A PCB AC adapter and a control method thereof

Abstract

The application relates to the field of adapters, in particular to a PCB AC adapter and a control method thereof. The adapter comprises a shell, a printed circuit board, an integrated AC input port, a DC output port, a power conversion module, a voltage / current sampling circuit, a control module and a surge protection circuit. The surge protection circuit comprises a parallel-connected pressure-sensitive resistor and gas discharge tube. The control method comprises the following steps: absorbing and discharging surge energy through the surge protection circuit, converting AC into DC and then performing voltage stabilization output, monitoring the output voltage and current in real time, cutting off the output when overvoltage or overcurrent occurs, and restoring when the condition disappears. The application solves the problem that the traditional adapter is easily damaged due to the large parasitic inductance leading to surge overshoot, and realizes the combination of ultra-high surge protection and high reliability in an ultra-small volume.

Description

Technical Field

[0001] This invention relates to the field of adapters, and more particularly to a PCB AC adapter and its control method. Background Technology

[0002] With the increasing prevalence of the Internet of Things (IoT), smart homes, industrial control, and portable electronic devices, the demand for miniaturized, highly reliable, and low-cost AC-DC power adapters is growing. These adapters not only need to provide a stable and clean DC output under normal operating conditions, but also must be able to operate safely and reliably in complex and harsh power grid environments.

[0003] However, traditional adapters often rely on a single varistor for surge protection, and their PCB layout lacks optimized parasitic inductance. This makes them susceptible to additional overshoot voltages during surges, rendering them unable to withstand high-amplitude surges. Consequently, the adapter is prone to damage during thunderstorms or in environments with unstable power grids, which can affect the normal operation of downstream electronic devices and even cause equipment failure. Summary of the Invention

[0004] The present invention aims to provide a PCB AC adapter and its control method to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A PCB AC adapter includes a housing, within which a printed circuit board is disposed. The printed circuit board integrates an AC input port, a DC output port, a power conversion module, a voltage sampling circuit, a current sampling circuit, and a control module. The printed circuit board also integrates a surge protection circuit connected between the AC input port and the power conversion module. The surge protection circuit includes at least a varistor and a gas discharge tube, which are connected in parallel.

[0007] Both the voltage sampling circuit and the current sampling circuit are connected between the DC output port and the control module.

[0008] The layout of the printed circuit board is configured such that the total parasitic inductance between the varistor and the gas discharge tube and the AC input port and the input terminal of the power conversion module is less than 50nH;

[0009] The surge protection circuit is configured to enable the adapter to withstand surge impacts conforming to a standard combination of waveforms, wherein the surge impact is defined as: a voltage peak value of 18kV to 22kV, a current peak value of 9kA to 11kA, voltage waveform time parameters of 1.2μs / 50μs, and current waveform time parameters of 8μs / 20μs; wherein 1.2μs and 8μs are the wavefront times of the voltage wave and current wave, respectively, and 50μs and 20μs are the half-peak times of the voltage wave and current wave, respectively.

[0010] Preferably, the surge protection circuit is configured to: clamp the voltage of the surge impact at the input terminal to the safe voltage range of the subsequent power conversion module through the coordinated operation of the varistor and the gas discharge tube; simultaneously, by controlling the total parasitic inductance below 50nH, suppress the additional overshoot voltage caused by the current change of the surge impact, wherein the additional overshoot voltage satisfies the following relationship with the total parasitic inductance and the rate of change of the surge impact current:

[0011]

[0012] in, For the additional overshoot voltage; The total parasitic inductance; The instantaneous value of the surge current; It is a differential operator that represents the rate of change with respect to time.

[0013] Preferably, the varistor is used to initially clamp the voltage of a surge impact, and its discharge current and the voltage across it satisfy its nonlinear volt-ampere characteristic:

[0014]

[0015] in, This represents the instantaneous discharge current of the varistor; Represents a time variable; This is a proportionality coefficient characterizing the conductivity of the varistor at a specific reference point; This represents the instantaneous voltage across the varistor; The reference voltage for the varistor; A coefficient characterizing the degree of nonlinearity in the voltage-current relationship of the varistor;

[0016] Furthermore, the rated voltage of the varistor is 175VAC, and the current carrying capacity is 10kA.

[0017] Preferably, when the energy of the surge impact exceeds a preset threshold, the gas discharge tube is broken down, and the voltage across its terminals drops to an arc sustaining voltage far below its breakdown voltage, thereby providing a low-impedance discharge path for the surge impact current. The breakdown voltage of the gas discharge tube is 1200V, and the maximum discharge current is 5kA.

[0018] Preferably, the insulation between the primary and secondary circuits of the adapter is configured to withstand a DC voltage of not less than 4750V or an AC voltage of 3000V for 3 seconds, and the leakage current is less than 10mA.

[0019] Preferably, the adapter is configured to operate continuously in an environment with an altitude of 0 to 100,000 feet, and the electrical clearance between its primary and secondary circuits is not less than 3.2 mm, and the creepage distance is not less than 6.4 mm.

[0020] Preferably, the control module includes a voltage feedback loop, which is configured such that the output voltage temperature coefficient of the DC output port is not higher than ±0.05% / ℃; the diameter of the printed circuit board is not greater than 35.5mm, and the total height of the printed circuit board and its components is not greater than 20mm.

[0021] A control method for a PCB AC adapter, used in any one of claims 1 to 7, comprising the following steps:

[0022] S1. Receives AC input voltage and absorbs and discharges energy from surge impacts occurring at the input terminal through the surge protection circuit with a total parasitic inductance of less than 50 nH.

[0023] S2. The AC power processed in S1 is converted into DC power through the power conversion module.

[0024] S3. The control module regulates the DC voltage obtained in S2 to obtain a stable DC voltage, which is then output from the DC output port.

[0025] S4. The output voltage and output current of the DC output port are monitored in real time through the voltage sampling circuit and the current sampling circuit. When the output voltage exceeds 110% of its rated value or the output current reaches 1.5A, the power conversion module is controlled to stop working to cut off the output.

[0026] Preferably, in S3, the control module dynamically adjusts the operating state of the power conversion module based on the feedback of the voltage sampling circuit, so as to control the ripple and noise peak of the DC output voltage below 68mVp-p, and the measurement bandwidth is DC-20MHz.

[0027] Preferably, the method further includes a recovery step S5:

[0028] After the power conversion module stops working due to S4, the output voltage and output current of the DC output port are continuously or intermittently monitored.

[0029] When the overvoltage or overcurrent condition that triggered the S4 action is detected to have disappeared, the power conversion module is automatically or restarted according to an external command to restore output.

[0030] The beneficial effects of this technical solution compared to existing technologies are as follows:

[0031] (1) This solution solves the problem of high-frequency parasitic inductance caused by improper PCB layout in traditional solutions by setting up a surge protection circuit that includes a varistor and a gas discharge tube connected in parallel, and configuring the total parasitic inductance between the varistor and the gas discharge tube and the AC input port and the power conversion module input terminal to be less than 50nH. The varistor first clamps the surge voltage initially. When the surge energy exceeds the preset threshold, the gas discharge tube breaks down to form a low-impedance discharge path, and the two work together to absorb the surge energy. At the same time, the low parasitic inductance design suppresses the additional overshoot voltage caused by the surge current change, so that the adapter can withstand high-amplitude surge impacts of 18kV to 22kV / 9kA to 11kA. It can still work stably in harsh environments such as thunderstorms and power grid fluctuations, avoiding damage to itself and failure of downstream equipment. This significantly improves the survivability and reliability of the adapter in extreme electromagnetic environments such as lightning strikes and power grid fluctuations, and effectively avoids damage to internal components caused by surges.

[0032] (2) By setting the total parasitic inductance to less than 50nH and clarifying that it, together with the surge current change rate, determines the additional overshoot voltage, the theoretical controllability and practical suppression of voltage overshoot during surges are achieved. Compared with the additional voltage spikes of hundreds or even thousands of volts generated by parasitic inductances of tens or even hundreds of nH in traditional layouts, this solution can control this overshoot voltage at an extremely low level, thereby providing sufficient safety margin for downstream devices, so that the adapter can withstand ultra-high surge impacts while its core power conversion module remains intact.

[0033] (3) By setting up a dual monitoring structure of voltage sampling circuit and current sampling circuit, combined with the coordinated control of the control module, comprehensive protection of output voltage and current is achieved. The voltage sampling circuit monitors the output voltage in real time to avoid the risk of overvoltage exceeding the rated value by 110%; the current sampling circuit accurately captures the output current and immediately triggers protection when it reaches the 1.5A overcurrent threshold, which solves the problems of single protection function and poor load stability of traditional adapters and ensures power supply safety.

[0034] (4) By setting the voltage feedback loop design of the control module, the voltage temperature coefficient of the DC output port is not higher than ±0.05% / ℃, and by dynamically adjusting the working state of the power conversion module, the output voltage ripple and noise peak are controlled below 68mVp-p (measurement bandwidth DC-20MHz). Compared with the output instability problem caused by the simplified design of traditional small adapters, this solution achieves a highly stable and low-ripple power supply output, which is suitable for the needs of sensitive electronic devices such as sensors and microcontrollers. Attached Figure Description

[0035] Figure 1 This is a flowchart of the method of the present invention;

[0036] Figure 2 This is a circuit diagram of the present invention;

[0037] Figure 3 for Figure 2 First enlarged schematic diagram of the middle section circuit;

[0038] Figure 4 for Figure 2 A second amplified schematic of the middle section circuit;

[0039] Figure 5 for Figure 2 A schematic diagram of the third amplification in the middle section of the circuit;

[0040] Figure 6 for Figure 2 A schematic diagram of the fourth amplification in the middle section of the circuit; Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0042] like Figure 1-6 The PCB AC adapter shown includes a housing made of one-piece plastic, which is a composite material of SABIC PC and nylon; the housing contains a printed circuit board, which integrates an AC input port, a DC output port, a power conversion module, a voltage sampling circuit, a current sampling circuit, and a control module.

[0043] AC input port: for connecting AC mains power ranging from 90VAC to 132VAC, with input frequency compatible with 50 / 60Hz.

[0044] DC output port: Used to output a stable DC voltage and matching load current. In this embodiment, the rated output voltage is 3.4V, with a tolerance range of ±5% (i.e., 3.23V to 3.57V), and the load current output range is 0A to 0.8A, which is suitable for 3W rated power supply requirements.

[0045] Power Conversion Module: Located in the central area of ​​the printed circuit board, this module employs an isolated switching power supply topology. Key components of this topology include a transformer providing electrical isolation and energy transfer, a primary-side main power switching transistor (MOSFET), a secondary rectifier diode, and an auxiliary startup resistor. The primary power MOSFET is controlled by a PWM drive signal output from the main control chip. The secondary rectifier diode rectifies the AC current induced on the transformer secondary side into DC current. The auxiliary startup resistor provides the initial startup voltage to the main control chip, ensuring stable module startup. This module is responsible for efficiently converting the input AC current into DC current, achieving an overall efficiency of no less than 70% under rated conditions.

[0046] Control Module: The control module uses a main control chip as its core to implement control functions. This main control chip is a domestically produced chip (model CR6223 from CR Microelectronics, adapted to isolated switching power supply topology and miniaturized printed circuit board layout). The control module receives feedback signals from the sampling circuit, generates PWM drive signals to control the power conversion module, and executes all protection and control logic.

[0047] The printed circuit board also integrates a surge protection circuit, which is connected between the AC input port and the power conversion module. The surge protection circuit includes at least a varistor and a gas discharge tube, which are connected in parallel. The varistor is an EPCOS B72214S0171K101 with a rated voltage of 175VAC and a current capacity of 10kA. Its small size and low parasitic parameters are beneficial for achieving the layout requirement of a total parasitic inductance of less than 50nH. The gas discharge tube is a Littelfuse 33730 with a breakdown voltage of 1200V and a maximum discharge current of 5kA. Its small size allows for close placement with the varistor, which helps reduce parasitic inductance and improve surge discharge efficiency.

[0048] Both the voltage and current sampling circuits are connected between the DC output port and the control module. The voltage sampling circuit consists of a precision resistor divider network, using Yageo RC0603FR-07100KL (100kΩ, 1%, 1 / 10W) and Yageo RC0603FR-0710KL (10kΩ, 1%, 1 / 10W) resistors. This design is small, highly accurate, and suitable for miniaturized printed circuit board layouts. The current sampling circuit consists of a sampling resistor and an amplifier circuit connected in series in the output loop. These circuits are used to accurately and in real-time measure the output voltage and current. The sampling resistor in the current sampling circuit is a Vishay WSL2010R0100FEA with a resistance of 0.01Ω, a power rating of 1W, and extremely low parasitic inductance, meeting the design requirements for accurate output current sampling and low parasitic parameters.

[0049] The printed circuit board layout is configured such that the varistor and gas discharge tube are placed close to the AC input port and the power conversion module input terminal, the copper foil trace length between the three is shortened to within 5mm, and the trace width is not less than 2mm, to reduce the parasitic inductance of the traces; at the same time, the traces are avoided from detours and crossings, so that the total parasitic inductance between the varistor and gas discharge tube and the AC input port and the power conversion module input terminal is less than 50nH;

[0050] The surge protection circuit is configured to enable the adapter to withstand surge impacts conforming to a standard combination of waveforms, wherein the surge impact is defined as: a voltage peak of 18kV to 22kV, a current peak of 9kA to 11kA, voltage waveform time parameters of 1.2μs / 50μs, and current waveform time parameters of 8μs / 20μs; wherein 1.2μs and 8μs are the wavefront times of the voltage wave and current wave, respectively, and 50μs and 20μs are the half-peak times of the voltage wave and current wave, respectively.

[0051] The surge protection circuit is configured to clamp the voltage of the surge impact at the input terminal to the safe voltage range of the subsequent power conversion module through the coordinated operation of the varistor and the gas discharge tube; at the same time, by controlling the total parasitic inductance below 50nH, it suppresses the additional overshoot voltage caused by the current change of the surge impact. The additional overshoot voltage satisfies the following relationship with the total parasitic inductance and the rate of change of the surge impact current:

[0052]

[0053] in, To add overshoot voltage; Total parasitic inductance; This represents the instantaneous value of the surge current. It is a differential operator that represents the rate of change with respect to time;

[0054] When a surge impact with a peak voltage of 18kV to 22kV and a peak current of 9kA to 11kA occurs at the AC input terminal, the surge current... The current will flow into the surge protection circuit through the AC input port. This is due to the inherent parasitic inductance between the varistor, the gas discharge tube, the input port, and the power conversion module input. surge current instantaneous change (i.e., rate of change) This can induce additional overshoot voltage. ;

[0055] This solution optimizes the printed circuit board layout to reduce the aforementioned total parasitic inductance. Strictly control it below 50nH. According to the formula, the surge current change rate... Under fixed conditions, parasitic inductance The reduction directly suppressed the additional overshoot voltage. The amplitude is controlled to ensure that it does not exceed the tolerance threshold of the power conversion module, thus achieving source control of overshoot voltage.

[0056] Varistors are used to initially clamp surge voltages, and their discharge current and the voltage across them satisfy their nonlinear volt-ampere characteristic.

[0057]

[0058] in, This indicates the instantaneous discharge current of the varistor; Represents a time variable; The proportionality coefficient characterizing the conductivity of a varistor at a specific reference point; This represents the instantaneous voltage across the varistor; This is the reference voltage for the varistor; A coefficient characterizing the degree of nonlinearity in the voltage-current relationship of a varistor;

[0059] Furthermore, the rated voltage of the varistor is 175VAC, and the current carrying capacity is 10kA.

[0060] In the initial stage of a surge, the input voltage rises instantaneously, and the instantaneous voltage across the varistor... Synchronous rise. According to the nonlinear volt-ampere characteristic formula of the varistor, its instantaneous discharge current... From material constants Reference voltage Nonlinear coefficients and instantaneous voltage Joint decision: When Exceed back, The ratio increases, combined with the nonlinear coefficient The amplification effect, instantaneous discharge current It is growing exponentially.

[0061] During this process, the varistor uses its own nonlinear characteristics to quickly clamp the surge voltage to a safe range based on the 175VAC rated voltage, while simultaneously dissipating the surge energy with a current capacity of 10kA. When the surge energy exceeds the preset threshold (ranging from 5kJ to 15kJ, adjustable according to the application scenario), the gas discharge tube is broken down to form a low-impedance path, which carries the remaining surge current. The two work together to complete the graded absorption and dissipation of surge energy, preventing the varistor from being damaged due to energy overload.

[0062] When the energy of the surge exceeds the preset threshold, the gas discharge tube breaks down, and the voltage across its terminals drops to an arc sustaining voltage (ranging from 20V to 50V) that is far below its breakdown voltage. This provides a low-impedance discharge path for the surge current. The breakdown voltage of the gas discharge tube is 1200V, and the maximum discharge current is 5kA, which can be adapted to surge current peak requirements of 9kA to 11kA.

[0063] The insulation between the primary and secondary circuits of the adapter is configured to withstand a DC voltage of not less than 4750V or an AC voltage of 3000V for 3 seconds, with a leakage current of less than 10mA.

[0064] The adapter is configured to operate continuously in environments ranging from 0 to 100,000 feet above sea level, with an electrical clearance of not less than 3.2 mm between its primary and secondary circuits and a creepage distance of not less than 6.4 mm.

[0065] The control module includes a voltage feedback loop, which is configured to ensure that the output voltage temperature coefficient of the DC output port is not higher than ±0.05% / ℃; the diameter of the printed circuit board is not greater than 35.5mm, and the total height of the printed circuit board and its components is not greater than 20mm.

[0066] A control method for a PCB AC adapter, used in the aforementioned PCB AC adapter, includes the following steps:

[0067] S1 receives AC input voltage and absorbs and discharges energy from surge impacts at the input terminal through a surge protection circuit with a total parasitic inductance of less than 50 nH.

[0068] S2. Convert the AC power processed by S1 into DC power through the power conversion module;

[0069] S3. The control module regulates the DC voltage obtained in S2 to obtain a stable DC voltage, which is then output from the DC output port.

[0070] The control module dynamically adjusts the operating state of the power conversion module based on feedback from the voltage sampling circuit, so as to control the ripple and noise peak of the DC output voltage below 68mVp-p, with a measurement bandwidth of DC-20MHz.

[0071] S4. The output voltage and output current of the DC output port are monitored in real time through the voltage sampling circuit and the current sampling circuit. When the output voltage exceeds 110% of its rated value or the output current reaches 1.5A, the power conversion module is controlled to stop working to cut off the output.

[0072] S5. After the power conversion module stops working due to S4, continuously or intermittently monitor the output voltage and output current of the DC output port; when the overvoltage or overcurrent condition that triggered the S4 action is detected to have disappeared, automatically or according to external instructions, restart the power conversion module to restore output.

[0073] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A PCB AC adapter, characterized in that: The device includes a housing, within which a printed circuit board is provided. The printed circuit board integrates an AC input port, a DC output port, a power conversion module, a voltage sampling circuit, a current sampling circuit, and a control module. The printed circuit board also integrates a surge protection circuit, which is connected between the AC input port and the power conversion module. The surge protection circuit includes at least a varistor and a gas discharge tube, which are connected in parallel. Both the voltage sampling circuit and the current sampling circuit are connected between the DC output port and the control module. The layout of the printed circuit board is configured such that the total parasitic inductance between the varistor and the gas discharge tube and the AC input port and the input terminal of the power conversion module is less than 50nH; The surge protection circuit is configured to enable the adapter to withstand surge impacts conforming to a standard combination of waveforms, wherein the surge impact is defined as: a voltage peak value of 18kV to 22kV, a current peak value of 9kA to 11kA, voltage waveform time parameters of 1.2μs / 50μs, and current waveform time parameters of 8μs / 20μs; wherein 1.2μs and 8μs are the wavefront times of the voltage wave and current wave, respectively, and 50μs and 20μs are the half-peak times of the voltage wave and current wave, respectively.

2. A PCB AC adapter as described in claim 1, characterized in that, The surge protection circuit is configured to: clamp the voltage of the surge impact at the input terminal to the safe voltage range of the subsequent power conversion module through the coordinated operation of the varistor and the gas discharge tube; simultaneously, by controlling the total parasitic inductance below 50nH, suppress the additional overshoot voltage caused by the current change of the surge impact, wherein the additional overshoot voltage satisfies the following relationship with the total parasitic inductance and the rate of change of the surge impact current: in, For the additional overshoot voltage; The total parasitic inductance; The instantaneous value of the surge current; It is a differential operator that represents the rate of change with respect to time.

3. A PCB AC adapter as described in claim 1, characterized in that, The varistor is used to initially clamp the voltage of a surge impact, and its discharge current and the voltage across it satisfy its nonlinear volt-ampere characteristic: in, This represents the instantaneous discharge current of the varistor; Represents a time variable; This is a proportionality coefficient characterizing the conductivity of the varistor at a specific reference point; This represents the instantaneous voltage across the varistor; The reference voltage for the varistor; A coefficient characterizing the degree of nonlinearity in the voltage-current relationship of the varistor; Furthermore, the rated voltage of the varistor is 175VAC, and the current carrying capacity is 10kA.

4. A PCB AC adapter as described in claim 1, characterized in that: When the energy of the surge impact exceeds a preset threshold, the gas discharge tube is broken down, and the voltage across its terminals drops to an arc sustaining voltage far below its breakdown voltage, thereby providing a low-impedance discharge path for the surge impact current. The breakdown voltage of the gas discharge tube is 1200V, and the maximum discharge current is 5kA.

5. A PCB AC adapter as described in claim 1, characterized in that: The insulation between the primary and secondary circuits of the adapter is configured to withstand a DC voltage of not less than 4750V or an AC voltage of 3000V for 3 seconds, with a leakage current of less than 10mA.

6. A PCB AC adapter as described in claim 5, characterized in that: The adapter is configured to operate continuously in environments ranging from 0 to 100,000 feet above sea level, with an electrical clearance of not less than 3.2 mm between its primary and secondary circuits and a creepage distance of not less than 6.4 mm.

7. A PCB AC adapter as described in claim 1, characterized in that: The control module includes a voltage feedback loop, which is configured such that the output voltage temperature coefficient of the DC output port is not higher than ±0.05% / ℃; the diameter of the printed circuit board is not greater than 35.5mm, and the total height of the printed circuit board and its components is not greater than 20mm.

8. A control method for a PCB AC adapter, used in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Receives AC input voltage and absorbs and discharges energy from surge impacts occurring at the input terminal through the surge protection circuit with a total parasitic inductance of less than 50 nH. S2. The AC power processed in S1 is converted into DC power through the power conversion module. S3. The control module regulates the DC voltage obtained in S2 to obtain a stable DC voltage, which is then output from the DC output port. S4. The output voltage and output current of the DC output port are monitored in real time through the voltage sampling circuit and the current sampling circuit. When the output voltage exceeds 110% of its rated value or the output current reaches 1.5A, the power conversion module is controlled to stop working to cut off the output.

9. The control method for a PCB AC adapter as described in claim 8, characterized in that: In S3, the control module dynamically adjusts the operating state of the power conversion module based on the feedback from the voltage sampling circuit, so as to control the ripple and noise peak of the DC output voltage below 68mVp-p, with a measurement bandwidth of DC-20MHz.

10. The control method for a PCB AC adapter as described in claim 8, characterized in that, It also includes recovery step S5: After the power conversion module stops working due to S4, the output voltage and output current of the DC output port are continuously or intermittently monitored. When the overvoltage or overcurrent condition that triggered the S4 action is detected to have disappeared, the power conversion module is automatically or restarted according to an external command to restore output.

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