Switch control circuit, switch circuit and constant off-time control method

Abstract

The invention provides a switch control circuit, a switch circuit and a constant off-time control method. When the on-time of the auxiliary tube reaches the constant off-time, it is detected whether the inductor current is less than the command current; The turn-off time; until the inductor current is less than the command current or less than a certain threshold of the command current, the main tube is turned on and the auxiliary tube is turned off; when the main tube is turned on and the auxiliary tube is turned off, it is detected in real time whether the inductor current exceeds the command current. Then the auxiliary pipe is turned on, and the supervisor is turned off again. The purpose of the present invention is to provide a switch control circuit, a switch circuit and a constant off-time control method, the purpose of which is to realize the voltage stabilization control of the output voltage, thereby realizing the voltage conversion with a smaller duty cycle.

Description

Technical field [0001] The present invention relates to the technical field, in particular to a switch control circuit, a switch circuit and a constant off time control method. Background technique [0002] Such as figure 1 As shown, the traditional constant off time (COT, Constant off time) control method realizes the conversion of the input voltage into the output voltage to drive the load by controlling the main switch tube to turn off at a constant time. In the buck circuit (BUCK circuit) figure 1 In (a), the upper tube M00 is the main switching tube, and the lower tube M01 is the freewheeling diode or auxiliary switching tube; in the boost circuit (BOOST circuit) figure 1 In (b), the lower tube M01 is the main switching tube, and the upper tube M00 is the freewheeling diode or auxiliary switching tube. [0003] In constant off-time control, after the main switch is turned on, when the inductor current (or main switch current) rises to the command current, the main switch is tu...

AI Technical Summary

Problems solved by technology

[0004] The circuit of the traditional scheme has some advantages of being relatively simple, easy to realize and relatively low cost, but mainly has the following disadvantages: 1. When the duty cycle is relatively small in constant off-time control, the dynamic response is relatively slow, such as image 3 shown

2. In the constant off-time control, the minimum duty cycle of the switching circuit is limited due to the fixed off-time of the main switch and the shortest on-time.

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