CN103402285A - Control circuit of LED (Light-emitting Diode) driver and control method thereof - Google Patents
Control circuit of LED (Light-emitting Diode) driver and control method thereof Download PDFInfo
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- CN103402285A CN103402285A CN2013102841810A CN201310284181A CN103402285A CN 103402285 A CN103402285 A CN 103402285A CN 2013102841810 A CN2013102841810 A CN 2013102841810A CN 201310284181 A CN201310284181 A CN 201310284181A CN 103402285 A CN103402285 A CN 103402285A
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Abstract
The invention relates to an LED (Light-emitting Diode) driver, which comprises an energy transmission unit connected with a load LED in series and used for providing electric power to the load LED, a switch circuit coupled with the energy transmission unit, and a fly-wheel diode for subsequent flow of the energy transmission unit. The LED driver is characterized by also comprising a control circuit, and the switch circuit for controlling to be coupled with the energy transmission unit, so that the electric power flowing through the load LED is controlled.
Description
Technical field
The present invention relates to LED and drive field, relate in particular to a kind of control circuit and control method thereof of LED driver.
Background technology
The current-voltage relation of LED is all the exponential type relation with conventional diode, when the forward voltage that applies with less dV/dt rate of change, can cause having the forward current of larger di/dt rate of change.Therefore, keeping the LED current constant is the best approach of driving LED.Fig. 1 is a kind of voltage-dropping type LED driver schematic diagram commonly used.The control method that this circuit adopts peak current to control, control the peak current and the valley point current that flow through inductance.Because inductance 107 is cascaded with load LED 109, so the average current of load LED and inductance average current equate.
Inductive current during sampling resistor 104 sampled power metal-oxide-semiconductor conducting obtains a sampled voltage signal, control chip 103 according to this signal sets the current peak of inductance 107, make the current peak reference voltage Vref fixing and chip of inductance 107 proportional.The turn-off time Toff of the sensibility reciprocal design power metal-oxide-semiconductor of voltage drop upper according to load LED109 and inductance, make the electric current valley of inductance 107 remain a fixed value.The inductance average current that fixing inductive current peak and fixing inductive current valley are fixed, namely load LED average current is fixed, and the current formula of load LED is:
Wherein Vref is the reference voltage of control chip 103 internal control inductive current peaks, the voltage drop when Vled is load LED109 forward conduction, and Toff is fixing turn-off time of the power tube set of frequency setting resistance 105, L is the inductance value of inductance.
Can find out from top formula, the load LED average current of existing voltage-dropping type LED driver is easy to be subject to the impact of various parameters, such as, different input voltage VIN, and inductance value L, and the voltage degradation during load LED109 forward conduction.The impact of these parameters has brought adverse effect to large-scale production and the application of LED lighting apparatus, and the variation of the LED of load simultaneously electric current also can be given the useful life of load LED and be brought adverse effect.Illumination proposes in the situation of high request more and more to LED in current market, and existing LED driver can not meet the demands.In view of this, the present invention will provide a kind of more high-performance, and the voltage drop during with input voltage, inductance value and load LED the forward conduction LED driver and the control method thereof that all have nothing to do.
The shortcoming of summing up prior art is: the impact that one, the average electrical of load LED fail to be convened for lack of a quorum and changed by inductance value; Its two, the fail to be convened for lack of a quorum impact of the voltage drop while being subject to load LED forward conduction of the average electrical of load LED; Its three, the average electrical of load LED fails to be convened for lack of a quorum and is subject to the impact that input voltage changes.
Summary of the invention
In order to solve the shortcoming of existing LED driver, the present invention proposes a kind of circuit and method of constant-current driving LED, adopts the load LED electric current of the LED driver of this scheme can obtain controlling comparatively accurately., according to a kind of LED driver of one embodiment of the invention, comprise an Energy Transfer unit of with load LED, connecting, for described load LED provides electric power; The switching circuit that couples with the Energy Transfer unit; And be the fly-wheel diode of Energy Transfer unit afterflow, it is characterized in that, described LED driver also comprises a control circuit, is used for controlling the switching circuit that couples with the Energy Transfer unit, thereby controls the electric power of the load LED that flows through.
Preferably, the control circuit of described LED driver comprises:
Current detection circuit, the electric current that all provides indication to flow through described Energy Transfer unit, and output electric current measure signal are provided when described switching circuit switches on and off;
The current peak control circuit, receive described current detection signal and the first reference voltage, and generation current peak value control signal;
Electric current valley control circuit, receive described current detection signal and the second reference voltage, and generation current valley control signal;
Pulse width modulating signal produces circuit and receives described current peak control signal and electric current valley control signal, produces a pulse width modulating signal control switch circuit and switches on and off, take the constant desired value as setting of the average current of keeping load LED;
Wherein, the average current of described load LED is only relevant with reference voltage;
The reference ground of LED driver and the reference ground of control circuit are not same with reference to ground;
Preferably, the reference of described control circuit ground is the end that Energy Transfer unit and load LED do not join.
Preferably, the switching circuit of described LED driver is comprised of power MOS pipe, pliotron or other switching mode devices.
Preferably, the Energy Transfer unit of described LED driver is a transformer, the main of transformer is coupled in series in current path between switching circuit and current detection circuit, or be coupled in series in current path between the reference ground of current detection circuit and LED driver the secondary and load LED coupled in parallel of transformer.
Preferably, the Energy Transfer unit of described LED driver is an inductance, and following description will replace the Energy Transfer unit with inductance.
Preferably, described LED driver is based on buck topology, any in the buck topology.
Preferably, the current detection circuit of described control circuit is coupled in series on current path between switching circuit and inductance, and one end and inductance couple, and the negative electrode of the other end and diode and the common port of switching circuit couple, comprise,
One current sense resistor, inductive current flow through this resistance, and produce the current detection signal of indication inductive current transient current on current sense resistor,
Preferably, the reference of described control circuit ground is the common port that switching circuit, current detection circuit and fly-wheel diode couple mutually.
Preferably, the current peak control circuit of described control circuit comprises,
The first averaging circuit, receive the first reference voltage and current detection signal, and export the first average value signal;
Preferably, the first averaging circuit of described current peak control circuit comprises the first error amplifier, the first error intergal electric capacity with its output, the in-phase input end of described error amplifier connects the first reference voltage, anti-phase input termination inductive current detection signal, it is output as the first average value signal.
The current peak testing circuit, receive described the first average value signal and current detection signal, output current peak value control signal;
Preferably, the current peak testing circuit of described current peak control circuit comprises the first comparator, and its in-phase input end connects current detection signal, described the first average value signal of anti-phase input termination, and it is output as the current peak control signal.
Preferably, the electric current valley control circuit of described control circuit comprises,
The second comparator, its in-phase input end connects the second reference voltage, and anti-phase input termination current detection signal, its output are electric current valley control signal,
Preferably, the pulse width modulating signal of described control circuit produces circuit and comprises a rest-set flip-flop, its termination current peak control signal that resets, set termination electric current valley control signal, the Q output is pulse width modulating signal, the pulse width modulating signal of output switches on and off for the switching circuit of controlling and inductance couples, to keep the desired value of load LED current constant as setting.
According to the LED driver of another preferred embodiment of the present invention, wherein, described LED driver is only variant with the first embodiment on control circuit,
Preferably, the current peak control circuit of the control circuit of described the present embodiment comprises,
The 3rd comparator, its in-phase input end connects current detection signal, and anti-phase input termination the first reference voltage, its output are the current peak control signal,
Preferably, the electric current valley control circuit of the control circuit of described the present embodiment comprises,
The second averaging circuit, receive the second reference voltage signal and current detection signal, and export the second average value signal,
Preferably, the second averaging circuit of described electric current valley control circuit comprises the second error amplifier, and the second error intergal electric capacity of its output, its in-phase input end connects the second reference voltage, anti-phase input termination current detection signal, it is output as the second average value signal
The electric current valley value detection circuit, receive described the second average value signal and current detection signal, output current valley control signal,
Preferably, the electric current valley value detection circuit of described electric current valley control circuit comprises the 4th comparator, and its in-phase input end connects described the second average value signal, anti-phase input termination current detection signal, and it is output as inductive current valley control signal.
According to the LED driver of another preferred embodiment of the present invention, described LED driver is only variant with the first embodiment on control circuit,
Preferably, the electric current valley control circuit of the control circuit of described the present embodiment comprises,
One zero current detecting circuit, its input is the common port of inductance and current detection circuit, output is electric current valley control signal, it is after zero that zero current detecting circuit utilizes inductive current, the principle of vibration appears in the common port of inductance and current detection circuit, and can detect inductive current is zero moment point.
Control method according to a kind of LED driver of first embodiment of the invention comprises the following steps:
First step current detection circuit detects inductive current, and the output electric current measure signal;
Second step current peak control circuit received current detection signal and the first reference voltage, output current peak value control signal;
The 3rd step electric current valley control circuit received current detection signal and the second reference voltage, output current valley control signal;
The 4th pace pulse bandwidth modulation signals produces circuit received current peak value control signal and electric current valley control signal, and the output pulse width modulation signal disconnects and the turn on-switch circuit, to keep the desired value of load LED current constant as setting.
Control method according to a kind of LED driver of second embodiment of the invention comprises the following steps:
First step current detection circuit detects inductive current, and the output electric current measure signal;
Second step the first averaging circuit receives described current detection signal and the first reference voltage, output the first average value signal;
The 3rd step current peak testing circuit receives described current detection signal and the first average value signal, output current peak value control signal;
The 4th step electric current valley control circuit received current detection signal and the second reference voltage, output current valley control signal;
The 5th pace pulse bandwidth modulation signals produces circuit received current peak value control signal and electric current valley control signal, and the output pulse width modulation signal disconnects and the turn on-switch circuit, to keep the desired value of load LED current constant as setting.
Control method according to a kind of LED driver of third embodiment of the invention comprises the following steps:
First step current detection circuit detects inductive current, and the output electric current measure signal;
Second step current peak control circuit received current detection signal and the first reference voltage, output current peak value control signal;
The 3rd step second averaging circuit receives described current detection signal and the second reference voltage, output the second average value signal;
The 4th step electric current valley value detection circuit receives described current detection signal and the second average value signal, output current valley control signal;
The 5th pace pulse bandwidth modulation signals produces circuit received current peak value control signal and electric current valley control signal, and the output pulse width modulation signal disconnects and the turn on-switch circuit, to keep the desired value of load LED current constant as setting;
As seen, adopt the beneficial effect of LED driver of the present invention to be: the electric current of load LED will be more accurate, and can not be subject to input voltage, the impact of inductance value and load LED forward voltage.
Description of drawings
Figure 1A is depicted as the theory diagram of a kind of LED driver that adopts prior art.
Figure 2 shows that the theory diagram according to the first embodiment of LED driver of the present invention.
Figure 3 shows that the theory diagram according to the second embodiment of LED driver of the present invention.
Fig. 4 A is depicted as the theory diagram according to the first implementing circuit of the control circuit of LED driver of the present invention.
Fig. 4 B is depicted as the oscillogram according to the first implementing circuit of the control circuit of LED driver of the present invention.
Fig. 5 A is depicted as the theory diagram according to the second implementing circuit of the control circuit of LED driver of the present invention.
Fig. 5 B is depicted as the oscillogram according to the second implementing circuit of the control circuit of LED driver of the present invention.
Fig. 6 A is depicted as the theory diagram according to the 3rd embodiment of LED driver of the present invention.
Fig. 6 B is depicted as the electric current valley control circuit schematic diagram according to the 3rd embodiment of LED driver of the present invention.
Figure 7 shows that the flow chart according to the first embodiment of the control method of a kind of LED driver of the present invention.
Figure 8 shows that the flow chart according to the second embodiment of the control method of a kind of LED driver of the present invention.
Figure 9 shows that the flow chart according to the 3rd embodiment of the control method of a kind of LED driver of the present invention.
Drawing reference numeral
100 start dropping resistor; 101 input filter capacitors; 102NTC resistance; 103 control chips; 104 sampling resistors; 105 frequency setting resistance; 106 power MOS pipes; 107 inductance; 108 diodes; 109 load LED; 110 output filter capacitors; 200 first embodiment; 201 load LED; 202 fly-wheel diodes; 203 Energy Transfer unit; 204 switching circuits; 205 current detection circuits; 206 first control circuit block diagrams; 210 current peak control circuits; 211 electric current valley control circuits; 212 pulse width modulating signals produce circuit; 214 input filter capacitors; 300 second embodiment; 301 current sense resistors; 302 switches; 303 inductance; 306 second control circuit block diagrams; 400 second control circuit the first embodiment; 401 second control circuit the first embodiment rest-set flip-flops; 402 first averaging circuits; 403 first error amplifiers; 404 first integral electric capacity; 405 current peak testing circuits; 406 first comparators; 407 second comparators; 408 second control circuit the first embodiment oscillograms; 500 second control circuit the second embodiment; 501 second control circuit the second embodiment rest-set flip-flops; 502 second averaging circuits; 503 second error amplifiers; 504 second integral electric capacity; 505 electric current valley value detection circuits; 506 the 3rd comparators; 507 the 4th comparators; 508 second control circuit the second embodiment oscillograms; 600 the 3rd embodiment; 602 zero current detecting circuits; 606 the 3rd embodiment control circuits; 611 the 3rd embodiment electric current valley control circuits; 700 first embodiment flow charts; The 701 flow chart first steps; 702 flow chart second steps; 703 the 3rd steps of flow chart; 704 the 4th steps of flow chart; 800 second embodiment flow charts; The 801 flow chart first steps; 802 flow chart second steps; 803 the 3rd steps of flow chart; 804 the 4th steps of flow chart; 805 the 5th steps of flow chart; 900 the 3rd embodiment flow charts; The 901 flow chart first steps; 902 flow chart second steps; 903 the 3rd steps of flow chart; 904 the 4th steps of flow chart; 905 the 5th steps of flow chart.
Embodiment
Below will describe specific embodiments of the invention in detail, should be noted that the embodiments described herein only is used for illustrating, be not limited to the present invention.In the following description,, in order to provide thorough understanding of the present invention, a large amount of specific detail have been set forth.Yet, it is evident that for those of ordinary skills: needn't adopt these specific detail to carry out the present invention.In other embodiments,, for fear of obscuring the present invention, do not specifically describe known circuit, material or method.
In whole specification, " embodiment ", " embodiment ", " a kind of implementing circuit ", " implementing circuit ", " example " or mentioning of " example " are meaned: special characteristic, structure or characteristic in conjunction with this embodiment or example description are comprised at least one embodiment of the present invention.Therefore, phrase " in one embodiment ", " in an embodiment ", " in a kind of implementing circuit ", " in implementing circuit ", " example " or " example " that occurs in each place of whole specification differs to establish a capital and refers to same embodiment or example.In addition, can, with any suitable combination and/or sub-portfolio with specific feature, structure or characteristic, be combined in one or more embodiment or example.In addition, it should be understood by one skilled in the art that at this accompanying drawing that provides be all for illustrative purposes, and accompanying drawing is drawn in proportion not necessarily.Should be appreciated that it can be directly connected or coupled to another element or can have intermediary element when claiming element " connection ", " being connected to " or " coupling ", " being couple to " another element.On the contrary, when claiming element " to be directly connected to " or during " being directly coupled to " another element, not having intermediary element.The identical identical element of Reference numeral indication.Term used herein " and/or " comprise any and all combinations of one or more relevant projects of listing.
With reference to figure 2, be depicted as the theory diagram 200 according to the first embodiment of LED driver of the present invention, comprise an Energy Transfer unit 203 of with load LED201, connecting, it provides electric power for described load LED201, and is the fly-wheel diode 202 of Energy Transfer unit 203 afterflows.The present invention can form buck topology structure, buck topological structure by switching circuit 204, Energy Transfer unit 203 and fly-wheel diode 202, in one embodiment, is the buck topology structure.Control circuit 206, detect the current signal that flows through Energy Transfer unit 203, is used for controlling the switching circuit 204 that couples with Energy Transfer unit 203, thereby control the electric power of Energy Transfer unit 203 to load LED201 transmission.Control circuit 206 further comprises: current detection circuit 205, couple with the common node of switching circuit 204, Energy Transfer unit 203 and diode 202, be used for when described switching circuit 204 switches on and off, the electric current that all provides indication to flow through described Energy Transfer unit 203, and output electric current measure signal Vcs.Current peak control circuit 210, receive described current detection signal Vcs and the first reference voltage VR1, and generation current peak value control signal Vpk, and its peak value that has represented inductive current is directly relevant with the first reference voltage.Electric current valley control circuit 211, receive described current detection signal Vcs and the second reference voltage VR2, and generation current valley control signal Vva, if can guarantee that whole LED driver 200 is operated in continuous current mode pattern (CCM pattern), or critical current mode pattern (CRM pattern), the valley of inductive current is just directly relevant with the second reference voltage so.Pulse width modulating signal produces circuit 212 and receives described current peak control signal Vpk and electric current valley control signal Vva, produce a pulse width modulating signal PWM1 control switch circuit 204 and switch on and off, to keep the desired value of load LED201 current constant as setting.Because the valley of the peak value of inductive current and inductive current is all only relevant with reference voltage, so the mean value of inductive current is also only relevant with reference voltage, simultaneously, inductance 203 and load LED201 series connection, so the electric current of the electric current of inductance 203 and load LED201 equates, so the average current of load LED201 is also only relevant with reference voltage.
Reference the ground of the reference of LED driver 200 ground and control circuit 206 is not same with reference to ground, in one embodiment, is the reference of the control circuit 206 of described LED driver 200 end that Energy Transfer unit 203 and load LED201 do not join.
, with reference to figure 3, be depicted as the second embodiment schematic diagram 300 according to LED driver of the present invention.The main distinction of Fig. 3 and Fig. 2 is that the position of current detection circuit 301 is different.The switching circuit 204 of wherein said LED driver 300 is comprised of power MOS pipe, pliotron or other switching mode devices 302.Current detection circuit 205 is coupled in series in the current path of switching circuit 204 and Energy Transfer unit 203, the common port coupled in series of one end and switching circuit 204, diode 202, the other end and Energy Transfer unit 203 coupled in series, the common port of current detection circuit 205 and Energy Transfer unit 203 are the reference ground of control circuit 306.In one embodiment, Energy Transfer unit 203 is transformers, the main of transformer is coupled in series in current path between switching circuit and current detection circuit, or be coupled in series in current path between the reference ground of current detection circuit and LED driver, secondary and the load LED coupled in parallel of transformer, diode 202 is simultaneously in parallel with current detection circuit 205 and transformer main.In one embodiment, Energy Transfer unit 203 is an inductance 303, one end and current detection circuit 205 coupled in series, the other end and load LED201 coupled in series, diode 202 is simultaneously in parallel with current detection circuit 205, inductance 303 and load LED201.In one embodiment, current detection circuit 205 is a resistance 301, and inductive current flows through resistance 301, and produces the current detection signal Vcs that is used to indicate the inductive current transient current on resistance 301.
Be the first implementing circuit 400 of the control circuit 306 of the second embodiment 300 with reference to figure 4A,, in conjunction with reference to figure 4B, can be easier to understand its operation principle.The current peak control circuit 210 of this control circuit 400 comprises, the first averaging circuit 402, it receives the first reference voltage VR1 and current detection signal Vcs, and export the first average value signal ILpk, described the first averaging circuit 402 comprises the first error amplifier 403, the first error intergal electric capacity 404 with its output, the first error amplifier 403 in-phase input ends meet the first reference voltage VR1, anti-phase input termination inductive current detection signal Vcs, it is output as the first average value signal ILpk.Current peak testing circuit 405, receive described the first average value signal ILpk and current detection signal Vcs, output current peak value control signal Vpk.Current peak testing circuit 405 comprises the first comparator 406, and its in-phase input end meets current detection signal Vcs, described the first average value signal ILpk of anti-phase input termination, and it is output as current peak control signal Vpk.The electric current valley control circuit 211 of control circuit 400 comprises, the second comparator 407, its in-phase input end meet the second reference voltage VR2, and anti-phase input termination current detection signal Vcs, its output are electric current valley control signal Vva.The pulse width modulating signal of control circuit 400 produces circuit 212 and comprises a rest-set flip-flop 401, its termination current peak control signal Vpk that resets, set termination electric current valley control signal Vva, the Q output is pulse width modulating signal PWM1, it switches on and off for the switching circuit 204 of controlling and current detection circuit 205 couples, to keep the desired value of load LED201 current constant as setting.The level of the first average value signal ILpk has represented the mean value of current detection signal Vcs and the accumulated error between the first reference voltage VR1, is used for controlling the peak value of inductive current.When the mean value of current detection signal Vcs during less than the first reference voltage VR1, the level of the first average value signal ILpk will raise, the inductive current peak of current peak testing circuit 405 controls simultaneously also can synchronously raise the mean value of motor current detection signal Vcs, make the mean value of current detection signal Vcs equal the first reference voltage VR1, vice versa.Current peak control signal Vpk has determined that by the first reference voltage VR1 the peak value of inductive current is ILpk/Rcs, electric current valley control signal Vva has determined that by the second reference voltage VR2 the valley of inductive current is VR2/Rcs, and the first reference voltage VR1 has also determined that the mean value of inductive current is VR1/Rcs simultaneously.
Be the second implementing circuit 500 of the control circuit 306 of the second embodiment 300 with reference to figure 5A,, in conjunction with reference to figure 5B, can more easily set forth its operation principle.The electric current valley control circuit 211 of this control circuit 500 comprises, the second averaging circuit 502, it receives the second reference voltage VR2 and current detection signal Vcs, and export the second average value signal ILva, described the second averaging circuit 502 comprises the second error amplifier 503, the second error intergal electric capacity 504 with its output, the second error amplifier 503 in-phase input ends meet the second reference voltage VR2, anti-phase input termination inductive current detection signal Vcs, it is output as the second average value signal ILva.Electric current valley value detection circuit 505, receive described the second average value signal ILva and current detection signal Vcs, output current valley control signal Vva.Electric current valley value detection circuit 505 comprises the 3rd comparator 506, and its in-phase input end meets current detection signal Vcs, described the second average value signal ILva of anti-phase input termination, and it is output as electric current valley control signal Vva.the current peak control circuit 210 of control circuit 500 comprises, the 4th comparator 507, its in-phase input end meets current detection signal Vcs, inverting input the first reference voltage VR1, its output is that the pulse width modulating signal generation circuit 212 of current peak control signal Vpk. control circuit 500 comprises a rest-set flip-flop 501, its termination current peak control signal Vpk that resets, set termination electric current valley control signal Vva, the Q output is pulse width modulating signal PWM1, switch on and off for the switching circuit 204 of controlling and current detection circuit 205 couples, to keep the desired value of load LED201 current constant as setting.The level of the second average value signal ILva has represented the mean value of current detection signal Vcs and the accumulated error between the second reference voltage VR2, is used for controlling the valley of inductive current.When the mean value of current detection signal Vcs during less than the second reference voltage VR2, the level of the second average value signal ILva will raise, the inductive current valley of electric current valley value detection circuit 505 controls simultaneously also can synchronously raise the mean value of motor current detection signal Vcs, make the mean value of current detection signal Vcs equal the first reference voltage VR2, vice versa.Electric current valley control signal Vva has determined that by the second reference voltage VR2 the valley of inductive current is ILva/Rcs, current peak control signal Vpk has determined that by the first reference voltage VR1 the peak value of inductive current is VR1/Rcs, and the second reference voltage VR2 has also determined that the mean value of inductive current is VR2/Rcs simultaneously.
Described the 3rd embodiment 600 of foundation LED driver of the present invention with reference to figure 6A, described LED driver is only variant with the second embodiment 300 on control circuit 606.The electric current valley control circuit 611 of the control circuit 606 of the LED driver 600 of the present embodiment comprises, a zero current detecting circuit 602 as shown in Figure 6B, its input is the common port of inductance 303 and current detection circuit 205, output is electric current valley control signal Vva, it is after zero that zero current detecting circuit 602 utilizes inductive current, inductance 303 and the principle of with the common port appearance of current detection circuit 205, vibrating, can detect inductive current is zero moment point.
Figure 7 shows that it comprises the following steps according to the flow chart of the first embodiment of the control method of a kind of LED driver of the present invention:
First step current detection circuit detects inductive current, and the output electric current measure signal;
Second step current peak control circuit received current detection signal and the first reference voltage, output current peak value control signal;
The 3rd step electric current valley control circuit received current detection signal and the second reference voltage, output current valley control signal;
The 4th pace pulse bandwidth modulation signals produces circuit received current peak value control signal and electric current valley control signal, and the output pulse width modulation signal disconnects and the turn on-switch circuit, to keep the desired value of load LED current constant as setting.
Figure 8 shows that it comprises the following steps according to the flow chart of the second embodiment of the control method of a kind of LED driver of the present invention:
First step current detection circuit detects inductive current, and the output electric current measure signal;
Second step the first averaging circuit receives described current detection signal and the first reference voltage, output the first average value signal;
The 3rd step current peak testing circuit receives described current detection signal and the first average value signal, output current peak value control signal;
The 4th step electric current valley control circuit received current detection signal and the second reference voltage, output current valley control signal;
The 5th pace pulse bandwidth modulation signals produces circuit received current peak value control signal and electric current valley control signal, and the output pulse width modulation signal disconnects and the turn on-switch circuit, to keep the desired value of load LED current constant as setting.
Figure 9 shows that it comprises the following steps according to the flow chart of the 3rd embodiment of the control method of a kind of LED driver of the present invention:
First step current detection circuit detects inductive current, and the output electric current measure signal;
Second step current peak control circuit received current detection signal and the first reference voltage, output current peak value control signal;
The 3rd step second averaging circuit receives described current detection signal and the second reference voltage, output the second average value signal;
The 4th step electric current valley value detection circuit receives described current detection signal and the second average value signal, output current valley control signal;
The 5th pace pulse bandwidth modulation signals produces circuit received current peak value control signal and electric current valley control signal, and the output pulse width modulation signal disconnects and the turn on-switch circuit, to keep the desired value of load LED current constant as setting;
As seen, adopt the beneficial effect of LED driver of the present invention to be: the electric current of load LED will be more accurate, and can not be subject to input voltage, the impact of inductance value and load LED forward voltage.
Although with reference to several exemplary embodiments, described the present invention, should be appreciated that term used is explanation and exemplary, nonrestrictive term.The spirit or the essence that do not break away from invention 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 should be in the spirit and scope that the claim of enclosing limits explain widely, therefore fall into whole variations in claim or its equivalent scope and remodeling and all should be the claim of enclosing and cover.
Claims (10)
1. a LED driver, comprise an Energy Transfer unit of with load LED, connecting, for described load LED provides electric power; The switching circuit that couples with the Energy Transfer unit; And be the fly-wheel diode of Energy Transfer unit afterflow, it is characterized in that, described LED driver also comprises a control circuit, is used for controlling the switching circuit that couples with the Energy Transfer unit, thereby controls the electric power of the load LED that flows through.
2. LED driver according to claim 1, is characterized in that, the control circuit of described LED driver comprises:
Current detection circuit, the electric current that all provides indication to flow through described Energy Transfer unit, and output electric current measure signal are provided when described switching circuit switches on and off;
The current peak control circuit, receive described current detection signal and the first reference voltage, and generation current peak value control signal;
Electric current valley control circuit, receive described current detection signal and the second reference voltage, and generation current valley control signal;
Pulse width modulating signal produces circuit and receives described current peak control signal and electric current valley control signal, produces a pulse width modulating signal control switch circuit and switches on and off, take the constant desired value as setting of the average current of keeping load LED;
Wherein, the average current of described load LED is only relevant with reference voltage;
The reference ground of LED driver and the reference ground of control circuit are not same with reference to ground.
3. control circuit according to claim 2, is characterized in that, the reference ground of described control circuit is the end that Energy Transfer unit and load LED do not join.
4. LED driver according to claim 1, is characterized in that, the switching circuit of described LED driver is comprised of power MOS pipe, pliotron or other switching mode devices.
5. LED driver according to claim 1, it is characterized in that, the Energy Transfer unit of described LED driver is a transformer, the main of transformer is coupled in series in current path between switching circuit and current detection circuit, or be coupled in series in current path between the reference ground of current detection circuit and LED driver the secondary and load LED coupled in parallel of transformer.
6. LED driver according to claim 1, is characterized in that, the Energy Transfer unit of described LED driver is an inductance, and following description will replace the Energy Transfer unit with inductance.
7. LED driver according to claim 1, is characterized in that, described LED driver is based on buck topology, any in the buck topology.
8. control circuit according to claim 2, it is characterized in that, the current detection circuit of described control circuit is coupled in series on current path between switching circuit and inductance, one end and inductance couple, the negative electrode of the other end and diode and the common port of switching circuit couple, comprise a current sense resistor, inductive current flows through this resistance, and produces the current detection signal of indication inductive current transient current on current sense resistor.
9. control circuit according to claim 2, is characterized in that, the common port that the reference ground of described control circuit couples mutually for switching circuit, current detection circuit and fly-wheel diode.
10. control circuit according to claim 2, is characterized in that, the current peak control circuit of described control circuit comprises,
The first averaging circuit, receive the first reference voltage and current detection signal, and export the first average value signal;
The current peak testing circuit, receive described the first average value signal and current detection signal, output current peak value control signal.
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| CN2013102841810A CN103402285A (en) | 2013-07-08 | 2013-07-08 | Control circuit of LED (Light-emitting Diode) driver and control method thereof |
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| CN2013102841810A CN103402285A (en) | 2013-07-08 | 2013-07-08 | Control circuit of LED (Light-emitting Diode) driver and control method thereof |
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| CN2013102841810A Pending CN103402285A (en) | 2013-07-08 | 2013-07-08 | Control circuit of LED (Light-emitting Diode) driver and control method thereof |
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| CN103442489A (en) * | 2013-09-01 | 2013-12-11 | 郑儒富 | Average pattern constant-current controlling circuit and controlling method for LED driving circuit |
| CN106205504A (en) * | 2016-08-12 | 2016-12-07 | 江西康铭盛光电科技有限公司 | A kind of LED backlight light adjusting system |
| CN104319998B (en) * | 2014-09-29 | 2017-12-05 | 矽力杰半导体技术(杭州)有限公司 | A kind of switching power source control circuit, Switching Power Supply and control method |
| CN107623966A (en) * | 2017-09-27 | 2018-01-23 | 上海晶丰明源半导体股份有限公司 | Drive control circuit, drive control chip, driving control system and method |
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| CN103442489A (en) * | 2013-09-01 | 2013-12-11 | 郑儒富 | Average pattern constant-current controlling circuit and controlling method for LED driving circuit |
| CN104319998B (en) * | 2014-09-29 | 2017-12-05 | 矽力杰半导体技术(杭州)有限公司 | A kind of switching power source control circuit, Switching Power Supply and control method |
| CN106205504A (en) * | 2016-08-12 | 2016-12-07 | 江西康铭盛光电科技有限公司 | A kind of LED backlight light adjusting system |
| CN107623966A (en) * | 2017-09-27 | 2018-01-23 | 上海晶丰明源半导体股份有限公司 | Drive control circuit, drive control chip, driving control system and method |
| CN107623966B (en) * | 2017-09-27 | 2024-04-26 | 上海晶丰明源半导体股份有限公司 | Drive control circuit, drive control chip, drive control system and method |
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Application publication date: 20131120 |