RC absorption circuit capable of improving EMC performance

Abstract

The invention discloses an RC absorption circuit capable of improving EMC performance. The RC absorption circuit comprises a power supply Vi and a field effect transistor Q1, the positive electrode ofthe power supply Vi is electrically connected with the drain electrode of the field effect transistor Q1, and the source electrode of the field effect transistor Q1 is electrically connected with thenegative electrode of the power supply Vi orderly via an inductor Lp1, an inductor Lp3, a diode D1, an inductor LP4 and an inductor Lp5. The two ends of the diode D1 are connected with capacitors CDin parallel, and the common connection end of the inductor Lp1 and the common connection end of the inductor Lp3 are electrically connected with the common connection end of the inductor Lp4 and the common connection end of the inductor Lp5 orderly via a capacitor Csnub and a resistor R. According to the RC absorption circuit capable of improving the EMC performance, the RC absorption circuit is placed on an energy switch switching point or in a ringing loop, the RC absorption circuit can change the ringing frequency, meanwhile, the capacitance effect of the RC absorption circuit can reduce dV/dt of a switch node, and therefore EMI is effectively restrained.

Description

technical field [0001] The invention belongs to the technical field of automotive electronics, and in particular relates to an RC snubber circuit for improving EMC (Electro Magnetic Compatibility, electromagnetic compatibility) performance. Background technique [0002] In the switching power supply and class D power amplifier of the car, due to the existence of parasitic parameters, the switching power supply circuit will produce switching ringing at the moment of switching action. The typical waveform of the switching node of the existing buck circuit (the junction of the two switches and the inductor), it can be seen that there are different degrees of ringing at the moment when the upper transistor is turned on. The existence of ringing may cause the switch tube to withstand a voltage exceeding its withstand voltage value and cause breakdown; on the other hand, the switch ringing is a high-frequency ringing far exceeding the switching frequency, accompanied by high dV / dt...

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Problems solved by technology

[0003] In general, in order to solve this problem in automotive electronic systems, common measures include optimization of wiring to reduce parasitic parameters of the line; selection of devices with good reverse characteristics of diodes; reduction of switching speed; the use of LC filter circuits in the front and rear stages, although it also plays a role The effect of suppressing low-frequency EMI, but in the high-frequency part of RE and CE, the effect is not very ideal. This is because the PCB area occupied by the LC circuit is used, and the current loop is also enlarged. Since any transmission line inevitably exists lead resistance, lead inductance, and stray capacitance due to

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