Digital Error Corrector for Phase Lead-Compensated Buck Converter in DVS Applications
Modern low-power system on a chip needs direct current converter with dynamic voltage scaling (DVS) ability for core power supply. The converter output should be accurate voltage across the full load current and voltage scaling range. An integrated buck converter for DVS application is proposed in this brief. Voltage mode phase lead compensation is implemented in the converter, with much smaller passive components than conventional type-III compensation. To improve accuracy, the output voltage error accompanied with load current and reference voltage caused by finite loop gain in analog control loop is corrected by the digital error corrector. The output voltage is compared by two comparators whose threshold voltage is about 10 mV above and below the reference voltage, respectively. The duty cycle is slightly adjusted by finite state machine according to outputs of the two comparators. Experimental results show that the converter is well regulated over an output range of 0.7-1.8 V, with step voltage of 25 mV. When load current suddenly changes between 170 and 500 mA, the overshoot and undershoot voltage are 32 and 50 mV, respectively. Load regulation is maintained about 1% throughout the full load range. The voltage error is within +/- 10 mV in the voltage scaling range.
digital error corrector buck converter phase lead compensation voltage mode control