Frequency response improvement of DSP controlled DC-DC converter with pole-zero cancellation technique

Abstract

-Reentry, the performance of the DSP and FPGA is developed remarkably. So, fully digital control is enabled in switch mode power supplies. However, in many cases, the control system is built by very complicatedly and very difficult theories such as the adaptive control. Furthermore, in most popular PID control, its design method of the parameters is not clear, so derivation of the optimal parameters is very difficult. This paper proposes revolutionary control technique which is cancelled the transfer function of the converter by using polezero-cancellation method. This technique is very simple and easy to stability design. I. INTRODUCTIONIn recent years many electronic circuits is digitized. However, only switch mode power supplies are consisted of the analog circuit till now. This is because the switch mode power supplied consisting of analog circuit is realized with low cost. However, almost circuits are digitized and the whole system is moved by processors. Therefore, it is difficult for switch mode power supplies to stay in the system as the analog circuit. Hence the digitization of the switch mode power supplies is necessary. So far, various examinations have been discussed about digital control of switch mode power supplies [1][2][3][4][5]. However, important parameters such as the switching frequency were impractical because the performance of CPU such as DSP or FPGA was not so good.Recently, due to the development of the semiconductor manufacture technology, the performance of CPU such as DSP and FPGA is developed remarkably.Therefore, expectation of the realization of the fully digital control switching power supply becomes higher.However, the control system is built by very complicatedly and very difficult theories such as the adaptive control or predictive control in many cases of the discussions of the digital controlled switch mode power supplies so far. On the other hand, also in the most popular and easiest control method such as PID control, the design method is not so clear, and the optimal design is difficult [6,7]. This paper proposes revolutionary control technique which is cancelled the transfer function of the converter by using pole-zero-cancellation method. This technique is very simple and easy to stability design of converter system. Furthermore, the arbitrary frequency characteristics can be created by introducing a new frequency characteristic. Here, the design method and system stability of the proposed control technique is examined by using buck converter and boost converter. II. CONVERTER ANALYSISFor the design of the control system, it is necessary to grasp correctly the characteristics of the converter in detail. The buck converter and boost converter as the controlled objects are shown in Fig. 1, 2, respectively. The dynamic characteristics of each converter can be derived by applying the state space averaging method [8,9]. The dynamic characteristic of duty to output voltage of each converter is derived following equation;where; Buck converter:

Optimized Digital Controllers for Switching-Mode DC-DC Step-Down Converter

“…A two-pole two-zero analog controller is mapped into the digital controller using bilinear transformation. In [3], the same authors (Abe et al) applied successfully the two-pole two-zero analog compensator to the buck and boost converters to ensure superior performance, yet without cancelling the RHP-zero in the case of the boost converter. The effect of change in the capacitance of the output capacitor in a PZC-based digitally controlled buck converter on the stability margin, and thus the performance, was investigated in [4].…”