The flow chart of the measurement is shown as in Figure 2. The variable high voltage DC power supply in the range of 0 to 4. For safety reason as well as to eliminate noise and to avoid electric shock the experimental setup was arranged properly. When the high speed switching occurs in kilovolt regime, electromagnetic induction EMI is expected to occur.
This effect was avoided by designing the circuit on one layer of printed circuit board PCB and all the components were soldered and sealed properly.
All the components and circuit are kept in isolated plastic case such illustrated as in Figure 3. The parameters such as the voltage switching, falling time and pulse duration were measured using the high voltage probe and oscilloscope.
Result and Discussion The typical high voltage switching signal measured by Tektronix oscilloscope is shown in Figure 4. After the high voltage supply is switched to ground, the voltage is raised again within 90 microseconds upper signal of Fig. In this experiment, the maximum supply of DC voltage was 4.
Figure 5 shows the switching signal at 4. The voltage reached its ground level within 3. The falling time of high voltage switching was measured using Tektronix high voltage probe and Tektronix oscilloscope 5 GHz sampling rate. The collected data of falling time were recorded.
Figure 6 shows a graph of the switching falling time versus applied voltage. A nonlinear graph is obtained with the average of switching falling time of 2. The developed circuit also produced negative voltage and small ripple in nanoseconds scale. The maximum negative voltages were measured and represented in Figure 7. The negative voltages were in linear relationship with the applied voltage. In certain case, this voltage could increase the Q-switching efficiency due to the full retardation of laser beam.
For commercial purpose, the circuit should produce sharp pulse with small ripple. The high voltage supplied to the avalanche transistor caused it to change its shape due to the piezoelectric effect. This effect could be eliminated by adding RC component in the circuit. Furthermore, by using PIC microcontroller, the pulse duration of trigger signal easily adjusted and controlled.
In addition, the developed circuit also able to operate in high repetition rate mode up to 1 MHz. Conclusion A simple high-voltage pulse switching circuit using avalanche transistor and PIC16F84A microcontroller was successfully developed and characterized.
The maximum operation voltage was 4. Acknowledgment The authors would like to express their thanks to Universiti Teknologi Malaysia and the Government of Malaysia for the financial support for this project.
References C. Design of reliable high voltage avalanche transistor pulsers. Lawrence Livermore National Laboratory. Fulkerson, D. Molina, A. Mar, F. Share This Paper. Figures and Tables from this paper. Citation Type. Has PDF.
Publication Type. More Filters. High-speed, high-voltage pulse generation using avalanche transistor. An investigation of non-traditional approach to narrowing the GPR pulses. In this paper an investigation is carried out on how to decrease the time duration of the pulses used in a ground penetrating radar GPR system.
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