Light source drivers for lighting fixtures

Abstract

The present disclosure relates to a light source driver for a light source of a lighting fixture. The present disclosure proposes monitoring a temperature change in a resistive element, or a parameter responsive to the cause of the temperature change, to facilitate determining whether the light source driver is compatible with an AC power source. The resistive element is connected in series between a rectifier device of the light source driver and an energy storage capacitor for storing charge to power the light source.

Description

[Technical Field]

[0001] The present invention relates to the field of lighting equipment, and more particularly to the field of fixture lighting for lighting equipment. [Background technology]

[0002] For example, there is a growing demand for highly configurable and dimmable lighting fixtures for use in consumer or industrial environments. There is a specific need for lighting fixtures (i.e., light-emitting devices) that can be used with a wide variety of different power supplies and / or controllers without affecting their operation, in order to facilitate the "hassle-free" connection of new lighting fixtures to existing power supplies.

[0003] In particular, it is desirable that lighting fixtures operate in accordance with the so-called principles of robustness and compatibility. When operating in accordance with these principles, the lifespan and operation of the lighting fixture must not be affected by connection to a wide variety of dimmers or AC power sources. In other words, the lighting fixture must have an unaffected lifespan when placed on an AC power source and operate without flicker or other optical output artifacts. If a lighting fixture can operate in accordance with these principles, it can be considered "compatible" with dimmers or other AC power sources.

[0004] Currently, to meet these requirements, lighting fixtures are generally designed with a high power factor (PF) architecture that does not include electrolytic capacitors. While these high power factor architectures offer advantages such as improved dimmer robustness and compatibility, they are generally more expensive and complex than low power factor architectures that utilize one or more electrolytic capacitors. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] There is a continuing demand to reduce the cost and complexity of lighting fixtures. [Means for solving the problem]

[0006] The present invention is defined by the claims.

[0007] According to an example of a certain aspect of the present invention, a light source driver for supplying power to a light source of a lighting device is provided. The driver includes a rectifier configured to receive AC power from an AC power source and output a rectified voltage for supplying power to the light source; an energy storage capacitor configured to receive and store the rectified voltage for supplying power to the light source; a series connection of a resistor and the energy storage capacitor coupled in parallel with the output of the rectifier; and a sensing element configured to monitor the temperature of the resistor, thereby facilitating the determination of whether the light source driver corresponds to the AC power source.

[0008] This disclosure acknowledges that some AC power supplies may supply extremely high (peak) currents. For example, an AC power supply that performs phase-cut dimming may produce high currents in the light source driver, particularly in the resistive element connected in series with the energy storage capacitor, (for example, for the purpose of current shaping to correct the power factor of the light source driver).

[0009] These high currents can significantly reduce the lifespan of the components of the light source driver, and in particular, overheating can significantly reduce the lifespan of the resistive elements. Therefore, the presence of high currents in the light source driver may mean that the light source driver is not sufficiently robust to or compatible with the AC power supply.

[0010] This disclosure proposes monitoring the temperature of the resistive element or a parameter that responds to the cause of the temperature change. This may include directly monitoring the temperature near the resistive element (e.g., a pad directly connected to the resistive element, or the resistive element itself), the voltage drop through the resistive element, or the current flowing through the resistive element. This parameter can be used to determine whether the light source is compatible with the AC power supply (e.g., whether it is sufficiently robust).

[0011] As previously stated, the resistive element may be useful for current shaping to control and / or improve the power factor of the light source driver. Therefore, preferably, the resistive element is a current shaping resistor.

[0012] Preferably, the light source driver further includes a switch in parallel with the resistor (R1), the switch being configured to close when the current passing through the resistor (R1) is less than a threshold.

[0013] Since the light source driver is not coupled to a phase-cut dimmer, if the light source driver is not exposed to extreme current peaks, it may be desirable that the resistive element be shunted after the light source driver is started to improve the power efficiency of the light source driver. Preferably, the shunting is performed when the inrush current flowing through the energy storage capacitor and therefore through the resistive element has passed and the current through the resistive element has fallen below a threshold.

[0014] Preferably, the temperature sensing element is configured to directly monitor a temperature that responds to a temperature change of the resistive element, for example, the temperature of the resistive element or the temperature near the resistive element. In other words, the temperature sensing element may have a temperature-sensitive element (such as a thermistor) that is in thermal contact with the resistive element.

[0015] In some embodiments, the LED lighting fixture further includes a control element configured to control the current flowing through the resistive element in accordance with a parameter monitored by the temperature sensing element.

[0016] Accordingly, a control element can be provided to control the current flowing through the resistive element, thereby facilitating the controllable robustness of the light source driver. Providing the control element can improve the compatibility of the light source driver for use with various dimming magnitudes and / or with various AC power sources. The controllability of the current flowing through the resistive element means that the temperature of the resistive element can be controlled, which improves the lifespan / service life of the resistive element (for example, by preventing the occurrence of high temperatures).

[0017] Optionally, the control element reduces the current flowing through the resistive element in response to a parameter monitored by the temperature sensing element breaching a first predetermined threshold. This embodiment provides a mechanism for reducing excess current in the resistive element (e.g., when the first predetermined threshold is breached) and thereby improving the lifespan of the light source driver. The first predetermined threshold may be a threshold for a parameter that indicates the lifespan of the resistive element or light source driver is affected (by a corresponding temperature change) by a predetermined amount and / or tolerance (e.g., by a set of desirable commercial properties or standards). For example, a particular standard may set a maximum allowable or recommended temperature for the resistive element at a predetermined level, and the first predetermined threshold may be a threshold indicating that the maximum allowable / recommended temperature has been reached or breached.

[0018] As another example, a resistive element may have a temperature rating (for example, according to the manufacturer's specifications). The first predetermined threshold may correspond to a threshold indicating that this temperature rating has been met or exceeded. The temperature rating may represent the maximum allowable temperature, the recommended maximum temperature, or a certain percentage (e.g., 90%) (as recommended by the manufacturer).

[0019] In other words, the first predetermined threshold may depend on the temperature rating of the resistive element or the recommended maximum temperature of the resistive element.

[0020] Preferably, the first predetermined threshold is selected to correspond to a temperature of 140°C for the resistive element. For example, if the temperature sensing element has a thermistor that is in thermal contact with the resistive element, the current through the resistive element may decrease as the thermistor reaches a temperature of 95 to 100°C.

[0021] The control element may be configured to control the current flowing through the resistive element by controlling the current flowing from the energy storage capacitor to the light source. In other words, the control element may be configured to control one or more characteristics (e.g., modulation, magnitude, etc.) of the current supplied to the light source by the energy storage capacitor in order to control the current flowing through the resistive element (electrically connected to the energy storage capacitor). This provides a highly customizable mechanism for controlling the average current flowing through the resistive element.

[0022] In particular, the control element may be configured to control the average current flowing from the energy storage capacitor to the light source in accordance with the parameters monitored by the temperature sensing element.

[0023] In at least one example, the control element controls the average current supplied to the light source by the energy storage capacitor using pulse width modulation techniques. In other words, the control element may use pulse width modulation techniques to control the average current supplied to the light source. This mechanism facilitates highly adaptable control of the average current.

[0024] In some embodiments, the control element has a buck and / or boost converter configured to control the current flowing from the energy storage capacitor to the light source, and the control of the buck and / or boost converter is in response to a parameter monitored by the temperature sensing element.

[0025] A buck and / or boost converter is a conventional mechanism for controlling the current between an energy storage capacitor and a light source and is commonly used to improve the power factor of the light source driver.

[0026] Thus, the buck / boost converter can control the current (and voltage) supplied to the light source. The operation of the buck / boost converter (if present) is in response to a parameter monitored by a temperature sensing device. The buck / boost converter provides a simple and widely available mechanism for controlling the current supplied to the light source (by the energy storage capacitor), and thus the current through the resistive element connected in series with the energy storage capacitor.

[0027] In some examples, the control element has a microcontroller configured to control the operation of the buck and / or boost converter in response to a parameter monitored by the temperature sensing element. The microcontroller may be configured to partially include the temperature sensing element.

[0028] The microcontroller may be configured to control the operation of the buck and / or boost converters using pulse width modulation techniques. That is, the microcontroller may be able to toggle (or manually control) the operation of the buck and / or boost converters using pulse width modulation techniques.

[0029] In some embodiments, the control element is configured to control the current flowing from the energy storage capacitor to the light source in accordance with the voltage at the current sensing node, and the temperature sensing element is configured to directly control the voltage at the current sensing node in accordance with a parameter monitored by the temperature sensing node.

[0030] Accordingly, in some examples, the operation of the control element may be configured to control the current flowing from the energy storage capacitor to the light source based on the voltage at a particular node (current source node). This may include, for example, appropriately controlling the current so that the voltage at the particular node is kept within a predetermined range.

[0031] If the control element includes a buck and / or boost converter, this may include appropriately controlling the switching of such converter to maintain a voltage at a particular node, or a voltage at a particular node that defines the peak / RMS current supplied to the light source.

[0032] Of course, the operation of the buck and / or boost converters can be overridden (for example, by a microcontroller).

[0033] Preferably, the temperature sensing element has a thermistor that responds to temperature changes. This provides a simple and low-cost mechanism for monitoring the temperature of the resistive element.

[0034] The thermistor may be positioned to monitor the temperature at the solder pad of the resistive element.

[0035] In at least one embodiment, the light source driver further comprises an output element configured to supply a user-perceptible output, the output element configured to control the user-perceptible output in accordance with a parameter monitored by the temperature sensing element. This provides the user with an indication that facilitates the determination of whether the light source driver (or a lighting fixture including the light source driver) is compatible with the AC power supply.

[0036] Optionally, the output element is configured to adjust the output perceptible to the user in response to a parameter monitored by the temperature sensing element exceeding a predetermined threshold.

[0037] The energy storage capacitor may be, for example, an electrolytic capacitor. However, other types of capacitors, such as ceramic capacitors and / or film (base) capacitors, may be used. The resistive element has any suitable resistor or impedance device, for example, a single resistor. The light source driver may be adapted for use with any suitable light source, such as an LED device (e.g., an LED string).

[0038] According to one aspect of the present invention, a lighting fixture is provided having a light source driver as described herein and a light source powered by the light source driver, such as an LED device (e.g., an LED string).

[0039] According to an example of a certain aspect of the present invention, a method is provided for operating a light source driver for a light source of a lighting device. The method includes the steps of: using a rectifier to receive AC power from an AC power source and output a rectified voltage for supplying power to the light source; using an energy storage capacitor to receive and store the rectified voltage for supplying power to the light source; using a resistor element to connect the output of the rectifier to the energy storage capacitor; and using a temperature sensing element to monitor a temperature change of the resistor element or a parameter that responds to the cause of the temperature change, thereby facilitating the determination of whether the light source driver corresponds to the AC power source.

[0040] These and other aspects of the present invention will be described and clarified with reference to the embodiments described below. [Brief explanation of the drawing]

[0041] For a better understanding of the present invention and to more clearly illustrate how it can be carried out, the accompanying drawings are referenced here, as merely one example. [Figure 1] This diagram illustrates the effect of phase-cut dimming on the voltage supplied to the lamp driver by the AC power supply. [Figure 2] A light source driver according to the first embodiment is shown in the diagram. [Figure 3] The effect of a light source driver according to one embodiment is illustrated. [Figure 4] A light source driver according to the second embodiment is shown. [Figure 5] A method according to one embodiment is illustrated. [Modes for carrying out the invention]

[0042] The present invention will be described with reference to the figures.

[0043] The detailed descriptions and specific examples illustrate exemplary embodiments of the apparatus, systems, and methods, but are for illustrative purposes only and should not be used to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the invention will be better understood from the following description, the appended claims, and the appended drawings. The figures are for illustrative purposes only and are not drawn to scale. The same reference numerals are used throughout the figures to indicate the same or similar parts.

[0044] The present invention provides a light source driver for a light source of a lighting fixture. This disclosure proposes monitoring a temperature change in a resistive element, or a parameter that responds to the cause of such temperature change, in order to facilitate the determination of whether the light source driver is compatible with an AC power supply. The resistive element is connected in series with an energy storage capacitor that receives a rectified voltage to store the charge that supplies power to the light source.

[0045] The fundamental concept of this invention is based on the recognition that the lifespan of a light source driver is affected by overheating of a resistive element connected in series with the energy storage capacitor. By monitoring temperature changes, or parameters that respond to the cause of temperature changes, potential overheating can be identified, thereby determining whether the AC power supply providing power to the light source driver is incompatible with the light source driver (i.e., causing overheating).

[0046] Other underlying concepts propose a method to solve the problem of overheating of this resistive element, thereby improving the responsiveness and lifespan of the light source driver.

[0047] Embodiments of the present invention can be employed in any suitable lighting system.

[0048] Figure 1 provides a graph 100 illustrating the effect of phase-cut dimming on the voltage supplied to the light source driver by the AC power supply (which undergoes phase-cut dimming).

[0049] An exemplary light source driver (not shown) comprises a rectifier and an energy storage capacitor (for supplying power to the light source). The input of the rectifier receives a voltage supplied by an AC power source, and the output of the rectifier is connected to the energy storage capacitor, and a resistive element may be connected in series with the energy storage capacitor, for example, at least for the purpose of current shaping.

[0050] The first waveform 110 illustrates the voltage level supplied by the AC power supply at a first dimming level (low-level dimming or "deep dimming," i.e., a dimming level for low-intensity light output, e.g., a 90-degree phase cut). The second waveform 120 illustrates the input current level supplied by the AC power supply at the first dimming level. As illustrated, phase-cut dimming produces a large spike in the input current, thereby resulting in high peak voltage and current.

[0051] If a second, higher dimming level (i.e., a dimming level for greater light output) is used, the peak voltage / current at the second dimming level 120 will be lower than the peak voltage / current at the higher dimming level 110.

[0052] This is the result of a phase-cut dimming process.

[0053] This larger peak voltage (at lower dimming levels) induces a larger current in the resistive element connected in series with the energy storage capacitor receiving the (rectified) AC power supply. The larger current increases the temperature of this resistive element (due to increased heat dissipation), which leads to a reduced lifespan for the resistive element and, therefore, a reduced lifespan for the light source driver.

[0054] This disclosure recognizes that the ability to monitor parameters in response to temperature rise (or the cause of temperature rise) and control / reduce the current flowing through a resistive element accordingly can increase the lifespan of a light source driver.

[0055] Figure 2 illustrates a light source driver 200 according to one embodiment of the present invention. The light source driver is configured to supply power to a lighting fixture 20 for a lighting device, and to a light source 295 of the present invention itself.

[0056] The light source driver 200 has a rectifier 210 configured to receive AC power from the AC power supply 290 and output a rectified voltage for supplying power to the light source 295. The illustrated rectifier 210 is a full-wave diode bridge rectifier. However, the rectifier 210 may be replaced with any other suitable rectifier, such as a half-wave diode bridge rectifier, a center-tap rectifier, etc.

[0057] The light source driver 200 further includes an energy storage capacitor C1 configured to receive and store the rectified voltage to be supplied to the light source. As is well known to those skilled in the art, the energy storage capacitor smooths the rectified voltage to supply a DC-like voltage to power the light source. Therefore, the energy storage capacitor C1 is sometimes referred to as a smoothing capacitor instead.

[0058] The energy storage capacitor may be, for example, an electrolytic capacitor. However, other types of capacitors, such as ceramic capacitors and / or film (base) capacitors, may be used. The energy storage capacitor C1 can be replaced by multiple energy storage capacitors (for example, arranged in parallel), as will be understood by those skilled in the art.

[0059] The light source driver 200 further includes a resistor R1 connected in series with the energy storage capacitor C1. The resistor R1 is illustrated to be connected between the energy storage capacitor C1 and ground or a reference voltage, but it may instead be arranged to connect the energy storage capacitor to the output of the rectifier 210. There may also be a series connection of the resistor R1 and the energy storage capacitor (C1) coupled in parallel with the output of the rectifiers (210, 410).

[0060] The resistive element R1 helps to shape the rectified voltage current, thereby smoothing the current supplied to the light source 295. The current shaping process is well known to those skilled in the art.

[0061] The light source driver 200 further includes an optional diode D1 that helps shape the current.

[0062] The light source driver 200 further includes temperature sensing elements T1, 254. The temperature sensing elements are configured to monitor a temperature change of a resistive element or a parameter that responds to the cause of the temperature change.

[0063] This may include, for example, directly measuring the temperature of the resistive element by monitoring the current passing through a thermistor T1 that is in thermal contact with the resistive element.

[0064] In the illustrated example, the temperature sensing element comprises a temperature monitoring module 254 (which may be formed as a microcontroller 250 for the light source driver 200) and a temperature sensor T1. The temperature sensor is adapted to respond to changes in the temperature of a resistive element, which are detected by the temperature monitoring module 254. In other words, the temperature monitoring module detects the temperature sensor's response to the temperature change of the resistive element.

[0065] The temperature sensor T1 may have, for example, a thermosistor, a thermocouple, or any other suitable sensor that responds to temperature changes.

[0066] The temperature sensor T1 may be thermally connected to a certain end (e.g., a solder pad) of the resistive element R1, as shown in the figure. This allows for direct and accurate monitoring of the temperature of the resistive element.

[0067] The temperature sensing elements T1 and 254 facilitate the determination of whether the light source driver is compatible with AC power (or a specific dimming level of AC power) by monitoring parameters that respond to temperature changes (or the cause of said temperature changes) of the resistive element R1. In particular, the temperature sensing elements 254 and T1 determine characteristics that identify whether the lifespan of the light source driver 200 is adversely affected by AC power (for example, by a specific dimming level of AC power).

[0068] In some embodiments, the light source driver 200 may be configured to adapt its operation in order to improve the light source driver's compatibility with AC power supplies.

[0069] The light source driver 200 may have a control element 256 that controls the current flowing through a resistive element according to a parameter monitored by a temperature sensing element.

[0070] In particular, the light source driver may have a control element 256 that reduces the current flowing through the resistive element in response to a parameter monitored by the temperature sensing element 254, T1 exceeding a first predetermined threshold. The first predetermined threshold may depend on the rating of the resistive element (e.g., recommended / maximum temperature rating, recommended / maximum current rating, or recommended / maximum voltage drop rating), and therefore may vary depending on the details of the implementation.

[0071] In the illustrated embodiment, the control element 256 is embodied as a microcontroller 250 capable of controlling the average current flowing from the energy storage capacitor to the light source using a buck and / or boost converter 293 (e.g., a buck converter, a boost converter, or a buck-boost converter). The control element 256 may also be embodied in the same microcontroller 250 as a certain embodiment of the temperature sensing element 254, T1.

[0072] The operation of buck converters, boost converters, or buck-boost converters is well known to those skilled in the art. Generally, buck, boost, or buck-boost converters are configured to controllably connect and disconnect a DC power supply (here, an energy storage capacitor C1) while maintaining a generally constant current supply (and voltage) to the output load.

[0073] The buck and / or boost converter may include a current sensing node and be configured to maintain the voltage at the current sensing node within a predetermined range (e.g., by employing hysteresis to do so). As another example, the voltage at the current sensing node may define the peak / RMS current supplied to the light source.

[0074] The control element 256 may be configured to control the average current supplied to the light source by the energy storage capacitor using pulse width modulation techniques. In particular, the control element 256 may be configured to control the operation of the buck and / or boost converter 293 using pulse width modulation techniques (for example, to alternately activate and deactivate the buck and / or boost converter, or to alternately allow or prevent the buck and / or boost converter from receiving power from the energy storage capacitor C1). This technique provides a well-studied adaptation for controlling the power / current flowing from the energy storage capacitor to the light source.

[0075] Therefore, the buck and / or boost converter controls the input node N COFor example, it may have a pulse width modulation node and be configured to control the operation of the buck and / or boost converter in response to a signal at a control input node (supplied, for example, by a microcontroller 250). For example, the buck and / or boost converter 293 may alternately activate and deactivate other components of the buck and / or boost converter in response to a signal at a control input node. In particular, the buck and / or boost converter may alternately allow or prevent it from receiving power from the energy storage capacitor C1 in response to a signal at a control input node.

[0076] Other methods for controlling or modulating the current flowing from the energy storage capacitor to the light source are obvious to those skilled in the art and may be embodied, for example, in hardware.

[0077] In a preferred example, the control element 256 is configured to reduce the average current flowing through the resistive element by appropriately modulating (pulse width) the current flowing from the energy storage capacitor to the light source, for example, when the temperature detected by the temperature sensor T1 exceeds a predetermined threshold. The predetermined threshold may depend on the temperature rating of the resistive element and therefore may vary depending on the details of the implementation.

[0078] By reducing the average current flowing through the resistive element, the amount of heat dissipated by the resistive element is reduced, thereby lowering the temperature of the resistive element and improving its lifespan.

[0079] Since the proposed method for reducing the average current can only be performed at deep dimming levels (see Figure 1), the impact of the reduction in average power / current on the light source 295 is minimal.

[0080] The light source driver 200 may have an output element 270 configured to supply a user-perceptible output, such as a visible output. The output element is configured to control the user-perceptible output in accordance with a parameter monitored by a temperature sensing element.

[0081] In this configuration, the output element 270 may provide a user-perceptible indicator of whether the light source driver 200 is compatible with AC power. Examples of suitable user-perceptible outputs include visible outputs, such as LED outputs, or audible outputs, such as buzzer outputs. Therefore, the output element may have one or more LEDs and / or one or more buzzers, but other suitable visible / audible outputs will be obvious to those skilled in the art.

[0082] Preferably, the output element is configured to adjust the user-perceivable output in response to a parameter monitored by a temperature sensing element exceeding a predetermined threshold, for example, a threshold indicating that the lifespan of the light source driver 200 is affected. For example, exceeding a predetermined threshold may trigger the output element to supply a user-perceivable output, such as light.

[0083] The output element 270 may be controlled by a microprocessor 250, which may be the same microprocessor used to monitor the temperature change of the resistive element R1, or parameters that respond to the cause of the temperature change.

[0084] In some examples, the output element 270 may be configured to communicate with an external user interface (e.g., a mobile device such as a mobile phone or smartphone) instead of being configured to supply an output that is perceptible to the user. Accordingly, the output element may be configured to transmit a (wireless) signal to the external user interface, which indicates whether the light source driver is compatible with AC power based on a parameter monitored by a temperature sensing element (e.g., whether the monitored parameter indicates that the temperature of the resistive element has exceeded or is expected to exceed a predetermined threshold).

[0085] The external user interface may be configured to modify user-perceptible warnings in response to signals received from the output element 270.

[0086] This mechanism provides a system for warning the user about incompatibility between the light source driver and the AC power supply.

[0087] The output element 270 may communicate with an external user interface (not shown) using any suitable communication protocol, for example, via the Internet or a wireless network. Suitable wireless communication protocols that may be used to communicate with an external device or interface include infrared links, ZigBee, Bluetooth, wireless local area network protocols such as those conforming to the IEEE 802.11 standard, and 2G, 3G, or 4G telecommunications protocols. Other forms will be readily apparent to those skilled in the art.

[0088] The light source driver 200 may omit the control element 256 or the output element 270, depending on the desired embodiment. In other words, the light source driver 200 may have the control element 256 and / or the output element 270.

[0089] The light source 295 may have an LED device such as an LED string. Other light sources 295 are also possible, such as halogen bulbs, but these are not very desirable for efficiency reasons.

[0090] The microcontroller 250 may also be configured to receive power from an energy storage capacitor. Similarly, the output element 270 (if present) may receive power from an energy storage capacitor.

[0091] The microcontroller 250 may be configured to perform further tasks and control the current flowing from the energy storage capacitor to the light source in order to perform these tasks.

[0092] For example, the microcontroller may be configured to receive user input or control input (e.g., from a radio signal) and to control the pulse width modulation of the buck and / or boost converter in response to the user input or control input (e.g., to further control the dimming of the light source 295).

[0093] As another example, the microcontroller itself may take over some of the tasks previously performed by the buck and / or boost converter 293, for example, by performing current sensing so that the operation of the buck and / or boost converter depends on the microcontroller 250 (e.g., rather than directly sensing the current itself), (e.g., control input node N CO The buck and / or boost converters may be controlled accordingly (using this method).

[0094] Other operations for microcontrollers will be obvious to those skilled in the art.

[0095] Figure 3 illustrates the effect of controlling the current flowing from the energy storage capacitor to the light source on the temperature of the resistive element R1. The x-axis t represents time (for four different scenarios), and the y-axis T(t) represents the temperature of the resistive element R1 at a specific point in time.

[0096] In the first scenario illustrated by the first period t1, the pulse width modulation of the current flowing from the energy storage capacitor to the light source, controlled by the microcontroller, is maintained at 70%. In the second period, the pulse width modulation is reduced to a lower value of 65%.

[0097] Specifically, during the first period, the buck and / or boost converter (which controls the current flowing from the energy storage capacitor to the light source) is permitted to draw power from the energy storage capacitor for 70% of the time. During the second period, the buck and / or boost converter is permitted to draw power for only 65% ​​of the time.

[0098] It can be seen that lower pulse width modulation (i.e., a lower average current flowing from the energy storage capacitor to the light source) results in a lower temperature for the resistive element.

[0099] Figure 3 also illustrates the effect of phase-cut dimming performed by an AC power supply on the temperature T(t) of the resistive element.

[0100] In the third scenario illustrated by the third period t3, phase-cut dimming is not performed by the AC power supply. In the fourth scenario illustrated by the fourth period t4, phase-cut dimming is performed by the AC power supply. Performing phase-cut dimming results in a higher temperature for the resistive element.

[0101] Therefore, Figure 3 illustrates how phase-cut dimming increases the temperature of the resistive element (comparison of t3 and t4), but it also shows how controlling the current flowing from the capacitive element to the light source can lower the temperature of the resistive element by reducing the average current flowing through the resistive element (comparison of t1 and t2).

[0102] At low dimming levels, the effect of reducing the average current flowing to the light source in order to lower the (average) temperature of the resistive element is minimal (because light brightness is no longer a priority and lower brightness levels are acceptable).

[0103] Figure 4 illustrates a light source driver 400 according to another embodiment of the present invention. The light source driver 400 is configured to supply power to a lighting fixture 40 for a lighting device, and to a light source 495 of the embodiment of the present invention itself.

[0104] Unless explicitly stated otherwise, the corresponding features of the light source driver 400 or the luminaire 40 may be embodied as described above with reference to Figure 2.

[0105] The light source driver 400 has a rectifier 410 that rectifies the voltage supplied by the AC power supply 490. A suitable embodiment of the rectifier 410 has been described previously. The light source driver further has an energy storage capacitor C1 and a resistive element R1, which can also be implemented as described previously. The light source driver 200 further has an (optional) diode D1.

[0106] The light source driver 400 further includes a temperature sensing element 450. The temperature sensing element is adapted to monitor the temperature of the resistive element R1, again using a thermistor, as before.

[0107] The control element 493 is adapted to control the current through the resistor element R1 in accordance with parameters monitored by the temperature sensing element 450. In particular, here the control element 493 controls the current sensing node N (for example, to maintain the voltage at the current sensing node within a predetermined range, or to define the peak current of the buck voltage and / or boost voltage). C It has a buck and / or boost converter configured to control the power / current supplied to the light source 495 based on the voltage at the point.

[0108] In this embodiment, the current passing through the resistive element R1 is not controlled via a microcontroller, but rather via a current sensing node N C The current is controlled by a temperature-sensing element that directly controls the buck and / or boost converters by controlling the voltage in the circuit.

[0109] Therefore, the current flowing through the resistive element R1 is controlled via hardware rather than through software (for example, via a properly configured microcontroller).

[0110] The control element 493 is thereby adapted to control the current through the resistive element R1 in accordance with a parameter monitored by the temperature sensing element 450. The control element 460 thereby implements a mechanism for directly controlling the temperature of the resistive element (e.g., the solder pad of a series resistor) via current control.

[0111] The temperature sensing element 450 has a temperature-sensitive element (e.g., a thermistor) T1.

[0112] As is well known in the art, the resistance through a thermistor changes with temperature. Properly positioning a thermistor, for example, in thermal contact with a resistive element R1 or its solder pad, makes it possible to monitor the temperature of the resistive element.

[0113] This embodiment proposes monitoring the voltage across the thermistor T1 using a voltage divider configuration, for example, by connecting the thermistor in series with a first additional resistor element R2 (connected between the thermistor and the ground / reference voltage). Thermistor T1 is connected to a high voltage V cc It is connected between (for example, 3.3V or the output of the rectifier 410) and the first additional resistor element R2. The voltage across the first additional resistor element R2 changes based on the resistance of the thermistor (and therefore the temperature of resistor element R1).

[0114] Those skilled in the art will know that a high voltage V supplied by an AC power supply 490 (for example, using the voltage output of a rectifier 410) cc It would be possible to provide this easily.

[0115] The voltage across the first additional resistor R2 controls the conductivity of the first transistor M1, i.e., the gate of the first transistor M1 is connected to the node between the thermistor T1 and the first additional resistor R2. A smoothing capacitor C2 may be placed to smooth the voltage supplied to the gate of the first transistor M1.

[0116] In this approach, the first transistor M1 is controlled to be conductive when the temperature across the thermistor exceeds a predetermined threshold. The value of the thermistor T1 and / or the first additional resistance element R2 can be selected to appropriately control (e.g., apply an appropriate voltage bias) the gate of the first transistor M1 when the temperature at the resistance element R1 (i.e., the temperature of the thermistor) reaches an acceptable threshold.

[0117] The drain or collector of the first transistor M1 is connected to a high voltage V cc . The source or emitter of the first transistor M1 is connected to the first end of the second additional resistance element R3. The second end of the second additional resistance element can be connected to ground or a reference voltage.

[0118] The first transistor and the second additional resistance element R3 together appropriately bias the voltage across the first additional resistance element and serve as an electrical buffer.

[0119] The temperature sensing element 450 may further include a second transistor M2 having a gate or base connected to the source or emitter of the first transistor M1, a drain or collector connected to the high voltage V cc , and a source or emitter to which the first end of the third additional resistance element R4 is connected. The second end of the third additional resistance element R4 is connected to the first end of the fourth additional resistance element R5, and the second end of the fourth additional resistance element R5 can be connected to ground or a reference voltage.

[0120] The second end of the third additional resistance element is also coupled to a current sensing node N C .

[0121] The second transistor M2 is controlled to be conductive when the current through the second additional resistance element R3 exceeds a predetermined threshold.

[0122] For the purposes of the present disclosure, the transistor may have any suitable transistor such as a bipolar junction transistor or a MOSFET. Other suitable transistors will be apparent to those skilled in the art.

[0123] Those skilled in the art will understand that in some embodiments, the second, third, and fourth additional resistors R3, R4, R5, the smoothing capacitor C2, and the transistors M1, M2 can be omitted by the appropriate selection of the first additional resistor R2.

[0124] The embodiment may have components from both described embodiments of the invention, for example, at least for the purpose of redundancy and / or combined and / or improved operation. In particular, the voltage across the first additional resistor element R1 (for the light source driver 400) may be supplied to a microcontroller (not shown) that controls the buck and / or boost converter 493 in a manner similar to that of the microcontroller of the light source driver 200.

[0125] As another example, the light source driver 400 may have the output elements described above.

[0126] Figure 5 illustrates a method 500 for operating a light source driver for a lighting device.

[0127] The method includes step 510, which uses a rectifier to receive AC power from an AC power source and output a rectified voltage for supplying power to a light source.

[0128] Method 500 also includes step 520 of using an energy storage capacitor to receive and store a rectified voltage for supply to a light source. This step can be carried out by connecting the output of the rectifier to the energy storage capacitor using a resistive element.

[0129] Method 500 also includes step 550, which uses a temperature sensing element to monitor a temperature change of a resistive element or a parameter that responds to the cause of the temperature change, thereby facilitating the determination of whether or not the light source driver is compatible with AC power.

[0130] Those skilled in the art will understand that the method can be adapted to implement any embodiment or concept of the present invention described with respect to an embodied light source driver.

[0131] Generally, embodiments are described in which the temperature sensing element has a thermistor (or other temperature-sensitive element), but other suitable sensors may be used. In particular, the temperature through a resistive element responds to the current through the resistive element.

[0132] Therefore, it may be possible to detect the current passing through a resistive element and control the current passing through the resistive element accordingly (for example, limiting the current passing through the resistive element). This can be done by setting the voltage at the current sensing node to be equal to the voltage across the resistive element (for example, using a buffer element).

[0133] Therefore, the temperature sensing element may have a current sensing element configured to monitor the current passing through the resistive element. Information about this current can be used to control the current passing through the resistive element.

[0134] For example, referring to Figure 4, (V cc The thermistor T1 (coupled between the first additional resistor R2) can be replaced with a sensing resistor connected between the node (located between the energy storage capacitor C1 and the resistor R1) and the first additional resistor R2. This can act as a voltage divider, supplying a voltage (at the node between the sensing resistor and the first additional resistor R2) in response to the current flowing through the resistor R1. This voltage can be connected to a current sensing node (e.g., via a buffer and bias device) to control the current flowing from the energy storage capacitor C1 to the light source 495 (and thereby control the current flowing through the resistor R1). A threshold for this control can be set by a reference voltage Vcc.

[0135] A person skilled in the art will be able to understand and achieve, in carrying out the claimed invention, variations to the disclosed embodiments by studying the drawings, specification and appended claims. In the claims, the word “has” does not exclude other elements or steps, and singular notation does not exclude plurality. A single processor or other unit may perform the functions of multiple items listed in the claims. The mere fact that certain means are listed in different dependent claims does not mean that combinations of these means cannot be used advantageously. Where the term “adapted to be” is used in the claims or specification, it should be noted that the term “adapted to be” is intended to be equivalent to the term “configured to be.” No reference numeral in the claims should be construed as limiting the scope.

Claims

1. A light source driver for supplying power to the light source of a lighting device, A rectifier configured to receive AC power from an AC power source and output a rectified voltage for supplying power to the light source, An energy storage capacitor configured to receive and store the rectified voltage supplied to the light source, A series connection of a resistive element and the energy storage capacitor is coupled in parallel with the output of the rectifier, A light source driver having a sensing element configured to monitor the temperature of the resistive element, the voltage across the resistive element, or the current flowing through the resistive element, thereby facilitating the determination of whether or not the light source driver is compatible with the AC power supply.

2. The light source driver according to claim 1, further comprising a switch in parallel with the resistive element, wherein the switch is configured to close when the current passing through the resistive element is less than a threshold.

3. The light source driver according to claim 1 or 2, further comprising a control element configured to control the current flowing through the resistive element in accordance with a parameter monitored by the sensing element.

4. The light source driver according to claim 3, wherein the control element reduces the current flowing through the resistive element in response to the parameter monitored by the detection element exceeding a first predetermined threshold.

5. The light source driver according to any one of claims 3 to 4, wherein the control element is configured to control the current flowing through the resistive element by controlling the current flowing from the energy storage capacitor to the light source.

6. The light source driver according to claim 5, wherein the control element controls the average current supplied to the light source by the energy storage capacitor using pulse width modulation technology.

7. The light source driver according to any one of claims 4 to 6, wherein the control element has a buck and / or boost converter configured to control the current flowing from the energy storage capacitor to the light source, and the control of the buck and / or boost converter is in accordance with parameters monitored by the sensing element.

8. The light source driver according to claim 7, further comprising a microcontroller configured to control the operation of the buck and / or boost converter in accordance with parameters monitored by the sensing element.

9. The light source driver according to claim 8, wherein the microcontroller controls the operation of the buck and / or boost converter using pulse width modulation techniques.

10. The control element is configured to control the current flowing from the energy storage capacitor to the light source in accordance with the voltage at the current sensing node. The light source driver according to any one of claims 3 to 9, wherein the sensing element is configured to directly control the voltage in the current sensing node in accordance with a parameter monitored by the temperature sensing node.

11. The light source driver according to any one of claims 1 to 10, wherein the sensing element is a thermistor that responds to temperature changes.

12. A light source driver according to any one of claims 1 to 11, further comprising an output element configured to supply a user-perceptible output, wherein the output element is configured to control the user-perceptible output in accordance with a parameter monitored by the sensing element.

13. The light source driver according to claim 12, wherein the output element is configured to adjust the output perceptible to the user in response to a parameter monitored by the detection element exceeding a predetermined threshold.

14. A lighting device comprising a light source driver according to any one of claims 1 to 13, and a light source configured to draw power from the energy storage capacitor.

15. A method for operating a light source driver for a light source of a lighting device, The steps include: using a rectifier to receive AC power from an AC power source and outputting a rectified voltage for supplying power to the light source; The steps include: using an energy storage capacitor to receive and store the rectified voltage for supply to the light source; A step of connecting a resistive element in series with the energy storage capacitor, wherein the series connection is coupled in parallel with the output of the rectifier, A method comprising the steps of using a sensing element to monitor the temperature of the resistive element or the current passing through the resistive element, thereby facilitating the determination of whether the light source driver is compatible with the AC power supply.

Images