Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

How can I possibly reduce the power dessipation

Status
Not open for further replies.
O

opins

Newbie level 4
Joined
Aug 5, 2007
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,327
MPPT

Hi every one,

I have just built a 40V, 5A, Maximum Power Point Tracker, using a buck topology, and it works considerably well, especially for low sun conditions.

I used P Mosfet for the switching, and complimentary transistors (BC639 and BC640) as the mosfet gate driver.

My problem the Mosfet gets very hot at mid switching condition.
How can I possibly reduce the power dessipation?

I also want to build another circuit for 50V, 10A load
My problem is how to get a about 3mH, that can withstand morethan 10A?

can I use double inductor?

e.g If i have a 4mH, 6A dual inductor (please see attached), can i parallel the leads to get 2mH, 12A inductor?

I have attached a picture of the inductor I used for the previous circuit
 

MPPT

why is the inductor getting hot? typically it will only get hot if there is a lot of current flowing when there is still voltage across the device.

this will either be due to I^2 R losses (Rds_on too high), or due to a fast switching rate -- on each cycle there is some amount of overlap between voltage falling and current rising, which means some amount of energy lost per cycle.

P-FETs tend to do worse in both regards. Perhaps you should look into using an N-FET. look up high-side gate drive schemes.

for inductors, yes, you can use 2 discrete inductors in parallel.
 

MPPT

You are showing a common mode choke. it's not suited as DC converter inductor, because it's getting saturated. Generally, I don't understand why you want to use such a high inductance. It would be only reasonable for low kHz switching frequencies.
 

Re: MPPT

thanks for your response,

N mosfet for low side switching buck converter? the issue is that i have not seen a comprehensive literature on that. but I will still search further.

I may probably try using a mosfet gate driver IC, will that reduce switching losses (switching freq is about 15Khz)?

I use large inductance because i want it to operate in continuous conduction mode, and also, the switching frequency is about 15Khz (I use low freq bcos the mppt tracking circuit utilises ripple correlation)
 

MPPT

N-FETs have been used for that purpose for a long time -- its also common to see the buck converter used with SCRs/Triacs (for AC), with IGBT's, or with other devices.

The large issue is with ground loops -- the output is connected between Vcc and the FET's drain. thus if the output's negative terminal is connected to a system ground by accident, it essentially shorts across the FET, removing all control from the circuit.

at 15khz, switching losses should be very low for many commercially available FETs. Rds_on and the I^2 R losses in the inductor will likely be the large sources of loss.

and as mentioned, you can also make a high-side driver for an N fet.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top