DRIVER FOR DRIVING A LOAD, AND CORRESPONDING LED-BASED LIGHTING DEVICE, AND CORRESPONDING METHOD OF OPERATING THE DRIVER - Patent application

Abstract

The present invention provides a driver for driving a load, comprising a power converter for converting an input into an output for powering the load, and a controller for controlling the output of the power converter by controlling a control voltage in a communication line provided between the power converter and the controller, the controller being configured to control the control voltage to be within a predetermined control voltage range, the power converter further being configured to communicate from the power converter to the controller by controlling the control voltage in the communication line to be outside the predetermined control voltage range.

Description

[Technical Field]

[0001] The present invention relates to a driver for driving a load, as well as to a corresponding LED-based lighting device and a corresponding method of operating said driver. [Background technology]

[0002] Typically, drivers are configured to convert a mains voltage into a voltage and current suitable for driving a particular load, for example, a load consisting of one or more light emitting diodes (LEDs). These drivers may include a switched mode power supply control integrated circuit (IC) that utilizes a buck converter or the like.

[0003] The amount of power converted by the driver may be set by an external control signal, for example, in a pulse width modulated or analog manner. The external control signal may be referred to as power conversion information content. The power conversion information content may be contained in a "high / low" ratio of a repetitive signal, for example, a 1 kHz pulse width modulated (PWM) signal. The power conversion information content may be contained in an analog signal of absolute amplitude voltage.

[0004] In either case, three separate building blocks can be recognized in a driver according to the present disclosure. The first building block is the power converter. The power converter may therefore receive a mains supply voltage and may be configured to convert the mains supply voltage into a particular power output suitable for driving a load. The load is identified as the second building block. The third building block is the controller itself. The controller therefore controls the power conversion by directly controlling the power converter. Often, these building blocks are physically separated. The present disclosure is particularly suited to situations where the controller is physically separated from the power converter.

[0005] In some cases, for example for safety reasons, the controller may need to receive information from the power converter, e.g., about the mains input voltage or the like. Unfortunately, the above-mentioned power control information is "communicated" using communication only in one direction, i.e., from the controller to the power converter. The power converter is generally a simple analog module without any communication possibilities. Adding intelligent building blocks, e.g., for two-way communication, not only increases the cost but also the complexity.

[0006] Therefore, there is a need to improve currently available drivers to enable communication back from the power converter to the controller in an uncomplicated manner. Summary of the Invention [Problem to be solved by the invention]

[0007] It would be advantageous to implement a driver that can communicate back from the power converter to the controller in an uncomplicated manner.

[0008] It would also be desirable to provide a light emitting diode (LED) based lighting device that includes an improved driver.

[0009] It would further be desirable to provide an improved method of operating the driver. [Means for solving the problem]

[0010] To better address one or more of these challenges, in a first aspect there is provided a driver for driving a load, comprising: a power converter for converting an input into an output for powering the load; and - a driver having a controller for controlling the output of the power converter by controlling a control voltage in a communication line provided between the power converter and the controller, the controller being configured to control the control voltage to be within a predetermined control voltage range; The power converter is further provided with a driver configured to communicate from the power converter to the controller by controlling the control voltage on the communication line to be outside the predetermined control voltage range.

[0011] The inventors have found that there is typically a communication line between the controller and the power converter to transmit the control voltage from the controller to the power converter, and the voltage, or more specifically the potential, on this communication line is typically within a predetermined control voltage range, for example between 600 mV and 1600 mV.

[0012] If 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 be alternately switched between a high voltage level threshold, e.g., at or near 1600 mV, and a low voltage level threshold, e.g., at or near 600 mV, with a certain duty cycle.

[0013] In either case, the inventors have found that there may be an unallocated voltage / unallocated voltage range available to be utilized by the power converter to communicate back to the controller. That is, for example, the power converter may lower the control voltage on the communication line below the low voltage level threshold, or may raise the control voltage on the communication line above the high voltage level threshold. In this manner, the power converter may communicate back to the controller.

[0014] The power converter may be connected to an alternating current (AC) mains power supply or any other suitable power source. Various types of power converters exist, each of which is suitable for use in a driver according to the present disclosure. For example, a half-wave rectifier passes only the positive portion of the AC supply voltage while blocking the negative portion of the AC supply voltage. This is typically achieved using a single diode.

[0015] In another example, a full-wave rectifier converts the entire AC supply voltage to a constant polarity at its output. The positive portion of the AC supply voltage is allowed to pass, and the negative portion of the AC supply voltage is converted to a positive portion. This can be accomplished using a bridge rectifier or by using two diodes in combination with a switch.

[0016] Generally, the power converter comprises a switched-mode power supply for providing output power to the load. The switched-mode power supply comprises an integrated circuit (IC), which can be considered the brain of the switched-mode power supply. The IC controls switches, e.g., field-effect transistors, whose switching rate determines the output of the power converter.

[0017] The communication line, and more specifically the control voltage present on the communication line, can be used as an input to the IC to control the output of the converter.

[0018] As previously mentioned, the control voltage present on the communication line may be a PWM voltage signal that alternates between a high level threshold and a low level threshold at a particular duty cycle. Such a PWM voltage signal may be filtered, smoothed, or the like in the power converter before being supplied to the IC.

[0019] As mentioned above, the control voltage signal present on the communication line may also be an analog voltage signal, which is controlled to be within the predetermined control voltage range, for example, between a high-level threshold and a low-level threshold, and such analog voltage signal may be filtered, smoothed, or the like in the power converter before being supplied to the IC.

[0020] The controller may be powered by a direct current (DC) power source output by the power converter, or may be powered in any other manner. In either case, the controller is configured to control or set a desired output power to the load. The controller may, for example, include a potentiometer for setting the desired output power. The controller may also include a wireless communication module configured to receive a particular set point for the output power to the load, the controller being configured to convert the received set point into a control voltage on the communication line.

[0021] The wireless communication module may be configured to communicate, for example, via Wi-Fi, via Bluetooth, or using any other known communication technology.

[0022] Furthermore, the wireless communication module may itself also be configured to transmit, i.e., communicate, e.g., information received from the power converter via the communication line may be communicated to the outside world.

[0023] The controller may comprise any type of hardware, such as a microcontroller, a field programmable gate array (FPGA), or the like. The controller may be powered via a power converter or may be powered using an auxiliary power source, such as a battery.

[0024] In an example, the driver includes the communication line, and the controller includes a controlled impedance connected to the communication line and is configured to control the controlled impedance to control the control voltage to be within the predetermined control voltage range.

[0025] In a further example, the power converter has a communicator impedance connected to the communication line and is configured to control the communicator impedance to control the control voltage to be outside the predetermined control voltage range.

[0026] The above example is directed to a voltage divider, which is a circuit configured to generate an output voltage that is a fraction of its input voltage. The communication line may, for example, be connected to a supply voltage via the controlled impedance and to ground via the communicator impedance.

[0027] In that case, the control voltage, i.e., the voltage present on the communication line, can be set by modifying either the control impedance or the communicator impedance. Generally, to control the power converter, the controller modifies the control impedance. However, when the power converter attempts to communicate back to the controller, the power converter modifies the communicator impedance. The communicator impedance may cause the control voltage present on the communication line to be outside the predetermined control voltage range.

[0028] In a further example, the controlled impedance comprises a first controlled impedance connected to the communication line and connected to a supply voltage, and a switch connected in series with a second controlled impedance, the switch and the second controlled impedance being arranged in parallel across the first controlled impedance, and the controller being configured to control the switch to control the controlled impedance.

[0029] In accordance with the above, the controller is configured 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, and in a second option, the controlled impedance is equal to the first controlled impedance cascaded in parallel with the second controlled impedance.

[0030] In another example, the power converter includes a communicator switch disposed in parallel across the communicator impedance, and the power converter is configured to control the switch to control the control voltage to be outside the predetermined control voltage range.

[0031] In one aspect of the present disclosure, the power converter has a communicator impedance and a communicator switch arranged in series with the communicator impedance, the communicator impedance or the communicator switch is connected to the communication line, and the power converter is configured to control the switch to control the control voltage to be outside the predetermined control voltage range.

[0032] In a further example, the controller is configured to read the control voltage on the communication line provided between the power converter and the controller.

[0033] In a second aspect of the present disclosure, - at least one LED for emitting light; - a driver according to any of the examples provided above, the driver being configured to drive the load, the load being the at least one LED.

[0034] It is noted that the advantages and definitions as disclosed with respect to the embodiments of the first aspect of the invention also correspond respectively to the embodiments of the second aspect of the invention, which are said LED-based lighting devices.

[0035] In an example, the LED-based lighting device includes an LED substrate having the at least one LED, the power converter is disposed at a first end of the LED-based lighting device, the controller is disposed at a second end of the LED-based lighting device, the second end being opposite the first end, and the LED substrate is disposed between the power converter and the LED substrate.

[0036] In a further example, the LED-based lighting device is an LED tube.

[0037] The driver according to the present disclosure may be used in retrofit light-emitting diode (LED) lamps. In the past, LED lighting devices utilizing LEDs have been developed for various lighting applications. Due to their long life and high energy efficiency, LED lamps are nowadays designed to replace traditional fluorescent lamps, i.e., for retrofit applications. For such applications, retrofit LED lamps are typically adapted to fit into the sockets of the respective lamp fixtures into which they are retrofitted. Furthermore, because lamp maintenance is typically performed by the user, retrofit LED lamps should ideally be easily operable in any type of suitable fixture without the need to rewire the fixture.

[0038] According to the present disclosure, the retrofit LED lamp may be either a retrofit LED tube or a retrofit LED photoluminescent lamp, such as a replacement LED tube for a fluorescent tube, which is a low-pressure mercury vapor gas discharge lamp that uses fluorescence to generate visible light.

[0039] In conventional fluorescent lamps, a ballast is typically used to limit the current through the lamp, which could otherwise rise to destructive levels due to a negative differential resistance artifact in the voltage-current characteristic of the fluorescent tube. Various types of ballasts exist, such as electronic ballasts, high frequency electronic ballasts, self-oscillating HF ballasts, magnetic ballasts, or digital ballasts.

[0040] Accordingly, a power converter according to the present disclosure may be connected to such a ballast and configured to convert the output of the ballast into an output suitable for driving at least one LED of the retrofit LED lamp.

[0041] In a third aspect of the present disclosure, there is provided a method of operating a driver according to any of the examples provided above, comprising: - controlling the output of the power converter by controlling, by the controller, the control voltage on the communication line provided between the power converter and the controller so that it is within a predetermined control voltage range; - communicating by controlling the control voltage on the communication line by the power converter to be outside the predetermined control voltage range.

[0042] These and other aspects of the invention will be elucidated and elucidated with reference to the following embodiments. [Brief explanation of the drawings]

[0043] [Figure 1] A schematic diagram of a driver driving a particular load is disclosed. [Figure 2] 1 discloses a schematic diagram of a retrofit light emitting diode (LED) based lighting device according to the present disclosure. [Figure 3] An example implementation of a driver according to the present disclosure is disclosed. [Figure 4] Further examples of driver implementations according to the present disclosure are disclosed. DETAILED DESCRIPTION OF THE INVENTION

[0044] A detailed description of the drawings and figures is presented below. It should be noted that the same reference signs in different figures indicate similar components or the same functionality of various components.

[0045] FIG. 1 shows a schematic diagram of a driver 1 driving a particular load 7, for example a light emitting diode (LED) based load.

[0046] A power converter 3 is provided to convert an input 2 into an output for powering a load 7. The power converter may receive the input 2 from an alternating current (AC) mains supply, any type of ballast, or the like. The power converter 3 converts the input to an output based on power control information 6 received from a controller 5.

[0047] In the following, the load is assumed to be an LED-based load. However, it should be noted that the present disclosure is not limited to LED-based loads. The present concept may be applicable to any kind of load.

[0048] The power control information 6 may, for example, be directed to a particular dimming level for the LED load. Generally, the power control information 6 falls within a predetermined control voltage range, with a high dimming factor at a low voltage threshold of the range and a low dimming factor at a high voltage threshold of the range.

[0049] The power control information 6 may also be an analog signal or a pulse width modulated (PWM) signal, where the signal alternates between a low voltage threshold of a range and a high voltage threshold of a range, and the duty cycle of the PWM signal provides the desired dimming level to be obtained.

[0050] Finally, a supply line 4 is provided between the power converter 3 and the controller for voltage reference purposes.

[0051] FIG. 2 discloses a schematic diagram of a retrofit light emitting diode (LED) based lighting device 21 according to the present disclosure.

[0052] It should be noted that drivers according to the present disclosure are particularly suited for retrofit LED-based lighting devices. Retrofit LED-based lighting devices are devices that are adapted to fit into the sockets of the respective lamp fixtures into which they are installed. Typically, retrofit LED-based lighting devices are designed to replace traditional fluorescent lighting, such as fluorescent tubes. As such, the connectors 22, 27 of the retrofit LED tubes may be co-located and have the same dimensions as the connectors of the lamps into which they are retrofitted.

[0053] 2 is directed to a retrofit LED-based light tube 21, i.e., a lighting device having an elongated shape. The retrofit LED-based light tube 21 comprises a housing 23, which comprises a power converter 24, an LED load 25, and a controller 26.

[0054] The power converter 24 is generally disposed at a first end of the LED-based lighting tube 21, and the controller is generally disposed at a second end opposite the first end of the LED-based lighting tube 21. The LED load 25 is disposed between the power converter 24 and the controller 26. The LED load 25 itself also has an elongated shape. Thus, the power converter 24 and the controller 26 are physically separated.

[0055] The length of the LED-based lighting tube 21, i.e., the length in the elongated direction, may be between 20 and 120 cm, more preferably between 40 and 80 cm. The tube may have a circular cross section, and the cross-sectional diameter may be between 10 and 50 mm, preferably between 20 and 30 mm.

[0056] It is foreseeable that in certain circumstances, for example for safety reasons, the controller 26 may need to receive information from the power converter 24. Such information may be directed to the mains input voltage. The controller 26 may use that information to improve the power control information sent to the power converter 24.

[0057] The communication line 29 between the controller 26 and the power converter 24 is utilized in two ways in accordance with the present disclosure. The communication line 29 is used to communicate power control information from the controller 26 to the power converter 24. Such power control information is communicated in the form of a control voltage, which is controlled by the controller to be within a predetermined control voltage range, for example, between 600 mV and 1600 mV.

[0058] This disclosure is directed to the concept that power converter 24 can also communicate back to controller 26. To do so, power converter 24 is configured to control the control voltage present on the communication line to be outside of a predetermined control voltage range, i.e., the power converter overrides the control voltage set on communication line 29.

[0059] The power converter may, for example, connect the communication line 25 directly to ground so that the control voltage present on the communication line 29 is 0V. Another option is for the power converter to ensure that the communication line 25 is floating. Both options are addressed with respect to Figures 3 and 4.

[0060] It should be noted that the protocol used to communicate from the power converter 24 to the controller may be based on an existing, known protocol. For example, the DALI protocol may be suitable. Thus, the power converter 24 and the controller 26 may have an open, i.e., standardized, interface between them. This allows for interchangeability of the controller and the power converter.

[0061] 3 and 4 disclose an example of a driver implementation according to the present disclosure.

[0062] Note that both embodiments are directed to a controlled impedance output of the controller, allowing a third level in the communication line that can be controlled by the power converter to communicate back to the controller.

[0063] 3 is directed to a first embodiment, in which the controller may be configured to generate a PWM signal, PWM_out, that controls the resistor divider network of resistors R2, R3, and R1.

[0064] A "low" signal at PWM_out causes the controller's transistor to conduct, placing R2 in parallel across R3, thereby forcing the voltage at the digital PWM, or DPWM, to a "high" state.

[0065] A "high" signal at PWM_out and the application of a 3.3V supply voltage causes the controller's transistors to be non-conductive, so a voltage divider network consisting of resistors R3 and R1 forces the voltage at the digital PWM, i.e., DPWM, to a "low" state.

[0066] By controlling the duty cycle of the PWM_out signal, the output of the power converter can be controlled.

[0067] The circuitry around switch J1 of the power converter is configured to control switch J1, for example, if the mains voltage drops, this is indicated by resistor divider R4 / R5 causing switch J1 to go from a blocking state to a normally conducting state which reduces the voltage at DPWM to ground.

[0068] Due to the fact that the 1-bit feedback signal is at the same level as the DPWM signal, this 1-bit feedback signal is also set to ground which can be detected by the controller, i.e. the controller is configured to detect when the control voltage on the communication line is outside a predetermined control voltage range.

[0069] Thus, this particular example is directed to the situation where a sag in the 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.

[0070] Note that this particular example is directed to communicating information regarding the mains supply voltage back to the controller. Other information may be communicated as well, such as overheating of any of the power converter's elements, or failure of any of the power converter's elements, or the like.

[0071] Furthermore, the communication may consist of a 1-bit communication as shown in Figures 3 and 4, but may also encompass other types of communication principles. Unused voltage ranges may be used in an analog fashion to send information back to the controller. Another option is that the 1-bit communication may be used as a sort of Morse code to convey information.

[0072] The embodiment shown in Figure 4 can be described as follows: The controller aspects of the embodiment shown in Figure 4 are in principle the same as those of the embodiment shown in Figure 3.

[0073] The main difference between the embodiment shown in Figure 4 and the embodiment shown in Figure 3 is in the power converter, and more specifically, it is directed to the way in which the power converter controls the control voltage outside of a predetermined control voltage range.

[0074] In Figure 3, switch J1 is configured to short-circuit resistor R1 so that the control voltage on the communication line is equal to the supply voltage. In Figure 4, switch M1 is normally switched on so that resistor R1 is directly connected to the communication line. When the power converter attempts to communicate back to the controller, it may deactivate switch M1 so that the communication line is floating. In that case, 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.

[0075] Those skilled in the art can understand and effect other modifications to the disclosed embodiments in practicing the claimed invention, from a study of the drawings, the specification, and the appended claims. In the claims, the word "comprise" does not exclude other elements or steps, and the singular does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used to advantage. A computer program may be stored / distributed on an appropriate medium, such as an optical storage medium or a solid-state medium, provided together with or as part of other hardware, or distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. a driver for driving a load, a power converter for converting an input to an output for powering the load; and a driver having a controller for controlling the output of the power converter by controlling a control voltage in a communication line provided between the power converter and the controller, the driver being configured to control the control voltage to be within a predetermined control voltage range; The power converter further includes a driver configured to communicate from the power converter to the controller by overriding the control voltage on the communication line to be outside the predetermined control voltage range.

2. 2. The driver of claim 1, wherein the driver includes the communication line, and the controller includes a controlled impedance connected to the communication line, and is configured to control the controlled impedance to control the control voltage to be within the predetermined control voltage range.

3. 3. A driver as claimed in any one of claims 1 to 2, wherein the driver comprises the communication line, the power converter comprises a communicator impedance connected to the communication line, and the driver is configured to control the communicator impedance to control the control voltage to be outside the predetermined control voltage range.

4. 3. The driver of claim 2, wherein the driver comprises the communication line, the controlled impedance comprises a first controlled impedance connected to the communication line and connected to a supply voltage, and a switch connected in series with a second controlled impedance, the switch and the second controlled impedance being arranged in parallel across the first controlled impedance, and the controller is configured to control the switch to control the controlled impedance.

5. 4. The driver of claim 3, wherein the power converter includes a communicator switch disposed in parallel across the communicator impedance, the power converter configured to control the switch to control the control voltage to be outside the predetermined control voltage range.

6. 4. The driver of claim 3, wherein the power converter has a communicator impedance and a communicator switch arranged in series with the communicator impedance, the communicator impedance or the communicator switch is connected to the communication line, and the power converter is configured to control the switch to control the control voltage to be outside the predetermined control voltage range.

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

8. at least one LED for emitting light; 8. An LED-based lighting device comprising: a driver according to any one of claims 1 to 7, configured to drive the load, the load being the at least one LED.

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

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

11. A method of operating a driver according to any one of claims 1 to 7, comprising the steps of: controlling the output of the power converter by controlling, by the controller, the control voltage in the communication line provided between the power converter and the controller so that it is within a predetermined control voltage range; and communicating by the power converter by overriding the control voltage on the communication line to be outside the predetermined control voltage range.

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