CN105307353A - LED driver and fault protection circuit and fault protection method thereof - Google Patents
LED driver and fault protection circuit and fault protection method thereof Download PDFInfo
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Abstract
The invention discloses an LED driver, a fault protection circuit and a fault protection method thereof. In one embodiment, the LED driver includes a voltage converting unit converting an input voltage into an output voltage applied to a first terminal of each LED string, and the fault protection method includes: setting an overvoltage threshold value as a default value; comparing the voltage at the second end of each LED string to an open circuit threshold to detect LED strings with zero current; when the current of any LED string is not zero, sampling and holding the output voltage to generate a sampling and holding signal; and when the overvoltage threshold value is a default value and the output voltage is greater than the sum of the sampling and holding signal and the bias voltage, disabling the LED string with the current being zero. The fault protection disclosed by the invention can effectively avoid the problem that the LED driver damages a circuit device with lower specification before a proper overvoltage threshold value is set in the prior art.
Description
Technical field
The present invention relates to electronic circuit, concrete but be not limited to relate to LED driver and fault secure circuit thereof and fault protecting method.
Background technology
LED is widely used in the display device of various electronic product because it has the plurality of advantages such as volume is little, low in energy consumption, luminous efficiency is high, the life-span is long.In the various application of multiple LED strip as backlight device, the fail safe of system cloud gray model and fault detect, error protection etc. are very important.Wherein, in order to the destruction from LED strip open fault, LED driver of the prior art is by setting overvoltage threshold V
oVPrealize.Particularly, when certain LED strip is opened a way, the voltage be connected on this LED strip pin reduces to 0, and LED driver makes output voltage rise, when output voltage reaches the overvoltage threshold V of setting
oVPtime, LED driver forbids the LED strip of this open circuit, and it is removed from voltage regulation loop.
For different application, usually need different driving voltages, the set point of overvoltage threshold also can be different.At present, in order to design and debug conveniently, in increasing LED-backlit driving chip, I is integrated with
2c (Intel-IntegratedCircuit) interface, can pass through I by the driving voltage needed for reality
2c interface register pair overvoltage threshold sets.For the demand of satisfied great majority application, usually in debug process, first choose maximum overvoltage threshold and be worth by default, and then pass through I according to practical application
2c interface resets suitable value.
But, in start-up course, if the LED strip that there is open circuit in LED load or do not use, and suitable overvoltage threshold is when being not yet set, the output voltage of LED driver can constantly rise until reach maximum default value, and this just requires that highest circuit devcie is all chosen in all application.If require that highest circuit devcie is also chosen in less application to driving voltage, the production cost of whole driver will be increased.
Summary of the invention
In order to solve a previously described problem or multiple problem; the present invention proposes a kind of LED driver and fault secure circuit thereof and guard method; compared with prior art, automatically detect before can being set at new overvoltage threshold and forbid the LED strip not using or open a way.
According to an aspect of the present invention, propose a kind of fault secure circuit for LED driver, this LED driver comprises voltage conversion unit, input voltage is converted to the output voltage being applied to each LED strip first end by it, this fault secure circuit comprises: over-voltage detection circuit, compare the overvoltage threshold of the feedback signal with programmable that represent output voltage to judge output voltage whether overvoltage, produce the first overvoltage fault-signal, wherein the default value of overvoltage threshold is greater than and resets value; Multiple open detection circuit, each open detection circuit is coupled to corresponding LED strip second end, by the voltage of this LED strip second end compared with open circuit threshold value, to judge that whether the electric current of this LED strip is for zero, produces detection signal of opening a way accordingly; Logic judging circuit, receives multiple open circuit detection signal, judges whether that the electric current of all LED strip is zero, produces Logic judgment signal; Sampling hold circuit, logic-based judges that signal carries out sampling to feedback signal and keeps, and produces sampling inhibit signal; Comparison circuit, its in-phase input end receiving feedback signals, that inverting input receives sampling inhibit signal and offset signal and be worth, feedback signal be compared with value with this by comparison circuit, produced the second overvoltage fault-signal at output; Logical circuit, receives the second overvoltage fault-signal and mode signal, exports a control signal, wherein when overvoltage threshold is default value, and the enable control signal of mode signal, when overvoltage threshold is for resetting value, the not enable control signal of mode signal; And circuits for triggering, reception control signal, the first overvoltage fault-signal and multiple open circuit detection signal, produce the triggering signal of forbidding or each LED strip enable.
According to a further aspect of the invention, propose a kind of LED driver, comprising: voltage conversion unit, receive input voltage, input voltage is converted to output voltage, and this output voltage is applied in the first end of each LED strip; Minimum value selection circuit, is coupled to the second end of each LED strip, to receive the voltage at each LED strip second end place, and provides minimum voltage in this LED strip second terminal voltage with regulation output voltage to voltage conversion unit; And above-mentioned fault secure circuit, according to the output voltage of voltage conversion unit and the voltage at multiple LED strip second end place, detect and the LED strip forbidden open circuit or do not use.
According to a further aspect of the invention, propose a kind of fault protecting method for LED driver, this LED driver comprises voltage conversion unit, input voltage is converted to the output voltage being applied to each LED strip first end by it, this fault protecting method comprises: setting overvoltage threshold is default value, and this value is greater than and resets value; By the voltage at each LED strip second end place compared with open circuit threshold value, to detect that electric current is the LED strip of zero, produce detection signal of opening a way accordingly; When the electric current of arbitrary LED strip is non-vanishing, sampling is carried out to the feedback signal representing output voltage and keeps, produce sampling inhibit signal; By feedback signal comparing with value with sampling inhibit signal and offset signal, produce the second overvoltage fault-signal; And when feedback signal is greater than overvoltage threshold or when overvoltage threshold is default value and feedback signal is greater than this and value, forbidding electric current is the LED strip of zero.
According to the error protection that the embodiment of the present invention provides, can effectively avoid in prior art before suitable overvoltage threshold is set, the problem of the lower specification circuit devcie of infringement that LED driver exists.In addition, this fault secure circuit has the advantages that structure is simple, cost is low, be easy to realization.
Accompanying drawing explanation
For a better understanding of the present invention, will describe the present invention according to the following drawings:
Fig. 1 is according to an embodiment of the invention for the module diagram of the fault secure circuit of LED driver;
Fig. 2 is the circuit diagram of LED driver according to an embodiment of the invention;
Fig. 3 is the circuit diagram of circuits for triggering 308 according to an embodiment of the invention;
Fig. 4 is the circuit diagram of partial fault protective circuit according to an embodiment of the invention;
Fig. 5 is according to an embodiment of the invention for the workflow diagram of the fault protecting method 600 of LED driver.
Describe the specific embodiment of the present invention in detail below with reference to the accompanying drawings.Run through the identical Reference numeral of institute's drawings attached and represent identical or similar parts or feature.
Embodiment
To specific embodiments of the invention be described in detail below, it should be noted that the embodiments described herein is only for illustrating, is not limited to the present invention.Below in detailed description of the present invention, in order to understand the present invention better, describe a large amount of details.But it will be understood by those skilled in the art that do not have these details, the present invention can implement equally.Set forth the present invention in order to clear, simplify the detailed description of some concrete structures and function herein.In addition, similar 26S Proteasome Structure and Function described in detail in certain embodiments, repeats no more in other embodiments.Although every term of the present invention describes one by one in conjunction with concrete example embodiment, these terms should not be construed as the exemplary implementations being confined to set forth here.
In whole specification, " embodiment ", " embodiment ", " example " or mentioning of " example " are meaned: the special characteristic, structure or the characteristic that describe in conjunction with this embodiment or example are at least one embodiment of the invention involved.Therefore, the phrase " in one embodiment " occurred in each place of whole specification, " in an embodiment ", " example " or " example " differ to establish a capital and refer to same embodiment or example.In addition, can with any suitable combination and/or sub-portfolio by specific feature, structure or property combination in one or more embodiment or example.In addition, it should be understood by one skilled in the art that the accompanying drawing provided at this is all for illustrative purposes, and accompanying drawing is not necessarily drawn in proportion.Should be appreciated that when claim " element " " be connected to " or " coupling " to another element time, it can be directly connected or coupled to another element or can there is intermediary element.On the contrary, when claim element " be directly connected to " or " being directly coupled to " another element time, there is not intermediary element.Identical Reference numeral indicates identical element.Term "and/or" used herein comprises any and all combinations of one or more relevant project listed.
Fig. 1 is according to an embodiment of the invention for the module diagram of the fault secure circuit of LED driver.As shown in Figure 1, LED strip S1 ~ Sn is connected in parallel, and wherein n is positive integer, and each LED strip comprises multiple LED component be connected in series.Voltage conversion unit 101 receives input voltage vin, input voltage vin is converted to output voltage Vout, and first end Vout being applied to each LED strip is with driving LED string.In one embodiment, voltage conversion unit 101 is boost converter.In other embodiments, voltage conversion unit 101 may have other topological structure, as buck converter, flyback transducer etc.
Fault secure circuit comprises over-voltage detection circuit 102, open detection circuit 103_1 ~ 103_n, logic judging circuit 104, sampling hold circuit 105, comparison circuit 106, logical circuit 107 and circuits for triggering 108.Over-voltage detection circuit 102 is coupled to the output of voltage conversion unit 101, receives output voltage Vout, is compared by output voltage Vout, produce the first overvoltage fault-signal S with overvoltage threshold Vovp
oV1.Wherein overvoltage threshold Vovp is programmable, and its default value is greater than and resets value.When the overvoltage threshold Vovp that output voltage Vout reaches current being detected, the first overvoltage fault-signal S
oV1for high level.
Open detection circuit 103_1 ~ 103_n is for detecting the LED strip of open circuit.Open detection circuit 103_x is coupled to the second end LEDx of corresponding LED strip Sx, receives and characterizes electric current I
sxvoltage V
lEDx, and by itself and open circuit threshold value V
oTHcompare, produce open circuit detection signal ZCx at output, wherein x=1,2 ..., n.It should be noted that, often will the second end of LED strip do not used to be shorted to ground in practical application, therefore open detection circuit 103_1 ~ 103_n also can be used for detecting the LED strip do not used.Owing to opening a way and not using the electric current of LED strip to be zero, it is the LED strip of zero that therefore open detection circuit 103_1 ~ 103_n can be used for detecting electric current.
Logic judging circuit 104, sampling hold circuit 105 and comparison circuit 106 form the overvoltage pre-detection circuit being different from over-voltage detection circuit 102 together.Overvoltage pre-detection circuit, before overvoltage threshold Vovp is reset, detects in LED load the LED strip opened a way or do not use, automatically to prevent output voltage Vout overshoot to the default value of overvoltage threshold Vovp.Wherein, logic judging circuit 104 is for judging whether that the electric current of all LED strip is zero, and it has n input to receive open circuit detection signal ZC1 ~ ZCn, produces the Logic judgment signal ZC representing judged result at output.Sampling hold circuit 105 has input, control end and output, wherein input is coupled to the output of voltage conversion unit 101 to receive output voltage Vout, the output receive logic that control end is coupled to logic judging circuit 104 judges signal ZC, logic-based judges signal ZC, sampling hold circuit 105 couples of output voltage Vout carry out sampling and keep, and produce sampling inhibit signal Vhold at output.Comparison circuit 106 has the in-phase input end receiving output voltage Vout and the inverting input receiving sampling inhibit signal Vhold and bias voltage Voffset sum value Vsum.In one embodiment, bias voltage Voffset is set to certain certain value.In another embodiment, bias voltage Voffset is that maximum conduction voltage drop between all LED strip is poor.Output voltage Vout with comparing with value Vsum, is produced the second overvoltage fault-signal S at output by comparison circuit 106
oV2.
Logical circuit 107 receives the second overvoltage fault-signal S
oV2the mode signal S of default value whether is equaled with the current overvoltage threshold Vovp of sign
mD, export a control signal S
oP.When LED driver just starts, overvoltage threshold Vovp is set to default value, and overvoltage pre-detection function is triggered, mode signal S
mDenable control signal S
oP.When overvoltage threshold Vovp is for resetting value, overvoltage pre-detection function is disabled, mode signal S
mDnot enable control signal S
oP.Circuits for triggering 108 have n input, the first control end, the second control end and n output, wherein the first control end reception control signal S
oP, the second control end receives the first overvoltage fault-signal S
oV1, n input receives open circuit detection signal ZC1 ~ ZCn, produces triggering signal Trg1 ~ Trgn to forbid respectively or each LED strip enable at n output.
When overvoltage threshold Vovp equals default value, control signal S
oPbe enabled, circuits for triggering 108 are based on the first overvoltage fault-signal S
oV1, control signal S
oPtriggering signal Trg1 ~ Trgn is produced with open circuit detection signal ZC1 ~ ZCn.As control signal S
oPbe in the state of being enabled and output voltage Vout is greater than and is worth Vsum time, fault secure circuit forbids by circuits for triggering 108 LED strip that electric current is zero.As control signal S
oPbe in not enabled state, circuits for triggering 108 are based on the first overvoltage fault-signal S
oV1triggering signal Trg1 ~ Trgn is produced with open circuit detection signal ZC1 ~ ZCn.
In one embodiment, fault secure circuit also comprises multiple short-circuit fault protection circuit.Each short-circuit fault protection circuit is coupled to the second end of corresponding LED strip, couples the voltage of LED strip second end and short-circuit threshold value judges whether this LED strip is short-circuited according to this correspondence.When this LED strip short circuit being detected, short-circuit fault protection circuit forbids this LED strip.
Fig. 2 is the circuit diagram of LED driver according to an embodiment of the invention.LED driver in Fig. 2 comprises voltage conversion unit 101, minimum value selection circuit 209 and fault secure circuit, and wherein minimum value selection circuit 209 is coupled to the second end of each LED strip, to receive the voltage V at LED strip second end place
lED1~ V
lEDn, and provide minimum voltage Vmin in this voltage with regulation output voltage Vout to voltage conversion unit 101.Minimum value selection circuit 209 can adopt multiple minimum voltage selection circuit of the prior art to realize, and is not described further here.Voltage conversion unit 201 receives minimum voltage Vmin, by its compared with reference voltage Vref to provide error amplification signal, according to this error amplification signal regulation output voltage Vout.
As shown in Figure 2, fault secure circuit comprises over-voltage detection circuit 202, open detection circuit 203_1 ~ 203_n, logic judging circuit 204, sampling hold circuit 205, comparison circuit 206, logical circuit 207 and circuits for triggering 208.Wherein over-voltage detection circuit 202 comprises overvoltage detection comparator, and the overvoltage threshold Vovp that its in-phase input end receives output voltage Vout, inverting input receives programmable, produces the first overvoltage fault-signal S at output
oV1.If Vout > is Vovp, then represent system overvoltage.
In the embodiment shown in Figure 2, open detection circuit 203_1 ~ 203_n comprises open circuit comparator CMP1 ~ CMPn, and the comparator CMPx that wherein opens a way has the corresponding LED strip second terminal voltage V of reception
lEDxin-phase input end and receive open circuit threshold value V
oTHinverting input, produce open circuit detection signal ZCx at output.Work as V
lEDx< V
oTH, open circuit detection signal ZCx is low level, characterizes the electric current I of the LED strip that couple corresponding to it
sXbe 0; Otherwise ZCx is high level, characterizes this LED strip and normally work.
As shown in Figure 2, logic judging circuit 204 comprises the NOR gate 241 that has n input.NOR gate 241 receives open circuit detection signal ZC1 ~ ZCn, produces Logic judgment signal ZC at output.Sampling hold circuit 205 comprises sampling switch pipe M1 and keeping capacitor C1, sampling switch pipe M1 has first end, the second end and control end, wherein first end receives output voltage Vout, and control end is coupled to logic judging circuit 204 and judges signal ZC with receive logic.Keeping capacitor C1 has first end and the second end, and wherein first end is coupled to second end of sampling switch pipe M1 to provide sampling inhibit signal Vhold, the second end ground connection.Comparison circuit 206 comprises comparator, its in-phase input end receives output voltage Vout, inverting input receive sampling inhibit signal Vhold and bias voltage Voffset be worth Vsum, output voltage Vout compares with value Vsum by comparator, produces the second overvoltage fault-signal S at output
oV2.
In the embodiment shown in Figure 2, logical circuit 207 comprises and door 271, and it has two inputs, respectively receiving mode signal S
mDwith the second overvoltage fault-signal S
oV2, produce control signal S at output
oP.When overvoltage threshold Vovp equals default value, mode signal S
mDfor high level, enable control signal S
oP, control signal S
oPlevel follow the second overvoltage fault-signal S
oV2level change.When overvoltage threshold Vovp is not equal to default value, mode signal S
mDsaltus step is low level, the second overvoltage fault-signal S
oV2conductively-closed.Now no matter the second overvoltage fault-signal S
oV2state how, control signal S
oPbe low level.
In the embodiment that Fig. 2 shows, circuits for triggering 208 are at control signal S
oPwith the first overvoltage fault-signal S
oV1control under, open circuit detection signal ZC1 ~ ZCn that open circuit detection comparator 203_1 ~ 203_n exports is stored or exports, to produce triggering signal Trg1 ~ Trgn.As shown in Figure 2, circuits for triggering 208 comprise or the d type flip flop DFF1 ~ DFFn of door 281 and edging trigger.Or door 281 has reception control signal S
oPfirst input end and receive the first overvoltage fault-signal S
oV1the second input.D type flip flop DFFx has data input pin D, input end of clock CLK and output Q, wherein data input pin D is coupled to corresponding open detection circuit 203_x to receive open circuit detection signal ZCx, input end of clock CLK is coupled to or the output of door 281, produces corresponding triggering signal Trgx at output.In one embodiment, each LED strip is enable or invalid by triggering signal Trg1 ~ TRgn being converted to data write internal register.If in the data of internal register be " 1 ", corresponding LED strip is enabled; If data are " 0 ", corresponding LED strip is disabled.
Embodiment referring to the error protection provided in Fig. 2 describes its operation principle.When LED driver starts, overvoltage pre-detection function is automatically triggered, and overvoltage threshold Vovp is set to default value, and output voltage Vout starts to rise.Now because Vout is lower, make the device in LED strip not reach threshold voltage and enter opening state, therefore in n LED strip, equal no current flows through, and Logic judgment signal ZC keeps high level.
When Vout rises to the threshold voltage making at least one LED strip conducting, have electric current to flow through in LED strip, Logic judgment signal ZC is low level by high level saltus step.Sampling hold circuit 206 is sampled and is kept Vout now as sampling inhibit signal Vhold.
In prior art, before overvoltage threshold Vovp is reset, if the LED strip that there is open circuit in LED load or do not use, Vout will rise until reach the default value of overvoltage threshold always.And in the present invention, Vout rise to sampling inhibit signal Vhold and bias voltage Voffset with value Vsum time, the second overvoltage fault-signal S
oV2be high level by low transition.
Because overvoltage threshold Vovp is still default value, the control signal S that logical circuit 207 exports
oPalso be high level by low transition.Now circuits for triggering 208 are at control signal S
oPrising edge triggered D flip flop, is exported as triggering signal Trg1 ~ Trgn at the output of circuits for triggering 208 by open circuit detection signal ZC1 ~ ZCn, forbidding electric current is the LED strip of 0, and by electric current be zero LED strip remove from voltage regulation loop.Then voltage conversion unit 201 carrys out regulation output voltage Vout according to the minimum voltage Vmin of residue LED strip.Therefore the fault secure circuit shown in Fig. 2 can detect open circuit or not use LED strip when LED driver starts, the circuit devcie of the lower specification in protection LED driver is from destruction.
When overvoltage threshold Vovp is reset, overvoltage pre-detection function is disabled, mode signal S
mDlow level will be changed into, not enable control signal S from high level
oP.Circuits for triggering 208 are based on the first overvoltage fault-signal S
oV1detect and the LED strip forbidden open circuit or do not use with open circuit detection signal ZCx.
In the debug process of reality, if the number of series LED is close to LED driver maximum permissible value in LED load, magnitude of voltage required during at least one LED strip conducting in LED load close to the default value of overvoltage threshold, and is even greater than default value with value Vsum.In this case, when output voltage Vout is greater than default value, circuits for triggering 208 are based on the first overvoltage fault-signal S
oV1detect and the LED strip forbidden open circuit or do not use with open circuit detection signal ZCx.
Fig. 3 is the circuit diagram of circuits for triggering 308 according to an embodiment of the invention, and circuits for triggering 308 comprise trigger element 308_1 ~ 308_n.Wherein trigger element 308_x comprises the first sub-trigger element Ax, the second sub-trigger element Bx and Trigger Logic unit Cx.First sub-trigger element Ax has first input end, the second input and output, wherein first input end reception control signal S
oPwith corresponding open circuit detection signal ZCx, produce the first sub-triggering signal S at output
trgx.Second sub-trigger element Bx has first input end, the second input and output, and wherein first input end receives the first overvoltage fault-signal S
oV1, the second input receives corresponding open circuit detection signal ZCx, produces the second sub-triggering signal OP at output
x.Trigger Logic unit Cx receives the first sub-triggering signal S
trgxwith the second sub-triggering signal OP
x, produce triggering signal Trgx at output.In the embodiment shown in fig. 3, the first sub-trigger element Ax comprises the d type flip flop of an edging trigger, and the second sub-trigger element Bx comprises one and door, Trigger Logic unit Cx comprise one or.In addition, shown in Fig. 3 first sub-trigger element A1 ~ An forms the first sub-circuits for triggering 308A, and second sub-trigger element B1 ~ Bn forms the first sub-circuits for triggering 308B, and Trigger Logic unit C1 ~ Cn forms trigger logic 308C.
Fig. 4 is the circuit diagram of partial fault protective circuit according to an embodiment of the invention, and this fault secure circuit is applicable in integrated LED driver.In the embodiment shown in fig. 4, fault secure circuit comprises feedback circuit 310 further, and its output being coupled to voltage conversion unit 101, to receive output voltage Vout, provides the feedback signal V representing output voltage Vout at output
fB.In one embodiment, feedback circuit 310 includes the resitstance voltage divider that resistor R1 and R2 is formed.
As shown in Figure 4, feedback circuit 310, logic judging circuit 304, sampling hold circuit 305 and comparison circuit 305 form overvoltage pre-detection circuit together.Wherein logic judging circuit 304 comprises NOR gate 341, not gate 342, NOR gate 343 and rest-set flip-flop 344.NOR gate 342 has n input, receives open circuit detection signal ZC1 ~ ZCn.Not gate 324 is for providing the complementary signal of enabling signal ENIC.NOR gate 343 has first input end, the second input and output, and wherein first input end is coupled to the output of NOR gate 341, and the second input receives the complementary signal of enabling signal ENIC.Rest-set flip-flop 344 has set end, reset terminal, output and complementary output end, and wherein set end is coupled to the output of NOR gate 343, and reset terminal is coupled to the output of NOR gate 341, provides Logic judgment signal ZC at complementary output end.Sampling hold circuit 305 logic-based judges that signal ZC is to feedback signal V
fBcarry out sampling to keep, produce sampling inhibit signal Vhold1.The in-phase input end receiving feedback signals V of comparison circuit 306
fB, inverting input receives sampling inhibit signal Vhold1 and offset signal Voffset1's and be worth, and produces the second overvoltage fault-signal S at output
oV2.In one embodiment, the maximum conduction voltage drop difference between offset signal Voffset1 with all LED strip is relevant.
In the embodiment shown in fig. 4, fault secure circuit also comprises optional timing circuit 311.Timing circuit 311 has the threshold value of preset duration, for forbidding overvoltage pre-detection function after rational preset duration threshold value.When the electric current of arbitrary LED strip is non-vanishing, timing circuit 311 starts timing, and when timing duration reaches the threshold value of preset duration, by the not enable control signal S of logical circuit 407
oP.Logical circuit 407 comprises and door 471 and or door 475.Or door 475 has first input end, the second input and output, wherein first input end is couple to the output of timing circuit 311, the second input receiving mode signal S
mD.Have first input end, the second input and output with door 471, wherein first input end is coupled to the output of comparison circuit 306 to receive the second overvoltage fault-signal S
oV2, the second input be coupled to or the output of door 475 with Received signal strength S
eN.In other embodiments, logical circuit may have the structure different from above-described embodiment to realize similar function.
First sub-circuits for triggering 408A comprises the d type flip flop DFFS1 ~ DFFSn of edging trigger.Wherein d type flip flop DFFSx has data input pin D, input end of clock CLK, set end S and output Q, wherein data input pin D receives corresponding open circuit detection signal ZCx, input end of clock CLK is coupled to the output of logical circuit 407, and set end S is coupled to not gate 312 signal S in a receiving mode
mDcomplementary signal, provide corresponding first sub-triggering signal S at output
trgx.
In the embodiment shown in fig. 4, when LED driver starts, enabling signal ENIC is high level, and overvoltage pre-detection function is automatically triggered.As the second overvoltage fault-signal S
oV1for high and with the signal S on the second input of door 471
eNfor time high, control signal S
oPbe enabled, enable or allow open circuit detection signal ZC1 ~ ZCn to appear at the output of d type flip flop DFFS1 ~ DFFSn, namely provide triggering signal Trg1 ~ Trgn. to work as overvoltage threshold Vovp and be not equal to default value, or when the timing duration of timing circuit 311 reaches the threshold value of preset duration, with the signal S on door 471 second input
eNfor low, overvoltage pre-detection function is disabled, control signal S
oPbe in not enabled state, open circuit detection signal ZC1 ~ ZCn is latched or does not allow to appear in the output of d type flip flop DFFS1 ~ DFFSn.
In addition, in the fig. 4 embodiment, when overvoltage threshold Vovp is not equal to default value, overpressure mode signal S
mDcomplementary signal d type flip flop DFFS1 ~ DFFSn is produced triggering signal Trg1 ~ Trgn whole set, enable all LED strip.Then fault secure circuit detects again to the open circuit in LED load or the LED strip that do not use, and during to prevent there is certain short circuit LED strip in LED load, every other LED strip is disabled.
Fig. 5 is according to an embodiment of the invention for the workflow diagram of the fault protecting method 600 of multi-string LED driver.This LED driver voltage conversion unit, is converted to the output voltage being applied to each LED strip first end by input voltage, this fault protecting method comprises the following steps:
Step S601: setting overvoltage threshold is default value, and its value is greater than and resets value.
Step S602: by the voltage of each LED strip second end compared with open circuit threshold value, to detect the LED strip that electric current is zero, produce detection signal of opening a way accordingly.
Step S603: when the electric current of arbitrary LED strip is non-vanishing, carries out sampling to output voltage and keeps, and produces sampling inhibit signal.
Step S604: by output voltage comparing with value with sampling inhibit signal and bias voltage, produce the second overvoltage fault-signal.If output voltage be greater than sampling inhibit signal and bias voltage and value, enter step S605, otherwise enter step 611.In one embodiment, bias voltage is set to a certain specific value.Wherein in an embodiment, the maximum conduction voltage drop that bias voltage is set between all LED strip is poor.
Step S605: if overvoltage threshold equals default value, enter step S620, forbidding electric current is the LED strip of zero.Otherwise enter step 611.
Step S610: setting overvoltage threshold is not equal to default value, then enters step S611.
Step S611: when output voltage is greater than overvoltage threshold, enter step S620, forbidding electric current is the LED strip of zero.In one embodiment, step S611 comprises: by output voltage compared with overvoltage threshold, produces the first overvoltage fault-signal; Based on the second overvoltage fault-signal with characterize the mode signal whether overvoltage threshold is default value, produce control signal; Based on control signal, the first overvoltage fault-signal and detection signal of opening a way accordingly, produce the triggering signal of forbidding or each LED strip enable.
In one embodiment, fault protecting method comprises step 607 further, starts timing when the electric current of arbitrary LED strip is non-vanishing, when timing duration reaches the threshold value of preset duration, enters step 611.
In one embodiment, fault protecting method comprises further, when overvoltage threshold is less than default value, and enable disabled LED strip.
In one embodiment, fault protecting method also comprises, and by the voltage of each LED strip second end compared with short-circuit threshold value, when the voltage of certain LED strip second end is greater than short-circuit threshold value, forbids this LED strip.
Although exemplary embodiment describe the present invention with reference to several, should be appreciated that term used illustrates and exemplary and nonrestrictive term.Spirit or the essence of invention is not departed from because the present invention can specifically implement in a variety of forms, so be to be understood that, above-described embodiment is not limited to any aforesaid details, and explain widely in the spirit and scope that should limit in claim of enclosing, therefore fall into whole change in claim or its equivalent scope and remodeling and all should be claim of enclosing and contained.
Claims (19)
1. for a fault secure circuit for LED driver, this LED driver comprises voltage conversion unit, and input voltage is converted to the output voltage being applied to each LED strip first end by it, and this fault secure circuit comprises:
Over-voltage detection circuit, compares to judge output voltage whether overvoltage, produces the first overvoltage fault-signal by the overvoltage threshold of the feedback signal with programmable that represent output voltage, wherein the default value of overvoltage threshold is greater than and resets value;
Multiple open detection circuit, each open detection circuit is coupled to corresponding LED strip second end, by the voltage of this LED strip second end compared with open circuit threshold value, to judge that whether the electric current of this LED strip is for zero, produces detection signal of opening a way accordingly;
Logic judging circuit, receives multiple open circuit detection signal, judges whether that the electric current of all LED strip is zero, produces Logic judgment signal;
Sampling hold circuit, logic-based judges that signal carries out sampling to feedback signal and keeps, and produces sampling inhibit signal;
Comparison circuit, its in-phase input end receiving feedback signals, that inverting input receives sampling inhibit signal and offset signal and be worth, feedback signal be compared with value with this by comparison circuit, produced the second overvoltage fault-signal at output;
Logical circuit, receives the second overvoltage fault-signal and mode signal, exports a control signal, wherein when overvoltage threshold is default value, and the enable control signal of mode signal, when overvoltage threshold is for resetting value, the not enable control signal of mode signal; And
Circuits for triggering, reception control signal, the first overvoltage fault-signal and multiple open circuit detection signal, produce the triggering signal of forbidding or each LED strip enable.
2. fault secure circuit as claimed in claim 1; wherein each open detection circuit includes an open circuit comparator; each open circuit comparator all has in-phase input end end, inverting input and output; wherein in-phase input end receives the voltage at corresponding LED strip second end place; inverting input receives open circuit threshold value, produces at output detection signal of opening a way accordingly.
3. fault secure circuit as claimed in claim 1, wherein logic judging circuit comprises the first NOR gate.
4. fault secure circuit as claimed in claim 1, wherein logic judging circuit comprises:
Second NOR gate, has multiple input and output, and wherein multiple input receives multiple open circuit detection signal;
3rd NOR gate, have first input end, the second input and output, wherein first input end is coupled to the output of the second NOR gate, and the second input receives the complementary signal of enabling signal; And
Rest-set flip-flop, has set end, reset terminal, output and complementary output end, and wherein set end is coupled to the output of the 3rd NOR gate, and reset terminal is coupled to the output of the second NOR gate, provides Logic judgment signal at complementary output end.
5. fault secure circuit as claimed in claim 1, wherein sampling hold circuit comprises:
Sampling switch pipe, have first end, the second end and control end, wherein first end couples with receiving feedback signals, and the output that control end is coupled to logic judging circuit judges signal with receive logic; And
Keeping capacitor, has first end and the second end, and wherein first end is coupled to the second end of sampling switch pipe, the second end ground connection.
6. fault secure circuit as claimed in claim 1; wherein logical circuit comprises first and door, and it has first input end, the second input and output, and wherein first input end receives the second overvoltage fault-signal; second input receiving mode signal, provides control signal at output.
7. fault secure circuit according to claim 1; comprise timing circuit further; it has the threshold value of preset duration; wherein when Logic judgment signal indication arbitrary LED strip electric current is non-vanishing, timing circuit starts timing; and when timing duration reaches the threshold value of preset duration; by the not enable control signal of logical circuit, this logical circuit comprises:
First or door, have first input end, the second input and output, wherein first input end is couple to the output of timing circuit, the second input receiving mode signal; And
Second and door, have first input end, the second input and output, wherein first input end is couple to the output of comparison circuit to receive the second overvoltage fault-signal, and the second input is coupled to the output of first or door, provides control signal at output.
8. fault secure circuit as claimed in claim 1, wherein circuits for triggering comprise:
First logical block, has first input end, the second input and output, wherein first input end reception control signal, and the second input receives the first overvoltage fault-signal;
Multiple trigger element, each trigger element all has first input end, the second input and output, wherein first input end is coupled to the output of the first logical block, second input is coupled to corresponding open detection circuit to receive detection signal of opening a way accordingly, produces corresponding triggering signal at output.
9. fault secure circuit as claimed in claim 8; wherein each trigger element comprises the d type flip flop of an edging trigger; its data input pin is coupled to the output of corresponding open detection circuit; input end of clock is coupled to the output of the first logical block, provides corresponding triggering signal at output.
10. fault secure circuit as claimed in claim 1, wherein circuits for triggering comprise multiple trigger element, and each trigger element comprises:
First sub-trigger element, has first input end, the second input and output, wherein first input end reception control signal, and the second input receives detection signal of opening a way accordingly, and output produces the first sub-triggering signal;
Second sub-trigger element, has first input end, the second input and output, and wherein first input end receives the first overvoltage fault-signal, and the second input receives detection signal of opening a way accordingly, and output produces the second sub-triggering signal; And
Trigger Logic unit, has first input end, the second input and output, and wherein first input end receives the first sub-triggering signal, and the second input receives the second sub-triggering signal, produces triggering signal at output.
11. fault secure circuits as claimed in claim 10; wherein the first sub-trigger element comprises the d type flip flop of edging trigger; it has data input pin, input end of clock, set end and output; wherein data input pin is coupled to the output of corresponding open detection circuit; input end of clock is coupled to the output of logical circuit; set end couples the complementary signal of signal in a receiving mode, provides corresponding first sub-triggering signal at output.
12. fault secure circuits according to claim 1; comprise multiple short-circuit fault protection circuit further; each short-circuit fault protection circuit is coupled to the second end of corresponding LED strip; the voltage of LED strip second end is coupled and short-circuit threshold value judges whether this LED strip is short-circuited according to this correspondence; when this LED strip short circuit being detected, short-circuit fault protection circuit forbids this LED strip.
13. 1 kinds of LED drivers, comprising:
Voltage conversion unit, receive input voltage, input voltage is converted to output voltage, and this output voltage is applied in the first end of each LED strip;
Minimum value selection circuit, is coupled to the second end of each LED strip, to receive the voltage at each LED strip second end place, and provides minimum voltage in this LED strip second terminal voltage with regulation output voltage to voltage conversion unit; And
As the fault secure circuit as described in arbitrary in claim 1 ~ 12, according to the output voltage of voltage conversion unit and the voltage at multiple LED strip second end place, detect and the LED strip forbidden open circuit or do not use.
14. drivers as claimed in claim 13, wherein voltage conversion unit receive minimum voltage, and by its compared with reference voltage to provide error amplification signal, according to this error amplification signal regulation output voltage.
15. 1 kinds of fault protecting methods for LED driver, this LED driver comprises voltage conversion unit, and input voltage is converted to the output voltage being applied to each LED strip first end by it, and this fault protecting method comprises:
Setting overvoltage threshold is default value, and this value is greater than and resets value;
By the voltage at each LED strip second end place compared with open circuit threshold value, to detect that electric current is the LED strip of zero, produce detection signal of opening a way accordingly;
When the electric current of arbitrary LED strip is non-vanishing, sampling is carried out to the feedback signal representing output voltage and keeps, produce sampling inhibit signal;
By feedback signal comparing with value with sampling inhibit signal and offset signal, produce the second overvoltage fault-signal; And
When feedback signal is greater than overvoltage threshold or when overvoltage threshold is default value and feedback signal is greater than this and value, forbidding electric current is the LED strip of zero.
16. fault protecting methods as claimed in claim 15, comprise further:
Timing is started, when timing duration reaches the threshold value of preset duration, by feedback signal compared with overvoltage threshold when the electric current of arbitrary LED strip is non-vanishing.
17. fault protecting methods as claimed in claim 15, comprise when overvoltage threshold equals to reset value, enable disabled LED strip further.
18. fault protecting methods as claimed in claim 15, comprise further by the voltage of each LED strip second end compared with short-circuit threshold value, when the voltage of certain LED strip second end is greater than short-circuit threshold value, forbid this LED strip.
19. fault protecting methods as claimed in claim 15, wherein forbidding electric current is that the method for the LED strip of zero comprises:
By feedback signal compared with overvoltage threshold, produce the first overvoltage fault-signal;
Based on the second overvoltage fault-signal with characterize the mode signal whether overvoltage threshold is default value, produce control signal; And
Based on control signal, the first overvoltage fault-signal and open circuit detection signal, produce the triggering signal of forbidding or enable each LED strip.
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| CN114079266A (en) * | 2020-08-18 | 2022-02-22 | 广东美的制冷设备有限公司 | High-voltage integrated module, intelligent power module, control method of intelligent power module and air conditioner |
| CN112333888A (en) * | 2020-11-23 | 2021-02-05 | 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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