auto shut-off facility. The circuit can be used for charging any high
current, high AH types battery with a full-charge auto cut-off feature.
The idea was requested by Mr. Rakesh Parmar.
In one of the earlier posts we learned a high current battery charger circuit based on a relay
total shut off concept, which used a relay to initiate the charging
process by switching ON the mains to the transformer and then shutting
off the mains as soon as the full charge level was reached for the
In the proposed triac based battery charger circuit the operational principle is exactly similar except the incorporation of a triac instead of a relay.
When mains power is applied the circuit does not switch ON by itself, and remains in a standby position.
indicated push button is positioned for initiating the charging
process, therefore as soon as this switch is pressed the triac is
momentarily shorted allowing the transformer to access the mains power
for that instant.
The above action also instantaneously allows the circuit to get powered for that particular period of time.
the battery to be in the discharged position, the above initialization
causes a voltage to appear at pin#2 of the opamp at a level lower than
the referenced pin#3 of the IC.
This in turn causes pin#6 of the
opamp to go high, activating the triac and also latching the transformer
in the powered position.
The entire circuit now gets latched and
powered even after the switched is released, providing the required
charging parameters to the battery. The red LED illuminates confirming
the charging initialization of the battery.
As the battery gets
charged, pin#2 potential gradually begins rising, until when finally it
goes above the reference level of pin#3, which immediately prompts the
output of the IC to go low. Te moment this happens the triac gate
trigger gets cut-off, breaking the latching action, and the entire
circuit gets switched OFF.
The circuit returns to its previous
standby position, until the next time when the switch is pushed again
for a new caging cycle.
If you liked this battery charger circuit using triac, please do share it with the others.