JP3676168B2 - Power supply control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply control device that controls supply of power to a large current load through a plurality of semiconductor switching elements connected in parallel.
[0002]
[Prior art]
Conventionally, this type of power supply control device is configured to supply power to a load via a semiconductor switching element (semiconductor switch) such as an FET. Therefore, to supply power to a large current load, the capacity of the switching element must be increased. I had to. However, a switching element having a large capacity is expensive and the cost of the device is increased.
[0003]
For this reason, in general, an inexpensive switching element having a relatively small capacity as shown in FIG. 5 is used in parallel connection. The power supply control device shown in FIG. 5 includes five power MOSFETs 1 connected in parallel, a driver 2 for driving these FETs 1, a charge pump 3 for supplying a predetermined voltage to the driver 2, and an overcurrent protection device. The fuse 4 is provided.
[0004]
The driver 2 supplies the power of the power source VB to the load 5 by simultaneously switching these five FETs.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional power supply control device shown in FIG. 5 described above, protection measures using the fuse 4 are taken against overcurrent caused by a short circuit of the load 5 or a short circuit of a wire harness that transmits power to the load 5. However, the fuse 4 is incapable of rare shorts (intermittent shorts) and cannot protect the wire harness or the load 5.
[0006]
The present invention has been made in order to solve the conventional problems as described above, and the object of the present invention is not to increase the cost of the apparatus and to reduce the size of the apparatus, but also to normal shorts as well as rare shorts. However, it is an object of the present invention to provide a power supply control device for a large current load that can perform a load or power line protection operation.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a feature of the invention of claim 1 is that a plurality of first semiconductor switching element groups having a plurality of overheat cutoff functions connected in parallel and the plurality of first semiconductor switching element groups are shared. A driving circuit for driving and supplying power from a power source to a load; and a switching circuit with a current oscillation type cutoff function connected in parallel to these semiconductor switching elements, and the switching circuit with the current oscillation type cutoff function The second semiconductor switching element that supplies a current from the power source to the load by switching control according to an input control signal, and the second semiconductor switching element in a state where the load is connected. A first reference voltage generating means for generating a first reference voltage having a voltage characteristic equivalent to an inter-terminal voltage characteristic; and the second semiconductor switch. A voltage that is equivalent to a voltage characteristic between the terminals of the second semiconductor switching element in a state where the load is connected, and a first detection means for detecting a difference between the voltage between the terminals of the chucking element and the first reference voltage; Second reference voltage generation means for generating a second reference voltage having characteristics; and second detection means for detecting a difference between the terminal voltage of the second semiconductor switching element and the second reference voltage; First control means for controlling on / off of the first semiconductor switching element group by the drive circuit according to a difference between the inter-terminal voltage detected by the first detection means and the first reference voltage And second control means for controlling on / off of the second semiconductor switching element according to the detection result of the second detection means.
[0008]
A feature of the invention of claim 2 is that a plurality of first semiconductor switching element groups connected in parallel and a drive circuit for driving the plurality of first semiconductor switching element groups in common and supplying power from a power source to a load And a switching circuit with a current oscillation type cutoff function connected in parallel to these semiconductor switching elements, and the switching circuit with the current oscillation type cutoff function is subjected to switching control according to an input control signal. A first semiconductor switching element for supplying a current from the power source to the load, and a first voltage characteristic equivalent to a voltage characteristic between terminals of the second semiconductor switching element in a state where the load is connected. First reference voltage generating means for generating a reference voltage of the second semiconductor switching element, a voltage between terminals of the second semiconductor switching element, and the first reference voltage A first detection means for detecting a difference; and a second reference for generating a second reference voltage having a voltage characteristic equivalent to a voltage characteristic between terminals of the second semiconductor switching element in a state where the load is connected. Voltage generating means; second detection means for detecting a difference between the terminal voltage of the second semiconductor switching element and the second reference voltage; and the terminal voltage detected by the first detection means; First control means for controlling the first semiconductor switching element group to be turned off by the drive circuit in accordance with a difference from the first reference voltage, and the second control means in accordance with a detection result of the second detection means. And a second control means for controlling on / off of the semiconductor switching element.
[0009]
The first semiconductor switching element group of the invention of claim 3 is a temperature sensor built-in FET group having an overheat cutoff function.
[0010]
The second semiconductor switching element of the invention of claim 4 is a temperature sensor built-in FET having a switching circuit with an overheat cutoff function.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of a power supply control device of the present invention. The power supply control device includes five normal thermal MOSFETs 11 connected in parallel, a driver 12 for driving these FETs 11, a charge pump 13 for supplying a predetermined voltage to the driver 12, and a current limiting circuit for the thermal MOSFET 11. A switching circuit 16 with a current oscillation type cutoff function connected in parallel via a resistor R is provided.
[0012]
The switching circuit 16 with a current oscillation type cutoff function includes a temperature sensor built-in FET 161, a driver 162 that drives the temperature sensor built-in FET 161, and a first overcurrent detection circuit 163 that detects an overcurrent flowing through the temperature sensor built-in FET 161. It has the same performance as the power supply control device disclosed in Japanese Patent Application No. 10-373877 (Japanese Patent Application Laid-Open No. 2001-36393) , has no shunt resistance, and does not require a microcomputer, so that an overload due to a short circuit on the downstream side, etc. A current can be detected.
[0013]
Here, the switching circuit 16 with the current oscillation type cutoff function of the present example includes a second overcurrent detection circuit 164 in addition to the above circuit. The second overcurrent detection circuit 164 detects an overcurrent slightly larger than that after the first overcurrent detection circuit 163 detects an overcurrent on the load 15 side, and feeds back a detection signal to the driver 162. . Further, the switching circuit 16 with the current oscillation type cutoff function of this example can be made into one chip including the above-described additional portion, and here, it is assumed that it is made into one chip.
[0014]
2 is a circuit diagram showing an internal configuration of the switching circuit 16 with a current oscillation type cutoff function shown in FIG. 1, and FIG. 3 is a circuit diagram showing an internal configuration of the temperature sensor built-in FET 161 shown in FIG. It is.
[0015]
In FIG. 2, the switching circuit 16 with a current oscillation type cutoff function of the present embodiment has a configuration in which the drain D-source S of the FET 161 with built-in temperature sensor as a semiconductor switch is connected in series to the path for supplying the power supply voltage VB to the load 15. It is. Here, an NMOS type having a DMOS structure is used for the temperature sensor built-in FET 161, but it can also be realized by a PMOS type.
[0016]
In the same figure, reference FETs QB1, QB2, resistors R1, R2, R5, R8, R10, RG, Rr, RV, Zener diode ZD1, diode D1, comparators CMP1, CMP2 are provided for the parts that drive and control the temperature sensor built-in FET 161. The configuration includes a driver 162 and a switch SW1. In addition, although "R" and the number and character which follow it are used for a resistor as a reference sign, while using it as a reference sign in the following description, it shall represent the resistance value of this resistance, respectively. Further, a portion 16 surrounded by a dotted line in FIG. 2 indicates a chip portion to be integrated in an analog manner.
[0017]
The load 15 is, for example, a headlight, a drive motor for a power window, or the like, and functions when a user or the like turns on the switch SW1. The driver 162 includes a source transistor Q5 whose collector side is connected to the potential VP and a sink transistor Q6 whose emitter side is connected to the ground potential (GND), which are connected in series, and a switching signal by switching the switch SW1 on and off. Based on the above, the source transistor Q5 and the sink transistor Q6 are turned on / off to output a signal for driving and controlling the temperature sensor built-in FET 161.
[0018]
More specifically, the temperature sensor built-in FET 161 as a semiconductor switch has a configuration as shown in FIG. In FIG. 3, the temperature sensor built-in FET QA includes a built-in resistor RG, a temperature sensor 121, a latch circuit 122, and an overheat cutoff FET QS. ZD1 is a Zener diode that bypasses the gate G when an overvoltage is applied to the gate G while maintaining the gate G and source S at 12 [V].
[0019]
In other words, when the temperature sensor 121 detects that the temperature sensor built-in FET 161 has risen to a temperature higher than a specified temperature, the temperature sensor built-in FET 161 used in this embodiment holds the detection information in the latch circuit 122. The overheat cutoff FET QS as the gate cutoff circuit is turned on to provide an overheat cutoff function for forcing the temperature sensor built-in FET 161 to be turned off.
[0020]
The temperature sensor 121 is formed by cascade-connecting four diodes, and the temperature sensor 121 is arranged and formed in the vicinity of the temperature sensor built-in FET 161 for mounting. As the temperature of the FET 161 with built-in temperature sensor increases, the resistance value of each diode of the temperature sensor 121 decreases. Therefore, when the gate potential of the FET Q51 is lowered to the “L” level, the FET Q51 changes from the on state to the off state. To do. As a result, the gate potential of the FET Q54 is pulled up to the potential of the gate control terminal (G) of the temperature sensor built-in FET QA, the FET Q54 changes from the OFF state to the ON state, and “1” is latched in the latch circuit 122. It becomes. At this time, since the output of the latch circuit 122 becomes “H” level and the overheat cutoff FET QS transits from the OFF state to the ON state, the true gate (TG) of the temperature sensor built-in FET QA and the source of the temperature sensor built-in FET QA ( SA) becomes the same potential, and the temperature sensor built-in FET QA transitions from the on state to the off state, thereby shutting off the overheat.
[0021]
Further, in the switching circuit 16 with the current oscillation type cutoff function of the present embodiment, an overcurrent due to a short-circuit fault occurring between the load 15 or the source (SA) of the FET 161 with built-in temperature sensor and the load 15 or an abnormal current due to an incomplete short-circuit fault. It also has a protection function against. Hereinafter, a configuration for realizing this protection function will be described with reference to FIG.
[0022]
First, the reference voltage generating means referred to in the claims is composed of a reference FET (second semiconductor switch) QB1 and a resistor (second load) Rr1. The drain and gate of the reference FET QB1 are connected to the drain (D) and the true gate (TG) of the temperature sensor built-in FET 161, respectively, the source (SB) of the reference FET QB1 is connected to one terminal of the resistor Rr1, and the other of the resistor Rr1 Are connected to the ground potential (GND). Thus, by integrating the drain (D) and gate (TG) of the reference FET QB1 and the temperature sensor built-in FET 161, integration on the same chip (16) can be facilitated.
[0023]
Further, the reference FET QB1 and the temperature sensor built-in FET QA are formed on the same chip (16) by the same process. Since the current detection method in this embodiment is performed by detecting the difference between the drain-source voltage VDSA of the temperature sensor built-in FET 161 and the reference voltage by the comparator CMP1, the reference FET QB and the temperature sensor built-in FET 161 are formed on the same chip. By doing so, common mode error factors in current detection, that is, the influence of power supply voltage, temperature drift and lot-to-lot variations can be eliminated (reduced). Further, since the resistor Rr1 is installed outside the chip 16, it can be made less susceptible to the influence of the temperature change of the chip 16 on the reference voltage, and highly accurate current detection can be realized.
[0024]
Further, the ratio of the number of parallel-connected transistors constituting each FET is set so that the current capacity of the reference FET QB is smaller than the current capacity of the temperature sensor built-in FET 161 (number of transistors of the reference FET QB: 1) <(temperature sensor The number of transistors of the built-in FET 161 is 1000).
[0025]
Further, the resistance value of the resistor Rr is set to be a value of resistance value of the load 102 × (number of transistors of the temperature sensor built-in FET 161: 1000 / number of transistors of the reference FET QB: 1) as described later. By setting the resistance Rr, when a load current (5 [A]) flows through the temperature sensor built-in FET 161 and a current of 5 [mA] flows through the resistor Rr1, the same drain-source voltage VDS as the temperature sensor built-in FET 161. Can be generated in the reference FET QB. Further, according to the circuit definition as described above, the configuration of the reference voltage generating means constituted by the reference FET QB and the resistor Rr can be miniaturized as much as possible, and the mounting space can be reduced and the device cost can be reduced.
[0026]
The variable resistor RV is installed outside the chip and connected in parallel to the resistor R2. The variable resistor RV is for applying a positive voltage to turn on the positive side of the comparator CMP1 after the temperature sensor built-in FET 161 is turned off. When the temperature sensor built-in FET 161 is on, the midpoint voltage of R1 and R2 is close to VB if the load is normal. When the load 15 is short-circuited, the midpoint voltage decreases, and when it becomes lower than the Rr end voltage, the comparator CMP1 is inverted. When the reference FET QB is turned off, the voltage of Rr approaches the ground potential, and the midpoint voltage becomes higher at a certain point, so that the comparator CMP1 is inverted.
[0027]
The comparator CMP1 forms part of the detection means referred to in the claims. A voltage obtained by dividing the voltage VDSA between the drain D and the source SA of the FET 161 with built-in temperature sensor by a resistor R1, a resistor R2, and a parallel resistor (R2‖RV) of the variable resistor RV is connected to the “+” input terminal of the comparator CMP1. It is supplied via R5. Further, the drain-source voltage VDSB of the reference FET QB is supplied to the "-" input terminal of the comparator CMP1. That is, when the potential supplied to the “+” input terminal is larger than the potential supplied to the “−” input terminal, the output becomes valid (“H” level), and the potential supplied to the “−” input terminal becomes “ It becomes invalid (“L” level) when the potential supplied to the “+” input terminal is small. As will be described later, the comparator CMP1 has a certain hysteresis.
[0028]
In the present embodiment, the second overcurrent detection circuit 164 includes a FET (third semiconductor switch) QB2 and a second comparator CMP2.
[0029]
Next, the operation of the present embodiment will be described. The driver 12 outputs a switching signal to the gates of five normal temperature sensor built-in FETs 11 connected in parallel, and controls the five FETs 11 to supply the power of the power source VB to the load 15. At this time, the temperature sensor built-in FET 161 of the switching circuit 16 with current oscillation type cutoff function is also switched by the driver 162, and a current flows from the power source VB to the load 15 through the resistor R. Since the switching circuit 16 with the current oscillation type cutoff function is used for overcurrent detection on the load 15 side, the current flowing to the load 15 side may be small, and therefore the capacitance of the temperature sensor built-in FET 161 may be small.
[0030]
When power is supplied to the load 15 as described above, if a short circuit occurs in the wire harness that transmits power to the load 15 or the load 15, the first overcurrent detection of the switching circuit 16 with a current oscillation type cutoff function The circuit 163 detects an overcurrent of the current flowing through the temperature sensor built-in FET 161 and outputs the detection signal to the driver 12.
[0031]
Upon receiving this detection signal, the driver 12 performs control to repeatedly turn on and off the five temperature sensor built-in FETs 11 in the case of a short circuit. In this case, since overcurrent flows through each temperature sensor built-in FET 11, The sensor built-in FET 11 is overheated in a short time, and the overcurrent flowing to the load 15 side is reliably cut off. In the case of a complete short circuit, a very large overcurrent flows through the five temperature sensor built-in FETs 11, so that these FETs 11 are instantaneously overheated and the overcurrent flowing to the load 15 side is reliably cut off. .
[0032]
However, even at this time, since the temperature sensor built-in FET 161 of the switching circuit 16 with the current vibration type cutoff function is still driven, when the supply of power from the five FETs 11 to the load 15 is stopped, the current vibration type cutoff function is provided. The switching circuit 16 tries to pass a larger current to the load 15. In that case, a resistance drop voltage larger than the resistance drop voltage of the resistor R1 is generated in the resistor R2, the overcurrent detection circuit 164 detects a larger overcurrent, and the detection signal is sent to the switching circuit 16 with the current oscillation type cutoff function. Output to the driver 162.
[0033]
When the driver 162 receives the detection signal, it performs control to repeatedly turn on and off the temperature sensor built-in FET 161. Therefore, the temperature sensor built-in FET 161 is overheated in a short time, and the switching circuit 16 with a current oscillation type cutoff function is also connected to the load 15 side. Current supply is stopped and overcurrent protection is completed.
[0034]
According to the present embodiment, when the switching circuit 16 with a current oscillation type cutoff function is connected in parallel to the five temperature sensor built-in FETs 11 connected in parallel, and an overcurrent flows to the load 15 side due to a short circuit or the like, By detecting the overcurrent using the overcurrent detection function of the switching circuit 16 with the current oscillation type cutoff function, it is possible to reliably perform overcurrent protection without using a fuse.
[0035]
In addition, the overcurrent detection function of the switching circuit 16 with the current oscillation type cutoff function is also effective for the short-circuit, and the wire harness and the like can be protected against the short-circuit by the overheat shutdown of the temperature sensor built-in FET 11. .
[0036]
Further, since the switching circuit 16 with a current oscillation type cutoff function can be made into one chip and only one is used, the number of wirings of the device is not increased, the device can be miniaturized, and its current supply capacity Since it is only necessary to use an inexpensive low-capacity type that is sufficient to operate the overcurrent detection function, it is possible to prevent the device from becoming expensive.
[0037]
Furthermore, if the malfunction such as the short circuit is repaired, the switching circuit 16 with the current oscillation type cutoff function is automatically restored and the apparatus can be operated again, so that the trouble of replacing the fuse can be saved.
[0038]
FIG. 4 is a circuit diagram showing a second embodiment of the power supply control device of the present invention. However, the same parts as those of the embodiment shown in FIG.
[0039]
In this example, five power MOSFETs 18 are used as semiconductor switching elements for supplying power to the load 15, and when the overcurrent is detected by the switching circuit 16 with a current oscillation type cutoff function, The control method for the power MOSFET 18 is different from that of the first embodiment, and other configurations are the same as those of the first embodiment shown in FIG.
[0040]
Next, the operation of the present embodiment will be described. When the driver 12 drives the five power MOSFETs 18 to supply power to the load 15, if a short circuit or the like occurs on the load 15 side, the overcurrent detection circuit 163 of the switching circuit 16 with the current oscillation type cutoff function 16 Detects an overcurrent and outputs a detection signal to the driver 12. When the driver 12 receives the detection signal, the driver 12 controls to turn off all of the five power MOSFETs 18 to cut off the overcurrent flowing to the load 15 side.
[0041]
According to the present embodiment, when the switching circuit 16 with a current vibration type cutoff function is connected in parallel to the five power MOSFETs 18 connected in parallel, and an overcurrent flows to the load 15 side due to a short circuit or the like, this current vibration type By detecting the overcurrent using the overcurrent detection function of the switching circuit 16 with the cutoff function, it is possible to reliably perform overcurrent protection without using a fuse.
[0042]
In addition, since only one switching circuit 16 with a current oscillation type cutoff function is used, the number of wirings of the device is not increased, and it is possible to avoid miniaturization of the device and its current supply capacity. Since it is only necessary to use an inexpensive low-capacity type that is sufficient to operate the overcurrent detection function, it is possible to prevent the device from becoming expensive.
[0043]
Further, when the trouble such as the short circuit is repaired, the switching circuit 16 with the current oscillation type interruption function is automatically restored and the apparatus can be operated again, so that the trouble of replacing the fuse can be saved.
[0044]
【The invention's effect】
As described above in detail, according to the power supply control device of the present invention, by connecting in parallel the switching circuit with a current oscillation type cutoff function for overcurrent detection to the FET with a built-in temperature sensor connected in parallel, Without increasing costs and without compromising miniaturization, it is possible to protect the load and the power supply line against rare shorts as well as normal shorts.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of a power supply control device of the present invention.
FIG. 2 is a circuit diagram of the switching circuit with a current oscillation type cutoff function shown in FIG. 1 of the present invention.
FIG. 3 is a circuit diagram of the temperature sensor built-in FET shown in FIG. 2 of the present invention.
FIG. 4 is a circuit diagram showing a second embodiment of the power supply control device of the present invention.
FIG. 5 is a circuit diagram showing an example of a conventional power supply control device.
[Explanation of symbols]
11, 161 FET with built-in temperature sensor
12, 162 Driver 13 Charge pump 15 Load 16 Current oscillation type switching circuit with cutoff function 18 Power MOSFET
163, 164 Overcurrent detection circuit

Claims (4)

A first semiconductor switching element group having a plurality of overheat cutoff functions connected in parallel;
A drive circuit that drives the plurality of first semiconductor switching element groups in common to supply power from a power source to a load;
A switching circuit with a current oscillation type cutoff function connected in parallel to these semiconductor switching elements;
Comprising
In addition, the switching circuit with the current oscillation type cutoff function has a second semiconductor switching element that supplies current from the power source to the load by switching control according to an input control signal;
First reference voltage generating means for generating a first reference voltage having a voltage characteristic equivalent to a voltage characteristic between terminals of the second semiconductor switching element in a state where the load is connected;
First detection means for detecting a difference between a terminal voltage of the second semiconductor switching element and the first reference voltage;
Second reference voltage generating means for generating a second reference voltage having a voltage characteristic equivalent to a voltage characteristic between terminals of the second semiconductor switching element in a state where the load is connected;
Second detection means for detecting a difference between a terminal voltage of the second semiconductor switching element and the second reference voltage;
First control means for controlling on / off of the first semiconductor switching element group by the drive circuit in accordance with a difference between the terminal voltage detected by the first detection means and the first reference voltage; ,
A power supply control device comprising: a second control unit that controls on / off of the second semiconductor switching element according to a detection result of the second detection unit. A plurality of first semiconductor switching element groups connected in parallel; a drive circuit for driving the plurality of first semiconductor switching element groups in common and supplying power from a power source to a load;
A switching circuit with a current oscillation type cutoff function connected in parallel to these semiconductor switching elements;
Comprising
In addition, the switching circuit with the current oscillation type cutoff function has a second semiconductor switching element that supplies current from the power source to the load by switching control according to an input control signal;
First reference voltage generating means for generating a first reference voltage having a voltage characteristic equivalent to a voltage characteristic between terminals of the second semiconductor switching element in a state where the load is connected;
First detection means for detecting a difference between a terminal voltage of the second semiconductor switching element and the first reference voltage;
Second reference voltage generating means for generating a second reference voltage having a voltage characteristic equivalent to a voltage characteristic between terminals of the second semiconductor switching element in a state where the load is connected;
Second detection means for detecting a difference between a terminal voltage of the second semiconductor switching element and the second reference voltage;
First control means for turning off the first semiconductor switching element group by the drive circuit in accordance with a difference between the terminal voltage detected by the first detection means and the first reference voltage;
A power supply control device comprising: a second control unit that controls on / off of the second semiconductor switching element according to a detection result of the second detection unit. 2. The power supply control device according to claim 1, wherein the first semiconductor switching element group is a temperature sensor built-in FET group having an overheat cutoff function. 3. The power supply control device according to claim 1, wherein the second semiconductor switching element is a temperature sensor built-in FET having a switching circuit with an overheat cutoff function.

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