Automotive Power Supply Regulator Circuit

[Kryex]

Automotive Power Supply Regulator Circuit

Hi

I am working on a tracking system for vehicles (both cars and trucks).
The system power supply is the vehicle's battery (which supplies 12V or 24, for cars and trucks respectively), which may have many fluctuations (spikes, negative voltages, noise, transient voltages, etc.).
The tracking system needs 5V and 500mA constant (it may peak at 700mA), which means a regulator circuit from the vehicle battery (12-24V) to 5V (500mA~700mA) is necessary.
Price is an important factor, it should be as cheap as possible.

I have designed the following circuit to deal with the voltage regulation:

**broken link removed**

What do you think?

Do you have a different suggestion? I am open to different circuits (specially more simple ones), which regulate the voltage to 5V and protects from the voltage irregularities in the vehicle's battery.

Thanks in advance.
If you need to know anything else let me know.

 

[Tahmid]

If you are to keep cost to a minimum, I guess the cheapest and probably simplest method would be to use a 7805 regulator. Doesn't really get much simpler. However, you'll have rather low efficiency as it is a linear regulator.

Hope this helps.
Tahmid.

 

[Kryex]

If you are to keep cost to a minimum, I guess the cheapest and probably simplest method would be to use a 7805 regulator. Doesn't really get much simpler. However, you'll have rather low efficiency as it is a linear regulator.

Hope this helps.
Tahmid.

But how would the 7805 handle all the surges and transient voltages in automobile's battery?

What would you do for the protection circuit?

 

[Tahmid]

Connect a bulk capacitor (between 330uF and 1000uF) and smaller decoupling capacitors (100nF) across the input and ground (pins 1 and 2, respectively). Connect a small filter capacitor (10uF to 220uF) and smaller decoupling capacitors (100nF) across the output and ground (pins 3 and 2, respectively).

Provided there is sufficient filtering, voltages upto 35V should not cause much problem.

Hope this helps.
Tahmid.

 

[Kryex]

This is meant for vehicles, so there are other factors to take into account, such as overvoltages, negative voltages, load dumps, etc. Capacitors alone are not enough to deal with them I believe.

 

[Tahmid]

May I ask, how you expect the circuit in post #1, to deal with these factors?

Will voltage rise above 35V? How high will the voltage rise to? What is the maximum voltage you expect at the input? If you do expect voltage greater than 35V, then you will need to use other regulators.

Why negative voltages? A single diode at the input will protect against negative voltage (as shown in circuit posted in #1).

If you do want to go the switching regulator route, you can take a look at LM2575. According to Newark, it's cheaper than AP1512.

 

[Kryex]

Automotive environments have several particularities, which make it hard to design a power supply circuit.

Yes, there may be voltage spikes higher than 35V (even higher than 100V), negative voltage drops, etc.

I am looking for the best protected power supply regulator circuit for automotive use, bearing in mind a low cost.

 

[papunblg]

May I ask, how you expect the circuit in post #1, to deal with these factors?

Will voltage rise above 35V? How high will the voltage rise to? What is the maximum voltage you expect at the input? If you do expect voltage greater than 35V, then you will need to use other regulators.

Why negative voltages? A single diode at the input will protect against negative voltage (as shown in circuit posted in #1).

If you do want to go the switching regulator route, you can take a look at LM2575. According to Newark, it's cheaper than AP1512.

The diode at input is for back emf , right?

 

[Tahmid]

Automotive environments have several particularities, which make it hard to design a power supply circuit.

Yes, there may be voltage spikes higher than 35V (even higher than 100V), negative voltage drops, etc.

I am looking for the best protected power supply regulator circuit for automotive use, bearing in mind a low cost.

So, adopt the same approach you did in the circuit previously provided by you.

The input diode protects against negative voltages, as it can only allow positive voltages. Connect a zener diode at the input to protect against the spikes. Since the spike is supposed to be very short, the zener can clamp it to the required voltage without getting damaged.