Improving Output Characteristics Of The Monolithically Integrated Switched-Capacitor DC-DC Converter By Parallel-connected CMOS

Based on a brief analysis on topological structure and operating principle of the two-stage serial and parallel SC DC-DC converter, a way to increase output power by parallel-connected CMOS proposed in this thesis for a monolithically integrated 12V-5V SC DC-DC converter.Simulation results indict that the parallel CMOS converter unit not only has a higher output current but also needs a smaller filter capacitor than the directly paralleled converter unit. In order to more effectively increase output current of the converter, we suggest to parallel connect several the CMOS units into a converter because CMOS circuits are easy to be parallel connected. But, the parallel connection results in big ripples, which may needs a big filter capacitor to overcome it. So it enhances the difficulty in the monolithic integration. A voltage-regulator circuit composed by capacitor, switch and compactor is connected with the main circuit, and it solves the conflict. The output voltage ripple is controlled within±0.1V; The affects arose by load resistor is basically eliminated. And the total filter is reduced to 5nF, which makes the monolithic integration possible.Simulations and experiments implemented by discrete-semiconductor devices show that dividing a constant capacitance into several circuits, and then connect them paralleled to a converter makes the output current bigger than that produced by a unit circuit composed by the equal capacitor. So it is a way to improve the output power. But the output power goes to saturation with the increasing of the parallel units. So the number of the parallel units should not overabundant.The 12V-5V SC DC-DC converter is designed to consist of 8 CMOS converter units. The output current reaches to 200 mA when the values of C1 and C2 are 500 pF, respectively. But the ripple is very big. In order to reduce the ripple, a regulator is connected with the main circuit, and the output current is reduced to 186mA. A paralleling unit is added as compensation. The output current reaches up to 200mA. Aiming at the difficulty to manufacture big area capacitor, PZT may be used to replace SiO2, which makes it possible to integrate capacitor into the chip and engross smaller area.