Supply and Regulator Circuit

Thread Starter

JulesP

Joined Dec 7, 2018
374
Hi again,

I'm building a circuit to supply 0-60V for the primary of a flyback transformer (not shown here) and also 12V to run a PWM circuit (see below).

I'm wondering if the circuit shown is a bit out of date in terms of up to date components. For example, I hear the LM317 is a good regulator and the 2N3055 is not used much these days.

Can I please have some advice on optimum components and therefore any adjustments to the circuit values/layout?

Thanks

Julian

Voltage Regulator Circuit.jpeg
 

dl324

Joined Mar 30, 2015
12,871
I'm wondering if the circuit shown is a bit out of date in terms of up to date components.
That's a terrible circuit. Where did you find it? You should always give credit for using the work of others. To give them credit and, in this case, let us know a site to avoid.
  1. We normally put the fuse on the primary.
  2. The 2N3055 (which is still a fine transistor) for a "regulator" is a joke. The voltage on the base won't be stable and neither will the output. The beta for power transistors are low, so significant current could be required from the pot. Depending on it's power rating and setting, it could burn up.
  3. 10,000 uF for the cap is pretty large. It would only need to be that large if you were planning on drawing a lot of current with a near 60V output.
  4. The 1.8k 2W resistor seems lame.
  5. If you marked MJE2955 as a replacement for 2N3055, it's the wrong polarity and it's from the same era as the supposedly out-of-date 2N3055.
 

Delta Prime

Joined Nov 15, 2019
991
hello there
:)
You're not to exceed 40 volts for the LM 317 the lm317hv can work up to 60 volts.
short circuiting the output terminals accidentally could cause an instant damage to theLM317HV
IC, that's why it is not recommended to force the IC to work at its full throttle. Below this limit, the internal short circuit protection feature could be expected to work normally and safeguard the IC from any possible short circuiting at the output.
 
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Thread Starter

JulesP

Joined Dec 7, 2018
374
Ok so how do I keep the regulator from working at full throttle, assuming the output is not shorted? I’m assuming this is a separate issue from the 0-60V output?
 

dl324

Joined Mar 30, 2015
12,871

dl324

Joined Mar 30, 2015
12,871
Ok so how do I keep the regulator from working at full throttle, assuming the output is not shorted? I’m assuming this is a separate issue from the 0-60V output?
A well designed voltage regulator IC (and most are) will handle the output being shorted. It might not handle the input being shorted, but that will be mentioned in the applications section of the datasheet. Or you could analyze the regulator circuit yourself and see if that could cause problems.
 

Dodgydave

Joined Jun 22, 2012
9,951
I would use a LM2596 buck regulator or similar, if you're going to drop from 40 to 12V , as it will get hot wasting the drop in voltage.
 

Thread Starter

JulesP

Joined Dec 7, 2018
374
It would have been a lame design 40+ years ago.
What are your requirements? What input voltage are you working with?
The input to the transistor is 48V and what is indicated out is 0-60 to feed to the regulator and to the flyback transformer.

As indicated on the schematic the input to the regulator is 48V from the mains transformer
 

Thread Starter

JulesP

Joined Dec 7, 2018
374
I would use a LM2596 buck regulator or similar, if you're going to drop from 40 to 12V , as it will get hot wasting the drop in voltage.
It might be easier if I rephrased my question as: can anyone suggest a circuit to provide an adjustable 0-60V for a flyback transformer (to raise to 30kV) and also 12V to run a PWM circuit?
 

Dodgydave

Joined Jun 22, 2012
9,951
It's better to use buck regulators for high to low voltages as they eliminate wasted heat , you can get them to give 1.25 to 60V if you want.
I wouldn't use the 2N3055 it's an old transistor and that design won't be stable.
 

Thread Starter

JulesP

Joined Dec 7, 2018
374
It's better to use buck regulators for high to low voltages as they eliminate wasted heat , you can get them to give 1.25 to 60V if you want.
I wouldn't use the 2N3055 it's an old transistor and that design won't be stable.
So a Buck regulator can replace the 2N3055 and provide two separate outputs- the 0-60V and a 12V? If so is there a ready made package doing that?
 

dl324

Joined Mar 30, 2015
12,871
The input to the transistor is 48V and what is indicated out is 0-60 to feed to the regulator and to the flyback transformer.
I can see that, but what are your requirements? I don't even have a power supply capable of providing 60V. If I needed one, I surely wouldn't try to use it to also provide a low voltage at high current; unless I designed it to be a switching supply. But switching supplies have their problems.
 

Thread Starter

JulesP

Joined Dec 7, 2018
374
I can see that, but what are your requirements? I don't even have a power supply capable of providing 60V. If I needed one, I surely wouldn't try to use it to also provide a low voltage at high current; unless I designed it to be a switching supply. But switching supplies have their problems.
The 0-60V is to power the primary of a flyback transformer where the output will be 0-30kV at around 2A-10mA.

I can use two separate Buck converters, a separate one for the 12V supply if needed, which would be cheaper than making a PCB and all the parts.
 

Papabravo

Joined Feb 24, 2006
16,094
The 0-60V is to power the primary of a flyback transformer where the output will be 0-30kV at around 2A-10mA.

I can use two separate Buck converters, a separate one for the 12V supply if needed, which would be cheaper than making a PCB and all the parts.
I don't see how that can work. Buck converters go from a higher voltage to a lower voltage.
The 12V supply should be a traditional mains to 12V supply, unless you need it to be portable, then maybe you could do a single SEPIC converter for say 13.8V to 11.2 on the input.
https://www.ti.com/lit/an/snva168e/snva168e.pdf

Using the primary voltage to control the output voltage is IMHO a dubious enterprise
 
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