Simplistic MosFET HV Shunt Regs

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merlin el mago

merlin el mago

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Salas said:
The MJE's resistor is better at 5K6. If having 180V in its enough for having stable 165Vout. Use the reg's trimmer to adjust. The trimmer has its middle pin connected to its lower pin. Rheostat. Measure drop across 15K. Drop/15K=Running current. Adjust value using Ohm's law for whatever you need.
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adamus said:
Edit - double post, see next post

Salas - we are talking about different resistors. Instead of the marginal 180v in, by changing the PS we can get a higher V in (there is a large voltage ddropping R in the PS circuit , the 15k)

Cheers

adam.
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Thank you guys for kind advice, I will follows Salas advice because don't need to modificate the PSU voltage:), I take note for future problems about voltage divider thank you Adam:)

Cheers

Felipe
 
H

Hearinspace

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I built up the first version with BC560C and MPSA92 last week and on the bench with dummy load it took a long time to settle. Twenty minutes after power up and setting it was still dropping 0.1VDC every 15 - 20 seconds. Has anybody else seen this? I don't want to put it in circuit until it is stable on the bench. I'm wondering if I need to learn about temperature compensation or some other wonderful new thing.

Thanks
 
Salas

Salas

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The BJT reference one with MPSA92 drifts more due to 3 tempcos and TO-92 error amp heating up. I remember it taking 10-15mins to settle. Up R4 to 4K7 so it runs less mW on MPSA92 for starters. Best for drift would be the later Jfet ref one with TO-126 driver. An easy to get J201 can work fine too if having no K170, with the trimmer half way at 500R for Rs will give you circa 0.35mA under Vbe potential. You can extrapolate the voltage reference resistor at its drain needed for your targeted voltage output.
 
merlin el mago

merlin el mago

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H

Hearinspace

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Salas said:
The BJT reference one with MPSA92 drifts more due to 3 tempcos and TO-92 error amp heating up. I remember it taking 10-15mins to settle. Up R4 to 4K7 so it runs less mW on MPSA92 for starters.
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Interesting . On first build the reg would take about 15 seconds to start pulling the voltage down. Now with the R4 = 4K7 it seems to be kicking in right away. Still takes a while to settle but the heatsinks are what was in the drawer and are undersized until I buy the right ones for the job. So far they look good and are not oscillating. I'll step up to one of the later circuit versions after I've used these for a bit.

Thanks again!
 
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Hearinspace

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I have a line stage on the go running VT-25s at about Vp=265VDC / Ip = 30mA.

Right now ICCS is set at ~ 60mA. Vin is about 300VDC and I'll push for as high a Vout as I can so as not to change the operating point of the 10Y more than I need to. I just want to see what sort of influence the shunt regulator will have on the preamp circuit. If it it looks good then next I'll raise the B+ by about 20VDC or so to get your recommended 50V across the CCS. If still good I'll do a newer version on a nice clean board !
 
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