hi friends,
Do you have an idea or circuit for "AC square wave constant voltage generator" with short circuit protection ? The spec: 1. The square wave output is 24v 200mA. 2. Max load's resistance is 8000 ohm 3. When the load's resistance is decreased,the current will drop to a value but the voltage always keep 24v. I have no idea how to keep 24v.
The frequency must be fixed between 100hZ and 100khZ.
"Doesn't AC stand for Alternating Current? Which would imply alternating (and therefore not constant) voltage."
Maybe he means constant amplitude?
I don't think it's unusual to speak of a "constant amplitude" AC source as "constant voltage" - even if, as you say, it isn't literally true?
... we could also ask whether this is really AC - ie alternating - or is it just pulsed DC?
ie, does the voltage swing between +24V and -24V (or +/-12V), or is it just 0V and 24V?
Anyway, you don't specify any load regulation for your generator. If you really did mean that max load is 8000 ohm, then you can select a trivial solution.
Just use a 24V linear voltage regulator and feed the 24V to a switch transistor controlled by a logic-level squarevave generator.
Place a 120 ohm resistor between transistor and connector.
Your short-circuit current will then be 24V/120ohm = 200mA.
Your open-circuit voltage will be 24V (minus a little loss in the switch transistor).
Your fully loaded current will be 24V / (120 + 8000) A = 0.00296A.
Your fully loaded volage will be 24V - 24 * 120 / (120 + 8000) V = 23.65V (minus a little loss in the switch transistor).
Your load regulation will be 1.5% which should be good enough for most usages.
But this is only valid if you by 200mA meant short-circuit current, and didn't mean max current at nominal load (which would be 120 ohm and not 8000 ohm).
Additionally
24 V on 800 ohm get 30 mA so you have to check your specification. For 800 ohm load you need at least a generator with 160 V.
For a simple on/off a switched constant current generator can do the job (the frequency can be the problem if too high).
You are an order of magnitude off. The specified load was 8 kohm, not 800 ohm, so it would take 1,6kV to drive 200mA through the load, and the power sent into the load would be 320W at 50% (?) duty cycle.