Regulating circuit of switching power supply and switching power supply

Abstract

The utility model discloses a regulating circuit of a switching power supply and the switching power supply, which are used for solving the problem that the output voltage ripple is larger when the switching power supply is in light load. According to the scheme, the working mode of the switching power supply is dynamically adjusted by introducing a voltage sampling circuit, a voltage loop circuit and two paths. A sampling voltage is compared with a preset reference voltage through a voltage loop circuit, a corresponding control signal is output according to a comparison result, and when a load is light, the control signal promotes a power supply to enter a duty ratio adjusting mode by controlling a first path to be switched on, so that stable voltage is output and ripples are reduced; and when the load is increased, the control signal promotes the switching power supply to enter a frequency modulation mode by controlling the conduction of the second path, so that the load fluctuation can be more flexibly coped, and the overall energy conversion efficiency is improved. Therefore, according to the utility model, not only can the large output ripple caused by frequency hopping work of the power supply in a large load range be prevented, but also the energy conversion efficiency in the circuit is improved.

Description

Technical Field

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

[0002] In the field of switching power supply application technology, soft-switching topologies such as LLC and LCC exhibit high gain under no-load conditions due to the characteristics of frequency modulation control. During the development of this invention, the inventors discovered at least the following problems in the prior art: to stabilize the output voltage, these topologies typically employ a burst operating mode (frequency hopping intermittent operation). However, this burst operating mode leads to increased output voltage ripple. When high accuracy of the output voltage is required under light load, existing technologies often employ methods such as dummy loads to suppress the impact of this operating mode. In many cases, a large dummy load is needed to force the power supply out of the burst operating mode.

[0003] It is evident that in existing technologies, switching power supplies exhibit significant output voltage ripple when operating under light load. Utility Model Content

[0004] The purpose of this invention is to provide a regulating circuit and a switching power supply that can not only prevent the power supply from operating with frequency hopping within a large load range, resulting in large output ripple, but also improve the energy conversion efficiency in the circuit.

[0005] This utility model provides a regulating circuit for a switching power supply, the switching power supply including a power chip and a power output terminal, and the regulating circuit including:

[0006] A voltage sampling circuit, whose output terminal is connected to the power output terminal of the switching power supply, is used to sample the output voltage of the switching power supply to obtain the sampled voltage;

[0007] A voltage loop circuit, whose input terminal is connected to the output terminal of the sampling circuit, is used to compare the sampled voltage with a preset reference voltage and output a corresponding control signal according to the comparison result. The control signal has a preset relationship with the difference between the preset reference voltage and the sampled voltage.

[0008] Two paths are provided, with the input terminal of each path connected to the output terminal of the voltage loop circuit. The output terminal of the first path is connected to the first mode terminal of the power chip, and the output terminal of the second path is connected to the second mode terminal of the power chip. Each path is used to turn on or off according to the control signal, and outputs a trigger signal to the corresponding mode terminal when it is turned on, so that the switching power supply works in the corresponding working mode.

[0009] When the first mode terminal receives the trigger signal, the switching power supply operates in duty cycle adjustment mode; when the second mode terminal receives the trigger signal, the switching power supply operates in frequency modulation mode.

[0010] Optionally, the voltage loop circuit includes:

[0011] An error amplifier is provided, with the preset reference voltage input at its non-inverting input, the inverting input connected to the output of the sampling circuit, and the output connected to the inputs of the two paths. It is used to compare the sampled voltage with the preset reference voltage and output a corresponding control signal based on the comparison result to drive the two paths.

[0012] Optionally, the positive power supply terminal of the error amplifier is connected to the positive terminal of the dual power supply, and the negative power supply terminal of the error amplifier is connected to the negative terminal of the dual power supply.

[0013] Optionally, the first path includes a first optical coupler, and the second path includes a second optical coupler;

[0014] The anode of the photodiode in the first optocoupler is grounded, the anode of the photodiode in the second optocoupler is connected to the power supply, the output terminal of the voltage loop circuit is connected to the cathode of the photodiode in the first optocoupler and the cathode of the photodiode in the second optocoupler respectively, the first end of the photodetector in the first optocoupler is connected to the first mode terminal of the power chip, the first end of the photodetector in the second optocoupler is connected to the second mode terminal of the power chip, and the second ends of the photodetectors in the first optocoupler and the second ends of the photodetectors in the second optocoupler are grounded;

[0015] The voltage loop circuit also includes:

[0016] The first diode has its cathode connected to the output of the error amplifier, and its anode connected to the cathode of the photodiode in each of the two optocouplers.

[0017] Optional, also includes:

[0018] A current feedback circuit, whose input terminal is connected to the power output terminal of the switching power supply and whose output terminal is connected to the first mode terminal of the power chip, is used to output the trigger signal to the first mode terminal when the output current of the switching power supply exceeds the current threshold, and adjust the voltage value of the first mode terminal so that the switching power supply operates in the duty cycle adjustment mode.

[0019] Optionally, it also includes: an indicator device, the input of which is connected to the output of the voltage loop circuit;

[0020] The voltage loop circuit is also used to output a corresponding indication control signal to the indication device according to the comparison result, so that the indication device outputs corresponding indication information according to the indication control signal, and the indication information is used to indicate the current working mode of the switching power supply.

[0021] Optionally, the current feedback circuit includes:

[0022] A current sampling circuit, whose input terminal is connected to the power output terminal of the switching power supply, is used to sample the output current of the switching power supply to obtain the sampled current.

[0023] A current loop circuit, whose input terminal is connected to the output terminal of the current sampling circuit, is used to output a conduction signal when the sampled current is greater than the current threshold.

[0024] The third path has its input terminal connected to the output terminal of the current loop circuit and its output terminal connected to the first mode terminal of the power chip, and is used to output the trigger signal according to the conduction signal.

[0025] Optionally, the second mode terminal includes the timing capacitor terminal and the timing resistor terminal of the power chip, and the adjustment circuit further includes:

[0026] A second diode, four resistors, and three capacitors;

[0027] The reference voltage output terminal of the power chip is connected to the non-inverting input terminal of the power chip, the cathode of the second diode, and the first terminal of the first resistor, respectively. The inverting input terminal of the power chip is grounded. The second terminal of the first resistor is connected to the first terminal of the first capacitor, the first terminal of the second resistor, and the anode of the second diode, respectively. The second terminal of the second resistor is connected to the timing resistor terminal of the power chip and the first terminal of the third resistor, respectively. The second terminal of the third resistor is connected to the first terminal of the fourth resistor, the first terminal of the second capacitor, and the output terminal of the first path, respectively. The first terminal of the third capacitor is connected to the timing capacitor terminal and the discharge terminal of the power chip, respectively. The second terminals of the first capacitor, the second capacitor, the third capacitor, and the fourth resistor are all grounded.

[0028] Optional, also includes:

[0029] The fifth resistor has its first end connected to the soft-start terminal of the power chip and its second end grounded.

[0030] To address the aforementioned technical problems, this application also provides a switching power supply, including the regulating circuit of the switching power supply as described above.

[0031] This invention provides a regulating circuit and a switching power supply to address the problem of large output voltage ripple in switching power supplies under light loads. The solution dynamically adjusts the operating mode of the switching power supply by introducing a voltage sampling circuit, a voltage loop circuit, and two paths. The voltage loop circuit compares the sampled voltage with a preset reference voltage and outputs a corresponding control signal based on the comparison result. When the load is light, the control signal activates the first path, causing the power supply to enter a duty cycle adjustment mode, ensuring a stable output voltage and reducing ripple. When the load increases, the control signal activates the second path, causing the switching power supply to enter a frequency modulation mode, which allows for more flexible handling of load fluctuations and improves overall energy conversion efficiency. Therefore, this invention not only prevents the power supply from operating at high frequencies over large load ranges, thus avoiding large output ripple, but also improves the energy conversion efficiency of the circuit. Attached Figure Description

[0032] To more clearly illustrate the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A structural block diagram of a regulating circuit for a switching power supply provided by this utility model;

[0034] Figure 2 A schematic diagram illustrating the specific implementation of the regulating circuit for a switching power supply provided by this utility model;

[0035] Figure 3 A circuit diagram of a voltage loop circuit provided by this utility model;

[0036] Figure 4 A circuit diagram of a voltage sampling circuit provided by this utility model;

[0037] Figure 5 A schematic diagram of a first pathway provided by this utility model;

[0038] Figure 6 A schematic diagram of a second pathway provided by this utility model;

[0039] Figure 7 A linear schematic diagram of the error amplifier provided by this utility model;

[0040] Figure 8 A schematic diagram of a current feedback circuit provided by this utility model;

[0041] Figure 9A schematic diagram of a third pathway provided by this utility model;

[0042] Figure 10 This is a schematic diagram of a power chip and its peripheral circuit provided by this utility model. Detailed Implementation

[0043] The core of this invention is to provide a regulating circuit and a switching power supply, which can not only prevent the power supply from operating with frequency hopping within a large load range, resulting in large output ripple, but also improve the energy conversion efficiency in the circuit.

[0044] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0045] Firstly, such as Figure 1 and Figure 2 As shown, this utility model provides a regulating circuit for a switching power supply. The switching power supply includes a power chip and a power output terminal. The regulating circuit includes: a voltage sampling circuit 11, whose input terminal is connected to the power output terminal of the switching power supply, for sampling the output voltage of the switching power supply to obtain a sampled voltage; a voltage loop circuit 12, whose input terminal is connected to the output terminal of the sampling circuit, for comparing the sampled voltage with a preset reference voltage, and outputting a corresponding control signal according to the comparison result, wherein the control signal has a preset relationship with the difference between the preset reference voltage and the sampled voltage; and two paths, the input terminal of each path is connected to the output terminal of the voltage loop circuit 12, the output terminal of the first path 13 is connected to the first mode terminal of the power chip, and the output terminal of the second path 14 is connected to the second mode terminal of the power chip. Each path is used to turn on or off according to the control signal, and outputs a trigger signal to the corresponding mode terminal when it is turned on, so that the switching power supply operates in the corresponding operating mode; wherein, when the first mode terminal receives the trigger signal, the switching power supply operates in duty cycle adjustment mode; when the second mode terminal receives the trigger signal, the switching power supply operates in frequency modulation mode.

[0046] In this embodiment, the adjustment circuit dynamically adjusts the operating mode of the switching power supply through a voltage sampling and processing mechanism, thereby optimizing its performance. First, the voltage sampling circuit 11 monitors the output voltage of the switching power supply in real time to obtain the current sampled voltage. Next, the voltage loop circuit 12 compares the sampled voltage with a preset reference voltage to obtain the voltage difference, and generates a corresponding control signal based on this difference. This control signal reflects the deviation between the actual output voltage and the desired voltage, thus determining the operating mode of the switching power supply.

[0047] When the load is light, the control signal activates the first path 13, causing the power supply to enter duty cycle adjustment mode. This mode can better stabilize the output voltage under light load conditions and significantly reduce output ripple, avoiding performance degradation caused by voltage instability. At the same time, the duty cycle adjustment mode allows the power supply to maintain high efficiency even when the output power is not high, avoiding the extra power consumption caused by using dummy loads in traditional technologies.

[0048] Under increased load conditions, the control signal activates the second path 14, causing the switching power supply to enter frequency modulation mode. This mode allows for more flexible handling of load fluctuations, providing the required output current while improving overall energy conversion efficiency. The activation of frequency modulation mode enables the switching power supply to maintain stable output with lower power consumption under heavy load conditions, reducing heat loss caused by high power consumption.

[0049] It is important to understand that the first mode port can be the comp port of the power chip, and the second mode port can be the RT port of the power chip.

[0050] In summary, this embodiment, through an effective voltage sampling and processing mechanism, flexibly switches the operating mode of the switching power supply, which not only improves the performance and stability under various load conditions, but also optimizes power consumption, broadens the application range of the power supply, avoids the inefficiency caused by frequent frequency adjustments, and achieves dual control over output voltage and power consumption.

[0051] like Figure 3 As shown, in a preferred embodiment, the voltage loop circuit 12 includes: an error amplifier U1, which receives a preset reference voltage at its non-inverting input terminal, connects its inverting input terminal to the output terminal of the sampling circuit, and connects its output terminal to the input terminals of the two paths, for comparing the sampled voltage with the preset reference voltage, and outputting a corresponding control signal according to the comparison result to drive the two paths.

[0052] In this embodiment, the core component of the voltage loop circuit 12 is the error amplifier U1, which dynamically generates control signals to adjust the operating mode of the switching power supply by comparing a preset reference voltage and a sampled voltage. The workflow is as follows: First, the non-inverting input of the error amplifier U1 receives the preset reference voltage, which is a stable reference voltage value, typically set at the desired output voltage level. Its inverting input receives the sampled voltage from the voltage sampling circuit 11, which reflects the current actual output state of the switching power supply.

[0053] In a preferred embodiment, the positive power supply terminal of error amplifier U1 is connected to the positive terminal of the dual power supply, and the negative power supply terminal of error amplifier U1 is connected to the negative terminal of the dual power supply. In this embodiment, the positive and negative power supply terminals of error amplifier U1 are connected to the positive (+Vcc) and negative (-Vcc) terminals of the dual power supply, respectively. This configuration provides the necessary power to error amplifier U1 to ensure its normal operation within the appropriate operating range. The dual power supply configuration helps to enhance the dynamic range and output capability of error amplifier U1, making it more flexible and accurate in processing input signals. When the voltage at the non-inverting input terminal of error amplifier U1 is less than the voltage at the inverting input terminal (i.e., when the sampling voltage is greater than the preset reference voltage), error amplifier U1 outputs a negative value (-Vcc); when the voltage at the non-inverting input terminal of error amplifier U1 is greater than the voltage at the inverting input terminal, error amplifier U1 outputs a positive value (+Vcc).

[0054] In a preferred embodiment, the circuit for outputting a preset reference voltage includes: two resistors connected in series, with the first end of the series connection connected to a power supply and the second end grounded. The junction of the two resistors serves as the output terminal for outputting the preset reference voltage and is connected to the non-inverting input terminal of the error amplifier U1. A capacitor is also included connected to the junction of the two resistors.

[0055] like Figure 4 As shown, in a preferred embodiment, the voltage sampling circuit includes two resistors connected in series, with the first end of the series connection connected to the power output terminal of the switching power supply. Figure 3 The second terminal of the series resistor (VOUT) is grounded, and the connection point of the two resistors serves as the output terminal (V-FB) of the voltage sampling circuit, which is connected to the inverting input terminal of the error amplifier U1.

[0056] Through the feedback mechanism of this error amplifier U1, the voltage loop circuit 12 can respond to load changes in real time and intelligently adjust its operating mode, thereby optimizing the performance and power consumption of the switching power supply. This solution not only ensures output stability under different load conditions but also improves the energy efficiency of the entire system, providing a more reliable power management solution for the equipment.

[0057] like Figure 5 and Figure 6As shown, in a preferred embodiment, the first path 13 includes a first optocoupler U2, and the second path 14 includes a second optocoupler U3; the anode of the photodiode in the first optocoupler U2 is grounded, the anode of the photodiode in the second optocoupler U3 is connected to the power supply, the output terminal of the voltage loop circuit 12 is connected to the cathode of the photodiode in the first optocoupler U2 and the cathode of the photodiode in the second optocoupler U3 respectively, the first end of the photodetector in the first optocoupler U2 is connected to the first mode terminal of the power chip, the first end of the photodetector in the second optocoupler U3 is connected to the second mode terminal of the power chip, and the second ends of the photodetectors in the first optocoupler U2 and the second end of the photodetectors in the second optocoupler U3 are grounded; the voltage loop circuit 12 further includes: a first diode D1, whose cathode is connected to the output terminal of the error amplifier U1, and whose anode is connected to the cathode of the photodiode in each of the two optocouplers respectively.

[0058] In this embodiment, the first optocoupler U2 and the second optocoupler U3 are used to achieve precise control of different operating modes of the power supply. The anode of the photodiode of the first optocoupler U2 is connected to the power supply, while the anode of the photodiode of the second optocoupler U3 is grounded. This configuration allows them to have different level references in signal processing. When the error amplifier U1 outputs a control signal, the levels of the first control signal and the second control signal are opposite, which ensures that only one optocoupler is conducting at any given time.

[0059] Specifically, when the voltage at the non-inverting input terminal is less than the voltage at the inverting input terminal, the error amplifier U1 outputs a negative level (-Vcc), and the first diode D1 is turned on. Since the anode of the first optocoupler U2 is grounded, a voltage difference is formed between the anode and cathode of the photodiode of the first optocoupler U2, which activates the photodetector of the first optocoupler U2. In this way, the first mode terminal of the power supply is triggered, thereby making the power supply work in the duty cycle adjustment mode.

[0060] When the voltage at the non-inverting input is greater than the voltage at the inverting input, the error amplifier U1 outputs a positive value (+Vcc), the first diode D1 is cut off, and the photodiode of the second optocoupler U3 is turned on, causing the power supply to switch to frequency modulation mode. In frequency modulation mode, the power supply can respond to heavy load conditions with higher efficiency and provide the required output current.

[0061] In this embodiment, as Figure 7As shown, due to the different power supply methods of the two isolation optocouplers, when the output voltage of the error amplifier is high (i.e., under heavy load), the optocoupler powered by the positive power supply can conduct, while the optocoupler powered by the negative power supply is cut off. At this time, the duty cycle is at its maximum and constant value, and the power supply operates in frequency conversion mode. When the output voltage of the error amplifier is below 0V (i.e., under light load), the optocoupler powered by the positive power supply is saturated, and the optocoupler powered by the negative power supply operates in the linear region. The operating frequency of the power supply is at its maximum and constant value, and the power supply operates in duty cycle adjustment mode. The two optocouplers powered by the positive and negative power supplies exhibit a linear relationship, thus achieving automatic adjustment of duty cycle and frequency conversion.

[0062] This design achieves secure transmission and precise switching of control signals through optocoupler isolation, ensuring that the power supply can flexibly adjust its operating mode according to different load conditions, thereby improving system efficiency and stability. Therefore, this optocoupler configuration effectively supports intelligent management and operational optimization of the switching power supply under various operating conditions.

[0063] In a preferred embodiment, the device further includes an indicator whose input is connected to the output of a voltage loop circuit. The voltage loop circuit is also used to output a corresponding indicator control signal to the indicator based on the comparison result, so that the indicator outputs corresponding indicator information based on the indicator control signal. The indicator information is used to indicate the current operating mode of the switching power supply.

[0064] Furthermore, after comparing the sampled voltage with the preset reference voltage, the voltage loop circuit 12 not only outputs a control signal to control the operating mode of the switching power supply (duty cycle mode or frequency modulation mode), but also outputs an indication control signal to the indication device. Based on the received indication control signal, the indication device outputs corresponding indication information, such as through LEDs, a display screen, or other display methods, to indicate the current operating mode of the switching power supply (duty cycle mode or frequency modulation mode). In this way, users can intuitively understand the operating status of the switching power supply through the indication information, facilitating monitoring and debugging.

[0065] like Figure 2 As shown, in a preferred embodiment, it further includes: a current feedback circuit, the input of which is connected to the power output terminal of the switching power supply, and the output of which is connected to the first mode terminal of the power chip, for outputting a trigger signal to the first mode terminal when the output current of the switching power supply exceeds the current threshold, adjusting the voltage value of the first mode terminal so that the switching power supply operates in duty cycle adjustment mode.

[0066] In this embodiment, the current feedback circuit is designed to achieve real-time monitoring and control of the switching power supply's output current, thereby enhancing the system's protection capabilities and stability. The current feedback circuit continuously monitors the output current of the switching power supply during operation. When the output current exceeds a preset current threshold, the current feedback circuit immediately generates a trigger signal, which is sent to the first mode terminal of the power chip. This mechanism ensures that the switching power supply can quickly switch to duty cycle adjustment mode under heavy load conditions or sudden load increases leading to overcurrent. Activation of the duty cycle adjustment mode allows the switching power supply to stabilize the output voltage by adjusting the duty cycle, while simultaneously controlling the output current to prevent overcurrent. This allows it to automatically adapt to instantaneous load fluctuations, maintaining output stability and preventing potential damage. Furthermore, the introduction of the current feedback circuit not only improves the power supply's response speed but also effectively reduces the risks caused by overcurrent, ensuring the safety and reliability of the equipment during operation.

[0067] It is important to understand that even under heavy load conditions (specifically, operating in frequency modulation mode), if an overcurrent occurs, the frequency modulation mode will gradually reduce the frequency until it reaches the minimum frequency. At this point, the frequency modulation mode will not function, and a trigger signal will be output to the first mode terminal through the current feedback circuit, causing the switching power supply to operate in duty cycle adjustment mode, thereby avoiding overcurrent.

[0068] like Figure 8 As shown, in a preferred embodiment, the current feedback circuit includes: a current sampling circuit, whose input terminal is connected to the power output terminal of the switching power supply, for sampling the output current of the switching power supply to obtain a sampled current; a current loop circuit, whose input terminal is connected to the output terminal of the current sampling circuit, for outputting a conduction signal when the sampled current is greater than a current threshold; and a third path, whose input terminal is connected to the output terminal of the current loop circuit and whose output terminal is connected to the first mode terminal of the power chip, for outputting a trigger signal according to the conduction signal.

[0069] In this embodiment, the current feedback circuit, through a current sampling and processing mechanism, aims to monitor and control the output current of the switching power supply in real time, thereby effectively protecting the switching power supply and improving system stability. Specifically, the current sampling circuit acquires the value of the output current in real time and generates a corresponding sampled current signal ( Figure 8 The I-FB signal reflects the current load condition of the power supply. The current loop circuit receives the output signal from the current sampling circuit, analyzes and compares it. When the sampled current exceeds the preset current threshold, the current loop circuit immediately outputs a conduction signal (IFB-CTRL), indicating that the current load condition has reached the overcurrent critical point. A third path can be achieved through an optocoupler (such as...). Figure 9As shown, the optocoupler receives the conduction signal from the current loop circuit and operates according to this signal. When the conduction signal appears, the photosensitive element inside the optocoupler will conduct, transmitting the trigger signal to the first mode terminal of the power chip. This signal causes the power supply to immediately switch to the duty cycle adjustment mode to control the output current and prevent damage caused by overcurrent.

[0070] Specifically, the current loop circuit includes an error amplifier, which is composed of an isolation optocoupler circuit.

[0071] This current feedback mechanism enables a rapid response when the load increases abnormally, ensuring the stability and safety of the power supply output. This design not only improves the power supply's response speed but also effectively reduces the risk of overcurrent, enhancing the reliability of the entire system under different load conditions and providing users with a safer power management solution.

[0072] like Figure 10 As shown, in a preferred embodiment, the second mode terminal includes the timing capacitor terminal CT and timing resistor RT of the power chip. The adjustment circuit also includes: a second diode D2, four resistors, and three capacitors. The reference voltage output terminal VREF of the power chip is connected to the non-inverting input terminal of the power chip, the cathode of the second diode D2, and the first terminal of the first resistor R1. The inverting input terminal of the power chip is grounded. The second terminal of the first resistor R1 is connected to the first terminal of the first capacitor C1, the first terminal of the second resistor R2, and the anode of the second diode D2. The second terminal of the second resistor R2 is connected to the timing resistor RT and the first terminal of the third resistor R3 of the power chip. The second terminal of the third resistor R3 is connected to the first terminal of the fourth resistor R4, the first terminal of the second capacitor C2, and the output terminal of the first path 13. The first terminal of the third capacitor C3 is connected to the timing capacitor terminal CT and the discharge terminal of the power chip. The second terminals of the first capacitor C1, the second capacitor C2, the third capacitor C3, and the second terminal of the fourth resistor R4 are all grounded.

[0073] The non-inverting input of the power supply chip is connected to the reference voltage output terminal VREF, and the inverting input is connected to GND. The internal error amplifier of the power supply chip operates in saturation. Controlling the output of the error amplifier allows the switching power supply to operate in variable duty cycle mode. The timing capacitor CT and timing resistor RT of the power supply chip determine the operating frequency. The operating frequency of the power supply chip can be changed by adjusting the resistance value connected to the timing resistor RT. The third resistor R3 determines the maximum operating frequency, and the combination of the third resistor R3 and the fourth resistor R4 determines the minimum operating frequency. The second resistor R2 and the third resistor R3 + the fourth resistor R4 are connected in parallel, which determines the maximum frequency for soft start. The first capacitor C1 determines the soft start time.

[0074] As a preferred embodiment, it further includes: a fifth resistor R5, the first end of which is connected to the soft-start terminal of the power chip, and the second end of which is grounded.

[0075] Specifically, the soft-start pin SS of the power chip is no longer connected to a capacitor, but to a resistor. This prevents starting in duty cycle mode, avoiding excessive current surges caused by starting directly in duty cycle mode. Instead, it uses frequency conversion mode for soft starting to avoid damaging the power supply or load.

[0076] Specifically, taking the SG3525 power supply as an example, a voltage loop drives two isolated optocouplers. The voltage loop uses an operational amplifier (op-amp) as the error amplifier U1, which is powered by a dual power supply. One of the isolated optocouplers is powered by a positive power supply, while the other is powered by 0V. When the load is heavy, the op-amp output level is high, and the first optocoupler U2 powered by 0V is cut off, with the feedback loop in frequency modulation mode. When the load is light, the op-amp output level is low. When the output level is below 0V, the first optocoupler U2 powered by 0V is turned on, and it operates in variable duty cycle mode. At this time, the first optocoupler U2 in the feedback loop controls pin 9 of the SG3525 to adjust the duty cycle, while the second optocoupler U3 powered by the positive power supply is saturated and its frequency no longer changes. The operating frequency at this time is determined by the third resistor R3.

[0077] Secondly, this application also provides a switching power supply, including the regulating circuit of the switching power supply as described above. For further details regarding the switching power supply, please refer to the above embodiments; these will not be repeated here.

[0078] It should also be noted that, in this specification, 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 apparatus 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 apparatus. 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 apparatus that includes said element.

[0079] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A regulating circuit for a switching power supply, characterized in that, The switching power supply includes a power chip and a power output terminal, and the regulating circuit includes: A voltage sampling circuit, whose input terminal is connected to the power output terminal of the switching power supply, is used to sample the output voltage of the switching power supply to obtain a sampled voltage; A voltage loop circuit, whose input terminal is connected to the output terminal of the sampling circuit, is used to compare the sampled voltage with a preset reference voltage and output a corresponding control signal according to the comparison result. The control signal has a preset relationship with the difference between the preset reference voltage and the sampled voltage. Two paths are provided, with the input terminal of each path connected to the output terminal of the voltage loop circuit. The output terminal of the first path is connected to the first mode terminal of the power chip, and the output terminal of the second path is connected to the second mode terminal of the power chip. Each path is used to turn on or off according to the control signal, and outputs a trigger signal to the corresponding mode terminal when it is turned on, so that the switching power supply works in the corresponding working mode. When the first mode terminal receives the trigger signal, the switching power supply operates in duty cycle adjustment mode; when the second mode terminal receives the trigger signal, the switching power supply operates in frequency modulation mode.

2. The regulating circuit of the switching power supply as described in claim 1, characterized in that, The voltage loop circuit includes: An error amplifier is provided, with the preset reference voltage input at its non-inverting input, the inverting input connected to the output of the sampling circuit, and the output connected to the inputs of the two paths. It is used to compare the sampled voltage with the preset reference voltage and output a corresponding control signal based on the comparison result to drive the two paths.

3. The regulating circuit of the switching power supply as described in claim 2, characterized in that, The positive power supply terminal of the error amplifier is connected to the positive terminal of the dual power supply, and the negative power supply terminal of the error amplifier is connected to the negative terminal of the dual power supply.

4. The regulating circuit of the switching power supply as described in claim 3, characterized in that, The first said path includes a first optical coupler, and the second said path includes a second optical coupler; The anode of the photodiode in the first optocoupler is grounded, the anode of the photodiode in the second optocoupler is connected to the power supply, the first end of the photodetector in the first optocoupler is connected to the first mode terminal of the power chip, the first end of the photodetector in the second optocoupler is connected to the second mode terminal of the power chip, and the second ends of the photodetectors in the first and second optocouplers are grounded. The voltage loop circuit also includes: The first diode has its cathode connected to the output terminal of the error amplifier, and its anode connected to the cathodes of the photodiodes in the two optocouplers.

5. The regulating circuit of the switching power supply as described in claim 1, characterized in that, Also includes: A current feedback circuit, whose input terminal is connected to the power output terminal of the switching power supply and whose output terminal is connected to the first mode terminal of the power chip, is used to output the trigger signal to the first mode terminal when the output current of the switching power supply exceeds the current threshold, and adjust the voltage value of the first mode terminal so that the switching power supply operates in the duty cycle adjustment mode.

6. The regulating circuit of the switching power supply as described in claim 5, characterized in that, The current feedback circuit includes: A current sampling circuit, whose input terminal is connected to the power output terminal of the switching power supply, is used to sample the output current of the switching power supply to obtain the sampled current. A current loop circuit, whose input terminal is connected to the output terminal of the current sampling circuit, is used to output a conduction signal when the sampled current is greater than the current threshold. The third path has its input terminal connected to the output terminal of the current loop circuit and its output terminal connected to the first mode terminal of the power supply. It is used to output the trigger signal according to the conduction signal, adjust the duty cycle of the switching power supply, and make the switching power supply work in constant current mode.

7. The regulating circuit of the switching power supply as described in claim 1, characterized in that, Also includes: The indicator device has its input terminal connected to the output terminal of the voltage loop circuit; The voltage loop circuit is also used to output a corresponding indication control signal to the indication device according to the comparison result, so that the indication device outputs corresponding indication information according to the indication control signal, and the indication information is used to indicate the current working mode of the switching power supply.

8. The regulating circuit of the switching power supply as described in any one of claims 1-7, characterized in that, The second mode terminal includes the timing capacitor terminal and the timing resistor terminal of the power chip, and the adjustment circuit further includes: A second diode, four resistors, and three capacitors; The reference voltage output terminal of the power chip is connected to the non-inverting input terminal of the power chip, the cathode of the second diode, and the first terminal of the first resistor, respectively. The inverting input terminal of the power chip is grounded. The second terminal of the first resistor is connected to the first terminal of the first capacitor, the first terminal of the second resistor, and the anode of the second diode, respectively. The second terminal of the second resistor is connected to the timing resistor terminal of the power chip and the first terminal of the third resistor, respectively. The second terminal of the third resistor is connected to the first terminal of the fourth resistor, the first terminal of the second capacitor, and the output terminal of the first path, respectively. The first terminal of the third capacitor is connected to the timing capacitor terminal and the discharge terminal of the power chip, respectively. The second terminals of the first capacitor, the second capacitor, the third capacitor, and the fourth resistor are all grounded.

9. The regulating circuit of the switching power supply as described in claim 8, characterized in that, Also includes: The fifth resistor has its first end connected to the soft-start terminal of the power chip and its second end grounded.

10. A switching power supply, characterized in that, Includes the regulating circuit of the switching power supply as described in any one of claims 1-9.

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