Hello, im trying to build a buck boost converter based of the classick buck converter circuit with the arduino providing the switching frequency. In my case i am using the arduino nano to generate a switching frequency of 50khz, although i have reached up to 100khz so that is an option aswell. The buck converter works, converting 12v to 60v however as soon as a load is applied to the output of the buck boost comverter, the voltage drops down to around 35v! [zxEfedMhETkgfmZzhGe7B9zRbj201WYTrXW5YrRq] Can anyone with some knowledge of buck converters explain to my why this is caused? Is there a solution to increase the maximum possible load? A few things i have thought of diode losses (such a large loss seems a bit extreme for this?) bad power mosfet? Tried changing to a few others, still getting voltage drops duty cycle? Tried changing it around, less duty cycle draws less idle current, higher percentage duty cycle draws more idle current, mosfet is hotter.

For how long will it keep working? See post #10...

3 hours so far, ill put a resistor on it to be safe.

Not to be safe.... ...to keep current below max pin current and below max be current... ...thus preventing damage to board and or transistor...

is the transistor not isolated well enough to avoid any current getting back to the pin on the base?

The pin delivers the current to the base.. Ipin = Ibe

You must keep the Arduino output current within safe limits. 20mA is what we design around to prevent damage to output pins. (5v (supply) - .7v (Vbe) ) / .02A = 215R use 220R We can increase this resistor value if there’s need, but start with 220R.

The base of the transistor is clamped to 0.7V and the Arduino will try its best to raise that voltage to a logic one level... and will fail.

In this case 1k or higher will work just as well... Not more than 100k!

Yes The lowest is ~220R We can increase this resistor value if there’s need, but start with 220R. However, a MOSFET would be recommended here instead of the BJT.

1k resistor added, glad I haven't damage my board yet. added 3 100v 470uf cap capacitors to the output, much more stable now with fluctuations of +-4v with no load voltage drop is now only about 10v (60v down to 50v). hopefully this can be further improved, im going to try changing to some different diodes

Buck boost converter

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Buck boost converter

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