Efficient control circuit of synchronous converter

Abstract

The invention provides an efficient control circuit of a synchronous converter, and the circuit comprises a power switch unit, a zero-cross detection unit , anoutput unit and a self-adjusting control unit; the power switch unit comprises a power tube, a synchronous rectifier tube, a first controller, and a second controller. The detection end of the zero-cross detection unit is connected with a switch node, and the output end of the zero-cross detection unit is connected with the second controller; the first end of the output unit is connected with the switch node, and the second end of the output unit is connected with the second end of the synchronous rectifier tube; and the first end of the self-adjusting control unit is connected to the first end of the power tube, the second end of the self-adjusting control unit is connected to the second controller, and the self-adjusting control unit comprises a clock module, a first sampling and holding module, a second sampling and holding module, an operational amplifier and a first comparator.

Description

technical field [0001] The invention relates to the field of circuits, and more specifically relates to a high-efficiency control circuit of a synchronous converter. Background technique [0002] Such as figure 1 As shown, when the common controller is running in DCM mode, the lower switch signal LS turns on the lower switch Q2 in the PWM_OFF phase, and the inductor current continues to flow until ZCD detects that the inductor current crosses zero, and the lower switch is turned off in the current cycle; the existing When the synchronous converter or controller operates in light-load DCM mode, the lower tube (freewheel tube) is turned on until the inductor current crosses zero in the PWM off phase, and the low Ron of the switch tube is used to save the conduction loss; however, the lower tube is in Turning on once in a cycle will cause switching loss; when the load current is small, the switching loss of the lower tube switching once will exceed the saved body diode freewhe...

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Problems solved by technology

[0002] like figure 1 As shown, when the common controller is running in DCM mode, the lower switch signal LS turns on the lower switch Q2 in the PWM_OFF phase, and the inductor current continues to flow until ZCD detects that the inductor current crosses zero, and the lower switch is turned off in the current cycle; the existing When the synchronous converter or controller operates in light-load DCM mode, the lower tube (freewheel tube) is turned on until the inductor current crosses zero in the PWM off phase, and the low Ron of the switch tube is used to save the conduction loss; however, the lower tube is in Turning on once in a cycle will cause switching loss; when the load current is small, the switching loss of the lower tube switching once will exceed the saved body diode freewheeling loss, so turning on the lower tube freewheeling will reduce the efficiency

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