Design of symmetrical half-bridge converter with a series coupling capacitor

Purpose With the advancement of technology, size, cost, and losses of the switched mode power supply (SMPS) have been decreasing. However, due to the high frequency switching, design of magnetic drives and isolation circuits are becoming a crucial factor in SMPS. This paper presents design criteria, procedure and implementation of AC-DC half bridge (HB) converter with lower cost, smaller size and lower voltage stress on the power switch. Design/Methodology/approach The HB converter is designed in a symmetrical mode with a series coupling capacitor. Isolated power supplies are used for the converter and control circuit. Further, a transformer based isolated gate driver is used to drive both MOSFETs. The control IC works in voltage control mode to regulate voltage by controlling the duty cycle of the MOSFETs. Findings Control characteristics and performance of the HB converter is simulated using the MATLAB software and prototype of 170 W HB converter is built to validate the analytical results under variable load current and source voltage. The power quality and variation of load voltage at 2 A, 5 A, 7 A are reported. Originality/value This paper presents the design of a low-cost HB converter in a symmetrical mode which saves the additional cost of symmetric correction circuit normally required in asymmetrical mode design. This paper also focuses on the selection of primary and secondary side switch, series coupling capacitor, commuting diode, isolated drive and charge equalizer resistor.

Calculation of Stress Intensity Factors at Both Ends of the Indenter under Eccentric Loads

During rock breaking by drill, cone rolls on the rock surface and contact between gear teeth and surface is basically positive Mode-I plane indentation and bias Mode-I plane indentation. During bias action, there will be an asymmetrical Mode-I singular stress field at both ends of the indenter. The stress field singularity is of the same order as Mode-I crack tip and with the same function distribution. In this paper, based on the J2 integral conservation law, a new method is established for solving stress intensity factor of bias Mode-I plane indentation, which not only provides respective stress intensity factor of both ends of the indenter but also compares relations between eccentricity, partial load, and stress intensity factor. The study not only provides a method for establishment of new cone drill engineering design but also improves rock layer boring efficiency.