Lamp circuit with disconnected lamp detecting device

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 curent 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,
• voltage to frequency converter means coupled to said voltage detecting means for producing a pulse signal having a frequency proportional to said detected output voltage,
• 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, and
• digital computer means coupled to receive said pulse signal from said voltage to frequency converter means and coupled to receive said voltage level detected signal from said zero voltage crossing detector for determining said predetermined time period as a half cycle of said AC current in response to said voltage level detected signal and for converting the number of pulses occuring in said pulse signal during said predetermined time period to produce an integral signal, said integral signal representing the number of pulses counted by said digital computer during said predetermined time period;
• wherein said AC power supply means supplies a small AC current to said plurality of series coupled isolation transformers which is insufficient to light said plurality of lamps.