03-08-2014, 12:57 AM
I would have used something like these for the output and the driver and a 220K resistor in place of the constant currant device.
The constant currant device is a legacy of bipolar regulators and is not needed with high gain FETs.
http://uk.mouser.com/ProductDetail/STMic...b%252bc%3d
They are voltage driven and have a huge ma per volt compared to valves.
You may need a little bit of biasing for the zena diode in the source of the driver.
I have used these SMPSU FETS for an analogue LED dimmer with the gates fed through high value resistors to fade in chains of LEDs to have the effect of an electronic ballast. I fitted a chain of zena diodes and a pot at one end.
Most of the SMPSU types have built in zena diodes in there gates and do not need external fitment.
The lamp faded in a bank at a time so there was only one FET dissipating analogue power at a time.
800V and 900V MOSFETS are made in huge quantities and are cheap as they are in wall warts and computer power supplies as well as flat screen TV sets.
Only the currant limiter needs to be low voltage bipolar.
The constant currant device is a legacy of bipolar regulators and is not needed with high gain FETs.
http://uk.mouser.com/ProductDetail/STMic...b%252bc%3d
They are voltage driven and have a huge ma per volt compared to valves.
You may need a little bit of biasing for the zena diode in the source of the driver.
I have used these SMPSU FETS for an analogue LED dimmer with the gates fed through high value resistors to fade in chains of LEDs to have the effect of an electronic ballast. I fitted a chain of zena diodes and a pot at one end.
Most of the SMPSU types have built in zena diodes in there gates and do not need external fitment.
The lamp faded in a bank at a time so there was only one FET dissipating analogue power at a time.
800V and 900V MOSFETS are made in huge quantities and are cheap as they are in wall warts and computer power supplies as well as flat screen TV sets.
Only the currant limiter needs to be low voltage bipolar.
