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Registered Member #2063
Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352
I recently built a 12v 200W PWM light dimmer for halogen lamps. it uses a 555 IC to generate PWM and a pot to adjust the duty cycle. im not sure about the frequency of th PWM but it can be easily adjusted by sawping a ceramic cap. so, will a high power/frequency PWM generator work as a flyback driver?
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
Haven't build one ... but if no one is going to jump in ...
I did google for schematics recently ... here's some :
This guy build the last one and has a youtube movie :
You just need to add the flyback and either a snubber (the second link) or a Zener+cap (the first link). Hell, might as well add both ... the snubber is there to damp oscillations, the Zener to protect the MOSFET from overly high drain-source voltage (although you can still kill it with high enough duty cycle simply by pulling too much current/power).
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
The Sony patent is interesting in that they divide down the EHT to drive the comparitor to adjust the duty cycle.
It would seem thay they were worried about X-Rays from the trinitron as it aged and presented less load. Other schemes of that era just had service personel set the HV with a probe.
Yes I have done it by winding around the exposed ferrite on a flyback from a monitor. Suprizingly powerful. And simple. Two inch arcs off 12v pwm I built off drawings from here. There site is hard to navigate but quite alot of good info. Look under diy home pulse control circuits
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driving a flyback with PWM?
