Arduino buck-boost converter

MrChips

Joined Oct 2, 2009
30,707
C2 and R8 constitute a filter circuit with a certain frequency response.

R2 and R7 are bias resistors. In this case, they are bleeder resistors to remove the charge from the gates of the MOSFETs when the input voltage is supposed to be zero volts.
 

Jony130

Joined Feb 17, 2009
5,487
Q2 and Q3 are act like a emitter followers, and they job is to quickly charge (Q2) and quickly discharge (Q3) the P-MOS (Q4) gate parasitic capacitance.
 

MrChips

Joined Oct 2, 2009
30,707
That is called a class B push-pull amplifier. When one transistor is on, the other is off.
In your circuit shown, yes, they are acting as opposing switches as the purpose of that circuit is to drive Q4 fully on hard or fully off as quickly as possible, i.e. you want the time spent during transition to be as short as possible.
 

MrChips

Joined Oct 2, 2009
30,707
R9, R10 and R11 constitute what is known as a voltage divider circuit that provides a sample of the output voltage fed back to A0. The wiper arm on R10 is adjustable to allow you to set the voltage feedback.

Zener diode D3 prevents the feedback voltage from exceeding 4.7V which could potentially damage the Arduino ATmega328 MCU chip.
 

MrChips

Joined Oct 2, 2009
30,707
Your buck-boost converter is a switching supply, isn't it? Driven by a PWM signal?

There will be lots of high frequency noise on your supply output.
 

Shagas

Joined May 13, 2013
804
Why is R2 even necessary? If the pin is high then there is nothing to bleed , when the pin is low then the gate can bleed through the pin.
 
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