A protection circuit and servo driver

Abstract

The present invention relates to a protection circuit and a servo driver, comprising: a first circuit, a second circuit, a circuit break detection circuit, a control circuit and a switch circuit, wherein the input end of the first circuit is connected to a power supply terminal; the input end of the circuit break detection circuit is connected to the output end of the first circuit, and the circuit break detection circuit generates a circuit break signal when the first circuit is broken; the input end of the control circuit is connected to the output end of the circuit break detection circuit, and the output end of the control circuit is connected to the second circuit through a switch circuit, and when the control circuit receives the circuit break signal, it drives the switch circuit to disconnect the second circuit from the first circuit. The technical solution of the present invention is that when it is detected that the first circuit loses power, the control circuit controls the switch circuit to work, so that the second circuit is disconnected from the first circuit, thereby protecting the second circuit.

Description

Technical Field

[0001] The invention belongs to the field of power-off protection, and in particular relates to a protection circuit and a servo driver. Background Art

[0002] In recent years, with the rapid development of economy and technology, various servo products have begun to be widely used in all aspects of national production and life. Among them, AC servo motors have the broadest application prospects due to their small size, simple structure, high power factor, and small moment of inertia.

[0003] With the continuous deepening of modern power electronics technology, microelectronics technology and control theory research, the control method of AC servo motor has also been rapidly developed. At present, PWM (Pulse Width Modulation) control technology is widely used in AC servo systems, that is, the main circuit power supply after rectification provides the required power for the servo motor through the inverter circuit controlled by PWM. However, when the servo drive loses power, since the main circuit power supply is generally stabilized by a large-capacity electrolytic capacitor, the voltage of the main circuit power supply usually drops slowly after power failure, while the voltage stabilizing capacitor in the control circuit power supply is generally small in capacity, and the voltage of the control circuit power supply drops rapidly after power failure.

[0004] Therefore, the following situation exists: when the gate voltage given by the control circuit power supply for controlling the power switch device drops to zero, the voltage of the main circuit power supply is still at a relatively high level; at this time, due to the Miller capacitance between the gate and the collector of the power switch device, the current of the main circuit power supply will flow through the Miller capacitance, thereby causing the gate potential of the power switch device to rise, resulting in the gate voltage no longer being controlled by the control circuit power supply. In extreme cases, it will cause the main circuit power supply to short-circuit. Summary of the invention

[0005] In order to solve the problem in the prior art that a main circuit may be short-circuited when a servo driver loses power, the present invention provides a protection circuit and a servo driver.

[0006] A protection circuit comprises: a first circuit, a second circuit, a disconnection detection circuit, a control circuit and a switch circuit.

[0007] The input end of the first circuit is connected to a power supply terminal;

[0008] The input end of the disconnection detection circuit is connected to the output end of the first circuit, and the disconnection detection circuit generates a disconnection signal when the first circuit is disconnected;

[0009] The input end of the control circuit is connected to the output end of the circuit break detection circuit, and the output end of the control circuit is connected to the second circuit through a switch circuit. When the control circuit receives a circuit break signal, it drives the switch circuit to disconnect the second circuit from the first circuit.

[0010] Furthermore, the control circuit includes: a first resistor, a second resistor, a third resistor and a transistor.

[0011] The first end of the third resistor is connected to the output end of the disconnection detection circuit, and the second end is connected to the base of the transistor and the first end of the second resistor respectively;

[0012] The collector of the transistor is connected to the input end of the switch circuit, and the emitter is connected to the first end of the first resistor;

[0013] The second end of the second resistor is connected to the second end of the first resistor;

[0014] A second end of the first resistor is grounded.

[0015] Furthermore, the transistor is a switching transistor.

[0016] Furthermore, the switch circuit includes: a first switch circuit and a second switch circuit.

[0017] Furthermore, the first switch circuit includes a first relay, the first current collector includes a first input circuit and a first output circuit, the first input circuit is connected to the output end of the control circuit, and the first output circuit is connected to the second circuit.

[0018] Furthermore, the first input loop includes: a first coil, a diode and a first capacitor,

[0019] The first end of the first coil is connected to the power terminal, and the second end is connected to the collector of the transistor;

[0020] The first end of the first capacitor is connected to the cathode of the diode and the first end of the first coil respectively, and the second end of the first capacitor is connected to the anode of the diode and the second end of the first coil respectively.

[0021] Furthermore, the first output circuit includes: a first switch, and the first switch is connected to the input end of the second switch circuit.

[0022] Furthermore, the second switch circuit includes: a second relay, the second relay includes a second input circuit and a second output circuit,

[0023] The second input circuit is connected to the first output circuit of the first relay, and the second output circuit is connected to the second circuit.

[0024] Furthermore, the second input loop includes: a second coil, a fourth resistor, a fifth resistor and a voltage stabilizing diode.

[0025] The first end of the second coil is connected to the first end of the fifth resistor, and the second end is grounded;

[0026] The second end of the fifth resistor is connected to the first end of the fourth resistor;

[0027] The second end of the fourth resistor is connected to the output end of the first switch circuit;

[0028] The positive electrode of the voltage stabilizing diode is connected to the second end of the second coil, and the negative electrode is connected to the first end of the second coil and the first end of the fifth resistor respectively.

[0029] Furthermore, the second output circuit includes: two linked single-pole double-throw switches, the fixed end of the first single-pole double-throw switch is connected to the output end of the first switch circuit, and the active end of the first single-pole double-throw switch is respectively connected to the input end of the second circuit or the fixed end of the first switch; the fixed end of the second single-pole double-throw switch is grounded, and the active end of the second switch is connected or disconnected from the input end of the second circuit.

[0030] A servo driver comprises any one of the protection circuits described above.

[0031] The technical solution provided by the present invention has the following advantages compared with the closest prior art:

[0032] According to the technical solution provided by the present invention, when it is detected that the first circuit loses power, the control circuit controls the switch circuit to operate so that the second circuit is disconnected from the first circuit, thereby protecting the second circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of a protection circuit in an embodiment of the present invention;

[0034] Figure 2 Schematic diagram of the overall power supply circuit of the universal servo controller in an embodiment of the present invention;

[0035] Figure 3 is a detailed structural diagram of a protection circuit in an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of a three-phase bridge PWM inverter topology in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0038] like Figure 1 As shown, an embodiment of the present invention provides a protection circuit, which includes: a first circuit, a second circuit, a disconnection detection circuit, a control circuit and a switch circuit.

[0039] The input end of the first circuit is connected to a power supply terminal;

[0040] The input end of the disconnection detection circuit is connected to the output end of the first circuit, and the disconnection detection circuit generates a disconnection signal when the first circuit is disconnected;

[0041] The input end of the control circuit is connected to the output end of the circuit break detection circuit, and the output end of the control circuit is connected to the second circuit through a switch circuit. When the control circuit receives a circuit break signal, it drives the switch circuit to disconnect the second circuit from the first circuit.

[0042] In the embodiment of the present application, when it is detected that the first circuit loses power, the control circuit controls the switch circuit to operate so that the second circuit is disconnected from the first circuit, thereby protecting the second circuit.

[0043] Figure 2 It is the overall power supply circuit of the general servo controller. When the servo drive loses power, the main circuit power supply generally has a large electrolytic capacitor for voltage stabilization ( Figure 2 C2 and C3 in the control circuit), so the voltage of the main circuit power supply usually drops slowly, while the voltage stabilizing capacitor in the control circuit power supply is generally small ( Figure 2 In C1, the control loop voltage drops rapidly; therefore, the following situation exists: when the gate voltage of the power switch device given by the control loop power supply ( Figure 4 When the voltage of the main circuit power supply is still at a relatively high voltage level, due to the Miller capacitance between the gate and collector of the power switch device, the main circuit current will flow through this capacitance, causing the gate potential to rise. At this time, the gate signal that should have been controlled by the control circuit has become uncontrollable. In extreme cases, it will cause a short circuit in the main circuit.

[0044] The present invention solves the problem of uncontrolled conduction of the power switch device when the servo drive is powered off, and can effectively avoid the risk of breakdown of the expensive power module when the servo drive is powered off.

[0045] When the control system detects that the servo drive has a power failure, the main control chip will send a drive signal to control the corresponding relay to perform related actions, forcing the electrolytic capacitor to be disconnected from the inverter bridge; and through the interconnection between the two relays, once the relay is actuated, the control signal does not need to be maintained continuously until the voltage on the electrolytic capacitor in the main circuit drops to zero charge, and the relay returns to its initial state, thus completing the power-off protection of the drive.

[0046] like Figure 3 As shown, in some embodiments of the present application, the control circuit includes: a first resistor, a second resistor, a third resistor and a triode,

[0047] The first end of the third resistor is connected to the output end of the disconnection detection circuit, and the second end is connected to the base of the transistor and the first end of the second resistor respectively;

[0048] The collector of the transistor is connected to the input end of the switch circuit, and the emitter is connected to the first end of the first resistor;

[0049] The second end of the second resistor is connected to the second end of the first resistor;

[0050] A second end of the first resistor is grounded.

[0051] The transistor may be a switching transistor or other transistors with switching characteristics.

[0052] In some embodiments of the present application, the switch circuit includes: a first switch circuit and a second switch circuit.

[0053] In some embodiments of the present application, the first switching circuit includes a first relay, the first current collector includes a first input circuit and a first output circuit, the first input circuit is connected to the output end of the control circuit, and the first output circuit is connected to the second circuit.

[0054] The first input loop includes: a first coil, a diode and a first capacitor,

[0055] The first end of the first coil is connected to the power terminal, and the second end is connected to the collector of the transistor;

[0056] The first end of the first capacitor is connected to the cathode of the diode and the first end of the first coil respectively, and the second end of the first capacitor is connected to the anode of the diode and the second end of the first coil respectively.

[0057] The first output loop includes: a first switch, and the first switch is connected to the input end of the second switch circuit.

[0058] In some embodiments of the present application, the second switch circuit includes: a second relay, the second relay includes a second input circuit and a second output circuit,

[0059] The second input circuit is connected to the first output circuit of the first relay, and the second output circuit is connected to the second circuit.

[0060] The second input circuit includes: a second coil, a fourth resistor, a fifth resistor and a voltage regulator diode.

[0061] The first end of the second coil is connected to the first end of the fifth resistor, and the second end is grounded;

[0062] The second end of the fifth resistor is connected to the first end of the fourth resistor;

[0063] The second end of the fourth resistor is connected to the output end of the first switch circuit;

[0064] The positive electrode of the voltage stabilizing diode is connected to the second end of the second coil, and the negative electrode is connected to the first end of the second coil and the first end of the fifth resistor respectively.

[0065] The second output circuit includes: two linked single-pole double-throw switches, the fixed end of the first single-pole double-throw switch is connected to the output end of the first switch circuit, and the active end of the first single-pole double-throw switch is respectively connected to the input end of the second circuit or the fixed end of the first switch; the fixed end of the second single-pole double-throw switch is grounded, and the active end of the second switch is connected or disconnected from the input end of the second circuit.

[0066] The specific implementation of this case is described in detail by taking a servo drive with a three-phase bridge PWM inverter topology as an example.

[0067] Correctly determine the occurrence of system power failure; when disconnected Figure 2 When the circuit breaker is turned on, the control circuit and the main circuit are cut off from the power supply. At this time, the entire servo control system enters the power-off stage, and the voltage of each circuit begins to drop. When the servo system is operating normally, if the motor accelerates rapidly or the motor load increases rapidly in a short period of time, the main circuit will also experience a voltage drop. In order to avoid erroneous detection of the system power-off behavior, it is obviously more reasonable to select the control circuit power supply voltage for detection. Since the power-off detection circuit is not the focus of the present invention, it will not be analyzed here.

[0068] When the system is detected to be powered off, the main control chip in the system will send out a control signal, which will be output as a control signal RELAY after an optical coupler isolation. Figure 3 As shown on the left side), the control signal RELAY turns on the control circuit (pins 1 and 2) of relay 1, and the armature is attracted, so that pins 3 and 4 of relay 1 are turned on.

[0069] exist Figure 3 The armature switches on pins 3, 4, and 5 of relay 2 should be Figure 2 The switch K1 in the figure; the armature switch on pins 6, 7, and 8 corresponds to Figure 2 Switch K2 in the circuit; it can be seen that when there is no control signal (indicating that the system has not detected the power-off action), the initial state of pins 3 and 4 in relay 2 is short-circuited connection, that is, Figure 2 The switch K1 in the circuit is in the closed state when the power supply is normal, which ensures the normal operation of the main circuit power supply; when the system loses power, as can be seen from the previous analysis, the 3rd and 4th pins of relay 1 are short-circuited, and then the 1st and 2nd pins of relay 2 have current flowing through them, and relay 2 performs corresponding actions, that is, the 3rd and 4th pins of relay 2 are disconnected, and the 3rd and 5th pins are closed; the 6th and 8th pins are disconnected, and the 7th and 8th pins are closed, corresponding to Figure 2 From the analysis, it can be seen that when the system loses power, switch K1 is controlled to open and switch K2 is controlled to close. This series of actions ensures that the main circuit power supply is powered off before the control circuit power supply, ensuring that the power switch device does not lose control, and at the same time provides the R6 circuit to release the energy in C2 and C3, ensuring the safety of the driver.

[0070] When relay 2 is controlled to operate, it is in a self-locking state, that is, relay 2 is no longer controlled by relay 1. Relay 2 will not return to its initial state until the potential of network NET1 drops below a certain value. This design solves the problem that the control signal RELAY cannot continue to control relay 2 after the system loses power due to rapid power loss in the control loop.

[0071] The present invention also provides a servo driver, which includes any one of the above protection circuits.

[0072] It should be noted that, in this document, relational terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0073] It is understood that the embodiments described herein may be implemented in hardware, software, firmware, middleware, microcode, or a combination thereof. For hardware implementation, the processing unit may be implemented in one or more application specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field programmable gate arrays (FPGA), general purpose processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in the present application, or a combination thereof.

[0074] For software implementation, the technology described herein can be implemented by a unit that performs the functions described herein. The software code can be stored in a memory and executed by a processor. The memory can be implemented in the processor or outside the processor.

[0075] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0076] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0077] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0078] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, ROM, RAM, disk or optical disk, etc., various media that can store program codes.

[0079] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A protection circuit, characterized in that: include: a first circuit, a second circuit, a disconnection detection circuit, a control circuit, and a switch circuit, The input end of the first circuit is connected to the power supply terminal; The input end of the disconnection detection circuit is connected to the output end of the first circuit, and the disconnection detection circuit generates a disconnection signal when the first circuit is disconnected; The input end of the control circuit is connected to the output end of the disconnection detection circuit, and the output end of the control circuit is connected to the second circuit through the switch circuit. When the control circuit receives the disconnection signal, it drives the switch circuit to disconnect the second circuit from the first circuit. The switch circuit comprises: a first switch circuit and a second switch circuit; The first switch circuit comprises: a first relay, the first relay comprises a first input circuit and a first output circuit, the first input circuit is connected to the output end of the control circuit, and the first output circuit is connected to the second switch circuit; The first input loop includes: a first coil, a diode and a first capacitor; A first end of the first coil is connected to a power supply terminal, and a second end of the first coil is connected to a collector of a transistor of a control circuit; The first end of the first capacitor is connected to the cathode of the diode and the first end of the first coil respectively, and the second end of the first capacitor is connected to the anode of the diode and the second end of the first coil respectively; The first output circuit includes: a first switch connected to an input end of the second switch circuit; The control circuit includes: a first resistor, a second resistor, a third resistor and a triode. A first end of the third resistor is connected to the output end of the disconnection detection circuit, and a second end is connected to the base of the transistor and the first end of the second resistor respectively; The collector of the transistor is connected to the second end of the first coil, and the emitter is connected to the first end of the first resistor; The second end of the second resistor is connected to the second end of the first resistor; The second end of the first resistor is grounded; The second switch circuit comprises: a second relay, the second relay comprises a second input circuit and a second output circuit, the second input circuit is connected to the first output circuit of the first relay, and the second output circuit is connected to the second circuit; When the system loses power, the main control chip in the system outputs a control signal RELAY, and the control signal RELAY causes the first and second pins of the first relay to be turned on, the armature to be attracted, and the third and fourth pins of the first relay to be turned on, wherein the first pin of the first relay is the first end of the first coil, the second pin is the second end of the first coil, and the third pin and the fourth pin are respectively the active end and the fixed end of the first switch in the first output circuit.

2. A protection circuit according to claim 1, characterized in that: The transistor is a switching transistor.

3. A protection circuit according to claim 1, characterized in that: The second input loop includes: a second coil, a fourth resistor, a fifth resistor and a voltage stabilizing diode, The first end of the second coil is connected to the first end of the fifth resistor, and the second end is grounded; The second end of the fifth resistor is connected to the first end of the fourth resistor; The second end of the fourth resistor is connected to the output end of the first switch circuit; The positive electrode of the voltage stabilizing diode is connected to the second end of the second coil, and the negative electrode is connected to the first end of the second coil and the first end of the fifth resistor respectively.

4. A protection circuit according to claim 1, characterized in that: The second output circuit includes: two linked single-pole double-throw switches, the fixed end of the first single-pole double-throw switch is connected to the output end of the first switch circuit, and the active end of the first single-pole double-throw switch is respectively connected to the input end of the second circuit or the fixed end of the first switch; the fixed end of the second single-pole double-throw switch is grounded, and the active end of the second switch is connected or disconnected from the input end of the second circuit.

5. A servo drive, characterized in that: The invention comprises the protection circuit described in any one of claims 1 to 4.

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