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Abstract The operating characteristics of the switched capacitor transformer are formulated and analyzed by means of the state‐space averaging method for the three types: 1/2‐step‐down type, 2‐step‐up type, and polarity inverting type. The following conclusions are obtained: (1) The static characteristic is equivalent to that of a battery with the induced voltage of the input times the transformer ratio and the output resistance represented by the duty ratio and the on‐resistances of the switches. (2) Using switches having small on‐resistances and selecting a high duty ratio and the frequency five to ten times the natural frequency of the circuit, the output resistance can be made small and a high transforming efficiency of 80 to 90 percent can be realized. (3) The dynamic characteristic is a first order for the step‐down type and a second order for the step‐up and polarization inverting type in which no oscillation results with a feedback. In comparison with a switching converter using a reactor, the present structure is superior in stability. These conclusions were confirmed experimentally. Next, as an application of the switched‐capacitor transformer, a dc‐dc converter with a 12‐V input and a 5‐V output was constructed. As a method for regulating the output, an on‐resistance control was used instead of a conventional PWM control and a frequency control. The test results are excellent as: (1) the ripple of the output voltage is reduced to one‐tenth that for the PWM control, (2) the maximum output power is 50 W (10 A) and the efficiency is 80 percent for the specified input and output, and (3) the load response is excellent.
Ueno et al. (1990) studied this question.