High efficiency small power module circuit and control method

Abstract

The application discloses a kind of high-efficiency small power module circuits, including input rectification filter circuit, primary side PWM controller, high-frequency isolation transformer and secondary side synchronous rectification circuit;The input end of input rectification filter circuit is connected with alternating current mains, and the output end provides DC bus voltage;Primary side PWM controller is integrated with power switch tube inside, the drain electrode or collector of the power switch tube is directly connected to the first end of the primary winding of high-frequency isolation transformer, and the second end of the primary winding is connected to DC bus voltage;High-frequency isolation transformer adopts EE19 series magnetic core, and the secondary winding is connected to the input end of secondary side synchronous rectification circuit;The output end of secondary side synchronous rectification circuit is the DC output end of the whole circuit.The application solves the technical problem that existing flyback AC-DC power supply cannot simultaneously consider ultra-small volume, extremely low cost and full wide voltage (especially low voltage condition) high efficiency in 36W power range in prior art.

Description

Technical Field

[0001] This invention relates to the field of switching circuits, and in particular to a high-efficiency small power supply module circuit and control method. Background Technology

[0002] In the field of switching power supply technology, especially for the standardized power level of 24V / 1.5A (36W) widely used in industrial control, smart homes and instrumentation, efficient, miniaturized and low-cost AC-DC power supply solutions have always been the goal pursued by the industry.

[0003] Currently, there are two main types of high-efficiency power supplies. One type uses an external SiC or high-voltage MOSFET paired with a large-size transformer (such as EE22 and above). While this solution can achieve high full-load efficiency, it is expensive, has complex drive circuits, and is prone to large voltage spikes and oscillations under high-frequency switching conditions, making EMI rectification extremely difficult. Especially when the input voltage is at a low voltage of 90V, switching losses increase sharply, efficiency drops significantly, and it is difficult to maintain high energy efficiency performance across the entire voltage range. The other type is a simple solution with a traditional transistor built-in controller. Although this structure is extremely low-cost and requires few external components, its overall efficiency is generally low due to the transistor's switching speed and on-state voltage drop, failing to meet current mid-to-high-end energy efficiency standards. Furthermore, it has large output ripple, concentrated heat loss, and low product added value.

[0004] It is evident that existing technologies generally suffer from problems such as high cost due to high efficiency, low efficiency due to low cost, poor low-voltage performance, large size, and complex mass production and debugging. There is currently no solution in the industry that can simultaneously achieve a minimalist built-in switch architecture, no external high-voltage power devices, no SiC required, use a small transformer like EE19, and balance high efficiency across the entire voltage range with no collapse at low voltage.

[0005] To address the aforementioned shortcomings, this invention provides a high-efficiency miniature power module circuit and control method. By integrating the power switching transistor into the primary-side controller, combining it with an EE19 miniature low-loss high-frequency transformer, and optimizing the timing of the secondary-side synchronous rectification, it achieves ultra-small size, low cost, and high-efficiency output characteristics across a wide voltage range without requiring any external high-voltage devices or SiC. Summary of the Invention

[0006] The technical solution of this invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a high-efficiency, small-sized power module circuit and control method, aiming to solve the problem that existing flyback AC-DC power supplies cannot simultaneously achieve ultra-small size, extremely low cost, and high efficiency across a wide voltage range (especially under low-voltage conditions) at the 36W power level.

[0007] To achieve the above objectives, this invention provides a high-efficiency small power module circuit and control method, including an input rectifier and filter circuit, a primary-side PWM controller, a high-frequency isolation transformer, and a secondary-side synchronous rectifier circuit. The input terminal of the input rectifier and filter circuit is connected to AC mains power, and the output terminal provides DC bus voltage. The primary-side PWM controller integrates a power switching transistor, the drain or collector of which is directly connected to the first terminal of the primary winding of the high-frequency isolation transformer, and the second terminal of the primary winding is connected to the DC bus voltage. The high-frequency isolation transformer uses an EE19 series magnetic core, and its secondary winding is connected to the input terminal of the secondary-side synchronous rectifier circuit. The output terminal of the secondary-side synchronous rectifier circuit serves as the DC output terminal of the entire circuit.

[0008] As a further embodiment of the present invention, it also includes an auxiliary power supply and feedback circuit. The high-frequency isolation transformer is further provided with an auxiliary winding. The output end of the auxiliary winding is connected to the power supply end of the primary-side PWM controller after rectification and filtering. The auxiliary winding is also connected to the feedback input end of the primary-side PWM controller via a voltage divider sampling circuit for indirectly adjusting the output voltage.

[0009] As a further embodiment of the present invention, the input rectifier filter circuit includes a full-wave rectifier bridge and at least two stages of electrolytic capacitor filter units connected in series, and a differential-mode inductor is connected in series between the two stages of electrolytic capacitors to suppress differential-mode interference.

[0010] As a further embodiment of the present invention, an RCD clamping absorption circuit is connected in parallel across the two ends of the primary winding. The RCD clamping absorption circuit consists of at least one resistor, one capacitor, and one fast recovery diode. The cathode of the fast recovery diode is connected to the first end of the primary winding, and the anode is grounded, in order to absorb voltage spikes generated by the leakage inductance of the transformer.

[0011] As a further embodiment of the present invention, the secondary-side synchronous rectification circuit includes a synchronous rectification controller and its built-in synchronous rectification power transistor. The switching timing of the synchronous rectification power transistor is matched with the switching timing of the built-in power switch transistor of the primary-side PWM controller: when the primary-side power switch transistor is turned off and the secondary-side winding is turned on, the synchronous rectification power transistor is turned on, replacing the traditional diode rectification.

[0012] As a further embodiment of the present invention, the output terminal of the secondary-side synchronous rectifier circuit is further connected in parallel with a freewheeling diode and an RC buffer circuit. The freewheeling diode provides a freewheeling path during the switching gap of the synchronous rectifier power transistor, and the RC buffer circuit is used to absorb high-frequency spikes.

[0013] As a further embodiment of the present invention, the EE19 series magnetic core is made of PC95 or PC44 material, the number of turns of the primary winding is 78 to 85 turns, the primary inductance is 1.0mH to 1.5mH, and the leakage inductance is no greater than 45μH.

[0014] As a further embodiment of the present invention, the entire circuit is integrated on a PCB board with a size of 50mm to 55mm, a width of 30mm to 35mm, and a thickness of no more than 2mm.

[0015] As a further embodiment of the present invention, the power switching transistor built into the primary-side PWM controller is a high-voltage transistor or a high-voltage MOSFET, and the entire circuit has no external high-voltage power switching devices or silicon carbide power devices.

[0016] The beneficial effects of this invention are as follows:

[0017] The high-efficiency miniature power module circuit and control method proposed in this invention achieves full-range high-efficiency output with a 90V low-voltage full-load efficiency of ≥88% and a 220V full-load efficiency of ≥90% within an ultra-small PCB size. This is achieved by integrating a power switching transistor into the primary-side PWM controller and eliminating the need for external high-voltage power devices and silicon carbide components. Combined with a high-frequency isolation transformer using EE19 series magnetic cores and a secondary-side synchronous rectification circuit, this completely solves the problem of severe low-voltage efficiency degradation in traditional solutions. Furthermore, by eliminating expensive external SiC and high-voltage MOSFETs, material costs are significantly reduced. The built-in switch operates smoothly without high-frequency sharp oscillations, making electromagnetic interference certification easy and ensuring good mass production consistency.

[0018] In addition, based on the EE19 small transformer and compact layout, it achieves an extremely small power supply size with the same energy efficiency level, taking into account low cost, small size and wide voltage high efficiency performance, and has extremely high commercial application value. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the high-efficiency small power module circuit and control method of the present invention.

[0021] Figure 2 This is a schematic block diagram illustrating the main control process of the high-efficiency small power module circuit and control method of the present invention.

[0022] Figure 3 This is a photograph of the actual primary-side controller switch of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] as follows:

[0025] Please see the appendix Figure 1-3 ,

[0026] like Figure 1 As shown, this embodiment provides a high-efficiency small power module circuit and control method, mainly applied to a 36W (24V / 1.5A) wide-voltage input AC-DC power supply. The circuit includes an input rectifier and filter circuit, a primary-side PWM controller U1, a high-frequency isolation transformer T1, and a secondary-side synchronous rectifier circuit U2. The input terminal of the input rectifier and filter circuit is connected to the AC mains lines L and N. The mains line L first passes through an input fuse F1 (2A / 250V) for overcurrent protection, while the N line is directly connected to the AC input terminal of the full-wave rectifier bridge BD1. The output terminal of the rectifier bridge BD1 is connected to a two-stage π-type filter network composed of an electrolytic capacitor EC1, a differential-mode inductor L1 (with parallel resistor R12), and an electrolytic capacitor EC2, ultimately outputting a smooth DC bus voltage Vbus.

[0027] The primary-side PWM controller U1 in this solution uses an integrated chip with a built-in power switching transistor (such as a high-voltage transistor or a high-voltage MOSFET). The drain (or collector) of its internal integrated power switching transistor is directly connected to one end (pin 5) of the primary winding of the high-frequency isolation transformer T1, and the other end (pin 4) of the primary winding is connected to the DC bus voltage Vbus. The circuit has no external high-voltage power switching transistors and no SiC devices.

[0028] The high-frequency isolation transformer T1 in this scheme uses an EE19 series magnetic core, preferably made of PC95 or PC44 material. The primary winding has 75 to 85 turns (preferably 82 turns in this embodiment), a primary inductance of 1.0 to 1.5 mH (preferably 1.3 mH in this embodiment), and a leakage inductance of no more than 45 μH. T1 has a primary winding T1A (pins 4 and 5), a secondary winding T1C (pins 6 and 7), and an auxiliary winding T1B (pins 1 and 3).

[0029] The primary winding is connected in parallel with an RCD clamping absorption circuit, which consists of resistors R1, R2, R3, and R4 (series voltage divider), capacitor C1, and fast recovery diode D1. The cathode of D1 is connected to pin 5 of the primary winding, and the anode is grounded. It is used to absorb voltage spikes generated by the transformer leakage inductance and protect the built-in power switch of U1.

[0030] In this circuit, pin 1 of the auxiliary winding T1B is connected to the anode of diode D2, and the cathode of D2 is connected to the positive terminal of electrolytic capacitor EC3 via current-limiting resistor R10. The terminals of EC3 provide the operating power VCC for the primary-side PWM controller U1. The feedback pin (FB) of U1 is connected to a voltage divider sampling network composed of resistors R5, R6, and R7, where R6 and R7 are connected in parallel and grounded. This network samples the voltage of the auxiliary winding to indirectly reflect the output voltage. Meanwhile, resistors R8 and R9 and capacitors C2 and C3 form a loop compensation network to ensure that the output voltage is stable at 24V.

[0031] Pin 7 of the secondary winding T1C is connected to the cathode of the freewheeling diode D3 via an RC snubber circuit (resistor R12, capacitor C5); pin 6 is connected to the corresponding input terminal of the synchronous rectifier controller U2. U2 integrates a synchronous rectifier power transistor, whose switching timing matches the built-in power switch of the primary winding U1. When the primary winding switch is turned off and the secondary winding voltage reverses, U2 controls the internal synchronous rectifier transistor to turn on, providing a current path for the load and reducing conduction losses caused by traditional diode rectification. D3, as an auxiliary freewheeling diode, provides a freewheeling path during the switching gap of the synchronous rectifier transistor, preventing voltage overshoot.

[0032] The DC power rectified on the secondary side passes through the output filter network. Parallel electrolytic capacitors EC4 and EC5 filter out high-frequency ripple, and resistor R14 acts as a light-load dummy load to improve no-load stability. An optional common-mode inductor LF2 can further suppress common-mode interference at the output. Finally, a stable 24V / 1.5A DC power is output from the OUT+ and GND ports.

[0033] In addition, the circuit is equipped with EMI suppression and safety protection components. Y capacitor CY1 is connected between the primary side ground (hot ground) and the secondary side ground (cold ground) to suppress common-mode interference. Optionally, Y capacitors CY2 and CY3 can be connected in parallel, with one end connected to the secondary side ground and the other end connected to the protective ground (earth ground) to further improve EMI performance.

[0034] Furthermore, to achieve the optimal balance between ultra-small size and high efficiency (as shown in the attached document) Figure 3 As shown in the figure, this embodiment provides a set of preferred parameters. The PCB substrate size is 53mm × 34mm, and the thickness is ≤2mm. The EE19 transformer core is made of PC95 material, with 82 turns in the primary winding, an inductance of 1.3mH, and a leakage inductance of 38μH. The primary-side PWM controller U1 has a built-in high-voltage transistor, and the switching frequency is set to 65kHz. The secondary-side synchronous rectification controller U2 uses a dedicated chip with a built-in low on-resistance MOSFET.

[0035] Under these parameters, the measured full-load efficiency of the entire unit is ≥88% with 90V AC input and ≥90% with 220V AC input. The efficiency shows no significant drop under low-voltage conditions, outperforming similar solutions using external SiC or MOSFETs. Furthermore, due to the smooth waveform and absence of high-frequency sharp oscillations from the built-in switching transistor, there is ample EMI testing margin, resulting in good mass production consistency.

[0036] In another embodiment, the high-efficiency miniature power module circuit and control method can have the following control modes.

[0037] Initiation phase,

[0038] After rectification and filtering, the mains power forms a DC bus voltage. The initial operating current of U1 is provided through the starting resistor (which can be integrated inside or outside U1). U1 starts to oscillate and drives the internal power switch to turn on and off.

[0039] Energy conversion stage,

[0040] U1 controls the internal power switching transistor to turn on and off at high frequency. When the switching transistor is on, the DC bus voltage is applied to the primary winding of the transformer, the primary current rises linearly, and the transformer stores magnetic energy; when the switching transistor is off, the primary current path is cut off, and the transformer's magnetic energy is coupled to the secondary winding and auxiliary winding through mutual inductance.

[0041] Secondary-side synchronous rectification stage,

[0042] The synchronous rectifier controller U2 detects the voltage change at the moment the primary-side switch turns off and promptly turns on the internal synchronous rectifier, allowing the secondary-side current to be output through a low-impedance path. Before the primary-side switch turns on, U2 turns off the synchronous rectifier in advance to prevent shoot-through. At the same time, the freewheeling diode D3 provides freewheeling current during the brief gap after the synchronous rectifier is completely turned off, avoiding voltage spikes.

[0043] Feedback stabilization phase,

[0044] The auxiliary winding voltage is sampled by voltage divider and then sent to the feedback pin of U1. The internal error amplifier of U1 compares the sampled value with the reference voltage to generate an error signal. The PWM duty cycle is adjusted through the loop compensation network to stabilize the output voltage at 24V.

[0045] Full voltage range adaptive,

[0046] When the input voltage varies within the range of 90V to 264V, U1 automatically adjusts the maximum duty cycle and switching frequency by detecting the bus voltage or auxiliary winding voltage to ensure stable output of rated power across the full voltage range, with a low-voltage full-load efficiency of no less than 88% and a high-voltage full-load efficiency of no less than 90%.

[0047] Overall, compared to existing technologies, this solution achieves full-width voltage range and high-efficiency output in an ultra-small size by integrating the power switching transistor in the primary-side PWM controller and eliminating the need for external high-voltage power devices and silicon carbide components. Combined with the EE19 series magnetic core high-frequency isolation transformer and the secondary-side synchronous rectification circuit, this solution achieves high efficiency output within an ultra-small size (as shown in the attached diagram). Figure 3 (Example shown). Secondly, this technical solution achieves a full-load efficiency of no less than 88% under 90V low-voltage input conditions and no less than 90% under 220V full-load conditions, solving the pain point of severe low-voltage efficiency collapse in traditional solutions. Its low-voltage performance is even superior to some mainstream SiC solutions. Due to the adoption of a minimalist built-in switch topology, expensive SiC devices, external high-voltage MOSFETs, and complex drive circuits are eliminated, significantly reducing material costs. At the same time, because the built-in switch operates with a smooth waveform and no high-frequency sharp oscillations, electromagnetic interference is easily certified, resulting in good mass production consistency and simple debugging.

[0048] Based on the EE19 miniature transformer and compact PCB layout (size can be as small as 53×34×2mm), an extremely small power supply size is achieved for the same energy efficiency level, which can be widely used in space- and cost-sensitive scenarios such as industrial control and smart homes (see attached). Figure 3 (As shown).

[0049] The secondary-side synchronous rectification circuit of this solution is precisely matched with the switching timing of the power switching transistor built into the primary-side PWM controller. Combined with the RCD clamping absorption circuit and the output filter network, it further reduces switching losses and conduction losses, and improves stability and reliability across the entire voltage range. With a minimalist architecture, extremely low cost and extremely small size, it achieves high-efficiency output under wide voltage and full operating conditions, and has extremely high commercial value.

[0050] The following points need to be explained:

[0051] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure. Other structures can be referred to the general design.

[0052] (2) Where there is no conflict, features of the same embodiment and different embodiments of this disclosure can be combined with each other.

[0053] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A high-efficiency miniature power supply module circuit, characterized in that, include Input rectifier and filter circuit, primary-side PWM controller, high-frequency isolation transformer, and secondary-side synchronous rectifier circuit; The input terminal of the input rectifier and filter circuit is connected to AC mains power, and the output terminal provides DC bus voltage; The primary-side PWM controller integrates a power switching transistor, the drain or collector of which is directly connected to the first end of the primary winding of the high-frequency isolation transformer, and the second end of the primary winding is connected to the DC bus voltage. The high-frequency isolation transformer uses an EE19 series magnetic core, and its secondary winding is connected to the input terminal of the secondary synchronous rectifier circuit. The output terminal of the secondary-side synchronous rectifier circuit serves as the DC output terminal of the entire circuit.

2. The high-efficiency miniature power module circuit according to claim 1, characterized in that, It also includes an auxiliary power supply and feedback circuit. The high-frequency isolation transformer is also provided with an auxiliary winding. The output end of the auxiliary winding is connected to the power supply end of the primary-side PWM controller after rectification and filtering. The auxiliary winding is also connected to the feedback input of the primary-side PWM controller via a voltage divider sampling circuit for indirectly adjusting the output voltage.

3. The high-efficiency miniature power module circuit according to claim 1, characterized in that, The input rectifier and filter circuit includes a full-wave rectifier bridge and at least two stages of electrolytic capacitor filter units connected in series, with a differential-mode inductor connected in series between the two stages of electrolytic capacitors to suppress differential-mode interference.

4. The high-efficiency miniature power module circuit according to claim 1, characterized in that, An RCD clamping absorption circuit is connected in parallel across the two ends of the primary winding. The RCD clamping absorption circuit consists of at least one resistor, one capacitor, and one fast recovery diode. The cathode of the fast recovery diode is connected to the first end of the primary winding, and the anode is grounded. It is used to absorb voltage spikes generated by the leakage inductance of the transformer.

5. The high-efficiency miniature power module circuit according to claim 1, characterized in that, The secondary-side synchronous rectification circuit includes a synchronous rectification controller and its built-in synchronous rectification power transistor. The switching timing of the synchronous rectification power transistor matches the switching timing of the built-in power switch transistor of the primary-side PWM controller: when the primary-side power switch transistor is turned off and the secondary-side winding is turned on, the synchronous rectification power transistor is turned on, replacing the traditional diode rectification.

6. The high-efficiency miniature power module circuit according to claim 5, characterized in that, The output of the secondary-side synchronous rectifier circuit is also connected in parallel with a freewheeling diode and an RC snubber circuit. The freewheeling diode provides a freewheeling path during the switching gap of the synchronous rectifier power transistor, and the RC snubber circuit is used to absorb high-frequency spikes.

7. The high-efficiency miniature power module circuit according to claim 1, characterized in that, The EE19 series magnetic cores are made of PC95 or PC44 material, with 78 to 85 turns in the primary winding, a primary inductance of 1.0mH to 1.5mH, and a leakage inductance of no more than 45μH.

8. The high-efficiency miniature power module circuit according to claim 1, characterized in that, The entire circuit is integrated on a single PCB board, which is 50mm to 55mm in size, 30mm to 35mm in width, and no more than 2mm in thickness.

9. The high-efficiency miniature power module circuit according to claim 1, characterized in that, The primary-side PWM controller has a built-in high-voltage transistor or a high-voltage MOSFET, and the entire circuit has no external high-voltage power switching devices or silicon carbide power devices.

10. A high-efficiency miniature power module circuit based on any one of claims 1 to 9, characterized in that, The control method includes the following steps: S1. By frequently switching the power switching transistor built into the primary-side PWM controller, the DC bus voltage is converted into a high-frequency pulse voltage and applied to the primary winding of the EE19 transformer. S2. The high-frequency voltage induced in the secondary winding of the transformer is rectified by the secondary synchronous rectifier circuit to output DC power. At the same time, the induced voltage in the auxiliary winding powers the primary PWM controller and samples the output voltage to feed back to the controller, forming a closed-loop voltage regulation control. Among them, within the wide voltage AC input range of 90V to 264V, the full-load efficiency of the whole machine is not less than 88% when the input is 90V and not less than 90% when the input is 220V.

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