Patent ID: 9225250
Filing Date: 2015-12-29
Classification: H02M

Abstract:
1. A control circuit for controlling an output of a power converter by a power switch, wherein a primary side of a transformer of the power converter, the power switch and a sensing resistor are connected in this order and in series to ground, the control circuit comprising: a peak current emulating unit for sampling a plurality of sampling voltages from the sensing resistor and then performing calculations using the sampling voltages and a linearity of a current through the sensing resistor, so as to obtain a real current sensing voltage and an initial current sensing voltage; an error amplifier for receiving a fixed reference voltage and a DC voltage generated from the output of the power converter and generating an error signal; a comparator for receiving the real current sensing voltage and the error signal and generating a transition signal; and a control signal generator for receiving the transition signal and generating a control signal to control the power switch, wherein the peak current emulating unit comprises: a sample and hold circuit for sampling the sampling voltages from the sensing resistor respectively at the plurality of sampling times; and a peak current calculating circuit for receiving the sampling voltages from the sample and hold circuit, and generating the real current sensing voltage and the initial current sensing voltage using the sampling voltages, wherein the sampling times comprise a first sampling time, a second sampling time, a third sampling time and a fourth sampling time; the sampling voltages corresponding respectively to the sampling times comprise a first sampling voltage, a second sampling voltage, a third sampling voltage and a fourth sampling voltage; the fourth sampling time is the time when the power switch turns off; and the time interval between the first sampling time and the second sampling time is the same as a propagation delay time of the power converter, wherein the peak current calculating circuit generates the real current sensing voltage by adding the fourth sampling voltage and the second sampling voltage and subtracting the first sampling voltage.