Patent Description:
DC/AC detection circuitries for driver for lighting means are known as such. They often rely on a comparison of the input AC voltage with threshold values, so that the presence or non-presence of the input voltage crossing the threshold values can be used for detecting the lack of an AC voltage or the presence of a DC voltage, for example, for emergency lighting devices. <CIT> discloses a known driver for lighting means being capable of converting an analog voltage signal corresponding to the line voltage to digital values indicating a waveform of the line voltage, calculating slopes corresponding to rising edges of the waveform using select values of the digital values, and determining a value of the line voltage based on the calculated slopes. <CIT> discloses a known isolated converter having a detection circuitry being arranged on a secondary side of the isolated converter. <CIT> discloses a known isolated converter having a detection circuitry being arranged on a primary side of the isolated converter.

Various arrangements for lighting systems are known which provide both conventional and emergency lighting devices. Such emergency lighting devices are intended to be activated when the conventional lighting is no longer operative, because the mains voltage supplied to the conventional lighting device is no longer available or malfunctions. An emergency lighting device is typically powered by a battery or other energy storage device.

A conventional lighting device is controlled by an on/off switch by means of which a user (or control system) can control whether the lighting is illuminated or not. Generally, the emergency lighting device is intended to be automatically illuminated when the absence of mains power or the malfunction of mains power for the conventional lighting device is detected in some way.

A lighting system comprising an emergency lighting device and a conventional lighting device may be considered to have two operating modes. In a normal mode, when the direct mains supply is operating, normally (within the normal voltage range), a switched mains input, controlled by an on/off switch, is monitored, and the lamp is illuminated or extinguished in dependence upon the switched mains input.

In an emergency mode, when the mains supply is not available or is malfunctioning (is outside the normal voltage range), the lamp is illuminated automatically, irrespective of the status of the switched mains input, using power from a battery or other storage element.

In some lighting systems it is possible to power the lamp in an emergency from a DC voltage at the mains input (which is normally powered by AC), provided from a centralized battery storage system.

Therefore, there is a need for an improved driver allowing to measure the frequency and voltage of an AC voltage, in particular, of a mains voltage.

The object of the present disclosure is achieved by a driver for an LED load according to claim <NUM>.

Advantageous implementations of the present disclosure are further defined in the dependent claims.

According to a first aspect, the disclosure relates to a driver for an LED load, comprising: input terminals for an optionally rectified AC voltage or AC voltage or DC voltage; output terminals for supplying the LED load, a detection circuitry connected to the input terminals, configured to obtain a signal representing a frequency of the AC voltage and an amplitude of a peak of each cycle of the AC voltage, and a control circuit being connected to the detection circuitry and supplied with said signal. The driver comprises a switched isolated converter, wherein the control circuit is arranged on a secondary side of the isolated converter, and the detection circuitry is arranged on a primary side of the isolated converter. The detection circuitry comprises a reference diode being configured to compare the AC voltage with a defined threshold voltage, and said signal includes timings of the AC voltage crossing the threshold value.

This provides the advantage that lower component counts and costs are achieved. Moreover, higher miniaturization is achieved due to the lower component count and, furthermore, there is no need for a primary side controller in order to obtain the signal, since the control circuit can be situated on the secondary side of the driver.

In an embodiment, the control circuit is configured to adapt an operation parameter of the driver depending on the signal supplied to the control circuit.

This provides the advantage that the operation of the driver can easily be chosen depending on the operation parameter.

In an embodiment, the control circuit is configured to send out an information derived from the signal over a wire-bound or a wireless interface of the driver.

This provides the advantage that the information can be sent out in an efficient and well-known way.

In an embodiment, the control circuit is configured to respond to the signal by switching an operation of the LED load to an emergency lighting means operation.

In an embodiment, the detection circuitry is configured to determine a rising edge threshold crossing of the AC voltage in order to produce the signal indicating the frequency of the AC voltage.

In an embodiment, the detection circuitry is configured to determine a time duration between the rising edge threshold crossing and a falling edge threshold crossing of the AC voltage in order to produce the signal indicating the peak amplitude of the AC voltage.

In an embodiment, the control circuit is configured to access a look-up table in order to convert the time duration between a rising edge threshold crossing and a falling edge threshold crossing of the AC voltage into a peak voltage value of the AC voltage.

In an embodiment, the driver comprises a flyback converter.

In an embodiment, the control circuit comprises a DALI interface.

According to a second aspect, the invention relates to a system comprising a central unit circuit connected to a driver according to the first aspect or any one of the implementation forms thereof, the driver being configured to communicate the peak voltage and the frequency of the AC voltage supplied to the driver to the central unit.

According to yet another aspect, the invention relates to an emergency lighting unit, comprising a driver as defined above as well as and LED load supplied by said driver.

Aspects of the present invention are described herein in the context of a driver for lighting means.

Various aspects of a driver for lighting means will be presented.

The term "LED luminaire" shall mean a luminaire with a light source comprising one or more LEDs or OLEDs. LEDs are well-known in the art, and therefore, will only briefly be discussed to provide a complete description of the invention.

Now referring to <FIG>, a driver <NUM> for lighting means is shown.

The driver for lighting means <NUM> comprises:.

The frequency of the peak of threshold crossing events can be used in order to have an information as to the frequency of the AC voltage.

Furthermore, the duty cycle (Ton time) of the time periods, during which the supplied AC voltage is higher than a given threshold value can be used by the control circuit in order to determine, for example, using an analytical function or a look-up table, the mains voltage peak value at a given frequency.

Information as to the mains voltage amplitude and the frequency can be used, for example, to change operating parameters of the driving circuitry. One example is the switching from regular lighting operation to an emergency lighting operation mode as described above, wherein the lighting means are supplied off a DC voltage, e.g. supplied by a central or local battery.

Furthermore, this information can be send out, for example, upon request over a bus communication, such as, for example, a DALI bus.

For flyback / buck topologies of the driver <NUM> with a microcontroller on a secondary side, the circuit shown in <FIG> can be used as detection circuit <NUM> to detect, for example, a mains state (AC, DC or no mains). The mains voltage is divided by a resistive divider having resistors R100, R101 and R102 and fed to a threshold element, such as e.g. a reference diode. If the voltage is higher than the threshold voltage implemented by the diode, the diode conducts. The output signal of the threshold element can be transmitted in a galvanically isolating manner. In the embodiment, the diode current flows through a LED of an optocoupler U100 so that the photo transistor of U100 conducts. On the secondary side of the optocoupler, this leads to the signal AC shown in <FIG>, wherein the curve <NUM> represents a mains voltage and the curve <NUM> represents a reference signal <NUM>.

In an embodiment, the signal shown in <FIG> can also be used for measuring the mains frequency. If the time between every rising edges is counted delta_t, the frequency f can be calculated as f = <NUM> / (delta_t * <NUM>).

In another embodiment, for mains voltage measurement, the pulse width of the on pulse has to be counted. The pulse width is relating to the peak voltage of the input signal and, therefore, also to the effective mains voltage.

A look-up table in the microcontroller or control circuit <NUM> can give the resulting input voltage for one specific frequency, as shown in <FIG>, wherein on times are shown as a function of mains voltage. For the curve <NUM>, the frequency is <NUM>, for the curve <NUM>, the frequency is <NUM>, while for the curve <NUM>, the frequency is <NUM>.

In this embodiment, it is not necessary to store look-up tables for all possible frequencies in the microcontroller. If the look-up table of one specific frequency is known, the mains voltage can be scaled simply by the factor of the frequency given in the look-up table over the measured frequency (f_lookuptable / f_measured).

Moreover, depending on the required accuracy, the following options can be used to save memory:.

Furthermore, in order to increase the accuracy, the following options can be used:.

As mentioned above and as it can be seen in <FIG>, for different frequencies, different on time/mains voltage curves can be prepared, which can lead to high requirements on the memory power.

Therefore, in another embodiment, only a limited number or even only one on time (t) / mains voltage curve is available, which is then calibrated as mentioned above. This advantageously leads to a reduction of data to be provided in a memory.

Therefore, by measuring the on time and the off time of an already existing AC/DC detection signal, the mains frequency as well as the mains voltage can be calculated. By making use of specific algorithms, this works for different mains frequencies with the same accuracy without the need of additional memory or look-up tables.

Moreover, during the manufacturing of the device, each device itself can be calibrated, such that the curve stored in the look-up table actually corresponds to that specific device.

<FIG> shows a system <NUM> comprising a driver <NUM> for lighting means according to an embodiment.

The system <NUM> shown in <FIG> comprises an LED driver <NUM> with a circuitry and frequency/amplitude evaluation as described before. Furthermore, the system <NUM> comprises a DALI control unit <NUM>, which pulls the information from the driver <NUM> and may be adapted to send it to a data gathering/processing unit <NUM>, which might be a central unit of a building in order, for example, to determine the power consumption of different appliances in a building.

In general, the LED driver <NUM> is configured to measure, for example, the mains data and the DALI control <NUM> is configured to query the mains data, such as mains voltage, mains current, mains power, mains frequency, etc. Those data can, then, be used by any algorithm for further data analysis (e.g., tracking power consumption for calculating energy cost). This algorithm can be cloud based or local.

Communication protocols such as e.g. "DALI <NUM> extensions" may command mains voltage and frequency measurements to be executed by the driver, e.g. triggered by a (e.g. extended) DALI command over a bus interface of the driver.

As shown in the embodiment, the driver may be an isolated driver. the isolation can be implemented by a transformer such as e.g. the transformer of a switched isolated converter, such as e.g. a flyback converter.

The detection circuit is arranged on the primary (mains) side of the isolation stage of the driver. The control circuit may be arrange on the primary side or the secondary side of the isolation stage. In the latter alternative, the detection circuit sends the detection signal to the control circuit e.g. using an optocoupler.

The control circuit may be a microcontroller.

The control circuit may be arranged on the secondary side of the isolated driver, and furthermore, to issue a control signal to a switch of a switched converter (e.g. buck or boost converter) arranged on the secondary side of the switched isolated converter.

Claim 1:
Driver (<NUM>) for an LED load (<NUM>) comprising:
- input terminals (101a, 101b) for an AC voltage;
- output terminals (104a, 104b) for supplying the LED load (<NUM>),
- a detection circuitry (<NUM>) configured to obtain a signal representing a frequency of the AC voltage and an amplitude of a peak of each cycle of the AC voltage, and
- a control circuit (<NUM>) being connected to the detection circuitry (<NUM>) and supplied with said signal,
wherein the driver (<NUM>) comprises a switched isolated converter,
wherein the control circuit (<NUM>) is arranged on a secondary side of the switched isolated converter,
wherein the detection circuitry (<NUM>) comprises a reference diode being configured to compare the AC voltage with a defined threshold voltage, and
wherein said signal includes timings of the AC voltage crossing the threshold voltage,
characterized in that:
the detection circuit (<NUM>) is connected to the input terminals (101a, 101b), wherein the detection circuit (<NUM>) is arranged on a primary side of the switched isolated converter.