Buck Converter Simulation Not working

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That circuit is not a proper converter design.
Q2 is upside down. The emitter needs to be up so it can act as an emitter follower, the same as the NPN does.

Q3 is configured as a source follower so it is never fully on, thus its dissipation will be high and the converter efficiency will be low.
It requires 50V at the gate to fully turn on (10V above the supply voltage), so you need a bootstrap driver for that.
 

First step: Correct obvious circuit errors:
- Flip Q2 emitter and collector
- Replace Z-diode D2 by a fast rectifier

Then check gate driver output voltage (voltage across R7) and correct component values if necessary. R3 and R4 are mostly useless, b.t.w.

I thought the same, but the gate driver has a floating supply and can work. A bootstrap circuit could be a practical way to avoid the isolated power supply.
 

FvM said:
................
I thought the same, but the gate driver has a floating supply and can work. A bootstrap circuit could be a practical way to avoid the isolated power supply.
Click to expand...
True. I missed that at first glance.
Isolated supplies are difficult in practice.
 

Optocoupler pin 4 must rise to a high enough voltage, in order to turn on Q1 and turn off Q2.

- - - Updated - - -

Your output voltage is high. The cause could be a long duty cycle. This simulation has 10 percent duty cycle.



Notice a 10uF capacitor is sufficient to smooth the output to a reasonable extent.
 

Your pulse input to the opto is only 1 kHz in your attached example. At this low frequency, the required L and C value will be large. It is better to have the frequency above audible range (20 KHz and above)

Below I made a few changes and use a frequency of 20 KHz. Results are now more realistic. The transient start up choke current is shown on the green plot.
 

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    M.Rehan

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Is it possible to achieve 100% duty cycle in case of buck converter using bootstrap circuit (IR2110)?
 

Is it possible to achieve 100% duty cycle in case of buck converter using bootstrap circuit (IR2110)?
Click to expand...
It's not possible. You need an auxiliary supply, e.g. a charge pump circuit to maintain a gate voltage above the positive supply. It's also important to reduce the quiescent current in on-state. Static current consumption as caused by R7 is unwanted.
 

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