It uses AC power to connect with LED lamp source, use linear switch to control the on and offs of LED light, the voltage of our LED light is around 36V(we use isulation ceremic board to isolate the LED chip).
Circuit principle of our driver:
.png)
The input voltage via ACL, ACN. After BD1 full bridge rectifier, the pulse AC connected directly to the light source module, composed of LED1 ~ LED5
dedicated drive chip control of S1, S2, S3, S4 in the corresponding four open point voltage respectively the LED1 ~ LED5 light; By R1 R2 and R3 and R4 resistance testing each LED
turn on current feedback back to the driver chip, through the comparison with the chip inside the benchmark level Vref to control the conduction of S1 to S5 state,
in order to achieve control of the LED work power S1 ~ S4 in the circuit and amplification state, adjust the current flow of each LED circuit, working voltage and current waveform
diagram as shown in figure 2:
(1).png)
input voltage ammeter waveform figure
2. analysis of system efficiency
In order to analyze conveniently, assuming that the input voltage is 220 VAC 50HZ, 5 groups of LED conduction voltage are 50 V,
the input a sinusoidal variation of the input voltage of 100V, 150 V respectively 200 v to 250 v LED1 LED5 conduction respectively, its working state as shown in figure 3:
Working status Conducting switch Conducting LED Conducting LED voltage Conducting occupy percentage
(2).png)
Switch working state
In order to analyze conveniently, we analyzed a quarter conduction cycle LED module on the voltage and current signals, assume that the input current I1,
4 pieces of the shaded part respectively represent the four groups LED when conduction current input voltage LED after open the threshold voltage of the LED to work in constant current state,
as shown in figure 4, more than to the LED is the pressure drop of the pressure drop will fall on the S1 ~ S4 switch, as shown in figure shown in a part of the Red Cross The power from the four main
circuit loop in the amplification of the state of the switch tube, when input voltage is not higher than 250V, S1 ~ S4 approximation to the work in the switch mode, loss is small, the input voltage exceeds 250V,
the additional voltage all fall on the S4, so the wastage of the S4 is the largest, the following is a approximate analysis of the system efficiency of power supply.
(3).png)
Drive current voltage waveform
The input power Pin is equal to the input voltage of sine the envelope of voltage, input current is the first series of LED working current,
namely I1, the calculation results(4).png)
Output power for the area of the shaded part is shown in figure 4, phase 1 LED no conduction, from phase 2 to phase 5 for LED actual conduction will, the calculation results: (5).png){kind=small}
System power efficiency of approximate calculation result is 188/161 = 86%, in the actual product design, if the higher section switch series, the area of the shaded part was close to voltage envelope,
the Pout is more close to the Pin, in theory, the series of infinity, Pout with Pin, also is the system power efficiency is 100%.
3.Reliability analysis
Rule out the use of environmental differences, circuit design and electronic circuit failure generally caused by the failure of electronic components, so the general Reliability theory system (Reliability) by
each of the components Reliability of multiplication and, assuming that the number of devices a system for 100, the system can be expressed as the overall Reliability:
Let's compare the technology of Our driver type and DC driver system reliability of power supply, Our electronic components used for resistance and semiconductor devices,
the number of no more than 20, and electronic components of DC drive power supply by general resistance capacitance semiconductor devices Electrolytic capacitor, etc, the total number of
devices can reach hundreds of, the reliability of the two ways, respectively:(6).png)
.
Assume that the components involved within the prescribed time failure rate is five over ten thousand, so the calculation results is(7).png){kind=small}
It is obvious that this system is superior to the DC drive power supply, and with the increase of power, DC power supply circuit complexity,
higher number of electronic components , system reliability difference will further highlight.
4. Dimming Feature.
By adjusting the AC input voltage waveform of the conduction phase Angle, and realize the dimmer phase modulation mode in traditional incandescent lamp dimming light is widely used in the method used in AC
driver module whether can also realize that move light on? The test results show that the cutting phase dimming method in piecewise linear power drive LED device
can realize the power adjustment function, but in the process of adjustment, will lead to varying degrees of visible stroboscopic and serious EMI problems.
As you can see in figure 6, because of the bidirectional thyristor dimmer in positive and negative half cycle of the cut or not completely symmetrical, cut it in to the LED module for phase modulation light, on
the positive and negative half cycle at the input power frequency cut asymmetric phase Angle, the positive half cycle conduction time of 2.45 ms, negative half cycle conduction time of 2.13 ms,
LED drive current flows module, 50 hz, lead to stroboscopic.
(8).png)
In order to realize the depth of the dimming in of our drive technology, at the same time avoid disoperation in depth the dimming power supply chips and LED stroboscope, the dimming can be adopt intensity-modulatedindicato method. See the diagram in figure 7, the principle of this kind of dimming method is to use standard 1 ~ 10 v analog dimming signal, first convert to 0 v ~ 1 v dc level, then the dc level to drive chip and internal reference
level When the input level changed from 0 v to 1 v, in the process of chip inside can change the signal output driver S1 ~ S4, makes the S1 ~ S4 in different state of amplification, then falls on S1 ~ S4 voltage levels
change determines the size of the current through the LED module, test shows that by the changes of 1 ~ 10 v voltage, can realize linear LED dimming.
8. Our LED controlled current source bias modulation dimmer schematic diagram
igure 8 waveform shows that the amplitude modulation dimming method can achieve depth in our LED module light changes,
the purpose of system stable operation at the same time, without the slightest stroboscopic appear, and there was no question of EMI.
(9).png)
Intensity-modulatedindicato dimming the ac input current waveform under different dimming range
2 actual product performance test and analysis
Figure 10 below also gives AC - dimming curve, HV module by the figure can be seen, the low light power covers 100% to 0% range,
and in the process of dimming, module power always maintain a smooth linear relationship.
(10).png)
Under the condition of driverless type work in the pulse of the current will cause the LED beam acceleration?
Let us through continuous 4000 hours to droop data show that as long as the current largest flow shall not exceed the rating,
(11).png)
lighting decay curve
By the above data are obvious, after 4000 hours of light test, basic didn't produce light failure, shows that the lamp works not accelerate the LED light failure process.
Conclusion:
1.The electronic components used by fewer and less species, specifications, less easy to logistics management;
2.Module on the use of all the components for the patch installation, small volume, low height, is advantageous for the optical lens design;
3.No electrolytic capacitor design, the use of components for resistance and semiconductor devices, by working environment, in theory, life is equal to the life of the LED light source of these components;
4.Line of the switch tube work in low frequency amplifier state, almost no high frequency interference;
5.Can be further realize the integration of the light source and drive type encapsulation, the LED light source and electronic components in the packaging side synchronous assembly,
further shorten the technological process, module of smaller volume, the design of other types of lamps and lanterns to bring huge imaginary space.
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