CN105792437A - LED drive circuit - Google Patents
LED drive circuit Download PDFInfo
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- CN105792437A CN105792437A CN201610262294.4A CN201610262294A CN105792437A CN 105792437 A CN105792437 A CN 105792437A CN 201610262294 A CN201610262294 A CN 201610262294A CN 105792437 A CN105792437 A CN 105792437A
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/40—Details of LED load circuits
- H05B45/44—Details of LED load circuits with an active control inside an LED matrix
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/10—Controlling the intensity of the light
- H05B45/14—Controlling the intensity of the light using electrical feedback from LEDs or from LED modules
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Abstract
The application provides an LED drive circuit. The LED drive circuit is characterized in that a non-isolated DC/DC conversion unit and a current stabilization unit which are connected in series at an output end drive an LED load jointly, a voltage loop control unit controls the phases of the output voltage ripples of the non-isolated DC/DC conversion unit and the current stabilization unit to be inverse according to a sampling signal VS for representing an output voltage V2 of the non-isolated DC/DC conversion unit, a feedback signal VFB relevant with the output ripple of the current stabilization unit and a DC reference signal Vref positively related with the output ripple, and enables the output voltage average value of the non-isolated DC/DC conversion unit to change along with the output ripple of the current stabilization unit, thereby reducing or even eliminating the ripples on the LED load, avoiding the situation that an output current has larger ripples, so that an LED lamp generates a glitter phenomenon, and guaranteeing the stable circuit and the optimal efficiency.
Description
Technical field
The present invention relates to LED actuation techniques field, particularly relate to a kind of LED drive circuit.
Background technology
LED, as a kind of novel illumination device, owing to its luminous efficiency is high, it is widely used in lighting field, and it typically requires constant-current driving, the LED driver driven as its current stabilization in the prior art is in order to realize characteristic with low cost and simple in construction, frequently with single-stage solution.
And adopt the LED driver of single-stage solution, owing to PFC (PowerFactorCorrection taken into account by needs, PFC) function, namely it controls loop needs very slow response speed just can have higher PF (PowerFactor, power factor) value, therefore, it is slower that it controls loop response speed, and this can cause output electric current to have bigger ripple, the cycle of this ripple is the half in input ac voltage cycle.When LED driver connects load, this current ripples will cause that stroboscopic phenomenon occurs in LED, and this stroboscopic phenomenon will affect the service life of LED, and human eye also has certain damage.
Summary of the invention
In view of this, the invention provides a kind of LED drive circuit, to solve the problem that prior art output electric current has bigger ripple and causes LED stroboscopic phenomenon occur.
To achieve these goals, the technical scheme that the embodiment of the present invention provides is as follows:
A kind of LED drive circuit, including:
Steady flow unit, the current value stable for controlling the output of described LED drive circuit；
The non-isolation DC that outfan is connected with the outfan of described steady flow unit/DC converter unit, described steady flow unit and described non-isolation DC/DC converter unit are provided commonly for driving LED load；
The feedback signal acquiring unit that input is connected with the outfan of described steady flow unit；Described feedback signal acquiring unit is for obtaining the output ripple of described steady flow unit, and generates the feedback signal relevant to described output ripple according to described output ripple；Described output ripple includes: output current ripple and/or described output voltage ripple；
DC reference acquiring unit, described DC reference acquiring unit is for generating the positively related DC reference signal with the size of described output ripple；
The Voltage loop control unit that two inputs are connected with the outfan of the outfan of described DC reference acquiring unit and described feedback signal acquiring unit respectively；The outfan of described Voltage loop control unit is connected with the control end of described non-isolation DC/DC converter unit；Described Voltage loop control unit is used for obtaining a sampled signal characterizing described non-isolation DC/DC converter unit output voltage, and receive described feedback signal and described DC reference signal, for controlling the output voltage of described non-isolation DC/DC converter unit, make the opposite in phase of the output voltage ripple of described non-isolation DC/DC converter unit and the output voltage ripple of described steady flow unit according to described feedback signal, and make the output voltage average value of described non-isolation DC/DC converter unit follow the size of described output ripple according to described DC reference signal and change.
Preferably, described feedback signal acquiring unit includes: block isolating circuit；The input of described block isolating circuit is connected with the outfan of described steady flow unit, and the outfan of described block isolating circuit is connected with the input of described Voltage loop control unit.
Preferably, described feedback signal acquiring unit includes: difference channel and block isolating circuit；Wherein:
Two inputs of described difference channel are connected with two outfans of described steady flow unit respectively, and described difference channel is for obtaining the output parameter of described steady flow unit；
The input of described block isolating circuit is connected with the outfan of described difference channel, described block isolating circuit is for obtaining the described feedback signal relevant to described steady flow unit output ripple according to described output parameter, and described feedback signal is input to described Voltage loop control unit.
Preferably, described DC reference acquiring unit includes: obtain the maximum value circuit that feedback signal maximum is described DC reference signal；The input of described maximum value circuit connects the outfan of described block isolating circuit, and the outfan of described maximum value circuit is the outfan of described DC reference acquiring unit.
Preferably, described DC reference acquiring unit includes: make described DC reference signal vary with temperature and the temperature sensing circuit of inverse change.
Preferably, described steady flow unit is isolated form topology, and described steady flow unit includes: primary side winding, the first vice-side winding, the first rectification module, the first resistance and the first switching tube；Wherein:
The outfan of described first vice-side winding is connected with the input of described first rectification module；
The outfan that outfan is described steady flow unit of described first rectification module；
Different name end is described steady flow unit input of described primary side winding；
The Same Name of Ends of described primary side winding passes sequentially through described first switching tube and another input of the described first resistance described steady flow unit of connection；
The control termination of described first switching tube is received and is driven signal.
Preferably, described steady flow unit also includes: the second vice-side winding and the second rectification module；The outfan of described second vice-side winding is connected with the input of described second rectification module；The outfan of described second rectification module is connected with the input of described non-isolation DC/DC converter unit.
Preferably, described Voltage loop control unit includes: adder and the first integrated transporting discharging；One input of described adder receives described DC reference signal, and another input of described adder receives described feedback signal；The outfan of described adder is connected with an input of described first integrated transporting discharging；Another input of described first integrated transporting discharging receives described sampled signal；
Or, described Voltage loop control unit includes: subtractor and the second integrated transporting discharging；One input of described subtractor receives described feedback signal；Another input of described subtractor receives described sampled signal；The outfan of described subtractor is connected with an input of described second integrated transporting discharging；Another input of described second integrated transporting discharging receives described DC reference signal；
Wherein, described feedback signal and described output ripple opposite in phase.
Preferably, described Voltage loop control unit includes: subtractor and the first integrated transporting discharging；One input of described subtractor receives described DC reference signal, and another input of described subtractor receives described feedback signal；The outfan of described subtractor is connected with an input of described first integrated transporting discharging；Another input of described first integrated transporting discharging receives described sampled signal；
Or, described Voltage loop control unit includes: adder and the second integrated transporting discharging；One input of described adder receives described feedback signal；Another input of described adder receives described sampled signal；The outfan of described adder is connected with an input of described second integrated transporting discharging；Another input of described second integrated transporting discharging receives described DC reference signal；
Wherein, described feedback signal is identical with described output ripple phase place.
Preferably, also including dimming control unit, described dimming control unit output dim signal, to described steady flow unit, makes the output electric current of described steady flow unit change.
The application provides a kind of LED drive circuit, controls, by steady flow unit, the current value that the output of described LED drive circuit is stable；Non-isolation DC/DC the converter unit connected by outfan drives LED load jointly with described steady flow unit；Obtained the output ripple of described steady flow unit by feedback signal acquiring unit, and generate the feedback signal VFB of described output ripple according to described output ripple；Then pass through DC reference acquiring unit and generate the positively related DC reference signal Vref of size with described output ripple；The last sampled signal VS being obtained a sign described non-isolation DC/DC converter unit output voltage V2 by Voltage loop control unit, and receive feedback signal VFB and DC reference signal Vref, the opposite in phase of the output voltage ripple of described non-isolation DC/DC converter unit and the output voltage ripple of described steady flow unit is controlled according to described sampled signal VS, and make the output voltage average value of described non-isolation DC/DC converter unit follow the size of described output ripple according to DC reference signal Vref and change, the output voltage ripple of described non-isolation DC/DC converter unit is made to offset with the output voltage ripple of described steady flow unit, and then make the ripple reduction in LED load even eliminate, output electric current is avoided to have bigger ripple and cause LED that stroboscopic phenomenon occurs.
Accompanying drawing explanation
In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, the accompanying drawing used required in embodiment or description of the prior art will be briefly described below, apparently, accompanying drawing in the following describes is only embodiments of the invention, for those of ordinary skill in the art, under the premise not paying creative work, it is also possible to obtain other accompanying drawing according to the accompanying drawing provided.
The structural representation of a kind of LED drive circuit that Fig. 1 provides for the embodiment of the present application；
A kind of signal waveform schematic diagram that Fig. 2 provides for another embodiment of the application；
Another signal waveform schematic diagram that Fig. 3 provides for another embodiment of the application；
The structural representation of a kind of LED drive circuit that Fig. 4 provides for another embodiment of the application；
The structural representation of another LED drive circuit that Fig. 5 provides for another embodiment of the application.
Detailed description of the invention
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, it is clear that described embodiment is only a part of embodiment of the present invention, rather than whole embodiments.Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under not making creative work premise, broadly fall into the scope of protection of the invention.
The invention provides a kind of LED drive circuit, to solve the problem that prior art output electric current has bigger ripple and causes LED stroboscopic phenomenon occur.
Concrete, as it is shown in figure 1, described LED drive circuit includes: steady flow unit 101, non-isolation DC/DC converter unit 102, feedback signal acquiring unit 103, DC reference acquiring unit 104 and Voltage loop control unit 105；Wherein:
The outfan series connection of steady flow unit 101 and non-isolation DC/DC converter unit 102；
The input of feedback signal acquiring unit 103 is connected with the outfan of steady flow unit 101；
Two inputs of Voltage loop control unit 105 are connected with the outfan of the outfan of feedback signal acquiring unit 103 and DC reference acquiring unit 104 respectively；The outfan of Voltage loop control unit 105 is connected with the control end of non-isolation DC/DC converter unit 102.
What deserves to be explained is, in Fig. 1, the anode of the outfan of steady flow unit 101 is connected with the positive pole of LED load, and the negative terminal of the outfan of non-isolation DC/DC converter unit 102 is connected with the negative pole of described LED load；In actual applications, it would however also be possible to employ the anode of outfan of non-isolation DC/DC converter unit 102 is connected with the positive pole of LED load, the negative terminal of the outfan of steady flow unit 101 is connected with the negative pole of described LED load；Fig. 1 is only the connected mode of a kind of example, steady flow unit 101 and non-isolation DC/DC converter unit 102 and described LED load and is not specifically limited, it is possible to determine according to the applied environment of its reality.
Concrete operation principle is:
Steady flow unit 101 controls the current value that the output of described LED drive circuit is stable；
Non-isolation DC/DC converter unit 102 and steady flow unit 101 drive LED load jointly；
Feedback signal acquiring unit 103 obtains the output ripple of steady flow unit 101, and generates the feedback signal VFB relevant to described output ripple according to described output ripple；
Optionally, described output ripple includes: output current ripple and/or output voltage ripple.
DC reference acquiring unit 104 generates the positively related DC reference signal Vref of size with described output ripple；
Voltage loop control unit 105 obtains a sampled signal VS characterizing non-isolation DC/DC converter unit 102 output voltage V2, and receive feedback signal VFB and DC reference signal Vref, make the opposite in phase of the output voltage ripple of non-isolation DC/DC converter unit 102 and the output voltage ripple of steady flow unit 101 according to sampled signal VS, and make the output voltage average value of non-isolation DC/DC converter unit 102 follow the size of output ripple of steady flow unit 101 according to DC reference signal Vref and change.
The described LED drive circuit that the application provides, by above-mentioned annexation and operation principle, control the opposite in phase of the output voltage ripple of non-isolation DC/DC converter unit 102 and the output voltage ripple of steady flow unit 101, and make the output voltage average value of non-isolation DC/DC converter unit 102 follow the size of described output ripple and change, the output voltage ripple of non-isolation DC/DC converter unit 102 is made to offset with the output voltage ripple of steady flow unit 101, and then make the ripple reduction in LED load even eliminate, output electric current is avoided to have bigger ripple and cause LED that stroboscopic phenomenon occurs.
What deserves to be explained is, in prior art, in order to avoid the stroboscopic phenomenon that output electric current has bigger ripple and causes LED to occur, adopt the LED driver of two-step scheme also by more selection, the input of following stage DC-DC converter is directly connected with the outfan of prime AC-DC converter, described prime AC-DC converter is used for realizing PFC function, described rear class DC-DC converter is used for realizing constant current or pressure-keeping functions, the control loop response speed of prime AC-DC converter can be very slow, without causing LED driver output current ripple problem, the control loop response speed of rear class DC-DC converter can be very fast, meet and quickly adjust and reduce output current ripple demand, solve single-stage solution Problems existing easily.
But two-step scheme not only structure is complicated, cost is high, and owing to input power has carried out two times transfer, makes the efficiency product that efficiency is two-stage circuit of LED driver.Such as front stage circuits efficiency is η 1, and late-class circuit efficiency is η 2, then prior art adopts the efficiency eta=η 1 × η 2 of the LED driver of two-step scheme, greatly reduces the efficiency of LED driver, increases loss, it is impossible to highlights the advantage that LED illumination System is energy-conservation.
And adopt the described LED drive circuit that the present embodiment provides, by above-mentioned connected mode and control principle, loop response speed without accelerating main circuit exports to realize low ripple, therefore while can ensure that higher PF value, if the efficiency of steady flow unit 101 is η 1, the efficiency of non-isolation DC/DC converter unit 102 is η 2, then the efficiency eta of described LED drive circuit is only slightly less than η 1, the efficiency eta of the described LED drive circuit degree less than η 1 depends on that non-isolation DC/DC converter unit 102 processes the size of power, the LED driver efficiency adopting two-step scheme in compared to existing technology is high and loss is low.
In concrete practical application, the DC reference signal Vref of DC reference acquiring unit 104 generation in Fig. 1 and the size positive correlation of described output ripple, specifically refer to, DC reference signal Vref changes in the same direction with the ripple size variation of steady flow unit 101 output voltage V1, namely the ripple of steady flow unit 101 output voltage V1 is more big, and DC reference signal Vref is also more big.
Shown in V1 in the output voltage waveforms of described steady flow unit such as Fig. 2, described feedback signal acquiring unit obtain V1 AC compounent obtain feedback signal VFB, described DC reference acquiring unit generates the positively related DC reference signal Vref of size with described output ripple, described Voltage loop control unit obtains a sampled signal VS characterizing non-isolation DC/DC converter unit output voltage V2, described Voltage loop control unit is according to VFB, Vref and VS exports control signal, described non-isolation DC/DC converter unit accepts described control signal, make self output voltage V2 with the AC compounent reverse with the AC compounent of V1.The output voltage Vled=V1+V2 of so obtained described LED drive circuit, its ripple will reduce.In order to the ripple output voltage Vled of described LED drive circuit on is completely eliminated, the size of the AC compounent of V2 should equal in magnitude with V1 AC compounent, in opposite direction.
Feedback signal acquiring unit 103 in Fig. 1 and the setting of DC reference acquiring unit 104, be to obtain the signal (Vref-VFB) reverse with the ripple of steady flow unit 101 output voltage V1, as shown in Figure 2；The valley of the peak value of steady flow unit 101 output voltage V1 corresponding (Vref-VFB)；And by (Vref-VFB) comparison signal as sampled signal VS, Voltage loop control unit 105 exports control signal VC according to both comparative results, the output voltage making non-isolation DC/DC converter unit 102 is equal in magnitude with steady flow unit 101 output voltage V1, in opposite direction, the ripple in LED load is eliminated with this.
Oscillogram as shown in Figure 3, in order to the ripple of the output voltage Vled of described LED drive circuit is completely eliminated, DC reference signal Vref should be greater than being equal to the half of V1 ripple peak-to-peak value, otherwise, (Vref-VFB) will appear from continuous 0 value, the ripple on the output voltage Vled of described LED drive circuit can not be completely eliminated；And, the value of DC reference signal Vref followed by the change of V1 ripple and changes, V1 ripple increases (V1 ' as shown in Figure 3), then Vref increases (Vref ' as shown in Figure 3), (Vref-VFB) also will increase, as shown in Figure 3 (Vref '-VFB ')；Otherwise, V1 ripple reduces, and Vref reduces.
Because the energy (DC voltage) that LED load obtains from described non-isolation DC/DC converter unit have passed through described steady flow unit and described non-isolation DC/DC converter unit two-stage circuit, its efficiency is lower than the efficiency merely through described steady flow unit, change so arranging DC reference signal Vref along with the change of the output voltage V1 ripple of described steady flow unit, can not only ensure to drop the effect of ripple, and circuit efficiency can be improved.So, it is most preferred that, the DC reference signal Vref half equal to the output voltage V1 ripple peak-to-peak value of described steady flow unit is set, or stable for holding circuit, slightly larger than its half.It is not specifically limited, all in the protection domain of the application herein.
In another embodiment, the sampled signal VS characterizing described non-isolation DC/DC converter unit output voltage V2 directly obtains from the outfan of described non-isolation DC/DC converter unit, as shown in Figure 4.
Preferably, as shown in Figure 4, described steady flow unit is isolated form topology, and described steady flow unit includes: primary side winding, first vice-side winding the 401, first rectification module, the first resistance R1 and the first switching tube K1；Wherein:
The outfan of the first vice-side winding 401 is connected with the input of described first rectification module；
The outfan that outfan is described steady flow unit of described first rectification module；
Different name end is described steady flow unit input of described primary side winding；
The Same Name of Ends of described primary side winding passes sequentially through the first switching tube K1 and the first resistance R1 and is connected to another input of described steady flow unit；
The control termination of the first switching tube K1 is received and is driven signal；Described driving signal controls described steady flow unit and realizes stable electric current output.
Preferably, described driving signal is the signal controlling the output of described steady flow unit current stabilization according to described steady flow unit primary current sampled signal.
Preferably, described primary current is obtained by the first resistance R1 sampling.
Preferably, as shown in Figure 4, described steady flow unit also includes: the second vice-side winding 402 and the second rectification module；The outfan of the second vice-side winding 402 is connected with the input of described second rectification module；The outfan of described second rectification module is connected with the input of described non-isolation DC/DC converter unit.
Voltage referring to Fig. 4, when described steady flow unit is isolated form topology, after the transformator that input voltage vin is described steady flow unit second vice-side winding 402 of described non-isolation DC/DC converter unit is rectified.
Preferably, as shown in Figure 4, described feedback signal acquiring unit includes: block isolating circuit；The input of described block isolating circuit connects the outfan of described steady flow unit, and the outfan of described block isolating circuit is connected with the input of described Voltage loop control unit.
Described steady flow unit shown in Fig. 4 and described feedback signal acquiring unit are only a kind of example, are not necessarily limited to this, it is possible to depending on the applied environment that it is concrete.
In another embodiment of the present invention, as shown in Figure 4, described DC reference acquiring unit includes: make DC reference signal Vref vary with temperature and the temperature sensing circuit of inverse change.
Owing to temperature is more low, the output electrochemical capacitor ESR of described steady flow unit and shown non-isolation DC/DC converter unit increases, and ripple increases.Therefore described DC reference acquiring unit includes described temperature sensing circuit, it is possible to make the DC reference signal Vref being input to described Voltage loop control unit change along with variations in temperature, and temperature raises, and DC reference signal Vref reduces；Temperature reduces, and DC reference signal Vref raises.Avoid temperature for the impact of output ripple；Ensure all to have under different temperatures to drop ripple effect preferably, also can guarantee that circuit stability and efficiency optimization simultaneously.
Optionally, described Voltage loop control unit includes: subtractor and the first integrated transporting discharging；One input of described subtractor receives DC reference signal Vref, and another input of described subtractor receives feedback signal VFB；The outfan of described subtractor is connected with an input of described first integrated transporting discharging；Another input of described first integrated transporting discharging receives sampled signal VS；
Or, described Voltage loop control unit includes: adder and the second integrated transporting discharging；One input of described adder receives feedback signal VFB；Another input of described adder receives sampled signal VS；The outfan of described adder is connected with an input of described second integrated transporting discharging；Another input of described second integrated transporting discharging receives DC reference signal Vref；
Wherein said feedback signal is identical with described output ripple phase place.
Or, optionally, described Voltage loop control unit includes: adder and the first integrated transporting discharging；One input of described adder receives described DC reference signal, and another input of described adder receives described feedback signal；The outfan of described adder is connected with an input of described first integrated transporting discharging；Another input of described first integrated transporting discharging receives described sampled signal；
Or, described Voltage loop control unit includes: subtractor and the second integrated transporting discharging；One input of described subtractor receives described feedback signal；Another input of described subtractor receives described sampled signal；The outfan of described subtractor is connected with an input of described second integrated transporting discharging；Another input of described second integrated transporting discharging receives described DC reference signal；
Wherein, described feedback signal and described output ripple opposite in phase.
The AC compounent that the effect of described block isolating circuit is the output voltage V1 obtaining described steady flow unit obtains feedback signal VFB, and is input to described Voltage loop control unit；DC reference signal Vref and feedback signal VFB subtract each other after as the reference signal of sampled signal VS, VS exports described control signal with (Vref-VFB) after comparing；Or the described control signal of output is compared after VS and VFB superposition with Vref.It is not specifically limited, all in the protection domain of the application herein.
In another embodiment, the sampled signal VS of described sign non-isolation DC/DC converter unit output voltage V2 directly obtains from the outfan of described non-isolation DC/DC converter unit, as shown in Figure 5.
Preferably, as it is shown in figure 5, described steady flow unit includes: primary side winding, first vice-side winding the 401, first switching tube K1, the first resistance R1, the first diode D1 and the first electric capacity C1；Wherein:
The anode of the first diode D1 and the Same Name of Ends of the first vice-side winding 401 are connected；
The negative electrode of the first diode D1 and one end of the first electric capacity C1 are connected；
The other end of the first electric capacity C1 and the different name end of the first vice-side winding 401 are connected；
Two outfans of the two ends of the first electric capacity C1 respectively described steady flow unit；
Different name end is described steady flow unit input of described primary side winding；
The Same Name of Ends of described primary side winding passes sequentially through the first switching tube K1 and the first resistance R1 and connects another input of described steady flow unit；
The control termination of the first switching tube K1 is received and is driven signal；.
Preferably, as it is shown in figure 5, described non-isolation DC/DC converter unit is buck circuit；Described non-isolation DC/DC converter unit includes: second switch pipe K2, the second diode D2 and the first inductance L1；Wherein:
The input of second switch pipe K2 is an input of described non-isolation DC/DC converter unit；
One end of the outfan of second switch pipe K2 and the negative electrode of the second diode D2 and the first inductance L1 is connected；
The anode of the second diode D2 is another input of described non-isolation DC/DC converter unit；
Two outfans of the other end of the first inductance L1 and the anode of the second diode D2 respectively described non-isolation DC/DC converter unit.
The input of described non-isolation DC/DC converter unit receives input voltage vin, at the outfan parallel connection high-frequency filter capacitor (i.e. the second electric capacity C2) of described non-isolation DC/DC converter unit, makes in the electric current of described LED load without high fdrequency component.
Preferably, as it is shown in figure 5, feedback signal acquiring unit 103 includes: difference channel and block isolating circuit；Wherein:
Two inputs of described difference channel are connected with two outfans of described steady flow unit respectively；
The outfan of described difference channel is connected with the input of described block isolating circuit；
The outfan of described block isolating circuit is connected with the input of the input of described Voltage loop control unit and described DC reference acquiring unit.
Preferably, as it is shown in figure 5, DC reference acquiring unit 104 includes: maximum value circuit；The input of described maximum value circuit is the input of described DC reference acquiring unit, connect the outfan of described block isolating circuit, the outfan of described maximum value circuit is the outfan of described DC reference acquiring unit, is connected to another input of Voltage loop control unit.
Described maximum value circuit acquisition feedback signal VFB the maximum negating feedback signal VFB are DC reference signal Vref.
Concrete, feedback signal acquiring unit 103 obtains the AC compounent of the output voltage V1 of described steady flow unit by described difference channel and described block isolating circuit；Owing to the maximum of AC signal is equivalent to the half of ripple peak-to-peak value, so obtain the maximum of the AC compounent of the output voltage V1 of described steady flow unit either directly through described maximum value circuit, just can obtain the half of the output voltage V1 ripple peak-to-peak value of described steady flow unit: V1 ripple is more big, then described maximum is more big.DC reference acquiring unit 104 includes maximum value circuit, utilizes maximum value circuit to obtain DC reference signal Vref；
In concrete practical application, it is possible to by (Vref-VFB) reference signal as VS, compare with VS and control second switch pipe K2 and make the AC compounent of its output voltage V2 in opposite direction with the AC compounent of V1, equal in magnitude；Or with Vref, the superposed signal (VS+VFB) of VFB and VS is compared control second switch pipe K2 makes the AC compounent of its output voltage V2 in opposite direction with the AC compounent of V1, equal in magnitude.
Further, the above difference channel, all it is because common ground problem; if by the negative terminal of steady flow unit 101 outfan directly as ground; then need not described difference channel, but now sampled signal VS will respective change, so difference channel should in no way limit the protection domain of the application.
It should be noted that because main power circuit is described steady flow unit, namely described LED drive circuit is current stabilization output, then LED load size variation, the size of V1 also can respective change.
Especially, when described LED drive circuit can also apply to dim, described LED drive circuit also includes dimming control unit, and the outfan output dim signal of described dimming control unit, to described steady flow unit, makes the output size of current of described steady flow unit change.Concrete dimming mode is similar with prior art, in the process of light modulation the size of V1 also can respective change, namely V1 can change, and excursion is determined by the output voltage range of described steady flow unit.When light modulation is used, because different size of current, ripple varies in size, and arranges Vref and follows ripple size variation in real time, can guarantee that and drops ripple effect and high efficiency under different electric current, and this circuit also has significant beneficial effect in light modulation is used.
In the present invention, each embodiment adopts the mode gone forward one by one to describe, and what each embodiment stressed is the difference with other embodiments, between each embodiment identical similar portion mutually referring to.For device disclosed in embodiment, owing to it corresponds to the method disclosed in Example, so what describe is fairly simple, relevant part illustrates referring to method part.
Below it is only the preferred embodiment of the present invention, makes to skilled artisans appreciate that or realize the present invention.The multiple amendment of these embodiments be will be apparent to one skilled in the art, and generic principles defined herein can without departing from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention is not intended to be limited to the embodiments shown herein, and is to fit to the widest scope consistent with principles disclosed herein and features of novelty.
Claims (10)
1. a LED drive circuit, it is characterised in that including:
Steady flow unit, the current value stable for controlling the output of described LED drive circuit；
The non-isolation DC that outfan is connected with the outfan of described steady flow unit/DC converter unit, described steady flow unit and described non-isolation DC/DC converter unit are provided commonly for driving LED load；
The feedback signal acquiring unit that input is connected with the outfan of described steady flow unit；Described feedback signal acquiring unit is for obtaining the output ripple of described steady flow unit, and generates the feedback signal relevant to described output ripple according to described output ripple；Described output ripple includes: output current ripple and/or described output voltage ripple；
DC reference acquiring unit, described DC reference acquiring unit is for generating the positively related DC reference signal with the size of described output ripple；
The Voltage loop control unit that two inputs are connected with the outfan of the outfan of described DC reference acquiring unit and described feedback signal acquiring unit respectively；The outfan of described Voltage loop control unit is connected with the control end of described non-isolation DC/DC converter unit；Described Voltage loop control unit is used for obtaining a sampled signal characterizing described non-isolation DC/DC converter unit output voltage, and receive described feedback signal and described DC reference signal, for controlling the output voltage of described non-isolation DC/DC converter unit, make the opposite in phase of the output voltage ripple of described non-isolation DC/DC converter unit and the output voltage ripple of described steady flow unit according to described feedback signal, and make the output voltage average value of described non-isolation DC/DC converter unit follow the size of described output ripple according to described DC reference signal and change.
2. LED drive circuit according to claim 1, it is characterised in that described feedback signal acquiring unit includes: block isolating circuit；The input of described block isolating circuit is connected with the outfan of described steady flow unit, and the outfan of described block isolating circuit is connected with the input of described Voltage loop control unit.
3. LED drive circuit according to claim 1, it is characterised in that described feedback signal acquiring unit includes: difference channel and block isolating circuit；Wherein:
Two inputs of described difference channel are connected with two outfans of described steady flow unit respectively, and described difference channel is for obtaining the output parameter of described steady flow unit；
The input of described block isolating circuit is connected with the outfan of described difference channel, described block isolating circuit is for obtaining the described feedback signal relevant to described steady flow unit output ripple according to described output parameter, and described feedback signal is input to described Voltage loop control unit.
4. LED drive circuit according to claim 3, it is characterised in that described DC reference acquiring unit includes: obtain the maximum value circuit that feedback signal maximum is described DC reference signal；The input of described maximum value circuit connects the outfan of described block isolating circuit, and the outfan of described maximum value circuit is the outfan of described DC reference acquiring unit.
5. LED drive circuit according to claim 1, it is characterised in that described DC reference acquiring unit includes: make described DC reference signal vary with temperature and the temperature sensing circuit of inverse change.
6. LED drive circuit according to claim 1, it is characterised in that described steady flow unit is isolated form topology, and described steady flow unit includes: primary side winding, the first vice-side winding, the first rectification module, the first resistance and the first switching tube；Wherein:
The outfan of described first vice-side winding is connected with the input of described first rectification module；
The outfan that outfan is described steady flow unit of described first rectification module；
Different name end is described steady flow unit input of described primary side winding；
The Same Name of Ends of described primary side winding passes sequentially through described first switching tube and another input of the described first resistance described steady flow unit of connection；
The control termination of described first switching tube is received and is driven signal.
7. LED drive circuit according to claim 6, it is characterised in that described steady flow unit also includes: the second vice-side winding and the second rectification module；The outfan of described second vice-side winding is connected with the input of described second rectification module；The outfan of described second rectification module is connected with the input of described non-isolation DC/DC converter unit.
8. LED drive circuit according to claim 1, it is characterised in that described Voltage loop control unit includes: adder and the first integrated transporting discharging；One input of described adder receives described DC reference signal, and another input of described adder receives described feedback signal；The outfan of described adder is connected with an input of described first integrated transporting discharging；Another input of described first integrated transporting discharging receives described sampled signal；
Or, described Voltage loop control unit includes: subtractor and the second integrated transporting discharging；One input of described subtractor receives described feedback signal；Another input of described subtractor receives described sampled signal；The outfan of described subtractor is connected with an input of described second integrated transporting discharging；Another input of described second integrated transporting discharging receives described DC reference signal；
Wherein, described feedback signal and described output ripple opposite in phase.
9. LED drive circuit according to claim 1, it is characterised in that described Voltage loop control unit includes: subtractor and the first integrated transporting discharging；One input of described subtractor receives described DC reference signal, and another input of described subtractor receives described feedback signal；The outfan of described subtractor is connected with an input of described first integrated transporting discharging；Another input of described first integrated transporting discharging receives described sampled signal；
Or, described Voltage loop control unit includes: adder and the second integrated transporting discharging；One input of described adder receives described feedback signal；Another input of described adder receives described sampled signal；The outfan of described adder is connected with an input of described second integrated transporting discharging；Another input of described second integrated transporting discharging receives described DC reference signal；
Wherein, described feedback signal is identical with described output ripple phase place.
10., according to the arbitrary described LED drive circuit of claim 1-9, it is characterised in that also include dimming control unit, described dimming control unit output dim signal, to described steady flow unit, makes the output electric current of described steady flow unit change.
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| CN110971849A (en) * | 2018-09-28 | 2020-04-07 | 强弦科技股份有限公司 | Power supply for liquid crystal television |
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