Resonant switch original buried

We call the switching converter that controls the switch on-time ratio pulse width modulation, or PWM for short. It is a switching converter with excellent control performance and has been widely used in electronic equipment. However, the proportion of its transformers, reactors and other magnetic devices and smoothing capacitors in the power supply volume is too large, and the switching frequency is subject to certain restrictions. It is far behind the corresponding development of electronic equipment itself in terms of small size, light weight and low cost. This is a problem that cannot be ignored in the development of today's electronic equipment. The resonant converter is a circuit method that is being researched and developed to solve such problems in switching regulated power supplies. The principle of resonant switching is as shown in the figure: Figure (a) is the current resonance type; Figure (b) is the voltage resonance type. During the current resonant conduction, the current waveform is sinusoidal; when the conduction time is about to end, the current is reduced to 0A, thus reducing the switching loss during startup and shutdown to zero, and also reducing the inrush current. This method is called zero current switching method. A switching method opposite to this zero-current switching method is zero-voltage switching. Its action is dual to that of a current switch. It reduces switching losses and surge voltage by making the voltage on the switch sinusoidal during the on and off times and reducing the voltage to zero before the next turn off. In this case, it is set that the current resonance type is driven by a voltage source, and the voltage resonance type is driven by a current source. Moreover, in Figure (b), when the current flowing to the diode in parallel with the switch changes direction, the switch is already in the off state, so it will not be affected by the diode storage effect. It can be seen that zero voltage is a circuit method more suitable for high-frequency switching than zero current switching.