JPS6369317A - Switch control circuit - Google Patents

Abstract

PURPOSE:To obtain a control circuit for an electronic switch with simple constitution ensuring the power-on reset of a control object circuit by using a control confirming signal representing the on-state of the control object circuit so as to control an off-signal only when the power supply of the control object rises completely. CONSTITUTION:When a voltage level transits from a low level to a high level at an on-signal input terminal 1, a high level is outputted at a control signal output terminal 3 and the control object circuit is turned on. Thus, the high level signal representing the on-state switching of the control object circuit is inputted to the control confirmation signal terminal 4, and then an output of an off-signal to the control confirmation signal terminal 4 is attained. Before the high level signal representing the power voltage of the control object circuit reaching a voltage VDD and the control object circuit to be switched is inputted to the control confirmation signal terminal 4, even if the voltage level transits from the low level to the high level at the off-signal input terminal 2, no low level is outputted to the output control signal output terminal 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a switch control circuit that generates and outputs on/off control signals by turning on and off a switch.

BACKGROUND OF THE INVENTION A control circuit for a conventional electronic switch is shown in FIG. In this circuit 14, by inputting a signal at a constant voltage level to the 11 ON signal input terminals or the 12 OFF signal input terminals, the 13 control signal output terminals are turned ON or OFF, regardless of whether the circuit to be controlled is ON or OFF. It is often done to output a control signal.

Problems to be Solved by the Invention In such a conventional circuit, an OFF control signal can be output to a control terminal regardless of whether the circuit to be controlled is on or off. However, when the switch is repeatedly turned on and off at high speed, a situation may occur in which the power supply voltage of the controlled circuit does not completely rise. As a result, the power supply voltage of the controlled circuit may rise or fall above or below the reset voltage level of the controlled circuit, making it impossible to secure the set time needed to reset the controlled circuit, making it difficult to ensure the power-on reset of the controlled circuit. Sometimes it doesn't work. A timing diagram showing such a state is shown in FIG.

In Fig. 4, vDD is the power supply voltage when the circuit to be controlled is turned on, vR3 is the threshold voltage at which power-on reset of the circuit to be controlled occurs, and "R8 represents the time during which the reset is applied." R8 is the target to be controlled. If the time required by the circuit is also shorter, the controlled circuit will not be reset reliably.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a control circuit for an electronic switch that has a simple configuration and can reliably perform power-on reset of a controlled circuit.

Means for Solving the Problems The present invention turns on and off by turning on and off a switch.
An on signal input terminal that inputs an on signal to the electronic switch control circuit that generates and outputs an off control signal, an off signal input terminal that inputs an off signal, and outputs an on/off control signal to the controlled circuit. and a control confirmation signal terminal for inputting a signal indicating that the circuit to be controlled which is to be turned on or off by the control signal is turned on, and An off signal can be output from the control signal output terminal to the controlled circuit only when a signal indicating that the control signal is input is input, and when a transition in the input voltage level of the on signal input terminal occurs, the control signal output terminal The switch control circuit outputs an on signal to the control signal output terminal, and outputs an off signal to the control signal output terminal when a transition in the input voltage level of the off signal input terminal occurs.

Function: With the above configuration, a control confirmation signal indicating that the controlled circuit has been turned on is used to perform control such that the off signal can be sent only when the power to the controlled circuit is fully powered up. As a result, it is possible to put into practical use a control circuit for an electronic switch that can reliably perform a power-on reset of a controlled circuit.

Examples Examples of the present invention will be described below. The area inside the dotted line indicated by 7 in FIG. 1 is a circuit diagram showing one embodiment of the switch control circuit of the present invention. Further, FIG. 2 shows a timing chart showing the operation of the circuit shown in FIG. 1 and the state of the power supply voltage of the circuit to be controlled, where vDD represents the power supply voltage when the circuit to be controlled is turned on.

In FIG. 1, 1 is an ON signal input terminal, 2 is an OFF signal input terminal, 3 is a control signal output terminal, 4 is a reset signal input terminal, and 6 and e are D flip-flops.

When the voltage level at the ON signal input terminal 1 changes from low level to high level, a high level is output to the control signal output terminal 3, and the controlled circuit is turned on. As a result, a high-level signal indicating that the circuit to be controlled is turned on is input to the control confirmation signal terminal 4, and from this point on, it becomes possible to output an OFF signal to the control confirmation signal terminal 4. Furthermore, when the voltage level changes from low level to high level at the off signal input terminal 2, a low level is output to the D flip-flop output of e, and is input to the clear terminal of the D flip-flop of 6, so the output control signal output terminal 3 A low level is output, and the controlled circuit is turned off. Second
As shown in the figure, the power supply voltage of the controlled circuit becomes vDD at the control confirmation signal terminal 4, indicating that it is turned on. Even if the signal changes from low level to high level, the low level cannot be output to the output control signal output terminal 3.

Effects of the Invention As described above, according to the present invention, it is possible to realize a control circuit for an electronic switch that reliably operates the power-on reset of the controlled circuit with an extremely simple circuit configuration, and is practical. extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a switch control circuit in an embodiment of the present invention, FIG. 2 is a timing diagram showing the operation of FIG. 1,
FIG. 3 is a circuit diagram of a conventional switch control circuit, and FIG. 4 is a timing diagram showing the operation of FIG. 3. 1...On signal input terminal, 2...Off signal input terminal, 3...Control signal output terminal, 4...
...Reset signal input terminal, 5...D flip-flop, 6...D flip-flop. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure w & 3 Figure l
4 Figure 'TR3

Claims (1)

[Claims] An on signal input terminal inputs an on signal to the control circuit of an electronic switch that generates and outputs an on/off control signal by turning the switch on and off; an off signal input terminal inputs an off signal; - A control signal output terminal that outputs an OFF control signal to the controlled circuit and a control confirmation signal terminal that inputs a signal indicating that the controlled circuit that is turned on and off by the control signal is turned on, and Only when a signal indicating that the controlled circuit is turned on is input to the confirmation signal terminal, an off signal can be output from the control signal output terminal to the controlled circuit, and the input voltage level of the on signal input terminal A switch control circuit that outputs an on signal to the control signal output terminal when a transition occurs, and outputs an off signal to the control signal output terminal when a transition occurs in the input voltage level of the off signal input terminal.