imulate a small Voltage Drop Out with MOSFET vs. parasitic capacitances - Electronic Circuits Projects Diagrams Free

dirkdiggler2oo2 · 21st December 2006, 09:56 AM

Hello,

i want to simulate a small voltage drop out (variable between 1us to 40us), the supply voltage is also variable (between +5V to +35V).

On the basis of the facts that a relay is to slow i think about a MOSFET, it should withstand high voltage and high current.

The problem i have is that to switch in MHz-range i need high current so that the MOSFET parasitic capacitances are reloaded and the waveform of switching have a rectangle signale form.

Does anybody know a solution to eliminate parasitic capacitances ?

Analog · 21st December 2006, 10:37 AM

I don't think the MOSFET would be the problem, many MOSFETs can switch in the MHz range (you didn't specify what frequency). The problem is what it is driving. The capacitance on the drive side will drastically effect the signal, because as we all know, you can't instantaneously change the voltage on a capacitor. What are you driving? What are its characteristic capacitance and inductance values???

dirkdiggler2oo2 · 21st December 2006, 11:22 AM

my switching frequency is between 25kHz (1/40us) up to 1MHz (1/1us).

I want to drive a pump, motor applikation so i have to provide min. 2A, but i don't know the capacitance and inductance valuesat time

Hero999 · 21st December 2006, 02:16 PM

Why do you want to do that?

Are you talking about PWM? Normally a lower frequency is used for that.

dirkdiggler2oo2 · 22nd December 2006, 09:42 AM

no pwm, i want to simulate a short break down of the power supply voltage

Analog · 22nd December 2006, 11:58 AM

Quote:

Originally Posted by dirkdiggler2oo2

no pwm, i want to simulate a short break down of the power supply voltage

It is unlikely that a power supply would drop out with a sharp drop like that. The filtering caps in a supply would prevent that from happening. Can you elaborate on what type of fault would drop the supply like that?

Sceadwian · 22nd December 2006, 02:29 PM

A fault on the circuit side, or wireing fault coming from the power supply. Just off the top of my head (not the original poster)

21st December 2006, 09:56 AM	(permalink)
dirkdiggler2oo2 New Member	imulate a small Voltage Drop Out with MOSFET vs. parasitic capacitances Hello, i want to simulate a small voltage drop out (variable between 1us to 40us), the supply voltage is also variable (between +5V to +35V). On the basis of the facts that a relay is to slow i think about a MOSFET, it should withstand high voltage and high current. The problem i have is that to switch in MHz-range i need high current so that the MOSFET parasitic capacitances are reloaded and the waveform of switching have a rectangle signale form. Does anybody know a solution to eliminate parasitic capacitances ?

21st December 2006, 10:37 AM	(permalink)
Analog Experienced Member	I don't think the MOSFET would be the problem, many MOSFETs can switch in the MHz range (you didn't specify what frequency). The problem is what it is driving. The capacitance on the drive side will drastically effect the signal, because as we all know, you can't instantaneously change the voltage on a capacitor. What are you driving? What are its characteristic capacitance and inductance values??? __________________ "Everything that is done in the world is done by hope." -Martin Luther "There are two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."-Albert Einstein

21st December 2006, 02:16 PM	(permalink)
Hero999 Experienced Member	Why do you want to do that? Are you talking about PWM? Normally a lower frequency is used for that. __________________ What's so bad about Microsoft? Get Opera it's simply a superb browser.

22nd December 2006, 02:29 PM	(permalink)
Sceadwian Experienced Member Blog Entries: 1	A fault on the circuit side, or wireing fault coming from the power supply. Just off the top of my head (not the original poster) __________________ Curiosity killed the cat; That's why they have nine lives.

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21st December 2006, 11:22 AM	(permalink)
dirkdiggler2oo2 New Member	my switching frequency is between 25kHz (1/40us) up to 1MHz (1/1us). I want to drive a pump, motor applikation so i have to provide min. 2A, but i don't know the capacitance and inductance valuesat time

22nd December 2006, 09:42 AM	(permalink)
dirkdiggler2oo2 New Member	no pwm, i want to simulate a short break down of the power supply voltage

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