IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, v.17, no.3, pp.585 - 597
Abstract
Wireless power transfer (WPT) technology applied to implantable medical devices (IMDs) significantly reduces the need for battery replacement surgery health conditions. This paper presents an on-/off-time sensing-based load-adaptive mode control of triple mode buck converter for implantable medical devices; the converter can adjust the control mode for low power consumption and achieve high power conversion efficiency (PCE) under a small active area. The three modes in the proposed system are the pulse width modulation (PWM), pulse frequency modulation (PFM), and ultra-low power (ULP) modes. The on-time sensor can be used to adjust the system from PWM to PFM modes, and the off-time sensor can be used to adjust the system from PFM to ULP modes. It is fabricated using TSMC 0.18 mu m CMOS technology. The input voltage lies in the range 2.2-5.0 V, the output voltage is 1.8 V, and the load current lies in the range 0.05-200 mA (x4000). The experimental results demonstrate the seamless mode transition under the step up/down load transient response. The peak PCE is approximately 94.3% at the 80 mA and the minimum PCE is approximately 65.4% within the load current range.