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Composition and Performance of LED Circuit

2019/05/12

Following is a brief analysis of the composition of the LED circuit has its performance:

I. Circuit Composition

When more LED products are needed, if all the LEDs are connected in series, the higher voltage of the LED driver will be required: if all the LEDs are connected in parallel, the larger current of the LED driver will be required. Series or parallel connection of all LED not only limits the strict use of LED, but also increases the cost of driver because of the large load current of parallel LED. The solution is to use parallel connection. The number of series and parallel LEDs is equally distributed, so that the voltage allocated to a series branch of LED is the same, the current on each LED in the same series branch is basically the same, the brightness is the same, and the current through each series branch is also similar.

II. Circuit Performance Analysis

When there is a short circuit in a series branch with poor quality of LED, the current through the series circuit will increase, and the LED in the series branch will be easily damaged, regardless of whether the voltage-stabilized driving mode or the constant-current driving mode is adopted. When the high current passes through the damaged series of LEDs, it is mostly shown as circuit break because of the large current passing through them. When a series branch of LED is disconnected, the output current of the driver will be reduced without affecting the normal operation of all the remaining LEDs if the voltage-stabilized driving mode is adopted.

If constant current LED drive mode is adopted, the current allocated in the remaining LED will increase because the output current of the driver remains unchanged, which will easily damage all the LED. The solution is to connect as many parallel LEDs as possible, so that when one of the LEDs is disconnected, the current allocated in the remaining LEDs is not large, so as not to affect the normal operation of the remaining LEDs.

The advantages of this series-to-parallel circuit are simple circuit, stable brightness, high reliability, and low requirement for device consistency. No special device is needed. Even if a single LED tube fails, the impact on the whole light-emitting module is small. In the case of great changes in the working environment, the effect of using this kind of light-emitting devices is ideal.

There is another connection method in the hybrid mode, that is, dividing the LED equally into groups in parallel, and then connecting each group in series. When there is a short circuit with poor quality of an LED, whether it is driven by voltage stabilizer or constant current, all the LED connected in parallel in this branch will not be bright. If constant-current LED drive mode is adopted, the output current of the driver remains unchanged. Except for the parallel branch parallel to the short-circuit LED, all the other LEDs work normally. Assuming that the number of parallel LEDs is large and the driving current of the driver is large, the current through this short circuit LED will increase. When a large current passes through this short-circuit LED, it can easily become a circuit breaker. Because there are many parallel LEDs, after disconnecting one LED, the average distribution current does not change much, and the rest of the LEDs can still work properly, so only one LED is not on in the whole LED lamp.

The main problem of the light-emitting elements consisting of parallel and series hybrid connections is that in a single group of parallel LEDs, due to the difference of devices and operating conditions, individual LED chips in a single group may lose PN junction characteristics and appear short circuit. Short-circuit of individual devices will cause the failure of LED to lose working current IF''''''', leading to the extinction of the whole set of LED. The total current will pass through the short-circuit device, and the longer short-circuit current will cause the internal bond alloy wire or other parts of the device to burn out, resulting in open circuit. At this time, the failed LED regains the current and returns to normal luminescence, but the working current IF is a little larger than the original one. This is the reason why the light-emitting elements of this connection form appeared first when several LEDs in a group were extinguished together. After a period of time, except one of the LEDs was not bright, the other LEDs returned to normal.

      III. Driver Selection

      From the above analysis, it can be seen that the combination of driver and load LED in series/parallel mode is very important. When driving power LED in constant current mode, parallel load is not suitable. Similarly, voltage stabilized LED driver is not suitable for series load.

Yiwu Fuwei e-commerce firm (IACS Co., Limited) is a very professional Led manufacturer who produces high quality outdoor led light. Our popular products are solar led lights, UFO lights, underwater lights and so on. If you have any question about the led product, please feel free to contact us.