High power factor light-emitting diode (LED) driving power supply and control circuit thereof

Abstract

The invention relates to a high power factor light-emitting diode (LED) driving power supply system. The system comprises a rectifying circuit, a transformer, a power switch and a control circuit, wherein the rectifying circuit inputs alternating current voltage and outputs periodic rectifying voltage; the phase of the rectifying circuit is the same as that of the alternating current voltage; the transformer is provided with a primary winding, a secondary winding and an auxiliary winding; the power switch is coupled to the primary winding; the control circuit is coupled to the power switch; the current in the primary winding of the transformer is controlled by the power switch, so that the envelope of a peak value of a current impulse in the primary winding is kept the same as the phase of the alternating current input voltage of the rectifying circuit, and constant mean output current is output; the current impulse characteristic of the secondary winding of the power switch in every switching period is determined by the switch-on time and the switch-off time of a secondary rectifying device; and the ratio of the switch-on time to the switch-off time is controlled to be shown as a specific expression. Through the high power factor LED driving power supply system and the control circuit thereof, a high power factor and constant current output are realized without a secondary constant-current constant-voltage feedback control circuit in a broad alternating current input voltage range.

Description

technical field [0001] The invention relates to the technical field of high power factor LED driving power supplies, in particular to a high power factor LED driving power supply system and a control circuit thereof. Background technique [0002] When the switching power supply is used to drive the LED light-emitting diode, in order to keep the luminous brightness of the diode constant, the switching power supply is generally required to have the function of constant current output. In particular, if the switching power supply used to drive the light-emitting diodes can satisfy the constant output current in the full voltage range, the light-emitting diode bulbs will obtain the same brightness when used in places with different AC power specifications, which is beneficial to the popularization and production costs of light-emitting diode bulbs decrease. [0003] In addition, there are certain requirements for the power factor of the light-emitting diode bulbs connected to t...

AI Technical Summary

Problems solved by technology

However, the existing single-stage PFC flyback circuit requires a constant current constant voltage feedback control circuit and an optocoupler device on the secondary side of the transformer, resulting in a complex system, large circuit size and increased cost

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