Power regulation circuit for high frequency electronic ballast for ceramic metal halide lamp
First Claim
1. An electronic ballast for igniting and maintaining a discharge arc in a light emitting discharge tube, a resistance of the discharge tube varying with a temperature of the discharge tube during operation, the ballast comprising:
- ballast circuitry including an oscillating inverter circuit for driving an LC tank network coupled to the discharge tube, the LC tank network applying a time varying voltage to the discharge tube, a peak-to-peak magnitude of the time varying voltage applied by the LC tank network being determined by a frequency of oscillation of the inverter circuit; and
power regulation circuitry coupled to the inverter circuit to vary the frequency of oscillation of the inverter circuit such that power applied to the discharge tube remains within a range of a predetermined desired power magnitude while the discharge tube resistance varies with temperature during operation of the discharge arc, wherein the power regulation circuitry is inductively coupled to the inverter circuit through the use of a transformer and a primary winding of the transformer is coupled to the inverter circuit and a secondary winding of the transformer is coupled to the power regulation circuitry.
1 Assignment
0 Petitions
Accused Products
Abstract
An electronic ballast for igniting and maintaining a discharge arc in a discharge tube of a ceramic metal halide lamp wherein a resistance of the discharge tube varies with a temperature of the discharge tube during operation. It is desirable to energize the discharge tube with a substantially constant value to prevent changes in color of the light emitted by the discharge tube that result from changes to the power applied to the discharge tube. The ballast includes ballast circuitry having an inverter circuit driving an LC tank network coupled to the discharge tube. The LC tank network applies a time varying voltage to the discharge tube wherein a peak-to-peak magnitude of the time varying voltage applied by the LC tank network is determined by a frequency of oscillation of the inverter circuit. The ballast circuitry further includes power regulation circuitry inductively coupled to the inverter circuit to vary the frequency of oscillation of the inverter circuit such that power applied to the discharge tube remains within a predetermined desired range while discharge tube resistance varies during operation. The power regulation circuitry includes an operational amplifier configured as a error amplifier. The operational amplifier compares a voltage drop across a sensor resistor in the inverter circuit with a set point reference voltage. The voltage drop across the sensor is proportional to a current through the discharge tube. When the voltage drop across the sensor resistor changes from the set point reference voltage because of changing resistance of the discharge tube, the output of the operational amplifier accordingly changes thereby changing a current though a secondary winding of a transformer. The transformer primary winding is coupled to the inverter circuit and changes a frequency of oscillation of the inverter circuit depending on the secondary winding current.
-
Citations
23 Claims
-
1. An electronic ballast for igniting and maintaining a discharge arc in a light emitting discharge tube, a resistance of the discharge tube varying with a temperature of the discharge tube during operation, the ballast comprising:
-
ballast circuitry including an oscillating inverter circuit for driving an LC tank network coupled to the discharge tube, the LC tank network applying a time varying voltage to the discharge tube, a peak-to-peak magnitude of the time varying voltage applied by the LC tank network being determined by a frequency of oscillation of the inverter circuit; and
power regulation circuitry coupled to the inverter circuit to vary the frequency of oscillation of the inverter circuit such that power applied to the discharge tube remains within a range of a predetermined desired power magnitude while the discharge tube resistance varies with temperature during operation of the discharge arc, wherein the power regulation circuitry is inductively coupled to the inverter circuit through the use of a transformer and a primary winding of the transformer is coupled to the inverter circuit and a secondary winding of the transformer is coupled to the power regulation circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
-
-
17. A method of maintaining a power applied to a light emitting discharge tube within a range of a predetermined desired power magnitude during maintenance of a discharge arc in the discharge tube given that a resistance of the discharge tube varies with temperature during operation of the discharge arc, the steps of the method comprising:
-
a) providing ballast circuitry including an oscillating inverter circuit for driving an LC tank network coupled to the discharge tube, the LC tank network applying a time varying voltage to the discharge tube to maintain the discharge arc, a peak-to-peak magnitude of the time varying voltage applied by the LC tank network being determined by a frequency of oscillation of the inverter circuit; and
b) controlling the frequency of oscillation of the inverter circuit with power regulation circuitry inductively coupled to the inverter circuit, the power regulation circuitry varying the frequency of oscillation of the inverter circuit by controlling a current through a transformer winding coupled to the inverter circuit such that power applied to the discharge tube remains within the range of the predetermined desired power magnitude, wherein the power regulation circuitry is inductively coupled to the inverter circuit through the use of a transformer and a primary winding of the transformer is coupled to the inverter circuit and a secondary winding of the transformer is coupled to the power regulation circuitry. - View Dependent Claims (18)
-
-
19. An electronic ballast for igniting and maintaining a discharge arc in a light emitting discharge tube, a resistance of the discharge tube varying with a temperature of the discharge tube during operation, the ballast comprising:
-
ballast circuitry including an oscillating inverter circuit for driving an LC tank network coupled to the discharge tube, the LC tank network applying a time varying voltage to the discharge tube, a peak-to-peak magnitude of the time varying voltage applied by the LC tank network being determined by a frequency of oscillation of the inverter circuit; and
power regulation circuitry coupled to the inverter circuit to vary the frequency of oscillation of the inverter circuit such that power applied to the discharge tube remains within a range of a predetermined desired power magnitude while the discharge tube resistance varies with temperature during operation of the discharge arc, wherein the frequency of oscillation of the inverter circuit exceeds a resonant frequency of the LC tank network and as discharge tube resistance decreases, the power regulation circuitry increases the frequency of oscillation of the inverter circuit to decrease the peak-to-peak magnitude of the time varying voltage applied by the LC tank network to the discharge tube. - View Dependent Claims (20, 21, 22)
-
-
23. A method of maintaining a power applied to a light emitting discharge tube within a range of a predetermined desired power magnitude during maintenance of a discharge arc in the discharge tube given that a resistance of the discharge tube varies with temperature during operation of the discharge arc, the steps of the method comprising:
-
a) providing ballast circuitry including an oscillating inverter circuit for driving an LC tank network coupled to the discharge tube, the LC tank network applying a time varying voltage to the discharge tube to maintain the discharge arc, a peak-to-peak magnitude of the time varying voltage applied by the LC tank network being determined by a frequency of oscillation of the inverter circuit; and
b) controlling the frequency of oscillation of the inverter circuit with power regulation circuitry inductively coupled to the inverter circuit, the power regulation circuitry varying the frequency of oscillation of the inverter circuit by controlling a current through a transformer winding coupled to the inverter circuit such that power applied to the discharge tube remains within the range of the predetermined desired power, wherein the frequency of oscillation of the inverter circuit exceeds a resonant frequency of the LC tank network and as discharge tube resistance decreases, the power regulation circuitry increases the frequency of oscillation of the inverter circuit to decrease the peak-to-peak magnitude of the time varying voltage applied by the LC tank network to the discharge tube.
-
Specification