Voltage Stepper

In order to power the motors on my robot, I need a source of 12 V. My first source of power was a 12 V sealed lead acid battery. Although these batteries are very good at providing a stable source of voltage for the amount of current I required for my use (between 500 mA to 1 A), there were two disadvantage with this battery type: they are heavy and they require a special charger that I find hard to come by.

To reduce the weight of my robot, I decided to replace the sealed lead acid battery with a voltage stepper circuit. National makes some nice integrated circuits that can be used for this purpose (LM2587). If you go on there Web site, you can use a design tool (Webench) to build a custom circuit based on your requirements. Here is the circuit that is recommended for stepping between 4 V to 6 V up to 12V (maximum 1 A current):

Voltage Stepper Circuit

Parts List for Voltage Stepper
Cin 100 uF electrolytic capacitor
Cout 180 uF electrolytic capacitor
D1 International Rectifier 6CWQ03FM (VFlatlo = 0.45 V)
Rfb1 1500 ohms resistance
Rfb2 13300 ohms resistance
Rcomp 2940 ohms resistance
L1 15 uH inductor (DCR = 0.027 ohms)
Ccomp 1 uF ceramic capacitor
Cinx 0.1 uF ceramic capacitor

Here is my implementation of this circuit:

To contact me, send an email to: martin.dubuc@rogers.com.

Last updated: December 20, 2002