A low switching frequency AC-DC boost converter for wireless powered miniaturized implants

Providing electrical power to an implantable microelectronic device (IMD) via wireless power transfer technology is critical to implant´s efficacy. The inductive coupling based wireless power transfer technology has been the primary approach to remotely power an IMD [1]. Reducing the coil size and improving efficiency are the two primary design goals for the power harvesting component in an IMD. A pulse-width-modulated (PWM) boost converter has been demonstrated to efficiently convert the low-voltage (much less than the regular diode´s turn-on voltage) AC power generated by a miniaturized receiving coil to a desired high-voltage DC power [2]. In [2], the switching frequency of the PWM is much higher than the frequency of the input AC power. The high switching frequency not only dissipates more power during the switching, which deteriorates the converter´s overall efficiency, but also prevents the circuit from handling the high-frequency input AC power. In this paper, a low switching frequency AC to DC boost converter is demonstrated. By aligning the PWM signal with the input AC, the boost converter is able to convert the AC power, whose amplitude is 500 mV at the open-circuit condition, to a >5 V DC output. The converter demonstrated in this paper has the potential to significantly improve the conversion efficiency by reducing the dissipated power associated with the PWM switch, especially when the input AC is at higher frequencies.