Bus capacitor DC soft start system

Abstract

A bus capacitor DC soft start system relates to the technical field of power electronics and can realize charging soft start of a bus capacitor. The system comprises a drive switch-on subsystem, a drive switch-off subsystem and a bus capacitor soft start loop. The driving opening subsystem comprises a driving opening energy supply unit, a driving opening unit and a driving undervoltage locking unit. And the bus capacitor soft starting loop is used for charging the bus capacitor. The bus capacitor soft starting loop comprises a power switch tube and a bus capacitor. The power switch tube is used for controlling charging of the bus capacitor. And the driving closing subsystem is used for driving the power switch tube to be closed. And the driving turn-on energy supply unit is used for providing driving voltage and current for the driving electrode of the power switch tube. And the driving opening unit is used for transmitting the driving voltage to the driving undervoltage locking unit. And the driving undervoltage locking unit is used for disconnecting the power switch tube when the driving voltage of the power switch tube is insufficient.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a bus capacitor DC soft start system. Background Art

[0002] To start a PV energy storage inverter without connecting to the grid and only to the battery, you must first charge the bus capacitor voltage to a level close to the battery voltage before closing the contactor or circuit breaker connecting the battery and bus capacitor. Otherwise, a significant current surge will occur, damaging electronic components and endangering the safety of the equipment. Summary of the Invention

[0003] The present application provides a bus capacitor DC soft start system, which can realize charging soft start of the bus capacitor.

[0004] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0005] In a first aspect, a bus capacitor DC soft-start system is provided, comprising a drive opening subsystem, a drive closing subsystem and a bus capacitor soft-start circuit; the drive opening subsystem comprises a drive opening energy supply unit, a drive opening unit and a drive undervoltage lockout unit; the bus capacitor soft-start circuit is used to charge the bus capacitor; the bus capacitor soft-start circuit comprises a power switch tube and a bus capacitor, the power switch tube is used to control the charging of the bus capacitor; the drive closing subsystem is used to drive the power switch tube to close; the drive opening energy supply unit is used to provide a driving voltage and current for the driving pole of the power switch tube; the drive opening unit is used to transmit the driving voltage to the driving undervoltage lockout unit; the driving undervoltage lockout unit is used to disconnect the power switch tube when the driving voltage of the power switch tube is insufficient.

[0006] In some embodiments, the driving undervoltage lockout unit includes: a first transistor, a fourth resistor, a fifth resistor, a second voltage-stabilizing diode, a sixth resistor and a third capacitor; the first electrode of the first transistor is connected to the driving opening unit; the third electrode of the first transistor is connected to the fifth resistor and the cathode of the second voltage-stabilizing diode in sequence; the fourth resistor is connected in parallel with the first electrode of the first transistor and the third electrode of the first transistor; the second electrode of the first transistor is connected to the driving electrode of the power switch tube, one end of the sixth resistor and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube and the anode of the second voltage-stabilizing diode.

[0007] In some embodiments, the driving undervoltage lockout unit includes: a first transistor, a second voltage-stabilizing diode, a comparator, a fourth resistor, a fifth resistor, a sixth resistor, an eleventh resistor, a twelfth resistor and a third capacitor; the first electrode of the first transistor is connected to the driving opening unit; the first electrode of the first transistor is also connected to the first power supply terminal of the comparator, the first end of the fifth resistor, and the first end of the eleventh resistor; the second end of the fifth resistor is connected to the positive input terminal of the comparator and the cathode of the second voltage-stabilizing diode; the second end of the eleventh resistor is connected to the first end of the twelfth resistor and the negative input terminal of the comparator; the third electrode of the first transistor is connected to the output terminal of the comparator; the fourth resistor is connected in parallel with the first and third electrodes of the first transistor; the second electrode of the first transistor is connected to the driving electrode of the power switch tube, one end of the sixth resistor and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube, the anode of the second voltage-stabilizing diode, the second end of the twelfth resistor and the second power supply terminal of the comparator.

[0008] In some embodiments, the driving undervoltage lockout unit includes: a first transistor, a comparator, a fifth resistor, an eleventh resistor, a fourth resistor, a sixth resistor and a third capacitor; the first electrode of the first transistor is connected to the driving opening unit, the positive power supply end of the comparator, and the first end of the fifth resistor; the second end of the fifth resistor is connected to the negative input end of the comparator and the first end of the eleventh resistor; the third electrode of the first transistor is connected to the output end of the comparator; the fourth resistor is connected in parallel with the first electrode and the third electrode of the first transistor; the second electrode of the first transistor is connected to the driving electrode of the power switch tube, one end of the sixth resistor and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube, the second end of the eleventh resistor and the negative power supply end of the comparator.

[0009] In some embodiments, the drive-on energy supply unit includes: a first resistor, a second resistor, a first capacitor and a first voltage-stabilizing diode; the drive-on unit includes a switch; the first resistor, the second resistor and the first capacitor are connected in sequence, the first voltage-stabilizing diode is connected in parallel with the first capacitor, the first resistor is connected to the bus capacitor soft-start loop, the connection point between the second resistor and the first capacitor is connected to the first end of the switch, and the first capacitor is connected to the first pole of the power switch tube.

[0010] In some embodiments, the driving undervoltage lockout unit includes: an integrated chip, a fifth resistor, an eleventh resistor, a twelfth resistor, a first transistor, a fourth resistor, a sixth resistor, and a third capacitor, wherein the integrated chip has an input hysteresis voltage setting function and includes a first comparator and a second comparator inside the integrated chip; the first electrode of the first transistor is connected to the driving opening unit, the positive power supply of the integrated chip, and the first end of the fifth resistor; the second end of the fifth resistor is connected to the negative input end of the first comparator inside the integrated chip and the first end of the eleventh resistor; the second end of the eleventh resistor is connected to the first end of the twelfth resistor and the positive input end of the second comparator inside the integrated chip; the third electrode of the first transistor is connected to the output end of the integrated chip; the fourth resistor is connected in parallel with the first electrode and the third electrode of the first transistor; the second electrode of the first transistor is connected to the driving electrode of the power switch tube, one end of the sixth resistor, and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube, the second end of the twelfth resistor, and the power ground of the integrated chip.

[0011] In some embodiments, the drive shutdown subsystem includes a drive locking unit; the drive locking unit includes: a fourth voltage-stabilizing diode, a third transistor, and a tenth resistor; the anode of the fourth voltage-stabilizing diode is connected to the first electrode of the third transistor; the second electrode of the third transistor is connected to one end of the tenth resistor, and the other end of the tenth resistor is connected to the drive electrode of the power switch tube; the third stage of the third transistor is connected to the first electrode of the power switch tube, and the cathode of the fourth voltage-stabilizing diode is connected to the drain of the power switch tube.

[0012] In some embodiments, the resistance of the sixth resistor is 100 times greater than the resistance of the tenth resistor.

[0013] In some embodiments, the drive shutdown subsystem also includes a drive unlocking unit; the drive unlocking unit includes a third diode; the cathode of the fourth voltage-stabilizing diode is connected to the drain of the power switch tube, including: the negative electrode of the third diode is connected to the drain of the power switch tube, and the anode of the third diode is connected to the cathode of the fourth voltage-stabilizing diode.

[0014] In some embodiments, the first transistor is a PNP transistor, the first electrode of the first transistor is the emitter, the second electrode is the collector, and the third electrode is the base; or, the first transistor is a PMOS field effect transistor, the first electrode of the first transistor is the source, the second electrode is the drain, and the third electrode is the gate.

[0015] The above system not only ensures the normal soft start of the bus capacitor, but also improves the reliability by adding the undervoltage lockout unit.

[0016] In a second aspect, a photovoltaic energy storage inverter is provided, comprising a controller and the bus capacitor DC soft-start system described in the first aspect, wherein the controller is electrically connected to the bus capacitor soft-start system.

[0017] In some embodiments, the controller is a single chip microcomputer.

[0018] In some embodiments, the controller is a digital signal processor.

[0019] In some embodiments, the controller is a field programmable gate array. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the bus capacitor DC soft-start system structure provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of the structure of a bus capacitor DC soft-start system provided in another embodiment of the present application;

[0022] Figure 3 A schematic diagram of the structure of a bus capacitor DC soft-start system provided in yet another embodiment of the present application;

[0023] Figure 4 A schematic diagram of the structure of a bus capacitor DC soft-start system provided in yet another embodiment of the present application;

[0024] Figure 5 This is a schematic diagram of the structure of a bus capacitor DC soft-start system provided in yet another embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] It should be noted that although a logical order is shown in the flowcharts, in some cases, the steps shown or described may be performed in a different order than that shown in the flowcharts. The terms "first," "second," and the like in the specification, claims, and drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0027] To start a PV energy storage inverter without connecting to the grid and only to the battery, you must first charge the bus capacitor voltage to a level close to the battery voltage before closing the contactor or circuit breaker connecting the battery and bus capacitor. Otherwise, a significant current surge will occur, damaging electronic components and endangering the safety of the equipment.

[0028] To address this issue, Related Art 1 proposes using a switch plus a current-limiting resistor to achieve pre-charging and soft-starting of the bus capacitor. However, this technique does not specify the implementation of the switch, and is generally understood to involve a mechanical switch, such as a relay, circuit breaker, or contactor. For high-voltage energy storage inverters exceeding several hundred volts, a DC contactor is typically required, but these are costly, bulky, and have high drive losses.

[0029] Related technology 2 proposes pre-charging the capacitor using a transformer, but the implementation of this method is relatively complex.

[0030] Based on this, an embodiment of the present application provides a bus capacitor DC cold start system, which uses a power switch tube and a current-limiting and power-limiting resistor in series to form the main charging current path from the battery to the bus capacitor. This system can not only ensure that the high-voltage battery provides a soft start pre-charging function for the bus capacitor, but also reduce the circuit volume, reduce costs, and have high reliability. Among them, the power switch tube refers to a transistor or field-effect tube that can withstand a large current, has a small leakage current, and has good saturation conduction and cutoff characteristics under certain conditions. It focuses on its function as an electronic switch, that is, it works in the on and off states and is used to control the on and off of the circuit.

[0031] Reference Figure 1 Compared with the traditional solution, the embodiment of the present application adds a driving undervoltage lockout unit ( Figures 1 to 5 The portion shown in the dashed box 3 in any of the items). During the process of driving the power switch Q2, if the voltage of the first capacitor C1 drops or the voltage of the first capacitor C1 is low, the second voltage regulator diode Z2 is turned off, and the first transistor Q1 is turned off. Because the third capacitor C3 is small, the gate voltage of the power switch Q2 also drops rapidly, and the power switch Q2 is quickly turned off. Without the drive lockout unit contained in the dashed box 3, the system would not monitor the voltage of the first capacitor C1. When the voltage of the first capacitor C1 is low and the switch S1 is still in the on state, the power switch Q2 will enter an incomplete conduction state. When the charging current flowing through the power switch Q2 to the bus capacitor C4 is large, it will cause significant losses in the power switch Q2 and may even damage the power switch Q2. The embodiment of the present application adds an undervoltage lockout, which can effectively avoid the incomplete conduction of the power switch Q2 and greatly reduce the risk of damage to the power switch Q2 due to insufficient voltage on the first capacitor C1.

[0032] Reference Figure 1The bus capacitor DC cold start system includes: a drive opening subsystem, a drive closing subsystem and a bus capacitor soft start circuit.

[0033] The bus capacitor soft start circuit is used to charge the bus capacitor. Figure 1 As shown in the dotted box 1, the bus capacitor soft-start circuit includes: a power interface, a bus capacitor C4, a first diode D1, a power switch tube Q2, a second diode D2, and a bus resistor R7. The power interface includes a positive power interface (not shown in the figure) and a negative power interface (not shown in the figure). The positive power interface, the first diode D1, the power switch tube Q2, the second diode D2, the bus resistor R7, the bus capacitor C4, and the negative power interface are connected in sequence. Among them, the bus resistor R7 refers to the resistor R7 as the resistor in the bus capacitor soft-start circuit.

[0034] Exemplarily, the power switch tube Q2 can be implemented as an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), a triode, a silicon carbide MOS, or a GANFET.

[0035] For example, if the power switch Q2 is a MOS tube, the cathode of the first diode D1 is connected to the drain of the power switch Q2. For another example, if the power switch Q2 is an IGBT or a triode, the cathode of the first diode D1 is connected to the collector of the power switch Q2. The positive power supply interface and the negative power supply interface can be connected to an external power supply. For example, referring to Figure 1 , external power source is represented by Bat. C4 can be charged through the power interface.

[0036] The drive-on subsystem is used to drive the power switch tube to turn on. The drive-on subsystem includes a drive-on energy supply unit, a drive-on unit, and a drive undervoltage lockout unit.

[0037] The drive opening energy supply unit is used to provide driving voltage and current for the driving pole of the power switch tube. Figure 1 As shown in the dotted box 2, the driving opening energy supply unit is connected in series with a series resistor and a driving energy storage capacitor, and the driving energy storage capacitor is connected in parallel with a voltage limiting functional component.

[0038] Specifically, the first resistor R1, the second resistor R2, and the first capacitor C1 are connected in sequence. A first voltage stabilizing diode Z1 is connected in parallel with the first capacitor C1. The first resistor R1 is connected to the cathode of the first diode D1. The connection point between the second resistor R2 and the first capacitor C1 is connected to one end of the switch S1. When the power supply connected to the bus capacitor soft-start loop is turned on, the first capacitor C1 is charged through the first resistor R1 and the second resistor R2, and the first voltage stabilizing diode Z1 limits the charging voltage of the first capacitor C1. Current flows through the first resistor R1 and the second resistor R2 to the switch S1.

[0039] Exemplarily, the switch S1 is a mechanical switch such as a relay or a button. In another exemplary embodiment, the switch S1 is an electronic switch such as a controlled optocoupler or a photo-metal-oxide-semiconductor solid-state relay (PhotoMOS).

[0040] In some embodiments, the first resistor R1 and the second resistor R2 are implemented as one resistor. For example, the first resistor R1 and the second resistor R2 are implemented as the same resistor.

[0041] In some other embodiments, the first resistor R1 and the second resistor R2 are implemented by multiple resistors. For example, the first resistor R1 is composed of two resistors, and the second resistor R2 is composed of two resistors.

[0042] The drive opening unit is used to transmit the drive voltage to the drive undervoltage lockout unit. Figure 1 As shown in the dashed box 4, the drive activation unit consists of a switch S1, a third resistor R3, and a second capacitor C2. The other end of switch S1 is connected to the third resistor R3 and the second capacitor C2 in sequence. When switch S1 is closed, current flows to the third resistor R3. The third resistor R3 provides current limiting. The second capacitor C2 provides filtering. The drive activation unit can receive a drive activation command or signal via the switch. After the switch is closed, the drive voltage is transmitted to the drive undervoltage lockout unit.

[0043] In some embodiments, the driving-on unit may not include the second capacitor C2 for filtering.

[0044] The driver undervoltage lockout unit is used to disconnect the power switch tube in time when the driving voltage of the power switch tube is insufficient. In other words, the driver undervoltage lockout unit is used to disconnect the power switch tube when the actual driving voltage received by the power switch tube is less than the driving voltage required by the power switch tube. Figure 1As shown in the dashed box 3, the driver undervoltage lockout unit consists of a drive voltage amplitude determination component and a drive energy output component. The driver undervoltage lockout unit can monitor the drive voltage amplitude provided to the power switch in real time and promptly disconnect the power switch when the drive voltage is insufficient.

[0045] The driver undervoltage lockout unit includes a first transistor Q1, a fourth resistor R4, a fifth resistor R5, a second Zener diode Z2, a sixth resistor R6, and a third capacitor C3. The first electrode of the first transistor Q1 is connected to the driver enable unit. The third electrode of the first transistor Q1 is connected to the cathode of the fifth resistor R5 and the second Zener diode Z2, in that order. The fourth resistor R4 is connected in parallel with the first electrode of the first transistor Q1 and the third electrode of the first transistor Q1. The second electrode of the first transistor Q1 is connected to the driver electrode (also known as the gate electrode) of the power switch Q2, one end of the sixth resistor R6, and one end of the third capacitor C3. The other end of the sixth resistor R6 is connected to the other end of the third capacitor C3, the first electrode of the power switch Q2, the first capacitor C1, the first Zener diode Z1, the second capacitor C2, and the anode of the second Zener diode Z2, serving as a common reference point for the drive voltage of the power switch Q2.

[0046] In some embodiments, the positions of the second voltage stabilizing diode Z2 and the fifth resistor R5 can be interchanged, that is, the third electrode of the first transistor Q1 is connected to the second voltage stabilizing diode Z2 and the fifth resistor R5 in sequence.

[0047] In some embodiments, the first electrode of the first transistor Q1 is connected to a connection point between the third resistor R3 and the second capacitor C2 in the driving-on unit.

[0048] The sixth resistor R6 and the third capacitor C3 provide filtering. The fifth resistor R5 limits the current in the path between the first transistor Q1 and the second Zener diode Z2. The second Zener diode Z2 is used to determine the threshold for the driving voltage. When the voltage at the input terminal of the first transistor Q1, i.e., the first terminal, increases, causing the voltage of the second Zener diode Z2 to reach the turn-on voltage, triggering it to turn on, the first transistor Q1 also turns on. After the first transistor Q1 turns on, the power switch Q2 receives the driving voltage. When this driving voltage exceeds the turn-on threshold voltage of the power switch Q2, the power switch Q2 begins to conduct and charges the bus capacitor C4.

[0049] In some embodiments, the regulated voltage of the second zener diode Z2 can be adjusted. For example, this can be achieved by connecting multiple zener diodes in series. Another example is by setting the fifth resistor R5 as an adjustable resistor. The regulated voltage of the second zener diode can be adjusted by referring to related art and will not be further described here.

[0050] By adjusting the stabilizing voltage of the second zener diode Z2, the gate voltage applied to the power switch Q2 can be adjusted. When the voltage at the first terminal of the first transistor Q1 decreases, the voltage at the second zener diode Z2 also decreases. When the voltage at the first terminal of the first transistor Q1 falls below the conduction threshold (an example of the second threshold) of the second zener diode Z2, the second zener diode Z2 and the first transistor Q1 are turned off. The voltage of the third capacitor C3 is discharged by the sixth resistor R6, causing the gate drive voltage of the power switch Q2 to quickly drop below the turn-on threshold voltage of the power switch Q2, turning off the power switch Q2. Therefore, the gate drive voltage of the power switch Q2 is controlled at two levels by the switch S1 and the first transistor Q1. S1 is controlled externally, and the first transistor Q1 cooperates with the fourth resistor R4, the fifth resistor R5, and the second zener diode Z2 to achieve automatic undervoltage lockout. When the terminal voltage of the first capacitor C1 is lower than the threshold set by the second voltage stabilizing diode Z2, the driving voltage cannot be applied to the gate of the power switch Q2 even if the switch S1 is turned on, thereby ensuring that the power switch Q2 does not operate in an undersaturated state at a low driving voltage, thereby reducing the risk of damage to the power switch Q2 due to large losses.

[0051] In some embodiments, the positions of the fifth resistor R5 and the second voltage stabilizing diode Z2 can be interchanged. For example, the third electrode of the first transistor Q1 is connected to the voltage stabilizing diode Z2 and the fifth resistor R5 in sequence.

[0052] In some embodiments, the driving undervoltage lockout unit may not include the fifth resistor R5 having a current limiting function.

[0053] In some embodiments, the driving undervoltage lockout unit may not include the sixth resistor R6 and the third capacitor C3 having a filtering function.

[0054] In some embodiments, the first transistor Q1 is a PNP transistor, wherein the first electrode of the first transistor Q1 is an emitter, the second electrode is a collector, and the third electrode is a base.

[0055] In some other embodiments, the first transistor Q1 is a PMOS field effect transistor, the first electrode of the first transistor Q1 is a source, the second electrode is a drain, and the third electrode is a gate.

[0056] The drive shutdown subsystem is used to drive the power switch tube to shut down. The drive shutdown subsystem includes a drive locking unit and a drive unlocking unit. In some embodiments, the drive shutdown subsystem also includes a drive shutdown energy supply unit.

[0057] The drive closing energy supply unit is used to provide the drive voltage and current for the drive locking unit. Figure 1The dashed box 5 shown, driving the shutdown energy supply unit includes: an eighth resistor R8, a ninth resistor R9, and a fifth capacitor C5. One end of the eighth resistor R8 is connected to the cathode of the first diode D1, and the other end of the eighth resistor R8 is connected to one end of the ninth resistor R9. The other end of the ninth resistor R9 is connected to one end of the fifth capacitor C5, and the other end of the fifth capacitor C5 is connected to the common reference point of the drive voltage of the power switch tube Q2. When the power supply Bat connected to the bus capacitor soft-start loop is turned on, current flows through the eighth resistor R8 and the ninth resistor R9 to the fifth capacitor C5. The fifth capacitor C5 is charged through the eighth resistor R8 and the ninth resistor R9.

[0058] Similar to the first resistor R1 and the second resistor R2 described above, the eighth resistor R8 and the ninth resistor R9 can be implemented by one resistor or by multiple resistors.

[0059] In some embodiments, the driving-off energy supply unit further includes a third voltage stabilizing diode Z3 , which is connected in parallel with the fifth capacitor C5 , and which limits the charging voltage of the fifth capacitor C5 .

[0060] The drive lock unit is used to speed up the shutdown of the power switch in the bus capacitor soft start circuit. Figure 1 As shown in the dotted box 6, the drive locking unit includes a series-connected drive resistor and a drive locking functional component.

[0061] The anode of the fourth voltage zener diode Z4 is connected to the first electrode of the third transistor Q3. The second electrode of the third transistor Q3 is connected to one end of the tenth resistor R10, and the other end of the tenth resistor R10 is connected to the gate electrode of the power switch Q2. The third electrode of the third transistor Q3 is connected to the first electrode of the power switch Q2. In other words, the third electrode of the third transistor Q3 is connected to the common reference point of the drive voltage of the power switch Q2. The cathode of the fourth voltage zener diode Z4 is connected to the drive-off energy supply unit.

[0062] The power switch Q2 itself can be slowly turned off by slowly discharging the energy of the third capacitor C3 through the sixth resistor R6. With the addition of the drive-lock unit (dashed-line box 6), when the third transistor Q3 is turned on, it is equivalent to adding a discharge circuit of the third capacitor C3 via the tenth resistor R10. The resistance of R10 is 50-1000 times smaller than that of R6 (for example, R10 is 10 kilo-ohms and R6 is 1000 kilo-ohms). Therefore, the establishment of the drive-lock unit can accelerate the discharge of the third capacitor C3 and accelerate the shutdown of the power switch Q2.

[0063] In some embodiments, the third transistor Q3 is a triode, wherein the first electrode of the third transistor Q3 is an emitter, the second electrode is a collector, and the third electrode is a base.

[0064] The driving unlocking unit is used to accelerate the discharge of energy of the fifth capacitor C5 in the driving energy supply unit when the power switch tube Q2 is turned on, thereby accelerating the conduction process of the power switch tube Q2. Figure 1 As shown in the dotted box 7, the unlocking drive unit includes a fast discharge component.

[0065] Exemplarily, the rapid discharge component is implemented by a third diode D3. The anode of the third diode D3 is connected to the drive-off energy supply unit via the connection point between the ninth resistor R9 and the fifth capacitor C5. The cathode of the third diode D3 is connected to the drive-off energy supply unit via the eighth resistor.

[0066] In some embodiments, the resistance of the sixth resistor R6 is much greater than the resistance of the tenth resistor R10. For example, the resistance of the sixth resistor R6 is 100 times greater than the resistance of the tenth resistor R10. For example, the resistance of the sixth resistor R6 is 1000 kilo-ohms, and the resistance of the tenth resistor R10 is 10 kilo-ohms. For another example, the resistance of the sixth resistor R6 is 500 kilo-ohms, and the resistance of the tenth resistor R10 is 5 kilo-ohms. When the terminal voltage of the fourth Zener diode Z4 exceeds its conduction voltage, the fourth Zener diode Z4 turns on, and the third transistor Q3 turns on. When the third transistor Q3 turns on, the tenth resistor R10 is connected in parallel between the gate and emitter of the power switch Q2. In other words, the gate of the power switch Q2 is connected to the emitter via the tenth resistor R10, and the tenth resistor R10 is connected in parallel with the sixth resistor R6 and the third capacitor C3. This rapidly reduces the resistance across the third capacitor C3, causing the voltage of the third capacitor C3 to discharge quickly, thereby dissipating the drive voltage of the power switch Q2. The power switch tube Q2 is reliably turned off, or in other words, the power switch tube Q2 is locked.

[0067] In some embodiments, the resistance of the tenth resistor R10 is much greater than the resistance of the third resistor R3. For example, the resistance of the tenth resistor R10 is greater than five times the resistance of the third resistor R3. For example, the resistance of the third resistor R3 is 100 ohms, and the resistance of the tenth resistor R10 is 5 kiloohms. For another example, the resistance of the third resistor R3 is 1 kiloohm, and the resistance of the tenth resistor R10 is 5 kiloohms.

[0068] When the power switch Q2 needs to be turned on, the current flowing out of the first transistor Q1 is much greater than the discharge current of the tenth resistor R10, so the gate voltage of the power switch Q2 is quickly established. At this time, the collector voltage of the power switch Q2 drops rapidly, and the third diode D3 simultaneously pulls it down, quickly turning off the third transistor Q3, and the third diode D3 drives the device to quickly unlock.

[0069] The working principle of the embodiment of the present application is explained below by describing two states: the switch S1 is disconnected and the switch S1 is connected after the external power supply Bat is connected.

[0070] When switch S1 is off, the current is divided into two main paths:

[0071] Path 1: Current flows from the positive terminal of the external power supply Bat, passing through the first diode D1, the eighth resistor R8, the ninth resistor R9, the fifth capacitor C5, the second diode D2, the bus resistor R7, and the bus capacitor C4, returning to the negative terminal of the external power supply Bat. The primary purpose of this path is to charge the fifth capacitor C5 in the drive-off energy supply unit. In some embodiments, the value of the fifth capacitor C5 is 100nF, C1 = 1000uF, C2 = 1-10uF, and C3 = 0.1-1uF. Due to the small capacitance of the fifth capacitor C5, it will charge rapidly and trigger the fourth Zener diode Z4 and the third transistor Q3 to turn on. Consequently, the power switch Q2 is reliably shut off via the tenth resistor R10.

[0072] Path 2: Current flows out from the positive terminal of the external power supply Bat, passes through the first diode D1, the first resistor R1, the second resistor R2, the first capacitor C1, the second diode D2, the bus resistor R7, and the bus capacitor C4, and returns to the negative terminal of the external power supply Bat. The main purpose of this path is to charge the first capacitor C1 in the drive opening energy supply unit to store sufficient driving energy for the subsequent driving of the power switch tube Q2. In some embodiments, the first capacitor C1 is a capacitor of the thousand uF level. For example, the value of the first capacitor C1 is 2000 uF, the value of the second capacitor C2 is 10 uF, the value of the third capacitor C3 is 20 uF, and the value of the fifth capacitor C5 is 100 nF. The first capacitor C1 is more than 100-1000 times larger than the second capacitor C2, the third capacitor C3, and the fifth capacitor C5. Due to the large capacity of the first capacitor C1, the voltage at the first capacitor C1 terminal rises slowly. After rising to the conduction voltage of the first voltage regulator diode Z1, the voltage at the first capacitor C1 terminal no longer rises and remains constant.

[0073] In some embodiments, the forward voltage of the first Zener diode Z1 is higher than a first threshold and lower than the maximum threshold withstand voltage of the power switch Q2. For example, the first threshold is 80% of the maximum threshold withstand voltage of the power switch Q2 at Z1. For example, if the threshold voltage VGSmax of the power switch Q2 is 20V, the Z1 regulated voltage can be 18V. This ensures a safe and reliable gate of the power switch Q2. In some embodiments, the forward voltage of the second Zener diode Z2 is lower than that of the first Zener diode Z1 and higher than the minimum turn-on threshold voltage of the power switch Q2.

[0074] When the switch S1 is in the on state:

[0075] In some embodiments, after the voltage of the first capacitor C1 approaches the voltage that triggers the first Zener diode Z1 to turn on, that is, the first capacitor C1 is nearly fully charged, the switch S1 is turned on.

[0076] In some embodiments, the controller determines the time required for the first capacitor C1 to charge to the regulated voltage value of the first Zener diode Z1, i.e., the time required for the first capacitor C1 to be fully charged. When the first capacitor C1 is nearly fully charged or fully charged, the controller turns on the switch S1. This ensures that the voltage of the first capacitor C1 is sufficiently high and the energy is sufficient, thereby completing the soft start of the bus capacitor C4 in one charge.

[0077] In some embodiments, the switch S1 can be controlled to be turned on and off by a controller.

[0078] After switch S1 is turned on, the first transistor Q1 is turned on, synchronously triggering the power switch Q2 to turn on. The bus capacitor C4 soft-start circuit Bat, the first diode D1, the power switch Q2, the second diode D2, the bus resistor R7, and the bus capacitor C4 are connected, and the external power supply Bat charges the bus capacitor C4. When switch S1 is turned on, current first flows through the third resistor R3, the first transistor Q1, the fifth resistor R5, and the second voltage-stabilizing diode Z2. Thereafter, the first transistor Q1 conducts normally. The drive current then flows through the third resistor R3 and the first transistor Q1, causing the gate voltage of the power switch Q2 to rise rapidly, quickly turning on the power switch Q2. The collector voltage of the power switch Q2 drops rapidly, and the third transistor Q3 is quickly turned off via the third diode D3. The fourth resistor R4 ensures the reliable shutoff of the first transistor Q1 when the first transistor Q1 is turned off. While the power switch Q2 is on, the first capacitor C1 has no energy source, and the voltage across the first capacitor C1 slowly drops. After the voltage at the first capacitor C1 drops to a level that turns off the second voltage stabilizing diode Z2, the first transistor Q1 turns off. Since the third capacitor C3 has a small capacitance, the gate voltage of the power switch Q2 also drops rapidly, turning off the power switch Q2.

[0079] Without the driver undervoltage lockout unit (Dash-line box 3), the voltage of first capacitor C1 is not monitored. If the voltage of C1 is low and S1 remains on, power switch Q2 will enter an undersaturated conduction state. A high charging current through power switch Q2, charging bus capacitor C4, can cause significant losses in power switch Q2, potentially damaging it. Therefore, the driver undervoltage lockout unit (Dash-line box 3) plays a crucial role in protecting power switch Q2.

[0080] In some embodiments, the driver undervoltage lockout unit can be implemented as Figure 2The dashed box 3 in the figure. The drive undervoltage lockout unit includes a drive voltage determination circuit, a fourth resistor R4, a first transistor Q1, a sixth resistor R6, and a third capacitor C3. The drive voltage determination circuit utilizes a comparator U1. The drive voltage determination circuit includes an eleventh resistor R11, a twelfth resistor R12, a fifth resistor R5, a second voltage stabilizing diode Z2, and the comparator U1. The first electrode of the first transistor Q1 is connected to the drive enable unit. The first electrode of the first transistor Q1 is also connected to the first power supply terminal of the comparator U1, the first end of the fifth resistor R5, and the first end of the eleventh resistor R11. The second end of the fifth resistor is connected to the positive input terminal of the comparator U1 and the cathode of the second voltage stabilizing diode Z2. The second end of the eleventh resistor R11 is connected to the first end of the twelfth resistor and the negative input terminal of the comparator U1. The third electrode of the first transistor Q1 is connected to the output terminal of the comparator U1. The fourth resistor R4 is connected in parallel with the first and third electrodes of the first transistor Q1. The second electrode of the first transistor Q1 is connected to the drive electrode (also called the gate electrode) of the power switch Q2, one end of a sixth resistor R6, and one end of a third capacitor C3. The other end of the sixth resistor R6 is connected to the other end of the third capacitor C3, the first electrode of the power switch Q2, the first capacitor C1, the first Zener diode Z1, the second capacitor C2, the anode of the second Zener diode Z2, the second end of the twelfth resistor R12, and the second power supply terminal of the comparator U1. The second Zener diode Z2 is used to generate a comparison reference voltage.

[0081] In some embodiments, Figure 2 The second Zener diode Z2 in is replaced by a reference chip.

[0082] In some embodiments, the driver undervoltage lockout unit can be implemented as Figure 3 The dotted box 3 in the figure. The driving voltage discrimination circuit of the undervoltage lockout unit uses an integrated chip U1 with a built-in reference. Among them, the first electrode of the first transistor Q1 is connected to the connection point of the third resistor R3 and the second capacitor C2. The first electrode of the first transistor Q1 is also connected to the first power supply terminal of the comparator U1 (or the positive power supply terminal of the comparator) and the first end of the fifth resistor R5. The second end of the fifth resistor R5 is connected to the negative input terminal of the comparator U1 and the first end of the eleventh resistor R11. The third electrode of the first transistor Q1 is connected to the output terminal of the comparator U1. The fourth resistor R4 is connected in parallel with the first electrode and the third electrode of the first transistor Q1. The second electrode of the first transistor Q1 is connected to the driving electrode of the power switch tube Q2, one end of the sixth resistor R6 and one end of the third capacitor C3. The other end of the sixth resistor R6 is connected to the other end of the third capacitor C3, the first electrode of the power switch tube Q2, the first capacitor C1, the first voltage regulator diode Z1, the second capacitor C2, the second end of the eleventh resistor R11, and the second power supply end of the comparator U1 (or the negative power supply end of the comparator U1).

[0083] In some embodiments, the driver undervoltage lockout unit can be implemented as Figure 4 The dashed box 3 in the figure. The driving voltage discrimination circuit for the undervoltage lockout unit uses an integrated chip U1 with an internal reference. Integrated chip U1 also has an input hysteresis voltage setting function. The first electrode of the first transistor Q1 is connected to the connection point between the third resistor R3 and the second capacitor C2. The first electrode of the first transistor Q1 is also connected to the first power supply terminal (positive power supply) of the integrated chip U1 and the first end of the fifth resistor R5. The second end of the fifth resistor R5 is connected to the negative input terminal of the first comparator within the integrated chip U1 and the first end of the eleventh resistor R11. The second end of the eleventh resistor R11 is connected to the first end of the twelfth resistor and the positive input terminal of the second comparator within the integrated chip U1. The third electrode of the first transistor Q1 is connected to the output terminal of the integrated chip U1. The fourth resistor R4 is connected in parallel with the first and third electrodes of the first transistor Q1. The second electrode of the first transistor Q1 is connected to the driving electrode of the power switch Q2, one end of the sixth resistor R6, and one end of the third capacitor C3. The other end of the sixth resistor R6 is connected to the other end of the third capacitor C3, the first electrode of the power switch tube Q2, the first capacitor C1, the first voltage regulator diode Z1, the second capacitor C2, the second end of the twelfth resistor R12 and the second power supply end (or power ground end) of the integrated chip U1.

[0084] In some embodiments, reference Figure 5 The first transistor Q1 and the third transistor Q3 may be field effect transistors, wherein Q1 is a P-channel field effect transistor and Q3 is an N-channel field effect transistor.

[0085] It should be noted that multiple embodiments of the present application can be combined with each other to form a new embodiment. The execution order between the steps of each process of the method embodiment is only exemplary and does not constitute a limitation on the execution order between the steps. The steps can also be executed in other orders.

[0086] Furthermore, the terms "including," "having," and any variations thereof, as used in the description of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not limited to the listed steps or units, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to the process, method, product, or apparatus.

[0087] It should be noted that in the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being more preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

Claims

1. A bus capacitor DC soft start system, characterized in that: It includes a drive opening subsystem, a drive closing subsystem and a bus capacitor soft starting circuit; the drive opening subsystem includes a drive opening energy supply unit, a drive opening unit and a drive undervoltage lockout unit; The bus capacitor soft-start circuit is used to charge the bus capacitor; the bus capacitor soft-start circuit includes a power switch tube and a bus capacitor, and the power switch tube is used to control the charging of the bus capacitor; The driving shutdown subsystem is used to drive the power switch tube to shut down; The driving opening energy supply unit is used to provide driving voltage and current for the driving electrode of the power switch tube; The driving opening unit is used to transmit the driving voltage to the driving undervoltage lockout unit; The driving undervoltage lockout unit is used to disconnect the power switch tube when the driving voltage of the power switch tube is insufficient.

2. The system according to claim 1, wherein: The driving undervoltage lockout unit includes: a first transistor, a fourth resistor, a fifth resistor, a second voltage stabilizing diode, a sixth resistor and a third capacitor; The first electrode of the first transistor is connected to the drive opening unit; the third electrode of the first transistor is connected to the fifth resistor and the cathode of the second voltage-stabilizing diode in sequence; the fourth resistor is connected in parallel with the first electrode of the first transistor and the third electrode of the first transistor; the second electrode of the first transistor is connected to the drive electrode of the power switch tube, one end of the sixth resistor and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube and the anode of the second voltage-stabilizing diode.

3. The system according to claim 1, wherein: The driving undervoltage lockout unit includes: a first transistor, a second voltage stabilizing diode, a comparator, a fourth resistor, a fifth resistor, a sixth resistor, an eleventh resistor, a twelfth resistor and a third capacitor; The first electrode of the first transistor is connected to the drive opening unit; the first electrode of the first transistor is also connected to the first power supply terminal of the comparator, the first end of the fifth resistor, and the first end of the eleventh resistor; the second end of the fifth resistor is connected to the positive input terminal of the comparator and the cathode of the second voltage-stabilizing diode; the second end of the eleventh resistor is connected to the first end of the twelfth resistor and the negative input terminal of the comparator; the third electrode of the first transistor is connected to the output terminal of the comparator; the fourth resistor is connected in parallel with the first and third electrodes of the first transistor; the second electrode of the first transistor is connected to the drive electrode of the power switch tube, one end of the sixth resistor and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube, the anode of the second voltage-stabilizing diode, the second end of the twelfth resistor and the second power supply terminal of the comparator.

4. The system according to claim 1, wherein: The driving undervoltage lockout unit includes: a first transistor, a comparator, a fifth resistor, an eleventh resistor, a fourth resistor, a sixth resistor and a third capacitor; The first electrode of the first transistor is connected to the drive opening unit, the positive power supply terminal of the comparator, and the first end of the fifth resistor; the second end of the fifth resistor is connected to the negative input terminal of the comparator and the first end of the eleventh resistor; the third electrode of the first transistor is connected to the output terminal of the comparator; the fourth resistor is connected in parallel with the first and third electrodes of the first transistor; the second electrode of the first transistor is connected to the drive electrode of the power switch tube, one end of the sixth resistor and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube, the second end of the eleventh resistor and the negative power supply terminal of the comparator.

5. The system according to any one of claims 1 to 4, characterized in that: The driving opening energy supply unit includes: a first resistor, a second resistor, a first capacitor and a first voltage stabilizing diode; the driving opening unit includes a switch; The first resistor, the second resistor and the first capacitor are connected in sequence, the first voltage regulator diode is connected in parallel with the first capacitor, the first resistor is connected to the bus capacitor soft-start loop, the connection point between the second resistor and the first capacitor is connected to the first end of the switch, and the first capacitor is connected to the first pole of the power switch tube.

6. The system according to any one of claims 1 to 4, characterized in that The driving undervoltage lockout unit includes: an integrated chip, a fifth resistor, an eleventh resistor, a twelfth resistor, a first transistor, a fourth resistor, a sixth resistor, and a third capacitor, wherein the integrated chip has an input hysteresis voltage setting function and includes a first comparator and a second comparator inside the integrated chip; The first electrode of the first transistor is connected to the drive opening unit, the positive power supply electrode of the integrated chip, and the first end of the fifth resistor; the second end of the fifth resistor is connected to the negative input end of the first comparator inside the integrated chip and the first end of the eleventh resistor; the second end of the eleventh resistor is connected to the first end of the twelfth resistor and the positive input end of the second comparator inside the integrated chip; the third electrode of the first transistor is connected to the output end of the integrated chip; the fourth resistor is connected in parallel with the first electrode and the third electrode of the first transistor; the second electrode of the first transistor is connected to the drive electrode of the power switch tube, one end of the sixth resistor and one end of the third capacitor; the other end of the sixth resistor is connected to the other end of the third capacitor, the first electrode of the power switch tube, the second end of the twelfth resistor and the power ground end of the integrated chip.

7. The system according to any one of claims 1 to 4, characterized in that The driving closing subsystem includes a driving locking unit; the driving locking unit includes: a fourth voltage stabilizing diode, a third transistor, and a tenth resistor; The anode of the fourth voltage stabilizing diode is connected to the first electrode of the third transistor; the second electrode of the third transistor is connected to one end of the tenth resistor, and the other end of the tenth resistor is connected to the driving electrode of the power switch tube; the third stage of the third transistor is connected to the first electrode of the power switch tube, and the cathode of the fourth voltage stabilizing diode is connected to the drain of the power switch tube.

8. The system according to any one of claims 1 to 4, characterized in that The driving closing subsystem further includes a driving unlocking unit; the driving unlocking unit includes a third diode; The cathode of the fourth voltage stabilizing diode is connected to the drain of the power switch tube, which includes: the cathode of the third diode is connected to the drain of the power switch tube, and the anode of the third diode is connected to the cathode of the fourth voltage stabilizing diode.

9. The system according to any one of claims 1 to 4, characterized in that The first transistor is a PNP transistor, wherein the first electrode of the first transistor is an emitter, the second electrode is a collector, and the third electrode is a base; or The first transistor is a PMOS field effect transistor, wherein the first electrode of the first transistor is a source, the second electrode is a drain, and the third electrode is a gate.

10. A photovoltaic energy storage inverter, characterized in that: It comprises a controller and the bus capacitor DC soft-start system according to any one of claims 1 to 9, wherein the controller is electrically connected to the bus capacitor soft-start system.

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