An anti-ringing circuit

Abstract

The invention belongs to the field of electronic technology, and in particular relates to an anti-ringing circuit. The present invention mainly uses a synchronous rectifier gate discharge circuit, the circuit does not immediately turn off the synchronous rectifier after zero crossing, but quickly discharges the synchronous rectifier grid to a very low potential to make its weak conduction When the voltage at both ends of the inductor is equal, the synchronous rectifier is completely turned off. At this time, the circuit is in a steady state, and SW will be stable and equal to the output voltage without oscillation, thus achieving the effect of anti-ringing.

Description

Technical field [0001] The invention belongs to the technical field of BUCK type DC-DC converters, and specifically 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 rectifier switch tube, and the capacitor C is the parasitic capacitance between the drain of PCH and NCH and the ground. In CCM mode, the inductor current does not cross zero during the entire cycle, and the capacitor C is The synchronous rectifier tube is short-circuited by NCH when it is turned on. When the power upper tube is turned on, it is short-circuited by the low-impedance circuit formed by the PCH and the power supply, so there will be no oscillation. However, in DCM mode, when the circuit crosses zero, the upper and lower tubes are closed at the same time. There is no low-impedance loop to short-circuit C. Therefore, the parallel connection of inductance L, p...

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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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