Light emitting diode driving circuit and controller thereof

• US 20090295776A1
• Filed: 09/30/2008
• Published: 12/03/2009
• Est. Priority Date: 05/30/2008
• Status: Abandoned Application

• Current Assignee: Green Solution Technology Co., Ltd., Niko Semiconductor Co., Ltd
• Original Assignee: Green Solution Technology Co., Ltd.
• Inventors: Yu, Chung-Che, Wang, Chen-Hsung
• Application Number:
  US12/285,189
• Publication Number:
  US 20090295776A1
• Time in Patent Office: Days
• US Class Current: 345/212
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2330/04 Display protection
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light emitting diode driving circuit comprising: a current control unit, a current detection unit, and a driving control unit. The current control unit connects to the current detection unit and comprises a control end, a first input/output end, and a second input/output end to individually produce an electric potential detection signal. The light emitting diode driving circuit determines whether driving the light emitting diode is unusual or not according to the electric potential detection signals to decide to start a protect mechanism. Furthermore, the present invention can receive any types of dimming signals to adjust the light of the light emitting diode.

Claims

1. A Light Emitting Diode (LED) driving circuit, comprising:

a conversion circuit, coupled to an input power source, for converting an input from the input power source into a direct current (DC) output signal to drive an LED module;

at least one current control unit, each of the current control units having a control pin, a first input/output (I/O) pin, and a second I/O pin, and the first I/O pin being coupled to the LED module;

at least one current detection unit, each of the current detection units being coupled to the second I/O pin of the respective current control unit to generate at least one detection signal; and

a driving control unit, coupled to the control pin and the first I/O pin of the current control unit as well as the current detection unit, adjusting voltage level of the control pin of the current control unit based on the detection signal from the current detection unit to stabilize current flowing through the LED module around a preset current value;

wherein, in case voltage level of one of the first I/O pins being higher than a first preset level, the driving control unit cuts off the respective current control unit.

2. The LED driving circuit according to claim 1, wherein the conversion circuit comprises:

a transformer, having a primary side and a secondary side, the primary side coupled to the input power source, and the secondary side generating the DC output signal through a rectifying unit;

a switch set, coupled to the primary side of the transformer, and switched between conducting state and off state based on a control signal;

an output capacitor, coupled to the secondary side of the transformer, for filtering out noise in the DC output signal;

a voltage detection unit, coupled to the secondary side of the transformer, for generating a voltage detection signal based on the DC output signal; and

a primary side control unit, generating the control signal based on the voltage detection signal to have the DC output signal stabilized around a preset voltage value.

3. The LED driving circuit according to claim 1, wherein the conversion circuit comprises:

an inductor, coupled to the input power source;

a switch, coupled to the inductor, switched between conducting state and off state based on a control signal;

a rectifying unit, having one end coupled to a coupling point between the inductor and the switch and the other end coupled to the LED module;

an output capacitor, coupled to a coupling point between the rectifying unit and the LED module for providing the DC output signal;

a voltage detection unit, coupled to one end of the LED module for detecting voltage level at the end to generate a voltage detection signal; and

a conversion control unit, generating the control signal based on the voltage detection signal to have voltage level at the end detected by the voltage detection unit stabilized around a preset voltage value.

4. The LED driving circuit according to claim 1, wherein the current control unit comprises:

a current mirror unit, having a plurality of semiconductor switches, each semiconductor switch having a control end, a first I/O end, and a second I/O end, wherein the control end is connected to the control pin, the first I/O end is coupled to the LED module, and the second I/O end is coupled to the corresponding current detection unit; and

a selection unit, coupled to the first I/O ends of the semiconductor switches, selectively output a level signal from one of the first I/O ends to the driving control unit.

5. The LED driving circuit according to claim 1, wherein the driving control unit receives an on/off signal, and is utilized to cut off the at least one current control unit based on the on/off signal.

6. The LED driving circuit according to claim 5, wherein the driving control unit detects the at least one control pin, and as one of the detected control pins having voltage level lower than a second preset level, the driving control unit cuts off the respective current control unit.

7. The LED driving circuit according to claim 5, wherein the driving control unit detects the at least one second I/O pin, and as voltage level of one of the detected second I/O pins lower than a third preset level over a preset period of time, the driving control unit cuts off the respective current control unit.

8. The LED driving circuit according to claim 1, wherein the driving control unit receives a DC dimming signal and outputs a pulse-width-modulation (PWM) signal based on the DC dimming signal.

9. A LED driving circuit, comprising:

a conversion circuit, coupled to an input power source, for converting an input from the input power source into a DC output signal to drive an LED module;

at least one current control unit, each of the current control units having a control pin, a first I/O pin, and a second I/O pin, and the first I/O pin being coupled to the LED module;

at least one current detection unit, each of the current detection units being coupled to the second I/O pin of the respective current control unit to generate at least one detection signal; and

a driving control unit, which is coupled to the control pin and the first I/O pin of the current control unit as well as to the current detection unit, adjusting voltage level of the control pin of the current control unit based on the at least one detection signal from the at least one current detection unit to stabilize current flowing through the LED module around a preset current value,

wherein the driving control unit generates a fault signal as voltage level of one of the first I/O pins higher than a first preset level.

10. The LED driving circuit according to claim 9, wherein the conversion circuit comprises:

a transformer, having a primary side and a secondary side, the primary side coupled to the input power source, and the secondary side generating the DC output signal through a rectifying unit;

a switch set, coupled to the primary side of the transformer, and switched between conducting state and off state based on a control signal;

an output capacitor, coupled to the secondary side of the transformer, for filtering out noise in the DC output signal;

a voltage detection unit, coupled to the secondary side of the transformer, for generating a voltage detection signal based on the DC output signal; and

a primary side control unit, generating the control signal based on the voltage detection signal to have the DC output signal stabilized around a preset voltage value.

11. The LED driving circuit according to claim 9, wherein the conversion circuit comprises:

an inductor, coupled to the input power source;

a switch, coupled to the inductor, switched between conducting state and off state based on a control signal;

a rectifying unit, having one end coupled to a coupling point between the inductor and the switch and the other end coupled to the LED module;

an output capacitor, coupled to a coupling point between the rectifying unit and the LED module for providing the DC output signal;

a voltage detection unit, coupled to one end of the LED module for detecting voltage level at the end to generate a voltage detection signal; and

a conversion control unit, generating the control signal based on the voltage detection signal to have voltage level at the end detected by the voltage detection unit stabilized around a preset voltage value.

12. The LED driving circuit according to claim 9, wherein the current control unit comprises:

a current mirror unit, having a plurality of semiconductor switches, each semiconductor switch having a control end, a first I/O end, and a second I/O end, wherein the control end is connected to the control pin, the first I/O end is coupled to the LED module, and the second I/O end is coupled to the corresponding current detection unit; and

a selection unit, coupled to the first I/O ends of the semiconductor switches, selectively output a level signal from one of the first I/O ends to the driving control unit.

13. The LED driving circuit according to claim 9, wherein the driving control unit receives an on/off signal, and is utilized to cut off the at least one current control units based on the on/off signal.

14. The LED driving circuit according to claim 13, wherein the driving control unit detects the at least one control pins, and as one of the detected control pins having voltage level lower than a second preset level, the driving control unit cuts off the respective current control unit.

15. The LED driving circuit according to claim 13, wherein the driving control unit detects the at least one second I/O pins, and as voltage level of one of the detected second I/O pins lower than a third preset level over a preset period of time, the driving control unit cuts off the respective current control unit.

16. The LED driving circuit according to claim 9, wherein the driving control unit receives a DC dimming signal and outputs a PWM signal based on the DC dimming signal.

17. A LED driving circuit controller, utilized to control an LED driving circuit for driving at least a first LED module, comprising:

a first current adjusting unit, generating a first current adjusting signal according to a first current detection signal indicating magnitude of current flowing through a first LED module to control a first power switch connected in series to the first LED module so as to have voltage level of the first current detection signal stabilized around a first preset voltage value; and

a signal processing unit, detecting a voltage signal from a first coupling point between the first power switch and the first LED module, receiving the first current detection signal, and generating a fault signal as either voltage level of the first current detection signal lower than a first preset level over a preset period of time or voltage level of the voltage signal from the first coupling point higher than a second preset level.

18. The LED driving circuit controller according to claim 17, wherein the signal processing unit further receives an on/off signal and controls the first current adjusting signal to cut off the first power switch when the on/off signal is at a level indicating off state.

19. The LED driving circuit controller according to claim 18, wherein the signal processing unit further detects voltage level of the first current adjusting signal as the on/off signal is not at the level indicating off state, and generates the fault signal when voltage level of the first current adjusting signal is lower than a third preset level.

20. The LED driving circuit controller according to claim 17, wherein the signal processing unit receives a DC dimming signal and outputs a PWM signal based on the DC dimming signal.

21. The LED driving circuit controller according to claim 20, wherein the signal processing unit controls the first current adjusting signal based on the PWM signal to turn off the first power switch periodically to dim the first LED module.

22. The LED driving circuit controller according to claim 17, further comprising a second current adjusting unit, generating a second current adjusting signal based on a second current detection signal indicating magnitude of current flowing through a second LED module driven by the LED driving circuit to control a second power switch connected in series with the second LED module so as to have voltage level of the second current detection signal stabilized around a second preset voltage value.

23. The LED driving circuit controller according to claim 22, wherein the signal processing unit further detects a voltage signal from a second coupling point between the second power switch and the second LED module and receives the second current detection signal, and generates the fault signal as either voltage level of the second current detection signal lower than the first preset level over the preset period of time or voltage level of the voltage signal from the second coupling point higher than the second preset level.

24. The LED driving circuit controller according to claim 22, wherein the first preset voltage value is substantially equal to the second preset voltage value.

25. The LED driving circuit controller according to claim 22, wherein the signal processing unit further receives an on/off signal and controls the first current adjusting signal and the second current adjusting signal to turn off the first power switch and the second power switch respectively when the on/off signal is at the turn-off level.

26. The LED driving circuit controller according to claim 25, wherein there is a default time interval between turn-off time of the first power switch and that of the second power switch.

27. The LED driving circuit controller according to claim 25, wherein the signal processing unit further detects level of the first current adjusting signal and that of the second current adjusting signal as the on/off signal is not at the turn-off level, and generates the fault signal as voltage level of the first current adjusting signal or the second current adjusting signal is lower than a third preset level.

28. The LED driving circuit controller according to claim 21, wherein the signal processing unit controls the first current adjusting signal and the second current adjusting signal based on the PWM signal to turn off the first power switch and the second power switch periodically to dim the first LED module and the second LED module respectively.

29. The LED driving circuit controller according to claim 28, wherein there is a default time interval between turn-off time of the first power switch and that of the second power switch.