CN102802324A

CN102802324A - Double-loop driving system

Info

Publication number: CN102802324A
Application number: CN2012103312256A
Authority: CN
Inventors: 周泽坤; 王鑫; 谭林; 吴传奎; 石跃; 明鑫; 王卓; 张波
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2012-09-10
Filing date: 2012-09-10
Publication date: 2012-11-28

Abstract

The invention discloses a double-loop driving system which concretely comprises a rectifying module, an error amplifier, a voltage controlled oscillator, a dead time generating module, a voltage-current converter, a current subtracter, a first capacitor, a comparator, a first OR gate, a driving module, a second capacitor, a first inductor, a first transformer, a first NMOS (N-channel mental-oxide-semiconductor) switching tube, a second NMOS switching tube, a third capacitor, a second inductor, a third inductor, a second transformer and a double-pole double-throw switch. When the double-loop driving system disclosed by the invention is used for LED (light emitting diode) driving, on the basis of an analog dimming loop, an accurate PWM (pulse width modulation) dimming loop is integrated; and on the premise of normal regulation of the analog dimming loop, according to the real-time current on an LED, the duty ratio of PWM signals which are externally input to PWM signals which actually participate in dimming is dynamically changed, thereby greatly improving the PWM dimming accuracy.

Description

A kind of double loop drive system

Technical field

The invention belongs to technical field of integrated circuits, be specially a kind of high precision double loop drive system that is applicable to controlled resonant converter, can be applied in high-power, the high-frequency LED driving.

Background technology

Power management chip is being undertaken the function of transformation, distribution, detection and other power managements to electric energy in electronic apparatus system; Therefore power management chip is indispensable as far as electronic system, and the quality of its performance also has direct influence to machine performance.The LLC controlled resonant converter is as the system architecture of emerging power management chip; There is switching loss little; The stress and the size of device are little; (therefore Electro Magnetic Interference, EMI) advantage such as little have obtained using widely in high-power, high-power drive system electromagnetic interference.

LLC resonant converter drives system generally is used for the LED of two-way or multichannel or the drive system of other loads; In order to improve the error between sampling precision and better each road of balance; Two-way load LED1, the LED2 that adopt positive and negative parallel connection when driving LED more; LED1 was driven simultaneously to capacitor C 1 charging when transformer output voltage V sout was positive, meanwhile capacitor C 2 discharge driving LED 2; LED2 was driven simultaneously to capacitor C 2 chargings when transformer output voltage V sout was negative, meanwhile capacitor C 1 discharge driving LED 1.Because the existence of LED shunt capacitance makes this system's loop foundation need the regular hour, and because the foundation of control loop receives the restriction of loop bandwidth and circuit pendulum rate, also needs the regular hour, therefore can reduce PWM light modulation precision.

Summary of the invention

The objective of the invention is in order to solve the problems referred to above that LLC resonant converter drives system exists, the present invention proposes a kind of double loop drive system.

Technical scheme of the present invention is: a kind of double loop drive system; Specifically comprise: rectification module, error amplifier, voltage controlled oscillator, Dead Time generation module, voltage current adapter, current subtraction device, first electric capacity, comparator; First or door, driver module, second electric capacity, first inductance, first transformer, the first nmos switch pipe, the second nmos switch pipe, the 3rd electric capacity, second inductance, the 3rd inductance, second transformer and a double-point double-throw switch; Wherein

The input of said rectification module is as the feedback sample input of said double loop drive system; The output of rectification module links to each other with the first input end of the negative end of error amplifier and voltage current adapter, and the positive input of error amplifier is used to import external analog light modulation reference level; The output of error amplifier links to each other with the input of voltage-controlled oscillator; The output of voltage controlled oscillator links to each other with the input of Dead Time generation module, and voltage controlled oscillator is used to produce the voltage signal variation opposite clock signal of an output frequency with error amplifier output; The Dead Time generation module produces two inputs that square-wave signal that two-way has the complementation of certain Dead Time is input to driver module respectively according to the clock signal of input; Second input of the positive input of error amplifier and voltage current adapter links to each other with double-point double-throw switch; Described double-point double-throw switch is by the pwm signal control of outside; When pwm signal when being high; Second input of voltage current adapter and the forward end of error amplifier link to each other, when pwm signal when low, second input of voltage current adapter links to each other with earth potential.First, second output of voltage current adapter links to each other with forward end, the negative input of current subtraction device module respectively; The output of current subtraction device module links to each other with an end of first electric capacity, the forward end of comparator; The other end earthing potential of first electric capacity; The reference voltage of the outside input of the negative sense termination of comparator; The first input end of the output termination first of comparator or door, first or the outside pwm signal of second input input of door, first or the output of door and the control end of driver module link to each other; The square-wave signal that the two-way of the output of the same frequency of driver module output has a complementation of certain Dead Time is input to first end of first inductance respectively and through second end of second electric capacity to first inductance; Two terminals of first inductance also link to each other with two inputs of first transformer respectively; First secondary output end of first transformer links to each other with source electrode with the grid of the first nmos switch pipe, is used to drive the first nmos switch pipe, and the drain electrode of the first nmos switch pipe connects outside high voltage source; The second subprime output of first transformer links to each other with source electrode with the grid of the second nmos switch pipe, is used to drive the second nmos switch pipe; The source electrode of the second nmos switch pipe also lotus root is connected to earth potential; The drain electrode of the second nmos switch pipe links to each other with an end of the first nmos switch pipe source electrode and the 3rd electric capacity; The other end of the 3rd electric capacity links to each other through second inductance and the first input end of second a transformer and end of the 3rd inductance; The second subprime output lotus root of second input of second transformer and the other end of the 3rd inductance, second transformer is connected to earth potential, and first secondary output end of second transformer is as the output of said drive system.

Beneficial effect of the present invention: with the LED driving is example, double loop drive system of the present invention, and on the basis of simulation light modulation loop, integrated accurate PWM light modulation loop.Under the prerequisite of the normal adjustment of simulation light modulation loop, according to the real-time current on the LED, dynamically change the extraneous duty ratio that is input to the pwm signal of actual participation light modulation, improved the precision of PWM light modulation largely; This external PWM is in high time, and the positive and negative two paths of LED electric current of sampling is respectively realized the accurately constant-current driving of LED through simulation light modulation loop, makes that the luminance difference between each paths of LEDs is minimum, has improved the precision of simulation light modulation.

Description of drawings

The double loop that Fig. 1 proposes for the present invention drives and is used for the structured flowchart that LED drives.

The double loop drive system operation principle sketch map that Fig. 2 proposes for the present invention.

Fig. 3 is simulation light modulation loop simulation result figure.

Fig. 4 is PWM light modulation loop simulation result figure.

Embodiment

Below in conjunction with accompanying drawing, be that example is done further explanation to double loop driving of the present invention with the LED driving.

As shown in Figure 1; Double loop drive system of the present invention; Specifically comprise: rectification module Rectifier; Error amplifier EA; Voltage controlled oscillator VCO; Dead Time generation module Dead Time Generator; Voltage current adapter V_IConverter; Current subtraction device Current Subtractor; The first capacitor C c; Comparator C omparator; First or the door Or1; Driver module Driver; The second capacitor C r1; The first inductance L p1; The first transformer TX1A; The first nmos switch pipe Q1; The second nmos switch pipe Q2; The 3rd capacitor C r2; The second inductance L r2; The 3rd inductance L p2; The second transformer TX2A and a double-point double-throw switch; Wherein

The input IN of said rectification module Rectifier is as the feedback sample input ISNS of said double loop drive system; The output OUT of rectification module Rectifier links to each other with the first input end B of the negative end of error amplifier EA and voltage current adapter, and the positive input of error amplifier is used to import external analog light modulation reference level Vref 1; The output of error amplifier EA links to each other with the input of voltage controlled oscillator VCO; The output of voltage controlled oscillator VCO links to each other with the input of Dead Time generation module Dead Time Generator, and voltage controlled oscillator VCO is used to produce the voltage signal variation opposite clock signal clk of an output frequency with error amplifier output; The Dead Time generation module produces two inputs 1 and 2 that square-wave signal CLK_1 and CLK_2 that two-way has the complementation of certain Dead Time are input to driver module respectively according to the clock signal of input; The second input A of the positive input of error amplifier EA and voltage current adapter V_I Converter links to each other with double-point double-throw switch; Described double-point double-throw switch is by the pwm signal control of outside; When pwm signal when being high; The second input A of voltage current adapter V_I Converter and the forward end of error amplifier EA link to each other, when pwm signal when low, the second input A of voltage current adapter V_I Converter links to each other with earth potential; First, second output C of voltage current adapter V_I Converter, D link to each other with forward end, the negative input of current subtraction device module respectively; The output of current subtraction device module links to each other with the end of capacitor C c, the forward end of comparator C omparator; The other end earthing potential of Cc; The reference voltage Vref 2 of the outside input of the negative sense termination of comparator C omparator; The first input end E of the output termination first of comparator C omparator or door Or1, first or the outside pwm signal of second input F input of door, first or the output of door Or1 and the control end 3 of driver module Driver link to each other; Square-wave signal A_OUT, the B_OUT that the two-way of the output of the same frequency of driver module Driver output has a complementation of certain Dead Time is input to first end of the first inductance L p1 respectively and through second end of the second capacitor C r1 to the first inductance L p1; Two terminals of the first inductance L p1 also link to each other with two inputs of the first transformer TX1A respectively; First secondary output end of the first transformer TX1A links to each other with source electrode with the grid of the first nmos switch pipe Q1, is used to drive the first nmos switch pipe Q1, and the drain electrode of Q1 meets outside high voltage source VDC; The second subprime output of the first transformer TX1A links to each other with source electrode with the grid of the second nmos switch pipe Q2, is used to drive the second nmos switch pipe Q2; The source electrode of Q2 also lotus root is connected to earth potential; The drain electrode of Q2 links to each other with the end of the source electrode of Q1 and the 3rd capacitor C r2; The other end of Cr2 links to each other through the second inductance L r2 and the TX2A first input end of second transformer and the end of the 3rd inductance L p2; The second subprime output lotus root of second input of TX2A and the other end of Lp2, the second transformer TX2A is connected to earth potential, and first secondary output end of the second transformer TX2A is as the output Vsout of said drive system.

Need to prove: high voltage source VDC can choose according to the actual conditions of nmos switch pipe, and its implication is clearly to those skilled in the art; " certain Dead Time " also is to adjust through the circuit parameter that changes the Dead Time generation module according to actual conditions; Body diode D1 among Fig. 1 and D2 are respectively the parasitisms of Q1 and Q2; Driver module Driver can adopt existing structure, as long as satisfy both-end output and enough output currents, those skilled in the art can choose according to actual needs; The first inductance L p1, the first transformer TX1A has constituted the first transformer unit TX1; The second inductance L r2, the 3rd inductance L p2, the second transformer TX2A has constituted the first transformer unit TX2.

Be that example describes with the LED driving among Fig. 1; The LED load is two-way load LED1, the LED2 of positive and negative parallel connection, specifically constitutes: the first rectifier diode Dr1, the second rectifier diode Dr2; The 4th capacitor C the 5th capacitor C 1; The 6th capacitor C 2, the one LED lamp string load LED1 and the 2nd LED lamp string load LED2 and the first sampling resistor Rs, wherein; The termination earth potential of the first sampling resistor Rs, the B end of the negative end of the other end and a LED lamp string load LED1, the forward end of the 2nd LED lamp string load LED2, the 5th capacitor C 1, the A end of the 6th capacitor C 2 link to each other as the feedback sample output; The end of the 4th capacitor C d links to each other with the output of drive system; The forward end of the other end and the first rectifier diode Dr1, the negative end of the second rectifier diode Dr2 link to each other; The forward end of the A of the negative end of the first rectifier diode Dr1 and the 5th capacitor C 1 end, a LED lamp string load LED1 links to each other in addition, and the B end of the forward end of the second rectifier diode Dr2 and the 6th capacitor C 2, the negative end of the 2nd LED lamp string load LED2 link to each other.

Be the principle of example explanation drive system of the present invention below with the LED driving.

As shown in Figure 1, adopt the LED drive system of drive system of the present invention to comprise two loops:

Simulation light modulation loop: form by rectification module Rectifier, error amplifier EA, voltage-controlled oscillator VCO, Dead Time generation module Dead Time Generator, driver module Driver, Cr1, TX1, Q1, Q2, Cr2, TX2, Cd, Dr1, Dr2, C1, C2, LED1 and LED2 and sampling resistor Rs; The major loop that is whole system also is a simulation light modulation loop; Wherein, The major function of Rectifier be the all-wave sampled voltage signal rectification of positive negative become positive half-wave voltage signal so that chip internal to the processing of sampled signal, the output of this module is as the negative sense input signal of error amplifier EA in addition; The major function of EA is the difference of amplifying simulation light modulation reference level (forward end input signal) and feedback signal (the negative end input signal is just through the LED of over commutation current sampling signal), output control voltage controlled oscillator VCO; The major function of VCO is to produce a variation of following input voltage signal (output of error amplifier EA), the clock signal of output frequency inverse variation; The major function of Dead Time generation module is two square-wave signals with complementation of certain Dead Time of clock signal generation according to input.

PWM light modulation loop: form by rectification module Rectifier, voltage current adapter V_I Converter, current subtraction device Current Subtractor, the first capacitor C c, comparator C omparator, Or1, driver module Driver, Cr1, TX1, Q1, Q2, Cr2, TX2, Cd, Dr1, Dr2, C1, C2, a LED lamp string load LED1, LED2 and the first sampling resistor Rs; The follower ring road that is whole system also is a PWM light modulation loop; Wherein, the major function of V_I Converter is to convert voltage signal into current signal; Current Subtractor module realizes subtracting each other of two electric currents, and generation error current signal also is accumulated on the capacitor C c.

Respectively the constant current principle of these two loops is analyzed explanation below:

1, simulation light modulation loop:

Electric current on the first sampling resistor Rs sampling LED lamp string is (in output voltage V _SOUTFor the electric current of the lamp string LED1 that samples correct time, in output voltage V _SOUTThe electric current of sampling lamp string LED2 when negative), rectification, relatively amplify as the simulation light modulation reference level of the negative input of error amplifier and error amplifier EA positive input after amplifying after; Output control voltage controlled oscillator VCO, the operating frequency of change system, the clock wire size CLK of VCO output is through after the Dead Time generation module DeadTime Generator; Produce two complementary square-wave signal control and driving module Driver with certain Dead Time, under the simulation light-modulating mode, the output signal A_OUT of driver module Driver; B_OUT also is the square-wave signal of the complementation that certain Dead Time is arranged of same frequency, and the switch of power controlling switching tube can know that by figure one the output A_OUT that works as driver module Driver is high after they boosted through isolated form driving transformer TX1; When B_OUT was low, power switch pipe Q1 opened, and the voltage that Vs is ordered is VDC; When the output B_OUT of driver module Driver is high, A_OUT is when low, and power switch pipe Q2 opens; The voltage that Vs is ordered is 0, so the voltage of Vs is a square-wave voltage that amplitude is VDC, and its frequency is by the output signal frequency decision of driver module; This square wave passes through by Cr2, Lr2, Lp2; Exporting driving LED lamp string through ideal transformer after the LLC resonant network of forming, when power switch pipe Q1 opened, Vsout was output as positive voltage; Lamp string LED1 is by the Vsout driven, and Vsout voltage is 1 charging of the 5th capacitor C in addition, and lamp string LED2 is driven by the 6th capacitor C 2; When power switch pipe Q2 opened, Vsout was output as negative voltage, and lamp string LED2 is by the Vsout driven, and Vsout voltage is 2 chargings of the 6th capacitor C in addition, and lamp string LED1 is driven by the 5th capacitor C 1.When the electric current on the LED lamp string was too high, sampled voltage was too high like this, made error amplifier EA output voltage reduce; The frequency of the clock signal clk of VCO output raises, the output signal A_OUT of driver module Driver, and the frequency of B_OUT raises; Power switch pipe Q1 so, the switching frequency of Q2 raises, and the frequency of Vs point voltage raises; Operating characteristic by the LLC controlled resonant converter can know that the second transformer TX2 output voltage reduces, and the LED electric current reduces; Whole like this loop forms negative feedback, reaches the effect of constant current.Principle is identical when the electric current on the LED lamp string reduces.Therefore after the high precision double loop drive system that is applicable to controlled resonant converter of the present invention's proposition is sampled to each road of two-way load respectively; Regulate respectively; Reach the purpose of constant current, improved the precision of simulation light modulation when reducing difference between each road load.

2, PWM light modulation loop:

At extraneous pwm signal when being high; After voltage on the first sampling resistor Rs sampling LED lamp string is handled through the Rectifier rectification; Carry out subtraction with simulation light modulation reference level through being admitted to current subtraction device Current Subtractor after the V_I Converter; This moment, Current Subtractor output current charged to Cc, changed the voltage that Vc is ordered; At extraneous pwm signal when low; Voltage on the sampling resistor Rs sampling LED lamp string handles the back through the Rectifier rectification and zero reference level carries out subtraction through being admitted to current subtraction device Current Subtractor after the voltage current adapter V_I Converter; Current subtraction device Current Subtractor output current is to capacitor C c discharge, and the voltage that Vc is ordered reduces.The voltage that Vc is ordered and second reference level Vref 2 are carried out or budget through Or1 with the extraneous pwm signal of importing through comparator C omparator relatively afterwards; The duty ratio that this part circuit realization is regulated extraneous pwm signal according to the actual current on the LED, thus the precision of PWM light modulation improved.After this pwm signal of actual participation PWM light modulation is the unlatching and the shutoff of output of the output ACU_PWM control and driving module Driver of Or1, and then the unlatching and the shutoff of control LED lamp string.At pwm signal when being high, loop is realized the constant current purpose through the EA major loop like this, when low, turn-offs LED at pwm signal, realizes the PWM light modulation.In addition if when the average current on the LED reduces in a PWM is high cycle; Sampled voltage reduces; The output current of current subtraction device Current Subtractor makes the Vc point voltage raise to capacitor C c charging, and the output signal of comparator C omparator is still reduced to second reference level Vref below 2 for high level until the Vc point voltage after pwm signal is reduced to low level; So the pwm signal of actual participation PWM light modulation promptly first or the duty ratio of the output ACU_PWM of door Or1 raise; As shown in Figure 2, then the average current of the LED in the one-period raises, and improves PWM light modulation precision.Therefore the high precision double loop drive system that is applicable to controlled resonant converter of the present invention's proposition is according to the dynamic duty ratio of regulating the pwm signal of actual participation light modulation of the size of load current actual value.

For Vref1, because it is the input signal of error amplifier EA, as long as therefore satisfy the common-mode input range of Vref1 at error amplifier EA.For Vref2, this fixing reference voltage should be after the chip soft start finishes, and when system's loop was started working, the initial voltage on the capacitor C c was generally the half the of chip internal supply voltage VDD.

The double loop drive system transient response simulation result that the present invention proposes is respectively like Fig. 3, shown in Figure 4.

Fig. 3 is a simulation light modulation loop simulation result, wherein, and I _LEDElectric current in the expression LED load; V _EAOUTThe output voltage of expression error amplifier EA is used for representing the stability of system's loop; V _SOUTThe secondary end output voltage of indication transformer TX2; V _ISNSThe sampled voltage of expression LED lamp string; V _ISNSAThe expression sampled voltage is through the voltage after the shaping.Figure can find out that every paths of LEDs samples the sampled voltage V that obtains separately thus _ISNSWaveform is a sinusoidal signal; Handle again through becoming greater than zero half-wave voltage signal after the shaping of Rectifier module; Two paths of LED obtains feedback signal individually like this, realizes constant current output separately, has improved the precision of simulation light modulation when reducing between each road load difference.

Fig. 4 simulates light modulation loop simulation result, wherein, and I _LEDElectric current in the expression LED load; Vc representes the output voltage of current subtraction device; PWM and ACU_PWM are respectively the pwm signal of extraneous input and the pwm signal of actual participation brightness adjustment control.Figure can find out that in 60% duty ratio, the cycle is under the pwm signal effect of 3.5ms if no high accuracy light modulation loop adopts traditional P WM light modulation thus, and the average current of LED is 82mA, than preset value 105mA, and average current loss 22%; If integrated high accuracy light modulation loop is in 60% duty ratio; Cycle is under the pwm signal effect of 3.5ms; The average current of LED is 100mA; Than preset value 105mA, the average current loss has only 5%, and therefore the PWM light modulation precision than this system of conventional analogue light modulation has obtained significantly improving.

To sum up can find out; The high precision double loop drive system of controlled resonant converter that is applicable to of the present invention is regulated the duty ratio of the pwm signal of actual participation light modulation according to the real-time current of load; Thereby improved PWM light modulation precision largely, reduced the error between each street lamp string based on LLC resonant converter drives system; This external PWM sampled to the LED on every road respectively in high time, realized constant-current driving through simulation light modulation loop, had also reduced the error between each street lamp string, had improved the precision of simulation light modulation.

Those of ordinary skill in the art will appreciate that embodiment described here is in order to help reader understanding's principle of the present invention, should to be understood that protection scope of the present invention is not limited to such special statement and embodiment.Those of ordinary skill in the art can make various other various concrete distortion and combinations that do not break away from essence of the present invention according to these teachings disclosed by the invention, and these distortion and combination are still in protection scope of the present invention.

Claims

1. double loop drive system; Specifically comprise: rectification module, error amplifier, voltage controlled oscillator, Dead Time generation module, voltage current adapter, current subtraction device, first electric capacity, comparator; First or door, driver module, second electric capacity, first inductance, first transformer, the first nmos switch pipe, the second nmos switch pipe, the 3rd electric capacity, second inductance, the 3rd inductance, second transformer and a double-point double-throw switch; Wherein