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Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
These transistors are used as flyback drivers operating with high voltage and low current, and are pretty good in this function. For reasons of efficiency and simplicity of the required power supply, practically nothing different is used (or was used, as they are practically obsolete) in CRT monitors and TVs. To deal with the required quite high base current, the drivers practically always use transformers. The required transformers and other parts of the driver circuitry can be found in in the same boards. It's useful to find the schematics of the boards. Entire sections, as the input switching power supply, can be used for other purposes.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Antonio wrote ...
These transistors are used as flyback drivers operating with high voltage and low current, and are pretty good in this function. For reasons of efficiency and simplicity of the required power supply, practically nothing different is used (or was used, as they are practically obsolete) in CRT monitors and TVs. To deal with the required quite high base current, the drivers practically always use transformers. The required transformers and other parts of the driver circuitry can be found in in the same boards. It's useful to find the schematics of the boards. Entire sections, as the input switching power supply, can be used for other purposes.
That's right, Antonio! The driver transformer needs a HV transistor to drive it sufficiently to provide meaty pulses to the LOPT driver base. It's a sheer waste of time trying to do it any other way with BJTs, in my view, but I see no reason why folk couldn't wind there own driver transformer on a chunky toroid.
Here is the same circuit modified as a simple HV generator with unwanted gubbins cut out:
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Well I did also get a whole bunch of IRFP630's. When I get around to ordering the parts for a big ZVS I'll get some extra ultrafast diodes to make a mini ZVS too.
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HV transistors
