Anti-ringing circuit

Abstract

The present invention belongs to the field of the electronic technology, and specifically relates to an anti-ringing circuit. A synchronization rectifier tube grid discharging circuit is employed, after a circuit is zero crossing, the synchronization rectifier tube is not closed immediately, and the synchronization rectifier tube grid rapidly discharges to a low potential to perform weak conduction, when the voltages at two ends of the inductor is equal, the synchronization rectifier tube is thoroughly turned off, and the circuit is located at a stable state, the voltage of a SW is equal to the output voltage without oscillation, therefore the anti-ringing effect is reached.

Description

technical field [0001] The invention belongs to the field of electronic technology, and in particular relates to an anti-ringing circuit. Background technique [0002] In the general BUCK type DC-DC converter architecture, such as figure 1 As shown, PCH is the power upper tube, NCH is the synchronous rectification switch tube, and capacitor C is the parasitic capacitance between the drains of PCH and NCH to ground. In CCM mode, the inductor current will not cross zero in the whole cycle, and the capacitor C is at When the synchronous rectifier tube is turned on, it is short-circuited by NCH, and when the power top tube is on, it is short-circuited by the low impedance loop formed by PCH and the power supply, so there will be no oscillation phenomenon. However, in DCM mode, when the circuit crosses zero, the upper and lower tubes are turned off at the same time. There is no low-impedance loop to short-circuit C. Therefore, the parallel connection of the inductance L, the par...

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Problems solved by technology

[0002] In the general BUCK type DC-DC converter architecture, such as figure 1 As shown, PCH is the power upper tube, NCH is the synchronous rectification switch tube, and capacitor C is the parasitic capacitance between the drains of PCH and NCH to ground. In CCM mode, the inductor current will not cross zero in the whole cycle, and the capacitor C is at When the synchronous rectifier tube is turned on, it is short-circuited by NCH, and when the power top tube is on, it is short-circuited by the low impedance loop formed by PCH and the power supply, so there will be no oscillation phenomenon. However, in DCM mode, when the circuit crosses zero, the upper and lower tubes are turned off at the same time. There is no low-impedance loop to short-circuit C. Therefore, the parallel connection of the inductance L, the parasitic capacitance C, the load capacitance CL and the load resistance R together constitutes the LC oscillation loop, and the SW terminal will form an obvious high-frequency oscillation. The fundamental wave of these oscillations Harmonics may be coupled to sensitive circuits such as RF through the magnetic field leakage of the inductor or parasitic capacitance, affecting the normal operation of the circuit

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