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Experiment 03 - Design of lightweight HV POWER SUPPLIES for EHD experiments

Engineer Xavier Borg - Blaze Labs Research

Wanting to start experimenting with high voltage? Frustrated of the heavy and expensive power supplies on the market? Bought a $3000 power supply to later find out it was useless for your application? Than, search no more. On this page you will find both do it yourself versions and ready assembled hv power supply kits, assembled and tested for those less experienced in electronics. All units, including version V1.0, has output capabilities matching those of branded power units costing over ten times their price. These are the same units we used to produce over 40 gramme force from our various EHD thruster designs.

Version V1.0 DIY

Following various attempts to produce the best power to weight ratio hv power supply, for use in my autonomous helium assisted EHD thruster, the first design (March 2002) utilised an OEM colour tv type line output transformer which has its driver circuitry built 'around it', no pcb. The below picture shows the power supply unit, that is battery operated. Weight is just 300 g and power input is approximately 80 W and output is 50 kV @ 0mA going down to 30kV at full load of 2.2mA. Driver circuit consists of a 555 oscillator and BU508DF output transistor. Capable of running continuously at 40Watts without heatsink. Note the transformer is the 50kV model OEM BRL050, others might need a different dc input to work properly, and will surely have different pinouts.

power supply schematic
Schematic of hv power supply

HVPS01 simulation
Simulation of HVPS01 thanks to Michel Jullian

80 W power supply
Photo of assembled power supply

When considering the use of this supply for an autonomous EHD thruster, one has to calculate the extra weight of battery packs required to drive this lightweight power unit, which in fact exceed the weight of the unit itself.

Weight of power supply is 300g
Weight for 100v battery pack is 480g
Weight for 12v Ni-Cd battery pack is 360g


Successful replications of HVPS01

JLN replication of HVPS01 Ether Sciences replication

Technical notes

C5 is used to improve the capacity of the low power high voltage battery bank during each pulse. If you are using a mains powered dc source instead of batteries, you may not need this.

The 4.7k adjustable preset R3 varies the frequency, but most important, it also varies the output voltage. So, set this to say 1k, then switch on the circuit, and increase it until your output reaches 30 kV. Note the circuit has been designed with lightweight as priority, and no circuit protections have been included in this version. If you keep on turning the pot without monitoring your output, you may easily blow up your transistor or in the worse case your hv transformer. In my application, I used a battery bank of 100 V, and got maximum voltage possible at R3 set to 2.2k. I highly suggest the BU508DF transistor. The best frequency will be in the range of 15 - 25 kHz.

Flybacks' resonance frequency is the standard tv line frequency equal to 15625 Hz. So you can also use a frequency meter at the output of the NE555 (without connecting the FBT) and vary the 4.7k adjustable resistor until you reach this value.

In my original design the transistor used was BU508DF. Some people have also successfully replicated this circuit with BU508A. The difference between this and a BU508A or BU208A is that the DF version has a built in damper diode and an insulated case. If you use the 'A' versions, then connect a fast switching TV damper diode such as BY228 or BY448 across CE to protect the transistor against high reverse voltages, and an external 50 Ohms across B-E. Without this diode the circuit may still work fine, as long as your EHD thruster or whatever is your load does not arc, but better be safe. I would prefer to use the plastic packaged (fully isolated) transistor (lighter and insulated) however if you have to work with the metal cased transistor make sure you insulate the case (collector), as this is connected to the high voltage dc supply. Also, try not to leave any metal part of the circuit unconnected. In particular, the core of the transformer is preferably connected to the common 0 V of the circuit. Just connect a short wire from the steel spring holding the core together, to 0 V. Any unconnected metal may charge up to hv and at any time may discharge in the form of a spark to any part of your circuit. Also, remember that once your circuit is not connected to ground, the 0 V is no longer at your body's potential, so it might not be pleasant to touch anything when switched on. Same applies to your load's negative terminal which might be at several kV below your earth potential.

BE CAREFUL, USE EXTREME CAUTION !!!, this device uses High Voltage, ALWAYS switch off the input and discharge the output to the ground through 10k/2W resistor before touching it. These plans are not intended for the inexperienced. User of this document should be very careful and experienced in High-Voltage electronics to try anything out !

Revised version HVPS02 with PWM and overboost controller 20.02.04

PWM HV PS
My newly designed Overboost PWM HV Power supply



This is an improved version of the previous design, fully loaded with new features and lower battery weight requirement. This one can vary the output voltage from absolute zero to a maximum voltage of 50kV @ 0mA. The output can also be pulse width modulated from 1Hz to 100Hz, with duty cycle fully variable from 0% to 100%, and amplitude setting from 0% to 100% of the rated voltage, thus enabling any pulse voltage amplitude to be set. It also senses load current and boosts the power output accordingly, making the unit over 80% efficient over the whole range. It has also a low voltage shutdown and overload shutdown protection to make it virtually indestructible. The weight for this supply is 575g and requires only one external battery of 12v - 13.8v to operate at its full rated output. This unit, thus eliminates the requirement for the 110v battery pack which weighed 480g in version 1.


Engineering mode HVPS03 supply 10.03.04

Engineering mode HV PS03
Final version of our Engineering mode HVPS03 power unit




Engineering mode HV PS03 waveforms

This is a full feature engineering mode HV power unit with improved reliability factors over the overboost unit shown above. It includes all features listed above with the addition of an electronic streamer/ spark detector which has been incorporated to instantly reduce the voltage until the streamer/ spark is below a preset current level. Further enhancements include input reverse polarity protection and protection against high current discharges entering the negative hv probe. This one can vary the output voltage from absolute zero to a maximum voltage of 50kV @ 0mA. Pot 2 varies the duty cycle from 0% to 100% (increasing in clockwise direction). The figures 4,5,6 show three different waveforms as pulse width is increased through 10%, 50% and 90%. When fully anticlockwise (0% duty cycle) or fully clockwise (100% duty cycle), no pulses appear at the output. Pot 3 sets the amplitude of the output voltage from absolute zero to full maximum voltage. At 100% duty cycle, the waveform becomes direct current and Pot 3 can be used to linearly vary the dc level of the non pulsed high voltage output. The pulse frequency can be varied from 1Hz to 100Hz, and amplitude from 0% to 100%, thus enabling any pulse voltage at specific frequency and duty cycle to be set at the required amplitude. Turning Pot 3 clockwise while in pulse mode, will increase the peak voltage of the waveform accordingly. Shown here are a few of the output waveform combinations that can be obtained with this unit. In the order top to bottom, figures 1,2,3 show varying frequency, figures 4,5,6 show varying duty cycle, and figures 7,8,9 show varying amplitudes. It also senses load current and boosts the power output accordingly, making the unit over 80% efficient over the whole range. It has also a low input voltage shutdown (10v), high input voltage cut-off (15v), and overload shutdown protection (>100W) to make it virtually indestructible. A monitoring output is included which you can use if you are not equipped with an hv probe. The output voltage can thus be displayed on a conventional voltmeter, at the ratio of 10mV per kV. The weight for this supply is 580g and requires only one external 12v battery to operate at its rated output. This unit, thus eliminates the requirement for the 110v battery pack which weighed an extra 480g in version 1. The 12v supply input can be obtained from lightweight batteries or even a regulated solar panel, according to your final application.

Technical specifications for HVPS03
Input voltage11v to 14v
Low input voltage cut off10v
High input voltage shut down15v
Reverse polarity protection10A fuse + diode
Max continous power75W
Efficiency at max output voltage90%
Thermal ShutdownYes
Output voltage0 to 50kV @ 13.5v dc
Max output voltage55kV @ 0mA
Output voltage type+dc
Streamer protection threshold2mA
Overboost current threshold1mA
Voltage monitor outputYes
Overload shutdown limit150Watts
Current sensinghv shunt
Pulse frequency1Hz to 100Hz
Pulse duty cycle0 to100%
Monitor voltage10mV per kV
Weight580g


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