A soft start circuit and power supply circuit

Abstract

The utility model discloses a soft start circuit and power supply circuit, apply to power supply technical field to solve the problem of low reliability of soft start circuit structure complex in prior art, specifically including soft start branch in the starting stage limit input to the current of external power converter circuit, the main contact of contactor is connected with the first end of soft start branch, the normally open contact of contactor is connected with the second end of soft start branch, the coil of contactor is connected with control module, and contactor is used to connect the positive output end of external power supply and the positive input end of external power converter circuit in normal operation stage, dry contact input module is used for detecting the on-off state of the normally closed contact of contactor, generates contactor state signal and sends to control module. In this way, a single contactor is used to replace multiple relays in parallel, and the normally closed contact state of the contactor is directly detected through the dry contact input module, which simplifies the structure of the soft start circuit and improves the reliability of the soft start circuit.

Description

Technical Field

[0001] This utility model relates to the field of power supply technology, and in particular to a soft start circuit and a power supply circuit. Background Technology

[0002] With the rapid development of power electronics technology, high-power power supplies have been widely used in industrial automation, new energy power generation, and electric vehicles. In high-power power supply design, large-capacity electrolytic capacitors are typically connected directly or indirectly at the input, generating significant inrush currents upon power-up, which may damage rectifier bridges, fuses, and other circuit components. To suppress inrush currents, existing technologies generally incorporate soft-start circuits.

[0003] Currently, soft-start circuits typically use multiple power relays connected in parallel to the main circuit. By gradually disconnecting current-limiting components through delay control, a smooth power supply startup is achieved. However, in practical applications, the lack of an effective status feedback mechanism when multiple power relays operate in parallel makes it impossible to monitor the operating status of each relay in real time. When some relays malfunction, the problem goes undetected, leading to uneven current distribution in each branch. In severe cases, this can cause overheating or even a complete power failure. Secondly, in some topologies (such as BOOST circuits), the main circuit carries a large current under normal operating conditions. If the main circuit needs to be disconnected under load, the arc generated during relay disconnection often burns out the contacts or fails to reliably disconnect the current. Existing technology struggles to reliably disconnect the main circuit in such situations. This is because directly disconnecting the circuit under high current conditions generates a strong arc, which may damage the relay contacts or cause other safety problems.

[0004] While existing soft-start circuits can mitigate current surges to some extent, their complex circuit structure and lack of effective status feedback mechanisms result in low overall reliability, making it difficult to meet the requirements of high-reliability power supply systems. Utility Model Content

[0005] This invention provides a soft-start circuit and a power supply circuit to solve the problems of complex structure and low reliability of existing soft-start circuits.

[0006] The technical solution provided by this utility model is as follows: On the one hand, this utility model provides a soft start circuit, including: a soft start branch, a contactor, a dry contact input module, and a control module; The first end of the soft starter branch is connected to the positive output terminal of the external power supply, the second end of the soft starter branch is connected to the positive input terminal of the external power converter circuit, and the control terminal of the soft starter branch is connected to the control module; the negative output terminal of the external power supply is connected to the negative input terminal of the external power converter circuit; the soft starter branch is used to limit the current input to the external power converter circuit during the startup phase. The main contacts of the contactor are connected to the first end of the soft starter branch, the normally open contacts of the contactor are connected to the second end of the soft starter branch, the coil of the contactor is connected to the control module, and the contactor is used to connect the positive output terminal of the external power supply and the positive input terminal of the external power converter circuit during normal operation. The input terminal of the dry contact input module is connected to the normally closed contact of the contactor, and the output terminal of the dry contact input module is connected to the control module. The dry contact input module is used to detect the on / off state of the normally closed contact of the contactor, generate a contactor status signal, and send it to the control module.

[0007] Optionally, the soft start branch includes: a soft start relay and a soft start resistor; The first terminal of the soft start relay is connected to the positive output terminal of the external power supply, the second terminal of the soft start relay is connected to the external power converter circuit via a soft start resistor, and the coil of the soft start relay is connected to the control module.

[0008] Optionally, the control module includes: a control board, a drive circuit, and an auxiliary power supply; The first power supply terminal of the control board is connected to the positive output terminal of the auxiliary power supply, and the second power supply terminal of the control board is connected to the negative output terminal of the auxiliary power supply; the output terminal of the control board is connected to the control terminal of the drive circuit. The first terminal of the drive circuit is connected to the first terminal of the coil of the soft start relay, the second terminal of the drive circuit is connected to the negative output terminal of the auxiliary power supply, the third terminal of the drive circuit is connected to the first terminal of the coil of the contactor, the fourth terminal of the drive circuit is connected to the negative output terminal of the auxiliary power supply, and the second terminals of the coils of the soft start relay and the contactor are connected to the positive output terminal of the auxiliary power supply.

[0009] Optionally, the drive circuit includes: a first controllable switch and a second controllable switch; The first controllable switch is connected in series between the first end of the coil of the soft start relay and the negative output terminal of the auxiliary power supply, and the control terminal of the first controllable switch is connected to the first output terminal of the control board. The second controllable switch is connected in series between the first end of the contactor coil and the negative output terminal of the auxiliary power supply, and the control terminal of the second controllable switch is connected to the second output terminal of the control board.

[0010] Optionally, the driving circuit may also include: a first diode and a first capacitor; The anode of the first diode is connected to the positive output terminal of the auxiliary power supply, and the cathode of the first diode is connected to the second terminal of the coil of the soft start relay, the second terminal of the coil of the contactor, and the first power supply terminal of the control board, respectively. The negative terminal of the first capacitor is connected to the negative output terminal of the auxiliary power supply, and the positive terminal of the first capacitor is connected to the cathode of the first diode.

[0011] Optionally, the dry contact input module includes: an optocoupler isolator; The input side of the optocoupler is connected in series with the normally closed contact of the contactor to form a detection circuit, and the output side of the optocoupler is electrically connected to the control module.

[0012] Optionally, the soft-start circuit may also include: a second capacitor; The positive terminal of the second capacitor is connected to the second terminal of the soft start branch, and the negative terminal of the second capacitor is connected to the negative input terminal of the external power converter circuit.

[0013] Optionally, the soft-start circuit may also include: a voltage acquisition module; The first input terminal of the voltage acquisition module is connected to the positive output terminal of the external power supply, and the second input terminal of the voltage acquisition module is connected to the negative output terminal of the external power supply; the third input terminal of the voltage acquisition module is connected to the second terminal of the soft starter branch, and the fourth input terminal of the voltage acquisition module is connected to the negative terminal of the second capacitor; the first output terminal of the voltage acquisition module is connected to the second input terminal of the control board; and the second output terminal of the voltage acquisition module is connected to the third input terminal of the control board.

[0014] Optionally, the voltage acquisition module includes: a first differential amplifier circuit and a second differential amplifier circuit; The first input terminal of the first differential amplifier circuit is connected to the positive output terminal of the external power supply, the second input terminal of the first differential amplifier circuit is connected to the negative output terminal of the external power supply, and the output terminal of the first differential amplifier circuit is connected to the second input terminal of the control board. The first input terminal of the second differential amplifier circuit is connected to the second terminal of the soft start branch, and the second input terminal of the second differential amplifier circuit is connected to the negative terminal of the second capacitor; the output terminal of the second differential amplifier circuit is connected to the third input terminal of the control board.

[0015] On the other hand, this utility model provides a power supply circuit, including: the above-mentioned soft start circuit and power converter circuit; The positive input terminal of the soft starter circuit is connected to the positive output terminal of the external power supply, the negative input terminal of the soft starter circuit is connected to the negative output terminal of the external power supply, the positive output terminal of the soft starter circuit is connected to the positive input terminal of the power converter circuit, and the negative output terminal of the soft starter circuit is connected to the negative input terminal of the power converter circuit.

[0016] The beneficial effects of this utility model are as follows: This invention replaces multiple relays in parallel with a single contactor, and directly detects the normally closed contact state of the contactor through a dry contact input module, simplifying the structure of the soft starter circuit and enabling real-time detection of the soft starter circuit's on / off state. The normally closed contact of the contactor is mechanically linked to the main contact. By detecting the on / off state of the normally closed contact, the dry contact module can directly, in real-time, and without error reflect the actual state of the soft starter circuit, improving its reliability. Furthermore, this invention uses a single contactor suitable for high-current applications, and the contactor's mechanical structure ensures rapid and synchronous contact disconnection, avoiding current concentration caused by asynchronous shutdown. When the contactor is normally shut off, the current flows only to the main contact, avoiding uneven current distribution caused by parallel components.

[0017] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of this invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the present invention and constitute a part of this invention, illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the present invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the first structure of the soft starter circuit in this embodiment of the present invention; Figure 2 This is a schematic diagram of a second structure of the soft starter circuit in an embodiment of this utility model; Figure 3 This is a schematic diagram of the third structure of the soft starter circuit in this embodiment of the present invention; Figure 4 This is a schematic diagram of the fourth structure of the soft starter circuit in this embodiment of the present invention; Figure 5 This is a schematic diagram of the fifth structure of the soft starter circuit in this embodiment of the present invention; Figure 6 This is a schematic diagram of the sixth structure of the soft starter circuit in this embodiment of the present invention; Figure 7 This is a schematic diagram of the seventh structure of the soft starter circuit in this embodiment of the present invention; Figure 8 This is a schematic diagram of the power supply circuit in an embodiment of the present invention.

[0019] Icons: 100 - Soft starter circuit; 110 - Soft starter branch; KM1 - Contactor; 120 - Dry contact input module; 121 - Optocoupler isolator; 130 - Control module; 131 - Control board; 132 - Drive circuit; 133 - Auxiliary power supply; 134 - First controllable switch; 135 - Second controllable switch; 140 - Voltage acquisition module; 141 - First differential amplifier circuit; 142 - Second differential amplifier circuit; 200 - Power supply circuit; 210 - Power converter circuit; K1 - Soft starter relay; R1 - Soft starter resistor; D1 - First diode; C1 - First capacitor; C2 - Second capacitor. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] This utility model embodiment provides a soft starter circuit 100, see reference. Figure 1 As shown, the soft starter circuit 100 includes at least: a soft starter branch 110, a contactor KM1, a dry contact input module 120, and a control module 130; The first terminal of the soft starter branch 110 is connected to the positive output terminal of the external power supply, the second terminal of the soft starter branch 110 is connected to the positive input terminal of the external power converter circuit, and the control terminal of the soft starter branch 110 is connected to the control module 130; the negative output terminal of the external power supply is connected to the negative input terminal of the external power converter circuit; the soft starter branch 110 is used to limit the current input to the external power converter circuit during the startup phase. The main contact of contactor KM1 is connected to the first end of the soft starter branch 110, the normally open contact of contactor KM1 is connected to the second end of the soft starter branch 110, the coil of contactor KM1 is connected to the control module 130, and contactor KM1 is used to connect the positive output terminal of the external power supply and the positive input terminal of the external power converter circuit during normal operation. The input terminal of the dry contact input module 120 is connected to the normally closed contact of the contactor KM1, and the output terminal of the dry contact input module 120 is connected to the control module 130. The dry contact input module 120 is used to detect the on / off state of the normally closed contact of the contactor KM1, generate the contactor KM1 status signal and send it to the control module 130.

[0022] exist Figure 1In the soft-start circuit 100 shown, the soft-start branch 110 can limit the current input to the external power converter circuit during startup, preventing overcurrent damage to the power devices in the external power converter circuit. Contactor KM1 is connected in parallel across the soft-start branch 110 via its main contacts and normally open contacts. This short-circuit is used after the soft-start branch 110 has completed startup, reducing conduction losses. The dry contact input module 120 detects the on / off state of the normally closed contacts of contactor KM1 and generates high / low level contactor KM1 status signals, which are sent to the control module 130. For example, a high-level contactor KM1 status signal corresponds to a normally closed contact being open, indicating that contactor KM1 is engaged; a low-level contactor KM1 status signal corresponds to a normally closed contact being closed, indicating that contactor KM1 is disengaged.

[0023] In practical applications, during the startup phase, the control module 130 first enables the soft-start branch 110. Current slowly charges the power converter through the soft-start branch 110, suppressing capacitor charging surges in the external power converter circuit. Simultaneously, the normally closed contact of the control contactor KM1 closes. The dry contact input module 120 detects the closure of the normally closed contact, generates a corresponding level contactor KM1 status signal, and feeds it back to the control module 130. During the switching phase, when the switching condition is met, the control module 130 drives the contactor KM1 coil to engage, the main contacts close, and the soft-start branch 110 is short-circuited. The switching condition is that the startup phase duration reaches a preset time threshold or the capacitor voltage in the external power converter circuit reaches a preset voltage value. Simultaneously, the normally closed contact opens, the signal of the dry contact input module 120 changes, and a corresponding level contactor KM1 status signal is fed back to the control module 130. During normal operation, the current output from the external power supply is directly transmitted to the external power converter circuit through contactor KM1, and the soft starter branch 110 is short-circuited to reduce heat loss. Simultaneously, when the dry contact input module 120 detects that the normally closed contact is closed, it corresponds to an abnormality in contactor KM1, such as contact sticking. Upon receiving the corresponding contactor KM1 status signal, the control module 130 issues an alarm and triggers protective actions such as disconnecting contactor KM1 to lock the output.

[0024] In this way, the present invention uses a single contactor KM1 instead of multiple relays connected in parallel, and directly detects the normally closed contact state of contactor KM1 through the dry contact input module 120, simplifying the structure of the soft starter circuit 100 and realizing real-time detection of the on / off state of the soft starter circuit 100. The normally closed contact of contactor KM1 is mechanically linked with the main contact. By detecting the on / off state of the normally closed contact, the dry contact module can directly, in real time, and without error reflect the actual state of the soft starter circuit 100, improving the reliability of the soft starter circuit 100. In addition, the use of a single contactor KM1 in the present invention is suitable for high-current applications, and the mechanical structure of contactor KM1 can ensure that the contacts open quickly and synchronously, avoiding current concentration caused by asynchronous shutdown. When contactor KM1 is normally shut off, the current only passes through the main contact of contactor KM1, avoiding the problem of uneven current distribution caused by parallel components.

[0025] In practical implementation, the soft-start branch in a soft-start circuit has various structures to achieve its function; see [reference needed]. Figure 2 As shown, the soft starter branch 110 includes: a soft starter relay K1 and a soft starter resistor R1; The first terminal of the soft start relay K1 is connected to the positive output terminal of the external power supply, the second terminal of the soft start relay K1 is connected to the external power converter circuit via the soft start resistor R1, and the coil of the soft start relay K1 is connected to the control module 130.

[0026] exist Figure 2 In the soft-start circuit 100 shown, the soft-start relay K1 can be either a mechanical relay or a solid-state relay. Its contact current must be higher than the rated current output by the power module, and its withstand voltage rating must be higher than the maximum output voltage of the power module. The soft-start resistor R1 is calculated based on the current limiting value and the power module's output voltage. During the startup phase, the control module 130 energizes the relay coil, causing the contacts to close. The current output from the external power supply flows through the soft-start relay K1 and the soft-start resistor R1 to the external power converter circuit. The soft-start resistor R1 limits the current flowing into the external power converter circuit to prevent surges.

[0027] In practical implementation, the control module in the soft starter circuit has various structures to achieve its function; see [reference needed]. Figure 3 As shown, the control module 130 includes: a control board 131, a drive circuit 132, and an auxiliary power supply 133; The first power supply terminal of the control board 131 is connected to the positive output terminal of the auxiliary power supply 133, and the second power supply terminal of the control board 131 is connected to the negative output terminal of the auxiliary power supply 133; the output terminal of the control board 131 is connected to the control terminal of the drive circuit 132. The first terminal of the drive circuit 132 is connected to the first terminal of the coil of the soft start relay K1, the second terminal of the drive circuit 132 is connected to the negative output terminal of the auxiliary power supply 133, the third terminal of the drive circuit 132 is connected to the first terminal of the coil of the contactor KM1, the fourth terminal of the drive circuit 132 is connected to the negative output terminal of the auxiliary power supply 133, and the second terminals of the coils of the soft start relay K1 and the contactor KM1 are connected to the positive output terminal of the auxiliary power supply 133.

[0028] exist Figure 3 In the soft-start circuit 100 shown, the auxiliary power supply 133 supplies power to the control board 131 and the drive circuit 132. The auxiliary power supply 133 can also supply power to other load modules, such as display modules, communication modules, and sensor signal conditioning modules. The drive circuit 132 includes two independent drive channels, which control the soft-start relay K1 and contactor KM1 respectively. Driven by the control board 131, the drive circuit 132 can connect or disconnect the coil of the soft-start relay K1 from the negative output terminal of the auxiliary power supply 133, thereby controlling the soft-start relay K1 by connecting or disconnecting the power supply circuit of its coil. Similarly, driven by the control board 131, the drive circuit 132 can connect or disconnect the coil of the contactor KM1 from the negative output terminal of the auxiliary power supply 133, thereby controlling the contactor KM1 by connecting or disconnecting the power supply circuit of its coil. The control board 131 is powered by the auxiliary power supply 133 and receives the contactor KM1 status signal from the dry contact input module 120 and other external signals. The control board 131 has a built-in MCU, PLC, or programmable logic device, runs a soft-start control algorithm, and dynamically adjusts control commands based on the input voltage, load current, and contactor KM1 status. The control board 131 can also send control signals (such as PWM or level signals) to the drive circuit 132 through corresponding I / O ports to control the timing of the soft-start relay K1 and contactor KM1. The control board 131 can also monitor the non-engaged state of contactor KM1 and trigger protective actions such as cutting off the drive signal, alarm, and output shutdown. Furthermore, during the shutdown phase, the downstream external power converter circuit is generally shut down first, and then contactor KM1 is disconnected. If the downstream external power converter circuit cannot be shut down or malfunctions, the control board 131 directly controls contactor KM1 to disconnect, avoiding the risk of overcurrent, overvoltage, and other abnormalities caused by continuous power supply to the downstream load.

[0029] In one possible implementation, see [reference] Figure 4 As shown, the drive circuit 132 includes: a first controllable switch 134 and a second controllable switch 135; The first controllable switch 134 is connected in series between the first end of the coil of the soft start relay K1 and the negative output terminal of the auxiliary power supply 133, and the control terminal of the first controllable switch 134 is connected to the first output terminal of the control board 131. The second controllable switch 135 is connected in series between the first end of the coil of contactor KM1 and the negative output terminal of auxiliary power supply 133, and the control terminal of the second controllable switch 135 is connected to the second output terminal of control board 131.

[0030] exist Figure 4 In the soft-start circuit 100 shown, both the first controllable switch 134 and the second controllable switch 135 can be transistors, MOSFETs, or relays. The control board 131 can drive the first controllable switch 134 to connect or disconnect the coil of the soft-start relay K1 from the negative output terminal of the auxiliary power supply 133, and the control board 131 can drive the second controllable switch 135 to connect or disconnect the coil of the contactor KM1 from the negative output terminal of the auxiliary power supply 133.

[0031] In one possible implementation, see [reference] Figure 5 As shown, the driving circuit 132 also includes: a first diode D1 and a first capacitor C1; The anode of the first diode D1 is connected to the positive output terminal of the auxiliary power supply 133, and the cathode of the first diode D1 is connected to the second terminal of the coil of the soft start relay K1, the second terminal of the coil of the contactor KM1, and the first power supply terminal of the control board 131. The negative terminal of the first capacitor C1 is connected to the negative output terminal of the auxiliary power supply 133, and the positive terminal of the first capacitor C1 is connected to the cathode of the first diode D1.

[0032] exist Figure 5 In the soft-start circuit 100 shown, the first diode D1 enables unidirectional conduction of the power path and also isolates it from other modules when the auxiliary power supply 133 supplies power to other modules through the same port. The first capacitor C1 absorbs high-frequency noise in the auxiliary power supply 133, providing low-noise power supply. Furthermore, when the auxiliary power supply 133 fails to supply power, it delays the power supply to the control board 131, drive circuit 132, contactor KM1, and soft-start relay K1, allowing the control board 131 to turn off contactor KM1 and soft-start relay K1, thus preventing damage to contactor KM1 and soft-start relay K1 due to current interruption. The capacitance of the first capacitor C1 can be determined using the following formula.

[0033]

[0034] Where P is the total power consumed by contactor KM1, relay and control board 131, t is the time required to delay power supply, V1 is the rated output voltage of auxiliary power supply 133, V2 is the minimum operating voltage of contactor KM1, relay and control board 131, and C is the minimum capacity of the first capacitor C1.

[0035] In practical implementation, the dry contact input module in the soft starter circuit has various structures to achieve its function; see [reference needed]. Figure 6 As shown, the dry contact input module includes: an optocoupler isolator 121; The input side of the optocoupler 121 is connected in series with the normally closed contact of the contactor KM1 to form a detection circuit, and the output side of the optocoupler 121 is electrically connected to the control module 130.

[0036] exist Figure 6 In the soft-start circuit 100 shown, when contactor KM1 is not engaged, its normally closed contact is closed, the detection circuit is connected, and the positive terminal of auxiliary power supply 133 passes sequentially through the normally closed contact of contactor KM1 and the input side of optocoupler to the negative terminal of auxiliary power supply 133. The LED on the input side of optocoupler isolator 121 is energized and illuminates, and the phototransistor on the output side of optocoupler isolator 121 is turned on, sending a low-level signal to control module 130. When contactor KM1 is engaged, its normally closed contact is open, the detection circuit is cut off, the LED on the input side of optocoupler isolator 121 is de-energized and does not illuminate, and the phototransistor on the output side of optocoupler isolator 121 is turned off, sending a high-level signal to control module 130.

[0037] In one possible implementation, see [reference] Figure 6 As shown, the soft starter circuit 100 also includes: a second capacitor C2; The positive terminal of the second capacitor C2 is connected to the second terminal of the soft start branch 110, and the negative terminal of the second capacitor C2 is connected to the negative input terminal of the external power converter circuit.

[0038] exist Figure 6 In the soft-start circuit 100 shown, the second capacitor C2 is used to reduce the voltage ripple input to the external power converter circuit. The inclusion of the second capacitor C2 requires a corresponding soft-start branch to be configured in the circuit. During the startup phase, the soft-start branch limits the current, controlling the charging rate of the second capacitor C2 and preventing surge impacts caused by excessive initial charging current.

[0039] In one possible implementation, see [reference] Figure 7 As shown, the soft starter circuit 100 also includes a voltage acquisition module 140; The first input terminal of the voltage acquisition module 140 is connected to the positive output terminal of the external power supply, and the second input terminal of the voltage acquisition module 140 is connected to the negative output terminal of the external power supply; the third input terminal of the voltage acquisition module 140 is connected to the second terminal of the soft starter branch 110, and the fourth input terminal of the voltage acquisition module 140 is connected to the negative terminal of the second capacitor C2; the first output terminal of the voltage acquisition module 140 is connected to the second input terminal of the control board 131; and the second output terminal of the voltage acquisition module 140 is connected to the third input terminal of the control board 131.

[0040] exist Figure 7 In the soft-start circuit 100 shown, the voltage acquisition module 140 is used to acquire the output voltage of the external power supply and send it to the control board 131. It also acquires the voltage between the second terminal of the soft-start branch 110 and the negative input terminal of the power converter and sends it to the control board 131. The control board 131 can monitor the output voltage of the external power supply and the stability of the voltage between the second terminal of the soft-start branch 110 and the negative input terminal of the power converter in real time. During the switching phase, the control board 131 can also determine the voltage difference across contactor KM1 based on the output voltage of the external power supply and the voltage between the second terminal of the soft-start branch 110 and the negative input terminal of the power converter, and control contactor KM1 to close when the voltage across contactor KM1 is less than a preset threshold. In addition, when the external power converter circuit of the subsequent stage is under load, there may be a situation where soft start fails. The voltage difference between the two ends of the soft start branch 110 can be determined according to the output voltage of the external power supply and the voltage between the second end of the soft start branch 110 and the negative input terminal of the power converter. When the voltage difference between the two ends of the soft start branch 110 is abnormal, the soft start relay K1 is controlled to disconnect the soft start branch 110.

[0041] In practical implementation, the voltage acquisition module in the soft-start circuit has various structures to achieve its function; see [reference needed]. Figure 7 As shown, the voltage acquisition module 140 includes: a first differential amplifier circuit 141 and a second differential amplifier circuit 142; The first input terminal of the first differential amplifier circuit 141 is connected to the positive output terminal of the external power supply, the second input terminal of the first differential amplifier circuit 141 is connected to the negative output terminal of the external power supply, and the output terminal of the first differential amplifier circuit 141 is connected to the second input terminal of the control board 131. The first input terminal of the second differential amplifier circuit 142 is connected to the second terminal of the soft start branch 110, the second input terminal of the second differential amplifier circuit 142 is connected to the negative terminal of the second capacitor C2, and the output terminal of the second differential amplifier circuit 142 is connected to the third input terminal of the control board 131.

[0042] Based on the same concept, this utility model embodiment also provides a power supply circuit, see reference. Figure 8As shown, the power supply circuit 200 includes: the aforementioned soft starter circuit 100 and the power converter circuit 210; The positive input terminal of the soft starter circuit 100 is connected to the positive output terminal of the external power supply, the negative input terminal of the soft starter circuit 100 is connected to the negative output terminal of the external power supply, the positive output terminal of the soft starter circuit 100 is connected to the positive input terminal of the power converter circuit 210, and the negative output terminal of the soft starter circuit 100 is connected to the negative input terminal of the power converter circuit 210.

[0043] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0044] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this utility model without departing from the spirit and scope of the embodiments of this utility model. Therefore, if these modifications and variations to the embodiments of this utility model fall within the scope of the claims of this utility model and their equivalents, then this utility model also intends to include these modifications and variations.

Claims

1. A soft-start circuit, characterized in that, include: Soft starter branch, contactor, dry contact input module and control module; The first end of the soft starter branch is connected to the positive output terminal of the external power supply, the second end of the soft starter branch is connected to the positive input terminal of the external power converter circuit, and the control terminal of the soft starter branch is connected to the control module; the negative output terminal of the external power supply is connected to the negative input terminal of the external power converter circuit; the soft starter branch is used to limit the current input to the external power converter circuit during the startup phase. The main contact of the contactor is connected to the first end of the soft starter branch, the normally open contact of the contactor is connected to the second end of the soft starter branch, the coil of the contactor is connected to the control module, and the contactor is used to connect the positive output terminal of the external power supply and the positive input terminal of the external power converter circuit during normal operation. The input terminal of the dry contact input module is connected to the normally closed contact of the contactor, and the output terminal of the dry contact input module is connected to the control module. The dry contact input module is used to detect the on / off state of the normally closed contact of the contactor, generate a contactor status signal, and send it to the control module.

2. The soft-start circuit according to claim 1, characterized in that, The soft starter branch includes: a soft starter relay and a soft starter resistor; The first terminal of the soft start relay is connected to the positive output terminal of the external power supply, the second terminal of the soft start relay is connected to the external power converter circuit via the soft start resistor, and the coil of the soft start relay is connected to the control module.

3. The soft-start circuit according to claim 2, characterized in that, The control module includes: a control board, a drive circuit, and an auxiliary power supply; The first power supply terminal of the control board is connected to the positive output terminal of the auxiliary power supply, and the second power supply terminal of the control board is connected to the negative output terminal of the auxiliary power supply; the output terminal of the control board is connected to the control terminal of the drive circuit. The first end of the drive circuit is connected to the first end of the coil of the soft start relay, the second end of the drive circuit is connected to the negative output terminal of the auxiliary power supply, the third end of the drive circuit is connected to the first end of the coil of the contactor, the fourth end of the drive circuit is connected to the negative output terminal of the auxiliary power supply, and the second end of the coil of the soft start relay and the second end of the coil of the contactor are connected to the positive output terminal of the auxiliary power supply.

4. The soft-start circuit according to claim 3, characterized in that, The driving circuit includes: a first controllable switch and a second controllable switch; The first controllable switch is connected in series between the first end of the coil of the soft start relay and the negative output terminal of the auxiliary power supply, and the control terminal of the first controllable switch is connected to the first output terminal of the control board. The second controllable switch is connected in series between the first end of the contactor coil and the negative output terminal of the auxiliary power supply, and the control terminal of the second controllable switch is connected to the second output terminal of the control board.

5. The soft-start circuit according to claim 3, characterized in that, The driving circuit further includes: a first diode and a first capacitor; The anode of the first diode is connected to the positive output terminal of the auxiliary power supply, and the cathode of the first diode is connected to the second terminal of the coil of the soft start relay, the second terminal of the coil of the contactor, and the first power supply terminal of the control board, respectively. The negative terminal of the first capacitor is connected to the negative output terminal of the auxiliary power supply, and the positive terminal of the first capacitor is connected to the cathode of the first diode.

6. The soft-start circuit according to any one of claims 3-5, characterized in that, The dry contact input module includes: an optocoupler isolator; The input side of the optocoupler is connected in series with the normally closed contact of the contactor to form a detection circuit, and the output side of the optocoupler is electrically connected to the control module.

7. The soft-start circuit according to claim 6, characterized in that, Also includes: Second capacitor; The positive terminal of the second capacitor is connected to the second terminal of the soft start branch, and the negative terminal of the second capacitor is connected to the negative input terminal of the external power converter circuit.

8. The soft-start circuit according to claim 7, characterized in that, Also includes: Voltage acquisition module; The first input terminal of the voltage acquisition module is connected to the positive output terminal of the external power supply, and the second input terminal of the voltage acquisition module is connected to the negative output terminal of the external power supply; the third input terminal of the voltage acquisition module is connected to the second terminal of the soft starter branch, and the fourth input terminal of the voltage acquisition module is connected to the negative terminal of the second capacitor; the first output terminal of the voltage acquisition module is connected to the second input terminal of the control board; and the second output terminal of the voltage acquisition module is connected to the third input terminal of the control board.

9. The soft-start circuit according to claim 8, characterized in that, The voltage acquisition module includes: a first differential amplifier circuit and a second differential amplifier circuit; The first input terminal of the first differential amplifier circuit is connected to the positive output terminal of the external power supply, the second input terminal of the first differential amplifier circuit is connected to the negative output terminal of the external power supply, and the output terminal of the first differential amplifier circuit is connected to the second input terminal of the control board. The first input terminal of the second differential amplifier circuit is connected to the second terminal of the soft start branch, and the second input terminal of the second differential amplifier circuit is connected to the negative terminal of the second capacitor; the output terminal of the second differential amplifier circuit is connected to the third input terminal of the control board.

10. A power supply circuit, characterized in that, include: The soft starter circuit and power converter circuit as described in any one of claims 1-9; The positive input terminal of the soft starter circuit is connected to the positive output terminal of the external power supply, the negative input terminal of the soft starter circuit is connected to the negative output terminal of the external power supply, the positive output terminal of the soft starter circuit is connected to the positive input terminal of the power converter circuit, and the negative output terminal of the soft starter circuit is connected to the negative input terminal of the power converter circuit.

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