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Solution to the Loss Problem of Key Switch Circuit

Release Time:2019-02-26

How to deal with the serious circuit loss when the key switch is used? Dongguan Dongkun Electronic Technology Co., Ltd. has said that today we will solve this problem.
The lower the output voltage of the key switch, the greater the influence of the rectifier voltage drop. If the output voltage is less than 5V, synchronous rectification must be used to achieve efficiency of more than 80%. But synchronous rectification makes the circuit complex, and at high frequency, the driving loss will increase significantly, which limits the improvement of efficiency. When the output voltage increases, the diode reverse recovery loss and buffer circuit loss will increase significantly. The conduction voltage drop of rectifier tube in low output voltage power supply is the main factor affecting the efficiency of the whole machine. The conduction loss can be estimated by multiplying the forward voltage drop of the diode by the output current.
The filter loss Pf of Dongguan key switch includes filter inductance loss and capacitance loss. If the inductor is in continuous mode, the main loss is the coil loss, and the core loss can be neglected. In the continuous mode of inductance, the ripple current of capacitor is smaller, and the capacitance loss is smaller. The total filter loss is less than 1% of the output power. If it is a flyback transformer, the Resr loss of the capacitor increases greatly, and the filter loss is the capacitor loss. Rectifier circuit loss Pr includes conduction loss caused by forward voltage drop of rectifier tube, turn-off loss caused by reverse recovery, and buffer circuit loss to avoid oscillating diode.
Under these conditions, the key switch can control the circuit loss well, so that there is no more excessive loss.


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