Phase detection and correction circuit for out-of-phase driving of pulse width modulator

Abstract

The invention discloses a phase detection and correction circuit for out-of-phase driving of a pulse width modulator. The phase detection and correction circuit is characterized by comprising a phase detection circuit consisting of two diodes Dm and Ds and a phase correction circuit consisting of a resistor R1 and a triode N1, wherein the cathode of the first diode Dm is connected with the driving end Drm of a master pulse width modulator (Master PWM); the cathode of the second diode Ds is connected with the driving end Drs of a slave pulse width modulator (Slave PWM); both the anodes of the first and second diodes Dm and Ds are connected with the base b of the triode N1 and one end of the resistor R1; the other end of the resistor R1 is connected with the collector c of the triode N1; the collector c of the triode N1 is connected with the voltage reference Vrefm of the master pulse width modulator (Master PWM) or the voltage reference Vrefs of the slave pulse width modulator (Slave PWM); and the emitter e of the triode N1 is connected with the fixed frequency triangular wave signal end OSCs of the slave pulse width modulator (Slave PWM).

Description

technical field [0001] The invention relates to a phase detection and phase correction circuit for out-of-phase driving of pulse width modulators, and is especially suitable for a switching power supply circuit where two pulse width modulators work synchronously. Background technique [0002] When two pulse width modulators work synchronously in a power system, the operating frequency of the two pulse width modulators is equal, and the two pulse width modulators will randomly enter the in-phase driving mode or out-of-phase driving mode when powered on model. Compared with the synchronous out-of-phase driving mode, the synchronous in-phase driving mode has the following disadvantages: (1) The power switch tubes driven by the two PWMs are turned on at the same time, so that the turn-on noise of the two power conversion circuits is superimposed, causing the power system switching The increase of noise will cause the power system to oscillate and lose working stability in serio...

AI Technical Summary

Problems solved by technology

Compared with the synchronous out-of-phase driving mode, the synchronous in-phase driving mode has the following disadvantages: (1) The power switch tubes driven by the two PWMs are turned on at the same time, so that the turn-on noise of the two power conversion circuits is superimposed, causing the power system switching The increase of noise will cause the power system to oscillate and lose working stability in serious cases; (2) The turn-off noise of the power switch tube driven by the two PWMs is sometimes superimposed, sometimes staggered, and the superposition of the turn-off noise is time-varying frequency, Thus weakening the filtering effect of the EMC filter at the power input end; (3) The fundamental frequency of the switching noise at the power input end is equal to the switching frequency, and the characteristic frequency of the electromagnetic compatibility (EMC) filter is low, and the filter volume is relatively large

Images