JP7345721B2 - Abnormal current detection circuit - Google Patents

Description

The present invention relates to an abnormal current detection circuit.

Conventionally, in order to detect abnormal current flowing through electronic circuits, LSIs, etc., measurement terminals have been provided and measurements have been taken discontinuously using a measuring device.
By the way, in embedded devices such as in-vehicle ECUs, it is desirable to perform measurements in the mounted state.

For this reason, a technique has been proposed in which a measurement circuit is built into the device in advance to facilitate measurement during manufacturing and mounting (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2001-249147

However, in the above conventional technology, when detecting current, the current is detected by cutting off the power supply to the target circuit (target element), and when the target circuit is always connected to the power supply, The problem was that it could not be applied.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an abnormal current detection circuit capable of detecting current even when a power supply to a target circuit (target element) is always connected.

In order to solve the above problems, the current detection circuit of the embodiment is an abnormal current detection circuit that detects an abnormal current in a target circuit that operates by constantly receiving power from a power supply, and includes a capacitor and detects the voltage of the power supply. a charge pump unit capable of boosting and applying a voltage to the target circuit; and a detection voltage that is a voltage at one end of the capacitor when a voltage is applied to the target circuit by the charge pump unit. An abnormality detection section that detects abnormal current.

According to the above configuration, even if the power supply to the target circuit (target element) is always connected, an abnormal current can be detected by flowing a current for abnormal current detection into the target circuit.

FIG. 1 is an explanatory diagram of an example of an electronic circuit device including a current detection circuit according to an embodiment. FIG. 2 is a processing flowchart of current detection processing according to the embodiment. FIG. 3 is an explanatory diagram of the operation of the electronic circuit device when the power is turned on. FIG. 4 is an explanatory diagram of the operation of the electronic circuit device during capacitor charging. FIG. 5 is an explanatory diagram of the operation of the electronic circuit device during capacitor discharge.

Exemplary embodiments of the invention will now be described in detail with reference to the drawings.
The configuration of the embodiment shown below, and the actions and results (effects) brought about by the configuration are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments. Further, according to the present invention, it is possible to obtain at least one of various effects (including derivative effects) obtained by the configuration.

FIG. 1 is an explanatory diagram of an example of an electronic circuit device including a current detection circuit according to an embodiment.
The electronic circuit device 10 includes a power source PW that supplies DC power, a target circuit CIR to be detected for current whose one end is connected to a low potential side terminal of the power source PW, and an anode connected to a high potential side terminal of the power source PW. A diode D1 whose cathode is connected to the target circuit CIR, a diode D2 whose anode is connected to the high potential side terminal of the power supply PW, a first switching element SW1 whose one end is connected to the cathode of the diode D2, and a first switching element SW1 whose cathode is connected to the target circuit CIR. It includes a resistor R3 whose one end is connected to the other end of the element SW1, and a resistor R4 whose one end is connected to the other end of the resistor R3 and whose other end is connected to the low potential side terminal of the power source PW.

The electronic circuit device 10 also includes a resistor R1 having one end connected to the high potential side terminal of the power source PW, a resistor R2 having one end connected to the other end of the resistor R1, and one end connected to the other end of the resistor R2. , a second switching element SW2 whose other end is connected to the low potential side terminal of the power supply PW, one end which is connected to the connection point between the first switching element SW1 and the resistor R3, and whose other end is connected to the connection point between the second switching element SW2 and the resistor R2. and a diode D3 whose anode is connected to the connection point between the first switching element SW1 and the resistor R3, and whose cathode is connected to the connection point between the diode D1 and the target circuit CIR.

In the above configuration, the target circuit CIR is configured as, for example, an ECU or the like having the same function as a microcomputer.
Further, the first switching element SW1, the second switching element SW2, the capacitor C, and the diode D3 constitute a charge pump section. Further, the connection point between the resistor R3 and the resistor R4 functions as a voltage measurement terminal and outputs a voltage signal Vmon.

When the current monitoring entity is the target circuit CIR, this voltage signal Vmon is input to an analog-to-digital conversion input terminal (not shown) of the target circuit CIR and is taken in as monitored voltage data.

Note that in FIG. 1, the power supply PW and the target circuit CIR are directly connected via the diode D1 for ease of understanding, but in reality, the target circuit CIR is normally closed (on state) in the driving state. ) is assumed to be connected via a power supply switch.

Next, the operation of the embodiment will be explained.
In the following explanation, it is assumed that the voltage signal Vmon is input by the current monitoring entity to an analog-to-digital conversion input terminal (not shown) of the target circuit CIR and taken in as monitored voltage data, and that the target circuit CIR itself detects abnormal current. Give an explanation.

FIG. 2 is a processing flowchart of current detection processing according to the embodiment.
In this case, in the initial state, the capacitor C is not charged and the voltage is 0V. Further, the first switching element SW1 is turned into an open state (off state) by the first switch control signal CSW1 outputted by the target circuit CIR, and the second switching element SW2 is turned into an open state (off state) by the second switch control signal CSW2 outputted by the target circuit CIR. It is assumed that the switch is in the open state (off state).

When a power supply switch (not shown) is closed and power is supplied (step S11), the target circuit CIR, which is the current monitoring main body, monitors the voltage signal Vmon (step S12).
Thereby, the target circuit CIR determines whether the capacitor C is normal or has a short-circuit failure based on the voltage of the voltage signal Vmon (step S13).

FIG. 3 is an explanatory diagram of the operation of the electronic circuit device 10 when the power is turned on.
In FIG. 3(A), arrows indicate current flow paths in a state where the first switching element SW1 and the second switching element SW2 are cut off.

Furthermore, the resistor R1, the resistor R2, the resistor R3, and the resistor R4 constitute a current supply path that can supply current to the capacitor C while the first switching element SW1 and the second switching element SW2 are cut off before charging the capacitor. are doing.

Specifically, if capacitor C has caused a short circuit failure (step S13; short circuit failure), the closed circuit of power supply PW → resistor R1 → resistor R2 → (capacitor C) → resistor R3 → resistor R4 → power supply PW is configured, so if the resistance value of the resistor R1 is r1, the resistance value of the resistor R2 is r2, the resistance value of the resistor R3 is r3, and the resistance value of the resistor R4 is r4, the voltage of the voltage signal Vmon=V×r4/ (r1+r2+r3+r4).

Here, the closed circuit to which current is supplied from the power source PW via the resistor R1, (capacitor C), resistor R3, and resistor R4 is connected to the capacitor C with the first switching element SW1 and the second switching element SW2 cut off. A first current supply circuit capable of supplying current to (low potential side: other end side of) is configured.

FIG. 3B is an explanatory diagram of the voltage of the voltage signal Vmon.
On the other hand, in a normal case, the capacitor C is charged and no current flows, so the voltage of the voltage signal Vmon becomes 0.

Therefore, by comparing the detected voltage with a predetermined threshold voltage set between voltage = V × r4 / (r1 + r2 + r3 + r4) and voltage = 0, the target circuit CIR determines whether the capacitor C is normal or short-circuited. This makes it possible to determine which type of failure is occurring.

In the judgment in step S13, if it is judged that the capacitor C is normal (step S13; normal), the target circuit CIR turns on the first switching element SW1 and the second switching element SW2, and turns on the capacitor C. Charge (step S14).

FIG. 4 is an explanatory diagram of the operation of the electronic circuit device 10 during capacitor charging.
In FIG. 4, arrows indicate current flow paths when capacitor C is charged.
First, the target circuit CIR outputs a first switch control signal CSW1 to close the first switching element SW1 (on state), and outputs a second switch control signal CSW2 to close the second switching element SW2. state (on state).

As a result, a closed circuit of power supply PW → diode D2 → first switching element SW1 → capacitor C → second switching element SW2 → power supply PW is formed, and a charging current flows through capacitor C, so that capacitor C is charged. becomes.

Here, the closed circuit in which current is supplied from the power source PW via the diode D2, the first switching element SW1, the capacitor C, and the second switching element SW2 is a state in which the first switching element SW and the second switching element SW2 are connected. This constitutes a second current supply circuit capable of supplying current to (the high potential side: one end side of) the capacitor C.

Subsequently, the target circuit CIR determines whether a predetermined charging time has elapsed since the first switching element SW1 and the second switching element SW2 were turned on (step S15).

In the determination in step S15, if the predetermined charging time has not yet elapsed (step S15; No), the target circuit CIR shifts the process to step S14 again to continue charging.

FIG. 5 is an explanatory diagram of the operation of the electronic circuit device 10 during capacitor discharge.
In FIG. 5(A), arrows indicate current flow paths when capacitor C is discharged.
In the judgment in step S15, if the predetermined charging time has elapsed (step S15; Yes), the target circuit CIR outputs the first switch control signal CSW1 and puts the first switching element SW1 in the open state (off state). ) and outputs the second switch control signal CSW2 to turn the second switching element SW2 into an open state (off state) (step S16).

As a result, the power supply PW and the capacitor C are connected in series, and function as a charge pump section and a power supply having a voltage of 2×V in the initial state.

At this time, a closed circuit of power supply PW → resistor R1 → resistor R2 → capacitor C → diode D3 → target circuit CIR → power supply PW is formed, and the discharge current from capacitor C is superimposed on the supply current from power supply PW. It will flow through the target circuit CIR.

FIG. 5B is a diagram illustrating the relationship between the voltage of the voltage signal Vmon and the elapsed time after the switch is shut off.
In FIG. 5(B), the curve CN is the current flowing through the target circuit CIR when an assumed normal current flows. Further, the curve CS is for a case where an abnormal current (small current) smaller than the assumed normal current flows as the current flowing through the target circuit CIR. Further, the curve CL indicates a case where an abnormal current (large current) that is larger than the assumed normal current flows as the current flowing through the target circuit CIR.

Therefore, the target circuit CIR monitors the voltage of the voltage signal Vmon (step S17) and determines whether an abnormal current is flowing based on the voltage after a predetermined period of time or the time until the predetermined voltage is reached. (Step S18).

Specifically, when determining whether or not an abnormal current is flowing based on the voltage after a predetermined time has elapsed, as shown in FIG. If the voltage VS is higher than the voltage VN that is assumed to be detected during normal operation by a predetermined voltage or more, an abnormal current (small current) that is smaller than the expected normal current is flowing. I judge that.

Further, as shown in FIG. 5(B), when the voltage of the voltage signal Vmon is a voltage VL that is lower by a predetermined voltage or more than the voltage VN that is assumed to be detected during normal operation after the predetermined time tR has elapsed, determines that an abnormal current (large current) is flowing that is higher than the expected normal current.

In addition, when determining whether or not an abnormal current is flowing based on the time it takes to reach a predetermined voltage, as shown in FIG. , V×r4/(r3+r4)), if the time tS is longer than the time tN that is assumed to be detected under normal conditions, the current is less than the expected normal current. It is determined that an abnormal current (small current) is flowing.

Furthermore, as shown in FIG. 5(B), when the time tL required to reach a predetermined voltage is shorter than the time tN (=threshold time) that is assumed to be detected under normal conditions, determines that an abnormal current (large current) is flowing that is higher than the expected normal current.

Then, in the judgment in step S18, if an abnormal current is detected (step S18; Yes), a notification that an abnormal current has been detected, a notification regarding the state of the abnormal current (large current or small current), and a power supply are provided. A post-abnormal current detection process is performed to cut off the current, etc., and the process ends (step S19).

Further, in the determination in step S18, if no abnormal current is detected (step S18; No), the process ends.
Further, the processing of steps S14 to S19 described above may be performed at predetermined time intervals while power is being supplied.

As described above, according to the present embodiment, even if there is a target circuit that requires constant power supply, it is possible to easily determine whether there is an abnormal current in the target circuit.
Furthermore, when the power is turned on, it is possible to reliably detect a short-circuit failure in the capacitor C functioning as a charge pump section.

Furthermore, when the electronic circuit device 10 of the embodiment is installed in an actual device, the voltage signal Vmon is used for voltage monitoring of the power source PW, and is used for dark current cutting when the electronic circuit device 10 is turned off. By using the first switching element SW1 together with the charge pump section, abnormal current can be detected without increasing the number of parts. Similarly, when the voltage between the resistor R1 and the resistor R2 is used for monitoring the voltage of the power source PW, the second switching element SW2 can have two functions: dark current cutting and charge pump section.

The target circuit CIR of this embodiment has a hardware configuration using a normal computer.
The program executed by the target circuit CIR of this embodiment is an installable or executable file that is recorded on a computer-readable recording medium such as a DVD, or a semiconductor storage device such as a USB memory or SSD. provided.

Furthermore, the program executed by the target circuit CIR of this embodiment may be stored on a computer connected to a network such as the Internet, and may be provided by being downloaded via the network. Further, the program executed by the target circuit CIR of this embodiment may be provided or distributed via a network such as the Internet.

Further, the program for the target circuit CIR of this embodiment may be provided by being incorporated in a ROM or the like in advance.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

For example, in the above explanation, it is assumed that the target circuit CIR is an ECU, and the target circuit CIR is also assumed to function as an abnormal current detection circuit, but the abnormal current detection circuit is provided separately from the target circuit CIR. If configured, it is also possible to use elements such as LSIs and diodes as the target circuit CIR. Further, a part of the abnormal current detection circuit may be incorporated into the target circuit CIR.

10 Electronic circuit device C Capacitor CIR Target circuit CSW1 First switch control signal CSW2 Second switch control signal D1 to D3 Diode PW Power supply R1 to R4 Resistor SW1 First switching element SW2 Second switching element VL, VN, VS Voltage Vmon Voltage signal tL, tN, tS Time tR Predetermined time

Claims (5)

An abnormal current detection circuit that detects abnormal current in a target circuit that operates by constantly receiving power from a power source,
a charge pump section including a capacitor and capable of boosting the voltage of the power source and applying a voltage to the target circuit;
an abnormality detection unit that detects the abnormal current based on a detection voltage that is a voltage at one end of the capacitor when a voltage is applied to the target circuit by the charge pump unit;
Abnormal current detection circuit with The abnormality detection section detects the abnormal current based on the detection voltage after a predetermined period of time has elapsed since the voltage boosted by the charge pump section was applied.
The abnormal current detection circuit according to claim 1. The abnormality detection section detects the abnormal current based on the time from when the boosted voltage is applied by the charge pump section until the detection voltage reaches a predetermined voltage.
The abnormal current detection circuit according to claim 1. The charge pump section includes a first switching element and a second switching element,
a first current supply path capable of supplying current to the other end of the capacitor while the first switching element and the second switching element are cut off;
a short-circuit failure detection unit that detects a short-circuit failure of the capacitor when the detection voltage exceeds a predetermined voltage in a state where current can be supplied to the other end of the capacitor via the first current supply path; and,
The abnormal current detection circuit according to any one of claims 1 to 3, comprising: a second current supply path capable of supplying current to one end of the capacitor in a state where the first switching element and the second switching element are connected;
After the short-circuit failure detection unit determines that the capacitor is normal in a state where current can be supplied to the other end of the capacitor via the first current supply path, the capacitor is supplied to the other end of the capacitor via the second current supply path. Based on the detection voltage when the capacitor is charged in a state where a current can be supplied to one end, and then a current can be supplied to the other end of the capacitor via the first current supply path. detecting the abnormal current;
The abnormal current detection circuit according to claim 4.

Images