Patent Grant
7315130
Aspects described herein relate generally to lighting devices, and more particularly to ballast circuitry for discharge lamps.
When designing lamps and associated circuitry, economic considerations are of paramount importance and often mean the difference between an acceptable design and an optimal design. Often, one or more of lamp size, manufacture cost, and/or energy efficiency dictate a majority of parameters associated with a given lamp design. Modern lamps come in a variety of sizes to accommodate multiple design variations. For instance, a T8 lamp size is approximately one inch in diameter, while a T12 lamp is approximately one and a half inches in diameter. Other sizes are also available to meet designer and consumer needs.
A gas discharge lamp is one example of what is known as a “negative resistance” device, which is a device that is capable of drawing an increasing amount of current until it either burns out the power source or itself. Often, such discharge lamps employ a ballast to control an amount of current flowing through a lamp circuit. A ballast may be as simple as resistor in series with a lamp, such as is utilized for the relatively low-powered neon lamp. More complex ballasts may be utilized for higher power applications, and may comprise resonant components such as capacitor and inductors. Typically, a reactive ballast is more efficient than a simple resistor.
Electronic ballasts utilize electronic circuitry to stabilize current for fluorescent lamps, high-intensity discharge lamps, and the like. Electronic ballasts may be started using one of several starting techniques, including “instant” start, “rapid” start, and “programmed” start. The instant start starts a lamp in the short term, because it starts and operates the ballast without preheating a cathode associated therewith, which results in low energy cost to start but wears out the lamp more rapidly than other starting protocols due to the violent nature of the starting method. The rapid starting technique starts the ballast and heats the cathode concurrently, resulting in a relatively long start time while mitigating the deleterious effects of a cold start on the lamp's cathode. Finally, the programmed start technique employs a cathode preheating period at low glow discharge current which increases the lamp's life for frequency switching applications.
With regard to energy efficiency, a lamp and/or ballast may be designed to minimize power losses as well as to effectively minimize power consumed by the lamp and/or ballast. In the case of manufacturing cost, it may be desirable to minimize a number of circuit components needed to perform a given function, as well as to design circuits such that perform a given function using a number of least-expensive parts and to avoid costly components such as integrated circuits and the like. With respect to ballast size, it may be desirable to design a circuit that occupies as little space as possible to perform the given function in order to facilitate utilization of the ballast in applications where space conservation is an issue. There is an unmet need in the art for systems and/or methods that facilitate overcoming deficiencies associated with the foregoing.
According to one or more aspects, a system that facilitates automated shutdown and restart of a ballast circuit for a lamp comprises a capacitor positioned in a parallel orientation to a base drive winding for a first transistor in an inverter circuit, a control line coupled to a voltage source that supplies a voltage to the ballast, and a switch in the control line that is manipulated to concurrently disable inverter oscillation and supply voltage to a trigger circuit coupled to the inverter.
According to other aspects, a method of automatically shutting down and restarting a ballast circuit for a lamp comprises employing a capacitor in parallel with a base drive winding for a bipolar junction transistor (BJT) in an inverter circuit, employing a control line with a switch from a voltage source to a trigger circuit coupled to the inverter circuit, and selectively closing the switch to supply a voltage to the trigger circuit and shut down the inverter circuit.
According to other features, a system that facilitates selectively shutting down and restarting an inverter in a ballast circuit for a lamp comprises means for providing a control signal to a trigger circuit coupled to an inverter in the ballast circuit, means for placing a capacitor in parallel with a base drive winding of a transistor in the inverter to shut down the inverter when a switch in the control line is closed, and means for placing the inverter in an oscillatory state when the switch is open.
In accordance with various aspects and features described herein, systems and methods are presented that facilitate reducing energy consumption by a lighting system. Such aspects and features may comprise reducing load power consumption by, for example, turning off one or more lamps associated with a given lamp ballast circuit and/or dimming a given lamp's power level to reduce power consumption. To achieve these goals, a control point may be inserted into a lamp ballast circuit, such as by connecting a switch to a hot or neutral power line.
An electronic ballast is described herein that facilitates performing a shutdown-startup protocol for the ballast and/or associated lamps. For example, the electronic ballast may be a trigger-start self-oscillating electronic ballast, and may be controlled using a few passive components and an active switcher without integrated circuits, if desired, even if the device to be controlled is a floating gate device. By placing a start up capacitor in parallel with a base drive winding in the circuit, inverter oscillation and the trigger circuit may be concurrently controlled. Accordingly, repetitive triggering may be mitigated after the ballast is shut down. In addition, a similar and/or identical control technique can be used for an end of lamp's life (EOL) protection circuit.
Bi-level control has become popular for high-intensity discharge (HID) lamp systems due to its simplicity and cost-efficiency. This control has also gained popularity for fluorescent discharge lighting systems with electronic ballasts due to high energy savings at low cost. According to various features, a current-fed self-oscillating program start ballast is described, such as may be utilized in a T5 lamp application, and is designed in a manner that mitigates problems associated with conventional integrated circuit (IC) controlled ballasts, which tend to be expensive. Additionally, IC driven ballasts tend to be less robust to operating conditions of the lighting system, and are therefore subject to higher failure rates that non-IC driven ballasts. In some systems, when a connection is made from a switching line to a neutral line, a signal is fed to a ballast control IC. The ballast responds to the signal by disabling the output of the control IC which, in turn, shuts down the lamps that are controlled by the IC.
With reference to
The PFC 102 and inverter 104 are coupled by a switching line 106 that facilitates triggering a shutdown/restart mechanism in accordance with various aspects. For instance, a switch 108 in switching line 106 may be triggered by a remote sensor (not shown), such as a motion sensor or the like, which detects a presence or absence of an occupant in an area that is illuminated by one or more lamps associated with ballast 100. When the motion sensor is activated, the switch 108 may be in an open state to permit the ballast to operate normally. When the motion sensor is not activated (e.g., when no occupants are detected), the switch 108 may be triggered to close, resulting in an initiation of the aforementioned events.
For instance, upon applying input power to the ballast 100, capacitor C5 is charged up by resistor R4. When a voltage across C5 reaches a breakdown voltage of diac D7, a high di/dt current is applied to the base drive winding W1 to initiate inverter oscillation. A diode D6 discharges the capacitor C5 when Q3 is on. In accordance with various aspects, Q3 may be a bipolar junction transistor (BJT). A low-voltage MOSFET Q4 is connected in parallel with diac D7. Zener diode D8, resistor R5 and capacitor C7 are in parallel and connected from gate to source of Q4. A resistor R1 is connected to one end of the switching line 106, and the other end of the switching line 106 is connected either to a “Neutral” or a “Hot” input line.
When the switch 108 in the switching line 106 is in an “off” position (e.g., the switch 108 is open), there is no voltage developed across the Q4 gate-to-source of a trigger circuit 110. Therefore, the Q4 switch is the off position, and the current-fed inverter 104 is in a normal operating condition. When the switching line 106 is on (or off in a case where reverse logic is utilized), the half-rectified input voltage will be scaled down and the averaged voltage is applied to the gate-to-source of the switch Q4. This voltage turns on Q4 and puts the capacitor C5 in parallel with winding W1 and resistor R3. The capacitor C5 effectively bypasses the base drive current away from Q3, and the inverter oscillation stops. At the same time, the switch Q4 prevents a voltage build up on the capacitor C5 from startup resistor R4. Upon opening the switch on the switching line 106, the Q4 gate-to-source voltage drops and Q4 turns off, and allow the C5 to charge by R4 at which point, the breakdown of the diode D7, the inverter restarts and ballast operation resumes.
Thus, upon applying power to the ballast 100 (e.g., turning on a light switch connected thereto), the PFC section 102 is operational. Current traversing the resistor R4 charges up capacitor C5. Once the voltage on capacitor C5 reaches a breakdown point of diac D7, the diac D7 breaks down and a high current (di/dt) is applied to the base of Q3, which turns on Q3. During a subsequent half-cycle of an applied voltage waveform, Q2 turns on and Q3 turns off. This sequence may repeat every half cycle with switches Q2 and Q3 alternating respective on and off states. Whenever switch Q3 turns on, capacitor C5 begins to discharge because D6 is conducting. However, when switch Q3 turns off the capacitor C5 is charging. Because the time constant associated with capacitor C5 is longer than the half-cycle period for which switch Q3 is in the off state, the voltage on C5 does not reach the breakdown voltage of the diac D7. By positioning capacitor C5 in parallel with the base drive winding W1 of Q3, current through the base of Q3 is reduced, thereby turning Q3 off and shutting down its portion of the circuit, and thus the ballast 100 shuts down as well.
According to an example, PFC circuit 304 may be operatively associated with four inverters 306, each of which may in turn be connected to two lamps. Each switch 310 may receive a signal from an independent source (e.g., a sensor), from a common source, or from some permutation thereof. For instance, switches 310 for two of the inverters 306 may be coupled to a common source or sensor, while switches for the other two of the inverters each have an independent source, for a total of three sources providing switching signals to the four inverters' switches 310. It will be appreciated that other combinations of sensor-to-switch connections are possible, and that the subject features are not limited to the foregoing example.
Upon an indication from a sensor that an occupant is not present in the area illuminated by a given lamp or pair of lamps associated with a particular inverter, it may be desirable to close the switch 310 for that inverter 306 to cause the ballast, and thus the associated lamps to shut down in order to conserve energy. The indication of the absence of an occupant may be an absence of a signal from a motion sensor. For instance, a switch 310 may remain open so long as a signal from a motion sensor associated with the switch is detected, and may close when the signal is no longer detected. Closing of the switch 310 may trigger the events described above with regard to
With regard to
It will be appreciated that the various examples and/or features described herein may employ reverse logic as well. For instance, a simple logic inverter may be placed between the remote sensor and the switch, such that the detection of an occupant may be perceived by the switch as an absence of a signal, a “low” signal (e.g., a zero-bit in binary), or the like, and the departure of the occupant from the monitored space be perceived by the switch as a “high” signal (e.g., and inverted low signal in this example). “Low” and “high” as used herein may relate to binary 0s and 1s, respectively, and may additionally or alternatively describe voltage and/or current amplitudes at which a respective signal is relayed form the sensor to the switch.
At 404, the closing of the switch causes a voltage to be applied to a gate-to-source portion of a MOSFET device connected between the switching line and the inverter, which places a capacitor in parallel with a base drive winding for a base junction of a BJT in the inverter circuit, such as is described above with regard to
At 506, the parallel capacitor may be permitted to discharge while the Q3 BJT is on, which may be a period associated with a first half-cycle of a high-frequency waveform reaching Q3. At the end of the first half-cycle, Q3 may be turned off and a second BJT, such as component Q2 described above, may be turned on for the duration of the second half-cycle of the waveform, at 508. At 510, during the second half-cycle, the parallel capacitor may be permitted to charge by resistor R4. At 512, at the beginning of a subsequent first half-cycle (e.g., of a next period of the waveform), Q2 may be turned off and Q3 may be turned on again, at which point the parallel capacitor begins to discharge by D6. The method may then revert to 506 for further iteration and oscillation of the inverter portion of the ballast. In this manner, the inverter portion of the circuit may be maintained in an on state until a switch in a switching line is closed to turn the inverter off.
In accordance with one or more aspects, examples of values that may be associated with the various components are presented below. However, it is to be understood that the following values are presented for illustrative purposes only, and that the subject components are not limited to such values, but rather may comprise any suitable values to achieve the aforementioned goals and to provide the functionality described herein.
The components of
The components of
The above concepts have been described with reference to various aspects. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the concepts be construed as including all such modifications and alterations.
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