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We are using a PC power supply to power our project, which is a Robotic arm. Since our power supply has a 12V output voltage, can anyone please advise how to step down the voltage (12V) to 6V.

Using a buck converter to step down the voltage to 6V is heating up the circuitry. It's also reducing the maximum rated current, which makes it unsuitable for the motors.

The L7806 regulator is also an option, but it drops the maximum achievable current. How to avoid this problem, where the current drops along with the voltage?

NOTE: We are using 5 servos, and looking for the simplest possible solution to step down the voltage to 6V and still deliver 7.5A.

Talat Malik
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  • What kind of PC power supply does not provide 5V? Can you provide a link to the manufacturer's datasheet for the PC power supply and for the "buck converter"? – Elliot Alderson May 07 '20 at 18:28
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    It looks like you have started the project using the wrong power-supply for the job. Now you have added in the wrong buck converter for the job. You need to start with your requirements. Please [edit] your question to tell us the voltage required and the current required as well as part numbers and links to datasheets for the parts you have tried. – Transistor May 07 '20 at 18:30
  • In order to supply the same current X with say 4% regulation at a lower DC voltage, the source impedance must be the same or better over the desired spectrum of the step loads. Then the RdsOn, DCR and ESR values need to be < 5% for low heat rise. Say you have a 10A supply then 4% voltage regulation with 5% total ESR you need 5V * 4% * 5% /10A= 1 mohm = Zout . What are your specs? If you are lost, use a PC PSU. – Tony Stewart EE75 May 07 '20 at 18:36
  • @ony Stewart Sunnyskyguy I'm already using the PC PSU. but im confused about regulator. that which regulator should i use to avoid the decrease in current rating? – Talat Malik May 07 '20 at 18:48
  • Why do you convert when the PC PSU already has 5V ,12V etc, just decouple the 5V to your servo coils with a low ESR bulk cap near load – Tony Stewart EE75 May 07 '20 at 18:51
  • Why cant your servos use 12V with PWM? Where are your design details and test results, photos to improve the quality of your design question – Tony Stewart EE75 May 07 '20 at 18:54
  • @ony Stewart Sunnyskyguy because theose servo motors operate on in range from 4.2-7V. and please kindly explain your 1st point that how to decouple? i didn't get it – Talat Malik May 07 '20 at 18:56
  • When wiring DC power place a low ESR Cap close to Load with a bus bar. – Tony Stewart EE75 May 07 '20 at 19:11
  • @ony Stewart Sunnyskyguy sorry forgot to mention earlier, we need 6V for servos. now what should i do please guide me – Talat Malik May 07 '20 at 19:27
  • What circuitry is heating up when using the buck converter? – Justin May 07 '20 at 19:34
  • Are you sure the numbers you are looking at are current **ratings** and not current **requirements**? For example, if you have an ideal, 100% efficient, buck converter with 12 V input and 6 V, 1 A output, it will only require 500 mA input. But that's a good thing. It means you only need to supply as much input power as the converter is providing as output power. – The Photon May 07 '20 at 19:35
  • @ThePhoton but we need 7.5Amps for servos. and this buck converter is not giving that current output. can you suggest any voltage regulator which can give the output current of 7.5Amps. – Talat Malik May 07 '20 at 19:39

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Your question lacks complete details to be answerable and also says 5V then 6V later.

Here is a 25A 6V DCDC with low Ron Push-Pull FETs , low DCR Coil and low ESR Caps.

You may compare your design with this and report differences with results. This was a free design by TI WebBench based on high efficiency >98%.

enter image description here

Tony Stewart EE75
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