METHOD FOR OPERATING AN LLC RESONANT CONVERTER FOR A LIGHT-EMITTING MEANS, CONVERTER, AND LED CONVERTER DEVICE

• US 20150077003A1
• Filed: 04/15/2013
• Published: 03/19/2015
• Est. Priority Date: 04/13/2012
• Status: Active Grant

• Current Assignee: Tridonic GmbH & Co. KG (Zumtobel Group AG)
• Original Assignee: Tridonic GmbH & Co. KG (Zumtobel Group AG)
• Inventors: Vonach, Christoph, Pereira, Eduardo
• Granted Patent: US 9,516,708 B2
• Time in Patent Office: Days
• US Class Current: 315/200.R
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/327 Burst dimming
• CPC Class Codes: H05B 45/36 Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI]
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An LLC resonant transformer (19) for a lamp (5) comprises a primary circuit (19) and a secondary side (30) galvanically isolated therefrom. During operation of the LLC resonant transformer (19), a first switch (21) and a second switch (22) of a half-bridge to which an LLC resonant circuit (25-27) of the primary circuit (19) is connected are actuated in a clocked fashion. A load (5) to which an output (35) on the secondary side (30) supplies energy is detected on the basis of a measured variable (iavg) acquired in the primary circuit (20). The half-bridge (21, 22) is variably controlled on the basis of the measured variable (iavg) that is acquired in the primary circuit (20) and indicates the load (5).

Claims

1. A method for operating an LLC resonant converter (19;

79) for a light-emitting means (3;

5;

50), wherein the LLC resonant converter (19;

79) has a primary-side circuit (20;

80), which comprises a half-bridge (21, 22) and an LLC resonant circuit (25-27), and a secondary side (13;

30) galvanically isolated therefrom, the method comprising;

controlling the half-bridge (21, 22) by clocked switching of switches (21, 22) of the half-bridge,

detecting a load (3;

5;

50), to which energy is supplied from an output (35) of the secondary side (13;

30), based on a measured variable (iavg) detected in the primary-side circuit (20;

80), and

adapting the control of the half-bridge (21, 22) on the basis of the measured variable (iavg) detected in the primary-side circuit (20;

80).

2. The method as claimed in claim 1, wherein the control of the half-bridge (21, 22) is adapted in such a way that a load-dependent shift in an output voltage (68) of the LLC resonant converter (19;

79) is at least partially compensated for.

3. The method as claimed in claim 2, wherein the adaptation of the control of the half-bridge (21, 22) comprises:

setting a frequency (93) at which a first switch (21) and a second switch (22) of the half-bridge are switched in clocked fashion.

4. The method as claimed in claim 3, wherein a control device (14) sets the frequency (93) automatically depending on the measured variable (iavg) using a table value query and/or by computer-based processing of the measured variable (iavg).

5. The method as claimed in claim 4, wherein at least one of the table value query or the computer-based processing is dependent on a load dependence of the output voltage (68) which occurs during permanent clocking of the half-bridge (21, 22).

6. The method as claimed in claim 1, wherein the measured variable (iavg) detected in the primary-side circuit (20;

80) is proportional to an average value of a current.

7. The method as claimed in claim 6, wherein the measured variable (iavg) detected in the primary-side circuit (20;

80) is proportional to an average value of a current through a resistor (23), which is connected between a switch (22) of the half-bridge and a reference potential.

8. The method as claimed in claim 6, wherein a peak value of the current (ipeak) is detected and an overcurrent protection operating mode for the light-emitting means (3;

5;

50) is initiated selectively depending on a threshold value comparison of the peak value (ipeak).

9. The method as claimed in claim 1, wherein a supply voltage (Vbus;

96) of the primary-side circuit (20;

80) is detected with time resolution, and wherein the control of the half-bridge (21, 22) is changed depending on a change in the supply voltage (Vbus;

96) over time.

10. The method as claimed in claim 9, wherein clocking (94) of the half-bridge (21, 22) is changed in time-dependent fashion, depending on a ripple of the supply voltage (Vbus;

96) of the primary-side circuit (20;

80).

11. The method as claimed in claim 1, wherein at least one of the following actions is implemented depending on the measured value (iavg):

power limitation;

fault detection for initiating a fault mode;

generation of a signal depending on the measured variable (iavg) and outputting of the signal to a signal bus (4).

16. A converter for a light-emitting means, comprising:

a primary-side circuit (20;

80) having a half-bridge (21, 22) and having an LLC resonant circuit (25-27),

a secondary side (13;

30), which is galvanically isolated from the primary-side circuit (20;

80) and which has an output (35) for supplying energy to the light-emitting means, and

a control device (14) for controlling the half-bridge (21, 22), wherein the control device is configured to detect a load (3;

5;

50) at the output (35) of the secondary side (13;

30) depending on a measured variable (iavg) detected in the primary-side circuit (20;

80) and to control the half-bridge (21, 22) in dependence thereon, which is configured for implementing the method as claimed in claim 2.

12. A converter for a light-emitting means, comprising:

a primary-side circuit (20;

80) having a half-bridge (21, 22) and having an LLC resonant circuit (25-27),

a secondary side (13;

30), which is galvanically isolated from the primary-side circuit (20;

80) and which has an output (35) for supplying energy to the light-emitting means, and

a control device (14) for controlling the half-bridge (21, 22), wherein the control device is configured to detect a load (3;

5;

50) at the output (35) of the secondary side (13;

30) depending on a measured variable (iavg) detected in the primary-side circuit (20;

80) and to control the half-bridge (21, 22) in dependence thereon.

13. The converter as claimed in claim 12, wherein the primary-side circuit (20;

80) has a resistor (23), which is connected in series with a switch (22) of the half-bridge, and wherein the control device (14) is configured to use an average value of the current through the resistor (23) or a variable proportional thereto as the measured variable (iavg) in order to at least partially compensate for a load-dependent shift in an output voltage of the converter (19;

79).

14. The converter as claimed in claim 13, wherein the control device (14) is configured to set a frequency (93) at which a first switch (21) and a second switch (22) of the half-bridge are switched in clocked fashion, depending on the measured variable (iavg).

15. The converter as claimed in claim 12, wherein the control device is configured to change clocking (90) of the half-bridge (21, 22) depending on a supply voltage (Vbus;

96) detected with time resolution of the primary-side circuit (20;

80).

17. An LED converter device, comprising the converter (19;

79) as claimed in claim 12, wherein the LED converter device (2) is configured as a constant voltage source.