Hi folks,
just looking for some of you to have a quick look over my two PSU designs for any flaws before I etch them. Cant decide between the TIP31C design or using a LM317 regulator. What do you think? I may do both and just test them separately.
Much appreciated.😀
Dom
just looking for some of you to have a quick look over my two PSU designs for any flaws before I etch them. Cant decide between the TIP31C design or using a LM317 regulator. What do you think? I may do both and just test them separately.
Much appreciated.😀
Dom
Bit hard to see with the colour scheme but the TIP31 version has errors. The presets will do nothing as they are AC coupled to ground. Also the error amp (Q1 and Q5) needs a reference voltage in the emitter (zener). The driver transistors appear as though you are trying to make a darlington out of them yet the 100 ohms still limit ultimate base current for the outputs. Also the BC337 is far to small a device as a driver.
The LM317 version will be limited in current delivery.
The LM317 version will be limited in current delivery.
The first circuit can deliver up to 9A constant current per channel while the second with the lm317/337 has a current output of 1~1.5 A. What is the power requirements of your amplifier?
I noticed that you use a 5K variable resistance for the LM317 and a 10K for the LM337 why is that?
Why don't you replace the LM317 with an LM338 and get the best of both worlds excellent regulation and high current output it has its limitations of course but the parts count is far less than the transistor circuit.
Best regards. 🙂
I noticed that you use a 5K variable resistance for the LM317 and a 10K for the LM337 why is that?
Why don't you replace the LM317 with an LM338 and get the best of both worlds excellent regulation and high current output it has its limitations of course but the parts count is far less than the transistor circuit.
Best regards. 🙂
Thanks Mooly. Updated the reference voltage not sure how I missed that😱 I thought the BC337 would be just enough to drive as its rated 0.8A. I have BD139/140 spare so I might just replace the BC337 with that. 100 ohms should have been 10 ohms just to limit the driver. Can you elaborate on the preset comment I don't see what's wrong here?😕
Cheers
Dom
sghr220 thanks for input. I'm building hexfet amp details here http://www.diyaudio.com/forums/solid-state/237219-fet-hex-explendit-amplifier-55.html#post3656739
The datasheet I have for LM317 has 2.2A output.
I reckon I need +2A/-2A per channel.
I would therefore build 2xLM PSU (one for each channel) but build only one TIP PSU for both channels.
The LM317 & LM337 have different internal resistances so require different values of resistors to set the output.
I would use LM338 but I don't want to buy more components as I already have loads of TIP31/32, BD139/140, BC337/327, IRF9540/540, LM137/337 etc
Cheers
Dom
The output current (peak current not constant) is a function of the Input-Output difference voltage...
An externally hosted image should be here but it was not working when we last tested it.
If the supply to the amp is +-35 VDC then @ 8 ohm load you're gonna need approximately twice that 2.2A am i right?
Could you point out that part of the datasheet as i don't recall seeing any dual supply circuit with different resistor values between the positive and negative halves.
The Vin-Vout difference I thought was the change in voltage your regulating, since I have Vin 40 volt and Vout 35 volt this is only a 5V difference, therefore 2.2A is okay. if I wanted 10V Vout this would be a 30V difference an therefore I can only have 1A constant current as the voltage across the LM317 will cause it to heat up too much and therefore de-rating it?
I'm sure I have it on one of the LM317 datasheets. It does show it on Soft Start
With a supply rails of +-35 VDC the amplifier output peak can be about 32VAC, if the load is an 8 Ohm impedance the current drawn is about 4A, the LM317 regulator cannot supply that even if the input-output difference is within 10V.
Best regards. 🙂
Best regards. 🙂
C5 and C17 are in the "earthy" end of the preset. This means the preset can not give a variable voltage on its wiper. All it will do at the moment is fully turn on the error amp and pull the regulator output down to minimum voltage.
Ah I see. Thanks Mooly. The reason I put that in was to try to provide a soft start up
I have updated the schematic below. I only have 15V 1N5352B Zeners.
That's looking better. One other thing, the three paralleled power transistors almost certainly won't share the current equally due to device differences and differences in temperature between them. You need three equal and low value resistors (say 0.22 to 0.47 ohm) in the emitter of each to help equalise the current sharing.
Thanks Mooly. I have updated schematic and created PCB below. Just waiting on RS to deliver my Developer powder tomorrow then I can get cracking.😀
1. I might prefer to have additional bias current flowing through reference diodes D5 and D6, above and beyond the emitter current of Q3 and Q7.
2. I also might prefer to have additional bias current flowing through predrivers Q4 and Q8, above and beyond the base current of T1-3 and T4-6.
3. Perhaps have you noticed p.325 in Bob Cordell's amplifier design book? He suggests installing a diode that is not present in your schematic.
4. It appears that "ground" is not routed on the blue layer; perhaps that means it is a "fill" or "flood" on another layer? If so you may want to investigate star-grounding and/or hierarchical star-grounding ("star on star"), e.g., Cordell pp. 357-8.
5. I might prefer to widen the blue-layer traces which carry supply current, especially the bridge-in, bridge-out, and REout traces. Visually, it appears there is plenty of room to make them significantly wider (lower R, lower L).
2. I also might prefer to have additional bias current flowing through predrivers Q4 and Q8, above and beyond the base current of T1-3 and T4-6.
3. Perhaps have you noticed p.325 in Bob Cordell's amplifier design book? He suggests installing a diode that is not present in your schematic.
4. It appears that "ground" is not routed on the blue layer; perhaps that means it is a "fill" or "flood" on another layer? If so you may want to investigate star-grounding and/or hierarchical star-grounding ("star on star"), e.g., Cordell pp. 357-8.
5. I might prefer to widen the blue-layer traces which carry supply current, especially the bridge-in, bridge-out, and REout traces. Visually, it appears there is plenty of room to make them significantly wider (lower R, lower L).
Thanks for your input transistormarkj. Much appreciated.
Comments are as follows:
1:Yeah the 2.2k resistors were for a different type of driver. My intention was just to build it and see what values i measure and then change the resistor values as needed but thanks for pointing that out i may lower them to 1K or so.
2. As 1.
3. Thanks for pointing me in the direction of this book; very interesting read. I shall insert the diodes although I'm not sure if i have beefy enough ones available. What type would you recommend?
4. Yes for clarity i uploaded the board layout without the ground plane. All the copper not used by the actual circuit will form GND (apart from clearance gaps obviously🙂). I was going to use a star ground but i never thought of splitting it into two using the star on star. (fig 16.8) The board i have is quite full but i may be able to alter it to suite the star on star approach.
5.My intention was to thicken the trace with solder and copper wire on high current traces rather than making them too wide to allow a good ground plane.
Cheers
Dom
Diodes that protect when the other rail fuse blows, need to carry enough current to blow this side's rail fuse. I use either the MUR1520 (15A, 200V) or the FFPF30UA60 (30A, 600V) depending on which one I have on hand in the parts bin. They are surprisingly inexpensive for the beefy specs they provide.
Final BRD and SCH before I etch.
Thanks for everyone's input.
If anyone wants the eagleCAD files just ask.
Thanks for everyone's input.
If anyone wants the eagleCAD files just ask.
An externally hosted image should be here but it was not working when we last tested it.
asked
Hi DomyBoy,
or anybody here.
please apologise to ask the old thread.
just curious if you got all the scheme worked good with high current load.
Any clue or results from your projects ?
i.e V out drop under low/high load measurements.
Transistor Heat etc.
thanks
Br
jacob
Hi DomyBoy,
or anybody here.
please apologise to ask the old thread.
just curious if you got all the scheme worked good with high current load.
Any clue or results from your projects ?
i.e V out drop under low/high load measurements.
Transistor Heat etc.
thanks
Br
jacob
Hi DomyBoy,
or anybody here.
please apologise to ask the old thread.
just curious if you got all the scheme worked good with high current load.
Any clue or results from your projects ?
i.e V out drop under low/high load measurements.
Transistor Heat etc.
thanks
Br
jacob
H Jacob
Yes got it all working. Have a look at my build here: https://www.youtube.com/watch?v=WGpau-raMho
Its a good stable power supply and can deliver decent currents however i recently upgraded the shunt transistors to TO-247 devices.
The voltage drop over the shunt transistor is around 11V that's with +-35Vdc output and 300VA 0-30-0-30 transformer. My mains is slightly high at 241V hence the high voltdrop. I recently changed the TIP31/TIP32 to a more robust TIP35/TIP36 which is a TO247 package and it is far better. the TIP31/32 couldn't handle the currents. I use a waterblock to cool the TIP35/36 as there is a lot of heat from the 10V drop over the transistors. As well as changing the transistors I upped the voltage to my power amp to +-45 which is the max that the regulator can output but this reduces the heat output from the transistors.
If you want me to measure various voltages just let me know.🙂
Cheers
Dom
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