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Voltage converter from 24V to 12V

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ziko

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24v to 12v converter schematic

Hi,

I need same schematics or address to find for this voltage convertor.
It should be about 1.5-2 Ampers

Thanks and regards,

Ziko
 

GrandAlf

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24v to 12v resistor

I presume there is some reason why you cannot just use a linear IC regulator. Possibly it is because you are concerned about dissipation. Have you considered switched mode down converter ICs. A web search will soon find you some appliction circuits. Search for something like "Switched mode regulators".
 

flatulent

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24v to 12v schematic

You have several options. If the load voltage does not need to be exactly 12 V you can use a 12 V zener type circuit in seriese with the 24 V source and the load. If the load draws nearly constant current you can use a series resistor. You can use a 12 V linear regualtor IC. If you need efficiency and only need one of the circuits, buying a DC-DC converter will probably be lower cost than making one.
 

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ziko

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24v to 12v converter schematics

Thanks for info. I need this converter for car radio (+12V) to be powered by truck with +24V


Ziko
 

flatulent

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24vdc 12vdc 7812 circuit

You have a further choice. Look at the truck battery. Some times they are two 12 V batteries wired in series. If this is the case, you can tap off the point between them for 12 V.
 

tjalps

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24v to 12v

Hello!

Check LM2786 at National Semiconductors. It's wery good switch down converter with minimal number of external components.

Best regards!
 

Pim

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dc 24v to 12v voltage convertor

If using a switched power converter you face the risk of getting radio interference/noise if you do not design and build the circuit correctly. Also, a car radio or similar can draw current that varies very much, it may depend on what music you listen on and how loud. A switched mode converter does not respond that very quickly to a varying load. If having truck batteries to power the whole thing I think that efficiency is not the main problem.

The easiest way would in my opinion be to use any industry standard 12 VDC linear regulator (the three-legged ones). And also include some form of over-voltage protection on the input of the regulator. If using long wires and shutting of a high load, voltage spikes may develop due to the inductance of the wires. The three-pin industry standard linear regulators are rather sensitive for overvoltage.

/Pim

tjalps said:
Hello!

Check LM2786 at National Semiconductors. It's wery good switch down converter with minimal number of external components.

Best regards!
 

flatulent

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24v to 12v converter circuits

This voltage transient protection is a good point. When starting the engine of the truck there will be voltage transients on the 24 V line from the inductance of the starting motor.

There is one famous case in the US Army many years ago when the two way radio had to be turned off when starting the engine or the radio would be damaged.

In the old Halicrafters HT32A short wave transmitter the power switch had to be left in the standby position for several seconds before being turned to the operate position or the radio would be damaged. So much for foolproof designs.
 

betanorm

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converter schematics

An idea to test:

If we connect two linear regulators in series such as 7818 then 7812 to convert 24(28V) to 12 Volts with diodes and capacitors at the inputs, can we find a solution for voltage transients during the engine start?

There should be protection diodes for negastive transitions...

For power dissipation, I think this will be a good and more reliable solution. All valuable electronics then would not be on the responsibility of one tiny semiconductor connection.
 

swordman

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24v to 12v converter

The best choise is lm series switchmode regulators
If u use 7818/12 u loss power (like termal energy)
 

jzo777n

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24v 12v converter circuit

You must also take consideration in phenomena that are called load dump.
It occurs when you change the load for the generator and the generator regulator is to slow to control it.
The pulse its several volts above nominal and for a couple of 100 ms
In newer car this is less of a problem because better regulation.

Then you have also the problem with transients as mention above.
More sources can be the headlamps, heating of rear window etc.

Some more information you can get from transient protection manufacture like Epcos, ST, General Semiconductor

Bosch has a nice handbook of automotive engineering.

jzo
 

jzo777n

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from 24v to 12v

You can also do a simple pre-regulator to a linear regulator with help of
a transistor, zenerdiode, resistor and a capacitor).
Connect the base to the zenerdiode.
Connect the resistor between the collector and base.
Input to the collector.
Output on the emitter to the linear regulator.
The capacitor in parallel with the zener.
 

wcarl

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24v to 12v circuit

you can use lm350
 

KamW

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resistor 24v to 12v

Simple circuit with 7812 worked fine. A lot of power is lost - it's not the problem in truck. You need radiator large enough. Problem is with high peak current used for car radio while in high volume. I have used additional transistor (check 7805 datasheet). I've made this circuit for friend, and it have been working for few years without any problem.

regards
KamW
 

betanorm

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does lm 7812 regulator can use to 24v to12v

You can use big capacitors at the 12 V side but with a protection diode parallel to 7812. It may be 4700 microfarads or more which is useful for large peak currents. I still recommend 7818 and 7812 in series in case of regulator failure and it would be better for heat dissipation for each regulator. 28 Volts is high enough to give damage...

I had experienced once with LM317T. I was using it with high currents and it suddenly broke and passed through all high voltage.
 

KamW

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design 24v to 12v resistor

Betanorm You are right High value capacitor could be used there. But fortunatelly there is very big capacitor in circuit. truck batery looks like very huge capacitor. Additionally often driver like to hear radio while truck is off, so radio circuit is connected nearly direct to acumulator.
In standard 78XX circuit with transistor there is serial resistor and transistor. So voltage regulator work with smal current ie. 300mA, rest of the current flow thru transistor. So problem with heat disipation is solved. It is no problem to use 6A transistor to work with 3A peak...
Using of protection diode is good idea. I've forgoten it and circuit work fine, but till time ...
The more importnant problem it was radiator. The truck had positive voltage on chasis(?) so be carefull with using it as radiator - it need very (!!!!!) good isolation, or additionally use isolated parts (7812F).
Additionally I've used 6A T fuse for supply protection in case of short circuit.

regards
KamW
 

betanorm

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automotive 24v transient protection circuit

KamW
Any linear regulator is like a variable series resistor, and it has current limitations. But an audio amplifier sometimes consumes high current peaks for very short durations which may be out of a power supply or a regulator current limits.

You can meet distorsion if your volume is high, especially for the low frequency sounds. If you put large capacitors to the power supply, that distorsion disappears or decreases. Even the trucks accumulator is like a huge capacitor, there is a variable resistor called regulator in series and that limits peak currents.

For positive supply chasis, you may use 7912 ??? and a PNP transistor...
 

__JR__

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need help to build a 24v to 12v converter

Hi ziko,

If you choose any solution based on series regulators, you have to deal with a 24W dissipation (24-12 V x 2A). You can't achieve this with only one TO-220 case component (transistor or regulator) and a reasonable size dissipator. If you choose a switched mode solution, the noise injected back to the 24V supply will be of main concern, not to the radio. But you can control this with not so big capacitors... National Semiconductors has a lot of solutions in this area... I would suggest you to use any of National's 3A SIMPLE SWITCHERS.

Good Luck!

__JR__
 

gzn

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voltage regulator 24v

If U can have samples of Micrel's devices , download from Micrel the Buck-IT Designer , a SW tool for choose the right Micrel device. It build for you a schematic with suggestions about thermal and layout..
 

KamW

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24v til 12v zener diode

Hi betanorm
Chasis it was wrong word, I don't know proper one. There was positive voltage on metal part of truck, while negative was wired. So use of truck metal as radiator was very dangerous.
_IR_ 24W for truck it was nothing. Of course switched mode regulators are OK, but as I found car electronics is a special kind of electronic. Often we think 12V is 12V for car 12V could be 9V or even 14. And who take care of wats in car.

Regards
KamW
 

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