Importance

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Abstract

A power supply for vacuum fluorescent displays has a source of a relatively high frequency signal which is provided to a power driver amplifier which is also supplied with a desired supply voltage. The output of the driver amplifier is a square-wave signal varying between approximately zero and the supply voltage; this signal is provided to the filament of the vacuum fluorescent display such that the filament is heated and is self-biased at a DC level which is substantially one-half the supply voltage level. Self-biasing a capacitor between the filament and ground, which also allows the RMS level of the voltage across the filament to be controlled by controlling the frequency of the output signal from the driver amplifier. The voltage may be regulated by comparing the RMS voltage across the filament with a reference and using the difference to control the frequency of oscillation of the source. A voltage multiplier may be connected to receive the square-wave output from the driver amplifier to produce a higher level DC voltage which can be used to supply the grid and plate drivers with the higher voltage needed for these elements. Two driver amplifiers may be connected together with circuitry to self-oscillate, with the outputs of the two amplifiers being connected across the filament to heat the filament and self-bias the filament at one-half the DC supply voltage level.

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