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WO2008156440A1 - Système et procédé de détection de courant - Google Patents

Système et procédé de détection de courant Download PDF

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Publication number
WO2008156440A1
WO2008156440A1 PCT/US2007/014013 US2007014013W WO2008156440A1 WO 2008156440 A1 WO2008156440 A1 WO 2008156440A1 US 2007014013 W US2007014013 W US 2007014013W WO 2008156440 A1 WO2008156440 A1 WO 2008156440A1
Authority
WO
WIPO (PCT)
Prior art keywords
current
voltage
proportional
load
recited
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2007/014013
Other languages
English (en)
Inventor
Harold Arthur Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Automotive Systems Company of America
Original Assignee
Panasonic Automotive Systems Company of America
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Panasonic Automotive Systems Company of America filed Critical Panasonic Automotive Systems Company of America
Priority to PCT/US2007/014013 priority Critical patent/WO2008156440A1/fr
Publication of WO2008156440A1 publication Critical patent/WO2008156440A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/462—Indexing scheme relating to amplifiers the current being sensed
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45138—Two or more differential amplifiers in IC-block form are combined, e.g. measuring amplifiers

Definitions

  • the present invention generally relates to automotive audio systems.
  • the present invention relates to a current sensing circuit having a wide common mode voltage tolerance, measurement device protection and current limiting.
  • An exemplary current sense circuit comprises a voltage-to-current converter circuit that is adapted to receive a voltage that is proportional to a load current drawn from a battery by a load and to produce a current proportional to the load current, and a current-to-voltage converter circuit that is adapted to receive the current proportional to the load current and to produce a voltage proportional to the load current based on a regulated voltage source.
  • FlG. 1 is a block diagram of a motorized vehicle in accordance with an exemplary embodiment of the present invention
  • FIG.2 is a block diagram of an audio subsystem of the vehicle shown in FIG. 1 in accordance with an exemplary embodiment of the present invention
  • FIG. 3 is a schematic diagram of a current sensing circuit in accordance with an exemplary embodiment of the present invention.
  • FIG. 4 is a process flow diagram of a method in accordance with an exemplary embodiment of the present invention.
  • FIG. 1 is a block diagram of a motorized vehicle in accordance with an exemplary embodiment of the present invention.
  • the motorized vehicle is generally represented by the reference number 10.
  • the exemplary motorized vehicle 10 comprises an engine 12, a power train 14, a plurality of electronic control systems 16 that may be adapted to control a number of vehicle systems (for example, the engine, the power train, a heating ventilation air conditioning (HVAC) system, to name a few examples), and a chassis 18.
  • HVAC heating ventilation air conditioning
  • the chassis 18 is adapted to support the engine 12, which is adapted to drive the power train 14.
  • an entertainment system which may provide audio/visual entertainment, computer networking capability or the like to occupants of the motorized vehicle 10.
  • the entertainment system 20 comprises an audio subsystem 22, the operation of which is explained in greater detail below.
  • FIG. 2 is a block diagram of the audio subsystem 22 of the vehicle 10 shown in FIG. 1 in accordance with an exemplary embodiment of the present invention.
  • the audio subsystem 22 comprises an audio processing module 102.
  • An active antenna 104 is adapted to receive a broadcast signal such as an AM/FM radio signal.
  • a broadcast signal such as an AM/FM radio signal.
  • the active antenna 104 may be adapted to receive other types of signals, such as satellite radio signals or the like.
  • the broadcast signal received by the active antenna 104 is delivered via a coaxial cable 106 to the audio processing module 102 via an antenna connector 108. As set forth below in greater detail, it may be desirable to measure a current flow being drawn by the active antenna 104.
  • a battery 110 such as a typical automotive battery, is adapted to deliver voltage to a main connector 112 of the audio processing module 102.
  • the battery is adapted to deliver an input voltage to a battery voltage input 116 of the main connector 112.
  • the main connector 112 may include inputs and/or outputs for additional signals.
  • the main connector 112 may include an external I/O signal 114 and/or a network communications signal such as a LAN signal 118.
  • the broadcast signal received by the active antenna 104 is delivered to a combiner 120.
  • the combiner 120 provides the signal to a primary AM/FM tuner 122, an optional secondary tuner 124 and a phantom power coupler 126.
  • the phantom power coupler 126 is adapted to couple DC voltage from the battery 110 onto the coaxial cable 106 feeding the active antenna 104, without compromising reception of radio signals on the coaxial cable 106.
  • Outputs from the primary AM/FM tuner 122 and the optional secondary tuner 124 are delivered to a digital IF processor 128 for processing.
  • the digital IF processor 128 is powered by a power amplifier 130, which receives power from battery voltage input 116 of the main connector 112.
  • a main microprocessor 132 is adapted to control the overall operation of the audio processing module 102.
  • the battery voltage input 1 16 provides power to the main microprocessor 132.
  • the digital IF processor 128 delivers demodulated audio to the power amplifier 130, which delivers amplified audio to the main connector 112.
  • control and status signals are exchanged between the digital IF processor 128 and the main microprocessor 132.
  • the main microprocessor 132 does not directly receive audio signals from the digital IF processor 128, but instead receives information in response to queries. That information may include information about the audio signals being processed.
  • the amplified audio signal from the power amplifier 130 is used to provide an audio program for occupants of the vehicle 10 (FIG. 1).
  • the main microprocessor 132 is adapted to measure the current drawn by the active antenna 104 using a current sense and short circuit protection circuit 134.
  • FIG. 3 is a schematic diagram of the current sense and short circuit protection circuit 134 (referred to hereafter as the current sense circuit 134) in accordance with an exemplary embodiment of the present invention.
  • the resistance values shown in FIG. 3 are exemplary in nature and not essential to the invention disclosed and claimed herein. Moreover, one of ordinary skill in the art would be able to identify appropriate component values for the current sense circuit 134 without undue experimentation given the benefit of the disclosure set forth herein.
  • the current sense circuit 134 is adapted to measure the current drawn by a load 202, which may comprise a resistance presented by the active antenna 104 (FIG. 2).
  • the current sense circuit 134 is adapted to measure the flow of current in the presence of a significant and variable voltage, and to avoid over-ranging an analog-to-digital converter or other measurement display device.
  • the main microprocessor 132 (FIG. 2) may comprise an analog-to-digital converter to provide a digital representation of a value of the current being drawn by the load 202.
  • the current sense 134 is powered by the battery 110 (FIG. 2).
  • Current drawn by the load 202 also passes through a current sense resistor 204.
  • the resistance of the current sense resistor 204 can be arbitrarily small to provide a minimal voltage drop between the battery 110 and the load 202.
  • the voltage drop across the current sense resistor 204 is applied differentially to an operational amplifier 206 via a first input resistor 208 and a second input resistor 210.
  • the current drawn by the load 202 also flows through a transistor 212.
  • the transistor 212 is held in saturation by base drive supplied by a transistor 214, which is also normally saturated.
  • the operational amplifier 206, the first input resistor 208 and the second input resistor 210 work in conjunction with a transistor 216, to form a voltage-to- current converter circuit 218, shown in dashed lines in FIG. 3.
  • the output current from the source of the transistor 216 is proportional to the voltage drop across the current sense resistor 204.
  • the voltage drop across the current sense resistor 204 is applied across the second input resistor 210. Because the input terminals of the operational amplifier 206 are high impedance, the current that flows through the second input resistor 210 also flows through the transistor 216.
  • the transistor 216 is desirably a Junction Field Effect Transistor (JFET) rather than a bipolar transistor because JFETs are voltage-biased. This means that the problem of variation in bias current present in a bipolar transistor is not present in a JFET. This characteristic results in improved temperature stability for the current sense circuit 134. As an additional advantage, the use of a JFET also results in a relatively small gate current (leakage current not necessary to the operation of the JFET) compared to the base current of a bipolar transistor. Because the gate current of a typical JFET is very small, the gate current is subject to less variation that could otherwise occur during the relatively wide temperature variations encountered in the engine compartment of a motor vehicle.
  • JFET Junction Field Effect Transistor
  • the output of the voltage-to-current converter 218 is one of the inputs applied to a current-to-voltage converter circuit 228 (shown in dashed lines in FIG. 3) that includes an operational amplifier 220, a resistor 222, a resistor 224 and a resistor 226. Also provided to the current-to-voltage converter circuit 228 are bias voltages derived from a regulated voltage source 230. The bias voltages are determined by the values of a resistor 232, a resistor 234 and a resistor 236.
  • converting a small voltage drop across the current sense resistor 204 into a current proportional to a load current drawn from the battery 110 and the subsequent re-conversion of the current to a voltage value proportional to the load current using the regulated voltage source 230 has the effect of reducing variations in sensed current based on temperature fluctuations. This is true because the regulated voltage source 230 is typically less susceptible to temperature variation than is the battery 110.
  • the circuitry around the operational amplifier 220 is adapted to provide a maximum output value when the current through the current sense resistor 204 is at a minimum. Moreover, the output voltage of the operational amplifier 220 falls as the current through the current sense resistor increases.
  • the zero-current output voltage and the gain of the output of the operational amplifier 220 are adjusted by varying the component values of the circuit components of the current-to-voltage converter circuit 228 (the resistors 224, 226, 232, 234 and 236).
  • the inverse-scaled output of the current-to-voltage converter circuit 228 prevents over-voltage damage to a circuit such as an analog-to-digital circuit that receives the output of the current-to-voltage converter circuit 228 because its output is at a predetermined maximum when the current being measured is zero, and falls to zero at some maximum current, determined by the choice of scaling components. A further increase in load current does not produce any fiirther change in output.
  • FIG.4 is a process flow diagram of a method in accordance with an exemplary embodiment of the present invention.
  • the process is generally referred to by the reference number 300.
  • the process begins.
  • a voltage that is proportional to a load current drawn from a battery by a load is received at block 304.
  • a current proportional to the load current is produced.
  • the current proportional to the load current is received at block 308.
  • a voltage proportional to the load current based on a regulated voltage source is produced.
  • the process ends at block 312.
  • exemplary embodiments of the present invention do not require tightly matched precision components to eliminate the effect of the varying common-mode voltage and/or varying temperature. Additionally, embodiments of the present invention do not require separate, isolated power supplies and/or expensive isolation components such as transformers or optical isolators. Unlike known current sense and short circuit protection circuits, exemplary embodiments of the present invention do not require additional components, such as clamping diodes, to protect against over-voltages at their outputs.
  • Known methods of current limiting usually require a series resistance in line with the load that can drop enough voltage to turn on a transistor, around 0.7 volts.
  • an exemplary embodiment of the present invention makes use of the output that is already there to supply the base drive for the current limiting transistor.
  • Exemplary embodiments of the present invention facilitate accurate current measurement over a wide range of operating conditions.
  • the current sense circuit 134 may be adapted to accurately sense current flow despite fluctuations in a range of operating temperatures at a measurement site from about -40 to +85 degrees Celsius and battery voltage swings ranging from about 9 to 16 volts.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

L'invention concerne un circuit de détection de courant (134). Un circuit de détection de courant (134) exemplaire comprend un circuit de conversion de tension en courant (218) adapté pour recevoir une tension proportionnelle à un courant de charge tiré d'une batterie (110) par une charge (202) et pour produire un courant proportionnel au courant de charge, ainsi qu'un circuit de conversion de courant en tension (228) adapté pour recevoir le courant proportionnel au courant de charge et pour produire une tension proportionnelle au courant de charge sur la base d'une source de tension régulée (230).
PCT/US2007/014013 2007-06-14 2007-06-14 Système et procédé de détection de courant Ceased WO2008156440A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2007/014013 WO2008156440A1 (fr) 2007-06-14 2007-06-14 Système et procédé de détection de courant

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2007/014013 WO2008156440A1 (fr) 2007-06-14 2007-06-14 Système et procédé de détection de courant

Publications (1)

Publication Number Publication Date
WO2008156440A1 true WO2008156440A1 (fr) 2008-12-24

Family

ID=40156470

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2007/014013 Ceased WO2008156440A1 (fr) 2007-06-14 2007-06-14 Système et procédé de détection de courant

Country Status (1)

Country Link
WO (1) WO2008156440A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6559720B1 (en) * 2001-10-26 2003-05-06 Maxim Integrated Products, Inc. GM-controlled current-isolated indirect-feedback instrumentation amplifier
US7268714B2 (en) * 2005-06-17 2007-09-11 Analog Devices, Inc. Rapid response current measurement system and method

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6559720B1 (en) * 2001-10-26 2003-05-06 Maxim Integrated Products, Inc. GM-controlled current-isolated indirect-feedback instrumentation amplifier
US7268714B2 (en) * 2005-06-17 2007-09-11 Analog Devices, Inc. Rapid response current measurement system and method

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