Patent Application
20240393493
This invention relates to a sensing circuit for consumer electronic devices such as television receivers, for example television displays and set-top boxes.
Consumer electronic devices are generally required to enter a low-power standby and/or off mode after a certain period of user inactivity. The device may then return to full power or operational mode in response to a user or sensor input. The device may be required to draw only very low power during off/standby mode, for example 0.5 W, or 1 W for devices with display, under EU regulation No. 1275/2008.
Hence, there is a need for a low power sensor for such devices, for detecting user presence. One such sensor is a passive infrared (PIR) sensor used to detect a person in proximity to the device. However, such sensors may be sensitive to noise which can lead to false triggers, hence switching on the full power mode of the device and wasting power. False triggers may also be inconvenient for audio-visual devices, which may then cause a disturbance by generating unwanted sound and/or images.
Aspects of the present invention are set out in the accompanying claims.
According to one embodiment, a consumer electronic device includes a low power sensor arranged to detect proximity of a person, and a controller arranged to modify the operation of the device in response to the low power sensor, for example by switching from standby or off mode to normal or full power mode.
The low power sensor may be a PIR sensor, such as a pyroelectric sensor. The sensor may output a small analogue signal which is supplied to a microcontroller for amplification and digital conversion.
The microcontroller may have an integrated reference voltage supply which is configured to provide an input to an integrated operational amplifier configured to supply power to the sensor. This provides a stable low power supply, thereby reducing noise and false triggering of the sensor. Also, there may be no need to provide an additional power supply for the sensor, so reducing the number of components required and allowing for a low-cost and compact sensing circuit.
There now follows, by way of example only, a detailed description of embodiments of the present invention, with references to the figures identified below.
A processor 4 controls an operational state of the device 1, for example by putting the device 1 in a low power mode if no user activity is detected for a predetermined length of time, as detected by sensing circuit 5. In the low power mode, the AV output 2 may be switched off or put in a low power mode which reduces the power drawn by the AV output 2. Additionally, the receiver 3 may be put in a low power mode, for example by suspending reception of programmes.
Sensing circuit 5 detects the presence of a user 6 and signals this to the processor 4 so as to wake the device 1 from the low power mode to a normal or full power mode in which the AV output 2 and the receiver 3 are switched on. Alternatively or additionally, the processor 4 may respond to the detection of a user 6 by the sensing circuit 5 to modify operation of the device 1 in other ways, for example to modify the AV output 2, such as by increasing audio volume or display brightness. The processor 4 may respond to the detection of a user 6 by reporting to a remote network node that the programming is being watched, for example for audience measurement.
The sensing circuit 5 comprises a low power sensor 8 and a microcontroller 7, which may be mounted on a PCB (not shown) which provides power, and connection from the microcontroller 7 to the processor 4.
The sensor 8 may be a PIR sensor, such as a pyroelectric sensor. The sensor may output a small analogue signal which is input to a microcontroller for amplification, filtering and digital conversion.
The sensor 8 receives a power supply voltage (Power In) from a power supply 11 on the PCB, such as a 3.3 V rail, and is connected to ground (GND) via the PCB. The sensor 8 provides an analog output signal (PIR) indicative of the property sensed by the sensor 8, such as changes in passive background infrared. The analog signal output from the PIR sensor is amplified and filtered by a first stage operational amplifier 10 within the microcontroller 7, and then by a second stage operational amplifier 12 within the microcontroller 7, with a DC offset controlled by a bias voltage 14 e.g. from a voltage divider connected to the PCB power supply 11. The resultant amplified and filtered analog signal is then input to an analog-to-digital converter (ADC) 16, which is processed and output as a digital signal, indicative of a motion event detected by the sensor 8, to the processor 4.
One problem with the conventional arrangement shown in
Since the sensor 8 is a low power device, such as a pyroelectric sensor, the output of the operational amplifier 21 is sufficient to power the sensor 8. This power supply is less susceptible to noise than the unregulated power supply 11 from the PCB, and does not require additional components. This arrangement provides a simple and reliable sensing circuit suitable for use in a consumer electronics device such as a media receiver.
In one specific embodiment, the microcontroller 7 is an MSP430™ microcontroller from Texas Instruments. The sensor 8 is a pyroelectric sensor from KEMET.
A similar arrangement to the above may be used in other microcontrollers having integrated operational amplifiers.
Alternative embodiments, which may become apparent to the skilled person on reading the above description, may nevertheless fall within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2114027.2 | Sep 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2022/052474 | 9/29/2022 | WO |
