Datapower, Inc.

Tek Tron Enterprises, Inc.

Gerald A Felper

Francis H Gerhard

A circuit for controlling low wattage gas discharge lamps comprised of a inductive coupling device, e.g., a transformer, a switching transistor, a current sensor, a comparator receiving a signal from the current sensor and driving the switching transistor, and a protective clamp circuit. The primary winding of the inductive coupling device receives a DC voltage and is also connected to the transistor. The transistor allows current to flow through the primary winding causing energy to be stored therein until the current sensor signals the comparator that a first threshold has been reached, the comparator then turns the switching transistor off and the inductive coupling device then enter a fly-back mode where the stored energy is applied to the lamp for a set period of time. The transistor then turns back on and this process is repeated so that the lamp receives a high frequency alternating voltage. The clamp circuit senses the voltage produced when the inductive coupling device enters the fly-back mode and, when this voltage reaches unsafe levels, the clamp circuit limits the energy stored in the inductive coupling device and thereby limits the voltage to a safe level. In one configuration, a boosting circuit is used to increase the first threshold to permit more energy to be stored in the primary winding and thereby increase the voltage applied to start the lamp.

Closed loop feedback control circuits for gas discharge lamps

A gas discharge lamp is connected across a step down auto transformer and in series with a solid state switching device and a resistor, and this combination is connected across a rectified AC voltage source. This switching device is controlled by a monostable multivibrator, the input of which is connected to the output of a comparator amplifier sensing the difference between the voltage drop across the above-mentioned resistor and a voltage which may be selected to vary light intensity. A starter aid conductor is placed adjacent the lamp and connected to the grounded side of the voltage source. This results in an efficient, high frequency operation of the lamp wherein the voltage gradient inside the lamp during starting ignition of the lamp is greatly increased to facilitate ignition despite the presence of the step down auto transformer, thereby permitting a decrease in the minimum fly back voltage necessary to start the lamp. As a result, reliability is increased.

Variable intensity control apparatus for operating a gas discharge lamp

A gas discharge lamp is connected in parallel with an inductor and in series with a solid state switching device and a resistor, and this combination is connected across a rectified AC voltage source. This switching device is controlled by a monostable multivibrator, the input of which is connected to the output of a comparator amplifier sensing the difference between the voltage drop across the above-mentioned resistor and a voltage which bears a predetermined relationship to the rectified AC signal of said source. This results in a high frequency operation of the lamp wherein the lamp current level is controlled or modulated in accordance with the rectified AC supply voltage, providing a high power factor lamp circuit without the normal heavy lamp ballast. In addition, a circuit is disclosed which prohibits the lamp from exhibiting a high resistance when the AC voltage is at a zero crossing point, protecting the solid state switching device and stabilizing the high frequency.

A gas discharge lamp is connected in parallel with an inductor and in series with a solid state switching device and a resistor, and this combination is connected across a DC voltage. This switching device is controlled by a monostable multivibrator, the input of which is connected to the output of a comparator amplifier sensing the difference between the voltage drop across the above mentioned resistor and the voltage of a variable reference voltage source. When the current through the inductor has increased to a point where the voltage drop across the resistor exceeds the voltage of the reference source, the comparator amplifier triggers the monostable multivibrator causing the solid state switching device to be turned off. This acts to collapse the magnetic field in the inductor thereby causing a large voltage to appear across the gas discharge lamp sufficient to light the lamp. At the end of the predetermined time period of the low output state of the monostable multivibrator, its output turns the solid state switching device on, allowing current to flow once again from the power supply through both the inductor and the lamp. The current flow through the lamp when the solid state switching device is on is in the opposite direction from the current flowing through the lamp when the solid state switching device is off. Thus, the lamp current is an alternating current. The intensity of the lamp is varied by varying the level of the reference voltage supplied to the comparator amplifier.

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Anaheim, CA, United States of America

Gerald A Felper