An isolated interlock detection circuit

Abstract

The application discloses an isolated interlocking detection circuit, comprising: a power supply and detection circuit, an isolated DC-DC power supply, a protection circuit, an enabling circuit and a switch to be detected; wherein the power supply and detection circuit is electrically connected with the isolated DC-DC power supply; the isolated DC-DC power supply is electrically connected with the protection circuit; the protection circuit is electrically connected with the enabling circuit; and the enabling circuit is electrically connected with the switch to be detected. The application has the beneficial effects that: the interlocking circuits are mutually isolated, and no isolating device other than the isolated DC-DC power supply and the enabling relay is needed; meanwhile, the contact impedance of a live connector can be detected, and the state of the interlocking contact failure can be effectively judged.

Description

Technical Field

[0001] This invention relates to the field of distributed energy storage, and more particularly to an isolated interlock detection circuit. Background Technology

[0002] Interlock detection has a wide range of applications in the field of battery energy storage, mainly used to determine whether connectors or switches are making good contact.

[0003] Currently, there are two main ways to implement interlock detection:

[0004] 1. Non-isolated solution: Output voltage at one end of the node and detect the voltage at the other end. This solution can only be applied when the node under test is not energized and cannot directly detect energized power harnesses; furthermore, the lack of isolation between multiple interlocked detection circuits will cause mutual interference, leading to incorrect detection results.

[0005] 2. Isolated solution for detecting secondary current. This solution requires more complex external circuitry such as an isolation optocoupler, and can only determine whether there is contact, not whether the contact is good or the contact resistance, thus limiting its application environments. Summary of the Invention

[0006] To address the limitations of existing isolated and non-isolated solutions in terms of limited application environments and complex peripheral circuits, this invention proposes an isolated interlock detection circuit.

[0007] Specifically, the present invention provides an isolated interlock detection circuit, comprising:

[0008] Power supply and detection circuit, isolated DC-DC power supply, protection circuit, enable circuit and switch under test;

[0009] The power supply and detection circuits are electrically connected to the isolated DC-DC power supply.

[0010] The isolated DC-DC power supply is electrically connected to the protection circuit;

[0011] The protection circuit and the enable circuit are electrically connected;

[0012] The enable circuit is electrically connected to the switch under test.

[0013] Furthermore, the power supply and detection circuit includes a constant voltage power supply and two acquisition units; the two acquisition units include a voltage acquisition unit and a current acquisition unit.

[0014] Furthermore, the isolated DC-DC power supply may be a power supply with feedback or without feedback.

[0015] Furthermore, the protection circuit includes: a current-limiting resistor, a freewheeling diode, and a reverse connection protection diode;

[0016] The two ends of the reverse polarity protection diode are electrically connected to the isolated DC-DC power supply.

[0017] The positive terminal of the freewheeling diode is electrically connected to the negative terminal of the reverse polarity protection diode;

[0018] The negative terminal of the freewheeling diode is electrically connected to one end of the current-limiting resistor;

[0019] The other end of the current-limiting resistor is electrically connected to the enable circuit.

[0020] Furthermore, the enabling circuit is used to prevent the energy storage system from leaking current through the interlock detection circuit.

[0021] Furthermore, the switch under test is a dry contact that is not energized or a power harness that is energized.

[0022] Furthermore, the formula for calculating the equivalent internal resistance R30 of the switch under test is as follows:

[0023]

[0024] in, R1 represents the efficiency of the isolated DC-DC power supply; R2 represents the current sensing resistor value; R1 represents the current limiting resistor value; U1 represents the voltage value acquired by the voltage acquisition unit; and U2 represents the voltage value obtained after the current acquired by the current acquisition unit is transformed.

[0025] The beneficial effects provided by this invention are: the interlocking circuits are isolated from each other, eliminating the need for isolation devices other than isolated DC-DC power supplies and enable relays; at the same time, it can detect the contact impedance of live connectors, effectively determining the state of poor interlocking contact. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the application of the present invention in the detection of relay contact resistance in the main circuit of an energy storage system;

[0028] Figure 3 This is a schematic diagram illustrating the application of the present invention in the interlock detection of connectors with bayonet mounts. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0030] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the circuit structure of the present invention.

[0031] This invention provides an isolated interlock detection circuit, comprising:

[0032] The circuit includes a power supply and detection circuit 10, an isolated DC-DC power supply 20, a protection circuit 30, an enable circuit 40, and a switch under test 50.

[0033] The power supply and detection circuit 10 is electrically connected to the isolated DC-DC power supply 20; it should be noted that the isolated DC-DC power supply 20 is unidirectional.

[0034] The isolated DC-DC power supply 20 is electrically connected to the protection circuit 30;

[0035] The protection circuit 30 is electrically connected to the enable circuit 40;

[0036] The enable circuit 40 is electrically connected to the switch under test 50.

[0037] Please refer to Figure 1 The power supply and detection circuit 10 includes a constant voltage power supply and two acquisition units; the two acquisition units include a voltage acquisition unit and a current acquisition unit. It should be noted that the current acquisition unit can be implemented using a shunt or other units or modules capable of current acquisition; in this invention, a voltage divider resistor R1 is used. As an example, the power supply and detection circuit 10 uses a stable +5V constant voltage source; U1 and U2 are the output terminals of the MCU isolated DC-DC power supply 20. The sampling voltage U1 is obtained from the voltage acquisition unit, and the sampling current is obtained from the current acquisition unit, and after conversion, the input current of the isolated DC-DC power supply 20 is obtained.

[0038] The isolated DC-DC power supply 20 may or may not have feedback. It should be noted that the isolated DC-DC power supply 20 is an integrated module. This module may or may not have feedback output. Its output voltage is a known value, and its efficiency can be considered a constant, or it can be obtained in advance through actual measurement, calibration, or other means.

[0039] The protection circuit 30 includes a current-limiting resistor, a freewheeling diode, and a reverse-connection protection diode. It should be noted that the protection circuit 30 is primarily used to protect the isolated DC-DC power supply 20, ensuring that the maximum power of the isolated DC-DC power supply 20 does not exceed its rated power. Furthermore, the freewheeling diode and the reverse-connection protection diode can be added, removed, or supplemented as needed.

[0040] The two ends of the reverse polarity protection diode are electrically connected to the isolated DC-DC power supply 20;

[0041] The positive terminal of the freewheeling diode is electrically connected to the negative terminal of the reverse polarity protection diode;

[0042] The negative terminal of the freewheeling diode is electrically connected to one end of the current-limiting resistor;

[0043] The other end of the current-limiting resistor is electrically connected to the enable circuit.

[0044] As one example, please refer to Figure 1 , Figure 1 The reverse polarity protection diode is diode D1, the freewheeling diode is diode D2, and the current-limiting resistor is resistor R2. Diode D1 is electrically connected to the isolated DC-DC power supply 20V.

[0045] The positive terminal of diode D2 is electrically connected to the negative terminal of diode D1;

[0046] The cathode of diode D2 is electrically connected to one end of resistor R2;

[0047] The other end of resistor R2 is electrically connected to the enable circuit.

[0048] The enable circuit 40 is used to prevent leakage current in the switch under test 40. (Still referencing...) Figure 1 It should be noted that, Figure 1 The enabling circuit 40 is implemented using switch K1. In other embodiments, other leakage protection modules or circuits may also be used.

[0049] The switch under test 40 is a non-energized dry contact or an energized power harness.

[0050] The MCU voltage sampling obtains voltage value U1, and the MCU current sampling obtains voltage value U2. Ignoring the voltage drop of the anti-reverse diode, the actual calculation result can be obtained from calibration; the voltage drop has no practical impact. Assuming the efficiency of the isolated DC-DC power supply 20 is fixed at η, and its maximum load is (U1-U2) / R2, overload will not occur. The isolated DC-DC power supply 20 has a 1:1 output, and its stable output voltage U1 (this value is determined by the isolated DC-DC power supply 20; for ease of calculation, we assume a stable output voltage U1) can be obtained through actual testing and table lookup. Given the equivalent resistance of the measured load R30, the following formula can be obtained:

[0051]

[0052] After calculation, we get

[0053]

[0054] Where: R30 is the internal resistance of the node under test, U1 / U2 is the voltage value collected by the MCU, and η is related to the working state of the isolated DC-DC converter, is a fixed value (e.g., 0.95), and is relatively stable within the rated power range. From the above formula, the state of the switch under test can be deduced from U1 / U2 collected by the MCU.

[0055] Please refer to Figure 2 , Figure 2It is a schematic diagram of the application of the present invention in detecting the contact resistance of the main circuit relay of an energy storage system.

[0056] The rated voltage of the energy storage system is 500V. K30 is the main positive contactor, and K31 is the main negative relay. The BMS system has completed self-check and started working, and discharges through the equivalent load RL.

[0057] In the interlock circuit, the power supply module is powered by +5V. The current sampling circuit has R1 = 0.2R, the current limiting resistor of the protection circuit is R2 = 10R, the enable circuit works, and the DCDC isolated DC-DC power supply 20 selects Chuan Tu Micro CA-IS3641.

[0058] When working normally, the system working current is 20mA. When it is detected that U2 > 20mV, K30 has normal contact and is working normally. When it is detected that U2 < 18mV, the contact resistance of K30 is too large and the interlock is abnormal. When it is detected that U2 < 5mV, the impedance of K30 is infinite, and an interlock failure is reported.

[0059] As another embodiment, please refer to Figure 3 , Figure 3 It is a schematic diagram of the application of the present invention in detecting the interlock of a connector with a bayonet.

[0060] For a certain 4PIN connector male head P1~P4, corresponding to the female head P1’~P4’. When the male and female heads are in good contact, the resistance of P2 / P3 is 50R; otherwise, the docking fails.

[0061] In the interlock circuit, the power supply module is powered by +5V. The current sampling circuit has R = = 0.2R, the current limiting resistor of the protection circuit is R2 = 10R, the enable circuit works, and the DCDC power supply module selects Mornsun W0505 as the isolated DC-DC power supply 20.

[0062] When working normally, the working current of the interlock detection circuit is 65mA. When it is detected that U2 = 10mv~15mv, such as 13mV, the connector is in good contact and P1 and P4 can be used normally; when it is detected that U2 > 15mV, the connector is in error; when it is detected that 5mV < U2 < 10mV, the connector is inserted wrongly or has poor contact, and an interlock abnormality is reported; when it is detected that U2 < 5mV, the impedance of the connector is infinite, and it is determined that the connector is not plugged in.

[0063] The beneficial effects of the present invention are: the interlock circuits are isolated from each other, and no isolation devices other than the isolated DC-DC power supply 20 and the enable relay are required; at the same time, the contact impedance of the live connector can be detected to effectively judge the state of poor interlock contact.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An isolated interlock detection circuit, characterized in that: include: The circuit includes a power supply and detection circuit (10), an isolated DC-DC power supply (20), a protection circuit (30), an enable circuit (40), and a switch under test (50). The power supply and detection circuit (10) is electrically connected to the isolated DC-DC power supply (20); the isolated DC-DC power supply (20) is a unidirectional power supply; the power supply and detection circuit (10) includes a constant voltage power supply and two acquisition units; The two acquisition units include a voltage acquisition unit and a current acquisition unit; the voltage acquisition unit obtains the sampling voltage U1, the current acquisition unit obtains the acquisition current, and after conversion, the input current of the isolated DC-DC power supply (20) is obtained; the current acquisition unit uses a current detection resistor; The isolated DC-DC power supply (20) is electrically connected to the protection circuit (30); The protection circuit (30) is electrically connected to the enabling circuit (40); the enabling circuit (40) is used to prevent leakage current in the switch under test (50); The enable circuit (40) is electrically connected to the switch under test (50); The protection circuit includes: a current-limiting resistor, a freewheeling diode, and a reverse connection protection diode; The two ends of the reverse polarity protection diode are electrically connected to the isolated DC-DC power supply (20); The positive terminal of the freewheeling diode is electrically connected to the negative terminal of the reverse polarity protection diode; The negative terminal of the freewheeling diode is electrically connected to one end of the current-limiting resistor; The other end of the current-limiting resistor is electrically connected to the enabling circuit; The formula for calculating the equivalent internal resistance R30 of the switch under test (50) is as follows: The formula for calculating the equivalent internal resistance R30 of the switch under test is as follows: In the above formula, R1 represents the efficiency of the isolated DC-DC power supply; R2 represents the current sensing resistor value; R1 represents the current limiting resistor value; U1 represents the voltage value acquired by the voltage acquisition unit; and U2 represents the voltage value obtained after the current acquired by the current acquisition unit is transformed.

2. The isolated interlock detection circuit as described in claim 1, characterized in that: The isolated DC-DC power supply (20) may be a power supply with or without feedback.

3. The isolated interlock detection circuit as described in claim 1, characterized in that: The switch under test (50) is a dry contact that is not energized or a power harness that is energized.

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