Fault condition of detection circuit

A ballast comprising:

• an inverter circuit to selectively energize one or more lamps, the inverter circuit having a transformer to provide voltage to the one or more lamps, wherein the transformer comprises:
• a core;
• a primary winding wound on the core and connected to a direct current (DC) voltage bus;
• and
• a secondary winding wound on the core for connecting to the one or more lamps;
• and
• a fault condition detection circuit connected to the inverter circuit to disable operation of the inverter circuit and thereby discontinue energization of the one or more lamps when a fault condition occurs, the fault condition detection circuit comprising:
• an other primary winding wound on the core of the transformer to receive a voltage signal proportional to a voltage across the secondary winding, the other primary winding having a first terminal and a second terminal, wherein the second terminal of the other primary winding is connected to ground potential;
• a high pass filter connected to the first terminal of the other primary winding to receive the voltage signal from the other primary winding, the high pass filter configured to pass the received voltage signal when the received voltage signal has a frequency exceeding a threshold frequency associated with normal operation and to block the received voltage signal when the received voltage signal has a frequency less than or equal to the threshold frequency associated with normal operation;
• a capacitor connected between the high pass filter and the ground potential to receive the voltage signal passed from the high pass filter and to store a voltage in response thereto;
• and
• an output terminal connected to the inverter circuit to provide a disabling signal to the inverter circuit based on the voltage stored by the capacitor.

A ballast comprising:

• a rectifier to receive an alternating current (AC) voltage signal from a power source and to produce a rectified voltage signal therefrom;
• a power factor correction circuit to receive the rectified voltage signal and to provide a corrected voltage signal;
• an inverter circuit to receive the corrected voltage signal and to provide a lamp voltage to energize one or more lamps, the inverter circuit having a transformer to provide voltage to the one or more lamps, wherein the transformer comprises:
• a core;
• a primary winding wound on the core and connected to the power factor correction circuit;
• and
• a secondary winding wound on the core to connect to the one or more lamps;
• and
• a fault condition detection circuit connected to the inverter circuit to disable operation of the inverter circuit and thereby discontinue energization of the one or more lamps when a fault condition occurs, the fault condition detection circuit comprising:
• an other primary winding wound on the core of the transformer to receive a voltage signal proportional to a voltage across the secondary winding, the other primary winding having a first terminal and a second terminal, wherein the second terminal of the other primary winding is connected to ground potential;
• a high pass filter connected to the first terminal of the other primary winding to receive the voltage signal from the other primary winding, the high pass filter configured to pass the received voltage signal when the received voltage signal has a frequency exceeding a threshold frequency associated with normal operation and to block the received voltage signal when the received voltage signal has a frequency less than or equal to the threshold frequency associated with normal operation;
• a capacitor connected between the high pass filter and the ground potential to receive the voltage signal passed from the high pass filter and to store a voltage in response thereto;
• and
• an output terminal connected to the inverter circuit to provide a disabling signal to the inverter circuit based on the voltage stored by the capacitor.