CN110418452B

CN110418452B - Circuit for monitoring a light-emitting circuit

Info

Publication number: CN110418452B
Application number: CN201810407341.9A
Authority: CN
Inventors: 施三保; 奚义义; 吴春林
Original assignee: Valeo Interior Controls Shenzhen Co Ltd
Current assignee: Valeo Interior Controls Shenzhen Co Ltd
Priority date: 2018-04-28
Filing date: 2018-04-28
Publication date: 2022-10-18
Anticipated expiration: 2038-04-28
Also published as: WO2019206330A1; CN110418452A

Abstract

The present disclosure provides a circuit for monitoring a lighting circuit, the lighting circuit comprising one or more lighting branches. The circuit includes one or more connection modules and an output module. Each of the one or more connection modules has a first end connected to the detection point in the corresponding branch and a second end connected to the first node, and is configured to control conduction of the current by comparing a potential difference between the detection point and the first node with a threshold voltage. The output module has a first terminal connected to the first node and a second terminal connected to an output terminal, and is configured to control an output in accordance with a potential of the first node.

Description

Circuit for monitoring a light-emitting circuit

Technical Field

The present disclosure relates to the field of electronic devices, and in particular, to a circuit for monitoring a light emitting circuit.

Background

Light emitting circuits are widely used in various industries. In particular, a light emitting circuit currently tends to use LEDs as a light emitting component for various fields such as architectural lighting, automobile headlights, backlights of liquid crystal display devices including personal computers and high-definition televisions, and flash lamps. In a large-area lighting system, a plurality of LED strings are generally used as an LED string. Especially in vehicle application, the LED string is likely to be broken, so that the LEDs in the string cannot illuminate normally, and even personal safety may be endangered.

Therefore, a circuit for monitoring a light emitting circuit capable of timely detecting an abnormal state of an LED is required.

Disclosure of Invention

The present disclosure is directed to providing a circuit for monitoring a light emitting circuit, which can detect an abnormal state of the light emitting circuit in time, effectively prevent a power source from being ignited, and can implement detection of the light emitting circuit with a simpler and more economical implementation scheme.

According to one aspect of the present disclosure, a circuit for monitoring a lighting circuit is provided, wherein the lighting circuit may comprise one or more lighting branches. In particular, the circuit may comprise one or more connection modules and an output module. Each of the one or more connection modules has a first end connected to the detection point in the corresponding branch and a second end connected to the first node, and is configured to control conduction of the current by comparing a potential difference between the detection point and the first node with a threshold voltage. The output module has a first terminal connected to the first node and a second terminal connected to an output terminal, and is configured to control an output in accordance with a potential of the first node.

As one example, the connection module may be configured to allow current to flow from the detection point to the first node in response to the potential difference being greater than the threshold voltage.

As another example, the connection module may be implemented as a diode, wherein an anode of the diode is connected to the detection point and a cathode of the diode is connected to the first node.

As another example, the output module may include a zener diode and a transistor, wherein a cathode of the zener diode is connected to the first node, and an anode thereof is connected to a gate of the transistor; and one of a drain and a source of the transistor is grounded and the other is connected to the output terminal.

As another example, the output module may include a zener diode and a transistor, wherein a cathode of the zener diode is connected to one of a source and a drain of the transistor, and an anode thereof is connected to ground; and a gate of the transistor is connected to the first node, and the other of the source and the drain thereof is connected to the output terminal.

As another example, the regulated voltage of the zener diode may be equal to the voltage at the detection point when the branch is operating normally.

As another example, the transistor may include a PNP type transistor.

As another example, the transistor may include an NPN type transistor.

As still another example, the circuit may further include a resistor having one end connected to the first node and the other end connected to the output block.

According to another aspect of the present invention, there is also provided a lighting system. The light emitting system may include: power supply, light emitting circuit and monitoring circuit. The lighting circuit includes one or more lighting branches, where each lighting branch includes one or more light emitting devices and a constant current source, and is configured to receive power from a power source to drive the one or more light emitting devices to emit light via the constant current source. The monitoring circuit may be configured to monitor the light emitting circuit and include: one or more connection modules, each of the one or more connection modules having a first terminal connected to the detection point in the corresponding branch and a second terminal connected to the first node, and configured to control conduction of a current by comparing a potential difference between the detection point and the first node with a threshold voltage; and an output module having a first end connected to the first node and a second end connected to an output terminal, and configured to control an output according to a potential of the first node.

Drawings

For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

fig. 1 shows a circuit diagram of one example of a circuit for monitoring a lighting circuit;

fig. 2 shows a circuit diagram of another example of a circuit for monitoring a lighting circuit;

FIG. 3 shows a block diagram of a circuit for monitoring a lighting circuit according to an example embodiment of the present disclosure;

FIG. 4 shows a circuit diagram of a circuit for monitoring a lighting circuit according to an example embodiment of the present disclosure; and

fig. 5 shows a circuit diagram of a circuit for monitoring a light emitting circuit according to another example embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "a", "an" and "the", and the like, as used herein, are also intended to include the meaning of "a plurality" and "the" unless the context clearly indicates otherwise. Furthermore, the terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components. In addition, in this specification, the terms "transistor" and "transistor" may be used interchangeably unless explicitly indicated.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

Some block diagrams and/or flow diagrams are shown in the figures. It will be understood that some blocks of the block diagrams and/or flowchart illustrations, or combinations thereof, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the instructions, which execute via the processor, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.

Accordingly, the techniques of this disclosure may be implemented in hardware and/or software (including firmware, microcode, etc.). In addition, the techniques of this disclosure may take the form of a computer program product on a computer-readable medium having instructions stored thereon for use by or in connection with an instruction execution system. In the context of this disclosure, a computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the instructions. For example, the computer readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. Specific examples of the computer readable medium include: magnetic storage devices such as magnetic tape or Hard Disk Drives (HDDs); optical storage devices, such as compact disks (CD-ROMs); a memory, such as a Random Access Memory (RAM) or a flash memory; and/or wired/wireless communication links.

Embodiments of the present disclosure provide a circuit for monitoring a lighting circuit including one or more lighting branches. The circuit can detect an abnormal state of the light emitting circuit in time and can realize the detection of the light emitting circuit with a simpler and more economical implementation scheme. The light emitting circuit according to the exemplary embodiment of the present invention can be applied to various fields, for example, can be applied to various illumination and indication systems such as architectural illumination, automobile headlights, backlights of liquid crystal display devices including personal computers and high-definition televisions, and flash lamps.

Fig. 1 shows a circuit diagram of one example of a circuit for monitoring a light emitting circuit. In particular, in the present application, the light emitting circuit is exemplarily implemented as an LED driving circuit, and the light emitting circuit includes a plurality of light emitting branches. In the circuit shown in fig. 1, the constant current source is close to the ground and far from the power source terminal, and thus is a low-side drive circuit. The circuit to the left of the dashed box of fig. 1 shows the low-side LED driving circuit, while the circuit inside the dashed box shows the circuit for monitoring the low-side LED driving circuit.

In the low-side LED driving circuit shown In fig. 1, three light emitting branches are included, and each light emitting branch is composed of one LED string (e.g., first strings D11, D12, and D13; second strings D21, D22, and D23; and nth strings Dn1, dn2, and Dn 3) including three LEDs and one constant current source (e.g., I1, I2, and In). In the low-side LED driver circuit, the LED string is directly connected to a power supply (shown as "VBAT"). It should be noted that the number of light emitting branches and the number of LEDs comprised by the LED string are merely exemplary and not limited thereto. The monitoring circuit within the dashed box is connected to the detection points in the light emitting branch via diodes (D1, D2 and D3) and has an auxiliary power supply (shown as "V _ 5V"). When the LEDs are all in the normal on-state, the auxiliary power supply generates a current through R1, D4 and R2, at which time a high voltage is obtained at the output point (vout). If one of the LEDs is open, e.g., D12 is open, then there will be current flowing through D1, and no more current will flow through D4, thus a low voltage is obtained at the output point (Vout).

Although the above circuit can realize monitoring of the low-side LED driving circuit, since the LED string is directly connected to the power supply in the low-side LED driving circuit, there is a risk of fire on the power supply. Therefore, a safer driving circuit and a safer monitoring circuit thereof are needed.

Fig. 2 shows a circuit diagram of another example of a circuit for monitoring a lighting circuit. In particular, fig. 2 proposes a high-side LED driving circuit and a circuit for monitoring the high-side LED driving circuit. By "high-side" LED drive circuit is meant that the constant current source is located on the power supply side and away from ground.

As shown in fig. 2, for each light emitting branch of the high-side LED driving circuit, the LED string is connected to a power supply via a constant current source. Because the resistance of the constant current source is infinite, the protection of the power supply can be realized, thereby effectively solving the problem of the power supply on fire, namely providing a safe drive circuit of the light-emitting circuit. For the above-mentioned drive circuit, a corresponding monitoring circuit is also required.

The circuitry for monitoring the high side LED driver circuit is shown in the dashed box of fig. 2. In this circuit, there is no auxiliary power supply, but each lighting branch needs to lead out one output terminal through the corresponding device, for example, for the first LED string consisting of D11, D12 and D13, the output terminal (vout 1) is LED out from the detection point through resistors R5 and R6; for the second LED string composed of D21, D22, and D23, the output terminal (vout 2) is LED out from the detection point through the resistors R3 and R4; and for the nth LED string composed of Dn1, dn2 and Dn3, an output terminal (vout n) is drawn from the detection point through resistors R1 and R2. In addition, it is necessary for the controller to reserve a corresponding number of ports to receive and analyze the output of each terminal. In this case, when the LEDs are all in a normal on state, each output terminal outputs a low voltage. However, if one of the LEDs is open, e.g., D12 is open, the voltage of the power supply will be applied directly to R5 and R6, so the output terminal vout 1 outputs a correspondingly high voltage. The controller determines that a disconnection occurs in the light emitting branch and outputs a corresponding notification signal in response to receiving a high voltage from the output terminal (vout 1).

Although the above circuit can realize monitoring of the high-side LED driving circuit, since each branch needs to lead out a corresponding output terminal and there is no shared component in the circuit, the monitoring circuit is expensive and complicated in structure.

In summary, there is a need for a circuit for monitoring a light emitting circuit, which can timely detect an abnormal state of a light emitting branch, effectively prevent a power source from being ignited, and can implement detection of the light emitting circuit with a simpler and more economical implementation scheme.

Fig. 3 shows a block diagram of a circuit for monitoring a lighting circuit according to an example embodiment of the present disclosure.

As shown in fig. 3, the circuit for monitoring a light emitting circuit includes one or more connection blocks denoted by reference numeral 110 and an output block P denoted by reference numeral 120. Specifically, the connection modules include a first connection module C1, a second connection module C2, and an nth connection module Cn, which are denoted by reference numerals 110-1, 110-2, and 110-n, respectively. Each of the one or more connection modules 110 has a first end connected to the detection point (e.g., the first detection point M1, the second detection point M2, the nth detection point Mn, etc.) in the corresponding branch and a second end connected to the first node a, and is configured to control conduction of the current by comparing a potential difference between the corresponding detection point and the first node a with a threshold voltage. Specifically, each of the connection blocks C1, C2, and Cn may be configured to allow a current to flow from the corresponding detection point to the first node in response to a potential difference across the connection block being greater than a threshold voltage. In one embodiment, the connection module may be implemented as a diode, wherein an anode of the diode is connected to the detection point and a cathode of the diode is connected to the first node, and the threshold voltage may be implemented as a turn-on voltage of the diode. That is, when the voltage across the diode is greater than its turn-on voltage, current is allowed to flow from the corresponding detection point (e.g., one of M1, M2, and Mn to the node a).

In addition, the output block P120 may have a first terminal connected to the first node a and a second terminal connected to an output terminal (vout), and be configured to control the magnitude of the output according to the potential of the first node a.

Additionally or alternatively, the circuit may further comprise a resistor having one end connected to the first node and the other end connected to the output module. The resistor is configured to limit the magnitude of current in the circuit to protect the circuit.

An example embodiment of a circuit for monitoring a light emitting circuit according to an example embodiment of the present disclosure will be described below with reference to fig. 4 and 5. In particular, fig. 4 shows a circuit diagram of a circuit for monitoring a light emitting circuit according to an example embodiment of the present disclosure. The circuitry to the left of the dashed box of fig. 4 shows a high-side LED driver circuit, while the circuitry inside the dashed box shows circuitry for monitoring a high-side LED driver circuit according to an exemplary embodiment of the present invention. As described above, the circuit includes the connection module 410 and the output module 420.

As shown in the dashed box of fig. 4, the connection module 410 is schematically implemented as diodes D1, D2 and Dn, and the output module 420 includes a zener diode ZD1 and a transistor Q1. Specifically, each of the diodes D1, D2, and Dn has an anode connected to a corresponding detection point (M1, M2, mn) in the lighting circuit and a cathode connected to the first node (i.e., node a). The cathode of the voltage stabilizing diode ZD1 is connected with the node A, the anode is connected with the grid G of the transistor Q1, and the stable voltage is approximately equal to the voltage of a detection point when the branch circuit works normally. For example, when there are three LEDs in the circuit, the zener diode ZD1 can be selected to have a reverse breakdown voltage of about 6V. It should be noted that the connection of the anode to the gate G of the transistor Q1 may be implemented by directly connecting the anode of the zener diode ZD1 to the gate G of the transistor Q1, or by connecting it to the gate G of the transistor Q1 via a resistor R1. In the present exemplary embodiment, one of the drain D and the source S of the transistor Q1 may be grounded, and the other may be connected to the output terminal (vout).

When the light emitting branch works normally, the voltage across the diodes D1, D2 and Dn is approximately the same, that is, the diodes D1, D2 and Dn are turned off and not turned on, because the voltage of ZD1 is approximately equal to the voltage at the detection point when the branch works normally. The output terminal (vout) is set to a floating level (high if there is an internal pull-up voltage). In this embodiment, the voltage of each LED may be about 2V, and the voltage of the series of three LEDs will be 6V. When the LED normally works, the diodes D1, D2 and Dn, the voltage stabilizing diode ZD1 and the triode Q1 do not work, so that the (V output) output is high level.

When a certain LED (e.g., D12) is open-circuited, the voltage difference across the diode D1 is greater than its turn-on voltage, so that the diode D1 is turned on, further causing the zener diode ZD1 to be breakdown-turned on. At this time, a current flows from the zener diode ZD1 to the transistor Q1. For the transistor Q1, the gate receives a high level, and therefore, the transistor Q1 is turned on, so that the output terminal (vout) outputs a low level. Specifically, when D11 is open, I1 will be in the maximum on state in order for the constant current source I1 to reach a predetermined constant current. Thus, the anode voltage of the diode D1 will be about the voltage of the power supply, in this example about 13V, which is greater than the PN junction voltage of the diode D1 (0.7V), the voltage of the zener diode ZD1 (about 6V) and the PN junction voltage of the transistor Q1 (0.7V), resulting in D1 being turned on, i.e., if it were, if

V input > V _PN (D1)+V _zD1 +V _be (Q1)，

The diode D1 is turned on. It should be noted that the same principle applies to diodes D2 and Dn. At this time, the zener diode ZD1 is broken down, and the transistor Q1 is turned on, so that the output terminal (vout) is at a low level.

It should be noted that the description of the control module is omitted in the drawings. The circuit may further comprise a control module, wherein the output terminal of the monitoring circuit may be connected to the control module such that the control module may determine that an open circuit has occurred within the lighting circuit in response to the output changing from a high level to a low level, and may therefore provide a corresponding indication signal.

Fig. 5 shows a circuit diagram of a circuit for monitoring a light emitting circuit according to another example embodiment of the present disclosure. Fig. 5 is the same principle as that shown in fig. 4, except for the connection manner. Specifically, as shown in fig. 5, the cathode of the zener diode ZD1 is connected to one of the source S and the drain D of the transistor Q1, and the anode thereof is connected to the ground. The gate G of the transistor Q1 may be connected to the node a, and the other of the source S and the drain D thereof is connected to an output terminal (vout). Since the operation principle of the embodiment shown in fig. 5 is the same as that of the embodiment shown in fig. 4, the detailed description thereof will be omitted.

In the circuits shown in fig. 4 and 5, a plurality of light emitting circuits share one set of monitoring circuit, so that the structure of the monitoring circuit is simplified, and the cost can be significantly reduced, thereby realizing a circuit for monitoring a light emitting circuit, which can detect an abnormal state of a light emitting circuit in time and effectively prevent a power source from being on fire with a simple and economical scheme.

It should be noted that although one exemplary embodiment of the present application has been described in the above description using a high-conduction NPN type transistor as an example, the present application may also use a low-conduction PNP type transistor. When a low-conductivity PNP transistor is used, a corresponding auxiliary power supply may be provided. Further, the transistor Q1 may be implemented as another transistor such as a MOSFET, in addition to being implemented as a bipolar transistor.

In summary, fig. 4 and 5 both show a lighting system. Wherein the lighting system may include: a power source; a lighting circuit comprising one or more lighting branches, wherein each lighting branch comprises one or more light emitting devices and a constant current source, and is configured to receive power from a power source to drive the one or more light emitting devices to emit light via the constant current source; and a monitoring circuit configured to monitor the light emitting circuit. The monitoring circuit may comprise one or

more connection modules

410, 510, each of the one or

more connection modules

410, 510 having a first end connected to a detection point M1, M2, mn in the respective branch and a second end connected to a first node a and being configured to control conduction of a current by comparing a potential difference between the detection point M1, M2, mn and the first node a with a threshold voltage; and an

output module

420, 520, the

output module

420, 520 having a first terminal connected to the first node a and a second terminal connected to an output terminal, and configured to control an output according to a potential of the first node a.

In addition, although the LED driving circuit is described in this specification as one string of every three LEDs and each string of LEDs has the same number of LED light emitting devices, the present invention is not limited thereto. The monitoring circuit according to an exemplary embodiment of the present invention may be applied not only to an LED driving circuit including other numbers of LED light emitting devices per string, but also to an LED driving circuit having different numbers of LED light emitting devices per string (e.g., a first string having 3 LEDs, a second string having 4 LEDs, and a third string having 3 LEDs). It should be noted that when the monitoring circuit according to the exemplary embodiment of the present invention is applied to the LED driving circuit having different numbers of LED light emitting devices for respective strings, the stabilization voltage of the zener diode is selected to be approximately equal to the maximum operating voltage among the operating voltages on the respective strings.

Furthermore, it should be noted that although the above describes separately in a divided form the implementation of the method according to an example embodiment of the present disclosure, the features described in the above described implementations may be combined in any way in a single implementation without departing from the concept of the present disclosure, and the features described in a single implementation may also be implemented separately in a plurality of implementations.

While the disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Accordingly, the scope of the present disclosure should not be limited to the above-described embodiments, but should be defined not only by the appended claims, but also by equivalents thereof.

Claims

1. A circuit for monitoring a lighting circuit, the lighting circuit including one or more lighting branches, comprising:

one or more connection modules (110, 410, 510), each of the one or more connection modules (110, 410, 510) having a first end connected to the detection point (M1, M2, mn) in the corresponding branch and a second end connected to the first node (a), and being configured to control conduction of a current by comparing a potential difference between the detection point (M1, M2, mn) and the first node (a) with a threshold voltage; and

an output module (120, 420, 520), the output module (120, 420, 520) having a first end connected to the first node (a) and a second end connected to an output terminal, and configured to control an output according to a potential of the first node (a); the output module (120, 420, 520) comprises a zener diode (ZD 1) and a transistor (Q1), wherein the regulated voltage of the ZD1 is equal to the voltage of the detection points (M1, M2, mn) when the branch normally operates.

2. The circuit of claim 1, wherein the connection module (110, 410, 510) is configured to allow current to flow from the detection point (M1, M2, mn) to the first node (a) in response to the potential difference being greater than the threshold voltage.

3. The circuit according to claim 1, wherein the connection module (110, 410, 510) is realized as a diode (D1, D2, dn), wherein the diode (D1, D2, dn) has an anode connected to the detection point (M1, M2, mn) and a cathode connected to the first node (a).

4. The circuit according to claim 1, wherein the first and second switches are connected to the first and second terminals,

wherein the cathode of the zener diode (ZD 1) is connected to the first node (a) and the anode thereof is connected to the gate of the transistor (Q1); and is provided with

One of the drain and the source of the transistor (Q1) is grounded, and the other is connected to the output terminal.

5. The circuit according to claim 1, wherein the first and second switches are connected to the first and second switches,

wherein the cathode of the zener diode (ZD 1) is connected to one of the source and drain of the transistor (Q1), and the anode thereof is connected to ground; and is

The gate of the transistor (Q1) is connected to the first node (a), and the other of the source and the drain thereof is connected to the output terminal.

6. The circuit of claim 1, wherein the transistor (Q1) comprises a PNP-type transistor.

7. The circuit of claim 1, wherein the transistor (Q1) comprises an NPN transistor.

8. The circuit according to claim 1, wherein the circuit further comprises a resistor (R1), the resistor (R1) being connected at one end to the first node (a) and at the other end to the output module (120, 420, 520).

9. A lighting system, comprising:

a power source;

a lighting circuit comprising one or more lighting branches, wherein each lighting branch comprises one or more light emitting devices and a constant current source, and is configured to receive power from a power source to drive the one or more light emitting devices to emit light via the constant current source; and

a monitoring circuit configured to monitor the light emitting circuit, comprising: