Discrete voltage reduction? - Electronic Circuits Projects Diagrams Free

HellTriX · 5th April 2008, 08:23 AM

Suppose I have this 12 by 12volt battery bank for ~163v.
I have Mosfet that are going to be using this full voltage, but
my control circuity is rated to 18v max or something like that.

What would be a few ways to reduce this voltage to safe levels for the
Op-amps, 555s, etc?

One what I was thinking was a couple transistors used as a voltage divider.
Would a transistor oscillator used as a PWM signal for a Mosfet be acceptable
to drop this voltage?

I'd like to try to build my own for this rather than use a buck converter thing.

But I'm just collecting ideas at this point.

BTW the control circuity would be low current, less then 2-3amps max, and
if I needed to keep it fairly stable I could drop that to as low as 100-200mA
for the voltage divider to stay within safe limits. Oh, and I would like the
voltage to remain between 12 and 18v. I guess I could use a voltage
regulator after a voltage divider or something. But ya. I don't know..

tnx

ericgibbs · 5th April 2008, 08:49 AM

hi,
Are the individual 12V battery terminals accessable.?

If Yes, you could use the bottom 2 batteries, referenced to the common end of the 12*12.

This would give 24V which could drive the 18V control voltage regulator, maybe a LM317.

If you are concerned about balancing the charging of the 12 *12 battery bank it would be possible to additional recharge the lower 2 batteries with a 24V floating charger.

The way you are proposing to reduce the voltage by a divider would be very inefficient.

Do you follow this.?

HellTriX · 5th April 2008, 09:44 AM

The inefficiency was one of my concerns. But loosing a few watts to run the drive circuity would be trivial in the short term. I was away of the imbalance of trying to take power off one or 2 of the batteries so was just looking for ways around it.

Another option I considered was a triode step down transformer with some sort of oscillator. This would be what, 75-95% efficient? Compared to 40% or something of a transistor voltage divider. But weight is an issue. It would need to be a khz transformer to make it light enough to be beneficial, otherwise a resistive approach would be better.

But I'd really like to keep the battery load balanced and not add complexity and wear and tear on the batteries by adding floating chargers.

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5th April 2008, 08:23 AM	(permalink)
HellTriX	Discrete voltage reduction? Suppose I have this 12 by 12volt battery bank for ~163v. I have Mosfet that are going to be using this full voltage, but my control circuity is rated to 18v max or something like that. What would be a few ways to reduce this voltage to safe levels for the Op-amps, 555s, etc? One what I was thinking was a couple transistors used as a voltage divider. Would a transistor oscillator used as a PWM signal for a Mosfet be acceptable to drop this voltage? I'd like to try to build my own for this rather than use a buck converter thing. But I'm just collecting ideas at this point. BTW the control circuity would be low current, less then 2-3amps max, and if I needed to keep it fairly stable I could drop that to as low as 100-200mA for the voltage divider to stay within safe limits. Oh, and I would like the voltage to remain between 12 and 18v. I guess I could use a voltage regulator after a voltage divider or something. But ya. I don't know.. tnx

5th April 2008, 08:49 AM	(permalink)
ericgibbs	hi, Are the individual 12V battery terminals accessable.? If Yes, you could use the bottom 2 batteries, referenced to the common end of the 1212. This would give 24V which could drive the 18V control voltage regulator, maybe a LM317. If you are concerned about balancing the charging of the 12 12 battery bank it would be possible to additional recharge the lower 2 batteries with a 24V floating charger. The way you are proposing to reduce the voltage by a divider would be very inefficient. Do you follow this.? __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

5th April 2008, 09:44 AM	(permalink)
HellTriX	The inefficiency was one of my concerns. But loosing a few watts to run the drive circuity would be trivial in the short term. I was away of the imbalance of trying to take power off one or 2 of the batteries so was just looking for ways around it. Another option I considered was a triode step down transformer with some sort of oscillator. This would be what, 75-95% efficient? Compared to 40% or something of a transistor voltage divider. But weight is an issue. It would need to be a khz transformer to make it light enough to be beneficial, otherwise a resistive approach would be better. But I'd really like to keep the battery load balanced and not add complexity and wear and tear on the batteries by adding floating chargers.