UC3825A: Control loop circuit doesn't work

xiaojun sun

Part Number: UC3825A
Other Parts Discussed in Thread: UC3825

Dear

I used UC3825DW to design a full-bridge power supply ,and the load is a 470Khz amplifer.

when the amplifer works on 70Ws and 100 ohm status, the UC3825 didn't work normally. it's supposed to output 70Volts, but it outputs 100Volts.

And then i used UC3825ADW, there are some improved, but still not work normally when amplifier output power higher than 100W.

BTW, what's the defference between UC3825ADW and UC3823ADW?

I guessed there are some interference due to large pulse current.

could you give me some suggestion?

over 5 years ago

0 Teng Feng over 5 years ago

TI__Genius 13660 points

Hi Xiaojun,

Your issue is that the output voltage can not be stabilized.

My suggestion is:

1. use the pure resistance load instead of the amplifier load to eliminate the cause of the load.

2. try to lower the bandwidth of voltage Loop to regulate output voltage.

The maximum deference between UC3825ADW and UC3823ADW is maximum duty cycle, The maximum duty cycle of UC3825ADW is 50% while the UC3823ADW is 100%. Please refer to the attached datasheet for more deference. Thanks.

uc3823a datasheet.pdf

Regards,

Teng

0 Teng Feng over 5 years ago in reply to Teng Feng

TI__Genius 13660 points

Hi Xiaojun,

In order to better solve the problem, could you please attach your circuit schematic. Thanks.

Regards,
Teng

0 Teng Feng over 5 years ago in reply to Teng Feng

TI__Genius 13660 points

Hi Xiaojun,

I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out). Thanks.

Regards,
Teng

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UC3825A: Control loop circuit doesn't work