Pre-charging system and method

Abstract

The present disclosure provides a pre-charge system and a pre-charge method for controlling the pre-charge system. The pre-charge system includes a load circuit and a pre-charge circuit. The load circuit includes an input terminal, an input switch and a bus capacitor. The pre-charge circuit is connected in parallel to both ends of the input switch and includes a pre-charge resistor and a pre-charge switch connected in series. The pre-charge method includes: when the load circuit is in a pre-charge mode, controlling the input switch to be in an off state, and controlling the pre-charge switch to be switched between an on state and an off state multiple times, and when the pre-charge switch is in the on state, the power consumption of the pre-charge resistor is greater than a power threshold and less than or equal to a limit power, and when the pre-charge switch is in the off state, the power consumption of the pre-charge resistor is 0; and when the load circuit is in a working mode, controlling the input switch to be in an on state.

Description

Technical Field

[0001] This disclosure relates to the field of power electronics technology, and in particular to a pre-charging system and method. Background Technology

[0002] To prevent overcurrent in the bus capacitors during startup, a pre-charge circuit can be used to pre-charge them. This pre-charge circuit typically includes a pre-charge switch and a pre-charge resistor. In existing pre-charge methods, such as... Figure 1 As shown, when pre-charging the bus capacitor, the pre-charging switch is kept in the on state to continuously charge the bus capacitor until the bus voltage on the bus capacitor reaches a preset value or the pre-charging switch has been on for a preset time, at which point the pre-charging switch is turned off to end the pre-charging process.

[0003] However, during the pre-charging process, because the pre-charging switch remains in the on state, the pre-charging resistor will continue to work and consume power. Furthermore, as... Figure 2 As shown, since the overload capacity of a resistor is inversely proportional to its load-carrying time, the overload capacity of the pre-charge resistor will gradually decrease as the working time of the pre-charge resistor increases, that is, the overload power of the pre-charge resistor will gradually decrease.

[0004] Based on the existing pre-charging methods and resistor characteristics, existing pre-charging circuits require the use of pre-charging resistors with large rated power, which not only restricts the type of pre-charging resistor but also increases its size and cost.

[0005] Therefore, developing a pre-charging system and method that can improve upon the aforementioned existing technologies is an urgent need. Summary of the Invention

[0006] The purpose of this disclosure is to provide a pre-charging system and method that controls a pre-charging switch to switch between an on and off state multiple times, causing the pre-charging resistor to operate intermittently at power consumption close to its limit. Therefore, a pre-charging resistor with a lower rated power can be used, reducing its size and cost, while also enabling the pre-charging system to complete pre-charging more quickly.

[0007] To achieve the above objectives, this disclosure provides a pre-charging method for controlling a pre-charging system, wherein the pre-charging system includes a load circuit and a pre-charging circuit. The load circuit includes an input terminal, an input switch, and a bus capacitor. The input terminal receives an input current, and the input switch is coupled between the input terminal and the bus capacitor. The pre-charging circuit is connected in parallel across the input switch and includes a pre-charging resistor and a pre-charging switch connected in series. The pre-charging method includes: when the load circuit is in a pre-charging mode, controlling the input switch to be in a closed state, and controlling the pre-charging switch to switch between a closed state and a conducting state multiple times, wherein when the pre-charging switch is in a conducting state, the power consumption of the pre-charging resistor is greater than a power threshold and less than or equal to the limiting power of the pre-charging resistor, the input current flows through the pre-charging resistor to charge the bus capacitor, and the bus voltage on the bus capacitor rises; when the pre-charging switch is in a closed state, the power consumption of the pre-charging resistor is 0, and the bus capacitor stops charging; and when the load circuit is in an operating mode, controlling the input switch to be in a conducting state.

[0008] To achieve the above objectives, this disclosure also provides a pre-charging system, comprising a load circuit, a pre-charging circuit, and a control circuit. The load circuit includes an input terminal, an input switch, and a bus capacitor. The input terminal receives an input current, and the input switch is coupled between the input terminal and the bus capacitor. The pre-charging circuit is connected in parallel across the input switch and includes a pre-charging resistor and a pre-charging switch connected in series. The control circuit is configured to execute the pre-charging method of this disclosure.

[0009] This disclosure provides a pre-charging system and method. By controlling a pre-charging switch to switch between an on and off state, a pre-charging resistor intermittently operates at a power consumption level greater than a power threshold but less than or equal to the maximum power limit, thereby maintaining the power consumption of the pre-charging resistor at a level close to the maximum power limit. Therefore, the pre-charging system can use a pre-charging resistor with a lower rated power, reducing the size and cost of the pre-charging resistor, while also enabling the pre-charging system to complete pre-charging more quickly. Furthermore, by intermittently dissipating heat from the pre-charging resistor, the overall system reliability can be improved. Attached Figure Description

[0010] Figure 1 The waveform of the bus capacitor and the switching timing of the precharge switch are shown when using the existing precharge method.

[0011] Figure 2 This is a schematic diagram showing the relationship between the overload power of a resistor and its operating time.

[0012] Figure 3 This is a schematic diagram of the circuit structure of a pre-charging system according to a preferred embodiment of the present disclosure.

[0013] Figure 4 for Figure 3The diagram shows the drive signal of the pre-charge switch and the waveform of the bus voltage.

[0014] Figure 5 for Figure 3 A schematic diagram showing the relationship between the power consumption of the pre-charge resistor and the operating time.

[0015] Explanation of reference numerals in the attached figures:

[0016] 1: Pre-charging system

[0017] 10: Pre-charge circuit

[0018] 11: Pre-charge resistor

[0019] 12: Pre-charge switch

[0020] 20: Load circuit

[0021] 21: Input end

[0022] 22: Input switch

[0023] 23: Rectifier circuit

[0024] Cbus: Bus capacitor

[0025] 30: Control circuit

[0026] S12: Drive signal

[0027] Vbus: Bus voltage

[0028] t0, t1, t2, t3, t4, t5: Time points

[0029] P1: Limiting power

[0030] P2: Power threshold

[0031] A, B: Time period Detailed Implementation

[0032] Some typical embodiments embodying the features and advantages of this disclosure will be described in detail in the following description. It should be understood that this disclosure can be varied in different implementations without departing from the scope of this disclosure, and the descriptions and illustrations therein are for illustrative purposes only and not intended to limit this disclosure.

[0033] Figure 3 This is a schematic diagram of the circuit structure of a pre-charging system according to a preferred embodiment of this disclosure. Figure 3As shown, the pre-charging system 1 includes a pre-charging circuit 10 and a load circuit 20. The load circuit 20 includes an input terminal 21, an input switch 22, and a bus capacitor Cbus. The input terminal 21 receives the input current, and the input switch 22 is coupled between the input terminal 21 and the bus capacitor Cbus. The pre-charging circuit 10 is connected in parallel across the input switch 22 and includes a pre-charging resistor 11 and a pre-charging switch 12 connected in series. The input current can be DC, which can be used to charge the bus capacitor Cbus. In some embodiments, when the input current is AC, i.e., AC is connected to the input terminal 21, the load circuit 20 further includes a rectifier circuit 23, which is coupled between the input switch 22 and the bus capacitor Cbus, for converting the AC to DC to charge the bus capacitor Cbus. Figure 3 The diagram illustrates a two-phase load circuit 20. In this embodiment, the load circuit 20 includes two input switches 22, and the pre-charging system 1 includes two pre-charging circuits 10, with each pre-charging circuit 10 connected in parallel to one of the two input switches 22. In practice, the number of phases in the load circuit 20 is not limited; it can be, for example, but is not limited to, single-phase, two-phase, or three-phase. When the number of phases in the load circuit 20 changes, the number of input switches 22 and pre-charging circuits 10 will also change accordingly. Furthermore, the pre-charging system 1 also includes a control circuit 30, which is electrically connected to the load circuit 20 and the pre-charging circuits 10 and is configured to control the operation of the pre-charging system 1. It should be noted that the pre-charging methods described subsequently in this disclosure are all executed by the control circuit 30 to control the operation of the pre-charging system 1.

[0034] The following is Figure 4 and Figure 5 The pre-charging method for controlling the pre-charging system 1 in this disclosure is illustrated by an example. Figure 4 In this context, S12 is the drive signal for the pre-charge switch 12, and Vbus is the bus voltage on the bus capacitor Cbus. For example... Figure 4 As shown, during the period from time t0 to t5, the load circuit 20 is in pre-charging mode, the control input switch 22 is in the off state, and the pre-charging switch 12 is controlled to switch between the on and off states multiple times. After time t5, the load circuit 20 is in operating mode, and the control input switch 22 is in the on state. Furthermore, when the load circuit 20 is in operating mode, the pre-charging switch 12 can be controlled to be in the off or on state. The specific operation of the pre-charging system 1 when the load circuit 20 is in pre-charging mode is described as follows.

[0035] At time t0, the pre-charge switch 12 is turned on. During the period from t0 to t1, the pre-charge switch 12 is in the on state, and the input current flows through the pre-charge resistor 11 to charge the bus capacitor Cbus, causing the bus voltage Vbus to rise. At time t1, the pre-charge switch 12 is turned off. During the period from t1 to t2, the pre-charge switch 12 is in the off state, the bus capacitor Cbus stops charging, and the bus voltage Vbus remains unchanged. In some embodiments, the bus voltage Vbus may also decrease slightly. Please refer to [link to relevant documentation]. Figure 4 and Figure 5 ,in Figure 5 This is a schematic diagram showing the relationship between the power consumption of the pre-charge resistor 11 and its operating time. Figure 5 The shaded area represents the actual operating region of the pre-charging resistor 11. At time t0, the power consumed by the pre-charging resistor 11 is equal to the limit power P1. In some embodiments, at time t0, the power consumed by the pre-charging resistor 11 can be any value that is less than the limit power P1 and greater than the power threshold P2. The limit power P1 is greater than the rated power of the pre-charging resistor 11. During the period from time t0 to t1, the pre-charging switch 12 is in the on state, causing the pre-charging resistor 11 to operate. As the operating time of the pre-charging resistor 11 increases, heat energy gradually accumulates in the pre-charging resistor 11, causing the maximum allowable power consumption of the pre-charging resistor 11 to gradually decrease and approach the power threshold P2. It should be noted that during the period from time t0 to t1, the power consumed by the pre-charging resistor 11 is always greater than the power threshold P2 and less than or equal to the limit power P1. During the period from time t1 to t2, the pre-charge switch 12 is in the off state, causing the pre-charge resistor 11 to stop working. The power consumption of the pre-charge resistor 11 is zero, so the pre-charge resistor 11 can dissipate heat, which causes the pre-charge resistor 11 to return to a state close to its initial state. The maximum allowable power consumption of the pre-charge resistor 11 gradually increases and approaches the limit power P1. In some embodiments, the maximum allowable power consumption of the pre-charge resistor 11 can be restored to be equal to the limit power P1.

[0036] Then, at time t2, the power consumed by the pre-charging resistor 11 is again equal to the limit power P1. In some embodiments, the power consumed by the pre-charging resistor 11 at this time may also be any value that is slightly less than the limit power P1 and greater than the power threshold P2. During the period from time t2 to t3, the pre-charging switch 12 is in the on state, the bus capacitor Cbus is charged, the bus voltage Vbus rises, and the pre-charging resistor 11 works again. As the working time of the pre-charging resistor 11 increases, the heat energy in the pre-charging resistor 11 gradually accumulates, causing the maximum allowable power consumption of the pre-charging resistor 11 to gradually decrease again and approach the power threshold P2. During the period from time t2 to t3, the power consumed by the pre-charging resistor 11 is greater than the power threshold P2 and less than or equal to the limit power P1. During the period from t3 to t4, the pre-charge switch 12 is in the off state, causing the pre-charge resistor 11 to stop working. At this time, the power consumption of the pre-charge resistor 11 is zero. The pre-charge resistor 11 dissipates heat and returns to a state close to its initial state. That is, the maximum allowable power consumption of the pre-charge resistor 11 gradually increases and approaches the limit power P1. In some embodiments, the maximum allowable power consumption of the pre-charge resistor 11 can be restored to be equal to the limit power P1. During the period from t3 to t4, the bus capacitor Cbus stops charging, and the bus voltage Vbus remains unchanged. In some embodiments, the bus voltage Vbus may also decrease slightly. During the period from t4 to t5, the pre-charge switch 12 is in the on state, the bus capacitor Cbus charges, and the bus voltage Vbus increases. Similarly, during the period from t4 to t5, the trend of the power consumption of the pre-charge resistor 11 is the same as that during the periods from t0 to t1 and from t2 to t3. It is understandable that, when the load circuit 20 is in pre-charge mode, the number of times the pre-charge switch 12 switches between the on and off states is not limited to, for example, the number of times the pre-charge system 1 switches between the on and off states is not limited to, for example, the number of times the pre-charge switch 12 switches between the on and off states. Figure 5 The number of times shown can be flexibly set according to the actual situation of the pre-charging system.

[0037] As described above, during time period A (i.e., between times t0 and t1, t2 and t3, and t4 and t5), the pre-charging resistor 11 operates and gradually accumulates heat, and the maximum allowable power consumption of the pre-charging resistor 11 gradually decreases and approaches the power threshold P2. During time period B (i.e., between times t1 and t2, t3 and t4, and after time t5), the pre-charging resistor 11 stops operating to dissipate heat, and the maximum allowable power consumption of the pre-charging resistor 11 gradually increases and approaches the limit power P1. In some embodiments, the maximum allowable power consumption of the pre-charging resistor 11 can recover to be equal to the limit power P1. Therefore, by controlling the pre-charging switch 12 to switch between the on and off states, the pre-charging resistor 11 intermittently operates with a power consumption greater than the power threshold P2 and less than or equal to the limit power P1, thereby maintaining the power consumption of the pre-charging resistor 11 at a level close to the limit power P1. The pre-charging method disclosed herein allows the pre-charging system 1 to use a pre-charging resistor 11 with a lower rated power, thereby reducing the size and cost of the pre-charging resistor 11 and enabling the pre-charging system 1 to complete pre-charging more quickly. Furthermore, by intermittently dissipating heat from the pre-charging resistor 11, the overall system reliability can be improved.

[0038] Furthermore, in the pre-charging method of this disclosure, it can be pre-set that when the load circuit 20 is in the pre-charging mode, it will automatically switch to the working mode if certain conditions are met. These specific conditions may include the load circuit 20 being in the pre-charging mode for a preset duration, the pre-charging switch 12 being switched a preset number of times, etc. However, this is not a limitation. The pre-charging method of this disclosure can also determine in real time whether to control the load circuit 20 to enter the working mode from the pre-charging mode. The criteria for determining whether to control the load circuit to enter the working mode from the pre-charging mode are not limited and can be determined according to the actual application environment and requirements. For example, in some embodiments, the bus voltage Vbus can be detected in real time (correspondingly, the pre-charging system 1 also includes a voltage sensor (not shown) electrically connected to the control circuit 30 and the bus capacitor Cbus). If the bus voltage Vbus is greater than or equal to a preset voltage, the load circuit 20 is controlled to enter the working mode from the pre-charging mode. In some embodiments, the cumulative on-time of the pre-charge switch 12 can be counted in real time. If the cumulative on-time is greater than or equal to a preset time, the load circuit 20 is controlled to enter the working mode from the pre-charge mode. In some embodiments, the difference between the bus voltage Vbus and the input voltage at the input terminal can be calculated in real time. If the difference is less than or equal to a preset value, the load circuit 20 is controlled to enter the working mode from the pre-charge mode. Furthermore, the timing and frequency of determining whether to control the load circuit 20 to enter the working mode from the pre-charge mode are not limited.

[0039] in addition, Figure 4 The specific durations of time periods A and B are not limited, as long as the power consumed by the pre-charging resistor 11 during operation is always greater than the power threshold P2 and less than or equal to the limit power P1. It should be noted that time periods A and B only represent the time periods when the pre-charging switch 12 is in the on and off states, respectively, and the duration of each time period A or B does not need to be the same.

[0040] Furthermore, in the pre-charging method of this disclosure, the durations of time periods A and B can be preset to simplify the switching control of the pre-charging switch 12. Of course, this is not a limitation; the pre-charging method of this disclosure can also adjust the durations of each time period A and B in real time. For example, when the load circuit 20 is in pre-charging mode, the pre-charging method further includes sensing the temperature of the pre-charging resistor 11 (correspondingly, the pre-charging system 1 also includes a temperature sensor (not shown) electrically connected to the control circuit 30 and the pre-charging circuit 10), and controlling the duration of the pre-charging switch 12 in the on and off states based on the temperature of the pre-charging resistor 11. The specific steps are as follows: First, the pre-charging switch 12 is controlled to be in the on state, and a first temperature of the pre-charging resistor 11 is sensed. Next, the first temperature of the pre-charging resistor 11 is compared with a first temperature threshold. When the first temperature of the pre-charging resistor 11 is greater than or equal to the first temperature threshold, the pre-charging switch 12 is controlled to switch from the on state to the off state. Next, the pre-charge switch 12 is kept in the off state, and a second temperature of the pre-charge resistor 11 is sensed. Then, the second temperature of the pre-charge resistor 11 is compared with a second temperature threshold. When the second temperature of the pre-charge resistor 11 is less than or equal to the second temperature threshold, the pre-charge switch 12 is controlled to switch from the off state to the on state. Finally, the aforementioned steps are repeated until the load circuit 20 enters the operating mode from the pre-charge mode. In some embodiments, the first temperature threshold is greater than the second temperature threshold.

[0041] In some embodiments, after the pre-charge switch 12 switches between the on state and the off state, the limit power P1 of the pre-charge resistor 11 can change dynamically, wherein the limit power P1 can be determined according to the type of the pre-charge resistor 11 and the duration of the pre-charge switch 12 in the on state each time.

[0042] In some embodiments, after the pre-charge switch 12 switches between the on state and the off state, the power threshold can be dynamically adjusted, wherein the power threshold can be determined based on the number of times the pre-charge switch 12 switches between the on state and the off state, the duration of each on state and off state of the pre-charge switch 12, the temperature coefficient of the pre-charge resistor 11, and the heat dissipation conditions.

[0043] In addition, in order to detect and shut down the system in a timely manner when a fault occurs in the pre-charging system 1, in some embodiments, when the load circuit 20 is in the pre-charging mode and the number of times the pre-charging switch 12 switches between the on and off states is equal to a preset number, if the bus voltage Vbus is less than a preset voltage and the difference between the bus voltage Vbus and the input voltage is greater than a preset value, then the load circuit 20 is controlled to enter the fault mode from the pre-charging mode and the pre-charging system 1 is controlled to shut down.

[0044] In summary, this disclosure provides a pre-charging system and method. By controlling the pre-charging switch to switch between an on and off state, the pre-charging resistor intermittently operates at a power consumption level greater than a power threshold but less than or equal to the maximum power limit, thereby maintaining the power consumption of the pre-charging resistor at a level close to the maximum power limit. Therefore, the pre-charging system can use a pre-charging resistor with a lower rated power, reducing the size and cost of the pre-charging resistor, while also enabling the pre-charging system to complete pre-charging faster. Furthermore, by intermittently dissipating heat from the pre-charging resistor, the overall system reliability can be improved.

[0045] It should be noted that the above are merely preferred embodiments for illustrating this disclosure, and this disclosure is not limited to the described embodiments. The scope of this disclosure is determined by the claims. Furthermore, this disclosure can be modified in various ways by those skilled in the art, but all such modifications will not depart from the protection sought by the claims.

Claims

1. A pre-charging method for controlling a pre-charging system, wherein the pre-charging system includes a load circuit and a pre-charging circuit, the load circuit including an input terminal, an input switch, and a bus capacitor, the input terminal receiving an input current, the input switch being coupled between the input terminal and the bus capacitor, the pre-charging circuit being connected in parallel across the input switch and including a pre-charging resistor and a pre-charging switch connected in series, the pre-charging method comprising: When the load circuit is in pre-charge mode, the input switch is controlled to be in the off state, and the pre-charge switch is controlled to switch between the on and off states multiple times. When the pre-charge switch is in the on state, the power consumption of the pre-charge resistor is greater than a power threshold and less than or equal to the limit power of the pre-charge resistor. The input current flows through the pre-charge resistor to charge the bus capacitor, and the bus voltage on the bus capacitor rises. When the pre-charge switch is in the off state, the power consumption of the pre-charge resistor is 0, and the bus capacitor stops charging. When the load circuit is in operating mode, the input switch is controlled to be in the ON state. The pre-charge switch can dynamically adjust the power threshold by switching between the on and off states. The power threshold is determined by the number of times the precharge switch switches between the on and off states, the duration of each on and off state of the precharge switch, the temperature coefficient of the precharge resistor, and the heat dissipation conditions.

2. The pre-charging method as claimed in claim 1, wherein when the load circuit is in the pre-charging mode, the pre-charging method further comprises: sensing the temperature of the pre-charging resistor, and controlling the duration of the pre-charging switch being in the on and off states based on the temperature of the pre-charging resistor.

3. The pre-charging method as described in claim 2, wherein controlling the duration of the pre-charging switch in the on and off states based on the temperature of the pre-charging resistor includes the following steps: S1: Control the pre-charge switch to be in the on state, and sense the first temperature of the pre-charge resistor; S2: Compare the first temperature of the pre-charge resistor with a first temperature threshold. When the first temperature of the pre-charge resistor is greater than or equal to the first temperature threshold, control the pre-charge switch to switch from the on state to the off state. S3: Keep the pre-charge switch in the off state and sense the second temperature of the pre-charge resistor; S4: Compare the second temperature of the pre-charge resistor with a second temperature threshold; when the second temperature of the pre-charge resistor is less than or equal to the second temperature threshold, control the pre-charge switch to switch from the off state to the on state; and S5: Repeat steps S1-S4 until the load circuit transitions from the pre-charge mode to the operating mode.

4. The pre-charging method as described in claim 3, wherein the first temperature threshold is greater than the second temperature threshold.

5. The pre-charging method as described in claim 1, wherein the maximum power can be dynamically changed after the pre-charging switch switches between an on state and an off state.

6. The pre-charging method as claimed in claim 5, wherein the limiting power is determined based on the type of the pre-charging resistor and the duration for which the pre-charging switch is in the on state each time.

7. The pre-charging method as described in claim 1, wherein when the load circuit is in the pre-charging mode, the bus voltage is detected in real time, and if the bus voltage is greater than or equal to a preset voltage, the load circuit is controlled to enter the working mode from the pre-charging mode.

8. The pre-charging method as described in claim 1, wherein when the load circuit is in the pre-charging mode, the cumulative conduction time of the pre-charging switch is counted in real time, and if the cumulative conduction time is greater than or equal to a preset time, the load circuit is controlled to enter the working mode from the pre-charging mode.

9. The pre-charging method as described in claim 1, wherein when the load circuit is in the pre-charging mode, the difference between the bus voltage and an input voltage is calculated in real time, and if the difference is less than or equal to a preset value, the load circuit is controlled to enter the working mode from the pre-charging mode.

10. The pre-charging method as described in claim 1, wherein when the load circuit is in the pre-charging mode and the number of times the pre-charging switch switches between the on and off states is equal to a preset number, if the bus voltage is less than a preset voltage and the difference between the bus voltage and an input voltage is greater than a preset value, then the load circuit is controlled to enter a fault mode from the pre-charging mode, and the pre-charging system is controlled to shut down.

11. The pre-charging method of claim 1, wherein the limiting power of the pre-charging resistor is greater than the rated power of the pre-charging resistor.

12. A pre-charging system comprising a load circuit, a pre-charging circuit, and a control circuit, wherein the load circuit includes an input terminal, an input switch, and a bus capacitor, the input terminal receives an input current, the input switch is coupled between the input terminal and the bus capacitor, the pre-charging circuit is connected in parallel across the two ends of the input switch, and includes a pre-charging resistor and a pre-charging switch connected in series, and the control circuit is configured to perform the pre-charging method according to any one of claims 1-11.

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