| Electronics > Beginners |
| A niche chip (LT4320) for mains powered AC -> low volt DC "linear" based psu ? |
| << < (12/20) > >> |
| tszaboo:
--- Quote from: Phaedrus on December 28, 2013, 04:57:59 pm ---Crack open one of our CoolerMaster V850 power supplies and tell me that's cheap crap. It may not be lab grade, but it's solid engineering and good build quality. ;) --- End quote --- wow, they are using double sided PCB, which is not from paper, and there are even smd components on a small board. They are only 20 years behind todays technology, not 25. To be honest, I really think that PC power supplies are lagging behind. A modern design would use planar magnetics, moderate-high switching frequency, multiple phases for DC-DC, SMD mosfets, power blocks like drMOS, and pulse skipping or other intelligent driving to increase efficiency for light loads. Also most PC power supply is standby power hog, because the lack of secondary circuits for that. Well I guess these will be standard in 20 years or so. |
| digsys:
--- Quote from: M. AndrĂ¡s ---im wondering if this chip could be used with pretty low rdson fets and its power supplied externally it doesnt need much so a small bridge rectifier from the main ac feed maybe? high power losses would be minimal too --- End quote --- Very unlikely. If you've ever looked at designing a FET bridge, there's a very tight relationship between the AC side and DC side. Supplying a separate low VAC for the charge pumps, even IF you could line up phases etc is unlikely worth it. Basically, the "control chip" watches the VAC level coming in, compares it to the DC level, and once it becomes +ve, switches the FET. On higher currents, it waits until the onboard Shottky conducts before doing so. You can see it in the waveforms. If you don't do this, at the instant of switch-on, depending on cap storage = app INP/OUT impedance, the VAC can suddenly DROP again, below DCV, in which case you now have current feeding BACK into the Transformer (in this case). It's only a short time, but can cause huge current spikes / losses. I'm about to make up a bi-dir current sense and really get a better picture. Having made these devices in the past (using optos, external charge pumps and isolated high speed logic control), it's a really very tricky design, which is why I was so impressed with it. ALL it needs is a 0V side referenced shutdown pin (maybe Ver2?) and it'd then truly be AWESOME !! I've tried to email them with suggestions, but it's impossible to find a tech feedback addy. You would have thought? Why do we need this? O/Temp, O/Current, O/Anything SHUTDOWN ! The perfect oN/oFF control of up to 20-30A with a 10uA 3V signal !!! woohooo heaven. |
| Phaedrus:
--- Quote from: NANDBlog on December 28, 2013, 09:02:40 pm --- --- Quote from: Phaedrus on December 28, 2013, 04:57:59 pm ---Crack open one of our CoolerMaster V850 power supplies and tell me that's cheap crap. It may not be lab grade, but it's solid engineering and good build quality. ;) --- End quote --- wow, they are using double sided PCB, which is not from paper, and there are even smd components on a small board. They are only 20 years behind todays technology, not 25. To be honest, I really think that PC power supplies are lagging behind. A modern design would use planar magnetics, moderate-high switching frequency, multiple phases for DC-DC, SMD mosfets, power blocks like drMOS, and pulse skipping or other intelligent driving to increase efficiency for light loads. Also most PC power supply is standby power hog, because the lack of secondary circuits for that. Well I guess these will be standard in 20 years or so. --- End quote --- It's a 300KHz LLC resonant full bridge. We use SMD mosfets for secondary rectification for the +12V rail, mounted on the bottom and heatsinked to the housing. We use pulse skipping to improve efficiency at light loads; at 10% load you can expect 85-87% efficiency (depending on if you have the 700W, 850W, or 1000W). Planar magnetics aren't cost-effective for us, and DrMOS has proven unreliable for us with few advantages over discrete components. You could buy something like this twenty years ago--in a bespoke device costing $10k+. Now you can get it in a consumer device for $80 - $150. And still they bitch? The snobbery of some engineers continues to astound. :=\ |
| necessaryevil:
I agree it is indeed amazing what you get for your bucks buying an ATX psu. I guess that making a more efficient ATX supply is not more cost effective (the reduction in electricity costs is not enough to pay back the higher initial costs). But back on topic. Would it be possible to make a batch of those pcb's (which will make it cheaper)? |
| tszaboo:
--- Quote from: Phaedrus on December 29, 2013, 12:25:20 am ---... --- End quote --- It looks like it has more features than I anticipated. Probably they did not take fully apart because of the SMD on the bottom. May I ask why was DrMOS unreliable? I'm recently looking into the possibility use them in industrial applications. The only downside I see right now, that the internal MOSFET sizes are not optimal for my output voltage (I need about 2-3-4 volt output, not 1.2-1.5V they are designed). Can you share some background information? |
| Navigation |
| Message Index |
| Next page |
| Previous page |