MDK Opto-Electro Tech Co., Ltd
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  Quality And Service

        Good products are manufactured from care. Compared with competitors, in procedures of the total quality control management - including market investigation, RD and design, material purchase, production planning, process control, inspection and test, marketing and service – a successful manufacturer should listen more carefully to its customers, design products more carefully, control production process more carefully, inspect products more carefully and supply service more carefully.

1. Sincerely respect the customers, carefully design the products: Some quality factors have closely related to manufacturing and using. Yet however, designing plays a decisive role in quality, because the satisfaction degree of quality mainly depends on designing process. If a poor design decides a low reliability, low economy and poor applicability a product, it cannot be compensated during production and application. A successful company always takes “User is the God” as its basic philosophy and works makes every effort to satisfy its customers.

2. Carefully control the production processes: As to the production process, the factors affecting the quality include five aspects: process operators, materials, machines, process methods and production environment. Product quality mainly depends on the qualities of processes and other factors and their variations. Therefore we pay much attention to the trainings on operators’ technical abilities and incoming QC. We make great effort on careful production process control and keeping good production environment.

3. Inspect strictly. Absence is better than lower quality. Technical inspection is a very important QC step in manufacturing. We hold the attitude that the next process is the customer and carefully take every inspection step. During inspections, materials, semi-finished products, finished product and manufacturing processes are strictly controlled according to the engineered standard. Prevention measures are carried out to guarantee that unqualified materials will not put into production, unqualified parts will not flow to the next process, unqualified semi-finished products will not be accepted and unqualified products will not delivered. We stress on the concept “Quality, the Life of an Enterprise” and always take precaution as our best measure in the total QC management. Quality control is the final check for one process while it is the pre-inspection for the later one. All the QC information is communicated between processes. This helps related processes take measures for improvement and thus a very efficient quality assurance system is formed.

4. Good service wins trust from customers. Management of sales process and use process is also an important step. The major task of these two processes is supplying customers quality service. It consists two aspects: sales service and after service. The former includes offer the customers optimized designs, introducing product characteristics and offer the best convenience for customers on leading time, delivery places and method of transportation. The later includes some technical service like after service and maintenance.

  Technical support

1. Survey on Drive Circuit for Backlight: The major function of LED drive circuit is converting the alternating current into direct current, meeting the voltage and current required for LED.

2. Three Main Methods for Backlight Connection:
1) . Series Connection: This circuit requires higher power voltage. Vt = VF of ea. LED = VF LED1+ VF LED2+ VF LED3…+ VF LEDn It = IF of an individual LED =IF LED1
2) . Parallel Connection: This circuit requires higher power current. Vt = VF of an individual LED = VF LED1 It = IF of ea. LED = IF LED1+ IF LED2+ IF LED3…+ IF LEDn
3) . Combined Connections: Vt = Sum of ea. LED VF in series = VF LED1+ VF LED2+ VF LED3…+ VF LEDn It = Sum of ea. LED IF in parallel = IF LED1+ IF LED2+ IF LED3…+ IF LEDn

3. Two Modes of Drive Circuits for Backlight:
1) . Constant Current Mode:
A. The current output by constant current drive circuit is constant. The related direct current voltage varies along with the changes of load. The greater the load resistance is, the higher the output voltage is.
B. Constant circuit is not affected by any short circuit. But no open load circuit is allowed.
C. Constant current driven LED is relatively ideal. But theoretically the current is too high.
2) . Voltage-stabilizing Mode
A. When all the parameters in the voltage-stabilizing circuit are determined, the input voltage is fixed while the output current varies along with the changes of load.
B. Voltage-stabilizing circuit is not affected by any open circuit. But short circuit is never allowed.
C. Voltage-stabilizing circuit driven LED appropriate resisters must be added to each LED.
D. The luminance changes when the current or voltage changes.

4. Choice of Regulator Diode:
1). Regarding to regulator diode: Voltage stabilizing diode functions protecting LED. When LED works in a condition of unstable voltage, voltage stabilizing diode can stabilize the voltage so as to avoid any damage to LED. This optimized design offers more stable quality of the product.
2). Regarding ESD: The antistatic grade of LED presently is around 800V. Electrostatic above 1500V can make serious damage on LED. In winter, the electrostatic on human bodies is normally between 1000V to 1500V. Direct contact of a human body can be a major cause to damage LED. During production, LED is strictly forbidden from contact from bare human bodies not equipped with anti-static devices. Antistatic devices include ESD clothing, ESD shoes / socks, ESD wrists, ESD headgears, ESD gloves / finger cots and etc. In some dry environment or some special backlight applied filed, electrostatic damage risk to LEDs might increase. Thus voltage stabilizing diode is applied to protect LEDS against the possible damage from electrostatics. We guarantee the IR leakage within 5V,10μA although the normal industrial standard is 5V,50μA

. 5. Attentions on Using Backlight
1). Electro Parameters:
A. A drive voltage little higher than the positive VF of the LED should be selected. But too high voltage might produce unnecessary heat.
B. LED should not be installed in a reverse way. When there is reverse current, an incorrect polarity protection (such as reverse diode) must be added.
C. Current for LED should not be greater than the rated value. Over load for long time may shorten the life of LED. If the current for LED is out of control and the LED works under greater current for long time, life of the LED will be affected and even may become unreliable.
D. Very tiny changes at the positive voltage for the LED might influence the electro properties of LED. Therefore, it is recommended that the drive circuit is installed with a temperature compensation function so as to help control the current when there are changes of some factors like input voltage or environmental temperature.
E. Drive circuit itself should be designed with a good input voltage tolerance.
2). Optic Parameters
A. Generally LED luminance is in proportion with the current. Especially the red and yellow LED can have a very good performance under greater current.
B. But green, blue and white color of LED may be saturated under strong current, resulting in lower luminary efficiency.
C. Input LED luminance is in proportion with the temperature. So in applications, circuit should be designed to reduce heat and measure for heat emission should taken.

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