Synchronous rectification driving circuit with low transmission delay

Abstract

The invention discloses a synchronous rectification drive circuit with low transmission delay. The synchronous rectification drive circuit mainly comprises a falling edge detection circuit, a pull-up current control circuit, a comparator CP1, a phase inverter N1, a monopulse trigger circuit 1, a monopulse trigger circuit 2, an RS trigger RS1, a pull-up tube Q1 and a pull-down tube Q2. According to the invention, pull-up current is established in advance by using falling edge detection and pull-down storage clearing operation is realized, pull-up output can be immediately carried out after the drain-source electrode voltage of the synchronous rectifier tube is detected to meet a turn-on condition, turn-on is realized, and transmission delay can be remarkably reduced; meanwhile, the pull-up current is controlled by the drain-source voltage falling edge of the synchronous rectifier tube and naturally reaches zero before turn-off, additional pull-up current forbidding operation is not needed, and turn-off delay can be reduced; in addition, the power consumption of the driving circuit can be reduced by maintaining a high level after conduction by using a grid capacitor of the synchronous rectifier tube.

Description

technical field [0001] The invention belongs to the technical field of power electronic conversion, in particular to a synchronous rectification drive circuit with low transmission delay. Background technique [0002] Buck, Boost, flyback, forward and other converters are widely used in various power conversion occasions due to their simple circuit structure, mature control technology, small size and low cost. As the demand continues to increase, the loss caused by the conduction voltage drop of the rectifier diode in the converter has gradually become the main limiting factor for the improvement of converter efficiency. [0003] The synchronous rectification technology is adopted, and the channel of the MOSFET is used to replace the conduction of the rectifier diode, which can effectively reduce the conduction loss of the rectifier tube and improve the efficiency of the converter. figure 1 The flyback converter with synchronous rectification control on the secondary side i...

AI Technical Summary

Problems solved by technology

When the turn-on delay is too long, such as image 3 As shown in (a), the synchronous rectifier S R It is turned on at the peak moment of the magnetizing inductor current, and within the turn-on delay S R The body diode conducts, because the body diode conduction voltage drop is much larger than S R The channel conduction voltage drop will increase the converter loss and reduce the efficiency; when the turn-off delay is too long, such as image 3 As shown in (b), S R When it is actually turned off, the source current flowing into it is negative, and the zero-current turn-off characteristic is lost. At the same time, the negative current will introduce circulating current, which will increase the current stress and increase the loss of the converter.

When designing a synchronous rectification drive circuit, the execution time of each logic step can be shortened by using high-speed devices, thereby shortening the total turn-on or turn-off delay, but this will increase the overall power consumption and cost of the circuit

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