Battery Charger Circuit Using SCR:-

 SCR Operating Modes:

• To turn on the SCR the small amount of voltage or voltage equal to break over voltage is required to the gate which will trigger the SCR and when the SCR is turned on, it will have very low resistance and allow the power to conduct and also increase the anode current. Even if we remove the gate voltage also it will be in conduction. The only way to make the SCR to turn off is to make the voltage to zero or make the current less than the handling current between the anode and cathode.
• There are two ways to turn on the SCR is the first way is to turn on by opening the gate and compensate the power supply to the break over voltage. And second way is to supplying the voltage to operate the SCR with less than break over voltage and applying the small amount of about 1.5V applied to the gate which will trigger the SCR.
• When the SCR is turned off it will have high resistance and restrict the current to the leakage current. To turn off the SCR from on state also have only one ways normally people think that if we stop the gate current the SCR will become turn off, but it will not this state is called “loss of control”, the only way is turnoff the SCR is reducing the supply voltage to zero.

Introduction to Battery Charger Using SCR:

The battery is charged with small amount of AC voltage or DC voltage. So if you want to charge your battery with AC source then should follow these steps, we need first limit the large AC voltage, need to filter the AC voltage to remove the noise, regulate and get the constant voltage and then give the resulting voltage to the battery for charging. Once charging is completed the circuit should automatically turned off.

Circuit Diagram of Battery Charger Using SCR:-

Circuit Diagram Explanation:

• The AC main voltage is given to the step down transformer the voltage should be down to 20V approx. the step down voltage is given to the SCR for rectification and SCR rectifies AC main voltage. This rectified voltage is used to charge battery.
• When the battery connecter to the charging circuit, the battery will not be dead completely and it will get discharged this will give the forward bias voltage to the transistor through the diode D2 and resistor R7 which will get turned on. When the transistor is turned on the SCR will get off.
• When the battery voltage is dropped the forward bias will be decreased and transistor gets turned off. When the transistor is turned off automatically the diode D1 and resistor R3 will get the current to the gate of the SCR, this will triggers the SCR and gets conduct. SCR will rectifies the AC input voltage and give to the battery through Resistor R6.
• This will charge the battery when the voltage drop in the battery decreases the forward bias current also gets increased to the transistor when the battery is completely charged the Transistor Q1 will be again turned on and turned off the SCR.