GB2552479A

GB2552479A - Thermostat, and method of operating a heating boiler controller and a thermostat

Info

Publication number: GB2552479A
Application number: GB1612790.4A
Authority: GB
Inventors: Gepperth Jürgen
Original assignee: tado GmbH
Current assignee: tado GmbH
Priority date: 2016-07-24
Filing date: 2016-07-24
Publication date: 2018-01-31
Anticipated expiration: 2036-07-24
Also published as: GB2552479B; GB201612790D0; DE102017006987B4; DE102017006987A1

Abstract

A thermostat (10) for communicating with a heating boiler controller (1), comprising: a terminal (12) for electrically connecting to a terminal (2) of the heating boiler controller for communicating with, and receiving electrical energy from, the heating boiler controller. A control device (Fig 2, 16) interprets a supply voltage (u1) of the heating boiler controller which is applied to the thermostats terminal as a signal. A transmitting module (13) produces current variations (i1) at the thermostats terminal for sending signals to the heating boiler controller. A power supply module (14) supplies power to the electronic components from the thermostats terminal and comprises a DC/DC boost converter circuit (20) with input connections (21) connected with the thermostats terminal and output connections (22) leading to the electronic components. The converter may be a peak current control boost converter. The control device operates the boost converter circuit such that an input current (i2) at its input connections remains constant within predefined boundaries such that the heating boiler controller will not interpret the input current as a signal. The power supply module may also comprise a DC/DC buck converter (30).

Description

(54) Title of the Invention: Thermostat, and method of operating a heating boiler controller and a thermostat Abstract Title: Thermostat for communicating with a heating boiler controller (57) A thermostat (10) for communicating with a heating boiler controller (1), comprising: a terminal (12) for electrically connecting to a terminal (2) of the heating boiler controller for communicating with, and receiving electrical energy from, the heating boiler controller. A control device (Fig 2, 16) interprets a supply voltage (u1) of the heating boiler controller which is applied to the thermostat’s terminal as a signal. A transmitting module (13) produces current variations (i1) at the thermostat’s terminal for sending signals to the heating boiler controller. A power supply module (14) supplies power to the electronic components from the thermostat’s terminal and comprises a DC/DC boost converter circuit (20) with input connections (21) connected with the thermostat’s terminal and output connections (22) leading to the electronic components. The converter may be a peak current control boost converter. The control device operates the boost converter circuit such that an input current (i2) at its input connections remains constant within predefined boundaries such that the heating boiler controller will not interpret the input current as a signal. The power supply module may also comprise a DC/DC buck converter (30).

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TITLE

Thermostat, and Method for Operating a Heating Boiler Controller and a Thermostat

TECHNICAL FIELD

In a first aspect, the present disclosure is directed at a method for operating a heating boiler controller and a thermostat, comprising the features of the preamble to claim 1.

In another aspect, the present disclosure is directed at a thermostat, comprising the features of the preamble to claim 2.

BACKGROUND

Heating boilers are widely used for heating buildings, building parts or other environments. Typically, a hearing boiler heats a liquid such as water which is then supplied to the environment to be heated, e.g. to a heat radiator located in this environment. Functions of a hearing boiler are controlled with a hearing boiler controller. The hearing boiler controller may in particular be configured to control the hearing boiler to set a desired temperature of the heated liquid, to set a current power consumption of the hearing boiler, and/or to control a pump or pump rate for transporting the heated liquid to the environment to be heated.

The hearing boiler controller communicates with a thermostat which may be arranged in the environment to be heated. The thermostat sends signals, for instance measured temperature signals, to the hearing boiler controller. The hearing boiler controller may also send signals to the thermostat, and may provide energy supply for the thermostat.

Such functions require correct communication between the hearing boiler controller and the thermostat. In particular, communication may be effected in that the hearing boiler controller sends signals as voltage variations, and the thermostat may send signals as current variations.

This is achieved with a generic method for operating a heating boiler controller and a thermostat. In this method, a terminal of the heating boiler controller and a terminal of the thermostat are electrically connected (e.g., with wires) for communicating with each other and for supplying electrical energy to the thermostat. A terminal may be considered as a socket, a jack, or any other connector configured to establish an electrical connection. The heating boiler controller sends signals to the thermostat by varying a supply voltage at its terminal (i.e., the voltage at the heating boiler controller’s terminal; this leads to a similar voltage at the thermostat’s terminal). The thermostat is configured to sense this supply voltage and decode it to read the sent signal. The heating boiler controller further interprets current variations at its terminal as signals from the thermostat. The thermostat comprises a transmitting module, with which it produces current variations at the thermostat’s terminal for sending signals. Furthermore, the thermostat comprises a power supply module connected with the thermostat’s terminal and connected with electronic components of the thermostat for supplying power to the electronic components via/from the thermostat’s terminal. The power supply module may thus transform the supply voltage of the heating boiler controller such that electronic components of the thermostat are supplied with power from the heating boiler controller.

Similarly, a generic thermostat for communicating with a heating boiler controller comprises:

a terminal for electrically connecting to a terminal of the heating boiler controller, and for communicating with the heating boiler controller and receiving electrical energy from the heating boiler controller;

a control device configured to, in a first operation mode, interpret a supply voltage of the heating boiler controller, which is applied to the thermostat’s terminal, as a signal;

a transmitting module configured to, in the first operation mode, produce current variations at the thermostat’s terminal for sending signals to the heating boiler controller;

a power supply module and electronic components, the power supply module being connected with the thermostat’s terminal and with the electronic components for supplying power to the electronic components via/from the thermostat’s terminal.

The communication via current variations (e.g., digital current signals with a sequence of high and low current values) must not be disturbed by the power supply. Problems may arise as the supply voltage of the heating boiler controller is varied for transmitting signals: This voltage variation should not lead to current variations (which would interfere with the transmission of signals from the thermostat to the heating boiler controller). Furthermore, if electronic components of the thermostat should have a varying power demand, this may produce a varying current, which again might falsely be regarded as a signal sent from the thermostat.

In known conventional methods, the above problems are addressed by using a linear regulator, such as a low dropout regulator, as a power supply module. A low dropout regulator converts the voltage (at the thermostat’s terminal) supplied from the heating boiler controller into a suitable lower voltage. This is done by heat dissipation: The voltage is reduced by converting electrical energy into heat. If the supply voltage from the heating boiler controller varies (e.g., due to transmission of signals in the form of voltage variations), the low dropout regulator ensures that it always outputs a constant voltage level (if it did not output a constant voltage, any following electronic components would possibly cause current variations). Furthermore, conventionally the electronic components are operated to have a constant power demand to avoid causing current variations that may falsely be regarded as signals.

However, such a conventional method has the disadvantage of inefficient use of energy. The low dropout regulator dissipates large amounts of energy in waste heat. The electronic components have a rather constant energy consumption although they may temporarily not need to be active (e.g., a wireless communication device is typically not always active; and a microcontroller may from time to time be turned into an energy saving “sleep mode”).

Hence, conventional thermostats have an unduly high energy consumption only to ensure that no unintended current variations occur that may falsely be interpreted as transmitted signals.

OBJECT OF THE INVENTION

An object of the present disclosure is to provide a thermostat, and a method for operating a heating boiler controller and a thermostat, which are particularly energy efficient while simultaneously ensuring a reliable communication between the heating boiler controller and the thermostat.

SUMMARY OF THE INVENTION

This object is solved with a method as defined in claim 1, and a thermostat as defined in claim 2.

Exemplary embodiments are given in the dependent claims and the following specification.

According to the invention, the generic method defined above is further characterized in that the power supply module comprises a DC/DC boost converter circuit, which may also be referred to as a DC/DC boost converter circuit system as it may comprise further components besides elements necessary for a DC/DC boost converter. The DC/DC boost converter circuit has input connections connected (directly or via further components) with the thermostat’s terminal and output connections leading (directly or via further components) to the electronic components. In operation, an input current and an input voltage are present at the input connections, and an output current and an output voltage are present at the output connections. The DC/DC boost converter circuit is controlled with a control device such that the input current remains constant within predefined boundaries such that the heating boiler controller will not interpret the input current as a signal. A power demand (energy consumption) of the electronic components of the thermostat may vary depending on a momentary operation of the electronic components; still this will not have a negative effect on the transmission of signals in the form of current variations, which is explained in more detail further below.

Similarly, the generic thermostat defined above is further characterized in that the power supply module comprises a DC/DC boost converter circuit with input connections connected with the thermostat’s terminal and output connections leading to the electronic components. In operation an input current and an input voltage are present at the input connections, and an output current and an output voltage are present at the output connections. The control device is configured to operate the DC/DC boost converter circuit in the first operation mode such that the input current remains constant within predefined boundaries such that the heating boiler controller will not interpret the input current as a signal.

A DC/DC boost converter circuit, also referred to as a step-up converter, is an electronic device that converts an input voltage into an output voltage, and has the advantage of a particularly high efficiency, in particular compared to a low dropout converter. The voltage conversion also affects the current drawn from the thermostat’s terminal (i.e., the input current of the DC/DC boost converter circuit). This characteristic is used for achieving the invention’s objects. In typical applications (not in the case of the present invention), a DC/DC boost converter circuit is operated such that a predefined desired voltage is output: if the input voltage fluctuates, the operation of the DC/DC boost converter circuit varies the input current (and thus also the output current) with the goal of maintaining the predefined desired output voltage. However, the invention operates the DC/DC boost converter circuit differently: If the input voltage fluctuates, the output voltage is allowed to vary and is not set to any specific values or value ranges. Instead, a current (which is indicative of or equal to the input current or output current) is sensed, and the DC/DC boost converter circuit is controlled such that this current is substantially constant. Hence, a DC/DC boost converter circuit is operated in a different way than conventionally, with the effects of providing a substantially constant current source (which does not interfere with signal transmission by current variation) with a high degree of efficiency.

The advantages over conventional thermostats that use a low dropout converter become readily understood in the following example: The heating boiler controller may vary its supply voltage for transmitting signals to the thermostat (e.g., it may output a sequence of high and low voltage levels). Despite this voltage variation, the thermostat’s power supply module is to output a substantially constant current. The low dropout converter achieves this by dissipating larger amounts of heat when the supply voltage rises. In contrast, the DC/DC boost converter circuit which is controlled as described above outputs a constant current with an efficiency of typically larger than 90%. A high efficiency also means very low heat production. This is a great advantage if one of the thermostat’s electronic/electric components is a thermometer for measuring an ambient temperature, i.e., a room temperature. Such a measurement would be negatively influenced when the thermostat itself produces much heat.

It may be preferable that the DC/DC boost converter circuit comprises a peak current control boost converter. The DC/DC boost converter circuit may comprise, amongst other elements, a switch, an inductor and/or a capacitor, and a diode. These elements may be arranged and function as follows. The diode is in series with the inductor. The switch may be arranged parallel to the capacitor. If the switch is closed, a current through the inductor increases and energy is saved in the inductor. When the switch is opened, the current flows via the inductor through the diode to the capacitor, wherein the current (or saved charge) in the inductor decreases. A voltage at output connections (i.e., behind the diode), depends on the durations for which the switch is opened or closed. In this way, the voltage at the output connections can be larger than a voltage at the input connections (i.e., a voltage at or before the inductor; this voltage is hereinbelow also referred to as supply voltage). Conventionally the durations for which the switch is opened or closed are controlled such that a desired output voltage is reached. In this disclosure, the durations are not controlled for outputting a desired voltage, but such that an input current is within predefined boundaries.

The control device may be configured to control switching states of the peak current control boost converter (i.e., durations of the afore-mentioned switch being opened or closed) such that the input current is within the predefined boundaries.

The predefined boundaries are chosen such that the current caused by the DC/DC boost converter circuit comprises no variations that would be interpreted by the heating boiler controller as signals. For instance, the predefined boundaries may comprise a predefined current range for the input current, to hold the input current substantially constant. In particular, the predefined boundaries may comprise a predefined current range which is smaller than a minimum current threshold above which the heating boiler controller regards a current variation as a signal from the thermostat. The minimum current threshold may in particular indicate the current threshold used to distinguish between a high level and a low level of a digital current signal.

The predefined boundaries may alternatively or additionally also comprise a maximum number of changes of the input current (the current as set with the DC/DC boost converter circuit) per time interval: As a digital current signal is composed of a sequence of high and low current values, a small number of current changes may be acceptable, i.e., may not be interpreted by the heating boiler controller as a signal. Furthermore, the predefined boundaries may alternatively or additionally comprise a maximum slope of the input current (i.e., a maximum speed of change of the input current), and the DC/DC boost converter circuit is operated such that any slope in the input current is below this maximum slope. As the heating boiler controller senses current variations by comparing a momentary current to a time average of the current, any slow current changes are acceptable as they will not be identified as current variations / signals.

A basic working principle of a peak current control boost converter is that it is configured to alternatively switch between at least a first switching state and a second switching state. The input current rises during said first state and decreases during said second state. For instance, a switch (such as a transistor) may be closed to start the first state in which a current progressively builds over an inductor (due to the inductance, the current rises gradually and does not jump to a final value), and energy is saved in the inductor. The switch may then be opened to initiate the second state: The current now flows through, e.g., a diode (which may be arranged parallel to the switch) and through the output connections of the peak current control boost converter. Time intervals for switching between the two states define the output voltage as well as the input current. The time intervals are set to adjust the input current, as explained below.

A peak current control boost converter also has an input terminal at which a control signal can be input to control switching between the first and second switching states. The control device supplies control signals to the input terminal of the peak current control boost converter, independent of the momentary output voltage of the peak current control boost converter but instead such that the input current remains constant within the predefined boundaries. In other words, the control signals set the time intervals for switching between the two states to achieve the above features of the input current.

This is in contrast to the conventional use of a peak current control boost converter: Typically the output voltage (or a related voltage characteristic of the output voltage) is used in a feedback loop to set the time intervals for switching. This procedure leads to a desired approximately constant output voltage, however, the input current may vary considerably. Therefore, the present invention does not use the output voltage in a feedback loop to set the time intervals for switching. Instead, the output voltage is allowed to vary in order to keep the input current within a certain range.

Such a control is important in the following example: The heating boiler controller may vary its supply voltage, e.g., for transmitting signals to the thermostat. In this case, the DC/DC boost converter circuit must avoid a change in the input current (which may be caused by the change in the supply voltage, and may falsely be interpreted as a signal sent by the thermostat). Therefore, when the heating boiler controller’s supply voltage (which is applied to the thermostat’s terminal) changes, the control device controls the DC/DC boost converter circuit not such that its output voltage remains constant but such that the input current remains constant within the predefined boundaries.

In this way, variations in the supply voltage (e.g., between a high voltage level and a low voltage level used for transmitting a digital signal) do not lead to increased energy consumption by the thermostat. In contrast, conventional thermostats usually simply convert both the high voltage level and the low voltage level to a desired output voltage by converting more electrical energy into heat if the high voltage level is applied.

The invention not only increases energy efficiency with regard to variations in the supply voltage. Further increases in energy efficiency can be achieved in case that a power demand of the electronic components of the thermostat varies depending on a momentary operation of the electronic components. For example, an electronic component may be a wireless transmission device. Such a device may be used to receive measured temperature values from other thermostats, or to communicate via an internet-enabled device (such as a modem) with, e.g., a server and/or a user’s smartphone. A wireless transmission device may be inactive and thus does not need any or much energy; however, in an active transmission state, the wireless transmission device may need a higher amount of energy. Another example of an electronic component is a microcontroller used to control functions of the thermostat, e.g., used for controlling the transmitting module (for communicating with the hearing boiler controller) and/or used for controlling the wireless transmission device. The microcontroller may be switchable between an active mode and a sleep mode, in which energy consumption is lower compared to the active mode. Such variations in the power demand are met by adjusting the input current. To this end, control of the DC/DC boost converter circuit is adjusted: The above-described predefined boundaries comprise a predefined current range, and the control device is configured to change the predefined current range to a new predefined current range depending on a momentary or future power demand of the electronic components. The change in the predefined current range entails a change in the input current. However, the control device may be configured to control the DC/DC boost converter circuit to maintain the input current within the new predefined current range at least for a predefined duration to avoid that the heating boiler controller falsely interprets a change in the input current as a signal from the thermostat. In this way it is possible to adjust the total power demand of the thermostat without the risk that the hearing boiler controller falsely assumes a current signal. The future power demand may be determined in the following way: When the microcontroller decides to wake an electronic component (such as the wireless transmission device), then the microcontroller / control device first instructs the DC/DC boost converter circuit to increase the input current to the new (higher) predefined current range; afterwards the microcontroller wakes the wireless transmission device and instructs the wireless transmission device to transmit any data.

During data transmission with the wireless transmission device, the energy demand of the wireless transmission device may vary considerably. However, in this case the control device may be configured to maintain the present current range and do not allow to transiently reduce the current range (which would save energy) because such frequent changes in the input current may be falsely interpreted as a signal sent by the thermostat.

The problems of a false interpretation of a current variation only arise if communication from the thermostat to the hearing boiler controller is based on a current signal (typically a digital current signal). However, the thermostat of the invention may also be configured to communicate with different kinds of hearing boiler controllers, and may hence be configured to transmit other signals than current signals. The above-described control of the input current may thus only be used in a first operation mode dedicated for communication (from the thermostat to the hearing boiler controller) by digital current signals, i.e. if the current variations are interpreted as a digital current signal, in which data / a signal is encoded as a sequence of high and low current levels. The thermostat’s components, in particular the control device, the transmitting module, and/or the DC/DC boost converter circuit, may be configured to switch between the first operation mode and at least a second operation mode. The transmitting module may be configured to, in the second operation mode:

produce an analogue output voltage at the thermostat’s terminal for sending signals to the heating boiler controller; in this case a height of the analogue output voltage encodes the data/signal to be transmitted; or produce a digital output voltage at the thermostat’s terminal for sending signals to the heating boiler controller; in this case the digital output voltage comprises a sequence of high and low voltage levels which encodes the data/signal to be transmitted.

Advantageously, the substantially constant input currents are only set if actually needed for ensuring safe communication. If the thermostat is used with another heating boiler controller (which is configured to receive signals in the form of analogue or digital voltages), then the input current of the thermostat may be allowed to vary without the above-defined boundaries. This may further improve energy efficiency. The transmitting module may be configured to switch between at least three operation modes to offer both the communication via an analogue output voltage and the communication via a digital output voltage.

When specific electronic circuits are described herein, it is to be understood that any circuits with the same topology may be used instead. That means, any electronic circuit with the same effects may be used, and single components/elements of the circuits may be replaced (e.g., a transistor acting as a switch in a peak current control boost converter may be replaced by any other switchable component). The expressions “DC/DC boost converter circuit “ and “peak current control boost converter” may thus also be understood as “DC/DC boost converter circuit topology” and “peak current control boost converter topology”, respectively.

The power supply module may also comprise a voltage converter for converting down a voltage and being arranged behind the DC/DC boost converter circuit. The reason being that the DC/DC boost converter circuit’s output voltage is larger than its input voltage (for producing a substantially constant input current); however, the electronic components need a considerably lower voltage for their power supply; the voltage desired for the electronic components is lower than the supply voltage of the heating boiler controller and thus also lower than the output voltage of the DC/DC boost converter circuit. Therefore, a voltage converter may be arranged between the DC/DC boost converter circuit and the electronic components for converting an output voltage of the DC/DC boost converter circuit into a lower voltage, i.e., lower relative to the output voltage of the DC/DC boost converter circuit.

It may be preferable that the voltage converter is operated to output a substantially constant lower voltage, independent of variations in the output voltage of the DC/DC boost converter circuit. During regular operation, the output voltage of the DC/DC boost converter circuit will fluctuate significantly, in particular when the hearing boiler controller varies its supply voltage for transmitting signals. Such voltage fluctuations are undesired for power supply of the electronic components, and are cancelled by the voltage converter.

The voltage converter may be a DC/DC buck converter, which offers a particularly good efficiency and thus produces only little heat. A power supply module comprising a combination of a DC/DC boost converter circuit (operated as described above) and a DC/DC buck converter thus allow to output any desired and substantially constant voltage while ensuring a substantially constant input current, independent of variations in the supply voltage. Compared to prior art variants in which the thermostat’s power supply module only comprises a low dropout converter for outputring a constant voltage and producing a constant current, energy efficiency is greatly improved and undesired heat production considerably reduced.

It is to be noted that relevant improvements over such prior art variants can already be achieved if the thermostat’s power supply module comprises a DC/DC boost converter circuit (operated as described above) followed by a low dropout converter or another linear regulator as the voltage converter. Although the low dropout converter leads to waste heat, the DC/DC boost converter circuit still leads to energy savings and reduced heat dissipation compared to prior art variants. For example, switching between energy saving modes and normal modes of electronic components (such as a microcontroller or a wireless transmission device) are possible; when such a switching occurs, the DC/DC boost converter circuit may once adapt its operation to amend the input current it draws (such a single change in input current is usually not interpreted as a digital signal which needs to consist of a sequence of high and low level currents). By this change in input current the DC/DC boost converter circuit is able to adjust the total power consumption of the thermostat. In contrast, prior art solutions with only a low dropout converter use this low dropout converter to output a voltage necessary for the following electronic components; this voltage is set by adapting a current through the low dropout converter - therefore, the low dropout converter cannot adapt the current for an energy saving mode without a simultaneous negative impact on the output voltage; but if in such a prior art case the electronic components produce a varying current, this may be falsely interpreted as a signal.

The disclosure also comprises a combination of a heating boiler controller and the thermostat described herein. The heating boiler controller may comprise a terminal for electrically connecting to the thermostat’s terminal, and being configured to output a supply voltage to the thermostat’s terminal for power supply of the thermostat; vary the supply voltage for transmitting signals to the thermostat; and interpret current variations at its terminal as signals from the thermostat.

For interpreting current variations as signals, the heating boiler controller may in particular compare a momentary current with an average current value. If a certain deviation to the average current value is determined, the heating boiler controller may judge the momentary current to constitute a high or low level of a digital signal.

Further advantages and features of the invention will become readily understood in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows schematically a first embodiment of a combination of a heating boiler controller and a thermostat of the invention.

Fig. 2 shows components of an exemplary power supply module of the thermostat of Fig. 1.

Fig. 3 shows components of another exemplary power supply module of the thermostat of Fig. 1.

Fig. 4 shows schematically a supply voltage output by a heating boiler controller and modulated to transmit a signal to the thermostat.

Fig. 5 shows schematically a current modulated by the thermostat to transmit a signal to a heating boiler controller.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows schematically a thermostat 10 of the invention, connected to a heating boiler controller 1. The invention is also directed at the combination of the thermostat 10 and the heating boiler controller 1. Furthermore an inventive method of operating the thermostat 10 and the heating boiler controller 1 will be described.

The heating boiler controller 1 is an electronic device connected to and configured to control a boiler or other device for producing heat. The heating boiler controller 1 generates control signals for the boiler dependent on signals received from one or more thermostats 10.

As used herein, a thermostat 10 is a device comprising a temperature sensor for measuring an ambient temperature and/or comprising communication means for receiving a measured temperature value of a remote temperature sensor (in which case the remote temperature sensor may also be regarded as part of the thermostat 10). The thermostat 10 is further configured to communicate with the heating boiler controller, in particular for sending measured temperature values through a transmitting module 13.

The thermostat 10 comprises a terminal 12 for establishing an electrical connection to a terminal 2 of the heating boiler controller 1. The electrical connection may be formed with wires / cables. The terminals 2,12 may be understood as any mechanical connectors configured to establish an electrical connection; e.g., each terminal 2,12 may be one or more sockets or cable clamps.

The electrical connection can be used for bidirectional communication and for power supply of the thermostat 10.

The power supply is effected in that the heating boiler controller 1 outputs a supply voltage ul which is then applied to the thermostat’s terminal 12 and components of the thermostat 10.

The supply voltage ul is not only used for power supply but also for transmitting information from the heating boiler controller 1 to the thermostat 10. To this end, the supply voltage ul is modulated.

Such a modulated supply voltage ul is schematically depicted in Figure 4. Figure 4 is a graph of voltage u versus time t, and plots the supply voltage ul. The supply voltage ul is modulated to form a sequence of high and low voltage levels, which encodes information as a digital signal (left part of the graph). If no signal is to be sent, the supply voltage ul remains constant (right part of the graph).

The thermostat 10 is configured to measure the supply voltage ul (or a voltage derived therefrom) to determine any signals.

For easier understanding, the supply voltage ul, i.e., the voltage that is output from the heating boiler controller 1, and the voltage thus caused at the thermostat’s terminal 12 or the voltage (input voltage u2) at the subsequent power supply module 14 may be jointly referred to as supply voltage or input voltage. While there may be certain deviations between the afore-mentioned voltages ul and u2, the voltages at the thermostat’s terminal or the subsequent power supply module 14 depend on (or may be a monotone function of) the supply voltage ul that is output from the heating boiler controller 1; for the technical features described herein, no distinction between such voltages is necessary, and hence descriptions to any one of these voltages ul, u2 may also apply to the respective other voltage u2, ul.

For sending signals from the thermostat 10 to the heating boiler controller 1, a transmitting module 13 is provided (Figure 1). The transmitting module 13 is configured to adjust or produce a current il (also referred to as current variations il). The current variations il are present in addition to a current i2 used for power supply of the thermostat 10. The currents il, i2 flow between the heating boiler controller 1 and the thermostat 10. The heating boiler controller 1 comprises a current measuring device for measuring a current at, e.g., its terminal 2 (this current is equal to or depends on the current i2 and the produced current variations il), and thus reads any signals sent from the thermostat 10.

A current i comprising the input current i2 and being modulated by the transmitting module is shown in Fig. 5. Fig. 5 is a graph of current i versus time t. In the left part of Fig. 5, the current i remains constant, meaning that no information is sent. In contrast, for transmitting a signal/information, the transmitting module 13 produces a current variation il (Fig. 1) and thus modulates the current i between high and low current values (right part of Fig. 5).

Such current variations as shown on the right side of Fig. 5 should only occur for sending signals; otherwise the current should remain substantially constant. In the prior art, this is often achieved in that the power supply module 14 constitutes of a low dropout converter. The low dropout converter outputs a constant voltage even if its input voltage (i.e., the supply voltage provided by the heating boiler controller) varies; a transiently higher input voltage will lead to the low dropout converter transiently producing more waste heat. A drawback of low dropout converters resides in low efficiency, and negative impacts on temperature measurements due to substantial amounts of produced waste heat.

Such shortcomings are overcome in that the power supply module 14 of Fig. 1 comprises a DC/DC boost converter 20, in particular a peak current-mode boost converter circuit or topology. The DC/DC boost converter 20 is switchable between different states. By controlling switching times of the DC/DC boost converter 20, a voltage u3 output by the DC/DC boost converter 20 and also an input current i2 of the DC/DC boost converter 20 can be adjusted. While typically the switching times of the DC/DC boost converter 20 are controlled to output a desired voltage u3, this disclosure adjusts the switching times such that the input current i2 remains within predefined boundaries, leading to a substantially constant input current i2. The output voltage u3 of the DC/DC boost converter 20 is allowed to vary arbitrarily (in contrast to the conventional use). Advantageously, this procedure leads to a substantially constant input current i2 (as shown on the left side of Fig. 5), without high amounts of waste heat.

Following the DC/DC boost converter 20, a DC/DC buck converter 30 is used. The DC/DC buck converter 30 converts the output voltage u3 of the DC/DC boost converter 20 to a lower voltage u4 to meet the voltage demands of electronic components 18 of the thermostat 10. The DC/DC buck converter 30 is operated to output a constant voltage u4, independent of variations in the output voltage u3 of the DC/DC boost converter 20.

The combination of the boost and buck converters 20 and 30 thus combines the advantages of outputting a constant voltage u4 and drawing a substantially constant current i2, while avoiding the inefficiency of a low dropout converter.

The electronic components 18 may, for example, comprise a microcontroller that is in particular used to send control demands 19 to the transmitting module 13. The electronic / electric components 18 may also comprise a temperature sensor for measuring an ambient temperature; or a wireless communication device. Such electronic components 18 may be switchable between an energy saving mode and a normal operation mode. Conventionally, no energy saving mode is used as this may lead to larger fluctuations in the current which may be falsely interpreted as signals sent by the thermostat. In contrast, when one of the electronic components 18 is to be set into an energy saving mode, the operation of the boost converter 20 is adjusted such that its input current i2 is within a new, lower, current range. The input current will then remain substantially constant within this new current range, and hence the one-time change in current will typically not be interpreted as a digital signal (which would consist of a longer sequence of alternating high and low current levels). When the input current of the boost converter 20 is changed in this way, this will also affect the boost converter’s 20 output voltage u3; however, this does not pose any problems as the buck converter 30 is used to step-down the boost converter’s 20 output voltage u3 to any desired lower voltage u4.

An example of a DC/DC boost converter 20 is further explained with reference to Fig. 2, which schematically shows important components of such a boost converter 20. The depicted example may be modified to include additional components, or specific components may be replaced by others having a similar function.

The DC/DC boost converter 20 of Fig. 2 comprises input connections 21, at which an input voltage u2 and an input current i2 are present. The input voltage u2 is derived from the supply voltage ul of the heating boiler controller and directly depends on said supply voltage. An inductor LI (or another energy storage device) is arranged following the input connections 21. Behind the inductor LI, an electric line bifurcates into two lines, one leading to a switch (transistor) Ql, the other leading to a diode DI followed by output connections

22.

As depicted in Fig. 2, such a DC/DC boost converter 20 may be formed as a peak current control boost converter. To this end, a control device 16 for controlling the switch Ql between an open and closed state may be considered to comprise a gate driver 25 (which is connected to the gate or base of the transistor Ql), a PWM (pulse width modulation) logic 27, an oscillator 24, and an error amplifier 26. The error amplifier 26 may form a current or voltage measuring unit configured to measure a current through a resistor R_sense or a voltage over the resistor R_sense which is arranged behind the switch Ql, i.e., between the switch Ql and ground GND.

The control device 16 further comprises an input terminal 23 at which a control voltage 28 can be input. The control voltage 28 (or control signal) determines the switching times for the switch Ql.

When the switch Ql is closed, a current flows though the inductor LI and further through the switch Ql, and the resistor R_sense to ground GND. Due to the inductance of inductor LI, the current will progressively raise after the switch Ql is closed. When the switch is opened, the current from inductor LI cannot flow through switch Ql but will instead flow through diode DI. Behind the diode DI, there may be a capacitor Cl or other components for providing a rather smooth or constant output voltage u3 at the following output connections 22.

A Zener diode D2 may be arranged between the diode DI and the output connections 22 (in particular in parallel to output connections 22) for limiting the output voltage u3 to a maximum value, thus protecting following electronics components from too high voltage.

At the output connections 22, an output voltage u3 and an output current i3 are present. The output voltage u3 is higher than the input voltage u2. The value of the output voltage u3, and whether or not the output voltage u3 is constant or varies significantly, depends on the control voltage 28, i.e., depends on the switching times of transistor Ql.

In conventional peak current control boost converters (also referred to as peak current-mode boost converters), the control voltage 28 is chosen such that the output voltage u3 is constant. To this end, the output voltage u3 is conventionally measured and used for generating the control voltage 28 (i.e., the control voltage 28 conventionally depends on the output voltage u3). In this regard the present disclosure varies significantly from the conventional use: According to the invention, the control voltage 28 is chosen such that the input current i2 remains within predefined boundaries, e.g., within a predefined current range. The inventors have understood that the control voltage 28 does not only affect the output voltage u3 but also the input current i2, and can thus be used as an efficient way to provide a current source or a substantially constant current (which can also be adjusted to other current ranges). Therefore, the control voltage 28 is not set in dependence of the output voltage u3 but instead such that predefined current limits are met. The control voltage 28 may be generated or determined by a microcontroller (not depicted) which may also be considered as part of the control device 16.

A further example of a DC/DC boost converter 20 is shown in Fig. 3. In this example, a conventionally available DC/DC peak current-mode boost 1C (integrated circuit) 32 is used. The 1C 32 comprises several connection pins, labelled with reference signs 35, 36, 23, 29, VDD, and GND in Fig. 3.

A transistor pin 35 connects gate driver 25 with switch/transistor Ql. A current measuring pin 36 connects error amplifier 26 with a position between transistor Ql and resistor R_sense to allow measuring a current/voltage at this point. The pins VDD and GND are connected with a power supply and ground, respectively.

A feedback pin 29 and a pin constituting the input terminal 23 are used differently in the invention compared to the conventional use for outputting a desired voltage u3.

Conventionally, the feedback pin 29 is supplied with a feedback voltage derived from the output voltage u3. In contrast the present design does not provide any input to the feedback pin 29. The pin constituting the input terminal 23, which is also referred to as a compensation pin, is conventionally also supplied with a voltage derived from the output voltage u3. This is again not the case in the present design, in which instead the voltage (i.e., the control voltage 28) applied to the pin constituting the input terminal 23 is calculated by a microcontroller of the thermostat 10 to adjust the input current i2. In particular, the control voltage 28 applied to input terminal 23 may also be calculated to minimize power dissipation at the electronic components 18.

Advantageously, many components of the power supply module 14 of the invention may be comprised of conventionally available components, offering reliable quality and low prices. By fundamentally changing the function of the DC/DC boost converter 20 (compared to conventionally available DC/DC boost converters), a current can be generated and adapted such that this current will not be falsely interpreted by the heating boiler controller as a digital current signal. Only current variations caused by the transmitting module 13 will then be large enough to be regarded as such digital current signals.

In this way, efficient DC/DC voltage conversion is effected, avoiding the considerable waste heat production of prior art devices, and simultaneously ensuring that no interfering currents are produced.

Claims

1. A method for operating a heating boiler controller (1) and a thermostat (10), wherein a terminal (2) of the heating boiler controller (1) and a terminal (12) of the thermostat (10) are electrically connected for communication and for supplying the thermostat (10) with electrical energy;

wherein the heating boiler controller (1) sends signals to the thermostat (10) by varying a supply voltage (ul) at its terminal (2);

wherein the thermostat (10) comprises a transmitting module (13) with which it produces current variations (il) at the thermostat’s terminal (12) for sending signals, and the heating boiler controller (1) interprets current variations (il) at its terminal (2) as signals from the thermostat (10);

wherein the thermostat (10) comprises a power supply module (14) for supplying power to the electronic components (18) via the thermostat’s terminal (12); characterized in that the power supply module (14) comprises a DC/DC boost converter circuit (20) with input connections (21) connected with the thermostat’s terminal (12) and output connections (22) leading to the electronic components (18), the DC/DC boost converter circuit (20) is controlled such that an input current (i2) at its input connections (21) remains constant within predefined boundaries such that the heating boiler controller (1) will not interpret the input current (i2) as a signal.

2. A thermostat (10) for communicating with a heating boiler controller (1), the thermostat (10) comprising:

a terminal (12) for electrically connecting to a terminal (2) of the heating boiler controller (1), and for communicating with the heating boiler controller (1) and receiving electrical energy from the heating boiler controller (1);

a control device (16) configured to, in a first operation mode, interpret a supply voltage (ul) of the heating boiler controller (1), which is applied to the thermostat’s terminal (12), as a signal;

a transmitting module (13) configured to, in the first operation mode, produce current variations (il) at the thermostat’s terminal (12) for sending signals to the heating boiler controller (1);

a power supply module (14) and electronic components (18), the power supply module (14) being configured to supply power to the electronic components (18) from the thermostat’s terminal (12), characterized in that the power supply module (14) comprises a DC/DC boost converter circuit (20) with input connections (21) connected with the thermostat’s terminal (12) and output connections (22) leading to the electronic components (18), the control device (16) being configured to operate the DC/DC boost converter circuit (20) in the first operation mode such that an input current (i2) at its input connections (21) remains constant within predefined boundaries such that the heating boiler controller (1) will not interpret the input current (i2) as a signal.

3. The thermostat of claim 2, wherein the DC/DC boost converter circuit (20) comprises a peak current control boost converter (20).

4. The thermostat of claim 2 or 3, wherein the predefined boundaries comprise a predefined current range which is smaller than a minimum current threshold above which the heating boiler controller regards a current variation as a signal from the thermostat (10).

5. The thermostat of claim 3 or 4, wherein the control device (16) is configured to control switching states of the peak current control boost converter (20) such that the input current (i2) is within the predefined boundaries.

6. The thermostat of any one of the claims 2 to 5, wherein the peak current control boost converter (20) is configured to alternatively switch between at least a first state and a second state, wherein the input current (i2) rises during the first state and decreases during the second state, wherein the peak current control boost converter (20) has an input terminal (23) at which a control signal (28) can be input to control switching between the first and second states, wherein the control device (16) supplies control signals (28) to the input terminal (23) of the peak current control boost converter (20), independent of a momentary output voltage (u3) at the peak current control boost converter’s (20) output connections (22) but instead such that the input current (i2) remains constant within the predefined boundaries.

7. The thermostat of any one of the claims 2 to 6, wherein, when the supply voltage (ul) at the thermostat’s terminal (12) changes, the control device (16) controls the DC/DC boost converter circuit (20) not such that its output voltage (u3) remains constant but such that the input current (i2) remains constant within the predefined boundaries.

8. The thermostat of any one of the claims 2 to 7, wherein a power demand of the electronic components (18) of the thermostat (10) varies depending on a momentary operation of the electronic components (18), wherein the predefined boundaries comprise a predefined current range, and the control device (16) is configured to change the predefined current range to a new predefined current range depending on a momentary or future power demand of the electronic components.

9. The thermostat of claim 8, wherein the control device (16) is configured to control the DC/DC boost converter circuit (20) to maintain the input current (i2) within the new predefined current range at least for a predefined duration to avoid that the heating boiler controller (1) falsely interprets a change in the input current (i2) as a signal from the thermostat (10).

10. The thermostat of any one of the claims 2 to 9, wherein the control device (16), the transmitting module (13), and the DC/DC boost converter circuit (20) are configured to switch between the first operation mode and at least a second operation mode, wherein the transmitting module (13) is configured to, in the second operation mode:

produce an analogue output voltage at the thermostat’s terminal (12) for sending signals to the heating boiler controller (1); or produce a digital output voltage at the thermostat’s terminal (12) for sending signals to the heating boiler controller (1).

11. The thermostat of any one of the claims 2 to 10, wherein the power supply module (14) comprises a voltage converter (30) which is arranged between the DC/DC boost converter circuit (20) and the electronic components (18) for converting an output voltage (u3) of the DC/DC boost converter circuit (20) into a lower voltage (u4), wherein the voltage converter (30) is operated to output a substantially constant lower voltage (u4) independent of variations in the output voltage (u3) of the DC/DC boost converter circuit (20).

12. The thermostat of claim 11, wherein the voltage converter (30) is a DC/DC buck converter (30).

13. Combination of a heating boiler controller (1) and the thermostat (10) of any one of the claims 2 to 12, the heating boiler controller (1) comprising a terminal (2) for electrically connecting to the thermostat’s terminal (12), and being configured to output a supply voltage (ul) to the thermostat’s terminal (12) for power supply of the thermostat (10);

vary the supply voltage (ul) for transmitting signals to the thermostat (10); and interpret current variations (il) at its terminal (2) as signals from the thermostat (10).

Intellectual

Property

Office

Application No: GB1612790.4 Examiner: Ms Janet Kohler