Simple control and high efficiency in the boost converter used to shape the line current to comply with the IEC 61000-3-2 regulations

This paper presents a method to design and control for boost converters used to shape the line current in order to comply with the IEC 61000-3-2 regulations. The method is based on shaping a line current waveform that can be obtained with an especially low value of the rms current passing through the boost's transistor. That type of line current waveform can be implemented easily with general-purpose IC controllers for switching mode power supplies (SMPS) according to (at least) three different control strategies. Using one of the three control strategies presented, no input-current feedback loop is needed and, then, "three-terminal off-line, PWM switches" (such as those belonging to the TOPSwitchreg-II family) can be used to implement the boost's transistor and all the control circuitry. The use of these "three-terminal off-line PWM switches" is possible due to the fact that the line waveform is obtained with a very low rms value of the current passing through the boost's transistor (using this method, the typical rms value of the current passing through the boost's transistor is around five times lower than the rms value of the line current). The drawback of the proposed method is that the voltage across the output must be maintained as close as possible to the peak value of the line voltage. However, this is not a serious problem because this situation is the same as the one of using a passive filter to shape the line current