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

Abstract

The invention discloses an alternating current limiting protection circuit and an alternating current 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 invention, the impact of bridge arm short-circuit direct connection of the commutation bridge circuit on a switching device can be effectively prevented, and device damage is avoided.

Description

Technical Field

[0001] The present invention relates to the field of AC current limiting protection circuit and rail transportation technology, and in particular to an AC current limiting protection circuit and an AC bridge commutation device. Background Art

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

[0003] The contactless voltage-stabilized power supply compensates the output voltage by transformer grading, and the output voltage is stabilized within the set range. At present, the power of the voltage-stabilized power supply generally includes 3.5KVA, 5KVA and 10KVA capacities.

[0004] The commutation bridge circuit (also called the contactless commutation bridge circuit) 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-T6. The bidirectional thyristors T3-T6 are AC switching devices capable of switching 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 switch 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 deviation of the input voltage from the expected value.

[0006] It should be noted that the input voltage, i.e. the input voltage of the signal power supply panel system (i.e. the signal power supply system, i.e. the railway signal power supply, specifically the contactless voltage stabilizer), comes from the power supply network along the railway. Due to objective conditions such as long distance or load fluctuation, this voltage often deviates from the rated value. This causes many electrical equipment to not operate stably. Therefore, a voltage stabilizer is needed to compensate for this voltage deviation, which refers to the contactless voltage stabilizer.

[0007] Due to external interference and other reasons, the bidirectional thyristor device may be turned on without control (i.e., risk), and there is also the possibility that it cannot be turned off controllably after being turned on (i.e., risk). Therefore, this contactless commutation bridge circuit has the risk of a bridge arm short-circuiting directly, which 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. Summary of the invention

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

[0010] To this end, the present invention 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 driving resistors R4-R5;

[0012] The collector of the switch tube T1 is used as the input end of the current limiting circuit, and is respectively 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;

[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, as the output end of the current limiting circuit, is respectively 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;

[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 a 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 signal flowing out of the current collection resistors SEN1 and SEN2 in the current limiting circuit, and determine whether there is overcurrent, and play the corresponding current limiting function when there is overcurrent.

[0022] It can be seen from the technical solution provided by the present invention that, compared with the prior art, the present invention 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, the bridge arm short circuit of the contactless commutation bridge circuit can be effectively protected from the impact of the direct connection of the bridge arm on the switching device (i.e., a bidirectional thyristor device), thereby avoiding damage to the device (i.e., a bidirectional thyristor device) caused by the bridge arm short circuit, and avoiding further accidents such as line fire, which has great practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of an existing contactless commutation bridge circuit (i.e., an AC bridge commutation circuit);

[0024] Figure 2 It is a principle diagram of an AC current limiting protection circuit provided by the present invention;

[0025] Figure 3 This is a working principle diagram of an embodiment 1 of an AC current limiting protection circuit provided by the present invention when applied to a contactless commutation bridge circuit (that is, 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 Embodiment 2 of an AC current limiting protection circuit provided by the present invention when applied to a contactless commutation bridge circuit (that is, when the AC current limiting protection circuit and the AC bridge commutation circuit together form an AC bridge commutation device);

[0027] Figure 5 It is a schematic diagram of an embodiment of a control circuit in an AC current limiting protection circuit provided by the present invention. 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0029] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and 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 driving resistors R4-R5.

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

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

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

[0036] The collector (i.e., terminal 1) of the switch tube T2 is used as the output end of the current limiting circuit, and is respectively 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;

[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 the present invention, for specific implementation, see Figure 4 As shown, the current limiting circuit also 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] The terminal 2 of the absorption capacitor C1 is connected to the collector (ie, the terminal 1) of the switch tube T2.

[0045] In the present invention, the control circuit 100 is connected to the current limiting circuit to collect the voltage signal 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, in a specific implementation, the switch tubes T1 and T2 are insulated-gate bipolar transistors (IGBT). The switch tubes T1 and T2 are implemented by IGBTs, and the drive of the IGBTs is provided by the control circuit (which serves as a drive circuit in this case) 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 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 according to the size of the voltage signal, and forces the short-circuit current to flow through the current limiting resistor R1, thereby limiting the continued 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 (i.e., terminal 1) of the switch tube T1, as the input end of the current limiting circuit, is connected to the input end live wire (L line) 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 regulated power supply (i.e., 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 regulated power supply (i.e., contactless voltage regulator) connected to the terminal 1 of the compensation transformer B1 mentioned below.

[0052] In the present invention, the collector (i.e., terminal 1) of the switch tube T2, 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 specific implementation, the collector (i.e., terminal 1) 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 (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-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 contactless voltage-stabilizing power supply (i.e., contactless voltage regulator) located outside. The purpose and function are: to compensate for the deviation of the input voltage of the contactless voltage-stabilizing power supply (i.e., contactless voltage regulator);

[0057] Terminal 2 of the compensation transformer B1 is connected to the live wire (L line) of the output end of the contactless voltage-stabilized power supply (i.e., the contactless voltage regulator) (the output end is connected to the live wire input end of the load device) to provide a compensated output voltage to provide stable power supply to the railway signal equipment 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, i.e., they share a common line. 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 railway tracks.

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

[0061] It should be noted that the contactless voltage stabilizer is the core equipment in the existing railway signal power supply, and is a mature and widely used equipment. For example, the contactless voltage stabilizer can adopt the MW-220 / 16 (3.5Kva), MW-220 / 23 (5Kva), MW-220 / 46 (10KVA) and other series of contactless voltage stabilizer modules produced by Tianjin Railway Signal Co., Ltd., which are mainly used in the general speed intelligent signal power supply screen as the core component of the voltage stabilization power supply.

[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 respectively connected to the live wire terminal and the neutral wire terminal of the load device;

[0063] In terms of specific implementation, Figure 3 , Figure 4 The terminal 2 of the compensation transformer B1 is connected to the live wire L of the output end 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 stabilizer (i.e., contactless voltage stabilizer) is the same line as the output neutral line (N line) of the contactless voltage stabilizer (i.e., contactless voltage stabilizer), that is, they share a line, see 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 switch tube T1 as the IGBT should be able to meet the maximum current of the commutation bridge circuit and leave a margin of more than one time. 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 according to the compensation current associated with the actual contactless voltage regulation power. For the 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 the 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 wirewound 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] Absorption capacitors C2 and C3 can use general parameters, and the power consumption is not high. The capacity is generally around 2200nF. The main functions of absorption capacitors C2 and C3 are: to absorb the oscillation current generated when the switch tube is turned off;

[0073] The absorption resistors R2 and R3 are used as damping resistors of the absorption circuit, and are mainly responsible for consuming the oscillation energy generated by the switch tube when switching. It depends on the actual situation. In the present invention, 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 planned inductance parameter of the short-circuit current loop will be relatively large, and the generated induced voltage 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 present invention 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 (IGBT) to achieve the current limiting function of the AC power frequency current.

[0080] For the present invention, since it is applied in an AC circuit, IGBT is a single-phase conduction switch tube, which can only conduct half of the waveform of the AC signal. Therefore, two switch tubes need to be connected in reverse phase, and the switch tube is required to have a body diode to conduct the negative half-wave of the signal. In this way, when the switch tube T1 is turned on and the switch tube T2 is reversed and cut off, the body diode D1 of the switch tube T1 will be turned on, completing the conduction function in the direction of the switch tube T1. The method and principle of reverse conduction are the same.

[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 reversely 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 for the commutation bridge circuit. The switch 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 and 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 determine 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 at both ends of 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 invention, in specific implementation, as 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 corresponding 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 a comparator U1A;

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

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

[0091] The output terminal 1 of the first control subcircuit 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 ends of the diode D4 and the one end of the switch tube T7 are connected to the drive power supply VDD terminal, so as 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 force the output level to be limited 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 the capacitor C4 is also connected to one end of the 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] Two ends of the diode D3 are connected to two ends of the resistor R7, that is, the resistor R7 and the diode D3 are connected in parallel, so as to realize the delay function of high level delay opening of the driving level and low level rapid shutdown;

[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) is connected to terminal 1 of the sampling resistor SEN1 in the current limiting circuit as terminal 3 of the first control subcircuit;

[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 1 end of resistor R6 is connected to the REF voltage reference end, where the voltage reference end should be set to the product of the current value of the preset current limit point and the sampling resistance. In other words, the reference value determines the action point of the current limit current.

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

[0107] The two ends of the diode D7 and the one end of the switch tube T9 are connected to the drive power supply VDD terminal, so as to introduce the drive power supply to the subsequent 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 force the output level to be limited 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 for delaying the driving level from the previous stage;

[0112] One end of the diode D6 is connected to one end of the resistor R9;

[0113] Two ends of the diode D6 are connected to 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 high level delay opening of the driving level and low level rapid shutdown;

[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) is connected to terminal 2 of the sampling resistor SEN2 in the current limiting circuit as terminal 4 of the second control subcircuit;

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

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

[0118] The 1 end of resistor R8 is connected to the REF voltage reference end. As above, the setting of the voltage reference end here should be the product of the current value of the preset current limit point and the sampling resistance. In other words, the reference value determines the action point of the current limit current.

[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 end 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 switch tube needs to be delayed is that the current flowing through the switch 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 switch tubes T7 and T8 and terminals 3 of the switch 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 by 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, in 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, the current will flow through the current collection resistors SEN1 and SEN2 to form a voltage signal, which is transmitted to the control circuit 100. The voltage signal is transmitted to the post-stage 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 it is overcurrent, the comparator changes from outputting a normal high level to outputting a low level (wherein the high level quickly discharges the electricity on the capacitors C4 and C5 through the discharge diodes D3 and D6, thereby becoming a low level), thereby outputting a low level at the two output ends of the control circuit 100 (including the 3 ends of T7 and T8, and the 3 ends of T9 and T10), thereby turning off the switch tubes T1 and T2 (IGBT tubes) in the current limiting circuit to achieve the current limiting function.

[0125] That is, the control circuit 100 is connected to the current limiting circuit to collect the voltage signal flowing out of the current collecting 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 is connected to the control circuit (as a sampling circuit at this time) 100 as a reference point of the control circuit 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 (i.e., terminal 3) of the switch tube T2 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 end of the driving circuit (two groups of push-pull driving circuits composed of switch tubes T7, T8, T9, and T10) includes 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 present invention, the present invention further 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., the 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), and its purpose and function are: to compensate for the deviation of the input voltage of the contactless voltage regulator;

[0136] Terminal 2 of the compensation transformer B1 is connected to the live wire (L line) of the output end of the contactless voltage-stabilized power supply (i.e., the contactless voltage regulator) located outside (the live wire of the output end is connected to the live wire input end of the load device matched with the contactless voltage-stabilized power supply), and is used to provide a compensated output voltage to provide stable power supply to the railway signal equipment 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, i.e., they share a common line. 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 railway tracks.

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

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

[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~T6 are ordinary, general bidirectional thyristors, which are of insulating type. In practical applications, bidirectional thyristors T3~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 principle of the present invention. These improvements and modifications should also be regarded as 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 driving resistors R4-R5; The collector of the switch tube T1 is used as the input end of the current limiting circuit, and is respectively 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; 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, as the output end of the current limiting circuit, is respectively 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; 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 a 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 collecting resistors SEN1 and SEN2 in the current limiting circuit, and to judge whether there is overcurrent, and to play a corresponding current limiting function when there is overcurrent.

2. The AC current limiting protection circuit according to claim 1, characterized in that: 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, characterized in that: 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 claim 1, 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, characterized in that: 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-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 contactless voltage-stabilized power supply located outside; 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) comprises a first control subcircuit; The first control subcircuit includes: switch tubes T7-T8, diodes D3-D5, resistors R6-R7 and a comparator U1A; The second control subcircuit includes: switch tubes T9-T10, diodes D6-D8, resistors R8-R9 and a comparator U1B; Wherein, for the first control sub-circuit, the output terminal 1 of the first control sub-circuit is connected to the terminal 2 of the resistor R4 in the current limiting circuit; The output terminal 1 of the first control subcircuit 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 ends of the diode D4 and the one end 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; Two ends of the diode D3 are connected to two ends of the resistor R7; Two terminals of the capacitor C4 are connected to the ground terminal GND; Terminal 2 of the comparator U1A, as the 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; The terminal 1 of the resistor R6 is connected to the REF voltage reference terminal.

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

8. An AC bridge commutation device, characterized in that: It comprises 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-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-stabilized 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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