Primary edge current reference generating circuit and method for high power factor constant-current switch power supply

Abstract

The invention relates to a primary edge current reference generating circuit and a primary edge current reference generating method for a high power factor constant-current switch power supply. The conventional primary edge current reference generating circuit is complicated. An input end of a first multiplier is used as an input end of the primary edge current reference generating circuit; an input end of a conduction angle detection circuit is used as another input end of the primary edge current reference generating circuit, and the output end of the conduction angle detection circuit is connected with another input end of the first multiplier; the output end of the first multiplier is used as an input end of a current loop; another input end of the current loop is used as the other input end of the primary edge current reference generating circuit; the output end of the current loop is connected with an input end of a second multiplier; another input end of the second multiplier is connected with the input end of the conduction angle detection circuit; and the output end of the second multiplier is used as the output end of the primary edge current reference generating circuit. Sampling hold is not required, so that the error caused by sample hold is eliminated, and the constant-current precision of the output current is improved.

Description

technical field [0001] The invention belongs to the technical field of switching power supplies, and relates to a primary side current reference generation circuit and method of a constant current switching power supply with high power factor. Background technique [0002] At present, many isolated power supplies such as mobile phone chargers and high-power LED drivers usually require the circuit to have the function of outputting constant current due to application requirements; IEC1000-3-2, etc., the above isolated power supply must also have power factor correction (PFC) function, figure 1 It is a commonly used single-stage power factor correction scheme at present: by detecting the output current on the secondary side of the transformer, after the secondary side is controlled by constant current, it is fed back to the primary side PFC control circuit through the optocoupler. figure 1 In the prior art solution shown, due to the existence of the secondary side current sam...

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Problems solved by technology

However, in the presence of a phase-controlled dimmer, the AC input signal will be missing when the dimming angle is different, and its rectification is no longer a complete half-wave, so the input feedforward signal Vff contains the phase-cut angle signal, The voltage feed-forward control will cause Iref to increase sharply with the increase of the phase-cut angle, and the input power will also increase sharply, so the above method is not suitable for the occasion of phase-controlled dimming

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