JPH097772A - Transistor type luminous energy regulating device - Google Patents

Abstract

PURPOSE: To reduce the used number of transistors. CONSTITUTION: Either one side of the output side transistor T2 of a multivibrator 1, and a transistor TA for amplifying at the next stage connected to the output side transistor T2, is made in a PNP type, while the other side in an NPN type. As a result, by using only one transistor fewer than the conventional method, for amplifying of a driving circuit, the illuminance control of a light source lamp can be carried out, and furthermore, the light source lamp is subjected to continuous current-carrying to improve the maximum illuminance easily, and the cost can be also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a transistor type light quantity adjusting device which changes the brightness of a light source according to the duty ratio of output pulses of a multivibrator.

[0002]

2. Description of the Related Art In this type of transistor type light quantity adjusting device, the brightness of the light source is changed by controlling the on-time of a drive transistor inserted in series with the light source according to the duty ratio of the multivibrator. ing.

FIG. 5 shows an example of such a general circuit.
Is an astable multivibrator, 2 is a drive circuit,
3 is a light source lamp, 4 is a zener diode for constant voltage, 5
Is a constant voltage resistor. The multivibrator 1 includes oscillating transistors T1 and T2, and the drive circuit 2 includes amplifying transistors TA1 and TA2 and a drive transistor TD. Resistors R1 to R11 and a capacitor C1.
.About.C4, a diode D1, etc. form a circuit as shown in the figure. S1 and S2 are terminals connected to a power source (not shown), and the terminal S2 has a ground (GND) potential.

The brightness of the light source lamp 3 is adjusted by adjusting the resistance R5 to change the duty ratio of the multivibrator 1. In the case of the circuit configuration shown in the figure, 2
Output side transistor T of the oscillation transistors
Since the drive transistor TD is turned on when 2 is off, the light source lamp 3 lights up brightest when the ratio of the off time of the transistor T2 is maximized.

Further, even when the ratio of the off time is maximized in this way, an extremely short on time is generated for each oscillation cycle. Therefore, if it is possible to prevent the drive transistor TD from turning off at the time of this on, the light source lamp 3 is continuously operated. The maximum illuminance can be improved by energizing. Therefore, in this circuit, two transistors TA1 and TA2 and a capacitor C are used.
The drive transistor TD is kept on even if the transistor T2 is turned on by breaking the waveform due to the combination of 3 and C4. Two transistors TA1 and TA2 are provided in the preamplifier section of the drive circuit 2.
Since it is necessary to use, there is a problem that the cost becomes higher by that amount.

[0006]

The present invention has been made in view of this point, and has been made with the object of reducing the number of transistors used.

[0007]

In order to achieve the above-mentioned object, according to the present invention, either one of an output side transistor of a multivibrator and a next stage amplification transistor connected to the output side transistor is a PNP type. , And the other is NPN type.

In this case, it is desirable to insert a resistor for constant voltage, which forms a constant voltage circuit in combination with a Zener diode connected in parallel with the multivibrator, on the emitter side of the output side transistor of the multivibrator.

[0009]

According to the present invention, when the off-time ratio of the output side transistor of the multivibrator is large, it becomes easy to turn on the amplifying transistor of the next stage, and the amplifying transistor is turned on 100% by synergistic action with the capacitor. It will be easy. Therefore, it is possible to easily control the illuminance of the light source lamp by using one transistor for amplification of the drive circuit and to improve the maximum illuminance by continuously energizing the light source lamp.
The number of transistors used is halved compared to the conventional example, and the cost can be reduced accordingly.

Further, if the number of amplifying transistors used is simply reduced, the drive transistor may turn on when the light amount is reduced by increasing the ratio of the off time of the output side transistor of the multivibrator, as will be described later. There is a possibility that the light amount cannot be fully narrowed down, resulting in a narrow light amount adjustment range. On the other hand, by inserting a resistor for constant voltage into the emitter side power supply circuit of the output side transistor of the multivibrator, when the light amount is reduced by increasing the off time ratio of the output side transistor of the multivibrator, the drive transistor It is possible to reliably turn off the light source, prevent the light amount adjustment range from being narrowed, and facilitate setting the constant of the multivibrator.

[0011]

EXAMPLE Next, an example of FIG. 1 will be described. Note that this embodiment is an example in which the circuit of FIG. 5 is improved, and the same portions as those of FIG. 5 are denoted by the same reference numerals. In the figure, TA is an amplifying transistor of the drive circuit 2. In this example, the transistor TA1 of FIG. 5 is omitted and the transistor TA2 is directly connected to the output side transistor T2 of the multivibrator 1. , The transistors T1 and T2 of the multivibrator 1 have NPN
While the PNP type is used, the amplifying transistor TA of the drive circuit 2 is used. The constant voltage resistor 5 is inserted in the power supply circuit on the emitter side of the output side transistor T2.

In this circuit, the transistor TA is turned on when the transistor T2 is turned on, and the latter is turned off when the former is turned off, and accordingly the drive transistor TD is turned on or off. Therefore, when the ratio of the ON time of the transistor T2 is maximized, the light source lamp 3 lights up brightest. Further, when the drive transistor TD is maintained in the on state during the short off time of the transistor T2 associated with the oscillation, the light source lamp 3 is continuously energized, and the maximum illuminance can be improved.

FIG. 2 shows the collector waveform of the transistor T2, which is between the GND and the Zener voltage on the off side where the ratio of the off time of the transistor T2 is large as shown in FIG. However, on the ON side where the ratio of the ON time is large, the switching is performed at a voltage considerably lower than the Zener voltage as shown in (b). Therefore, the amplification transistor TA
By using a PNP type transistor opposite to the transistor T2, the base voltage of the transistor TA becomes close to the GND level when the transistor TA is turned off, and the transistor TA is easily turned on.

As described above, by making the transistor T2 and the transistor TA have mutually opposite types, it becomes easy to turn on the transistor TA when the off-time ratio of the transistor T2 is large, and the waveform is distorted by the capacitor C4. By synergistic action with the action, it becomes easy to turn on the transistor TA 100%. Therefore, one transistor TA for amplifying the drive circuit 2 is used to control the illuminance of the light source lamp 3 without any trouble, and the light source lamp 3 is continuous, that is, 1
Since it is easy to improve the maximum illuminance by energizing at 00%, the number of transistors used can be reduced by half compared with the conventional example of FIG. 5, and the cost can be reduced accordingly.

By the way, in FIG. 1, the constant voltage resistor 5 is inserted on the emitter side of the transistor T2. However, even if this resistor 5 is inserted in the power supply circuit on the collector side as shown in FIG. Can be reduced. However, in this case, when the potential of the terminal S1 becomes equal to or higher than the Zener voltage, even if the transistor T2 is off, the current i bypassing the constant voltage resistor 5 flows as shown by the arrow, and as a result, the resistor R9 There is a possibility that a voltage drop occurs, the transistor TA is turned on, and the drive transistor TD is also turned on. Therefore, even if an attempt is made to reduce the light amount by increasing the off-time ratio of the transistor T2, the light amount cannot be sufficiently reduced, resulting in another problem that the light amount adjustment range is narrowed.

On the other hand, in the circuit of FIG. 1, since the transistor TA is not turned on due to the generation of the bypass current as described above, it is possible to obtain a light quantity adjusting device having a wide adjustment range by sufficiently narrowing the light quantity. . Further, since the collector voltage of the transistor T2 does not fluctuate when the transistor T2 is off, it becomes easy to set the constant of the multivibrator 1 properly and stabilize its operation. Therefore,
It is desirable to insert the constant voltage resistor 5 on the emitter side of the transistor T2 as shown in FIG.

In the above example, the multivibrator 1 is used.
The transistors T1 and T2 of the drive circuit 2 are NPN type, and the transistor TA of the drive circuit 2 is PNP type. However, these relationships are reversed, and the transistors T1 and T2 are PNP type and the transistor TA is NPN type. You can also FIG. 4 is an example in which the same circuit as that of FIG. 1 is configured by reversing the transistor type, and the present invention can be implemented in any combination by making necessary circuit changes according to the transistor type.

[0018]

As is apparent from the above description, the transistor type light quantity adjusting device of the present invention includes either one of the output side transistor of the multivibrator and the amplifying transistor of the next stage connected to this output side transistor. The PNP type and the other is the NPN type.

Therefore, when the off-time ratio of the output side transistor of the multivibrator is large, it becomes easy to turn on the amplifying transistor in the next stage, and it is easy to turn on the amplifying transistor 100% by synergistic action with the capacitor. Therefore, it is possible to reduce the cost by using one transistor for amplification, to control the illuminance of the light source lamp without any trouble, and to improve the maximum illuminance by continuously energizing the light source lamp.

In the case where the constant voltage resistor is inserted in the power supply circuit connected to the emitter side of the output side transistor of the multivibrator, the off time of the output side transistor of the multivibrator is increased to reduce the light amount. At times, the drive transistor can be reliably turned off, a device with a wide light amount adjustment range can be obtained, and constant setting of the multivibrator becomes easy.

[Brief description of drawings]

FIG. 1 is a connection diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment.

FIG. 3 is an explanatory diagram of an operation of the same embodiment.

FIG. 4 is a connection diagram of a modified example of the same embodiment.

FIG. 5 is a connection diagram of a conventional example.

[Explanation of symbols]

 1 Multivibrator 2 Drive circuit 3 Light source lamp 4 Zener diode 5 Resistor for constant voltage TD drive transistor T2 Multivibrator output side transistor TA Amplifying transistor

Claims (2)

[Claims] 1. The brightness of the light source is changed by changing the duty ratio of the output pulse of the multivibrator and controlling the on-time ratio of the drive transistor inserted in series with the light source according to the duty ratio. In the light quantity adjusting device according to claim 1, one of the output side transistor of the multivibrator and the amplification transistor of the next stage connected to the output side transistor is PNP.
Type, and the other type is an NPN type transistor type light quantity adjusting device. 2. A transistor according to claim 1, wherein a constant voltage resistor forming a constant voltage circuit in combination with a Zener diode connected in parallel to the multivibrator is inserted in an emitter side power supply circuit of an output side transistor of the multivibrator. Type light intensity adjustment device.