JP2003319671A - Charge-and-discharge control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charge-and-discharge control circuit by which an inrush current to a capacitor for the stabilization of power supply is limited and useless power consumption is prevented. <P>SOLUTION: A relay L1 is interposed in a power supply wire 42 which connects the power supply 46 to the capacitor C. The relay L1 is connected to an earth wire 44 through a resistor R1. A resistor R2 and a relay L2 are connected in series to a by-pass wire 43 which by-passes the relay L1. When the power supply 46 starts to supply power, the relay L2 is first turned on, by which a voltage divided by the resistor R1 and the resistor R2 is applied to the capacitor C. Then, the relay L1 is turned on and a voltage of the power supply 46 is applied as it is to the capacitor C. As no current flows through the resistor R1 at that time, useless power consumption is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge / discharge control circuit that controls charging and discharging of a capacitor for stabilizing power supplied to a motor drive circuit.

[0002]

2. Description of the Related Art A vehicle such as an automobile is equipped with a device (for example, a power steering device) incorporating an electric motor (typically a motor). This type of device includes an electric motor drive circuit for driving the electric motor. The electric motor drive circuit receives electric power from the power supply and supplies electric motor current to the electric motor. In this type of device, it may be desired to supply a large electric motor current to the electric motor in a short time. Therefore, both ends of the capacitor are connected to a power supply line and a ground line that connect the power supply and the motor drive circuit, and the power stored in the capacitor is used to prepare for large-scale power supply in a short time. A conventional example of a charge / discharge control circuit for controlling the charging and discharging of the power source stabilizing capacitor will be described with reference to FIGS.

In the charge / discharge control circuit shown in FIG. 5, a power source stabilizing capacitor C is connected to a power source line 50 and a ground line 52 which connect the power source to the motor drive circuit. The relay L1 is inserted in the power supply line 50 connecting the power supply and the capacitor C. The power supply line 50a on the power supply side of the relay L1 and the power supply line 50b on the capacitor side are connected by a bypass line 54. A relay L2 and a resistor R1 are inserted in the bypass line 54. Bypass line 54 and power line 5 on the capacitor side
A resistor R2 is connected between a connection point with 0b (point A in the figure) and the capacitor C. To start supplying power from the power supply to the motor drive circuit, first, only the relay L2 is turned on (contacts are closed). As a result, the capacitor C
A voltage divided by the resistors R1 and R2 is applied to. Therefore, the rush current into the capacitor C at the start of charging is suppressed. When charging of the capacitor C is completed by the divided voltage, the relay L1 is turned on next. Therefore, the power supply voltage Vin is applied to both ends of the capacitor C,
The capacitor C is further charged. After the relay L1 is turned on, the relay L2 is turned off (the contact is opened). on the other hand,
When stopping the driving of the electric motor by the electric motor drive circuit,
The relay L1 is turned off. As a result, the supply of electric power from the power source to the electric motor drive circuit is stopped. The electric power stored in the capacitor C is discharged by the resistor R2.

In the charge / discharge control circuit shown in FIG. 6, a relay L1 is inserted in a power supply line 56 connecting a power supply and a capacitor C. One end of the resistor R1 is connected to the relay L1.
The other end of the resistor R1 is connected to the ground wire 58. Relay L
1 connects the power supply line 56a on the power supply side and the power supply line 56b on the capacitor side in the ON state, and connects the power supply line 56b on the capacitor side and the resistor R1 in the OFF state. When the supply of electric power from the power source to the electric motor drive circuit is started, the relay L1 is turned on. As a result, the power supply voltage Vin is applied to both ends of the capacitor C, and charging of the capacitor C is started.
On the other hand, when stopping the driving of the electric motor by the electric motor drive circuit, the relay L1 is turned off. As a result, the supply of electric power from the power source to the electric motor drive circuit is stopped. Capacitor C
The electric power stored in is discharged by the resistor R1.

[0005]

In the conventional technique shown in FIG. 5, the resistor R2 is directly connected to the power supply line 50 and the ground line 52. Therefore, although the rush current to the capacitor C at the start of charging can be suppressed, there is a problem that the power is continuously consumed by the resistor R2 while the power is being supplied from the power supply to the motor drive circuit. On the other hand, in the conventional technique shown in FIG. 6, the resistor R1 is connected to the power supply line 56 via the relay L1.
Therefore, the electric power is not consumed by the resistor R1 while the electric power is supplied from the power source to the electric motor drive circuit. However, in the conventional technique shown in FIG. 6, when power supply to the motor drive circuit is started from the power supply, the power supply voltage is applied to the capacitor C as it is. For this reason, the rush current into the capacitor C at the start of charging becomes large, and problems such as welding and damage to the relay L1 occur.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to limit the inrush current to the capacitor at the start of charging and consume unnecessary power during the operation of the motor drive circuit. It is to provide a charge / discharge control circuit which is not operated.

[0007]

Means for Solving the Problems, Actions and Effects The invention of the present application, which was created to solve the above problems, charges a capacitor whose both ends are connected to a power supply line connecting a power supply and a motor drive circuit and a ground line. A circuit for controlling discharge,
It is provided with one resistance (first resistance, second resistance), two relays (first relay, second relay), and a bypass line. First
The relay is inserted in the power supply line that connects the power supply and the capacitor. The first resistor has one end connected to the first relay and the other end connected to a ground wire. The bypass line bypasses the first relay and connects the power line on the power source side of the first relay and the power line on the capacitor side. A second resistor and a second relay are inserted in this bypass line. The first relay connects the power supply line on the power supply side and the power supply line on the capacitor side in the ON state,
In the off state, the power line on the capacitor side and the first resistor are connected. The second relay allows the bypass wire to be energized in the on state and disables the bypass wire in the off state. Then, when the power supply from the power supply to the electric motor drive circuit is started, the second relay is turned on, and the first relay is turned on after a predetermined time has elapsed since the second relay was turned on. When discharging from the capacitor, both the first relay and the second relay are turned off.

When power is started to be supplied from the power supply to the motor drive circuit in the charge / discharge control circuit, first the second
Only the relay is turned on and the first relay remains in the off state. Therefore, the bypass line can be energized and the first
The power supply line on the capacitor side of the relay is connected to the first resistor. Therefore, the voltage divided by the first resistor and the second resistor is applied to the capacitor, and the rush current at the start of charging is limited. When the charging by the voltage divided by the first resistance and the second resistance is completed, the first relay is turned on.
Therefore, the power supply line on the power supply side of the first relay and the power supply line on the capacitor side are connected, and the power supply line on the capacitor side and the first resistor are not connected. Therefore, the power supply voltage is directly applied to the capacitor to charge the capacitor, and at this time, the first voltage is applied.
No power is supplied to the resistor. Therefore, useless power consumption is prevented. To terminate the power supply from the power supply to the motor drive circuit and discharge the power stored in the capacitor,
Both the first relay and the second relay are turned off, and the power stored in the capacitor is consumed by the first resistor.

In the charge / discharge control circuit, the voltage applied to the capacitor changes in two steps by each operation of the first relay and the second relay at the start of power supply. That is, the voltage is changed in two steps by operating the two relays twice.
Therefore, by monitoring the voltage applied to the capacitor, it is possible to detect an abnormality in the first relay and the second relay.

Specifically, both the first relay and the second relay are off before the electric power is supplied to the electric motor drive circuit. Therefore, if the first relay and the second relay are normal (no relay contact welding), the voltage applied to the capacitor is 0V. On the contrary, if the voltage applied to the capacitor is 0V before the power is supplied to the motor drive circuit,
It can be determined that the first relay or the second relay is welded. Therefore, the charge / discharge control circuit is configured to detect the voltage applied to the capacitor, and the first relay or the voltage detection circuit when the voltage detected by the voltage detection circuit is not 0V before the start of power supply to the motor drive circuit. It is preferable that a first notifying unit for notifying that the second relay is welded in the ON state is further added. At this time, if the voltage detected before the start of the power supply is the voltage divided by the first resistor and the second resistor, it can be determined that the second relay is welded. When the detected voltage is the power supply voltage, it can be determined that welding has occurred in the first relay (whether welding has occurred in the second relay will be separately confirmed).

Next, when the second relay is turned on to start the supply of electric power to the motor drive circuit, if the second relay is normal, the voltage divided by the first resistor and the second resistor is applied to the capacitor. To be done. On the contrary, if the voltage applied to the capacitor is 0V, it can be determined that the second relay is disconnected. Therefore, in the charge / discharge control circuit, when the voltage detected by the voltage detection circuit is 0V after the second relay is turned on and before the first relay is turned on, the second relay is turned on. It is preferable that a second notifying unit for notifying that the wire is disconnected is further added.

When the first relay is turned on, if the first relay is normal, the voltage applied to the capacitor becomes equal to the power supply voltage. On the contrary, when the voltage applied to the capacitor is not equal to the power supply voltage, it can be determined that the first relay is welded in the off state. Therefore, in the charge / discharge control circuit, a third notifying unit is further added for notifying that the first relay is welded in the OFF state when the voltage after the ON operation of the first relay does not become the power supply voltage. It is preferable.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is a charge / discharge control circuit for a motor drive circuit of an electric power steering device. First, a schematic configuration of the power steering device will be described with reference to FIG. FIG. 3 shows a schematic configuration of the electric power steering device. The electric power steering device includes an input shaft 12 having a handle 10 fixed at one end. One end of the output shaft 14 is connected to the other end of the input shaft 12 via the torque detection device 22.
The torque detection device 22 is a device that detects the torque acting on the input shaft 12. A rack shaft 16 of a rack and pinion mechanism meshes with the other end of the output shaft 14. Both ends of the rack shaft 16 are connected to a mechanism that steers the direction of the wheels 20. A motor 18 that slides the rack shaft 16 in the lateral direction is mounted on the rack shaft 16. The motor 18 is connected to an ECU (electronic control unit) 24. The torque detection device 22 and the vehicle speed sensor (not shown) are also included in the ECU 2.
4 is connected. The ECU 24 has a motor drive circuit that outputs a motor drive signal to the motor 18, and a CPU that controls the motor drive circuit.

In this electric power steering device,
When the handle 10 is rotated, the input shaft 12 is rotated.
When the input shaft 12 rotates, the output shaft 14 rotates. When the output shaft 14 rotates, the rack shaft 16 slides in the lateral direction (vehicle width direction). When the rack shaft 16 slides, the wheels 20 change direction. The CPU of the ECU 24 calculates the assist torque generated by the motor 18 from the torque detected by the torque detection device 22 and the vehicle speed detected by the vehicle speed sensor. The calculated assist torque is applied to the rack shaft 16 by the motor 18. Ie EC
The CPU of U24 outputs an appropriate motor drive signal to the motor drive circuit. When the motor drive signal is output, the motor 18 rotates and the rack shaft 16 slides laterally.
Therefore, the steering force of the steering wheel 10 is reduced.

Next, a circuit connecting the ECU 24 and the power source will be described. FIG. 4 schematically shows the configuration of a circuit that connects the power supply and the ECU 24. As shown in FIG. 4, the power supply 46 and the ECU 24 are connected to the power supply line 42 and the ground line 4
Connected by four. A precharge / discharge circuit 40 is inserted between the power supply 46 and the ECU 24. The precharge / discharge circuit 40 will be described in detail with reference to FIG.

FIG. 1 shows a circuit diagram of the precharge / discharge circuit 40. As shown in FIG. 1, a power source stabilizing capacitor C is connected to the power source line 42 and the ground line 44. Power line 50 connecting power source 46 and capacitor C
A main relay L1 is inserted in the. Main relay L
One end of the resistor R1 is connected to 1. The other end of the resistor R1 is connected to the ground wire 44. The main relay L1 is
In the ON state, the power supply line 42a on the power supply side is connected to the power supply line 42b on the capacitor side, and in the OFF state, the power supply line 42b on the capacitor side is connected to the resistor R1. The power line 42a on the power source side of the main relay L1 and the power line 42b on the capacitor side are
It is connected by a bypass line 43. A precharge relay L2 and a resistor R2 are inserted in series in the bypass line 43. The precharge relay L2 can energize the bypass line 43 (close the relay contact) in the ON state,
In the off state, the bypass line cannot be energized (the relay contact is opened). The main relay L1 and the precharge relay L2 are connected to the CPU 28. The CPU 28 controls ON / OFF of the main relay L1 and the precharge relay L2. The CPU 28 includes a voltage detection circuit 32 for detecting a voltage applied to the capacitor 32 and a main relay L.
1 and an indicator 3 for informing the abnormality of the precharge relay L2
0 is connected. The CPU 28 of the present embodiment is an ECU
Power is supplied from the power supply 46 through a power supply line (not shown) different from the power supply line 42 and housed in the unit 24.
The CPU 28 may operate by receiving power supply from a power supply different from the power supply 46.

Next, the above-mentioned precharge / discharge circuit 4
The operation of 0 will be described with reference to FIG. FIG. 2 shows a temporal change of the voltage applied to the capacitor C when the main relay L1 and the precharge relay L2 are turned on in a normal state. As shown in FIG.
When the driver turns on the ignition, first,
Power supply to the CPU 28 is started from the power supply 46. CP
When the voltage applied to U28 becomes the operation start voltage of the CPU 28, the CPU 28 first confirms whether or not the voltage detected by the voltage detection circuit 32 is 0V. If the detected voltage is 0 V, the main relay L1 and the precharge relay L2 are in the off state, and thus it is determined to be normal. On the contrary, if the detected voltage is not 0V, the main relay L1 or the precharge relay L2 is welded in the ON state,
The fact is displayed on the display unit 30.

Next, the CPU 28 controls the precharge relay L
Turn on 2. When the precharge relay L2 is turned on, the bypass line 43 can be energized, and the capacitor C starts to be charged. At this time, since the power line 42b on the capacitor side and the resistor R1 are connected by the main relay L1, the voltage divided by the resistors R1 and R2 is applied to the capacitor C. Therefore, the inrush current can be suppressed to a low level, and the welding and damage (wear) of the main relay L1 and the precharge relay L2 can be prevented.

After a lapse of a predetermined time from turning on the precharge relay L2, the CPU 28 determines whether the voltage detected by the voltage detection circuit 32 is a value obtained by dividing the power supply voltage by the resistors R1 and R2. . When the detected voltage has a divided value, it is determined that the precharge relay L2 is operating normally. On the contrary, when the detected voltage becomes 0 V, it is determined that the precharge relay L2 does not operate normally (that is, the precharge relay L2 is disconnected), and the fact is displayed on the display unit 30.

When a predetermined time has passed after confirming whether the precharge relay L2 is operating normally,
The CPU 28 turns on the main relay L1. When the main relay L1 is turned on, the power supply voltage V appears across the capacitor C.
In is applied, and the capacitor C is further charged. When a predetermined time has passed since the main relay L1 was turned on, CP
U28 determines whether the voltage detected by the voltage detection circuit 32 is the power supply voltage Vin. When the detected voltage reaches the power supply voltage Vin, the main relay L1 is determined to be operating normally. On the contrary, when the detected voltage does not reach the power supply voltage Vin, it is determined that the main relay L1 is welded in the off state, and the fact is displayed on the display unit 30.

After checking the operation of the main relay L1,
The CPU 28 turns off the precharge relay L2. After that, the ECU 24 starts a normal operation. When the ECU 24 operates normally, the resistor R1 is not connected to the power supply line 42, so that the resistor R1 does not consume unnecessary power.

When the ignition is turned off, C
The PU 28 turns off the main relay L1. When the main relay L1 is turned off, the power stored in the capacitor C is consumed by the resistor R1. Therefore, the voltage detection circuit 3
The voltage detected at 2 gradually decreases as shown in FIG. 2 and finally becomes 0V.

As is clear from the above description, in this embodiment, since the inrush current to the capacitor C at the start of the power supply from the power source 46 is suppressed to a low level, the main relay L1 and the precharge relay L2 are welded or damaged. Is prevented. Further, after the charging of the capacitor C is completed and the operation is shifted to the normal operation, no current flows through the discharging resistor R1, so that useless power consumption is prevented. Further, by monitoring the voltage applied to the capacitor C, the abnormality of the relays L1 and L2 is detected. Furthermore, by connecting the discharge resistor R1 to the main relay L1, a discharge-dedicated relay is not provided.

The preferred embodiment of the present invention has been described above in detail, but this is merely an example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. You can Further, the technical elements described in the present specification or the drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Further, the technique illustrated in the present specification or the drawings achieves a plurality of purposes at the same time, and achieving the one purpose among them has technical utility.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a precharge / discharge circuit according to the present embodiment.

FIG. 2 is a diagram showing a graph in which the horizontal axis represents the elapsed time from the ignition on and the vertical axis represents the voltage of a capacitor in the precharge / discharge circuit according to the present embodiment.

FIG. 3 is a diagram schematically showing a schematic configuration of a power steering device.

FIG. 4 is a diagram schematically showing a circuit that connects an ECU of the power steering device and a power supply.

FIG. 5 is a circuit diagram showing an example of a conventional charge / discharge control circuit.

FIG. 6 is a circuit diagram showing another example of a conventional charge / discharge control circuit.

[Explanation of symbols]

10 ... Handle 12 ... Input shaft 14 ... Output shaft 16 ... Rack shaft 18 ... Motor 20 ... wheels 24 ... ECU (electronic control unit) 28 ... CPU 30..Display 32 .. Voltage detection circuit 42 ... Power line 43..Bypass line 44 ... Ground wire

Claims (4)

[Claims] 1. A circuit for controlling charging and discharging of a capacitor whose both ends are connected to a power supply line and a ground line connecting a power supply and a motor drive circuit, and which is inserted into a power supply line connecting the power supply and the capacitor. A relay, a first resistor having one end connected to the first relay and the other end connected to a ground wire, and a power supply line on the power supply side of the first relay and a power supply line on the capacitor side bypassing the first relay A bypass line, a second resistor inserted in the bypass line, and a second relay inserted in the bypass line. The first relay connects the power line on the power supply side and the power line on the capacitor side in the ON state. In the OFF state, the power line on the capacitor side is connected to the first resistor, and the second relay allows the bypass line to be energized in the ON state, and disables the bypass line in the OFF state, so that the power supply is connected to the motor drive circuit. Electricity When the supply is started, the second relay is turned on, the first relay is turned on after a lapse of a predetermined time after the second relay is turned on, and when the capacitor is discharged, the first relay is turned on. And a second relay are both turned off. 2. A voltage detection circuit for detecting a voltage applied to the capacitor, and a first voltage detection circuit when the voltage detected by the voltage detection circuit is not 0V before the start of power supply to the motor drive circuit.
The first notifying means for notifying that the relay or the second relay is welded in the ON state is further added.
The charging / discharging control circuit according to. 3. When the voltage detected by the voltage detection circuit is 0V after the second relay is turned on and before the first relay is turned on, the second relay is disconnected. The charging / discharging control circuit according to claim 1, further comprising a second notifying unit for notifying the fact. 4. The third notifying means for further notifying that the first relay is welded in the OFF state when the voltage after the ON operation of the first relay does not become the power supply voltage is added. The charge / discharge control circuit described.