Load current-sensing circuit integrated in high-frequency PWM/PFM hybrid DC–DC buck converter

An average current-sensing circuit integrated in a hybrid DC–DC buck converter is presented. Both the high-side and the low-side switch currents are fully sensed by detecting the filtered smooth voltage of the switch node, which maintains a substantially constant mode changing point and seamless transition between pulse width modulation (PWM) and pulse frequency modulation (PFM) under various duty cycles. The achieved mode changing point is almost independent of temperature and supply voltage. The proposed circuit is suitable for high-frequency hybrid DC–DC applications.