WO2016082787A1

WO2016082787A1 - Circuit failure detection device, led based light emitting apparatus and light/signal emitting device for a vehicle

Info

Publication number: WO2016082787A1
Application number: PCT/CN2015/095759
Authority: WO
Inventors: Sanbao SHI
Original assignee: Valeo Vision
Priority date: 2014-11-27
Filing date: 2015-11-27
Publication date: 2016-06-02
Also published as: CN105657947B; CN105657947A

Abstract

The present disclosure provides a circuit failure detection device, a LED based lighting apparatus and a light and/or signal emitting device. The circuit failure detection device includes: voltage input terminals; a circuit gating unit including parallel branches, each of which has both ends electrically connected to a first parallel node and a second parallel node respectively, the voltage input terminals being electrically connected to the parallel branches respectively, the circuit gating unit being configured to, in each of the parallel branches, conduct a circuit from the voltage input terminal to the first parallel node only if the voltage of the corresponding voltage input terminal is greater than the sum of the voltage of the first parallel node and a first threshold, and conduct a circuit from the second parallel node to the voltage input terminal only if the voltage of the second parallel node is greater than the sum of the voltage of the corresponding voltage input terminal and a second threshold; and a failure signal generating unit, which has both ends connected to the first parallel node and the second parallel node respectively.

Description

CIRCUIT FAILURE DETECTION DEVICE, LED BASED LIGHT EMITTING APPARATUS AND LIGHT/SIGNAL EMITTING DEVICE FOR A VEHICLE

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Chinese Patent Application No. 201410708940.6 filed on November 27, 2014 in the State Intellectual Property Office of China, the disclosure of which is incorporated in entirety herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to the field of lighting and circuit failure detection, in particular to a circuit failure detection device, an LED based light emitting apparatus including the circuit failure detection device and a light/signal emitting device for a vehicle.

Description of the Related Art

The failure detection of open circuit and short circuit in a circuitry is very crucial to ensure normal operation of a circuit system. For example, in a typical drive circuit for light emitting diode (LED) string, it often needs to detect whether there is a failure of open circuit and a failure of short circuit of the LED or not. The conventional failure diagnostic unit often only can detect one of the failure of open circuit and the failure of short circuit. Thus, in practice, it needs to combine diagnostic circuits for detecting various failures, which increases the complexity of system.

SUMMARY OF THE INVENTION

An object of the present disclosure is to provide a circuit failure detection device that can detect both the failure of open circuit and the failure of short circuit in circuitry using one same set of circuit units and has a relatively simple structure.

Another object of the present disclosure is to provide an LED based lighting apparatus and a light/signal emitting device for a vehicle that have the circuit failure detection device and can ensure the safety and reliability of LED based lighting.

An embodiment of the present invention provides a circuit failure detection device comprising: n voltage input terminals configured to input n voltages respectively； a circuit gating unit comprising n parallel branches connected in parallel to each other, each of which has both ends electrically connected to a first parallel node and a second parallel node respectively, the n voltage input terminals being electrically connected to the n parallel branches respectively, the circuit gating unit being configured to, in each of the n parallel branches, conduct a circuit from the voltage input terminal to the first parallel node only if the voltage of the corresponding voltage input terminal is greater than the sum of the voltage of the first parallel node and a first threshold, and conduct a circuit from the second parallel node to the voltage input terminal only if the voltage of the second parallel node is greater than the sum of the voltage of the corresponding voltage input terminal and a second threshold, where n is an integer equal to or greater than2； and a failure signal generating unit, which has both ends connected to the first parallel node and the second parallel node respectively and is configured to generate a failure signal if the maximal value of the voltages of the n voltage input terminals is greater than the sum of the minimum value of the voltages of the n voltage input terminals and a third threshold.

In an embodiment, each of the parallel branches is provided with a first gating element and a second gating element connected in series, the first gating element being located between the first parallel node and the voltage input terminal and the second gating element being located between the second parallel node and the voltage input terminal.

In an embodiment, the failure signal generating unit comprises a switching element configured to generate the failure signal.

In an embodiment, the failure signal generating unit comprises a first resistor and a second resistor, the switching element being a PNP transistor, and wherein the first resistor is electrically connected between the first parallel node and an emitter electrode of the PNP transistor, the second resistor is electrically connected between a base electrode and the emitter electrode of the PNP transistor, the base electrode of the PNP transistor being electrically connected to the second parallel node, the failure signal being generated by a collector electrode of the PNP transistor.

In an embodiment, the base electrode of the PNP transistor is electrically connected to the second parallel node via a current limiting resistor.

In an embodiment, the third threshold is:

H₃＝V_DA+V_DB+V_BE× (R₁+R₂) /R₂,

where V_DA is a voltage drop across the first gating element in the parallel branch which is electrically connected to the voltage input terminal with the maximal voltage among the n voltage input terminals, V_DB is a voltage drop across the second gating element in the parallel branch which is electrically connected to the voltage input terminal with the minimum voltage among the n voltage input terminals, V_BE is a voltage between the emitter electrode and the base electrode of the PNP transistor, R₁ is the resistance of the first resistor and R₂ is the resistance of the second resistor.

In an embodiment, the circuit failure detection device further comprises a signal conversion and output unit configured to convert the failure signal into a failure output signal and to output it.

In an embodiment, the signal conversion and output unit comprises a NPN transistor, which has a base electrode configured to receive the failure signal from the failure signal generating unit, an emitter electrode electrically connected to a low electrical level and a collector electrode electrically connected to a high electrical level, and wherein the NPN transistor is conducted if the base electrode of the NPN transistor has received the failure signal from the failure signal generating unit, otherwise, the NPN transistor is cut off.

In an embodiment, the signal conversion and output unit comprises a N type field effect transistor, which has a gate electrode configured to receive the failure signal from the failure signal generating unit, a source electrode electrically connected to a low electrical level and a drain electrode electrically connected to a high electrical level, and wherein the N type field effect transistor is conducted if the gate electrode of the N type field effect transistor has received the failure signal from the failure signal generating unit, otherwise, the N type field effect transistor is cut off.

In an embodiment, the circuit failure detection device further comprises a failure output signal processing unit configured to receive the failure output signal outputted from the signal conversion and output unit and to process data thereof.

In an embodiment, the failure output signal processing unit comprises a microcontroller or a signal comparer.

In an embodiment, the first gating element and the second gating element both are diodes, the first gating element having an anode electrically connected to the voltage input terminal and a cathode electrically connected to the first parallel node, the second gating element having an anode electrically connected to the second parallel node and a cathode electrically connected to the voltage input terminal.

In an embodiment, if the maximal value of the voltages of the n voltage input terminals is greater than the sum of the minimum value of the voltages of the n voltage input terminals and the third threshold, the voltage of the first parallel node and the voltage of the second parallel node will be between the maximal value and the minimum value of the voltages of the n voltage input terminals and the voltage of the first parallel node is greater than that of the second parallel node.

An embodiment of the present invention provides an LED based light emitting apparatus comprising: an LED constant current controlling unit comprising n parallel LED branches, each of which has an LED string and a constant current source, the LED string being electrically connected between the constant current source and a high electrical level for the controlling unit, the constant current source being electrically connected between the LED string and a low electrical level for the controlling unit, the LED string comprising one LED or at least two LEDs electrically connected in series, wherein the LED string in all of the parallel LED branches have the same number of LEDs, where n is an integer equal to or greater than 2； and a circuit failure detection device as described in any one of the above embodiments, wherein each of the n parallel LED branches is provided with one diagnostic node, the n diagnostic nodes in the n parallel LED branches being electrically connected to the n voltage input terminals in the circuit failure detection device respectively, and wherein in normal work state, the difference between the maximal value and the minimum value of the voltages of the n diagnostic nodes in the n parallel LED branches is not more than the third threshold.

In an embodiment, the diagnostic node in each parallel LED branch is located between the LED string and the constant current source.

In an embodiment, the diagnostic node in each parallel LED branch is located between the LED string and the high electrical level for the controlling unit.

An embodiment of the present invention provides a light/signal emitting device for a vehicle comprising a circuit failure detection device as described in any one of the above embodiments, or an LED based light emitting apparatus as described in any one of the above embodiments.

At least one above embodiments of the present disclosure can detect a failure of open circuit and a failure of short circuit of a circuit to be detected, e.g., a circuit for LED string, by a circuit gating unit and a failure signal generating unit. By means of the circuit failure detection device and the LED based lighting apparatus according to the present disclosure, the detection of the failure of open circuit and the failure of short circuit may be achieved by low complexity and low power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic circuit diagram showing a circuit failure detection device according to an embodiment of the present invention；

Fig. 2 is a schematic circuit diagram showing an LED based lighting apparatus including the circuit failure detection device according to an embodiment of the present invention；

Fig. 3 is a schematic view showing a work of the LED based lighting apparatus shown in Fig. 2 in case that a failure of short circuit occurs in the LED string； and

Fig. 4 is a schematic view showing a work of the LED based lighting apparatus shown in Fig. 2 in case that a failure of open circuit occurs in the LED string.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The embodiments of the present invention will be further explained below with reference to the figures and examples. Throughout the description, same or similar reference numbers indicate the same or similar members. The following embodiments along with the figures are only used to explain the general concept of the present invention, instead of being intended to limit the scope of the present invention.

Fig. 1 schematically shows a circuit failure detection device 100 according to an embodiment of the present invention. The circuit failure detection device 100 includes n voltage input terminals j1, j2, …jn, a circuit gating unit 101 and a failure signal generating unit 102. The n voltage input terminals j1, j2, …jn are configured to input n voltages respectively, for example, connected to n voltages from the external of the circuit failure detection device 100. The circuit gating unit 101 includes n parallel branches B1, B2, …, Bn connected in parallel to each other, each of which has both ends electrically connected to a first parallel node A1 and a second parallel node A2 respectively, the n voltage input terminals j1, j2, …jn being electrically connected to the n parallel branches B1, B2, …, Bn respectively. The circuit gating unit 101 may be configured to, in each of the n parallel branches B1, B2, …, Bn, conduct a circuit from the voltage input terminal j1, j2, …jn to the first parallel node A1 only if the voltage of the corresponding voltage input terminal j1, j2, …jn is greater than the sum of the voltage of the first parallel node A1 and a first threshold, and conduct a circuit from the second parallel node A2 to the voltage input terminal j1, j2, …jn only if the voltage of the second parallel node A2 is greater than the sum of the voltage of the corresponding voltage input terminal j1, j2, …jn and a second threshold, where n is an integer equal to or greater than 2.

In an embodiment, each of the parallel branches is provided with a first gating element D1A, D2A, …, DnA and a second gating element D1B, D2B, …, DnB connected in series. In the embodiment shown in Fig. 1, each of the parallel branches only has one first gating element D1A, D2A, …, DnA and one second gating element D1B, D2B, …, DnB, however, the embodiments of the present invention are not limited to this. As an example, each of the parallel branches may also have a plurality of first gating elements and/or a plurality of second gating elements.

As illustrated in Fig. 1, the n voltage input terminals j1, j2, …jn are electrically connected to the n parallel branches B1, B2, …, Bn respectively. In each of the parallel branches, the first gating element D1A, D2A, …, DnA is located between the first parallel node A1 and the voltage input terminal j1, j2, …jn and the second gating element D1B, D2B, …, DnB is located between the second parallel node A2 and the voltage input terminal j1, j2, …jn. In this case, the first gating element D1A, D2A, …, DnA is configured to conduct a circuit from the corresponding voltage input terminal j1, j2, …jn to the first parallel node A1 only if the voltage of the corresponding voltage input terminal j1, j2, …jn is greater than the sum of the voltage of the first parallel node A1 and a first threshold, and the second gating element D1B, D2B, …, DnB is configured to conduct a circuit from the second parallel node A2 to the voltage input terminal j1, j2, …jn corresponding to the second gating element D1B, D2B, …, DnB only if the voltage of the second parallel node A2 is greater than the sum of the voltage of the corresponding voltage input terminal j1, j2, …jn and a second threshold, where n is also an integer equal to or greater than 2.

As illustrated in Fig. 1, the failure signal generating unit 102 has both ends connected to the first parallel node A1 and the second parallel node A2 respectively and is configured to generate a failure signal if the maximal value of the voltages of the n voltage input terminals j1, j2, …jn is greater than the sum of the minimum value of the voltages of the n voltage input terminals j1, j2, …jn and a third threshold.

By means of combination of the circuit gating unit 101 and the failure signal generating unit 102, if the potential difference between any two of the voltage input terminals j1, j2, …jn is higher than the third threshold, the failure signal generating unit 102 may generate the failure signal. When the failure of open circuit or the failure of short circuit occurs in the circuit, e.g., the drive circuit for the LED string, it will often cause the voltage to change significantly. For example, in the example shown in Fig. 2, an LED constant current controlling unit 200 includes three branches connected in parallel. Each of the three branches has an LED string composed of m LEDs connected in series which is electrically connected between a constant current source and a high electrical level (in convenience of description, it will below be called as a high electrical level for the controlling unit) , and the constant current source is also electrically connected to a low electrical level (in convenience of description, it will below be called as a low electrical level for the controlling unit) . Three diagnostic nodes are provided between the constant current source and the LED string in the three branches, respectively. And the three diagnostic nodes are electrically connected to three voltage input terminals j1, j2, …jn in the circuit failure detection device 100 respectively (in this example, three voltage input terminals j1, j2, …jn are shown) . In this case, if the circuit for the LED string in a certain branch in the LED constant current controlling unit 200 is open, as shown in Fig. 4, the voltage at the diagnostic node corresponding to the certain branch will be reduced significantly； otherwise, if the circuit for the LED string in a certain branch in the LED constant current controlling unit 200 is shorten, as shown in Fig. 3, the voltage at the diagnostic node corresponding to the certain branch will be increased significantly. Thus, the both cases will cause the potential difference among the voltage input terminals in the circuit failure detection device 100 to become large significantly. The third threshold may be determined as actually required such that the potential difference among the respective voltage input terminals in the circuit failure detection device 100 is less than the third threshold when the LED constant current controlling unit 200 works normally and the potential difference among the respective voltage input terminals is greater than the third threshold when the failure of short circuit or the failure of open circuit occurs in the LED constant current controlling unit 200. In this way, the failure signal generating unit 102 will generate the failure signal if the failure of short circuit or the failure of open circuit occurs in the LED constant current controlling unit 200, so as to achieve detection of the failure in the circuit.

It should be noted that in the failure detection of the circuit for the LED string, it often is not necessary to distinguish the failure of short circuit and the failure of open circuit from each other, because the LED string will typically be replaced in entirety in considerations of economy and operability, whether the failure is a failure of open circuit or a failure of short circuit. That is, as long as one LED in the LED string is wrong, the LED string will be considered to be wrong in entirety.

As an example, the failure signal generating unit 102 may include a switching element Q1 configured to generate the failure signal. In an example, the failure signal generating unit 102 further includes a first resistor R1 and a second resistor R2. The switching element Q1 may be a PNP transistor. The first resistor R1 is electrically connected between the first parallel node A1 and an emitter electrode of the PNP transistor, and the second resistor R2 is electrically connected between a base electrode and the emitter electrode of the PNP transistor. The base electrode of the PNP transistor is electrically connected to the second parallel node A2, and the failure signal is generated by a collector electrode of the PNP transistor. In the example, the third threshold may be determined by the following eq. 1:

H₃＝V_DA+V_DB+V_BE× (R₁+R₂) /R₂ (eq. 1)

where H₃ is the third threshold, V_DA is a voltage drop across the first gating element D1A, D2A, …, DnA in the parallel branch B1, B2, …Bn which is electrically connected to the voltage input terminal with the maximal voltage among the n voltage input terminals j1, j2, …jn, V_DB is a voltage drop across the second gating element D1B, D2B, …, DnB in the parallel branch B1, B2, …Bn which is electrically connected to the voltage input terminal with the minimum voltage among the n voltage input terminals j1, j2, …jn, V_BE is a voltage between the emitter electrode and the base electrode of the PNP transistor, R1 is the resistance of the first resistor and R2 is the resistance of the second resistor.

As an example, in order to prevent too large current from damaging the switching element Q1, a current limiting resistor R3 may be provided to be electrically connected between the second parallel node A2 and the base electrode of the PNP transistor or a gate electrode of a P type filed effect transistor.

As an example, the P type filed effect transistor may be a MOS type filed effect transistor. As an example, the switching element Q1 may be packaged integrally with the first resistor R1 and the second resistor R2 to improve the stability of devices and to reduce the volume thereof.

In an example, the circuit failure detection device 100 may further include a signal conversion and output unit 103 configured to convert the failure signal into a failure output signal and to output it. The signal conversion and output unit 103 may contribute to stability or prominence of output signals, or may also separate the failure signal generating unit 102 from the subsequent circuits to prevent the subsequent circuits disturbing the normal work of the failure signal generating unit 102.

As an example, the signal conversion and output unit 103 may include a NPN transistor Q2, which has a base electrode configured to receive the failure signal from the failure signal generating unit 102, an emitter electrode electrically connected to a low electrical level and a collector electrode electrically connected to a high electrical level. In the example, the NPN transistor Q2 is conducted if the base electrode of the NPN transistor Q2 has received the failure signal from the failure signal generating unit 102, otherwise, the NPN transistor Q2 is cut off. As an example, in order to prevent too large current from damaging the NPN transistor Q2, a current limiting resistor R4 may be provided to be electrically connected between the high electrical level and the collector electrode of the NPN transistor. When the NPN transistor Q2 is conducted, the voltage on the collector electrode will become reduced significantly to form a failure output signal.

Alternatively, the NPN transistor Q2 in the above example may be replaced by an N type field effect transistor. In this case, the N type field effect transistor has a gate electrode configured to receive the failure signal from the failure signal generating unit 102, a source electrode electrically connected to a low electrical level and a drain electrode electrically connected to a high electrical level, and the N type field effect transistor is conducted if the gate electrode of the N type field effect transistor has received the failure signal from the failure signal generating unit 102, otherwise, the N type field effect transistor is cut off. As such, in order to prevent too large current from damaging the N type field effect transistor, a current limiting resistor R4 may be provided to be electrically connected between the high electrical level and the drain electrode of the N type field effect transistor. When the N type field effect transistor is conducted, the voltage on the drain electrode will become reduced significantly to form a failure output signal. As an example, the N type filed effect transistor may be a MOS type filed effect transistor.

As an example, the circuit failure detection device 100 may further include a failure output signal processing unit 104 configured to receive the failure output signal outputted from the signal conversion and output unit 103 and to process data thereof. For example, the failure output signal processing unit 104 includes a microcontroller or a signal comparer. However, the failure output signal processing unit 104 is not necessary. In an example, the signal conversion and output unit 103 may display the failure by directly outputting the failure output signal to such as an indicator or a warner.

In the embodiments of the present invention, the first gating element D1A, D2A, …, DnA and the second gating element D1B, D2B, …, DnB may both be diodes. As illustrated in Fig. 1, the first gating element D1A, D2A, …, DnA has an anode electrically connected to the voltage input terminal j1, j2, …, jn and a cathode electrically connected to the first parallel node A1, and the second gating element D1B, D2B, …, DnB has an anode electrically connected to the second parallel node A2 and a cathode electrically connected to the voltage input terminal j1, j2, …, jn. The first threshold may for example be a positive voltage drop of the first gating element and the second threshold may for example be a positive voltage drop of the second gating element. Besides being the diodes, the first gating element and the second gating element may also be any other types of elements known in the art as long as they meet the requirements of gating in the above embodiments.

In the embodiments of the invention, in case that the maximum value of the voltages at the n voltage input terminals j1, j2, …, jn is greater than the sum of the minimum value of the voltages of the n voltage input terminals j1, j2, …, jn and the third threshold, the voltage of the first parallel node A1 and the voltage of the second parallel node A2 will be between the maximal value and the minimum value of the voltages of the n voltage input terminals j1, j2, …, jn and the voltage of the first parallel node A1 is greater than that of the second parallel node A2.

As discussed above, in the embodiments of the present invention, all of the circuit gating unit 101, the failure signal generating unit 102 and the signal conversion and output unit 103 may be composed of simple circuit elements. Further, when no failures occur in the circuit to be detected, the potential difference among the voltage input terminals is not sufficient to cause the circuit failure detection device 100 to form an entire loop. Thus, the circuit failure detection device 100 has advantages of simple structure and low power consumption.

The work principle of the circuit failure detection device 100 according to the embodiment of the present invention will be described below with reference to the Figs. 3-4, taking the failure detection of the LED string as an example. The connection relations between the constant current controlling unit 200 and the circuit failure detection device 100 in Figs. 3-4 are same to those shown in Fig. 2, and thus the details thereof will be omitted below.

Fig. 3 shows the case where a failure of short circuit occurs in the LED string. If the LED D2m in the middle branch of the LED constant current controlling unit 200 is shorten, the voltage at the diagnostic node Diag_2 will be increased, thus, the potential difference between the diagnostic node Diag_2 and the diagnostic nodes Diag_1 and Diag_n in the normal work branches will be greater than the third threshold. In this way, the first gating element D2A corresponding to the diagnostic node Diag_2 will be conducted, and then the second gating elements D1B and DnB in the other parallel branches will also be conducted and the switching element Q1 will also be conducted due to increase of the potential difference or current and generate a failure signal. The flowing path of the current at that time is indicated by arrows in Fig. 3. In case that the signal conversion and output unit 103 is provided, the failure signal is then converted into a failure output signal, for example by conducting the N type field effect transistor or NPN type transistor Q2.

Fig. 4 shows the case where a failure of open circuit occurs in the LED string. If the LED string in the middle branch of the LED constant current controlling unit 200 is in the open circuit, the voltage at the diagnostic node Diag_2 will be reduced, thus, the potential difference between the diagnostic node Diag_2 and the diagnostic nodes Diag_1 and Diag_n in the normal work branches will also be greater than the third threshold. In this way, the first gating elements D1A, DnA corresponding to the diagnostic node Diag_2 will be conducted, and then the second gating element D2B in the other parallel branch will also be conducted and the switching element Q1 will also be conducted due to increase of the potential difference or current and generate a failure signal. The flowing path of the current at that time is indicated by arrows in Fig. 4. In case that the signal conversion and output unit 103 is provided, the failure signal is then converted into a failure output signal, for example by conducting the N type field effect transistor or NPN type transistor Q2.

As discussed above, whether the failure of open circuit or the failure of short circuit occurs in the LED string, the circuit failure detection device 100 can achieve detection of failure to generate the failure signal.

It should be noted that, although Figs. 2-4 show three parallel branches in the LED constant current controlling unit 200, the embodiments of the present invention are not limited to this, for example, the LED constant current controlling unit 200 may have two, four or more parallel branches. Each LED string may for example have one, two, three or more LEDs.

An embodiment of the present invention also provides an LED based light emitting apparatus 300. It includes: an LED constant current controlling unit 200 and a circuit failure detection device 100 as described in any of the above embodiments. The LED constant current controlling unit 200 includes n parallel LED branches, each of which has an LED string DS1, DS2, …, DSn and a constant current source C1, C2, …, Cn. The LED string DS1, DS2, …, DSn is electrically connected between the constant current source C1, C2,…, Cn and a high electrical level for the controlling unit. The constant current source C1, C2, …, Cn is electrically connected between the LED string DS1, DS2, …, DSn and a low electrical level for the controlling unit. The LED string DS1, DS2, …, DSn may include one LED or at least two LEDs electrically connected in series. The LED strings DS1, DS2, …, DSn in all of the parallel LED branches have the same number of LEDs such that there are substantially same voltages at the corresponding positions in all of parallel LED branches when the LED strings DS1, DS2, …, DSn work normally. In the embodiment, n is an integer equal to or greater than 2. In the embodiment, each of the n parallel LED branches is provided with one diagnostic node Diag_1, Diag_2, …, Diag_n, and the n diagnostic nodes Diag_1, Diag_2, …, Diag_n in the n parallel LED branches are electrically connected to the n voltage input terminals j1, j2, …, jn in the circuit failure detection device 100 respectively. And in normal work state, the difference between the maximal value and the minimum value of the voltages of the n diagnostic nodes Diag_1, Diag_2, …, Diag_n in the n parallel LED branches is not more than the third threshold.

As an example, the diagnostic node Diag_1, Diag_2, …, Diag_n in each parallel LED branch is located between the LED string DS1, DS2, …, DSn and the constant current source C1, C2, …, Cn. Alternatively, the diagnostic node Diag_1, Diag_2, …, Diag_n in each parallel LED branch may also be located between the LED string DS1, DS2, …, DSn and the high electrical level for the controlling unit. The diagnostic node Diag_1, Diag_2, …, Diag_n may be arranged any positions as long as the above potential difference is less than the third threshold if the circuit normally works and is greater than the third threshold if a failure occurs in the circuit.

The LED based lighting apparatus 300 according to an embodiment of the present invention has the circuit failure detection device 100, and thus can detect the failure of short circuit and the failure of open circuit in the LED strings quickly and correctly so as to improve the reliability in operation.

An embodiment of the present invention also provides a light/signal emitting device for a vehicle. It includes a circuit failure detection device 100 as described in any one of the above embodiments, or an LED based light emitting apparatus 300 as described in any one of the above embodiments. The light/signal emitting device may also detect the failure of open circuit and the failure of short circuit in the LED strings quickly and correctly.

It should be noted that the embodiments of the present invention are not limited to application for the vehicle. They may also be used in all kinds of lighting and/or signaling applications, such as road lights, detection lights, billboard lights, signal indicators.

Although the present disclosure is explained with reference to figures, all of the embodiments shown in figures are intended to explain the preferred embodiments of the present invention by ways of examples, instead of being intended to limit the present invention.

Apparently, it would be appreciated by those skilled in the art that various changes or modifications may be made in the present disclosure without departing from the principles and spirit of the disclosure, which are intended to be covered by the present invention as long as these changes or modifications fall within the scope defined in the claims and their equivalents.

Claims

A circuit failure detection device (100) comprising:

n voltage input terminals (j1, j2, …jn) configured to input n voltages respectively；

a circuit gating unit (101) comprising n parallel branches (B1, B2, …, Bn) connected in parallel to each other, each of which has both ends electrically connected to a first parallel node (A1) and a second parallel node (A2) respectively, the n voltage input terminals (j1, j2, …jn) being electrically connected to the n parallel branches (B1, B2, …, Bn) respectively, the circuit gating unit (101) being configured to, in each of the n parallel branches (B1, B2, …, Bn) , conduct a circuit from the voltage input terminal (j1, j2, …jn) to the first parallel node (A1) only if the voltage of the corresponding voltage input terminal (j1, j2, …jn) is greater than the sum of the voltage of the first parallel node (A1) and a first threshold, and conduct a circuit from the second parallel node (A2) to the voltage input terminal (j1, j2, …jn) only if the voltage of the second parallel node (A2) is greater than the sum of the voltage of the corresponding voltage input terminal (j1, j2, …jn) and a second threshold, where n is an integer equal to or greater than 2； and

a failure signal generating unit (102) , which has both ends connected to the first parallel node (A1) and the second parallel node (A2) respectively and is configured to generate a failure signal if the maximal value of the voltages of the n voltage input terminals (j1, j2, …jn) is greater than the sum of the minimum value of the voltages of the n voltage input terminals (j1, j2, …jn) and a third threshold.
The circuit failure detection device (100) according to claim 1, wherein each of the parallel branches (B1, B2, …, Bn) is provided with a first gating element (D1A, D2A, …, DnA) and a second gating element (D1B, D2B, …, DnB) connected in series, the first gating element (D1A, D2A, …, DnA) being located between the first parallel node (A1) and the voltage input terminal (j1, j2, …jn) and the second gating element (D1B, D2B, …, DnB) being located between the second parallel node (A2) and the voltage input terminal (j1, j2, …jn) .
The circuit failure detection device (100) according to claim 2, wherein the failure signal generating unit (102) comprises a switching element (Q1) configured to generate the failure signal.
The circuit failure detection device (100) according to claim 3, wherein the failure signal generating unit (102) comprises a first resistor (R1) and a second resistor (R2) , the switching element (Q1) being a PNP transistor, and wherein the first resistor (R1) is electrically connected between the first parallel node (A1) and an emitter electrode of the PNP transistor, the second resistor (R2) is electrically connected between a base electrode and the emitter electrode of the PNP transistor, the base electrode of the PNP transistor being electrically connected to the second parallel node (A2) , the failure signal being generated by a collector electrode of the PNP transistor.
The circuit failure detection device (100) according to claim 4, wherein the base electrode of the PNP transistor is electrically connected to the second parallel node (A2) via a current limiting resistor (R3) .
The circuit failure detection device (100) according to claim 4, wherein the third threshold is:

H₃＝V_DA+V_DB+V_BE×(R₁+R₂)/R₂,

where V_DA is a voltage drop across the first gating element (D1A, D2A, …, DnA) in the parallel branch (B1, B2, …Bn) which is electrically connected to the voltage input terminal with the maximal voltage among the n voltage input terminals (j1, j2, …jn) , V_DB is a voltage drop across the second gating element (D1B, D2B, …, DnB) in the parallel branch (B1, B2, …Bn) which is electrically connected to the voltage input terminal with the minimum voltage among the n voltage input terminals (j1, j2, …jn) , V_BE is a voltage between the emitter electrode and the base electrode of the PNP transistor, R₁ is the resistance of the first resistor and R₂ is the resistance of the second resistor.
The circuit failure detection device (100) according to claim 1, further comprising a signal conversion and output unit (103) configured to convert the failure signal into a failure output signal and to output it.
The circuit failure detection device (100) according to claim 7, wherein the signal conversion and output unit (103) comprises a NPN transistor, which has a base electrode configured to receive the failure signal from the failure signal generating unit, an emitter electrode electrically connected to a low electrical level and a collector electrode electrically connected to a high electrical level, and wherein the NPN transistor is conducted if the base electrode of the NPN transistor has received the failure signal from the failure signal generating unit, otherwise, the NPN transistor is cut off.
The circuit failure detection device (100) according to claim 7, wherein the signal conversion and output unit (103) comprises a N type field effect transistor, which has a gate electrode configured to receive the failure signal from the failure signal generating unit, a source electrode electrically connected to a low electrical level and a drain electrode electrically connected to a high electrical level, and wherein the N type field effect transistor is conducted if the gate electrode of the N type field effect transistor has received the failure signal from the failure signal generating unit (102) , otherwise, the N type field effect transistor is cut off.
The circuit failure detection device (100) according to any one of claims 7-9, further comprising a failure output signal processing unit (104) configured to receive the failure output signal outputted from the signal conversion and output unit (103) and to process data thereof.
The circuit failure detection device (100) according to claim 10, wherein the failure output signal processing unit (104) comprises a microcontroller or a signal comparer.
The circuit failure detection device (100) according to any one of claims 1-6, wherein the first gating element (D1A, D2A, …, DnA) and the second gating element (D1B, D2B, …, DnB) both are diodes, the first gating element (D1A, D2A, …, DnA) having an anode electrically connected to the voltage input terminal (j1, j2, …, jn) and a cathode electrically connected to the first parallel node (A1) , the second gating element (D1B, D2B, …, DnB) having an anode electrically connected to the second parallel node (A2) and a cathode electrically connected to the voltage input terminal (j1, j2, …, jn) .
The circuit failure detection device (100) according to any one of claims 1-9, wherein if the maximal value of the voltages of the n voltage input terminals (j1, j2, …, jn) is greater than the sum of the minimum value of the voltages of the n voltage input terminals (j1, j2, …, jn) and the third threshold, the voltage of the first parallel node (A1) and the voltage of the second parallel node (A2) will be between the maximal value and the minimum value of the voltages of the n voltage input terminals (j1, j2, …, jn) and the voltage of the first parallel node (A1) is greater than that of the second parallel node (A2) .
An LED based light emitting apparatus (300) comprising:

an LED constant current controlling unit (200) comprising n parallel LED branches, each of which has an LED string (DS1, DS2, …, DSn) and a constant current source (C1, C2, …, Cn) , the LED string (DS1, DS2, …, DSn) being electrically connected between the constant current source (C1, C2, …, Cn) and a high electrical level for the controlling unit, the constant current source (C1, C2, …, Cn) being electrically connected between the LED string (DS1, DS2, …, DSn) and a low electrical level for the controlling unit, the LED string (DS1, DS2, …, DSn) comprising one LED or at least two LEDs electrically connected in series, wherein the LED string (DS1, DS2, …, DSn) in all of the parallel LED branches have the same number of LEDs, where n is an integer equal to or greater than 2； and

a circuit failure detection device (100) according to any one of claims 1-13,

wherein each of the n parallel LED branches is provided with one diagnostic node (Diag_1, Diag_2, …, Diag_n) , the n diagnostic nodes (Diag_1, Diag_2, …, Diag_n) in the n parallel LED branches being electrically connected to the n voltage input terminals (j1, j2, …, jn) in the circuit failure detection device (100) respectively, and wherein in normal work state, the difference between the maximal value and the minimum value of the voltages of the n diagnostic nodes (Diag_1, Diag_2, …, Diag_n) in the n parallel LED branches is not more than the third threshold.
The LED based light emitting apparatus (300) according to claim 14, wherein the diagnostic node (Diag_1, Diag_2, …, Diag_n) in each parallel LED branch is located between the LED string (DS1, DS2, …, DSn) and the constant current source (C1, C2, …, Cn).
The LED based light emitting apparatus (300) according to claim 14, wherein the diagnostic node (Diag_1, Diag_2, …, Diag_n) in each parallel LED branch is located between the LED string (DS1, DS2, …, DSn) and the high electrical level for the controlling unit.
Light/signal emitting device for a vehicle comprising a circuit failure detection device (100) according to any one of claims 1-13, or an LED based light emitting apparatus (300) according to at least claim 14 to 16.