A Simple Digital Autotuning For Analog Controller in SMPS

This paper discusses the self-tuning capabilities of an analog current-mode controller for switch-mode power supplies. The proposed tuning techniques are based on the insertion of nonlinear (NL) blocks in the analog control loop and the generation of a controlled oscillation on the output voltage, in order to measure the closed-loop properties like gain margin, phase margin, and crossover frequency and to tune the analog controller according to the desired specifications. The NL blocks are based either on the NL gain or NL phase. The most relevant properties are as follows: 1) the oscillation amplitude is controlled by the NL action during the tuning procedure; 2) A/D converters are not required; 3) the parameter variations can be obtained with ancillary analog blocks (variable gain operational transconductance amplifier, switched capacitors, etc.); and 4) the tuning digital control algorithm is simple. Experimental results on a 10 A, 1.5 V point-of-load converter, where the controller tuning has been implemented using components off-the-shelf and a field-programmable gate array are provided to show the properties of the proposed system.