Timeline for Impedance equivalent for oscillating switch in SPICE AC simulation
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
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| Aug 5, 2018 at 16:50 | vote | accept | Voltage Spike♦ | ||
| Aug 5, 2018 at 9:50 | answer | added | LvW | timeline score: 2 | |
| Aug 4, 2018 at 22:58 | history | edited | Voltage Spike♦ | CC BY-SA 4.0 |
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| Aug 4, 2018 at 6:37 | comment | added | a concerned citizen |
I would guess the switches act like a regular sampler, with the usual sinc frequency response, but the aliasing here occurs volens-nolens. For example, a .TRAN freq sweep from 100 to 1k, with fs=1k, will not give the usual sampled symmetry, but something mingled. I don't know how to represent such an aliasing difference in .AC. Furthermore, as carloc mentions, it is dependent on the duty cycle, if this would be the case.
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| Aug 3, 2018 at 4:36 | vote | accept | Voltage Spike♦ | ||
| Aug 3, 2018 at 4:36 | |||||
| Aug 2, 2018 at 23:01 | comment | added | carloc | You should basically use an averaged equivalent circuit. E.g. R2 acts as a resistor while its switch is on and as open circuit otherwise, so for a given voltage its average current is D (duty cycle) times the DC one. In simpler terms R2(D)=R2/D. The same obviously goes for R1 and its own switch. Of course for the above to be meaningful you have to keep your AC analysis well below switching frequency. | |
| Aug 2, 2018 at 22:45 | answer | added | user136077 | timeline score: 1 | |
| Aug 2, 2018 at 22:30 | comment | added | Voltage Spike♦ | @ElliotAlderson What about a chopper amplifier or a delta sigma converter? I'd still like to do AC analieses on them, the switching frequency still affects the AC network. | |
| Aug 2, 2018 at 21:55 | comment | added | Elliot Alderson | It doesn't make sense to have a switch change in an ac sweep. By definition the circuit is in "steady state", with no transient effects. If you want to wiggle a switch you need to run a transient simulation. Do it at different frequencies if necessary, but as far as SPICE is concerned it will be multiple transient simulations. | |
| Aug 2, 2018 at 21:51 | history | edited | Voltage Spike♦ | CC BY-SA 4.0 |
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| Aug 2, 2018 at 21:50 | comment | added | Voltage Spike♦ | @EE_socal The switch models only work in a transient simulation, I want to run an AC sweep. | |
| Aug 2, 2018 at 20:56 | comment | added | EE_socal | Ltspice has switch models | |
| Aug 2, 2018 at 20:44 | comment | added | Elliot Alderson | What simulator are you planning to use? Many have a built-in switch primitive. | |
| Aug 2, 2018 at 20:06 | history | asked | Voltage Spike♦ | CC BY-SA 4.0 |
