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提出了一种适用于反激式AC-DC芯片的高效、可修调振荡器电路。相对于传统的振荡器,增加了一块模式控制电路,通过检测负载反馈端电压,可灵活选择两种不同的工作模式,产生不同频率,从而实现芯片在所有负载下都可以保持较高的工作效率。修调电路可以对主电容充放电电流进行调节,实现频率抖动,从而减小EMI的影响。利用华润上华0.8μm 40V高压BCD工艺,对提出的电路进行仿真验证。结果表明,所有负载下变换器转换效率均可达到85%,负载变化时,频率可变范围为22～66kHz,修调电路实现4%的频率抖动。
An efficient and tunable oscillator circuit suitable for flyback AC-DC chips is proposed. Compared with the traditional oscillator, a mode control circuit is added. By detecting the voltage of the load feedback terminal, two different operating modes can be flexibly selected to generate different frequencies so that the chip can maintain high working efficiency under all loads . Trim circuit can charge and discharge the main capacitor current regulation, to achieve frequency jitter, thereby reducing the impact of EMI. The use of China Resources Shanghua 0.8μm 40V high voltage BCD process, the proposed circuit simulation. The results show that the conversion efficiency of the converter under all loads can reach 85%. When the load is changed, the frequency range is 22 ~ 66kHz, and the trimming circuit achieves 4% frequency jitter.