HV voltage switch with power MOSFETs - Page 1
Forum section: electronics / projects

author: fracton
author_rank: Contributor
timestamp: August 30, 2024, 05:46:54 pm
content: Hi,I am trying to build a high-voltage switch with a push-pull configuration using the high-voltage SiC-based n-channel power MOSFETs (MSC750SMA170B 1700 V, 750 mΩ). Also, there are a couple of others with similar characteristics but faster rise and fall times. I am looking for some advice and general practices to follow while designing such high-voltage pulsing circuits and implementing them on a PCB.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 30, 2024, 05:54:09 pm
content: What are you switching? How often?

author: fracton
author_rank: Contributor
timestamp: September 12, 2024, 04:49:02 pm
content: I'm trying to build an ultrafast pulser circuit (nanosecond rise times). For this, I would have to switch a positive high voltage (HV) from a power source that can deliver up to 5kV at 2mA.

author: inse
author_rank: Super Contributor
timestamp: September 12, 2024, 06:00:34 pm
content: kV/ns? This will create a spontaneous black hole that consumes the contraption and it’s creator.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 12, 2024, 09:58:11 pm
content: Have you considered a triggered spark gap? Easier to build as a one-off, if finicky. Perhaps a hydrogen thyratron? Not the cheapest or easiest to use, but a lot easier to design in.If something akin to an EFT generator (or, for a more physics application, beam kicker pulser), I would suggest common-ground stages and power combiners. No need for cascodes and tricky gate driving.Tim

author: Marco
author_rank: Super Contributor
timestamp: September 12, 2024, 11:22:22 pm
content: At that speed it seems more a task forGANthan SIC.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 13, 2024, 02:06:04 am
content: Assuming it's into some modest impedance (like EFT's 50Ω output, or even a modest length of transmission line), I suspect the power level of GaN isn't quite enough, and SiC would be the best choice.Probably close though, with GaN getting bigger and bigger these days.Also much less robust, but that might not matter for short pulses; depends.Tim

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: September 13, 2024, 01:09:06 pm
content: https://www.behlke.com/might be worth a look. used them in one of my projects and can't complain.

author: fracton
author_rank: Contributor
timestamp: September 17, 2024, 02:09:24 pm
content: Yes, I've used HV pulse generators built out of Behlke's switches. But, looking to built a low-cost customised alternative for TOF experiments.

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 17, 2024, 03:26:40 pm
content: Does anyone know how such a FET works?In principle I can imagine a series of FETs with their gates coupled to an insulated transformer winding each. But how to ensure that all FETs trigger simultaneously? Does anyone know of an example circuit or teardown?

author: fracton
author_rank: Contributor
timestamp: September 17, 2024, 06:13:41 pm
content: Thanks, this looks like an interesting project. However, for now SiC MOSFETs seem to be a cheaper alternative and they come higher Vds. For example, here are a few power SiC MOSFETs I have been trying out for this projects:-MSC750SMA170B-IMBF170R1K0M1Both these MOSFETs have a Vds breakdown voltage of 1700V, the standard for SiC Power devices.Would you have any suggestion on designing a PCB for such High Voltage modules.

author: Marco
author_rank: Super Contributor
timestamp: September 18, 2024, 10:27:51 am
content: I'd try the UnitedSIC/Qorvo 1700V SIC JFET.

author: fracton
author_rank: Contributor
timestamp: September 21, 2024, 06:11:00 am
content: Quote from: T3sl4co1l on August 30, 2024, 05:54:09 pmUnfortunately, I don't have the schematic of the circuit I am trying. However, my current design is a modification the circuit attached here. I have tried to swap out the components in this design with newer ICs.