Modified projected cross point control — a large signal analysis

Abstract

Modified projected cross point control (PCPC) is introduced and discussed in this paper. Compared to the existing PCPC method, the hardware implementation of the proposed modified method is simpler. This modified PCPC method benefits from the advantages of traditional fixed-and variable-frequency current mode control approaches. For instance, as argued in this paper, while modified PCPC is a fixed-frequency approach, it is stable for the entire range of the duty cycle similar to the variable-frequency hysteresis current mode control scheme. Other advantages and large-signal characteristics of modified PCPC are discussed by comparing it with the well-known peak and average current mode control methods.

Modified projected cross point control — a small signal analysis

“…Modified PCPC has been comprehensively discussed in [15]. Without loss of generality, a buck converter is used to introduce the principles of operation of the modified PCPC method.…”

“…Note that in (16) in contrast to (15), the effect of feedback gain F vo is not considered because of its negligible effect on the transfer function. By, comparing (15) and (16) it is clear that unlike PCMC, in modified PCPC, not only loop gain of modified PCPC is completely independent of the load but also its dependency on D is negligible.…”

“…On the other hand, the cross over frequency is always more than a specific high value which guarantees high speed for the closed loop system. According to (15) and (19), if D increases, f c will increase which means any disturbances in large signal will be rejected sooner. Next, the loop gain of modified PCPC will be compared with ACMC.…”

“…Using (15) and considering Fig. 4, the crossover frequency for the entire range of D in modified PCPC can be expressed as: (19), it can be seen that the maximum crossover frequency in modified PCPC is less than half the switching frequency, therefore according to the Nyquist sampling theory the system is always stable.…”

“…In [15], a modified PCPC has been introduced which benefits from a simpler implementation. Modified PCPC benefits from the advantages of both fixfrequency and variable frequency current-mode controllers.…”