HK1026093B - Emergency telephone with automatic low-battery signaling - Google Patents

Description

Emergency telephone with automatic low battery signaling

Technical Field

The present invention relates generally to wireless telecommunication devices, and in particular to a battery monitoring system for a wireless portable telephone.

Background

Portable cellular telephones provide radiotelephone communications using conventional (wired) telephones and other cellular telephones. These handsets are powered by small rechargeable batteries that typically provide a limited hour of active call time. Once the battery is discharged, the battery must be recharged or replaced before the phone can be used to make more phone calls. While some types of cellular telephones utilize larger, e.g., automotive, battery powered or plug-in electrical wall outlets, the present invention relates to cellular telephones that utilize small batteries sufficient to provide portable operation. In fact, the present invention relates to devices and techniques for periodically monitoring the amount of charge remaining in the battery and issuing a low battery alarm when appropriate during the time the user sets the telephone in the "off" state.

Cellular telephones are conventionally used as portable telephones that can be accessed by a user when the user wishes to make or receive a telephone call. Furthermore, the telephone may transition to a low power standby state while awaiting receipt of a telephone communication, as described in US patent 5179724 entitled "conserving power of a handheld mobile telephone during a receive mode of operation". Low power wait states with battery monitoring functions have been developed for non-cellular telephone applications such as computers in US patent 5600282 and japanese patent publication JA-0238933, entitled "low power oscillator circuit". However, when a user is not making a telephone call and does not desire to receive a call, the cellular telephone is typically turned off to conserve the charge stored in the battery. By turning off the cellular telephone, all power consuming components of the telephone are turned off, as described in U.S. patent No. 5570025. This minimizes the current drawn from the battery and thereby extends the time period during which the cellular telephone can operate after a single battery charge. Thus, many existing cellular telephones do not perform any function when turned off.

When the cellular phone is in the power-on state, the cellular phone may notify its user when the remaining battery charge amount is low. The user may be notified of the low charge battery condition just before the cellular telephone ceases operation. Moreover, most existing cellular telephones have a low charge alarm that is implemented as an "audible" beep "or message on the display of the telephone to alert the user to: the battery needs to be recharged. To determine that the battery is low and issue a warning, some cellular telephones include an electronic circuit to monitor the state of charge of the battery and issue a warning when the battery charge falls below a certain level. The cellular phone must be powered in order to execute programs and operate circuits to monitor the battery and issue warnings.

Cellular telephones have many uses, including use in emergency calling police, ambulances or trailers. In fact, some users have indicated a desire to load cellular telephones in their automobiles or other vehicles for emergency situations only. For example, a minor's parents may load a cellular telephone in their car and tell their children that the telephone is only used in an emergency. Also, the climber can carry a small-weight cellular phone to request rescue in case of emergency. In addition, emergency cellular telephones may be purchased in the future that have a single function of calling a predetermined emergency telephone number, such as at home or "911" at power-up.

If the cellular telephone is used as an emergency telephone, it is important: the battery is fully charged when the phone is powered up and a call is placed on the phone.

Batteries suitable for use in emergency cellular telephones must be able to remain inactive for months without having to be replaced or recharged. These batteries must provide sufficient current to power the phone and allow a call to be sent from the phone after months of inactivity, if not a year, the emergency battery will lose its charge if the phone is left for an additional period of time. The battery also loses its charge if the phone is left to stand for too long due to the self-discharge characteristics of the battery, or if the phone allows the battery to trickle down or if the battery fails. In either case, the battery may not be fully charged when an emergency occurs and the cellular telephone is powered up for a distress call. The inability of an emergency cellular telephone to operate will only make the emergency worse and prevent someone needing assistance from calling the police, ambulance, or seeking other assistance. Therefore, it is necessary to ensure that: the battery used to power the emergency cellular telephone stores sufficient energy to power the telephone after a long period of inactivity. In addition, it is necessary to ensure that: the battery in the emergency cellular telephone will give a warning when the battery charge is lost.

It is known in the art to retrofit a cellular telephone into a roadside emergency call box for use. As described in U.S. patent nos. 4788711 and 5377256, cellular telephones are constantly installed in roadside telephone call boxes and are preprogrammed into calling police dispatch centers or other governmental organizations. The installation of cellular telephones in wayside call boxes does not necessarily create a battery problem, here because these constantly placed telephones can be powered using the power line of the utility company. In addition, the call box cell phones are always on so that they can be monitored by the dispatch center and periodically perform self-maintenance functions. For example, a cellular telephone is preprogrammed to periodically and automatically call a dispatch center and verify that it is functioning properly or report the detected difficulty of the telephone with respect to its operation. If the battery backup in the cell phone is discharged, the active cell phone will detect a low charge on the battery and report the low battery condition to the dispatch center the next time the phone automatically makes a status call. However, since the present invention performs the battery test and alarm functions when the telephone is turned off, and the emergency call box performs neither the "off" nor "state functions, the apparatus and method employed by the cellular telephone placed in the wayside call box does not constitute prior art of the present invention.

Many cellular telephone users purchase telephones for security applications, and particularly primarily for emergency use, which should have low cost and long battery life. The safety telephone (also called an emergency telephone) most likely contains an alkaline battery or another battery type that exhibits a long shelf life. Although the security phone is rarely used, it is important that the phone is able to successfully make a call when powered up, since the phone is used in an emergency. In order to successfully place a call, a number of requirements must be met, one of which is sufficient battery capacity. However, since the secure phone may be stored in an out-of-sight location and rarely used, the user may forget to replace or recharge the battery when needed. Existing cellular telephones contain a low battery alarm but are not suitable for use as a security telephone because the alarm occurs only after the user turns on the telephone and no battery test or alarm is conducted while the telephone is off.

Disclosure of Invention

A cellular telephone includes a low power timer that operates when the telephone is in an off state. This timer "wakes up" (powers up) the processor in the phone at predetermined intervals (e.g., once per day or once per week). After each timer-controlled "wake-up", the processor performs a test to estimate the remaining battery capacity. This can be done by measuring the battery voltage as a load is placed on the battery or using other conventional battery power monitoring techniques. If the battery capacity is sufficient, the phone processor shuts down and restarts the timer. If the battery capacity is low, an alarm is issued.

The alarm may consist of up to a predetermined number of automatic cellular telephone calls (which the user or carrier is built into the phone using the keypad and/or system connector) and other conventional alarms of the phone such as beeps, displays, etc. If an alarm call is set, the called number may be the subscriber's wire line number, another cellular number, or a carrier number. Once a call is established, an "alert" can include a tone, a combination of tones, a voice message (which requires speech synthesis in the phone), or data.

Drawings

FIG. 1 is an exemplary block diagram of a cellular telephone;

FIG. 2 is an example block diagram of a battery monitor circuit coupled to a microcontroller of a cellular telephone; and

fig. 3A and 3B are software flow diagrams for monitoring battery charge level, issuing low battery alarms, and controlling the receiver by the microcontroller.

Detailed Description

Fig. 1 shows a block diagram of a hand-held mobile cellular telephone 100 in connection with the present invention. While the principles of the present invention are particularly well suited for use in small hand-held portable telephones, the principles of the present invention are equally applicable to any type of battery-operated wireless communication device in which it is desirable to reduce power consumption. The components of the cellular telephone are conventional, except for a battery monitoring circuit which is active even when the telephone is turned off.

The cellular telephone 100 of the present invention includes a transceiver 112 having a transmitter 114 and a receiver 116 coupled to a common antenna 118. The transmitter and receiver circuits 114, 116 are controlled by a microcontroller 120, which may be one of many commonly available microcontrollers. For transmission or reception, the audio signal passes through an audio processing circuit 122, the audio processing circuit 122 converts the received audio signal into a signal suitable for a speaker 124, and converts an electrical signal from a microphone 126 into a signal suitable for the transmitter circuit 114. In addition, the audio processing circuit 122 may receive a synthesized speech signal, such as "low battery alert," from a speech generator 128 controlled by the microcontroller 120.

The microcontroller 120 also controls the display 130 of the cellular telephone and receives input signals from the telephone keypad 132. For example, a keypad may be used to enter a telephone number to be stored in a memory location assigned to the user for setting the information location 134 in a non-volatile memory 136 associated with the microcontroller. Executable program instructions may also be stored in location 135 in non-volatile memory. The microcontroller may also access volatile memory 138 as a temporary storage location.

The current for operating the components of the cellular telephone is provided by a battery 140, such as an alkaline battery, which is connected to most of the components of the telephone by a switch 142. A voltage regulator 218 connected to the battery provides a uniform voltage (Vcc) to the other electrical components in the phone except for the test circuitry. When the switch is Open (OFF), the battery is disconnected from the other components of the phone, except for the test circuit 148, which is always coupled to the battery. In addition to the battery, the telephone can also be powered by a transformer 144 connected to a charging terminal 146 on the telephone, which can also be used to recharge the battery when a rechargeable battery is used.

The battery test circuit is shown in fig. 2 and described in subsequent paragraphs. For this circuit description, "set" or "high" refers to the higher logic level of the two active digital output states, while "reset" or "low" refers to the lower logic level of the two active digital output states.

The battery test circuit 148 monitors the charge level of the battery 140 by applying a load to the battery and then measuring the battery voltage. A load may be placed on the battery by switching on circuitry within the phone. The test circuit outputs a digital value corresponding to the battery voltage, which is indicative of the battery state of charge. The voltage level output from the battery 140 is applied to an analog-to-digital (a/D) converter 206, the converter 206 converts the voltage level input from the battery to a digital value, which is output from the converter on bus 208 to the microcontroller 120, which compares the digital value representing the amount of battery charge to a predetermined value stored in the non-volatile memory 136 (fig. 1) to determine whether the amount of battery charge is sufficient to power the telephone and perform emergency wireless communications. If the battery charge level is below a predetermined level, the microcontroller initiates an alarm sequence.

The test circuit 148 includes a counter 202, an oscillator 210, an analog-to-digital (A/D) converter 206, and resistors R2 and R3. External to the test circuit 148 but associated with this circuit 148 are diodes D1-D5, other resistors (R1), a switch (Sn), a voltage regulator 218, a voltage clamp 220, a battery 140, and a microcontroller 120. The oscillator 210 provides a clock signal that is used by the counter 202 to time the standby period (not powered) of the cellular telephone and particularly the period between the occurrence of the microcontroller wake-up. The counter 202 has a clock input from the oscillator, a load input 203 from the microcontroller 120, and an output to the battery switch (S1) 142. The counter 202 may be made up of a multi-stage flip-flop circuit, with one stage per counter bit, or may be some conventional counting circuit. Each clock pulse from oscillator 210 decrements the counter value by 1. When the counter value equals 0, two actions occur within the counter: (1) disabling the clock pulse from the oscillator to clock the counter and thereby stopping the counting process, and (2) the output of the counter is set to close switch S1142. This causes power to be applied to the microprocessor and other telephone circuitry. When the counter is running and has a non-zero count value, the counter output is low for switch S1142. When the load input 203 from the microprocessor 120 is high, the counting process is disabled and the counter 202 is loaded with a predetermined non-zero value (initialization value) corresponding to a predetermined inactive period. The counter 202 operates (counts) when the load input 203 is low and the counter value is not equal to zero. When the load input 203 becomes low and the count value is not equal to 0, the counter 202 operates (counts). The time required for the counter 202 to reach zero when the load 203 input changes from high to low depends on the predetermined value loaded into the counter 202 and the frequency of the oscillator 210. These values may be selected to produce a one day to one week timeout period or another period stored in memory.

The a/D converter 206 (and the oscillator 210 as well as the counter 202) has an analog voltage input directly from the battery 140 that is not disconnectable by the switch S1. The converter has an enable input 212 and a digital output 213 to bus 208. the a/D conversion process produces a digital value that is proportional to or representative of the analog voltage level from the battery. The converter 206 is enabled during the wake-up process that is enabled when the counter 202 switches power to the microcontroller through switch S1. When the enable input 212 of the converter 206 is high, voltage conversion is performed and a digital value is sent to the microcontroller, which conversion occurs when the other telephone circuitry is powered up so that the battery voltage is measured with the load applied to the battery. When the converter 206 enables input low, no conversion is performed and there is no voltage level on the digital output 213.

The switch (S1)142 powers up the microcontroller 120 and other telephony circuits 214 when closed, while the test circuit 148 receives power independently of the switch. By a control voltage V_CNTLSwitch S1 is activated. When controlling the voltage V_CNTLWhen low, switch S1 is open. When the control voltage is high, switch S1 is closed. Switch S2 corresponds to the user power button and is normally off, which is pressed by the user to turn the phone on and off. Diode (D)₁、D₂And D₃) And resistor R1 is used as a "logical OR" gate 250 (FIG. 1) when (1) button S2 is pressed, (2) counter 202 outputs a high enable signal, OR (3) the microcontroller sets the output to D₃When so, the door 250 activates switch S1. Once diode D₁、D₂Or D₃Is set high and a control voltage is applied to switch S1 to close the switch.

Fig. 3A and 3B are simplified flow diagrams 300 depicting the program instruction logic stored in memory 135 necessary to control the battery monitoring function. When the user presses switch S2 (which may be a key on the keyboard 132), diode D is given₂The cell voltage is applied to the anode of (a), so that the control voltage to S1 is high. This condition closes switch S1, thereby applying battery voltage to regulator 218. The regulator applies a regulated voltage to the microcontroller 120 and other telephone circuits 214, which test the output V of the clamp circuit 220 when the microcontroller begins to execute its program_CLMPTo determine whether the switch is closed (indicating power up resulting from the user input step 304). If the clamping voltage is high, indicating that the user switch S2 is closed, the microcontroller sets a diode D₃Is high, which provides a second current source to R1 to maintain V_CNTLHigh (to close switch S1) and continue to power up the phone. Diode D in step 306₃This arrangement "locks" the telephone in the ON state, allowing the user to release switch S2 and still keep the telephone ON. To diode D₃Until the user turns off the phone or the phone automatically turns off.

When the phone is turned on by the user (as detected by the microcontroller through the clamp output), program execution moves to a set of instructions that provide the functionality required by the user for normal cellular telephone service, which functionality (represented by step 308) is conventional and not relevant to the present invention.

In step 310, to diode D₄The microcontroller output is set to disable the counter from counting and load the counter with an initialization value. In addition, the output is set to the diode D₅The microcontroller on line 230 can monitor the battery voltage by activating the a/D converter to output a digital value of the battery voltage on bus (line) 208. To turn off the phone, the user presses switch S2 again, which is detected by the microcontroller by monitoring the output of the clamp circuit. After detecting the closure of switch S2, the microcontroller resets the given diode D on line 231₃To cause switch S1 to open and disconnect power to the microcontroller and other telephone circuitry 214.

After the microcontroller is no longer powered up, the diode D₄The input goes low to cause counter 202 to start counting. Likewise, the microcontroller not powering up would allow diode D₅Low and disables a/D converter 206. While the telephone is in the off state, the counter counts the standby period, and when a count value of zero (0) is reached, the counting process is stopped and the counter output is set. With the output of this setting, voltage is applied to close switch S1, which applies battery voltage to the voltage regulator, which powers the microcontroller. When the microcontroller begins executing instructions, i.e., wakes up, it first tests the output of the band circuit 220 to determine if switch S2 is closed (indicating a power up caused by a user input-see step 304). For this case, switch S2 is not closed because power is applied by the test circuit, not the user. The microcontroller then sets the output to diode D₃This provides a second current source to keep switch S1 closed, which action "locks" the phone in the ON state in step 312. To diode D₃Output of the microcontroller is at the execution of the battery testThe test is held high while ensuring that the microcontroller and other telephone circuitry is powered up during the battery test.

After the microprocessor is turned on with the test circuit, the microprocessor sets line 232 up to diode D in step 314₄To reinitialize the counter with a counter start value. The load signal applied by the microprocessor also disables the counter while the microcontroller is powered up.

A battery test is performed by the microcontroller in step 316 by first switching on the other phone circuitry (to place a load on the battery). Under known load conditions, the battery voltage represents the remaining battery capacity. The microcontroller loads the battery by controlling internal circuitry to turn on or power selected circuitry such as logic, audio processing, memory, DSP, receiver or transmitter circuitry. Means for controlling the powering up of the circuit are widely used to perform a "sleep" mode that conserves battery capacity during the normal operating mode and are well known in the art. Alternatively, the phone can contain a load (resistor) and a switch dedicated to loading the battery for testing purposes, wherein the switch is controlled by the microcontroller to perform the test.

The microcontroller sets diode D in step 318₅To start the a/D converter 206, the microcontroller compares the digital representation of the battery voltage level received from the a/D converter to a stored threshold battery level in step 320. If the battery value comparison indicates that the battery capacity is sufficient, the microcontroller resets diode D in step 322₃To open switch S1 and to open the telephone. If the microcontroller determines that the battery charge is insufficient, a battery alarm may be issued. As shown in fig. 3B, when the process 300 determines that a low battery alarm is issued, the process may initiate a series of visual, audible, and wireless alarms. In step 324, the program determines whether the phone is set (e.g., the settings already stored in memory location 134) to issue a visual low battery alert, and if so, the visual alert will appear on display 130 in step 326. Also, the same applies toIn steps 328 and 332, the microcontroller determines whether the telephone is set to issue audible and wireless (telephone call) alerts. If activated, the microcontroller causes an alert signal to be sounded from the telephone set in step 330 and/or the transmitter circuitry 114 sends an alert signal, such as a synthesized voice alert, to a predetermined telephone number in step 334.

At the end of the battery test (and any alarms, if appropriate), by resetting to diode D in step 322 or 336₃To turn off the telephone, i.e., to open switch S1. When switch S1 becomes open, the microcontroller no longer receives power from the regulator. After the microcontroller is no longer powered up, the diode D₄Low causing the counter load input on line 232 to be low. This allows the counter 202 to start working with the initialized value of the load counter while the load input is high. And with diode D on line 230₅The input goes low and the a/D converter is also disabled, including disabling the output signal of the a/D converter. This ensures that the signal output from the a/D converter is not applied to the unpowered microcontroller.

One special case involves installing a battery in a cellular phone from an initial state without a battery. For this case, the test circuit is powered up with the battery and the counter 202 in the test circuit 148 is assumed to be at a random value. Thus, the time interval between battery installation and the first battery test will be random (corresponding to a range of values from zero (the battery test starting immediately after installation of the battery) to a time period corresponding to the maximum counter value). Subsequent battery tests will be counted for each required time interval as described above. If desired, the test circuit can be configured to load the counter with a predetermined value at the time of battery installation to ensure a known time interval between battery installation and the first test. However, this is considered to increase the cost with little benefit, and thus is not included in the preferred embodiment.

A second special case involves the user attempting to switch on the phone while a battery test initiated by the counter is in progress. Since the user may press switch S2 during the counter-initiated battery test, the output of the pinch circuit 220 is continuously sampled during the test. If the microcontroller detects that switch S2 has been pressed, the counter-initiated battery test is terminated and the user' S cell phone is fully turned on and normal user operation is performed, which may include audible and visual low battery alarms.

Claims (8)

1. A wireless communication device (100) operable in one of a plurality of states including a power-off state (322) and a battery test state (316, 318), the device comprising:

a battery (140) having an amount of charge for powering the device;

a battery charge level monitoring circuit (206, 148) coupled to the battery for generating a battery charge level signal proportional to a battery charge level; and

a processor (120), coupled to the battery charge monitoring circuit, for detecting a battery charge signal when a timer (202) has caused the device to enter a battery test state and generating an alarm signal when the battery charge signal is below a predetermined level, wherein the wireless communication device is characterized by:

a timer (202) coupled to the battery and operable in a power-off state to cause the device to enter a battery test state (312) when a predetermined period of time has elapsed while the device is in the power-off state; and

wherein the generating of the alert signal includes powering up communication circuitry in the device to establish automatic wireless communication to a preselected telephone number to send a low battery charge alert (334).

2. The wireless communication device of claim 1, further comprising a communication circuit (116, 122) that powers on during the battery test state.

3. The wireless communication device of claim 1, wherein the battery charge level monitoring circuit (206) is turned off (322) during the power-off state.

4. The wireless communication device of claim 1, wherein the timer (202) is turned off and reinitialized (314) during the battery test state.

5. A wireless communication device according to claim 1 wherein the device is a cellular telephone having a transmitter circuit (114), an antenna (118) and a synthesized voice circuit (122) controllable by a processor (120), and the alert signal comprises sending a cellular telephone communication signal via the transmitter and antenna to a telephone number stored in a memory (136) accessible by the processor, and causing the synthesized voice circuit to send the synthesized voice low battery alert during the communication.

6. A method for automatically generating a low battery alert in a wireless communication device (100) operable in a plurality of states including a power-off state (322) and a battery test state (316, 318) and having a battery (140) for providing power, the method characterized by the steps of:

a. while the device is in the powered-off state, operating a timer in the device to measure a predetermined time period while it remains in the powered-off state;

b. after a predetermined period of time has elapsed, causing the device to enter a battery test state;

c. detecting the charge of the battery and generating a battery charge signal proportional to the battery charge;

d. generating an alert signal if the battery charge has dropped below a predetermined amount of charge and establishing wireless communication to a preselected telephone number to transmit the alert signal; and

e. after step (c), if the battery charge level exceeds a predetermined level, then the power to one or more of the circuits, processor and monitoring circuit is cut off and the process returns to step (a).

7. The method of claim 6, wherein step (c) is further performed by applying an electrical load to the battery (316).

8. The method of claim 7, wherein the low battery alert comprises a voice alert (330).