I have trouble about controlling Double Pulse Circuit.

Thread Starter

Lee dong hun

Joined Feb 14, 2016
Hello, I tried to measure Irr of DUT, So I made circuit using LM5114

Almost of circuit is soldered.
_8CD65CB8_-5_2D00_1_Lee dong hun.JPG

And this is example of Irr test circuit
Example_Lee dong hun.JPG


1. ATMEGA8A makes 10us pulse 2 time (It will be more shorter if this circuit works)

2. LM5114B receive signal and controls the gate of IRFP250

3. When first waveform reach to the gate of IRFP250, it passes current through 70uH -> IRFP250

4. While gate is turned off, current in Inductor pass through DUT forward side.

5. And the second waveform reach to the gate of IRFP250, DUT makes reverse current instant.

Meausrement Result
5_2D00_1_Lee dong hun.PNG

1. OSC1 : Idd(10V), OSC2 : OC1A

First waveform reach 650mA. Not high as expected, and second wave is unsatisfied ( maybe due to 0.1Ω )
5_2D00_2_Lee dong hun.PNG

2. OSC1 : Idut, OSC2 : OC1A

Yes, 550mA passed through DUT forward position

5_2D00_3_Lee dong hun.png

3. OSC1 : Idut, OSC2 : OC1A

What is that? Rising founded on Irr curve? Something went wrong.

Measurement Equipment

Source : Keithley 2636B, Keithley 2651A

Oscilloscope : DPO2012B(100MHz)

OSC Probe I have : TPP0200 Passive Probe (Default, 200MHz), TCP2020 Current Probe (>50MHz), Active Probe

Defect I can guess

0. Board : I'm not using PCB currently. It is on Perfboard and there is many parastic capacitors on each copper hole - but not sure how much effect on the test.

If I fix some defects and sure i can test Irr, I'm going to make PCB

1. Probe : I also want to use 'shunt regulator' to measure Irr, but i cannot trust voltage accuracy of Passive Probe.

If i use proper probe, then long-wire can be deleted on circuit.

Active probe support under 7V, so it is not suitable for measurement.

2. Long wire : As I said, due to current probe. Is this make Lloop?

3. Equipment : Maybe 2651A limit output current...? I set its limit to 5A now.

4. 0.1Ω : to limit Idd(10V). According to Example Circuit - there is no resistor on FET.

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Joined Oct 15, 2009
The IRFP250 datasheet always shows 10V pulses for the gate drive.
You are using only 5V to drive the gate!
Do use 10V - 12V supply for the LM5114B!

Good luck, Peter