JPH0221314Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a room lamp fade-out circuit for an automobile, and more particularly to a room lamp fade-out circuit that can control the illuminance of the room lamp when opening and closing a door.

[Prior Art] As a conventional room lamp fade-out circuit, there is a configuration shown in FIG. 3.

In the figure, the power supply voltage V _DD is applied to an operational amplifier through a time constant circuit consisting of a door switch SW that is linked to the opening and closing of the door, resistors R ₁ , R ₂ , and a capacitor C ₁ .
Supplied to the non-inverting input of IC ₁ . The operational amplifier IC ₁ is a voltage follower with 100% voltage negative feedback from the output to the inverting input, and has high input impedance and low output impedance. The output of this voltage follower is used as a control power source to change the duty of the voltage-controlled duty control circuit A, and its oscillation output turns on and off the transistors to blink the room lamp _L1 .

For example, the duty control circuit A connects capacitors C ₂ and C ₃ to the inverting and non-inverting inputs of comparator IC ₂ as shown in Fig. 5, and repeatedly inverts the output by charging and discharging to cause oscillation. The duty is varied by the control voltage applied to the non-inverting input, and the explanation of its operation will be omitted.

In this configuration, when door switch SW ₁ is turned on (door open), capacitor is connected through resistor R ₁ .
C ₁ is charged, and the charging voltage (voltage at point a) rises rapidly due to the time constant determined by R ₁ and C ₁ as shown in FIG. 4A. This voltage is applied to the control voltage terminal b of the duty control circuit A through a buffer provided by the operational amplifier _IC1 , and is output with a duty of 100%. Therefore, the transistor T _r1 remains on, and the room lamp L ₁ is turned on.

On the other hand, when switch SW ₁ is turned off (door closed), the charge in capacitor C ₁ is discharged through resistor R ₂ with a time constant of R ₂ C ₁ as shown in Figure 4A.
The voltage at point b changes from V _DD to 0V, and the duty also changes from 100 to 0% accordingly. Therefore,
Transistor T _r1 turns on and off repeatedly Lamp L ₁
fades while blinking. At this time, the oscillation of duty control circuit A (duty < 100%)
The total lighting time t ₁ during which the voltage at point b falls below the starting voltage, and the dimming time t ₂ from which oscillation starts until the duty reaches 0% are determined by the time constants of resistor R ₂ and capacitor C ₁ . will be determined.

[Problem that the invention attempts to solve]

In the conventional room lamp fade-out circuit as described above, the total lighting time of the lamp from the time of switch-off is
Fine adjustment of t ₁ and dimming time t ₂ is difficult, and in order to lengthen t ₁ and t ₂ , it is necessary to increase the resistance value of resistor R ₂ and the capacitance of capacitor C ₁ .

The present invention has been developed in view of the above-mentioned conventional problems, and is a room lamp phasing system that makes it possible to easily adjust the illuminance of the room lamp by changing the full lighting time and dimming time of the room lamp after the door is closed. The purpose is to provide a closed-out circuit.

[Means for solving problems]

In order to achieve the above object, the room lamp fade-out circuit constructed according to the present invention charges at a first time constant by switching the door switch in response to the door opening/closing operation. and generates as a control voltage a charging/discharging voltage of a capacitor that is discharged with a second time constant larger than the first time constant by switching according to the operation of the door from opening to closing, and the control voltage In the interior lamp fade-out circuit, which uses the oscillation output of a voltage-controlled duty control circuit whose duty is variable depending on A non-inverting amplifier having a negative feedback circuit and having a gain that can be changed by adjusting the amount of negative feedback by the resistor negative feedback circuit is connected to the input side of the voltage-controlled duty control circuit, It is characterized in that the control voltage non-invertingly amplified by the non-inverting amplifier is input to the voltage-controlled duty control circuit.

[Effect]

In the above configuration, by adjusting the amount of negative feedback by adjusting the resistance value of the resistor negative feedback circuit included in the non-inverting amplifier and varying the gain of the non-inverting amplifier, the amount of negative feedback generated by charging and discharging the capacitor can be adjusted. The level of the control voltage is increased or decreased. When the level of the control voltage is increased or decreased in this way, the timing at which the duty of the oscillation output of the voltage-controlled duty control circuit gradually decreases from 100% changes. Therefore, by adjusting the gain of the non-inverting amplifier, the total lighting time and dimming time of the room lamp after the door is closed can be easily adjusted.

[Example of idea]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. 3 are denoted by the same reference numerals.

In Fig. 1, the door switch SW ₁ has a resistor R ₃ ,
It is supplied through the transistor T _r2 to a time constant circuit including resistors R ₁ and R ₂ and a capacitor C ₁ , and is connected to the non-inverting input of an operational amplifier IC ₃ forming a non-inverting amplifier. Operational amplifier IC ₃ has a resistor from the output to the inverting input side
Negative feedback is applied by R ₄ and R ₅ , and the output (gain) can be varied by varying the resistance values of resistors R ₄ and R ₅ .

In this configuration, when switch SW ₁ is turned on (door is opened/opened), transistor T _r2 is turned on,
Capacitor C ₂ is charged through resistor R ₁ . At this time, the output of operational amplifier IC ₃ becomes instantaneous V _DD as shown in Fig. 2 A, and duty control circuit A
The output becomes 100% duty, transistor T _r1 is turned on, and room lamp L ₁ is fully lit.

On the other hand, when door switch SW ₁ is turned off (door closed), transistor T _r2 is turned off and operational amplifier IC _{3 is} turned off.
The non-inverting input voltage at point a gradually decreases with the time constant of C ₁ R ₂ . At this time, since the non-inverting amplifier has a gain of (R ₄ + R ₅ )/R ₅ , its output is held by the gain and remains saturated for a period of time t' ₁ , as shown in Figure 2 (b). Then, the transistor T _r1 is turned on and the lamp L ₁ is kept fully lit. After that, when the voltage at point a drops below the oscillation start voltage of operational amplifier IC ₃ , the duty is 0% due to the time constant of C ₁ R ₂ and gain (R ₄ + R ₅ )/5.
The duty control circuit A oscillates for a period of time t' ₂ , the transistor T _r1 repeats on and off, and the lamp L ₁ blinks and gradually dims.

Therefore, by varying the feedback resistors R ₄ and R ₅ of the non-inverting amplifier and changing the gain, the door switch can be controlled.
The total lighting time t′ ₁ and the dimming time t′ ₂ after SW ₁ is turned off can be adjusted. For example, if you increase this gain, t′ ₁ and t′ ₂ will become longer, and if you decrease this gain, t′ ₁ and t′ 2 will become longer.
t′ ₂ can be shortened.

[Effect of idea]

As explained above, according to the present invention, the total lighting time and dimming time of the room lamp after the door is closed can be easily adjusted by changing the resistance value of the resistor negative feedback circuit of the non-inverting amplifier and adjusting the gain. Therefore, there is no need to use a large capacity capacitor for setting the time constant in order to extend the total lighting time.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the room lamp fade-out according to the present invention, Fig. 2 is a waveform diagram of each part of the circuit shown in Fig. 1, Fig. 3 is a circuit diagram showing a conventional fade-out circuit, and Fig. 4 is a circuit diagram showing an embodiment of the room lamp fade-out circuit according to the present invention. FIG. 3 is a waveform diagram of each part of the circuit, and FIG. 5 is a circuit diagram showing an embodiment of a voltage-controlled duty control circuit in the present invention and a conventional fade-out circuit. A... Voltage controlled duty control circuit, IC ₂ , IC ₃ ... Operational amplifier, R ₁ , R ₂ , R ₄ , R ₅
...Resistor, C ₁ ... Capacitor, T _r1 , T _r2 ... Transistor, L ₁ ... Room lamp, SW ₁ ... Door switch.

Claims (1)

[Scope of Claim for Utility Model Registration] The first invention is based on the switching of a door switch that is linked to the opening and closing of a door in response to the operation of the door from closing to opening.
A control voltage is generated as a charging/discharging voltage of a capacitor that is charged with a time constant of The room lamp faucet is designed to gradually dim the room lamp by turning on and off a switching element using the oscillation output of a voltage-controlled duty control circuit whose duty is variable according to the control voltage. In the output circuit, a non-inverting amplifier having a resistor negative feedback circuit and whose gain can be changed by adjusting the amount of negative feedback by the resistor negative feedback circuit is connected to the input of the voltage-controlled duty control circuit. 2. A room lamp fade-out circuit, wherein the control voltage non-invertingly amplified by the non-inverting amplifier is input to the voltage-controlled duty control circuit.