A half-bridge switching power supply circuit based on sg3525

Abstract

The utility model discloses a kind of half-bridge switching power supply circuit based on SG3525, it is characterized by, including half-bridge power conversion circuit, drive transformer, main control chip SG3525, high-frequency power transformer, rectifier filter circuit, amplifier and soft start circuit;DC output end is connected with the half-bridge power conversion circuit, the main control chip SG3525 generates two-way complementary PWM pulse, two-way the PWM pulse is connected with the half-bridge power conversion circuit by the drive transformer;The midpoint of the half-bridge power conversion circuit generates square wave voltage connection primary side of the high-frequency power transformer;The secondary side voltage of the high-frequency power transformer is connected with the main control chip SG3525 by the rectifier filter circuit, the amplifier.A kind of half-bridge switching power supply circuit based on SG3525, makes full use of the soft start, shutdown and error amplification function of SG3525 chip, in combination with peripheral circuit design, to a core controller has realized to wide input voltage, high isolation requirement power supply Multidimensional management and protection.

Description

Technical Field

[0001] This utility model belongs to the field of power electronics technology, specifically relating to a half-bridge switching power supply circuit based on SG3525. Background Technology

[0002] In existing technologies, switching power supplies that achieve a wide input voltage range (e.g., 400V-800VDC) often employ flyback or two-transistor forward topologies. However, flyback topologies have several drawbacks: in high-voltage, high-power applications, the switching transistors experience high voltage stress, and voltage spikes caused by transformer leakage inductance are difficult to handle, resulting in lower efficiency and reliability; low power transfer density and relatively large transformer size, hindering power supply miniaturization; and large output ripple, placing high demands on subsequent filtering circuits. Two-transistor forward topologies have the following drawbacks: although the switching transistor voltage stress is lower, their magnetic reset mechanism typically limits the maximum duty cycle to below 50%. At the lower input voltage limit, a high transformer turns ratio is required to maintain output, which in turn leads to an excessively small duty cycle at the upper input voltage limit, making control loop optimization difficult; the topology is relatively complex, using more power devices than half-bridge topologies, resulting in higher costs. Utility Model Content

[0003] To address the aforementioned issues, this invention proposes a half-bridge switching power supply circuit based on the SG3525. Employing a half-bridge topology, this switching power supply device features a wide range of DC input voltage and high-reliability output, making it particularly suitable for industrial equipment with large input voltage fluctuations and high requirements for output stability and safety.

[0004] A half-bridge switching power supply circuit based on SG3525 adopts the following technical solution:

[0005] A half-bridge switching power supply circuit based on SG3525 includes a half-bridge power conversion circuit, a drive transformer, a main control chip SG3525, a high-frequency power transformer, a rectifier and filter circuit, an amplifier, and a soft-start circuit.

[0006] The DC output terminal is connected to the half-bridge power conversion circuit. The main control chip SG3525 generates two complementary PWM pulses, and the two PWM pulses are connected to the half-bridge power conversion circuit through the drive transformer.

[0007] The midpoint of the half-bridge power conversion circuit generates a square wave voltage that is connected to the primary side of the high-frequency power transformer; the secondary voltage of the high-frequency power transformer is connected to the main control chip SG3525 via the rectifier filter circuit and the amplifier.

[0008] As a further embodiment of this invention, the main control chip SG3525 is connected to a soft-start capacitor.

[0009] As a further embodiment of this invention, an auxiliary power supply is connected in series between the high-frequency power transformer and the main control chip SG3525.

[0010] As a further embodiment of this invention, a DC blocking capacitor is connected in series on the primary side of the high-frequency power transformer.

[0011] As a further embodiment of this invention: the half-bridge power conversion circuit includes two MOSFETs connected in series, and the two MOSFETs connected in series are connected to the DC output terminal.

[0012] As a further embodiment of this invention: the MOSFET is an N-channel MOSFET with Rds(on) and a withstand voltage of 900V or higher.

[0013] As a further embodiment of this utility model, the rectifier and filter circuit outputs 24V DC power.

[0014] As a further embodiment of this invention, the amplifier is a TL431.

[0015] As a further aspect of this utility model: the drive transformer adopts a ferrite core, and the primary-to-secondary turns ratio is designed to be 1:1.

[0016] As a further embodiment of this invention, the magnetic core of the high-frequency power transformer is selected as PQ32 / 20.

[0017] The beneficial effects of this utility model are:

[0018] A half-bridge switching power supply circuit based on SG3525 is disclosed. The DC input voltage is sent to the half-bridge power conversion circuit. The main control chip SG3525 generates two complementary PWM pulses. These two pulses drive the half-bridge power conversion circuit through a drive transformer, achieving electrical isolation and ensuring the dead time of the two drive signals. The square wave voltage generated at the midpoint of the half-bridge is applied to the primary side of the high-frequency power transformer. The energy is coupled to the secondary side through the transformer. The secondary side voltage is rectified and filtered by the output rectifier circuit to obtain a stable 24V DC output. The output voltage is sampled by a resistor divider network and sent to an amplifier. The amplifier transmits the error signal to the main control chip SG3525 through a feedback isolation optocoupler, forming a closed-loop control to achieve precise and stable output voltage.

[0019] A half-bridge switching power supply circuit based on the SG3525 chip fully utilizes the chip's soft-start, shutdown, and error amplification functions. Combined with peripheral circuit design, a single core controller enables multi-dimensional management and protection of power supplies with wide input voltage and high isolation requirements. This allows for stable operation within a wide input range of 400V-800V, representing a high-efficiency and high-reliability power supply topology that resolves the conflict between wide input voltage and high efficiency and reliability. Furthermore, the rich peripheral functions of the SG3525 chip, combined with the peripheral circuit design, achieve complex high-reliability control at a relatively low cost, resulting in a high cost-performance ratio. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a half-bridge switching power supply circuit based on SG3525;

[0021] Figure 2 This is a simplified schematic diagram of the SG3525 chip. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. It should be understood that this application is not limited to the exemplary embodiments disclosed herein. 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.

[0023] In the embodiments of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0024] The SG3525 chip is a high-performance, feature-rich, and versatile monolithic integrated PWM control chip. It is simple, reliable, and easy to use, with a push-pull output drive that increases its driving capability. It features overcurrent protection, adjustable frequency, and the ability to limit the maximum duty cycle. Figure 2 The schematic diagram of the SG3525 chip is shown below:

[0025] 1. Inv.input (Pin 1): Inverting input of the error amplifier. In a closed-loop system, this pin is connected to the feedback signal. In an open-loop system, this pin is connected to the compensation signal input (Pin 9) to form a follower.

[0026] 2. Noninv.input (pin 2): Non-inverting input of the error amplifier. This pin is connected to the given signal in both closed-loop and open-loop systems. Depending on the requirements, different types of feedback networks can be connected between this pin and the compensation signal input (pin 9) to form proportional, proportional-integral, and integral regulators.

[0027] 3. Sync (pin 3): External synchronization signal input terminal for the oscillator. Connecting an external synchronization pulse signal to this terminal enables synchronization with external circuits.

[0028] 4. OSC.Output (pin 4): Oscillator output.

[0029] 5. CT (pin 5): Oscillator timing capacitor input terminal.

[0030] 6.RT (pin 6): Oscillator timing resistor input terminal.

[0031] 7. Discharge (pin 7): Oscillator discharge terminal. An external discharge resistor is connected between this terminal and pin 5 to form a discharge circuit.

[0032] 8. Soft-Start (Pin 8): Soft-start capacitor connection terminal. This terminal is typically connected to a 5-volt soft-start capacitor.

[0033] 9. Compensation (Pin 9): PWM comparator compensation signal input. Connecting different types of feedback networks between this pin and pin 2 can construct proportional, proportional-integral, and integral regulators.

[0034] 10. Shutdown (Pin 10): External shutdown signal input. A high level at this pin disables the controller output. This pin can be connected to a protection circuit for fault protection.

[0035] 11. OutputA (Pin 11): Output terminal A. Pins 11 and 14 are two complementary output terminals.

[0036] 12. Ground (pin 12): Signal ground.

[0037] 13.Vc (pin 13): Output stage bias voltage input terminal.

[0038] 14. OutputB (Pin 14): Output terminal B. Pin 14 and pin 11 are two complementary output terminals.

[0039] 15. Vcc (pin 15): Bias power supply input terminal.

[0040] 16. Vref (pin 16): Reference power supply output. This pin outputs a reference voltage with excellent temperature stability.

[0041] In this embodiment, the main control chip SG3525 has an oscillation frequency set to 100kHz. Full-wave rectification is used, and a 100V / 20A dual Schottky diode is selected.

[0042] like Figure 1 As shown, a half-bridge switching power supply circuit based on SG3525 includes a half-bridge power conversion circuit, a drive transformer, a main control chip SG3525, a high-frequency power transformer, a rectifier and filter circuit, an amplifier, and a soft-start circuit. The DC output terminal is connected to the half-bridge power conversion circuit. The main control chip SG3525 generates two complementary PWM pulses, which are connected to the half-bridge power conversion circuit through the drive transformer. A square wave voltage is generated at the midpoint of the half-bridge power conversion circuit and connected to the primary side of the high-frequency power transformer. The secondary voltage of the high-frequency power transformer is connected to the main control chip SG3525 through the rectifier and filter circuit and the amplifier.

[0043] Specifically, a half-bridge switching power supply circuit based on the SG3525 is a half-bridge switching power supply with an input of 400-800VDC and an output of 24V / 4A. It is particularly suitable for industrial equipment with large input voltage fluctuations and high requirements for output stability and safety. Its complete connection relationship and working principle are as follows:

[0044] The DC input voltage (400-800V) is sent to the half-bridge power conversion circuit; the main control chip SG3525 generates two complementary PWM pulses, which drive the half-bridge power conversion circuit through a drive transformer. It has good symmetry, achieves electrical isolation, and ensures the dead time of the two drive signals.

[0045] The square wave voltage generated at the midpoint of the half-bridge is applied to the primary side of the high-frequency power transformer. The energy is coupled to the secondary side through the transformer. After the secondary side voltage is rectified and filtered by the output rectifier circuit, a stable 24V DC output is obtained. The output voltage is sampled by the resistor divider network and sent to the amplifier. The amplifier transmits the error signal to the main control chip SG3525 through the feedback isolation optocoupler, forming a closed-loop control to achieve precise and stable output voltage.

[0046] A half-bridge switching power supply circuit based on the SG3525 chip fully utilizes the chip's soft-start, shutdown, and error amplification functions. Combined with peripheral circuit design, a single core controller enables multi-dimensional management and protection of power supplies with wide input voltage and high isolation requirements. This allows for stable operation within a wide input range of 400V-800V, representing a high-efficiency and high-reliability power supply topology that resolves the conflict between wide input voltage and high efficiency and reliability. Furthermore, the rich peripheral functions of the SG3525 chip, combined with the peripheral circuit design, achieve complex high-reliability control at a relatively low cost, resulting in a high cost-performance ratio.

[0047] In this embodiment, the main control chip SG3525 is connected to a soft-start capacitor. Specifically, a 4.7μF electrolytic capacitor Css is connected to Pin 8 of the main control chip SG3525. Upon power-up, the chip's internal constant current source charges this capacitor, causing the COMP pin voltage to rise slowly. This allows the duty cycle of the PWM pulse to gradually increase from zero to its steady-state value, effectively suppressing the power-on inrush current. At startup, the circuit effectively limits the current surge, preventing damage to the main control chip SG352 and other components due to excessive current. This makes the circuit startup process smoother and safer, greatly improving the circuit's reliability and stability.

[0048] In overall circuit design, the voltage stress on the switching transistors in a half-bridge topology is relatively low, approximately at the input voltage level. This characteristic makes it particularly suitable for high-voltage applications. Combined with a soft-start, comprehensive collaborative protection mechanism, the topology greatly enhances the circuit's survivability under harsh input conditions.

[0049] In this embodiment, an auxiliary power supply is connected in series between the high-frequency power transformer and the main control chip SG3525. Specifically, the addition of the auxiliary power supply provides a stable operating voltage for the main control chip SG3525, ensuring that the main control chip SG3525 can output control signals normally and stably under various operating conditions, thereby ensuring the stable operation of the entire circuit.

[0050] In this embodiment, a DC blocking capacitor is connected in series on the primary side of the high-frequency power transformer. Specifically, a 2.2μF / 630V CBB DC blocking capacitor is connected in series. By employing a drive transformer in conjunction with a half-bridge topology and a DC blocking capacitor connected in series on the primary side, the DC blocking capacitor effectively isolates the DC component, preventing DC current from entering the high-frequency power transformer and avoiding DC magnetization of the transformer core. The DC blocking capacitor connected in series in the half-bridge main circuit can automatically compensate for minor asymmetries, ensuring drive safety while fundamentally solving the problem of bias saturation in the power transformer.

[0051] In this embodiment, the half-bridge power converter circuit includes two MOSFETs connected in series and connected to the DC output terminal. The MOSFETs are N-channel MOSFETs with an Rds(on) of 900V or higher. Specifically, two PWM pulses drive the two MOSFETs through a single drive transformer, exhibiting good symmetry. The MOSFETs can be selected as IXFH10N90; this selection allows the MOSFETs to maintain low on-resistance while withstanding high voltage, reducing power loss, improving circuit conversion efficiency, and enabling stable operation even at high output power.

[0052] In this embodiment, the rectifier and filter circuit outputs 24V DC power. Specifically, in this circuit, the 24V DC power provides a stable and clean DC power supply for the subsequent load, meeting the load's requirements for voltage stability and power quality, and ensuring that the load can operate normally and stably.

[0053] In this embodiment, the amplifier is a TL431. Specifically, the reference terminal of the TL431 is set by a voltage divider using two precision resistors (e.g., 1kΩ and 10kΩ), with a reference voltage of 2.5V. This allows the amplifier to output a stable reference voltage, providing an accurate reference signal for the circuit's feedback control and ensuring the stability and accuracy of the circuit's output voltage. The optocoupler is a PC817, with its collector connected to the COMP pin of the SG3525 and its emitter grounded. The use of the optocoupler achieves electrical isolation, separating the control circuit from the main circuit. This effectively prevents interference signals from the main circuit from entering the control circuit, improving the circuit's anti-interference capability and further ensuring stable circuit operation.

[0054] In the overall circuit design, the system maintains good dynamic response and stability over a wide input voltage range and has low output ripple through a compensation network consisting of the SG3525 internal error amplifier and the external TL431, combined with smooth soft start.

[0055] In this embodiment, the drive transformer uses a ferrite core, and the primary-to-secondary turns ratio is designed to be 1:1. Specifically, the 1:1 primary-to-secondary turns ratio ensures that the drive voltage amplitude is sufficient and consistent. Ferrite cores have advantages such as low high-frequency loss and high permeability, which can meet the performance requirements of the drive transformer under high-frequency operation.

[0056] In this embodiment, the magnetic core of the high-frequency power transformer is selected as PQ32 / 20. Specifically, the number of primary winding turns is calculated based on the minimum input voltage and the maximum duty cycle to ensure that the magnetic core is not saturated; the number of secondary winding turns is calculated based on the output voltage and rectification method. The high-frequency power transformer can operate efficiently and stably under different input and output conditions, improving the transformer's energy conversion efficiency, reducing energy loss, and also reducing transformer heat generation, extending the transformer's service life, and providing a strong guarantee for the stable operation of the entire circuit.

[0057] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or 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.

[0058] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. 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 this application. Therefore, this application 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 half-bridge switching power supply circuit based on SG3525, characterized in that, It includes a half-bridge power conversion circuit, a drive transformer, a main control chip SG3525, a high-frequency power transformer, a rectifier and filter circuit, an amplifier, and a soft-start circuit; The DC output terminal is connected to the half-bridge power conversion circuit. The main control chip SG3525 generates two complementary PWM pulses, and the two PWM pulses are connected to the half-bridge power conversion circuit through the drive transformer. The midpoint of the half-bridge power conversion circuit generates a square wave voltage that is connected to the primary side of the high-frequency power transformer; the secondary voltage of the high-frequency power transformer is connected to the main control chip SG3525 via the rectifier filter circuit and the amplifier.

2. The half-bridge switching power supply circuit based on SG3525 according to claim 1, characterized in that, The main control chip SG3525 is connected to a soft-start capacitor.

3. The half-bridge switching power supply circuit based on SG3525 according to claim 2, characterized in that, An auxiliary power supply is connected in series between the high-frequency power transformer and the main control chip SG3525.

4. The half-bridge switching power supply circuit based on SG3525 according to claim 3, characterized in that, The primary winding of the high-frequency power transformer is connected in series with a DC blocking capacitor.

5. The half-bridge switching power supply circuit based on SG3525 according to any one of claims 1-4, characterized in that, The half-bridge power conversion circuit includes two MOSFETs connected in series, which are connected to the DC output terminal.

6. The half-bridge switching power supply circuit based on SG3525 according to claim 5, characterized in that, The MOSFET is an N-channel MOSFET with Rds(on) and a withstand voltage of 900V or higher.

7. The half-bridge switching power supply circuit based on SG3525 according to claim 5, characterized in that, The rectifier and filter circuit outputs 24V DC power.

8. The half-bridge switching power supply circuit based on SG3525 according to claim 5, characterized in that, The amplifier is a TL431.

9. The half-bridge switching power supply circuit based on SG3525 according to claim 5, characterized in that, The drive transformer uses a ferrite core and the primary-to-secondary turns ratio is designed to be 1:

1.

10. The half-bridge switching power supply circuit based on SG3525 according to claim 4, characterized in that, The magnetic core of the high-frequency power transformer is PQ32 / 20.

Images