JP2013156874A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for preventing sudden stop of voltage supply from a power supply circuit.SOLUTION: A power supply circuit includes: a switching regulator for performing driving to step down input voltage; a series regulator connected to the switching regulator in parallel and configured to perform driving to step down the input voltage; and a control circuit for stopping driving of the series regulator when the input voltage exceeds a predetermined voltage value. With this configuration, when the switching regulator of the power supply circuit has not been driven because of a failure or the like before an electronic device starts operating, the power supply circuit can be prevented from suddenly stopping voltage supply to the electronic device while the electronic device is operating. Furthermore, the safety of a system using the power supply circuit can be secured.

Description

  The present invention relates to a power supply circuit that steps down a voltage.

  A power supply circuit that steps down an input voltage from a battery power supply and outputs the voltage to an electronic device is configured as follows. For example, the power supply circuit includes an input unit to which a voltage is input and an output unit from which the stepped-down voltage is output, and is connected between the input unit and the output unit in parallel with the switching regulator. A series regulator is provided to step down the input voltage and output it to the electronic device. Specifically, the switching regulator is normally driven to output a voltage obtained by stepping down the input voltage. If the target voltage is not obtained due to load fluctuations, etc., the target voltage can be obtained by driving the series regulator. To be able to. Note that there is Patent Document 1 as a material for explaining the technology related to the present invention.

Japanese Patent Laid-Open No. 11-3126

  However, in the configuration in which the series regulator is driven when the target voltage cannot be obtained by the step-down process of the switching regulator, the series regulator is continuously driven when the switching regulator is not driven due to a failure or the like. In such a case, when the series regulator is continuously driven when the input voltage is higher than a predetermined voltage, energy loss exceeding the allowable range may occur from the series regulator, and the series regulator may be damaged. As a result, an electronic device that receives a voltage supply from the power supply circuit may suddenly stop during the operation.

  An object of the present invention is to prevent a sudden supply stop of a voltage from a power supply circuit.

  In order to solve the above-described problems, the present invention provides a switching regulator that performs driving to step down an input voltage, a series regulator that is connected in parallel to the switching regulator and performs driving to step down the input voltage, and the input voltage And a control circuit for stopping the driving of the series regulator when the value exceeds a predetermined voltage value.

  In the power supply circuit, the control circuit according to the present invention stops driving the series regulator regardless of a driving state in which the switching regulator steps down the input voltage.

  The present invention also includes a first series regulator provided between an input unit to which an input voltage is applied and an output unit that outputs a voltage obtained by stepping down the input voltage, and the input unit and the output unit. A second series regulator provided in series with the first series regulator, and depending on whether a switching regulator is connected in parallel to the first series regulator, the first series regulator A control circuit for setting a resistance value of a resistance element connected to an input terminal of the analog arithmetic circuit.

  Furthermore, in the power supply circuit according to the present invention, when the switching regulator is connected, the control circuit sets a resistance value of the resistance element in correspondence with a first target voltage of a voltage divided using the resistance element. When the switching regulator is not connected, the first target voltage of the voltage divided using the resistance element according to the input voltage and a second voltage value higher than the first target voltage The resistance value of the resistance element is set in correspondence with one of the target voltages.

According to the present invention, when the input voltage exceeds a predetermined voltage value, the driving of the series regulator is stopped, so that the switching regulator of the power supply circuit is not already driven due to a failure or the like before the electronic device starts operating. In this case, it is possible to prevent the power supply circuit from suddenly stopping the supply of voltage to the electronic device during the operation of the electronic device. In addition, the safety of the system using this power supply circuit can be ensured.
In addition, according to the present invention, the control circuit stops driving the series regulator regardless of the driving state in which the switching regulator steps down the input voltage, so that the switching regulator does not continuously drive due to a failure or the like. In addition, the series regulator can be continuously driven to prevent the series regulator from failing.

  Furthermore, according to the present invention, the resistance value of the variable resistor connected to the input terminal of the analog arithmetic circuit of the first series regulator is set according to the presence or absence of the switching regulator connected in parallel with the first series regulator. Therefore, it is possible to design as needed without changing the basic circuit configuration, and the versatility of the IC can be improved.

FIG. 1 is a diagram illustrating a circuit configuration of a power supply circuit according to the first embodiment. FIG. 2 is a diagram illustrating a driving state of the regulator according to the input voltage. FIG. 3 is a diagram illustrating a circuit configuration of the power supply circuit according to the second embodiment. FIG. 4 is a diagram illustrating a circuit configuration of the power supply circuit according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are exemplifications, and do not limit the technical scope of the present invention.

<First Embodiment>
<1-1. Power supply circuit>
FIG. 1 is a circuit diagram of the power supply circuit 1. The power supply circuit 1 steps down and outputs an input voltage from a battery power supply (for example, the battery power supply 3 shown in FIG. 1) in order to supply a voltage for operating an ECU (Electronic Control Unit) mounted on the vehicle, for example. In the present embodiment, for example, it is employed as a power supply circuit for supplying constant power to a microcomputer of an engine control ECU that controls driving of the engine.
When the engine is started, power from the battery power supply 3 is supplied to the power supply circuit 1 by operating an ignition switch (not shown). Then, the power from the battery power source 3 is converted to a constant power by the power circuit 1, and the operating power is supplied to the microcomputer, whereby the microcomputer starts the engine control process. As a result, the engine control ECU starts to be driven, and engine drive control is performed.

Next, the background of the functional arrangement of the power supply circuit 1 in the present embodiment will be described. In order to reduce the cost of the engine control ECU, it is conceivable to simplify the configuration by integrating the configuration such as the switching regulator 10 as one IC.
However, when the switching regulator 10 is incorporated in the IC 2, there is a limitation on the current capability. Therefore, it is desirable to adopt a general-purpose switching regulator 10 and externally attach the general-purpose switching regulator 10 to the IC 2.
However, when the general-purpose switching regulator 10 is employed, it is necessary to support this because the minimum operating voltage of the switching regulator 10 is high.
This time, the first series regulator 11 that is driven at a low voltage is adopted as the support function, and the first series regulator 11 is driven even at a low voltage so that power is supplied to the microcomputer.

  The power supply circuit 1 includes a switching regulator 10, a first series regulator 11, a second series regulator 12, between an input unit 401 to which an input voltage from the battery power supply 3 is applied and an output unit 402 that supplies a stepped down voltage to the ECU. A control circuit 13, a polar capacitor 21, and a capacitor 22 are mainly provided. Here, the first series regulator 11 and the second series regulator 12 are connected in series, and the first series regulator 11 and the switching regulator 10 are connected in parallel.

  The polar capacitor 21 of the power supply circuit 1 is, for example, an electrolytic capacitor, and one end is connected to the collector of the PNP transistor 111, one end of the capacitor 103, and one end of the resistor 112 via the terminal T3 of the IC2. . The other end of the polar capacitor 21 is connected to the ground.

  Further, the capacitor 22 is, for example, a ceramic capacitor, and one end thereof is connected to one end of the polar capacitor 21 and an emitter of a PNP transistor 201 of the second series regulator 12 described later. The other end of the capacitor 22 is connected to the ground.

  The power supply circuit 1 also includes an IC (Integrated Circuit) 2 in a part thereof, and elements inside the IC 2 are connected to elements outside the IC 2 via terminals T1 to T6.

<1-2. Switching regulator>
The switching regulator 10 is driven so that a voltage (for example, DC voltage 14V) from the battery power supply 3 is used as an input voltage, and the input voltage is stepped down to a predetermined voltage (for example, DC voltage 6.5V). The switching regulator 10 mainly includes a switching circuit unit 101, a coil 102, a capacitor 103, and a diode 104. Note that all the voltages described below are DC voltages.

  The switching circuit unit 101 has one end connected to the battery power supply 3 and the other end connected to one end of a coil 102 described later and the cathode of the diode 104. The switching circuit unit 101 is connected to the ground. The switching circuit unit 101 converts an input voltage from the battery power supply 3 into a voltage corresponding to switching control of a switching element (for example, an N channel MOS FET (Metal Oxide Semiconductor Field Effect Transistor)) provided in the switching circuit unit 101. And output.

  One end of the coil 102 is connected to the other end of the switching circuit unit 101 and the cathode of the diode 104. The other end of the coil 102 is connected to one end of a capacitor 103 and a collector of a PNP transistor 111 described later. A feedback loop that outputs a voltage to the switching circuit unit 101 is formed at the other end of the coil 102.

  One end of the capacitor 103 is connected to the other end of the coil 102 and the collector of the PNP transistor 111. The other end of the capacitor 103 is connected to the ground.

  The anode of the diode 104 is connected to the ground, and the cathode is connected to the other end of the switching circuit unit 101 and one end of the coil 102.

  The coil 102, the capacitor 103, and the diode 104 smooth the voltage output from the switching circuit unit 101 and output the smoothed voltage to the collector of the PNP transistor 111. For example, when the voltage value of the input voltage supplied from the battery power supply 3 to the switching regulator 10 is 14 V, the switching regulator 10 steps down the voltage output from the switching regulator 10 to 6.5 V by switching control and smoothing processing. And output. As a result, charges are accumulated in the polar capacitor 21 and the capacitor 22 of the power supply circuit 1, and these potentials are maintained at around 6.0V to 6.5V.

<1-3. First Series Regulator>
The first series regulator 11 mainly includes a PNP transistor 111, a resistor 112, a resistor 113, an error amplifier 114, a reference power supply 115, an OR circuit 116, and a buffer 117. The emitter of the PNP transistor 111 is connected to the battery power source 3, and the base is connected to the output terminal of the buffer 117 via the terminal T2 of the IC2. The collector is connected to one end of the capacitor 103, one end of the resistor 112 via the terminal T3 of the IC2, and one end of the polar capacitor 21.

  One end of the resistor 112 is connected to the collector of the PNP transistor 111, one end of the capacitor 103, and one end of the polar capacitor 21 via a terminal T3. The other end of the resistor 112 is connected to one end of the resistor 113 and the non-inverting input terminal of the error amplifier 114.

  One end of the resistor 113 is connected to the other end of the resistor 112 and the non-inverting input terminal of the error amplifier 114, and the other end of the resistor 113 is connected to the ground.

  The error amplifier 114 is an analog arithmetic circuit, and includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The non-inverting input terminal is connected to the other end of the resistor 112 and one end of the resistor 113. The inverting input terminal is connected to one end of the reference power supply 115. The output terminal is connected to one input terminal of the OR circuit 116.

  One end of the reference power supply (for example, 1.25 V) 115 is connected to the inverting input terminal of the error amplifier 114, and the other end of the reference power supply 115 is connected to the ground.

One input terminal of the OR circuit 116 is connected to an output terminal of the error amplifier 114, and the other input terminal of the OR circuit 116 is connected to an output terminal of an AND circuit 306 of the control circuit 13 described later. The output terminal of the OR circuit 116 is connected to the input terminal of the buffer 117.
The input end of the buffer 117 is connected to the output end of the OR circuit 116, and the output end of the buffer 117 is connected to the base of the PNP transistor 111 via the terminal T2.

  Here, a target voltage (hereinafter referred to as “first target voltage”) at the contact CP1 to which the collector of the PNP transistor 111 of the first series regulator 11, one end of the resistor 112, and one end of the capacitor 103 are connected. For example, 6.0V. In this case, a voltage obtained by dividing 6.0V by the resistor 112 and the resistor 113 is applied to the non-inverting input terminal of the error amplifier 114. The resistance values of the resistor 112 and the resistor 113 are set in advance so that the voltage of the contact CP2 corresponding to the divided voltage and the voltage of the reference power supply 115 are the same voltage (for example, 1.25 V). . For example, when the resistance value of the resistor 112 is RΩ, the resistance value of the resistor 113 is R / 3.8Ω.

  When the power supply circuit 1 is actually driven, when the voltage divided by the resistor 112 and the resistor 113 is lower than the voltage of the reference power supply 115, that is, when the voltage of the contact CP1 is lower than the first target voltage, A Low signal is output from the output terminal of the error amplifier 114 to one input terminal of the OR circuit 116. When a low signal is output from the output terminal of the AND circuit 306 of the control circuit 13 to be described later and a low signal is input to the other input terminal of the OR circuit 116, a low signal is output from the output terminal of the OR circuit 116. Is output.

  The Low signal output from the output terminal of the OR circuit 116 is transmitted to the base of the PNP transistor 111 via the buffer 117 and the terminal T2. As a result, a current flows between the emitter and collector of the PNP transistor 111, charges are accumulated in the polar capacitor 21 and the capacitor 22, and the potential of CP1 is raised to a potential corresponding to the first target voltage.

  When the power supply circuit 1 is actually driven, when the voltage divided by the resistor 112 and the resistor 113 is higher than the voltage of the reference power supply 115, that is, when the voltage of the contact CP1 is higher than the first target voltage. The High signal is output from the output terminal of the error amplifier 114 to one input terminal of the OR circuit 116. When either one of the Low signal and the High signal is output from the output terminal of the AND circuit 306 of the control circuit 13 described later and is input to the other input terminal of the OR circuit 116, at least the OR circuit. Since the signal at one of the input terminals is a High signal, the High signal is output from the output terminal of the OR circuit 116. The High signal output from the output terminal of the OR circuit 116 is transmitted to the base of the PNP transistor 111 via the buffer 117 and the terminal T2. As a result, no current flows between the emitter and collector of the PNP transistor 111, the charges of the polar capacitor 21 and the capacitor 22 are reduced, and the potential of CP1 is lowered to a potential corresponding to the first target voltage.

Here, in the conventional technique, when the switching regulator is normally driven, the target voltage of the contact (for example, the portion corresponding to the contact CP1) is 6.0V, and the actual voltage is, for example, about 6.5V, the error amplifier The voltage at the contact corresponding to the voltage applied to the non-inverting input terminal (for example, the portion corresponding to the contact CP2) is higher than the voltage of the reference power supply (1.25V). Therefore, a high signal is output from the output terminal of the error amplifier to one input terminal of the OR circuit.
A high signal is transmitted from the OR circuit to the base of the PNP transistor via the buffer regardless of the type of signal input from the AND circuit of the control circuit to the other input terminal of the OR circuit. As a result, the control of the PNP transistor is turned off, and no current flows between the emitter and collector of the PNP transistor. As described above, in the conventional technique, the charge is accumulated in the polar capacitor and the capacitor by the processing of the switching regulator, and the control in which the potential of the contact is raised to the potential corresponding to the target voltage is continuously performed.

  When the switching regulator is normally driven, the series regulator is stopped without being driven. However, when the switching regulator breaks down due to disconnection or the like in the switching circuit unit and does not drive normally, the voltage at the contact (for example, the portion corresponding to the contact CP1) falls below the voltage corresponding to the target voltage. Therefore, instead of the switching regulator, the series regulator is driven to set the voltage at the contact to a voltage corresponding to the target voltage. In this case, a current is continuously passed between the emitter and collector of the PNP transistor, resulting in energy loss.

  If the process of stepping down the input voltage of the battery power source is continuously performed only with the series regulator, the allowable energy loss of the PNP transistor may be exceeded. As a result, when the PNP transistor fails, the series regulator may not be driven, and the voltage supply from the power supply circuit may suddenly stop during the operation of the ECU. May stop the user's safety.

  In order to solve such a problem, when the voltage value of the input voltage exceeds a first reference voltage (for example, 8V) described later, in the technique of the first embodiment, the control circuit 13 has the first series regulator. 11 is stopped. That is, regardless of the driving state in which the switching regulator 10 steps down the input voltage (regardless of the voltage at the contact CP1), if the voltage value of the input voltage is higher than the first reference voltage, the first series regulator is driven. 13 stops. Details thereof will be described below.

<1-4. Control circuit>
The control circuit 13 mainly includes a resistor 301, a resistor 302, a comparator 303, a reference power supply 304, an inverter 305, and an AND circuit 306. One end of the resistor 301 is connected to the battery power source 3 via the terminal T1. The other end of the resistor 301 is connected to one end of the resistor 302 and a non-inverting input terminal of the comparator 303. One end of the resistor 302 is connected to the other end of the resistor 301, and the other end of the resistor 302 is connected to the ground.
The non-inverting input terminal of the comparator 303 is connected to the other end of the resistor 301 and one end of the resistor 302. The inverting input terminal of the comparator 303 is connected to the reference power supply 304, and the output terminal of the comparator 303 is connected to one input terminal of the AND circuit 306.

One end of a reference power supply (for example, 1.25 V) 304 is connected to the inverting input terminal of the comparator 303, and the other end is connected to the ground.
The input terminal of the inverter 305 is connected to the terminal T 6, and the output terminal of the inverter 305 is connected to the other input terminal of the AND circuit 306. A low signal is input to the input terminal of the inverter 305 via the terminal T6.

One input terminal of the AND circuit 306 is connected to the output terminal of the comparator 303, and the other input terminal is connected to the output terminal of the inverter 305. The output terminal of the AND circuit 306 is connected to the other input terminal of the OR circuit 116 of the first series regulator 11.
In the control circuit 13, for example, when the voltage value of the battery power supply 3 as an input voltage is 8V, the voltage of the contact CP3 obtained by dividing the input voltage by the resistor 301 and the resistor 302 is the voltage of the reference power supply 304 (for example, 1.25V The resistance values of the resistor 301 and the resistor 302 are set in advance so as to be the same voltage as in FIG. For example, if the resistor 301 is RΩ, the resistance value of the resistor 302 is R / 5.4Ω.

  A voltage for controlling the driving of the first series regulator 11 is referred to as a first reference voltage (for example, 8V). When the input voltage exceeds the first reference voltage, the driving of the first series regulator is stopped. Specifically, when the input voltage exceeds the first reference voltage, the voltage value of the contact CP3 divided by the resistor 301 and the resistor 302 exceeds 1.25V, and the voltage exceeding 1.25V is the non-inverting input of the comparator 303. Applied to the terminal. Then, the comparator 303 compares the voltage value applied to the non-inverting input terminal with the voltage value of the reference power source 304 applied to the inverting input terminal. As a result, since the voltage value applied to the non-inverting input terminal is higher, the High signal is output from the output terminal of the comparator 303, and the High signal is input to one input terminal of the AND circuit 306. Since the High signal from the output terminal of the inverter 305 is input to the other input terminal of the AND circuit, the High signal is output from the output terminal of the AND circuit 306 to the other input terminal of the OR circuit 116.

  Since the High signal is input to the other input terminal of the OR circuit 116, the signal input to the one input terminal of the OR circuit 116 is either the High signal or the Low signal. A high signal is output from the output terminal. This High signal is transmitted to the base of the PNP transistor 111 via the buffer 117 and the terminal T2. As a result, the control of the PNP transistor 111 is turned off, and no current flows between the emitter and the collector.

  As described above, when the input voltage exceeds the first reference voltage, the driving of the first series regulator 11 is stopped, so that the switching regulator 10 of the power supply circuit 1 is already caused by a failure or the like before the ECU starts the operation. When not driven, it is possible to prevent the power supply circuit 1 from suddenly stopping the supply of voltage to the microcomputer of the ECU during operation of the ECU. Moreover, the safety of the vehicle system using this power supply circuit 1 can be ensured. Further, such control is performed regardless of the driving state in which the switching regulator 10 steps down the input voltage. That is, since the switching is performed regardless of the driving state of the switching regulator 10, the first series regulator 11 is continuously driven when the switching regulator 10 is not continuously driven due to a failure or the like. Can be prevented from breaking down.

  When the input voltage is lower than the first reference voltage, the driving of the first series regulator 11 is controlled according to the voltage value of the contact CP1 with respect to the first target voltage. Specifically, when the input voltage is lower than the first reference voltage, the voltage value of the contact CP3 divided by the resistor 301 and the resistor 302 is lower than 1.25V, and the voltage lower than 1.25V is the non-inverting input terminal of the comparator 303. To be applied. Then, the comparator 303 compares the voltage value applied to the non-inverting input terminal with the voltage value of the reference power source 304 applied to the inverting input terminal. As a result, since the voltage value applied to the non-inverting input terminal is lower, the Low signal is output from the output terminal of the comparator 303 and input to one input terminal of the AND circuit 306. In addition, since the High signal from the output terminal of the inverter 305 is input to the other input terminal of the AND circuit, the Low signal is output from the output terminal of the AND circuit 306 to the other input terminal of the OR circuit 116.

  When a Low signal is input to the other input terminal of the OR circuit 116 and a High signal is input to one input terminal of the OR circuit 116, the buffer 117 and the terminal T2 are used. The High signal is transmitted to the base of the PNP transistor 111 and no current flows between the emitter and the collector. When a Low signal is input to one input terminal of the OR circuit 116, the Low signal is transmitted to the base of the PNP transistor 111 via the buffer 117 and the terminal T2, and the current between the emitter and the collector is Flowing.

<1-5. Graph of drive status of each regulator>
Here, the drive state according to the input voltage of the switching regulator 10 and the 1st series regulator 11 is demonstrated using FIG. FIG. 2 is a diagram illustrating a driving state according to the input voltage of each regulator. The horizontal axis of the graph shown in FIG. 2 indicates the input voltage (V), and the vertical axis indicates the output voltage (V). The upper diagram of FIG. 2 shows a driving state corresponding to the input voltage of the switching regulator 10. The switching regulator 10 outputs an output voltage of 6.5V while the input voltage is between 14V and 8V. When the input voltage is between 8V and 6V, the value of the output voltage decreases with a predetermined slope. When the input voltage is 6V or less, the output voltage becomes 0V.

  The lower diagram of FIG. 2 shows a driving state according to the input voltage of the first series regulator 11. The first series regulator 11 has an input voltage of 14V to 8V and an output voltage of 0V. This is because the High signal is output from the output terminal of the AND circuit 306 of the control circuit 13 to the input terminal of the OR circuit 116 of the first series regulator 11 in the circuit diagram of the power supply circuit 1 shown in FIG. Is transmitted to the PNP transistor 111, the control of the PNP transistor 111 is turned off, and no current flows between the emitter and the collector. When the input voltage is 8V, the output voltage is 6V, and thereafter the output voltage is maintained at 6V while the input voltage drops from 8V. Thereafter, until the input voltage further decreases to 3 V, the output voltage decreases from 6 V with a predetermined slope. When the input voltage falls below 3V, the output voltage becomes 0V.

  As described above, the ranges of the input voltages driven by the switching regulator 10 and the first series regulator 11 are different from each other. In particular, the input voltage of the first series regulator 11 is the first reference voltage (8V). If it exceeds, do not drive.

<1-6. Second Series Regulator>
Returning to FIG. 1, the second series regulator will be described. The second series regulator 12 mainly includes a PNP transistor 201, a resistor 202, a resistor 203, an error amplifier 204, a reference power source 205, and a buffer 206. The emitter of the PNP transistor 201 is connected to one end of the capacitor 22, and the base is connected to the output end of the buffer 206 via the terminal T4 of IC2. The collector is connected to one end of the resistor 202 and one end of the polar capacitor 23 via a terminal T5 of the IC2.

  One end of the resistor 202 is connected to the collector of the PNP transistor 201 and one end of the polar capacitor 23 via a terminal T5. The other end of the resistor 202 is connected to one end of the resistor 203 and the non-inverting input terminal of the error amplifier 114.

  One end of the resistor 203 is connected to the other end of the resistor 202 and the non-inverting input terminal of the error amplifier 204, and the other end of the resistor 203 is installed on the ground.

  The error amplifier 204 is an analog arithmetic circuit, and includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The non-inverting input terminal is connected to the other end of the resistor 202 and one end of the resistor 203. The inverting input terminal is connected to one end of the reference power source 205. The output terminal is connected to the input terminal of the buffer 206.

One end of a reference power supply (for example, 1.25 V) 205 is connected to the inverting input terminal of the error amplifier 204, and the other end is connected to the ground.
The input end of the buffer 206 is connected to the output end of the error amplifier 204, and the output end of the buffer 206 is connected to the base of the PNP transistor 201.

  Then, a target voltage (hereinafter referred to as “specific target voltage”) at the contact CP4 to which the collector of the PNP transistor 201 of the second series regulator 12, one end of the resistor 202, and one end of the polar capacitor 23 are connected. For example, 5.0V. In this case, a voltage obtained by dividing 5.0 V by the resistor 202 and the resistor 203 is a voltage applied to the non-inverting input terminal of the error amplifier 204. The resistance values of the resistor 202 and the resistor 203 are set in advance so that the voltage of the contact CP5 corresponding to the divided voltage and the voltage of the reference power supply 205 are the same voltage (for example, 1.25 V). . For example, when the resistance value of the resistor 202 is RΩ, the resistance value of the resistor 203 is R / 3Ω.

  When the power supply circuit 1 is actually driven, when the voltage of the contact CP5 divided by the resistor 202 and the resistor 203 is lower than the voltage of the reference power supply 205, that is, the voltage of the contact CP4 is lower than the specific target voltage. When low, a low signal is output from the output terminal of the error amplifier 204 to the input terminal of the buffer 206. Then, the Low signal output from the output terminal of the buffer 206 is transmitted to the base of the PNP transistor 201 via the terminal T4. As a result, a current flows between the emitter and collector of the PNP transistor 201, charges are accumulated in the polar capacitor (for example, electrolytic capacitor) 23 and the capacitor (for example, ceramic capacitor) 24, and the potential of CP4 becomes the specific target voltage. Raised to the corresponding potential.

  Further, when the power supply circuit 1 is actually driven, when the voltage of the contact CP5 divided by the resistor 202 and the resistor 203 is higher than the voltage of the reference power supply 205, that is, the voltage of the contact CP4 is higher than the specific target voltage. When it is high, a high signal is output from the output terminal of the error amplifier 204 to the input terminal of the buffer 206. The High signal output from the output end of the buffer 206 is transmitted to the base of the PNP transistor 201 via the terminal T4. As a result, no current flows between the emitter and collector of the PNP transistor 201, the charges of the polar capacitor 23 and the capacitor 24 are reduced, and the potential of CP4 is lowered to a potential corresponding to the specific target voltage. In this manner, the potentials of the polar capacitor 23 and the capacitor 24 are adjusted to a potential corresponding to the specific target voltage, and a voltage for driving the ECU that is the electronic device is supplied from the output unit 402.

  The operation of the power supply circuit 1 described above will be described from when the engine is started (when processing of the ECU microcomputer is started). First, when an ignition switch (not shown) is operated, power from the battery 3 is supplied to the power supply circuit 1. If the switching regulator 10 has already failed at the time of startup, power is not supplied from the switching regulator 10 to the microcomputer even if the input voltage rises to 0V to 14V.

On the other hand, in the first series regulator 11, when the input voltage reaches 3V from 0V as shown in the lower diagram of FIG. 2, the power supply to the microcomputer is started (low voltage support). If it exceeds the above, the drive of the first series regulator 11 is stopped by the action of the control circuit 13, and the power supply to the microcomputer is stopped. Thereby, it is possible to prevent the first series regulator 11 from continuing to operate and failing.
Furthermore, when the engine is started, that is, before the engine control ECU starts driving for actual travel, the power supply to the microcomputer is stopped and the engine drive control is stopped, so that the switching regulator 10 remains broken. The vehicle can be prevented from traveling in advance, and a high power supply function and a fail-safe function can be realized while being a low-cost ECU.

<Second Embodiment>
Next, a second embodiment will be described. The differences between the second embodiment and the first embodiment are as follows. The power supply circuit 1 described in the first embodiment has a configuration in which the switching regulator 10 is connected in parallel to the first series regulator 11. Here, by connecting the switching regulator 10 to the first series regulator 11 in parallel, the number of components of the power supply circuit 1 may increase, which may hinder downsizing of the power supply circuit 1. Therefore, the following circuit configuration is desirable according to the size of the power supply circuit 1 required at the time of design. That is, a power supply circuit (for example, the power supply circuit 1a shown in FIG. 3) in which the switching regulator 10 is connected in parallel to the first series regulator 11a, and the switching regulator 10 are not connected in parallel to the first series regulator 11a (the switching regulator is IC2a). There is a need for a technique that can easily select a power supply circuit (for example, the power supply circuit 1 b shown in FIG. 4) without changing the basic circuit configuration of the power supply circuit 1.

  Hereinafter, as a second embodiment, a power supply circuit capable of changing the circuit setting according to whether or not the switching regulator 10 is connected to the IC 2a shown in FIGS. 3 and 4 will be described. The configuration in the second embodiment is substantially the same as that in the first embodiment. Below, it demonstrates centering around difference.

<2-1. New configuration of IC>
FIG. 3 is a diagram illustrating a circuit configuration of the power supply circuit 1a according to the second embodiment. FIG. 4 is a diagram illustrating a circuit configuration of the power supply circuit 1b according to the second embodiment. The difference in configuration between the power supply circuit 1a and the power supply circuit 1b shown in FIGS. 3 and 4 and the power supply circuit 1 shown in FIG. 1 is as follows. In FIGS. 3 and 4, first, the IC 2a has a basic circuit configuration. When the switching regulator 10 is connected in parallel to the first series regulator 11a included in the IC 2a (power supply circuit 1a shown in FIG. 3), and when the switching regulator 10 is not provided in the IC 2a (power supply circuit shown in FIG. 4). In order to realize 1b) by changing the setting in the circuit of the IC 2a which is the basic circuit configuration (changing the mode setting), a new configuration is provided in FIGS. 3 and 4 compared to the configuration in FIG. Yes.

  Specifically, the first series regulator 11a of the IC 2a in FIGS. 3 and 4 newly includes a resistor 113a, a resistor 113b, and a switch 118. The control circuit 13a newly includes a resistor 311, a resistor 312, a comparator 313, a reference power source 314, an inverter 315, and an AND circuit 316. Thus, using the circuit element newly provided in the IC 2a, the mode setting in the circuit of the IC 2a is performed according to whether or not the switching regulator 10 is connected.

<2-2. Explanation of modes>
Here, before describing in detail the configuration for changing the circuit setting of the IC 2a depending on whether or not the switching regulator 10 is connected in parallel to the first series regulator 11a, the functional difference of each mode. Will be described. The case where the switching regulator 10 is connected in parallel to the first series regulator 11a is referred to as “low loss mode”, for example. In this “low loss mode”, as shown in FIG. 3, the switching regulator 10 is connected in parallel with the first series regulator 11a, and the switching regulator 10 normally steps down the input voltage from the battery power supply 3 and contacts CP1. Is driven to a first target voltage (for example, 6V). Then, by driving the second series regulator 12 connected in series with the first series regulator 11a, the voltage stepped down by the switching regulator 10 is lowered so that the voltage at the contact CP4 becomes a specific target voltage (for example, 5V). Supply voltage to ECU microcomputer.

  The first series regulator 11 a supports the step-down process of the switching regulator 10, and the step-down process in the power supply circuit 1 in this case is realized mainly by driving the switching regulator 10. Therefore, the step-down processing using the switching regulator 10 has less energy loss in each regulator as compared with the case where the step-down processing is driven only by the first series regulator 11a and the second series regulator 12. A mode in which the switching regulator 10 is connected to the first series regulator 11a to perform step-down processing is referred to as a “low loss mode”. When the mode is set to the “low loss mode”, the low signal is set to be input to the input terminal of the inverter 305 at the time of setting as described later.

  Next, a case where the switching regulator 10 is not connected in parallel to the first series regulator 11a (a case where the switching regulator 10 is not provided in the IC 2a) is referred to as a “heat distribution mode”, for example. In this mode, the switching regulator 10 is not connected in parallel to the first series regulator 11a as shown in FIG. 4, but only the first series regulator 11a and the second series regulator 12 are connected in series.

In the above-described “low loss mode”, the switching regulator 10 drives the voltage of the contact CP1 to be the first target voltage (for example, 6V), and the second series regulator 12 sets the voltage of the contact CP4 to the specific target voltage (for example, for example). 5V). In contrast, in the “heat distribution mode”, a second reference voltage (for example, 11 V) is set with respect to the voltage of the battery power source 3 as an input voltage, and when the input voltage exceeds the second reference voltage, The first series regulator 11a drives the voltage at the contact CP1 to the second target voltage (for example, 10V), and the second series regulator 12 drives the voltage at the contact CP4 to the specific target voltage (for example, 5V). To do.

  In the “heat distribution mode”, when the input voltage is lower than the second reference voltage, the first series regulator 11a drives the voltage at the contact CP1 to be the first target voltage (for example, 6V), and the second The series regulator 12 drives the voltage at the contact CP4 to a specific target voltage (for example, 5V).

  Thereby, when the input voltage exceeds the second reference voltage, for example, when the input voltage is 14V, the first series regulator 11a steps down the input voltage 14V to 10V (when the current is 100mA, the energy loss (power consumption) ) Is 0.4W), and the second series regulator 12 steps down 10V to 5V (if the current is 100mA, the energy loss (power consumption) is 0.5W).

  When the input voltage is lower than the second reference voltage, for example, when the input voltage is 8V, the first series regulator 11a steps down the input voltage 8V to 6V (when the current is 100mA, energy loss (power consumption)). The second series regulator 12 steps down 6V to 5V (if the current is 100mA, the energy loss (power consumption) is 0.1W). A mode in which the step-down processing is mainly performed by two series regulators is referred to as a “heat dispersion mode”. With this configuration, the energy loss of each series regulator can be distributed to be approximately equal. When the mode is set to the “heat distribution mode”, a high signal is set to be input to the input terminal of the inverter 305 at the time of setting as described later.

<2-3. Details of IC circuit configuration>
Next, details of the circuit configuration according to whether or not the switching regulator 10 is connected in parallel will be described with reference to FIGS. One end of the resistor 113a of the first series regulator 11a of FIGS. 3 and 4 is connected to the other end of the resistor 112, and the other end of the resistor 113a is connected to one end of the resistor 113b. One end of the resistor 113b is connected to the resistor 113a, and the other end of the resistor 113b is connected to the ground.
One end of the switch 118 is connected between the other end of the resistor 113a and one end of the resistor 113b. The other end of the switch 118 is connected between the other end of the resistor 113b and the ground.

  Here, the combined resistance value of the resistor 113a and the resistor 113b is, for example, the same resistance value as the resistor 113 described in the first embodiment, and when the resistance value of the resistor 112 is RΩ, the resistor 113a and the resistor 113b The combined resistance value is R / 3.8Ω.

Next, the control circuit 13a that controls on / off of the switch 118 according to the type of mode set in the IC 2a will be described. One end of the resistor 311 of the control circuit 13 a shown in FIGS. 3 and 4 is connected to one end of the resistor 301. The other end of the resistor 311 is connected to one end of the resistor 312 and the non-inverting input terminal of the comparator 313. One end of the resistor 312 is connected to the other end of the resistor 311, and the other end of the resistor 312 is connected to the ground.
The non-inverting input terminal of the comparator 313 is connected to the other end of the resistor 311 and one end of the resistor 312. The inverting input terminal of the comparator 313 is connected to the reference power supply 314, and the output terminal of the comparator 313 is connected to one input terminal of the AND circuit 316.

One end of a reference power supply (for example, 1.25 V) 314 is connected to the inverting input terminal of the comparator 313, and the other end is connected to the ground.
The input terminal of the inverter 315 is connected to the output terminal of the inverter 305, and the output terminal of the inverter 315 is connected to the other input terminal of the AND circuit 316. Here, when the mode is set to the “low loss mode” in which the switching regulator 10 is connected to the first series regulator 11 a, the low signal is set to be input to the input terminal of the inverter 305 at the time of setting. Further, when the mode is set to the “heat distribution mode” without connecting the switching regulator 10 to the first series regulator 11a, the High signal is set to be input to the input terminal of the inverter 305 at the time of setting.

  One input terminal of the AND circuit 316 is connected to the output terminal of the comparator 313, and the other input terminal of the AND circuit 316 is connected to the output terminal of the inverter 315. The output terminal of the AND circuit 316 is configured to output a signal to the switch 118 of the first series regulator.

  The resistance values of the resistance 311 and the resistance 312 of the control circuit 13a are 11V when the input voltage from the battery power source 3 divided by the resistance 311 and the resistance 312 is the second reference voltage (for example, 11V), and the resistance 301 and the resistance 312. The voltage of the contact CP6 divided by 302 is set in advance so as to be the same voltage as the voltage of the reference power source 314 (for example, 1.25 V). For example, if the resistor 311 is RΩ, the resistance value of the resistor 312 is R / 7.8Ω.

  When the switching regulator 10 is set to the “low loss mode” connected to the first series regulator 11a, the Low signal is input to the input terminal of the inverter 305, and the High signal from the output terminal of the inverter 305 is The signal is input to the input terminal of the inverter 315. Then, the Low signal is input from the output terminal of the inverter 315 to the other input terminal of the AND circuit 316, so that the Low signal is output from the output terminal of the AND circuit 316 to the switch 118, and the switch 118 is turned off. It becomes.

  As a result, the first series regulator 11a causes the voltage of the contact CP1 to correspond to the first target voltage (for example, 6V) and divides 6V by the resistance 112 and the combined resistance of the resistance 113a and the resistance 113b. The resistance value of the resistance element that divides the voltage of the contact CP1 so that the voltage of the contact CP2 is the same as the voltage of the reference power supply 115 (if the resistance value of the resistor 112 is RΩ, the resistance 113a and the resistance 113b Set the combined resistance to R / 3.8Ω.

  Further, when the switching regulator 10 is set to a “heat distribution mode” that is not connected to the first series regulator 11 a, a high signal is input to the input terminal of the inverter 305, and a low signal from the output terminal of the inverter 305 is received. The signal is input to the input terminal of the inverter 315. A High signal is input from the output terminal of the inverter 315 to the other input terminal of the AND circuit 316. In addition, the voltage at the contact CP <b> 6 divided by the resistor 311 and the resistor 312 is input to one input terminal of the comparator 313. Further, the voltage of the reference power supply 314 is input to the other input terminal of the comparator 313, and the comparator 313 compares the voltage of the contact CP6 with the voltage of the reference power supply 314. When the input voltage exceeds the second reference voltage, the voltage at the contact CP6 exceeds the voltage of the reference power supply 314, and a High signal is output from the output terminal of the comparator 313 to one input terminal of the AND circuit 316. . As a result, the HIGH signal is output from the output terminal of the AND circuit 316 to the switch 118, and the switch 118 is turned on.

  As described above, the control circuit 13a associates the voltage at the contact CP1 with the second target voltage (for example, 10V) that is higher than the first target voltage, and divides 10V between the resistor 112 and the resistor 113a. The resistance value of the resistance element that divides the voltage of the contact CP1 so that the voltage of the contact CP2 is 1.25 V, which is the same as the voltage of the reference power supply 115 (when the resistance value of the resistor 112 is RΩ, The combined resistance value of the resistor 113b is set to R / 7Ω.

  When the switch 118 is turned on in this way, the current flowing through the resistor 113a and the resistor 113b when the switch 118 is turned off flows through the resistor 113a without passing through the resistor 113b, and then the switch 118 is turned on. It will flow into the ground through the route. For this reason, it can be said that the resistance 113a and the resistance 113b are a kind of variable resistance whose combined resistance value changes depending on on / off of the switch 118.

  When the “heat distribution mode” is set, a high signal is input to the input terminal of the inverter 305, and a low signal from the output terminal of the inverter 305 is input to the input terminal of the inverter 315. A High signal is input from the output terminal of the inverter 315 to the other input terminal of the AND circuit 316. In addition, the voltage at the contact CP <b> 6 divided by the resistor 311 and the resistor 312 is input to one input terminal of the comparator 313. Further, the voltage of the reference power supply 314 is input to the other input terminal of the comparator 313, and the comparator 313 compares the voltage of the contact CP6 with the voltage of the reference power supply 314. When the input voltage is lower than the second reference voltage, the voltage at the contact CP6 is lower than the voltage of the reference power source 314, and a Low signal is output from the output terminal of the comparator 313 to one input terminal of the AND circuit 316. . As a result, a Low signal is output from the output terminal of the AND circuit 316 to the switch 118, and the switch 118 is turned off.

  As described above, when the voltage of the contact CP1 is made to correspond to the first target voltage (for example, 6V) and the voltage of 6V is divided by the resistor 112, the resistor 113a, and the resistor 113b, the control circuit 13a The resistance value of the resistance element (when the resistance value of the resistor 112 is RΩ, the combined resistance value of the resistor 113a and the resistor 113b is R / 3.8Ω) so that the voltage of CP2 is 1.25V which is the same as the voltage of the reference power supply 115. Set. As a result, it is possible to design as necessary without changing the basic circuit configuration, and the versatility of the IC 2a can be improved.

  In this way, the control circuit 13a has an input terminal of the error amplifier 114 that is an analog arithmetic circuit of the first series regulator 11a depending on whether or not the switching regulator 10 is connected in parallel to the first series regulator 11a. Is set to the resistance value (the combined resistance value of the resistance 113a and the resistance 113b) of the resistance element (the resistance 113a and the resistance 113b).

  That is, when the switching regulator 10 is connected in parallel to the first series regulator 11a, the resistance value of the resistance element is set in accordance with the first target voltage of the voltage divided using the resistance element, and the switching regulator 10 Are not connected in parallel to the first series regulator 11a, the first target voltage of the voltage divided using the resistance element according to the input voltage and the second target having a voltage value higher than the first target voltage. The resistance value of the resistance element is set in correspondence with one of the target voltages. As a result, it is possible to design as necessary without changing the basic circuit configuration, and the versatility of the IC 2a can be improved.

<Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made. Below, such a modification is demonstrated. In addition, all the forms including the form demonstrated in the said embodiment and the form demonstrated below are combinable suitably.

  In the above embodiment, the voltage values of the first target voltage (6.0V), the second target voltage (10V), the reference power supply 115 (1.25V), etc. are examples, and other voltage values may be used. .

  In the above embodiment, the PNP transistor 111 and the PNP transistor 201 are examples of switching elements. Even if the circuit configuration is changed to another switching element (for example, an NPN transistor), Good.

  In the above embodiment, the error amplifier 114 and the error amplifier 204 are examples of an analog arithmetic circuit, and the circuit configuration may be changed to another analog arithmetic circuit.

  Further, in the above embodiment, the voltage values of the input voltage and the output voltage corresponding to the driving of each regulator illustrated in FIG. 2 are examples, and other characteristics can be used as long as the input / output voltage characteristics of each regulator are maintained. It may be changed to a voltage value.

  Further, in the above embodiment, hysteresis may be used for the driving state according to the input voltage described in FIG. For example, a hysteresis may be applied to a change in the output voltage of the input voltage 8V in the driving state of the first series regulator in the lower diagram of FIG. 2 so that frequent output voltage fluctuations at 8V are not performed.

DESCRIPTION OF SYMBOLS 1 ... Power supply circuit 10 ... Switching regulator 11 ... First series regulator 12 ... Second series regulator 13 ... Control circuit

Claims (4)

A switching regulator that drives to step down the input voltage;
A series regulator that is connected in parallel to the switching regulator and that drives to step down the input voltage;
A control circuit for stopping driving of the series regulator when the value of the input voltage exceeds a predetermined voltage value;
A power supply circuit comprising: The power supply circuit according to claim 1,
The control circuit stops driving the series regulator regardless of the driving state of the switching regulator;
A power circuit characterized by. A first series regulator provided between an input unit to which an input voltage is applied and an output unit that outputs a voltage obtained by stepping down the input voltage;
A second series regulator provided between the input unit and the output unit and connected in series with the first series regulator;
A control circuit for setting a resistance value of a resistance element connected to an input terminal of an analog arithmetic circuit of the first series regulator according to whether or not a switching regulator is connected in parallel to the first series regulator; ,
A power supply circuit comprising: The power supply circuit according to claim 3,
When the switching regulator is connected, the control circuit sets a resistance value of the resistance element corresponding to a first target voltage of a voltage divided using the resistance element, and the switching regulator is not connected In this case, according to the input voltage, either the first target voltage of the voltage to be divided using the resistance element or the second target voltage having a voltage value higher than the first target voltage Setting a resistance value of the resistance element in correspondence with
A power circuit characterized by.

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