IRS21944 high side is blowing when voltage reaches ~200Vdc at VCC - Page 1
Forum section: electronics / projects

author: Johnguy
author_rank: Newbie
timestamp: August 13, 2025, 05:39:35 pm
content: Hello im bulding synchronus buck converter and i'm using IRS21844 as low/high-side driverthe problem is when VCC is around 80V everything is working fine when VCC reaches ~200V the driver is burning its heats up only low side is switchingi replace this driver with IR2104 and its OK even when VCC is 200V

author: xvr
author_rank: Frequent Contributor
timestamp: August 14, 2025, 12:17:25 pm
content: QuoteThis is not a problem - it's a miracle. By datasheet maximum Vcc is 20V."Fully operational to +600 V" from datasheet belong to the high side part of driver - Vs, HO & Vb.

author: Johnguy
author_rank: Newbie
timestamp: August 14, 2025, 12:21:59 pm
content: I meant VCC as net on kicad not driver's pin

author: Psi
author_rank: Super Contributor
timestamp: August 14, 2025, 12:34:51 pm
content: Is C3 rated to 600V. It's not going to be happy if C3 arcs inside and shorts the HV side to the LV side.Edit: ops, na VS is high side too.Also is D1 reverse leakage potentially causing a problem, datasheet says its 1uA reverse leakage so at least its not 1mA,but is it perhaps unhappy with IC VCC getting 1uA from 200V during periods when the IC is drawing much less than 1uA?Probably unlikely to be that though.Next time you blow one up testing i would have the scope on IC VCC set to trigger at 21V. See if it triggers and what you getOr, could try slap a 12V 19VC TVS across IC VCC to gnd, just to see if it helps.For C15 the 100nF might be a bit small to prevent a noisy supply when its so close to 200V switching.Try put a 4.7uF in parallel. Just for a bit more supply decoupling from the inductive shit show happening next door.

author: Johnguy
author_rank: Newbie
timestamp: August 14, 2025, 04:08:55 pm
content: IR2104 has also 20v limit on VCC but i will try tvs on VCCi think the problem isnt in VCC

author: Psi
author_rank: Super Contributor
timestamp: August 15, 2025, 12:27:40 am
content: What's the output voltage and switching frequency?

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 15, 2025, 04:01:29 am
content: How are you supplying the 12V to power the chip?Can you send the layout of your board? Where are the capacitors placed in your design?

author: Johnguy
author_rank: Newbie
timestamp: August 15, 2025, 02:10:39 pm
content: I replaced IR2104 back to IRS21844 and added Snubbers C = 100pF and R = 27Ohms (before I didn;t have caps) and it works.I changed pwm width to 0% at startthanks for everyone for help

author: H.O
author_rank: Frequent Contributor
timestamp: August 15, 2025, 10:01:42 pm
content: With snubbers, you mean C2/R2 & C5/R11?So in reality, the problematic circuit (ie what you ACTUALLY built) did not match the schematic you showed in the first post?Once your circuit (ie what you ACTUALLY built) DID match the schematic it all worked as expected.Is that what you're saying?

author: xavier60
author_rank: Super Contributor
timestamp: August 16, 2025, 03:22:24 am
content: Negative voltage spikes at the switching node can overcharge the bootstrap capacitor. It's good practice to put some low value resistance in series with the diode.

author: moffy
author_rank: Super Contributor
timestamp: August 16, 2025, 04:07:55 am
content: Quote from: xavier60 on August 16, 2025, 03:22:24 amThat makes sense as the IRS21844 with its higher drive current should switch the MOSFETs harder and cause greater ringing, which would also explain why the different snubber values solved the issue.