The function of each pin of VIPER22A is as follows:
The 5678 pin is connected to the drain of the internal FET.
Pin 12 is the source of the internal FET, pin 3 is the feedback input, and pin 4 is VDD.
Generally, the voltage (about 300V) of 5678 pin after AC220 is rectified by bridge stack.
12 pins are grounded, 4 pins output 18V, 5V also has 18V via 7805, and 3 pins are voltage feedback and an external 18V regulator to form a voltage stabilizing circuit.
Extended data:
VIPER22A belongs to Viper series, and its common model is VIPER 12A (output power is less than VIPER22A).
This series of chips adopts the patented technology of VIPOWER MO-3 of ST, and integrates a dedicated current-mode PWM controller and a high-voltage power field-effect MOS transistor on the same chip, which not only reduces the number of components, system cost and power consumption, but also reduces the standby power consumption, which is less than 1W, and meets the energy-saving standards such as Der Blaue Engel and Energy Star.
Because the output power of VIPER22A is about 10W, it is a very cheap single-ended low-power power conversion integrated circuit with good performance. In addition, it has few peripheral devices and is easy to use. It is widely used in satellite receiver, DVD, induction cooker and LCD TV auxiliary switching power supply circuit. The auxiliary power supply of PWL37C power board used in TCL LCD TV adopts this IC, and the related circuit is shown in figure 1.
It is worth mentioning that in normal operation, the 4-pin power supply (VDD) of VIPER22A should be no less than 15V. If the mains voltage is lower than AC90V, the initial power supply mechanism inside VIPER22A usually stops working by itself, resulting in Viper 22a being unable to start reliably. In addition, the normal working voltage range of the 3-pin adjustment input control terminal is 0 V-1V.
Baidu Encyclopedia-Viper 22a