JP2009195024A - Load driver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load driver that prevents the operation of a load part from being stopped due to a temporary short circuit or noise and is suitable to be adopted as an apparatus for driving the load part requiring safety and reliability. <P>SOLUTION: The load driver 1 includes a first switch part 30 connected in series with a supply path from a power supply part 100 to the load part 200 and a second switch part 40 connected in series with the supply path and in parallel with the first switch part 30. The second switch part 40 brings the supply path into conduction together with the first switch part 30 to drive the load part. The second switch part 40 employs an apparatus that enables current flowing through at least the supply path when a short circuit occurs in the supply path to normally flow to a conductive path conducted by the second switch part 40. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a load drive device that includes a switch unit connected in series to a supply path extending from a power supply unit to a load unit, and drives the load unit by conducting the supply path to the switch unit.

In the load driving device as described above, when it is detected that the supply path is short-circuited to the power supply unit or the ground (including a short-circuit with a certain resistance value, so-called half-short; the same applies hereinafter), the load is immediately applied. Generally, the load driving device itself and the load unit are protected by stopping or limiting the power supply to the unit (see Patent Documents 1 and 2).
JP 2007-181349 A JP 09-46200 A

  However, as described above, in the configuration in which the power supply to the load unit is stopped or restricted, the power supply is immediately stopped or restricted even by a temporary short circuit or noise, and the operation of the load unit may be stopped. . In particular, in a device that drives a load section that requires safety and reliability by detecting submersion, the power supply may be immediately stopped or restricted even by a half short to the ground due to water, and the operation of the load section may be stopped. There is.

  In addition, the load driving device as described above is used as a device for driving a load portion that requires safety and reliability for its operation, such as an engine, a brake, a headlamp, a power window, etc. in a vehicle. There are points of concern.

The fact that the operation of the load section immediately stops due to a false detection due to a short circuit or noise means that the operation of the engine, brake, headlamp, and power window in the vehicle is not immediately performed. This is because the passengers of the vehicle may be at risk.

The present invention has been made in order to solve such a problem, and an object of the present invention is to prevent the operation of the load unit from being stopped by a temporary short circuit and to provide a load unit for which safety and reliability are required. It is providing the load drive apparatus suitable for employ | adopting as an apparatus which drives.

  In order to solve the above-described problem, a first switch unit connected in series to a supply path from a power supply unit to a load unit is provided, and the supply path is made conductive to the first switch unit, thereby The load driving device that drives the load section may be configured as shown in a first configuration (claim 1) described below.

  In this configuration, a second switch unit connected in series to the supply path and in parallel with the first switch unit is provided, and the second switch unit is supplied together with the first switch unit. The load section is configured to be driven by conducting the path, and the second switch section receives a current flowing through the supply path when at least a short circuit occurs in the supply path. A device that can normally flow through a conduction path through which the two switch units are conducted is used.

  In the case of the load driving device configured as described above, even if a temporary short circuit occurs in the supply path under the condition where the supply path is made conductive by the first and second switch units, the supply path at that time Since the current flowing through the second switch section can be normally (that is, not damaged) flowing through the conduction path of the second switch section, the operation of the load section can be continued during that time.

  In addition, even if a continuous short circuit occurs, the current flowing through the supply path can be continuously supplied to the conduction path by the second switch unit at that time, so that another protection device mounted on the supply path Until the supply path is opened by the fuse or switch, at least the operation of the load unit can be continued.

  Thus, for example, it is suitable for use as a device for driving a load unit that requires safety and reliability for its operation, such as an engine, a brake, a headlamp, and a power window in a vehicle. Even if a short circuit occurs, the vehicle's engine, brakes, headlamps, power window, etc. can be operated continuously for a certain period of time. This is because it can be lowered.

  Further, with the above configuration, since the supply path can be conducted by each of the two switch sections, even if one of the switch sections fails, the conduction of the supply path can be continued by the other switch section.

  In this configuration, when the supply path is branched into a plurality of paths so as to reach each of the plurality of load sections from the power supply section, the load driving device is provided in each of the paths after the branch. Alternatively, only one load driving device may be provided on the path before the branch.

  In the latter case, the above configuration may be changed to a second configuration (claim 2) shown below. In this configuration, each of the first and second switch sections is connected in a path section before branching from the power supply section to each of the plurality of load sections in the supply path.

  With this configuration, it becomes possible to operate a plurality of load units integrally with a single load drive device, and it is not necessary to provide a load drive device for each of the plurality of load units. This effect becomes more prominent as the number of load sections increases from the viewpoint of manufacturing cost and apparatus simplification.

  Further, in each of the above-described configurations, a specific configuration for realizing conduction of the supply path by the first and second switch units may be a third configuration (claim 3) described below. Conceivable.

  In this configuration, each of the first and second switch units includes a reception terminal that receives a command from the outside of the switch unit, an input terminal connected to the power supply unit side in the supply path, and the supply path A switching element having an output terminal connected to the load section side in the power supply section side of the supply path is connected to the input terminal, the load section side of the supply path is connected to the output terminal, and the input The terminal and the reception terminal are connected via a first resistance element (R11 in the first switch unit, R21 in the second switch unit), and a second resistance element (first switch unit) is connected to the reception terminal. Is connected to one end of R12, and in the second switch section, one end of R22). Then, when the signal level of each of the other ends of the second resistance element is changed from the initial H level to the L level, the power source divided by the first and second resistance elements (divided power source) is Applied between the input terminal and the receiving terminal, and receiving a signal according to the applied divided power supply from the receiving terminal as a command from the outside so as to conduct between the input terminal and the output terminal It is configured.

  With this configuration, for each of the second resistance elements in each switch unit, the signal level at the other end is set to H level as an initial value, and the signal level is changed to L level during the driving period of the load unit. Thus, conduction of the supply path by each switch unit can be realized.

In this configuration, for example, the following can be considered as the switching elements as the first and second switch sections.
(1) Bipolar transistor having a base terminal as an acceptance terminal, an emitter terminal as an input terminal, and a collector terminal as an output terminal (2) a gate terminal as an acceptance terminal, and a source terminal as an input terminal or an output terminal Or a field effect transistor (FET) having a drain terminal
(3) IGBT (Insulated Gate Bipolar Transistor) having a gate terminal as a reception terminal, an emitter terminal as an input terminal, and a collector terminal as an output terminal
As a specific application, for example, it is conceivable to employ a bipolar transistor for the first switching unit and an FET or IGBT for the second switching unit.

  In addition, the capacitance between the input terminal and the reception terminal of the switch unit described above is a capacitance that is considered as a parasitic capacitance formed between the terminals and a capacitance defined by a capacitor connected therebetween. It is a capacitance or the total capacitance of these.

  By the way, in the third configuration, when it is assumed that the first switch unit is a device that cannot flow a large current at the time of a short circuit (hereinafter referred to as “short circuit current”), the first and second switches Even if a short circuit occurs in the supply path in a state where the supply path is conducted by the unit, most of the short-circuit current flows through the conduction path in the second switch unit from each capability. Therefore, under such a situation, the influence on the first switch part by the short-circuit current is small.

  However, in a situation where a short circuit has already occurred in the supply path prior to conducting the supply path to the first and second switch sections, the first switch section is connected to the supply path before the second switch section. If this is made conductive, a large current flows due to a short circuit, and this first switch may be damaged.

  Therefore, it is desirable that the conduction by the second switch unit is performed before the conduction by the first switch unit. For this purpose, a fourth configuration (claim 4) in which the above-described configuration is shown below can be considered.

  In this configuration, the resistance value of each resistance element in each of the first and second switch units, and the capacitance between the input terminal and the receiving terminal are the second value in the first switch unit. The resistance value r12 of the resistance element and the time constant T11 (= r12 · c1) defined by the capacitance c1 between the input terminal and the receiving terminal are the second value in the second switch section. The resistance value r22 of the resistance element and the time constant T21 (= r22 · c2) defined by the capacitance c2 between the input terminal and the receiving terminal are determined to be larger (T21 <T11). Specified value.

  In this configuration, the time constant defined by the resistance value of the second resistance element and the capacitance between the input terminal and the reception terminal is larger in the first switch unit than in the second switch unit. Therefore, even if the signal level of each of the other ends of the second resistance element in the first and second switch sections is changed from the H level to the L level at the same timing, the signal level on one end side of the second resistance element is reduced to the L level. The time until reaching the level is longer in the first switch unit.

  As a result, the time until the appropriate divided power supply is applied between the input terminal and the receiving terminal is also longer in the first switch unit, and as a result, the timing at which the first switch unit conducts the supply path is This is later than the timing in the second switch section.

  Thus, since the conduction of the supply path by the second switch unit can be performed before the conduction by the first switch unit, prior to conducting the supply path by the first and second switch units. It is possible to prevent the first switch from being damaged even in a situation where a short circuit has already occurred in the supply path.

  In the third and fourth configurations described above, when the conduction of the supply path by the first and second switch units is terminated, the signal level on the other end side of the second resistance element is changed from L level to H level. It will return to.

  At this time, if the second switch unit ends the conduction of the supply path before the first switch unit, if the short circuit that has occurred in the supply path continues, The first switch unit may be damaged.

For this reason, it is desirable that the end of conduction by the first switch is performed before that by the second switch unit.
For this purpose, it is conceivable that the third and fourth configurations are the fifth configuration (Claim 5) as described below.

  In this configuration, the resistance value of each resistance element in each of the first and second switch units, and the capacitance between the input terminal and the receiving terminal are the first value in the second switch unit. A time constant T22 (= r21 · c2) defined by the resistance value r21 of the resistance element and the capacitance c2 between the input terminal and the receiving terminal is the first switch portion in the first switch section. It is determined to be larger than the time constant T12 (= r11 · c1) defined by the resistance value r11 of the resistance element and the capacitance c1 between the input terminal and the receiving terminal (T22> T12). Specified value.

  In this configuration, the time constant defined by the resistance value of the first resistance element and the capacitance between the input terminal and the receiving terminal is larger in the second switch unit than in the first switch unit. Therefore, even if the signal level of each of the other ends of the second resistance element in the first and second switch sections is returned from the L level to the H level at the same timing, the signal level on one end side of the second resistance element is not increased. The time for returning to the H level is longer in the second switch unit.

  As a result, the time until the divided power supply is not properly applied between the input terminal and the receiving terminal is also longer in the second switch unit, so that the first switch unit conducts the supply path. The timing to end is earlier than the timing in the second switch unit.

  Thus, the conduction of the supply path by the first switch unit can be terminated before the conduction of the second switch unit, and therefore the conduction of the supply path by the first and second switch units is terminated. Even in a situation where the short circuit continues, it is possible to prevent the first switch from being damaged.

  Further, as described above, when the second switch unit is made of a switching element, the divided power source divided by the first and second resistance elements is applied between the reception terminal and the input terminal, A signal corresponding to the divided power supply is received by the reception terminal, and conduction of the supply path is realized.

At this time, in order to connect the supply path to the second switch section, a divided power supply having a certain level is required. Therefore, it is desirable to make the divided power supply as high as possible.
For this purpose, it is conceivable that each of the above-described configurations is as shown in a sixth configuration (claim 6).

In this configuration, a device having a resistance value (r22 << r21) sufficiently larger than that of the second resistance element is used for the first resistance element in the second switch section.
If it is this structure, the 1st resistance element which determines the voltage-divided power supply applied between an acceptance terminal-input terminal among the 1st, 2nd resistance elements in a 2nd switch part is enough rather than a 2nd resistance element Therefore, the level of the divided power supply in the power supply can be made as high as possible. As a result, it is possible to realize conduction of the supply path even in a certain range where the level of the power supply is low as compared with the case where the first resistance element does not have a sufficiently large resistance value.

  Further, as described above, when the first switch unit is made of a switching element, the divided power source divided by the first and second resistance elements is applied between the reception terminal and the input terminal, A signal corresponding to the divided power supply is received by the reception terminal, and conduction of the supply path is realized.

At this time, since a certain amount of voltage-divided power supply is required to connect the supply path to the first switch unit, it is desirable to increase the voltage-divided power supply as much as possible.
For this purpose, it is conceivable that each of the above-described configurations is as shown in a seventh configuration (claim 7).

In this configuration, a device having a resistance value (r12 << r11) sufficiently larger than that of the second resistance element is used for the first resistance element in the first switch section.
If it is this structure, the 1st resistance element which determines the voltage-divided power supply applied between an acceptance terminal-input terminal among 1st, 2nd resistance elements in a 1st switch part is more enough than a 2nd resistance element Therefore, the level of the divided power supply in the power supply can be made as high as possible. As a result, it is possible to realize conduction of the supply path even in a certain range where the level of the power supply is low as compared with the case where the first resistance element does not have a sufficiently large resistance value.

  Further, in the case where the fuse provided in the supply path is configured to be blown by a current flowing due to a short circuit generated in the supply path, an eighth configuration in which each of the above-described configurations is shown below. (Claim 8) is preferable.

  In this configuration, in the second switch unit, a current that causes the fuse to blow when at least a short circuit occurs in the supply path normally flows through the conduction path that is conducted by the second switch part. Devices that can be used.

  With this configuration, even if a continuous short circuit occurs in the supply path, the current flowing through the supply path at that time can continue to flow through the conduction path by the second switch unit until the fuse is blown. Until the supply path is opened due to the fusing, at least the operation of the load section can be continued.

Embodiments of the present invention will be described below with reference to the drawings.
1. Overall Configuration As shown in FIG. 1, the load driving device 1 is configured to receive a power supply from a power supply unit (battery in the present embodiment) 100 and drive a plurality of load units 200, respectively. A device implemented as part of an electronic control unit.

  In the present embodiment, the load unit 200 is an engine, a brake, a headlamp, a power window, and the like in a vehicle, and a relay for supplying power to these. In the figure, only this relay is shown. Assume that it is shown as a load unit 200.

  The load driving device 1 includes a power supply terminal 10 connected to the power supply unit 100, a load terminal 20 connected to the load unit 200, a power supply path from the power supply terminal 10 to the load terminal 20 (hereinafter simply referred to as “supply”). The first switch unit 30 connected in series to the path) is provided, and the load unit 200 connected via the load terminal 20 by connecting the supply path to the first switch unit 30 is provided. It is comprised so that it may drive.

  In the path from the power supply unit 100 to the power supply terminal 10, when a short circuit occurs in the supply path, a large current (hereinafter referred to as “short-circuit current”) flowing in the supply path is detected to open the path. A protective device (for example, a fuse or a switch) 300 is provided.

  Among the above, the first switch unit 30 includes a base terminal as a receiving terminal that receives a command from the outside, an emitter terminal as an input terminal connected to the power supply terminal 10 side in the supply path, and a load terminal in the supply path. And a collector terminal as an output terminal connected to the side 20, and a switching element (so-called bipolar transistor) that is operated by a power supply from the power supply unit 100.

  In the first switch unit 30, the input terminal and the power supply terminal 10 (the power supply unit side in the supply path) are connected, and the output terminal and the load terminal 20 (the load unit side in the supply path) are connected. The input terminal and the reception terminal are connected via the first resistance element R11, and one end of the second resistance element R12 is connected to the reception terminal. A capacitor C is connected in parallel to the first resistance element R11 that connects the input terminal and the reception terminal. The other end of the second resistance element R12 is connected to a control circuit (not shown).

  When the signal level at the other end of the second resistance element R12 becomes L level, the power source (divided power source) divided by the first resistance element R11 and the second resistance element R12 is connected between the input terminal and the reception terminal. A signal corresponding to the divided power supply applied in this way is received from the receiving terminal as an external command, and the input terminal and the output terminal are brought into conduction.

  Further, the load driving device 1 includes a second switch unit 40 connected in series with the supply path and in parallel with the first switch unit 30, and the second switch unit 40 is connected to the first switch unit 40. By connecting the supply path together with the switch unit 30, the load unit 200 connected via the load terminal 20 is driven.

  The second switch unit 40 includes a gate terminal as a receiving terminal for receiving a command from the outside, a source terminal as an input terminal connected to the power supply terminal 10 side in the supply path, and a load terminal 20 side in the supply path A switching element (so-called field effect transistor, FET: Field Effect Transistor) that operates with a power supply from the power supply unit 100.

  In the second switch section 40, the input terminal and the power supply terminal 10 are connected, the output terminal and the load terminal 20 are connected, and the input terminal and the reception terminal are connected via the first resistance element R21. One end of the second resistance element R22 is connected to the reception terminal. In addition, a zener diode ZD is connected in parallel to the first resistance element R21 that connects the input terminal and the reception terminal so that the voltage between the terminals is constant. Note that the other end of the second resistance element R22 is connected to a control circuit (not shown), like the first switch unit 30.

  When the signal level at the other end of the second resistance element R22 becomes L level, the power source (divided power source) divided by the first resistance element R21 and the second resistance element R22 is connected between the input terminal and the reception terminal. A signal corresponding to the divided power supply applied in this way is received from the receiving terminal as an external command, and the input terminal and the output terminal are brought into conduction.

  Moreover, the device which can normally flow a short circuit current to the conduction | electrical_connection path | route which this 2nd switch part 40 conducted is used for the 2nd switch part 40 mentioned above. On the other hand, the first switch unit 30 does not consider the short-circuit current, that is, the short-circuit current cannot normally flow through the conduction path, but the load can be driven steadily even at a low voltage (for example, 3.5 V or less). The device is in use.

  In addition, the first switch unit 30 and the second switch unit 40 are each of the supply paths branched into a plurality of paths so as to reach each of the plurality of load units 200 inside the electronic control unit. It is connected to the route part before branching. In addition, a backflow prevention diode Dn (n is a number of 1 or more) is connected in series to each of the plurality of paths branched in the supply path.

  In the load driving device 1 as described above, elements other than those related to the first switch unit 30 (second switch unit 40, first resistance element R21, second resistance element R22, Zener diode ZD, diode Dn) and internal Assuming the case where only a current that does not activate the protection device 300 flows in the supply path when a short circuit occurs, each wiring has a characteristic that at least allows such a current to flow normally. Has been.

The resistance values and capacitances connected to the first switch unit 30 and the second switch unit 40 are determined so as to satisfy the following conditions (1) to (4). ing.
(1) The time constant T11 (= r12 · c1) defined by the resistance value r12 of the second resistance element R12 and the capacitance c1 of the capacitor C in the first switch unit 30 is It is larger than the time constant T21 (= r22 · c2) defined by the resistance value r22 of the two-resistance element R22 and the capacitance (gate capacitance) c2 considered as a parasitic capacitance between the reception terminal and the input terminal. (T21 <T11).
(2) The time constant T22 (=) defined by the resistance value r21 of the first resistance element R21 in the second switch section 40 and the capacitance c2 considered as a parasitic capacitance between the reception terminal and the input terminal. r21 · c2) is larger than the time constant T12 (= r11 · c1) defined by the resistance value r11 of the first resistance element R11 and the capacitance c1 of the capacitor C in the first switch unit 30 (T22). > T12).
(3) The first resistance element R21 in the second switch unit 40 has a sufficiently larger resistance value than the second resistance element R22 (r22 << r21).
(4) The first resistance element R11 in the first switch unit 30 has a sufficiently larger resistance value than the second resistance element R12 (r12 << r11).

Based on these conditions, in the present embodiment, the following values are determined as the respective values when the level Vcc of the power supplied from the power supply unit 100 is 12V.
The resistance value r11 of the first resistance element R11 in the first switch unit 30 is 4.7 kΩ.
The resistance value r12 of the second resistance element R12 in the first switch unit 30 is 375Ω.
-Capacitance c1 of the capacitor C in the first switch unit 30: 0.047 μF
The resistance value r21 of the first resistance element R21 in the second switch unit 40: 300 kΩ
The resistance value r22 of the second resistance element R22 in the second switch unit 40: 1 kΩ
-Gate capacitance c2 in the second switch section 40: 2000 pF
2. Operation of Load Drive Device 1 Next, the operation of the load drive device 1 after the electronic control device is activated will be described with reference to FIGS. The electronic control unit is activated when the power switch 400 is switched to the on side.

  First, immediately after the start of the electronic control device, the control circuit outputs an H level signal (here, the same signal level as the power supply from the power supply unit 100) to the load driving device 1 side (see “Startup” in FIG. 2). "reference).

  At this time, the outputs from the power supply terminal 10 and the control circuit are each at the H level, and both the first switch unit 30 and the second switch unit 40 follow the path composed of the first and second resistance elements. An appropriate current does not flow, and an appropriate divided power source is not applied between the input terminal and the receiving terminal, so that the conduction of the supply path is not performed.

  Thereafter, after a predetermined initialization process is performed, the electronic control unit outputs an L level (here, ground level) signal from the control circuit to the load driving unit 1 side ("drive" in the figure). reference).

  Here, the time constant T11 (= r12 · c1) defined by the resistance value r12 of the second resistance element R12 and the capacitance c1 of the capacitor C in the first switch unit 30 is the time in the second switch unit 40. It is larger than the constant T21 (= r22 · c2) (T21 <T11).

  Therefore, even if the L level signal is input to the second resistance elements R12 and R22 at the same timing to the first switch section 30 and the second switch section 40 side, The time until the signal level on the one resistance element side becomes the L level is longer in the first switch unit 30.

  As a result, the time until the appropriate divided power supply is applied between the input terminal and the reception terminal is also longer in the second switch unit, and as a result, the timing t1 at which the first switch unit conducts the supply path. Is later than the timing t2 in the second switch section (see t1 and t2 in the figure; t2 <t1).

  Thus, the supply path is made conductive by the first switch unit 30 and the second switch unit 40, and thereafter, the operation of the load unit 200 that receives the power supplied from the power supply unit 100 is started.

  Thereafter, if a short circuit occurs in the supply path under the condition where the supply path is made conductive by the first switch unit 30 and the second switch unit 40, the short circuit current at the time of the short circuit is determined by the difference in capacity. Most of them flow only through the conduction path in the second switch unit 40.

  If the short circuit here is temporary, a short circuit current flows through the second switch unit 40 while the short circuit is occurring, so that the power supply to the load unit 200 is interrupted. The power supply is continued before and after the short circuit occurs.

  On the other hand, even if the short circuit here is continuous, since the short circuit current flows through the second switch unit 40 at least until the supply path is opened by the protection device 300, the load is loaded for a certain period. The power supply to the unit 200 is continued.

  Further, when the conduction of the supply path by each of the first switch unit 30 and the second switch unit 40 is terminated, the electronic control unit outputs a signal output from the control circuit, that is, the other end of the second resistance elements R12 and R22. The signal level on the side is returned from the L level to the H level (see “END” in FIG. 3).

  Here, the time constant T22 (= r21 · c2) defined by the resistance value r21 of the first resistance element R21 and the capacitance c2 between the input terminal and the reception terminal in the second switch unit 30 is the first value. Is larger than the time constant T12 (= r11 · c1) in the switch unit 30 (T22> T12).

  Therefore, even if the signal levels of the other ends of the second resistance elements R12 and R22 in the first switch section 30 and the second switch section 40 are returned from the L level to the H level at the same timing, the second resistance elements The time until the signal level on one end side of R12 and R22 returns to the H level is longer in the second switch unit 40.

As a result, the time until the divided power supply is not properly applied between the input terminal and the receiving terminal is longer in the second switch unit 40, and as a result, the first switch unit 30 is connected to the supply path. The timing t3 at which the conduction is ended is earlier than the timing t4 in the second switch section 40 (see t3 and t4 in the figure; t3 <t4).
3. Operation and Effect With the load driving device 1 configured as described above, a temporary short circuit occurs in the supply path in a state where the supply path is conducted by the first switch unit 30 and the second switch unit 40. Even if it does, since the electric current which flows through a supply path | route at that time can be normally sent through the conduction | electrical_connection path | route by the 2nd switch part 40 (that is, without being damaged), operation | movement of the load part 200 can be continued also in the meantime. it can.

  Further, even if a continuous short circuit occurs, the current flowing through the supply path can be continuously supplied to the conduction path by the second switch unit 40 at that time, and thus the protection device 300 mounted on the supply path. Thus, at least the operation of the load section can be continued until the supply path is opened.

  Thereby, for example, it is suitable for use as a device for driving the load unit 200 that requires safety and reliability for its operation, such as an engine, a brake, a headlamp, and a power window in a vehicle.

  Even if a short circuit occurs, the vehicle's engine, brakes, headlamps, power window, etc. can be operated continuously for a certain period of time. This is because it can be lowered.

  In the above embodiment, since the supply path can be conducted by each of the two switch units, even if one of the switch units breaks down, the conduction of the supply path can be continued by the other switch unit.

  Further, in the above-described embodiment, the first switch unit 30 and the second switch unit 40 in the load driving device 1 are paths before branching among the supply paths branching into a plurality of paths. Connected in part. Therefore, it becomes possible to operate a plurality of load units integrally with one load drive device 1, and it is not necessary to provide the load drive device 1 for each of the plurality of load units 200. This effect becomes more prominent as the number of load sections increases from the viewpoint of manufacturing cost and apparatus simplification.

  Further, in the above embodiment, the signal level at the other end is set to the H level as the initial value for each of the second resistance elements R12 and R22 in each switch unit, and the signal level is set to the L level during the driving period of the load unit 200. By changing to, conduction of the supply path by each switch unit can be realized.

  In the above-described embodiment, the time constant defined by the resistance value of the second resistance element and the capacitance between the input terminal and the reception terminal is higher in the first switch unit 30 than in the second switch unit 40. It is getting bigger. Therefore, even if the signal level of the other end of the second resistance element in the first switch unit 30 and the second switch unit 40 is changed from the H level to the L level at the same timing, the one end side of the second resistance element The time until the signal level reaches the L level is longer in the first switch unit 30.

  As a result, the first switch unit 30 also conducts the supply path as a result of the first switch unit 30 becoming longer in the time until an appropriate divided power supply is applied between the input terminal and the reception terminal. The timing is later than the timing in the second switch unit 40.

  Thus, since the conduction of the supply path by the second switch unit 40 can be performed before the conduction by the first switch unit 30, the supply path by the first switch unit 30 and the second switch unit 40. It is possible to prevent the first switch unit 30 from being damaged even in a situation where a short circuit has already occurred in the supply path prior to conducting the current.

  In the above embodiment, the second switch unit 40 has a time constant defined by the resistance value of the first resistance element and the capacitance between the input terminal and the reception terminal in the second switch unit 40 rather than in the first switch unit 30. It is getting bigger. Therefore, even if the signal level of each of the other ends of the second resistance elements in the first switch unit 30 and the second switch unit 40 is returned from the L level to the H level at the same timing, one end side of the second resistance element The time until the signal level returns to the H level is longer in the second switch unit 40.

  As a result, the time until the divided power supply is not properly applied between the input terminal and the receiving terminal is longer in the second switch unit 40, and as a result, the first switch unit 30 is connected to the supply path. The timing to end the conduction is earlier than the timing in the second switch unit 40.

  Thus, the end of the conduction of the supply path by the first switch unit 30 can be performed before the conduction by the second switch unit 40, so that the first switch unit 30 and the second switch unit 40 It is possible to prevent the first switch unit 30 from being damaged even under a situation in which a short circuit continues when terminating the conduction of the supply path.

  Moreover, in the said embodiment, 1st resistance element R21 which determines the voltage-divided power supply applied between an acceptance terminal-input terminal among 1st resistance element R21 and 2nd resistance element R22 in the 2nd switch part 40 is the following. Since the resistance value is sufficiently larger than that of the second resistance element R22, the level of the divided power source in the power source can be made as high as possible. As a result, the conduction of the supply path can be realized even in a certain range where the level of the power supply is low as compared with the case where the first resistance element R21 does not have a sufficiently large resistance value.

  Moreover, in the said embodiment, 1st resistive element R11 which determines the voltage-divided power supply applied between an acceptance terminal-input terminal among 1st resistive element R11 in the 1st switch part 30, and 2nd resistive element R12 is as follows. Since the resistance value is sufficiently larger than that of the second resistance element R12, the level of the divided power supply in the power supply can be made as high as possible. As a result, it is possible to realize conduction of the supply path even in a certain range where the level of the power supply is low as compared with the case where the first resistance element R11 does not have a sufficiently large resistance value.

  Moreover, in the said embodiment, the resistance value of 2nd resistive element R12 in the 1st switch part 30 is a sufficiently small value compared with 1st resistive element R11. Therefore, it is possible to sufficiently suppress the heat generation of the second resistance element R12 when the first switch unit 30 is conducting through the supply path.

In the above embodiment, the resistance value r11 of the first resistance element R11 is sufficiently larger than the resistance value r12 of the second resistance element R12. Therefore, normally, as shown in [Expression a] below, an output current (a signal that is an output from the first switch unit 30) Iout to be determined based on the first resistance element R11 and the second resistance element R12, As shown in [Expression b] below, it can be determined without considering the resistance value r11 of the first resistance element R11.
[Formula a] Iout = (((((Vcc · Vbe) ^ 2) / R12) − (Vbe / R11)) · Hfe
[Formula b] Iout = (((((Vcc · Vbe) ^ 2) / R12)) · Hfe
* Vcc: voltage of the power supplied from the power supply unit 100 Vbe: voltage between the base terminal and the emitter terminal in the first switch unit 30 Hfe: direct current amplification factor in the first switch unit 30 The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various forms can be taken as long as they belong to the technical scope of the present invention. Nor.

  For example, in the above-described embodiment, the first switch unit 30 and the second switch unit 40 in the load driving device 1 are paths before branching among the supply paths branching into a plurality of paths. The structure connected in the part was illustrated. However, the load driving device 1 composed of these switch units may be provided for each path portion after branching.

  Moreover, in the said embodiment, what used the field effect transistor as the 2nd switch part 40 was illustrated. However, the second switch unit 40 may be any device that can flow a short-circuit current, and may be an IGBT, for example.

Circuit diagram showing overall configuration of load driving device Timing chart showing operation of load driving device (1/2) Timing chart showing the operation of the load drive device (2/2)

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Load drive device, 10 ... Power supply terminal, 20 ... Load terminal, 30 ... 1st switch part, 40 ... 2nd switch part, 100 ... Power supply part, 200 ... Load part, 300 ... Protection apparatus, 400 ... Power supply Switch, C ... capacitor, Dn ... diode, R11 ... first resistance element, R12 ... second resistance element, R21 ... first resistance element, R22 ... second resistance element, ZD ... zener diode.

Claims (8)

A load driving device that includes a first switch unit connected in series to a supply path from a power supply unit to a load unit, and drives the load unit by causing the first switch unit to conduct the supply path. There,
A second switch unit connected in series to the supply path and in parallel with the first switch unit, the second switch unit being connected to the supply path together with the first switch unit; Is configured to drive the load section,
The second switch unit uses a device that can normally flow the current flowing through the supply path to the conduction path conducted by the second switch part when at least a short circuit occurs in the supply path. A load driving device characterized by that. In the case where the supply path branches into a plurality of paths to reach each of the plurality of load units from the power supply unit,
The said 1st, 2nd switch part each is connected in the path | route part before branching from the power supply part to each of several load parts among the said supply path | routes. Load drive device. The first and second switch parts are
Switching each having a receiving terminal for receiving a command from the outside of the switch section, an input terminal connected to the power supply section side in the supply path, and an output terminal connected to the load section side in the supply path An element,
The power supply section side in the supply path is connected to the input terminal, the load section side in the supply path is connected to the output terminal, and the input terminal and the reception terminal are connected to a first resistance element (R11 in the first switch section). , The second switch part is connected via R21), and one end of a second resistance element (R12 in the first switch part, R22 in the second switch part) is connected to the receiving terminal,
When the signal level of each of the other ends of the second resistance element is changed from the initial H level to the L level, the power source (divided power source) divided by the first and second resistance elements is the input terminal. Configured to receive a signal from the reception terminal as a command from the outside as a command from the outside and to conduct between the input terminal and the output terminal. The load driving device according to claim 1, wherein the load driving device is provided. The resistance value of each resistance element in each of the first and second switch sections and the capacitance between the input terminal and the receiving terminal are the resistance of the second resistance element in the first switch section. The value r12 and the time constant T11 (= r12 · c1) defined by the capacitance c1 between the input terminal and the receiving terminal are the resistance of the second resistance element in the second switch section. The value r22 and a value determined to be larger than the time constant T21 (= r22 · c2) defined by the capacitance c2 between the input terminal and the receiving terminal (T21 <T11). The load driving device according to claim 3, wherein the load driving device is defined. The resistance value of each resistance element in each of the first and second switch sections and the capacitance between the input terminal and the reception terminal are the resistance of the first resistance element in the second switch section. The value r21 and the time constant T22 (= r21 · c2) defined by the capacitance c2 between the input terminal and the receiving terminal are the resistance of the first resistance element in the first switch section. The value r11 and the value obtained so as to be larger than the time constant T12 (= r11 · c1) defined by the capacitance c1 between the input terminal and the receiving terminal (T22> T12). The load driving device according to claim 3 or 4, wherein the load driving device is defined. In the second switch unit,
The device having a resistance value (r22 << r21) sufficiently larger than that of the second resistance element is used for the first resistance element. The load driving device described. In the first switch unit,
7. The device according to claim 3, wherein a device having a sufficiently larger resistance value (r12 << r11) than the second resistor element is used for the first resistor element. The load driving device described. In the case where the fuse provided in the supply path is configured to be blown by a current flowing due to a short circuit generated in the supply path,
For the second switch unit, a device that can normally flow a current that blows the fuse when a short circuit occurs in at least the supply path to a conduction path that is conducted by the second switch part is used. The load driving device according to claim 1, wherein the load driving device is provided.

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