This paper proposes a dual-section average (DSA) analog-to-digital converter (ADC) to achieve a closed-loop digital pulse width modulation (DPWM) DC-DC converter with performance compatible to that by the analog PWM converter. For a 2.4V input voltage, a regulated output voltage of 1.2V can provide output current of 600mA without any off-chip compensators. Besides, the output ripple can be reduced to about 8mVp.p by theoretical result. The test chip was fabricated in 0.35μm CMOS technology. Owing to the parasitic resistance, the output ripple of the experimental result is within 8mVp.p. Furthermore, the transient recovery time is within 50μs when load current changes from 120mA to 600mA, or vice versa.