JPH0623165Y2 - Failure prevention circuit by reverse connection of DC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a circuit for preventing a failure caused by reverse connection of a DC power supply.

(Prior Art) A DC power supply must be connected without making a mistake in its polarity, and the reverse connection of the polarity results in various obstacles to other devices connected to the electronic circuit. A circuit of this type has been known in the past, because a failure prevention circuit that always outputs a correct voltage to the output terminal is desired even if the circuit is mistakenly reversed.

"Polarity protection device for DC power supply" according to Japanese Utility Model Laid-Open No. 51-65608 is an example thereof. In this device, when the polarity is wrong and a reverse voltage is applied as shown in FIG. It is a circuit that switches and outputs a normal voltage all the time.However, after the reverse voltage is applied, there is a slight difference in response time until the relay operates. It appears instantly at the output terminal. The reverse voltage pulse sometimes causes the semiconductor in the device to be damaged.

As shown in Fig. 4, the "fault prevention circuit by reverse connection of DC power supply" according to Japanese Examined Patent Publication No. 63-62982 connects the collectors of a pair of PNP type transistors, and connects the emitters to the input power supply respectively. The collectors of a pair of NPN-type transistors are connected to each other, and the emitters are connected to the input power supply. Since the output terminals are between the collector connection points, when one of the PNP transistors is turned on and the other is turned off when power is applied, that is, the collector voltage is always the high potential of the input voltage regardless of the polarity of the power supply. Side potential. Similarly, in the case of an NPN type transistor, its collector is always on the low potential side of the input voltage regardless of the polarity of the power supply. This circuit does not generate an instantaneous reverse voltage pulse as in the circuit shown in FIG. 3, but due to the use of a high-power transistor, its heat generation cannot be avoided and the device is downsized. The heat generation may adversely affect the performance of other parts in the device.

(Purpose of the present invention) As described above, the conventional "fault prevention circuit by reverse connection of DC power supply"
Still has the above problems.

The present invention is intended to solve these problems, and provides a stable fault prevention circuit that does not generate a momentary reverse voltage pulse and does not leave a problem related to heat generation.

(Structure and operation of the present invention) The failure prevention circuit by the reverse connection of the DC power source according to the present invention uses two relays, and each relay switch is switched by the operation of the relay coil so that the polarity of the output terminal is always constant.
Therefore, input terminals and output terminals are each connected to a relay switch, and each of these switches has two terminals that switch in the ON / OFF state.
Connect between the ON and OFF terminals. On the other hand, two rectifiers are connected in series facing each other, and one set of two rectifiers is connected in parallel with relay coils to make two identical circuits, and these circuits are connected in parallel between the input terminal and the relay switch. The relay coil is connected and configured to control the relay switch by the relay coil.

The relay switch is always off and is turned on by energizing the relay coil. Only when the relay switch is switched, the current flowing from the input terminal is output to the output terminal, so that the momentary voltage pulse having the wrong polarity is not generated.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

(Embodiment) FIG. 1 shows an embodiment of a fault prevention circuit by reverse connection of a DC power source according to the present invention, in which 1a and 1b represent input terminals, 2a and 2b represent output terminals, and the polarities of the input terminals 1a and 1b. However, the output terminal 2a has a positive pole and the output terminal 2b has a negative pole due to a relay and a diode connected in the middle.
Become a pole. In the figure, 3a, 3b, 4a, and 4b are switches that operate when the relay coils 5a and 5b are energized. The terminal 6a of the switch 3a is the input terminal 1a, and the terminal 6b of the switch 3b is the input terminal 1b. On the other hand, the terminal 7a of the switch 4a is connected to the output terminal 2a, and the terminal 7b of the switch 4b is connected to the output terminal 2b. The switch 3a is provided with terminals 8aa and 8ab whose contacts are turned on and off. In the figure, the terminals are connected to the terminal 8ab, and the switch 3b is provided with terminals 8ba and 8bb whose contacts are turned on and off. Has been. And switch 4
Similarly, a is provided with terminals 9aa and 9ab, and switch 4b is provided with terminals 9ba and 9bb.
ab, terminal 8ab is terminal 9ba, terminal 8ba is terminal 9bb,
Further, the terminal 8bb is connected to the terminal 9aa. That is, ON
Connect the terminals to the OFF terminals.

On the other hand, the diode 11a is connected in parallel with the relay coil 5a, and the diode 10a is further connected in series. The diode 10a is connected between the input terminal 1a and the terminal 6a of the switch 3a, and the other end of the relay coil 5a is input. It is connected between the terminal 1b and the terminal 6b of the switch 3b. Further, the relay coil 5b and the diode 11b are connected in parallel, and the diode 1
0b are connected in series, and the diode 10b has an input terminal 1b.
And the terminal 6b of the switch 3b, and the other end of the relay coil 5b is connected between the input terminal 1a and the terminal 6a of the switch 3a.

By the way, when each relay coil 5a, 5b is not energized, each switch 3a, 3b, 4a, 4b is in the OFF state, and when the relay coil 5a, 5b is energized to operate, it is turned ON.
Becomes Normally, the input terminal 1a has a positive pole, and the input terminal 1b
The negative pole is connected to the switches 3a and 3b.
Is OFF and the contacts are connected to 8aa and 8ba. Now, if the polarities connected to the input terminals 1a and 1b are mistakenly reversed, the voltage of the + pole that has entered the input terminal 1b is applied from the switch 3b to the terminal 8ba and the voltage is applied to the terminal 9bb. The switch 4b is not connected to the terminal 9bb. Similarly, the negative pole that has entered the input terminal 1a is also the same, and no voltage is applied to the output terminals 2a and 2b. This means that no instantaneous reverse voltage pulse is generated by switching the switch. However, the +
If the poles are connected, the current will flow through diode 10b,
Energize the relay coil 5b to turn on the switches 3a and 3b.
Switch to the ON state. Then, as shown in the figure,
The positive polarity voltage is output to the output terminal 2a, and the negative polarity voltage is output to the output terminal 2b.

Of course, in the normal state, input terminals 1a and 1b are +
If the pole and-pole are connected, the current flowing through the diode 10a energizes the relay coil 5a, and as a result, switches 4a and 4b are turned on. Therefore,
The positive pole is output to the output terminal 2a and the negative pole is output to the output terminal 2b, and the output terminals 2a and 2b always maintain a fixed polarity regardless of the polarities of the input terminals 1a and 1b.

FIG. 2 shows another embodiment according to the present invention. If a voltage (for example, 12 V) of normal polarity (+ pole, -pole) is applied to the input terminals 1a and 1b of this circuit, the Zener diode
Because 12a almost no current flows through the base of the transistor Q _1, a bias is not applied between the emitter and thus transistor to Q ₁ collector, emitter between the
It is in the OFF state.

On the other hand, the current flowing through the diode 13a is the transistor Q ₂ based collectors for biasing between the emitter, the emitter between the turned ON, a current flows through the relay coil 5a from the diode 10a, the relay switch 4a energization of the relay coil 5a 4b is switched to the ON state. Therefore, a voltage having a normal polarity acts on the output terminals 2a and 2b.

Here, the polarity is normal, but the input terminals 1a, 1b are
When a voltage higher than usual (for example, 24V) is applied to the zener diode 12a, the Zener diode 12a rapidly flows a current, and as a result, the base and the emitter of the transistor Q ₁ are biased, so that the collector and the emitter are turned on. Since the current flowing through the diode 13a flows into the emitter through the collector of the transistor Q ₁ , the base bias of the transistor Q ₂ is not added,
The collector and the emitter are turned off, and no current flows through the relay coil 5a. As a result, the relay switches 4a and 4b are turned off, and the output terminal 2
No voltage acts on a and 2b.

On the other hand, positive electrode, the input terminal 1a to the input terminal 1b - when reverse voltage polarity is applied, the base of the transistor Q _4,
Because of the bias between the emitters, the collector-emitter is turned on, and the current flows through the diode 10b to the relay coil 5b to switch the relay switches 3a and 3b to the on state. As a result, the output terminals 2a and 2b have normal polarities. Voltage is applied.

The above embodiment is a specific example of the present invention and should not be construed as being limited to this embodiment, but the following effects can be obtained.

(Effect) The circuit of the present invention uses two relays, and controls the flow of electricity by a rectifier to operate each relay separately and output regardless of the polarity connected to the input terminal. A voltage having a constant polarity is always output to the terminal. Moreover, because it is a relay circuit, there is no extra heat generation phenomenon, it becomes a stable circuit, and after connecting with the wrong polarity, the momentary reverse voltage pulse may occur due to the deviation of the response time while the switch is switched by the relay. Nor.

[Brief description of drawings]

1 and 2 are embodiments showing a fault prevention circuit by reverse connection of a DC power source of the present invention, and FIGS. 3 and 4 show conventional circuits, respectively. 1 …… input terminal, 2 …… output terminal 3,4 …… switch, 5 …… relay coil, 6,7,8,9 …… terminal, 10,11 …… diode.

Claims (1)

[Scope of utility model registration request] 1. In a fault prevention circuit by a reverse connection of a DC power source, which always outputs a voltage of a normal polarity to an output terminal without being influenced by the polarity of a voltage input to an input terminal, two rectifiers are connected to each other. Two relay switches that are connected in series in the opposite direction and one of them is connected to a relay coil in parallel and two sets of circuits are connected in parallel between the input and output terminals, and operated by these relay coils. Is connected between the input and output terminals so that the output terminal maintains a normal polarity.