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BluesPowerMini: Dual Shunt Regulator power supply

Luxman Amplifiers India

doors666

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Finally the board for the mini version of the BluesPower Shunt regulator pcb arrived. This one is basically a toned down version of its big brother. Its pretty much the same circuit that is being used in BumbleBee preamp.

Main differences with the BluesPower:
1. No CRC filter at the input.
2. Single zener to set the voltage. Blues power supports 3 zeners.
3. Less output pads. 2 per rail and 3 for ground (1 can be used for earthing). BluesPower supports 4 per rail and ground and another for earthing.
4. No buffer for the zener voltage, drives the gain stage directly.
5. Only film cap for zener filter, you can fit an electrolytic there if you want, but not both unless you use bottom of the board.
6. Second ccs doesnt have a split resistor and a cap, but just a resistor.
7. Doesnt support the flowery heatsinks. You need flat heatsinks. Might need insulation.
8. All of the resistors supported are 0.25w, so not really suitable for high voltage builds like for tube gear, those need 2w resistors that are supported by BluesPower.
9. This uses the more common BC550 and BC560 small signal transistors.
10. Single indicator LED, tied to the +ve rail only. I should have connected this to both the rails.

The power fets are at the edge of the board and you can use any flat heatsink. For larger currents, the TO-3 heatsinks are will be a good choice. You will need to insulate atleast one of them. In my build, the ccs fet dissipates less heat, so I have used a smaller heatsink for that and insulated that. The heatsinks are anodized anyway, so they are non conducting, but I insulated anyway just to be safe.

This build I am running at about 75ma. With the teensy heatsinks shown, it runs barely warm without load (which is the most heat dissipating), but keep in mind that I am in bangalore and its weather has been quite cool these past few days. This is suitable for two dual opamps like BBS preamp or CNC phono or any other one or two opamp project. Of course you can run it at higher currents too (e.g. for a headphone amp), you just need to provide suitable heatsinks. Apart from the power fets, nothing else will dissipate any significant heat.

Unfortunately, I ended up using different caps for the output by mistake, I have both ky and kze of same value in the same bag and just soldered them without checking. Need to change that.

BTW, neither of these regulators use any jfets, so that headache is not there. Although if you need matched output voltages for both the rails, you will need to match the zeners. Its quite easy to do that, just need a larger voltage supply than the zener voltage and a suitable resistor. You can also match them in circuit, solder two wires for zener and connect the zeners to them (just tie the wire to zener or use a breadboard) and measure output voltages till you find matching ones.

I used 16v zeners. These are 5% tolerance, After trying 5, I got 2 that had a voltage of 16.58v. These set the output voltage to 17.24v exactly. The output voltage is zener voltage + 0.65v. Perfect for those 18v opamps. Transformer is 18-0-18v. Both my dmm and oscilloscope failed to detect any ripple. I need to use soundcard and RMAA to measure it. I am going to replace the LM317+CRC power supply from my BBS preamp as well as in my basic B1 build.

Pictures:

Partly soldered boards for clarity









Completely soldered board, 9v battery is for comparison. I have the berg connectors for the led for the time being.




Simulations show ripple at about -159db. the load is 40ma DC and 10ma RMS AC at 1khz. output impedance at 1khz is 1.5 milliohm, at 20khz it is 2.2 milliohm, at 100khz it is 8.3 milliohm. That is about a 1000 times better output impedance than the standard 9v batteries which I believe have an output impedance of about 3 ohms.

I am going to make kits soon for this one. Let me know if anyone is interested.
 
Last edited:

doors666

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Blues Power Mini Shunt Regulator Kit

Blues Power Mini Shunt Regulator Kit

Finally the kits for the Blues Power Mini builds are ready. Few more days for the Blues Power big shunt regulator kits.

The schematic, BOM, Build Guide etc and images are on the site here.

Some details on the parts:

Bulk caps ELNA RKD 2200uf 35v 125C
Mosfet for shunt elements IRF510 and IRF9540
CCS Transistors TIP31C and TIP32C

TO92 transistors Philips BC550C and Fairchild BC560B
0.1uf 63v epcos polyester caps

Split resistor cap for main ccs Nichicon VR 220uf 35v
Output caps These should not be too high in value, keep them at 470uf max. Dont put caps with too low ESR. Max cap dia is 10.5mm. I have the following options available. Please let me know which ones you want.

Nichicon PJ 330uf 25v 105C
Panny FC 105C 470uf/25v, 330uf/35v, 220uf/35v
UCC LXZ 330uf/25v 105C
ELNA RJJ 100uf 35v 105

You also need to specify the zener diode voltage. Your output voltage will be about 0.65v more than the zener voltage. Zeners have 5% tolerance. You need to match the zeners if you want same output voltage on both the +ve and -ve rail. I will provide 5 zeners so that matching ones can be chosen if needed. I have quite a few zeners, 7.5, 8.2, 9.1, 10, 12, 15, 16, 18, 20, 24 etc.

For setting the total ccs current, two resistor values are provided 8.2R and 10R. Each value has 5 pieces for matching the currents. The first will give you about 80ma of current and the second about 65ma. Leaving aside about 12-13ma for the shunt regulator and about 10ma for the shunt element, you will get about 40ma and 55ma max load current. These should be ok with upto 3 dual opamps, assuming you are not using a particularly current hungry one. If you need more current, let me know. Heatsink needs to be correctly sized though. Small commercial heatsinks like I used in the pic in the prev post (the larger of the two) can only handle the 10R 65ma. With 8.2R 80ma, in my setup, it was at 50C after couple of hrs of use with the BBS preamp as the load. Dual TO3 heatsinks will be a good idea for the 80ma or slightly higher currents.

Let me know if any one is interested or if you need help configuring it.

Kit Picture:

 
Last edited:

doors666

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finally got a decent heat sink for this supply, quite cheap too. its the dual TO-3 heatsink that fits perfectly.



Now it running with a 6R current setting resistor. I just soldered a 22R at the bottom of the existing 8.2R, lazy guy that I am...:).. Its running at about 108ma shunt current now. The heatsinks are still quite cool, the temperature went up from about 26C to 41C, giving an increase of about 15C. I think I can easily use a 5.6R resistor with this, which will give me about 115ma total shunt current with a little bit more heat dissipation.
 
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