Electronic control unit

Abstract

To provide an electronic control device capable of suppressing increase in physical size.SOLUTION: An electronic control device comprises: a first terminal 21 for receiving a control signal; a second terminal 22 connected with a low potential side of a battery 30, and a third terminal 23 connected with a high potential side of the battery 30; an operation circuit 40 that performs a predetermined operation; a first resistor 61 connected with the first terminal 21; a second resistor 62 arranged between the first resistor 61 and the operation circuit 40 so as to be connected in series with the first resistor 61; a surge absorption circuit 70 that is connected between the second terminal 22 and a first node N1 between the first resistor 61 and the second resistor 62, and configured including Zener diodes 71 and 72 to apply surge currents I1 and I2; and a Zener diode 80 whose cathode is connected with a second node N2 between the second resistor 62 and the operation circuit 40 and whose anode is connected with the second terminal 22. The surge absorption circuit 70 has a configuration that has a reverse breakdown voltage equal to or more than a battery voltage of the battery 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electronic control device. [Background technology]

[0002] Conventionally, electronic control devices have been proposed that can protect operating circuits and the like from surges and abnormal battery connections (see, for example, Patent Document 1). Specifically, these electronic control devices have an input terminal connected to an external circuit, a high power supply terminal connected to the high potential side of the battery, and a low power supply terminal connected to the low potential side of the battery. These electronic control devices also have a protection circuit to handle abnormal currents that occur when an excessive surge voltage is applied to the operating circuit or when the battery is connected in reverse.

[0003] In this electronic control device, the protection circuit is configured by connecting a diode and a capacitor in series, and the capacitance of the capacitor is set to be large enough to prevent the voltage across it from becoming too large when a surge occurs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6349217 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the electronic control device described above is likely to be large in size because it is equipped with a capacitor with a sufficiently large capacity.

[0006] In view of the above, an object of the present invention is to provide an electronic control device that can prevent the size from increasing. [Means for solving the problem]

[0007] In order to achieve the above object, claim 1 provides an electronic control device that receives a control signal from an external circuit (10) and is connected to a battery (30), the electronic control device comprising: a first terminal (21) to which the control signal is input; a second terminal (22) connected to the low potential side of the battery; a third terminal (23) connected to the high potential side of the battery; an operating circuit (40) that performs a predetermined operation; a first resistor (61) connected to the first terminal; and a resistor (62) connected in series with the first resistor between the first resistor and the operating circuit. a surge absorbing circuit (70) connected between a first connection point (N1) between the first resistor and the second resistor and the second terminal and including Zener diodes (71, 72) to pass surge currents (I1, I2); and a Zener diode (80) having a cathode connected to a second connection point (N2) between the second resistor and the operating circuit and an anode connected to the second terminal, the surge absorbing circuit having a reverse withstand voltage equal to or higher than the battery voltage of the battery.

[0008] According to this, since a surge absorption circuit is provided between the first resistor and the second resistor, when a surge is applied to the first terminal, the surge current can be passed through the surge absorption circuit, protecting the operating circuit. Furthermore, since the reverse withstand voltage of the surge absorption circuit is set to be equal to or greater than the battery's withstand voltage, abnormal current when the battery is reverse-connected flows from the first terminal to the external circuit via the Zener diode, the second resistor, and the first resistor. In this case, the abnormal current can be limited by the first and second resistors, preventing malfunctions in the electronic control device or the external circuit connected to the first terminal due to the abnormal current. As described above, this electronic control device can handle surges and abnormal currents, while avoiding size increase due to the absence of a capacitor.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 2 is a circuit diagram of an electronic control device according to the first embodiment. [Figure 2] FIG. 4 is a diagram showing a surge current generated in an electronic control device. [Figure 3] 10A and 10B are diagrams showing abnormal currents that occur when a battery is reversely connected to an electronic control device; [Figure 4] FIG. 10 is a circuit diagram of an electronic control device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, parts that are identical or equivalent to each other will be denoted by the same reference numerals.

[0012] (First embodiment) A first embodiment will be described with reference to the drawings. The electronic control device of this embodiment is suitable for use as an electronic control device for controlling electronic devices mounted on a vehicle or the like.

[0013] 1, the electronic control device 1 has a first terminal 21 to which a control signal is input as an input signal from an external circuit or an MCU (abbreviation of Micro Controller Unit) 10, which serves as an external control unit. The electronic control device 1 also has a second terminal 22 connected to the low potential side of a battery 30 and maintained at ground potential, and a third terminal 23 connected to the high potential side of the battery 30.

[0014] Furthermore, the electronic control device 1 includes an operating circuit 40, a power supply circuit 50, a first resistor 61, a second resistor 62, a surge absorbing circuit 70, a Zener diode 80, and the like.

[0015] In this embodiment, the actuation circuit 40 includes a buffer 41 and a switching circuit 42. The switching circuit 42 includes, for example, a logic circuit, a driver circuit, a switching element, etc., and is connected to electronic components (not shown) and outputs drive signals that adjust the operation of the electronic components based on control signals from the MCU 10.

[0016] The power supply circuit 50 is connected to the battery 30 via the third terminal 23, and generates a predetermined voltage based on the voltage of the battery 30. The power supply circuit 50 applies the predetermined voltage to the switching circuit 42 and the like. The battery 30 is also connected to the MCU 10 via a power supply circuit (not shown). The MCU 10 performs predetermined processing by receiving the predetermined voltage adjusted by the power supply circuit (not shown).

[0017] The first resistor 61 and the second resistor 62 are arranged in series between the first terminal 21 and the operating circuit 40. Specifically, the first resistor 61 is arranged on the first terminal 21 side, and the second resistor 62 is arranged on the operating circuit 40 side. In this embodiment, the resistance value of the first resistor 61 is smaller than the resistance value of the second resistor 62. Although not particularly limited, for example, the resistance value of the first resistor 61 is set to 1 kΩ, and the resistance value of the second resistor 62 is set to 9 kΩ.

[0018] In the electronic control device 1 of this embodiment, the voltage of the first terminal 21 may become high. For this reason, the electronic control device 1 is preferably configured with elements having a high intrinsic breakdown voltage, and is preferably formed using, for example, an SOI (abbreviation for Silicon on Insulator) substrate. Specifically, the SOI substrate is configured by stacking a semiconductor layer made of silicon on a support substrate made of silicon with an insulating film interposed therebetween. The first resistor 61 and the second resistor 62 are configured by forming diffused resistors in the semiconductor layer. In addition to the first resistor 61 and the second resistor 61, the electronic control device 1 of this embodiment also has the first to third terminals 21 to 23, the operating circuit 40, the power supply circuit 50, the surge absorption circuit 70, the Zener diode 80, and the like formed on the SOI substrate. In other words, the electronic control device 1 of this embodiment is configured as a single chip.

[0019] The surge absorbing circuit 70 is arranged to connect a first connection point N1 between the first resistor 61 and the second resistor 62 and the second terminal 22. In this embodiment, the surge absorbing circuit 70 is configured by connecting in series a first Zener diode 71 whose cathode is connected to the first connection point N1 and a second Zener diode 72 whose cathode is connected to the second terminal.

[0020] The surge absorbing circuit 70 is configured so that its overall reverse withstand voltage is equal to or greater than the battery voltage so as not to break down when the battery 30 is reverse-connected. In this embodiment, a plurality of second Zener diodes 72 are connected in series, so that the reverse withstand voltage of the surge absorbing circuit 70 is equal to or greater than the battery voltage. Although two second Zener diodes 72 are shown in FIG. 1, the number of second Zener diodes 72 can be changed as appropriate depending on the battery voltage of the connected battery 30.

[0021] The Zener diode 80 is arranged to connect a second connection point N2 between the second resistor 62 and the operating circuit 40 and the second terminal 22. Specifically, the Zener diode 80 is arranged such that the cathode is connected to the second connection point N2 and the anode is connected to the second terminal 22.

[0022] The above is the configuration of the electronic control unit 1 in this embodiment. Next, the operation and effects of the electronic control unit 1 in this embodiment will be described.

[0023] First, we will explain what happens when a surge is applied to the electronic control device 1. The surge here refers to a surge based on static electricity or the like applied from a human body or the like when assembling or servicing a vehicle, or a surge based on parasitic capacitance or the like formed between the electronic control device and a nearby device or the like.

[0024] As shown in FIG. 2 , in this embodiment, a second resistor 62 having a resistance value greater than that of the first resistor 61 is disposed between the first resistor 61 and the operating circuit 40. Therefore, when a surge occurs at the first terminal 21, surge currents I1 and I2 flow through a surge absorption circuit 70 disposed between the first connection point N1 and the second terminal 22. Specifically, when a positive surge is applied to the first terminal 21, surge current I1 flows from the first resistor 61 to the surge absorption circuit 70. When a negative surge is applied to the first terminal 21, surge current I2 flows from the surge absorption circuit 70 to the first resistor 61. Therefore, most of the surge currents I1 and I2 are absorbed by the first resistor 61 and the surge absorption circuit 70. Furthermore, because the resistance value of the second resistor 62 is greater than the resistance value of the first resistor 61, it is possible to prevent a large voltage from being applied to the operating circuit 40.

[0025] For example, when a surge current I1 flows, the voltage V1 at the first terminal 21 is expressed by the following formula 1. That is, assuming that the surge current is I1, the voltage at the first connection point N1 is V2, the resistance value of the first resistor 61 is R1, and the resistance value of the second resistor 62 is sufficiently larger than the resistance value of the first resistor 61, the voltage V1 is expressed by the following formula 1.

[0026] (Math 1)V1=R1×I1+V2 The voltage V2 at the first connection point N1 is expressed by the following formula 2, where I1 is the surge current, Rz is the dynamic resistance of the first Zener diode 71, Vz is the Zener voltage, Vf is the forward voltage of the second Zener diode 72, and Rf is the dynamic resistance.

[0027] (Math 2)V2=(Rz×I1)+Vz+(2×Vf)+(2×Rf×I1) 3, if the battery 30 is disposed with its polarity reversed relative to the electronic control device 1, an abnormal current I3 flows through the second terminal 22 of the electronic control device 1. In this case, because the reverse withstand voltage of the surge absorption circuit 70 is set to be equal to or greater than the battery voltage, the abnormal current I3 flows through the Zener diode 80, the second resistor 62, and the first resistor 61 in that order. Therefore, in the electronic control device 1 of this embodiment, when the abnormal current I3 flows, the abnormal current I3 can be limited by the first resistor 61 and the second resistor 62. This makes it possible to prevent malfunctions caused by the abnormal current I3 from occurring in the electronic control device 1 or the MCU 10 connected to the first terminal 21.

[0028] In this case, the resistance value of the second resistor 62 may be set based on the value of the current that flows when the battery 30 is connected in reverse, but by setting the resistance value to be sufficiently high, it is possible to reduce the voltage generated in the Zener diode 80. Therefore, by adjusting the resistance value of the second resistor 62, it is possible to reduce the size of the Zener diode 80.

[0029] According to the present embodiment described above, the surge absorption circuit 70 is provided between the first resistor 61 and the second resistor 62. Therefore, when a surge is applied to the first terminal 21, the surge currents I1 and I2 can flow via the surge absorption circuit 70, and the operating circuit 40 can be protected.

[0030] Furthermore, a Zener diode 80 having a cathode connected to the second connection point N2 is disposed between the second resistor 62 and the operating circuit 40. The surge absorption circuit 70 has a reverse withstand voltage equal to or greater than the battery withstand voltage. Therefore, if the battery 30 is connected in reverse, the abnormal current I3 flows from the first terminal 21 to the MCU 10 via the Zener diode 80, the second resistor 62, and the first resistor 61. Therefore, the abnormal current I3 can be limited by the first resistor 61 and the second resistor 62, and malfunctions in the electronic control device 1 or the MCU 10 connected to the first terminal 21 due to the abnormal current can be prevented.

[0031] As described above, the electronic control device 1 of this embodiment can cope with surges and abnormal connections of the battery 30, while preventing the device from becoming large in size because it does not include a capacitor.

[0032] (1) In this embodiment, the resistance value of the second resistor 62 is set to be larger than the resistance value of the first resistor 61, so that when a surge is applied, it is possible to prevent a large voltage from being applied to the actuation circuit 40 side.

[0033] (2) In this embodiment, the electronic control device 1 is configured on a single chip, with the first to third terminals 21 to 23, the operating circuit 40, the power supply circuit 50, the first resistor 61, the second resistor 62, the surge absorbing circuit 70, the Zener diode 80, etc., formed on an SOI substrate. Therefore, for example, when the electronic control device 1 is mounted on a mounting member such as a vehicle, there is no need to provide resistors equivalent to the first resistor 61 and the second resistor 62 on the mounting member side, and the configuration of the mounting member side can be simplified.

[0034] (Second embodiment) A second embodiment will be described. This embodiment is different from the first embodiment in that the configuration of the surge absorbing circuit 70 is changed. As the rest of the configuration is the same as the first embodiment, a description thereof will be omitted here.

[0035] 4, in the electronic control device 1 of this embodiment, the surge absorption circuit 70 does not include a first Zener diode 71, but includes a second Zener diode 72, a first diode 73, and a second diode 74. Specifically, the first diode 73 is disposed between the first connection point N1 and the second Zener diode 72, with the cathode connected to the first connection point N1 and the anode connected to the second Zener diode 72. The second diode 74 is disposed between the first connection point N1 and the power supply circuit 50, with the cathode connected to the power supply circuit 50 and the anode connected to the first connection point N1.

[0036] In such an electronic control device 1, when a positive surge is applied to the first terminal 21, the surge current I1 flows to the power supply circuit 50 side via the second diode 74, so that the operating circuit 40 can be protected.

[0037] According to the present embodiment described above, surges and abnormal connections of the battery 30 can be handled without providing a capacitor, and therefore the same effects as those of the first embodiment can be obtained.

[0038] (1) In this embodiment, the surge absorption circuit 70 includes a first diode 73 and a second diode 74. Therefore, the surge current I1 flows to the power supply circuit 50 side via the second diode 74. In this way, even if the surge current I1 is allowed to flow, the operating circuit 40 can be protected.

[0039] (Other embodiments) Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0040] For example, in each of the above embodiments, the resistance value of the first resistor 61 may be greater than the resistance value of the second resistor 62.

[0041] In addition, in each of the above embodiments, at least some of the first to third terminals 21 to 23, the operating circuit 40, the power supply circuit 50, the first resistor 61, the second resistor 62, the surge absorbing circuit 70, the Zener diode 80, etc. of the electronic control device 61 may be formed on a member separate from the SOI substrate.

[0042] Furthermore, in the second embodiment, the cathode of the second diode 74 may be connected to the third terminal 23 instead of the power supply circuit 50. [Explanation of symbols]

[0043] 10 MCU 21 1st terminal 22 2nd terminal 23 3rd terminal 40 Operating circuit 61 1st resistance 62 2nd resistor 70 Surge absorption circuit 71 First Zener diode 72 Second Zener diode 80 Zener diode N1 First connection point N2 Second connection point

Claims

1. An electronic control device that receives a control signal from an external circuit (10) and is connected to a battery (30), a first terminal (21) to which the control signal is input; a second terminal (22) connected to the low potential side of the battery, and a third terminal (23) connected to the high potential side of the battery; an actuation circuit (40) for performing a predetermined operation; a first resistor (61) connected to the first terminal; a second resistor (62) disposed between the first resistor and the actuation circuit and connected in series with the first resistor; a surge absorption circuit (70) connected between a first connection point (N1) between the first resistor and the second resistor and the second terminal, the surge absorption circuit including Zener diodes (71, 72) for passing surge currents (I1, I2); a Zener diode (80) having a cathode connected to a second connection point (N2) between the second resistor and the operating circuit and an anode connected to the second terminal; The surge absorption circuit has a reverse voltage resistance equal to or greater than the battery voltage of the battery.

2. 2. The electronic control device according to claim 1, wherein the second resistor has a resistance value greater than that of the first resistor.

3. 3. The electronic control device according to claim 1, wherein the surge absorption circuit is configured by connecting in series a first Zener diode (71) whose cathode is connected to the first connection point and a second Zener diode (72) whose cathode is connected to the second terminal.

4. 3. The electronic control device according to claim 1, wherein the surge absorption circuit is configured to include a first diode (73) having a cathode connected to the first connection point, a Zener diode (72) having a cathode connected to the second terminal and an anode connected to the first diode, and a second diode (74) having an anode connected to the first connection point and a cathode connected to the third terminal or a portion connected to the third terminal.

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