CN104185350B - Multipath LED constant current drive circuit and its control method - Google Patents
Multipath LED constant current drive circuit and its control method Download PDFInfo
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- CN104185350B CN104185350B CN201410465582.0A CN201410465582A CN104185350B CN 104185350 B CN104185350 B CN 104185350B CN 201410465582 A CN201410465582 A CN 201410465582A CN 104185350 B CN104185350 B CN 104185350B
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Abstract
Disclose a kind of multipath LED constant current drive circuit and its control method.The multipath LED constant current drive circuit is used for the multi-way LED lamp for driving multiple output channels, including：Voltage regulator, for receiving input voltage and public output voltage being provided to multiple output channels；Multiple current control modules, are separately positioned in multiple output channels, the driving current for adjusting multiple output channels respectively；And minimum voltage selecting module, it is arranged on the feedback control loop of voltage regulator, for selecting minimum sampled voltage from the sampled voltage of multiple output channels, and minimum sampled voltage is supplied to voltage regulator, wherein, voltage regulator adjusts output voltage according to minimum sampled voltage, and multiple current control modules provide switching signal to minimum voltage selecting module respectively, for sampled voltage to be selectively accessing into feedback control loop.The multipath LED constant current drive circuit improves reliability and conversion efficiency, and allows the LED that is individually replaced failure.
Description
Technical field
The present invention relates to field of power supplies, more specifically to a kind of multipath LED constant current drive circuit and its controlling party
Method.
Background technology
In illumination and backlight application, often multi-way LED lamp serial or parallel connection is used, includes one per paths of LEDs lamp
Or multiple LEDs being connected in series.Due to the LED characteristics of luminescence, LED luminous intensity is determined by the electric current for flowing through LED.It is existing
Constant current driver circuit for LED be independently adjusted the electric current of each paths of LEDs lamp, by controlling the electric current per paths of LEDs constant, remain stable
Luminous intensity.
In a kind of multipath LED constant current drive scheme, using multiple independent voltage changers, distinguish to multi-way LED lamp
Each required output voltage and constant driving current are provided.The multipath LED constant current drive scheme is used for multi-way LED lamp
Multiple independent voltage changers, as a result cause the cost height of driving chip, volume big and inefficient.
In another multipath LED constant current drive scheme, multi-way LED lamp is connected in parallel, voltage changer, which is provided, to be used for
The common driver of multi-way LED lamp is driven to move voltage.Connected respectively respective current control module per paths of LEDs lamp.Current control mould
Block adjusts the electric current for flowing through every paths of LEDs lamp, so as to maintain the luminance balance of every paths of LEDs lamp.The multipath LED constant current drive scheme pin
Voltage changer is shared to multi-way LED lamp, so as to advantageously reduce the cost and volume of driving chip.
However, in the multipath LED constant current drive scheme of above-mentioned shared voltage changer, voltage changer is according to maximum
Load regulation output voltage.If open circuit occurs for certain paths of LEDs lamp, voltage changer improves output voltage as much as possible, as a result
Output voltage is out of control.
In the case of output voltage is out of control, the loss of multipath LED constant current drive circuit is big, inefficiency, or even leads
Cause multipath LED constant current drive circuit and/or damaged as the LED of load because output voltage is too high.
The content of the invention
In view of this, the invention provides a kind of multipath LED constant current drive circuit and its control method, the LED multi-path is permanent
Stream drive circuit for load disconnect situation provide protection against so that improve LED constant-current drive circuits reliability and
Conversion efficiency.
According to an aspect of the present invention there is provided a kind of multipath LED constant current drive circuit, for driving multiple output channels
Multi-way LED lamp, the multipath LED constant current drive circuit includes：Voltage regulator, for receiving input voltage and to multiple defeated
Go out passage and public output voltage is provided；Multiple current control modules, are separately positioned in the multiple output channel, for dividing
The driving current of the multiple output channel is not adjusted；And minimum voltage selecting module, it is arranged on the voltage regulator
On feedback control loop, sampled for selecting minimum sampled voltage from the sampled voltage of the multiple output channel, and by minimum
Voltage is supplied to voltage regulator, wherein, the voltage regulator adjusts output voltage according to minimum sampled voltage, the multiple
Current control module provides switching signal to the minimum voltage selecting module respectively so that when LED accesses output channel,
The sampled voltage of corresponding output channel is accessed feedback control loop by minimum voltage selecting module, when LED disconnects from output channel,
Minimum voltage selecting module disconnects the sampled voltage of corresponding output channel from feedback control loop.
Preferably, the minimum voltage selecting module includes：Voltage source；Multiple diodes；And multiple switch, wherein,
Between voltage source and each output channel of the multiple output channel, it is connected in series corresponding in the multiple diode
A corresponding switch in one diode and the multiple switch.
Preferably, the anode of each diode in the multiple diode is connected to voltage source.
Preferably, each current control module in the multiple current control module includes constant-current control circuit, described
Constant-current control circuit includes：The first transistor, the first transistor includes first end, the second end and control end, described the
Electric current flow to the second end from first end during one transistor turns；Sampling resistor, the sampling resistor and the first transistor string
Connection connection；And first operational amplifier, the first input end of first operational amplifier receives the sampling electricity of sampling resistor
Pressure, the second input receives reference current, and output end is connected to the control end of the first transistor.
Preferably, the constant-current control circuit also includes being connected in parallel between the first end of the first transistor and the second end
The first current source.
Preferably, the electric current that first current source is provided is 10uA to 200uA.
Preferably, the constant-current control module also includes switching signal generative circuit, the switching signal generative circuit bag
Include：Second operational amplifier, the first input end of second operational amplifier receives first threshold voltage, and the second input connects
It is connected to the first end of the first transistor；3rd operational amplifier, the first input end of the 3rd operational amplifier is connected to
The first end of one transistor, the second input receives second threshold voltage；Rest-set flip-flop, the reset terminal of the rest-set flip-flop is received
The output signal of second operational amplifier, set end connection receives the output signal of the 3rd operational amplifier, and output end provides institute
State switching signal；And delay circuit, the delay circuit be connected to the second operational amplifier output end and RS triggering device
Reset terminal between.
Preferably, the first input end of second operational amplifier and the 3rd operational amplifier is in-phase end, described the
Second input of two operational amplifiers and the 3rd operational amplifier is end of oppisite phase.
Preferably, first threshold voltage is less than second threshold voltage.
Preferably, the constant-current control module also includes soft starting circuit, and the soft starting circuit includes：Second crystal
Pipe, the second transistor includes first end, the second end and control end, and when the second transistor is turned on, electric current is from first end
It flow to the second end；The second current source being connected in series with the second transistor；And it is connected in the of second transistor in parallel
Electric capacity between one end and the second end, wherein, the control end of the second transistor receives corresponding constant-current control module respectively
Switching signal.
Preferably, the soft starting circuit also includes：Third transistor, the third transistor includes first end, second
End and control end, when the third transistor is turned on, electric current flow to the second end from first end；Wherein, the second transistor and
The control end of the third transistor receives the switching signal of corresponding constant-current control module, the of the third transistor respectively
One end is connected to the control end of the first transistor, and the second end of the third transistor is connected to the first transistor
Second end.
It is many for driving according to another aspect of the present invention there is provided a kind of control method of multipath LED constant current drive circuit
The multi-way LED lamp of individual output channel, methods described includes：Public output voltage is provided to multiple output channels；And use
Multiple current control modules adjust the driving current of the multiple output channel respectively；Wherein, output channel is accessed in LED
When, the sampled voltage of corresponding output channel is accessed into feedback control loop；And when LED disconnects from output channel, will be corresponding defeated
The sampled voltage for going out passage disconnects from feedback control loop.
Preferably, methods described also includes judging that LED accesses output channel according to sampled voltage, and the judgement includes：
Detect whether sampled voltage is more than first threshold voltage；In the case of sampled voltage is more than first threshold voltage, by delay
After time, further whether detection sampled voltage is more than second threshold voltage, and second threshold voltage is more than first threshold voltage；
In the case of sampled voltage is more than both first threshold voltage and second threshold voltage, LED access output channel is confirmed.
Preferably, methods described also includes judging that LED disconnects from output channel according to sampled voltage, described to judge bag
Include：Detect whether sampled voltage is less than first threshold voltage；In the case of sampled voltage is less than first threshold voltage, by prolonging
After the slow time, further whether detection sampled voltage is less than second threshold voltage, and second threshold voltage is more than first threshold electricity
Pressure；In the case of sampled voltage is less than both first threshold voltage and second threshold voltage, confirm that LED is disconnected from output channel
Open.
Multipath LED constant current drive circuit and its control method, do not have when LED disconnects according to an embodiment of the invention
Output channel is permanently closed, but the sampled voltage of corresponding output channel is broken from feedback control loop.In LED from disconnected
When open state is accessed again, the sampled voltage of corresponding output channel is accessed into feedback control loop again.
Therefore, the protection work(disconnected for LED is provide not only according to the multipath LED constant current drive circuit of the present invention
Can, and allow the access again of LED, consequently facilitating being individually replaced the LED of failure.
In a preferred embodiment, in the constant-current control circuit of current control module, in addition to it is connected in first in parallel
The first current source between the first end of transistor and the second end.Even if sampled voltage is raised caused by interference, due to the first electricity
The presence in stream source, can drag down this interference voltage, so that the problem of the driving that will not make a mistake.
In a preferred embodiment, in the constant-current control circuit of current control module, in addition to soft starting circuit.It is soft to open
Dynamic circuit can use the charge-discharge circuit of transistor AND gate capacitance connection.Connect again from off-state detecting LED
It is fashionable, the soft starting circuit of current control module in corresponding output channel is driven again, in order to avoid the overtension of output.
Brief description of the drawings
By description referring to the drawings to the embodiment of the present invention, above-mentioned and other purposes of the invention, feature and
Advantage will be apparent from, in the accompanying drawings：
Fig. 1 is the schematic circuit of existing multipath LED constant current drive circuit；
Fig. 2 is the illustrative circuitry of the current control module used in the multipath LED constant current drive circuit shown in Fig. 1
Figure；
Fig. 3 is the schematic electricity of the minimum voltage selecting module used in the multipath LED constant current drive circuit shown in Fig. 1
Lu Tu；
Fig. 4 is the schematic circuit of the multipath LED constant current drive circuit according to the present invention；
Fig. 5 is the schematic electricity of the minimum voltage selecting module used in the multipath LED constant current drive circuit shown in Fig. 4
Lu Tu；
Fig. 6 is the current control module signal of the first example used in the multipath LED constant current drive circuit shown in Fig. 4
Property circuit diagram；
Fig. 7 is the current control module signal of the second example used in the multipath LED constant current drive circuit shown in Fig. 4
Property circuit diagram；
Fig. 8 is the oscillogram of the multipath LED constant current drive circuit according to the present invention；And
Fig. 9 is the flow chart of the control method of the multipath LED constant current drive circuit according to the present invention.
Embodiment
Several preferred embodiments of the present invention are described in detail below in conjunction with accompanying drawing, but the present invention is not restricted to
These embodiments.The present invention covers any replacement made in the spirit and scope of the present invention, modification, equivalent method and side
Case.
Thoroughly understand in order that the public has to the present invention, be described in detail in present invention below preferred embodiment specific
Details, and description without these details can also understand the present invention completely for a person skilled in the art.
Fig. 1 is the schematic circuit of existing multipath LED constant current drive circuit 100.Each of LED1 into LEDn
Including multiple LED being connected in series.Then, LED1 to LEDn is connected in parallel as multipath LED constant current drive circuit 100
Load, formed N paths of LEDs lamps.The multipath LED constant current drive circuit 100 includes voltage regulator 101, for adjusting N respectively
N number of current control module 102-1 of paths of LEDs lamp obtains sampled voltage to provide minimum sampled voltage to 102-n, from N paths of LEDs lamp
Minimum voltage selecting module 103, minimum sampled voltage compared to provide the operation amplifier of feedback voltage with reference voltage
Device 104.
Voltage regulator 101 receives input voltage vin and produces output voltage Vout.Output voltage Vout should expire
Sufficient LED and current control module 102-1 to 102-n operating voltage requirement.In actual circuit, voltage regulator 101
Feedback control actually depend on the LED all the way (i.e. voltage drop maximum load all the way) of minimum sampled voltage.
Current control module 102-1 to 102-n adjusts the electric current for flowing through every paths of LEDs lamp, one of electric current control respectively
Molding block 102-1 is as shown in Figure 2.Current control module 102-1 includes transistor Q11, sampling resistor R11 and operational amplifier
A11.Transistor Q11 and sampling resistor R11 are connected in series between LED and ground.Transistor Q1 first end and LED phase
Even, the second end is connected with sampling resistor R11.The end of oppisite phase of operational amplifier A 11 is connected to transistor Q11 and sampling resistor R11
Intermediate node, the in-phase end of operational amplifier A 11 receives reference current Iref, and the output end of operational amplifier A 11 is connected to
Transistor Q11 control end.The output end output error current signal of operational amplifier A 11.According to error current Signal Regulation
Transistor Q11 conducting state so that the electric current for flowing through transistor Q11 maintains the steady state value corresponding with reference current Iref.
Minimum voltage selecting module 103 selects minimum sampled voltage.Minimum voltage selecting module 103 is for example including voltage source
Vcc, N number of diode D21 to D2n and resistance R21, as shown in Figure 3.N number of diode D21 to D2n negative electrode is respectively connecting to respectively
From LED and respective current control module intermediate node, anode is connected to intermediate node.The intermediate node is connected to fortune
Calculate the first input end of amplifier 104.The intermediate node is also connected to voltage source Vcc via resistance R21.Minimum voltage selects mould
Minimum sampled voltage Vmin of the block 103 substantially by the voltage clamp of intermediate node in the N paths of LEDs lamp.
The first input end of operational amplifier 104 receives minimum sampled voltage Vmin, and the second input receives reference voltage
Vref, output end provides feedback signal Vfb.Feedback voltage meets following relation, Vfb=K* (Vref- with minimum sampled voltage
Vmin), wherein K is the gain of operational amplifier 104.
Above-mentioned multipath LED constant current drive circuit 100 can provide the output voltage and driving current needed for each paths of LEDs lamp.
However, if open circuit occurs for certain paths of LEDs lamp, corresponding sampled voltage is 0.Minimum voltage selecting module 103 selects 0V conducts
Minimum sampled voltage, causes that the output voltage Vout of voltage regulator 101 is out of control and output voltage Vout is too high.As a result, connect
It will overheat and even damage in other LEDs of multipath LED constant current drive circuit 100.
In order to solve the problem of voltage is out of control when LED disconnects, if untapped defeated known to circuit configuration phase
Go out passage, then the hot end of corresponding output channel can be grounded.If in addition, circuit work during LED open circuit,
It can further detect whether the sampled voltage of corresponding output channel is close to 0., can be with if sampled voltage is close to 0
Corresponding output channel is disconnected at minimum voltage selecting module 103.
In the existing improvement project of both the above, corresponding output channel is permanently closed when LED disconnects.Even if
Access LED again in the output channel, can not also reactivate the output channel.Prior art selection is permanently closed
Corresponding output, the problem of mainly considering external interference, because external interference is likely to result in the road voltage rise (being more than zero), if
Now drive corresponding output then to cause fault again, therefore permanent closing can only be selected.
Fig. 4 is the schematic circuit of the multipath LED constant current drive circuit according to the present invention.The multipath LED constant current drives
Dynamic circuit 200 include voltage regulator 101, N number of current control module 102-1 to 102-n for adjusting N paths of LEDs lamps respectively,
Sampled voltage is obtained from N paths of LEDs lamp to provide the minimum voltage selecting module 103 of minimum sampled voltage, by minimum sampled voltage
To provide the operational amplifier 104 of feedback voltage compared with reference voltage.
Voltage regulator 101 receives input voltage vin and produces output voltage Vout.Output voltage Vout should expire
Sufficient LED and current control module 102-1 to 102-n operating voltage requirement.In actual circuit, voltage regulator 101
Feedback control actually depend on the LED all the way (i.e. voltage drop maximum load all the way) of minimum sampled voltage.
It is different from the multipath LED constant current drive circuit 100 according to prior art shown in Fig. 1, current control module 102-1
To 102-n, not only regulation flows through the electric current of every paths of LEDs lamp respectively, and provide N number of switch letter to minimum voltage selecting module 103
Number K1 to Kn.
Minimum voltage selecting module 103 for example including voltage source Vcc, N number of diode D21 to D2n, N number of switch S21 extremely
S2n and resistance R21, as shown in Figure 5.N number of diode D21 to D2n connects respectively with N number of switch S21 to S2n so that N number of two pole
Pipe D21 to D2n negative electrode switchs the LED that is each connected to and respective current control module via corresponding one respectively
Intermediate node, N number of diode D21 to D2n anode is connected to intermediate node.The intermediate node is connected to operational amplifier 104
First input end.The intermediate node is also connected to voltage source Vcc via resistance R21.The switch of N number of switch S21 to S2n
State is by N number of switching signal K1 to Kn controls.Minimum voltage selecting module 103 is substantially by the voltage clamp of intermediate node in described
Minimum sampled voltage in N paths of LEDs lamps.During the work of multipath LED constant current drive circuit 200, if it is defeated to detect certain road
Go out the sampled voltage of passage close to 0, then corresponding current control modules of the current control module 102-1 into 102-n judges that this is adopted
The generation of sample voltage is due to that LED disconnections are also due to interference signal, and according to the switch of judged result output varying level
Signal.For example, the switching signal of high level represents that switch should be closed, low level switching signal represents that switch should disconnect.
N number of switch S21 to S2n in minimum voltage selecting module 103 is selectively closed off or disconnected according to switching signal, so that by phase
The sampled voltage for the output channel answered is switched in or out minimum voltage selecting module 103.
In addition, during the work of multipath LED constant current drive circuit 200, if the LED of certain road output channel connects again
Enter, then corresponding current control modules of the current control module 102-1 into 102-n will detect that normal sampled voltage, example
Such as export the switching signal of high level.Corresponding switch closure in minimum voltage selecting module 103, so that will be corresponding defeated
The sampled voltage for going out passage accesses minimum voltage selecting module 103 again.
In the multipath LED constant current drive circuit 200 according to the present invention, do not closed permanently when LED disconnects
Output channel, but the sampled voltage of corresponding output channel is broken from feedback control loop.When LED is accessed again, by phase
The sampled voltage of output channel is answered to access feedback control loop again.Therefore, according to the multipath LED constant current drive circuit 200 of the present invention
The defencive function disconnected for LED is provide not only, and allows the access again of LED, consequently facilitating being individually replaced out
The LED of existing failure.
According to other aspects of the multipath LED constant current drive circuit 200 of the present invention with shown in Fig. 1 according to prior art
Multipath LED constant current drive circuit 100 is identical, thus repeats no more for brevity.
Fig. 6 is the current control module of the first example used in the multipath LED constant current drive circuit 200 shown in Fig. 4
Schematic circuit.Figure 6 illustrates current control module 102-1 be, for example, N number of current control module 102-1 to 102-n
In one, flow through the electric current of LED all the way for adjusting.Current control module 102-1 includes being used to provide constant current
Transistor Q11, sampling resistor R11 and operational amplifier A 11, and put for providing switching signal K1 current source I11, computing
Big device A12 and A14, delay circuit A13 and rest-set flip-flop A15.
Transistor Q11 and sampling resistor R11 are connected in series between LED and ground.Transistor Q1 first end and LED
It is connected, the second end is connected with sampling resistor R11.The end of oppisite phase of operational amplifier A 11 is connected to transistor Q11 and sampling resistor
R11 intermediate node, the in-phase end of operational amplifier A 11 receives reference current Iref, the output end connection of operational amplifier A 11
To transistor Q11 control end.The output end output error current signal of operational amplifier A 11.Adjusted according to error current signal
Save transistor Q11 conducting state so that the electric current for flowing through transistor Q11 remains corresponding with reference current Iref constant
Value.
Sampled voltage can be obtained in transistor Q11 first end and the second end.In the example depicted in fig. 6, in crystalline substance
Body pipe Q11 first end obtains sampled voltage VLED1.Current source I11 is connected in transistor Q11 first end and the second end in parallel
Between.Current source I11 allows the influence that current control module 1021 excludes the interference signal.Even if caused by interference signal
Sampled voltage VLED1 is raised, and due to current source I11 presence, can be dragged down this interference signal, so as to will not make a mistake
The problem of driving.
The end of oppisite phase of operational amplifier A 12 is connected to receive sampled voltage VLED1, same phase with transistor Q11 first end
End receives first threshold voltage Vref1, and output end is connected to rest-set flip-flop A15 reset terminal R via delay circuit A13.Computing
Amplifier A14 in-phase end is connected with transistor Q11 first end to receive sampled voltage VLED1, and end of oppisite phase receives the second threshold
Threshold voltage Vref2, output end is connected directly to rest-set flip-flop A15 set end S.Due to the characteristic of rest-set flip-flop, only working as
The sampled voltage VLED1 at preceding moment is more than second threshold voltage (such as 3V) and the sampled voltage VLED1 of previous moment is more than
First threshold voltage (such as 0.1V), the switching signal K1 of rest-set flip-flop A15 outputs is just high level, to indicate to believe the sampling
Number VLED1 access minimum voltage selecting module 103.Delay circuit A13 determines current time and the period of previous moment.
Fig. 7 is the current control module of the second example used in the multipath LED constant current drive circuit 200 shown in Fig. 4
Schematic circuit.Figure 7 illustrates current control module 102-1 be, for example, N number of current control module 102-1 to 102-n
In one, flow through the electric current of LED all the way for adjusting.Current control module 102-1 includes being used to provide constant current
Transistor Q11, sampling resistor R11 and operational amplifier A 11, and put for providing switching signal K1 current source I11, computing
Big device A12 and A14, delay circuit A13 and rest-set flip-flop A15.
According to the current control module 102-1 of the second example with according to the current control module 102-1 of the first example not
It is that current control module 102-1 also includes current source I12, electric capacity C11, transistor Q12 and the crystalline substance for soft start with part
Body pipe Q13.Current source I12 and transistor Q12 are connected between power supply and ground.Transistor Q12 first end and current source
I12 is connected, and the second end ground connection, control end receives switching signal K1.Current source I12 and transistor Q12 intermediate node provide base
Quasi- electric current Iref.Transistor Q13 first end is connected with transistor Q11 control end, the second end and transistor Q11 the second end
It is connected, control end receives switching signal K1.
The state disconnected in LED, the switching signal K1 of current control module 102-1 outputs is always low level, crystal
Pipe Q12 and Q13 are both turned on.Correspondingly, electric capacity C11 is uncharged, and transistor Q11 disconnects.When LED is accessed, switch letter
Number K1 is changed into high level, and transistor Q12 and Q13 disconnect, and current source I12 charges to electric capacity C11, gradually steps up operation amplifier
The current potential of device A11 in-phase end, until reaching reference current Iref, so as to realize current control module 102-1 soft start.
Other aspects of the current control module 102-1 according to the second example shown in Fig. 7 with shown in Fig. 6 according to first
The current control module 102-1 of example is identical, thus repeats no more for brevity.
Below with reference to the flow chart shown in the oscillogram and Fig. 9 shown in Fig. 8, basis as shown in Figure 4 is further illustrated
The control method of the multipath LED constant current drive circuit 200 of the present invention.The current control mould of the multipath LED constant current drive circuit 200
Block 102-1 to 102-n is as shown in Figure 7.
The two-way output channel of multipath LED constant current drive circuit 200 is only described as example.In two-way output channel
In, LED1 connects the load as multipath LED constant current drive circuit 200 all the time, and LEDx is in multipath LED constant current drive circuit 200
Working condition in dynamic access or disconnection.
In moment t0, multipath LED constant current drive circuit 200 performs step S01, wherein system electrification.
During moment t0 to t3, multipath LED constant current drive circuit 200 performs step S02, wherein system soft start.
Since moment t0, the output voltage Vout of voltage changer 101 is gradually increasing.Correspondingly, accessed
LED1 sampled voltage VLED1 is gradually increasing.Because LEDx is not accessed, therefore in this step, VLEDx and ILEDx are kept
For 0.
In moment t1, in the current control module 102-1 connected with LED1, current source I11 starts working.Current source
The electric current that I11 is provided is 10uA to 200uA, for example, provide 50uA constant current, i.e. ILED1=50uA.
In moment t2, VLED1 reaches startup threshold values (i.e. second threshold voltage Vref2, such as 3V), and current source I12 is to electricity
Hold C11 chargings, so that soft start current control module 102-1.
In moment t3, current control module 102-1 soft start is completed, and sampled voltage VLED1 is accessed into feedback control loop.
In step S03, in the working condition of multipath LED constant current drive circuit 200, whether detection LEDx accesses.
In moment t4, LEDx access.In the current control module 102-x connected with LEDx, current source Ix1 starts work
Make, for example, 50uA constant current, i.e. ILEDx=50uA are provided.
In moment t5, VLEDx reaches that (i.e. VLEDx is simultaneously greater than first threshold voltage Vref1 and Second Threshold to startup threshold values
Voltage Vref2, first threshold voltage Vref1 are, for example, 0.1V, and second threshold voltage Vref2 is, for example, 3V), current source Ix2 to
Electric capacity Cx1 charges, so that soft start current control module 102-x.
In moment t6, current control module 102-x soft start is completed.
During moment t4 to t6, multipath LED constant current drive circuit 200 performs step S04-S06.As VLEDx ＞ 0.1v,
Next step is carried out, detection again is confirmed whether VLEDx ＞ 3v, if then judging load access, and sampled voltage VLEDx is connect
Enter feedback control loop.Due to current source Ix1 presence,
Disconnected in moment t7, LEDx.Because LEDx is not accessed, therefore VLEDx and ILED quickly change into 0.
During a period of time after moment t7, multipath LED constant current drive circuit 200 performs step S04 and S08-
S10.As VLEDx≤0.1v, after tamper-resistant time, next step is carried out, detection again is confirmed whether VLEDx≤0.1v,
If then judging that load disconnects, and sampled voltage VLEDx is disconnected from feedback control loop.
According to embodiments of the invention as described above, these embodiments do not have all details of detailed descriptionthe, not yet
It is only described specific embodiment to limit the invention.Obviously, as described above, it can make many modifications and variations.This explanation
Book is chosen and specifically describes these embodiments, is in order to preferably explain the principle and practical application of the present invention, so that affiliated
Technical field technical staff can be used using modification of the invention and on the basis of the present invention well.The present invention is only by right
The limitation of claim and its four corner and equivalent.
Claims (14)
1. a kind of multipath LED constant current drive circuit, the multi-way LED lamp for driving multiple output channels, the multipath LED constant current
Drive circuit includes：
Voltage regulator, for receiving input voltage and public output voltage being provided to multiple output channels；
Multiple current control modules, are separately positioned in the multiple output channel, logical for adjusting the multiple output respectively
The driving current in road, and judge whether LED accesses output channel to produce switching signal according to sampled voltage；And
It is logical for receiving the multiple output on minimum voltage selecting module, the feedback control loop for being arranged on the voltage regulator
The sampled voltage in road, and select minimum sampling electric in the sampled voltage of at least some output channels from the multiple output channel
Pressure is supplied to voltage regulator,
Wherein, the multiple current control module provides switching signal to the minimum voltage selecting module respectively so that in LED
When lamp accesses output channel, the sampled voltage of corresponding output channel is accessed feedback control loop by minimum voltage selecting module, in LED
When being disconnected from output channel, minimum voltage selecting module disconnects the sampled voltage of corresponding output channel from feedback control loop, in LED
Lamp from off-state access again when, the sampled voltage of corresponding output channel is accessed feedback loop by minimum voltage selecting module again
Road,
The voltage regulator adjusts the public output voltage according to minimum sampled voltage.
2. multipath LED constant current drive circuit according to claim 1, wherein, the minimum voltage selecting module includes：
Voltage source；
Multiple diodes；And
Multiple switch,
Wherein, between voltage source and each output channel of the multiple output channel, it is connected in series the multiple two pole
A corresponding switch in a corresponding diode and the multiple switch in pipe.
3. multipath LED constant current drive circuit according to claim 2, wherein each two pole in the multiple diode
The anode of pipe is connected to voltage source.
4. multipath LED constant current drive circuit according to claim 1, wherein, it is every in the multiple current control module
Individual current control module includes constant-current control circuit, and the constant-current control circuit includes：
The first transistor, the first transistor includes first end, the second end and control end, when the first transistor is turned on
Electric current flow to the second end from first end；
Sampling resistor, the sampling resistor is connected in series with the first transistor；And
First operational amplifier, the first input end of first operational amplifier receives the sampled voltage of sampling resistor, second
Input receives reference current, and output end is connected to the control end of the first transistor.
5. multipath LED constant current drive circuit according to claim 4, wherein, the constant-current control circuit also includes parallel connection
It is connected to the first current source between the first end of the first transistor and the second end.
6. multipath LED constant current drive circuit according to claim 5, wherein, the electric current that first current source is provided is
10uA to 200uA.
7. multipath LED constant current drive circuit according to claim 4, wherein, the constant-current control circuit also includes switch
Signal generating circuit, the switching signal generative circuit includes：
Second operational amplifier, the first input end of second operational amplifier receives first threshold voltage, the second input
It is connected to the first end of the first transistor；
3rd operational amplifier, the first input end of the 3rd operational amplifier is connected to the first end of the first transistor, the
Two inputs receive second threshold voltage；
Rest-set flip-flop, the reset terminal of the rest-set flip-flop receives the output signal of the second operational amplifier, and set end connection is received
The output signal of 3rd operational amplifier, output end provides the switching signal；And
Delay circuit, the delay circuit is connected between the output end of the second operational amplifier and the reset terminal of rest-set flip-flop.
8. multipath LED constant current drive circuit according to claim 7, wherein, second operational amplifier and the 3rd fortune
The first input end for calculating amplifier is in-phase end, and the second input of second operational amplifier and the 3rd operational amplifier is
End of oppisite phase.
9. multipath LED constant current drive circuit according to claim 8, wherein, first threshold voltage is less than Second Threshold electricity
Pressure.
10. multipath LED constant current drive circuit according to claim 4, wherein, the constant-current control circuit also includes soft
Start-up circuit, the soft starting circuit includes：
Second transistor, the second transistor includes first end, the second end and control end, when the second transistor is turned on
Electric current flow to the second end from first end；
The second current source being connected in series with the second transistor；And
It is connected in the electric capacity between the first end of second transistor and the second end in parallel,
Wherein, the control end of the second transistor receives the switching signal of corresponding constant-current control circuit respectively.
11. multipath LED constant current drive circuit according to claim 10, wherein the soft starting circuit also includes：
Third transistor, the third transistor includes first end, the second end and control end, when the third transistor is turned on
Electric current flow to the second end from first end；
Wherein, the control end of the second transistor and the third transistor receives opening for corresponding constant-current control circuit respectively
OFF signal,
The first end of the third transistor is connected to the control end of the first transistor, the second end of the third transistor
It is connected to the second end of the first transistor.
12. a kind of control method of multipath LED constant current drive circuit, the multi-way LED lamp for driving multiple output channels is described
Method includes：
Public output voltage is provided to multiple output channels；
Adjust the driving current of the multiple output channel respectively using multiple current control modules；
On feedback control loop, minimum is selected to adopt from the sampled voltage of at least some output channels in the multiple output channel
Sample voltage；
Judge whether LED accesses output channel to produce switching signal according to sampled voltage；And
The public output voltage is adjusted according to minimum sampled voltage,
Wherein, when LED accesses output channel, the sampled voltage of corresponding output channel is accessed into feedback control loop,
When LED disconnects from output channel, the sampled voltage of corresponding output channel is disconnected from feedback control loop, and
When LED is accessed again from off-state, the sampled voltage of corresponding output channel is accessed into feedback control loop again.
13. control method according to claim 12, the judgement includes：
Detect whether sampled voltage is more than first threshold voltage；
In the case of sampled voltage is more than first threshold voltage, after time delay, further detection sampled voltage is
No to be more than second threshold voltage, second threshold voltage is more than first threshold voltage；
In the case of sampled voltage is more than both first threshold voltage and second threshold voltage, confirm that LED access output is logical
Road.
14. the control method according to claim 12 or 13, the judgement includes：
Detect whether sampled voltage is less than first threshold voltage；
In the case of sampled voltage is less than first threshold voltage, after time delay, further detection sampled voltage is
No to be less than second threshold voltage, second threshold voltage is more than first threshold voltage；
In the case of sampled voltage is less than both first threshold voltage and second threshold voltage, confirm LED from output channel
Disconnect.
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| CN104537982B (en) * | 2014-12-22 | 2016-10-05 | 苏州佳世达电通有限公司 | Display |
| CN104578326B (en) | 2015-02-06 | 2017-09-15 | 南京矽力杰半导体技术有限公司 | Control circuit, integrated circuit, switched mode converter and constant current control method |
| CN106163027B (en) * | 2015-03-26 | 2018-12-04 | 苏州璨宇光学有限公司 | Light source drive device and light source driving method |
| CN104822198B (en) * | 2015-04-20 | 2017-12-05 | 南京矽力杰半导体技术有限公司 | A kind of control circuit and control method of LED multi-path lamp string |
| CN105142293B (en) * | 2015-09-16 | 2017-12-26 | 英特格灵芯片(天津)有限公司 | A kind of feedback driving circuit |
| CN105657899B (en) * | 2016-02-22 | 2017-12-05 | 南京矽力杰半导体技术有限公司 | Multipath LED constant current drive circuit and its control method |
| KR102345096B1 (en) * | 2017-03-21 | 2021-12-30 | 현대자동차주식회사 | Current control apparatus, Vehicle having the same |
| CN109769323A (en) * | 2019-03-25 | 2019-05-17 | 杭州士兰微电子股份有限公司 | A kind of LED drive circuit and control method |
| DE102019113864B4 (en) * | 2019-05-23 | 2023-06-15 | Elmos Semiconductor Se | Process for controlling the output voltage of a voltage regulator |
| CN111586936B (en) * | 2020-05-28 | 2023-04-07 | 歌尔科技有限公司 | Multi-path constant current driving circuit and multi-path constant current driving device |
| CN111712018B (en) * | 2020-06-30 | 2021-12-07 | 深圳市微源半导体股份有限公司 | Multichannel LED drive circuit with open-circuit fault detection function |
| CN113727487B (en) * | 2020-10-22 | 2023-06-23 | 杰华特微电子股份有限公司 | Driving method and driving circuit for multi-channel LED lamp string |
| US11923711B2 (en) * | 2021-10-14 | 2024-03-05 | Amogy Inc. | Power management for hybrid power system |
| CN114399978B (en) * | 2022-03-24 | 2022-07-01 | 南京浣轩半导体有限公司 | Control method and system for dynamic energy saving of LED backlight |
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