EHT uses our core IGBT-based switching technology to produce novel power supplies for a variety of challenging applications. Custom supplies typically include fiber optic gate control, high voltage isolation, and precision timing. Each supply is carefully designed to generate a customer specified waveform tailored to a precise application. Combining rapid rise and fall times, PWM control, resonant and tail biter topologies, and extensive circuit design expertise, EHT can design a power supply to generate almost any waveform you may need. Below are illustrative examples of EHT-developed custom power supplies delivered to both commercial companies and research institutions.
Fast Magnetic Reduction/Reestablishment Supply
EHT designed a power supply to drive magnetic field coils. The supply was required to produce a 5 kA, 500 kHz PWM output with a fast rise time. Additionally, the supply needed to be capable of quickly reducing and reestablishing the magnetic field (rise/fall times were independently controlled). Two IPM-16Ps were used with two capacitor banks to produce the magnet current waveform shown in the figure (Ch1).
High Current Magnet Driver with Pulse Width Modulation Capabilities
This supply highlights the ability to operate the IPMs in parallel. High switching frequencies and precise pulse width resolution allow for much finer PWM control than other IGBT based PWM power supplies. EHT developed a power supply capable of switching 40 kA at 100 kHz PWM for driving an inductive load (electromagnet coils). The supply consisted of sixteen IPM-16PPs operating in parallel at 2.5 kA per module for ~ 10 ms. The figure shows the collector-emitter voltage of the IGBT (Ch2) and the current in the load (Ch3). Midway through the pulse, the pulse width was changed to change the current in the load.
Pulse Width Modulation Current Stepping for Plasma Arc
EHT built a PWM supply that was capable of stepping the current in a plasma arc. Using the fast switching (1 MHz) nature of the IPM-16P, the supply was used to produce a current waveform in a resistive load that initially jumped to 5 kA and then a specified time later increased to 10 kA. The fall time for the current was set by the L/R time of the load.
Series Stack of IPMs for Electron Gun Driver
EHT developed a 10 kV, 1 kA electron gun driver. This power supply used twelve IPMs in a series stack configuration and was capable of fast rise/fall times. The power supply was used in a demanding plasma physics laboratory setting, where high voltage noise isolation was critical. The figure shows the inverted load voltage (Ch1), the collector-emitter voltage across the series stack as measured with a resistive voltage divider (Ch2) and the gate signal (Ch4). The rise time was less than 40 ns. Other potential applications include: Klystron drivers, particle accelerator modulators, and tube replacements.
Piezoelectric Crystal Driver for Fast Puff Valve Applications
Using an IPM-4PP, EHT built a supply for driving piezoelectric crystals. The supply featured an adjustable output voltage (up to 1 kV) and current limited load (1 A) so as not to damage the crystal. The supply was capable of driving the crystal at 100 kHz. The piezoelectric crystal was part of a custom fast puff valve designed for precision gas handling control in fusion experiments. The figure shows the collector-emitter voltage across the IGBT during switching.
Half-Bridge Resonant Circuit
Using two IPM-16Ps, EHT has constructed half-bridges to drive series resonant (LC) tank circuits, which have been used for driving coils and antennas to generate inductively coupled plasmas and helicon plasma waves. These circuits can be operated at high frequency operation (up to 5 MHz). EHT has produced tank circuits with high Q ranging from 10 – 60, which allows the half-bridge to produce high voltage (40 kV) across the antenna. Higher power operation is possible with the addition of a transformer and/or additional IPMs operating in parallel. For fast capacitor bank charging, an additional rectifier can be added to the circuit to produce a DC output on the capacitor.