초록 ▼

A lamp circuit is provided having a constant current-type AC power source and a plurality of isolation transformers coupled in series with the AC power source. The secondary circuit of each isolation transformer is connected to an electric lamp. The output voltage of the constant current-type AC pow

A lamp circuit is provided having a constant current-type AC power source and a plurality of isolation transformers coupled in series with the AC power source. The secondary circuit of each isolation transformer is connected to an electric lamp. The output voltage of the constant current-type AC power source is detected to determine the times when the output voltage crosses the zero voltage level. A disconnected lamp in the circuit results in a distortion of the output voltage waveform due to the magnetic-saturation characteristics of the isolation transformer coupled to the disconnected lamp. The output voltage waveform is integrated over time between the time periods when the output voltage signal crosses the zero axis. The result of the integration is compared with a reference value. When the integrated value exceeds the reference value, an alarm signal is generated. The number of disconnected lamps may also be determined and displayed. The circuit includes a device for supplying a small current to the plurality of isolation transformers such that the status of the lamps in a circuit can be determined without illuminating any of the lamps in the circuit.

대표청구항 ▼

A lamp circuit, comprising: AC power supply means for supplying an AC current; a plurality of isolation transformers coupled in series with each other, said series coupled plurality of isolation transformers being coupled to receive said AC current from said AC power supply means; a plurality of lam

A lamp circuit, comprising: AC power supply means for supplying an AC current; a plurality of isolation transformers coupled in series with each other, said series coupled plurality of isolation transformers being coupled to receive said AC current from said AC power supply means; a plurality of lamps, each one of said plurality of lamps being coupled to one of said plurality of isolation transformers respectively; and disconnected lamp detecting means coupled to said AC power supply means for detecting an output voltage of said AC power supply means and for determining a voltage-time integral of said detected output voltage during a predetermined time period, comprising, voltage detecting means coupled to said AC power supply means for detecting said output voltage of said AC power supply means, comprising zero voltage crossing detector means coupled to said voltage detecting means for receiving said detected output voltage and for producing a voltage level detected signal when said detected output voltage crosses the zero voltage level, wherein said predetermined time period is a half cycle of said AC current as detected by said zero voltage crossing detector means, and voltage-time integral determining means coupled to said voltage detecting means for receiving said detected output voltage and for determining said voltage-time integral of said output voltage during said predetermined time period; wherein said AC power supply means comprises means for supplying to said plurality of series coupled isolation transformers a small current which is insufficient to light said plurality of lamps.