CN203259615U - System detecting LED short circuits in LED strings or matching performance between LED strings - Google Patents
System detecting LED short circuits in LED strings or matching performance between LED strings Download PDFInfo
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- CN203259615U CN203259615U CN 201320122651 CN201320122651U CN203259615U CN 203259615 U CN203259615 U CN 203259615U CN 201320122651 CN201320122651 CN 201320122651 CN 201320122651 U CN201320122651 U CN 201320122651U CN 203259615 U CN203259615 U CN 203259615U
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Abstract
The utility model discloses a system detecting LED short circuits in a plurality of LED strings or detecting the matching performance between the LED strings. Each LED string has one end connected to the same power supply output end and the other end respectively connected to a corresponding switch. Firstly, first current acquisition units acquire a first current of each LED string when the power supply output end outputs a first voltage. Then, a calculation unit calculates the difference between the minimum current among the first currents of the LED strings and each of other currents. A comparison unit then compares each difference value with a comparison threshold value. Lastly, a determining unit determines that the LED strings corresponding to those other currents with a difference larger than the threshold value suffer LED short circuits or do not match the LED string corresponding to the minimum current. By means of the system, the number and the area of control chip base pins can be reduced.
Description
Technical field
Embodiment of the present utility model relates to LED and drives the field, is specifically related to the system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings.
Background technology
Light emitting diode (Light Emitting Diode, referred to as LED) be widely adopted in multiple environment, such as architectural lighting, vehicle head taillight, comprise the backlight and flashlamp etc. of the liquid crystal display of personal computer and HDTV.Compare with the conventional light source such as incandescent lamp and fluorescent light and so on, LED has the efficient height, directivity is good, color stability is good, reliability is high, the life-span is long, the remarkable advantage such as little and Environmental security of volume.
Usually, a plurality of LED are conspired to create a LED string, and in a lot of environment, for example in the backlight and flashlamp of the liquid crystal display that comprises personal computer and HDTV, use in parallel a plurality of LED strings.
In the use procedure of LED, the corresponding LED in each LED string may short circuit.
Therefore, can detect in time, correctly, easily the short circuit of LED in the LED string, thirst for very much.
Fig. 1 is the synoptic diagram according to the detection LED short circuit of prior art.For simplicity, only show a LED string 101.In the prior art, direct-detection is compared it as the voltage in the drain electrode of the MOSFET of the conducting of control LED string 101 or the switch 102 of closing with a compare threshold.If it is high that the voltage ratio compare threshold in the drain electrode is wanted, in the expression LED string 101 the LED short circuit is arranged; If the voltage ratio compare threshold in the drain electrode is low, there is not the LED short circuit in the expression LED string 101.
Yet the MOSFET drain electrode is a high pressure pin, and sometimes its voltage will arrive 100V.Therefore, integrated unit for detection of LED short circuit in the LED string in control chip 103 can significantly enlarge chip area.In addition, owing to there is a plurality of LED string, and need to carry out the whether detection of short circuit of its LED to each LED string, therefore by detecting the voltage in the MOSFET drain electrode, whether go here and there in have LED short circuit, can increase the number of the pin of control chip 103 if detecting corresponding LED.
In addition, because the difference on making between the LED, therefore for identical electric current, the voltage drop between the LED string also has sizable difference.In other words, for identical power supply output, the electric current between the LED string may have sizable difference.This is for the detection whether the LED short circuit is arranged in the LED string, can produce wrong result, therefore be preferably in the LED string for before the specific environment, each LED string is carried out matching detects, with coupling each other namely each other the difference of voltage drop be used for same specific environment less than the LED string of a compare threshold.
The utility model content
This instructions aims to provide a kind of method and system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings, can solve the problem that exists in the aforesaid correlation technique.
According to one side of the present utility model, a kind of system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings has been proposed, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, described system comprises: a plurality of the first electric currents obtain the unit, be used for obtaining when power output end is exported the first voltage the first electric current of each LED string; Computing unit be used for to calculate the difference between each of the first electric current minimum current of each LED string and other electric currents; Comparing unit is used for described difference and a compare threshold are compared; And determining unit, be used for that difference is defined as the LED short circuit greater than the corresponding LED string of those other electric currents of described compare threshold or the LED string corresponding with minimum current do not mate.
According to another aspect of the present utility model, a kind of system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings has been proposed, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, described system comprises: a plurality of the first electric currents obtain the unit, be used for obtaining when power output end is exported the first voltage the first electric current of each LED string; Change the unit, be used for changing the second voltage that outputs to of described power output end; A plurality of the second electric currents obtain the unit, are used for obtaining when power output end output second voltage the second electric current of each LED string; Whether whether determining unit is used for the first electric current and the second electric current according to each LED string that obtains, determine to have in each LED string LED short circuit or each LED string to mate.
According to another aspect of the present utility model, a kind of system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings has been proposed, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, described system comprises: a plurality of the first voltages obtain the unit, be used for obtaining when each LED string all is in identical electric current the first voltage of the control end of respective switch; Computing unit be used for to calculate the difference between each of the first voltage maximum voltage of control end of respective switch and other voltages; Comparing unit is used for described difference and a compare threshold are compared; And determining unit, be used for that difference is defined as the LED short circuit greater than the corresponding LED string of those other voltages of described compare threshold or the LED string corresponding with maximum voltage do not mate.
According to another aspect of the present utility model, a kind of system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings has been proposed, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, described system comprises: a plurality of the first voltages obtain the unit, be used for to obtain all to be in identical electric current at each LED string, and power output end is when exporting the first voltage the first voltage of the control end of respective switch; Change the unit, be used for changing the second voltage that outputs to of described power output end; A plurality of second voltages obtain the unit, are used for obtaining when described power output end output second voltage the second voltage of the control end of respective switch; And determining unit, be used for the first voltage and second voltage according to the control end of the respective switch that obtains, determine whether to have in each LED string LED short circuit or each LED string whether to mate.
According to the utility model, can reduce number and the area of control chip pin, generally show as voltage on high-tension that switch terminal because no longer detect it, wherein this switch terminal does not need to be connected to control chip if not in order to detect the LED string whether the LED short circuit being arranged.
Description of drawings
Accompanying drawing described herein is used to provide further understanding of the present utility model, consists of the application's a part, and illustrative examples of the present utility model and explanation thereof are used for explaining the utility model, do not consist of improper restriction of the present utility model.In the accompanying drawings:
Fig. 1 is the synoptic diagram according to the detection LED short circuit of prior art;
Fig. 2 is the exemplary environments that the utility model can be implemented therein;
Fig. 3 shows the LED short circuit of going here and there according to a plurality of LED of the detection of an embodiment of the present utility model or detects the block diagram of the system of the matching between a plurality of LED strings;
Fig. 4 shows the synoptic diagram that obtains the unit according to the first electric current of an embodiment of the present utility model;
Fig. 5 shows the LED short circuit of going here and there according to a plurality of LED of the detection of another embodiment of the present utility model or detects the block diagram of the system of the matching between a plurality of LED strings;
Fig. 6 show according to an embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings; And
Fig. 7 show according to another embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings;
Fig. 8 shows the LED short circuit of going here and there according to a plurality of LED of the detection of another embodiment of the present utility model or detects the block diagram of the system of the matching between a plurality of LED strings;
Fig. 9 shows the synoptic diagram according to the electric current setting unit of an embodiment of the present utility model;
Figure 10 shows the LED short circuit of going here and there according to a plurality of LED of the detection of another embodiment of the present utility model or detects the block diagram of the system of the matching between a plurality of LED strings;
Figure 11 show according to an embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings; And
Figure 12 show according to another embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings.
In all accompanying drawings, identical label represents same or analogous feature or function.
Embodiment
Need to prove that in the situation of not conflicting, embodiment and the feature among the embodiment among the application can make up mutually.Describe below with reference to the accompanying drawings and in conjunction with the embodiments the utility model in detail.
Fig. 2 is the exemplary environments that the utility model can be implemented therein.The below is described in greater detail.
This environment 200 comprises power supply 243, LED string 242-1,242-2 and 242-3, switch 241-1,241-2 and 241-3 and resistor R1, R2 and R3.
Certainly, those skilled in the art will appreciate that power supply 243 also can be BUCK transducer or BUCK-BOOST transducer.
The other end of LED string 242-1,242-2 and 242-3 is connected respectively to corresponding switch 241-1,241-2 and 241-3.Switch 241-1,241-2 and 241-3 can be MOSFET, also can be bipolar transistors.Here, be without loss of generality, suppose that switch 241-1,241-2 and 241-3 are MOSFET.
More specifically, the other end of LED string 242-1,242-2 and 242-3 is connected respectively to the drain electrode of switch 241-1,241-2 and 241-3.And the source electrode of switch 241-1,241-2 and 241-3 is respectively by resistor R1, R2 and R3 ground connection.
Can apply control signal (not illustrating among Fig. 2) by the grid at switch 241-1,241-2 and 241-3 respectively, come the conducting of gauge tap 241-1,241-2 and 241-3 and close, thus the conducting of control LED string 242-1,242-2 and 242-3 and closing.
In the following description, in order to simplify, suppose that each LED string 242-1,242-2 are identical with the number of LED among the 242-3.
It is pointed out that number that the utility model is not limited to LED string is 3 situation.The utility model also is applicable to the number of LED string greater than 3 or less than 3, such as 2 or 4,5,6 s' etc. situation.
Fig. 3 shows the block diagram according to the system of the matching between 3 LED strings shown in the LED short circuit of 3 LED strings shown in detection Fig. 2 of an embodiment of the present utility model or detection Fig. 2.
As described in Figure 3, this system 300 comprises that 3 the first electric currents obtain unit 301-1,301-2 and 301-3, is used for obtaining respectively when power supply 243 outputs the first voltage the first electric current of each LED string 242-1,242-2 and 242-3;
Computing unit 302 be used for to calculate the difference between each of the first electric current minimum current of each LED string 242-1,242-2 and 242-3 and other electric currents;
Comparing unit 303 is used for difference and a compare threshold are compared; And
Determining unit 304 is used for that difference is defined as the LED short circuit greater than the corresponding LED string of those other electric currents of described compare threshold or the LED string corresponding with minimum current do not mate.
Wherein, the size of described compare threshold is corresponding with the number of the LED of the short circuit that will detect or with match-on criterion is not corresponding.For example above-mentioned compare threshold can be set as for detection of 1 LED short circuit, 2 LED short circuits or 3 LED short circuits.If above-mentioned compare threshold is set as for detection of 3 LED short circuits, the situation with 1 or 2 LED short circuit is considered as not being short-circuited so.
For example, suppose that the first electric current of LED string 242-1 is 110 milliamperes, the first electric current of LED string 242-2 is 120 milliamperes, and the first electric current of LED string 242-3 is 130 milliamperes.
Can think the corresponding LED string of minimum current in the first electric current, namely LED string 242-1 is not short-circuited and as the benchmark that detects each LED string matching.In the situation of the general volt-ampere characteristic of knowing each LED, and know in the situation of LED number, electric power output voltage etc. of each LED string, described compare threshold can be set.For example, be without loss of generality, described compare threshold is 15 milliamperes.
Like this, because the difference between the first electric current of LED string 242-1 and LED string 242-2 is 10 milliamperes, less than 15 milliamperes of threshold values, therefore thinking does not have LED to be short-circuited among the LED string 242-2 and LED string 242-1 and LED go here and there 242-2 and mate.And the difference between the first electric current of LED string 242-1 and LED string 242-3 is 20 milliamperes, and greater than 15 milliamperes of threshold values, therefore thinking has LED to be short-circuited among the LED string 242-3 and LED string 242-1 and LED go here and there 242-3 and do not mate.
The first electric current obtains unit 301-1,301-2 and is under the identical or substantially the same bias voltage by the grid at corresponding MOSFET with 301-3, obtains the first electric current of each LED string.
According to an embodiment of the present utility model, in the process of the first electric current that obtains each LED string, this bias voltage immobilizes, and for example is in all the time 5V, under this bias value, and the complete conducting of corresponding MOSFET, and the resistance value between its drain electrode and the source electrode is very low.
In this embodiment, the first electric current acquisition unit 301-1,301-2 and 301-3 obtain the first electric current of each LED string by the voltage of the source electrode of the corresponding MOSFET of sampling.
In addition, according to an embodiment of the present utility model, in system 300, can also comprise analog to digital converter (not shown among Fig. 3), be used for the voltage of described sampling is carried out analog to digital conversion.
Because the voltage less (for example 0-1V) of this sampling for correct electric current is provided, can carry out analog to digital conversion to this sampled voltage, converts for example 8 bits to, to represent a value in the 0-255 milliampere.
According to an embodiment of the present utility model, in the process of the first electric current that obtains each LED string, described bias voltage controllably changes, wherein by the electric current of each LED string is set, described bias voltage changes, wherein the first electric current of each LED string be satisfy described be biased under the bias threshold or two bias threshold between maximum current in the electric current is set.
For simplicity, figure 4 illustrates for the process that realizes above-mentioned the first electric current obtaining each LED string, the first electric current that described bias voltage controllably changes obtains unit 301-1.
Obtain unit 301-2 and 301-3 about the first electric current, structure is similar.
Particularly, the first electric current obtains unit 301-1 and comprises the first operational amplifier 4122, and its reverse input end is connected with the grid of switch 241-1, and input end is connected with bias threshold (for example 4.5V) in the same way; The first electric current digital to analog converter 4123, it is controlled by the output of the first operational amplifier 4122; And second operational amplifier 4124, its in the same way input end be connected with the output terminal of the first digital to analog converter 4123, reverse input end is connected with the source electrode of switch 241-1, output terminal is connected with the grid of switch 241-1.
At first, 4123 values of the first electric current digital to analog converter are set, wherein the electric current of LED string 242-1 is corresponding with the value of this first electric current digital to analog converter 4123, the output of the first electric current digital to analog converter 4123 is set, be equivalent to arrange the electric current of LED string 242-1, and judge under this value, whether the grid voltage of switch 241-1 (for example passes through the first operational amplifier 4122 greater than bias threshold, in the situation of grid voltage greater than bias threshold of switch 241-1,4122 outputs 0 of the first operational amplifier, in the situation of grid voltage less than bias threshold of switch 241-1,4122 outputs 1 of the first operational amplifier).If grid voltage is not greater than bias threshold, increase so the value of the first electric current digital to analog converter 4123 outputs (because increase the value of the first electric current digital to analog converter 4123 outputs, the grid voltage of switch 241-1 is increased), judge that again under new value, whether the grid voltage of switch 241-1 is greater than bias threshold.Carry out said process, until the grid voltage of switch 241-1 equals or is substantially equal to bias threshold always.Get the first electric current that the maximum current in the electric current is gone here and there for each LED that arranges that is biased under the bias threshold.
In addition, although do not illustrate among Fig. 4, but it will be appreciated by those skilled in the art that, the first electric current obtains unit 301-1 can also comprise the another one operational amplifier, the grid of an one input end connecting valve 241-1, and another input end connects another bias threshold, for example the bias threshold than above-mentioned is a little little, for example 4V, and its output terminal controls described the first electric current digital to analog converter 4123, is used for arranging the output of the first electric current digital to analog converter 4123.In such embodiment, the first electric current of each LED string is that the grid bias that satisfies switch arranges maximum current in the electric current between two bias threshold.
Need to prove; above-mentioned embodiment has only exemplarily been described a kind of embodiment that can obtain by the electric current of LED string 242-1; in the practical application, can realize that other embodiment of this function or effect all should be included protection domain of the present utility model in.
In the situation that compare threshold can not be set, for example owing to do not know the general volt-ampere characteristic of each LED, just can not adopt above-mentioned system described in conjunction with Figure 3 300 to detect the LED short circuit of a plurality of LED strings or detect the matching of a plurality of LED between going here and there.
Fig. 5 shows the block diagram according to the system of the matching between 3 LED strings shown in the LED short circuit of 3 LED strings shown in detection Fig. 2 of an embodiment of the present utility model or detection Fig. 2.This system 500 can solve said system 300 indeterminable problems.
As described in Figure 5, described system 500 comprises: 3 the first electric currents obtain unit 501-1,501-2 and 501-3, are used for obtaining when power supply 243 output terminals are exported the first voltage the first electric current of each LED string 242-1,242-2 and 242-3; Change unit 502, be used for changing the second voltage that outputs to of described power supply 243 output terminals; 3 the second electric currents obtain unit 503-1,503-2 and 503-3, are used for obtaining when power supply 243 output terminals output second voltage the second electric current of each LED string 242-1,242-2 and 242-3; Whether whether determining unit 504 is used for according to each LED string 242-1, the 242-2 that obtains and the first electric current and the second electric current of 242-3, determine to have among each LED string 242-1,242-2 and the 242-3 LED short circuit or each LED string to mate.
The first electric current obtains unit 501-1,501-2 can be identical with 503-3 with the acquisition of the second electric current unit 503-1,503-2 with 501-3, and identical with 301-3 with the foregoing acquisition of the first electric current unit 301-1,301-2.
In addition, it is pointed out that as previously mentioned that obtaining the first electric current has dual mode, therefore, preferably, it is corresponding with the employed mode of acquisition the first electric current to obtain the employed mode of the second electric current.
Described second voltage can be higher than described the first voltage, also can be lower than described the first voltage, and the difference between second voltage and the first voltage can be with relevant such as number of the LED that will detect short circuit etc.Be higher than at described second voltage in the situation of described the first voltage, determining unit 504 will have than the minimum current in the second electric current of each LED string also the LED string of the first large electric current be defined as the LED short circuit or do not mated.
For example, suppose that at the first voltage be in the situation of 60V, the first electric current of LED string 242-1 is 100 milliamperes, the first electric current of LED string 242-2 is 120 milliamperes, the first electric current of LED string 242-3 is 150 milliamperes, is in the situation of 66V at second voltage, and the second electric current of LED string 242-1 is 130 milliamperes, the second electric current of LED string 242-2 is 160 milliamperes, and the second electric current of LED string 242-3 is 200 milliamperes.So definite LED string 242-3 has the LED short circuit or does not mate with LED string 242-1 and 242-2, because its electric current under the first less voltage, all also large than the electric current of LED string 242-1 under larger second voltage, if there is not LED to be short-circuited, this situation is substantially impossible.
Similarly, be lower than at described second voltage in the situation of described the first voltage, determining unit 504 will have than the minimum current in the first electric current of each LED string also the LED string of the second large electric current be defined as the LED short circuit or do not mated.
For example, suppose that at the first voltage be in the situation of 60V, the first electric current of LED string 242-1 is 100 milliamperes, the first electric current of LED string 242-2 is 120 milliamperes, the first electric current of LED string 242-3 is 150 milliamperes, is in the situation of 54V at second voltage, and the second electric current of LED string 242-1 is 75 milliamperes, the second electric current of LED string 242-2 is 90 milliamperes, and the second electric current of LED string 242-3 is 110 milliamperes.So definite LED string 242-3 has the LED short circuit or does not mate with LED string 242-1 and 242-2, because its electric current under less second voltage, all also large than the electric current of LED string 242-1 under the first larger voltage, if there is not LED to be short-circuited, this situation is substantially impossible.
Said system 300 and 500 can be to realize with hardware (for example control chip) mode, also can realize with software (for example computer program code) mode, even also can realize with the mode that software and hardware combines.
Fig. 6 show according to an embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, and the other end is connected respectively to corresponding switch.
As shown in Figure 6, method 600 comprises step S610, is used for obtaining when power output end is exported the first voltage the first electric current of each LED string; Step S620 be used for to calculate the difference between each of the first electric current minimum current of each LED string and other electric currents; Step S630 is used for described difference and a compare threshold are compared; And step S640, be used for that difference is defined as the LED short circuit greater than the corresponding LED string of those other electric currents of described compare threshold or the LED string corresponding with minimum current do not mate.
Fig. 7 show according to another embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, and the other end is connected respectively to corresponding switch.
As shown in Figure 7, method 700 comprises step S710, is used for obtaining when power output end is exported the first voltage the first electric current of each LED string; Step S720 is for the second voltage that outputs to that changes described power output end; Step S730 is used for obtaining when power output end output second voltage the second electric current of each LED string; And step S740, be used for the first electric current and the second electric current according to each LED string that obtains, determine whether to have in each LED string LED short circuit or each LED string whether to mate.
For simplicity, in the method described in above-mentioned Fig. 6 and Fig. 7, suppose that the number of LED in each LED string is identical.
According to an embodiment of the present utility model, in the method described in above-mentioned Fig. 6 and Fig. 7, respective switch is the MOSFET/ bipolar transistor, and the described other end is connected respectively to the collector of drain electrode/bipolar transistor of corresponding MOSFET.
According to an embodiment of the present utility model, in the method described in above-mentioned Fig. 6 and Fig. 7, be under the identical bias voltage by the base stage at grid/bipolar transistor of corresponding MOSFET, obtain the first electric current and second electric current of each LED string.
According to an embodiment of the present utility model, in the method described in above-mentioned Fig. 6 and Fig. 7, in the process of the first electric current that obtains each LED string and the second electric current, described bias voltage remains unchanged, the voltage of the emitter of the source electrode/bipolar transistor by the corresponding MOSFET that samples obtains the first electric current and second electric current of each LED string.
According to an embodiment of the present utility model, in the method described in above-mentioned Fig. 6 and Fig. 7, comprise that also step carries out the analog to digital conversion (not shown) to the voltage of described sampling.
According to an embodiment of the present utility model, in the method described in above-mentioned Fig. 6 and Fig. 7 in the process of the first electric current that obtains each LED string and the second electric current, described bias voltage controllably changes, wherein by the electric current of each LED string is set, described bias voltage changes, wherein the first electric current of each LED string and the second electric current be satisfy described be biased under the bias threshold or two bias threshold between maximum current in the electric current is set.
According to an embodiment of the present utility model, in the method described in above-mentioned Fig. 7,
Described second voltage can be higher than described the first voltage, also can be lower than described the first voltage, be higher than at described second voltage in the situation of described the first voltage, to have than the minimum current in the second electric current of each LED string also the LED string of the first large electric current be defined as the LED short circuit or do not mated, be lower than at described second voltage in the situation of described the first voltage, will have than the minimum current in the first electric current of each LED string also the LED string of the second large electric current be defined as the LED short circuit or do not mated.
According to an embodiment of the present utility model, in the method described in above-mentioned Fig. 6, the size of described compare threshold is corresponding with the number of the LED of the short circuit that will detect or with match-on criterion is not corresponding.
Describe in the above in all embodiments, grid bias by making each switch is identical, by measuring the electric current (the first electric current or the first and second electric currents) of each LED string, determine whether the LED of each LED string has short circuit or each LED string whether to mate.
In embodiment described below, electric current by making each LED string is identical, the voltage (the first voltage or the first and second voltages) of the corresponding MOSFET grid by measuring each LED string, whether whether the LED that determines each LED string has short circuit or each LED to go here and there mates.
Fig. 8 shows the block diagram according to the system of the matching between 3 LED strings shown in the LED short circuit of 3 LED strings shown in detection Fig. 2 of an embodiment of the present utility model or detection Fig. 2.
As shown in Figure 8, this system 800 comprises that three the first voltages obtain unit 801-1,801-2,801-3, be used for obtaining at each LED string 242-1,242-2, when 242-3 is in identical electric current the first voltage of the control end of respective switch 241-1,241-2,241-3;
Computing unit 802 be used for to calculate the difference between each of the first voltage maximum voltage of control end of respective switch 241-1,241-2,241-3 and other voltages;
Comparing unit 803 is used for described difference and a compare threshold are compared; And
Determining unit 804 is used for that difference is defined as the LED short circuit greater than the corresponding LED string of those other voltages of described compare threshold or the LED string corresponding with maximum voltage do not mate.
Wherein, the size of described compare threshold is corresponding with the number of the LED of the short circuit that will detect or with match-on criterion is not corresponding.For example above-mentioned compare threshold can be set as for detection of 1 LED short circuit, 2 LED short circuits or 3 LED short circuits.If above-mentioned compare threshold is set as for detection of 3 LED short circuits, the situation with 1 or 2 LED short circuit is considered as not being short-circuited so.
For example, suppose that the first voltage of grid of the MOSFET241-1 of LED string 242-1 is 4.4V, the first voltage of the grid of the MOSFET241-2 of LED string 242-2 is 4.2V, and the first voltage of the grid of the MOSFET241-3 of LED string 242-3 is 4.0V.
Can think the corresponding LED string of maximum voltage in grid the first voltage, namely LED string 242-1 is not short-circuited and as the benchmark that detects each LED string matching.In the situation of the general volt-ampere characteristic of knowing each LED, and know in the situation of LED number, electric power output voltage etc. of each LED string, described compare threshold can be set.For example, be without loss of generality, described compare threshold is 0.3V.
Like this, because the difference between MOSFET grid the first voltage of LED string 242-1 and LED string 242-2 is 0.2V, less than threshold value 0.3V, therefore thinking does not have LED to be short-circuited among the LED string 242-2 and LED string 242-1 and LED go here and there 242-2 and mate.And the difference between MOSFET grid the first voltage of LED string 242-1 and LED string 242-3 is 0.4V, and greater than threshold value 0.3V, therefore thinking has LED to be short-circuited among the LED string 242-3 and LED string 242-1 and LED go here and there 242-3 and do not mate.
The first voltage obtains unit 801-1,801-2 and 801-3 can by the voltage (for example utilizing analog to digital converter) on the grid of sampling MOSFET241-1,241-2,241-3, obtain corresponding the first voltage.
In addition, make each LED string 242-1,242-2,242-3 all be in the first identical electric current and can realize by electric current setting unit shown in Figure 9.
This electric current setting unit 900 obtains unit 301-1 with the first electric current shown in Figure 4 and compares, and difference is to have removed the first operational amplifier 4122 and relative line.
In the situation that compare threshold can not be set, for example owing to do not know the general volt-ampere characteristic of each LED, just can not adopt above-mentioned system described in conjunction with Figure 8 800 to detect the LED short circuit of a plurality of LED strings or detect the matching of a plurality of LED between going here and there.
Figure 10 shows the block diagram according to the system of the matching between 3 LED strings shown in the LED short circuit of 3 LED strings shown in detection Fig. 2 of an embodiment of the present utility model or detection Fig. 2.This system 1000 can solve said system 800 indeterminable problems.
As described in Figure 10, described system 1000 comprises: 3 the first voltages obtain unit 1001-1,1001-2,1001-3, be used for obtaining all being in identical electric current at each LED string, and when power supply 243 output terminals are exported the first voltage, the first voltage of the grid of corresponding MOSFET241-1,241-2,241-3;
Change unit 1002, be used for changing the second voltage that outputs to of power output end;
3 second voltages obtain unit 1003-1,1003-2,1003-3, are used for obtaining when power supply 243 output terminals output second voltage the second voltage of the grid of corresponding MOSFET241-1,241-2,241-3; And
Whether whether determining unit 1004 is used for the first voltage and second voltage according to the grid of the corresponding MOSFET241-1, the 241-2 that obtain, 241-3, determine to have in each LED string LED short circuit or each LED string to mate.
The first voltage obtains that unit 1001-1,1001-2 and 1001-3 can to obtain unit 1003-1,1003-2 identical with 1003-3 with second voltage, and to obtain unit 801-1,801-2 identical with 801-3 with foregoing the first voltage.
The second voltage of described power supply 243 output terminals output can be higher than the first voltage of described power supply 243 output terminals output, also can be lower than the first voltage of described power supply 243 output terminals output, difference between the first voltage that the second voltage of power supply 243 output terminals output and power supply 243 output terminals are exported can be with relevant such as the number of the LED that will detect short circuit etc.Be lower than at the second voltage of described power supply 243 output terminals output in the situation of the first voltage of described power supply 243 output terminals output, the LED string that determining unit 1004 has a second voltage less than the maximum voltage in the first voltage of the control end of respective switch with its switch control end has been defined as the LED short circuit or has not mated.
For example, suppose that the first voltage in the output of power supply 243 output terminals is in the situation of 66V, the first voltage of the MOSFET241-1 grid of LED string 242-1 is 4.5V, the first voltage of the MOSFET241-2 grid of LED string 242-2 is 4.3V, the first voltage of the MOSFET241-3 grid of LED string 242-3 is 4.1V, and the second voltage of exporting at power supply 243 output terminals is in the situation of 60V, the second voltage of the MOSFET241-1 grid of LED string 242-1 is 4.8V, the second voltage of the MOSFET241-2 grid of LED string 242-2 is 4.6V, and the second voltage of the MOSFET241-3 grid of LED string 242-3 is 4.4V.So definite LED string 242-3 has the LED short circuit or does not mate with LED string 242-1 and 242-2, because the voltage of the grid of its MOSFET under the second voltage of less power supply 243 output terminals output, all the voltage of grid under the first voltage of larger power supply 243 output terminals output than the MOSFET of LED string 242-1 is also little, if there is not LED to be short-circuited, this situation is substantially impossible.
Similarly, be higher than at the second voltage of described power supply 243 output terminals output in the situation of the first voltage of described power supply 243 output terminals output, the LED string that determining unit 1004 has first voltage also less than the maximum voltage in the second voltage of respective switch with the control end of its switch has been defined as the LED short circuit or has not mated.
For example, suppose that the first voltage in the output of power supply 243 output terminals is in the situation of 66V, the first voltage of the MOSFET241-1 grid of LED string 242-1 is 4.8V, the first voltage of the MOSFET241-2 grid of LED string 242-2 is 4.6V, the first voltage of the MOSFET241-3 grid of LED string 242-3 is 4.4V, second voltage in the output of power supply 243 output terminals is in the situation of 72V, the second voltage of the MOSFET241-1 grid of LED string 242-1 is 4.5V, the second voltage of the MOSFET241-2 grid of LED string 242-2 is 4.3V, and the second voltage of the MOSFET241-3 grid of LED string 242-3 is 4.1V.So definite LED string 242-3 has the LED short circuit or does not mate with LED string 242-1 and 242-2, because the voltage of the control end of its switch under the first voltage of less power supply 243 output terminals output, all the voltage of control end under the second voltage of larger power supply 243 output terminals output than the switch of LED string 242-1 is also little, if there is not LED to be short-circuited, this situation is substantially impossible.
Said system 800 and 1000 can be to realize with hardware (for example control chip) mode, also can realize with software (for example computer program code) mode, even also can realize with the mode that software and hardware combines.
Figure 11 show according to an embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, and the other end is connected respectively to corresponding switch.
As shown in figure 11, described method 1100 comprises step S1110, obtains when each LED string all is in identical electric current the first voltage of the control end of respective switch; Step S1120 calculates the difference between each of maximum voltage and other voltages in first voltage of control end of respective switch; Step S1130 compares described difference and a compare threshold; And step 1140, difference is defined as the LED short circuit greater than the corresponding LED of those other voltages of described compare threshold string or the LED string corresponding with maximum voltage do not mate.
Figure 12 show according to another embodiment of the present utility model for detection of the LED short circuit of a plurality of LED string or detect the process flow diagram of the method for the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, and the other end is connected respectively to corresponding switch.
As shown in figure 12, described method 1200 comprises: step S1210, obtain to be in identical electric current at each LED string, and power output end is when exporting the first voltage the first voltage of the control end of respective switch; Step S1220 changes the second voltage that outputs to of described power output end; Step S1230 obtains when power output end output second voltage, the second voltage of the control end of respective switch; And step S1240, according to the first voltage and the second voltage of the control end of the respective switch that obtains, determine whether to have in each LED string LED short circuit or each LED string whether to mate.
For simplicity, in the method described in above-mentioned Figure 11 and Figure 12, suppose that the number of LED in each LED string is identical.
According to an embodiment of the present utility model, in the method described in above-mentioned Figure 11 and Figure 12, respective switch is the MOSFET/ bipolar transistor, the described other end is connected respectively to the collector of drain electrode/bipolar transistor of corresponding MOSFET, and described control end is the base stage of grid/bipolar transistor of MOSFET.
According to an embodiment of the present utility model, in the described method of above-mentioned Figure 12, the second voltage of described power output end output can be higher than the first voltage of described power output end output, also can be lower than the first voltage of described power output end output, be lower than at the second voltage of described power output end output in the situation of the first voltage of described power output end output, the LED string that the control end of its switch is had a second voltage less than the maximum voltage in the first voltage of the control end of respective switch has been defined as the LED short circuit or has not mated, be higher than at the second voltage of described power output end output in the situation of the first voltage of described power output end output, the LED string that the control end of its switch is had first voltage also less than the maximum voltage in the second voltage of respective switch has been defined as the LED short circuit or has not mated.
According to an embodiment of the present utility model, in the described method of above-mentioned Figure 11, the size of described compare threshold is corresponding with the number of the LED of the short circuit that will detect or with match-on criterion is not corresponding.
The above is preferred embodiment of the present utility model only, is not limited to the utility model, and for a person skilled in the art, the utility model can have various modifications and variations.All within spirit of the present utility model and principle, any modification of doing, be equal to replacement, improvement etc., all should be included within the protection domain of the present utility model.
Claims (18)
1. system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, it is characterized in that, described system comprises:
A plurality of the first electric currents obtain the unit, are used for obtaining when power output end is exported the first voltage the first electric current of each LED string;
Computing unit be used for to calculate the difference between each of the first electric current minimum current of each LED string and other electric currents;
Comparing unit is used for described difference and a compare threshold are compared; And
Determining unit is used for that difference is defined as the LED short circuit greater than the corresponding LED string of those other electric currents of described compare threshold or the LED string corresponding with minimum current do not mate.
2. system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, it is characterized in that, described system comprises:
A plurality of the first electric currents obtain the unit, are used for obtaining when power output end is exported the first voltage the first electric current of each LED string;
Change the unit, be used for changing the second voltage that outputs to of described power output end;
A plurality of the second electric currents obtain the unit, are used for obtaining when power output end output second voltage the second electric current of each LED string;
Whether whether determining unit is used for the first electric current and the second electric current according to each LED string that obtains, determine to have in each LED string LED short circuit or each LED string to mate.
3. system according to claim 1 and 2 is characterized in that, respective switch is the MOSFET/ bipolar transistor, and the described other end is connected respectively to the collector of drain electrode/bipolar transistor of corresponding MOSFET.
4. system according to claim 3, it is characterized in that, described a plurality of the first electric currents obtain unit and a plurality of the second electric current and obtain the unit and be under the bias voltage by the base stage at grid/bipolar transistor of corresponding MOSFET, obtain the first electric current and second electric current of each LED string.
5. system according to claim 4, it is characterized in that, in the process of the first electric current that obtains each LED string and the second electric current, described bias voltage remains unchanged, the voltage of the emitter of the source electrode/bipolar transistor by the corresponding MOSFET that samples obtains the first electric current and second electric current of each LED string.
6. system according to claim 5 is characterized in that, also comprises:
Analog to digital converter is used for the voltage of described sampling is carried out analog to digital conversion.
7. system according to claim 4, it is characterized in that, in the process of the first electric current that obtains each LED string and the second electric current, described bias voltage controllably changes, wherein by the electric current of each LED string is set, described bias voltage changes, wherein the first electric current of each LED string and the second electric current be satisfy described be biased under the bias threshold or two bias threshold between maximum current in the electric current is set.
8. system according to claim 2 is characterized in that,
Described second voltage can be higher than described the first voltage, also can be lower than described the first voltage, be higher than at described second voltage in the situation of described the first voltage, determining unit will have than the minimum current in the second electric current of each LED string also the LED string of the first large electric current be defined as the LED short circuit or do not mated, be lower than at described second voltage in the situation of described the first voltage, determining unit will have than the minimum current in the first electric current of each LED string also the LED string of the second large electric current be defined as the LED short circuit or do not mated.
9. system according to claim 1 and 2 is characterized in that, the number of LED is identical in each LED string.
10. system according to claim 1 is characterized in that, the size of described compare threshold is corresponding with the number of the LED of the short circuit that will detect or with match-on criterion is not corresponding.
11. system according to claim 2 is characterized in that, it is identical unit that described a plurality of the first electric currents obtain unit and described a plurality of the second electric currents acquisitions unit.
12. system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, it is characterized in that, described system comprises:
A plurality of the first voltages obtain the unit, are used for obtaining when each LED string all is in identical electric current the first voltage of the control end of respective switch;
Computing unit be used for to calculate the difference between each of the first voltage maximum voltage of control end of respective switch and other voltages;
Comparing unit is used for described difference and a compare threshold are compared; And
Determining unit is used for that difference is defined as the LED short circuit greater than the corresponding LED string of those other voltages of described compare threshold or the LED string corresponding with maximum voltage do not mate.
13. system that detects the LED short circuit of a plurality of LED strings or detect the matching between a plurality of LED strings, one end of wherein said a plurality of LED strings is connected to identical power output end, the other end is connected respectively to corresponding switch, it is characterized in that, described system comprises:
A plurality of the first voltages obtain the unit, be used for obtaining all being in identical electric current at each LED string, and power output end are when exporting the first voltage the first voltage of the control end of respective switch;
Change the unit, be used for changing the second voltage that outputs to of described power output end;
A plurality of second voltages obtain the unit, are used for obtaining when described power output end output second voltage the second voltage of the control end of respective switch; And
Whether whether determining unit is used for the first voltage and second voltage according to the control end of the respective switch that obtains, determine to have in each LED string LED short circuit or each LED string to mate.
14. according to claim 12 or 13 described systems, it is characterized in that, respective switch is the MOSFET/ bipolar transistor, and the described other end is connected respectively to the collector of drain electrode/bipolar transistor of corresponding MOSFET, and described control end is the base stage of grid/bipolar transistor of MOSFET.
15. system according to claim 13 is characterized in that,
The second voltage of described power output end output can be higher than the first voltage of described power output end output, also can be lower than the first voltage of described power output end output, be lower than at the second voltage of described power output end output in the situation of the first voltage of described power output end output, the LED string that determining unit has a second voltage less than the maximum voltage in the first voltage of the control end of respective switch with the control end of its switch has been defined as the LED short circuit or has not mated, be higher than at the second voltage of described power output end output in the situation of the first voltage of described power output end output, the LED string that determining unit has first voltage also less than the maximum voltage in the second voltage of respective switch with the control end of its switch has been defined as the LED short circuit or has not mated.
16. according to claim 12 or 13 described systems, it is characterized in that the number of LED is identical in each LED string.
17. system according to claim 12 is characterized in that, the size of described compare threshold is corresponding with the number of the LED of the short circuit that will detect or with match-on criterion is not corresponding.
18. system according to claim 13 is characterized in that, it is identical unit that described a plurality of the first voltages obtain unit and described a plurality of second voltages acquisitions unit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201320122651 CN203259615U (en) | 2013-03-18 | 2013-03-18 | System detecting LED short circuits in LED strings or matching performance between LED strings |
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| CN 201320122651 CN203259615U (en) | 2013-03-18 | 2013-03-18 | System detecting LED short circuits in LED strings or matching performance between LED strings |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103983892A (en) * | 2014-06-05 | 2014-08-13 | 安徽江淮汽车股份有限公司 | Electric wire short circuit detection method and system and short circuit warning circuit |
| CN114114064A (en) * | 2020-08-11 | 2022-03-01 | 西安钛铂锶电子科技有限公司 | Display unit detection method and device |
-
2013
- 2013-03-18 CN CN 201320122651 patent/CN203259615U/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103983892A (en) * | 2014-06-05 | 2014-08-13 | 安徽江淮汽车股份有限公司 | Electric wire short circuit detection method and system and short circuit warning circuit |
| CN114114064A (en) * | 2020-08-11 | 2022-03-01 | 西安钛铂锶电子科技有限公司 | Display unit detection method and device |
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Address after: 300457, room 2, building 19, No. 701-2 West Ring Road, Tanggu economic and Technological Development Zone, Tianjin, China Patentee after: IWATT INTEGRATED CIRCUITS TECHNOLOGY (TIANJIN) LTD. Address before: 300457, room 2, building 19, No. 701-2 West Ring Road, Tanggu economic and Technological Development Zone, Tianjin, China Patentee before: iWatt Integrated Circuits Technology (Tianjin) Ltd. |
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