LED light emitting device

• US 8,519,642 B2
• Filed: 08/05/2010
• Issued: 08/27/2013
• Est. Priority Date: 08/14/2009
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Korea Semiconductor Limited (ON Semiconductor Corporation)
• Inventors: Lee, Hak-Hee, Jung, Il-Young, Ahn, Byunghak, Lee, Eung-Woo
• Primary Examiner(s): CRAWFORD, JASON
• Application Number:
  US12/850,996
• Publication Number:
  US 20110037407A1
• Time in Patent Office: 1,118 Days
• Field of Search: 315/209.R, 315/210, 315/224, 315/287, 315/291, 315/294, 315/297, 315/302, 315/307, 315/312
• US Class Current: 315/312
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs

Abstract

An LED light emitting device includes LED channels with LEDs, a transformer that converts an input voltage and supply an output voltage to the LED channels, a controller, and an LED driver. The controller controls the transformer according to a first feedback signal for interrupting power supply to the LED channels when a dimming off state in which currents are not supplied to the plurality of LED channels occurs or when a state in which the maximum channel voltage of a plurality of channel voltages corresponding to voltages applied to the LED channels, respectively, is an overvoltage and a defective state in which the plurality of LED channels include an open state are maintained during a predetermined threshold period. The LED driver generates information on the dimming off state and information on the defective state.

Claims

1. An LED light emitting device including a plurality of LED channels including a plurality of LEDs, comprising:

a transformer configured to convert an input voltage and supply an output voltage to the plurality of LED channels;

a controller configured to control the transformer according to a first feedback signal for interrupting power supply to the plurality of LED channels when a dimming off state in which currents are not supplied to the plurality of LED channels occurs or when a state in which the maximum channel voltage of a plurality of channel voltages corresponding to voltages applied to the plurality of LED channels, respectively, is an overvoltage and a defective state in which the plurality of LED channels include an open state are maintained during a predetermined threshold period; and

an LED driver configured to generate information on the dimming off state and information on the defective state, the LED driver comprising a first feedback signal generator that includes a first photo diode emitting beams corresponding to a first sink current and a second sink current, and a first photo transistor in which a current corresponding to an amount of beam emitted by the first photo diode flows,

wherein the LED driver is connected to a secondary side of the transformer, the controller is connected to a primary side of the transformer insulated from the secondary side, and the first feedback signal is generated according to the information on the dimming off state and the information on the defective state.

2. The LED light emitting device of claim 1, wherein:

the LED driver further comprises a first feedback signal controller including a first sink current source for supplying the first sink current when the dimming off state occurs, and a second sink current source for supplying the second sink current when the defective state occurs.

3. The LED light emitting device of claim 2, wherein:

the LED driver further includes a defect sensor configured to receive a first current when at least one of the plurality of LED channels is in an open state, to receive a second current when the maximum channel voltage is an overvoltage, and to control the first feedback signal controller such that the second sink current flows in the first feedback signal generator when a voltage charged by the first current and the second current is equal to or greater than a defect voltage for determining the defective state.

4. The LED light emitting device of claim 3, wherein:

the defect sensor includes a capacitor;

a first switch connected between the capacitor and a first current source for supplying the first current;

a second switch connected between the capacitor and a second current source for supplying the second current; and

a comparator configured to receive a voltage charged in the capacitor and the defect voltage and to compare them,

wherein an output voltage of the comparator is transferred to the first feedback signal controller.

5. The LED light emitting device of claim 2, wherein:

the LED driver further includes a dimming-off determining unit configured to determine the dimming off state by using a plurality of dimming signals controlling current supply to the plurality of LED channels, and the dimming-off determining unit controls the first feedback signal controller such that the first sink current flows in the first feedback signal generator.

6. The LED light emitting device of claim 2, wherein:

the first feedback signal controller includes;

a first switch connecting the first sink current source and the first feedback signal generator; and

a second switch connecting the second sink current source and the second feedback signal generator, and

wherein the second sink current is larger than the first sink current.

7. The LED light emitting device of claim 2, wherein:

the controller includes;

a power switch connected to the primary side of the transformer; and

a protection controller including a current mirror circuit for coping a current flowing in the first photo transistor and supplying currents to a first resistor and a second resistor, and

the power switch is turned off according to a dimming off signal generated by supplying the current to the first resistor and a protection signal generated by supplying the current to the second resistor.

8. The LED light emitting device of claim 7, wherein:

the controller further includes;

an SR latch configured to receive the protection signal through a set terminal and generate and maintain a signal for turning off the power switch at a time point when the protection signal changes form a first level to a second level; and

a gate driver configured to generate a gate signal for controlling the switching operation of the power switch according to an output signal of the SR latch and the dimming off signal.

9. The LED light emitting device of claim 7, wherein:

the controller further includes a PWM controller configured to control the operation of the power switch according to a second feedback signal based on the minimum channel voltage of the plurality of channel voltages and to maintain the second feedback signal corresponding to a start time point of the dimming off state during the dimming off state period.

10. The LED light emitting device of claim 9, further comprising:

a second feedback signal generator configured to generate a second feedback signal to correspond to a comparison voltage corresponding to the minimum channel voltage, and to constantly maintain the second feedback signal corresponding to the start time point of the dimming off state during the dimming off state.

11. The LED light emitting device of claim 10, wherein:

the LED driver further includes a second feedback signal controller configured to control the second feedback signal generator such that the minimum channel voltage is maintained at a predetermined minimum reference voltage.

12. The LED light emitting device of claim 7, wherein the first resistor has a resistance value smaller than the second resistor.

13. The LED light emitting device of claim 1, wherein:

the controller controls the operation of the transformer according to a second feedback signal based on a minimum channel voltage of the plurality of channel voltages, and maintains the second feedback signal corresponding to a start time point of the dimming off state.

14. The LED light emitting device of claim 13, further comprising:

a second feedback signal generator configured to generate the second feedback signal to correspond to a comparison voltage corresponding to the minimum voltage, and to constantly maintain the second feedback signal corresponding to the start time point of the dimming off state.

15. The LED light emitting device of claim 14, wherein:

the LED driver further includes a second feedback signal controller configured to control the second feedback signal generator such that the minimum channel voltage is maintained at a minimum reference voltage.

16. The LED light emitting device of claim 15, wherein:

the second feedback signal controller includes;

a shunt regulator including a first terminal to receive the minimum channel voltage, a second terminal grounded, and a third terminal connected to the second feedback signal generator, and configured to interrupt the second terminal and the third terminal when the minimum channel voltage is smaller than the minimum reference voltage and to connect the second terminal and the third terminal when the minimum channel voltage is equal to or greater than the minimum reference voltage; and

a capacitor connected between the third terminal and the first terminal,

the comparison voltage is a voltage of the third terminal.

17. The LED light emitting device of claim 16, wherein:

the second feedback signal generator includes;

a second photo diode having a cathode electrode connected to the third terminal and an anode to which a predetermined current is supplied;

a second feedback signal generator including a second photo transistor in which a current corresponding to an amount of beam emitted by the second photo diode flows; and

a switch configured to be turned off during the dimming off period so as to interrupt current supply to the second photo diode.

18. An LED light emitting device including a plurality of LED channels including a plurality of LEDs, comprising:

a transformer configured to convert an input voltage and supply an output voltage to the plurality of LED channels;

a controller configured to control the transformer according to a first feedback signal for interrupting power supply to the plurality of LED channels when a dimming off state in which currents are not supplied to the plurality of LED channels occurs or when a state in which the maximum channel voltage of a plurality of channel voltages corresponding to voltages applied to the plurality of LED channels, respectively, is an overvoltage and a defective state in which the plurality of LED channels include an open state are maintained during a predetermined threshold period; and

an LED driver configured to generate information on the dimming off state and information on the defective state,

wherein the LED driver is connected to a secondary side of the transformer, the controller is connected to a primary side of the transformer insulated from the secondary side, the first feedback signal is generated according to the information on the dimming off state and the information on the defective state, and the controller controls the operation of the transformer according to a second feedback signal based on a minimum channel voltage of the plurality of channel voltages and maintains the second feedback signal corresponding to a start time point of the dimming off state.

19. The LED light emitting device of claim 18, further comprising:

a second feedback signal generator configured to generate the second feedback signal to correspond to a comparison voltage corresponding to the minimum voltage, and to constantly maintain the second feedback signal corresponding to the start time point of the dimming off state.

20. The LED light emitting device of claim 19, wherein:

the LED driver further includes a second feedback signal controller configured to control the second feedback signal generator such that the minimum channel voltage is maintained at a minimum reference voltage.

21. The LED light emitting device of claim 20, wherein:

the second feedback signal controller includes;

a shunt regulator including a first terminal to receive the minimum channel voltage, a second terminal grounded, and a third terminal connected to the second feedback signal generator, and configured to interrupt the second terminal and the third terminal when the minimum channel voltage is smaller than the minimum reference voltage and to connect the second terminal and the third terminal when the minimum channel voltage is equal to or greater than the minimum reference voltage; and

a capacitor connected between the third terminal and the first terminal,

the comparison voltage is a voltage of the third terminal.

22. The LED light emitting device of claim 21, wherein:

the second feedback signal generator includes;

a second photo diode having a cathode electrode connected to the third terminal and an anode to which a predetermined current is supplied;

a second feedback signal generator including a second photo transistor in which a current corresponding to an amount of beam emitted by the second photo diode flows; and

a switch configured to be turned off during the dimming off period so as to interrupt current supply to the second photo diode.