JPWO2019087746A1 - Power supply switching circuit, power supply IC and in-vehicle electronic control device - Google Patents

Abstract

Provided is a power supply switching circuit or the like capable of outputting a voltage independent of the voltage of the first power supply using the first power supply while switching between the first power supply and the second power supply according to the voltage of the second power supply. The output terminal OUT is connected to a first node 26 that connects a current path connected to the first power supply V1 and a current path connected to a second power supply V2 that supplies a voltage lower than the first power supply V1. The resistor 20 is connected to the first power supply V1. The Zener diode 22 is connected to the resistor 20 in series. The NMOS 23 (transistor) has a gate (control electrode) connected to the second node 27 that connects the resistor 20 and the Zener diode 22, and the first power supply V1 and the output terminal according to the voltage applied to the gate. Turn on/off the current path between OUT. The second diode 24 rectifies the current flowing through the current path between the second power supply V2 and the output terminal OUT.

Description

The present invention relates to a power supply switching circuit, a power supply IC, and an in-vehicle electronic control device.

2. Description of the Related Art Semiconductor integrated circuits (ICs) mounted on electronic control devices have been highly functionalized and highly integrated, and accordingly, power consumption has increased, and loss and heat generation have increased. When the heat generation of a semiconductor increases, an expensive package with low thermal resistance is required to dissipate the heat, or the cost of the heat dissipation structure and the heat dissipation material of the board or housing on which the semiconductor is mounted is increased. Issues arise. In order to minimize the cost for these heat dissipation measures, it is required to reduce the power consumption and heat generation of the semiconductor.

Even in in-vehicle electronic control devices, semiconductors such as microcomputers and ICs that are mounted are becoming highly functional and highly integrated, and power consumption is also increasing. Among them, a power supply IC for generating a power supply for a microcomputer and a driver IC for driving an actuator load are required to have large power consumption for driving a large current.

The power consumption of these ICs can be roughly divided into the power consumption by the drive current for generating the power supply of the microcomputer and driving the actuator, and the power consumption of the internal power supply circuit for driving and signal processing the DCDC power supply and the driver circuit.

Conventionally, the power consumption of this internal power supply circuit was small relative to the power consumption of the entire IC, so the effect of reducing the power consumption of the internal power supply circuit was small. However, as the functionality and integration of ICs have advanced, the power consumption and heat generation rate of this internal power supply circuit have increased and the impact has increased.

In the in-vehicle electronic control device, there is a battery as a main power source to be supplied, and this battery voltage is directly or stepped down or stepped up to generate a desired voltage required for control. In order to reduce the power consumption of the internal power supply circuit, it is generally considered that the applied voltage or the consumed current is reduced. If the consumption current is constant, the driven voltage can be reduced to reduce the power consumption. It will be possible.

Here, the functions of the internal power supply circuit of the power supply IC are a reference voltage inside the IC, generation of a reference clock, driving of each DCDC power supply, driving of each driver circuit, communication function with a microcomputer, and the like. Therefore, when the internal circuit is driven by the voltage that is stepped down from the battery voltage by the DCDC power supply, the internal power supply circuit is first driven by the battery. After that, the voltage stepped down by the DCDC power source needs to be supplied to the internal power supply circuit, and a circuit for switching between the battery voltage and the stepped down voltage is required.

In a semiconductor integrated circuit, a power supply switching technique for selecting a plurality of voltages is known. For example, when the technique described in Patent Document 1 is applied to a transceiver IC of the Flex Ray standard, it can operate properly without requiring an excessive circuit current even in the low power consumption mode.

FIG. 7 is a configuration diagram of the power supply switching circuit described in Patent Document 1. When applied to the Flex Ray transceiver IC, V102 corresponds to the battery voltage VBAT, and V101 corresponds to the VCC power supply voltage. When the VCC power supply voltage is lower than a predetermined voltage, the PMOS 105 is activated to supply power from V102.

By activating the PMOS 105, the power supply circuit of FIG. 7 realizes a power supply switching circuit that operates properly without flowing any current other than the current flowing through the transceiver IC even in the low power consumption mode.

JP 2012-222844 JP

It is necessary to switch the voltage connected to the internal power supply circuit so that it is driven at a lower voltage in order to reduce the power consumption generated in the internal power supply circuit of the semiconductor integrated circuit mounted in the electronic control device and the heat generation accompanying it. ..

The output voltage of the switching circuit described in the above-mentioned Patent Document 1 is a voltage that is lower than V101 and V102 by the forward voltage of the diode. That is, this output voltage depends on the voltages of V101 and V102, and when the voltage difference is large, the output voltage to be switched changes greatly.

When the switching circuit described in Patent Document 1 is applied to the connection of the semiconductor integrated circuit to the internal power supply circuit and the battery voltage and the DCDC power supply voltage are switched and driven, the output voltage to be switched depends on the battery voltage and the DCDC power supply voltage. Change greatly.

When V101 suddenly drops in power supply, activation of the PMOS 105 is delayed due to the time constant generated in the resistor string 116, the gate capacitance of the PMOS 105, and the like, and the output voltage may drop at the moment of switching. ..

The internal power supply circuit of the integrated circuit needs to constantly and stably generate the reference voltage and the reference clock. However, if the voltage fluctuates greatly or a momentary voltage drop occurs due to switching, there is a problem in stable operation during switching, such as fluctuations in the reference voltage and reference clock, or a decrease in the internal power supply circuit output. There is.

It is an object of the present invention to switch a first power supply and a second power supply according to a voltage of a second power supply, and to output a voltage that does not depend on the voltage of the first power supply by using the first power supply. To provide.

In order to achieve the above object, the present invention connects to a first node that connects a current path connected to a first power supply and a current path connected to a second power supply that supplies a voltage lower than the first power supply. An output terminal, a resistor connected to the first power supply, a Zener diode connected in series with the resistor, and a control electrode connected to a second node connecting the resistor and the Zener diode. And flows through a transistor that turns on/off a current path between the first power supply and the output terminal and a current path between the second power supply and the output terminal according to the voltage applied to the control electrode. A second diode that rectifies the current.

According to the present invention, it is possible to output a voltage that does not depend on the voltage of the first power supply using the first power supply while switching between the first power supply and the second power supply according to the voltage of the second power supply. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a power supply switching circuit diagram which concerns on Embodiment 1 of this invention. It is a power supply switching circuit diagram which concerns on the modification 1 of Embodiment 1 of this invention. It is a power supply switching circuit diagram which concerns on the modification 2 of Embodiment 1 of this invention. It is a power supply switching circuit diagram which concerns on Embodiment 2 of this invention. It is a block diagram of the power supply IC which concerns on Embodiment 3 of this invention. 7 is a time chart of the power supply IC according to the third embodiment of the present invention. FIG. 9 is a circuit diagram showing a configuration of a power supply switching circuit described in Patent Document 1.

Hereinafter, configurations of a power supply switching circuit, a power supply IC, and an in-vehicle electronic control device according to Embodiments 1 to 3 of the present invention will be described in detail with reference to the accompanying drawings. In each figure, the same reference numerals indicate the same parts. In the present embodiment, it is an object of the present invention to continuously operate the internal power supply circuit in a stable manner at the time of switching the power supply and reduce the power consumption of the internal power supply circuit by switching the power supply.

(Embodiment 1)
FIG. 1 is a circuit diagram of a power supply switching circuit 12 according to the first embodiment of the present invention.

The power supply switching circuit 12 of FIG. 1 includes a Zener diode 22, a resistor 20, an NMOS 23 (N-channel Metal Oxide Semiconductor), and a second diode 24.

Here, the output terminal OUT is connected to a first node 26 that connects a current path connected to the first power supply V1 and a current path connected to a second power supply V2 that supplies a voltage lower than the first power supply V1. It The resistor 20 is connected to the first power supply V1. The Zener diode 22 is connected to the resistor 20 in series. The NMOS 23 (transistor) has a gate (control electrode) connected to the second node 27 that connects the resistor 20 and the Zener diode 22, and the first power supply V1 and the output terminal according to the voltage applied to the gate. Turn on/off the current path between OUT. The second diode 24 rectifies the current flowing through the current path between the second power supply V2 and the output terminal OUT.

First, when the first power supply V1 is supplied, a current is supplied to the Zener diode 22 via the resistor 20, and the voltage of the second node 27 is biased by the voltage of the Zener diode 22 and the voltage of the second diode. It

The rise of the voltage of the second node 27 activates the NMOS 23, and the first node 26 is biased according to the gate-source voltage of the NMOS 23. In this way, the voltage is output to the first node 26 by the supply of the first power supply V1. At this time, the second diode 24 has a function of preventing backflow.

Here, the output terminal voltage V3 of the first node 26 hardly depends on the first power supply V1, and becomes a constant voltage V3A0=Vz-Vgs determined by the voltage Vz of the Zener diode 22 and the gate-source voltage Vgs of the NMOS 23. ..

This voltage V3 is a voltage for driving the internal power supply circuit 13, and needs to be higher than the output voltage of the internal power supply circuit 13. The supply of the voltage V3 causes the internal power supply circuit 13 to generate the output voltage V4.

Here, when the second power supply V2 is supplied, when the second power supply V2 becomes more than the voltage Vf2 of the second diode 24 from the voltage V3A0=Vz-Vgs supplied from the first power supply V1, the second power supply V2 A current flows from V2 to the first node 26.

At that time, the first node voltage V3B becomes the voltage V2-Vf2 and is supplied from the second power supply V2, and the power supply of V3 is switched from the first power supply V1 to the second power supply V2.

Because of switching to the second power supply V2, the voltage of V3A0 needs to be set lower than the voltage of V2-Vf2.

Assuming that the current consumption of the internal power supply circuit 13 is the current I3, the power consumption is changed from V1×I3 when the first power supply V1 is supplied to V2×I3 when the second power supply V2 is supplied, and the second power supply V2 is By lowering it, power consumption of the internal power supply circuit and heat generation accompanying it can be reduced.

Next, when the second power supply V2 is lowered, the gate-source voltage Vgs of the NMOS 23 is sufficiently opened when the V2-Vf2 voltage becomes lower than the V3A0 voltage, similarly to the switching from V1 to V2. As a result, the NMOS 23 is activated, a current is supplied from the first power supply V1, and the power supply voltage is switched.

(Modification 1)
FIG. 2 is a circuit diagram of the power supply switching circuit 12A according to the first modification of the first embodiment of the present invention. This is a configuration in which a second capacitor 25 arranged between the first node 26 and the internal power supply circuit 13 is added to the power supply switching circuit 12 shown in FIG. That is, one end of the second capacitor 25 is connected to the output terminal OUT.

Considering the case where V2 sharply drops at the time of switching from V2 to V1, it is conceivable that the current supply from the NMOS 23 is delayed and the voltage of V3 drops momentarily. Therefore, the stable operation of the internal power supply circuit is maintained by connecting the second capacitor 25 and supplying the current from the second capacitor 25 at the time of sharp switching.

(Modification 2)
FIG. 3 is a circuit diagram of the power supply switching circuit 12B according to the second modification of the first embodiment of the present invention. This is a configuration in which a first diode 21 arranged between the second node 27 and the Zener diode 22 is added to the power supply switching circuit 12A shown in FIG. That is, the first diode 21 has an anode connected to the second node 27 and a cathode connected to the cathode of the Zener diode 22. The first diode 21 cancels the negative temperature characteristic of the voltage of the NMOS 23 (transistor).

In detail, the power supply switching circuit 12B of FIG. 3 includes a Zener diode 22, a first diode 21, a resistor 20, an NMOS 23, a second diode 24, and a second capacitor 25.

First, when the first power supply V1 is supplied, a current is supplied to the first diode 21 and the zener diode 22 via the resistor 20, and the voltage of the second node 27 is equal to the voltage of the zener diode 22 and the second diode. Biased with voltage.

The rise of the voltage of the second node 27 activates the NMOS 23, and the first node 26 is biased according to the gate-source voltage of the NMOS 23. In this way, the voltage is output to the first node 26 by the supply of the first power supply V1. At this time, the second diode 24 has a function of preventing backflow.

Here, the output terminal voltage V3 of the first node 26 hardly depends on the first power supply V1, and is a constant voltage determined by the voltage Vz of the Zener diode 22, the voltage Vf1 of the first diode 21, the gate-source voltage Vgs of the NMOS 23. The voltage V3A=Vz+Vf1-Vgs.

That is, the reference voltage generated by the Zener diode 22 and the first diode 21 is applied to the gate (control electrode) of the NMOS 23 (transistor), so that the output terminal OUT has a constant voltage that does not depend on the voltage of the first power supply V1. V3A=Vz+Vf1-Vgs (first voltage) is output from the first power supply V1 via the NMOS 23 (transistor).

Regarding the temperature characteristic, the first diode 21 has a negative temperature characteristic, but the gate and source voltages of the NMOS 23 also have a negative temperature characteristic, so that the temperature dependences cancel each other out. By using the Zener diode 22 having small temperature dependence, the voltage V3 can be output to the first node 26 having small temperature dependence.

This voltage V3 is a voltage for driving the internal power supply circuit 13, and needs to be higher than the output voltage of the internal power supply circuit 13. The supply of the voltage V3 causes the internal power supply circuit 13 to generate the output voltage V4.

Here, when the second power supply V2 is supplied, when the second power supply V2 becomes higher than the voltage V3A=Vz+Vf1-Vgs supplied from the first power supply V1 and more than the voltage Vf2 of the second diode 24, the second power supply A current flows from V2 to the first node 26.

At that time, the first node voltage V3B becomes the voltage V2-Vf2 and is supplied from the second power supply V2, and the power supply of V3 is switched from the first power supply V1 to the second power supply V2.

That is, when the voltage of the second power supply V2 is higher than the predetermined voltage (Vz+Vf1-Vgs+Vf2), the output terminal OUT outputs the second voltage (V2-Vf2) from the second power supply V2 via the second diode 24.

Because of switching to the second power supply V2, the voltage of V3A needs to be set lower than the voltage of V2-Vf2.

Assuming that the current consumption of the internal power supply circuit 13 is the current I3, the power consumption is changed from V1×I3 when the first power supply V1 is supplied to V2×I3 when the second power supply V2 is supplied, and the second power supply V2 is By lowering it, power consumption of the internal power supply circuit and heat generation accompanying it can be reduced.

Next, when the second power supply V2 is lowered, similarly to the switching from V1 to V2, when the V2-Vf2 voltage becomes lower than the V3A voltage, the gate-source voltage Vgs of the NMOS 23 is sufficiently opened. As a result, the NMOS 23 is activated, a current is supplied from the first power supply V1, and the power supply voltage is switched.

That is, when the voltage of the second power supply V2 is lower than the predetermined voltage (Vz+Vf1-Vgs+Vf2), the output terminal OUT outputs a constant voltage V3A=Vz+Vf1-Vgs (first voltage) from the first power supply V1 via the NMOS 23 (transistor). Output.

(Summary of Embodiment 1)
As described above, the power supply switching circuit according to the first embodiment of the present invention can switch the output voltage V3 from the first power supply V1 to the second power supply V2 when the V2 voltage becomes equal to or higher than the desired voltage. Accordingly, by setting the V2 voltage to be lower than the V1 voltage, it is possible to reduce power consumption and heat generation of the internal power supply circuit 13 connected to V3. Further, it is possible to output a voltage that does not depend on the voltage of the first power supply by using the first power supply while switching between the first power supply and the second power supply according to the voltage of the second power supply.

(Embodiment 2)
FIG. 4 is a circuit diagram of the power supply switching circuit 12C according to the second embodiment of the present invention. This is a configuration in which a third diode 29 arranged between the first node 26 and the NMOS 23 is added to the power supply switching circuit 12. That is, the third diode 29 has an anode connected to the source of the NMOS 23 (transistor) and a cathode connected to the first node 26. Thereby, even if the V2 voltage becomes higher than the V1 voltage, it is possible to prevent the backflow of the current to the first power supply V1.

However, as compared with the configuration of the first embodiment, there is a point that the lower limit operating voltage range at a low voltage becomes higher by Vf3 which is the forward voltage of the third diode.

The V2 voltage for switching the power supply is a voltage such that V2-Vf2>Vz+Vf1-Vgs-Vf3.

(Summary of Embodiment 2)
As described above, the power supply switching circuit according to the second embodiment of the present invention switches the output voltage V3 from the first power supply V1 to the second power supply V2 when the V2 voltage becomes equal to or higher than a desired voltage, as in the first embodiment. You can Accordingly, by setting the V2 voltage to be lower than the V1 voltage, it is possible to reduce the power consumption and heat generation of the internal power supply circuit 13 connected to V3. Further, even if the V2 voltage becomes higher than the V1 voltage, it is possible to prevent the current from flowing back to the first power supply V1.

(Embodiment 3)
FIG. 5: is a block diagram of the vehicle-mounted electronic control unit 31 provided with the power supply IC11 which concerns on Embodiment 3 of this invention. The power supply IC 11 includes a power supply switching circuit 12 (or 12A to 12C), an internal power supply circuit 13, a step-down switching regulator 14, a series power supply 15, and a driver circuit 16.

In this power supply IC 11, the battery 10 is connected to the first power supply V1 of the power supply switching circuit 12, and the output voltage V5 obtained by smoothing the switching output of the step-down switching regulator 14 by the inductor 17 and the first capacitor 18 is connected to the second power supply V2. Connected. That is, the first power supply V1 is the battery 10 (battery power supply), and the second power supply V2 is the step-down switching regulator 14. Further, the internal power supply circuit 13 is connected to the output terminal voltage V3.

The output voltage V4 of the internal power supply circuit 13 is connected to the step-down switching regulator 14, each series power supply 15, and the driver circuit 16, and becomes a power supply voltage for driving each circuit. The step-down switching regulator 14 is connected to the battery 10 and steps down the battery 10 to generate the voltage V5 required for the series power supply 15. The voltage V5 is the negative feedback voltage of the step-down switching regulator 14.

Next, the series power supply 15 generates a plurality of power supply voltages V6 and V7 necessary for the microcomputer 30 and a power supply voltage V8 for various sensors 34 for detecting information necessary for vehicle control by reducing the voltage V5. Further, the driver circuit 16 drives a plurality of actuator loads 32, 33 mounted on the vehicle.

First, assuming that the consumption current of V3 flowing in the internal power supply circuit 13 is I3, when the power is supplied from the V1 voltage of the power supply switching circuit 12, the power consumption P0 from the battery 10 is V0×I3.

Next, the power supply switching circuit 12 raises the V2 voltage, which is lower than the V1 voltage, to a desired voltage or higher, so that the V5 voltage is connected to the internal power supply circuit 13. As a result, as described in the first embodiment, the power consumption P1 of the internal power supply circuit 13 driven by a lower V2 voltage is reduced to V5×I3.

Here, considering the power consumption of the power supply IC 11, since the current I3 of the internal power supply circuit 13 is newly supplied via V5, the power consumption of the step-down switching regulator 14 increases.

Assuming that the efficiency of the step-down switching regulator 14 is K and the power consumption P1 of the internal power supply circuit 13, the power P0' consumed by the battery 10 is converted in the relationship of P1/P0'=K. That is, if the current flowing from the battery 10 is I0', then (V5*I3)/(V0*I0')=K.

Here, assuming that the battery 10 voltage is 14V, the V5 voltage is 6V, and the conversion efficiency is 90%, I0′=V5/V0×I3×1/K=I3×0.476, which is the consumption of the power supply IC after the power supply is switched. The electric power P0′=V0×I0′=V0×I3×0.476=P0×0.476. That is, by switching the power supply, the power consumption of the internal power supply circuit 13 can be reduced to about half.

When V5 voltage is generated from the battery 10 in place of the step-down switching regulator 14 by the series power supply, the current I3 consumed in the internal power supply circuit 13 eventually flows from the battery 10 and is consumed as the power supply IC 11. Since the electric power is the same as the case where V1 of the power source switching circuit 12 is used, there is no effect of reducing the power consumption. Therefore, in order to apply the power supply switching circuit 12 to the power supply IC 11 including the second power supply, the configuration of the step-down switching regulator 14 with less power conversion loss is required.

Next, the operation when the power supply of the power supply IC 11 is terminated will be described. The power supply IC 11 generates a plurality of power supplies that drive the microcomputer 30, and it is necessary to end the internal power supply circuit 13 after the plurality of power supplies have ended normally.

That is, in the end sequence, when the V5 voltage becomes lower than the desired voltage, the internal power supply circuit 13 is stably driven from the V0 voltage by the operation of the power supply switching circuit 12, so that the power supply IC 11 can be reliably operated. It is possible to complete the end sequence.

Further, even in the normal operation, even when the V5 voltage is unintentionally lowered due to some factor, the operation of the power supply switching circuit 12 stably drives the internal power supply circuit 13 from the V0 voltage. Further, when the V5 voltage is restored to the normal voltage, the internal power supply circuit 13 is driven by the V5 voltage, and the power consumption is similarly reduced.

FIG. 6 is a time chart of the power supply IC according to the third embodiment. t0 indicates the timing when the activation signal is input. The period from t0 to t1 is a start-up period in which the internal power supply circuit 13, the step-down switching regulator 14, and each series power supply 15 mounted on the power supply IC 11 are started.

In this start-up period, first, the internal voltage V3A=Vz+Vf1−Vgs of the power supply switching circuit 12 is supplied from the battery voltage V0. The supply of V3 causes the internal power supply circuit 13 to activate the V4 voltage. When the internal power supply circuit 13 is activated and the generation of the internal reference voltage and the internal clock is completed, the step-down switching regulator 14 is activated and the output voltage V5 rises.

Here, when the V5 voltage exceeds the desired voltage Vz+Vf1−Vgs+Vf2, the operation of the power supply switching circuit 12 supplies power from V5 to the internal power supply circuit 13, and the power consumption of the power supply IC 11 is reduced. At this time, the V3 voltage becomes V3B=V5-Vf2.

That is, in the startup sequence, the internal power supply circuit 13 is started by the constant voltage V3A=Vz+Vf1-Vgs (first voltage), and the step-down switching regulator 14 is started by the V4 voltage (third voltage) supplied from the internal power supply circuit 13. After that, the step-down switching regulator 14 supplies the output voltage V5 to the internal power supply circuit 13.

From t1 to t2 indicates the normal operation period of the power supply IC11. During this period, the vehicle-mounted electronic control device including the microcomputer continues the normal operation, and the power consumption of the power supply IC 11 becomes the largest. Since the V5 voltage is constantly output during that period and the power consumption of the internal power supply circuit 13 is reduced to about half, the power consumption of the power supply IC 11 is suppressed and the heat generation thereof is also reduced.

From t2 to t3 indicates the end period of the power supply IC 11. Due to the fall of the start signal, the step-down switching regulator 14 and each series power supply 15 are shut off, and finally the termination sequence in which the internal power supply circuit is turned off is started.

When the V5 voltage becomes lower than the desired voltage Vz+Vf1−Vgs+Vf2 during the termination period of the power supply IC11, the internal power supply circuit 13 is switched to the drive from the battery power supply V0 by the operation of the power supply switching circuit 12, and the stable operation is continued. It becomes possible. That is, in the termination sequence, when the voltage supplied from the step-down switching regulator 14 to the internal power supply circuit 13 is lower than the predetermined voltage (Vz+Vf1-Vgs+Vf2), the power supply switching circuit 12 supplies V3A (first voltage) to the battery 10 (battery power supply). ) Through the NMOS 23 (transistor).

At this time, the effect of reducing the power consumption of the internal power supply circuit 13 disappears, but the power supply IC 11 is operating in the end period and the operation of the vehicle-mounted control device by the microcomputer is stopped, so that the power consumption of the power supply IC 11 as a whole is sufficient. Since it is low, it does not affect heat generation.

Similarly, during the startup period of the power supply IC 11, the power consumption of the internal power supply circuit 13 is not reduced, but since the power consumption of the entire power supply IC is sufficiently small, it does not affect heat generation.

Here, the internal power supply circuit 13 generates a constant output voltage V4 (third voltage) from the input voltage V3A=Vz+Vf1-Vgs (first voltage) or V3B=V5-Vf2 (second voltage). The internal power supply circuit 13 supplies the output voltage V4 to the step-down switching regulator 14.

(Summary of Embodiment 3)
As described above, when the power supply switching circuit 12 is applied to the power supply IC 11, the step-down switching regulator output voltage V5 becomes equal to or higher than a desired voltage. By switching to V5, the power consumption of the internal power supply circuit 13 can be reduced. Further, during the start-up period and the end period of the power supply IC, even when the power supply of the internal power supply circuit 13 is switched due to the change of the V5 voltage, the internal power supply circuit 13 can continue the operation stably.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are included. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add/delete/replace other configurations with respect to a part of the configurations of the respective embodiments.

Although the step-down switching regulator 14 is provided inside the power supply IC 11 in the above embodiment, it may be provided outside the power supply IC 11.

Although the NMOS 23 is used as the transistor in the above embodiment, an NPN bipolar transistor may be used.

The embodiment of the present invention may have the following aspects.

(1). The first power supply has an output terminal to which a current path supplied from the first power supply via the NMOS transistor and a current path supplied from the second power supply via the rectifying diode are connected. Connected to the resistor for correcting the temperature characteristic and the Zener diode for generating the reference voltage, and the reference voltage generated by the Zener voltage and the forward voltage of the diode is connected to the gate of the NMOS transistor. A voltage that does not depend on the power supply voltage is supplied from the first power supply to the output terminal, and when the second power supply voltage is higher than the desired voltage supplied from the first power supply to the output terminal, a current flows from the second power supply to the output terminal. A power supply switching circuit characterized by being supplied.

(2). In the power supply switching circuit according to (1), when the second power supply voltage is lower than a desired voltage supplied from the first power supply to the output terminal, the first power supply voltage is supplied from the first power supply through an NMOS transistor. A power supply switching circuit characterized in that a voltage independent of the voltage is supplied to an output terminal.

(3). In the power supply switching circuit according to (1) or (2), the first power supply is a battery power supply, and the second power supply is a step-down switching regulator.

(4). The power supply switching circuit according to any one of (1) to (3), wherein the output terminal is connected to an internal power supply circuit in the IC.

(5). The power supply switching circuit according to any one of (1) to (4), wherein a diode for preventing backflow is provided in the first power supply.

(6). An on-vehicle electronic control device including the power supply switching circuit according to any one of (1) to (5), wherein the power supply switching circuit is mounted on a power supply IC.

(7). In the in-vehicle electronic control device including the power supply switching circuit according to any one of (1) to (5), the internal power supply is driven by using a battery voltage at the time of startup, and the step-down switching regulator is started, and then the step-down switching regulator. An in-vehicle electronic control device comprising a power supply IC that applies the voltage of 1. to the internal power supply.

(8). In the on-vehicle electronic control device including the power supply switching circuit according to any one of (1) to (5), when the voltage of the step-down switching regulator that was driving the internal power supply is equal to or lower than a predetermined voltage when stopped. The vehicle-mounted electronic control device, further comprising: the power supply IC that switches to the battery voltage.

According to (1) to (8), it is possible to stably switch the power supply to the internal power supply circuit with a small voltage fluctuation. When applied to an on-vehicle electronic control device, by switching between the battery voltage and the step-down switching regulator output voltage, the power consumption of the internal power supply circuit can be reduced and the heat generation of the IC can be reduced. Further, by reducing the heat generation of the IC, a low-cost package having a relatively large thermal resistance can be selected, the heat dissipation structure of the housing of the vehicle-mounted control device for finally radiating the heat generation of the IC can be simplified, and the cost of the heat dissipation material can be reduced. There is an effect that the cost of the in-vehicle control device can be reduced, for example.

10... Battery 11... Power supply IC
12, 12A, 12B... Power supply switching circuit 13... Internal power supply circuit 14... Step-down switching regulator 15... Series power supply (external drive power supply)
16... Driver circuit 17... Inductor 18... First capacitor 20... Resistor 21... First diode 22... Zener diode 23... NMOS
24... 2nd diode 25... 2nd capacitor 26... 1st node 27... 2nd node 28... I3 current 29... 3rd diode 30... Microcomputer 31... In-vehicle electronic control unit 32, 33... Actuator load 34... Sensor

Claims (12)

An output terminal connected to a first node connecting a current path connected to the first power supply and a current path connected to a second power supply that supplies a voltage lower than the first power supply;
A resistor connected to the first power supply,
A Zener diode connected in series with the resistor,
A control electrode connected to a second node connecting the resistor and the Zener diode is provided, and a current path between the first power supply and the output terminal is turned on according to a voltage applied to the control electrode. / A transistor that turns off,
A second diode that rectifies a current flowing through a current path between the second power source and the output terminal;
A power supply switching circuit comprising: The power supply switching circuit according to claim 1,
The power supply switching circuit further comprising a capacitor whose one end is connected to the output terminal. The power supply switching circuit according to claim 2,
The power supply switching circuit further comprising a first diode having an anode connected to the second node and a cathode connected to the cathode of the Zener diode. The power supply switching circuit according to claim 3,
The power supply switching circuit further comprising a third diode having an anode connected to the transistor and a cathode connected to the first node. The power supply switching circuit according to claim 3,
The output terminal is
By applying the reference voltage generated by the zener diode and the first diode to the control electrode of the transistor, a first voltage that does not depend on the voltage of the first power supply is passed from the first power supply through the transistor. Output,
A power supply switching circuit, wherein when the voltage of the second power supply is higher than a predetermined voltage, the second voltage is output from the second power supply via the second diode. The power supply switching circuit according to claim 5,
The output terminal is
A power supply switching circuit, wherein when the voltage of the second power supply is lower than the predetermined voltage, the first voltage is output from the first power supply via the transistor. The power supply switching circuit according to claim 5,
The first power source is
Battery power,
The second power source is
A power supply switching circuit characterized by being a step-down switching regulator. The power supply switching circuit according to claim 3,
The first diode is
A power supply switching circuit, which cancels a negative temperature characteristic of the voltage of the transistor. A power supply IC including the power supply switching circuit according to claim 7.
The step-down switching regulator,
And an internal power supply circuit that generates a third voltage from the first voltage or the second voltage,
The internal power supply circuit is
A power supply IC, wherein the third voltage is supplied to the step-down switching regulator. A power supply IC including the power supply switching circuit according to claim 9.
In the startup sequence, the internal power supply circuit is started by the first voltage, the step-down switching regulator is started by the third voltage supplied from the internal power supply circuit, and then the step-down switching regulator is supplied to the internal power supply circuit by voltage. Power supply IC characterized by supplying A power supply IC including the power supply switching circuit according to claim 9.
In the termination sequence, the power supply switching circuit outputs the first voltage from the battery power supply via the transistor when the voltage supplied from the step-down switching regulator to the internal power supply circuit is lower than the predetermined voltage. Characteristic power supply IC. An in-vehicle electronic control device including the power supply switching circuit according to claim 7.
The step-down switching regulator,
And an internal power supply circuit that generates a third voltage from the first voltage or the second voltage,
The internal power supply circuit is
An in-vehicle electronic control device, wherein the third voltage is supplied to the step-down switching regulator.

Images