Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic 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

[SOLVED] PTC resettable fuses in parallel

Status
Not open for further replies.

ArticCynda

Advanced Member level 1
Joined
May 8, 2013
Messages
424
Helped
82
Reputation
164
Reaction score
81
Trophy points
1,308
Activity points
4,047
Hi everyone,

I'm designing a power supply circuit that can take inputs from USB (max. 500mA) and a DC jack (max. 1A). I'd prefer to protect both with a PTC resettable fuse.

Can I wire 2 PTCs with a trip current of 500mA in parallel to act as a 1A PTC for the DC jack? Is this a good practice? If not, why?

Thanks in advance!
 

hobbyckts

Advanced Member level 1
Joined
Mar 12, 2015
Messages
481
Helped
88
Reputation
176
Reaction score
85
Trophy points
28
Activity points
2,457
Its better to have jumper selection whenever you are switching between these two supplies.

Mainly when you are using fuses in parallel how come current will get divide?
 

E-design

Advanced Member level 5
Joined
Jun 1, 2002
Messages
2,014
Helped
507
Reputation
1,016
Reaction score
407
Trophy points
1,363
Activity points
14,195
The trip current of these fuses will not be exact. If any one fuse opens less at than 500mA, the remaining one will open soon after since it tries to pass all the current. I think you will find that the circuit will always trip at a much lower current than you expect. It is not a good idea to parallel them up.
 

ArticCynda

Advanced Member level 1
Joined
May 8, 2013
Messages
424
Helped
82
Reputation
164
Reaction score
81
Trophy points
1,308
Activity points
4,047
Thanks for the response, I suspected it might behave that way, similarly to why you can't parallel diodes to get the effect of a higher current diode, but wanted to check to be sure.
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top