A feedback controlled coil driver for transcutaneous power transmission

Abstract

A fully integrated feedback controlled coil driver for transcutaneous power transmission was proposed to power biomedical implants. For a normal power transmission operation, the voltage across the switch that energizes the coil is sampled and compared with ground, followed by an integration to obtain an optimal on-time for the switch such that the coil current was maximized for a given DC input power. The coil driver also provides ASK modulation on the coil current by changing the size of the switch according to the input data. In the normal power transmission operation, a peak-to-peak coil current of ~730mA was obtained with a power dissipation of 71.6mW at 5V.

A Discrete Controlled Fully Integrated Class E Coil Driver With Power Efficient ASK Modulation for Powering Biomedical Implants

“…3(d), may go negative enough to turn on the parasitic diode of before starts to turn on at . In this case, will be charged through the parasitic diode of and may even begin to increase and reach a positive value before starts to turn on [32]. In this case, the power loss will be even higher than the power loss of discharging due to the additional power loss on the parasitic diode.…”

“…PREVIOUS COIL DRIVER DESIGN In the literature, different techniques to operate the turn-on time of the switch near the optimal on-time for class E coil drivers have been investigated [28]- [31]. To achieve automatically and accurately, a feedback controlled technique was proposed previously in [32]. The architecture of the previous coil driver design is shown in Fig.…”

“…First, a large was required such that the overall bandwidth of the coil driver could be set to a value much lower than . Furthermore, besides adding for improving the phase margin, a switched-capacitor resistor in the S/H was used to have better control on the DC gain as well as the effective pole location of the S/H in order to achieve an overall stability of the coil driver [32]. In addition, was added to reduce the ripple on .…”

“…Fig. 2(b) shows an alternative class E topology [4], [32]- [35], which is also referred to be the resonant DC-AC converter topology [34]. It has the advantage of using only one discrete component besides the primary coil.…”

“…However, when metallic/magnetic objects or even implants are placed nearby or inside , the operating conditions change and the coil driver will no longer operate at the optimal condition. To address these challenges, a fully integrated feedback controlled coil driver was proposed recently [32] to achieve the optimal switching condition automatically even for different operating conditions. Only one discrete capacitor besides is required.…”