JP3520291B2 - Vehicle electric load control circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle electric load control circuit.

[0002]

2. Description of the Related Art As a conventional electric load control circuit for a vehicle, for example, one described in Japanese Patent Application Laid-Open No. 5-162631 "Vehicle control device" is known.

This conventional vehicle control device is a control device provided with a drive field effect transistor for controlling energization of the solenoid valve drive solenoid coil in series with the solenoid valve drive solenoid coil. By providing a backflow prevention diode on the ground side of the field effect transistor for use, the backflow prevention diode is prevented from being damaged when the drive power source is connected in reverse polarity.

[0004]

However, although not disclosed in the above-mentioned conventional example, in a system in which a driving field effect transistor is driven by pulse-wise modulation control (hereinafter, abbreviated as PWM control), , A flywheel diode is used to make the current efficient. That is, in the system driven by the PWM control, as shown in the relationship diagram between the output command value waveform and the voltage waveform in FIG. 4, at the time of switching when switching the driving field effect transistor,
Surge voltage is generated. This surge voltage can be removed by interposing a Zener diode, but as shown in FIG. 5, since the rising of the current becomes gradual, the average current value decreases and the current efficiency deteriorates. Become. Therefore, by connecting the flywheel diode described above in parallel with the coil instead of the Zener diode, a current waveform as shown in FIG.
As a result, the average current value increases and the current efficiency can be improved.

However, since the driving field effect transistor has a parasitic diode incorporated in parallel, when the flywheel diode is connected in parallel with the coil, the flywheel diode and the parasitic diode are connected to the driving power source and the ground. In order to prevent the backflow prevention diode from being damaged when the polarity of the drive power supply is connected in reverse, the coil and flywheel diode and the drive field effect transistor must be connected in series. It is necessary to interpose a backflow prevention diode. Therefore, in a system in which a plurality of coils are provided, it is necessary to provide a flywheel diode and a backflow prevention diode for each coil in order to protect and improve current efficiency when the drive power source is reversely connected.
As a result, there is a problem in that the number of parts and the mounting area on the board increase. The present invention has been made by paying attention to the conventional problems as described above, and in an electric load control circuit for a vehicle that drives a plurality of electric load driving field effect transistors such as coils by PWM control, the number of parts is reduced. An object of the present invention is to provide an electric load control circuit for a vehicle, which can suppress the increase and protect the current when the drive power source is reversely connected and improve the current efficiency.

[0006]

In order to achieve the above object, in the electric load control circuit for a vehicle according to the first aspect of the present invention, an electric load interposed between a power source and a ground, A field effect transistor for driving an electric load, which is provided between the electric load and the ground and is provided in parallel with a parasitic diode which allows only a flow from the ground to the power supply direction, and the field effect transistor for driving the pulse. A control circuit driven by the wise modulation control, and between the downstream side of the electric load and the driving field effect transistor and the upstream side of the electric load, which is interposed between the downstream side and the upstream side of the electric load, A flywheel diode that allows only the flow of current, and is interposed between the flywheel diode and the power supply and between the ground and the flywheel diode. Reverse connection prevention transistor operated by the voltage difference generated, and a means provided with a. The electric load control circuit for a vehicle according to claim 2 is the electric load control circuit for a vehicle according to claim 1, wherein the reverse connection preventing transistor has a base on a ground side via a resistor and an emitter on a flywheel diode side. , The collectors are connected to the power supply side, respectively. The electric load control circuit for a vehicle according to claim 3 is the electric load control circuit for a vehicle according to claim 1 or 2, wherein pulse-width modulation of a driving field effect transistor is provided between the base of the reverse connection prevention transistor and the ground. The switch means connected only during the control is interposed.

[0007]

In the electric load control circuit for a vehicle according to the present invention, as described above, the flywheel diode that allows only the flow of current from the downstream side to the upstream side of the electric load is connected to the downstream side of the electric load. By interposing it between the driving field effect transistor and the upstream side of the electric load, a sharp drop in the current waveform when the driving field effect transistor is off is eliminated, and as a result, the average current value is reduced. The current efficiency can be improved by increasing. In addition, the reverse connection prevention transistor, which operates due to the voltage difference generated between the ground and the flywheel diode, is interposed between the flywheel diode and the power supply, so that the drive field effect transistor can be prevented from being damaged when the drive power supply is reversely connected. Can be protected. Further, the reverse connection prevention transistor does not have to increase the number of components because only one common circuit is required to be provided even when there are a plurality of electric loads. According to a second aspect of the present invention, there is provided a vehicle electric load control circuit according to the first aspect, wherein the reverse connection preventing transistor has a base connected to a ground side through a resistor.
Since the emitter is connected to the flywheel diode side and the collector is connected to the power supply side, the reverse connection prevention transistor is turned on by the voltage difference due to this resistance, so the reverse connection prevention transistor can be configured without requiring a complicated configuration. You can According to a third aspect of the present invention, there is provided a vehicle electric load control circuit according to the first or second aspect, wherein the drive field effect transistor is PWM-controlled between the base of the reverse connection prevention transistor and the ground. By interposing the switch means connected only to, the extra current is prevented from flowing out to the ground when the PWM control is not performed, thereby further improving the current efficiency.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. (Embodiment 1 of the invention) First, the configuration of an electric load control circuit for a vehicle according to Embodiment 1 of the invention shown in FIG. 1 will be described.

FIG. 1 is a diagram showing a vehicle electric load control circuit according to a first embodiment of the present invention. That is, in the electric load control circuit for a vehicle according to Embodiment 1 of the present invention, as shown in FIG. 1, the solenoid valve driving solenoid coil 3 forming an electric load is interposed between the power source 1 and the ground 2a. A coil driving field effect transistor 5 provided with a parasitic diode 4 in parallel between the solenoid valve driving solenoid coil 3 and the ground 2a for allowing only a flow from the ground 2a toward the power source 1 is interposed. It is equipped. That is, in the coil driving field effect transistor 5, the source side is connected to the ground 2 side, the drain side is connected to the cathode side of the solenoid valve driving solenoid coil 3, and the gate side is connected to the microprocessor unit MPU side.

This microprocessor unit MPU
Constitutes a control circuit in the claims, and a PW for driving the coil driving field effect transistor 5 by PWM control is provided in the microprocessor unit MPU.
The M control circuit is provided.

The cathode side of the solenoid valve driving solenoid coil 3 and the coil driving field effect transistor 5 are also described.
Solenoid valve driving solenoid coil 3 between the drain side and
A flywheel diode 6 that allows only a current flow from the cathode side to the anode side of the solenoid valve driving solenoid coil 3 is interposed between the flywheel diode 6 and the anode side.

Further, a reverse connection preventing transistor 7 which operates by a voltage difference generated between the ground 2b and the flywheel diode 6 is interposed between the flywheel diode 6 and the power source 1. That is, the reverse connection prevention transistor 7 has its base connected to the ground 2b side via the resistor 9, its emitter connected to the flywheel diode 6 side, and its collector connected to the power supply 1 side.

In the figure, 8 is a bias resistor,
Reference numeral 10 is a reverse bias diode that is incorporated in parallel between the emitter and collector of the reverse connection prevention transistor 7.

Next, the operation and effect of the first embodiment of the present invention will be described. Since the electric load control circuit for a vehicle according to Embodiment 1 of the present invention is configured as described above,
When the power supply 1 is normally connected, a voltage difference is generated between the ground 2b and the flywheel diode 6 and a base current flows, so that the reverse connection prevention transistor 7 is turned on. Since it is connected in parallel to the valve driving solenoid coil 3, the flywheel current generated when the PWM control of the coil driving field effect transistor 5 is turned off is applied to the solenoid valve driving solenoid coil 3 by the coil driving field effect. Current can be applied in the same direction as when the transistor 5 is turned on.

Therefore, the current waveform as shown in FIG. 6 is obtained, and the effect that the average current value is increased to enable efficient current control is obtained.

Further, when the power supply is reversely connected, both grounds 2a and 2b have the same potential, so that no current flows through the base of the reverse connection preventing transistor 7, and therefore the reverse connection preventing transistor 7 is turned off. It becomes a state.

Therefore, the current flowing through the parasitic diode 4 of the coil driving field effect transistor 5 and the flywheel diode 6 is cut off, whereby the coil driving field effect when the power source is reversely connected. The effect that the destruction of the transistor 5 can be prevented can be obtained. When the power source is reversely connected, the solenoid valve driving solenoid coil 3 is routed through the parasitic diode 4 of the coil driving field effect transistor 5.
However, since the current is limited by the large resistance of the solenoid valve driving solenoid coil 3, the coil driving field effect transistor 5 is not destroyed.

The reverse connection prevention transistor 7 has a base connected to the ground 2b side via the resistor 9, an emitter connected to the flywheel diode 6 side, and a collector connected to the power source 1 side, as described above. Since the reverse connection prevention transistor 7 can be turned on by the voltage difference due to the resistor 8, the reverse connection prevention transistor can be configured without requiring a complicated configuration.

Next, another embodiment of the present invention will be described. In the description of the other embodiments of the present invention, the same components as those of the first embodiment of the invention will be designated by the same reference numerals, and the description thereof will be omitted. Only the differences will be described.

Embodiment 2 of the Invention An electric load control circuit for a vehicle according to Embodiment 2 of the present invention has two solenoid valve driving solenoid coils 3a and 3b as shown in the circuit configuration of FIG. Therefore, the coil driving field effect transistors 5a and 5b having parasitic diodes 4a and 4b are provided corresponding to the solenoid valve driving solenoid coils 3a and 3b, and the flywheel diode 6a. , 6b are provided independently of each other.

Further, since the reverse connection prevention transistor 7 constitutes a simple switching circuit, even when there are a plurality of solenoid valve driving solenoid coils 3a and 3b, only one common circuit is provided and the function is exerted. Therefore, the number of parts is not increased.

(Embodiment 3 of the Invention) An electric load control circuit for a vehicle according to Embodiment 3 of the present invention has a circuit configuration shown in FIG. In the control circuit, a switching transistor 11 constituting a switch means connected between the base of the reverse connection prevention transistor 7 and the ground 2b only when at least one of the driving field effect transistors 5a and 5b is in PWM control. Is newly interposed, and the other configuration is the same as that of the second embodiment of the present invention.

That is, since the reverse connection prevention transistor 7 is connected through the resistor 8 between the emitter and the base, the base side is directly connected to the ground 2b as in the first embodiment (FIG. 1) of the invention. If so, the current flows unnecessarily even when the drive field effect transistors 5a and 5b are not under PWM control.
Therefore, as described above, the driving field effect transistor 5 is
When neither a or 5b is in PWM control, by outputting a control voltage to the base to turn off the switching transistor 11, an extra current is prevented from flowing to the ground 2b when not in PWM control, As a result, the effect that the current efficiency can be further improved can be obtained.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to the embodiments of the present invention, and design changes and the like without departing from the scope of the present invention. Even so, it is included in the present invention.

[0025]

As described above, in the electric load control circuit for a vehicle according to the first aspect of the present invention, the electric load interposed between the power source and the ground and the electric load and the ground are provided. An electric load driving field effect transistor provided with a parasitic diode in parallel, which is interposed and allows only a flow from the ground to the power supply direction; and a control circuit for driving the driving field effect transistor by pulse-wise modulation control. A flywheel interposed between the downstream side of the electric load and the driving field effect transistor and the upstream side of the electric load and allowing only a current flow from the downstream side to the upstream side of the electric load. Operated by the voltage difference between the diode and the flywheel diode, which is interposed between the flywheel diode and the power supply. In the electric load control circuit for a vehicle, which drives a plurality of electric load driving field effect transistors such as coils by PWM control, the reverse power supply reverse circuit is provided while suppressing an increase in the number of parts. It is possible to obtain an effect that protection at the time of connection and improvement of current efficiency can be achieved. The electric load control circuit for a vehicle according to claim 2 is the electric load control circuit for a vehicle according to claim 1, wherein the reverse connection preventing transistor has a base on a ground side via a resistor and an emitter on a flywheel diode side. Since the collectors are respectively connected to the power supply side, the reverse connection prevention transistor can be configured without requiring a complicated configuration. The electric load control circuit for a vehicle according to claim 3 is the electric load control circuit for a vehicle according to claim 1 or 2, wherein pulse-width modulation of a driving field effect transistor is provided between the base of the reverse connection prevention transistor and the ground. Since the switch means connected only during the control is provided as the means, the PW
It is possible to prevent an extra current from flowing out to the ground when the M control is not performed, whereby the current efficiency can be further improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a vehicle electric load control circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a vehicle electric load control circuit according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a vehicle electric load control circuit according to a third embodiment of the present invention.

FIG. 4 is a voltage waveform characteristic diagram with respect to an output command value in a conventional example.

FIG. 5 is a current waveform diagram when a Zener diode is used.

FIG. 6 is a current waveform diagram when a flywheel is used.

[Explanation of symbols]

MPU Microprocessor unit (control circuit) 1 power supply 2 grand 2a grand 2b ground 3 Solenoid valve drive solenoid coil (electric load) 3a Solenoid valve drive solenoid coil (electric load) 3b Solenoid valve driving solenoid coil (electric load) 4 Parasitic diode 5 Driving field effect transistor 5a Driving field effect transistor 5b Driving field effect transistor 6 Flywheel diode 7 Reverse connection prevention transistor 8 resistance 11 Switching transistor (switch means)

─────────────────────────────────────────────────── ─── Continued Front Page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02J 7/14 B60R 16/02 H02H 7/00 H02H 11/00 F16K 31/06 H01F 7/08

Claims (3)

(57) [Claims] 1. An electric load interposed between a power source and a ground, and a parasitic diode which is interposed between the electric load and the ground and permits only a flow from the ground to the power source in parallel. An electric load driving field effect transistor provided, a control circuit for driving the driving field effect transistor by pulsewise modulation control, a portion between the downstream side of the electric load and the driving field effect transistor, and an upstream side of the electric load. A flywheel diode interposed between the flywheel diode and a power source, the flywheel diode being interposed between the flywheel diode and the power source, and allowing only a current flow from the downstream side to the upstream side of the electric load. An electric load control for a vehicle, comprising: a reverse connection prevention transistor that operates by a voltage difference generated between the wheel diode and the wheel diode. circuit. 2. The reverse connection preventing transistor according to claim 1, wherein a base thereof is connected to a ground side through a resistor, an emitter is connected to a flywheel diode side, and a collector is connected to a power supply side. Electric load control circuit for vehicles. 3. A switch means connected between the base of the reverse connection prevention transistor and the ground only during pulse-wise modulation control of the driving field effect transistor. Two
The electric load control circuit for vehicle according to.