Okada
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I am designing an Automatic Battery Charger using PIC16F73. I am using a 9-0-9V 5A transformer for it. I will be designing a Buck Converter. The input voltages to the Buck Converters are as below.
The input voltage range to the transformer (230V to 9-0-9V 5A) is 170V to 245V
230V to 24V (9-0-9V)
N = Vsec/Vpri = 0.0783
Vsec = N * Vpri
Vsec(L) = 0.783 * 170 = 13.311
Vsec(M) = 0.104 * 245 = 19.1835
Vpk(L) = 13.311 * 1.1412 = 18.82
Vpk(M) = 19.1835 * 1.4142 = 27.13
So, my voltages are above 14.4V needed for boost charging and 13.8V used for trickle charging.
How should I proceed further ? PWM duty will be adjusted to get boost voltage and trickle charge voltages but how to detect the voltage needed to be applied to the battery that is 14.4V or 13.8V ?
I am designing like this.
When battery is not connected or battery is removed then charging stops and there will be no output voltage.
When battery is connected, it will measure the battery voltage and if battery voltage is less than 10.4V then charger will start in boost mode and while charging if battery voltage reaches 13.8V then charger will shift to trickle charge mode.
Is this method correct ?
I am using ACS712 5A type to monitor the battery current. If high current is drawn then charger will be switched off.
There will be saftey fuses.
Here is the rough schematic. I have not yet calculated the buck converter inductor and capacitor values.
- - - Updated - - -
This is the mosfet I will be using. This is the best mosfet I found.
FDP8860
or
STI260N6F6
or
STP260N6F6
Very low Rds(on) < 0.003 Ohms
My charging current will not exceed 2.5A.
So, power dissipated in mosfet
Pd(mosfets) will be 2 x 2.5 * 2.5 * 0.003 = 37.5 mW
The input voltage range to the transformer (230V to 9-0-9V 5A) is 170V to 245V
230V to 24V (9-0-9V)
N = Vsec/Vpri = 0.0783
Vsec = N * Vpri
Vsec(L) = 0.783 * 170 = 13.311
Vsec(M) = 0.104 * 245 = 19.1835
Vpk(L) = 13.311 * 1.1412 = 18.82
Vpk(M) = 19.1835 * 1.4142 = 27.13
So, my voltages are above 14.4V needed for boost charging and 13.8V used for trickle charging.
How should I proceed further ? PWM duty will be adjusted to get boost voltage and trickle charge voltages but how to detect the voltage needed to be applied to the battery that is 14.4V or 13.8V ?
I am designing like this.
When battery is not connected or battery is removed then charging stops and there will be no output voltage.
When battery is connected, it will measure the battery voltage and if battery voltage is less than 10.4V then charger will start in boost mode and while charging if battery voltage reaches 13.8V then charger will shift to trickle charge mode.
Is this method correct ?
I am using ACS712 5A type to monitor the battery current. If high current is drawn then charger will be switched off.
There will be saftey fuses.
Here is the rough schematic. I have not yet calculated the buck converter inductor and capacitor values.
- - - Updated - - -
This is the mosfet I will be using. This is the best mosfet I found.
FDP8860
or
STI260N6F6
or
STP260N6F6
Very low Rds(on) < 0.003 Ohms
My charging current will not exceed 2.5A.
So, power dissipated in mosfet
Pd(mosfets) will be 2 x 2.5 * 2.5 * 0.003 = 37.5 mW
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