High-voltage large-current slow start control circuit and method based on MOS (Metal Oxide Semiconductor) tube

Abstract

The invention provides a slow start control circuit and method for high voltage and large current. The circuit comprises an MOS tube energizing array, a DC-DC power supply module, a timing circuit and a gate drive circuit. The MOS tube energizing array comprises a plurality of N-channel power MOS tubes which are connected in parallel, drain electrodes of the N-channel power MOS tubes are jointly connected with an external power supply, and source electrodes of the N-channel power MOS tubes are jointly connected with a load; and the timing circuit is used for converting a low level provided for the high-voltage side gate driving chip U3 into a high level after a preset duration is prolonged, triggering the driving chip U3 to work, and controlling the MOS tube energizing array to be conducted after the driving chip U3 works, so that a high-voltage power supply is provided for a load after being delayed.

Description

Technical Field

[0001] This invention belongs to the field of power supply control technology, specifically relating to a high-voltage, high-current soft-start control circuit and method based on MOSFETs. Background Technology

[0002] Currently, high-current, high-voltage power supplies commonly use mechanical switches such as contactors and circuit breakers when connected to the power grid or load. This approach has an inherent flaw: at the moment of connection and disconnection, the physical contact action can cause arcing (spraying). Under high-voltage, high-current conditions, the arcing problem is particularly prominent, leading to the following key issues: 1. Safety hazards: High-energy electric arcs can easily cause fires and severely burn the contacts, leading to increased contact resistance and equipment damage.

[0003] 2. Low reliability: Contact erosion significantly shortens the lifespan of the device, requiring frequent replacement and resulting in high maintenance costs.

[0004] 3. System impact: The surge current at the moment of connection impacts the power supply and load, affecting system stability.

[0005] Existing mechanical switches cannot fundamentally solve the problems of arcing and impact caused by sudden changes in voltage and current. Summary of the Invention

[0006] This invention provides a high-voltage, high-current soft-start control circuit and method based on MOSFETs, aiming to solve the problem of arcing (sparking) caused by the physical contact action when using mechanical switches such as contactors and circuit breakers to connect high-voltage, high-current power supplies in the prior art, as well as the resulting safety hazards, device burn-out, electromagnetic interference and surge current impact.

[0007] The present invention provides a first aspect of a soft-start control circuit for high voltage and high current, comprising: a MOSFET power-on array, a DC-DC power supply module, a timing circuit, and a gate drive circuit; The MOSFET power array consists of multiple N-channel power MOSFETs connected in parallel. The drains of each N-channel power MOSFET are connected to an external power supply, and the sources are connected to a load. The DC-DC power module is connected to an external power source to convert the voltage of the external power source and supply power to the timing circuit and the gate drive circuit. The timing circuit includes: a timer chip U2, a resistor R5, and a capacitor C1; the first end of capacitor C1 is connected to the output terminal of the DC-DC power module, the second end of capacitor C6 is connected to the first end of resistor R5 and the trigger pin of the timer chip U2, and the second end of resistor R5 is grounded. The gate drive circuit uses a high-voltage side gate drive chip U3. The input is connected to the output of the timer chip U2, and the output is connected to the gate of the MOSFET power-on array through a gate resistor. The timing circuit is used to extend the preset time and then convert the low level provided to the high-voltage side gate driver chip U3 to a high level, triggering the driver chip U3 to work. After the driver chip U3 works, it controls the MOS transistor power array to conduct, thereby providing the high-voltage power supply to the load after a delay.

[0008] Optionally, the DC-DC power module includes a converter U1 and a filter circuit.

[0009] Optionally, the filter circuit includes: aluminum electrolytic capacitor C2, ceramic capacitor C3, electrolytic capacitor C5 and ceramic capacitor C6; An aluminum electrolytic capacitor C2 and a ceramic capacitor C3 are connected in parallel and placed on the input voltage side of converter U1; Electrolytic capacitor C5 and ceramic capacitor C6 are connected in parallel and set on the output voltage side of converter U1.

[0010] Optionally, aluminum electrolytic capacitor C2 has a withstand voltage of 250V, ceramic capacitors C3 and C6 have a capacitance of 100nF, and electrolytic capacitor C5 has a capacitance of 470μF.

[0011] Optionally, a capacitor is connected in parallel between the gate and source of each MOSFET.

[0012] Optionally, a 0.001Ω precision sampling resistor can be connected in series with each source pin of the MOSFET and then connected in parallel.

[0013] Optionally, the MOSFET has a VDSS ≥ 180V, a continuous current ID ≥ 200A, and an on-resistance Rds < 5mΩ.

[0014] Optionally, the gate drive circuit may employ a charge pump circuit or a bootstrap circuit.

[0015] A second aspect of the present invention provides a slow-start control method for high voltage and high current, which is implemented using a slow-start control circuit for high voltage and high current as described in any one of the first aspects.

[0016] This invention provides a high-voltage, high-current soft-start control circuit and method based on MOSFETs, which has the following advantages: Intrinsic safety: Through timing control, arcing and sparking when the power is turned on are completely eliminated, solving the inherent pain point of mechanical switches at the root.

[0017] High reliability: Fully electronic control, no mechanical wear and contact erosion, and a lifespan far exceeding that of mechanical switches.

[0018] Soft start and surge suppression: The smooth conduction characteristics of the MOSFET effectively suppress the charging surge current of the capacitive load, achieving true "soft start".

[0019] Easy to expand: The unique low drive current requirement and multi-transistor parallel capability allow the circuit to be easily expanded in a modular manner to adapt to applications with different voltage and current levels, which is cost-effective. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a block diagram illustrating the basic principle of the present invention; Figure 2 This is a flowchart illustrating the overall process of this invention. Figure 3 This is the circuit diagram for the power module; Figure 4 This is a timing circuit diagram; Figure 5 This is a diagram of the gate drive circuit. Figure 6 This is a circuit diagram of a MOSFET power-on array. Figure 7 Shape of the drone soft-start device Figure 1 ; Figure 8 Shape of the drone soft-start device Figure 2 . Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0024] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0026] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0028] like Figure 1-6 As shown, the present invention provides a soft-start control method and circuit for high voltage and high current, including: a MOS transistor power-on array, a DC-DC power supply module, a timing circuit, and a gate drive circuit; the core concept is: by introducing a controlled "electronic switch delay", the two actions of "mechanical connection" and "electrical conduction" are separated in time.

[0029] This invention first ensures that the external physical connection (such as a plug being inserted into a socket) is stably established, and then conducts the power MOSFET without sparks through a gate drive circuit controlled by a timing circuit, thereby achieving a safe soft start.

[0030] The specific implementation method of the control circuit is as follows: (I) Power Path and Power Supply Initialization Power path: The positive terminal of the external high-voltage power supply is directly connected to the drain of the N-channel power MOSFET array, and its source is connected to the load, forming the main power channel.

[0031] Auxiliary power supply path: An external high-voltage power supply is simultaneously connected to a wide-input DC-DC power module. This module is responsible for converting the high-voltage input (e.g., 10V-180V) to a stable low voltage (e.g., 5V-12V), providing operating power for subsequent timing circuits and gate drive circuits. This design ensures that the power supply of the control circuit is independent of the main power switching state.

[0032] (ii) Generation of delayed trigger signal The core of the timing circuit is an RC delay network. Its working principle is as follows: a constant current is used to charge a timing capacitor. When the capacitor voltage reaches a preset threshold voltage, the circuit state flips, generating a trigger signal.

[0033] Key technical parameter: The delay time T_delay is determined by the formula T_delay≈k*R*C, where R is the resistance of the charging resistor, C is the capacitance of the timing capacitor, and k is a constant related to the circuit topology. By precisely configuring the ratio of R and C, the delay T_delay can be set in the range of hundreds of milliseconds to several seconds. This delay is much greater than the jitter time of mechanical contact, which is sufficient to ensure the complete stability of the physical connection.

[0034] (III) Establishment of gate drive voltage and MOSFET turn-on The gate drive circuit receives a trigger signal from the timing circuit. Its core function is to generate a gate-source voltage V_gs that is relative to the source of the MOS transistor and higher than its threshold voltage V_th.

[0035] One possible implementation involves using a charge pump circuit or a bootstrap circuit as the gate drive circuit. It utilizes the stable voltage provided by the power supply module to generate a gate drive voltage higher than the source voltage upon receiving a trigger signal. For a high-side N-channel MOSFET, its source voltage is close to ground potential before turn-on and close to the drain voltage after turn-on. The drive circuit must ensure a sufficiently high V_gs (typically 12V-15V) is provided at the moment of turn-on to allow the MOSFET to quickly enter a low-impedance state.

[0036] (iv) Power extension and static switching characteristics Parallel multi-MOSFET technology: Since this invention is applied to static switches (switching frequency close to 0Hz), the gate holding current after the MOSFET is turned on is extremely small. Therefore, a single gate drive circuit is capable of driving multiple power MOSFETs connected in parallel. To achieve current sharing, a small gate resistor should be connected in series with the gate of each MOSFET to suppress parallel loop oscillations.

[0037] Device selection: Power MOSFETs should be N-channel enhancement-type MOSFETs with a VDSS (drain-source breakdown voltage) higher than the system's highest voltage with sufficient margin, and an ID (continuous drain current) that meets the system's maximum current requirement. Their on-resistance R_ds(on) should be as low as possible to reduce conduction losses.

[0038] (v) Fundamental advantages The key to the entire turn-on process lies in the timing: stable physical connection → power-on of control circuit → delay and waiting → electronic switch conduction. Since the MOSFET starts conducting under zero current / zero voltage conditions (because the load has not yet established voltage), and its conduction process is controlled by V_gs, it is a smooth resistance change process, thus fundamentally avoiding sudden current changes and the resulting arcing phenomenon.

[0039] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. This embodiment takes the control of a 120V, 200A DC power supply system as an example, but the present invention is not limited to these specific parameters.

[0040] I. System Overall Connections and Power Path Reference Figure 1 , Figure 2 The positive terminal of an external high-voltage power supply (Vin=120VDC) is connected through input terminal J1. Subsequently, voltage is applied to the drain of a MOSFET array consisting of N-channel power MOSFETs Q1 to Q8 connected in parallel. The sources of the MOSFETs are connected to the output terminal J2 to supply power to the downstream load.

[0041] Key selection criteria: MOSFETs (Q1-Q8) should be selected with a withstand voltage VDSS≥180V, continuous current ID≥200A (up to 240A or more after parallel connection), and on-resistance Rds(on)<5mΩ. TOLL (lead-free TO leaded) packages are preferred to optimize thermal performance and power density under high current.

[0042] II. DC-DC Power Module Reference Figure 3The power module U1 employs a wide input voltage range isolated DC-DC converter (e.g., input range 10V-180VDC, output 12VDC / 1A). Its positive input terminal (Vin+) is connected after the positive terminal of an external high-voltage power supply, and its negative input terminal (Vin-) is connected to power ground (PGND). Its 12V stable output voltage (VCC) powers the entire control circuit, and its ground is control ground (GND).

[0043] Filtering Design: A 22μF aluminum electrolytic capacitor C2 (250V withstand voltage) and a 100nF ceramic capacitor C3 are connected in parallel near the input pin of U1 to provide energy storage and absorb high-frequency noise on the power line. A 470μF electrolytic capacitor C5 and a 100nF ceramic capacitor C6 are connected in parallel between VCC and GND at the output terminal to provide stable instantaneous current and filter out high-frequency interference.

[0044] III. Timing Circuit Reference Figure 4 (Timing circuit diagram) The core of the timing circuit is a monostable trigger composed of a time base chip U2 (such as NE555).

[0045] Delay setting: The delay time is determined by resistor R5 and capacitor C1, and the calculation formula is T_delay≈1.1*R5*C1. To achieve a delay of approximately 4 seconds, R5=76.8kΩ and C1=47μF are selected. This delay is much greater than the mechanical jitter time that may occur when the plug is inserted into the socket (usually <100ms).

[0046] Operating logic: After the circuit is powered on, the charging of capacitor C1 can be regarded as a closed circuit. The TRIG and THRES pins are at a high level, and the OUT output is turned off. During the capacitor charging process, the potential of the TRIG and THRES pins drops. When the potential of the TRIG and THRES pins is lower than 1 / 3VCC, the OUT output is high and remains high. This high level is the drive signal of U3.

[0047] One end of R5 connected to C1 is also connected to the cathode of diode D2 and the THRES pin of U2, while the anode of diode D2 is grounded; one end of C7 is connected to the CONT pin of U2, and the other end is grounded.

[0048] Among them, the THRES pin (threshold terminal) is a voltage detection pin. When the input voltage is higher than 2 / 3VCC, it triggers the chip to reset, causing the output terminal to turn low.

[0049] CONT pin (control voltage terminal): Used to adjust the reference level of the threshold and trigger terminals. By default, an external 0.01μF capacitor needs to be connected to GND to filter out interference.

[0050] D2 is used to adjust the charging and discharging path to set specific timing parameters, and C7 is used for filtering to stabilize the internal reference voltage. Together, they ensure the timing accuracy and waveform stability of the 555 timer.

[0051] IV. Gate Drive Circuit Reference Figure 5 The gate drive circuit uses a high-voltage side gate drive chip U3, which integrates a charge pump and can generate a gate voltage higher than that of the source.

[0052] Signal connection: Connect the input (IN) of U3 to the output of U2. Connect the power supply pin (VDD) of U3 to VCC (12V).

[0053] Output and Protection: Refer to Figure 5 and Figure 6 The output of U3 corresponds to the gates of eight parallel MOSFETs (Q1~Q8), each gate connected in series with an independent 510Ω resistor (R8~R15); capacitors (C9~C16) are connected in parallel between the gate and source of each MOSFET; a 51kΩ resistor R16 is also connected in series in the gate circuit of Q1, and R16 is shared with a 500kΩ resistor R18 and one end of C9~C16. This circuit extends the rise time of Vgs through the gate RC circuit. Resistors R16 and R18 are used to release the gate charge when the drive circuit is not working, ensuring reliable turn-off of the MOSFETs, enabling soft start-up of capacitive loads and suppressing inrush current.

[0054] V. Detailed Explanation of the Work Process Connection and Power-on: Plug the external 120V power cord into the system socket. The physical connection process may be accompanied by slight bouncing and sparking, which is the problem this invention aims to solve.

[0055] Control circuit initialization: Power module U1 is powered on and outputs a stable VCC (12V). Timing circuit U2 begins a 4-second delay. At this time, although the physical connection is complete, the main circuit is still in the open state because the MOSFET is not turned on.

[0056] Delay waiting: During the 4-second delay period, any vibrations caused by unstable mechanical contact have completely subsided, and the system is in a state of rest.

[0057] Triggering and Soft Start: After a 4-second delay, U2 outputs a high level, triggering the driver chip U3 to operate. With the assistance of an external RC soft-start circuit, the gate voltage Vgs output by U3 slowly rises from 0V to 12V. MOSFETs Q1-Q8 then gradually enter the linear region (ohmic region) from the off-region, their equivalent resistance continuously decreasing, allowing the output voltage to smoothly rise from 0V to 120V. This achieves soft-start charging of capacitive loads, significantly suppressing inrush current and effectively preventing arcing.

[0058] Stable operation: When Vgs reaches 12V, the MOSFET enters the fully conducting state and operates with extremely low Rds(on), and the system enters an efficient and stable power supply state.

[0059] VI. Key Designs and Alternative Solutions Current sharing among multiple transistors: To achieve current sharing, a 0.001Ω precision sampling resistor (not shown in the figure) is connected in series to the source pins of Q1-Q8 and then connected in parallel. A symmetrical, low-impedance PCB layout (aluminum / copper substrate is recommended) is used to ensure that the parasitic parameters of each transistor are consistent, thereby achieving current balance.

[0060] Thermal design: Due to the excellent thermal performance of the TOLL package, the MOSFET is mounted on an aluminum heatsink or water-cooled plate with an insulating thermal pad to ensure that the junction temperature is below the safe value at the maximum current of 200A.

[0061] Alternative solutions: The timing circuit can also be implemented by software delay of a microcontroller (MCU), and the driving circuit can also adopt the "transformer isolation + driver IC" solution, all of which fall within the protection scope of this invention.

[0062] Through the specific electronic circuit implementation described above, this invention reliably achieves safe and arc-free access to 120V / 200A high voltage and high current, effectively solving the core pain points in the background technology.

[0063] In a specific embodiment, the slow-start control method and circuit for high voltage and high current provided by the present invention are applied to a drone as a drone slow-start device.

[0064] like Figure 7 and Figure 8 As shown, one end of the drone soft-start device is connected to the drone's load. When the drone is powered on, the battery is connected to the other end of the device. The device conducts after a delay of three to five seconds after the battery is connected, eliminating power-on sparks, slowing down the aging of the plug and ESC, and protecting the operator's safety.

[0065] The main functions of the drone soft-start device are as follows: a) Input voltage: Rated 24S, can operate normally with a battery input voltage of 10~102V; b) Operating current: Under cooling conditions with a wind speed of 5m / s, it can continuously operate at a maximum current of 250A; c) Delay time: 4S (±1S); d) Protection rating: IP67 waterproof and dustproof rating; e) Operating ambient temperature: -40~60℃; f) Weight: Not more than 550g; g) External dimensions: 89.6±0.2mm (length) × 98±0.2mm (width) × 25±0.2mm (height); h) Continuous working time: Under the cooling conditions of a wind speed of 5m / s, the 250A current will continue to work for 1 hour.

[0066] The drone soft-start device mainly consists of a shell, circuit board, power chip, delay chip, NMOS high-side static drive switch, NMOS transistor, resistor, capacitor, circuit board, busbar, shell, welding bracket, wires, and epoxy resin potting compound. Its specific working principle is as follows: The drone soft-start device circuit board integrates a DC power module, a delay module, a MOSFET driver module, and a MOSFET switch module, all connected to wires via a housing. When the drone is connected to a battery, the front-end voltage is input to the drone soft-start device. After being stepped down by the DC power module, it triggers the delay module to start timing. After a delay of 3-5 seconds, the delay module outputs a control signal to the MOSFET driver module, which then outputs a drive voltage to the MOSFET gate, turning on the MOSFET and allowing the downstream load to be powered by the battery. This achieves a 3-5 second delay before the drone powers on after being connected to the battery, preventing instantaneous arcing upon power-on.

[0067] The heat dissipation requirements are fully considered in the casing design. In addition to arranging heat dissipation slots on the external structure, thermal grease is applied to the circuit board and the casing mounting surface to effectively transfer heat to the heat sink.

[0068] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A soft-start control circuit for high voltage and high current, characterized in that, include: MOSFET power-on array, DC-DC power supply module, timing circuit, gate drive circuit; The MOSFET power array consists of multiple N-channel power MOSFETs connected in parallel. The drains of each N-channel power MOSFET are connected to an external power supply, and the sources are connected to a load. The DC-DC power module is connected to an external power source to convert the voltage of the external power source and supply power to the timing circuit and the gate drive circuit. The timing circuit includes: a timer chip U2, a resistor R5, and a capacitor C1; the first end of capacitor C1 is connected to the output terminal of the DC-DC power module, the second end of capacitor C6 is connected to the first end of resistor R5 and the trigger pin of the timer chip U2, and the second end of resistor R5 is grounded. The gate drive circuit uses a high-voltage side gate drive chip U3. The input is connected to the output of the timer chip U2, and the output is connected to the gate of the MOSFET power-on array through a gate resistor. The timing circuit is used to extend the preset time and then convert the low level provided to the high-voltage side gate driver chip U3 to a high level, triggering the driver chip U3 to work. After the driver chip U3 works, it controls the MOSFET power-on array to conduct, thereby providing the high-voltage power supply to the load after a delay.

2. The soft-start control circuit for high voltage and high current according to claim 1, characterized in that, The DC-DC power module includes a converter U1 and a filter circuit.

3. The soft-start control circuit for high voltage and high current according to claim 2, characterized in that, The filter circuit includes: aluminum electrolytic capacitor C2, ceramic capacitor C3, electrolytic capacitor C5, and ceramic capacitor C6; An aluminum electrolytic capacitor C2 and a ceramic capacitor C3 are connected in parallel and placed on the input voltage side of converter U1; Electrolytic capacitor C5 and ceramic capacitor C6 are connected in parallel and set on the output voltage side of converter U1.

4. The soft-start control circuit for high voltage and high current according to claim 3, characterized in that, The aluminum electrolytic capacitor C2 has a withstand voltage of 250V, the ceramic capacitors C3 and C6 have a capacitance of 100nF, and the electrolytic capacitor C5 has a capacitance of 470μF.

5. The soft-start control circuit for high voltage and high current according to claim 1, characterized in that, A capacitor is connected in parallel between the gate and source of each MOSFET.

6. The soft-start control circuit for high voltage and high current according to claim 1, characterized in that, A 0.001Ω precision sampling resistor is connected in series with each of the source pins of the MOSFET and then connected in parallel.

7. The soft-start control circuit for high voltage and high current according to claim 1, characterized in that, The MOSFET has a VDSS ≥ 180V, a continuous current ID ≥ 200A, and an on-resistance Rds < 5mΩ.

8. The soft-start control circuit for high voltage and high current according to claim 1, characterized in that, The gate drive circuit uses a charge pump circuit or a bootstrap circuit.

9. A soft-start control method for high voltage and high current, characterized in that, It is implemented using the soft-start control circuit for high voltage and high current as described in any one of claims 1-8.

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