JP2016226079A - Power supply circuit and on-vehicle power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit and the like, capable of suppressing overshoot voltage of a load circuit even when input voltage has abruptly risen after the input voltage has reduced.SOLUTION: A switching power supply 100 receives a first voltage V1 as input, and outputs a second voltage V2 obtained by stepping down the first voltage V1. A linear power supply 200 includes a transistor T2 that receives the second voltage V2 as input and outputs a third voltage V3 obtained by smoothing the second voltage V2. A full-on determination circuit 300 determines whether or not the transistor T2 is in a full-on state. An output voltage changeover circuit 400, when it has been determined that the transistor T2 is not in the full-on state, makes output voltage setting of the switching power supply 100 be a first setting value; and, when it has been determined that the transistor T2 is in the full-on state, makes the output voltage setting of the switching power supply 100 be a second setting value lower than the first setting value.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power supply circuit and an in-vehicle power supply system.

  In a power supply circuit or the like that steps down an input voltage and outputs a predetermined voltage, a technique for suppressing an overshoot voltage when the power supply rises is known (see, for example, Patent Document 1).

  In Patent Document 1, “a reference potential adjustment unit that adjusts the reference potential to the same level as the output level and supplies it to the differential amplification unit when the applied power supply voltage is lower than the desired DC voltage is provided. As a result, even when the power supply voltage is lower than the desired DC voltage, the differential amplifier can maintain a balanced state, and when the power supply voltage suddenly rises, no overshoot occurs and large output fluctuations are suppressed. It is described that it has the effect of being able to be performed ”(see [Effects of the Invention] of Patent Document 1).

JP 2005-250664 A

  In Patent Document 1, the power supply circuit uses the operation region of the output transistor as follows: “The control signal CON of the node N2 is at the last potential (VCC−Vt = 0.8 V) as to whether a current flows through the PMOS 41 or not. . "

  In such a power supply circuit, for example, current cannot be output when the input voltage drops. Alternatively, when a current is drawn, the output level is lowered, the differential amplifier cannot maintain the balanced state, and overshoot occurs when the input voltage is restored.

  An object of the present invention is to provide a power supply circuit and an in-vehicle power supply system that can suppress an overshoot voltage of a load circuit even when the input voltage suddenly increases after the input voltage decreases.

  In order to achieve the above object, according to the present invention, a switching power supply that outputs a second voltage obtained by stepping down the first voltage is input, the second voltage is input, and the first voltage is input. A linear power supply including a transistor that outputs a third voltage obtained by smoothing the voltage of 2, a full-on determination circuit that determines whether or not the transistor is in a full-on state, and when the transistor is determined not to be in a full-on state, If the output voltage setting of the switching power supply is the first set value and it is determined that the transistor is in the full-on state, the output voltage setting of the switching power supply is set to a second set value that is smaller than the first set value. An output voltage switching circuit.

  According to the present invention, it is possible to provide a power supply circuit capable of suppressing the overshoot voltage of the load circuit even when the input voltage suddenly increases after the input voltage decreases. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is an example of the block diagram of the power supply circuit by the 1st Embodiment of this invention. It is an example of the timing chart of the power supply circuit shown in FIG. FIG. 2 is an example of a block diagram illustrating a full-on determination circuit shown in FIG. 1. It is an example of the block diagram which showed the structure of the full-on determination circuit and linear power supply which are shown in FIG. 5 is an example of a timing chart of a power supply circuit including a full-on determination circuit and a linear power supply shown in FIG. It is an example of a block diagram explaining a full-on determination circuit (modification 1). FIG. 7 is an example of a block diagram illustrating a configuration of a full-on determination circuit illustrated in FIG. 6. 8 is an example of a timing chart of a power supply circuit including the full-on determination circuit shown in FIG. It is an example of a block diagram explaining a full-on determination circuit (modification 2). FIG. 10 is an example of a block diagram illustrating a configuration of a full-on determination circuit illustrated in FIG. 9. 11 is an example of a timing chart of a power supply circuit including a full-on determination circuit shown in FIG. It is an example of a block diagram of the output voltage switching circuit shown in FIG. It is an example of the block diagram of the switching power supply shown in FIG. It is an example of the timing chart of the power supply circuit containing the switching power supply shown in FIG. It is an example of the block diagram of the power supply circuit by the 2nd Embodiment of this invention. It is an example of the timing chart of the power supply circuit shown in FIG. It is an example of the block diagram of the power supply circuit by the 3rd Embodiment of this invention. It is an example of the timing chart of the power supply circuit shown in FIG. It is an example of the block diagram of the vehicle-mounted power supply system containing the power supply circuit by embodiment of this invention. It is an example of the timing chart of the vehicle-mounted power supply system shown in FIG.

  Hereinafter, the configuration and operational effects of a power supply circuit according to an embodiment of the present invention will be described with reference to the drawings. In each figure, the same numerals indicate the same parts.

(First embodiment)
In the present embodiment, an example of a power supply circuit capable of suppressing the output overshoot voltage will be described. The power supply circuit steps down the voltage of the external power supply and supplies a predetermined voltage. For example, the power supply circuit steps down the voltage of the battery power supply and supplies a predetermined voltage to the on-vehicle electronic control device.

  FIG. 1 is an example of a block diagram of a power supply circuit 1 according to the first embodiment of the present invention. The power supply circuit 1 includes a switching power supply 100, a linear power supply 200 (series regulator), a full-on determination circuit 300, and an output voltage switching circuit 400. In the power supply circuit 1, for example, an MCU (Micro Controller Unit) 2 is connected to the output V 3 as a load.

  The switching power supply 100 outputs a stepped-down V2 using V1 as an input power supply (input voltage). The linear power supply 200 outputs a stepped down V3 using V2 as an input power supply. The full-on determination circuit 300 determines whether or not the linear power supply 200 is in a full-on state, and outputs the result as V30 (High / Low). Details of V30 will be described later with reference to FIG.

  In the present specification, the full-on state is a state in which the output MOS of the power supply circuit normally operating in the MOS saturation region is operating in the non-saturation region.

  The output voltage switching circuit 400 receives V30 as an input, switches the output voltage setting of the switching power supply 100, and outputs the result as V40 (High / Low). Details of V40 will be described later with reference to FIG.

  FIG. 2 is an example of a timing chart of the power supply circuit 1 shown in FIG.

  At time t0, since the power supply circuit 1 is operating normally, the full-on determination is not made. The switching power supply 100 and the linear power supply 200 output voltages of voltage setting 1 and voltage setting A, respectively.

  The input voltage V1 decreases, and at time t1, the full-on determination circuit 300 determines that it is in the full-on state. At this time, the output voltage switching circuit 400 sets the output V2 of the switching power supply 100 to the voltage setting 2.

  By the way, the minimum input voltage required for the linear power supply 200 to output the voltage setting A is the voltage setting A + (Ron × Iout), assuming that the on-resistance of the output transistor T2 is Ron and the current flowing through T2 is Iout. It is represented by

  Here, the voltage setting 2 is preferably set to a value higher than the minimum input voltage of the linear power supply 200 and lower than the maximum rating of the MCU 2 including the overshoot voltage at the time of startup of the switching power supply 100.

  In other words, the voltage setting 2 (second setting value) may be equal to or higher than the minimum input voltage of the linear power supply 200. The voltage setting 2 (second setting value) may be set to be equal to or lower than the maximum rated voltage of the MCU 2 (load circuit) to which the third voltage V3 output from the linear power supply 200 is applied. If overshoot is taken into consideration, voltage setting 2 (second set value) should be equal to or less than the value obtained by subtracting the first overshoot amount of second voltage V2 from the maximum rated voltage of MCU 2 (load circuit). Good.

  When V1 rises above the minimum input voltage of switching power supply 100 and linear power supply 200 at time t2, switching power supply 100 rises as much as possible to voltage setting 2. At this time, the linear power supply 200 rises with V2, but the maximum value of the output voltage is limited to V2 or less.

  Here, if the voltage setting 2 is set within the above range, an overshoot voltage exceeding the maximum rating of the MCU 2 will not occur in the output V3 of the linear power supply 200.

  At time t3, the voltage setting 2 is maintained for (t4-t3) as the time until the output V3 of the linear power supply 200 is stabilized after the full-on determination of the linear power supply 200 is canceled, and the normal voltage setting is performed. Return to 1. Here, the power supply circuit 1 returns to normal operation.

  As described above, the switching power supply 100 receives the first voltage V1 and outputs the second voltage V2 obtained by stepping down the first voltage V1. The linear power supply 200 includes a transistor T2 that receives the second voltage V2 and outputs a third voltage V3 obtained by smoothing the second voltage V2. The full-on determination circuit 300 determines whether or not the transistor T2 is in a full-on state. When the output voltage switching circuit 400 determines that the transistor T2 is not in the full-on state, the output voltage setting of the switching power supply 100 is set to the first setting value (voltage setting 1), and it is determined that the transistor T2 is in the full-on state. In this case, the output voltage setting of the switching power supply 100 is set to a second setting value (voltage setting 2) smaller than the first setting value.

  Thereby, even when the input voltage suddenly rises after the input voltage drops, the overshoot voltage of the load circuit can be suppressed.

(Full-on determination circuit)
A full-on determination circuit 300 according to the first embodiment of the present invention will be described with reference to FIGS. 3 and 4.

  FIG. 3 is an example of a block diagram illustrating the full-on determination circuit 300 shown in FIG. Full-on determination circuit 300 receives an internal signal from linear power supply 200 and outputs full-on determination V30. The other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  FIG. 4 is an example of a block diagram showing the configuration of full-on determination circuit 300 and linear power supply 200 shown in FIG.

  The linear power supply 200 includes, for example, an output transistor T2, voltage dividing resistors R4 and R5, a reference voltage Vb (reference voltage generation circuit), an OPA (Operational Amplifier) 201, and a level shifter 202. As described below, the full-on determination circuit 300 determines whether or not the transistor T2 is in a full-on state based on the voltage V20 at the internal node of the linear power supply 200.

  The output transistor T2 receives V2 as an input, and outputs a stepped down voltage as V3 based on the control signal of V22. The voltage dividing resistors R4 and R5 divide the voltage V3 and output a divided voltage V21.

  The OPA 201 uses the divided voltage V21 as an inverting input, the reference voltage Vb as a non-inverting input, and outputs the result of amplifying the difference as V20.

  The level shifter 202 receives V20 as an input and outputs a control signal V22 that drives the output transistor T2.

  Here, since the output transistor T2 is controlled by negative feedback so that Vb and V21 are equal, the voltage setting A of V3 is set to Vb × (R4 + R5) / (R5).

  The full-on determination circuit 300 includes, for example, a reference voltage Vc (reference voltage generation circuit) and a comparator 301. The comparator 301 uses V20 as a non-inverting input, Vc as an inverting input, and outputs a full-on determination V30.

  Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  FIG. 5 is an example of a timing chart of the power supply circuit 1 including the full-on determination circuit 300 and the linear power supply 200 shown in FIG.

  At time t0, the power supply circuit 1 is operating normally, the input voltage V21 of the OPA 201 is controlled to the same value as the reference voltage Vb, and the voltage V20 at the internal node of the linear power supply 200 causes the transistor T2 to be in the saturation region. It is in a controllable range.

  When the output voltage V2 of the switching power supply 100 falls below the minimum input voltage of the linear power supply 200 at time t1, the input voltage of the OPA 201 constantly becomes inverting input V21 <non-inverting input Vb, and the internal node of the linear power supply 200 The voltage V20 deviates from the normal operating range and increases to the power supply voltage of the OPA 201. As a result, the output transistor T2 is in a full-on state.

  The comparator 301 compares the voltage V20 of the internal node of the linear power supply 200 with the reference voltage Vc. If V20 is equal to or higher than Vc, the comparator 301 determines that it is in a full-on state, and sets V30 to High logic (hereinafter simply referred to as H). . Here, the reference voltage Vc is preferably set to about the upper limit of the normal operating range of V20.

  When the input voltage V2 of the linear power supply 200 rises at time t2, V21 increases and V20 starts to decrease.

  When V20 becomes Vc or less at time t3, the full-on determination circuit sets V30 to Low logic (hereinafter simply referred to as L).

  Thus, the full-on determination of the linear power supply 200 can be performed with a simple configuration in which the voltage V20 at the internal node of the linear power supply 200 is monitored by the comparator 301.

(Modification 1 of full-on determination circuit)
Another configuration example of the full-on determination circuit 300 according to the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 6 is a block diagram illustrating a full-on determination circuit 300 (Modification 1). The full-on determination circuit 300 receives the input voltage V1 of the switching power supply 100 and outputs the result of the full-on determination as V30.

  That is, the full-on determination circuit 300 determines whether or not the transistor T2 of the linear power supply 200 is in a full-on state based on the first voltage V1 input to the switching power supply 100.

  Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  FIG. 7 is an example of a block diagram showing the configuration of full-on determination circuit 300 shown in FIG. The full-on determination circuit 300 includes, for example, a reference voltage Vc (reference voltage generation circuit) and a comparator 301. The comparator 301 uses V1 as an inverting input, Vc as a non-inverting input, and outputs a full-on determination V30.

  Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  Here, the reference voltage Vc is approximately the sum of the minimum input voltage of the linear power supply 200 and the voltage drop in the full-on state of the switching power supply 100. This is because, if the input voltage V2 of the linear power supply 200 is equal to or lower than the minimum input voltage of the linear power supply 200, the linear power supply 200 is necessarily in a full-on state.

  FIG. 8 is an example of a timing chart of the power supply circuit 1 including the full-on determination circuit 300 shown in FIG.

  Since the input voltage V1 is equal to or higher than Vc at time t0, the full-on determination circuit 300 outputs L.

  When V1 becomes less than Vc at time t1, full-on determination circuit 300 outputs H.

  When V1 becomes equal to or higher than Vc at time t2, the full-on determination circuit 300 outputs L. At this time, it takes time until the linear power supply 200 itself is not in the full-on state even after the input voltage rises. Therefore, although the normal operation range is not restored, this full-on determination can be used as a guide.

(Modification 2 of full-on determination circuit)
Another exemplary configuration of the full-on determination circuit 300 according to the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 9 is a block diagram illustrating a full-on determination circuit 300 (Modification 2). Full-on determination circuit 300 receives input voltage V2 of linear power supply 200 and outputs the result of full-on determination as V30.

  That is, the full-on determination circuit 300 determines whether or not the transistor T2 of the linear power supply 200 is in a full-on state based on the second voltage V2 output from the switching power supply 100.

  FIG. 10 is an example of a block diagram showing a configuration of full-on determination circuit 300 shown in FIG.

  The comparator 301 uses V2 as an inverting input, Vc as a non-inverting input, and outputs a full-on determination V30.

  Here, the reference voltage Vc is about the minimum input voltage of the linear power supply 200.

  Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  FIG. 11 is an example of a timing chart of the power supply circuit 1 including the full-on determination circuit 300 shown in FIG.

  Since the input voltage V2 is equal to or higher than Vc at time t0, the full-on determination circuit 300 outputs L.

  When V2 becomes less than Vc at time t1, full-on determination circuit 300 outputs H.

  When V2 becomes equal to or higher than Vc at time t2, the full-on determination circuit 300 outputs L. At this time, it takes time until the linear power supply 200 itself is not in the full-on state even after V2 rises. Therefore, although the normal operation range is not restored, this full-on determination can be used as a guide.

  In this way, the linear power supply full-on determination can be indirectly performed with a simple configuration in which the input voltage V2 of the linear power supply 200 is monitored by the comparator 301. The switching power supply 100 and the linear power supply 200 are physically connected to each other. Even when it is difficult to monitor the voltage V20 of the internal node of the linear power supply 200, such as being arranged far away from each other, the effect of the embodiment of the present invention can be obtained.

(Output voltage switching circuit)
Next, a configuration example of the output voltage switching circuit 400 according to the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 12 is an example of a block diagram of the output voltage switching circuit 400 shown in FIG. The output voltage switching circuit 400 includes, for example, a delay circuit 401 and an OR logic 402.

  FIG. 13 is an example of a block diagram of the switching power supply 100 shown in FIG. The switching power supply 100 includes, for example, a switch element T1, a free wheel diode D1, an inductor L1, a capacitor C1 (capacitor / capacitor), voltage dividing resistors R1 to R3, a switch 102, a reference voltage Va (reference voltage generation circuit), and a PWM control unit 101. Have.

  The voltage dividing resistors R1 to R3 divide V2 and output V11. The switch 102 is connected in parallel with R1, and the control signal (V40) is opened at L and closed at H.

  The PWM control unit controls the switch element T1 so that the reference voltage Va and the divided voltage V11 by the voltage dividing resistors R1 to R3 are equal. That is, the voltage of the output line V2 of the switching power supply is set to voltage setting 1 = Va × (R1 + R2 + R3) / R3 when the switch 102 is open, and voltage setting 2 = Va when the switch 102 is closed. X (R2 + R3) / R3 is set.

  The operation of the switching power supply 100 itself is omitted because it is publicly known. Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  FIG. 14 is an example of a timing chart of the power supply circuit 1 including the switching power supply 100 shown in FIG.

  At time t0, the power supply circuit 1 is operating normally, and the full-on determination circuit 300, the delay circuit 301, and the OR logic 302 output L. At this time, the output voltage switching circuit 400 sets the output voltage setting of the switching power supply 100 to the voltage setting 1.

  When the full-on state is determined at time t1 and V30 becomes H, the output voltage switching signal V40 also becomes H. At this time, the output voltage setting of the switching power supply 100 is set to the voltage setting 2.

  At time t2, switching power supply 100 rises as much as possible to voltage setting 2, and the output voltage at this time is not less than the minimum input voltage of linear power supply 200 and less than the maximum rating of MCU2.

  At time t3, V30 becomes L, but the delay circuit output V41 is delayed for a certain period until it becomes L. Therefore, V40 maintains H, and the output V2 of the switching power supply 100 is voltage setting 2 for the delay time. Maintained. Here, the delay time is preferably set to about the time until the linear power supply 200 is stabilized after the full-on determination is canceled.

  At time t4, V40 becomes L, the output voltage of the switching power supply is switched to the voltage setting 1, and the power supply circuit 1 returns to the normal state.

  That is, the output voltage switching circuit 400 sets the output voltage setting of the switching power supply 100 to the voltage setting 2 (second setting value), and then determines that the transistor T2 is not in the full-on state, the switching power supply 100 after a predetermined time has elapsed. Is set to voltage setting 1 (first set value).

  Thus, the overshoot voltage of the linear power supply 200 can be limited with a simple configuration such as the OR logic 402, the delay circuit 401, and the switch 102.

  As described above, the output voltage V2 of the switching power supply 100 is once raised at the voltage setting 2 that is less than the maximum rating of the MCU2 at the time of returning from the full-on state with a simple configuration, and the full-on state of the linear power supply 200 is released. After that, by returning to the voltage setting 1 that is a normal operating voltage, the overshoot voltage at the time of recovery can be suppressed to be equal to or lower than the maximum rated voltage of the MCU 2.

  In the present embodiment, the voltage dividing resistor is used for switching the voltage setting of the switching power supply 100, but the intent is to switch the output voltage. As a method, for example, the reference voltage may be switched. As long as the voltage dividing resistance is changed, any switching may be performed.

(Second Embodiment)
The minimum input voltage of the linear power supply 200 is determined by the on-resistance of the element used for T2 and the load current flowing through the MCU2. The higher the on-resistance of T2, the higher the minimum input voltage, and the higher the load current, the higher the minimum input voltage. For this reason, depending on use conditions, the value of voltage setting 2 becomes large, and it is necessary to set it to be equal to or higher than the maximum rated voltage of MCU2. At this time, due to the overshoot voltage of the switching power supply 100, the overshoot voltage of the output voltage V3 of the linear power supply 200 may not be suppressed below the maximum rated voltage of the MCU2.

  Such an overshoot voltage of the switching power supply 100 can be suppressed by slowing the rise of the output voltage setting.

  In the present embodiment, another example regarding the output voltage switching circuit 400 will be described in consideration of the above. FIG. 15 is an example of a block diagram of the power supply circuit 1 according to the second embodiment of the present invention.

  The output voltage switching circuit 400 has a voltage slope 403. The voltage slope 403 receives the full-on determination V30, outputs a predetermined voltage Vd to the V40 when the full-on determination is performed, and increases the voltage of V40 to Va or more by a predetermined voltage change rate when the full-on determination is canceled.

  In the switching power supply 100, the PWM control unit 101 causes the lower voltage of the reference voltage Va and the output V40 of the output voltage switching circuit 400 to be equal to the divided voltage V11 by the voltage dividing resistors R1 and R3. The switch element T1 is controlled. That is, the voltage of the output line V2 of the switching power supply 100 is set to V40 × (R1 + R3) / R3 when Va> V40, and to the voltage setting 1 = Va × (R1 + R3) / R3 when Va <V40. Is set.

  Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  FIG. 16 is an example of a timing chart of the power supply circuit 1 shown in FIG.

  At time t0, the full-on determination V30 is L, and the output V40 of the output voltage switching circuit 400 is equal to or higher than Va. Therefore, the output voltage of the switching power supply 100 is the voltage setting 1.

  When the full-on determination V30 becomes H at time t1, V40 becomes a voltage Vd less than Va, and the output voltage of the switching power supply is set to voltage setting 2 = Vd × (R1 + R3) / R3. Here, the voltage setting 2 is set to a value that is less than the maximum rated voltage of the MCU 2 including the rising overshoot voltage of the switching power supply 100.

  At time t2, switching power supply 100 rises as much as possible to voltage setting 2. When full-on determination is canceled at time t3, the voltage setting value increases according to the predetermined voltage change rate.

  Eventually, at time t4, V40> Va, and the voltage converges to the normal voltage setting 1. Here, the predetermined voltage change rate may be suppressed to such an extent that the overshoot voltage of the switching power supply 100 and the linear power supply 200 does not become a problem.

  That is, the output voltage switching circuit 400 sets the output voltage of the switching power supply 100 when the output voltage setting of the switching power supply 100 is set to the voltage setting 2 (second setting value) and then the transistor T2 is determined not to be in the full-on state. Is gradually changed from voltage setting 2 (second setting value) to voltage setting 1 (first setting value) at a predetermined voltage change rate.

  Thus, even when the on-resistance of the linear power supply 200 is high or the load current is large, the output voltage V2 of the switching power supply 100 is gradually raised from the voltage setting 2 that is less than the maximum rating of the MCU2, and the normal voltage By returning to the setting, the overshoot of the linear power supply at the time of return can be prevented below the maximum rating of MCU2.

(Third embodiment)
FIG. 17 is an example of a block diagram of the power supply circuit 1 according to the third embodiment of the present invention. The power supply circuit 1 includes a notification circuit 500. Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  The notification circuit 500 notifies the MCU 2 of the full-on state while the output voltage switching circuit 400 is switching the output voltage setting of the switching power supply 100. Upon receiving this notification, the MCU 2 limits the operation to the minimum necessary and suppresses current consumption.

  That is, when it is determined that the transistor T2 of the linear power supply 200 is in the full-on state, the notification circuit 500 notifies the MCU 2 (load circuit) to reduce the power consumption.

  FIG. 18 is an example of a timing chart of the power supply circuit 1 shown in FIG.

  At time t0, the full-on determination is not made, and the output V40 of the output voltage switching circuit 400 is L. Therefore, the notification circuit 500 also does not notify. Here, in FIG. 18, the output V50 of the notification circuit 500 is H when notifying the full-on state, and is L when not notifying.

  At time t1, when V40 becomes H due to the full-on determination, V50 also becomes H, and the current consumption of MCU2 decreases.

  At time t2, the switching power supply 100 rises as much as possible to the voltage setting 2. At this time, since the current consumption of the MCU 2 is suppressed, the minimum input voltage of the linear power supply is also suppressed low, and therefore the value of the voltage setting 2 can be set to a lower value.

  Thereafter, when the linear power supply 200 becomes stable and V40 becomes L at time t3, the output voltage V2 of the switching power supply 100 returns to the original state, V50 also becomes L, and the current consumption of the MCU2 returns during normal operation.

  Thus, even when the load current is large, the overshoot voltage at the time of recovery can be suppressed by limiting the current consumption of the MCU 2 while the output voltage setting is set to be less than the maximum rated voltage.

(Application examples)
In the present embodiment, an example in which the power supply circuit 1 according to the first to third embodiments of the present invention is applied to an on-vehicle electronic control device will be described. FIG. 19 is an example of a block diagram of the in-vehicle power supply system 10 including the power supply circuit 1 according to the embodiment of the present invention.

  The in-vehicle power supply system 10 includes a power supply circuit 1, an MCU 2, a battery 3, a starter motor 4, and an alternator 5.

  The power supply circuit 1 receives V1 and outputs a voltage V3.

  The MCU 2 uses the V3 as a power source and performs various controls relating to the operation of the automobile.

  The battery 3 stores an output voltage of an alternator 5 described later when the engine is operating, and outputs the stored voltage when the engine is stopped.

  The starter motor 4 operates when the engine is started, and starts the engine using V1 as a power source.

  The alternator 5 is a generator that utilizes the rotation of the engine, and outputs a voltage to V1 during engine operation.

  Other configurations have the same functions as the configurations denoted by the same reference numerals shown in FIG. 1 and have not been described.

  FIG. 20 is an example of a timing chart of the in-vehicle power supply system 10 shown in FIG.

  Here, as an example of the voltage value, the output voltage of the alternator 5 is 14 V, the voltage setting 1 of the switching power supply 100 is 6.5 V, the voltage setting A of the linear power supply 200 is 5.0 V, and the minimum input voltage of the linear power supply Is described as 5.1V. Here, it is assumed that the maximum rated voltage of the MCU 2 is 6.0V and the voltage setting 2 is set to 5.2V.

  During the period up to time t0, the engine is stopped and the starter motor 4 and the alternator 5 are stopped. The power supply circuit 1 inputs a voltage stored in the battery power supply 3 and outputs a voltage of 5V to the MCU 2.

  At time t0, since a large current flows through the starter motor 4, the voltage V1 of the battery power supply 3 temporarily decreases, and in some cases falls below 5V. As the battery voltage V1 decreases, the output V2 of the switching power supply 100 and the output V3 of the linear power supply 200 also decrease sequentially.

  At time t1, the linear power supply 200 is determined to be in the full-on state, and at the same time, the output voltage setting of the switching power supply 100 is set from 6.5V (voltage setting 1) to 5.2V (voltage setting 2). At this time, the switching power supply 100 and the linear power supply 200 are fully turned on and the maximum supply of the output voltage V3 is continued.

  Thereafter, the engine is started, the alternator 5 starts to charge the battery 3, the voltage V1 is restored, and the switching power supply 100 rises as much as possible to 5.2V (voltage setting 2).

  At this time, assuming that the overshoot voltage of the switching power supply 100 is 0.3 V, the output of the linear power supply 200 is limited to 5.5 V or less even if an overshoot voltage occurs, and thus the maximum rating is 6 Never exceed 0V.

  At time t2, after the full-on determination of the linear power supply 200 is canceled, the linear power supply 200 returns to the normal operating range.

  At time t3, the output voltage setting of the switching power supply 100 returns from 5.2V (voltage setting 2) to 6.5V (voltage setting 1), and the power supply circuit 1 returns to normal operation.

  As described above, when the battery voltage temporarily decreases, the overshoot voltage of the power supply circuit 1 when the battery voltage V1 is restored can be obtained by a simple configuration that switches the output voltage V2 of the switching power supply 100. ) Or below the maximum rating.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. The signal polarity shown in the timing chart is an example, and the present invention is not limited to this. In addition, part or all of the above-described configurations may be realized by, for example, one integrated circuit or a plurality of integrated circuits.

  Further, each of the above-described configurations, functions, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

V1 ... Input voltage V2 ... Switching power supply output V3 ... Linear power supply output V11 ... Switching power supply feedback voltage V20 ... Linear power supply internal node V30 ... Full-on determination output V40 ... Output voltage switching circuit output V41 ... Delay circuit output V50 ... Notification to MCU2 Signals Va to Vd: Reference voltage T1: Switch element (switching element)
D1... Freewheeling diode L1... Inductor C1. Capacitances R1 to 3... Output voltage feedback voltage dividing resistor T2 of switching power supply... Linear power supply output transistors R4 to 5. ... MCU (Micro Controller Unit)
DESCRIPTION OF SYMBOLS 3 ... Battery 4 ... Starter motor 5 ... Alternator 10 ... In-vehicle power supply system 100 ... Switching power supply 101, 111 ... PWM control part 102 ... Switch 200 ... Linear power supply (series regulator)
201 ... OPA
202 ... T2 drive level shifter 300 ... full-on determination circuit 301 ... comparator 400 ... output voltage switching circuit 401 ... delay circuit 402 ... OR logic 500 ... notification circuit

Claims (11)

A switching power supply that receives a first voltage and outputs a second voltage obtained by stepping down the first voltage;
A linear power supply including a transistor that receives the second voltage and outputs a third voltage obtained by smoothing the second voltage;
A full-on determination circuit for determining whether or not the transistor is in a full-on state;
When it is determined that the transistor is not in a full-on state, the output voltage setting of the switching power supply is set to a first setting value. When it is determined that the transistor is in a full-on state, the output voltage setting of the switching power supply is set to the first setting value. An output voltage switching circuit having a second set value smaller than the set value of 1,
A power supply circuit comprising: The power supply circuit according to claim 1,
The second set value is
The power supply circuit, wherein the third voltage output from the linear power supply is equal to or lower than a maximum rated voltage of a load circuit to which the third voltage is applied. The power supply circuit according to claim 1,
The second set value is
A power supply circuit characterized by being equal to or higher than the minimum input voltage of the linear power supply. The power supply circuit according to claim 1,
The output voltage switching circuit is
After setting the output voltage setting of the switching power supply to the second setting value, if it is determined that the transistor is not in a full-on state, the output voltage setting of the switching power supply is set to the first setting value after a predetermined time has elapsed. A power supply circuit characterized by that. The power supply circuit according to claim 1,
The output voltage switching circuit is
After setting the output voltage setting of the switching power supply to the second set value, if it is determined that the transistor is not in a full-on state, the output voltage setting of the switching power supply is changed from the second set value to a predetermined voltage change rate. And gradually changing to the first set value. The power supply circuit according to claim 1,
The full-on determination circuit includes:
A power supply circuit that determines whether or not the transistor is in a full-on state based on a voltage of an internal node of the linear power supply. The power supply circuit according to claim 1,
The full-on determination circuit includes:
A power supply circuit comprising: determining whether or not the transistor is in a full-on state based on the first voltage input to the switching power supply. The power supply circuit according to claim 1,
The full-on determination circuit includes:
A power supply circuit comprising: determining whether or not the transistor is in a full-on state based on the second voltage output from the switching power supply. The power supply circuit according to claim 2,
A power supply circuit further comprising: a notification circuit that notifies the load circuit to reduce power consumption when it is determined that the transistor is in a full-on state. The power supply circuit according to claim 2,
The second set value is
The power supply circuit, which is equal to or less than a value obtained by subtracting an initial overshoot amount of the second voltage from a maximum rated voltage of the load circuit. Battery,
A starter motor driven by a voltage applied from the battery when starting the engine;
An alternator for charging the battery when the engine is operated;
A switching power supply that outputs a second voltage obtained by stepping down the first voltage when the first voltage is input from the battery or the alternator, and the second voltage is input and the second voltage is smoothed. A linear power supply including a transistor that outputs a third voltage, a full-on determination circuit that determines whether or not the transistor is in a full-on state, and an output voltage setting of the switching power supply when a determination is made that the transistor is not in a full-on state. And a power supply circuit having an output voltage switching circuit that sets an output voltage setting of the switching power supply to a second setting value smaller than the first setting value when it is determined that the transistor is in a full-on state. When,
An in-vehicle power supply system comprising:

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