Patent ID: 9397576
Filing Date: 2016-07-19
CPC Classification: H02M

Claim Text:
1. A control circuit for controlling an input power or an output current of a converter, wherein the converter comprises a transformer and a power switch, and the power switch is electrically coupled to a primary winding of the transformer, the control circuit comprising: a current sensing unit electrically coupled to the power switch, the current sensing unit configured to sense a current flowing through the power switch, and to convert the current into a voltage; a current emulating unit electrically coupled to an auxiliary winding of the transformer, the power switch, and the current sensing unit, the current emulating unit configured to determine a propagation delay period according to a voltage transient time of the auxiliary winding and a turn-off time of the power switch, to retrieve a plurality of sampling times in a conduction period of the power switch according to the propagation delay period, to obtain a plurality of sampling voltages at the sampling times by the current sensing unit, and to obtain a peak current and a valley current flowing through the power switch according to the sampling voltages; a control unit configured to generate a control signal according to the peak current and the valley current, wherein the control signal is configured to control the power switch so as to control the input power or the output current of the converter, wherein the sampling times comprises a first sampling time, a second sampling time, and a third sampling time, wherein a time interval between the first sampling time and the second sampling time is substantially equal to the propagation delay period, and the third sampling time is the turn-off time of the power switch.