Li-Ion Battery Charger

This circuit is built around LM3647 an Universal Battery Charger, This Circuit is an untested design. It is based on application hints and was provided as an example to the user. This circuit gives a 12V DC from mains or battery and the battery is also charged when power resumes.

Li-Ion Battery Charger U1D monitors charge current and U1B monitors battery voltage these values are the feedback to charge controller U3. U1C drives Q2 to Control the charging process by switching in PWM. The LM7812 with a 2N6107 Current Booster Regulate the battery and mains DC to a 12V for powering the Product Circuits.

Li-Ion Battery Charger – del90005

Portable electronics have got a big boost due to batteries like Li-Ion. Here is a decade old circuit to charge a large battery. It can be scaled up or down in power. It has current and voltage limit protections.

Digital 5V Power Supply using L296

This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST. The advantage of using a switching regulator is that there is not much Heat Dissipation in this circuit.

Switching Battery Charger with L296 – del20031

Digital 5V Power Supply using L296

If you had to build the same with a series regulator, it would be very big due to external transistor and a huge heat sink. This circuit takes a small place on PCB, efficiency is high so power is saved and reliability of product improves, lastly the thermal gradients within the cabinet is avoided so that any form of drift or component specs variation can be avoided.

L296 and L296P are stepdown power switching regulators 4 A at a voltage variable from 5.1 V to 40 V.  External programmable limiting current. Soft start, remote inhibit, thermal protection, a reset output for microprocessors.

The Schottky rectifier BYW80 is used as it switches very fast 200V-20A-35nS. The Inductor and Capacitor is for the filter to get a ripple free DC from the Chopped DC output. There may be a small high frequency ripple riding on the DC signal of 5V in most SMPS circuits. So for very sensitive circuits use extra filters and shields.

The Current output is limited, and can be reduced further with a resistor from Pin 4 to ground. Also if the feedback to Pin 10 is thru a Voltage Divider then more voltage can be set at the output. See the datasheet and application notes for other design details and circuits.

Battery Backup Supply

This is a 9V power supply which will work even on power failure. It uses a rechargeable battery and regulators. A transformer with 15-0-15 AC volts output is required.

From my Power Electronic Circuits

Battery Backup Supply

In the first regulator U1 the output is lifted up by 1.4V and in the second regulator U2 by a resistor divider. In the second regulator the voltage across resistor R3 is 5V, so the current is 5V / 1K = 5mA this adds to the quiescent current of 5mA from the regulators ground terminal and flows into the resistors R1 and R2 in parallel which form 404 ohms, 10mA thru 404 ohms is 4V. So the output will be 5 + 4 = 9V. Note that the charge and discharge paths of the battery are separated with diodes.

+5 to -5 using a 555 Astable Multivibrator

This is a very simple -5V supply using one 555, useful for analog blocks using FET Opamps using low power. This circuit came up when i had to design limited by inventory. It worked well for its need. It converts Positive Five Volts to Negative Five Volts to create a dual supply.

 This +5 to -5 using a 555 Astable Multivibrator.is not a high efficiency design, in fact it cannot take a heavy load. Circuits having some CMOS Opamps and a A/D convertor is ok. Even very small battery designs must avoid this circuit.

This suits well when you want to power an analog amp which has to measure voltages which swing on either sides of zero. It can be used in a LCD based portable measuring instrument running on a rechargeable 9V battery.

Powering a strain gauge amp may be one use, another may be like a RTD temperature meter for -50 to +150 deg C.