In this thesis, a red green and blue (RGB) laser diode driver (LDD) is designed, assembled and tested, which can work as a standalone device or an internal component fully controlled by a laser projector. In particular, the thesis explores a multi-channel RGB LDD for a retrofitted laser projector, targeting projectors for home, business and education. If laser diodes (LDs) with the same color are connected in series, a higher forward voltage is required, making most commercial LDDs unsuitable for this application due to their insufficient compliance voltages. If the connections of all the LDs are in parallel, issues on size and cost arise since many LDs are used in this case. Another problem to use the commercial LDDs for RGB laser projection is that there are no proper communication interfaces to link the LDDs to the laser projector. In order to solve these problems by taking advantage of all the features of iC-HTG, an integrated circuit with automatic current control functionality, both the hardware circuits and the software for an eight-channel LDD are designed. Experimental results show that all the RGB channels can achieve compliance voltage of 23 V within the required working current range, which can drive up to 5 blue, 4 green or 10 red LDs in series in each single channel. It is confirmed experimentally that the designed LDD can fulfill the requirements on driving current (i.e. 1% accuracy and 1% stability). The protection functions of the developed LDD are also explored and verified experimentally. It can detect the open laser connection before the LDD channels are enabled. Fast over-current protection can be achieved within 1.5 µs. Circuit interfaces and protocols of the communications enable the multi-channel RGB LDD to work as a standalone device or an internal component of the laser projector. / Thesis / Master of Applied Science (MASc)

Laser Diodes (LDs) are semiconductor coherent lightening devices which are widely used in many fields such as defence, industry, medical and optical communications. They have advantageous characteristics such as having higher electrical-to-optical and optical-to-optical conversion efficiencies from pump source to useful output power when compared to flash lamps, which makes them the best devices to be used in range finding applications. Optical output power of lasers depends on current through LDs. Therefore, there is a relationship between operating life and work performance of LDs and performance of drive power supply. Even, weak drive current, small fluctuations of drive current can result in much greater fluctuations of optical output power and device parameters which will reduce reliability of LDs. In this thesis, a hardware for a fast and high power pulsed LD driver is designed for laser range finder and is based on linear current source topology. The driver is capable of providing pulses up to 120A with 250&mu / s pulse width and frequencies ranging from 20Hz to 40Hz. It provides current pulses for two LD arrays controlled with a proportional-integral (PI) controller and protect LDs against overcurrents and overvoltages. The proposed current control in the thesis reduces current regulation to less than 1% and diminishes overshoots and undershoots to a value less than 1% of steady-state value, which improves safe operation of LDs. Moreover, protection functions proposed in the thesis are able to detect any failure in driver and interrupt LD firing immediately, which guarantees safe operation of LDs.