Patent Publication Number: US-2010110018-A1

Title: Portable electronic device including touch-sensitive input device and method of controlling same

Description:
FIELD OF TECHNOLOGY 
     The present disclosure relates to portable electronic devices that include touch-sensitive input device and the provision of tactile feedback for such input devices. 
     BACKGROUND 
     Electronic devices, including portable electronic devices, have gained widespread use and can provide a variety of functions including, for example, telephonic, electronic messaging and other personal information manager (PIM) application functions. Portable electronic devices can include several types of devices including mobile stations such as simple cellular telephones, smart telephones, wireless PDAs, and laptop computers with wireless 802.11 or Bluetooth capabilities. Touch-sensitive input devices are useful for input on a portable electronic device. 
     Devices such as PDAs or smart telephones are generally intended for handheld use and ease of portability. Smaller devices are generally desirable for portability. Touch screen devices constructed of a display, such as a liquid crystal display, with a touch-sensitive overlay are useful on such handheld devices as such handheld devices are small and are therefore limited in space available for user input and output devices. Further, the screen content on the touch screen devices can be modified depending on the functions and operations being performed. 
     Touch-sensitive input devices suffer from inherent disadvantages relating to user interaction and response. In particular, errors may be made in selecting features using touch-sensitive input devices such as double entry during selection as a result of a lack of touch feedback. While touch screen devices that provide feedback such as audio feedback are known, such devices do not provide a desirable tactile feedback. Further improvements in provision and control of tactile feedback in touch-sensitive devices are desirable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures, wherein: 
         FIG. 1  is a simplified block diagram of components including internal components of a portable electronic device according an aspect of an embodiment; 
         FIG. 2  is a front view of an exemplary portable electronic device in a portrait orientation; 
         FIG. 3A  is a top view of a portion of an exemplary touch screen display unit in a landscape orientation, showing hidden detail; 
         FIG. 3B  is a side view of portions of the touch screen display unit of  FIG. 3A ; 
         FIG. 3C  is a side view of portions of the touch screen display unit of  FIG. 3A ; 
         FIG. 3D  illustrates an exemplary circuit for controlling a charge on the piezoelectric patch transducer in accordance with an embodiment; 
         FIG. 4  is a flow chart illustrating a method of controlling a portable electronic device including a touch screen display unit; 
         FIG. 5A  is a top view of a portion of another exemplary touch screen display unit in a landscape orientation, showing hidden detail; 
         FIG. 5B  is a side view of portions of the touch screen display unit of  FIG. 5A ; 
         FIG. 5C  is a another side view of portions of the touch screen display unit of  FIG. 5A ; 
         FIG. 6A  is a top view of a portion of another exemplary touch screen display unit in landscape orientation, showing hidden detail; 
         FIG. 6B  is a side view of portions of the touch screen display unit of  FIG. 6A ; 
         FIG. 7A  is a top view of a portion of another exemplary touch screen display unit in a landscape orientation, showing hidden detail; 
         FIG. 7B  is a side view of portions of the touch screen display unit of  FIG. 7A ; 
         FIG. 8A  is a top view of a portion of yet another exemplary touch screen display unit in a landscape orientation, showing hidden detail; and 
         FIG. 8B  is a side view of portions of the touch screen display unit of  FIG. 8A . 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limited to the scope of the embodiments described herein. 
     The disclosure generally relates to an electronic device, which in the embodiments described herein is a portable electronic device. Examples of portable electronic devices include mobile, or handheld, wireless communication devices such as pagers, cellular phones, cellular smart-phones, wireless organizers, personal digital assistants, wirelessly enabled notebook computers and the like. 
     The portable electronic device may be a two-way communication device with advanced data communication capabilities including the capability to communicate with other portable electronic devices or computer systems through a network of transceiver stations. The portable electronic device may also have the capability to allow voice communication. Depending on the functionality provided by the portable electronic device, it may be referred to as a data messaging device, a two-way pager, a cellular telephone with data messaging capabilities, a wireless Internet appliance, or a data communication device (with or without telephony capabilities). The portable electronic device may also be a portable device without wireless communication capabilities as a handheld electronic game device, digital photograph album, digital camera and the like. 
     Referring to  FIG. 1 , there is shown therein a block diagram of an exemplary embodiment of a portable electronic device  20 . The portable electronic device  20  includes a number of components such as the processor  22  that controls the overall operation of the portable electronic device  20 . Communication functions, including data and voice communications, are performed through a communication subsystem  24 . Data received by the portable electronic device  20  can be decompressed and decrypted by a decoder  26 , operating according to any suitable decompression techniques (e.g. YK decompression, and other known techniques) and encryption techniques (e.g. using an encryption technique such as Data Encryption Standard (DES), Triple DES, or Advanced Encryption Standard (AES)). The communication subsystem  24  receives messages from and sends messages to a wireless network  1000 . In this exemplary embodiment of the portable electronic device  20 , the communication subsystem  24  is configured in accordance with the Global System for Mobile Communication (GSM) and General Packet Radio Services (GPRS) standards. The GSM/GPRS wireless network is used worldwide and it is expected that these standards will be superseded eventually by Enhanced Data GSM Environment (EDGE) and Universal Mobile Telecommunications Service (UMTS). New standards are still being defined, but it is believed that they will have similarities to the network behavior described herein, and it will also be understood by persons skilled in the art that the embodiments described herein are intended to use any other suitable standards that are developed in the future. The wireless link connecting the communication subsystem  24  with the wireless network  1000  represents one or more different Radio Frequency (RF) channels, operating according to defined protocols specified for GSM/GPRS communications. With newer network protocols, these channels are capable of supporting both circuit switched voice communications and packet switched data communications. 
     Although the wireless network  1000  associated with the portable electronic device  20  is a GSM/GPRS wireless network in one exemplary implementation, other wireless networks may also be associated with the portable electronic device  20  in variant implementations. The different types of wireless networks that may be employed include, for example, data-centric wireless networks, voice-centric wireless networks, and dual-mode networks that can support both voice and data communications over the same physical base stations. Combined dual-mode networks include, but are not limited to, Code Division Multiple Access (CDMA) or CDMA2000 networks, GSM/GPRS networks (as mentioned above), and future third-generation (3G) networks like EDGE and UMTS. Some other examples of data-centric networks include WiFi 802.11, Mobitex™ and DataTAC™ network communication systems. Examples of other voice-centric data networks include Personal Communication Systems (PCS) networks like GSM and Time Division Multiple Access (TDMA) systems. 
     The processor  22  also interacts with additional subsystems such as a Random Access Memory (RAM)  28 , a flash memory  30 , a display  32  with a touch-sensitive overlay  34  connected to an electronic controller  36  that together make up a touch-sensitive display  38 , an auxiliary input/output (I/O) subsystem  40 , a data port  42 , a speaker  44 , a microphone  46 , short-range communications  48  and other device subsystems  50 . The touch-sensitive overlay  34  and the electronic controller  36  provide a touch-sensitive input device and the processor  22  interacts with the touch-sensitive overlay  34  via the electronic controller  36 . 
     Some of the subsystems of the portable electronic device  20  perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. By way of example, the display  32  and the touch-sensitive overlay  34  may be used for both communication-related functions, such as entering a text message for transmission over the network  1000 , and device-resident functions such as a calculator or task list. 
     The portable electronic device  20  can send and receive communication signals over the wireless network  1000  after network registration or activation procedures have been completed. Network access is associated with a subscriber or user of the portable electronic device  20 . To identify a subscriber according to the present embodiment, the portable electronic device  20  uses a SIM/RUIM card  52  (i.e. Subscriber Identity Module or a Removable User Identity Module) inserted into a SIM/RUIM interface  54  for communication with a network such as the network  1000 . The SIM/RUIM card  52  is one type of a conventional “smart card” that can be used to identify a subscriber of the portable electronic device  20  and to personalize the portable electronic device  20 , among other things. In the present embodiment the portable electronic device  20  is not fully operational for communication with the wireless network  1000  without the SIM/RUIM card  52 . By inserting the SIM/RUIM card  52  into the SIM/RUIM interface  54 , a subscriber can access all subscribed services. Services may include: web browsing and messaging such as e-mail, voice mail, Short Message Service (SMS), and Multimedia Messaging Services (MMS). More advanced services may include: point of sale, field service and sales force automation. The SIM/RUIM card  52  includes a processor and memory for storing information. Once the SIM/RUIM card  52  is inserted into the SIM/RUIM interface  54 , it is coupled to the processor  22 . In order to identify the subscriber, the SIM/RUIM card  52  can include some user parameters such as an International Mobile Subscriber Identity (IMSI). An advantage of using the SIM/RUIM card  52  is that a subscriber is not necessarily bound by any single physical portable electronic device. The SIM/RUIM card  52  may store additional subscriber information for a portable electronic device as well, including datebook (or calendar) information and recent call information. Alternatively, user identification information can also be programmed into the flash memory  30 . 
     The portable electronic device  20  is a battery-powered device and includes a battery interface  56  for receiving one or more rechargeable batteries  58 . In at least some embodiments, the battery  58  can be a smart battery with an embedded microprocessor. The battery interface  56  is coupled to a regulator (not shown), which assists the battery  58  in providing power V+ to the portable electronic device  20 . Although current technology makes use of a battery, future technologies such as micro fuel cells may provide the power to the portable electronic device  20 . 
     The portable electronic device  20  also includes an operating system  60  and software components  62  to  72  which are described in more detail below. The operating system  60  and the software components  62  to  72  that are executed by the processor  22  are typically stored in a persistent store such as the flash memory  30 , which may alternatively be a read-only memory (ROM) or similar storage element (not shown). Those skilled in the art will appreciate that portions of the operating system  60  and the software components  62  to  72 , such as specific device applications, or parts thereof, may be temporarily loaded into a volatile store such as the RAM  28 . Other software components can also be included, as is well known to those skilled in the art. 
     The subset of software applications  62  that control basic device operations, including data and voice communication applications, will normally be installed on the portable electronic device  20  during its manufacture. Other software applications include a message application  64  that can be any suitable software program that allows a user of the portable electronic device  20  to send and receive electronic messages. Various alternatives exist for the message application  64  as is well known to those skilled in the art. Messages that have been sent or received by the user are typically stored in the flash memory  30  of the portable electronic device  20  or some other suitable storage element in the portable electronic device  20 . In at least some embodiments, some of the sent and received messages may be stored remotely from the device  20  such as in a data store of an associated host system that the portable electronic device  20  communicates with. 
     The software applications can further include a device state module  66 , a Personal Information Manager (PIM)  68 , and other suitable modules (not shown). The device state module  66  provides persistence, i.e. the device state module  66  ensures that important device data is stored in persistent memory, such as the flash memory  30 , so that the data is not lost when the portable electronic device  20  is turned off or loses power. 
     The PIM  68  includes functionality for organizing and managing data items of interest to the user, such as, but not limited to, e-mail, contacts, calendar events, voice mails, appointments, and task items. A PIM application has the ability to send and receive data items via the wireless network  1000 . PIM data items may be seamlessly integrated, synchronized, and updated via the wireless network  1000  with the portable electronic device subscriber&#39;s corresponding data items stored and/or associated with a host computer system. This functionality creates a mirrored host computer on the portable electronic device  20  with respect to such items. This can be particularly advantageous when the host computer system is the portable electronic device subscriber&#39;s office computer system. 
     The portable electronic device  20  also includes a connect module  70 , and an information technology (IT) policy module  72 . The connect module  70  implements the communication protocols that are required for the portable electronic device  20  to communicate with the wireless infrastructure and any host system, such as an enterprise system, that the portable electronic device  20  is authorized to interface with. 
     The connect module  70  includes a set of APIs that can be integrated with the portable electronic device  20  to allow the portable electronic device  20  to use any number of services associated with the enterprise system. The connect module  70  allows the portable electronic device  20  to establish an end-to-end secure, authenticated communication pipe with the host system. A subset of applications for which access is provided by the connect module  70  can be used to pass IT policy commands from the host system to the portable electronic device  20 . This can be done in a wireless or wired manner. These instructions can then be passed to the IT policy module  72  to modify the configuration of the device  20 . Alternatively, in some cases, the IT policy update can also be done over a wired connection. 
     Other types of software applications can also be installed on the portable electronic device  20 . These software applications can be third party applications, which are added after the manufacture of the portable electronic device  20 . Examples of third party applications include games, calculators, utilities, etc. 
     The additional applications can be loaded onto the portable electronic device  20  through at least one of the wireless network  1000 , the auxiliary I/O subsystem  40 , the data port  42 , the short-range communications subsystem  48 , or any other suitable device subsystem  50 . This flexibility in application installation increases the functionality of the portable electronic device  20  and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using the portable electronic device  20 . 
     The data port  42  enables a subscriber to set preferences through an external device or software application and extends the capabilities of the portable electronic device  20  by providing for information or software downloads to the portable electronic device  20  other than through a wireless communication network. The alternate download path may, for example, be used to load an encryption key onto the portable electronic device  20  through a direct and thus reliable and trusted connection to provide secure device communication. 
     The data port  42  can be any suitable port that enables data communication between the portable electronic device  20  and another computing device. The data port  42  can be a serial or a parallel port. In some instances, the data port  42  can be a USB port that includes data lines for data transfer and a supply line that can provide a charging current to charge the battery  58  of the portable electronic device  20 . 
     The short-range communications subsystem  48  provides for communication between the portable electronic device  20  and different systems or devices, without the use of the wireless network  1000 . For example, the short-range communications subsystem  48  may include an infrared device and associated circuits and components for short-range communication. Examples of short-range communication standards include standards developed by the Infrared Data Association (IrDA), Bluetooth, and the 802.11 family of standards developed by IEEE. 
     In use, a received signal such as a text message, an e-mail message, or web page download is processed by the communication subsystem  24  and input to the processor  22 . The processor  22  then processes the received signal for output to the display  32  or alternatively to the auxiliary I/O subsystem  40 . A subscriber may also compose data items, such as e-mail messages, for example, using the touch-sensitive overlay  34  on the display  32  that are part of the touch-sensitive display  38 , and possibly the auxiliary I/O subsystem  40 . The auxiliary subsystem  40  may include devices such as: a mouse, track ball, infrared fingerprint detector, or a roller wheel with dynamic button pressing capability. A composed item may be transmitted over the wireless network  1000  through the communication subsystem  24 . 
     For voice communications, the overall operation of the portable electronic device  20  is substantially similar, except that the received signals are output to the speaker  44 , and signals for transmission are generated by the microphone  46 . Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, can also be implemented on the portable electronic device  20 . Although voice or audio signal output is accomplished primarily through the speaker  44 , the display  32  can also be used to provide additional information such as the identity of a calling party, duration of a voice call, or other voice call related information. 
     Reference is first made to the  FIGS. 2 ,  3 A and  3 B to describe an embodiment of a portable electronic device  20  including a touch-sensitive input surface which can be a touch screen display unit indicated generally by the numeral  80  and a method of controlling the portable electronic device  20 . Although embodiments herein describe a touch screen display, the present disclosure is not limited to a touch screen display and any suitable touch-sensitive input surface is possible. The touch screen display unit  80  includes a base  82 , the touch-sensitive display  38  and an actuating arrangement  84 . The touch-sensitive display  38  includes the display  32  and the touch-sensitive overlay  34  connected to a controller  36  and disposed on the display  32  for detecting a touch event thereon. The touch-sensitive display  38  is connected to and moveable relative to the base  82 . The actuating arrangement includes an elastically deformable substrate  86  between the touch-sensitive display  38  and the base  82 , and a piezoelectric patch transducer  90  fixed to the substrate  86  and configured for modulation of a charge at the patch transducer  90  to apply a bending force on the substrate  86  for applying a force to the touch-sensitive display  38 . 
     A front view of an exemplary portable electronic device  20  in portrait orientation is shown in  FIG. 2 . The portable electronic device  20  includes a housing  92  that houses the internal components that are shown in  FIG. 1  and frames the touch-sensitive display  38  such that the touch-sensitive display  38  is exposed for user-interaction therewith when the portable electronic device  20  is in use. It will be appreciated that the touch-sensitive display  38  may include any suitable number of user-selectable features, for example, in the form of virtual buttons for user-selection of, for example, applications, options, or keys of a keyboard for user entry of data during operation of the portable electronic device  20 . 
     The touch-sensitive display  38  can be any suitable touch screen display such as a capacitive touch screen display. A capacitive touch-sensitive display  38  includes the display  32  and the touch-sensitive overlay  34 , as shown in  FIG. 1 , in the form of a capacitive touch-sensitive overlay  34 . It will be appreciated that the capacitive touch-sensitive overlay  34  includes a number of layers in a stack and is fixed to the display  32  via a suitable optically clear adhesive. The layers can include, for example a substrate fixed to the LCD display  32  by a suitable adhesive, a ground shield layer, a barrier layer, a pair of capacitive touch sensor layers separated by a substrate or other barrier layer, and a cover layer fixed to the second capacitive touch sensor layer by a suitable adhesive. The capacitive touch sensor layers can be any suitable material such as patterned indium tin oxide (ITO). 
     In the present example, the X and Y location of a touch event are both determined with the X location determined by a signal generated as a result of capacitive coupling with one of the touch sensor layers and the Y location determined by the signal generated as a result of capacitive coupling with the other of the touch sensor layers. Each of the touch-sensor layers provides a signal to the controller  36  as a result of capacitive coupling with a suitable object such as a finger of a user or a conductive object held in a bare hand of a user resulting in a change in the electric field of each of the touch sensor layers. The signals represent the respective X and Y touch location values. It will be appreciated that other attributes of the user&#39;s touch on the touch-sensitive display  38  can be determined. For example, the size and the shape of the touch on the touch-sensitive display  38  can be determined in addition to the location (X and Y values) based on the signals received at the controller  36  from the touch sensor layers. 
     Referring still to  FIG. 2 , it will be appreciated that a user&#39;s touch on the touch-sensitive display  38  is determined by determining the X and Y touch location and user-selected input is determined based on the X and Y touch location and the application executed by the processor  22 . Thus a feature or virtual button displayed on the touch-sensitive display  38  may be selected by matching the feature or button to the X and Y location of a touch event on the touch-sensitive display  38 . A feature or button selected by the user is determined based on the X and Y touch location and the application. 
     Reference is now made to  FIGS. 3A ,  3 B and  3 C to describe an exemplary touch screen display unit  80 . As described,  FIG. 3A  is a top view of a portion of the exemplary touch screen display unit  80  in a landscape orientation, showing hidden detail, including the actuating arrangement  84 .  FIGS. 3B and 3C  are side views of portions of the touch screen display unit  80  and, for the purpose of illustration and ease of understanding, are not drawn to scale. Although not shown, the components shown in  FIGS. 3A to 3C  are housed within the housing  92  ( FIG. 2 ). In the present example, the base  82  is a printed circuit board. The printed circuit board provides the base  82  for the actuating arrangement  84  and provides mechanical support and electrical connection for electronic components for the portable electronic device  20 . In the present example, the actuating arrangement  84  is supported on one side of the printed circuit board while the opposing side provides mechanical support and electrical connection for other components of the portable electronic device  20 . 
     The actuating arrangement  84  includes the substrate  86  and the piezoelectric patch transducer  90 . The substrate  86  is a metal substrate such as aluminum, magnesium or any other suitable substrate capable of elastic deformation. In the present example, the substrate  86  includes an arcuate body  94  with a concave side of the arcuate body  94  facing the touch-sensitive display  38 . The arcuate body  94  can be any suitable shape for bending. In the present example, as shown in  FIG. 3A , the arcuate body is generally hour-glass shaped such that the width of arcuate body  94  is smallest at the center, closest to the base  82 . The arcuate body  94  therefore extends from the center, adjacent the base  82 , toward the touch-sensitive display  38  such that each end  96  is adjacent the touch-sensitive display  38 . A pair of feet  98  extend inwardly with a respective one of the pair of feet  98  extending in from each end  96  of the substrate  86 , providing support for the touch-sensitive display  38 . Alternatively, the feet can extend outwardly. 
     The piezoelectric patch transducer  90  is a flexible transducer that is fixed to the arcuate body  94  in any suitable manner, for example, using an adhesive such as an epoxy, and extends longitudinally along the arcuate body  94  such that the patch transducer  90  is also arcuate-shaped. The electric charge on the patch transducer can be modulated by modulating an applied voltage or current to the patch transducer  90 , resulting in a contraction of the length and/or width of the patch transducer  90  which results in an inward flexing force of the patch transducer  90  on the arcuate body  94 , to decrease the radius of curvature of the arcuate body  94  and the patch transducer  90 . The removal of the electric charge on the patch transducer  90  releases the contractual force of the patch transducer  90 , thereby releasing the flexing force on the arcuate body  94  caused by the patch transducer  90 . Thus, modulation of the electric charge by controlling the applied voltage or current results in changes to forces on the touch-sensitive display  38 .  FIG. 3B  shows a side view of portions of the touch screen display unit  80  absent the flexing force from the patch transducer  90 .  FIG. 3C  shows a side view of portions of the touch screen display unit  80  with the flexing force from the patch transducer (resulting from an electrical charge on the patch transducer  90 ). Although the flexing force from the patch transducer  90  applies to increase the curvature of the substrate  186  (decreasing the radius of curvature), it will be appreciated that the flexing force may not result in the movement depicted in  FIG. 3C  as movement of the touch-sensitive display  38  may be constrained by, for example, the housing or by a counter-force applied by a user pushing the touch-sensitive display  38  with his or her finger. Further,  FIGS. 3B and 3C  are not to scale. These figures and the curvatures shown in the substrate  86  and patch transducer  90  are exaggerated for the purpose of the present explanation. Movement may be small by comparison to that shown in the Figures. 
     It will now be appreciated that a flexing force on the arcuate body  94  is translated through the arcuate body  94  and feet  98  to the touch-sensitive display  38 . Flexing movement of the patch transducer  90  and arcuate body  94  is translated to the touch-sensitive display  38  as a force is applied to move the touch-sensitive display  38  away from the base  82  as a result of the force applied by the patch transducer  90  on the arcuate body  94 . The force is then removed when the electrical charge of the patch transducer  90  is removed. It will be appreciated that the substrate material and thickness can be chosen based on stiffness, a stiffer substrate, permitting less deflection. 
     The portable electronic device  20  can be controlled by controlling the movement of the touch-sensitive display  38  using the patch transducer  90 . For example, when a touch event is determined at the touch-sensitive display  38 , the patch transducer  90  can be controlled by modulating the applied voltage or current to control the charge on the patch transducer  90 . For example, a current can be applied to increase the charge on the patch transducer  90  to cause application of a bending force to the substrate  86  by the patch transducer  90  and the charge on the patch transducer can be removed via a controlled discharge current causing a release of the bending force, thereby providing tactile feedback to the user of the device. 
     As indicated, the charge at the patch transducer can be controlled by modulating the applied voltage or by modulating the applied current to charge the capacitance and controlling the discharge. The mechanical work performed by the piezoelectric patch transducer  90  can be controlled to provide generally consistent force and movement of the touch-sensitive display  38  in response to detection of a touch. Fluctuations in mechanical work performed as a result of, for example, temperature, can be reduced by modulating the current to control the charge. 
     Reference is now made to  FIG. 3D  which illustrates an exemplary circuit for controlling a charge on the piezoelectric patch transducer  90  in accordance with an embodiment. The exemplary circuit is indicated generally by the numeral  120  including the elements identified below.
     C 1  Input capacitor for Step-Up (boost) SMPS (switch mode power supply)   L 1  Power Inductor for SMPS   Q 2  Switch Transistor for SMPS   D 1  Diode for SMPS   C 2  Output Capacitor for SMPS   R 2 , R 3  Voltage divider feedback for SMPS   R 1  sense resistor for SMPS switch current   U 1  Current mode PWM controller IC for SMPS   

     Those skilled in the art will appreciate that the piezoelectric patch transducer  90  has similar electrical properties to a capacitor. The mechanical work performed (force*displacement) by the piezoelectric patch transducer  90  can be controlled by controlling the charge. The charge of the piezoelectric patch transducer  90  is expressed as 
     
       
      
       Q 
       piezo 
       =C 
       piezo 
       *V 
       piezo  
      
     
     where: Q is charge;
         C is capacitance; and   V is voltage.       

     A coefficient, referred to as the D 31  coefficient of a piezoelectric material composition provides the relationship between voltage and force. The D 31  coefficient and the relative dielectric constant, (Er) of a given piezoelectric material composition vary inversely with temperature, however. Therefore, if the charge of the piezoelectric patch transducer  90  is controlled within a small range, the variance of the mechanical work of the piezoelectric patch transducer  90  can be small. The current can be controlled as the current flowing in or out of a capacitor (which has similar electrical properties to the piezoelectric patch transducer  90 ) is given by: 
     
       
      
       I=C*dV/dT  
      
     
     where I is current;
         C is capacitance; and   dV/dT is differential voltage or instantaneous rate of voltage change.
 
With I and dT held constant, then as C decreases, dV increases. Thus the charge is controlled since Q piezo =C piezo *V piezo .
       

     The circuit  120  includes a boost SMPS in the form of a step-up SMPS that includes the elements U 1 , C 1 , L 1 , D 1 , Q 2 , R 1 , R 2  and R 3 . This provides a current limiter that includes R 4 , R 5 , U 3  and PNP transistor Q 3  with a voltage of suitable potential to control the charge on the piezoelectric patch transducer  90  via a limited current up to the desired voltage level. Q 1 , R 7  and R 8  translate the logical level control signals to the required high voltages to turn the current limiter on and off. 
     The elements R 9 , R 10 , R 11 , U 4  and NPN transistor Q 4  form another current limiter which is used to control the reduction of the charge on the piezo patch transducer via a limited current. 
     As indicated, the elements U 1 , C 1 , L 1 , D 1 , Q 2 , R 1 , R 2  and R 3  form a step-up SMPS to provide the high voltage rail for the circuit  120 . Those skilled in the art will appreciated that this circuit is an asynchronous boost SMPS. The Supply Voltage Vboost is set high enough to provide enough voltage to the current limiter circuit so that the desired charge level on the piezoelectric patch transducer  90  is achieved when the capacitance is at its lowest value. When the capacitance of the piezoelectric patch transducer  90  is at its maximum, the voltage required is lower. The circuit is self compensating since current and time are controlled by the system. 
     The resistors R 4 , R 5 , U 3  and PNP transistor Q 3  form the current limiter. U 3  and the base-emitter junction of Q 3  clamp the voltage across R 4  to V U3 −V be3 . The value of R 4  is chosen to limit the current by the following formula: 
         l (limit)=( V   U3   −V   be3 )/ R 4 
     where I is the current;
         Vu is the voltage generated at the resistor, V be3  is the forward voltage; and   R 4  is the resistance       

     Vbe changes with temperature. The reference voltage of U 3  is chosen to be high enough, for example, a reference voltage of 2.5 Volts may be chosen so that the Vbe change (normally less than 200 mV) from 0 to 70° C. is negligible. 
     The CHARGE_ENABLE and DISCHARGE_ENABLE signals are held low by processor  22 . To increase the charge and move the touch screen display  38  away from the base  82 , the processor  22  drives the CHARGE_ENABLE signal high for a period of time (such as, for example, 1 ms to 30 mS). During periods when the charge is increased, the DISCHARGE_ENABLE signal is held low by processor  22 . To decrease the charge and move the touch screen display  38  toward the base  82 , the processor  20  drives the DISCHARGE_ENABLE signal high for a period of time (such as, for example, 1 ms to 30 ms). During periods when the charge is decreased, the CHARGE_ENABLE signal is held low by the processor  22 . 
     For control over the increase and decrease in the charge on the piezoelectric patch transducer  90  (and hence to modulate the mechanical work), processor  22  may drive the CHARGE_ENABLE or DISCHARGE_ENABLE signals high for a predetermined period of time with a varying duty cycle so as to control the value of the current. For example, a PWM signal on the CHARGE_ENABLE line with a 50% duty cycle reduces the constant current by 50%. The PWM rate should be above 20 kHz to avoid introducing audio noise. 
     Reference is now made to  FIG. 4  to describe a method of controlling the portable electronic device  20  according to one embodiment. It will be appreciated that the steps of  FIG. 4  can be carried out by routines or subroutines of software executed by the processor  22 . Coding of software for carrying out such steps is well within the scope of a person of ordinary skill in the art having regard to the present description. 
     The portable electronic device  20  is turned to an on or awake state in any suitable manner (step  100 ). In the on or awake state, user-selectable features such as icons or virtual buttons or keys are rendered on the touch-sensitive display  38 . Such user-selectable features can include, for example, icons for selection of an application for execution by the processor  22 , buttons for selection of user options, keys of a virtual keyboard, keypad or any other suitable user-selectable icons or buttons. 
     A touch event is detected upon user touching of the touch-sensitive display  38 . Such a touch event can be determined upon a user touch at the touch-sensitive display  38  for selection of, for example, an Internet browser application, an email application, a calendar application, or any other suitable application, option, or other feature within an application (step  102 ). The X and Y location of the touch event are determined (step  104 ) and it is determined if the X and Y location of the touch event correspond to a user-selectable feature (step  106 ). Thus, it is determined if the X and Y location of the touch corresponds to a user-selectable icon, a virtual button or key or any other suitable feature rendered on the display  32 . 
     If the X and Y location of the touch event corresponds with the location of a user-selectable feature, the capacitive charge at the patch transducer  90  is controlled by controlling the applied voltage or current (step  108 ). For example, a suitable current can be applied to the patch transducer  90 , causing a flexing force to be applied to the arcuate body  94  from the patch transducer  90  and resulting in a force on the touch-sensitive display  38 . With the reduction of the electrical charge on the piezo patch transducer at the actuating arrangement  84 , the force applied by the actuating arrangement  84  on the touch-sensitive display  38  is reduced. Thus, tactile feedback is provided for the user as the touch-sensitive display  32  is caused or permitted to move in relation to the base  82 . The charge and/or discharge current applied to the piezoelectric patch transducer  90  may be modulated in any suitable manner to provide a desirable tactile feedback. The process ends at step  110 . 
     It will be appreciated that the flow chart shown is simplified for the purpose of explanation. A further touch event can be detected again and steps  102  to  110  can be repeated, for example. In other embodiments, the voltage applied to the piezoelectric patch transducer  90  can be modulated in any suitable manner in response to an event to control the charge at the patch transducer. 
     In an alternative embodiment, the portable electronic device can include a force sensor for determining the force applied to the touch-sensitive display  38  by the user. The force applied to the touch-sensitive display  38  by the user during the touch event can be determined in addition to determining the X and Y location of the touch event and it is also determined if the force applied to the touch-sensitive display  38  by the user exceeds a threshold force and the tactile feedback provided as described with reference to step  108  is provided in response to both determination that the X and Y location of the touch event corresponds to the location of a user-selectable feature as described and determination that the that the applied force by the user meets or exceeds the threshold applied force. Thus, tactile feedback is not provided for a touch with an applied force by the user on the touch-sensitive display  38  that is less than the threshold. The force sensor can be disposed in any suitable location for measuring the applied force to the touch-sensitive display  38 . A force sensor such as a force-sensitive resistor or a capacitive force sensor or any other suitable force sensor can be located between the arcuate body  94  and the base  82 . Alternatively, multiple force sensors can be located between the substrate  86  and the touch-sensitive display  38 . For example, a force sensor can be located at each respective one of the feet  98 . 
     Referring now to  FIG. 4  and to  FIGS. 1 to 3C , a particular example of controlling an electronic device is provided in which a user touching the touch-sensitive display  38  at a user-selectable feature is detected (step  102 ) and the touch location is determined (step  104 ). The touch location is then determined to correspond to a user-selectable feature (step  106 ). The force on the touch-sensitive display  38  by the actuating arrangement  84  can be controlled by controlling the charge. The charge on the piezoelectric patch transducer  90  is controlled in the present example by modulating the applied current and controlling the discharge current to provide forces and controlled movement of the touch-sensitive display  38 , giving the user a desirable tactile feedback upon selection of a feature on the touch-sensitive display  38  (step  108 ). In the present example, the current applied to the piezoelectric patch transducer  90  is modulated in response to determination that the touch location corresponds to a user-selectable feature resulting in movement of the touch-sensitive display  38  to provide a desirable tactile feedback. Thus, current can be applied to charge up the capacitance of the piezoelectric patch transducer  90 . 
     Reference is now made to  FIGS. 5A and 5B  to describe another exemplary touch screen display unit. The reference numerals used previously in describing the touch screen display unit shown in  FIGS. 3A to 3C  will be used again raised by  100  for ease of reference. 
       FIG. 5A  shows a top view of a portion of the exemplary touch screen display unit  180  in a landscape orientation, showing hidden detail, including the actuating arrangement  184 .  FIGS. 5B and 5C  show side views of portions of the touch screen display unit  180  and, for the purpose of illustration and ease of understanding, are not drawn to scale. A base  182  is provided for mechanically supporting the actuating arrangement  184 . The base  182  can be a printed circuit board for providing the mechanical support and for providing electrical connection for electronic components for the portable electronic device  20 . In the present example, the actuating arrangement  184  is supported on one side of the printed circuit board while the opposing side provides mechanical support and electrical connection for other components of the portable electronic device  20 . The actuating arrangement  184  includes the substrate  186  and the piezoelectric patch transducer  190  and is supported on the base  182  by an intermediary spacer  199 . Thus, the substrate  186  sits on the spacer  199 . 
     The substrate  186  can be a metal substrate such as aluminum, magnesium or any other suitable substrate capable of elastic deformation. The substrate  186  includes an arcuate body  194  with a convex side of the arcuate body  194  facing the touch-sensitive display  138 . The arcuate body  194  can be any suitable shape such as hour-glass shaped, as shown in  FIG. 5A , with the width of the arcuate body  194  being smallest at the apex, closest to the touch-sensitive display  138 . End portions  196  of the arcuate body  194  extend farthest from the touch-sensitive display  138 . Each leg  197  extends from a respective one of the end portions  196 , toward the touch-sensitive display  138  and generally perpendicular thereto and a respective foot  198  extends inwardly or outwardly from each leg  197  to support the touch-sensitive display  138 . 
     The piezoelectric patch transducer  190  is a flexible transducer that is fixed to the arcuate body  194  and extends longitudinally along the arcuate body  194  such that the patch transducer  190  is also arcuate-shaped. The charge on the patch transducer can be modulated by modulating an applied voltage or current to the patch transducer  190  and controlling the discharge current. An applied voltage or current to the patch transducer  190  can be modulated to increase the charge on the piezoelectric patch transducer  190  resulting in a force to cause flexing of the arcuate body  194 , to increase the radius of curvature of the arcuate body  194  and the patch transducer  190 . A discharge current reduces the electrical charge on the piezo patch transducer and releases the flexing force on the arcuate body  194  caused by the patch transducer  190 . 
       FIG. 5B  shows a side view of portions of the touch screen display unit  180  absent the flexing force from the patch transducer  190 .  FIG. 5C  shows a side view of portions of the touch screen display unit  180  with the flexing force from the patch transducer  190  (from the charge). Although the flexing force from the patch transducer  190  applies to straighten the substrate  186  (increasing the radius of curvature), it will be appreciated that the flexing force may not result in the movement depicted in  FIG. 5C  as the movement of the touch-sensitive display  138  may be constrained by, for example, the housing or by user-application of a force on the touch-sensitive display  38 . Further,  FIGS. 5B and 5C  are exaggerated for the purpose of the present explanation. Any movement of the touch-sensitive display  138  is small by comparison to that shown in the Figures. 
     The flexing force on the arcuate body  194  is translated through the arcuate body  194 , through the legs  197  and the feet  198  to the touch-sensitive display  138 . Flexing movement of the patch transducer  190  and arcuate body  194  is thereby translated to the touch-sensitive display  138  as the force is applied to move the touch-sensitive display  138  away from the base  182  as a result of the force applied by the patch transducer  190  on the arcuate body  94 . The force can also be removed by discharging the capacitance. Thus, the charge at the patch transducer is controlled. 
     As in the first-described example, control of the charge at the patch transducer  190  provides forces and controlled movement of the touch-sensitive display  138 , giving the user a desirable tactile feedback upon selection of a feature on the touch-sensitive display  138 . The steps of the method of controlling the electronic device as shown in  FIG. 4  and described above can be carried out using the exemplary touch screen display unit  180  shown in  FIGS. 5A to 5C . The method described above with reference to  FIG. 4  and  FIGS. 3A to 3C  is similar and therefore is not further described herein. 
     Reference is now made to  FIGS. 6A and 6B  to describe another exemplary touch screen display unit. The reference numerals used previously in describing the touch screen display unit shown in  FIGS. 3A to 3C  will be used again raised by  200  for ease of reference. 
       FIG. 6A  shows a top view of a portion of the exemplary touch screen display unit  280  in a landscape orientation, showing hidden detail, including the actuating arrangement  284 .  FIG. 6B  shows a side view of portions of the touch screen display unit  280  and, for the purpose of illustration and ease of understanding, is not drawn to scale. A base  282  is provided for mechanically supporting the actuating arrangement  284 . Again, the base  282  can be a printed circuit board for providing the mechanical support and for providing electrical connection for electronic components for the portable electronic device  20 . In the present example, the base  282  includes cut-away portions or apertures therein for accommodating portions of the actuating arrangement  284  as described below. 
     The actuating arrangement  284  includes the substrate  286  and the piezoelectric patch transducer  290  and is supported near the center of the substrate  286 , by the base  282 . The substrate  286  can be a metal substrate such as aluminum, magnesium or any other suitable substrate capable of elastic deformation. In the present exemplary embodiment, the substrate  286  includes an arcuate body  294  with a convex side of the arcuate body  294  facing the touch-sensitive display  238 . As shown in  FIG. 6A , the arcuate body  294  is hour-glass shaped such that the width of the arcuate body  294  is smallest at the apex, closest to the touch-sensitive display  238 . End portions  296  of the arcuate body  294  extend farthest from the touch-sensitive display  238 . A respective leg  297  extends from each of the end portions  296 , toward the touch-sensitive display  238  and generally perpendicular thereto and a respective foot  298  extends inwardly from each leg  297  to support the touch-sensitive display  238 . As indicated above, the substrate  286  extends through cut-away portions (apertures) of the base  282  such that a central portion of the arcuate body  294  is located between the base  282  and the touch-sensitive display  238  and the end portions  296  extend at least partly through the base  282 . Each leg  296  extends from a respective one of the end portions  296 , at least partly through the base  282 , toward the touch-sensitive display  238 . It will be appreciated that the present example is similar to that shown in  FIGS. 5A and 5B , with the exception that the substrate  286  is supported directly on the base  282  and the ends  296  as well as the legs  297  extend at least partly through apertures in the base  282 . The cut-away portions of the base  282  provide for a touch screen display unit  280  that is thin by comparison to the thickness of the touch screen display unit  180  of  FIGS. 5A to 5C , thus resulting in reduced overall device thickness. 
     Again, the piezoelectric patch transducer  290  is a flexible transducer that is fixed to the arcuate body  294  and extends longitudinally along the arcuate body  294  such that the patch transducer  290  is also arcuate-shaped. 
     The operation of the actuating arrangement  284  is similar to that described above with reference to  FIGS. 5A to 5C  and therefore need not be further described herein. As in the above-described examples, control of the patch transducer  290  by control of the charge provides forces and controlled movement of the touch-sensitive display  238 , giving the user a desirable tactile feedback upon selection of a feature on the touch-sensitive display  238 . The steps of the method of controlling the electronic device as shown in  FIG. 4  and described above can be carried out using the exemplary touch screen display unit  280  shown in  FIGS. 6A and 6B . The method described above with reference to  FIG. 4  is similar and therefore also need not be further described herein. 
     Reference is now made to  FIGS. 7A and 7B  to describe yet another exemplary touch screen display unit. The reference numerals used previously in describing the touch screen display unit shown in  FIGS. 3A to 3C  will be used again raised by  300  for ease of reference. 
       FIG. 7A  shows a top view of a portion of the exemplary touch screen display unit  380  in a landscape orientation, showing hidden detail, including the actuating arrangement  384  and the base  382 .  FIG. 7B  shows a side view of portions of the touch screen display unit  380  and, for the purpose of illustration and ease of understanding, is not drawn to scale. The base  382  is provided for mechanically supporting the actuating arrangement  384 . Again, the base  382  can be a printed circuit board for providing the mechanical support and for providing electrical connection for electronic components for the portable electronic device  20 . In the present example, the base  382  includes cut-away portions or apertures therein for accommodating portions of the actuating arrangement  384  as described below. 
     The actuating arrangement  384  includes the substrate  386  and a pair of piezoelectric patch transducers  390  and is supported near the center of the substrate  386 , by the base  382 . The substrate  386  can be a metal substrate such as aluminum, magnesium or any other suitable substrate capable of elastic deformation. In the present exemplary embodiment, the substrate  386  includes an arcuate body  394  with a convex side of the arcuate body  394  facing the touch-sensitive display  338 . As shown in  FIG. 7A , the arcuate body  394  includes two generally rectangular sections with end portions  396  that extend farthest from the touch-sensitive display  338  and a center that is closest to the touch-sensitive display  338 . A respective leg  397  extends from each of the end portions  396 , towards the touch-sensitive display  338  and generally perpendicular thereto. A pair of feet  398  extend inwardly from the legs  397  with each foot  398  joining the legs  397  on a respective side of the arcuate body  394 . The touch-sensitive display  338  is supported on the feet  398 . As indicated above, the substrate  386  extends through cut-away portions (apertures) of the base  382  such that a central portion of the arcuate body  394  is located between the base  382  and the touch-sensitive display  338  and the end portions  396  extend at least partly through the base  382 . Each leg  397  extends from each of the end portions  396 , at least partly through the base  382 , toward the touch-sensitive display  338 . In  FIG. 7A , portions of the base  382  are shown in ghost-outline for the purpose of illustration of the present example. As shown, the base  382  includes generally rectangular cut-away portions to accommodate ends  396  of the arcuate body  394 . 
     Each of the piezoelectric patch transducers  390  is a flexible transducer that is fixed to the arcuate body  394  and extends longitudinally along a respective one of the generally rectangular sections such that the patch transducers  390  are also arcuate-shaped. 
     It will be appreciated that although the exact structure of the base  382  and the substrate  386  of the present example differs from that shown and described in relation to  FIGS. 6A and 6B , and a pair of patch transducers  390  are employed rather than a single patch transducer, the operation of the actuating arrangement  284  may be similar to that described above with reference to  FIGS. 6A and 6B  and therefore need not be further described herein. Control of the patch transducers  390  by control the charge by modulation of the applied voltage or current and discharge of capacitance provides forces and controlled movement of the touch-sensitive display  338 , giving the user a desirable tactile feedback upon selection of a feature on the touch-sensitive display  338 . The steps of the method of controlling the electronic device as shown in  FIG. 4  and described above can be carried out using the exemplary touch screen display unit  380  shown in  FIGS. 7A and 7B . The method described above with reference to  FIG. 4  is similar and therefore also need not be further described herein. 
     Referring now made to  FIGS. 8A and 8B , yet another exemplary touch screen display unit will be described. The reference numerals used previously in describing the touch screen display unit shown in  FIGS. 3A to 3C  will be used again raised by  400  for ease of reference. 
       FIG. 8A  shows a top view of a portion of the exemplary touch screen display unit  480  in a landscape orientation, showing hidden detail, including the actuating arrangement  484  and the base  482 .  FIG. 8B  shows a side view of portions of the touch screen display unit  480  and, for the purpose of illustration and ease of understanding, is not drawn to scale. The base  482  is provided for mechanically supporting the actuating arrangement  484 . Again, the base  482  can be a printed circuit board for providing the mechanical support and for providing electrical connection for electronic components for the portable electronic device  20 . In the present example, the base  482  includes cut-away portions or apertures therein for accommodating portions of the actuating arrangement  484  as described below. 
     The actuating arrangement  484  includes the substrate  486  and four piezoelectric patch transducers  490  and is supported near the center of the substrate  486 , by the base  482 . The substrate  486  can be a metal substrate such as aluminum, magnesium or any other suitable substrate capable of elastic deformation. Similar to the embodiment described above with reference to  FIGS. 7A and 7B , the substrate  486  of the present exemplary embodiment includes an arcuate body  494  with a convex side of the arcuate body  494  facing the touch-sensitive display  438 . As shown in  FIG. 8A , the arcuate body  494  includes two generally rectangular sections with end portions  496  that extend farthest from the touch-sensitive display  438  and a center that is closest to the touch-sensitive display  438 . A respective leg  497  extends from each of the end portions  496 , towards the touch-sensitive display  438  and generally perpendicular thereto. A pair of feet  498  extend inwardly or outwardly from the legs  497  with each foot  498  joining the legs  497  on a respective side of the arcuate body  494 . The touch-sensitive display  438  is supported on the feet  498 . As indicated above, the substrate  486  extends through cut-away portions (apertures) of the base  482  such that a central portion of the arcuate body  494  is located between the base  482  and the touch-sensitive display  438  and the end portions  496  extend at least partly through the base  482 . Each leg  497  extends from each of the end portions  496 , at least partly through the base  482 , toward the touch-sensitive display  438 . In  FIG. 7A , portions of the base  482  are shown in ghost-outline for the purpose of illustration of the present example. As shown, the base  482  includes generally rectangular cut-away portions to accommodate ends  496  of the arcuate body  494 . 
     Each of the piezoelectric patch transducers  490  is a flexible transducer that is fixed to the arcuate body  494  with two patch transducers  490  extends longitudinally along each one of the generally rectangular sections such that each of the patch transducers  490  is also arcuate-shaped. As shown in  FIG. 8A , a respective patch transducer  490  is located on each side of center of each of the rectangular sections. 
     It will be appreciated that although four patch transducers  490  are employed rather than a single patch transducer, the operation of the actuating arrangement  284  may be similar to that described herein above and therefore need not be further described herein. Control of the four patch transducers  490  by control of the charge at each by modulating the applied voltage or current and controlling the discharge of capacitance provides forces and controlled movement of the touch-sensitive display  438 , giving the user a desirable tactile feedback upon selection of a feature on the touch-sensitive display  438 . The steps of the method of controlling the electronic device as shown in  FIG. 4  and described above can be carried out using the exemplary touch screen display unit  480  shown in  FIGS. 8A and 8B . The method described above with reference to  FIG. 4  is similar and therefore also need not be further described herein. The patch transducers  490  may be controlled together or controlled separately for providing different forms of tactile feedback based on, for example, touch location or feature selection. 
     In embodiments, the patch transducer can be used for providing tactile feedback as described as well as for providing a vibration, for example, for a notification of receipt of an email, cellular phone call, for a reminder or any other suitable notification. Such vibration notifications can be provides using the same patch transducer and by controlling the charge and discharge of capacitance at the patch transducer. Thus, a further device such as, for example, a vibratory motor is not needed for vibration of the device. 
     In other exemplary embodiments, the actuating arrangement can differ substantially. In particular, the shape of the substrate  86  can differ from that shown and described. Furthermore, an additional patch transducer or patch transducers can be employed on an opposing side of the substrate  86 . for energy harvesting or for providing an applied force in the opposing direction (for actuation in an opposing direction), for example. It will be appreciated that the present disclosure is not limited to the use of the virtual keyboards shown as many other keyboard types are possible including, for example, other reduced keyboards or other full keyboards in either of the orientations. 
     In the above-described embodiments, the piezoelectric patch transducer is employed between a touch-sensitive display and a base of the portable electronic device. In other embodiments, a piezoelectric patch transducer can be employed with a substrate in a bending configuration between any base and any suitable input. In some embodiments, the piezoelectric patch transducer can be employed with a substrate in a bending configuration between a base and a touch-sensitive input control pad. In other embodiments, the piezoelectric patch transducer can be employed with a substrate in a bending configuration between a base and a touch-sensitive surface. The piezoelectric patch transducer provides a robust actuator that is relatively thin and therefore does not add significantly to the thickness of the device while providing a desirable tactile feedback to the user. 
     The piezoelectric patch transducer or patch transducers can be controlled to apply a bending force to the substrate, thereby causing the elastically deformable substrate to curve (or further curve). The bending force can be controlled such that a desirable tactile feedback is provided upon detection of a touch-input at the touch-sensitive display. Further, the tactile feedback may be controlled to provide different tactile feedback for touch events at different areas on the touch-sensitive display. Thus, feedback may be controlled such that touching the touch-sensitive display at an area that does not correspond to a virtual button or feature, for example, does not result in provision of tactile feedback while touching the touch-sensitive display at an area that corresponds to a virtual button or feature results in provision of such tactile feedback. Further still, the tactile feedback can be controlled such that different feedback is provided for different user-selectable features on the touch-sensitive display or for different areas of the touch-sensitive display, for example. It will also be appreciated that tactile feedback can be selectively provided based on applied force by the user when touching the touch-sensitive display. Thus, tactile feedback is provided when the applied force meets or exceeds a threshold. 
     According to one aspect, there is provided a touch-sensitive input unit. The touch-sensitive input unit includes a base, a touch-sensitive input surface for detecting a touch event thereon, the touch-sensitive input surface connected to and moveable relative to the base, and an actuating arrangement comprising an elastically deformable substrate between the touch-sensitive input surface and the base, and a piezoelectric patch transducer fixed to the substrate for controlling a bending force on the substrate to control a force on the touch-sensitive input surface by modulating a charge at the patch transducer. 
     According to another aspect, there is provided a portable electronic device that includes a base, a display device, a touch-sensitive input surface and a controller connected to the touch-sensitive input surface for detecting a touch event thereon, the touch-sensitive input surface connected to and moveable relative to the base, and an actuating arrangement comprising an elastically deformable substrate between the touch-sensitive input surface and the base, and a piezoelectric patch transducer fixed to the substrate for controlling a bending force on the substrate to control a force on the touch-sensitive input surface by modulating a charge at the patch transducer. Operational components include a processor connected to the display device, the controller and the touch-sensitive input surface for modulating the charge at the patch transducer to thereby control the bending force. 
     According to yet another aspect, there is provided a method of controlling a portable electronic device that includes detecting a touch event at the touch-sensitive input surface, and, modulating a charge at the piezoelectric patch transducer for controlling a bending force on the substrate and thereby controlling a force on the touch-sensitive display in response to detecting the touch event. 
     According to still another embodiment, there is provided a computer-readable medium having computer-readable code embodied therein for execution by a processor in a portable electronic device for detecting a touch event at the touch-sensitive input surface and, modulating a charge at the piezoelectric patch transducer for controlling a bending force on the substrate and thereby controlling a force on the touch-sensitive display in response to detecting the touch event. 
     Advantageously, the piezoelectric patch transducer can be configured and controlled to apply a bending force to the substrate, thereby causing a change in curvature of the elastically deformable substrate. The bending force can be controlled by controlling the charge at the piezoelectric patch transducer such that a desirable tactile feedback is provided upon detection of a touch-input at the touch-sensitive display. Current or voltage may be applied to build up capacitive charge and thereby apply the bending force to the substrate. Capacitance may then be discharged to cause or permit movement of the touch-sensitive display. Further, the tactile feedback may be controlled to provide different tactile feedback for touch events at different areas on the touch-sensitive display. As indicated, feedback may be controlled such that touching the touch-sensitive display at an area that does not correspond to a virtual button or feature, for example, does not result in provision of tactile feedback while touching the touch-sensitive display at an area that corresponds to a virtual button or feature results in provision of such tactile feedback. Further still, the tactile feedback can be controlled such that different feedback is provided for different user-selectable features on the touch-sensitive display or for different areas of the touch-sensitive display, for example. Further, the tactile feedback may be provided in response to determination of an externally applied force that exceeds a threshold. Thus, tactile feedback is provided when the user touches the touch-sensitive display with sufficient force to exceed the threshold. 
     The actuating arrangement with the piezoelectric patch transducer provides a robust actuator capable of bending or further bending for desired and controlled movement of the touch-sensitive display, thereby providing desirable tactile feedback in response to a touch event on the touch-sensitive display. Further, the piezoelectric patch transducer is thin, therefore not adding significantly to the required thickness of the device while providing a desirable tactile feedback to the user. 
     While the embodiments described herein are directed to particular implementations of the portable electronic device and the method of controlling the portable electronic device, it will be understood that modifications and variations may occur to those skilled in the art. All such modifications and variations are believed to be within the sphere and scope of the present disclosure.