Pattern Layout Example 18

Reference Design of Power Supply 19

Important Notes 21

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Electrical Characteristics

• The STR-A6059H is used as an example for the STR-A6000 series.

• 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) 5  3 13.8 15.3 16.8 V

Operation Stop Voltage1VCC(OFF) 5  3 7.3 8.1 8.9 V

Circuit Current in Operation ICC(ON) VCC = 12 V 5  3 – – 2.5 mA

Minimum Start Voltage VST(ON) 5  3 – 38 – V

Startup Current ISTARTUP VCC = 13.5 V 5  3 3.7 2.5 1.5 mA

Startup Current Threshold Biasing Voltage1VCC(BIAS) ICC = 100 A5  3 8.5 9.5 10.5 V

Average Operation Frequency2fOSC(AVG) 8  3 90 100 110 kHz

Frequency Modulation Deviation2f8  3 – 8 – kHz

Maximum Duty Cycle DMAX 8  377 83 89 %

Minimum On-Time2tON(MIN) – – 470 – ns

Leading Edge Blanking Time2tBW – – 280 – ns

OCP Compensation Coefficient2DPC – – 33 – mV/s

OCP Compensation Duty Cycle Limit DDPC ––36–%

OCP Threshold Voltage at Zero Duty Cycle VOCP(L) 1  3 0.70 0.78 0.86 V

OCP Threshold Voltage at 36% Duty Cycle VOCP(H) VCC = 32 V 1  3 0.81 0.9 0.99 V

Maximum Feedback Current IFB(MAX) VCC = 12 V 4  3 340 230 150 A

Minimum Feedback Current IFB(MIN) 4  3 30 15 7A

FB/OLP Pin Oscillation Stop Threshold

Voltage VFB(STB) 4  3 0.85 0.95 1.05 V

OLP Threshold Voltage VFB(OLP) 4  3 7.3 8.1 8.9 V

OLP Delay Time tOLP 4  354 68 82 ms

OLP Operation Current ICC(OLP) VCC = 12 V 5  3 – 300 600 A

FB/OLP Pin Clamp Voltage VFB(CLAMP) 4  3 11 12.8 14 V

Brown-In Threshold Voltage VBR(IN) VCC = 32 V 2  3 5.2 5.6 6 V

Brown-Out Threshold Voltage VBR(OUT) VCC = 32 V 2  3 4.45 4.8 5.15 V

BR Pin Clamp Voltage VBR(CLAMP) VCC = 32 V 2  3 6 6.4 7 V

BR Function Disabling Threshold Voltage VBR(DIS) VCC = 32 V 2  3 0.3 0.48 0.7 V

VCC Pin OVP Threshold Voltage VCC(OVP) 5  326 29 32 V

Latch Circuits Holding Current3ICC(LATCH) VCC = 9.5 V 5  3 – 700 – A

Thermal Shutdown Temperature Tj(TSD) – 135 – – °C

1VCC(BIAS) > VCC(OFF) always.

2Refer to individual product datasheet for details; value differs among products.

3A latch circuit is a circuit operated with Overvoltage Protection function (OVP) and/or Thermal Shutdown Protection function (TSD) in operation.

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Reference Parameter Comparison Between STR-A6000M Type and STR-A6000H/HD Types

Characteristic Symbol

Different ratings

UnitSTR-A6000M Type STR-A6000H / HD Types

Min. Typ. Max. Min. Typ. Max.

Average Operation Frequency fOSC(AVG) 60 67 74 90 100 110 kHz

Frequency Modulation Deviation f5 8kHz

Minimum Duty Cycle tON(MIN) 540 470 ns

Leading Edge Blanking Time tBW 340 280 ns

OCP Compensation Coefficient DPC 22 33 mV/s

Electrical Characteristics of MOSFET Unless otherwise specified, TA is 25°C

Characteristic Symbol Conditions Pins Min. Typ. Max. Unit

Drain-to-Source Breakdown Voltage* VDSS 8 – 1 650 – – V

Drain Leakage Current IDSS 8 – 1 – – 300 A

On-Resistance* RDS(ON) 8 – 1 – – 6 

Switching Time* tf8 – 1 – – 250 ns

Thermal Resistance* Rch-C

The thermal resistance between

the channels of the MOSFET and

the case. Case temperature, TC, is

measured at the center of the case

top surface.

– – – 22 °C/W

*Refer to individual product datasheet for details; value differs among products.

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

D/S T

VCC

4S/OCP

FB/OLP

GND

DRV

PWM OSC

REG

Slope

Compensation

6.4 V

REG

Fe edback

Control

OCP

Drain Peak Current

Compe nsa tion

7 V

12.8 V

LEB

OLP

OVP TS D

Startup

UVLO

Brown-In/

Brown-Out

7,8

Functional Block Diagram

Pin List Table

D/ST

VCC

S/OCP

GND

FB/OLP

Number Name Function

1 S/OCP MOSFET source, and input for Overcurrent Protection (OCP) signal

2 BR Input for Brown-In and Brown-Out detection voltage

3 GND Ground

4 FB/OLP Feedback signal input for constant voltage control signal, and input of Overload

Protection (OLP) signal

5 VCC Power supply voltage input for Control Part and input of Overvoltage Protection

(OVP) signal

6 – (Pin removed)

7, 8 D/ST MOSFET drain, and input of the startup current

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

VAC

C5 R1

BR1

PC 1

OCP

CRD clamp snubber

C（CR）

Dumper snubber

1234

D/ST D/ST

S/OCP FB/OLPGND

VCC

87 5

STR-A6000

C10

D51

C51

R51

R52

U51

R54

R56

C52

PC1

R53

R55

L51

C53

VOUT

GND

VAC

C5 R1

BR1

PC 1

OCP

CRD clamp snubber

C（CR）

Dumper snubber

1234

D/ST D/ST

S/OCP FB/OLPGND

VCC

87 5

STR-A6000

D51

C51

R51

R52

U51

R54

R56

C52

PC1

R53

R55

L51

C53

VOUT

GND

Typical application circuit example, enabled Brown-In/Brown-Out function (DC line detection)

Typical application circuit example, disabled Brown-In/Brown-Out function

Typical Application Circuit

The following drawings show circuits enabled and disabled the

Brown-In/Brown-Out function.

The following design features should be observed:

• The PCB traces from the D/ST pins should be as wide as pos-

sible, in order to enhance thermal dissipation.

• 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.

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

０～１５°

0.25

+0.1

-0.05

6.5

9.4 ±0.3

0.5 ±0.1

0.89 TYP

4.2 ±0.3

3.3

3.4 ±0.1

±0.2

(7.6 TYP)

2.54 TYP

-0.05

±0.2

±0.57.5

+0.3

1.0 1.52

Unit： mm

Part Number

Lot Number

Sanken Control Number

A60xxx

SK YMD

Y is the last digit of the year (0 to 9)

M is the month (1 to 9, O, N, or D)

D is a period of days (1 to 3):

1 – 1st to 10th

2 – 11th to 20th

3 – 21st to 31st

Part Number

Lot Number

Sanken Control Number

A60xxH

SK YMD D

Y is the last digit of the year (0 to 9)

M is the month (1 to 9, O, N, or D)

D is a period of days (1 to 3):

1 – 1st to 10th

2 – 11th to 20th

3 – 21st to 31st

STR-A6xxH or STR-A6xxM STR-A6xxHD

Package Diagram

Marking Diagram

Pb-free.Device composition compliant with the RoHS directive.

• DIP8 package

• The following show a representative type of DIP8.

• The pin 6 is removed to provide greater creepage and clearance isolation between

the high voltage pins (pins 7 and 8: D/ST) and the low voltage pin (pin 5: VCC).

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Functional Description

• All of the parameter values used in these descriptions are typical

values, according to the STR-A6059H specification, unless they

are specified as minimum or maximum.

• With regard to current direction, "+" indicates sink current (to-

ward the IC) and "–" indicates source current (from the IC).

Startup Operation

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) = 38 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 con-

nected 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.

During the IC operation, the rectified voltage from the auxiliary

winding voltage, VD , of figure 1 becomes a power source to the

VCC pin.

The winding turns of winding D should be adjusted so that the

VCC pin voltage is applied to equation (1) within the specifica-

tions 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.

CC(BIAS)(max) < VCC < VCC(OVP)(min) (1)

⇒ 10.5 (V) < VCC < 26.0 (V)

The startup time, tSTART , is determined by the value of C2, and it is

approximately given as below:

tSTART C2|ISTARTUP|

VCC(ON) – VCC(INT)

× (2)

where:

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 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 (Undervolt-

age Lockout) circuit and reverts to the state before startup.

VAC

D2 R2

BR1

VCC

GND

D/ST

7,8

Figure 1. VCC pin peripheral circuit

Figure 2. VCC versus ICC

= 2.5 mA (max)

CC(ON)

Stop

Start

CC(ON)

pin voltage

15 V

CC(OFF)

8.5 V

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

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.

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.

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.

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.

The FB/OLP pin voltage is internally added the slope compensa-

tion at the feedback control (refer to Function Block Diagram

section), and the target voltage, VSC , is generated. The IC com-

pares 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.

Time

VCC(OFF)

VCC(ON)

VCC(BIAS)

IC startup Startup success

Target

Operating

Voltage

Bias Assist period

Increasing by

output voltage rising

Startup failure

pin voltage

Figure 3. VCC pin voltage during startup period

PC1

FB/OLP

S/OCP

GND

OCP

ROCP

Figure 4. FB/OLP pin peripheral circuit

Figure 5. Drain current, ID

, and FB comparator in steady operation

VSC

Target voltage including

Slope Compensation

OCP pin voltage

FB Comparator

Drain current

VROCP

–

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

• 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 wave-

form 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 funda-

mental operating frequency as shown in figure 6. This is called

the subharmonics phenomenon.

In order to avoid this, the IC incorporates the Slope Compensa-

tion 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 compen-

sate VSC, the subharmonics phenomenon is suppressed.

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 = 280 ns (340 ns

for STR-A6000M type), is built-in.

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 fig-

ure 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.

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

Figure 6. Drain current, ID

, waveform in subharmonic oscillation

ON1

Target voltage

without Slope Compensation

ON2

ttt

Output

current, IOUT

Drain

current, ID

Normal operation Normal operationStandby operation

Burst oscillation

Below several kHz

Figure 7. Auto Standby mode timing

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

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 aux-

iliary 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 f =

± 4% superposed on the average operation frequency, fOSC(AVG)

The conduction noise with this function is smaller than that with-

out this function, and this function can simplify noise filtering of

the input lines of power supply.

Brown-In and Brown-Out Function

This function stops switching operation when it detects low input

line voltage, and thus prevents excessive input current and over-

heating. During Auto Standby mode, this function is disabled.

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.

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 volt-

age increases to VBR(IN) = 5.6 V or more and the VCC pin voltage

Figure 8. The circuit used to disable the Brown-In and Brown-Out function

Figure 9. Brown-In and Brown-Out function controlled by DC line detection

87 5

D/ST D/ST

S/OCP

PC1

OCP

BR pin is connected to GND

GND FB/OLP

PC1

OCP

1234

D/ST D/ST

S/OCP FB/OLP

GND

VCC

87 5

C10

68 ms

BR(OUT)

= 4.8 V

BR(IN)

= 5.6 V

BR pin voltage

BR(DIS)

= 0.48 V

Drain current, I

VCC pin voltage

CC(ON)

CC(OFF)

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

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 volt-

age, 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 volt-

age, and thus it minimizes the influence from C1 charging and

discharging time, or load conditions, on the detecting voltage.

This method is set together with the High-Speed Latch Release

function.

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 volt-

age 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 F 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.

• High-Speed Latch Release

The Brown-In and Brown-Out function by AC line detection

shown in figure 10 can quickly release the latch mode when the

AC input, VAC, is turned off.

When the Overvoltage Protection function (OVP) or Thermal

Shutdown function (TSD) are activated, the IC stops switching

Figure 10. Brown-In and Brown-Out function controlled by AC line detection

PC1

OCP

1234

D/ST D/ST

S/OCP FB/OLPGND

VCC

87 5

C10

68 ms

BR(OUT)

= 4.8 V

BR(IN)

= 5.6 V

BR pin voltage

BR(DIS)

= 0.48 V

Drain current, I

VCC pin voltage

CC(ON)

CC(OFF)

VAC

BR1

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

operation in latch mode. Releasing the latch mode is done by

decreasing the VCC pin voltage below VCC(OFF) = 8.1 V after

unplugging the AC input, or by decreasing the BR pin voltage

below VBR(OUT) = 4.8 V.

This method of unplugging the AC input will spend much time

until the VCC pin voltage decreases below VCC(OFF) = 8.1 V,

because the release time is determined by discharge time of C1.

In contrast, the configuration of the BR pin peripheral circuit

shown in figure 10 makes the releasing process faster. Because

the BR pin voltage immediately decreases to VBR(OUT) = 4.8 V

or less when the AC input, VAC, is turned off, and thus the latch

mode is quickly released.

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 volt-

age, 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.

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 differ-

ence 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) = 0.9 V, constantly

OCP(ONTime) (V) = VOCP(L)(V) + DPC (mV/s)

× On Time (s). (3)

where:

VOCP(L) is the OCP threshold voltage at zero duty cycle (V),

0.78 V

DPC is the OCP compensation coefficient (mV/s), 33 mV/s,

and

On Time is the the on-time of the duty cycle (s):

On Time = On Duty / fOSC(AVG)

In addition, the products suffixed D have an additional OCP func-

tion which operates during leading edge blanking period, tBW.

During tBW from the moment when the power MOSFET is turn-

ing on, the OCP threshold voltage becomes VOCP(LEB) = 1.55 V.

This function operates as protection at the condition such as out-

put windings shorted or unusual withstand voltage of secondary-

side diodes. After tBW

, the OCP threshold voltage is changed to

the value given by the above equation (3).

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.

High AC input

Output Voltage, V

OUT

(V)

Output Current , I

OUT

（A)

Low AC input

Variance resulting

from propagation delay

Figure 12. Relationship of duty cycle and OCP threshold voltage after

compensation

Figure 11. Output current at OCP without input compensation

OCP Threshold Voltage after

Compensated, VOCP(ONTime) (V)

Duty Cycle, D (%)

1.0

015 36 80

0.5

85VAC (as an example)

265 VAC (as an example)

VOCP(H)

VOCP(L)

About 0.83

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

When the VCC pin voltage decreases to VCC(BIAS) = 9.5 V, the

startup circuit provides the Startup Current, ISTARTUP, to the VCC

pin in order to prevent the VCC pin voltage from decreasing

to VCC(OFF) = 8.1 V or less. Thus, the IC maintains latch mode.

Releasing latch mode is done by decreasing the VCC pin volt-

age below VCC(OFF) = 8.1 V after unplugging the AC input. In

the Brown-In and Brown-Out function by AC line detection,

described above, releasing latch mode is done by the High-Speed

Latch Release decreasing the BR pin voltage below VBR(OUT)

= 4.8 V.

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.

The output voltage of the secondary-side at OVP operation,

VOUT(OVP), is approximately given as below:

OUT(OVP)

× 29 (V)

(normal operation)

OUT

(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

from the secondary-side 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 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

OLP state.

This operation reduces power stress on the power MOSFET and

secondary-side rectifier. Furthermore, this reduces power con-

sumption, because the switching period in this intermittent opera-

tion is shorter than non-switching interval. When the fault condi-

tion is removed, the IC returns to normal operation automatically.

PC1

FB /OLP

VCC

GND

D2 R2

Figure 13. FB/OLP pin peripheral circuit

Figure 14. OLP operation waveforms

VCC pin

voltage

FB/OLP pin

voltage

Drain

current,

CC(OFF)

FB(OLP)

OLP

CC(ON)

Non-switching interval

OLP

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Thermal Shutdown Function (TSD)

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 in latch

mode, in the same way as the Overvoltage Protection function

(OVP), described above.

Releasing the latch mode is done by decreasing the VCC pin volt-

age below VCC(OFF) = 8.1 V after unplugging the AC input. In the

Brown-In and Brown-Out function by AC line detection, releas-

ing the latch mode is done by High-Speed Latch Release decreas-

ing the BR pin voltage below VBR(OUT) = 4.8 V.

Design Notes

Peripheral Components

Take care to use the proper rating and proper type of components.

• Input and output electrolytic capacitors

Apply proper design margin to accommodate ripple current,

voltage, and temperature rise.

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

Choose a low inductance and high surge-tolerant type. Because

a high frequency switching current flows to ROCP

, a high induc-

tance resistor may cause poor operation.

• BR pin peripheral circuit

The Brown-In and Brown-Out function has two types of detec-

tion method: AC line or DC line. Refer to Brown-In and Brown-

Out Function section for more details.

• 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, and should be connected close to these pins.

The reference value of C3 is about 2200 pF to 0.01 F, 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 F (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.

VAC

PC1

ROCP

1234

D/ST D/ST

OCP

FB/

OLP

GND

VCC

87 5

C10

Figure 15. IC peripheral circuit

Figure 16. VCC pin peripheral circuit

Figure 17. VCC versus IOUT with and without resistor R2

Output Current, I

OUT

VCC

With R2

Without R2

pin voltage

VCC

GND

Added

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

For alleviating C2 peak charging, it is effective to add some

value R2, of several tenths of ohms to several ohms, in series

with D2 (see figure 16). The optimal value of R2 should be de-

termined 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

A typical phase compensation circuit with a secondary-side

shunt regulator (U51) is shown in figure 18.

The reference value of C52 is about 0.047 to 0.47 F, and should

be adjusted based on actual operation in the application.

• Transformer

Apply proper design margin to core temperature rise due to core

loss and copper loss.

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 cur-

rent and a current density of about 3 to 4 A/mm2.

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.

 Use litz wire.

 Thicken the wire gauge.

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 de-

sign 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 wind-

ing 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 stabi-

lized output winding of secondary-side windings, controlled to

constant voltage.

T1 D51

C51

R51

R52

U51

R54

R56

C52

PC1

R53

R55

L51

C53

VOUT

GND

Figure 18. Peripheral circuit around secondary-side shunt regulator (U51)

Figure 19. Winding structural examples

P1, P2 㧦 Primary main winding

㧦

Primary auxiliary winding

㧦

Secondary stabilized output winding

S2㧦Secondary output winding

Margin tape

P1 S1 D S2 S1 P2

Bobbin

Winding structural example (b)

Margin tape

P1 S1 P2 S2 D

Bobbin

Winding structural example (a

)

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

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 compo-

nent layouts should be done to comply with all safety guidelines.

Furthermore, because the power MOSFET has a positive ther-

mal coefficient of RDS(ON)

, consider it when preparing a thermal

design.

Figure 21 shows a circuit layout design example.

• 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 F 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 F) close to the VCC pin

and the GND pin is recommended.

(3) ROCP Trace Layout

OCP 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 switch-

ing 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 in-

crease margin against the power MOSFET breakdown voltage,

and reduces stress on the clamp snubber circuit and losses in it.

Figure 21. Peripheral circuit example around the IC

Figure 20. High frequency current loops (hatched areas)

C5 R1

D2 R2

T1 D51

C51

PC1

OCP

1234

D/ST D/ST

S/OCP FB/OLPGND

VCC

87 5

Main power circuit trace

GND trace for the IC

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Pattern Layout Example

The following show the PCB pattern layout example and the

schematic of dual outputs circuit with STR-A6000 series.

Figure 22. PCB circuit trace layout example

Figure 23. Circuit schematic for PCB circuit trace layout

T1 D51

R52

U51

P1 S1

PC 1

L51

GND

C52

R53

TH1

t°

12 4

D/ST D/ST

BRS/OCP FB/OLP

VCC

87 5

STR-A6000

GND

OUT2

GND

VOUT1

D6 R2

D52

C51 C53

C54

R51 R54

R55

R56

R57

R58

R59

R60

R61

JW51 JW52

JW1 JW2

JW3 CP1

C55

C56

CN51

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Reference Design of Power Supply

As an example, the following show circuit schematic, bill of materi-

als, a power supply specification, and transformer specification.

Figure 24. Reference design schematic

Bill of Materials

Symbol Part type Ratingsa

Recommended

Sanken Parts Symbol Part type Ratingsa

Recommended

Sanken Parts

F1 Fuse 250 VAC, 3 A R4bMetal oxide 330 k, 1 W

L1cCM inductor 3.3 mH R7 General 330 k

L2cInductor 470 HR8

bGeneral 2.2 M

TH1cNTC thermistor Short R9bGeneral 2.2 M

D1 General 600 V, 1 A EM01A PC1 Photocoupler PC123 or equivalent

D2 General 600 V, 1 A EM01A U1 IC – STR-A6059H

D3 General 600 V, 1 A EM01A T1 Transformer See the specification

D4 General 600 V, 1 A EM01A L51 Inductor 5 H

D5 Fast recovery 1000 V, 0.5 A EG01C D51 Schottky 90 V, 4 A FMB-G19L

D6 Fast recovery 200 V, 1 A AL01Z C51 Electrolytic 680 F, 10 V

C1cFilm, X2 0.047 F, 275 V C52cCeramic 0.1 F, 50 V

C2 Electrolytic 10 F, 400 V C53 Electrolytic 330 F, 10 V

C3 Electrolytic 10 F, 400 V C55cCeramic 1000 pF, 1 kV

C4 Ceramic 1000 pF, 630 V R51 General 220 

C5 Electrolytic 22 F, 50 V R52 General 1.5 k

C6cCeramic 0.01 F R53cGeneral 22 k

C7cCeramic 1000 pF R54 General, 1% Short

C8cCeramic Open R55 General, 1% 10 k

C9 Ceramic, Y1 2200 pF, 250 V R56 General, 1% 10 k

R1cGeneral Open R57 General Open

R2cGeneral 4.7 U51 Shunt regulator VREF = 2.5 V, TL431 or

equivalent

R3 General 1.5 , 1/2 W

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.

bResistors 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.

cIt is necessary to be adjusted based on actual operation in the application.

T1 D51

R52

U51

PC1

L51

C52R53

TH1

12 4

D/ST D/ST

BRS/OCP FB/OLP

VCC

87 5

STR-A6000

GND

5V/1.5A

D6 R2

C51 C53

R51 R54

R55

R56

R57

CP1

C55

t°

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

Power Supply Specification

IC STR-A6059H

Input Voltage 85 to 265 VAC

Maximum Output Power 7.5 W (max)

Output Voltage 5 V

Output Current 1.5 A (max)

Transformer specification

 Primary inductance, LP : 704 H

 Core size: EI-16

 AL-value: 87 nH/N2 (Center gap of about 0.26 mm)

 Winding specification

Location Symbol Number of Turns

(T)

Wire

(mm)

Configuration

Primary winding P1 73 2UEW-Ø0.18 2 layers, solenoid winding

Auxiliary winding D 17 2UEW-Ø0.18×2 Solenoid winding

Output winding S1-1 6 TEX-Ø0.3×2 Solenoid winding

Output winding S1-2 6 TEX-Ø0.3×2 Solenoid winding

Bobbin D

VDC

D/ST

VCC

GND

S1-2

S1-1

Cross-section view ٨ mark shows the start point of winding

SANKEN ELECTRIC CO., LTD.

STR-A6000-AN, Rev. 4.1

• 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 prod-

ucts 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 semicon-

ductor 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 equip-

ment 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 distribu-

tion network.

• The contents in this document must not be transcribed or copied without Sanken’s written consent.

IMPORTANT NOTES