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A digital current-mode controller for dc-dc converters is introduced. The current-mode loop is sensorless, relying on constants and internal loop states; removing the need to sense controlled voltages or currents for the inner loop. Furthermore, a fast current-mode control mechanism is implemented by utilizing dead-beat control. The resulting controller is robust and surprisingly uncomplicated. It is well suited to VLSI integration in a low geometry process. An interesting aspect of this control scheme is that it facilitates the application of a low resolution PWM.

This paper demonstrates a dc-dc converter application in which a multi-bit digital sigma-delta modulator pre-processes the duty-cycle value before application to the DPWM, increasing the effective resolution of the DPWM dramatically. In this method, the DPWM duty-cycle command is pre-processed by a multi-bit digital sigma-delta modulator, so that the DPWM quantization noise will be shaped in frequency. As a result, the total quantization noise at the output of the dc-dc converter is reduced, and the effective resolution of the DPWM in the control loop is increased dramatically. A prototype converter was seen to perform with an effective DPWM resolution of at least 11 bits, with an actual DPWM resolution of less than 6 bits.I.