A potted DC-DC power module

Abstract

This invention discloses a potted DC-DC power module, including a PWM control circuit, a main power switching circuit, a transformer, a synchronous rectification and output filtering circuit, and a feedback sampling and isolation control circuit. The PWM control circuit drives the main power switching transistor to periodically turn on and off, transferring primary-side energy to the secondary side via the transformer. On the secondary side, a synchronous rectification control chip drives a MOSFET for rectification, which, combined with an LC filter network composed of inductors and capacitors, outputs a stable DC voltage. The feedback sampling and isolation control circuit transmits the output voltage deviation signal to the primary side through voltage divider sampling, precise reference comparison, and optocoupler isolation, achieving closed-loop voltage regulation. This invention features a compact structure, high conversion efficiency, low output ripple, fast dynamic response, and multiple protection functions such as overcurrent, short circuit, and undervoltage protection, making it suitable for industrial, scientific research, and military applications requiring high efficiency and reliability.

Description

Technical Field

[0001] This utility model belongs to the field of switching power supply technology, and in particular relates to a potted DC-DC power supply module. Background Technology

[0002] As an important branch of electronic power supplies, switching power supply modules can be divided into AC / DC and DC / DC module power supplies according to their input power form. Their basic structure integrates miniaturized switching power supply circuits into a compact module housing, retaining only input and output pins, allowing users to directly integrate them into various electronic devices. Due to their advantages such as small size, light weight, high efficiency, high power density, wide input range, low power consumption, and high reliability, modular power supplies have experienced rapid development in recent years. Power ranges are generally between 5W and 350W, and they are widely used in industrial automation control, LED lighting, scientific instruments, communication equipment, and military equipment. With the continuous improvement of the performance and functional requirements of electronic systems, the miniaturization, high frequency, and high efficiency of modular power supplies have become a research focus of continuous attention in the industry, and the requirements for their power capacity, conversion efficiency, and environmental adaptability are also constantly increasing.

[0003] In existing technologies, the most common DC / DC module power supply circuit structure adopts the RCC (self-excited) topology. This type of circuit achieves DC input to DC output conversion through the coordinated action of startup, positive feedback, overcurrent detection, and voltage regulation control. RCC circuits utilize frequency conversion control to maintain output stability, and their structure is simple and low-cost. However, this type of circuit is prone to intermittent oscillations at high power output, causing the oscillation period to fluctuate significantly between hundreds and thousands of hertz. This results in significant noise from the transformer and other magnetic components, and reduces circuit conversion efficiency. Furthermore, frequency instability increases output ripple noise, reducing the power supply's dynamic response and electromagnetic compatibility performance. Therefore, RCC circuits are generally only suitable for low-power applications and cannot meet the development requirements of high-performance, small-size, and high-reliability DC / DC module power supplies. Utility Model Content

[0004] To solve the above-mentioned technical problems, this utility model provides a potted DC-DC power module.

[0005] Specifically, the technical solution provided by this utility model is as follows:

[0006] A potted DC-DC power module includes an input terminal, an output terminal, a PWM control circuit, a switching transistor Q2, a transformer, a synchronous rectification and output filtering circuit, and a feedback sampling and isolation control circuit.

[0007] The input terminal is used to connect to an external DC power supply and is connected to the primary winding T1-A of the transformer. The secondary winding T1-B of the transformer is connected to the output terminal, and the output terminal is used to connect to the load. The synchronous rectification and output filtering circuit is set between the secondary winding T1-B of the transformer and the output terminal, and is used to rectify and smooth the AC voltage coupled from the secondary winding T1-B into a stable DC output.

[0008] The switching transistor Q2 is connected in series in the circuit containing the primary winding T1-A of the transformer, and is used to control the on / off state of the circuit containing the primary winding T1-A of the transformer; the PWM control circuit includes a PWM controller U1 connected to the switching transistor Q2, and the PWM controller U1 is used to output a PWM signal to drive the switching transistor Q2 according to the feedback signal of the feedback sampling and isolation control circuit; the feedback sampling and isolation control circuit is used to sample and compare the voltage at the output terminal, and transmit the deviation signal to the PWM controller U1 through an optocoupler.

[0009] Furthermore, the module also includes an auxiliary power supply circuit for powering the PWM controller U1. The auxiliary power supply circuit includes a second secondary winding T1-C of a transformer connected to the power supply input terminal of the PWM controller U1, a diode D4 for rectifying the AC voltage coupled from the second secondary winding T1-C, a current-limiting resistor R6, and a filter capacitor C24.

[0010] Furthermore, the undervoltage protection pin of the PWM controller U1 is connected to the input terminal through a voltage divider resistor, which is used to turn off the switching transistor Q2 when the input voltage is lower than the set threshold, thus providing input undervoltage protection function.

[0011] Furthermore, the current detection pin of the PWM controller U1 is connected to the circuit where the primary winding T1-A of the transformer is located, and is used to turn off the switching transistor Q2 when the detected current exceeds the set threshold, providing overcurrent protection function.

[0012] Furthermore, the synchronous rectification and output filtering circuit includes a synchronous rectifier tube Q3 and a rectifier controller U3. The rectifier control chip U3 is used to drive and control the turn-on and turn-off timing of the synchronous rectifier tube Q3. One end of the secondary winding T1-B of the transformer is connected to the drain of the synchronous rectifier tube Q3. The source of the rectifier tube Q3 is grounded. The gate of the rectifier tube Q3 is connected to the drive output pin VG of the rectifier controller U3 through a resistor R29. The drain of the rectifier tube Q3 is also connected to the VD pin of the rectifier controller U3 through a resistor R33. The source of the rectifier tube Q3 is connected to the VSS pin of the rectifier controller U3. The source of the rectifier tube Q3 is also connected to the SET pin of the rectifier controller U3 through a resistor R13 and to the VCC pin of the rectifier controller U3 through a capacitor C26. The HVIN pin of the rectifier controller U3 is connected to the positive terminal of the output through a resistor R28.

[0013] Furthermore, the other end of the secondary winding T1-B of the transformer is connected to the negative terminal of the output terminal through an inductor L3 and a capacitor C2 connected in series. The connection point between the inductor L3 and the capacitor C2 serves as the positive terminal of the output terminal. A capacitor C4 is connected in parallel on the series branch of the inductor L3 and the capacitor C2. The inductor L3, the capacitor C2, and the capacitor C4 constitute an LC filter network.

[0014] Furthermore, the feedback sampling and isolation control circuit includes a Zener diode U2 and an optocoupler LED OT1-B; the reference voltage terminal of the Zener diode U2 is connected to the output terminal through a voltage divider network composed of several resistors, the anode of U2 is grounded, the cathode of U2 is connected to the cathode of the LED OT1-B, and the anode of the LED OT1-B is connected to the output terminal through a current-limiting resistor; the collector of the phototransistor OT1-A of the optocoupler is connected to the optocoupler feedback pin of the PWM controller U1.

[0015] Furthermore, a branch consisting of resistor R17 and capacitor C16 is connected between the reference voltage terminal of the Zener diode U2 and its cathode to adjust the phase characteristics of the loop; capacitor C11 is connected in parallel with the current limiting resistor R4 to suppress high-frequency noise; resistor R5 is connected in parallel with the light-emitting diode OT1-B to provide bias current to the light-emitting diode and improve its linear operating range.

[0016] This invention replaces the traditional RCC self-excited control method with high-frequency PWM control, maintaining a stable main switching frequency and avoiding the intermittent oscillation problem that easily occurs in existing RCC circuits during high-power output. This significantly reduces the noise of the transformer and related magnetic components, and improves the stability of energy transmission and the conversion efficiency of the circuit. The drive network of the main power switching circuit is precisely designed, which not only ensures the fast and reliable turn-on and turn-off of the MOSFET, but also effectively suppresses spikes and ringing generated during the switching process, reducing electromagnetic interference to the system.

[0017] In the output rectification section, this invention introduces a MOSFET rectification scheme driven by a synchronous rectification control chip. Compared with traditional diode rectification, this significantly reduces conduction losses, enabling the module to maintain high efficiency even under low-voltage, high-current output conditions. The synchronous rectification devices, combined with an RC snubber network, not only improve the switching waveform but also further enhance the system's stability and reliability under high-frequency operating conditions. The accompanying LC output filter network effectively reduces output ripple, improves the purity of the DC output, and provides more stable power support for downstream loads.

[0018] In the voltage regulation and control stage, this invention adopts a closed-loop control method with precision reference sampling and optocoupler isolation feedback, ensuring high accuracy of the output voltage and fast dynamic response capability. The feedback loop has been optimized with compensation design, enabling the system to maintain output stability when dealing with load changes and input fluctuations. Furthermore, the optocoupler isolation structure ensures safe isolation between the high and low voltage sides, improving the module's anti-interference capability and long-term operational reliability.

[0019] Furthermore, the system boasts comprehensive protection features, integrating input undervoltage protection, cycle-by-cycle overcurrent protection, output short-circuit protection, and soft-start functionality. This allows for rapid response under abnormal operating conditions, effectively preventing overheating or damage to power devices, and ensuring smooth operation after fault resolution. The combination of these protection mechanisms and control strategies not only extends the module's lifespan but also provides enhanced operational safety for the application system. Attached Figure Description

[0020] The accompanying drawings are provided to further understand the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation thereof.

[0021] Figure 1 This is a circuit diagram provided in an embodiment of the present utility model;

[0022] Figure 2 This is a schematic diagram of the circuit principle provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0024] This embodiment provides a potted DC-DC power module that uses a PWM control chip to control the module output. This stabilizes the module's switching frequency within a set range, increasing output stability and reducing output ripple noise caused by frequency conversion. The PWM control chip can adjust the on-time of the switching transistors based on output feedback, thereby controlling the input power of the transformer or inductor, resulting in higher module output power and efficiency.

[0025] like Figure 1 As shown, this DC-DC power module mainly consists of an input filter circuit, a main control circuit, a switch drive and transformer isolation circuit, a synchronous rectification and output filter circuit, a feedback sampling and isolation circuit, and a protection circuit. For ease of understanding, the following description is in conjunction with the appendix. Figure 1 Each item will be described in detail.

[0026] (1) Input filter circuit

[0027] The positive terminal of the input is connected to VIN+, and the negative terminal is connected to AGND. A capacitor C9 is connected in parallel at the input to filter the DC input power supply and suppress high-frequency ripple and transient interference at the input.

[0028] (2) Main control circuit

[0029] The main control chip U1 is a PWM controller (VPC218XB), and its pin configuration is as follows:

[0030] VIN (pin 2) is connected to the input power supply, and VDD (pin 4) is the control power input terminal, which is powered by the auxiliary power supply circuit. The auxiliary power supply circuit is an auxiliary starting branch composed of transformer T1-C winding, diode D4, resistor R6 and capacitor R24, which provides the necessary energy for the starting process.

[0031] The GATE pin (pin 5) outputs a PWM drive signal to drive the main power switch Q2. The CS pin (pin 7) is the current sensing terminal, connected to the main power circuit via resistor R10 for overcurrent protection. The COM pin (pin 1) is the feedback terminal, receiving the isolated feedback signal of the output voltage through the phototransistor OT1-A of the optocoupler OT1. Specifically, the collector of OT1-A is connected to COM, the emitter is grounded, and a filter capacitor C25 is connected between the collector and emitter. The filter capacitor C25 effectively suppresses high-frequency noise and spike interference in the feedback signal, further improving the stability of the control circuit and the accuracy of the output voltage regulation. The RT pin (pin 8) and SS pin (pin 9) are set with external resistors and capacitors (such as R24 and C22) to set the oscillation frequency and soft-start time, respectively.

[0032] (3) Switch drive and transformer isolation circuit

[0033] The main power switch Q2 is controlled by U1, and its gate is connected to the GATE pin of U1. Its drain is connected to the positive input terminal through the primary winding of transformer T1-A, and its source is grounded through resistor R8, forming the main energy loop. A resistor R15 is connected across the gate and source of Q2. Transformer T1 has multiple windings: T1-A is the main power winding, which is connected in series with Q2 to form the main switching loop; T1-B is the secondary winding, which, together with synchronous rectifier Q3 and inductor L3, forms the output rectification and filtering circuit; T1-C is the auxiliary winding, which supplies power to U1.

[0034] (4) Synchronous rectification and output filtering circuit

[0035] The secondary winding T1-B of transformer T1 is responsible for transferring energy from the primary side to the load side. To reduce rectification losses and improve rectification efficiency, this part adopts a synchronous rectification scheme, supplemented by an LC filter network to achieve smooth and stable output.

[0036] like Figure 1 As shown, one end of T1-B is connected to the negative terminal (ground) of the output through an inductor L3 and a capacitor C2 connected in series. The connection between inductor L3 and capacitor C2 serves as the positive terminal of the output. A capacitor C4 is connected in parallel on the series branch of inductor L3 and capacitor C2. Inductor L3, capacitor C2, and capacitor C4 form an LC filter network to achieve smooth and stable output. The other end of T1-B is connected to the drain of synchronous rectifier Q3. The source of Q3 is grounded. The gate of Q3 is connected to the VG pin of synchronous rectifier control chip U3 through resistor R29. The drain of Q3 is also connected to the VD pin of U3 through resistor R33. The source of Q3 is connected to the VSS pin of U3. The source of Q3 is also connected to the SET pin of U3 through resistor R13 and to the VCC pin of U3 through capacitor C26. The HVIN pin of U3 is connected to the positive terminal of the output through resistor R28.

[0037] A resistor R2 and a capacitor C1 are connected in series between the drain and source of Q3, forming an RC snubber network (RC snubber circuit). When Q3 is turned off during synchronous rectification, the leakage inductance of the transformer secondary winding T1-B and the energy in the output inductor L3 cause a high voltage spike and ringing at the drain. C1 provides a bypass path for the drain at the moment Q3 is turned off, temporarily storing the spike current in the capacitor, thereby suppressing the drain voltage surge. R2 releases the energy stored in C1 as heat, preventing energy from oscillating repeatedly in the circuit and avoiding high-frequency resonance. This effectively prevents the drain of Q3 from experiencing excessively high transient voltage, improving the reliability and lifespan of the device.

[0038] The synchronous rectification control chip U3 drives and controls the on and off timing of the synchronous rectifier diode Q3, achieving efficient rectification of the energy output from the secondary winding T1-B of the transformer. When the main power switch Q2 is turned off on the primary side, the magnetic field of transformer T1 is released, and a positive voltage is generated in the T1-B winding. The VD pin of U3 samples the drain potential of Q3 through resistor R33, and the VSS pin is connected to the source of Q3 (ground reference). By comparing the potential difference between VD and VSS, the current winding is determined to be in the forward conduction phase. When a positive polarity is detected, the VG pin of U3 outputs a high level, which is applied to the gate of Q3 through resistor R29, causing Q3 to quickly turn on. At this time, the current in the T1-B winding flows through the drain → source → ground loop of Q3. When the primary side switch Q2 turns on again, the polarity of the T1-B winding reverses. The VD pin detects the change in drain potential, and the internal comparator of U3 determines that it is a reverse polarity, immediately pulling the VG output low to turn off Q3 and block possible reverse current backflow.

[0039] U3 sets the dead time and detection threshold based on the resistance value of the SET pin (externally connected to R13), ensuring an appropriate interval between the on / off state of Q3 and the switching of the primary-side switch Q2 to prevent cross-conduction. The HVIN pin is connected to the positive terminal of the output through R28, serving as the high-side power supply for U3 and ensuring a stable drive voltage under different load conditions. C26 is used to improve signal stability and suppress high-frequency noise interference to the detection logic.

[0040] In this embodiment, U3 uses the MK9180X synchronous rectifier controller.

[0041] (5) Feedback sampling and isolation circuit

[0042] To ensure output voltage stability and promptly adjust the duty cycle of the main power switch when input conditions or load change, this embodiment designs a closed-loop regulation circuit based on secondary-side sampling, optocoupler isolation, and primary-side feedback control. This circuit detects changes in the output voltage in real time on the secondary side and transmits the adjustment signal to the primary-side control chip via optocoupler, thereby dynamically changing the switching control strategy and achieving high-precision regulated output.

[0043] At the output terminal, resistors R1, R9, R22, and R23 form a multi-stage voltage divider network, which reduces the voltage at the positive terminal of the output terminal to a suitable level according to a predetermined ratio. The voltage signal after voltage division is sent to the reference voltage terminal of the Zener diode U2 (an adjustable voltage regulator with a reference voltage terminal). The positive terminal of the output terminal is connected in series with resistor R4, the light-emitting diode OT1-B of optocoupler OT1, and the cathode of U2, while the anode of U2 is grounded.

[0044] To improve the system's frequency response and stability, a branch consisting of resistor R17 and capacitor C16 is connected between the reference voltage terminal and the cathode of U2 to adjust the loop's phase characteristics. Resistor R4 is connected in parallel with capacitor C11 to provide a low-impedance path at high frequencies, suppressing the impact of high-frequency noise on the control loop. OT1-B is connected in parallel with resistor R5 to provide bias current to the LED and improve its linear operating range.

[0045] The LED OT1-B of the optocoupler OT1 is located on the secondary side, and its luminous intensity reflects the deviation of the output voltage. The phototransistor OT1-A of OT1 is located on the primary side, and its collector is connected to the COM pin of the PWM control chip U1. During operation, when the output voltage is higher than the set value, the sampled voltage after voltage division increases, exceeding the reference voltage of U2. The voltage between the cathode and ground of U2 decreases accordingly, thereby increasing the current flowing through OT1-B and enhancing its luminous intensity. The optical signal from OT1-B is isolated by the optocoupler and applied to the phototransistor OT1-A on the primary side, enhancing its conduction capability and lowering its collector voltage. The collector of OT1-A is connected to the COM pin of the PWM control chip U1. The voltage drop causes U1 to reduce the duty cycle of the main switch, causing the output voltage to fall back to the set value. Conversely, when the output voltage is lower than the set value, the sampled voltage after voltage division is lower than the reference, the cathode current of U2 decreases, the luminous intensity of OT1-B weakens, the conduction of OT1-A weakens, and the collector voltage rises, causing U1 to increase its duty cycle, causing the output voltage to rise back to the target value.

[0046] Throughout the closed-loop control, the optocoupler OT1 achieves electrical isolation between the secondary-side output voltage sampling signal and the primary-side PWM control circuit, ensuring safe isolation between the high and low voltage sides and reliable signal transmission.

[0047] (6) Protection circuit

[0048] This embodiment also incorporates multi-level protection functions on both the primary and secondary sides to prevent circuit damage caused by abnormal input, sudden load changes, or device failures, and to improve the reliability of system operation. The protection circuit mainly includes functions such as input undervoltage protection, overcurrent protection, output short-circuit protection, and soft-start surge suppression. Its implementation relies on the internal protection logic of the control chip U1 and the external detection, limiting, and delay networks.

[0049] Input undervoltage protection circuit: This circuit also includes undervoltage protection. The UVP (pin 3) of U1 samples the input voltage through voltage divider resistors R31 and R32. When the input voltage drops below a set threshold, the detected voltage after voltage division is lower than the internal reference of U1. U1 immediately stops outputting drive pulses to the GATE terminal, turns off the main power MOSFET Q2, and cuts off energy transfer, thereby preventing device overheating and magnetic component saturation caused by excessive duty cycle under low voltage conditions. When the input voltage recovers above the threshold, U1 restarts and gradually restores output through a soft-start process.

[0050] Overcurrent protection circuit: Overcurrent protection relies on the current sensing terminal (CS pin) of U1 and the sampling resistor network of the main circuit. The source of Q2 is connected to ground through the sampling resistor, and the CS pin senses the instantaneous current of the main circuit through this resistor. When a sudden load change or output short circuit causes the current to exceed the set threshold, the voltage detected by the CS pin exceeds the threshold of the internal comparator, and U1 immediately shuts off the drive signal for the current cycle to prevent the current from continuing to rise. In the event of overcurrent in multiple consecutive cycles, U1 enters hiccup mode, reducing the average output power through intermittent switching, and automatically resumes normal operation after the fault is cleared.

[0051] Output short-circuit protection circuit: Output short-circuit protection works in conjunction with overcurrent protection. When a short circuit occurs at the output terminal, the load impedance approaches zero, and the current rises sharply, triggering the overcurrent detection at the CS terminal. Simultaneously, the feedback loop detects a sharp drop in output voltage. At this time, the feedback voltage is lower than the set value, and U1 may attempt to increase the duty cycle. However, due to the continuous triggering of the overcurrent limit at the CS terminal, the controller enters a low duty cycle or hiccup protection mode, significantly reducing device stress and preventing overheating of the transformer, synchronous rectifier Q3, and its driver U3.

[0052] The soft-start function is set by the SS pin of U1 and the external capacitor C22. After the module is powered on or the protection is released, the voltage at the SS pin rises slowly from zero. The controller gradually increases the PWM duty cycle, causing the conduction time of Q2 to increase smoothly. This avoids sudden current surges on the primary side and overshoots in the secondary side output voltage, reducing charging surge impacts on the output filter capacitors (C4, C2, etc.). This process also effectively reduces EMI spikes and extends the lifespan of power devices.

[0053] The above describes the main circuit structure of the DC / DC power module provided in this embodiment. (See reference...) Figure 2During operation, the external DC power supply is first filtered by the low-pass filter circuit at the input terminal to suppress high-frequency noise and transient interference. The filtered power is directly fed into the main power conversion circuit, and also provides operating power to the PWM control chip U1 through the auxiliary power supply circuit consisting of the transformer auxiliary winding T1-C, rectifier diode D4, resistor R6, and filter capacitor C24. At the same time, the power is fed to the UVP terminal of U1 through voltage divider resistors R31 and R32 to realize input undervoltage detection. When the detected voltage is lower than the threshold, the control chip immediately stops working to prevent abnormal operation.

[0054] In the main power conversion path, the filtered DC voltage is applied to the primary-side switching circuit formed by the main power MOSFET Q2 and the transformer T1-A winding. The GATE pin of the PWM control chip U1 outputs a drive pulse to the gate of Q2, controlling its periodic on and off. During conduction, the input voltage stores energy in the transformer core through the primary side of T1-A; during off, the stored energy is released and coupled to the output side through the secondary winding T1-B. To suppress primary-side voltage spikes and dv / dt, Q2 is also equipped with an absorption buffer network consisting of D3, C10, and related devices.

[0055] On the secondary side, the AC voltage induced by T1-B enters the synchronous rectification and filtering network. The synchronous rectification section consists of MOSFET Q3 and synchronous rectification control chip U3. U3 determines the voltage polarity of T1-B in real time through detection terminals such as VD and VSS, and drives the gate of Q3 through VG pin and R29. When the forward conduction condition of the secondary winding is detected, U3 quickly turns on Q3, allowing the current to flow to the load through a low-resistance path; when the polarity is reversed, U3 turns off Q3 in time to prevent reverse current backflow. The rectified current enters the LC filter network composed of inductor L3, capacitor C2, and parallel capacitor C4 to smooth the output voltage, reduce ripple, and ensure that the load receives a stable DC voltage output.

[0056] The output voltage is sampled by a voltage divider network consisting of resistors R1, R9, R22, and R23 and then fed to the REF pin of the Zener diode U2. This voltage is compared with the internal reference voltage, generating a deviation current. U2 adjusts the current flowing through OT1-B based on the comparison result, thereby changing its luminous intensity. The phototransistor OT1-A of the optocoupler OT1 is located on the primary side. As the luminous intensity of OT1-B changes, the conduction level of OT1-A changes, and the potential at the COM pin changes accordingly. This affects the PWM modulation of U1, which in turn adjusts the duty cycle of Q2, bringing the output voltage back to the set value and achieving closed-loop voltage regulation.

[0057] Throughout operation, U1 not only adjusts its duty cycle based on feedback signals but also monitors the UVP and CS terminals in real time to achieve input undervoltage protection and cycle-by-cycle overcurrent protection. When the input voltage drops, the load is short-circuited, or the current is excessive, U1 immediately stops driving or enters hiccup mode to reduce the average power output. After the fault is cleared, U1 smoothly restores the output through a soft-start process set by the SS pin and capacitor C22, avoiding surge impact. Through the above workflow, the various functional modules work together to achieve a high-efficiency, low-ripple, and fully protected isolated DC / DC power converter.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it; under the concept of this utility model, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of different aspects of this utility model as described above. For the sake of brevity, they are not provided in detail; although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A potted DC-DC power module, characterized in that, It includes the input terminal, output terminal, PWM control circuit, switching transistor Q2, transformer, synchronous rectification and output filtering circuit, and feedback sampling and isolation control circuit; The input terminal is used to connect to an external DC power supply and is connected to the primary winding T1-A of the transformer. The secondary winding T1-B of the transformer is connected to the output terminal, and the output terminal is used to connect to the load. The synchronous rectification and output filtering circuit is set between the secondary winding T1-B of the transformer and the output terminal, and is used to rectify and smooth the AC voltage coupled from the secondary winding T1-B into a stable DC output. The switching transistor Q2 is connected in series in the circuit containing the primary winding T1-A of the transformer, and is used to control the on / off state of the circuit containing the primary winding T1-A of the transformer; the PWM control circuit includes a PWM controller U1 connected to the switching transistor Q2, and the PWM controller U1 is used to output a PWM signal to drive the switching transistor Q2 according to the feedback signal of the feedback sampling and isolation control circuit; the feedback sampling and isolation control circuit is used to sample and compare the voltage at the output terminal, and transmit the deviation signal to the PWM controller U1 through an optocoupler.

2. The DC-DC power module as described in claim 1, characterized in that, It also includes an auxiliary power supply circuit for powering the PWM controller U1. The auxiliary power supply circuit includes a second secondary winding T1-C of a transformer connected to the power supply input terminal of the PWM controller U1, a diode D4 for rectifying the AC voltage coupled from the second secondary winding T1-C, a current-limiting resistor R6, and a filter capacitor C24.

3. The DC-DC power module as described in claim 1, characterized in that, The undervoltage protection pin of the PWM controller U1 is connected to the input terminal through a voltage divider resistor. It is used to turn off the switching transistor Q2 when the input voltage is lower than the set threshold, thus providing input undervoltage protection.

4. The DC-DC power module as described in claim 1, characterized in that, The current detection pin of the PWM controller U1 is connected to the circuit where the primary winding T1-A of the transformer is located, and is used to turn off the switching transistor Q2 when the detected current exceeds the set threshold, providing overcurrent protection.

5. The DC-DC power module as described in claim 1, characterized in that, The synchronous rectification and output filtering circuit includes a synchronous rectifier tube Q3 and a rectifier controller U3. The rectifier control chip U3 is used to drive and control the timing of the synchronous rectifier tube Q3 to turn on and off. One end of the secondary winding T1-B of the transformer is connected to the drain of the synchronous rectifier Q3. The source of the rectifier Q3 is grounded. The gate of the rectifier Q3 is connected to the drive output pin VG of the rectifier controller U3 through resistor R29. The drain of the rectifier Q3 is also connected to the VD pin of the rectifier controller U3 through resistor R33. The source of the rectifier Q3 is connected to the VSS pin of the rectifier controller U3. The source of the rectifier Q3 is also connected to the SET pin of the rectifier controller U3 through resistor R13 and to the VCC pin of the rectifier controller U3 through capacitor C26. The HVIN pin of the rectifier controller U3 is connected to the positive terminal of the output through resistor R28.

6. The DC-DC power module as described in claim 5, characterized in that, The other end of the secondary winding T1-B of the transformer is connected to the negative terminal of the output terminal through an inductor L3 and a capacitor C2 connected in series. The connection point between the inductor L3 and the capacitor C2 serves as the positive terminal of the output terminal. A capacitor C4 is connected in parallel on the series branch of the inductor L3 and the capacitor C2. The inductor L3, the capacitor C2 and the capacitor C4 constitute an LC filter network.

7. The DC-DC power module as described in claim 1, characterized in that, The feedback sampling and isolation control circuit includes a Zener diode U2 and an optocoupler LED OT1-B. The reference voltage terminal of the Zener diode U2 is connected to the output terminal through a voltage divider network composed of several resistors. The anode of U2 is grounded, and the cathode of U2 is connected to the cathode of the LED OT1-B. The anode of the LED OT1-B is connected to the output terminal through a current-limiting resistor. The collector of the phototransistor OT1-A of the optocoupler is connected to the optocoupler feedback pin of the PWM controller U1.

8. The DC-DC power module as described in claim 7, characterized in that, The Zener diode U2 has a branch consisting of resistor R17 and capacitor C16 connected between its reference voltage terminal and its cathode to adjust the phase characteristics of the loop; the current-limiting resistor R4 is connected in parallel with capacitor C11 to suppress high-frequency noise; the light-emitting diode OT1-B is connected in parallel with resistor R5 to provide bias current to the light-emitting diode and improve its linear operating range.

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