Here is a flyback switching power supply circuit built using UC2844. There is a problem

西里古1992

Here is a flyback switching power supply circuit built using UC2844. There is a problem [Copy link]

 

The LC filter circuit composed of the L1 inductor and the C17 capacitor shown in the figure was used in the previous TOP series or other switching power supply circuits without any problems. Then, after the transformer was redesigned using UC2844, the transformer made a very loud and harsh sound under full load conditions after power-on. After removing L1, the sound became much smaller. What's going on?

maychang

From the last schematic diagram, the feedback is sampled from the right side of L1 through L2. After L1 is short-circuited, the open-loop amplitude-frequency and phase-frequency characteristics of the feedback loop are changed.

maychang

Do you have an oscilloscope? Use it to check if there is a large audio ripple across R20.

tagetage

Agree with what was said above, let's take a look at the waveforms at both ends of L1.

led2015

Recalculate and adjust the values of L1 inductance and C17 capacitance.

不亦心

This question has been asked before, the diagrams are the same. The optocoupler and 431 power supply is taken from C15

西里古1992

led2015 posted on 2024-9-21 19:57 Try recalculating and adjusting the values of L1 inductance and C17 capacitance

The L1 inductance was adjusted around 4.7uH, and changed to 3.3uH and 6.8uH, but there was no effect

西里古1992

maychang posted on 2024-9-21 15:02 From the last electrical schematic diagram, the feedback is sampled from the right side of L1 through L2. After L1 is short-circuited, the open-loop amplitude-frequency and phase-frequency characteristics of the feedback loop are changed.

Other power supply solutions also use this circuit and inductance value, no problem

maychang

Sirigu1992 posted on 2024-9-29 11:05 Other power supply solutions also use this circuit and inductance value, no problem

[Other power supply solutions also use this circuit and inductance value, no problem]

Weather forecasts now report pollen concentrations every day. Most people will have no problems breathing in these pollens, but some people do have problems breathing in certain types of pollen, sneezing, tearing, or even asthma, which can be life-threatening.

Is your [other power supply] exactly the same as the circuit in the first post?

maychang

Sirigu1992 posted on 2024-9-29 11:05 Other power supply solutions also use this circuit and inductance value, no problem

[Other power supply solutions also use this circuit and inductance value, no problem]

Pay attention to Bu Yixin’s reply on the 6th floor.

西里古1992

maychang posted on 2024-9-29 11:17 [Other power supply solutions also use this circuit and inductance, no problem] Now the weather forecast reports the pollen concentration every day. Most people inhale these...

The transformer is different, and the TOP series tubes are used on the primary side, and the secondary side is the same.