JPH04317832A - Vehicle indicator lamp control circuit - Google Patents

Abstract

PURPOSE:To provide a vehicle indicator lamp control circuit which can be small and lightweight and whose electric power loss is small and also which can conduct surely the action of control to reduce the light of the indicator lamp at nighttime. CONSTITUTION:Two condensers C3, C4 at a charge pump portion 22 are charged in series and discharged in parallel by making transistors Tr5, Tr6 at a changeover control portion 20 ON and OFF alternately by means of AC pulse signals from an oscillation portion 18. As a result, voltage can be lowered without power loss, and voltage control can be made by making transistors Tr7, Tr8 at an indication control portion 24 switching surely at daytime and at nighttime, so vision indication having an excellent visual recognition property can be made by lighting an indication portion 26 indicator lamp with an illumination that is according to a situation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indicator lamp control circuit for a vehicle instrument panel.

0002

[Prior Art] Conventional vehicle instrument panels are equipped with indicator lamps that visually display the operating status of an air conditioner (A/C) in an easy-to-understand manner by emitting light from a light emitting diode (LED) or a bulb. It is set up.

[0003] Such indicator lamps have visibility problems in that if the illuminance is adjusted during the daytime when the surrounding area is bright, it will be dazzling at night, and conversely, if it is adjusted at nighttime, it will be difficult to see during the daytime. It is preferable to change the illuminance.

FIG. 10 is a circuit diagram of a conventional indicator lamp control circuit. As shown in FIG. 10, the conventional indicator lamp control circuit includes a display circuit 10, a night illumination circuit 12, and a constant voltage circuit 14.

The display circuit 10 includes a plurality of light emitting diodes (D1) and (D2) as indicator lamps.

In the night lighting circuit 12, a light (L) and a battery power source (+V) are connected in series with a switch (S) in between.

The constant voltage circuit 14 is connected to the display circuit 10.
and the night lighting circuit 12, and the voltage from the power source 16 is changed by opening and closing the switch of the night lighting circuit 12 and is supplied to the display circuit 10.

Next, the operation of the conventional example will be explained. As shown in FIG. 10, during the daytime, the transistor (Tr2) is off, so the transistor (Tr1) is turned on, and the current from the power supply 16 flows through the resistor (R1) and the transistor (Tr1).
The signal is supplied to the display circuit 10 through Tr1).

Further, at night, when the switch (S) of the night illumination circuit 12 is closed, the light (L) is turned on and the base potential of the transistor (Tr2) is increased to turn on the transistor (Tr2). As a result, the base potential of the transistor (Tr1) decreases and the transistor (Tr1) is turned off, so the current path starts from the power supply 16, passes through the resistors (R1) and (R2), and then passes through the transistor (Tr2) and the resistor (R3). and is supplied to the display circuit 10. Therefore, the voltage applied to the display circuit 10 during nighttime is lower than during the daytime because it passes through the resistors (R2) and (R3) more. In this way, the conventional indicator lamp control circuit controls the illuminance of the indicator lamp during daytime and nighttime by lowering the voltage through the resistor.

0010

As described above, in the conventional indicator lamp control circuit, the transistor (Tr1) of the constant voltage circuit 14 and ( The illuminance of the indicator lamp was controlled by switching Tr2) to change the current path and change the resistance.

As described above, the conventional indicator lamp control circuit is of the dropper type that lowers the voltage by increasing the resistance at night, and the voltage difference is released as heat, so the efficiency is 40~ There was a problem in that the power loss was only about 50% and the power loss was large. In particular, in the case of a vehicle's indicator lamp control circuit, it is important to promote power saving because a battery power source with a small capacity is used.

In addition, in the conventional indicator lamp control circuit, since various resistances are mounted on the harness, the switching operation of the transistor tends to be unstable and uncertain, and there is a problem that the indicator lamp does not dim at night. There is.

[0013] The present invention has been made with the aim of solving the above-mentioned problems, and has a method that reduces power loss, allows for a smaller and lighter circuit, and ensures reliable control operation for dimming the indicator lamp at night. The purpose of the present invention is to provide a vehicle indicator lamp control circuit that can perform the following functions.

[0014]

[Means for Solving the Problems] In order to solve the above problems, the vehicle indicator lamp control circuit of the present invention includes an oscillator that generates an AC pulse signal, and an oscillator that generates an AC pulse signal, and a circuit that alternately operates two transistors using the AC pulse signal. a switching control unit that switches the current path by switching; a charge pump unit that charges two capacitors in series and discharges them in parallel by switching the switching control unit; and a charge pump unit that charges two capacitors in series and discharges them in parallel; The present invention is characterized by comprising a display control unit that supplies power to the indicator lamp via a resistor when the lamp is turned on, and a display unit that causes the indicator lamp to emit light using electric power controlled by the display control unit.

[0015]

[Operation] According to the vehicle indicator lamp control circuit according to the present invention, by switching the transistor with an AC pulse signal to change the current path, and repeating the process of charging two capacitors in series and discharging them in parallel. , it becomes possible to lower the power supply voltage without power loss, and this power supply can be used to suppress the current consumption of the display control unit.
Further, the circuit can be made smaller. In addition, the illuminance of the indicator lamp is increased during the daytime, and the illuminance is lowered at night to prevent glare, making the indicator lamp more visible.The voltage drop is also effectively utilized to provide good visual display. operation can be ensured.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a vehicle indicator lamp control circuit according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a circuit configuration diagram according to Embodiment 1 of the present invention. As shown in FIG. 1, the vehicle indicator lamp control circuit of the first embodiment includes an oscillation section 18, a switching control section 20, a charge pump section 22, a display control section 24, and a display section 26.
It is made up of.

The feature of the present invention is that the switching control section 20 switches the current path using the AC pulse signal generated by the oscillation section 18, and the charge pump section 22 changes the power supply voltage to 2.
By charging two capacitors in series and repeatedly discharging them in parallel, the power supply voltage can be lowered without loss. Then, the display control section 24 is driven using the power, and controls each indicator lamp of the display section 26 to an appropriate illuminance.

The oscillation section 18 uses an astable multivibrator here, and has transistors (Tr3) and (
Tr4) is alternately switched at an oscillation frequency determined by the time constants of the capacitor and resistor. This oscillation unit 18 outputs an AC pulse signal having a constant frequency.

The switching control section 20 switches the current path by alternately switching the two transistors (Tr5) and (Tr6) using the AC pulse signal output from the oscillation section 18.

The charge pump unit 22 switches the current path by the switching control unit 20 to connect the two capacitors (C3) and (C4) to the power supply voltage (12V in this case).
) to charge in series and discharge in parallel repeatedly. As a result, the above transistor (Tr5), (
Since Tr6) is used in the saturation region of the transistor, it can drop the power supply voltage of 12V to 6V without power loss. In contrast, in the past, resistors were used to drop the voltage, and the voltage difference was released as heat, resulting in large power losses.

The display control section 24 includes a transistor (T
r7) and (Tr8), and the night light switch 30 is connected to their bases via resistors (R14) and (R15), respectively. Resistors (R14) and (R15) are connected to the night light switch 30.
25). Also, the transistor (
Between the emitter and collector of Tr7) and (Tr8),
Bypasses are provided through resistors (R16) and (R17), respectively.

The display section 26 receives the voltage applied from the display control section 24 through the respective resistors (R18) to (R24).
An indicator lamp (not shown) is lit via the button. This indicator lamp uses an LED here,
The operating status of each part is visually displayed on the vehicle's instrument panel by lighting it up.

FIG. 2 is a block diagram showing the connection state of each component according to the first embodiment of the present invention. As shown in FIG. 2, in the first embodiment, the oscillation section 18 and charge pump section 22 are used in the control section 20 to switch the power supply voltage from the battery power supply 28 to charge two capacitors in series and in parallel. While repeating the discharge, the voltage is sent to the display control unit 24, where the voltage is controlled to provide an appropriate visual display at night and during the day, and an indicator lamp is lit on the display unit 26.

[0025]The operation according to the first embodiment will now be described in detail. As shown in FIG. 1, in the astable multivibrator of the oscillation unit 18, transistors (Tr3) and (Tr4) are alternately turned on and off at a constant frequency.
is repeated. As a result, an AC pulse signal is output from the oscillation unit 18, and the transistor (T
r5) and (Tr6) are turned on and off alternately. For example, when the transistor (Tr4) of the oscillation section 18 is turned on and the transistor (Tr3) is turned off, the transistor (Tr5) of the switching control section 20 is turned on and the transistor (Tr6) is turned off. As a result, the current path from the battery power supply 28 is connected to the transistor (Tr5).
The liquid flows through the diode (D3) while charging the capacitor (C3), and flows to the display control unit 24 while also charging the capacitor (C4).

Next, the astable multivibrator of the oscillation section 18 is reversed, and the transistor (Tr4) is turned off.
When the transistor (Tr3) turns on, the switching control section 20
The transistor (Tr5) is turned off, and the transistor (Tr6) is turned on. This allows the battery power supply 28
The current path from is cut off by the transistor (Tr5). However, as mentioned above, the capacitors (C3) and (C4
) is charged with electric charge, and the transistor (T
r6) is ON, a charging current flows from the positive terminal of the capacitor (C3) through the emitter of the transistor (Tr6) to the display control unit 24 side, and display control is also performed from the positive terminal side of the capacitor (C4). A charging current flows to the portion 24 side.

In this manner, the oscillation section 18 can lower the voltage of the battery power source 28 from 12V to 6V without power loss by continuously repeating the above operation at its oscillation frequency.

Then, the transistor (
Since the night light switch 30 is open during the daytime, the transistors (Tr7) and (Tr8) are
The base of Tr8) falls to ground and base current flows,
ON works. Therefore, the voltage from the switching control section 20 is 6V.
is directly applied to the display section 26 side through the transistors (Tr7) and (Tr8), so there is no voltage drop in the display control section 24.

On the other hand, at night, the night light switch 30
is closed, each transistor (Tr7), (Tr
The base potential of 8) rises, the base current stops flowing, and the OFF operation occurs. As a result, the voltage 6V from the switching control section 20 is applied to the display section 26 side via the resistors (R16) and (R17), and the voltage decreases.

In this way, the display control section 24 controls the voltage applied to the indicator lamp of the display section 26 in accordance with the opening/closing operation of the night light switch 30, and lowers the applied voltage during the nighttime than during the daytime. By dimming the indicator lamp, it is now possible to provide a visual display with illuminance appropriate for the situation.

Furthermore, conventionally, the 12V from the battery power supply 28 is used as is without lowering the power supply voltage. For this reason, for example, even if you try to turn off the transistors (Tr7) and (Tr8) in the display control unit 24 of FIG. There was a problem that the base current would flow and turn on.

However, in the first embodiment, the oscillation section 18 and
The switching control section 20 and the charge pump section 22 reduce the voltage applied to the display control section 24 to 6V without power loss. Therefore, transistors (Tr7), (Tr
8) can now reliably perform OFF operation until the base voltage is half that, 6V, and there is no need to worry about voltage drop due to the resistance of the harness.

Furthermore, in the past, since the power supply voltage was used as it was, the voltage was dropped by the resistors (R18) to (R24) of the display section 26. Therefore, there was a problem that the resistive load became large, the circuit became large, and the power loss was large. However, in the first embodiment, the voltage is lowered to 6V without power loss at the stage before the display control unit 24, so the resistor (R1
8) to (R24) are reduced, the circuit can be made smaller, and power loss can be reduced.

Embodiment 2 FIGS. 3, 4 and 5 are examples of circuit diagrams of the oscillation section in Embodiment 2. The oscillating sections shown in FIGS. 3 to 5 correspond to the oscillating section 18 of the first embodiment, and each has an output terminal 30.

FIG. 6 is a circuit diagram of the switching control section in the second embodiment. The switching control section in FIG. 6 corresponds to the switching control section 20 in the first embodiment. The input terminal 32 shown in FIG. 6 is connected to any output terminal 30 of the oscillation section shown in FIGS. 3 to 5 above, and receives an AC pulse signal from the oscillation section.

The operation of the switching control section shown in FIG.
When "H" is input to the transistor (Tr9) and (
Tr10) are both turned on, and the transistor (Tr11)
Since both are turned on, "L" is output from the output terminal 34 and "H" is output from the output terminal 36.

Conversely, when "L" is input to the input terminal 32, both transistors (Tr9) and (Tr10) become O.
To turn off, the transistor (Tr11) is also turned off,
"H" is output from the output terminal 34, and "L" is output from the output terminal 36.

FIG. 7 is a circuit diagram of the charge pump section in the second embodiment. The charge pump section in FIG. 7 corresponds to the charge pump section 22 in the first embodiment. Input terminals 38 and 40 shown in FIG.
The output terminals 34 and 3 of the switching control section shown in FIG.
6 are connected, and when one is "H", the other becomes "L", and this is repeatedly inverted at a constant period.

The operation of the charge pump section in FIG. 7 is such that when "H" is input to the input terminal 38 and "L" is input to the input terminal 40, the transistors (Tr12) and (Tr13
) and (Tr14) are turned on, and the transistor (Tr15
), (Tr16) and (Tr17) are turned OFF. At this time, the current path from the battery power supply 28 passes through the transistor (Tr12), the capacitor (C5), the transistor (Tr13), and the capacitor (C6).
It is output to the output terminal 42. At this time, capacitor (C3
) and (C5) are charged in series.

Furthermore, "L" is input to the input terminal 38,
When "H" is input to the input terminal 40, transistors (Tr12), (Tr13) and (Tr14) are turned off.
F, transistors (Tr15), (Tr16) and (
Tr17) is turned on. Therefore, no current is supplied from the battery power source 28, and the charged capacitor (C
5) is output to the output terminal 42 through the transistor (Tr15), and is also output from the positive terminal of the charged capacitor (C6) to the transistor (Tr1
6) and is output to the output terminal 42. in this way,
Charge two capacitors in series with the power supply voltage,
Since discharge is repeated in a parallel state, the voltage can be lowered to 6V without power loss as in the first embodiment.

Note that the configurations of the display control section and the display section at the next stage are the same as those in the first embodiment, so a repeated explanation will be omitted.

As described above, the vehicle indicator lamp control circuit of the second embodiment has less power loss as in the first embodiment, and the circuit can be made smaller and lighter, and the indicator lamp can be dimmed at night. control operations can be performed reliably.

Embodiment 3 FIG. 8 is a circuit configuration diagram according to Embodiment 3 of the present invention. As shown in FIG. 8, the basic configuration is the same as that of the first embodiment. The characteristic configuration of the third embodiment is that the oscillation section 1
8, one terminal of the capacitor (C1) is not connected to the collector of the transistor (Tr3) from which the output voltage is taken out, but is connected to the emitter of the emitter follower transistor (Tr18), and the base of the transistor (Tr18) and the transistor ( It is connected to the collector of Tr3), and the AC pulse signal of the oscillation unit 18 is output only from here. The switching control unit 20 includes a transistor (T
r19) constitutes an inverter circuit, a signal obtained by inverting the signal from the oscillation section 18 by the inverter is inputted to the transistor (Tr5), and a signal from the oscillation section 18 is inputted to the transistor (Tr6) for switching control. It is carried out. As a result, the transistors (Tr5) and (Tr6) are alternately turned on and off.

The reason for this configuration is that when the rise of the AC pulse signal output from the oscillation section 18 is delayed due to the capacitor or resistor and the waveform is blunted, the switching control section 2
To prevent this, two transistors that alternately switch at 0 may turn on at the same time, and a power supply voltage that exceeds the rating flows to the display load side of the subsequent stage, which can easily cause deterioration in the durability of the load or damage it. It is.

Therefore, the operation of the third embodiment will be explained below. When the transistor (Tr4) in FIG. 8 is OFF and the transistor (Tr3) is ON, the transistor (Tr4) is OFF and the transistor (Tr3) is ON.
Since the base of the transistor (r4) is reverse biased by the charge of the capacitor (C1), it remains in the OFF state and the transistor (
Tr3) is turned on due to the base current flowing through the resistor (R9).
maintain the condition. However, the capacitor (C1) has a resistance (R
8) to the battery power supply 28, and the potential of the capacitor (C1) changes from a negative potential to the transistor (T
The transistor (Tr4) turns on from the moment the base-emitter voltage of the transistor (Tr3) reaches the
) turns off. When the transistor (Tr3) is turned off, the transistor (Tr18) is turned on, and the resistor (R8) turns on the transistor (Tr4).

FIG. 9 shows a waveform diagram of each part of the transistor in the oscillation section of FIG.
Waveform diagram of collector voltage (VC) of No. 3, (c) is Tr4
(d) is a waveform diagram of the collector voltage (VC) of Tr4.

As shown in FIG. 9(a), the transistor (
The rising portion A of the base voltage waveform of Tr3) is dull because the capacitor (C2) is charged and current flows through the resistor (R9), but the falling portion B is steep. Therefore, the collector voltage of the transistor (Tr3) in FIG. 8 is different from the emitter follower transistor (Tr18).
), it became possible to obtain a rising waveform with no rounding as shown in FIG. 9(b). In the third embodiment, the collector voltage waveform of the transistor (Tr3) without rounding is used as the output waveform of the oscillation section 18, and is inverted by the inverter of the switching control section 20 to produce the other output waveform.

On the other hand, as shown in FIG. 9(c), the rising waveform of the base voltage of the transistor (Tr4) is also blunted for the same reason as in FIG. 9(a). The collector voltage waveform of the transistor (Tr4) is different from that of the transistor (TR3) because the capacitor (C2) is connected to the collector side.
) is OFF, the capacitor (C2) is charged and the resistor (
Since current flows through R5), the rising portion indicated by C in the figure is rounded. However, in the third embodiment, the collector voltage waveform of this transistor (Tr4) is not used as the output signal of the oscillation section 18, so there is no problem.

In this way, in the third embodiment, since the rising waveform of the AC pulse signal of the oscillation section 18 is shaped, the two transistors (Tr5) and (T
Since the switching of r6) is now performed alternately and accurately, and the power supply voltage is no longer directly applied to the display load side, the durability of the load is improved and there is no fear of damage.

[0050]

As explained above, according to the vehicle indicator lamp control circuit of the present invention, the charge pump section repeats charging and discharging while switching the switching control section using an AC pulse signal from the oscillation section, thereby improving efficiency. It can drop the voltage well. As a result, power loss is low, the circuit can be made smaller and lighter, and the display control unit can accurately control the voltage between night and daytime, so the indicator lamp on the display can be adjusted to match the illuminance depending on the situation. It has become possible to turn on the lights, making it possible to provide visual display with good visibility.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing the connection state of each component according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram of an oscillation section in Example 2.

FIG. 4 is a circuit diagram of an oscillation section in Example 2.

FIG. 5 is a circuit diagram of an oscillation section in Example 2.

FIG. 6 is a circuit diagram of a switching control section in Embodiment 2.

FIG. 7 is a circuit diagram of a charge pump section in Example 2.

FIG. 8 is a circuit configuration diagram according to a third embodiment of the present invention.

9 is a waveform diagram of each part of a transistor in the oscillation section of FIG. 8; FIG.

FIG. 10 is a circuit diagram of a conventional indicator lamp control circuit.

[Explanation of symbols]

18 Oscillation section 20 Switching control section 22 Charge pump section 24 Display control section 26 Display section

Claims (1)

[Claims] 1. A vehicle indicator lamp control circuit that visually displays the operating status of each part of a vehicle by causing an indicator lamp on an instrument panel to emit light, comprising: an oscillator that generates an AC pulse signal;
a charge pump section that charges two capacitors in series and discharges them in parallel by switching the switching control section; A display control unit that supplies output current to the indicator lamp via a resistor when the night lighting lamp is turned on, and a display unit that causes the indicator lamp to emit light using electric power controlled by the display control unit. Indicator lamp control circuit for vehicles.