Lamp driver for an LED lamp and method for controlling an LED lamp

Abstract

Lamp driver (10) for an LED lamp (1), comprising a voltage input terminal (101) designed to connect the lamp driver to a power source, a boost converter circuit (120) connected to the voltage input terminal (101), a voltage output terminal (102) adapted to connect an LED (11) to the lamp driver (10), and a shutdown circuit (140) for providing a shutdown signal, which is connected to the voltage input terminal (101) to detect an input voltage of the voltage input terminal (101), and which is connected to the boost converter circuit (120) to control at least one active component (1201) of the boost converter (120), wherein the shutdown circuit (140) is arranged to switch off the boost converter circuit (120) when a shutdown voltage is detected at the voltage input terminal (101), wherein the voltage output terminal (102) still provides an operating voltage for the LED (11) during the switch-off of the boost converter circuit (120), wherein the lamp driver (10) further comprises a step-down converter circuit (130) connected to the boost converter circuit (120) and connected to the voltage output terminal (102),wherein the step-down converter circuit is arranged in series and between the step-up converter circuit and the voltage output terminal.,

Description

Technical area

[0001] The present invention relates to a lamp driver for an LED lamp and an LED lamp containing such a lamp driver. background

[0002] LED lamps are well-known and widely used lighting devices as efficient alternatives to incandescent bulbs.

[0003] However, currently available LED lamp drivers pass the electromagnetic interference (EMC) test for either conventional ballasts or electronic ballasts. Therefore, the operating range of currently available LED lamp drivers is limited.

[0004] To solve this problem, especially when the LED lamp is connected to a conventional ballast, large-value capacitors can be used, which generally results in larger capacitor sizes and higher costs. However, this is disadvantageous for LED technology. Regarding the electronic ballast, they require a resistive load, and if the driver has a large input capacitor, this is incompatible with the electronic ballast.

[0005] This means that currently available LED lamp drivers, especially MR16 lamps, can work correctly with either a conventional ballast or an electronic ballast.

[0006] US 8,680,784 B2 describes a dimmable LED driver with an input interface, a sensor coupled to the power source and dimmer for detecting a voltage drop caused by the dimmer, and a control circuit for generating a control signal from the voltage signal to control the LED driver. US 2011 / 0248640 A1 describes a lighting device with an LED array, wherein the LED array comprises a switch array comprising one or more controllable switches for modifying a topology of the LED array. Description of the invention

[0007] In view of the above-described disadvantages of currently known LED lamps, it is an object of the present invention to provide a lamp driver for an LED lamp that is suitable for both a conventional ballast and an electronic ballast. A further object of the present invention is to provide an LED lamp for operation with both a conventional ballast and an electronic ballast.

[0008] This object is achieved by a lamp driver and an LED lamp according to the independent claims. Preferred embodiments are specified by the dependent claims, the description, and the drawings.

[0009] Accordingly, a lamp driver for an LED lamp is specified.The lamp driver comprises a voltage input terminal configured to connect the lamp driver to a power source, a boost converter circuit connected to the voltage input terminal, a voltage output terminal configured to connect an LED to the lamp driver, a shutdown circuit for providing a shutdown signal, connected to the voltage input terminal to detect an input voltage of the voltage input terminal, and connected to the boost converter circuit to control at least one active component of the boost converter, wherein the shutdown circuit is arranged to switch off the boost converter circuit when a shutdown voltage is detected at the voltage input terminal, wherein the voltage output terminal still provides an operating voltage for the LED during the switch-off of the boost converter circuit.The lamp driver further comprises a buck converter circuit connected to the boost converter circuit and connected to the voltage output terminal, the buck converter circuit being arranged in series and between the boost converter circuit and the voltage output terminal.

[0010] The voltage input terminal of the lamp driver is designed to connect the lamp driver to a power source, in particular via a conventional ballast or an electronic ballast. Preferably, the power source itself is a lampholder.

[0011] Furthermore, the voltage input terminal is connected to the boost converter circuit, which provides a voltage at the voltage output terminal. Therefore, the boost converter circuit provides a voltage at the voltage output terminal, preferably via a buck converter.

[0012] The lamp driver's shutdown circuit comprises two connections: one for sensing an input voltage at the lamp driver's voltage input terminal and one for controlling the boost converter, specifically the boost converter's active component. Thus, the boost converter is controlled by the shutdown circuit based on the voltage at the voltage input.

[0013] The shutdown circuit itself is configured to shut down the boost converter whenever a shutdown voltage is present at the voltage input terminal. A shutdown signal can be used for this purpose, e.g., to shut down the active component of the boost converter, so that the boost converter becomes inactive upon the shutdown signal.

[0014] The boost converter itself may comprise a normal boost converter structure, e.g. at least one transistor with the function of boosting voltage.

[0015] Furthermore, the boost converter is designed so that an operating voltage is still provided at the voltage output terminal during shutdown. Therefore, the boost converter includes at least one branch that is active, even during shutdown due to a shutdown signal from the shutdown circuit. For example, the boost converter is a two-terminal network comprising an upper branch and a lower branch, where the upper branch and the lower branch are connectable via a transistor. In this case, the boost converter has two functions, depending on the state of the transistor. When the transistor is on, the boost converter is on, and when the transistor is off, the boost converter is off or turned off.

[0016] Therefore, the proposed arrangement enables two states: a first state in which the lamp driver is capable of operating correctly with a conventional ballast, and a second state in which the lamp driver is capable of operating correctly with an electronic ballast. In particular, the proposed lamp driver passes EMC testing with both a conventional ballast and an electronic ballast. Furthermore, no large-value capacitances or capacitors are required. Therefore, a small and inexpensive lamp driver is created that solves the aforementioned technical problems.

[0017] In a preferred embodiment, a second converter can be used to control the LED current. The second converter can be arranged between the boost converter and the LED to provide a constant LED current. The second converter can be a buck converter or a converter of any other topology capable of providing a constant LED current.

[0018] According to at least one embodiment of the lamp driver, the boost converter circuit comprises at least one transistor which is controlled by the turn-off circuit via the turn-off signal and which is arranged to turn off the boost converter circuit.

[0019] The boost converter may also comprise a plurality of transistors controlled by the shutdown circuit, e.g., by a single shutdown signal or a plurality of different shutdown signals. However, the transistor or transistors are arranged to shut down the boost converter, in particular the boost function of the boost converter.

[0020] According to at least one embodiment of the lamp driver, the boost converter circuit comprises at least one inductor that is operative during turn-off to provide the operating voltage for the LED.

[0021] For example, the boost converter is a two-port network comprising an upper branch and a lower branch, the upper branch and the lower branch being connectable via a transistor. In this case, the inductor is preferably arranged in the upper branch, which is operational during normal operation and during shutdown. Therefore, the upper branch comprising the inductor is operational regardless of the state of the transistor connecting the upper and lower branches. Therefore, the inductor is operational even during shutdown of the boost converter. Thus, the inductor is operational during both states of the boost converter's transistor.

[0022] Therefore, a dual use of an inductor is proposed, in particular to overcome the technical problems described above.

[0023] According to at least one embodiment of the lamp driver, the lamp driver further comprises a buck converter circuit connected to the boost converter and connected to the voltage output terminal.

[0024] Preferably, the buck converter circuit is arranged in series and between the boost converter circuit and the voltage output terminal. Therefore, the buck converter circuit is always in operation, regardless of the state of the transistor of the boost converter circuit or the state of the boost converter itself, due to the fact that the boost converter includes a branch that is always in operation.

[0025] Therefore, the lamp driver comprises at least one boost converter circuit and one buck converter circuit, wherein the buck converter circuit is connected behind the boost converter circuit, and wherein the boost converter is controllable via the shutdown circuit having an on-state and an off-state, wherein the buck converter is in operation during the off-state of the boost converter circuit and is in operation during the on-state of the boost converter circuit.

[0026] According to at least one embodiment of the lamp driver, the buck converter circuit comprises at least one capacitance or capacitor, and during turn-off of the boost converter circuit, the at least one capacitor and the at least one inductor of the boost converter circuit, which is in operation during turn-off, form an LC filter against electromagnetic interference.

[0027] Therefore, during the turn-off of the boost converter circuit, a part of the boost converter circuit, in particular the inductor, and a part of the boost converter circuit, in particular the capacitor, form an LC circuit, in particular an LC filter against electromagnetic interference.

[0028] Therefore, the inductor of the boost converter circuit and the capacitor of the boost converter circuit are arranged and designed to form an LC filter during turn-off of the boost converter circuit, in particular for connecting the lamp driver to an electronic ballast and a conventional ballast.

[0029] According to at least one embodiment of the lamp driver, the shutdown circuit further comprises a detection circuit for detecting the input voltage of the voltage input terminal.

[0030] Preferably, the detection circuit is arranged to detect a voltage at the voltage input terminal, for example by comprising a measuring circuit.

[0031] According to at least one embodiment of the lamp driver, the shutdown circuit further comprises a control circuit for providing the shutdown signal to switch off the boost converter circuit.

[0032] For this purpose, the control circuit receives a voltage signal of the input voltage through the detection circuit and compares this voltage value with a predetermined setpoint value, and if the received voltage value exceeds the predetermined setpoint value, a shutdown signal is provided to switch off the boost converter circuit, in particular by switching off the active component of the boost converter circuit, in particular the transistor of the boost converter circuit, which is controlled by the shutdown circuit.

[0033] Furthermore, an LED lamp is specified. The LED lamp comprises a lamp driver as described above and at least one LED connected to the voltage output terminal of the lamp driver. This means that all features disclosed for the lamp driver are also disclosed for the LED lamp, and vice versa.

[0034] The LED can therefore be operated with a conventional ballast and an electronic ballast.

[0035] Furthermore, a method for controlling an LED lamp is provided, comprising at least one boost converter circuit. The method comprises the following steps: detecting an input voltage of the LED lamp, comparing the detected input voltage with a predetermined target voltage, and switching off the boost converter circuit based on the comparison of the detected input voltage with the predetermined target value, so that at least one component of the boost converter is still in operation. Short description of the drawings

[0036] Preferred embodiments of the invention are explained below with reference to the drawings. Fig. 1A shows an example embodiment of the lamp driver connected to an electronic ballast and an LED. Fig. 1B shows an example embodiment of the lamp driver connected to a conventional ballast and an LED. Fig. 2 shows an exemplary embodiment of a lamp driver 10. Fig. 3 shows another exemplary embodiment of the lamp driver 10. Detailed description of the invention

[0037] Preferred embodiments of the invention are described below with reference to the drawings. Elements that are identical or similar, or have an identical or similar effect, are provided with the same reference numerals in the figures. Repetition of the description of such elements can be omitted to avoid redundant descriptions.

[0038] The figures and the proportions of the elements depicted in the figures should not be considered to scale. Rather, individual elements may be exaggerated to facilitate better representation and / or understanding.

[0039] Fig. 1A shows, by way of example, the typical structure of an embodiment of a lamp driver connected to an electronic ballast, in particular a lamp driver 10 of an LED lamp 1.

[0040] The electronic ballast 2 is connected to the lamp driver 10, which is connected to at least one LED 11.

[0041] The electronic ballast 2 can be connected to a power source, e.g., a socket (not shown). Furthermore, the electronic ballast 2 includes an EMC filter 21 and an electromagnetic circuit 22 to ensure that the LED lamp passes the EMC test.

[0042] The lamp driver 10 is connected to the electronic ballast 2 via the voltage input terminal 101 and is connected to the LED 11 via the voltage output terminal 102.

[0043] The LED 11 is at least one LED or a plurality of LEDs.

[0044] Fig. 1B shows, by way of example, the typical structure of an embodiment of a lamp driver connected to a conventional ballast, in particular a lamp driver 10 of an LED lamp 1.

[0045] The conventional ballast 3 is connected to the lamp driver 10, which is connected to at least one LED 11.

[0046] The conventional ballast 3 can be connected to the power supply, e.g., a socket (not shown). Furthermore, the conventional ballast 3 includes a transformer to ensure that the LED lamp passes the EMC test.

[0047] The lamp driver 10 is connected to the electronic ballast 2 via the voltage input terminal 101 and is connected to the LED 11 via the voltage output terminal 102.

[0048] With reference to Fig. 1A and Fig. 1B and the background of the invention, currently available LED lamp drivers pass the electromagnetic interference test (EMC test) either for conventional ballasts or for electronic ballasts.

[0049] Fig. 2 shows an exemplary embodiment of a lamp driver 10 connected to a plurality of LEDs 11.

[0050] The lamp driver 10 includes a voltage input terminal 101 configured to connect the lamp driver to a power source. The power source may include the electronic ballast or the conventional ballast, or the electronic ballast or the conventional ballast may be part of a lamp including such a lamp driver 10.

[0051] The lamp driver 10 further comprises a diode bridge 110 which is designed to provide an operating voltage for the boost converter circuit 120.

[0052] The boost converter circuit 120 includes at least one transistor 121, which is controlled by the shutdown circuit 140 via the shutdown signal and is arranged to turn off the boost converter circuit 120. Preferably, the transistor 121 is a MOSFET. Furthermore, the boost converter circuit 120 includes at least one inductor 1202, which is operative during the shutdown of the boost converter circuit 120.

[0053] The lamp driver 10 further comprises a buck converter circuit 130 which is connected to the boost converter circuit 120 and which is connected to the voltage output terminal 102.

[0054] The buck converter circuit 130 includes at least one capacitor 1301, and during turn-off of the boost converter circuit, the at least one capacitor 1301 and the at least one inductor of the boost converter circuit that is in operation during turn-off 121 form an LC filter for electromagnetic interference.

[0055] Furthermore, the lamp driver 10 comprises a shutdown circuit 140.

[0056] The shutdown circuit 140 is arranged to detect an input voltage at the voltage input terminal 101 and is arranged to provide a shutdown signal to the at least one transistor 121 of the boost converter circuit 1201 in order to switch off the boost converter circuit 1201 due to a shutdown voltage at the voltage input terminal 101. Therefore, the shutdown circuit 140 is arranged to control the at least one active component 121 of the boost converter. In particular, the shutdown circuit 140 is arranged to switch off the boost converter circuit 120 when a shutdown voltage is detected at the voltage input terminal 101, wherein the voltage output terminal 102 still provides an operating voltage for the LED 11 during the switch-off of the boost converter circuit 120.

[0057] In particular, the boost converter circuit 120 is used to obtain good compatibility with an electronic ballast, and / or the boost stage of the boost converter circuit 120 can be turned off without affecting the buck converter circuit 130.

[0058] Therefore, a dual use of an inductor 1202 is proposed, and thus Fig. 2 shows a lamp driver 10 with two states: a first state in which the lamp driver 10 is capable of operating correctly with a conventional ballast, and a second state in which the lamp driver 10 is capable of operating correctly with an electronic ballast. In particular, the proposed lamp driver 10 passes the EMC test with both a conventional ballast and an electronic ballast. Furthermore, no large-value capacitors are required. Therefore, a small and inexpensive lamp driver is provided that solves the above-mentioned technical problems.

[0059] Fig. 3 shows another exemplary embodiment of a lamp driver 10 connected to a plurality of LEDs 11.

[0060] The lamp driver 10 includes a voltage input terminal 101 configured to connect the lamp driver to a power source. The power source may include the electronic ballast or the conventional ballast, or the electronic ballast or the conventional ballast may be part of a lamp including such a lamp driver 10.

[0061] The lamp driver 10 further comprises a diode bridge 110 with a first, a second, a third, and a fourth diode 1101, 1102, 1103, 1104 arranged to provide an operating voltage for the boost converter circuit 120. Furthermore, the diode bridge 110 is grounded via the ground terminal 1105.

[0062] The boost converter circuit 120 includes at least one transistor 1201 controlled by the shutdown circuit 140 via the shutdown signal and arranged to turn off the boost converter circuit 120. Furthermore, the boost converter circuit 120 includes at least one inductor 1202, a resistor 1203, and a diode 1204 that are operative during the turn-off of the boost converter circuit 120.

[0063] The lamp driver 10 further comprises a buck converter circuit 130 connected to the boost converter circuit 120 and connected to the voltage output terminal 102. The buck converter circuit 130 includes at least one capacitor 1301, and during turn-off of the boost converter circuit, the at least one capacitor 1301 and the at least one inductor of the boost converter circuit, which is operational during turn-off 121, form an LC filter for electromagnetic interference.

[0064] Furthermore, the lamp driver 10 comprises a shutdown circuit 140.

[0065] The shutdown circuit 140 includes a detection circuit 1401 for detecting an input voltage at the voltage input terminal 101 and a control circuit 1402 for providing a shutdown signal to the transistor 121 of the boost converter circuit 121 to turn off the boost converter circuit 121 due to a shutdown voltage at the voltage input terminal 101.

[0066] The detection circuit 1401 includes a diode D1, a resistor R1, another resistor R2, and a capacitor C1. The diode D1 is connected in series with the resistor R1, which is connected in series with the resistor R2 and the capacitor C1, which are connected in parallel.

[0067] The control circuit 1402 includes a transistor Q1, another transistor Q2, a resistor R3, and another resistor R4. Resistor R3 is connected to the base of transistor Q1 and the collector of transistor Q2, and resistor R4 is connected to the base of transistor Q2. Therefore, transistor Q2 operates as a switch. Specifically, when the detection circuit 141 detects that the lamp driver is connected to an electronic ballast via the input voltage at the input terminal of the lamp driver 101, transistors Q1, Q2 are turned on, and the boost converter circuit 120 is turned on. When the detection circuit 141 detects that the lamp driver is connected to a conventional ballast via the input voltage at the input terminal of the lamp driver 101, transistors Q1, Q2 are turned off, and the boost converter circuit 120 is turned off or in the shutdown process.When the boost converter circuit 120 is off, the inductor 1202 is in operation, but the boost converter circuit does not boost the input voltage.

[0068] As a result, the lamp driver 10 will pass the EMC test with both the electronic ballast and the conventional ballast. Furthermore, the provided lamp driver does not affect the performance of the lamp or the LEDs. Furthermore, no other EMC components are required, so the cost of the provided lamp driver is comparatively low.

[0069] Therefore, the shutdown circuit 140 is arranged to control the at least one active component 121 of the boost converter. In particular, the shutdown circuit 140 is arranged to shut down the boost converter circuit 120 when a shutdown voltage is detected at the voltage input terminal 101, wherein the voltage output terminal 102 still provides an operating voltage for the LED 11 during the shutdown of the boost converter circuit 120.

[0070] Preferably, the lamp driver 10 comprises a controller 150 arranged at the voltage output terminal 120 to control the voltage provided by the buck converter circuit 130. List of reference symbols 1 LED lamp 2 electronic ballast 3 conventional ballast 10 lamp drivers 101 Voltage input terminal 102 Voltage output terminal 110 Diode bridge 1101 first diode of the diode bridge 1102 second diode of the diode bridge 1103 third diode of the diode bridge 1104 fourth diode of the diode bridge 1105 Grounding 120 boost converter circuit 1201 transistor of the boost converter circuit 1202 Inductor of the boost converter circuit 1203 Boost converter circuit resistance 1204 diode of the boost converter circuit 130 buck converter circuit 1301 capacitor of the buck converter circuit 140 shutdown circuit 141 Detection circuit of the shutdown circuit 142 Control circuit of the shutdown circuit 150 Lamp driver control 11 variety of LEDs C1 Capacitor of the detection circuit D1 diode of the detection circuit R1 first resistor of the detection circuit R2 second resistor of the detection circuit R3 first resistor of the control circuit R4 second resistor of the control circuit Q1 first transistor of the control circuit Q2 second transistor of the control circuit

Claims

[1] Lamp driver (10) for an LED lamp (1), comprising a voltage input terminal (101) designed to connect the lamp driver to a power source, a boost converter circuit (120) connected to the voltage input terminal (101), a voltage output terminal (102) adapted to connect an LED (11) to the lamp driver (10), and a shutdown circuit (140) for providing a shutdown signal, which is connected to the voltage input terminal (101) to detect an input voltage of the voltage input terminal (101), and which is connected to the boost converter circuit (120) to control at least one active component (1201) of the boost converter (120), wherein the shutdown circuit (140) is arranged to switch off the boost converter circuit (120) when a shutdown voltage is detected at the voltage input terminal (101), wherein the voltage output terminal (102) still provides an operating voltage for the LED (11) during the switch-off of the boost converter circuit (120), wherein the lamp driver (10) further comprises a step-down converter circuit (130) connected to the boost converter circuit (120) and connected to the voltage output terminal (102),wherein the step-down converter circuit is arranged in series and between the step-up converter circuit and the voltage output terminal., [2] The lamp driver (10) of claim 1, wherein the boost converter circuit (120) comprises at least one transistor (1201) controlled by the turn-off circuit (140) via the turn-off signal and arranged to turn off the boost converter circuit (120). [3] Lamp driver (10) according to claim 1 or 2, wherein the boost converter circuit (120) comprises at least one inductor (1202) which is operative during turn-off to provide the operating voltage for the LED (11). [4] Lamp driver (10) according to claim 1 or 3, wherein the buck converter circuit (130) comprises at least one capacitor (1301) and wherein during the turn-off of the boost converter circuit (120), the at least one capacitor (1301) and the at least one inductor (1202) of the boost converter circuit (120) which is in operation during the turn-off form an LC filter against electromagnetic interference. [5] The lamp driver (10) according to claim 1 or 2, wherein the shutdown circuit (140) further comprises a detection circuit (141) for detecting the input voltage of the voltage input terminal (101). [6] The lamp driver of claim 1 or 2, wherein the shutdown circuit (140) further comprises a control circuit (142) for providing the shutdown signal to turn off the boost converter circuit (120). [7] Lamp (1) comprising at least one lamp driver (10) according to claim 1 or 2, wherein at least one LED (11) is connected to the voltage output terminal (102) of the lamp driver (10). [8] Method for controlling an LED lamp (1) with a lamp driver (10) according to one of claims 1 to 6, comprising the following steps: - Detecting an input voltage of the LED lamp (1), - Comparing the detected input voltage with a specified target voltage, - Switching off the boost converter circuit (120) based on the comparison of the detected input voltage with the predetermined target value so that at least one component (1202) of the boost converter (120) is still in operation.

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