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Digitally Controlled Point of Load Converter with Very Fast Transient Response
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| Author(s) |
ANDERSEN M. A. E.; JAKOBSEN Lars T. |
| Abstract |
This paper presents a new Digital Self-Oscillating Modulator (DiSOM) that allows the duty cycle to be changed instantly. The DiSOM modulator is shown to have variable switching that is a function of the duty cycle. Compared to a more traditional digital PWM modulator based on a counter and comparator the DiSOM modulator allows the sampling frequency of the output voltage control loop to be higher than the switching frequency of the power converter, typically a DC/DC converter. The features of the DiSOM modulator makes it possible to design a digitally controlled DC/DC converter with linear voltage mode control and very fast transient response. The DiSOM modulator is combined with a digital PID compensator algorithm is implemented in a hybrid CPLD/FPGA and is used to control a synchronous Buck converter, which is used in typical Point of Load applications. The computational time is only three clock cycles from the time the A/D converter result is read by the control algorithm to the time the duty cycle command is updated. A typical POL converter has been built and the experimental results show that the transient response of the converter is very fast. The output voltage overshoot is only 2.5\% of the nominal output voltage when a load step of 50\% - 100\% of nominal output current is applied to the converter. The settling time is approximately 8 PWM cycles. |
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| Filename: | 0781-epe2007-full-12421607.pdf |
| Filesize: | 507.1 KB |
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| Type |
Members Only |
| Date |
Last modified 2008-01-11 by System |
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