An Extremely Low Ripple High Voltage Power Supply for Pulsed Current Applications

This article describes the development of an 18 kV, 30 kW power supply for a pulsed current load with the maximum current of 20 A and a di/dt equal to 100 A/μs. The achieved output ripple is less than 0.01%. In such a high level of precision, the most important issues are considerable difference between the instantaneous and average output powers, as well as insufficient reaction speed of the converter to the fast load change. Very low level of the voltage feedback and its sensitivity to the noise. The first issue necessitates a notable overdesign of the converter switches if the output voltage precision is dedicated to the converter. The second issue raises the problems relevant to observing the voltage ripple and providing it for the control loop. This article proposes, a fast and high current linear regulator developed based on the load current feedforwarding. Using this approach, the fast regulator compensates the voltage change caused by a high level of instantaneous power. The main converter maintains the average power. Thus, there is no need for converter overdesigning. Furthermore, the problems relevant to the high voltage feedback and providing it for the control loop are removed. The voltage feedback is solely served to correct the current loop probable error. Hence, the sensitivity of the control loop against the existing noise is minimized. Despite existing a 600 nF capacitor as the output capacitor, the output voltage drop is less than 0.01% in a wide range of the output current pulse up to 250 μs. The power supply is constructed and experimental results are provided to verify the mentioned specifications.