[014] 38 Years of Current-Mode Control

A short summary of the important features of current-mode control, and links to the definitive free book on the topic.

38 Years of Current-Mode Control

20016 marks the 38th anniversary of the publication of a landmark paper on current-mode control. Since then, current-mode has become the industry standard for controlling switching power supplies. To mark the occasion, we are making available, for the first time ever, a free downloadable copy of the definitive book on current-mode control.

In 1978, Cecil Deisch published a paper that introduced current-mode control in a practical and easy-to-understand circuit. While this was not the first publication on current-mode control, it was the one that popularized it in industry. Up until that time, power supply designers had used voltage-mode control for switching power supplies. In voltage mode control, a sawtooth ramp is compared to a voltage from an error amplifier to set the duty cycle of the power switch of the converter. In this way, the output voltage and inductor currentare indirectly controlled.

Current-mode control directly controls the peak of the switch (or inductor) current, and as soon as it was introduced, it became widely accepted as a preferred method of control. It offered the following advantages:

1. Peak current limiting on a cycle-by-cycle basis;

2. Damping of the LC-filter characteristic;

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