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Yes that is true if I remember correctly I loaded mine with a resistor so it had a constant load on it. Many of the walwart transformers are the same way they also need to be loaded to some degree. It dont need much but it needs something on it.
Probably not even worth it huh, just get the things the expert decided would be best and move from there lol?
C12 is on the rectified 120VAC mains line, which is ~170V DC when rectified, so 200V caps should be fine as long as you don't supply more than 120Vrms to the bridge rectifier. 2200uF should do quite well at modest power levels. Voltage ripple across a filtered supply is determined by:
Vpk = I / (2fC) f = 120Hz for a full bridge rectifier I = Irms of the primary coil C = filter capacitance in farads
As for how much Vpk is too much for audio or a silent arc.... it is pretty subjective and/or affected by many variables. Less is always better, you just have to weigh it against the extreme cost of high C values.
The power draw of a SSTC is limited by the primary coil and the capacitive coupling of a load to the secondary coil. What regulators are you referencing in:
wrote ... For C12, I have two 1100uf 200v lytic caps laying around, would those be sufficient? They were going into a vintage power supply, but eh, I am just going to sell the supply, wont do me any good anyways, not much better than an LM317 with lots of filtering caps. I would like to run it hard if I can, but I am not sure what running a SSTC hard really is.. So if you could elaborate more on that I would be appreciative. You seem to reference adding more power, but isnt the power draw limited to the voltage regulators?
I control the power input to my SSTCs with a variac, which varies the AC voltage applied to the half bridge. The current draw of a SSTC primary is complexly related to the DC buss voltage. For example: my large SSTC draws 1Arms of current between 15Vac (minimum operating voltage) and 45Vac, and then gradually increases in current draw as the applied voltage is increased. At around 60Vac nearly 5Arms is drawn. At 120Vac input to the bridge rectifier a little more than 10Arms is drawn. I = V / R, if R is (nearly) constant then increasing V increases I.
More turns on the primary reduces current draw by increasing impedance, but this also increases the inductive kick back-emf voltage the half bridge sees across C7 and C8 and the ultrafast bypass diodes. I use 10turns of 10AWG wire, and it gets very warm above 500VA input.
You also need high capacitance on the 12v rails because the gate drive chips can draw a lot of peak power. The averaged power drawn on the 12v and 5v rails is quite low though, less than 1amp. The switching frequency and gate capacitance of the mosfets determines how much peak current the gate drive chips require: I = C dV/dT. I use a 50V 2200uF cap after each the LM7812 and LM7805. I also use two of these caps before the LM7812 because I am using an old 20Vac stepdown transformer which cannot normally supply 1A without sagging to about 13Vac. This large supply capacitance between the low voltage bridge rectifier and the regulators keeps the peak current demand on the old transformer low, which lets it run easier. You may not need such high capacitance before the regulators if your low voltage supply is beefier, but always use at least 22uF before and after all LM regulator chips to prevent oscillations.
With TC driver boards, all chips should be decoupled with a >0.1uF pulse-capable cap across their supply rails directly at the chip.
An interupter can be as simple as an astable 555 timer oscillator fed in to pin 3 of both the UCC chips. Pulsewidth doesn't really matter as this design can run just fine CW mode.
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SSTC questions from a newbie
