A protection circuit and a driver

Abstract

The present application provides a protection circuit and driver, belonging to the field of circuit protection technology. The present application detects the temperature of the brake resistor through a temperature protection module and outputs an indication signal according to the temperature, and sends an indication signal to the control module; obtains the bus voltage value through the control module, responds to the indication signal, increases the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module, generates a control signal according to the bus voltage value, the increased discharge voltage threshold and the cut-off discharge voltage threshold, and sends a control signal to the switch module; the switch module is turned on or off according to the control signal, wherein when the switch module is turned on, the brake resistor is connected to the discharge circuit of the servo driver, and when the switch module is turned off, the brake resistor is disconnected from the discharge circuit. Improve the discharge conditions, reduce the discharge time, and avoid excessive temperature of the brake resistor due to excessive discharge time.

Description

Technical Field

[0001] The present application relates to the field of circuit protection technology, and in particular to a protection circuit and a driver. Background Art

[0002] When the servo drive brakes, part of the load's kinetic energy will be converted into electrical energy, which can increase the bus voltage to 800V or above. At this time, a braking resistor is needed to release this energy to prevent the bus voltage from rising too high and breaking down the capacitor, thus affecting the service life of the energy storage capacitor.

[0003] In general, a resistor with a fixed resistance and a fixed power is used as a brake resistor. The brake resistor discharges when the bus voltage is higher than a certain discharge voltage threshold V1, and stops discharging when it is lower than a certain voltage threshold V2 (V1>V2), and so on until the discharge is completed. Figure 1 As shown, when the bus voltage is higher than V1, the bus voltage is converted into an isolated digital signal through voltage sampling and A / D conversion circuit, and then enters the main control chip. The digital signal is compared with the preset discharge threshold V1. When it is higher than the discharge threshold V1, the chip sends a discharge signal. After receiving the signal, the driver chip drives the brake tube IGBT (insulated gate bipolar transistor) to turn on, thereby quickly consuming part of the electrical energy of the main capacitor.

[0004] However, in the current discharge circuit, the discharge voltage threshold and the cut-off discharge voltage threshold are fixed. If the pre-set discharge voltage threshold and the cut-off discharge voltage threshold are relatively low, it may cause the discharge frequency to be too high and the discharge time to be too long, thereby causing the temperature of the brake resistor to be too high and reducing the service life of the brake resistor. Summary of the invention

[0005] The purpose of the embodiment of the present application is to provide a protection circuit and a driver to solve the problem of excessive temperature of the brake resistor in the discharge circuit. The specific technical solution is as follows:

[0006] In a first aspect, a protection circuit is provided, the protection circuit being used to protect a brake resistor in a servo drive, characterized in that the circuit comprises: a temperature protection module, a switch module and a control module;

[0007] The temperature protection module is used to detect the temperature of the brake resistor and output an indication signal according to the temperature, and send the indication signal to the control module;

[0008] The control module is used to obtain the bus voltage value, increase the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module in response to the indication signal, generate a control signal according to the bus voltage value, the increased discharge voltage threshold and the cut-off discharge voltage threshold, and send the control signal to the switch module;

[0009] The switch module is used to be turned on or off according to the control signal, wherein when the switch module is turned on, the brake resistor is connected to the discharge circuit of the servo driver, and when the switch module is turned off, the brake resistor is disconnected from the discharge circuit.

[0010] Optionally, the temperature protection module includes a first thermistor, a first voltage-dividing resistor and a first comparator;

[0011] The first thermistor is arranged on the brake resistor, and is used to detect the temperature of the brake resistor. One end of the first thermistor is connected to the first power supply, and the other end is connected in series with the first voltage-dividing resistor and then grounded.

[0012] The inverting end of the first comparator is connected to the end of the first voltage-dividing resistor away from the ground end, the inverting end of the first comparator is connected to the first divided voltage at both ends of the first voltage-dividing resistor, the output end of the first comparator is connected to the control module, and the non-inverting end of the first comparator is connected to the first comparison voltage.

[0013] Optionally, as the temperature of the first thermistor increases with the temperature of the brake resistor, the resistance of the first thermistor decreases, and the first divided voltage of the first voltage divider resistor increases. When the first divided voltage is greater than the first comparison voltage, the first comparator outputs a first low-level signal and sends the first low-level signal to the control module. The control module increases the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module in response to the first low-level signal.

[0014] Optionally, the circuit further includes a comparison voltage output circuit;

[0015] The comparison voltage output circuit is used to output the first comparison voltage. The comparison voltage output circuit includes a third voltage-dividing resistor and a fourth voltage-dividing resistor. The third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series. An end of the third voltage-dividing resistor away from the fourth voltage-dividing resistor is connected to a second power supply, and an end of the fourth voltage-dividing resistor away from the third voltage-dividing resistor is grounded. The in-phase end of the first comparator is connected to a node between the third voltage-dividing resistor and the fourth voltage-dividing resistor.

[0016] Optionally, the temperature protection module further includes a second thermistor, a second voltage-dividing resistor and a second comparator, wherein the second thermistor is the same as the first thermistor, the second comparator is the same as the first comparator, and the second voltage-dividing resistor is smaller than the first voltage-dividing resistor;

[0017] The second thermistor is arranged on the brake resistor, and is used to detect the temperature of the brake resistor. One end of the second thermistor is connected to the first power supply, and the other end is connected in series with the second voltage-dividing resistor and then grounded.

[0018] The inverting end of the second comparator is connected to the end of the second voltage-dividing resistor away from the ground end, the inverting end of the second comparator is connected to the second divided voltage at both ends of the second voltage-dividing resistor, the output end of the second comparator is connected to the control module, and the non-inverting end of the second comparator is connected to the second comparison voltage, wherein the second comparison voltage is the same as the first comparison voltage.

[0019] Optionally, the temperature of the second thermistor increases with the temperature of the braking resistor, the resistance of the second thermistor decreases, and the second divided voltage of the second voltage divider resistor increases. When the second divided voltage is greater than the second comparison voltage, the second comparator outputs a second low-level signal and sends the second low-level signal to the control module; the control module responds to the second low-level signal and sends an alarm signal to cause the servo drive to stop working according to the alarm signal.

[0020] Optionally, the control module includes a main control chip and a driver chip;

[0021] One end of the driving chip is connected to the main control chip, and the other end is connected to one end of the braking resistor through the switch module.

[0022] Optionally, the switch module includes: an insulated gate bipolar transistor IGBT, the IGBT gate is connected to the driving chip, the IGBT collector is connected to one end of the braking resistor, and the IGBT emitter is connected to the negative electrode of the DC power supply.

[0023] Optionally, the circuit further includes a voltage sampling module;

[0024] The voltage sampling module is used to collect the bus voltage value at both ends of the main capacitor in the servo driver, convert the bus voltage value into a digital signal and send it to the control module.

[0025] Optionally, the circuit further includes an inverter module;

[0026] The inverter module is used to convert the electricity in the servo drive into AC power.

[0027] In a second aspect, a driver is provided, wherein the driver comprises the protection circuit described in the first aspect.

[0028] Beneficial effects of the embodiments of the present application:

[0029] An embodiment of the present application provides a protection circuit and a driver. The present application detects the temperature of the braking resistor through a temperature protection module and outputs an indication signal based on the temperature, and sends the indication signal to the control module; obtains the bus voltage value through the control module, responds to the indication signal, increases the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module, generates a control signal based on the bus voltage value, the increased discharge voltage threshold and the cut-off discharge voltage threshold, and sends the control signal to the switch module; the switch module is turned on or off according to the control signal, wherein when the switch module is turned on, the braking resistor is connected to the discharge circuit of the servo driver, and when the switch module is turned off, the braking resistor is disconnected from the discharge circuit.

[0030] The temperature protection module of the embodiment of the present application outputs an indication signal according to the detected temperature of the brake resistor, and the control module increases the discharge voltage threshold and the cut-off discharge voltage threshold according to the indication signal. Because the bus voltage fluctuates within a certain range, when the discharge voltage threshold and the cut-off discharge voltage threshold are increased, it is equivalent to improving the discharge condition and lowering the cut-off discharge condition, that is, when the bus voltage rises to between the original discharge voltage threshold and the increased discharge voltage threshold, and when the bus voltage falls to between the increased cut-off discharge voltage threshold and the original cut-off discharge voltage threshold, discharge is required before increasing the threshold, but not after increasing the threshold, so the number of discharges can be reduced, and then the discharge time can be reduced, thereby avoiding excessive temperature of the brake resistor due to excessive discharge time.

[0031] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 A conventional discharge circuit diagram provided in an embodiment of the present application;

[0034] Figure 2 A circuit diagram of a protection circuit provided in an embodiment of the present application;

[0035] Figure 3 A curve diagram showing the relationship between thermistor and brake resistor temperature provided in an embodiment of the present application. DETAILED DESCRIPTION

[0036] 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.

[0037] Since the discharge voltage threshold and the cut-off discharge voltage threshold are fixed in the current discharge circuit, if the preset discharge voltage threshold and the cut-off discharge voltage threshold are relatively low, it may cause the discharge frequency to be too high and the discharge time to be too long, thereby causing the temperature of the brake resistor to be too high and reducing the service life of the brake resistor. To this end, an embodiment of the present application provides a protection circuit, which is arranged in the discharge circuit and is used to protect the brake resistor in the servo drive. Figure 2 As shown, the circuit includes: a temperature protection module, a switch module and a control module;

[0038] The temperature protection module is used to detect the temperature of the brake resistor and output an indication signal according to the temperature, and send the indication signal to the control module;

[0039] The control module is used to obtain the bus voltage value, increase the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module in response to the indication signal, generate a control signal according to the bus voltage value, the increased discharge voltage threshold and the cut-off discharge voltage threshold, and send the control signal to the switch module;

[0040] The switch module is used to be turned on or off according to the control signal, wherein when the switch module is turned on, the brake resistor is connected to the discharge circuit of the servo driver, and when the switch module is turned off, the brake resistor is disconnected from the discharge circuit.

[0041] In an embodiment of the present application, the temperature of the braking resistor is detected by a temperature protection module, and an indication signal is output according to the temperature of the braking resistor and sent to the control module; the control module responds to the indication signal, increases the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module, and obtains the bus voltage value through the control module, and then generates a control signal according to the bus voltage value, the increased discharge voltage threshold and the cut-off discharge voltage threshold, and finally sends the control signal to the switch module; the switch module is turned on or off according to the control signal, and when the switch module is turned on, the braking resistor is connected to the discharge circuit of the servo drive, and when the switch module is turned off, the braking resistor is disconnected from the discharge circuit.

[0042] In the embodiment of the present application, the bus voltage fluctuates within a certain range. When the discharge voltage threshold and the cut-off discharge voltage threshold are increased, it is equivalent to improving the discharge conditions and lowering the cut-off discharge conditions. That is, when the bus voltage rises to between the original discharge voltage threshold and the increased discharge voltage threshold, and when the bus voltage falls to between the increased cut-off discharge voltage threshold and the original cut-off discharge voltage threshold, discharge is required before increasing the threshold, but not after increasing the threshold. Therefore, the number of discharges can be reduced, thereby reducing the discharge time, thereby avoiding excessive temperature of the brake resistor due to excessive discharge time.

[0043] In yet another embodiment of the present application, the temperature protection module includes a first thermistor, a first voltage-dividing resistor, and a first comparator;

[0044] The first thermistor is arranged on the brake resistor, the first thermistor RT1 is used to detect the temperature of the brake resistor, one end of the first thermistor RT1 is connected to the first power supply VCC+, and the other end is connected in series with the first voltage-dividing resistor R1 and then grounded;

[0045] The inverting end of the first comparator 1 is connected to the end of the first voltage-dividing resistor R1 away from the ground end, the inverting end of the first comparator 1 is connected to the first divided voltage across the first voltage-dividing resistor R1, the output end of the first comparator 1 is connected to the control module, and the non-inverting end of the first comparator 1 is connected to the first comparison voltage.

[0046] In another embodiment of the present application, Figure 3 As shown, the temperature of the first thermistor RT1 increases with the temperature of the braking resistor, and the resistance of the first thermistor RT1 decreases. Preferably, the first thermistor RT1 may be an NTC resistor, and the first divided voltage of the first voltage-dividing resistor R1 increases. When the temperature of the braking resistor reaches T1, the temperature of the first thermistor RT1 is also T1. At this time, the first divided voltage is greater than the first comparison voltage, and the first comparator outputs a first low-level signal and sends the first low-level signal to the control module. The control module increases the discharge voltage threshold V1 and the cut-off discharge voltage threshold V2 pre-stored in the control module in response to the first low-level signal.

[0047] Exemplarily, assuming that the pre-stored discharge voltage threshold and the cut-off discharge voltage threshold are 800V and 750V respectively, when the temperature of the brake resistor rises to T1, the temperature of the first thermistor RT1 also rises to T1, the resistance decreases, and the first divided voltage of the corresponding first voltage-dividing resistor R1 increases. When the first divided voltage is greater than the first comparison voltage, that is, the inverting end of the first comparator 1 is higher than the non-inverting end, and the first low-level signal is input, the control module responds to the first low-level signal, and increases the pre-stored discharge voltage threshold in the control module from 800V to 850V, and increases the cut-off discharge voltage threshold from 750V to 800V. The specific adjustment needs to be determined based on the withstand voltage value of the main capacitor and the withstand voltage value of the inverter module. When adjusting, it is necessary to consider the smallest of the withstand voltage values ​​of the two, and leave a certain margin. For example, if the withstand voltage value of the main capacitor is 860V and the withstand voltage value of the inverter module is 880V, the adjusted discharge voltage threshold needs to be less than 860V.

[0048] In yet another embodiment of the present application, the circuit further comprises a comparison voltage output circuit;

[0049] The comparison voltage output circuit is used to output the first comparison voltage. The comparison voltage output circuit includes a third voltage-dividing resistor R3 and a fourth voltage-dividing resistor R4. The third voltage-dividing resistor R3 and the fourth voltage-dividing resistor R4 are connected in series. One end of the third voltage-dividing resistor R3 away from the fourth voltage-dividing resistor R4 is connected to the second power supply VCC+, and one end of the fourth voltage-dividing resistor R4 away from the third voltage-dividing resistor R3 is grounded. The in-phase end of the first comparator 1 is connected to the node between the third voltage-dividing resistor R3 and the fourth voltage-dividing resistor R4.

[0050] In another embodiment of the present application, the temperature protection module further includes a second thermistor RT2, a second voltage-dividing resistor R2 and a second comparator 2, wherein the second thermistor RT2 is the same as the first thermistor RT1, the second comparator 2 is the same as the first comparator 1, and the second voltage-dividing resistor R2 is smaller than the first voltage-dividing resistor R1;

[0051] The second thermistor RT2 is arranged on the brake resistor, and the second thermistor RT2 is used to detect the temperature of the brake resistor. One end of the second thermistor RT2 is connected to the first power supply VCC+, and the other end is connected in series with the second voltage-dividing resistor R2 and then grounded;

[0052] The inverting end of the second comparator 2 is connected to the end of the second voltage-dividing resistor R2 away from the ground end, the inverting end of the second comparator 2 is connected to the second voltage-dividing end of the second voltage-dividing resistor R2, the output end of the second comparator 2 is connected to the control module, the inverting end of the second comparator 2 is connected to the second comparison voltage, wherein the second comparison voltage is the same as the first comparison voltage, and the first thermistor RT1, the second thermistor RT2, the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 satisfy the formula

[0053] In another embodiment of the present application, Figure 3 As shown, the temperature of the second thermistor RT2 increases with the temperature of the brake resistor, the resistance of the second thermistor RT2 decreases, and the second divided voltage of the second voltage-dividing resistor R2 increases. When the second divided voltage is greater than the second comparison voltage, the second comparator 2 outputs a second low-level signal and sends the second low-level signal to the control module; the control module responds to the second low-level signal and sends an alarm signal to stop the servo driver from working according to the alarm signal. Avoid the brake resistor from overheating and damaging the discharge circuit.

[0054] In yet another embodiment of the present application, the control module includes a main control chip and a driver chip;

[0055] One end of the driving chip is connected to the main control chip, and the other end is connected to one end of the braking resistor through the switch module.

[0056] In another embodiment of the present application, the switch module includes: an insulated gate bipolar transistor IGBT, the IGBT gate is connected to the driving chip, the IGBT collector is connected to one end of the braking resistor, and the IGBT emitter is connected to the negative electrode of the DC power supply.

[0057] In yet another embodiment of the present application, the circuit further includes a voltage sampling module;

[0058] The voltage sampling module is used to collect the bus voltage value across the main capacitor in the servo drive, convert the bus voltage value into a digital signal and send it to the control module. The preferred voltage sampling module can be an A / D conversion chip, which transmits the real-time waveform of the bus voltage change to the isolated A / D conversion chip, converts it into an isolated digital signal, and then sends the digital signal to the control module.

[0059] In yet another embodiment of the present application, the circuit further comprises an inverter module;

[0060] The inverter module is used to convert the electricity in the servo driver into AC power and generate AC voltage and current output to the motor according to the drive module drive signal. It is composed of 6 switching tubes to form a full-bridge circuit. The switching tubes are IGBT tubes or MOS tubes.

[0061] Based on the same technical concept, an embodiment of the present application further provides a driver, which includes the protection circuit described in the above embodiment.

[0062] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants 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, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0063] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A protection circuit, which is used to protect a brake resistor in a servo drive, characterized in that: The circuit comprises: a temperature protection module, a switch module and a control module; The temperature protection module is used to detect the temperature of the brake resistor and output an indication signal according to the temperature, and send the indication signal to the control module; The control module is used to obtain the bus voltage value, increase the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module in response to the indication signal, generate a control signal according to the bus voltage value, the increased discharge voltage threshold and the cut-off discharge voltage threshold, and send the control signal to the switch module; The switch module is used to be turned on or off according to the control signal, wherein when the switch module is turned on, the brake resistor is connected to the discharge circuit of the servo driver, and when the switch module is turned off, the brake resistor is disconnected from the discharge circuit.

2. The protection circuit according to claim 1, characterized in that: The temperature protection module includes a first thermistor, a first voltage-dividing resistor and a first comparator; The first thermistor is arranged on the brake resistor, and is used to detect the temperature of the brake resistor. One end of the first thermistor is connected to the first power supply, and the other end is connected in series with the first voltage-dividing resistor and then grounded. The inverting end of the first comparator is connected to the end of the first voltage-dividing resistor away from the ground end, the inverting end of the first comparator is connected to the first divided voltage at both ends of the first voltage-dividing resistor, the output end of the first comparator is connected to the control module, and the non-inverting end of the first comparator is connected to the first comparison voltage.

3. The protection circuit according to claim 2, characterized in that: As the temperature of the first thermistor increases with the temperature of the brake resistor, the resistance of the first thermistor decreases, and the first divided voltage of the first voltage-dividing resistor increases. When the first divided voltage is greater than the first comparison voltage, the first comparator outputs a first low-level signal and sends the first low-level signal to the control module. In response to the first low-level signal, the control module increases the discharge voltage threshold and the cut-off discharge voltage threshold pre-stored in the control module.

4. The protection circuit according to claim 2, characterized in that: The circuit also includes a comparison voltage output circuit; The comparison voltage output circuit is used to output the first comparison voltage. The comparison voltage output circuit includes a third voltage-dividing resistor and a fourth voltage-dividing resistor. The third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series. An end of the third voltage-dividing resistor away from the fourth voltage-dividing resistor is connected to a second power supply, and an end of the fourth voltage-dividing resistor away from the third voltage-dividing resistor is grounded. The in-phase end of the first comparator is connected to a node between the third voltage-dividing resistor and the fourth voltage-dividing resistor.

5. The protection circuit according to claim 2, characterized in that: The temperature protection module further includes a second thermistor, a second voltage-dividing resistor and a second comparator, wherein the second thermistor is the same as the first thermistor, the second comparator is the same as the first comparator, and the second voltage-dividing resistor is smaller than the first voltage-dividing resistor; The second thermistor is arranged on the brake resistor, and is used to detect the temperature of the brake resistor. One end of the second thermistor is connected to the first power supply, and the other end is connected in series with the second voltage-dividing resistor and then grounded. The inverting end of the second comparator is connected to the end of the second voltage-dividing resistor away from the ground end, the inverting end of the second comparator is connected to the second divided voltage at both ends of the second voltage-dividing resistor, the output end of the second comparator is connected to the control module, and the non-inverting end of the second comparator is connected to the second comparison voltage, wherein the second comparison voltage is the same as the first comparison voltage.

6. The protection circuit according to claim 5, characterized in that: As the temperature of the second thermistor increases with the temperature of the brake resistor, the resistance of the second thermistor decreases, and the second divided voltage of the second voltage-dividing resistor increases. When the second divided voltage is greater than the second comparison voltage, the second comparator outputs a second low-level signal and sends the second low-level signal to the control module; the control module responds to the second low-level signal and sends an alarm signal to stop the servo driver from working according to the alarm signal.

7. The protection circuit according to claim 1, characterized in that: The control module includes a main control chip and a driver chip; One end of the driving chip is connected to the main control chip, and the other end is connected to one end of the braking resistor through the switch module.

8. The protection circuit according to claim 7, characterized in that: The switch module comprises: an insulated gate bipolar transistor IGBT, wherein the IGBT gate is connected to the driving chip, the IGBT collector is connected to one end of the braking resistor, and the IGBT emitter is connected to the negative electrode of the DC power supply.

9. The protection circuit according to claim 1, characterized in that: The circuit also includes a voltage sampling module; The voltage sampling module is used to collect the bus voltage value at both ends of the main capacitor in the servo driver, convert the bus voltage value into a digital signal and send it to the control module.

10. The protection circuit according to claim 1, characterized in that: The circuit also includes an inverter module; The inverter module is used to convert the electricity in the servo drive into AC power.

11. A driver, characterized in that: The driver comprises the protection circuit according to any one of claims 1-10.

Images