Author Topic: Step down DC voltage before switching regulator  (Read 762 times)

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Offline desertgregTopic starter

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Step down DC voltage before switching regulator
« on: February 28, 2019, 09:59:00 pm »
I have a couple switching regulator circuits I like to use which support (say for example) a range of around 17V down to close to 5V for a 5V output.  I want to use one of these on a battery powered robot which has a VIn of around 32V.  Rather than use a different switching regulator I was wondering if there is a simple "reasonable / ok" method for stepping down from 30 to within range of the regulator.  I should probably just find another regulator but I thought there might be other solutions that I'm not aware of since the input stage wouldn't need accurate regulation, just something like "cut the voltage in half without wasting power".
 

Offline kjr18

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Re: Step down DC voltage before switching regulator
« Reply #1 on: March 01, 2019, 05:48:31 am »
That's a lot of batteries ;D
There is no way to lower the voltage without wasting power, even the best optimized switching regulators waste a bit of it. You have two ways to solve this, either use a pre-regulator, or use a regulator with wider voltage input. But beware of efficiency, even if your regulator says it has high efficiency, it won't be when regulating with that voltage difference.

I don't really know about your robot, but for example if you need not much power, you could try tapping of from fewer batteries, but only when this is possible and won't discharge these battteries too much. It all depends on what you  need.
 

Offline josip

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Re: Step down DC voltage before switching regulator
« Reply #2 on: March 01, 2019, 10:24:07 am »
I have a couple switching regulator circuits I like to use which support (say for example) a range of around 17V down to close to 5V for a 5V output.  I want to use one of these on a battery powered robot which has a VIn of around 32V.  Rather than use a different switching regulator I was wondering if there is a simple "reasonable / ok" method for stepping down from 30 to within range of the regulator.  I should probably just find another regulator but I thought there might be other solutions that I'm not aware of since the input stage wouldn't need accurate regulation, just something like "cut the voltage in half without wasting power".

For powering microcontrollers from higher voltage I am using RT6208. In my case it is 25V down to 3.3V with 100mA current. If this current is not enough in your case, I guess that you can find similar device with higher current possibility.
 


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