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Re: Ghost Noting
 2/8/2006 11:34 AM |
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| R.G. | Re: Ghost Noting
Bad idea. The inductor will do whatever it has to to keep the current flowing. The current will be whatever was flowing in the inductor when the attempt at interruption was made. The induced voltage will be the pre-interruption current times the resistance and that can be large indeed. The diodes make a low resistance clamp, so the voltage is clamped to ground instead of hundreds of volts minus.
They would, about onece per attempt at interruption. This is a standard use of diodes in switching power supplies, to give the inductor a clamped place to stand when the current is interrupted. In such applications, the diode clamps once per cycle at 50kHz to over 1MHz. Note that the reversed diode is not breaking over, it's forward conducting. The diode needs to be high enough voltage not to break over reverse.
I don't think so. If it's just forward clamping, the current is low, just the sum of the PI and preamp plate currents. A 1A diode like th 1N4007 has a repetitive surge rating of around 100A peak, so the current spikes won't kill it. You do need to arrange to keep the reverse voltage under 1kV, but the reverse direction voltage (that is, the normal B+ supply voltage, which is in the reverse direction to the diode) is limited by some biggish capacitors on each side of the inductor, so the inductor would have to overfill those capcitors to overvolt the diode solidly. Instantaeous overvoltages would be clamped by the caps. | |||
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| Ray Ivers R.G., |