数字控制DC-DC变换器的延时离散模型及影响分析

Discrete-time modeling of digital controlled DC-DC converters and the effects of time delay

为分析数字控制DC-DC变换器延时对系统性能的量化影响,详细概括和总结不同延时情况,并对其进行重新归纳和对比分析。在DC-DC变换器状态空间模型的基础上,建立包含延时在内的数字控制DC-DC变换器的小信号离散模型,并对各种延时情况的离散模型进行分析。以Buck变换器为例,采用常用的PI补偿器,在系统相位裕度相同时,分析补偿器有解且系统性能最优的情况,得到不同延时情况下系统带宽下降为没有延迟时的30%～80%的结论。实验结果证明所得结论的正确性。建立的数字控制DC-DC变换器延时离散模型和延时影响的量化分析结论,为数字控制延时问题研究以及延时补偿问题分析提供理论依据。

The delay forms in practical applications are summarized in detail in order to analyze the quantization effects of the inherent time delay introduced by zero-order-hold effect and the computational time delay in digital controlled DC-DC converters. The exact small signal discrete-time models with time delay for digital controlled DC-DC converters are established. The models,which based on well-known approaches to discrete-time modeling,take modulator effects and delays in the control loop into account. Take the Buck converter as an example. Using common compensation controller PI,the maximum band-width of the system is obtained while PI controller has solution and system has the same phase margin. It is shown that,compared with no time delay control,the control loop bandwidths decreased to 30% ～ 80% because of the time delay. The discrete-time model and the conclusion of quantization effects of time delay are proved by experimental results,which provide theoretical basis for studying time delay problem in digital controlled DC-DC converters.