Driver for driving a load, and corresponding LED-based lighting device and corresponding method of operating the driver

Abstract

A driver for driving a load, the driver comprising a power converter for converting an input into an output for powering the load, a controller for controlling the output of the power converter by controlling a control voltage on a communication line provided between the power converter and the controller, wherein the controller is arranged to control the control voltage within a predetermined control voltage range, wherein the power converter is further arranged to communicate from the power converter to the controller by controlling the control voltage on the communication line outside the predetermined control voltage range.

Description

Background Art

[0001] Typically, a driver is arranged to convert the mains voltage into a voltage and current suitable for driving a specific load, such as a load consisting of one or more light emitting diodes (LEDs). These drivers may be equipped with a switch mode power supply control integrated circuit (IC) utilizing a buck converter or any similar device.

[0002] The amount of power converted by the driver can be set by an external control signal, such as a pulse-width modulated or analog signal. The external control signal can be referred to as power conversion information content. The power conversion information content can be contained in the "high / low" ratio of a repetitive pulse-width modulated (PWM) signal, such as a 1 kHz signal. The power conversion information content can also be contained in an analog signal, such as an absolute magnitude voltage.

[0003] In any case, in a driver according to the present disclosure, three separate building blocks can be identified. The first building block is the power converter. Thus, the power converter can receive a mains supply voltage and can be arranged to convert the mains supply voltage into a specific power output suitable for driving a load. The load is identified as the second building block. The third building block is the controller itself. Thus, the controller controls the power conversion by directly controlling the power converter. Typically, these structural units are physically separate. The present invention is particularly applicable to situations where the controller and power converter are physically separate.

[0004] In some cases, for example, for safety reasons, the controller may need to receive information from the power converter regarding, for example, the mains input voltage. Unfortunately, this power control information is only "transmitted" using one-way communication (i.e., only from the controller to the power converter). Power converters are typically simple analog modules with no communication capabilities. Adding intelligent building blocks for, for example, two-way communication would increase both cost and complexity.

[0005] Therefore, there is a need to improve currently available drivers in that they are able to communicate from the power converter back to the controller in an uncomplicated manner. Summary of the Invention

[0006] It would be advantageous to implement a driver that can communicate from a power converter back to a controller in an uncomplicated manner.

[0007] It would also be desirable to achieve a light emitting diode (LED) based lighting device comprising an improved driver.

[0008] It would also be desirable to provide a method of operating the improved drive.

[0009] In order to better solve one or more of these problems, in a first aspect, a driver for driving a load is provided, the driver comprising:

[0010] a power converter for converting an input into an output for supplying power to a load; a controller for controlling the output of the power converter by controlling a control voltage provided on a communication line between the power converter and the controller, wherein the controller is arranged to control the control voltage within a predetermined control voltage range;

[0011] Wherein the power converter is further arranged to communicate from the power converter to the controller by controlling a control voltage of the communication line outside the predetermined control voltage range.

[0012] The inventors have found that there is usually a communication line between the controller and the power converter for transmitting the control voltage from the controller to the power converter. The voltage, more specifically the potential, on the communication line is usually within a predetermined control voltage range, for example, between 600mV and 1600mV.

[0013] When the control voltage is an analog voltage, it can be any voltage between 600 mV and 1600 mV. In the case of a PWM signal, the signal can alternatively switch between a high voltage level threshold (e.g., 1600 mV or close to 1600 mV) and a low voltage level threshold (e.g., 600 mV or close to 600 mV) at a certain duty cycle.

[0014] In any case, the inventors have discovered that there may be unassigned voltages / unassigned voltage ranges that can be utilized by the power converter for communication back to the controller. That is, for example, the power converter can pull the control voltage on the communication line below a low voltage level threshold, or can push the control voltage on the communication line above a high voltage level threshold. In this manner, the power converter can communicate back to the controller.

[0015] The power converter can be connected to an AC mains power source, or any other suitable power source. There are different types of power conversion, each suitable for use in a driver according to the present disclosure. For example, a half-wave rectifier allows only the positive portion of the AC mains voltage to pass, while blocking the negative portion. This is typically achieved using a single diode.

[0016] In another example, a full-wave rectifier converts the entire AC supply voltage to one constant polarity at its output. The positive portion of the AC supply voltage is allowed to pass through, and the negative portion of the AC supply voltage is converted to a positive portion. This can be achieved by using a bridge rectifier or by using two diodes combined with a switch.

[0017] Typically, a power converter includes a switched-mode power supply (SMS) for delivering output power to a load. A SMS has an integrated circuit (IC), which can be considered the brain of the SMS. The IC controls switches, such as field-effect transistors, with the switching rate of the switches determining the output of the power converter.

[0018] The communication line, and more specifically, the control voltage present on the communication line, may be used as an input to the IC for controlling the output of the converter.

[0019] As described above, the control voltage present on the communication line can be a PWM voltage signal, wherein the PWM voltage signal alternates between a high-level threshold and a low-level threshold at a specific duty cycle. Such a PWM voltage signal can be filtered, smoothed, or similarly processed at the power converter before being provided to the IC.

[0020] As described above, the control voltage signal present on the communication line may also be an analog voltage signal, wherein the analog voltage signal is controlled to be within a predetermined control voltage range, such as between a high-level threshold and a low-level threshold. Such an analog voltage signal may be filtered or otherwise processed at the power converter before being provided to the IC.

[0021] The controller may be powered by a DC power supply output by the power converter, or may be powered in any other manner. In any case, the controller is configured to control or set a desired output power to the load. The controller may also include, for example, a potentiometer for setting the desired output power. The controller may also include a wireless communication module, the wireless communication module being configured to receive a specific set point for the output power to the load, wherein the controller is configured to convert the received set point into a control voltage on the communication line.

[0022] The wireless communication module may for example be arranged to communicate via Wi-Fi, via Bluetooth or using any other known communication technology.

[0023] In addition, the wireless communication module can also be configured to transmit, i.e. communicate, itself. For example, information received from the power converter via the communication line can be transmitted to the outside world.

[0024] The controller may include any type of hardware, such as a microprocessor, a microcontroller, a field programmable gate array (FPGA), or any similar hardware. The controller may be powered by a power converter, or may be powered using an auxiliary power source such as a battery.

[0025] In one example, the driver comprises a communication line, and the controller comprises a control impedance connected to the communication line and is arranged to control the control impedance to control the control voltage within the predetermined control voltage range.

[0026] In another example, the power converter comprises a communicator impedance connected to the communication line and is arranged to control the communicator impedance to control the control voltage outside a predetermined control voltage range.

[0027] The above examples involve voltage dividers. A voltage divider is a circuit that is arranged to produce an output voltage that is a fraction of its input voltage. For example, a communication line can be connected to a supply voltage via a controlled impedance and can be connected to ground via a communicator impedance.

[0028] The control voltage, i.e., the voltage present on the communication line, can then be set by modifying either the control impedance or the communicator impedance. Typically, the controller modifies the control impedance to control the power converter. However, in cases where the power converter is intended to communicate back to the controller, the communicator impedance is modified by the power converter. The communicator impedance can cause the control voltage present on the communication line to be outside a predetermined control voltage range.

[0029] In another example, the controlled impedance comprises a first controlled impedance connected to a communication line and to a supply voltage, and comprises a switch connected in series with a second controlled impedance, wherein the switch and the second controlled impedance are placed in parallel with the first controlled impedance, and wherein the controller is arranged to control the switch to control the controlled impedance.

[0030] According to the above, the controller is arranged to control the output impedance (i.e., the controlled impedance) to two options: in a first option, the controlled impedance is equal to the first controlled impedance; in a second option, the controlled impedance is equal to the first controlled impedance cascaded with the second controlled impedance.

[0031] In another example, the power converter includes a communicator switch placed in parallel with the communicator impedance, wherein the power converter is arranged to control the switch to control the control voltage outside a predetermined control voltage range.

[0032] In one aspect of the present disclosure, the power converter includes a communicator impedance and a communicator switch placed in series with the communicator impedance, wherein the communicator impedance or the communicator switch is connected to the communication line, and wherein the power converter is arranged to control the switch to control the control voltage outside the predetermined control voltage range.

[0033] In another example, the controller is arranged to read a control voltage provided on a communication line between the power converter and the controller.

[0034] In a second aspect of the present disclosure, a lighting device based on a light emitting diode (LED) is provided, comprising:

[0035] at least one LED for emitting light;

[0036] The driver according to any example provided above, wherein the driver is arranged to drive a load being the at least one LED.

[0037] Note that the advantages and definitions disclosed with respect to the embodiments of the first aspect of the invention being a driver also correspond to the embodiments of the second aspect of the invention being an LED-based lighting device, respectively.

[0038] In one example, an LED-based lighting device includes an LED board having the at least one LED, and wherein the power converter is positioned at a first end of the LED-based lighting device, and wherein the controller is positioned at a second end of the LED, the second end being opposite the first end, and wherein the LED board is positioned between the power converter and the LED board.

[0039] In another example, the LED-based lighting device is an LED light tube.

[0040] The driver according to the present invention can be used in retrofit light-emitting diode (LED) lamps. LED lighting devices have been developed in the past, using LEDs for various lighting applications. Due to their long lifespan and high energy efficiency, LED lamps are now also being designed to replace traditional fluorescent lamps, i.e., for retrofit applications. For such applications, the retrofitted LED lamp is typically adapted to fit into the socket of the corresponding lamp being retrofitted. Furthermore, since lamp maintenance is typically performed by the user, the retrofitted LED lamp should ideally be easy to operate with any suitable lamp type, without requiring rewiring of the fixture.

[0041] According to the present disclosure, the retrofit LED lamp can be any one of a retrofit LED tube or a retrofit LED photoluminescent lamp. The retrofit LED tube is an alternative LED tube for fluorescent tubes, such as low-pressure mercury vapor gas discharge lamps that use fluorescence to generate visible light.

[0042] Typically, a ballast is used in conventional fluorescent lamps to limit the current through the lamp, which could otherwise rise to damaging levels due to negative differential resistance artifacts in the lamp's voltage-current characteristic. Different types of ballasts exist, such as electronic ballasts, high-frequency electronic ballasts, self-oscillating HF ballasts, magnetic ballasts, or digital ballasts.

[0043] Thus, a power converter according to the present disclosure may be connected to such a ballast and may be arranged to convert the output of the ballast into an output suitable for driving at least one LED of a retrofit LED lamp.

[0044] In a third aspect of the present disclosure, there is provided a method of operating a drive according to any one of the examples provided above, wherein the method comprises the following steps:

[0045] The controller controls the output of the power converter by controlling a control voltage provided on a communication line between the power converter and the controller within a predetermined control voltage range;

[0046] Communication is performed by the power converter by controlling the control voltage of the communication line to be outside a predetermined control voltage.

[0047] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A schematic diagram of a driver for driving a specific load is disclosed;

[0049] Figure 2 A schematic diagram of a modified light emitting diode (LED)-based lighting device according to the present disclosure is disclosed;

[0050] Figure 3 An example of an implementation of a driver according to the present disclosure is disclosed;

[0051] Figure 4 Another example of an implementation of a driver according to the present disclosure is disclosed. DETAILED DESCRIPTION

[0052] A detailed description of the drawings is given. Note that the same reference numerals in different figures indicate similar components or the same function of different components.

[0053] Figure 1 A schematic diagram of a driver 1 is shown, which drives a specific load 7, for example a load based on a light emitting diode LED.

[0054] A power converter 3 is provided for converting an input 2 to an output for powering a load 7. The power converter may receive the input 2 from alternating current AC, mains power, from any type of ballast, etc. The power converter 3 converts the input to an output based on power control information 6 received from a controller 5.

[0055] In the following, it is assumed that the load is an LED-based load. However, it should be noted that the present disclosure is not limited to LED-based loads. The concept can be applied to any type of load.

[0056] The power control information 6 may for example be directed to a specific dimming level of the LED load. Typically, the power control information 6 is within a predetermined control voltage range, wherein a high dimming factor is obtained at a low voltage threshold of the range, and wherein a low dimming factor is obtained at a high voltage threshold of the range.

[0057] The power control information 6 may also be an analog signal or a pulse width modulated PWM signal. In the case of a PWM signal, the signal alternates between a low voltage threshold of the range and a high voltage threshold of the range, wherein the duty cycle of the PWM signal provides the desired dimming level to be achieved.

[0058] Finally, a power line 4 is provided between the power converter 3 and the controller for voltage reference purposes.

[0059] Figure 2 A schematic diagram of a modified light emitting diode (LED) based lighting device 21 according to the present disclosure is disclosed.

[0060] Note that drivers according to the present disclosure are particularly suitable for retrofitting LED-based lighting devices. Retrofitting LED-based lighting devices are devices that fit into the socket of a corresponding lamp being retrofitted. Typically, retrofitting LED-based lighting devices are designed to replace traditional fluorescent lamps, such as fluorescent tubes. As such, the connectors 22, 27 of the retrofitted LED tube can be placed in the same location and have the same dimensions as the connectors of the lamp they are retrofitting.

[0061] Figure 2 The invention relates to a retrofitted LED-based lighting tube 21 , ie a lighting device having an elongated shape. The retrofitted LED-based lighting tube 21 comprises a housing 23 , which includes a power converter 24 , an LED load 25 and a controller 26 .

[0062] The power converter 24 is typically located at a first end of the LED-based lighting tube 21, and the controller is typically located at a second end of the LED-based lighting tube 21, opposite the first end. An LED load 25 is located between the power converter 24 and the controller 26. The LED load 25 itself also has an elongated shape. Therefore, the power converter 24 and the controller 26 are physically separate.

[0063] The length of the LED-based lighting tube 21, i.e. in the elongated direction, may be between 20 cm and 120 cm, and more preferably between 40 cm and 80 cm. The tube may have a circular cross-section, wherein the diameter of the cross-section may be between 10 mm and 50 mm, and preferably between 20 mm and 30 mm.

[0064] It is foreseeable that in some cases, for example for safety reasons, the controller 26 may need to receive information from the power converter 24. Such information may relate to the mains input voltage. The controller 26 may use this information to improve the power control information sent to the power converter 24.

[0065] According to the present disclosure, the communication line 29 between the controller 26 and the power converter 24 is used in two ways. The communication line 29 is used to transmit power control information from the controller 26 to the power converter 24. This power control information is transmitted in the form of a control voltage, where the control voltage is controlled by the controller within a predetermined control voltage range, for example, between 600 mV and 1600 mV.

[0066] The present disclosure relates to the concept that the power converter 24 can also communicate back to the controller 26. To do so, the power converter 24 is arranged to control the control voltage present on the communication line to be outside a predetermined control voltage range. That is, the power converter overrides the control voltage set on the communication line 29.

[0067] The power converter can, for example, connect the communication line 25 directly to ground, so that the control voltage present on the communication line 29 is 0 V. Another option is that the power converter ensures that the communication line 25 becomes floating. Figure 3 and Figure 4 Explain both options.

[0068] Note that the protocol used to communicate from the power converter 24 to the controller can be based on an existing known protocol. For example, the DALI protocol may be suitable. The power converter 24 and the controller 26 can therefore have an open or standardized interface between them. This allows for interchangeability of the controller and the power converter.

[0069] Figure 3 and 4 An example of an implementation of a driver according to the present disclosure is disclosed.

[0070] Note that both implementations involve a controlled impedance output of the controller that enables third level communication on the communication line controlled by the power converter back to the controller.

[0071] Figure 3 Relating to a first implementation, here the controller may be arranged to generate a PWM signal, PWM_out, which controls the resistors R2, R3 and the R1 resistor divider network.

[0072] A "low" signal at PWM_out will put the controller's transistor into the on-state and will cause R2 to be connected in parallel across R3, causing the voltage at the digital PWM (ie DPWM) to go into the "high" state.

[0073] A "high" signal at PWM_out and an applied supply voltage of 3.3V will result in a non-conducting state of the controller's transistors. Thus, the voltage divider network comprising resistor R3 and resistor R1 brings the voltage at the digital PWM (i.e., DPWM) to a "low" state.

[0074] By controlling the duty cycle of the PWM_out signal, the output of the power converter can be controlled.

[0075] The circuitry around switch J1 of the power converter is arranged to control switch J1. For example, when the mains voltage drops, this will be indicated at the resistor divider R4 / R5, changing switch J1 from a blocking state to a normally conducting state, thereby reducing the voltage at the DPWM to ground.

[0076] Due to the fact that the 1-bit feedback signal is at the same level as the DPWM signal, the 1-bit feedback signal will also be set to ground, which can be sensed by the controller. That is, the controller is arranged to sense that the control voltage on the communication line is outside a predetermined control voltage range.

[0077] This particular embodiment therefore relates to the case where a drop in mains supply voltage is communicated from the power converter to the controller. Note that any type of information may be communicated from the power converter to the controller.

[0078] It should be noted that this particular example relates to transmitting information about the mains supply voltage back to the controller. Other information may also be transmitted, such as overheating of any component of the power converter, or failure of any component of the power converter, or any similar information.

[0079] In addition, communications may include Figure 3 and 4 1-bit communication is shown, but other types of communication principles can also be included. The unused voltage range can be used in an analog manner to transmit information back to the controller. Another option is that the 1-bit communication can be used as a kind of Morse code to transmit information.

[0080] Figure 4 The shown implementation can be explained as follows. Figure 4 The controller aspects of the shown implementation are in principle equivalent to Figure 3 Controller aspects of the implementation shown.

[0081] Figure 3 The implementation shown is similar to Figure 3 The main difference between the illustrated implementations lies in the power converter. More particularly, the invention relates to the way in which the power converter controls the control voltage outside a predetermined control voltage range.

[0082] exist Figure 3In , the switch J1 is arranged to short-circuit the resistor R1 so that the control voltage at the communication line is equal to the supply voltage. Figure 3 In the example, switch M1 is normally closed, so that resistor R1 is directly connected to the communication line. In the event that the power converter wants to communicate back to the controller, it can deactivate switch M1, causing the communication line to become floating. The control voltage on the communication line will be equal to the controller's 3.3V, which is also outside the predetermined control voltage range.

[0083] Other variations of the disclosed embodiments may be understood and implemented by those skilled in the art in practicing the claimed invention by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may perform the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or solid-state medium provided with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. Any reference signs in the claims should not be construed as limiting their scope.

Claims

1. A driver for driving a load, the driver comprising: a power converter for converting an input into an output for supplying power to the load; a controller for controlling the output of the power converter by controlling a control voltage provided on a communication line between the power converter and the controller, wherein the controller is arranged to control the control voltage within a predetermined control voltage range; Wherein the power converter is further arranged for communicating from the power converter to the controller by overwriting the control voltage on the communication line outside the predetermined control voltage range.

2. The driver of claim 1 , wherein the driver comprises the communication line, and wherein: The controller comprises a control impedance connected to the communication line and is arranged to control the control impedance to control the control voltage within the predetermined control voltage range.

3. A driver according to any one of the preceding claims, wherein the driver comprises the communication line, and wherein: The power converter comprises a communicator impedance connected to the communication line and is arranged for controlling the communicator impedance for controlling the control voltage outside the predetermined control voltage range.

4. The driver of claim 2, wherein the driver comprises the communication line, and wherein: The controlled impedance comprises a first controlled impedance (R3) connected to the communication line and to a supply voltage, and comprises a switch connected in series with a second controlled impedance (R2), wherein the switch and the second controlled impedance (R2) are placed in parallel with the first controlled impedance (R3), and wherein the controller is arranged to control the switch to control the controlled impedance.

5. The driver according to claim 3, wherein: The power converter comprises a communicator switch (J1) placed in parallel with the communicator impedance (R1), wherein the power converter is arranged to control the switch (J1) to control the control voltage outside the predetermined control voltage range.

6. The driver according to claim 3, wherein: The power converter comprises a communicator impedance (R1) and a communicator switch placed in series with the communicator impedance (R1), wherein the communicator impedance (R1) or the communicator switch is connected to the communication line, and wherein the power converter is arranged to control the switch to control the control voltage outside the predetermined control voltage range.

7. A driver according to any preceding claim, wherein the controller is arranged to read out the control voltage on the communication line provided between the power converter and the controller.

8. A lighting device based on a light emitting diode (LED), comprising: at least one LED for emitting light; The driver according to any one of claims 1 to 7, wherein the driver is arranged to drive a load as the at least one LED.

9. The LED-based lighting device of claim 8 , wherein the LED-based lighting device comprises an LED board having the at least one LED, and wherein the power converter is positioned at a first end of the LED-based lighting device, and wherein the controller is positioned at a second end of the LED-based lighting device, the second end being opposite the first end, and wherein the LED board is positioned between the power converter and the LED board.

10. The LED-based lighting device according to any one of claims 8-9, wherein the LED-based lighting device is an LED light tube.

11. A method of operating a drive according to any one of claims 1 to 7, wherein the method comprises the following steps: controlling, by a controller, the output of the power converter by controlling the control voltage on the communication line provided between the power converter and the controller within a predetermined control voltage range; The power converter performs communication by overwriting the control voltage of the communication line beyond the predetermined control voltage.

Images