Ring-type switching power supply constant current drive circuit diagram

Published:2011/3/30 3:29:00 Author:Nicole | Keyword: switching power supply, constant current drive | From:SeekIC

It is essentially a simple series regulator. The load is a fixed resistor RB. Even if the input voltage Ui changes, the current flowing through RB is constant. This will not only significantly reduce the loss of the resistance, but also to prevent intermittent oscillation. AC is in range of 100 ~ 200V, the power can work continuously. In the ring-type switching power supply, the loss of the drive circuit of supply switching transistor base current is considerable. In addition to ensuring the switching transistor can fully turn with the minimum input voltage, the voltage UB on the transformer winding is in direct proportion to the input voltage Ui. when Ui rises, the drive current Id increases too, and the incremental losses of the base resistance Rb, can increase with the square of increasing part of Id. When the drive current ID is increasing, the current of the branch of regulator diode must be increased, it may cause oscillation, that is, the switching works in a period of time, but will stop working in the adjacent time. Over and over again, the frequency of oscillation is about several hundred to several thousand Hertz. To solve these problems, that is, when the input voltage changes, it can adopt constant current drive to remain drive current unchanged, as shown below.



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