JP2022118936A - Boosting device - Google Patents

Abstract

To provide a boosting device preventing erroneous determination of overcurrent abnormality, capable of shortening a startup time by simplifying a circuit configuration.SOLUTION: A boosting switching element 25 in a boosting device 301 is provided between one end of a coil 21 with the other end connected to a power supply 15, and the ground, and boosts voltage at the one end of the coil 21 through switching operation. A drive circuit 41 causes the boosting switching element 25 to be PWM operated. An overcurrent monitoring circuit 44 monitors current flowing through the boosting switching element 25. A control unit 50 determines abnormality based on notification from the overcurrent monitoring circuit 44 and takes measures. The overcurrent monitoring circuit 44 transmits a notification signal to the control unit 50 if a first condition for current flowing through the boosting switching element 25 is met. The control unit 50 determines abnormality and takes measures if a second condition for the notification signal received from the overcurrent monitoring circuit 44 is met.SELECTED DRAWING: Figure 1

Description

The present invention relates to a booster device.

2. Description of the Related Art Conventionally, there has been known a boosting device that boosts an input power supply voltage and outputs the boosted voltage.

There is also known a technique for preventing erroneous determination due to a temporary overcurrent such as when power is turned on in an overcurrent protection circuit that determines an abnormality and stops operating when an overcurrent is detected. For example, the switching regulator disclosed in Patent Document 1 limits the current by discharging the capacitor of the soft start circuit when overcurrent is detected.

Japanese Patent Application Laid-Open No. 2014-3850

Since the switching regulator of Patent Document 1 uses a soft-start circuit, the circuit configuration becomes complicated, and it takes a long time to start up when the power is turned on.

SUMMARY OF THE INVENTION The present invention has been created in view of the above-mentioned points, and its object is to provide a boosting device that simplifies the circuit configuration and shortens the start-up time in a boosting device that prevents erroneous determination of an overcurrent abnormality. That's what it is.

The present invention is a booster that boosts an input power supply voltage and outputs it. The booster includes a boost switching element (25), drive circuits (41, 42), an overcurrent monitoring circuit (44), and control units (50, 42).

The boost switching element is provided between the ground and the other end of the coil (21), one end of which is connected to the power supply (15), and boosts the voltage of the other end of the coil by switching operation. The drive circuit PWM-operates the boost switching element. The overcurrent monitoring circuit monitors the current flowing through the boost switching element. The control unit determines an abnormality based on the notification from the overcurrent monitoring circuit and takes measures.

The overcurrent monitoring circuit transmits a notification signal to the control unit when a first condition is satisfied regarding the state of the current flowing through the boost switching element. When the second condition is satisfied for the notification signal received from the overcurrent monitoring circuit, the control unit determines that there is an abnormality and takes action.

In the present invention, the overcurrent monitoring circuit does not make an abnormality determination merely by detecting an overcurrent, but transmits a notification signal to the control unit when the first condition is satisfied. Further, the control unit judges abnormality for the first time when the second condition is established, and takes measures. Therefore, it is possible to avoid erroneously determining that an overcurrent is abnormal when the power is turned on or when the initial check is performed.

Also, in the present invention, unlike the prior art of Patent Document 1, a soft start circuit is not used, and an overcurrent is detected with respect to an overcurrent threshold set below the rating of the boost switching element when the power is turned on or during the initial check. power on while In other words, erroneous determination is prevented by preventing the second condition from being satisfied while assuming that the first condition is likely to be satisfied at the time of power-on or initial check. This simplifies the circuit configuration and shortens the start-up time.

FIG. 2 is a configuration diagram of the booster and its periphery according to the first embodiment; 1 is a schematic configuration diagram of an electric power steering device to which a booster device according to a first embodiment is applied; FIG. FIG. 4 is a circuit diagram showing overcurrent that occurs when a diode or coil short-circuits. 4 is a time chart showing the operation of the booster according to the first embodiment; 4 is a time chart for explaining an example in which a first condition is satisfied; FIG. 4 is a configuration diagram of an overcurrent detection threshold value setting unit; 5 is a flowchart showing processing when overcurrent is detected; Flowchart of abnormality determination. 4 is a flowchart showing processing for preventing erroneous determination. 4 is a flow chart showing measures to be taken when an abnormality is determined; The block diagram of the booster by 2nd Embodiment, and its periphery.

A plurality of embodiments of the boosting device of the present invention will be described below with reference to the drawings. The first and second embodiments are collectively referred to as "this embodiment". A booster device according to the present embodiment boosts a power supply voltage in an electric power steering device for a vehicle. The reference numerals of the boosting devices of the first and second embodiments are denoted as "301" and "302", respectively, and the common matters are described as the description of the boosting device 301. FIG. 1st Embodiment and 2nd Embodiment differ in the element which functions as a "control part."

(First embodiment)
FIG. 1 shows the configuration of a booster device 301 and its surroundings according to the first embodiment. The booster circuit 20 boosts and outputs the power supply voltage input from the battery 15 so that the operation can be continued even when the voltage of the battery 15 is low. A voltage before being boosted by the boosting circuit 20 is denoted as VL, and a voltage after being boosted is denoted as VH. The inverter 60 also converts the DC power of the battery 15 into AC power and supplies the AC power to the motor 80 . Motor 80 is, for example, a three-phase brushless motor.

The booster circuit 20 is a chopper type booster circuit including a coil 21, a diode 23, a capacitor 24, and a booster MOS 25 as a "boost switching element". The boost MOS 25 is composed of an n-channel MOSFET. In this specification, MOSFET is omitted and simply referred to as "MOS".

One end of the coil 21 is connected to the battery 15 as a "power supply". Elements such as a power relay 16 and a diode (not shown) may be connected between the battery 15 and the coil 21 . The power relay 16 may be a mechanical relay or a semiconductor switching element. The diode 23 has an anode connected to the other end of the coil 21 and a cathode connected to the output terminal. A capacitor 24 is provided between the cathode of the diode 23 and the ground.

The boost MOS 25 is provided between the connection point N at the other end of the coil 21 and the ground. That is, the drain terminal is connected to the connection point N, and the source terminal is grounded. A gate terminal of the boosting MOS 25 is connected to the drive circuit 41 . The boost MOS 25 performs switching operation based on the PWM command signal output from the drive circuit 41 . Accompanying this, the coil 21 repeats accumulation and release of inductive energy, so that the voltage at the other end of the coil 21, that is, the output side is boosted. In short, the boosting MOS 25 boosts the voltage on the output side of the coil 21 by switching operation.

The boosting device 301 of the first embodiment includes at least the boosting MOS 25 among the components of the boosting circuit 20 . The booster 301 also includes a drive circuit 41, an overcurrent monitoring circuit 44, and a microcomputer 50 as a "control section". The drive circuit 41 causes the boost MOS 25 to perform PWM operation. The overcurrent monitoring circuit 44 monitors the current flowing through the boost MOS 25 and detects overcurrent. The technical significance of the overcurrent monitoring circuit 44 will be described later.

The boost MOS 25, the drive circuit 41 and the overcurrent monitoring circuit 44 are built in the same IC. This IC is referred to herein as an ASIC 40, which stands for Application Specific IC. When the overcurrent monitoring circuit 44 detects overcurrent, the overcurrent monitoring circuit 44 commands the drive circuit 41 to forcibly turn off the boost MOS 25 as a protection function. The ASIC 40 and the microcomputer 50 that constitute the booster 301 communicate with each other. The microcomputer 50 determines an abnormality based on the notification from the overcurrent monitoring circuit and takes measures. Specifically, the overcurrent monitoring circuit 44 outputs a notification signal indicating overcurrent detection to the microcomputer 50 .

In addition, the microcomputer 50 instructs the drive circuit 41 to stop the operation of the boosting MOS 25, for example, as a measure at the time of abnormality determination. Further, the microcomputer 50 monitors a monitoring voltage, which is "a voltage monitored by a circuit before or after boosting". For example, as the voltage of the circuit before boosting, the power supply voltage of the battery 15, that is, the pre-relay voltage VLa on the battery 15 side of the power supply relay 16 in FIG. 1 is monitored. Alternatively, the post-relay voltage VLb between the power relay 16 and the coil 21 may be monitored. Alternatively, the boosted voltage VH, which is the voltage of the circuit after boosting, may be monitored.

FIG. 2 shows a schematic configuration of a steering system 99 including an electric power steering (denoted as "EPS" in the drawing) device 90. As shown in FIG. Although the electric power steering device 90 in FIG. 2 is of a column assist type, the booster device 301 of the present embodiment can also be applied to a rack assist type electric power steering device. A steering system 99 includes a steering wheel 91, a steering shaft 92, a steering torque sensor 94, a pinion gear 96, a rack shaft 97, wheels 98, an electric power steering device 90, and the like.

A pinion gear 96 provided at the tip of the steering shaft 92 meshes with a rack shaft 97 . A pair of wheels 98 are provided at both ends of the rack shaft 97 via tie rods or the like. When the driver rotates the steering wheel 91, the steering shaft 92 connected to the steering wheel 91 rotates. A steering torque sensor 94 provided in the middle of the steering shaft 92 detects the steering torque trq. Rotational motion of the steering shaft 92 is converted into linear motion of the rack shaft 97 by the pinion gear 96 , and the pair of wheels 98 are steered at an angle corresponding to the amount of displacement of the rack shaft 97 .

The electric power steering device 90 includes a boost device 301, an inverter 60, a motor 80, a reduction gear 89 and the like. In this embodiment, the microcomputer 50 which is one element of the booster device 301 also functions as a motor control device in the electric power steering device 90 . A microcomputer 50 as a motor control device acquires information such as steering torque trq, steering speed, and vehicle speed from the outside, and drives the motor 80 so that the motor 80 outputs a desired assist torque calculated from these information. Control. The assist torque output by the motor 80 is transmitted to the steering shaft 92 via the reduction gear 89 .

Next, with reference to FIG. 3, an example of occurrence of an overcurrent abnormality caused by an element failure of the booster circuit 20 will be described. If the coil 21 short-circuits, the electric power of the battery 15 is applied directly to the boost MOS 25 without being converted into inductive energy, and when the boost MOS 25 is turned on, an overcurrent flows as indicated by the dashed-dotted arrow. If the diode 23 short-circuits, the current discharged from the capacitor 24 flows backward through the diode 23, and when the boost MOS 25 is turned on, an overcurrent flows through the boost MOS 25 as indicated by the two-dot chain line arrow. As a result, the boosting MOS 25 may be destroyed.

In order to protect the boost MOS 25 in such a case, it is required to detect an overcurrent and to take measures such as stopping power supply in the event of an abnormality. However, on the other hand, when the power is turned on, even if the circuit is normal, overcurrent may be temporarily detected, and it is required to prevent erroneous determination of abnormality.

However, if a soft-start circuit is used as in the prior art of Patent Document 1 (Japanese Patent Application Laid-Open No. 2014-3850), the circuit configuration becomes complicated and the start-up time at power-on becomes long. Accordingly, the present embodiment aims at simplifying the circuit configuration and shortening the start-up time in a booster device that prevents erroneous determination of an overcurrent abnormality.

Next, with reference to FIGS. 4 to 10, a series of processes from overcurrent detection to measures at the time of abnormality determination according to the present embodiment will be described. In the description of the flow charts of FIGS. 7 to 10, the symbol "S" indicates a step.

The time chart of FIG. 4 shows the overcurrent detection notification operation by the overcurrent monitoring circuit 44 . A communication interval from the overcurrent monitoring circuit 44 to the microcomputer 50 is set to 1 ms, for example. When the boost operation permission signal is on, the drive circuit 41 performs the switching operation of the boost MOS 25 at a PWM cycle of 5 ms, ie, a frequency of 200 kHz, for example. Therefore, the boosting MOS 25 is turned on and off 200 times during the communication interval of 1 ms.

As shown in FIG. 5, the duty ratio is represented by "Ton/T", where Ton is the ON time of the boosting MOS 25 in one PWM period T, and Toff is the OFF time. During normal operation of the booster 301, the duty ratio is calculated according to the boost output target value, and the PWM command signal is generated. FIG. 5 shows the command signal when the duty ratio is approximately 50%.

An overcurrent threshold used for overcurrent detection by the overcurrent monitoring circuit 44 is set for the current when the boost MOS 25 is turned on. The overcurrent threshold is set below the breakdown resistance, mainly based on the rating of the boost MOS 25 and the solder reliability of substrate mounting. Also, the overcurrent threshold may be variably set according to the heat generation of the boost MOS 25 .

For example, in the configuration shown in FIG. 6, the overcurrent threshold calculation unit 43 provided in the ASIC 40 calculates the overcurrent threshold according to the current heat generation of the boost MOS 25 and outputs it to the overcurrent monitoring circuit 44 . The heat generated by the boosting MOS 25 may be detected by a temperature sensor, or may be estimated by adding Joule heat calculated from the current square value or the like to the initial temperature. For example, the greater the heat generated by the booster MOS 25, the lower the overcurrent threshold, thereby facilitating overcurrent detection.

The overcurrent monitoring circuit 44 counts the number of overcurrent detections for each communication interval. As shown in FIG. 5, each time the overcurrent monitoring circuit 44 detects an overcurrent, the drive circuit 41 forcibly turns off the boost MOS 25 and continues the off state until the next duty-on timing. Therefore, in the switch operation at the time of overcurrent detection, the ON time is shortened by the time indicated by the two-dot chain line with respect to the PWM command signal. Since the boost MOS 25 is forcibly turned off, the current becomes 0. As long as the cause of the overcurrent continues, the current becomes equal to or greater than the overcurrent threshold again in the next duty-on period, and the overcurrent is detected.

For example, when the booster 301 is powered on or in the overboost mode in the initial check, the overcurrent state occurs temporarily after the boost operation permission signal is turned on. During that period, the overcurrent monitoring circuit 44 counts the number of overcurrent detections for each communication interval. Then, when the number of times of overcurrent detection for each communication interval exceeds a predetermined number of times, N times, the overcurrent monitoring circuit 44 determines that the state of the current flowing through the boosting MOS 25 has satisfied the first condition, and notifies An overcurrent flag is output as a signal. On the other hand, when the boost operation permission signal is off before the start of the boost operation or after the temporary overcurrent state ends, the number of overcurrent detections per communication interval becomes N times or less, and the overcurrent flag is not output. .

Here, the count of the number of times of overcurrent detection is not limited to the case where overcurrent is detected continuously every cycle as shown in [Example 1] of FIG. Even if the current is not detected, the total number of times should be counted. In addition to the case where the current actually falls below the threshold value as shown in [Example 2], it also includes the case where the current reaches the threshold value but fails to count due to a detection error. In short, the overcurrent flag is output when the total number of overcurrent detections for each communication interval exceeds N times, regardless of whether it is continuous or discontinuous.

After that, it is assumed that an element such as a coil or a diode short-circuits at time tx, resulting in a permanent overcurrent abnormality (that is, intrinsic abnormality). After that, overcurrent is always detected, and the total number of overcurrent detections for each communication interval exceeds N times, and an overcurrent flag is output. When the overcurrent flag received from the overcurrent monitoring circuit 44 continues for a predetermined determination time or longer, the microcomputer 50 determines that "the second condition is satisfied" and determines an abnormality. Then, the microcomputer 50 changes the step-up operation permission signal from ON to OFF, and stops the operation of the step-up MOS 25 as a measure at the time of abnormality determination.

Flowcharts of FIGS. 7 and 8 show the basic flow of the above process. In the flowchart and the following description of the flowchart, the microcomputer 50 of the first embodiment is generalized and referred to as a "controller". Therefore, the same flowchart and the same description are used in the second embodiment. In S11 of FIG. 7, it is determined whether the overcurrent monitoring circuit 44 has detected overcurrent. In the case of YES in S11, the drive circuit 41 turns off the boosting MOS 25 in S12, and continues the off state until the next duty-on timing.

In S13 of FIG. 8, the overcurrent monitoring circuit 44 counts the number of overcurrent detections for each communication interval with the control unit. In S14, it is determined whether or not the number of times of overcurrent detection has exceeded a predetermined number N times. In the case of YES in S14, the overcurrent monitoring circuit 44 determines that the first condition is met, and transmits an overcurrent flag as a notification signal to the control unit.

In S26, the control unit determines whether the notification signal from the overcurrent monitoring circuit 44 has continued for the determination time or longer. In the case of YES in S26, the control unit determines in S30 that the second condition is satisfied, and determines an abnormality. Subsequently, the control unit performs treatment in S40. In the case of NO in S26, the control unit determines that the second condition is not satisfied.

In the determination of the second condition, for example, the determination time may be set to a time longer than the maximum time of the overcurrent state when the power is turned on or in the overboost mode in the initial check. As a result, even if the first condition is met, the second condition is not met when the power is turned on or in the overboost mode in the initial check. Alternatively, an erroneous determination may be prevented by having the control unit change the abnormality determination process according to the situation such as when the power is turned on. Next, an example of processing for preventing erroneous determination will be described with reference to FIG.

FIG. 9 shows processing in which the control unit sets the determination time to a different value depending on the situation, or masks the notification signal. Here, it is assumed that the power supply voltage corresponding to the pre-relay voltage VLa in FIG. 1 is monitored as the "monitoring voltage". Specifically, the control unit sets the determination time to a different value according to the operation mode or power supply voltage of the booster 301, or masks the notification signal in a specific operation mode or a specific power supply voltage range. In this manner, the control unit judges an abnormality based on the notification from the overcurrent monitoring circuit 44, the power supply voltage monitoring value, the internal values such as the status code, that is, based on the external and internal information.

In steps S21 to S24 of FIG. 9, success or failure is determined in order for the four determination items relating to "specific operation mode or specific monitoring voltage". The order of these judgments is arbitrary. In S21, it is determined whether or not the booster 301 is powered on. In general, when power is turned on, an erroneous determination is likely to occur due to rush current.

In S22, it is determined whether or not it is time to temporarily increase the boosted output target value in the initial check for diagnosing circuit abnormalities at startup. In the initial check, the boost output target value is made higher than the normal value to diagnose that the boost function is normal.

In S23, it is determined whether the power supply voltage is equal to or lower than a predetermined voltage threshold. As the power supply voltage becomes lower, the step-up ratio becomes larger, and a large current flows. In S24, it is determined whether the absolute value of the time rate of change of the power supply voltage is equal to or greater than a predetermined voltage fluctuation threshold, that is, whether the power supply voltage has suddenly fluctuated. For example, when the power supply voltage is interrupted for some reason and then restored, there is a possibility that a large current will flow instantaneously, so erroneous determination is likely to occur.

If YES in any one of S21 to S24, in S25 the control unit sets the determination time longer than the reference value or masks the notification signal. By setting the determination time longer than the reference value in a specific operation mode or a specific power supply voltage, the second condition is less likely to be satisfied, and erroneous determination can be prevented. Moreover, by masking the notification signal in a specific operation mode or a specific power supply voltage, the possibility that the second condition is satisfied is eliminated, and an erroneous determination is reliably prevented. In S23 and S24, instead of the pre-relay power supply voltage VLa, the post-relay voltage VLb or the post-boost voltage VH may be used as the "monitoring voltage" and compared with the threshold.

FIG. 10 shows an example of measures to be taken when an abnormality is determined. If the controller determines that there is an abnormality and YES in S41, the controller stops the operation of the booster MOS 25 in S42, or changes the duty ratio to operate the booster MOS 25. FIG. FIG. 4 exemplifies a case where the operation of the boost MOS 25 is stopped, but it is possible to change the duty ratio and operate the boost MOS 25 in a restricted manner depending on the state of element failure.

The microcomputer 50 as a control unit further uses the electric power of the battery 15 to control the drive of the motor 80 of the electric power steering device 99 . The microcomputer 50 may further stop driving the motor 80 or limit the output of the motor 80 in S43 as a measure at the time of abnormality determination. When stopping driving, only the communication of input/output signals used for control may be continued, or the system including the communication system may be shut down.

(Action and effect of the first embodiment)
As described above, in the first embodiment, the overcurrent monitoring circuit 44 does not determine abnormality merely by detecting overcurrent, but transmits a notification signal to the microcomputer 50 when the first condition is satisfied. Further, the microcomputer 50 determines abnormality for the first time when the second condition is satisfied, and takes measures. Therefore, it is possible to avoid erroneously determining that an overcurrent is abnormal when the power is turned on or when the initial check is performed. Further, when an abnormality is determined due to an element failure or the like, the microcomputer 50 stops the operation of the boosting MOS 25, thereby preventing the PWM operation from being continued in a broken state.

In addition, in the first embodiment, unlike the prior art of Patent Document 1, a soft start circuit is not used, and an overcurrent is detected with respect to an overcurrent threshold set below the rating of the boost MOS 25 at the time of power-on or initial check. Power on while In other words, erroneous determination is prevented by preventing the second condition from being satisfied while assuming that the first condition is likely to be satisfied at the time of power-on or initial check. This simplifies the circuit configuration and shortens the start-up time.

Further, when the microcomputer 50 receives the notification signal from the overcurrent monitoring circuit 44, in addition to determining whether the notification signal is to be continued based on the determination time, it performs processing such as changing the determination time based on the operation mode, power supply voltage, etc., masking the notification signal, and the like. Abnormalities can be determined in combination and comprehensively. Therefore, it is possible to determine an abnormality and take measures according to the situation. Furthermore, if the design of the determination conditions is changed due to a power supply fluctuation test, constant change of an external element, etc., it will be easier to deal with it by changing the condition settings with software.

In addition, in the first embodiment, the boost MOS 25, the drive circuit 41 and the overcurrent monitoring circuit 44 are built in the same ASIC 40, so the layout on the substrate is compact. Note that the ASIC 40 may be integrated with each function other than the boosting device. In addition, since the microcomputer 50 performs the function of the "control section", it is advantageous in terms of arithmetic processing capability and communication with the outside.

(Second embodiment)
Next, with reference to FIG. 11, a second embodiment will be described. In the booster 302 of the second embodiment, the drive circuit 42 in the ASIC 40 also functions as a "control section". That is, the notification signal generated when the first condition is established is not transmitted from the overcurrent monitoring circuit 44 of the ASIC 40 to the microcomputer 50, but is transmitted from the overcurrent monitoring circuit 44 to the drive circuit 42 inside the ASIC 40. . The drive circuit 42 that has received the notification signal determines whether the second condition is true or not, and when the second condition is satisfied, determines that there is an abnormality, and takes measures. Also, the information on the power supply voltage may be acquired by the drive circuit 42 instead of the microcomputer 50 .

The effects of the second embodiment can be similarly interpreted by replacing the "microcomputer 50" in the description of the control section of the first embodiment with the "drive circuit 42". When focusing only on the functions of overcurrent detection and abnormality determination, as indicated by the dashed line in FIG. 11, the second embodiment does not require the microcomputer 50, so the booster 302 can be configured more simply. . In addition, the operation of the boosting MOS 25 can be immediately stopped without delay in communication when an abnormality is determined, thereby improving reliability.

However, since the ASIC 40 cannot actually process the same amount of calculation as the microcomputer 50, the microcomputer 50 is required for driving control calculations of the motor 80 and the like. Therefore, the drive circuit 42 and the microcomputer 50 may share the function of the "control section" and cooperate with each other by having the drive circuit 42 also serve as part of the function of the "control section."

(Other embodiments)
(a) The "first condition" in the overcurrent monitoring circuit is when the number of times of overcurrent detection exceeds a predetermined number of times continuously or intermittently at each communication interval with the control unit. It may be established when the current or the integrated value of the current squared value exceeds the threshold for each interval.

(b) Regarding the "second condition" in the control unit, as an interpretation that the notification signal (e.g., overcurrent flag) "continues" for the determination time or longer, for example, in the case of a short interruption within a predetermined time, it continues may be regarded as In other words, only when the interruption time exceeds a predetermined time, it may be treated as continuation failure, and the timer may be reset. Further, instead of the determination time, the success or failure of the second condition may be determined based on the number of times or frequency of reception of the notification signal within a predetermined period.

(c) The boost switching element is not limited to a MOSFET, and may be composed of an FET other than MOSFETE or a bipolar transistor. The boost switching element, the drive circuit, and the overcurrent monitoring circuit are not limited to being built in the same ASIC 40, but may be mounted directly on the board or built in separate ICs. Also, a capacitor or the like may be used as the "power supply" in addition to the battery 15 .

(d) The present invention is not limited to driving an assist motor of an electric power steering device, but may be used to drive any electric actuator or to output an electric device.

The present invention is not limited to such embodiments, and can be embodied in various forms without departing from the scope of the invention.

The controller and techniques described in this disclosure may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by the computer program. may be Alternatively, the controls and techniques described in this disclosure may be implemented by a dedicated computer provided by configuring the processor with one or more dedicated hardware logic circuits. Alternatively, the control units and techniques described in this disclosure can be implemented by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. It may also be implemented by one or more dedicated computers configured. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible recording medium.

15 ... battery (power supply),
21 ... coil,
25 ... boost MOS (boost switching element),
301, 302... Booster,
41 ... drive circuit,
42 ... drive circuit (control unit [second embodiment]),
44 ... overcurrent monitoring circuit,
50 . . . microcomputer (control unit [first embodiment]).

Claims (15)

A booster for boosting and outputting an input power supply voltage,
a boosting switching element (25) provided between the other end of a coil (21) having one end connected to a power supply (15) and ground, and boosting the voltage of the other end of the coil by switching operation;
a drive circuit (41, 42) for PWM-operating the boost switching element;
an overcurrent monitoring circuit (44) for monitoring the current flowing through the boost switching element;
a control unit (50, 42) that determines an abnormality based on the notification from the overcurrent monitoring circuit and takes action;
with
The overcurrent monitoring circuit transmits a notification signal to the control unit when a first condition is satisfied regarding the state of the current flowing through the boost switching element,
The booster device, wherein the control unit determines an abnormality and takes measures when a second condition is satisfied with respect to the notification signal received from the overcurrent monitoring circuit. The overcurrent monitoring circuit counts the number of overcurrent detections for each communication interval with the control unit,
2. The booster device according to claim 1, wherein when the number of times of overcurrent detection exceeds a predetermined number of times, it is determined that the first condition is met and the notification signal is output. 3. The control unit according to claim 1, wherein when the notification signal from the overcurrent monitoring circuit continues for a predetermined determination time or more, the control unit determines that the second condition is met, determines an abnormality, and takes measures. booster. 4. The booster device according to claim 3, wherein the control unit sets the determination time to a different value or masks the notification signal depending on the situation. The control unit sets the determination time to a different value according to the operation mode of the boosting device or the monitoring voltage that is the voltage monitored by the circuit before or after boosting, or sets the determination time to a specific operation mode. 5. The boosting device according to claim 4, wherein said notification signal is masked within a specific monitoring voltage range. 6. The booster device according to claim 5, wherein the controller sets the determination time longer than a reference value or masks the notification signal when the power source of the booster device is turned on. 7. The control unit according to claim 5, wherein when temporarily increasing the boost output target value in the initial check of the booster device, the control unit sets the determination time longer than a reference value or masks the notification signal. A booster device as described. 8. The control unit according to any one of claims 5 to 7, wherein when the monitoring voltage is equal to or lower than a predetermined voltage threshold, the control unit sets the determination time longer than a reference value or masks the notification signal. booster. 5 to 5, wherein, when the absolute value of the time rate of change of the monitoring voltage is equal to or greater than a predetermined voltage fluctuation threshold, the control unit sets the determination time longer than a reference value or masks the notification signal. 9. The booster device according to any one of 8. The drive circuit forcibly turns off the boost switching element each time the overcurrent monitoring circuit detects an overcurrent, and continues the off state until the next duty-on timing. A booster device as described. The booster according to any one of claims 1 to 10, wherein an overcurrent threshold used for overcurrent detection by said overcurrent monitoring circuit is variably set according to heat generation of said boost switching element. 12. The control unit according to any one of claims 1 to 11, wherein the control unit stops the operation of the boost switching element or changes the duty ratio to operate the boost switching element as a measure when the abnormality is determined. booster. A boosting device in which the control unit further controls the driving of a motor (80) using the power of the power supply,
13. The booster device according to claim 12, wherein the control unit further stops driving the motor or limits the output of the motor as a measure when the abnormality is determined. The booster device according to any one of claims 1 to 13, wherein said boost switching element, said drive circuit and said overcurrent monitoring circuit are incorporated in the same IC (40). The booster device according to any one of claims 1 to 14, wherein said drive circuit (42) also serves at least part of the function as said control section.

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