Constant current switching power supply and its constant current controller

Abstract

The invention relates to a constant current switching power supply and a constant current controller of the constant current switching power supply. The constant current controller comprises a FB waveform detecting module, a triangular wave generating module, a waveform control module and an output module, wherein the FB waveform detecting module, the triangular wave generating module, the waveform control module and the output module are connected in sequence. The waveform control module is used for receiving triangular waves output by the triangular wave generating module and for controlling output voltage waveforms of the output module according to triangular wave output control signals, so that the output voltage waveforms of the output module have periodic variation, moreover each period comprises a plurality of pulses, and the interval between any two adjacent pulses is unequal to others. The constant current switching power supply comprises a transformer, a voltage division circuit, a main switch tube, an output circuit and the constant current controller. The constant current switching power supply and the constant current controller can achieve switch frequency jittering, are conducive to reduction of the peak level of electromagnetic interference and to reduction of design cost of a system EMI filter, and meanwhile maintain high-precision constant current output.

Description

technical field [0001] The invention relates to the field of switching power supplies, more specifically, to a constant current switching power supply and a constant current controller thereof. Background technique [0002] figure 1 It is a schematic circuit diagram of a constant current controller in PFM mode in the prior art. Such as figure 1 As shown, the existing constant current controller in PFM mode includes an FB waveform detection module 100 , a triangular wave generation module 200 , a comparator 250 and an output module 400 connected in sequence. figure 2 It is a working waveform diagram of a constant current controller in PFM mode in the prior art. From figure 2 It can be seen that after the system is stable, Tons and T of the existing PFM mode constant current controller remain unchanged for a certain specific output power, so the switching frequency of the existing PFM mode constant current controller (i.e. Operating frequency) f=1 / T is fixed, and its ou...

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Problems solved by technology

[0003] However, the peak level of electromagnetic interference in the circuit is related to the switching frequency of the constant current controller. When the switching frequency of the constant current controller is fixed, the peak level of electromagnetic interference is relatively large, which is not conducive to the EMI filter design, which increases the design cost of the system EMI filter

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