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

Swithing Regulation question

Status
Not open for further replies.
I

ilter

Member level 4
Joined
Jul 22, 2005
Messages
77
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
2,095
Dear all,
I have some questions.
1.I design swithing regulator.Do buffer need to add between nonoverlap circuit and power mos?
2.How do I decide power mos's length.
3.If I use one regulator and LDO in parallel. Sometimes LDO is on and Sometims SW is on. If LDO is on and SW nmos is off , is it ok? Which thing do I take care?
4.LDO need one capacitor to compensation. If my output current is bigger, my esr is smaller then phase margin is better? why?
Thanks very much?
 

(1) yes, you need ,because the great gate-cap of pass transistor.
(2) as short as you if process is permited
(3) ok
(4) how about your op in LDO?
 

paley said:
(1) yes, you need ,because the great gate-cap of pass transistor.
(2) as short as you if process is permited
(3) ok
(4) how about your op in LDO?
Click to expand...

"A" means error amp and buffer in my picture.
 

I am learning about buck regulator.
How much current is enough to control power FET with given Qgs and Qgd?
 

Thanks you!
I have another question: How do I calculate Qgate of power MOSFET with Vds?
Ex: Qg=4.5n with Vds=10v(datasheet)
Qg=? with Vds=5.5v?
 

your idea is good.
 

Calculate Qg in this way:
Qg = Cgs*Vgs + Cgd*Vgd + Cgb*Vgb in my understanding.
 

Sorry for my late response. Did you find the answers you needed in the app. notes? If not, let me know.
 

Thanks inventor!
My friend said "for most power MOSFETs the appoximation can be useful:
Cgd=2*Crss1.sqrt(Vds1/Vdsoff)"
Is he right?

Added after 1 minutes:

sorry, i mean Crss1 is Crss at Vds1(datasheet)
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top