Fast transient voltage-mode buck regulator applying ramp signal with a variable DC-offset scheme

A ramp signal with variable DC-offset (RSVDC) scheme implemented in a voltage-mode controlled buck voltage regulator is proposed. To enhance the response of the voltage-mode controlled buck regulator during the load transient, the variable DC-offset ramp signal is applied to drive the duty cycle full or zero, so that the output voltage can instantly respond with load change. The model, compensator and loop gain of the proposed buck regulator are derived and demonstrated. The transistor-level of the RSVDC circuit including the hysteretic comparator, oscillator and the output feedback voltage amplifier is also presented. The controller using the RSVDC scheme was implemented by the TSMC 0.35 µm 2P4M process. The simulated and experimental results show that the transient response using the RSVDC scheme is about 10 µs, when the load changes from 0.1 to 1 A under a 5–1.8 V voltage conversion. The test results validate the feasibility of the RSVDC control scheme in a buck voltage regulator to fulfil a simple structure, assured stability and fast transient response requirements.