A switching power supply starting circuit for a medium-voltage contactor

Abstract

The present invention relates to a switching power supply starting circuit for a medium-voltage contactor, which includes an input rectifier circuit, a voltage stabilizing circuit, a fast start circuit, a restart circuit, a control chip, a high-frequency coil, and a protection control module arranged in sequence. One end of the primary winding of the high-frequency coil is connected to the first output terminal of the input rectifier circuit, and the other end is connected to the control chip. One end of its auxiliary winding is connected to the restart circuit, and the other end is connected to the second output terminal of the input rectifier circuit and grounded together. The protection control module is respectively connected to the control chip and the secondary winding of the high-frequency coil. Compared with the prior art, the present invention has the advantages of fast starting speed and high reliability.

Description

Technical Field

[0001] The present invention relates to the field of medium-voltage contactors, and particularly to a switching power supply startup circuit for a medium-voltage contactor. Background Art

[0002] Medium-voltage contactors are used in three-phase systems with a rated voltage below 12 kV and a rated frequency of 50 / 60 Hz. As an electrical protection device, they are particularly suitable for protecting electrical equipment such as motors, transformers, and capacitor banks, and are widely used in the power industry, industrial and mining enterprises, petrochemical industry, papermaking and metallurgy industries, etc. For the closing and opening of contactors, special control methods are required. Commonly used contactor controls include magnetic latching, electric latching, and mechanical latching working modes.

[0003] The electric latching module is widely used in the control of medium-voltage contactors due to its outstanding advantages of energy conservation and flexible control. As a protection device, medium-voltage contactors have strict requirements for the breaking and closing times. For example, AEG's technical requirements for medium-voltage contactors state that the time from sending a signal to the contactor breaking or closing should not be greater than 100 ms. The shorter this time, the smaller the harm caused by electrical accidents.

[0004] As a power supply with high efficiency, wide input range, wide output range, large output current, and low ripple, a switching power supply is applied in various instruments and equipment. The switching power supply is commonly controlled by a PWM control chip, which provides various functions while performing PWM regulation of the switching power supply, such as overvoltage protection, undervoltage protection, overheat protection, soft start, constant power control, overload protection, and automatic restart protection. Commonly used switching power supply design topologies are as Figure 1 shown.

[0005] After the power supply is energized at the power input terminal, the system charges the capacitor C1 through the resistor R1. When the charging voltage reaches the trigger voltage for the chip to work, the electrical energy charged into C1 from the power-on will drive the switching power supply chip to work for a short period of time. When the chip is working, the switching power supply outputs a PWM signal to drive the high-frequency coil T1 to work. After the high-frequency coil works, the coil auxiliary winding will provide continuous electrical energy for the switching power supply chip to keep the chip in a continuous working state. When a certain fault is detected, the chip triggers protection and stops outputting the PWM signal, and the power supply from the auxiliary winding to the switching power supply chip also disappears. When the electrical energy in C1 is consumed to the point where it cannot maintain the system operation, the chip stops working, and the power supply charges C1 through R1 again to drive the switching power supply chip to work. If the fault disappears, the auxiliary winding will provide continuous energy to keep the switching power supply chip working continuously. If the fault does not disappear, R1 and C1 will repeatedly charge to attempt to start the power supply until the fault disappears, thereby achieving the purpose of automatic restart of the switching power supply in case of a fault.

[0006] The switching power supply startup mechanism of the resistor R1 and the capacitor C1 has the following disadvantages:

[0007] 1) Due to the startup mechanism of the switching power supply and the existence of the charge and discharge time of resistor R1 and capacitor C1, the power-on time of the system cannot meet the requirement of fast startup.

[0008] 2) The startup time of the power supply can be improved by removing resistor R1 and capacitor C1, but the system will lose its protection function, reducing the stability of the system.

[0009] 3) The startup time of the power supply can be reduced by decreasing the values of resistor R1 and capacitor C1. However, the value of resistor R1 needs to be in the MΩ level to ensure a wide input voltage range, and capacitor C1 also has the function of filtering the power supply ripple of the auxiliary winding and cannot be reduced without limit, which will reduce the reliability. Summary of the Invention

[0010] The purpose of the present invention is to provide a switching power supply startup circuit for a medium-voltage contactor to overcome the defects existing in the above-mentioned prior art.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] A switching power supply startup circuit for a medium-voltage contactor is used to quickly start the coil of the medium-voltage contactor. The startup circuit includes an input rectifier sub-circuit, a voltage regulator sub-circuit, a fast startup sub-circuit, a restart sub-circuit, a control chip, a high-frequency coil, and a protection control module, which are arranged in sequence. One end of the primary winding of the high-frequency coil is connected to the first output terminal of the input rectifier sub-circuit, and the other end is connected to the control chip. One end of its auxiliary winding is connected to the restart sub-circuit, and the other end is connected to the second output terminal of the input rectifier sub-circuit and grounded together. The protection control module is respectively connected to the control chip and the secondary winding of the high-frequency coil.

[0013] The input rectifier sub-circuit includes a bridge rectifier diode and a third capacitor connected in parallel with the output terminal of the bridge rectifier diode.

[0014] The voltage regulator sub-circuit includes a voltage regulator tube and a third resistor. The positive electrode of the voltage regulator tube is grounded, and the negative electrode is connected to the first output terminal of the input rectifier sub-circuit through the third resistor.

[0015] The fast startup sub-circuit includes a triode, a first optocoupler, a second capacitor, and a second resistor. The base of the triode is connected between the voltage regulator tube and the third resistor, the collector is connected to the positive electrode of the first output terminal of the input rectifier sub-circuit, the emitter is connected to the first end of the switching part of the first optocoupler, the second end of the switching part of the first optocoupler is connected to the control chip through a first diode, the negative electrode of the light-emitting part of the first optocoupler is grounded through the second resistor, and the positive electrode is connected to the first output terminal of the input rectifier sub-circuit through the second capacitor.

[0016] The described restart sub - circuit includes a first resistor and a first capacitor. The negative electrode of the first capacitor is grounded, and the positive electrode is connected to the first output terminal of the input rectifier sub - circuit through the first resistor. The positive electrode of the first capacitor is connected to the control chip through a second diode and is connected to one end of the auxiliary winding of the high - frequency coil through a third diode with reverse setting.

[0017] The cs pin of the described control chip is grounded through a fourth resistor, the GND pin is grounded, and the FB pin, the first Drain pin, and the second Drain pin are respectively connected to the protection control module.

[0018] When starting the coil, the second resistor and the second capacitor are charged, and the first optocoupler conducts, providing startup electrical energy for the control chip. After the control chip starts, the charge of the second capacitor continues to increase, and the auxiliary winding of the high - frequency coil and the fast - start sub - circuit jointly provide operating electrical energy for the control chip. When the charge in the second capacitor reaches the threshold charge, the first optocoupler turns off, and the auxiliary winding of the high - frequency coil provides operating electrical energy for the control chip. When a system fault occurs, the first resistor and the first capacitor charge and discharge, driving the control chip to restart.

[0019] The model of the described control chip is.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1) Fast startup speed: The optocoupler is conducted through the charging process of R2 and C2, so that the VDD of the control chip obtains a fast and stable voltage through D4, and the system starts quickly to work. The original startup time typical value is greater than 85 ms, and after improvement, the startup time is less than 15 ms, meeting the usage requirements of the medium - voltage contactor.

[0022] 2) The system is stable and reliable: A fast - start circuit is added on the basis of the original circuit, and various power protection functions can still operate normally without sacrificing the stability of the system, ensuring the original protection mechanism of the switching - power - supply chip and not changing various parameters of the original startup circuit, and the system reliability is not affected. Description of the Drawings

[0023] Figure 1 is the original switching - power - supply startup circuit;

[0024] Figure 2 is the switching - power - supply startup circuit of the present invention; Detailed Embodiment

[0025] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0026] Embodiment

[0027] As Figure 2As shown in the figure, the present invention provides a switching power supply starting circuit for a medium-voltage contactor, which is used to quickly start the coil of the medium-voltage contactor. The circuit includes an input rectifier circuit, a voltage regulator circuit, a fast start circuit, a restart circuit, a control chip U1, a high-frequency coil T1, and a protection control module, which are arranged in sequence. One end of the primary winding of the high-frequency coil T1 is connected to the first output terminal of the input rectifier circuit, and the other end is connected to the control chip U1. One end of its auxiliary winding is connected to the restart circuit, and the other end is connected to the second output terminal of the input rectifier circuit and grounded together. The protection control module is respectively connected to the control chip U1 and the secondary winding of the high-frequency coil T1.

[0028] The input rectifier circuit includes a bridge rectifier diode D1 and a third capacitor C3 connected in parallel with the output terminal of the bridge rectifier diode D1. The input rectifier circuit is connected to the input current, converts the input alternating current into direct current, and the converted voltage The converted voltage is output to the subsequent sub-circuits and the high-frequency coil T1.

[0029] The voltage regulator circuit includes a voltage regulator diode D2 and a third resistor R3. The positive electrode of the voltage regulator diode D2 is grounded, and the negative electrode is connected to the first output terminal of the input rectifier circuit through the third resistor R3.

[0030] The fast start circuit includes a triode D3, a first optocoupler U2, a second capacitor C2, and a second resistor R2. The base of the triode D3 is connected between the voltage regulator diode D2 and the third resistor R3, the collector is connected to the positive electrode of the first output terminal of the input rectifier circuit, the emitter is connected to the first end of the switching part of the first optocoupler U2, the second end of the switching part of the first optocoupler U2 is connected to the control chip U1 through a first diode D4, the negative electrode of the light-emitting part of the first optocoupler U2 is grounded through the second resistor R2, and the positive electrode is connected to the first output terminal of the input rectifier circuit through the second capacitor C2.

[0031] The restart circuit includes a first resistor R1 and a first capacitor C1. The negative electrode of the first capacitor C1 is grounded to GND1, the positive electrode is connected to the first output terminal of the input rectifier circuit through the first resistor R1, the positive electrode of the first capacitor C1 is connected to the control chip U1 through a second diode D5, and is connected to one end of the auxiliary winding of the high-frequency coil T1 through a reversely arranged third diode D7.

[0032] The cs pin P3 of the control chip U1 is grounded through a fourth resistor R4, the GND pin P8 is grounded, and the FB pin P3, the first Drain pin P5, and the second Drain pin P6 are respectively connected to the protection control module.

[0033] In this embodiment, the connection relationship of the protection control module is as follows: the FB pin P3 of the control chip U1 is grounded through the fifth capacitor U5 and connected to the first end of the switching part of the second optocoupler U3. The second end of the switching part of the second optocoupler U3 is grounded. The first Drain pin P5 and the second Drain pin P6 of the control chip U1 are respectively connected to the other end of the primary winding of the high-frequency coil T1 through the fourth diode D6 and the fourth capacitor C4 and the fifth resistor connected in parallel with each other. The positive pole of the power output terminal DC OUT is grounded through the inductor L1, the eighth capacitor C8, the secondary winding of the high-frequency coil T1, and the tenth resistor R10 and the eleventh resistor R11 connected to each other in sequence. One end of the ninth resistor R9 is connected between the eighth capacitor C8 and the inductor L1 and is connected to the eighth resistor R8 and the three-terminal voltage stabilizing diode U4 in sequence and then grounded. The negative poles of the seventh capacitor C7 and the ninth capacitor C9 are both grounded, and the positive poles are respectively connected to both ends of the inductor L1. The positive pole of the light-emitting part of the second optocoupler U3 is connected between the eighth resistor R8 and the ninth resistor R9, and the negative pole of the light-emitting part is connected to the first end of the three-terminal voltage stabilizing diode U4 through the eighth capacitor C8. One end of the seventh resistor R7 is connected to the second end of the three-terminal voltage stabilizing diode U4, and the other end is connected to the negative pole of the light-emitting part of the second optocoupler U3. There is also a capacitor YC1 connected between the ground of the start-up module part and the ground of the protection control module.

[0034] The start-up working stage of this embodiment is as follows:

[0035] The first stage: The second resistor R2 and the second capacitor C2 are charged. During the charging process, the light-emitting diode of the first optocoupler U2 conducts, and the collector and emitter of the first optocoupler U2 conduct, so that the VDD pin of the control chip U2 obtains a fast and stable power supply voltage through the first diode D4, and the system starts quickly to work;

[0036] The second stage: After the control chip U1 starts, as time goes by, the charge of the second capacitor C2 continues to increase, and the auxiliary winding of the high-frequency coil T1 and the fast start sub-circuit jointly provide working electrical energy for the control chip U1;

[0037] The third stage: When the charge in the second capacitor C2 reaches the threshold charge, the first optocoupler U2 turns off, and the auxiliary winding of the high-frequency coil T1 provides working electrical energy for the control chip U1;

[0038] The implementation of the fault restart function of this embodiment is as follows:

[0039] When the system fails, the control chip U1 triggers protection, and the power supply to the control chip U1 from the auxiliary winding of the high-frequency coil T1 disappears. When the electric energy in the first capacitor C1 is consumed to the point where it cannot maintain the system operation, the power supply charges the first capacitor C1 again through the first resistor R1 to drive the control chip U1 to restart. If the fault disappears, the auxiliary winding of the high-frequency coil T1 will provide continuous energy for the control chip U1 to keep working; if the fault does not disappear, the first resistor R1 and the first capacitor C1 will repeatedly charge to attempt to start the control chip U1 until the fault disappears, thereby achieving the purpose of automatic restart of the switching power supply in case of failure.

[0040] The startup module of the present invention is used to achieve the rapid startup and automatic restart in case of failure of the system. The protection control module is used to achieve multiple protections for the switching power supply, such as overvoltage protection, undervoltage protection, overheat protection, soft start, constant power control, overload protection, etc. The protection control module is the prior art of the switching power supply.

[0041] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A switching power supply starting circuit for a medium-voltage contactor, which is used to quickly start the coil of the medium-voltage contactor, and is characterized in that, The starting circuit includes an input rectifier circuit, a voltage stabilizing circuit, a quick start circuit, a restart circuit, a control chip (U1), a high-frequency coil (T1), and a protection control module, which are arranged in sequence. One end of the primary winding of the high-frequency coil (T1) is connected to the first output terminal of the input rectifier circuit, and the other end is connected to the control chip (U1). One end of its auxiliary winding is connected to the restart circuit, and the other end is connected to the second output terminal of the input rectifier circuit and grounded together. The protection control module is respectively connected to the control chip (U1) and the secondary winding of the high-frequency coil (T1); The input rectifier circuit includes a bridge rectifier diode (D1) and a third capacitor (C3) connected in parallel with the output terminal of the bridge rectifier diode (D1); The voltage stabilizing circuit includes a voltage stabilizing diode (D2) and a third resistor (R3). The positive electrode of the voltage stabilizing diode (D2) is grounded, and the negative electrode is connected to the first output terminal of the input rectifier circuit through the third resistor (R3); The quick start circuit includes a triode (D3), a first optocoupler (U2), a second capacitor (C2), and a second resistor (R2). The base of the triode (D3) is connected between the voltage stabilizing diode (D2) and the third resistor (R3). The collector is connected to the positive electrode of the first output terminal of the input rectifier circuit, and the emitter is connected to the first end of the switching part of the first optocoupler (U2). The second end of the switching part of the first optocoupler (U2) is connected to the control chip (U1) through a first diode (D4). The negative electrode of the light-emitting part of the first optocoupler (U2) is grounded through the second resistor (R2), and the positive electrode is connected to the first output terminal of the input rectifier circuit through the second capacitor (C2); The restart circuit includes a first resistor (R1) and a first capacitor (C1). The negative electrode of the first capacitor (C1) is grounded, and the positive electrode is connected to the first output terminal of the input rectifier circuit through the first resistor (R1). The positive electrode of the first capacitor (C1) is connected to the control chip (U1) through a second diode (D5), and is connected to one end of the auxiliary winding of the high-frequency coil (T1) through a reversely arranged third diode (D7); The cs pin (P4) of the control chip (U1) is grounded through a fourth resistor (R4), the GND pin (P8) is grounded, and the FB pin (P3), the first Drain pin (P5), and the second Drain pin (P6) are respectively connected to the protection control module; When the coil is started, the second resistor (R2) and the second capacitor (C2) are charged, and the first optocoupler (U2) conducts to provide startup electrical energy for the control chip (U1); after the control chip (U1) is started, the charge of the second capacitor (C2) continues to increase, and the auxiliary winding of the high-frequency coil (T1) and the fast startup sub-circuit jointly provide working electrical energy for the control chip (U1); when the charge in the second capacitor (C2) reaches the threshold charge, the first optocoupler (U2) cuts off, and the auxiliary winding of the high-frequency coil (T1) provides working electrical energy for the control chip (U1); when the system fails, the first resistor (R1) and the first capacitor (C1) charge and discharge to drive the control chip (U1) to restart; The model of the control chip (U1) is KP2011.

Images