[PIC] Synchronous Buck Converter for MPPT

[Odion]

Hello! I am working on a synchronous buck converter for solar Mppt! I did the asynchronous version with ATmega328 early last year! I want to implement this with pic18f26k22…..
now the challenge is I need to generate two pwms 180 deg out of phase. I’m using microC pro which has the pwm1_Init & pwm2_init functions. How do I make them not come on together?

 

[BradtheRad]

Do you intend to charge a battery? That's a consideration since you don't want current to flow backwards at any time.

Do you intend to have 2 transistors... one conducting while the other is Off? They must be oriented so current always goes through the inductor in one direction.
They must be biased accordingly.

To gain efficient utilization of the solar panel, you shall draw continual smooth current at maximum power it can produce. You may find the easiest method to achieve this is by interleaving two or more converters.

 

[Odion]

Do you intend to charge a battery? That's a consideration since you don't want current to flow backwards at any time.

Do you intend to have 2 transistors... one conducting while the other is Off? They must be oriented so current always goes through the inductor in one direction.
They must be biased accordingly.

To gain efficient utilization of the solar panel, you shall draw continual smooth current at maximum power it can produce. You may find the easiest method to achieve this is by interleaving two or more converters.

Thanks a lot for the quick response! Yes it’s for charging batteries
The switching is for two mosfet bank at 180 deg out of phase with each other in the synchronous rectification.
I intend to achieve for one phase first

 

[BradtheRad]

How do I make them not come on together?

Synchronous means you wish to have a transistor do the same job as the diode. My simulations of buck converters show that the transistor must be upside-down because current flows from ground up through the inductor. This occurs during the second half of the cycle because the inductor is generating current toward the battery.

It's tricky to turn on the transistor for the proper length of time. As battery voltage rises, it wants to force current backward through the system. If the transistor remains On, it permits current to discharge from the battery.

Normally the diode by itself is sufficient to solve this problem by preventing current to flow backward from the output stage.

To bias the transistor properly, there's a chance you can derive a bias automatically via the inductor terminal, or via ground. Try various biasing arrangements. Try NPN, try PNP, etc. The aim is to make the transistor turn off at the moment the inductor stops generating current.