CN210609813U

CN210609813U - LED short-circuit protection circuit and light-emitting device

Info

Publication number: CN210609813U
Application number: CN201921003337.2U
Authority: CN
Inventors: 张洪波; 刘娜; 张炜
Original assignee: BCD Shanghai Micro Electronics Ltd
Current assignee: BCD Shanghai Micro Electronics Ltd
Priority date: 2019-06-27
Filing date: 2019-06-27
Publication date: 2020-05-22
Anticipated expiration: 2029-06-27

Abstract

The utility model discloses a LED short-circuit protection circuit and illuminator, include: the voltage detection circuit is connected with a preset detection position on a branch where an LED in the LED linear circuit is located and used for detecting a voltage signal of the preset detection position; the short circuit judging circuit is used for judging whether a voltage signal at the moment is greater than a preset first voltage threshold value or not when the total voltage waveform input by the branch where the LED is positioned is at a preset waveform position, and if so, judging that the LED with a short circuit exists in the LED linear circuit; if not, judging that the short-circuited LED does not exist in the LED linear circuit; and the short-circuit protection circuit is used for carrying out LED short-circuit protection on the LED linear circuit when the short-circuit judgment circuit judges that the LED linear circuit has a short-circuit LED. Therefore, the LED short-circuit protection circuit can perform LED short-circuit protection on the LED linear circuit when short-circuited LEDs exist, and therefore safety and reliability of the LED linear circuit are improved.

Description

LED short-circuit protection circuit and light-emitting device

Technical Field

The utility model relates to a LED linear circuit protection field especially relates to a LED short-circuit protection circuit and illuminator.

Background

Currently, LEDs (Light Emitting diodes) are widely used due to their advantages of good shock resistance, high reliability, long lifetime, etc., for example, many Light Emitting devices include an LED linear circuit (a plurality of LEDs are connected in series) as shown in fig. 1. However, in the operation process of the LED linear circuit such as fig. 1, one or more LEDs are prone to short circuit, and when the LEDs are short-circuited, the voltage across the other components on the branch where the LEDs are located in the LED linear circuit is increased, even exceeds the safe voltage, so that the safety and reliability of the LED linear circuit are reduced.

Therefore, how to provide a solution to the above technical problem is a problem that needs to be solved by those skilled in the art.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a LED short-circuit protection circuit and illuminator can detect out the LED that whether exists the short circuit among the LED linear circuit based on the principle that the voltage at all the other components and parts both ends of its place branch road when the LED short circuit rises to carry out LED short-circuit protection to LED linear circuit when there is the LED of short circuit among the LED linear circuit, and then improved LED linear circuit's security and reliability.

In order to solve the technical problem, the utility model provides a LED short-circuit protection circuit, include:

the voltage detection circuit is connected with a preset detection position on a branch where an LED in the LED linear circuit is located and used for detecting a voltage signal of the preset detection position;

the short circuit judging circuit is connected with the output end of the voltage detection circuit and used for judging whether the voltage signal at the moment is greater than a preset first voltage threshold value or not when the total voltage waveform input by the branch circuit where the LED is located is at a preset waveform position, and if so, judging that the LED with the short circuit exists in the LED linear circuit; if not, judging that short-circuited LEDs do not exist in the LED linear circuit;

and the short-circuit protection circuit is connected with the output end of the short-circuit judgment circuit and is used for carrying out LED short-circuit protection on the LED linear circuit when the short-circuit judgment circuit judges that the short-circuited LED exists in the LED linear circuit.

Preferably, the voltage detection circuit includes a first comparison circuit, wherein:

a first end of the first comparison circuit is connected with the preset detection position, a second end of the first comparison circuit is connected with the preset first voltage threshold, and an output end of the first comparison circuit is used as an output end of the voltage detection circuit;

the first comparison circuit is used for judging whether the voltage signal of the preset detection position is greater than the preset first voltage threshold value or not, and if so, generating a high level signal; if not, a low level signal is generated.

Preferably, the short circuit determination circuit includes:

the first end of the first comparison circuit is connected with the voltage division circuit of the total voltage waveform, the second end of the first comparison circuit is connected with a preset second voltage threshold, and the first comparison circuit is used for judging whether a voltage division signal of the voltage division circuit is larger than the preset second voltage threshold or not, and if yes, a high level signal is generated; if not, generating a low level signal;

the short-circuit detection circuit is respectively connected with the output end of the first comparison circuit and the output end of the second comparison circuit and is used for detecting whether the level output by the first comparison circuit is high level at the moment when the rising edge and/or the falling edge of the waveform output by the second comparison circuit are/is, and if yes, judging that a short-circuited LED exists in the LED linear circuit; and if not, judging that the short-circuited LED does not exist in the LED linear circuit.

Preferably, the short circuit detection circuit comprises a not gate, a first D-type flip-flop, a second D-type flip-flop, an and gate and a first nor gate; wherein:

the input end of the not gate is connected with the output end of the second comparison circuit and the D end of the first D-type trigger respectively, the output end of the not gate is connected with the D end of the second D-type trigger and the first input end of the AND gate respectively, the CK end of the first D-type trigger is connected with the output end of the first comparison circuit and the CK end of the second D-type trigger respectively, the Q end of the first D-type trigger is connected with the second input end of the AND gate, the output end of the AND gate is connected with the first input end of the first NOR gate, the second input end of the first NOR gate is connected with the Q end of the second D-type trigger, and the output end of the first NOR gate is used as the output end of the short circuit detection circuit; the first D-type flip-flop and the second D-type flip-flop are used for keeping a level signal output by a Q end consistent with a level signal input by a CK end when a rising edge signal is input by a D end;

the short circuit detection circuit is specifically used for judging that a short-circuited LED exists in the LED linear circuit when the first NOR gate outputs a low level; and when the first NOR gate outputs a high level, judging that the short-circuited LED does not exist in the LED linear circuit.

Preferably, the short circuit determination circuit further includes:

and the false trigger prevention circuit is connected with the output end of the short circuit detection circuit and is used for detecting the level output by the first NOR gate after the total voltage waveform input by the branch circuit where the LED is positioned passes through a preset period number from the start of the LED linear circuit entering work, and judging that the LED with the short circuit exists in the LED linear circuit when the first NOR gate outputs a low level and judging that the LED with the short circuit does not exist in the LED linear circuit when the first NOR gate outputs a high level.

Preferably, the false trigger prevention circuit includes a counter and a second nor gate; wherein:

the counting end of the counter is connected with the output end of the second comparison circuit, the output end of the counter is connected with the first input end of the second NOR gate, the second input end of the second NOR gate is connected with the output end of the first NOR gate, and the output end of the second NOR gate is used as the output end of the false trigger prevention circuit; wherein the counter is used for outputting a high level by default; accumulating the number of rising edge signals or falling edge signals output by the second comparison circuit from the beginning of the work of the LED linear circuit, and converting from high level to low level to output when the number reaches a preset number threshold;

the false triggering prevention circuit is specifically used for judging that a short-circuited LED exists in the LED linear circuit when the second NOR gate outputs a high level; and when the second NOR gate outputs a low level, judging that the short-circuited LED does not exist in the LED linear circuit.

Preferably, the short-circuit protection circuit is specifically configured to control the LED linear circuit to work for M duty cycles every N duty cycles when the short-circuit determination circuit determines that there is a short-circuited LED in the LED linear circuit, so as to perform LED short-circuit protection on the LED linear circuit; wherein M is more than or equal to 1 and less than N, and M, N are integers.

Preferably, the short-circuit protection circuit comprises a third nor gate and a fourth nor gate; wherein:

a first input end of the third nor gate is connected with an output end of the short circuit judging circuit, a second input end of the third nor gate is connected with an output end of the fourth nor gate, an output end of the third nor gate is connected with a first input end of the fourth nor gate, and a second input end of the fourth nor gate is connected with a signal setter; wherein the signal setter is configured to default that the output of the fourth NOR gate is inactive; controlling the output of the fourth NOR gate to function for N-M duty cycles within every N duty cycles of the LED linear circuit, starting from the determination by the short determination circuit that there is a short LED in the LED linear circuit;

the LED linear circuit is specifically used for normal operation when the output of the fourth NOR gate is not functional; and stopping operation when the output of the fourth NOR gate is active.

Preferably, the first comparison circuit and the second comparison circuit are both comparators, wherein:

the positive input end of the comparator is used as the first end of the first comparison circuit and the second comparison circuit, the negative input end of the comparator is used as the second end of the first comparison circuit and the second comparison circuit, and the output end of the comparator is used as the output end of the first comparison circuit and the second comparison circuit.

In order to solve the technical problem, the utility model also provides a light emitting device, including the linear circuit of LED, still include any kind of LED short-circuit protection circuit of the aforesaid.

The utility model provides a LED short-circuit protection circuit, include: the voltage detection circuit is connected with a preset detection position on a branch where an LED in the LED linear circuit is located and used for detecting a voltage signal of the preset detection position; the short circuit judging circuit is connected with the output end of the voltage detecting circuit and used for judging whether the voltage signal at the moment is greater than a preset first voltage threshold value or not when the total voltage waveform input by the branch circuit where the LED is located is in a preset waveform position, and if yes, judging that the LED with the short circuit exists in the LED linear circuit; if not, judging that the short-circuited LED does not exist in the LED linear circuit; and the short-circuit protection circuit is connected with the output end of the short-circuit judging circuit and is used for carrying out LED short-circuit protection on the LED linear circuit when the short-circuit judging circuit judges that the short-circuited LED exists in the LED linear circuit.

Therefore, the LED short-circuit protection circuit can detect whether the LED with the short circuit exists in the LED linear circuit or not based on the principle that the voltages at the two ends of the other components of the branch where the LED is located are increased when the LED is in the short circuit, so that the LED short-circuit protection is carried out on the LED linear circuit when the LED with the short circuit exists in the LED linear circuit, and the safety and the reliability of the LED linear circuit are improved.

The utility model also provides a light-emitting device has the same beneficial effect with above-mentioned LED short-circuit protection circuit.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the prior art and the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic diagram of a prior art LED linear circuit;

fig. 2 is a schematic structural diagram of an LED short-circuit protection circuit according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an LED short-circuit protection circuit according to an embodiment of the present invention;

fig. 4 is an application schematic diagram of an LED short-circuit protection circuit according to an embodiment of the present invention;

fig. 5 is a waveform chart of an LED short-circuit protection circuit when the LED linear circuit provided by the embodiment of the present invention normally works;

fig. 6 is a waveform curve diagram of an LED short-circuit protection circuit when an LED short circuit occurs in an LED linear circuit provided in an embodiment of the present invention;

fig. 7 is a waveform curve diagram of the short-circuit protection triggered when the voltage division Vdivide drops when the LED short circuit occurs in the first LED linear circuit provided in the embodiment of the present invention;

fig. 8 is a waveform curve diagram of the short-circuit protection triggered when the voltage Vdivide drops when the LED short circuit occurs in the second LED linear circuit provided in the embodiment of the present invention;

fig. 9 is a graph of Pro waveform when an LED short circuit occurs in an LED linear circuit according to an embodiment of the present invention;

fig. 10 is a waveform chart illustrating the prevention of the LED short-circuit protection when the LED linear circuit provided by the embodiment of the present invention is started in normal operation;

fig. 11 is a waveform curve diagram of a Gate _ M1 of a switch tube when an LED short circuit occurs in an LED linear circuit according to an embodiment of the present invention.

Detailed Description

The core of the utility model is to provide a LED short-circuit protection circuit and illuminator, can detect out whether there is the LED of short circuit in the LED linear circuit based on the principle that the voltage at all the other components and parts both ends of its place branch road when the LED short circuit rises to carry out LED short-circuit protection to the LED linear circuit when there is the LED of short circuit in the LED linear circuit, and then improved LED linear circuit's security and reliability.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 2, fig. 2 is a schematic structural diagram of an LED short-circuit protection circuit according to an embodiment of the present invention.

This LED short-circuit protection circuit includes:

the voltage detection circuit 1 is connected with a preset detection position on a branch where an LED in the LED linear circuit is located and is used for detecting a voltage signal of the preset detection position;

the short circuit judging circuit 2 is connected with the output end of the voltage detecting circuit 1 and is used for judging whether a voltage signal at the moment is greater than a preset first voltage threshold value or not when the total voltage waveform input by the branch circuit where the LED is located is in a preset waveform position, and if so, judging that the LED with a short circuit exists in the LED linear circuit; if not, judging that the short-circuited LED does not exist in the LED linear circuit;

and the short-circuit protection circuit 3 is connected with the output end of the short-circuit judgment circuit 2 and is used for carrying out LED short-circuit protection on the LED linear circuit when the short-circuit judgment circuit 2 judges that the short-circuited LED exists in the LED linear circuit.

It should be noted that the preset of the present application is set in advance, and only needs to be set once, and the reset is not needed unless the modification is needed according to the actual situation.

Specifically, the LED short-circuit protection circuit of the present application includes a voltage detection circuit 1, a short-circuit determination circuit 2 and a short-circuit protection circuit 3, and its working principle is:

first, the operation principle of the LED linear circuit of fig. 1 will be explained. In fig. 1, ac power output from the ac power source is rectified into steamed bread waves (Vbus) by the rectifier bridge, and the steamed bread waves are respectively input into the voltage dividing branch (composed of the first resistor R1 and the second resistor R2) and the branch (composed of a plurality of LEDs connected in series, the switching tube M1 and the voltage dividing resistor Rcs) where the LEDs are located. When the LED linear circuit is ready to enter into operation, the LED linear circuit controls the switching tube M1 to be turned on, so that the LED is powered on to emit light. If a short-circuited LED appears on a branch where the LED is located during operation of the LED linear circuit, voltage at two ends of other components on the branch where the LED is located may be increased, for example, when the total voltage waveform input by the branch where the LED is located is in the same waveform position, the voltage Vcs at two ends of the voltage dividing resistor Rcs on the branch where the LED is located (where the short-circuited LED is not present) is less than the voltage Vcs at two ends of the voltage dividing resistor Rcs on the branch where the LED is located (where the short-circuited LED is present).

It should be noted that the LED short-circuit protection circuit of the present application is a short-circuit protection circuit provided for an LED linear circuit (fig. 1 is only one LED linear circuit) such as fig. 1, and the LED short-circuit protection circuit of the present application can also be applied to other LED linear circuits based on the same protection principle.

In detail, the present application sets a detection position in advance on a branch where an LED is located in an LED linear circuit (for example, the LED linear circuit in fig. 1 may select a connection point between the switch M1 and the voltage dividing resistor Rcs). In the working process of the LED linear circuit, the voltage detection circuit 1 is adopted to detect the voltage of the set detection position, so that a voltage signal corresponding to the set detection position is obtained.

Considering that the voltage at the set detection position changes to a certain extent before and after the short-circuited LED appears on the branch where the LED is located, based on the total voltage waveform (such as a bread wave) input by the branch where the LED is located, the present application can set a waveform position where the total voltage waveform input by the branch where the LED is located in advance, so as to observe the change of the voltage at the set detection position when the total voltage waveform input by the branch where the LED is located is at the preset waveform position.

Based on this, this application sets up a first voltage threshold in advance, and the theory of setting is: when the total voltage waveform input by the branch where the LED is located is in a preset waveform position, if the voltage signal corresponding to the set detection position is greater than the set first voltage threshold value, indicating that a short-circuited LED exists in the LED linear circuit; otherwise, the LED linear circuit is indicated to have no short-circuited LED. Therefore, when the total voltage waveform input by the branch where the LED is located is at the preset waveform position, the short circuit determination circuit 2 is adopted to determine whether the voltage signal corresponding to the set detection position is greater than the set first voltage threshold, and if so, determine that the LED with the short circuit exists in the LED linear circuit; if the voltage is not greater than the set first voltage threshold, the LED linear circuit is judged to have no short-circuited LED, and therefore the LED short-circuit condition is detected in time when the short-circuited LED appears on the branch circuit where the LED is located. Then, this application adopts short-circuit protection circuit 3 to carry out LED short-circuit protection (for example can directly control LED linear circuit stop work) to LED linear circuit when short-circuit decision circuit 2 detects LED short-circuit situation to prevent that the voltage at other components and parts both ends from exceeding self safe voltage on the branch of LED place, and then improved LED linear circuit's security and reliability.

Referring to fig. 3, fig. 3 is a schematic diagram of a specific structure of an LED short-circuit protection circuit according to an embodiment of the present invention. The LED short-circuit protection circuit is based on the above embodiment:

as an alternative embodiment, the voltage detection circuit 1 includes a first comparison circuit, wherein:

a first end of the first comparison circuit is connected with a preset detection position, a second end of the first comparison circuit is connected with a preset first voltage threshold, and an output end of the first comparison circuit is used as an output end of the voltage detection circuit 1;

the first comparison circuit is used for judging whether the voltage signal of the preset detection position is greater than a preset first voltage threshold value or not, and if so, generating a high level signal; if not, a low level signal is generated.

Specifically, the voltage detection circuit 1 of the present application may select the first comparison circuit, so as to compare the voltage signal corresponding to the preset detection position with the preset first voltage threshold (Vref1), so as to determine whether the voltage signal corresponding to the preset detection position is greater than the preset first voltage threshold.

The first comparison circuit generates a high level signal when the voltage signal corresponding to the preset detection position is greater than the preset first voltage threshold, and generates a low level signal when the voltage signal corresponding to the preset detection position is not greater than the preset first voltage threshold, so that the short circuit judgment circuit 2 judges whether a short-circuited LED exists in the LED linear circuit based on the high and low level signal output by the first comparison circuit when the total voltage waveform input by the branch where the LED is located is at the preset waveform position.

As an alternative embodiment, the short circuit determination circuit 2 includes:

the first end of the first comparison circuit is connected with the voltage division circuit of the total voltage waveform, the second end of the first comparison circuit is connected with a second comparison circuit of a preset second voltage threshold value, and the first comparison circuit is used for judging whether a voltage division signal of the voltage division circuit is larger than the preset second voltage threshold value or not, and if yes, a high level signal is generated; if not, generating a low level signal;

the short-circuit detection circuit is respectively connected with the output end of the first comparison circuit and the output end of the second comparison circuit and is used for detecting whether the level output by the first comparison circuit is a high level at the moment when the rising edge and/or the falling edge of the waveform output by the second comparison circuit are/is, and if yes, judging that the LED with the short circuit exists in the LED linear circuit; if not, judging that the short-circuited LED does not exist in the LED linear circuit.

Specifically, the short circuit determination circuit 2 of the present application includes a second comparison circuit and a short circuit detection circuit, and its operating principle is:

considering that if a waveform position is selected from the total voltage waveform input by the branch where the LED is located (since the total voltage waveform is a waveform with a period change, the total voltage waveform of the present application corresponds to a same waveform position in each period), the voltage in the total voltage waveform includes both a voltage greater than the total voltage waveform at the preset waveform position and a voltage less than the total voltage waveform at the preset waveform position, so that the manner of determining that the total voltage waveform is at the set waveform position may be: acquiring a target voltage of the total voltage waveform at a set waveform position in advance; in the working process of the LED linear circuit, comparing the waveform voltage of the total voltage waveform with a target voltage, and if one waveform position is selected from the rising waveforms of the total voltage waveform, when the waveform voltage rises to the target voltage, considering that the total voltage waveform is at the set waveform position at the moment; if a waveform position is selected in the falling waveform of the total voltage waveform, when the waveform voltage falls to the target voltage, the total voltage waveform is considered to be at the set waveform position.

Based on this principle, the present application may also use a voltage dividing circuit in the LED linear circuit (to divide the total voltage waveform input by the branch where the LED is located, such as the first resistor R1 and the second resistor R2 in fig. 1), to compare the voltage dividing signal (the reduced total voltage waveform) of the voltage dividing circuit with the preset second voltage threshold (Vref2), and consider that: if a waveform position is selected from rising waveforms of the total voltage waveform, the total voltage waveform is at the set waveform position when a voltage division signal of the voltage division circuit rises to a preset second voltage threshold; if a waveform position is selected from the descending waveforms of the total voltage waveform, the total voltage waveform is at the set waveform position when the voltage division signal of the voltage division circuit descends to the preset second voltage threshold value. Therefore, the voltage division signal of the voltage division circuit is compared with the preset second voltage threshold value by the second comparison circuit, a high level signal is generated when the voltage division signal of the voltage division circuit is larger than the preset second voltage threshold value, and a low level signal is generated when the voltage division signal of the voltage division circuit is not larger than the preset second voltage threshold value, so that the total voltage waveform is determined to be in the set waveform position according to the rising edge or the falling edge of the square wave output by the second comparison circuit.

Considering that when the total voltage waveform is at the set waveform position, if the first comparison circuit outputs a high level signal, it indicates that a short-circuited LED exists in the LED linear circuit; if the first comparison circuit outputs a low level signal, it is indicated that there is no short-circuited LED in the LED linear circuit, so that the short-circuit detection circuit is adopted to detect whether the level output by the first comparison circuit is a high level at the moment of the rising edge or the falling edge of the waveform output by the second comparison circuit, and if the level is the high level, it is determined that there is a short-circuited LED in the LED linear circuit; if the level is low, it is determined that there is no short-circuited LED in the LED linear circuit. It can be understood that the short circuit detection circuit of the present application may also detect whether the level output by the first comparison circuit is a high level at the time when the rising edge of the waveform output by the second comparison circuit is located, and detect whether the level output by the first comparison circuit is a high level at the time when the falling edge of the waveform output by the second comparison circuit is located, and determine that there is a short-circuited LED in the LED linear circuit when both are high levels, or determine that there is no short-circuited LED in the LED linear circuit.

As an alternative embodiment, the short detection circuit includes an inverter INV, a first D type flip-flop DFF1, a second D type flip-flop DFF2, an AND gate AND, AND a first NOR gate NOR 1; wherein:

the input end of an inverter INV is respectively connected with the output end of the second comparison circuit AND the D end of the first D-type flip-flop DFF1, the output end of the inverter INV is respectively connected with the D end of the second D-type flip-flop DFF2 AND the first input end of an AND gate AND, the CK end of the first D-type flip-flop DFF1 is respectively connected with the output end of the first comparison circuit AND the CK end of the second D-type flip-flop DFF2, the Q end of the first D-type flip-flop DFF1 is connected with the second input end of the AND gate AND, the output end of the AND gate AND is connected with the first input end of the first NOR gate NOR1, the second input end of the first NOR gate NOR1 is connected with the Q end of the second D-type DFF2, AND the output end of the first NOR gate NOR1 is used as the output end of the short-circuit detection circuit; the first D-type flip-flop DFF1 and the second D-type flip-flop DFF2 are used for keeping the level signal output by the Q end consistent with the level signal input by the CK end when the rising edge signal is input by the D end;

the short-circuit detection circuit is specifically used for judging that a short-circuited LED exists in the LED linear circuit when the first NOR gate NOR1 outputs a low level; when the first NOR gate NOR1 outputs a high level, it is determined that there is no short-circuited LED in the LED linear circuit.

Specifically, the short circuit detection circuit of the present application includes an inverter INV, a first D-type flip-flop DFF1, a second D-type flip-flop DFF2, an AND gate AND, AND a first NOR gate NOR1, AND its operation principle is:

the level signal Out1A output by the second comparison circuit is subjected to an inverted signal Out1B of Out1A through an inverter INV, and when a rising edge arrives in the Out1A, the first D-type flip-flop DFF1 detects the level signal Out2 of the first comparison circuit input at the CK end, so that the self Q end outputs a level signal which is the same as that of Out 2. The level signal output by the Q end of the first D-type flip-flop DFF1 AND the Out1B are subjected to AND operation through an AND gate, meanwhile, when a rising edge arrives in the Out1B, the second D-type flip-flop DFF2 detects the level signal Out2 of the first comparison circuit input by the CK end, the Q end of the second D-type flip-flop DFF2 outputs the level signal which is the same as that of the Out2, AND then the level signal output by the AND gate AND the level signal output by the Q end of the second D-type flip-flop DFF2 are subjected to operation through a NOR gate INV to output the corresponding level signal.

Based on this, in the case where there is a short-circuited LED in the LED linear circuit: when the rising edge in the Out1A arrives, the Q end of the first D type flip-flop DFF1 outputs a high level signal; when the rising edge in Out1B arrives, the AND gate AND outputs a high signal, the Q terminal of the second D-type flip-flop DFF2 outputs a high signal, AND the NOR gate NOR1 outputs a low signal. In case there is no shorted LED in the LED linear circuit: when the rising edge in the Out1A arrives, the Q end of the first D-type flip-flop DFF1 outputs a low level signal, AND the AND gate AND outputs a low level signal; when the rising edge in Out1B arrives, the Q terminal of the second D-type flip-flop DFF2 outputs a low signal, and the NOR gate NOR1 outputs a high signal. The short detection circuit of the present application determines that there is a short LED in the LED linear circuit when the first NOR gate NOR1 outputs a low level and determines that there is no short LED in the LED linear circuit when the first NOR gate NOR1 outputs a high level.

As an alternative embodiment, the short circuit determination circuit 2 further includes:

the false trigger prevention circuit is connected with the output end of the short circuit detection circuit and used for detecting the level output by the first NOR gate NOR1 after the total voltage waveform input by the branch circuit where the LED is located passes through a preset cycle number from the start of the LED linear circuit, and judging that the LED with the short circuit exists in the LED linear circuit when the first NOR gate NOR1 outputs a low level and judging that the LED with the short circuit does not exist in the LED linear circuit when the first NOR gate NOR1 outputs a high level.

Further, the short circuit determination circuit 2 of the present application further includes a false triggering prevention circuit, and the working principle thereof is as follows;

in consideration of the fact that the LED linear circuit is prone to misjudgment of short-circuit LEDs due to unstable waveforms in the initial working stage, the short-circuit detection circuit is added with the false triggering prevention circuit, and the purpose is to enable the short-circuit detection circuit to default that short-circuit LEDs do not exist in the LED linear circuit in the initial working stage of the LED linear circuit and to give judgment right of the short-circuit LEDs to the false triggering prevention circuit. The false triggering prevention circuit starts when the LED linear circuit enters work, the level output by the first NOR gate NOR1 is detected after the total voltage waveform input by the branch where the LED is located passes through the preset cycle number (namely, the judgment of the short-circuit LED is carried out at the moment), then according to the judgment principle, the LED with the short circuit exists in the LED linear circuit is judged when the first NOR gate NOR1 outputs low level, and the LED without the short circuit exists in the LED linear circuit is judged when the first NOR gate NOR1 outputs high level, so that the false judgment of the short-circuit LED at the initial working stage of the LED linear circuit is prevented, and the false triggering of the subsequent short-circuit protection is prevented.

As an alternative embodiment, the false trigger prevention circuit comprises a counter CT and a second NOR gate NOR 2; wherein:

the counting end of the counter CT is connected with the output end of the second comparison circuit, the output end of the counter CT is connected with the first input end of the second NOR gate NOR2, the second input end of the second NOR gate NOR2 is connected with the output end of the first NOR gate NOR1, and the output end of the second NOR gate NOR2 is used as the output end of the false trigger prevention circuit; wherein, the counter CT is used for outputting a high level by default; accumulating the number of rising edge signals or falling edge signals output by the second comparison circuit from the beginning of the work of the LED linear circuit, and converting from high level to low level to output when the number reaches a preset number threshold;

the false triggering prevention circuit is specifically used for judging that a short-circuited LED exists in the LED linear circuit when the second NOR gate NOR2 outputs a high level; when the second NOR gate NOR2 outputs a low level, it is determined that there is no short-circuited LED in the LED linear circuit.

Specifically, the false trigger prevention circuit of the present application includes a counter CT and a second NOR gate NOR2, and its operation principle is:

as the first NOR gate NOR1 outputs a low level when there is a short-circuited LED in the LED linear circuit and the first NOR gate NOR1 outputs a high level when there is no short-circuited LED in the LED linear circuit, it is known from the operating principle of the second NOR gate NOR2 that: when the first NOR gate NOR1 outputs a high level, the second NOR gate NOR2 outputs a low level regardless of whether the counter CT outputs a high level or a low level; when the first NOR gate NOR1 outputs a low level, the output level of the second NOR gate NOR2 is high or low depending on the output level of the counter CT (the counter CT outputs a high level, the second NOR gate NOR2 outputs a low level; the counter CT outputs a low level, and the second NOR gate NOR2 outputs a high level), so that the counter CT should output a low level if the output of the first NOR gate NOR1 is active when there is a short-circuited LED in the LED linear circuit.

Since the false triggering prevention circuit is intended to disable the output of the first NOR gate NOR1 when a short-circuited LED is present in the LED linear circuit at the initial stage of operation of the LED linear circuit, the counter CT of the present invention outputs a high level by default after the LED linear circuit starts to operate, indicating that no short-circuited LED is present in the LED linear circuit by default at the initial stage of operation of the LED linear circuit. Then, the counter CT counts the number of rising edge signals or falling edge signals (adjacent rising edges or adjacent falling edges are separated by one working period) output by the second comparing circuit from the LED linear circuit, and when the number of rising edge signals or falling edge signals reaches a preset number threshold, the counter CT will change from high level to low level to output, so that the output of the first NOR gate NOR1 is valid when there is a short-circuited LED in the LED linear circuit, that is, the normal short-circuit determination operation is performed.

As an optional embodiment, the short-circuit protection circuit 3 is specifically configured to, when the short-circuit determination circuit 2 determines that there is a short-circuited LED in the LED linear circuit, control the LED linear circuit to work for only M duty cycles in every N duty cycles, so as to perform LED short-circuit protection on the LED linear circuit; wherein M is more than or equal to 1 and less than N, and M, N are integers.

Specifically, the manner of protecting the LED linear circuit by the short-circuit protection circuit 3 of the present application may be: when short-circuited LEDs exist in the LED linear circuit, the LED linear circuit is controlled to work for M work periods (M < N) in every N work periods, for example, the LED linear circuit works for 1 work period in every 5 work periods, and therefore the LED linear circuit is protected.

As an alternative embodiment, the short-circuit protection circuit 3 includes a third NOR gate NOR3 and a fourth NOR gate NOR 4; wherein:

a first input terminal of the third NOR gate NOR3 is connected to the output terminal of the short-circuit determination circuit 2, a second input terminal of the third NOR gate NOR3 is connected to the output terminal of the fourth NOR gate NOR4, an output terminal of the third NOR gate NOR3 is connected to a first input terminal of the fourth NOR gate NOR4, and a second input terminal of the fourth NOR gate NOR4 is connected to the signal setting device; wherein the signal setter is configured to default that the output of the fourth NOR gate NOR4 is inactive; controlling the output of the fourth NOR gate NOR4 to function for N-M duty cycles within each N duty cycles of the LED linear circuit, starting from the short determination circuit 2 determining that there is a short LED in the LED linear circuit;

the LED linear circuit is specifically configured to operate normally when the output of the fourth NOR gate NOR4 is inactive; the operation is stopped when the output of the fourth NOR gate NOR4 is active.

Specifically, the short-circuit protection circuit 3 of the present application includes a third NOR gate NOR3 and a fourth NOR gate NOR4, and its operation principle is:

based on the connection between the third NOR gate NOR3 and the fourth NOR gate NOR4, the high/low of the level signal Reset output by the signal setting device determines the high/low of the level signal Pro output by the fourth NOR gate NOR4 (the high/low of the two output level signals are opposite), the high/low of the level signal Pro output by the fourth NOR gate NOR4 determines whether the LED linear circuit is working (the application does not limit the one-to-one correspondence between the high/low of the level signal Pro and the working of the LED linear circuit, it is considered that the output of the fourth NOR gate NOR4 is working (corresponding to the high level or the low level), the LED linear circuit is not working, the output of the fourth NOR gate NOR4 is not working (corresponding to the low level or the high level), the LED linear circuit is working normally, so the signal setting device of the application defaults to the output of the fourth NOR gate NOR4 after the LED linear circuit starts working, so that the LED linear circuit can work normally. Then, the signal setter controls the output of the fourth NOR gate NOR4 to operate, starting from the LED with the short circuit in the LED linear circuit, for N-M duty cycles in every N duty cycles of the LED linear circuit, so that the LED linear circuit operates for only M duty cycles in every N duty cycles.

As an alternative embodiment, the first comparison circuit and the second comparison circuit are both comparators, wherein:

the positive input end of the comparator is used as the first ends of the first comparison circuit and the second comparison circuit, the negative input end of the comparator is used as the second ends of the first comparison circuit and the second comparison circuit, and the output end of the comparator is used as the output ends of the first comparison circuit and the second comparison circuit.

Specifically, the first comparison circuit and the second comparison circuit of the present application may both use comparators (the first comparison circuit uses the first comparator D1, and the second comparison circuit uses the second comparator D2), and the first voltage threshold Vref1 accessed by the first comparator D1 and the second voltage threshold Vref2 accessed by the second comparator D2 may both be obtained by dividing voltages of a dc power supply.

Referring to fig. 4, fig. 4 is an application schematic diagram of an LED short-circuit protection circuit according to an embodiment of the present invention. Fig. 4 is a schematic diagram of the LED short-circuit protection circuit of the present application applied to the LED linear circuit of fig. 1, and the following explains the operation principle of the embodiment of fig. 4:

referring to fig. 5, fig. 5 is a waveform diagram of an LED short-circuit protection circuit in normal operation of an LED linear circuit according to an embodiment of the present invention. The line voltage division Vvoltage obtains an inverted signal Out1B of output signals Out1A and Out1A through a second comparator D2; the detection voltage Vcs passes through the first comparator D1 to obtain the output signal Out 2. If the rising edge of Out1A or the rising edge of Out1B respectively detects that the level corresponding to Out2 is low, Pro does not function and is low.

Referring to fig. 6, fig. 6 is a waveform chart of an LED short-circuit protection circuit when an LED short circuit occurs in an LED linear circuit according to an embodiment of the present invention. Pro is active and high when both the rising edge of Out1A and the rising edge of Out1B detect that the level corresponding to Out2 is high (detection may be performed on either the rising edge of Out1A or the rising edge of Out 1B).

Referring to fig. 7, fig. 7 is a waveform diagram illustrating the short-circuit protection triggered when the voltage Vdivide drops when the LED short circuit occurs in the first LED linear circuit according to an embodiment of the present invention. When the 1 st rising edge of the Out1A detects that the level corresponding to the Out2 is high level, the output DFF1_ Out is high level; when the 2 nd rising edge of Out1A detects that the level corresponding to Out2 is low, DFF1_ Out goes from high to low. AND processing is carried Out on the DFF1_ Out AND the Out1B to obtain an AND _ Out signal, Pro is triggered to be at a high level by the high level of the AND _ Out, AND the purpose is to trigger Pro to be at the high level when the Vdevide drops.

Referring to fig. 8, fig. 8 is a waveform diagram illustrating the short-circuit protection triggered when the voltage Vdivide drops when the LED short circuit occurs in the second LED linear circuit according to an embodiment of the present invention. When the 1 st rising edge of the Out1B detects that the level corresponding to the Out2 is high level, the output DFF2_ Out is high level; when the 2 nd rising edge of Out1B detects that the level corresponding to Out2 is low, DFF2_ Out goes from high to low. DFF2_ Out high triggers Pro high.

Referring to fig. 9, fig. 9 is a graph illustrating Pro waveforms when an LED short circuit occurs in an LED linear circuit according to an embodiment of the present invention. If the rising edge of Out1A or the rising edge of Out1B detects that the level corresponding to Out2 is high, Pro is high, and every N-1 cycles can be set as high and 1 cycle as low.

Referring to fig. 10, fig. 10 is a waveform chart illustrating the prevention of the LED short-circuit protection from entering into the LED linear circuit when the LED linear circuit is normally operated and started according to an embodiment of the present invention. When the LED linear circuit works normally and starts, the output signal Counter _ Out of the Counter CT in the first n periods is at a high level, so that the NOR1_ Out cannot act on Pro in the first n periods, and Pro is kept at a low level (n is a positive integer).

Referring to fig. 11, fig. 11 is a waveform chart of a switching tube Gate _ M1 when an LED short circuit occurs in an LED linear circuit according to an embodiment of the present invention. When the level corresponding to Out2 is detected to be high level by any rising edge of Out1A or Out1B, Pro is high level, the output Gate is low level through the Driver module, and the switching tube M1 is closed. The Gate goes low for N-1 consecutive periods, turning M1 off, followed by 1 period high, turning M1 on, and M1 cycles through this state.

The utility model also provides a light-emitting device, including the linear circuit of LED, still include any kind of LED short-circuit protection circuit of above-mentioned.

The utility model provides a please refer to above-mentioned LED short-circuit protection circuit's embodiment for the introduction of illuminator, the utility model discloses no longer describe here.

It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An LED short-circuit protection circuit, comprising:

2. The LED short protection circuit of claim 1, wherein the voltage detection circuit comprises a first comparison circuit, wherein:

3. The LED short protection circuit of claim 2, wherein the short determination circuit comprises:

4. The LED short protection circuit of claim 3, wherein the short detection circuit comprises a NOT gate, a first D-type flip-flop, a second D-type flip-flop, an AND gate, and a first NOR gate; wherein:

5. The LED short protection circuit of claim 4, wherein the short determination circuit further comprises:

6. The LED short protection circuit of claim 5, wherein the false trigger prevention circuit comprises a counter and a second NOR gate; wherein:

7. The LED short-circuit protection circuit according to any one of claims 4 or 6, further comprising:

the short-circuit protection circuit is specifically configured to control the LED linear circuit to work for M duty cycles in every N duty cycles when the short-circuit determination circuit determines that there is a short-circuited LED in the LED linear circuit, so as to perform LED short-circuit protection on the LED linear circuit; wherein M is more than or equal to 1 and less than N, and M, N are integers.

8. The LED short protection circuit of claim 7, wherein the short protection circuit comprises a third NOR gate and a fourth NOR gate; wherein:

9. The LED short protection circuit of claim 7, wherein said first and second comparison circuits are comparators, wherein:

10. A light emitting device comprising an LED linear circuit, and further comprising an LED short circuit protection circuit as claimed in any one of claims 1 to 9.