JPH049619Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a voltage output circuit, particularly one used for an output circuit of a control device or the like.

In general, control equipment such as temperature controllers, counters, timers, various detection switches, etc.
Its operating status is often output in the form of voltage. Furthermore, it is often convenient to provide these control devices with light emitting diodes (hereinafter referred to as LEDs) for displaying operation. Therefore, conventionally, as shown in FIG. 1, an output switching circuit 1 consisting of a transistor T5 for controlling on/off the output voltage appearing at the output terminals P1 and P2 according to the control input signal VS, A constant voltage circuit 2 consisting of a resistor R8 and a Zener diode D4 for making the output voltage applied to P2 constant, LETD1, D2 for operation display, and these LEDs D1, D2
A voltage output circuit having a circuit 3 etc. for driving was used. In this case, output terminals P1, P
2 is provided for arbitrary use by the user, so sufficient protection measures must be taken against overloads, short circuits, unexpected accidents, etc.
In particular, in this type of output circuit, the output terminals P1, P
2 and the inside of the device are common wiring paths (GND line, etc.)
Since the transformer is directly connected to the transformer, if protective measures are not taken, internal elements may be destroyed or the transformer may be burnt out. Therefore, in the conventional circuit shown in Figure 1,
Overcurrent detection resistor R in series with output terminals P1 and P2
The resistor R11, the resistor R10, and the transistor T4 constitute an output protection circuit 4 that forcibly turns off the switching circuit 1 when the output current exceeds a certain level. Also,
Circuit 3 that drives LEDD1 and D2 is an inverter T
1. Transistors T2, T3 and resistors R1 to R6
It is composed of: Other resistors R7, R9 and Zener diode D are connected to switching circuit 1.
This is for limiting the input voltage of the transistor T5.

By the way, the conventional voltage output circuit as shown in FIG. 1 has a drawback in that the overcurrent detection resistor 11 of the output protection circuit 4 increases the output impedance. Also, the current seen from the input voltage source VD of the constant voltage circuit 2 is
There was a problem in that it varied greatly depending on the state of the load connected to 2. Furthermore, LEDD1, D2
The lighting drive current source for LEDD1 and LEDD1 is obtained in parallel from the input voltage source VD in addition to the output current.
There was a problem in that the current consumption of the entire circuit increased by the current consumption of D2. The brightness of the LEDs D1 and D2 was also unstable due to the influence of the change in the load condition. Furthermore, the first
As shown in the figure, the drive circuit 3 for displaying the operation on the LEDs D1 and D2 uses a large number of elements and is highly complex, resulting in a large and costly circuit. It was also the cause.

This invention was made to solve the conventional problems as described above, and its purpose is to output a voltage output that is controlled on and off according to a control input signal to an output terminal via a constant voltage circuit. give to
In addition, in a voltage output circuit of a control device, etc. that has an LED for indicating operation, a sufficient output protection function is ensured without increasing the output impedance, and the voltage output circuit is not easily affected by the condition of a load arbitrarily connected by the user. In addition, there is an LED for operation indication.
To provide a voltage output circuit which can significantly reduce the current consumption of the entire circuit in spite of the fact that it has the same characteristics, and which can be constructed at low cost with a relatively small number of used elements and a simple circuit. In order to achieve the above object, this invention provides a voltage output that is controlled on and off according to a control input signal to an output terminal via a constant voltage circuit, and is used in control equipment etc. that has a light emitting diode for operation display. In the voltage output circuit, a constant current circuit is interposed between the constant voltage circuit and the input voltage source of the constant voltage circuit, and further, the input current of the constant voltage circuit drives the light emitting diode, and the above operation is performed. At least two display light emitting diodes are provided, and each light emitting diode is inserted in series between the constant current circuit and the constant voltage circuit, and is connected in parallel to each other, and is opened/closed by the control input signal. The present invention is characterized in that a switching circuit causes all of the output current of the constant current circuit to flow through only one selected light emitting diode.

Hereinafter, preferred embodiments of this invention will be described in detail based on the drawings. In each figure, the same parts or corresponding parts are denoted by the same reference numerals.

FIG. 2 shows an embodiment of a voltage output circuit for control equipment, etc. according to this invention. The circuit shown in the figure includes an output switching circuit 1 consisting of a transistor T5 for controlling on/off voltage output at output terminals P1 and P2 according to a control input signal VS, and a constant voltage circuit using a Zener diode D4. 2 and a constant current circuit 5. The control input signal VS is applied to the base of the transistor T5 via resistors R12 and R13. Further, the constant current circuit 5 includes a transistor T6, a Zener diode D5, and resistors R14 and R15. Then, the constant current circuit 5 is interposed between the constant voltage circuit 2 and the input voltage source VD of the constant voltage circuit 2, and the input current of the constant voltage circuit 2 also lights up the operation display LEDs D1 and D2. It is designed to be driven. Furthermore, in the embodiment, LEDD1, D2
Two (or more) LEDs are provided, each LEDD
1 and D2 are constant current circuit 5 and constant voltage circuit 2, respectively.
The output current of the constant current circuit 5 is applied to only one selected LED D1 or D2 by a switching circuit 6 which is inserted in series between the LEDs and connected in parallel with each other and which is opened and closed by the control input signal VS. I'm trying to let everything flow. The switching circuit 6 in this case consists of a transistor T7 interposed in series with one LEDD2 and the other LEDD2.
1 and a diode D6 interposed in series with the diode D6. The conduction of the transistor T7 is controlled by the control input signal VS via the resistor R16. Also,
A diode D7 is inserted in parallel between the emitter and base of the transistor T7 for protection.

Now, in the voltage output circuit configured as described above, it goes without saying that first, the output voltage appearing at the output terminals P1 and P2 is made constant by the constant voltage circuit 2. Furthermore, the output terminals P1 and P2 are only provided with an output switching circuit 1, and are not provided with anything equivalent to a conventional overcurrent detection resistor. Therefore, the output impedance during normal operation can be kept sufficiently low. but,
Since the output current that can flow from the output terminals P1 and P2 is limited by the constant current circuit 5, a current-limited drooping characteristic appears in the event of an overload or short circuit, and a reliable protective operation is performed. . The limiting current value at this time can be freely set by the Zener voltage value of the Zener diode D5 of the constant current circuit 5 and the value of the resistor R14. This allows the current seen by the input voltage source VD to be stabilized without being influenced by the load connected by the user. To drive the operation display LEDD1 or D2, the forward voltages of LEDD1, D2 and diode D6 are set to Vf1, Vf2, and Vf, respectively.
6, and when the collector-emitter saturation voltage of transistor T7 is VCES, Vf2 + Vf
By establishing the relationship 6>Vf1+VCES in advance, even with an extremely simple circuit configuration,
The two LEDs D1 and D2 can be turned on alternately according to the control input signal VS. In this case, 2
One of the LEDs D1 and D2 is selected.
Since all of the output current of the constant current circuit 5 flows only through LEDD1 or D2, its lighting
There is an advantage that the code of LED D1 or D2 is stabilized, and that the entire circuit current is stabilized without being affected by changes in the display state caused by the LED. What is most noteworthy is that it is used to display its operation.
This means that the current for driving LEDD1 and D2 to light up does not have to be drawn separately from the input voltage source VD, which makes it possible to simplify the circuit configuration and significantly reduce the current consumption of the entire circuit. It is now possible to save money.

As described above, compared to conventional circuits, the voltage output circuit of this invention is able to perform output protection and drive the operation display LED with a simpler circuit configuration, and the circuit current can also be controlled by the load. It can be stabilized without being affected by the state or operating state, and furthermore, the current consumption can be significantly reduced.

In addition, at least two operation display LEDs are provided, and each LED is inserted in series between the constant current circuit and the constant voltage circuit, and connected in parallel to each other, and is controlled by a switch circuit that opens and closes depending on the control input signal. Since the entire output current of the constant current circuit is made to flow through only one selected LED, multiple LEDs can be turned on alternately according to the control input signal even with an extremely simple circuit configuration. . Furthermore, since all of the output current of the constant current circuit flows only through the selected LED, the brightness of the operation display LED can be stabilized without being affected by the load state or the like.

Furthermore, since the current for driving the operation display LED does not need to be drawn separately from the input voltage source, the circuit configuration can be simplified, and
This means that the power consumption of the entire circuit can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional voltage output circuit, and FIG. 2 is a circuit diagram showing an embodiment of the voltage output circuit according to this invention. 1... Output switching circuit, 2... Constant voltage circuit, 5... Constant current circuit, 6... LED lighting drive circuit, D1, D2... LED (light emitting diode),
VD...Input voltage source, VS...Control input signal,
GND...Common side wiring path.

Claims (1)

[Scope of utility model registration request] In a voltage output circuit of a control device, etc., which provides a voltage output that is controlled on and off according to a control input signal to an output terminal via a constant voltage circuit, and has a light emitting diode for operation display, the constant voltage circuit and the corresponding constant voltage circuit are used. A constant current circuit is interposed between the input voltage source of the voltage circuit, and the light emitting diode is driven to light by the input current of the constant voltage circuit, and at least two light emitting diodes for operation display are provided, each of which has a constant current circuit. The light emitting diodes are each inserted in series between the constant current circuit and the constant voltage circuit, and are connected in parallel to each other, and the light emitting diodes are connected in parallel to each other, and one of the light emitting diodes is selected to emit light by a switching circuit that opens and closes in response to the control input signal. A voltage output circuit characterized in that all of the output current of the constant current circuit is made to flow through only the diode.