Control circuit of electric power converter

Abstract

The invention relates to a control circuit of a power converter. The control circuit outputs a switching signal to control a switch of the power converter and further to control the output power of the power converter and comprises an oscillator and a frequency eliminator. The oscillator generates a pulse signal and is coupled with the frequency eliminator, the frequency eliminator, is used for eliminating the frequency for the pulse signal to generate a control signal with a fixed pulse width, and the fixed pulse width controls the maximum turn-on time of a switching period of the switching signal, so as to really control the maximum turn-on time of the switch and further the maximum output power of the power converter. The invention can accurately control the maximum output power of theconverter and enhance the stability as well.

Description

technical field [0001] The present invention relates to a power converter, in particular to a control circuit of the power converter. Background technique [0002] Nowadays, due to the advancement of science and technology, many electronic products have been developed to meet the needs of the people. The functions of these electronic products are becoming more and more powerful, and bring many conveniences to the lives of the people today. Most of the current electronic devices require a power converter, which receives an input power and outputs a regulated output power according to the input power to provide the power required by the electronic device. [0003] see figure 1 , which is a circuit diagram of a prior art power converter. As shown in the figure, the prior art power converter includes a transformer T 1 , which has a primary winding NP and a secondary winding N S , primary side winding N P One end is coupled to an input voltage V IN , primary side winding N ...

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Problems solved by technology

However, when the high threshold signal V H , low threshold signal V L When one of the parameters of the reference voltage level drifts, the pulse width of the control signal MDC will drift, so the switching signal V PWM The switching period will drift with the

In addition, since the sawtooth wave generating circuit 10 is susceptible to interference or other factors, it cannot generate an accurate sawtooth wave signal V SAW , so with the reference voltage (V H +V L / 2) After the comparison, the pulse width of the generated control signal MDC cannot be precisely fixed, so the switching signal V PWM The maximum on-time of the switch will be affected, so that it is impossible to precisely control the switch Q 1 The maximum on-time of the power converter cannot be accurately controlled.

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