Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P5/00—Coupling devices of the waveguide type
  • H01P5/02—Coupling devices of the waveguide type with invariable factor of coupling
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05F—STATIC ELECTRICITY; NATURALLY-OCCURRING ELECTRICITY
  • H05F3/00—Carrying-off electrostatic charges
  • H05F3/04—Carrying-off electrostatic charges by means of spark gaps or other discharge devices
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H1/00—Details of emergency protective circuit arrangements
  • H02H1/04—Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of dc component by short circuits in ac networks
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/0213—Electrical arrangements not otherwise provided for
  • H05K1/0254—High voltage adaptations; Electrical insulation details; Overvoltage or electrostatic discharge protection ; Arrangements for regulating voltages or for using plural voltages
  • H05K1/0257—Overvoltage protection
  • H05K1/026—Spark gaps

Definitions

• the present invention generally relates to a system and method for protecting electronic devices.
• exemplary embodiments of the present invention relate to an electrostatic discharge (ESD) protection circuit that protects an electronic component from an ESD pulse by providing a path for the ESD pulse to follow to a ground plane before the ESD pulse damages the electronic component.
• ESD electrostatic discharge
• Some microwave radio frequency (RF) devices have very low tolerances to ESD shocks.
• an ESD pulse having a magnitude of no more than 100 or 200 volts can damage sensitive components of some RF devices. This is unfortunate, because some RF applications require resistance to much greater ESD discharges, even up to and above 15 kV.
• many RF devices are very sensitive to shunt capacitance because of their operating frequencies. This sensitivity to shunt capacitance presents an added requirement for an ESD protection circuit to have very low capacitance, perhaps less than one picofarad.
• a typical system approach is to guide ESD energy away from a signal path to a return (ground) path as quickly as possible, in order to shield any ESD-sensitive component connected to the signal path from the ESD signal.
• shunt devices may include inductors, polymer devices, and spark gap devices.
• the shunt inductor approach can be utilized as an RF choke, where the RF impedance is large enough to not to influence the RF performance.
• V(t) L * ⁇ 1 Equation 1 dt
• V(t) is the voltage across an inductor at time t and where L is the inductance of the inductor.
• an inductor is capable of responding to an instantaneous voltage change, but is not capable of responding to an instantaneous current change. Because an inductor does not have a trigger voltage (as do polymer and spark gap ESD devices), the inductor begins to return energy to ground immediately, subject to the maximum current of its windings. For this reason, low capacitance polymer and spark gap ESD devices are typically placed in parallel with an inductor to assist in increasing the current capacity of the overall ESD protection circuit. Such typical ESD protection circuits, however, may not provide robust enough protection for RF components in hostile ESD environments.
• An electronic device having an ESD protection circuit comprises an electronic component having a signal input conductor.
• An exemplary ESD protection circuit includes a spark gap in series with a high pass quarter wave transformer. The exemplary ESD protection circuit is adapted to discharge an ESD pulse from the signal input conductor of the electronic component to a ground plane via the spark gap and/or the high pass quarter wave transformer.
• FIG. 1 is a block diagram of an electronic device in accordance with an exemplary embodiment of the present invention.
• FIG. 2 is a schematic circuit diagram of an ESD protection circuit in accordance with an exemplary embodiment of the present invention.
• FIG. 3 is a top view of a spark gap circuit that is useful in constructing an ESD protection circuit in accordance with an exemplary embodiment of the present invention
• FIG. 4 is a schematic circuit diagram of a high pass quarter wave transformer that is useful in constructing an ESD protection circuit in accordance with an exemplary embodiment of the present invention.
• FIG. 5 is a process flow diagram of a method of constructing an ESD protection circuit in accordance with an exemplary embodiment of the present invention.
• FIG. 1 is a block diagram of an electronic device in accordance with an exemplary embodiment of the present invention.
• the electronic device is generally referred to by the reference number 100.
• the exemplary electronic device 100 illustrated in FIG. 1 is an RF reception device (such as an automotive radio, for example) for receiving and playing RF audio signals or the like.
• the electronic device 100 may in other exemplary embodiments comprise other types of devices such as computer systems or components, televisions, television set top boxes, DVD players, personal audio players, cameras or the like, to name just a few examples.
• exemplary embodiments of the present invention may be useful for protecting any sort of electronic device that is subject to damage by discharging ESD pulses.
• the various functional blocks shown in FIG. 1 may comprise hardware elements (including circuitry), software elements (including computer code stored on a machine-readable medium) or a combination of both hardware and software elements.
• the exemplary electronic device 100 illustrated in FIG. 1 comprises a signal input 102.
• the signal input 102 may comprise an input from an RF antenna or other signal source.
• an ESD protection circuit 104 is adapted to protect an electronic component such as a processing electronics block 106 from a discharge of an ESD pulse.
• the electronic component 106 may comprise an RF processing circuit that is adapted to receive an input signal from the signal input 102.
• the electronic device 100 further comprises one or more speakers 108 (which may comprise headphones) for delivering an audio output signal to a user.
• FIG. 2 is a schematic circuit diagram of an ESD protection circuit in accordance with an exemplary embodiment of the present invention.
• the ESD protection circuit is generally referred to by the reference number 200.
• a signal input 202 is adapted to receive an input signal corresponding to, for example, an RF audio program or the like.
• the ESD protection circuit 200 employs a spark gap 204 in series with a high pass quarter wave transformer 208 to provide ESD protection to an ESD-sensitive RF device 210.
• An exemplary embodiment of the present invention may additionally comprise a low capacitance ESD element 206 in parallel with the spark gap 204 and the high pass quarter wave transformer 208 to provide additional ESD protection to the ESD-sensitive RF device 210.
• FIG. 3 is a top view of a spark gap circuit that is useful in constructing an ESD protection circuit in accordance with an exemplary embodiment of the present invention.
• the spark gap circuit is generally referred to by the reference number 300.
• the spark gap circuit 300 shown in FIG. 3 represents a layout of a portion of an RF connector disposed on a printed circuit board component of an electronic device.
• the spark gap circuit 300 includes a signal input conductor 302 that is adapted to carry a signal such as an RF audio input signal or the like.
• the signal input conductor 302 is implemented as a connector pad of a printed circuit board.
• the signal input conductor 302 may be adapted to carry an input signal received via the signal input 202 (FIG. 2).
• the spark gap circuit 300 includes a ground plane 304.
• the spark gap circuit 300 is adapted to provide an electrical path between the signal input conductor 302 and the ground plane 304 when an ESD pulse exceeding a threshold voltage strikes the signal input conductor 302.
• the spark gap circuit 300 comprises one or more spark gap pads 306.
• the spark gap pads 306 are generally triangular in shape and are formed as an integral part of the ground plane 304. Because the spark gap pads 306 are formed as an integral part of the ground plane 304, the shunt capacitance of the spark gap pads 306 is very minimal and transparent to operating frequencies up to about 4GHz.
• a vertex of each of the generally triangular spark gap pads 306 is oriented to point in the general direction of the signal input conductor 302. It may be desirable to provide a backup set of spark gap pads to extend the life of the spark gap circuit 300 relative to the use of a single set of spark gap pads.
• spark gap pads 306 may be positioned at a substantially high point of current density with respect to the signal input conductor 302. This location may vary depending on individual system design considerations. Those of ordinary skill in the art will appreciate that a wide variety of criteria may be employed to design the exact size and shape of the spark gap pads 306. An example of such a design criteria is to assume an air discharge value of 30 volts per millimeter of separation between the signal input conductor 302 and the ground plane 304. In one exemplary embodiment, the signal input conductor 302 is positioned about 4mm from the ground plane 304. In such an embodiment, the spark gap circuit 300 would have an activation voltage of about 120 volts. In other words, an ESD pulse exceeding a threshold voltage of about 120 volts would be discharged to the ground plane 304 via the spark gap pads 306.
• solder mask negative line 308 (shown as a dashed line) is free from solder mask.
• FIG. 4 is a schematic circuit diagram of a high pass quarter wave transformer that is useful in constructing an ESD protection circuit in accordance with an exemplary embodiment of the present invention.
• the exemplary high pass quarter wave transformer shown in FIG. 4 is generally referred to by the reference number 400.
• an ESD protection circuit in accordance with an exemplary embodiment of the present invention comprises a spark gap circuit such as the spark gap circuit 300 (FIG. 3) in series with a high pass quarter wave transformer such as the high pass quarter wave transformer 400.
• the exemplary high pass quarter wave transformer 400 comprises a capacitive element 402 connect as shown in FIG. 4 in parallel with a first inductive element 404 (connected to a first terminal of the capacitive element 402) and in parallel with a second inductive element 406 (connected to a second terminal of the capacitive element 402).
• a capacitive element 402 connects as shown in FIG. 4 in parallel with a first inductive element 404 (connected to a first terminal of the capacitive element 402) and in parallel with a second inductive element 406 (connected to a second terminal of the capacitive element 402).
• L is the inductance of the first inductive element 404 and the second inductive element 406
• Zo is the characteristic impedance of the high pass quarter wave transformer 400
• Fo is center frequency
• the properties of the high pass quarter wave transformer 400 make it useful in mitigating an ESD strike.
• the first inductive element 404 and the second inductive element 406 each serve as shunt inductive elements that have lower impedance to allow the high pass quarter wave transformer 400 to transfer more ESD energy to the ground plane 304 (FIG. 3).
• the capacitive element 402 in an exemplary embodiment of the present invention has a small value to provide a high impedance series path to the ESD sensitive RF device 210 (FIG. 2 that is being protected. The high impedance of the capacitive element 402 forces more ESD energy to be shunted to the ground plane 304 (FIG. 3) via the first inductive element 404 and the second inductive element 406.
• the high pass quarter wave transformer 400 is a single stage transformer having a relatively narrow bandwidth so that most of the energy received by the high pass quarter wave transformer 400 is reflected back to the source.
• a high pass quarter wave transformer structure in accordance with an exemplary embodiment of the present invention desirably employs a minus 90 degree phase that occurs at the output of the transformer. In this manner, the ESD energy from an ESD pulse is largely remove from the signal input conductor 302 (FIG. 3) and is returned through the ground plane 304 (FIG. 3).
• a high pass quarter wave transformer in an ESD protection circuit in accordance with an exemplary embodiment of the present invention provides matching from a real source impedance to a real load impedance.
• quarter wave transformers are used for lossless RF isolation from the source and load impedances because the maximum power transfer only occurs at odd multiples of a quarter wave.
• isolation is provided between the ESD protection circuit 200 (FIG. 2) and the ESD sensitive RF device 210 (FIG. 2) being protected.
• the high pass quarter wave transformer 208 provides isolation from broadband energy without sacrificing voltage standing wave ratio (VSWR).
• the isolation from broadband energy provided by the high pass quarter wave transformer 208 is in part related to the properties of a Fourier transform of an ESD pulse.
• the signal waveform of an ESD pulse is similar to an exponential decay.
• the Fourier transform of an exponential decay is similar to a very broadband energy across the spectrum.
• FIG. 5 is a process flow diagram of a method of constructing an ESD protection circuit such as the ESD protection circuit 200 (FIG. 2) in accordance with an exemplary embodiment of the present invention.
• the process is generally referred to by the reference number 500.
• the process begins.
• the ESD protection circuit resulting from the process 500 is adapted for use in an electronic device 100 (FIG. 1) having a signal input conductor 302 (FIG. 3).
• a spark gap such as the spark gap 204 (FIG. 2) is provided.
• the spark gap is connected in series with a high pass quarter wave transformer such as the high pass quarter wave transformer 208 (FIG. 2).
• the resulting ESD protection circuit is adapted to discharge an ESD pulse from the signal input conductor 302 (FIG. 3) to a ground plane 304 (FIG. 3) via the spark gap 204 (FIG. 2) and/or the high pass quarter wave transformer 208 (FIG. 2).
• the process ends.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Emergency Protection Circuit Devices (AREA)
• Amplifiers (AREA)
• Semiconductor Integrated Circuits (AREA)

Priority Applications (5)

Applications Claiming Priority (1)

Publications (1)

Family

ID=42059970

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (2)

Citations (7)

Family Cites Families (16)

• 2008
  • 2008-09-25 KR KR1020117009162A patent/KR101478870B1/ko not_active IP Right Cessation
  • 2008-09-25 WO PCT/US2008/011118 patent/WO2010036218A1/en active Application Filing
  • 2008-09-25 JP JP2011528987A patent/JP5209119B2/ja not_active Expired - Fee Related
  • 2008-09-25 CN CN2008801313082A patent/CN102165662A/zh active Pending
  • 2008-09-25 EP EP08816319A patent/EP2329573A4/en not_active Ceased

Patent Citations (7)

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