Buck operation using IR2117 gate driver

[Kellish]

Hello everyone...
I am trying to simulate the circuit using IR2117 gate driver on MULTISIM BLUE. I am having some issues regarding this IC. Just for making it clear, Pin1 is Vcc , Pin2 is IN from PWM source, Pin3 common, Pin5 Vb, Pin6 HO, Pin7 Vs. I am getting no voltages on HO output in order to drive the gate driver. Can someone help me with it. I think there is some issue with the capacitor between Vb and Vs but cant get it...

 

[Minder]

Here is a charge pump calculator.
https://www.silabs.com/support/Pages/bootstrap-calculator.aspx
M.

 

[Alec_t]

Q2 collector voltage looks suspicious.

 

[duke37]

How can a buck convertor produce 40V from 20V?

 

[Kellish]

How can a buck convertor produce 40V from 20V?

Its actually a maximum range of Lamp

 

[(*steve*)]

Ground the anode of D1

 

[Alec_t]

Doing so will fry D1 and/or the FET in the real world.

Edit: Scrub that.

 

[(*steve*)]

Doing so will fry D1 and/or the FET in the real world.

Why?

At present that entire part of the circuit is floating. There is no way (aside from stray capacitance) of getting any energy in there.

A buck topology requires the anode of the schottky diode and the capacitor to have a low impedance connection to the negative rail of the power source -- in this case it appears also to be ground.

 

[Alec_t]

Oops. You're right.