A feedback circuit for improving the output current accuracy of a switching power supply

Abstract

The utility model relates to the technical field of switching power supply, especially a feedback circuit for improving switching power supply output current precision, including inductance T3 and signal processing module, the first winding of inductance T3 and switching power supply's output module electricity is connected, and the second winding of inductance T3 is connected with the control chip U2 of switching power supply's input module through signal processing module, significantly improve output current precision, at the same time, solve the problem that feedback circuit stability is insufficient, response speed is slow and circuit structure is complex.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply technology, and in particular to a feedback circuit for improving the accuracy of the output current of a switching power supply. Background Technology

[0002] Switching power supplies typically employ primary-side feedback or secondary-side feedback to improve output current accuracy. Primary-side feedback indirectly samples the output voltage through the auxiliary winding of the transformer. Its accuracy is affected by the coupling degree between the auxiliary and secondary windings, resulting in poor load regulation and sampling voltage errors exceeding ±5%, thus leading to poor output current accuracy. Secondary-side feedback, on the other hand, connects the secondary-side output circuit of the transformer to the control chip of the primary-side input circuit via an optocoupler. The adjusted output current accuracy is better than primary-side feedback, but it suffers from the following problems:

[0003] (1) Insufficient electrical characteristic stability: The current transfer ratio (CTR) and insulation performance of optocouplers are easily affected by temperature fluctuations and light intensity. High temperature or long-term use may cause parameter drift and increase the risk of output signal distortion. In low temperature or strong electromagnetic interference environment, photosensitive elements may fail, resulting in abnormal switching action.

[0004] (2) Limited response speed: The signal transmission of optocouplers needs to go through an "electric-optical-electric" conversion process, and the response time is usually in the range of microseconds to milliseconds, which is difficult to meet the needs of high-frequency circuits or fast dynamic response; compared with new devices such as digital isolators, its bandwidth and transmission rate are obviously inferior.

[0005] (3) High cost and complexity of peripheral circuits of optocouplers: The feedback system of optocouplers needs to be equipped with peripheral circuits such as controllable voltage regulators and compensation networks, and the material cost is significantly higher than that of primary-side feedback. Utility Model Content

[0006] To address the aforementioned shortcomings, the purpose of this invention is to propose a feedback circuit for improving the output current accuracy of switching power supplies. This significantly improves the output current accuracy while solving the problems of insufficient stability, slow response speed, and complex circuit structure of the feedback circuit.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] A feedback circuit for improving the output current accuracy of a switching power supply includes an inductor T3 and a signal processing module; the first winding of the inductor T3 is electrically connected to the output module of the switching power supply, and the second winding of the inductor T3 is electrically connected to the control chip U2 of the input module of the switching power supply via the signal processing module.

[0009] Furthermore, the first winding of the inductor T3 is connected in series with the positive terminal of the output module, one end of the second winding of the inductor T3 is connected to the GND ground terminal, and the other end of the second winding of the inductor T3 is electrically connected to the signal processing module.

[0010] Furthermore, the number of coils in the first winding of the inductor T3 is smaller than the number of coils in the second winding of the inductor T3.

[0011] Furthermore, the turns ratio of the first winding and the second winding of the inductor T3 is 1:100.

[0012] Furthermore, the first winding of the inductor T3 has only one turn of coil.

[0013] Furthermore, the signal processing module includes a diode D21, a capacitor C14, resistors R60, R61, R57, and a capacitor C13; the other end of the second winding of the inductor T3 is electrically connected to the anode of the diode D21, the cathode of the diode D21, one end of the capacitor C14, one end of the resistor R60, and one end of the resistor R61 are all electrically connected to one end of the resistor R57, the other end of the resistor R57 is electrically connected to one end of the capacitor C13, the other ends of the capacitor C14, the other ends of the resistor R60, the other ends of the resistor R61, and the other ends of the capacitor C13 are all grounded, and the other end of the resistor R57 is electrically connected to the CT terminal of the control chip U2.

[0014] The technical solution provided by this utility model can include the following beneficial effects: by introducing a feedback path composed of inductor T3 and signal processing modules (such as rectification and noise reduction), the traditional secondary-side optocoupler feedback method is completely replaced; by utilizing inductor magnetic coupling to quickly feed back the voltage signal of the output module to the control chip U2, the problems of temperature sensitivity, CTR drift, and slow response speed of optocouplers are avoided, thereby significantly improving the accuracy and stability of the output current. At the same time, this feedback path eliminates the need for optocouplers and their complex external compensation circuits, which helps to simplify circuit design, reduce costs, and improve system reliability. Attached Figure Description

[0015] Figure 1 This is a circuit diagram of a feedback circuit for improving the output current accuracy of a switching power supply, which is one embodiment of this utility model.

[0016] The components include: input module 1, output module 2, inductor T3, signal processing module 11, diode D21, capacitor C14, resistor R60, resistor R61, resistor R57, and capacitor C13. Detailed Implementation

[0017] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0018] In the description of embodiments of this utility model, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of embodiments of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0019] In the description of the embodiments of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this utility model according to the specific circumstances.

[0020] The following is combined Figure 1 This invention describes a feedback circuit for improving the output current accuracy of a switching power supply according to an embodiment of the present invention.

[0021] A feedback circuit for improving the output current accuracy of a switching power supply includes an inductor T3 and a signal processing module 11; the first winding of the inductor T3 is electrically connected to the output module 2 of the switching power supply, and the second winding of the inductor T3 is electrically connected to the control chip U2 of the input module 1 of the switching power supply via the signal processing module 11.

[0022] This utility model proposes a preferred embodiment of a feedback circuit for improving the output current accuracy of a switching power supply, such as... Figure 1 As shown, by introducing a feedback path consisting of inductor T3 and signal processing module 11 (e.g., rectification, noise reduction), the traditional secondary-side optocoupler feedback method is completely replaced. The voltage signal from output module 2 is quickly fed back to control chip U2 (e.g., a RED2833 chip) using inductor magnetic coupling, avoiding the temperature sensitivity, CTR drift, and slow response speed problems associated with optocouplers, thus significantly improving the accuracy and stability of the output current. Simultaneously, this feedback path eliminates the need for optocouplers and their complex external compensation circuitry, simplifying circuit design, reducing costs, and improving system reliability.

[0023] It should be noted that there are various types of main circuits for switching power supplies composed of transformer T4, input module 1, and output module 2, which are not limited here.

[0024] Furthermore, the first winding of inductor T3 is connected in series with the positive terminal of output module 2, one end of the second winding of inductor T3 is connected to GND ground, and the other end of the second winding of inductor T3 is electrically connected to signal processing module 11.

[0025] In this embodiment, the first winding of inductor T3 is connected in series with the positive terminal of output module 2. When the output current of output module 2 flows through the first winding, the second winding can sense the current proportionally (turns ratio). After being processed by signal processing module 11, the sensed current is stably fed back to control chip U2.

[0026] Furthermore, the number of coils in the first winding of inductor T3 is smaller than the number of coils in the second winding of inductor T3.

[0027] In this embodiment, given that the output current of the output module 2 is usually quite large, if a step-down transmission design is adopted, the number of coils in the first winding connected in series with the positive terminal of the output module 2 will be greater than the number of coils in the second winding, resulting in very high line loss, severe overheating of the first winding, and even burning out the inductor T3. Therefore, it is preferable to use a design where the number of coils in the first winding is smaller than the number of coils in the second winding, and a step-up design is adopted to avoid severe overheating. Furthermore, the weak current signal collected by the first winding is magnetically amplified to the second winding, which also facilitates the subsequent identification of the collected signal. At the same time, since the turns ratio of the first winding and the second winding is constant, the induced signal of the second winding will also be proportional to the collected signal of the first winding, ensuring the accuracy of the collected signal during transmission.

[0028] Furthermore, the turns ratio of the first winding and the second winding of inductor T3 is 1:100.

[0029] In this embodiment, the turns ratio of the first winding and the second winding of inductor T3 is further limited to 1:100. The main considerations are as follows: the turns ratio of the second winding is 100 for high inductance design, typically around 40mH, with a minimum inductance of ≥25mH, to improve the accuracy of the current sampling. If the number of turns is reduced, the inductance will decrease, requiring a magnetic core with higher permeability to achieve the same inductance. However, magnetic cores with higher permeability are relatively scarce, and the cost will increase. In addition, if the turns ratio of the second winding is further increased, the proportion of the first winding will be smaller, resulting in a smaller sampling current. An excessively small current will significantly reduce the sampling accuracy, and an excessively small signal is easily interfered with, leading to detection errors. Therefore, the turns ratio of the first winding and the second winding is preferably limited to 1:100.

[0030] Furthermore, the first winding of inductor T3 has only one turn of coil.

[0031] In this embodiment, since the output current of the output module 2 is usually relatively large, if the number of turns increases, the line loss of the first winding will also increase, and it is difficult to produce more turns, which increases the cost (the cost of the second winding will also increase accordingly); therefore, the first winding preferably has only one coil wound in series with the positive terminal of the output module 2, and the line loss is very small and can be basically ignored.

[0032] Furthermore, the signal processing module 11 includes a diode D21, a capacitor C14, resistors R60, R61, R57, and a capacitor C13; the other end of the second winding of the inductor T3 is electrically connected to the anode of the diode D21, the cathode of the diode D21, one end of the capacitor C14, one end of the resistor R60, and one end of the resistor R61 are all electrically connected to one end of the resistor R57, the other end of the resistor R57 is electrically connected to one end of the capacitor C13, the other ends of the capacitor C14, the other ends of the resistor R60, the other ends of the resistor R61, and the other ends of the capacitor C13 are all grounded, and the other end of the resistor R57 is electrically connected to the CT terminal of the control chip U2.

[0033] In this embodiment, diode D21 in signal processing module 11 is used for rectification, and resistors R60 and R61 form a sampling resistor. After being filtered by RC consisting of resistor R57 and capacitor C13, the signal is fed back to the CT terminal of control chip U2. The signal is compared with the DIM terminal signal of control chip U2 to control the output PWM signal, thereby changing the operating frequency and controlling the output current of output module 2.

[0034] Other configurations and operations of a feedback circuit for improving the output current accuracy of a switching power supply according to an embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0035] In this specification, the terms "embodiment," "example," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0036] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A feedback circuit for improving the output current accuracy of a switching power supply, characterized in that: It includes an inductor T3 and a signal processing module; the first winding of the inductor T3 is electrically connected to the output module of the switching power supply, and the second winding of the inductor T3 is electrically connected to the control chip U2 of the input module of the switching power supply via the signal processing module; The first winding of the inductor T3 is connected in series with the positive terminal of the output module, one end of the second winding of the inductor T3 is connected to the GND ground terminal, and the other end of the second winding of the inductor T3 is electrically connected to the signal processing module. The signal processing module includes a diode D21, a capacitor C14, resistors R60, R61, R57, and a capacitor C13. The other end of the second winding of the inductor T3 is electrically connected to the anode of the diode D21. The cathode of the diode D21, one end of the capacitor C14, one end of the resistor R60, and one end of the resistor R61 are all electrically connected to one end of the resistor R57. The other end of the resistor R57 is electrically connected to one end of the capacitor C13. The other ends of the capacitor C14, resistor R60, resistor R61, and capacitor C13 are all grounded. The other end of the resistor R57 is electrically connected to the CT terminal of the control chip U2.

2. The feedback circuit for improving the output current accuracy of a switching power supply according to claim 1, characterized in that: The number of coils in the first winding of the inductor T3 is smaller than the number of coils in the second winding of the inductor T3.

3. The feedback circuit for improving the output current accuracy of a switching power supply according to claim 2, characterized in that: The turns ratio of the first winding and the second winding of the inductor T3 is 1:

100.

4. A feedback circuit for improving the output current accuracy of a switching power supply according to claim 3, characterized in that: The first winding of the inductor T3 has only one turn of coil.

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