boost converter oscillation with fast recovery diode not using schottky diode.

Hyun woo Kim1

Other Parts Discussed in Thread: TPS61170

Hi, I changed from schottky diode to fast recovery diode to improve off time ringing voltage. but the boost converter is oscillated.

my boost converter 's switching frequency is 1MHz. why oscillation occured with fast recovery diode ?

over 5 years ago

0 Jasper Li over 5 years ago

TI__Mastermind 46905 points

Hi Hyun,

what device is used? does the diode support 1MHz switching frequency?

0 Helen chen over 5 years ago

TI__Mastermind 40080 points

Dear Sir,

What is the part number of the boost converter you used and what is the Vin, Vo, Io?

fast recovery diode has much longer recovery time and hence severe interference.

0 Hyun woo Kim1 over 5 years ago in reply to Helen chen

Intellectual 460 points

Dear Helen,

I use another vendor's converter and they can't explain exactly it . so, I can't help posting in TI website.

You mean fast recovery diode has longer recovery time than schottky diode ?

could you explain detail why having longer recovery time is interfere with converter operation ?

Please below in/out condition

(1) Vin : 5V

(2) Vout : 10V

(3) Iout : 0.3A

(4) Switching frequency : 1MHz

0 Hyun woo Kim1 over 5 years ago in reply to Jasper Li

Intellectual 460 points

Dear Jasper ,

could you tell me how to check supporting 1MHz switching frequency of diode ?

There is no any data on diode datasheet.

Do I have to inquiry about it at diode vendor ?

Best regards,

0 Helen chen over 5 years ago in reply to Hyun woo Kim1

TI__Mastermind 40080 points

Dear Sir,

It is also depend on the layout. Generally for 1MHz operaiton, you need to choose schottky diode or <10ns trr fast recovery diode.

What is the spec of the diode?

And the last, suggest you choose TI part. :) Our part TPS61170 is very fit for this application.

0 Hyun woo Kim1 over 5 years ago in reply to Helen chen

Intellectual 460 points

Dear Helen,

Please refer to the below diode spec,

Vf : 1.3V

junction capacitance : 18pF

reverse recovery time : 150ns

0 Helen chen over 5 years ago in reply to Hyun woo Kim1

TI__Mastermind 40080 points

150ns reverse recovery time is really too long, you need to found a <20ns reverse recovery diode.

0 Hyun woo Kim1 over 5 years ago in reply to Helen chen

Intellectual 460 points

Dear Helen,

Could you explain detail why there is abnormal operation with long reverse recovery time ?

Best Regards,

0 Helen chen over 5 years ago in reply to Hyun woo Kim1

TI__Mastermind 40080 points

Dear Sir,

For the boost converter, in the high frequency operation. When the low side FET off, then the output diode on. When the output diode off, then the low side FET on. If the diode exist long reverse recovery time, then when the FET on, the diode will still last a 150ns long reverse recover time instead of turn off immediately, this long and big reverse recovery energy will cause abnormal, at low Vin and high Vo condition, it may even longer than the required diode off time, and results in the output abnormal.

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boost converter oscillation with fast recovery diode not using schottky diode.