FI124042B - Control systems for lighting matrices, especially LED matrices - Google Patents

Description

Control system for lighting arrays, in particular LED arrays

The invention relates to a method for supplying power 5 to luminaire arrays according to the preamble of claim 1.

The invention also relates to a lighting matrix control system.

The use of LEDs in lighting is increasing rapidly as they achieve good efficiency.

The problem with the prior art is that a lamp of high luminous efficacy has to be fitted with several rows of LEDs, since only 40 V / 3 V LEDs can be placed in one row. The voltage limitation is due to the fact that 40 V is considered a safe voltage. 15 Rows cannot be connected in parallel because the characteristic of the LED is very non-linear and the voltage control leads to an indefinite power in each LED row.

Thus, the known solution is that a chopper operating with a normal electric coil generates a voltage of> 40 V and utilizing this voltage each LED line (different colors or one color) 2 0 is controlled by separate hackers.

Thus, in practical known solutions, it is necessary to mow the current in each row and control the chipper for each row. This results in an N-row lamp requiring ™ one N + l chipper and a color-adjustable LED system 3N + 1 chipper.

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The object of the invention is to solve the prior art problems described above and, for this purpose, to provide a completely new type of method and system for power supply.

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oo σ> c \ j 30 The method is based on the fact that with a normal chipper, either using mechanical or electrical energy storage, a variety of frequencies are generated by pulse modulation. Each frequency is routed through a filter (either mechanical or electrical) to the desired LED array.

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Led: The amplitude and phase of the current through the array (or the common current across all arrays) is measured and phase information is used to lock each frequency to the frequency of the resonant circuit in question. Amplitude is used to control the light output of the LED array.

5 When using mechanical resonances, either a piezo-crystal with an additional oscillator attached to adjust the impedance level and frequency is used. Another option is to use a mechanical vibrator based on a permanent magnet, which is already inherently impedance compatible. In particular, the magnetically controlled vibrator can also be used to cool the LEDs. In this case, automatically higher power will result in 10 more powerful ventilation.

More specifically, the method according to the invention is characterized in what is stated in the characterizing part of claim 1.

The system according to the invention, in turn, is characterized by what is stated in the characterizing part of claim 10.

The invention provides considerable advantages.

The method according to the invention makes it possible to control LED luminaires as well as other luminaires with good efficiency, small size and low cost electronics.

The invention makes it possible to a) reduce the size of the main chopper (if a mechanical "coil" is used) ^ and b) the chips controlling the LED rows can be replaced by a resonant circuit (mechanical or cm 2 electric). The method also allows the control of a plurality of separate lamps or a row of lamps so that only the current of the main chopper is measured.

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The invention will now be described, by way of example and with reference to the accompanying drawings, with reference to the accompanying drawings, (CT) K 30 Figure 1 schematically illustrates one lamp according to the invention with a power supply device.

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Figure 2 is a graph showing the power supply waveform used in the invention.

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Figure 3 graphically illustrates a waveform of the invention which is a filtered chopper output.

Fig. 4a shows the substitution of piezo-crystal.

Fig. 4b shows a replacement circuit for a magnetically controlled vibrator.

The lighting is usually controlled by separate switches and the LEDs have 10 switches for each LED, which measures the current and adjusts the voltage as needed. The present invention provides a method in which each lamp or row of lamps is controlled by a single chopper utilizing frequency multiplexing.

Figure 1 illustrates in general a method for controlling light. A switch consisting of a switch 5 15 generates a pulse width modulation based signal of FIG. 2. The coil associated with the chopper (usually also the additional capacitance to ground) filters the signal so that the final envelope is substantially as shown in Figure 3.

Typically, the output of the chopper 5 is a DC voltage, but in the present invention the "DC voltage" 20 varies so that it contains N signals of different frequencies. After filtering, the signal is as in Figure 3. In Figure 3, the three normalized frequencies are: 1, 1.4, 1.7. The frequency ranges are selected only because the signal shape is seen for a few periods. In practice, the frequency differences are smaller. Since the energy storage 4 behind the chopper 5 is also capacitively loaded, this must be taken into account in the design of cnj, 2 5, o cp ^ The signal of Fig. 3 is coupled through the resonant circuits 2 of Fig. into connected LED rows 21. 1

Each line-specific resonant circuit 2 "selects" from the signal only a frequency corresponding to its own resonant frequency (O) 0]. The amplitudes of the different sines determine how much power is applied to each LED array 21. Because the LED has a very non-linear characteristic (the voltage across it is almost constant), power must be controlled by the current. Since the current in each row is at 4 different frequencies, it is sufficient to measure only the total current and by separating the different frequency components, for example by means of a phase-locked loop, the currents of each LED row are determined separately. The measurement can be made directly from the current of the coil connected to the chopper 5 by induction, by applying a magnetometer 3 (MEMS or whatever) to the conductor or, of course, by means of a separate resistor 5. However, a resistor is a disadvantage because it consumes power. Magnetometer 3 is useful because it measures both the DC component and all AC components. Of course, the current of each line can be measured individually, as is the case today, but it increases the cost of the device unnecessarily. This alternative is also illustrated in Fig. 1. The current is made desirable by individually adjusting the amplitudes of the various voltages by controlling 10 phase-modulated signals (see Fig. 2).

Since the frequency of the resonant circuit 2 may differ significantly from the nominal one, the frequencies produced by the chopper 5 need to be adaptively adapted to correspond to the frequencies of the resonant circuits 2. This can be easily done by measuring the phases of the currents in relation to the phases of the voltages 15 and adjusting the frequency of the voltages accordingly. All in all, the measurement is done simply by measuring the amplitudes and phases of the currents with a phase-sensitive detector and adjusting the amplitudes of the voltages for power control and the steps for adjusting the frequencies to resonant circuits.

2 0 Resonant circuits

The resonant circuit 2 can be realized by serial connection of the coil and capacitor in the normal way.

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δ 2 5 Switching provides a reasonable situation where only less than 2% of power is lost. The problem O) is more of a size because a small-loss transformer at a reasonably low frequency ^ requires a large coil.

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In general, mechanical resonance is capable of storing energy in excess of σ> o] 30 an electric coil of equivalent size. This means that the resonant circuit should be realized by a mechanical resonant circuit. We can use either a piezo-oscillator oscillator or a magnetic current-controlled resonant circuit. In addition to its small size, the mechanical resonance circuit 5 has the advantage of having a high index of goodness. In addition, it is possible to integrate a mechanical vibrator near the LEDs so that we can also use motion to ventilate the LEDs. Of course, in this case, we use the power for ventilation.

However, this is a less expensive way compared to installing a fan or 5 large metal radiator strips in the luminaire.

Fig. 4a shows a substitution of a piezo-crystal. Due to the piezo parallel capacitance 12, the structure generates both a series resonance that determines mechanical resonance as well as a parallel resonance which is dependent on both mechanical resonance and stray capacitance.

However, the oscillator is preferably used in series resonance, so the stray capacitance is irrelevant. However, it appears as a capacitive load, so it should be taken into account in the overall system design. With a typical crystal, the effective series resistor 13 is reasonably high, so the efficiency remains poor. Of course, making a thin and wide crystal will reduce the series resistor 13. However, it is preferable to apply mechanical resonance on the crystal so as to reduce the effective series resistance. In this situation, the resonant frequency is determined by the extra resonant circuit and the piezo-actuator acts only as a device to convert the voltage into motion. In Fig. 4a, reference numeral 10 denotes the coil in the alternate circuit and reference numeral 11 the serial capacitance.

2 0 If we use a magnetically controlled oscillator in the resonant circuit, we can depict it by the alternate circuit shown in Fig. 4b. The magnetic resonance circuit is based on the force exerted by the current passing through the permanent magnet 15 and the coil 14. In this solution, it is possible to choose whether the coil 14 is moving (compare loudspeaker) or the magnet 15. If the coupling coefficient is high, the circuit edust represents a ground resonant circuit. Power is well coupled to LEDs at a single cvj ^ 2 5 frequency, but tends to "short-circuit" currents for other LEDs. It is therefore advantageous to put a capacitor in series after the coil, whereby the mechanical resonant circuit acts as an efficient coil and generates a series resonant circuit with the capacitor. In this case of x o, the other frequencies see this resonant circuit as open.

o0 o) 30 The mechanical resonance circuit can also be used in a chopper to reduce losses.

° In this context, it is also advantageous to include a transformer in this connection. This means, in the case of piezo, that the piezo body forms a single structure in terms of mechanical vibration 6, but is provided with an intermediate electrode for picking up the output power. In a magnetic vibrator, two coils are introduced into the system and the speeds are selected so that the desired conversion ratio is achieved.

5 Since the diodes are not completely identical and may be broken by one, the LED array can rectify the signal. Rectification itself is not detrimental as it only biases the diodes to a different operating point. In this solution, breaking the single diode does not completely turn off the lamp. Due to self-biasing and alternating electricity, the remaining diodes provide light output.

SUMMARY This invention discloses a method in which lamps, and in particular LED lamps, can be controlled by a single chip using frequency multiplexing. The procedure also results in the currents (wattages) of all lamps being measured with a single current meter. Further, this application describes the utilization of mechanical resonance for making frequency filters. The method according to the invention is clearly less expensive than the present solutions and smaller in size. The efficiency is at least of the same order as the current solutions, but since several hackers are not needed, it may be possible to improve the efficiency of the device too, especially if a mechanical resonant circuit is also used as the energy storage for the chopper 2 0.

Thus, in practice, the invention provides each LED row with cut-off DC power through bandpass filters so that each luminaire row receives its frequency spectrum from the full power λ spectrum.

™ 25 σ> 1 The invention is generally applicable to lighting. Since LED is a new and growing lighting technology, it is worthwhile to implement it first. One application is also LED illuminated displays, x

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cö For the purposes of this application, luminaire 20 is understood to mean both a conventional luminaire with elements σ> oj 30 in close proximity to one another and a larger luminaire assembly in which different parts of the luminaire may be located, for example, in different rooms of a building.

Claims (16)

A method of power supply of a lamp, wherein the lamp (20) is formed by a plurality of rows (21) consisting of lighting elements (1), wherein the method 5 power is input row-specific (21) into the lamp (20), characterized in that 10. the power is input into each illumination line (21) on a predetermined frequency band. Method according to claim 1, characterized in that the power is controlled to each line through a bandpass filter (2). 15 Method according to any of the preceding claims, characterized in that an electric filter is used as filter (2). Process according to any of the preceding claims, characterized in that a piezoelectric filter is used as filter (2). 20 Process according to any of the preceding claims, characterized in that a filter (2) is used as a mechanical filter. CO 1- Method according to any of the preceding claims, characterized in that the power intended for input C is generated by pulse width modulation. Process according to any of the preceding claims, characterized in that the x o-lighting elements (1) are LEDs. co o o] 30 Method according to any of the preceding claims, characterized in that the total current input to the lamp 3 is measured (3). A power supply system of a lamp, wherein the lamp (20) is formed by a plurality of rows (21) consisting of illuminating elements (1), the system comprising means for inputting the power specific (21) in the lamp (20), characterized in that the system comprises means for inputting the power in each illumination line (21) on a predetermined frequency band. System according to claim 9, characterized in that the power is controlled to each line through a bandpass filter (2). System according to any of the preceding claims, characterized in that as filter (2) an electric filter is used. System according to any of the preceding claims, characterized in that a piezoelectric filter is used as filter (2). 2 0 System according to any of the preceding claims, characterized in that a filter (2) is used as a mechanical filter. System according to any of the preceding claims, characterized in that the power intended for CO 1 input is generated by pulse width modulation. ™ 25 o System according to any of the preceding claims, characterized in that the lighting elements (1) consist of LEDs. X cc CL ro System according to any of the preceding claims, characterized in that the total current input to the lamp 0 is measured (3). δ C \ 1