WO2003061347A1

WO2003061347A1 - Signal light comprising light-emitting diodes

Info

Publication number: WO2003061347A1
Application number: PCT/EP2003/000427
Authority: WO
Inventors: Reiner Kirschke; Fabian Zink
Original assignee: Stührenberg GmbH
Priority date: 2002-01-19
Filing date: 2003-01-17
Publication date: 2003-07-24
Also published as: AU2003206740A1

Abstract

The invention relates to a signal light with a circuit board on which light-emitting diodes are arranged in several parallel serial circuits, each controlled by a transistor wired as voltage supply. Said serial circuits are connected in common, by means of a circuit for determining the total current thereof, to a rectified voltage source. The transistors are connected to current-determining emitter resistances and on the base side are each connected by means of dropping resistors to a reference voltage, determined by a zener diode and at least one further voltage source, regulated by means of a bridge circuit such that the total current is kept approximately constant when individual series circuits drop out.

Description

Signal light with LEDs

The invention relates to a signal lamp with a circuit board, on which light-emitting diodes are arranged in a plurality of parallel series circuits, each of which is driven by a transistor connected as a current source, these series circuits being connected together to a supply voltage via a circuit determining their total current.

Such signal lights are known from DE 29 25 692. In this known circuit, the transistors are connected as maximum current sources in that the light-emitting diodes are connected in the source path of a MOSFET. If individual LEDs fail due to an internal short circuit, the monitored current remains unaffected.

In addition, the maximum total current is limited by a MOSFET current source transistor. Failures of individual light-emitting diode series circuits are not monitored, but a different current distribution of the total current to the individual branches occurs if one or more current branches fail, if the sum of the individual maximum current limits of all branches is greater than the overall limited maximum current. In this way, brightness compensation occurs when individual branches fail. The reporting of a malfunction is in one such a case of redundancy utilization is not provided. Even if so many branches of the light-emitting diode arrays fail that the total current is undercut, there is no message for the supply circuit.

Furthermore, from DE 199 10 142 AI a circuit is known in which several series of light-emitting diodes are fed via current source circuits which consist of transistors with emitter resistors and a stabilized base voltage. The bases of a number of current source transistors are connected directly to a Zener diode reference voltage source which has a series resistance, so that in the event of failure of a diode chain, under certain circumstances an increase in reference voltage and thus an increase in current in the diodes for the purpose of brightness compensation.

Furthermore, it is known from WO 99/40459 to monitor the brightness of light-emitting diodes of a traffic signal light by means of a photo sensor, the photo signal of which is evaluated in one or more threshold value circuits which trigger a pre-warning signal and / or a switch-off signal in each case when the threshold value is undershot. Controlling the current depending on the incident sunlight is not provided.

An arrangement for optically checking the brightness of the light-emitting diode arrangement is known from WO 99/40459. The openings are in the form of bores or the like. distributed between the LEDs. This arrangement brings with it the problem that the light coming from the light-emitting diodes when energized first radiates to the lens and then only to a small extent, depending on the degree of reflection and contamination of the lens, is reflected and then only partially passes through the openings and reaches the sensor. On the other hand, sunlight striking the diffusing screen enters the luminaire almost without weakening and falls on the circuit board and partly through the openings in it, which, depending on the angle of incidence of sunlight, may hit the sensor with a significantly higher luminous flux than through the LEDs. Both disturbing effects lead individually and, in particular, cumulatively to very considerable incorrect measurements, which entail deviations in the result of the evaluation in one direction or the other and question the whole purpose of the measuring and evaluation device.

It is an object of the invention to provide a circuit arrangement which provides better controllability and a higher level of interference immunity and which provides better detectability in the event of partial failure and / or solar radiation.

The solution is that the transistors are connected to current-determining emitter resistors and are connected on the base side via series resistors to a reference voltage, which is determined by a Zener diode and at least one additional voltage source, which is controlled by a bridge circuit so that the total current is approximately constant is held when some of the series circuits fail.

Advantageous refinements are specified in the subclaims. If a light-emitting diode fails due to an interruption or the current source transistor of a series circuit, the effect of the control circuit has practically no effect on the current consumption of the overall circuit. Since the number of light-emitting diodes is at most eight, preferably six or fewer, the number of light-emitting diode series is accordingly 12 or more, preferably 15 to 18, if the standard brightness of conventional traffic signals plus a reserve with commercially available light-emitting diodes is to be provided. As a result, the brightness is still above the permissible lower limit if no more than 20% of the light-emitting diodes, for example three series of 15, have failed. A total shutdown is only required if a fourth series of 15 fails. 18 derailleurs, each with five LEDs, are also a useful grouping.

The series connections of six light-emitting diodes can advantageously be operated in each case with a reference voltage of a Zener diode, as well as a regulator voltage source and / or a control voltage source placed thereon. The supply voltage is obtained by a full-wave rectification of a 24 V low voltage. One of the regulator voltage sources preferably serves to stabilize the overall current in the event of failure of individual light-emitting diode chains, and another regulator voltage source serves to increase the current in the event of extreme external light incidence. Since the rectified peak voltage is 33.6V, a voltage of 16V, at which the maximum current has already been reached, is reached at a phase angle of 30 ° and exceeded up to 150 °, so that a full LED current flows at least 80% of the time.

The light-emitting diodes of the individual series circuits are advantageously statistically mixed on the switching The circuit board is distributed so that even if the maximum number of series connections fails, there is no misleading, meaningful pattern from the dark areas.

The openings under each of the light emitting diodes are arranged and are only large enough that the crystal of the light emitting diode covers the corresponding opening and that the light emitting diode has a diode housing on the side and side of the board.

The white-looking, light-scattering diode housing serves as a light guide for secondary light emerging laterally from the LED crystal and light reflecting from the interfaces of the lens, which reaches the rear through the diode housing through the circuit board hole into the rear luminaire room, where the at least one sensor is arranged ,

Incident sunlight is focussed on the front of the crystal through the diffusing screen and is intercepted there and shaded against the circuit board opening on the back.

The board is preferably i.a. impermeable to light through the conductor tracks that serve to energize the diode.

The detection of the light-emitting diode light passing through the cutouts by only a few or one sensor is favored by reflective, in particular white, surfaces of the space located to the rear of the printed circuit board. The board is also preferably white on the back.

The light-emitting diode housing is closed off at the front by a clear focusing lens or disk. The side and the rear part of the diode housing widens diverging from the centrally inserted crystal towards the lens, the angle of the housing extension roughly corresponding to the physically determined radiation angle of the crystal. The emitted light is predominantly fed to the lens and is emitted by the lens as useful light through the lens. Only a small but always defined portion of the diode light finds its way through the diode housing and the hole in the board to the sensor. In contrast, the maximum amount of sunlight reaching the sensor is irrelevant. This prevents the light sensor from entering the non-linear saturation range when bright sunlight hits the lens. Since the LEDs are operated with clocked DC voltage, the LED light on the light sensor generates an alternating signal with the clock frequency. If the light-emitting diodes are operated in direct voltage mode, the sensor lighting changes suddenly when switching on and off a signal phase. The level of the alternating light signal component or the step signal component is evaluated in each case and compared with one or more predefined threshold values, and if one of the higher threshold values is undershot and the lowest threshold value is undershot, a fault warning or a fault message is output by switching off.

A change in the brightness of the large number of light-emitting diodes of a signal light occurs due to aging of the light-emitting diodes, through a change in the ambient temperature, through a change in the supply voltage and through failure of individual light-emitting diodes or of a light-emitting diode group connected in series. The light emitting diode voltage or the current is usually stabilized to a maximum, so that the monitoring essentially detects the aging limits and an impermissible number of failures. Since these processes take years or occur relatively infrequently, a malfunction notification provides the option of replacing the circuit board with the light-emitting diodes as part of a general inspection before such a malfunction occurs that causes the signal system to be switched off and therefore requires special maintenance.

Irrespective of this, the quasi-constant sensor signal component is preferably derived by a low-pass filter, which corresponds to the irradiated ambient lighting. With this, the current supply to the light-emitting diodes is advantageously controlled higher, so that better visibility of the signal light is achieved under unfavorable lighting conditions, but otherwise no unnecessary current is consumed, which would also accelerate aging.

Advantageous configurations are shown in FIGS. 1-7.

Fig. 1 shows a section of the LED series circuits;

Fig. 2 shows the feed circuit and monitoring circuit;

Fig. 3 shows a timing chart;

Fig. 4 shows a light emitting diode arrangement;

Fig. 5 shows a cross section through a traffic signal lamp;

6 shows an enlarged detail for the installation of light-emitting diodes;

Fig. 7 shows schematically a light sensor signal evaluation circuit.

1 shows a section of the series circuits S1, S2 ... S15, each of which consists of a current source and six light-emitting diodes, called LEDs, L1-L6, L7-L12, L85-L90. The current source consists in each case of an emitter follower transistor T1, T2 ... T15, or a correspondingly switched MOSFET transistor whose control electrode 10 is acted upon by a reference voltage REF, each of which is supplied by a bidirectionally rectified supply voltage US through a series resistor 21 and one connected to ground Zener diode 20 and voltage source transistors UT1, UT2, which are negative-coupled and are fed with regulator currents at their base. The supply voltage US is obtained from an AC voltage by means of full-wave rectification, and is supplied via the series of light-emitting diodes L1-L90 to the collector 12 of the transistor T1, T2 ... T15, the emitter of which is connected to a common measuring resistor via a current-determining negative feedback resistor RG RM is connected to ground, at which a total current measurement signal IG drops.

The reference voltage REF, which is fed to the individual current source transistors Tl-T15 of the series circuits which are decoupled with emitter resistors RE, via decoupled base resistors RB, consists of two or three components. The first determines a minimum current component and is obtained with a zener diode 20, the zener current of which is supplied via a series resistor 21 from the supply voltage US. A second lower current component is determined by a control voltage source UTl, which consists of a transistor fed with a negative feedback resistor GRl from the collector to the base, the base of which is fed by a comparator circuit VB, a bridge circuit B, one branch of which is made up of the LED series and the measuring resistor RM and the like another branch consists of bridge resistors RBl, RB2, which is fed by a reference voltage REF1, which does not include the voltage of the control voltage source UTl. The comparator circuit consists of a current mirror circuit which is fed to the measuring transistor VB via a resistor RK from the Zener diode voltage UZ. As a result, the current control loop is closed and the current in the measuring resistor RM is approximately constant, even if individual series circuits of the light-emitting diodes fail. If individual LED series fail, this current regulator circuit ensures the constancy of the total current and a corresponding increase in the individual currents through a Adaptation of the reference voltage REF increased with the first control voltage source UT1.

The respective control current generates a measurement voltage in the resistor RK, which is a measure for the detuning of the bridge B and is fed directly or inverted with an inverter I to earth as a measurement signal MS of the monitoring circuit 3. The more diode chains fail, the stronger the current control and the larger the measurement signal MS.

A control voltage source UT2, which lies outside the current control loop, supplies the third component of the reference voltage REF. The control voltage source UT2 also consists of a transistor connected from the collector to the base with a negative feedback resistor GR2. Its base is powered by a power source that delivers a current depending on a measurement of the ambient brightness caused by sunlight. The brightness measurement signal HS supplies a suitably arranged photo element PH via a low-pass filter TP, so that the changing brightness of the light-emitting diodes, which are fed with half-waves, does not produce any signal component.

Instead of this current control, there is also the alternative, analogously to this or partly combined with this, of obtaining a photosensor signal from the light-emitting diodes via a high-pass filter HP and supplying it to the bridge transistor VB on the input side in a summing circuit, as shown in dashed lines.

The circuit which generates the reference voltage REF is advantageously bridged with a capture zener diode AZ which limits the reference voltage REF to a maximum value and in the event of faults in the control or Regulator circuit is effective and then limits the maximum current of the LEDs.

Fig. 2 shows a supply circuit and the monitoring circuit 3. The mains voltage UN is reduced in the transformer TR to a low voltage of 24 V and via two normally closed contact sets RR1, RR2 of fault signaling relay R1, R2 to a full-wave rectifier GL which supplies the half-wave voltage as supply voltage US to the series circuits S1 - S15. The supply voltage US is also led via a diode D to a smoothing circuit C, which supplies a supply voltage UV for the monitoring circuit 3.

In the monitoring circuit 3 there is a first comparator VI, to which the measurement signal MS is fed at an input, which signals the respective current level in the series circuits and, because of its half-wave supply, consists of a sequence of 100 Hz pulses which, owing to the voltage source feed are flattened. The second comparator input is connected to a first comparison voltage RV1, which is obtained analogously to the reference voltages REF, the series circuits with a Zener diode ZI, but with a lower Zener voltage and a voltage divider, from the pulsating supply voltage US, and thus a similar, but somewhat more likely, saturation flattening , temporal course as the measurement signal MS. The first comparison voltage RV1 is set by the voltage divider to such a level that it is always exceeded by the measurement signal MS when at least 80% of the series circuits S1-S15 are live, ie in the example at most three of the series circuits have failed. In this case, the first comparator VI provided with a hysteresis outputs a 100 Hz pulse series IS at its output. Furthermore, a clock signal CLK is generated with a second hysteresis comparator V2, which consists of a constant reference voltage RV2 and a 100 Hz signal sequence derived from the pulsating supply voltage US, each of which exceeds the associated reference voltage RV2 in a shorter period of time than the measurement voltage MS of its reference voltage RVl possibly exceeds.

The two comparator output signals IS, CLK are combined in an antivalence gate circuit AG, so that a 200 Hz pulse signal PS is present at their output because of the different duration of the two mutually centered pulse signals if the measuring voltage MS reaches the prescribed level. However, an equivalent gate circuit can optionally be used to get a 200 Hz pulse signal.

The pulse signal PS is then divided into two separate signal paths, on each of which the presence of the pulse signal PS is checked by a time filter F1, F2, the output signal of which keeps a shunt transistor TS1, TS2 switched on as long as the 200 Hz pulse signal PS is present.

The shunt transistors TSl, TS2 are each parallel to a fault relay Rl, R2, which is bistable and is in series with a supply circuit, the supply current of which is derived when the shunt TSl, TS2 is switched on. In the event of a fault, i.e. in the absence of a 200 Hz pulse signal or an error on the filter F1, F2 or on the shunt transistor TS1, TS2, the associated fault signaling relay R1, R2 switches over and switches the entire device off and on the network side emits the alarm message AM. For the purpose of checking the filter and relay circuits, a test button PT1, PT2 is provided in each branch of the pulse signal PS, the actuation of which simulates a malfunction and the corresponding relay must trigger the disconnection process.

Fig. 3 shows the waveforms on the comparators VI, V2 and the antivalence gate AG.

FIG. 4 shows an example of a statistical distribution of 15 series of 6 light-emitting diodes on a circular area, the series-associated light-emitting diodes L1-L6, L7-L12, etc., each having the same reference letters A-P. The distribution is chosen in such a way that no significant light pattern is produced even with any three failed series A - P.

For other numbers of diodes in the series, corresponding adjustments of the reference voltage circuits and the number of series must be carried out professionally. When using more powerful light-emitting diodes that can be expected on the market in the future, or with traffic signal lights other than those that are standardized in road traffic, the total number of light-emitting diodes and the series distribution can be adapted to the requirements.

The monitoring circuit, which monitors the measurement signal MS in a first comparator VI with respect to a first reference voltage value RV1, can be expanded in a corresponding manner with a further comparator which is set to a higher reference voltage and, for example, if only three of the series circuits S1-S15 fail triggers a warning that can be triggered with suitable means, e.g. with short-term or frequency signals, is output to the control systems via the network connection or another communication path.

5 shows a cross section of a traffic signal light, which has a housing 10, which is closed at the front with a diffusing screen 11, behind which a circuit board 1 is arranged at a distance, which carries LED light-emitting diodes Lx on the front, which are wired to the circuit board with a voltage supply, are connected in particular by means of current source circuits with current limitation of the half-waves.

The light-emitting diodes Lx consist of a light-emitting diode crystal plate 26 which is arranged approximately centrally in a light-emitting diode housing 22 parallel to the circuit board 1, which is funnel-shaped from the crystal and has a clear lens 27 or a disk 28 - shown in broken lines - in front of this conical recess 23. finally wears. The diode housing 22 is laterally and in its rear wall 24 made of translucent, light-scattering material that directs light emitting diode to the rear wall 24 of the diode housing, which exits there.

The circuit board 1 has an opening 17, in particular a bore, under the light-emitting diode crystals 26, the opening width W of which is smaller than the crystal dimensions A, so that the crystal 26 in each case fully covers the hole 17 underneath.

Diode light, which arrives at the diode housing rear wall 24 via the diode housing 22 and exits there, passes through the bore 17 and strikes one or more scattered at least one light sensor 30, which is arranged on the rear side of the circuit board 1. The walls of the room, which is enclosed by the circuit board 1 and the rear wall of the lamp 14, are advantageously coated with a light-scattering layer 2B, 14B, in particular white or silvery color, and the bore 17 is preferably edge-side with a metallic coating of the type Via 18 provided that supports the flow of light. The light from the numerous light-emitting diodes mixes in the white rear space in such a way that a few photosensors 30 or even just one are sufficient to generate a sensor signal SS which contains an appropriate signal component from all light-emitting diodes. Due to the shading of incident sunlight, so little reaches the sensor that it always works in the linear sensitive range.

Fig. 6 shows the area with a light emitting diode 20 enlarged and axially cut. The light that is emitted centrally in the light-emitting diode crystal 26 usually spreads out at an angle of approximately 60 ° and is largely parallelized by the lens 27 and thus falls on the lens 11, which is optically active, e.g. prismatic and cylindrical structure is provided, which produces a prescribed asymmetrical light distribution on the outlet side.

Incident parallel sunlight is broken down into bundles by the lens structure and possibly focused by the lenses 27 onto the light-emitting diode crystals 26. This crystal 26 is in each case opaque and, because of its larger dimension A, shades the hole 17 of the width W lying underneath. Dash-dotted lines indicate a path of the light-emitting diode radiation which is reflected on the inner lens surface and is guided from the diode housing 22 to its rear wall 24 and from there falls through the bore 17 and along its reflective lining 18 onto the white scattering surface 14B. Their scattered light spreads between the opposite white scattering surfaces 14B, 2B until it reaches the light sensor 30. The diode housing 22 is tapered behind the lens 27 from the front of the crystal 26 at a larger angle than its light emission angle.

7 shows an evaluation circuit 31 of the sensor signal SS, which is differentiated and / or band-filtered in a filter circuit 32, which may result in a continuous exposure signal component, e.g. stems from scattered light from the sun, is suppressed or branched off for control purposes as an ambient brightness signal UHS and the useful light signal NS is separated.

This signal NS of the light-emitting diode brightness is supplied to at least one first comparator Vll, to which a first threshold value SW1 is supplied at the other input.

In addition, a clock signal TS is obtained from the power supply NT of the light-emitting diodes Lx each at the time of the maximum of the half-wave drive voltage, with which the negated output signal of the comparator Vll is passed to a first holding circuit 33 so that when the first threshold value SW1 is undershot the useful holding signal NS sets the first holding circuit 33, which emits a prewarning signal VW, for example as a short-term signal to a first relay R11 in the control circuit IQ of the light-emitting diodes Lx, which can be measured on the side of the AC voltage supply. Analogously, a second comparator V21 is fed with the useful light signal NS and a second, relatively lower threshold value SW 2, the inverted output signal of which is transferred to a fault message memory 34 with the clock signal TS. The fault message SM is used, for example, via a second relay R21 to switch off the diodes Lx. In a suitable manner, for example as shown by temporary or permanent interruption of the power supply circuit NT, the fault states WV, SM are reported externally to the control center (not shown). The holding circuits 33, 34 are reset with a switch RS during maintenance or repair.

The ambient brightness signal part UHS is advantageously used in an energization control circuit BS to raise the maximum light-emitting diode current, which is supplied to the light-emitting diodes Lx connected in chains from maximum current sources IQ.

LIST OF REFERENCE NUMBERS

I circuit board

2B white circuit board coating

3 monitoring circuit

10 lamp housing

II lens

14 housing rear wall

14B white circuit board coating

17 breakthroughs, holes

18 plated-through holes

20 zener diode

21 series resistor to 20

22 LED housing

23 conical recess

24 diode housing rear wall

26 light emitting diode crystal

27 lens

28 cover plate

30 light sensor

31 evaluation circuit

32 filters

33 Warning memory

34 Fault message memory A crystal dimension

AG Antivalence Gate

AM fault report

AZ interception zener diode

B bridge circuit

BS lighting circuit

C smoothing capacitor

CLK clock signal

D diode Fl, F2 filter GL rectifier

GRl, GR2 negative feedback resistors

HP high pass

HS brightness signal

I inverter

IG total current

IQ diode power source

IS pulse signal

Lx LEDs (x = 1 - 90)

MS measurement signal

NS useful light signal

NT Nezteil

PH photosensor

PS 200 Hz signal

PT1, PT2 test button

R1, R2 relays

Rll, R21 fault relay

RB base resistors

RBl, RB2 bridge resistors

RE emitter resistors

REF reference voltage

REFl auxiliary reference voltage

RK resistance

RM measuring resistor

RR1, RR2 normally closed contact records

RS reset

RVl 1st reference voltage

RV2 2nd reference voltage

Sx series connections (x = 1 - 15)

SM fault message

SS sensor signal

SW1 1st threshold

SW2 2nd threshold TP low pass

TR transformer

TS clock signal

TSl, TS2 shunt transistor

Tx transistor (x = 1 - 15)

UHS ambient brightness signal

UN mains voltage

US supply voltage

UTl, UT2 voltage sources

UV supply voltage

UZ Zener voltage

VI, V2 comparators

V11, V21 comparators

VB bridge comparison circuit

VW warning signal

W breakthrough distance

ZI Zener diode for RVl

Claims

claims

1. Signal light with a circuit board (1), on which light-emitting diodes (Lx) are arranged in several parallel series circuits (x), each of which is controlled via a transistor (Tx) connected as a current source, these series circuits (Sx) together via one whose total current (IG) determining circuit are connected to a full-wave rectified supply voltage (US), characterized in that the transistors (Tx) are connected to current-determining emitter resistors (RE) and on the base side via series resistors (RB) with a reference voltage (REF) are connected, which is determined by a Zener diode (Lx) and at least one further voltage source (UTl), which is controlled in a regulating manner via a bridge circuit (B) in such a way that the total current is kept approximately constant when individual ones of the series circuits (S1-S15) fail without power.

2. Signal light according to claim 1, characterized in that the supply voltage (US) is obtained by rectifying a 24 V 50 Hz AC voltage and 4 to 8 of the LEDs (Lx) are contained in one of the series circuits (Sx) and the reference voltage ( REF) corresponds approximately to half the peak voltage of the half-wave supply voltage (US).

3. Signal light according to one of the preceding claims, characterized in that all currents of the series circuits (Sx) flow through a measuring resistor (RM), which is part of the bridge circuit (B), and a measuring signal from a bridge comparator circuit (VB) (MS) is coupled out, which is fed to a first comparator (VI), on the other hand a first comparison voltage (RV1) is fed, which is dimensioned such that the first comparator (VI) only delivers an output signal (IS) when a the specified proportion of the series connections (Sx) draw current.

4. Signal light according to claim 3, characterized in that the predetermined proportion is 80%.

5. Signal light according to claim 3, characterized in that with a second comparator (V2) from the clocked supply voltage (US) a clock signal (CLK) is derived, the pulses to the clocking of the supply voltage (US) centered and shorter than the output signals (IS ) of the first comparator (VI).

6. Signal light according to claim 5, characterized in that the output signal (IS) and the clock signal (CLK) are fed to an antivalence gate (AG) or an equivalence gate, whose pulse output signal (PS), which occurs at a sufficient level of the measurement signal (MS), a filter circuit (Fl) is supplied which, in the presence of the pulse output signal (PS) with twice the frequency of the clock signal (CLK), connects a shunt transistor (TSl) which is connected in parallel to a bistable relay (Rl) connected to a supply circuit, the normally closed contact pair (RRl ) disconnects the mains voltage (UN) from a supply voltage rectifier (GL) and thus issues the alarm message (AM).

7. Signal light according to claim 6, characterized in that an earthed test button (PTl) is connected to the input of the filter circuit (Fl).

8. Signal light according to one of claims 6 or 7, characterized in that the filter, shunt and relay circuits

(Fl, TSl, Rl; F2, TS2, R2) is double.

9. Signal light according to one of the preceding claims, characterized in that the LEDs

(Ll - L6; L2 - L12 ...) in the light emitting diode series (A - P) are so distributed over a circular area of a circuit board (1) that in the event of a failure of 20% of the light emitting diode series (A - P) in any combination there is no significant light pattern.

10. Signal light according to one of the preceding claims, characterized in that the bridge comparison circuit (VB) is a current mirror circuit, the mirror current of the regulator voltage source (UTl) is fed to the base of a transistor-coupled transistor.

11. Signal light according to one of the preceding claims, characterized in that between the zener diode (20) and the first voltage source (UTl), a second voltage source (UT2) is connected in series, which is controlled by a brightness signal (HS), which from in the signal lamp is irradiated with sunlight by a photosensor (PH).

12. Signal light according to claim 11, characterized in that from the photosensor signal with a low-pass filter (TP) a sunlight component is separated as the brightness signal (HS).

13. Signal light according to claim 12, characterized in that a light-emitting diode brightness signal is obtained from the photosensor signal by means of a high-pass filter and possibly rectification, which is supplied as an additional actual signal component to the regulation of the total current (IG).

14. Signal light according to claim 12, characterized in that the brightness signal (HS) via a current source transistor and a collector-coupled transistor of the second voltage source (UT2) is supplied on the base side.

15. Signal light according to one of claims 11 to 14, characterized in that the reference-side bridge branch (RBl, RB2) is fed by an auxiliary reference voltage (REFl), which is composed of the voltage of the Zener diode (20) and the second voltage source.

16. Signal light according to one of the preceding claims, characterized in that the reference voltage (REF) is bridged by an interception zener diode (AZ) whose Zener voltage corresponds to the upper permissible limit of the brightness-controlled and current-controlled reference voltage (REF).

17. Signal light according to one of the preceding claims, characterized in that it contains a circuit board (1) in a lamp housing (10), which is completed by a structured diffusing screen (11), light-emitting diodes (Lx) on the diffusing plate side on the switching board (1). are distributed and on the other hand the circuit board (1) is arranged at least one light-sensitive sensor (30) Receives light of the light emitting diodes (Lx) through openings (17) in the circuit board (1) and whose sensor signal (SS) is fed to an evaluation circuit (31), which when the light emitting diodes (Lx) are energized, their brightness when a predetermined minimum is exceeded (SW2) checked and if it is undershot, it issues a fault message (SM), and the openings (17) are each arranged under one of the ^{• •} light-emitting diodes (Lx) and are only large enough that the crystal (26) of the light-emitting diode (Lx ) shadows the corresponding opening (17) against sunlight entering from the front, and that the light-emitting diode (Lx) has a diode housing (22) which is diffusely translucent on the circuit board side and laterally and transparent on the front side.

18. Signal light according to claim 17, characterized in that the circuit board (12) the light housing (10) outside of the openings (17) light-tight to a rear wall (14) and this and / or the circuit board (12) to the rear wall

(14) is / are coated to scatter light, in particular white.

19. Signal light according to claim 17 or 18, characterized in that the openings (17) are bores which have a reflective perforated wall lining (18).

20. Signal light according to one of claims 17 - 19, characterized in that the diode housing (22) on the front of the crystal (26) up to a front cover plate (28) or lens (27) is flared with an angle greater than 60 °.

21. Signal light according to one of claims 17 - 20, characterized in that one or more sensors (30) on the back of the circuit board (1) are arranged so that the light of all light-emitting diodes (Lx) each have an approximately proportional share in the total sensor signal (SS ) provide.

22. Signal light according to one of claims 17 - 21, characterized in that the sensor signal (SS) via a high-pass filter (32) is supplied as a useful light signal (NS) to the evaluation circuit (31) and, if appropriate, a direct-current signal component via a low-pass filter ( UHS) is separated.

23. Signal light according to one of claims 17 - 22, characterized in that the evaluation circuit (31) contains at least one comparator (Vll, V21) to which the useful light signal (NS) is fed on the input side and a first lower and possibly a second higher threshold value ( SW1, SW2) and the output signal of the comparator (Vll, V21) at the time of a respective current maximum of the light-emitting diode current is then taken over into a holding circuit (33, 34) when the useful light signal (NS) has the relevant threshold value (SW1, SW2) below.

24. Signal light according to one of claims 17 - 23, characterized in that the state of the hold circuit (33), the falling below at least one higher threshold value (SW1) is signaled as a warning (VW) to a control center of the signal light.

25. Signal light according to one of claims 17 - 24, characterized in that the state of the Holding circuit (34), which signals that the value falls below the lower threshold value (SW2) as a fault message (SM) to a control center.

26. Signal light according to claim 24 or 25, characterized in that the warning (VW) is signaled by a temporary interruption in the supply of the LEDs (Lx) and the signaling of the fault message (SM) by a permanent interruption in the supply of the LEDs (Lx ) he follows.

27. Signal light according to one of claims 17 - 26, characterized in that the openings (17) each have a bore diameter (W) which is smaller than the respective dimension (A) of the LED (Lx) arranged concentrically thereto.

28. Signal light according to claim 22, characterized in that after separation of the useful signal (NS) from the sensor signal (SS) the remaining one

Direct current signal component (UHS) dependent on sunlight irradiation is supplied to an energization control circuit (BS) which, according to sunlight irradiation, energizes the light-emitting diodes

(Lx) and this proportionally increases the threshold values

(SW1, SW2) lifts.