Abstract: Method for preventing a high voltage circuit form generating excessive high voltage, wherein the method comprises the following steps: a) reading a digital representation of a reference value associated with one of a plurality of operation modes stored in a memory; b) verifying the integrity of the representation of the reference value; c) providing a sensed signal representing the output voltage of the high voltage circuit; d) comparing the sensed signal with the reference value; e) inhibiting the generation of the high voltage output if the comparison in step (d) indicates excessive high voltage.

Abstract: A video display includes a scanner operable at a first frequency and a higher second frequency. A switch mode power supply drives a transformer with three secondaries. First and second rectifiers & filters are associated with the first and second secondaries. A rectifier is coupled to the third secondary and by way of a switch to the first filter. Feedback from the first filter controls the SMPS. In a first operating mode, the scanner is operated at the first frequency, the switch is open, the scanner supply is a first voltage from the first filter, and ancillary equipment is supplied with a third voltage by the second filter. In a second operating mode, the scanner is operated at the second frequency, the switch is closed, the scanner supply is a second voltage, higher than the first, from the first filter, and ancillary equipment is supplied with the same third voltage.

Abstract: An apparatus and a method for protecting a video display device, having an anode and a cathode, against excessive beam current conditions. In particular, the present invention protects the video display device against zero-biasing of the device, wherein the cathode driver circuit is supplied by a plurality of power supplies and the loss of anyone of the power supplies causes zero-biasing of the cathode.

Abstract: A power supply for a video display tube includes a deflection transformer with a primary winding powered with a scan voltage which has a first value when displaying signal according to a first video standard and a second voltage when displaying video according to a second standard. A secondary winding of the transformer produces filament voltage for the display tube. A variable coupler couples the filament voltage to the filament of the picture tube in an amount established by a control signal. A memory produces a first control signal in response to the first scan voltage and a second control signal in response to the second scan voltage. The first and second control signals are selected so that the voltage coupled from the transformer to the filament is the same at both scan voltages.

Abstract: Method for preventing a high voltage circuit form generating excessive high voltage, wherein the method comprises the following steps:

Abstract: A power supply for a video display tube includes a deflection transformer with a primary winding powered with a scan voltage which has a first value when displaying signal according to a first video standard and a second voltage when displaying video according to a second standard. A secondary winding of the transformer produces filament voltage for the display tube. A variable coupler couples the filament voltage to the filament of the picture tube in an amount established by a control signal. A memory produces a first control signal in response to the first scan voltage and a second control signal in response to the second scan voltage. The first and second control signals are selected so that the voltage coupled from the transformer to the filament is the same at both scan voltages.

Abstract: A frequency compensation circuit influences an X-radiation protection (XRP) circuit in a high voltage regulator circuit for a cathode ray tube (CRT) to operate properly under varying frequencies of voltage energizing a high voltage transformer. The frequency compensation circuit includes an input to a source of first voltage related to a high voltage output of the high voltage regulator circuit, a voltage source generator responsive to a high voltage generator frequency of the CRT. A voltage controlled circuit is responsive to the voltage source generator for controlling conveyance of the first voltage to the XRP circuit so that a relatively constant proportion of the high voltage output is reported to the XRP circuit under varying high voltage generator frequencies.

Abstract: A high-voltage power supply of a video display apparatus provides an ultor voltage and a focus voltage to a cathode ray tube. A low-voltage power supply provides a variable voltage to a primary winding of a flyback transformer of the high-voltage power supply. The magnitude of the variable voltage is responsive to first and second feedback signals provided by first and second negative feedback paths. The first feedback signal is derived from the ultor voltage and is used to regulate the ultor voltage. The second feedback signal is provided by the low-voltage power supply via a path that bypasses the high-voltage power supply, and is summed with the first feedback signal to ensure that the focus voltage remains at or above a predetermined minimum voltage.