Archive for the ‘Power’ Category.

Single LiPo cell protection and charger

Single cell lithium polymer battery cell is very handsome power source for many applications. Unfortunately it is quite dangerous when such battery cell is not properly protected and charged. I prepared simple 1S LiPo battery protection and Charger on two, single sided small PCB modules. I separated Protection from the charger when only protection is needed.


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This is heart shaped four RGB led badge:

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Low power DC/DC module with AS1337

This is small module for AS1337. The shematic is simple and provides all required components to operate AS1337. The PCB is 18x15mm miniature module with all pins at one side (S


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NCP3065 Step-down

This was one of my first designs when I started designing power LED circuits. The DC/DC controller is ON-Semi NCP3065. It requires power inductor, schottky diode and some other passives. NCP3065 is PWM controller suitable for many topologies, including buck, boost or sepic. Circuit presented here is classical step down buck (click to enlarge):

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White LED – Simple Step-Up

I’ve got samples of interersting DC/DC converter from TI:  TPS61040. Main application is to drive small white LEDs from a battery cell or two. Input voltage range is from 1,8V to 6V. Ideal for two AA or single Li-xx cell. Schematics is very simple. Only few external components are required: a coil, caps and schottky diode:

Led driver TPS61040 schematic

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2S LiPo Battery pack

IMGP3715.jpg2S Battery pack is very useful. It can be used to supply 5V electronic circuit without DC/DC. With help of a simple boost a 2S battery can drive 3 power LED lamp with reasonable currents. Etc…

Let’s see what is required for reliable, safe lithium polymer batter pack with two serially connected cells (2S LiPo battery pack).

Obviouslly, at least two cells are needed. Unfortunately, LiPo cells are very dangerous if used over specified limits. Most dificult is maximum cell voltage during charge. If cells are aexposed to voltages above 4,2V they can burn, but not at the charging, this could happen at any time after charging.  The absolute maximum charging voltage is 4.25V per cell. To avoid burning down the house and other troubles, a battery protection circuit board (PCB) is a must with LiPo cells.

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