Inductive Powering Apparatus for Capsule Device

Abstract

A capsule device with an inductive powering apparatus is disclosed. The capsule device comprises a secondary coil to generate an induced secondary voltage when a first alternating magnetic field is coupled to the secondary coil externally. Embodiments of the present invention utilize a power conversion device to convert the induced secondary voltage into a DC output voltage for the capsule device. In particular, the power conversion device comprises a voltage booster to generate the DC voltage from a lower induced secondary voltage. Accordingly, the system can be operated using a lower secondary voltage, which will reduce the influence of magnetic flux on the circuit boards inside the capsule.

Description

FIELD OF THE INVENTION

The present invention relates to diagnostic imaging inside the human body. Particularly, the present invention relates to a capsule device incorporating inductive power to operate the capsule device, such as to retrieve image data or sensing data from the capsule device, after the capsule device exits from the human body.

BACKGROUND

Devices for imaging body cavities or passages in vivo are known in the art and include endoscopes and autonomous encapsulated cameras. Endoscopes are flexible or rigid tubes that pass into the body through an orifice or surgical opening, typically into the esophagus via the mouth or into the colon via the rectum. An image is formed at the distal end using a lens and transmitted to the proximal end, outside the body, either by a lens-relay system or by a coherent fiber-optic bundle. Alternatively, the endoscope might record an image electronically at the distal end, for example using a CCD or CMOS array, and transfer the image data as an electrical signal to the proximal end through a cable. Because of the difficulty traversing a convoluted passage, endoscopes cannot easily reach the majority of the small intestine and special techniques and precautions, that add cost, are required to reach its entirety. The cecum and ascending colon also require significant effort and skill to reach with an endoscope. An alternative in vivo image sensor that addresses many of these problems is a capsule endoscope. A camera is housed in a swallowable capsule along with a radio transmitter for transmitting data to transmit images recorded by the digital camera and/or sensing data to a base-station receiver or transceiver and data recorder outside the body. Another autonomous capsule camera system with on-board data storage was disclosed in the U.S. patent application Ser. No. 11/533,304, filed on Sep. 19, 2006.

For the above in vivo devices, a large amount of image data is collected traversing through a lumen in the human body such as the gastrointestinal (GI) tract. The images captured, along with other information, are stored in the on-board archival memory inside the capsule camera. The archival memory may come in various forms of non-volatile memories. After the capsule camera exits from the anus, it is retrieved to recover the data stored on-board. In a conventional approach, it would require a fairly expensive data access system that includes opening the capsule and docking it. Therefore, it is desirable to develop a system that allows data retrieval from the capsule camera without opening the sealed enclosure. Also, the internal battery in the capsule device after it exits from a human body is mostly depleted. There is a need to power the capsule device externally.

BRIEF SUMMARY OF THE INVENTION

A capsule device with an inductive powering apparatus is disclosed. The capsule device comprises a secondary coil to generate an induced secondary voltage when a first alternating magnetic field is coupled to the secondary coil externally. The magnetic field also causes a second induced voltage on at least one first trace of the PCB. This second induced voltage may affect performance of electronic circuits on the PCB. Additionally, induced currents in conductive materials within the capsule produce heat, which may degrade the performance or reliability of capsule components. Embodiments of the present invention utilize a power conversion device to convert the induced secondary voltage into a DC output voltage for the capsule device, wherein the power conversion device comprises a voltage booster to generate the DC output voltage from a lower induced secondary voltage. Accordingly, the lower induced secondary voltage allows for reduced magnetic flux which in turn will cause a lower second induced voltage on said at least one first trace of the PCB and reduced capsule heating. The capsule device is powered by an internal battery when the capsule device travels in the GI track. The battery is turned off or disconnected from the electronic subsystem of the capsule device when the capsule device exits from the human body or is placed in a docking station.

One aspect of the present invention addresses the voltage booster design. In one embodiment, the voltage booster comprises a voltage multiplier. The multiplication factor of the voltage multiplier may correspond to two, three or four. The voltage booster may also comprise a rectifier and a charge pump. Another aspect of the present invention addresses the secondary coil design. In one embodiment, the secondary coil is implemented based on printed circuit and at least a portion of the printed circuit board is flexible. The printed circuit includes multiple turns of conductive traces. The printed circuit may include a cut-out area surrounded by said multiple turns of conductive traces. Furthermore, the printed circuit includes a flexible extended portion to form a connection cable, and the connection cable includes second traces to couple with said multiple turns of conductive traces and the PCB. The connection cable can be bent to cause the printed circuit in a fold-back position adjacent to the PCB when the flexible printed circuit and the PCB are packaged inside the housing.

Another aspect of the present invention addresses the transmitter design. In one embodiment, the transmitter corresponds to an optical transmitter using a light source. The light source is used to transmit an optical signal through an optical path to an external optical receiver, and the optical path goes through a cut-out area of the printed circuit. The transmitter may correspond to a wireless transmitter using a radio frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of the system architecture of an optical wireless docking system according to the present invention.

FIGS. 2A-B illustrate an exemplary optical wireless docking system according to the present invention, where the system is configured with longitudinal-field geometry.

FIG. 3 illustrates an exemplary optical wireless docking system according to the present invention, where the system is configured with alternative longitudinal-field geometry.

FIG. 4A illustrates an exemplary voltage doubler circuit.

FIG. 4B illustrates another exemplary voltage doubler circuit.

FIG. 4C illustrates an exemplary 4-stage voltage multiplier circuit.

FIG. 5 illustrates an exemplary block diagram of power arrangement including inductive power and battery power for a capsule device, where the inductive powering device includes a voltage multiplier.

FIG. 6 illustrates an exemplary block diagram of power arrangement including inductive power device and battery power for a capsule device, where the inductive powering device includes a rectifier and a charge pump.

FIG. 7 illustrates a top view of an exemplary secondary coil implemented based on flexible printed circuits.

FIG. 8 illustrates a side view of an exemplary packaging comprising two printed circuit boards and the secondary coil implemented based on flexible printed circuits.

DETAILED DESCRIPTION OF THE INVENTION

It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the systems and methods of the present invention, as represented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, etc. In other instances, well-known structures, or operations are not shown or described in detail to avoid obscuring aspects of the invention. The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of apparatus and methods that are consistent with the invention as claimed herein.

In order to overcome the shortcoming in a conventional docking system, an optical wireless docking system according to the present invention is disclosed herein. A wireless docking system is attractive because the capsule need not be opened or precisely aligned. After the capsule camera exits from the anus, the batteries inside are likely to be either depleted or nearly depleted. Therefore, power must be supplied from outside the capsule, by magnetic induction for example. Also, data has to be transmitted wirelessly, such as by an optical or radio means.

In one embodiment according to the present invention, the docking system utilizes inductive powering and optical transmission. Nevertheless, radio transmission may also be used to practice the present invention. Any optical source requiring very little space to fit into the capsule may be considered. The optical source should be able to support fast data transmission. The amount of data stored in a capsule camera may be as much as 500 Mbytes and the data size will continue to grow along with the trend of high-resolution demand. If 1 Mbps (million bits per second) transmission speed is supported, it may take around 100 minutes to read out 500 Mbytes data if overhead in data transmission protocol is taken into account. Therefore, it is preferable to select an optical source that can support higher data rate. As one example, the optical source can be a directly modulated LED or Vertical-Cavity Surface-Emitting Laser diode (VCSEL) with a target bit rate of 10 Mbps.

Exemplary system architecture is shown in FIG. 1, where LED 116 is used as a light source and a Photo Diode (PD) is used as the receiver. Control circuit 115 is shown inside capsule camera 110. Control circuit 115 will read data stored in the archival memory (not shown) and process the retrieved data so that the data can be properly transmitted by light source 116. Light emitted from light source 116 will travel through the transparent window (not explicitly shown) of the capsule camera. The light from light source 116 will be received by a light receiving device such as photo diode 125 at docking system 120. The received signal will be properly amplified by amplifier 126. The amplified signal is then processed by receiver circuit 127 where data and clock will be recovered. The data recovered can be stored on a medium such as a flash drive or computer hard disk drive. Alternatively, the data recovered may be provided to a workstation or a display station for further processing or viewing.

The output buffer from control circuit 115 will provide needed power for light source 116. For example, 2-10 mA current may be provided, which should be adequate to drive either an LED or VCSEL. The LED wavelength may be in the near Infrared (NIR), for example at 830 nm. Other LED wavelengths may also be used to practice the present invention. With a 3V drive voltage, the correct drive current is produced with series resistance 117. A bit rate of 10 Mbps or more can be achieved.

The receiver consists of photodiode 125, trans-impedance amplifier 126, and data/clock recovery module 127. This module could be implemented using a limiting amplifier and a PLL. However, this functionality could be performed digitally by sampling the waveform and using DSP to recover data and clock. The use of a UART might obviate the need for clock recovery. The interface protocol may be used for the intended operation around 10 Mbps frequency range. Other standard digital data interfaces may also be used. In FIG. 1, optical link is shown as a wireless link between the capsule device and the docking device, a radio frequency (RF) link may also be used as the wireless link.

Inductive coupling relies on the mutual inductance of a primary coil outside the capsule and a secondary coil inside the capsule. The primary is driven by a sinusoidal voltage, and the secondary signal is rectified to produce a DC voltage. Exemplary system architecture is shown in FIG. 1. The system comprises capsule camera 110 and docking system 120. The inductive power is supplied from docking system 120 to capsule camera 110 through coupling coils 122 and 111. Coil 122 at the docking system side is referred to as the primary side and coil 111 on the capsule camera side is referred to as the secondary side. At the primary side, signal source 121 provides the driving signal to primary coil 122. While a sinusoidal driving signal is shown, other alternating signals such as square wave or triangular wave may also be used. The driving signal from signal source 121 may be amplified by amplifier 123. Various other known means of producing an alternating current may be utilized to drive the primary. The voltage across primary coil 122 is named primary voltage V1 and the voltage across secondary coil 111 is named secondary voltage V2. It is well known in the art that the induced alternating voltage at the secondary side can be converted into a DC voltage to be used by the circuits inside the capsule camera. Rectifiers are often used for converting AC power to DC power. Two rectifiers 112a and 112b are shown in FIG. 1 to provide different DC outputs as required by the capsule camera. A by-pass capacitor (118) is connected to the voltage output of rectifier 112a to reduce possible transient voltage. Furthermore, the circuits in the capsule device can be configured to charge rechargeable batteries inside the capsule device when the capsule device is docked in the docking device. For example, a rechargeable battery (not shown in FIG. 1) can be coupled to the voltage output from rectifier 112a and the rechargeable battery can be charged from the inductive power. Depending on the capsule camera design, it may require more or fewer voltage outputs. The rectifiers may also be integrated into a package or a module. The rectifier may be followed by a simple regulator, such as a Zenor-diode circuit or other voltage control circuits, to allow larger variability and stability in secondary voltage. Additionally, the rectifier may include voltage multiplication with a Greinacher or Cockcroft-Walton circuit. The components are selected to minimize the volume in order to fit into the limited space available inside the capsule camera. A voltage multiplier allows a smaller and lighter secondary coil to be used but requires additional diodes and capacitors.

The ratio of the secondary to primary voltage is:

$\begin{array}{cc}\frac{V_2}{V_1}=\beta \frac{N_2}{N_1},& \left(1\right)\end{array}$

where N₂ is the number of secondary coil turns, N₁ is the number of primary coil turns. The coupling coefficient is the ratio of the coil fluxes:

$\begin{array}{cc}\beta =\frac{{\phi }_2}{{\phi }_1}.& \left(2\right)\end{array}$

The flux through a coil is given by integration of the flux density through a surface defined by the coil perimeter

$\begin{array}{cc}{\phi }_i={\int }_SB_i·S_i.& \left(3\right)\end{array}$

The coupling coefficient β can be increased by making the secondary coil area larger and by designing pole pieces for the primary and/or secondary that concentrate the magnetic flux. For sinusoidal modulation of the primary at frequency f, the flux amplitude in the primary and secondary is given by

$\begin{array}{cc}{\phi }_i=\frac{V_i}{\sqrt{2}\pi {\mathrm{fN}}_i}& \left(4\right)\end{array}$

As mentioned before, the secondary coil is located inside the capsule camera. In order to properly couple the electro-magnetic field from the primary coil to the secondary coil, the two coils have to be correctly positioned and aligned. On the other hand, in order to read out data from the capsule camera optically, light passage has to be provided between the light source and the light detector. Accordingly, one exemplary system configuration to provide light passage as well as magnetic field coupling is shown in cross section in FIGS. 2A and 2B, where FIG. 2B represents a bottom view of the capsule camera. The type of arrangement is called longitudinal-field geometry.

Primary coil 221 wraps around capsule housing 210 of capsule 200. Secondary coil 214 is on the perimeter of bottom PCB 212 in the capsule. Primary coil 221 and secondary coil 214 should be centered on the same plane. Secondary coil 221 can also be implemented as a printed circuit as a spiral on multiple layers of PCB 212, although the practical pitch of the traces limits the number of turns. Alternatively, a coil can be produced with thin-gauge insulated wires held in shape with shellac and mounted to the PCB as a through-hole or surface mount component.

Light source 216 (LED or VCSEL) sits on the center of the board facing down. Batteries 211 are located at the other end of the capsule camera so that the batteries will not block light passage 224 from the light source to the light receiver. Lens 223 may be used to focus the light onto light receiver 225 such as a photodiode. Optional Band Pass Filter (BPF) 222 for the light can be installed in light passage 224 between light source 216 and light receiver 225. The components including the primary coil 221, the light BPF 222, the lens 223, the light receiver 225 and associated Printed Circuit Board 226 are housed in the docking system 220. The arrangement is symmetrical so that the rotational orientation of the capsule is not significant to the inductive coupling or the received optical power. A disadvantage is that eddy currents will be induced in the traces and power planes on PCB 212 itself. These currents can cause heating problem and also produce noise in the circuit. In the worst case, where a circuit trace forms a loop around the PCB, the induced voltage in the trace is proportional to V₂/N₂. Increasing the number of turns will decrease the noise but increase the volume occupied by the secondary coil. The noise can also be limited by minimizing the loop area of traces.

FIG. 3 illustrates another primary coil arrangement where ferrite core 320 for the primary coil on the primary side can reduce the magnetic flux reaching the batteries. The ferrite core 320 is also referred to as a primary core in this disclosure. The primary core may have a shell structure to enclose the primary coil. The shell has an opening to allow the capsule device to be docked through the opening. The primary core may be a ferrimagnetic material or may be a ferromagnetic material such as steel. A ferrite has the advantage of low electrical conductivity and, as a result, low eddy current loss. Coin-cell silver oxide or lithium batteries have high energy density and a round package that fits well in a capsule, but these generally have steel cases that could be inductively heated, creating the potential for battery bursting. The core also will reduce the electromagnetic field emitted by the system, which might be an issue for electromagnetic compatibility (EMC) requirement compliance. Photodiode 326, mounted on PCB 328, sits above post piece 325. Primary coil 322 is wrapped around post piece 325. Signal source 324 provides driving signal to primary coil 322. This design has no lens, but uses VCSEL 316, which has an output beam with much lower divergence than an LED.

In the capsule environment, the components are tightly packaged in the capsule housing. The secondary coil (214) is located closely within the proximity of the printed circuit board (212) inside the housing according to exemplary configuration as shown in FIG. 2 and FIG. 3. While the flux from the primary coil will couple to the secondary coil, the flux will also couple to the traces on the PCB. Therefore, the flux from the primary coil will cause induced voltage or current on the traces of the PCB. The induced voltage or current on the traces of the PCB will be more prominent particularly for long traces. In order to alleviate the issue of influence of flux from the primary coil (221 or 322) on the circuits, an embodiment according to the present invention utilizes a voltage multiplier to provide a desired DC output voltage from the induced secondary voltage. Due to the use of the voltage multiplier, a lower secondary voltage (i.e., V2 in FIG. 1) at the output of the secondary coil can be used.

According to equations (1)-(4), if the number of primary coil turns (N₁) and the number of secondary coil turns (N₂) as well as the coupling coefficient are maintained to be the same as before, the reduced voltage requirement on the secondary voltage (V₂) implies reduced primary voltage (V₁) requirement. In other words, the required flux from the primary coil is reduced due to the reduced voltage requirement on the secondary voltage (V₂). Accordingly, the induced current or voltage in the traces or power planes of the PCB (212) is reduced. Alternatively, the turns of the secondary coil (i.e., N2) can be reduced while maintaining the same influence on the circuit board by the flux from the primary coil. In other words, the secondary coil can be made smaller or thinner when the turns of the secondary coil is reduced. Furthermore, it can also be configured to have reduced secondary voltage at the secondary coil as well as reduced turns of the secondary coil. Another advantage of the voltage multiplier is reduced heating of the capsule arising from induced currents in conductive materials within the capsule such as the batteries, PCB traces, solder, and integrated-circuit packages and semiconductor substrates.

Voltage multiplier is a known technology in the field of power supply design. Voltage multiplier is a type of AC-to-DC power conversion device that can produce a high DC voltage from a source with lower AC voltage. Voltage multiplier typically comprises of diodes and capacitors and the voltage multiplier may be made up of multiple stages. Each stage is comprised of one diode and one capacitor. FIG. 4A illustrates an example of two-stage voltage multiplier that will produce a DC output voltage roughly two times the peak AC supply voltage. FIG. 4B illustrates an alternative voltage doubler arrangement. FIG. 4C illustrates an example of four-stage voltage multiplier that will produce a DC output voltage roughly four times the peak AC supply voltage. Based on the requirement for a specific application, any integer multiplication factor can be selected. In practice, the output DC voltage will be lower than the nominal integer multiple due to the voltage drops across the diodes

FIG. 5 illustrates an example of a power supply for the capsule system. The block diagram describes the aspect of power arrangement for the circuits inside the capsule housing. The capsule mainly relies on the battery power (510) when the capsule travels inside the human body. After the capsule exits from the human body, it is retrieved and placed in the docking station to download the captured image data as well as other sensing data recorded. When the capsule device exits from the human body, the internal battery may be exhausted or below an operable threshold. Embodiments according to the present invention will supply power to the capsule device inductively when the capsule device is placed in the docking station without the need to open up the housing. In this case, the induced secondary voltage from the secondary coil (520) is processed by voltage multiplier 522 to produce an output DC voltage that is multiple times of the peak AC supply voltage from the secondary coil. In order to provide a constant output voltage, an optional regulator (524) may be used. The regulated DC output from the induced secondary voltage is than supplied to the capsule electronics (530) such as light source, image sensor, processing circuits, controller, memory, etc. Since the internal battery will not be used after the capsule exits from the human body, a switch (512) is used to disconnect or turn off the battery from the capsule electronics. An optional regulator (524) may be used to regulate the power from the battery.

As mentioned above, the use of voltage multiplier can deliver the same DC output voltage based on a lower induced secondary voltage. Any device that can deliver a higher DC output voltage can reduce the required secondary voltage. Consequently, any such device will help to alleviate the induced voltage or current on the traces or power planes of the PCB. For convenience, a term, voltage booster is introduced in this disclosure, where the voltage booster refers to a circuit or a device that can produce a DC output voltage higher than a DC input voltage or the peak voltage of an AC input. Accordingly, the voltage multiplier is a type of voltage booster.

While the voltage multiplier can be used to lower the requirement on the induced secondary voltage, other devices or circuits may also be used to achieve the same goal. For example, a rectifier may be used to convert the induced secondary voltage to a first DC voltage and a DC-DC converter or a charge pump can be used to boost the first DC voltage to a desired DC output voltage. FIG. 6 illustrates an example of voltage booster using a rectifier and a charge pump. A rectifier (610) is used to convert the induced AC voltage from the secondary coil (520) into a first DC voltage. Charge pump (630) can be used to boost the voltage to a desired level. An optional regulator (620) can be used to regulate the first DC voltage from rectifier 610. Similarly, an optional regulator (640) can be used to regulate the boosted DC output from charge pump 640.

The secondary coil can be made of insulated wires wound in turns. A means to manufacture space-compact coil is to use printed circuit, where conductive traces (710) are formed on a printed circuit board as shown in FIG. 7. The conductive traces can be formed on a single layer or multiple layers. Since the induced voltage at the secondary coil has to be connected to the power conversion circuits, the printed circuit board may have a flexible section that forms a cable connector (720) by extending traces on the cable (not shown in FIG. 7) and adding conductive contacts at the edge of the cable. The printed circuit may be entirely a flexible circuit (typically on a polyimide substrate). Alternatively, it may have a rigid-flex construction where rigid PCB material (e.g. FR4) is selectively laminated to flexible PCB material so that some areas are rigid and some flexible. The section 710 may be rigid and the section 720 may be flexible. The section 710 may have flexible substrate but a stiffener (e.g. polyimide, FR4, or PET) may be laminated to selectively stiffen that section. When more wire turns are needed, multi-layer PCB technology known in the field can be used. A via (730) can be used to connect traces between PCB layers.

As mentioned before, an optical path has to be provided to allow the light source such as a laser diode inside the capsule to transmit optical signal to an external optical receiver. Accordingly, the flexible printed circuit board has a cut-out area to allow the optical passage to go through and also to avoid blockage by components on the PCB when the flexible printed circuit board is assembled in the housing. Alternatively, a transparent substrate may be used to allow the light path to go through. The light from a light source, such as a laser, will pass through polyimide so it is not essential to have a cut-out area to make a ring-shape secondary-coil PCB. The use of the transparent substrate can simplify the manufacturing process of the secondary coil PCB. Nevertheless, the ring shape secondary-coil PCB has the advantage of allowing for less optical loss, providing space for high profile components on the PCB, and allowing for less-transparent substrate materials such as FR4

FIG. 8 illustrates an example of secondary coil and PCB arrangement according to an embodiment of the present invention. The secondary coil, implemented as a flexible printed circuit (810), is connected to PCB 820 through connection cable 830. As mentioned before, the connection cable may be manufactured as part of the flexible printed circuit (810). A light source (840) is mounted on PCB 820, which may also have other components mounted (not shown). The PCB (820) may have components mounted on both sides. Alternatively, an additional PCB (850) may be used to accommodate more components. For example, a multi-chip package (MCP, 860) is shown in FIG. 8, where the MCP may include processor/controller and memory devices. The two PCBs may be connected through a flexible printed circuit cable (870). The light source (840) can penetrate through the cut-out area of the flexible printed circuit (810) so that its light path won't be blocked by the flexible printed circuit (810). For the example shown in FIG. 8, the magnetic field may cause significant induced voltage or current on the traces or power planes of the PCBs 820 and 850 or in metal pads and traces and conductive silicon substrates within the MCP. The use of voltage multiplier or charge pump can reduce the required voltage at the secondary coil, and consequently alleviate the induced voltage or current on the traces or power planes of the PCB.

The above description is presented to enable a person of ordinary skill in the art to practice the present invention as provided in the context of a particular application and its requirements. Various modifications to the described embodiments will be apparent to those with skill in the art, and the general principles defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed. In the above detailed description, various specific details are illustrated in order to provide a thorough understanding of the present invention. Nevertheless, it will be understood by those skilled in the art that the present invention may be practiced.

The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described examples are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. A capsule device comprising: an archival memory for storing data captured by the capsule device while travelling inside a gastrointestinal (GI) track of a human body;a transmitter to transmit the data after the capsule device exits from the human body;a first PCB (printed circuit board), wherein at least one electronic component for the capsule device is mounted on the first PCB;a secondary coil to generate an induced secondary voltage when a first alternating magnetic field is coupled to the secondary coil externally, wherein the first alternating magnetic field also causes a second induced voltage or current on at least one first trace of the first PCB;a power conversion device to convert the induced secondary voltage into a DC output voltage for the capsule device, wherein the power conversion device comprises a voltage booster to generate the DC output voltage from a lower induced secondary voltage, and wherein the lower induced secondary voltage requires a lower first alternating magnetic field that causes a lower second induced voltage on said at least one first trace of the first PCB; anda capsule housing, wherein the archival memory, the transmitter, the first PCB, the secondary coil, and the power conversion device are sealed in the capsule housing.

2. The capsule device of claim 1, wherein the voltage booster comprises a voltage multiplier.

3. The capsule device of claim 2, wherein a multiplication factor of the voltage multiplier corresponds to two, three or four.

4. The capsule device of claim 1, wherein the voltage booster comprises a charge pump.

5. The capsule device of claim 1, wherein the secondary coil is implemented using a secondary-coil PCB and the secondary-coil PCB includes multiple turns of conductive traces.

6. The capsule device of claim 5, wherein the secondary-coil PCB includes a cut-out area surrounded by said multiple turns of conductive traces.

7. The capsule device of claim 5, wherein the secondary-coil PCB includes an extended portion to form a connection cable, and wherein the connection cable is made of flexible printed circuit and the connection cable includes second traces to couple with said multiple turns of conductive traces and the first PCB.

8. The capsule device of claim 7, wherein the connection cable is bent to cause the secondary-coil PCB in a fold-back position adjacent to the first PCB when the secondary-coil PCB and the first PCB are packaged inside the housing.

9. The capsule device of claim 1, wherein the transmitter corresponds to an optical transmitter using a light source.

10. The capsule device of claim 9, wherein the secondary coil is implemented based on a secondary-coil PCB and the secondary-coil PCB includes multiple turns of conductive traces.

11. The capsule device of claim 10, wherein the light source is used to transmit an optical signal through an optical path to an external optical receiver, and wherein the optical path goes through a cut-out area of the secondary-coil PCB.

12. The capsule device of claim 9, wherein the secondary coil is implemented based on a secondary-coil PCB and the secondary-coil PCB includes multiple turns of conductive traces, and wherein the secondary-coil PCB uses a transparent substrate.

13. The capsule device of claim 12, wherein the light source is used to transmit an optical signal through an optical path to an external optical receiver, and wherein the optical path goes through a clear area of the secondary-coil PCB where no conductive traces block the optical path.

14. The capsule device of claim 1 further comprising a battery, wherein the battery supplies power to electronic subsystem of the capsule device when the capsule device travels in the GI track.

15. The capsule device of claim 14, wherein the battery is turned off or disconnected from the electronic subsystem of the capsule device when the capsule device exits from the human body or is placed in a docking station.

16. The capsule device of claim 1, wherein the transmitter corresponds to a wireless transmitter using a radio frequency.

17. A capsule device comprising: an archival memory for storing data captured by the capsule device while travelling inside gastrointestinal (GI) track of a human body;a transmitter to transmit the data after the capsule device exits from the human body;a secondary coil to generate an induced secondary voltage when a first alternating magnetic field is coupled to the secondary coil externally, wherein the secondary coil is implemented using a secondary-coil PCB and the secondary-coil PCB includes multiple turns of conductive traces;a power conversion device to convert the induced secondary voltage into a DC output voltage for the capsule device; anda capsule housing, wherein the archival memory, the transmitter, the secondary coil, and the power conversion device are sealed in the capsule housing.

18. The capsule device of claim 17, wherein the secondary-coil PCB includes a cut-out area surrounded by said multiple turns of conductive traces.

19. The capsule device of claim 17, wherein at least a portion of the secondary-coil PCB is made of flexible printed circuit.

20. The capsule device of claim 17, wherein the secondary-coil PCB includes an extended portion to form a connection cable, and wherein the connection cable is made of flexible printed circuit and the connection cable includes second traces to couple with said multiple turns of conductive traces and the power conversion device.

21. The capsule device of claim 17, wherein the secondary-coil PCB includes multiple layers of the conductive traces and wherein a via is used to interconnect the multiple layers of the conductive traces.

22. The capsule device of claim 17, wherein the secondary-coil PCB uses a transparent substrate.