Patent Publication Number: US-2022221887-A1

Title: Voltage regulator and in-vehicle backup power supply

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national stage of PCT/JP2020/017930 filed on Apr. 27, 2020, which claims priority of Japanese Patent Application No. JP 2019-091925 filed on May 15, 2019, the contents of which are incorporated herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a voltage regulator and an in-vehicle backup power supply. 
     BACKGROUND 
     JP 2015-201170A discloses a voltage regulation circuit having a low-dropout voltage regulator and a current source. In this circuit, the low-dropout voltage regulator has an output unit joined to a power supply input portion of a load circuit, and is configured to provide a power supply voltage to the load circuit. The current source is joined to a power supply input portion of the load circuit and an output portion of the low-dropout voltage regulator, and provides a current to the load circuit to reduce the current provided to the load circuit by the low-dropout voltage regulator. 
     A voltage regulator such as a linear regulator has a function of outputting a predetermined output voltage based on an input voltage. However, depending on the usage environment, there may be cases where the setting of the output voltage needs to be changed in accordance with the situation. In order to meet such a demand, a plurality of voltage regulators having different output voltages may be prepared. However, simply increasing the number of voltage regulators makes an apparatus larger and more complex. 
     Therefore, it is an object of the present invention to provide a technique capable of realizing a configuration in which a value of voltage output from a voltage regulator can be set and changed, while suppressing an increase in the size of an apparatus and keeping the apparatus from being complex. 
     SUMMARY 
     A voltage regulator according to an embodiment of the present disclosure is a voltage regulator configured to receive an input voltage based on power supplied via a first conductive path, and output an output voltage to a second conductive path. The voltage regulator includes a control unit, an input circuit, a transistor, a switch and an element portion. The control unit includes a plurality of output terminals. The input circuit unit is electrically connected to the plurality of output terminals. The transistor includes a first terminal electrically connected to the input circuit unit. The switch is electrically connected to the first conductive path, the second conductive path, and the transistor. The element portion is interposed between a second terminal of the transistor and the second conductive path, wherein the control unit operates to switch a state of each of the plurality of output terminals to either a first state or a second state, the input circuit unit applies a voltage corresponding to a combination of the first states at the plurality of output terminals to the first terminal, electricity flows through the transistor when at least one of the output terminals is in the first state, the switch is turned on when electricity flows through the transistor, and the element portion sets the output voltage applied to the second conductive path to a voltage corresponding to the voltage applied to the first terminal. 
     An in-vehicle backup power supply according to an embodiment of the present disclosure, includes a power storage unit electrically connected to the above first conductive path and the above voltage regulator. Wherein, the control unit switches at least one of the plurality of output terminals to the first state in response to establishment of a backup condition. 
     Advantageous Effects of Invention 
     According to the present disclosure, it is possible to realize a configuration in which the value of the voltage output from the voltage regulator can be set and changed, while suppressing an increase in the size of an apparatus and keeping the apparatus from being complex. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a circuit diagram illustrating a configuration of a voltage regulator according to an embodiment. 
         FIG. 2  is an explanatory diagram illustrating a relationship between an output from each port and a base voltage of a transistor in the voltage regulator according to the embodiment. 
         FIG. 3  shows an electrical configuration of an in-vehicle power supply system in which the voltage regulator according to the embodiment is applied as a discharge circuit from a power storage element. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     First, embodiments of the present disclosure will be listed and described. 
     In the voltage regulator according to an embodiment of the present disclosure: 
     (1) The control unit operates to switch a state of each of the plurality of output terminals to either the first state or the second state. The input circuit unit applies a voltage corresponding to a combination of the first states at the plurality of output terminals to the first terminal. Electricity flows through the transistor when at least one of the output terminals is in the first state, and the switch is turned on when electricity flows through the transistor. The element portion sets the output voltage applied to the second conductive path to a voltage corresponding to the voltage applied to the first terminal. 
     In the voltage regulator having the above-described configuration, the value of the output voltage is not limited to a predetermined fixed value, and the output voltage value can be changed. In addition, because a configuration in which the output voltage value can be changed based on the control by the control unit without using a large number of voltage regulators is adopted, it is possible to realize a “configuration in which an output voltage value can be set and changed”, while suppressing an increase in the size of an apparatus and keeping the apparatus from being complex. 
     (2) The transistor may also be an NPN-type bipolar transistor, the first terminal may also be the base of the bipolar transistor, and the second terminal may also be the emitter of the bipolar transistor. The element portion may also be a Zener diode having a cathode electrically connected to the second conductive path and an anode electrically connected to the emitter. Further, the above voltage regulator may also include a resistor portion having one end electrically connected to the emitter and the other end electrically connected to the ground. The Zener diode may also set the output voltage applied to the second conductive path to a value corresponding to the sum of the Zener voltage of the Zener diode and the emitter voltage of the transistor. 
     This voltage regulator can stably switch the output voltage applied to the second conductive path to a value corresponding to the base voltage simply by changing the base voltage applied to the bipolar transistor, and such a configuration can be realized with a simpler element configuration. 
     (3) The first state may also be a state in which one of a high-level voltage and a low-level voltage is applied, and the second state may also be a state in which the other of a high-level voltage and a low-level voltage is applied. The input circuit unit may also include a series configuration portion in which a plurality of first resistor portions are connected in series between the first terminal and the ground, and a plurality of second resistor portions. At one end, the plurality of second resistor portions may also be electrically connected to the plurality of output terminals, respectively. Also, at the other end, the plurality of second resistor portions may also be electrically connected to a plurality of inter-element conductive paths in the series configuration portion, respectively. 
     In this voltage regulator, the voltage applied to the first terminal can be switched in stages based on the control of the plurality of output terminals by the control unit, and such a configuration can be realized with a simple configuration in which “the plurality of first resistor portions and the plurality of second resistor portions” are the main components. In addition, the control unit only has to switch the plurality of output terminals to a high-level voltage or a low-level voltage, thus the control of the control unit is also simplified. 
     (4) An in-vehicle backup power supply according to an embodiment of the present disclosure includes: a power storage unit electrically connected to the first conductive path; and the voltage regulator according to any one of (1) to (3) described above, wherein the control unit switches at least one of the plurality of output terminals to the first state in response to establishment of a backup condition. 
     This in-vehicle backup power supply has the same effects as the voltage regulator according to (1) to (3) described above. 
     Specific examples of a voltage regulator and an in-vehicle backup power supply according to the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. 
     The voltage regulator of the present disclosure will be described with reference to  FIGS. 1 and 2 . A voltage regulator  10  shown in  FIG. 1  has a configuration in which an input voltage is input based on power that is supplied via a first conductive path  91 , and an output voltage is output to a second conductive path  92 . The voltage regulator  10  includes a control unit  20 , an input circuit unit  30 , a transistor  41 , a switch  43 , a Zener diode (element portion)  45 , a resistor (resistor portion)  47 , and a resistor  49 . 
     The control unit  20  is configured as, for example, a microcomputer, and includes a memory such as a CPU, a ROM, or a RAM. The control unit  20  operates, for example, on the bases of electric power supplied from a power supply, and can operate on power that is supplied from a backup power supply even when the supply of power from the power supply is interrupted. The control unit  20  has ports (output terminals) P 1  and P 2 . The control unit  20  operates to switch a state of each of the ports P 1  and P 2  to either a first state or a second state. The first state is, for example, a state in which a voltage signal (high-level signal) of a voltage (Vcc) higher than the ground voltage (0V) is output. In other words, the first state is a state in which a predetermined high-level voltage is applied to the port (output terminal). The high-level voltage (Vcc) is, for example, 5V. Note that in this specification, the voltage means a potential difference from a ground potential (0V), unless otherwise specified. The second state is, for example, a state in which a voltage signal (low-level signal) of the ground voltage (0V) is output. In other words, the second state is a state in which a predetermined low-level voltage is applied to the port (output terminal). 
     The input circuit unit  30  is electrically connected to the ports P 1  and P 2 . The input circuit unit  30  applies a voltage corresponding to a combination of the first state and the second state of the ports P 1  and P 2  to the base (first terminal) of the transistor  41  described later. The input circuit unit  30  includes a series configuration portion  31  and resistors (second resistor portions)  37  and  39 . One end of the resistor  37  is connected to the port P 1 . The one end of the resistor  37  and the port P 1  have the same potential. One end of the resistor  39  is connected to the port P 2 . The one end of the resistor  39  and the port P 2  have the same potential. The series configuration portion  31  includes resistors (first resistor portions)  33  and  35 . The resistors  33  and  35  are connected in series between the base of the transistor  41  and the ground. One end of the resistor  33  is connected to the other end of the resistor  37  and the base of the transistor  41 . The one end of the resistor  33 , the other end of the resistor  37 , and the base of the transistor  41  have the same potential. One end of the resistor  35  is connected to the other end of the resistor  33  and the other end of the resistor  39 . The one end of the resistor  35 , the other end of the resistor  33 , and the other end of the resistor  39  have the same potential. In this manner, the other end of the resistor  37  and the other end of the resistor  39  are connected to inter-element conductive paths  93  and  94  in the series configuration portion  31 , respectively. The other end of the resistor  35  is connected to the ground, and has the ground potential. 
     The transistor  41  is configured as an NPN-type bipolar transistor. The base (first terminal) of the transistor  41  is electrically connected to the input circuit unit  30 . The collector of the transistor  41  is connected to the other end of the resistor  49  described later and the gate of the switch  43 . The collector of the transistor  41 , the other end of the resistor  49 , and the gate of the switch  43  have the same potential. The emitter (second terminal) of the transistor  41  is connected to one end of the resistor  47  described later and the anode of the Zener diode  45 . The emitter of the transistor  41 , the one end of the resistor  47 , and the anode of the Zener diode  45  have the same potential. The transistor  41  is in an electricity-flowing state when at least one of the ports P 1  and P 2  is in the first state, and allows a current to flow from the collector to the emitter. 
     The switch  43  is configured as a P-channel MOSFET. The switch  43  is electrically connected to the first conductive path  91 , the second conductive path  92 , and the transistor  41 . Specifically, the gate of the switch  43  is connected to the other end of the resistor  49  and the collector of the transistor  41 . The source of the switch  43  is connected to the first conductive path  91 . The source of the switch  43  and the first conductive path  91  have the same potential. The drain of the switch  43  is connected to the second conductive path  92 . The drain of the switch  43  and the second conductive path  92  have the same potential. The switch  43  is turned on when the transistor  41  is in the electricity-flowing state. 
     The Zener diode  45  is interposed between the emitter of the transistor  41  and the second conductive path  92 . The anode of the Zener diode  45  is connected to the emitter of the transistor  41  and one end of the resistor  47 . The cathode of the Zener diode  45  is connected to the second conductive path  92 . The cathode of the Zener diode  45  and the second conductive path  92  have the same potential. The Zener diode  45  sets an output voltage applied to the second conductive path  92  to a voltage corresponding to the voltage applied to the base of the transistor  41 . Specifically, the Zener diode  45  sets the output voltage applied to the second conductive path  92  to a value corresponding to the sum of the Zener voltage and the emitter voltage of the transistor  41 . 
     The resistor  47  is interposed between the transistor  41 , the Zener diode  45 , and the ground. One end of the resistor  47  is connected to the emitter of the transistor  41  and the anode of the Zener diode  45 . The other end of the resistor  47  is connected to the ground, and has the ground potential. 
     The resistor  49  is interposed between the first conductive path  91  and the transistor  41 . One end of the resistor  49  is connected to the first conductive path  91 . The one end of the resistor  49  and the first conductive path  91  have the same potential. The other end of the resistor  49  is connected to the collector of the transistor  41  and the gate of the switch  43 . 
     Next, control of an output voltage performed by the voltage regulator  10  will be described. 
     First, the control unit  20  operates to switch the state of each of the ports P 1  and P 2  to either the first state or the second state. That is to say, the control unit  20  outputs a high-level signal (a voltage signal having a magnitude of Vcc) or a low-level signal (a voltage signal having a magnitude of 0V) from the port P 1  and the port P 2 . 
     The input circuit unit  30  applies a voltage corresponding to a combination of the first state and the second state at the ports P 1  and P 2  to the base of the transistor  41  described later. As shown in  FIG. 2 , for example, when a high-level signal is output from the port P 1  and a high-level signal is output from the port P 2 , the voltage is divided by the input circuit unit  30 , and a voltage Vb having a magnitude of Vccx0.8 is applied to the base of the transistor  41 .  FIG. 2  shows the voltage Vb in a case where the resistors  33  and  35  and the resistors  37  and  39  all have the same resistance value. When a high-level signal is output from the port P 1  and a low-level signal is output from the port P 2 , the voltage is divided by the input circuit unit  30 , and a voltage Vb having a magnitude of Vccx0.6 is applied to the base of the transistor  41 . When a low-level signal is output from the port P 1  and a high-level signal is output from the port P 2 , the voltage is divided by the input circuit unit  30 , and a voltage Vb having a magnitude of Vccx0.2 is applied to the base of the transistor  41 . When a low-level signal is output from the port P 1  and a low-level signal is output from the port P 2 , the voltage is divided by the input circuit unit  30 , no voltage is applied to the base of the transistor  41 , and the voltage regulator  10  is turned off. 
     The transistor  41  is in an electricity-flowing state when at least one of the ports P 1  and P 2  is in the first state (in a state where a high-level signal is output), and allows a current to flow from the collector to the emitter. Because a current flows through the resistor  49  when the transistor  41  is in the electricity-flowing state, a voltage is applied to the gate of the switch  43 , and the switch  43  is turned on. When the switch  43  is turned on, a voltage is applied to the Zener diode  45 . When the voltage applied to the Zener diode  45  (the output voltage applied to the second conductive path  92 ) increases to a certain level, a current flows from the cathode side to the anode side. When at least one of the ports P 1  and P 2  is in the first state, the Zener diode  45  breaks down, and the potential difference between the cathode and the anode is kept at the Zener voltage. 
     In this manner, the Zener diode  45  sets the output voltage Vout applied to the second conductive path  92  to a voltage corresponding to the voltage Vb applied to the base of the transistor  41 . Specifically, the Zener diode  45  sets the output voltage Vout to a voltage corresponding to the sum of the Zener voltage Vz and the emitter voltage V 1  of the transistor  41 . In the example shown in  FIG. 1 , when the emitter voltage of the transistor  41  is a voltage V 1  and the base-emitter voltage of the transistor  41  is a voltage Vbe, V 1 =Vb−Vbe, thus Vout=VZ+V 1 =Vz+Vb−Vbe. V 1  is equal to the voltage across the resistor  47 . In this manner, as shown in  FIG. 2 , the control unit  20  operates so as to switch the state of each of the ports P 1  and P 2  to either the first state or the second state, so that it is possible to apply a plurality of types of Vb to the base of the transistor  41 , and it is possible to change the output voltage Vout accordingly. As described above, the single voltage regulator  10  can output output voltages of a plurality of magnitudes. 
     Next, an in-vehicle power supply system  100  (hereinafter also referred to as a power supply system  100 ) to which an in-vehicle backup power supply (hereinafter also referred to as a backup power supply) of the present disclosure is applied will be described with reference to  FIG. 3 . The power supply system  100  shown in  FIG. 3  includes an in-vehicle power supply unit  101  (hereinafter also referred to as a power supply unit  101 ), a backup power supply  110 , a load  103 , a charging circuit  105 , and is configured as a system capable of supplying power to the load  103 . The backup power supply  110  includes an in-vehicle power storage unit  102  (hereinafter also referred to as a power storage unit  102 ), a control unit  20 , and a discharge circuit  106 . 
     The power supply unit  101  functions as a main power supply. The power storage unit  102  functions as a backup power supply, and serves as a power supply source when power supply from the power supply unit  101  is interrupted. The power storage unit  102  is electrically connected to the first conductive path  91 . The charging circuit  105  is a circuit that performs a charging operation of charging the power storage unit  102  based on power that is supplied from the power supply unit  101 . The discharge circuit  106  is a circuit that performs a discharge operation of discharging power stored in the power storage unit  102 . The discharge circuit  106  is electrically connected to the first conductive path  91  and the second conductive path  92 . The discharge circuit  106  and the control unit  20  constitute the voltage regulator  10 . 
     The discharge circuit  106  receives, from the control unit  20 , a discharge instruction signal instructing that the power storage unit  102  be discharged or a discharge stop signal instructing that discharge of the power storage unit  102  be stopped, and performs a discharge operation of passing a discharge current from the power storage unit  102  to the load  103  and a cutoff operation of cutting off the discharge current. The control unit  20  transmits a discharge instruction signal in response to the establishment of a backup condition. In other words, the control unit  20  switches at least one of the plurality of ports P 1  and P 2  to the first state. Here, a backup condition is established, for example, when the voltage of the conductive path  191  falls to a predetermined threshold value or lower. 
     When the discharge circuit  106  receives a discharge instruction signal from the control unit  20 , the discharge circuit  106  performs a step-down operation using the voltage of the first conductive path  91  to which the output voltage of the power storage unit  102  is applied as an input voltage, and performs a discharge operation so as to apply a changed output voltage to the second conductive path  92  on the output side. When the discharge circuit  106  receives a discharge stop signal from the control unit  20 , the discharge circuit  106  stops such a discharge operation, and performs a cutoff operation so as to bring a portion between the second conductive path  92  and the power storage unit  102  into a non-conductive state. When the discharge circuit  106  is performing the discharge operation, the output current (discharge current) output from the discharge circuit  106  is supplied to the load  103 . 
     The control unit  20  switches at least one of the ports P 1  and P 2  to the first state in response to the establishment of the backup condition (for example, a case where the value of the voltage of a conductive path  191  falls below a predetermined threshold value). In this manner, the control unit  20  can change the output voltage that is output from the discharge circuit  106  to the load  103  according to the type of switching of the ports P 1  and P 2  (see  FIG. 2 ). 
     Such a voltage regulator  10  can be used for an initial check as to whether or not an output voltage of an appropriate voltage is output from the power storage unit  102 . 
     As described above, in the voltage regulator  10  of the present disclosure, the control unit  20  operates to switch the state of each of the plurality of ports P 1  and P 2  to either the first state or the second state. The input circuit unit  30  applies a voltage corresponding to the combination of the first states at the plurality of ports P 1  and P 2  to the base of the transistor  41 . The transistor  41  is in the electricity-flowing state when at least one of the ports P 1  and P 2  is in the first state, and the switch  43  is turned on when the transistor  41  is in the electricity-flowing state. The Zener diode  45  sets the output voltage applied to the second conductive path  92  to a voltage corresponding to the voltage applied to the base of the transistor  41 . 
     In the voltage regulator  10  having such a configuration, the value of the voltage to be output is not limited to a predetermined fixed value, and the output voltage value can be changed. In addition, because the configuration in which the output voltage value can be changed based on the control performed by the control unit  20  without using a large number of voltage regulators is adopted, it is possible to realize a “configuration in which an output voltage value can be set and changed”, while suppressing an increase in the size of an apparatus and keeping the apparatus from being complex. 
     In the voltage regulator  10  of the present disclosure, the transistor  41  is an NPN-type bipolar transistor. The Zener diode  45  has a cathode electrically connected to the second conductive path  92  and an anode electrically connected to the emitter of the transistor  41 . Further, the voltage regulator  10  includes the resistor  47  having one end electrically connected to the emitter of the transistor  41  and the other end electrically connected to the ground. The Zener diode  45  sets the output voltage applied to the second conductive path  92  to a value corresponding to the sum of the Zener voltage of the Zener diode  45  and the emitter voltage of the transistor  41 . 
     This voltage regulator  10  can stably switch the output voltage applied to the second conductive path  92  to a value corresponding to the base voltage simply by changing the base voltage applied to the transistor  41 , and such a configuration can be realized with a simpler element configuration. 
     In the voltage regulator  10  of the present disclosure, the first state can be a state in which one of a high-level voltage and a low-level voltage is applied, and the second state is a state in which the other of a high-level voltage and a low-level voltage is applied. The input circuit unit  30  includes the series configuration portion  31  in which the plurality of resistors  33  and  35  are connected in series between the base of the transistor  41  and the ground, and the plurality of resistors  37  and  39 . At one end, the plurality of resistors  37  and  39  are electrically connected to the plurality of ports P 1  and P 2 , respectively. Also, at the other end, the plurality of resistors  37  and  39  are electrically connected to the plurality of inter-element conductive paths  93  and  94  in the series configuration portion  31 , respectively. 
     In this voltage regulator  10 , the voltage applied to the base of the transistor  41  can be switched in stages based on the control of the plurality of ports P 1  and P 2  by the control unit  20 , and such a configuration can be realized with a simple configuration in which “the plurality of resistors  33  and  35  and the plurality of resistors  37  and  39 ” are the main components. In addition, the control unit  20  only has to switch the plurality of ports P 1  and P 2  to the high-level voltage or the low-level voltage, thus the control of the control unit  20  is also simplified. 
     OTHER EMBODIMENTS OF THE PRESENT DISCLOSURE 
     It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The following embodiments can be adopted, for example. 
     In the embodiment, the control unit  20  has two ports P 1  and P 2 . However, in another embodiment, the control unit  20  may also have three or more ports. 
     In the embodiment, the resistance values of the resistors  33  and  35  and the resistors  37  and  39  are all the same (see  FIG. 2 ). However, the resistance value of each resistor may also be freely changed. By changing the resistance value of each resistor, output voltages of various magnitudes can be output.