JP2023108192A - power supply circuit - Google Patents

Abstract

To provide a power supply circuit capable of detecting heating abnormality caused by a current flowing through a parasitic diode when a reverse connection protective element is in an off-state.SOLUTION: A power supply circuit 201 supplies power from a battery 15 to an inverter circuit (load drive circuit) 60 for driving a motor (load) 80. A reverse connection protective element 52 is composed of a FET having a parasitic diode 527 which conducts a forward current representing a current via the inverter circuit 60 from a positive electrode side of the battery 15 to a negative electrode of the battery 15. An abnormality detection circuit 48 detects heating abnormality of the reverse connection protective element 52 based on a voltage between DSs of a power relay element 51 as "an object element". The power relay element 51 is arranged near the reverse connection protective element 52, and has a characteristic of rising an ON resistance between DSs when a temperature rises by heat transfer from the reverse connection protective element 52. When the heating abnormality of the reverse connection protective element 52 is detected by the abnormality detection circuit 48, electric conduction of the forward current is stopped.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power supply circuit.

Conventionally, there is known a technique for protecting circuit elements from overheating in a power supply circuit that supplies power to a load drive circuit. For example, in the power supply device disclosed in Patent Document 1, the current flowing through the semiconductor switch provided in the current path is detected based on the drain-source voltage, and the temperature rise of the semiconductor switch is estimated from the square value of the detected current. be.

JP 2009-142146 A

There is a power supply circuit equipped with a reverse connection protection element that cuts off current in the opposite direction when the positive and negative electrodes of a battery are connected in the opposite direction. For example, the reverse connection protection element is composed of an FET (Field Effect Transistor) having a parasitic diode that conducts forward current. When the battery is connected in the normal direction and the forward current is applied, basically the reverse connection protection element is turned ON.

However, if the reverse connection protection element has a fixed OFF failure, heat may be generated if the current continues to flow only through the parasitic diode. In this case, the drain-source voltage of the reverse connection protection element is determined by the forward voltage of the parasitic diode. In general, the drain-source voltage of an FET has a temperature characteristic that increases as the temperature increases, whereas the voltage drop of a parasitic diode has a temperature characteristic that decreases as the temperature increases. Therefore, the heat generation abnormality cannot be detected based on the drain-source voltage of the reverse connection protection element.

The present invention was created in view of this point, and its purpose is to provide a power supply circuit that can detect heat generation abnormalities due to current flowing through a parasitic diode when the reverse connection protection element is OFF.

The present invention is a power supply circuit that supplies power from a battery (15) to a load drive circuit (60) that drives a load (80), comprising a reverse connection protection element (52) and an abnormality detection circuit (48). And prepare.

Assuming that the positive and negative electrodes of the battery are connected in the normal direction, the reverse connection protection element is connected to the power supply line (Lp) connecting the positive electrode of the battery and the high potential side of the load drive circuit, or the negative electrode of the battery. and the low potential side of the load drive circuit. The reverse connection protection element is composed of a field effect transistor having a parasitic diode (527) that conducts forward current, which is current from the positive side of the battery through the load drive circuit to the negative side of the battery.

The abnormality detection circuit detects a heat generation abnormality of the reverse connection protection element based on the drain-source voltage of the "target element". The target element is an element composed of a field effect transistor placed near the reverse connection protection element, and when the temperature rises due to heat transfer from the reverse connection protection element, the ON resistance between the drain and source increases. have

"Near the reverse connection protection element" means a range where heat transfer from the reverse connection protection element reaches sufficiently, based on the common technical knowledge in the relevant technical field. For example, the target element may be a power relay element provided on the power supply line. Alternatively, the target element may be an element constituting a load drive circuit such as an inverter circuit.

When the abnormality detection circuit detects the heat generation abnormality of the reverse connection protection element, the supply of the forward current is stopped. For example, a power relay element provided in the power supply line may be cut off, or the drive of the load drive circuit may be stopped.

In the present invention, focusing on the fact that the target element placed in the vicinity of the reverse connection protection element rises in temperature due to heat transfer from the reverse connection protection element, based on the increase in the drain-source voltage of the target element, reverse connection protection It indirectly detects the heat generation of the element. Thereby, when the reverse connection protection element is turned off, it is possible to detect a heat generation abnormality caused by a forward current flowing through the parasitic diode. For example, when a heat generation abnormality is detected even though an ON signal is commanded to the reverse connection protection element, it can be estimated to be an OFF sticking failure.

In addition, when the abnormality detection circuit detects the heat generation abnormality of the reverse connection protection element, the forward current is stopped, so that the reverse connection protection element and the entire circuit can be protected from overheating.

2 is a circuit diagram of a power supply circuit according to the first embodiment; FIG. The figure which shows the example arrange|positioned in the (a) same surface of a board|substrate, (b) the front and back surface of a board|substrate, and (c) the power relay element (target element) and reverse connection protection element. 4 is a flowchart for explaining abnormality detection processing according to the first embodiment; FIG. 4 is a circuit diagram of a power supply circuit according to a second embodiment; 9 is a flowchart for explaining abnormality detection processing according to the second embodiment; The circuit diagram of the power supply circuit according to the third embodiment.

A plurality of embodiments of the power supply circuit of the present invention will be described with reference to the drawings. The first to third embodiments are collectively referred to as "this embodiment". In this embodiment, the “load” is the motor 80 , specifically the three-phase AC motor, and the “load drive circuit” is the inverter circuit 60 . The power supply circuit supplies power from the battery 15 to the inverter circuit 60 that drives the motor 80 . For example, the motor 80 is a vehicle control brake motor, and the battery 15 is a vehicle battery of about 12V.

As for the code of the power supply circuit of each embodiment, the number of the embodiment is attached to the third digit following "20". In the description of the embodiments, the field effect transistor is referred to as "FET", and the drain-source is referred to as "between DS". In the drawing, the drain is denoted as "D", the source as "S", the switching circuit and the switching signal as "SW circuit" and "SW signal". The FET used in this embodiment is an N-channel MOSFET (metal oxide semiconductor field effect transistor).

(First embodiment)
The power supply circuit 201 of the first embodiment will be described with reference to FIGS. 1 to 3. FIG. As shown in FIG. 1 , the power supply circuit 201 turns ON/OFF the power relay element 51 and the reverse connection protection element 52 provided in the power supply path from the battery 15 to the inverter circuit 60, and the respective elements 51 and 52. The switching circuits 41 and 42 and an abnormality detection circuit 48 that detects an abnormality of the reverse connection protection element 52 are included.

Assuming that the positive and negative electrodes of the battery 15 are connected in the normal direction, the power line Lp connects the positive electrode of the battery 15 and the high potential side of the inverter circuit 60 . The ground line Lg connects the negative electrode of the battery 15 and the low potential side of the inverter circuit 60 . In the first embodiment, the power relay element 51 is provided on the battery 15 side of the power line Lp, and the reverse connection protection element 52 is provided on the inverter circuit 60 side of the power line Lp.

The power relay element 51 and the reverse connection protection element 52 are composed of FETs. The power relay element 51 has a drain connected to the positive electrode side of the battery 15 and a source connected to the reverse connection protection element 52 . The parasitic diode 517 of the power relay element 51 conducts a reverse current, which is a current directed from the high potential side of the inverter circuit 60 to the positive electrode of the battery 15 .

The reverse connection protection element 52 has a drain connected to the high potential side of the inverter circuit 60 and a source connected to the power relay element 51 . The parasitic diode 527 of the reverse connection protection element 52 conducts a forward current, which is a current from the positive terminal of the battery 15 to the negative terminal of the battery 15 via the inverter circuit 60 . When the positive and negative electrodes of the battery 15 are accidentally connected in the opposite direction to the normal direction, if the reverse connection protection element 52 is turned off, a reverse current flows from the low potential side to the high potential side of the inverter circuit 60. Therefore, the inverter circuit 60 is protected.

The power relay switching circuit 41 and the reverse connection protection element switching circuit 42 turn ON/OFF the power relay element 51 and the reverse connection protection element 52 respectively according to the command from the control unit 40 . The control unit 40 is composed of, for example, a microcomputer, and controls operations of a power relay switching circuit 41, a reverse connection protection element switching circuit 42, an inverter element switching circuit 46, and the like, based on commands from a host vehicle control circuit. The abnormality detection circuit 48 detects the DS voltage Vds of the power relay element 51, and detects the heat generation abnormality of the reverse connection protection element 52 based on the DS voltage Vds. The principle will be described later.

The inverter circuit 60 has six inverter elements 61 to 66 each composed of a FET and connected in a bridge. Inverter elements 61, 62 and 63 are U-phase, V-phase and W-phase upper arm elements, and inverter elements 64, 65 and 66 are U-phase, V-phase and W-phase lower arm elements. In the circuit example of FIG. 1, shunt resistors 71, 72 and 73 for detecting phase currents are connected to the low potential sides of lower arm elements 64, 65 and 66, respectively. By operating the inverter elements 61 to 66 according to the switching signal from the inverter element switching circuit 46 , the DC power of the battery 15 is converted into three-phase AC power and supplied to the motor 80 .

In such a circuit, from the viewpoint of fail-safe, it is required to detect the failure of the element at the time of initial check or during normal operation. In general, the DS voltage of the FET has a temperature characteristic that increases as the temperature rises. Therefore, it is possible to detect an overheating abnormality in the ON state of the FET as in the prior art of Patent Document 1 (Japanese Patent Application Laid-Open No. 2009-142146). be. On the other hand, since the voltage drop of the parasitic diode has a temperature characteristic that becomes lower as the temperature rises, if the reverse connection protection element 52 has an OFF stuck failure and the current continues to flow only through the parasitic diode 527 and heat is generated, Abnormal heat generation cannot be detected based on the DS voltage.

Therefore, in the present embodiment, an element composed of an FET arranged in the vicinity of the reverse connection protection element 52 is defined as a "target element". The target element has a characteristic that the ON resistance between DS increases when the temperature rises due to heat transfer from the reverse connection protection element 52 . The abnormality detection circuit 48 indirectly detects the heat generation abnormality of the reverse connection protection element 52 by detecting the DS voltage of the target element whose temperature has increased due to heat transfer. If heat is generated even though the reverse connection protection element 52 is ON-operated, it is presumed that a forward current continues to flow only through the parasitic diode 527 due to an OFF sticking failure.

In the first embodiment, the power relay element 51 is used as the target element. The power relay element 51 is arranged in the vicinity of the reverse connection protection element 52 , and its temperature rises due to heat transfer from the reverse connection protection element 52 . It is assumed that the power relay element 51 itself has been confirmed to be normal by an initial check or the like.

When the abnormality detection circuit 48 detects the heat generation abnormality of the reverse connection protection element 52 based on the DS-to-DS voltage Vds of the power relay element 51 , the abnormality detection circuit 48 outputs a cutoff signal to the power relay switching circuit 41 to cut off the power relay element 51 . As a result, the forward current flowing through the parasitic diode 527 of the reverse connection protection element 52 is stopped.

Moreover, the abnormality detection circuit 48 will notify the control part 40, if the heat generation abnormality of the reverse connection protection element 52 is detected. The control unit 40 that has received the notification may output a drive stop signal to the inverter element switching circuit 46 . In addition, an alarm display or a buzzer may be used to notify the user (driver in a vehicle) of the abnormality.

FIG. 2 shows a preferred configuration example in which the power relay element 51, which is the target element, is arranged in the vicinity of the reverse connection protection element 52 in order to obtain good heat transfer characteristics. In the example shown in FIG. 2( a ), a power relay element 51 and a reverse connection protection element 52 are mounted adjacent to each other on the same surface (surface 31 ) of the substrate 30 . In the example shown in FIG. 2B, the power relay element 51 and the reverse connection protection element 52 are mounted on the front surface 31 and the back surface 32 of the substrate 30 at the same location. The heat generated by the reverse connection protection element 52 is transferred to the power relay element 51 on the opposite side of the substrate 30 .

In the example shown in FIG. 2( c ), the power relay element 51 and the reverse connection protection element 52 are housed in the same package of the element module 500 . In this configuration, heat is positively transferred from the reverse connection protection element 52 to the power relay element 51 within the package while suppressing heat transfer to peripheral elements.

The flowchart of FIG. 3 shows the abnormality detection processing according to the first embodiment. In the description of the flowchart, the symbol "S" means step. In S<b>11 , the control unit 40 turns on the power relay element 51 and the reverse connection protection element 52 by the power relay switching circuit 41 and the reverse connection protection element switching circuit 42 . At S<b>12 , the inverter element switching circuit 46 starts driving the inverter circuit 60 to supply power to the motor 80 .

In S13, the abnormality detection circuit 48 determines whether the DS voltage Vds of the power relay element 51, which is the target element, is greater than a threshold. If YES in S13, the abnormality detection circuit 48 outputs a cutoff signal to the power relay switching circuit 41 in S14. The power relay switching circuit 41 that has received the cutoff signal cuts off the power relay element 51 . As a result, the forward current flowing through the parasitic diode 527 of the reverse connection protection element 52 is stopped. Although the control unit 40 receiving the notification from the abnormality detection circuit 48 may output a cutoff signal to the power relay switching circuit 41, the abnormality detection circuit 48 may output a cutoff signal directly to the power relay switching circuit 41. , allowing for faster treatment.

Further, as an optional step, in S15, the control unit 40 receiving the notification from the abnormality detection circuit 48 may output a drive stop signal to the inverter element switching circuit 46 to stop driving the inverter circuit 60. FIG. This prevents the inverter circuit 60 from continuing to operate after the power supply is stopped. If NO in S13, the process ends.

As described above, the abnormality detection circuit 48 of the first embodiment generates heat even though the reverse connection protection element 52 is ON-operated based on the DS voltage Vds of the power relay element 51 which is the target element. It is estimated that the reverse connection protection element 52 is stuck in the OFF state. Therefore, abnormal heat generation of the reverse connection protection element 52 can be detected during normal operation. In addition, the reverse connection protection element 52 and the entire circuit can be protected from overheating by interrupting the power supply relay element 51 and stopping the forward current when an abnormality is detected.

(Second embodiment)
The power supply circuit 202 of the second embodiment will be described with reference to FIGS. 4 and 5. FIG. In the second embodiment, no power relay element is provided on the power line Lp. When the external power switch 16 provided between the positive electrode of the battery 15 and the power supply circuit 202 is in the ON state, the voltage of the battery 15 is constantly applied to the inverter circuit 60 . For example, in a system mounted on a vehicle, an ignition switch corresponds to the external power switch 16 .

In the second embodiment, one or more elements (FETs) forming the inverter circuit 60 are used as target elements. Basically, it is preferable to select an element that is arranged closest to the reverse connection protection element 52 on the substrate and has the maximum amount of heat transfer as the target element. In addition, points such as that the element itself is thermally stable and that it is less susceptible to disturbance from other heat sources are points for selecting the target element.

In the example shown in FIG. 4, the U-phase upper arm element 61 is the target element. The abnormality detection circuit 48 detects a heat generation abnormality of the reverse connection protection element 52 based on the DS voltage Vds of the U-phase upper arm element 61 . It is assumed that the normality of the inverter elements 61-66 has already been confirmed by an initial check or the like.

The flowchart of FIG. 5 shows the abnormality detection process according to the second embodiment. Each step number S21, S22, S23, S25 in FIG. 5 corresponds to S11, S12, S13, S15 in FIG. In S<b>21 , the control unit 40 turns ON the reverse connection protection element 52 by the reverse connection protection element opening/closing circuit 42 . In S<b>22 , the inverter element switching circuit 46 starts driving the inverter circuit 60 to supply power to the motor 80 .

In S23, the abnormality detection circuit 48 determines whether the DS voltage Vds of the inverter element 61, which is the target element, is greater than a threshold. In the case of YES in S23, the controller 40, which has received the notification from the abnormality detection circuit 48, outputs a drive stop signal to the inverter element switching circuit 46 in S25 to stop driving the inverter circuit 60. FIG. As a result, the forward current flowing through 527 of the reverse connection protection element 52 is stopped. If NO in S23, the process ends.

In this way, even if the elements of the inverter circuit 60 are used as target elements, the same effects as in the first embodiment can be obtained. The target element is not limited to the U-phase upper arm element 61 but may be the V-phase or W-phase upper arm elements 62 and 63 . Alternatively, the DS voltage Vds of each upper arm element 61, 62, 63 may be detected, and the abnormality may be detected based on the maximum value.

(Third Embodiment)
A power supply circuit 203 according to the third embodiment will be described with reference to FIG. In the third embodiment, the reverse connection protection element 52 is provided on the ground line Lg connecting the negative electrode of the battery 15 and the low potential side of the inverter circuit 60 . In this configuration, the reverse connection protection element 52 has the drain connected to the negative electrode side of the battery 15 and the source connected to the low/high potential side of the inverter circuit 60 . It is the same in that the parasitic diode 527 conducts forward current.

As in the first embodiment, the power relay element 51 is used as the target element in the third embodiment. The power relay element 51 is arranged in the vicinity of the reverse connection protection element 52 , and its temperature rises due to heat transfer from the reverse connection protection element 52 . The operations of the abnormality detection circuit 48 and the power relay switching circuit 41 are the same as in the first embodiment. In the third embodiment, the same effect as in the first embodiment can be obtained.

(Other embodiments)
(a) The load is not limited to a multiphase motor such as a three-phase motor, and may be a DC motor or an actuator other than a motor. The load drive circuit is not limited to an inverter circuit, and may be an H bridge circuit or the like.

(b) In the second embodiment, assuming a circuit configuration without a power supply relay element, an element constituting a load drive circuit is used as a target element. However, even in a circuit configuration including a power relay element, an element that constitutes the load drive circuit may be preferentially selected as the target element depending on the heat transfer characteristics from the reverse connection protection element. Alternatively, both the power relay element and the element forming the load drive circuit may be used as target elements.

As described above, the present invention is not limited to such an embodiment, and can be embodied in various forms without departing from the spirit of the present invention.

15 Batteries,
201-203 power supply circuit,
41 ... power relay switching circuit,
48 ... anomaly detection circuit,
51... power supply relay element, 517... parasitic diode,
52 reverse connection protection element, 527 parasitic diode,
60... Inverter circuit (load drive circuit),
80 motor (load),
Lp: power supply line, Lg: ground line.

Claims (4)

A power supply circuit that supplies power from a battery (15) to a load drive circuit (60) that drives a load (80),
Assuming that the positive electrode and the negative electrode of the battery are connected in the normal direction, a power supply line (Lp) connecting the positive electrode of the battery and the high potential side of the load drive circuit, or the negative electrode of the battery and the A parasitic diode that is provided on a ground line (Lg) that connects the low potential side of the load drive circuit and conducts a forward current that is a current that flows from the positive electrode of the battery to the negative electrode of the battery via the load drive circuit. A reverse connection protection element (52) composed of a field effect transistor having (527);
It is an element composed of a field effect transistor arranged near the reverse connection protection element, and when the temperature rises due to heat transfer from the reverse connection protection element, the ON resistance between the drain and source increases. An abnormality detection circuit (48) for detecting a heat generation abnormality of the reverse connection protection element based on the drain-source voltage of the target element,
with
A power supply circuit in which the supply of the forward current is stopped when the abnormality detection circuit detects a heat generation abnormality of the reverse connection protection element. The power relay element (51) is provided on the power supply line and is composed of a field effect transistor having a parasitic diode (517) that conducts a reverse current that is a current flowing from the high potential side of the load drive circuit to the positive electrode of the battery. )and,
a power relay switching circuit (41) for turning on/off the power relay element;
further comprising
2. The power supply circuit according to claim 1, wherein the power relay opening/closing circuit cuts off the power relay element when the abnormality detection circuit detects the heat generation abnormality of the reverse connection protection element. 3. The power supply circuit according to claim 2, wherein said target element is said power relay element. 3. The power supply circuit according to claim 1, wherein said target element is an element constituting said load drive circuit.

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