So bear with me. I started a thread a while ago discussing the use of to photovoltaic driver to drive N-MOS in high side switching applications. After discussion and research this does not seem like the best way forward. So I have a new approach I want to try with you.
Why am I going through this trouble?
- I want to use N-FET for their lower RDSon vs size and price.
- I want to be able to PWM.
- I want to be able to be 100% duty cycle
- I want to switch high side because I dont have easy access to the low side.
- I want bi-directional because there is current consumers and providers in both ends, depending on the situation.
- The IC's available on the market seems to be either solid state on/off kind of drive, or PWM only. I have yet not found a combination.
So: How about driving the high side N-FET's with a conventional stock standard low side MOSFET driver, fed by a 10 volt higher voltage than the bus? A low side driver is cheap, readily available off the shelf, even in these challenging times in the IC market.
As I see it, there is two ways of doing it. Common ground or "isolated ground". With common ground the voltage needs to be increased to about 10V over the rail voltage. The feeding circuit does not need to be isolated as the ground is shared. The other way, where source acts as ground / "isolated ground", the voltage generated basically only has to be +10V in reference to that ground. The source of the mosfets.. In this case the unit generating the voltage needs to be isolated.
Isolated ground:
Common ground:
Driver:
Please shoot your thoughts!