Single-Inductor Multiple-Output Inverter With Precise and Independent Output Voltage Regulation

In this article, a single-inductor multiple-output (SIMO) inverter with precise and independent output voltage regulation is presented. This SIMO inverter with controllable output voltage enables each individual transmitting coil in a multicoil wireless power transfer system to be driven by a tightly regulated constant-voltage source. This is especially useful for the wireless charging of rechargeable batteries when they act as a constant-current (CC) load in the CC charging phase. By precisely regulating the source voltage at each transmitting coil, a constant load current at the corresponding receiver can be achieved at a particular resonant frequency and mutual inductance between the transmitting and receiving coil. The closed-form expressions of the sinusoidal-like output voltage and resonant inductor current as a function of the duty ratio of the main switch are also analytically derived. An experimental prototype of a single-inductor three-output inverter with a single time-multiplexed analog-based controller employing the type II compensation is implemented. It is experimentally verified that the individual ac outputs can be accurately and independently controlled. The maximum error between the target and measured peak voltage values is shown to be within 1.14%.