st7155 › datasheets › st7155.pdf · omax = 2 1 × l p × f sw × i pp 2 (1) where l p indicates...

ST7155

http://www.stcomponent.com V 1.0 1 of 10

5W LOW STANDBY CC/CV PRIMARY-SIDE POWER SWITCH

DESCRIPTION The STComponent ST7155 is a flyback power control IC with original side control. Constant output voltage (CV) and constant output current (CC) can be provided without using opto-coupler and TL431. The ST7155 adopts quasi-resonant (QR) discontinuous conduction mode (DCM) of valley bottom switch, which can reduce switching loss. It adopts switching frequency modulation and multi-mode operation technology of primary current peak amplitude (FM and AM), which ensures high conversion efficiency in full load and linear range, and meets Level VI Energy Efficiency Standard. The ST7155 has built-in high-voltage start-up circuit and 650V high-voltage power MOSFET, which has low standby power consumption (less than 75mW); and the built-in circuit includes over/under-voltage protection, output open/short circuit protection, CS open/short circuit protection, over-current protection, over-temperature protection and other comprehensive protection functions. DEVICE SUMMARY

Ordering Code Package Type Output Power Shipping Marking (1)

ST7155B SOP-7 5W Tube

3

Figure 1: Internal Schematic Diagram

TO-220

7155 YM

2018/2/7 1:29to-247 _

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100%

to-247

2 1 3 TO-247

2

1 7

4

3 5

6

VDD NC FB CS SW

SW

GND

ST7155BR SOP-7 5W Taping reel

Note 1: Y: Year code. M: Month code.

FEATURES n Primary-Side Sensing and Regulation Without

TL431 and Opto-Couple n Integrated 650V Power MOSFET n Internal HV Start-Up Circuit Reduced Standby

Power Consumption < 75mW @ 230VAC n Quasi-Resonant Valley Bottom Conduction

Achieve High Efficiency n Frequency Jitter Simplifies EMI Compatibility n Built-in Over/Under Voltage Protection, Output

Open/Short Circuit Protection, CS Open/Short Circuit Protection, Over Current Protection, Over Temperature Protection

n Needn’t External Compensation Capacitor

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ST7155


PIN CONFIGURATION

INTERNAL SCHEMATIC DIAGRAM

Sampling -

+

Cable Compensation

Constant Voltage

Controller EA

Logic Core

QR Control

Under-Voltage Protection

FB OVP (6V)

Regulated Power Supply OVP/UVLO

OTP

Gate Driver

OCP

HV Start-up

Vref

+

-

Current Limit Bandgap

Reference Voltage

Err Amp.

R1 R2

+

-


Reference Voltage

Err Amp.

R1 R2

+

-


Reference Voltage

Err Amp.

R1 R2

+

-


Reference Voltage

Err Amp.

R1 R2

SW

SW

CS

VDD

GND

FB 4

5

6

3

7

1

NC 2

Pin Name SOP-7 Function Description Pin Configuration

VDD 1 Power supply.

1 Base

Emitter Collector

3

2

1 7

4

3 5

6

VDD NC FB CS SW

SW

GND

NC 2 Not connection.

FB 3 The voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary winding reflecting output voltage.

CS 4 Current sense input.

SW 5, 6 Drain pin of internal MOSFET.

GND 7 Ground.

ST7155


ABSOLUTE MAXIMUM RATINGS (2)

TA = 25°C, All voltage respect to GND unless otherwise specified.

PARAMETER SYMBOL RATINGS UNIT

Supply Voltage Pin VDD VDD -0.3 ~ 28 V

FB Pin Voltage VFB -0.3 ~ 5.5 V

CS Pin Voltage VCS -0.3 ~ 5.5 V

SW Pin Voltage VSW -0.3 ~ 650 V

Power Dissipation PD 780 mW

Operating Junction Temperature TJ 0 ~ +150 °C

Storage Temperature Range Tstg -55 ~ +150 °C

Soldering Temperature (10 Seconds) Tsolder 260 °C

ESD Protection, Human Body Model HBM 2000 V Note 2: Absolute Maximum Ratings are those values beyond which the device could be permanently damaged. Exposure to

absolute-maximum-rated conditions for extended periods may affect device reliability.

Thermal Data

PARAMETER SYMBOL RATINGS UNIT

Thermal Resistance, Junction-to-Ambient RθJA 146 °C/W

Thermal Resistance, Junction-to-Case RθJC 97 °C/W

ST7155


ELECTRICAL CHARACTERISTICS TA = 25°C, unless otherwise noted.

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT

VDD Section

VDD Operating Voltage VDD 8 25 V

VDD Start-Up Threshold VDDon 15 17.5 20 V VDD Under Voltage Shutdown Threshold VDDoff 5 6.5 8 V

VDD Over Voltage Protect VDDovp 26 27 28 V

VDD Start-Up Charge Current Ichg VSW = 100V, VDD = 0V 0.9 mA

Start-Up Current Istart VDD = VDDoff – 1V 4 µA

Operating Current ICC VDD = VDDoff + 1V 0.85 1 mA

Current Sense Input Section Minimum Over Current Threshold VTH(min) 485 500 515 mV

Maximum Over Current Threshold VTH(max) 590 mV

Leading Edge Blanking Time tLEB 300 ns

FB Section Feedback Reference Voltage Threshold Vref(FB) 2.475 2.5 2.525 V

Output Over Voltage Protection Threshold VFB(OVP) 2.85 3 3.15 V

Output Under Voltage Protection Threshold VUVP Constant current mode 1.55 V

Minimum Turn-Off Time toff(min) 2.0 µs Maximum Cable Compensation Current Icable VFB = 0V 40 45 50 µA

Maximum Operating Frequency fMAX 90 kHz

Thermal Section Thermal Shutdown Temperature Threshold TSD 145 °C

Thermal Shutdown Hysteresis THYS 30 °C

Power MOSFET Section Drain-Source Breakdown Voltage BVDSS VGS = 0V, ID = 0.25mA 650 V

Drain-Source ON State Resistance

Rdson ID = 0.5A 8 10 Ω

ST7155


TYPICAL APPLICATION CIRCUIT

R2

AC Input

+

-


Reference Voltage

Err Amp.

R1 R2

+

-


Reference Voltage

Err Amp.

R1 R2

+

-


Reference Voltage

Err Amp.

R1 R2

+

-


Reference Voltage

Err Amp.

R1 R2

+

2

1 7

4

3 5

6

VDD NC FB CS SW

SW

GND

-

R1

ST7155 RCS

NA

NP NS DC Output

Figure 1: ST7155 Typical Application Circuit FUNCTIONAL DESCRIPTION

Introduction The ST7155 is a flyback AC/DC power supply control with primary-side control. Constant output voltage (CV) and constant output current (CC) can be provided without using opto-coupler and TL431 to meet the needs of most mobile phone chargers and adapters. Built-in high-voltage startup module, with low standby power consumption and high conversion efficiency, meets the Level VI Energy Efficiency Standard. Start-up and Under-voltage ST7155 uses built-in high-voltage start-up technology. By using internal high-voltage circuit to start-up MOSFET, the external capacitor of VDD port can be charged quickly to improve start-up time. When the VDD voltage reaches the threshold of chip opening, the internal control circuit of the chip starts to work, and the system continues to supply power through the transformer auxiliary winding source. When the VDD voltage drops to the under-voltage threshold, the internal control circuit of the chip stops working and the chip re-enter the start-up state.

ST7155


CC/CV Operation The ST7155 realizes CC/CV (constant current/constant voltage) output by flyback control system with primary-side control. Its output characteristic curve is shown in the Figure 2.

VOUT

IO

100%

±5%

±5%

Figure 2: Output Feature Curve

In charger applications, the charger starts charging the battery from CC portion of the curve until it is nearly full charged and smoothly switches to operate in CV portion of the curve. The CC portion provides a constant output current within a certain range of output voltage, and the CV portion provides a constant output voltage under certain conditions of output current. Operation Switching Frequency The switching frequency of ST7155 is adaptively controlled according to the load conditions and the operation modes. For flyback operating in DCM, the maximum output power is given by

VOUT

IO

100%

±5%

±5%

POMAX = 1 2 × LP × FSW × IPP2 (1)

Where LP indicates the inductance of primary winding; FSW is operation switching frequency and IPP is the peak current of primary winding. CC Operation Model Under CC mode operation, the current of CS pin accurately adjusts the secondary average current. As the system operates in DCM mode, the secondary average output current is determined with reference to Figure 3 below, peak current (IPP), turns ratio (NP/NS), secondary demagnetization time (TDM), and switching period (TSW). Ignoring the effects of inductance leakage, the average output current is obtained from equation (3). In CC mode, the auxiliary winding operates at frequency modulation mode (FM) at any lower than the target output voltage, as long as the auxiliary winding holds VDD above the UVLO shutdown threshold when the average output current reaches the specified reference current.

Primary-side peak current: IPP = VCS/RCS (2)

Secondary-side peak current: ISP = IPP × (NP/NS) (3)

VOUT

IO

100%

±5%

±5%

POMAX = 1 2 × LP × FSW × IPP2 (1)

Output current: IO = 1 2 × ISP × = × × × (4)

TDM TSW

1 2

VCS RCS

NP NS

TDM TSW

ST7155


IPP

ISP

TON TDM

TSW

Figure 3: Current Waveform of DCM mode CV Operation Mode In CV mode, ST7155 uses pulse sampling VFB voltage and keeps it until the next sampling. The sampling voltage is compared with the internal reference voltage (Vref(FB)) and the error is amplified. The output of the amplifier will reflect the load and turn off the switch to control the output voltage. Under heavy load conditions, the circuit operates in PFM mode, the peak current IPP of the primary-side remains unchanged, and the working frequency decreases with the decrease of the output current. When the frequency decreases to about 30kHz, the chip enters the PWM mode, the frequency modulation becomes very slow, and the IPP decreases with the decrease of the output current. When the chip VCS modulates to about 170mV, the chip enters the no-load mode, the IPP remains unchanged, and the working frequency decreases with the decrease of the output current. Figure 4 illustrates the relation waveform. ISP

VCS (mV)

VCS

FSW (kHz)

500

170 30 FSW

PWM PFM PFM

Standby

IO (A)

Figure 4: Switching Frequency, VCS vs. Load

The relationship between output voltage (VO) and Vref is:

VOUT

IO

100%

±5%

±5%

POMAX = 1 2 × LP × FSW × IPP2 (1)


TDM TSW

1 2

VCS RCS

NP NS

TDM TSW

Vref × R1 + R2

R1 = × (VO + ΔV) (5)

NA NS

ST7155


Where Vref is the internal FB feedback reference voltage; R1 and R2 are the external divider resistors connected to FB pin; NS is number of secondary windings; NA is the number of auxiliary winding turns and ΔV indicates the voltage drop of the output diode. Quasi-Resonant (QR) Control The ST7155 has built-in quasi-resonant control circuit. In CV mode, the circuit keeps the control switch on at the bottom of the valley by detecting the period time of each self-resonance. In this way, the switching loss of the system can be reduced, and the system efficiency can be improved. Compensation for OCP The ST7155 designed OCP compensation function to ensure the consistency of output current under CC mode. The circuit linearly compensates the internal CS over-current detection threshold voltage by determining the turn-on time of the MOSFET switch. Typically, the opening time is between 1.5µs and 6.5µs, and the overcurrent detection threshold voltage of CS terminal varies linearly from 500mV to 590mV. For opening time exceeding 6.5µs, the threshold is fixed at 590mV. Cable Compensation The cable compensation of ST7155 is to compensate the loss and voltage drop of the output line through the output current of FB pin, which flows into the external divider resistors and changes the voltage feedback value. The compensation current decreases inversely with the output load current, so the compensation voltage of FB will increase when the load current decreases from full load to no load. The magnitude of line compensation can be adjusted by setting the external resistors values of FB pin. The compensation amplitude formula is:

VOUT

IO

100%

±5%

±5%

POMAX = 1 2 × LP × FSW × IPP2 (1)


TDM TSW

1 2

VCS RCS

NP NS

TDM TSW

Vref × R1 + R2

R1 = × (VO + ΔV) (5)

NA NS

ΔV VO

= (6) Icable × (R1//R2)

2.5 Where ΔV is load compensation voltage; VO is output voltage; Icable is the internal maximum compensation current. Protection Function The ST7155 has several internal built-in protection functions, such as Over-Temperature Protection (OTP), Output Voltage Protection (output over-voltage/under-voltage and short circuit), cycle-by-cycle Over-Current Protection (OCP), CS pin open/short circuit protection, MOSFET’s gate drive clamp protection, VDD Over-voltage/Under-voltage Protection, open-loop protection, etc. The high reliability of the whole system is guaranteed.

ST7155


PACKAGE DIMENSION

SOP-7

SYMBOL Dimensions in Millimeters Dimensions in Inches

MIN MAX MIN MAX A 1.350 1.750 0.053 0.069

A1 0.100 0.250 0.004 0.010 A2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 D 4.700 5.100 0.185 0.200 E1 3.700 4.100 0.150 0.157 E 5.800 6.200 0.228 0.244 e 1.270 (BSC) 0.050 (BSC) L 0.400 1.270 0.016 0.050 θ 0° 8° 0° 8°

ST7155


NOTICE Information furnished by STComponent is believed to be accurate and reliable. However, no responsibility is assumed for its use. Customers are responsible for their products and applications using STComponent components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. STComponent reserves the right to make changes to their products or specification without notice. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete.

st7155 › datasheets › st7155.pdf · omax = 2 1 × l p × f sw × i pp 2 (1) where l p indicates...

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