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.

How to eliminate hard switching effects?

Status
Not open for further replies.

seyyah

Advanced Member level 2
Joined
Oct 7, 2001
Messages
646
Helped
8
Reputation
16
Reaction score
8
Trophy points
1,298
Activity points
6,231
hard switching snubber -resonant -soft

How can we eliminate dips or peaks which occur at rising or falling edges of the switching pulses?
 

vdaniel

Full Member level 4
Joined
Oct 8, 2004
Messages
204
Helped
8
Reputation
16
Reaction score
0
Trophy points
1,296
Activity points
2,157
The question is too common. There are a lots and lots of different kinds of switching pulses.

Varuzhan
 

IanP

Advanced Member level 5
Joined
Oct 5, 2004
Messages
7,942
Helped
2,311
Reputation
4,624
Reaction score
531
Trophy points
1,393
Location
West Coast
Activity points
66,416
Without going into details, you can try to use a snubber circuit.
Have a look in here:
**broken link removed**
Regards,
IanP
 

seyyah

Advanced Member level 2
Joined
Oct 7, 2001
Messages
646
Helped
8
Reputation
16
Reaction score
8
Trophy points
1,298
Activity points
6,231
Switchings are pwm switchings up to 20KHz. Actually i use a snubber. May be it needs tuning. I need some info to calculate parameters, can you offer something? Also someone proposed me to connect an rc filter to the gate , but i couldn't understand the use of this. Does this method make any sense to you?
 

VVV

Advanced Member level 5
Joined
Nov 26, 2004
Messages
1,582
Helped
384
Reputation
768
Reaction score
88
Trophy points
1,328
Activity points
19,971
Connecting a filter at the gate will slow down the MOSFETs. With slower rise/fall times the induced voltages (in parasitic inductances) will be lower.

The down side is that you will increase switching losses in the transistors. Generally, only a resistor in series with the MOSFET gate is sufficient. I would not add the capacitor.
 

seyyah

Advanced Member level 2
Joined
Oct 7, 2001
Messages
646
Helped
8
Reputation
16
Reaction score
8
Trophy points
1,298
Activity points
6,231
A zener diode may suffice may be, what do you think?
 

power-twq

Full Member level 6
Joined
Jun 10, 2005
Messages
373
Helped
8
Reputation
16
Reaction score
3
Trophy points
1,298
Activity points
4,550
you can use RC snubber circuit to have a try.

seyyah said:
How can we eliminate dips or peaks which occur at rising or falling edges of the switching pulses?
 

Ice-Tea

Full Member level 2
Joined
Jan 1, 2005
Messages
145
Helped
27
Reputation
58
Reaction score
26
Trophy points
1,308
Location
Belgium
Activity points
873
Maybe this is a stupid suggestion, depending on your experience level, but have you checked your measuring method? Per example, measuring with a scope with long ground leads will also result in perceived ringing on edges?
 

yongchai

Junior Member level 1
Joined
Jun 11, 2005
Messages
15
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
1,420
If you mean the peak/dip at rising/falling edge of 'switching signal' (PWM signal to gate), then you should add a resistor in series to the gate of the mosfet. If I'm not wrong, larger resistance value will increase the rising time, and therefore reduce the peak magnitude. However, switching loss will increase. So, need to set a balance.
 

seyyah

Advanced Member level 2
Joined
Oct 7, 2001
Messages
646
Helped
8
Reputation
16
Reaction score
8
Trophy points
1,298
Activity points
6,231
R should eliminate but didn't help so much. I can't increase the resistor very much. Snubber may help, thanks
 

vaibhav.k

Advanced Member level 4
Joined
Apr 12, 2006
Messages
114
Helped
9
Reputation
18
Reaction score
3
Trophy points
1,298
Location
India
Activity points
1,779
Best snubber circuit is RCD snubber with polyster type cap which reduces almost 60 to 80% spikes
 

Kurniawan

Junior Member level 1
Joined
Sep 5, 2006
Messages
18
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,355
first, you must to ensure that your pulse gate of switcher can truly on and off. The second, Your PS must be in continuous conduction mode. Circuit of snubber maybe complex and difficult, if not work in big power maybe u can select device over your design ( current and voltage capability ).
 

drabos

Full Member level 6
Joined
Jan 3, 2006
Messages
399
Helped
45
Reputation
90
Reaction score
15
Trophy points
1,298
Activity points
3,755
I have the same problem, but my device is in integrated circuit. and the inductance is the bonding wire. The breakdown voltage is very little. I can't decrease the rise time. And I can't connect anything with parallel to the bonding wire.
Any idea?
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top