CN202889703U - DC light-modulation type LED drive circuit - Google Patents
DC light-modulation type LED drive circuit Download PDFInfo
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- CN202889703U CN202889703U CN2012204205384U CN201220420538U CN202889703U CN 202889703 U CN202889703 U CN 202889703U CN 2012204205384 U CN2012204205384 U CN 2012204205384U CN 201220420538 U CN201220420538 U CN 201220420538U CN 202889703 U CN202889703 U CN 202889703U
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Abstract
The utility model relates to a DC light-modulation type LED drive circuit, comprising a main power-supply Buck converter, a standby power-supply Buck converter, a mainboard microcontroller, N LED lamp strings, N LED lamp-current control circuits and a PWM signal-to-DC light modulation circuit. Output of the main power-supply Buck converter provides power for the N LED lamp strings by an output filter circuit. Output ends of the N LED lamp strings are connected with the corresponding LED lamp-current control circuits. The PWM signal-to-DC light-modulation circuit is used for converting PWM light-modulation signals into simulation DC light-modulation signals, and controlling current values when each LED lamp strings operates by means of the LED lamp current control circuits. The LED drive circuit is relatively high in conversion efficiency, relatively low in design cost, and problems of picture water-ripple interference caused by conventional low-frequency PWM light modulation and abnormal LED-drive noises of power supply products are eliminated.
Description
Technical field
The utility model relates to liquid crystal display product LED fluorescent tube Driving technique, particularly a kind of direct current light modulating LED drive circuit.
Background technology
As shown in Figure 1, Fig. 1 is the existing liquid crystal display product LED lamp tube drive circuit that is applied in.AC mains (90Vrms ~ 264Vrms) after bridge rectifier (diagram does not draw) carries out full-wave rectification, (be called for short: pfc circuit to power factor correction circuit again, Power Factor Correction) (illustrates and do not draw) direct current that boosts about rear output one 400V, this direct current is through main power source Buck change-over circuit 1 " change into the 24V direct current after the step-down; through the Boost booster circuit 2 that LED drives " after export just like: the direct current about 100V is to the LED fluorescent tube, each LED lamp string output of LED fluorescent tube independently connects respectively a constant-current source circuit 31 "; 32 " ... 3n "; constant-current source circuit usually adopts as shown in Figure 2; constant-current source circuit adopts three-terminal shunt regulator constant current control during as the LED lamp works such as: AZ432, and the reference edge of this AZ432 (R end) is a fixed reference comparative voltage 1.25V; The dimming mode of this led drive circuit is the dimming mode of the low frequency pulse-width modulation of PWM, also is called the dimming mode (this Burst-mode light modulating frequency generally is arranged on about 200HZ ~ 1KHZ) of burst mode (Burst-mode).This existing drive circuit adopts the 400V of pfc circuit output through main power source Buck change-over circuit 1 " output one 24V direct current drives through LED again after the step-down Boost boost converter offers the LED fluorescent tube after boosting; carry out through boosting after the first step-down can making the whole power supply conversion efficiency step-down of LED power panel after twice power conversion, and design cost rising problem.And constant-current circuit adopts as: its price of AZ432 three-terminal shunt regulator is more expensive, (be called for short: LM358 price OP) is suitable with inner integrated 2 amplifiers for an AZ432 price, the benchmark comparative voltage of AZ432 is higher 1.25V in addition, when LED lamp string output current is larger, cause easily the power consumption of loss resistance on such as the R33 of Fig. 2 to increase, thereby also have influence on the conversion efficiency that whole LED drives.In addition, adopt the PWM light modulation of low frequency, cause easily picture to produce the water wave wave interference, and LED drives the element such as inductance and produces different mail topic during work.
Summary of the invention
In view of this, the purpose of this utility model provides a kind of direct current light modulating LED drive circuit, can eliminate existing PWM light modulation generation picture water wave wave interference and power supply product LED because of the employing low frequency and drive the problems such as different sound, and conversion efficiency is better, design cost is lower.
The utility model adopts following scheme to realize: a kind of direct current light modulating LED drive circuit, comprise main power source Buck transducer, standby power Buck transducer and mainboard micro controller, and characterized by further comprising:
N bar LED lamp string, the output of described main power source Buck transducer are exported a low-voltage ripple after output filter circuit carries out filtering direct current is as this N bar LED lamp electric input voltage of acting in collusion to make each other's confessions;
N LED lamp current control circuit, N the LED lamp current control circuit that the output of described N bar LED lamp string is corresponding with this is electrically connected, size of current when working in order to control each LED lamp string;
One reference voltage source generating circuit, it receives the Vsb voltage by described standby power Buck transducer output, and produces a reference voltage Vref 1;
One pwm signal turns the direct current light adjusting circuit, it receives the described reference voltage Vref 1 that PWM dim signal that described mainboard micro controller provides and exported by described reference voltage source generating circuit and changes into an analog DC dim signal and offers described LED lamp current control circuit, size of current when LED lamp current control circuit is controlled each LED lamp string work according to the direct voltage size of this analog DC dim signal, thereby the luminosity size when reaching each LED lamp string work of control;
One ON-OFF control circuit, it receives a switching signal and the Vsb voltage by described standby power Buck transducer output of the output of described mainboard micro controller, whether to export work that a control voltage controls described N LED lamp current control circuit;
One LED fluorescent tube output voltage feedback control circuit, the reference voltage Vref 1 that its reception one is exported by this reference voltage source generating circuit, receive simultaneously one by this ON-OFF control circuit export one control voltage, and detect respectively the minimum voltage of described LED lamp string output by diode, this LED fluorescent tube output voltage feedback control circuit detects the feedback compensation signal that a reference voltage Vref 1 that minimum LED lamp string output end voltage and this reference voltage source generating circuit export compares rear output one each LED lamp string input terminal voltage of control by this diode; And
One output feedback control circuit, it is detected the input of described output filter circuit and output end voltage and decides this output feedback control circuit to be defeated by the feedback quantity size of described main power source Buck transducer according to a feedback compensation signal of described LED fluorescent tube output voltage feedback control circuit output, to reach the voltage of the rational LED of control fluorescent tube input; Wherein N is the natural number more than or equal to 1.
In the utility model one embodiment, described LED lamp current control circuit comprises:
One transistor, the output of this transistorized collector electrode and described LED lamp string is electrically connected;
One LED lamp string stream sampling resistor, one end ground connection; And
One amplifier, the output of described transistorized base stage and this amplifier is electrically connected, and the other end of the reverse input end of described transistorized emitter and this amplifier and LED lamp string stream sampling resistor is electrically connected; The non-inverting input of this amplifier and described PWM dim signal turn direct current light adjusting circuit output and are electrically connected, size of current when controlling respectively this LED lamp string work to receive an analog DC dim signal, the feeder ear reception one of this amplifier is controlled voltage as the power supply input voltage of this amplifier by one of ON-OFF control circuit output, this ON-OFF control circuit exports by the micro controller of mainboard that a switching signal determines whether will be for this amplifier provides required supply power voltage, thereby whether reaches each LED lamp current control circuit work of control.
In the utility model one embodiment, described transistor is replaced with metal-oxide-semiconductor.
In the utility model one embodiment, described generating circuit from reference voltage comprises:
One transistor, its collector electrode receive the direct current voltage by described standby power Buck transducer generation,
One three-terminal shunt regulator, its cathode terminal and described transistorized base stage are electrically connected anode tap ground connection;
One resistance R 51 is electrically connected between described transistorized collector electrode and the base stage;
One resistance R 52, an end of this resistance R 52 and described transistorized emitter are electrically connected, and the reference edge of the other end and described three-terminal shunt regulator is electrically connected;
One resistance R 53, an end of this resistance R 53 and the reference edge of described three-terminal shunt regulator are electrically connected, other end ground connection; And
One capacitor C 51, an end of this capacitor C 51 and described transistorized emitter are electrically connected other end ground connection.
In the utility model one embodiment, it is that the pwm signal of a negative light modulation turns the direct current light adjusting circuit that described pwm signal turns the direct current light adjusting circuit, and it comprises transistor Q81, capacitor C 81 and resistance R 81, R82, R83, R86, R87; Described resistance R 83 1 terminations are received a PWM dim signal of described mainboard micro controller output, and the base stage of the other end of this resistance R 83 and described transistor Q81 is electrically connected; Described transistor Q81 grounded emitter, the end of collector electrode and described resistance R 81, R82 is electrically connected; The other end of described resistance R 82 receives a reference voltage Vref 1, and an end of the other end of described resistance R 81 and described capacitor C 81 and an end of described resistance R 86 are electrically connected; The other end of described resistance R 86 and described resistance R 87 1 ends are electrically connected, the other end ground connection of the other end of described resistance R 87, capacitor C 81.
In the utility model one embodiment, it is that the pwm signal of a positive light modulation turns the direct current light adjusting circuit that described pwm signal turns the direct current light adjusting circuit, it comprises transistor Q82, Q81, capacitor C 81, resistance resistance R 81, R82, R83, R84, R85, R86, R87, described resistance R 85 1 terminations are received a PWM dim signal of described mainboard micro controller output, and the base stage of the other end of this resistance R 85 and described transistor Q82 is electrically connected; The end of described resistance R 83, R84 and the collector electrode of described transistor Q82 are electrically connected, and the base stage of the other end of described resistance R 83 and described transistor Q81 is electrically connected; The end of the collector electrode of described transistor Q81 and described resistance R 82, R81 is electrically connected; The other end of described resistance R 84, R82 receives a reference voltage Vref 1; One end of the other end of described resistance R 81 and described capacitor C 81 and an end of described resistance R 86 are electrically connected; The other end of described resistance R 86 and described resistance R 87 1 ends are electrically connected, the grounded emitter of the other end of the other end of described resistance R 87, capacitor C 81, transistor Q81 and Q82.
In the utility model one embodiment, described ON-OFF control circuit comprises:
One resistance R 41, a termination of this resistance R 41 is received a switching signal of mainboard micro controller output;
One transistor Q41, the other end of its base stage and described resistance R 41 is electrically connected, grounded emitter;
One transistor Q42, the collector electrode of its base stage and described transistor Q41 is electrically connected, emitter receives a direct current by described standby power Buck transducer output, and collector electrode controls the amplifier that whether this direct current will be offered described LED lamp current control circuit and LED fluorescent tube output voltage feedback control circuit inside according to the switching signal that described resistance R 41 receives by this transistor Q42.
In the utility model one embodiment, described LED fluorescent tube output voltage feedback control circuit comprises an amplifier OP71, transistor Q71, capacitor C 71 and resistance R 73, R72, R71; Described amplifier OP71 non-inverting input receives a reference voltage Vref 1, one end of described resistance R 73 and the feeder ear of described amplifier OP71 receive the control voltage of described ON-OFF control circuit output, the other end of described resistance R 73 and the reverse input end of described amplifier OP71, one end of capacitor C 71 is electrically connected, one end of the other end of described capacitor C 71 and resistance R 72 is electrically connected, the output of these resistance R 72 other ends and described amplifier OP71 and the base stage of transistor Q71 are electrically connected, the ground end ground connection of this amplifier OP71, one end of the emitter of described transistor Q71 and resistance R 71 is electrically connected, the other end ground connection of resistance R 71.
The utility model is compared to existing drive circuit, and its conversion efficiency is better, design cost is lower, and the utility model can be eliminated and existingly produce picture water wave wave interference and power supply product LED drives the problems such as different sound because of the PWM light modulation simultaneously.
Description of drawings
Fig. 1 is existing led drive circuit principle schematic.
Fig. 2 is the physical circuit figure of constant-current source circuit among Fig. 1.
Fig. 3 is the principle schematic of the utility model embodiment led drive circuit.
Fig. 4 a and Fig. 4 b are the physical circuit figure of the utility model embodiment LED lamp current control circuit.
Fig. 5 is the physical circuit figure of the utility model embodiment generating circuit from reference voltage.
Fig. 6 a is the physical circuit figure that the pwm signal of the negative light modulation of the utility model embodiment turns the direct current light adjusting circuit.
Fig. 6 b is the physical circuit figure that the pwm signal of the positive light modulation of the utility model embodiment turns the direct current light adjusting circuit.
Fig. 7 is the physical circuit figure of the utility model embodiment ON-OFF control circuit.
Fig. 8 is the physical circuit figure of the utility model embodiment LED fluorescent tube output voltage feedback control circuit.
Fig. 9 is a concrete led drive circuit physical circuit figure among the utility model embodiment.
Embodiment
Below in conjunction with drawings and Examples the utility model is described further.
As shown in Figure 3, present embodiment provides a kind of direct current light modulating LED drive circuit, comprise main power source Buck transducer, standby power Buck transducer (Buck transducer, that is: buck power converter) and the mainboard micro controller (be called for short: MCU, Micro Control Unit), characterized by further comprising: N bar LED lamp string, the output of described main power source Buck transducer are exported a low-voltage ripple after output filter circuit carries out filtering direct current is as this N bar LED lamp electric input voltage of acting in collusion to make each other's confessions; N LED lamp current control circuit, N the LED lamp current control circuit that the output of described N bar LED lamp string is corresponding with this is electrically connected, size of current when working in order to control each LED lamp string; One reference voltage source generating circuit, it receives the Vsb voltage by described standby power Buck transducer output, and produces a stable and reference voltage Vref 1 comparatively accurately; One pwm signal turns the direct current light adjusting circuit, it receives the reference voltage Vref 1 that PWM dim signal that described mainboard micro controller provides and exported by described reference voltage source generating circuit and changes into an analog DC dim signal and offers described LED lamp current control circuit, size of current when LED lamp current control circuit is controlled each LED lamp string work according to the direct voltage size of this analog DC dim signal, thereby the luminosity size when reaching each LED lamp string work of control finally reaches the whole high-high brightness of controlling liquid crystal display picture;
One ON-OFF control circuit, it receives a switching signal and the Vsb voltage by described standby power Buck transducer output of the output of described mainboard micro controller, whether to export work that a control voltage controls described LED lamp current control circuit;
One LED fluorescent tube output voltage feedback control circuit, the reference voltage Vref 1 that its reception one is exported by this reference voltage source generating circuit, receive simultaneously one by this ON-OFF control circuit export one control voltage, and detect respectively the minimum voltage of described each LED lamp string output by diode, this LED fluorescent tube output voltage feedback control circuit detects the feedback compensation signal that a reference voltage Vref 1 that minimum LED lamp string output end voltage and this reference voltage source generating circuit export compares rear output one each LED lamp string input terminal voltage of control by this diode; And
One output feedback control circuit, it is detected the input of described output filter circuit and output end voltage and decides this output feedback control circuit to be defeated by the feedback quantity size of described main power source Buck transducer according to a feedback compensation signal of described LED fluorescent tube output voltage feedback control circuit output, to reach the voltage of the rational LED of control fluorescent tube input; Wherein N is the natural number more than or equal to 1.
Please continue referring to Fig. 3, AC mains is given boost direct current about rear output one 400V of pfc circuit (diagram does not draw) again after bridge rectifier (diagram do not draw) carries out full-wave rectification, the direct current of the output one low-voltage ripple after 1 conversion of main power source Buck transducer is carried out filtering by output filter circuit 11 of the direct current about this 400V is as the input supply power voltage of LED fluorescent tube, the output of each LED lamp string LED1 ~ LEDn connects respectively LED lamp current control circuit 61 in the LED fluorescent tube, 62 ... 610 ends of 6n, 620 ends ... the 6n0 end, the effect of LED lamp current control circuit is the size of current when controlling each LED lamp string work, thereby the luminosity size when reaching each LED lamp string work of control finally reaches the whole high-high brightness of controlling liquid crystal display picture; 403 terminations of ON-OFF control circuit 4 are received mainboard micro controller 3 outputs one switching signal, receive the Vsb voltage (Vsb is generally the 5V direct current) by 2 outputs of standby power Buck transducer by 402 terminations simultaneously, and export one by 401 ends of ON-OFF control circuit 4 and control voltage, by 611 ends, 621 ends ... 6n1 brings in control LED lamp current control circuit 61,62 ... whether 6n works, and brings in by 702 and controls simultaneously LED fluorescent tube output voltage feedback control circuit 7 and whether work; Reference voltage source generating circuit 5 is received the Vsb voltage of being exported by standby power Buck transducer 2 by 501 terminations, and exports a reference voltage Vref 1 from 502 ends; Pwm signal turns direct current light adjusting circuit 8 and receives mainboard micro controller 3 outputs one PWM dim signal from 801 terminations, receive a Vref1 reference voltage from 802 terminations simultaneously, export an analog DC dim signal from 803 ends, and by 612 ends, 622 ends ... the 6n2 end offers respectively LED lamp current control circuit 61,62 ... 6n regulates each LED lamp string stream size; LED fluorescent tube output voltage feedback control circuit 7 is received a reference voltage Vref 1 from 701 terminations, receive a control voltage of an ON-OFF control circuit 4 outputs from 702 terminations, pass through respectively diode D71, D72 from 703 ends ... D7n detects respectively corresponding lamp string LED1, LED2 ... the output voltage of that minimum LED lamp string in the LEDn output, and export a feedback compensation signal from 704 ends and give output feedback control circuit 12; Output feedback control circuit 12 is respectively from 602 ends, the voltage of 603 ends detecting output filter circuit 11 inputs and output, and export a feedback compensation signal according to 704 ends from LED fluorescent tube output voltage feedback control circuit 7 simultaneously and decide 604 ends of exporting feedback control circuit 12 to export to the feedback quantity size of main power source Buck transducer 1, so that control is also exported a rational voltage to the LED lamp works, that is: export a feedback compensation signal to output feedback control circuit 12 by 704 ends in the LED fluorescent tube output voltage feedback control circuit 7, guarantee that the electric current of all LED lamp strings when work in the LED fluorescent tube all can be controlled normally, allow simultaneously the pressure drop that drops between LED lamp current control circuit internal electrical crystal collector electrode (drain electrode) and the emitter (source electrode) lower more reasonable, make all LED lamp current control circuit internal electrical crystal temperature effects lower, make the power source integral conversion efficiency higher.
In order to allow those skilled in the art better understand the utility model, the below simply introduces each circuit.
See also Fig. 4 a, Fig. 4 a is a physical circuit figure of LED lamp current control circuit 61, NPN electric crystal Q61 collector electrode (610 end) is electrically connected with the output of LED1 lamp string, the output of Q61 base stage and OP61 amplifier is electrically connected, the end of Q61 emitter and OP61 amplifier reverse input end and LED lamp string stream sampling resistor R61 is electrically connected, R61 other end ground connection, OP61 amplifier non-inverting input (612 end) receives the accurate position of the direct current dim signal (Vdim) that the PWM dim signal turns output 803 outputs of direct current light adjusting circuit 8, one control voltage of the 401 ends output of OP61 amplifier feeder ear (611 end) receiving key control circuit 4 is as OP61 amplifier power supply input voltage, the earth terminal ground connection of OP61 amplifier.According to empty short characteristics: the V+=V-of amplifier, and V+=Vdim, so V-=Vdim, (V+ is OP61 non-inverting input voltage; V-is OP61 reverse input end voltage) and LED1 is the lamp string size of current ILED1=V-/R61=Vdim/R61 in when work, that is: when the Vdim voltage quasi position that turns the 803 ends output of direct current light adjusting circuit 8 when the PWM dim signal becomes large, electric current I LED1 when LED1 is the work of lamp string also becomes greatly, and the whole high-high brightness of liquid crystal display picture will brighten; When the Vdim voltage quasi position that turns the 803 ends output of direct current light adjusting circuit 8 when the PWM dim signal diminished, the electric current I LED1 when LED1 is the work of lamp string also diminished, and the whole high-high brightness of liquid crystal display picture is with dimmed.Fig. 4 b is LED lamp current control circuit 61 another physical circuit figure, the difference of itself and Fig. 4 a is that the metal-oxide-semiconductor of Q61 NPN electric crystal with the N raceway groove replaced, that is: Q61 drain electrode (610 end) is electrically connected with the output of LED1 lamp string, the output of Q61 grid and OP61 amplifier is electrically connected, and Q61 source electrode and OP61 amplifier reverse input end are electrically connected.
See also Fig. 5, Fig. 5 is reference voltage source generating circuit 5, NPN electric crystal Q51(501 end) receives a 5V direct voltage (Vsb) by 2 generations of standby power Buck transducer, Q51 base stage and a three-terminal shunt regulator U51(are electrically connected such as: cathode terminal AZ432) (K end), between the collector electrode of Q51 and base stage, connect a resistance R 51, this resistance R 51 provides a bias voltage for the cathode terminal of Q51 base stage and U51, the emitter of Q51 (502 end) is electrically connected with an end of resistance R 52 and capacitor C 51, it is Vref1 that the emitter of Q51 is exported a reference voltage, one end of the reference edge of resistance R 52 other ends and three-terminal shunt regulator U51 (R end) and resistance R 53 is electrically connected, the anode tap of three-terminal shunt regulator U51 (A end), resistance R 53, capacitor C 51 other end ground connection, if U51 adopts model such as AZ432, because the reference edge (R end) of AZ432 is the voltage of a 1.25V, so Vref1=1.25V* (R52+R53)/R53.
See also Fig. 6 a and Fig. 6 b, pwm signal of the present utility model turns the direct current light adjusting circuit and both can adopt the pwm signal of negative light modulation to turn the direct current light adjusting circuit, also can adopt the pwm signal of positive light modulation to turn the direct current light adjusting circuit.Fig. 6 a is that the pwm signal of a negative light modulation turns the direct current light adjusting circuit, resistance R 83 1 ends (801 end) receive a PWM dim signal of mainboard micro controller 3 outputs, the R83 other end and NPN electric crystal Q81 base stage are electrically connected, the Q81 grounded emitter, Q81 collector electrode and resistance R 81, R82 one end is electrically connected, resistance R 82 other ends (802 end) receive a reference voltage Vref 1, resistance R 81 other ends and capacitor C 81 1 ends and resistance R 86 1 ends are electrically connected, resistance R 86 other ends (803 end) are electrically connected with resistance R 87 1 ends, pwm signal turns direct current light adjusting circuit 8 and exports once resistance, electric capacity carries out passing through divider resistance R86 after the RC filtering again, obtain a direct current dim signal Vdim after the R87 dividing potential drop to LED lamp current control circuit 61,62 ... the amplifier OP61 of 6n, OP62 ... size of current when the non-inverting input of OP6n is controlled each LED lamp string work, wherein, resistance R 86, the resistance of R87 is much larger than resistance R 81, R82; When 801 ends are the High signal, the conducting of Q81 NPN electric crystal, this moment, a part of electric charge on the capacitor C 81 was by resistance R 81 ground of releasing, resistance R 81 and capacitor C 81 form a discharge constant t=R81*C81, when 801 ends are the Low signal, the cut-off of Q81NPN electric crystal, this moment, the Vref1 voltage of 802 ends will be by resistance R 81, R82 is to capacitor C 81 chargings, resistance R 81, R82 and capacitor C 81 form charging constant t=(R81+R82) * C81, if 801 ends output PWM duty ratio (duty ratio D=Thigh/T, Thigh is PWM high level High signal duration, T is the PWM cycle) increase, then the C81 capacitor discharge time is elongated, and the charging interval shortens, this moment 803 end dim signal current potential step-downs, each LED lamp string operating current will reduce; If 801 ends output PWM duty ratio duty reduces, then the C81 capacitor discharge time shortens, and the charging interval is elongated, and this moment, 803 end dim signal current potentials uprised, and each LED lamp string operating current will increase.Fig. 6 b is that the pwm signal of a positive light modulation turns the direct current light adjusting circuit, Duo a resistance R 84, R85 and a NPN electric crystal Q82 than Fig. 6 a, that is: when 801 ends are the High signal, the Q82 conducting, base voltage with the Q81 electric crystal during Q82 conducting drags down, so that the Q81 cut-off, this moment, the Vref1 voltage of 802 ends will be by resistance R 81, R82 to capacitor C 81 chargings, and resistance R 81, R82 and capacitor C 81 form charging constant t=(R81+R82) * C81; When 801 ends are the Low signal, Q82 cut-off, the base voltage of Q81 electric crystal raises during the Q82 cut-off, so that the Q81 conducting, a part of electric charge on this moment capacitor C 81 is by resistance R 81 ground of releasing, resistance R 81 and capacitor C 81 form a discharge constant t=R81*C81; If 801 ends output PWM duty ratio duty increases, then the C81 capacitor charging time is elongated, and shorten discharge time, and this moment, 803 end dim signal current potentials uprised, and each LED lamp string operating current will increase; If 801 ends output PWM duty ratio duty reduces, then the C81 capacitor charging time shortens, and discharge time is elongated, this moment 803 end dim signal current potential step-downs, each LED lamp string operating current will reduce.
Please refer to Fig. 7, Fig. 7 is the physical circuit figure of ON-OFF control circuit, an end (403) of resistance R 41 receives mainboard micro controller 3 outputs one switching signal among the figure, the base stage of resistance R 41 other ends and NPN electric crystal Q41 is electrically connected, the grounded emitter of Q41, the base stage of the collector electrode of Q41 and PNP electric crystal Q42 is electrically connected, Q42 emitter (402 end) receives a 5V direct current (Vsb) by 2 outputs of standby power Buck transducer, and Q42 collector electrode (401 end) controls whether the 5V direct current will be offered each LED lamp current control circuit 61 according to the switching signal of 403 ends input by electric crystal Q42,62 ... the inner amplifier OP61 of 6n, OP62 ... 611 of OP6n, 621 ... 702 feeder ears of 6n1 feeder ear and LED fluorescent tube output voltage feedback control circuit 7 inner amplifier OP71.
See also Fig. 8, the amplifier OP71 non-inverting input (701 end) of LED fluorescent tube output voltage feedback control circuit 7 receives a reference voltage Vref 1, one control voltage of one end of resistance R 73 and 4 outputs of the feeder ear of OP71 (702 end) receiving key control circuit, the reverse input end of the R73 other end and amplifier OP71,703 end (D71, D72 ... the anode of D7n), one end of capacitor C 71 is electrically connected, capacitor C 71 other ends and resistance R 72 1 ends are electrically connected, the base stage of the output of resistance R 72 other ends and amplifier OP71 and NPN electric crystal Q71 is electrically connected, the ground end ground connection of amplifier OP71, the emitter of electric crystal Q71 and resistance R 71 are electrically connected, resistance R 71 other end ground connection, electric crystal Q71 collector electrode is electrically connected with the feedback divider resistance R121 of output feedback control circuit 12 and the end of R122, R121 other end ground connection, the output of another termination output filter circuit 11 of R122.Wherein capacitor C 71, resistance R 72 and amplifier OP71 form an integrating circuit, capacitor C 71, resistance R 72 is connected on and forms a deep negative feedback circuit between the output of OP71 and the reverse input end, V+=V-according to OP, V+=Vref1, the reverse input end voltage V-=Vref1 of OP71 then, so the minimum pressure drop of inside NPN electric crystal collector electrode between over the ground that drops in the LED lamp current control circuit is: Vref1-Vfi (or for the inside N-channel MOS pipe in the LED lamp current control circuit drains over the ground minimum pressure drop is: Vref1-Vfi), Vfi is diode D7i (the forward conduction voltage of 1≤i≤n), that is: the LED lamp current control circuit 6i that i string LED lamp string is corresponding (the electric crystal Q6i among 1≤i≤n) (collector electrode of 1≤i≤n) over the ground between voltage Vci=Vref1-Vfi(or be inside N-channel MOS pipe drain electrode voltage to earth Vdi=Vref1-Vfi in the LED lamp current control circuit), the inside NPN electric crystal collector electrode in the i string LED lamp tube current control circuit to voltage Vcei=Vci-Vdim=Vref1-Vfi-Vdim(between the emitter or be inside N-channel MOS pipe in the i string LED lamp tube current control circuit drain and source electrode between voltage Vdsi=Vdi-Vdim=Vref1-Vfi-Vdim).
Fig. 9 is that a concrete led drive circuit is electrically connected schematic diagram among the utility model one embodiment, and its dimming mode adopts the positive dimming mode of analog DC.This circuit has following characteristics:
1, directly gives the LED lamp works after the 400V voltage process main power source Buck change-over circuit conversion of PFC output.
2, adopt the OP amplifier to control each LED lamp string operating current.
3, mainboard micro controller (MCU) is offered PWM dim signal that the LED fluorescent tube drives and turn electric current when changing into the analog DC electricity after the conversion of direct current light adjusting circuit and regulating each LED lamp string work by pwm signal.
4, have frequency compensated integral feedback circuit (that is: LED fluorescent tube output voltage feedback control circuit) and detect each LED lamp string output end voltage and regulate and control LED fluorescent tube input terminal voltage by be designed to one by amplifier OP, make the pressure drop that drops between LED lamp current control circuit internal electrical crystal collector electrode (drain electrode) and the emitter (source electrode) more reasonable, that is: control LED fluorescent tube input terminal voltage by this feedback circuit, guarantee that the electric current of all LED lamp strings when work all can be controlled normally, allow simultaneously the pressure drop that drops between LED lamp current control circuit internal electrical crystal collector electrode (drain electrode) and the emitter (source electrode) lower, make all LED lamp current control circuit internal electrical crystal temperature effects lower, make the power source integral conversion efficiency higher.
Whether 5, control each LED lamp current control circuit by an ON-OFF control circuit will work, this ON-OFF control circuit can directly be turned off all LED lamp strings during at complete dark picture at liquid crystal display product, to reach larger DCR(DCR:Dynamic Contrast Ratio namely: the dynamic contrast rate) bright and dark ratio.
Be noted that at last led drive circuit, the aforesaid led drive circuit of the every employing of liquid crystal display product is the utility model rights protection scope.The above person of thought, it only is preferred embodiment of the present utility model, when not limiting the scope that the utility model is implemented with this, the simple equivalence of namely generally doing according to the utility model claim and invention description content changes and modifies in the scope that all still belongs to the utility model patent lid.
Claims (8)
1. a direct current light modulating LED drive circuit comprises main power source Buck transducer, standby power Buck transducer and mainboard micro controller, characterized by further comprising:
N bar LED lamp string, the output of described main power source Buck transducer are exported a low-voltage ripple after output filter circuit carries out filtering direct current is as this N bar LED lamp electric input voltage of acting in collusion to make each other's confessions;
N LED lamp current control circuit, N the LED lamp current control circuit that the output of described N bar LED lamp string is corresponding with this is electrically connected, size of current when working in order to control each LED lamp string;
One reference voltage source generating circuit, it receives the Vsb voltage by described standby power Buck transducer output, and produces a reference voltage Vref 1;
One pwm signal turns the direct current light adjusting circuit, it receives the described reference voltage Vref 1 that PWM dim signal that described mainboard micro controller provides and exported by described reference voltage source generating circuit and changes into an analog DC dim signal and offers described LED lamp current control circuit, size of current when LED lamp current control circuit is controlled each LED lamp string work according to the direct voltage size of this analog DC dim signal, thereby the luminosity size when reaching each LED lamp string work of control;
One ON-OFF control circuit, it receives a switching signal and the Vsb voltage by described standby power Buck transducer output of the output of described mainboard micro controller, whether to export work that a control voltage controls described N LED lamp current control circuit;
One LED fluorescent tube output voltage feedback control circuit, the reference voltage Vref 1 that its reception one is exported by this reference voltage source generating circuit, receive simultaneously one by this ON-OFF control circuit export one control voltage, and detect respectively the minimum voltage of described LED lamp string output by diode, this LED fluorescent tube output voltage feedback control circuit detects the feedback compensation signal that a reference voltage Vref 1 that minimum LED lamp string output end voltage and this reference voltage source generating circuit export compares rear output one each LED lamp string input terminal voltage of control by this diode; And
One output feedback control circuit, it is detected the input of described output filter circuit and output end voltage and decides this output feedback control circuit to be defeated by the feedback quantity size of described main power source Buck transducer according to a feedback compensation signal of described LED fluorescent tube output voltage feedback control circuit output, to reach the voltage of the rational LED of control fluorescent tube input; Wherein N is the natural number more than or equal to 1.
2. direct current light modulating LED drive circuit according to claim 1 is characterized in that, described LED lamp current control circuit comprises:
One transistor, the output of this transistorized collector electrode and described LED lamp string is electrically connected;
One LED lamp string stream sampling resistor, one end ground connection; And
One amplifier, the output of described transistorized base stage and this amplifier is electrically connected, and the other end of the reverse input end of described transistorized emitter and this amplifier and LED lamp string stream sampling resistor is electrically connected; The non-inverting input of this amplifier and described PWM dim signal turn direct current light adjusting circuit output and are electrically connected, size of current when controlling respectively this LED lamp string work to receive an analog DC dim signal, the feeder ear reception one of this amplifier is controlled voltage as the power supply input voltage of this amplifier by one of ON-OFF control circuit output, this ON-OFF control circuit exports by the micro controller of mainboard that a switching signal determines whether will be for this amplifier provides required supply power voltage, thereby whether reaches each LED lamp current control circuit work of control.
3. direct current light modulating LED drive circuit according to claim 2, it is characterized in that: described transistor is replaced with metal-oxide-semiconductor.
4. direct current light modulating LED drive circuit according to claim 1, it is characterized in that: described reference voltage source generating circuit comprises:
One transistor, its collector electrode receive the direct current voltage by described standby power Buck transducer generation,
One three-terminal shunt regulator, its cathode terminal and described transistorized base stage are electrically connected anode tap ground connection;
One resistance R 51 is electrically connected between described transistorized collector electrode and the base stage;
One resistance R 52, an end of this resistance R 52 and described transistorized emitter are electrically connected, and the reference edge of the other end and described three-terminal shunt regulator is electrically connected;
One resistance R 53, an end of this resistance R 53 and the reference edge of described three-terminal shunt regulator are electrically connected, other end ground connection; And
One capacitor C 51, an end of this capacitor C 51 and described transistorized emitter are electrically connected other end ground connection.
5. direct current light modulating LED drive circuit according to claim 1, it is characterized in that: it is that the pwm signal of a negative light modulation turns the direct current light adjusting circuit that described pwm signal turns the direct current light adjusting circuit, and it comprises transistor Q81, capacitor C 81 and resistance R 81, R82, R83, R86, R87; Described resistance R 83 1 terminations are received a PWM dim signal of described mainboard micro controller output, and the base stage of the other end of this resistance R 83 and described transistor Q81 is electrically connected; Described transistor Q81 grounded emitter, the end of collector electrode and described resistance R 81, R82 is electrically connected; The other end of described resistance R 82 receives a reference voltage Vref 1, and an end of the other end of described resistance R 81 and described capacitor C 81 and an end of described resistance R 86 are electrically connected; The other end of described resistance R 86 and described resistance R 87 1 ends are electrically connected, the other end ground connection of the other end of described resistance R 87, capacitor C 81.
6. direct current light modulating LED drive circuit according to claim 1, it is characterized in that: it is that the pwm signal of a positive light modulation turns the direct current light adjusting circuit that described pwm signal turns the direct current light adjusting circuit, it comprises transistor Q82, Q81, capacitor C 81, resistance R 81, R82, R83, R84, R85, R86, R87, described resistance R 85 1 terminations are received a PWM dim signal of described mainboard micro controller output, and the base stage of the other end of this resistance R 85 and described transistor Q82 is electrically connected; The end of described resistance R 83, R84 and the collector electrode of described transistor Q82 are electrically connected, and the base stage of the other end of described resistance R 83 and described transistor Q81 is electrically connected; The end of the collector electrode of described transistor Q81 and described resistance R 82, R81 is electrically connected; The other end of described resistance R 84, R82 receives a reference voltage Vref 1; One end of the other end of described resistance R 81 and described capacitor C 81 and an end of described resistance R 86 are electrically connected; The other end of described resistance R 86 and described resistance R 87 1 ends are electrically connected, the grounded emitter of the other end of the other end of described resistance R 87, capacitor C 81, transistor Q81 and Q82.
7. direct current light modulating LED drive circuit according to claim 1, it is characterized in that: described ON-OFF control circuit comprises:
One resistance R 41, a termination of this resistance R 41 is received a switching signal of mainboard micro controller output;
One transistor Q41, the other end of its base stage and described resistance R 41 is electrically connected, grounded emitter;
One transistor Q42, the collector electrode of its base stage and described transistor Q41 is electrically connected, emitter receives a direct current by described standby power Buck transducer output, and collector electrode controls the amplifier that whether this direct current will be offered described LED lamp current control circuit and LED fluorescent tube output voltage feedback control circuit inside according to the switching signal that described resistance R 41 receives by this transistor Q42.
8. direct current light modulating LED drive circuit according to claim 1, it is characterized in that: described LED fluorescent tube output voltage feedback control circuit comprises an amplifier OP71, transistor Q71, capacitor C 71 and resistance R 73, R72, R71; Described amplifier OP71 non-inverting input receives a reference voltage Vref 1, one end of described resistance R 73 and the feeder ear of described amplifier OP71 receive the control voltage of described ON-OFF control circuit output, the other end of described resistance R 73 and the reverse input end of described amplifier OP71, one end of capacitor C 71 is electrically connected, one end of the other end of described capacitor C 71 and resistance R 72 is electrically connected, the output of these resistance R 72 other ends and described amplifier OP71 and the base stage of transistor Q71 are electrically connected, the ground end ground connection of this amplifier OP71, one end of the emitter of described transistor Q71 and resistance R 71 is electrically connected, the other end ground connection of resistance R 71.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012204205384U CN202889703U (en) | 2012-08-23 | 2012-08-23 | DC light-modulation type LED drive circuit |
| TW101223652U TWM451772U (en) | 2012-08-23 | 2012-12-06 | DC dimming LED driving circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012204205384U CN202889703U (en) | 2012-08-23 | 2012-08-23 | DC light-modulation type LED drive circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN202889703U true CN202889703U (en) | 2013-04-17 |
Family
ID=48081084
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2012204205384U Expired - Fee Related CN202889703U (en) | 2012-08-23 | 2012-08-23 | DC light-modulation type LED drive circuit |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN202889703U (en) |
| TW (1) | TWM451772U (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102833916A (en) * | 2012-08-23 | 2012-12-19 | 冠捷显示科技（厦门）有限公司 | DC (direct current) dimming type LED (Light Emitting Diode) drive circuit |
| CN105050298A (en) * | 2015-09-09 | 2015-11-11 | 广州达森灯光股份有限公司 | LED dimming circuit device |
| CN106211485A (en) * | 2016-08-31 | 2016-12-07 | 杰华特微电子（杭州）有限公司 | Current control circuit and apply its LED drive circuit |
| CN108601132A (en) * | 2018-02-01 | 2018-09-28 | 普联技术有限公司 | LED light modulating devices |
| CN109688659A (en) * | 2018-12-21 | 2019-04-26 | 太仓电威光电有限公司 | LED drive power mould group and the integral LED car light for applying it |
| CN113630933A (en) * | 2021-09-18 | 2021-11-09 | 上海三思电子工程有限公司 | LED driver, driving circuit and driving method |
| CN109688659B (en) * | 2018-12-21 | 2024-04-30 | 太仓电威光电有限公司 | LED driving power supply module and integrated LED car lamp applying same |
-
2012
- 2012-08-23 CN CN2012204205384U patent/CN202889703U/en not_active Expired - Fee Related
- 2012-12-06 TW TW101223652U patent/TWM451772U/en unknown
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102833916A (en) * | 2012-08-23 | 2012-12-19 | 冠捷显示科技（厦门）有限公司 | DC (direct current) dimming type LED (Light Emitting Diode) drive circuit |
| CN102833916B (en) * | 2012-08-23 | 2014-10-15 | 冠捷显示科技（厦门）有限公司 | DC (direct current) dimming type LED (Light Emitting Diode) drive circuit |
| CN105050298A (en) * | 2015-09-09 | 2015-11-11 | 广州达森灯光股份有限公司 | LED dimming circuit device |
| CN105050298B (en) * | 2015-09-09 | 2019-01-22 | 广州达森灯光股份有限公司 | LED light adjusting circuit device |
| CN106211485A (en) * | 2016-08-31 | 2016-12-07 | 杰华特微电子（杭州）有限公司 | Current control circuit and apply its LED drive circuit |
| CN108601132A (en) * | 2018-02-01 | 2018-09-28 | 普联技术有限公司 | LED light modulating devices |
| CN108601132B (en) * | 2018-02-01 | 2019-12-10 | 普联技术有限公司 | LED light modulation device |
| CN109688659A (en) * | 2018-12-21 | 2019-04-26 | 太仓电威光电有限公司 | LED drive power mould group and the integral LED car light for applying it |
| CN109688659B (en) * | 2018-12-21 | 2024-04-30 | 太仓电威光电有限公司 | LED driving power supply module and integrated LED car lamp applying same |
| CN113630933A (en) * | 2021-09-18 | 2021-11-09 | 上海三思电子工程有限公司 | LED driver, driving circuit and driving method |
| CN113630933B (en) * | 2021-09-18 | 2024-02-27 | 上海三思电子工程有限公司 | LED driver, driving circuit and driving method |
Also Published As
| Publication number | Publication date |
|---|---|
| TWM451772U (en) | 2013-04-21 |
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