A continuous switching mode boost switch-cap regulator with PWM control scheme and fast transient response

In modern portable devices, multiple power sources with wide voltage range could be used while a stable supply voltage is required. In order to extend battery lifetime or supply source from energy harvester, boost regulator is needed to support certain analog functions like precision analog circuit or LED driver. In such applications, a switch-cap boost regulator is usually used. In this paper, mechanism of charge injection rate control and PWM injection time control to regulate switch-cap power stage is examined along with system level modeling. Resemblance of its model to LDO and multi-stage amplifier is pointed out, implying that certain techniques used in LDO and multi-stage amplifier could also apply to switch-cap regulator design, such as transient response enhancement scheme. An architecture utilizing charge injection rate control and charge injection period control is proposed to control a voltage doubler charge pump power stage, along with transient enhancement scheme. With the proposed control scheme, the switch-cap boost regulator could regulate the voltage from near the input voltage up to theoretical voltage doubler output with fast transient response and stable switching tones across load current.