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I am doing a sound amplifier using LTspice and I would like to know if someone know why my gate driver output has spikes only when it is connected to the half-bridge circuit.

enter image description here

The INP terminal is receiving a sine PWM signal from a comparator on the high-side driver and an inverted one on the low-side driver.

High-side driver output (without connecting it to a half-bridge):

High-side driver output (with a half bridge connected to it): enter image description here

Those spikes are also happening on the low-side driver. Btw, it is not affecting the entire circuit, but I would like to know how to make those spikes disappear. Any suggestions?

Hiei1
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  • Those are usually signs of cross-conduction. Without showing the rest of the schematic, it's impossible to tell. Check your sources, plot only the waveforms they generate and see that the tr and tf do not interfere with each other. – a concerned citizen Mar 05 '21 at 16:34
  • If you're asking why the spikes appear in the simulation, it is because it is modelling the parasitics of the MOSFETs. If you build the circuit, it should look similar. – rdtsc Mar 05 '21 at 17:09
  • I just added the right-hand part circuit. The gate driver inputs are coming from a comparator, which compares a sinusoidal signal to a triangle signal, making a sine PWM signal – Hiei1 Mar 05 '21 at 17:47
  • @rdtsc Do you have an idea on how to block those spikes? – Hiei1 Mar 05 '21 at 17:54
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    @Hiei1 Do you have any sort of dead-time? Try adding series resistors to the gates, 10 Ohms or so. Also, add some labels to the nodes (press F4), nobody can tell where those N00x nodes are. – a concerned citizen Mar 05 '21 at 17:55
  • @aconcernedcitizen not yet. Just added a resistor and the spikes have decreased a little but not everything. Do you know how can I add dead-time without changing the sources? – Hiei1 Mar 05 '21 at 18:01
  • @Hiei1 Try something similar. But if you intend to build this amplifier, you will need more than simply placing those ICs and hoping it will work well. Unless you have very large (relative) dead-time, you will get some sort of cross-conduction, you will need proper gate drivers, snubbers, protections, and those LC values are too high (don't forget the speakers will also attenuate since they'll be woofers, it seems). You may need to know a bit more, it's not quite as simple. – a concerned citizen Mar 05 '21 at 18:25
  • @aconcernedcitizen Cheers mate. Already doing research, thank you very much for the guidance. – Hiei1 Mar 05 '21 at 18:46

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