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Switching Power Supply Controller
LYW1921L is a high performance PSR Switching Mode Power Supply Controller that can provide high precision constant voltage and constant current output performance, especially suitable for small power offline charger applications.
At the same time, LYW1921L also supports quasi-resonant step-down LED constant-current and constant-voltage output applications, as long as SEL pin is connected to GND pin.


1. Mobile Phone charger

2. AC/DC power adapter

3. LED lighting


1. Integration of 650V MOSFET

2. Adjustable line loss compensation

3. Support flyback and buck topological applications

4. Constant current compensation of integrated line voltage and load voltage

5. Perfect protection function:

        Short circuit protection / Over temperature protection

        Cycle time flow protection / Front blanking

        Over voltage protection / Clamp protection

6. Primary side constant voltage control

7. Primary side constant current control

8. Support quasi-resonant step-down constant current output applications

9. Multi-mode constant pressure operation

10. Encapsulation: DIP-7

Electrical Parameters:

1. VDD power supply voltage: 11-27VDC, 34.5VDC Max

2. VDD operating current: 0.3~0.9mA

3. VDD starting current: 2μA

4. VDD on voltage: 15-17.5VDC

5. VDD turn-off voltage: 8-10vdc

6. VDD clamp voltage: 32.5-36.5VDC

7. Power MOSFET leakage source breakdown voltage: 650V

8. Minimum shutdown time: 2μS

9. The maximum shutdown time: 4mS