I've spent a few days searching with google, but all I can dig up are poorly written articles about the difference between modified sine wave (MSW) and pure sine wave (PSW) inverters, without going into the actual electronics.
Basically, I'd like to know how PSW inverters actually generate a sine wave at their output.
I assume that the conversion starts the same way as for a modified sine wave inverter - i.e. battery voltage (12V) is chopped into a ~30kHz square wave and fed to a transformer to boost it to >300VAC (@ 30kHz), then it's rectified and fed to the output stage.
It's my understanding that at this stage a MSW inverter uses transistors to turn the ~340VDC into a 50Hz, 240V DC (RMS) quasi-square wave that sort of approximates a sine wave (aka a "modified sine wave") - by simply switching on and off the transistors at the right intervals.
But how does a pure sine wave inverter do it? Does it use PWM of the transistors and a capacitor across the input? Or some kind of magnetic component to smooth out the waveform?
Could you have a signal-generating IC inside the inverter that makes a perfect sine wave as a reference, then use a comparator and voltage divider to compare inverter's actual output with the sine wave reference and adjust PWM to maintain a perfect sine wave regardless of load?
Could you add electronics to a MSW inverter, or something to the output, to make it PSW?
Basically, I'd like to know how PSW inverters actually generate a sine wave at their output.
I assume that the conversion starts the same way as for a modified sine wave inverter - i.e. battery voltage (12V) is chopped into a ~30kHz square wave and fed to a transformer to boost it to >300VAC (@ 30kHz), then it's rectified and fed to the output stage.
It's my understanding that at this stage a MSW inverter uses transistors to turn the ~340VDC into a 50Hz, 240V DC (RMS) quasi-square wave that sort of approximates a sine wave (aka a "modified sine wave") - by simply switching on and off the transistors at the right intervals.
But how does a pure sine wave inverter do it? Does it use PWM of the transistors and a capacitor across the input? Or some kind of magnetic component to smooth out the waveform?
Could you have a signal-generating IC inside the inverter that makes a perfect sine wave as a reference, then use a comparator and voltage divider to compare inverter's actual output with the sine wave reference and adjust PWM to maintain a perfect sine wave regardless of load?
Could you add electronics to a MSW inverter, or something to the output, to make it PSW?