Detailed explanation of the design scheme of high-power blue LED light source driving circuit

Abstract: In order to capture the image information of underwater targets, reduce the cost of underwater imaging system, by using high-power blue LED instead of traditional laser as light source, combined with CCD imaging technology, adjust the divergence angle of the beam to illuminate the underwater target scene, The key features of the target or the target are illuminated to achieve imaging of the underwater target. A constant voltage constant current driving circuit based on high power blue LED composed of IRIS4011 is designed. The driving circuit stably and reliably controls the LED to work at rated power. Through underwater imaging experiments, information of underwater targets is collected, and the experimental results show that tracking and receiving target information within a narrow field of view is greatly reduced. The effect of backscattered light on imaging quality is improved, and the signal-to-noise ratio and the working distance of the system are improved.

Semiconductor (LED) lighting technology, which is known as "green lighting", is developing rapidly. LED has the advantages of low power consumption, long service life, small size, and environmental protection. Through the continuous development of high-intensity blue LEDs, several generations of devices with higher brightness have been produced. The efficiency of LEDs based on silicon carbide die materials introduced around 1990 is about 0.04 lm/W, and the light intensity is very high. There are rarely more than 15 mcd. The first GaN-based utility LED appeared in the mid-1990s. There are also many companies that produce GaN LEDs with different substrates (such as sapphire and silicon carbide) that emit light in colors such as green, blue or violet. The invention of high-brightness blue LEDs makes it possible to implement a true-color advertising display that displays true-color, full-motion video images. With the continuous advancement of technology, it is currently possible to produce blue LEDs with a power of up to 100 W and a luminous flux of up to 2 000 lm. Therefore it has a wide

For the application of the promising technology, it is necessary to conduct in-depth research. The underwater imaging system is an underwater imaging system based on the low-loss window of seawater to blue-green light (480-540 nm). It can be used not only in ordinary water, but also in turbid water, even on the dark sea floor. This paper is mainly based on the research of high power blue LED underwater imaging system. The high-power blue LED (≥50 W) light source driving circuit is an important part of the research and analysis of underwater imaging systems based on high-power blue LEDs.

1 Basic principles and circuit design

For underwater imaging systems, the choice of source is critical, and the stability, uniformity, response speed, and wavelength range of the light source are key to system imaging. The light emitted by the blue LED passes through the aqueous medium - the target reflection - the aqueous medium - the receiving optical system, and finally images on the imaging sensor (CCD, ICCD). This determines that the LED must work in the fast pulse drive mode. Currently, the drive circuits on the market are generally used in the slow pulse drive mode (on the order of μs), which is far from meeting our requirements. Therefore, we must solve the problem of fast pulse drive circuit by ourselves, especially to realize high power LED with high power fast pulse of ns order. Based on the actual needs of this experiment, we have developed such a fast pulse drive circuit. The basic function of the circuit is to generate low-frequency, fast, high-power drive current pulse signals. The frequency and period accuracy of the output pulse is high, and the stability is good. The pulse signal width is adjustable in 5 steps in 20-100 ns, and the output is 50. Operates at a reference frequency of Hz. The pulse signal passes through the driving circuit and outputs a fast pulse signal to drive the output current switch to generate a large current pulse signal to drive a high power LED. In order to meet the design requirements and objectives, we use a crystal oscillator circuit to generate a high-precision frequency/cycle reference pulse as a built-in signal source. By dividing the reference pulse multiple times to generate an output pulse signal of the desired frequency, a frequency-stabilized pulse can be obtained. The signal, while achieving frequency selection. After the frequency-divided pulse signal is passed through the pulse width forming circuit to realize the pulse width adjustment, and then through the current switching circuit, a large current pulse is generated to cause the LED to emit light. The driving circuit is mainly composed of the following parts: a signal source, a frequency dividing circuit, a frequency selection, a pulse width circuit, a TTL output, a driving circuit, and a current switching circuit. Its block diagram is shown in Figure 1.

Figure 1 Circuit structure block diagram