Supply circuit having a monitoring function

Abstract

The invention relates to a supply circuit having a monitoring function, comprising a first current branch (2) having a first controllable path (20) and at least one consumer (21) arranged in series therewith, and a second current branch (3) having a second controllable path (30) and at least one consumer (31) arranged in series therewith. A controllable converter (4) is connected to the first and the second current branches (2, 3) for supplying a total current. A control circuit (5) having a control input which is connected to the set input (10), wherein the control circuit (5) is coupled to the first controllable path (20) in order to set a current through the first current branch (2) on the basis of a provided first set signal (10). The second controllable path (30) is coupled to the first current branch (2) and to the set input (10), thereby forming a dependent control loop which is influenced by the current flowing in the first circuit (2) and by the forward voltage of the two consumers (21 and 31), and is designed to control a current through the second current branch (3) additionally on the basis of an operating state through the first current branch (2) and a second set signal. In addition, a current-controlled monitoring circuit is provided, which is in each case connected to a node between the respective current branch and the consumer arranged in series therewith and is designed to generate an error signal in response to a predefined deviation of one of the currents flowing into the current-controlled monitoring circuit, said currents representing the state of the respective consumer.

Description

[0001] 2024 PF01076

[0002] 1

[0003] POWER CIRCUIT WITH A WATCH FUNCTION

[0004] The present application claims priority from German patent application DE 10 2024 125 198 . 0 of 3 September 2024, the publication of which

[0005] 5. The present invention relates to a supply circuit with a monitoring function for multiple consumers and, in particular, light sources such as optoelectronic components.

[0006] BACKGROUND

[0007] Interchangeable bulbs are frequently used in various automotive applications for headlights. These bulbs are equipped with a locking mechanism and are inserted into the headlight as needed. In addition to their primary function, these bulbs must also be suitable for different operating modes and therefore, besides the actual components—often optoelectronic—they also incorporate converters and other control circuits to achieve, for example, different light intensities or operating modes. A typical application is interchangeable bulbs for so-called low-beam and high-beam headlights, where different road illumination and beam patterns are required depending on the operating condition.

[0008] While the operating state is externally determined, the light source itself should determine the current, voltage, and other parameters for the respective operating mode. Primarily, the luminous intensity should be variable. For this purpose, several light sources are often installed in the headlight and individually controlled. In the past, it was common practice to control the individual light sources independently and to install them separately in the headlight. This results, for example, in a number of primary light sources being used for low-beam operation and a number of secondary light sources for high-beam operation.

[0009] To meet the different requirements, the state of the art, for example, provides for assemblies with several 2024 PF01076

[0010] To operate two optoelectronic components in parallel, which are in turn connected in series. This so-called parallel operation of LED strings (i.e., several optoelectronic components in series) is possible due to the different forward voltages of the LEDs.

[0011] 5. However, this is difficult. The problem can be circumvented by performing appropriate binning, i.e., selecting individual LEDs with suitable forward voltages. However, this additional selection process increases costs. Alternatively, a separate current transformer and control circuit can be provided for each branch, which also increases costs. With a single transformer, either balancing resistors in the individual strings are necessary, or the aforementioned tight forward voltage binning is performed. Furthermore, depending on the operating conditions, significant power losses occur, which are determined by the specific design used.

[0012] Furthermore, individual light sources are subject to aging, meaning that over time, failures of the light sources or even the control circuits can occur. In the former case, this is referred to as a short circuit, which can lead either to a complete interruption of the current flow ("open") or to a de facto conduction ("short"). The latter can lead to significantly higher energy consumption.

[0013] There is therefore a need to detect faults in the light sources or assemblies and to indicate them externally so that a control circuit can take appropriate measures. At the same time, especially for automotive applications, different operating modes for the LED strings installed in the respective light sources should be freely configurable, both with regard to the selection of individual strings and the current through the branches. To prevent potential damage due to excessive heat generation, a so-called derating behavior in the various current branches is also desired.

[0014] This means that the individual power branches are controlled differently with regard to their power consumption or current flow. 2024 PF01076

[0015] 3 to control the current through the strings, while simultaneously detecting faults in the various operating modes in a cost-effective but also safe manner.

[0016] 5 SUMMARY OF THE INVENTION

[0017] This need is addressed by the subject matter of the independent patent claims. Further developments and embodiments of the proposed principle are specified in the dependent claims.

[0018] The inventor proposes a combined solution that uses a converter and a power transistor as the controllable path or controllable current source for each current branch, thus enabling various operating states. Simultaneously, the current branches can be monitored in a current-controlled manner without needing to be switched on, allowing for any fault combination of the monitored LED branches. This ensures the detection of a lamp defect in each branch, independent of the operating state of that branch or any other branch.

[0019] This is achieved, firstly, by an inventive interconnection of the controllable sections, which are provided for setting the operating states for the individual current branches. In this configuration, one controllable section of a current branch acts as a current controller, while the other controllable section operates as an "inverse follower." This behavior corresponds to an inverse control loop. This means that the controllable section of the first current branch controls the current through the first current branch in such a way that the total current remains essentially constant, with the current in the first branch being regulated to a setpoint.

[0020] For example, the controllable path of the second branch increases the current through the second branch when the total current increases or the current through the first branch decreases. This results in the total current through the converter, which is then divided among the five respective branches. 2024 PF01076

[0021] 4

[0022] Thus, according to the principle of the invention, the second controllable section follows the controllable section in the first current branch in an inverse manner. Simultaneously, a control system is provided which adjusts the first controllable section to the required setpoint current value using the first controllable section.

[0023] 5 branches are set. This regulates the operating point of the individual optoelectronic components in the respective branches in such a way that an optimal operating point is achieved with very low losses in the controllable paths and the control circuit.

[0024] The monitoring of the individual branches is current-controlled, i.e., via a tap within the current branch, from which a small current is drawn and fed to the monitoring circuit, regardless of the state of the controllable section. A fault in the current branch leads to a change in the current flow. In this way, two types of faults can be detected for each current branch, independent of the branch's operating state ("inactive," "active," or "inverse follower"): firstly, an "open" fault, in which no current can flow through the loads, and secondly, a short circuit, in which a higher than desired current flows through the loads. These possible fault signals can also be logically combined in a very simple way.

[0025] In some aspects, the inventor proposes a power supply circuit with a monitoring function. This comprises a first current branch with a first controllable section and at least one load arranged in series with it, as well as a second current branch arranged in parallel with a second controllable section and at least one load arranged in series with it.

[0026] The term "consumer" here refers to one or more current-consuming elements. These can be connected to each other in series or parallel. In lighting applications, for example in the automotive sector, such consumers include, for instance, a number of optoelectronic components. These can be connected in series, in parallel, or a combination thereof. 2024 PF01076

[0027] 5

[0028] Furthermore, a set input is provided to supply a respective set signal for controlling the first and second controllable sections, so that the respective current branches can be activated with a corresponding set input. For the supply of a total

[0029] A controllable converter is provided for the first and second current branches, which is connected to them.

[0030] According to the invention, the supply circuit with a monitoring function further comprises a control circuit with a control input connected to the set input. The control circuit is also coupled to the first controllable path for adjusting the current through the first current branch depending on a provided first set signal. The second controllable path is coupled to the first current branch and the set input, forming a control loop, and is configured to control the current through the second current branch depending on an operating state through the first current branch and a second set signal at the set input.

[0031] This allows the total current to be set to a fixed, predetermined value. The supply circuit with a monitoring function further includes a current-controlled monitoring circuit, which is connected to a node between the respective current branch and the load connected in series with it. The monitoring circuit is configured to generate a fault signal in response to a predefined deviation of any of the currents in the branch to or from the monitoring circuit.

[0032] The proposed principle takes advantage of the fact that optoelectronic components, especially those connected in series, are generally operated with current control, using a shunt connected in series with the load for current sensing. The current control can be implemented as a negative follower, as mentioned above, or simply as a series regulator, which can also serve as an on / off switching element for the corresponding branch. 2024 PF01076

[0033] 6

[0034] For fault detection, a tap is used between the regulator / shunt and the load in each branch. A portion of the current is taken from the tap and fed to the monitoring circuit. In this way, the current in the monitoring circuit is detected.

[0035] 5 and used for monitoring. If a fault occurs in a load, the current drawn or supplied to the monitoring circuit changes. In the event of an open circuit, no current flows into the branch at all; in the event of a short circuit, the voltage drop across the load changes, which also results in a change in the current drawn. The current required for monitoring is significantly lower than the operating current, so the loads are not activated. However, even when one or more current branches are switched off, a small amount of power is consumed, which can be orders of magnitude lower than the power consumed during operation.

[0036] According to the invention, the monitoring circuit evaluates, in some aspects, a change in current through the load or its voltage drop across it, depending on the operating state in the respective current branch. In this way, a fault can be reliably detected regardless of the operating state. Furthermore, by monitoring the current in the branch to the monitoring circuit, it is possible to reliably detect both an open circuit and a short circuit, for example, by comparison with one or more setpoint values.

[0037] In some aspects, an error signal output of the current-controlled monitoring circuit is connected to an error signal input of the controllable converter. This allows the converter to be switched to a safe state in some cases when an error signal is present, thus preventing further damage or danger to a user.

[0038] In some aspects, as already mentioned, the current-controlled monitoring circuit is designed to detect a short circuit or an open circuit caused by the respective consumer in the first and second circuits independently of the respective set signals and to record them in 2024 PF01076

[0039] 7

[0040] The response is to generate an error signal. It is possible to encode the state of the set signal, i.e., the state of the respective branch, in the error signal, so that the error signal contains information about the error itself as well as the target and / or actual state.

[0041] 5 stand of the branch provides .

[0042] In some aspects, the current-controlled monitoring circuit is designed to generate fault signals based on the type of fault, particularly the type of short circuit. Thus, the fault type, for example, an "open" (open short circuit) or a closed short circuit, is encoded in the fault signal. This allows different measures to be taken based on the type of fault.

[0043] For this purpose, a window comparator may be provided in the monitoring circuit in some aspects. The monitoring circuit is designed, in some aspects, to identify a type of short circuit by evaluating the current flowing through the node with at least two setpoints, primarily using the window comparator. These setpoints are, in some aspects, derived from the supply voltage provided by the converter or from the total supply current. In some aspects, the monitoring circuit is designed to perform a current-to-voltage conversion, so that a voltage signal is generated from the diverted current. This voltage signal can then be compared with setpoints. In other aspects, a comparison of the current signal with a setpoint current signal is also conceivable.

[0044] Several aspects concern the design of the current-controlled monitoring circuit. This can, for example, include a current path comprising at least one bipolar transistor. A base terminal is coupled to one of the nodes for supplying the tapped current. The current at the base controls the conductivity of the base-emitter junction. It is possible to easily provide and link five different logic functions here. For example, two or more bipolar transistors can be connected in series, each with its base terminal connected to a 2024 PF01076

[0045] 8 are connected to one of the taps in the current branches. This creates a logic AND gate; a parallel connection of these transistors implements a logic OR gate.

[0046] 5. Several further aspects deal with the regulation of the current through the current branches in the different operating modes of the current branches. In some aspects, a control input of the second controllable path is coupled to the node in the first current branch, particularly by forming negative feedback. The first current branch can nominally be switched between an on and an off state. With a total current through both current branches specified by the converter, the current in the second branch is then determined by the current in the first branch, from which the control signal for the feedback to the controlled path of the second current branch is derived. The total current remains constant, so that, for example, a temperature- or other-related change in the current through the first branch leads to a corresponding change in the current in the second branch.

[0047] In some further aspects, the supply circuit with a monitoring function includes a current-controlled voltage divider with a current-controlled section, whose control terminal is connected to the set input and coupled to the controllable section of the first current branch via a resistor for operating point adjustment. This serves to set a defined, fixed current through the first current branch.

[0048] In some other aspects, the converter is designed to interrupt current flow to the first and / or second current branch in the event of a fault signal. For this purpose, the fault signal is fed to the converter. To enable at least partial operation to be maintained if necessary, some aspects include an identification of the branch in which the fault occurred, which the converter then evaluates. Depending on this, the converter can then switch off the faulty branch while the other branch continues to operate. 2024 PF01076

[0049] BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Further aspects and embodiments according to the proposed principle will be discussed in relation to the various embodiments and components.

[0051] 5 games are revealed, which are described in detail in conjunction with the accompanying drawings.

[0052] Figure 1 shows a first embodiment of a circuit arrangement according to some aspects of the proposed principle;

[0053] Figure 2 shows a second embodiment of a circuit arrangement according to some aspects of the proposed principle;

[0054] Figure 3 represents a third embodiment of a circuit arrangement according to some aspects of the proposed principle;

[0055] Figure 4 is a diagram showing the respective branch current as a function of a total current set by the converter, which is set in a circuit arrangement according to some aspects of the proposed principle.

[0056] DETAILED DESCRIPTION

[0057] The following embodiments and examples illustrate various aspects and their combinations according to the proposed principle. The embodiments and examples are not always to scale. Likewise, various elements may be enlarged or reduced to highlight individual aspects. It is understood that the individual aspects and features of the embodiments and examples shown in the figures can readily be combined without affecting the principle of the invention.

[0058] Furthermore, the individual figures, features, and aspects are not necessarily depicted in the correct size, and the proportions between the individual elements may not be entirely accurate. Some aspects and features are emphasized by being shown enlarged. Terms such as "above," "above," "below," 2024 PF01076

[0059] 10

[0060] However, terms like "below", "larger", "smaller", and the like are correctly represented in relation to the elements in the figures. Thus, it is possible to derive such relationships between the elements from the illustrations.

[0061] 5

[0062] The circuit arrangement 1 comprises a first current branch 2 and a second current branch 3, which are connected in parallel to a current-controlled converter 4. The current-controlled converter 4 supplies the two current branches with a corresponding current. Each current branch includes at least one optoelectronic component 21 or 31, which is connected in series with a controllable section 20 and 30, respectively. The current through the respective current branch can be set by means of the controllable sections 20 and 30. Accordingly, the current in the two branches is divided between the respective parallel strands by adjusting the two controllable sections.

[0063] The total current is provided by the controller 4 and corresponds to the sum of the two individual currents in current branches 2 and 3. According to the proposed principle, the first controllable path 20 includes a control input 201, which is connected to a control circuit 5. The control circuit 5 detects a signal in the first current branch, which corresponds to a current through this current branch. This can be, for example, a voltage drop across the optoelectronic component 21, a voltage drop across the controllable path 20, a voltage drop across a current shunt, or even the current itself through the respective current branch.

[0064] Depending on this, the control circuit 5 regulates the controllable section so that a desired and predefined setpoint current value is established. The second controllable section 30 comprises a set input 301 and a control input 302. In this case, the set input 301 completely switches off the second controllable section 30, thus disconnecting the second current branch 3 from the converter 4 and preventing current flow. The control input 302, on the other hand, is connected to a tap. In this embodiment, the tap is located within the area of ​​the controllable section, but it can also be located in the current branch between the controllable section 20 2024 PF01076

[0065] 11 and the consumer 21 are located. It is essential that the tapped signal is fed to the second controllable section 30. The second controllable section is now implemented, depending on a current flow and an operating state of the first controllable section (predefined).

[0066] 5 (via the tapped signal) to regulate the current through the second current branch. It should be noted that the regulation in the second current branch 3 is not a regulation with an independent setpoint. Rather, the setpoint is derived from the current setpoint of the converter 4 and the current through the first current branch 2. This current, corresponding to the difference between the setpoints of 4 and 2, is then kept constant – even in the event of a possible voltage change of the optoelectronic component 31.

[0067] By means of a set signal at the set input 10 of the control circuit 5, the second current branch 3 can be switched into two different operating states. This is, firstly, the disconnection of the second current branch 3 from the converter 4 by a corresponding signal at the set input 301, and secondly, the activation of the second current branch with simultaneous current control as explained above. At the same time, the set input deactivates the controller 5 when the second current branch 3 is disconnected from the converter 4. This results in two possible states, as follows.

[0068] In a so-called LB operation, for example, low-beam operation in the automotive sector for illuminating an apron, the first current branch 2 is activated and current regulation is performed by the converter 4. The current is thus determined by the converter 4, and the second current branch 3 is switched off. In this state, the current through the first current branch 2 follows without further regulation; that is, the current through the first circuit is determined by the total current of the converter 4. The first circuit 2 operates in switching mode.

[0069] In a second operating state, the second current branch 35 is now activated. Simultaneously, the first current branch 2 is regulated to a target current value. This results, firstly, from analog control via the control loop 5 and, secondly, from the detection of a voltage (2024 PF01076).

[0070] 12. Current drop or current flow and simultaneous control in the second current branch through the controllable section. Accordingly, the current through the second current branch 3 results on the one hand from the specified total transformer 4 and the current flowing through the first current branch 2.

[0071] 5

[0072] The circuit arrangement of Figure 1 also includes a current-controlled monitoring circuit 6, which is connected to a node 62 in the first current branch 2 and to a node 63 in the second current circuit. A small current is drawn from these nodes and supplied to the current-controlled monitoring circuit 6. The current-controlled monitoring circuit 6 is designed to detect the drawn current (flowing into the monitoring circuit) and generate a fault signal in response. A change in this current allows conclusions to be drawn about the state of the load. In the event of a short circuit, the voltage drop across the load, or the potential at the tap, changes. Although the control transistor downstream of the load keeps the current through the load constant, the changing voltage drop leads to a change in the current supplied to the monitoring circuit.The fault signal is fed to the control circuit 5 and the converter 4 in order to, for example, switch them off or to be able to take further measures.

[0073] Fault detection can be performed as follows. Assume that current branch 2 has a faulty load that produces an open circuit, i.e., an "open" state. Then, no current flows through the tap and thus also into the monitoring circuit 6, regardless of the operating state and the control of the current-controlled system 20. The monitoring circuit 6 therefore detects a fault. If, on the other hand, the load 21 has a closed short circuit ("short") (for example, one of the series-connected optoelectronic components fails with a short circuit), the current flow also changes due to the lower voltage drop across the load, both in the inactive state of the controlled system and in the activated state. The changed current flow can be detected by comparison with a setpoint. 2024 PF01076

[0074] 13

[0075] Similarly, a fault and its type can also be determined in the second current branch 3. Both fault signals can be logically combined, or they can be passed on individually to the control unit 5. For example, it can be provided that in the event of a short circuit,

[0076] 5 “short” in branch 2 to deactivate this and also the regulation in branch 3 in order to be able to maintain at least partial operation.

[0077] Figure 2 shows a further embodiment of the invention. Components with the same function bear the same reference numerals.

[0078] In this embodiment, in contrast to the previous embodiment 2, additional switching elements 22 and 32 are connected in the respective current branches 2 and 3. Furthermore, the controllable section 20 is no longer regulated; instead, it now exhibits a fixed current when current branch 2 is activated.

[0079] The control loop also includes a set input 10, which allows each of the two current branches 2 and 3 to be selectively activated or deactivated by switch 22 or 33. This arrangement allows the two current branches to be operated independently and separately. Furthermore, the existing control of the second controllable path remains in place as an inverse follower of the first controllable path. When both current branches are activated, the current through the first current branch is set by adjusting a fixed operating point in the controllable path 20. In this operating mode, the current through the second current branch 3 is controlled by detecting a signal derived from the first current branch, taking the total current into account.If the total current or the current through the first branch changes, the second circuit adjusts in such a way that the total current is restored. Accordingly, the current through the second branch is the difference between the total current and the current through the first branch. 2.5.

[0080] The current-controlled monitoring circuit also activates in both branches here, regardless of the switch position of switches 22 and 32 2024 PF01076

[0081] 14 takes a partial current from each branch and evaluates it to determine a possible fault in the current branch. This is also done taking into account the set signal, which is transmitted via an interface between the control unit 5 and the current-controlled monitoring unit.

[0082] 5 circuit (node ​​61) is communicated. This allows the fault signal provided at fault signal output 64 to also contain information about which of the respective current branches is damaged and what type of fault it is.

[0083] Figure 3 now shows a embodiment of a circuit arrangement according to the proposed principle.

[0084] The circuit arrangement includes a converter 4, which is configured here as a controlled current source. In addition to outputs for selecting the two current branches 43, the converter also has a fault signal input 44, which allows the converter 4 to be switched off or its setpoint current to be influenced in the event of a fault, indicated by the monitoring circuit 6.

[0085] Controllable sections 2 and 3 are arranged in parallel to converter 4. Controllable section 2 comprises three series-connected optoelectronic components D1, D2, and D3 in the form of light-emitting diodes (LEDs), which are grouped together as optoelectronic component 21. A forward voltage would drop across each of the LEDs in normal operation. Controllable section 200 is implemented using a field-effect transistor M1, whose source and drain terminals are connected in series with component 21. A resistor RI is also provided between the field-effect transistor M1 and the ground potential terminal GND. This resistor serves to set an operating point and thus forms part of a control circuit 5, which will be explained in more detail later.

[0086] The second controllable circuit 3 also comprises three diodes D4, D5, and D6 connected in series, forming the optoelectronic component 5 31. Here too, a field-effect transistor M2 is provided as part of the controllable circuit 300 and is connected in series with the three LEDs D4, D5, and D6 in the current branch 3. 2024 PF01076

[0087] 15

[0088] Parallel to the second current branch 3 is a selection branch with a resistor R4, the base of which is connected to the selection terminal 43 of the converter for activating or deactivating current branch 3. The gate terminal of the field-effect transistor

[0089] 5 M2 of line 300 forms the control terminal 301 and is connected to the selection branch. A second node 302 is connected via a further resistor R3 to a node between the field-effect transistor M1 of line 200 and the optoelectronic component 21 of the first current branch 2.

[0090] Circuit 5 further includes a second selection branch, which is connected to the selection terminal 43 of the converter. This path for activating and / or deactivating the first branch 2 leads to the base of a bipolar transistor Q1, which together with a resistor R2 forms a controlled path 50. A further connection between the bipolar transistor Q1 and the resistor R2 leads to the control input 201, which serves as the gate terminal of the field-effect transistor M1.

[0091] Operation at a predetermined total current through the converter 4 is now achieved via a corresponding set signal at the selection outputs 43. If this set signal is at a logic low level L for both outputs, the set input GM2 and node 302 in the selection branch connected to the gate of the second field-effect transistor 300 are pulled to a low potential. This causes transistor M2 to switch off, and the junction 300 completely switches off the second current branch 3. In this context, the field-effect transistor M2 thus acts as a switch.

[0092] Simultaneously, after the operating point is set, the base of transistor Q1 is pulled to a low potential by resistors R5 and RI in the controlled path 50, so that the base-emitter path of transistor Q1 becomes high-impedance. This results in a high-level signal at the control input 201 of the field-effect transistor 200, so that it essentially switches on. Accordingly, transistor M1 of the first path 20 also operates in switching mode, and current flows through the first current branch 2 without a 2024 PF01076

[0093] 16 independent control. The current through the first current branch 2 is essentially determined by the converter 4.

[0094] If, on the other hand, the two selection outputs 43 are high impedance, then the result is

[0095] 5. A different picture emerges. In the controlled circuit 50, a voltage is applied to the base of transistor Q1, resulting from the voltage drop across resistors R5 and RI. The operating point setting (current setpoint setting for the first current branch 2) of the base of transistor Q1 leads to a controlled potential at tap GM1 or 201 and the gate terminal of the field-effect transistor M1, and thus to a regulated current through the first current branch 2.

[0096] Specifically, the channel of the field-effect transistor Ml of the path 200 is opened or closed by the potential at tap 201. If the base of transistor Ql decreases accordingly, its resistance increases. This increases the potential at tap 201, and consequently, the field-effect transistor 200 reduces its channel resistance, thus increasing the current through the first current branch 2. Conversely, if the voltage at the base of the bipolar transistor Ql increases, the voltage at the gate terminal of transistor 200 decreases, and the current flow through current branch 2 decreases.

[0097] In the second current branch 3, a high potential is applied to the gate terminal (R4) in the high-impedance case of the selector output 43, causing the field-effect transistor 300 to conduct and resulting in a current flow through the second current branch. The resistor R3 between the tap 302 and a node between the optoelectronic component 21 and the field-effect transistor M1 of the controlled section 200 of the first current branch 2 serves to inversely control the current through the second current branch 3. This ensures that forward voltage differences between the loads 21 and 31 are compensated for while keeping the currents in current branches 2 and 3 constant.

[0098] In particular, voltage division occurs here through resistors R3 and R4. A reduction of the channel resistance of the field-effect transistor 200 (e.g., by regulation when the impedance of the load 21 increases to keep the current in the first current branch constant) 2024 PF01076

[0099] 17

[0100] 2) leads to a decrease in the potential at tap 302. This increases the channel resistance of transistor M2 in path 300. Transistor M2 thus follows the behavior of transistor M1 in reverse. This maintains the current distribution across both branches.

[0101] 5 constant ( @ I out converter 4 = constant ) .

[0102] Conversely, if the impedance of load 21 decreases, the channel resistance of transistor M1 increases due to the control circuit 5, and the process described above occurs with the opposite sign. If load 31 now experiences a change in its impedance, this would also lead to a change in current in the first branch 2, which is counteracted by the control circuit 5 by changing the channel resistance of transistor M1. A process as described above then occurs again.

[0103] The required resistance values ​​of the drain-source paths in the two field-effect transistors 200 and 300 are automatically adjusted by the feedback. Resistors R3, R4, and R5 determine the basic operating point and thus also the main power dissipation in the circuit.

[0104] Furthermore, additional taps are provided in each branch 2 and 3, specifically between the respective loads 21 and 32 and the associated controlled sections 200 and 300. The first node KP leads via a resistor 620 and a first bipolar transistor, while the second node KP in branch 3 leads via a resistor 630 to a second bipolar transistor 67. The two bipolar transistors 66 and 67 are connected in series and form a logic AND gate in the current-controlled monitoring circuit 6. The bipolar transistors are connected in series with another current-limiting resistor 68 between the supply potential and ground potential. An error signal can be tapped at a tap 64 in the current-controlled monitoring circuit and is fed to the converter 4 at the error signal input 44.

[0105] The currents to be evaluated for fault monitoring are taken from the nodes KP shown in Figure 3 and fed to the two bipolar transistors. 2024 PF01076

[0106] 18 gates are supplied. As already mentioned, the current evaluation is independent of the selection signals at output 43, i.e., independent of which current branch is currently active. Resistors 620 and 630 are used to set the operating point and the switching voltage.

[0107] 5 hold and thus determine the sensitivity of the error monitoring.

[0108] In a fault-free case, i.e., with an intact load 21 or 31, the following applies with an inactive branch 2 or 3. A very small current flows through the respective load, determined by the resistor 620 or 630, into the base-emitter path of the respective transistors and drives them. This generates a logic low level at tap 64.

[0109] If a load in an inactive branch causes a current interruption ("open"), the corresponding transistor switches off and tap 64 is pulled to a high logic level, indicating an error signal. However, a short circuit ("short") can only be detected to a limited extent in this configuration, namely only when the selection signals are evaluated simultaneously. Alternatively, a second monitoring branch can be provided to cover this case with another series connection of bipolar transistors (e.g., with opposite polarity). Alternatively, a window comparator can be used, so that the signal from node KP of each branch must be within a certain window.

[0110] The situation is similar for switched-on current branches. With an intact, i.e., fault-free, load, the voltage drop at the node drives a current through the base-emitter junction of the first and second transistors 62, 63. The following applies to the voltage drop at the first node KP in the first current branch 2:

[0111] UKP = U trans i s tor_200 + U R1 5. The voltage drop thus results from the voltage drop across transistor 200 and the voltage drop across resistor RI. For the voltage drop at node KP in branch 3, it now follows that this is 2024 PF01076

[0112] 19 is equal to the voltage drop across transistor 300. The two voltage drops are also equal in the case of equal voltages through the respective loads and equal currents through them.

[0113] 5. To further adjust the operating point for fault detection in the current-controlled monitoring circuit, the respective transistors 66 and 67 can be biased at their bases or their sensitivity can be damped by additional networks (not shown). These additional networks can be connected to a constant voltage or to the supply voltage U0 or the voltage driving the LED (+). This allows information from these voltages to be incorporated into the fault detection.

[0114] A (symmetry) resistor can also be inserted into the source path of transistor M2 of controlled circuit 300. It would then be arranged in parallel with RI and serves to relieve the load on M2. It is also conceivable to equip the second current branch with a circuit similar to controlled circuit 50, thus designing the second current branch 50 as a complete regulator. With the proposed measures, a simple yet effective current-controlled monitoring system is implemented, which identifies a fault in the branches even before the two (or further) current branches are activated. This allows further measures to be taken in advance, thus preventing further damage to the component.

[0115] In some aspects, it is necessary to perform so-called derating, i.e., a desired reduction of the total current even without a fault. The total current is deliberately reduced, for example, to prevent further heating of the optoelectronic components. For this purpose, the circuit, according to the proposed principle, allows the current in the second current branch 3 to be reduced if the total current—defined by the converter 4—changes and, in particular, decreases. As already explained, the total current is the sum of the two individual currents in current branches 2 and 3, with the total current being adjustable by the converter 4. If the total current is now changed, 2024 PF01076

[0116] For example, in equation 20, the current in the second branch should be reduced first when both branches are operating simultaneously, so that the sum of both currents equals the total current. At the same time, the current in the first branch should essentially remain the same.

[0117] The voltage at 5 is kept constant. Only when a minimum is reached is the second current branch switched off and the first current branch transitions to the switching operation described above. To prevent unwanted activation of the fault detection in the derating case (e.g., due to a decrease in current flow to the base of transistor 67), the fault detection can be influenced accordingly or switched off during this specific state.

[0118] A change in the current in the second current branch in response to a change in the total current is achieved by the circuit arrangement according to the invention by means of inverse feedback from the second controllable path 30 and the field-effect transistor M2 of the second path 300 to the first controllable path 20 and the first field-effect transistor 200. With a decreasing total current, the control circuit 50 and the operating point setting ensure a substantially constant current behavior in the first current branch 2. In other words, the current through the optoelectronic component 2 in the first current branch 2 remains substantially constant, since the channel of the field-effect transistor M1 of the first controlled path 200 is increasingly driven. Accordingly, the potential at the node between the optoelectronic component 21 and the field-effect transistor 200 continues to decrease, so that the potential at the tap 302 also decreases.Accordingly, the channel resistance in the field-effect transistor 300 increases, causing the current in the current branch 3 to decrease.

[0119] This effect can be illustrated in Figure 4, which shows the path current through the two current branches 2 and 3 as a function of the total current. The total current is indicated on the x-axis and lies between 1 A and 2 A. It results from the sum of the two individual currents in branches 2 and 3. It can be seen that when the total current on the x-axis changes, for example from 1.4 A to 1.8 A, the current in the first current branch 2 remains essentially constant. In contrast, the current in the second current branch increases with a High-Beam 2024 PF01076

[0120] - 21 -

[0121] The current decreases from approximately 0.55 A to approximately 0.9 A. In this range of the total current, with both the first and second current branches activated, de-rating occurs solely through the current flow in the second branch. Only when the current falls below a minimum value of approximately 1 A is the second current branch completely switched off, and the current reduction occurs solely through the first current branch.

[0122] 2024 PF01076

[0123] - 22 -

[0124] REFERENCE MARK LIST

[0125] 1 Circuit arrangement

[0126] 2, 2 ä branch

[0127] 5 4 converter

[0128] 5 Control circuit 10 Set input 20 Controllable path 21 Load, optoelectronic component 22 Switch 30 Controllable path 31 Load, optoelectronic component

[0129] 32, 32 ' Switch 41 Temperature sensor 5 43 Selection output 44 Error signal input 50 Route

[0130] 62, 63 Node 66, 67 Transistor 0

[0131] 200 controllable section 201 control input , tap 301 set input 302 control input 5 300 controllable section 620 , , 630 resistance KP node

[0132] M1, M2 Field-effect transistor D1 . .. D6 LEDs 0 RI , R2 Resistor R3 , R4 Resistor

Claims

2024PF01076 - 23 - PATENT CLAIMS 1. Supply circuit with a monitoring function; comprising a first current branch (2) with a first controllable section 5 (20) and at least one consumer arranged in series therewith (21) ; a second current branch (3) with a second controllable section (30) and at least one load (31) arranged in series therewith; a set input for providing a respective set signal for controlling the first and second controllable sections; a controllable converter (4) which is connected to the first and second current branches (2, 3) to supply a total current; - a control circuit (5) with a control input connected to the set input (10), wherein the control circuit (5) is coupled to the first controllable section (20) for adjusting a current through the first current branch (2) depending on a provided first set signal; wherein the second controllable section (30) is coupled to the first current branch (2) and to the set input (10) in a control loop and is configured to control a current through the second current branch (3) depending on an operating state through the first current branch (2) and a second set signal at the set input; a current-controlled monitoring circuit (6) which is connected to a node between the respective current branch (2, 3) and the load arranged in series with it and is configured to generate an error signal in response to a predefined deviation of one of the currents at the monitoring circuit.

2. Supply circuit with a monitoring function according to claim 1, wherein an error signal output of the current-controlled monitoring circuit is connected to an error signal input of the controllable converter5 (4). 2024 PF01076 24 3. Supply circuit with a monitoring function according to one of the preceding claims, wherein the current-controlled monitoring circuit is configured to detect a short circuit and / or an open circuit caused by the respective consumer in the first and second 5. To detect the circuit independently of the respective set signals and to generate an error signal.

4. Supply circuit with a monitoring function according to one of the preceding claims, wherein the current-controlled monitoring circuit is configured to generate fault signals based on the type of fault, in particular the type of short circuit and / or open circuit.

5. Supply circuit with a monitoring function according to claim 4, wherein the current-controlled monitoring circuit has a window comparator, wherein a type of short circuit is carried out by evaluating the current flowing through the node, in particular to the monitoring circuit with at least two setpoint values.

6. Supply circuit with a monitoring function according to one of the preceding claims, wherein the current-controlled monitoring circuit has a current path comprising at least one bipolar transistor whose base terminal is coupled to one of the nodes.

7. Supply circuit with a monitoring function according to one of the preceding claims, wherein a control input of the second controllable section (30) is coupled to the node in the first current branch.

8. Supply circuit with a monitoring function according to one of the preceding claims, further comprising a current-controlled voltage divider with a current-controlled section, the control terminal of which is connected to the set input and coupled to the controllable section of the first current branch via a resistor for operating point setting. 2024 PF01076 25 9. Supply circuit with a monitoring function according to one of the preceding claims, wherein the converter is configured to prevent current to the first and / or second current branch in the event of an error signal.

10. Circuit arrangement according to one of the preceding claims, wherein the second controllable section is configured to control a current through the second current branch as a function of a voltage drop across at least a part of the first current branch, in particular comprising the consumer; Voltage drop across the first controllable path in the first current branch; and Current flow through the first controllable section in the first current branch; to be adjusted.

11. Supply circuit with a monitoring function according to one of the preceding claims, wherein the control circuit ( 5 ) comprises a section ( 50 ) consisting of a resistor and a current-controlled section with an intermediate tap which is connected to a control input of the first controllable section.

12. Light sources, including: A circuit arrangement according to one of the preceding claims, a housing in which the circuit arrangement is arranged, A socket for inserting the light source into a headlight, wherein the at least one optoelectronic component of the second current branch is arranged such that, in operation, a light cone generated by this component overlaps only minimally with a light cone formed by the at least one optoelectronic component of the first current branch.

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