DC-DC Applications

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I would like to ask if the FB pin of the DC-DC BUCK chip can be directly connected to the ground through a resistor to output all the inputs?

maychang

“Can the FB pin of a DC-DC BUCK chip be connected directly to ground via a resistor to output all inputs?”

It would be better to remove the Buck chip, inductor, etc. and connect the load directly to the DC input terminal.

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maychang posted on 2019-11-2 07:54 "Can the FB pin of the DC-DC BUCK chip be directly connected to the ground with a resistor to output all inputs?" It would be better to remove the B ...

It is more direct to remove it. I just thought of this question and wanted to ask whether it is possible to use the BUCK chip in this way, because some BUCKs have current limiting. If only the current limiting of the chip is used, can FB be connected to the ground? In principle, it should work. After all, FB = 0, PWM is 100% duty cycle, input full scale output

maychang

Aka Time Period Published on 2019-11-3 19:33 It is more direct to remove it. I just thought of this question and wanted to ask whether it is possible to use BUCK chips in this way, because some BUCKs have current limiting. If only...

I'm afraid you need to look at the chip datasheet. Remember that some Buck circuit chips have bootstrap, which is used to power the MOS tube inside the driver chip. This kind of Buck circuit chip with bootstrap must output pulses and cannot be directly connected.

PowerAnts

Find a buck controller with a maximum duty cycle of 100%, usually using P-MOS

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PowerAnts posted on 2019-11-4 08:31 Looking for a BUCK controller with a maximum duty cycle of 100%, usually using P-MOS

Does this mean that the BUCK circuit can sometimes use 100% duty cycle output?

qiushenghua

Our chip often triggers protection when FB is short-circuited to ground.

(Of course, we usually use Buck-Boost. If there is no protection, the output voltage will be very high, which may easily burn out the back-end devices.)

From this perspective, the idea of shorting FB directly to ground is dangerous.

qwqwqw2088

The FB feedback pin of the DCDC chip is usually connected to the error amplifier internally, which is compared with the reference voltage to adjust the output voltage. Incorrect FB voltage will lead to incorrect output voltage.

Follow the manual

PowerAnts

Aka Time Period Published on 2019-11-4 14:09 Does this mean that the BUCK circuit can also sometimes use 100% duty cycle output?

It's not "sometimes", it's "some". Look at the last column on the 5th floor, it clearly lists the maximum duty cycle as 100%

PowerAnts

Buck open loop will not cause the output voltage to exceed the input voltage, so the concerns of 7th and 8th floor are completely unnecessary.

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PowerAnts posted on 2019-11-5 09:57 The BUCK open loop will not cause the output voltage to exceed the input voltage, so the concerns of the 7th and 8th floors are completely unnecessary

OK, thanks for learning.