CN102281665B - Control circuit, light-emitting diode driver using control circuit and control method - Google Patents
Control circuit, light-emitting diode driver using control circuit and control method Download PDFInfo
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Abstract
The invention relates to a control circuit, a light-emitting diode driver using the control circuit and a control method. The control circuit applied to the light-emitting diode (LED) driver comprises a counter, a sampling circuit and a signal source circuit. The counter responds to the Front Edge of a brightness control signal to calculate count parameters for indicating the working period length of the brightness control signal. The sampling circuit responds to the Rear Edge of the brightness control signal to sample the most significant bit (MSB) of the count parameters so as to obtain a sampled signal. When the sampled signal corresponds to a termination value and a start value, the sampled signal represents that the working period length is greater than a time threshold value and is smaller than the time threshold value respectively. The signal source circuit responds to the termination value and the start value of a first sampled signal to provide reference voltage signals corresponding to a second level and a first level (lower than the second level) respectively so as to drive a Boost Converter of the LED driver.
Description
Technical field
The present invention relates to a kind of control circuit, and relate to especially one and be applied to the control circuit in light-emitting diode (Light Emitting Diode, LED) driver.
Background technology
In the epoch now of making rapid progress in development in science and technology, LED drive has been developed the life with convenient people.In an application example, LED is applied in flat-panel screens as back light.In general, LED light source module is used booster driving circuit (Boost Converter), comes to produce driving voltage in response to brightness control signal, so that LED light source module is driven.For instance, brightness control signal (Dimming) is pulse wave width modulation (Pulse Width Modulate, PWM) signal, and this booster driving circuit is activation in the duration of work (Duty Cycle) of pwm signal, to produce accordingly driving voltage.
But in practical situations, the operation that booster driving circuit produces driving voltage cannot provide stable driving voltage because the duration of work of brightness control signal (Dimming) is too short often; So, also make jointly LED light source module that stable brightness cannot be provided, make the situation of flat-panel screens generation display frame flicker.So, how designing the LED driver of stabilized driving voltage can be provided is one of direction of constantly endeavouring of industry.
Summary of the invention
According to an aspect of the present invention, a kind of control circuit is proposed, be applied in LED driver, optionally to control the position standard of reference voltage signal, LED drive circuit comprises booster driving circuit (Boost Converter), in order to according to reference voltage signal and brilliance control (Dimming) signal driver LED circuit.Control circuit comprises counter, sample circuit and signal source circuit.Counter is in response to leading edge (Front Edge) the count parameter of brightness control signal, and to indicate the duration of work length of brightness control signal, count parameter comprises n position, and n is greater than 1 integer.Sample circuit samples and obtains the first sampled signal the MSB in n position in response to the trailing edge (Rear Edge) of brightness control signal.In the time that the first sampled signal corresponds to termination numerical value, represent that duration of work length is more than or equal to very first time threshold, in the time that the first sampled signal corresponds to initial numerical value, represent that duration of work length is less than very first time threshold.Signal source circuit provides in response to the termination numerical value of the first sampled signal the reference voltage signal that corresponds to second voltage position standard, and the initial numerical value that responds the first sampled signal provides the reference voltage signal that corresponds to the first voltage level.The first voltage level is lower than second voltage position standard.
According to control circuit of the present invention, also comprise: logical circuit, in order to logical addition is carried out in described n position, to produce control signal; And first multiplexer, receive described control signal and described MSB, and be coupled to described sample circuit, described the first multiplexer provides described MSB to described sample circuit in response to the described termination numerical value of described the first sampled signal, and controls signal to described sample circuit described in providing in response to the described initial numerical value of described the first sampled signal.
Preferably, in this control circuit, described sample circuit also samples and obtains the second sampled signal described control signal in order to the trailing edge in response to described brightness control signal, in the time that described the second sampled signal corresponds to described termination numerical value, represent that described duration of work length is more than or equal to described the second time threshold, described signal source circuit provides in response to the described termination numerical value of described the second sampled signal the described reference voltage signal that corresponds to described the first voltage level.
Preferably, in this control circuit, described sample circuit also samples and obtains the second sampled signal described control signal in order to the trailing edge in response to described brightness control signal, in the time that described the second sampled signal corresponds to described initial numerical value, represent that described duration of work length is less than described the second time threshold, described signal source circuit provides the described reference voltage signal that corresponds to described second voltage position standard in response to the described initial numerical value of the second sampled signal.
According to control circuit of the present invention, also comprise: logical circuit, in order to described brightness control signal and reset signal are carried out to logical addition computing, cover reset signal to produce, described counter resets to initial numerical value in response to the described reset signal that covers by described count parameter; Wherein, described sample circuit, in response to described reset signal described the first sampled signal of resetting, makes described the first sampled signal correspond to described termination numerical value.
According to a further aspect in the invention, propose a kind of LED driver, in order to LED circuit is driven, LED driver comprises booster driving circuit, node, current regulator and control circuit.Booster driving circuit is activation in the duration of work of brightness control signal, accurate with the position according to reference voltage signal control output voltage signal.Node has bias voltage signal.Current regulator is connected in series via node and LED circuit, and current regulator determines to flow through the operating current of LED circuit in response to bias voltage signal.It is accurate that control circuit is optionally controlled the position of reference voltage signal, comprising counter, sample circuit and signal source circuit.Counter is in response to the leading edge count parameter of brightness control signal, and to indicate the duration of work length of brightness control signal, count parameter comprises n position, and n is greater than 1 integer.Sample circuit samples and obtains the first sampled signal the MSB in n position in response to the trailing edge of brightness control signal.In the time that the first sampled signal corresponds to termination numerical value, represent that duration of work length is more than or equal to very first time threshold, in the time that the first sampled signal corresponds to initial numerical value, represent that duration of work length is less than very first time threshold.Signal source circuit provides in response to the termination numerical value of the first sampled signal the reference voltage signal that corresponds to second voltage position standard, and the initial numerical value that responds the first sampled signal provides the reference voltage signal that corresponds to the first voltage level.The first voltage level is lower than second voltage position standard.
In accordance with a further aspect of the present invention, a kind of control method is proposed, be applied in LED driver, accurate optionally to control the position of reference voltage signal, LED drive circuit comprises that booster driving circuit is with according to reference voltage signal and brightness control signal driving LED circuit.Control method comprises following step.First in response to the leading edge count parameter of brightness control signal, to indicate the duration of work length of brightness control signal, count parameter comprises n position, and n is greater than 1 integer.Then in response to the trailing edge of brightness control signal, the MSB in n position is sampled and obtains the first sampled signal, to determine very first time threshold.In the time that the first sampled signal corresponds to termination numerical value, judge that duration of work length is more than or equal to very first time threshold, and provide in response to this initial numerical value of the first sampled signal the reference voltage signal that corresponds to second voltage position standard.In the time that the first sampled signal corresponds to initial numerical value, judge that duration of work length is less than very first time threshold, and provide in response to the termination numerical value of the first sampled signal the reference voltage signal that corresponds to the first voltage level.
According to control method of the present invention, also comprise: logical addition is carried out to produce control signal in described n position; And in response to the described termination numerical value of described the first sampled signal, described MSB is carried out to sampling operation; And in response to the described initial numerical value of described the first sampled signal, described control signal is carried out to sampling operation.
Preferably, this control method also comprises: the trailing edge in response to described brightness control signal samples and obtains the second sampled signal described control signal; In the time that described the second sampled signal corresponds to described termination numerical value, judge that described duration of work length is more than or equal to described the second time threshold, and provide described the second sampled signal to trigger described the first event; Described termination numerical value in response to described the second sampled signal provides the described reference voltage signal that corresponds to described the first voltage level; And in the time that described the second sampled signal corresponds to described initial numerical value, judge that described duration of work length is less than described the second time threshold, and the described reference voltage signal that corresponds to described second voltage position standard is provided in response to the described initial numerical value of described the second sampled signal.
For foregoing of the present invention can be become apparent, preferred embodiment cited below particularly, and coordinate appended graphicly, be described in detail below:
Brief description of the drawings
Fig. 1 shows according to the calcspar of the light-emitting diode (LED) module of the embodiment of the present invention.
Fig. 2 shows the detailed circuit diagram of the current regulator 20b1-20bm in Fig. 1.
Fig. 3 shows the detailed block diagram of the control circuit 20c in Fig. 1.
Embodiment
Please refer to Fig. 1, it shows according to the calcspar of the light-emitting diode (LED) module of the embodiment of the present invention.For instance, light-emitting diode (Light Emitting Diode, LED) module 1 is applied in liquid crystal display as backlight module.LED module 1 comprises LED circuit 10 and LED driver 20.For instance, LED circuit 10 comprise LED series circuit a1, a2 that m is connected in parallel to each other ..., am, m is greater than 1 natural number.
Node N1-Nm couples with LED series circuit a1-am respectively.On each node N1-Nm, have bias voltage signal V1, V2 ..., Vm.For instance, the accurate accurate cross-pressure that deducts corresponding LED series circuit a1-am two ends in position that equals the output voltage signal Vout that booster driving circuit 20a provides in the position of each bias voltage signal V1-Vm.For instance, each LED series circuit a1-am is identical by quantity and characteristic close, and LED is in series, and therefore bias voltage signal V1-Vm for example has identical in fact voltage level.
Current regulator 20b1-20bm is connected in series via node N1-Nm and LED series circuit a1-am respectively.Each current regulator 20b1-20bm is in response to corresponding bias voltage signal V1-Vm, operating current I1, the I2 of the LED circuit corresponding with it that determine to flow through ..., Im.In an example, the detailed circuit diagram of current regulator 20b1-20bm as shown in Figure 2.Current regulator 20b1-20bm comprise respectively transistor T 1, T2 ..., Tm, and comprise respectively operational amplifier OA1, OA2 ..., OAm.The position that each operational amplifier OA1-OAm is biased into bias voltage signal Vset according to bias voltage signal Vset by the source electrode of corresponding transistor T 1-Tm is accurate.For instance, bias voltage signal Vset is provided by bias circuit (not shown).Under desirable operational scenario, the voltage difference (being drain electrode-source electrode cross-pressure of transistor T 1-Tm) of bias voltage signal V1-Vm and bias voltage signal Vset is greater than in fact the operated in saturation district of each transistor T 1-Tm) and the critical voltage of linear operating region, so, the transistor T 1-Tm controllable flow of operation in operated in saturation district has stable and identical in fact current value through each LED series circuit a1-am operating current I1-Im, provides even and stable backlight with driving LED circuit 10.
But booster driving circuit 20a is only activation in the duration of work of brightness control signal Spwm, the operation that output voltage signal Vout is controlled.So, in the too short operational circumstances of the duration of work of brightness control signal Spwm, booster driving circuit 20a may be shorter than the operant response time of booster driving circuit 20a itself because of the duration of work of brightness control signal Spwm, and cannot effectively produce the metastable output voltage signal Vout in position.So, cannot stably operate in the unstable and unsettled situation of LED circuit 10 luminosity of the size of operated in saturation district, operating current I1-Im by making jointly bias voltage signal V1-Vm that transistor T 1-Tm in accurate unstable, the current regulator 20b1-20bm in position occurs.In an operational instances, the duration of work of brightness control signal Spwm has the lower critical time threshold of 8 microseconds, in other words,, in the time that the duration of work of brightness control signal Spwm is less than 8 microsecond, the position unstable situation of accurate generation of output voltage signal Vout will significantly increase.
Please refer to Fig. 3, it shows the detailed block diagram of the control circuit 20c of Fig. 1.In an example, control circuit 20c comprises counter c1, sample circuit c2 and signal source circuit c3.Counter c1 is in response to leading edge (Front Edge) the count parameter of brightness control signal Spwm, and to indicate the length of duration of work of brightness control signal Spwm, wherein count parameter comprises n position, and n is greater than 1 integer.In an example, n equals 4, and count parameter comprises a b0, b1, b2 and b3, the leading edge that this leading edge of brightness control signal Spwm is it.
Further, counter c1 comprises replacement pin, frequency pin and four output connecting pins, and the leading edge (being for example rising edge) of the frequency signal OSCLK that the reset signal RST1 replacement count parameter that counter c1 receives in response to this replacement pin is numerical value 0, receive in response to this frequency pin increases progressively 1 and through four output connecting pin carry-out bit b0-b3 thus by this count parameter.For instance, reset signal RST1 is provided by logical circuit L2, and it for example has with brightness control signal Spwm the rising edge simultaneously triggering.Accordingly, counter c1 can be controlled by reset signal RST1, from time point corresponding to the rising edge of brightness control signal Spwm, in response to the rising edge of frequency signal OSCLK, this count parameter is increased progressively to 1.For instance, logical circuit L2 is for example logical addition computing door (lock), and the cycle of frequency signal OSCLK equals 1 microsecond.
Sample circuit c2 comprises replacement pin and frequency pin, the reset signal RST replacement sampled signal VC that sample circuit c2 receives in response to this replacement pin is numerical value 0, and receive the brightness control signal after anti-phase through frequency pin thus, with the rising edge of the brightness control signal after anti-phase in response to this, (be the trailing edge of brightness control signal Spwm, the inversion signal (inversion signal of the b3 that ascends the throne) of the most significant bits in contraposition b0-b3 samples to obtain sampled signal VC.Wherein sampled signal VC indicates in the time that the duration of work of brightness control signal Spwm finishes, and whether the numerical value of this count parameter is more than or equal in fact numerical value 8 (is numerical value (1000)
2), in other words, indicate the duration of work length of brightness control signal Spwm whether to be more than or equal in fact cycle or lower critical time threshold 8 microseconds of 8 frequency signal OSCLK.
In the time that sampled signal VC corresponds to termination numerical value 0 (b3 that ascends the throne equals the situation of numerical value 1), the duration of work length that represents brightness control signal Spwm is more than or equal to this lower critical time threshold 8 microseconds, and the output driving force of booster driving circuit 20a is sufficient and electric current (electric current of each LED series circuit a1-am that flows through) that each current regulator 20b1-20bm provides and the brightness of each LED series circuit a1-am are difficult for occurring unsettled situation.In the time that sampled signal VC corresponds to initial numerical value 1 (b3 that ascends the throne equals the situation of numerical value 0), the duration of work length that represents brightness control signal Spwm is less than this lower critical time threshold 8 microseconds, and the output driving force of booster driving circuit 20a not enough and electric current that each current regulator 20b1-20bm provides and the unsettled situation of brightness of each LED series circuit a1-am may occur.
Signal source circuit c3 comprises voltage source c3a and c3b.Signal source circuit c3, in response to the sampled signal VC and the VCB (being the inversion signal of sampled signal VC) that correspond to respectively initial numerical value 1 and termination numerical value 0, provides the reference voltage signal Vref that corresponds to voltage level V1; And in response to corresponding to respectively the sampled signal VC and the VCB that stop numerical value 0 and initial numerical value 1, provide the reference voltage signal Vref that corresponds to voltage level V2.Wherein voltage level V2 is higher than voltage level V1.Accordingly, control circuit 20c is optionally less than this lower critical time when threshold 8 microsecond at the duration of work of brightness control signal Spwm, provides the reference voltage signal Vref that corresponds to voltage level V2 to drive booster driving circuit 20a.
In an example, control circuit 20c also comprises logical circuit L0 and multiplexer mux1.Logical circuit L0 contraposition b0-b3 carries out logical addition, to produce control signal ovf.Multiplexer mux1 is coupled to sample circuit c2, and reception control signal ovf and MSB b3.Multiplexer mux1 provides MSB b3 to sample circuit c2 in response to the termination numerical value 0 of sampled signal VC, and provides control signal ovf to sample circuit c2 in response to the initial numerical value 1 of sampled signal VC.Under initial state, the rising edge of reset signal RST triggered before the rising edge of brightness control signal Spwm triggers, and sampled signal VC is reset as numerical value 0, accordingly, multiplexer mux1 provides MSB m3 to carry out sampling operation to sample circuit c2 accordingly.
In an operational instances, sampled signal VC in previous operation (because the duration of work length of brightness control signal Spwm is less than this lower critical time threshold 8 microseconds) be set to initial numerical value 1, and control circuit 20c is to provide the reference voltage signal that corresponds to voltage level V2, booster driving circuit 20a is driven.Accordingly, multiplexer mux1 will provide control signal ovf to sample to sample circuit c2 accordingly.Similar in appearance to aforementioned sample circuit c2, the inversion signal of MSB b3 is sampled to obtain the operation of sampled signal VC, correspond at sampled signal VC3 under the situation of initial numerical value 1, sample circuit c2 also carries out sampling operation to the inversion signal of control signal ovf accordingly, to produce next record sampled signal, it is in order to instruction in the time that the duration of work of brightness control signal Spwm finishes, and whether the numerical value of this count parameter is more than or equal in fact numerical value 15 (is numerical value (1111)
2), in other words, indicate the duration of work length of brightness control signal Spwm whether to be more than or equal in fact cycle or threshold of upper crash time 15 microseconds of 15 frequency signal OSCLK.
When sampled signal VC corresponds to while stopping when numerical value 0 (b0-b3 that ascends the throne all corresponds to the situation of numerical value 1), the duration of work length that represents brightness control signal Spwm is more than or equal to crash time threshold 15 microseconds on this, in other words, being greater than significantly lower critical time threshold 8 microseconds comes longly.So, signal source circuit c3, in response to corresponding to respectively the sampled signal VC and the VCB that stop numerical value 0 and initial numerical value 1, provides the reference voltage signal Vref that corresponds to voltage level V1.In other words, when the duration of work length of brightness control signal Spwm is more than or equal to crash time threshold 15 microseconds on this and is greater than significantly the lower critical time when threshold 8 microsecond, control circuit 20c switches to voltage level V1 with reference to voltage signal Vref from voltage level V2, drives the electric energy losing quantity of driver 20 entirety to reduce LED.
In the time that sampled signal VC corresponds to initial numerical value 1 (wherein at least one is not the situation of numerical value 1 to the b0-b3 that ascends the throne), represent that the duration of work length of brightness control signal Spwm is less than this time threshold 15 microseconds.So, signal source circuit c3, in response to the sampled signal VC and the VCB that correspond to respectively initial numerical value 1 and termination numerical value 0, corresponds to the reference voltage signal Vref (having the reference voltage signal Vref of higher levels) of voltage level V2 to provide constantly.In other words, when the duration of work of brightness control signal Spwm is less than on this crash time when threshold 15 microsecond, control circuit 20c provides the reference voltage signal Vref that corresponds to voltage level V2 constantly, to avoid, position at brightness control signal Spwm is accurate is not stably greater than this when threshold 7 microsecond lower critical time, switches to voltage level V1 with reference to voltage signal Vref from voltage level V2.In general, signal occurring in entity circuit is often subject to the interference of circuit noise and the accurate unsettled situation in position occurs.In the control circuit 20c of the present embodiment, by the design of this lower critical and threshold of upper crash time, effectively avoid control circuit 20c too sensitively the position standard of reference voltage signal Vref to be switched, to reduce the impact of the operation of circuit noise on control circuit 20c.
In an example, the control circuit 20c of the present embodiment also comprises logical circuit L1 and multiplexer mux2.Logical circuit L1 carries out logical addition computing to brightness control signal Spwm and frequency signal OSCLK, to produce the frequency signal after covering, frequency signal after wherein covering is activation in the duration of work of brightness control signal Spwm, and is outward disabled at the duration of work of brightness control signal Spwm.
Multiplexer mux2 is accurate in response to the position of the output signal of multiplexer mux1, and carrying out the optionally frequency signal using brightness control signal Spwm and after covering provides to sample circuit c2 as sampling control signal, to drive it to carry out corresponding sampling operation.In the time that the output signal of multiplexer mux1 corresponds to numerical value 0, multiplexer mux2 provides brightness control signal after anti-phase to sample circuit c2 via inverter INV, carry out sampling operation, i.e. operation described in previous embodiment of the present invention to control sample circuit c2 according to the rising edge of the brightness control signal after anti-phase (being falling edge/trailing edge of brightness control signal Spwm).
In the time that the output signal of multiplexer mux1 corresponds to numerical value 1, multiplexer mux2 provide anti-phase via inverter INV and cover after frequency signal to sample circuit c2, to drive it to drive sample circuit c2 to carry out sampling operation in the duration of work of brightness control signal Spwm.In other words, via the switching of multiplexer mux2, sample circuit c2 is optionally before the duration of work of brightness control signal Spwm not yet finishes, according to anti-phase and cover after frequency signal carry out sampling operation, to accelerate the service speed of control circuit 20c output sampled signal VC and VCB.
The control circuit of the embodiment of the present invention is to be applied in LED driver, and it is application: counter calculates the time span of the duration of work of the brightness control signal that corresponds to LED driver; Multiplexer carrys out the MS of multidigit count parameter that reference count produces) and this multidigit count parameter carry out the numerical value of the control signal of logical addition generation, determine respectively lower critical threshold and upper critical threshold; Sample circuit and signal source circuit come optionally the reference voltage of LED driver to be switched to higher second standard from first lower standard according to critical on this and lower critical threshold, or it is switched to first lower standard from higher second standard.So, than traditional LED driver, the control circuit of the embodiment of the present invention and apply its LED driver can be effectively to adjust accordingly the position of reference voltage of LED driver in the time that the duration of work of brightness control signal is less than this lower critical threshold or be greater than critical threshold on this accurate, and have advantages of accordingly and can stabilized driving voltage be provided and can there is stable brightness by driving LED light source module by driving LED driver.
In sum, although the present invention discloses as above with a preferred embodiment, so it is not in order to limit the present invention.The technical field of the invention technical staff, without departing from the spirit and scope of the present invention, when doing various changes and retouching.Therefore the scope that, protection scope of the present invention ought define depending on accompanying claims is as the criterion.
Primary clustering symbol description
1: light-emitting diode (LED) module 10: circuit of LED
A1-am: light-emitting diode series circuit 20: LED drive
200a: multiplexer 200b: amplifier
200c: comparator 200d: sensing and compensating circuit
200e: control circuit SW1, SW2: switch
L: energy storage component N1-Nm: node
20b1-20bm: current regulator T1-Tm: transistor
OA1-OAm: operational amplifier c1: counter
C2: sample circuit c3: signal source circuit
L0-L2: logical circuit mux1, mux2: multiplexer
INV: inverter c3a, c3b: voltage source.
Claims (9)
1. a control circuit, be applied in light-emitting diode (LED) driver, optionally to control the position standard of reference voltage signal, described LED drive comprises booster driving circuit, in order to according to described reference voltage signal and brightness control signal driving LED circuit, described control circuit comprises:
Counter, in order to the forward position count parameter in response to described brightness control signal, to indicate the duration of work length of described brightness control signal, described count parameter comprises n position, n is greater than 1 integer;
Sample circuit, in order to the rear edge in response to described brightness control signal, the highest order in described n position is sampled and obtains the first sampled signal, in the time that described the first sampled signal corresponds to termination numerical value, represent that described duration of work length is more than or equal to very first time threshold value, in the time that described the first sampled signal corresponds to initial numerical value, represent that described duration of work length is less than described very first time threshold value; And
Signal source circuit, described termination numerical value in response to described the first sampled signal provides the described reference voltage signal that corresponds to second voltage position standard, and the described initial numerical value that responds described the first sampled signal provides the described reference voltage signal that corresponds to the first voltage level;
Wherein, described the first voltage level is lower than described second voltage position standard.
2. control circuit according to claim 1, also comprises:
Logical circuit, in order to logical addition is carried out in described n position, to produce control signal; And
The first multiplexer, receive described control signal and described highest order, and be coupled to described sample circuit, described the first multiplexer provides described highest order to described sample circuit in response to the described termination numerical value of described the first sampled signal, and controls signal to described sample circuit described in providing in response to the described initial numerical value of described the first sampled signal.
3. control circuit according to claim 2, wherein said sample circuit also samples and obtains the second sampled signal described control signal in order to the rear edge in response to described brightness control signal, in the time that described the second sampled signal corresponds to described termination numerical value, represent that described duration of work length is more than or equal to the second time threshold, described signal source circuit provides in response to the described termination numerical value of described the second sampled signal the described reference voltage signal that corresponds to described the first voltage level.
4. control circuit according to claim 2, wherein said sample circuit also samples and obtains the second sampled signal described control signal in order to the rear edge in response to described brightness control signal, in the time that described the second sampled signal corresponds to described initial numerical value, represent that described duration of work length is less than the second time threshold, described signal source circuit provides the described reference voltage signal that corresponds to described second voltage position standard in response to the described initial numerical value of the second sampled signal.
5. control circuit according to claim 1, also comprises:
Logical circuit, in order to described brightness control signal and reset signal are carried out to logical addition computing, covers reset signal to produce, and described counter resets to initial numerical value in response to the described reset signal that covers by described count parameter;
Wherein, described sample circuit, in response to described reset signal described the first sampled signal of resetting, makes described the first sampled signal correspond to described termination numerical value.
6. light-emitting diode (LED) driver, in order to LED circuit is driven, described LED drive comprises:
Booster driving circuit, in order to be activation in the duration of work of brightness control signal, accurate with the position according to reference voltage signal control output voltage signal;
Node, has bias voltage signal;
Current regulator, is connected in series via described node and described LED circuit, and described current regulator is in response to described bias voltage signal determine the to flow through operating current of described LED circuit; And
Control circuit, in order to optionally to control the position standard of described reference voltage signal, described control circuit comprises:
Counter, in order to the forward position count parameter in response to described brightness control signal, to indicate the duration of work length of described brightness control signal, described count parameter comprises n position, n is greater than 1 integer;
Sample circuit, in order to the rear edge in response to described brightness control signal, the highest order in described n position is sampled and obtains the first sampled signal, in the time that described the first sampled signal corresponds to termination numerical value, represent that described duration of work length is more than or equal to very first time threshold value, in the time that described the first sampled signal corresponds to initial numerical value, represent that described duration of work length is less than described very first time threshold value; And
Signal source circuit, described termination numerical value in response to described the first sampled signal provides the described reference voltage signal that corresponds to second voltage position standard, and the described initial numerical value that responds described the first sampled signal provides the described reference voltage signal that corresponds to the first voltage level;
Wherein, described the first voltage level is lower than described second voltage position standard.
7. a control method, be applied in light-emitting diode (LED) driver, optionally to control the position standard of reference voltage signal, described LED drive comprises booster driving circuit, in order to according to described reference voltage signal and brightness control signal driving LED circuit, described control method comprises:
In response to the forward position count parameter of described brightness control signal, to indicate the duration of work length of described brightness control signal, described count parameter comprises n position, and n is greater than 1 integer;
Rear edge in response to described brightness control signal samples and obtains the first sampled signal the highest order in described n position, and described the first sampled signal is in order to determine very first time threshold value;
In the time that described the first sampled signal corresponds to termination numerical value, judge that described duration of work length is more than or equal to described very first time threshold value, and the described reference voltage signal that corresponds to second voltage position standard is provided; And
In the time that described the first sampled signal corresponds to initial numerical value, judge that described duration of work length is less than described very first time threshold value, and the described reference voltage signal that corresponds to the first voltage level is provided.
8. control method according to claim 7, also comprises:
Logical addition is carried out to produce control signal in described n position; And
Described termination numerical value in response to described the first sampled signal carries out sampling operation to described highest order; And
Described initial numerical value in response to described the first sampled signal carries out sampling operation to described control signal.
9. control method according to claim 8, also comprises:
Rear edge in response to described brightness control signal samples and obtains the second sampled signal described control signal;
In the time that described the second sampled signal corresponds to described termination numerical value, judge that described duration of work length is more than or equal to the second time threshold, and provide described the second sampled signal to trigger the first event;
Described termination numerical value in response to described the second sampled signal provides the described reference voltage signal that corresponds to described the first voltage level; And
In the time that described the second sampled signal corresponds to described initial numerical value, judge that described duration of work length is less than described the second time threshold, and provide in response to the described initial numerical value of described the second sampled signal the described reference voltage signal that corresponds to described second voltage position standard.
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| CN201010204220.8A Expired - Fee Related CN102281665B (en) | 2010-06-11 | 2010-06-11 | Control circuit, light-emitting diode driver using control circuit and control method |
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| TWI584680B (en) * | 2016-03-25 | 2017-05-21 | 茂達電子股份有限公司 | An operation method for led dimming device |
| CN110853570B (en) * | 2019-11-20 | 2021-11-02 | 北京集创北方科技股份有限公司 | LED display device and driving method and chip thereof |
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| KR20070065411A (en) * | 2002-03-27 | 2007-06-22 | 산요덴키가부시키가이샤 | Display device, mobile terminal, and luminance control method in mobile terminal |
| US6819011B2 (en) * | 2002-11-14 | 2004-11-16 | Fyre Storm, Inc. | Switching power converter controller with watchdog timer |
| CN100474990C (en) * | 2006-11-02 | 2009-04-01 | 立锜科技股份有限公司 | Backlight control circuit capable of automatically adjusting voltage and control method for luminous element |
| CN201001216Y (en) * | 2007-01-24 | 2008-01-02 | 先礼群 | High power LED drive circuit |
| CN101316466B (en) * | 2007-05-30 | 2011-12-07 | 联阳半导体股份有限公司 | Constant-current driving circuit |
| US7825610B2 (en) * | 2008-03-12 | 2010-11-02 | Freescale Semiconductor, Inc. | LED driver with dynamic power management |
| JP4655111B2 (en) * | 2008-05-20 | 2011-03-23 | 日本テキサス・インスツルメンツ株式会社 | LED device and LED drive circuit |
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