Please advise on the problem of unstable output of two power supply channels

kal9623287

Please advise on the problem of unstable output of two power supply channels [Copy link]

 

I would like to ask about the unstable power supply problem. If two output voltages are loaded at the same time, the voltage will be relatively stable. If one output voltage is loaded, the voltage of the other output voltage will float and deviate.

For example, 12V with 1.5A load, 5V no-load will float to 6V
5V with 1.5A load, 12V no-load will float to 13V

How to solve it?

maychang

[I would like to ask about the unstable power supply problem. If two output voltages are loaded at the same time, the voltage will be relatively stable. If a load is added to one output, the voltage of the other output will float and deviate.]

This thing is called cross regulation, which means that the load change of one channel affects the output of another channel.

maychang

How to solve it?

It is not possible to completely solve this problem unless two independent flyback switching power supplies are used.

chunyang

You can only add resistance as internal load, at the expense of reduced efficiency.

led2015

Does it mean that the design of the power supply is unreasonable? Maybe the load of the power supply is unbalanced?

dabiaoke

The cross regulation rate can be improved by increasing the feedback. The resistance of the feedback resistor is converted according to the load power. The resistance with high power is small.

nemo1991

This is an unsolvable problem, one primary side and two secondary sides, usually the main power supply is selected for feedback. The other one is without feedback.

For power supplies without feedback, additional converters can be added externally.

kal9623287

nemo1991 posted on 2023-3-20 20:24 This is an unsolvable problem. There is one primary side and two secondary sides. Usually the main power supply is selected for feedback. The other one is without feedback. For...

Can an additional converter be added externally?

How to calculate the power of this transformer?

Or is there any way to change the circuit?

不亦心

The consequence of weighted feedback is that both paths are unstable.

The solution is to redesign the transformer to ensure that the leakage inductance of the two secondary windings is as close to the square of the turns ratio as possible.

kal9623287

Bu Yixin posted on 2023-3-28 21:18 The consequence of weighted feedback is that both paths are unstable. The solution is to redesign the transformer to ensure that the leakage inductance of the two secondary windings is as close to the average turn ratio as possible...

Redesign the transformer?

Is there no way to change the circuit, teacher?

不亦心

kal9623287 posted on 2023-3-29 11:21 Redesign the transformer? Is there no way to change the circuit, teacher?

Put a 104 capacitor across the anodes of the two rectifier diodes to see if there is any improvement.

kal9623287

Bu Yixin posted on 2023-3-29 23:32 Put a 104 capacitor across the anodes of the two rectifier diodes to see if there is any improvement

OK, let’s test it first.