Automatic clamping circuit

Abstract

The invention relates to an automatic clamping circuit which comprises a clamping switch M1, a master power switch M2, a first diode D1, a second diode D2, a first resistor R1, a first capacitor C1 and a coil N1, when the clamping switch M1 is MOSFET, a grid electrode and a source electrode of the clamping switch M1 is respectively connected with a cathode and an anode of the first diode D1, and the grid electrode and a drain electrode are respectively connected with a cathode and an anode of the second diode D2; a drain electrode of the master power switch M2 is connected with a cathode of the first diode D1 in series, an anode of the first diode D1 is connected with the coil N1 in series, and the first resistor R1 is connected with the cathode and the anode of the first diode D1 in parallel to form an RD parallel circuit; the first capacitor C1 is connected with a drain electrode of the clamping switch M1 to form a series circuit, and the series circuit is connected with the coil N1 in parallel to form a closed circuit; the first capacitor Ci is controlled by the clamping switch M1 and is used for releasing and absorbing partial energy of the coil N1.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a switching converter with voltage clamping. Background technique [0002] At present, the main power switch M2 of the switching power supply generally uses a MOSFET or a triode. At the moment when the main power switch M2 is turned off, the leakage inductance causes a high peak voltage. The existing technology uses an RCD or a complex active clamping circuit to deal with it. For this peak voltage, the traditional RCD consumes this part of energy through resistance heating, which reduces the efficiency of the converter; the use of the existing active clamp is better than the RCD method, but because the drive of the clamp switch M1 is floating, Therefore, complex driving technology must be used to control the on and off of the clamp switch M1, so a complex and expensive IC is required, and the number of auxiliary devices is large, the cost is high and it is suscep...

AI Technical Summary

Problems solved by technology

[0002] At present, the main power switch M2 of the switching power supply generally uses a MOSFET or a triode. At the moment when the main power switch M2 is turned off, the leakage inductance causes a high peak voltage. The existing technology uses an RCD or a complex active clamping circuit to deal with it. For this peak voltage, the traditional RCD consumes this part of energy through resistance heating, which reduces the efficiency of the converter; the use of the existing active clamp is better than the RCD method, but because the drive of the clamp switch M1 is floating, Therefore, complex driving technology must be used to control the on and off of the clamp switch M1, so a complex and expensive IC is required, and the number of auxiliary devices is large, the cost is high and it is susceptible to interference, and the reliability is difficult to improve; Figure 1 It is a circuit structure diagram of a traditional converter with RCD absorption. Figure 2 is a voltage waveform diagram between the drain and source of the main power switch M2. The peak voltage can be read as 850V, and there are multiple ringings, which will generate poor EMI; image 3 It is a known active clamping circuit. In the figure, PWM1 is a pulse width modulation signal generated by the main control chip, which is used to drive the main power switch M2; PWM2 is another floating pulse width modulation signal generated by a high-cost chip. Used to drive clamp switch M1

Images