JP2014064129A - Current detection circuit and power supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detection circuit and a power supply control device that have a simple configuration.SOLUTION: A current detection circuit 10A includes an IC 21 for detecting a load current IL supplied to a load L on the basis of a detection current Is2 output from a selected switching element 16B selected from a plurality of sense MOSFETs 16A-16C. As to the selected switching element 16B, a sense MOSFET capable of reducing an error in the detection of the current supplied to the load resulting from a temperature characteristic of a ratio of a shunt current Im1-Im3 to a detection current Is corresponding to the shunt current Im1-Im3, with a temperature characteristic of the shunt current Im1-Im3 is selected as the selected switching element.

Description

  The present invention relates to a current detection circuit and a power supply control device.

  Conventionally, a high-power semiconductor switching element such as a power MOSFET is interposed in a power supply line connecting a power source and a load, and power supply to the load is controlled by turning on and off the semiconductor switching element. Technology is provided.

  In Patent Document 1, a sense MOSFET that detects that an overcurrent has flowed through a power MOSFET or the like is arranged in parallel with the power MOSFET, and a current detection resistor is connected to the sense MOSFET. When the voltage drop at the resistor for use exceeds a predetermined level, it is assumed that an overcurrent has occurred in the power MOSFET, and the semiconductor switching element is turned off to cut off energization.

JP 2007-104488 A

  By the way, since the power MOSFET has a current capacity, when the current flowing through the load increases, a plurality of power MOSFETs may be arranged in parallel. When detecting the load current supplied to the load via the power MOSFET based on the sense current output from the sense MOSFET, a configuration for detecting all the sense currents is required, and the configuration becomes complicated. There is a problem that it is easy.

  The present invention has been completed based on the above situation, and an object thereof is to provide a current detection circuit and a power supply control device capable of simplifying the configuration.

  A current detection circuit according to the present invention is a current detection circuit that is provided in a circuit having an input unit that receives power supply and an output unit that outputs power to the outside and detects a current supplied to a load. Among the supplied currents, a plurality of power switching elements for switching off and sharing each of the shared currents shared by the plurality of conductive paths, and a plurality of conductive paths corresponding to the power switching elements, respectively. A plurality of detection switching elements and a current supplied to the load via the plurality of power switching elements based on a detection current output from a selection switching element among the plurality of detection switching elements. A detecting section for detecting, and the selective switching element is supplied with a temperature characteristic of a ratio between the shared current and the detection current corresponding to the shared current to the load. The error given to the detection of a current that has a characteristic where said said detection switching element capable of reducing the temperature characteristic of the flow diversion ratio among the sharing current is selected as said selected switching device.

  According to this configuration, in order to detect the current supplied to the load via the power switching element based on the detection current output from the selected switching element selected from the plurality of detection switching elements, for example, a plurality of Compared to the case where the current supplied to the load is detected based on the total of the detection currents of the detection switching elements, there is no need for a configuration for performing detection and processing for all the detection currents. The configuration can be simplified.

Here, when the diversion ratios of the plurality of conductive paths from the power input unit to the output unit are different for each detection switching element, the detection switching element is based on the detection current output from any one of the detection switching elements. When the current supplied to the load is detected, the difference in temperature characteristics due to the difference in the diversion ratio for each conductive path is not taken into account, so that an error may occur in the detection of the current supplied to the load.
In addition, the ratio between the shared current and the detection current corresponding to the shared current also varies depending on the temperature characteristics, and there is a possibility that an error may occur in the detection of the current supplied to the load.

In view of this, in this configuration, the selective switching element causes an error given to detection of the current supplied to the load by the temperature characteristic of the ratio between the shared current and the detection current corresponding to the shared current to be divided between the shared currents. The detection switching element that can be reduced by the temperature characteristic of the ratio is selected as the selective switching element.
In this way, the error given to the detection of the current supplied to the load by the temperature characteristic of the ratio between the shared current and the detection current corresponding to the shared current is determined by the temperature characteristic of the current dividing ratio between the shared currents. It becomes possible to cancel (cancel) each other to some extent, and it is possible to suppress detection errors of the current supplied to the load caused by temperature characteristics. Therefore, it is possible to simplify the configuration for detection of the current detection circuit while suppressing detection errors.

In addition to the above configuration, the following configuration is preferable.
The selection switching element is a detection switching corresponding to the power switching element in which the inclination of the shunt ratio of each of the shared currents is opposite to the inclination of the temperature characteristic of the detection current in the ratio. An element is selected as the selective switching element.
In this way, the selection switching element can be selected by comparing the inclination of the temperature characteristic of the detection current in the ratio and the inclination of the temperature characteristic of the shunt ratio, so that the selection of the selection switching element is facilitated. It becomes possible to do.

When the selection switching element has a plurality of detection switching elements having an inclination on the opposite side, the absolute value of the inclination of the temperature characteristic of the detection current and the temperature characteristic of the diversion ratio of each of the shared currents The switching element for detection in which the absolute value of the slope is the closest is selected.
In this way, when there are a plurality of detection switching elements in which the slope of the temperature characteristic of the shunt ratio of each shared current is opposite to the slope of the temperature characteristic of the detection current, the load is the most. A switching element for detection that reduces a detection error of a supplied current can be selected as a selective switching element.

The plurality of detection switching elements are arranged side by side, and the input unit and the output unit are both provided at one end side in the arrangement direction of the plurality of detection switching elements.
When the input unit and the output unit are both provided on one end side in the arrangement direction of the plurality of detection switching elements as in this configuration, the shunt ratio for the plurality of detection switching elements is However, according to the configuration of the present invention, it is possible to suppress the detection error of the current supplied to the load in the circuit configuration in which such a detection error is likely to occur.

The power switching element and the detection switching element are mounted on a circuit board, and the conductive path is a pattern printed on the circuit board.
In this way, the configuration of the current detection circuit can be simplified.

The power switching element and the detection switching element are housed in a package to constitute a semiconductor switch.
In this way, the current detection circuit can be configured by using the semiconductor switch in which the power switching element and the detection switching element are housed in the package as discrete components, thereby reducing the manufacturing cost and the configuration. Can be simplified.
-It has a control part which controls the power interruption of the switching element for electric power according to the detection result by the detection part.

  According to the present invention, it is possible to simplify the configuration of the current detection circuit and the power supply control device.

The figure which shows schematically the state by which the power supply control apparatus was distribute | arranged to the path | route from the power supply of Embodiment 1 to load. The figure which shows the electric constitution of the current detection circuit The figure which shows roughly the state by which the semiconductor switch was mounted in the conductive path from an input part to an output part The figure which shows the electrical constitution for explaining sense ratio The figure which shows the temperature characteristic of the change rate of the electric current for detection by the temperature characteristic of sense ratio Diagram showing the resistance of the path from the input unit to the output unit Figure showing the temperature characteristics of the diversion ratio Figure showing the rate of change of the temperature characteristics of the diversion ratio The figure which shows the relationship between each change rate of the detection current, the shunt ratio, and the change rate of the load current The figure which shows the electrical constitution of the current detection circuit of Embodiment 2. The figure which shows the state where the semiconductor switch was mounted in the conductive path from the input part to the output part Figure showing the temperature characteristics of the rate of change of the diversion ratio The figure which shows the relationship between each change rate of sense ratio and shunt ratio and change rate of load current

<Embodiment 1>
The first embodiment will be described below with reference to FIGS.
As shown in FIG. 1, the power supply control device 10 is provided in a path from a power source B (battery) of a vehicle such as an automobile (not shown) to a load L such as a lamp, a motor, and a heater of the vehicle and is supplied to the load L. This is to control the power.

  The power supply control device 10 includes a current detection circuit 10A that detects a load current IL supplied to the load L. The current detection circuit 10A is mounted on the conductive path 11 of the circuit board 12, as shown in FIG. Electronic parts 15A to 15C, 16A to 16C, 17, 20, and 21 are provided.

  The circuit board 12 has a conductive path 11 in which copper foil is printed and wired. On this conductive path 11, an input unit 13 that receives power supply from the power source B side and power to the external load L side are provided. An output unit 14 for outputting is provided.

  The electronic components 15A to 15C, 16A to 16C, 17, 20, and 21 include three (a plurality of) power MOSFETs 15A to 15C that perform disconnection to the load L (the “power switching element” of the configuration of the present invention). An example) and three (a plurality of) sense MOSFETs 16A to 16C (corresponding to the configuration of the present invention) provided corresponding to the power MOSFETs 15A to 15C in order to detect the load current IL supplied to the load L An example of a “switching element”, a potential adjustment unit 17 that adjusts the output-side potential of the sense MOSFET 16B with respect to the power MOSFETs 15A to 15C, a conversion unit 20 that converts a current from the potential adjustment unit 17 into a voltage signal, And an IC (Integrated Circuit) 21 that receives a voltage signal from the unit 20.

  The power MOSFETs 15A to 15C are N-type. In the conductive path 11 from the input unit 13 to the output unit 14, the drain is connected to the input unit 13 side, and the source is connected to the output unit 14 side. Electric power is supplied to one load L via (a plurality of) power MOSFETs 15A to 15C. Note that power is supplied to one load L through the plurality of power MOSFETs 15A to 15C when each of the power MOSFETs 15A to 15C has a current capacity that can be supplied. This is because it is necessary to shunt the current through the plurality of power MOSFETs 15A to 15C.

The power MOSFETs 15 </ b> A to 15 </ b> C and the sense MOSFETs 16 </ b> A to 16 </ b> C are arranged in parallel to each other, and their drains and gates are electrically connected to have the same potential.
The sense MOSFETs 16A to 16C are provided to detect the load current IL, and the source side of the sense MOSFET 16B is configured to be able to output a detection current Is corresponding to the amount of the shared current Im2 shared by the power MOSFET 15B. The source sides of the sense MOSFETs 16A and 16C are open.

  As shown in FIG. 3, the power MOSFETs 15 </ b> A to 15 </ b> C and the sense MOSFETs 16 </ b> A to 16 </ b> C are housed (integrally) in a synthetic resin package 22 to constitute semiconductor switches 23 </ b> A to 23 </ b> C. FIG. 3 schematically shows the relationship between the conductive path 11 from the input unit 13 to the output unit 14 and the semiconductor switches 23A to 23C interposed in the conductive path 11, and the potential adjusting unit 17 is omitted. ing.

The conductive path 11 has a first conductive path 11A continuous with the input unit 13 and a second conductive path 11B continuous with the output unit 14, and these conductive paths 11 are arranged in parallel.
An input unit 13 is provided at the left end (one end side) of the first conductive path 11A, and an output unit 14 is provided at the left end (one end side) of the second conductive path 11B.

  The semiconductor switches 23A to 23C have the same configuration and are arranged in the conductive path 11 at predetermined intervals, and the drain terminals DT constituting the common drain of the power MOSFETs 15A to 15C and the sense MOSFETs 16A to 16C, and the power A source terminal ST constituting the sources of the MOSFETs 15A to 15C, a detection current output terminal CT constituting the sources of the sense MOSFETs 16A to 16C, and a gate terminal GT constituting a common gate of the power MOSFETs 15A to 15C and the sense MOSFETs 16A to 16C It is equipped with.

  Then, the drain terminal DT of each of the semiconductor switches 23A to 23C is electrically connected to the first conductive path 11A by soldering or the like on the first conductive path 11A, and the source terminal ST is soldered on the second conductive path 11B. The second conductive path 11B is electrically connected by attaching or the like.

The gate terminal GT of each of the semiconductor switches 23A to 23C is connected to the terminal of the IC 21 through a conductive path (not shown).
Of the three semiconductor switches 23A to 23C, the detection current output terminal CT of the semiconductor switch 23B is connected to the potential adjusting unit 17 via a conductive path (not shown).

As shown in FIG. 2, the potential adjustment unit 17 is for holding the output side potentials (source potentials) of the power MOSFETs 15 </ b> A to 15 </ b> C and the sense MOSFETs 16 </ b> A to 16 </ b> C, and includes an operational amplifier 18 and an FET 19. ing.
The input side of the operational amplifier 18 is electrically connected to the source of one sense MOSFET 16B and the sources of three (plural) power MOSFETs 15A to 15C.

The output side of the operational amplifier 18 is electrically connected to the gate of the FET 19. As a result, the differential output of the operational amplifier 18 is fed back to the input (positive phase input) via the gate and drain of the FET 19.
By feeding back the differential output of the operational amplifier 18 in this manner, an imaginary short circuit is achieved in which the positive-phase input potential and the negative-phase input potential of the operational amplifier 18 are almost the same. As a result, the sources of the power MOSFETs 15A to 15C and the sense MOSFET 16A have the same potential, and the detection current Is2 having a stable and constant ratio to the shared current Im2 flowing through the power MOSFET 15B can be supplied to the sense MOSFET 16B.

The converter 20 converts the current output from the source of the FET 19 into a voltage signal and outputs the voltage signal to the IC 21.
The IC 21 detects the load current IL supplied to the load L based on the voltage signal received from the conversion unit 20, and controls on / off of the power MOSFETs 15A to 15C and the sense MOSFETs 16A to 16C.

  Specifically, when a voltage signal is received from the conversion unit 20, one sense MOSFET 16B (an example of the “selection switching element” having the configuration of the present invention) selected in advance from the three sense MOSFETs 16A to 16C. ) Is multiplied by a predetermined correction coefficient (a coefficient corresponding to the selected switching element) to obtain a value (a value based on the detection current). Note that a method of selecting a selection switching element from the three sense MOSFETs 16A to 16C will be described later.

Then, the IC 21 loads the load current IL based on the number obtained by multiplying the total detection current value obtained by multiplying the detection current Is of the sense MOSFET 16B by the correction coefficient and the sense ratio SR (shared current Im2 / detection current Is2). Is detected. For detection of the load current IL, a correction value may be used for the total detection current value, or a correspondence map with the total detection current value may be used.
Here, the method for obtaining the sense ratio SR is, for example, that the sense ratio SR, which is the ratio of any one of the three semiconductor switches 23A to 23C to the shared current Im1 (to Im3), is set in advance. Measured and the sense ratio SR of other semiconductor switches may be the same.
In this way, since the IC 21 detects the load current IL supplied to the load L, the IC 21 is an example of the “detection unit” having the configuration of the present invention.

  Further, according to this detection result, a signal is given to the gate (control input) of the power MOSFETs 15A to 15C (and the sense MOSFETs 16A to 16C), and when an overcurrent flows, the power MOSFETs 15A to 15 (and the sense MOSFETs 16A to 16A). The power supply control device 10 can be configured by controlling the power supply to the load L so as to turn off 16C). Therefore, the IC 21 is an example of a “control unit” that is a configuration of the present invention.

  Here, as shown in FIG. 5, the detection current Is has a temperature characteristic, which may cause a first error (error due to the temperature characteristic of the detection current Is) in the detection value of the load current IL. is there. A method for eliminating the first error will be described later.

となる。
但し、
ｒ１〜ｒ４：隣の半導体スイッチまでの導電路（パターン）の抵抗
Ｒ：半導体スイッチの抵抗
α：半導体スイッチの温度特性（0.6%/deg)
β：導電路（銅パターン）の温度特性(0.44%/deg) Further, in the present embodiment, as shown in FIG. 3, there are an input unit 13 and an output unit 14 on one end side of the conductive path 11, and the resistances of a plurality of paths from the input unit 13 to the output unit 14 are different. The temperature characteristics of the shunt ratio DR of the shared currents Im1 to Im3 output from -15C are also different.
Specifically, as shown in the circuit diagram in which the current detection circuit 10A of FIG. 6 is modeled, it is arranged on three paths A to C (a plurality of conductive paths 11) from the input unit 13 to the output unit 14. The shared currents I1 to I3 output from each of the semiconductor switches 23A to 23C are I (I = I1 + I2 + I3)

It becomes.
However,
r1 to r4: resistance of conductive path (pattern) to adjacent semiconductor switch R: resistance of semiconductor switch α: temperature characteristic of semiconductor switch (0.6% / deg)
β: Temperature characteristics of conductive path (copper pattern) (0.44% / deg)

Since the formula for obtaining the detection current is different as in the above formula, the shunt ratio DR (of the power MOSFETs 15A to 15C) of the semiconductor switches 23A to 23C is different as shown in FIG.
Here, since α ≠ β, the environmental temperature characteristics (ambient temperature characteristics) of the semiconductor switches 23A to 23C and the copper pattern are different, and the ratio of the currents I1 to I3 changes when the environmental temperature changes. Accordingly, I1 in FIG. 7 has a slightly downward slope, and I3 has a slightly upward slope.

As a result, the path A passing through the semiconductor switch 23A has a smaller resistance of the conductive path 11 than the other semiconductor switches 23B and 23C, as shown in FIG. The influence of the temperature characteristics of the switch 23A is large. Therefore, when the environmental temperature is low, the value of the detection current I1 increases, and as the environmental temperature increases, the value of the detection current I1 decreases.
On the other hand, for the path C passing through the semiconductor switch 23C, since the resistance of the conductive path 11 is larger than that of the other semiconductor switches 23A and 23B, the influence of the resistance of the conductive path 11 is larger than that of the semiconductor switch 23C, and the environmental temperature is low. As the value of the detection current I3 decreases and the environmental temperature increases, the value of the detection current I3 increases.

  On the other hand, for the path B passing through the semiconductor switch 23B, the resistance of the conductive path 11 is located in the middle with respect to the other semiconductor switches 23A and 23C. When the environmental temperature is low, the value of the detection current I2 is slightly small, and when the environmental temperature is high, the value of the detection current I2 is slightly increased.

  Therefore, as described above, when the load current IL supplied to the load L is detected based on the detection current Is of one selected sense MOSFET, the load current IL is determined according to the temperature characteristics of the selected sense MOSFET. There is a possibility that a second error (an error due to the temperature characteristic of the diversion ratio DR) occurs in the detection of.

  Therefore, in the present embodiment, while allowing the first error due to the environmental temperature characteristic of the detection current Is described above and the second error due to the environmental temperature characteristic of the shunt ratio DR to occur separately, (error) A sense MOSFET that cancels (cancels) these errors with each other is selected as a selection switching element.

Specifically, for each of the semiconductor switches 23A to 23C, the temperature characteristic of the shunt ratio DR is obtained for the current detection circuit 10A.
For example, as described above, the temperature characteristic of the detection current Is can be obtained as follows. The detection current Is of the short path of the conductive path 11 is not detected by actually measuring the temperature characteristic of the shunt ratio DR. Since the detection current Is of the long path of the conductive path 11 is strongly influenced by the resistance of the conductive path 11, the rate of change of the diversion ratio DR is defined in advance based on the length of the conductive path 11. You can do it. It should be noted that the temperature characteristics of the diversion ratio DR may be obtained by actually measuring.

When the temperature characteristics of the shunt ratio DR for each of the semiconductor switches 23A to 23C are obtained, the slope on the side opposite to the slope of the detection current Is due to the temperature characteristic (change rate) of the sense ratio SR (the slope opposite to positive and negative). ) Is selected as a selection switching element used for detecting the load current IL. In FIG. 8, a sense MOSFET having a temperature characteristic (change rate) of a shunt ratio with an upward slope to a temperature characteristic (change ratio) of the detection current Is with a downward slope is selected.
Here, as in the present embodiment, when there are a plurality of sense MOSFETs (16B, 16C) having a slope of the detection current Is due to the temperature characteristic of the sense ratio SR and a slope of the shunt ratio in the opposite direction, The sense MOSFET 16B having the shunt ratio DR with the closest absolute value of the slope is selected as the selective switching element. The slope of each temperature characteristic is the slope at a predetermined temperature (for example, 25 ° C.) or the average value of a plurality of slopes in a predetermined temperature range is compared when the temperature characteristic is not linear. The slope of the power temperature characteristic may be used.

Then, the detection current Is2 (the sense MOSFETs 16A to 16C) output from the selection switching element (sense MOSFET 16) is multiplied by the reciprocal of the sense ratio SR and a predetermined correction coefficient set in advance according to the selection switching element. In addition, the load current IL supplied to the load L is detected (the load current is detected based on the detection current and the sense ratio).
As a result, as shown in FIG. 9, it is possible to obtain a rate of change LR of the load current IL in which the influence of the temperature characteristic of the sense ratio SR and the influence of the temperature characteristic of the shunt ratio DR are canceled to some extent.

According to the present embodiment, the following operations and effects are achieved.
(1) According to the present embodiment, the power MOSFETs 15A to 15C (for power) based on the detection current Is output from the selection switching element 16B selected from among the plurality of sense MOSFETs 16A to 16C (detection switching elements)) In order to detect the load current IL supplied to the load L via the switching element), for example, the load current IL supplied to the load L is detected based on the total of the detection currents of the plurality of sense MOSFETs 16A to 16C. In comparison, it is not necessary to have a configuration for performing detection and processing for all the detection currents, so that the configuration for detection can be simplified.

Here, the sense ratio SR, which is the ratio between the shared current Im2 and the detection current Is corresponding to the shared current Im2, also varies due to temperature characteristics, and the first error is detected in the detection of the current supplied to the load L. May occur.
Further, for each of the power MOSFETs 15A to 15C, when the path resistance shunt ratios of the plurality of conductive paths 11 from the power input unit 13 to the output unit 14 are different, the temperature characteristics of the shared currents Im1 to Im3 are different. When the load current IL supplied to the load L is detected based on the detection current Is output from each sense MOSFET, the difference in the temperature characteristics for each conductive path 11 is not taken into account, and thus the current is supplied to the load L. An error may occur in the detection of the load current IL.
In addition, the ratio between the shared current and the detection current corresponding to the shared current also varies depending on the temperature characteristics, and there is a possibility that an error may occur in the detection of the current supplied to the load.

On the other hand, in the present embodiment, the selection switching element gives an error that the temperature characteristic of the ratio between the shared current Im2 and the detection current Is corresponding to the shared current Im2 gives to the detection of the load current IL between the shared currents. The sense MOSFET 16B (detection switching element) that can be reduced by the temperature characteristic of the shunt ratio DR is selected as the selective switching element.
In this way, the error given to the detection of the load current IL by the change in the temperature characteristic of the sense ratio SR, which is the ratio between the shared current Im2 and the detection current Is corresponding to the shared current Im2, is determined between the shared currents. With this temperature characteristic, it becomes possible to cancel (cancel) the influences of the temperature characteristic to some extent, and it is possible to suppress the detection error of the load current IL caused by the environmental temperature characteristic. Therefore, it is possible to simplify the configuration for detection of the current detection circuit 10A while suppressing detection errors.

(2) The selection switching element corresponds to the power MOSFET 15B in which the slope of the shunt ratio DR of each of the shared currents Im1 to Im3 is the opposite slope with respect to the slope of the temperature characteristic of the detection current Is in the sense ratio (ratio). The sense MOSFET 16B to be selected is selected as the selective switching element.
In this way, the selection switching element can be selected by comparing the gradient of the temperature characteristic of the detection current Is in the sense ratio (ratio) with the gradient of the temperature characteristic of the shunt ratio DR. It becomes possible to easily select the element.

(3) When there are a plurality of sense MOSFETs (detection switching elements) having an inclination on the opposite side, the selection switching element has an absolute value of the inclination of the temperature characteristic of the detection current Is and each of the shared currents Im1 to Im3. The detection switching element that has the closest absolute value of the gradient of the temperature characteristic of the diversion ratio DR is selected.
In this way, when there are a plurality of sense MOSFETs in which the gradient of the temperature characteristic of the current dividing ratio DR of each of the divided currents Im1 to Im3 is the opposite gradient with respect to the gradient of the temperature characteristic of the detection current Is, It becomes possible to select the sense MOSFET 16B that minimizes the detection error of the load current IL supplied to the load as the selective switching element.

(4) The plurality of sense MOSFETs 16A to 16C (switching elements for detection) are arranged side by side, and both the input unit 13 and the output unit 14 are arranged in the direction in which the plurality of sense MOSFETs 16A to 16C (switching elements for detection) are arranged. Is provided on one end side.
When the input unit 13 and the output unit 14 are both provided at one end side in the arrangement direction of the plurality of sense MOSFETs 16A to 16C as in the present embodiment, the path resistance shunting for the plurality of sense MOSFETs 16A to 16C is performed. The ratios are likely to be different and detection errors are likely to occur. However, according to the configuration of the above embodiment, the detection error of the current supplied to the load L can be suppressed in the circuit configuration in which such detection errors are likely to occur. It becomes possible.

(5) The power MOSFETs 15 </ b> A to 15 </ b> C and the sense MOSFETs 16 </ b> A to 16 </ b> C are mounted on the circuit board 12, and the conductive path 11 is a pattern printed on the circuit board 12.
In this way, the configuration of the current detection circuit 10A can be simplified.

(6) The power MOSFETs 15A to 15C and the sense MOSFETs 16A to 16C are accommodated in the package 22 to constitute the semiconductor switches 23A to 23C.
In this manner, the current detection circuit 10A can be configured using the semiconductor switches 23A to 23C in which the power MOSFETs 15A to 15C and the sense MOSFETs 16A to 16C are accommodated in the package 22 as discrete components, so that the manufacturing cost can be reduced. It is possible to simplify the configuration while reducing.

となる。
但し、
ｒ１〜ｒ２：隣の半導体スイッチまでの導電路（パターン）の抵抗
Ｒ：半導体スイッチの抵抗
α：半導体スイッチの温度特性（0.6%/deg)
β：導電路（銅パターン）の温度特性(0.44%/deg) <Embodiment 2>
A second embodiment will be described with reference to FIGS. 10 to 13.
In the current detection circuit 10A of the first embodiment, the load current IL is shunted to the three power MOSFETs 15A to 15C provided in the semiconductor switches 23A to 23C, and three senses corresponding to each power MOSFET 15A to 15C. Although the MOSFETs 16A to 16C are provided, the current detection circuit 24 of the second embodiment has a load current IL of two power MOSFETs 26A and 26B provided in the semiconductor switches 25A and 25B as shown in FIG. The two sense MOSFETs 27A and 27B are provided corresponding to the power MOSFETs 26A and 26B. Hereinafter, the same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
Specifically, as shown in the circuit diagram in which the current detection circuit of FIG. 11 is modeled, each of the three paths A to C (the plurality of conductive paths 11) from the input unit 13 to the output unit 14 is arranged. The shared currents I1 to I2 output from the semiconductor switches 23A to 23C are I (I = I1 + I2) as a whole,

It becomes.
However,
r1 to r2: resistance of conductive path (pattern) to adjacent semiconductor switch R: resistance of semiconductor switch α: temperature characteristic of semiconductor switch (0.6% / deg)
β: Temperature characteristics of conductive path (copper pattern) (0.44% / deg)

  As shown in FIG. 12, the shunt ratio DR of the two sense MOSFETs 27A and 27B in the current detection circuit 24 has a smaller resistance of the conductive path 11 than the MOSFET 27B in the path passing through the sense MOSFET 27A. When the influence of the temperature characteristic is large and the environmental temperature is low, the detected current value is large, and the detected current value has a slope that decreases as the environmental temperature increases.

  On the other hand, for the path passing through the sense MOSFET 27B, since the resistance of the conductive path 11 is larger than that of the MOSFET 27A, the influence of the resistance of the conductive path 11 is larger than that of the sense MOSFET 27A. As the temperature increases, the detected current value has a slope that increases.

The sense MOSFETs 27A and 27B have the same configuration as in the first embodiment, and the sense ratio SR, which is the ratio of the detection current Is to the shared current Im in the sense MOSFETs 27A and 27B, has temperature characteristics. .
Further, regarding the temperature characteristics of the shunt ratio DR, when the detection currents IA and IB output from the sense MOSFETs 27A and 27B are measured, the temperature characteristics as shown in FIG. 12 are obtained.

  Therefore, in the second embodiment, the first error due to the temperature characteristic of the sense ratio SR and the second error due to the temperature characteristic of the shunt ratio DR are allowed to occur (individually, the error due to the temperature characteristic is individually determined). A sense MOSFET that cancels (cancels) the influence on the detection of the load current IL is selected as a selective switching element.

  Then, as shown in FIG. 13, a sense MOSFET 27B that obtains a temperature characteristic of the current dividing ratio DR between the slope of the detection current Is due to the temperature characteristic of the sense ratio SR and the slope on the opposite side (the slope opposite to the positive and negative) is selected. Choose as.

  The number obtained by multiplying the detection current Is output from the selected sense MOSFET 27B and the sense ratio SR is multiplied by a predetermined correction coefficient set in advance according to the selected sense MOSFET. The load current IL supplied to the load L is detected. Thereby, it is possible to obtain a rate of change LR of the load current IL in which the influence of the temperature characteristic of the sense ratio SR and the influence of the temperature characteristic of the shunt ratio DR are canceled to some extent.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.
(1) In the above embodiment, the current detection circuits 10A and 24 and the power supply control device 10 are provided with two or three semiconductor switches. However, the present invention is not limited to this, and there are four or more semiconductor switches. The present invention may be applied to. In accordance with this, the present invention may be applied to a case where four or more sense MOSFETs or power MOSFETs are provided.

(2) In the above embodiment, the sense MOSFET or the power MOSFET is used as the switching element. However, the present invention is not limited to this. For example, a relay or the like may be used.

(3) In the above embodiment, the conductive path 11 is a copper foil printed on a printed wiring, but is not limited thereto. For example, a conductor such as a copper alloy, aluminum, or an aluminum alloy may be used as the conductive path.

DESCRIPTION OF SYMBOLS 10 ... Electric power supply control apparatus 10A, 24 ... Current detection circuit 11 ... Conductive path 12 ... Circuit board 13 ... Input part 14 ... Output part 15A-15C, 26A, 26B ... Power MOSFET (switching element for electric power)
16A-16C, 27A, 27B ... sense MOSFET (switching element for detection)
16B Sense MOSFET (selective switching element)
17 ... Potential adjustment unit 20 ... Conversion unit 21 ... IC (detection unit, control unit)
22 ... Packages 23A to 23C, 25A, 25B ... Semiconductor switch B ... Power supply L ... Loads Im1-Im3 ... Shared currents Is1-Is3, Is ... Detection current IL ... Load current DR ... Shunt ratio SR ... Sense ratio LR ... Load current Rate of change

Claims (7)

A current detection circuit that is provided in a circuit having an input unit that receives power supply and an output unit that outputs power to the outside and detects a current supplied to a load,
Among the currents supplied to the load, a plurality of power switching elements for cutting off and sharing the shared current shared by the plurality of conductive paths,
A plurality of switching elements for detection provided in a plurality of conductive paths corresponding to each of the power switching elements, and capable of outputting a detection current;
A detection unit configured to detect a current supplied to the load via the plurality of power switching elements based on the detection current output from a selection switching element among the plurality of detection switching elements. ,
The selective switching element has an error that the temperature characteristic of the ratio between the shared current and the detection current corresponding to the shared current gives to the detection of the current supplied to the load by the temperature characteristic between the shared currents. A current detection circuit in which the detection switching element that can be reduced is selected as the selection switching element. The selection switching element is a detection switching element corresponding to the power switching element in which the inclination of the shunt ratio of each shared current is opposite to the inclination of the temperature characteristic of the detection current in the ratio. Is selected as the selection switching element. In the case where there are a plurality of the detection switching elements having the slope on the opposite side, the selective switching element has an absolute value of the slope of the temperature characteristic of the detection current and an absolute value of the slope of the temperature characteristic of the shunt ratio. The current detection circuit according to claim 2, wherein the detection switching element having the closest value is selected. The plurality of detection switching elements are arranged side by side,
4. The current detection circuit according to claim 1, wherein the input unit and the output unit are both provided on one end side in the arrangement direction of the plurality of detection switching elements. 5. The power switching element and the detection switching element are mounted on a circuit board,
The current detection circuit according to claim 1, wherein the conductive path is a pattern printed on the circuit board. The current detection circuit according to claim 1, wherein the power switching element and the detection switching element are housed in a package to constitute a semiconductor switch. The power supply control device according to any one of claims 1 to 6, further comprising a control unit that controls power interruption of the power switching element according to a detection result by the detection unit.

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