A MOS current-mode boost DC-DC converter with the duty-ratio-independent frequency characteristics

In order to elevate an input voltage of less than 1-V to an output voltage of from several volts to 10-V while also realizing a large output-current capability, a wide feedback-loop frequency bandwidth under a high duty-ratio condition and a high power efficiency, we developed a MOS current-mode boost DC-DC converter which utilizes the quadratic compensation slope with the output voltage dependency and the variable gain amplifier in front of the error amplifier. The frequency characteristics of the total feedback loop were independent of the duty-ratio change. A test chip was fabricated by using a 0.18-um high-voltage CMOS process. The resulting 1 MHz operational MOS current-mode boost DC-DC converter converted input voltages of 0.4-V to 5.3-V to output voltages of 1-V to 6-V, realized 50 mA and 150 mA of output currents for input voltages of 1-V and 1.8-V, respectively, realized a feedback-loop frequency bandwidth of 70 kHz with a 1-V input and a duty-ratio of 81%, and realized 75% and 90% power efficiency for the 1-V and 2.5-V inputs, respectively, when the output voltage was 5.3 V.