Patent Description:
Driver devices in a switched mode power supply (SMPS) topology are generally known in the area of standard driver devices for lighting applications, as well as in the specific field of emergency lighting applications.

Isolated driver devices implement an isolation barrier between a first circuit and a second circuit of the driver device using a transformer. The isolation barrier between the first circuit on a primary side of the transformer and the second circuit on the secondary side of the transformer enables to isolate galvanically circuit parts with high voltages from circuit parts with safe lower voltages, thereby fulfilling SELV (Safety Extra Low Voltage) requirements. The first circuit on the primary side of the isolation barrier (SELV barrier) includes the mains supply interface, and therefore includes portions on a mains supply voltage level. The second circuit on the secondary side of the isolation barrier provides a load current to connected lighting devices, which the driving device supplies.

A control circuit, often implemented based on a microcontroller, controls the switch arranged in the primary circuit of the driver device implemented in flyback topology. The driver device may arrange the microcontroller for controlling the switch on the primary side of the isolation barrier.

The microcontroller may also provide the capability to measure, monitor, process, and/or record a mains supply voltage. Monitoring the mains supply voltage is a characteristic feature for emergency driver devices, which switch into an emergency mode of operation backed by a battery when detecting a mains supply failure. Thus, information on mains supply voltage needs not to be transferred over the isolation barrier.

In driving devices using a secondary side processing, however, the information on the actual mains supply voltage needs to be transferred over the isolation barrier in order to process the transferred information in a control circuit on the secondary side of the isolation barrier.

In order to transfer information such as an actual value or an actual state of the mains supply voltage over the isolation barrier, additional electronic circuit elements such as an optocoupler (sometimes called opto-isolator, optical isolator, photocoupler) are necessary. The optocoupler represents an additional and expensive circuit element and requires additional space on a printed circuit board, and therefore increases cost and complexity of the driver device when monitoring or measuring the supply voltage is a requirement.

<CIT> discloses a power converter that powers an LED fixture from a power supply.

The power converter comprises a primary circuit with a primary winding, and a switch in series connection with the primary winding. In a conductive state, the switch connects the primary winding to the power supply. A secondary circuit comprises a secondary winding that is coupled magnetically with the primary winding for providing power to the LED fixture in response to a switching of the switch. The power converter further comprises a sensing circuit configured to generate a signal representative of the output voltage of the secondary winding. An edge of the signal represents an edge of the output voltage of the secondary winding in response to the switching of the switch. A detecting circuit derives timing data from the edges of the signal, to estimate a load of the power converter from at least one output parameter of the power converter, and to determine a momentary value of a voltage of the power supply from the timing data and the estimated load of the power converter. <CIT> discloses a driver for operating LED loads. The driver comprises terminals for connecting at least one LED load, a circuit for providing a constant DC voltage starting from a mains voltage supply, a control unit, a switch in series with the LED load when connected to the terminals. The end of the switch opposite to the terminals is connected to ground potential. The control unit controls the switch with pulse width modulation for dimming. The driver comprises a detection circuit in parallel with the switch, which outputs a detection signal via a pin, the detection signal representing the potential at a connection point between the switch and the LED load.

Thus, it is an object of the invention to improve isolated, switched mode driver devices with a capability to at least detect, and even measure a mains supply voltage without increasing complexity and cost significantly.

The driver device in a first aspect and the method for operating the driver device in a second aspect according to the independent claims define the invention and provide solutions to the problem. The dependent claims define further advantageous features of the invention.

The driver device comprises a primary circuit including a controlled switch and supplied by a mains supply voltage, and a secondary circuit providing a load current. The driver device further comprises an isolation stage including a transformer with a primary winding and a secondary winding. The isolation stage is configured to isolate the primary circuit on a primary side and the secondary circuit on a secondary side by an isolation barrier. The driver device comprises a control circuit arranged on the secondary side of the isolation barrier. The transformer further comprises an additional secondary winding arranged on the secondary side. The additional secondary winding is in phase with the primary winding. The control circuit is configured to determine presence and/or a value of the mains supply voltage for a time in which the controlled switch is conducting based on a voltage signal provided by the additional secondary winding.

The driver device is a switched mode power supply (SMPS) in a flyback topology. The flyback topology provides isolation between a primary side and a secondary side by a SELV barrier.

The voltage signal provided by the additional secondary winding provides the basis for the control circuit on the secondary side of the transformer for determining presence or absence of the mains supply voltage. The voltage signal is in phase with the voltage across the primary winding of the transformer. The voltage induced in the secondary winding when the controlled switch is switched on (in a conducting state) is converted depending on a winding ratio between the primary winding and the additional secondary winding (measurement winding or auxiliary winding). The control circuit may accordingly determine presence or absence of a voltage over the primary winding of the transformer based on the voltage signal provided by the additional secondary winding. The control circuit may even determine (measure) a value of the voltage over the primary winding based on the voltage signal provided by the additional secondary winding, as long as this voltage signal depends on predetermined circuit parameters of the electronic circuit layout. The predetermined circuit parameters are in particular a winding ratio of the primary winding and the additional secondary winding.

Further predetermined electronic circuit parameters of the electronic circuitry are, e.g. for example electronic circuit parameters of resistive voltage divider stages, that process the voltage signal before it is supplied to the control circuit in form of a DC voltage. Thereby, a DC voltage provided to the control circuit tracks an actual value of the (rectified) mains supply voltage over the primary winding while the controlled switch is conducting. The rectified mains supply voltage depends on the mains supply voltage provided to the primary circuit of the driver circuit. The control circuit is enabled to convert the supplied DC voltage accordingly to an actual value (voltage amplitude value) of the mains supply voltage currently present at a mains supply input of the driver circuit.

Therefore, the driver device according to the first aspect provides the capability to determine presence, absence, or even an actual value of the mains supply voltage using the control circuit arranged on the secondary side of the isolation barrier without requiring an expensive optocoupler.

The voltage signal which is induced in the additional secondary winding is independent from a current load at a load output of the secondary circuit, as the voltage signal is induced during a time in which the switch of the primary circuit is in a conducting state. Thus load variations do not adversely affect the measurement of the mains supply voltage.

Determining values for the mains supply voltage enables to determine power consumption of the driver device and thereby to provide a key parameter for building automation and monitoring system, e.g. in order to perform power metering and collect power metering data from the individual devices connected to the communication interface.

The mains supply voltage may be a rectified AC mains supply voltage.

A dedicated primary side control circuit arranged on the primary side of the isolation barrier typically controls operation of the controlled switch of the primary circuit.

The dependent claims define further advantageous embodiments of the driver device.

The driver device according to a preferred embodiment comprises a rectifier circuit arranged on the secondary side of the isolation barrier. The rectifier circuit is configured to rectify the voltage signal provided by the additional secondary winding in order to generate a rectified voltage signal.

The rectifier circuit may include a first diode and a second diode.

The rectifier circuit may comprise a first resistor and a second resistor, wherein the first resistor and the second resistor are connected in series with the first diode.

According to an advantageous embodiment, the driver device comprises a peak detector circuit arranged on the secondary side of the isolation barrier for generating a DC voltage from the rectified voltage signal provided by the rectifier circuit.

The peak detector circuit can include a capacitor and a resistive divider network arranged in parallel with the capacitor.

The resistive divider network is configured to generate a DC voltage in a first voltage range from the rectified voltage signal for the AC mains supply voltage in a second voltage range. The first voltage range may be smaller than the second voltage range by at least one order of magnitude, in particular the second voltage range reaches from o V to <NUM> V and the first voltage range reaches from o V to <NUM> V.

Thus, the mains supply voltage can be measured by the control circuit after converting it into a usual voltage range for application to an analogue input of a microcontroller. The voltage applied to the control circuit is a stable DC voltage, which can be measured by the analogue to digital converter present in most current microcontroller circuits.

The control circuit according to an embodiment comprises an analogue-to-digital converter circuit configured to obtain the DC voltage provided by the peak detector circuit.

The control circuit can be configured to determine presence or absence of the mains supply voltage based on the DC voltage provided by the peak detector circuit. Alternatively or additionally, the control circuit is configured to calculate an actual value of the mains supply voltage based on the DC voltage provided by the peak detector circuit.

The control circuit according to an embodiment is configured to convert the DC voltage provided by the rectifier circuit to the value of the mains supply voltage based on (using) a predetermined winding ratio of the primary winding and the additional secondary winding.

The control circuit according to an embodiment is configured to convert the DC voltage provided by the rectifier circuit to the value of the mains supply voltage based on (using) electronic circuit parameter values of the rectifier circuit and the peak detector circuit.

According to an embodiment, the control circuit is configured to determine a frequency of the mains supply voltage based on the DC voltage.

The control circuit may be configured to record the determined value of the mains supply voltage in a memory.

The memory may be an internal memory of the control circuit, for example a memory storing a log file including one or more values of operating parameter(s) of the driver device. The memory may be a storage device arranged externally to the driver device, for example at a central control facility or a remote server.

The driver device comprises a transfer circuit configured to transfer mains supply voltage data determined by the control circuit over the isolation barrier to a communication interface of the driver device arranged on the primary side of the isolation barrier.

Thus, the mains supply voltage data, e.g. data on presence or absence of the mains supply voltage at a mains supply input of the driver device, or data including actual or historic voltage values of the mains supply voltage may be available externally to the driver device. Thus, power consumption calculations based on actual measurements or a monitoring of the mains supply concerning the individual driver device becomes possible without installing additional measurement equipment in the field. Optocouplers represent a possibility to implement the transfer circuit.

The communication interface may perform communication based on a wireless and/or wire-bound communication standard, in particular based on a DALI standard.

The Digital Addressable Lighting Interface (DALIRTM) enables network-based light devices. The extension D4i of the certified DALI-<NUM> standard in particular refers to collecting and storing of diagnostic and maintenance data, which explicitly include performance data of driver devices such as driver external supply voltage (mains supply voltage) and driver external supply frequency (electric grid frequency). The driver device according to the first aspect therefore offers advantages for implementing driver devices fulfilling corresponding requirements concerning measurement and/or monitoring of the external supply voltage of a driver device in a highly economical manner.

Determining amplitude values for the mains supply voltages enables to determine power consumption of the driver device and thereby to provide a key parameter for building automation and monitoring purposes.

According to an advantageous embodiment, the driver device includes the control circuit configured to determine a mains supply voltage frequency based on the voltage signal.

Knowledge on values or stability of the mains supply voltage at the input of the driver device may provide valuable insight into the AC supply network and support failure search in the AC supply network.

Preferably, the control circuit is a microcontroller circuit. Current microcontroller circuits include AD-converter circuits and corresponding AD-converter inputs and are therefore well suited to process the DC voltage provided by the rectifier circuit. Furthermore, the microcontroller circuit has the processing capability to convert the DC voltage to the corresponding value of the mains supply voltage based on the predetermined electric characteristics of the transformer, and the electric circuit parameters of the rectifier circuit and the peak detector circuit. The microcontroller circuit further offers the capability to record the determined AC mains supply voltage value in a memory of the driver device, for example in a log file including mains supply voltage data, or to generate a signal to a communication interface. The signal to the communication interface may include mains supply voltage data including one or more values for the mains supply voltage, and/or a time series of amplitude values of the mains supply voltage and/or frequency values of the mains supply voltage.

The driver device has a flyback converter topology. Additionally, the driver device may be an emergency driver device, in particular an emergency lighting driver device.

The second aspect concerns a method for operating a driver device comprising a switched mode power supply in a flyback topology, wherein the driver device comprises a primary circuit including a controlled switch. A mains supply voltage supplies the primary circuit. The driver device further comprises a secondary circuit providing a load current to a load, and an isolation stage including a transformer with a primary winding and a secondary winding. The isolation stage is configured to isolate the primary circuit on a primary side and the secondary circuit on a secondary side by an isolation barrier. The driver device comprises a control circuit arranged on the secondary side of the isolation barrier. The method is characterized by a step of providing a voltage signal by an additional secondary winding of the transformer on the secondary side, wherein the additional winding is arranged in phase with the primary winding. The method further comprises a step of determining, by the control circuit, presence of the mains supply voltage and/or an actual value (amplitude value) of the mains supply voltage for a time in which the controlled switch is conducting based on the voltage signal to generate mains supply voltage data.

The method further comprises a step of transferring, by a transfer circuit, the mains supply voltage data determined by the control circuit over the isolation barrier to a communication interface arranged on the primary side.

The discussion of embodiments refers to the figures, in which.

Same reference signs in different figures denote same or corresponding elements. The description of embodiments using the figures omits a discussion of same reference signs for different figures where considered possible without adversely affecting intelligibility for sake of a concise description.

<FIG> shows a simplified block diagram of a driver device <NUM> according to a preferred embodiment.

The driver device <NUM> comprises a primary circuit <NUM> including a controlled switch <NUM>. The driver device <NUM> is an isolated switched mode power supply (lamp driver, ballast) in a flyback topology.

The primary circuit <NUM> of the driver device <NUM> comprises a mains supply input <NUM> for connecting to an AC mains voltage (mains supply voltage VAC). The mains supply voltage VAC may be a 230V/<NUM> mains supply, for example.

The primary circuit <NUM> according to <FIG> includes characteristic elements of a mains supply interface, for example, an EMI filter <NUM> and a subsequent bridge rectifier <NUM>. The bridge rectifier <NUM> provides a rectified mains supply voltage VAC_RECT for the primary circuit <NUM> of the driver device <NUM>.

The driver device <NUM> comprises an isolation stage including a transformer <NUM>. The transformer <NUM> comprises a primary winding <NUM> forming part of the primary circuit <NUM> and a secondary winding <NUM> forming part of the secondary circuit <NUM>.

The isolation stage isolates the primary circuit <NUM> on a primary side and the secondary circuit on a secondary side by the isolation barrier <NUM>. The isolation barrier <NUM> is a SELV barrier providing galvanic separation (electric isolation) between the primary side and the secondary side.

Furthermore, the isolation barrier <NUM> provides galvanic isolation between the primary circuit <NUM> and the secondary circuit <NUM>.

The primary circuit <NUM> arranges a controlled switch <NUM> in series with the primary winding <NUM>.

primary side control circuit not shown in <FIG> controls the switch <NUM> to switch between a conducting state and a non-conducting state in a generally known manner for a SMPS, e.g. a flyback converter. The flyback topology provides isolation between the primary side and the secondary side by the isolation barrier <NUM>.

The secondary winding <NUM> of the transformer <NUM> forms part of the secondary circuit <NUM>.

The secondary circuit <NUM> of the driver device <NUM> generates a load current ILED (DC load current) and provides the generated load current ILED to a load <NUM>. The secondary circuit <NUM> includes a diode D3 and further circuit elements such as a secondary side LED driver <NUM> actually outputting the load current ILED.

The load may be a lighting module comprising one or more LEDs.

The transformer <NUM> further comprises an additional secondary winding <NUM> arranged on the secondary side. The additional secondary winding <NUM> is in phase with the primary winding <NUM> on the primary side. The additional secondary winding <NUM> provides a voltage signal VIND on the secondary side of the isolation barrier. During a time in which the switch <NUM> is controlled to be in a conducting state, the voltage signal VIND induced in the additional secondary winding <NUM> depends on the rectified mains supply voltage VAC_RECT and therefore also on the mains supply voltage VAC.

In particular, an amplitude value of the induced voltage signal VIND depends on the rectified mains supply voltage VAC_RECT, and further, additionally on a winding ratio of the transformer <NUM> comprising the additional secondary winding <NUM> and the primary winding <NUM>.

During the time in which the switch <NUM> is in the conducting state, the effects of the actual load <NUM> at the output of the secondary circuit <NUM> will be small.

The voltage signal VIND is input to a rectifier circuit <NUM>. The rectifier circuit <NUM> applies the voltage signal VIND to a resistor R1, a resistor R2 and a diode D1, which are arranged in series. The common terminal of the resistor R1 and the resistor R2 is connected to an anode of a (second) diode D2 of the rectifier circuit <NUM>. At the cathode terminal of the diode D2, the rectifier circuit <NUM> provides a rectified voltage VRECT.

The rectifier circuit <NUM> in particular enables to suppress influence from the load <NUM> on the rectified voltage VRECT.

The rectified voltage VRECT forms the input to a peak detector circuit <NUM>. The peak detector circuit <NUM> applies the rectified voltage VRECT over a capacitor C1. In parallel to the capacitor C1, the peak detector circuit <NUM> arranges a resistive divider network. The resistive divider network according to <FIG> includes two resistors, a resistor R3 and a resistor R4, which are connected in series. The peak detector circuit <NUM> provides at the common terminal of the resistors R3 and R4 an output in form of the DC voltage VDC over the resistor R4.

The peak detector circuit <NUM> in particular enables to generate a DC voltage in a suitable voltage range in order to be provided to an analogue-to-digital converter forming part of most current microprocessors.

The resistive divider network generates the DC voltage VDC in a first voltage range from the rectified voltage signal VRECT, The first voltage range is adapted to the input voltage range of the A/D-converter input terminal <NUM> of the control circuit <NUM>. The first voltage range may range from <NUM> V to <NUM> V, for example.

The peak detector circuit <NUM> provides the generated DC voltage VDC to the A/D-converter input <NUM> of the control circuit <NUM>. The driver device <NUM> comprises the control circuit <NUM> arranged on the secondary side of the isolation barrier <NUM>. The control circuit <NUM> preferably is a microcontroller circuit.

The control circuit <NUM> determines presence or absence of the mains supply voltage VAC and VAC_RECT for a time in which the controlled switch <NUM> is in a conducting state from the voltage signal VDC provided by peak detector circuit <NUM>. The voltage signal VDC provided by peak detector circuit <NUM> bases on the voltage signal VIND provided by the secondary winding <NUM>.

Additionally or alternatively, the control circuit <NUM> determines a value of the mains supply voltage VAC (and VAC_RECT) for a time in which the controlled switch <NUM> is conducting from the DC voltage VDC provided by peak detector circuit <NUM>. The DC voltage VDC provided by peak detector circuit <NUM> bases on the additional voltage signal VIND provided by the secondary winding <NUM>.

In particular, the control circuit <NUM> converts the actual value of the DC voltage VDC, which is a value in the first voltage range, into a voltage value for the mains supply voltage VAC, which is a voltage value in a second voltage range.

The first voltage range is typically smaller than the second voltage range by at least one order of magnitude. For example, the second voltage range reaches from o V to <NUM> V and the first voltage range reaches from <NUM> V to <NUM> V.

For determining from the actual value of the DC voltage VDC the corresponding actual value of the mains supply voltage VAC, the control circuit <NUM> may use a lookup-table. Alternatively, the control circuit <NUM> may be adapted to calculate the actual value of the mains supply voltage VAC from the measured actual value of the DC voltage VDC by using a mathematical formula, which regards the respective electric circuit parameters of the transformer <NUM>, the rectifier circuit <NUM> and the peak detector circuit <NUM>.

The control circuit <NUM> determines or measures the actual value of the mains supply voltage VAC_RECT over the primary winding <NUM> based on the voltage signal provided by the additional secondary winding <NUM>. The DC voltage VDC depends on predetermined circuit parameters of the electronic circuit layout, in particular the winding ratio of the primary winding <NUM> and the additional secondary winding <NUM>, and predetermined electronic circuit parameters of the electronic circuitry that processes the voltage signal VIND in order to generate the DC voltage VDC. Thereby, the DC voltage VDC provided to the A/D-converter input <NUM> of the control circuit <NUM> tracks an actual value of the (rectified) mains supply voltage VAC_RECT over the primary winding <NUM> while the controlled switch <NUM> is in the conducting state.

The control circuit <NUM> is enabled to convert the supplied DC voltage VDC accordingly to an actual value (actual voltage amplitude value) of the mains supply voltage VAC currently present at a mains supply input <NUM> of the driver circuit <NUM>.

A dedicated primary side control circuit not shown in <FIG> and arranged on the primary side of the isolation barrier <NUM> typically controls operation of the controlled switch <NUM> of the primary circuit <NUM>.

The control circuit <NUM> may determine and/or calculate further parameters of the AC mains supply to the driver device <NUM>.

In particular, the control circuit <NUM> may determine a frequency of the mains supply voltage VAC based on the voltage signal VIND.

The control circuit <NUM> may be configured to record the determined value of the mains supply voltage in a memory internal to the control circuit <NUM> or external to the control circuit <NUM>.

The memory may be an internal memory of the control circuit <NUM>, for example, a memory storing a log file including one or more values of operating parameter(s) of the driver device <NUM>. The memory may be a storage device externally to the driver device, for example at a central control facility or at a remote server.

The rectifier circuit <NUM> and the peak detector circuit <NUM> correspond to filtering circuitry arranged on the secondary side of the isolation barrier <NUM> for rectifying and filtering the voltage signal provided by the secondary winding <NUM> in order to generate the DC voltage signal VDC provided to the control circuit <NUM>.

The DC voltage VDC represents the filtered and rectified voltage signal VIND provided by the additional secondary winding <NUM>. The DC voltage VDC is scaled independently of the load current ILED provided by the secondary circuit <NUM> to the load <NUM>.

<FIG> presents a chart for illustrating peaks of mains supply voltage to a driver device <NUM> the embodiment uses for transfer over the isolation barrier <NUM>. <FIG> depicts characteristic curves for a driver device <NUM> implemented in a flyback topology.

The upper curve <NUM> of <FIG> depicts the actual mains power supply voltage VAC_RECT with a first time resolution of <NUM> per division.

The lower part of <FIG> depicts a curve <NUM> showing the actual mains power supply voltage VAC_RECT with a second time resolution of <NUM> per division. The lower curve <NUM> represents a zoom view of a portion of the upper curve <NUM>.

In particular, during a time period in which the switch <NUM> on the primary side of the isolation barrier <NUM> is in a conducting state, peaks of the mains power supply voltage VAC_RECT induce a voltage signal in the further secondary winding <NUM>. Thus, the further secondary winding <NUM> enables to transfer an information on the actual value of the mains power supply voltage VAC_RECT from the primary side of the isolation barrier <NUM> to the secondary side of the isolation barrier <NUM>.

<FIG> illustrates the interdependency between mains supply voltage and the DC voltage VDC at an input of the control circuit <NUM> according to an embodiment.

The voltage VDC is shown on the abscissa (x-axis) of the diagram in a range from <NUM> mV to <NUM> mV. The depicted range corresponds to a characteristic input voltage range of an A/D-converter input terminal <NUM> of a microcontroller implementing the control circuit <NUM>.

The corresponding mains supply voltage VAC, here the rectified mains supply voltage VAC_RECT, is shown on the ordinate (y-axis) of <FIG> ranging from <NUM> to <NUM> V.

<FIG> shows an almost linear dependency of the mains supply voltage VAC and the DC voltage VDC in a characteristic supply voltage amplitude range from <NUM> V to <NUM> V. <FIG> further shows that the linear dependency is independent from an actual load at the output of the driver device <NUM>. This is achieved by the electric circuit parameters and layout of the rectifier circuit <NUM> and the peak detection circuit <NUM> with the resistive divider network.

<FIG> demonstrates that the circuit topology of the rectifier circuit <NUM> and the peak detection circuit <NUM> enables to minimize a shift in the conversion from the actual measured DC voltage VDC. <NUM> to the mains supply voltage VAC,RECT due to different loads <NUM> at the output of the driver device <NUM>. The driver device <NUM> is therefore capable to provide an actual value for the mains supply voltage VAC_RECT, which is independent from a current load at the output of the driver device <NUM>.

<FIG> shows a block diagram of a driver device <NUM>' according to an embodiment including a communication interface <NUM>.

The driver device <NUM>' corresponds in most aspects to the driver device <NUM> discussed with reference to <FIG>. The driver device <NUM>' comprises a communication interface <NUM>.

The communication interface <NUM> is connected via signal lines <NUM> to a transfer circuit <NUM>. The transfer circuit <NUM> further is connected via signal lines <NUM> to the control circuit <NUM>. The signal lines <NUM>, <NUM> in combination with the transfer circuit <NUM> enable a bidirectional communication between the communication interface <NUM> arranged on the primary side of the isolation barrier <NUM> and the control circuit <NUM> on the secondary side of the isolation barrier <NUM>.

The transfer circuit <NUM> may use optocouplers(s) for transferring signals over the isolation barrier <NUM> without compromising the galvanic isolation between the primary side of the isolation barrier <NUM> and the secondary side of the isolation barrier <NUM>.

The control circuit <NUM> generates a signal including mains supply voltage information and transmits the signal to the communication interface <NUM> via the transfer circuit <NUM>.

The communication interface <NUM> depicted in <FIG> is a DALIRTM interface and is connected to an external bus via bus terminals <NUM>.

The external bus may be a wireless or a wired bus. The driver device <NUM>' can communicate with other devices via the external bus. In particular, the driver device <NUM>' may generate communication signals for transmission to the other devices including data such as the mains supply voltage information received from the control circuit <NUM> via the transfer circuit <NUM>. Data such as the mains supply voltage information received from the control circuit <NUM> via the transfer circuit <NUM> may be used to determine power consumption of the driver device <NUM>' and thereby to provide a key parameter for a building automation and monitoring system, e.g., in order to perform power metering and collect power metering data from the individual devices as, e.g., driver device <NUM>' connected to the communication interface <NUM>.

<FIG> illustrates method steps performed by the control circuit <NUM> for operating an isolated, primary side switched driver device <NUM>, <NUM>' according to an embodiment.

In step S1, the control circuit <NUM> obtains an actual voltage value VDC at the A/D-converter input terminal <NUM>.

In step S2, control circuit <NUM> determines a mains supply voltage information based on the obtained DC voltage value VDC. In particular, the control circuit <NUM> converts the obtained DC voltage value VDC into a value of the actual mains supply voltage VAC corresponding to the obtained actual voltage value of the DC voltage VDC. The control circuit <NUM> may determine from the obtained actual voltage value of the DC voltage VDC whether a mains supply voltage VAC is currently present at the mains supply input <NUM> of the driver device <NUM>, <NUM>'.

The control circuit <NUM> may record the determined actual value of the mains supply voltage VAC in the memory.

Claim 1:
Driver device comprising a switched mode power supply in a flyback topology, the driver device comprising
a primary circuit (<NUM>) including a controlled switch (<NUM>) and supplied by a mains supply voltage (VAC),
a secondary circuit (<NUM>) configured to provide a load current (ILED),
an isolation stage including a transformer (<NUM>) with a primary winding (<NUM>) and a secondary winding (<NUM>), the isolation stage configured to isolate the primary circuit (<NUM>) on a primary side and the secondary circuit (<NUM>) on a secondary side by an isolation barrier (<NUM>), and
a control circuit (<NUM>) arranged on the secondary side, and whereby
the transformer (<NUM>) comprises an additional secondary winding (<NUM>) arranged in phase with the primary winding (<NUM>) on the secondary side, and
characterized in that the control circuit (<NUM>) is configured to determine presence and/or a value of the mains supply voltage (VAC) for a time in which the controlled switch (<NUM>) is conducting based on a voltage signal (VIND) provided by the additional secondary winding (<NUM>) for generating mains supply voltage data, and
the driver device comprises a transfer circuit (<NUM>) configured to transfer the mains supply voltage data determined by the control circuit (<NUM>) over the isolation barrier (<NUM>) to a communication interface (<NUM>) arranged on the primary side.