Datasheet

ManualsBrandsSTMICROELECTRONICS ManualsPMICsPMIC - AC/DC converter, offline switcher Flyback DIP-7

July 2010 Doc ID 15133 Rev 5 1/31

VIPER27

Off-line high voltage converters

Features

■ 800 V avalanche rugged power section

■ PWM operation with frequency jittering for low

EMI

■ Operating frequency:

– 60 kHz for L type

– 115 kHz for H type

■ Standby power < 50 mW at 265 Vac

■ Limiting current with adjustable set point

■ Adjustable and accurate overvoltage

protection

■ On-board soft-start

■ Safe auto-restart after a fault condition

■ Hysteretic thermal shutdown

Application

■ Auxiliary power supply for consumer and home

equipments

■ ATX auxiliary power supply

■ Low / medium power AC-DC adapters

■ SMPS for set-top boxes, DVD players and

recorders, white goods

Description

The device is an off-line converter with an 800 V

rugged power section, a PWM control, two levels

of over-current protection, overvoltage and

overload protections, hysteretic thermal

protection, soft-start and safe auto-restart after

any fault condition removal. Burst mode operation

and device very low consumption help to meet the

standby energy saving regulations.

Advance frequency jittering reduces EMI filter

cost. Brown-out 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 start-up circuit is

embedded in the device.

Figure 1. Typical topology

DIP-7

SO16 narrow

DC input high voltage

wide range

DC Output voltage

VIPER27

DRAIN

VDD

CONT

GND

Table 1. Device summary

Order codes Package Packaging

VIPER27LN / VIPER27HN DIP-7

Tub e

VIPER27HD / VIPER27LD

SO16 narrow

VIPER27HDTR / VIPER27LDTR Tape and reel

www.st.com

Summary of content (31 pages)

PAGE 1
VIPER27 Off-line high voltage converters Features ■ 800 V avalanche rugged power section ■ PWM operation with frequency jittering for low EMI ■ Operating frequency: – 60 kHz for L type – 115 kHz for H type SO16 narrow DIP-7 SO 16 Description ■ Standby power < 50 mW at 265 Vac ■ Limiting current with adjustable set point ■ Adjustable and accurate overvoltage protection ■ On-board soft-start ■ Safe auto-restart after a fault condition ■ Hysteretic thermal shutdown The device is an off-li
PAGE 2
Contents VIPER27 Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Typical power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1 Maximum ratings . . . . .
PAGE 3
VIPER27 Block diagram 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 I DDch 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.
PAGE 4
Pin settings 3 VIPER27 Pin settings Figure 3. Note: Connection diagram (top view) The copper area for heat dissipation has to be designed under the DRAIN pins. Table 3. Pin description Pin n. Name SO16N 1 1...2 GND This pin represents the device ground and the source of the power section. - 4 N.A. Not available for user. It can be connected to GND (pins 1-2) or left not connected. 2 5 VDD Supply voltage of the control section.
PAGE 5
VIPER27 Electrical data 4 Electrical data 4.1 Maximum ratings Table 4. Absolute maximum ratings Value Symbol Parameter Unit Min VDRAIN Drain-to-source (ground) voltage 800 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 (limited by TJ = 150 °C) VCONT Control input pin voltage (with ICONT = 1 mA) -0.3 Self limited V VFB Feed-back voltage -0.3 5.
PAGE 6
Electrical data 4.3 VIPER27 Electrical characteristics (TJ = -25 to 125 °C, VDD = 14 V(a); unless otherwise specified) Table 6. Power section Symbol Parameter VBVDSS Break-down voltage IDRAIN = 1 mA, VFB = GND TJ = 25 °C OFF state drain current VDRAIN = max rating, VFB = GND 60 μA IDRAIN = 0.4 A, VFB = 3 V, VBR = GND, TJ = 25 °C 7 Ω IDRAIN = 0.4 A, VFB = 3 V, VBR = GND, TJ = 125 °C 14 Ω IOFF RDS(on) COSS Table 7.
PAGE 7
VIPER27 Table 8. Electrical data Controller section Symbol Parameter Test condition Min Typ Max Unit Feed-back pin VFBolp Over load 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 -150 -200 -280 μA -3 μA IFB RFB(DYN) HFB VFB = 0.3 V Feed-back sourced current 3.3 V < VFB < 4.8 V Dynamic resistance VFB < 3.
PAGE 8
Electrical data Table 8. VIPER27 Controller section (continued) Symbol Parameter Test condition Min Typ Max Unit Brown out protection VBRth Brown out threshold Voltage falling 0.41 0.45 0.
PAGE 9
VIPER27 Electrical data Figure 4. Minimum turn-on time test circuit VDRAIN 14 V GND DRAIN VDD DRAIN 90 % TONmin 50 Ω CONT 10 % IDRAIN BR FB 30 V 3.5 V Time IDLIM Time Figure 5. Brown out threshold test circuit VBR GND DRAIN VBRth+VBRhyst VBRth VDD DRAIN VDIS IBR Time IDRAIN Time 10 kΩ CONT IBRhyst IBRhyst BR FB 14 V 30 V 2V Time Figure 6.
PAGE 10
Typical electrical characteristics 5 VIPER27 Typical electrical characteristics Figure 7. Current limit vs TJ Figure 8. Figure 9. Drain start voltage vs TJ Figure 10. HFB vs TJ Figure 11. Brown out threshold vs TJ 10/31 Switching frequency vs TJ Figure 12.
PAGE 11
VIPER27 Typical electrical characteristics Figure 13. Brown out hysteresis current Figure 14. Operating supply current vs TJ (no switching) vs TJ Figure 15. Operating supply current (switching) vs TJ Figure 16. current limit vs RLIM Figure 17. Power MOSFET on-resistance Figure 18.
PAGE 12
Typical electrical characteristics VIPER27 Figure 19.
PAGE 13
VIPER27 6 Typical circuit Typical circuit Figure 20. Min-features flyback application D3 AC IN R1 C2 BR Vout 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 14
Operation descriptions 7 VIPER27 Operation descriptions VIPER27 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 start up circuits with soft-start feature, the PWM logic, the current limit circuit with adjustable set point, the second over current circuit, the burst mode management, the brown-out circuit, the UVLO circuit, the auto-restart circuit and the thermal protection circuit.
PAGE 15
VIPER27 7.3 Operation descriptions Power-up and soft-start up If the input voltage rises up till the device start threshold, VDRAIN_START, the VDD voltage begins to grow due to the IDDch current (see Table 7 on page 6) coming from the internal high voltage start up circuit. If the VDD voltage reaches VDDon threshold (see Table 7 on page 6) the power MOSFET starts switching and the HV current generator is turned OFF. See Figure 23 on page 16.
PAGE 16
Operation descriptions VIPER27 Figure 23. Timing diagram: normal power-up and power-down sequences VIN VIN < VDRAIN_START HV startup is no more activated VDRAIN_START VDD regulation is lost here time VDDon VDDoff VDD(RESTART) VDRAIN time IDD time IDDch (3mA) Normal operation Power-on time Power-off Figure 24.
PAGE 17
VIPER27 7.4 Operation descriptions 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 on page 6) the power MOSFET is switched OFF, the energy transfers to the IC interrupted and consequently the VDD voltages decreases, Figure 23 on page 16.
PAGE 18
Operation descriptions 7.7 VIPER27 Current mode conversion with adjustable current limit set point The device is a current mode converter: the drain current is sensed and converted in voltage that is applied to the non inverting pin of the PWM comparator. This voltage is compared with the one on the feed-back pin through a voltage divider on cycle by cycle basis.
PAGE 19
VIPER27 Operation descriptions Where: ● VOVP is the OVP threshold (see Table 8 on page 7) ● VOUT OVP is the converter output voltage value to activate the OVP set by designer ● NAUX is the auxiliary winding turns ● NSEC is the secondary winding turns ● VDSEC is the secondary diode forward voltage ● VDAUX is the auxiliary diode forward voltage ● ROVP together RLIM make the output voltage divider Than, fixed RLIM, according to the desired IDlim, the ROVP can be calculating by: Equation 4 1 – k
PAGE 20
Operation descriptions 7.9 VIPER27 About CONT pin Referring to the Figure 27, through the CONT pin, the below features can be implemented: 1. Current limit set point 2. Over voltage protection on the converter output voltage The Table 9 on page 20 referring to the Figure 27, lists the external components needed to activate one or plus of the CONT pin functions. Figure 27.
PAGE 21
VIPER27 Operation descriptions When the feedback pin voltage reaches the threshold VFBlin an internal current generator starts to charge the feedback capacitor (CFB) and when the feedback voltage reaches the VFBolp threshold, the converter is turned off and the start up phase is activated with reduced value of IDDch to 0.6 mA, see Table 7 on page 6.
PAGE 22
Operation descriptions VIPER27 Equation 7 fPFB = RFB(DYN) + RFB1 2 ⋅ π ⋅ CFB ⋅ RFB(DYN) ⋅ RFB1 ( ) 1 2 ⋅ π ⋅ CFB1 ⋅ RFB1 + RFB(DYN) ) Equation 8 fPFB1 = ( The RFB(DYN) is the dynamic resistance seen by the FB pin. The CFB1 capacitor fixes the OLP delay and usually CFB1 results much higher than CFB. The Equation 5 can be still used to calculate the OLP delay time but CFB1 has to be considered instead of CFB.
PAGE 23
VIPER27 7.11 Operation descriptions Burst-mode operation at no load or very light load When the load decrease the feedback loop reacts lowering the feedback pin voltage. If it falls down the burst mode threshold, VFBbm, the power MOSFET is not more allowed to be switched on. After the MOSFET stops, as a result of the feedback reaction to the energy delivery stop, the feedback pin voltage increases and exceeding the level, VFBbm + VFBbmhys, the power MOSFET starts switching again.
PAGE 24
Operation descriptions VIPER27 Figure 31.
PAGE 25
VIPER27 7.13 Operation descriptions 2nd level over current protection and hiccup mode The VIPER27 is protected against short circuit of the secondary rectifier, short circuit on the secondary winding or a hard-saturation of fly-back transformer. Such as anomalous condition is invoked when the drain current exceed the threshold IDMAX, see Table 8 on page 7. To distinguish a real malfunction from a disturbance (e.g. induced during ESD tests) a “warning state” is entered after the first signal trip.
PAGE 26
Package mechanical data 8 VIPER27 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 10. DIP-7 mechanical data mm Dim. Min. Typ. A 5.33 A1 0.38 A2 2.92 3.30 4.95 b 0.36 0.46 0.56 b2 1.14 1.52 1.78 c 0.20 0.25 0.36 D 9.
PAGE 27
VIPER27 Package mechanical data Figure 33.
PAGE 28
Package mechanical data Table 11. VIPER27 SO16 narrow mechanical data mm Dim. Min. Typ. A 1.75 A1 0.1 A2 1.25 b 0.31 0.51 c 0.17 0.25 D 9.8 9.9 10 E 5.8 6 6.2 E1 3.8 3.9 4 e 0.25 1.27 h 0.25 0.5 L 0.4 1.27 k 0 8 ccc 28/31 Max. 0.
PAGE 29
VIPER27 Package mechanical data Figure 34.
PAGE 30
Revision history 9 VIPER27 Revision history Table 12. 30/31 Document revision history Date Revision Changes 16-Jan-2009 1 Initial release 20-Jul-2009 2 Added SO16 narrow package. 22-Oct-2009 3 Updated Table 5 on page 5. 16-Jun-2010 4 Updated Figure 3 on page 4 and Table 3 on page 4. 30-Jul-2010 5 Updated Figure 11, Figure 12 and Figure 13.
PAGE 31
VIPER27 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.