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Robust DC-DC converter which can covers extensive load changes and also input voltage changes with one controller is needed. The demand to suppressing output voltage changes becomes still severer. We proposed an approximate 2DOF digital controller which realizes the startup response and dynamic load response independently. The controller makes the control bandwidth wider, and at the same time makes a variation of the output voltage small at sudden changes of loads and input voltages. In this paper, a new approximate 2DOF digital control system with additional zeros is proposed. Using additinal zeros second-order differential transfer characteristics between equivalent disturbances and an output voltage are realized. Therefore the new controller makes variations of the output voltage smalerl at sudden changes of loads and input voltages. This controller is actually implemented on a DSP and is connected to a DC-DC converter. Experimental studies demonstrate that this type of digital controller can satisfy given severe specifications.

Robust PWM power amplifiers whose transient response characteristics do not deteriorate against an extensive load changess and/or direct-current power-supply voltage changes are needed. In this paper, a digital robust controller with bumpless mode switching for PWM power amplifiers which can satisfy such demands and can extend the range of capacitive load wider is proposed. It is necessary to measure the value of load to implement this bumpless mode switching automatically according to t h e load range. Thus. the method of estimating capacitive load is shown. Although it is necessary to use current for estimating capacitive load;it will become expensive if a current sensor is used. Therefore. an easy current estimating method which can be performed more cheaply is shown. The current estimated by this method is used for capacity estimation and current feedback. The bumpless mode switching is automatically performed by estimating a capacitive value, without specifying the value of capacitive load beforehand. That is, the value of capacitive load is estimated during DDC execution. a n d the control mode is automatically switched bumplessly according to this estimated value. The digital controller equipped with capacity estimation and the bumpless mode switchina is realized bv a DSP. An exoeriment Shows that -the digital controller with t h e proposed bumpless mode can satisfy larger speciflcations.

If the lines which connect the output terminal of a DCDC converter and the load are long, the voltage actually crossing to the load will change greatly due to the impedances of the lines, producing drops in voltage. In this paper, a separate terminal apart from the output terminal of DC-DC converter senses the voltage across to the load, and it leads it to the load. As a result, the voltage across to the load is adjusted so that it does not experience large changes. This method is called remote sensing. When the lines become long, the usual method of adjusting the voltage across to the load cannot sufficiently suppress changes in it. In this paper, a robust digital controller to suppress the change in the voltage across the load is proposed. Experimental studies using DSP demonstrate that this type of digital controller successfully suppresses it.