Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
  • G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
  • G05F3/02—Regulating voltage or current
  • G05F3/08—Regulating voltage or current wherein the variable is DC
  • G05F3/10—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics
  • G05F3/16—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics being semiconductor devices
  • G05F3/20—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
  • G05F3/26—Current mirrors
  • G05F3/262—Current mirrors using field-effect transistors only
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
  • H03K5/22—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral
  • H03K5/24—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude
  • H03K5/2472—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude using field effect transistors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
  • G01S17/88—Lidar systems specially adapted for specific applications
  • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/002—Switching arrangements with several input- or output terminals
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/04—Modifications for accelerating switching
  • H03K17/041—Modifications for accelerating switching without feedback from the output circuit to the control circuit
  • H03K17/0412—Modifications for accelerating switching without feedback from the output circuit to the control circuit by measures taken in the control circuit
  • H03K17/04123—Modifications for accelerating switching without feedback from the output circuit to the control circuit by measures taken in the control circuit in field-effect transistor switches
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/14—Modifications for compensating variations of physical values, e.g. of temperature
  • H03K17/145—Modifications for compensating variations of physical values, e.g. of temperature in field-effect transistor switches
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/483—Details of pulse systems
  • G01S7/484—Transmitters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/483—Details of pulse systems
  • G01S7/486—Receivers
  • G01S7/4868—Controlling received signal intensity or exposure of sensor
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K2217/00—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
  • H03K2217/0081—Power supply means, e.g. to the switch driver

Definitions

• the present invention relates generally to current driver circuits, and more particularly to a gallium nitride (GaN) field effect transistor (FET) based current driver circuit with the capability to adjust the output current based on a reference current and to maintain a constant output current for a given reference current despite changes in temperature, circuit impedances, supply voltage, and the like.
• GaN gallium nitride
• FET field effect transistor
• Typical current driver circuits include a current mirror, a driver, and a control transistor.
• the reference current input to the current mirror is replicated in the output driving current.
• the driver receives a control signal indicating the pulses for the driving current and drives the control transistor.
• the control transistor turns off or on the current mirror based on the control signal, to prevent or enable the current mirror to generate the driving current.
• FIG. 1 is a schematic of a conventional current driver circuit 100, which includes a current mirror 120, a control signal driver 140, and its corresponding control transistor 135.
• Current mirror 120 includes transistors 125 and 130.
• the drain terminal and the gate terminal of transistor 130 are connected together and receive a reference current IREF.
• the source terminal of transistor 130 is connected to ground 1 10.
• the gate terminal of transistor 125 is connected to the gate and drain terminals of transistor 130 and also receives IREF.
• the source terminal of transistor 125 is connected to ground 1 10.
• the drain terminal of transistor 125 is connected to a supply voltage node 1 15, which provides a high driving supply voltage VHV.
• Transistor 125 generates the output current of current mirror 120, the driver current IDRV, by drawing from the high driving supply voltage VHV.
• Transistor 125 acts as a driving transistor, such that when a load, e.g. a laser diode, is connected in series with the supply voltage node 1 15 and transistor 125, driving current IDRV flows through the laser diode and causes it to output a laser beam.
• Control signal driver 140 receives control signal CTL 105 and drives the gate terminal of control transistor 135, which acts as a switch controlling current mirror 120 and driving current IDRV.
• the drain terminal of transistor 135 is connected to the gate term inal of transistor 125 and the gate and drain term inals of transistor 130.
• the source term inal of transistor 135 is connected to ground 1 10.
• control transistor 135 acting as a closed switch the gate terminals of driving transistor 125 and transistor 130 are connected to ground 1 10, causing them to act as open switches and preventing reference current IREF and driving current IDRV from flowing through current mirror 120.
• control transistor 135 acting as an open switch the voltages on the gate terminals of transistor 130 and driving transistor 125 can increase above the threshold voltage VTM, turning them on and allowing current mirror 120 to generate driving current
• IDRV based on the reference current IREF.
• Some implementations of current driver circuit 100 such as a light detection and ranging (lidar) system must generate a specific value of the driving current IDRV, or a constant value of the driving current IDRV, controlled in a feedback system.
• a very large driving current IDRV and a very high pulse frequency are used to drive a laser diode and image an environment.
• the reference current IREF must be very large and quickly charge the input capacitance Ciss of driving transistor 125.
• a driving transistor 125 with a Ciss of 600 picoFarads (pF) must be charged to 5 volts (V) in one nanosecond (ns), resulting in an IREF of 3 amperes (A).
• V 5 volts
• ns nanosecond
• traces with only a single ohm (W) impedance result in a 3V drop when 3A of current passes through.
• finer control over the value of the driving current IDRV gives finer control over the intensity of light emitted by the laser diode, which enables the lidar system to adjust the light intensity based on the range of distances the lidar system is imaging.
• current driver circuit 100 a fixed voltage is applied to the gate terminal of driving transistor 125 and IREF and transistor 130 omitted, the gate-to-source voltage VGS must turn on driving transistor 125 and generate the desired driving current despite changes based on variations in temperature, circuit impedances, supply voltage as discussed above, and process variation in the transistor technology.
• the actual driving current IDRV varies greatly over temperature, circuit impedances, supply voltage, and process variation.
• Such a current driver circuit cannot be used to achieve the desired distance or range resolution required by the lidar system over all environmental or system conditions.
• the present invention addresses the disadvantages of conventional driver circuits, discussed above, by providing a current driver circuit capable of adjusting the output current based on a reference current and maintaining a constant output current for a given reference current despite changes in temperature, circuit impedances, supply voltage, and the like.
• the present invention is an adjustable current driver circuit comprising a circuit for charging a storage capacitor from a first supply voltage based on an externally provided reference current, and a pulse controller circuit, responsive to a control signal, for connecting the storage capacitor to the gate of a power transistor to drive and allow current to flow through the power transistor, or for disconnecting the storage capacitor from gate of the power transistor and connecting the gate of the power transistor to ground, to prevent current from flowing through the power transistor.
• the circuit for charging the capacitor preferably comprises a current mirror.
• the power transistor is preferably a high current, high slew-rate gallium nitride (GaN) field effect transistor (FET) connected to a second supply voltage, the second supply voltage being greater than the first supply voltage.
• the current mirror and the pulse generator circuit comprise a plurality of GaN FET transistors, all of which are substantially smaller in size than the GaN FET power transistor.
• a resistor may be connected to the pulse generator circuit and the power transistor for discharging the charge on the storage capacitor and shutting down the flow of current through the power transistor in the event that the control signal is stuck on.
• FIG. 1 illustrates schematics of a conventional current driver circuit.
• FIG. 2 illustrates an adjustable current driver circuit according to the present invention.
• FIG. 2 illustrates an adjustable current driver circuit 200 according to the present invention.
• the circuit of the present invention which can be implemented as a low-power integrated circuit, provides an adjustable output driver current for use in LiDAR or other similar GaN driver applications.
• the circuit creates an appropriate gate-to-source voltage, VGS , for a high-current GaN driver FET 295 to obtain a desired, high slew-rate output current (typically, tens of Gaga-Amps/second).
• An externally provided reference current IREF is used to create the required VGS needed for the driver FET 295.
• the VGS created by the circuit adjusts variations in process traits, temperature or supply voltage.
• the VGS voltage is stored on an external capacitor 250.
• the value of capacitor 250 far exceeds the parasitic capacitance Ciss of the large GaN driver FET 295, but is still practical in size given the low value of input capacitance for GaN FETs.
• any charge lost on capacitor 250 due to the charge transfer to driver FET 295 is replenished by the reference charging circuit ICHG, which is on the same order of magnitude as the reference current IREF, SO that the same desired rapid and large driver current can be obtained on the next command pulse to produce the next rapid and large slew-rate pulse.
• the instantaneous draw of current from the supply to charge the gate of the driver FET 295 is highly reduced due to the charge already being pre-stored in the capacitor prior to the generation of the output current pulse . This reduces supply voltage spiking.
• the circuit preferably includes a safe driver shut-down in the event the command signal gets stuck on, as described in further detail below.
• adjustable current driver circuit 200 includes current mirror 220, capacitor 250, pulse controller 270, and driving transistor 295.
• Current mirror 220 receives the reference current IREF, in this example from external current source 245, and outputs a charging current ICHG from supply voltage Vdd 215B for charging capacitor 250.
• current mirror 220 includes transistors 225, 230, 235, and 240, connected together in a conventional arrangement.
• Pulse controller 270 includes transistors 280 and 285.
• Transistors 225, 230, 235, and 240 in current mirror 220, transistors 280 and 285 in pulse controller 270, and driving transistor 295, are all preferably enhancement mode GaN FET semiconductor devices, which are all preferably monolithically integrated onto a single semiconductor die. .
• Current mirror 220 has a conventional topology, with the gate and drain terminals of transistor 225 connected together and receiving IREF, in this example from current source 245.
• the source terminal of transistor 225 is connected to the drain terminal of transistor 235.
• the gate terminal of transistor 235 is connected to the gate and drain terminals of transistor 240, and to source terminal of transistor 230, at node 255.
• the gate terminal of transistor 230 is connected to the gate and drain terminals of transistor 225.
• the drain terminal of transistor 230 is connected to supply voltage source 215B.
• the charging current ICHG is drawn from supply voltage source 215B by current mirror 220 based on the reference current IREF and charges capacitor 250 to a desired voltage that will be applied to the gate terminal of driving transistor 295.
• Changes to the value of IREF result in changes in the value of charging current ICHG and the charge stored in capacitor 250.
• Variation of IREF offers dynamic control of the voltage across capacitor 250, such that capacitor 250 can apply different voltages to the gate terminal of driving transistor 295 in response to variations in temperature, supply voltage, circuit impedances, and process variations.
• variation of IREF enables dynamic control of the driving current IDRV through driving transistor 295 by controlling the voltage applied to its gate terminal.
• the capacitance of capacitor 250 is much larger than the input capacitance Ciss of driving transistor 295 to ensure it can store charge from ICHG such that the voltage across capacitor 250 is the desired VGS for driving transistor 295.
• current mirror 220 receives the reference current IREF and generates the charging current ICHG from supply voltage source 215B to control the supply voltage Vdd available for adjustable current driver circuit 200.
• the reference current IREF is applied directly to node 255 and directly charges capacitor 250.
• the near-instantaneous energy needed for driving transistor 295 is largely drawn from the charge stored on capacitor 250, rather than from a supply voltage source, which greatly reduces supply voltage spiking from the near-instantaneous current draw from the supply voltage source.
• the reduced supply voltage spiking reduces resistive and inductive noise spikes in other pre-driver circuits as well.
• Charge drawn from capacitor 250 is replenished by ICHG while driving transistor 295 acts as an open switch.
• ICHG is a similar order of magnitude as IREF and is sufficient to recharge capacitor 250 in between pulses of transistor 295 despite its much smaller magnitude.
• the driving current IDRV pulses every microsecond (ps), and driving transistor 295 acts as a closed switch for 5 ns.
• ICHG charges capacitor 250 over the intervening 995 ns before the next pulse of driving current IDRV.
• Pulse controller 270 is connected at its input to node 255 and at its output to the gate terminal of driving transistor 295 at node 290, and receives a control signal CTL 205.
• Controller 270 includes driver 275 and transistors 280 and 285.
• Driver 275 receives CTL 205 and is connected to the gate terminals of transistors 280 and 285.
• the drain terminal of transistor 280 is connected to node 255, and the source terminal of transistor 280 is connected to the gate terminal of driving transistor 295 at node 290.
• the drain terminal of transistor 285 is connected to the gate terminal of driving transistor 295 and the source terminal of transistor 280 at node 290.
• transistor 285 acts as an open switch, disconnecting the gate terminal of driving transistor 295 from ground 210.
• Transistor 280 acts as a closed switch, connecting the gate terminal of transistor 295 to capacitor 250 at node 255. Charge stored in capacitor 250 increases the voltage on the gate terminal of driving transistor 295 above its threshold voltage VTM, causing it to turn on and generate a driving current IDRV proportional to IREF.
• transistor 280 acts as an open switch, disconnecting the gate terminal of driving transistor 295 from capacitor 250.
• Transistor 285 acts as a closed switch, connecting the gate terminal of driving transistor 295 to ground 210, and causes the gate voltage of driving transistor 295 to quickly decrease to ground.
• the drain terminal of driving transistor 295 is connected to a second supply voltage source 215A, which provides a supply voltage VHV that is much higher than the supply voltage Vdd from supply voltage source 215B.
• the source terminal of driving transistor 295 is connected to ground 210.
• the driving current IDRV is drawn from the second supply voltage source 215A.
• a resistor 260 is connected to node 290 and ground 210 as a safety feature, in the event pulse controller 270 malfunctions and causes driving transistor 295 to be turned on for more than a predetermined safety threshold length of time.
• Resistor 260 discharges capacitor 250 to zero over a period of time, in response to CTL 205 or pulse controller 270 indicating driving transistor 295 is to be turned on for more than the safety threshold length of time.
• resistor 260 reduces the gate voltage of driving transistor 295 below its threshold voltage VTM, turning off driving transistor 295 and stopping flow of driving current IDRV.
• the resistance of resistor 260 is chosen to implement the desired safety threshold length of time before driving transistor 295 is turned off.
• the reference current IREF is highly scaled down compared to the IREF input to current driver circuit 100 shown in FIG. 1 .
• the much larger driving current IDRV is drawn from the much larger supply voltage source 215A and is achieved based on the relative sizes of transistors in current mirror 220 compared to driving transistor 295.
• transistors 235 and 240 are substantially the same size, and driving transistor 295 is approximately 30,000 times the size of transistors 235 and 240.
• a driving current IDRV equal to 30 A is achieved with a reference current IREF of only 1 mA.
• IREF a small reference current IREF is sufficient to generate a driving current IDRV several orders of magnitude larger that slews on the order of tens of GA/second with a reduced impact on the supply voltage available in the integrated circuit. Varying the magnitude of IREF proportionally varies the magnitude of IDRV.
• adjustable current driver circuit as part of a lidar system, varying the magnitude of IREF proportionally varies the magnitude of IDRV and the corresponding intensity of light emitted by the laser diode driven by IDRV.
• the lidar system can carefully control the light intensity based on the range of distances it is imaging and environmental conditions.
• IDRV can be dynamically adjusted as the lidar system images the environment to accommodate changes in the environmental conditions as well. Dynamic adjustment of IDRV enables the lidar system to adjust for different distances, maintain a constant light intensity over different environmental and process conditions, and/or modulate the light intensity over time to implement a time-of-flight imaging process.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Nonlinear Science (AREA)
• Electromagnetism (AREA)
• Computer Networks & Wireless Communication (AREA)
• Remote Sensing (AREA)
• Automation & Control Theory (AREA)
• Control Of Electrical Variables (AREA)
• Electronic Switches (AREA)
• Power Conversion In General (AREA)

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• 2019
  • 2019-09-03 KR KR1020217010022A patent/KR102674752B1/ko active Active
  • 2019-09-03 US US16/558,409 patent/US10749514B2/en active Active
  • 2019-09-03 CN CN201980071354.6A patent/CN112956119B/zh active Active
  • 2019-09-03 JP JP2021512507A patent/JP7612567B2/ja active Active
  • 2019-09-03 EP EP19858441.9A patent/EP3847739A4/en active Pending
  • 2019-09-03 WO PCT/US2019/049341 patent/WO2020051138A1/en not_active Ceased
  • 2019-09-04 TW TW108131917A patent/TWI743555B/zh active

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