Because of the VF value characteristics of LEDs, some VF values will change with the temperature and current, which is generally not suitable for parallel design. However, in some cases, we have to solve the problem of driving cost of multiple LEDs in parallel. These designs can be used for reference.

Note that the VF value needs to be divided into grades. The LEDs with the same VF value should be used on the same product as far as possible. The product can ensure that the error current is within 1mA and the LED is in a relatively constant current state.

Using integrated triodes can keep the current of each LED consistent. These triodes are produced under the same temperature environment and the same process conditions β The same value can ensure that each current is basically the same. The constant current part can be designed in this way when the requirements are not very high. A stable voltage or a stable PWM voltage value drives the stabilized triode bias voltage to achieve a basic constant current.

Using an IC with high accuracy as the constant current reference source, R can set the IC output current. Once the value of R resistance is determined, it can be replaced by a fixed resistance. The use of multi triode integrated devices can reduce the use of IC, thus reducing the cost of design products.

Linear high-power LED constant current output can be used in parallel. In product design, we often cannot find a driving IC with large current. Generally, it is rare to see an IC with a nominal 2A or above, and the IC with a nominal 2A may not be used to the limit. The reason for the cost of IC process greater than 1a is that MOS tubes are external, and the external MOS tube circuit is complex and the reliability is reduced. Parallel operation is an effective design method.

Dd312 parallel reference design is adopted to directly drive three 6wled. Enabling PWM control signals requires proper isolation to avoid mutual interference and driving capacity problems. The en enabling voltage should meet the requirements of the specification, and do not damage the EN pin too high. Generally, IC withstand voltage refers to load and power supply. If there is no indication of excitation voltage, please do not exceed 5V design.

For this kind of detection, the LED constant current drive IC at one end of the LED can also be designed and driven in parallel. In fact, the IC works alone and finally works together in parallel. The DC-DC mode works at a higher frequency. It should be noted that the PCB layout should avoid cross design. The respective filter and bypass capacitors should be close to the IC, and the load current will finally be combined.