TPS61178: Vin greater than Vout

Weiwei Su

Part Number: TPS61178

Hi all,

Can this booster converter work under certain condition where Vin maybe greater than Vout? I understand that Vout will not be regulated once Vin > Vout but I just want to be sure that the chip can tolerate this.

Thanks

over 1 year ago

+1 Fergus He over 1 year ago

TI__Genius 13995 points

Hi Weiwei,

The device will not regulate if Vout is higher than target.

Note that when Vin is close to Vout target, the output ripple will be large due to minimum on time.

Please refer to this thread.

(+) TPS61088: Operation when Vin is greater than Vout - Power management forum - Power management - TI E2E support forums

Best Regards

Fergus

0 Weiwei Su over 1 year ago in reply to Fergus He

Prodigy 130 points

Hi Fergus,

Just tested the board, Designed Vout is 9V, Vin Max is 8.4V, Vin Min is 5.2V and Iout is set at 2A. When Vin is 8.4V, Actual Vout is 8.97V (Looks Good). When connected to load (2 strings of 3x High Power LEDs with a LED Linear Driver IC), it is unable to pull max 2A current (LED Driver's Rsns is set for 2A drive and LED's Vf is 8.55V when drive under 2A current), It only about to get about 1.45A or so. It can only drive to 2A if I tune down the Vin to about 6.62V。 Is it because the output ripple you mentioned?

0 Fergus He over 1 year ago in reply to Weiwei Su

TI__Genius 13995 points

Hi Weiwei,

Due to your schematic, the turn on time calculated is about 387ns, which is larger than the minimum turn on time.

So, it may be not the output ripple problem.

The problem may result in wrong parameters of the outside devices.

You can have a test of the input voltage, inductor current, output voltage and so on.

It will easier for us to analysis if we have more clues.

Best Regards

Fergus

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TPS61178: Vin greater than Vout