150w dual-output flyback switching power supply

Abstract

The utility model discloses a 150W double -way output flyback switching power supply, including flyback converter, the flyback converter adopts CCM mode work, LD5760W power management control chip, LD5760W power management control chip is connected to the flyback converter for controlling its work, transformer, the transformer is connected in the flyback converter, plays the dual role of inductance and transformer, and the function of energy storage inductance is also played. The utility model discloses a flyback converter's CCM mode is adopted, and the flyback transformer of special design is combined LD5760W power management chip, realizes a kind of power 150W double -way output, wide grid input switching power supply, not only has simple structure, input and output electrical isolation, the advantages such as wide range of buck-boost, but also significantly improved output power, adapted to global grid range, ensured the stability and reliability under various loads and grid voltage variation.

Description

Technical Field

[0001] This utility model belongs to the field of switching power supply technology, and in particular relates to a 150W dual-output flyback switching power supply. Background Technology

[0002] With the widespread use of electronic products, switching power supplies, as key components of electronic devices, are increasingly widely used. Flyback converters, due to their simple, reliable, low-cost, and easy-to-implement topology, have become one of the most commonly used topologies. However, traditional flyback converters are generally limited to output power below 100W and have a single input grid voltage, which restricts their application in modern electronic devices.

[0003] Modern electronic devices place increasingly higher demands on power supplies, requiring not only greater output power but also adaptability to global grid voltage variations. Traditional flyback converters, limited by their output power and input voltage range, can no longer meet these requirements. Therefore, designing a switching power supply capable of outputting 150W of power, featuring dual outputs, and adaptable to a wide grid input range has become particularly important. Utility Model Content

[0004] This utility model addresses the problems in the prior art by proposing the following technical solution:

[0005] A 150W dual-output flyback switching power supply includes:

[0006] A flyback converter, wherein the flyback converter operates in CCM mode;

[0007] The LD5760W power management control chip is connected to the flyback converter and is used to control its operation.

[0008] The transformer, connected in the flyback converter, serves as both an inductor and a transformer, and also functions as an energy storage inductor.

[0009] The dual-output circuit outputs a voltage and current of 15V / 5A and -15V / 5A respectively from the flyback converter.

[0010] Wide-range input circuitry, adaptable to mains voltage inputs from 85VAC to 264VAC.

[0011] As a preferred embodiment of the above technical solution, the LD5760W power management control chip has a dynamic self-powering function, which can supply power to the controller during startup, transient, latching, and standby periods.

[0012] As a preferred embodiment of the above technical solution, an air gap is provided in the magnetic core of the transformer to prevent the magnetic core from saturating when the load current is large.

[0013] As a preferred embodiment of the above technical solution, the flyback converter further includes an input electrolytic capacitor. The value of the input electrolytic capacitor is related to the input power and is used to stabilize the input voltage. Its value range is 2~3μF / W.

[0014] As a preferred embodiment of the above technical solution, the flyback converter further includes a current sensing resistor connected between the source and ground of the MOSFET to detect the inductor current and ensure that the converter operates in continuous conduction mode within the rated power range.

[0015] As a preferred embodiment of the above technical solution, the switching power supply further includes a feedback circuit, which is connected to the LD5760W power management control chip to detect changes in the output voltage and adjust the operating state of the flyback converter to maintain the stability of the output voltage.

[0016] As a preferred embodiment of the above technical solution, the input grid voltage range of the switching power supply is 85VAC to 264VAC, and the grid frequency is 50Hz or 60Hz.

[0017] As a preferred embodiment of the above technical solution, the flyback converter operates at a frequency of 65kHz or 100kHz, and can automatically fold back to a minimum level of 26kHz when the power decreases.

[0018] As a preferred embodiment of the above technical solution, the switching power supply also includes overvoltage protection, overcurrent protection and short circuit protection functions, with a protection response time ≤100ms.

[0019] The beneficial effects of this utility model are as follows:

[0020] This practical switching power supply achieves 150W high-power output and dual-channel (+15V / 5A and -15V / 5A) independent power supply through optimized flyback converter design and the use of the LD5760W power management chip. Its wide voltage input range of 85VAC-264VAC is compatible with global power grid standards, and the CCM operating mode significantly reduces switching losses, improving the overall efficiency to over 88%. It adopts a precision-designed PQ3230 magnetic core transformer and synchronous rectification technology to ensure an output voltage regulation rate of ≤±1% over a wide load range, and integrates multiple protection functions for overvoltage, overcurrent, and short circuit (response time ≤100ms), greatly improving the stability and reliability of the power supply. Attached Figure Description

[0021] Figure 1 The diagram shown illustrates the working principle of the flyback converter.

[0022] Figure 2 The diagram shows a comparison of the FET and rectifier currents in the flyback converter under CCM and DCM modes.

[0023] Figure 3 The diagram shown is a pinout of the LD5760W power management control chip.

[0024] Figure 4 The diagram shown is a power supply block diagram of a CCM mode flyback converter.

[0025] Figure 5 The diagram shown is a CCM mode flyback switching power supply based on the LD5760W chip.

[0026] Figure 6 The diagram shown is a CCM mode switch control circuit diagram;

[0027] Figure 7 The diagram shows the current waveform and current ripple coefficient of the MOSFET in the embodiment. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0029] Example

[0030] A 150W dual-output flyback switching power supply includes: a flyback converter, wherein the flyback converter operates in CCM mode;

[0031] Firstly, flyback converters are widely used in switching circuits of internal power supplies due to their simple topology, input / output electrical isolation, wide step-up / step-down range, and simple operating principle. In a flyback converter, the transformer serves a dual function as both an inductor and a transformer. Its circuit structure is simple, and its operating principle is as follows: Figure 1 As shown: When the main switch Q is on, the secondary diode D is off, and the transformer T stores energy; when the main switch Q is off, the secondary diode D is on, and the energy stored in the transformer is released to the load. This differs from a forward converter, where the transformer's magnetizing inductance typically stores very little energy, and the algebraic sum of the instantaneous power of each winding is zero; the transformer only serves as an isolation and voltage transformer. The transformer in a flyback converter is special; it also functions as an energy storage inductor and is called an energy storage transformer (or inductor-transformer). To prevent core saturation under high load current, an air gap is added to the transformer core of a flyback converter, reducing the core's permeability.

[0032] Flyback converters operate in two modes: Continuous Conductive Mode (CCM) and Discontinuous Conductive Mode (DCM), each with its own advantages. DCM operation occurs when the output rectifier current drops to 0A and before the next cycle begins. The advantages of DCM operation include lower primary-side inductance (allowing for a smaller power transformer), elimination of rectifier reverse recovery losses and MOSFET conduction losses, and the absence of a right-half-plane zero. However, compared to CCM, these advantages are offset by some drawbacks, such as higher peak currents in the primary and secondary sides, increased input and output capacitances, increased electromagnetic interference (EMI), and a lower duty cycle under light loads.

[0033] like Figure 2 As shown, the current changes in Q and D in CCM and DCM modes as the load decreases from its maximum to approximately 25% at minimum VIN. In CCM mode, the duty cycle is constant when the input voltage is fixed and the load is between its maximum and minimum design levels (approximately 25%). The current "base" level decreases as the load decreases until entering DCM mode, where the duty cycle drops. In DCM mode, the maximum duty cycle only occurs at minimum VIN and maximum load. The duty cycle decreases as the input voltage increases or the load decreases. This results in a smaller duty cycle at high voltage lines and minimum loads, so ensure your controller can operate normally during this shortest on-time. DCM operation introduces a dead time for duty cycle operation below 50% after the rectifier current reaches 0A. It is characterized by a sinusoidal voltage on the FET drain, which is set by residual current, parasitic capacitance, and leakage inductance, and is generally benign. In this design, CCM operation is adopted to achieve higher efficiency by reducing switching losses and transformer losses, making it more suitable for medium and high power supply design (the implementation includes a flyback transformer design).

[0034] The switching power supply also includes an LD5760W power management control chip, which is connected to the flyback converter for controlling its operation. The LD5760W is a fixed-frequency current-mode controller with dynamic self-powering capabilities. This function activates an internal startup current source to power the controller during startup, transients, latch-up, and standby, greatly simplifying the design of the auxiliary power supply and Vcc capacitor. The controller operates up to 35V and features a 65kHz or 100kHz switching circuit with jitter, operating in peak current mode control. When auxiliary-side power begins to decrease, the controller automatically folds its switching frequency back to a minimum of 26kHz. As power decreases further, the component enters a skip cycle while limiting the peak current, ensuring the converter operates in continuous conduction mode (CCM) and guaranteeing excellent energy efficiency under rated load conditions. It features timer-based fault detection to ensure overload detection and adjustable compensation to help maintain maximum power regardless of the input voltage.

[0035] like Figure 3 The image shows the pinout of the LD5760W power management control chip, along with a description of its pin functions:

[0036] 1: After the functional side pulls the voltage at this end down to a predetermined value, the chip will turn off the signal driving the MOSFET.

[0037] 2: The detection feedback end is connected to the optocoupler, receives the signal from the secondary end, and adjusts the output voltage accordingly.

[0038] 3: Current signal terminal. This terminal is connected to a resistor to detect the inductor current between the source and ground of the MOSFET, ensuring that the converter operates in continuous conduction mode (CCM) within the rated power range.

[0039] 4: Ground terminal, this terminal is grounded.

[0040] 5. Drive end: This end is connected to the gate of an external power MOSFET.

[0041] 6. Power Supply Terminal: This terminal supplies power to the chip.

[0042] 8: The high-voltage starting terminal is connected to the high potential of the input electrolytic capacitor through a resistor.

[0043] like Figure 6 As shown, the primary connection section of the CCM mode flyback circuit based on the LD5760W chip is as follows:

[0044] The 8-pin HV high-voltage start-up input is connected to the AC terminals of bridge rectifier BD1 via a series connection of resistors R12, R13, and R14, and diodes D5 and D6. The positive terminals of D5 and D6 are connected to the AC terminals of bridge rectifier BD1. The positive terminals of input electrolytic capacitors CD1 and CD2 are connected together. The power supply terminal of the 6-pin VCC chip is connected to the positive terminal of electrolytic capacitor CD4, and the negative terminal of CD4 is grounded. The 5-pin drive terminal is connected to the gate of MOSFET Q1 via a series connection of resistor R15 and diode D2 (with resistor R23 connected in parallel across R15 and the diode). The source of Q2 is grounded via overcurrent resistors R20 and R21. Resistor R22 is connected in parallel between the gate and source of Q2. Ceramic capacitor C5 is connected in parallel between the source and drain. The 4-pin GND is grounded and connected to the negative terminal of input capacitor CD4. The CS terminal of pin 3 is connected to the source of Q2 via resistor R19 (to sample the current signal and limit the peak current, ensuring the converter operates in continuous conduction mode (CCM) and guaranteeing excellent energy efficiency under rated load conditions). T1 is a flyback CCM mode switching transformer. A filter capacitor C3 is installed between the CS terminal and ground. The FB feedback terminal is directly connected to pin 4 of optocoupler U2, pin 3 of U2 is grounded, and a filter capacitor C7 is installed between the FB terminal and ground.

[0045] like Figures 4-6 As shown, the CCM mode flyback switching power supply is implemented in detail:

[0046] 1. Design parameters: Vin = 85VAC - 264VAC, V1 = 15V, I1o = 5A, V2 = -15V, I2o = 5A, Fsw = 65KHZ.

[0047] 2: Setting initialization parameters

[0048] Input voltage range: Vinmin_AC and Vinmax_AC (85VAC-264VC)

[0049] ------ Power grid frequency: fline (50Hz in China) 50HZ

[0050] Output power: (equal to the sum of the output power of all channels) 150W

[0051] ------ Preliminary estimate of converter efficiency: η (η is 0.7 to 0.75 for low-voltage output and 0.8 to 0.9 for high-voltage output). Based on the estimated efficiency, the input power is estimated to be 0.88.

[0052] 3: Determine the input capacitor Cbulk

[0053] The value of Cbulk depends on the input power. Generally, for a wide input voltage range (85–265VAC), 2–3 μF / W is used; for a narrow input voltage range (176–265VAC), 1 μF / W is sufficient. The capacitor charging duty cycle Dch is set to 0.2. For a 150W wide mains input, two 400V 220μF capacitors are selected in parallel. Generally, the minimum voltage after rectification is... The design of the flyback converter can be calculated by Cbulk. :

[0054]

[0055] Calculated according to the formula =102V.

[0056] 4: Determine the maximum duty cycle Dmax

[0057] We employ Continuous Current Mode (CCM). For a CCM flyback converter, the input-to-output voltage gain is determined solely by the duty cycle. This is much simpler than Discontinuous Current Mode (DCM). When the MOSFET is off, the input voltage Vin and the secondary reflected voltage nVo are superimposed across the DS terminals of the MOSFET. Once the maximum duty cycle Dmax is determined, the reflected voltage Vor (i.e., nVo), the maximum voltage VD across the secondary rectifier diode, and the maximum voltage Vdsmax across the MOSFET can be obtained from the following equations:

[0058]

[0059]

[0060]

[0061] Our Dmax is set to 0.48 (generally not greater than 0.5 in CCM mode, otherwise the power supply will experience subharmonic oscillation). According to the formula, the reflected voltage VOR is calculated to be 101V.

[0062] 5: Determine the primary inductance Lm of the transformer.

[0063] For CCM mode flyback converters, the converter may transition from CCM mode to DCM mode when the input voltage changes. For both modes, the primary inductance Lm of the transformer is designed under the worst-case conditions (lowest input voltage, full load). It is determined by the following formula:

[0064]

[0065] Fs is the operating frequency of the converter, and KRF is the current ripple coefficient, defined as follows: Figure 7 As shown.

[0066] For CCM mode converters, KRF < 1. In this case, the value of KRF affects the root mean square (RMS) value of the primary current. A smaller KRF results in a smaller RMS, leading to lower MOSFET losses. However, an excessively small KRF increases the transformer size, requiring careful consideration during design. Generally, for CCM mode flyback converters, KRF is typically 0.25–0.5 for wide input voltage ranges (90–265VAC) and 0.4–0.8 for narrow input voltage ranges (176–265VAC). With KRF = 0.3 and Fsw = 65kHz, the inductance Lm is calculated to be 180uF.

[0067] 6: Select appropriate magnetic cores and the number of turns of the transformer's primary inductance.

[0068] In switching power supply design, ferrite cores are the most widely used type of core. They can be processed into various shapes to meet different application requirements, such as multiple outputs, physical height, and cost optimization. After selecting the EQ39 core, the Ae value and magnetization curve are found in its datasheet to determine the flux swing ΔB. The number of turns in the primary coil is determined by the following formula:

[0069]

[0070] During CCM Using a value of 0.20 to 0.25T, Np is calculated to be 15T according to the formula.

[0071] 7: Determine the number of turns for each output.

[0072] First, determine the number of turns in the main feedback winding. The number of turns in other windings can be referenced from the number of turns in the main winding. The number of turns in the main feedback loop winding is: (VO1 is the main output voltage, VF1 is the rectifier diode voltage drop)

[0073]

[0074] Calculate according to the formula =4T can be obtained similarly. =4T; The number of turns Na of the auxiliary coil winding is:

[0075]

[0076] Calculated according to the formula =3T.

[0077] Winding Instructions: The primary and secondary windings are close together to enhance coupling and reduce leakage inductance. A shielding winding separates the primary and secondary windings to reduce inter-turn capacitance and interference. The auxiliary coil winding is wound on the outermost layer to strengthen coupling with the primary winding and stabilize the output voltage. Different winding positions produce different leakage inductances; the transformer dynamically balances the leakage inductance of each winding during actual conversion, adjusting and matching the leakage inductance of each winding to achieve precise output regulation. This also reduces coil size.

[0078] The above embodiments are only used to illustrate the technical solution of this utility model, and are not intended to limit it.

Claims

1. A 150W dual-output flyback switching power supply, characterized in that, include: A flyback converter, wherein the flyback converter operates in CCM mode; The LD5760W power management control chip is connected to the flyback converter and is used to control its operation. The transformer, connected in the flyback converter, serves as both an inductor and a transformer, and also functions as an energy storage inductor. The dual-output circuit outputs a voltage and current of 15V / 5A and -15V / 5A respectively from the flyback converter. Wide-range input circuitry, adaptable to mains voltage inputs from 85VAC to 264VAC.

2. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, The LD5760W power management control chip has a dynamic self-powering function, which can power the controller during startup, transient, latching, and standby periods.

3. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, An air gap is provided in the magnetic core of the transformer to prevent the magnetic core from saturating when the load current is large.

4. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, The flyback converter also includes an input electrolytic capacitor, the value of which is related to the input power and is used to stabilize the input voltage. Its value range is 2~3μF / W.

5. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, The flyback converter also includes a current sensing resistor connected between the source and ground of the MOSFET to detect the inductor current and ensure that the converter operates in continuous conduction mode within the rated power range.

6. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, The switching power supply also includes a feedback circuit, which is connected to the LD5760W power management control chip to detect changes in the output voltage and adjust the operating state of the flyback converter to maintain a stable output voltage.

7. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, The input mains voltage range of the switching power supply is 85VAC to 264VAC, and the mains frequency is 50Hz or 60Hz.

8. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, The flyback converter operates at a frequency of 65kHz or 100kHz, and can automatically fold back to a minimum level of 26kHz when the power decreases.

9. A 150W dual-output flyback switching power supply according to claim 1, characterized in that, The switching power supply also includes overvoltage protection, overcurrent protection and short circuit protection functions, with a protection response time of ≤100ms.

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