With a lot of cheap buck converters, that you can purchase for less than one $ you can do very nice things:
The buck converters having an enabe input can act as a power output to much higher voltages e.g. to drive things at 12V or 24v that do not need to be switched at a high frequency.
But you can even get a bit further and control to a certain extend the output voltage:
Almost every buck converter has a voltage divider between the output and a "FB" comparator input at a fixed voltage, usually 1,2v or 0,8V (read the specs).
If you inject a limited current into the voltge divider, you can influence the output voltage.
In the example given I have used a PWM output, followed by a low pass filter and a 100k resistor to inject a voltage control into the buck controller.
I can control the output of the buck controller from 5,5v (PWM output set to 0) down to ~0,8V PWM output set to 255).
Another digital input switches the buck converter on/off.
Of course with different resitor values for R1, you can control much higher voltages...
Enjoy!
Erratum: R10 should be 39k instead of 100K.
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I would advise caution when doing this. Switch mode power supplies are very sensitive to PCB layout and this sensitivity increases the more current you try to draw from them.
At the best of times these ultra cheap converters are rubbish. Increasing the voltage output is only going to reduce the stability of the output. Especially as you have now changed the feedback loop.
Grumpy_Mike:
I would advise caution when doing this. Switch mode power supplies are very sensitive to PCB layout and this sensitivity increases the more current you try to draw from them.
At the best of times these ultra cheap converters are rubbish. Increasing the voltage output is only going to reduce the stability of the output. Especially as you have now changed the feedback loop.
You are right: I should have specified that you should not power voltage sensitive devices with this hack.
Many current cheap buck converters are however better than the reputation they got from the ages of the infamous XL4016.
Indeed with my hack, you reduce the feed-back ratio by 1/3, I knew that and checked thoroughsly, but the MP1584 ran just fine, even under 1A load at 12V.
by serendipity I found out, that another engineer did it as well, even injecting PWM almost directly into the feed-back circuit.
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