Circuit for reducing total harmonic distortion and increasing power factor

Abstract

The invention discloses a circuit for reducing total harmonic distortion and increasing a power factor. The circuit comprises a control circuit, an on-time generation circuit, a logic circuit and a switching circuit, wherein the control circuit acquiring an input voltage Vin change to generate a time signal A and feeds the time signal A back to the logic circuit. The on-time Ton generation circuitgenerates a time signal PWM. When the input voltage Vin is high, the logic circuit determines that the time signal PWM fed back by the on-time Ton generation circuit is the on-time Ton. When the input voltage Vin is low, the logic circuit determines that the time signal A fed back by the control circuit is the on-time Ton. A delay time inversely proportional to the input voltage is generated at the input voltage valley to prolong the on-time, thereby reducing the total harmonic distortion and increasing the power factor of a voltage-source system.

Description

technical field [0001] The invention belongs to the field of voltage source integrated circuits, in particular to a circuit for reducing total harmonic distortion and improving power factor. Background technique [0002] In AC-DC power supply, fluorescent lamp drive, and LED drive systems, low power factor PF will cause harm to interference circuit voltage and increased system loss. In the prior art, it is improved by controlling the on-time Ton. [0003] The power factor PF is the ratio of active power to apparent power in the system, [0004] PF=P 有功功率 / P 视在功率 =cosα / (1+THD 2 )1 / 2, [0005] Among them, α is the phase difference between the current fundamental wave and the voltage signal, and THD is the total harmonic distortion. [0006] Low power factor PF will cause interference circuit voltage and increase system loss. The active PF correction circuit is widely used in power supply, fluorescent lamp drive, LED drive and other fields to realize the function of impro...

AI Technical Summary

Problems solved by technology

However, the duty cycle D decreases with the increase of the circuit voltage Vin, and the average value Iav of the input current Iin is not proportional to the circuit voltage Vin

The active power factor correction circuit with a fixed on-time Ton only guarantees that the peak value Ipk of the instantaneous current I is proportional to the circuit voltage Vin, and cannot guarantee that the average value Iav of the input current Iin is proportional to the circuit voltage Vin, so the conventional technology Only the fixed on-time Ton is controlled, and a lower THD value cannot be achieved

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