Primary side controllers drive higher power modules into smaller form factors
1 min read
National Semiconductor has introduced what it claims to be the industry's first full bridge pulse width modulation (pwm) controllers to integrate all four primary side bridge mosfet gate drivers. The LM5045 and LM5046 are designed to deliver efficiency and power density in quarter brick and eighth brick power modules used in high input voltage communications infrastructure applications.
The energy efficient controllers convert the design of full bridge topology based power converters into small form factor power supplies by reducing the number of external power components needed with existing full bridge solutions.
For applications requiring zero voltage switching to minimise emi due to switching noise, the LM5046 PWM controller contains features necessary to implement a phase shifted full bridge topology. Available in thermally enhanced 5 x 5 x 0.8mm LLP and 4.4 x 9.7 x 0.9mm TSSOP packages, the full bridge controllers operate on the primary side of an isolated dc/dc converter with input voltage up to 100V. The devices provide 2A high and low side gate drivers for the four external bridge mosfetsin addition to the control signals for the secondary side synchronous rectifier mosfets - and an internal high voltage start up regulator.
Intelligent start up of the synchronous rectifiers allows monotonic turn on of the power converter, even with pre-bias load conditions. The synchronous rectifier control signals offer independent and programmable leading/trailing edge dead times between the primary and secondary mosfet control signals for optimising efficiency, and the SR signals are limited to 5V for use with digital isolators.
