An isolated ac-dc switching power supply circuit

Abstract

The utility model provides a kind of isolated AC-DC switching power supply circuit, it is related to power supply circuit technical field. Including TL494 controller drive multipath transformer realizes high efficiency power conversion, in combination with optocoupler isolation feedback and multistage operational amplifier improves control accuracy, and integrates overcurrent, overvoltage and temperature protection mechanism. Its modular design supports extension, applicable to industry and consumer electronics field, with low noise, high reliability and cost advantage.

Description

Technical Field

[0001] This utility model relates to the field of power supply circuit technology, specifically to an isolated AC-DC switching power supply circuit, which is suitable for industrial electronic equipment and consumer electronic products. Background Technology

[0002] Switching power supplies are widely used due to their advantages such as high efficiency and miniaturization.

[0003] Traditional switching power supply designs may have the following problems: (1) Single-output design is difficult to meet the multi-voltage requirements of complex equipment; (2) Insufficient feedback control accuracy leads to poor output voltage stability; (3) Single protection function lacks comprehensive protection against surges, overcurrents, overvoltages and temperatures; (4) Weak high-frequency noise suppression capability affects the normal operation of sensitive electronic equipment. Therefore, this utility model proposes an isolated AC-DC switching power supply circuit to at least partially solve the problems that may exist in the prior art. Utility Model Content

[0004] The purpose of this invention is to provide an isolated AC-DC switching power supply circuit that works in conjunction with multi-stage filtering and noise suppression components, effectively reducing high-frequency switching noise, meeting EMC standards, and improving the electromagnetic compatibility of the power supply.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0006] An isolated AC-DC switching power supply circuit includes:

[0007] The input filtering module includes a common-mode inductor, a rectifier bridge, and surge suppression components;

[0008] The power conversion module consists of a TL494 controller, MOSFETs, a multi-channel transformer, and an energy storage inductor.

[0009] The feedback control module implements closed-loop control based on a TL431 reference source, optocouplers, and multi-stage operational amplifiers.

[0010] The protection module integrates overcurrent, overvoltage, and temperature protection, as well as a TVS diode.

[0011] The output filtering module includes a large-capacity electrolytic capacitor and an LC filter network.

[0012] Optionally, the multi-channel transformer adopts a push-pull topology.

[0013] Optionally, in the feedback control module, the feedback signal of the optocoupler is amplified for error through a TL431 reference source.

[0014] Optionally, the protection module further includes an adjustable resistor and a magnetic ring inductor for dynamically adjusting the protection threshold.

[0015] Optionally, in the output filtering module, the low-dropout linear regulator is an SS8050 transistor.

[0016] This utility model has at least the following advantages or beneficial effects:

[0017] The system comprises an input filtering module, including a common-mode inductor, a rectifier bridge, and surge suppression components; a power conversion module consisting of a TL494 controller, MOSFETs, a multi-channel transformer, and an energy storage inductor; a feedback control module based on a TL431 reference source, optocouplers, and multi-stage operational amplifiers for closed-loop control; a protection module integrating overcurrent, overvoltage, and temperature protection, as well as TVS diodes; and an output filtering module including large-capacity electrolytic capacitors and an LC filter network. The combination of the multi-channel transformer and the TL494 controller achieves a power conversion efficiency >90%; optocoupler-isolated feedback and multi-stage operational amplifiers ensure output voltage accuracy of ±1%; multiple protection mechanisms work together to improve system reliability by over 30%; modular design facilitates expansion and debugging; high-frequency filter capacitors and shielded inductors reduce noise, and EMI performance meets Class B standards. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A first part of the circuit diagram of an isolated AC-DC switching power supply circuit provided in an embodiment of the present invention;

[0020] Figure 2 The second part of the circuit diagram of an isolated AC-DC switching power supply circuit provided in an embodiment of the present invention is shown. Detailed Implementation

[0021] To make the objectives, features, and advantages of this utility model more apparent and understandable, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0022] Please refer to Figures 1 to 2 As shown in the figure, this embodiment provides an isolated AC-DC switching power supply circuit with high-frequency noise suppression function, including: a high-efficiency multi-output switching power supply circuit, characterized in that it includes: an input filtering module, comprising common-mode inductors T1 and T6, rectifier bridges D15 and D10, surge suppression components RT1, C9, and C47; a power conversion module, composed of a TL494 controller U7, MOSFETs Q6 and Q9, multi-channel transformers T2, T4, and T5, and energy storage inductors L1 and L3; a feedback control module, based on a TL431 reference source U4, an optocoupler U5, and a multi-stage operational amplifier LM358, with U1, U2, and U6 implementing closed-loop control; a protection module, integrating overcurrent, overvoltage, and temperature protection, and a TVS diode D8; the above-mentioned output filtering module, comprising large-capacity electrolytic capacitors C37 and C39, and an LC filter network L2 and C36.

[0023] The AC power supply is filtered by common-mode inductors T1 and T6 to remove common-mode noise. After being converted to DC by rectifier bridges D15 and D10, surge current is suppressed by NTC resistor RT1 and capacitors C9 and C47. The PWM signal output by the TL494 controller U7 drives MOSFETs Q6 and Q9, which are coupled by transformers T2, T4, and T5 to generate multiple DC voltages. The output voltage is sampled by the TL431 controllable precision voltage regulator U4 and fed back to the TL494 through optocoupler U5 to adjust the duty cycle to stabilize the output. When overcurrent or overvoltage is detected, the OC pin of U3 is triggered to turn off, the TVS diode D8 absorbs the voltage spike, and the heat sink HS1 and NTC work together to dissipate heat. Electrolytic capacitors C37 and C39 and LC network L2 and C46 filter out high-frequency ripple, and the low dropout regulator Q1 provides 5V control power.

[0024] In some embodiments of this application, please refer to Figures 1 to 2 As shown, an isolated AC-DC switching power supply circuit is disclosed, wherein the multi-channel transformers T2, T4, and T5 adopt a push-pull topology. Specifically, the primary windings of T4 and T5 are obtained by rectifying the output of T2. The two sets of secondary windings of T5 are respectively connected to transistors Q8 and Q5 and transistors Q2 and Q4. Transistors Q8 and Q5 and transistors Q2 and Q4 respectively form a push-pull amplifier. The push-pull circuit of the secondary windings of T5 controls the operation of the transformer and the primary windings of the transformer T2 and the high-frequency transformer T3 directly connected to it.

[0025] It should be noted that the push-pull amplifier, composed of two transistors, is a classic circuit. A push-pull circuit is an output circuit that connects two transistors of different polarities. The push-pull circuit uses two power BJTs or MOSFETs with identical parameters, existing in the circuit in a push-pull configuration. Each transistor is responsible for amplifying the positive and negative half-cycles of the waveform. During operation, only one of the two symmetrical power switching transistors is turned on at a time, resulting in low conduction losses and high efficiency.

[0026] Furthermore, in the feedback control module, the feedback signal from optocoupler U5 is amplified for error amplification via a TL431 controllable precision voltage regulator U4 reference source. Since the TL431 integrates a 2.5V precision reference source and an error amplifier, it can amplify the difference between the sampled voltage and the reference voltage and transmit it to the control terminal through the optocoupler U5, effectively improving the accuracy of the feedback loop. On the other hand, the error amplifier characteristics (non-comparator) of the TL431 make it more suitable for closed-loop control. Combined with the linear transmission characteristics of optocoupler U5, it can maintain stable loop gain over a wide temperature range, avoiding performance fluctuations caused by temperature drift of the optocoupler U5's current amplification factor. The electrical isolation characteristics of optocoupler U5 can block the direct connection between the main power circuit and the control circuit, improving the system's anti-interference capability and safety. In this structure, the TL431 acts as both an error amplifier and participates in signal processing at the isolation terminal, achieving functional integration.

[0027] As an example, the protection module also includes an adjustable resistor R50 and a magnetic ring inductor L3 for dynamically adjusting the protection threshold. The adjustable resistor enables stepless adjustment of the protection threshold to adapt to different operating conditions (such as overcurrent / overvoltage protection points); the magnetic ring inductor suppresses transient interference and improves the ability to quickly suppress surges or high-frequency noise; compared with digital solutions, analog devices are lower in cost and more reliable, and the magnetic ring inductor has low temperature drift, which, combined with the metal film resistor, ensures long-term stability of the threshold.

[0028] Furthermore, in the output filtering module, the low-dropout linear regulator Q1 is an SS8050 transistor. For example... Figure 2As shown, the SS8050 transistor and LMD358 operational amplifier are combined, with the LM358 serving as its control terminal. Specifically, the SS8050 is an NPN structure. When operating in the amplification region, its base voltage is controlled by the LM358, achieving emitter-following output and reducing voltage drop. By detecting the difference between the output voltage and the reference voltage, the base current of the SS8050 is adjusted to form closed-loop regulation. The SS8050 transistor, as a low-dropout linear regulator (LDO), has the following advantages: low saturation voltage drop, typically 0.5V@500mA, suitable for scenarios with small input-output voltage differences; maximum collector current of 1.5A, capable of driving medium to high loads; general-purpose NPN transistor, significantly cheaper than dedicated LDO chips; fast switching speed, effectively suppressing load transient fluctuations.

[0029] In a specific example, such as Figure 1 and Figure 2 As shown, the input power supply is filtered and rectified into DC voltage through common-mode inductors T1 and T6 and rectifier bridges (such as D15 and D10). Capacitors C9 and C47, and NTC / PTC components RT1 and PTC1 are used to suppress inrush current and noise, ensuring the stability of the input power supply. A TL494, i.e., U7, is used as a PWM controller to drive MOSFETs such as Q6 and Q9 to achieve DC-DC conversion. Transformers T2, T4, and T5, and inductors L1 and L3 are used for voltage transformation and energy storage, supporting multiple outputs. A feedback loop is constructed using a TL431 controllable precision voltage regulator U4 and an optocoupler U5, and the output voltage is precisely adjusted by changing the PWM duty cycle. Multiple operational amplifiers such as LM358, U1, U2, and U6, are used for signal amplification and comparison, enhancing control accuracy.

[0030] Overcurrent protection, such as the OC pin of U3, overvoltage protection, such as DZ1 and DZ2, and temperature protection (such as the heatsink HS1) ensure safe circuit operation. The aforementioned fast recovery diodes, such as D13, and TVS diodes, such as D8, can be used to suppress voltage spikes. For output filtering and voltage regulation, large-capacity electrolytic capacitors, such as C37 and C39 (preferably 1000μF), and LC filter networks, such as L2 and C46, ​​smooth the output voltage and reduce ripple. The aforementioned low-dropout linear regulator Q1 provides a stable low-voltage power supply to the control circuit.

[0031] This power supply utilizes a combination of TL494 and MOSFETs to achieve a high-efficiency switching power supply design suitable for medium-to-high power applications. A multi-transformer design supports complex power supply topologies (such as push-pull or half-bridge), improving energy utilization. TL431 and optocoupler-isolated feedback ensure high output voltage accuracy and interference immunity. The multi-stage operational amplifier circuit LM358 provides flexible analog signal processing to adapt to diverse control requirements. Common-mode inductors and TVS diodes at the input effectively suppress EMI and surges. Comprehensive overcurrent, overvoltage, and temperature protection enhances system reliability. Connectors J1, J2, and J3 facilitate the expansion of external devices or debugging, achieving modularity and scalability. The aforementioned magnetic ring inductor L3 and adjustable resistors, such as R50, allow for flexible adjustment of circuit parameters. High-frequency filtering capacitors, such as C7 and C14, and the GMDG (distributed air gap) transformer T3 reduce high-frequency noise, making it suitable for sensitive electronic equipment. A well-designed grounding GND layout reduces ground loop interference. The aforementioned heatsink HS1 works in conjunction with the NTC, avoiding over-reliance on expensive cooling solutions.

[0032] The circuit structure described in this application provides highly efficient power management capabilities, combining high-precision control with robust protection functions, making it suitable for industrial or consumer electronics applications. Its advantages also include modular design, low-noise optimization, and a balance between cost and performance.

[0033] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

[0034] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0035] 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.

[0036] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0037] The isolated AC-DC switching power supply circuit provided by this utility model has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. An isolated AC-DC switching power supply circuit, characterized in that, include: The input filtering module includes common mode inductor T1, common mode inductor T6, rectifier bridge D15, rectifier bridge D10, and surge suppression components composed of RT1, C9, and C47. The power conversion module consists of a TL494 controller U7, MOSFET Q6, MOSFET Q9, multiplex transformers T2, T4, and T5, and energy storage inductors L1 and L3. The feedback control module implements closed-loop control based on the TL431 reference source U4, optocoupler U5, and a multi-stage operational amplifier consisting of LM358 and U1, U2, and U6. The protection module integrates overcurrent, overvoltage, and temperature protection, as well as TVS diode D8. The output filtering module includes large-capacity electrolytic capacitors C37 and C39, as well as an LC filter network composed of L2 and C36.

2. The switching power supply circuit according to claim 1, characterized in that, The multi-channel transformers T2, T4, and T5 all adopt a push-pull topology.

3. The switching power supply circuit according to claim 1, characterized in that, In the feedback control module, the feedback signal of the optocoupler U5 is amplified by the TL431 reference source U4.

4. The switching power supply circuit according to claim 1, characterized in that, The protection module also includes an adjustable resistor R50 and a magnetic ring inductor L3 for dynamically adjusting the protection threshold.

5. The switching power supply circuit according to claim 1, characterized in that, In the output filtering module, the low-dropout linear regulator Q1 is an SS8050 transistor.

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