Problem in DC2DC converter in MPPT charge controller

[Mithun_K_Das]

Recently I've designed MPPT solar charge converter. The MPPT is working fine. But the Problem is the DC to DC Converter. I'm using P-Channel MOSFETs for switching. Problem is P-Channel MOSFETs are not available in high power ratings in my local markets. I need to use N-Channel MOSFETs. But if N-Channel MOSFETs are used it will need extra gate driving circuit. I tried with Opto-Coupler (P817C) for gate driving. I realized that the FETs are getting much more Heated than the P-Channel FETs. I measured the gate voltage, Its not sufficient(2.36Vp).

Is there any way so that I can use N-Channel MOSFETs efficiently?

 

[iukhan]

Do either of the following
1. If possible use the N-Channel Mosfet of DC-DC converter in Low/ground side.
2. Use Bootstrap circuit for driving
3. Use Mosfet driving IC

 

[Mithun_K_Das]

I like to choose the first one. I think it will reliable. Do you have any reference for 'N-Channel Mosfet of DC-DC converter in Low/ground side'?

 

[Tahmid]

You might be able to alter the circuit configuration to have the switching MOSFET operate as the low side switch. It will still be a DC-DC converter with the N-channel MOSFET being the switching device. The circuit configuration is just changed to enable the MOSFET to work as a low side switch instead of a high side switch to simplify drive. Just shuffle around the combination of inductor, MOSFET and diode.

 

[Prince Vegeta]

can you give me something useful about MPPT? I work on a project similar to yours, it's solar inverter.

we want to add MPPT to out project and I didn't have the time to search from scratch, so if you have something to help me I'll be happy to have it ^_^.

Especially the concept.

 

[Mithun_K_Das]

Prince Vegeta please read my other posts. Something valuable is there.

Tahmid, If I use FETs in low side and the inductor in positive will it work? I need buck converter. But I'm worried if it will work as a buck converter or boost converter when N-Channel MOSFETs are in low side.

 

[BradtheRad]

Here is a schematic showing how to construct a buck converter with an NPN (or N-mosfet) at the low side.



You would substitute your own values for components.

The .1 ohm resistor is a 'token' to represent the fact that the coil has some amount of resistance.

 

[Tahmid]

Tahmid, If I use FETs in low side and the inductor in positive will it work? I need buck converter. But I'm worried if it will work as a buck converter or boost converter when N-Channel MOSFETs are in low side.

Buck or boost depends on the configuration of the inductor around the MOSFET and not whether the MOSFET is a high-side or low-side switch.

For N-channel MOSFET operating as low-side switch for buck converter:

Hope this helps.
Tahmid.

 

[Mithun_K_Das]

Thank you BradtheRad and Tahmid. I'll try this circuit soon. Today I've made one using bootstrap in clock driving. Still now its working fine.