in the high-frequency switching power supply, DC-DC conversion circuit, the power switch voltage dominated signal forced moderation is enlightened, the current is turned off, this working method is called hard switch. Traditional PWM switching methods belong to the hard-switching techniques, goes without saying that it's wrong.
(1) switch tube either turned on or off, voltages and currents are not zero, the sustain voltage of the power device, the current stress, the switch presence of power consumption, and the higher the switching frequency, the power consumption is greater .
(2) when the switch is off, the rational element in the circuit and the capacitive element will produce high amplitude peak voltage and peak current caused by the persecution of the switching devices, and the higher the switching frequency the greater infringement.
(3) followed by increased operating frequency will produce significant electromagnetic annoyance impact of the circuit and the grid and peripheral electronic equipment.
The shutdown process
Fantasy current first drops to zero, the voltage and then slow to rebound to the off-state value, and turn-off losses is approximately zero. As the power switch off before the current has landed to zero, which would address the rational off peak voltage problem, and fantasy conduction process is the voltage has dropped to zero first, the current and then slow to rise to the off-state value, conduction loss is approximately zero. The voltage on the power switch tube junction capacitance zero to solve the problem of the capacitive conduction current spikes. Know how hard switching decision brought a variety of adverse factors, has taken a variety of approaches. Which are soft switching quasi-resonant switching, Application resonance techniques, so that the power switch turned on and off to achieve zero voltage or zero current, underlying dispel switching losses. The resonance type switch can be divided into the zero-current switching type (ZCS) and zero-voltage switching the type (ZVS); the gripping manner divided into a pulse width modulation (PWM) and pulse phase shift grasp (PS). The actual utilization of the PWM soft switching converters are used for low-power DC-DC switching power supply PS soft switching converter for high-power DC-DC switching power supply.
following the first volume of the number of common soft-switching converter.
1 zero-current switching quasi-resonant converter
Figure 1 is a quasi-resonant converter zero-current switching (ZCS-QRC) fundamental circuit. Resonant capacitor C and the rectifier diode D connected in parallel, the resonant inductor and the active switch (transistor or an MOS transistor) S series. S is turned on and off at zero current, whereas D ON and OFF at zero voltage, Because the L and C resonance, generating an oscillating current through the S, and zero, which leads to a natural commutation. The characteristics of this circuit is to reduce the loss when the shutdown, but there capacitance loss at turn, when the stored energy in the capacitor in the S tube conduction spent in the tube S, and S tube is proportional to the switching frequency.
http://www.gridtieinverter.de/
zero-voltage switching quasi-resonant converter
Figure 2 is a quasi-resonant converter zero voltage switching (ZVS-QRC) based circuits. Resonant capacitor C and the active switching device S parallel resonant inductor L and D series, S just closed off, the voltage on the capacitor C is gradually picked up, and, with the inductor L resonance occurs, and thus S is turned on at zero voltage with Off off, and the rectifier diode D is turned on at zero current with the shutdown. The characteristics of this circuit is the voltage of the switching device is the whole constitutes a quasi-sine wave, zero voltage according to the invention for the switch is turned on premise, to reduce the loss when turned. There is a problem the switch tube there is excess voltage stress,power inverter, this stress is proportional to the size of the load, in addition to the rectifying diode junction capacitance and resonance inductance caused by the resonance will occur electromagnetic annoyance.
the
3 zero voltage switching multi-resonant converter
Figure 3 is zero voltage switching Multiresonant the converter fundamental circuit. Resonant capacitor C at the same time with the switch tube and diode in parallel,Grid tie inverter, so that S and D are able to zero voltage carried out the conversion, the interests of this circuit is a multi-resonant circuit to switch tube output capacitance diode junction capacitance, transformer leakage sense parasitic parameters amount to receive to the resonant circuit, greatly decrease the switching loss and noise. The defect of the circuit is the switching tube, the rectifier diode has suffered a large voltage and current.
沒有留言:
張貼留言