Switching power supply with constant current output and a method for controlling constant current of a switching power supply

Abstract

The application discloses a switching power supply with constant current output and a method for controlling constant current of a switching power supply, wherein the switching power supply comprises a detection circuit and a logic control chip, and the detection circuit is configured to output a feedback voltage. The feedback voltage is a sum voltage of a first voltage and a second voltage, and the second voltage represents output current of the switching power supply. The logic control chip is configured to receive the feedback voltage and compare the feedback voltage with a reference voltage. When the output current changes, the logic control chip changes turn on time of the switching power supply based on comparison result to control the output current constant. The reference voltage set by a switching power supply with constant voltage output is very high, while operating current requirement of constant current drive is very small, and the reference voltage is too high relative to the second voltage, so the first voltage is introduced to bear part of the reference voltage, so that constant current reference is lowered, so as to take into account needs of constant current drive and power consumption.