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i have a circuit whenever a.c fails dc should get activated (like a ups)am using IRF9540N,how this possible with the pwm signals of mcu?how can i set pwm duty cycles
Not ups,but similar circuit...i want to know only how this particular switching occurs by using pwm,i mean when main power fails it should get power from a battery,i have told like ups because when a.c off the battery of ups will start working automatically like that
While the PIC does contain a hardware PWM module, you can not use it to generate PWM signals at frequencies as low as 50 Hz. You can use the PIC Timer1 and the compare module for PWM. You can also make use of the interrupt.
Then why do you need PWM? You can just use a relay to switch on your battery of 20v when ac fails. step down your ac to 5v ac and convert it to dc and give it to mcu. if that pin is high then it means ac is present, if ac fails that pin goes low, so mcu will operate the relay and swirch on the battery.
You need to detect presence or absence of mains. Rectify the AC to DC and feed it into an optocoupler. Make sure you use a current limiting resistor. Use the transistor side of the optocoupler for the rest of the circuit.
Instead of rectifying the AC, you may feed the AC to an optocoupler such as TLP620. That's the first part of your required circuit- mains detection.
Then why do you need PWM? You can just use a relay to switch on your battery of 20v when ac fails. step down your ac to 5v ac and convert it to dc and give it to mcu. if that pin is high then it means ac is present, if ac fails that pin goes low, so mcu will operate the relay and swirch on the battery.
I think he want to avoid general usage of relay. PIC sense is there AC power, if there is AC then PIC drive MosFETs for inverter, in case of AC power outage PIC start to drive MosFETs of inverter. I'm right?
In such scenario, design should have protection and some kind of hysteresis when AC power is back, to prevent linking of both systems together.
I think he want to avoid general usage of relay. PIC sense is there AC power, if there is AC then PIC drive MosFETs for inverter, in case of AC power outage PIC start to drive MosFETs of inverter. I'm I right?
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