Be a bit more specific. Is it DC, bipolar DC, AC, etc. and how precise should it be? A very crude way of DC implementation would be a parallel combination of a current source with a 15 volt zener. However, this method does have its limitations. After zener breakdown, it becomes a current limited voltage source.
I tried to use a 15V zener diode, but this did not work, because too much current flows through this zener diode. It would be very nice, if nearly no current flows through the zener or through any other component for voltage limitation.
In another simulation I used a resistor, but (like I already mentioned) this doesn't work in this case, because too much current flows through this resistor.
Or do you know current sources in Pspice, where I simply can determine a maximum voltage or a maximum of electrical power or the internal resistance? (Because in the standard model I didn't find these options)
Try this subcircuit. It's a voltage limited current source with two parameters to pass into; VL is the limiting voltage and OC is the prelimiting output current. The current output begins to drop when its terminal voltage begins to exceed 0.99VL and after 1.01VL is essentially zero.
Unfortunately this does not work in my simulation. I changed OC to 40.8A, but I only get 10A as output current.
What else can I try to get this work?
Or are there any other possible solutions I could try?
Maybe it helps you, when I discribe my problem a little better: I need a current source with up to 200A and with a maximum voltage of 15V. The circuit is very complex and I am not allowed to post it here. The problem is, that I have two stages:
1) The current flows through a closed switch.
2) Nearly no current flows, because of a back-biased optocoupler. In this case I need a voltage limitation of 15V.
These two stages are alternating. Furthermore the 40.8A should flow through the circuit, when the switch is closed and nearly no current should flow through other components used for voltage limitation.
Closed Switch: The current source will deliver 40.8A provided your circuit impedance is low enough to keep its terminal voltage under 14.85 volts. If it exceeds that then the current is reduced in order to keep the terminal voltage under ~15 volts. This is why you're only getting 10A from the current source.
Open Switch: The current is reduce to whatever the leakage is through your back-biased optocoupler while maintaining ~15 volts output.
Is it possible to see some of your front end circuit where the current source attaches?
Be a bit more specific. Is it DC, bipolar DC, AC, etc. and how precise should it be? A very crude way of DC implementation would be a parallel combination of a current source with a 15 volt zener. However, this method does have its limitations. After zener breakdown, it becomes a current limited voltage source.
Thank you very much for your reply.
I need to simulate a DC current source.
I tried to use a 15V zener diode, but this did not work, because too much current flows through this zener diode. It would be very nice, if nearly no current flows through the zener or through any other component for voltage limitation.
In another simulation I used a resistor, but (like I already mentioned) this doesn't work in this case, because too much current flows through this resistor.
Or do you know current sources in Pspice, where I simply can determine a maximum voltage or a maximum of electrical power or the internal resistance? (Because in the standard model I didn't find these options)
Try this subcircuit. It's a voltage limited current source with two parameters to pass into; VL is the limiting voltage and OC is the prelimiting output current. The current output begins to drop when its terminal voltage begins to exceed 0.99VL and after 1.01VL is essentially zero.
.SUBCKT VL_CS Iout Irtn
+PARAMS: VL=15 OC=10
V1 2 3 DC {2.0*oc}
V2 0 3 DC {oc/1000}
R1 1 2 1K
S1 1 3 IOUT IRTN limit
G1 IOUT IRTN 1 0 -1
.MODEL limit VSWITCH
+Roff=1002 Ron=500.25m
+Voff={0.99*vl} Von={1.01*vl}
.ENDS
Unfortunately this does not work in my simulation. I changed OC to 40.8A, but I only get 10A as output current.
What else can I try to get this work?
Or are there any other possible solutions I could try?
Maybe it helps you, when I discribe my problem a little better: I need a current source with up to 200A and with a maximum voltage of 15V. The circuit is very complex and I am not allowed to post it here. The problem is, that I have two stages:
1) The current flows through a closed switch.
2) Nearly no current flows, because of a back-biased optocoupler. In this case I need a voltage limitation of 15V.
These two stages are alternating. Furthermore the 40.8A should flow through the circuit, when the switch is closed and nearly no current should flow through other components used for voltage limitation.
Closed Switch: The current source will deliver 40.8A provided your circuit impedance is low enough to keep its terminal voltage under 14.85 volts. If it exceeds that then the current is reduced in order to keep the terminal voltage under ~15 volts. This is why you're only getting 10A from the current source.
Open Switch: The current is reduce to whatever the leakage is through your back-biased optocoupler while maintaining ~15 volts output.
Is it possible to see some of your front end circuit where the current source attaches?
Ok, thanky you very much for your information.
But I can't change the circuit. So I won't be able to use your model in this circuit?
No, unfortunately this is not possible.