Load drive device
Patent Information
- Application Number
- JP2023127181
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-08-03
- Publication Date
- 2025-02-14
Smart Images
Figure 2025022518000001_ABST
Abstract
Description
[Technical field]
[0001] The present disclosure relates to a load driver. [Background technology]
[0002] Conventionally, a load driving device has been proposed that includes a main transistor that turns on between the load and the positive terminal of a battery based on a control signal output from a control circuit, thereby causing a load current to flow from the battery through the load to ground (see, for example, Patent Document 1).
[0003] The load driver includes a main transistor, a sensing transistor, a detection resistor element, a reference resistor element, a comparison current output section, and a comparator circuit. The main transistor and the load are connected in series between the positive terminal of the battery and ground.
[0004] The terminal to which the main transistor and the load are commonly connected is referred to as a first common connection terminal. The sensing transistor is disposed between the first common connection terminal and the positive terminal of the battery, and the detection resistor element is disposed between the sensing transistor and the first common connection terminal.
[0005] The sense transistor, together with the main transistor, is controlled to be turned on based on a control signal output from the control circuit. Therefore, when the sense transistor is turned on, a sense current flows from the positive terminal of the battery through the sense transistor and the detection resistor element to the first common connection terminal. The sense current is a current proportional to the load current.
[0006] The output voltage of the battery is input to the power supply terminal of the comparator circuit. The terminal to which the sense transistor and the detection resistor element are commonly connected is referred to as the second common connection terminal. The sense voltage output from the second common connection terminal is applied to the non-inverting input terminal of the comparator circuit.
[0007] The comparison current output section and the reference resistance element are connected in series between the positive terminal of the battery and the first common connection terminal. The comparison current output section supplies a constant current to the first common connection terminal through the reference resistance element based on the output voltage of the battery.
[0008] A terminal to which the comparison current output section and the reference resistance element are commonly connected is referred to as a third common connection terminal. The threshold voltage output from the third common connection terminal is input to an inverting input terminal of the comparator circuit.
[0009] The comparator circuit compares the sense voltage with a threshold voltage based on the output voltage of the battery, and when the sense voltage is greater than the threshold voltage, the comparator circuit determines that the load current flowing through the main transistor is equal to or greater than the threshold, and outputs a high-level signal to the control circuit.
[0010] Accordingly, when the control circuit receives a high-level signal from the comparator circuit, it turns off the main transistor. That is, when the comparator circuit determines that a load current equal to or greater than the threshold flows through the main transistor, the control circuit turns off the main transistor. This makes it possible to prevent an excessive load current from flowing through the main transistor. [Prior art documents] [Patent documents]
[0011] [Patent Document 1] JP 2017-152923 A Summary of the Invention [Problem to be solved by the invention]
[0012] In the load driver of Patent Document 1, the control circuit turns off the main transistor when it determines that a load current equal to or greater than a threshold flows through the main transistor, thereby preventing the main transistor from breaking down due to an excessive load current.
[0013] However, when the main transistor is fully on, the voltage between the source terminal and the drain terminal of the main transistor becomes extremely small, so that the voltage between the first common connection terminal and ground becomes almost the same as the battery output voltage, and almost no current flows from the positive terminal of the battery through the comparison current output section to the reference resistor element.
[0014] Therefore, the threshold voltage output from the third common connection terminal to the inverting input terminal of the comparator circuit is approximately the same as the output voltage of the battery. In other words, the threshold voltage input to the inverting input terminal of the comparator circuit falls outside the input voltage range. The input voltage range is the range in which the comparator circuit itself can operate normally at the voltage input to the inverting input terminal.
[0015] Therefore, when the main transistor is fully on, the comparator circuit cannot correctly determine whether the sense voltage is greater than the threshold voltage, and therefore cannot determine whether a load current equal to or greater than the threshold flows through the main transistor.
[0016] In view of the above, an object of the present disclosure is to provide a load driving device that determines whether a load current is equal to or greater than a threshold value. [Means for solving the problem]
[0017] In order to achieve the above object, the present invention provides a load driving device for driving a load (2) disposed between a positive terminal of a power source (Ba) and a ground, comprising: a main transistor (50) disposed between a positive terminal of the power supply and a load, and configured to cause a load current to flow from the positive terminal of the power supply to the load when the main transistor is turned on; a detection circuit power supply (20) that outputs a detection power supply voltage obtained by adding a constant voltage (Vf) to a power supply output voltage (Vcc) from a power supply output terminal (20a); When a terminal to which the main transistor and the load are commonly connected is defined as a first common connection terminal (101), a first resistor element (34) is disposed between the first common connection terminal and a power supply output terminal; a comparison current output section (36) that supplies a constant current (Ik) from an output terminal of the detection circuit power supply through a first resistor element to a first common connection terminal; a second resistor element (35) disposed between the positive terminal of the power source and the first common connection terminal; a sense element (40) disposed between a positive terminal of the power supply and the second resistor element, and configured to cause a sense current proportional to a load current to flow through the second resistor element to a first common connection terminal; a comparison section (33) that determines whether or not a load current is greater than a threshold by determining whether or not an output voltage of the second common connection terminal is greater than an output voltage of the third common connection terminal based on an output voltage of a detection circuit power supply, where a terminal to which the second resistance element and the sense element are commonly connected is defined as a second common connection terminal (103) and a terminal to which the first resistance element and the comparison current output section are commonly connected is defined as a third common connection terminal (102); and an off control section (S130) that turns off the main transistor when the comparison section determines that the load current is greater than the threshold value. Therefore, the comparator determines whether the output voltage of the second common connection terminal is greater than the output voltage of the third common connection terminal based on the output voltage of the detection circuit power supply, and can therefore determine whether the load current is greater than the threshold even when the main transistor is fully on. As a result, it is possible to provide a load driver that determines whether or not a load current is equal to or greater than a threshold value. The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]
[0018] [Figure 1] 2 is a diagram showing a detailed configuration of an electric circuit of a load driving device according to a first embodiment of the present disclosure. FIG. [Diagram 2]2 is a timing chart showing a change in output voltage of a boost power supply in the first embodiment of FIG. 1. [Diagram 3] 2 is a timing chart showing changes in a first logic signal output from a logic circuit in the first embodiment of FIG. 1. [Figure 4] 2 is a timing chart showing changes in a second logic signal output from the logic circuit in the first embodiment of FIG. 1. [Diagram 5] 2 is a timing chart showing changes in the operating state of a current source of a detection circuit power supply in the first embodiment of FIG. 1. [Figure 6] 2 is a timing chart showing a change in output voltage of a detection circuit power supply in the first embodiment of FIG. 1. [Figure 7] 2 is a timing chart showing changes in the operating state of a current source of the detection circuit in the first embodiment of FIG. 1. [Figure 8] 2 is a timing chart showing a change in output voltage of a common connection terminal of a detection circuit in the first embodiment of FIG. 1. [Figure 9] 2 is a flowchart showing a control process of the logic circuit in the first embodiment of FIG. 1. [Figure 10] FIG. 4 is a diagram showing a detailed configuration of an electric circuit of a load driving device of a first comparative example in the first embodiment. [Figure 11] FIG. 4 is a diagram showing a detailed configuration of a part of an electric circuit of a load driving device of a second comparative example in the first embodiment. [Figure 12] 13 is a diagram showing a detailed configuration of a part of an electric circuit of a load driving device of a third comparative example in the first embodiment. FIG. [Figure 13] FIG. 11 is a diagram showing a detailed configuration of an electric circuit of a load driving device of a fourth comparative example in the first embodiment. [Figure 14] FIG. 11 is a diagram showing a detailed configuration of an electric circuit of a load driving device according to a second embodiment of the present disclosure. [Figure 15] FIG. 13 is a diagram showing a detailed configuration of an electric circuit of a load driving device according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings for the sake of simplicity of description.
[0020] (First embodiment) The circuit configuration of a load driving device 1 for a vehicle according to the first embodiment is shown in Fig. 1. The load driving device 1 according to the present embodiment is a circuit that drives a load 2 mounted on an automobile.
[0021] In this embodiment, the load 2 may be, for example, various electrical devices such as a light-emitting element, an electric motor, etc. Specifically, the load driving device 1 includes a boost power supply 10, a detection circuit power supply 20, a detection circuit 30, a sensing transistor 40, a main transistor 50, and a driving circuit 60, as shown in FIG.
[0022] The boost power supply 10 is a power supply circuit that boosts an input voltage and outputs a voltage higher than the output voltage of the vehicle-mounted battery Ba from an output terminal 11. For example, the output voltage of the vehicle-mounted battery Ba is used as the input voltage. For example, a charge pump circuit that boosts the input voltage by charging and discharging a capacitor is used as the boost power supply 10.
[0023] As shown in FIG. 1, the detection circuit power supply 20 includes transistors 21a and 21b, resistive elements 22a and 22b, a current source 23, transistors 24 and 25, a clamp circuit 26, and a capacitor 27.
[0024] The emitter terminals of the transistors 21a and 21b are connected to the output terminal 11 of the boost power supply 10. The base terminals of the transistors 21a and 21b are connected to the collector terminal of the transistor 21a. The collector terminal of the transistor 21a is connected to the collector terminal of the transistor 25 via the current source 23.
[0025] The emitter terminal of the transistor 25 is connected to the ground. The base terminal of the transistor 25 is connected to the logic circuit 3. The transistor 25 is controlled by the logic circuit 3 to be turned on or off, thereby connecting or disconnecting between the current source 23 and the ground.
[0026] The resistive element 22a is disposed between the emitter terminal of the transistor 21a and the output terminal 11 of the boost power supply 10. The current source 23 is a constant current source that flows a constant current Ia from the output terminal 11 of the boost power supply 10 through the emitter terminal and collector terminal of the transistor 21a and the transistor 25 to ground.
[0027] In this embodiment, the current source 23 and the transistors 21a and 21b constitute a reference current source 28 that supplies a constant current Ib from the output terminal 11 of the boost power supply 10 to the common connection terminal 100, as will be described later.
[0028] The resistive element 22b is disposed between the emitter terminal of the transistor 21b and the output terminal 11 of the boost power supply 10. The clamp circuit 26 is disposed between the positive terminal of the vehicle battery Ba.
[0029] The clamp circuit 26 generates a constant voltage between the output terminal 11 of the boost power supply 10 and the positive terminal of the vehicle battery Ba. Specifically, the clamp circuit 26 makes the voltage between the common connection terminal 100 (i.e., the base terminal of the transistor 24) and the positive terminal of the vehicle battery Ba a constant voltage.
[0030] Here, the common connection terminal 100 is a fourth common connection terminal to which the collector terminal of the transistor 21b, the anode terminal of the diode 26a of the clamp circuit 26, and the base terminal of the transistor 24 are commonly connected.
[0031] Specifically, the clamp circuit 26 includes diodes 26a, 26b connected in series between the common connection terminal 100 and the positive terminal of the vehicle-mounted battery Ba. The diodes 26a, 26b each have an anode terminal connected to the common connection terminal 100 and a cathode terminal connected to the positive terminal of the vehicle-mounted battery Ba.
[0032] The anode terminal of the diode 26a is connected to the common connection terminal 100. The cathode terminal of the diode 26a is connected to the anode terminal of the diode 26b. The cathode terminal of the diode 26b is connected to the positive terminal of the vehicle-mounted battery Ba.
[0033] Here, when the constant voltage generated between the anode terminal and the cathode terminal of each of the diodes 26a, 26b is Vf, the voltage between the common connection terminal 100 and the positive terminal of the vehicle-mounted battery Ba becomes 2Vf.
[0034] The transistor 24 is a current amplifying transistor that amplifies a current flowing from the common connection terminal 100 to the base terminal and flows the output current between the collector terminal and the emitter terminal. That is, the transistor 24 constitutes an emitter follower circuit.
[0035] Here, when the constant voltage between the base terminal and the emitter terminal of the transistor 24 is Vf, the voltage between the emitter terminal of the transistor 24 (i.e., the power output terminal 20a) and the positive terminal of the vehicle battery Ba becomes a constant voltage (i.e., Vf). In the transistor 24, the base terminal constitutes the control terminal, the collector terminal constitutes the input terminal, and the emitter terminal constitutes the output terminal.
[0036] In this embodiment, the emitter terminal of the transistor 24 and the capacitor 27 are connected to the power output terminal 20a of the detection circuit power supply 20. Therefore, when the output voltage of the vehicle battery Ba is Vcc, the voltage between the power output terminal 20a of the detection circuit power supply 20 and the ground (i.e., the detection power supply voltage) becomes Vcc+Vf.
[0037] The transistor 24 in this embodiment is connected between the output terminal 11 of the boost power supply 10 and the positive terminal of the vehicle battery Ba. The collector terminal of the transistor 24 is connected to the output terminal 11 of the boost power supply 10. The base terminal of the transistor 24 is connected to the common connection terminal 100.
[0038] The capacitor 27 is disposed between the emitter terminal of the transistor 24 and the positive terminal of the vehicle battery Ba. The capacitor 27 stabilizes the voltage between the emitter terminal of the transistor 24 and the positive terminal of the vehicle battery Ba.
[0039] The detection circuit 30 determines whether a load current If flowing through the drain terminal and the source terminal of the main transistor 50 is equal to or greater than a threshold. Specifically, the detection circuit 30 includes transistors 31a and 31b, a current source 32, a comparator circuit 33, and resistance elements 34 and 35, as shown in FIG.
[0040] The transistors 31a and 31b form a current mirror circuit. The emitter terminals of the transistors 31a and 31b are connected to the power output terminal 20a of the detection circuit power supply 20. The base terminals of the transistors 31a and 31b are connected to the collector terminal of the transistor 31a.
[0041] The emitter terminal of the transistor 31a is connected to the power output terminal 20a of the detection circuit power supply 20. The collector terminal of the transistor 31a is connected to a current source 32. The current source 32 constitutes a constant current source that flows a constant current It from the power output terminal 20a of the detection circuit power supply 20 through the emitter terminal and collector terminal of the transistor 31a to ground.
[0042] The current source 32 is disposed between the emitter terminal of the transistor 31a and ground. In this embodiment, the current source 32, together with the transistors 31a and 31b, constitutes a comparison current output section 36 that passes a constant current Ik from the power output terminal 20a of the detection circuit power supply 20 to the resistor element 34, as will be described later.
[0043] The transistor 31b is disposed between the power output terminal 20a of the detection circuit power supply 20 and the common connection terminal 101. The common connection terminal 101 is a first common connection terminal to which the main transistor 50 and the load 2 are commonly connected.
[0044] As the transistor 31a operates, a constant current Ik flows between the collector terminal and the emitter terminal of the transistor 31b. The constant current Ik is a current proportional to the constant current It flowing between the collector terminal and the emitter terminal of the transistor 31a.
[0045] The resistive element 34 is a first resistive element disposed between the collector terminal of the transistor 31b and the common connection terminal 101. The resistive element 34 converts the constant current Ik flowing through the transistor 31b into a voltage.
[0046] The emitter terminal of the transistor 31b is connected to the power output terminal 20a of the detection circuit power supply 20. The collector terminal of the transistor 31b is connected to the resistive element .
[0047] It should be noted that bipolar transistors are used as the transistors 21a, 21b, 24, 25, 31a, and 31b.
[0048] A common connection terminal 102 is connected to the inverting input terminal of the comparator circuit 33. The common connection terminal 102 is a second common connection terminal to which the collector terminal of the transistor 31b and the resistive element 34 are commonly connected.
[0049] A common connection terminal 103 is connected to the non-inverting input terminal of the comparator circuit 33. The common connection terminal 103 is a third common connection terminal to which the source terminal of the sensing transistor 40 and the resistive element 35 are commonly connected.
[0050] The power supply output terminal 20a of the detection circuit power supply 20 is connected to the power supply input terminal of the comparator circuit 33. The comparator circuit 33 is a comparison unit that determines whether the output voltage VSE of the common connection terminal 103 is greater than the output voltage VRE of the common connection terminal 102, based on the voltage provided from the power supply output terminal 20a of the detection circuit power supply 20.
[0051] This determines whether the load current If flowing through the drain terminal and source terminal of the main transistor 50 is equal to or greater than the threshold value.
[0052] The output voltage VSE is a voltage between the common connection terminal 103 and the ground. As will be described later, the output voltage VSE is a voltage indicating the sense current Ih flowing between the drain terminal and the source terminal of the sensing transistor 40. The output voltage VRE is a voltage indicating a threshold value to which the output voltage VSE is compared.
[0053] The sensing transistor 40 is a sensing element connected between the positive terminal of the vehicle-mounted battery Ba and the common connection terminal 103. The resistive element 35 is a second resistive element connected between the common connection terminals 101, 103. The sensing transistor 40 connects or disconnects the positive terminal of the vehicle-mounted battery Ba and the common connection terminal 103 by being turned on or off.
[0054] The drain terminal of the sense transistor 40 is connected to the positive terminal of the vehicle battery Ba. The source terminal of the sense transistor 40 is connected to the common connection terminal 103. The gate terminal of the sense transistor 40, together with the gate terminal of the main transistor 50, is connected to the output terminal of the drive circuit 60.
[0055] Here, a sense current Ih proportional to a load current If flowing between the drain terminal and the source terminal of the main transistor 50 flows between the drain terminal and the source terminal of the sensing transistor 40 .
[0056] Therefore, the comparator circuit 33 determines whether the output voltage VSE of the common connection terminal 103 is greater than the output voltage VRE of the common connection terminal 102, thereby determining whether the load current If is greater than a threshold value.
[0057] In this embodiment, the sensing transistor 40 is an n-channel MOSFET.
[0058] The main transistor 50 is connected between the positive terminal of the vehicle-mounted battery Ba and the common connection terminal 101. The main transistor 50 connects or disconnects the positive terminal of the vehicle-mounted battery Ba and the common connection terminal 101 by turning on or off.
[0059] The drain terminal of the main transistor 50 is connected to the positive terminal of the vehicle-mounted battery Ba. The source terminal of the main transistor 50 is connected to the common connection terminal 101.
[0060] In this embodiment, the main transistor 50 is an n-channel MOSFET.
[0061] The drive circuit 60 is controlled by the logic circuit 3 to control the sensing transistor 40 and the main transistor 50. The drive circuit 60 is operated by the output voltage of the boost power supply .
[0062] The logic circuit 3 is composed of a microcomputer, a memory, etc. The logic circuit 3 controls the sensing transistor 40 and the main transistor 50 based on the output signal of the comparator circuit 33 and the output signal of the electronic control device.
[0063] Next, the operation of the load driving device 1 of this embodiment will be described with reference to FIGS. 2, 3, 4, 5, 6, 7, 8 and 9. FIG.
[0064] Fig. 2 is a timing chart of the output voltage of the boost power supply 10. Fig. 3 is a timing chart of a first logic signal output from the logic circuit 3 to the boost power supply 10. Fig. 4 is a timing chart of a second logic signal output from the logic circuit 3 to the transistor 25.
[0065] Fig. 5 is a timing chart showing the operation state of the current source 23. Fig. 6 is a timing chart showing the output voltage of the detection circuit power supply 20. Fig. 7 is a timing chart showing the operation state of the current source 32. Fig. 8 is a timing chart showing the output voltage of the common connection terminal 102.
[0066] 2, when the vehicle power switch is turned on, the output voltage of the vehicle battery Ba is applied to the load driving device 1 via the vehicle power switch. After that, at timing tb, when the logic circuit 3 receives a start signal from an electronic control device (not shown), the signal level of the first logic signal output from the logic circuit 3 to the boost power supply 10 transitions from a low level to a high level, as shown in FIG.
[0067] Accordingly, the boost power supply 10 boosts the output voltage (ie, input voltage) of the vehicle-mounted battery Ba, and outputs to the detection circuit power supply 20 an output voltage higher than the output voltage of the vehicle-mounted battery Ba. Next, at timing tc, when the logic circuit 3 receives a load drive command signal from the electronic control device, the signal level of the second logic signal provided from the logic circuit 3 to the base terminal of the transistor 25 transitions from a low level to a high level, as shown in FIG. 4.
[0068] The load drive command signal is a signal that the electronic control device uses to command the load drive device 1 to drive the load 2. Then, the transistor 25 turns on based on the second logic signal from the logic circuit 3. Therefore, the transistor 25 is a switch that connects between the current source 23 and the ground.
[0069] That is, the logic circuit 3, as a first switch control section, turns on the transistor 25 to connect between the reference current source 28 and the ground. At this time, the current source 23 of the reference current source 28 changes from an OFF state to an ON state based on the output voltage of the boost power supply 10, as shown in FIG.
[0070] Therefore, the current source 23 causes a constant current Ia to flow from the output terminal 11 of the boost power supply 10 through the resistor element 22a, the emitter and collector terminals of the transistor 21a, the current source 23, and the emitter and collector terminals of the transistor 25 to ground.
[0071] Accordingly, a constant current Ib proportional to the constant current Ia flows from the output terminal 11 of the boost power supply 10 to the common connection terminal 100 through the resistor element 22b, the emitter terminal and the collector terminal of the transistor 21b.
[0072] At this time, a current Is flows from the common connection terminal 100 to the positive terminal of the vehicle battery Ba through the clamp circuit 26. Accordingly, the voltage between the common connection terminal 100 and the positive terminal of the vehicle battery Ba becomes 2Vf. The current Is is a portion of the constant current Ib that flows from the common connection terminal 100 to the clamp circuit 26.
[0073] Meanwhile, a base current flows from the common connection terminal 100 to the base terminal of the transistor 24. This causes the transistor 24 to turn on based on the base current. This causes an output current to flow from the output terminal 11 of the boost power supply 10 through the collector terminal and emitter terminal of the transistor 24 to the power supply output terminal 20a.
[0074] Here, the base current is the current other than the current Is (i.e., a part of the current) of the constant current Ib. The output current is the current obtained by amplifying the base current. As a result, the transistor 24 operates as an emitter follower circuit, and an output current larger than the base current flows between the collector terminal and the emitter terminal of the transistor 24.
[0075] In this case, the output voltage of the vehicle-mounted battery Ba is the battery voltage, and Vf is the constant voltage between the base terminal and the emitter terminal of the transistor 24. If the voltage obtained by adding Vf to the battery voltage is the battery voltage +Vf, then the output voltage output from the power output terminal 20a of the detection circuit power supply 20 to the detection circuit 30 becomes the battery voltage +Vf, as shown in Fig. 6.
[0076] 7, the current source 32 is turned on based on the output voltage of the power supply output terminal 20a of the detection circuit power supply 20. At this time, the current source 32 causes a constant current It to flow from the power supply output terminal 20a through the collector terminal and emitter terminal of the transistor 31a and the current source 32 to ground.
[0077] At this time, a constant current Ik flows from the power supply output terminal 20a to the ground through the collector terminal and emitter terminal of the transistor 31b, the resistive element 34, and the load 2. The constant current Ik is an output current proportional to the constant current It.
[0078] At this time, the output voltage of the power supply output terminal 20a of the detection circuit power supply 20 is applied to the power supply terminal of the comparator circuit 33. Therefore, the comparator circuit 33 operates by the voltage output from the power supply output terminal 20a of the detection circuit power supply 20.
[0079] When the signal level of the drive signal applied from the drive circuit 60 to the gate terminal of the sensing transistor 40 and the gate terminal of the main transistor 50 becomes high, the sensing transistor 40 and the main transistor 50 are both turned on.
[0080] At this time, the main transistor 50 connects between the positive terminal of the vehicle-mounted battery Ba and the load 2. This causes a load current If to flow from the positive terminal of the vehicle-mounted battery Ba through the main transistor 50 and the load 2 to ground.
[0081] On the other hand, a sense current Ih flows from the positive terminal of the vehicle-mounted battery Ba to ground through the sensing transistor 40 and the load 2. The sense current Ih is a current proportional to the load current If.
[0082] Furthermore, at timing tc in FIG. 8, when the output voltage is applied from the power output terminal 20a of the detection circuit power supply 20 to the detection circuit 30, the output voltage of the common connection terminal 102 rises and the output voltage VRE is output from the common connection terminal 102.
[0083] This output voltage VRE is supplied to an inverting input terminal of the comparator circuit 33. On the other hand, the output voltage VSE of the common connection terminal 103 is supplied to a non-inverting input terminal of the comparator circuit 33.
[0084] Here, the output voltage VRE is the voltage between the common connection terminal 102 and the ground, and is a voltage indicating a threshold value. The output voltage VSE is the voltage between the common connection terminal 103 and the ground, and is a voltage indicating the sense current Ih.
[0085] Thus, the comparator circuit 33 compares the output voltage VRE of the common connection terminal 102 with the output voltage VSE of the common connection terminal 103 using the voltage output from the detection circuit power supply 20, thereby comparing the load current If with the threshold value.
[0086] For example, the load current If flows normally from the positive terminal of the vehicle-mounted battery Ba to ground through the main transistor 50 and the load 2. In this case, the current value of the sense current Ih flowing from the positive terminal of the vehicle-mounted battery Ba to ground through the sensing transistor 40 and the load 2 is small. Therefore, the output voltage VSE of the common connection terminal 103 is smaller than the output voltage VRE of the common connection terminal 102.
[0087] Therefore, the comparator circuit 33 determines that the load current If is less than the threshold value. Therefore, the level of the output signal output from the comparator circuit 33 to the logic circuit 3 becomes low. This means that the comparator circuit 33 outputs an enabling command to the logic circuit 3 to enable the main transistor 50 to be turned on.
[0088] For example, when a short circuit occurs between the common connection terminal 101 and ground, bypassing the load 2, an excessive load current If flows from the positive terminal of the vehicle-mounted battery Ba to ground through the main transistor 50. In this case, the value of the sense current Ih that flows from the positive terminal of the vehicle-mounted battery Ba to ground through the sensing transistor 40 becomes large.
[0089] At this time, the output voltage VSE of the common connection terminal 103 becomes greater than the output voltage VRE of the common connection terminal 102. For this reason, the comparator circuit 33 determines that the load current If is greater than the threshold value.
[0090] As a result, the level of the output signal output from the comparator circuit 33 to the logic circuit 3 becomes high. This means that the comparator circuit 33 outputs an inhibition command to the logic circuit 3 to inhibit the main transistor 50 from being turned on.
[0091] The logic circuit 3 of the present embodiment controls the sensing transistor 40 and the main transistor 50 based on the output signal of the comparator circuit 33 . Specifically, the logic circuit 3 repeatedly executes the control process according to the flowchart of Fig. 9. Fig. 9 is a flowchart showing the control process performed by the logic circuit 3.
[0092] First, in step S100, the logic circuit 3 determines whether or not an ON command for turning on the main transistor 50 has been received from the electronic control device.
[0093] At this time, when the logic circuit 3 has not received an ON command from the electronic control device, the logic circuit 3 determines NO in step S100. Accordingly, in step S130, the logic circuit 3 outputs an OFF control signal to the drive circuit 60 to turn off the main transistor 50.
[0094] Accordingly, the signal level of the drive signal provided from the drive circuit 60 to the gate terminal of the sensing transistor 40 and the gate terminal of the main transistor 50 becomes low, thereby turning off both the sensing transistor 40 and the main transistor 50.
[0095] At this time, the sense transistor 40 opens the gap between the positive terminal of the vehicle battery Ba and the load 2. The main transistor 50 opens the gap between the positive terminal of the vehicle battery Ba and the load 2.
[0096] On the other hand, when the logic circuit 3 receives an ON command from the electronic control device, the logic circuit 3 determines YES in step S100. At this time, the logic circuit 3 outputs an ON control signal for turning on the main transistor 50 to the drive circuit 60 in step S110.
[0097] Accordingly, the signal level of the drive signal provided from the drive circuit 60 to the gate terminal of the sensing transistor 40 and the gate terminal of the main transistor 50 becomes high, thereby turning on both the sensing transistor 40 and the main transistor 50.
[0098] At this time, the sense transistor 40 connects between the positive terminal of the vehicle-mounted battery Ba and the load 2. The main transistor 50 connects between the positive terminal of the vehicle-mounted battery Ba and the load 2.
[0099] As a result, a load current If flows from the positive terminal of the vehicle-mounted battery Ba to ground through the main transistor 50 and the load 2. A sense current Ih flows from the positive terminal of the vehicle-mounted battery Ba to ground through the sensing transistor 40 and the load 2.
[0100] Next, in step S120, the logic circuit 3 determines whether or not it has received from the comparator circuit 33 an inhibition command for inhibiting the main transistor 50 from being turned on.
[0101] At this time, when the signal level output from the comparator circuit 33 to the logic circuit 3 is at a low level, the logic circuit 3 determines that an inhibition command has not been received from the comparator circuit 33 and makes a NO determination in step S120.
[0102] That is, the logic circuit 3 determines that it has received an authorization command permitting turning on of the main transistor 50 from the comparator circuit 33. Accordingly, the logic circuit 3 returns to the ON process of step S110.
[0103] Therefore, the logic circuit 3 repeats the NO determination in step S120 and the ON process in step S110 as long as it determines that the permission command has been received from the comparator circuit 33. This causes the sensing transistor 40 and the main transistor 50 to be maintained in an ON state.
[0104] Thereafter, when the signal level output from the comparator circuit 33 to the logic circuit 3 changes from low to high, the logic circuit 3 determines in step S120 that an inhibition command has been received from the comparator circuit 33 and makes a YES determination.
[0105] At this time, the logic circuit 3 outputs an OFF control signal for turning off the main transistor 50 to the drive circuit 60 in step S130.
[0106] Accordingly, the signal level of the drive signal provided from the drive circuit 60 to the gate terminal of the sensing transistor 40 and the gate terminal of the main transistor 50 becomes low, thereby turning off both the sensing transistor 40 and the main transistor 50.
[0107] At this time, the sense transistor 40 opens the gap between the positive terminal of the vehicle battery Ba and the load 2. The main transistor 50 opens the gap between the positive terminal of the vehicle battery Ba and the load 2.
[0108] This stops the load current If from flowing from the positive terminal of the vehicle-mounted battery Ba to ground through the main transistor 50 and the load 2. The sense current Ih from flowing from the positive terminal of the vehicle-mounted battery Ba to ground through the sensing transistor 40 and the load 2 is stopped.
[0109] Furthermore, when the logic circuit 3 receives a load drive stop signal from the electronic control device, the signal level of the second logic signal provided from the logic circuit 3 to the base terminal of the transistor 25 transitions from high level to low level.
[0110] The load drive stop signal is a signal that the electronic control device sends to the load drive device 1 to stop driving the load 2. Then, the transistor 25 turns off based on the second logic signal from the logic circuit 3. As a result, the transistor 25 opens the gap between the current source 23 and the ground.
[0111] That is, the logic circuit 3, functioning as the second switch control section, turns off the transistor 25 to open the connection between the reference current source 28 and the ground. At this time, the current source 23 changes from the on state to the off state.
[0112] As a result, the transistors 21a, 21b, and the transistor 24 are turned off. At this time, the transistors 31a and 31b are turned off, and the current source 32 is turned off. As a result, the constant current Ik stops flowing from the power supply output terminal 20a through the transistor 31b, the resistive element 34, and the load 2 to the ground.
[0113] According to the present embodiment described above, the load driving device 1 includes a driving circuit 60 that drives the load 2 arranged between the positive terminal of the vehicle-mounted battery Ba and ground.
[0114] The main transistor 50 is disposed between the positive terminal of the vehicle-mounted battery Ba and the load 2, and when turned on, causes a load current If to flow from the positive terminal of the vehicle-mounted battery Ba to ground through the load 2. The detection circuit power supply 20 outputs a detection power supply voltage, which is the sum of the output voltage Vcc of the vehicle-mounted battery Ba and a constant voltage Vf, from a power supply output terminal 20a.
[0115] When a terminal to which the main transistor 50 and the load 2 are commonly connected is defined as a common connection terminal 101, the resistive element 34 is disposed between the common connection terminal 101 and the power supply output terminal 20a.
[0116] The comparison current output section 36 causes a constant current Ik to flow from the power output terminal 20a of the detection circuit power supply 20 to the common connection terminal 101 through the resistive element 34. The resistive element 34 is disposed between the common connection terminals 102 and 101.
[0117] The sensing transistor 40 is disposed between the positive terminal of the vehicle-mounted battery Ba and the resistance element 35 , and passes a sense current Ih proportional to the load current If through the resistance element 35 to the common connection terminal 101 .
[0118] A terminal to which the resistance element 34 and the comparison current output section 36 are commonly connected is referred to as a common connection terminal 102 , and a terminal to which the resistance element 35 and the sensing transistor 40 are commonly connected is referred to as a common connection terminal 103 .
[0119] The comparator circuit 33 determines whether the load current If is greater than a threshold by determining whether the output voltage VSE of the common connection terminal 103 is greater than the output voltage VRE of the common connection terminal 102 based on the output voltage of the detection circuit power supply 20.
[0120] The comparator circuit 33 determines that the load current If is greater than the threshold value when the output voltage VSE of the common connection terminal 103 is greater than the output voltage VRE of the common connection terminal 102. Accordingly, the logic circuit 3 includes, as an off control unit, step S130 for controlling the drive circuit 60 to turn off the main transistor 50.
[0121] Therefore, the comparator circuit 33 determines whether the output voltage VSE of the common connection terminal 103 is greater than the output voltage VRE of the common connection terminal 102 based on the output voltage of the detection circuit power supply 20.
[0122] Therefore, even when the main transistor 50 is fully on, it is possible to determine whether the load current If is greater than the threshold value. As a result, it is possible to provide a load driving device 1 that determines whether the load current If is equal to or greater than a threshold value.
[0123] Also, as shown in FIG. 10, a load driving device 1A in which a control circuit 3A controls a main transistor 50 and a sensing transistor 40 based on an output signal of a comparator circuit 33 is considered. 10, the comparison current output section 36 passes a constant current through the resistance element 34 to the common connection terminal 101 based on the output voltage of the vehicle-mounted battery Ba, not based on the detection circuit power supply 20. As a result, the output voltage VRE is applied from the common connection terminal 102 to the inverting input terminal of the comparator circuit 33.
[0124] However, when the main transistor 50 is in a fully-on state, the voltage between the drain terminal and the source terminal of the main transistor 50 becomes extremely small, so that the voltage between the common connection terminal 101 and the ground becomes approximately the same as the output voltage of the vehicle battery Ba.
[0125] Therefore, the comparison current flowing from the comparison current output section 36 to the resistance element 34 decreases. The comparison current stops flowing from the comparison current output section 36 to the resistance element 34 .
[0126] As a result, the output voltage VRE (i.e., threshold voltage) provided from the common connection terminal 102 to the inverting input terminal of the comparator circuit 33 becomes substantially the same as the output voltage of the in-vehicle battery Ba. In other words, a normal threshold voltage cannot be output from the common connection terminal 102 to the inverting input terminal of the comparator circuit 33.
[0127] Therefore, when the comparator circuit 33 is operated by the output voltage of the vehicle-mounted battery Ba, the comparator circuit 33 cannot operate normally.
[0128] This causes a problem that, when the main transistor 50 is fully on, the comparator circuit 33 cannot determine the load current flowing through the main transistor 50 at a normal threshold value. Note that in Fig. 10, the same reference symbols as those in Fig. 1 indicate the same things, and their explanations will be omitted.
[0129] In contrast, the comparator circuit 33 of this embodiment operates by the detection power supply voltage output from the power output terminal 20a of the detection circuit power supply 20. The detection power supply voltage is a voltage obtained by adding a constant voltage Vf to the output voltage Vcc of the vehicle-mounted battery Ba, and is greater than the output voltage Vcc of the vehicle-mounted battery Ba. This allows the comparison current output unit 36 and the comparator circuit 33 to operate correctly.
[0130] It is also possible to apply the output voltage of the boost power supply 10, which is greater than the output voltage Vcc of the vehicle battery Ba, directly to the power supply input terminal of the comparator circuit 33. However, since the output voltage of the boost power supply 10 contains a large amount of ripple, there is a risk of deterioration in the accuracy of the output current of the current source in the detection circuit 30 and malfunction due to noise.
[0131] In order to suppress ripples contained in the output voltage of the boost power supply 10, it is possible to provide a CR filter 29 as shown in Fig. 11. The CR filter 29 includes a resistive element 22X and a capacitor 27X that are connected in series between the output terminal 11 of the boost power supply 10 and the positive terminal of the vehicle battery Ba.
[0132] Here, when the CR filter 29 is configured as a part of a semiconductor power switch such as an IPD, the resistance value of the resistive element 22X is large and the capacitance of the capacitor 27X is small. Therefore, the resistive element 22X limits the current flowing from the output terminal 28a of the CR filter 29 to the detection circuit 30. Therefore, there are cases where the current required for the detection circuit 30 cannot be flowed from the output terminal 28a of the CR filter 29 to the detection circuit 30.
[0133] 12, a transistor 24X may be disposed between the output terminal 11 of the boost power supply 10 and the detection circuit 30 to configure an emitter follower circuit. In this case, the transistor 24X can pass a necessary current to the detection circuit 30.
[0134] However, when a ripple larger than the constant voltage Vf between the base terminal and the emitter terminal of the transistor 24X occurs in the output voltage of the boost power supply 10, the transistor 24X cannot remove the noise contained in the output voltage of the boost power supply 10. As a result, the transistor 24X outputs an output voltage containing noise to the detection circuit 30. This may cause the detection circuit 30 to malfunction.
[0135] In contrast, the transistor 24 of this embodiment uses the clamp circuit 26 to clamp the output voltage of the boost power supply 10 to a voltage sufficiently low for output to the detection circuit 30. Therefore, the output voltage provided from the transistor 24 to the detection circuit 30 is not affected by excessive ripples, and there is no risk of the detection circuit 30 malfunctioning.
[0136] Furthermore, as shown in FIG. 13, in the load driving device 1B, a current mirror circuit 210 may be provided which includes transistors 210a and 210b and supplies a constant current Im to the detection circuit 30A based on the output voltage of the boost power supply 10 (i.e., a charge pump circuit).
[0137] The detection circuit 30A compares the output voltage of the common connection terminal 103 with a threshold voltage based on the power supply voltage output from the current mirror circuit 210.
[0138] When the detection circuit 30A determines that the output voltage of the common connection terminal 103 is greater than the threshold voltage, it turns on the transistor 65. Therefore, regardless of the output of the drive circuit 60, the sensing transistor 40 and the main transistor 50 can be turned off.
[0139] However, when the detection circuit 30A requires a current exceeding the constant current Im output by the current mirror circuit 210, the power supply voltage output from the current mirror circuit 210 to the detection circuit 30A becomes unstable, causing the operation state of the detection circuit 30A to become unstable.
[0140] In contrast, in the detection circuit power supply 20 of the present embodiment, an emitter follower circuit is configured using the transistor 24, so that it is possible to supply a sufficiently large current from the detection circuit power supply 20 to the detection circuit 30. This makes it possible to prevent the operating state of the detection circuit 30 from becoming unstable.
[0141] Second embodiment In the above first embodiment, an example in which the capacitor 27 is disposed between the power output terminal 20a of the detection circuit power supply 20 and the positive terminal of the vehicle-mounted battery Ba has been described.
[0142] However, instead of this, as shown in FIG. 14, a capacitor 27 may be disposed between the common connection terminal 100 and the positive terminal of the vehicle-mounted battery Ba.
[0143] In this case, the capacitor 27 can stabilize the voltage between the base terminal of the transistor 24 and the positive terminal of the vehicle battery Ba. Therefore, the voltage between the power output terminal 20a of the detection circuit power supply 20 and the positive terminal of the vehicle battery Ba can be stabilized. In Fig. 14, the same reference numerals as those in Fig. 1 indicate the same things, and the description thereof will be omitted.
[0144] According to the present embodiment described above, like the first embodiment, it is possible to provide a load driving device 1 that determines whether or not the load current is equal to or greater than a threshold value.
[0145] Third embodiment In the second embodiment, an example has been described in which the transistor 25 is provided in the load driving device 1 to connect or disconnect between the reference current source 28 and the ground.
[0146] However, instead of this, a third embodiment of the load driving device 1 in which a transistor 25 is provided to connect or disconnect between the comparison current output section 36 and the ground will be described with reference to FIG.
[0147] In the load driving device 1 of this embodiment, the transistors 21a and 21b, the resistive elements 22a and 22b, and the current source 23 shown in Fig. 14 are deleted. In Fig. 15, the same reference numerals as those in Fig. 14 indicate the same things, and the description thereof will be omitted.
[0148] In this embodiment, a transistor (that is, a switch) 25 is disposed between the current source 32 of the detection circuit 30 and ground. Therefore, the logic circuit 3 turns on the transistor 25 at the same timing as the main transistor 50 is turned on.
[0149] Accordingly, the transistor 25 connects between the transistor 31a and the ground. That is, the logic circuit 3, as a first switch control section, turns on the transistor 25 to connect between the comparison current output section 36 and the ground. Accordingly, a constant current Ik flows from the power output terminal 20a of the detection circuit power supply 20 to the resistance element 34 through the transistor 31b.
[0150] Therefore, the output voltage VRE is provided from the common connection terminal 102 to the inverting input terminal of the comparator circuit 33. In addition, the output voltage VSE is provided from the common connection terminal 103 to the non-inverting input terminal of the comparator circuit 33. At this time, the comparator circuit 33 can compare the output voltage VRE of the common connection terminal 102 with the output voltage VSE of the common connection terminal 103.
[0151] On the other hand, the logic circuit 3 turns off the transistor 25 at the timing when the main transistor 50 is turned off. Accordingly, the transistor 25 opens the gap between the transistor 31a and the ground. That is, the logic circuit 3, as the second switch control section, turns off the transistor 25 to open the gap between the comparison current output section 36 and the ground.
[0152] Accordingly, current stops flowing from the power output terminal 20a of the detection circuit power supply 20 through the transistor 31b and the resistor element 34 to the common connection terminal 101. In this case, the output voltage VRE stops being applied from the common connection terminal 102 to the inverting input terminal of the comparator circuit 33.
[0153] Therefore, the comparator circuit 33 stops comparing the output voltage VRE of the common connection terminal 102 with the output voltage VSE of the common connection terminal 103. According to the present embodiment described above, like the first embodiment, it is possible to provide a load driving device 1 that determines whether or not the load current is equal to or greater than a threshold value.
[0154] (Other embodiments)
[0155] (a) In the above first to third embodiments, an example has been described in which the load driving device 1 of the present disclosure is applied to a vehicle. However, instead of this, the load driving device 1 of the present disclosure may be applied to various devices other than a vehicle.
[0156] (b) In the above first to third embodiments, the boost power supply 10 is configured by a charge pump circuit. However, instead of this, the boost power supply 10 may be configured by using a boost transformer.
[0157] (c) In the above first to third embodiments, bipolar transistors are used as the transistors 21a, 21b, 24, 25, 31a, and 31b. However, instead of this, various semiconductor elements (for example, field effect transistors) other than bipolar transistors may be used as the transistors 21a, 21b, 24, 25, 31a, and 31b.
[0158] (d) In the above first to third embodiments, examples have been described in which n-channel MOSFETs are used as the sensing transistor 40 and the main transistor 50. However, instead of this, semiconductor elements other than n-channel MOSFETs (for example, bipolar transistors, insulated gate bipolar transistors) may be used. Also, p-channel MOSFETs may be used as the sensing transistor 40 and the main transistor 50.
[0159] (e) In the above first to third embodiments, an example was described in which the clamp circuit 26 was configured with two diodes 26a, 26b.
[0160] However, instead of this, the clamp circuit 26 may be configured with one diode or three or more diodes. Also, the clamp circuit 26 may be configured with elements other than diodes.
[0161] (f) In the above first to third embodiments, the output voltage VRE is provided to the inverting input terminal of the comparator circuit 33, and the output voltage VSE is provided to the non-inverting input terminal of the comparator circuit 33.
[0162] However, if the output voltage VRE and the output voltage VSE are compared, the configuration is not limited to one in which the output voltage VRE is applied to the inverting input terminal of the comparator circuit 33 and the output voltage VSE is applied to the non-inverting input terminal of the comparator circuit 33.
[0163] (g) In the above first to third embodiments, an example has been described in which the control process in Fig. 9 is executed by the microcomputer of the logic circuit 3. However, instead of this, the control process in Fig. 9 may be configured by the hardware configuration of the logic circuit 3.
[0164] (h) Note that the present disclosure is not limited to the above-described embodiments, and can be appropriately modified within the scope of the claims. Moreover, the above-described embodiments are not unrelated to each other, and can be appropriately combined, except when the combination is clearly impossible. Moreover, in each of the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except when they are specifically stated to be essential or when they are clearly considered to be essential in principle. Moreover, in each of the above-described embodiments, when the numbers, values, amounts, ranges, etc. of the components of the embodiments are mentioned, they are not limited to the specific numbers, except when they are specifically stated to be essential or when they are clearly limited to a specific number in principle. Moreover, in each of the above-described embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., except when they are specifically stated to be essential or when they are clearly limited to a specific shape, positional relationship, etc. in principle. [Explanation of symbols]
[0165] 1 Load driver 2. Load 3 Logic Circuits 20 Detection circuit power supply 20a Power output terminal 33 Comparator Circuit 34 Resistance element 35 Resistance element 36 Comparison current output section 50 Main transistor 101 Common connection terminal 103 Common connection terminal Vcc Output voltage Vf constant voltage
Claims
1. A load driving device that drives a load (2) disposed between a positive terminal of a power source (Ba) and ground, a main transistor (50) disposed between the positive terminal of the power supply and the load, and configured to cause a load current to flow from the positive terminal of the power supply to the load when the main transistor is turned on; a detection circuit power supply (20) that outputs a detection power supply voltage obtained by adding a constant voltage (Vf) to the output voltage (Vcc) of the power supply from a power supply output terminal (20a); When a terminal to which the main transistor and the load are commonly connected is defined as a first common connection terminal (101), a first resistor element (34) is disposed between the first common connection terminal and the power supply output terminal; a comparison current output section (36) that flows a constant current (Ik) from an output terminal of the detection circuit power supply through the first resistor element to the first common connection terminal; a second resistor element (35) disposed between the positive terminal of the power source and the first common connection terminal; a sense element (40) disposed between the positive terminal of the power supply and the second resistance element, and configured to pass a sense current proportional to the load current through the second resistance element to the first common connection terminal; a comparison unit (33) that determines whether the load current is greater than a threshold value by determining whether an output voltage of the second common connection terminal is greater than an output voltage of the third common connection terminal based on an output voltage of the detection circuit power supply, where a terminal to which the second resistance element and the sense element are commonly connected is a second common connection terminal (103) and a terminal to which the first resistance element and the comparison current output unit are commonly connected is a third common connection terminal (102); an off control unit (S130) that turns off the main transistor when the comparison unit determines that the load current is greater than the threshold; A load driving device comprising:
2. The detection circuit power supply a boost power supply (10) that outputs an output voltage from an output terminal (11) that is higher than an output voltage of the power supply; a clamp circuit (26) for generating a constant voltage between the positive terminal of the power supply and the output terminal of the boost power supply; a current amplifying transistor (24) having a control terminal connected to the fourth common connection terminal (100), an input terminal connected to the output terminal of the boost power supply, and an output terminal connected to the power supply output terminal (20a), where the terminal to which the output terminal of the boost power supply and the clamp circuit are commonly connected is defined as a fourth common connection terminal (100); 2. The load driving device of claim 1, wherein the current amplifying transistor outputs the detection power supply voltage from the power supply output terminal by flowing an output current, which is an amplified version of a current input from the output terminal of the boost power supply through the fourth common connection terminal, from the input terminal to the output terminal, with the constant voltage set between the control terminal and the positive terminal of the power supply by the clamp circuit.
3. 3. The load driving device of claim 2, wherein the clamp circuit has a plurality of diodes (26a, 26b) whose anode terminals are arranged on the fourth common connection terminal side and whose cathode terminals are arranged on the positive terminal side of the power supply, and the plurality of diodes are connected in series between the fourth common connection terminal and the positive terminal of the power supply.
4. 3. The load driving device according to claim 2, further comprising a capacitor (27) connected between the power supply output terminal of the detection circuit power supply and the positive terminal of the power supply to stabilize the voltage between the power supply output terminal and the positive terminal of the power supply.
5. 3. The load driving device according to claim 2, further comprising a capacitor (27) connected between the fourth common connection terminal and the positive terminal of the power supply to stabilize the voltage between the fourth common connection terminal and the positive terminal of the power supply.
6. a reference current source (28) that generates a constant current (Ib) flowing from the output terminal of the boost power supply to the fourth common connection terminal; a part of a current flowing from the output terminal of the boost power supply to the fourth common connection terminal flows from the fourth common connection terminal through the clamp circuit to a positive terminal of the power supply, whereby the clamp circuit generates the constant voltage; 3. The load driving device according to claim 2, wherein the remaining current other than the portion of the current flowing from the output terminal of the boost power supply to the fourth common connection terminal flows to the control terminal, thereby causing the output current to flow from the input terminal to the output terminal of the current amplification transistor.
7. a switch (25) that connects or disconnects the reference current source (28) and ground by turning it on or off; a first switch control section (3) that turns on the switch to connect between the reference current source and ground; a second switch control unit (3) that turns off the switch to open a connection between the reference current source and ground, When the first switch control unit turns on the switch, the output current flows from the input terminal to the output terminal of the current amplifying transistor, thereby outputting the detection power supply voltage from the power supply output terminal, 7. The load driving device of claim 6, wherein when the second switch control unit turns off the switch, the output current is stopped from flowing from the input terminal of the current amplification transistor to the output terminal, and the detection power supply voltage is stopped from being output from the power supply output terminal.
8. a switch (25) that connects or disconnects the comparison current output unit (36) and ground by turning it on or off; a first switch control section (3) that turns on the switch to connect between the comparison current output section and ground; a second switch control section (3) that turns off the switch to open a connection between the comparison current output section and ground, When the first switch control unit turns on the switch, the constant current flows from the comparison current output unit through the first resistor element to the first common connection terminal; 2. The load driving device according to claim 1, wherein when the second switch control unit turns off the switch, the flow of the constant current from the comparison current output unit through the first resistance element to the first common connection terminal is stopped.
Citation Information
Patent Citations
Load drive device
JP2017152923A