A 10 V-to-1 V Double Step-Down Buck Converter Using Time-Based Current Mode Control with Minimum Delay Frequency Difference Phase Adder for 1 MHz Operation

An extreme step-down ratio buck converter is proposed using a double step-down (DSD) buck converter architecture and a single time-based current mode PWM controller able to generate two non-overlapping control signal phases. Current sampling for two inductors is implemented with a multiplexer and a pair of VCOs only, which treats the two inductors as one inductor operating at double the frequency. This is achieved without the use of any large external passive components in the controller while remaining stable. The type-II time-based controller uses a VCO, a frequency difference phase adder (FDPA), and a phase detector, generating a control signal with fully integrated components with minimum area. FDPA for proportional control also significantly limits the signal delay of the high gain controller, allowing the use of time-based control technique at <10 MHz, which improves converter efficiency. The proposed time-based current mode controller DSD buck converter is simulated in 130 nm BCD technology operating at 1 MHz for 10 V to 1 V conversion. The simulated peak efficiency is 82.2% at 0.4 A, and recovers from a 1.8 A loading and unloading current step in 5.75 μs and 9.9 μs, respectively.