LED DRIVER CIRCUIT

• US 20100060189A1
• Filed: 01/19/2007
• Published: 03/11/2010
• Est. Priority Date: 04/21/2006
• Status: Active Grant

• Current Assignee: Tridoniticatco GmbH & Company KG
• Original Assignee: Tridoniticatco GmbH & Company KG
• Inventors: Stevens, Frederick, Wallhead, Geoff, Mair, Alexander, Rohner, Daniel
• Granted Patent: US 8,680,778 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H02J 9/065 for lighting purposes
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An emergency-lighting device for operating a light-source, in particular an LED, comprises an energy storage unit, a charging circuit, to be supplied with a mains supply voltage (U_in), for charging the energy storage unit during charging operation, the charging circuit comprising a potential separation, and also a driver circuit, supplied by the energy storage unit during emergency-light operation, for operating the light-source. Furthermore a control unit is provided which is designed for monitoring the state of the mains supply voltage (U_in) during charging operation and, when an emergency condition is detected, for activating emergency-light operation, the control unit ascertaining the state of the mains supply voltage (U_in) on the basis of operating variables of the emergency-lighting device which are measured on the output side of the charging circuit.

Claims

1. A circuit for operating at least one LED, comprising:

a driver circuit with a coil and with a switch which is connected in series with the coil and clocked at a high frequency,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal to a control unit which ascertains the temporally averaged value of the current through the LED on the basis of the value of the registering signal at the end of the on-time cycle and also on the basis of the value at the end of the demagnetizing phase.

2. A circuit according to claim 1,

wherein the control unit adjusts the switching-frequency and/or the pulse duty factor in a manner depending at least on the registered temporal mean value of the current through the LED.

3. A circuit according to claim 1,

wherein for the purpose of dimming the LED the control unit superimposes a comparatively low-frequency modulation on the high-frequency timing of the switch, and/or

wherein, for the purpose of dimming, the mean value of the current through the LED is effected by adjustment of the pulse duty factor and/or of the switching-frequency of the switch which is clocked at a high frequency.

4. A circuit according to claim 3,

wherein the low-frequency modulation is a pulse-width modulation.

5. A circuit according to claim 1,

wherein the driver circuit is supplied from a battery and/or from an AC mains voltage.

6. A circuit according to claim 5,

comprising a unit for registering the battery-discharge current which is functionally connected to the control unit, wherein for the purpose of regulating the battery-discharge current the current through the LED is adjustable in a manner depending on the registered battery-discharge current.

7. A circuit according to claim 5,

wherein the battery is connected to a charging circuit supplied with mains voltage.

8. A circuit according to claim 7,

wherein the driver circuit dims the LED if the mean value of the mains voltage falls below a threshold value.

9. A circuit according to claim 7,

wherein the charging circuit comprises a flyback converter.

10. A circuit according to claim 9,

wherein the flyback converter is gated in pulsed manner if the mean value of the mains voltage falls below a threshold value.

11. A circuit according to claim 5, further comprising a circuit for registering the battery voltage.

12. A circuit according to claim 11,

wherein the current through the LED is adjustable in a manner depending on an output signal of the circuit for registering the battery voltage.

13. A circuit according to claim 5,

wherein the battery-charging current is registered.

14. A circuit according to claim 1,

wherein the control unit registers the LED voltage.

15. A circuit according to claim 1,

wherein the control unit carries out a test measurement of electrical parameters at start-up, to determine whether an LED or which LED is connected to the driver circuit.

16. A circuit according to claim 15,

wherein the control unit adjusts the operating current through the LED in a manner depending on the outcome of the test measurement.

17. A circuit according to claim 15,

wherein the test measurement comprises the application of a relatively small test current by appropriate triggering of the driver circuit and in the measuring of the resulting LED voltage.

18. A circuit according to claim 1,

wherein the control unit increases the LED current at start-up, by appropriate triggering of the switch of the driver circuit, from a low value to a stationary operating value.

25. An emergency-lighting device,

comprising a circuit according to claim 1.

19. A circuit for operating at least one LED, comprising:

a driver circuit with a coil and with a switch which is connected in series with the coil and clocked at a high frequency,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal to a control unit,

further comprising a unit for registering the battery-discharge current which is functionally connected to the control unit, wherein for the purpose of regulating the battery-discharge current the current through the LED is adjustable, in a manner depending on the registered battery-discharge current, by adjustment of the switching behavior of the switch of the driver circuit.

20. A circuit for operating at least one LED, comprising:

a driver circuit with a coil and with a switch which is connected in series with the coil and clocked at a high frequency, wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED, wherein in the demagnetizing-current path when the switch is open a current-registering means is provided,

further comprising a circuit for registering the battery voltage, wherein the current through the LED is adjustable, in a manner depending on an output signal of the circuit for registering the battery voltage, by adjustment of the switching behavior of the switch of the driver circuit.

21. A circuit for operating at least one LED, comprising:

a driver circuit with a coil and with a switch connected in series with the coil and clocked at a high frequency,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal to a control unit,

the control unit carrying out a test measurement of electrical parameters at start-up, in order to determine whether an LED or which LED is connected to the driver circuit.

22. A circuit according to claim 21,

wherein the control unit adjusts the operating current through the LED in a manner depending on the outcome of the test measurement.

23. A circuit according to claim 21,

wherein the test measurement comprises the application of a relatively small test current by appropriate triggering of the driver circuit and in the measuring of the resulting LED voltage.

24. A circuit for operating at least one LED, comprising:

a driver circuit with a coil and with a switch which is connected in series with the coil and clocked at a high frequency,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal to a control unit,

the control unit increasing the LED current at start-up, by appropriate triggering of the switch of the driver circuit, from a low value to a stationary operating value.

26. A process for ascertaining the current through an LED which is operated by a circuit that comprises:

a coil and a switch connected in series with the coil,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal,

wherein the temporally averaged value of the current through the LED is ascertained on the basis of the value of the registering signal at the end of the on-time cycle and also on the basis of the value at the end of the demagnetizing phase.

27. A process for operating an LED with a circuit that comprises:

a coil and a switch which is connected in series with the coil,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal,

wherein the LED is operated from a battery,

wherein the battery-discharge current is registered and for the purpose of regulating the battery-discharge current the current through the LED is adjusted, in a manner depending on the registered battery-discharge current, by adjustment of the switching behavior of the switch of the driver circuit.

28. A process for operating an LED with a circuit that comprises:

a coil and a switch which is connected in series with the coil,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal,

wherein the LED is operated from a battery,

wherein the battery voltage is registered and the current through the LED is adjusted, in a manner depending on an output signal of the circuit for registering the battery voltage, by adjustment of the switching behavior of the switch of the driver circuit.

29. A process for operating an LED with a circuit that comprises:

a coil and a switch which is connected in series with the coil,

wherein when the switch is closed the coil is magnetized and when the switch is open the coil demagnetized in the form of a current through the LED,

wherein in the demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal,

wherein the LED voltage is increased at start-up of the circuit, by appropriate triggering of the switch of the driver circuit, from a low value to a stationary operating value.