HV Shunt Regulator PCB - Page 25 - diyAudio
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Old 9th June 2012, 09:47 PM   #241
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I'm a little worried that R16 should be a "beefier" trimpot (Bourns 3296W 500mW specified). At mid-rotation, under full load conditions it will be maxed-out.
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Old 9th June 2012, 10:49 PM   #242
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Looks pretty good -- will have to test for output impedance next:

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Old 29th June 2012, 11:35 AM   #243
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Hi, any pcb left for me? I want four pieces...Thanks in advance for the quick answer.
Regards,
Horia.
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Old 5th July 2012, 07:54 PM   #244
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Only 6 PCB left.

Lordvader, I guest you're testing the circuit with a load attached. The tests voltages on this circuit depends on using the same very test load, in this case 22K. If you use a different value, you may get other results.

At the first look I think you have problem because you're testing this circuit in the wrong way. Shunt regulator can be confusing compare to a standard serie regulator.

R12 voltage. First this is the shunt current reading resistor. The total regulator current (LOAD + shunt, here current passing throught R12) is set by R16. IF THE SET CURRENT is too low for the load, the shunt regulator output will be ZERO... Hence the need to check the regulator with the same test resistance, or to know exactly what you're doing.

This regulator can supply a maximum of 125ma AND a minimum of 20ma. A shunt regulator regulate the output voltage by shorting to ground some of the source current, loading the voltage.
First you need to calculate (or test with a regulator serie supply) what will be the normal load current at your needed voltage, example 30ma. Then you add some shunt current, example 20ma. That gives a total of 50ma. So you need to adjust R16 in order to get this current. Turn R16 until the output HV increase, and that you start to have so current going throught R12, then set it for 20ma in R12.

Last edited by Algar_emi; 5th July 2012 at 08:15 PM.
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Old 5th July 2012, 08:33 PM   #245
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I'm modifying one of the boards to use the DN2540 instead of the aux power source for the error amplifier.
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Old 5th July 2012, 08:34 PM   #246
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Other voltages
pin 2 = 7V (fine)
pin 3 = 1.2V (wrong !!!)
Pins 2 and three are the input of a differential amplifier. They have to be the same when your regulator is at the correct output voltage. pin2 is the reference volatge, here 7V. Pin3 at 1.2 volt simply indicates that your output voltage is too low, probably because your cannot supply enough current, see before...Nothing wrong there.
pin 6 = 0.9V (correct for mostfet shunt) 0.9V indicates that the circuit is not working, again current to low.
pin 7 = 10.6V (correct) IC supply, correct.

Checking other voltages, the voltages immediately after T2 are way low. RAW DC coming in about 300V, but after T2 the voltages are 65V.
What should the initial position of R3 be ? The documentation has no mention of a default value ...R3 is simply a resistive voltage divider formed by R19+R18 and R13+R17 You can simply calculate the preset value by knowing that at the correct output voltage the output of this voltage divider has to be 7.0V. With the default values used on the schematic for R17-R19 the possible adjustable range is 230 to 470V as indicated on the notes. In equation 7V = Vset x (R17+R13)/(R18+R19+R17+R13) or 7V = Vset x (R13 + 4K7) / (304K7 + R13)

For example for a minimum of 230V, R13 = 0 (set to minimum) so 230V x (4K7/304K7) = 6.98V, very close to 7V... It works.

Again for this reg to work, you need a pcb input voltage higher than 20V than the value you want to set the reg to. For example for 230V at the output, you need at least 250V at the input.

IMPORTANT. There is a trade-off to do here. DON'T use an input voltage higher than needed, or you can exceed the power dissipation of the CCS. For example, you cannot use a 500V input voltage with a 230V output voltage at 50ma. That would mean that the CCS would have to drop 270V (500-230) and dissipate 13.5W (270V x 50ma). It would certainly get really hot and destroy.

So use an input voltage near the output you want. USE the proper power transformer.

Read all the notes on the schematic CAREFULLY. It explains everything you need to know about this board.

Hope it help.
SB
Attached Images
File Type: jpg Shunt Regulator_v1.1_Schematic_with notes_small.jpg (80.1 KB, 465 views)

Last edited by Algar_emi; 5th July 2012 at 08:38 PM.
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Old 6th July 2012, 02:31 AM   #247
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Thanks for getting back to me.
I should have some spare time over the weekend to restest some things.

I did my testing with a 2.8K resistor, to simulate ~210V, @ 78ma.
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Old 6th July 2012, 08:11 PM   #248
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This is what I was thinking of -- it can be found in Supertex application note AN-D30.

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Old 18th August 2012, 01:10 PM   #249
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How many PCB left? I am interested in two, possibly four.
Thanks a lot.
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Old 19th March 2013, 01:49 AM   #250
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I have just 2 PCB left fo sale. Contact me if interested. SB
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