Frequency converter control circuit with brake early warning indication and frequency converter

Abstract

The utility model discloses a frequency converter control circuit with brake early warning indication and a frequency converter, and the frequency converter control circuit with brake early warning indication evaluates the current power generation state of the frequency converter and monitors the real-time temperature of a brake device on a brake circuit according to the voltage amplitude and duration of a DC bus. Therefore, the indicating circuit is driven to perform dynamic early warning on the frequency converter at present, an operator is prompted to adjust a load operation scheme or perform shutdown inspection, failure of a brake unit caused by non-standard operation of the operator is avoided, and the service life of the frequency converter is prolonged. Meanwhile, the failure risk of the brake unit is reduced through an early warning mechanism, a high-power frequency converter does not need to be replaced due to short-term overload operation, and the equipment investment cost is saved.

Description

Technical Field

[0001] The utility model relates to the technical field of frequency converters, and particularly relates to a frequency converter control circuit and a frequency converter with a braking warning indication. Background Technique

[0002] The braking unit of a frequency converter is an important part of the frequency converter. It allows the motor to stop quickly and smoothly when needed. Based on the regenerative power generation state of the motor, when the motor speed exceeds the set value during deceleration or stop due to a large inertia load, the motor enters the power generation state. At this time, the braking unit starts to work. To prevent the DC voltage from being too high due to the motor being in the power generation state, the braking unit is connected to the DC circuit, and the voltage increment is converted into the active power consumption of the braking resistor, thereby achieving rapid braking.

[0003] Before the frequency converter is used in cooperation with the motor, core parameters such as power, voltage, current, control mode, load type, and environmental adaptability are usually considered comprehensively, so that the rated power of the frequency converter is slightly larger than the rated power of the motor. However, in some industrial scenarios, the motor often operates overloaded. When the motor frequently changes from the overloaded operation state to the stop state, the DC bus voltage of the frequency converter is overvoltage for a long time, which easily causes damage to the braking resistor or power device of the braking unit, resulting in the failure of the braking function. This is often caused by the operator's inability to intuitively understand the current operating conditions of the frequency converter braking unit and the overloaded motor. If a higher-power frequency converter is configured to adapt to the motor to solve the above problems, the cost will increase significantly.

[0004] In view of this, it is urgent to design a frequency converter control circuit with a braking warning indication, which can intuitively present the current operating status of the frequency converter to the operator, so as to adjust the actual operation to avoid the failure of the braking unit. Content of the Utility Model

[0005] To solve the above problems, the utility model provides a frequency converter control circuit and a frequency converter with a braking warning indication.

[0006] In the first aspect of the utility model, a frequency converter control circuit with a braking warning indication is provided, which includes a power supply circuit, a processing circuit, a common-mode suppression circuit, a rectification circuit, and an inversion circuit connected in sequence. A DC bus voltage exists between the rectification circuit and the inversion circuit. A braking circuit is connected between the DC bus voltages. It also includes a DC voltage sampling circuit, a voltage comparison circuit, an analog-to-digital conversion circuit, a temperature sampling circuit, and an indication circuit. The power supply circuit is respectively connected to the DC voltage sampling circuit, the voltage comparison circuit, the analog-to-digital conversion circuit, the temperature sampling circuit, and the indication circuit. The input end of the DC voltage sampling circuit is at the DC bus voltage. The output end of the DC voltage sampling circuit is respectively connected to the input end of the voltage comparison circuit and the input end of the analog-to-digital conversion circuit. The output end of the voltage comparison circuit is connected to the input end of the braking circuit. The output end of the analog-to-digital conversion circuit is connected to the input end of the processing circuit. The temperature sampling circuit collects the temperature of the braking device on the braking circuit. The output end of the temperature sampling circuit is connected to the input end of the processing circuit. The output end of the processing circuit is connected to the input end of the indication circuit.

[0007] Based on the first aspect, in a possible implementation, the DC voltage sampling circuit includes a first resistor, a second resistor, a third resistor, a first capacitor, a first TVS diode, and a voltage follower. The first resistor and the second resistor are connected in series between the DC bus voltages. The first capacitor and the first TVS diode are respectively connected in parallel at both ends of the second resistor. The non-inverting input end of the voltage follower is connected to one end of the second resistor. The inverting input end of the voltage follower is connected to the output end of the voltage follower. The output end of the voltage follower is connected to one end of the third resistor. The other end of the third resistor is grounded.

[0008] Based on the first aspect, in a possible implementation, the voltage comparison circuit includes a fourth resistor, a fifth resistor, a second capacitor, and a voltage comparator. One end of the fourth resistor is respectively connected to the output end of the voltage follower and the non-inverting input end of the voltage comparator. The other end of the fourth resistor is grounded. The second capacitor is connected in parallel at both ends of the fourth resistor. The inverting input end of the voltage comparator is connected to a reference voltage. One end of the fifth resistor is connected to a high level. The other end of the fifth resistor is connected to the output end of the voltage comparator. The output end of the voltage comparator is connected to the input end of the braking circuit.

[0009] Based on the first aspect, in a possible implementation, the braking circuit includes a sixth resistor and a power switching device. The control end of the power switching device is connected to the output end of the voltage comparator. The sixth resistor and the power switching device are connected in series, and one end of the sixth resistor and one end of the power switching device are respectively connected to the DC bus voltage.

[0010] Based on the first aspect, in a possible implementation, the analog-to-digital conversion circuit includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third capacitor, and an operational amplifier. The non-inverting input terminal of the operational amplifier is respectively connected to one end of the eighth resistor and one end of the ninth resistor. The other end of the eighth resistor is connected to the output end of the voltage follower. The other end of the ninth resistor is connected to a high level. The inverting input terminal of the operational amplifier is respectively connected to one end of the seventh resistor, one end of the eleventh resistor, and one end of the third capacitor. The other end of the third capacitor is respectively connected to the output end of the operational amplifier and one end of the tenth resistor. The other end of the eleventh resistor is connected to the other end of the tenth resistor. The other end of the tenth resistor is connected to the input end of the processing circuit.

[0011] Based on the first aspect, in a possible implementation, the indication circuit includes an LED driving chip, a twelfth resistor, a thirteenth resistor, a fourth capacitor, a second TVS diode, a light-emitting diode, and a protection diode. One end of the twelfth resistor is connected to a high level. The other end of the twelfth resistor is respectively connected to the first pin of the LED driving chip and the negative electrode of the second TVS diode. The positive electrode of the second TVS diode is grounded. The fourth capacitor is connected in parallel across the two ends of the second TVS diode. The output end of the processing circuit is connected to the second pin of the LED driving chip. The positive electrode of the light-emitting diode is connected to a high level. The negative electrode of the light-emitting diode is connected to the fourth pin of the LED driving chip. The protection diode is reversely connected in parallel across the two ends of the light-emitting diode. One end of the thirteenth resistor is respectively connected to the fifth pin and the sixth pin of the LED driving chip. The other end of the thirteenth resistor is grounded. The eighth pin of the LED driving chip is grounded.

[0012] Based on the first aspect, in a possible implementation, the model of the LED driving chip is TX6410.

[0013] Based on the first aspect, in a possible implementation, the temperature sampling circuit includes a temperature sampling chip and a fourteenth resistor. The first pin of the temperature sampling chip is grounded. The second pin of the temperature sampling chip is connected to the input end of the processing circuit. The third pin of the temperature sampling chip is connected to a high level. The two ends of the fourteenth resistor are respectively connected to the second pin and the third pin of the temperature sampling chip.

[0014] In a possible implementation based on the first aspect, a filter circuit is further included, and the filter circuit is connected between the DC bus voltages.

[0015] In the second aspect of the present utility model, a frequency converter is provided, which includes the frequency converter control circuit with braking warning indication as described above.

[0016] The working mechanism of the frequency converter control circuit with braking warning indication in this technical solution includes:

[0017] (1) The DC bus voltage is collected in real time through the DC voltage sampling circuit, and a threshold value is set in combination with the voltage comparison circuit. When the motor generates regenerative energy feedback due to inertia, if the voltage exceeds the safe range, the braking circuit is automatically connected, and the excess electrical energy is converted into heat energy through the braking resistor for consumption, avoiding damage to the frequency converter caused by too high DC bus voltage;

[0018] (2) The DC bus voltage amplitude and duration are monitored through the DC voltage sampling circuit and the analog-to-digital conversion circuit. The current power generation state of the frequency converter is evaluated according to the DC bus voltage amplitude and duration, and the processing circuit drives the indication circuit to perform overload braking warning;

[0019] (3) The real-time temperature of the braking device on the braking circuit is monitored through the temperature sampling circuit. When the real-time temperature of the braking device exceeds its critical protection value, the processing circuit drives the indication circuit to perform braking device protection warning.

[0020] The frequency converter control circuit with braking warning indication in this technical solution evaluates the current power generation state of the frequency converter according to the DC bus voltage amplitude and duration and monitors the real-time temperature of the braking device on the braking circuit, thereby driving the indication circuit to perform dynamic warning on the current frequency converter, prompting the operator to adjust the load operation plan or stop for inspection, avoiding the failure of the braking unit caused by the operator's non-standard operation, and extending the service life of the frequency converter; at the same time, the risk of braking unit failure is reduced through the warning mechanism, and there is no need to replace a high-power frequency converter due to short-term overload operation, saving the equipment investment cost. Description of the Drawings

[0021] Figure 1 It is a block diagram of the frequency converter control circuit according to an embodiment of the present utility model.

[0022] Figure 2 It is a schematic diagram of the DC voltage sampling circuit according to an embodiment of the present utility model.

[0023] Figure 3 It is a schematic diagram of the voltage comparison circuit according to an embodiment of the present utility model.

[0024] Figure 4 It is a schematic diagram of the braking circuit according to an embodiment of the present utility model.

[0025] Figure 5 This is the schematic diagram of the analog-to-digital conversion circuit in the embodiment of the present utility model.

[0026] Figure 6 This is the schematic diagram of the indication circuit in the embodiment of the present utility model.

[0027] Figure 7 This is the schematic diagram of the temperature sampling circuit in the embodiment of the present utility model. Specific implementation manners

[0028] To make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0029] Embodiment 1

[0030] Combined with the attached Figure 1 to the attached Figure 7 The technical solution of the present utility model is a frequency converter control circuit with braking warning indication, including a power supply circuit 1, a processing circuit 2, and a common-mode suppression circuit 3, a rectification circuit 4, and an inversion circuit 5 connected in sequence. A DC bus voltage Ud is between the rectification circuit 4 and the inversion circuit 5. A braking circuit 6 is connected between the DC bus voltages Ud. It further includes a DC voltage sampling circuit 7, a voltage comparison circuit 8, an analog-to-digital conversion circuit 9, a temperature sampling circuit 10, and an indication circuit 11. The power supply circuit 1 is respectively connected to the DC voltage sampling circuit 7, the voltage comparison circuit 8, the analog-to-digital conversion circuit 9, the temperature sampling circuit 10, and the indication circuit 11. The input end of the DC voltage sampling circuit 7 is at the DC bus voltage Ud. The output end of the DC voltage sampling circuit 7 is respectively connected to the input end of the voltage comparison circuit 8 and the input end of the analog-to-digital conversion circuit 9. The output end of the voltage comparison circuit 8 is connected to the input end of the braking circuit 6. The output end of the analog-to-digital conversion circuit 9 is connected to the input end of the processing circuit 2. The temperature sampling circuit 10 collects the temperature of the braking device on the braking circuit 6. The output end of the temperature sampling circuit 10 is connected to the input end of the processing circuit 2. The output end of the processing circuit 2 is connected to the input end of the indication circuit 11.

[0031] In this embodiment, the power supply circuit 1 is an independent switching power supply that converts the external power supply into a stable DC operating voltage to provide corresponding DC operating voltages for the DC voltage sampling circuit 7, the voltage comparison circuit 8, the analog-to-digital conversion circuit 9, the temperature sampling circuit 10, and the indication circuit 11 respectively. The following embodiments are uniformly described using high-level voltage.

[0032] In this embodiment, the processing circuit 2 obtains the DC voltage signal fed back by the analog-to-digital conversion circuit 9 and the braking device temperature signal fed back by the temperature sampling circuit 10. The processing circuit 2 outputs an LED drive signal to the indication circuit 11 to achieve different braking warning indications.

[0033] In this embodiment, the processing circuit 2 is selected from the STM32F407 / G4 series or the STM32F103 / G0 series.

[0034] The working mechanism of the frequency converter control circuit with braking warning indication in this embodiment includes:

[0035] (1) The DC bus voltage Ud is collected in real time through the DC voltage sampling circuit 7, and a threshold value is set in combination with the voltage comparison circuit 8. When the motor causes regenerative energy feedback due to inertia, if the voltage exceeds the safe range, the braking circuit 6 is automatically connected, and the excess electrical energy is converted into heat energy through the braking resistor and consumed to prevent the DC bus voltage Ud from being too high and damaging the frequency converter.

[0036] (2) The amplitude and duration of the DC bus voltage Ud are monitored through the DC voltage sampling circuit 7 and the analog-to-digital conversion circuit 9. The current power generation state of the frequency converter is evaluated based on the amplitude and duration of the DC bus voltage Ud, and the processing circuit drives the indication circuit 11 to perform overload braking warning.

[0037] (3) The real-time temperature of the braking device on the braking circuit 6 is monitored through the temperature sampling circuit 10. When the real-time temperature of the braking device exceeds its critical protection value, the processing circuit drives the indication circuit 11 to perform braking device protection warning.

[0038] In this embodiment, as shown in the appendix Figure 2As shown, the DC voltage sampling circuit 7 includes a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a first TVS diode TVS1, and a voltage follower U1. The first resistor R1 and the second resistor R2 are connected in series between the DC bus voltage Ud. The first capacitor C1 and the first TVS diode TVS1 are respectively connected in parallel across both ends of the second resistor R2. The non-inverting input terminal of the voltage follower U1 is connected to one end of the second resistor R2. The inverting input terminal of the voltage follower U1 is connected to the output terminal of the voltage follower U1. The output terminal of the voltage follower U1 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is grounded. The output terminal of the voltage follower U1 outputs the Ud_samples signal to the input terminal of the voltage comparison circuit 8. The DC voltage sampling circuit 7 samples the DC bus voltage Ud through the voltage-dividing resistors of the first resistor R1 and the second resistor R2. The anti-parallel connected first TVS diode TVS1 can effectively suppress electrostatic discharge and surge voltage. The voltage follower U1 ensures the stability and efficiency of signal transmission through its high input impedance and low output impedance characteristics.

[0039] In this embodiment, as shown in the attached Figure 3 figure, the voltage comparison circuit 8 includes a fourth resistor R4, a fifth resistor R5, a second capacitor C2, and a voltage comparator U2. One end of the fourth resistor R4 is respectively connected to the output terminal of the voltage follower U1 and the non-inverting input terminal of the voltage comparator U2. The other end of the fourth resistor R4 is grounded. The second capacitor C2 is connected in parallel across both ends of the fourth resistor R4. The inverting input terminal of the voltage comparator U2 is connected to the reference voltage Vref. One end of the fifth resistor R5 is connected to the high level, and the other end of the fifth resistor R5 is connected to the output terminal of the voltage comparator U2. The output terminal of the voltage comparator U2 outputs the signal_Bd signal to the input terminal of the braking circuit 6.

[0040] In this embodiment, as shown in the attached Figure 4 figure, the braking circuit 6 includes a sixth resistor R6 and a power switch device Q1. The control terminal of the power switch device Q1 is connected to the output terminal of the voltage comparator U2. The sixth resistor R6 and the power switch device Q1 are connected in series. One end of the sixth resistor R6 and one end of the power switch device Q1 are respectively connected to the DC bus voltage Ud. The power switch device Q1 uses a MOS transistor.

[0041] In this embodiment, as shown in the attached Figure 5As shown, the analog-to-digital conversion circuit 9 includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a third capacitor C3, and an operational amplifier U3. The non-inverting input terminal of the operational amplifier U3 is respectively connected to one end of the eighth resistor R8 and one end of the ninth resistor R9. The other end of the eighth resistor R8 is connected to the output terminal of the voltage follower U1. The other end of the ninth resistor R9 is connected to a high level. The inverting input terminal of the operational amplifier U3 is respectively connected to one end of the seventh resistor R7, one end of the eleventh resistor R11, and one end of the third capacitor C3. The other end of the third capacitor C3 is respectively connected to the output terminal of the operational amplifier U3 and one end of the tenth resistor R10. The other end of the eleventh resistor R11 is connected to the other end of the tenth resistor R10. The other end of the tenth resistor R10 outputs a Ud_ad signal to the input terminal of the processing circuit 2.

[0042] In this embodiment, as shown in the attached Figure 6 As shown, the indication circuit 11 includes an LED driver chip U4, a twelfth resistor R12, a thirteenth resistor R13, a fourth capacitor C4, a second TVS diode TVS2, a light-emitting diode LED, and a protection diode D1. One end of the twelfth resistor R12 is connected to a high level. The other end of the twelfth resistor R12 is respectively connected to the first pin of the LED driver chip U4 and the negative electrode of the second TVS diode TVS2. The positive electrode of the second TVS diode TVS2 is grounded. The fourth capacitor C4 is connected in parallel across the second TVS diode TVS2. The output terminal of the processing circuit 2 outputs a PWM_led signal to the second pin of the LED driver chip U4. The positive electrode of the light-emitting diode LED is connected to a high level. The negative electrode of the light-emitting diode LED is connected to the fourth pin of the LED driver chip U4. The protection diode D1 is reversely connected in parallel across the light-emitting diode LED. One end of the thirteenth resistor R13 is respectively connected to the fifth pin and the sixth pin of the LED driver chip U4. The other end of the thirteenth resistor R13 is grounded. The eighth pin of the LED driver chip U4 is grounded.

[0043] In this embodiment, the model of the LED driver chip U4 is TX6410.

[0044] In this embodiment, as shown in the attached Figure 7As shown, the temperature sampling circuit 10 includes a temperature sampling chip U5 and a fourteenth resistor R14. The first pin of the temperature sampling chip U5 is grounded. The second pin of the temperature sampling chip U5 outputs a signal_temp signal to the input end of the processing circuit. The third pin of the temperature sampling chip U5 is connected to a high level. Both ends of the fourteenth resistor R14 are respectively connected to the second pin and the third pin of the temperature sampling chip U5. The model of the temperature sampling chip U5 is DS18B20.

[0045] In this embodiment, a filtering circuit 12 is further included, and the filtering circuit 12 is connected between the DC bus voltage Ud.

[0046] To better illustrate the way for the inverter control circuit in this embodiment to achieve braking warning, the following is described in combination with a warning method of an inverter:

[0047] When the DC bus voltage Ud < 620V, the inverter system operates in a steady state, the braking circuit 6 is not triggered, and the light-emitting diode LED is in a green constant-on state;

[0048] When 620V ≤ DC bus voltage Ud < 750V, the inverter system enters the normal braking state, the braking circuit 6 is triggered for rapid braking, and the light-emitting diode LED is in a red flashing state;

[0049] When the DC bus voltage Ud > 750V and the duration for which the DC bus voltage Ud exceeds 750V lasts for more than 2s, the inverter system enters the abnormal braking state, the braking circuit 6 is triggered for rapid braking, and the light-emitting diode LED is in a yellow flashing state for overloading braking warning;

[0050] When the temperature sampling circuit 10 detects that the temperature of the sixth resistor R6 on the braking circuit 6 exceeds 190°C, the light-emitting diode LED is in an alternating red and yellow flashing state for braking device protection warning.

[0051] The inverter control circuit with braking warning indication in this embodiment evaluates the current power generation state of the inverter according to the amplitude and duration of the DC bus voltage and monitors the real-time temperature of the braking device on the braking circuit, thereby driving the indication circuit to perform dynamic warning on the current inverter, prompting the operator to adjust the load operation plan or stop for inspection, avoiding the failure of the braking unit caused by the operator's non-standard operation, and extending the service life of the inverter; at the same time, the risk of braking unit failure is reduced through the warning mechanism, and there is no need to replace a high-power inverter due to short-term overload operation, saving the equipment investment cost.

[0052] Embodiment 2

[0053] Combined with the attached Figure 1 to the attached Figure 7, the technical solution of the present utility model is an inverter, including the inverter control circuit with braking warning indication described in Embodiment 1.

[0054] It should also be noted that in this specification, 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 actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the presence of additional identical elements in the process, method, article or device including the said element.

[0055] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be obvious 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 utility model. Therefore, the present utility model will not be limited to these embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A frequency converter control circuit with a braking warning indication, comprising a power supply circuit, a processing circuit, and a common-mode suppression circuit, a rectification circuit, and an inversion circuit connected in sequence. A DC bus voltage exists between the rectification circuit and the inversion circuit, and a braking circuit is connected between the DC bus voltages. It is characterized in that It also includes a DC voltage sampling circuit, a voltage comparison circuit, an analog-to-digital conversion circuit, a temperature sampling circuit, and an indication circuit; the power supply circuit is respectively connected to the DC voltage sampling circuit, the voltage comparison circuit, the analog-to-digital conversion circuit, the temperature sampling circuit, and the indication circuit; the input end of the DC voltage sampling circuit is at the DC bus voltage, the output end of the DC voltage sampling circuit is respectively connected to the input end of the voltage comparison circuit and the input end of the analog-to-digital conversion circuit, the output end of the voltage comparison circuit is connected to the input end of the braking circuit, the output end of the analog-to-digital conversion circuit is connected to the input end of the processing circuit, the temperature sampling circuit collects the temperature of the braking device on the braking circuit, the output end of the temperature sampling circuit is connected to the input end of the processing circuit, and the output end of the processing circuit is connected to the input end of the indication circuit.

2. The frequency converter control circuit with a braking warning indicator according to claim 1, characterized in that, The DC voltage sampling circuit includes a first resistor, a second resistor, a third resistor, a first capacitor, a first TVS diode, and a voltage follower. The first resistor and the second resistor are connected in series between the DC bus voltage. The first capacitor and the first TVS diode are respectively connected in parallel at both ends of the second resistor. The non-inverting input end of the voltage follower is connected to one end of the second resistor. The inverting input end of the voltage follower is connected to the output end of the voltage follower. The output end of the voltage follower is connected to one end of the third resistor, and the other end of the third resistor is grounded.

3. The frequency converter control circuit with a braking warning indication according to claim 2, characterized in that, The voltage comparison circuit includes a fourth resistor, a fifth resistor, a second capacitor, and a voltage comparator. One end of the fourth resistor is respectively connected to the output end of the voltage follower and the non-inverting input end of the voltage comparator. The other end of the fourth resistor is grounded. The second capacitor is connected in parallel at both ends of the fourth resistor. The inverting input end of the voltage comparator is connected to a reference voltage. One end of the fifth resistor is connected to a high level. The other end of the fifth resistor is connected to the output end of the voltage comparator. The output end of the voltage comparator is connected to the input end of the braking circuit.

4. A frequency converter control circuit with a braking warning indication according to claim 3, characterized in that, The braking circuit includes a sixth resistor and a power switch device. The control end of the power switch device is connected to the output end of the voltage comparator. The sixth resistor and the power switch device are connected in series. One end of the sixth resistor and one end of the power switch device are respectively connected to the DC bus voltage.

5. The frequency converter control circuit with a braking warning indication according to claim 2, characterized in that, The analog-to-digital conversion circuit includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third capacitor, and an operational amplifier. The non-inverting input terminal of the operational amplifier is respectively connected to one end of the eighth resistor and one end of the ninth resistor. The other end of the eighth resistor is connected to the output terminal of the voltage follower. The other end of the ninth resistor is connected to a high level. The inverting input terminal of the operational amplifier is respectively connected to one end of the seventh resistor, one end of the eleventh resistor, and one end of the third capacitor. The other end of the third capacitor is respectively connected to the output terminal of the operational amplifier and one end of the tenth resistor. The other end of the eleventh resistor is connected to the other end of the tenth resistor. The other end of the tenth resistor is connected to the input terminal of the processing circuit.

6. A frequency converter control circuit with a braking warning indication according to any one of claims 1 to 5, characterized in that, The indication circuit includes an LED driving chip, a twelfth resistor, a thirteenth resistor, a fourth capacitor, a second TVS diode, a light-emitting diode, and a protection diode. One end of the twelfth resistor is connected to a high level. The other end of the twelfth resistor is respectively connected to the first pin of the LED driving chip and the negative electrode of the second TVS diode. The positive electrode of the second TVS diode is grounded. The fourth capacitor is connected in parallel across the two ends of the second TVS diode. The output terminal of the processing circuit is connected to the second pin of the LED driving chip. The positive electrode of the light-emitting diode is connected to a high level. The negative electrode of the light-emitting diode is connected to the fourth pin of the LED driving chip. The protection diode is reversely connected in parallel across the two ends of the light-emitting diode. One end of the thirteenth resistor is respectively connected to the fifth pin and the sixth pin of the LED driving chip. The other end of the thirteenth resistor is grounded. The eighth pin of the LED driving chip is grounded.

7. The frequency converter control circuit with a braking warning indicator according to claim 6, characterized in that, The model of the LED driving chip is TX6410.

8. A frequency converter control circuit with a braking warning indication according to any one of claims 1 to 5, characterized in that, The temperature sampling circuit includes a temperature sampling chip and a fourteenth resistor. The first pin of the temperature sampling chip is grounded. The second pin of the temperature sampling chip is connected to the input terminal of the processing circuit. The third pin of the temperature sampling chip is connected to a high level. The two ends of the fourteenth resistor are respectively connected to the second pin and the third pin of the temperature sampling chip.

9. A frequency converter control circuit with a braking warning indication according to any one of claims 1 to 5, characterized in that, It further includes a filtering circuit, and the filtering circuit is connected between the DC bus voltages.

10. A frequency converter, characterized in that, It includes the frequency converter control circuit with braking warning indication according to any one of claims 1 to 9.

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