This disclosure relates to lighting devices in general, and more particularly to switches for portable lighting devices.
Portable lighting devices such as flashlights are typically equipped with user operable controls such as switches to selectively turn on and off light sources. In some cases, switches may be provided at locations that are remote from a power source and/or other electronics of the lighting device. For example, a switch may be located in the tailcap of a flashlight to permit a user to conveniently actuate the switch with a thumb without interfering with the user's grasp of the flashlight body. In such implementations, the flashlight may be provided with the light source located at the front (e.g., head end), a battery in the middle (e.g., intermediate portion held by the user), and the switch in the tailcap.
This remote positioning of the switch relative to other components can complicate the physical implementation of electrical circuits of the lighting device. For example, in some cases, one or more additional circuit paths may be required to be provided between the tailcap switch and other electrical components in the head end of the flashlight. To accommodate such circuit paths, a conductive sleeve may be disposed between the flashlight housing and the battery. Unfortunately, such sleeves add weight and can require the flashlight housing to increase in size (e.g., resulting in potentially undesirable extra bulk) and/or require the battery to decrease in size (e.g., resulting in potentially less available power storage available).
In other cases, to avoid the above-noted drawbacks resulting from adding additional circuit paths, the switch may be implemented as a mechanical switch electrically connected to the flashlight body. In such implementations, the switch may provide the ground path for the light source, thus requiring the switch to pass the electrical current used to drive the light source. Unfortunately, this can be problematic for many high power implementations, such as light sources capable of capable of providing 1500 lumens using drive currents of 5 Amps. In particular, some lightweight mechanical switches may not be able to sustain high currents for longer than several minutes without suffering breakdown (e.g., through melting, circuit failure, or other faults). Moreover, mechanical switches capable of sustaining such currents may require the use of specialized materials and/or larger sized components, all of which can add prohibitive weight and cost and require users to exert large amounts of force to physically operate the switches.
In one embodiment, a lighting device includes a light source; and a power control circuit comprising: an inductor, a power transistor configured to pass an operating current associated with the light source, and one or more capacitors configured to keep the power transistor turned on to pass the operating current, wherein the one or more capacitors are configured to be periodically charged in response to a voltage spike generated across the inductor.
A method includes activating a light source of a lighting device comprising: the light source, and a power control circuit comprising an inductor, a power transistor, and one or more capacitors; passing, by the power transistor, an operating current associated with the light source; periodically generating a voltage spike across the inductor; and charging the one or more capacitors in response to the voltage spike to keep the power transistor turned on to continue the passing.
The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the present invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly.
Embodiments of the present disclosure and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.
In accordance with various embodiments set forth herein, a lighting device may be provided with a power control circuit including a user operable switch (e.g., a mechanical switch), a power transistor, and an inductor. The inductor may be periodically pulsed by connecting and disconnecting a voltage source (e.g., a battery) across the inductor to cause a voltage spike to appear across the inductor. This voltage spike may be rectified and captured by one or more capacitors used to drive a gate of the power transistor which passes substantial current (e.g., up to approximately 5 Amps or 6 Amps) associated with a light source of the lighting device. As a result, the current associated with a high power light source is not required to pass through the user operable mechanical switch.
As shown, lighting device 100 includes a head 120, an intermediate portion 130, and a tailcap 140 having a user operable surface 142. External portions of these features collectively provide a body 110 (e.g., a housing) for lighting device 100. In some embodiments, body 110 may be implemented with conductive materials (e.g., aluminum or others) to provide one or more circuit paths between various components of lighting device 100.
Battery 710 may be used to provide a power source (e.g., a voltage source) for the various components of lighting device 100 through a positive node 712 and a negative node 714. Power control circuit 720 may be used to selectively connect negative node 714 of battery 710 to body 110 to provide a return circuit path from light source 330 and other components to battery node 714. In addition, power control circuit 720 may include a user operable mechanical switch 318, a power transistor, an inductor, and other components further discussed herein.
Controller 730 may be implemented as a microcontroller, processor, and/or any appropriate logic device to provide appropriate control signals to operate driver 740, switches 750, and switch 770. In some embodiments, controller 730 may also be implemented to receive programming signals superimposed on node 712 (e.g., external programming signals providing configuration data to update the configuration and operation of controller 730).
Driver 740 receives control signals from controller 730 to selectively turn on (e.g., activate) and turn off (e.g., deactivate) light source 330. Switches 750 (e.g., individually labeled as 750A and 750B) may be implemented, for example, as transistors to selectively disconnect battery node 712 from driver 740 and capacitor 760, thus interrupting power from battery 710 to driver 740 and capacitor 760.
Resistor 752 and a parasitic diode in electronic switch 750B connects battery node 712 to controller 730, even when switches 750 are off which permits controller 730 to receive power (e.g., during startup or when switches 750 are temporarily disconnected while power control circuit 720 is pulsed through the selective connection and disconnection of a bypass circuit path in blocks 1430 and 1440 discussed herein).
Capacitor 760 is charged by battery 710 while switches 750 are closed and may be used to provide power to driver 740 while switches 750 are open. In this regard capacitor 760 is also referred to as a light source capacitor and a head capacitor.
Switch 770 (e.g., also referred to as a temporary switch) is selectively closed by controller 730 to periodically connect battery node 712 to body 110 through resistor 772, thus effectively shorting battery node 712 to body 110.
Mechanical switch 318 may be selectively closed and opened by a user to selectively connect control block 830 to body 110. Power transistor 810 passes current received from body 110 to provide a return path for high currents passed by light source 330 (e.g., operating currents) to permit high current operation without requiring such high currents to pass through mechanical switch 318.
Inductor 820 produces voltage spikes generated in response to the periodic shorting (e.g., connection) and unshorting (e.g., disconnection) of battery node 712 to body 110 as discussed herein. Control block 830 operates to selectively turn on and off power transistor 810 in response to the operation of mechanical switch 318 as discussed herein. Various components of control block 830 are discussed further herein in relation to the operation of power control circuit 720.
In block 1010, power control circuit 720 is initially at a rest state with all capacitors discharged and power transistor 810 off. Also in block 1010, controller 730, driver 740, switches 750, switch 770, and light source 330 are off.
In block 1020, a user operates (e.g., engages) mechanical switch 318. This causes control block 830 to become electrically connected to body 110 (block 1030) and this provides initial voltage for control block 830. As shown in
In block 1040, the increased voltage at node 814 causes current to flow and begin charging capacitors 850 and 852 within microseconds. In some embodiments, capacitor 760 may be relatively large while capacitors 850 and 852 may be relatively small. As a result, the vast majority of the battery voltage (e.g., less the voltage drops of diodes 854 and 856 and additional components of circuit 700) will appear across capacitors 850 and 852 which is sufficient to begin operation of power control circuit 720.
Referring further to
As shown in
In block 1050, after capacitors 840, 850, and 852 are sufficiently charged (e.g., above a threshold of 1.6 volts across capacitor 840), this will be sufficient to activate a Schmitt trigger circuit 860. As a result, the Schmitt trigger circuit 860 will provide a voltage through a voltage follower circuit (e.g., provided by a transistor 861, a transistor 862, and a resistor 863) to gate 812 to turn on power transistor 810 (block 1060). As discussed, capacitor 840 may charge more slowly due to an RC time constant. This serves to delay the activation of Schmitt trigger circuit 860 during the turn on process of
The current flow through mechanical switch 318 can be further understood as follows. When mechanical switch 318 is closed in block 1020, a current pulse (e.g., under 0.5 Amps limited by resistor 722) flows for several 10's of microseconds from body 110 through mechanical switch 318 to control block 830 to charge capacitors 840 and 850. After capacitors 840 and 850 are charged, the current through mechanical switch 318 drops to less than one milliamp until power transistor 810 turns on several milliseconds later (block 1060). After power transistor 810 turns on, the current through mechanical switch 318 reverses to 3 to 5 micro-Amps DC in the opposite direction from control block 830 to power transistor 810 with no pulse current. The pulse current instead flows directly from inductor 820 through diodes 880 and 882 to capacitors 840 and 850.
In block 1210, controller 730 receives power from battery 710 through the closed power transistor 810, the metal body 110, the resistor 752, and the parasitic diode inside electronic switch 750B. This allows the head capacitor 760 to charge up to nearly the full voltage of battery 710. This voltage is routed into controller 730 through power connection 751 causing internal logic of controller 730 to boot up (e.g., become operational). In block 1220, controller 730 waits (e.g., for approximately 30 milliseconds after block 1210) to receive possible serial data superimposed on battery node 712 and received by the “SENSE” input to possibly reconfigure controller 730. In this regard, controller 730 may be reprogrammed (e.g., reconfigured) through serial data pulsed on node 712 (e.g., through a connection to an external device) if desired. As shown in
In block 1230 (e.g., approximately 32 milliseconds after block 1020), controller 730 turns on switches 750 to connect battery 710 to driver 740 and capacitor 760. In block 1240, capacitor 760 is connected to the full battery voltage and driver 740 receives full power as a result of the turning on of switches 750. In block 1250, controller 730 provides a control signal to driver 740 to turn on light source 330. Also at this time, the operation of a boost converter within controller 730 may cause a temporary boost in voltage provided to power control circuit 720. As shown in
In block 1410, controller 730 provides a control signal to driver 740 to turn off light source 330. In block 1415, controller 730 turns off switches 750 to interrupt (e.g., disconnect) the electrical connection from battery 710 to driver 740 and capacitor 760. As discussed, capacitor 760 was previously charged (e.g., beginning in block 1240). Accordingly, in block 1420, capacitor 760 may operate to temporarily supply power to driver 740 and light source 330 while switches 750 are off.
In block 1425, the voltage at inductor node 821 briefly spikes as the current through inductor 820 drops from full operating current (e.g., while light source 330 was powered) down to zero as a result of the turning off of light source 330 (e.g., block 1410) and/or the turning off of switches 750 (e.g., block 1420).
In block 1430, controller 730 closes switch 770 to connect battery node 712 to body 110 through resistor 772. In some embodiments, resistor 772 may be implemented with a relatively low value, which effectively causes a short from battery node 712 to body 110 through resistor 772 and switch 770. As a result, a temporary bypass circuit path is connected between nodes 712 and 714 comprising resistor 772, switch 770, body 110, power transistor 810, and inductor 820 (e.g., power transistor 810 and inductor 820 are provided by power control circuit 720).
In block 1435, as a result of the shorting of battery node 712 to body 110, the current through inductor 820 increases (e.g., up to 3 to 4 Amps associated with a battery voltage of 3 to 4 volts in some embodiments). This is evidenced in
In block 1440 (e.g., 3.5 microseconds after block 1430), controller 730 opens switch 770 to interrupt the short from battery node 712 to body 110 through resistor 772 and switch 770 (e.g., the temporary bypass circuit path is disconnected between nodes 712 and 714). In block 1445, a voltage spike is induced across inductor 820 as a result of the opening of switch 770 and resulting change in current through inductor 820.
In block 1450, the voltage spike is rectified by diodes 880 and 882 to charge capacitors 850 and 852. This additional charging of capacitors 850 and 852 causes nodes 851 and 853 to be maintained at sufficient voltages to keep Schmitt trigger circuit 860 activated to provide sufficient voltage to gate 812 to keep power transistor 810 turned on until the next iteration of the process of
For example, in the case of change in current of 3 Amps decaying to zero in 200 nanoseconds, approximately 300 nano-Coulombs of charge may be provided for capacitors 850 and 852. By repeating the process of
In block 1455 (e.g., 5 microseconds after block 1430), controller 730 turns on switches 750 to restore (e.g., reconnect) the electrical connection from battery 710 to driver 740 and capacitor 760. In block 1460, controller 730 provides a control signal to driver 740 to turn on light source 330. In block 1465, capacitor 760 begins charging again and driver 740 receives power as a result of the turning on of switches 750.
As shown, the process of
For example, referring again to
At block 1610, the user disengages mechanical switch 318 which interrupts the connection between power control circuit 720 and body 110. At block 1620, capacitors 840 and 850 begin to discharge. In this regard, capacitor 850 provides a current through resistor 876 as evidenced by the voltage change at node 814 shown in
At block 1630, after the voltages of capacitors 840 and 850 are sufficiently discharged, Schmitt trigger circuit 860 is deactivated. As a result, in block 1640, the voltage at gate 812 is driven below the threshold voltage of power transistor 810 which turns off.
When power transistor 810 is off and mechanical switch 318 is disengaged, then there is no longer a circuit path between battery node 714 and body 110. As a result, in block 1650, the rest of circuit 700 slowly loses voltage including controller 730, driver 740, light source 330, and other components.
In block 1660, the voltage at node 822 gradually returns to a rest voltage slightly below that of battery 710. Accordingly, at block 1670, power control circuit 720 and all components of circuit 700 are turned off and the lighting device 100 is completely turned off because they no longer have sufficient voltage to operate (e.g., the voltage of head capacitor 760 decreases to a point where all circuit operations cease).
In view of the present disclosure, it will be appreciated that by periodically connecting and disconnecting battery node 712 to body 110 (e.g., through a small resistor 772 and switch 770), currents can be rapidly introduced to and removed from inductor 820 which results in voltage spikes appearing across inductor 820. These voltage spikes are rectified by diodes 880 and 882 to charge capacitors 850 and 852 to keep Schmitt trigger circuit 860 activated and thus keep power transistor 810 turned on. As a result, power transistor 810 remains available to pass large currents associated with light source 330 (e.g., a majority, substantially all, or all of the operating current associated with light source 330) without requiring mechanical switch 318 to pass them. For example, in some embodiments, diodes 880 and 882 may pass small currents averaging approximately 100 uA to 200 uA (e.g., 8 mA to 16 mA RMS) in comparison with up to 6 Amps passed by power transistor 810, and mechanical switch 318 may pass only approximately 3 to 5 microamps DC with no pulse current at all during normal operation (e.g., mechanical switch 318 may pass approximately one millionth of the current passed by power transistor 810).
As a result, the heating experienced by mechanical switch 318 will be small, thus increasing its reliability in comparison to conventional designs where larger currents are required to pass through the mechanical switches without the aid of a power transistor to pass the majority of the current instead. Accordingly, lighting device 100 may be operated with one or more large current light sources 330 while still being controlled by a relatively small mechanical switch 318 that does not require specialized materials or bulk associated with passing large currents. Moreover, such an approach permits the use of a power transistor 810 to be operated in the tailcap 140 or other remote portion of the lighting device 100 without requiring an additional dedicated control circuit path (e.g., through a conductive sleeve or other implementation) for operating the power transistor 810.
Although multiple capacitors have been discussed, any desired number of capacitors may be used in various embodiments. For example, in some cases, a single capacitor may be used to keep power transistor 810 turned on.
Where applicable, various embodiments provided by the present disclosure can be implemented using hardware, software, or combinations of hardware and software. Also where applicable, the various hardware components and/or software components set forth herein can be combined into composite components comprising software, hardware, and/or both without departing from the spirit of the present disclosure. Where applicable, the various hardware components and/or software components set forth herein can be separated into sub-components comprising software, hardware, or both without departing from the spirit of the present disclosure. In addition, where applicable, it is contemplated that software components can be implemented as hardware components, and vice-versa.
Software in accordance with the present disclosure, such as program code and/or data, can be stored on one or more computer readable mediums. It is also contemplated that software identified herein can be implemented using one or more general purpose or specific purpose computers and/or computer systems, networked and/or otherwise. Where applicable, the ordering of various steps described herein can be changed, combined into composite steps, and/or separated into sub-steps to provide features described herein.
Embodiments described above illustrate but do not limit the invention. It should also be understood that numerous modifications and variations are possible in accordance with the principles of the present invention. Accordingly, the scope of the invention is defined only by the following claims.
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Number | Date | Country | |
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20210116079 A1 | Apr 2021 | US |