Load suppression for battery-powered devices

Abstract

The apparatus includes a radio (302) that operates according to a predetermined schedule and a battery (304) configured to provide power for radio operation of the radio (302). A radio controller (306) is configured to control the radio operation. A voltage indicator circuit (308) monitors the voltage of the battery (304) and provides an output signal (424) that indicates sufficient battery voltage for radio operation. When the output signal (424) is active, the radio controller (306) operates the radio (302) according to the predetermined schedule. When the output signal (424) is inactive, the radio controller (306) adjusts the operation of the radio (302) to maintain radio operation.

Description

Background Art

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[0001] Typical time - synchronized radios have a predetermined schedule for transmitting or receiving. This operation requires a certain amount of power, and the amount of power depends greatly on the schedule. In a battery - powered device, when the battery reaches a point where it cannot supply enough power to maintain the required radio operation, the voltage level drops. At this point, there is a risk that the available voltage will fall below the reset voltage of the radio, causing the radio to be reset and unable to perform its predetermined operations. Especially when multiple resets occur in a short period of time, the radio may not be able to recover from the reset state and malfunction even though there is still sufficient power remaining in the battery.

[0002] The load on the radio affects the operation of the battery over time and with temperature. Under certain conditions or due to the aging of the battery, there may not be enough power to fully execute the predetermined schedule for transmission or reception. Due to the decrease in battery output, the device may fall into a reset or offline state without warning.

Summary of the Invention

Means for Solving the Problems

[0003] The device of the present invention includes a radio that operates according to a predetermined schedule and a battery configured to supply power for the radio operation of the radio. The radio control unit is configured to control the radio operation. The voltage indicating circuit monitors the voltage of the battery and provides an output signal indicating that the voltage required for the radio operation is ensured. When the output signal is active, the radio control unit operates the radio according to the predetermined schedule. When the output signal is inactive, the radio control unit adjusts the operation of the radio to maintain the radio function.

[0004] The radio load suppression method of the present invention includes monitoring the available power from the device's battery and controlling the radio frequency (RF) operation of the radio based on that power. The control of the RF operation includes operating the radio according to a known transmit or receive schedule if there is sufficient power from the battery to perform scheduled RF operations, and adjusting the RF operation to maintain radio functionality if there is insufficient power. [Brief explanation of the drawing]

[0005] [Figure 1] This is a block diagram of a location recognition system in which embodiments of the disclosure may be implemented. [Figure 2] This is a graph of wireless operation in a conventional system. [Figure 3] This is a block diagram of a load suppression device according to an embodiment of the present disclosure. [Figure 4] Figure 3 is a circuit diagram of the load suppression device. [Figure 5] This is a graph of wireless operation in a system employing an embodiment of the disclosure. [Modes for carrying out the invention]

[0006] This disclosure provides embodiments of a method for suppressing the load on a wireless device in a location recognition system. While such a system is described, wireless suppression based on various embodiments of the present invention can also be applied to other devices that have a wireless device that is battery-operated and driven by limited power. Examples include wireless field devices used for industrial process monitoring and control.

[0007] In devices equipped with radio equipment, the amount of power consumed by the radio varies depending on the number of transmissions (TX) and receptions (RX). Battery-powered devices have a limited amount of power they can supply. One example of this is the Rosemount WirelessHART location anchor, which uses a time-synchronized radio to communicate with location tags and is powered by a battery.

[0008] Figure 1 is a block diagram of a location system 100 to which embodiments of the present disclosure may be applied. The location recognition system 100 includes a host 102 connected to a plurality of gateways 104. The gateways operate a gateway network 110 connected to a plurality of anchors 106. In one embodiment, the anchors 106 are connected to the gateways 104 on the WirelessHART network 110. Each anchor 106 connects to a tag 108 to measure distance and determine the location of each tag. The system operates based on a synchronized time clock and communicates according to a schedule of wireless communication powered by batteries inside the tags and anchors.

[0009] In this type of system, each anchor 106 synchronizes with the WirelessHART network 110, and each tag 108 synchronizes with the anchor 106. To maintain synchronization, the anchor 106 near the tag 108 periodically transmits beacon messages using location information radio. The tag 108 uses these messages to synchronize its clock and extract location distance information. This information is sent back to the receiving anchor 106 and then forwarded to the host system 102. In this type of system 100, keeping the anchors online and operational is crucial for keeping the tag 108 connected to the location system 102.

[0010] Through comprehensive time synchronization, each location anchor 106 executes a radio schedule, during which it transmits beacons or receives data from tags 108. This schedule is repeated at frame intervals (e.g., 16-20 seconds, but may vary without exceeding the scope of this disclosure), and the number of scheduled receptions within a frame depends on the number of tags 108 that the anchor 106 is targeting. Consequently, the load on each anchor 106 varies, making it challenging to design a power supply that can handle all conditions.

[0011] Embodiments of this disclosure are provided to ensure that the wireless power consumption of an anchor does not exceed the range that a normal battery can supply. Under these conditions, the battery maintains its voltage and powers the wireless load. However, if the battery is depleted or the ambient temperature drops, this type of system may face problems. As the battery degrades, its internal resistance increases, causing a voltage drop when drawing a large current. As the voltage drop increases, the system becomes inoperable and the device resets. Unless the power consumption changes significantly, the device may not fully recover until the battery is replaced. In the case of an anchor, when the device resets, it is disconnected from the WirelessHART network and loses connection with nearby tags.

[0012] In addition to battery degradation, similar effects occur in low-temperature environments. In either case, resetting is undesirable behavior and can occur before the battery is completely depleted. As a result, the device becomes unusable even if there is still battery charge remaining, shortening its actual lifespan.

[0013] This situation is illustrated in the graph in Figure 2. Radio RF operation is shown on line 200, and battery voltage is shown on line 202. The voltage indicator signal is shown on line 204, and the device's micro-reset signal is shown on line 206. When radio RF operation begins at time 200a, the battery voltage also begins to decrease, eventually reaching the threshold voltage 210, and falling below this at point 200b. At point 200b, the voltage indicator signal changes from active to inactive due to the voltage drop associated with the radio's RF operation, indicating that the battery voltage has fallen below the threshold voltage 210. Large load currents, such as position radio RF reception, cause the voltage drop. At time 200c, the battery voltage drops to the low voltage limit 211. At this point, the battery can no longer supply enough voltage to power the device, and the device is reset. As a result, the device is disconnected from the network, and RF operation stops. Once the voltage recovers, at time 200d the device recovers from the reset and rejoins the network. At time 200e, RF operation resumes, but because the voltage has only partially recovered, it quickly reaches the low voltage limit of 211 and resets again at time 200f. This process may be repeated as long as the device successfully reconnects. As a result, even with sufficient battery power remaining, the device's operation becomes unstable and performance degrades. When the device recovers, it is often because the battery output improves due to changes in ambient conditions. However, if the reset is repeated excessively, the device may be permanently disconnected from the network and unable to reconnect. In such cases, even though there is still usable power remaining in the battery, the high radio load renders the remaining battery unusable.

[0014] Embodiments of radio load suppression in this disclosure are used to extend battery life and reduce the possibility of device reset. Instead of executing a predetermined transmit and receive schedule, the anchor controls the radio RF operation based on the power available to the device. When the device has good power, the radio follows the full schedule. However, if the power supply drops, the device senses this drop and automatically adjusts and compensates for the scheduled RF operation.

[0015] Location systems, particularly tags and anchors, are susceptible to power loss due to battery degradation, aging, and ambient conditions when deployed in remote locations and powered by internal batteries. As shown in Figure 3, an anchor 106 or tag 108, which is a device with suppressed wireless operation, is shown in a block diagram. In one embodiment, the device 300 includes a radio 302 that operates on a predetermined schedule and a battery 304 that supplies power for its wireless operation. A wireless control unit 306 is connected to the radio 302 and controls the wireless operation. A voltage indicator circuit 308 is connected to the battery and further to the wireless control unit, monitors the battery voltage, and provides an output signal indicating that the voltage required for wireless operation is secured.

[0016] When battery power is sufficient, the output signal from the voltage indicator circuit 308 is active, and the radio control unit 306 operates the radio 302 according to a predetermined schedule. If the battery power falls below a threshold and is not sufficient for full-scheduled RF operation, the output signal becomes inactive. In this case, the radio control unit 306 adjusts the operation of the radio 302 to maintain a supply voltage above the reset voltage of the radio 302. As one form of adjustment, the radio operation is disabled when the output signal is inactive, preventing a reset. Even if the radio is disabled, it is not disconnected from the network and does not reconnect. As another form, when the output signal is inactive, the operation of the radio is adjusted by changing the schedule to reduce the frequency of radio operation. In one further embodiment, when the output signal is inactive, the radio control unit is configured to provide a low voltage warning.

[0017] As long as the battery supplies sufficient voltage for normal operation, the radio control unit is configured to follow a predetermined schedule, checking the battery voltage after each transmit and receive, and suppressing the load if the output signal is inactive. Battery voltage checks are performed at the start of all scheduled RF operations. In one embodiment, monitoring continues even after the RF operation has started. If the battery voltage falls below the threshold required for the safe operation of the radio, the output signal becomes inactive, and RF operation is suppressed.

[0018] Referring to Figure 4, the details of the circuit 400 according to the embodiment of Figure 3 are shown in schematic form. The circuit 400 comprises a radio 302 having an antenna 402, a battery 304, a radio control unit 306, and a voltage indicator circuit 308. Other components include a voltage regulator 404, a power-sharing resistor 406, a large-capacity power storage component 408, and a decoupling capacitor 410.

[0019] The voltage indicator circuit 308 includes a sensing resistor 412 connected between the positive battery terminal and the non-inverting input of the comparator 414 (e.g., an operational amplifier connected as a positive voltage comparator), which is given as the input voltage to the comparator 414 at node 426. The voltage divider 416, which provides the reference voltage, has its midpoint 418 (i.e., threshold voltage) connected to the inverting input of the comparator 414. With this configuration, if the battery voltage at node 426 is higher than the reference voltage at node 418, the output signal 424 becomes active (high level). Conversely, if the voltage at node 426 is lower than the voltage at node 418, the output signal becomes inactive.

[0020] The threshold voltage at node 418 is determined by a portion of the voltage Vreg output by the voltage regulator 404. One end of the voltage divider 416 is supplied with Vreg, and the other end is connected to ground. Therefore, the voltage supplied to the midpoint node 418 is a constant percentage of Vreg, and by selecting the values ​​of resistors 420 and 422, the voltage at node 418 is adjusted to the threshold voltage mentioned above. When the voltage at the positive terminal of the battery, i.e., the battery voltage, falls below the voltage at node 418, the amplifier output signal 424 becomes inactive. When signal 424 becomes inactive, the radio control unit 306 suppresses RF operation.

[0021] Other low-voltage detection circuits may also be used without departing from the scope of this disclosure.

[0022] The operations of the embodiments of the present disclosure are shown in graph form in FIG. 5. The wireless RF operation is shown on line 500, the battery voltage is shown on line 502, the voltage indication signal is shown on line 504, and the microreset signal of the device is shown on line 506. When the wireless RF operation starts at time 500a, the battery voltage also begins to decrease. The voltage indication signal 504 is determined by a voltage indication circuit such as circuit 308, for example, and indicates voltage monitoring. When the voltage drops to the low voltage threshold 510 (voltage level Vt) for safe operation, at time 500b, the voltage indication circuit deactivates the voltage indication signal 504. This signal instructs the wireless control unit to suppress the RF operation, and as a result, the RF operation is controlled at time 500c.

[0023] As yet another additional configuration of the embodiments of the present disclosure, a large-capacity storage component (e.g., a large-capacity capacitor) can be added to assist in situations where the wireless operation becomes highly loaded. Thereby, the duty cycle is reduced, and even a low-voltage battery can exhibit its full capabilities. In one embodiment, a large-capacity storage component 408 is added such that the initial current of the wireless load is fully or almost fully supplied by the large-capacity storage component 408. Thereby, even when the battery is weak, a certain number of wireless tasks can be executed without duty cycle control. The large-capacity storage component is charged by the battery during the time in the RF standby state. When the wireless operation becomes larger than the charge stored in large capacity, the battery supplies additional current, and the wireless load suppression operates as described above. By using a large-capacity capacitor, since it is charged during the RF operation standby, power can be drawn even with a low-capacity battery, and as a result, the available battery life can be extended.

[0024] The large-capacity storage component 408 and its usage method will be described later. In order to smooth out the power consumption spikes that cause the battery voltage to drop, the large-capacity storage component 408 is used in one embodiment. The large-capacity storage component 408 is composed of a large-capacity capacitor or a series of large-capacity capacitors in one embodiment. The large-capacity storage component 408 is connected between the terminals of the battery 304, and its operation is smoothed by the power sharing resistor 406. The large-capacity storage component 408 is charged when the RF operation is on standby, and when the RF operation is performed, the charged energy is supplied as the initial power.

[0025] Specifically, in this embodiment, the battery load is kept as low and stable as possible. In particular, the large current load during wireless transmission shortens the usable life of the battery. This problem becomes more serious when the battery deteriorates and its equivalent series resistance (ESR) increases. In order to reduce the peak load of the battery, the power sharing resistor 406 and the large-capacity storage component 408 are used in front of the voltage regulator 404. The power sharing resistor 406 plays two roles. That is, to relax the current when recharging the large-capacity storage component 408 during the RF standby period, and to make the large-capacity storage component 408 bear most of the peak current during RF transmission. The voltage indication circuit 308 monitors the voltage of the battery 304 via the detection resistor 412 and the comparator 414, and determines whether the battery can support the RF operation. When the battery voltage begins to drop, the wireless control unit receives the non-active output signal 424 and suppresses the RF operation to prevent the battery voltage from dropping. During the suppression period, an alarm is notified to the user, and in one embodiment, it is notified via the wireless interface.

[0026] Radios can operate in multiple operating modes. Two examples of modes are: 1) single-message transmission and reception mode, and 2) continuous reception mode (usually lasting several seconds). Mode 1 is scheduled reception, where the radio is active only when reception is scheduled. Mode 2 is open listening mode, where the receiver is activated and waits for a message to arrive. Open listening can last for several minutes, but is usually scheduled within a range of approximately 16 seconds or less. Transmissions are all scheduled or performed for very short periods. Continuous transmission is not permitted by the Federal Communications Commission (FCC).

[0027] Mode 1 is typically used when all devices in the system are time-synchronized. In this configuration, devices operate on a time schedule that repeats every frame time (e.g., 16 seconds). The radio is turned on only when it is scheduled to transmit and receive, and transmits or receives a single message. In this case, the typical on time for the radio is 4-8 milliseconds per message. In this configuration, the battery voltage is checked only immediately before the transmit or receive operation. Within a frame time, hundreds of transmits and receives may occur in relatively short intervals, with an off time of approximately 20 milliseconds between each transmit and receive. The battery voltage is checked immediately before each transmit and receive, and if it is above the threshold, operation continues. Otherwise, load suppression is initiated.

[0028] Load suppression can take several different forms without departing the scope of this disclosure. For example, it can involve delaying the transmission and reception schedule, i.e., reducing the frequency of transmission and reception. In one embodiment, all wireless RF operations are stopped and no operation is performed until the battery voltage exceeds a threshold.

[0029] In Mode 2, the receiver is active for a longer period (e.g., about 10 seconds), so a single voltage check at startup may not adequately account for the current consumed by the radio during reception. In this case, in one embodiment, voltage checks are performed continuously while the radio is receiving. If the battery voltage drops to a threshold during reception, voltage suppression is implemented, such as stopping the radio until power is restored.

[0030] In one embodiment, when the output signal drops, the wireless control unit issues a warning. A status warning flag is set, indicating that RF suppression has been activated. This status flag is periodically transmitted to the host system using WirelessHART's additional status command 48. The host system can monitor the flag and determine when battery replacement is needed.

[0031] According to the wireless load suppression described herein, power-limited devices can adjust their power consumption according to available power. This extends overall battery life and allows the device to operate for longer periods. Reducing the wireless load prevents device resets, maintains connectivity with the WirelessHART network, and provides users with advance warnings about battery replacement. During this time, the device maintains connectivity to the location system and reduces its impact on surrounding tags and devices.

[0032] Embodiments of this disclosure provide a wireless load suppression device and method for dynamically adjusting wireless power consumption according to the power available from the device's battery. This embodiment helps maintain the battery voltage and prevent the device from resetting. As a result, battery life is extended, and the user can be notified early that the device is nearing the end of its lifespan.

[0033] As a result of embodiments of this disclosure, the device can transmit and receive as much as possible based on the available power. When the battery weakens due to degradation or temperature effects, the speed at which it can respond to the wireless current demand slows down. In this case, wireless operation is suppressed and the average current load is reduced to prevent a system reset.

[0034] Embodiments of this disclosure offer several advantages over existing systems. These advantages include, for example, a reduction in average radio current, prevention of device resets when the battery is low, extended device uptime / battery life, improved likelihood of reporting critical battery status to the user, and reduced anchor downtime by allowing the user time to plan battery replacement. Furthermore, they also have the effect of reducing the positioning error of nearby tags caused by anchors going offline.

Claims

1. A time-synchronous radio that operates according to a predetermined schedule for wireless transmission and wireless reception, A battery configured to supply power for the operation of the aforementioned radio, A wireless control unit that controls the operation of the wireless device, A voltage indicator circuit configured to monitor the voltage of the battery and provide an output signal indicating whether the battery voltage is sufficient for the operation of the radio, Equipped with, When the output signal is active, the wireless control unit operates the wireless device according to the predetermined schedule. When the output signal is inactive, the wireless control unit adjusts the operation of the wireless device to maintain its operation. Device.

2. The wireless device communicates via a network, The apparatus according to claim 1, wherein maintaining the operation of the radio includes suppressing the transmission and reception of the radio before the battery voltage reaches the reset voltage, thereby maintaining the connection with the network.

3. The apparatus according to claim 2, wherein the network is a WirelessHART type network.

4. The apparatus according to claim 1, wherein maintaining the operation of the radio device includes maintaining a supply voltage greater than the reset voltage of the radio device.

5. The apparatus according to claim 1, wherein the wireless control unit adjusts the operation of the wireless device by disabling the wireless device when the output signal is inactive.

6. The apparatus according to claim 1, wherein the wireless control unit adjusts the operation of the wireless device by changing the schedule to reduce the operating frequency of the wireless device when the output signal is inactive.

7. The apparatus according to claim 1, wherein the wireless control unit is configured to provide a low voltage warning when the output signal is inactive.

8. The wireless control unit, In accordance with the predetermined schedule, the voltage of the battery is checked each time before each transmission or reception in the predetermined schedule. When the output signal is inactive, it is configured to suppress the load. The apparatus according to claim 1.

9. The apparatus according to claim 1, wherein the wireless control unit is further configured to monitor the output signal during transmission and reception of the wireless device, and to suppress transmission and reception when the output signal switches to inactive.

10. The apparatus according to claim 1, further comprising a high-capacity storage component coupled between the battery and the wireless control unit, configured to supply power to the battery before it is used for transmission and reception.

11. The apparatus according to claim 10, wherein the large-capacity storage component is charged by power from the battery when the radio is in standby mode.

12. The aforementioned high-capacity storage component includes a high-capacity capacitor that is charged by the aforementioned battery, When transmission or reception is performed according to the predetermined schedule, power for the radio is supplied by activating the large-capacity capacitor for supplying power for transmission or reception. The apparatus according to claim 10.

13. The apparatus according to claim 12, wherein the large-capacity storage component further comprises a power-sharing resistor coupled between the battery and the large-capacity capacitor.

14. The aforementioned voltage indicator circuit is A comparator having an inverting input, a non-inverting input, and an output, A detection resistor connected between the positive terminal of the battery and the non-inverting input of the comparator, A voltage divider that provides a reference voltage and is connected to the inverting input of the comparator, Equipped with, The comparator is configured to output an active signal when the battery voltage exceeds the reference voltage, and to output an inactive output signal when the battery voltage falls below the reference voltage. The apparatus according to claim 1.

15. A method for suppressing the wireless load of an apparatus comprising a time-synchronous radio that operates according to a predetermined schedule for wireless transmission and wireless reception, and a battery configured to supply power for the operation of the radio, The available power from the aforementioned battery is monitored, Based on the available power from the battery, the radio frequency (RF) operation of the radio is controlled. This includes, The control of the RF operation is as follows: If the battery has sufficient power for the scheduled RF operation, the radio will be operated according to a known transmit and receive schedule. If the battery does not have enough power for the scheduled RF operation, the RF operation will be adjusted to maintain the operation of the radio. A method for suppressing wireless load in a device, including the following.

16. The wireless device communicates via a network, The method according to claim 15, wherein the control of the RF operation for maintaining the operation of the radio includes suppressing the transmission and reception of the radio before the battery voltage reaches the reset voltage in order to maintain the connection with the network.

17. The method according to claim 16, wherein the network is a WirelessHART type network.

18. Monitoring the available power means The voltage indicator circuit detects the battery voltage, The detected battery voltage is compared with the low voltage threshold, The output signal is provided which is active when the battery has sufficient power and inactive when it does not have sufficient power. The method according to claim 15, including the following:

19. The RF operation of the aforementioned radio is controlled by the radio control unit. The wireless control unit receives the output signal and adjusts the operation of the wireless device by disabling the wireless device when the output signal is inactive. The method according to claim 18.

20. The method according to claim 18, wherein the control of the RF operation of the radio is performed by changing the schedule to reduce the operating frequency of the radio when the output signal is inactive.

21. Before each transmission or reception in the predetermined schedule, the battery voltage is detected each time. When the output signal is inactive, load suppression is performed. The method according to claim 18, further comprising the following:

22. During the transmission and reception of the aforementioned wireless device, the output signal is monitored. When the output signal is switched to inactive, the transmission and reception are suppressed. The method according to claim 18, further comprising the following:

23. The method according to claim 15, further comprising charging a high-capacity storage component configured to supply power for transmission and reception during the standby period of the RF operation.

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