B
Bernhard Kuemel
- Jan 1, 1970
- 0
Hi sed!
I made a variable duty cycle regulator to get a 170 W heater down to
about 30 W with a NAND that feeds back to its input capacitor via 2
resistors and another NAND drives a power MOSFET:
http://bksys.at/bernhard/img/44/regulator.jpg
(image + circuit diagram)
It did work, but produced EMI, so I added various inductors and a
diode as seen in the circuit diagram, but not in the photo. About 80
turns over a bundle of soft iron wire was not enough, so I tried a
ferrite insulation transformer, a big self wound coil on a EI core
of a former (silicon steel?) transformer and a microwave oven
transformer primary. The latter two eliminated the EMI but were too
noisy, acoustically.
I played a bit with the HV output of the MOT and when I arced to the
structure of my table the lamp went to full 100 W. The second NAND
had died appearently and went high permanently. My table top is wood
with plastic cover. The control circuit uses 0,3-0,6 mA, so I think
the NAND is not abused by driving the MOSFET.
The power of the lamp was fluctuating somewhat (other than beats
from the 50 Hz from the line and the regulating frequency) and when
I touch the fixed resistor I get bigger fluctuations and when I hold
it tighter the lamp may go out at all.
Any recommendations on how to eliminate the EMI (quietly) and why
the NAND died?
Parts list:
HEF4092BP 4 NAND Schmitt triggered
470 nF
22Kohm variable (actually only 18K)
47Kohm fixed
1N4148 2 diodes
STP3NC60FP PowerMesh II MOSFET, 600 V, 2 A
2 A bridge rectifier
10 V SMPS from a cell phone
various inductors
UF4007 diode
230 V rms main power
Thanks, Bernhard
I made a variable duty cycle regulator to get a 170 W heater down to
about 30 W with a NAND that feeds back to its input capacitor via 2
resistors and another NAND drives a power MOSFET:
http://bksys.at/bernhard/img/44/regulator.jpg
(image + circuit diagram)
It did work, but produced EMI, so I added various inductors and a
diode as seen in the circuit diagram, but not in the photo. About 80
turns over a bundle of soft iron wire was not enough, so I tried a
ferrite insulation transformer, a big self wound coil on a EI core
of a former (silicon steel?) transformer and a microwave oven
transformer primary. The latter two eliminated the EMI but were too
noisy, acoustically.
I played a bit with the HV output of the MOT and when I arced to the
structure of my table the lamp went to full 100 W. The second NAND
had died appearently and went high permanently. My table top is wood
with plastic cover. The control circuit uses 0,3-0,6 mA, so I think
the NAND is not abused by driving the MOSFET.
The power of the lamp was fluctuating somewhat (other than beats
from the 50 Hz from the line and the regulating frequency) and when
I touch the fixed resistor I get bigger fluctuations and when I hold
it tighter the lamp may go out at all.
Any recommendations on how to eliminate the EMI (quietly) and why
the NAND died?
Parts list:
HEF4092BP 4 NAND Schmitt triggered
470 nF
22Kohm variable (actually only 18K)
47Kohm fixed
1N4148 2 diodes
STP3NC60FP PowerMesh II MOSFET, 600 V, 2 A
2 A bridge rectifier
10 V SMPS from a cell phone
various inductors
UF4007 diode
230 V rms main power
Thanks, Bernhard