TW201330685A - LED driving device with feedback control for reducing power consumption - Google Patents

LED driving device with feedback control for reducing power consumption Download PDF

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Publication number
TW201330685A
TW201330685A TW101100949A TW101100949A TW201330685A TW 201330685 A TW201330685 A TW 201330685A TW 101100949 A TW101100949 A TW 101100949A TW 101100949 A TW101100949 A TW 101100949A TW 201330685 A TW201330685 A TW 201330685A
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Taiwan
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voltage
current
led
mosfet
driving
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TW101100949A
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Chinese (zh)
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TWI448191B (en
Inventor
Guo-Ying Hu
Wei-Cheng Tu
Zhong-You Lai
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Univ Nat Taipei Technology
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Publication of TWI448191B publication Critical patent/TWI448191B/en

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Abstract

A light-emitting diode driving device with feedback control to reduce power loss, comprising a main power stage circuit, a plurality of current regulators, a detector and a control unit, wherein a main power stage circuit can provide a driving voltage to be loaded on the LED string; a MOSFET component of each current regulator is connected between an output terminal of an operational amplifier and a current limiting resistor, and the voltage across the current limiting resistor is equal to the dimming signal by the virtual short circuit characteristic of the operational amplifier. The dimming signal is proportional to the current flowing through each of the LED strings; the detector obtains the gate voltage of the MOSFET components and outputs a maximum gate voltage; the control unit generates a modulation according to the change of the maximum gate voltage and The processing is a feedback voltage that causes each MOSFET component to operate at the knee point of its characteristic curve close to the saturation region to reduce unnecessary power loss.

Description

Feedback control light-emitting diode driving device for reducing power loss

The invention relates to a light-emitting diode driving device for an LED light string, in particular to a light-emitting diode driving device capable of dynamic feedback control to reduce power loss.

Light Emitting Diode (LED) has gradually replaced many traditional luminaries because it is environmentally friendly (without mercury), small in size, long in life, fast in response, high in luminous efficiency, and strong in appearance and shock resistance. Sources, and related applications are becoming more widespread.

Referring to FIG. 1, a dimming circuit 9 of a single LED string is directly regulated for the voltage across the current sensing resistor Rs, so that a stable and tunable current can be obtained, and feedback control is performed by the controller. The advantage is that the change of the forward voltage of the LED component of the LED string can be avoided, and the current is changed, but the disadvantage is that only the dimming of the single LED string can be controlled, and it cannot be applied to multiple sets of parallel LED strings.

Referring to FIG. 2, a dimming driving circuit 8 for multiple sets of LED light strings LS1~LSN, the main power stage circuit 80 generates a driving voltage Vo for the LED light strings LS1~LSN, and the LED light strings LS1~LSN and the connection N The linear current regulators 81~8N are used, and the characteristics of the maximum voltage across conduction are taken by using multiple sets of diodes in parallel, and the comparator EA automatically detects the lowest crossover voltage Vd among the N sets of linear current regulators 81~8N . Min , however, this connection method will allow the feedback voltage to pass through the diode and then connect to the comparator EA, so that the error of the diode voltage drop V f will be generated first, and the feedback voltage value is low. The effect is more pronounced, which in turn causes the feedback voltage to be disturbed and the accuracy of the adjustment to be affected.

However, since the driving voltage Vo generated by the main power stage circuit 80 of the dimming driving circuit 8 is fixed, dimming to a light load (reducing the current on the LED string) as the LED dimming signal fluctuates, or when An increase in the temperature of the LED causes additional power loss on the transistor Q 1 of the linear current regulator, which easily causes damage to the transistor Q 1 and does not save power consumption. In addition, when the main power stage circuit is a single-stage AC-DC voltage converter and the feedback control of the lowest voltage across V d.min is adopted, the low frequency chopping of the driving voltage Vo is for the linear current regulator. The 汲 extreme voltage of the transistor Q 1 varies greatly and is not easily controlled.

Accordingly, it is an object of the present invention to provide a light emitting diode driving apparatus capable of dynamic feedback control to reduce power loss.

Therefore, the LED control device for reducing the power loss of the feedback control of the present invention is applied to a plurality of sets of LED light strings, each of the LED light strings having an input end, an output end, and a plurality of series connected to the input end and the output An LED light emitting device between the terminals, the LED driving device comprises a main power level circuit, a plurality of current regulators, a detector and a control unit.

The main power stage circuit has a PWM controller, a switching element that is regulated to be turned on or off by a control signal of the PWM controller, a voltage converter and an energy storage device, and the voltage converter converts an input voltage into one Driving voltage, when the switching element is turned on, an input voltage is supplied to the energy storage device and storing energy, and when the switching element is turned off, energy stored in the energy storage device can continuously supply the driving voltage to be loaded on the LED light string Total input.

The number of the current regulators is consistent with the number of the LED strings. Each of the current regulators has an operational amplifier, a MOSFET component and a current limiting resistor. The operational amplifier has an output terminal and a dimming signal. a non-inverting input terminal and an inverting input terminal connected to the current limiting resistor, the MOSFET component is connected between the output terminal of the operational amplifier and the current limiting resistor, and a source (S) is connected to the current limiting resistor, The gate (G) is connected to the output end of the operational amplifier, and the drain (D) is connected to the output end of each of the LED strings. The voltage across the current limiting resistor makes the voltage across the current limiting resistor equal to the dimming. The signal is such that the dimming signal is proportional to the current flowing through each of the LED strings.

The detector is electrically connected to each of the current regulators, and has a plurality of diodes corresponding to the number of LED strings. The anode ends of the diodes obtain the gates of the current regulators from the current regulators. The pole voltages and the cathode terminals are connected to each other and output a maximum gate voltage.

The control unit is electrically connected between the detector and the PWM controller, generates a modulation variable according to the change of the maximum gate voltage, and uses the modulation variable processing to supply the PWM controller to a feedback voltage. The PWM controller uses the feedback voltage to control a control signal for turning on or off the switching element, and the voltage across the drain (D) and the source (S) of each MOSFET element decreases with the brightness of each of the LED strings. When falling, each of the MOSFET components operates at a knee point of its characteristic curve close to the saturation region to reduce unnecessary power loss on each of the MOSFET components.

Preferably, the LED control device for reducing the power loss of the feedback control of the present invention further includes an energy recovery module electrically connected between the energy storage device and the total input end of the LED light strings, and the energy is The recycling module has an inductance component connected in parallel with the total input terminal and a capacitor component connected in series to the inductor component and grounded.

The function of the LED control device for reducing the power loss of the feedback control of the present invention is to match the current regulator to the detector and the control unit of the maximum gate voltage, so that the LED string is caused when the load changes and the temperature changes. The voltage drop changes, or the dimming mode changes, the control unit can know the minimum crossover voltage of the current regulator according to the change of the maximum gate voltage, so as to dynamically adjust the driving voltage, so that when the dimming is down, the MOSFET component The cross-voltage between the drain and the source decreases as the brightness of the LED string decreases, and the MOSFET component operates at the lowest point to reduce unnecessary power loss on the MOSFET component, thereby improving efficiency.

The foregoing and other objects, features, and advantages of the invention are set forth in the <RTIgt;

Referring to FIG. 3, in a preferred embodiment of the LED driving device 100 of the plurality of LED strings 6 of the present invention, the LED driving device 100 includes a control unit 1, a main power stage circuit 2, and an energy source. The recycling module 3, a linear current adjustment module 4 and a detector 5 are described below.

The main power stage circuit 2 has a bridge rectifier 21 and a flyback conversion module 22, and the flyback conversion module 22 has a PWM controller L6562, a voltage regulator controller L7812, and a control by the PWM controller L6562 . The signal is controlled to be turned on or off by a switching element Q m , a voltage converter T1 and an accumulator Co. The voltage converter T1 converts an input voltage Vin into a driving voltage Vo, and when the switching element Q m is turned on, the input voltage Vin supplies the energy storage device Co and stores energy. When the switching element Q m is turned off, the energy stored in the energy storage device Co can continuously supply the driving voltage Vo to the total input terminal 601 of the plurality of LED light strings 6 .

In this embodiment, the flyback conversion module 22 is composed of a clamp (RCD clamp) circuit and a conventional flyback converter. The clamp circuit is used to reduce the voltage surge of the main power switch Q m caused by the leakage inductance of the transformer. The model of the PWM controller used is L6562, and the third winding is required to generate a Zero Current Detector (ZCD) signal to the L6562. The parameter design of each component is shown in Table 1.

Referring to FIG. 4, the relevant waveforms of the flyback conversion module 22 operating in the critical conduction mode include four working modes, mode one is t 0 ≦t≦t 1 , and mode two is t 1 ≦t≦t 2 , Mode 3 is t 2 ≦t≦t 3 , and mode 4 is t 3 ≦t≦t 0 +T s . Since its working principle is not the focus of this patent, it will not be described here.

Referring to FIG. 3, the plurality of LED light strings 6 includes four sets of LED light strings LS1~LS4, and each of the LED light strings LS1~LS4 has an input end, an output end, and a plurality of series connected between the input end and the output end. The LED light-emitting element, the input end of each LED light string LS1~LS4 is connected to a total input end 601; the energy recovery module 3 is electrically connected between the energy storage device Co and the total input end 601 of the LED light strings LS1~LS4 The energy recovery module 3 has an inductance element L R connected in parallel with the total input terminal 601 and a capacitance element C R connected in series to the inductance element L R and grounded.

Referring to FIG. 5, the energy recovery module 3 is configured to suppress the correlation waveform of the low frequency chopping, wherein T ac is the line frequency period of the AC input power source, and the input voltage v ac ( t )= V ac, pk sin(ω ac t ) Input current i a c ( t )= I ac , pk sin(ω ac t ), input voltage peak value is V ac , pk , input current peak value is I ac , pk , angular frequency ω ac =2π/ T ac , input The power p in ( t ) = v ac ( t ) i ac ( t ). For a resistive load, the drive voltage Vo divided by the output impedance is the output current I o , so the output current ripple Δi o is proportional to the magnitude of the drive voltage Vo Δv o . The current defining the inductive component L R is i LR , and the voltage across the capacitive component C R is V CR ; when the instantaneous input power is greater than the power required by the load, ie T ac /8 to 3 T ac /8, From the inductance element L R , most of the excess energy is transferred to the capacitive element C R for storage, so the current i LR of the inductance element L R is a positive current, and the voltage v CR of the capacitive element C R rises; When the power is less than the energy required by the load, that is, 3 T ac /8 to 5 T ac /8, the energy recovered by the capacitive element C R is returned to the load by the inductance element L R to supplement the insufficient load. Energy, so the current i LR of the inductance element L R is a negative current, and the voltage v CR on the capacitance element C R drops. That is to say, the more energy stored in the energy storage device C o is stored on the capacitive element C R through the inductance element L R , and when the instantaneous input power is insufficient, the recovered energy is used as a supplement, so The effect of suppressing output low frequency chopping can be achieved.

In addition, the instantaneous total output power p sum is the sum of the instantaneous power p R of the energy recovery module 3 plus the load power P o . If the p sum is closer to p in , the energy for charging and discharging the output capacitor is smaller, so the energy is smaller. The generated driving voltage Vo is also relatively small in low frequency chopping.

Referring to FIG. 6, the linear current adjustment module 4 has a plurality of current regulators 41-44. The number of the current regulators 41-44 is four, which is consistent with the number of the LED strings LS1~LS4, and each current adjustment. 41 to 44 has an operational amplifier OP, a MOSFET element Q 1 and a limiting resistor R LS1, the operational amplifier having an output terminal OP, a non-inverting input receives a dimming signal (+) and a connector The inverting input terminal (-) of the current limiting resistor R LS1 is connected between the output terminal of the operational amplifier OP and the current limiting resistor R LS1 , and the source (S) is connected to the current limiting resistor R LS1 and the gate ( G) connected to the output terminal of the operational amplifier OP, the drain (D) is connected to the output end of each LED string, and the voltage across the current limiting resistor R LS1 is equal to the dimming signal by the virtual short circuit characteristic of the operational amplifier OP. The optical signal is proportional to the current I LS1 flowing through each of the LED strings LS1 to LS4.

The detector 5 is electrically connected to each of the current regulators 41 to 44, and has four diodes D g1 to D g4 corresponding to the number of LED light strings, and the anode terminals of the respective diodes D g1 to D g4 are self-current The regulators 41 to 44 obtain the gate voltages V g1 to V g4 of the current regulators 41 to 44 and the cathode terminals are connected to each other and output a maximum gate voltage V g,max .

Referring to FIG. 3 and FIG. 6 , the control unit 1 is electrically connected between the detector 5 and the PWM controller L6562 , and generates a modulation variable according to a change of the dimming command SW1 and the maximum gate voltage V g,max . And using the modulation variable processing to supply a feedback voltage v fb to the PWM controller L6562 , so that the PWM controller L6562 uses the feedback voltage v fb to control the control signal that the switching element Q m is turned on or off, and each MOSFET element Q 1 When the voltage across the drain (D) and the source (S) decreases as the brightness of each LED string decreases, the MOSFET element Q 1 operates at a knee point of its characteristic curve close to the saturation region. The unnecessary power loss on each MOSFET element Q 1 is reduced, the principle of which is detailed below.

Referring to FIG. 7 to FIG. 9, FIG. 7 is an IsSpice analog circuit of the current regulator 41, FIG. 8 is an analog waveform inputting a dimming command representing a full load (350 mA), and FIG. 9 is an input representing a light load (70 mA). The analog waveform of the optical command; note that the horizontal axis under the waveform diagram is the driving voltage Vo, and the voltage across the voltage of the MOSFET element Q 1 v ds1 changes as the driving voltage Vo changes, the driving voltage Vo gradually decreases, and the voltage across the voltage v ds1 On the contrary, the driving voltage Vo gradually increases, and the voltage across the voltage v ds1 also rises. When the knee point reaching the characteristic curve of the MOSFET element Q 1 continues to rise, the gate voltage v g1 will be due to the constant current. lowered to a fixed reverse voltage level; therefore, by determining the gate voltage v g1 reaches the knee point of a MOSFET characteristic curve Q element, thereby driving voltage that corresponds to Vo. It can be seen from FIG. 8 and FIG. 9 that the fully loaded gate voltage v g1 is slightly larger than the light load gate voltage v g1 , but both are near 5 volts, and as long as the knee point of the characteristic curve of the MOSFET element Q 1 is reached, the gate is The pole voltage v g1 will have a reversal phenomenon, so it is suitable as a reference for the feedback control driving voltage Vo, which can accurately control the operation under the minimum cross pressure and avoid unnecessary power loss.

Referring to FIG. 10, when the MOSFET element Q 1 operates in the saturation region, its I LS current is not affected by the change of V ds , and is only proportional to V gs , but if the MOSFET element Q 1 is operated in the linear region, In order to meet the characteristics of the virtual short circuit of the operational amplifier, the gate voltage V gs will change with the change of V ds to keep the current of the LED string LS1~LS4 current I LS constant, but the I LS current change in this interval is affected by V The influence of ds is severe, so it is difficult to control its current. Therefore, the control principle of the present invention is to make the voltage across the MOSFET element Q 1 to a minimum value and the current is easy to control, so the control strategy is to control the voltage as close as possible to the saturation region of the knee of the characteristic curve.

See FIGS. 11 and 12, respectively, down to the light and the light is changed to increase the time to MOSFET element Q 1 and the drain voltage of the gate voltage signal to further illustrate the principles of operation. Wherein, the gate voltage signal is the voltage across the V gs plus the upper limit current resistor R LS , and the voltage of the drain voltage is V ds plus the voltage across the upper limit current resistor R LS . For convenience of explanation, the crossover of the current limiting resistor R LS is ignored here. Pressure.

11, when the down light, the dimming command when the load changes from 50% to 20% load, due to the constant current, the gate voltage signal by V gs 3 (A point) to the change in V gs 1 (B point) and into the saturation region of MOSFET elements Q 1, while the driving voltage Vo of the converter starts to change down, while the drain terminal voltage is also decreased. After the knee point when the drain voltage of MOSFET elements Q into ohmic zone 1, due to the constant current, the gate voltage at this time the signal will decrease with the drain voltage rapidly increases to V gs 5 (C point), this when the driving voltage Vo is stopped down and becomes a state of back adjustments, so that the MOSFET operating element Q 1 knee point (D point) of the output characteristic curve thereof as much as possible. When up to the light, as shown in FIG. 12, when the dimming command by the 20% load to 50% load, due to the constant current, the gate voltage signal by V gs 1 (A point) to the rapidly changing V gs 5 (point B) and enter the ohmic region of the MOSFET, while the driving voltage Vo of the converter begins to change upward, and the 汲 extreme voltage also increases. At this time, the current I LS will rise along the curve of V gs 5 (to Point C). Due to the constant current, when the drain voltage continues to increase and the dimming command is satisfied, the gate voltage signal will rapidly decrease to V gs 3 (point D) as the drain voltage increases. will stop the voltage Vo becomes upregulated MOSFET element Q 1 so that the operating point of the knee of its characteristic curve of the output as possible.

At a constant current, the gate signal V gS at full load is larger than the light load because of the large current I LS , so the gate voltage signal is slightly larger than the gate voltage signal at light load. However, regardless of the light-load or full Also, when the voltage across the MOSFET element Q 1 is lowered to V ds exceeds the output characteristic curve of the knee point, the gate signal V gs all will greatly increase. According to this characteristic, it is only necessary to appropriately select a level slightly higher than the gate voltage signal under full load at the time of design as the basis for judging the knee point. Taking FIG. 8 as an example, the selected MOSFET element Q 1 has a V g , max measured at full load of about 4.2 V, so the judgment level is set to 5 volts.

The modulation control principle of the driving voltage Vo is described below with reference to FIG. 3. The control unit 1 has a voltage dividing module 11, an analog/digital conversion module 12, a field programmable gate array (hereinafter referred to as FPGA) 13, and an active The low-pass filter circuit 14, a gain adjustment 16, an instruction interface 15 and an optocoupler 17; the voltage divider module 11 has a Scaler1 and a Scaler2, and the analog/digital conversion module 12 has an ADC1 and an ADC2, Scaler1 And Scaler2 uses the voltage division principle to reduce the voltage value.

Referring to FIG. 13, in the simplified feedback circuit of the driving voltage Vo, the driving voltage Vo is sent to the ADC1 of the analog/digital conversion module 12 via Scaler1 of the voltage dividing module 11 (ie, the voltage division of the resistor R d1 and the resistor R d2 ). Converted into digital information, and obtained the Scaler2 (using resistor divider) of the detector 5, and then sent to the ADC2 of the analog/digital conversion module 12 to convert into digital information, and then send the information to the FPGA; The FPGA adjusts the read signal (the principle is described later) and outputs a corresponding F_PWM. For example, if the digital information read is represented by 2.5 volts, F_PWM is a PWM signal with a duty cycle of 2.5/3.3=75.8%, and the F_PWM signal is passed by the active low-pass filter 1 when the variable variable is not added. It is filtered into a constant current level (3.3 × 75.8% = 2.5 V) as a feedback voltage v fb . Since the voltage command of the L6562 is 2.5 volts, if the voltage feedback signal is added with a positive or a negative modulation variable and then output, the voltage command is changed to 2.5-vary. Therefore, the feedback voltage v fb can be dynamically adjusted by the added modifier variable, thereby achieving the purpose of adjusting the driving voltage Vo level.

The field effect programmable gate array 13 has a dimming and driving voltage changing module 130, an SPI1 module 131, an SPI2 module 132 and a PLL module 133. The signal SDI1 received by the field effect programmable gate array 13 represents the serial data signal of ADC1 and the signal SDI2 represents the serial data signal of ADC2, and the output signal thereof Represents the enable signal and signal of ADC1 Representing the enable signal of ADC2; in addition, the received dimming command SW1 is a signal generated by a push button, pressed to a low level and not high on time, and the PLL module 133 is an external oscillator. The frequency is adjusted to the clock signal required by each module and provided to each module. The SPI1 module 131 and the SPI2 module 132 are serial peripheral interfaces, and the serial data of ADC1 and ADC2 are stored in the temporary register. The dimming and driving voltage change module 130 is used for reading.

Referring to FIG. 14, the state 0 of the dimming and driving voltage change module 130 represents the initial state. The dimming and driving voltage change module 130 is also internally set with three load states, respectively, 20% load is state=1, 50% load is state=2, and 100% load is state=3, and the dimming command SW1 from the command interface 15 can be accepted to change its load state. The dimming command SW1 is set: "command=0" represents the switch Pressing, and "command = 1" means that the switch is released, its up dimming setting mode is "dimming = 0", and its upward dimming setting mode is "dimming = 1".

Referring to FIG. 15, the flow of the dimming and driving voltage change module 130 performing the upward dimming is introduced as follows. When the command after the start is 0 (step S101), the dimming function is performed, and when the dimming is 0 (step S102), it represents Upward dimming; drive voltage Vo increases by =1 (represents activation of drive voltage increase) (step S103); determines whether state = 0 (step S104); if yes, represents the initial state, here is the set duty cycle = 200 and status = 1 (step S105); if not, determine whether it is in state 1? If it is state 1, it means to be up to state 2, so it is set to enter responsibility cycle = 500 and state = 2 (step S107); if it is not state 1, it means to be up to state 3, so set the entry duty cycle = 1000, state = 3 and Dimming = 1 (step S108); on the other hand, the command = 1 will simultaneously determine the maximum gate voltage V g,max of the detector 5, when the command = 1, the maximum gate voltage V g,max The digital information vg<threshold value, and the driving voltage Vo is increased by =1 (representing the activation of the driving voltage increase) (step S111); if so, the driving voltage Vo is increased by =0 (representing the disable "drive voltage increase") ( Step S112).

Referring to FIG. 16, the dimming and driving voltage change module 130 performs a downward dimming process, and when the start command=0 (step S201), the dimming function is performed, and when the dimming=1 (step S202), it represents Down-lighting, the driving voltage Vo is lowered by 1 (representing the enablement of the driving voltage reduction) (step S203), determining whether it is in the state = 3 (step S204), and if so, representing the full load, it is necessary to downgrade to the duty cycle = 500 and State = 2 (step S205), if not full, enter duty cycle = 200 and state = 1 and dimming = 0 (step S206); on the other hand, command = 1 will also perform the maximum gate of the detector 5 The reading of the voltage V g,max is judged, when the command = 1, the digital information of the maximum gate voltage V g,max is vg>the threshold value and the driving voltage Vo is lowered to 1 (representing the enablement of the driving voltage reduction)" (step S211) time), so that the driving voltage Vo = 0 decrease (representing disabled "to reduce the driving voltage") (step S212), thus ensuring the driving voltage Vo is maintained in the vicinity of the MOSFET device 1 Q characteristic curve of the knee point.

Referring to FIG. 17 is a waveform related to the driving voltage Vo chopping when the energy recovery module 3 is not added, and FIG. 18 is a waveform related to the driving voltage Vo chopping when the energy recovery module 3 is added, and FIG. 18 is added to the energy recovery module 3 After that, the chopping wave of the driving voltage Vo, which is originally about 2.6 volts, can be effectively reduced to 1.3 volts. In addition, it can be found that when the current i LR of the inductance element L R is positive, the capacitive element C R is storing energy, so The voltage v CR increases upwards, and also represents that the instantaneous input power of the interval is greater than the power required by the load; and when the current i LR of the inductance element L R is negative, the capacitive element C R is releasing energy, so the voltage thereof v CR decreases downwards, which also means that the instantaneous input power of this interval is less than the power required by the load.

Referring to FIG. 19 and FIG. 20, respectively, the conversion efficiency and the power factor value (PF) versus the load current of the LED driving device 100 are shown, and the conversion performance and the power factor of the system of FIG. 19 and FIG. 20 are respectively shown. The value vs. load current curve shows that the overall efficiency of the system at full load is about 87%, and the power factor is about 0.96. However, at light load, the output current is small due to the small output current. There is modulation, so the driving voltage Vo at light load is also lower than the rated driving voltage Vo of the converter, so the situation that the input current is low will cause the total harmonic distortion to increase and the power factor to decrease. Further, when the light-emitting diode driving device 100 operates at a light load, since the switching frequency of the switching element Q m is high, the switching loss is greatly increased, thereby affecting the overall efficiency.

Referring to FIG. 21 and FIG. 22, respectively, the total harmonic distortion (THD) versus load current curve of the LED driving device 100 and the harmonic distribution diagram under full load are respectively operated at 36.3 ° C under full load. Comparing the subharmonic distribution with the IEC 61000-3-2 Class C harmonic limit specification, it is known that the proposed LED driver has compliance with the IEC 61000-3-2 Class C harmonic limit specification.

In summary, the function of the LED driving device 100 of the plurality of LED light strings 6 of the present invention is to cooperate with the current regulators 41 to 44, and the detector 5 and the control unit with the maximum gate voltage V g,max are added . 1. Therefore, the control unit 1 can know the current regulator according to the change of the maximum gate voltage V g,max regardless of the fluctuation of the voltage drop of the LED string 6 when the load changes or the temperature changes, or the dimming mode changes. the minimum of the voltage across 41 to 44 to dynamically adjust the driving voltage Vo, the voltage across the energy is lowered such that when the down light, the MOSFET drain element Q 1 and the source of the ends with the LED string 6 lowered luminance, Moreover, the MOSFET element Q 1 is operated at the lowest point to reduce unnecessary power loss on the MOSFET element Q 1 , thereby improving efficiency, and overcoming the fact that the conventional driving voltage Vo is fixed and cannot reduce the unnecessary power loss on the MOSFET element Q 1 , so It is indeed possible to achieve the object of the invention.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

[知知]

9. . . Dimming circuit

8. . . Dimming drive circuit

80. . . Main power stage circuit

81~8N. . . Linear current regulator

[This creation]

100. . . Light-emitting diode driving device

1. . . control unit

11. . . Voltage dividing module

12. . . Analog/digital conversion module

13. . . Field effect programmable gate array

130. . . Dimming and driving voltage change module

131. . . SPI1 module

132. . . SPI2 module

133. . . PLL module

14. . . Active low pass filter circuit

16. . . Gain adjustment

15. . . Instruction interface

17. . . Optocoupler

2. . . Main power stage circuit

twenty one. . . Bridge rectifier

twenty two. . . Flyback converter module

3. . . Energy recovery module

4. . . Linear current adjustment module

41~44. . . Current regulator

5. . . Detector

6. . . Multiple sets of LED light strings

601. . . Total input

S101~108, S111, S112, S201~206, S211, S212. . . step

Figure 1 illustrates a dimming circuit diagram of a single LED string;

2 is a circuit diagram showing a dimming drive circuit for a plurality of sets of LED light strings;

3 is a circuit diagram showing a preferred embodiment of a light-emitting diode driving apparatus for reducing power loss of feedback control of the present invention;

4 is a diagram showing correlation waveforms of the flyback conversion module of FIG. 3 operating in a critical conduction mode;

FIG. 5 is a diagram showing correlation waveforms of the energy recovery module of FIG. 3 for suppressing low frequency chopping; FIG.

6 is a circuit diagram showing the linear current adjustment module of FIG. 3 having four current regulators and a detector having four diodes;

Figure 7 is an IsSpice analog circuit illustrating the current regulator of Figure 6;

Figure 8 is an analog waveform diagram illustrating the dimming command of the analog circuit input of Figure 7 representing full load;

Figure 9 is a diagram showing an analog waveform diagram of the dimming command representing the light load of the analog circuit input of Figure 7;

Figure 10 is a diagram showing the operation of a MOSFET component of a current regulator;

Figure 11 is a graph showing changes in the operation curve of the MOSFET element of the current regulator when it is dimmed downward;

FIG. 12 is a graph showing changes in an operation curve of a MOSFET element as a current regulator when it is dimmed upward;

Figure 13 is a simplified feedback circuit diagram illustrating a driving voltage;

14 is a diagram showing a load state of internal setting of a dimming and driving voltage change module of a light-emitting diode driving device with feedback control reduced power loss according to the present invention;

15 is a flow chart of the dimming and driving voltage changing module of the LED driving device for reducing power loss of the feedback control according to the present invention;

16 is a flow chart of performing dimming of a dimming and driving voltage change module of a light-emitting diode driving device with feedback control to reduce power loss according to the present invention;

17 is a waveform diagram of driving voltage chopping when a conventional light-emitting diode driving device is not added to an energy recovery module;

18 is a waveform diagram of driving voltage chopping when the energy-recovery module of the light-emitting diode driving device for reducing the power loss of the feedback control of the present invention is added;

19 is a graph showing conversion performance versus load current of a light-emitting diode driving device with feedback control reduced power loss according to the present invention;

20 is a graph showing the power factor value of the light-emitting diode driving device for reducing the power loss of the feedback control of the present invention;

21 is a graph of total harmonic distortion versus load current of a light-emitting diode driving device with feedback control reduced power loss according to the present invention;

Fig. 22 is a view showing the distribution of harmonics at full load of the light-emitting diode driving device with reduced power loss in the feedback control of the present invention.

100. . . Light-emitting diode driving device

1. . . control unit

11. . . Voltage dividing module

12. . . Analog/digital conversion module

13. . . Field effect programmable gate array

130. . . Dimming and driving voltage change module

131. . . SPI1 module

132. . . SPI2 module

133. . . PLL module

14. . . Active low pass filter circuit

16. . . Gain adjustment

15. . . Instruction interface

17. . . Optocoupler

2. . . Main power stage circuit

twenty one. . . Bridge rectifier

twenty two. . . Flyback converter module

3. . . Energy recovery module

4. . . Linear current adjustment module

5. . . Detector

6. . . Multiple sets of LED light strings

601. . . Total input

Claims (2)

  1. A light-emitting diode driving device with feedback control for reducing power loss is applied to a plurality of groups of LED light strings, each of the LED light strings having an input end, an output end, and a plurality of series connected between the input end and the output end The LED light-emitting component comprises: a main power stage circuit having a PWM controller, a switching element regulated by the control signal of the PWM controller, a voltage converter and a storage The voltage converter converts an input voltage into a driving voltage. When the switching element is turned on, the input voltage supplies the energy storage device and stores energy. When the switching element is turned off, the energy storage device stores the energy storage device. The energy of the device can continuously supply the driving voltage to the total input end of the LED string; the number of current regulators, the number of which matches the number of the LED strings, each of the current regulators having an operational amplifier, a MOSFET a component and a current limiting resistor, the operational amplifier having an output, a non-inverting input receiving a dimming signal, and an inverting input connected to the current limiting resistor, the MOSFET component Connected to the output terminal of the operational amplifier and the current limiting resistor, and the source is connected to the current limiting resistor, the gate is connected to the output end of the operational amplifier, and the drain is connected to the output end of each LED string. The characteristic of the virtual short circuit of the operational amplifier is such that the voltage across the current limiting resistor is equal to the dimming signal, so that the dimming signal is proportional to the current flowing through each of the LED strings; a detector and an electrical connection are respectively a current regulator having a plurality of diodes corresponding to the number of LED strings, wherein the anode ends of the diodes obtain the gate voltages of the current regulators from the current regulators and the cathode terminals are connected to each other and output a maximum gate voltage; and a control unit electrically connected between the detector and the PWM controller, generating a modulation variable according to the change of the maximum gate voltage, and using the modulation variable to process a feedback The voltage is supplied to the PWM controller, and the PWM controller uses the feedback voltage to control a control signal that the switching element is turned on or off, and the voltage across the drain and the source of each of the MOSFET components follows the LED string. Reduced brightness When reduced, so that each of the working elements thereof MOSFET characteristic curve of the knee point of near saturation zone to reduce the unnecessary power loss of each of the MOSFET devices.
  2. The LED driving device for reducing power loss according to the feedback control described in claim 1 further includes an energy recovery module electrically connected between the energy storage device and the total input end of the LED light strings And the energy recovery module has an inductance component connected in parallel with the total input terminal and a capacitor component connected in series to the inductance component and grounded.
TW101100949A 2012-01-10 2012-01-10 Feedback control to reduce power consumption light-emitting diode driving device TWI448191B (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI554923B (en) * 2014-09-10 2016-10-21 王村益 Touch display apparatus and touch display method

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016197263A1 (en) * 2015-06-12 2016-12-15 Abbeydorney Holdings Ltd. Power efficient led drivers
TWI620467B (en) * 2017-05-26 2018-04-01 Newvastek Co Ltd Energy recovery device

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Publication number Priority date Publication date Assignee Title
US7550933B1 (en) * 2008-01-03 2009-06-23 System General Corp. Offline control circuit of LED driver to control the maximum voltage and the maximum current of LEDs
US7919936B2 (en) * 2008-08-05 2011-04-05 O2 Micro, Inc Driving circuit for powering light sources
TWI378743B (en) * 2008-11-13 2012-12-01 Young Lighting Technology Corp Light emitting diode driving circuit
US8044609B2 (en) * 2008-12-31 2011-10-25 02Micro Inc Circuits and methods for controlling LCD backlights
US8502461B2 (en) * 2010-05-25 2013-08-06 Green Solution Technology Co., Ltd. Driving circuit and control circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI554923B (en) * 2014-09-10 2016-10-21 王村益 Touch display apparatus and touch display method

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