TPS92682-Q1: Low frequency oscillations under light load

Jessica Wu74

Part Number: TPS92682-Q1

Could you please help to confirm if the Drain voltage oscillations on the MosFet as below is because of TPS92682-Q1 work under DCM mode under light load? If it is because it work under DCM mode, then could you please kindly help to share some theory analysis about why there would has the low frequency oscillations here? Since currently, my customer need to provide relate test result to OEM but they could not explain the reason why the waveform look like following picture shows, thank you very much for your support .

Red: Vdrian to ground(MosFET) Yellow: Vgate to ground.

Best regards

Jie

over 4 years ago

0 Jessica Wu74 over 4 years ago

TI__Expert 5990 points

Hi Team,

+Add more information about the test condition

Vin=12V, Vout=45V with two output parallel into one output and the output current is 300mA in total, design as CV boost . Fsw=400KHz

Best regards

Jie

0 Caroline Fuschino over 4 years ago in reply to Jessica Wu74

TI__Intellectual 1675 points

Hello Jie,

We will get back to you on Tuesday July 6 after the US holiday.

Best Regards,

Caroline

0 Tuan Tran74 over 4 years ago in reply to Caroline Fuschino

TI__Mastermind 18890 points

Jie,

If the current is dis-continuous then the the oscillation that you see is cause by the resonant circuit created by the parasitic capacitance of the FET, output diode and the magnitizing current of inductor when current reaches zero. This is normal with DCM regulator when current reaches zero.

Thanks Tuan

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TPS92682-Q1: Low frequency oscillations under light load