No-load protection circuit controlled by hysteresis current mode and control method of no-load protection circuit

Abstract

The invention provides a no-load protection circuit controlled in a hysteresis current mode and a control method of the no-load protection circuit. The no-load protection circuit comprises an MOSFET and a current detection resistor. The inverting input end of the hysteresis operational amplifier is connected to the voltage detection point of the current detection resistor, the non-inverting input end of the hysteresis operational amplifier is connected to the output end of the error amplifier, and the output end of the hysteresis operational amplifier is connected to the grid electrode of the MOSFET; the non-inverting input end of the error amplifier is connected to a reference voltage, the inverting input end of the error amplifier is connected to a feedback voltage, and the output end of the error amplifier is connected to the non-inverting input end of the hysteresis operational amplifier and connected to the compensation capacitor; one end of the compensation capacitor is connected to the output end of the error amplifier, and the other end is grounded; the feedback resistor is connected in series between the output voltage and the ground and is used for dividing the output voltage to obtain feedback voltage; the hysteresis voltage and the compensation voltage are compared through the hysteresis operational amplifier, the on-off state of the MOSFET is controlled, transmission of input energy is adjusted, and stability and no-load protection of the output voltage are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of no-load protection circuit control, and in particular to a no-load protection circuit controlled by a hysteresis current mode and a control method thereof. Background Art

[0002] Overvoltage protection (OVP) is a key technology for ensuring safe operation of power supply systems. Traditional OVP no-load protection circuits typically use a reference feedback potential (Vfb) derived from the output voltage as a basis for judgment, setting an upper limit (Vovp_H) and a lower limit (Vovp_L). When the output voltage exceeds Vovp_H, no-load protection is triggered, and when the voltage drops below Vovp_L, the circuit resumes operation. Although this design is simple, it also has some significant shortcomings.

[0003] First, traditional OVP protection circuits usually require a secondary test on the output voltage, which not only increases the complexity of the circuit but may also cause additional delays and instability. Second, Vovp_H and Vovp_L are usually set at both ends of the reference voltage Vfb, which may cause the output voltage to rise too high when no-load, even reaching 1.2 times or more of the reference voltage, and only resume operation when the voltage drops below the reference voltage. In this case, the output voltage will repeatedly operate in the form of a triangular wave, generating large voltage ripple. This phenomenon is called "hiccup mode". Figure 1 This mode not only affects the stability of the system, but may also cause damage to components in the circuit due to frequent voltage fluctuations.

[0004] Furthermore, traditional OVP protection circuits lack sufficient adaptability to input voltage fluctuations and load variations. Fixed-threshold detection methods cannot dynamically adjust the protection threshold, making it difficult to maintain output voltage stability under complex operating conditions. Fixed-threshold detection is also prone to false triggering in noisy environments, further impacting system reliability.

[0005] Based on this, a new solution for no-load circuit control with hysteretic current mode control is needed. Summary of the Invention

[0006] In view of this, the embodiments of this specification provide a no-load protection circuit and a control method thereof with hysteresis current mode control. By combining the hysteresis voltage with the compensation voltage, a constant voltage effect of the output voltage is achieved when the output voltage is no-load, thereby playing a no-load protection (Over Voltage Protection) role in the circuit.

[0007] The embodiments of this specification provide the following technical solutions:

[0008] The embodiments of this specification provide a no-load protection method based on hysteresis current mode control, comprising the following steps:

[0009] The output voltage V o The feedback voltage V is obtained by dividing the feedback resistors Ru and Rd. fb ;

[0010] The error amplifier U1 compares the feedback voltage V fb and reference voltage V ref , output compensation voltage V comp ;

[0011] The current flowing through MOSFET M1 is converted into a voltage signal V through the current detection resistor Rsense sense ;

[0012] The voltage signal V is compared by the hysteresis operational amplifier A1 sense and the compensation voltage V comp , controlling the switching state of the MOSFET M1;

[0013] When working normally, the compensation voltage V comp Automatically adjusts at V comp _L <V comp <V comp _H, when the voltage signal V sense Rising to V sense _H, turn off the MOSFET M1; when the voltage signal V sense Drop to V sense _L, turn on the MOSFET M1;

[0014] When no-load or light-loaded, the compensation voltage V comp Drop to V comp _L, by setting V sense _L<0 or lower than the offset low voltage of the hysteresis operational amplifier A1, thereby avoiding excessive input energy and achieving output voltage stability.

[0015] The embodiments of this specification further provide a no-load protection circuit based on hysteresis current mode control, comprising:

[0016] MOSFET M1, whose drain is connected to the power input terminal V in , the source is connected to the current detection resistor Rsense;

[0017] The current detection resistor Rsense has one end connected to the source of the MOSFET M1 and the other end connected to the ground, and is used to convert the current flowing through the MOSFET M1 into a voltage signal V sense ;

[0018] The hysteresis operational amplifier A1 has its inverting input connected to the voltage detection point V of the current detection resistor Rsense sense , the non-inverting input is connected to the output of the error amplifier U1 V comp , the output end is connected to the gate of the MOSFET M1;

[0019] The error amplifier U1 has its non-inverting input connected to the reference voltage V ref , the inverting input is connected to the feedback voltage V fb , the output end is connected to the non-inverting input end of the hysteresis operational amplifier A1 and is connected to the compensation capacitor Ccomp;

[0020] Compensation capacitor Ccomp, one end of which is connected to the output terminal V of the error amplifier U1 comp , the other end is connected to the ground;

[0021] Feedback resistors Ru and Rd are connected in series to the output voltage V o and ground, used to divide the output voltage V o Get the feedback voltage V fb ;

[0022] Wherein, the hysteresis operational amplifier A1 compares the hysteresis voltage V sense and the compensation voltage V comp , controlling the switching state of the MOSFET M1 to adjust the transmission of input energy and achieve output voltage stability and no-load protection.

[0023] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0024] 1. Dynamic threshold adjustment: Through hysteresis current mode control, the overvoltage protection threshold can be dynamically adjusted to adapt to load changes and input voltage fluctuations.

[0025] 2. High-precision control: Use operational amplifiers such as A1 and current detection resistors such as Rsense to achieve high-precision current detection and feedback control.

[0026] 3. Strong anti-noise capability: The RC network formed by the compensation capacitor Ccomp and the resistor Rd suppresses noise and jitter, improving system stability.

[0027] 4. Fast response: Hysteresis current mode control can quickly respond to sudden load changes and prevent the output voltage from exceeding the safe range in a short time.

[0028] 5. No-load protection: When the load is open, it can still achieve constant voltage output, effectively preventing device damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] Figure 1 This is a schematic diagram of the traditional OVP protection circuit showing a triangular wave output voltage when the load is open;

[0031] Figure 2 This is a diagram showing the output voltage stability of the no-load protection based on hysteresis current mode control in this application;

[0032] Figure 3 This is a schematic diagram of the OVP protection circuit based on hysteresis current mode control in this application;

[0033] Figure 4 is the hysteresis voltage V in this application sense and compensation voltage V comp The relationship diagram between

[0034] Figure 5 The hysteresis voltage V is the normal working state in this application. sense and compensation voltage V comp Schematic diagram of the dynamic interaction relationship between them;

[0035] Figure 6 This is a schematic diagram of stabilizing the output voltage by regulating energy transmission through pulse frequency modulation (PFM) under no-load or light-load conditions in this application;

[0036] Figure 7 This is a specific implementation circuit diagram of the OVP protection circuit based on hysteresis current mode control in this application. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0038] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0039] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0040] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0041] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples, however, one skilled in the art will appreciate that the examples can be practiced without these specific details.

[0042] In modern electronic circuit design, overvoltage protection (OVP) is a key technology for ensuring the safe operation of power systems. This OVP function is particularly important in applications using boost topology circuits, such as LED drivers and battery chargers. These applications often require maintaining a stable output voltage even when the load is open or lightly loaded to prevent excessive output voltage from damaging sensitive components in the circuit.

[0043] Traditional OVP no-load protection circuits usually use a reference feedback potential V introduced from the output voltage.fb As a basis for judgment, set an upper limit value V ovp _H and a lower limit value V ovp _L. When the output voltage exceeds V ovp _H, the no-load protection is triggered, and when the voltage drops to V ovp When the value is below _L, the work is resumed. Although this design is simple, it also has some obvious shortcomings.

[0044] First, traditional OVP protection circuits usually require a secondary detection on the output voltage, which not only increases the complexity of the circuit but also may cause additional delays and instability. ovp _H and V ovp _L is usually set at the reference voltage V fb This may cause the output voltage to rise too high when no-load, even reaching 1.2 times or more of the reference voltage, and the output voltage will not resume operation until the voltage drops below the reference voltage. In this case, the output voltage will repeatedly work in the form of a triangular wave, generating large voltage ripple. This phenomenon is called "hiccup mode". Figure 1 This mode not only affects the stability of the system, but may also cause damage to components in the circuit due to frequent voltage fluctuations.

[0045] Furthermore, traditional OVP protection circuits lack sufficient adaptability to input voltage fluctuations and load variations. Fixed-threshold detection methods cannot dynamically adjust the protection threshold, making it difficult to maintain output voltage stability under complex operating conditions. Fixed-threshold detection is also prone to false triggering in noisy environments, further impacting system reliability.

[0046] Therefore, developing an OVP control method that can dynamically adjust the protection threshold, quickly respond to load changes, and effectively suppress voltage ripple is of great significance for improving the performance and reliability of the power supply system.

[0047] Based on this, the embodiment of this specification proposes a new solution of no-load protection circuit and control method based on hysteresis current mode control, which uses the hysteresis current mode algorithm to convert the dynamic hysteresis voltage V sense With the compensation voltage V comp The coupled comparator enables adaptive adjustment of the PWM duty cycle, automatically maintaining a stable output voltage during input fluctuations or no-load conditions, while eliminating the redundant hardware required by traditional OVP. This design overcomes the limitations of traditional fixed-threshold protection, achieving high-precision and high-reliability no-load protection. It is suitable for power systems with stringent efficiency and compatibility requirements, such as LED drivers and battery chargers.

[0048] The following describes the technical solutions provided by various embodiments of the present application in conjunction with the accompanying drawings.

[0049] In traditional BOOST topology circuits, when the load is open, the output voltage rises rapidly, potentially damaging the device. Traditional OVP control methods typically use fixed threshold voltage detection, which has the following shortcomings:

[0050] Slow response: Fixed threshold detection cannot quickly respond to sudden load changes, causing the output voltage to exceed the safe range in a short period of time.

[0051] Poor adaptability: The threshold voltage cannot be adjusted dynamically, making it difficult to adapt to input voltage fluctuations and load changes.

[0052] Weak noise immunity: In noisy environments, fixed threshold detection is prone to false triggering, affecting system stability.

[0053] This application relates to a no-load protection (OVP) control method in a BOOST topology circuit, particularly suitable for applications requiring constant voltage output and potentially facing the risk of open-circuit load, such as LED driving and battery charging. This application proposes a no-load protection control method based on hysteresis current mode control. By combining a hysteresis voltage with a compensation voltage, this method achieves a constant voltage effect on the output voltage when no-load, thus providing no-load protection (OVP) in the circuit.

[0054] like Figure 3 As shown, the present application provides a no-load protection circuit based on hysteresis current mode control, including: a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) such as M1, a hysteresis operational amplifier such as A1, an error operational amplifier such as U1, a current detection resistor such as Rsense, a compensation capacitor such as Ccomp, and feedback resistors for output voltage divider such as Ru and Rd.

[0055] Among them, MOSFET M1, its drain is connected to the power input terminal V in , the source is connected to the current detection resistor Rsense;

[0056] The current detection resistor Rsense has one end connected to the source of the MOSFET M1 and the other end connected to the ground, and is used to convert the current flowing through the MOSFET M1 into a voltage signal V sense ;

[0057] The hysteresis operational amplifier A1 has its inverting input connected to the voltage detection point V of the current detection resistor Rsense sense, the non-inverting input is connected to the output of the error amplifier U1 V comp , the output end is connected to the gate of the MOSFET M1;

[0058] The error amplifier U1 has its non-inverting input connected to the reference voltage V ref , the inverting input is connected to the feedback voltage V fb , the output end is connected to the non-inverting input end of the hysteresis operational amplifier A1 and is connected to the compensation capacitor Ccomp;

[0059] Compensation capacitor Ccomp, one end of which is connected to the output terminal V of the error amplifier U1 comp , the other end is connected to the ground;

[0060] Feedback resistors Ru and Rd are connected in series to the output voltage V o and ground, used to divide the output voltage V o Get the feedback voltage V fb ;

[0061] Wherein, the hysteresis operational amplifier A1 compares the hysteresis voltage V sense and the compensation voltage V comp , controlling the switching state of the MOSFET M1 to adjust the transmission of input energy and achieve output voltage stability and no-load protection.

[0062] like Figure 3 For example, design a no-load protection circuit based on hysteresis current mode control. Through A1 hysteresis current mode control, combined with U1's output compensation voltage, V sense _L is set to meet V sense _L<0 or lower than the offset voltage of operational amplifier A1, then V sense Unable to detect V sense _L voltage, dynamically adjust the overvoltage protection threshold to adapt to load changes and input voltage fluctuations.

[0063] In the embodiments of this specification, the no-load protection circuit based on hysteresis current mode control directly implements no-load protection in the hysteresis current mode control, without the need for redundant circuits to perform secondary detection on the output voltage for control, thus saving circuit components.

[0064] In some embodiments, the invention further includes an overvoltage protection circuit, wherein feedback resistors Ru and Rd are connected to the output voltage V o and ground, used to detect the output voltage V oWhether it exceeds the safety range, and triggering a protection mechanism when it exceeds, turning off the MOSFET M1; an overcurrent protection circuit, connected between the current detection resistor Rsense and the ground, for detecting whether the current flowing through the MOSFET M1 exceeds the safety range, and triggering a protection mechanism when it exceeds, turning off the MOSFET M1.

[0065] In some embodiments, the invention further includes: an input filter capacitor connected to the power input terminal V comp The RC grid formed between and ground and resistor Rd is used to filter out high-frequency noise in the input power supply, such as Figure 3 and Figure 7 Example. Or, output filter capacitor, connected at the output voltage V o Between and ground, used to filter out high-frequency noise in the output voltage, such as Figure 7 shown.

[0066] like Figure 7 As shown, by dynamically coupling hysteretic current-mode control and compensation voltage, a stable output voltage and no-load protection function are achieved under different load conditions (including no load, light load, and normal load). The core of the circuit is to ensure the balance between input and output energy through feedback mechanism and dynamic adjustment, thereby achieving high-precision and high-reliability voltage regulation.

[0067] Stable output voltage: Maintain the output voltage V under load changes (including no load, light load and normal load) and input voltage fluctuations O around the set target value.

[0068] No-load protection: When the load is open or lightly loaded, it prevents the output voltage from being too high to avoid damaging the components in the circuit.

[0069] Normal working state: output voltage V o The feedback voltage V is obtained by dividing the feedback resistors Ru and Rd. fb Feedback voltage V fb With reference voltage V ref Make a comparison.

[0070] The function of the error amplifier: The error amplifier U1 compares the feedback voltage V fb and reference voltage V ref , output compensation voltage V comp .

[0071] When V fb Lower than V ref When V comp Increase, prompting the circuit to increase energy transmission; on the contrary, when V fb Higher than V ref When V compReduce, reduce energy transfer.

[0072] Current detection and hysteresis control: The current flowing through MOSFET M1 is converted into a voltage signal V through the current detection resistor Rsense sense .

[0073] Hysteresis op amp A1 compares V sense and V comp , controls the switching state of MOSFETM1.

[0074] When V sense Rising to V sense _H, turn off MOSFET M1; when V sense Down to Vs ense _L, turn on MOSFETM1.

[0075] Function of compensation circuit: Compensation capacitor Ccomp is connected to V comp It is used between the pin and ground to stabilize the control loop, suppress noise and jitter, and improve system stability.

[0076] No-load or light-load state: 1. Compensation voltage drops. When no-load or light-load, the feedback voltage V fb decreases, resulting in the compensation voltage V comp drops to Vcomp_L.

[0077] 2. Switch to PFM mode: When V comp Drop to V comp When the output voltage is 0, the circuit switches to pulse frequency modulation (PFM) mode. In PFM mode, the circuit controls energy transfer by adjusting the pulse frequency rather than the pulse width to maintain a stable output voltage.

[0078] 3. Avoid overvoltage: By setting V sense _L<0 or lower than the offset low voltage of operational amplifier A1 to avoid excessive input energy and thus achieve output voltage stability.

[0079] Among them, the protection function:

[0080] Overvoltage protection: When the output voltage V o When the voltage exceeds the set upper limit, the protection mechanism is triggered and MOSFET M1 is turned off to prevent the output voltage from being too high and damaging the components in the circuit.

[0081] Overcurrent protection: When the current flowing through MOSFET M1 exceeds the set upper limit, the protection mechanism is triggered and MOSFET M1 is turned off to prevent overcurrent from damaging components in the circuit.

[0082] Functions of auxiliary circuits: Input filter capacitors filter out high-frequency noise in the input power supply to ensure input power stability. Output filter capacitors filter out high-frequency noise in the output voltage to ensure output voltage stability.

[0083] Figure 7 Diodes D2 to D5, D2 and D3 are usually used for clamping protection to prevent the output voltage Vo from exceeding the safe range. The anode of D2 is connected to the output voltage V o , the cathode is connected to a high voltage source (such as Vclamp). The anode of D3 is connected to ground, and the cathode is connected to the output voltage V o D4 and D5 are usually used for input protection to prevent the input voltage V in Exceed the safety range or reverse. The anode of D4 is connected to the input voltage V in , the cathode is connected to a high voltage source (such as Vclamp). The anode of D5 is connected to ground, and the cathode is connected to the input voltage V in .

[0084] Among them, clamp protection: prevent the output voltage V o Protect the components in the circuit from being damaged by high voltage when the voltage exceeds the set safety range. Input protection: prevent the input voltage V in It can also prevent the input voltage from exceeding the set safety range and protect the circuit from damage.

[0085] Inductor L1 is usually connected to the input voltage V in and the output voltage V o It is used for energy storage and filtering. One end is connected to the input voltage V in , the other end is connected to the output voltage V o Energy storage: Stores energy during the switching cycle to ensure output voltage stability. Filtering: Smoothes the output voltage and reduces switching noise.

[0086] Diode D1 is usually used to prevent input voltage from reverse or provide protection. The anode is connected to the input voltage V in , the cathode is connected to the ground. Function: Prevent the input voltage from reversing: Prevent the input voltage V in Protection circuit: Provides additional protection to ensure that the input voltage is within a safe range.

[0087] Diode D is usually used to prevent reverse current or provide a fast discharge path. The anode is connected to the output voltage Vo and the cathode is connected to the ground. Function: Prevent reverse current: Prevent the output voltage V o Reverse current will damage the circuit. Fast discharge: Provides a fast discharge path to ensure that the circuit can respond quickly when the load changes.

[0088] Power Supply Voltage Vcc: Vcc is typically a stable power supply voltage used to power the control circuit. It is connected to the power supply terminal of the control circuit, such as the error amplifier U1 and the hysteresis operational amplifier A1. Function: Power supply: Provides a stable power supply to the control circuit to ensure its normal operation.

[0089] Output filter capacitor Co. Connection: Connect between the output voltage Vo and ground. It filters high-frequency noise from the output voltage, ensuring output voltage stability. Filtering: Smoothes the output voltage and reduces high-frequency noise. Energy storage: Provides instantaneous energy during load changes, ensuring output voltage stability.

[0090] The driver circuit is connected between the output of hysteresis operational amplifier A1 and the gate of MOSFET M1, providing sufficient drive capability. The overvoltage protection circuit, connected between the output voltage Vo and ground, detects whether the output voltage exceeds a safe range and triggers the protection mechanism. The overcurrent protection circuit, connected between the current sense resistor Rsense and ground, detects whether the current flowing through MOSFET M1 exceeds a safe range and triggers the protection mechanism.

[0091] Input filter capacitor in the filter circuit: connected to the power input terminal V in Output filter capacitor: Connected between the output voltage V o Between the pin and ground, it filters out high-frequency noise in the output voltage.

[0092] In combination with the above embodiments, the present application further provides a no-load protection method based on hysteresis current mode control, comprising the following steps:

[0093] The output voltage V o The feedback voltage V is obtained by dividing the feedback resistors Ru and Rd. fb ;

[0094] The error amplifier U1 compares the feedback voltage V fb and reference voltage V ref , output compensation voltage V comp ;

[0095] The current flowing through MOSFET M1 is converted into a voltage signal V through the current detection resistor Rsense sense ;

[0096] The voltage signal V is compared by the hysteresis operational amplifier A sense and the compensation voltage V comp , controlling the switching state of the MOSFET M1;

[0097] When working normally, the compensation voltage Vcomp Automatically adjusts at V comp _L <V comp <V comp _H, when the voltage signal V sense Rising to V sense _H, turn off the MOSFET M1; when the voltage signal V sense Drop to V sense _L, turn on the MOSFET M1;

[0098] When no-load or light-loaded, the compensation voltage V comp Drop to V comp _L, by setting V sense _L<0 or lower than the offset low voltage of the hysteresis operational amplifier A1, thereby avoiding excessive input energy and achieving output voltage stability.

[0099] In some embodiments, the following steps are also included:

[0100] Filter out high-frequency noise in the input power supply through the input filter capacitor;

[0101] Alternatively, high-frequency noise in the output voltage can be filtered out through an output filter capacitor.

[0102] In some embodiments, when the load is not in use or is light, the circuit switches to a pulse frequency modulation (PFM) mode to control energy transmission by adjusting the pulse frequency instead of the pulse width, thereby further improving the stability and efficiency of the system.

[0103] This application adopts a hysteresis current mode algorithm to combine the hysteresis voltage with the compensation voltage to control the input hysteresis voltage V sense The output voltage V is compensated by the error amplifier. comp The comparison is used to adjust the PWM duty cycle, thereby controlling the output voltage so that the output voltage and input voltage are in a balanced state to achieve the circuit no-load protection function.

[0104] The principle of this embodiment is as follows (refer to Figure 3 ), can be used as an example, but is not limited to this.

[0105] Output voltage V o The feedback voltage V is obtained by dividing the feedback resistors Ru\Rd fb , the error amplifier U1 is used to compare the feedback voltage V fb and reference voltage V ref The output of the error amplifier is used as the compensation signal voltage V comp , you will get a voltage range value V comp _H and V comp_L; the current flowing through M1 MOS is converted into feedback voltage V through resistor Rense sense (can be positive or negative voltage), feedback voltage V sense With the compensation voltage V comp Acting on the hysteresis voltage comparator A1, controlling the switch element MOSFET M1 to adjust the input energy transmission and realize closed-loop control; the hysteresis voltage V sense The voltage V sense _H and V sense _L, and the compensation voltage V comp _H, V comp The relationship between _L is as follows Figure 4 ; When in normal operation, the compensation voltage V comp Automatically adjusts to V comp _L <V comp <V comp _H interval, in this interval when Vsense triggers the upper limit V sense _H, Vg is turned off, otherwise it is triggered to V sense _L, Vg is turned on, such as Figure 5 , when working at no load or light load, V comp The voltage will drop to V comp _L, at this time, you need to use the parameter V sense _L is set to meet V sense _L<0 or lower than the offset voltage of operational amplifier A1, then V sense Unable to detect V sense _L voltage, Vg will not appear high level drive MOS M1, thus avoiding excessive input energy into the output voltage to stabilize near the target value, at this time the working mode will become PFM (pulse frequency modulation) mode to regulate energy transmission, such as Figure 6 .

[0106] Advantages and beneficial effects of this application:

[0107] Dynamic threshold adjustment: Through hysteretic current mode control, the overvoltage protection threshold can be dynamically adjusted to adapt to load changes and input voltage fluctuations.

[0108] High-precision control: Operational amplifier A1 and current detection resistor Rsense are used to achieve high-precision current detection and feedback control.

[0109] Strong anti-noise capability: The RC network formed by the compensation capacitor Ccomp and the resistor Rd suppresses noise and jitter, improving system stability.

[0110] Fast response: Hysteretic current mode control can quickly respond to sudden load changes and prevent the output voltage from exceeding the safe range in a short time.

[0111] No-load protection: When the load is open, it can still achieve constant voltage output, effectively preventing device damage.

[0112] In combination with the above embodiments, the present application further provides a BOOST boost topology circuit, which is provided with a no-load protection circuit based on hysteresis current mode control as described in any one of the above technical solutions.

[0113] In summary, the core innovation of this application is the dynamic coupling control of the hysteresis current mode and the compensation voltage, that is, through the hysteresis current mode algorithm, the dynamic hysteresis voltage V sense With the compensation voltage V comp The coupled comparator enables adaptive adjustment of the PWM duty cycle, automatically maintaining a stable output voltage during input fluctuations or no-load conditions, while eliminating the redundant hardware required by traditional OVP. This design overcomes the limitations of traditional fixed-threshold protection, achieving high-precision and high-reliability no-load protection, making it suitable for power systems with stringent efficiency and compatibility requirements (such as LED drivers and battery chargers).

[0114] This application compares V sense (Reflects the input current state) and V comp (Reflecting output voltage errors), dynamic threshold adjustment is achieved, ensuring the system always operates at the optimal balance point. Traditional OVP relies solely on fixed threshold voltage detection, which has a slow response and cannot adapt to input fluctuations.

[0115] Technical advantages summary:

[0116] Dynamic hysteresis window: through V comp Adjust the hysteresis threshold in real time to balance response speed and stability.

[0117] Energy balance control: V sense With V comp The coupling comparison ensures real-time matching of input and output energy to avoid overvoltage or undervoltage.

[0118] Hardware simplification: No independent OVP detection module is required, and BOM cost is reduced through algorithm integration.

[0119] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.

[0120] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A no-load protection method based on hysteresis current mode control, characterized in that: The following steps are involved: The output voltage V o The feedback voltage V is obtained by dividing the feedback resistors Ru and Rd. fb ; The error amplifier U1 compares the feedback voltage V fb and reference voltage V ref , output compensation voltage V comp ; The current flowing through MOSFET M1 is converted into a voltage signal V through the current detection resistor Rsense sense ; The voltage signal V is compared by the hysteresis operational amplifier A1 sense and the compensation voltage V comp , controlling the switching state of the MOSFETM; When working normally, the compensation voltage V comp Automatically adjusts at V comp _L <V comp <V comp _H, when the voltage signal V sense Rising to V sense _H, turn off the MOSFET M1; when the voltage signal V sense Drop to V sense _L, turn on the MOSFET M1; When no-load or light-loaded, the compensation voltage V comp Drop to V comp _L, by setting V sense _L<0 or lower than the offset low voltage of the hysteresis operational amplifier A1, thereby avoiding excessive input energy and achieving output voltage stability.

2. The no-load protection method according to claim 1, characterized in that: The following steps are also included: Filter out high-frequency noise in the input power supply through the input filter capacitor; Alternatively, high-frequency noise in the output voltage can be filtered out through an output filter capacitor.

3. The no-load protection method according to claim 1, characterized in that: At no load or light load, the circuit switches to pulse frequency modulation (PFM) mode, which controls energy transfer by adjusting the pulse frequency instead of the pulse width.

4. A no-load protection circuit based on hysteresis current mode control, characterized in that: include: MOSFET M1, whose drain is connected to the power input terminal V in , the source is connected to the current detection resistor Rsense; The current detection resistor Rsense has one end connected to the source of the MOSFET M1 and the other end connected to the ground, and is used to convert the current flowing through the MOSFET M1 into a voltage signal V sense ; The hysteresis operational amplifier A1 has its inverting input connected to the voltage detection point V of the current detection resistor Rsense sense , the non-inverting input is connected to the output of the error amplifier U1 V comp , the output end is connected to the gate of the MOSFET M1; The error amplifier U1 has its non-inverting input connected to the reference voltage V ref , the inverting input is connected to the feedback voltage V fb , the output end is connected to the non-inverting input end of the hysteresis operational amplifier A1 and is connected to the compensation capacitor Ccomp; Compensation capacitor Ccomp, one end of which is connected to the output terminal V of the error amplifier U1 comp , the other end is connected to the ground; Feedback resistors Ru and Rd are connected in series to the output voltage V o and ground, used to divide the output voltage V o Get the feedback voltage V fb ; Wherein, the hysteresis operational amplifier A1 compares the hysteresis voltage V sense and the compensation voltage V comp , controlling the switching state of the MOSFET M1 to adjust the transmission of input energy and achieve output voltage stability and no-load protection.

5. The no-load protection circuit according to claim 4, characterized in that: Also includes: Overvoltage protection circuit, feedback resistors Ru and Rd are connected to the output voltage V o and ground, used to detect the output voltage V o Whether it exceeds the safety range, and if so, triggering the protection mechanism to turn off the MOSFET M1; The overcurrent protection circuit is connected between the current detection resistor Rsense and the ground, and is used to detect whether the current flowing through the MOSFET M1 exceeds a safe range, and trigger a protection mechanism when the current exceeds the safe range to turn off the MOSFET M1.

6. The no-load protection circuit according to claim 4, characterized in that: Also includes: Input filter capacitor, connected to the power input V comp The RC grid formed between MOSFET and ground and resistor Rd is used to filter out high-frequency noise in the input power supply.

7. The no-load protection circuit according to claim 4, characterized in that: Also includes: Output filter capacitor, connected to the output voltage V o Between 1 and 2, it is used to filter out high-frequency noise in the output voltage.

8. A BOOST boost topology circuit, characterized in that: A no-load protection circuit based on hysteresis current mode control is provided as claimed in any one of claims 4 to 7.

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