Novel high efficiency low ripple charge pump using variable frequency modulation

A novel charge pump with variable frequency modulation (VFM) is proposed in this paper. To provide base for its design and improvement, detailed models for VFM charge pump are derived. And it is successfully implemented for the charge pump to introduce a voltage controlled oscillator (VCO) to control the switching frequency, which results in its high efficiency and low ripple output both at high load and light load. The chip is designed and fabricated in TSMC 0.35um mixed signal process. The simulation and test results show that high efficiency (up to 75%) and very low ripple output ( around 10 mV) is realized as expected. Besides, the accuracy of the model's prediction is proved.