Soft start protection circuit and air conditioning system

Abstract

The utility model discloses a kind of soft-start protection circuit and air conditioning system, including rectifier unit, bus capacitor unit and inverter unit connected in turn;Protection unit, including switching device and current-limiting resistor, protection unit and the negative side of bus capacitor unit are connected in series, and protection unit is used to protect bus capacitor unit;Soft-start unit, it is connected with protection unit;Soft-start unit is used to the on-off of switching device of protection unit, to make the charging current of bus capacitor unit flow through switching device or current-limiting resistor. Thus by the negative side of protection unit and bus capacitor unit connection in series, when soft-start protection circuit is in power-on initial state, soft-start unit is turned on, leading to protection unit cut-off, to make charging current flow through the current-limiting resistor of protection unit after again flowing into bus capacitor unit, to limit the peak value of charging current, reduce the impact of instantaneous charging current on switching device in protection unit, avoid switching device to be damaged.

Description

Technical Field

[0001] This utility model relates to the field of electrical technology, and in particular to a soft-start protection circuit and an air conditioning system. Background Technology

[0002] In motor drive circuits, due to design requirements, the circuit is divided into a rectifier circuit, an energy storage and filter circuit, and a drive circuit. When the power is turned on, the energy storage and filter circuit experiences a large charging current, affecting the stability of the entire device, shortening the lifespan of capacitors, and even damaging circuit components. Therefore, as... Figure 1 As shown, a current-limiting resistor R0 is usually added to the bus in front of the bus capacitor C0 to limit the charging current, avoid current spikes, and achieve the purpose of soft start. After the bus capacitor C0 is charged to the set threshold, or after the MCU unit is powered on and there is a delay, the driving switching device K1 short-circuits the current-limiting resistor to reduce the loss caused by the current-limiting resistor.

[0003] Therefore, when the current-limiting resistor R0 is placed on the DC bus, the switching device K1 used to short-circuit the current-limiting resistor R0 needs to withstand a large bus charging current, which can easily lead to damage. Utility Model Content

[0004] This invention provides a soft-start protection circuit and an air conditioning system to solve the problem in the prior art where the switching devices used to short-circuit the current-limiting resistor on the DC bus of the circuit need to withstand a large bus charging current, which can easily lead to damage.

[0005] The technical solution of this utility model is a soft-start protection circuit, including a rectifier unit, a bus capacitor unit, and an inverter unit connected in sequence; it also includes:

[0006] The protection unit contains a switching device and a current-limiting resistor. The protection unit is connected in series with the negative side of the bus capacitor unit. The protection unit is used to protect the bus capacitor unit.

[0007] A soft-start unit is connected to the protection unit; the soft-start unit is used to switch the switching device of the protection unit on and off, so that the charging current of the bus capacitor unit flows through the switching device or the current-limiting resistor.

[0008] Furthermore, the protection unit includes a switching device Q1 and a PTC current-limiting resistor RT;

[0009] The gate of the switching device Q1 is connected to the output terminal of the soft-start unit, and the drain of the switching device Q1 and the first terminal of the PTC current-limiting resistor RT are both connected to the negative side of the bus capacitor unit.

[0010] The source of the switching device Q1 and the second terminal of the PTC current-limiting resistor RT are both grounded.

[0011] Furthermore, the soft-start unit includes a switching device Q2, resistors R1, R2, and R3, and a capacitor C5;

[0012] The gate of the switching device Q2 is connected to the second end of the resistor R2 and the second end of the resistor R3 respectively. The first end of the resistor R3 is used to connect to the signal output terminal of the main control unit, and the first end of the resistor R2 is used to connect to the 3.3V pin.

[0013] The drain of the switching device Q2, the first end of the resistor R1, and the first end of the capacitor C5 are all connected to the gate of the switching device Q1. The second end of the resistor R1 is used to connect to the 15V pin.

[0014] The source of the switching device Q2 and the second terminal of the capacitor C5 are both grounded.

[0015] Furthermore, the switching devices Q1 and Q2 are one of a bidirectional thyristor, an insulated gate bipolar transistor, or an insulated gate field-effect transistor.

[0016] Furthermore, the soft-start protection circuit also includes:

[0017] The first detection unit is connected to the negative side of the bus capacitor unit; the first detection unit is used to detect the negative side voltage of the bus capacitor unit.

[0018] The second detection unit is connected to the positive side of the bus capacitor unit; the second detection unit is used to detect the positive side voltage of the bus capacitor unit.

[0019] Furthermore, the first detection unit includes resistors R3, R4, R5, and R6;

[0020] The first end of the resistor R3 is connected to the negative side of the bus capacitor unit, and the second end of the resistor R3 is connected in series with resistors R4, R5 and R6 and then grounded.

[0021] Furthermore, the connection node of resistors R5 and R6 is used to connect to the first sampling terminal of the main control unit.

[0022] Furthermore, the second detection unit includes resistors R7, R8, R9, and R10;

[0023] The first end of the resistor R7 is connected to the positive side of the bus capacitor unit, and the second end of the resistor R7 is connected in series with resistors R8, R9 and R10 and then grounded.

[0024] Furthermore, the connection node of resistors R9 and R10 is used to connect to the second sampling terminal of the main control unit.

[0025] Furthermore, the bus capacitor unit includes two sets of bus capacitors connected in parallel, and each set of bus capacitors contains two bus capacitors connected in series.

[0026] The positive terminal of each group of bus capacitors is connected to the input terminal of the second detection unit, and the negative terminal of each group of bus capacitors is simultaneously connected to the protection unit, the soft start unit, and the first detection unit.

[0027] Furthermore, the inverter unit includes three bridge arms, each of which consists of two power effect transistors arranged in series;

[0028] The first end of all the bridge arms is connected to the positive side of the bus capacitor unit, the second end of all the bridge arms is grounded, and the midpoint of all the bridge arms is used to connect to the target device.

[0029] This utility model also proposes an air conditioning system, including an outdoor unit, wherein the outdoor unit includes the soft-start protection circuit described above.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] This invention connects the protection unit and the negative side of the bus capacitor unit in series. When the soft-start protection circuit is in the initial power-on state, the soft-start unit is in the conducting state, causing the protection unit to be in the cut-off state. This allows the charging current to flow completely through the current-limiting resistor of the protection unit before flowing into the bus capacitor unit. The current-limiting resistor of the protection unit limits the peak value of the charging current, reduces the impact of the instantaneous charging current on the switching devices in the protection unit, avoids damage to the switching devices, extends the service life of the bus capacitor unit, and improves the stability of the soft-start protection circuit. Attached Figure Description

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this invention are used to distinguish different objects and not to describe a particular order.

[0033] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The background section shows the existing circuit diagram of bus capacitors and current-limiting resistors on the bus in the prior art.

[0035] Figure 2 The circuit diagram is for the first soft-start protection circuit proposed in this utility model;

[0036] Figure 3 This is a block diagram of the first soft-start protection circuit proposed in this utility model;

[0037] Figure 4 This is a circuit diagram of the second soft-start protection circuit proposed in this utility model.

[0038] Figure label:

[0039] 10. Rectifier unit;

[0040] 20. Bus capacitor unit;

[0041] 30. Inverter unit;

[0042] 40. Protection Unit;

[0043] 50. Soft start unit;

[0044] 60. First detection unit;

[0045] 70. Second detection unit;

[0046] 80. Main control unit. Detailed Implementation

[0047] To make the technical problem to be solved, the technical solution, and the beneficial effects 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 merely illustrative of the present utility model and are not intended to limit the present utility model. Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the present utility model, and does not imply that every embodiment of the present utility model must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0048] The principle and structure of this utility model will be described in detail below with reference to the accompanying drawings and embodiments.

[0049] In some embodiments, such as Figures 2-3 As shown, this utility model proposes a soft-start protection circuit, including a rectifier unit 10, a bus capacitor unit 20, and an inverter unit 30 connected in sequence; it also includes:

[0050] The protection unit 40 contains a switching device and a current-limiting resistor. The protection unit 40 is connected in series with the negative side of the bus capacitor unit 20. The protection unit 40 is used to protect the bus capacitor unit 20.

[0051] A soft-start unit 50 is connected to the protection unit 40; the soft-start unit 50 is used to switch the switching device of the protection unit 40 on and off, so that the charging current of the bus capacitor unit 20 flows through the switching device or the current limiting resistor.

[0052] It should be noted that the rectifier unit 10 proposed in this embodiment is used to rectify three-phase 220V AC power into pulsating DC power (preferably 540V); the bus capacitor unit 20 is used to filter out the high-frequency ripple component in the pulsating DC power and stabilize the bus voltage; the inverter unit 30 is used to invert the filtered DC power into AC power of a specified frequency and output it to the target device 90 (preferably a three-phase motor); and the rectifier unit 10, the bus capacitor unit 20 and the inverter unit 30 sequentially constitute a three-level energy conversion link, with the bus capacitor unit 20 serving as both the output energy storage element of the rectifier unit 10 and the input energy buffer element of the inverter unit 30.

[0053] Furthermore, the soft-start protection circuit proposed in this embodiment also includes a main control unit 80, the signal output terminal of which is connected to the soft-start unit 50.

[0054] In this way, when the soft-start protection circuit is in the initial power-on state, the soft-start unit 50 is in the conducting state, causing the protection unit 40 to be in the cut-off state. This allows the charging current to flow completely through the current-limiting resistor of the protection unit 40 before flowing into the bus capacitor unit 20. This allows the current-limiting resistor of the protection unit 40 to limit the peak value of the charging current, reducing the impact of the instantaneous charging current on the switching devices in the protection unit 40, avoiding damage to the switching devices, and even preventing the current spikes generated by the bus capacitor unit 20 during charging from damaging the capacitor components in the bus capacitor unit 20 or the entire soft-start protection circuit, thus extending the service life of the bus capacitor unit 20.

[0055] When the bus capacitor unit 20 is charged to a set threshold (e.g., 80% of the bus voltage), the main control unit 80 will detect this state and trigger the corresponding control logic. That is, the main control unit 80 will send a low-level signal to the soft-start unit 50, so that the soft-start unit 50 is in the off state, causing the protection unit 40 to be in the on state. This causes the current limiting resistor of the protection unit 40 to be short-circuited, so that the charging current flows completely through the switching device of the protection unit 40 before flowing into the bus capacitor unit 20, effectively reducing the power consumption generated by the protection unit 40.

[0056] When the entire soft-start protection circuit is in normal working condition, the main control unit 80 will continuously send a low-level signal to the soft-start unit 50, causing the soft-start unit 50 to be in the off state, resulting in the protection unit 40 being in the on state. This allows the current-limiting resistor of the protection unit 40 to be short-circuited, causing the charging current to flow completely through the switching device of the protection unit 40 before flowing into the bus capacitor unit 20. At this time, the bus capacitor unit 20 can charge and discharge normally. Since the charging and discharging current of the bus capacitor unit 20 is much smaller than the bus operating current, the pulse current tolerance of the protection unit 40 is higher than that of the charging and discharging current of the bus capacitor unit 20, thereby preventing the charging and discharging current of the bus capacitor unit 20 from damaging the components inside the protection unit 40.

[0057] Therefore, this utility model connects the protection unit 40 in series with the negative side of the bus capacitor unit 20. When the soft-start protection circuit is in the initial power-on state, the soft-start unit 50 is in a conducting state, causing the protection unit 40 to be in a cut-off state. This allows the charging current to flow completely through the current-limiting resistor of the protection unit 40 before flowing into the bus capacitor unit 20. The current-limiting resistor of the protection unit 40 limits the peak value of the charging current, reducing the impact of the instantaneous charging current (equivalent to the change in current di / dt per unit time, the same throughout) on the switching devices within the protection unit 40. This prevents damage to the switching devices and even avoids damage to the capacitor components within the bus capacitor unit 20 or the entire soft-start protection circuit caused by current spikes generated during charging. This extends the service life of the bus capacitor unit 20 and improves the stability of the soft-start protection circuit.

[0058] In some embodiments, such as Figure 2 As shown, the protection unit 40 includes a switching device Q1 and a PTC current-limiting resistor RT;

[0059] The gate of the switching device Q1 is connected to the output terminal of the soft-start unit 50, and the drain of the switching device Q1 and the first terminal of the PTC current-limiting resistor RT are both connected to the negative side of the bus capacitor unit 20.

[0060] The source of the switching device Q1 and the second terminal of the PTC current-limiting resistor RT are both grounded.

[0061] Thus, when the soft-start protection circuit is in the initial power-on state, the soft-start unit 50 is in the conducting state, causing the switching device Q1 to be in the cut-off state. This allows the charging current to flow completely through the PTC current-limiting resistor RT before flowing into the bus capacitor unit 20. Since the PTC current-limiting resistor RT is a positive temperature coefficient thermistor, it is a semiconductor electronic component whose resistance increases significantly with increasing temperature. It has a low resistance value at low temperatures, but its resistance value increases as the heat generated by the charging current increases. This effectively limits the current spike when the soft-start protection circuit is in the initial power-on state, so that the switching device Q1 does not have to bear the full short-circuit current, reducing the impact of the instantaneous charging current on the switching device Q1, avoiding damage to the switching device Q1, and even preventing the peak charging current from damaging the capacitor components in the bus capacitor unit 20 or the entire soft-start protection circuit. This extends the service life of the bus capacitor unit 20 and improves the stability of the soft-start protection circuit.

[0062] When the entire soft-start protection circuit is in normal working condition, the main control unit 80 continuously sends a low-level signal to the soft-start unit 50, causing the soft-start unit 50 to be in the off state. This causes the switching device Q1 to be in the conducting state, so that the PTC current-limiting resistor RT is short-circuited. This allows the charging current to flow completely through the switching device Q1 before flowing into the bus capacitor unit 20. Furthermore, the switching device Q1 has bidirectional conduction characteristics after being turned on, meaning that the bus capacitor unit 20 can charge and discharge normally at this time. Since the charging and discharging current of the bus capacitor unit 20 is much smaller than the bus operating current, the pulse current tolerance of the protection unit 40 is higher than that of the charging and discharging current of the bus capacitor unit 20, thereby preventing the charging and discharging current of the bus capacitor unit 20 from damaging the components inside the protection unit 40.

[0063] Of course, in other embodiments (not shown in the figure), multiple PTC current-limiting resistors RT can be connected in series, which is not limited here.

[0064] In some embodiments, to ensure that the soft-start unit 50 can better switch the switching device Q1 on and off, so that the charging current of the bus capacitor unit 20 flows through the switching device Q1 or the PTC current-limiting resistor RT, such as... Figure 2 As shown, the soft-start unit 50 includes a switching device Q2, a resistor R1, a resistor R2, a resistor R3, and a capacitor C5;

[0065] The gate of the switching device Q2 is connected to the second end of the resistor R2 and the second end of the resistor R3 respectively. The first end of the resistor R3 is used to connect to the signal output terminal RELAY of the main control unit 80, and the first end of the resistor R2 is used to connect to the 3.3V pin.

[0066] The drain of the switching device Q2, the first end of the resistor R1, and the first end of the capacitor C5 are all connected to the gate of the switching device Q1. The second end of the resistor R1 is used to connect to the 15V pin.

[0067] The source of the switching device Q2 and the second terminal of the capacitor C5 are both grounded.

[0068] It should be noted that the bus voltage is stepped down by a switching power supply circuit (not shown, the same throughout the text) to obtain stable output voltages of 15V and 3.3V respectively; among them, the 15V output voltage is used to power the switching device Q1, and the 3.3V output voltage is used to power the main control unit 80 and the switching device Q2.

[0069] Thus, when the soft-start protection circuit is in the initial power-on state, the gate of switching device Q2 is pulled up to 3.3V through resistor R2, making switching device Q2 in the conducting state. Because switching device Q2 is conducting, the gate of switching device Q1 is pulled down to ground through switching device Q2, causing switching device Q1 to be in the cut-off state. This allows the charging current to flow completely through the PTC current-limiting resistor RT before flowing into the bus capacitor unit 20, so that the PTC current-limiting resistor RT limits the peak value of the charging current, reducing the impact of the instantaneous charging current on switching device Q1, avoiding damage to switching device Q1, and even preventing the current spikes generated in the bus capacitor unit 20 during charging from damaging the capacitor components in the bus capacitor unit 20 or the entire soft-start protection circuit, extending the service life of the bus capacitor unit 20 and improving the stability of the soft-start protection circuit.

[0070] When the bus capacitor unit 20 is charged to a set threshold (e.g., 80% of the bus voltage), the main control unit 80 detects this state and triggers the corresponding control logic. That is, the main control unit 80 sends a low-level signal to the switching device Q2, causing the gate voltage of the switching device Q2 to drop to a low level, and the switching device Q2 changes from the on state to the off state. After the switching device Q2 is turned off, the gate of the switching device Q1 is pulled up to 15V through the resistor R1, causing the switching device Q1 to conduct. This causes the PTC current limiting resistor RT to be short-circuited, so that the charging current flows completely through the switching device Q1 before flowing into the bus capacitor unit 20, effectively reducing the power consumption generated by the PTC current limiting resistor RT.

[0071] When the entire soft-start protection circuit is in normal working condition, the main control unit 80 will continuously send a low-level signal to the soft-start unit 50, causing the switching device Q2 to be cut off and the switching device Q1 to be turned on. After the switching device Q1 is turned on, it has bidirectional conduction characteristics, and the bus capacitor unit 20 can be charged and discharged normally. Since the charging and discharging current of the bus capacitor unit 20 is much smaller than the bus operating current, the pulse current withstand capability of the protection unit 40 is higher than that of the charging and discharging current of the bus capacitor unit 20, thereby avoiding damage to the components inside the protection unit 40 by the charging and discharging current of the bus capacitor unit 20.

[0072] In some embodiments, the switching devices Q1 and Q2 are one of a bidirectional thyristor, an insulated-gate bipolar transistor, or an insulated-gate field-effect transistor. Of course, the switching devices Q1 and Q2 can also be other similar switching devices, which are not limited here.

[0073] It should be noted that in this embodiment, both switching devices Q1 and Q2 are illustrated using insulated-gate field-effect transistors (MOS transistors).

[0074] Compared to using relays as switching devices, this embodiment uses insulated gate field-effect transistors as the switching devices within the soft-start unit 50, which reduces the parameter requirements for the switching devices, simplifies the circuit design, and reduces costs while also reducing the area occupied by the PCB board.

[0075] Furthermore, the bidirectional conduction characteristics of the switching device Q1 are as follows: when the insulated gate field-effect transistor is turned on, it is equivalent to a resistive channel, and the direction of its current is determined by the polarity of the external voltage, rather than by the characteristics of the device itself; when the drain voltage of the switching device Q1 is higher than that of the source, electrons flow from the source to the drain (forward conduction); when the source voltage of the switching device Q1 is higher than that of the drain, electrons flow in the reverse direction, realizing a reverse current path (reverse conduction); and the gate voltage of the switching device Q1 only controls the formation of the conductive channel, which is equivalent to a non-polarized resistor, thus enabling bidirectional current.

[0076] In some embodiments, to ensure the stability and safety of the soft-start protection circuit during the charging process of the bus capacitor unit 20, such as... Figure 3 As shown, the soft-start protection circuit further includes:

[0077] The first detection unit 60 is connected to the negative side of the bus capacitor unit 20; the first detection unit 60 is used to detect the bus voltage on the negative side of the bus capacitor unit 20.

[0078] The second detection unit 70 is connected to the positive side of the bus capacitor unit 20; the second detection unit 70 is used to detect the bus voltage on the positive side of the bus capacitor unit 20.

[0079] Therefore, when the soft-start protection circuit is in the initial power-on state, and switching device Q2 is on while switching device Q1 is off, the main control unit 80 can continuously monitor the negative side voltage of the bus capacitor unit 20 through the first detection unit 60, and cooperate with the second detection unit 70 to continuously monitor the positive side voltage of the bus capacitor unit 20. This is because the negative side of the bus capacitor unit 20 is usually at the reference ground potential, but its actual voltage fluctuates due to leakage current and grounding faults. Therefore, it is necessary to obtain the negative side voltage sampling value U of the bus capacitor unit 20. - Combined with the positive side voltage sampling value U + Thus, the actual bus voltage (Ubus = U) can be calculated. + -U - Then, the charging voltage Uc is dynamically calculated.

[0080] Where Rlim is the pre-charge current-limiting resistor and C is the capacitance value. By comparing Uc (the negative terminal sample reflects the actual voltage of the capacitor) with Ubus in real time, the system can determine the charging progress and ensure the stability and safety of the charging process.

[0081] In this way, when the main control unit 80 detects that the charging voltage Uc of the bus capacitor unit 20 reaches the set threshold (e.g., 80% of the bus voltage), the main control unit 80 will send a low-level signal to the switching device Q2, so that the switching device Q2 is in the off state and the switching device Q1 is in the on state, thereby causing the PTC current limiting resistor RT to be short-circuited, so that the charging current flows completely through the switching device Q1 before flowing into the bus capacitor unit 20, effectively reducing the power consumption generated by the protection unit 40.

[0082] Specifically, to ensure that the first detection unit 60 performs voltage division sampling and avoids overvoltage damage; current limiting protection is implemented to prevent sudden short circuits or surge currents from burning out sensitive devices (such as the first sampling terminal DC1), such as... Figure 2 As shown, the first detection unit 60 includes resistors R3, R4, R5 and R6;

[0083] The first end of the resistor R3 is connected to the negative side of the bus capacitor unit 20, and the second end of the resistor R3 is connected in series with resistors R4, R5 and R6 and then grounded.

[0084] Furthermore, the connection node of resistors R5 and R6 is used to connect to the first sampling terminal of the main control unit 80.

[0085] Of course, in other embodiments, two resistors within the first detection unit 60 can be connected in series according to the actual situation (e.g., Figure 4 (As shown), three or more, without limitation.

[0086] Specifically, to ensure that the second detection unit 70 performs voltage division sampling and avoids overvoltage damage, current limiting protection is implemented to prevent sudden short circuits or surge currents from burning out sensitive devices (such as the second sampling terminal DC2), such as... Figure 2 As shown, the second detection unit 70 includes resistors R7, R8, R9 and R10;

[0087] The first end of the resistor R7 is connected to the positive side of the bus capacitor unit 20, and the second end of the resistor R7 is connected in series with resistors R8, R9 and R10 and then grounded.

[0088] Furthermore, the connection node of resistors R9 and R10 is used to connect to the second sampling terminal DC2 of the main control unit 80.

[0089] Of course, in other embodiments, two resistors within the second detection unit 70 can be connected in series according to the actual situation (e.g., Figure 4 (As shown), three or more, without limitation.

[0090] In some embodiments, to increase the withstand voltage of the bus capacitor unit 20, in order to ensure the reliable operation of the soft-start protection circuit and optimize the dynamic response of the soft-start protection circuit, such as... Figure 2 As shown, the bus capacitor unit 20 includes two sets of bus capacitors connected in parallel, and each set of bus capacitors contains two bus capacitors connected in series.

[0091] The positive terminal of each group of bus capacitors is connected to the input terminal of the second detection unit 70, and the negative terminal of each group of bus capacitors is simultaneously connected to the protection unit 40, the soft start unit 50 and the first detection unit 60.

[0092] Specifically, the bus capacitor unit 20 includes capacitors C1, C2, C3, and C4. The negative terminal of capacitor C1 and the positive terminal of capacitor C3 are connected in series to form a bus capacitor, and the negative terminal of capacitor C2 and the positive terminal of capacitor C4 are connected in series to form a bus capacitor. At the same time, the positive terminal side of the bus capacitor unit 20 (equivalent to the positive terminals of capacitor C1 and C2) is connected to the first end of resistor R7, and the negative terminal side of the bus capacitor unit 20 (equivalent to the negative terminals of capacitor C3 and C4) is connected to the first end of resistor R3.

[0093] Of course, in other embodiments, the bus capacitor unit 20 can be a single capacitor (e.g., Figure 4 (As shown) or two capacitors connected in series, or two capacitors connected in parallel, without limitation.

[0094] In some embodiments, to ensure that the inverter unit 30 can convert the filtered DC power into AC power of a specified frequency and stably output it to the target device 90, such as... Figure 2As shown, the inverter unit 30 includes three bridge arms, each of which consists of two power effect transistors arranged in series.

[0095] The first end of all the bridge arms is connected to the positive side of the bus capacitor unit 20, the second end of all the bridge arms is grounded, and the midpoint of all the bridge arms is used to connect to the target device 90.

[0096] It should be noted that the target device 90 proposed in this embodiment is illustrated by a three-phase motor; and the power effect transistor proposed in this embodiment is illustrated by an insulated gate bipolar transistor (IGBT).

[0097] In some embodiments, the present invention also provides an air conditioning system including an outdoor unit, wherein the outdoor unit includes the soft-start protection circuit described above.

[0098] Specifically, the optimal circuit for the soft-start protection circuit proposed in this embodiment is as follows:

[0099] The input terminal of the rectifier unit 10 is connected to the mains power. The output terminal of the rectifier unit 10 is connected to the positive terminal of capacitor C1, the positive terminal of capacitor C2, the first terminal of resistor R7, and the first terminal of the three bridge arms. The second terminals of the three bridge arms are all grounded, and the midpoints of the three bridge arms are all connected to the three-phase motor. The second terminal of resistor R7 is connected to resistors R8, R9, and R10 in series and then grounded. The connection node of resistors R9 and R10 is used to connect to the second sampling terminal DC2 of the main control unit 80.

[0100] The gate of the switching device Q2 is connected to the second end of the resistor R2 and the second end of the resistor R3 respectively. The first end of the resistor R3 is used to connect to the signal output terminal RELAY of the main control unit 80, and the first end of the resistor R2 is used to connect to the 3.3V pin.

[0101] The drain of switching device Q2, the first terminal of resistor R1, and the first terminal of capacitor C5 are all connected to the gate of switching device Q1. The second terminal of resistor R1 is used to connect to the 15V pin. The drain of switching device Q1 is connected to the negative terminals of capacitors C3 and C4, the first terminal of PTC current-limiting resistor RT, and the first terminal of resistor R3. The second terminal of resistor R3 is connected to ground via resistors R4, R5, and R6 in series. The connection point of resistors R5 and R6 is used to connect to the first sampling terminal of main control unit 80. The positive terminal of capacitor C3 is connected to the negative terminal of capacitor C1, and the positive terminal of capacitor C4 is connected to the negative terminal of capacitor C2.

[0102] The source of switching device Q1, the source of switching device Q2, the second terminal of PTC current-limiting resistor RT, and the second terminal of capacitor C5 are all grounded.

[0103] Thus, when the soft-start protection circuit is in the initial power-on state, the gate of switching device Q2 is pulled up to 3.3V through resistor R2, making switching device Q2 in the conducting state. Because switching device Q2 is conducting, the gate of switching device Q1 is pulled down to ground through switching device Q2, making switching device Q1 in the cut-off state. This causes the charging current to flow completely through the PTC current-limiting resistor RT before flowing into the bus capacitor unit 20. This allows the PTC current-limiting resistor RT to limit the peak value of the charging current, reducing the impact of the instantaneous charging current on switching device Q1 and preventing damage to switching device Q1. It also prevents the current spikes generated in the bus capacitor unit 20 during charging from damaging the capacitor components in the bus capacitor unit 20 or the entire soft-start protection circuit, extending the service life of the bus capacitor unit 20 and improving the stability of the soft-start protection circuit.

[0104] When the bus capacitor unit 20 is charged to a set threshold (e.g., 80% of the bus voltage), the main control unit 80 detects this state and triggers the corresponding control logic. That is, the main control unit 80 sends a low-level signal to the switching device Q2, causing the gate voltage of the switching device Q2 to drop to a low level, and the switching device Q2 changes from the on state to the off state. After the switching device Q2 is turned off, the gate of the switching device Q1 is pulled up to 15V through the resistor R1, causing the switching device Q1 to conduct. This causes the PTC current-limiting resistor RT to be short-circuited, so that the charging current flows completely through the switching device Q1 before flowing into the bus capacitor unit 20, effectively reducing the power consumption generated by the PTC current-limiting resistor RT. Moreover, this design is suitable for the bus capacitor unit of the drive motherboard of the air conditioner outdoor unit. It can solve the impact of the high di / dt generated by the charging of the bus capacitor after power failure on the components, play a protective role, improve the stability and safety of the circuit, reduce manufacturing costs, and extend the service life of the bus capacitor.

[0105] When the entire soft-start protection circuit is in normal working condition, the main control unit 80 will continuously send a low-level signal to the soft-start unit 50, causing the switching device Q2 to be cut off and the switching device Q1 to be turned on. After the switching device Q1 is turned on, it has bidirectional conduction characteristics, and the bus capacitor unit 20 can be charged and discharged normally. Since the charging and discharging current of the bus capacitor unit 20 is much smaller than the bus operating current, the pulse current withstand capability of the protection unit 40 is higher than that of the charging and discharging current of the bus capacitor unit 20, thereby avoiding damage to the components inside the protection unit 40 by the charging and discharging current of the bus capacitor unit 20.

[0106] Obviously, the embodiments described above are only some embodiments of this utility model, not all embodiments. The accompanying drawings show preferred embodiments of this utility model, but do not limit the patent scope of this utility model. This utility model can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this utility model. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this utility model specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this utility model.

Claims

1. A soft-start protection circuit, comprising a rectifier unit (10), a bus capacitor unit (20), and an inverter unit (30) connected in sequence; characterized in that, Also includes: The protection unit (40) contains a switching device and a current-limiting resistor. The protection unit (40) is connected in series with the negative side of the bus capacitor unit (20). The protection unit (40) is used to protect the bus capacitor unit (20). A soft-start unit (50) is connected to the protection unit (40); the soft-start unit (50) is used to switch the switching device of the protection unit (40) so that the charging current of the bus capacitor unit (20) flows through the switching device or the current limiting resistor.

2. The soft-start protection circuit according to claim 1, characterized in that, The protection unit (40) includes a switching device Q1 and a PTC current-limiting resistor RT; The gate of the switching device Q1 is connected to the output terminal of the soft-start unit (50), and the drain of the switching device Q1 and the first terminal of the PTC current-limiting resistor RT are both connected to the negative side of the bus capacitor unit (20). The source of the switching device Q1 and the second terminal of the PTC current-limiting resistor RT are both grounded.

3. The soft-start protection circuit according to claim 2, characterized in that, The soft-start unit (50) includes a switching device Q2, resistors R1, R2, and R3, and a capacitor C5; The gate of the switching device Q2 is connected to the second end of the resistor R2 and the second end of the resistor R3 respectively. The first end of the resistor R3 is used to connect to the signal output terminal of the main control unit (80), and the first end of the resistor R2 is used to connect to the 3.3V pin. The drain of the switching device Q2, the first end of the resistor R1, and the first end of the capacitor C5 are all connected to the gate of the switching device Q1. The second end of the resistor R1 is used to connect to the 15V pin. The source of the switching device Q2 and the second terminal of the capacitor C5 are both grounded.

4. The soft-start protection circuit according to claim 3, characterized in that, The switching devices Q1 and Q2 are one of the following: bidirectional thyristor, insulated gate bipolar transistor, or insulated gate field-effect transistor.

5. The soft-start protection circuit according to any one of claims 1 to 4, characterized in that, The soft-start protection circuit also includes: The first detection unit (60) is connected to the negative side of the bus capacitor unit (20); the first detection unit (60) is used to detect the negative side voltage of the bus capacitor unit (20); The second detection unit (70) is connected to the positive side of the bus capacitor unit (20); the second detection unit (70) is used to detect the positive side voltage of the bus capacitor unit (20).

6. The soft-start protection circuit according to claim 5, characterized in that, The first detection unit (60) includes resistors R3, R4, R5 and R6; The first end of the resistor R3 is connected to the negative side of the bus capacitor unit (20), and the second end of the resistor R3 is connected in series with resistors R4, R5 and R6 and then grounded. Furthermore, the connection node of resistors R5 and R6 is used to connect to the first sampling terminal of the main control unit (80).

7. The soft-start protection circuit according to claim 5, characterized in that, The second detection unit (70) includes resistors R7, R8, R9 and R10; The first end of the resistor R7 is connected to the positive side of the bus capacitor unit (20), and the second end of the resistor R7 is connected in series with resistors R8, R9 and R10 and then grounded. Furthermore, the connection node of resistors R9 and R10 is used to connect to the second sampling terminal of the main control unit (80).

8. The soft-start protection circuit according to claim 5, characterized in that, The bus capacitor unit (20) includes two sets of bus capacitors connected in parallel, and two bus capacitors are connected in series in each set of bus capacitors. The positive side of each group of bus capacitors is connected to the input terminal of the second detection unit (70), and the negative side of each group of bus capacitors is simultaneously connected to the protection unit (40), the soft start unit (50) and the first detection unit (60).

9. The soft-start protection circuit according to claim 1, characterized in that, The inverter unit (30) includes three bridge arms, each of which consists of two power effect transistors arranged in series; The first end of all the bridge arms is connected to the positive side of the bus capacitor unit (20), the second end of all the bridge arms is grounded, and the midpoint of all the bridge arms is used to connect to the target device.

10. An air conditioning system, comprising an outdoor unit, characterized in that, The outdoor unit of the air conditioner includes the soft-start protection circuit as described in any one of claims 1 to 9.

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