Presence detection device with low power consumption

Abstract

Presence detection device (10), comprising: a detection circuit (14) configured to: receive a presence signal indicative of a first voltage level and a reference signal indicative of a second voltage level; to receive an alarm signal at predetermined intervals; compare the first voltage level with the second voltage level in response to the wake-up signal; and generate a first output indicative of an external power source (23) electrically coupled to a vehicle (12) for charging one or more batteries (53) in the vehicle (12) based on the comparison of the first voltage level to the second voltage level; wherein the presence detection device (10) comprises a flip-flop circuit (34) configured to store the first output in response to a clock signal; and wherein the presence detection device (10) comprises a bypass capacitor (42a) configured to receive a second output from the flip-flop circuit (34) as a single pulse to reduce power consumption.

Description

Technical area

[0001] Aspects of the present invention relate to a low power proximity detection apparatus in conjunction with various battery charging applications. Background of the invention

[0002] US Patent No. 8,305,033 B2 ("the '033 patent") to Cavanaugh discloses a presence sensing circuit suitable for use with an on-board vehicle charger, such as, but not limited to, those charging types used in hybrid vehicles and hybrid electric vehicles, to facilitate power conservation during a period when it is not required or otherwise undesirable for the on-board charger to check the connection of a harness or other connection used to connect the on-board charger to a charging station or other power source. US Patent No. 6,437,460 B1 discloses a low-power supervisory controller. US Patent No. 2015 / 0352967 A1 discloses a method and apparatus for waking control devices.

[0003] The object of the invention is to provide an improved, in particular more energy-efficient, more reliable or more precise, presence detection device.

[0004] The object is achieved by a presence detection device according to at least one of the independent claims. Summary of the invention

[0005] A occupancy detection device comprising a sensing circuit is provided. The sensing circuit is configured to detect a occupancy signal indicative of a first voltage level and a reference signal indicative of a second voltage level, and to receive a wake-up signal at predetermined intervals. The sensing circuit is further configured to compare the first voltage level to the second voltage level in response to the wake-up signal and generate a first output indicative of an external power source electrically coupled to a vehicle for charging one or more batteries in the vehicle based on the comparison of the first voltage level to the second voltage level. The occupancy detection device further comprises a flip-flop circuit configured to store the first output in response to a clock signal.The presence detection device further includes a bypass capacitor configured to receive a second output from the flip-flop circuit as a single pulse to reduce power consumption.

[0006] From the above content, at least a flip-flop circuit configured to store the first output in response to a clock signal and the bypass capacitor configured to receive a second output from the flip-flop circuit as a single pulse to reduce power consumption are to be emphasized as being according to the invention. Short description of the drawings

[0007] The embodiments of the present invention are particularly pointed out in the appended claims. However, other features of the various embodiments will become more apparent and better understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 illustrates an apparatus for providing low power occupancy detection according to one embodiment; Fig. 2 illustrates a graphical representation of various waveforms corresponding to various signal inputs to an event storage circuit according to one embodiment; Fig. 3 is a graphical representation of a waveform generating a wake-up event for a microcontroller according to one embodiment; and Fig. 4 shows a graphical representation of various waveforms provided to the device according to one embodiment. Detailed description

[0008] While detailed embodiments of the present invention are disclosed herein as needed, it should be understood that the disclosed embodiments are merely descriptive of the invention that may be embodied in different and alternative forms. The figures are not necessarily drawn to scale; some features may be exaggerated or reduced in size to better show details of individual components. Therefore, specific structural and functional details disclosed herein are not to be considered limiting, but are for descriptive purposes only to teach those skilled in the art how to variously employ the present invention. Embodiments of the present invention generally include a plurality of circuits, electrical devices, and at least one control device.All references to the circuits, the at least one control device, the further electrical devices, and the operation thereof are not intended to be limited to encompassing only what is illustrated and described herein. While certain reference numerals may be assigned to the various circuits, the control device, and the further electrical devices disclosed, these reference numerals are not intended to limit the scope of application of the various circuits, the control device, and the further electrical devices. Such circuits, further electrical devices, and such a control device may be combined and / or separated from one another in any manner based on a desired particular electrical application.

[0009] It should be noted that each control device disclosed herein may include any number of microprocessors, integrated circuits, and memory devices (e.g., FLASH memory, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations thereof) and software that cooperate to perform the operations disclosed herein. Furthermore, each control device disclosed herein uses one or more microprocessors to execute a computer program provided on a non-transitory computer-readable medium programmed to perform any number of the functions disclosed herein.Furthermore, each control device provided herein includes a housing and a varying number of microprocessors, integrated circuits, and storage devices (e.g., FLASH memory, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations thereof) disposed within the housing. The control device(s) disposed herein include hardware-based inputs and outputs for receiving data from and transmitting data to other hardware-based devices, as described below.

[0010] Presence sensing circuits detect the presence of a cable harness when it is connected to a vehicle (and to an external power supply) to charge the vehicle's battery. Once the presence sensing circuit detects that a cable harness is connected to the vehicle, the presence sensing circuit generates an output indicating to the vehicle that it can receive power from an AC source at the vehicle's home, a commercial facility, or another charging system.In situations where the harness is not plugged into or operatively connected to the vehicle to allow battery charging, it is necessary to intermittently energize the occupancy detection circuitry so that the occupancy detection circuitry can monitor the presence of the harness while the other controls and electrical devices in the vehicle are in a sleep mode. This condition of energizing the occupancy detection circuitry while the vehicle is in sleep mode requires the consumption of a large amount of quiescent current and depletes the stored current in one or more batteries in the vehicle.Thus, there is a need to provide a low power presence detection circuit that detects the proximity of a cable harness or the actual connection of the same to the power source and to the vehicle while maintaining a low quiescent current to reduce battery power consumption in those situations where the battery is not being charged.

[0011] Fig. 1 shows an apparatus 10 according to one embodiment for providing low-power presence sensing in a vehicle 12. The apparatus 10 includes a sensing circuit 14, a holding circuit 16, an event storage circuit 18, and a pulse generating circuit 20. A switch 22 is operatively connected to the sensing circuit 14. The switch 22 provides a PROXIMITY signal indicating whether a cable harness 21 is connected to the vehicle 12 and an external power supply 23 to the vehicle for charging one or more batteries 53 in the vehicle 12. The cable harness 21 may be portable or mounted on or near an electrical outlet to determine the power from the electrical output and supply the determined power to the one or more batteries 53 in the vehicle 12.

[0012] The detection circuit 14 includes a plurality of resistors 24a-24n, a comparison circuit 26, and at least one capacitor 28. A WAKE signal is transmitted to the detection circuit 14 to provide a voltage at predetermined intervals. Generally, the detection circuit 14 is not energized all the time (or continuously) when the vehicle 12 is in the OFF state (e.g., when the vehicle ignition is in the OFF state). In one example, the WAKE signal is applied every 256 ms and for a period of 400 µs. This condition helps reduce current consumption in the device 10 when the vehicle 12 is in the OFF state. The device 10 may receive the WCKEN signal from a System Base Chip ("SBC") that includes a built-in timer and has wake-up sample detection capability.The SBC may be provided in the device 10 or arranged in an electronic vehicle control device in the vehicle 12.

[0013] When a user connects the cable harness 21 to the vehicle 12 and the external power supply 23 to the vehicle 12, the switch 22 transmits a low voltage in the PROXIMITY signal to the comparator 26. The comparator 26, when sensed by a high voltage in the WAKE signal (e.g., power is supplied at the predetermined interval when the vehicle 12 is in a sleep mode or a wake-up mode), compares the low voltage (or voltage level) (see PIN 3 on the comparator 26) to a reference voltage (or a reference signal having a different voltage level) (see PIN 4 on the comparator 26) provided by a VREF_WAKE signal. The VREF WAKE signal is derived from the WAKE signal and is located at a different voltage level than the WAKE signal.A voltage divider (not shown) is provided to provide the VREF_WAKE signal with a voltage different from the WAKE signal. If the comparator 26 determines that the low voltage is less than the reference voltage, the comparator 26 outputs a high output value (e.g., 5 V). A terminal output 30 of the detection circuit 14 transmits the high output value to the hold circuit 16.

[0014] When the user disconnects the cable harness 21 from the vehicle 12 and / or the external power source 23 to the vehicle 12, the switch 22 transmits a high signal in the PROXIMITY signal to the comparator 26. When the comparator 26 is sensed by a high voltage in the WAKE signal (e.g., current is supplied at a predetermined interval to reduce the quiescent current), the comparator 26 compares the high voltage (see PIN 3 of the comparator 26) with the reference voltage (see PIN 4 of the comparator 26) established by the VREF_WAKE signal. If the comparator 26 determines that the high voltage is higher than the reference voltage, the comparator 26 outputs a low output value (e.g., 0 V). The terminal output 30 of the sense circuit 14 transmits the low output value to the hold circuit 16.Generally, the moment the cable harness 21 is connected to the vehicle 12 and the external power source 23, the switch 22 switches to produce a low output value, and the detection circuit 14 switches to produce a high output value. The moment the cable harness is disconnected from the vehicle and / or the external power source, the switch 22 switches to produce a high output value, and the detection circuit 14 switches to produce a low output value.

[0015] The hold circuit 16 includes a diode circuit 32. In one example, the diode circuit 32 may be a Schottky diode. An event storage circuit 18 includes a flip-flop circuit 34, resistors 36a-36n, capacitors 38a-38n, and a diode circuit 40. In one example, the flip-flop circuit 34 may be a D-type flip-flop. The hold circuit 16 is configured to hold the output received from the detection circuit 14 for a period of time such that the flip-flop circuit 34 is capable of receiving a high voltage on the WAKE-UP signal to wake up the flip-flop circuit 34 so that the flip-flop circuit 34 can receive the output from the detection circuit 14. An input (or clock signal) is transmitted to the flip-flop circuit 34 (for example, at input 1 (or CLK) of the flip-flop circuit 34) to detect the state of the input "D".Diode circuit 40 ensures a fast fall time and a slow rise time for the clock signal transmitted to input 1 of flip-flop 34. Because the clock signal may be slow, flip-flop 34 is susceptible to resampling on a negative edge of the clock signal (i.e., for a positive-edge triggered flip-flop 34).

[0016] Generally, the strobe signal data (e.g., the data received from terminal output 30 and latch 16 at flip-flop 34 (received at input "D")) is on a positive, or rising, edge. Latch 16 ensures that the data applied to input D of flip-flop 34 is present before the positive edge of the clock signal arrives at input CLK of flip-flop 34, and further ensures that the data applied to input D is valid after the strobe signal transitions low.For example, the latch circuit 16 stores the output from the detection circuit 14 for a certain period of time to ensure that the event storage circuit 18, upon wake-up, is able to receive (or capture) the output value from the detection circuit 14 either when the switch 22 is released (e.g., no vehicle charging is in progress) or when the switch 22 is connected (e.g., vehicle charging is in progress). For example, the latch circuit 16 maintains the information state transmitted at an input "D" during both a positive edge and a negative edge of the clock signal to ensure that the flip-flop circuit 34 forms a valid output value at "Q" of the flip-flop circuit 34. In this case, the flip-flop circuit 34 stores the output value from the detection circuit 14, and the flip-flop circuit 34 does not repeat the same event again.Since the flip-flop circuit 34 does not repeat the same event (i.e., the output, Q, remains at the same level until the cable set 21 is disconnected), the quiescent current consumption is reduced by this condition.

[0017] Pulse generating circuit 20 includes a diode circuit 40, a plurality of capacitors 42a-42n, and a resistor 44. In one example, diode circuit 40 may be a Schottky diode. Capacitor 42a (or a bypass capacitor) of pulse generating circuit 20 is operatively connected to an output of flip-flop circuit 34, enabling flip-flop circuit 34 to consume power only when switch 22 is transitioning from either closed-to-open or open-to-closed. Generally, when the output of detection circuit 14 is applied to latch circuit 16 and subsequently to flip-flop circuit 34 at input "D," flip-flop circuit 34 will pass such output (i.e., the state of switch 22 or the presence detection) to capacitor 42a of pulse generating circuit 20.It should be noted that capacitor 42a passes the output from flip-flop circuit 34 as a single pulse and at a non-constant level to diode circuit 40, thereby reducing power consumption (or reducing quiescent current consumption) for event storage circuit 18. Pulse generation circuit 20 provides an output value to one or more microprocessors 51 in vehicle 12 such that vehicle 12 is charged when flip-flop circuit 34 forms a high output value (or output, Q from flip-flop circuit 34 is high).

[0018] In general, diode circuit 40 enables positive pulse generation. For example, if flip-flop circuit 34 produces a low output value, the remainder of the diode (i.e., the diode position at the top of diode circuit 40) discharges capacitor 42a. The output value from diode circuit 40 is transmitted to the IO_1 input of the SBC (or to the other microprocessors 51), which forms a periodic sampling synchronization. Capacitor 42n is similar to capacitor 42a in that capacitor 42n produces an output (or is discharged) when flip-flop circuit 34 produces a low output value upon detachment of cable assembly 21. An inverting buffer 46 (or switch) is provided to convert a negative pulse into a positive pulse.

[0019] Fig. 2 shows a graphical representation 120 of various waveforms corresponding to different signal inputs to device 10 and the corresponding effect on the event latch circuit according to one embodiment. As shown in the figure, waveform 122 corresponds to the PROXIMITY signal provided by switch 22 to detection circuit 14. Waveform 124 corresponds to a signal provided to flip-flop 34 at input "D" of event latch circuit 18. Waveform 126 corresponds to a signal provided to input "CLK" (i.e., the clock input or clock signal) in flip-flop 34. Waveform 128 corresponds to a signal provided by output "Q" to flip-flop 34.

[0020] As shown at point 140, switch 22 forms a positive-going edge to negative-going edge transition. This condition corresponds to the case where wiring harness 21 is connected to both vehicle 12 and external power source 23 for charging the one or more batteries 53 in vehicle 12. At point 142, the output from detection circuit 14 goes high (e.g., comparison circuit 26 outputs a high output), which is then applied to the "D" input of flip-flop 34. For each pulse of the clock signal that is high, the corresponding input value applied to the "D" input of flip-flop 34 is recorded. As can be seen from waveform 128, the "Q" output from flip-flop 34 goes high as the PROXIMITY signal transitions from the positive-going edge to the negative-going edge.

[0021] Fig. 3 shows a graphical representation 150 of the waveforms that generates a wake-up event for a microcontroller (not shown) according to one embodiment. As shown in the figure, waveform 122 corresponds to the PROXIMITY signal communicated from switch 22 to detection circuit 14. Generally, device 10 is capable of detecting connection and disconnection of harness 21. As such, either a rising or falling waveform may be used. For example, waveform 154 corresponds to a wake-up event in a microcontroller when the PROXIMITY signal transitions from the positive edge to the negative edge. As previously mentioned, in this example, such a transition corresponds to the closed switch 22, indicating that harness 21 has been connected to vehicle 12 and to external power source 23 for charging vehicle 12.

[0022] Fig. 4 shows a graphical representation 200 of different waveforms communicated to device 10 according to one embodiment. It can be seen that the WAKE signal is high at predetermined intervals to power (or sample) various portions of device 10 to reduce power consumption. At point 202, a positive-edge to negative-edge transition can be seen in the PROXIMITY signal. This condition corresponds to a change in electrical resistance, or switch 22 is switched to indicate electrical connection of harness 21 to vehicle 12 and external power source 23. Point 204 corresponds to a time at which the wake event occurs (i.e., harness 21 is connected to vehicle 12 and external power source 23).The detection circuit 14 detects the event and generates a high output value, which is captured at the "D" input of the flip-flop circuit 34 at the next positive edge in the WAKE signal. The flip-flop circuit 34, in turn, generates a positive edge at the "Q" output (see signal Q in ). Fig. 6). The pulse generation circuit 20 forms a signal IO_1 comprising a voltage pulse for waking the one or more microprocessors in the vehicle 12. Once the presence event is detected (i.e., the wiring harness 21 is connected to the vehicle 12 and the external power source 23), the one or more microprocessors wake the vehicle 12 (or other vehicle electronics) to begin a charging process.

[0023] As shown, the Q signal remains high until another wake-up event is detected (see point 206). Prior to point 206 in the graph 200, the PROXIMITY signal can be seen transitioning from a negative edge to a positive edge. This condition indicates that the harness 21 has been disconnected from the vehicle 12 and / or the external power source 23. The switch 22 transmits the PROXIMITY signal, which represents the previously described condition. The detection circuit 14 detects the event and forms a low output value, which is received at the "D" input of the flip-flop circuit 34 at the next positive edge in the WAKE signal. The flip-flop circuit 34, in turn, provides a negative edge at the "Q" output (see signal Q in Fig.6). The pulse generation circuit 20 forms the signal IO_1, which includes a voltage pulse to indicate to the one or more microprocessors in the vehicle 12 that the vehicle is no longer charging.

Claims

[1] Presence detection device (10) comprising: a detection circuit (14) configured to: receive a presence signal indicative of a first voltage level and a reference signal indicative of a second voltage level; to receive an alarm signal at predetermined intervals; compare the first voltage level with the second voltage level in response to the wake-up signal; and generate a first output indicative of an external power source (23) electrically coupled to a vehicle (12) for charging one or more batteries (53) in the vehicle (12) based on the comparison of the first voltage level to the second voltage level; wherein the presence detection device (10) comprises a flip-flop circuit (34) configured to store the first output in response to a clock signal; and wherein the presence detection device (10) comprises a bypass capacitor (42a) configured to receive a second output from the flip-flop circuit (34) as a single pulse to reduce power consumption. [2] The presence detection device of claim 1, wherein the detection circuit (14) comprises a comparison circuit (26) configured to compare the first voltage level with the second voltage level in response to the wake-up signal. [3] The presence detection device of claim 2, wherein the comparison circuit (26) is further configured to receive the wake-up signal at the predetermined intervals while the vehicle (12) is in a sleep mode and to compare the first voltage level with the second voltage level while the vehicle (12) is in the sleep mode. [4] The presence detection device according to any one of claims 2 or 3, wherein the comparison circuit (26) is further configured to generate a first output indicative of the external power source (23) electrically connected to the vehicle (12) when the first voltage level is lower than the second voltage level. [5] A presence detection device according to claim 4, wherein the flip-flop circuit (34) includes a D flip-flop. [6] The presence detection device of claim 1, further comprising a hold circuit (16) configured to store the first output before the flip-flop circuit (34) stores the output. [7] A presence detection device according to claim 6, wherein the holding circuit (16) includes a diode circuit (32) for storing the first output before a positive edge of the clock signal is received in the flip-flop circuit (34). [8] A presence detection device according to any one of claims 6 or 7, wherein the holding circuit (16) includes a diode circuit (32) for storing the first output before a negative edge of the clock signal is received in the flip-flop circuit (34). [9] The presence sensing device of claim 1, wherein the second output indicates the external power source (23) electrically coupled to the vehicle (12) for charging the one or more batteries (53) in the vehicle (12). [10] A presence detection device according to claim 1, comprising an event storage circuit (18) indicating that the external power source (23) is coupled to the vehicle (12). [11] A presence detection device according to claim 10, wherein the event storage circuit (18) comprises the flip-flop circuit (34). [12] A presence detection device according to any one of the preceding claims, wherein the detection circuit (14) is configured to provide the first output of the flip-flop circuit (34).

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