SE539826C2

SE539826C2 - Compensation unit configured to be connected between a control unit and at least one LED lamp

Info

Publication number: SE539826C2
Application number: SE1451288A
Authority: SE
Inventors: Österlund Henrik
Original assignee: Scania Cv Ab
Priority date: 2014-10-29
Filing date: 2014-10-29
Publication date: 2017-12-12
Also published as: BR102015026375A2; DE102015013309B4; DE102015013309A1; SE1451288A1

Description

Compensation unit configured to be connected between a control unit and at least one LED lamp Field of the invention The present invention relätes to a compensation unit, and a method in relation to the compensation unit, according to the preambles of the independent claims.

In particular the present invention relätes to the use of a compensation unit that enables control units configured for a specific type of detection of an electronic load to determine the working status of a light emitting diode (LED) (i.e. if it is broken or not) even if it is connected to an output of the control unit configured for detection of the status of an incandescent filament lamp.

Backqround of the invention It is a known problem that the large difference in current consumption between a LED and a filament lamp with corresponding luminance makes it difficult to construct driver electronics adapted to discover failures related to an electric breakdown, e.g. related to a damaged electrical cable or a non-working lamp (LED lamp or filament lamp).

In the present application the term LED lamp is used to designate a unit comprising one or many light emitting diodes (LEDs) arranged together as a single unit. In the unit one or many resistors may be included to support the function of the LED(s).

More specifically, the above problem may arise at vehicles, e.g. busses, trucks or cars, where the directional indicators traditionally included filament lamps but now instead use LED lamps. For indicators at certain positions, e.g. a lower directional indicator at a bus, there are legal requirements that the driver should receive an indication when a lamp is out of order. If a control unit for the indicators is configured for use in connection with filament lamps, but if instead LED lamps are used, the control unit probably will not work as required.

There are different methods to determine if there is a failure along the circuit including the control unit - the lamp - earth, i.e. if the electric cable or the lamp is broken. One common method includes that the control unit applies a current through a measurement resistor within the control unit and then through the lamp to earth. The voltage at the output of the control unit is measured and if the voltage is above a predefined threshold it is determined that a failure is detected. The measurement is performed during a very short initial test pulse preferably applied before each flashing pulse of the directional indicator. After the test pulse the full operational current is applied to the lamp.

During the test pulse a fully functional filament lamp displays a considerably smaller resistance than a fully functional LED lamp, i.e. there is a much smaller voltage over the filament lamp than over the LED lamp during the test pulse. Therefore, the control unit may detect the presence of a fully functional LED lamp as a failure, which is not correct.

This problem may be solved in many different ways.

One solution that is commonly used is to arrange one or more external resistors connected in parallel in order to increase the load so much that the control unit will consider it (the LED lamp and the resistors) as a filament lamp. However, this solution nas high energy consumption, generates heat and it is often difficult to dimension the resistors, which is dependent e.g. upon the construction of the LED lamp, the structure of the control unit, and the used voltages.

Another way is to arrange a more advanced electronic circuit between the control unit and the LED lamp in order to measure the current and create a higher load for the control unit in order to simulate that it is connected to a filament lamp. It is then possible to exactly dimension and adapt the electronic circuit to the LED lamp. This solution is relatively complex and expensive, and may have similar problems as the resistor solution above (high energy consumption and heat generation).

The following documents disclose various aspects of the technical field.

EP-2000359 relätes to a connection unit provided with a semiconductor switch for controlling a trailer light including e.g. a light emitting diode and being switchable by a control device, where the control device communicates with a data network of a drawing vehicle.

US-2004/0061450 relätes to a vehicular lamp including a break detection unit for detecting breaking of a light source and notifying the outside of the lamp body of the detection result.

EP-2685789 discloses a directional LED indicator system including capabilities of detecting a failure of an LED.

EP-1458222 relätes to a lamp failure warning device for an LED comprising a switch means for connecting one or many load resistors in parallel with the LED in order to simulate a conventional filament lamp.

Many of the known solutions discussed above include complex circuitry and may not be applicable in connection with control systems using short test pulses in order to determine the status of the LED lamp.

Thus, the object of the present invention is to remove the above stated drawbacks of the presently used solutions in relation to detection of failure of a LED lamp when connected to a control unit configured to detect failures of conventional filament lamps. The drawbacks with the presently used technique are e.g. that they are often technically complex and therefore expensive, they have high energy consumption, and in addition they are not applicable for working in connection with control systems using short test pulses.

One further object is to provide for failure detection using existing control units in vehicles, i.e. it should not be necessary to exchange the existing control unit if LED lamps are used instead of filament lamps.

Summarv of the invention The above-mentioned objects are achieved, or at least mitigated, by the present invention according to the independent claims.

Preferred embodiments are set forth in the dependent claims.

The present invention relätes to a compensation unit that facilitates for control units configured for a specific type of detection of an electronic load to determine the working status of a LED lamp (i.e. if it is broken or not) even if it is connected to an output of a control unit configured for detection of the status of an incandescent filament lamp.

According to the present invention a compensation unit is provided which is configured to be arranged between the control unit and the LED lamp (a directional indicator or other lights). The compensation unit is a very simple electronic circuit that includes only two or three cheap standard components.

In particular the compensation unit includes a housing configured to enclose, protect and seal the components as the compensation unit is mounted in a rough environment.

The compensation unit is provided with one input connection line for connection to an electrical line connected to the control unit, and one output connection line for connection to an electrical line connected to the LED lamp. The input and output connection lines pass through the wall of the housing in sealed feed through openings.

During the test pulse, that preferably occurs just before each flash pulse for the directional indicator, the compensation unit will simulate a filament lamp by creating a load that corresponds to the load of a filament lamp, but after a short period of time, when the test pulse nas terminated, it will have very little influence of the control unit and a very low current consumption.

If there is a failure of the LED lamp the load simulation capability of the compensation unit will cease and the control unit will detect the failure. The compensation unit will preferably be located close to the LED lamp.

According to one embodiment the compensation unit comprises a capacitor unit and a resistor unit being connected in parallel to earth. These are dimensioned such that the measurement during the test pulse will result in a measurement voltage being below the failure detection threshold when the LED lamp is working normally, and above the failure detection threshold when the LED lamp is broken. Generally, the specific values of the components of the compensation unit must be adapted to each specific application because the characteristics of the different control units and LEDs differ.

The capacitor unit loads the output of the control unit when it is charged during the test pulse enough for the measurement voltage over the measurement resistor in the control unit to be below the detection threshold and the control unit will therefore consider that a sufficiently large load being connected. When the flashing pulse nas terminated the capacitor is discharged through the resistor of the compensation unit and through the LED lamp. All this provided that the LED lamp is working normally.

If the LED lamp "disappears" the capacitor will not be sufficiently discharged between the flashings because the discharge must be through the resistor in the compensation unit which is dimensioned such that the capacitor cannot be discharged during the time period between the test pulses and this will keep up the measurement voltage over the measurement resistor. This results in that only a small amount of current is required in order to recharge it during next test pulse and the control unit will then consider it as the load is too low and a failure will be detected.

The solution according the invention is applicable for a LED lamp of a type including resistors and the actual light emitting diode, but the solution is applicable also for other types.

The present invention is advantageous at least in the following aspects: - It is simple, robust and considerably cheap.

- It is easy to be applied on vehicles designed for conventional filament lamps. - It is adaptable to different control units and LED lamps. One possible embodiment would be to use variable components in the compensation unit. - A further advantage is that it suppresses the flashes that might occur in LEDs caused by specific control units continuously sending out short current pulses to detect if a trailer has been coupled to the vehicle.

Short description of the appended drawinqs Figure 1 is a diagram illustrating test pulses for failure detection of a lamp where a lamp failure is detected. Figure 2 is a diagram illustrating test pulses for failure detection of a lamp where a functional lamp is detected. Figure 3 is a schematic block diagram of a known failure detection system. Figure 4 is a schematic block diagram illustrating a failure detection system including a compensation unit according to the present invention. Figure 5 is a schematic block diagram illustrating a failure detection system including a compensation unit according to an embodiment of the present invention. Figure 6 illustrates different views of the compensation unit according to an embodiment of the present invention. Figure 7 is a schematic flow diagram illustrating the method according to the present invention.

Detailed description of preferred embodiments of the invention The present invention will now be described in detail with references to the appended figures. Throughout the figures the same or similar item has the same reference sign.

In figure 3 is illustrated a schematic block diagram of a known lamp failure detection system. A control unit 4 is provided configured to apply a test pulse 6 to the lamp 3 to be tested. The lamp could be a filament lamp or a LED lamp. The test pulse 6 is applied via a measurement resistor 32 within the control unit 4. Preferably, the control unit 4 also comprises circuitry to generate and apply pulses applicable for controlling directional indicators of a vehicle. The circuitry comprises e.g. an amplifying unit 34 configured to amplify an applied voltage to a required voltage level. The directional indicator pulses 7 are illustrated in figures 1 and 2 and occur normally immediately after each test pulse.

The test pulse may have a duration of approximately 20 ms and a voltage of 24 Volt. They are generated at a regular frequency of 1/T, where T is the time period between two consecutive test pulses. T is normally in the range of 0.5 - 1.5 seconds. The voltage U at the output of the control unit 4 is measured during the test pulse and the voltage U is compared to a threshold value Ut, see figures 1 and 2. The threshold value Ut is naturally determined in dependence of the voltage amplitude of the test pulse. According to one typical example Ut is in the range of 13-17 Volt, e.g. 15 Volt. Figure 1 is a diagram illustrating test pulses for failure detection of a lamp where a lamp failure is detected, i.e. if the filament of a lamp is broken the voltage measured at the output of control unit 4 would be close to the voltage amplitude of the test pulse which is above Ut and a lamp failure is detected by the control unit. However, as discussed in the background section this situation may also occur when the lamp is a fully functional LED lamp because a LED lamp corresponds to a small load in comparison to a filament lamp that does not lower the voltage as much as a filament lamp during the test pulse. Therefore, the control unit may detect the presence of a fully functional LED lamp as a failure, which is not correct. Figure 2 is a diagram illustrating test pulses for failure detection of a lamp where a working lamp is detected.

Thus, the intention of the present invention is to enable correct failure detection irrespectively if a filament lamp or a LED lamp is used, and in particular to correctly detect a fully functional LED lamp such that the diagram in that case is as in figure 2.

Figure 4 is a schematic block diagram illustrating a failure detection system including a compensation unit according to the present invention.

A compensation unit 2 is provided configured to be connected between a control unit 4 for lamp failure status detection using test pulses 6 and at least one LED lamp 8 including at least one light emitting diode (LED).

The compensation unit 2 includes a housing 10 configured to enclose and protect components mounted within the housing 8, as the compensation unit may be mounted at a vehicle in a rough environment.

The compensation unit 2 is provided with one input connection line 12, e.g. an insulated electrical cable, for connection to an electrical line 14 connected to the control unit 4, and one output connection line 16, e.g. an insulated electrical cable, for connection to an electrical line 18 connected to the LED lamp 8.

The input and output connection lines (12, 18) pass through the wall 20 (se figure 6) of the housing 10 in one or two sealed feed through openings (22, 24) (se figure 6). In addition the housing 10 is provided with an earth connection point 26 configured to be connected to earth potential. The earth potential may be common to the earth potential of the LED lamp.

The components comprise one capacitor unit 28 having a capacitor value Ci and one resistor unit 30 having a resistor value Ri.

Preferably, each of the capacitor unit and the resistor unit comprises one capacitor component and resistor component, respectively. However, each unit may be embodied by a plurality of components, e.g. the resistor unit may comprise two or more resistor components connected such that the compound resistor value is Ri.

The capacitor unit and the resistor unit are connected in parallel between the input connection line 12 and the earth connection point 26, and that the input connection line 12 is connected to the output connection line 16. The values O, Ri are chosen in dependence of characteristics of the control unit 4 and characteristics of the LED lamp 8, and of a time period T between test pulses 6, such that the control unit 4 correctly detects the failure status of said LED lamp 8. According to one embodiment the capacitor value is in the range of 100-200 |iF and the resistor value is in the range of 6.0 - 8.0 kQ, and advantageously the capacitor value is approximately 150 |iF and the resistor value is approximately 6.8 kQ.

The characteristics of the LED lamp include the internal resistance of the LED(s) and also of resistor values of resistors, if any, arranged within the LED lamp. According to one embodiment the characteristics of the control unit includes a resistor value R, e.g. in the range of 500-800 Q, and approximatively 700 Q, of a measurement resistor and a failure detection voltage threshold Ut, which may be in the range of 13-17 Volt, e.g. 15 Volt, provided a test pulse amplitude of 24 Volt. The time period T is preferably in the range of 0.5 - 1.5 seconds.

In the case where a LED lamp includes a number of individual LEDs, e.g. 20 LEDs, the compensation unit may be set to result in a failure detection when all individual LEDs fail, or when a predetermined number, e.g. half of the LEDs fail.

The capacitance and resistance values of the components of the compensation unit are chosen such that the accumulated charge of the capacitor unit is kept at a level where a subsequent test pulse will result in a clear indication of the measurement voltage U measured at the output of the control unit, i.e. the measured voltage level should be well below the voltage threshold Ut when the LED lamp is working.

The purpose of the resistor is to set the thresholds with/without LED including a margin around the threshold. In addition it also allows the capacitor to continue discharging between the test pulses, e.g. in connection with the flashings of the directional indicators, but also prevents that the capacitor remains charged if no lamp is connected.

According to one alternative the resistor unit and capacitor unit may be variable components that may be adapted to different control units and LED lamps.

If many LED lamps are connected to the same output of the control unit it is necessary, irrespectively if all LED lamps should be failure-monitored or not, to include a diode to insulate the lamps from each other and to prevent the capacitor from being discharged through the wrong lamp. One such embodiment is illustrated in figure 5. Thus, according to this embodiment the components comprise a diode 36 connected in its forward direction between the input connection line and the capacitor unit and resistor unit. In the set-up illustrated in figure 5, only the lower LED lamp is monitored by the control unit.

As the compensation unit should be robust it comprises only few different parts; according to one embodiment the components of the unit comprise not more than three electrical components.

Figure 6 illustrates different views of the compensation unit according to one embodiment of the present invention.

As described above the input and output connection lines (12, 16) pass through the wall 20 of the housing 10 in one or two sealed feed through openings (22, 24). In addition the housing 10 is provided with an earth connection point 26 configured to be connected to earth potential. In this embodiment the connection point includes a hole for attaching the unit to e.g. the chassis of the vehicle.

The compensation unit may have a size of approximately 50x35x30 mm and may be made from a suitable plastic and sealed by an epoxy resin. Each of the input and output connection lines 12, 16 are provided, at their respective ends, with a contact member configured to, respectively, be connected to the electrical line 14 connected to the control unit 4, and to the electrical line 18 connected to the LED lamp 8.

The present invention also relätes to a method which now will be described with references to figure 7.

Thus, the method is intended to be applied in relation to a compensation unit 2 configured to be connected between a control unit 4 for lamp failure status detection using test pulses 6 and at least one LED lamp 8 including at least one light emitting diode (LED). The compensation unit 2 includes a housing 10 configured to enclose and protect components mounted within the housing 8. The compensation unit 2 is provided with one input connection line 12, for connection to an electrical line 14 connected to the control unit 4, and one output connection line 16, for connection to an electrical line 18 connected to the LED lamp 8. The input and output connection lines (12, 18) pass through the wall 20 of the housing 10 in one or two sealed feed through openings (22, 24). The housing 10 is provided with an earth connection point 26 configured to be connected to earth potential. The input connection line 12 is connected to the output connection line 16. Further features of the compensation unit are discussed above when describing the compensation unit.

The method comprises the steps of: -Connecting a compensation unit between the control unit and the LED lamp. The compensation unit comprises one capacitor unit having a capacitor value Ci and one resistor unit having a resistor value Ri, the capacitor unit and the resistor unit are connected in parallel between the input connection line and an earth connection point. The values Ci, Ri are chosen in dependence of characteristics of the control unit 4 and characteristics of the LED lamp 8, and of a time period T between test pulses 6. -Applying consecutive test pulses to the LED lamp via the compensation unit.

-Charging the capacitor unit, -Determining a measurement voltage to be used by the control unit 4 to correctly detect the failure status of said LED lamp 8.

-Discharging the capacitor unit.

According to one embodiment, characteristics of the control unit include a resistor value R of a measurement resistor and a failure detection voltage threshold Ut. These features are further discussed above.

In a further embodiment the method comprises providing a diode to be connected in its forward direction between the input connection line and the capacitor unit and resistor unit.

The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

1. Kompensationsenhet (2), konfigurerad för att kopplas in mellan enstyrenhet (4) för detektion av felstatus hos lampor med användning avtestimpulser (6) och minst en LED-lampa (8), innefattande minst enljusemitterande diod (LED), varvid kompensationsenheten (2) innefattar ett hus (10), konfigurerat för attinnesluta och skydda komponenter som monterats inuti huset (10), varvid kompensationsenheten (2) är utrustad med an anslutningslinje (12) förinmatning, för anslutning till en elektrisk ledning (14) som är ansluten tillstyrenheten (4), och en anslutningslinje (16) för utmatning, för anslutning till enelektrisk ledning (18) som är ansluten till LED-lampan (8), och varvidanslutningslinjerna (12, 16) för inmatning och utmatning passerar genom husets(10) vägg (20) genom en eller tvà genomföringsöppningar (22, 24), varvid huset (10) är försett med en jordanslutningspunkt (26), konfigurerad för attanslutas till jordpotentialen, kännetecknad av att nämnda komponenter innefattar en kondensatorenhet (28)med ett kondensatorvärde C1 och en resistorenhet (30) med ett resistorvärde F11,varvid kondensatorenheten och resistorenheten är parallellkopplade mellananslutningslinjen (12) för inmatning och nämnda jordanslutningspunkt (26), och avatt nämnda anslutningslinje (12) för inmatning är ansluten till nämndaanslutningslinje (16) för utmatning, varvid nämnda värden C1, F11 har valts som enfunktion av karakteristika hos styrenheten (4) och karakteristika hos LED-lampan(8), och som en funktion av en tidsperiod T mellan testimpulserna (6), sä attnämnda styrenhet (4) pä ett korrekt sätt detekterar felstatus hos nämnda LED- lampa (8).

2. Kompensationsenhet enligt patentkrav 1, varvid nämndakarakteristika hos styrenheten innefattar ett resistorvärde R fràn en mätresistoroch en spänningströskel för feldetektion, UT.

3. Kompensationsenhet enligt patentkrav 1 eller 2, varvid nämnda komponenter innefattar en diod (36) som i framätriktningen är ansluten mellan 14 anslutningslinjen för inmatning och nämnda kondensatorenhet och resistorenhet.

4. Kompensationsenhet enligt nàgot av patentkraven 1-3, varvidnämnda tidsperiod T ligger inom omràdet 0,5-1,5 sekunder.

5. Kompensationsenhet enligt nàgot av patentkraven 1-4, varvidnämnda kondensatorvärde ligger inom omràdet 100-200 uF och nämndaresistorvärde ligger inom omràdet 6,0-8,0 kQ.

6. Kompensationsenhet enligt nàgot av patentkraven 1-5, varvidnämnda kondensatorvärde är ungefär 150 uF och nämnda resistorvärde ärungefär 6,8 kQ.

7. Kompensationsenhet enligt nàgot av patentkraven 1-6, varvidnämnda LED-lampa är en riktningsindikator i ett fordon.

8. Kompensationsenhet enligt nàgot av patentkraven 1-7, varvid nämnda komponenter innefattar färre än tre elektriska komponenter.

9. Förfarande avseende en kompensationsenhet (2), konfigurerad för attkopplas in mellan en styrenhet (4) för detektion av felstatus hos lampor medanvändning av testimpulser (6) och minst en LED-lampa (8), innefattande minsten ljusemitterande diod (LED), varvid kompensationsenheten (2) innefattar ett hus (10), konfigurerat för attinnesluta och skydda komponenter som monterats inuti huset (10), varvid kompensationsenheten (2) är utrustad med an anslutningslinje (12) förinmatning, för anslutning till en elektrisk ledning (14) som är ansluten tillstyrenheten (4), och en anslutningslinje (16) för utmatning, för anslutning till enelektrisk ledning (18) som är ansluten till LED-lampan (8), och varvidanslutningslinjerna (12, 16) för inmatning och utmatning passerar genom husets(10) vägg (20) genom en eller tvà genomföringsöppningar (22, 24), varvid huset (10) är försett med en jordanslutningspunkt (26), konfigurerad för att anslutas till jordpotentialen, kännetecknat av att nämnda anslutningslinje (12) för inmatning är ansluten tillnämnda anslutningslinje (16) för utmatning, varvid förfarandet innefattar följande steg: -anslutning av en kompensationsenhet mellan nämnda styrenhet och nämndaLED-lampa, varvid nämnda kompensationsenhet innefattar en kondensatorenhetmed ett kondensatorvärde G1 och en resistorenhet med ett resistorvärde Fh,varvid kondensatorenheten och resistorenheten är parallellkopplade mellananslutningslinjen för inmatning och nämnda jordanslutningspunkt, varvid nämndavärden C1,R1 har valts som en funktion av karakteristika hos styrenheten (4) ochkarakteristika hos LED-lampan (8), och som en funktion av en tidsperiod T mellantestimpulserna (6), -applicering av pà varandra följande testimpulser pà nämnda LED-lampa vianämnda kompensationsenhet, -laddning av nämnda kondensatorenhet, -fastställande av en mätspänning som skall användas av nämnda styrenhet (4) föratt pà ett korrekt sätt detektera felstatus hos nämnda LED-lampa (8), -urladdning av nämnda kondensatorenhet.

10. Förfarande enligt patentkrav 9, varvid nämnda karakteristika hosstyrenheten innefattar ett resistorvärde R fràn en mätresistor och en spänningströskel för feldetektion, UT.

11. Förfarande enligt patentkrav 9 eller 10, varvid nämnda förfarandeinnefattar tillhandahällande av en diod som i framätriktningen skall kopplas inmellan anslutningslinjen för inmatning och nämnda kondensatorenhet och resistoren het.