A master unit power supply switching circuit and a control method thereof

Abstract

The application discloses a master control unit power supply switching circuit and a control method thereof, which is used for controlling the master control unit to switch the power supply to a standby power after power failure; the master control unit power supply switching circuit comprises a MOS transistor, a lithium battery and a charging circuit; when the battery voltage is detected to be lower than a certain value, the MOS transistor is controlled to be turned on to charge when the voltage is normally lower than 3.5V; when the voltage is higher than 4.2V, the battery is ensured to be in a saturated and full state, the battery charging function can be terminated after a period of time, the MOS transistor is controlled to be turned off to stop charging; the master control unit power supply switching circuit adopts two MOS transistors to be connected to form interconnection, and the output current cannot flow back to the lithium battery end. The application can effectively solve the problem that the master control unit can be normally powered when the system equipment suddenly loses power or fails to power, the process of real-time data acquisition and storage is handled, and the data can be transmitted to the upper control center platform through communication.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a main control unit power supply switching circuit and its control method. Background Technology

[0002] With the continuous development of power electronics technology, on the one hand, the requirements for the real-time performance and storability of critical data acquisition from system equipment are becoming increasingly stringent. The ability to acquire and re-analyze key data provides an important basis for further improving system stability. On the other hand, the protection requirements for system equipment, especially for vulnerable core components such as IGBTs and SiC, are becoming increasingly demanding. These real-time data acquisition, storage, and timely response protection mechanisms for devices are particularly important before and after sudden power outages or equipment malfunctions. During operation, a power outage may involve changes in various external and internal parameters, as well as the real-time status of the operating control drive. Therefore, it is difficult to develop targeted response mechanisms for equipment protection, or even increasing the cost of protection design may not be sufficient to perfectly protect all types of equipment. Currently, to address these needs, more and more manufacturers are adding backup power supplies to power the main control unit. After a power outage, the system immediately switches to the backup power supply to continue powering the main control unit, ensuring its normal operation, real-time data acquisition and storage, and simultaneously detecting a power outage. The main control unit then issues a protection mechanism, shutting down key input and output signals of relevant equipment to prevent abnormal damage to equipment and critical components. There are generally two options for adding backup power. One is to directly use a backup power supply UPS, which is an uninterruptible power supply containing an energy storage device, to provide uninterrupted power to some equipment with high power stability requirements. The other is to place a button battery in the main control processor, which can save relevant important parameters and data information after the system equipment loses power.

[0003] While the above two solutions are feasible, they have the following drawbacks: 1) UPS power supplies are relatively large, limiting space for equipment modules; even small-capacity UPS power supplies are expensive; UPS power supplies have long response times, making them unsuitable for main control equipment that is sensitive to charging and discharging. 2) Using button batteries can store relevant real-time data, but they are difficult to maintain, cannot confirm whether the power supply is normal, and lack detection methods; furthermore, they can only process data and cannot ensure the normal communication function of the main control unit, preventing continued communication with the host computer for data exchange, and also losing the main control function, leading to random states in the main control and an inability to respond to timely protective measures for the equipment. Summary of the Invention

[0004] 1. The technical problem to be solved:

[0005] To address the aforementioned technical problems, this invention provides a main control unit power supply switching circuit. This circuit enables the main control unit to switch power supplies in nanosecond-level hardware response after a power outage, ensuring a stable and normal power supply to the main control unit. This allows for real-time data acquisition and storage, normal communication, and timely handling of response measures after system equipment power failure. This circuit effectively protects against damage and malfunctions of equipment and critical components, and also provides timely protection against abnormal operating conditions of other external load devices, further improving the operational reliability of the entire circuit network.

[0006] 2. Technical Solution:

[0007] A main control unit power supply switching circuit is used to switch the power supply of the main control unit to a backup power supply after the main control unit is powered off. The circuit is characterized by comprising a main control unit power supply switching circuit, a lithium battery and its charging circuit; the main control unit power supply switching circuit is connected to the lithium battery to control whether the lithium battery is used to power the main control unit.

[0008] The lithium battery and its charging circuit include a control circuit and a charging circuit; wherein the trigger signal CL_BT of the control circuit is issued by the corresponding pin of the control chip of the main control unit; the trigger signal CL_BT is connected to the current limiting resistor R5 through the circuit and then connected to the base of the transistor Q2; the emitter of the transistor Q2 is grounded to AGND, and the collector is connected to the gate of the control MOS transistor Q1; A resistor R1 is connected in parallel between the source and gate of MOSFET Q1; the source of MOSFET Q1 is connected to the negative terminal of diode D1, and the positive terminal of diode D1 is connected to the power supply; the drain of MOSFET Q1 is connected to the power supply pin of charging chip U1; the power supply pin of charging chip U1 in the charging circuit is connected to ground after being connected in series with bypass filter capacitor C1; the chip charging current control pin of charging chip U1 is connected to ground after being connected in series with resistor R2; the charging output pin of charging chip U1 is connected to lithium battery BT1 for charging management; a bypass filter capacitor C2 is connected in parallel between the positive and negative terminals of lithium battery BT1; the positive terminal of lithium battery BT1 is connected to resistor R3 and then to resistor R4, and finally grounded to AGND; resistors R3 and R4 form a voltage divider, and the circuit connected between them forms a net point AD_BT, which is connected to the sampling port of the control chip of the main control unit;

[0009] The drain of MOSFET Q3 in the power supply switching circuit of the main control unit is connected to the output voltage of lithium battery BT1; the source of MOSFET Q3 is connected to the source of MOSFET Q4, and Q3 and Q4 are connected in a butt joint configuration; that is, the gates of Q3 and Q4 are shorted and then connected in series with resistor R6 and grounded; the shorted gates of Q3 and Q4 are connected to the negative terminal of diode D3, and the positive terminal of D3 is connected to the power supply; the drain output of MOSFET Q4 is connected to the power supply MVCC of the main control unit; the drain of MOSFET Q4 is connected to the negative terminal of diode D2, and the positive terminal of diode D2 is connected to the power supply.

[0010] Furthermore, the charging chip U1 is model number BL4054.

[0011] Furthermore, the power supply is 5.3V.

[0012] A switching method for a main control unit power supply switching circuit, comprising:

[0013] Lithium battery charging and discharging control: When the sampling voltage of the sampling port of the main control unit's control chip drops to the preset voltage value, the control signal CL_BT sent by the main control unit's control chip is at a high level, the MOSFET is turned on, and the lithium battery BT1 is charged; when the sampling voltage reaches the preset value, after charging continues for a period of time and the voltage value does not change, the control signal CL_BT becomes low level, the MOSFET is turned off, and the lithium battery BT1 stops charging.

[0014] Main control unit power supply switching control: When the power supply is present, diode D2 is turned on, the gate electrodes of MOSFETs Q3 and Q4 are at a high level, Q4 is turned off, and the circuit is not connected. Therefore, in this state, the power supply participates in the power supply, and the lithium battery power supply is in the off state. When the power supply suddenly loses power or fails to supply power, diode D2 is turned off, the gate electrodes of MOSFETs Q3 and Q4 are at a low level, and both Q3 and Q4 are in the on state. At this time, the lithium battery participates in the power supply, realizing the rapid power supply switching of the hardware circuit and continuing to maintain the normal power supply of the main control unit.

[0015] 3. Beneficial effects:

[0016] (1) The lithium battery charging circuit of this solution not only ensures the normal voltage storage of the lithium battery and prevents it from failing due to prolonged consumption, but also ensures that the lithium battery is not kept in a charging state for a long time. Overcharging and over-discharging will damage the lithium battery and reduce its service life. The charging on and off are controlled by a MOSFET; the charging chip BL4054 is used to charge the lithium battery while protecting it, thereby extending the service life of the lithium battery. Moreover, the charging circuit of this solution is very small in size and has a very low cost, making it very suitable for the charging control circuit of the main control unit.

[0017] (2) The main control unit power supply switching circuit in this scheme has a simple structure. It uses two P-channel MOSFETs connected in parallel to form an interconnect, ensuring that the output current cannot flow back to the lithium battery. This circuit can also use a single diode connected in parallel with the main control unit power supply to achieve the function of power supply switching. However, the forward voltage drop of the diode is generally relatively high, around 0.7V. For the voltage of lithium battery power supply, this greatly reduces the efficiency of lithium battery use and reduces working time. The on-resistance of the MOSFET is generally within 100 milliohms, and the voltage loss is very low, almost negligible. Using a MOSFET also has the reverse current protection function of a diode, and can also reduce losses, greatly improving the efficiency of lithium battery power supply. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of a lithium battery charging circuit in a specific embodiment;

[0019] Figure 2 This is a circuit diagram of the main control unit switching circuit in a specific embodiment. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings.

[0021] As attached Figure 1 , 2 As shown, a main control unit power supply switching circuit is used to switch between the main power supply and the backup power supply after the main control unit of the system equipment is powered off; it includes a main control unit power supply switching circuit, a lithium battery and its charging circuit; the main control unit power supply switching circuit is connected to the lithium battery and controls whether the lithium battery is used to supply power to the system equipment. Specific implementation examples:

[0023] As attached Figure 1 , 2 This document provides a detailed circuit diagram and parameters for this embodiment. The main control unit is powered by 5.3V, which is the most common voltage for control units. In the system, most devices use 24V input power, so the design converts the power to 5V for communication and control. A lithium battery (BTV) serves as the backup power supply. When the 5.3V power supply fails, the BTV immediately takes over powering the main control unit.

[0024] like Figure 1 The diagram shows a lithium battery charging circuit, which consists of a control circuit and a charging circuit. The control process is as follows:

[0025] 1) In the circuit, the net point CL_BT is the trigger signal for the charging control circuit. It can be issued by the control chip pin of the main control unit and connected to the base of transistor Q2 through the current-limiting resistor R5. The emitter of Q2 is grounded to AGND, and the collector is connected to the gate of the control MOSFET Q1. When the control signal CL_BT is high, transistor Q2 is turned on, and the collector is pulled low. When CL_BT is low, transistor Q2 is turned off, and the collector is pulled up to a high level through the connecting resistor R1. R1 is connected to the negative terminal of the anti-reverse diode D1. The positive terminal of D1 is connected to the 5.3V power supply. Through diode D1, the voltage drop of D1 is approximately 0.3V, so the voltage across resistor R1 is 5V. The negative terminal of D1 is also connected to the source and gate of the MOSFET. The voltage change between the source and gate controls the MOSFET's turn-on and turn-off. When the voltage is 0V, the MOSFET is off; when the voltage is 5V, the MOSFET is on. The drain of the MOSFET is connected to the power supply pin of the charging chip in the charging circuit. In summary, when the control signal CL_BT is high, the MOSFET is turned on, enabling the charging function; when the control signal CL_BT is low, the MOSFET is turned off, terminating the charging function.

[0026] 2) The charging circuit uses battery management chip U1, model BL4054. Pin 4 of U1 is the power supply pin, connected to the drain of MOSFET Q1. C1 is the bypass filter capacitor for management chip U1. Pin 5 of U1 is connected to R2 and then grounded. Pin 5 is the chip's charging current control pin. The calculated charging current is IBAT = (VPROG / R2)*1000 = (1V / 1.65K)*1000 = 600mA. Therefore, when the charging control resistor R2 is 1.65, the charging current to the lithium battery is 600mA. Pin 1 of U1 is left floating; this pin mainly serves as a switch output for charging status and can be left unconnected. Pin 2 of U1 is the power ground pin, connected to AGND. Pin 3 of U1 is the charging output pin, connected to lithium battery BT1 for charging management. C2 is the bypass filter capacitor for lithium battery BT1. The positive terminal of BT1 is connected to resistor R3, then to R4, and finally grounded to AGND. Resistors R3 and R4 form a voltage divider connected to the net point AD_BT. AD_BT is connected to the sampling port of the main control unit's control chip. The resistance values ​​of R3 and R4 should be chosen to be as large as possible within the allowable sampling current to reduce battery wear. The voltage divider value must not exceed the maximum sampling voltage of the main control unit's control chip. When the voltage drops to a certain value, the charging function is activated, and the net point CL_BT is set high. When the lithium battery is fully charged, the net point CL_BT is pulled low, and the charging function is deactivated.

[0027] like Figure 2 The circuit shown is the power supply switching circuit for the main control unit, which consists of MOSFET circuits.

[0028] 1) In the circuit, the net point BTV is the power supply voltage of the lithium battery. The net point BTV is connected to the drain of MOSFET Q3, and the source of Q3 is connected to the source of MOSFET Q4. The two transistors are connected in a butt joint configuration. Their gates are shorted and grounded through resistor R6. MOSFET D3 is connected to the 5.3V power supply through reverse connection protection. The presence of the 5.3V mains power supply controls the gate of the MOSFET. The drain output of Q4 is connected to the net point MVCC, which is the power supply of the main control unit.

[0029] 2) In the circuit, diode D2 (anti-reverse diode) and MOSFETs Q3 and Q4 form a dual-power supply switching circuit. When the main power supply 5.3V is present, diode D2 conducts, the gate electrodes of MOSFETs Q3 and Q4 are at a high level, Q4 is cut off, and the circuit is not conducting. Therefore, in this state, the main power supply 5.3V participates in power supply, and the lithium battery power supply is cut off. When the main power supply 5.3V suddenly fails or is interrupted by a fault, diode D2 is cut off, the gate electrodes of MOSFETs Q3 and Q4 are at a low level, and both Q3 and Q4 are conducting. Therefore, in this state, the lithium battery participates in power supply, forming a fast power switching of the hardware circuit and continuing to maintain the normal power supply of the main control power supply.

[0030] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A control method for a main control unit power supply switching circuit, characterized in that: The main control unit power supply switching circuit is used to switch the power supply of the main control unit to the backup power supply after the main control unit is powered off; it includes the main control unit power supply switching circuit, the lithium battery and its charging circuit; the main control unit power supply switching circuit is connected to the lithium battery to control whether the lithium battery is used to power the main control unit. The lithium battery and its charging circuit include a control circuit and a charging circuit. The trigger signal CL_BT of the control circuit is issued by the corresponding pin of the control chip in the main control unit. The trigger signal CL_BT is connected to the current-limiting resistor R5 and then to the base of transistor Q2. The emitter of transistor Q2 is grounded to AGND, and its collector is connected to the gate of the control MOSFET Q1. A resistor R1 is connected in parallel between the source and gate of MOSFET Q1. The source of MOSFET Q1 is connected to the cathode of diode D1, and the anode of diode D1 is connected to the power supply. The drain of MOSFET Q1 is connected to the power supply of the charging chip U1. Pins; the power supply pin of the charging chip U1 in the charging circuit is connected to ground after being connected in series with a bypass filter capacitor C1; the chip charging current control pin of the charging chip U1 is connected to ground after being connected in series with a resistor R2; the charging output pin of the charging chip U1 is connected to the lithium battery BT1 for charging management; a bypass filter capacitor C2 is connected in parallel between the positive and negative terminals of the lithium battery BT1; the positive terminal of the lithium battery BT1 is connected to a resistor R3 and then to a resistor R4, and finally grounded to AGND; resistors R3 and R4 form a voltage divider, and the circuit connected between them forms a net point AD_BT, which is connected to the sampling port of the control chip of the main control unit; The drain of MOSFET Q3 in the power supply switching circuit of the main control unit is connected to the output voltage of lithium battery BT1; the source of MOSFET Q3 is connected to the source of MOSFET Q4, and MOSFETs Q3 and Q4 are connected in a butt joint configuration; that is, the gates of MOSFETs Q3 and Q4 are shorted and then connected in series with resistor R6 and grounded; the shorted gates of MOSFETs Q3 and Q4 are connected to the negative terminal of diode D3, and the positive terminal of diode D3 is connected to the power supply; the drain output of MOSFET Q4 is connected to the power supply MVCC of the main control unit; the drain of MOSFET Q4 is connected to the negative terminal of diode D2, and the positive terminal of diode D2 is connected to the power supply. The charging chip U1 is model BL4054; The power supply is 5.3V; Control methods include: Lithium battery charging and discharging control: When the sampling voltage of the sampling port of the main control unit's control chip drops to the preset voltage value, the control signal CL_BT sent by the main control unit's control chip is at a high level, the MOSFET is turned on, and the lithium battery BT1 is charged; when the sampling voltage reaches the preset value, after charging continues for a period of time and the voltage value does not change, the control signal CL_BT becomes low level, the MOSFET is turned off, and the lithium battery BT1 stops charging. Main control unit power supply switching control: When the power supply is present, diode D2 is turned on, the gate electrodes of MOSFETs Q3 and Q4 are at a high level, MOSFET Q4 is turned off, and the circuit is not connected. Therefore, in this state, the power supply participates in the power supply, and the lithium battery power supply is in the off state. When the power supply suddenly loses power or fails to supply power, diode D2 is turned off, the gate electrodes of MOSFETs Q3 and Q4 are at a low level, and MOSFETs Q3 and Q4 are both turned on. At this time, the lithium battery participates in the power supply, realizing the rapid power switching of the hardware circuit and continuing to maintain the normal power supply of the main control unit.

Images