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Microcontroller based Lead acid battery charger

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--BawA--

--BawA--

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Hi
I am designing a Microcontroller based battery charger. The specifications are

Topology: Forward converter (RCD clamp)
Input voltage : 125 V to 260 V
Output Voltage : 14.2
Frequency : 100KHz
Output power : 150 Watts

Microcontroller will be monitoring current and voltage of the battery and will adjust the duty cycle accordingly. Now i have confusion related to sensing the current and voltage, What should be the sampling rate for sensing current and voltage? and how to calculate it?
 

The easiest way is to set the current by using the micro to input a reference voltage into the error amplifier which sets the charge current.
Sample rate is for if you are actually using the micro to do the error amplifier, which is much more difiicult in code.
 

Dear treez
i will set a PI controller in my microcontroller to generate the dutycycle. I'll measure the current going to the battery using ADC and then i'll compare that value to reference current value to calculate the error. Now my question is at what rate should i trigger ADC to take the sample current if my pwm frequency is 100KHz ?
 

well there is no point doing it any faster than 100khz.
As long as you have analog overcurrent protection, you can do the sampling at some very low frequency if you want, say a couple of 100 hertz.
Though if you slowly give it a software soft start, and you have the fast analog overcurrent protection, then you can sample at slower than that if you want.....a battery isn't exactly a transient load.
 

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