A power adapter circuit

Abstract

This invention provides a power adapter circuit, including a fuse, an electromagnetic interference (EMI) filter circuit, a rectifier bridge, a control unit, a switching transformer, a rectifier filter assembly, a feedback assembly, and a power connector. The feedback assembly is connected to the control unit via an optocoupler. A thermistor is connected in series between the neutral wire of the mains power and the EMI filter circuit. This power adapter circuit can monitor changes in the output voltage in real time and adjust the conduction time of the switching transistor accordingly to ensure output voltage stability, providing a stable power supply to the load and preventing the power adapter from overheating. The EMI filter circuit in the input section effectively suppresses high-frequency interference signals in the power grid and interference generated by the power supply itself, improving the circuit's anti-interference capability and reducing the impact on surrounding electronic equipment. By adopting a switching power supply operating mode, combined with a high-efficiency switching transformer and control chip, the power conversion efficiency is improved, and energy loss is reduced.

Description

Technical Field

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

[0002] A power adapter is a power conversion device for small portable electronic devices and appliances. It generally consists of components such as a casing, switching transformer, inductor, capacitor, control IC, and PCB board. Its working principle is to convert AC input to DC output. It is widely used in the field of portable projectors.

[0003] The power adapters of existing portable projectors generally work continuously during use to power the internal battery of the portable projector. When the power adapter works for a long time, it is prone to overheating and damage to the internal components of the power adapter. Utility Model Content

[0004] The purpose of this invention is to provide a power adapter to solve the problem of overheating in existing power adapters.

[0005] This utility model provides a power adapter circuit, including a fuse, an electromagnetic interference filter circuit connected to the fuse, a rectifier bridge connected to the electromagnetic interference filter circuit, a control unit connected to the rectifier bridge, a switching transformer connected to the control unit, a rectifier filter assembly connected to the switching transformer, a feedback assembly connected to the rectifier filter assembly, and a power connector connected to the rectifier filter assembly. The feedback assembly is connected to the control unit via an optocoupler, and a thermistor is connected in series between the neutral wire of the mains power and the electromagnetic interference filter circuit.

[0006] The aforementioned power adapter circuit, through its feedback and voltage regulation design, can monitor changes in output voltage in real time and adjust the conduction time of the switching transistor in a timely manner to ensure output voltage stability, providing a stable power supply to the load and preventing the power adapter from overheating. The electromagnetic interference filtering circuit in the input section effectively suppresses high-frequency interference signals in the power grid and interference generated by the power supply itself, improving the circuit's anti-interference capability and reducing the impact on surrounding electronic equipment. By adopting a switching power supply operating mode, combined with a high-efficiency switching transformer and control chip, the power conversion efficiency is improved and energy loss is reduced.

[0007] Furthermore, the electromagnetic interference filtering circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, and a common-mode inductor;

[0008] The first end of the first resistor is connected to the live wire of the mains power, the first end of the third resistor and the first end of the first capacitor, and the second end of the first resistor is connected to the first end of the second resistor.

[0009] The second terminal of the second resistor is connected to the second terminal of the fourth resistor and the neutral wire of the mains power supply;

[0010] The first end of the third resistor is also connected to the first input end of the common mode inductor, and the second end of the third resistor is connected in series with the first end of the fourth resistor;

[0011] The second end of the fourth resistor is also connected to the second input end of the common-mode inductor;

[0012] The two output terminals of the common-mode inductor are connected to the rectifier bridge.

[0013] Furthermore, the control unit includes a power control chip and a field-effect transistor connected to the power control chip;

[0014] The drain of the field-effect transistor is connected to the input terminal of the switching transformer, the source and gate of the field-effect transistor are connected to the power control chip, and the source of the field-effect transistor is also grounded.

[0015] The power control chip is also connected to the input terminal of the switching transformer.

[0016] Furthermore, the rectifier filter assembly includes a first rectifier diode, a second rectifier diode, a first electrolytic capacitor, a second electrolytic capacitor, a second capacitor, a third capacitor, and a fourth capacitor;

[0017] The positive terminal of the first rectifier diode is connected to the first terminal of the second capacitor and the output terminal of the switching transformer, and the negative terminal of the first rectifier diode is connected to the second terminal of the second capacitor, the positive terminal of the first electrolytic capacitor and the feedback component.

[0018] The positive terminal of the second rectifier diode is connected to the first terminal of the third capacitor and the output terminal of the switching transformer, and the negative terminal of the second rectifier diode is connected to the second terminal of the third capacitor, the positive terminal of the second electrolytic capacitor and the feedback component.

[0019] The negative terminals of both the first electrolytic capacitor and the second electrolytic capacitor are connected to the power connector;

[0020] The fourth capacitor is connected in parallel with the second electrolytic capacitor.

[0021] Furthermore, the feedback component is a voltage reference chip;

[0022] One end of the voltage reference chip is connected to the rectifier filter component, and the other end is connected to the optocoupler.

[0023] Furthermore, it also includes a Zener diode, the anode of which is connected to the cathode of the second rectifier diode, and the cathode of which is connected to the cathode of the first rectifier diode.

[0024] Furthermore, the first end of the current sampling resistor is connected to the gate of the field-effect transistor, and the second end of the current sampling resistor is connected to the power control chip. Attached Figure Description

[0025] Figure 1 This is a circuit diagram of the power adapter circuit in the first embodiment of this utility model.

[0026] In the diagram: F1 - Fuse; NTC1 - Thermistor; BD1 - Rectifier Bridge; LF1 - Common Mode Inductor; CX1 - First Capacitor; RX1 - First Resistor; RX2 - Second Resistor; RX3 - Third Resistor, RX4 - Fourth Resistor; U1 - Power Control Chip; Q2 - Field Effect Transistor; T1 - Switching Transformer; D1 - First Rectifier Diode; D6 - Second Rectifier Diode; EC4 - First Electrolytic Capacitor; EC5 - Second Electrolytic Capacitor; C3 - Second Capacitor, C16 - Third Capacitor, C17 - Fourth Capacitor; U2 - Voltage Reference Chip; U3 - Optocoupler; Resistor; ZD1 - Zener Diode; R10 - Current Sampling Resistor.

[0027] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this utility model. Detailed Implementation

[0028] To facilitate understanding of this utility model, a more comprehensive description will be given below with reference to the accompanying drawings. Several embodiments of this utility model are shown in the drawings. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this utility model will be more thorough and complete.

[0029] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] Please see Figure 1 This utility model provides a power adapter circuit, including a fuse F1, an electromagnetic interference filter circuit connected to the fuse F1, a rectifier bridge BD1 connected to the electromagnetic interference filter circuit, a control unit connected to the rectifier bridge BD1, a switching transformer T1 connected to the control unit, a rectifier filter assembly connected to the switching transformer T1, a feedback assembly connected to the rectifier filter assembly, and a power connector CON1 connected to the rectifier filter assembly. The feedback assembly is connected to the control unit through an optocoupler U3, and a thermistor NTC1 is connected in series between the neutral wire of the mains power and the electromagnetic interference filter circuit.

[0032] The power adapter circuit described above, through the design of the feedback and voltage regulation section, can monitor the changes in output voltage in real time and adjust the conduction time of the switching transistor in a timely manner to ensure the stability of the output voltage, provide a stable power supply to the load, and prevent the power adapter CON1 from overheating.

[0033] Specifically, in this embodiment, the fuse F1 automatically melts when the current in the circuit is too high, protecting downstream circuit components from damage. The thermistor NTC1 limits the surge current at power-on, preventing large current from impacting the circuit. Simultaneously, the thermistor NTC1 can also detect ambient temperature for temperature control.

[0034] In one embodiment of this utility model, the electromagnetic interference filtering circuit includes a first resistor RX1, a second resistor RX2, a third resistor RX3, a fourth resistor RX4, a first capacitor CX1, and a common-mode inductor LF1.

[0035] The first end of the first resistor RX1 is connected to the live wire of the mains power, the first end of the third resistor and the first end of the first capacitor, and the second end of the first resistor RX1 is connected to the first end of the second resistor RX2.

[0036] The second terminal of the second resistor RX2 is connected to the second terminal of the fourth resistor RX4 and the neutral wire of the mains power supply;

[0037] The first end of the third resistor RX3 is also connected to the first input end of the common mode inductor LF1, and the second end of the third resistor RX3 is connected in series with the first end of the fourth resistor RX4.

[0038] The second terminal of the fourth resistor RX4 is also connected to the second input terminal of the common-mode inductor LF1;

[0039] The two output terminals of the common-mode inductor LF1 are connected to the rectifier bridge BD1.

[0040] The circuit design described above uses the first resistor RX1, the second resistor RX2, the third resistor RX3, the fourth resistor RX4, the first capacitor CX1, and the common-mode inductor LF1 to form an EMI (electromagnetic interference) filter circuit. This circuit filters out high-frequency interference signals from the power grid and prevents interference generated by the power supply itself from being fed back to the power grid.

[0041] In one embodiment of this invention, the control unit includes a power control chip U1 and a field-effect transistor Q2 connected to the power control chip U1. The drain of the field-effect transistor Q2 is connected to the input terminal of the switching transformer T1, and the source and gate of the field-effect transistor Q2 are connected to the power control chip. The source of the field-effect transistor Q2 is also grounded. The power control chip U1 is also connected to the input terminal of the switching transformer T1. The power control chip U1 generates pulse signals to control the conduction and cutoff of the field-effect transistor Q2, thereby controlling the energy transfer of the switching transformer T1. Specifically, the field-effect transistor Q2, as a switching element, periodically conducts and cuts off under the drive of the output signal of the power control chip U1, causing a changing current to be generated in the primary winding of the switching transformer T1.

[0042] In one embodiment of this utility model, the rectifier filter assembly includes a first rectifier diode D1, a second rectifier diode D6, a first electrolytic capacitor EC4, a second electrolytic capacitor EC5, a second capacitor C3, a third capacitor C16, and a fourth capacitor C17. The positive terminal of the first rectifier diode D1 is connected to the first terminal of the second capacitor C3 and the output terminal of the switching transformer T1, and the negative terminal of the first rectifier diode D1 is connected to the second terminal of the second capacitor C3, the positive terminal of the first electrolytic capacitor EC4, and the feedback assembly EC5. The positive terminal of the second rectifier diode D6 is connected to the first terminal of the third capacitor C16 and the output terminal of the switching transformer T1, and the negative terminal of the second rectifier diode D6 is connected to the second terminal of the third capacitor C16, the positive terminal of the second electrolytic capacitor EC5, and the feedback assembly. The negative terminals of both the first electrolytic capacitor EC4 and the second electrolytic capacitor EC5 are connected to the power connector CON1. ​​The fourth capacitor C17 is connected in parallel with the second electrolytic capacitor EC5.

[0043] The aforementioned rectifier and filter assembly uses first rectifier diode D1 and second rectifier diode D6 to rectify the AC power output from the secondary winding of switching transformer T1 into DC power. First electrolytic capacitor EC4, second electrolytic capacitor EC5, second capacitor C3, third capacitor C16, and fourth capacitor C17 combine to form a filter circuit to smooth the rectified DC voltage, reduce ripple, and provide a stable DC output. Simultaneously, this rectifier and filter assembly can convert mains power into the precise and stable voltage required by electronic equipment. With one constant current and one constant voltage dual output, the external adapter can extend the projector's lifespan and effectively control the machine's surface temperature.

[0044] In one embodiment of this utility model, the feedback component is a voltage reference chip U2; one end of the voltage reference chip U2 is connected to the rectifier filter component, and the other end is connected to the optocoupler U3.

[0045] In the aforementioned power adapter circuit, the AC input voltage is filtered by fuse F1, an electromagnetic interference filter circuit, rectifier bridge BD1, and third and fourth electrolytic capacitors EC2 and EC3 to obtain a high-voltage DC VH. VH supplies power to the power control chip U1 and the field-effect transistor Q2. The power control chip U1 outputs a pulse signal to control the conduction and cutoff of the field-effect transistor Q2, generating a changing current in the primary winding of the switching transformer T1, which induces a voltage in the secondary winding through electromagnetic induction. The AC voltage output from the secondary winding is rectified by the first rectifier diode D1 and the second rectifier diode D6, and filtered by the first electrolytic capacitor EC4, the second electrolytic capacitor EC5, the second capacitor C3, the third capacitor C16, and the fourth capacitor C17 to obtain a stable DC output voltage, which supplies power to the load. The output voltage is fed back to the primary winding through a feedback circuit composed of a voltage reference chip U2, an optocoupler U3, etc. The power control chip U1 adjusts the pulse width according to the feedback signal to maintain a stable output voltage.

[0046] This invention employs a switching power supply operating mode, combining a high-efficiency switching transformer T1 and a voltage reference chip U2, thereby improving the power supply conversion efficiency and reducing energy loss.

[0047] Specifically, in this embodiment of the invention, a Zener diode ZD1 is also provided to provide overvoltage protection. When the output voltage abnormally rises above the Zener diode ZD1's regulation value, the Zener diode ZD1 will reverse-bias breakdown and conduct, causing a change in current. This change is transmitted to the control unit through the feedback circuit. After detecting the signal change, the power control chip U1 adjusts the operating state of the MOSFET Q2 to reduce the output voltage, preventing damage to subsequent circuits due to overvoltage. This achieves the overvoltage protection function.

[0048] In one embodiment of this invention, a current sampling resistor R10 is also included. When the current of the field-effect transistor Q2 is too large, the voltage drop across R10 will increase. This voltage signal will be fed back to the overcurrent detection circuit inside the power control chip U1. Once the set threshold is exceeded, the power control chip U1 will control the field-effect transistor Q2 to turn off, thereby preventing damage to the component due to overcurrent.

[0049] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A power adapter circuit, characterized by, The device includes a fuse, an electromagnetic interference (EMI) filter circuit connected to the fuse, a rectifier bridge connected to the EMI filter circuit, a control unit connected to the rectifier bridge, a switching transformer connected to the control unit, a rectifier filter assembly connected to the switching transformer, a feedback assembly connected to the rectifier filter assembly, and a power connector connected to the rectifier filter assembly. The feedback assembly is connected to the control unit via an optocoupler. A thermistor is connected in series between the neutral wire of the mains power and the EMI filter circuit.

2. The power adapter circuit of claim 1, wherein, The electromagnetic interference filtering circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, and a common-mode inductor. The first end of the first resistor is connected to the live wire of the mains power, the first end of the third resistor and the first end of the first capacitor, and the second end of the first resistor is connected to the first end of the second resistor. The second terminal of the second resistor is connected to the second terminal of the fourth resistor and the neutral wire of the mains power supply; The first end of the third resistor is also connected to the first input end of the common mode inductor, and the second end of the third resistor is connected in series with the first end of the fourth resistor; The second end of the fourth resistor is also connected to the second input end of the common-mode inductor; The two output terminals of the common-mode inductor are connected to the rectifier bridge.

3. The power adapter circuit of claim 1, wherein, The control unit includes a power control chip and a field-effect transistor connected to the power control chip; The drain of the field-effect transistor is connected to the input terminal of the switching transformer, the source and gate of the field-effect transistor are connected to the power control chip, and the source of the field-effect transistor is also grounded. The power control chip is also connected to the input terminal of the switching transformer.

4. The power adapter circuit of claim 1, wherein, The rectifier and filter assembly includes a first rectifier diode, a second rectifier diode, a first electrolytic capacitor, a second electrolytic capacitor, a second capacitor, a third capacitor, and a fourth capacitor; The positive terminal of the first rectifier diode is connected to the first terminal of the second capacitor and the output terminal of the switching transformer, and the negative terminal of the first rectifier diode is connected to the second terminal of the second capacitor, the positive terminal of the first electrolytic capacitor and the feedback component. The positive terminal of the second rectifier diode is connected to the first terminal of the third capacitor and the output terminal of the switching transformer, and the negative terminal of the second rectifier diode is connected to the second terminal of the third capacitor, the positive terminal of the second electrolytic capacitor and the feedback component. The negative terminals of both the first electrolytic capacitor and the second electrolytic capacitor are connected to the power connector; The fourth capacitor is connected in parallel with the second electrolytic capacitor.

5. The power adapter circuit of claim 1, wherein, The feedback component is a voltage reference chip; One end of the voltage reference chip is connected to the rectifier filter component, and the other end is connected to the optocoupler.

6. The power adapter circuit of claim 4, wherein, It also includes a Zener diode, the positive terminal of which is connected to the negative terminal of the second rectifier diode, and the negative terminal of which is connected to the negative terminal of the first rectifier diode.

7. The power adapter circuit of claim 3, wherein, It also includes a first end of a current sampling resistor connected to the gate of the field-effect transistor, and a second end of the current sampling resistor connected to the power control chip.

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