VOICE COILS FOR USE WITH TEMPERATURE SENSORS AND DEVICES INCLUDING THE SAME
20230032222 · 2023-02-02
Inventors
Cpc classification
G01K1/026
PHYSICS
G01K7/427
PHYSICS
H04R2499/11
ELECTRICITY
H04R2430/01
ELECTRICITY
H04R7/045
ELECTRICITY
International classification
G01K1/02
PHYSICS
G01K7/42
PHYSICS
Abstract
A panel audio loudspeaker having a panel extends in a plane and an actuator is coupled to the panel. The actuator includes a voice coil attached to and extending from the panel along an axis, a magnet assembly suspended from the panel via one or more springs, and a temperature sensor in electrical contact with the coil at three different axial locations. The temperature sensor is configured, during operation of the device, to measure a temperature of the coil based on voltage measurements at the three different axial locations.
Claims
1. A device comprising: a panel audio loudspeaker comprising a panel extending in a plane and an actuator coupled to the panel, the actuator comprising: a voice coil attached to and extending from the panel along an axis; a magnet assembly suspended from the panel via one or more springs; and a temperature sensor in electrical contact with the coil at three different axial locations, the temperature sensor being configured, during operation of the device, to measure a temperature of the coil based on voltage measurements at the three different axial locations.
2. The device of claim 1, wherein the panel comprises an OLED display.
3. The device of claim 1, wherein the three different axial locations comprises: a first location positioned at a first end of the voice coil attached to the panel, a second location positioned at a second end of the voice coil opposite the first end, and a third location positioned between the first and second locations.
4. The device of claim 3, wherein the third location is positioned closer to the first location than to the second location.
5. The device of claim 3, wherein the temperature sensor comprises one or more data processors programmed to measure the temperature of the coil by determining an electrical resistance of each of one or more portions of the voice coil based on the voltage measurements.
6. The device of claim 5, wherein the one or more data processors are further configured to generate a temperature measurement for each of three portions of the voice coil, the three portions of the voice coil including a first portion that extends from the first to the third location, a second portion that extends from the second to the third location, and a third portion that extends from the first to the second location.
7. The device of claim 5, wherein the one or more data processors are further configured to correlate the electrical resistance of each of the one or more portions of the voice coil to a temperature measurement of a corresponding portion of the voice coil.
8. The device of claim 5, wherein the one or more data processors are further configured to generate a temperature curve using the resistance measurements for each of the three portions of the voice coil.
9. The device of claim 5, wherein the one or more data processors are further programmed to estimate a temperature of the panel based on the temperature of the coil.
10. The device of claim 9, wherein the device is configured to change one or more settings of the device based on the estimated temperature of the panel.
11. The device of claim 10, wherein the one or more settings comprises a brightness of the display and a volume of audio output by the device.
12. A mobile device comprising: an electronic display panel extending in a plane; a chassis attached to the electronic display panel and defining a space between a back panel of the chassis and the electronic display panel; an electronic control module housed in the space, the electronic control module comprising a processor; a panel audio loudspeaker comprising an actuator coupled to the display panel, the actuator comprising: a voice coil attached to and extending from the panel along an axis; and a magnet assembly suspended from the panel via one or more springs; and a temperature sensor in electrical contact with the coil at three different axial locations, the temperature sensor being configured, during operation of the device, to measure a temperature of the coil based on voltage measurements at the three different axial locations; and wherein during operation of the actuator the one or more springs flex to accommodate axial displacements of the magnet assembly relative to the voice coil.
13. The mobile device of claim 12, wherein the mobile device is a smartphone or tablet computer.
14. A wearable device comprising: an electronic display panel extending in a plane; a chassis attached to the electronic display panel and defining a space between a back panel of the chassis and the electronic display panel; an electronic control module housed in the space, the electronic control module comprising a processor; a panel audio loudspeaker comprising an actuator coupled to the display panel, the actuator comprising: a voice coil attached to and extending from the panel along an axis; and a magnet assembly suspended from the panel via one or more springs; and a temperature sensor in electrical contact with the coil at three different axial locations, the temperature sensor being configured, during operation of the device, to measure a temperature of the coil based on voltage measurements at the three different axial locations; and wherein during operation of the actuator the one or more springs flex to accommodate axial displacements of the magnet assembly relative to the voice coil.
15. The wearable device of claim 14, wherein the wearable device is a smart watch or a head-mounted display.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
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[0018]
[0019]
[0020]
[0021]
[0022]
[0023] Like reference symbols in the various drawings indicate like elements.
DETAILED DESCRIPTION
[0024] In certain aspects, the disclosure features voice coil actuators for panel audio loudspeakers, such as distributed mode loudspeakers (DMLs), that include temperature sensors for monitoring the temperature of the voice coil and/or the panel or other components which may experience undesirable heating due to heating of the voice coil during operation. Such loudspeakers can be integrated into a mobile device, such as a mobile phone. For example, referring to
[0025] Mobile device 100 also produces audio output. The audio output is generated using a panel audio loudspeaker that creates sound by causing the flat panel display to vibrate. The display panel is coupled to an actuator, such as a distributed mode actuator, or DMA. The actuator is a movable component arranged to provide a force to a panel, such as touch panel display 104, causing the panel to vibrate. The vibrating panel generates human- audible sound waves, e.g., in the range of 20 Hz to 20 kHz.
[0026] In addition to producing sound output, mobile device 100 also produces haptic output using the actuator. For example, the haptic output can correspond to vibrations in the range of 180 Hz to 300 Hz.
[0027]
[0028] Referring to
[0029] Actuator 300 further includes a magnet 304 that fits within a space formed by voice coil 302. Actuator 300 further includes posts 308a and 308b, which are attached to panel 306. In this embodiment, panel 306 is attached to display 104, although in other embodiments, panel 306 can form part of display 104 and voice coil 302 and posts 308a and 308b are attached directly to the display.
[0030] The magnetic field produced by magnet 304 runs along the x-direction as it passes through coil 302. In some embodiments, a pole piece is attached to the top surface of magnet 304 to better focus the magnetic field produced by the magnet in the x-direction. Magnet 304 is attached to a cup 310, which is mechanically coupled by two elastic components, 312a and 312b, (e.g., springs) to posts 308a and 308b. Elastic components 312a and 312b connect cup 310 to posts 308a and 308b, respectively. Elastic components 312a and 312b can flex to allow magnet 304 and cup 310 to move in the z-direction, in response to coil 302 being energized, which induces a magnetic field that surrounds the coil and interacts with the magnetic field of the magnet.
[0031] Each of the three terminals at positions P.sub.1, P.sub.2, and P.sub.3 of coil 302 are electrically coupled to a temperature sensor 240, e.g., by wires that are connected at one end to the coil and at the opposite end to the temperature sensor.
[0032] The three terminals at positions P.sub.1, P.sub.2, and P.sub.3 partition coil 302 into discrete lengths. A first length that extends between P.sub.1 and P.sub.2 is labeled L.sub.1, while a second length that extends between P.sub.2, and P.sub.3 is labeled L.sub.2. The sum of the lengths L.sub.1 and L.sub.2 is equal to the total length of coil 302, which is labeled L.sub.2. While
[0033] In the embodiment illustrated in
[0034] Temperature sensor 240 can determine a voltage at each of the three terminals, relative to a common, ground terminal. Temperature sensor 240 can also determine the voltage of one of the terminals at positions P.sub.1, P.sub.2, and P.sub.3 relative to one of the other terminals.
[0035] During the operation of actuator 300, coil 302 is energized by a current from a power supply. Knowing the magnitude of the current flowing through coil 302, and the voltage across two of the terminals of the coil, temperature sensor 240 can calculate the resistance of the length of coil between the two terminals. While the current passes through coil 302, the coil is expected to heat up. In general, as the temperature of a conductor increases, the resistivity of the conductor also increases. Therefore, temperature sensor 240 is configured to correlate the change in resistance of a length of coil 302 to a change in temperature of the length of the coil.
[0036] Because one end of coil 302 is in free air, while the opposite end is attached to panel 306, the temperatures at positions P.sub.1 and P.sub.2 are expected to be different. For example, because coil 302 is attached to panel 306, some of the heat of the coil is transferred to the panel. Accordingly, the temperature at position P.sub.1 should be less than the temperature at position P.sub.2, with a temperature gradient being formed between the two positions.
[0037] Accordingly, it is expected that the temperature of coil 302 at position P.sub.2 be approximately the same as the temperature of panel 306 at the portion of the panel that is attached to the coil. It is particularly useful to approximate the temperature of coil 302 at position P.sub.1, as this temperature is likely to be the same as the temperature of the portion of display 104 that is in contact with the coil.
[0038] Panel 306 can include an electronic display panel or can be attached to an electronic display panel, such as an OLED display, which may be sensitive to heat. Because coil 302 transfers some of its heat to panel 306, it is useful to monitor the temperature of the coil to prevent the panel from reaching temperatures that would damage the electronic display panel.
[0039] A first-order approximation of the coil temperature can be made by measuring the initial resistance of the length L.sub.c when the coil is not energized, measuring the resistance of the length L.sub.c when the coil is energized, and using these resistance measurements to determine a change in resistance of the length L.sub.c. For example, temperature sensor 240 can measure the voltages at positions P.sub.1 and P.sub.2, and therefore, the voltage drop across the length L.sub.c. Using the voltage drop across L.sub.c, temperature sensor 240 can determine the resistance of length L.sub.c, and using the change in resistance of L.sub.c, data processor 320 can approximate the change in temperature of coil 302.
[0040] The first-order approximation of the coil temperature can be used to determine a first-order approximation of the display temperature. For example, the relationship between the change in coil temperature and the change in display temperature can be found experimentally, and the equation relating the two can be programmed into data processor 320, as described in greater detail below with respect to
[0041] More specifically, when the change in temperature of a coil is determined using terminals at the two endpoints of the coil, the approximation determines the change in temperature of the midpoint of the coil. Because the equation derived experimentally using two-terminals does not account for the gradient across the coil, the approximation of the change in display temperature using the two-terminal equation will be of limited use.
[0042] A coil that includes an additional terminal positioned between the two ends of the coil allows a temperature sensor to measure the resistance across portions of the coil. Measuring the resistance across multiple portions of the coil allows for the coil temperature to be approximated at multiple points along the coil. Therefore, the additional terminal can allow temperature sensor 240 to account for the temperature gradient across coil 302, which improves the approximation of the change in display temperature compared to the two- terminal approximation.
[0043] By measuring the voltages at positions P.sub.1 and P.sub.3, temperature sensor 240 can determine the resistance across the length of coil L.sub.1. Similarly, temperature sensor 240 can determine the resistance across the length of coil L.sub.2. Using the change in the resistances of the lengths L.sub.1 and L.sub.2 from when coil 302 is at room temperature to when the coil temperature has increased as a result of being energized, temperature sensor 240 can approximate the change in temperatures of the lengths L.sub.1 and L.sub.2.
[0044] More specifically, the temperature measurement across L.sub.1 approximates the temperature of the coil at the midpoint between positions P.sub.1 and P.sub.3. In the embodiment shown in
the midpoint between positions P.sub.1 and P.sub.3, at which the temperature measurement across L.sub.1 is approximated, is at
[0045] Just as the temperature measurement across L.sub.1 approximates the coil temperature at a midpoint between positions P.sub.1 and P.sub.3, the temperature measurement across L.sub.2 approximates the coil temperature at the midpoint between positions P.sub.2 and P.sub.3. The midpoint between these two points, at which the temperature measurement across L.sub.2 is approximated, is at
[0046] Approximating the change in coil temperature of lengths L.sub.1, L.sub.2, and L.sub.c yields three measurements at different axial locations along coil 302. Using these three measurements, allows temperature sensor 240 to improve upon the first-order approximation described above by accounting for the temperature gradient formed across coil 302. For example, the relationship between the change in coil temperature at each of the three points,
and the change in display temperature can be found experimentally.
[0047] After determining an equation relating the changes in coil temperature to the change in panel temperature, the equation can be programmed into data processor 320. For example, an equation can be derived by measuring the change in resistance across various portions of the coil as a function of the length of those portions. For each of the different lengths that are sampled, an accompanying display temperature measurement is made. These data points are used to plot the resistance versus tap location and the panel temperature versus tap location. An example of such a plot is shown with respect to
[0048]
[0049] The y-axis is also unitless and shows the change in resistance of portions of the coil. For example, calling R.sub.1 the resistance across L.sub.1 when coil 302 is not energized and R.sub.1'the resistance across L.sub.1 when the coil is energized, then the change in the resistance across L.sub.1 is ΔR.sub.1=R.sub.1′/R.sub.1. Similarly, if R.sub.2 is the resistance across L.sub.2 when the coil is not energized and R.sub.2′ is the resistance across L.sub.2 when the coil is energized, then the change in the resistance across L.sub.2 is ΔR.sub.2=R.sub.2 ′/R.sub.2. Plot 400 shows ΔR.sub.1 and ΔR.sub.2 with respect to the tap location. Curves 404 and 406 corresponds to ΔR.sub.1 and ΔR.sub.2, respectively.
[0050] Plot 400 also shows the change in display temperature, ΔT, in relation to ΔR.sub.1 and ΔR.sub.2. Any suitable method can be used to determine the change in temperature. In general, a temperature sensor is used to measure the initial display temperature, T, at position P.sub.1 when the coil is not energized. After the coil has been energized, the temperature sensor can measure the temperature of the display again to determine another temperature measurement, T′ and ΔT is the quotient T′/T. Curve 402 corresponds to ΔT.
[0051] Plot 400 shows that a linear relationship exists between ΔR.sub.1,ΔR.sub.2, and ΔT. This relationship can be programmed into data processor 320 and used to determine the change in display temperature after the coil has been energized. While plot 400 shows a linear relationship between ΔR.sub.1,ΔR.sub.2, and ΔT the relationship can have other functional forms. For example, the relationship may be linear when coil 302 has been energized for a relatively long time (e.g., 10s of seconds or over a minute), but when the coil has not been energized for a long time, the relationship between ΔR.sub.1,ΔR.sub.2, and ΔT may be quadratic.
[0052] In some embodiments, the temperature at the display can be determined as follows. Referring to
[0053] Referring to
[0054] In general, other mathematical methods can be used to predict the panel temperature from the three terminal measurements.
[0055] In some implementations, data processor 320 can account for the duration of time that coil 302 has been energized and choose a relationship between resistance and temperature according to the duration. For example, when the coil goes from an unenergized state to an energized state, data processor 320 can determine the change in display temperature using a quadratic relationship. Upon reaching a certain threshold time the data processor 320 can choose an equation with a different functional form.
[0056] By monitoring the change in the temperature of display 104, temperature sensor 240 can approximate the change in display temperature and prevent the display temperature from reaching a critical value that may result in the display being damaged.
[0057] To prevent heat damage to display 104, device 100 can be configured to change one or more settings of the device based on the estimated temperature of the display. For example, if the estimated temperature reaches or exceeds a threshold temperature, device 100 can change (e.g., lower) the brightness of the electronic display and/or change (e.g., lower) the volume of audio output by the device.
[0058] Not only is it useful to estimate the temperature of panel 306, it is also useful to estimate the coil temperature at each of multiple points along the coil. While temperature sensor 240 can approximate the temperature at each of three locations along coil 302, that is, at
in some situations it is useful to approximate the temperature at other points along the coil. For example, estimating the temperature at the free end of coil 302, z = L.sub.c, can be useful if the free end of the coil is close to or connected to a heat-sensitive component of device 100. The temperature at other portions of coil 302 may be of interest for similar reasons.
[0059] Just as an equation relating the changes in coil temperature to the change in panel temperature can be derived and programmed into data processor 320, the changes in temperature of the three points along coil 302 can be used to derive the temperature at another point along the coil. In this way, data processor 320 can approximate temperature of coil 302 at points other than the three described above.
[0060] In some implementations, the positions of the three terminals can be different from the positions P.sub.1, P.sub.2, and P.sub.3, shown in
the third terminal of the coil can be at a position P.sub.3′ located at
Having a terminal at position P.sub.3′ allows temperature sensor 240 to approximate the temperature of the bottom quarter of the coil, which is farthest from the connection to panel 306. A temperature sensor connected to a coil having a third terminal at position P.sub.3′ can be used to more accurately approximate the temperature of the coil at z =L.sub.c, compared to temperature sensor 240 that is connected to coil 302.
[0061] Temperature sensor 240 can measure the temperature of coil 302 at the audio frequency of the coil, which is the frequency of the signal that is used to energize the coil. The audio frequency of the coil may be relatively high, e.g., upwards of 40 kHz. In general, the temperature of coil 302 may change more quickly than does the temperature of display 104. Therefore, while temperature sensor 240 may measure the temperature of coil 302 at the audio frequency of the coil, the temperature sensor may measure the temperature of display 104 at a lower frequency.
[0062] In general, the disclosed actuators are controlled by an electronic control module, e.g., electronic control module 220 in
[0063] Processor 610 may be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions. For example, processor 610 can be a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or combinations of such devices.
[0064] Memory 620 has various instructions, computer programs or other data stored thereon. The instructions or computer programs may be configured to perform one or more of the operations or functions described with respect to the mobile device. For example, the instructions may be configured to control or coordinate the operation of the device's display via display driver 630, signal generator 640, one or more components of I/O module 650, one or more communication channels accessible via network/communications module 660, one or more sensors (e.g., biometric sensors, temperature sensors, accelerometers, optical sensors, barometric sensors, moisture sensors and so on), and/or actuator 210.
[0065] Signal generator 640 is configured to produce AC waveforms of varying amplitudes, frequency, and/or pulse profiles suitable for actuator 210 and producing acoustic and/or haptic responses via the actuator. Although depicted as a separate component, in some embodiments, signal generator 640 can be part of processor 610. In some embodiments, signal generator 640 can include an amplifier, e.g., as an integral or separate component thereof
[0066] Memory 620 can store electronic data that can be used by the mobile device. For example, memory 620 can store electrical data or content such as, for example, audio and video files, documents and applications, device settings and user preferences, timing and control signals or data for the various modules, data structures or databases, and so on. Memory 620 may also store instructions for recreating the various types of waveforms that may be used by signal generator 640 to generate signals for actuator 210. Memory 620 may be any type of memory such as, for example, random access memory, read-only memory, Flash memory, removable memory, or other types of storage elements, or combinations of such devices.
[0067] As briefly discussed above, electronic control module 600 may include various input and output components represented in
[0068] Each of the components of I/O module 650 may include specialized circuitry for generating signals or data. In some cases, the components may produce or provide feedback for application-specific input that corresponds to a prompt or user interface object presented on the display.
[0069] As noted above, network/communications module 660 includes one or more communication channels. These communication channels can include one or more wireless interfaces that provide communications between processor 610 and an external device or other electronic device. In general, the communication channels may be configured to transmit and receive data and/or signals that may be interpreted by instructions executed on processor 610. In some cases, the external device is part of an external communication network that is configured to exchange data with other devices. Generally, the wireless interface may include, without limitation, radio frequency, optical, acoustic, and/or magnetic signals and may be configured to operate over a wireless interface or protocol. Example wireless interfaces include radio frequency cellular interfaces, fiber optic interfaces, acoustic interfaces, Bluetooth interfaces, Near Field Communication interfaces, infrared interfaces, USB interfaces, Wi-Fi interfaces, TCP/IP interfaces, network communications interfaces, or any conventional communication interfaces.
[0070] In some implementations, one or more of the communication channels of network/communications module 560 may include a wireless communication channel between the mobile device and another device, such as another mobile phone, tablet, computer, or the like. In some cases, output, audio output, haptic output or visual display elements may be transmitted directly to the other device for output. For example, an audible alert or visual warning may be transmitted from the electronic device 100 to a mobile phone for output on that device and vice versa. Similarly, the network/communications module 660 may be configured to receive input provided on another device to control the mobile device. For example, an audible alert, visual notification, or haptic alert (or instructions therefore) may be transmitted from the external device to the mobile device for presentation.
[0071] The actuator technology disclosed herein can be used in panel audio systems, e.g., designed to provide acoustic and / or haptic feedback. The panel may be a display system, for example based on OLED of LCD technology. The panel may be part of a smartphone, tablet computer, or wearable devices (e.g., smartwatch or head-mounted device, such as smart glasses).
[0072] Other embodiments are in the following claims.