JP4017183B2 - Automotive temperature controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an on-vehicle temperature control device used for temperature adjustment of an on-vehicle warmed object such as a car seat heater or a truck nap heater.
[0002]
[Prior art]
As shown in FIG. 4, this type of in-vehicle temperature control apparatus 1 is connected to an in-vehicle warming object 3 such as a car seat heater in which the filaments of the heating wires 2 are meandered and arranged as shown in FIG. The temperature of the heating wire 2 is adjusted by controlling the current control element 5 such as a power MOS FET connected in series to the heating wire 2 by the temperature signal voltage Vt from the thermistor 4 disposed in the vicinity of the heating wire 2. .
[0003]
In the in-vehicle temperature control apparatus 1, an abnormally high voltage is superimposed on the power supply voltage when the battery is broken or the battery terminal is disconnected, so that it is necessary to have a configuration that can withstand the abnormally high voltage. Regarding this, a test method for transient voltage generated at the time of load dump is specified in the automobile standard (JASO D001), the test voltage is 70 V, and the decay time constant τ is 200000 μs. When the test voltage is applied and the current control element 5 is in an ON state, an excessive current of 23.3 A at the maximum flows to the current control element 5 when the resistance value of the heating wire 2 is 3Ω. The element 5 generates heat significantly, and if the size and current rating of the current control element 5 are inappropriate, the current control element 5 will fail. Therefore, as shown in FIG. 6, the current control element 5 has a large shape in which the size of the resin mold portion 5a is 8.5 mm × 10 mm or more in anticipation of a margin, and the test voltage whose current capacity is a transient voltage is used as a heating wire. In order to select a large high current rating with a high current capacity equal to or greater than the current value obtained by adding a margin to the value divided by the resistance value of 2 and to dissipate the heat of the current control element 5 that rises rapidly, It was necessary to provide the plate 5b. Also, due to these restrictions, the current control element 5 is small and low cost, and the surface mounting type cannot be used, and is limited to the type having a lead electrode.
[0004]
However, in the current control element 5 having the large heat sink 5b with the large high current rating described above, it is difficult to cope with the downsizing and cost reduction of the on-vehicle temperature control device 1 that has been increasingly demanded recently. It has become. Therefore, in order to avoid the use of the current control element 5 having the large heat sink 5b with the large high current rating, the current control element 5 is turned off during the period in which the abnormal high voltage is superimposed on the power supply voltage. It is possible. That is, when the current control element 5 is in the ON state, a current having a value obtained by dividing the voltage value of the abnormally high voltage superimposed on the power supply voltage by the resistance value of the heating wire 2 flows to the current control element 5. However, if the current control element 5 is OFF, no current flows and the current control element 5 does not generate heat. Thus, in order to turn off the current control element 5 while the abnormally high voltage is superimposed on the power supply voltage, a voltage comparison such as a comparator connected to the control terminal of the current control element 5 as shown in FIG. The unit U3 compares the power supply voltage with a preset reference voltage for turning off the current control element 5, and forcibly sets the drive signal Vd of the current control element 5 during a period when the power supply voltage exceeds the reference voltage. Therefore, it is necessary to provide an abnormal high voltage protection circuit 6 that is at a low level.
[0005]
[Problems to be solved by the invention]
Thus, since the abnormal high voltage is superimposed on the power supply voltage in the case of the battery failure or the battery terminal disconnection, the in-vehicle temperature control device 1 needs to be configured to withstand this abnormal high voltage. For this purpose, a current control element 5 having a large high current rating is used, and a large heat sink 5b must be provided in order to release the heat of the current control element 5 that rises rapidly. Although it was difficult to reduce the size and cost of 1, a large heat sink 5b with a large high current rating was provided by a method of turning off the current control element during the period when the abnormally high voltage was superimposed on the power supply voltage. Use of the current control element 5 can be avoided. For that purpose, a means for turning off the current control element can be considered during the period when the abnormally high voltage is superimposed on the power supply voltage as described above. By means of a voltage comparator such as a comparator connected to the control terminal of the current control element 5, The power supply voltage is compared with a preset reference voltage for turning off the current control element 5, and the drive signal of the current control element 5 is forcibly set to a low level while the power supply voltage exceeds the reference voltage. It was necessary to provide an abnormal high voltage protection circuit 6.
[0006]
However, since the on-vehicle temperature control device 1 needs to protect against overvoltage and reverse polarity noise in addition to the abnormally high voltage at the time of load dump, the temperature signal voltage Vt of the thermistor 4 and the reference voltage Vs for temperature control are set. In comparison, the temperature adjustment circuit unit 12 that obtains the drive signal Vd of the current control element 5 uses protective elements such as a high voltage preventing Zener diode ZD1, a resistor R4, and a reverse voltage preventing diode D1. Of course, since the above-described abnormal high voltage protection circuit 6 also requires a similar protection element, the number of parts is greatly increased, and the current control element 5 having a large heat sink 5b with a large high current rating is provided. There was a problem that the effect of miniaturization and cost reduction by avoiding the use would be greatly reduced.
[0007]
The present invention has been made based on such points, and the object of the present invention is to realize a vehicle-mounted temperature control device that is safe, small and low-cost even when an abnormally high voltage is superimposed on the power supply voltage. There is to do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a vehicle-mounted temperature control device according to claim 1 of the present invention cuts off a current control element driven by a thermistor temperature signal and a current flowing through the current control element when the thermistor is disconnected. A temperature-control device for vehicle that includes at least a thermistor disconnection protection circuit and adjusts the temperature of a vehicle-mounted warmed object in which a heating element of the wire is disposed, according to a temperature signal of the thermistor, By connecting a switch that is turned on when an abnormally high voltage is superimposed on the voltage in series with the thermistor , the thermistor disconnection protection circuit is operated in a pseudo manner for substantially the same period as the abnormally high voltage superimposed period. It is a feature.
According to a second aspect of the present invention, there is provided the on-vehicle temperature control device, wherein a switch that is turned on when an abnormally high voltage is superimposed on the power supply voltage of the on-vehicle temperature control device is connected in series with the thermistor, and a connection point between the switch and the thermistor. Is compared with a reference voltage for operating the thermistor disconnection protection circuit, so that the thermistor disconnection protection circuit is operated in a pseudo manner for substantially the same period as the abnormal high voltage superposition period. It is what.
The on- vehicle temperature control device according to claim 3 is characterized in that the current control element is a surface mount type in which a resin mold portion is 6 mm × 7 mm or less and does not include a heat sink.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. The resistance value of the thermistor 4 has a negative temperature characteristic with respect to temperature, but when a resistor R1 is connected in series to the thermistor 4 as shown in FIG. 1, the voltage divided by the thermistor 4 and the resistor R1 is The temperature characteristic is positive with respect to temperature. This voltage is input as a temperature signal voltage Vt to the inverting input terminal of the comparator U1 which is a voltage comparator, while the reference voltage Vs set to an arbitrary value by the resistor R5 connected to the power supply line 7 is input to the comparator U1. When input to the non-inverting input terminal, for example, when the temperature of the heating wire 2 is low, the resistance value of the thermistor 4 is high, so that the temperature signal voltage Vt is lower than the reference voltage Vs. Then, the output of the comparator U1 becomes high level. If the current control element 5 is connected to the output of the comparator U1, a current flows through the heating wire 2 and the temperature of the heating wire 2 rises. On the other hand, when the temperature of the heating wire 2 becomes high, the resistance value of the thermistor 4 decreases and the temperature signal voltage Vt rises. However, when the temperature signal voltage becomes higher than the reference voltage Vs, the output of the comparator U1 becomes low level and the heating wire 2 When the current stops, the temperature of the heating wire 2 stops increasing. Thereafter, when the temperature of the heating wire 2 decreases with the passage of time and the temperature signal voltage Vt becomes equal to or lower than the reference voltage Vs, the current of the heating wire 2 is turned on and the temperature rises again. By repeating this, the temperature of the heating wire 2 is adjusted to a temperature corresponding to the reference voltage Vs.
[0010]
If the thermistor 4 is disconnected due to an abnormal external force or impact, the resistance value of the thermistor 4 becomes infinite and the temperature signal voltage Vt drops to almost 0V. In this case, since the temperature signal voltage Vt becomes lower than the reference voltage Vs, the current of the heating wire 2 is turned on, and the temperature of the heating wire 2 rises without limit. Therefore, when the temperature signal voltage Vt drops below the reference voltage Vc different from the reference voltage Vs for temperature adjustment, the current of the heating wire 2 is cut off to prevent the temperature of the heating wire 2 from rising unlimitedly. A built-in thermistor disconnection protection circuit 8 is a countermeasure generally taken.
[0011]
In the on-vehicle temperature control device 1 configured as described above, the emitter of the PNP transistor Q1 is connected to the connection point between the resistor R1 and the thermistor 4, the collector is connected to the GND terminals of the comparators U1 and U2, and the base and the comparators U1 and U2 are connected. If the Zener diode ZD2 is connected between the GND terminals and the resistor R5 is connected between the power supply line 7 and the base, the abnormally high voltage is superimposed on the power supply voltage, the secondary circuit voltage Va rises, and the base voltage becomes the Zener voltage of the Zener diode ZD2. When the value exceeds the value, the transistor Q1 is turned on, the voltage of the resistor R1 becomes almost 0V, and the same operation as when the thermistor 4 is disconnected can be performed. Thus, by operating the thermistor disconnection protection circuit 8 in a pseudo manner, the output of the comparator U2 becomes low level, and the current control element 5 can be turned off. The PNP transistor Q1, the Zener diode ZD2, and the resistor R1 are connected in a range that can protect against overvoltage and reverse polarity noise, and therefore no individual protection circuit is required, so that the number of parts can be reduced, thereby reducing the size. A great effect can be obtained for cost reduction.
[0012]
【Example】
Embodiments of the present invention will be further described below with reference to the drawings. In FIG. 1, the thermistor 4 has one end connected to the other end of the resistor R1 connected to the GND terminals of the comparators U1 and U2, and the inverting input terminal of the comparator U1, the non-inverting input terminal of the comparator U2, and the emitter of the PNP transistor Q1. Is also connected. A reference voltage Vs obtained by dividing the secondary circuit voltage Va by the resistors R6, R7, and R8 is applied to the non-inverting input terminal of the comparator U1. The output of the comparator U1 is wired-ORed with the output of the comparator U2, and is connected to the control terminal of the current control element 5 through the transistor Q2, the diode D2, and the resistor R9. A reference voltage Vc obtained by dividing the secondary circuit voltage Va by the resistors R6, R7, and R8 is applied to the inverting input terminal of the comparator U2. The collector of the PNP transistor Q1 is connected to the GND terminals of the comparators U1 and U2, the base is connected to the GND terminals of the comparators U1 and U2 through the Zener diode ZD2, and the comparators U1 and U2 are connected through the resistor R5. Connected to the Vcc terminal.
[0013]
The thermistor disconnection protection circuit 8 comprises a comparator U2 and resistors R6, R7, R8, and the temperature signal voltage Vt at the non-inverted input terminal of the comparator U2 is disconnected from the thermistor 4 from the reference voltage Vc input to the inverted input terminal of the comparator U2. Due to the failure, the output of the comparator U2 becomes low level. At the same time, the current control element 5 is turned off by setting the control terminal of the current control element 5 to low level regardless of the output of the wired OR connected comparator U1. .
[0014]
On the other hand, the emitter of the PNP transistor Q1 is also connected to the non-inverting input terminal of the comparator U2. When the abnormal high voltage is superimposed on the power supply voltage as shown in FIG. 2A, the base voltage of the PNP transistor Q1 is This exceeds the Zener voltage of the Zener diode ZD2, and as a result, a current flows through the Zener diode ZD2. Then, the PNP transistor Q1 is turned ON, the voltage between the emitter and the collector is lowered, and the voltage at the inverting input terminal of the comparator U2 is almost 0V. As a result, the output of the comparator U2 becomes low level. As a result, the current control element 5 is turned off, and the voltage applied to the heating wire 2 is turned off for substantially the same period as the period when the abnormal high voltage is superimposed on the power supply voltage, as shown in FIG. This is the same operation as the thermistor disconnection protection circuit 8 is activated due to the disconnection failure of the thermistor 4, and it can be said that the thermistor disconnection protection circuit 8 is operated in a pseudo manner.
[0015]
In addition, since the on-vehicle temperature control device 1 needs to protect against overvoltage and reverse polarity noise in addition to the abnormally high voltage at the time of load dump, the signal of the thermistor 4 and the reference voltage Vs for temperature control are compared. The temperature adjusting circuit unit 12 that obtains a drive signal for the current control element 5 uses protective elements such as a high voltage preventing Zener diode ZD1, a voltage dropper resistor R4, and a reverse voltage preventing diode D1. However, since the PNP transistor Q1, the Zener diode ZD2 and the resistor R5 for operating the thermistor disconnection protection circuit 8 in a pseudo manner are protected by the protection elements, individual protection circuits are unnecessary. ,
[0016]
In FIG. 1, the comparators U1 and U2 use a dual type (BA10393: manufactured by ROHM) with a single power source, and the current control element 5 has a resin mold portion 5a as shown in FIG. A .5 mm surface mount type power MOS FET (2SK3483-Z: manufactured by NEC) was mounted without a heat sink. Zener voltages of the Zener diodes ZD1 and ZD2 are 12 V and 9 V, respectively, and 2SA1587 (manufactured by Toshiba) is used as the PNP transistor Q1.
[0017]
In the above embodiment, a test was performed based on the test method of the automobile standard (JASO D001). As a result, even if the on-vehicle warming object 3 having a resistance value of the heating wire 2 of 3Ω (about 60 W) was connected, No sudden heat generation or failure was observed.
[0018]
【The invention's effect】
As described above, according to the present invention, at least a current control element that is driven by a temperature signal of the thermistor and a thermistor disconnection protection circuit that interrupts a current flowing through the current control element when the thermistor is disconnected, A vehicle-mounted temperature control device that adjusts the temperature of the vehicle-mounted warmed object in which the heating element of the strip is arranged by the temperature signal of the thermistor, when an abnormally high voltage is superimposed on the power supply voltage of the vehicle-mounted temperature control device By operating the thermistor disconnection protection circuit in a pseudo manner for substantially the same period as the superposition period of the abnormal high voltage, the use of a current control element having a large heat sink with a large high current rating is avoided, for example, A surface mount type current control element having a resin mold portion of 6 mm × 7 mm or less can be used without a heat sink. Further, by arranging a circuit for operating the thermistor disconnection protection circuit in a pseudo manner within a range where the protection element protects against overvoltage and reverse polarity noise, individual protection elements are not necessary. Therefore, even when an abnormally high voltage is superimposed on the power supply voltage, it is safe, small, and low in cost, for example, an in-vehicle temperature used for temperature adjustment of an in-vehicle warming object such as a car seat heater or a truck nap heater. An adjusting device can be realized.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of an on-vehicle temperature control device according to the present invention.
FIGS. 2A and 2B are diagrams showing waveforms of respective parts of the on-vehicle temperature control device according to the present invention, wherein FIG. 2A shows a waveform in which an abnormally high voltage is superimposed on the power supply voltage of the on-vehicle temperature control device, and FIG. The waveform applied to the heating line when the waveform of a) is applied to the on-vehicle temperature control device is shown.
FIGS. 3A and 3B are diagrams illustrating a configuration of a current control element used in an embodiment of the present invention, where FIG. 3A is a top view and FIG. 3B is a side view.
FIG. 4 is a diagram for explaining the configuration of an in-vehicle warming object.
FIG. 5 is a circuit diagram showing a conventional on-vehicle temperature control device.
6A and 6B are diagrams illustrating a configuration of a current control element used in a conventional example, in which FIG. 6A is a top view and FIG. 6B is a side view.
[Explanation of symbols]
U1, U2 Comparators R1-R12 Resistors D1, D2 Diodes ZD1, ZD2, ZD3 Zener diodes Q1, Q2 Transistor E DC power supply 1 In-vehicle temperature control device 2 Heating wire 3 In-vehicle warming product 4 Thermistor 5 Current control element 5a Resin mold part 5b Heat sink 6 Abnormal high voltage protection circuit 7 Power supply line 8 Thermistor disconnection protection circuit 12 Temperature adjustment circuit Vt Temperature signal voltage Vs Reference voltage Vc for temperature adjustment Reference voltage Va for thermistor disconnection protection Secondary circuit voltage

Claims (3)

In-vehicle use in which at least a current control element driven by a temperature signal of the thermistor and a thermistor disconnection protection circuit for interrupting a current flowing through the current control element when the thermistor is disconnected are provided, and a heating element of the filament is disposed A vehicle-mounted temperature control device that adjusts the temperature of the warmed object according to the temperature signal of the thermistor, and a switch that is turned on when an abnormally high voltage is superimposed on the power supply voltage of the vehicle-mounted temperature control device is connected in series with the thermistor doing, vehicle temperature control apparatus characterized by being configured the thermistor disconnection protection circuit to operate substantially the same period, pseudo the overlap period of the abnormally high voltage. The on-vehicle temperature control device according to claim 1, wherein a switch that is turned on when an abnormally high voltage is superimposed on a power supply voltage of the on-vehicle temperature control device is connected in series with the thermistor, and a connection point between the switch and the thermistor is connected. By comparing the voltage with a reference voltage for operating the thermistor disconnection protection circuit, the thermistor disconnection protection circuit is configured to operate in a pseudo manner for substantially the same period as the abnormal high voltage superposition period. In-vehicle temperature control device. The on-vehicle temperature control device according to claim 1 or 2 , wherein the current control element is a surface mount type in which a resin mold portion is 6 mm x 7 mm or less and does not include a heat sink. Temperature control device.

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