资 源 简 介
大功率led驱动器控制回路的补偿与测量
数学模型总是有助于确定某一特定设计的最佳补偿元件。然而,补偿一个WLED电流调节升压转换器的环路比补偿相同的转换器配置为电压的调节,有点不同。
测量一个WLED电流调节升压转换器的控制回路是繁琐的传统方法由于在低阻抗的反馈(FB)引脚和顶侧FB电阻的不足。在“设计师的系列,第五部分:电流模式控制建模”1,Ray Ridley提出了一个简化的,一个电流模式控制的Boost变换器的小信号控制模型。以下说明如何修改Ridley的模型,它适合一个WLED电流调节升压转换器;它还解释了如何测量升压转换器的控制回路。
Loop components
As shown in Figure 1, any adjustable DC/DC converter can be modified to provide a higher or lower regulated output voltage from an input voltage. In this configuraTIon, if we assume ROUT is a purely resisTIve load, then VOUT = IOUT &TImes; ROUT. When used to power LEDs, a DC/DC converter actually controls the current through the LEDs by regulaTIng the voltage across the low-side FB resistor as shown in Figure 2. Because the load itself (the LEDs) replaces the upper FB resistor, the traditional small-signal control-loop equations no longer apply. The DC load resistance is: