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February 2012 Doc ID 022218 Rev 1 1/35

VIPER37

VIPerPlus family: fixed frequency offline converter

Features

■ 800 V avalanche rugged power section

■ PWM operation with adjustable limiting current

■ 30 mW standby power at 265 Vac

■ Operating frequency:

– 60 kHz for L type

– 115 kHz for H type

■ Frequency jittering for low EMC

■ Output overvoltage protection

■ High primary current protection (2

OCP)

■ Input undervoltage setting (brownout)

■ Onboard soft-start

■ Safe auto-restart after a fault condition

■ Hysteretic thermal shutdown

Applications

■ SMPS for set-top boxes, DVD players and

recorders, white goods

■ Auxiliary power supply for consumer and home

equipment

■ ATX auxiliary power supply

■ Low / medium power AC-DC adapters

Description

This device is an offline converter with an 800 V

rugged power section, a PWM control, two levels

of overcurrent protection, overvoltage and

overload protection, hysteretic thermal protection,

soft-start, and safe auto-restart after the removal

of any fault condition. Burst mode operation and

very low device consumption help to meet the

standby energy saving regulations.

Advance frequency jittering reduces EMI filter

costs. Brownout function protects the switch

mode power supply when the rectified input

voltage level is below the normal minimum level

specified for the system. The high voltage startup

circuit is embedded in the device.

Figure 1. Typical topology

SDIP10

DC input high voltage

wide range

DC Output voltage

VIPER37

DRAINDRAIN

DRAIN

BRVDD CONT FBGND

Table 1. Device summary

Order codes Package Packaging

VIPER37LE

SDIP10 Tube

VIPER37HE

www.st.com

Summary of content (35 pages)

PAGE 1
VIPER37 VIPerPlus family: fixed frequency offline converter Features ■ 800 V avalanche rugged power section ■ PWM operation with adjustable limiting current ■ 30 mW standby power at 265 Vac ■ Operating frequency: – 60 kHz for L type – 115 kHz for H type SDIP10 Description ■ Frequency jittering for low EMC ■ Output overvoltage protection ■ High primary current protection (2nd OCP) ■ Input undervoltage setting (brownout) ■ Onboard soft-start ■ Safe auto-restart after a fault condition ■
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Contents VIPER37 Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Typical power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1 Maximum ratings . . . . .
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VIPER37 Contents 9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Block diagram VIPER37 1 Block diagram Figure 2. Block diagram VDD VDD Vcc BR DRAIN + Vin_OK VBRth Internal Supply bus & Ref erence Voltages SUPPLY & UVLO HV_ON Istart-up 15uA UVLO SOFT START OCP BLOCK - CONT OTP OCP BURST + . OVP LOGIC + THERMAL SHUTDOWN OSCILLATOR PWM TURN-ON LOGIC LEB S Q R1 R2 6uA + OVP 2nd OCP LOGIC Ref OLP OVP OTP Rsense BURST-MODE LOGIC BURST FB GND 2 Typical power Table 2.
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VIPER37 3 Pin settings Pin settings Figure 3. Note: Connection diagram (top view) '.$ $2!). 6$$ $2!). #/.4 $2!). &" $2!). "2 $2!). The copper area for heat dissipation must be designed under the DRAIN pins. Table 3. Pin description Pin n. Name 1 GND This pin represents the device ground and the source of the power section. 2 VDD Supply voltage of the control section. This pin also provides the charging current of the external capacitor during startup time. 3 4 5 6...
PAGE 6
Electrical data VIPER37 4 Electrical data 4.1 Maximum ratings Table 4. Absolute maximum ratings Value Symbol Parameter Unit Min. Max. VDRAIN Drain-to-source (ground) voltage V EAV Repetitive avalanche energy (limited by TJ = 150 °C) 5 mJ IAR Repetitive avalanche current (limited by TJ = 150 °C) 1.5 A 3 A IDRAIN Pulse drain current VCONT Control input pin voltage -0.3 6 V VFB Feedback voltage -0.3 5.5 V VBR Brownout input pin voltage -0.
PAGE 7
VIPER37 4.3 Electrical data Electrical characteristics (TJ = -25 to 125 °C, VDD = 14 V(a); unless otherwise specified). Table 6. Power section Symbol Parameter VBVDSS IOFF RDS(on) COSS Test condition Min. Breakdown voltage IDRAIN = 1 mA, VFB = GND TJ = 25 °C 800 OFF state drain current VDRAIN = max. rating, VFB = GND, TJ = 25 °C 60 µA IDRAIN = 0.4 A, VFB = 3 V, VBR = GND, TJ = 25 °C 4.5 Ω IDRAIN = 0.
PAGE 8
Electrical data VIPER37 Table 7. Symbol Supply section Parameter Test condition Min. Typ. Max. Unit 60 80 100 V VDRAIN = 120 V, VBR = GND, VFB = GND, VDD = 4 V -2 -3 -4 mA VDRAIN = 120 V, VBR = GND, VFB = GND, VDD = 4 V after fault. -0.4 -0.6 -0.8 mA Operating voltage range After turn-on 8.5 23.5 V VDD clamp voltage IDD = 20 mA 23.
PAGE 9
VIPER37 Electrical data Table 8. Controller section Symbol Parameter Test condition Min. Typ. Max. Unit Feedback pin VFBolp Overload shutdown threshold 4.5 4.8 5.2 V VFBlin Linear dynamics upper limit 3.2 3.5 3.7 V VFBbm Burst mode threshold Voltage falling 0.6 V VFBbmhys Burst mode hysteresis Voltage rising 100 mV IFB RFB(DYN) HFB Feedback sourced current VFB = 0.3 V -150 3.3 V < VFB < 4.8 V Dynamic resistance VFB < 3.
PAGE 10
Electrical data VIPER37 Table 8. Controller section (continued) Symbol Parameter Test condition Min. Typ. Max. Unit Overcurrent protection (2nd OCP) IDMAX Second overcurrent threshold 1.7 A Overvoltage protection VOVP Overvoltage protection threshold TSTROBE Overvoltage protection strobe time 2.7 3 3.3 2.
PAGE 11
VIPER37 Electrical data Figure 4. Minimum turn-on time test circuit V(DRAIN) 14 V GND DRAIN VDD DRAIN CONT DRAIN FB DRAIN BR DRAIN 90 % TONmin 50 Ω 10 % Time I(DRAIN) IDLIM 30 V 3.5 V Time Figure 5. Brownout threshold test circuits 14 V IBRhyst V(BR) GND DRAIN VDD DRAIN VBRth+VBRhyst VBRth CONT DRAIN VDIS FB DRAIN BR DRAIN Time IBRhyst 30 V 2V I(BR) 10 kΩ I(DRAIN) Time Time Figure 6.
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Typical electrical characteristics VIPER37 5 Typical electrical characteristics Figure 7. Current limit vs. TJ Figure 8. ,'/,0 ,'/,0# & )26& )26&# & Switching frequency vs. TJ 7- >&@ Drain start voltage vs. TJ ". W Figure 10. HFB vs.
PAGE 13
VIPER37 Typical electrical characteristics Figure 11. Brownout threshold vs. TJ Figure 12. Brownout hysteresis vs. TJ 9%5WK 9%5WK# & 9%5+\VW 9%5+\VW# & 7- >&@ 7- >&@ ". W ". W Figure 13. Brownout hysteresis current vs. TJ Figure 14.
PAGE 14
Typical electrical characteristics VIPER37 Figure 15. Operating supply current (switching) vs. TJ Figure 16. Current limit vs. RLIM ,'' ,'' # & ,'/,0 ,'/,0# .2KP 5OLP >N2KP@ 7- >&@ ". W Figure 17. Power MOSFET ON resistance vs. TJ ". W Figure 18.
PAGE 15
VIPER37 Typical electrical characteristics Figure 19. Thermal shutdown 6$$ 6$$ON 6$$OFF 6$$ 2%34!24 WLPH )$2!).
PAGE 16
Typical circuit 6 VIPER37 Typical circuit Figure 20. Min-features flyback application D3 Vout R1 AC IN C2 BR C1 C5 AC IN D1 GND D2 R2 R3 VVcc DD OPTO DRAIN R5 BR CONTROL C3 R4 CONT FB C6 GND SOURCE U2 C4 R6 Figure 21.
PAGE 17
VIPER37 Efficiency performances for a typical flyback converter The efficiency of the converter has been measured in different load and line voltage conditions. In accordance with the ENERGY STAR® average active mode testing efficiency method, the efficiency measurements have been performed at 25%, 50% and 75% and 100% of the rated output power, at both 115 VAC and 230 VAC. Table 9. Power supply efficiency, VOUT = 5 V, VIN = 115 VAC %Load Iout Vout Pout Pin Efficiency 25% 0.75 5.04 3.78 4.
PAGE 18
Efficiency performances for a typical flyback converter VIPER37 Figure 23.
PAGE 19
VIPER37 8 Operation description Operation description The device is a high-performance low-voltage PWM controller chip with an 800 V avalanche rugged power section. The controller includes: the oscillator with jittering feature, the startup circuits with soft-start feature, the PWM logic, the current limit circuit with adjustable set point, the second overcurrent circuit, the burst mode management, the brownout circuit, the UVLO circuit, the auto-restart circuit, and the thermal protection circuit.
PAGE 20
Operation description 8.3 VIPER37 Power-up and soft-start If the input voltage rises up to the device start threshold VDRAIN_START, the VDD voltage begins to grow due to the IDDch current (see Table 7) coming from the internal high voltage startup circuit. If the VDD voltage reaches the VDDon threshold (see Table 7), the Power MOSFET starts switching and the HV current generator is turned off (see Figure 25).
PAGE 21
VIPER37 Operation description Figure 24. IDD current during startup and burst mode 6$$ 6$$ON 6$$OFF T 6&" 6&"OLP 6&"LIN 6&"BMHYS 6&"BM T 6$2!). T )$$ )$$ )$$ T )$$CH M! 34!24 50 "5234 -/$% ./2-!, -/$% ./2-!, -/$% Figure 25. Timing diagram: normal power-up and power-down sequences 6). 9,1 9'5$,1B67$57 +9 VWDUWXS LV QR PRUH DFWLYDWHG 6$2!).?34! 24 6$$ UHJXODWLRQ LV ORVW KHUH WLPH 6$$ON 6$$OFF 6$$ 2%34!24 6$2!).
PAGE 22
Operation description VIPER37 Figure 26. Timing diagram: soft-start I DRAIN tss IDlim t V FB V FBolp V FBlin t 8.4 Power down operation At converter power down, the system loses regulation as soon as the input voltage is so low that the peak current limitation is reached. The VDD voltage drops and when it falls below the VDDoff threshold (see Table 7) the Power MOSFET is switched OFF, the energy transfers to the IC interrupted and consequently the VDD voltages decrease, Figure 25.
PAGE 23
VIPER37 Operation description Figure 27. Timing diagram: behavior after short-circuit 6$$ 6KRUW FLUFXLW RFFXUV KHUH 6$$ON 6$$OFF 6$$ 2%34!24 6&" WLPH 6&"OLP 6&"LIN 75(3(7,7,21 6$3 WLPH [ 75(3(7,7,21 )$$ WLPH )$$CH M! WLPH 8.6 Oscillator The switching frequency is internally fixed to 60 kHz or 115 kHz. In both cases the switching frequency is modulated by approximately ±4 kHz (60 kHz version) or ±8 kHz (115 kHz version) at a 250 Hz (typ.
PAGE 24
Operation description 8.8 VIPER37 Overvoltage protection (OVP) The device can monitor the converter output voltage. This operation is done by the CONT pin during Power MOSFET OFF-time, when the voltage generated by the auxiliary winding tracks the converter's output voltage, through turn ratio N (see Figure 28). AUX -------------N SEC In order to perform the output voltage monitor, the CONT pin must be connected to the aux.
PAGE 25
VIPER37 Operation description The resistor values are such that the current sourced and sunk by the CONT pin are within the rated capability of the internal clamp. Figure 28.
PAGE 26
Operation description Table 11. VIPER37 CONT pin configurations Function / component RLIM (1) ROVP DAUX IDlim reduction See Figure 16 No No OVP ≥ 80 kΩ See Equation 4 Yes IDlim reduction + OVP See Figure 16 See Equation 4 Yes 1. RLIM must be fixed before ROVP. 8.10 Feedback and overload protection (OLP) The device is a current mode converter: the feedback pin controls the PWM operation, controls the burst mode, and actives the overload protection.
PAGE 27
VIPER37 Operation description After the startup time, tSS, during which the feedback voltage is fixed at VFBlin, the output capacitor may not be at its nominal value and the controller interprets this situation as an overload condition. In this case, the OLP delay helps to avoid an incorrect device shutdown during the startup phase.
PAGE 28
Operation description VIPER37 Figure 30. FB pin configuration 1 From sense FET PWM To PWM Logic + PWM CONTROL - Cfb BURST BURST-MODE LOGIC BURST-MODE REFERENCES OLP comparator To disable logic + - 4.8V Figure 31. FB pin configuration 2 From sense FET PWM To PWM Logic + PWM CONTROL - Rfb1 Cfb BURST Cfb1 BURST-MODE REFERENCES BURST-MODE LOGIC OLP comparator + 4.8V 8.
PAGE 29
VIPER37 Operation description Figure 32. Burst mode timing diagram, light load management 9&203 9)%EP 9)%EPK\V 9)%EP TIME ,'' ,'' ,'' TIME ,'5$,1 ,'B%0 TIME %XUVW 0RGH 8.12 Brownout protection Brownout protection is a not-latched shutdown function activated when a condition of mains undervoltage is detected. The brownout comparator is internally referenced to VBRth,Table 8, and disables the PWM if the voltage applied at the BR pin is below this internal reference.
PAGE 30
Operation description VIPER37 Figure 33. Brownout protection: BR external setting and timing diagram 6). 6).ON 6).OFF 6$2!).?34!24 6"2 6"2TH 9'' 9,1B'& 9',6 6IN?/+ 'LVDEOH 5+ %5 6$$ 5/ 9%5WK & )"2 )"2HYST 9LQB2. 6$$ON 6$$OFF 6$$ 2%34!24 ,%5K\VW 6$3 6/54 When the VINon and the VINoff levels are fixed, with reference to Figure 33, the following relationships can be established for the calculation of the resistors RH and RL: Equation 9 RL = − VBRhyst IBRhyst + VINon − VINoff
PAGE 31
VIPER37 Operation description In order to enable the brownout function, the BR pin voltage must be higher than the maximum VDIS threshold (150 mV), see Table 8. 8.13 2nd level overcurrent protection and hiccup mode The device is protected against short-circuit of the secondary rectifier, short-circuit on the secondary winding, or a hard-saturation of the flyback transformer. Such an anomalous condition is invoked when the drain current exceeds the threshold IDMAX (see Table 8).
PAGE 32
Package mechanical data 9 VIPER37 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: www.st.com. ECOPACK is an ST trademark. Table 12. SDIP10 mechanical data mm Dim. Min. Typ. A 5.33 A1 0.38 A2 2.92 4.95 b 0.36 0.56 b2 0.51 1.15 c 0.2 0.36 D 9.02 10.16 E 7.62 8.
PAGE 33
VIPER37 Package mechanical data Figure 35.
PAGE 34
Revision history 10 VIPER37 Revision history Table 13.
PAGE 35
VIPER37 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.