JP2010207068A - Power supply apparatus and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply apparatus capable of being made compact. <P>SOLUTION: A power supply apparatus includes an inductor (L1) one end of which is connected to an input terminal side, a switching element (Q1) connected between the other end of the inductor and a reference potential, a switching element (Q2) connected to the other end of the inductor, and a capacitor (C1) connected between the switching element Q2 to serve as an output terminal side and the reference potential. The switching elements Q1 and Q2 are configured by a GaN-based transistor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply device such as a DC-DC converter (direct current voltage converter) and an electronic device including the power supply device, and more particularly to a power supply device and an electronic device that can be reduced in size.

  A battery is used as a power source for mobile phones, digital cameras, game machines and other portable electronic devices. For example, batteries such as lithium ion and lithium polymer are widely used because they are compact and have a long life. In addition, the driving voltage for operating each unit in the electronic device is diversified. For this reason, it is necessary to increase or decrease the voltage supplied from a battery or the like to generate the required driving voltage.

  FIG. 1A shows a general boost chopper type circuit. A coil (inductor) L and a diode D are connected in series with the battery B, and a transistor Q and a capacitor C are connected in parallel with the battery B, respectively. The transistor Q is turned on and off in response to a PWM signal from a PWM circuit (not shown), energy is stored in the coil L when the transistor Q is turned on, and energy is released from the coil L when the transistor Q is turned off, The boosted voltage Vout superimposed on the voltage Vb of the battery B is output.

  FIG. 1B is a general step-down chopper type circuit. A transistor Q and a coil L are connected in series with the battery B, and a diode D and a capacitor C are connected in parallel with the battery B. The transistor Q switches in response to the PWM signal. When the transistor Q is turned on, energy is stored in the coil L. When the transistor Q is turned off, energy is released from the coil L, and the stepped down voltage Vout is output. The These techniques are disclosed in Patent Document 1, for example.

  Further, Patent Document 2 boosts the input voltage when an output voltage higher than the input voltage of the battery is required, and reduces the input voltage when a voltage lower than the input voltage is required. A buck-boost switching regulator is disclosed.

JP 2000-253653 A JP-A-2005-117828

  However, in a conventional DC-DC converter composed of a chopper circuit or the like, the size of inductors and capacitors as circuit components is large, which has been an obstacle to miniaturization of the power supply device. In particular, since the switching transistor is composed of an FET using a silicon substrate, the switching frequency is limited. For this reason, it has been difficult to reduce the size and space of portable telephones and other electronic devices that need to be equipped with such a power supply device.

  It is an object of the present invention to provide a power supply device that can be reduced in size and an electronic apparatus equipped with such a power supply device.

  A power supply device according to the present invention includes an inductor having one end connected to the input terminal side, a first switching element connected between the other end of the inductor and a reference potential, and a first switch connected to the other end of the inductor. 2 switching elements, a control circuit for controlling driving of the first and second switching elements, a capacitor connected between the second switching element on the output terminal side and the reference potential, The second switching element is an FET transistor formed of a GaN-based compound.

  Preferably, a control signal for driving at a frequency of 1 MHz or more is input to the gate of the first switching element. Preferably, the inductor, the first and second switching elements, the control circuit and the capacitor are modularized and accommodated in one package. Preferably, the package is a surface mount package.

  The power supply device according to the present invention is connected between the first switching element having one end connected to the input terminal side, the other end of the first switching element and the reference potential, and is turned on when the first switching element is off. A second switching element; an inductor having one end connected to the other end of the first switching element; a control circuit for controlling driving of the first and second switching elements; and the other end of the inductor on the output terminal side And a capacitor connected between the reference potential, and the first and second switching elements are FET transistors formed of a GaN-based compound.

  Preferably, a control signal for driving at a frequency of 1 MHz or more is input to the gate of the first switching element. Preferably, the inductor, the first and second switching elements, the control circuit and the capacitor are modularized and accommodated in one package. Preferably, the package is a surface mount package.

  Furthermore, the power supply device according to the present invention includes a first inductor having one end connected to the input terminal side, a first switching element connected between the other end of the first inductor and a reference potential, and the first A first diode having an anode connected to the other end of the inductor, a first capacitor connected between the cathode of the first diode and a reference potential, and one end on the cathode side of the first diode. A second switching element to be connected, a second diode connected between the other end of the second switching element and a reference potential and turned on when the second switching element is off; and the other end of the switching element And a second capacitor connected between the other end of the second inductor on the output terminal side and a reference potential, and the first and second switches. Wherein the switching element is a FET transistor formed in a GaN-based compound.

  Preferably, a control signal that is driven at a frequency of 1 MHz or more is input to the gate elements of the first and second switching elements. Preferably, the first and second inductors, the first and second switching elements, the first and second diodes, and the first and second capacitors are modularized and accommodated in one package. A heat dissipation surface is formed on at least one of the first surface and the second surface, and the input terminal, the output terminal, and the reference potential are provided as external terminals.

  According to the present invention, it is possible to increase the frequency of the control signal for the switching element and to drive the switching element at a higher speed than the conventional power supply device, so that the inductance is reduced by reducing the winding of the inductor and reducing the ferrite core. (Inductance = AL value × winding square) can be reduced, and the inductor itself can be miniaturized. Furthermore, since the ripple is reduced, the capacitance of the capacitor can be reduced, and the capacitor can be modularized. Therefore, the power supply device can be made smaller and lighter than the conventional power supply device, and the electronic device on which the power supply device is mounted can also be reduced in size.

  By reducing the size of the inductor and the capacitor as described above, it becomes easy to modularize the circuit components including these, and the modularized package can be easily mounted on the circuit board. In particular, by modularizing a surface mounting package, the package can be automatically mounted on a circuit board by a mounter. Further, by modularizing the power supply device, it is only necessary to form at least the input terminal, the output terminal, and the reference potential terminal (ground) as external terminals, so that the package can be downsized. Furthermore, heat radiation can be promoted by adding a heat sink.

  By using heat-dissipating parts attached to the board, convex parts or parts of the casing of electronic equipment, convex parts of the lid, etc. It is possible to further reduce the size.

FIG. 1A is a diagram illustrating a configuration of a general chopper type booster circuit, and FIG. 1B is a diagram illustrating a configuration of a general chopper type step-down circuit. 2A and 2B are circuit diagrams showing the configuration of the power supply device according to the embodiment of the present invention. It is a circuit diagram which shows another structure of the power supply device in the Example of this invention. It is a circuit diagram which shows the structure of the drive control part of the switching element shown in FIG. 2, FIG. It is sectional drawing which shows the structural example of GaN-FET. 6A and 6B are diagrams illustrating an example of a package configuration of a power supply device mounted on an electronic device. It is a figure which shows the example of the other package structure of a power supply device. It is a figure which shows the example of the other package structure of a power supply device. It is a figure which shows the example of the module of a power supply device. It is sectional drawing which shows the example of SiCMOSFET used for a switching element.

  The best mode for carrying out the present invention will be described in detail with reference to the drawings. Here, an example of a power supply device as a DC-DC converter capable of converting an output voltage of an input voltage such as a battery using a step-up chopper circuit, a step-down chopper circuit, and a step-up / step-down chopper circuit will be described.

  2 and 3 are circuit diagrams showing a configuration of a power supply device as a DC-DC converter according to an embodiment of the present invention. 2A, 2B, and 3 are circuit diagrams in the case where a power supply device as a DC-DC converter is realized by a step-up chopper circuit, a step-down chopper circuit, and a step-up / step-down chopper circuit, respectively.

  As shown in FIG. 2A, a power supply device 10 using a boost chopper circuit includes an inductor L1 having one end connected to an input terminal Vin, a switching element Q1 connected between the other end of the inductor L1 and a reference potential G, A switching element Q2 connected in series to the other end of the inductor L1, a capacitor C1 connected between the output terminal Vout and the reference potential G, and a control circuit 40 that controls switching of the switching elements Q1, Q2 are included. Is done.

  An input voltage Ein supplied from a battery or a device such as a power supply in the previous stage is supplied between the input terminal Vin on the main current side and the reference potential terminal G (GND), and the output terminal Vout on the main current side and the reference potential terminal A load is connected between G. A capacitor can be connected to the input side.

  The switching elements Q1 and Q2 are transistors formed of a GaN-based compound. In this embodiment, an example of an n-type field effect transistor (FET) is shown. The drain as one end of the switching element Q1 is connected to the inductor L1, and the source as the other end of the switching element Q1 is connected to the reference potential G. A pulse width modulation signal (PWM signal) as a control signal from the control circuit 40 described later is input to the gate of the transistor as the control terminal of the switching element Q1, and the transistor as the switching element Q1 is switched by this PWM signal. That is, on / off control is performed. Similarly, the drain of the switching element Q2 is connected to the inductor L1, the source is connected to the output terminal Vout, and the pulse width modulation signal (PWM signal) as a control signal from the control circuit 40 is input to the gate. The switching element Q2 performs the same function as that of the diode shown in FIG. 1, but since the FET is used, the current loss can be made smaller than that of the diode.

  FIG. 4 is a block diagram illustrating an internal configuration example of the control circuit 40. The control circuit 40 includes a monitor voltage detection unit 41 that detects a monitor voltage such as an output voltage for feedback control, and a PWM signal generation unit 42 that generates a PWM signal for on / off control of the switching element Q1 using the monitor voltage. Consists of including. The monitor voltage detector 41 includes a resistor that divides the output voltage, and outputs a voltage corresponding to the divided result as a monitor voltage.

  The PWM signal generation unit 42 includes an error amplifier 421 that outputs an error voltage obtained by amplifying an error between the monitor voltage and the reference voltage, a transmission circuit 422 that generates a triangular wave having a set frequency, and an inclination with respect to a change in time axis. A PWM signal generation circuit 423 that compares the inclination level of the triangular wave and the error voltage to generate a PWM signal having a duty according to the error.

  In FIG. 5, the structural example of GaN-FET50 as a transistor formed with the GaN-type compound is shown in a cross section. As shown in the figure, a GaN-FET 50 includes, for example, a SiC or sapphire substrate 51, a GaN layer epitaxially grown thereon or a GaN-based semiconductor layer 52 having a heterostructure of AlGaN and GaN, and a GaN-based semiconductor layer. A source electrode 53 and a drain electrode 54 formed on 52, a thermal oxide film 56 formed by thermally oxidizing the GaN-based semiconductor layer 52, an insulating film 57 formed thereon, and an insulating film 57 The gate electrode 55 formed and the element isolation region 58 are included. FIG. 5 is an example of a typical GaN-FET.

  In this embodiment, by adopting a transistor formed of a GaN-based compound as the switching elements Q1 and Q2, the frequency of the triangular wave, that is, the frequency of the PWM signal can be increased. For example, the switching frequency of a transistor using a silicon substrate is about several tens of KHz to one hundred KHz, whereas the switching frequency of a GaN-based transistor can be 1 MHz or more, for example, it should be increased to about several tens of MHz. Can do.

  In the power supply device 10 with the boost chopper circuit configured as described above, if the output voltage Eout output between the output terminals Vout-G is the input voltage Ein between the input terminals Vin-G and the duty D of the PWM signal, Eout = Ein / (1-D).

  Next, the power supply device 20 using the step-down chopper circuit shown in FIG. The power supply device 20 includes a switching element Q1 having one end connected to the input terminal Vin side, a switching element Q2 connected between the switching element Q1 and a reference potential G (GND), and turned on when the switching element Q1 is off. An inductor L2 having one end connected to the other end and a capacitor C2 connected between the other end of the inductor L2 on the output terminal Vout side and the reference potential G are configured.

  Similarly to the power supply device 10, the power supply device 20 is also supplied with an input voltage Ein supplied from a device such as a battery or a previous power supply between the input terminal Vin on the main current side and the reference potential terminal G (GND). A load is connected between the output terminal Vout on the current side and the reference potential terminal G.

  Similarly to the power supply device 10, the switching element Q1 of the power supply device 20 is a transistor formed of a GaN-based compound, and an example thereof is a field effect transistor (FET). Therefore, one end of the switching element Q1 is the drain of the transistor, and the other end of the switching element Q1 is the source of the transistor. The control terminal of the switching element Q1 is a gate of a transistor, and a pulse width modulation signal (PWM signal) as a control signal from the control circuit 40 is input to this gate, and the PWM signal is used as the switching element Q1. These transistors are on / off controlled. Similarly to the case of the power supply device 10, the frequency of the transistor as the switching element Q1 can be set to 1 MHz or higher, for example, as high as several tens of MHz. The switching element Q2 is obtained by replacing the diode shown in FIG. 1, and the switching element Q2 can also be composed of a GaNFET.

  In the power supply device 20 using the step-down chopper circuit configured as described above, if the output voltage Eout output between the output terminals Vout and G is the input voltage Ein between the input terminals Vin and G and the duty D of the PWM signal, Eout = Ein x D.

  As shown in FIG. 3, the power supply device 30 using the step-up / step-down chopper circuit includes the power supply device 10 using the step-up chopper circuit described in FIG. 2A and the power supply device 20 using the step-down chopper circuit described in FIG. Are combined as the first stage (input side) and the second stage (output side), respectively.

  Similarly to the power supply apparatus 10 and the power supply apparatus 20, the power supply apparatus 30 is also supplied with an input voltage between the input terminals Vin-G and a load connected between the output terminals Vout-G. A transistor formed of a GaN compound is a field effect transistor (FET) as an example. As a result, it is driven by a PWM signal having a frequency of 1 MHz or more, for example, up to about several tens of MHz.

  The switching elements Q1 and Q2 shown in FIGS. 2 and 3 are driven by the control circuit 40, but need to be driven and controlled by adjusting the timing of the switching elements Q1 and Q2 (not shown). As an example of drive control, the step-up / step-down chopper circuit is driven and controlled in the determined operation mode by determining the boost mode, the step-down mode, and the step-up / step-down mode based on the detected output voltage in relation to the input voltage. For example, in the boost mode, one of the switching elements Q1 is always turned on, and the other switching element is turned on / off. In the step-down mode, one switching element is always turned off, and on / off control is performed on the other switching element. In the step-up / step-down mode, the two switching elements are both turned on / off. The switching element Q2 is switching-controlled so as to function in the same manner as the diode of FIG.

  Thus, since the power supply devices 10, 20, and 30 in this embodiment are driven by a PWM signal having a high frequency of 1 MHz or more, the inductor windings can be reduced and the size of the ferrite core used therefor can be reduced. As a result, the inductor itself can be made smaller. Further, since the ripple is reduced, the capacitance of the capacitor can be reduced as compared with the conventional case. As a result, it is possible to reduce the size of a relatively large circuit component so far. Thus, one semiconductor device or one semiconductor module in which an inductor and a capacitor are also built-in can be configured.

  6A and 6B show a mounting example in which the power supply device 60 of the present embodiment is applied to the electronic device 70. FIG. The mobile phone or other electronic device 70 includes a power supply device 60 integrated as a microchip including a package such as a ball grid array (BGA), and a plurality of balls formed on the back surface of the package include solder or the like. It is mounted on the substrate 61 using A heat generating component surface such as a switching element such as a transistor is disposed on at least one side of the first surface (front surface) and the second surface (back surface) of the power supply device 60. As shown in FIG. 5A, the heat radiating member 62 provided on the substrate 61 is fixed to be in contact with the second surface (mounting surface) side as the heat radiating surface of the power supply device 60. The heat radiating member 62 can come into contact with a heat radiating component (for example, a bracket or a plate) attached to the substrate 61. Further, as shown in FIG. 5B, a part of the metal lid 63 of the electronic device 70 is brought into contact with the first surface (front surface) as the heat radiating surface of the power supply device 60 as the heat radiating surface 64. May be. The heat radiating member is made of a metal such as aluminum or copper having a high thermal conductivity, for example. In addition, when a part of housing | casing of the electronic device 70 is planar, the power supply device 60 may be made into a convex shape and may be made to contact, and heat conduction may be made favorable. Furthermore, in the example shown in FIGS. 6A and 6B, the heat dissipation surface is formed on one side of the package, but the heat dissipation surface may be formed on both sides of the package.

  Since the modularized power supply apparatus 60 incorporates the control circuit 40 and the like, its external connection terminals are three terminals of an input terminal Vin, an output terminal Vout, and a reference potential terminal G (GND). Can be made smaller.

  FIG. 7 shows a configuration example of another power supply device 60. As shown in FIGS. 7A and 7B, the power supply device 60A is modularized into a surface mount package having a resin package main body 70 and external leads 72 extending from both sides of the main body 70 in a gull wing shape. Is done. The package may be in various forms such as TSOP, SOP, and QFP. Preferably, the package is large enough to be automatically mounted on a circuit board by a surface mounting mounter. Further, it may be a package having electrodes or lands instead of external leads. In the package 70 shown in FIG. 7B, the switching elements Q1 and Q2, the control circuit, and the inductor are modularized. Three external leads 72 extend from both sides of the package 70. Three of them are leads (NC) that are not internally connected.

  Further, as shown in FIG. 7C, the power supply device 60 </ b> B includes a discrete type package having a package main body 74, three external leads 76 projecting from the lower portion of the package main body 74, and a heat sink 78. It is also possible. The external lead 76 described above is electrically connected to the DC-DC converter by a bonding wire or the like within the package body.

  Although the example shown in FIG. 7 shows an example of a three-terminal external lead, the power supply device may have a four-terminal or five-terminal configuration. As shown in FIG. 8A, the power supply device 60C includes four terminals including an external terminal 76A. For example, the external terminal 76 </ b> A can supply an external control signal for switching on / off of the control circuit 40 to the control circuit 40. Furthermore, as shown in FIG. 8B, the power supply device 60D includes five terminals including external terminals 76A and 76B. In this case, the external terminal 76B can be used for voltage adjustment of the output voltage Vout, and functions as an external terminal for supplying the output voltage Vout to the control circuit 40. This voltage adjustment function does not necessarily need to be executed in a 5-terminal power supply device, but may be executed in a 4-terminal power supply device as shown in FIG. Further, the package having the 4-terminal or 5-terminal external leads shown in FIGS. 8A and 8B may be a surface mounting package as shown in FIG. 6 or FIG.

  FIG. 9 is a diagram illustrating various module examples of the power supply device. The power supply device shown in FIG. 9A is an example in which the inductor, the switching element FET, and the control circuit are modularized, and the power supply device shown in FIG. 9B is an example in which the output capacitor is further modularized. In the case of a configuration including an input capacitor in the input stage of the DC-DC converter, an example is shown in which the power supply device can be modularized including the input capacitor, as shown in FIG. A ceramic capacitor having a small capacity and size can be used as a modularized capacitor.

  In the conventional power supply device, it is possible to reduce the size by increasing the switching frequency of the FET using the silicon substrate. However, when the frequency is increased, power loss due to switching is large, which is not practical. On the other hand, in the GaN-based FET as in this embodiment, not only the on-resistance is lower than the silicon FET, but also the gate input capacitance (Ciss) and the source-drain output capacitance (Coss) are remarkably high. Therefore, the power loss is smaller than that of the silicon FET, and the switching frequency can be increased to MHz. Furthermore, if the switching frequency of the GaN-based FET can be increased to about 10 MHz, the power loss due to switching can be reduced to an almost negligible level. In addition, since the inductor windings can be reduced and the ferrite core can be made smaller, the inductance (inductance = AL value × winding square) can be reduced, and the inductor itself can be reduced in size. A modularized power supply device for surface mounting can be obtained. In this case, since the ripple is also reduced, the capacitance of the capacitor can be reduced, and a power supply device in which the capacitor, the control circuit, and the inductor are modularized can be obtained. By modularizing the power supply device in the surface mounting package, the power supply device can be automatically mounted on the circuit board by the mounter. For this reason, the productivity of the electronic device including the power supply device can be improved, and the electronic device can be reduced in size and weight.

In the above-described embodiment, an example in which the switching transistor is configured by a GaN-based FET has been described. However, it is also possible to configure the switching transistor from a MOSFET made of SiC (silicon carbide, silicon carbide). SiC has a wider band gap, higher dielectric breakdown voltage, and better thermal conductivity than Si. For this reason, the SiC power MOSFET has higher conversion efficiency than the silicon MOSFET, and can reduce the loss by about half. As shown in FIG. 11, in the SiC MOSFET 100, for example, an n-type SiC drift layer 104 is formed by epitaxial growth on an n-type SiC substrate 102, and a pair of p-type base regions 106 are formed in the drift layer 104. formed, the n-type source region 108 is formed in the base region 106, on the SiC substrate surface to form a gate oxide film 110 of SiO ₂ or the like, then, to form the gate electrode 112 and source electrode 114.

As the switching transistor, a MOS transistor in which MoO ₃ (molybdenum oxide) is formed on a silicon substrate can be used.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Deformation / change is possible.

10, 20, 30, 60, 60A, 60B, 60C, 60D: power supply device 40: control circuit 41: monitor voltage detector 42: PWM signal generator 50: GaN-FET
51: substrate 52: GaN-based semiconductor layer 53: source electrode 54: drain electrode 55: gate electrode 56: thermal oxide film 57: insulating film 58: element isolation region 61: substrate 62, 64: heat dissipation member 63: lid 70: electron Devices L1, L2: Inductors Q1, Q2: Switching elements D1, D2: Diodes C1, C2: Capacitor Vin: Input terminal Vout: Output terminal G (GND): Reference potential terminal

Claims (13)

An inductor having one end connected to the input terminal side;
A first switching element connected between the other end of the inductor and a reference potential;
A second switching element connected to the other end of the inductor;
A control circuit for controlling driving of the first and second switching elements;
A second switching element on the output terminal side and a capacitor connected between the reference potential,
A power supply device, wherein the first and second switching elements are FET transistors formed of a GaN-based compound. The power supply device according to claim 1, wherein a control signal for driving at a frequency of 1 MHz or more is input to the gate of the first switching element. The power supply device according to claim 1 or 2, wherein the inductor, the first and second switching elements, the control circuit, and a capacitor are modularized and accommodated in one package. The power supply device according to claim 3, wherein the package is a surface mounting package. A first switching element having one end connected to the input terminal side;
A second switching element connected between the other end of the first switching element and a reference potential and turned on when the first switching element is off;
An inductor having one end connected to the other end of the first switching element;
A control circuit for controlling driving of the first and second switching elements;
It has a capacitor connected between the other end of the inductor on the output terminal side and a reference potential,
A power supply device, wherein the first and second switching elements are FET transistors formed of a GaN-based compound. The power supply device according to claim 5, wherein a control signal for driving at a frequency of 1 MHz or more is input to the gate of the first switching element. The power supply device according to claim 5 or 6, wherein the inductor, the first and second switching elements, the control circuit, and a capacitor are modularized and accommodated in one package. The power supply device according to claim 7, wherein the package is a surface mount package. A first inductor having one end connected to the input terminal side;
A first switching element connected between the other end of the first inductor and a reference potential;
A first diode having an anode connected to the other end of the first inductor;
A first capacitor connected between a cathode of the first diode and a reference potential;
A second switching element having one end connected to the cathode side of the first diode;
A second diode connected between the other end of the second switching element and a reference potential and turned on when the second switching element is off;
A second inductor having one end connected to the other end of the switching element;
A second capacitor connected between the other end of the second inductor on the output terminal side and a reference potential;
The power supply device, wherein the first and second switching elements are FET transistors formed of a GaN-based compound. The power supply device according to claim 9, wherein a control signal that is driven at a frequency of 1 MHz or more is input to the gate elements of the first and second switching elements. The first and second inductors, the first and second switching elements, the first and second diodes, and the first and second capacitors are modularized and housed in one package, The power supply device according to claim 9, wherein a heat dissipation surface is formed on at least one of the first surface and the second surface, and the input terminal, the output terminal, and a reference potential are provided as external terminals. An inductor having one end connected to the input terminal side;
A first switching element connected between the other end of the inductor and a reference potential;
A second switching element connected to the other end of the inductor;
A control circuit for controlling driving of the first and second switching elements;
A second switching element on the output terminal side and a capacitor connected between the reference potential,
A power supply device, wherein the first and second switching elements are SiC MOSFET transistors. A first switching element having one end connected to the input terminal side;
A second switching element connected between the other end of the first switching element and a reference potential and turned on when the first switching element is off;
An inductor having one end connected to the other end of the first switching element;
A control circuit for controlling driving of the first and second switching elements;
It has a capacitor connected between the other end of the inductor on the output terminal side and a reference potential,
A power supply device, wherein the first and second switching elements are SiC MOSFET transistors.

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