CN203368857U - Flyback dimmable LED driving system - Google Patents

Abstract

The utility model discloses a flyback dimmable LED driving system which comprises an input circuit unit used for rectifying power voltage and providing overcurrent protection and overvoltage protection, a fly-back inverter unit which is connected with the input circuit unit and used for providing DC output and realizing constant current voltage limiting feedback, an output circuit unit which is connected with the flyback inverter unit and used for receiving direct current of the flyback inverter circuit unit and inputting and storing energy for LED luminescence, a feedback loop unit which is connected with the output circuit unit and used for circuit sampling of the output circuit unit and constant output of the circuit, and a dimming control circuit unit which is connected with the feedback loop unit and used for guaranteeing that current flowing through a light modulator is higher than holding current and controlling output current and brightness of LED lamps. Through flyback topology and a SSL2103 dedicated chip, efficiency and stability of the LED driving system are raised.

Description

A kind of inverse-excitation type variable optical LED driving system

Technical field

The utility model belongs to the illumination LED studying technological domain, relates in particular to a kind of inverse-excitation type variable optical LED driving system and circuit.

Background technology

The characteristics such as LED has that light efficiency is high, low, the environmental protection of consuming energy, the life-span is long, volume is little, easy care, startup are rapid, as the 4th generation lighting source or green light source, now be widely used in the fields such as various demonstrations, decoration, backlight, general lighting and urban landscape.

From Physical Characteristic Analysis, LED is equivalent to a constant voltage load that less equivalent series resistance ESR is arranged, because the value of ESR is very little, the slight variation of electric power output voltage or load voltage will cause very large curent change, the luminous flux of LED is directly proportional to electric current, therefore, between constant voltage driving and constant current driving, constant-current driving LED is obviously a suitable scheme.Luminous flux and the electric current of LED are directly proportional; Its pressure drop increases along with the increase of electric current, along with the reduction of temperature, reduces.

The development of LED lighting technology faces four challenges greatly of light quality, light efficiency performance, reliability and simplicity of design aspect, adopt traditional driver to have that power factor is low, luminous efficiency is not high, electrical network is disturbed to the problems such as large, that the power grid quality impact is serious, therefore select special-purpose LED illumination chip, adopt reverse exciting topological, realize that the variable optical LED driving system with constant current voltage limiting feedback has certain Research Significance.

Bidirectional triode thyristor, at a bidirectional trigger diode DIAC of silicon controlled driving stage series connection, have a RC network at the other end of bidirectional trigger diode; Regulate the change that resistance can realize thyristor operating angle α, when capacitance voltage rises to the conducting voltage of diode, the Diac triggering and conducting, the SCR control utmost point adds triggering signal, the reliable conducting of controllable silicon, once controlled silicon conducting, the voltage instantaneous at controllable silicon two ends reduces to zero, electric capacity discharges rapidly by resistance, and load voltage (VR1) equals the civil power input.When capacitance voltage drops into conducting voltage when following, the Diac cut-off, the controllable silicon anode current is reduced to be less than and maintains electric current, the controllable silicon cut-off, load voltage equals zero.

The light modulation principle be summarized as utilize controllable silicon to the sine wave of alternating current with cutting, the electric circuit inspection commutating voltage changes and reduces output current by lowering duty ratio and frequency of oscillation, to reach the purpose of light modulation.

But LED adopts traditional driver to have the problems such as power factor is low, luminous efficiency is not high, large on the electrical network interference, that the power grid quality impact is serious.

The utility model content

The purpose of the utility model embodiment is to provide a kind of inverse-excitation type variable optical LED driving system and circuit, is intended to solve LED and adopts traditional driver to have that power factor is low, luminous efficiency is not high, on electrical network, disturbs large, power grid quality to affect serious problem.

The utility model embodiment is achieved in that a kind of inverse-excitation type variable optical LED driving system, and this inverse-excitation type variable optical LED driving system comprises:

Input circuit unit, for supply voltage is carried out to rectification, provide overcurrent protection and overvoltage protection;

The inverse-excitation type inverter unit, connect input circuit unit, for direct current output being provided and realizing the constant current voltage limiting feedback;

Output circuit unit, connect the inverse-excitation type inverter unit, receives the direct current of inverse-excitation type inverter unit, is used to the luminous input of LED and storage power;

The feedback control loop unit, be connected with output circuit unit, for the circuit sampling to output circuit unit, realizes the output that circuit is constant;

The adjusting control circuit unit, be connected with the feedback control loop unit, for guaranteeing the electric current that flows through dimmer, maintaining on electric current, controls the brightness of output current and LED lamp.

Further, the circuit of input circuit unit adopts rectifying and wave-filtering structure, L2=6.8mH, C2=C3=150nF;

Specifically being connected to of circuit: the left end of rectifier bridge BD1 connects the RGND end, and right-hand member connects diode D3, inductance L 2 and capacitor C 2, the capacitor C 3 diode D3 that is connected in parallel.

Further, the inverse-excitation type inverter unit adopts and drives chip SSL2103 to build the inverse-excitation type drive system, and the inverse-excitation type inverter unit is connected to:

Chip SSL2103 is directly started by the mains-supplied after rectification by 14 pin, the 12 pin output drive signals of chip SSL2103 drive outside Q3 pipe, transformer primary winding exoergic, auxiliary winding output energy is to LED, auxiliary winding passes through R22, D7, C8 guarantees chip operation for VCC provides galvanic current to press, D8 prevents the too high defective chip of supply power voltage; During chip operation, after in upper one-period, transformer primary side inductance and RC oscillating circuit have discharged, 13 pin voltage starting oscillations, detect waveform by 13 pin and 10 pin, when vibrating to the lowest point, open and guaranteed that like this loss is minimum, now chip SSL2103 sends and opens signal, the transformer primary side inductance starts energy storage afterwards, 11 pin voltages rise, and while rising to threshold value, chip SSL2103 sends cut-off signals; If input voltage is very low, 11 pin voltages risings are very slow, and 8 pin have been set the upper limit to the rise time, have limited maximum duty cycle, when the time, reach in limited time, and chip can send cut-off signals equally; Transformer can produce the high pressure spike in switch moment and damage element, and D5 is used for as the high pressure spike provides path, and D4 is used for limiting the maximum of high pressure spike.

Further, the inverse-excitation type inverter unit comprises: with transformer, power supply or former limit winding Np, output or the secondary winding Ns of three coils, auxiliary winding Na;

The transformer calculation procedure is as follows, and the calculation of the oscillation frequency formula is as follows:

$f_{\mathrm{ring}}=\frac{1}{2\×\mathrm{\π}\×\sqrt{L_p\×C_p}}$

Wherein: L _pthe inductance of former limit winding, by designer's value; C _pdrain parasitic capacitance, suggestion Cp=117pF;

According to our computed duty cycle δ of the parameter of input and output ₁numerical value (being the time of former limit charging), and then can obtain δ ₂(being the time of secondary charging):

${\mathrm{\&delta;}}_1=\frac{1-\frac{f_{\mathrm{conv}}}{{2\mathrm{<figure-callout\; id="1"\; label="f\; ring"\; filenames="HSA0000093241280000012.png,HSA0000093241280000022.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{ring}}}}{1+\frac{V_{\mathrm{buffaur}}\&times;I_{\mathrm{LED}}}{P_{\mathrm{in}}\&times;n}}$ ${\mathrm{\&delta;}}_2=1-{\mathrm{\&delta;}}_1-\frac{{\mathrm{<figure-callout\; id="2"\; label="f\; conv"\; filenames="HSA0000093241280000022.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{conv}}}{2\&times;f_{\mathrm{ring}}}$

Wherein: suggestion V _buffavr=(310+220)/2=265V; The utility model P _in=50W; f _convby designer's value, get 75kHz here;

Calculate the turn ratio of former limit and secondary:

V _zener＝V _{DRAIN_max}-V _{buff_max}-25

Wherein: V _zenerit is the withstand voltage of Zener diode D4; V _{dRAI_max}the 13 pin maximum voltages of chip SSL2103 and the smaller value of switching tube drain electrode maximum voltage; V _{buff_max}=384V;

Umber of turn is calculated by the experience equation: n=43.417 * Vout ^-3/4=3.153, and result is subject to n _maxrestriction: n _max=V _zener/ V _out=5.5, so n=3;

Calculate former limit peak current (I _ppk) and secondary peak current (I _spk):

$I_{\mathrm{spk}}=\frac{2\&times;I_{\mathrm{LED}}}{{\mathrm{\&delta;}}_z}{I}_{\mathrm{ppk}}=\frac{I_{\mathrm{spk}}}{n}$

Wherein: I _lED=1.24;

Check former limit inductance:

$L_p=\frac{2\&times;P_{\mathrm{in}}}{{\mathrm{<figure-callout\; id="2"\; label="I\; ppk"\; filenames="HSA0000093241280000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_{\mathrm{ppk}}^{}\&times;f_{\mathrm{conv}}}$

If result of calculation is different from design load, revise the design load cycle calculations, until deviation minimum, Lp=914 μ H here;

Former limit umber of turn can calculate by following formula,

$N_p=\frac{L_p\&times;I_p}{B_{\max }\&times;A_e}\&ap;57$

Ns＝Np/n＝19

Wherein: Ae=86.9mm ²; Bmax=275mT means peakflux density; N is the turn ratio of former limit and secondary; Ip=1.2 * Ippk;

Can calculate by following formula the turn ratio of auxiliary winding and secondary,

$m=\frac{N_a}{N_s}=\frac{V_{\mathrm{aux}}}{V_{\mathrm{led}}+V_{D6}}$

Wherein: Na is the number of turn of auxiliary winding; Ns is the number of turn of secondary winding; Vaux is the voltage that auxiliary winding produces; V _d6d6 conducting voltage (0.3～0.7V); Vled is the voltage of LED string;

So auxiliary umber of turn Na=Ns * m=11.

Further, the circuit of adjusting control circuit unit is connected to: the resistance R 1 of input and capacitor C 1, due to voltage spikes and current spike that C13 produces while being used for suppressing light modulation, after 14 pin of chip SSL2103 detect the voltage input, 1 human hair combing waste of chip SSL2103 goes out to drive signal, Q2 is open-minded, provide electric current to guarantee that dimmer can not turn-off, 9 pin of chip SSL2103 detect the electric current in main circuit, when electric current is very little, illustrate that the dimmer electric current is also very little, now the driving Q1 of 2 pin chip SSL2103 is open-minded, form bleed-off circuit, R11//R12//C5 vibration and R12//C5 vibration coordinate the chip internal oscillating circuit that the minimum and maximum operating frequency of chip is set, the variation of input voltage passes to 5 pin of chip SSL2103 by the dividing potential drop of R2 and R10, control output current, thereby control the brightness of LED lamp.

Further, the circuit of feedback control loop unit is connected to: output current is sampled by R25, and when electric current does not reach the value of setting, Q1 and Q2 are in saturation region, and electric current flows through respectively Q1 and Q2, in the loop of optocoupler, does not have electric current to flow through; When output current increase until ILED * R25=IQ2 * (R27+R29), now Q1 and Q2 form mirror current source, IQ1=IQ2, R27+R29>R26 is set herein, the part of the electric current on R26 can flow to optocoupler by R30 and D3 so, and optocoupler passes to signal 8 pin of chip SSL2103 again, and the duty ratio upper limit is reduced, output current reduces, and realizes the purpose of constant current.

Further, in the circuit of output circuit unit, output capacitance C9, C10, C17 are 1000 μ F; C11 is 2.2nF, and R25 is 0.1 Ω.

Inverse-excitation type variable optical LED driving system and circuit that the utility model provides, adopt reverse exciting topological by input circuit unit, inverse-excitation type inverter unit, adjusting control circuit unit, feedback control loop unit, output circuit unit, complete civil power is changed to the required operating voltage of LED, realize isolation and anti-interference function simultaneously; Dimming function is realized by the break-make of switching tube in the adjusting control circuit unit; The utility model is 4 connection in series-parallel, 10 LED lamp pearls of every string by utilizing the SSL2103 ASIC-based and having made load, the LED driver model machine that gross power is 50W, main functional modules of system etc. is analyzed and designed, experiment result reveal is in input voltage 208V-253V scope, the power factor of model machine is more than 0.9, efficiency is higher than 82%, and ripple is less than 35%.Efficiency of the present utility model is high, and power factor is high, the wide and stable and reliable operation of dimming scope.

The accompanying drawing explanation

Fig. 1 is the circuit connection diagram of the input circuit unit that provides of the utility model embodiment;

Fig. 2 is the circuit connection diagram of the inverse-excitation type inverter unit that provides of the utility model embodiment;

Fig. 3 is the circuit connection diagram of the adjusting control circuit unit that provides of the utility model embodiment;

Fig. 4 is the circuit connection diagram of the feedback control loop unit that provides of the utility model embodiment;

Fig. 5 is the connection diagram of the output circuit unit that provides of the utility model embodiment;

Fig. 6 is the power factor that the utility model embodiment provides, output current, efficiency curve diagram;

Fig. 7 is the dimming curve schematic diagram that the utility model embodiment provides.

Embodiment

In order to make the purpose of this utility model, technical scheme and advantage clearer, below in conjunction with embodiment, the utility model is further elaborated.Should be appreciated that specific embodiment described herein is only in order to explain the utility model, and be not used in restriction the utility model.

Inverse-excitation type variable optical LED driving system and circuit that the utility model provides.For convenience of explanation, only show the part relevant to the utility model.

The inverse-excitation type variable optical LED driving system of the utility model embodiment, this inverse-excitation type variable optical LED driving system comprises:

Input circuit unit, for supply voltage is carried out to rectification, provide overcurrent protection and overvoltage protection;

The inverse-excitation type inverter unit, connect input circuit unit, for direct current output being provided and realizing the constant current voltage limiting feedback;

Output circuit unit, connect the inverse-excitation type inverter unit, receives the direct current of inverse-excitation type inverter unit, is used to the luminous input of LED and storage power;

The feedback control loop unit, be connected with output circuit unit, for the circuit sampling to output circuit unit, realizes the output that circuit is constant;

The adjusting control circuit unit, be connected with the feedback control loop unit, for guaranteeing the electric current that flows through dimmer, maintaining on electric current, controls the brightness of output current and LED lamp.

As the prioritization scheme of the utility model embodiment, the circuit of input circuit unit adopts rectifying and wave-filtering structure, L2=6.8mH, C2=C3=150nF;

Specifically being connected to of circuit: the left end of rectifier bridge BD1 connects the RGND end, and right-hand member connects diode D3, inductance L 2 and capacitor C 2, the capacitor C 3 diode D3 that is connected in parallel.

As the prioritization scheme of the utility model embodiment, the inverse-excitation type inverter unit adopts and drives chip SSL2103 to build the inverse-excitation type drive system, and the inverse-excitation type inverter unit is connected to:

Chip SSL2103 is directly started by the mains-supplied after rectification by 14 pin, the 12 pin output drive signals of chip SSL2103 drive outside Q3 pipe, transformer primary winding exoergic, auxiliary winding output energy is to LED, auxiliary winding passes through R22, D7, C8 guarantees chip operation for VCC provides galvanic current to press, D8 prevents the too high defective chip of supply power voltage; During chip operation, after in upper one-period, transformer primary side inductance and RC oscillating circuit have discharged, 13 pin voltage starting oscillations, detect waveform by 13 pin and 10 pin, when vibrating to the lowest point, open and guaranteed that like this loss is minimum, now chip SSL2103 sends and opens signal, the transformer primary side inductance starts energy storage afterwards, 11 pin voltages rise, and while rising to threshold value, chip SSL2103 sends cut-off signals; If input voltage is very low, 11 pin voltages risings are very slow, and 8 pin have been set the upper limit to the rise time, have limited maximum duty cycle, when the time, reach in limited time, and chip can send cut-off signals equally; Transformer can produce the high pressure spike in switch moment and damage element, and D5 is used for as the high pressure spike provides path, and D4 is used for limiting the maximum of high pressure spike.

As the prioritization scheme of the utility model embodiment, the inverse-excitation type inverter unit comprises: with transformer, power supply or former limit winding Np, output or the secondary winding Ns of three coils, auxiliary winding Na;

The transformer calculation procedure is as follows, and the calculation of the oscillation frequency formula is as follows:

$f_{\mathrm{ring}}=\frac{1}{2\&times;\mathrm{\&pi;}\&times;\sqrt{L_p\&times;C_p}}$

Wherein: L _pthe inductance of former limit winding, by designer's value; C _pdrain parasitic capacitance, suggestion Cp=117pF:

According to our computed duty cycle δ of the parameter of input and output ₁numerical value (being the time of former limit charging), and then can obtain δ ₂(being the time of secondary charging):

${\mathrm{\&delta;}}_1=\frac{1-\frac{f_{\mathrm{conv}}}{{2\mathrm{<figure-callout\; id="1"\; label="f\; ring"\; filenames="HSA0000093241280000012.png,HSA0000093241280000022.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{ring}}}}{1+\frac{V_{\mathrm{buffaur}}\&times;I_{\mathrm{LED}}}{P_{\mathrm{in}}\&times;n}}$ ${\mathrm{\&delta;}}_2=1-{\mathrm{\&delta;}}_1-\frac{{\mathrm{<figure-callout\; id="2"\; label="f\; conv"\; filenames="HSA0000093241280000022.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{conv}}}{2\&times;f_{\mathrm{ring}}}$

Wherein: suggestion V _buffavr=(310+220)/2=265V; The utility model P _in=50W; f _convby designer's value, get 75kHz here;

Calculate the turn ratio of former limit and secondary:

V _zener＝V _{DRAIN_max}-V _{buff_max}-25

Wherein: V _zenerit is the withstand voltage of Zener diode D4; V _{dRAI_max}the 13 pin maximum voltages of chip SSL2103 and the smaller value of switching tube drain electrode maximum voltage; V _{buff_max}=384V;

Umber of turn is calculated by the experience equation: n=43.417 * Vout ^-3/4=3.153, and result is subject to n _maxrestriction: n _max=V _zener/v _out=5.5, so n=3;

Calculate former limit peak current (I _ppk) and secondary peak current (I _spk):

$I_{\mathrm{spk}}=\frac{2\&times;I_{\mathrm{LED}}}{{\mathrm{\&delta;}}_2}{I}_{\mathrm{ppk}}=\frac{I_{\mathrm{spk}}}{n}$

Wherein: I _lED=1.24;

Check former limit inductance:

$L_p=\frac{2\&times;P_{\mathrm{in}}}{I_{\mathrm{ppk}}^2\&times;f_{\mathrm{conv}}}$

If result of calculation is different from design load, revise the design load cycle calculations, until deviation minimum, Lp=914 μ H here;

Former limit umber of turn can calculate by following formula,

$N_p=\frac{L_p\&times;I_p}{B_{\max }\&times;A_e}\&ap;57$

Ns＝Np/n＝19

Wherein: Ae=86.9mm ²; Bmax=275mT means peakflux density; N is the turn ratio of former limit and secondary; Ip=1.2 * Ippk;

Can calculate by following formula the turn ratio of auxiliary winding and secondary,

$m=\frac{N_a}{N_s}=\frac{V_{\mathrm{aux}}}{V_{\mathrm{led}}+V_{D6}}$

Wherein: Na is the number of turn of auxiliary winding; Ns is the number of turn of secondary winding; Vaux is the voltage that auxiliary winding produces; V _d6d6 conducting voltage (0.3～0.7V); Vled is the voltage of LED string;

So auxiliary umber of turn Na=Ns * m=11.

A prioritization scheme as the utility model embodiment, the circuit of adjusting control circuit unit is connected to: the resistance R 1 of input and capacitor C 1, due to voltage spikes and current spike that C13 produces while being used for suppressing light modulation, after 14 pin of chip SSL2103 detect the voltage input, 1 human hair combing waste of chip SSL2103 goes out to drive signal, Q2 is open-minded, provide electric current to guarantee that dimmer can not turn-off, 9 pin of chip SSL2103 detect the electric current in main circuit, when electric current is very little, illustrate that the dimmer electric current is also very little, now the driving Q1 of 2 pin chip SSL2103 is open-minded, form bleed-off circuit, R11//R12//C5 vibration and R12//C5 vibration coordinate the chip internal oscillating circuit that the minimum and maximum operating frequency of chip is set, the variation of input voltage passes to 5 pin of chip SSL2103 by the dividing potential drop of R2 and R10, control output current, thereby control the brightness of LED lamp.

A prioritization scheme as the utility model embodiment, the circuit of feedback control loop unit is connected to: output current is sampled by R25, and when electric current does not reach the value of setting, Q1 and Q2 are in saturation region, electric current flows through respectively Q1 and Q2, in the loop of optocoupler, does not have electric current to flow through; When output current increase until ILED * R25=IQ2 * (R27+R29), now Q1 and Q2 form mirror current source, IQ1=IQ2, R27+R29>R26 is set herein, the part of the electric current on R26 can flow to optocoupler by R30 and D3 so, and optocoupler passes to signal 8 pin of chip SSL2103 again, and the duty ratio upper limit is reduced, output current reduces, and realizes the purpose of constant current.

As the prioritization scheme of the utility model embodiment, in the circuit of output circuit unit, output capacitance C9, C10, C17 are 1000 μ F; C11 is 2.2nF, and R25 is 0.1 Ω.

Below in conjunction with drawings and the specific embodiments, application principle of the present utility model is further described.

The inverse-excitation type variable optical LED driving system of the utility model embodiment comprises: input circuit unit, inverse-excitation type inverter unit, adjusting control circuit unit, feedback control loop unit, output circuit unit;

Input circuit unit, for supply voltage is carried out to rectification, provide overcurrent protection and overvoltage protection;

The inverse-excitation type inverter unit, connect input circuit unit, for direct current output being provided and realizing the constant current voltage limiting feedback;

Output circuit unit, connect the inverse-excitation type inverter unit, receives the direct current of inverse-excitation type inverter unit, is used to the luminous input of LED and storage power;

The feedback control loop unit, be connected with output circuit unit, for the circuit sampling to output circuit unit, realizes the output that circuit is constant;

The adjusting control circuit unit, be connected with the feedback control loop unit, for guaranteeing the electric current that flows through dimmer, maintaining on electric current, controls the brightness of output current and LED lamp.

As shown in Figure 1, the circuit diagram of input circuit unit, input circuit adopts the rectifying and wave-filtering structure, and diode D3 is for anti-backflow, and the parameter of ∏ mode filter is calculated by following formula:

$f_{\mathrm{cutoff}}=\frac{1}{2\mathrm{\&pi;}\sqrt{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HSA0000093241280000012.png,HSA0000093241280000022.png"\; state="\{\{state\}\}">L</figure-callout>}1\&times;\frac{C3\&times;C2}{C3+\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HSA0000093241280000022.png"\; state="\{\{state\}\}">C</figure-callout>}2}}}$

The utility model switching frequency is chosen 75kHz, and shearing frequency arranges 7kHz, calculates L2=6.8mH, C2=C3=150nF.

Specifically being connected to of circuit: the left end of rectifier bridge BD1 connects the RGND end, and right-hand member connects diode D3, inductance L 2 and capacitor C 2, the capacitor C 3 diode D3 that is connected in parallel;

As shown in Figure 2, the utility model adopts the LED illumination special driving chip SSL2103 of NXP company to build the inverse-excitation type drive system,

When access during civil power, because chip is not worked, can't driving power switching tube Q3, the energy storage of transformer primary winding, auxiliary winding is output not, and auxiliary winding is not also to chip power supply, and now chip is directly started by the mains-supplied after rectification by 14 pin (HVDETC); Afterwards, chip 12 pin (GATE) output drive signal drives outside Q3 pipe, transformer primary winding exoergic, auxiliary winding output energy is to LED, and auxiliary winding is by R22, D7, C8 guarantees chip operation for VCC provides galvanic current to press, and D8 prevents the too high defective chip of supply power voltage;

Because switching loss is positively correlated with switching voltage, in order to improve luminous efficiency, make native system be operated in discontinuous mode;

During chip operation, after in upper one-period, transformer primary side inductance and RC oscillating circuit have discharged, 13 pin (DRAIN) voltage starting oscillation, detect waveform by 13 pin (DRAIN) and 10 pin (AUX), open and guaranteed that like this loss is minimum when vibrating to the lowest point, now chip sends and opens signal, the transformer primary side inductance starts energy storage afterwards, 11 pin (SOURCE) voltage (is the voltage on R19, the variation of this voltage has embodied the variation of primary current) rise, while rising to threshold value, chip sends cut-off signals; If input voltage is very low, the rising of 11 pin (SOURCE) voltage is very slow, and 8 pin (PWMLMT) have been set the upper limit to the rise time, have limited maximum duty cycle, when the time, reach in limited time, and chip can send cut-off signals equally,

When system works, instantaneous input voltage is less, and primary current rises slower, and because maximum service time is restricted, so current peak is also less, this means that the input voltage size variation is followed in the variation of size of current, realizes PFC;

Transformer can produce the high pressure spike in switch moment and damage element, and D5 is used for as the high pressure spike provides path, and D4 is used for limiting the maximum of high pressure spike;

The utility model needs a transformer with three coils: a power supply or former limit winding Np; Export or secondary winding Ns for one; An auxiliary winding Na, the transformer calculation procedure is as follows:

1. the calculation of the oscillation frequency formula is as follows:

$f_{\mathrm{ring}}=\frac{1}{2\&times;\mathrm{\&pi;}\&times;\sqrt{L_p\&times;C_p}}$

Wherein: L _pthe inductance of former limit winding, by designer's value; C _pdrain parasitic capacitance, suggestion Cp=117pF;

2. according to our computed duty cycle δ of the parameter of input and output ₁numerical value (being the time of former limit charging), and then can obtain δ ₂(being the time of secondary charging):

${\mathrm{\&delta;}}_1=\frac{1-\frac{f_{\mathrm{conv}}}{{2\mathrm{<figure-callout\; id="1"\; label="f\; ring"\; filenames="HSA0000093241280000012.png,HSA0000093241280000022.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{ring}}}}{1+\frac{V_{\mathrm{buffaur}}\&times;I_{\mathrm{LED}}}{P_{\mathrm{in}}\&times;n}}$ ${\mathrm{\&delta;}}_2=1-{\mathrm{\&delta;}}_1-\frac{{\mathrm{<figure-callout\; id="2"\; label="f\; conv"\; filenames="HSA0000093241280000022.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{conv}}}{2\&times;f_{\mathrm{ring}}}$

Wherein: suggestion V _buffavr=(310+220)/2=265V; The utility model P _in=50W; f _convby designer's value, get 75kHz here,

3. calculate the turn ratio of former limit and secondary:

V _zener＝V _{DRAIN_max}-V _{buff_max}-25

Wherein: V _zenerit is the withstand voltage of Zener diode D4; V _{dRAI_max}it is the smaller value of chip 13 pin (DRAIN) maximum voltage and switching tube drain electrode maximum voltage; V _{baff_max}=384V,

Umber of turn is calculated by the experience equation: n=43.417xVout ^-3/4=3.153, and result is subject to n _maxrestriction: n _max-V _zener/ V _out=5.5, so n=3

4. calculate former limit peak current (I _ppk) and secondary peak current (I _spk):

$I_{\mathrm{spk}}=\frac{2\&times;I_{\mathrm{LED}}}{{\mathrm{\&delta;}}_2}{I}_{\mathrm{ppk}}=\frac{I_{\mathrm{spk}}}{n}$

Wherein: I _lED=1.24,

5. check former limit inductance:

$L_p=\frac{2\&times;P_{\mathrm{in}}}{I_{\mathrm{ppk}}^2\&times;f_{\mathrm{conv}}}$

If result of calculation is different from design load, revise the design load cycle calculations, until deviation minimum, Lp=914 μ H here

Former limit umber of turn can calculate by following formula,

$N_p=\frac{L_p\&times;I_p}{B_{\max }\&times;A_e}\&ap;57$

Ns＝Np/n＝19

Wherein: Ae=86.9mm ²; Bmax=275mT means peakflux density; N is the turn ratio of former limit and secondary; Ip=1.2 * Ippk;

Can calculate by following formula the turn ratio of auxiliary winding and secondary,

$m=\frac{N_a}{N_s}=\frac{V_{\mathrm{aux}}}{V_{\mathrm{led}}+V_{D6}}$

Wherein: Na is the number of turn of auxiliary winding; Ns is the number of turn of secondary winding; Vaux is the voltage that auxiliary winding produces; V _d6d6 conducting voltage (0.3～0.7V); Vled is the voltage of LED string,

So auxiliary umber of turn Na=Ns * m=11;

Being connected to of the circuit of inverse-excitation converting circuit unit:

Chip is directly started by the mains-supplied after rectification by 14 pin; Afterwards, chip 12 pin output drive signals drive outside Q3 pipe, transformer primary winding exoergic, auxiliary winding output energy is to LED, and auxiliary winding is by R22, D7, C8 guarantees chip operation for VCC provides galvanic current to press, and D8 prevents the too high defective chip of supply power voltage; During chip operation, after in upper one-period, transformer primary side inductance and RC oscillating circuit have discharged, 13 pin voltage starting oscillations, detect waveform by 13 pin and 10 pin, when vibrating to the lowest point, opens and guaranteed that like this loss is minimum, now chip sends and opens signal, the transformer primary side inductance starts energy storage afterwards, and 11 pin voltages (be the voltage on R19, the variation of this voltage has embodied the variation of primary current) rise, while rising to threshold value, chip sends cut-off signals; If input voltage is very low, 11 pin voltages risings are very slow, and 8 pin have been set the upper limit to the rise time, have limited maximum duty cycle, when the time, reach in limited time, and chip can send cut-off signals equally.

As shown in Figure 3, the resistance R 1 of input and capacitor C 1, C13 produce while being used for suppressing light modulation due to voltage spikes and current spike.

As mentioned before, the dimmer electric current need to reach On current and open and can open, may cause the phenomenon of again turn-offing in conducting moment because removing triggering signal, after 14 pin (HVDET) detect the voltage input, 1 pin (SBDR) sends the driving signal, Q2 is open-minded, provide electric current to guarantee that dimmer can not turn-off, 9 pin (ISENSE) detect the electric current in main circuit, when electric current is very little, illustrate that the dimmer electric current is also very little, now 2 pin (WBDR) drive Q1 open-minded, form bleed-off circuit, the electric current that dimmer is flow through in assurance is maintaining on electric current, can effectively improve the flicker caused because electric current is too low and the phenomenon of turning off the light, R11//R12//C5 vibration and R12//C5 vibration coordinate the chip internal oscillating circuit that the minimum and maximum operating frequency of chip is set, dimmer changes the size of input voltage, and the variation of input voltage passes to 5 pin (BRT) by the dividing potential drop of R2 and R10, controls output current, thereby controls the brightness of LED lamp.

As shown in Figure 4, output current is sampled by R25, and when electric current does not reach the value of setting, Q1 and Q2 are in saturation region, and electric current flows through respectively Q1 and Q2, in the loop of optocoupler, does not have electric current to flow through; When output current increases until ILED * R25=IQ2 * (R27+R29), now Q1 and Q2 form mirror current source, IQ1=IQ2.R27+R29>R26 is set herein, and the part of the electric current on R26 can flow to optocoupler by R30 and D3 so, and optocoupler passes to 8 pin (PWMLMT) to signal again, and the duty ratio upper limit is reduced, and output current reduces, and realizes the purpose of constant current.

As shown in Figure 5, the value of output circuit device determines by LED number, voltage and current in LED string, and the size of current ripples is determining that buffer capacitor is should value how many, and buffer capacitor can calculate by following equation:

$C=\sqrt{\frac{1}{{\left(\frac{\mathrm{\&Delta;I}}{I_{\mathrm{LED}}}\right)}^2}-1}/(4\mathrm{\&pi;}\&times;f_{\mathrm{supply}}\&times;R)$

Wherein: I _lEDbe output current, Δ I is current ripples, f _supplybe mains frequency, R is the dynamic electric resistor of LED string.

Load of the present utility model is 4 string LED parallel connections, 10 lamps of every string.Each lamp pearl voltage 3.3V, electric current 0.31A, the typical dynamic electric resistor of LED is 0.6 Ω, whole load dynamic electric resistor is 1.5 Ω.Mains frequency is 50Hz, and the ripple ratio gets 0.3.The output capacitance of selecting after calculating is 3000 μ F;

C11 be connected to and secondary circuit between, suppress the capacitive coupling between former limit, secondary and auxiliary winding.In order to meet the requirement of application, the value of this electric capacity must be much larger than the value of coupling capacitance.According to experience, preferably choose 20 times.If so Ccoup=100pF, C11 should>2nF.If need the safety isolation, this electric capacity should guarantee to bear the voltage (Yn type) of EN132400 regulation.Here use 2.2nF.

In order to reduce the wastage, need to select a less R25, select 0.1 Ω here.

In conjunction with experimental data, the utility model is described further:

Do not connect the experimental result under dimmer condition

After completing experimental prototype, load is accessed to the output of driving power, drive system is tested, the specified input of this drive system is 230V/50Hz, nominal load is 10LEDs*4string, but because mains input voltage is not constant, and also can there be some deviations in load LED, therefore need under the scope of the 90%-110% of civil power, be tested, data are in Table 1, power factor, output current, the change curve of efficiency is shown in Fig. 6

Table 1 does not connect the experimental data under dimmer condition

From above data, the power factor of system reduces along with the increase of civil power, along with the increase of load, increases, and the line regulation under different civil powers is ± 2%; The output current of system increases along with the increase of civil power, along with the increase of load, reduces, and line regulation is ± 2%; The efficiency of system is 82.75% at rated operation point, line regulation is ± and 1%, illustrate that this systematic function is better;

Experimental result under the access dimmer condition

Dimmer is accessed to the input of driver, from the light modulation angle, maximum the beginning adjusted to low-angle, output current data under the different angles of flow is in Table 2, output current is shown in Fig. 7 about the dimming curve at light modulation angle, known output current reduces along with reducing of light modulation angle, and middle slope is larger, the two ends slope is less, obviously brightness also can be according to same curvilinear motion, this dimming curve is pleasant for human eye, and meet the dimming curve standard NEMA SSL-6 of national electrical manufacturers association about solid-state illumination, dimming effect is better

The output current of table 2 under the different angles of flow

The angle of flow/°	Output current/mA	The angle of flow/°	Output current/mA
				165.6	1.25	93.6	0.69
151.2	1.22	79.2	0.45
				136.8	1.21	64.8	0.2
122.4	1.16	50.4	0.09
				108	0.95	36	0

Verification experimental verification, the displaying ratio of voltage waveform is 1/500, and the current waveform display ratio is 0.1V/A, and the current waveform distortion is less, can follow preferably voltage waveform, illustrates that power factor is higher; The output current maximum is 1.4A, and minimum value is 1.05A, and mean value is 1.24A, and the ripple rate is (1.4-1.05) ÷ 1.24=28%, meets the requirement of LED drive system,

The utility model utilizes the SSL2103 ASIC-based and made load is 4 connection in series-parallel, 10 LED lamp pearls of every string, the LED driver model machine that gross power is 50W, main functional modules of system etc. is analyzed and designed, experiment result reveal is in input voltage 208V-253V scope, and the power factor of model machine is more than 0.9, and efficiency is higher than 82%, ripple is less than 35%, illustrate that this system has efficiency high, power factor is high, the advantages such as the wide and stable and reliable operation of dimming scope.

The foregoing is only preferred embodiment of the present utility model; not in order to limit the utility model; all any modifications of doing within spirit of the present utility model and principle, be equal to and replace and improvement etc., within all should being included in protection range of the present utility model.

Claims (7)

1. an inverse-excitation type variable optical LED driving system, is characterized in that, this inverse-excitation type variable optical LED driving system comprises:

Input circuit unit, for supply voltage is carried out to rectification, provide overcurrent protection and overvoltage protection;

The inverse-excitation type inverter unit, connect input circuit unit, for direct current output being provided and realizing the constant current voltage limiting feedback;

Output circuit unit, connect the inverse-excitation type inverter unit, receives the direct current of inverse-excitation type inverter unit, is used to the luminous input of LED and storage power;

The feedback control loop unit, be connected with output circuit unit, for the circuit sampling to output circuit unit, realizes the output that circuit is constant;

The adjusting control circuit unit, be connected with the feedback control loop unit, for guaranteeing the electric current that flows through dimmer, maintaining on electric current, controls the brightness of output current and LED lamp.

2. inverse-excitation type variable optical LED driving system as claimed in claim 1, it is characterized in that, the circuit of input circuit unit adopts the rectifying and wave-filtering structure, specifically being connected to of circuit: the left end of rectifier bridge BD1 connects the RGND end, right-hand member connects diode D3, inductance L 2 and capacitor C 2, the capacitor C 3 diode D3 that is connected in parallel.

3. inverse-excitation type variable optical LED driving system as claimed in claim 1, is characterized in that, the inverse-excitation type inverter unit adopts and drives chip SSL2103 to build the inverse-excitation type drive system.

4. inverse-excitation type variable optical LED driving system as claimed in claim 3, is characterized in that, the inverse-excitation type inverter unit comprises: with transformer, power supply or former limit winding Np, output or the secondary winding Ns of three coils, auxiliary winding Na.

5. inverse-excitation type variable optical LED driving system as claimed in claim 1, it is characterized in that, the circuit of adjusting control circuit unit is connected to: the resistance R 1 of input and capacitor C 1, due to voltage spikes and current spike that C13 produces while being used for suppressing light modulation, after 14 pin of chip SSL2103 detect the voltage input, 1 human hair combing waste of chip SSL2103 goes out to drive signal, Q2 is open-minded, provide electric current to guarantee that dimmer can not turn-off, 9 pin of chip SSL2103 detect the electric current in main circuit, when electric current is very little, illustrate that the dimmer electric current is also very little, now the driving Q1 of 2 pin chip SSL2103 is open-minded, form bleed-off circuit, R11//R12//C5 vibration and R12//C5 vibration coordinate the chip internal oscillating circuit that the minimum and maximum operating frequency of chip is set, the variation of input voltage passes to 5 pin of chip SSL2103 by the dividing potential drop of R2 and R10, control output current, thereby control the brightness of LED lamp.

6. inverse-excitation type variable optical LED driving system as claimed in claim 1, it is characterized in that, the circuit of feedback control loop unit is connected to: output current is sampled by R25, when electric current does not reach the value of setting, Q1 and Q2 are in saturation region, electric current flows through respectively Q1 and Q2, in the loop of optocoupler, does not have electric current to flow through; When output current increase until ILED * R25=IQ2 * (R27+R29), now Q1 and Q2 form mirror current source, IQ1=IQ2, R27+R29>R26 is set herein, the part of the electric current on R26 can flow to optocoupler by R30 and D3 so, and optocoupler passes to signal 8 pin of chip SSL2103 again.

7. inverse-excitation type variable optical LED driving system as claimed in claim 1, is characterized in that, in the circuit of output circuit unit, output capacitance C9, C10, C17 are 1000 μ F; C11 is 2.2nF, and R25 is 0.1 Ω.

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