CN105307353B - L ED driver and fault protection circuit and fault protection method thereof - Google Patents
L ED driver and fault protection circuit and fault protection method thereof Download PDFInfo
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- CN105307353B CN105307353B CN201510821504.4A CN201510821504A CN105307353B CN 105307353 B CN105307353 B CN 105307353B CN 201510821504 A CN201510821504 A CN 201510821504A CN 105307353 B CN105307353 B CN 105307353B
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Abstract
In one embodiment, the L ED driver includes a voltage conversion unit that converts an input voltage to an output voltage applied to a first end of each L ED string, the fault protection method includes setting an over-voltage threshold to a default value, comparing a voltage at a second end of each L ED string to an open threshold to detect L ED strings with zero current, sample-holding the output voltage when the current of any of the L ED strings is not zero, and disabling the L ED string with zero current when the over-voltage threshold is the default value and the output voltage is greater than the sum of the sample-hold signal and the bias voltage.
Description
Technical field
The present invention relates to electronic circuits, are particularly but not limited to be related to LED driver and its fault secure circuit and failure is protected
Maintaining method.
Background technology
LED is widely used in respectively due to it is with many advantages, such as small, low in energy consumption, luminous efficiency is high, long lifespan
In the display equipment of kind electronic product.In multiple LED strings as in the various applications of backlight device, the safety of system operation with
And fault detect, error protection etc. are very important.Wherein, in order to from LED string open fault destruction, in the prior art
LED driver by setting overvoltage threshold VOVPTo realize.Specifically, it opens a way when some LED goes here and there, is connected to LED strings
Voltage on pin is reduced to 0, and LED driver rises output voltage, when output voltage reaches the overvoltage threshold V of settingOVPWhen,
LED driver disables the LED strings of the open circuit, and it is removed from voltage regulation loop.
For different applications, it is often necessary to which different driving voltages, the setting value of overvoltage threshold also can be different.At present,
In order to design and debug conveniently, I is integrated in more and more LED backlight driving chips2C (Intel-Integrated
Circuit) interface can pass through I according to actually required driving voltage2C interface register pair overvoltage threshold is set.It is full
The demand of the most of applications of foot usually in debugging process, first chooses maximum overvoltage threshold as default value, then further according to
Practical application passes through I2C interface resets suitable value.
However, in start-up course, if there is open circuit or the LED not used strings in LED load, and suitable over-pressed threshold
When value has not yet been set, the output voltage of LED driver can constantly rise until reaching maximum default value, and this requires institutes
Highest circuit devcie is all chosen in some applications.If the smaller application of driving voltage requirement is also chosen highest
Circuit devcie, it will increase the production cost of entire driver.
Invention content
In order to solve the problems, such as previously described one or multiple problems, the present invention proposes a kind of LED driver and its event
Barrier protection circuit and guard method, compared with prior art, can automatically detect before new overvoltage threshold is set and disable not
Using or open circuit LED go here and there.
According to an aspect of the present invention, it proposes a kind of fault secure circuit for LED driver, LED drivings
Device includes voltage conversion unit, converts input voltage into the output voltage for being applied to each LED strings first end, which protects
Protection circuit includes：Over-voltage detection circuit compares the feedback signal for representing output voltage with the overvoltage threshold of programmable
To judge whether output voltage is over-pressed, the first over-voltage fault signal is generated, wherein the default value of overvoltage threshold, which is more than, resets
Value；Multiple open detection circuits, each open detection circuit are coupled to corresponding LED strings second end, by the electricity of LED string second ends
Whether pressure is zero with the electric current for judging LED strings compared with open circuit threshold value, generates corresponding open circuit detection signal；Logic is sentenced
Deenergizing receives multiple open circuit detection signals, and the electric current for judging whether all LED strings is zero, generates logic judgment signal；It adopts
Sample holding circuit, logic-based judge that signal carries out feedback signal sampling holding, generate sampling and keep signal；Comparison circuit,
Its in-phase input end receives feedback signal, and inverting input receives sampling keeps signal and offset signal and value, comparison circuit
By feedback signal with should compare with value, the second over-voltage fault signal is generated in output terminal；Logic circuit receives the second overvoltage event
Hinder signal and mode signal, export a control signal, wherein when overvoltage threshold is default value, mode signal enables control letter
Number, when overvoltage threshold is reset value, the not enabled control signal of mode signal；And trigger circuit, reception control signal,
First over-voltage fault signal and multiple open circuit detection signals generate disabling or the trigger signal of enabled each LED strings.
According to a further aspect of the invention, it is proposed that a kind of LED driver, including：Voltage conversion unit receives input
Voltage converts input voltage into output voltage, which is applied in the first end of each LED strings；Minimum value selects
Circuit is coupled to the second end of each LED strings, to receive the voltage at each LED strings second end, and is carried to voltage conversion unit
The minimum voltage gone here and there for the LED in the second terminal voltage is to adjust output voltage；And above-mentioned fault secure circuit, according to voltage
Voltage at the output voltage of converting unit and multiple LED string second ends detects and disables the LED strings opened a way or do not used.
According to a further aspect of the invention, it is proposed that a kind of fault protecting method for LED driver, the LED drive
Dynamic device includes voltage conversion unit, converts input voltage into the output voltage for being applied to each LED strings first end, the failure
Guard method includes：Overvoltage threshold is set as default value, which is more than reset value；By the electricity at each LED string second ends
Pressure, to detect that electric current is gone here and there as zero LED, generates corresponding open circuit detection signal compared with open circuit threshold value；When any LED goes here and there
Electric current when being not zero, sampling holding is carried out to the feedback signal for representing output voltage, sampling is generated and keeps signal；By feedback letter
Number with sampling keep signal and offset signal and value compared with, the second over-voltage fault signal of generation；And when feedback signal is big
In overvoltage threshold or when overvoltage threshold for default value and feedback signal be more than should and during value, LED strings that disabling electric current is zero.
The error protection provided according to embodiments of the present invention can effectively avoid in the prior art in suitable overvoltage threshold
The problem of relatively low specification circuit devcie is damaged before being set, existing for LED driver.In addition, the fault secure circuit has knot
Structure is simple, at low cost, the characteristics of being easily achieved.
Description of the drawings
It in order to better understand the present invention, will the present invention will be described in detail according to the following drawings：
Fig. 1 is the module diagram according to the fault secure circuit for LED driver of one embodiment of the invention；
Fig. 2 is the circuit diagram according to the LED driver of one embodiment of the invention；
Fig. 3 is the circuit diagram according to the trigger circuit 308 of one embodiment of the invention；
Fig. 4 is the circuit diagram that circuit is protected according to the partial fault of one embodiment of the invention；
Fig. 5 is the work flow diagram according to the fault protecting method 600 for LED driver of one embodiment of the invention.
The specific embodiment that the present invention will be described in detail below with reference to the accompanying drawings.The reference numeral identical through all attached drawings
Represent identical or similar component or feature.
Specific embodiment
Specific embodiments of the present invention are described more fully below, it should be noted that the embodiments described herein is served only for illustrating
Illustrate, be not intended to restrict the invention.In detailed description of the present invention below, for a better understanding of the present invention, description
A large amount of details.It will be understood by those skilled in the art, however, that without these details, the present invention can equally be implemented.For
The present invention is illustrated clearly, simplifies the detailed description of some concrete structures and function herein.In addition, in some implementations
The similar structure and function being had been described in example, repeats no more in other embodiments.Although the items of the present invention
Term describes one by one with reference to specific example embodiment, but these terms showing of being not intended to be limited to illustrate here
Model embodiment.
Throughout the specification, meaning is referred to " one embodiment ", " embodiment ", " example " or " example "
It：It is comprised at least one embodiment of the present invention with reference to a particular feature, structure, or characteristic that the embodiment or example describe.
Therefore, the phrase " in one embodiment ", " in embodiment ", " example " occurred in each place of the whole instruction
Or " example " is not necessarily all referring to the same embodiment or example.It furthermore, it is possible to will be specific with any appropriate combination and/or sub-portfolio
Feature, structure or characteristic combine in one or more embodiments or example.In addition, those of ordinary skill in the art should manage
Solution, attached drawing is provided to the purpose of explanation provided herein, and attached drawing is not necessarily drawn to scale.It should be appreciated that work as
Claim " element " " being connected to " or during " coupled " to another element, it can be directly connected or coupled to another element or can be with
There are intermediary elements.On the contrary, when claiming element " being directly connected to " or " being directly coupled to " another element, there is no cental elements
Part.Identical reference numeral indicates identical element.Term "and/or" used herein includes what one or more correlations were listed
Any and all combination of project.
Fig. 1 is the module diagram according to the fault secure circuit for LED driver of one embodiment of the invention.Such as figure
Shown in 1, LED strings S1~Sn is connected in parallel, and wherein n is positive integer, and each LED strings include multiple LED components being connected in series with.Electricity
Converting unit 101 is pressed to receive input voltage vin, input voltage vin is converted into output voltage Vout, and Vout is applied to often
The first end of a LED string is to drive LED to go here and there.In one embodiment, voltage conversion unit 101 is boost converter.Other
In embodiment, voltage conversion unit 101 may have other topological structures, such as buck converter, flyback converter.
Fault secure circuit includes over-voltage detection circuit 102, open detection circuit 103_1~103_n, logic judging circuit
104th, sampling hold circuit 105, comparison circuit 106, logic circuit 107 and trigger circuit 108.102 coupling of over-voltage detection circuit
The output terminal of voltage conversion unit 101 is connected to, output voltage Vout is received, output voltage Vout is compared with overvoltage threshold Vovp
Compared with the first over-voltage fault signal S of generationOV1.Wherein overvoltage threshold Vovp is programmable, and its default value is more than again
Setting value.When detecting that output voltage Vout reaches current overvoltage threshold Vovp, the first over-voltage fault signal SOV1For high electricity
It is flat.
Open detection circuit 103_1~103_n is used to detect the LED strings of open circuit.Open detection circuit 103_x is coupled to
The second end LEDx of corresponding LED strings Sx, receives characterization electric current ISxVoltage VLEDx, and by itself and open circuit threshold value VOTHIt compares,
Output terminal generates open circuit detection signal ZCx, wherein x=1,2 ..., n.It should be noted that it will often not used in practical application
The second end of LED strings is shorted to ground, therefore open detection circuit 103_1~103_n can also be used for the LED strings that detection does not use.
Due to opening a way and being zero without using the LED electric currents gone here and there, open detection circuit 103_1~103_n can be used for detecting electric current
The LED for being zero goes here and there.
Logic judging circuit 104, sampling hold circuit 105 and comparison circuit 106 are formed together different from overvoltage detection
The over-pressed pre-detection circuit of circuit 102.Over-pressed pre-detection circuit detects automatically before overvoltage threshold Vovp is reset
The LED strings opened a way or do not used in LED load are flushed to the default value of overvoltage threshold Vovp to prevent output voltage Vout from crossing.Its
In, logic judging circuit 104 is used to judge whether that the electric current of all LED strings to be zero, is opened a way with n input terminal with receiving
Signal ZC1~ZCn is detected, the logic judgment signal ZC for representing judging result is generated in output terminal.Sampling hold circuit 105 has
Input terminal, control terminal and output terminal, wherein input terminal are coupled to the output terminal of voltage conversion unit 101 to receive output voltage
Vout, the output terminal that control terminal is coupled to logic judging circuit 104 receive logic judgment signal ZC, and logic-based judges signal
ZC, sampling hold circuit 105 carry out sampling holding to output voltage Vout, and generating sampling in output terminal keeps signal Vhold.Than
Compared with circuit 106 there is the in-phase input end for receiving output voltage Vout and receive sampling and keep signal Vhold and bias voltage
The inverting input of the sum of Voffset values Vsum.In one embodiment, bias voltage Voffset is set to certain certain value.
In another embodiment, bias voltage Voffset is that the maximum conduction voltage drop between all LED strings is poor.Comparison circuit 106 will
Output voltage Vout compares with value Vsum, and the second over-voltage fault signal S is generated in output terminalOV2。
Logic circuit 107 receives the second over-voltage fault signal SOV2Whether it is equal to acquiescence with the current overvoltage threshold Vovp of characterization
The mode signal S of valueMD, export a control signal SOP.When LED driver just starts, overvoltage threshold Vovp is set to
Default value, over-pressed preliminary examination brake are triggered, mode signal SMDEnabled control signal SOP.When overvoltage threshold Vovp is sets again
During definite value, over-pressed preliminary examination brake is disabled, mode signal SMDNot enabled control signal SOP.Trigger circuit 108 is defeated with n
Enter end, the first control terminal, the second control terminal and n output terminal, wherein the first control terminal receives control signal SOP, the second control terminal
Receive the first over-voltage fault signal SOV1, n input terminal receives open circuit detection signal ZC1~ZCn, in n output terminal generation triggering
Signal Trg1~Trgn is gone here and there with disabling or enabling each LED respectively.
When overvoltage threshold Vovp is equal to default value, control signal SOPIt is enabled, trigger circuit 108 is based on the first over-voltage fault
Signal SOV1, control signal SOPTrigger signal Trg1~Trgn is generated with open circuit detection signal ZC1~ZCn.As control signal SOP
It is more than in the state of being enabled and output voltage Vout and during value Vsum, fault secure circuit disables electricity by trigger circuit 108
The LED strings that stream is zero.As control signal SOPIn not enabled state, trigger circuit 108 is based on the first over-voltage fault signal SOV1With
Open circuit detection signal ZC1~ZCn generates trigger signal Trg1~Trgn.
In one embodiment, fault secure circuit further includes multiple short-circuit fault protection circuits.Each short trouble is protected
Protection circuit is coupled to the second end of corresponding LED strings, is judged according to the voltage of correspondence coupling LED string second ends with short-circuit threshold value
Whether LED strings occur short circuit.When detecting LED string short circuits, short-circuit fault protection circuit disables LED strings.
Fig. 2 is the circuit diagram according to the LED driver of one embodiment of the invention.LED driver in Fig. 2 turns including voltage
Unit 101, minimum value selection circuit 209 and fault secure circuit are changed, wherein minimum value selection circuit 209 is coupled to each
The second end of LED strings, to receive the voltage V at LED string second endsLED1~VLEDn, and provide the electricity to voltage conversion unit 101
Minimum voltage Vmin in pressure is to adjust output voltage Vout.Minimum value selection circuit 209 may be used of the prior art more
Kind minimum voltage selection circuit is realized, is not described herein in detail.Voltage conversion unit 201 receives minimum voltage Vmin, by itself and ginseng
It examines voltage Vref to compare to provide error amplification signal, output voltage Vout is adjusted according to the error amplification signal.
As shown in Fig. 2, fault secure circuit includes over-voltage detection circuit 202, open detection circuit 203_1~203_n, patrol
Collect decision circuitry 204, sampling hold circuit 205, comparison circuit 206, logic circuit 207 and trigger circuit 208.It is wherein over-pressed
Detection circuit 202 includes over-pressed detection comparator, and in-phase input end receives output voltage Vout, inverting input reception can compile
The overvoltage threshold Vovp of journey setting generates the first over-voltage fault signal S in output terminalOV1.If Vout>Vovp, then it represents that system
Overvoltage.
In the embodiment shown in Figure 2, open detection circuit 203_1~203_n includes open circuit comparator CMP1~CMPn,
Wherein open circuit comparator CMPx, which has, receives the second terminal voltage V of corresponding LED stringsLEDxIn-phase input end and receive open circuit threshold value
VOTHInverting input, generate open circuit detection signal ZCx in output terminal.Work as VLEDx<VOTH, open circuit detection signal ZCx is low electricity
It is flat, characterize the electric current I of the LED strings of corresponding couplingSXIt is 0；Otherwise ZCx is high level, characterizes LED string normal works.
As shown in Fig. 2, logic judging circuit 204 includes a nor gate 241 with n input terminal.Nor gate 241 connects
Open circuit detection signal ZC1~ZCn is received, logic judgment signal ZC is generated in output terminal.Sampling hold circuit 205 includes sampling switch
Pipe M1 and holding capacitor device C1, sampling switch pipe M1 have first end, second end and control terminal, and wherein first end receives output electricity
Vout is pressed, control terminal is coupled to logic judging circuit 204 to receive logic judgment signal ZC.Holding capacitor device C1 has first end
And second end, wherein first end are coupled to the second end of sampling switch pipe M1 and keep signal Vhold, the second termination to provide sampling
Ground.Comparison circuit 206 includes comparator, and in-phase input end receives output voltage Vout, and inverting input receives sampling and keeps
Signal Vhold and bias voltage be Voffset's and value Vsum, comparator by output voltage Vout with and value Vsum compare,
Output terminal generates the second over-voltage fault signal SOV2。
In the embodiment shown in Figure 2, logic circuit 207 includes being received respectively there are two input terminal with door 271, tool
Mode signal SMDWith the second over-voltage fault signal SOV2, control signal S is generated in output terminalOP.It writes from memory when overvoltage threshold Vovp is equal to
When recognizing value, mode signal SMDFor high level, control signal S is enabledOP, control signal SOPLevel follow the second over-voltage fault believe
Number SOV2Level change.When overvoltage threshold Vovp is not equal to default value, mode signal SMDSaltus step is low level, and second is over-pressed
Fault-signal SOV2It is shielded.At this time no matter the second over-voltage fault signal SOV2State how, control signal SOPIt is low level.
In the embodiment shown in Fig. 2, trigger circuit 208 is in control signal SOPWith the first over-voltage fault signal SOV1Control
Under, it by the open circuit detection signal ZC1~ZCn storages for detection comparator 203_1~203_n outputs of opening a way or exports, to generate
Trigger signal Trg1~Trgn.As shown in Fig. 2, trigger circuit 208 includes or the d type flip flop DFF1 of door 281 and edging trigger~
DFFn.Or door 281 has reception control signal SOPFirst input end and receive the first over-voltage fault signal SOV1Second input
End.D type flip flop DFFx has data input pin D, input end of clock CLK and output terminal Q, and wherein data input pin D is coupled to
Corresponding open detection circuit 203_x is to receive open circuit detection signal ZCx, and input end of clock CLK is coupled to or the output of door 281
End generates corresponding trigger signal Trgx in output terminal.In one embodiment, each LED string can be by by trigger signal
Trg1~TRgn be converted into data write-in internal register come enable or in vain.If the data in internal register are " 1 ", phase
The LED strings answered are enabled；If data are " 0 ", corresponding LED strings are disabled.
Its operation principle is described referring to the embodiment of the error protection provided in Fig. 2.When LED driver starts, mistake
Pressure preliminary examination brake is automatically triggered, and overvoltage threshold Vovp is set to default value, and output voltage Vout is begun to ramp up.At this time by
It is relatively low in Vout so that the device in LED strings does not reach threshold voltage and enters opening state, therefore without electricity on n LED string
Stream flows through, and logic judgment signal ZC keeps high level.
When Vout rises to the threshold voltage for making at least one LED strings conducting, there is electric current to flow through in LED strings, logic is sentenced
Break signal ZC is low level by high level saltus step.Sampling hold circuit 206 samples and Vout at this time is kept to be kept as sampling
Signal Vhold.
In the prior art, before overvoltage threshold Vovp is reset, if having what is opened a way or do not use in LED load
LED goes here and there, and Vout will rise default value until reaching overvoltage threshold always.And in the present invention, Vout rises to sampling and keeps
Signal Vhold and bias voltage be Voffset's and during value Vsum, the second over-voltage fault signal SOV2It is high electricity by low transition
It is flat.
Since overvoltage threshold Vovp is still default value, the control signal S that logic circuit 207 exportsOPAlso by low transition
For high level.Trigger circuit 208 is in control signal S at this timeOPRising edge triggering d type flip flop, will open circuit detection signal ZC1~
ZCn is exported as trigger signal Trg1~Trgn in the output terminal of trigger circuit 208, and the LED that disabling electric current is 0 goes here and there, and will be electric
The LED strings that stream is zero are removed from voltage regulation loop.Then the minimum voltage that voltage conversion unit 201 is gone here and there according to remaining LED
Vmin adjusts output voltage Vout.Therefore fault secure circuit shown in Fig. 2 can detect open when LED driver starts
Road is gone here and there without using LED, protects the circuit devcie damage of the relatively low specification in LED driver.
When overvoltage threshold Vovp is reset, over-pressed preliminary examination brake is disabled, mode signal SMDIt will be from high level
It is changed into low level, not enabled control signal SOP.Trigger circuit 208 is based on the first over-voltage fault signal SOV1It is detected with open circuit
Signal ZCx is detected and is disabled the LED strings opened a way or do not used.
In practical debugging process, if the number of series LED is close to LED driver maximum permissible value in LED load,
At least one LED goes here and there voltage value required when being connected close to the default value of overvoltage threshold in LED load, and with value Vsum even
Through being more than default value.In this case when output voltage Vout is more than default value, trigger circuit 208 is based on the first over-voltage fault
Signal SOV1It is detected with open circuit detection signal ZCx and disables the LED strings opened a way or do not used.
Fig. 3 is according to the circuit diagram of the trigger circuit 308 of one embodiment of the invention, and trigger circuit 308 includes trigger element
308_1~308_n.Wherein trigger element 308_x includes the first sub- trigger element Ax, the second sub- trigger element Bx and triggering is patrolled
Collect unit Cx.First sub- trigger element Ax has first input end, the second input terminal and output terminal, and wherein first input end receives
Control signal SOPWith corresponding open circuit detection signal ZCx, the first sub- trigger signal S is generated in output terminalTrgx.Second son triggering is single
First Bx has first input end, the second input terminal and output terminal, and wherein first input end receives the first over-voltage fault signal SOV1,
Second input terminal receives corresponding open circuit detection signal ZCx, and the second sub- trigger signal OP is generated in output terminalx.Trigger logic list
First Cx receives the first sub- trigger signal STrgxWith the second sub- trigger signal OPx, trigger signal Trgx is generated in output terminal.In Fig. 3 institutes
In the embodiment shown, the first sub- trigger element Ax includes the d type flip flop of an edging trigger, and the second sub- trigger element Bx includes one
A and door, triggering logic unit Cx include one or.In addition, first sub- trigger element A1~An shown in Fig. 3 forms first
Sub- trigger circuit, second sub- trigger element B1~Bn form the first sub- trigger circuit, and triggering logic unit C1~Cn forms triggering
Logic circuit.
Fig. 4 is the circuit diagram that circuit is protected according to the partial fault of one embodiment of the invention, which is applicable in
In integrated LED driver.In the embodiment shown in fig. 4, fault secure circuit further comprises feedback circuit 310, coupling
The output terminal of voltage conversion unit 101 is connected to receive output voltage Vout, represents output voltage Vout's in output terminal offer
Feedback signal VFB.In one embodiment, feedback circuit 310 includes the resitstance voltage divider of resistor R1 and R2 composition.
As shown in figure 4, feedback circuit 310, logic judging circuit 304, sampling hold circuit 305 and comparison circuit 305
Over-pressed pre-detection circuit is formed together.Wherein logic judging circuit 304 include nor gate 341, NOT gate 342, nor gate 343 and
Rest-set flip-flop 344.Nor gate 341 has n input terminal, receives open circuit detection signal ZC1~ZCn.NOT gate 342 opens for providing
The complementary signal of dynamic signal ENIC.Nor gate 343 has first input end, the second input terminal and output terminal, wherein the first input
End is coupled to the output terminal of nor gate 341, and the second input terminal receives the complementary signal of enabling signal ENIC.Rest-set flip-flop 344 has
There are set end, reset terminal, output terminal and complementary output end, wherein set end is coupled to the output terminal of nor gate 343, reset terminal
The output terminal of nor gate 341 is coupled to, logic judgment signal ZC is provided in complementary output end.Sampling hold circuit 305 is based on patrolling
Collecting judges signal ZC to feedback signal VFBSampling holding is carried out, sampling is generated and keeps signal Vhold1.The same phase of comparison circuit 306
Input terminal receives feedback signal VFB, inverting input receive sampling keep signal Vhold1 and offset signal Voffset1's and
Value generates the second over-voltage fault signal S in output terminalOV2.In one embodiment, offset signal Voffset1 and all LED go here and there
Between maximum conduction voltage drop difference it is related.
In the embodiment shown in fig. 4, fault secure circuit further includes optional timing circuit 311.Timing circuit 311 has
There is the threshold value of preset duration, for disabling over-pressed preliminary examination brake after rational preset duration threshold value.When the electricity of any LED strings
Timing circuit 311 starts timing when stream is not zero, and when timing duration reaches the threshold value of preset duration, passes through logic circuit
407 not enabled control signal SOP.Logic circuit 407 includes and door 471 and/or door 475.Or door 475 has first input end, the
Two input terminals and output terminal, wherein first input end are couple to the output terminal of timing circuit 311, the second input terminal reception pattern letter
Number SMD.There is first input end, the second input terminal and output terminal with door 471, wherein first input end is coupled to comparison circuit
306 output terminal is to receive the second over-voltage fault signal SOV2, the second input terminal is coupled to or the output terminal of door 475 is to receive letter
Number SEN。
First sub- trigger circuit 408A includes d type flip flop DFFS1~DFFSn of edging trigger.Wherein d type flip flop DFFSx
With data input pin D, input end of clock CLK, set end S and output terminal Q, wherein data input pin D receptions are opened accordingly
Signal ZCx is detected on road, and input end of clock CLK is coupled to the output terminal of logic circuit 407, and set end S is coupled to NOT gate 312 to connect
Receive mode signal SMDComplementary signal, provide corresponding first sub- trigger signal S in output terminaltrgx。
In the embodiment shown in fig. 4, when LED driver starts, enabling signal ENIC be high level, over-pressed pre-detection
Function is automatically triggered.As the second over-voltage fault signal SOV1For height and with the signal S on the second input terminal of door 471ENFor height
When, control signal SOPIt is enabled, enables or open circuit detection signal ZC1~ZCn is allowed to appear in d type flip flop DFFS1~DFFSn
Output terminal, that is, provide trigger signal Trg1~Trgn. when overvoltage threshold Vovp is not equal to default value or timing circuit 311
Timing duration when reaching the threshold value of preset duration, with the signal S on 471 second input terminal of doorENTo be low, over-pressed preliminary examination brake
It is disabled, control signal SOPIn not enabled state, open circuit detection signal ZC1~ZCn is latched or does not allow to appear in D and touches
In the output for sending out device DFFS1~DFFSn.
In addition, in the fig. 4 embodiment, when overvoltage threshold Vovp is not equal to default value, overpressure mode signal SMDIt is mutual
D type flip flop DFFS1~DFFSn is generated trigger signal Trg1~Trgn whole set by complement signal, enables all LED strings.So
Fault secure circuit detects the open circuit in LED load or the LED not used strings again afterwards, and to prevent in LED load, there are certain
Every other LED strings are disabled during a short circuit LED strings.
Fig. 5 is the workflow according to the fault protecting method 600 for multi-string LED driver of one embodiment of the invention
Figure.The LED driver voltage conversion unit converts input voltage into the output voltage for being applied to each LED strings first end, should
Fault protecting method includes the following steps：
Step S601：Overvoltage threshold is set as default value, and its value is more than reset value.
Step S602：The voltage of each LED string second ends is compared with open circuit threshold value, to detect electric current as zero LED
String generates corresponding open circuit detection signal.
Step S603：When the electric current of any LED strings is not zero, sampling holding is carried out to output voltage, sampling is generated and protects
Hold signal.
Step S604：By output voltage with sampling keep signal and bias voltage and value compare, it is over-pressed to generate second
Fault-signal.If output voltage is more than sampling keeps signal and bias voltage and value, S605 is entered step, otherwise enters step
Rapid 611.In one embodiment, bias voltage is set to a certain specific value.Bias voltage in one of the embodiments,
The maximum conduction voltage drop being set between all LED strings is poor.
Step S605：If overvoltage threshold is equal to default value, S620, the LED strings that disabling electric current is zero are entered step.Otherwise
Enter step 611.
Step S610：Overvoltage threshold is set not equal to default value, subsequently into step S611.
Step S611：When output voltage is more than overvoltage threshold, S620, the LED strings that disabling electric current is zero are entered step.
In one embodiment, step S611 includes：Output voltage with overvoltage threshold is compared, generates the first over-voltage fault signal；Base
In the second over-voltage fault signal and characterization overvoltage threshold whether be default value mode signal, generate control signal；Based on control
Signal, the first over-voltage fault signal and corresponding open circuit detection signal generate the triggering letter of disabling or enabled each LED strings
Number.
In one embodiment, fault protecting method further comprises, starts to count when the electric current of any LED strings is not zero
When, when timing duration reaches the threshold value of preset duration, enter step 611.
In one embodiment, fault protecting method further comprises, when overvoltage threshold is less than default value, enables banned
LED goes here and there.
In one embodiment, fault protecting method further includes, by each LED string voltages of second end and short-circuit threshold value phase
Compare, when the voltage of some LED string second ends is more than short-circuit threshold value, disable LED strings.
Although exemplary embodiment describing the present invention with reference to several, it is to be understood that, term used is explanation and shows
Example property, term and not restrictive.The spirit or reality that can be embodied in a variety of forms without departing from invention due to the present invention
Matter, it should therefore be appreciated that above-described embodiment is not limited to any aforementioned details, and should be in the spirit that appended claims are limited
With widely explained in range, therefore the whole variations fallen into claim or its equivalent scope and remodeling all should be accompanying power
Profit requirement is covered.
Claims (18)
1. a kind of fault secure circuit for LED driver, which includes voltage conversion unit, will input electricity
Pressure is converted to the output voltage for being applied to each LED strings first end, which includes：
Over-voltage detection circuit compares with the overvoltage threshold of programmable the feedback signal for representing output voltage defeated to judge
Whether over-pressed go out voltage, generate the first over-voltage fault signal, the wherein default value of overvoltage threshold is more than reset value；
Multiple open detection circuits, each open detection circuit are coupled to corresponding LED strings second end, by LED string second ends
Whether voltage is zero with the electric current for judging LED strings compared with open circuit threshold value, generates corresponding open circuit detection signal；
Logic judging circuit receives multiple open circuit detection signals, and the electric current for judging whether all LED strings is zero, generates logic
Judge signal；
Sampling hold circuit receives logic judgment signal, wherein when logic judgment signal represents that the electric current of any LED strings is not zero
When, sampling hold circuit carries out feedback signal sampling holding, generates sampling and keeps signal；
Comparison circuit, in-phase input end reception feedback signal, inverting input reception sampling holding signal and offset signal
And feedback signal with should compare with value, the second over-voltage fault signal is generated in output terminal by value, comparison circuit；
Logic circuit, including first and door, first receives the second over-voltage fault signal with the first input end of door, first with door
Second input terminal reception pattern signal, first exports a control signal with door in output terminal, wherein when overvoltage threshold is acquiescence
During value, mode signal enables control signal, when overvoltage threshold is reset value, the not enabled control signal of mode signal；With
And
Trigger circuit receives control signal, the first over-voltage fault signal and multiple open circuit detection signals, generates disabling or enabled
The trigger signal of each LED strings, wherein when feedback signal is more than overvoltage threshold or when overvoltage threshold is default value and feedback letter
Number be more than should and value when, disabling electric current be zero LED string.
2. fault secure circuit as described in claim 1, wherein each open detection circuit includes an open circuit comparator,
Each open circuit comparator is respectively provided with in-phase input end end, inverting input and output terminal, and wherein in-phase input end receives corresponding LED
Voltage at string second end, inverting input receive open circuit threshold value, and corresponding detection signal of opening a way is generated in output terminal.
3. fault secure circuit as described in claim 1, wherein logic judging circuit include the first nor gate.
4. fault secure circuit as described in claim 1, wherein logic judging circuit include：
Second nor gate, has multiple input end and output terminal, and plurality of input terminal receives multiple open circuit detection signals；
Third nor gate, has first input end, the second input terminal and output terminal, and wherein first input end is coupled to second or non-
The output terminal of door, the second input terminal receive the complementary signal of enabling signal；And
Rest-set flip-flop, has set end, reset terminal, output terminal and complementary output end, and wherein set end is coupled to third or non-
The output terminal of door, reset terminal are coupled to the output terminal of the second nor gate, and logic judgment signal is provided in complementary output end.
5. fault secure circuit as described in claim 1, wherein sampling hold circuit include：
Sampling switch pipe, has first end, second end and control terminal, and wherein first end couples to receive feedback signal, control terminal
The output terminal of logic judging circuit is coupled to receive logic judgment signal；And
Holding capacitor device has a first end and a second end, and wherein first end is coupled to the second end of sampling switch pipe, the second termination
Ground.
6. fault secure circuit according to claim 1, further comprises timing circuit, the threshold with preset duration
Value, wherein timing circuit starts timing, and be up in timing when logic judgment signal represents that any LED string electric current is not zero
To preset duration threshold value when, by the not enabled control signal of logic circuit, which includes：
First or door, there is first input end, the second input terminal and output terminal, wherein first input end is couple to timing circuit
Output terminal, the second input terminal reception pattern signal；And
Second and door, there is first input end, the second input terminal and output terminal, wherein first input end is couple to comparison circuit
For output terminal to receive the second over-voltage fault signal, the second input terminal is coupled to the output terminal of first or door, and control is provided in output terminal
Signal processed.
7. fault secure circuit as described in claim 1, wherein trigger circuit include：
First logic unit, has first input end, the second input terminal and output terminal, and wherein first input end receives control letter
Number, the second input terminal receives the first over-voltage fault signal；
Multiple trigger elements, each trigger element are respectively provided with first input end, the second input terminal and output terminal, wherein the first input
End is coupled to the output terminal of the first logic unit, and the second input terminal is coupled to corresponding open detection circuit and is opened accordingly with receiving
Signal is detected on road, and corresponding trigger signal is generated in output terminal.
8. fault secure circuit as claimed in claim 7, wherein each trigger element includes the D triggerings of an edging trigger
Device, data input pin are coupled to the output terminal of corresponding open detection circuit, and input end of clock is coupled to the first logic unit
Output terminal, provide corresponding trigger signal in output terminal.
9. fault secure circuit as described in claim 1, wherein trigger circuit include multiple trigger elements, each trigger element
Including：
First sub- trigger element, has first input end, the second input terminal and output terminal, and wherein first input end receives control letter
Number, the second input terminal receives corresponding open circuit detection signal, and output terminal generates the first sub- trigger signal；
Second sub- trigger element, has first input end, the second input terminal and output terminal, and wherein first input end receives the first mistake
Fault-signal is pressed, the second input terminal receives corresponding open circuit detection signal, and output terminal generates the second sub- trigger signal；And
Logic unit is triggered, there is first input end, the second input terminal and output terminal, wherein first input end receives the first son and touches
It signals, the second input terminal receives the second sub- trigger signal, and trigger signal is generated in output terminal.
10. fault secure circuit as claimed in claim 9, wherein the first sub- trigger element includes the d type flip flop of edging trigger,
It is coupled to corresponding open circuit inspection with data input pin, input end of clock, set end and output terminal, wherein data input pin
The output terminal of slowdown monitoring circuit, input end of clock are coupled to the output terminal of logic circuit, set end coupling signal in a receiving mode it is mutual
Complement signal provides corresponding first sub- trigger signal in output terminal.
11. fault secure circuit according to claim 1 further comprises multiple short-circuit fault protection circuits, each short
Road fault secure circuit is coupled to the second end of corresponding LED strings, and the voltage of LED string second ends and short-circuit threshold are coupled according to the correspondence
Value come judge the LED string whether short circuit occurs, when detect the LED string short circuit when, short-circuit fault protection circuit disables the LED
String.
12. a kind of LED driver, including：
Voltage conversion unit receives input voltage, converts input voltage into output voltage, which is applied in each
The first end of LED strings；
Minimum value selection circuit is coupled to the second end of each LED string, to receive the voltage at each LED strings second end, and to
Voltage conversion unit provides the minimum voltage in the LED the second terminal voltages of string to adjust output voltage；And
Fault secure circuit as described in any in claim 1~11, according to the output voltage of voltage conversion unit and multiple
Voltage at LED string second ends detects and disables the LED strings opened a way or do not used.
13. LED driver as claimed in claim 12, wherein voltage conversion unit receive minimum voltage, and by itself and reference
Voltage compares to provide error amplification signal, and output voltage is adjusted according to the error amplification signal.
14. a kind of fault protecting method for LED driver, which includes voltage conversion unit, will input electricity
Pressure is converted to the output voltage for being applied to each LED strings first end, which includes：
Overvoltage threshold is set as default value, which is more than reset value；
Voltage at each LED string second ends with open circuit threshold value is compared, to detect that electric current is gone here and there as zero LED, generates phase
The open circuit detection signal answered；
When the electric current of any LED strings is not zero, sampling holding is carried out to the feedback signal for representing output voltage, sampling is generated and protects
Hold signal；
By feedback signal with sampling keep signal and offset signal and value compare, the second over-voltage fault signal of generation；And
When feedback signal be more than overvoltage threshold or when overvoltage threshold for default value and feedback signal be more than should and during value, disabling electricity
The LED strings that stream is zero.
15. fault protecting method as claimed in claim 14, further comprises：
Start timing when the electric current of any LED strings is not zero, when timing duration reaches the threshold value of preset duration, by feedback letter
Number compared with overvoltage threshold.
16. fault protecting method as claimed in claim 14 further comprises, when overvoltage threshold is equal to reset value, making
It can forbidden LED strings.
17. fault protecting method as claimed in claim 14 further comprises the voltage of each LED string second ends and short circuit
Threshold value compares, and when the voltage of some LED string second ends is more than short-circuit threshold value, disables LED strings.
18. fault protecting method as claimed in claim 14, wherein the method for LED strings that disabling electric current is zero includes：
Feedback signal with overvoltage threshold is compared, generates the first over-voltage fault signal；
Based on the second over-voltage fault signal and characterization overvoltage threshold whether be default value mode signal, generate control signal；With
And
Based on control signal, the first over-voltage fault signal and open circuit detection signal, the triggering of disabling or enabled each LED strings is generated
Signal.
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| CN106535393B (en) * | 2016-10-26 | 2018-05-15 | 广东工业大学 | A kind of mode of resonance LED flow equalizing circuit control methods |
| CN110049594A (en) * | 2019-04-10 | 2019-07-23 | 欧普照明股份有限公司 | A kind of load overvoltage protection circuit and protection chip |
| CN112637991A (en) * | 2019-09-20 | 2021-04-09 | 台达电子工业股份有限公司 | Power supply applied to light emitting diode and operation method thereof |
| CN110798935B (en) * | 2019-11-19 | 2021-10-08 | 深圳欧创芯半导体有限公司 | LED lamp string control method, device and system and terminal equipment |
| KR102285564B1 (en) * | 2020-04-09 | 2021-08-04 | (주)실리콘인사이드 | Fault detectable led back-light unit |
| 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 |
| CN112333888B (en) * | 2020-11-23 | 2022-12-02 | 湖北久之洋红外系统股份有限公司 | Multi-constant-current-driven LED and LD open-circuit fault detection circuit and detection method |
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| JP2014220200A (en) * | 2013-05-10 | 2014-11-20 | キヤノン株式会社 | Illuminating device and control method thereof |
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| US7675245B2 (en) * | 2007-01-04 | 2010-03-09 | Allegro Microsystems, Inc. | Electronic circuit for driving a diode load |
| US9258860B2 (en) * | 2012-11-29 | 2016-02-09 | Beyond Innovation Technology Co., Ltd. | Load driving apparatus relating to light-emitting-diodes |
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| CN101916547A (en) * | 2010-07-14 | 2010-12-15 | 成都芯源系统有限公司 | Driver for driving a plurality of light emitting elements and display device |
| JP2014220200A (en) * | 2013-05-10 | 2014-11-20 | キヤノン株式会社 | Illuminating device and control method thereof |
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