Constant current control circuit of power converter and its constant current control method

Abstract

The application discloses a constant current control circuit of a power converter and a constant current control method thereof. The constant current control circuit includes a sample and hold unit, coupled to the current detection resistor of the power converter, for storing the current detection voltage of the current detection resistor; a first capacitor, for storing the comparison voltage; a discharge unit, coupled to the sampling Between the holding unit and the first capacitor, it is used to control the discharge current of the first capacitor according to the reference voltage and the current detection voltage stored in the sample and hold unit; the charging unit, coupled to the first capacitor, is used to control the discharge current of the first capacitor according to the reference voltage and the ground voltage controlling the charging current of the first capacitor; and a comparator, used for comparing the comparison voltage and the reference voltage to generate a comparison result, and outputting a control signal according to the comparison result to control the working cycle of the power converter. The above solution can improve the line regulation rate of the power converter to provide a more stable power supply.

Description

technical field [0001] The present application relates to a constant current control circuit of a power converter, in particular to a constant current control circuit of a power converter capable of improving line regulation and a related constant current control method. Background technique [0002] see figure 1 , figure 1 It is a schematic circuit diagram of a power converter in the prior art. Such as figure 1 As shown, the power converter 100 in the prior art includes a power switch 110 and a current detection resistor Rs, the power switch 100 is coupled to the main winding P1 of the power converter 100 , and the current detection resistor Rs is coupled to the power switch 110 . In order to control the power converter 100 to operate in the constant current mode, the control circuit 120 of the prior art power converter 100 controls the on and off states of the power switch 110 according to the current detection voltage Vcs of the current detection resistor Rs, so that ...

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Problems solved by technology

Therefore, if Figure 4 As shown, when the input voltage Vin of the power converter 100 of the prior art changes, the average output current Io of the power converter 100 of the prior art fluctuates greatly, that is to say, the power converter 100 of the prior art has a constant Poor line regulation in current mode

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