Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Silicon controlled rectifier ignition
Reexamination Certificate
1999-09-03
2001-04-24
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Silicon controlled rectifier ignition
C315S161000
Reexamination Certificate
active
06222326
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable.
FIELD OF THE INVENTION
The present invention relates to circuits that energize a load, and more particularly, to ballast circuits for energizing a plurality of lamps.
BACKGROUND OF THE INVENTION
There are many types of ballast circuits for energizing devices that emit visible light, such as fluorescent lamps. A so-called electronic ballast receives a relatively low frequency AC (Alternating Current) input signal and provides a relatively high frequency AC output signal to one or more lamps. Typically, the low frequency input signal corresponds to a standard 110 volt, 60 Hz signal which is selectively applied to the ballast by means of a conventional wall switch.
One type of electronic ballast includes a rectifier which receives the AC input signal and provides a DC (Direct Current) signal to an inverter. The inverter can be a resonant inverter which provides a relatively high frequency AC signal to the lamps at operational voltage and current levels which cause the lamps to emit light.
Generally, the ballast is coupled to a source of AC energy via a switch, for example a conventional wall switch, which controls the flow of energy to the ballast for turning the lamps on and off. That is, when the switch is set to an on position the AC signal is applied to the ballast which energizes the lamps such that they emit light. And when the switch is set to an off position, the AC signal is not applied to the ballast and the lamps do not emit light. However, conventional ballasts are not adapted for coupling to more than one AC input signal and do not provide independent control over multiple lamps coupled to the ballast.
It would, therefore, be desirable to provide a ballast circuit adapted for receiving more than one AC input signal and independently controlling a plurality of lamps coupled to the ballast.
SUMMARY OF THE INVENTION
The present invention provides a ballast circuit that allows independent control over a plurality of lamps. Although the invention is primarily shown and described as a ballast for a lamp, it is understood that the invention has other applications as well, such as motor control circuits and voltage regulators.
In one embodiment, a ballast circuit has a plurality of input terminals for coupling to first and second AC energy sources and output terminals for connecting to first and second lamps. The ballast energizes the first lamp when a first AC energy signal, which corresponds to the first AC energy source, is applied to the ballast and energizes the second lamp when a second AC energy signal, which corresponds to the second AC energy source, is applied to the ballast. The ballast controls the flow of energy to each of the first and second lamps independently.
In an exemplary embodiment, the ballast includes a rectifier having AC input terminals coupled to the first and second AC energy sources and DC output terminals coupled to a boost converter. The boost converter provides DC energy to positive and negative rails of the first and second inverters which independently energize a respective one of the first and second lamps. A first control signal path, which provides a path for a first control signal, extends from the rectifier to the first inverter. The first control signal has a state corresponding to the presence of the first AC signal. A second control signal path extends from the rectifier to the second inverter to provide a circuit path for a second control signal. The second control signal has a state which corresponds to the presence of the second AC input signal. The first and second control signals selectively disable a respective one of the first and second inverters.
In an exemplary embodiment, the rectifier includes six rectifying diodes coupled so as to form first, second and third AC input terminals and positive and negative DC output terminals. The AC input terminals are adapted for receiving first and second AC input signals. In one embodiment, the first input terminal is coupled to a first black wire, the second input terminal is coupled to first and second white wires, and the third input terminal is coupled to a second black wire. It is understood that the first and second white wires can comprise a single wire or two wires that are electrically coupled. The first black and white wires (and first AC input signal) can correspond to a first 110 volt, 60 Hz signal and the second black and white wires (and second AC input signal) can correspond to a second 110 volt, 60 Hz signal. The DC output terminals are coupled to a boost converter which energizes the positive and negative rails of the first and second inverters. The first inverter powers a first pair of lamps and the second inverter powers a second pair of lamps.
In one embodiment, the first inverter has first and second switching elements coupled in a half bridge configuration with the conduction state of the switching elements being controlled by respective first and second control circuits. Similarly, the second inverter, also having a half-bridge configuration, has third and fourth switching elements controlled by respective third and fourth control circuits. A first control signal path extends from the first AC input terminal of the rectifier to the first control circuit. When the first AC input signal is not present, the first inverter is disabled by the first control circuit such that the first switching element is prevented from transitioning to a conductive state. And when the first AC signal is present, the first inverter is enabled such that the first control circuit alternately biases the first switching element to conductive and non-conductive states so as to allow resonant operation of the inverter and provide AC energy to the first lamp. Similarly, a second control signal path extends from the third AC input terminal to the third control circuit and the second inverter is enabled by the presence of the second AC input signal at the rectifier.
In an alternative embodiment, a first inductive element is coupled to the first AC input terminal and a second inductive element, which is inductively coupled to the first inductive element, is coupled to the second AC input terminal. A third inductive element, which is inductively coupled to the first and second inductive elements, forms a part of a first inverter disable circuit. Similarly, a fourth inductive element is coupled to the second AC input terminal, a fifth inductive element is coupled to the third AC input terminal, and a sixth inductive element forms a part of a second inverter disable circuit. The sixth inductive element is inductively coupled to the fourth and fifth inductive elements.
When the first and second AC input signals are both present, the flux generated by the first and second inductive elements cancels each other and the flux generated by the fourth and fifth inductors cancels each other. In the case where, the first AC input signal is not present and the second AC input signal is present, the flux generated by the second inductive element is not canceled such that a voltage appears on the third inductive element. This voltage biases a transistor in the first inverter disable circuit to a conductive state for disabling the second switching element, which disables the first inverter. Similarly, when the first AC input signal is present and the second AC input signal is not present, a voltage develops on the sixth inductive element that disables the second inverter. Thus, the first AC input signal energizes the first lamp and the second AC input signal energizes the second lamp independently of each other.
In a further embodiment of the invention, a ballast includes a first lamp control circuit coupled to a first lamp and a second lamp control circuit coupled to a second lamp. A first signal detector circuit is adapted for receiving a first AC input signal and a second signal detector is adapted for receiving a second AC input signal. The first signal detector provides a signal to the first lamp control circuit indicating whether the first AC
Electro-Mag International, Inc.
Nutter & McClennen & Fish LLP
Tran Thuy Vinh
Wong Don
LandOfFree
Ballast circuit with independent lamp control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ballast circuit with independent lamp control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ballast circuit with independent lamp control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2475317