the circuit is fine and will work but with lower efficiency. the regulator u used r linear regulators which r very less efficient of about 60% and dissipate lots of power as heat in case the load is very small. You will end up wasting power.
Instead, u can ideally use one high current (in ur case 6 A) switching regulator with power factor correction to attain maximum efficiency of 98-99% using any small PIC MCU. there r lots of application note on high power buck convertor on microchip website. The op voltage can be configured to 24V. You can use this o/p directly for 24V peripherals. In case of lower voltage like 5V or 3.3V, u can use any good linear regulator with regulated 24V as i/p and regulated o/p, the efficiency will be good enough. If used the single chip switching regulators from linear technology or analog devices, the efficiency will increase and the power dissipation will decrease further.
The circuit will be a bit complex but ur efficiency and regulation will be higher.
hope that helps.
I'm a noob to circuit design, but I am building a custom controller for my pool equipment and need to have 5v DC, 12v DC and 24v DC. The native transformer in the system is a 24v AC unit which I need to keep. To solve my problem, I've created a single circuit which supplies all of the DC voltages that I need. I believe that I've sized the capacitors properly and have chosen a combination of a bridge rectifier and 3 voltage regulators to provide the voltages I need.
I'm assuming that I may generate quite a bit of heat if I put too much load on the 5v circuit, so I'm planning to put a heat sink on that IC and measure temperature of the enclosure to make sure I stay within operating temperature. I also think I'm cutting it a bit close on the 24v DC line. My transformer puts out closer to 28v AC, but there is definitely some signal loss through the circuit. Fortunately, the only thing I need 24v DC for is a few relays and their minimum voltage to activate is 18v DC.
I've uploaded the circuit diagram to Skydrive and made it public. If anyone has time for a quick review, I would really appreciate your comments. I'm getting ready to break out the soldering iron. Also, if anyone would like the Visio of the circuit I'd be glad to share. I've included a parts list in case any other readers would like to try this at home.
Circuit design - https://skydrive.live.com/redir?resid=A7637C7D6CC3DC5!23878
No it does not ...Does this power supply look okay?
I'm a noob to circuit design, but I am building a custom controller for my pool equipment and need to have 5v DC, 12v DC and 24v DC. The native transformer in the system is a 24v AC unit which I need to keep. To solve my problem, I've created a single circuit which supplies all of the DC voltages that I need. I believe that I've sized the capacitors properly and have chosen a combination of a bridge rectifier and 3 voltage regulators to provide the voltages I need.
I'm assuming that I may generate quite a bit of heat if I put too much load on the 5v circuit, so I'm planning to put a heat sink on that IC and measure temperature of the enclosure to make sure I stay within operating temperature. I also think I'm cutting it a bit close on the 24v DC line. My transformer puts out closer to 28v AC, but there is definitely some signal loss through the circuit. Fortunately, the only thing I need 24v DC for is a few relays and their minimum voltage to activate is 18v DC.
I've uploaded the circuit diagram to Skydrive and made it public. If anyone has time for a quick review, I would really appreciate your comments. I'm getting ready to break out the soldering iron. Also, if anyone would like the Visio of the circuit I'd be glad to share. I've included a parts list in case any other readers would like to try this at home.
Circuit design - https://skydrive.live.com/redir?resid=A7637C7D6CC3DC5!23878
:idea::idea::idea:Is this the part you suggest:
https://www.mouser.com/ProductDetail/Texas-Instruments/LM2576T-50-NOPB/?qs=X1J7HmVL2ZE00R3IkTMYRw==
Most definitely go with that part or one of it's equivalents. You will also need an inductor, a Shottky diode and some low ESR capacitors but the difference in performance is well worth the price. Even with all three regulators on a small heat sink it should run quite cool at full load. In your existing design it would produce around 90W of heat so you would not only need a large heat sink but a cooling fan as well.
I'm working on pool equipment as well at the moment, just out of curiosity, what is it you are building?
Brian.
That's not quite how they work. It's easier to think of them this way in aquatic terms:
You have a water tank and you want to maintain a constant flow from an outlet connection near it's bottom. You don't want the tank to run dry and you don't want it to overflow. There are two methods to achieve it, one is the linear regulator analogy, you pour as much water into the tank as you take from it to maintain the level, the other is the switch mode analogy, you let it almost empty then fill it up in one go. Both achieve the same end but one takes up all your time and effort, the other gives you breaks when you are doing nothing.
Putting it in electrical terms, a linear regulator converts unused energy into heat, a bit like a tank full of water that isn't doing anythng useful because the level is higher than it needs to be. The switch mode regulator tops up the output only when it is needed. That's why the low ESR (low Equivalent Series Resistance = a good capacitor) is needed, it's the tank in the analogy. Just as in a linear regulator, the power loss is the voltage dropped across it multiplied by the current flowing through it. In your 5V circuit, the drop is about 30V - 5V = 25V multiplied by 2Amps = 50 Watts. In a switch mode supply some magic happens! the power is switched on and off in a series pass transistor, when it is turned off, no current flows through it so the power loss is V x zero = zero and when it's turned on it looks like a short circuit so (almost) no voltage is dropped across it and zero x I = zero. In a perfect world no power is lost at all, always either V or I is zero. The voltage is kept steady by controlling the amount of time the transistor is turned on relative to it's off time. The other bit of magic is the diode and inductor, These do two things, firstly the current flowing into the capacitor is restricted by the inductor so the voltage doesn't jump up and down as the transistor turns on and off and secondly, the way it does it is by absorbing some of the current to build up a magnetic field in it's core. When the transistor switches off, no more current is 'pushed' through it and the magnetic field starts to collapse. The magnetism is converted back to electricity and in such polarity that the diode conducts and allows it to flow into the capacitor. so the capacitor is topped up twice per switching cycle. It's a very efficient process and designed properly can reach almost 100% efficiency. Compare that with your linear design, on the 5V rail to produce (5V x 2A) 10W of regulated power you waste 50W in heat.
You might be able to use a linear regulator for the 24V line but the voltage at it's input can reach Sqrt(2) x 24V = 34V so you are actually dropping more than you expected. The actual voltage depends on how well the transformer output holds up under load.
You can contact me through my web site, you can see it in my profile on Edaboard. I warn you that I get several hundred emails every day so it may take a while for yours to reach the top of the pile!
Brian.
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