Linearized Discrete Charge Balance Control with Simplified Algorithm for DCM Buck Converter

Abstract

In this paper, a linearized discrete charge balance (LDCB) control strategy is proposed for buck converter operating in discontinuous conduction mode (DCM). For DC-DC power converters, discrete charge balance (DCB) control is an attractive approach to improve the output voltage transient response. However, as a non-linear control strategy, the algorithm is complex, which is difficult for implementation. To reduce the complexity, this paper proposes the LDCB control strategy that is derived through linearizing conventional DCB controller. By deriving the differential functions of the DCB control algorithm, the small signal relationship between the input and output of DCB controller is explored. Furthermore, based on the relationship, the LDCB controller is formed through three parallel feed loops to the duty ratio. As a linear control approach, the achieved LDCB controller is greatly simplified for implementation. This not only saves the hardware cost, but also reduces the calculation lag, which provides potential to improve the switching frequency. Besides, since the LDCB controller shares the same small signal model as that of DCB controller, it achieves similar control loop bandwidth and transient performance. Effectiveness of the proposed LDCB control is verified by zero/pole plots, transient analyses and experimental results.

Exact Mathematical Analysis of DC-DC Converters Employing Type 3 Controllers

“…All these studies have been confirmed on clasical converters [7][8][9][10], or new converters [11][12][13][14][15][16], or quadratic converters [17][18][19]. Other high complex approaches investigate the stability analysis of DC-DC converters with DCM (Discontinuous Conduction Mode) operation [20][21][22][23][24] employing a model described by a system of two vector equations: a state equation and another equation that represents a constraint, which is usually non-dynamic. This constraint defines the control law of the converter.…”

“…the extractor vector that provides the voltage v C1 from the state vector. According to equation (19), at the time when the two voltages in (19) become equal, it can be written that: (20) From equations (18) and (20) one can now determine the value of the duty cycle n d of the active swicth. To derive the non-dynamic constraint, one has to write the relationship defining the duty cycle in the form: (21) It is known [12] that the state vector at time…”

State Switched Discrete-Time Model and Digital Predictive Voltage Programmed Control for Buck Converters

“…For predictive and many other control strategies, the accuracy of the converter model is a determinant issue that affects the control performance. To facilitate digital controller design and analysis, discrete-time models have been intensely studied [17,18], and a widely accepted modeling approach is state averaging. Although state averaged discrete-time models can be directly derived through standard Z-transform, the transform error leads to a degraded accuracy [19].…”