This may sound a nonsense question for some of you but I was trying to visualize how an SMPS initializes. Below is a block-diagram taken from a particular SMPS datasheet: http://docs-europe.electrocomponents.com/webdocs/0e77/0900766b80e777c4.pdf
And before posing my question, I would like to make the assumption that all the electronic circuitry in an SMPS is DC powered by the SMPS’s DC output itself. So I assume there is no internal battery or such sort of thing.
If the above statement is true, here is my confusion as follows:
Let’s say the SMPS is switched on, and we started to observe what is happening inside the circuit at an extremely slow motion. My logic says that first the AC input power is delivered to the rectifiers and then rectified to a DC voltage. So far so good.
But just after that moment, the electronic circuitry should start chopping the DC voltage with PWM to provide a high frequency AC for the transformer. But for that to happen the electronic circuitry should already been supplied with a DC voltage which were not created yet at the output.
How initially the electronic circuitry gets DC voltage is very peculiar and confusing for me.
Does anyone have an idea?