Patent ID: 8274268
Filing Date: 2012-09-25
Classification: H02M,Y02B

Abstract:
1. A control circuit applied to a switching circuit comprising a high side transistor and a low side transistor, the switching circuit being connected to an output circuit, the control circuit comprising: a pulse width modulation (PWM) logic circuit configured to generate a control signal to the switching circuit to output a current in a PWM manner; a PWM comparator configured to generate an input signal of the PWM logic circuit; an error amplifier configured to amplify and output the voltage difference between the divided voltage of the output voltage of the output circuit and a first reference voltage to the PWM comparator; a voltage matching circuit configured to generate and output a voltage mapping to the output current of the switching circuit to the PWM comparator; a pulse stop logic circuit configured to generate a signal to stop the operation of the PWM logic circuit; a light load comparator configured to detect the voltage difference between the divided voltage of the output voltage of the output circuit and a second reference voltage and to control the pulse stop logic circuit; and a zero current comparator configured to detect the current flowing through the low side transistor and to output a zero current signal to the pulse stop logic circuit; wherein the pulse stop logic circuit determines whether to stop or resume the operation of the PWM logic circuit according to the output signals of the light load comparator and the zero current comparator; wherein when a clock signal changes state from low to high, the PWM logic circuit activates the high side transistor and deactivates the low side transistor; and when the amplified signal of the voltage difference between the divided voltage of the output voltage of the output circuit and a first reference voltage is smaller than the sum of the output voltage of the switching circuit and a slope compensation signal, the PWM logic circuit deactivates the high side transistor and activates the low side transistor.