Abstract:
In one embodiment, a corrosion-resistant switching mechanism for enabling a user to control an internal signal of an electronic device id disclosed. The switching mechanism comprises: an environmentally-exposed, manually-adjustable switch having an input and a switched output; a first component configured to provide an AC signal to input of said manually-adjustable switch; and an environmentally-isolated second component to control the internal signal in response to receipt of the AC signal from the switched output.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the priority of Australian Patent No. 20030904139, filed Aug. 7, 2003. The entire disclosure and contents of the above application is hereby incorporated by reference herein.  
         [0002]     This application is related to U.S. Pat. Nos. 4,532,930, 6,537,200, 6,565,503, 6,575,894, and 6,697,674. The entire disclosure and contents of the above patents are hereby incorporated by reference herein. 
     
    
     BACKGROUND  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates generally to switching mechanisms and, more particularly, to corrosion-resistant switching mechanisms.  
         [0005]     2. Related Art  
         [0006]     Switching mechanisms are provided in electronic devices to allow manual selection of various operational settings. Such settings are provided to enable a user to, for example, select features, functions of the device, to set values used by the device, etc. The exposure of such switching mechanisms to moisture can cause corrosion and/or accelerate degradation of the mechanism. In particular, moisture can have significant adverse effects on the electrical contacts within a switching mechanism.  
         [0007]     Some switching mechanisms are more likely to become exposed to moisture, depending on the function of the device in which the switching mechanisms are implemented, and the environment in which the device is used. One example of such electronic devices are those components of medical devices which are worn by a patient (also referred to herein as a recipient). Such medical devices are designed to assist, replace, monitor or otherwise support biological systems of the recipient. Many such medical devices often include one or more sensors, processors, controllers or other functional components that are permanently or temporarily implanted in the patient. Typically, such implantable devices require the transfer of power and/or information with external components that are worn by the patient.  
         [0008]     One particular example of a medical device having patient-worn components is a prosthetic hearing device. Prosthetic hearing devices such as hearing aids and cochlear™ implants usually include a component that is worn behind the ear of the recipient of the device. This wearable device has miniature user-operable switching mechanisms which are typically exposed to and adversely affected by moisture from, for example, perspiration, rain and humidity.  
       SUMMARY  
       [0009]     In accordance with one aspect of the present invention, a corrosion-resistant switching mechanism for enabling a user to control an internal signal of an electronic device is disclosed. The switching mechanism comprises: an environmentally-exposed, manually-adjustable switch having an input and a switched output; a first component configured to provide an AC signal to the input of said manually-adjustable switch; and an environmentally-isolated second component to control the internal signal in response to receipt of the AC signal from the switched output, wherein the AC signal does not have a DC component.  
         [0010]     In accordance with another aspect of the present invention, an electronic device is disclosed. The device comprises: at least one electronic component; and a switching mechanism comprising at least one manually-operated switch to control operational setting of at least one electronic component, wherein the switch selectively connects to an input line and a switched output line, wherein the input line conducts only an AC signal which does not have a DC component.  
         [0011]     In accordance with a further aspect of the present invention, a corrosion-resistant switching mechanism for use in a device is disclosed. The switching mechanism comprises: an environmentally-exposed, manually-adjustable switch having an input and a switched output; a first component configured to provide an AC signal to said input of said manually-adjustable switch; and a second component to provide to the device an internal signal in response to receipt of the AC signal from said switched output, wherein the AC signal does not have a DC component.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a perspective view of one embodiment of a hearing prosthesis in which embodiments of the present invention may be implemented.  
         [0013]      FIG. 2A  is a perspective view of one embodiment of the speech processor unit illustrated in  FIG. 1 .  
         [0014]      FIG. 2B  is a side view of the embodiment of the speech processor unit illustrated in  FIG. 2A .  
         [0015]      FIG. 2C  is a bottom view of the embodiment of the speech processor unit illustrated in  FIG. 2A .  
         [0016]      FIG. 3  is a high-level functional block diagram of one embodiment of a switching mechanism of the present invention.  
         [0017]      FIG. 4  is a schematic block diagram of one embodiment of a switching mechanism of the present invention.  
         [0018]      FIG. 5  is a schematic block diagram of one embodiment of the detection channel component illustrated in  FIG. 3 .  
         [0019]      FIG. 6  is a functional block diagram of another embodiment of a switching mechanism of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0020]     Embodiments of the present invention are directed to switching mechanisms which are substantially resistant to corrosion or other degradation due to exposure to moisture. Generally, a corrosion-resistant switching mechanism of the present invention switchingly conducts a balanced alternating current (AC) signal (that is, an AC signal having no direct current (DC) component) through an environmentally-exposed switch which is then used to control an internal signal that is usable by the implementing host device. The contacts of the environmentally-exposed switch, which can be a single-pole/single-throw; multi-pole/multi-throw, potentiometer or other type of switch, does not corrode or otherwise degrade with exposure to moisture due to the absence of a DC component in the switched signal. The other components of the switching mechanism, which may include one or more additional switches, are not exposed to the environment and, therefore, may utilize AC signals having a DC component, or DC signals, without risk of corrosion. The switching mechanism of the present invention is particularly beneficial for use in electronic devices implementing switches which are exposed to the environment to enable a person to control operational settings in the device.  
         [0021]     Embodiments of the present invention are described below in connection with one type of electronic device, a speech processor unit of a prosthetic hearing device (also referred to as a cochlear™ prosthesis, cochlear™ implant system, cochlear™ prosthetic device and the like). Prosthetic hearing devices use direct electrical stimulation of auditory nerve cells to bypass absent or defective hair cells that normally transduce acoustic vibrations into neural activity. Such devices generally use multi-contact electrodes inserted into the scala tympani of the cochlea so that the electrodes may differentially activate auditory neurons that normally encode differential pitches of sound. Such devices are also used to treat a smaller number of patients with bilateral degeneration of the auditory nerve. For such patients, a prosthetic hearing device provides stimulation of the cochlear nucleus in the brainstem.  
         [0022]     Exemplary cochlear™ implant systems in which the present invention may be implemented include, but are not limited to, those systems described in U.S. Pat. Nos. 4,532,930, 6,537,200, 6,565,503, 6,575,894 and 6,697,674, which are hereby incorporated by reference herein.  FIG. 1  is a schematic diagram of an exemplary cochlear™ implant system  100  in which embodiments of the present invention may be implemented. Cochlear™ implant system  100  comprises external component assembly  142  which is directly or indirectly attached to the body of the recipient, and an internal component assembly  144  which is temporarily or permanently implanted in the recipient. External assembly  142  typically comprises audio pickup devices (not shown) for detecting sounds, a speech processor unit  116  that converts the detected sounds into a coded signal, a power source (not shown), and an external transmitter unit  106 . External transmitter unit  106  comprises an external coil  108 , and, preferably, a magnet  110  secured directly or indirectly to external coil  108 . Speech processor unit  116  processes the output of the audio pickup devices that may be positioned, for example, by the ear  122  of the recipient. Speech processor unit  116  generates stimulation signals which are provided to external transmitter unit  106  via cable  118 .  
         [0023]     Internal component assembly  144  comprises an internal receiver unit  112 , a stimulator unit  126 , and an electrode array  134 . Internal receiver unit  112  comprises an internal receiver coil  124  and a magnet  140  fixed relative to internal coil  124 . Internal receiver unit  112  and stimulator unit  126  are hermetically sealed within a housing  128 . Internal coil  124  receives power and data from transmitter coil  108 . A cable  130  extends from stimulator unit  126  to cochlea  132  and terminates in an electrode array  134 . The received signals are applied by array  134  to the basilar membrane  136  thereby stimulating the auditory nerve  138 .  
         [0024]     Collectively, transmitter antenna coil  108  (or more generally, external coil  108 ) and receiver antenna coil  124  (or more generally, internal coil  124 ) form an inductively-coupled coil system of a transcutaneous transfer apparatus  102 . Transmitter antenna coil  108  transmits electrical signals to the implantable receiver coil  124  via a radio frequency (RF) link  114 . Internal coil  124  is typically a wire antenna coil comprised of at least one and preferably multiple turns of electrically insulated single-strand or multi-strand platinum or gold wire. The electrical insulation of internal coil  124  is provided by a flexible silicone molding (not shown). In use, implantable receiver unit  112  may be positioned in a recess of the temporal bone adjacent to ear  122  of the recipient.  
         [0025]      FIGS. 2A-2C  are perspective views of an external speech processor unit  116  of cochlear™ implant system  100 , introduced above with reference to  FIG. 1 . Speech processor unit  116 , as noted, has a configuration to facilitate it being operationally positioned behind the ear of the recipient. As such, speech processor unit  116  is exposed to moisture from, for example, perspiration, rain and humidity.  
         [0026]     External speech processor unit  116  comprises a variety of environmentally-exposed miniature switches  202 ,  204 ,  206  to enable the recipient of cochlear™ implant system  100  to select various operational settings. For example, a single-pole/multi-throw switch  204  is provided on a spine  208  of speech processor unit  116 . In the illustrative embodiment, switch  204  is used by the recipient to select one of a number of switch positions each associated with an available speech processing program, and an “off” position which turns speech processor unit  116  off.  
         [0027]     Similarly, the adjacent miniature switch  202  is a potentiometer switch that enables the recipient to adjust the volume and/or sensitivity of cochlear™ implant system  100 . In addition, a linear, three-position miniature switch  206  is provided on the underside of speech processor unit  116 , as best shown in  FIG. 2C . Miniature switch  206  is provided to enable the recipient to switch between different listening situation options. The above and other operational features of a cochlear™ implant system are considered well-known to those of ordinary skill in the art and, therefore, are not described further herein.  
         [0028]      FIG. 3  is a functional block diagram of one embodiment of a switching mechanism of the present invention. Switching mechanism  300  comprises components  301  that are exposed to the environment and components  303  that are not exposed to, or isolated from, the environment. Environmentally-exposed components  301  comprise a user-operable switch  302 . Switch  302  can be, as noted, a single-pole/single-throw; multi-pole/multi-throw, single-pole/multi-throw, potentiometer or other type of user-controllable switch. Environmentally-isolated components  303  comprise an alternating current (AC) signal generator circuit  304  that generates an AC signal  312  that has no direct current (DC) component.  
         [0029]     Switch  302  switches AC signal  312  in response to the user&#39;s adjustment  305  of switch  302 . Depending on the configuration of switch  302 , there may be one or more switch-control lines  314  connecting switch  302  and control circuit  306 . Control circuit  306  receives one or more input lines  308  from the host system, here speech processor unit  116 . Each input line  308  is controllably connected to a corresponding output line  310 , referred to herein as switched output line  310 . Control circuit  306  connects at least one input line  308  with its corresponding switched output line  310  in response to the receipt of AC signal  312  over one switch-control line  314 . Thus, by controlling switch  302 , a user controls the passage of a signal on one or more input lines  308  to a corresponding one or more output lines  310 .  
         [0030]     Because switch  302  switches an AC signal  312  which does not have a DC component, the contacts of switch  302  do not readily corrode or otherwise degrade in the presence of moisture. As such, the fact that corrosion-resistant switch  302  is exposed to the external environment does not adversely affect the performance of switching mechanism  300 . Also, the other components  304 ,  306  of switching mechanism  300 , which may include one or more additional switches, are not exposed to the environment. Such components, then, may utilize and/or generate AC signals, DC signals and/or other signals without being subject to corrosion due to moisture exposure.  
         [0031]      FIG. 4  is a schematic block diagram of one embodiment of a corrosion-resistant switching mechanism  400  of the present invention. This embodiment of switching mechanism  400  is implemented in speech processor unit  116  shown in  FIGS. 1 and 2 A- 2 C to provide single-pole/multi-throw switch  204 . As noted, in the exemplary application introduced above, switch  204  is used by the recipient of cochlear™ implant system  100  to select which of a number of available speech processing programs is to be currently implemented in speech processor unit  116 , or to turn off the unit.  
         [0032]     Switching mechanism  400  comprises environmentally-exposed components  401  and environmentally-isolated components  403 . Environmentally-exposed components  401  are subject to the incursion of moisture while environmentally-isolated components  403  are internal components which are sufficiently shielded, covered, etc., to substantially prevent intrusion of moisture.  
         [0033]     Environmentally-exposed components  401  comprise switch  402  implementing single-pole/multi-throw switch  204 . Switch  204  has a plurality of contacts comprising a common contract  460  and a plurality of switched contacts  462 A- 462 N. In the embodiment depicted in  FIG. 4 , three switched contacts  462  are shown with each being connected to a channel though components  403 , as described herein. User operation  305  of switch  204  causes common contact  460  to be electrically connected to a desired one of the plurality of switched contracts  462 .  
         [0034]     Environmentally-isolated components  403  comprise AC signal generator circuit  404  and a control circuit  406 . AC signal generator circuit  404  generates an AC signal  412 . As with AC signal  312  introduced above, AC signal  412  has no DC component. AC signal  412  is provided to environmentally-exposed components  401 ; that is, single-pole/multi-throw switch  204 .  
         [0035]     AC signal generator circuit  404  comprises a local oscillator  450  which generates an AC signal  451 . Oscillator  450  is connected to common contact  460  of switch  402 , and to control circuit  406 , as described below. In this embodiment, oscillator  450  does not necessarily generate an AC signal; but may generate a square pulse signal which has a finite average (DC) value. AC signal generator circuit  404  further comprises at least one coupling capacitor  454  that filters the DC component of AC signal  451  so that AC signal  412  is balanced. As one of ordinary skill in the art would appreciate, AC signal generator circuit  404  can be implemented with a variety of different components in a corresponding variety of configurations. For example, in one alternative embodiment, the type of oscillator implemented in circuit  404  generates a pure AC signal without a DC component, thereby eliminating the need to include coupling capacitor  454 .  
         [0036]     The elimination of DC current flow at contacts  460 ,  462  of switch  402  improves the immunity of switch  402  against corrosion due to electrochemical etching under DC conditions when moisture is present between such contacts. In turn, this provides improved reliability and extends the longevity of switch  402  and the host electronic device, here speech processor unit  116 . Another advantage of certain embodiments of the switching mechanism of the present invention is that the magnitude of AC signal  412  is not significant. This improves the mechanical reliability of switch  402  and extends its life.  
         [0037]     Control circuit  406  comprises one or more channel detector circuits  454 A- 454 N. In the embodiment shown in  FIG. 4 , the quantity of detection channel circuits  454  corresponds to the quantity of switched contacts  462 A- 462 N of switch  402 . Each detector circuit  454 A- 456 N controls the operation of a corresponding switch  464 A- 464 N. Each switch  464 A- 464 N has an input line  408 A- 408 N and a corresponding output line  410 A- 410 N. Operation of each switch  464 A- 464 N causes the switch to connect or disconnect its input line  408 A- 408 N and corresponding output line  410 A- 410 N.  
         [0038]     As noted, control circuit  406  has an input connected to the output of local oscillator  450 . In the embodiment shown in  FIG. 4 , this input is provided to an input  456 A- 456 N of each channel detector circuit  454 A- 454 N. Thus, each detector circuit  454 A- 454 N receives at an input  456 A- 456 N AC signal  451 .  
         [0039]     Each channel detector circuit  454 A- 454 N also comprises a second input  458 A- 458 N each connected to one switched contact  462 A- 462 N of switch  402 . This second input receives AC signal  412  when switch  204  is positioned such that common contact  460  is switchedly connected to the appropriate switched contact  462  in switch  402 . When a detection channel  454  receives  451  at its second input  458 , detection circuit  454  activates its corresponding switch  464  to connect its input and output lines  408 ,  410 . Since only one channel detector circuit  454  can receive AC signal  412  at any given time, at most only one switch  464  is activated at any given time.  
         [0040]     It should be appreciated that internal switches  464  can switch any type of signal traveling over lines  408  and  410  which can be utilized by speech processor unit  116 . Because switches  464  are not exposed to the environment and, therefore, are not subject to the accumulation of moisture, switches  464  are not subject the corrosion due to electrochemical etching under DC conditions when moisture is present between the contacts of the switches. In other words, switching mechanism  400  comprises two switches to controllably connect lines  408  and  410 . One switch which is isolated from the environment is connected to lines  408  and  410  while the other switch  402  is exposed to the environment and switches an AC signal. User manipulation of the environmentally-exposed switch  402  indirectly controls the operation of environmentally-isolated switches  464 .  
         [0041]      FIG. 5  is a schematic block diagram of one embodiment of a channel detector circuit  454  of  FIG. 4 . Each circuit  454  comprises a serially-connected arrangement of a multiplier  502 , a low pass filter  504 , a voltage comparator  506 , and a noise filter  508 , as shown. Multiplier  502  receives AC signal  412  at input  458  of circuit  454  which, as noted, is connected to the output of environmentally-exposed switch  402 . Multiplier  502  also receives AC signal  451  at input  456  of circuit  454  which, as noted, is connected to the output of oscillator  450 .  
         [0042]     When circuit  454  receives AC signal  412  and AC signal  451 , the output of multiplier  502  is at its maximum, since both input signals  412 ,  451  have the same frequency and phase. The output signal from multiplier  402  is filtered using low pass filter  504  and thereafter applied to the input of voltage comparator  506 .  
         [0043]     Voltage comparator  506  compares the filtered signal from low pass filter  504  using reference voltage  510 . The output of voltage comparator  506  is gated against a reference time window generated in the noise masker/timer  508 . When comparator  506  remains active for a pre-determined period of time, the output of noise masker  508  is activated and in turn, actuates corresponding electronic switch  464 . This has the advantage of minimizing false switching due to noise, interference or “bouncing” of mechanical switch  402 . Thus, when switch  402  is adjusted by the user such that AC signal  412  is provided to channel detector circuit  454 , corresponding switch  464  is activated to connect input line  408  with switched output line  410 .  
         [0044]      FIG. 6  is a schematic block diagram of one embodiment of a corrosion-resistant switching mechanism  600  of the present invention. This embodiment of switching mechanism  600  is implemented in speech processor unit  116  shown in  FIGS. 1 and 2 A- 2 C to provide one of the above-noted user-operable switches, potentiometer  202 . As noted, potentiometer  202  is implemented in cochlear™ implant system  100  to enable the recipient to adjust the volume and/or sensitivity of the audio signal generated by system  100 . One advantage of using a potentiometer as compared with a single- or multi-pole switch is that the physical construction of a potentiometer usually provides a greater seal which protects the switch from moisture ingress.  
         [0045]     Switching mechanism  600  comprises environmentally-exposed components  601  and environmentally-isolated components  603 . Environmentally-exposed components  601  comprise switch  602  implementing potentiometer switch  202 . Switch  602  receives an AC signal  612  from an AC signal generator circuit  604 . Switch  602  has a resistive pot  605  with a user-controllable  305  contact arm  607  which drives the output of switch  602 . User operation of contact arm  607  causes a change in the magnitude of AC signal  612  which is output from switch  602 . The signal generated by switch  602  is referred to as AC signal (adjusted)  658  herein.  
         [0046]     Environmentally isolated components  603  comprise AC signal generator circuit  604  and control circuit  606 . AC signal generator circuit  604  generates AC signal  612 . As noted above in connection with similarly-generated AC signals, AC signal  612  is an AC signal which has no DC component. AC signal  612  is provided to environmentally-exposed components  601 ; in this embodiment, potentiometer switch  202 , as noted above. AC signal generator circuit  604  comprises an oscillator  650  which preferably is a low-power oscillator that generates an AC signal  651 . As with AC signal  451 , AC signal  651  typically would have a DC component. The output of oscillator  654  is connected to the input of switch  602  through a coupling capacitor  654 . Coupling capacitor  654  filters the DC component of AC signal  651  so that AC signal  612  is balanced. The output of AC signal generator circuit  604  and the output of oscillator  650  are connected to control circuit  606 , as described in detail below. As with AC signal generator circuit  504 , one of ordinary skill in the art would appreciate that AC signal generator circuit  604  can be implemented in a number of different ways to provide what is commonly referred to as AC signal  612 .  
         [0047]     Control circuit  606  comprises a multiplier  670  that, as noted, receives AC signal  612  directly from AC signal generator circuit  604 . Multiplier  670  also receives AC signal (adjusted)  658  from switch  602 . The AC signal (adjusted)  658  generated by potentiometer  202  has a peak voltage that is proportional to AC signal  612 , according to a physical position of potentiometer  202 . Multiplier  670  multiplies AC signal (adjusted)  658  from potentiometer  202  with AC signal  612  generated by AC signal generator circuit  604 . As with the multiplier described herein with reference to the embodiment shown in  FIG. 4 , multiplier  670  effectively cancels noise appearing in AC signal  612  because signals  612  and  658  have matching frequency and phase.  
         [0048]     The signal generated by multiplier  670  has a DC component which has a magnitude which depends on the amplitude of AC signal  651 . This signal is applied to an amplitude detector  674  which restores the signal into a DC analog signal which can then be applied as the first of two input signals to an analog-to-digital (A/D) converter  676 .  
         [0049]     A/D converter  676  also receives a reference voltage from voltage reference block  672 . A DC reference voltage signal is generated by block  672  based on AC signal  651  received from local oscillator  650 . The DC signal generated by voltage reference  672  has a voltage that matches a full-scale-voltage range of A/D converter  676 . It should be appreciated that the use of a reference voltage derived from the same source signal causes a cancellation of unwanted signals and noise, thereby reducing the adverse effects of interference and insuring accuracy of control circuit  606 .  
         [0050]     The output of A/D converter  676  generates a digital code that represents the position of contract arm  607  along pot  605  of potentiometer  202 . Each one or more bits of the digital rives an output line  678 A- 678 N of A/D converter  676 . Thus, A/D converter  676  es in response to the two DC input signals by activating one of a plurality of outputs,  678 N, depending on the position of potentiometer  202 . Each output  678  in turn activates a particular one of switching banks  654 A- 654 N. A/D converter  676  preferably also includes hysteresis circuitry to minimize output instability.  
         [0051]     Each output  678  of A/D converter  676  is connected to and controls the operation of one of the plurality of switching banks  654 A- 654 N. Each switching bank  654  has a plurality of input lines  608  and a corresponding plurality of switched output lines  610 . When A/D converter  676  activates a switch  654 , all input lines  608  of that switch are connected to their corresponding output lines  610 .  
         [0052]     Thus, of the switch bank  654  is activated at any given time depends on the position of potentiometer switch  202 . The one or more signals switchingly controlled by switch banks  654  are internal signals usable by host implant device  100 .  
         [0053]     All documents, patents, journal articles and other materials cited in the present application are hereby incorporated by reference.  
         [0054]     Although the present invention has been fully described in conjunction with several embodiments thereof with reference to the accompanying drawings, it is to be understood that various changes and modifications may be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.