JPH085455Y2 - EC mirror drive voltage supply circuit with heater - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] EC mirror when a vehicle anti-glare mirror (hereinafter referred to as EC mirror) using an electrochromic element (hereinafter referred to as ECD) also has a heater function The present invention relates to a drive voltage supply circuit for ECD, more specifically, a drive voltage supply circuit for an ECD with a heater.

[Prior Art] Conventional vehicle-mounted mirrors are used to prevent fog on the mirror surface.
A method has been used in which a planar heating element is attached to the back surface of an Al mirror or a Cr mirror or a reflecting film is also used as the heating element, or a transparent conductive film is attached to the front surface or the back surface of the mirror to form a heating element.
In the case of EC mirrors as well, the appearance of EC mirrors with a heater is expected to prevent the clouding of the mirror surface caused by a sudden change in the ambient temperature, as with ordinary vehicle mirrors.

[Problems to be solved by the invention] The voltage for driving the EC mirror is generally given a negative temperature characteristic for the purpose of improving the durability of the ECD, but the conventional one is the EC mirror and its driving circuit. On the assumption that they are placed in the same temperature atmosphere, that is, a driving voltage having a negative temperature characteristic with respect to a temperature change in the atmosphere in which the driving circuit is placed is supplied to the EC mirror. . However, there are few cases where the drive circuit and the EC mirror are placed in the same atmosphere, and when heated by a heater like an EC mirror with a heater, a completely different atmosphere, that is, the drive circuit and
Since the EC mirror is placed under different temperatures, it is almost useless even if the drive circuit has a negative temperature characteristic.

In consideration of the fact that only the EC mirror causes a temperature rise due to a heater or other factors, the present invention aims to supply an appropriate driving voltage having a negative characteristic that does not cause deterioration to the EC mirror in such a case. .

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a drive voltage supply circuit for an EC mirror with a heater, wherein the temperature of an EC mirror using an electrochromic device (ECD) is changed by a heater. A drive voltage detection circuit that detects a drive voltage applied to the ECD and outputs a drive voltage signal, and a reference voltage for applying an optimum drive voltage according to the temperature of the EC mirror are changed and set. A reference voltage control circuit having a reference voltage setting means, a comparison circuit which inputs the drive voltage signal and the reference voltage signal, compares and judges the magnitude of these, and outputs a judgment signal, and the judgment signal which is input. A control circuit for controlling a drive voltage value based on the judgment signal is connected to the heater to select ON / OFF of the heater, and the reference voltage setting means is connected to the front. A switch for changing and setting the reference voltage is provided, the heater is controlled by turning on / off the switch, and the reference voltage is changed to apply an optimum drive voltage to the temperature of the EC mirror. It is characterized by that.

For example, the reference voltage setting means is provided in close contact with the adjustment resistor connected to the terminal of the comparison circuit and the EC mirror, and is also connected in series with the adjustment resistor to change the temperature of the EC mirror. On the other hand, a thermistor showing a negative characteristic, and a resistor connected to the connection point between the adjusting resistor and the thermistor and connected to the switch,
The resistor is connected to the break contact when the thermistor is connected to the make contact of the switch, or the resistor is connected to the make contact when the thermistor is connected to the break contact of the switch. Become.

Further, when the reference voltage control circuit turns on the switch and raises the temperature of the EC mirror by the heater, a first ramp waveform generation that lowers the drive voltage corresponding to the temperature rising characteristic of the temperature is generated. When turning off the circuit and the temperature of the EC mirror by turning off the switch,
A second ramp waveform generating circuit that raises the drive voltage in accordance with the temperature drop characteristic of the temperature, the first ramp waveform generating circuit is connected to the make contact of the switch,
The second ramp waveform generating circuit is connected to the break contact of the switch.

[Operation] Since the present invention has the above-mentioned configuration, when the EC mirror is heated by the heater, the reference voltage control circuit of the comparison circuit (operational amplifier) provided in the feedback stabilization circuit of the drive voltage supply circuit is the EC mirror. A reference voltage with a negative temperature characteristic is generated in response to temperature rise and is input to the positive phase input pin of the operational amplifier, so the drive voltage controlled via the transistor by the output of the operational amplifier also corresponds to the temperature change of the EC mirror. Then, an optimum drive voltage having a negative characteristic is supplied.

Embodiments <First Embodiment> The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a drive voltage supply circuit for an EC mirror with a heater according to the present invention.

In the figure, 1 is a drive voltage detection circuit, 2 is an operational amplifier, 3 is a transistor, 4 is a reference voltage control circuit, 7 is a heater provided in close contact with an EC mirror, and 8 is a double switch.

The drive voltage detection circuit 1 is composed of a resistor R ₁ and a resistor R ₂ connected in series, one end of the resistor R ₁ is supplied with power via the transistor 3, and the supplied voltage is the resistor R ₁ and the resistor R _2. It is divided by and. Then, the divided voltage is supplied to the ECD as a drive voltage.

The potential at the connection point between the resistor R ₁ and the resistor R ₂ is input to the two anti-phase input pins of the operational amplifier 2 as a drive voltage signal.

On the other hand, the reference voltage signal from the reference voltage control circuit 4 is input to the positive phase input pin of the operational amplifier 2.

The reference voltage control circuit 4 comprises a resistor R ₃ , a resistor R ₄ , an adjusting resistor (reference voltage setting means) R ₅ and a resistor R ₈ . resistance
R ₈ and the resistor R ₃ are connected in series and are connected between the power supply and the positive phase input pin of the operational amplifier 2, and the resistor R ₄ and the resistor R ₅ are connected in parallel so that the ground and the operational amplifier 2 are connected. It is connected between the positive-phase input pin and. However, adjustment resistor R ₅
Is connected to the grounded state via the switch 8 when the switch 8 is turned on.

Therefore, when the switch 8 is off, the reference voltage signal input to the positive phase input pin of the operational amplifier 2 is a voltage obtained by dividing the power supply voltage by the combined resistance of the resistors R ₈ and R ₃ and the resistor R _4. It becomes a value. When the switch 8 is turned on, the voltage is divided by the combined resistance of the resistors R ₈ and R ₃ and the combined resistance of the resistors R ₄ and R ₅ .

Then, in the operational amplifier 2, the magnitude of the reference voltage signal and the magnitude of the drive voltage signal are compared, and the result is output to the base of the transistor 3. Based on this transistor 3
Controls the drive voltage value supplied to the ECD.

Based on the above configuration, if the EC mirror becomes cloudy,
When the switch 8 is turned on, the EC mirror is heated by the heater 7. Therefore, since the temperature of the EC mirror changes (rises), the driving voltage up to that point is not optimal. Adjustment resistor R ₅
If the temperature of the EC mirror reaches a predetermined temperature (maximum saturation temperature) by the heater 7 by adjusting the resistance value of
Make the drive voltage of D the optimum drive voltage.

At this time, the resistance value of the adjusting resistor R ₅ is set so that the drive voltage becomes optimum based on the following conditions.

EC mirror reference temperature …… 25 ℃ Standard drive voltage 1.35Vmax (1) Temperature coefficient of drive voltage …… −2.5mV / ℃ (2) Here, the reference temperature and standard reference voltage are the temperature before the heater is turned on and It means a reference voltage signal.

Under the above conditions, when the maximum saturation temperature reaches 60 ℃, the optimum drive voltage is 1.35Vmax-2.5mV / ℃ × 35 (℃) = 1.26Vmax, and this optimum drive voltage is output. Adjustment resistor R ₅
Set.

Therefore, when the adjustment switch R ₅ is set in advance and the double switch 8 is turned on, power is supplied to the heater 7 for heating and the adjustment resistor R ₅ is applied to the positive-phase input pin of the operational amplifier 2.
The reference voltage signal determined by is input. When the switch 8 is turned off, the heater 7 is turned off and one end of the adjusting resistor R ₅ is released so that it does not function and the resistor
Input the reference voltage signal determined by R ₃ , R ₄ and R ₈ .

In addition, in FIG. 1, as shown by the dotted line, the adjustment resistor
An off-delay timer 5 may be provided in connection with R ₅ . At this time, the other end of the off-delay timer 5 is connected to the switch 8 and the short-circuit wire 5a for invalidating the operation of the switch 8 is grounded.

As a result, even when the double switch 8 is turned off, the adjusting resistor R ₅ is in the grounded state for a predetermined time by the off-delay timer 5, and the drive voltage under the high temperature condition is maintained. That is, even immediately after the heater 7 in the high temperature state is cut off, the driving voltage under the high temperature condition is applied to the ECD surface in the high temperature state for a predetermined time, so that the deterioration of the EC mirror can be prevented. Become.

<Second Embodiment> Next, a second embodiment will be described with reference to the circuit diagram shown in FIG.

The reference voltage control circuit 4 in this embodiment has a first ramp waveform generation circuit 10 and a second ramp waveform generation circuit 11 (both are reference voltage setting means), and the triple switch 9 has two sets. It has a make contact and a set of break contacts, one of the make contacts is connected to the heater 7, and the other make contact is connected to the first ramp waveform generating circuit 10 having a voltage drop characteristic. Further, the break contact is connected to the second ramp waveform generating circuit 11 having the voltage rising characteristic.

The first and second ramp waveform generating circuits 10 and 11 are basically based on a Miller integrating circuit having a falling characteristic or a rising characteristic that causes the driving voltage to fall or rise in an analog manner with time. A transistor or the like is added to have a function of stopping the descent or resetting.

The falling characteristics and the rising characteristics of the driving voltage in the first and second ramp waveform generating circuits 10 and 11 are set as follows.

The temperature difference between the maximum saturation temperature of the EC mirror reached by heating the heater and the reference temperature (25 ° C), the time required to reach the maximum saturation temperature from the reference temperature, and the EC mirror The time required to fall to the reference temperature is set, respectively, and according to the conditions (1) and (2), the voltage drop characteristic with respect to the time between heater heating (3) The voltage rise characteristic with respect to the time when the heater is off (4) A reference voltage signal to the operational amplifier 2 is generated so that an optimum drive voltage satisfying the above characteristics (3) and (4) can be output.

Therefore, when the triple switch 9 is turned on, a low drive voltage is applied corresponding to the temperature rise of the EC mirror, and when the triple switch 9 is turned off, the temperature of the EC mirror is lowered. Since a correspondingly high driving voltage is applied, the ECD deterioration can be prevented more completely.

<Third Embodiment> Next, a third embodiment will be described with reference to FIG.

In the present embodiment, the reference voltage control circuit 4 is
The thermistor (reference voltage setting means) R _{th, which} is connected in series with the adjusting resistance (reference voltage setting means) R ₆ and exhibits negative characteristics, has a resistance of 4
And a structure connected in parallel with.

The thermistor R _th is arranged in the vicinity of or on the surface of the EC mirror, and the resistance value of the thermistor R _th , that is, the reference voltage signal is changed in accordance with the temperature change of the EC mirror.

The thermistor R _th , resistance R ₃ , resistance R ₄ , adjustment resistance R ₆
Is set to satisfy the above conditions (1) and (2) when the EC mirror is at 25 ° C.

Since the EC mirror has a negative characteristic with respect to temperature change, the reference voltage signal input to the positive-phase input pin of the operational amplifier 2 also shows a negative characteristic, and the drive voltage decreases as the EC mirror temperature rises. Like Similarly, as the temperature of the EC mirror decreases, the drive voltage also increases as the temperature of the EC mirror decreases.

With the above-described configuration, the optimum drive voltage can be supplied by following the temperature of the EC mirror that fluctuates due to the heater or other factors, and the ECD deterioration can be prevented.

4 and 5 are modifications of the circuit in FIG.

The reference voltage control circuit 4 in FIG. 5 has an adjusting resistor (reference voltage setting means) R ₆ , a resistor (reference voltage setting means) R _7, and a thermistor (reference voltage setting means) R _th . The resistor R ₇ is connected in series with the adjusting resistor R _6, and is connected to one of the make terminals of the switch 9, and the adjusting resistor R ₆ is also connected.
A thermistor R _th is connected in series to R ₆ and is connected to the break terminal of the switch 9.

Therefore, as the temperature of the EC mirror decreases, the thermistor R _th
The value of changes and the optimum drive voltage can be supplied accordingly.

The reference voltage control circuit 4 shown in FIG.
Has an adjusting resistor (reference voltage setting means) R ₆ , a resistance reference voltage setting means) R ₇ , a thermistor (reference voltage setting means) R _th, and an off-delay timer 5.

Then, the adjusting resistor R _{6 is connected} to the resistor R ₇ and the off-delay timer 5
Are sequentially connected in series and are connected to the break connection of the switch 9. The thermistor R _th is connected in series to the adjusting resistor R ₆ and is connected to one of the make contacts of the switch 9.

Therefore, when the switch 9 is turned off, the thermistor
Instead of R _th , a drive voltage corresponding to the maximum temperature is supplied to the ECD through a resistor R ₇ and an off delay timer 5 for a predetermined time determined by the off delay timer 5.

[Advantage of the Invention] As described above, the present invention is a comparison circuit (op amp) having a negative characteristic reference voltage control circuit capable of supplying a negative characteristic drive voltage in response to the temperature change of the EC mirror. Since a feedback stabilization circuit using is provided,
We were able to provide a drive voltage supply circuit for an EC mirror with a heater that prevents deterioration and improves durability by supplying an optimum drive voltage when using an EC mirror with a heater that is used to prevent clouding of the EC mirror.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and FIG.
FIG. 4 is a circuit diagram showing an embodiment, FIG. 3 is a circuit diagram showing a third embodiment, and FIGS. 4 and 5 are modified circuit diagrams of the third embodiment. 1 ... Drive voltage detection circuit, 2 ... Operational amplifier, 3 ... Transistor, 4 ... Reference voltage control circuit, 5 ...
Ofudereitaima, 7 ...... heater, 8 ...... 2-way switch, 9 ...... 3-way switch, 10, 11 ...... ramp generator circuit, R ₁ to R ₄ ...... resistor, R _5, R ₆ ...... adjustment Resistance, R ₇ , R ₈ ......
Resistance, R _th …… Thermistor.

Claims (3)

[Scope of utility model registration request] 1. A drive voltage supply circuit for an EC mirror with a heater, wherein the temperature of an EC mirror using an electrochromic element (ECD) is changed by a heater, the drive voltage applied to the ECD is detected, and the drive voltage is detected. A drive voltage detection circuit that outputs a signal, a reference voltage control circuit that includes a reference voltage setting unit that changes and sets a reference voltage for applying an optimum drive voltage according to the temperature of the EC mirror, the drive voltage A signal and the reference voltage setting signal are input, a comparison circuit that compares and judges the magnitude of these signals and outputs a determination signal, and a control circuit that receives the determination signal and controls the drive voltage value based on the determination signal And a switch for connecting the heater to select ON / OFF of the heater and connecting the reference voltage setting means to change and set the reference voltage. Then, the heater is controlled by turning on / off the switch, and the reference voltage is changed to apply a drive voltage most suitable for the temperature of the EC mirror. Drive voltage supply circuit. 2. The reference voltage setting means is provided in close contact with the adjusting resistor connected to the terminal of the comparison circuit and the EC mirror, and is connected in series with the adjusting resistor.
A thermistor that exhibits a negative characteristic with respect to the temperature change of the EC mirror, and a resistor that is connected to the connection point between the adjustment resistor and the thermistor and is connected to the switch, wherein the thermistor is The resistor is connected to a break contact when connected to a make contact, or the resistor is connected to a make contact when the thermistor is connected to a break contact of the switch. Drive voltage supply circuit for EC mirror with heater. 3. When the reference voltage control circuit turns on the switch and raises the temperature of the EC mirror by the heater, the drive voltage is lowered corresponding to the temperature raising characteristic of the temperature. A ramp waveform generating circuit; and a second ramp waveform generating circuit that raises the drive voltage in response to the temperature drop characteristic of the temperature when the temperature of the EC mirror is lowered by turning off the switch. The driving of the EC mirror with a heater according to claim 1, wherein the first ramp waveform generating circuit is connected to a make contact of the switch, and the second ramp waveform generating circuit is connected to a break contact of the switch. Voltage supply circuit.