JP4420142B1 - Vehicle power supply - Google Patents

Abstract

A power supply device for a vehicle having an idle stop function is provided with a low-loss boost converter circuit that compensates for a voltage drop of the battery at the start of the engine and has a protection function when the battery is erroneously connected to the reverse polarity. A vehicle power supply device is realized.
A series circuit composed of two MOSFETs (32, 33) and an inductor (31) connected in series is connected to both ends of the DC power source, and the two MOSFETs (32, 33) and the inductor (31) connected in series are connected. A diode (34) is connected to the connection point, and a capacitor (35) is connected in parallel to the two MOSFETs (32, 33) connected in series. The two MOSFETs (32, 33) are connected in series so that their body diodes have opposite polarities.
[Selection] Figure 1

Description

  The present invention relates to a vehicle power supply device, and more particularly, to a vehicle power supply device mounted on an idle stop vehicle that automatically stops an engine when the vehicle is stopped when waiting for a signal or the like.

  In recent years, for the purpose of reducing fuel consumption and reducing emissions, an idle stop vehicle has been put into practical use in which the engine is automatically stopped when the vehicle stops, such as waiting for a signal.

  In this type of vehicle, based on predetermined idle determination information such as vehicle speed and accelerator opening, the engine is automatically stopped when the vehicle is estimated to be stopped, and then an engine start condition that represents the driver's intention to start When is established, the engine is automatically started by a starter to prepare for starting.

  Generally, since the starter for starting the engine consumes a large amount of power, there is a possibility that the voltage of the battery output system temporarily decreases at the moment of starting the engine.

  Such a phenomenon becomes prominent particularly when the battery used as the power source becomes exhausted due to urban driving or the like that frequently stops and starts.

  When such a voltage drop occurs, the microcomputer used for the electrical equipment in the vehicle is reset, and the stored content such as the learning content up to that point is lost, or the lighting of the instrument is The problem of temporarily darkening and greatly impairing the quality of the vehicle may occur.

Therefore, in an idle stop vehicle, a configuration has been proposed in which a voltage compensation booster circuit is provided to prevent a voltage drop in the battery output system when the engine is restarted, and the booster circuit is operated during the starter operation period when the engine is started. ing. (See Patent Document 1)
In addition, since the battery can be replaced by the consumer, it is assumed that the battery is connected with the wrong polarity, and a protection circuit is provided to prevent current from flowing when the battery is connected in reverse. Has been. (See Patent Document 2)

JP 2005-237149 A Japanese Patent Laid-Open No. 2-197441

  At the time of engine restart as described above, in a circuit that compensates for a decrease in output voltage due to a large starter power consumption by a boost converter, no current flows when the battery is accidentally connected in reverse polarity. A method for configuring the protection circuit to be described will be described with reference to FIGS.

  In FIG. 7, a battery 1 provided as a DC power source, a first load 6, a first capacitor 2, a boost converter circuit 3, a control circuit 4 for controlling the boost converter circuit 3, and the boost converter circuit 3. And a connector 5 to which an output voltage is supplied. The connector 5 is connected to a second load (not shown).

  The first load 6 includes a starter 61, an engine 62, and a generator 63. The starter 61 is supplied with a DC voltage from the battery 1 when the engine is started, and starts the engine 62. When the engine is started, electric power is generated by the generator 63 using the rotation as a power source, and this is used as charging power for the battery 1.

  The step-up converter circuit 3 includes an inductor 31, a first semiconductor switching element 32 including a field effect transistor, a first diode 34, a second capacitor 35, a second diode 36, The inductor 31 and the first semiconductor switching element 32 are connected in series to both ends of the battery 1. The inductor 31 and the first semiconductor switching element 32 are connected to each other. The anode of the first diode 34 is connected to the connection point, the output terminal of the connector 5 is connected to the cathode of the first diode 34, and the second capacitor 35 is connected to both ends of the connector 5. .

  In automobiles, the user can often replace the battery 1 by himself / herself, and even if the user mistakenly reverses the polarity of the battery 1 in the vehicular power supply device, the current flows in the reverse direction. It is required to provide a protection circuit that does not flow in In order to realize this function, for example, the relay switch 8 shown in FIG. 7 or the third diode 9 shown in FIG. 8 may be used to energize only when a forward current flows. The vehicle power supply device has a problem that the output current is very large, the forward power loss of the third diode 9 and the power consumption of the relay switch 8 become so large that they cannot be ignored, and the life of the battery 1 is shortened. .

  Also, in large vehicles equipped with a power steering device, because the vehicle weight is large, the motor used in the power steering device is also required to have high power, and as a result, to prevent the motor size from becoming large, A voltage higher than the output voltage (12V) of a conventional lead storage battery may be required. In this case as well, a large current flows, and the loss cannot be ignored in a power supply device using a conventional diode or relay switch.

In order to solve the above problems, the vehicle power supply device of the present invention is
A boost converter circuit connected to a DC power supply;
A voltage detection circuit for detecting an output voltage of the DC power supply;
A control circuit that drives the boost converter circuit according to the output voltage detected by the voltage detection circuit to set the output voltage to a predetermined value,
The boost converter circuit includes:
A series circuit composed of at least one inductor and two semiconductor switching elements connected in series to each other is connected to both ends of the DC power supply,
At least one rectifying element connected to a connection point between the at least one inductor and the two semiconductor switching elements connected in series;
And at least one capacitor connected in parallel to the two semiconductor switching elements connected in series with each other,
The two semiconductor switching elements are connected in series so that their body diodes have opposite polarities.

  Preferably, when the load connected to the DC power supply is in a heavy load state and the output voltage of the DC power supply decreases transiently, the control circuit outputs the boost converter with an output voltage of the DC converter. The boost converter circuit is controlled so as to be an output voltage of a power supply.

  Preferably, the load of the boost converter is a power steering device, and the control circuit controls an output voltage of the boost converter circuit in accordance with steering rotation angle information in the power steering device. And

  More preferably, the two semiconductor switching elements are both N-channel MOSFETs, and drain terminals or source terminals are connected in series.

More preferably, of the two semiconductor switching elements, the low-voltage side semiconductor switching element is controlled by the control circuit,
The high-voltage side semiconductor switching element is configured as a self-driven element including a diode for applying a bias voltage to the control terminal.

  According to the present invention, in a vehicle power supply device having a boost converter circuit for compensating for a drop in battery voltage due to a transient increase in load or for supplying a voltage higher than the supply voltage of the battery, A circuit that prevents current from flowing in the reverse direction when it is erroneously connected to the reverse polarity can be realized with low loss.

  Further, by configuring the body diodes of the two FETs to have opposite polarities, a mechanical switch such as a relay switch becomes unnecessary, and the occurrence of sparks and noise can be suppressed.

It is a circuit diagram explaining the 1st Embodiment of this invention. In the 1st Embodiment of this invention, it is a circuit diagram when a battery is normally connected. In the 1st Embodiment of this invention, it is a circuit diagram when a battery is reversely connected. It is a circuit diagram explaining the 2nd Embodiment of this invention. It is a circuit diagram explaining the 3rd Embodiment of this invention. It is a circuit diagram explaining the 4th Embodiment of this invention. It is a circuit diagram of the power supply device for vehicles aiming at the battery reverse connection prevention of the prior art example. It is a circuit diagram of the other vehicle power supply device for the purpose of the battery reverse connection prevention of a prior art example.

  Embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

<< First Embodiment >>
FIG. 1 is a circuit diagram illustrating a configuration of a vehicle power supply device according to a first embodiment of the present invention.
In FIG. 1, a vehicle power supply device according to the present invention includes a battery 1 provided as a DC power supply, a first load 6, a first capacitor 2, a boost converter circuit 3, and a control for controlling the boost converter circuit 3. A circuit 4 and a connector 5 to which an output voltage of the boost converter circuit 3 is supplied are provided, and a second load (not shown) is connected to the connector 5.

  The first load 6 includes a starter 61, an engine 62, and a generator 63. The starter 61 is supplied with a DC voltage from the battery 1 when the engine is started, and starts the engine 62. When the engine is started, electric power is generated by the generator 63 using the rotation as a power source, and this is used as charging power for the battery 1.

  The step-up converter circuit 3 includes an inductor 31, a first semiconductor switching element 32 and a second semiconductor switching element 33 each including a field effect transistor (MOSFET), a first diode 34, and a second diode 34. Capacitor 35, second diode 36, bias resistor 37, and discharge resistor 38, and inductor 31, second semiconductor switching element 33, and first semiconductor switching element with respect to both ends of battery 1. 32 are connected in series, and the first semiconductor switching element 32 and the second semiconductor switching element 33 are configured such that the drains are connected so that the body diodes 321 and 331 have opposite polarities. Yes. The anode of the first diode 34 is connected to the connection point between the inductor 31 and the second semiconductor switching element 33, and the output terminal of the connector 5 is connected to the cathode of the first diode 34. A second capacitor 35 is connected to both ends.

  A second diode 36 having an anode connected to the connection point of the first capacitor 2 and the inductor 31 and a cathode connected to the gate terminal of the second semiconductor switching element 33 via the bias resistor 37, A discharge resistor 38 connected between the gate and the source of the semiconductor switching element 33 is provided. The control circuit 4 monitors the input voltage supplied from the battery 1 and the output voltage by the output voltage detection circuit 7, so that the output voltage supplied to the second load becomes a predetermined value. The semiconductor switching element 32 is controlled to be turned on / off.

  When the load connected to the battery (DC power supply) 1 is in a heavy load state and the voltage of the DC power supply drops transiently, the control circuit 4 uses the output voltage of the boost converter circuit 3 as the voltage of the DC power supply. The boost converter circuit 3 is controlled so that

  FIG. 2 is a circuit block diagram when the polarity of the battery 1 is normally connected. The first load 6 including the starter 61, the engine 62, and the generator 63 in FIG.

  When a DC voltage is supplied from the battery 1 and the control circuit 4 applies a voltage to the gate terminal of the first semiconductor switching element 32 to turn on the first semiconductor switching element 32, a current flows in the inductor 31, and the inductor A voltage is generated at both ends of 31. As a result, the second diode 36 is turned on, a voltage is applied to the gate terminal of the second semiconductor switching element 33 via the bias resistor 37, and the second semiconductor switching element 33 is also turned on. In this way, a current flows in the closed loop of the positive terminal of the battery 1 → the inductor 31 → the second semiconductor switching element 33 → the first semiconductor switching element 32 → the negative terminal of the battery 1.

  Subsequently, when the first semiconductor switching element 32 is turned off by the control signal from the control circuit 4, the energy accumulated in the inductor 31 charges the second capacitor 35 via the first diode 34 during the ON period. To be released. In this way, a current flows in the closed loop of the positive terminal of the battery 1 → the inductor 31 → the first diode 34 → the second capacitor 35 → the negative terminal of the battery 1.

  Next, in FIG. 3, it is assumed that the polarity of the battery 1 is erroneously connected in reverse. FIG. 3 is a circuit block diagram when the polarity of the battery 1 is reversely connected.

  When the battery 1 is reversely connected, the body diode 321 of the first semiconductor switching element 32 is turned on because a forward bias is applied, but the body diode 331 of the second semiconductor switching element 33 is reversely biased. Do not turn on. That is, by using two semiconductor switching elements (32 and 33) for the switch of the boost converter circuit 3 and connecting them in series so that their body diodes (321 and 331) have opposite polarities, the polarity of the battery 1 can be mistaken. Can be prevented from flowing through the boost converter circuit 3, and as a result, the load connected to the output of the boost converter circuit 3 can be prevented from being broken or malfunctioning. be able to.

  In this case, the second semiconductor switching element 33 is inevitably turned on when the battery 1 is normally connected without being controlled by the control circuit 4 or the like due to the presence of the second diode 36. Is configured as a self-driving element that is inevitably turned off when it is erroneously connected to the reverse polarity.

  Further, the output voltage of the boost converter circuit 3 is set to be equal to the supply voltage of the battery 1 for the purpose of compensating for the transient decrease in the supply voltage of the battery 1 when the starter 61 is started as described above. Of course, it is possible to set an output voltage higher than that.

  Further, when used in a power steering device for a vehicle having a large vehicle weight, it is necessary to control the stress according to the steering angle of the steering that the driver has decided, so the steering rotation angle information from the second load is controlled by the control circuit 4. And the output voltage of the boost converter circuit 3 can be appropriately controlled.

<< Second Embodiment >>
FIG. 4 is a circuit diagram illustrating the configuration of the vehicle power supply device according to the second embodiment of the present invention.
The second embodiment is different from the first embodiment in that on / off control of the second semiconductor switching element 33 is realized by the control circuit 4. If the control circuit 4 is configured to be able to detect the voltage across the inductor 31, it is possible to perform on / off control of each of the first semiconductor switching element 32 and the second semiconductor switching element 33.
Since other points are the same as those of the first embodiment, description thereof is omitted.

<< Third Embodiment >>
FIG. 5 is a circuit diagram illustrating the configuration of a vehicle power supply device according to a third embodiment of the present invention.
The third embodiment is different from the second embodiment in that the connection order of the first semiconductor switching element 32 and the second semiconductor switching element 33 is reversed. If the on / off control of each of the first semiconductor switching element 32 and the second semiconductor switching element 33 is performed by the control circuit 4, the first semiconductor switching element 32 is connected to the high voltage side as shown in FIG. The second semiconductor switching element 33 may be disposed on the low voltage side.
Since other points are the same as those of the first embodiment, description thereof is omitted.

<< Fourth Embodiment >>
FIG. 6 is a circuit diagram illustrating the configuration of a vehicle power supply device according to the fourth embodiment of the present invention.
The fourth embodiment is different from the second embodiment in that the second embodiment uses an N-channel FET for the second semiconductor switching element 33, whereas the fourth embodiment The point is that a P-channel FET is used for the second semiconductor switching element 33. If the control circuit 4 is configured to perform on / off control of each of the first semiconductor switching element 32 and the second semiconductor switching element 33, a P-channel FET is used for the second semiconductor switching element 33, The same operation can be realized if a negative potential is applied to the gate terminal.
Since other points are the same as those of the first embodiment, description thereof is omitted.

DESCRIPTION OF SYMBOLS 1 Battery 2 1st capacitor 3 Boost converter circuit 31 Inductor 32 1st semiconductor switching element 321 Body diode of 1st semiconductor switching element 33 2nd semiconductor switching element 331 Body diode of 2nd semiconductor switching element 34 1st Diode 35 35 second capacitor 36 second diode 37 bias resistor 38 discharge resistor 4 control circuit 5 connector 6 first load 61 starter 62 engine 63 generator 7 output voltage detection circuit 8 relay switch 9 third diode

Claims (5)

A boost converter circuit connected to a DC power supply;
A voltage detection circuit for detecting an output voltage of the DC power supply;
A control circuit that drives the boost converter circuit according to the output voltage detected by the voltage detection circuit to set the output voltage to a predetermined value,
The boost converter circuit includes:
A series circuit composed of at least one inductor and two semiconductor switching elements connected in series to each other is connected to both ends of the DC power supply,
At least one rectifying element connected to a connection point between the at least one inductor and the two semiconductor switching elements connected in series;
And at least one capacitor connected in parallel to the two semiconductor switching elements connected in series with each other,
The two semiconductor switching elements are a vehicle power supply device in which the body diodes are connected in series in opposite directions.   In the control circuit, when the load connected to the DC power supply is in a heavy load state and the voltage of the DC power supply decreases transiently, the output voltage of the boost converter circuit becomes the voltage of the DC power supply. The vehicle power supply device according to claim 1, wherein the boost converter circuit is controlled to be   The load of the boost converter circuit is a power steering device, and the control circuit controls an output voltage of the boost converter circuit in accordance with steering rotation angle information in the power steering device. The vehicle power supply device described in 1.   4. The vehicle power supply device according to claim 1, wherein the two semiconductor switching elements are both N-channel MOSFETs, and drain terminals or source terminals are connected to each other.   The two semiconductor switching elements have their drain terminals connected to each other, the low-voltage side semiconductor switching element is controlled by the control circuit, and the high-voltage side semiconductor switching element includes a diode for applying a bias voltage to the control terminal. The vehicular power supply device according to claim 4, which is configured as a self-driven element.

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