Better have a pre-regulator to bring 24V to 15 or even 14.5V as suggested by AudioGURU, perhaps by using another LM371, therafter the final LM317 will take care of the 12V at 1.5Amps.

However, you need to mount both with suitable Heatsinks.

the best is DC-DC converter. with a series pass transistor. You may try with a rather old chip like MC34063-- the datasheet gives applications and suitable layouts also.

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Sarma.

 

I agree, a pre-regulator is probably the most ideal solution, it doesn't have to be fancy, the Black regulator previously posted would be ideal. When a linear regulator is added to a switching regulator it forms a hybrid regulator which is often used in large high-quality switching power supplies.

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I meant either a set of LM317s or a dirct DC-DC converter considering the current demand of around 0.6 amps.

black regulators appears OK but for component count. please see the datasheet of MC34063A. perhaps the OP could complete the work with reduced components.

__________________
Regards,
Sarma.

 

hi Sarma,
If its a series voltage regulator, series transistor, bypass transistor or 10Watt resistor the 'excess' power is always going to be dissipated as heat.

The 10W resistor is the cheapest and simplest option.

Regards

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in the case of series resistor, the input voltage available for LM317 will change as per the load current.

In view of power economy, i feel the switch based solutions are efficient and perhaps may not be so costly. with an additional 5 or 6 components the job is done.
Datasheet of MC34063 attached.pehaps there are cheaper Switches available off late.

as the power requirement is more than the capacity of this IC , an additional pass transistor may be required.

__________________
Regards,
Sarma.

 

Hi Sarma.

As its a 'one off' project I would still use the cheapest option, resistor.

In the past I have reduced 'excess' voltages by removing a few turns off the transformer secondary,
thats a 'zero' component cost way of doing it

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Lovely Eric--the Zero component way..

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Regards,
Sarma.

 

Loving all the feedback and discussion. This project is experimental but may not be a one off. If I can get it to work efficiently and reliably for a low cost we may integrate this circuit into quite a few of our panels. A majority of our panels utilize 24VDC and these lights are all 12VDC. Some of the simple panels that can run entirely on 12V it's not needed or larger panels where there is ample space we just add a 12V power supply to run them but where space is tight or cost if a factor, adding a 2nd power supply just for the neon light isn't an option.

Would that 10W resistor need a heat sink of any kind?

 

hi,
The resistor should be mounted so that it get rid of the heat, not tight down onto a pcb, standing clear and away from heat sensitive components.

Some types have a 'brass' type body, that are designed to bolt to the metal enclosure

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