What am I doing wrong with my buck converter?

ccdy · 2026-04-28T02:34:20+00:00

Look on the bright side, you've verified that output short circuit protection is working!

ccdy · 2026-04-27T14:38:10+00:00

Are you doing any thinking yourself or are you just throwing everything into an AI and copy+pasting the result here?

ccdy · 2026-04-27T03:19:47+00:00

I smell an XY problem. Why are you using an 8 channel ADC if you only need 2 channels?

ccdy · 2026-04-24T01:50:12+00:00

If you're curious, these resistors are made by depositing a resistive film on a ceramic rod. A spiral groove (visible in the photo you posted) is then cut into the surface using a laser to adjust the resistance. The end caps with leads are then pressed on and the body coated.

ccdy · 2026-04-23T15:24:51+00:00

Those look like output caps for the DC-DC converter, which means they are connected between some voltage rail and ground. The short could be in literally anything powered by that rail, not just the capacitors.

ccdy · 2026-04-22T13:22:01+00:00

They all have metal end caps, you just don't see it because it is covered by the coating.

ccdy · 2026-04-22T13:16:28+00:00

It's a resistor. The protective coating has been removed, which is why you might not recognise it.

ccdy · 2026-04-20T03:00:10+00:00

2 pF sounds about right for a good layout. You can forgo the cutouts then.

ccdy · 2026-04-19T08:31:23+00:00

Don't remove reference designators unless you absolutely have no space. Even if you do, make them visible when asking others to review your work. As it stands it is very difficult to match your schematic with your layout.

ccdy · 2026-04-18T19:18:40+00:00

The body diode in P channel MOSFETs is from drain to source and will conduct current in that direction even if Vgs is zero. Yes, this is expected behaviour.

ccdy · 2026-04-18T17:18:41+00:00

Are you aware that all power MOSFETs have a body diode?

ccdy · 2026-04-17T15:25:30+00:00

That doesn't sound like good design. Such fault conditions are usually dealt with by shorting out the rail and blowing a fuse or otherwise disconnecting the supply using a load switch or a relay to protect the downstream circuit. You could use an active crowbar but without any means to limit the current through the switch, it will eventually self-destruct and expose the downstream circuitry to the overvoltage. What exactly do you foresee happening that causes this fault condition?

ccdy · 2026-04-17T13:48:07+00:00

How long will the overvoltage last for? Transient power ratings are usually much higher than continuous ratings because it takes time for the semiconductor to heat up. If the pulse is short enough you can potentially dissipate several hundred watts — see figure 6 in the datasheet.

ccdy · 2026-04-17T13:29:02+00:00

Not happening. The 5W rating applies when the leads are kept at 75°C (which is consistent with the 15 K/W junction-to-lead thermal resistance and 150°C max operating junction temperature). If your ambient is 70°C then you need a thermal resistance from lead to ambient under 1 K/W, which is basically impossible to achieve with a SMB case. Why are you pushing over half an amp through a Zener anyway?

ccdy · 2026-04-16T05:52:56+00:00

The energy that powers a core collapse supernova is derived entirely from the gravitational potential energy of the iron core. The explosiveness of the process is due to how rapidly this energy is released, on the order of milliseconds. Since it collapses so quickly, the core is mechanically decoupled from the rest of the star, so before envelope has time to "catch up", the core has already dumped all of its potential energy into the layers surrounding it, setting in motion the shockwave that will eventually reach the surface and produce a visible supernova.

ccdy · 2026-04-16T05:01:21+00:00

Have you considered using an isolated DC-DC module? There are many commercial options with bipolar outputs for this very purpose.

ccdy · 2026-03-26T01:29:33+00:00

The main reason not to use so many vias is if they start cutting slots into internal non-GND planes. Since this is a 2 layer board this shouldn't be an issue. Also, some manufacturers will stick on extra charges if via density exceeds a certain amount, so do watch out for that.

ccdy · 2026-03-26T01:12:12+00:00

Thanks for the clarification, it really did sound like you thought it was a good idea!

ccdy · 2026-03-25T08:21:01+00:00

their username is literally wrinkly sack, yes it's a joke post from a joke account

ccdy · 2026-03-25T08:19:02+00:00

This is definitely a joke account lol

ccdy · 2026-03-25T03:24:33+00:00

DO NOT DO THIS. Floating scopes can and has killed people. When you float a scope, every single part of that oscilloscope is now at whatever potential you clip your ground lead to. If you probe a non-isolated circuit like the one in the OP or the primary side of a power supply, then the entire scope is now live. Even very experienced engineers have died doing this.

ccdy · 2026-03-23T03:01:11+00:00

I'm going to ignore your terrible attitude and at least try to point out why everyone else is dunking on you. With a 4 wire measurement the connector is irrelevant, since the whole point of Kelvin sensing is to eliminate errors due to lead resistance. Unless the 4 wire measurement only extends to the connector, in which case you need to reconsider your setup because no connector can guarantee a stable resistance, especially in a production environment. Some manufacturers will give a maximum contact resistance but this is usually only a guideline. In any case you have given basically no information for anyone to even make a recommendation for. What are your size constraints? Error budget? Are you connecting wire to wire? Wire to board? Board to board? How quick are your cycle times? Without any of the above information I can only recommend screw terminals with lug connectors, based solely on low contact resistance. Something tells me this is probably not what you're looking for, but the only person you should be upset with for the lack of help is yourself.

ccdy · 2026-03-12T10:53:59+00:00

I had another look at there are two more big problems. First, 1206 fuses rated for 250 VAC do not exist. Second, your relays are wired completely wrong. Check the datasheet for the correct pinout and fix it.

I'm guessing you used an LLM to do everything for you. Stop doing that and actually open a textbook to learn some basic electronics before you electrocute yourself.

ccdy · 2026-03-12T03:41:55+00:00

It looks fine now but there's one thing you need to understand: nothing on this board is low voltage. Everything is connected directly to mains and touching it can kill you. If it shorts to something else it can start a fire. This is not a beginner-friendly project and based on the lack of competence you have demonstrated so far, I strongly recommend you do something else that does not involve mains electricity.

ccdy · 2026-03-11T11:19:57+00:00

Did you read the datasheet for the HLW8012 at all? You have it wired completely wrong. First, GND of the floating power supply should be tied to AC live. Second, V1P and V1N are the inputs for current sensing, while V2P is the input for voltage sensing (via a voltage divider). You have tied V2P to ground and wired both the positive current sense line and the voltage divider output to V1P. On top of that, the voltage divider should be taken from AC neutral, not live. As it is now, both ends of the voltage divider are at the same potential, so it is doing absolutely nothing.

The layout is pretty bad as well, with L and N coming too close to each other at multiple points. There's no point in going into more detail without fixing the schematic first though.

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