Operating circuit for LEDs, having dimming signal comprising high-frequency modulated pulse packet signal with harmonized frequencies

• US 9,433,041 B2
• Filed: 03/21/2013
• Issued: 08/30/2016
• Est. Priority Date: 03/21/2012
• Status: Active Grant

• Current Assignee: Tridonic GmbH & Co. KG (Zumtobel Group AG)
• Original Assignee: Tridonic GmbH & Co. KG (Zumtobel Group AG)
• Inventors: Mitterbacher, Andre, Keller, Ueli, Pereira, Eduardo
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): COOPER, JONATHAN G
• Application Number:
  US14/386,256
• Publication Number:
  US 20150084544A1
• Time in Patent Office: 1,258 Days
• Field of Search: 315/291, 315/294, 315/297, 315/307
• US Class Current: 1/1
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/327 Burst dimming
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

The invention relates to a method for activating at least one LED, which is supplied with a direct current voltage or a rectified alternating current voltage and which by means of a coil (L1) and a first switch (S1) clocked by a control/regulating unit (SR) provides a supply voltage for at least one LED, wherein when the first switch (S1) is switched on the coil (L1) temporarily stores energy that discharges via a diode (D1) and at least one LED when the first switch (S1) is switched off and wherein the control unit (SR) activates the first switch (S1) by means of a dimming signal. Said method is characterized in that the dimming signal is generated by externally combining a low-frequency signal and a high-frequency signal, wherein the pulse width (TON*LF) of the low-frequency signal is selected as an integral multiple of the cycle duration of the high-frequency signal.

Claims

1. An operating circuit for at least one LED, to which a DC voltage or rectified AC voltage is supplied, and which provides a supply voltage for at least one LED by means of a coil (L1) and a first switch (S1) clocked by a control unit (SR), wherein when the first switch (S1) is switched on, energy is buffer-stored in the coil (L1), which is discharged via a diode (D1) and via at least one LED when the first switch (S1) is switched off, the control unit (SR) actuates the first switch (S1) with a dimming signal, wherein the dimming signal is generated by linking of a low-frequency signal and a high-frequency signal, and wherein the operating circuit is arranged such that a pulse width (TON*LF) of the low-frequency signal, which is defined as a width of a pulse packet of the high-frequency, is selected as an integral multiple of the period (T_HF) of the high-frequency signal and wherein the operating circuit is arranged in order to generate the high-frequency signal dependent on a control loop, at least the first switch (S1) is clocked depending on at least one predefined reference value for a current and/or voltage within the operating circuit and a comparison with an actual value, the control unit (SR) is arranged to turn on the first switch when a zero crossing of the current through the coil (L1) occurs.

2. The operating circuit as claimed in claim 1, wherein the control unit (SR) links the low-frequency signal and the high-frequency signal internally to give the dimming signal, and outputs the dimming signal at an output of the control unit (SR).

3. The operating circuit as claimed in claim 2, wherein, during dimming of the LED, the frequency of the low-frequency signal is changed.

4. The operating circuit as claimed in claim 3, wherein the change in the frequency of the low-frequency signal is selected depending on the change in the pulse width (TON*LF) of the low-frequency signal.

5. The operating circuit as claimed in claim 2, wherein a change in the frequency and the pulse width (TON*LF) of the low-frequency signal is performed such that a pulse control factor of the low-frequency signal remains constant at a constant dimming level.

6. The operating circuit as claimed in claim 1, wherein the low-frequency signal is a low-frequency-pulsed signal, in the range of from 100 Hz to 1000 Hz.

7. The operating circuit as claimed in claim 1, wherein the high-frequency signal is a high-frequency-pulsed signal, in the region of 50 kHz.

8. The operating circuit as claimed in claim 1, wherein a change in a brightness of the LED is performed by a change in the frequency of the low-frequency signal.

9. The operating circuit as claimed in claim 1, wherein the low-frequency signal is dependent on at least one of the dimming level of the LED or the high-frequency signal is dependent on at least one of the current or the voltage through the LED.

10. A method for actuating at least one LED, to which a DC voltage or rectified AC voltage is supplied, and which provides a supply voltage for at least one LED by means of a coil (L1) and a first switch (S1) clocked by a control unit (SR), wherein, when the first switch (S1) is switched on, energy is buffer-stored in the coil (L1), which is discharged via a diode (D1) and via at least one LED when the first switch (S1) is switched off, wherein the control unit (SR) actuates the first switch (S1) with a dimming signal, the dimming signal is generated by external linking of a low-frequency signal and a high-frequency signal, wherein the operating circuit is arranged such that a pulse width (TON*LF) of the low-frequency signal, which is defined as a width of a pulse packet of the high frequency, is selected as an integral multiple of the period (T_HF) of the high-frequency signal and wherein the operating circuit is arranged in order to generate the high-frequency signal dependent on a control loop, at least the first switch (S1) is clocked depending on at least one predefined reference value for a current and/or voltage within the operating circuit and a comparison with an actual value, the control unit (SR) is arranged to turn on the first switch when a zero crossing of the current through the coil (L1) occurs.