The invention relates to a
digital control device and method for an LLC (
logical link control) synchronously-rectified
resonant converter. The device comprises a
digital signal processor, a primary high-frequency
driving circuit, a current sampling detection circuit, a
voltage sampling detection circuit and a secondary high-frequency
driving circuit, wherein the
digital signal processor judges an operation area of a circuit according to an output
voltage fed back by the
voltage sampling detection circuit, after the circuit performs three-pole two-zero compensation, the values of an on-
chip period register are respectively changed so as to generate high-frequency driving signals which are then output to the primary and secondary high-frequency driving circuits by the
digital signal processor; the current sampling detection circuit detects a secondary output current which is then output to the
digital signal processor, then the
digital signal processor judges whether an overloading or
overcurrent phenomenon (generated in the process of area switching) occurs according to the size of the current so as to
cut off the primary and secondary high-frequency driving circuits in time. In the invention, the LLC
resonant converter is subjected to the following
digital control by a
digital signal processing chip-
peripheral timer combined circuit: the advanced conduction of secondary synchronous rectifying tubes is realized by the design of
software / hardware auxiliary circuits, and the control on secondary driving signals is performed by adding a 555
timer, so the application of a
timer in a DSP (
digital signal processing)
chip is reduced, thereby effectively solving the problem of
conduction loss of synchronous rectifying tubes introduced in the process of underloading in the traditional control strategy; and the application of a PWM (pulse-width modulation) port of the
digital signal processing chip is reduced, thereby improving the reliability of the whole device.