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Tell me please.
Power supply TOP223YN.
Typical Flyback Application.
There is a breakdown between the control input and the ground.
The voltage of the feedback winding is 15 volts.
The output voltage of the secondary winding is 14 volts. Current 1.4 amperes.
Or as not connected with the load. And moments of start or stop.

It would be helpful if you posted a schematic.
The control pin on a TOPSwitch is not like the feedback pin on a standard SMPS control IC - it is low impedance, so it can look like a short if you are not driving it properly. The TOPSwitch control pin is used both to power the IC and to control the duty cycle.
The traditional way to drive the TOPSwitch control pin is with the output of an optocoupler. If you choose an alternate means of regulation, you will need to drive the control pin with a suitable resistance so that there is sufficient current to satisfy both the supply and control current requirements for the TOPSwitch. This is covered in detail in the TOPSwitch data sheet.

Again, a schematic of what you are attempting would be helpful.

Good day!
The scheme is classic.

AC-DC_Converters.jpg134.82 KB

You shouldn't need a resistor in series with the optocoupler. The circuit looks more or less OK as presented. When you say there is a breakdown between control and ground, what is the circuit doing that leads you to make that conclusion?
BTW, you can check to make sure that the control pin is working properly by looking at it with a voltmeter or oscilloscope. As you slowly turn up the input voltage, the control pin should charge the 47 uF capacitor to ~ 5.7V, and the part should try to start. If you don't see this voltage, you could have a short somewhere on the control pin circuit or a bad part. That 47uF capacitor serves a double purpose as both energy storage and as frequency compensation . It is charged by a high voltage current source built in to the integrated switching fet. of the TOPSwitch.

Good day!

Periodically there is a breakdown between the ground and the control input. Defective PWM controllers?
Controllers work different times and then fail. There is no overload or overheating.

Where did you get the parts you are using? I have never encountered that sort of problem in my experience with the part.

Does the part recover from the breakdown? Also, if you look at the control pin with an oscilloscope, does the voltage collapse completely or to some intermediate level?

If the TOPSwitch temporarily loses feedback, the voltage at the control pin will ramp down to ~4.7V and initiate a restart.. Does the voltage in your case ramp down, or is it a more sudden collapse?