A line voltage compensation circuit and compensation method thereof

Abstract

The present invention provides a line voltage compensation circuit and a compensation method thereof, which are applied to an LED drive circuit or an AC / DC constant current circuit. The line voltage compensation circuit includes: a line voltage sampling module for sampling the primary side line voltage of a transformer, And comparing the sampling voltage with the shutdown threshold voltage, generating a first processing signal when the sampling voltage is less than the shutdown threshold voltage, and generating a second processing signal when the sampling voltage is greater than or equal to the shutdown threshold voltage; The off-delay adjustment module is connected to the line voltage sampling module, and is used to process the preset on-off signal and the first processing signal or the second processing signal to generate a switching signal, so as to adjust different line voltages based on the switching signal The turn-off delay of the lower primary switching tube is used to adjust the actual turn-on time of the primary switching tube under different line voltages, so that the primary input currents under different line voltages are equal. The invention solves many problems existing in the existing line voltage compensation circuit.

Description

technical field [0001] The invention relates to the field of integrated circuit design, in particular to a line voltage compensation circuit and a compensation method thereof. Background technique [0002] In linear drive circuits and AC / DC constant current circuits for loads such as LEDs, an open-loop working mode is often used; in order to achieve a constant and accurate input current, it is required that the peak current ipk of the primary side should be kept constant under different line voltages. [0003] The traditional line voltage compensation circuit is generally as figure 1 As shown, in an ideal situation, there is no switching delay in the control system, and Vref is used as the turn-off threshold for different line voltages. At this time, Vref=ipk_th×Rcs, that is, ipk_th is used as the turn-off threshold for different line voltages, then the LED drive The input current ipk of the primary side of the circuit or AC / DC constant current circuit is consistent, specif...

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Problems solved by technology

[0007] 2. Since the turn-off threshold Vref is a value with a weak temperature coefficient, it is best not to introduce another temperature coefficient in the superimposed compensation range, but figure 1 The line compensation circuit shown introduces additional temperature coefficient error due to the design of the fixed offset comparator (consisting of a resistor and a current source)

[0008] 3. Since different line voltages correspond to different turn-off thresholds (ie ipk_thH and ipk_thL), different ipks need to be tested separately during chip testing, and the testing process is complicated

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