Novel Interleaved Hysteretic Control for VR (2006)
In order to achieve the faster VR response, the nonlinear control functions are used in the recent VR. The hysteretic control method is one of the fastest nonlinear control methods. We have demonstrated that with hysteretic control method, only 4 Al-polymer capacitors are needed at 300kHz switching frequency whereas it needs 12 Al-polymer capacitors with the linear control method. However, it's very difficult to achieve the interleaving and the constant frequency, which prevents using the hysteretic control method in multiphase VR.
CPES proposed novel hysteretic control method scheme and Fig.1 shows the operating principle. An additional loop is added to adjust the hysteretic band. The hysteretic band width is modified to synchronize the duty turn-on signal and the reference clock. By slowly adjusting the hysteretic band through a phase lock loop (PLL) with a fixed frequency and interleaved clock reference for each phase, constant frequency and interleaving can be realized in the steady state. On the other hand, slow band changing will make this controller perform as conventional hysteretic control during the transient for fast dynamic response. After the transient, each phase will be pulled back to interleaving status through its band adjustment.