Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
  • H05B45/58—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits involving end of life detection of LEDs
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
  • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

• the subject matter of the present disclosure relates to lighting devices and, more particularly, to failure protection (e.g., short circuit and component breakdown) for lighting devices with light emitting diodes (LEDs).
• failure protection e.g., short circuit and component breakdown
• LEDs light emitting diodes
• LEDs Light-emitting diodes
• Examples of LEDs include an LED chip which emits light, a color conversion module including translucent sealing materials (e.g. epoxy resin and/or silicone resin), and a phosphor layer that covers the LED chip.
• translucent sealing materials e.g. epoxy resin and/or silicone resin
• phosphor layer that covers the LED chip.
• LEDs and the lighting devices in which they are found have advantages such as longer life, excellent responsiveness, and a compact configuration in comparison with incandescent lamps. Because LEDs are themselves a small and light-weight configuration, the formation of thin and three-dimensional lighting fixtures provides further advantages such as enhancing a degree of freedom in the design of lighting fixtures.
• the present disclosure describes embodiments of a protection device for use with lighting devices that include light-emitting diodes (LEDs). These protection devices activate in response to a variety of failure conditions including short circuit conditions and component breakdown conditions. Moreover, protection devices of the present disclosure meet industry requirements and standards, including, but not limited to: Underwriters Laboratories (UL) Class 2. [0004] Other features and advantages of the disclosure will become apparent by reference to the following description taken in connection with the accompanying drawings.
• UL Underwriters Laboratories
• FIG. 1 depicts a block diagram of an exemplary lighting device that includes light-emitting diodes
• FIG. 2 depicts a schematic diagram of a topology for an exemplary protection device for use in the lighting device of FIG. 1;
• FIG. 3 depicts a schematic diagram of a topology for an exemplary lighting device that includes the protection device of FIG. 2;
• FIG. 4 depicts a plot of voltage for various signals of a lighting device such as the lighting devices of FIGS. 1, 2, and 3.
• FIG. 1 illustrates a block diagram of an exemplary lighting device 100 with features that prevent damage during failure conditions that can include either or both of short circuit conditions and single component breakdown conditions. Such failure conditions cause rapid changes in current and/or voltage that can damage components in the lighting device 100.
• industry standards e.g., Underwriters Laboratories (UL) standards
• UL Underwriters Laboratories
• embodiments of the lighting device 100 are configured to satisfy such industry standards and, in one embodiment, address both short circuit conditions and component breakdown conditions using a robust and cost-effective circuit design.
• the lighting device 100 includes a light engine 102 with one or more light-emitting diodes 104 as the primary light source.
• the light engine 102 couples with a drive device 106 that provides a drive signal to operate the LEDs 104.
• the drive device 106 has components such as an LED driving circuit 108 and a feedback circuit 110, both of which comprise various configurations of discrete electrical elements (e.g., resistors, capacitors, transistors, etc.). Failure conditions can occur when one or more of these elements fail or when a short-circuit occurs, e.g., at the light engine 102. These failure conditions often manifest themselves as changes to one or more operating conditions (e.g., current and/or voltage) of the lighting device 100 and, in particularly, to a rapid increase in drive signal current at the light engine 102.
• operating conditions e.g., current and/or voltage
• a protection device 114 couples with the feedback circuit 110.
• the protection device 114 limits the drive signal current in response to the short circuit as well as in response to failure of one or more electrical elements.
• the protection device 114 maintains the drive signal current at or below a level that permits continued operation of the light-emitting diode during the failure.
• the protection device 114 includes a reference component 116, a comparator component 118 (e.g., an op-amp), and a switching component 120 (e.g., a field effect transistor (FET) or a metal oxide field effect transistor (MOSFET)).
• FET field effect transistor
• MOSFET metal oxide field effect transistor
• an external current input e.g., an alternating current (AC) input
• the drive device 106 converts the AC input to the drive signal current, which causes the LEDs 104 to emit light.
• the feedback circuit 112 monitors the drive signal current and generates an input signal that the protection device 114 receives. Changes in the properties of the input signal determine whether the protection device 114 limits the drive signal current.
• the comparator component 118 compares the input signal to a reference signal from the reference component 116. The comparator 118 generates a switching signal that operates the switch component 120 between its open and closed positions. Deviation of the input signal from the reference signal causes the comparator 118 to change the switching signal, thereby causing the protection device 114 to limit the drive signal current.
• the protection device 112 also includes a reset component 122, which couples with the switch component 120 to open and close the switch component 120 at periodic or pre-determined intervals.
• a timing circuit or other configuration of components measure the pre-determined interval. The timing circuit can activate concurrently with the protection device 112 in response to the failure condition. Expiration of the pre-determined interval opens the switch component 120 to remove the current limiting features of the protection device 114 from the drive device 106. The presence of the failure condition will cause the protection device 114 to re-engage until the end of the next pre-determined interval. On the other hand, if the failure condition is no longer present, then the protection device 114 remains disengaged and the lighting device 100 will continue to operate normally until the next failure occurs and the protection device 114 engages to limit the drive signal current.
• FIGS. 2 and 3 depict topologies for an exemplary lighting device 200.
• the topologies show various components (e.g., resistors, capacitors, switches, diodes, etc.) that are useful for the present design. This disclosure does, however, contemplate other configurations of such components that would form topologies other than that shown the figures.
• FIG. 2 focuses on the configuration of electrical elements for use in an exemplary protection device 214.
• the protection device 214 includes a reference component 216, a comparator component 218, a switching component 220, and a reset component 222.
• the reference component 216 includes a voltage supply 224, a resistor 226, and a capacitor 228. These electrical elements generate a reference voltage Vr, which acts as a threshold to determine the operation of the protection device 200 as contemplated herein.
• the comparator component 218 includes an op-amp 230 having a first input that receives the reference voltage Vr. A second input of the op-amp 230 receives a feedback voltage Vb from the feedback circuit (not shown).
• the op-amp 230 also has an output that couples with the switch component 220 and the reset component 222. During operation, the op-amp 230 compares the reference voltage and the feedback voltage to deliver a switching signal from the output to the switch component 220 and the reset component 222.
• the switch component 220 includes a fault switch 234 that is responsive to the switching signal.
• the reset component 222 includes resistors (e.g., resistor 236 and resistor 238), a capacitor 240, a diode 242, and a reset switch 244. Both the fault switch 234 and the reset switch 244 can comprise a MOSFET and/or related switching element.
• the switching signal changes the position of the fault switch 234 to lower the properties of an output signal that the protection device 214 provides to the drive circuit 206.
• the topology of FIG. 3 shows details of an LED driving circuit 208 and a feedback circuit 210 found in the lighting device 200.
• the feedback circuit 210 includes an opto-coupler 246 and a voltage divider 248 comprising resistors (e.g., resistor 250, resistor 252, and resistor 254) and a capacitor 256.
• a regulator circuit 258 couples to the voltage divider 248 and to the protection device 214.
• the regulator circuit 258 provides the feedback voltage Vb.
• the regulator circuit 258 includes a resistor 260, a capacitor 262, and a regulator switch 264.
• the feedback circuit 210 also includes a Zener diode 266, a rectifier 268, and a transformer 272.
• the regulator circuit 258 provides a clamping voltage Va that controls operating frequency of a converter 276 (e.g., a half-bridge DC-DC converter) to get a drive voltage Vo that is appropriate for light-emitting diodes of the lighting device 200.
• failure conditions in the lighting device 200 will cause the feedback voltage Vb to drop below the reference voltage Vr. This drop causes the switching voltage of the switching signal from the op-amp 230 to exceed the gate voltage of the fault switch 242.
• the fault switch 234 closes in response to the switching voltage. Closing the fault switch 234 drives the clamping voltage Va lower, which changes the operating frequency of the converter 276. In one example, the operating frequency increases and can reach about 300 kHz or more. At these operating frequencies, the drive signal voltage Vo and drive signal current are reduced to levels that maintain and protect the components of the lighting device 200 and that meet industry standards (e.g., UL standards).
• FIG. 4 depicts plots of voltage for various components to help describe operation of the reset component 222.
• the plots show voltage for each of the clamping voltage Va, the switching voltage Vd, and a capacitor voltage Vc for the capacitor 228.
• initiation of the fault condition causes the capacitor 228 to begin to charge, as evident by the increasing capacitor voltage Vc.
• the reset switch 244 closes and the fault switch 242 opens, which causes the clamping voltage Va to increase.
• the feedback voltage Vb also increases because of Miller effect principles at the regulator switch 264. Artisans skilled in the electrical arts will recognize the Miller effect.
• the switching voltage Vd drops and the capacitor voltage Vc discharges through the output of the op-amp 230.
• the Miller effect finishes, and if the fault condition is present, the feedback voltage Vb becomes low and the switching voltage Vd becomes high. In this configuration, the reset is complete and the reset component 222 begins another cycle.

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• Circuit Arrangement For Electric Light Sources In General (AREA)

Applications Claiming Priority (1)

Publications (2)

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ID=48288465

Family Applications (1)

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• 2011
  • 2011-11-10 CN CN201180076237.2A patent/CN104025712B/zh not_active Expired - Fee Related
  • 2011-11-10 CA CA2857527A patent/CA2857527A1/en not_active Abandoned
  • 2011-11-10 EP EP11875405.0A patent/EP2777365A4/de not_active Withdrawn
  • 2011-11-10 WO PCT/CN2011/082056 patent/WO2013067704A1/en active Application Filing

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