Sharif Digital Repository

Mostly, the high voltage DC power supplies have output voltage ripple. In such an applications like power supply of microwave lamps in radar systems, low output voltage ripple is an important point of operational characteristics. On the other hand, measuring the low voltage ripple will be a challenge that can lead to recognize of its reasons and reduce its amplitude. In this thesis, different ways of ripple measurement constraints is described, then a method based on high pass filters for output voltage ripple measurement is implemented. The impact of components tolerance and their parasitic components like shunt parasitic resistance of a capacitor in filter operational characteristics is... 

The TWT is highly sensitive to the ripple amplitude of its power supply output voltage. If the amplitude of the output voltage's ripple exceeds a certain limit, the amplitude of the undesired harmonics in the power spectrum of the TWT is greatly increased. Increasing the amplitude of undesired harmonics in the TWT output power spectrum reduces the accuracy and performance of the TWT. Therefore, for optimum TWT performance, a low-ripple power supply is essential. Typically, a low-frequency rectifier or high-frequency switching structure is used to build a high-voltage DC power supply. In this thesis, the different structures of high voltage DC power supplies are studied. Next, by focusing on... 

Short-circuit fault detection is mandatory in a high voltage DC power supply to prevent fatal damage. The majority of converters employ a single sensor to detect the short-circuit fault. This attribute increases the interference vulnerability of the fault detection system in the presence of noise. Therefore, miss detections and false alarms are possible to occur. Miss detections and false alarms are harmful catastrophes in most applications. A commonly used method to suppress the noise impacts is using a low-bandwidth low-pass filter. However, the use of the low-bandwidth low-pass filter reduces the speed of fault detection due to the filter delay. This paper proposes a fast fault detection... 

High DC voltage is widely used in many applications such as X-Ray machines ,CRT , photocopy machines and etc. One idea to produce this high DC voltage is to use transformers, but it will be large in volume. We can increase frequency to reduce the volume of transformers but high voltage of primary and secondary winding will limited this volume reduction. Furthermore high turn ratio in transformers increases non idealities that cause voltage and current spike, and increase loss and noise. The main goal of this thesis is to reduce differential mode voltages on transformers to reduce the volume of power supply. Voltage multiplier will be used to reduce differential mode voltage. Voltage... 

In recent years, semiconductor devices have incrementally taken the place of microwave tubes beneficially. However, microwave tubes are still indispensable in very high voltage usages (10 Kilowatts to 10 Megawatts) and high frequencies (Gigahertz and higher). Concerning that these tubes are of the most sensitive and expensive parts of such systems, protection measures are of high importance. One of the phenomena that cause failure or degradation of tubes is electric arc in cathode of the tubes and dissipating energy due to that. In order to prevent the tubes from undergoing such harm, protection must be put into consideration. Furthermore, the limit of this dissipating energy determines the... 

High voltage DC/DC converters are widely used in lasers, microwave tubes supplies, X-ray equipment, medical and industrial applications. Each of these applications have special attention to certain parameters such as output voltage ripple, fast stability, repeatability and accuracy. For power modulation in microwave tubes, the anode-cathode supply need to be varied. Generally such variations needs a high voltage DC supply so that, in a certain frequency each point can be controlled in specific voltage. Anode- cathode current flow is too low (in milliamps scale) so, the load of converter output can be assumed to be zero. The goal of this thesis is to design a DC/DC converter for Variable... 

RF amplifier are one of the most important part of communication industry. microwave tubes are of the most sensitive and expensive parts of such systems, protection measures are of high importance. One of the phenomena that cause failure or degradation of tubes is electric arc in cathode of the tubes and dissipating energy due to that. In order to prevent the tubes from undergoing such harm, protection must be put into consideration. Furthermore, the limit of this dissipating energy determines the capacitor needed at the output of the power supply of the cathode. Since the value of the capacitor is directly proportionate to the amount of ripple of the output voltage, an exact calculation of... 

High voltage dc power supplies are commonly used in medical equipment, microwave lamps, X-ray equipment and radio transmission systems. In radio Transmission power supplies the output voltage quality is of great importance and the output voltage ripple must be very low. In addition usage of low frequency transformer and rectifier needs large bulk capacitors to reduce output voltage ripple. Moreover, to reduce energy discharged into load in load short circuit faults the output capacitance should be as low as possible. An approach to solve this problem is to use a diode rectifier and a switching power supply in series configuration. The Advantage is that the switching power supply provides a...