Abstract:
A proposed smart batteryless backup device is designed for the reception of data transmitted by controlled equipment, backing up said data in the case of the controlled equipment power failure or in accordance with several program requirements, and also for the subsequent restoration. Proposed device improves trust level of the backup if device is powered by interface signal lines and doesn&#39;t have batteries and electrical characteristics of the backup device fluctuating due to humidity and temperature influences as well as during device lifetime.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is the first application filed for the present invention. 
     TECHNICAL FIELD 
     The present invention relates to smart batteryless backup devices using volatile and non-volatile memories. 
     BACKGROUND OF THE INVENTION 
     One of the most important problems that appear during operation of any electronic systems is possibility to store log messages (LOG) and back them up in the case of power loss (further “power down event”). These log messages can help to investigate the reason why the electronic system failure happened and help avoid future failure conditions. 
     Many systems include storage devices like hard drives, flash cards etc. These devices can store log information during electronic system operation and store this information in the case of a power failure. But some embedded system like “set-up boxes” that are very critical to the cost, to the mechanical size and designed to work stand-alone without human supervision do not have hard drives or writable flash to store log information. In these systems log information is usually located in SRAM during its operation and can not be restored after a power failure. This problem for the embedded systems can be solved by using an additional electronic device that carries out the backup function. In case that power of the main apparatus fails, the backup device stores all LOG information in the internal non-volatile memory by using its internal power source. 
     The batteries and the capacitors are used in backup devices as the internal power source. Difficulties using batteries are widely known, but also capacitors (and especially super capacitors) that have replaced batteries are not free from shortcomings. Their electrical characteristics can vary under the influence of external factors: humidity and temperatures as well as during lifetime. This leads to the fact that the value of the accumulated charge will be uncertain, especially, if a charge time is limited. The charge time depends on the capacitance of the capacitor and on the diverted current of the external power source. In most cases backup devices use the main power source of the embedded system. But in case when backup device is made as an external device the interface between embedded system (like RS232 serial interface) and backup device is used as the external power source for the backup device. In the case of RS232, the interface has no dedicated power lines and the problem of accumulating charge becomes very important. 
     Backup devices use accumulated charge for saving LOG information in non-volatile memory. The value of accumulated charge defines the size of the backup information that can be written. 
     None of the known backup devices can backup LOG information in case the value of accumulated charge is unpredictable. Because existing backup devices may not complete the backup process, therefore the restore process after this will also be unpredictable. It is very important for the backup system to have the information about the exact size of the LOG information that was backed up. 
     There are many patents concerning the backup process, but none of them solve the previously discussed problem. 
     Some of the proposals are described in the US Pat. App. 20050283648 by Ashore [1], in the US Pat. App. 20060015683 by Ashore [2], in the US Pat. App. 20060080515 by Spiers et al. [3] etc. 
     In US Pat Appl. 20050283648 Ashmore offers a back-up RAID controller using the back-up battery of the reserve power supply that is coupled to main power source for charging. 
     In following US Pat Appl. 20060015683 Ashmore describes a write-caching redundant array of disks (RAID) and offers advantage back-up RAID controller that includes main CPU and additional faster memory controller that is capable of performing the flush operation of the write-posted data. The memory controller is coupled to the volatile memory and the non-volatile memory. This RAID controller uses the main power source and a secondary power source, for example, a capacitor charged by main power source. In the case if the power source fails the CPU is excluded from receiving main power supply, the memory controller performs necessary operations and the secondary power source, for example, capacitor is used only for providing power to the memory controller and two memories. 
     Several Patent Applications offered by J. Dorny US Pat. Appl. 20040073388 [4], 20050144356 [5] and 20050149663 [6] describe a logger and a method for its use. Computerized method for data loggers according to last Application U.S. Pat. 20050149663 offers a method for estimating the remaining energy capacity of a battery while the battery is powering a digital processor system. The offered method comprises: selecting a predetermined battery consumption characteristics for a particular processor activity. 
     Spiers et al. [3] US Pat. Appl. 20060080515 proposes a data storage system including a primary data storage device and a backup data storage device. It proposes a data storage system including a primary data storage device and a backup data storage device. The backup data storage device includes a power source, for example, capacitor, battery, or any suitable power source. Said storage system uses a overwriting of the data from volatile memory to non-volatile memory. But the problem related to the value of accumulated charge is nowhere considered. 
     Present invention focuses on solving the problem related to guarantied backup information in backup devices with an unpredictable value of accumulated charge. 
     BRIEF SUMMARY OF INVENTION 
     The present invention provides a smart batteryless backup device that uses capacitors rather than batteries to supply power in the event of a loss of main power and has means for intelligent backup controlling. 
     The first aspect of the present invention is an opportunity to use simple, cheap and widespread interfaces between backup device and external system, including interfaces that don&#39;t have dedicated power supply lines like the serial interface RS-232. 
     The second aspect consists of using an internal capacitor as the power source for the backup operation that increases the lifetime of the device, allows maintenance-free operating and makes this device suitable to be used for controlling various remote apparatus. 
     The third aspect of the present invention consists of the fact that the components of the backup device are specifically chosen so that this device records the size of the correctly stored backup information that makes the backup device independent from the value of accumulated charge of the internal capacitor. 
     The forth aspect of the present invention is the capability to completely restore copied information regardless of when the copied process was interrupted and guarantee it. 
     The fifth aspect consists in that the proposed device introduces additional operations that enhance the possibility of external apparatus diagnostics. 
     The sixth aspect of the present invention consists of the fact that the backup operation can be controlled by a special set of commands that allow the memory&#39;s size to be reduced, and therefore reduce the capacitance and charge time of the internal capacitor. 
     At last, the points mentioned above allow for the creation of simple and cheap devices having practically unlimited lifetime, suitable for use in remote systems and maintenance free. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a smart batteryless backup device according to the present invention. 
         FIGS. 2   a  and  2   b  are a main part of the flowchart illustrating an operation of the device ( FIG. 1 ). 
         FIG. 3  is the flowchart illustrating the process of separating the information stream. 
         FIGS. 4   a  and  4   b  illustrate the operation of the backup device during voltage dropping. 
         FIGS. 5   a  and  5   b  illustrate several fragments of a circuit design of the backup device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a block diagram illustrating a smart batteryless backup device (further “backup device”)  100  according to the present invention is shown. This backup device is shown as a part of a computerized system  10 . The computerized system  10  comprises the backup device  100 , an external computerized apparatus  200  and an external interface bus  300  that is coupled said backup device  100  to the apparatus  200  via an external interface port  117 . The external computerized apparatus  200  comprises of a central block  201 , for example, a processor, a main power source  202 , and an interface port  203  to which said external interface  300  is connected. 
     The backup device  100  includes a control block  110  based, for example, on the base of a microcontroller (it is not shown). This control block  110  controls all operation of the backup device  100 . The control block  110  includes a counter that is inside each microcontroller (it isn&#39;t shown). 
     The control block  110  includes a power supply input  112 , control inputs  113  and  114 , an internal interface port  111  and interface ports  115  and  116 . The interface port  115  is used for connecting a volatile random access memory block (VMB)  120  to said control block  110 , and the interface port  116  is used for connection a non-volatile memory block (NVMB)  130  to said control block  110 . 
     The information from said external computerized apparatus  200  goes via said external interface  300 , said external interface port  117 , an interface conversion block  140  and the control block  110  to said volatile memory block (VMB)  120 . 
     The interface conversion block  140  connects the external interface port  117  and said control block  110  via the internal interface port  111 . Said interface conversion block  140  transforms the external interface  300  to the incoming interface of the control block  110 . For example, in case that the external interface  300  is RS232 serial interface and said incoming interface of the control block  110  is the same serial interface but operates only with TTL level of signals, the interface conversion block  140  makes just voltage conversion between the two interfaces. 
     The volatile memory block (VMB)  120  is configured as the cycled buffer and is controlled by the control block  110 . The write operation to the volatile memory block (VMB)  120  can only take place until a loss of a voltage across said external interface  300  happened (“power failure event”) or a corresponding instruction will be received from the external interface  300  (it&#39;s named as “stop”). 
     The present invention uses two arrays of non-volatile memory cells, correspondently “a data array of non-volatile memory cells (DNVM)” and “a parameter array of non-volatile memory cells (PNVM)”. The data array of non-volatile memory cells is intended for storing data (messages) that were transferred from the volatile memory block  120  after occurrence of “power failure event” or said instruction “stop”. 
     The non-volatile memory block  130  is coupled to the interface port  116  of said control block  110 . The data array of non-volatile memory cells (DNVM) is implemented inside of the non-volatile memory block (NVMB)  130 . 
     The parameter array of non-volatile memory cells (PNVM) is intended for holding supplemental information (it is named as “parameter” array) about the data stored in the data array of non-volatile memory cells (DNVM). In simple case said parameter includes at least a size (N) of the data that are written in the data array of non-volatile memory cells (DNVM). The determination of value N is executed by said counter that is implemented inside the control block  110 . In advance case said parameter can include additional information about power failure event, for example, a datum, time, etc. Said parameter array of non-volatile memory cells (PNVM) can be implemented in control block  110  (for example inside microcontroller) or inside of the non-volatile memory block (NVMB)  130 . 
     The backup device  100  includes a power conversion block  150 , an electricity accumulating block, and an element of an unidirectional conductivity. Given embodiment of said backup device  110  comprises said accumulating block made in the form of one capacitor  160  and said element of unidirectional conductivity made in the form a diode  170 . 
     The input of the power conversion block  150  is connected to one or more lines of the external interface  300  via an external interface port  117 . The output  151  of the power conversion block  150  is connected to a first terminal  171  of the diode  170 , a second terminal  172  of said diode is coupled to an ungrounded terminal  161  of the capacitor  160  and an input  112  of the control block  110 . The power conversion block  150  and the diode  170  is a charging circuit for the capacitor  160  that supplies power to the control block  110 . 
     The main power source  202  supplies power to said apparatus  200 , said external interface bus  300 , and said backup device  100  that don&#39;t have their own power source. In case of RS232 interface, the lines RTS and DTR are used by the power conversion block  150  for charging the capacitor  160 . 
     The backup device  100  comprises means for “power failure event” detecting, for example, a first voltage detectors  180 , and means for backup controlling, for example, a second voltage detector  190  for monitoring voltages across this power conversion block  150  and said capacitor  160  correspondently. 
     An input of the first voltage detector  180  is connected to the output  151  of the power conversion block  150  and checks the power conversion block output voltage Vout. The output of the first voltage detector  180  is connected to the first control input  113  of the control block  110 . This voltage detector  180  determines the power conversion block voltage falling below Vdown corresponding to said case “power failure event”. Vdown is the first predetermined threshold. This happens when power from the external interface  300  fails or when the external interface losses connection or operates improperly. 
     An input of the second voltage detector  190  is coupled to the ungrounded terminal  161  of the capacitor  160 . The second voltage detector  190  output is coupled to the control input  114  of the control block  110 . The second voltage detector determines the voltage dropping across the capacitor  160  below a second predetermined value VminDNVM+ΔV, where ΔV≧0 and VminDNVM is the minimum operational voltage of DNVM. 
     Referring now to  FIG. 2   a  and  FIG. 2   b , a base part of the flowchart that illustrates an operation of the backup device  100 . In these Figures it is selected three base parts: Start up, Normal operation ( FIG. 2   a ) and Backup mode ( FIG. 2   b ). 
     “Start up”. The backup device  100  starts its operation after power is present at power supply input  112  of the control block  110 . This is the “Power on” ( 410 ). Said backup device  100  waits for a condition when the power conversion block output voltage Vout will be more than Vdown ( 415 ). This condition is detected by the first voltage detector  180 . The backup device reads parameters (for example size of the previous backup) ( 420 ) and then checks them ( 425 ). 
     If this size isn&#39;t equal to zero, then said backup device copies the contents of said the DNVM to said the VMB ( 430 ) (N words) and then goes to the “normal operation” mode. If this size is equal to zero, then was no backup information in the DNVM and said backup device switches directly to the “normal operation” mode. 
     “Normal operation”. During “normal operation” mode the backup device receives information from ECA (External Computerized Apparatus) ( 440 ) and analyzes this information ( 445 ). If this information is a command then the backup device checks the type of command received. If, for example, it is “read” command ( 455 ), the backup device sends all information from the VMB to the ECA ( 460 ). If this is the data the backup device stores these data in the VMB ( 450 ). 
     In case when “power failure event” is detected by the first voltage detector  180  ( 465 ), the “normal mode” of operation will be interrupted and the backup device executes the interrupt and switches to the “backup mode”. The backup device copies information (in full or in part, for example, N words) from the VMB to the DNVM ( 470 ). This operation will continue until the voltage drop across the capacitor  160  Vc more then VminDNVM+ΔV ( 475 ) or when all information from the VMB was coped to the DNVM. The second voltage detector  190  indicates condition when Vc less or equal then VminDNVM+ΔV. On the next step the backup device writes said backup parameters to the PNVM ( 480 ). 
     After the backup device finishes writing backup parameter to the PNVM ( 480 ) it waits for the condition when Vc&gt;Vdown ( 485 ). If it&#39;s happened then the backup device returns from “backup mode” of operation to the “normal mode” of operation. If this condition doesn&#39;t happen and Vc becoming lower then power level necessary for the backup device operation the backup device stops its operation. 
     Referring now to  FIG. 3  that illustrates the process dividing information stream. The incoming information stream from the ECA to the backup device is separated by a procedure ( 510 ) into two streams: a data stream and a command stream. The data stream is copied into the VMB. The command stream is separated by procedure ( 520 ) into setting command ( 530 ) and operation command ( 540 ), and these two are used for the control operation of said backup device  100 . The examples of the operation commands are: (1) “read” (“reading data from VMB to ECA”)—the backup device  100  sends said backup information from the VMB to the external interface  300 ; (2) “stop”—the backup device  100  stops writing the incoming data from the external interface  300  until all information is read back from VMB to the external interface  300 ; (3) “capture”—the backup device  300  starts to write information from the external interface  300  to the VMB from the first address up to the last address of the VMB (without overwriting), overwriting will be enabled only after the moment when information is read from VMB to the external interface  300 . An example of setting commands is “blocking following backup”—this command preserves the last executed “backup” until backup information is read from the VMB to the external interface  300 . Another example of a command for said backup device  100  could be the use of a dedicated command line(s) from the external interface  300  for control operations of said backup device  100 . 
     The use of commands for controlling the operation of backup device  100  prevents previously captured data from being overwritten because of the VMB and the NVMB size limitations. These commands allow the size of the memories and internal capacitor to be reduced. 
       FIG. 4 . illustrates the backup process. The moment  601  (point “c”) corresponds to the case when the first voltage detector  180  indicates a “power failure event”. In this case the voltage drop across said capacitor  160  is equal to (Vdown−Vd−Vp), where Vd is equal to the voltage drop across the element of unidirectional conductivity, for example, diode  170 . If said element of unidirectional conductivity and said means for failure event detecting are connected to different outputs of the power conversion block than Vp is equal to the potential difference between ungrounded terminals of two power conversion block outputs, the first one is coupled to said means for failure event detecting, the second one is coupled to said element of unidirectional conductivity. In case when said element of unidirectional conductivity and said means for failure event detecting are connected to the common output of the power conversion block than Vp is equal to zero. 
     The present invention uses two embodiments: (1) the parameter array of non-volatile memory cells PNVM is integrated together with said control block  110  and the data array of non-volatile memory cells DNVM is implemented in the form of the non-volatile memory block NVMB  130 , and (2) the data array of non-volatile memory cells DNVM and the parameter array of non-volatile memory cells PNVM are implemented as the non-volatile memory block NVMB  130 . 
     In the case of the first embodiment  FIG. 4   a  the curve of the capacitor discharge is the curve “c-n-m-p”. During the time interval  601 - 602  the data has to be stored in the NVMB  130 . After the time moment  602  when the second voltage detector indicates that the voltage dropped below VminDNVM+ΔV (where ΔV≧0) the NVMB is inactive and its power consumption is negligible. During the time interval  602 - 605  the parameter has to be stored and the time constant for the interval  602 - 605  is significantly more than for the interval  601 - 602 . 
     In the case of the second embodiment  FIG. 4   b  the curve of the capacitor discharge is the curve “c-n-m-q” and VminPNVM=VminDNVM, where VminPNVM is the minimum operational voltage of the PNVM. This curve corresponds to the voltage drop across said capacitor  160  that is equal to operating voltage of said NVMB  130 . During the time interval  601 - 602 - 604  two procedures must be executed: the data has to be stored from the VMB into the NVMB (interval  601 - 602 ) and the parameter has to be stored into the same NVMB (interval  602 - 605 ). The moment  602  (point “n”) is indicated by the second voltage detector when the voltage drops below VminDNVM+ΔV, where ΔV&gt;0. 
     For the backup device operation the characteristics of used components must satisfy the following relations. The time interval of discharge from one voltage V 1  to another V 2  is equal to: 
     ΔT=Req*C*ln (V 1 /V 2 )}, where: Req is the equivalent average resistance of the load circuit for the capacitor  160 , C is the capacitance of the capacitor  160 . 
     In the case of the first embodiment all said characteristics must be chosen so that said time interval ΔT ( 602 - 605 ) for V 1 =VminDNVM+ΔV and V 2 =VminPNVM must be sufficient for storing the parameter, and ΔT( 601 - 602 ) for V 1 =Vdown−Vd and V 2 =VminDNVM+ΔV must be sufficient for storing at least one unit of data. 
     In the case of the second embodiment all said characteristics must be chosen so that said time interval ΔT ( 602 - 604 ) for V 1 =VminDNVM+ΔV and V 2 =VminDNVM=VminPNVM must be sufficient for storing the parameter, and ΔT( 601 - 602 ) for V 1 =Vdown-Vd and V 2 =VminDNVM+ΔV must be sufficient for storing at least one unit of data. 
     In the  FIG. 1  one embodiment of said backup device is shown. The  FIG. 5  illustrates additional possibilities of said backup device  100 . 
     The  FIG. 5   a  shows that the means for “power failure event” detecting  180  and the means for backup controlling  190  may comprise more than one voltage detector (or corresponding comparator). The voltage detectors  181  and  182  may be set to the predetermined thresholds Vdown and Vup≧Vdown that enable hysteresis for complex switching. The voltage detectors  191 ,  192  and  193  may be set to the predetermined thresholds VminPNVM, VminDNVM and VminDNVM+ΔV correspondingly. The thresholds VminPNVM and VminDNVM allow the starting of restoring backup information from the DNVM to the VMB without waiting for the recovery of the voltage to the value Vdown. All voltage detector outputs are connected to the control inputs  113   a ,  113   b ,  114   a ,  114   b  and  114   c  of the control block  110  correspondingly. 
     The  FIG. 5   b  offers said accumulating block  160  comprising two capacitors C 161  and C 162 , where the capacitance of said capacitor C 162  is significantly less than the capacitance of C 161 . This embodiment allows the reduction of “dead zone”. The capacitor C 162  has enough capacitance for copying the minimal information unit and the parameter. The capacitor C 161  is connected to said power conversion block  150  via controllable element of unidirectional conductivity  170  that is turned off when the capacitor C 162  is not fully charged. A voltage detector  183  detects this state (C 162  being fully charged) and turns on said element  170 . 
     The incorporation of a buzzer in said backup device provides a way of the energy-independence display of this backup device state (Isn&#39;t shown). 
     The inclusion of a voltage multiplier in structure of the power conversion block allows to increase duration of said time intervals due to increase in the time that is necessary for the capacitor charge and to improve the time moment of said Vdown determination (Isn&#39;t shown).