CN105186485B - A kind of misconnection protection circuit - Google Patents

Abstract

The invention relates to a misconnection protection circuit, comprising at least two misconnection protection circuits; each misconnection protection circuit includes a control branch and a power supply branch; the control branch includes a resistor and a relay; the relay The voltage level is adapted to the level of the input voltage; the resistor and the coil of the relay are connected in series to the power supply input; the power supply branch includes normally open contacts corresponding to the respective relays, and the normally open contacts After being connected in series, it is connected between the power supply input terminal and the power supply output terminal. The state of the corresponding normally open contacts is controlled by the relay. Only when the input terminal of each misconnection protection circuit is correctly connected to the corresponding voltage, all the relays can work normally. The multiple sets of normally open contacts corresponding to each relay are Closed, the power supply input terminal of the misconnection protection circuit can be connected to the power supply output terminal. The problem of wrong connection can be effectively prevented, and the safety of power supply is improved.

Description

A misconnection protection circuit

technical field

The invention belongs to the field of circuit protection, and in particular relates to a wrong connection protection circuit.

Background technique

Instrumentation, medical equipment, automotive electronics, etc. have many precision components inside, which require various voltages, such as 5V and 12V. However, the power supply voltage has polarity. If the power supply voltage is reversed, if the input circuit itself has no protection circuit, it will burn out some components and even cause the electrolytic capacitor to explode. In addition, the power supply voltage is also limited by the voltage range. Even if the input polarity is connected correctly, if a higher power supply voltage is connected, it will also cause burnout of the load and some components.

The protection circuit in the prior art, as shown in Figure 1, includes a Zener diode ZD1, which is reversely connected to the negative power supply circuit, and its anode is connected to the base of the triode Q1 through the resistor R2, and the collector of Q1 is connected through the resistor R1, The relay K1 is connected to the negative power supply circuit; the two auxiliary switches of the relay K1 are respectively connected to the positive power supply circuit and the negative power supply circuit. When the input terminal is connected normally, that is, the A terminal is connected to the positive voltage, and the B terminal is connected to the negative voltage, the working voltage of the relay K1 is negative and does not work. When the input terminal voltage is reversely connected, that is, the A terminal is connected to the negative voltage, the B terminal is connected to the positive voltage, the relay K1 is connected to the forward voltage, and the Zener diode is also connected to the forward voltage. Wear, the base of the transistor Q1 gets the circuit of ZD1, Q1 is turned on, the relay K1 is charged and closed, its two auxiliary switches act, and the negative voltage of the power supply A terminal is introduced into the negative pole of the power receiving terminal through one of the switches of the relay K1, and the power supply B The positive voltage at the terminal is also introduced to the positive terminal of the receiving terminal through another switch of the relay K1. So that the receiving end always gets the correct voltage.

Although the protection circuit in the prior art can effectively prevent the problem of voltage reverse connection by switching the positive and negative voltage polarities, it cannot prevent wrong connection. For example, if the 5V power supply voltage is wrongly connected to 12V voltage, it will cause the load and some components to be burned, causing serious losses.

Contents of the invention

The object of the present invention is to provide a misconnection protection circuit to solve the problem that the protection circuit in the prior art cannot prevent misconnection.

To achieve the above object, the solution of the present invention includes:

A misconnection protection circuit, comprising at least two misconnection protection circuits; each misconnection protection circuit includes a control branch and a power supply branch; the control branch includes a resistor and a relay; the voltage level of the relay is It is adapted to the level of the input voltage; the resistor and the coil of the relay are connected in series to the power supply input; the power supply branch includes normally open contacts corresponding to the respective relays, and the normally open contacts are connected in series between the power supply input and the power supply output.

The two ends of the coil of the relay are connected in antiparallel with a Zener diode.

The wrong connection protection circuit also includes an anti-reverse diode, a series resistance of the anti-reverse diode and a coil of a relay, one end of the anode of which is connected to the power supply input end, and one end of the cathode is connected in series with the resistor.

The beneficial effects of the present invention are: the state of the corresponding normally open contact is controlled by the relay, and only when the input end of each misconnection protection circuit is correctly connected to the corresponding voltage, all the relays can work normally, and the corresponding Multiple groups of normally open contacts are closed, and the power supply input terminal of the misconnection protection circuit can be connected to the power supply output terminal. The problem of wrong connection can be effectively prevented, and the safety of power supply is improved.

Description of drawings

Fig. 1 is a protection circuit diagram in the prior art;

Fig. 2 is the circuit diagram of embodiment 1 of the present invention;

Fig. 3 is a circuit diagram of Embodiment 2 of the present invention.

Detailed ways

Example 1

As shown in Figure 2, the misconnection protection circuit of Embodiment 1 of the present invention includes a misconnection protection circuit 1 arranged between the power supply input terminals U1, U1- and the power supply output terminals U1+, U1-; Misconnection protection circuit 2 between U2- and the power supply output terminal and U2+, U2-. The power supply input end is connected to the power supply, and the power supply output end is connected to the load.

The wrong connection protection branch 1 includes a control branch 1: the positive input terminal U1A is connected to the negative input terminal U1B through the anti-reverse diode D1, the resistor R1, and the coil of the relay J1, and the voltage regulator diode Z1 is connected in reverse parallel with the coil of the relay J1; And a power supply branch 1: the positive input terminal U1A is connected to the positive output terminal U1+ through the series connected switches J1A and J2A.

The wrong connection protection branch 2 includes a control branch 2: the positive input terminal U2A is connected to the negative input terminal U2B through the anti-reverse diode D2, the resistor R2, and the coil of the relay J2, and the Zener diode Z2 is connected in reverse parallel with the coil of the relay J2; And a power supply branch 2: the positive input terminal U2A is connected to the positive output terminal U2+ through the series connected switches J1B and J2B.

The above-mentioned switches J1A and J1B are normally open contacts of the relay J1; switches J2A and J2B are normally open contacts of the relay J2.

Among them, the breakdown voltage U _Z1 of the Zener diode Z1 is equal to the normal working voltage of the relay J1, which ensures that the working voltage of the relay J1 will not be greater than its rated voltage; at the same time, it plays the role of a freewheeling diode to prevent the coil of the relay J1 from bifurcating when the power is off. The harm caused by the high reverse electromotive force generated by the terminal. The resistance value of the current limiting resistor R1 In the formula, U ₁ is the voltage at the input terminal of U1, U _D1 is the conduction voltage drop of the anti-reverse diode D1, and I _J1 is the normal working current of the relay J1. The breakdown voltage U _Z2 of the Zener diode Z2 is equal to the normal working voltage of the relay J1, which ensures that the working voltage of the relay J2 will not be greater than its rated voltage; at the same time, it plays the role of a freewheeling diode to prevent the voltage generated at both ends of the relay J2 coil when the power is off. The harm caused by the higher reverse electromotive force. The resistance value of the current limiting resistor R2 In the formula, U ₂ is the voltage at the input terminal of U2, U _D2 is the conduction voltage drop of the anti-reverse diode D2, and I _J2 is the normal working current of the relay J2. By selecting the working voltage of the relay in the higher input voltage level loop to be greater than the rated voltage of the lower input voltage level loop, the relay in the higher input voltage level loop can not work normally when inputting a lower voltage level.

For convenience of description, it is assumed that the input terminal of U1 is fixedly connected to a lower voltage level, such as 5V, and the input terminal of U2 is fixedly connected to a higher voltage level, such as 12V. Then the working voltage of the relay J2 is greater than the rated voltage of the relay J2.

When it is connected normally, that is, when the input terminal of U1 is connected with 5V voltage and the input terminal of U2 is connected with 12V voltage, both relay J1 and relay J2 are at normal working voltage, and they are both working and conducting. The normally open contacts J1A, J1B and J2A, J2B is closed, and the input end supplies power to the output end normally.

When the input terminal of U1 is connected to 12V voltage and the input terminal of U2 is connected to 5V voltage, the relay J1 will work with electricity, and its normally open contacts J1A and J1B will be closed; the relay J2 does not reach the operating voltage, so the relay J2 does not work, and its normally open contacts Points J2A and J2B are both in the disconnected state, so that the power supply positive input terminals of the misconnection protection circuit 1 and the misconnection protection circuit 2 cannot be connected to the power receiving positive input terminal, which functions as a voltage level misconnection protection function.

When the polarity of the U1 input terminal or U2 input terminal is connected incorrectly, the relay J1 or relay J2 cannot work, the two sets of normally open contacts of the relay J1 or relay J2 are disconnected, and the positive input terminal of the power supply cannot be connected to the receiving terminal. Electrically positive input terminal, which has the function of reverse polarity protection.

To sum up, only when the input terminal of U1 is correctly connected to 5V voltage and the input terminal of U2 is correctly connected to 12V voltage, can both relay J1 and relay J2 work normally, and the two sets of normally open contacts of relay J1 and relay J2 are closed. The power supply input terminal of the protection circuit 1 and the wrong connection protection circuit 2 can be connected to the power supply output terminal.

In the above embodiment, both ends of the relay J1 are connected in antiparallel to the Zener diode Z1, and both ends of the relay J2 are connected in antiparallel to the Zener diode Z2. As other implementation manners, one or both of the relay J1 and the relay J2 are not connected in parallel to a Zener diode.

In the above embodiment, the misconnection protection circuit 1 is connected to the output terminal of U1 through the anti-reverse diode D1, the resistor R1 and the coil of the relay J1 connected in series; the misconnection protection circuit 2 is connected through the anti-reverse diode D2, Resistor R2 and the coil of relay J2 are connected to the output terminal of U2. As other implementation manners, one or both of the misconnection protection circuit 1 and the misconnection protection circuit 2 are not connected in series with anti-reverse diodes.

Example 2

As shown in FIG. 3 , the misconnection protection circuit includes n sets of input voltages, and the misconnection protection circuit includes corresponding misconnection protection circuits 1 to 1 to n. Each misconnection protection circuit has the same structure, and the working voltage of each relay is adapted to the input voltage level. For example, the wrong connection protection circuit n includes a control branch n: the positive input terminal UnA is connected to the negative input terminal UnB through the anti-reverse diode Dn, resistor Rn, and the coil of the relay Jn, and the Zener diode Zn is connected in reverse parallel with the coil of the relay Jn ; and a power supply branch n: the positive input terminal UnA is connected to the positive output terminal Un+ through a series switch JnA and JnA. Only when the input terminal of each misconnection protection circuit is correctly connected to the corresponding voltage, the relay J1, relay J2...relay Jn can all work normally, and the relay J1, relay J2...relay Jn The corresponding n groups of normally open contacts are all closed, and the power supply input terminal of the wrong connection protection circuit 1 and the wrong connection protection circuit 2 can be connected to the power supply output terminal of the wrong connection protection circuit n.

Claims (3)

1. A misconnection protection circuit, characterized in that: comprise at least two misconnection protection circuits; each misconnection protection circuit includes a control branch and a power supply branch; the control branch includes a resistor and a relay coil The voltage level of the relay coil is adapted to the level of the input voltage; the resistor and the relay coil are connected in series between the positive pole of the power supply input end and the negative pole of the power supply input end; the power supply branch circuit includes corresponding to each relay coil The normally open contacts are connected in series with the normally open contacts corresponding to the relay coils and connected between the positive pole of the power supply input end and the positive pole of the power supply output end. 2. The wrong connection protection circuit according to claim 1, characterized in that: Zener diodes are connected in antiparallel to both ends of the relay coil. 3. The misconnection protection circuit according to claim 1, characterized in that: the misconnection protection circuit also includes an anti-reverse diode, an anti-reverse diode series resistance and a relay coil, one end of its anode is connected to the power supply input terminal, and the negative end of the cathode A resistor is connected in series at one end.