02-11-2021, 09:14 AM
The resistance certainly matters. At field scan frequencies the resistance is dominant, though as you can see from my photos, inductance certainly matters during flyback. At line scan frequencies the inductance is dominant, resistance causes losses and non-linearity. At intermediate frequencies, in the low kHz range, there must be a range where both matter equally.
For line scan, as you use higher EHT and wider angle deflection, efficiency really matters. At the end of each forward stroke you have 0.5 * L * I^2 of energy stored in the scan coil. So multiply by scan rate to get total power that might be used. This energy has got to go somewhere during flyback. It can be disspated in a resistor (and lossy elements of the circuit) or recovered, at least in part. That's what efficiency diodes are about. I once did a calculation for first generation UK colour TVs and reckoned the line timebase would use over 2kW of power if there was no energy recovery.
The same rules apply to field scan too, but because the scan rate is so much lower, the total power is too. Hence it's rarely worth trying to recover the scanning energy. It's probably been done, but I can't cite any examples.
For line scan, as you use higher EHT and wider angle deflection, efficiency really matters. At the end of each forward stroke you have 0.5 * L * I^2 of energy stored in the scan coil. So multiply by scan rate to get total power that might be used. This energy has got to go somewhere during flyback. It can be disspated in a resistor (and lossy elements of the circuit) or recovered, at least in part. That's what efficiency diodes are about. I once did a calculation for first generation UK colour TVs and reckoned the line timebase would use over 2kW of power if there was no energy recovery.
The same rules apply to field scan too, but because the scan rate is so much lower, the total power is too. Hence it's rarely worth trying to recover the scanning energy. It's probably been done, but I can't cite any examples.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
