X-ray or gamma ray systems or devices – Electronic circuit – X-ray source power supply
Reexamination Certificate
2000-06-29
2001-10-02
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
X-ray source power supply
C378S103000
Reexamination Certificate
active
06298116
ABSTRACT:
The invention relates to an X-ray examination apparatus which includes a DC voltage source which is to be connected to a mains voltage and whereto there are connected an accumulator with a charging circuit for this accumulator as well as a high voltage generator for an X-ray tube, the accumulator being charged in a standby mode and being dischargeable via the high voltage generator.
An X-ray examination apparatus of this kind is known from United States patent U.S. Pat. No. 4,053,778. The accumulator in the apparatus described therein can be charged in a standby mode, but energy is drawn from the accumulator each time when an X-ray exposure takes place. Consequently, the accumulator is frequently loaded so that its service life is undesirably reduced.
It is an object of the invention to use accumulators in a manner such that their service life is significantly prolonged.
To this end, an X-ray apparatus of the kind set forth according to the invention is characterized in that there is provided a power gate circuit via which power can be drawn from the mains up to a maximum value, it being possible to charge the accumulator for as long as this maximum value has not yet been reached, and via which, when a power in excess of said maximum value is required, the surplus beyond said maximum value is delivered by the accumulator. In other words, when the load current required for an X-ray exposure is less than the current which can be safely drawn from the mains, it is provided by the mains. When a surplus of current can be drawn from the mains, such a surplus will be used to charge the accumulator. It is only when the maximum current to be drawn from the mains is reached that a further required surplus current will be delivered by the accumulator. Evidently, the maximum current to be drawn from the mains is co-determined by the current drawn by further power supply units for further parts or components of the X-ray examination apparatus. The mains is thus efficiently used, the accumulator nevertheless not being unnecessarily discharged, thus prolonging the service life of the accumulator. It is to be noted that, of course, it is also possible to charge the accumulator in periods during which the high voltage generator of the X-ray apparatus does not constitute a load for the mains.
A simple and efficient embodiment of the power gate circuit includes a first diode (D
1
) via which power can be drawn from the mains up to a maximum value, and a second diode (D
2
) via which the surplus said maximum value is delivered by the accumulator.
The DC voltage source in a specific embodiment is provided with a power control unit which includes a current sensor for measuring the mains current, and also a controllable rectifier unit with a filter, the output voltage of the DC voltage source being reduced in the rectifier unit when the maximum mains current is reached, the second diode (D
2
) also becoming conductive when said output voltage drops below that across the accumulator. The rectifier unit may include, for example, a thyristor bridge circuit or a circuit with switching transistors which are controlled by the power control unit. As a result of this step it is achieved that, in the case of maximum loading of the mains, the output voltage of the DC voltage source decreases until the instant at which the second diode (D
2
) becomes conductive and power is delivered by the accumulator.
REFERENCES:
patent: 4053778 (1977-10-01), Franke
patent: 5187737 (1993-02-01), Watanabe
patent: 5200984 (1993-04-01), Laeuffer
patent: 5408484 (1995-04-01), Weimel
patent: 5546441 (1996-08-01), Stage
patent: 6169782 (2001-01-01), Zetterlund
Methley Peter Brian
Van Der Heijden Theodorus Antonius
Kiknadze Irakli
Kim Robert H.
U.S. Philips Corporation
Vodopia John F.
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