Texas Instruments Corporation

Xiaojun Xu

Xianhui Dong

Nan Jiang

Lin Sheng

Shuchun Zhang

Daniel Jing

A DC-to-DC converter includes first and second switches. If on, the first switch provides a signal path through a common node to an output voltage node. If on, the second switch provides a signal path through the common node to the output voltage node. Control logic provides first and second control signals to control the first and second switches. A node produces a first voltage that ramps up from zero during initialization, and a soft start controller controls the second control signal while the first voltage is not greater than a predefined level. While the first voltage is not greater than the predefined level, the soft start controller keeps the second control signal at a higher level to maintain on the second switch, and transitions the second control signal to a lower level only when the first control signal transitions from a lower level to a higher level.

Soft start controller of a converter

PWM control circuits and soft start circuitry thereof are presented in which a source follower circuit provides an input to a pulse generator error amplifier during startup according to a lower one of an internal soft start circuit ramp signal and a voltage across and externally connected capacitor, with a current source connected to the source follower to limit the charging current supplied to the externally connected capacitor.

Power converter soft start circuit

One embodiment of the invention relates to a switching control system for controlling an isolated power supply. The system includes a pulse-width modulation (PWM) switching controller configured to generate at least one primary switching signal having a first duty-cycle for activating at least one primary-side switch of the isolated power supply. A synchronous rectifier (SR) switching controller is configured to generate at least one SR switching signal having a second duty-cycle for activating at least one SR switch of the isolated power supply to conduct an output current through a secondary winding of a transformer and an output inductor to generate an output voltage, the second duty-cycle being independent of the first duty-cycle in a soft-start mode.

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Beijing, China

Xiaojun Xu