Control circuit, switching power supply and electronic device
By combining a current transformer, a demagnetizing module, and a sampling module, the problems of inaccurate current sampling and magnetic core saturation are solved, achieving demagnetization and overcurrent protection of the current transformer, and improving the sampling frequency and protection accuracy of the switching power supply.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HUNAN MEGMEET ELECTRICAL TECH CO LTD
- Filing Date
- 2025-05-20
- Publication Date
- 2026-06-02
AI Technical Summary
Existing current sampling methods cannot accurately represent the real current, resulting in insufficient overcurrent protection accuracy, and the magnetic core of the current transformer is prone to saturation failure and low sampling frequency.
By combining a current transformer, a demagnetizing module, a sampling module, and a control module, the current transformer can be demagnetized and overcurrent protected by detecting the charge information and instantaneous current magnitude during the switching power supply cycle.
This technology effectively demagnetizes current transformers, ensures sampling accuracy, improves the precision and frequency of overcurrent protection, and enhances the performance and reliability of switching power supplies.
Smart Images
Figure CN224319235U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic circuits, specifically to control circuits, switching power supplies, and electronic equipment. Background Technology
[0002] In the field of modern power electronics, charge control is widely used due to its excellent dynamic characteristics, light-load efficiency, and ripple suppression. Charge control often requires sampling the charge information in the power loop, i.e., the integral of the current, as the inner-loop control quantity for controlling the input power. However, directly sampling the current integral cannot represent the true current, and when used for overcurrent protection, setting the protection threshold based on charge information is not accurate enough, which is not conducive to the overcurrent protection of the circuit.
[0003] Common current sampling methods include resistance sampling, Hall effect chip sampling, and current transformer sampling. When sampling circuits collect the current flowing through a power switch, the unidirectional pulses (current only flows during the on-state) cause the current transformer core to become unidirectionally magnetized. If not demagnetized, the core will gradually saturate, leading to sampling distortion or even failure. Traditional current transformer sampling circuits use resistors for demagnetization, but if the resistor is too small, the losses are too high; if the resistor is too large, demagnetization is incomplete. This results in a relatively low sampling frequency for the sampling circuit. Utility Model Content
[0004] To address the aforementioned issues, this application provides a control circuit, a switching power supply, and electronic equipment capable of detecting charge information representing power and instantaneous current magnitude within a switching power supply cycle, and achieving demagnetization of the current transformer.
[0005] One technical solution adopted in this application is: providing a control circuit, the control circuit including: a current transformer, the current transformer being disposed in the circuit of the power switch of the switching power supply; a demagnetizing module, connected between the first and second ends of the secondary winding of the current transformer; a sampling module, connected to the first end of the secondary winding of the current transformer; and a control module, connected to the control terminal of the power switch and the sampling module.
[0006] In one embodiment, the demagnetizing module includes: a first diode, the cathode of which is connected to a first end of the secondary winding of a current transformer and a sampling module; and a Zener diode, the anode of which is connected to the anode of the first diode and the cathode of which is connected to a second end of the secondary winding of the current transformer.
[0007] In one embodiment, the sampling module includes: a sampling capacitor, the first end of which is connected to the first end of the secondary winding of a current transformer and the control module, and the second end of which is grounded; and a control switch, the first end of which is connected to the first end of the sampling capacitor, the second end of which is grounded, and the control terminal of which is connected to the control module.
[0008] In one embodiment, the control circuit further includes a protection module connected to the second end of the secondary winding of the current transformer, the sampling module, and the control module.
[0009] In one embodiment, the protection module includes: a sampling resistor, a first end of which is connected to the sampling module and ground, a second end of which is connected to the second end of the secondary winding of a current transformer; and a comparator, a first input of which is connected to the second end of the sampling resistor, the second input of which is configured to input a reference voltage, and an output of which is connected to the control module.
[0010] In one embodiment, the control circuit further includes a second diode, the anode of which is connected to the first end of the secondary winding of the current transformer, and the cathode of which is connected to the control module and the sampling module.
[0011] In one embodiment, the control circuit further includes an inductor connected in parallel with the secondary winding of the current transformer.
[0012] In one embodiment, the power switch and the control switch form a complementary switch pair. When the power switch is on, the control switch is off, and when the power switch is off, the control switch is on.
[0013] This application also provides a switching power supply, which includes the control circuit described above.
[0014] This application also provides an electronic device that includes a switching power supply as described above.
[0015] One technical solution adopted in this application is to provide a control circuit, which includes: a current transformer disposed in the circuit of a power switch in a switching power supply; a demagnetizing module connected between the first and second terminals of the secondary winding of the current transformer; a sampling module connected to the first terminal of the secondary winding of the current transformer; and a control module connected to the control terminal of the power switch and the sampling module. Through this method, the charge information representing power and the instantaneous current magnitude within a switching power supply cycle can be detected, thereby achieving control and overcurrent protection of the power switch, and demagnetizing the current transformer. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] in:
[0018] Figure 1 This is a schematic diagram of the structure of the first embodiment of the control circuit provided in this application;
[0019] Figure 2 This is a schematic diagram of the structure of the second embodiment of the control circuit provided in this application;
[0020] Figure 3 This is a schematic diagram of the third embodiment of the control circuit provided in this application;
[0021] Figure 4 This is a schematic diagram of the fourth embodiment of the control circuit provided in this application;
[0022] Figure 5 This is a schematic diagram of the structure of an embodiment of the switching power supply provided in this application;
[0023] Figure 6 This is a schematic diagram of the structure of an embodiment of the electronic device provided in this application. Detailed Implementation
[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are only for explaining this application and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0025] The terms "first," "second," etc., used in this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.
[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0027] In switching power supplies, the power switch is one of the core components. It is a semiconductor device (such as MOSFET, IGBT, etc.) that can quickly turn on and off. Its core function is to control the transfer of energy through high-frequency switching action to achieve voltage or current conversion. The operating state (on / off) of the power switch is driven by the control circuit. Therefore, the control circuit will affect the performance, efficiency, and reliability of the switching power supply.
[0028] Charge control is a unique control strategy in switching power supplies, widely used due to its excellent dynamic characteristics, light-load efficiency, and ripple suppression. In switching power supplies, charge is typically related to the current waveform during the power switch's conduction period. By adjusting the power switch's conduction time (or frequency), the amount of charge transferred per cycle is controlled, indirectly stabilizing the output voltage or current.
[0029] See Figure 1 , Figure 1 This is a schematic diagram of the structure of the first embodiment of the control circuit provided in this application. The control circuit 100 includes: a current transformer Lm, a demagnetizing module 10, a sampling module 20, and a control module 30.
[0030] The current transformer Lm is installed in the circuit of the power switch P of the switching power supply; the demagnetizing module 10 is connected between the first and second ends of the secondary winding of the current transformer Lm; the sampling module 20 is connected to the first end of the secondary winding of the current transformer Lm; and the control module 30 is connected to the control terminal of the power switch P and the sampling module 20.
[0031] Specifically, the current transformer Lm is essentially a special type of transformer, consisting of a primary winding, a secondary winding, and a magnetic core. When the power switch P is turned on, current flows through the primary winding, generating magnetic flux in the magnetic core, which induces a current in the secondary winding. Simultaneously, due to the unidirectional pulse (current only flows during the period when the power switch P is on), the magnetic core of the current transformer Lm is unidirectionally magnetized. If not demagnetized, the magnetic core will gradually saturate, leading to sampling distortion or even failure. Therefore, the demagnetization module 10 is needed to release the residual magnetism of the current transformer Lm.
[0032] The induced current on the secondary winding of the current transformer Lm is proportional to the current flowing through the primary winding (i.e., the current flowing through the power switch P). During the conduction period of the power switch P, the sampling module 20 samples the charge information in the induced current to monitor the output current of the switching power supply in real time. This allows the control module 30 to control the conduction time of the power switch P through the voltage signal output by the sampling module 20, thereby stabilizing the output voltage or current of the switching power supply.
[0033] See Figure 2 , Figure 2This is a schematic diagram of the structure of the second embodiment of the control circuit provided in this application. The control circuit 100 includes: a current transformer Lm, a demagnetizing module 10, a sampling module 20, and a control module 30.
[0034] The current transformer Lm is installed in the circuit of the power switch P of the switching power supply; the demagnetizing module 10 is connected between the first and second ends of the secondary winding of the current transformer Lm; the sampling module 20 is connected to the first end of the secondary winding of the current transformer Lm; and the control module 30 is connected to the control terminal of the power switch P and the sampling module 20.
[0035] In some embodiments, the demagnetizing module 10 includes: a first diode D1 and a Zener diode Z.
[0036] The cathode of the first diode D1 is connected to the first end of the secondary winding of the current transformer Lm and the sampling module 20; the anode of the Zener diode Z is connected to the anode of the first diode D1, and the cathode of the Zener diode Z is connected to the second end of the secondary winding of the current transformer Lm.
[0037] Specifically, when the power switch P is turned on, an induced current appears in the secondary winding of the current transformer Lm. The first diode D1 can prevent the current from flowing in reverse, protecting the subsequent circuit components from damage and playing a role in protecting the circuit. The Zener diode Z has a stable reverse breakdown voltage. When the voltage in the circuit exceeds its reverse breakdown voltage, the Zener diode Z will enter the reverse breakdown state, keeping the voltage relatively stable and playing a role in voltage regulation and clamping, preventing excessive voltage from damaging other components in the circuit.
[0038] When the power switch P is open and no current flows through the primary winding of the current transformer Lm, Lm acts as a magnetizing inductor, generating an induced voltage. When the voltage generated by the magnetizing inductor causes the reverse voltage across the Zener diode Z to reach its regulated value, Zener diode Z undergoes reverse breakdown. At this time, Zener diode Z acts as a low-resistance component, providing a path for the current, i.e., a demagnetizing circuit. The current in this circuit demagnetizes the current transformer Lm, consuming the energy stored in Lm and gradually weakening its magnetic field. This prevents excessive voltage or other adverse effects caused by the energy stored in Lm.
[0039] In one embodiment, the control circuit 100 further includes an inductor L, which is connected in parallel with the secondary winding of the current transformer Lm.
[0040] In this context, inductance L increases the total inductance of the secondary winding of the current transformer Lm, thereby extending the decay time of the demagnetizing current and making the demagnetizing process smoother. In high-frequency pulse applications, such as switching power supplies and motor drives, the core reset time is short. If the demagnetizing time is insufficient, the core may not be able to fully reset, leading to cumulative saturation. Inductance L can extend the demagnetizing time. When the current on the primary winding is large, the current transformer Lm has high energy storage. By shunting the demagnetizing current through inductance L, overload of the Zener diode Z can be avoided.
[0041] See Figure 3 , Figure 3 This is a schematic diagram of the third embodiment of the control circuit provided in this application. The control circuit 100 includes: a current transformer Lm, a demagnetizing module 10, a sampling module 20, and a control module 30.
[0042] The current transformer Lm is installed in the circuit of the power switch P of the switching power supply; the demagnetizing module 10 is connected between the first and second ends of the secondary winding of the current transformer Lm; the sampling module 20 is connected to the first end of the secondary winding of the current transformer Lm; and the control module 30 is connected to the control terminal of the power switch P and the sampling module 20.
[0043] Figure 3 The control circuit 100 shown is Figure 2 The main difference in the control circuit 100 shown is the addition of components to the sampling module 20 and the second diode D2. Therefore, the following mainly describes the added components to the sampling module 20 and the second diode D2. For other components in the control circuit 100, please refer to [link to relevant documentation]. Figure 2 The related descriptions of the illustrated embodiments, for example Figure 3 The demagnetizing module 10 in the middle can be found in [reference]. Figure 2 The description of the demagnetization module 10 is omitted here.
[0044] In some embodiments, the sampling module 20 includes a sampling capacitor C and a control switch SW.
[0045] The sampling capacitor C is connected to the first terminal of the secondary winding of the current transformer Lm and the control module 30, and the second terminal of the sampling capacitor C is grounded; the first terminal of the control switch SW is connected to the first terminal of the sampling capacitor C, the second terminal of the control switch SW is grounded, and the control terminal of the control switch SW is connected to the control module 30.
[0046] The control switch SW can be a MOS transistor, specifically an NMOS transistor, and its operating state is controlled by the gate (i.e., control terminal) voltage signal of the NMOS transistor. In other embodiments, the control switch SW can also be a PMOS transistor, a triode, or other semiconductor devices, which will not be listed here.
[0047] Specifically, there is a linear relationship between the voltage of the sampling capacitor C and the charge it stores. The charge information in the power circuit can be sampled by integrating the induced current through the sampling capacitor C.
[0048] When power switch P is turned on, the induced current flows through the sampling capacitor C to charge it, at which point the control switch SW is turned off. The induced current accumulates charge on the sampling capacitor C, causing the first voltage signal Vcs1 across the sampling capacitor C to increase over time. Vcs1 is input to the control module 30, which converts it into a digital or analog signal and compares it with a preset threshold. When Vcs1 is greater than the preset threshold, the control module 30 generates a first control signal through a control algorithm (such as a PI regulator) to drive the power switch P to turn on or off, thereby changing the on-time of the power switch P.
[0049] In one embodiment, the power switch P and the control switch SW form a complementary switch pair. When the power switch P is on, the control switch SW is off, and when the power switch P is off, the control switch SW is on.
[0050] When the first voltage signal Vcs1 is greater than the preset threshold, the control module 30 controls the power switch P to turn off. At this time, the control switch SW turns on, and the voltage across the sampling capacitor C is discharged and reset through the control switch SW, waiting for the power switch P to turn on again to re-integrate the induced current.
[0051] In one embodiment, the control circuit 100 further includes: a second diode D2, the anode of the second diode D2 being connected to the first end of the secondary winding of the current transformer Lm, and the cathode of the second diode D2 being connected to the control module 30 and the sampling module 20.
[0052] Specifically, the secondary winding of the current transformer Lm typically outputs alternating current (or pulsating current), while the sampling capacitor C requires unidirectional current to accumulate charge. The second diode D2, through its unidirectional conduction characteristic, rectifies the alternating current into a unidirectional pulsating current, thereby accumulating DC voltage on the sampling capacitor C. Simultaneously, the second diode D2 also protects the circuit from reverse voltage, preventing capacitor damage or charge leakage.
[0053] See Figure 4 , Figure 4 This is a schematic diagram of the fourth embodiment of the control circuit provided in this application. The control circuit 100 includes: a current transformer Lm, a demagnetizing module 10, a sampling module 20, and a control module 30.
[0054] The current transformer Lm is installed in the circuit of the power switch P of the switching power supply; the demagnetizing module 10 is connected between the first and second ends of the secondary winding of the current transformer Lm; the sampling module 20 is connected to the first end of the secondary winding of the current transformer Lm; and the control module 30 is connected to the control terminal of the power switch P and the sampling module 20.
[0055] Figure 4 The control circuit 100 shown is Figure 3 The main difference in the control circuit 100 shown is the addition of descriptions of the components added to the protection module 40. Therefore, the following mainly describes the components added to the protection module 40. For other components in the control circuit 100, please refer to [link to relevant documentation]. Figure 3 The related descriptions of the illustrated embodiments, for example Figure 4 The sampling module 20 in the middle can be seen in Figure 3 The description of the sampling module 20 is omitted here.
[0056] In some embodiments, the control circuit 100 further includes a protection module 40, which is connected to the second end of the secondary winding of the current transformer Lm, the sampling module 20, and the control module 30.
[0057] In some embodiments, the protection module 40 includes a sampling resistor R and a comparator U.
[0058] The sampling resistor R is connected to the sampling module 20 and ground at its first end, and to the second end of the secondary winding of the current transformer Lm at its second end. The comparator U is connected to the second end of the sampling resistor R at its first input end, and is configured to input a reference voltage at its second input end. The comparator U is connected to the control module 30 at its output end.
[0059] Specifically, the first voltage signal Vcs1 is the integral of the induced current over time. Due to the nonlinear relationship between current and charge, small errors in current sampling will be accumulated and amplified during the integration process, causing the charge to deviate from the true value. At the same time, when directly integrating the current, the selection of the integration time window may be inaccurate (e.g., the start and end times of the switching transistor's conduction time are difficult to synchronize precisely), causing the integrated value to deviate from the true charge.
[0060] Due to errors in direct current integration, overcurrent protection thresholds may not accurately correspond to the actual overcurrent point. For example, the set threshold may trigger protection when the actual current has not reached a dangerous level, or it may not trigger protection when the actual current has already exceeded the overcurrent limit. Furthermore, direct integration requires a certain time window to obtain the result, and the system may not be able to respond in time when an overcurrent occurs, leading to equipment damage.
[0061] Voltage and current are instantaneously correlated across the sampling resistor R. Therefore, the voltage across the sampling resistor R can reflect the instantaneous current value passing through the resistor in real time. When the power switch P is turned on, the voltage across the sampling resistor R is collected and compared with a reference voltage. This reference voltage is usually a threshold voltage set according to the circuit design requirements and safety standards. This threshold voltage corresponds to the maximum current value that the circuit can withstand, i.e., the overcurrent value. The second voltage signal Vcs2 across the sampling resistor R is input to the first input terminal of the comparator U and compared with the reference voltage. When Vcs2 is greater than the reference voltage, the output terminal of the comparator U outputs a protection signal to the control module 30. Based on this protection signal, the control module 30 outputs a second control signal to control the power switch P to turn off or adjust its on-time to reduce the current in the circuit and achieve overcurrent protection.
[0062] See Figure 5 , Figure 5 This is a schematic diagram of a switching power supply embodiment provided in this application. The switching power supply 1000 includes a control circuit 100, which is the control circuit 100 described above, and will not be repeated here.
[0063] See Figure 6 , Figure 6 This is a schematic diagram of an embodiment of the electronic device provided in this application. The electronic device 2000 includes a switching power supply 1000, which is the switching power supply 1000 as described above, and will not be repeated here.
[0064] One technical solution adopted in this application is to provide a control circuit, which includes: a current transformer disposed in the circuit of a power switch in a switching power supply; a demagnetizing module connected between the first and second terminals of the secondary winding of the current transformer; a sampling module connected to the first terminal of the secondary winding of the current transformer; and a control module connected to the control terminal of the power switch and the sampling module. Through this method, the charge information representing power and the instantaneous current magnitude within a switching power supply cycle can be detected, thereby achieving control and overcurrent protection of the power switch, and demagnetizing the current transformer.
[0065] In the several embodiments provided in this application, it should be understood that the disclosed methods and devices can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.
[0066] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.
[0067] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.
[0068] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.
Claims
1. A control circuit applied to a switching power supply, characterized in that, The control circuit includes: A current transformer, wherein the current transformer is disposed in the circuit of the power switch of the switching power supply; A demagnetizing module is connected between the first and second ends of the secondary winding of the current transformer; The sampling module is connected to the first end of the secondary winding of the current transformer; The control module connects the control terminal of the power switch and the sampling module.
2. The control circuit according to claim 1, characterized in that, The demagnetizing module includes: The first diode, the cathode of which is connected to the first end of the secondary winding of the current transformer and the sampling module; A Zener diode, wherein the anode of the Zener diode is connected to the anode of the first diode, and the cathode of the Zener diode is connected to the second end of the secondary winding of the current transformer.
3. The control circuit according to claim 1, characterized in that, The sampling module includes: A sampling capacitor, the first end of which is connected to the first end of the secondary winding of the current transformer and the control module, and the second end of which is grounded; A control switch, wherein the first terminal of the control switch is connected to the first terminal of the sampling capacitor, the second terminal of the control switch is grounded, and the control terminal of the control switch is connected to the control module.
4. The control circuit according to claim 1, characterized in that, The control circuit also includes: The protection module is connected to the second end of the secondary winding of the current transformer, the sampling module, and the control module.
5. The control circuit according to claim 4, characterized in that, The protection module includes: A sampling resistor, the first end of which is connected to the sampling module and ground, and the second end of which is connected to the second end of the secondary winding of the current transformer; A comparator, wherein the first input terminal of the comparator is connected to the second terminal of the sampling resistor, the second input terminal of the comparator is configured to input a reference voltage, and the output terminal of the comparator is connected to the control module.
6. The control circuit according to claim 1, characterized in that, The control circuit also includes: The second diode has its anode connected to the first end of the secondary winding of the current transformer, and its cathode connected to the control module and the sampling module.
7. The control circuit according to claim 1, characterized in that, The control circuit also includes: An inductor, wherein the inductor is connected in parallel with the secondary winding of the current transformer.
8. The control circuit according to claim 3, characterized in that, The power switch and the control switch form a complementary switch pair. When the power switch is on, the control switch is off, and when the power switch is off, the control switch is on.
9. A switching power supply, characterized in that, The switching power supply includes the control circuit as described in any one of claims 1-8.
10. An electronic device, characterized in that, The electronic device includes the switching power supply as described in claim 9.