B+ regulator

[Frederico Acardi]

It's not a regulator, I think.

 

[gerrittube]

Hi Frederico,

By changing the zener value you can regulate the output voltage. Or you can add a potentiometer for a variable voltage.

Regards, Gerrit

 

[Frederico Acardi]

Thank you I thought it was acting like a big inductor.

 

[Bigun]

B+ is only 300V in my case,
3A would include a margin as that would be the maximum peak power that would be rare in practice.

It's a PP 6P45S triode connected - they can and will peak 1.5A each channel at full blast if there's a transient... On average, the current stays below 1A though, and idle is 80mA per tube. The load is ~1k plate to plate...

an impressive amp.

and Schmitz77 has the solution !

I had read somewhere that shunt regulators are better suited than series in the case of inductive loads as the can sink current. Not sure if that would ring (pun?) true with adequate rail capacitance.

 

[oemcar]

Maybe my T-reg fits the bill?

T-reg HV regulator | Linear Audio NL

Jan

Hopefully B+ can be regulated w/ something simpler-
Penciled something up linked below. 'Net research doesn't seem to like series/shunt designs for hi voltage apps... but I'd think the series'd zeners change the operating range dynamic from total V to affected V..
Thoughts?

 

[Francois G]

This is a very basic but reliable regulator. You can change component values for different voltages.

gerrittube, could you talk about or recommend a value for the resistor shown at the MOSFET gate?

Thanks.

 

[v4lve lover]

Most of the capacitance is bootstrapped, anything between 100 Ohms and 1K will do as a grid stopper.



Id be more concerned about your choice of mosfet. There are some specially made to work as DC regulators, the IXYS L2 series is an example, these have higher DC overload potential and hence are harder to kill. This part is expensive but hard to kill
IXTH30N60L2 IXYS




I suggest a modified circuit with transistor current limiting and an additional RC stage between the zener stack and the mosfet.

 

[gerrittube]

Hi Francois,

I use a gate resistor of 1K, it’s not very critical.

Regards, Gerrit

 

[oemcar]

Audio Note M7 Line Preamp

This is a very basic but reliable regulator. You can change component values for different voltages. Make sure the MOSFET you use has internal protective diodes or add them to this circuitry. The IRF420 is just one example, there are lot’s of better MOSFET’s available.

I built several using various MOSFET’s, one of them does 600 VDC @ 500 mA (continuous load...).

Regards, Gerrit

Problem w/ FET is gate voltage headroom needed- I don't have it unless I build separate reference circuit...
I'm bridge rectifying 240vac to dual 330uf(s) PI network to extract much E as possible. The shown 340V is product of 240 x 1.414- no load. Since FET's require 8-10vdc of gate E over target out of +300, I chose Bipolar to maximize I out- sorry for not being more descriptive.
Jim

 

[Diabolical Artificer]

"I built several using various MOSFET’s, one of them does 600 VDC @ 500 mA (continuous load...)." When I looked at building a regulated screen grid supply recently all the mosfet's I looked at have very low current capability at high voltage. Look at any SOA graph's for high voltage mosfets and you'll see what I mean.

If you use a bipolar not many are rated for high voltage and those that are have very small hfe, the best series pass device for HV is a valve or valves in parallel.

There are several design's out there for HV regulators but not many have really good SC protection.

Andy.

 

[v4lve lover]

Look at the L2 series mosfets i have specified earlier, they are expensive but they can stand the current at high voltage, their SOA is up to a factor five better than a switching optimized device.

 

[Diabolical Artificer]

See what you mean,that's a lot better than the ones i looked at,in a TO-247/TO-3P package too, better heat dissipation. Nice looking mosfet for HV regulation but at £10 each not cheap.

A.

 

[oemcar]

If you use a bipolar not many are rated for high voltage and those that are have very small hfe, the best series pass device for HV is a valve or valves in parallel.
Andy.

Thats what I was asking in post 25-
Not sure if Vce will ever see hi voltage? Seems to me that value would be delta V, or 60V max Vce. Perhaps during warm up- but if properly biased Vcb, then emitter should follow and all voltages should come up at similar rate- unless a big current change during warm up.

Think I'll try circuit w/ NTE376 and monitor voltages. W/ Vce of 300v, there's safety margin. Yeah it's kinda pricey.
Jim

 

[astouffer]

One of my regulators used a BJT scavenged from an old monitor. It was rated for 1200vdc and even had the insulated package. It was a 2SDxxxx series number.

 

[longspeak]

v4lve lover, the linear series from IXYS is a good tip!

Here is one that is 1500V and seems like a good SOA for most B+ applications:

 

[v4lve lover]

Your welcome, its just a bit sad to use these in a primitive capacitor multiplier, I think these would run fine in Jan's T-Reg. That is a real regulator in the truest sense.



if you don't need the 1500V capability, stay with the 5-600V devices.


I use the 75V 80A part in my regulator for 833 not because you need that much safe operating area in that application, just because its a bombproof FET and has some nice behaviour around 5A