Power supply circuit analysis of pulsed semiconductor

Power supply circuit analysis of pulsed semiconductor laser

Pulsed semiconductor lasers have the advantages of high peak power and small size, and are widely used in the fields of laser ranging, lidar and free space laser communication. In laser detection and laser communication, system bandwidth, operating distance, accuracy, anti-interference and low power consumption and other performance depend on the quality of the laser pulse emitted by the semiconductor laser, and the optical pulse emitted by the semiconductor laser is directly modulated by the electrical pulse generated by the laser power supply, the optical pulse characteristics generated by the laser to a certain extent depends on the design of the pulse driving power supply, pumping The amplitude of current and pulse width determine the peak power of laser pulse. Therefore, the design of pulsed power supply for pulsed semiconductor laser is a key technology in laser application.

In this paper, the equivalent circuit of the pulsed semiconductor laser drive power supply is given, and the LRC circuit model is established. According to the analytical results of the linear constant coefficient second order homogeneous differential equation, the main characteristic parameters of the circuit are analyzed, and the current 2 time curve is obtained. The calculated results are compared with the experimental results.

Establishment and analysis of Power Supply Circuit model of pulsed semiconductor laser;

FIG. 1 and FIG. 2 show the general form and corresponding equivalent circuit of pulsed semiconductor laser drive circuit respectively. Where,L is the parasitic inductance (because there are discharge capacitors, switching components and lasers in the circuit, there are parasitic inductance in the discharge loop),C is the energy storage capacitance, and R is the total resistance of the circuit, including the laser equivalent resistance, switching component resistance and circuit series resistance. In order to reduce the volume, the energy storage element is generally selected capacitance, considering the discharge speed, the power MOSFET tube is used as the switching element.

Assuming that the capacitor is charged to a voltage of V at the beginning, the discharge circuit of the circuit can be regarded as a series RLC circuit with zero input response. The current on the capacitor decays very quickly, perhaps in less than 1 cycle, the current decays to zero. However, as long as the direction of current changes, that is, negative current occurs, it is not what we want. 

According to the derivation of the above formula, the circuit parameters satisfying the R>2L/C relationship are designed. The driver circuit of the pulsed semiconductor laser as shown in FIG.  The experimental results are compared with the theoretical calculation.

The high current and narrow pulse width directly modulated power supply is an important guarantee for the peak power output of pulsed semiconductor lasers. The equivalent circuit and LRC circuit model of the pulsed semiconductor laser drive power supply are established. The analytical solutions of the linear constant coefficient second order homogeneous differential equations are analyzed and compared with the experimental results. The results show that when the main parameters of the power supply meet the relation of R≥2L/C, a relatively ideal non-oscillating discharge process can be obtained. The measured pulse waveform and its characteristics are in agreement with the calculated results.

According to the model established by LRC circuit equation, the large current and narrow pulse width driving power supply of pulsed semiconductor laser is analyzed and calculated theoretically. The experimental data show that when the main parameters of the power supply meet the relation of R≥L/C, a relatively ideal non-oscillating discharge process can be obtained. Using the corresponding circuit parameters, the discharge waveform with the peak current of 43A and the pulse width of 30ns can be obtained, and the laser output pulse width is 27ns.