Digital control device and method for LLC (logical link control) synchronously-rectified resonant converter

Abstract

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.

Description

technical field [0001] The invention belongs to the field of communication power supply and LED lighting, and in particular relates to a digital LLC synchronous rectification resonant converter control device and method. [0002] Background technique [0003] Compared with the traditional DCDC topology, the primary side MOS transistor of the LLC resonant converter can realize zero-voltage turn-on in a wider frequency range, and can improve its own efficiency with the increase of the primary side input voltage, which is more suitable for working in the power factor backend of the correction circuit. Therefore, the LLC resonant converter gradually replaces the traditional DCDC topology and is used in high-power applications. [0004] The traditional LLC synchronous rectification resonant converter generates resonance through resonant inductor, resonant capacitor and transformer to realize soft switching. [0005] The working state of the LLC synchronous rectification reson...

AI Technical Summary

Problems solved by technology

However, the current transformer has parasitic inductance, which is easy to delay the current signal and the turn-on signal. At the same time, the current transformer increases the cost and volume, and is easy to be interfered, so it is rarely used

[0009] When the LLC synchronous rectification resonant converter is working in a light load state, the current flowing through the secondary synchronous rectifier is earlier than the corresponding primary side driving high-level signal, and the traditional control method is not easy to advance the secondary synchronous rectification tube turn-on time, resulting in turn-on losses

Images