12 to 5v (890mA to 500mA)dc converter help

[redh0rze]

i have a small problem and i need your urgent replies

I have a Solar Panel that generates 17V which been directly connected to my 12V Dc battery, the problem is how to use that power to generate enough voltage and current to operate by charging my mobile phone which requires 5V dc with a 900mA max up to 500mA min.

Which of these converters should i use to supply the requirement Voltage and current?

1. 12V to 5V DC converter using Zener diode and transistor

**broken link removed**

This simple converter uses a zener diode and a transistor to convert 12V dc from a battery to 5V DC with a maximum current of 1A. The circuit is very easy to construct and requires only 3 electronic parts, the resistor, Zener diode and transistor. The transistors is TIP41C, zener diode is 1N4732A or any zener with the same voltage drop and power. Resistor is 7ohm 7W and preferably wire-wound type. This converter is useful in powering devices that uses 5V such as USB powered devices and chargers.
The output voltage is given by the formula :
Vout = Zener voltage + 0.65V , where 0.65V is the base-emitter voltage of the transistor

2.)12V to 5V buck converter using 555 timer IC

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converter schematic

This buck converter is driven by 555 timer IC and converts 12V dc from a battery to 5V dc. The 555 IC (operated in a stable mode ) generates pulses of voltages of 42% duty cycle. This pulses turns the transistor on and off and drives the inductor L (buck converter circuit), and as a result generates 5V dc output. For this configuration,
Ra =20K
Rb =27K
C =1nF
Q = TIP41C or any of the same specs
Cout = 2200uF (higher the better)

3.)12V to 5V DC converter using 7805 regulator IC

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This simple converter project uses 7805 IC to convert 12V dc from a battery to 5V DC. This converter also can be made even only one component, the 7805 regulator. Converter can produce a maximum current of 1.5A (with heatsink) at 5V from an input of 8V to 15V. The capacitors are optional and can be omitted.
This is suitable for powering devices that uses 5V DC such as chargers,USB devices and others

 

[Boncuk]

You posted a lot of details which are not required as long as you do not post the maximum current your solar panel can supply.

Boncuk

 

[RMMM]

If you have a heatsink, #3 will do at those currents.

You may conisider a 12v zener regulator before the 7805 to reduce the wattage dissipation in the 7805 further.

 

[RMMM]

You posted a lot of details which are not required as long as you do not post the maximum current your solar panel can supply.

Boncuk

I may have read it wrong, but I was thinking he was charging the phone from the battery..? And the panel was charging the battery.

I think he wants to be sure the 17v from the panel doesn't "jump" the battery and put 17v on the mobile phone.

Alas, we will know when he returns.

 

[MikeMl]

Here is the circuit I would use.