Switch power supply controller and switch power supply including the switch power supply controller

Abstract

The invention provides a switch power supply controller of a voltage reduction structure and a switch power supply including the switch power supply controller. The switch power supply controller comprises a zero cross detection circuit, a variable conduction time length control circuit and a driving signal generation circuit. The variable conduction time length control circuit receives a compensation voltage and a driving signal of a switch tube so that a conduction time square of the switch tube of the switch power supply is inversely proportional to turn-off time of the switch tube and is directly proportional to a switch period square of the switch tube, and a turn-off signal is generated. The driving signal generation circuit generates a driving signal according to a zero-cross signal and the turn-off signal. The driving signal is transmitted to a grid end of the switch tube and responds to the zero-cross signal. The driving signal controls conduction of the switch tube and responds to the turn-off signal. The driving signal controls turn-off of the switch tube. By using the controller and the power supply of the invention, a power factor of the switch power supply controlled by a critical conduction mode of the voltage reduction structure can be optimized and total harmonic distortion is reduced.

Description

technical field [0001] The invention relates to switching power supply technology, in particular to a switching power supply controller with power factor adjustment function and critical conduction mode control in a step-down structure, and a switching power supply including the switching power supply controller. Background technique [0002] Traditional AC power supply, with power factor adjustment (PFC) function, buck structure LED constant current driver in critical conduction mode such as figure 1 As shown, it mainly includes: AC input rectifier circuit 101 , AC input source 102 , input capacitor Cin, inductor L1 , switch tube M1 , sampling resistor Rs, freewheeling diode D1 , output capacitor Cbulk, and constant current switching power supply controller 100 . Wherein, the constant current switching power supply controller 100 is used to receive the feedback signal FB, and the sampling resistor Rs samples the output current to drive the switch tube M1. [0003] Wherein,...

AI Technical Summary

Problems solved by technology

However, with a fixed on-time (T on constant), critical conduction mode control, the input current I in cannot fully follow the input voltage V in changes, the power factor becomes worse, and the total harmonic distortion increases, so the power factor of the current traditional circuit is not particularly ideal, and the total harmonic distortion is also relatively large

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