数字控制环路提高效率

　　数字控制环路提高效率

　　有一个不断推动更高的效率，功率转换器设计。此外，需要支持高水平的计算处理能源效率导致了负荷的创作具有高度动态的行为，随着处理器和外设激活和去激活基于他们的工作量。这是推动电源转换器架构的变化，从模拟到数字实现。

　　开关模式功率转换器的操作本质上是数字的，因为它依赖于从一个转换器的另一侧的离散电荷分组转移到另一个。该技术主要是基于采样的状态在离散点的时间，以确定多久的开关，提供电荷应保持在。然而，尽管这种明显的数字结构，大多数实现是基于模拟控制电路。

　　Under the pulse-width modulation （PWM） scheme employed by most switched-mode power supplies， the converter supplies a packet of charge to the output rail by first turning on one of two parallel FETs. The high-side FET is activated for a certain amount of time determined by the PWM controller. During this on time， the output voltage swings up towards the input voltage. The current flows into an inductor that is used as temporary storage for the charge. The current in the inductor rises linearly with its slope given by the formula （Vin - Vout）/L.

　　Once the controller switches off the high-side FET， the low-side switch is kept off for a short period. This prevents an unwanted and wasteful shoot-through of power across the two FETs. Then the low-side FET is activated for a short period and then allowed to switch on. The inductor current then begins to fall with a slope of -Vout/L until the low-side FET is turned off and the cycle begins again. As a result， the current on the output side tends to oscillate above and below an average level. Filtering by the inductor and output capacitors helps smooth the current and voltage delivered to the load.