Patent Grant
9041293
This application claims the benefit of Taiwan application Serial No. 100149019, filed Dec. 27, 2011, the disclosure of which is incorporated by reference herein in its entirety.
1. Technical Field
The disclosed embodiments relate in general to a lamp power-saving system, and more particularly to a lamp control system, a lamp power-saving system and a power-saving method therefor.
2. Description of the Related Art
The lighting industry selects and applies light sources from earlier incandescent light bulbs, fluorescent lamps (e.g., straight-tube fluorescent lamps and compact fluorescent lamps), halogen lamps and metal halide lamps to current light-emitting diode (LED) lamps. These light sources are demanded according to conditions in different environments. LED light sources, being small in volume, high in light intensity and diversified in color, are prevalent in the lighting industry nowadays.
For a fluorescent lamp, an electronic ballast is required. A common electronic ballast is a single-function control structure capable of only activating a lamp and controlling a lighting current limit. Due to the single function of the electronic ballast, the electronic ballast is unable to fulfill low power consumption lighting since the power saving efficiency is low, and thus also offers insufficient competitiveness. As a result, fluorescent lamps are faced with the jeopardy of market competitiveness as well as technical development.
The disclosure is directed to a lamp control system, a lamp power-saving system and a power-saving method therefor.
According to one embodiment, a lamp control system is provided. The lamp control system includes a lamp control unit and a system control unit. The lamp control unit, including a power conversion circuit and a preheat and lighting circuit, is for controlling a fluorescent lamp. The power conversion circuit, including a DC signal input terminal and an AC signal output terminal, converts a DC signal to an AC signal and output the AC signal. The preheat and lighting circuit, coupled to the AC signal output terminal and two terminals of the fluorescent lamp, preheats and activates the fluorescent lamp, and outputs a feedback signal indicating a current flowing through the fluorescent lamp. In response to the feedback signal, the system control unit controls the preheat and lighting circuit. In response to the feedback signal indicating the fluorescent lamp is in a preheat mode, the system control unit enables the preheat and lighting circuit to preheat the fluorescent lamp. In response to the feedback signal indicating the fluorescent lamp is lighted, the system control unit controls the preheat and lighting circuit to stop preheating.
According to another embodiment, a lamp power-saving system is provided. The lamp power-saving system includes a power management unit and the foregoing lamp control system. The power management unit includes an AC power input terminal and a DC signal output terminal. The DC signal input terminal of the power conversion unit is coupled to the DC signal output terminal of the power management unit.
According to an alternative embodiment, a power-saving method for a lamp power-saving system is provided. The method includes steps below. A lamp control unit is provided to control a fluorescent lamp. The lamp control unit includes a power conversion circuit and a preheat and lighting circuit. The preheat and lighting circuit, coupled to the power conversion circuit and two terminals of the fluorescent lamp, preheats and activates the fluorescent lamp, and outputs a feedback signal indicating a current passing through the fluorescent lamp. When the feedback signal indicates the fluorescent lamp is in a preheat mode, a resonant circuit of the preheat and lighting circuit is enabled to preheat the fluorescent lamp via a current path provided by a diode bridge of the preheat and lighting circuit. When the feedback signal indicates the fluorescent lamp is lighted, the current path of the preheat and lighting circuit is disconnected to stop preheating.
In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
Embodiments of a lamp control system, a lamp power-saving system and a power-saving method for a lamp power-saving system shall be described below.
A lamp control system 1 depicted in
In response to the feedback current signal Is1, the system control unit 20 controls the preheat and lighting circuit 12 in the lamp control unit 10 to enable the lamp control unit 10 to operate in different operating modes. For example, in response to the feedback signal Is1 indicating the fluorescent lamp 90 is in a preheat mode, the system control unit 20 enables the preheat and lighting circuit 12 to preheat the fluorescent lamp 90. In response to the feedback signal Is1 indicating the fluorescent lamp 90 is lighted, the system control unit 20 controls the preheat and lighting circuit 12 to stop preheating and to further allow the fluorescent lamp 90 function normally. By terminating the preheating, energy consumption is reduced. In another embodiment, e.g., with a mechanism for dimming control or bias control shown in
Referring to
In this embodiment, in response to the feedback signal Is1, the system control unit 20 controls the switching device to enable the lamp control unit 10 to operate in different operating modes. For example, in response to the feedback signal Is1 indicating the fluorescent lamp 90 is in a preheat mode, the system control unit 20 enables the switching device, e.g., through a first control signal Sc1 for enabling, to turn on the switch unit Q of the switching device, so as to allow the resonance circuit 210 to perform preheating at the two terminals of the fluorescent lamp 90 via a path provided by the diode bridge BD. In the preheat mode, the AC signal (e.g., a current in high-frequency square waves) outputted from the power conversion unit 111 is filtered by the resonance circuit 210 to become sinusoidal waves for preheating filaments at the two terminals of the fluorescent lamp 90. In response to the feedback signal Is1 indicating the fluorescent lamp 90 is lighted, the system control unit 20 disables the switching device, e.g., through a control signal Sc1 indicating disabling, to turn off the switch unit Q of the switching device so as to further stop preheating the fluorescent lamp 90. At this point, through the inductor Lr1 of the resonance circuit 210, the current of the AC signal outputted form the power conversion circuit 111 directly enters and lights the fluorescent lamp 90. Meanwhile, power saving is achieved since the current no longer passes through the path provided by the capacitor Cr1 and the diode bridge BD.
In another embodiment, in response to a dimming signal, the system control unit 20 enables the switching device after the fluorescent lamp 90 is activated, so as to allow the resonance circuit 210 to again perform preheating at the two terminals of the fluorescent lamp 90 via the path provided by the diode bridge BD to stabilize light output of the fluorescent lamp 90 in a dimming mode. In an embodiment, the preheat and lighting circuit 200 further includes an anti-surge device 230, e.g., an inductor Lh. The anti-surge device 230 is coupled between the resonance circuit 210 and the diode bridge BD. In a dimming mode, an instantaneous surge current may be evoked when the resonance circuit 210 again performs preheating. The anti-surge device 230 is capable of mitigating or suppressing effects that the surge current imposes on the overall circuit. In another embodiment, the preheat and lighting circuit 200 further includes an isolation circuit 220 coupled to one of the two terminals of the fluorescent lamp 90. For example, the isolation circuit 220 receives the DC signal Vdc to provide a divided voltage to the connected terminal of the fluorescent lamp 90. Referring to
Based on the embodiments of the lamp control system 1, other extended circuit elements or circuit units may be added to develop into a lamp power-saving system, e.g., a lamp power-saving system as shown in a block diagram in
For example, the power management unit 80 includes a filter circuit 81, a bridge rectification circuit 83 and a power factor correction circuit 85. The filter circuit 81 is coupled to an AC power source. The power factor correction circuit 85 outputs a high-voltage DC signal. For example, the filter circuit 81 includes an inductor and a capacitor, and is for removing noises in the AC power signal to reduce harmonic components and improve power quality. For example, the bridge rectification circuit 83 rectifies a 60 Hz AC power signal to a 120 Hz DC power signal to provide the power characteristics required by the system. For example, the power factor correction circuit 85 adjusts a phase angle difference of voltage and current to achieve in-phase voltage and current. The power factor correction circuit 85 further functions in cooperation with the filter circuit 81 to enhance power efficiency.
Based on the lamp power-saving system in
In one embodiment, the system control unit 40 includes a first determination circuit 41. According to the feedback signal Is1, the first determination circuit 41 outputs the first control signal Sc1 for activating or terminating preheating of the preheat and lighting circuit 12.
In one embodiment, the lamp power-saving system 40 further includes a dimming control unit 50 coupled to the power conversion circuit 111. In response to a setting signal Sdc, the dimming control unit 50 outputs a dimming signal SDim and controls the power conversion circuit 111 for dimming. In one embodiment, the system control unit 40 further includes a second determination circuit 43. In response to the dimming signal SDim, after the fluorescent lamp 90 is activated, the second determination circuit 43 preheats the fluorescent lamp 90 through the first control signal Sc1 for enabling the preheat circuit 115 in the preheat and lighting circuit 12. Alternatively, the second determination circuit 43 enables the switch unit Q of the switching device and allows the resonance circuit 210 to perform preheating at the two terminals of the fluorescent lamp 90 via the path provided by the diode bridge BD. For example, the dimming control unit 50 is implemented by a dimming control unit 650 in
In another embodiment, the lamp power-saving system 400 further includes a bias control circuit 70 coupled to one of the two terminals of the fluorescent lamp 90. In response to the dimming signal SDim, after the fluorescent lamp 90 is activated, the second determination circuit 43 of the system control unit 40, apart from enabling the preheat circuit 115 or the switch unit Q of the switching device, further enables the bias control circuit 70 by outputting a second control signal Sc2 to generate a bias signal for eliminating standing waves generated by the fluorescent lamp 90.
In yet another alternative embodiment, the lamp power-saving system 400 further includes a protection control circuit 60 coupled to a control terminal of the power conversion circuit 111. In response to the feedback signal Is2 indicating an overcurrent event, the protection control circuit 60 provides a bypass (or a path) connecting to the control terminal of the power conversion circuit 111 to stop the power conversion circuit 111 from outputting the AC signal at the AC signal output terminal N2. For example, the protection control circuit 60 is a protection control circuit 660 in
The lamp control unit 610 includes a power conversion circuit 611 and a preheat and lighting circuit 620. The power conversion circuit 611 is for performing DC-to-AC conversion. For example, the power conversion circuit 611 implemented by a half-wave bridge configuration, which includes a lamp dimming driving circuit 612 and two switch units. For example, the two switch units are two power transistors Q1 and Q2 connected in series to form a switching device. The lamp dimming driving circuit 612 outputs two pulse signals having different phases, and generates control signals via resistors Rg1 and Rg2 to alternately turn on the two switch units Q1 and Q2 so as to convert the DC signal Vdc to a high-frequency AC signal, thereby fulfilling the characteristics for lighting a fluorescent lamp. The power conversion circuit 611 further includes a frequency output terminal for outputting a frequency signal Vi, a frequency control terminal for receiving a frequency-change signal Vo, and a control terminal for outputting a signal SG. The power conversion circuit 611 further includes a resistor Rt coupled to the lamp dimming driving circuit 612 and the signal SG and a capacitor Ct coupled to the signal SG and ground. The power conversion circuit 611 further includes two diodes D1 and D2 coupled to the switch units Q1 and Q2, respectively. Through the frequency control terminal, the frequency of the high-frequency AC signal outputted from the power conversion circuit 611 may be modified to fulfill the characteristics for lighting a fluorescent lamp or alternatively to be utilized for dimming. For example, the lamp dimming driving circuit 612 is a driver, 6574 or 2028 manufactured by STM.
In
The system control unit 640 includes a first determination circuit 641 and a second determination circuit 643. The first determination circuit 641 includes a comparator I and a rectifier diode D3. The second determination circuit 643 includes a comparator II, a delay circuit BUF and a diode D4. When the lamp is activated, the preheat circuit first generates the preheat current that flows through the lamp filaments, and the current transformer CT1 then senses the current of the lamp and outputs a feedback signal Is1 to the comparator I of the first determination circuit 641. The comparator I of the first determination circuit 641 compares the feedback signal Is1 with a threshold Vref1. When the feedback signal Is1 is smaller than or equal to the threshold Vref1, the comparator I transmits a first control signal Sc1 for enabling (e.g., a high-level logic signal) to trigger the switching device, e.g., to turn on the switch unit Q3. When the feedback signal Is1 is greater than the threshold Vref1 indicating that the lamp is lighted, majority of preheating current generated by the lighting circuit is flown to the fluorescent lamp, and the current transformer CT1 instantaneously detects the current of the fluorescent lamp and outputs the feedback signal Is1 to the comparator I so as to make comparison with the threshold Vref1. Meanwhile, the comparator I transmits a first control signal Sc1 indicating disabling (e.g., a low-level logic signal) to turn off the switch unit Q3 and thus disconnecting the preheat circuit including the capacitor Cr1.
The dimming control unit 650 is coupled to a frequency output terminal and a frequency control terminal of the power conversion circuit 611. In response to a setting signal Sdc, the dimming control unit 650 outputs a dimming signal SDim to control the power conversion circuit 611 via the frequency control terminal to performing dimming. As shown in
The system enters a dimming standby mode after the lamp is fully activated. In a non-dimming condition, the dimming signal SDim outputted from the secondary side of the transformer T2 is zero. The dimming signal SDim is compared with a threshold Vref2 (Vref2>Vref1) by the comparator II, and is passed through the delay circuit BUF to obtain a low-level logic signal. Pointing this way, the system maintains the original lighting condition. In a dimming condition, the dimming signal SDim outputted from the secondary side of the transformer T2 is non-zero. The dimming signal SDim is compared by the comparator II, and is passed through the delay circuit BUF to obtain an enable signal (e.g., a high-level logic signal). The system is then in a dimming mode, and so the enable signal turns on the switch unit Q3 to again activate the preheat circuit. The activated preheat circuit then allows the current to flow through filaments of the fluorescent lamp for dimming current compensation, thereby stabilizing a low-power output of the fluorescent lamp. When the switch unit Q3 is instantaneously turned on and the preheating device is activated, an instantaneous surge current is rushed into the capacitor Cr1. However, the serially connected inductor Lh is capable of suppressing and absorbing the instantaneous surge current, so that the units or circuits are prevented from damages resulted by the instantaneous voltage change in the capacitor Cr1.
The delay circuit in the second determination circuit 643, e.g., a buffer, is for buffering signals outputted by the comparator II to prevent the signals outputted by the comparator II from clashing with the signals outputted by the comparator I. A delay period of the delay circuit is set to greater than an activation period, e.g., the delay period is set to approximately 3 seconds. More specifically, when the lamp is fully activated, the switch unit Q3 then receives the conduction control triggered by the signal outputted by the second determination circuit 643 to further enter the dimming mode.
The protection control circuit 660 is coupled to the control terminal (for outputting the signal SG) of the power conversion circuit 611. In response to the feedback Is2 indicating an overcurrent event, the protection control circuit 660 provides a bypass connecting to the control terminal, so as to prompt the power conversion circuit 611 to stop outputting the AC signal. The protection control circuit 660 includes at least two rectifiers (e.g., diodes D8 and D9), a current limiter (e.g., a resistor R1), a filter (e.g., a capacitor C1), a level determination element (e.g., a diode element ZD) and a protection controller (e.g., silicon-controlled element SR). In the event of an activation failure of the fluorescent lamp, a rectification effect is likely incurred. The rectification effect causes an instantaneous rise in the current such that the risen current may even exceed the rated current of the fluorescent lamp. At this point, the current transformer CT2 senses the current of the fluorescent lamp and outputs the feedback signal Is2. When a level between the current limiter (i.e., the resistor R1) and the filter (i.e., the capacitor C1) exceeds a threshold set by the level determination element (i.e., the diode ZD), the current passes through the diode element ZD and triggers the conduction of the silicon-controlled element SR. Hence, the driving signal SG from the control terminal of the power conversion circuit 611 is bypassed to a ground terminal to terminate operations of the power conversion circuit 611, i.e., to stop outputting the AC signal. For example, the level determination element is a zener diode or a diode-for-alternating-current (DIAC). For example, the protection controller is a triode-for-alternating current (TRIAC), or a silicon-controlled rectifier (SCR).
Further, in an open circuit formed when the fluorescent lamp is removed or is not connected to an enabled lighting circuit, the power conversion circuit does not provide any output. Under such conditions, the lamp power-saving system 400 enters automatic open-circuit protection to prevent an open-circuit high voltage from damaging the lamp power-saving system 400.
For example, in a dimming mode, standing waves are incurred in the fluorescent lamp when the fluorescent lamp is in state of having a low optical output power e.g. about lower than 10%. In this case, the switch unit Q4 of the switching device is enabled by receiving the second control signal Sc2 outputted by the second determination circuit 743 so as to generate a bias signal. The bias signals then passes through the fluorescent lamp to eliminate the standing waves.
In this embodiment, the preheat circuit further includes a capacitor Cr2 coupled to the two terminals of the fluorescent lamp, with the capacitor Cr1 being far greater than Cr2. Before activating the fluorescent lamp, the preheat current flows through the filaments of the fluorescent lamp and passes through the preheat circuit including the capacitors Cr1 and Cr2. A target of such approach is also to provide a current for heating the filaments at the two terminals of the fluorescent lamp to achieve a soft activation. Thus, the lamp is prevented from a high-voltage activation, which may lead to blackening of the lamp head or even reduce the lifespan of the lamp. Further, when the preheat circuit including the capacitor Cr1 is disconnected, the capacitor Cr2 is capable of providing a DC bias to the fluorescent lamp, so that the fluorescent lamp is still lighted by a sufficient rated voltage in a stable lighted condition.
Details of the preheat circuit including the capacitors Cr1 and Cr2 are to be described below. When the fluorescent lamp is activated, in a preheat mode, the switch unit Q3 is turned on by the first control signal Sc1 for enabling. Meanwhile, a minute current also passing through the circuit of the capacitor Cr2 can be neglected. When the fluorescent lamp is lighted, the switch unit Q3 is turned off by the first control signal Sc1 indicating disabling. Similarly, a minute current also passing through the circuit of the capacitor Cr2 can similarly be neglected.
The disclosure further provides a method for a lamp power-saving system. According to one embodiment, the method includes: A) providing a lamp control unit for controlling a fluorescent lamp; the fluorescent lamp including a power conversion circuit and a preheat and lighting circuit; the preheat and lighting circuit, being coupled to the power conversion circuit and two terminals of the fluorescent lamp, for preheating and activating the fluorescent lamp, and outputting a feedback signal indicating a current passing through the fluorescent lamp; B) when the feedback signals indicates the fluorescent lamp is in a preheat mode, enabling a resonance circuit of the preheat and lighting circuit to preheat the preheat and lighting circuit via a current path provided by a diode bridge; and C) when the feedback signal indicates the fluorescent lamp is lighted, disconnecting the current path in the preheat and lighting circuit to stop preheating. In one embodiment, the method further includes: D) when a dimming signal indicates dimming is required, after the fluorescent lamp is lighted, entering a dimming mode to enable the resonance circuit of the preheat and lighting circuit to preheat via a current path provided by the diode bridge. In another embodiment, the method further includes: E) when entering the dimming mode, inputting a bias signal to one of the two terminals of the fluorescent lamp to suppress standing waves generated by the fluorescent lamp. In another alternative embodiment, the method further includes a step of adding a protection mechanism. For example, the method further includes: F) when the feedback signal indicates an overcurrent event, providing a bypass connecting to a control terminal of the power conversion circuit to stop the power conversion circuit from outputting an AC signal to the preheat and lighting circuit. The method is applicable to the various embodiments of the foregoing lamp control system and the lamp power-saving system, and to embodiments realized by other circuit structures.
In conclusion, several embodiments of the lamp control system, the lamp power-saving system and the power-saving method for the lamp power-saving system are as disclosed above. In some embodiments, the lamp control system disconnects the preheat circuit after preheating is completed to reduce energy consumption. Further, the lamp control system may be implemented in different forms to provide design flexibilities in lamp control. For example, in some embodiments when dimming needed by dimming control, the preheat circuit again provides a current to the fluorescent lamp to stabilize a light output of the fluorescent lamp and thus to prolong the lifespan of the fluorescent lamp. Moreover, the mechanism of bias control may be added to suppress instantaneous standing waves of dimming. Further, the protection control mechanism may also be implemented so that the lamp control system enters a protection mode to stop operating and hence prevents hazards when the fluorescent lamp encounters an abnormality. Therefore, the above lamp control system may be implemented as a lamp power-saving system for achieving integrated, high efficiency and low power consumption lighting. Consequently, the control design of the fluorescent lamp becomes more flexible for favoring reduction in implementation cost, thereby increasing market competitiveness of the fluorescent lamp as well as promoting green lighting techniques to applications of different circumstances.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
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