JPH033967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load driving device that includes a timer circuit in which a time constant is set using a resistor and a capacitor, and drives a load for a certain period of time.

Generally, in a load driving device, a time constant circuit is connected to the input stage of a switch device such as a transistor, and the switch device is turned on for a predetermined time set by the circuit to drive the load. In such a timer-equipped load drive device, in order to prevent the characteristics of the time constant circuit from changing due to fluctuations in the power supply voltage,
It is common practice to combine a time constant circuit with a constant voltage circuit.

A drawback of the above-described device is that the constant voltage circuit consumes current even after the load has been driven by the timer time determined in the time constant circuit.

The present invention aims to eliminate the above-mentioned drawbacks, and is cleverly constructed so that the switch device is energized and the constant voltage circuit is activated only when the load is being driven.

An embodiment of the present invention is shown in FIG. 1, where 1 is a DC power supply (for example, one installed in a car) that supplies power to the following circuits. 2 is a load such as a solenoid, and its negative side is controlled by a circuit package 4.
3 is a switch, and from the moment this switch changes from OFF to ON, it operates to energize load 2 for the set timer time.

The circuit package 4 includes a first load driving transistor 5, a second transistor 6 complementary to this transistor, a capacitor 9 and a resistor 7 forming a time constant circuit, and a capacitor 1 for preventing malfunction.
7, a resistor 13 and a capacitor 15 forming a trigger circuit, a resistor 8 and a constant voltage element 10 forming a constant voltage circuit, and a diode 19 for discharging the capacitors 9 and 15.

Next, the operation of the above circuit will be explained. First, when the switch 3 is open, the first transistor 5 is off and the load 2 is not energized. At this time, capacitors 9, 17 and 15 are connected to L 1 and L ₁ shown in FIG. 1, respectively.
The path L ₂ and L ₃ are in a discharge state.

Next, when switch 3 closes, the second
The charging current of the trigger capacitor 15 flows from the emitter to the base of the transistor 6 via the resistor 13. Therefore, the second transistor 6 is turned on. As a result, the first transistor 5 is also turned on via the resistor 11. Therefore, the load 2 becomes energized and operates.

Furthermore, when both the second transistor 6 and the first transistor 5 are in the on state, the capacitor 9, the resistor 7, and the resistor 8 that constitute the time constant circuit
Charging current flows through. This current becomes the base current of the second transistor and holds both transistors in the on state.

As capacitor 9 is charged, its base current decreases and finally second transistor 6 is turned off. At the same time, the first transistor 5 is also turned off, and the current-carrying path of the load 2 is cut off.
In other words, the time constant circuit composed of the first capacitor 9 and the first resistor 7 determines approximately the timer time (the resistor 8 is sufficiently smaller than the resistor 7).

Therefore, the current consumption of this circuit after this timer period is only that flowing through the resistor 18, and becomes a very small value.

On the other hand, the constant voltage circuit consisting of the constant voltage element 10 and the resistor 8 operates only during the timer period by turning on the first transistor 5, and charges the resistor 7 and the capacitor 9 within a constant voltage (voltage determined by the constant voltage element). This function serves to prevent changes in the timer time due to fluctuations in the power supply 1. In addition, the capacitor 17 is connected to a second capacitor in order to prevent the trigger circuit from re-triggering when the voltage of the power supply 1 suddenly increases after the timer period.
It is connected between the base and emitter of the transistor 6.

Note that, as in this example, coupling the time constant CR circuit and the trigger CR circuit to one transistor 6 has the advantage that the malfunction prevention capacitor 17 only needs to act on that transistor.

The load 2 may be a lamp or a coil load such as a solenoid. In the case of a coil load, the constant voltage element 10 also acts as a reverse surge absorber.

The device of the present invention can also be implemented by the following modifications.

(1) In the example shown in Figure 1, when switch 3 is turned on, load 2 is activated for a certain period of time as long as it continues to be turned on, but when switch 3 is instantaneously closed with a single touch, the load is applied for a certain period of time. can also be activated. For this reason, as shown in Figure 2,
The connection position of the switch 3 may be changed.

(2) As the first and second switch devices, PNP,
Instead of using NPN transistors,
FETs and relays can be used.

(3) The output signal for operating the load may be taken not from the first transistor 5 (first switch device) but from the output of the second transistor 6 (second switch device). In this case, for example, like the first transistor 5, a third transistor may be provided which receives the output of the second transistor 6 at its base, and the load may be operated by the output of this third transistor. Also, resistor 11
A light emitting diode as a load may be connected in series to the path passing through.

(4) The trigger circuits 13, 15, 19 may be configured to act on the base of the first transistor 5.

(5) Zener diodes and ordinary diodes can also be used in constant voltage circuits.

(6) The load may be an electrical circuit that emits light or whose output state changes directly as a mechanical operation, or that performs electrical calculations or memory only during its operation.

As described above, the device of the present invention has the effect that the constant voltage circuit operates only during the timed operation, and the constant voltage circuit operates stably, and no power is consumed in the constant voltage circuit after the timed operation ends. Furthermore, according to the second invention set forth in claim 2, the invention set forth in claim 1 can be achieved by using two transistors commonly used as semiconductor switch devices. It is possible to contribute to the implementation of the present invention by proposing a more specific and simple circuit configuration for implementation.

[Brief explanation of drawings]

FIG. 1 is an electrical wiring diagram showing an embodiment of the present invention;
FIG. 2 is an electrical wiring diagram showing another embodiment of the present invention. 2...Load, 3...Trigger switch, 5...First transistor, 6...Second transistor,
7, 9...Resistance and capacitor for time constant, 8, 1
0...Resistance for constant voltage and constant voltage element, 13, 15
...Resistance and capacitor for trigger.

Claims (1)

[Scope of Claims] 1. A first switch device that conducts or interrupts conduction according to an input signal; a second switch device for supplying the first switch device to the first switch device; a time constant circuit that generates an output signal for a predetermined period of time and supplies it to the second switch device through the first switch device; a constant voltage circuit connected between the output end of the first switch device to which the time constant circuit is connected and a power supply line in order to apply a constant voltage to the constant circuit; a trigger device that applies a trigger signal to one of the input terminals in order to conduct the switch device; and a load device connected to respond to the output signal of either the first or second switch device. Load drive device. 2. A first transistor that conducts or shuts off in response to a base input, and supplies current to the load via the output terminal when conductive; A first transistor that conducts or shuts off in response to a base input, and supplies a base input to the first transistor when conductive; a second transistor that conducts the first transistor by applying a constant voltage, one end of which is connected to a power supply line that is commonly connected to the load, and the other end of which is connected to the output end of the first transistor via a resistor; a constant voltage circuit that generates a potential that is a predetermined potential apart from the potential of the power supply line at a connection point between the constant voltage element and the resistor; a constant voltage generation point of the constant voltage circuit and the second transistor; It consists of a resistor and a capacitor connected between the first transistor and the second transistor, and when the first transistor is conductive, the base input is applied to the second transistor for a predetermined period of time through the first transistor, and the second transistor is connected for that period of time. A load driving device comprising: a time constant circuit that makes a transistor conductive; and a trigger device that provides a trigger signal to a base input of the second transistor to make the second transistor conductive.