I designed and practically tested a high-side buck converter. The input voltage is set to 10 volts from a DC power supply, and a pulse generator is used to generate the PWM signal, which is set to 5 volts peak-to-peak, 10 kHz, and a 50% duty cycle. A gate driver is used and fed from a 15-volt power supply, with its ground separate from the circuit's common ground. The load is a resistive load of 10 ohms. The output voltage is 8 volts, which is not as expected (5 volts)

 

Hi sale,
Welcome to AAC.
Please post a circuit diagram of the project.

E

 

 

What did you use for your inductor? What value is it? What is its saturation current?

 

You don't want to simulate with the default MOSFET and Diode. You should select actual parts.

Like this for example

 

Your schematic does not match your circuit description.
Post the complete circuit.

For a proper supply, you need negative feedback from the output to the PWM generator to regulate the output voltage to the desired value.

 

Your schematic does not match your circuit description.
Post the complete circuit.

For a proper supply, you need negative feedback from the output to the PWM generator to regulate the output voltage to the desired value.

Agreed. Starting with an open loop design is useful for understanding the basic operation.

 

The inductor of the DC buck converter influences the duty cycle of the MOSFET thats why you are getting this issue.This is a known issue for all DC-DC converters.The storage element influences the on and off time and this creates harmonics in the output.

 

I used another inductor with higher inductance, which resulted in an output of 5 volts for 50% of the duty cycle as expected. However, when I increased the duty cycle, I obtained a higher output, but it was lower than expected. For example, I got 7 volts for an 80% duty cycle. Is that expected, as the converter is not ideal?

 

I used another inductor with higher inductance, which resulted in an output of 5 volts for 50% of the duty cycle as expected. However, when I increased the duty cycle, I obtained a higher output, but it was lower than expected. For example, I got 7 volts for an 80% duty cycle. Is that expected, as the converter is not ideal?

What did you use for your inductor? What value is it? What is its saturation current?

 

A generic schematic lifted from Google and a verbose description is not enough to diagnose your problem.
Please show the actual, COMPLETE schematic, the one you actually tested, including all component values.
If you don’t have a schematic editor, draw a clean schematic and take a steady, focused picture.
And showing a breadboard is helpful but not sufficient without the schematic.

 

Your results would be expected if your circuit has higher losses as the duty cycle increases. Notice in the example I provided in post #5, that a duty cycle of 54% was required to get an output of +5V from a +10V input at a load current of approximately 5 Amps.