AC-DC (alternating current-direct current) regulator with high-precision constant current output function

Abstract

The invention relates to an AC-DC (alternating direct-direct current) regulator with a high-precision constant current output function. The regulator comprises a transformer and a power tube which is connected at a main winding side of the transformer, wherein the voltage corresponding to main winding current is higher than reference voltage; and a grid of the power tube is controlled to be turned off. The regulator is characterized by comprising a delay locking ring and a reference voltage adjusting circuit, wherein the delay locking ring is used for comparing a first lasting time spent on that the main winding current rises up to a peak value and a second lasting time spent on that the main winding current expectedly rises up to a goal current value; and the reference voltage adjusting circuit is used for adjusting the reference voltage by utilizing the comparing result. According to an AC-DC circuit with high precision, disclosed by the embodiment of the invention, the output current can not be different along with different saturation deterioration times of devices and can not be different along with different stray capacitance values and the like generated by the devices and PCBs (printed circuit boards), so that constant current values of products can be output with the high precision.

Description

technical field [0001] The invention relates to an AC-DC regulator with high precision constant current output. Background technique [0002] In flyback AC-DC applications, it is sometimes necessary to implement a constant voltage constant current (CV / CC) characteristic for the secondary output. figure 1 A circuit for realizing constant current is shown, figure 2 signaled figure 1 The output waveform of the circuit. In practice, when the current limit signal (OCP) turns off the power transistor Q0, due to the existence of the desaturation time of the power transistor and the charging and discharging time of the parasitic capacitance (total Td), the inductor current of the main winding continues to rise, The secondary rectifier has current output until flyback. During this period of time, the actual peak value of the inductor current of the main winding is greater than the target value, and the desaturation time of the power tube varies with the difference of the device,...

AI Technical Summary

Problems solved by technology

During this period of time, the actual peak value of the inductor current of the main winding is greater than the target value, and the desaturation time of the power tube varies with the difference of the device, and the size of the parasitic capacitance is different from the difference between the circuit PCB wiring and the transformer and other devices, so the difference between the products The current constant current characteristic deviation is relatively large, and the accuracy is low

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