Flyback converter, control circuit and control method therefor
AssigneeSilergy Semiconductor Technology (Hangzhou) LTD
InventorHuiqiang Chen
Life of this patent
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Abstract
The disclosure relates to a flyback converter, a control circuit and a control method therefor. In the control method, a power stage circuit is controlled at a light load to operate alternatively in a pulse-width modulation mode (e.g., a constant switching frequency mode) and in a constant on time mode, in accordance with a voltage compensation signal. Thus, output energy may decrease rapidly and smoothly, without need for the control circuit to stop working. The flyback converter has increased efficiency at the light load and decreased output voltage ripple.
Claims19
A control circuit for controlling a power stage circuit of a flyback converter, the control circuit comprising:
- a compensation circuit configured to generate a voltage compensation signal which represents a difference between an output voltage of said power stage circuit and a reference voltage;
- a control signal generating circuit configured to generate a switching control signal for controlling a power switch of said power stage circuit in accordance with said voltage compensation signal;
- and
- wherein only at a light load condition, said switching control signal is configured to adjust a switching cycle and an on time period of said power switch in accordance with said voltage compensation signal, in order to control said power stage circuit to operate continuously to decrease an energy delivered to a secondary side of said flyback converter.
A method of controlling a power stage circuit of a flyback converter, the method comprising:
- generating a voltage compensation signal which represents a difference between an output voltage of said power stage circuit and a reference voltage;
- generating a switching control signal for controlling a power switch of said power stage circuit in accordance with said voltage compensation signal;
- and
- only at a light load condition, adjusting an on time period and a switching cycle of said power switch by said switching control signal in accordance with said voltage compensation signal to control said power stage circuit to operate continuously to decrease an energy delivered to a secondary side of said flyback converter.
Dependencies are inferred from the claim text.