Driving scheme for minimizing ignition flash
First Claim
Patent Images
1. A ballast for powering a load having a lamp, comprising:
- an inverter operating at a varying switching frequency whereby power is delivered to the load such that a voltage is applied and current flows through the lamp; and
drive circuitry for controlling the switching frequency and includingovervoltage comparator means for determining when the lamp voltage is at or above and when the lamp voltage falls below a predetermined threshold;
switching means for changing to a first switching state during lamp ignition in response to the overvoltage comparator means determining the lamp voltage to be at or above the predetermined threshold and for changing to and remaining in a second switching state in response to the overvoltage comparator means for the first time thereafter determining the lamp voltage to be below the predetermined threshold; and
an error detecting device for receiving and comparing a feedback voltage to a dim voltage based on the switching means being in its second switching state wherein the feedback voltage is based on an input signal representing a lamp condition and wherein the dim voltage represents a desired level of power for the lamp and producing an output signal representing the adjustment required in the switching frequency of the inverter for the feedback voltage to be made equal to the dim voltage.
1 Assignment
0 Petitions
Accused Products
Abstract
A ballast for powering a lamp at deep dim levels. Driving circuitry includes a feedback loop which compares a desired dim level to a signal representing actual lamp power consumption. The loop is closed once the signal representing actual lamp power consumption equals the desired dim level. During ignition, a switch in response to the lamp voltage reaching or exceeding a predetermined threshold opens the feedback loop. The feedback loop is closed once the lamp has been ignited. By closing the loop as soon as the lamp has been ignited, ignition flash is minimized.
30 Citations
14 Claims
-
1. A ballast for powering a load having a lamp, comprising:
-
an inverter operating at a varying switching frequency whereby power is delivered to the load such that a voltage is applied and current flows through the lamp; and drive circuitry for controlling the switching frequency and including overvoltage comparator means for determining when the lamp voltage is at or above and when the lamp voltage falls below a predetermined threshold; switching means for changing to a first switching state during lamp ignition in response to the overvoltage comparator means determining the lamp voltage to be at or above the predetermined threshold and for changing to and remaining in a second switching state in response to the overvoltage comparator means for the first time thereafter determining the lamp voltage to be below the predetermined threshold; and an error detecting device for receiving and comparing a feedback voltage to a dim voltage based on the switching means being in its second switching state wherein the feedback voltage is based on an input signal representing a lamp condition and wherein the dim voltage represents a desired level of power for the lamp and producing an output signal representing the adjustment required in the switching frequency of the inverter for the feedback voltage to be made equal to the dim voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. A method for controlling ignition flash by a lamp, comprising:
-
operating an inverter at a varying switching frequency whereby power is delivered to the lamp such that a voltage is applied to and current flows through the lamp; and controlling the switching frequency by changing a switch to a first switching state during lamp ignition in response to the lamp voltage being at or above a predetermined threshold; changing the switch to and maintaining the switch in a second switching state, when the lamp voltage for the first time thereafter drops below the predetermined threshold; comparing a feedback voltage to a dim voltage based on the switch being in its second switching state wherein the feedback voltage is based on an input signal representing a lamp condition and wherein the dim voltage represents a desired level of power for the lamp and producing an output signal representing the adjustment required in the switching frequency of the inverter for the feedback voltage to be made equal to the dim voltage. - View Dependent Claims (10, 11, 12, 13, 14)
-
Specification