PWM high side IRF9540N

Thread Starter

sharan_vshnu

Joined Jan 27, 2021
4
Here I'm trying to build a PWM high side driver with the control of Arduino.I used a 12V LED (0.28A) as the load.When i directly connect it to a battery my current consumption is 0.28A and while I try the high side circuit.Its max current is 0.15A. I tried changing the resistor values of R1, R2 & R3.Please help me find the solution.



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jpanhalt

Joined Jan 18, 2008
11,088
Your ammeter is just attached to a 100 Ω (R4) resistor. It does not read the current to the LED's. Moreover, it will not read the peak current, but something lower depending on the PWM duty cycle and frequency. If you want peak current, put a small value resistor in series with the drain of Q3 and measure the voltage across it with your oscilloscope.
 

Thread Starter

sharan_vshnu

Joined Jan 27, 2021
4
Your ammeter is just attached to a 100 Ω (R4) resistor. It does not read the current to the LED's. Moreover, it will not read the peak current, but something lower depending on the PWM duty cycle and frequency. If you want peak current, put a small value resistor in series with the drain of Q3 and measure the voltage across it with your oscilloscope.
Drain is connected with a small resistance 100ohm to measure current in Proteus but on breadboard I kept a LED load mentioned above(0.28A). My PWM actions are fine my main problem is the current loss.Please help me
 

jpanhalt

Joined Jan 18, 2008
11,088
It is increasingly fuzzy what you are doing. If the 100Ω resistor is to replace the LED, its maximum current is 0.12A at 12V. What current did you read? In your original post, you say 0.15A. That violates E=IR, if your supply really is just 12V and not 15V.

Maybe it is time to draw the whole circuit and show the actual results (volts and current) you got at various points.
 
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