On Wed, Apr 9, 2025 at 02:50 PM, <ankitk.ace@...> wrote:
Amidst all the discussion I overlooked some of the key concepts that are essential to these simulations and I can certainly use a second opinion from you.
Ankit,
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I will try to address your questions.?
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3) All measurements made by the .meas statements are done after the simulation has ended. They are done by a post processing step and have access to all signals throughout the simulation.
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4) The simulation results will be good if the models are good. Actual hardware measurements always have variations due to component tolerances. Unless you repeat your hardware measurements with multiple devices from different production batches you will be measuring only a single part whose parameters could be anywhere within the tolerances shown on the parts datasheets.?
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1 and 2) The double pulse test is a way to measure the turn on and turn off characteristics of a device with a known on-state load current and known off-state withstand voltage. In a double pulse test the inductor current is ramped up during the first pulse to a known value by controlling the first pulse width. The device under test is then turned off and the on to off behavior of the device can be measured at that current. During the off time the inductor current remains nearly constant because there is only the low voltage across the forward biased upper device body diode across the inductor to reduce the current. Then the device under test is turned on again during the second pulse and the off to on behavior of the device can be measured during this transition. During these tests the inductor is basically performing the function of the constant current limiter in my circuits. Because the device under test is used to set the inductor current, the turn off transition is measured first at the end of the first pulse. Then the turn on transition is measured second when the device under test is turned back on at the beginning of the second pulse. Using an identical device for the upper device in the double pulse test circuit allows you to measure the characteristics of the body diode of those devices. That body diode turns on at the transition at the end of the first pulse, and it turns off at the transition at the beginning of the second pulse.?
Both methods can be used in simulation, but the classic double pulse test circuit is more applicable to real hardware measurements because it does not need ideal diodes or current sources. A charged inductor is a very good approximation of an ideal current source, which is why it is used for the double pulse test. The known drain voltage is applied to the inductor for a fixed time (the width of the first pulse) to charge the inductor up to a known current level. For the remained of the test that current remains nearly constant at that value.
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HTH
