July 2010 Doc ID 15585 Rev 4 1/40
40
VIPER25
Off-line high voltage converters
Features
■ 800 V avalanche rugged power section
■ Quasi-resonant (QR) control for valley
switching operation
■ 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
Applications
■ Adapters for PDA, camcorders, shavers,
cellular phones, cordless phones, videogames
■ Auxiliary power supply for LCD/PDP TV,
monitors, audio systems, computer, industrial
systems, LED driver, No el-cap LED driver,
utility power meter
■ 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, double
levels of overcurrent 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 helps to meet
the standby energy saving regulations. The quasi-
resonant feature reduces EMI filter cost. Brown-
out and brown-in 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
SO
-
16
DIP-7
SO16 narrow
%5
=&'
'5$,1
*1'
9'')%
6)0%2
'&2XWSXW9ROWDJH
'&,QSXW9ROWDJH
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Table 1. Device summary
Order codes Package Packaging
VIPER25LN / VIPER25HN DIP-7 Tube
VIPER25HD / VIPER25LD
SO16 narrow
Tube
VIPER25HDTR / VIPER25LDTR Tape and reel
www.st.com
Contents VIPER25
2/40 Doc ID 15585 Rev 4
Contents
1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Typical power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5 Typical electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6 Typical circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 Operation description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.1 Power section and gate driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.2 High voltage startup generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.3 Power-up description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.4 Power-down description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.5 Auto-restart description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.6 Quasi-resonant operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.7 Frequency foldback function and valley skipping mode . . . . . . . . . . . . . . 22
7.8 Double blanking time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.9 Starter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.10 Current limit set point and feed-forward option . . . . . . . . . . . . . . . . . . . . . 24
7.11 Overvoltage protection (OVP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.12 Summary on ZCD pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.13 Feedback and overload protection (OLP) . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.14 Burst-mode operation at no load or very light load . . . . . . . . . . . . . . . . . . 32
7.15 Brown-out protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
7.16 2nd level over current protection and hiccup mode . . . . . . . . . . . . . . . . . 34