Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
  • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
  • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
  • G05F1/10—Regulating voltage or current 
  • G05F1/46—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC
  • G05F1/56—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices
  • G05F1/565—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
  • G05F1/569—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection
  • G05F1/573—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection with overcurrent detector
  • G05F1/5735—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection with overcurrent detector with foldback current limiting
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
  • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
  • G05F1/10—Regulating voltage or current 
  • G05F1/46—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC
  • G05F1/56—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices
  • G05F1/575—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices characterised by the feedback circuit
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
  • H02H9/001—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection limiting speed of change of electric quantities, e.g. soft switching on or off

Definitions

• This relates in general to electronic circuitry, and in particular to electronic current-limiting apparatus.
• Some electronic power supply regulators may include over-current protection circuitry. Over-current protection may prevent catastrophic failure of regulator components, particularly power transistor output stages, in the event of a short circuit or a heavy loading condition at the regulator output.
• Some power supply regulators may use a sense transistor to sense an overdrive condition and a current clamp to temporarily reduce the drive signal to the power output stage while the overdrive condition exists.
• sense transistor-based current clamps traditionally have poor direct current (DC) accuracy. Inaccuracies may be due to a combination of channel length modulation effects, sense element to pass element matching, and variations in process, supply and/or temperature (PVT).
• electronic current-limiting apparatus includes a pass element to receive a voltage regulation control input signal on a voltage regulation control input path and to allow a magnitude of current flow through the pass element proportional to a magnitude of the voltage regulation control input signal.
• a fast transient feedback circuit is communicatively coupled to the voltage regulation control input path to receive the voltage regulation control input signal and to decrease the magnitude of the voltage regulation control input signal in an over-current condition.
• a precision feedback circuit is communicatively coupled to the voltage regulation control input path to receive the voltage regulation control input signal and to decrease the magnitude of the voltage regulation control input signal in the over-current condition. The precision feedback circuit more accurately controls the over-current condition than control provided by the fast transient feedback circuit by correcting for a component characteristic mismatch between the pass element and at least one component of the precision feedback circuit.
• FIG. 1 is a block diagram of electronic current-limiting apparatus, according to a first example embodiment.
• FIG. 2 is a block diagram of electronic current-limiting apparatus, according to a second example embodiment.
• FIG. 3 is a circuit diagram of electronic current-limiting apparatus, according to example embodiments.
• FIG. 4 is a block diagram of a current- limited voltage regulator, according to example embodiments.
• FIGS. 1 and 2 are block diagrams of electronic current-limiting apparatus 100 and 200, according to first and second example embodiments.
• the current-limiting apparatus 100 and 200 include a pass element 110.
• the pass element 110 is embodied as a power MOSFET 215 in the current-limiting apparatus 200.
• the pass element 110 receives a voltage regulation control input signal 114 on a voltage regulation control input path 115.
• the pass element 110 allows a magnitude of current flow through a current channel of the pass element 110 that is proportional to the magnitude of the voltage regulation control input signal 114.
• the current-limiting apparatus 100 and 200 both include a fast transient feedback circuit 118 and a precision feedback circuit 124 operating in parallel.
• the fast transient feedback circuit 118 is communicatively coupled to the voltage regulation control input path 115.
• the fast transient feedback circuit 118 receives the voltage regulation control input signal 114 and decreases the magnitude of the voltage regulation control input signal 114 on the path 115 in an over-current condition.
• the fast transient feedback circuit 118 includes a fast transient current sense element 128 communicatively coupled to the voltage regulation control input path 115.
• the fast transient current sense element 128 receives the voltage regulation control input signal 114 and generates a fast transient feedback sense current ISENSE F. ISENSE F is proportional to the magnitude of current flow through the pass element 110.
• the fast transient feedback circuit 118 of the current-limiting apparatus 100 includes a first current comparator 135 communicatively coupled to the output of the fast transient current sense element 128.
• the first current comparator 135 compares ISENSE F to a first reference current I(REF F) and generates a first current clamp control signal CC F.
• Some embodiments of the fast transient feedback circuit 118 include a current mirror 210, as shown in FIG. 2 for the current-limiting apparatus 200.
• the current mirror 210 is communicatively coupled between the fast transient current sense element 128 and the first current comparator 135.
• the current mirror 210 generates a first attenuated sense current of ratio 1/N(ISENSE_F) for comparison to the first reference current I(REF F).
• the fast transient feedback circuit 118 includes a first over-current clamp 150 communicatively coupled to an output of the first current comparator 135.
• the first over-current clamp 150 receives the first current clamp control signal CC F. Responsive to CC F, the first over-current clamp 150 conducts to clamp the voltage regulator control input path 115 and to decrease the magnitude of the voltage regulation control input signal 114. The magnitude of current flow through the pass element 110 associated with the over-current condition decreases as a result.
• the current-limiting apparatus 100 and 200 include a precision feedback circuit 124, which is communicatively coupled to the voltage regulation control input path 115.
• the precision feedback circuit 124 receives the voltage regulation control input signal 114 as representative of the magnitude of current flow through the pass element 110/pass transistor 215.
• the precision feedback circuit 124 operates in parallel with the fast transient feedback circuit 118 to decrease the magnitude of the voltage regulation control input signal 114 in an over-current condition. Although slower to react, the precision feedback circuit 124 can more accurately control the over-current condition than control provided by the fast transient feedback circuit 118.
• the precision feedback circuit 124 effects more precise control by correcting for one or more component characteristic mismatches between the pass element 110/pass transistor 215 and one or more components of the precision feedback circuit 124.
• the precision feedback circuit 124 includes a precision current sense element 155.
• the precision current sense element 155 is implemented using a geometrical size that is an integer semiconductor finger fraction of the pass element 110/pass transistor 215. Doing so can enhance characteristic matching between the precision current sense element 155 and the pass element 110/pass transistor 215.
• the precision current sense element 155 is communicatively coupled to the voltage regulation control input path 115.
• the precision current sense element 155 receives the voltage regulation control input signal 114 and generates a precision feedback current sense signal ISENSE PS.
• ISENSE PS is proportional to the magnitude of current flow through the pass element 110/pass transistor 215.
• the precision feedback circuit 124 of the current-limiting apparatus 100 includes an element matching circuit 158.
• a first input 160 of the element matching circuit 158 is communicatively coupled to the output of the precision current sense element 155.
• a second input 161 is communicatively coupled to a voltage regulation output path 162.
• a negative feedback element 165 is communicatively coupled between an output 168 of the element matching circuit 158 and the first input 160.
• the inner feedback loop 173 so formed causes a signal at the first input 160 to track the voltage at the regulation output path 162.
• One or more component characteristic mismatches between the pass element 110 and the precision current sense element 155 are compensated via the inner feedback loop 173.
• the current-limiting apparatus 200 includes a component characteristic-matching inner loop 230 in place of the loop 173 of the current- limiting apparatus 100.
• the apparatus 200 includes a signal comparator 235 with a first input 240 communicatively coupled to an output of the precision current sense element 155.
• a second input 241 is communicatively coupled to the voltage regulation output path 162.
• the precision feedback circuit 124 includes a negative feedback element 165 communicatively coupled between an output of the signal comparator 235 and the first input 240.
• the inner loop 230 causes a signal at the first input 240 to track the voltage at the regulator output path 162. Doing so compensates for characteristic mismatches between the pass transistor 215 and the precision current sense element 155.
• the signal comparator 235 generates a precision feedback sense current ISENSE P.
• Some embodiments of the precision feedback circuit 124 include a current ratio apparatus 250 coupled to the output of the signal comparator 235.
• the current ratio apparatus 250 divides ISENSE_P by a factor N to yield a second attenuated sense current 1/N(ISENSE_P).
• the current ratio apparatus 250 can be implemented using one or more current mirrors, geometrical finger size ratios between interconnected stages, and other methods.
• the precision feedback circuit 124 includes a second current comparator 180.
• the second current comparator 180 is communicatively coupled to an output 168 of the element matching circuit 158 in the case of the current- limiting apparatus 100 of FIG. 1.
• the second current comparator 180 is communicatively coupled to an output of the signal comparator 235 or to the output of the current ratio apparatus 250 in the case of the current- limiting apparatus 200 of FIG. 2.
• Either the precision feedback sense current ISENSE P or the second attenuated feedback sense current 1/N(ISENSE_P), as applicable, is compared to a second reference current I(REF P).
• a second current clamp control signal CC P is generated at the output of the second current comparator 180 in the event of an over-current condition.
• the precision feedback circuit 124 includes a second over-current clamp 185 communicatively coupled to the second current comparator 180.
• the second over-current clamp 185 receives the second current clamp control signal CC P and decreases the magnitude of the voltage regulation control input signal 1 14.
• the magnitude of over-current flow through the pass element 110 of the current- limiting apparatus 100 (FIG. 1) and/or through the pass transistor 215 of the current- limiting apparatus 200 (FIG. 2) is decreased as a result.
• FIG. 3 is a circuit diagram of electronic current-limiting apparatus 300, according to example embodiments.
• the current- limiting apparatus 300 includes a pass transistor 215.
• the pass transistor 215 receives a voltage regulation control input signal 114 at a gate terminal 310.
• the pass transistor 215 allows a magnitude of current flow through a current channel associated with the pass transistor 215 that is proportional to the magnitude of the voltage regulation control input signal 114.
• the current-limiting apparatus 300 includes a fast transient feedback circuit 315 and a precision feedback circuit 318.
• the fast transient feedback circuit 315 and the precision feedback circuit 318 operate in parallel to first control the fastest rise-time current transients and then to more precisely control over-current as the precision feedback circuit 318 engages.
• the fast transient feedback circuit 315 is communicatively coupled to the voltage regulation control input path 115 to receive the voltage regulation control input signal 114.
• the fast transient feedback circuit 315 interprets the magnitude of current flow through the pass transistor 215 from the magnitude of the voltage regulation control input signal 114.
• the fast transient feedback circuit 315 decreases the magnitude of the voltage regulation control input signal 114 in an over-current condition, thereby decreasing drive to the pass transistor 215 and alleviating the over-current condition.
• the fast transient feedback circuit 315 includes a fast transient current sense transistor 322 gate-coupled to the voltage regulation control input path 115.
• the current sense transistor 322 receives the voltage regulation control input signal 1 14 and generates a fast transient sense current ISENSE F.
• ISENSE F is proportional to the magnitude of current flow through the pass transistor 215.
• the fast transient feedback circuit 315 includes an N-ratio current mirror 325 communicatively coupled to the fast transient current sense transistor 322.
• the N-ratio current mirror 325 receives ISENSE F at a current mirror source transistor 328.
• the current mirror 325 generates a first attenuated sense current 1/N(ISENSE_F) through a current channel of a current mirror output transistor 333. Either ISENSE F, or 1/N(ISENSE_F) in the case of a current mirror 325 implementation, is compared to a first reference current I(REF F).
• the first reference current I(REF F) is generated by a first reference current source 337.
• the first current reference source 337 in coupled in series with the current channel of the current mirror output transistor 333.
• the fast transient feedback circuit 315 includes a first over-current clamp transistor 340.
• the first over-current clamp transistor 340 is gate-coupled to a node 341 between the first reference current source 337 and the current channel of the current mirror output transistor 333.
• the first attenuated sense current 1/N(ISENSE_F) exceeds the first reference current I(REF F), causing the gate 343 of the clamp transistor 340 to be pulled low.
• the first over-current clamp transistor 340 accordingly conducts and clamps the voltage regulation control input signal 114 on the input path 115.
• the gate 310 of the pass transistor 215 is clamped for decreasing the magnitude of current flow through the pass transistor 215 and thereby alleviating the over-current condition.
• the current- limiting apparatus 300 includes a precision feedback circuit 318, which is communicatively coupled to the voltage regulation control input path 115 to receive the voltage regulation control input signal 114.
• the precision feedback circuit 318 decreases the magnitude of the voltage regulation control input signal 114 in an over-current condition more accurately than control provided by the fast transient feedback circuit 315.
• the precision feedback circuit 318 operates more accurately by compensating for one or more component characteristic mismatches between the pass transistor 215 and the precision feedback circuit 318.
• the precision feedback circuit 318 includes a precision current sense transistor 350 communicatively coupled to the voltage regulation control input path 115.
• the precision current sense transistor 350 receives the voltage regulation control input signal 114 as representative of the magnitude of current flow through the pass transistor 215.
• the precision current sense transistor 350 generates a precision feedback current sense signal ISENSE PS proportional to the magnitude of current flow through the pass transistor 215.
• the precision current sense transistor 350 is fabricated to result in a geometrical size that is an integer semiconductor finger fraction of the pass transistor 215. Doing so can enhance characteristic matching between the two devices.
• the precision feedback circuit 318 includes an OTA 355.
• a first input 358 of the OTA 355 is communicatively coupled to an output of the precision current sense transistor 350.
• a second input 362 of the OTA 355 is communicatively coupled to a voltage regulation output path 162.
• the OTA 355 generates a precision feedback sense current ISENSE P on output 368.
• the precision feedback circuit 318 includes a characteristic matching feedback transistor 365.
• the feedback transistor 365 is gate-coupled to the output 368 of the OTA and is current channel coupled to the first OTA input 358.
• the OTA 355 and the feedback transistor 365 operate as an inner component matching loop 372 within the precision feedback circuit 318.
• the inner matching loop 372 causes a signal at the first OTA input 358 to track the regulator output voltage and to thereby compensate for one or more component characteristic mismatches between the pass transistor 215 and the precision current sense transistor 350.
• the precision feedback circuit 318 includes a second reference current source 375.
• the second reference current source 375 generates a second reference current I(REF P).
• a precision loop transistor 380 is gate-coupled to the output 368 of the OTA 355 and is channel-coupled between a voltage rail 383 and the second reference current source 375.
• the precision loop transistor 380 receives ISENSE P at its gate 385 and generates a second attenuated sense current 1/N(ISENSE_P) for comparison to the second reference current I(REF P).
• the precision feedback circuit 318 includes a second over-current clamp transistor 390.
• the clamp transistor 390 is gate-coupled to a node 392 between the second reference current source 375 and the current channel of the precision loop transistor 380.
• the clamp transistor 390 is driven to conduct during an over-current condition when the second attenuated sense current 1/N(ISENSE_P) is greater than the second reference current I(REF P), causing the node 392 to be pulled low. Conduction of the clamp transistor 390 decreases the magnitude of the voltage regulation control input signal 114. Excess current flow through the pass transistor 215 associated with the over-current condition decreases as a result.
• the current-limiting apparatus 300 as described and shown in FIG. 3 is implemented with PMOS and NMOS transistors suitable for the voltage rails V(IN) 395 and ground 383.
• NMOS and PMOS transistors are suitable for other voltage rail pairs, and transistor types other than MOSFET (e.g., bipolar transistor types) are possible.
• FIG. 4 is a block diagram of a current-limited voltage regulator 400, according to example embodiments.
• the current-limited voltage regulator 400 includes the elements associated with the current-limiting apparatus 200, arranged as described in connection with
• the current-limited voltage regulator 400 includes a voltage divider 410.
• the voltage divider 410 is communicatively coupled between an output 162 of the voltage regulator 400 and a voltage rail 383 to provide an output voltage sense signal V(SENSE).
• the voltage regulator 400 includes a voltage regulation error amplifier 420 communicatively coupled to the voltage divider 410.
• the error amplifier 420 receives V(SENSE), compares V(SENSE) to a reference voltage input V(REF), and generates the voltage regulation control input signal 114.
• Apparatus described herein are potentially useful in applications other than current-limited voltage regulation apparatus.
• Examples of the electronic current- limiting apparatus 100, 200 and 300, and of the current-limited voltage regulation apparatus 400 provide a general understanding of structures of various embodiments, which may be incorporated into semiconductor analog and digital circuits for use in receptacle power converters, electronic circuitry used in computers, communication and signal processing circuitry, single-processor or multi-processor modules, single or multiple embedded processors, multi-core processors, data switches, and application-specific modules including multi-layer, multi-chip modules, among others.
• Such apparatus and systems may further be included as sub-components within a variety of electronic systems, such as televisions, cellular telephones, personal computers (e.g., laptop computers, desktop computers, handheld computers, tablet computers), workstations, radios, video players, audio players (e.g., MP3 (Motion Picture Experts Group, Audio Layer 3) players), vehicles, medical devices (e.g., heart monitor, blood pressure monitor), set top boxes, and others.
• televisions e.g., laptop computers, desktop computers, handheld computers, tablet computers
• workstations e.g., radios, video players, audio players (e.g., MP3 (Motion Picture Experts Group, Audio Layer 3) players), vehicles, medical devices (e.g., heart monitor, blood pressure monitor), set top boxes, and others.
• MP3 Motion Picture Experts Group, Audio Layer 3
• apparatus implement a fast transient precision current limiter, such as may be included in an electronic voltage regulator.
• the current limiter includes two current sense element/current clamp control loops.
• a fast response time control loop first engages and clamps a current spike.
• a precision control loop then engages to more accurately clamp the output current to a programmed set point by matching component electrical characteristics of a precision current sense element to those of a pass element, including a pass transistor.
• Each of the control loops includes a current sense element coupled to a voltage regulation control input.
• Voltage regulation control circuitry senses the over-current condition as a voltage drop at the voltage regulator output terminals.
• the voltage regulation control circuitry responds by increasing the magnitude of a voltage regulation control drive signal to a pass element through which current from the voltage regulator flows to the load. Accordingly, large increases in the voltage regulation control drive signal are indicative of an over-current condition.
• the sense elements associated with the two current-limiting control loops sense large increases in the voltage regulation control drive signal as over-current conditions.
• the precision control loop includes an inner loop to linearize the precision current sense element.
• the inner loop forces the drain-to-source voltage (VDS) of the precision sense element to track the VDS of the regulator pass element. A more precise clamping operation results. Overall speed is not sacrificed as the fast response time control loop operates in parallel to protect circuitry while the precision control loop engages.
• the linearization loop includes an element matching circuit which may, in some embodiments, be implemented as a signal comparator, such as an operational transconductance amplifier (OTA).
• OTA operational transconductance amplifier
• the linearization loop effectively causes the precision current sense element to follow the VDS of the regulator output pass element.
• the comparator generates a more accurate precision sense signal to be compared to a precision reference source representing the selected clamping point. A more precise clamping operation results. Overall speed is not sacrificed, because the fast response time clamping loop operates in parallel to protect circuitry while the precision clamping loop engages.

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• Automation & Control Theory (AREA)
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• Continuous-Control Power Sources That Use Transistors (AREA)

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• 2013
  • 2013-05-28 US US13/903,736 patent/US9793707B2/en active Active
• 2014
  • 2014-05-28 EP EP14804381.3A patent/EP3005012A4/en active Pending
  • 2014-05-28 CN CN201480029067.6A patent/CN105229551A/zh active Pending
  • 2014-05-28 JP JP2016516785A patent/JP6585037B2/ja active Active
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