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HOME   Technical Tips

3.7V to 5V CONVERTER

Low power 5V or 9V from 3.7V lithium ion cell. The 5V can power the projects that use LCD, output current up to 10mA. The 9V version can power most digital multimeters that run on PP3, output current up to 5mA. The output voltage is regulated by the zener diode and the output current is limited by the value of L1.

Circuit Description
See also Technical Tips

The hex inverter 4049 CMOS are used as a free running oscillator. BC337 charges the coil when it's on, and when it's off the coil dumps its charge via the diode 1N4148 into the output capacitor.
When output voltage exceeds the zener voltage BC337 is switched on and stops the oscillator until output voltage drops below the zener voltage.
Table for selecting components.

Output R1 R2 R3 Z1 L1
5V 22K 220R 470R 4.7V 220 - 680 uH
9V 10K 2K2 100K 9.1V 1 - 2.2 mH

Cmos 4049UB can also be 4049B.
Equivalent to BC337 can be used.
Coil can be the smallest physical size available.
Resistors are 5% tolerance.

 



  



13.02.2015 - 12:48
Name: Zarif
Comment: can I use this with NI-CAD?

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