I am in the process of designing a lightweight power supply using all surface mount components. A driving circuit powers a piezoelectric transformer using halfwave DC at 65.5kHz. The driving voltage is 1.25V to 41V, while the current is adjusted with the voltage to be the only constant. The AC output (75-2460V) is rectified and stored in a capacitor. A special IGBT is used to discharge the capacitive discharge circuit at a variable frequency of 1-100Hz.
My problem is stepping the voltage up further. I need a final output of around 50kV and at the high current from the capacitive discharge circuit a cockroft walton multiplier type circuit would be WAY TOO BIG AND HEAVY. Because of the relatively low frequency it is actually extremely hard to nearly impossible and expense to use a custom multiplier.
I need suggestions on how to solve my problem please. This is for aerospace application so I'd say weight is one of the biggest considerations. The second of course is a reliable system with a long life span.
This does entail that a wire wound transformer will not fit the application either, as they are bulky and heavy and sometimes not reliable systems during constant operation.
Attached is the schematic for the circuit without a secondary circuit to step the voltage up further to that needed for application.
PARTS LIST:
C1 - 0.1μF
C2 - 1μF
C3 - 10pF to 1nF 5kV protective isolation capacitor
C4 - (presently undefined value) 5kV discharge capacitor
D1 - 100V rectifier diode (regulator protection)
D2, D3 - SM3F 3kV rectifier diode
D4 - Freewheeling diode
R1 - 240Ω
R2 - 200Ω
S1 - NPN
S2 - MOSFET - IRF9Z24NS
S3 - IGBT - IXEL40N400
78M05B - 5V Positive Fixed Voltage Regulator
OM7646 - 1.25V-57V Positive Adjustable Voltage Regulator
AD8400 (R-8 package) Digital Potentiometer
The max dissipation of the piezoelectric transformer (PT) is 7 watts, but because of the capacitive discharge circuit the output is much greater then the input. The frequency of 67kHz is the resonant frequency of the PT.
PT INPUT: 6.88watts - 1.25V to 41V @ 0.168amps (constant current when voltage is adjusted)
PT OUTPUT: 2.46kV @ 0.0028amps
I do not know how to calculate the capacitive discharge output (dependant of frequency), but I think that is all the information that I know at this time.
Regards,
Uriah George
uriahgeorge@yahoo.com
My problem is stepping the voltage up further. I need a final output of around 50kV and at the high current from the capacitive discharge circuit a cockroft walton multiplier type circuit would be WAY TOO BIG AND HEAVY. Because of the relatively low frequency it is actually extremely hard to nearly impossible and expense to use a custom multiplier.
I need suggestions on how to solve my problem please. This is for aerospace application so I'd say weight is one of the biggest considerations. The second of course is a reliable system with a long life span.
This does entail that a wire wound transformer will not fit the application either, as they are bulky and heavy and sometimes not reliable systems during constant operation.
Attached is the schematic for the circuit without a secondary circuit to step the voltage up further to that needed for application.
PARTS LIST:
C1 - 0.1μF
C2 - 1μF
C3 - 10pF to 1nF 5kV protective isolation capacitor
C4 - (presently undefined value) 5kV discharge capacitor
D1 - 100V rectifier diode (regulator protection)
D2, D3 - SM3F 3kV rectifier diode
D4 - Freewheeling diode
R1 - 240Ω
R2 - 200Ω
S1 - NPN
S2 - MOSFET - IRF9Z24NS
S3 - IGBT - IXEL40N400
78M05B - 5V Positive Fixed Voltage Regulator
OM7646 - 1.25V-57V Positive Adjustable Voltage Regulator
AD8400 (R-8 package) Digital Potentiometer
The max dissipation of the piezoelectric transformer (PT) is 7 watts, but because of the capacitive discharge circuit the output is much greater then the input. The frequency of 67kHz is the resonant frequency of the PT.
PT INPUT: 6.88watts - 1.25V to 41V @ 0.168amps (constant current when voltage is adjusted)
PT OUTPUT: 2.46kV @ 0.0028amps
I do not know how to calculate the capacitive discharge output (dependant of frequency), but I think that is all the information that I know at this time.
Regards,
Uriah George
uriahgeorge@yahoo.com
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