Can you make a 20-265V ultra-wide input flyback power supply?

As a beginner in power supply , I cannot produce any decent work. Recently, I have been studying a power supply that claims to have an ultra-wide input range. I have some experience with it. I would like to share it with you here and hope it will be useful to you.

How wide is the ultra-wide input range? Currently, the input voltage is as low as 20V and as high as 265V. Of course, from the test results, the range should be wider; the output is 5V/1A, and the output ripple is temporarily set to be less than 100mVpp. The basic idea is: single-ended flyback , current control mode, and discontinuous mode. The actual picture of the PCB proofing is posted here:

The picture is very clear, even the IC and resistance can be seen, everyone can see that the IC is the universal UC3843, so if you want me to put a schematic diagram, it is not necessary. Here I tell you that the switching frequency is set at 40KHz, and a 1N60 MOS tube is used alone to make a current source to start, and then shut down. As for the rest of the circuit, it is no different from the configuration of the regular 3843. First, let's take a look at the test waveform under DC20V:

The first is the MOS tube drain voltage, which remains in DCM under full load and minimum input. The second figure is the output ripple, which is measured directly with a ground clamp and is within 50mVpp. The frequency is the ripple of the switching frequency. It is estimated that if better capacitors are used, it can be further reduced.

20VDC is a test for the switch tube. This 5W power supply may need a 10A MOSFET to maintain low conduction loss. Fortunately, the driving capability of 3843 is acceptable. The input rectifier bridge is also under great pressure. The corresponding current will be calculated together with the transformer design later .

Next, let's look at the test waveforms at 265VAC. First, the gate voltage at full load.