What Is a Pulse Power Supply?
A Pulse Power Supply is a device that generates high voltages of several kilovolts in a very short period of time.
It is characterized by a high voltage (~30kV) output repeated at a high frequency (~100kHz) despite the extremely fast rise time of the voltage. In addition, since the output is not continuous and there is a cooling time, the temperature rise of the equipment itself and the space can be suppressed.
These devices are used in academic and industrial fields that require high voltage output (e.g., power supplies for plasma generation).
Uses of Pulse Power Supplies
1. For Plasma Generation
Plasma generation requires a high output voltage, and Pulse Power Supply is the ideal power source for plasma generation. The power supplied can be controlled by changing the pulse width and frequency, which is convenient when high-density energy is required for plasma generation.
Pulse Power Supply is widely used as a power source for plasma-applied equipment. They are used to apply charged particles such as light, electrons, and ions generated from plasma to objects, and for sterilization and water treatment using shock wave generation from pulsed discharge.
2. For Excimer Lasers
Pulse Power Supply with short duration and high output power is required to drive high power and high efficiency lasers such as excimer lasers, which require instantaneous excitation of laser gas. There are also applications for driving such high-power lasers. We are contributing to the development of semiconductor lithography technology.
3. Others
Pulse Power Supply is also used in Pulse Power Supply for EUV and Plasma CVD, which adsorbs and deposits thin films and fine particles on the surface of substrates.
Plasma CVD is used as insulating and protective coatings for semiconductors. It is also useful for coating cutting tool edges and gear contact areas with carbon nitride or titanium nitride.
Small Pulse Power Supply also has applications in instrumentation. They supply high-speed, high-voltage pulses to scanning electron microscopes SEM and mass spectrometry MS.
Principles of Pulse Power Supplies
Pulse Power Supply is divided into a charger and a pulse generator.
1. Charger
AC power input to Pulse Power Supply is first converted to DC by a rectifier circuit, then boosted through an inverter for output. Then, it is charged to the first-stage capacitor in the pulse generator section.
2. Pulse Generation
The charged power is converted into pulses by insulated gate bipolar transistors (IGBTs), a type of power semiconductor capable of high- speed switching of large powers.
In addition to the IGBTs, an element called a saturable reactor is used. The saturable reactor has a high magnetic permeability in the low current range and does not allow current to pass through, but as the current increases and the magnetic flux density exceeds a certain level, the current can pass through. This circuit is called a magnetic compression circuit.
Next, the generated pulse voltage is induced in a saturable reactor in the next stage. The voltage is then boosted and, using the magnetic compression circuit, a short pulse compressed to less than 100 ns can be delivered to the load. The charging voltage characteristics of the circuit are determined by the relationship between the charging rate of the capacitor and the saturation value of the saturable reactor.
If the inductance of the reactor is smaller than that of the first stage, the pulse voltage can be generated in a shorter time. If shorter pulses are required, a multistage supersaturated reactor is available.
Features of Pulse Power Supply
1. Instantaneous Output
Pulse Power Supply can store energy in a capacitor when the output is 0, so it can generate instantaneous high output energy when it is ON.
2. Fast Start-up and Fast Repetition
General power supplies require time to reach the upper limit of output when turned on. Pulse Power Supply, on the other hand, has an extremely short rise time, reaching its upper limit in microseconds to nanoseconds. It is also possible to repeat this output at high speed.
3. Low Heat Generation
Since Pulse Power Supply can control the output time, it can be operated intermittently to provide cooling time. This reduces the temperature rise of the equipment and space. Therefore, they can be used to power heat-sensitive equipment.
4. Long Service Life
All solid-state, which can provide stable pulse output for a long period of time.