Power Supply for Class-D amplifier module
I've built several small (~500mA) dual rail power supplies; mostly 12-15V stuff for a pair of opamps each. These have been very simple designs since the current is very low.
However, I'm looking at my first "serious" dual rail linear PSU, something to power one Class-D amp. The module I'm currently considering is the ICEpower 500A, a 500W (@4Ohms) amplifier module. It requires a dual-rail power supply between 45V and 80V, with 75V being "recommended".
With the smaller power supplies it was easy to get started, but this seems like something else. I'm hoping for a few resources / pointers in the right direction as to where I can find information on building something like this. Perhaps I've missed it, but I couldn't really find very much!
Phill
I've built several small (~500mA) dual rail power supplies; mostly 12-15V stuff for a pair of opamps each. These have been very simple designs since the current is very low.
However, I'm looking at my first "serious" dual rail linear PSU, something to power one Class-D amp. The module I'm currently considering is the ICEpower 500A, a 500W (@4Ohms) amplifier module. It requires a dual-rail power supply between 45V and 80V, with 75V being "recommended".
With the smaller power supplies it was easy to get started, but this seems like something else. I'm hoping for a few resources / pointers in the right direction as to where I can find information on building something like this. Perhaps I've missed it, but I couldn't really find very much!
Phill
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I remember that when I was in my early twenties I was in the same situation. I managed to rescue one broken amplifier in guitar repair shop, it was about 50$. Bringing it back to my home caused my first backpain😱 but it was worth it
... It had a gigantic transformer with 50+50V
... It had a gigantic transformer with 50+50V
The ICEpower A-series amps don't use a dual-rail supply for the high-power. You need a dual +/- 12V supply for the front end circuitry and and then a single high-power rail of what you describe. The high-power rail can be made simply by a transformer, a rectifier bridge and a couple of electrolytics.
I did my own PSU-board some years ago (see here - no boards left though). I'll see if I can get a pdf of the schematic out for you.
I realized as I crawled into bed last night that I didn't remember seeing +/- ve but was making an assumption! The 12V lines should be pretty easy.
That simple, eh? Fantastic. If you can dig out the schematic that would make my life easier, I can find some components on DigiKey and put together some new boards.
Thanks!
I've put together a quick schematic and board of what I think will work for this. It's a pretty simple design:
Schematic
PCB
(*Note, the reverse plane of the board is +V from the rectifier, joining all of the +ve contacts)
Any feedback appreciated.
One thing I have realized is that I'm going to need a fairly beefy transformer. The idea is to build a pair of monoblocks; this means that I'm going to be dealing with 500W per mono block, at around 90% efficiency that's around 550W. Multiply by three gives me around 1500VA transformer requirement. That blows my plans for 1U chassis per mono block!
I'll post my 12V boards as well (in case anyone needs them) but it's a design already in several of my components including the I/V stage of a DAC and SE > Differential stage for a preamp so I know that one is good.
Schematic
PCB
(*Note, the reverse plane of the board is +V from the rectifier, joining all of the +ve contacts)
Any feedback appreciated.
One thing I have realized is that I'm going to need a fairly beefy transformer. The idea is to build a pair of monoblocks; this means that I'm going to be dealing with 500W per mono block, at around 90% efficiency that's around 550W. Multiply by three gives me around 1500VA transformer requirement. That blows my plans for 1U chassis per mono block!
I'll post my 12V boards as well (in case anyone needs them) but it's a design already in several of my components including the I/V stage of a DAC and SE > Differential stage for a preamp so I know that one is good.
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I would exclude the mounting pads from the ground pour.
You will want to connect to the chassis PE in one spot only.
(and also eventually through a "ground breaker circuit")
Usually a "star ground" works well.
See here for example:
Ground Loops
I don´t know the Icepower modules but maybe you´d also want to include a fuse on the secondary side.
And last but not least: If you are making the effort of making your own PCB, I´d include the +-12V-circuitry as well and make it as compact as possible (see Nisbeth´s PCBs). Otherwise it´d be cheaper and quicker to buy these ready-made.
You will want to connect to the chassis PE in one spot only.
(and also eventually through a "ground breaker circuit")
Usually a "star ground" works well.
See here for example:
Ground Loops
I don´t know the Icepower modules but maybe you´d also want to include a fuse on the secondary side.
And last but not least: If you are making the effort of making your own PCB, I´d include the +-12V-circuitry as well and make it as compact as possible (see Nisbeth´s PCBs). Otherwise it´d be cheaper and quicker to buy these ready-made.
You LED arrangement is a bit off - you only need a series resistor and not a voltage divider.
My schematic is attached BTW - apologies if it is a bit messy 🙂
It doesn't really work that way in practice. You only need full power if you want to play sine waves at full blast and nobody really does that in audio.
Audio signals contain much less energy (app. 1/8th is a common rating for music) and so you need less power supply. A big PA amp would often be designed for around 1/3 power, so around 200VA for a single channel is fine, and even less would work, especially for a home amp. Of course there might be some benefit to audiophile overkill, but you don't need it.
Attachments
joesnd,
Thanks for the input - ground is already excluded and I have a fuse board (has three fuse holders) "upstream", so each circuit will have it's own fuse on the primary side of the transformer. The holes on this board are just that, holes, and I'll be using nylon standoffs as well. I'll have separate boards simply because I already have the +/- board already (leftovers from another project...)
Nisbeth,
Really appreciate the input here. I'll swap around the resistor circuit to a simple series resistor. Thanks for the advice on the transformer; I'd been trying to reconcile that since my current amp clearly does't have this size transformer in it and it's 380W Class AB! This makes a lot of sense.
Nisbeth,
Thanks for the input - ground is already excluded and I have a fuse board (has three fuse holders) "upstream", so each circuit will have it's own fuse on the primary side of the transformer. The holes on this board are just that, holes, and I'll be using nylon standoffs as well. I'll have separate boards simply because I already have the +/- board already (leftovers from another project...)
Nisbeth,
Really appreciate the input here. I'll swap around the resistor circuit to a simple series resistor. Thanks for the advice on the transformer; I'd been trying to reconcile that since my current amp clearly does't have this size transformer in it and it's 380W Class AB! This makes a lot of sense.
Nisbeth,