GB2587345A

GB2587345A - Light switch

Info

Publication number: GB2587345A
Application number: GB1913617.5A
Authority: GB
Inventors: Englezopoulos Kostantinos; Mitrione Nicola
Original assignee: Luceco PLC
Current assignee: Luceco PLC
Priority date: 2019-09-20
Filing date: 2019-09-20
Publication date: 2021-03-31
Also published as: GB201913617D0

Abstract

A smart light switch, which is compatible with LED lamps and which does not contain a neutral wire, comprises a power input terminal for receiving power from an external power source, an output terminal for connection to at least one light, a user input mechanism which is capable of being controlled manually, a wireless transceiver for sending and receiving a signal, a control unit, which may comprise an optocoupler, a power storage assembly and a charging unit for the power storage assembly. The light switch may include a dimmer mechanism using the trailing edge method and may be small enough to fit an existing wall socket.

Description

Light Switch [0001] The present invention relates to a smart light switch. In particular the invention relates to a smart light switch compatible with lighting circuits containing no neutral wire.

BACKGROUND

[0002] 'Smart' wireless lighting control devices become increasingly popular in recent years. Smart switches usually comprise the ability to be controlled locally via a mechanical input mechanism and wirelessly through an RE (radio frequency) technology, ultimately connecting the device to the internet either directly or through a central control device (hub). Being lighting control devices, they need to be very responsive and always accessible to the user.

[0003] WiFi is ubiquitous in households and all mobile phones can maintain a stable WiFi connection thus making them industry standard for setting up/configuring smart devices.

Using alternative technologies such as Bluetooth/Zigbee etc. would require a hub, which in the end would still use VViFi to make it a smart device system with internet connectivity.

[0004] Hubs can therefore act as bridges between the switching/dimming apparatus and the user. The hubs usually connect to a local WiFi network and an RF technology/protocol is then used for the hub to communicate with various slave switches. This is an undesirable solution for customers since various devices are needed in order to operate the system. Further to this, hubs tend to 'bulk up' quickly, rendering them slow and overloaded, let alone they take up physical space. A 'universal hub' to maintain inter-polarity between manufacturers is not easy to make and is also a relatively very expensive solution for average consumers. This in most cases goes together with an unavoidable vendor locking on the system/platform. It becomes clear that a hub would be a solution to avoid, making it important that the smart device to operate standalone on a provided WiFi network.

[0005] Smart switches require a continuous power supply to enable wireless control of the light fixtures and WiFi ICs are extremely power hungry, especially in the given scenario when required to work quickly, reliably and ideally maintain a live connection.

[0006] Traditional light switches usually have one wire entering (live in) and one wire exiting (live out). They function by opening and closing the circuit, thus controlling the power to the lights. When the circuit is broken, no power flows through the switch.

[0007] The 3-way loop system in the UK makes it difficult for smart switches to operate since the current they draw needs to go through the load continuously in contrast to traditional switching. This means the circuit cannot break at any point since there is no neutral available for the smart switch to operate independently. Traditionally in the case of dimming, the neutral wire would be used for the smart switch to get its own power easily without interfering with the load.

[0008] A solution to resolve the above in newly built installations is by adding a neutral wire into the lighting circuit switch sockets. As mentioned above, the majority of existing installations do not provide access to a neutral wire (hence the no-neutral convention) which leaves the user with the option of re-wiring their lighting circuit, which is a very costly process.

[0009] Another solution to the problem is by using the WiFi IC on the bulb itself, which is known as a "Smart Bulb" and requires the traditional wall switches to be constantly on (WiFi ICs will require constant power). This means the user is limited on the selection of light bulbs and more importantly he cannot physically control the switch. An external "hub" solution could bridge a low power battery operated wall switch as a "client" to control the bulb, but this again goes against the purpose of having WiFi on the lamp itself Most usually the above "WiFi bulbs" are only be controllable by an app. Not having physical access to the switch is neither user friendly nor safe as a phone might not be readily available in emergencies.

[0010] In regard to both customer value and environmental purposes it would be best if the lamps outlived their use and life expectancy. Most dimmable bulbs in households are almost brand new, and with an expected life of LEDs averaging at 50 000 hours they would go to waste, and this is best avoided.

[0011] A No-Neutral WiFi light-control which allows both local (hardware controls and wireless local) and completely remote control using a server back-end with (user interfaces) in form of simple web and app control is sought out for in the market.

[0012] Using smart switches to control LEDs is of particular interest due to their high efficiency and long-life expectations. To power an LED, a transformer is required to reduce the mains voltage significantly (usually less than five volts), and the resulting current flow is complex. Typically, the LED will take a high current for a short period at the start of the mains half cycle and virtually no current for the remainder of the cycle. This makes the LEDs sensible to small currents and easy to be at "dimmed" state or a low flicker state if exactly at threshold, thus making it hard to continuously draw large amounts of current required for a WiFi connection without the user noticing.

[0013] Furthermore, not only does the dimming method for LEDs vary from other loads but such dimmable LED lamps in particular have been also only recently introduced at a low cost and are easily accessible from local stores. This creates a big range of the quality/design of the LED lamp circuitry, thus making it a requirement for the switch to be compatible with both top and low-end priced LED bulbs.

[0014] Powering the smart switch by a battery seems unavoidable due to the power requirements of a highly responsive switch (which requires to maintain an internet connection for frequent server communication). However, it is undesirable to have a short 'battery life' which would require the user to manually recharge/change the battery frequently. For this reason, there is a requirement to have an automatic continuous battery recharge mechanism. This is very difficult to achieve without access to both neutral and live wires as the recharge needs to happen continuously through the load.

[0015] When drawing small amounts of current in a No-Neutral battery recharge method, it is not difficult for the load to be slightly dimmed on, due to the load's small current threshold. This is not only visually noticeable by the user but also slowly degrades the lamp lifetime as it is always on (over leak current). There is therefore a requirement to minimise this effect while maintaining appropriate battery levels for the switch to operate and remain highly responsive (no lengthy sleep intervals) as required for both household & industrial applications.

[0016] It is of course mandatory that the switch fits into existing sockets. That gives very tight constraints on the device size of which a large component to consider is the battery (with temperature/heat dissipation of constant use taken into consideration).

[0017] Until recent years a reliable, small factor low power and inexpensive WIFI chip (with an integrated antennae) was not readily available. Price alone would have made the device inaccessible to that target audience even if the lower power requirements would have been met.

[0018] It is at least one object of the present invention to obviate or at least mitigate at least one or more of the aforementioned problems.

[0019] An object of the present invention is to provide a smart light switch which will work in lighting circuits with no neutral wire or a hub.

BRIEF SUMMARY OF THE DISCLOSURE

[0020] A lighting apparatus control switch for a lighting circuit comprising: a power input terminal for receiving power from an external power source; a user input mechanism which is capable of being controlled manually; a wireless transceiver for sending and receiving a signal; an output terminal for connection to at least one light; a control unit which is operatively connected with, an optocoupler, the user input mechanism and the wireless transceiver, a power storage assembly and a charging unit for the power storage assembly, and the output terminal; wherein a signal is sent from the user input mechanism or the wireless transceiver to the control unit to modify an output algorithm; wherein the optocoupler detects a signal from the power input terminal and then sends a signal to the control unit, the received signal in the control unit is used within the output algorithm to set the amount of the PWM (pulse width modulation) duty cycle, which edits the outgoing power from the output terminal, controlling the brightness of the at least one light, and adjusts the outgoing power from the charging unit to the power storage assembly; with the proviso that the switch and the external power source has no neutral wire. The wireless transceiver may be controlled by a mobile phone via multicast DNS. The wireless transceiver may be controlled through a server.

The lighting apparatus control switch may further comprise an override device which is capable of locking and/or unlocking the control of the lighting apparatus.

The lighting apparatus control switch may be capable of operating with minimal leakage current for a prolonged period of time.

The response rate of the lighting apparatus control switch may adapt based on a user's last activity. If the user has been active recently, the switch will be more responsive than if the switch has been inactive for a period of time.

The lighting apparatus control switch may not be susceptible to normal fluctuations in the mains supply.

The lighting apparatus control switch may be small enough to fit existing wall sockets.

These sockets may be single or double, or any shape of standard socket.

The lighting apparatus control switch may be capable of providing an override input mechanism which can be used to disable remote control of the switch.

The lighting apparatus control switch may comprise a plurality of switches to assume control of the main line, thus allowing for a staircase control scenario known as two-way switching.

The lighting apparatus control switch may be capable of adjusting its operation, pulse width modulation upper and lower limits, and battery recharge levels based on the connected load.

The lighting apparatus control circuit may be capable of operating while recharging the battery with minimal leakage current for a prolonged time without unintentionally causing led glow when the load is meant to be switched off.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is a simplified schematic version of the lighting apparatus switch mechanism.

Figure 2 is a greater detailed version of the schematic in Figure 1. Figure 3 is a schematic of the zero cross detection circuit.

Figure 4 is a schematic of the battery recharge circuit.

Figure 5 is a schematic of the AC/DC detail, part of the battery recharge circuit. Figure 6 is a schematic of the mains power for the control unit Figure 7 is a schematic of the pulse width modulation and core MCU circuit. Figure 8 is a schematic of the WiFi IC circuit.

DETAILED DESCRIPTION

[0022] The smart light switch will be compatible with many different LED lamps, with wattages between 6W-250W coming from a variety of manufacturers and will work via WIFI 802.11 and via manual control. The lower wattage threshold of only 6W is extremely important as the switch is able to operate with pulling minimum amount of current while keeping the load off, and lower wattages have a lower current threshold before the start producing a visible light output.

[0023] An ESP8266 has been chosen as a low power W Fi IC with a competitive price, thus keeping the target BOM (bill of materials) low enough to meet the market expectations.

[0024] [0025] The dimmer mechanism may use the trailing edge method, utilising a N-MOS to drive loads in the lower wattage range with smooth, silent dimming control, absent of any acoustic noise. The dimmer controlled by the MCU (micro control unit) will change the brightness of a lamp from a minimum to a maximum brightness (e.g. 0 to 60% for example).

[0026] Such circuits are susceptible for noise/interference and drifting of zero crossing when doing ZCD (zero-cross detection) when using a transistor approach to achieve this. The cause is usually other loads in the same circuit, like washing machines, or other motor operated circuits which can introduce such noise (harmonics etc). This de-synchronisation of the PWM output and the ZCD input is a cause of lamp flicker; they need to remain synchronised for a smooth operation. To avoid lamp-flicker which is related to the above cause, an optocoupler can be used to get a ZCD (see Figure 3). It sends a low voltage signal to MCU, which in turn generates an PWM (pulse with modulation) output to keep the output PWM (pulse width modulation) in sync with the mains power. The ZCD is made with an optocoupler and every time the signal main crosses zero, a signal is sent to MCU, thus remaining in sync when the zero moves (the PWM will chop the main and therefore move the zero since all circuit operates on the same line). The ZCD can be made with an optocoupler and every time the main signal crosses zero, a signal is sent to the MCU. The zero-crossing detection is essentially a circuit that detects when the signal crosses the OV level. It can be built in different ways, but an opto-insulated solution, an optocoupler has been chosen. It uses a very small area used on PCB which is critical for the WFi switch fitting in a single socket 47mm x 47mm. Essentially the usable area is smaller than that because the WIFI ant has need to be free of obstruction around for avoid EMI. Opto-diode input is easy to polarise using just two 0805 resistor, is stable with a good slew rate. Ultimately it also offers opto-insulation from input main voltage 230Va.c and low voltage dc in output. By using an optodiode the problems of noise/interference and drifting of zero crossing when using a transistor approach has also been resolved.

[0027] As in Figure 1, a WiFi 802.11 module is used to connect to the network directly through a router without using any form of hub, gateway, bridge 433 MHz, BLE, etc. The switch can be set up in such a way as to allow local control through the router directly, using the switch's IP for example. Given the ability of the switch to be setup either as a station point (SP) or an access point (AP), wireless local control is possible through either of these approaches. The switch is capable of receiving and parsing credentials from a relevant mobile app and store the AP network credentials such as SSID and password so that automatic reconnection upon reset is possible without requiring reconfiguration.

[0028] The switch may work simply as light toggle ON/OFF or a dimmable light via manual control or via an app. Manual switching/dimming control is possible on the unit with an input mechanism, for example, two push buttons UP and DOWN.

[0029] Available leakage current which can be used from a lamp without switching it on differs broadly due to the LED driver variations which exist. To keep the switch compatible with LED lamps from various manufacturers an AC/DC converter of high efficiency may be used. This works with a leakage current which is less than 3mA A.G. approximately, which is sent to the battery for recharge. A battery such as a LiPo 3.7V 800mAh may be used. A monitoring circuit stops the recharge when the voltage value of the battery goes over 4.2V D.C. By using an AC/DC step-down it is possible to completely turn OFF a larger selection of LED lamps without using the switch to break the main's power, thus allowing the battery to keep the circuit alive.

[0030] The MCU, holds the WiFi IC on light sleep when not used, and frequently making requests for any updates on the brightness/state of light from the server. This ensures that the battery is not wasted waiting, which is critical for the device functionality. DTIM (Delivery Traffic Indication Message) spikes are still manageable with our chosen fetch intervals, while allowing our switch to maintain an MDNS active for the app to quickly control the switch without having to go through the server, thus allowing local control.

[0031] An additional mechanism actively disables ESP (WiFi module) and puts MSP (micro controller) in very low power state in case there is a main outage thus preserving the battery. Credentials are also stored in FRAM (Ferroelectric Random Access Memory) in case of a worst possible scenario of a very prolonged outage. In this case the switch resumes normal interactions and recharging once power is restored.

[0032] The battery recharge unit (Figure 4) may charge the battery with different amounts of current depending on which value of brightness of the lamp the user has selected. When the load is fully off the battery continues to charge slowly. The battery recharge is made in two parts: 1) AC/DC step down converter, (Figure 5 & 6) and 2) Control battery charge.

[0033] For example, when the PWM is in the range of 0% to 60% and the AC/DC converter has an input voltage somewhere between 230-80 V A.G.: It generates an output at 5.6 V, with the current depending on the resistors as selected by the MCU, (R5), (R7) of the control battery MCP7383.

[0034] Recharge Current is therefore selected via software by the MCU at different values of PWM (Figure 7). When the lamp needs to stay OFF, the transistor Ti is in conduction. For example, for PWM = 0% to PWM = 20% this part of the circuit provides around 23mA. For a PWM between (21% to 40%), the transistor Ti turns off, while T2 turns on and provides around 38mA. When the brightness of the lamp is between a PWM of 41%-60%, the transistor Ti turns on again, while T2 is turn off, it provides around 23mA.

[0035] The PWM from MCU controls T4 which in turn drives MOS Q1. The specific LiPo battery can re-charge until 4.2V, this value is too high for some of the circuit's ICs which have an absolute maximum value at 3.6V, the series of diodes D1, D2 and D3, D4, warrantee the right voltage range for MSP and ESP.

[0036] Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention.

Claims

CLAIMS1. A lighting apparatus control switch for a lighting circuit comprising: a power input terminal for receiving power from an external power source; a user input mechanism which is capable of being controlled manually; a wireless transceiver for sending and receiving a signal; an output terminal for connection to at least one light; a control unit which is operatively connected with, an optocoupler, the user input mechanism and the wireless transceiver, a power storage assembly and a charging unit for the power storage assembly, and the output terminal; wherein a signal is sent from the user input mechanism or the wireless transceiver to the control unit to modify an output algorithm; wherein the optocoupler detects a signal from the power input terminal and then sends a signal to the control unit, the received signal in the control unit is used within the output algorithm to set the amount of the PWM (pulse width modulation) duty cycle, which edits the outgoing power from the output terminal, controlling the brightness of the at least one light, and adjusts the outgoing power from the charging unit to the power storage assembly; with the proviso that the switch and the external power source has no neutral wire.
2. A lighting apparatus control switch according to claim 1, wherein the wireless transceiver can be controlled by a mobile phone via multicast DNS.
3. A lighting apparatus control switch according to any preceding claim, wherein the wireless transceiver can be controlled through a server.
4. A lighting apparatus control switch according to any preceding claim, further comprising an override device which is capable of locking and/or unlocking the control of the lighting apparatus.
5. A lighting apparatus control switch according to any preceding claim, wherein the apparatus is not susceptible to normal fluctuations in the mains supply.
6. A lighting apparatus control switch according to any preceding claim, wherein the apparatus is small enough to fit existing wall sockets.
7. A lighting apparatus control switch according to any preceding claim, wherein the apparatus is capable of providing an override input mechanism which can be used to disable remote control of the switch.
8. A lighting apparatus control switch according to any preceding claim, wherein the apparatus comprises a plurality of switches to assume control of the main line, thus allowing for a staircase control scenario known as two-way switching.
9. A lighting apparatus control switch according to any preceding claim, wherein the apparatus is capable of adjusting its operation, pulse width modulation upper and lower limits, and battery recharge levels based on the connected load.
10. A lighting apparatus control circuit which is capable of operating while recharging the battery with minimal leakage current for a prolonged time without unintentionally causing led glow when the load is meant to be switched off.
11. A lighting apparatus control switch according to any preceding claim, wherein the apparatus is capable of operating with minimal leakage current for a prolonged period of time.
12. A lighting apparatus control switch according to any preceding claim, wherein the response rate of the apparatus adapts based on a user's last activity.
13. A lighting apparatus control switch according to any preceding claim, wherein the apparatus can switch the load off, without any visible dimming while still providing enough charge for the circuit operation/battery recharge.