Control circuit of battery charging relay

Abstract

The utility model is suitable for the technical field of battery charging, and provides a control circuit which can avoid the problem that a charging relay at a battery end is damaged or adhered due to overlarge current at the moment of actuation under various abnormal conditions. The control circuit comprises a resistor R1, a diode VD3, a main relay K1, a diode VD1, an auxiliary relay K2, a diode VD2, a main relay control circuit, an auxiliary relay control circuit and an equivalent capacitor Cout.

Description

Technical Field

[0001] The utility model relates to the technical field of battery charging, in particular to a control circuit of a battery charging relay. Background Art

[0002] At present, the industry basically has a relay in series with the battery charging port, which is generally directly controlled to close and disconnect the relay. Figure 1 , lack of effective control of the pull-in action; generally, before charging the battery, there is no large-capacity capacitor Cout at the output end of the charger. In this case, when the relay is directly pulled in, there will be no large current flowing through the charging relay, so there will be no problem; but when there is a large-capacity capacitor at the output end of the charger and the voltage is low, or the battery voltage Vbat_P is much higher than Vin_P, the charging relay K1 will be pulled in, which will cause the instantaneous current to be too large, and there is a high possibility of damaging the relay contacts. In addition, at engineering sites with poor specific environments, there are repeated failures of battery-side charging relays or contactors sticking. Utility Model Content

[0003] In view of the above problems, the utility model proposes a control circuit and a control method that can also avoid the problem of damage or adhesion of the battery end charging relay due to excessive instantaneous current when it is pulled in under various abnormal conditions. At the same time, the output end of the charger that charges the battery is also allowed to have a large-capacity filter capacitor. A branch consisting of two contacts of the auxiliary relay K2, a diode VD3 and a resistor R1 is connected to the original main relay K1. Before the charger starts charging the battery, the battery Vbat_P first supplies the charger output terminal Vin_P via the resistor R1, the two contacts of the auxiliary relay K2 and the diode VD3. For charging, the auxiliary relay K2 is a small current ordinary AC normally open relay; each time before the main relay K1 is energized, the auxiliary relay K2 must be energized first. The battery pre-charges the battery input terminal through the resistor R1, the auxiliary relay K2 and the diode VD3, and the main relay K1 is controlled to be energized after the preset fixed delay time Ton. The disadvantage of this method is that the capacitance Cout of the charger output terminal is uncertain under abnormal conditions, so it is inconvenient to determine a very suitable value for the preset fixed delay time. Setting a larger fixed delay time Ton will provide better adaptability.

[0004] In order to achieve the above objectives, the specific instructions are as follows:

[0005] A control circuit of a battery charging relay comprises: a resistor R1, a diode VD3, a main relay K1 and a diode VD1 connected in reverse parallel on its control line package, an auxiliary relay K2 and a diode VD2 connected in reverse parallel on its control line package, a main relay control circuit, an auxiliary relay control circuit, and an equivalent capacitor Cout at the output end of a charger.

[0006] Furthermore, the main relay K1 and the auxiliary relay K2 are both normally open relays, one contact of the main relay K1 is connected to the charger output positive terminal Vin_P, one end of the capacitor Cout and the cathode of the diode VD3, the other contact of the main relay K1 is connected to the battery positive terminal Vbat_P and one end of the resistor R1, the anode of the diode VD3 is connected to a contact of the relay K2, the other contact of the relay K2 is connected to the other end of the resistor R1, and the charger output positive terminal Vin_P is also the battery charging input positive terminal.

[0007] Furthermore, one end of the control coil of the main relay K1 is connected to the cathode of the diode VD1 and the power supply VCC, and the other end of the control coil of the main relay K1 is connected to the anode of the diode VD1 and the main relay control circuit.

[0008] Furthermore, one end of the control coil of the auxiliary electrical appliance K2 is connected to the cathode of the diode VD2 and the power supply VCC, and the other end of the control coil of the main relay K2 is connected to the anode of the diode VD2 and the auxiliary relay control circuit.

[0009] Furthermore, the negative input Vin_N of the charger is connected to the other end of the capacitor Cout and the negative end Vbat_N of the battery. The negative end Vbat_N of the battery is also the working ground GNDS_D of the control circuit.

[0010] Furthermore, the main relay control circuit controls the closing and opening of the main relay K1, and the auxiliary relay control circuit controls the closing and opening of the auxiliary relay K2.

[0011] In addition, the main control unit circuit of the battery is required to control the main relay control circuit and the auxiliary relay control circuit to ensure the realization of the above functions. The main control unit circuit of the battery is not elaborated in detail here.

[0012] The working principle and control method of the utility model are specifically described as follows:

[0013] Before the charger is normally connected and outputs normally, the auxiliary relay control circuit first closes the normally open relay K2, so that the positive terminal of the battery Vbat_P charges the equivalent capacitor Cout of the output terminal Vin_P of the charger through the circuit branch composed of the resistor R1 in series with the auxiliary relay K2 contact and the diode VD3.

[0014] Under normal circumstances, the output end of the charger is equivalent to a capacitor or sampling resistor with relatively small capacity. Since the sampling resistor has a relatively large resistance and consumes very little current, the influence of the sampling resistor is ignored here, that is, the capacitance of the capacitor Cout is relatively small, and the voltage of the output end Vin_P of the charger rises to be basically equal to the battery voltage in a very short time; in special cases or abnormal circumstances, if the equivalent Cout of the output end of the charger is larger, the voltage of the output end Vin_P of the charger needs about Ton to rise to be approximately equal to the battery voltage, where Ton = 5·Cout·R1.

[0015] After a delay of Ton, the auxiliary relay K2 is disconnected and the main relay K1 is attracted. In this case, the attraction of the main relay K2 will not generate excessive instantaneous current, thereby avoiding damage or adhesion of the contacts of the main relay K1.

[0016] The main relay K1 is energized, and the auxiliary relay K2 is disconnected at the same time or with a slight delay, so as to ensure that the auxiliary relay K2 is in the disconnected state except when the battery is pre-charging the charger.

[0017] Since the equivalent Cout capacitance at the charger output terminal is uncertain, it is inconvenient to set a fixed delay. When the preset fixed delay Ton is much smaller than 5*Cout*R1, there will be a certain voltage difference between the two contacts when the main relay K1 is energized, and there will still be a large instantaneous current. However, compared with directly energizing the main relay K1 without pre-charging the equivalent Cout at the charger output terminal, there will be a great improvement.

[0018] Compared with the prior art, the advantages of the utility model are as follows: by adding fewer electronic components, reasonable control of the battery charging port relay is achieved, and basically zero voltage attraction between the two contacts of the battery charging relay is achieved, and the attraction current is very small, which greatly reduces the main relay attraction instantaneous current under abnormal conditions at the output end of the charger, optimizes and solves the problem of relay contact adhesion or damage caused by excessive attraction instantaneous current, and significantly improves reliability; fewer electronic components are added, the increased cost is very small, the circuit is simple, and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a prior art solution.

[0020] Figure 2 It is a principle block diagram of the utility model.

[0021] Figure 3 It is a circuit diagram of an embodiment of the utility model. DETAILED DESCRIPTION

[0022] In order to make the technical means implemented by the utility model clear and understandable, the technical solution of the utility model is further described below in conjunction with the accompanying drawings. Figure 2The specific implementation method of the battery control system will not be further described.

[0023] The utility model technical solution Figure 2 The specific implementation is described as follows:

[0024] The control circuit includes: a resistor R1, a diode VD3, a main relay K1 and a diode VD1 inversely connected to its control line package, an auxiliary relay K2 and a diode VD2 inversely connected to its control line package, a main relay control circuit, an auxiliary relay control circuit, and an equivalent capacitor Cout at the output end of the charger.

[0025] Specifically, refer to Figure 3 The main relay K1 and the auxiliary relay K2 are both normally open relays. One contact of the main relay K1 is connected to the charger output positive terminal Vin_P, one end of the capacitor Cout and the cathode of the diode VD3. Another contact of the main relay K1 is connected to the battery positive terminal Vbat_P and one end of the resistor R1. The anode of the diode VD3 is connected to one contact of the relay K2. The other contact of the relay K2 is connected to the other end of the resistor R1. The charger output positive terminal Vin_P is also the battery charging input positive terminal.

[0026] Furthermore, one end of the control coil of the main relay K1 is connected to the power supply VCC (+12VDC) and the cathode of the diode VD1, the anode of the diode VD1 is connected to the other end of the control coil of the main relay and the collector of the NPN transistor VT2, the base of the NPN transistor VT2 is connected to one end of the resistor R6, one end of the resistor R9 and one end of the capacitor C2, the other end of the resistor R6 is connected to the control signal K1_DRV of the main relay K1, the emitter of the NPN transistor VT2, the other end of the resistor R9 and the other end of the capacitor C2 and the negative end of the charger output Vin_N are connected to the negative end of the battery Vbat_N, and the negative end of the battery Vbat_N is also the working location GNDS_D.

[0027] Furthermore, one end of the auxiliary relay K2 control line package is connected to the power supply VCC (+12VDC) and the cathode of the diode VD2, the anode of the diode VD2 is connected to the other end of the auxiliary relay control line package and the collector of the NPN transistor VT1, the base of the NPN transistor VT1 is connected to one end of the resistor R12, one end of the resistor R2 and one end of the capacitor C1, the other end of the resistor R12 is connected to the control signal K2_DRV of the auxiliary relay K2, and the emitter of the transistor VT1, the other end of the resistor R2 and the other end of the capacitor C1 are connected to the negative terminal GNDS_D of the battery.

[0028] Furthermore, the control signal K2_DRV of the auxiliary relay K2 and the control signal K1_DRV of the main relay K1 are output by the battery control unit circuit.

[0029] The working principle of this embodiment is described as follows:

[0030] Before the charger is normally connected and outputs normally, the battery control unit first outputs the control signal K2_DRV of the auxiliary relay K2 as a high level, and the auxiliary relay K2 is energized, so that the positive terminal Vbat_P of the battery charges the equivalent capacitor Cout of the output terminal Vin_P of the charger through the circuit branch composed of the resistor R1 in series with the auxiliary relay contact and the diode VD3.

[0031] After a delay of time Ton, where Ton is approximately 5*Cout*R1, the battery control unit outputs a control signal K2_DR1 of a high level for the main relay K1, closing the main relay K1. In this case, closing the main relay K1 will not generate excessive instantaneous current, thereby avoiding damage or adhesion to the contacts of the main relay K1. At the same time or after a slight delay, the battery control unit outputs a control signal K2_DRV of a low level for the auxiliary relay K2, disconnecting the auxiliary relay K2, so as to maintain the relay in a disconnected state except during the pre-charging period.

[0032] Every time the main relay K1 is energized, the voltage difference across its contacts is less than 1V, which is close to zero-voltage opening. This can effectively limit the current flowing through the contacts of the main relay K1 when the main relay K1 is energized, avoiding adhesion, damage or damage to the main relay K1 due to excessive instantaneous current, thereby improving the reliability of the circuit.

[0033] The above is only a typical implementation of the utility model, and the protection scope of the utility model is not limited to the above implementation. All technical solutions belonging to the principle of the utility model belong to the protection scope of the utility model. For those skilled in the art, several improvements made without departing from the principle of the utility model should also be regarded as the protection scope of the utility model.

Claims

1. A control circuit for a battery charging relay, characterized in that: The control circuit includes a resistor R1, a diode VD3, a main relay K1, a diode VD1, an auxiliary relay K2, a diode VD2, a main relay control circuit, an auxiliary relay control circuit and an equivalent capacitor Cout; one contact of the main relay K1 is connected to the charger output positive terminal Vin_P, one end of the equivalent capacitor Cout and the cathode of the diode VD3, another contact of the main relay K1 is connected to the battery positive terminal Vbat_P and one end of the resistor R1, the anode of the diode VD3 is connected to a contact of the auxiliary relay K2, and the auxiliary relay Another contact of the device K2 is connected to the other end of the resistor R1, one end of the main relay K1 control package is connected to the power supply VCC and the cathode of the diode VD1, the anode of the diode VD1 is connected to the main relay control circuit and the other end of the main relay K1 control package, one end of the auxiliary relay K2 control package is connected to the power supply VCC and the cathode of the diode VD2, the anode of the diode VD2 is connected to the auxiliary relay control circuit and the other end of the auxiliary relay K2 control package, and the other end of the equivalent capacitor Cout is connected to GNDS_D.

2. The control circuit according to claim 1, characterized in that: The main relay control circuit includes a resistor R6, a resistor R9, a capacitor C2 and a transistor VT2, the collector of the transistor VT2 is connected to the anode of the diode VD1, the base of the transistor VT2 is connected to one end of the resistor R6, one end of the resistor R9 and one end of the capacitor C2, the other end of the resistor R6 is connected to the control signal K1_DRV of the main relay K1, and the emitter of the transistor VT2, the other end of the resistor R9 and the other end of the capacitor C2 are all connected to GNDS_D.

3. The control circuit according to claim 2, characterized in that: The auxiliary relay control circuit includes a resistor R2, a resistor R12, a capacitor C1 and a transistor VT1, the collector of the transistor VT1 is connected to the anode of the diode VD2, the base of the transistor VT1 is connected to one end of the resistor R12, one end of the resistor R2 and one end of the capacitor C1, the other end of the resistor R12 is connected to the control signal K2_DRV of the auxiliary relay K2, and the emitter of the transistor VT1, the other end of the resistor R2 and the other end of the capacitor C1 are all connected to GNDS_D.

4. The control circuit according to claim 3, characterized in that: The transistor VT1 and the transistor VT2 are both NPN transistors.

5. The control circuit according to any one of claims 1 to 4, characterized in that: The main relay K1 and the auxiliary relay K2 are both normally open relays.

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