Isolated switch converter as well as controller and control method thereof

Abstract

The invention discloses an isolated switch converter as well as a controller and a control method thereof. The control method comprises the following steps of: sampling an output signal of the switch converter so as to generate a feedback signal; based on the difference between the feedback signal and a reference signal, generating a compensation signal; comparing the compensation signal with a modulation signal so as to generate a first comparison signal; detecting whether a primary switch tube is turned off, and then generating a primary turnoff detection signal; based on the primary turnoff detection signal and the first comparison signal, generating a secondary control signal to control a secondary switch tube; sending the first comparison signal to an isolating circuit so as to generate a synchronization signal isolated from the first comparison signal; based on the synchronization signal, generating a primary control signal to control the primary switch tube.

Description

technical field [0001] The present invention relates to an electronic circuit, in particular to an isolated switch converter and its controller and control method. Background technique [0002] Synchronous rectification is a technology that uses power metal-oxide-semiconductor field-effect transistors (MOSFETs) to replace rectifier diodes to reduce losses, and it can greatly improve the efficiency of switching power supplies. The power MOSFET is a voltage-controlled device, and its volt-ampere characteristic is linear when it is turned on. When using a power MOSFET as a rectifier, it is required that its gate voltage must be synchronized with the phase of the rectified voltage. [0003] figure 1 It is the waveform diagram of the existing intelligent synchronous rectification technology, wherein Vds is the drain-source voltage of the secondary switching tube, Isec is the current flowing through the secondary winding, and CTRLS is the control signal of the secondary switchin...

AI Technical Summary

Problems solved by technology

[0004] The existing intelligent synchronous rectification technology turns off the secondary switching tube after the primary switching tube is turned on, which easily leads to the simultaneous conduction of the primary switching tube and the secondary switching tube (shoot through), reducing the efficiency of the switching power supply or even Damage to switching power supply

Moreover, in the actual circuit, due to the MOSFET's own characteristics and the delay of the control circuit, it takes a while from Vds increasing to greater than -70mV until the secondary switch is turned off, which undoubtedly further increases the possibility of direct connection

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