Light source driver for a luminaire

Abstract

A light source driver for a light source of a luminaire. The disclosure proposes monitoring a parameter responsive to a temperature change in a resistive element or a cause thereof, in order to determine whether the light source driver is compatible with an AC power supply. The resistive element is connected in series between a rectifying device of the light source driver and an energy storage capacitor for storing charge to power the light source.

Description

Technical Field

[0001] This invention relates to the field of lighting facilities, and more particularly to the field of luminaires for lighting facilities. Background Technology

[0002] There is a growing demand for highly configurable and dimmable lighting fixtures, for example, in consumer or industrial environments. In particular, there is a need for luminaires (i.e., light-emitting devices) that are compatible with a wide variety of power sources / supplies and / or controllers without affecting their operation, facilitating seamless connection of new luminaires to existing power sources / supplies.

[0003] Specifically, luminaires are expected to operate according to the so-called robustness and compatibility principles. When operating according to these principles, the lifespan and operation of the luminaire should not be affected by connection to various dimmers or AC power supplies. In other words, when placed on an AC power supply, the luminaire should have an unaffected lifespan and operate without flicker and / or other light output artifacts. If a luminaire can operate according to these principles, it can be considered "compatible" with dimmers or other AC power supplies.

[0004] Currently, to meet these requirements, luminaires are designed with high power factor (PF) architectures, which typically do not include electrolytic capacitors. These high power factor architectures benefit from improved dimmer robustness and compatibility, but are more expensive and complex than low power factor architectures that typically utilize one or more electrolytic capacitors.

[0005] There has always been a desire to reduce the cost and complexity of lighting fixtures. Summary of the Invention

[0006] This invention is defined by the claims.

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

[0008] This disclosure recognizes that some AC power supplies can provide extremely high (peak) current. For example, an AC power supply performing phase-cut dimming can result in high current in the light source driver, and particularly in the resistive element connected in series with the energy storage capacitor (e.g., for the purpose of current shaping to modify the power factor of the light source driver).

[0009] These high currents can significantly reduce the lifespan of components in a light source driver, particularly resistive elements due to overheating. Therefore, the presence of high current in a light source driver may indicate that the driver is not robust enough or is incompatible with AC power.

[0010] This disclosure proposes parameters for monitoring the response to temperature changes in a resistive element or their causes. This may include directly monitoring the temperature near the resistive element (e.g., at pads directly connected to the resistive element or the resistive element itself), the voltage drop across the resistive element, or the current flowing through the resistive element. This parameter can be used to determine whether the light source is compatible (e.g., sufficiently robust) with respect to an AC power supply.

[0011] As previously mentioned, resistive elements can be used for current shaping to control and / or improve the power factor of a light source driver. Therefore, preferably, the resistive element is a current-shaping resistor.

[0012] Preferably, the light source driver further includes a switch connected in parallel with the resistive element (R1), wherein the switch is arranged to close when the current through the resistive element (R1) is below a threshold.

[0013] When the light source driver is not exposed to extreme current peaks because it is not coupled to the phase-cut dimmer, it may be desirable to shunt the resistive element after the light source driver starts up to improve the power efficiency of the light source driver. Preferably, the shunt is performed when the inrush current flowing through the energy storage capacitor and therefore through the resistive element has passed and the current flowing through the resistive element has dropped below a threshold.

[0014] Preferably, the temperature sensing element is configured to directly monitor the temperature in response to temperature changes in 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 include a temperature-sensitive element (such as a thermistor) that is in thermal contact with the resistive element.

[0015] In some embodiments, the LED illuminator further includes a control element configured to control the current flowing through the resistive element in response to parameters monitored by the temperature sensing element.

[0016] Therefore, control elements can be provided to regulate the current flowing through the resistive element, thereby enhancing the controllability and robustness of the light source driver. Providing control elements increases the compatibility of light source drivers used with different dimming amplitudes and / or different AC sources. Controllability of the current flowing through the resistive element means that the temperature of the resistive element can be controlled, thus allowing for increased lifespan / service life of the resistive element (e.g., by avoiding 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 exceeding a first predetermined threshold. This embodiment provides a mechanism for reducing overcurrent in the resistive element (e.g., overcurrent occurring when the first predetermined threshold is exceeded), thereby extending the service life of the light source driver. The first predetermined threshold may be a threshold (by a corresponding temperature change) indicating that the service life of the resistive element or the light source driver will be affected by more than a predetermined and / or permissible amount (e.g., according to a set of standards or desired commercial characteristics). For example, some standards may set a maximum permissible or recommended temperature for the resistive element at a predetermined level, and the first predetermined threshold may be a threshold indicating that the maximum permissible / recommended temperature has been reached / exceeded.

[0018] As another example, a resistive element may have a temperature rating (e.g., according to the manufacturer's specifications). A first predetermined threshold may correspond to a threshold indicating whether the temperature rating has been met or exceeded. The temperature rating may indicate the maximum permissible temperature (as recommended by the manufacturer), a recommended maximum temperature, or a fixed percentage thereof (e.g., 90%).

[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 the temperature of the resistive element at 140°C. For example, in the case where the temperature sensing element includes a thermistor in thermal contact with the resistive element, the current through the resistive element can be reduced in response to the thermistor reaching a temperature between 95 and 100°C.

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

[0022] Specifically, the control element can be configured to control the average current flowing from the energy storage capacitor to the light source in response to parameters monitored by the temperature sensing element.

[0023] In at least one example, the control element uses pulse width modulation (PWM) to control the average current supplied to the light source by the energy storage capacitor. In other words, the control element can use PWM to control the average current supplied to the light source. This mechanism facilitates the control of a highly adaptive average current.

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

[0025] Buck and / or boost converters are a common mechanism for controlling the current between energy storage capacitors and light sources, and are often used to improve the power factor of light source drivers.

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

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

[0028] The microcontroller can be configured to use pulse width modulation (PWM) technology to control the operation of buck and / or boost converters. That is, the microcontroller can use PWM to trigger the operation of the buck and / or boost converters (or manually control the operation).

[0029] In some embodiments, the control element is configured to control the current flowing from the energy storage capacitor to the light source in response to 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 response to parameters monitored by the temperature sensing node.

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

[0031] In cases where 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 maintaining a voltage at a particular node that defines the peak / RMS current supplied to the light source.

[0032] Of course, the operation of buck and / or boost converters can be overwritten (e.g., via a microcontroller).

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

[0034] A thermistor can be positioned to monitor the temperature at the pads of a resistive element.

[0035] In at least one embodiment, the light source driver further includes an output element configured to provide a user-perceptible output, wherein the output element is configured to control the user-perceptible output in response to parameters monitored by a temperature sensing element. This provides the user with an indication to easily determine whether the light source driver (or the illuminator containing the light source driver) is compatible with AC power.

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

[0037] Energy storage capacitors may include, for example, electrolytic capacitors. However, other capacitor types, such as ceramic capacitors and / or film (based) capacitors, may be used. Resistive elements include any suitable resistive or impedance device, such as 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 invention, a illuminator is provided, comprising 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 one aspect of the present invention, a method for operating a light source driver for a light source of a lighting device is provided. The method includes: receiving AC power from an AC power source using a rectifier and outputting a rectified voltage for powering the light source; using a storage capacitor to receive and store the rectified voltage for powering the light source; using a resistive element to connect the output of the rectifier to the storage capacitor; and using a temperature sensing element to monitor parameters responding to temperature changes in the resistive element or their causes, thereby facilitating the determination of whether the light source driver is compatible with the AC power source.

[0040] These and other aspects of the invention will become apparent and will be illustrated from the embodiments described below. Attached Figure Description

[0041] To better understand the invention and to more clearly illustrate how the invention can be implemented, reference will now be made to the accompanying drawings by way of example only, in which:

[0042] Figure 1 The effect of phase-cut dimming on the voltage supplied to the lamp driver by the AC power supply is shown;

[0043] Figure 2 A light source driver according to a first embodiment is shown;

[0044] Figure 3 The effect of the light source driver according to the embodiment is shown;

[0045] Figure 4 A light source driver according to a second embodiment is shown; and

[0046] Figure 5 A method according to an embodiment is shown. Detailed Implementation

[0047] The invention will be described with reference to the accompanying drawings.

[0048] It should be understood that while the detailed description and specific examples illustrate exemplary embodiments of the apparatus, system, and method, they are intended for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, system, and method of the present invention will become more readily apparent from the following description, the appended claims, and the accompanying drawings. It should be understood that the drawings are merely schematic and not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to denote the same or similar parts.

[0049] This invention provides a light source driver for a light source in an illuminator. The disclosure proposes monitoring parameters that respond to temperature changes in a resistive element or their causes to determine 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 for storing charge to power the light source.

[0050] The basic concept of this invention is based on the understanding that the lifespan of a light source driver is affected by overheating of the resistive element connected in series with the energy storage capacitor. By monitoring parameters that respond to or cause temperature changes, potential overheating can be identified, thereby determining that the AC power supply powering the light source driver is incompatible with the light source driver (i.e., causing overheating).

[0051] Other basic concepts propose methods to overcome the overheating problem of this resistive element, thereby improving the compatibility and service life of the light source driver.

[0052] The embodiments of the present invention can be used in any suitable lighting fixture.

[0053] Figure 1 A diagram 100 is provided 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).

[0054] An exemplary light source driver (not shown) includes a rectifier and a storage capacitor (for powering 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 storage capacitor. A resistive element may be connected in series with the storage capacitor (e.g., at least for current shaping purposes).

[0055] The first waveform 110 shows the voltage level provided by the AC power supply at a first dimming level (at a low dimming level or "deep dimming," i.e., a dimming level designed for low-intensity light output, such as 90-degree phase cut). The second waveform 120 shows the input current level provided by the AC power supply at the first dimming level. As shown, phase-cut dimming causes large spikes in the input current, resulting in high peak voltage and current.

[0056] If a second higher dimming level is to be used (i.e., a dimming level designed for a larger intensity of light output), the peak voltage / current at the second dimming level 120 will be less than the peak voltage / current at the higher dimming level 110.

[0057] This is the result of the phase-cut dimming process.

[0058] The larger peak voltage (at low light levels) induces a larger current in the resistive element connected in series with the energy storage capacitor receiving (rectified) AC power. This larger current increases the temperature of the resistive element (due to increased heat dissipation), which shortens the lifespan of the resistive element and consequently, the lifespan of the light source driver.

[0059] This disclosure recognizes that the ability to monitor parameters in response to a temperature rise (or its cause) and to control / reduce the current flowing through the resistive element accordingly can increase the service life of the light source driver.

[0060] Figure 2 A light source driver 200 according to an embodiment of the present invention is shown. The light source driver is configured to power a light source 295 of an illuminator 20 of a lighting device (which is itself an embodiment of the present invention).

[0061] The light source driver 200 includes a rectifier 210 configured to receive AC power from an AC power supply 290 and output a rectified voltage to power the light source 295. The rectifier 210 shown is a full-wave diode bridge rectifier. However, the rectifier 210 can be replaced by any other suitable rectifier, such as a half-wave diode bridge rectifier, a center-tapped rectifier, etc.

[0062] The light source driver 200 also includes an energy storage capacitor C1, which is configured to receive and store the rectified voltage used to power the light source. The energy storage capacitor smooths the rectified voltage to provide a DC-like voltage for powering the light source, as is well known to those skilled in the art. Therefore, the energy storage capacitor C1 can alternatively be labeled as a smoothing capacitor.

[0063] The energy storage capacitor may be, for example, an electrolytic capacitor. However, other capacitor types may be used, such as ceramic capacitors and / or (based on) film capacitors. As will be understood by those skilled in the art, the energy storage capacitor C1 may be replaced by multiple energy storage capacitors (e.g., arranged in parallel).

[0064] The light source driver 200 also includes a resistive element R1 connected in series with the energy storage capacitor C1. The resistive element R1 is shown connected between the energy storage capacitor C1 and ground or a reference voltage, but it can alternatively be positioned to connect the energy storage capacitor to the output of the rectifier 210. A series connection of the resistive element R1 and the energy storage capacitor (C1) coupled in parallel to the output of the rectifiers (210, 410) may also exist.

[0065] The resistor R1 helps shape the current of the rectified voltage, which helps smooth the current supplied to the light source 295. The current shaping process is well known to those skilled in the art.

[0066] The light source driver 200 also includes (optionally) a diode D1, which helps with current shaping.

[0067] The light source driver 200 also includes temperature sensing elements T1, 254. The temperature sensing elements are configured to monitor parameters in response to temperature changes in the resistive element or their causes.

[0068] For example, this could include directly measuring the temperature of the resistive element, for instance, by monitoring the current passing through a thermistor T1 that is in thermal contact with the resistive element.

[0069] In the example shown, the temperature sensing element includes a temperature monitoring module 254 (which can be formed as an aspect of a microcontroller 250 for a light source driver 200) and a temperature sensor T1. The temperature sensor is adapted to respond to a temperature change of the resistive element detected by the temperature monitoring module 254. In other words, the temperature monitoring module detects the response of the temperature sensor to a temperature change of the resistive element.

[0070] The temperature sensor T1 may include, for example, a thermistor, a thermocouple, or any other suitable sensor that responds to temperature changes.

[0071] As shown in the figure, the temperature sensor T1 can be thermally connected to one end of the resistive element R1 (e.g., a pad). This allows for direct and accurate monitoring of the temperature of the resistive element.

[0072] By monitoring parameters responding to temperature changes (or their causes) in response to resistive element R1, temperature sensing elements 254 and T1 help determine whether the light source driver is compatible with AC power (e.g., whether it is compatible with a specific dimming level of the AC power). In particular, temperature sensing elements 254 and T1 determine characteristics that identify whether the lifespan of the light source driver 200 is adversely affected by the AC power (e.g., by a specific dimming level of the AC power).

[0073] In some embodiments, the light source driver 200 can be configured to adapt to the operation of the light source driver 200 in order to improve the compatibility of the light source driver with AC power supply.

[0074] The light source driver may include a control element 256 that controls the current flowing through the resistive element in response to parameters monitored by the temperature sensing element.

[0075] Specifically, the light source driver may include 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 ratings of the resistive element (e.g., a recommended / maximum temperature rating, a recommended / maximum current rating, or a recommended / maximum voltage drop rating) and therefore may vary depending on the implementation details.

[0076] In the illustrated embodiment, control element 256 is implemented as an aspect of microcontroller 250, which may use buck and / or boost converter 293 (e.g., buck converter, boost converter, or buck-boost converter) to control the average current flowing from the energy storage capacitor to the light source. Control element 256 may be implemented as an aspect of temperature sensing elements 254, T1, within the same microcontroller 250.

[0077] The operation of buck, boost, 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, energy storage capacitor C1) to and from the output load while maintaining a normally constant current supply (and voltage) to the output load.

[0078] Buck and / or boost converters may include a current sensing node and are configured to maintain the voltage at the current sensing node within a predetermined range (e.g., by employing hysteresis). As another example, the voltage at the current sensing node may define the peak / RMS current supplied to the light source.

[0079] Control element 256 can be configured to use pulse width modulation (PWM) techniques to control the average current supplied to the light source by the energy storage capacitor. Specifically, control element 256 can be configured to use PWM techniques to control the operation of the buck and / or boost converter 293 (e.g., alternately activating and deactivating the buck and / or boost converter, e.g., alternately allowing or preventing the buck and / or boost converter from receiving power from the energy storage capacitor C1). This method provides a well-studied and adaptive approach for controlling the power / current flowing from the energy storage capacitor to the light source.

[0080] Therefore, buck and / or boost converters may include control input node N. CO For example, a pulse width modulation node, and can be configured to control the operation of the buck and / or boost converter in response to a signal at the control input node (e.g., a signal provided by microcontroller 250). For example, the buck and / or boost converter 293 can alternately activate and deactivate other components of the buck and / or boost converter in response to a signal at the control input node. In particular, the buck and / or boost converter can alternately allow or prevent the buck and / or boost converter from receiving power from the energy storage capacitor C1 in response to a signal at the control input node.

[0081] Other methods for controlling or modulating the current flowing from the energy storage capacitor to the light source will be apparent to those skilled in the art, and may be implemented, for example, in hardware.

[0082] In a preferred embodiment, control element 256 is configured to reduce the average current flowing through the resistive element in response to a temperature exceeding a predetermined threshold, for example, by appropriately modulating (pulse width) the current flowing from the energy storage capacitor to the light source. The predetermined threshold may depend on the temperature rating of the resistive element and therefore may vary depending on the implementation details.

[0083] By reducing the average current flowing through the resistive element, the heat dissipated by the resistive element is reduced, thereby lowering the temperature of the resistive element and extending its service life.

[0084] Since the proposed method for reducing average current may only occur at deep dimming levels (see...), Figure 1 Therefore, the impact of the reduction in the average power / current of the light source 295 is minimal.

[0085] The light source driver 200 may include an output element 270 configured to provide a user-perceptible output, such as a visual output. The output element is configured to control the user-perceptible output in response to parameters monitored by a temperature sensing element.

[0086] In this way, output element 270 can provide a user-perceptible indication of whether the light source driver 200 is compatible with AC power. Examples of suitable user-perceptible outputs include visual outputs, such as LED outputs, or audio outputs (such as buzzer outputs). Output elements may therefore include one or more LEDs and / or one or more buzzers, although other suitable visual / auditory outputs will be apparent to those skilled in the art.

[0087] Preferably, the output element is configured to adjust the user-perceptible output in response to a parameter monitored by the temperature sensing element exceeding a predetermined threshold (e.g., a threshold indicating that the lifespan of the light source driver 200 will be affected). As an example, passing the predetermined threshold can trigger the output element to provide a user-perceptible output (such as light).

[0088] The output element 270 can be controlled by a microprocessor 250, which can be the same microprocessor used to monitor parameters in response to temperature changes in the resistive element R1 or their causes.

[0089] In some examples, instead of being configured to provide a user-perceptible output, output element 270 can be configured to communicate with an external user interface (e.g., a mobile device, such as a cellular phone or smartphone). Thus, the output element can be configured to transmit a (wireless) signal to the external user interface based on parameters monitored by a temperature sensing element (e.g., if the monitored parameters indicate that the temperature of the resistive element has exceeded or is predicted to exceed a predetermined threshold), indicating whether the light source driver is compatible with AC power.

[0090] The external user interface can be configured to modify user-perceptible alarms in response to signals received from output element 270.

[0091] This mechanism provides a system for warning users that the light source driver is incompatible with the AC source.

[0092] Output element 270 can communicate with an external user interface (not shown) using any suitable communication protocol, such as via the Internet, wireless networks, etc. Suitable wireless communication protocols for communicating with external devices or interfaces include infrared links, Zigbee, Bluetooth, wireless LAN protocols such as those according to the IEEE 802.11 standard, 2G, 3G, or 4G telecommunications protocols, etc. Other formats will be apparent to those skilled in the art.

[0093] The light source driver 200 may omit the control element 256 or the output element 270 depending on the desired implementation. In other words, the light source driver 200 may include the control element 256 and / or the output element 270.

[0094] The light source 295 may include an LED device (such as an LED string). Other light sources 295 (e.g., halogen bulbs) may also be considered, but are less preferred due to efficiency reasons.

[0095] The microcontroller 250 can also be configured to receive power from the energy storage capacitor. Similarly, the output element 270 (if present) can receive power from the energy storage capacitor.

[0096] The microcontroller 250 can be configured to perform additional tasks and control the current flowing from the energy storage capacitor to the light source to perform these tasks.

[0097] For example, the microcontroller can be configured to receive user input or control input (e.g., from a wireless signal) and, in response to the user input or control input, control the pulse width modulation of the buck and / or boost converter (e.g., to further control the dimming of the light source 295).

[0098] As another example, the microcontroller itself can perform some of the tasks previously performed by the buck and / or boost converter 293, such as performing current sensing and controlling the buck and / or boost converter in response to it (e.g., using control input node N). CO This makes the operation of the buck and / or boost converters dependent on the microcontroller 250 (e.g., rather than directly sensing the current itself).

[0099] Other operations of the microcontroller are obvious to those skilled in the art.

[0100] Figure 3 The effect of controlling the current flowing from the energy storage capacitor to the light source on the temperature of the resistive element R1 is shown. The x-axis t represents time (for four different cases), and the y-axis T(t) represents the temperature of the resistive element R1 at a specific time point.

[0101] In the first case, as shown by the first time 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 time period, the pulse width modulation is reduced to a lower value of 65%.

[0102] Specifically, for the first time period, the buck and / or boost converter (which controls the current flowing from the energy storage capacitor to the light source) is allowed to draw power from the energy storage capacitor for 70% of the time. For the second time period, power is only allowed to be drawn for 65% of the time.

[0103] It can be seen that lower pulse width modulation (i.e., lower average current flowing from the energy storage capacitor to the light source) leads to lower temperature of the resistive element.

[0104] Figure 3The effect of phase-cut dimming performed by an AC power supply on the temperature T(t) of the resistive element is also shown.

[0105] In the third case, shown by the third time period t3, the AC power supply does not perform phase-cut dimming. In the fourth case, shown by the fourth time period t4, the AC power supply performs phase-cut dimming. The execution of phase-cut dimming results in a higher temperature of the resistive element.

[0106] therefore, Figure 3 It shows how phase-cut dimming increases the temperature of the resistive element (compare t3 to t4), and also illustrates how controlling the current flowing from the capacitive element to the light source can reduce the temperature of the resistive element by reducing the average current flowing through the resistive element (compare t1 to t2).

[0107] At low light levels, reducing the average current flowing to the light source to lower the (average) temperature of the resistive element has minimal impact (because light brightness is no longer a priority, and lower brightness levels are acceptable).

[0108] Figure 4 A light source driver 400 according to another embodiment of the present invention is shown. The light source driver 400 is configured to power a light source 495 of an illuminator 40 of a lighting device (which is itself an embodiment of the present invention).

[0109] Unless otherwise explicitly stated, the corresponding features of the light source driver 400 or illuminator 40 can be found as previously referenced. Figure 2 To implement as described.

[0110] The light source driver 400 includes a rectifier 410 that rectifies the voltage supplied by the AC power supply 490. Suitable embodiments of the rectifier 410 have been previously described. The light source driver also includes a storage capacitor C1 and a resistive element R1, which may also be implemented as previously described. The light source driver 200 also includes (optionally) a diode D1.

[0111] The light source driver 400 also includes a temperature sensing element 450. The temperature sensing element is adapted to reuse a thermistor to monitor the temperature of the resistive element R1.

[0112] Control element 493 is adapted to control the current through resistive element R1 in response to parameters monitored by temperature sensing element 450. Specifically, control element 493 here includes a buck and / or boost converter configured based on current sensing node N. C The voltage at the current sensing node is used to control the power / current supplied to the light source 495 (e.g., to maintain the voltage at the current sensing node within a predetermined range or where the voltage defines the "peak" current of the buck and / or boost voltage).

[0113] In this embodiment, the current through the resistive element R1 is not controlled by a microcontroller, but rather by a temperature sensing element controlling the current sensing node N. C The voltage at the point is used to directly control the buck and / or boost converters to control the current.

[0114] Therefore, the current through the resistive element R1 is controlled via hardware, rather than in software (e.g., via a properly configured microcontroller).

[0115] Therefore, control element 493 is adapted to control the current through resistor element R1 in response to parameters monitored by temperature sensing element 450. Thus, control element 460 performs a mechanism for directly controlling the temperature of resistor element (e.g., pads of series resistor) via current control.

[0116] Temperature sensing element 450 includes a temperature-sensitive element (e.g., a thermistor) T1.

[0117] As is well known in the art, the resistance of a thermistor changes in response to temperature. Proper positioning of the thermistor (e.g., thermal contact with the resistive element R1 or its pads) enables monitoring of the temperature of the resistive element.

[0118] This embodiment proposes using a voltage divider device to monitor the voltage across the thermistor T1, for example, by connecting the thermistor in series with a first additional resistive element R2 (which is connected between the thermistor and the ground / reference voltage). Thermistor T1 is connected to a high voltage V. cc (For example, 3.3V or the output of rectifier 410) and the first additional resistive element R2. The voltage across the first additional resistive element R2 varies based on the resistance of the thermistor (and therefore the temperature of the resistive element R1).

[0119] Those skilled in the art can easily provide a high voltage V supplied by AC power supply 490. cc (For example, using the voltage output of rectifier 410).

[0120] The voltage across the first additional resistor R2 controls the conductivity of the first transistor M1; that is, 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 can be placed to smooth the voltage supplied to the gate of the first transistor M1.

[0121] In this way, when the temperature across the thermistor exceeds a predetermined threshold, the first transistor M1 is controlled to turn on. The values ​​of the thermistor T1 and / or the first additional resistor element R2 can be selected to appropriately control the gate of the first transistor T1 (e.g., apply an appropriate voltage bias) when the temperature at the resistor element R1 (i.e., the temperature of the thermistor) reaches an acceptable threshold.

[0122] 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 terminal of the second additional resistor R3. The second terminal of the second additional resistor can be connected to ground or a reference voltage.

[0123] The first transistor and the second additional resistor element R3 together properly bias the voltage across the first additional resistor element and act as an electrical buffer.

[0124] The temperature sensing element 450 may further include a second transistor M2, which has: a gate or base connected to the source or emitter of the first transistor M1, and a connection to a high voltage V. cc The drain or collector of the first additional resistor R4 is connected to the source or emitter of the second additional resistor R5. The second terminal of the third additional resistor R4 is connected to the first terminal of the fourth additional resistor R5, which can be connected to ground or a reference voltage.

[0125] The second terminal of the third additional resistor element is also coupled to the current sensing node N. C .

[0126] When the current through the second additional resistor element R3 exceeds a predetermined threshold, the second transistor M1 is turned on.

[0127] For the purposes of this disclosure, transistors may include any suitable transistor, such as a bipolar junction transistor or a MOSFET. Other suitable transistors will be apparent to those skilled in the art.

[0128] Those skilled in the art will understand that in some embodiments, by appropriately selecting the first additional resistor element R2, the second, third, and fourth additional resistor elements R3, R4, R5, the smoothing capacitor C2, and the transistors M1 and M2 can be omitted.

[0129] The embodiments may include components from two of the embodiments of the present invention, for example, at least for the purpose of redundancy and / or combination / improvement of operation. In particular, the voltage across the first additional resistive element R1 (for the light source driver 400) may be provided to a microcontroller (not shown) that controls the buck and / or boost converter 493 in a manner similar to that of the microcontroller for the light source driver 200.

[0130] As another example, the light source driver 400 may include the output element described above.

[0131] Figure 5 A method 500 for operating a light source driver for a lighting device is shown.

[0132] The method includes step 510: using a rectifier to receive AC power from an AC power source and output a rectified voltage for powering a light source.

[0133] Method 500 further includes step 520: using a storage capacitor to receive and store the rectified voltage used to power the source. This step can be performed by connecting the output of the rectifier to the storage capacitor using a resistive element.

[0134] Method 500 further includes step 550: using a temperature sensing element to monitor parameters in response to temperature changes in the resistive element or their causes, thereby facilitating the determination of whether the light source driver is compatible with the AC power supply.

[0135] Those skilled in the art will understand that this method can be applied to perform any embodiment or concept of the invention as described with reference to the implemented light source driver.

[0136] While embodiments of temperature sensing elements comprising thermistors (or other temperature-sensitive elements) have been generally described, other suitable sensors may be used. In particular, the temperature of a resistive element responds to the current flowing through it.

[0137] Therefore, the current through the resistive element can be sensed and the current through the resistive element can be controlled in response (e.g., the current through the resistive element can be limited). This can be done by setting the voltage at the current sensing node to be equal to the voltage across the resistive element (e.g., using a buffer element, etc.).

[0138] Therefore, the temperature sensing element may include 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.

[0139] As an example, return to the reference. Figure 4 Thermistor T1 (which is coupled to V) cc The connection between the anode (located between the energy storage capacitor C1 and the first additional resistive element R2) and the first additional resistive element R2 can be replaced by a sensing resistive element connected between the anode (located between the energy storage capacitor C1 and the resistive element R1) and the first additional resistive element R2. This can act as a voltage divider, providing a voltage in response to the current through the resistive element R1 (at the node between the sensing resistive element and the first additional resistive element R2). This voltage can be connected to a current sensing node (e.g., via a buffer and biasing device) to control the current flowing from the energy storage capacitor C1 to the light source 495 (thus controlling the current through the resistive element R1). The threshold for control can be a reference voltage V. cc To set it up.

[0140] From a study of the accompanying drawings, disclosure, and appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. A single processor or other unit can 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 imply that combinations of these measures cannot be advantageously used. If the term "suitable" is used in the claims or description, it should be noted that the term "suitable" is intended to be equivalent to the term "configured as." Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A light source driver (200, 400) for powering a light source (295, 495) of a lighting device (20, 40), the driver comprising: A rectifier (210, 410) is configured to receive AC power from an AC power source and output a rectified voltage for powering the light source. An energy storage capacitor (C1) is configured to receive and store the rectified voltage used to power the light source; The series connection of the resistive element (R1) and the energy storage capacitor (C1) is coupled in parallel to the output of the rectifier (210, 410) and the light source (295, 495), wherein the series connection is adapted to receive AC tangent power and to induce a current in the resistive element (R1) by the AC tangent power at a dimming level intended for low intensity light output. as well as Sensing element (T1, 254, 450), the sensing element is configured to monitor the following parameters: The temperature of the resistive element (R1), wherein the temperature is adapted to increase due to the current; The voltage across the resistive element (R1), or The current flowing through the resistive element (R1), and The light source driver (200, 400) is adapted to use the monitored parameters to determine whether the light source driver is compatible with the AC power supply.

2. The light source driver (200, 400) according to claim 1 further includes a switch connected in parallel with the resistive element (R1), wherein the switch is arranged to close when the current through the resistive element (R1) is below a threshold value.

3. The light source driver according to claim 1 or 2 further includes a control element (256, 293, 493) configured to control the current flowing through the resistive element in response to the parameter monitored by the sensing element.

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

5. The light source driver of claim 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 (256) uses pulse width modulation technology to control the average current supplied to the light source by the energy storage capacitor.

7. The light source driver according to any one of claims 4 to 6, wherein the control element comprises a buck and / or boost converter (293, 493) configured to control the current flowing from the energy storage capacitor to the light source, wherein the control of the buck and / or boost converter is responsive to the parameters monitored by the temperature sensing element.

8. The light source driver of claim 7, wherein the control element comprises a microcontroller (250) configured to control the operation of the buck and / or boost converter in response to parameter monitoring performed by the temperature sensing element.

9. The light source driver according to claim 8, wherein the microcontroller (250) uses pulse width modulation technology to control the operation of the buck and / or boost converter (293).

10. The light source driver according to any one of claims 4, 5, 6, 8 and 9, wherein: The control element (493) is configured to respond to the current sensing node (N) C The voltage at the point is used to control the current flowing from the energy storage capacitor to the light source; as well as The temperature sensing element (450) is configured to directly control the voltage at the current sensing node in response to the parameters monitored by the temperature sensing node.

11. The light source driver according to any one of claims 1, 2, 4, 5, 6, 8 and 9, wherein the temperature sensing element comprises a thermistor (T1) responsive to temperature changes.

12. The light source driver according to any one of claims 1, 2, 4, 5, 6, 8 and 9, further comprising an output element (270) configured to provide a user-perceptible output, wherein the output element is configured to control the user-perceptible output in response to the parameter monitored by the temperature sensing element.

13. The light source driver of claim 12, wherein the output element (270) is configured to adjust the user-perceptible output in response to the parameter monitored by the temperature sensing element exceeding a predetermined threshold.

14. A lighting device (20, 40) comprising a light source driver (200, 400) according to any one of claims 1 to 13 and a light source (295, 495) configured to draw power from the energy storage capacitor (C1).

15. A method (500) for operating a light source driver for a lighting device, the method comprising: The (510) rectifier is used to receive AC power from the AC power source and output a rectified voltage for powering the light source. A (520) energy storage capacitor is used to receive and store the rectified voltage used to power the light source; A resistive element is connected in series with the energy storage capacitor, wherein the series connection is coupled in parallel with the output of the rectifier and the light source (295, 495), and is used to receive AC tangent power, and to induce a current in the resistive element (R1) by the AC tangent power at a dimming level intended for low-intensity light output; and The following parameters are monitored using a (550) sensing element: The temperature of the resistive element (R1), wherein the temperature is adapted to increase due to the current; The voltage across the resistive element (R1); or The current flowing through the resistive element (R1), and Determine whether the light source driver is compatible with the AC tangent power at a dimming level intended for low-intensity light output.

Images