ELECTRONIC LOCK WITH POWER FAILURE CONTROL CIRCUIT

• US 20120169453A1
• Filed: 12/30/2010
• Published: 07/05/2012
• Est. Priority Date: 12/30/2010
• Status: Active Grant

• Current Assignee: Sargent Mfg Co (Assa Abloy AB)
• Original Assignee: Sargent Mfg Co (Assa Abloy AB)
• Inventors: Bryla, Mark, Morse, Steve, Wren, Chris
• Granted Patent: US 9,019,067 B2
• Time in Patent Office: Days
• US Class Current: 340/3.1
• CPC Class Codes: E05B 2047/0057 Feeding
• CPC Class Codes: E05B 2047/0059 by transfer between frame and wing
• CPC Class Codes: E05B 2047/0087 Electric spare devices, e.g. auxiliary batteries or capacitors for back up
• CPC Class Codes: E05B 47/00 Operating or controlling locks or other fastening devices by electric or magnetic means electric permutation locks E05B49/00
• CPC Class Codes: E05B 47/0001 with electric actuators; Constructional features thereof for vehicles E05B81/04
• CPC Class Codes: E05C 1/08 with latching action
• CPC Class Codes: G05B 19/042 using digital processors G05B19/05 takes precedence
• CPC Class Codes: Y10T 292/1014 Operating means
• CPC Class Codes: Y10T 70/7113 Projected and retracted electrically

Abstract

An electronic lock with power failure control circuit includes a lock mechanism having a latchbolt movable between extended and a retracted positions and an electrically powered lock actuator to lock and unlock the latchbolt. The power failure control circuit includes a microcontroller and the lock is connected to a primary power source and an auxiliary power source, preferably supercapacitors and charger that can be turned on by the microcontroller and off when the charger signals a full charge. A power monitor circuit detects low voltage on the primary power supply and sets a power failure interrupt causing the microcontroller to execute power failure instructions that control the actuator so that the lock is placed into a desired locked or unlocked final state during the power failure. upon detection of the return of good power, the system resets the lock.

Claims

1. An electronic lock comprising:

a lock including a latchbolt movable between an extended and a retracted position, the lock having a locked state and an unlocked state, the latchbolt being prevented from moving to the retracted position when the lock is in the locked state;

a lock control circuit including a microcontroller and a memory having a stored control program including microcontroller executable instructions for a power failure state and microcontroller executable instructions for a normal power state;

a primary power supply input to the lock control circuit adapted for connection to a primary source of electrical power;

an electrically powered lock actuator connected to the microcontroller, the lock actuator being responsive to a signal from the microcontroller to move the lock between the locked state and the unlocked state;

a power monitor circuit having an input connected to the primary power supply input to detect a power failure condition, a control output and a signal output connected to the microcontroller, the power monitor circuit signaling the microcontroller via a power failure signal applied to the signal output when a power failure condition is detected at the primary power supply input;

an auxiliary power supply having a power output; and

an electrically controllable switch circuit having a primary power input connected to the primary power supply input, an auxiliary power input connected to the auxiliary power output of the auxiliary power supply, a power output connected to provide power to the microcontroller and the lock actuator and a control input connected to the control output of the power monitor circuit, the power monitor circuit controlling the switch circuit to select between the primary source of electrical power and the auxiliary power supply;

the microcontroller executing the microcontroller executable instructions for the power failure state after receiving the power failure signal from the power monitor circuit.

2. The electronic lock of claim 1 wherein the switch circuit includes a diode circuit having first and second power inputs and a power output, the first power input receiving power from the primary power supply input, the second power input receiving power from the auxiliary power supply power output and the power output being connected to provide power to the microcontroller and the lock actuator from the auxiliary power supply during a power failure condition.

3. The electronic lock of claim 2 wherein the diode circuit uses Schottky diodes.

4. The electronic lock of claim 1 wherein the power monitor circuit includes a lower voltage threshold and monitors a voltage at the primary power supply input, the power monitor circuit sending the power failure signal to the microcontroller when the voltage at the primary power supply input is below the lower voltage threshold.

5. The electronic lock of claim 4 wherein the power monitor circuit further includes an upper voltage threshold, power monitor circuit signaling the microcontroller to stop executing the microcontroller executable instructions for the power failure state and begin executing the microcontroller executable instructions for the normal power state when the voltage at the primary power supply input rises above the upper voltage threshold.

6. The electronic lock of claim 1 further including a voltage regulator circuit connected between the power output of the electrically controllable switch and the microcontroller.

7. The electronic lock of claim 1 wherein the auxiliary power supply includes at least one supercapacitor and a supercapacitor charger connected to the microcontroller, the supercapacitor charger having an input for turning on and off the charger and an output for signaling the microcontroller when the at least one supercapacitor is charged, the microcontroller turning on the charger to charge the at least one supercapacitor and turning off the charger when the at least one supercapacitor is charged.

8. The electronic lock of claim 7 wherein the microcontroller prevents execution of the microcontroller executable instructions for the power failure state until after the supercapacitor charger has signaled the at least one supercapacitor is charged.

9. The electronic lock of claim 8 wherein the microcontroller enables setting of a power failure interrupt after the supercapacitor charger has signaled the at least one supercapacitor is charged and the microcontroller sets the power failure interrupt after the power failure interrupt has been enabled and after receiving the power failure signal from the power monitor circuit.

10. The electronic lock of claim 9 wherein the microcontroller handles the power failure interrupt by discontinuing execution of instructions for the normal power state and setting a power failure flag, the microcontroller then returning to the execution of instructions for the normal power state, one such normal power state instruction including checking the power failure flag, the microcontroller leaving the normal power state and entering the power failure state and executing the microcontroller executable instructions for the power failure state only after checking the power failure flag during execution of the normal power state instructions and detecting that the power failure flag has been set.

11. The electronic lock of claim 1 wherein the microcontroller executable instructions for the power failure state include a power failure loop, the power failure loop instructions including a check to determine if power has returned.

12. The electronic lock of claim 11 wherein the power failure loop instructions reset the microcontroller if power has returned.

13. The electronic lock of claim 12 wherein the microcontroller waits a preset period of time after detecting that power has returned before resetting the microcontroller.

14. The electronic lock of claim 13 wherein the microcontroller repeatedly checks that power has returned while waiting the preset period of time before resetting the microcontroller.

15. The electronic lock of claim 1 further including an LED indicator connected to the microcontroller, the microcontroller blinking the LED to indicate the power failure state.

16. The electronic lock of claim 1 wherein the microcontroller disables a WiFi radio after entering the power failure state and before signaling the electrically powered lock actuator to move between the locked state and the unlocked state.

17. A system for shutting down and restarting an electronic lock under power failure conditions comprising:

a microcontroller including a stored control program having a plurality of microcontroller executable instructions;

a lock actuator output adapted for connection to a lock actuator, the lock actuator output being connected to the microcontroller and the microcontroller sending a signal to the lock actuator output to switch the lock actuator between a locked and an unlocked state;

a primary power supply input adapted for connection to a primary source of electrical power;

an auxiliary power supply having at least one supercapacitor for providing auxiliary power and a supercapacitor monitoring and charging circuit connected to the microcontroller;

an electrically controllable switch circuit connected to the primary power supply input and the auxiliary power supply to supply auxiliary power during a power failure condition;

a power monitor circuit having a comparator, the power monitor circuit being connected to the primary power supply input to detect the power failure condition, the power monitor circuit also being connected to the microcontroller to signal a good power condition and the power failure condition, the power monitor circuit also being connected to the electrically controllable switch circuit and the power monitor circuit switching the electrically controllable switch circuit upon detection of the power failure condition;

a visual indicator operable by the microcontroller to indicate the power failure condition;

the microcontroller executable instructions including;

a normal power loop of microcontroller executable instructions organized as a cooperative multitasking loop of tasks and executed by the microcontroller to operate the electronic lock in normal power conditions, the normal power loop including;

an instruction checking to determine if the power monitor circuit has signaled detection of a power failure condition;

an instruction checking to determine if the at least one supercapacitor is fully charged;

an instruction for turning on the supercapacitor charging circuit to charge the at least one supercapacitor when the at least one supercapacitor is not fully charged; and

an instruction for turning off the supercapacitor charging circuit when the at least one supercapacitor is fully charged;

a power failure loop of microcontroller executable instructions;

the microcontroller executing the power failure loop after the power monitor circuit has signaled detection of a power failure condition, the power failure loop including;

an instruction checking to determine if the power monitor circuit has signaled the good power failure condition,

an instruction resetting the microcontroller after the power monitor circuit has signaled the good power failure condition;

at least one instruction turning on the visual indicator to signal the power failure condition after the power monitor circuit has signaled detection of the power failure condition;

at least one instruction sending the signal to the lock actuator output to switch the lock actuator to a desired locked or unlocked state for the power failure condition after the power monitor circuit has signaled detection of the power failure condition.

18. A method for shutting down and restarting an electronic lock under power failure conditions comprising:

monitoring a primary power supply with a comparator circuit to detect a power failure condition and a good power condition by comparing a voltage of the primary power supply to a reference voltage;

executing tasks in a loop during the good power condition;

switching to an auxiliary power supply having at least one supercapacitor in the power failure condition to supply power to the electronic lock from the at least one supercapacitor during the power failure condition;

setting the electronic lock to a desired locked or unlocked state after detecting the power failure condition;

repeatedly monitoring a charge level of the at least one supercapacitor during the good power condition;

turning on a supercapacitor charger during the good power condition when the charge level of the at least one supercapacitor is below a desired level;

turning off the supercapacitor charger during the good power condition when the charge level of the at least one supercapacitor has reached a desired level;

turning on a visual indicator during the power failure condition; and

resetting the electronic lock after the power failure condition has been detected if the good power condition is subsequently detected for a predetermined period of time.

19. The method of claim 18 wherein the step of executing tasks in a loop during the good power condition includes the steps of:

checking to detect a power failure condition after a first indication that the charge level of the at least one supercapacitor has reached a desired level;

setting a power failure flag upon detection of the power failure condition and returning to tasks in the loop executed during the good power condition; and

checking if the power failure flag has been set, and thereafter executing the steps of setting the electronic lock to a desired locked or unlocked state for the power failure condition, turning on a visual indicator and resetting the electronic lock after the power failure condition has been detected if the good power condition is subsequently detected.

20. The method of claim 19 further including the step of turning off power consuming functions prior to the step of setting the electronic lock to a desired locked or unlocked state in the power failure condition.