TWM653795U - Light emitting diode driving circuit - Google Patents

Abstract

A light emitting diode driving circuit electrically connected to the light emitting diode array. The light emitting diode array includes a plurality of light strings. The light strings are electrically connected to a first current terminal and are configured to receive a driving current from the first current terminal. The light emitting diode driving circuit includes a constant current source, a plurality of resistor, a detection circuit and a determination circuit. The constant current source is electrically connected between the light strings and the second current source, and the constant current source is configured to control the driving current to be constant current. First ends of the resistors are respectively connected to the light strings, and the second ends of the resistors are connected to a reference to a reference voltage. The determination circuit is configured to output a failure determination signal.

Description

LED driver circuit

This case relates to a light-emitting diode driving circuit, and more particularly to a light-emitting diode driving circuit with a light-emitting diode fault detection function.

Nowadays, LEDs are often used as the light source of car lights due to their many advantages, such as fast response speed and low cost. For driving safety, the light intensity of car lights is usually regulated by laws and regulations. However, the light source components of car lights are more prone to failure due to factors such as usage conditions and power supply voltage. In this case, if any LED in the car light fails and the driving method is not adjusted, the light intensity of the car light may not meet the legal regulations or seriously affect driving safety.

Therefore, how to provide a LED driving circuit capable of performing fault detection on the LED is an important issue in the field.

The present disclosure provides a light-emitting diode driving circuit. The light-emitting diode driving circuit is electrically connected to a light-emitting diode matrix. The light-emitting diode matrix includes a plurality of light strings. Each of the light strings includes a plurality of light-emitting diodes. The light strings are electrically connected to a first current terminal and receive a driving current from the first current terminal. The light-emitting diode driving circuit includes a constant current source, a plurality of resistors, a detection circuit, and a judgment circuit. The constant current source is electrically connected between the light strings and the second current terminal to control the driving current to be a constant current. The first ends of the plurality of resistors are electrically connected to the light strings, respectively, and the second ends of the plurality of resistors are electrically connected to a reference potential. The detection circuit is electrically connected between the resistors and the light strings, and the detection circuit includes a plurality of diode units. Each of the diode units includes a first diode and a second diode connected in series. The judgment circuit includes a first comparator and a second comparator. The first comparator has a first first input terminal, a first second input terminal, and a first output terminal. The first first input terminal of the first comparator is electrically connected to the first diodes. The first second input terminals of the first comparator are used to receive a first floating potential. The first output terminal of the first comparator is used to output a first judgment signal. The second comparator has a second first input terminal, a second second input terminal and a second output terminal. The second first input terminal of the second comparator is electrically connected to the second diodes. The second second input terminal of the second comparator is used to receive a second floating potential. The second output terminal of the second comparator is used to output a second judgment signal. The first floating potential and the second floating potential change with the reference potential.

The present disclosure provides another LED driving circuit. The LED driving circuit is electrically connected to a LED matrix. The LED matrix includes a plurality of light strings, each of which includes a plurality of LEDs. The light strings are electrically connected to a first current terminal and receive a driving current from the first current terminal. The LED driving circuit includes a constant current source, a plurality of resistors, a detection circuit, and a comparator. The constant current source is electrically connected between the light strings and the second current terminal, and the constant current source is used to control the driving current to be a constant current. The first ends of a plurality of resistors are electrically connected to the light strings, and the second ends of the resistors are electrically connected to a reference potential. The detection circuit is electrically connected between the resistors and the light strings. The detection circuit includes a plurality of diodes. The anodes of the diodes are used to receive biased DC currents, and the cathodes of the diodes are electrically connected to the resistors, respectively. The comparator has a first input terminal, a second input terminal, and an output terminal. The first input terminal of the comparator is electrically connected to the anodes of the diodes. The second input terminal of the comparator is used to receive a floating potential. The output terminal of the comparator is used to output a first judgment signal, wherein the floating potential varies with the reference potential.

The present disclosure provides another LED driving circuit. The LED driving circuit is electrically connected to a LED matrix. The LED matrix includes a plurality of light strings. Each of the light strings includes a plurality of LEDs, wherein the light strings are electrically connected to a first current terminal and receive a driving current from the first current terminal. The LED driving circuit includes a constant current source, a plurality of resistors, a detection circuit, and a comparator. The constant current source is electrically connected between the light strings and a second current terminal, and the constant current source is used to control the driving current to be a constant current. The first ends of the plurality of resistors are electrically connected to the light strings, and the second ends of the resistors are electrically connected to reference potentials. The detection circuit is electrically connected between the resistors and the light strings, and the detection circuit includes a plurality of diodes. The anodes of the diodes are electrically connected to the resistors, respectively. The comparator has a first input terminal, a second input terminal, and an output terminal. The first input terminal of the comparator is electrically connected to the cathodes of the diodes. The second input terminal of the comparator is used to receive a floating potential. The output terminal of the comparator is used to output a judgment signal, wherein the floating potential varies with the reference potential.

In summary, the LED driving circuit disclosed herein includes a plurality of current branches, each branch including a light string and a resistor electrically connected in series, wherein the light string and the resistor of each current branch are electrically connected to a diode, and the diode turns off or turns on the electrical path from the input end of the comparator to the current branch according to the voltage drop of the resistor of each current branch, thereby outputting a fault judgment signal through the comparator for detecting whether a component in the light string has failed.

The following is a detailed description of the embodiments with the attached diagrams, but the embodiments provided are not intended to limit the scope of the disclosure, and the description of the structure operation is not intended to limit its execution order. Any device with equal functions produced by the re-combination of components is within the scope of the disclosure. In addition, the diagrams are for illustration purposes only and are not drawn according to the original size. For ease of understanding, the same or similar components in the following description will be marked with the same symbols.

Unless otherwise specified, the terms used in the entire specification and patent application generally have the ordinary meaning of each term used in this field, in the content disclosed herein and in the specific content. In addition, the terms "include", "include", "have", "contain", etc. used in this article are open terms, which means "including but not limited to". In addition, "and/or" used in this article includes any one or more items in the relevant enumerated items and all combinations thereof.

Please refer to Figure 1A, which is a schematic diagram of a lighting system 100 in normal operation according to an embodiment of the present disclosure. In some embodiments, the lighting system 100 can be a heavy motorcycle headlight module. In other embodiments, the lighting system 100 can be a car headlight module, a light motorcycle headlight module, etc., but the present invention is not limited thereto. In some embodiments, the lighting system 100 can be a brake light module. In some embodiments, the lighting system 100 can be a running light. In still other embodiments, the lighting system 100 can be a headlight, a taillight, a turn signal, etc., but the present invention is not limited thereto.

As shown in FIG. 1A , the lighting system 100 includes a light emitting diode matrix ARR and a light emitting diode driving circuit 10. In some embodiments, the light emitting diode matrix ARR includes light emitting diodes L ₁₁ -L _nn arranged in a matrix. Further, the light emitting diode matrix ARR includes lamp strings LS ₁ -LS _n , and each of the lamp strings LS ₁ -LS _n includes a plurality of serially connected light emitting diodes. Specifically, the light emitting diodes L ₁₁ -L _1n are electrically connected in series to form the lamp string LS ₁ , the light emitting diodes L ₂₁ -L _2n are electrically connected in series to form the lamp string LS ₂ , and so on. The light-emitting diodes L _n1 -L _nn are electrically connected in series to form a light string LS _n .

In some embodiments, the LED matrix ARR is electrically connected to the LED driving circuit 10. In some embodiments, the LED driving circuit 10 includes a detection circuit DETa, a judgment circuit CL, and resistors _RS1 - _RSn . In some embodiments, the lamp strings _LS1 - _LSn in the LED matrix ARR are respectively connected in series with corresponding resistors _RS1 - _RSn to form a plurality of current branches, and the plurality of current branches are electrically connected in parallel between the first current terminal I _IN and the second current terminal I _OUT . Specifically, the lamp string _LS1 and the resistor _RS1 are electrically connected in series between the first current terminal I _IN and the second current terminal I _OUT , the lamp string _LS2 and the resistor _RS2 are electrically connected in series between the first current terminal I _IN and the second current terminal I _OUT , and so on, the lamp string LS _n and the resistor _RSn are electrically connected in series between the first current terminal I _IN and the second current terminal I _OUT . In some embodiments, the first current terminal I _IN can be understood as the current input terminal of the lighting system 100, and the second current terminal I _OUT can be understood as the current output terminal of the lighting system 100.

In some embodiments, the first end of the light string LS ₁ ~LS _n is electrically connected to the first current terminal I _IN and receives the driving current I from the first current terminal I _IN (only marked at the second current terminal I _OUT ). In some embodiments, the first end of the resistor R _S1 ~ _RSn is electrically connected to the second end of the light string LS ₁ ~LS _n , respectively, and the second end of the resistor R _S1 ~ _RSn is electrically connected to the second current terminal I _OUT via the constant current source 20. It should be noted that each of the light strings LS ₁ ~LS _n of the present disclosure has two ends, wherein if the first end (e.g., one end close to the first current terminal I _IN ) is an anode (/cathode), then the second end (e.g., one end close to the resistor R _S1 ~ _RSn ) is a cathode (/anode). In some embodiments, the driving current I flows from the first current terminal I _IN to the second current terminal I _OUT through the current branch composed of the light strings LS ₁ ~LS _n and the resistors RS ₁ ~RS _n . In other words, the driving current I is split into a plurality of currents Is at the first current terminal I _IN , and flows to the second current terminal I _OUT through the plurality of current branches composed of the light strings LS ₁ ~LS _n and the resistors RS ₁ ~RS _n and the constant current source 20. Under ideal conditions, for example, the light strings LS ₁ ~LS _n have LEDs of the same specifications and quantity, and the current Is of each branch is substantially the same.

In some embodiments, the constant current source 20 is electrically connected between the light strings LS ₁ -LS _n and the second current terminal I _OUT . In some embodiments, the constant current source 20 is electrically connected to the current path of the driving current I. In some embodiments, the constant current source 20 is used to generate a constant output current, that is, the constant current source 20 is used to control the driving current I to be a constant current.

In some embodiments, the detection circuit DETa is electrically connected between the resistors _RS1 - _RSn and the light strings _LS1 - _LSn , for example, through nodes _N1 - _Nn . In some embodiments, the detection circuit DETa includes diode units _DU1 - _DUn . In some embodiments, each _of the diode units _DU1 - _DUn includes two diodes, for example, the diode unit _DU1 includes diodes _D1A and _D1B , and so on, the diode unit _DUn includes diodes _DnA and _DnB . In some embodiments, the cathodes of diodes _D1A - _DnA are electrically connected to the first ends of resistors _RS1 - _RSn (i.e., nodes _N1 - _Nn ), and the anodes of diodes _D1A - _DnA are electrically connected to the determination circuit CL. In some embodiments, the anodes of diodes _D1B - _DnB are electrically connected to the first ends of resistors _RS1 - _RSn via nodes _N1 - _Nn , and the cathodes of diodes _D1B - _DnB are electrically connected to the determination circuit CL. In some embodiments, diodes _D1A - _DnA and _D1B - _DnB can be implemented by PN junction diodes. In some embodiments, diodes _{D1A~DnA and D1B~DnB can be implemented by Zener diodes. In some embodiments, diodes D1A ~DnA and D1B ~ DnB can be implemented} by Schottky diodes, which have a voltage drop of about 0.2 volts or less, a low voltage error when used, and a small deviation value under high and low temperature conditions.

In some embodiments, the determination circuit CL includes comparators 16-17 and an OR gate 18. In some embodiments, a first input terminal (e.g., an inverting input terminal, indicated by "-" in the figure) of the comparator 16 is electrically connected to the anode of the diodes _D1A - _DnA , and a second input terminal (e.g., a non-inverting input terminal, indicated by "+" in the figure) of the comparator 16 is used to receive the floating potential _{Vref_min} . In some embodiments, a first input terminal (e.g., a non-inverting input terminal) of the comparator 17 is electrically connected to the cathode of the diodes _D1B - _DnB , and a second input terminal (e.g., an inverting input terminal) of the comparator 17 is used to receive the floating potential _{Vref_max} .

In some embodiments, the second input terminal of the comparator 16 is electrically connected to the floating voltage source 14 and is used to receive the floating potential V _{ref_min} provided by the floating voltage source 14. In some embodiments, the second terminal (e.g., the negative electrode) of the floating voltage source 14 is electrically connected to the reference potential V _ref . In some embodiments, since the driving current I is controlled to be a constant current, if the potential V _IN of the first current terminal I _IN floats, the potential on the current path of the driving current I will float accordingly. That is, the reference potential V _ref will float/change with the potential V _IN of the first current terminal I _IN . Therefore, by coupling the second end of the floating voltage source 14 to the reference potential V _ref , since the floating potential V _{ref_min} is equal to the reference potential V _ref plus a fixed positioning difference provided by the floating voltage source 14, the value of the floating potential V _{ref_min} can fully respond to the change of the potential V _IN of the first current terminal I _IN . Therefore, for the comparator 16, the second end of the comparator 16 will not receive an incorrect comparison reference due to the change of the potential V _IN of the first current terminal I _IN , which will make the comparison result meaningless. On the contrary, the related art connects the second end of the floating voltage source 14 to the ground, so it will be affected by the change of the input terminal potential. In contrast, the judgment result of the present disclosure is not affected by the change of the potential V _IN of the first current terminal I _IN .

In some embodiments, the second input terminal of the comparator 17 is electrically connected to the floating voltage source 15 and is used to receive the floating potential V _{ref_max} provided by the floating voltage source 15. In some embodiments, the second terminal (e.g., the negative electrode) of the floating voltage source 15 is electrically connected to the reference potential V _ref . In some embodiments, since the driving current I is controlled to be a constant current, if the potential V _IN of the first current terminal I _IN floats, the potential on the current path of the driving current I will float accordingly. That is, the reference potential V _ref will float/change with the potential V _IN of the first current terminal I _IN . Therefore, by coupling the second end of the floating voltage source 15 to the reference potential V _ref , since the floating potential V _{ref_max} will be equal to the reference potential V _ref plus a fixed positioning difference provided by the floating voltage source 15, the value of the floating potential V _{ref_max} can fully respond to the change of the potential V _IN of the first current terminal I _IN . Therefore, for the comparator 17, the second end of the comparator 17 will not receive an incorrect comparison reference due to the change of the potential V _IN of the first current terminal I _IN , which will make the comparison result meaningless. On the contrary, the related art connects the second end of the floating voltage source 15 to the ground, so it will be affected by the change of the input terminal potential. In contrast, the judgment result of the present disclosure is not affected by the change of the potential V _IN of the first current terminal I _IN .

In some embodiments, the bias current source 11 is electrically connected to the anode of the diodes D _1A to D _nA and the first input terminal of the comparator 16. In some embodiments, the bias current source 11 is used to provide a bias current I _{bias_min} so that the diodes D _1A to D _nA are at a working point to maintain basic operation. In some embodiments, the bias current I _{bias_min} is 0.5 to 1.5 mA. In other embodiments, the bias current I _{bias_min} can be implemented by a larger or smaller current. In some embodiments, the diodes D _1A to D _nA , the resistors _RS1 to _RSn , and the comparator 16 form a fault open circuit detection circuit, and how the fault open circuit detection circuit operates will be described in detail in subsequent embodiments.

In some embodiments, the bias current source 12 is electrically connected to the cathode of the diodes D _1B ~D _nB and the first input terminal of the comparator 17. In some embodiments, the bias current source 12 is used to provide a bias current I _{bias_max} so that the diodes D _1B ~D _nB are at a working point. In some embodiments, the bias current I _{bias_max} is 0.5~1.5mA. In other embodiments, the bias current I _{bias_max} can be implemented by a larger or smaller current. In some embodiments, the diodes D _1B ~D _nB , the resistors _RS1 ~ _RSn and the comparator 17 form a fault short circuit detection circuit, and how the fault short circuit detection circuit operates will be described in detail in the subsequent embodiments.

To clearly explain the fault open circuit detection under normal operation and fault open circuit, please refer to FIG. 1A and FIG. 1B. FIG. 1B is a schematic diagram of the operation of the LED driver circuit 100 according to an embodiment of the present disclosure when the LED _L22 fails to open circuit. In some embodiments, when the light string _LS1 ~ _LSn operates normally and the LED _L22 therein fails to open circuit, the potentials _Vs1 ~ _Vsn at the nodes _N1 ~ _Nn and the potential _{Vs_min} at the inverting input terminal of the comparator 16 can be shown in Table 1 below. V _S1 V _S2 ... V _Sn V _{s_min} Normal operation I _s *R _S I _s *R _S ... I _s *R _S [I _s *R _S +V _DA ] L ₂₂ Fault open I _s '*R _S 0 ... I _s '*R _S [0+V _DA ] Table I

In Table 1, the potential of the second end of the resistor _RS2 is assumed to be 0 volts. _RS represents the resistance value of each of the resistors _RS1 ~ _RSn , and _VDA represents the voltage drop of each of the diodes _D1A ~ _DnA . In some embodiments, when the light-emitting diodes _L11 ~ _Lnn in the light strings _LS1 ~ _LSn are in normal operation, each of the aforementioned branch lines has the same voltage drop, so that the amplitude of the _current Is flowing through each branch line is the same. In some embodiments, each of the light strings _LS1 ~ _LSn has the same number of light-emitting diodes, and these light-emitting diodes have the same specifications. In some embodiments, the resistance values of the resistors _RS1 ~ _RSn are the same, and the diodes _D1A ~ _DnA have the same specifications. In some embodiments, when the light strings LS ₁ to LS _n operate normally, the current flowing through each light string LS ₁ to LS _n can be represented by (I/n), and the voltage V _S1 to V _Sn is the voltage across the resistors RS ₁ to RS _n , which can be represented by (I/n)*RS _n , where "I" represents the amplitude of the driving current, "n" represents the number of light strings LS ₁ to LS _n , and RS _n represents the resistance value of each of the resistors RS ₁ to RS _n . As shown in FIG. 1A , when the light strings LS ₁ to LS _n operate normally, the amplitudes of the current _IS flowing through the light strings LS ₁ to LS _n are substantially the same, and the diodes D _1A to D _nA maintain the potential difference between their two ends at a certain voltage (the voltage drop of the diode, for example, 0.7 volts). The voltage _{Vs_min} at the inverting input terminal of the comparator 16 can be represented by [ _Is * _RS + _VDA ], where _RS represents the resistance value of each of the resistors _RS1 - _RSn , and _VDA represents the voltage drop of each of the diodes _D1A - _DnA . In some embodiments, if the diodes _D1A - _DnA are implemented by Schottky diodes, their voltage drop is very small, and [ _Is * _RS + _VDA ] can be approximated as [ _Is * _RS ]. In some embodiments, the signals coupled to the two terminals of the comparator 16 can be swapped, that is, the first terminal is coupled to the floating potential V _{ref — min} and the second terminal is coupled to the potential V _{s — min} , and the lighting system 100 is determined to have an open circuit fault when the output terminal of the comparator 16 outputs a low logic level.

In some embodiments, the floating potentials V _{ref_min} and V _{ref_max} are set values, and these two set voltage values can be set as upper and lower limits with the cross-voltage values V _S1 ~V _Sn as the center value. When any of the floating potentials V _{ref_min} and V _{ref_max} exceeds this upper and lower value range, it means that one or more light-emitting diodes have short-circuited or open-circuited failures. The difference between the upper and lower limits and the cross-voltage values V _S1 ~V _Sn center value needs to be determined based on the voltage drop value of a single light-emitting diode and its distribution range, and can generally be 0.4 volts to 2.6 volts.

As shown in FIG. 1B , when the LED _L22 in the light string _LS2 fails and becomes open, the current flowing through the light string _LS2 decreases to substantially no current flowing, and the current Is' flowing into other light strings increases slightly. At this time, the voltage across the resistor _RS2 is 0 volts, that is, the potential of the node N2 is zero, so that the diode _D2A conducts the current path from the inverting input terminal of the comparator 16 to the resistor RS2 (for example, if the diode _D2A is a Zener diode, the conduction voltage is about 0.2 volts or less, and the deviation value under high and low temperature conditions is small, and the I _{bias_min} provided by the bias current source 11 is sufficient to enable the diode _D2A to be turned on), and the diode _D2B is not conducting, so the non-inverting input terminal of the comparator 17 is not conducting to the current path of the resistor _RS2 , so that the potential V _{s_min} of the inverting input terminal of the comparator 16 is equal to the resistor R The potential of the first end of _S2 (ie, the potential of the node N2), then the potential V _{s_min} is compared with the floating potential V _{ref_min} . When the potential V _{s_min} is less than the floating potential V _{ref_min} , the determination signal V _DET1 output by the comparator 16 is at a high logic level.

As mentioned above, when at least one LED of the light strings LS ₁ to LS _n (e.g., LED L ₂₂ ) fails to open, the determination signal V _DET1 output by the comparator 16 is at a high logic level. Therefore, the determination signal V _DET1 at a high logic level indicates that at least one of the LEDs L ₁₁ to L _nn fails to open, and the determination signal V _DET1 at a low logic level indicates that the LEDs L ₁₁ to L _nn do not fail to open. That is, the determination signal V _DET1 is used to provide open information related to the LEDs L ₁₁ to L _nn .

In some embodiments, when the LED _L22 fails and opens, since the potentials of the first ends of the diodes _D1A and _DnA are less than the potentials of their second ends (for example, the potential of the first end of _DnA is equal to the potential of the node N2, which is substantially 0), the diodes _D1A to _DnA except the diode _D2A are in the off state. In some embodiments, when the LED _L22 fails and opens, since the potential of the first end of the diode _D2B (the potential of the node N2) is not greater than the potential of the second end of the diode _D2B , the diode _D2B is in the off state. In some embodiments, when the light-emitting diode _L22 fails and opens, the potentials of the two ends of the diodes _D1B ~ _DnB except the diode _D2B will be stabilized at a certain voltage (the voltage drop of a general diode is 0.7 volts, or the voltage drop of a Zener diode is 0.1 volts), so that the potential _{Vs_max} of the non-inverting input terminal of the comparator 17 can be represented by [ _Is '* _Rs - _VDB ], where _VDB represents the voltage drop of each of the diodes _D1B ~ _DnB . In some embodiments, when at least one LED (for example, LED L ₂₂ ) of the light strings LS ₁ -LS _n fails and becomes open, the determination signal V _DET2 output by the comparator 17 is at a low logic level.

In some embodiments, when the light strings LS ₁ to LS _n are operating normally, the fault determination signal V _{DET_OUT} output by the gate 18 according to the determination signals V _DET1 and V _DET2 is at a low logic level. On the other hand, when at least one LED (e.g., the LED L ₂₂ ) of the light strings LS ₁ to LS _n fails and becomes open, the fault determination signal V _{DET_OUT} output by the gate 18 according to the determination signals V _DET1 and V _DET2 is at a high logic level.

In order to clearly explain the fault short circuit detection under normal operation and fault short circuit, please refer to FIG. 1A and FIG. 1C. FIG. 1C is a schematic diagram of the operation of the LED driver circuit 100 according to an embodiment of the present disclosure when the LED _L22 is faulty and short circuited. In some embodiments, when the light string _LS1 ~ _LSn is operating normally and the LED _L22 therein is faulty and short circuited, the potentials _Vs1 ~ _Vsn of the nodes _N1 ~ _Nn and the potential _{Vs_max} of the non-inverting input terminal of the comparator 17 can be shown in Table 2 below. V _S1 V _S2 ... V _Sn V _{s_max} Normal operation I _s *R _S I _s *R _S ... I _s *R _S [I _s *R _S -V _DB ] L ₂₂ Fault short circuit I _s ''*R _S I _k *R _S ... I _s ''*R _S [I _k *R _S -V _DB ] Table II

In Table 2, the potential of the second end of resistor _RS2 is assumed to be 0 volts. _RS represents the resistance value of each of resistors _RS1 ~ _RSn , and V _DB represents the conduction voltage of each of diodes _D1B ~ _DnB . In some embodiments, when the light-emitting diodes _L11 ~ _Lnn in the light strings _LS1 ~ _LSn are in normal operation, each of the aforementioned branch lines has the same voltage drop, so that the amplitude of the current I _s flowing through each branch line is the same. In some embodiments, each of the light strings _LS1 ~ _LSn has the same number of light-emitting diodes, and these light-emitting diodes have the same specifications. In some embodiments, the resistance values of resistors _RS1 ~ _RSn are the same, and the diodes _D1B ~ _DnB have the same specifications.

As shown in FIG. 1A , when the light strings LS ₁ to LS _n operate normally, the amplitudes of the currents I _S flowing through the light strings LS ₁ to LS _n are substantially the same, and the diodes D _1B to D _nB maintain the potential difference between their two ends at a certain voltage (the voltage drop of the diode, for example, 0.7 volts), so that the voltage V _{s_max} at the non-inverting input end of the comparator 17 can be represented by [I _s *R _S -V _DB ], where R _S represents the resistance value of each of the resistors R _S1 to R _Sn , and V _DB represents the voltage drop of each of the diodes D _1B to D _nB . In some embodiments, the floating potential V _{ref_max} is set based on [I _s *R _S -V _DB ] so that the comparator 17 outputs a low logic level when the light strings LS ₁ to LS _n operate normally. For example, the floating potential V _{ref_max} is set to be greater than [I _s *R _S -V _DB ] so that the potential V _{s_max} of the non-inverting input terminal of the comparator 17 is less than the floating potential V _{ref_max} when the light strings LS ₁ to LS _n operate normally. In some embodiments, if the diodes D _1A to D _nA are implemented by Schottky diodes, their voltage drop is very small, and [I _s *R _S -V _DB ] can be regarded as [I _s *R _S ]. In some embodiments, the signals coupled to the two terminals of the comparator 17 can be swapped, that is, the first terminal is coupled to the floating potential V _{ref — max} and the second terminal receives the potential V _{s — max} , and the comparator 17 outputs a low logic level to determine that a short circuit occurs in the lighting system 100 .

As shown in FIG. 1C , when the LED L ₂₂ in the lamp string LS ₂ fails and short-circuits, the current I _k flowing through the lamp string L ₂₂ increases (because the equivalent resistance of the lamp string LS ₂ is smaller than that of other lamp strings), and the current I _s ' flowing into other lamp strings decreases. At this time, the potential of the node N ₂ rises, the diode D _2B conducts the current path from the first end of the resistor RS ₂ to the non-inverting input terminal of the comparator 17, and D _2A does not conduct RS ₂ to V _{S_min} , so that the potential of the non-inverting input terminal of the comparator 17 rises to the potential of the first end of the resistor RS ₂ , which is greater than the floating potential V _{ref_max} , and the judgment signal V _DET2 output by the comparator 17 is at a high logic level. In some embodiments, when at least one LED (eg, LED L ₂₂ ) of the light strings LS ₁ -LS _n fails and is short-circuited, the determination signal V _DET2 output by the comparator 17 is at a high logic level.

In some embodiments, the high logic level of the determination signal V _DET2 indicates that at least one of the LEDs L ₁₁ -L _nn is short-circuited, and the low logic level of the determination signal V _DET2 indicates that the LEDs L ₁₁ -L _nn are not short-circuited. That is, the determination signal V _DET1 is used to provide short-circuit information related to the LEDs L ₁₁ -L _nn .

In some embodiments, when the light emitting diode _L22 fails to short-circuit, since the potentials of the first ends of the diodes _D1B and _DnB are less than the potentials of the second ends thereof, the diodes _D1B to _DnB except the diode _D2B are in the off state. In some embodiments, when the light emitting diode _L22 fails to open-circuit, since the potential of the second end of the diode _D2A (the potential of the node _N2 ) is higher than the potential of the first end of the diode _D2A , the diode _D2A is in the off state. In some embodiments, when the light-emitting diode _L22 fails and short-circuits, since the diodes _D1A ~ _DnA except _D2A will stabilize the potentials at both ends at a certain voltage (the voltage drop of the diode, for example, 0.7 volts, or the Zener diode has a voltage drop of 0.1V), the potential Vs_min of the inverting input terminal of the comparator 16 can be represented by [ _Is ''* _Rs + _VDA ], where _VDA represents the voltage drop of each of the diodes _D1A ~ _DnA . In some embodiments, [I _s ''*R _S +V _DA ] is greater than the floating potential V _{ref_min} , and the determination signal V _DET1 output by the comparator 16 when the LED L ₂₂ fails and shorts out is at a low logic level. In some embodiments, when at least one LED of the lamp strings LS ₁ to LS _n (e.g., the LED L ₂₂ ) fails and shorts out, the determination signal V _DET2 output by the comparator 16 is at a low logic level.

In some embodiments, when the light strings LS ₁ to LS _n are operating normally, the fault determination signal V _{DET_OUT} output by the gate 18 according to the determination signals V _DET1 and V _DET2 is at a low logic level. On the other hand, when at least one light emitting diode (e.g., light emitting diode L ₂₂ ) of the light strings LS ₁ to LS _n is short-circuited, the fault determination signal V _{DET_OUT} output by the gate 18 according to the determination signals V _DET1 and V _DET2 is at a high logic level. In other words, the fault determination signal V _{DET_OUT} output by the gate 18 can be used to determine whether at least one of an open circuit event or a short circuit event occurs in the ARR.

Please refer to FIG. 2. FIG. 2 is a schematic diagram of a constant current source 20 according to an embodiment of the present disclosure. In some embodiments, the constant current source 20 is a constant current source composed of an operational amplifier and a transistor. In other embodiments, the constant current source 20 can be implemented by other circuits capable of realizing a constant current function, and the present invention is not limited thereto. As shown in FIG. 2, the constant current source 20 includes an operational amplifier 21, transistors M1, Q1, and resistors R1 and R2. In some embodiments, the operational amplifier 21 is electrically connected to a positive power terminal V+ and a negative power terminal V-. In some embodiments, the output terminal of the operational amplifier 21 is electrically connected to the gate terminal of the transistor M1, and the transistor M1 is electrically connected between the first terminal of the transistor Q1 and the gate terminal of the transistor Q1. In some embodiments, when the driving current I changes, the operational amplifier 21 adjusts the output voltage according to the reference potential Vr and the potential of the first terminal of the resistor R2, and the transistor M1 adjusts the potential of the gate terminal of the transistor Q1 according to the output of the operational amplifier 21, so that the reference potential Vr is equal to the potential of the first terminal of the resistor R2, thereby controlling the driving current I to be a constant current. In other words, the reference potential Vr is reflected to the first end of the resistor R2 via negative feedback (virtual ground), so that the driving current I flowing through the resistor R2 becomes a fixed current, and this circuit becomes a constant current source.

Please refer to FIG. 3. FIG. 3 is a schematic diagram of an illumination system 300 according to an embodiment of the present disclosure. As shown in FIG. 3, the illumination system 300 includes light-emitting diodes L ₁₁ ~L _nn arranged in a matrix and a light-emitting diode driving circuit 30 electrically connected to the light-emitting diodes L ₁₁ ~L _nn . In some embodiments, the light-emitting diode driving circuit 30 includes diodes D _1A ~D _nA and D _1B ~D _nB , resistors _RS1 ~ _RSn , comparators 16 and 17, or a gate 18, a constant current source 20, bias current sources 11 and 12, floating voltage sources 14 and 15, an inverter 31, and a switch circuit S3. In some embodiments, the output terminal of the OR gate 18 is electrically connected to the control terminal of the switch circuit S3 via the inverter 31. In some embodiments, the switch circuit S3 is electrically connected between the constant current source 20 and the second current terminal I _OUT . In some embodiments, when the fault judgment signal V _{DET_OUT} output by the OR gate 18 is at a low logic level, the switch circuit S3 is turned on to conduct the current path of the driving current I. On the other hand, when the fault judgment signal V _{DET_OUT} output by the OR gate 18 is at a high logic level, the switch circuit S3 closes the current path of the driving current I, so that the light-emitting diodes L ₁₁ ~L _nn stop operating.

In some embodiments, the bias current source 11 can be implemented by a resistor electrically connected between the first current terminal I _IN and the inverting input terminal of the comparator 16 to provide a bias current I _{bias_min} to the diodes D _1A to D _nA so that the diodes D _1A to D _nA are at a working point to maintain basic operation. In some embodiments, the bias current source 12 can be implemented by a resistor electrically connected between the second current terminal I _OUT and the non-inverting input terminal of the comparator 17 to provide a bias current I _{bias_max} to the diodes D _1B to D _nB so that the diodes D _1B to D _nB are at a working point to maintain basic operation.

Please refer to FIG. 4. FIG. 4 is a schematic diagram of an illumination system 400 according to an embodiment of the present disclosure. As shown in FIG. 4, the illumination system 400 includes an LED driving circuit 40 and LEDs L ₁₁ -L _nn . In some embodiments, the LED driving circuit 400 includes diodes D _1A -D _nA and D _1B -D _nB , resistors _{RS1 -RSn} , comparators 16 and 17, or a gate 18, a constant current source 20, bias current sources 11 and 12, floating voltage sources 14 and 15, and a driving power source 41. Compared with the LED driver circuit 10 in FIGS. 1A to 1C , the LED driver circuit 40 in FIG. 4 further includes a driver power 41. In some embodiments, a first pin of the driver power 41 is electrically connected to a first current terminal I _IN , and a second pin of the driver power 41 is electrically connected to a second current terminal I _OUT . In some embodiments, a third pin of the driver power 41 is electrically connected to an output terminal of an OR gate 18 to adjust the amplitude of the driver current I according to the output of the OR gate 18. In other embodiments, a third pin of the driver power 41 is electrically connected to an output terminal of a comparator 16 to adjust the amplitude of the driver current I according to the output of the comparator 16. In some further embodiments, the third pin of the driving power source 41 is electrically connected to the output terminal of the comparator 17 to adjust the amplitude of the driving current I according to the output of the comparator 17. In some embodiments, if the determination signal V _DET1 output by the comparator 16 is at a high logic level (indicating that a light-emitting diode in one current branch has a fault open circuit), the driving power source 41 increases the current flowing into the light-emitting elements of other branches, thereby performing light supplementation.

Please refer to FIG. 5A, which is a schematic diagram of an illumination system 500a according to an embodiment of the present disclosure. As shown in FIG. 5A, the illumination system 500a includes a light-emitting diode matrix ARR and a light-emitting diode driving circuit 50a. In some embodiments, the light-emitting diode driving circuit 50a includes a detection circuit DET and a determination circuit CL. In some embodiments, the light-emitting diode matrix ARR, the detection circuit DET, and the determination circuit CL of FIG. 5A correspond to the light-emitting diode matrix ARR, the detection circuit DET, and the determination circuit CL in FIG. 1A, respectively, and will not be described in detail here. In some embodiments, the output end of the judgment circuit CL is electrically connected to the display module DISP, and the display module DISP is used to display the fault prompt of the LED driving circuit 500 according to the fault judgment signal V _{DET_OUT} output by the judgment circuit CL. The LED driving circuit fault prompt includes a LED short circuit prompt, a LED open circuit prompt, a LED driving circuit forced shutdown prompt, and a driving current adjustment prompt. The above prompts are only examples for illustration and are not used to limit the content of this disclosure.

Please refer to FIG. 5B, which is a schematic diagram of an illumination system 500b according to an embodiment of the present disclosure. As shown in FIG. 5B, the illumination system 500b includes a light-emitting diode matrix ARR and a light-emitting diode driving circuit 50b. In some embodiments, the light-emitting diode driving circuit 50b includes a detection circuit DET, a determination circuit CL, a control circuit CON, and a light-emitting module LEM. In some embodiments, the light-emitting diode matrix ARR, the detection circuit DET, and the determination circuit CL of FIG. 5A correspond to the light-emitting diode matrix ARR, the detection circuit DET, and the determination circuit CL in FIG. 1A, respectively, and will not be described in detail here. In some embodiments, the control circuit CON is electrically connected to the output terminal of the OR gate 18 in the determination circuit CL to instruct the light emitting module LEM to perform fill light according to the fault determination signal V _{DET_OUT} .

Please refer to FIG. 6, which is a schematic diagram of an illumination system 600 according to an embodiment of the present disclosure. As shown in FIG. 6, the illumination system 600 includes LEDs _L11 ~ _Lnn and an LED driving circuit 60. In some embodiments, the LED driving circuit 60 includes a detection circuit DETb, resistors _RS1 ~ _RSn , a comparator 16, a bias current source 11, and a floating voltage source 14. In some embodiments, the detection circuit DETb includes diodes _D1A ~ _DnA . In some embodiments, the detection circuit DETb in the LED driving circuit 60 is an open circuit detection circuit. Compared with the LED driving circuit 10 in FIG. 1A , the LED driving circuit 60 omits the short circuit detection structure. The LED driving circuit 60 can still perform fault open circuit detection on the LEDs L ₁₁ -L _nn normally. The relevant embodiments described in the embodiment of FIG. 1B have been described in detail and will not be repeated here.

Please refer to FIG. 7, which is a schematic diagram of an illumination system 700 according to an embodiment of the present disclosure. As shown in FIG. 6, the illumination system 700 includes LEDs _L11 ~ _Lnn and an LED driving circuit 70. In some embodiments, the LED driving circuit 70 includes a detection circuit DETc, resistors _RS1 ~ _RSn , a comparator 17, a bias current source 12, and a floating voltage source 15. In some embodiments, the detection circuit DETc includes diodes _D1B ~ _DnB . In some embodiments, the detection circuit DETc in the LED driving circuit 70 is a short circuit detection circuit. Compared with the LED driving circuit 10 in FIG. 1A , the LED driving circuit 70 omits the open circuit detection structure. The LED driving circuit 70 can still detect the fault short circuit of the LEDs L ₁₁ -L _nn normally. The relevant embodiments described in the embodiment of FIG. 1C have been described in detail and will not be repeated here.

Please refer to FIG. 8, which is a schematic diagram of an illumination system 800 according to an embodiment of the present disclosure. As shown in FIG. 8, the illumination system 800 includes LEDs _L11 ~ _Lnn and an LED driving circuit 80. In some embodiments, the LED driving circuit 80 includes a detection circuit DETa, resistors _RS1 ~ _RSn , bias current sources 11~12, floating voltage sources 14~15, and a determination circuit CL. In some embodiments, the operation of the detection circuit DETa, resistors _RS1 - _RSn , bias current sources 11-12, floating voltage sources 14-15, and judgment circuit CL in the LED driving circuit 80 corresponds to the operation of the detection circuit DETa, resistors _RS1 - _RSn , bias current sources 11-12, floating voltage sources 14-15, and judgment circuit CL in FIG. 1A, and will not be repeated here. Compared with the LED driving circuit 10 in FIG. 1A, the LED driving circuit 80 is electrically connected between the first current terminal I _IN and the anode terminal of the lamp string _LS1 - _LSn . In some embodiments, based on the potential relationship between the first current terminal I _IN and the second current terminal I _OUT , the LED driving circuit 80 is a high voltage detection structure configured at the high voltage end, and its internal component connection relationship corresponds to the LED driving circuit 10 configured at the low voltage end, and can achieve the same/similar functions as the LED driving circuit 10. Therefore, it will not be repeated here.

In summary, the detection circuit DETa of the LED driving circuit 10 of the present disclosure can detect whether the LEDs L ₁₁ -L _nn in a plurality of current branches are faulty, thereby simplifying the circuit design and further improving the circuit operation efficiency.

Although the present disclosure has been disclosed in the form of implementation as above, it is not intended to limit the content of the present disclosure. Any person with ordinary knowledge in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the content of the present disclosure shall be subject to the definition of the attached patent application scope.

In order to make the above and other purposes, features, advantages and embodiments of the present disclosure more clearly understood, the attached symbols are described as follows: 10, 30, 40, 50a, 50b, 60, 70, 80: LED driving circuit 11, 12: bias current source 14, 15: floating voltage source 16, 17: comparator 21: operational amplifier 18: OR gate 20: constant current source 31: inverter 41: driving power supply 100, 300, 400, 500a, 500b, 600, 700, 800: lighting system ARR: LED matrix CL: judgment circuit D _1A ~D _nA , D _1B ~D _nB : diode DET, DETa, DETb, DETc: detection circuit DU ₁ ~ DU _n : diode unit DISP: display module I: driving current I _{bias_min} , I _{bias_max} : bias current I _IN : first current terminal I _OUT : second current terminal I _s , I _s ', I _s '', I _k : current L ₁₁ ~ L _nn : light-emitting diode LS ₁ ~ LS _n : light string N ₁ ~ N _n : node _RS1 ~ _RSn , R1, R2: resistor M1: transistor Q1: transistor S3: switch circuit V+: positive power terminal V-: negative power terminal V _{DET_OUT} : fault judgment signal V _DET1 , V _DET2 : judgment signal V _IN , V _{s_min} , V _{s_max} , V _S1 ~ V _S : potential V _ref , V _r : reference potential V _{ref_min} , V _{ref_max} : floating potential

In order to make the above and other purposes, features, advantages and embodiments of the present disclosure more clearly understandable, the attached drawings are described as follows: Figure 1A is a schematic diagram of a lighting system according to an embodiment of the present disclosure under normal operation. Figure 1B is a schematic diagram of the operation of a light-emitting diode in a lighting system according to an embodiment of the present disclosure under an open circuit fault. Figure 1C is a schematic diagram of the operation of a light-emitting diode in a lighting system according to an embodiment of the present disclosure under a short circuit fault. Figure 2 is a schematic diagram of a circuit of a constant current source according to an embodiment of the present disclosure. Figure 3 is a schematic diagram of a lighting system according to an embodiment of the present disclosure. Figure 4 is a schematic diagram of a lighting system according to an embodiment of the present disclosure. FIG. 5A is a schematic diagram of a lighting system according to an embodiment of the present disclosure. FIG. 5B is a schematic diagram of a lighting system according to an embodiment of the present disclosure. FIG. 6 is a schematic diagram of a lighting system according to an embodiment of the present disclosure. FIG. 7 is a schematic diagram of a lighting system according to an embodiment of the present disclosure. FIG. 8 is a schematic diagram of a lighting system according to an embodiment of the present disclosure.

10: LED driving circuit

11,12: Bias current source

14,15: Floating voltage source

16,17: Comparator

18: Or gate

20: The source of the constant flow

100: Lighting system

ARR: LED Matrix

CL: judgment circuit

DETa: Detection circuit

D _1A ~D _nA ,D _1B ~D _nB : diode

DU ₁ ~DU _n : Diode unit

I: Driving current

I _{bias_min} ,I _{bias_max} : bias current

I _IN : First current terminal

I _OUT : Second current terminal

I _s : Current

L ₁₁ ~L _nn : LED

LS ₁ ~LS _n : Light string

N ₁ ~N _n : Node

R _S1 ~R _Sn : Resistance

V _{DET_OUT} : Fault detection signal

V _DET1 , V _DET2 : judgment signal

V _IN ,V _{s_min} ,V _{s_max} ,V _S1 ~V _Sn : Potential

V _ref : reference potential

V _{ref_min} , V _{ref_max} : floating potential

Claims (10)

A light-emitting diode driving circuit is electrically connected to a light-emitting diode matrix, wherein the light-emitting diode matrix includes a plurality of light strings, each of which includes a plurality of light-emitting diodes, wherein the light strings are electrically connected to a first current terminal and receive a driving current from the first current terminal, and the light-emitting diode driving circuit includes: A constant current source is electrically connected between the light strings and a second current terminal to control the driving current to be a constant current; A plurality of resistors, whose first ends are electrically connected to the light strings respectively, and whose second ends are electrically connected to a reference potential respectively; A detection circuit is electrically connected between the resistors and the light strings, and includes a plurality of diode units, wherein each of the diode units includes a first diode and a second diode connected in series; and A judgment circuit includes: A first comparator having a first first input terminal electrically connected to the first diodes, a first second input terminal for receiving a first floating potential, and a first output terminal for outputting a first judgment signal; and A second comparator having a second first input terminal electrically connected to the second diodes, a second second input terminal for receiving a second floating potential, and a second output terminal for outputting a second judgment signal, wherein the first floating potential and the second floating potential change with the reference potential. The LED driving circuit as described in claim 1 further includes: a first floating voltage source, whose first end is electrically connected to the first first input terminal of the first comparator, and whose second end is electrically connected to the reference potential, wherein the first floating voltage source is used to provide the first floating potential; and a second floating voltage source, whose first end is electrically connected to the second first input terminal of the second comparator, and whose second end is electrically connected to the reference potential, wherein the second floating voltage source is used to provide the second floating potential. A light-emitting diode driving circuit as described in claim 1, wherein the first first input terminal of the first comparator is electrically connected to the anode terminals of the first diodes and a first bias current source, the cathode terminals of the first diodes are electrically connected to the first terminals of the resistors, respectively, and the first judgment signal is used to provide open-circuit information related to the light-emitting diodes. A light-emitting diode driving circuit as described in claim 1, wherein the second first input terminal of the second comparator is electrically connected to the cathode terminals of the second diodes and a second bias current source, the anode terminals of the second diodes are electrically connected to the first terminals of the resistors, respectively, and the second judgment signal is used to provide short-circuit information related to the light-emitting diodes. The light-emitting diode driving circuit as described in claim 1 further includes an OR gate electrically connected to the first output terminal of the first comparator and the second output terminal of the second comparator, for generating a fault judgment signal according to the first judgment signal and the second judgment signal. The LED driving circuit as described in claim 5 further includes: A switching circuit electrically connected between the constant current source and the second current terminal, and wherein when the fault judgment signal is at a high logic level, the switching circuit shuts off the current path of the driving current. The LED driving circuit as described in claim 5 further includes: A driving power source, whose first pin is electrically connected to the first current terminal, whose second pin is electrically connected to the second current terminal, and whose third pin is electrically connected to an output terminal of the OR gate, wherein the driving power source is used to provide a driving current to the light strings, and wherein the driving power source is further used to adjust the amplitude of the driving current according to the fault judgment signal. The LED driving circuit as described in claim 5 further includes: a light-emitting module; and a control circuit electrically connected to an output terminal of the OR gate and the light-emitting module, for instructing the light-emitting module to perform supplementary lighting according to the fault judgment signal. A light-emitting diode driving circuit is electrically connected to a light-emitting diode matrix, wherein the light-emitting diode matrix includes a plurality of light strings, each of which includes a plurality of light-emitting diodes, wherein the light strings are electrically connected to a first current terminal and receive a driving current from the first current terminal, and the light-emitting diode driving circuit includes: A constant current source is electrically connected between the light strings and a second current terminal to control the driving current to be a constant current; A plurality of resistors, whose first ends are electrically connected to the light strings respectively, and whose second ends are electrically connected to a reference potential respectively; A detection circuit electrically connected between the resistors and the light strings, and comprising a plurality of diodes, wherein the anodes of the diodes are used to receive a bias DC current, and wherein the cathodes of the diodes are electrically connected to the resistors respectively; and a comparator having a first input terminal electrically connected to the anodes of the diodes, a second input terminal for receiving a floating potential, and an output terminal for outputting a first judgment signal, wherein the floating potential varies with the reference potential. A light-emitting diode driving circuit is electrically connected to a light-emitting diode matrix, wherein the light-emitting diode matrix includes a plurality of light strings, each of which includes a plurality of light-emitting diodes, wherein the light strings are electrically connected to a first current terminal and receive a driving current from the first current terminal, and the light-emitting diode driving circuit includes: A constant current source is electrically connected between the light strings and a second current terminal to control the driving current to be a constant current; A plurality of resistors, whose first ends are electrically connected to the light strings respectively, and whose second ends are electrically connected to a reference potential respectively; A detection circuit electrically connected between the resistors and the light strings, and comprising a plurality of diodes, wherein the cathodes of the diodes are used to receive a bias DC current, and wherein the anodes of the diodes are electrically connected to the resistors respectively; and a comparator having a first input terminal electrically connected to the cathodes of the diodes, a second input terminal for receiving a floating potential, and a second output terminal for outputting a judgment signal, wherein the floating potential varies with the reference potential.

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