Using low‐cost microcontrollers to implement variable hysteresis‐width comparators for switching power converters

Abstract

Hysteretic comparators are often used to implement sliding-mode controllers or other type of discontinuous regulators for power switching converters. Their design is usually performed analogically yielding robust and fast controllers that can even allow converter operation with high values of duty cycle. A new analogue implementation based on a low-cost microcontroller is described in this study showing the mentioned advantages plus the flexibility of a programmable digital system. The proposed comparator employs some microcontroller peripherals without consuming execution time of the control algorithm and without requiring interruption management. It provides variable hysteresis width to obtain constant switching frequency in sliding-mode strategies and can be used in any type of hard switching converter. The dynamic performance of the method is verified experimentally in a boost converter-based rectifier with power factor correction and output voltage regulation in one single stage. The boost converter operates in sliding mode with constant switching frequency and results in a total harmonic distortion of the input current <1%.

Min-Type Control Strategy of a DC–DC Synchronous Boost Converter

“…A practical implementation of the control law (13) requires the introduction of hysteresis around the switching surface [26] in order to obtain finite switching frequency required by the power devices. The hysteresis function can be implemented analogically [27] or digitally by using some microcontroller peripherals as reported in [28]. Nonetheless, the resulting dynamics and the sliding dynamics are strictly speaking the same only when the hysteresis width tends to zero.…”

Heterodyne multiplier‐based inverter

“…In recent years there have been several attempts to realise the frequency multiplication method in the field of power electronics inverters [3][4][5][6][7][8][9][10][11][12][13][14][15], on the assumption that it would allow the generation of cleaner signals, i.e. with relatively low THD values.…”

Co-Design of the Control and Power Stages of a Boost-Based Rectifier with Power Factor Correction Depending on Performance Criteria

“…Moreover, i r must be in phase with the converter input voltage (v in ), which corresponds to the output of the diode bridge, i.e., v in = v pk • | sin(w • t)|; hence, i r is defined as i r = i pk • | sin(w • t)|, where w is the angular frequency of the AC source. The outer loop is typically implemented with a PI controller, either with analog [1,14-17] or digital circuitry [18][19][20], since it rejects load perturbations, it provides zero steady-state error, and its parameters can be tuned by frequency response [16,19]. Moreover, the PFC system regulated by a PI controller is relatively simple because the inner loop deals with the system nonlinearities and the time-varying reference.…”

“…Moreover, the PFC system regulated by a PI controller is relatively simple because the inner loop deals with the system nonlinearities and the time-varying reference. Nevertheless, in many cases the design procedure of the PI controller of the outer loop is not provided [14,15,18,20] or it is not clearly explained [16,17,19].…”