200 V – 240 V 1-phase plasma power supply functional description

For CSA models, Alternating Current (AC) power enters the system through the power switch (S1). For CE/CCC models, AC power is routed through the Electromagnetic Interference (EMI) board (PCB2) before it reaches the power switch. AC power goes from the power switch to the input diode bridge (D6). The voltage from the diode bridge supplies the Power Factor Correction (PFC) boost converter, which provides a nominal 400 VDC bus voltage. The bus wires then supply voltage and current to the inverter and the flyback circuit power supply (Direct Current (DC) to DC converter) on the power board (PCB3). The power board provides noise suppression and spike protection. A "soft start" is implemented via the power board resistor and relays.

The PFC boost converter consists of an insulated gate bipolar transistor (IGBT Q2), PFC choke, and control circuit. It provides a 400 VDC bus voltage when the input AC voltage is between 200 VAC – 240 VAC.

The inverter consists of a dual Insulated-gate Bipolar Transistor (IGBT) package (Q1), the power transformer, an output current sensor, and the control circuit. The inverter operates as a pulse-width modulated half-bridge circuit driving an isolation transformer. The output of the isolation transformer is rectified by the output bridge (Q10).

The output circuitry consists of 2 current sensors located on the power Printed Circuit Board (PCB), the pilot arc IGBT (inside the Q10 module), and the output choke.

The Digital Signal Processor (DSP) on the power PCB monitors and regulates the system operation and safety circuits. The adjustment knob on the display PCB (PCB1) is used to set the output current to the desired value between 9 A – 45 A. The system compares the set-point to the output current by monitoring the current sensors and adjusting the pulse-width output of each inverter IGBT (Q1). A trip coil on the power switch provides over-voltage protection.