JPS6245475Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a power supply control circuit that controls opening and closing of a power supply path according to the operating state of a load.

A conventional device of this type is shown in FIG. In the figure, 1 is the power switch, 2 is the fuse that protects the circuit, and 3 is the abnormality detection signal.
NPN transistor turns on and blows fuse 2 to stop power supply to load 5; 4 is a memory circuit that controls transistor 3; 6 is a load abnormality detection circuit; 7 is a gate circuit for connection with memory circuit 4. It is.

Next, the operation will be explained.

Even if the power switch 1 is turned on, if there is no abnormality in the circuit, the detection signal from the load abnormality detection circuit 6 will not be output, the output of the memory circuit 4 will maintain OV, and the power will be supplied to the load 5 and the load abnormality detection circuit 6. continue to be supplied.

Next, when an abnormality occurs in the load, the detection signal from the load abnormality detection circuit 6 is given to the memory circuit 4 through the gate circuit 7, and the output of the memory circuit 4 is NPN.
Generates enough positive voltage to turn on transistor 3. As a result, a current exceeding the rated current of fuse 2 flows, forcibly blowing fuse 2,
The power supply to the load is cut off to prevent the load 5 from being destroyed.

Since the conventional power supply control circuit is configured as described above, a high power transistor 3 is required that can flow a current sufficient to blow the fuse 2. A fuse memory circuit 4 and a gate circuit 7 are required.
There were disadvantages such as the circuit was complicated, the cost was high, and the fuse 2 had to be replaced.

Furthermore, if the load abnormality detection circuit 6 fails, an abnormality detection signal is output even if there is an abnormality in the load 5, so there is a drawback that the load 5 may be destroyed.

This idea was made in order to eliminate the drawbacks of the conventional ones as described above, and by providing a switching element in the power supply path of the load and controlling this switching element according to the operating state of the load, it is easy and simple. It is an object of the present invention to provide a current control circuit that can reliably protect a load at low cost and that can be easily maintained.

An embodiment of this invention will be described below with reference to the drawings. In Fig. 2, 8 is a relay driving PNP transistor, 9 is a relay driving PNP transistor 8
NPN transistor that controls ON/OFF of 11
In order to quickly discharge the capacitor 10 when the power switch 1 is turned from ON to OFF, the diode 12 is located together with the capacitor 15, and the PNP transistor 9
a resistor for supplying a pulsed positive voltage to the base of 14;
is a resistor to quickly discharge the capacitor 15 when the power switch 1 is turned from ON to OFF, and 17 is installed together with the resistor 13 to allow the signal of the load abnormality detection circuit 6 to flow in one direction. This diode prevents the pulsed positive voltage generated by the load abnormality detection circuit 6 from flowing into the load abnormality detection circuit 6.

The control circuit 20 is composed of the above-mentioned numerals 8 to 17.

18 is a relay that turns on and off the supply of power to the load 5, and 18a is its excitation coil;
18b is its relay contact. Note that this second
In the figure, numerals 1, 5, and 6 correspond to the same numerals in Fig. 1, and the load abnormality detection circuit 3 in this case outputs a predetermined voltage (for example, "1" output) when the load 5 is normal. However, the output is configured to be zero in the event of an abnormality.

In FIG. 2, when the power switch 1 is turned on, a time-pulsed positive voltage with a time constant determined by the capacitor 15 and the resistor 13 is applied to the base of the NPN transistor 9. It will be ON temporarily for a period of time. For this reason, the PNP transistor 8 is turned on, current flows through the excitation coil 18a, and its contact 18b closes to supply current to the load 5. On the other hand, the output voltage of the PNP transistor 8 is determined by the capacitor 10 and the resistor 12 for a certain period of time, and a pulsed positive voltage is again applied to the base of the NPN transistor 9, forming a closed loop. load 5 for a period of time very stably by applying a positive voltage.
can supply power to.

If the load is normal while power is being supplied within this certain period of time, a positive voltage is output. This turns on the NPN transistor 9,
By turning on the PNP transistor 8 and turning on the relay 18, power is continuously supplied.

When the load abnormality detection circuit 6 determines that the load 5 is abnormal, its output becomes Ov, so the NPN transistor 9 is turned off, the PNP transistor 8 is turned off, the relay 18 is turned off, and the power supply is cut off.

In addition, resistor 14 turns power switch 1 from ON to OFF.
This resistor is used to quickly discharge the capacitor 15 when the capacitor 15 is returned to its normal state. The diode 11 is also used to quickly discharge the capacitor 10 when the current switch 1 is turned back from ON to OFF.

Although the above embodiment has been described using the relay 18 as the switching element for opening and closing the power supply path of the load 5, the same effect can be obtained by using a control element such as a transistor or a thyristor.

As described above, according to this invention, a switching element is provided when power is supplied to the load, and this switching element is controlled according to the load condition, and the self-check function of the load abnormality detection circuit is included in the control loop. As a result, the load can be reliably protected and its maintenance and restoration operations can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional power supply control circuit, and FIG. 2 is a connection diagram showing a power supply control circuit according to an embodiment of the present invention. In the figure, 5 is the load, 6 is the load abnormality detection circuit, and 18
2 is a switching element, and 20 is a control circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] A switching element that is connected in series to the power supply path of the load and opens and closes the supply path, a control element that controls the opening and closing of this switching element, and a control element that detects the operating state of the load and outputs a normal/abnormal signal depending on the state. a load abnormality detection circuit, a first supplying a charging current having the same polarity as a normal signal outputted from the load abnormality detection circuit when the load is normal to the control element for a predetermined time after power supply to the load is started; A charging path and a second charging path that is charged by the output voltage of the control element driven by the charging current and that supplies this charging current to the control element again are formed to input a start signal to the control element. A power supply control circuit further comprising: a control circuit for driving and controlling the control element according to a normal/abnormal signal subsequently output from the load abnormality detection circuit.