High Efficiency Charge Pump Based DC-DC Converter for Wide Input/Output Range Applications

Portable electronic devices are taking an indispensable part in people's everyday life. To meet the growing needs of people, the number of function blocks inside the portable devices keeps on increasing but the portable devices tend to be small and exquisite. As a result, the power supply must be very compact and also very efficient during battery lifetime. Charge pump regulators are considered as an ideal solution in low power portable applications for their compact sizes and low cost. However, traditional charge pumps are not very efficient for battery powered applications because of the input voltage variations and the requirement for output regulation. The power rating of charge pumps is also very limited. A Multi-modes regulated charge pump with improved efficiency over wide input and load range is proposed. It can realize 2x, 1.5x, and 1.33x conversion modes. During each mode, the output voltage is regulated by a controlled current source. A hybrid control scheme is proposed. By using device segmentation control and pulse skipping modulation according to the load condition, the efficiency can be improved over a wide load range. Simulation and test results are provided to verify the control scheme.;For automotive system and telecommunication systems, the input voltage varies much wider than in portable applications. For industry applications, the front-end bus voltage is relatively stable, but can be selected from 12V, 24V, and 48V. However, customers prefer a high performance one-fits-all power supply to avoid additional time and cost for re-design. Therefore, a power supply that can operate under a very wide input voltage range is a must for these applications. The most popular non-isolated step-down DC-DC converter, Buck regulator, usually shows a low efficiency at high input voltage. In addition, a high step-down ratio creates significant challenges for the PWM controller design because it has to control very narrow PWM pulses. A high efficiency charge-pump based wide input range Buck converter is proposed. The first stage is a multi-modes charge-pump and the second stage is a synchronous buck converter. The charge-pump is unregulated and adaptively switches between 1x, 0.5x, and 0.33x modes according to the input voltage. It does the rough voltage conversion while the Buck converter does the fine voltage regulation. Theoretical analysis proves that the total efficiency will be improved, especially at the high input voltage. It also simplifies the compensator design and benefits the transient performance. Experiment results show the highest efficiency improvement is 7% at heavy load and 16% at light load.;Similar merits can be found when combining a Multi-modes Charge Pump with a Boost converter for high gain applications, such as driving a long LED string from a single lithium battery. A high gain Transformerless LED driver is proposed and verified by the experiment. The efficiency improvement is 10% when driving 11-12 LEDs from 2.7V input voltage.