JPH0210676Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flip-flop circuit suitable for driving a load such as a defogger circuit for an automobile rear window.

Such a conventional flip-flop circuit is constructed as shown in FIG. 1, for example. The power supply B is connected to a load H such as a defogger heater via a relay switch RS that is turned on when the relay coil RC is excited, and is also connected to a load H such as a defogger heater via an ignition switch S1 to the relay coil RC and further to a surge voltage absorbing Connected to Zener diode ZD1.
The switch S1 is grounded via a resistor R8 and a momentary switch S2 that drives a load H.
One end of the resistor R1 is connected to the switch S1, and the other end is connected to the collector of the transistor Q1 whose emitter is grounded, and is also connected to the base of the transistor Q2 whose emitter is grounded via the resistor R2 and the diode D3. has been done. The base of transistor Q2 is grounded through resistor R5. The collector of transistor Q2 is a relay coil.
It is connected to RC and to the base of transistor Q1 via resistor R3 and diode D1. The base of transistor Q1 is resistor R4
is grounded through. The anode of diode D1 is connected to switch S2 via diode D2 and capacitor C1, and the cathode of diode D2 is connected to the collector of transistor Q1 via resistor R6. The anode of diode D3 is connected to switch S2 via diode D4 and capacitor C2, and the cathode of diode D4 is connected to the collector of transistor Q2 via resistor R7. The flip-flop circuit is composed of capacitors C1 and C2, diodes D1 to D4, resistors R1 to R8, relay coil RC, and transistors Q1 and Q2.
When the transistor Q1 is turned on, the transistor Q2 is turned off. In this state, the relay coil RC is not excited, so the load H is not energized.

When switch S1 is turned on and transistor Q1 is turned on, one end of capacitor C1 is grounded through resistor R6, the collector and emitter of transistor Q1, and the other end is connected to power supply B through resistor R8. Therefore, the voltage of power supply B is stored in capacitor C1. At this time, when the switch C2 is turned on, the other end of the capacitor C1 is grounded, so that a negative voltage is applied to one end of the capacitor C1. As a result, diode D1 is turned off via diode D2, the base voltage of transistor Q1 is cut off, and transistor Q1 is turned off. Then, the collector potential of transistor Q1 rises, and this rise is applied to the base of transistor Q2 via resistor R2 and diode D3, turning on transistor Q2. When transistor Q2 is turned on, relay coil RC is excited, relay switch RS is turned on, and load H is energized. When transistor Q2 is turned on, one end of capacitor C2 is grounded via resistor R7, the collector and emitter of transistor Q2, and therefore capacitor C2 is charged via resistor R8. On the other hand, capacitor C
The charged charge of 1 is discharged through the resistors R8, R1, and R6 because the transistor Q1 is turned off.

When switch S2 is turned on again, capacitor C
Since the other end of the capacitor C2 is grounded, a negative voltage is generated at one end of the capacitor C2, the diode D3 is turned off via the diode D4, and the base voltage of the transistor Q2 becomes zero. As a result, transistor Q
2 is turned off, the excitation of the relay coil RC is released, and the relay switch RS is turned off.
Since the base voltage of transistor Q1 increases,
turns on. The charge of capacitor C2 is the resistance R
8. Discharged via relay coil RC and resistor R7.

However, such flip-flop circuits have the disadvantage that when the voltage drops, for example when a light is turned on, the state is reversed. In addition, the state may become unstable due to power transmission noise that occurs when connecting a horn, buzzer, etc.
There were cases where the relay caused chattering.

The present invention has been devised in view of such a situation, and it is an object of the present invention to provide a flip-flop circuit that does not easily reverse its state or cause chattering.

Embodiments of the present invention will be described below with reference to FIGS. 2 and 3. In these figures, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and their details will be omitted.

In FIG. 2, a diode D5 is connected between the connection point of capacitors C1 and C2 and switch S2 and a resistor R8, and a transistor Q1
A capacitor C3 is connected between the collector of the diode D5 and the anode of the diode D5, and the rest of the structure is the same as that in FIG.

The operation when the switches S1 and S2 are operated is the same as that described above.

When the power supply voltage drops, in the circuit shown in Figure 1, the drop is transferred to the capacitor C via the resistor R8.
1 and C2, and the operation was as easy as turning on switch S2. However, in the circuit shown in Fig. 2, diode D5
Since the capacitors C1 and C2 are connected in the opposite direction to such a drop, the potential at the common connection point of the capacitors C1 and C2 does not drop. Therefore, there is little possibility that the state will be reversed due to a voltage drop.

On the other hand, if inductive noise is superimposed on the power supply, when transistor Q1 is on, switch S
1. Relay coil RC, resistor R3, capacitor C
3. In the collector-emitter path of transistor Q1, and when transistor Q2 is on,
Inductive noise will flow through the collector-emitter paths of switch S1, resistor R1, capacitor C3, resistor R3, and transistor Q2, so there is little chance that the relay and RS will cause chatter.

Figure 3 shows that when integrating a flip-flop circuit (the part surrounded by a dashed line in the figure shows the part to be integrated), in order to protect the circuit from surge voltage, resistor R9 is connected to switch S1 and resistor R.
1, and the resistor R1 and the resistor R9
The connection point of
This is the same as in the figure.

As described above, the present invention has a simple structure that allows the state of the flip-flop to be easily reversed.
Chattering can be prevented.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional flip-flop, Figure 2 is a circuit diagram of a flip-flop according to the present invention, and Figure 3 is a circuit diagram of a flip-flop according to the present invention.
The figures each represent a circuit diagram of a flip-flop according to another embodiment of the present invention. S1...Ignition switch, S2...Load drive switch, H...Load, RC...Relay coil, RS...Relay switch.

Claims (1)

[Claims for Utility Model Registration] A first transistor constituting a flip-flop circuit whose collector and emitter are connected between a power supply and ground and whose base is connected to the collector of a second transistor to be described later; a second transistor constituting the flip-flop circuit that is connected between a power source and ground via a coil, and whose base is connected to the collector of the first transistor; and the bases of the first and second transistors and the power source. A flip-flop circuit comprising: a pair of capacitors connected through a diode, and a capacitor connected between the base and collector of the first transistor.