An Improved Hysteresis Voltage Mode of Synchronous Rectifier Buck Circuit

Abstract

To achieve high power and high efficiency over a wide load range, an improved hybrid hysteresis voltage mode for Buck circuit is proposed in this paper. The strategy and workflow of the proposed improved hybrid hysteresis voltage mode are demonstrated step by step. The output voltage performance of the Buck circuit with proposed hysteresis voltage mode is compared with the same circuit with typical hysteresis voltage mode. Numerical simulation results show that with the introduction of the PD link, the overshoot can be completely controlled or eliminated; with the introduction of the dynamic voltage reference, the static difference can be completely negligible; relatively stable input voltage improves its steady-state working frequency and the electromagnetic interference significantly. Thus, the proposed control strategy can not only achieve satisfied performance, but also provide a basis for further design and optimization. INDEX TERMS Buck circuit, Hysteresis voltage mode, Ripple elimination, Static difference.

A Hybrid Constant On-Time Mode for Buck Circuits

“…A classical Buck circuit's equivalent model is shown in Figure 2a, and its simplified model is shown in Figure 2b. Following the same modeling process described in [7], the second-order differential equation for the Buck circuit, whose structure is given in Figure 1, can be derived step by step.…”

“…Table 1 also lists the default values for the constant parameters. Based on the dynamics equation of the Buck circuit described in Equation ( 7), the stability can be analyzed with the eigenvalues of the Jacobian matrix of the left side of the Equation (7). When the real parts of all the eigenvalues are negative, the system will converge to the equilibrium point.…”

“…In the authors' previous work [7], an improved hybrid hysteresis voltage mode for Buck circuits was proposed. When controlling a synchronous rectifier Buck circuit, a hysteresis voltage mode improved by hysteresis voltage schemes can provide a lower voltage drop ratio in the case of proper LC (inductance and capacitance) parameter design, a high dynamic response speed with a high frequency and low ripple rate of steadystate output and large load current change, as well as an acceptable range of steady-state operating frequency change.…”

“…The hysteresis voltage mode can greatly improve the singlephase current output capacity and effect of the Buck circuit, which is conducive to improve the power supply performance when the dynamic capacity of the single-phase power supply is greatly required, such as in the case of a high-level operation equipment power supply, class-D power amplifier, precision experimental instrument and precision inverter welding machine. The results from [7] showed that the accuracy and robustness of the system were much better than PWM-based control modes. When the load current changed greatly, the controller began to adjust the power semiconductors immediately based on the feedback voltage.…”

“…A high ratio and low resistance lead to a small width and high frequency, which is unreasonable. To simplify the design process, a control mode with only one logical judgment point (a singularity point for a control dynamical system) should be adopted; in contrast, the hybrid hysteresis voltage proposed in [7] has two points of this kind. The constant on-time (COT) voltage mode is confirmed to be such a kind of controlling mode, which is designed for light-load applications to achieve high efficiency and a fast transient response.…”