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Shunt Regulator

Hi,

Devices:

  1. BJT Transistor :
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  1. DC TO DC Converter :
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  2. Zener Diode :
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Schematics:

Figure 1 and Figure 2

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Problem Description:

A) Figure 1 works fine. The problem is that Q1 gets hot after ten to twenty minutes. I am thinking of using two ZTX651 in parallel as shown in Figure 2. This might divide the current and lower the heat dissipation.

Am I right? Or should I use a BJT with Vce greater than 100Volts and Pt = 5 Watts?

B) I read about Shunt regulator circuits on the following link.

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Is this better approach than putting the BJT in series with the load? Any pointers on how to choose the transistor for this approach. Any comments!

jess

Reply to
jsscshaw88
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306

minutes. I am thinking of using two ZTX651 in parallel as shown in = Figure 2. This might divide the current and lower the heat dissipation.=20

=3D 5 Watts?=20

Any pointers on how to choose the transistor for this approach. Any = comments!=20

I think your issue is even more basic. How to analyze when a shunt regulator, a series regulator, or a switcher is more appropriate.

The issues start from voltage, current, regulation accuracy, cost effectiveness, waste heat and heat sinking, and variable output requirements.

Many other can tribute to this, but engineering judgment becomes part of the picture. Eapecially for what i provide in this post.

Please provide:

Supply voltage (or voltage range), Supply current range, regulation accuracy (in both voltage and current as needed), total power to be provided, noise and ripple requirements, efficiency versus available waste heat limits, et cetera,,

All of these matter in choice of power supply technology choices. Help us help you by either being more specific or asking for tradeoff information (within a more limited range).

?-)

Reply to
josephkk
[big snip]

If you remember the thread on "Parallel LC Circuit" which you posted to = July=20

6, and another thread on "Zener Diode and Bridge Rectification", this is =

part of a project which seems to require obtaining power from within a=20 Helmholtz coil running at 100kHz, and it looks like it needs to power = some=20 electronics at 3.3VDC and about 5W. If you consider that information as = the=20 actual requirement, it greatly simplifies the entire design. You just = need=20 to design the pickup coil so that it provides at least 5VAC and probably =

30VAC maximum (judging from 10-60V range). It may even be possible to = use a=20 capacitor or inductor as a current limiter and use a 5W 5V zener and a = 3.3V=20 linear LDO. Or get one of the $2 LM2596 switching circuits which will = handle=20 the 30V input with high efficiency.

This seems like a series of bad design decisions and multiple attempts = to=20 patch them up without looking at the whole picture and designing the = whole=20 thing accordingly.

Paul=20

Reply to
P E Schoen

July=20

=20

some=20

the=20

need=20

=20

use a=20

3.3V=20

handle=20

to=20

whole=20

Could be. But with no internal evidence in the thread that this case actually is or is not related; is not clear. YMMV

?-)

Reply to
josephkk

Hi,

Yes, it is related to all those past posts.

jess

Reply to
jsscshaw88

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