JP7511985B2 - Load drive system and control device - Google Patents

Description

The present invention relates to a load drive system and a control device for driving a load.

In recent years, with the advancement of vehicle electrification, the number of sensors, loads, and ECUs installed in vehicles is steadily increasing. As one approach to addressing this issue, a system has been proposed in which small load drive units that drive the loads are placed near the loads in each area of the vehicle, and the loads are driven in accordance with communications, making it easy to add functions (see, for example, Patent Document 1).

In addition, when driving a load using a semiconductor such as a FET (field effect transistor), reverse connection of the power supply causes a short circuit between the power supply and ground, resulting in a large current flow. This requires protection against reverse connection, and switching elements are provided to protect against reverse connection (see, for example, Patent Document 2).

In addition to the above, Patent Document 2 also describes detecting abnormalities in the switching element for protection against reverse polarity.

JP 2015-58767 A JP 2019-54500 A

Due to the semiconductor circuit configuration, measures to prevent reverse polarity are necessary when driving a motor, but reverse polarity measures may not be necessary when driving a resistive load or lamp. Therefore, if a load drive unit (drive section) is constructed to accommodate both those with and without reverse polarity measures, there is a problem in that the unit cannot be standardized or made smaller.

In view of the above problems, the present invention aims to provide a load drive system and control device that allows for standardization and miniaturization of the drive unit.

The invention made to solve the above problem is a load driving system comprising a load, a driving unit that drives the load, and a control unit that supplies power from a DC power source to the multiple driving units and performs a predetermined control, and the control unit is characterized in that a protection element that protects the load when the DC power source is reverse-connected is provided in the power supply line connected to each of the driving units.

As described above, according to the present invention, the control unit has a protective element, so there is no need to provide a protective element for each drive unit, making it possible to standardize and miniaturize the drive units.

1 is a block diagram showing a hardware configuration of a load driving system according to an embodiment of the present invention; 4 is a flowchart of an abnormality detection operation of the load driving system shown in FIG. 1 .

An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing the hardware configuration of a load driving system according to an embodiment of the present invention. As shown in FIG. 1, the load driving system 1 includes a power supply box 2, a motor load driving unit 3, a lamp driving unit 4, a load 5, and wiring 6.

In the configuration of FIG. 1, the power supply box 2, the motor load drive unit 3, and the lamp drive unit 4 are connected to each other as separate units, for example, by a wire harness. In other words, the motor load drive unit 3 and the lamp drive unit 4 are disposed near the load 5.

The power supply box 2 includes fuses 21 and 25, a reverse polarity protection FET 22, a voltage detection unit 23, and a control unit 24. The power supply box 2 functions as a control unit that supplies power from a battery (not shown), which is a DC power source, to the motor load drive unit 3 and the lamp drive unit 4 and performs predetermined control.

One end of the fuse 21 is connected to the battery (positive electrode), and the other end is connected to the reverse polarity protection FET 22. That is, the fuse 21 is connected to the power supply path between the battery and the reverse polarity protection FET 22. Also, one end of the fuse 25 is connected to the battery (positive electrode), and the other end is connected to the lamp driving unit 4. That is, the fuse 25 is connected to the power supply path between the battery and the lamp driving unit 4, which will be described later.

The reverse connection protection FET 22 is provided between the fuse 21 and the motor load drive unit 3. The reverse connection protection FET 22 is a protection element configured to protect the motor load drive unit 3 and the load 5 when the power supply is reverse-connected to the motor load drive unit 3 or the load 5. That is, in the power supply BOX 2 (control unit), a protection element that protects the load 5 when the battery (power supply) is reverse-connected is provided on the power supply line 6a connected to each of the motor load drive units (drive unit).

The reverse connection protection FET 22 is composed of a switching element 22a and a protection diode 22b. The switching element 22a is a P-channel MOSFET, with its source connected to the fuse 21 side, its drain connected to the motor load drive unit 3 side, and its gate connected to the control unit 24.

The protective diode 22b is connected in parallel with the switching element 22a between the fuse 21 and the motor load drive unit 3. The protective diode 22b is a diode with an anode connected to the fuse 21 side and a cathode connected to the motor load drive unit 3 side. Note that the protective diode 22b in this embodiment is formed by a parasitic diode in the switching element 22a, which is a P-channel MOSFET. In other words, the protective diode 22b is configured integrally with the switching element 22a.

In the circuit configuration described above, if the battery is reverse-connected while the load drive system 1 is not operating, the protection diode 22b of the reverse connection protection FET 22 is reverse-connected to the battery, preventing overcurrent from flowing to the motor load drive unit 3 or the load 5.

The voltage detection unit 23 detects the voltage across both ends of the reverse connection protection FET 22 and transmits the detection result to the control unit 24. In other words, the voltage detection unit 23 detects the potential difference between the drain and source of the switching element 22a.

The control unit 24 detects an abnormality in the reverse connection protection FET 22 based on the detection result of the voltage detection unit 23, and transmits a control signal to the motor load drive unit 3 and the lamp drive unit 4 via the communication line 6b described later. The control unit 24 is composed of, for example, a microcomputer having a CPU, RAM, ROM, etc. In other words, the control unit 24 functions as a detection unit that detects abnormalities in the protection elements.

The motor load drive unit 3 is made up of motor load drive units 3A and 3B. That is, in this embodiment, multiple motor load drive units are provided. The motor load drive unit 3A functions as a drive section that drives the load 5A. The motor load drive unit 3B drives the load 5B. The motor load drive unit 3A and the motor load drive unit 3B have the same configuration, and the configuration of the motor load drive unit 3A will be described below as a representative example.

The motor load drive unit 3A includes a control unit 31 and a motor drive circuit 32. The control unit 31 receives power from the power supply box 2 via the power line 6a. The control unit 31 also controls the motor drive circuit 32 based on a control signal received from the power supply box 2 via the communication line 6b, thereby controlling the rotation of the load 5 and its operation such as turning it on or off.

The motor drive circuit 32 is a known bridge circuit composed of switching elements 32a to 32d such as power FETs. The motor drive circuit 32 controls the rotation of the motor M, which is a load, under the control of the control unit 31.

The lamp driving unit 4 functions as a driving section that drives the load 5C (lamp L) described below. In other words, the lamp driving unit 4 controls the switching of the lamp L between on and off.

The load 5 consists of loads 5A, 5B, and 5C. Loads 5A and 5B are motors M. Motors M are installed in various locations on the vehicle seat, for example, to recline the seat or move the seat forward and backward. Load 5C is lamp L, as described above. Examples of lamps L include room lamps and map lamps installed in the passenger compartment of the vehicle.

The wiring 6 electrically connects the power supply box 2 to the motor load drive unit 3 and the lamp drive unit 4. The wiring 6 includes a power supply line 6a, a communication line 6b, and a ground line (GND) 6c.

The power supply line 6a is a wire that supplies power from the battery via the reverse polarity protection FET 22. The communication line 6b is a wire that transmits control signals from the control unit 24. The ground line 6c is a wire that grounds (sets to ground level) the power supply box 2, the motor load drive unit 3, and the lamp drive unit 4.

In the load drive system 1 configured as described above, the motor M is a load that requires measures to be taken in case the power supply is reverse-connected, and the lamp L is a load that does not require measures to be taken in case the power supply is reverse-connected. Therefore, the motor load drive unit 3 (3A, 3B) is a first drive unit to which a load that requires measures to be taken in case the power supply is reverse-connected is connected, and the lamp drive unit 4 is a second drive unit to which a load that does not require measures to be taken in case the power supply is reverse-connected is connected. The reverse connection protection FET 22, which is a protective element, is connected to the power line 6a to the drive unit to which the load that requires measures to be taken in case the power supply is reverse-connected is connected.

Next, the abnormality detection operation of the reverse connection protection FET 22 in the above-mentioned load driving system 1 will be described with reference to the flowchart in FIG. 2. The flowchart shown in FIG. 2 is executed by the control unit 24 of the power supply box 2.

First, the load driving unit (motor load driving unit 3) determines whether the load 5 (5A and 5B) is ON or not (step S1). If the load 5 is OFF (step S1; load OFF), the flow chart ends. On the other hand, if the load 5 is ON (step S1; load ON), the drain-source (D-S) voltage (potential difference) of the reverse connection protection FET 22 is obtained from the voltage detection unit 23 (step S2).

Next, it is determined whether the voltage acquired in step S2 is equal to or greater than a certain value, such as 0.7 V (step S3). If the acquired voltage is less than the certain value (step S3; less than the certain value), it is determined that the reverse connection protection FET 22 is normal (step S4) and the flow chart ends. On the other hand, if the acquired voltage is equal to or greater than the certain value (step S3; equal to or greater than the certain value), it is determined that the reverse connection protection FET 22 is abnormal (step S5).

When the load 5 is ON, it means that power is being supplied from the battery, and the switching element 22a of the reverse polarity protection FET 22 is normally ON. In this state, it is known that the potential difference between D and S, which is the voltage across both ends of the switching element 22a, is normally very low (for example, if the ON resistance of the switching element 22a is 10 mΩ, the voltage drop when a current of 5 A is applied is 50 mV).

On the other hand, when the switching element 22a fails and the ON resistance becomes high, the potential difference between D and S becomes approximately equal to the forward voltage drop of the protective diode 22b. If the switching element 22a fails and electricity continues to flow using the protective diode 22b, which is a parasitic diode, the power loss in the reverse connection protection FET 22 will cause abnormal heat generation, and it is necessary to stop the current. However, even if the reverse connection protection FET 22 is turned OFF to stop the current, the current cannot be stopped because the protective diode 22b is connected to the load 5 in the forward direction. Therefore, in this embodiment, as described below, the motor load drive unit 3 turns off the load 5 in the event of an abnormality.

When it is determined that the reverse connection protection FET 22 is abnormal, it outputs a load drive unit stop signal to the motor load drive unit 3 via the communication line 6b (step S6). When the motor load drive unit 3 receives the load drive unit stop signal, the control unit 31 stops the drive circuit 32 and stops the target load, that is, the load 5 (motor M) (step S7). That is, when the control unit 24 (detection unit) detects an abnormality in the reverse connection protection FET 22 (protection element), the control unit 24 (control unit) controls the multiple motor load drive units 3 (drive units) to stop the load 5.

As is clear from the above description, the power supply box 2 is equipped with a control unit 24 that supplies power from a battery (power source) to multiple motor load drive units 3 (drive units) that drive the loads and performs predetermined control, and the control unit 24 is provided with a reverse connection protection FET 22 (protective element) on the power supply line 6a connected to each of the motor load drive units 3 (drive units) to protect the loads 5 if the battery (power source) is reverse connected, forming a control device according to one embodiment of the present invention.

According to this embodiment, the load driving system 1 includes a load 5, a motor load driving unit 3 that drives the load 5, and a power supply box 2 that supplies power from a power source to the multiple motor load driving units 3 and performs a predetermined control. In the power supply box 2, a reverse connection protection FET 22 that protects the load when the power supply is reverse connected is connected to the power supply line 6a to the multiple motor load driving units 3.

By configuring the load drive system 1 as described above, the power supply box 2 has a reverse polarity protection FET 22, so there is no need to provide a reverse polarity protection FET 22 for each motor load drive unit 3, making it possible to standardize and miniaturize the motor load drive unit 3.

In addition, since the motor load drive unit 3 can be standardized and miniaturized, it is easier to place the motor load drive unit 3 near the load 5 (motor M).

The power supply box 2 also includes a control unit 24 that detects an abnormality in the reverse connection protection FET 22, and when the control unit 24 detects an abnormality in the reverse connection protection FET 22, the control unit 24 controls the multiple motor load drive units 3 to stop the load 5. In this way, when it is detected that the reverse connection protection FET 22 has entered an abnormal state such as a failure, the motor load drive units 3 can be made to stop the load 5.

The power supply box 2 has a drive section consisting of a motor load drive unit 3 to which a load requiring countermeasures in case of reverse connection of the power supply is connected, and a lamp drive unit 4 to which a load not requiring countermeasures in case of reverse connection of the power supply is connected, and the reverse connection protection FET 22 is connected to the power supply line to the motor load drive unit 3 to which a load requiring countermeasures in case of reverse connection of the power supply is connected. In this way, it is possible to group the load drive units requiring countermeasures against reverse connection and the load drive units not requiring countermeasures against reverse connection and take countermeasures against them. This makes it possible to reduce the cost of the system.

In addition, the lamp driving unit 4 receives power through the fuse 25, which allows for cost reduction and miniaturization of the unit (driving section) that does not require a reverse polarity protection FET 22.

The control unit 24 detects the abnormality based on the voltage across the reverse polarity protection FET 22, so it is possible to set thresholds etc. according to the characteristics of the switching elements etc. that make up the reverse polarity protection FET 22, making it easy to detect abnormalities.

Furthermore, the present invention is not limited to the above-described embodiment. In other words, a person skilled in the art can implement various modifications according to conventional knowledge without departing from the gist of the present invention. As long as such modifications still include the configuration of the load drive system and control device of the present invention, they are of course included in the scope of the present invention.

1 Load driving system 2 Power supply box (control unit, control device)
22 FET 22 (protection element) for protection against reverse connection
24 Control unit (detection unit)
3 Motor load drive unit (drive section, first drive section)
4 Lamp driving unit (second driving section)
5. Load

Claims (4)

Load and
A drive unit that drives the load;
A control unit that supplies power from a DC power source to the plurality of drive units and performs predetermined control;
Equipped with
the plurality of drive units are composed of a first drive unit to which a load requiring a measure in the event that the DC power supply is reverse-connected is connected, and a second drive unit to which a load requiring no measure in the event that the DC power supply is reverse-connected is connected,
A load driving system characterized in that in the control unit, a protection element that protects the load when the DC power supply is reverse connected is provided in a power supply line connected to the first driving unit . The control unit includes a detection unit that detects an abnormality in the protection element,
2. The load driving system according to claim 1, wherein, when the detection unit detects an abnormality in the protection element, the control unit controls each of the driving units to stop the load. 3. The load driving system according to claim 2 , wherein the detection unit detects the abnormality based on a voltage across the protection element. a control unit that supplies power from a DC power source to a plurality of drive units that drive a load and performs predetermined control;
the plurality of drive units are composed of a first drive unit to which a load requiring a measure in the event of reverse connection of the DC power supply is connected, and a second drive unit to which a load requiring no measure in the event of reverse connection of the DC power supply is connected,
The control unit is characterized in that a protection element that protects the load when the DC power supply is reverse connected is provided in a power supply line connected to the first drive unit .

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