隔离变换器输出带预偏置电压启动的研究

Start-up Scheme for Isolated DC/DC Converters with Output Pre-bias Voltage

详细分析了采用同步整流的DC/DC隔离变换器在输出有预偏置电压情况下不能正常启动的原因。在现有解决方案的基础上提出了一种控制简单,可靠性高的启动方案。该方案仅仅是在启动时使同步整流管的脉宽由传统的从大到小变成从小到大,而不改变模块在稳态时的性能。与现有方案相比,新方案具有一致性好,成本低,效率高的优点。现以一个48V输入,3.3V/100W输出的有源箝位正激变换器为例,验证了它的工作原理,给出了其实验结果。

This paper presents a simple method for start-up of isolated DC/DC converter with output pre-bias voltage after analyzing the cause of abnormal start-up.The new scheme only changes the duty cycle of synchronous rectifier MOSFET when starting up without changing the stable performance of the converter.Compared with conventional schemes,the new scheme has the advantages of well consistency,low cost and high efficiency.A 48V input, 3.3V/100W output active clamp forward converter is built and experimental results are presented to verify the principle of the proposed scheme.