1. Technical Field
The present disclosure relates to light emitting diode (LED) light sources, and particularly to an LED light bar with balanced resistance for LEDs thereof, whereby current from the power source can be evenly distributed to the LEDs.
2. Description of Related Art
Referring to
It is thus desirable to provide an LED light bar which can overcome the limitations described.
Referring to
The wire lines 23 connected between the electrical power source 24 and the welding pads 26, 27, 28, 29 have lengths different from each other. The longer the length of the wire line 23 is, the larger the resistance of the wire line 23 is. That is, the resistance of the wire line 23 is in proportion to the length of the wire line 23. In detail, r1 represents the resistance of the pair of wire lines 23 connecting the pair of welding pads 29 with the electrical power source 24; r2 represents the resistance of the pair of wire lines 23 connecting the pair of welding pads 28 with the electrical power source 24; r3 represents the resistance of the pair of wire lines 23 connecting the pair of welding pads 27 with the electrical power source 24; and r4 represents the resistance of the pair of wire lines 23 connecting the pair of welding pads 26 with the electrical power source 24. The relation among r1, r2, r3 and r4 meets following inequality: r1<r2<r3<r4.
Referring to
Referring to
The intervals of the welding pad units 270, 280, 290 of the welding pads 27, 28, 29 decrease from the pair of welding pads 29 near the electrical power source 24 to the pair of welding pads 27 far from the electrical power source 24. That is, the interval of the welding pad units 270 of each welding pad 27 is smaller than that of the welding pad units 280 of each welding pad 28; the interval of the welding pad units 280 of each welding pad 28 is smaller than that of the welding pad units 290 of each welding pad 29. Therefore, the actual areas of the welding pads 27, 28, 29 increase from the pair of welding pads 29 near the electrical power source 24 to the pair of welding pads 27 far from the electrical power source 24. The resistances of the welding pads 27, 28, 29 decrease from the pair of welding pads 29 near the electrical power source 24 to the pair of welding pads 27 far from the electrical power source 24. Since the pair of welding pads 26 farthest from the electrical power source 24 are not divided into welding pad units, each welding pad 26 has the delimited area the same as its actual area, and the resistance of each welding pad 26 is the smallest when compared with that of each of the welding pads 27, 28, 29.
In detail, R1 represents the resistance of the pair of welding pads 29; R2 represents the resistance of the pair of welding pads 28; R3 represents the resistance of the pair of welding pads 27; and R4 represents the resistance of the pair of welding pads 26. The relation among R1, R2, R3 and R4 meets following inequality: R1>R2>R3>R4. The resistances r1, r2, r3, r4 of the wire lines 23 and the resistances R1, R2, R3, R4 of the welding pads 26, 27, 28, 29 meet following equalities: r1+R1=r2+R2=r3+R3=r4+R4.
According to the disclosure, the resistances of the wire lines 23 increase from the welding pad 29 near the electrical power source 24 to the welding pad 26 far from the electrical power source 24. The resistances of the welding pad 26, 27, 28, 29 gradually decrease from the pair of welding pads 29 near the electrical power source 24 to the pair of welding pads 26 far from the electrical power source 24. A total resistance of one pair of the welding pads 26, 27, 28, 29 and the wire lines 23 which are connected to the corresponding one of the LED chips 22 is the same as a total resistance of another pair of the welding pads 26, 27, 28, 29 and the wire lines 23 which are connected to the corresponding another one of the LED chips 22. That is, the resistance between each LED chip 22 and the electrical power source 24 is the same as another and balanced. The working current flowing through each LED chip 22 is thus the same as another. Therefore, the working current can be evenly distributed among the LED chips 22, whereby the LED chips 22 can have a uniform life of use.
Referring to
Differences between the LED light bar 20a of the second embodiment and LED light bar 20 of the first embodiment are in that: the welding pads 26a, 27a, 28a, 29a each are not divided into welding pad units, each welding pad 26a, 27a, 28a, 29a is a one-piece pad. However, the widths and lengths of the welding pads 26a, 27a, 28a, 29a are different from each other. The welding pads 26a, 27a, 28a, 29a have actual areas gradually increased from one pair near the electrical power source 24a to another pair far from the electrical power source 24a. The welding pads 26a, 27a, 28a, 29a have resistances gradually decreased from one pair near the electrical power source 24a to another pair far from the electrical power source 24a. A total resistance of the welding pads 26a, 27a, 28a, 29a and the wire lines 23a which are connected to the one LED chip 22a is the same as a total resistance of the welding pads 26a, 27a, 28a, 29a and the wire lines 23a which are connected to another LED chip 22a. That is, the resistance between each LED chip 22a and the electrical power source 24a is also the same as another.
It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
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101114683 | Apr 2012 | TW | national |