Control circuit of BUCK convertor

Abstract

The invention provides a control circuit of a BUCK converter. The control circuit of the BUCK converter comprises a voltage comparison circuit and an on-off control circuit. The voltage comparison circuit compares a detection voltage with a preset voltage and outputs a comparison result to the on-off control circuit. The current value of the preset voltage can charge a junction capacitance voltageof a second switching tube Q2 of the BUCK converter to be larger than or equal to the input voltage of the BUCK converter. When the detection voltage is larger than or equal to the preset voltage, the on-off control circuit controls the second switching tube Q2 to be turned off, an inductor L current continues to charge the Q2 junction capacitor, and finally the voltage of the Q2 junction capacitor is equal to the input voltage Vin. When the voltage of the Q2 junction capacitor is equal to the input voltage Vin, the drain-source voltage of the Q1 is zero, the turn-on time of the next period of the Q1 is just reached, and the tube voltage of the Q1 is reduced to zero, so that the turn-on of the zero-point voltage reduces the turn-on loss, and the efficiency of the BUCK converter is improved.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a control circuit of a BUCK converter. Background technique [0002] Switching direct current-direct current (DC-DC for short) converters are more and more widely used in the fields of computers, automation or electronic instruments due to their advantages of stable output voltage and high efficiency. The BUCK converter is a common DC-DC converter, and the BUCK converter is also called a step-down converter. [0003] figure 1 is a schematic diagram of a BUCK converter, such as figure 1 As shown, the BUCK converter includes a first switch tube Q1, a second switch tube Q2, an inductor L, a first capacitor C1 and a control circuit. The control circuit is used to drive the switch tubes Q1 and Q2 to conduct alternately in a complementary manner. When Q1 is closed and Q2 is disconnected, the input voltage charges the first capacitor C1 through the inductor L; when ...

AI Technical Summary

Problems solved by technology

[0004] In the light-load mode of the BUCK converter, the inductor L current will appear, and the inductor L current will discharge to the ground through the second switch tube Q2, resulting in power loss; the first switch tube Q1 will gradually reduce the tube voltage drop during the turn-on process, and the load As the current gradually increases, during this process, the voltage and current of the switch tube will have an overlapping area, resulting in energy loss

At light load, the switching loss of the rectifier switching tube will account for a large part of the current power, resulting in low light load efficiency

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