TIDA-010071: TIDA-010071, AUX Power(+13V), VS

Hello, 

"TIDA-010071 In which part of the AUX POWER circuit should the element value be changed?"

can you please elaborate more on your question? 

The CH3 Vds at switching node waveform looks as expected. Can you pls describe more on VS (prim vol sense) circuit? e.g. a snapshot of the circuit

Regards

Lei 

Hello, 

"TIDA-010071 In which part of the AUX POWER circuit should the element value be changed?"

can you please elaborate more on your question? 

The CH3 Vds at switching node waveform looks as expected. Can you pls describe more on VS (prim vol sense) circuit? e.g. a snapshot of the circuit

Regards

Lei 

The TIDA-010071 circuit has been changed and is being used. The output voltage keeps going up and down repeatedly.

Regard

Jaeyup

Hello

do you have a scope pic of output voltage? at which load condition? 

Thanks 

Lei

Thanks for your help. First, when a 0.2A load is applied, the output drops to 0V. So now the test continues at no-load.

< CH3 : VS(Voltage Sesense : UCC28740 VS Pin), CH4 : Vout(+12Vfb in Circuit)

The corresponding net drain (prim tab node 2) was not connected, and C1 was also removed.

The experimental result shows the same phenomenon that the output voltage goes up and then goes down and then repeats.

Is there any way to do more?

If you see the repeated rise and fall of the output voltage, there seems to be a problem with the VS pin, FB pin, or CS pin, but I'm not sure..

There is one weird thing on your scope pic that the waveform of prim sensing voltage(HV) is opposite to the Vds. 

The measurement seems to be wrong.

I am experimenting by changing the values of the time constant, but it is still not output as a constant voltage and fluctuates.

<CH1 : Vout(12Vfb) // CH2 : VDS(Q2)  // CH4 : VS(R19 voltage across both ends)

 < UCC 28740 Reference Guide Waveform>

The waveforms of VS and Vds of UCC28740 look the same.

However, in my circuit, it can be seen that the noise or voltage SPIKE of the VS waveform is very high.

Which element do you need to change the value of to adjust that part?

The measurement seems to be wrong.

I am experimenting by changing the values of the time constant, but it is still not output as a constant voltage and fluctuates.

<CH1 : Vout(12Vfb) // CH2 : VDS(Q2)  // CH4 : VS(R19 voltage across both ends)

 < UCC 28740 Reference Guide Waveform>

The waveforms of VS and Vds of UCC28740 look the same.

However, in my circuit, it can be seen that the noise or voltage SPIKE of the VS waveform is very high.

Which element do you need to change the value of to adjust that part?

It is still difficult to proceed with the test with the same phenomenon...

has been removed. But it's the same. (L1)