Technical Field

The invention relates to a load type detection method.

In particular, the invention relates to an automatic load type detection method for universal dimmer devices, which are used for dimming and controlling the light in lighting systems, allowing to adjust the current supplied to a load connected to the device.

Background of the Invention

The dimmable lighting system, that is, the lighting system with adjustable lighting level, basically consists of 2 parts. The first is a commercially available light source suitable for dimming; The second is dimmers, which are control devices that create electrical voltage according to the desired lighting level and suitable for the first element.

Dimmer devices are devices that are generally used in lighting systems to dim and control the light, and to adjust the current supplied to a load connected to the device.

Dimmer devices work with the principle of dimming the RMS- root mean square value of the alternating current with forward-phase dimming and reverse-phase dimming (reverse-phase dimming) methods.

In the forward-phase dimming method, the current is cut at the zero crossing of the voltage signal and can be turned on at any point of the voltage signal according to the dimming level. In the reverse-phase dimming method, the current opens at the zero crossing of the voltage signal and can be cut at any point of the voltage signal according to the dimming level. When controlling capacitive loads, the voltage should always be turned on at the zero crossing of the voltage signal in order to avoid high inrush current. Therefore, reverse-phase dimming method is used in capacitive loads.

When controlling inductive loads, the current should always be interrupted at the zero crossing of the voltage signal in order to avoid sudden voltage spikes due to electromagnetic induction. Therefore, forward-phase dimming method is used in inductive loads.

Universal dimmers are devices that can control all three load types (resistive, capacitive and inductive). These devices can control all load types using the current throttling method suitable for the type of load connected. Automatic load type detection is very important in order not to damage the equipment of the device and to control the connected load stably.

One of the available techniques for automatic load type detection; It is based on a short current signal to the load connected to the device. As soon as the current supplied to the load is cut off, the device determines the type of load by measuring the voltage on the load. When the current to the inductive loads is interrupted, a voltage rise occurs due to electromagnetic induction.

The device decides whether the load type is inductive or not by comparing the measured voltage with a threshold value. If the load type is inductively determined, the connected load is controlled by the forward-phase dimming method. If the load type is not detected inductively, the connected load is controlled by the reversephase dimming method.

Another technique that provides automatic load type detection is the voltage ringing effect caused by inductive loads.

In this technique, the load connected to the device is primarily controlled by the reverse-phase dimming method. In the reverse-phase dimming method, a voltage resonant effect occurs on inductive loads as the voltage supplied to the load connected to the device is suddenly cut off at the peak of the voltage signal. The technique in question is based on the detection of this ringing effect. When the ringing effect is detected, the type of load connected to the device is determined inductively. However, this ringing effect causes high voltage jumps in the electronic circuit and can damage the circuit elements.

Therefore, the use of this technique causes the need for protective elements against the ringing effect in the circuit and increases the cost.

Yet in another previous technique; The load type is determined by measuring the time between zero crossings of the current and voltage signals on the load. In inductive loads, the current signal lags behind the voltage signal. In capacitive loads, the current signal is ahead of the voltage signal. By measuring the time differences between the zero crossing points of the two signals, the phase difference between the signals is calculated.

The direction and magnitude of the phase difference and the load type are determined. However, the zero-crossing points of the current signals drawn by some low-power dimmable LED lamps with capacitive load type are not obvious since they have very low current values at the time of zero-crossing.

Therefore, techniques that determine the load type by only looking at the time between current and voltage zero-crossings can cause dimmable LED lamps to be misclassified.

In the European patent application numbered EP0618667B1 in the literature, “Using semiconductor switches which can be turned off, it is possible to control the alternating current flowing through a load using the phase-gating principle or the phase-chopping principle. However, it is necessary to operate with phase-gating for an inductive load and with phase-chopping for a capacitive load. A method and a device are intended to be created which allow no attention to be paid to the respective type of load. To this end, according to the invention, a test program is initiated first of all when the mains voltage is applied, by means of which the type of load is determined and, subsequently, phase-gating is used for an inductive load and phase-chopping for a capacitive and/or resistive load.” statements are included. In said application, a dimming method and inductive load detection in lighting devices are disclosed.

Again, in the European patent application numbered EP1313205B1 in the literature, "The device has a rectifier, load switch, devices for detecting voltage and current null crossings and a control unit that periodically switches the load switch on and off, determines a first interval's start and stop times from current and voltage null crossings with the load switch on, determines second interval start and stop times from the voltage and current null crossings with the load switch off and compares intervals to determine load type. The device has a rectifier circuit, a load switch connected to the rectifier output, devices for detecting voltage and current null crossings and a control unit that periodically switches the load switch on and off, determines a first interval's (tEA) start and stop times from the current and voltage null crossings with the load switch on, determines second interval's (tAE) start and stop times from the voltage and current null crossings with the load switch off and compares the lengths of the intervals to determine the type of load.” statements are included.

In the mentioned application, the method of determining the load type by phase difference measurement of the lighting load is disclosed.

Again in the literature, in the US patent application numbered US8698466B2, "Disclosed is an inductive load detection circuit for detecting the presence of an inductive load on a dimmer circuit. The detection circuit provides for enhanced detection of the inductive load by detecting voltage ringing resulting from a turn-off of a switching element in the circuit. The ringing can be enhanced by providing a faster turn-off rate in an initial period than a turn-off rate in a steady state period. Also disclosed is a dimmer circuit comprising the inductive load detection circuit.” statements are included.

In the mentioned application, voltage ringing effect and inductive load detection method are disclosed. For the reasons mentioned above, a new automatic load type detection method was needed for universal dimmer devices.

Purpose of the Invention

Starting from this position of the technique, the aim of the invention is to introduce a new automatic load type detection method for universal dimmer devices that eliminates the existing disadvantages.

Another aim of the invention is to present a method that enables to detect whether the load connected to the device has a linear circuit or not.

Another aim of the invention is to provide a method in which even low power dimmable LED lamps with capacitive load type can be detected safely.

Another aim of the invention is to introduce a method in which only the full mains voltage is supplied to the connected load during the load type determination and the load type can be determined without using a false current throttling method.

Explanation of Figures

Figure - 1 View of the algorithm that detects whether the current signal is sinusoidal in the load type detection method for the universal dimmer devices that are the subject of the invention

Figure - 2 The view of the algorithm that detects the load type for the universal dimmer devices that are the subject of the invention

Figure - 3 Graphical view of the comparison of a sample LED lamp current signal with hypothetical sinusoidal

Figure - 4 Graphical view of the method of finding the phase difference between the zero crossings of current and voltage signals

Reference Numbers

1. Current Signal 2. Hypothetical Sinusoidal

3. Difference Between Hypothetical Sinusoidal Equivalent Points of Current Signal

4. Voltage Signal on Inductive Load

5. Current Signal on Inductive Load

6. Phase Difference Between Current and Voltage Signals Zero Crossings

Reference Numbers of Method Steps

100. Sampling of Current Signal

200. Normalization of Current Samples

300. Calculation of Root Mean Squared Error of Current Signal by Comparison with a Hypothetical Sinusoidal

400. Comparison of the Calculated Root Mean Error Value with an Experimentally Determined Threshold Value

500. Determination of Linearity of Load Circuit by Whether the Current Signal is Sinusoidal or not

600. Deciding on Load Type by Calculating Phase Difference Between Current and Voltage Signals Zero Crossings

Detailed Description of the Invention

In this detailed explanation, the innovation, which is the subject of the invention, is explained only with examples that will not have any limiting effect for a better understanding of the subject.

The invention is an automatic load type detection method for universal dimmer devices, which are used for dimming and controlling the light in lighting systems, allowing to adjust the current supplied to a load connected to the device, characterized in that; includes method steps; sampling of the current signal (1) (100) supplied to a load connected to the device, normalizing the current samples (200) to prevent the current amplitude from affecting the error calculation, calculating the root mean-squared error of current signal (1) by comparison with the hypothetical sinusoidal (2) (300) in order to determine whether the relevant current signal (1) resembles a sinusoidal or not, comparison of the calculated root mean error value with an experimentally determined threshold value to decide whether the signal is sinusoidal or not (400) and determining the linearity of the load circuit by whether the current signal (1) is sinusoidal or not (500).

In Figure-1 , the view of the algorithm that detects whether the current signal is sinusoidal in the load type detection method for the universal dimmer devices, which is the subject of the invention, is illustrated.

In Figure - 2, the view of the algorithm that detects the load type for the universal dimmer devices, which is the subject of the invention, is illustrated.

Figure - 3 illustrates the graphic view of the comparison of the low power LED lamp current signal (1) with the hypothetical sinusoidal (2).

Figure - 4 illustrates the graphical view of the method of finding the phase difference between current and voltage signals zero crossings (6).

The invention is an automatic load type detection technique used in universal dimmer devices. In a prior art, the determination of the load type is provided by measuring the phase difference between current and voltage signals zero crossings (6) and finding the phase difference. This technique was developed with linear circuit loads in mind.

In linear circuit loads, when a sinusoidal voltage signal with frequency f is given to the load, the current passing through the load becomes a sinusoidal with frequency f. However, most dimmable LED and CFL lamps have a non-linear circuit and draw a non-sinusoidal current when a sinusoidal voltage signal is given.

Especially in low-power LED lamps, zero-crossings of the current signal cannot be detected precisely because the current value has very low values at the points near the zero-crossing of the current signal (1). This causes the aforementioned prior art to not produce accurate results in lamps with non-linear circuits such as dimmable LEDs. In the present invention, the current signal (1) given to a load connected to the device is sampled (100) firstly and the obtained current samples are normalized (200), then the root mean square error is calculated by comparing the said current signal (1) with a hypothetical sinusoidal (2). (300). In order to determine whether the said current signal (1) is sinusoidal, the current signal (1) is first sampled for half a period.

Here, the hypothetical sinusoidal (2) is formed by calculating the shape that the current signal (1) should have when a real sinusoidal is assumed. In a true sinusoidal, the apex of the sinusoidal is the midpoint of the two zero-crossing points. Therefore, the peak of the hypothetical sinusoidal (2) is also calculated as the midpoint of the current signal (1).

Looking at the aforementioned Figure-3, it can be seen that the peak of the hypothetical sinusoidal (2) and the midpoint of the current signal (1) intersect. When calculating the root mean squared error, the squares of the differences between the corresponding points of the current signal (1) and the hypothetical sinusoidal (2) (3) are taken. The square root of the arithmetic mean of these squares gives the root mean square error (RMSE).

Root Mean Squre Error

By comparing the calculated root mean square error value with an experimentally determined threshold value (400), it is decided whether the current signal is sinusoidal or not.

The linearity of the load circuit is determined (500) by whether the current signal is sinusoidal or not. In other words, it is decided whether it is a dimmable (dimmable) LED lamp or CFL.

If the current signal is not sinusoidal, the load connected to the device does not have a linear circuit. In the present invention, such loads are classified as capacitive LED or CFL. If the current signal is sinusoidal, the load connected to the device has a linear circuit. Therefore, zero crossings are evident and the load type is decided by calculating the phase difference between the current and voltage signals zero crossings (6) (600).

When the current signal on the inductive load (5) is detected as sinusoidal, the steps (600) to decide the load type are applied by calculating the phase difference between current and voltage signals zero crossings (6) belonging to the prior art.

The phase difference between the positive or negative current and voltage signals zero crossings (6) is obtained by subtracting the value of the microcontroller time counter at the moment of zero crossing of the current signal on the inductive load (5) and the value of the time counter of the microcontroller at the moment of zero crossing of the voltage signal on the inductive load (4).

The phase difference between current and voltage signals zero crossings (6) is compared with the experimentally determined positive and negative threshold values. If the phase difference between current and voltage signals zero crossings (6) is higher than the positive threshold value, the load type is inductive; if it is lower than the negative threshold, the load type is capacitive; and threshold values, the load type is determined as resistive.