一种数字自动选频DC-DC控制器的设计

esign and implementation of digital auto selectable frequency DC-DC controller

设计了一个数字自动选频DC-DC控制器。该控制器根据负载情况自动选择一个频率工作,工作频率固定且成倍数关系,后级能进行有效滤波,降低电磁干扰(Electro-Magnetic Interference,EMI)。对于负载情况的判断,提出一种新的数字判断方法,省去了电流采样电路。同时,为了进一步提高系统的瞬态响应,系统添加了非线性控制技术。数字自动选频DC-DC控制器使用CPLD进行了测试验证。测试结果显示,在输入电压3.3V,输出电压1.8V,DC-DC正常工作。在宽负载范围内,控制器通过自动切换工作频率维持了较高的效率,且能对EMI有效滤波。当负载在100～350mA跳变,电压过冲限制在50mV以内。

A digital auto selectable frequency DC-DC controller was presented.The switching frequency was automatically selected.As a result,the output harmonics of the DC-DC were located at multiples of 512 kHz over a wide load range,thus made the problem of EMI solvable.A novel digital load current detection method was proposed,which eliminated the current sensing circuit.In order to achieve a fast transient response,a nonlinear control scheme was exploited during the load transition.The prototype of the controller was emulated with a CPLD.The supply voltage is 3.3 V.The experimental results show that the converter is well regulated with an output voltage 1.8 V.Thanks to the auto selectable frequency technique,the controller exhibits a significant efficiency improvement at light load,and the output harmonics are also made predictable,which greatly relaxes the on-board EMI filter design.The transient voltage overshoot is no more than 50 mV with the load current skipping between 100 mA and 350 mA.