HT7A6312 Low Cost Power Supply in Flyback Configuration

AN0374E V1.20 1 / 16 March 1, 2018

HT7A6312 Flyback Configuration Low Cost Power Supply

D/N: AN0374E

Features

This switching power device has an isolated buck architecture and has the following features:

• Wide operating voltage range

• Stable output voltage requirements

• Under conditions of no-load the input power consumption is lower than 150mW

• Over temperature protection and output short circuit protection

Typical System Characteristics

(Open Frame @ Room Temperature)

Parameter Wide Range (90VAC ~ 265VAC)

Input AC Frequency 47Hz~63Hz

Output voltage (VOUT) 18VDC

Output current (IOUT) 400mA(max)

Efficiency > 85% @ 115VAC，> 80% @ 230VAC

Standby Power Consumption < 0.15W @ 115VAC，< 0.15W @ 230VAC

Output Short Circuit Power Consumption < 2.5W @ 115VAC，< 0.1W @ 230VAC

Output Short Circuit Protection Yes

Over Temperature Protection Yes

HT7A6312 Low Cost Power Supply in Flyback Configuration

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Application Circuit and Component List

VSS

FB

VCC

SW

SW

SW

SW

VSS

AC C1C2 C3

Cs

C5

C9

18V

C6

C8

U1 HT7A6312

U2

U3

D1

D3

D2

D4

L1

T1Rs

R1

R2

R3

R4

R5

R6

R7

Ds

D5

D6

1234

8657

C4

L2

F1

RT1

C7

Rfb

Component Package Parameter Manufacturer C1 DIP 0.1µF/275VAC

C2,C3 DIP EL 10µF/400V C4 DIP EL 330µF/50V C5 DIP EL 10µF/50V C6 SMD0603 CE 47NF C7 DIP Y-CAPACITOR 1NF/400V C8 SMD0603 CE 100NF C9 (N.C) CS DIP 1NF/1KV

D1,D2,D3,D4,DS DO-41 1N4007, 1KV/1A D5 SMB GS1MF, 1KV/1A D6 DO-15 SR2200, 200V/2A L1 DR 9X12 DR CORE 470µH L2 JUMP WIRE F1 DIP 1A/250VAC

RT1 JUMP WIRE R1 SMD0603 RES 4R7 R2 SMD0603 RES 4.7K R3 SMD0603 RES 220 R4 SMD0603 RES 1K R5 SMD0603 RES12K R6 SMD0603 RES 15K R7 SMD0603 RES 4.3K

RFB SMD0603 RES 100 RS DIP 51KΩ, 1W T1 EE19 EE19, 3.2MH U1 DIP8 HT7A6312 HOLTEK U2 SOP-4 PC817 U3 TO-92 TL431

HT7A6312 Low Cost Power Supply in Flyback Configuration

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System Board Introduction

Top View

Bottom View

Functional Description The HT7A6312 is a highly functionally integrated device which uses an integrated PWM

controller with current mode control to drive an integrated high voltage power MOSFET.

Users can use either an isolated or non-isolated type architecture for system control

according to their requirements. In the isolated type architecture, the output signal is

transmitted to the primary side through a photo-coupler. However in the non-isolated

architecture, the input side and the output side use the same ground. The output signal is

directly sent back to the HT7A6312 to implement output voltage driving. In addition, the

HT7A6312 operates with an excellent low standby current and uses a Burst Mode

function to achieve low system standby power consumption.

The HT7A6312 contains several system protection functions, such as output short circuit

protection, IC over voltage protection and over temperature protection, etc. which ensure

that the system operates safely and with higher reliability.

Pin Description

• VSS The VSS pin is the power MOSFET source and the IC ground reference.

• FB

This is the feedback input pin. It defines the peak inductor current that can pass through the integrated MOSFET. When the logic signal on the FB pin is “0”, it corresponds to the maximum peak inductor current. An FB resistor with the resistance of 100Ω is connected to prevent from aging and strengthen the reliability of operations in hostile environment.

• VCC

The VCC pin is designed with a UVLO function. When the VCC voltage exceeds 14.5V (typ.), the HT7A6312 will start operation. When the VCC voltage is lower than 8V (typ.), the HT7A6312 will be turned off.

HT7A6312 Low Cost Power Supply in Flyback Configuration

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• SW The SW pin is connected to the drain of the integrated MOSFET. It is also used as the input pin for the internal high voltage start up JFET.

Transformer Design The T1 transformer specifications are as follows:

1

5

3

21 0.23mm X 75Ts

45 0.15mm X 43Ts

Need Gap:3pin - 1pin Lp=3.2mH

Transformer EE19 SPEC

1KHz/ 1V

2

4

12 0.23mm X 75Ts

Triple Insulated wire 97 0.4mm X 43Ts

9

7

3 2

7

5

0.23mm x 14Ts

Tape 2Ts

Tape 1Ts0.23mm x 13Ts

Copper file 0.01t 1.2Ts

0.4mm x 15Ts

0.4mm x 14Ts

0.4mm x 14Ts

Tape 2Ts 9

2 0.23mm x 14Ts1 0.23mm x 13Ts

45 0.15mm x 43TsTape 2Ts

Tape 1Ts5 Copper file 0.01t 1.2Ts

Test Data Test Condition: Room Temperature

AC input voltage range: 85VAC ~ 265VAC, IOUT is 0A ~ 400mA (max.)

The AC input power consumption is for a no-load condition:

VAC (V) 85 115 135 180 230 265

Pin(W) 0.116 0.12 0.12 0.12 0.119 0.123

Vout(V) 18.06 18.06 18.06 18.06 18.06 18.06

Iout(mA) 0

System efficiency with different load conditions:

115VAC

Vout(V) 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06

Iout(mA) 10.1 20.08 30.15 40.05 50.1 60.15 80.11 100.06 200.15 300.09 400.12

Pin(W) 0.363 0.588 0.77 0.968 1.2 1.4 1.776 2.17 4.23 6.342 8.483

η(%) 50.25 61.67 70.72 74.72 75.4 77.59 81.46 83.28 85.45 85.46 85.18

230VAC

Vout(V) 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06 18.06

Iout(mA) 10.1 20.08 30.15 40.05 50.1 60.15 80.11 100.06 200.15 300.09 400.12

Pin(W) 0.3877 0.63 0.877 1.098 1.29 1.529 1.949 2.304 4.306 6.356 8.567

η(%) 47.05 57.56 62.09 65.87 70.14 71.05 74.23 78.43 83.95 85.27 84.35

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AC Input Power Consumption - No-load

AC Input Power Consumption - Output Short Circuit

System Efficiency - Different Load Conditions

Standby Power

0

0.05

0.1

0.15

0.2

85 115 145 175 205 235 265Vac(V)

Pin

(W)

Pout(W) at Output Short

0

0.5

1

1.5

2

2.5

3

85 115 230 265

Vac(V)

Pin

(W)

Efficiency vs. Iout(mA)

0

10

20

30

40

50

60

70

80

90

100

10 40 70 100 130 160 190 220 250 280 310 340 370 400Iout(mA)

Effi

cien

cy(%

)

115V/60Hz230V/50Hz

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Output Voltage Stability - Different Load Conditions

SW Pin Voltage Waveform - 115VAC, No-load Output

SW Pin Voltage Waveform - 230VAC, No-load Output

Vout(V) vs. Iout(mA)

17

17.2

17.4

17.6

17.8

18

18.2

18.4

18.6

18.8

19

0 50 100 150 200 250 300 350 400Iout(mA)

Vou

t(V)

115V/60Hz230V/50Hz

HT7A6312 Low Cost Power Supply in Flyback Configuration

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SW Pin Voltage Waveform - 115VAC, Full-load Output

SW Pin Voltage Waveform - 230VAC, Full-load Output

SW Pin Voltage Waveform - 115VAC, Output Short Circuit

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SW Pin Voltage Waveform - 230VAC, Output Short Circuit

Output Voltage Ripple - 115VAC

Output Voltage Ripple - 230VAC

HT7A6312 Low Cost Power Supply in Flyback Configuration

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Voltage Ripple - 115VAC, Load-variant Output

Voltage Ripple - 230VAC, Load-variant Output

Output Voltage Waveform - 115VAC, No-load Start Up

HT7A6312 Low Cost Power Supply in Flyback Configuration

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Output Voltage Waveform - 230VAC, No-load Start Up

Output Voltage Waveform - 115VAC, Full-load Start Up

Output Voltage Waveform - 230VAC, Full-load Start Up

HT7A6312 Low Cost Power Supply in Flyback Configuration

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Output Voltage Waveform - 115VAC, No-load Turn Off

Output Voltage Waveform - 230VAC, No-load Turn Off

Output Voltage Waveform - 115VAC, Full-load Turn Off

HT7A6312 Low Cost Power Supply in Flyback Configuration

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Output Voltage Waveform - 230VAC, Full-load Turn Off

Full-load Conduction Measurement - 115VAC

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Full-load Conduction Measurement - 230VAC

HT7A6312 Low Cost Power Supply in Flyback Configuration

AN0374E V1.20 14 / 16 March 1, 2018

Full-load Radiatied Measurement - 110VAC

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Full-load Radiatied Measurement - 230VAC

Versions and Revision

Date Author Issue and Revision Note

2015.04.16 詹作晟 V1.00, First version.

2015.06.04 詹作晟 Version 1.10. The application circuit was modified.

2018.02.12 陳佳宏 Version 1.20 updated contents: 1. Application Circuit and Component List 2. The figures and FB pin description of the System

Board Introduction section.

Reference Files

Reference file: HT7A6312 Data Sheet.

For more information, refer to the Holtek official website www.holtek.com.

HT7A6312 Low Cost Power Supply in Flyback Configuration

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