A Low Standby Power Primary-Side Regulated Flyback Controller with Fast Dynamic Response

Primary-side regulated (PSR) flyback controller has been widely used in low power charger applications for its simple structure, low cost, good electrical isolation and compact volume. However, limited by traditional primary-side sensing technology, PSR flyback controller suffers from poor dynamic response. A low standby power PSR flyback controller with fast dynamic response has been presented, and novel feedback comparison and sampler combo controlling circuit has been presented in the paper. An offline PSR controller containing the proposed speedup circuit and driving directly power bipolar junction transistor (BJT) was fabricated in Episil 1.0 mu m 40 V/5V EPI-HVCMOS process. Measured result shows that, in the entire universal input-voltage range (90 Vac-264 Vac) and 5V 1.0A output power, the proposed PSR controller achieves standby power less than 22mW and average efficiency line end with 20 AWG 1.5 m up to 78%. The output voltage of the proposed PSR controller becomes stable within 3.3 ms when load current changes abruptly from 0 to 1A and from 1A to 0.