Power-off brake protection circuit

Abstract

The utility model discloses a power-off brake protection circuit, which relates to the technical field of motor control, aims to prevent the problem of overcharging of a system power supply caused by reverse driving of a motor by external force, and comprises a power supply voltage detection module connected with a power supply, the power supply voltage detection module is connected with a level conversion module, the level conversion module is connected with a phase voltage detection module through a filtering module, the phase voltage detection module is connected with phase voltage of the direct current motor, and the level conversion module outputs grid voltage to the direct current motor. The output end of the power voltage detection module is connected with a first control signal, a low-side MOS tube can be effectively turned on in a low-power-consumption sleep mode, the active braking function is achieved, meanwhile, the capacity of controlling a power-off braking circuit in a multi-mode selection mode is achieved, the power-off braking function can be forbidden when a large-current event is detected in the braking period, and the braking safety is improved. And power supply short-circuit faults are avoided.

Description

Technical Field

[0001] This utility model belongs to the field of motor control technology, specifically relating to a power failure braking protection circuit. Background Technology

[0002] In the field of DC motor control, power-off braking protection circuits are particularly important to ensure the motor can safely stop operating under specific conditions and to prevent problems such as overcharging of the system power supply due to external forces driving the motor in reverse. However, existing power-off braking technologies mainly rely on pure hardware implementation, resulting in relatively simple functions and a lack of flexibility. Especially when the circuit is in a low-power sleep mode, traditional power-off braking circuits struggle to effectively turn on the low-side MOSFET while maintaining a low quiescent current to achieve active braking. Furthermore, they cannot detect high-current events during braking and promptly disable the power-off braking function to avoid power supply short-circuit faults.

[0003] For example, there is a Chinese patent with publication number CN116896291A, which relates to the present invention providing a motor control circuit and a motor power-off braking circuit. The motor control circuit includes: a power supply for outputting a power supply voltage; an anti-reverse filtering module whose input terminal is connected to the power supply voltage; a motor drive module whose power supply terminal is connected to the output terminal of the anti-reverse filtering module and whose output terminal is connected to the motor; a control module whose power supply terminal is connected to the output terminal of the anti-reverse filtering module and whose first signal terminal is connected to the control terminal of the motor drive module; and a motor power-off braking circuit whose first connection terminal is connected to the power supply voltage, whose second connection terminal is connected to the second signal terminal of the control module, and whose third connection terminal is connected to at least one phase of the motor. Compared with the prior art, the present invention uses pure hardware to realize the braking of the motor in the event of power failure. This circuit has the characteristics of simple circuit structure, low cost, no software, and flexible control. Moreover, it can meet the power failure braking requirements without external power supply. However, the Chinese patent with publication number CN116896291A is difficult to effectively turn on the low-side MOS transistor while maintaining a low static current of the power supply to realize the active braking function. Furthermore, it cannot detect large current events during braking and disable the power failure braking function in time to avoid the occurrence of power supply short circuit faults. Utility Model Content

[0004] To prevent the system power supply from being overcharged due to reverse drive of the motor by external forces, this utility model proposes a power-off braking protection circuit. It can effectively turn on the low-side MOSFET in low-power sleep mode to realize active braking function. It also has the ability to select multiple modes to control the power-off braking circuit, and can disable the power-off braking function when a large current event is detected during braking to avoid power short circuit faults.

[0005] To achieve the above objectives, this utility model adopts the following technical solution: a power failure braking protection circuit, including a power supply voltage detection module connected to a power supply, a voltage regulator module connected to the power supply, a level conversion module connected to the power supply voltage detection module, a phase voltage detection module connected to the level conversion module through a filter module, an electrical connection between the voltage regulator module and the phase voltage detection module, a low-side MOSFET of a DC motor connected to the phase voltage detection module, a gate control voltage output by the level conversion module to the DC motor, a first enable control terminal connected to the output terminal of the power supply voltage detection module, and a first control signal input at the first enable control terminal.

[0006] In this technical solution, while maintaining a low quiescent current in the power supply, the low-side MOSFET is turned on. The driver can actively brake the external half-bridge motor by shorting the back electromotive force on the motor terminals. This helps dissipate the energy in the low-side MOSFET and prevents the system power supply from overcharging due to reverse drive of the motor by external forces. The PVDD voltage is detected by the power supply voltage detection module. When the voltage exceeds a certain threshold, the power-off braking mode is activated. The low-side MOSFET is disabled to protect the power supply when a large current event is detected during braking by the phase voltage detection module.

[0007] Preferably, the power supply voltage detection module includes a MOSFET M1, the drain of the MOSFET M1 is connected to the first terminal of a resistor R2, the second terminal of the resistor R2 is connected to a level conversion module, and the gate of the MOSFET M1 is connected to a second enable control terminal.

[0008] Preferably, the source of MOSFET M1 is connected to the first terminal of resistor R1 and the anode of Zener diode Z4, the second terminal of resistor R1 and the cathode of Zener diode Z4 are both connected to the input terminal of the level conversion module, the source of MOSFET M1 is connected to the digital ground line, and the power supply voltage detection module can detect the power supply voltage PVDD and control the potential of the first control signal.

[0009] Preferably, the power supply voltage detection module includes a voltage regulation unit, which is composed of three Zener diodes Z1, Z2, and Z3 connected in series. The cathode of Zener diode Z1 is connected to the power supply, and the anode of Zener diode Z3 is connected to the input terminal of the level conversion module.

[0010] Preferably, the phase voltage detection module receives the phase voltage and reference voltage of the low-side MOSFET of the DC motor at its input terminal, and the output terminal of the phase voltage detection module is connected to the input terminal of the level conversion module through a filter module. The output control terminal of the level conversion module is connected to the gate of the low-side MOSFET M2 of the DC motor. The output control voltage GLx of the phase voltage detection module controls the gate of the low-side MOSFET M2, which is used to disable the low-side MOSFET M2 when a large current event is detected during braking.

[0011] Preferably, the phase voltage detection module includes a comparator. The non-inverting input of the comparator is connected to the drain of the low-side MOSFET M2 and the source of the MOSFET M3 of the DC motor, and the phase voltage is input. The inverting input of the comparator is connected to the voltage regulator module and the reference voltage is input. The output of the comparator serves as the output of the phase voltage detection module and is connected to the input of the level conversion module through a filter module. When the phase voltage SHx is higher than the reference voltage VPOB_VDS, the comparator outputs a high level. After passing through the filter circuit, the level conversion circuit is controlled to force the level conversion output voltage to be set low, thus disabling the power-off braking function.

[0012] Preferably, the filtering module is an RC filter circuit. The first end of the filtering module is connected to the output end of the phase voltage detection module, and the second end of the filtering module is connected to the input end of the level conversion module. The filtering module can filter the output signal of the phase voltage detection module to eliminate the influence of glitches on subsequent circuits.

[0013] Preferably, the filtering module includes a resistor R3. The first end of the resistor R3 is connected to the output terminal of the phase voltage detection module. The first end of the resistor R3 is connected to a capacitor C1 and the input terminal of the level conversion module. The other end of the capacitor C1 is connected to the digital ground line.

[0014] Preferably, the input terminal of the level conversion module is connected to the first enable control terminal, and the output terminal of the level conversion module is connected to the gate control voltage of the low-side MOSFET M2 of the DC motor. The level conversion module can raise the input signal with the first internal power supply voltage V5INT as the power supply voltage to the output signal with the second internal power supply voltage VPOB as the power supply voltage, thereby controlling the opening and closing of the low-side MOSFET M2.

[0015] Preferably, the input terminal of the voltage regulator module is connected to the power supply, and the voltage regulator module outputs a first internal power supply voltage and a second internal power supply voltage. The voltage regulator module generates a reference voltage through the first internal power supply voltage V5INT and supplies power to the phase voltage detection module through the second internal power supply voltage VPOB.

[0016] The beneficial effects of this utility model are:

[0017] 1) It can effectively turn on the low-side MOSFET in low-power sleep mode to realize active braking function, and has the ability to select multiple modes to control the power-off braking circuit, providing greater flexibility and adaptability, and better meeting the needs of different application scenarios.

[0018] 2) By detecting the phase voltage during braking and comparing it with the reference voltage, combined with filtering and level conversion, the power-off braking function can be disabled in time when a high current event is detected, thus avoiding power short circuit faults caused by high current and improving the safety and reliability of the system. Attached Figure Description

[0019] Figure 1 This is a block diagram of a power-off braking protection circuit according to the present invention.

[0020] Figure 2 This is a circuit diagram of a power-off braking protection circuit according to the present invention.

[0021] Figure reference numerals: Power supply voltage PVDD; Phase voltage SHx; Gate control voltage GLx; Reference voltage VPOB_VDS; First internal power supply voltage V5INT; Second internal power supply voltage VPOB; First control signal BREAK; Second control signal nSLEEP. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this utility model and are only used to explain this utility model. They do not limit the scope of protection of this utility model. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0023] Example 1

[0024] This embodiment provides a power failure braking protection circuit, such as Figure 1 As shown, it includes a power supply, a voltage regulator module, a power supply voltage detection module, a phase voltage detection module, a filter module, and a level conversion module. It can effectively turn on the low-side MOSFET in low-power sleep mode to realize active braking function. It also has the ability to select multiple modes to control the power-off braking circuit, and can disable the power-off braking function when a large current event is detected during braking to avoid power short circuit faults.

[0025] The voltage regulator module is used to generate the first internal power supply voltage V5INT and the second internal power supply voltage VPOB, providing stable power support for each module in the circuit.

[0026] The input terminal of the power supply voltage detection module is connected to the power supply PVDD, and the output terminal is connected to the first control signal BREAK input to the first enable control terminal, i.e. the power-off braking enable control terminal, to monitor the changes in PVDD voltage in real time.

[0027] When the PVDD voltage exceeds the set threshold, the power supply voltage detection module will set the power-off braking enable signal high, thereby activating the power-off braking mode.

[0028] The input terminal of the phase voltage detection module is connected to the phase voltage SHx and the reference voltage VPOB_VDS, and the output terminal is connected to the level conversion module through the filter module.

[0029] During braking, the phase voltage detection module is responsible for detecting changes in phase voltage and comparing it with a reference voltage.

[0030] If the phase voltage is detected to be lower than the reference voltage, it indicates that no large current event has occurred. The comparator outputs a low-level signal, which, after filtering and level conversion, maintains the on-state of the low-side MOSFET and continues to perform the braking operation.

[0031] When the phase voltage is higher than the reference voltage, the comparator outputs a high-level signal. After the filter circuit composed of R3 and C1 filters out the glitches, the control level conversion circuit forces the output voltage to be low, thereby disabling the power-off braking function and effectively avoiding power supply short-circuit faults caused by high current events.

[0032] The input terminal of the level conversion module is connected to the power-off braking enable control terminal, and the output terminal is connected to the gate control voltage GLx of the low-side MOSFET. Its main function is to raise the input signal V5INT, which is the power supply voltage, to the output signal VPOB, which is the power supply voltage, thereby realizing effective control of the gate control voltage of the low-side MOSFET and ensuring that the low-side MOSFET can be reliably turned on or off at the appropriate voltage.

[0033] In addition, the power-off braking function is enabled via the BRAKE pin, which offers multiple pull-up methods, giving users the freedom to flexibly choose the control method according to actual needs.

[0034] Specifically, an internal overvoltage monitoring method can be selected, that is, by disconnecting the BRAKE pin, the power-off braking function can be automatically activated solely by relying on the power supply voltage detection module.

[0035] By default, when the BRAKE pin is left floating, the power supply voltage detection module will take over the activation of the power-off braking function.

[0036] The detection module continuously monitors the PVDD pin voltage. Once the voltage exceeds the set threshold, it will automatically turn on the low-side MOSFET, thereby enabling power-off braking.

[0037] This approach is particularly suitable for application scenarios that are cost-sensitive and have relatively simple control requirements.

[0038] Alternatively, MCU control can be selected. The MCU can stably output a high-level signal, or use sensors to detect the motor's operating status and then dynamically switch the output based on the detected status information or voltage rise.

[0039] The MCU digital output pin connected to the BRAKE pin can directly determine whether the power-off braking function is enabled, realizing precise control of the power-off braking function and meeting the diverse control needs of motor braking function in complex systems.

[0040] If the user wishes to completely disable the power-off braking function, this can be achieved by directly shorting the BRAKE pin to ground. In this case, both the internal PVDD voltage detection and the power-off braking function are disabled, providing the system with high flexibility and configurability.

[0041] In normal operating mode, nSLEEP is set to high level. At this time, M1 is turned on, the BRAKE potential is forcibly pulled low, the power-off braking function is disabled, and the motor can run normally.

[0042] When entering sleep mode, nSLEEP is set to low level, M1 is turned off, and the BRAKE potential is controlled by the PVDD voltage and the MCU control signal.

[0043] If the BRAKE pin is left floating and the PVDD voltage exceeds a certain threshold, the BRAKE potential will be pulled up by the voltage regulation of Zener diodes Z1, Z2, and Z3, which will increase the gate control voltage of the low-side MOSFET M2, activate the power-off braking circuit, and put the motor into braking mode.

[0044] If the BRAKE pin is connected to an external MCU, the MCU can force the BRAKE potential to rise by outputting a high-level signal. This will also increase the gate control voltage of the low-side MOSFET M2, thus activating the power-off braking circuit and achieving braking control of the motor.

[0045] If the phase voltage SHx is lower than the reference voltage VPOB_VDS when the power-off braking circuit is on, the comparator outputs a low-level signal. The level conversion output is controlled by the signal at its input terminal, the low-side MOSFET remains on, and braking continues.

[0046] When the phase voltage SHx is higher than the reference voltage VPOB_VDS, the comparator outputs a high-level signal. After the signal is filtered out by the R3 and C1 filter circuit, the control level conversion circuit forces the output voltage to be low, thereby disabling the power-off braking function. This effectively avoids power supply short-circuit faults caused by high current events and ensures the safe and stable operation of the system.

[0047] In summary, this utility model provides a flexible, reliable, and safe power-off braking protection circuit that can effectively control the braking of a DC motor under different operating modes and take timely protective measures in abnormal situations. It has high practical value and promotional significance.

[0048] Example 2

[0049] This embodiment takes a typical motor control system as an example to further illustrate the technical solution of this utility model. The motor control system adopts a power failure braking protection circuit of this utility model.

[0050] The power failure braking protection circuit includes a power supply voltage detection module. The input terminal of the power supply voltage detection module is connected to the power supply, which outputs a power supply voltage PVDD. The power supply is connected to a voltage regulator module.

[0051] The voltage regulator module is used to generate the first internal supply voltage V5INT and the second internal supply voltage VPOB.

[0052] The input terminal of the power supply voltage detection module is connected to the power supply voltage PVDD, and the output terminal is connected to the power-off braking enable control terminal. It is used to detect the PVDD voltage. When the voltage exceeds a certain threshold, the power-off braking enable is set high, and the power-off braking mode is activated.

[0053] like Figure 2 As shown, the power supply voltage detection module includes a MOSFET M1. The drain of the MOSFET M1 is connected to the first end of a resistor R2. The second end of the resistor R2 is connected to a level conversion module. The gate of the MOSFET M1 is connected to a second enable control terminal. The second enable control terminal receives a second control signal nSLEEP generated internally by the power-off braking protection circuit.

[0054] The source of MOSFET M1 is connected to the first terminal of resistor R1 and the anode of Zener diode Z4. The second terminal of resistor R1 and the cathode of Zener diode Z4 are both connected to the input terminal of the level conversion module. The source of MOSFET M1 is connected to the digital ground line. The power supply voltage detection module can detect the power supply voltage PVDD and control the potential of the first control signal BREAK.

[0055] The power supply voltage detection module also includes a voltage regulation unit, which is composed of three Zener diodes Z1, Z2 and Z3 connected in series. The cathode of Zener diode Z1 is connected to the power supply, and the anode of Zener diode Z3 is connected to the input terminal of the level conversion module.

[0056] The power supply voltage detection module is connected to a level conversion module. The input terminal of the level conversion module is connected to the first control signal BREAK, and the output terminal of the level conversion module is connected to the gate control voltage of the low-side MOSFET M2 of the DC motor.

[0057] The input terminal of the level conversion module is connected to the power-off braking enable control terminal, and the output terminal is connected to the gate control voltage GLx of the low-side MOSFET. It can raise the input signal with the first internal power supply voltage V5INT as the power supply voltage to the output signal with the second internal power supply voltage VPOB as the power supply voltage, thereby controlling the opening and closing of the low-side MOSFET.

[0058] The level conversion module is connected to the phase voltage detection module through the filter module. The phase voltage detection module is connected to the phase voltage of the DC motor. The level conversion module outputs the gate control voltage GLx to the DC motor.

[0059] The input of the filtering module is connected to the phase voltage detection module, and the output is connected to the level conversion module to filter out the glitches in the phase voltage detection module.

[0060] In this embodiment, the filtering module is an RC filter circuit. The first end of the filtering module is connected to the output end of the phase voltage detection module, and the second end of the filtering module is connected to the input end of the level conversion module. The filtering module can filter the output signal of the phase voltage detection module to eliminate the influence of glitches on subsequent circuits.

[0061] Specifically, the filtering module includes a resistor R3. The first end of the resistor R3 is connected to the output of the phase voltage detection module, and the other end of the resistor R3 is connected to a capacitor C1 and the input of the level conversion module. The other end of the capacitor C1 is connected to the digital ground line.

[0062] The input of the phase voltage detection module is connected to the phase voltage SHx and the reference voltage VPOB_VDS. The output signal of the output terminal is controlled by a filtering module with an analog RC filter to control the gate control voltage of the low-side MOSFET M2 of the DC motor. This voltage is used to disable the low-side MOSFET when a large current event is detected during braking.

[0063] Since the normal overcurrent protection circuit is disabled in low-power sleep mode, such a circuit is needed to prevent power supply short circuits caused by high current events.

[0064] Preferably, the phase voltage detection module includes a comparator. The non-inverting input of the comparator is connected to the drain of the low-side MOSFET M2 and the source of the low-side MOSFET M3 of the DC motor, thereby obtaining the phase voltage of the low-side MOSFET of the DC motor. The inverting input of the comparator is connected to a voltage regulator module, thereby obtaining a reference voltage VPOB_VDS based on the second internal supply voltage VPOB. The output of the comparator is connected to the input of a level conversion module through a filter module. The output control terminal of the level conversion module is connected to the gate of the low-side MOSFET M2 of the DC motor, and outputs a gate control voltage to M2, thereby disabling the power-off braking function. Specifically, when the phase voltage SHx is higher than the reference voltage VPOB_VDS, the comparator outputs a high level. After passing through the filter circuit, the level conversion circuit is controlled to force the level conversion output voltage to be low, thus disabling the power-off braking function.

[0065] The output of the power supply voltage detection module is connected to the first control signal BREAK.

[0066] The power-off braking function is enabled via the BRAKE pin, which can be pulled high in several different ways. The BRAKE pin can remain high in low-power sleep mode, or it can be set high as the supply voltage rises. Several control methods for the BRAKE pin are described in detail below.

[0067] The first type is internal overpressure monitoring.

[0068] By disconnecting the BRAKE pin and relying on the power supply voltage detection module, the power-off braking function can be set to be automatically enabled in low-power sleep mode.

[0069] By default, the BRAKE pin is left floating. The power-off braking function is enabled by the power supply voltage detection module. The power supply voltage detection module will detect the voltage of the PVDD pin and turn on the low-side MOSFET when the voltage exceeds the voltage threshold to enable power-off braking.

[0070] The second method is MCU control.

[0071] The MCU can output a stable high level, or it can use sensors to detect the motor's operating status or switch the output based on voltage rise.

[0072] The MCU digital output connected to the BRAKE pin can directly control whether the power-off braking function is enabled.

[0073] The third option is to disable it.

[0074] By shorting the BRAKE pin directly to ground, the internal PVDD voltage detection and power-off braking function can be disabled.

[0075] In this embodiment, the power supply is DC 12V, and the voltage regulator module outputs a first internal power supply voltage V5INT of 5V and a second internal power supply voltage VPOB of 3.3V.

[0076] The power supply voltage detection module is set to a threshold of 10V. When the PVDD voltage exceeds 10V, the power-off braking enable signal is set high.

[0077] The reference voltage VPOB_VDS of the phase voltage detection module is set to 350mV.

[0078] In normal operating mode, the motor runs at rated speed. At this time, nSLEEP is high, M1 is turned on, the BRAKE pin is pulled low, and the power-off braking function is disabled.

[0079] When the system needs to enter sleep mode, nSLEEP goes low and M1 is turned off.

[0080] Suppose that the BRAKE pin is floating at this time, and due to some reason, such as an unexpected connection of external power, the PVDD voltage rises to 12V, exceeding the set threshold of 10V, which will trigger the power-off braking function.

[0081] At this time, the power supply voltage detection module is activated, the BRAKE potential is pulled high, and the level conversion module raises the V5INT signal to the VPOB level, causing the gate control voltage of the low-side MOSFET M2 to increase, M2 is turned on, and the motor enters the braking state.

[0082] At this time, the phase voltage detection module monitors the motor phase voltage in real time. If the motor generates a back electromotive force due to external force during braking, causing the phase voltage SHx to be higher than the reference voltage by 2V, the comparator outputs a high level. After being filtered by R3 and C1, the control level conversion module sets the output voltage low, M2 is turned off, and the power-off braking function is disabled to avoid damage to the system from high current.

[0083] If the system needs to resume normal operation at this time, the MCU can output a high level to the BRAKE pin to force the BRAKE potential to rise and restart the power-off braking function, or adjust the system state through other control logic to ensure the safe operation of the motor.

Claims

1. A de-energized brake protection circuit, characterized in that, The power supply voltage detection module is connected with a power supply, and the power supply is connected with a voltage stabilizing module.

2. A de-energized brake protection circuit according to claim 1, characterized in that The MOS tube M1 is connected with the first end of the resistor R2, and the second end of the resistor R2 is connected with the level conversion module.

3. A de-energized brake protection circuit according to claim 2, characterized in that The source of the MOS tube M1 is connected with the first end of the resistor R1 and the anode of the Zener diode Z4.

4. A de-energized brake protection circuit according to any one of claims 1 or 2 or 3, characterized in that, The voltage stabilizing unit is connected with the power supply, and the anode of the Zener diode Z3 is connected with the input end of the level conversion module.

5. A de-energized brake protection circuit according to claim 1, characterized in that, The input end of the phase voltage detection module inputs the phase voltage of the DC motor low-side MOS tube and the reference voltage, and the output end of the phase voltage detection module is connected with the input end of the level conversion module through the filter module.

6. A de-energized brake protection circuit according to claim 1 or 5, characterized in that, The comparator is connected with the drain of the DC motor low-side MOS tube M2 and the source of the MOS tube M3, and the output end of the comparator is connected with the input end of the level conversion module through the filter module.

7. A de-energized brake protection circuit according to claim 1, characterized in that The filter module is an RC filter circuit, the first end of the filter module is connected with the output end of the phase voltage detection module, and the second end of the filter module is connected with the input end of the level conversion module.

8. A de-energized brake protection circuit according to claim 1 or 7, characterized in that, The filter module includes the resistor R3, the first end of the resistor R3 is connected with the output end of the phase voltage detection module, the second end of the resistor R3 is connected with the first end of the capacitor C1 and the input end of the level conversion module, and the second end of the capacitor C1 is connected with the digital ground.

9. The de-energized brake protection circuit of claim 1, wherein, The input end of the level conversion module is connected with the first enable control end, and the output control end of the level conversion module is connected with the gate of the DC motor low-side MOS tube M2.

10. The de-energized brake protection circuit of claim 1 or 5, wherein, The input end of the voltage stabilizing module is connected with the power supply, the voltage stabilizing module outputs the first internal power supply voltage and the second internal power supply voltage, the first internal power supply voltage generates the reference voltage, and the second internal power supply voltage supplies power for the phase voltage detection module.

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