TPS40210-Q1: Device not working at high current

Rajesh Chauhan

Part Number: TPS40210-Q1
Other Parts Discussed in Thread: TPS40210

Hi,

I am designing a boost converter with TPS40210 part. Specifications are Vi=45V, Vo=60, Iout=700mA.

I used Webench to generate the schematics and choosing the components. Schematics is attached. Now I am trying to test the device for my application. I found that it works fine till 500mA load current and suddenly becomce unstabe after that till 550mA and collepse completely after that. Could anyone please giude me what is wrong with my circuit. I have used most of the compoents as mentioned in schematis. Sense resistor is .05ohm instead of .06ohm. Let me know if any other information is needed. Orrder of capture below is

1. Schematics

2. Stable waveform

3. Unstable waveform

Best Regards,

Rajesh

over 8 years ago

0 EricLee over 8 years ago

TI__Guru 59971 points

Hello
I think you need more filtering at ISNS. Please try larger CB8 ( 470p~2.2nF)
Thanks

0 Vental Mao over 8 years ago

TI__Expert 5745 points

It seems that some issues in the loop respond, Please use the Webench to get the compensation value or use the datasheet to get the value of them. Thank you!

0 Rajesh Chauhan over 8 years ago in reply to EricLee

TI__Prodigy 30 points

Hi Lee,

Thanks it seems you are correct however i have to put a bit high 4.7nF cap and now i am able to regulate till my required cuurent value. But i am getting the inductor current waveform as attached. Is it a correct behavior due to low duty cycle i have.

Best Regards,

Rajesh

0 EricLee over 8 years ago in reply to Rajesh Chauhan

TI__Guru 59971 points

Hello
I seems you had two issues. Please use WEBENCH to find the right compensation values and test it again.
Thanks

0 Rajesh Chauhan over 8 years ago in reply to EricLee

TI__Prodigy 30 points

Hello,

I tried webbench and also simulated with the values it provided me and there is no problem in simulation but putting these values in test providing me unstable inductor current values.

Best Regards,

Rajesh

0 EricLee over 8 years ago in reply to Rajesh Chauhan

TI__Guru 59971 points

There is also a possibility too much filtering at CS can cause the instability. Please try smaller filter capacitor.

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TPS40210-Q1: Device not working at high current