JP2012122462A - Electromagnetic load control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the breakage of a discharge means caused by an overcurrent, in an electromagnetic load control device having the discharge means.SOLUTION: When a boosting voltage reaches a prescribed threshold or higher, this electromagnetic load control device makes a discharge device discharge electricity, and controls a discharge operation so that a discharge current is lowered to a prescribed current threshold or lower.

Description

  The present invention relates to an apparatus for controlling a current supplied to an electromagnetic load.

  Conventionally, in an internal combustion engine control device for automobiles, motorcycles, agricultural machinery, industrial machinery, marine aircraft, etc., which uses gasoline or light oil as fuel, an injector that directly injects fuel into a cylinder for the purpose of improving fuel efficiency and output. It is used. Such an in-cylinder direct injection type injector requires a lot of energy for the valve opening operation of the injector using fuel pressurized to a high pressure as compared with the conventional method. Further, in order to cope with improvement in control performance (responsiveness) and high rotation (high speed control), it is necessary to supply this energy to the injector in a short time.

  A circuit for driving such an injector generates a voltage higher than the battery voltage by using a booster circuit, and ON / OFF drives a switching element connected thereto. The injector is driven by flowing a current using the boosted voltage and energizing a large current in a short time, and high-pressure in-cylinder direct injection can be realized.

  The following Patent Document 1 describes a configuration and an operation example of an electromagnetic load control device that supplies a large current to an injector.

JP 2008-115848 A

  In the technique described in Patent Document 1, load current flowing through the injector is returned to the booster circuit in order to improve boosting efficiency as much as possible. In addition, a discharging means for preventing over-boosting is provided, and discharging is performed when the boosted voltage is equal to or higher than a threshold value to drop the boosted voltage.

  At this time, only the resistance component of the discharge means limits the discharge current flowing through the discharge means. For this reason, an excessive discharge current exceeding the rated current of the discharge means flows, and the discharge means may be destroyed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent the discharge means from being damaged by an overcurrent in the electromagnetic load control device including the discharge means.

  The electromagnetic load control device according to the present invention controls the discharge operation so as to cause the discharge device to discharge when the boosted voltage becomes equal to or higher than a predetermined threshold value, and to suppress the discharge current below the predetermined current threshold value.

  According to the electromagnetic load control device of the present invention, it is possible to reduce the risk of damaging the discharge device due to an excessive discharge current.

1 is a circuit diagram of an electromagnetic load control device according to Embodiment 1. FIG. 3 is a timing chart illustrating an operation of the electromagnetic load control device according to the first embodiment. 6 is a circuit diagram of an electromagnetic load control device according to a second embodiment. FIG. 6 is a timing chart showing the operation of the electromagnetic load control device according to the second embodiment. FIG. 6 is a circuit diagram of an electromagnetic load control device according to a third embodiment. It is a figure which shows the circuit structure of the electromagnetic load control apparatus described in patent document 1. FIG. It is a timing chart which shows operation | movement of the electromagnetic load control apparatus shown in FIG.

<Conventional electromagnetic load control device>
Before describing the embodiment of the present invention, the circuit configuration and operation of the electromagnetic load control device described in Patent Document 1 will be described for comparison. Thereafter, the electromagnetic load control device according to the embodiment of the present invention will be described.

  FIG. 6 is a diagram showing a circuit configuration of the electromagnetic load control device described in Patent Document 1. As shown in FIG. The electromagnetic load control device shown in FIG. 6 is a device that controls energization of the current supplied to the injector. The apparatus shown in FIG. 6 generates a voltage higher than the battery voltage by using a booster circuit, and drives the switching element ON / OFF to control energization of the boosted voltage. Thereby, the injector is driven by flowing a current using the boosted voltage, and a large current is applied in a short time, thereby realizing direct in-cylinder injection with a high pressure.

  6 includes a battery 101, a current detector 104, a current detection resistor 106, a boosting coil 107, a boosting switching element 109, a boosting control unit 111, a boosting diode 112, a discharging means 113, and a boosting capacitor. 114, an overvoltage controller 116, and a voltage detector 118. These configurations are for boosting the voltage supplied by the battery 101 and supplying the boosted voltage 117 to the VH high-side switching element 140 described later.

  The step-up coil 107, the step-up switching element 109, and the step-up capacitor 114 correspond to the step-up circuit in the present invention.

  Battery 101, current detection resistor 106, and boosting capacitor 114 are connected to ground 100.

  The battery 101 supplies the battery voltage 102 to the booster coil 107 and a VB high-side switching element 146 described later. The step-up control unit 111 outputs a step-up switching signal 110 to the step-up switching element 109 to control ON / OFF of the step-up switching element 109 and control an operation of stepping up the battery voltage 102. The current detector 104 detects the charging current 108 flowing through the boost switching element 109 based on the potential difference 120 across the current detection resistor 106 and outputs the detection result to the boost control unit 111.

  The discharging means 113 is a device that lowers the boosted voltage 117 by discharging, and is connected in parallel to the boosting diode 112. The overvoltage control unit 116 outputs an overvoltage discharge control signal 115 to the discharging unit 113 to control the discharging unit 113 to be turned on / off. The boosting capacitor 114 is charged with charge based on the boosted voltage 117. The voltage detector 118 detects the boosted voltage 117. When the boost voltage 117 decreases, the boost decrease detection signal 105 is output to the boost control unit 111, and when the boost voltage 117 becomes an overvoltage, the overvoltage detection signal 119 is output to the overvoltage controller 116.

  6 further includes an injector driver control unit 130, a VH driver driving unit 134, a VB driver driving unit 135, a low side driver driving unit 136, a VH high side switching element 140, and a VH high side backflow prevention diode 141. , An injector load 142, a low-side switching element 143, a VB high-side backflow prevention diode 145, a VB high-side switching element 146, and a free-wheeling diode 147.

  The VH driver driving unit 134 outputs a VH high side driving signal 137 in accordance with the VH high side control signal 131 output from the injector driver control unit 130, and drives and controls the VH high side switching element 140. The VB driver driving unit 135 outputs a VB high side driving signal 138 according to the VB high side control signal 132 output from the injector driver control unit 130, and drives and controls the VB high side switching element 146. The low side driver drive unit 136 outputs a low side drive signal 139 in accordance with the low side control signal 133 output from the injector driver control unit 130 to drive and control the low side switching element 143. The return diode 147 returns the back electromotive force from the injector load 142) to the boost side.

  FIG. 7 is a timing chart showing the operation of the electromagnetic load control device shown in FIG. Hereinafter, the operation of the electromagnetic load control apparatus shown in FIG. 6 will be described with reference to FIG.

  When the battery voltage 101 is supplied, the electromagnetic load control device starts operating. When the boost switching element 109 is turned ON / OFF, the boost voltage 117 is generated. The boosted voltage 117 is boosted to a voltage 117d shown in FIG.

  A load current is supplied to the injector load 142 at a timing 125 shown in FIG. 7, and driving of the injector load 142 is started. The injector driver drive unit 130 outputs a VH high side drive signal 131, a VB high side drive signal 132, and a low side control signal 133. In response to this, the switching elements 140, 146, and 143 on the VH, VB, and low side repeat ON / OFF, respectively, and supply the load drive current 144 shown in FIG. 7 to the injector load 142.

  The VH high side switching element 140 is turned on by the VH high side control signal 131, and the boosted voltage 117 and the current are supplied to the injector load 142 by the charge charged in the boosting capacitor 114. At this time, the boosted voltage 117 gradually decreases as shown in FIG. When the boosted voltage 117 drops below a predetermined threshold 117a, the voltage detector 118 detects this and outputs a voltage drop detection signal 105 to the boost controller 111. The step-up control unit 111 outputs a step-up switching signal 110 to turn on / off the step-up switching element 109.

  The current detection resistor 106 detects a charging current 108 that flows during a period in which the step-up switching element 109 is ON. When the charging current 108 reaches a predetermined charging current threshold 108a, the charging current detection signal 120 reaches the predetermined threshold 120a. The boost control unit 111 turns off the boost switching element 109 at this time. At this time, the charging current 108 is charged to the boost capacitor 114 via the boost diode 112, whereby the boost voltage 117 is boosted again to a predetermined boost voltage level 117d.

  Thereafter, when the drive of the injector load 142 is completed at the timing 126 shown in FIG. 7, the low-side switching element 143 is turned OFF. As a result, the load drive current 144 becomes a counter electromotive current and is returned to the booster side via the return diode 147. At this time, the return current is charged in the boost capacitor 114, and the boost voltage 117 rises.

  When the boost voltage 117 continues to increase due to the reflux current and exceeds a predetermined voltage threshold value 117b, the voltage detector 118 detects this and outputs an overvoltage detection signal 119 to the overvoltage control unit 116. The overvoltage control unit 116 outputs an overvoltage discharge control signal 115 to the discharging means 113 in response to the overvoltage detection signal 119. The discharge means 113 is turned on in accordance with the overvoltage discharge control signal 115, and a discharge current 123 flows through the discharge means 113 to cause discharge. Along with this, the boost voltage 117 decreases. At this time, the step-up switching element 109 is OFF, and the discharge current 123 flows to the battery 101.

  When the boosted voltage 117 drops below the predetermined voltage 117c, the voltage detector 118 detects this, and changes the overvoltage detection signal 119 to a low level. As a result, the discharging means 113 is turned off, and the discharging operation is stopped. As a result, over-boosting of the boost voltage 117 is prevented, and damage to circuit components due to over-boosting is prevented.

  Here, in the discharging operation, the discharging means 113 is turned on when the boosted voltage 117 becomes equal to or higher than the predetermined voltage threshold 117b, and continues to be turned on until it becomes less than 117c. The discharge current 123 has a value determined by the potential difference between the boosted voltage 117 and the battery voltage 102 and the resistance component of the discharge means 113. This discharge current continues to flow while the boosted voltage 117 is equal to or higher than the predetermined threshold 117b.

  At this time, since only the resistance component of the discharge means 113 limits the discharge current 123, there is a possibility that the discharge current 123 exceeding the rated current allowed for the discharge means 113 flows. The discharge means 113 may be damaged by the excessive discharge current 123.

  In order to prevent the excessive discharge current 123 from flowing, it is necessary to stop the discharge operation of the discharge means 113. However, in the circuit configurations and timing charts shown in FIGS. 6 to 7, the discharge means 113 is operated based on whether or not the boosted voltage 117 has reached the threshold value 117b. For this reason, it is considered that the discharge current 123 may not always be properly controlled.

<Embodiment 1>
FIG. 1 is a circuit diagram of an electromagnetic load control device according to Embodiment 1 of the present invention. The circuit shown in FIG. 1 differs from the circuit configuration described in FIG. 6 described above in that the current detection resistor 106 is arranged on the upstream side of the booster coil 107 (side closer to the battery 101). The current detector 104 outputs the current detection signal 103 to both the boost control unit 111 and the overvoltage control unit 116. The overvoltage control unit 116 performs ON / OFF control of the discharging unit 113 based on detection results from the voltage detector 118 and the current detector 104.

  FIG. 2 is a timing chart showing the operation of the electromagnetic load control device according to the first embodiment. The timing chart shown in FIG. 2 corresponds to FIG. 7 described above. Hereinafter, the operation of the electromagnetic load control device according to the first embodiment will be described with reference to FIG.

  The operation until the boost control unit 111 boosts the boosted voltage 117 to the voltage threshold 117d is the same as the timing chart described in FIG. However, the arrangement position of the current detection resistor 106 for detecting the charging current 108 is different between FIG. 6 and FIG.

  When the boosted voltage 117 continues to rise and exceeds a predetermined voltage threshold 117b, the overvoltage control unit 116 turns on the discharging means 113. As a result, a discharge current 123 flows through the discharge means 113 and discharge occurs. At this time, the step-up switching element 109 is OFF, and the discharge current 123 flows to the battery 101 via the current detection resistor 106.

  In the circuit configuration shown in FIG. 1, unlike the circuit configuration shown in FIG. 6, the current detection resistor 106 is arranged on the upstream side of the booster coil 107, so that the current detection resistor 106 and the current detector 104 are discharged. The current 123 can be detected. That is, the discharge current 123 can be detected using the same detection circuit as that for detecting the charging current 108.

  When the discharge current 123 reaches a predetermined current threshold 123a, the charge current detection signal 120 (here, the detection result of the discharge current 123) reaches the predetermined threshold 120b. The overvoltage control unit 116 turns off the discharging means 123 at this time.

  At this time, if the amount of discharge current is not sufficient and the boosted voltage 117 still maintains a voltage equal to or higher than the predetermined threshold value 117c, the overvoltage control unit 116 sets the overvoltage discharge control signal 115 to high again and turns on the discharging unit 113. To cause the discharge current 123 to flow.

  The overvoltage control unit 116 repeatedly performs the operation of turning on / off the discharging unit 123 until the boosted voltage 117 becomes less than the predetermined threshold value 117c. When the boosted voltage 117 becomes less than the predetermined threshold value 117c, the overvoltage detection signal 119 becomes low and the discharging operation of the discharging means 113 stops.

<Embodiment 1: Summary>
As described above, according to the electromagnetic load control device according to the first embodiment, the discharge current 123 can be detected using the current detection resistor 106 and the current detector 104. As a result, the discharge means 113 can be turned off before the discharge current 123 becomes excessive while the discharge means 113 is discharging in order to lower the over-boosted boost voltage 117. That is, the risk of damaging the discharge means 113 due to the excessive discharge current 123 can be reduced.

  Further, in the electromagnetic load control device according to the first embodiment, since the current detection resistor 106 is arranged on the upstream side of the step-up coil 107, a charging current is obtained using a single current detection resistor 106 and a current detector 104. 108 and the discharge current 123 can be detected, which is advantageous in terms of circuit cost and mounting area.

  Even if the current detection resistor 106 is disposed between the discharge means 123 and the booster coil 107, both the charge current 108 and the discharge current 123 are detected using the single current detection resistor 106 and the current detector 104. can do. However, in this case, since the potential on the upstream side of the current detector 104 becomes the battery voltage 102 or becomes zero when the step-up switching element 109 is turned ON / OFF, current detection is performed with the voltage across the current detection resistor 106. Is not always a desirable arrangement.

<Embodiment 2>
In the first embodiment, the configuration in which the discharge current 123 is suppressed by turning off the discharge unit 113 when the discharge current 123 reaches the predetermined current threshold 123b has been described. In Embodiment 2 of the present invention, a configuration for suppressing the discharge current 123 with a simpler configuration will be described.

  FIG. 3 is a circuit diagram of the electromagnetic load control device according to the second embodiment. The circuit shown in FIG. 3 differs from the circuit shown in FIG. 1 in that the current detection resistor 106 is arranged downstream of the booster coil 107 and the booster switching element 109 as in FIG.

  Further, the overvoltage control unit 116 does not directly control the discharging unit 113 but outputs an overvoltage protection signal 121 to the duty control unit 122. The duty control unit 122 performs ON / OFF control of the discharging unit 113 according to the overvoltage protection signal 121. By controlling the ON duty period of the discharge means 113, the discharge current 123 can be controlled. Note that the duty ratio that is ON / OFF controlled by the duty control unit 122 can be varied by the duty setting signal 122b output from the duty setting means 122a.

  FIG. 4 is a timing chart showing the operation of the electromagnetic load control device according to the second embodiment. Hereinafter, the operation of the electromagnetic load control device according to the second embodiment will be described with reference to FIG.

  The timing chart shown in FIG. 4 is substantially the same as that in FIG. 2, but the operation subject that outputs the overvoltage discharge control signal 115 is different. When the overvoltage detection signal 119 becomes high, the overvoltage control unit 116 sets the overvoltage protection signal 121 to high. The duty control unit 122 outputs an overvoltage discharge control signal 115 having a predetermined ON duty period to the discharging unit 113, and controls the discharging unit 113 to be turned on / off. The ON duty period can be set to about 10 μs or less, for example.

  The discharging means 113 is automatically turned off after continuing the ON state for a predetermined period. As a result, the discharge current 123 flowing during the ON period is limited to a value less than the predetermined current value 123a regardless of the ON resistance value of the discharge means 113. The longer the low period with respect to the high period of the overvoltage discharge control signal 115, the lower the value of the discharge current 123.

  In the second embodiment, since the discharge current 123 is suppressed only by the duty control of the discharge means 113 without detecting the discharge current 123, it is necessary to set the ratio between the ON duty and the OFF duty appropriately in advance. is there. Specifically, the range of the discharge current 123 may be predicted in advance according to the assumed characteristics of the injector load 142, the rating of the discharge means 113, and the duty ratio may be determined based on this. At this time, the duty ratio can be set from, for example, a microcomputer via the duty setting means.

<Embodiment 2: Summary>
As described above, according to the electromagnetic load control device according to the second embodiment, when the boosted voltage 117 exceeds the threshold value 117b, the discharge unit 113 is turned on / off with a predetermined duty ratio, and the discharge current 123 is suppressed. Can do.

  Note that, similarly to the second embodiment, a configuration in which the discharge unit 113 is driven and controlled with a predetermined duty ratio can be used under the circuit configuration of the first embodiment. In this case, since the current detection resistor 106 can be used only for detecting the charging current 108 and not for detecting the discharging current 123, the operation of the overvoltage control unit 116 is further simplified. That is, in the first embodiment, a plurality of processes for determining whether or not the discharge current 123 exceeds the threshold value 123b occur within a short time. In the second embodiment, this determination is omitted, and the ON / OFF control of the discharge unit 113 is performed. Therefore, the control process is simplified as a whole.

  Even when the discharge current 123 is detected using the current detection resistor 106 under the circuit configuration of the first embodiment, the present embodiment replaces the configuration in which the overvoltage control unit 116 directly controls the ON / OFF of the discharge means 113. As shown in FIG. 2, the discharging means 113 can be ON / OFF controlled by duty control.

<Embodiment 3>
FIG. 5 is a circuit diagram of the electromagnetic load control device according to the third embodiment of the present invention. In the circuit shown in FIG. 5, unlike the circuit shown in FIG. 3, one end of the discharging means 113 is connected between the boosting capacitor 114 and the boosting coil 107, and the other end is grounded. Other configurations are the same as those of the second embodiment.

  In the third embodiment, the discharge current 123 does not return to the battery 101 but flows to GND. Even in this case, the discharge current 123 can be suppressed by controlling the ON duty of the discharge means 113 as in the second embodiment. Note that the discharge current 123 may be supplied to the GND via a resistor or a coil, and the discharge current 123 may be appropriately suppressed.

<Embodiment 4>
Each of the above-described configurations, functions, processing units, etc. can be realized as hardware by designing all or a part of them, for example, with an integrated circuit, and the processor executes a program that realizes each function. It can also be realized as software. Information such as programs and tables for realizing each function can be stored in a storage device such as a memory or a hard disk, or a storage medium such as an IC card or a DVD.

  For example, one or more functional units of the boost control unit 111, the overvoltage control unit 116, the duty control unit 122, the injector driver control unit 130, the VH driver driving unit 134, the VB driver driving unit 135, and the low side driver driving unit 136. Can also be implemented on an integrated circuit.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  100: GND, 101: battery, 102: battery voltage, 103: current detection signal, 104: current detector, 105: boost detection signal, 106: current detection resistor, 107: boost coil, 108: charging current, 109: Step-up switching element, 110: Step-up switching signal, 111: Step-up control unit, 112: Step-up diode, 113: Discharge means, 114: Step-up capacitor, 115: Overvoltage discharge control signal, 116: Overvoltage control unit, 117: Step-up Voltage: 118: Voltage detector, 119: Overvoltage detection signal, 120: Charge current detection signal, 130: Injector driver control unit, 131: VH high side control signal, 132: VB high side control signal, 133: Low side control signal, 134: VH driver driving unit, 135: VB driver driving unit, 13 : VH high-side drive signal, 138: VB high-side drive signal, 136: Low-side driver drive unit, 139: Low-side drive signal, 140: VH high-side switching element, 141: VH high-side backflow prevention diode, 142: Injector load 143: Low-side switching element, 144: Load drive current, 145: VB high-side backflow prevention diode, 146: VB high-side switching element, 147: Freewheeling diode.

Claims (5)

An apparatus for controlling a current supplied to an electromagnetic load,
A booster circuit for boosting a negative overvoltage applied to the electromagnetic load;
A discharge device that discharges charges accumulated when the booster circuit boosts the negative overvoltage;
A current detector for detecting a discharge current flowing through the discharge device;
A voltage detector for detecting a voltage boosted by the booster circuit;
A control unit for controlling the discharge operation of the discharge device;
With
The controller is
When the voltage detector detects a voltage equal to or higher than a predetermined threshold, the discharge device is discharged, and the discharge current flowing through the discharge device is suppressed to a predetermined current threshold or lower. The controller is
When the voltage detector detects a voltage equal to or higher than a predetermined voltage threshold, the discharge device is energized to cause a discharge current to flow. When the discharge current detected by the current detector exceeds the current threshold, the discharge device is de-energized. The electromagnetic load control device according to claim 1, wherein the discharge current is suppressed to be equal to or lower than the current threshold by repeating the operation of stopping the discharge current. The current detector is
3. The device according to claim 1, wherein the booster circuit is disposed at a position where both the boost current flowing through the booster circuit and the discharge current can be detected when boosting the load voltage. Electromagnetic load control device. The electromagnetic load control device according to any one of claims 1 to 3, wherein the current detector is disposed upstream of the booster circuit. The controller is
When the voltage detector detects a voltage equal to or higher than a predetermined voltage threshold, the discharge device is energized to flow a discharge current, and after a predetermined time has elapsed, the discharge device is de-energized to stop the discharge current, The electromagnetic load control device according to claim 1, wherein the discharge current is suppressed to be equal to or less than the current threshold value.

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