Abstract: Current limit protection is provided to ensure that the current flow within the transistor inverter does not exceed a predetermined safe level to thereby cause damage to the various components such as the transistor inverters. The current in the primary of the transformer is sensed and a representative signal is compared with a reference signal to provide a digital output indicating whether a safe limit has been exceeded. A logic network then operates on the output signal to shut down or reduce the system operation accordingly. In the event of a shut-down, current decay is accommodated by shutting off only the top transistors in the inverter diagonals so as to thereby allow the remaining current to flow in the bottom transistors and diodes.

Abstract: An inverter receives a d.c. voltage and delivers to an X-ray tube, by way of a high-voltage transformer, filter, and rectifier, a high-voltage d.c. output. The inverter is driven in response to control signals which are responsive to the difference between a voltage demand signal and a voltage feedback signal. The control signals are also responsive to various status conditions of the system which are monitored by a microprocessor. Inputs to the microprocessor include various signals which are indicative of voltage or current conditions. In this way, such conditions as an over-voltage at the output, an unbalance between the anode and cathode with respect to ground, or an excessive current flow are detected and precautionary measures are quickly taken to prevent further damage to the system.

Abstract: In an X-ray generator system having a pulse-width-modulated transistor inverter with associated flywheel diodes, method and apparatus is provided to sense when a diode associated with a non-pulse-width-modulated transistor is conducting and for inhibiting the turning on of that transistor during such period, to thereby avoid the transition from reverse conduction to direct conduction in an uncontrolled manner.

Abstract: In an X-ray generator operating with a pulse-width-modulated transistor inverter, circuitry is provided to sense the collector-emitter voltage of each of the transistors and to responsively turn off the transistor when that voltage level reaches a predetermined threshold level which is indicative of a problem. Provision is included to inhibit the operation of the protective circuit during the time period in which the transistor is turning on so as to thereby allow for higher voltages during that critical period.