Alternating current limiting protection circuit and alternating current bridge type reversing device

Abstract

The utility model discloses an AC current-limiting protection circuit and an AC bridge type reversing device. The AC current-limiting protection circuit comprises a current-limiting circuit and a control circuit. The current limiting circuit comprises a switching tube T1; the collector electrode of the T1 is connected with the terminal 1 of the resistor R1, the terminal 1 of the resistor R2 and the cathode of the diode D1; the emitter of the T1 is connected with the terminal 1 of the resistor SEN1, the anode of the D1 and the terminal 2 of the capacitor C2; the C2 terminal 1 is connected with the R2 terminal 2; a collector electrode of the T2 is connected with a terminal 2 of the R1, a cathode of the D2 and a terminal 2 of the resistor R3; the emitter of the T2 is connected with the terminal 2 of the resistor SEN2, the anode of the D2 and the terminal 1 of the absorption capacitor C3; a terminal 1 of C3 is connected with a terminal 1 of R3; a terminal 2 of the SEN1 is connected with a terminal 1 of the SEN2 and is grounded; and grid electrodes of the T1 and the T2 are respectively connected with the control circuit through a resistor R4 and a resistor R5. According to the utility model, the bridge arm short circuit direct connection of the commutation bridge circuit can be effectively prevented from impacting a switching device, and the device is prevented from being damaged.

Description

Technical Field

[0001] The utility model relates to the technical field of AC current limiting protection circuit and rail transportation, in particular to an AC current limiting protection circuit and an AC bridge type commutation device. Background Art

[0002] Rail transit is an important form of transportation, and the signal power supply system is one of the most important core components of rail transit. The contactless voltage-stabilized power supply (i.e., contactless voltage stabilizer) is the core of the signal power supply system (i.e., signal power supply panel system, also known as railway signal power supply). After the signal power supply system is stabilized by the contactless voltage-stabilized power supply, it provides a stable operating voltage for subsequent railway signal equipment (i.e., as load equipment) such as lighting equipment and switch equipment.

[0003] Contactless voltage-stabilized power supplies use transformer-graded compensation to stabilize the output voltage within a set range. Currently, standard power supplies include 3.5kVA, 5kVA, and 10kVA capacities.

[0004] The commutation bridge circuit (also called the contactless commutation bridge circuit), which serves as a contactless commutation compensation circuit, is the main part of the contactless voltage-stabilized power supply circuit.

[0005] See also Figure 1 As shown, the contactless commutation bridge circuit includes four bidirectional thyristors T3 to T6. The bidirectional thyristors T3 to T6 are AC switching devices that can switch AC signals. Figure 1 The contactless commutation bridge circuit shown controls the phase of the input voltage of the compensation transformer B1 by controlling the opening sequence of the switching tubes (i.e., bidirectional thyristors T3 to T6) on the bridge arms, thereby obtaining output voltages of different phases. This output voltage is then superimposed on the input voltage to compensate for the input voltage deviation from the expected value.

[0006] It's important to note that the input voltage of the signal power supply system (i.e., the signal power supply system, also known as the railway signal power supply, specifically a contactless voltage regulator) comes from the power supply network along the railway line. Due to objective conditions such as long distances and load fluctuations, this voltage often deviates significantly from the rated value, causing many electrical devices to operate unstably. Therefore, a voltage stabilization device is required to compensate for this voltage deviation, specifically a contactless voltage regulator.

[0007] Due to external interference and other reasons, the bidirectional thyristor device has the possibility of uncontrolled conduction (i.e. risk), and there is also the possibility of uncontrollable shutdown after conduction (i.e. risk). Therefore, this contactless commutation bridge circuit has the risk of direct short circuit of the bridge arm. The short circuit can cause damage to the bidirectional thyristor device and even accidents such as line fire.

[0008] Therefore, a protection circuit is needed to deal with this risk factor. However, there is currently no technology that can effectively solve the above technical problems. Utility Model Content

[0009] The purpose of the utility model is to provide an AC current limiting protection circuit and an AC bridge type commutation device in view of the technical defects in the prior art.

[0010] To this end, the utility model provides an AC current limiting protection circuit, which includes a current limiting circuit and a control circuit;

[0011] The current limiting circuit includes: a switch tube T1, a switch tube T2, a current sampling resistor SEN1, a current sampling resistor SEN2, a current limiting resistor R1, an absorption resistor R2, an absorption resistor R3, an absorption capacitor C2 and an absorption capacitor C3, and drive resistors R4 to R5;

[0012] The collector of the switch tube T1 serves as the input terminal of the current limiting circuit, and is connected to the terminal 1 of the current limiting resistor R1, the terminal 1 of the absorption resistor R2, and the cathode of the diode D1 respectively;

[0013] The emitter of the switch tube T1 is connected to the terminal 1 of the current sampling resistor SEN1, the anode of the diode D1 and the terminal 2 of the absorption capacitor C2 respectively;

[0014] Terminal 1 of the absorption capacitor C2 is connected to terminal 2 of the absorption resistor R2;

[0015] The collector of the switch tube T2 serves as the output end of the current limiting circuit, and is connected to the terminal 2 of the current limiting resistor R1, the cathode of the diode D2, and the terminal 2 of the absorption resistor R3 respectively;

[0016] The emitter of the switch tube T2 is connected to the terminal 2 of the current sampling resistor SEN2, the anode of the diode D2 and the terminal 1 of the absorption capacitor C3 respectively;

[0017] Terminal 1 of the absorption capacitor C3 is connected to terminal 1 of the absorption resistor R3;

[0018] Wherein, the terminal 2 of the current sampling resistor SEN1 and the terminal 1 of the current sampling resistor SEN2 are connected and grounded at the same time;

[0019] The gate of the switch tube T1 is connected to the control circuit (100) via the driving resistor R4;

[0020] The gate of the switch tube T2 is connected to the control circuit (100) via the driving resistor R5;

[0021] The control circuit is connected to the current limiting circuit and is used to collect the voltage signals flowing out of the current collection resistors SEN1 and SEN2 in the current limiting circuit, and to determine whether there is overcurrent, and to play the corresponding current limiting function when there is overcurrent.

[0022] It can be seen from the technical solution provided by the above utility model that, compared with the prior art, the utility model provides an AC current limiting protection circuit and an AC bridge commutation device, which are scientifically designed. The protection circuit is applied to a contactless commutation bridge circuit (i.e., an AC bridge commutation circuit). By combining with the contactless commutation bridge circuit, it can effectively protect the bridge arm short circuit of the contactless commutation bridge circuit from directly impacting the switching device (i.e., a bidirectional thyristor device), avoid damage to the device (i.e., a bidirectional thyristor device) caused by the bridge arm short circuit, and avoid further accidents such as line fire, which has great practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The schematic diagram of an existing contactless commutation bridge circuit (i.e., an AC bridge commutation circuit) is shown below:

[0024] Figure 2 This is a schematic diagram of an AC current limiting protection circuit provided by the utility model;

[0025] Figure 3 This is a working principle diagram of the first embodiment of an AC current limiting protection circuit provided by the utility model, when applied to a contactless commutation bridge circuit (i.e., when the AC current limiting protection circuit and the AC bridge commutation circuit together form an AC bridge commutation device);

[0026] Figure 4 This is a working principle diagram of the second embodiment of an AC current limiting protection circuit provided by the utility model when applied to a contactless commutation bridge circuit (i.e., when the AC current limiting protection circuit and the AC bridge commutation circuit together form an AC bridge commutation device);

[0027] Figure 5 This is a principle diagram of an embodiment of a control circuit in an AC current limiting protection circuit provided by the utility model. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In the description of this patent, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," and "set" should be understood in a broad sense. For example, they can refer to fixed connection or set, detachable connection or set, or integral connection or set. Those skilled in the art will understand the specific meanings of the above terms in this patent based on the specific circumstances.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0031] See also Figures 2 to 5 The present invention provides an AC current limiting protection circuit, which is an AC current limiting protection circuit applied to an AC bridge commutation circuit (i.e., a contactless commutation bridge circuit), and includes a current limiting circuit and a control circuit 100;

[0032] The current limiting circuit includes a switch tube T1, a switch tube T2, a current sampling resistor SEN1, a current sampling resistor SEN2, a current limiting resistor R1, an absorption resistor R2, an absorption resistor R3, an absorption capacitor C2 and an absorption capacitor C3, and drive resistors R4-R5.

[0033] The collector of the switch tube T1 (i.e., terminal 1) serves as the input terminal of the current limiting circuit, and is connected to terminal 1 of the current limiting resistor R1, terminal 1 of the absorption resistor R2, and the cathode of the diode D1 respectively;

[0034] The emitter of the switch tube T1 (i.e., terminal 2) is connected to terminal 1 of the current sampling resistor SEN1, the anode of the diode D1, and terminal 2 of the absorption capacitor C2 respectively;

[0035] Terminal 1 of the absorption capacitor C2 is connected to terminal 2 of the absorption resistor R2;

[0036] The collector of the switch tube T2 (i.e., terminal 1) serves as the output end of the current limiting circuit, and is connected to terminal 2 of the current limiting resistor R1, the cathode of the diode D2, and terminal 2 of the absorption resistor R3 respectively;

[0037] The emitter of the switch tube T2 (i.e., terminal 2) is connected to terminal 2 of the current sampling resistor SEN2, the anode of the diode D2, and terminal 1 of the absorption capacitor C3 respectively;

[0038] Terminal 1 of the absorption capacitor C3 is connected to terminal 1 of the absorption resistor R3;

[0039] Wherein, the terminal 2 of the current sampling resistor SEN1 and the terminal 1 of the current sampling resistor SEN2 are connected and grounded at the same time;

[0040] The gate of the switch tube T1 (i.e., terminal 3) is connected to the control circuit 100 via the driving resistor R4;

[0041] The gate of the switch tube T2 (ie, terminal 3 ) is connected to the control circuit 100 via the driving resistor R5 .

[0042] In this utility model, the specific implementation is as follows Figure 4 As shown, the current limiting circuit further includes: an absorption capacitor C1;

[0043] Terminal 1 of the absorption capacitor C1 is connected to the collector (i.e., terminal 1) of the switch tube T1;

[0044] Terminal 2 of the absorption capacitor C1 is connected to the collector (ie, terminal 1) of the switch tube T2.

[0045] In the present invention, the control circuit 100 is connected to the current limiting circuit, and is used to collect the voltage signals flowing out of the current collection resistors SEN1 and SEN2 in the current limiting circuit, and determine whether there is overcurrent. When there is overcurrent, the corresponding current limiting function is performed.

[0046] In the present invention, the switches T1 and T2 are insulated-gate bipolar transistors (IGBTs). The switches T1 and T2 are implemented by IGBTs, which are driven by a control circuit (which serves as a drive circuit) 100 .

[0047] It should be noted that in the present invention, the switch tubes T1 and T2 are IGBT switch tubes, which are respectively used to provide AC positive phase and negative phase current inputs for the commutation bridge circuit (i.e., AC bridge commutation circuit), and can protect the positive half-wave overcurrent and negative half-wave overcurrent of the current.

[0048] The current sampling resistors SEN1 and SEN2 are used to collect the positive half-wave and negative half-wave of the overcurrent respectively.

[0049] When a direct short circuit occurs in the commutation bridge circuit, the short-circuit current will flow through the current sampling resistor SEN1 or SEN2 and generate a voltage signal on the current sampling resistor SEN1 or SEN2. The control circuit 100 determines whether to turn off the switch tube T1 or the switch tube T2 based on the size of the voltage signal, forcing the short-circuit current to flow through the current limiting resistor R1, thereby limiting the further increase of the current. Therefore, it plays a certain protective role for the system where the contactless regulator is located and the switch tube devices of the commutation bridge.

[0050] In the present invention, in a specific implementation, the collector of the switch tube T1 (i.e., terminal 1) serves as the input end of the current limiting circuit and is connected to the live wire (L line) of the input end of the contactless voltage regulator (i.e., contactless voltage regulator);

[0051] It should be noted that, in the present invention, the live wire (L line) of the input end of the contactless voltage-stabilized power supply (i.e., the contactless voltage regulator) connected to the collector (i.e., terminal 1) of the switching tube T1 is the same line as the live wire (L line) of the input end of the contactless voltage-stabilized power supply (i.e., the contactless voltage regulator) connected to the terminal 1 of the compensation transformer B1 mentioned below.

[0052] In the present invention, the collector of the switch tube T2 (i.e., terminal 1), as the output end of the current limiting circuit, is connected to the input neutral line (N line) of the contactless voltage regulator (i.e., contactless voltage regulator) through an AC bridge commutation circuit;

[0053] In a specific implementation, the collector (i.e., terminal 1) of the switch tube T2 is connected to terminal 1 of the original bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T6 in the AC bridge commutation circuit (i.e., the contactless commutation bridge circuit);

[0054] It should be noted that terminal 1 of the bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T6 are input terminals of the AC bridge commutation circuit.

[0055] AC bridge commutation circuit (i.e. contactless commutation bridge circuit), including bidirectional thyristors T3 to T6 and compensation transformer B1;

[0056] Terminal 1 of the compensation transformer B1 is connected to the live wire (L line) of the input terminal of the external contactless voltage regulator (i.e., contactless voltage regulator). Its purpose and function are to compensate for the deviation of the input voltage of the contactless voltage regulator (i.e., contactless voltage regulator);

[0057] Terminal 2 of the compensation transformer B1 is connected to the live wire (L line) of the output terminal of a contactless voltage-stabilized power supply (i.e., a contactless voltage regulator) (this output terminal is connected to the live wire input terminal of the load device) and is used to provide a compensated output voltage to provide stable power supply to the railway signaling equipment serving as the load device.

[0058] It should be noted that the input neutral line (N line) of the contactless voltage regulator (i.e., the contactless voltage regulator) is the same as the output neutral line (N line) of the contactless voltage regulator. Figure 3 、 Figure 4 shown.

[0059] It should be noted that the load equipment is, for example, railway signaling equipment such as lighting equipment and switch equipment on the railway track.

[0060] It should be noted that terminals 1 and 2 of the compensation transformer B1 are respectively connected to the input and output terminals of a contactless voltage-stabilized power supply (i.e., a contactless voltage regulator), so that the voltage between terminals 1 and 2 is superimposed on the input terminal of the contactless voltage regulator, thereby compensating for the input voltage and completing the compensation for the input voltage deviation.

[0061] It should be noted that contactless voltage stabilizers are core components of existing railway signal power supplies, featuring mature technology and widespread application. For example, contactless voltage stabilizers can utilize the MW-220 / 16 (3.5kVA), MW-220 / 23 (5kVA), and MW-220 / 46 (10kVA) series of contactless voltage stabilizer modules manufactured by Tianjin Railway Signal Co., Ltd. These are primarily used in conventional intelligent signal power supply panels as core components for voltage stabilization.

[0062] In a specific implementation, the live wire output terminal and the neutral wire output terminal of the contactless voltage-stabilized power supply (i.e., the contactless voltage regulator) are connected to the live wire output terminal and the neutral wire output terminal of the load device respectively;

[0063] In terms of specific implementation, Figure 3 、 Figure 4 Terminal 2 of the compensation transformer B1 is connected to the live wire L of the output terminal of the contactless voltage regulator (i.e., the contactless voltage regulator);

[0064] In specific implementation, the input neutral line (N line) of the contactless voltage regulator (i.e., contactless voltage regulator) is the same as the output neutral line (N line) of the contactless voltage regulator (i.e., contactless voltage regulator). Figure 3 、 Figure 4 shown.

[0065] Terminal 3 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T6 and terminal 1 of the bidirectional thyristor T5 respectively;

[0066] Terminal 4 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T4 respectively;

[0067] After the terminal 2 of the bidirectional thyristor T4 and the terminal 2 of the bidirectional thyristor T5 are converged and intersected, they are connected to the input neutral line (N line) of the contactless voltage regulator (ie, the contactless voltage regulator).

[0068] It should be noted that the choice of the IGBT switch tube T1 should be able to meet the maximum current of the commutation bridge circuit and leave more than twice the margin. The tube's withstand voltage should be above 1000V, and it must have its own body diode (i.e. diode D1), because the commutation bridge drives an inductive load, and turning off the current will generate a very high voltage.

[0069] In specific implementation, the switching tube current should be selected based on the compensation current associated with the actual contactless voltage regulation power. For a voltage regulation power of 3.5-5Kv, the maximum compensation current is 7A. Considering the double overload impact and the actual model, 20A can be selected. For a voltage regulation power of 10Kva, the maximum compensation current is 14A. Considering the double overload impact and the actual model, 60A is very reliable.

[0070] Because the current limiting resistor R1 has a relatively large power consumption, a wire-wound non-inductive resistor can be selected, which is a ceramic resistor of more than 50W to reduce the induced electromotive force during the switching process.

[0071] It should be noted that the current sampling resistors SEN1 and SEN2 are generally selected to be in the milliohm level according to design requirements, with a power of more than 5W, leaving a margin of more than double to prevent excessive temperature rise.

[0072] The absorption capacitors C2 and C3 can use general parameters, and the power consumption is not high. The capacitance is generally around 2200nF. The main function of the absorption capacitors C2 and C3 is to absorb the oscillation current generated when the switch is turned off.

[0073] Absorption resistors R2 and R3 serve as damping resistors of the absorption circuit, and are mainly responsible for consuming the oscillation energy generated by the switch tube when switching. According to actual conditions, in this utility model, a 51Ω-3W wire-wound resistor can be used.

[0074] Among them, the capacity of the absorption capacitor C1 will be relatively large, because the inductance parameter of the short-circuit current loop will be relatively large, and the induced voltage generated will be very high. Usually, the present invention selects a 4UF capacitor with a withstand voltage of 600V.

[0075] In the present invention, in a specific implementation, the switch tube T1 and the diode D1 can be integrated together, that is, the switch tube T1 has a body diode D1;

[0076] The switch tube T2 and the diode D2 can be integrated together, that is, the switch tube T2 has a body diode D2.

[0077] In order to more clearly understand the technical solution of the present invention, the working principle of the present invention is described below.

[0078] The AC current limiting protection circuit of the utility model uses a resistor in an AC circuit to limit the short-circuit current of the system, which can effectively protect short-circuit devices and maintain stable operation of the system.

[0079] The present invention can use two DC switching tubes (IGBTs) to achieve the current limiting function of the AC power frequency current.

[0080] Because the present invention is used in AC circuits, IGBTs are single-phase switching transistors that can only conduct half of the AC signal waveform. Therefore, two switching transistors must be connected in anti-phase. Furthermore, the switching transistors must have body diodes to freewheel the negative half-wave of the conducting signal. This allows for the conduction of the negative half-wave of the signal when switch T1 is on and switch T2 is off in the reverse phase. This allows switch T1's body diode D1 to conduct, completing the conduction function in the direction of T1. The reverse conduction method and principle are similar.

[0081] It should be noted that when reverse conduction occurs, the switch tube T2 is turned on first, allowing current to flow through, and the switch tube T1 is reverse-cut off, but the body diode D2 of the switch tube T2 is turned on, allowing the current flowing through the switch tube T2 to pass through the body diode D2.

[0082] The input end of the switch tube T1 is connected to the input end of the commutation bridge (i.e., the AC bridge commutation circuit). When the switch tube T1 is turned on, it provides an energy source to the commutation bridge circuit. The switching control of T1 is connected to the control circuit 100 through the driving resistor R4 and is completed by the control circuit.

[0083] The output end of the switch tube T1 is connected to the current collection resistor SEN1. The current flowing through the switch tube T1 forms a voltage signal here, which is transmitted to the control circuit 100 to determine whether there is an overcurrent problem. If an overcurrent phenomenon occurs, the control circuit 100 will detect whether there is an overcurrent phenomenon by judging the voltage signal of the current collection resistor SEN1, and then control the switch tube T1 to be disconnected (i.e., turned off) by driving the resistor R4 to prevent the short-circuit current from continuing to increase.

[0084] The input end of the switch tube T1 is also connected to the current limiting resistor R1 and one end of the absorption capacitor C1.

[0085] When the switch tube T1 is turned off, the short-circuit current cannot disappear immediately, so it is forced to flow through the current-limiting resistor R1. The impedance of the current-limiting resistor R1 is used to limit the current. Since the short-circuit current is mostly inductive current, a large induced voltage will be generated when it is forced to be turned off. An absorption capacitor C1 is connected in parallel across the current-limiting resistor R1 to limit the amplitude of the induced voltage.

[0086] In the opposite direction, when the switch tube T2 is overcurrent, after the switch tube T2 is turned off, the short-circuit current is also forced to flow through the current limiting resistor R1, and the magnitude of the short-circuit current is controlled by the limiting effect of the resistor R1.

[0087] In the present utility model, the specific implementation is as follows: Figure 5 As shown, the control circuit 100 includes a first control sub-circuit and a second control sub-circuit, two control sub-circuits with the same functions. The first control sub-circuit and the second control sub-circuit correspond to the positive half-wave and the negative half-wave of the alternating current, respectively.

[0088] The first control subcircuit includes: switch tubes T7-T8, diodes D3-D5, resistors R6-R7 and comparator U1A;

[0089] The second control sub-circuit includes: switch tubes T9-T10, diodes D6-D8, resistors R8-R9 and comparator U1B;

[0090] Wherein, for the first control sub-circuit, the output terminal 1 of the first control sub-circuit is connected to the 2nd terminal of the resistor R4 in the current limiting circuit;

[0091] The output terminal 1 of the first control sub-circuit is also connected to the terminal 1 of the diode D4, the terminal 2 of the diode D5, the terminal 3 of the switch tube T7, and the terminal 3 of the switch tube T8 respectively;

[0092] The two terminals of the diode D4 and the one terminal of the switch tube T7 are connected to the drive power supply VDD terminal, which is used to introduce the drive power supply to the subsequent switch tube;

[0093] One end of the switch tube T8 and one end of the diode D5 are connected to the ground terminal GND, which is used as a reference ground for the subsequent switch tube;

[0094] It should be noted that diodes D4 and D5 are limiting diodes, which are used to forcibly limit the output level between the driving power supply VDD terminal (VDD is the universal IGBT driving voltage, specifically 12V) and the ground terminal GND (ground voltage, 0V), thereby protecting the subsequent switching tube.

[0095] The two ends of the switch tube T7 and the two ends of the switch tube T8 are connected to one end of the capacitor C4 after they converge and intersect;

[0096] One end of capacitor C4 is also connected to one end of resistor R7 to form an RC delay circuit for delaying the driving level from the previous stage;

[0097] One end of the resistor R7 is also connected to one end of the diode D3;

[0098] The two ends of the diode D3 are connected to the two ends of the resistor R7, that is, the resistor R7 and the diode D3 are connected in parallel, realizing the delay function of delaying the opening of the high level of the driving level and quickly shutting off the low level;

[0099] Two terminals of the capacitor C4 are connected to the ground terminal GND;

[0100] Terminal 2 of the comparator U1A (which is a three-terminal device) serves as the input terminal 3 of the first control sub-circuit and is connected to terminal 1 of the sampling resistor SEN1 in the current limiting circuit;

[0101] Terminal 3 of the comparator U1A is connected to terminal 2 of the resistor R6;

[0102] Terminal 1 of the comparator U1A is connected to terminal 2 of the resistor R7;

[0103] The 1st terminal of resistor R6 is connected to the REF voltage reference terminal. The voltage reference terminal should be set to the product of the current value of the preset current limit point and the sampling resistor value. In other words, the reference value determines the action point of the current limit.

[0104] It should be noted that two ends of the resistor R7 are connected to two ends of the diode D3, and then connected to one output end of the preceding comparator U1A. The driving level output by the comparator U1A according to the current situation is output from one end thereof.

[0105] Wherein, for the second control sub-circuit, the output terminal 2 of the second control sub-circuit is connected to the 2 ends of the resistor R5 in the current limiting circuit;

[0106] Output terminal 2 of the second control subcircuit is also connected to terminal 1 of diode D7, terminal 2 of diode D8, terminal 3 of switch tube T9, and terminal 3 of switch tube T10;

[0107] The 2 ends of the diode D7 and the 1 end of the switch tube T9 are connected to the drive power supply VDD terminal, which is used to introduce the drive power supply for the subsequent stage switch tube;

[0108] One end of the switch tube T10 and one end of the diode D8 are connected to the ground terminal GND, which is used as a reference ground for the subsequent switch tube;

[0109] It should be noted that diodes D7 and D8 are limiting diodes, which are used to forcibly limit the output level between the VDD terminal of the driving power supply 12V (VDD is the universal IGBT driving voltage, specifically 12V) and the GND ground terminal GND (ground voltage, 0V), thereby protecting the subsequent switching tube.

[0110] The two ends of the switch tube T9 and the two ends of the switch tube T10 are connected to one end of the capacitor C5 after they converge and intersect;

[0111] One end of the capacitor C5 is connected to one end of the resistor R9 to form an RC delay circuit, which is used to delay the driving level from the previous stage;

[0112] Connect one end of the diode D6 to one end of the resistor R9;

[0113] The two ends of the diode D6 are connected to the two ends of the resistor R9, that is, the resistor R9 and the diode D6 are connected in parallel, so as to realize the delay function of delaying opening when the driving level is high and quickly shutting off when the driving level is low;

[0114] Two terminals of the capacitor C5 are connected to the ground terminal GND;

[0115] Terminal 6 of the comparator U1B (which is a three-terminal device) serves as the input terminal 4 of the second control subcircuit and is connected to terminal 2 of the sampling resistor SEN2 in the current limiting circuit;

[0116] Terminal 5 of the comparator U1B is connected to terminal 2 of the resistor R8;

[0117] Terminal 7 of the comparator U1B is connected to terminal 2 of the resistor R9;

[0118] Connect the 1st terminal of resistor R8 to the REF voltage reference terminal. As above, the voltage reference terminal should be set to the product of the current value of the preset current limit point and the sampling resistor value. In other words, the reference value determines the action point of the current limit.

[0119] It should be noted that the 2 ends of the resistor R9 are connected to the 2 ends of the diode D6, and then connected to the 7-terminal output of the previous comparator U1B. The driving level output by the comparator U1B according to the current situation is output from its 7-terminal.

[0120] It should be noted that, in the present invention, the reason why the driving level of the switching tube needs to be delayed is that the current flowing through the switching tube is an AC current. If a short circuit or overload occurs, the time is about 10mS, which requires that the driving level protection time should be maintained at about 10mS. Therefore, after the driving level is restored to a high level at terminal 1 of the comparator U1A and terminal 7 of the comparator U1B, the resistors R7 and R9 charge the subsequent capacitors C4 and C5. After a delay of about 10mS, the output end of the driving stage (specifically including terminals 3 of the switching tubes T7 and T8 and terminals 3 of the switching tubes T9 and T10) is driven to a high level, thereby completing a current limiting cycle.

[0121] In order to more clearly understand the technical solution of the present invention, the working principle of the control circuit 100 is described below.

[0122] In the present invention, the control circuit 100 is a circuit specially designed for the present invention, and its main function is to realize the necessary control required for the current limiting function.

[0123] See also Figure 5 As shown, during normal operation, for the control circuit 100, its drive circuit (two groups of push-pull drive circuits composed of switch tubes T7, T8, T9, and T10) outputs a high level, so that T1 and T2 in the current limiting circuit are normally opened, and the circuit works normally.

[0124] When the circuit is overloaded or short-circuited, current will flow through the current collection resistors SEN1 and SEN2 to form a voltage signal, which is transmitted to the control circuit 100. This voltage signal is transmitted to the subsequent comparator circuit in the control circuit 100. The comparator determines whether the current is in an overcurrent state based on the voltage value of the current collection resistor. If overcurrent occurs, the comparator changes its normal high-level output to a low-level output (wherein the high-level output quickly discharges the charge on the capacitors C4 and C5 through the discharge diodes D3 and D6, thereby becoming a low-level output). As a result, a low-level output is output at the two output terminals of the control circuit 100 (including the terminals T7 and T8, and the terminals T9 and T10), thereby turning off the switch tubes T1 and T2 (IGBT tubes) in the current limiting circuit and realizing the current limiting function.

[0125] That is, the control circuit 100 is connected to the current limiting circuit, and is used to collect the voltage signals flowing out of the current collection resistors SEN1 and SEN2 in the current limiting circuit, and determine whether there is overcurrent. When there is overcurrent, the corresponding current limiting function is performed.

[0126] In the present invention, in a specific implementation, the terminal 2 of the current sampling resistor SEN1 and the terminal 1 of the current sampling resistor SEN2 intersect at a node A;

[0127] Node A is connected to the GND terminal on the control circuit 100 so that the reference ground signals of the two circuits are at the same level, so that the circuit can realize all functions.

[0128] It should be noted that the other ends of the current sampling resistors SEN1 and SEN2 are connected and grounded, and the node A serves as a reference point of the control circuit 100 and is connected to the control circuit (which serves as a sampling circuit at this time) 100 .

[0129] In the present invention, in a specific implementation, the gate (i.e., terminal 3) of the switch tube T1 is connected to the terminal 3 (i.e., the drive output end) of the switch tubes T7 and T8 on the control circuit 100 as the drive output end through the drive resistor R4, which is the output point of the drive level.

[0130] In the present invention, in a specific implementation, the gate of the switch tube T2 (i.e., terminal 3) is connected to the terminals 3 (i.e., the drive output end) of T9 and T10 on the control circuit 100 of the drive output end through the drive resistor R5, which is the output point of the drive level.

[0131] It should be noted that, for the control circuit 100, the driving output ends of the driving circuit (two groups of push-pull driving circuits composed of switch tubes T7, T8, T9, and T10) include three ends of the switch tubes T7 and T8 and three ends of the switch tubes T9 and T10.

[0132] Based on the AC current limiting protection circuit provided by the above utility model, the utility model also provides an AC bridge commutation device, which includes the AC current limiting protection circuit as described above, and an AC bridge commutation circuit;

[0133] The AC current limiting protection circuit is connected to the AC bridge commutation circuit.

[0134] In specific implementation, the AC bridge commutation circuit (i.e., contactless commutation bridge circuit) includes bidirectional thyristors T3 to T6 and a compensation transformer B1;

[0135] Terminal 1 of the compensation transformer B1 is connected to the live wire (L line) of the input terminal of the external contactless voltage regulator (i.e., contactless voltage regulator). Its purpose and function are: to compensate for the deviation of the input voltage of the contactless voltage regulator;

[0136] Terminal 2 of compensation transformer B1 is connected to the live wire (L line) at the output end of an external contactless voltage-stabilized power supply (i.e., a contactless voltage regulator) (this output live wire is connected to the live wire input end of the load device supporting the contactless voltage-stabilized power supply). It is used to provide a compensated output voltage to provide stable power supply to the railway signaling equipment serving as the load device.

[0137] It should be noted that the input neutral line (N line) of the contactless voltage regulator (i.e., the contactless voltage regulator) is the same as the output neutral line (N line) of the contactless voltage regulator. Figure 3 、 Figure 4 shown.

[0138] It should be noted that the load equipment is, for example, railway signaling equipment such as lighting equipment and switch equipment on the railway track.

[0139] It should be noted that terminals 1 and 2 of the compensation transformer B1 are respectively connected to the input and output terminals of a contactless voltage-stabilized power supply (i.e., a contactless voltage regulator), so that the voltage between terminals 1 and 2 is superimposed on the input terminal of the contactless voltage regulator, thereby compensating for the input voltage and completing the compensation for the input voltage deviation.

[0140] Terminal 3 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T6 and terminal 1 of the bidirectional thyristor T5 respectively;

[0141] Terminal 4 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T4 respectively;

[0142] After the terminal 2 of the bidirectional thyristor T4 and the terminal 2 of the bidirectional thyristor T5 are converged and intersected, they are connected to the input neutral line (N line) of the contactless voltage regulator (ie, the contactless voltage regulator).

[0143] In specific implementation, the collector (i.e., terminal 1) of the switch tube T2 in the AC current limiting protection circuit serves as the output end of the current limiting circuit and is connected to the input neutral line (N line) of the contactless voltage regulator (i.e., contactless voltage regulator) through the AC bridge commutation circuit.

[0144] Furthermore, terminal 1 of the bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T6 serve as input terminals of the AC bridge commutation circuit and are connected to the collector of the switch tube T2.

[0145] It should be noted that, in the present invention, the compensating transformer B1 is an ordinary, general power frequency transformer. In the present invention, its transformation ratio parameter is 220:7, and this ratio can also be adjusted according to the specific compensation deviation value.

[0146] Similarly, bidirectional thyristors T3 to T6 are ordinary, general bidirectional thyristors, and are of the insulating type. In practical applications, bidirectional thyristors T3 to T6 use "BTA41-600B bidirectional thyristors". The thyristor current is above 40A and the withstand voltage should be higher than 600V, which can generally meet the reliability requirements of practical applications.

[0147] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An AC current limiting protection circuit, characterized in that: It includes a current limiting circuit and a control circuit (100); The current limiting circuit includes: a switch tube T1, a switch tube T2, a current sampling resistor SEN1, a current sampling resistor SEN2, a current limiting resistor R1, an absorption resistor R2, an absorption resistor R3, an absorption capacitor C2 and an absorption capacitor C3, and drive resistors R4 to R5; The collector of the switch tube T1 serves as the input terminal of the current limiting circuit, and is connected to the terminal 1 of the current limiting resistor R1, the terminal 1 of the absorption resistor R2, and the cathode of the diode D1 respectively; The emitter of the switch tube T1 is connected to the terminal 1 of the current sampling resistor SEN1, the anode of the diode D1 and the terminal 2 of the absorption capacitor C2 respectively; Terminal 1 of the absorption capacitor C2 is connected to terminal 2 of the absorption resistor R2; The collector of the switch tube T2 serves as the output end of the current limiting circuit, and is connected to the terminal 2 of the current limiting resistor R1, the cathode of the diode D2, and the terminal 2 of the absorption resistor R3 respectively; The emitter of the switch tube T2 is connected to the terminal 2 of the current sampling resistor SEN2, the anode of the diode D2 and the terminal 1 of the absorption capacitor C3 respectively; Terminal 1 of the absorption capacitor C3 is connected to terminal 1 of the absorption resistor R3; Wherein, the terminal 2 of the current sampling resistor SEN1 and the terminal 1 of the current sampling resistor SEN2 are connected and grounded at the same time; The gate of the switch tube T1 is connected to the control circuit (100) via the driving resistor R4; The gate of the switch tube T2 is connected to the control circuit (100) via the driving resistor R5; The control circuit (100) is connected to the current limiting circuit and is used to collect voltage signals flowing out of the current collection resistors SEN1 and SEN2 in the current limiting circuit, and to determine whether there is overcurrent, and to perform a corresponding current limiting function when there is overcurrent.

2. The AC current limiting protection circuit according to claim 1, wherein: Also includes: Absorption capacitor C1; Terminal 1 of the absorption capacitor C1 is connected to the collector of the switch tube T1; Terminal 2 of the absorption capacitor C1 is connected to the collector of the switch tube T2.

3. The AC current limiting protection circuit according to claim 1, wherein: The collector of the switch tube T1 is connected to the live wire of the input end of the contactless voltage-stabilized power supply.

4. The AC current limiting protection circuit according to any one of claims 1 to 3, characterized in that: The collector of the switch tube T2 is connected to the input neutral line of the contactless voltage-stabilized power supply through an AC bridge commutation circuit.

5. The AC current limiting protection circuit according to claim 4, wherein: The collector of the switch tube T2 is connected to the terminal 1 of the original bidirectional thyristor T3 and the terminal 1 of the bidirectional thyristor T6 of the AC bridge commutation circuit; AC bridge commutation circuit, including bidirectional thyristors T3 to T6 and compensation transformer B1; Terminal 1 of the compensation transformer B1 is connected to the live wire L of the input terminal of the external contactless voltage-stabilized power supply; Terminal 2 of the compensation transformer B1 is connected to the live wire of the output terminal of the external contactless voltage-stabilized power supply; Terminal 3 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T6 and terminal 1 of the bidirectional thyristor T5 respectively; Terminal 4 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T4 respectively; Terminal 2 of the bidirectional thyristor T4 and terminal 2 of the bidirectional thyristor T5 are connected to the input neutral line of the contactless voltage-stabilized power supply after being converged and intersected.

6. The AC current limiting protection circuit according to any one of claims 1 to 5, characterized in that: A control circuit (100) includes a first control subcircuit; The first control subcircuit includes: switch tubes T7-T8, diodes D3-D5, resistors R6-R7 and comparator U1A; The second control sub-circuit includes: switch tubes T9-T10, diodes D6-D8, resistors R8-R9 and comparator U1B; Wherein, for the first control sub-circuit, the output terminal 1 of the first control sub-circuit is connected to the 2nd terminal of the resistor R4 in the current limiting circuit; The output terminal 1 of the first control sub-circuit is also connected to the terminal 1 of the diode D4, the terminal 2 of the diode D5, the terminal 3 of the switch tube T7, and the terminal 3 of the switch tube T8 respectively; The two terminals of the diode D4 and the one terminal of the switch tube T7 are connected to the driving power supply VDD terminal; One end of the switch tube T8 and one end of the diode D5 are connected to the ground terminal GND; The two ends of the switch tube T7 and the two ends of the switch tube T8 are connected to one end of the capacitor C4 after they converge and intersect; One end of capacitor C4 is also connected to one end of resistor R7; One end of the resistor R7 is also connected to one end of the diode D3; Connect two terminals of the diode D3 to two terminals of the resistor R7; Two terminals of the capacitor C4 are connected to the ground terminal GND; Terminal 2 of the comparator U1A, serving as input terminal 3 of the first control sub-circuit, is connected to terminal 1 of the sampling resistor SEN1 in the current limiting circuit; Terminal 3 of the comparator U1A is connected to terminal 2 of the resistor R6; Terminal 1 of the comparator U1A is connected to terminal 2 of the resistor R7; One end of the resistor R6 is connected to the REF voltage reference terminal.

7. The AC current limiting protection circuit according to claim 6, wherein: The control circuit (100) further includes a second control subcircuit; The output terminal 2 of the second control sub-circuit is connected to the 2 ends of the resistor R5 in the current limiting circuit; Output terminal 2 of the second control subcircuit is also connected to terminal 1 of diode D7, terminal 2 of diode D8, terminal 3 of switch tube T9, and terminal 3 of switch tube T10; The 2 ends of the diode D7 and the 1 end of the switch tube T9 are connected to the driving power supply VDD terminal; One end of the switch tube T10 and one end of the diode D8 are connected to the ground terminal GND; The two ends of the switch tube T9 and the two ends of the switch tube T10 are connected to one end of the capacitor C5 after they converge and intersect; One end of capacitor C5 is connected to one end of resistor R9; Connect one end of the diode D6 to one end of the resistor R9; Connect two terminals of the diode D6 to two terminals of the resistor R9; Two terminals of the capacitor C5 are connected to the ground terminal GND; Terminal 6 of the comparator U1B serves as the input terminal 4 of the second control sub-circuit and is connected to terminal 2 of the sampling resistor SEN2 in the current limiting circuit; Terminal 5 of the comparator U1B is connected to terminal 2 of the resistor R8; Terminal 7 of the comparator U1B is connected to terminal 2 of the resistor R9; One end of the resistor R8 is connected to the REF voltage reference terminal.

8. An AC bridge commutation device, characterized in that: comprising an AC current limiting protection circuit as claimed in any one of claims 1 to 7, and an AC bridge commutation circuit; The AC current limiting protection circuit is connected to the AC bridge commutation circuit.

9. The AC bridge commutation device according to claim 8, characterized in that: AC bridge commutation circuit, including bidirectional thyristors T3 to T6 and compensation transformer B1; Terminal 1 of the compensation transformer B1 is connected to the live wire L of the input terminal of the contactless voltage regulated power supply; Terminal 2 of the compensation transformer B1 is connected to the live wire of the output terminal of the contactless voltage-stabilized power supply; Terminal 3 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T6 and terminal 1 of the bidirectional thyristor T5 respectively; Terminal 4 of the compensation transformer B1 is connected to terminal 2 of the bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T4 respectively; Terminal 2 of the bidirectional thyristor T4 and terminal 2 of the bidirectional thyristor T5 are connected to the input neutral line of the contactless voltage-stabilized power supply after being converged and intersected.

10. The AC bridge commutation device according to claim 8, characterized in that: Terminal 1 of the bidirectional thyristor T3 and terminal 1 of the bidirectional thyristor T6 are connected to the collector of the switch tube T2.

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