Method and apparatus for vacuum fluorescent display power supply
AssigneeDelco Electronics Corporation
InventorWayne A. Madsen
Life of this patent
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Abstract
A power supply for a VF display generates a DC filament voltage from a battery by either a switched transformer supply or a monolithic regulator circuit. Where a higher-than-battery voltage is needed for anode and grid voltages, another monolithic regulator circuit or the switched transformer is used. An H-switch develops an alternating voltage from the DC voltage and applies it to the display filament. A controller for the H-switch is a logic circuit including flip-flops which toggle in response to a low frequency pulsed dimmer signal to synchronize the filament half cycles with the dimmer phases. Slew rate control ramps the H-switch control signal to produce a trapezoidal waveform in the filament current having reduced radio frequency emissions.
Claims15
In a vacuum fluorescent display having an anode, a grid and a filament, the filament having two ends for connection to a power supply, a power supply for providing suitable filament voltage from a battery comprising:
- a regulator coupled to the battery for producing a DC voltage for anode and grid excitation and a DC filament voltage for filament excitation;
- a switching circuit connected to the filament ends and to the regulator for applying the filament voltage in alternate directions across the filament, thereby producing an alternating current in the filament;
- and
- a control for operating the switching circuit to effect the switching at a desired frequency.
In a vacuum fluorescent display having an anode, a grid and a filament, the filament having two ends for connection to a power supply, a power supply for providing suitable filament voltage from a battery comprising:
- a regulator coupled to the battery for producing a DC filament voltage for filament excitation and a reference voltage;
- an H-switch connected to the regulator and having two inputs respectively supplied by the filament voltage and the reference voltage and two outputs each connected to an end of the filament, thereby producing an alternating current in the filament;
- and
- a control for operating the H-switch to effect the switching at a desired frequency.
In a vacuum fluorescent display having an anode, a grid and a filament, the filament having two ends for connection to two corresponding outputs of a power supply, and a battery power source, a method of supplying AC current to the filament comprising the steps of:
- generating from the battery a regulated DC filament voltage;
- generating from the DC filament voltage a trapezoidal AC waveform;
- and
- applying the trapezoidal AC waveform across the filament to generate a trapezoidal waveform filament current.
Dependencies are inferred from the claim text.