An ac-dc power converter circuit based on active valley fill technique

Abstract

The utility model discloses an AC-DC power supply converter circuit based on active valley filling technology, including rectifier bridge, high frequency filter capacitance, primary winding, charging winding, charging diode and high frequency transformer, the circuit of high frequency transformer is additionally provided with charging winding same with its polarity except setting up primary winding, rectifier bridge is set at the current input, and the high frequency filter capacitance, high frequency transformer and valley filling capacitance are connected respectively, the loop between rectifier bridge and valley filling capacitance is provided with discharge diode, charging diode is connected on the line between valley filling capacitance and discharge diode, and is connected with charging winding. The utility model discloses a charging winding on the high frequency transformer of conversion circuit, and it is charged for a low voltage valley filling capacitance by converter high frequency pulse through charging diode, can avoid the transient large impact current of electrifying moment, expands the conduction angle of input alternating current, and reduces the pulsation wave.

Description

Technical Field

[0001] This utility model belongs to the field of power converter technology, and in particular relates to an AC-DC power converter circuit based on active valley filling technology. Background Technology

[0002] Many electronic devices and appliances require stable direct current (DC) power to operate, but the original AC power supply is unstable alternating current (AC). Therefore, when using AC mains power to supply electronic devices, a power converter is usually needed to convert the unstable AC mains power into stable DC power suitable for the operation of electronic devices. The AC input terminals of AC-DC power converters that achieve this conversion mainly have the following four circuit structures:

[0003] 1. The input AC mains power is rectified into pulsating unidirectional DC power by a diode rectifier circuit, and then the pulsating DC power is filtered by a large-capacity capacitor to form a relatively smooth DC power. Then, an electronic converter circuit is used to perform high-frequency pulse width modulation conversion to convert it into stable DC power.

[0004] 2. After the converter rectifier circuit, two large-capacity capacitors and three diodes are used to form a passive valley-filling circuit in which the two large-capacity capacitors are connected in parallel for charging and discharging. This can expand the conduction width of the input current in the half-cycle of the sine wave to a certain extent.

[0005] 3. Higher-end AC-DC power converters do not directly use large-capacity capacitors for filtering after rectification. Instead, they first use a boost circuit to track the rectified unidirectional sine wave voltage waveform and perform high-frequency boost conversion to output high-voltage DC power that is higher than the peak voltage of the input sine wave. Then, the boosted DC power is transformed a second time to form a stable DC power output.

[0006] 4. Another solution is to use an isolation converter to directly perform high-frequency isolation conversion on the rectified unidirectional sine wave instead of filtering it with a large-capacity capacitor after AC mains rectification, so as to obtain DC power at the secondary output of the converter.

[0007] Each of these four methods has its own drawbacks.

[0008] The defects of the first circuit structure:

[0009] Before power is applied, the filter capacitor after the rectifier circuit is empty. If the moment the power is applied happens to be the high voltage value of the mains sine wave, the high voltage will charge the empty large-capacity capacitor, generating a large transient inrush current. When a large number of such power supplies are used together, it may cause a transient drop in the grid voltage, thereby interfering with the operation of other electrical equipment on the grid. In severe cases, it may even cause the circuit breaker to trip. The strong inrush current will then cause an upward surge voltage under the effect of the parasitic inductance of the mains line, threatening the safety of electronic equipment on the grid.

[0010] In addition, because the input mains power cannot provide current to the equipment during the entire sine wave cycle when the power converter is working, the current can only be concentrated in the part near the peak of the half cycle of the sine wave, forming a narrow pulse with a large peak value. As a result, even if the load of the three phase lines A / B / C is evenly configured, the current cannot overlap and cancel each other on the neutral line, resulting in the neutral line current being the sum of the currents of the three phase lines. Excessive neutral line current can cause the neutral line to heat up or even burn out, leading to accidents.

[0011] The drawbacks of the second type of circuit:

[0012] It can only charge and discharge at half the peak value of the input AC voltage, so the conduction angle extension is limited. The conduction width of the input current does not expand much within half a sine wave cycle. In high-power applications, when the loads of the three phase lines A / B / C are balanced, the overlap of the neutral current is not high, so they can only partially cancel each other out. This causes the neutral line to bear a large current and generate a large neutral line loss. Moreover, this scheme still has a current surge when charging the empty capacitor during power-on.

[0013] The drawbacks of the third type of circuit:

[0014] Although it can make the input AC current waveform track the input voltage waveform, the circuit structure is complex, the converter is large and expensive, and when the input AC voltage is high, the circuit will still charge the empty boost capacitor after the boost inductor instantly, forming a large inrush current.

[0015] The drawback of the fourth type of circuit:

[0016] This circuit structure results in no output from the secondary side of the converter when the input mains power crosses zero. Even with large-capacity capacitors used for filtering in the secondary side, it is impossible to eliminate significant output fluctuations, making it difficult to meet usage requirements. Performing a secondary conversion in the secondary side would lead to a complex circuit structure, high cost, and low conversion efficiency.

[0017] Therefore, it is necessary to propose a power converter based on an active valley-filling circuit solution to address the problems existing in the input circuit of current AC-DC power converters. Utility Model Content

[0018] This invention provides an AC-DC power converter circuit based on active valley filling technology to solve the problems mentioned in the background art.

[0019] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0020] An AC-DC power converter circuit based on active valley-filling technology includes a rectifier bridge, a high-frequency filter capacitor, a primary winding, a charging winding, a charging diode, a valley-filling capacitor, a discharging diode, and a high-frequency transformer. The circuit is characterized in that, in addition to the primary winding, a charging winding with the same polarity as the primary winding is added and electrically connected to the high-frequency transformer. The rectifier bridge is located at the current input terminal, and connected to it are the high-frequency filter capacitor, the high-frequency transformer, and the valley-filling capacitor. A discharging diode is provided between the rectifier bridge and the valley-filling capacitor circuit. The charging diode is connected to the line between the valley-filling capacitor and the discharging diode, and is also connected to the charging winding.

[0021] Preferably, the polarity of the charging winding is the same as that of the primary winding, but the number of its coil turns is one-third to one-fifth of that of the primary winding.

[0022] Compared to existing technologies, the advantages of this invention are as follows: This invention does not use a large-capacity filter capacitor directly after rectification. Instead, it incorporates a low-voltage energy storage valley-fill capacitor. This valley-fill capacitor can only be charged sequentially by the high-frequency pulses generated by the converter circuit through the primary winding and charging winding of the high-frequency transformer. Furthermore, the charging diodes charge the capacitor according to the turns ratio of these two windings, charging it sequentially to one-fifth to one-third to one-third of the peak value of the input AC current. Therefore, no instantaneous large inrush current is generated when the power is switched on. Additionally, there is no large-capacity high-voltage capacitor for energy storage after rectification. When the input voltage of the converter circuit is higher than the voltage on the energy storage capacitor during operation, the input energy directly powers the converter circuit through the rectifier bridge, enabling its operation. Only when the input AC voltage is lower than the voltage on the energy storage capacitor will the energy storage capacitor discharge through the discharge diode to provide input energy to the converter circuit and maintain continuous output. This expands the conduction angle of the AC input current. In high-power applications, when the three-phase A / B / C power with the same frequency and amplitude and a conduction angle difference of 120 degrees is equal or similar in load capacity, the current of the three phase lines can effectively overlap on the neutral line and cancel each other out, which can effectively reduce the neutral line current and reduce the neutral line loss. Furthermore, due to the presence of the valley filler capacitor, it can provide energy to the converter near the zero crossing of the input AC current, thereby keeping the converter output uninterrupted and effectively reducing the output ripple at the converter output terminal. Attached Figure Description

[0023] Figure 1 This is the circuit diagram of this utility model. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] like Figure 1 As shown, this utility model is an AC-DC power converter circuit based on active valley-filling technology, mainly including a rectifier bridge 1, a high-frequency filter capacitor 2, a primary winding 3, a charging winding 4, a charging diode 5, a valley-filling capacitor 6, a discharge diode 7, and a high-frequency transformer 8. The key feature is that, in addition to the primary winding 3, a charging winding 4 with the same polarity as the primary winding 3 is also added and electrically connected to the high-frequency transformer 8. The rectifier bridge 1 is located at the current input terminal, and connected to it are the high-frequency filter capacitor 2, the high-frequency transformer 8, and the valley-filling capacitor 6. A discharge diode 7 is provided between the circuit of the rectifier bridge 1 and the valley-filling capacitor 6. The charging diode 5 is connected to the line between the valley-filling capacitor 6 and the discharge diode 7, and is connected to the charging winding 4.

[0026] It should be noted that the polarity of the charging winding 4 is the same as that of the primary winding 3, but the number of its coil turns is one-third to one-fifth of that of the primary winding 3.

[0027] The working principle of this utility model is as follows:

[0028] Rectifier bridge 1 converts the input AC power into unidirectional pulsating DC power. High-frequency filter capacitor 2 provides a high-frequency current path for the high-frequency switching converter circuit. In addition to the primary winding 3, the high-frequency transformer 8 adds a charging winding 4 with the same polarity as the primary winding 3, but with one-third to one-fifth the number of turns. The charging winding 4, through charging diode 5, generates multiple high-frequency pulses from the high-frequency transformer 8, charging the valley filler capacitor 6 to one-third to one-fifth of the input peak voltage according to the turns ratio of the primary winding 3 and the charging coil 4. The valley filler capacitor 6 is then connected to the positive terminal of the input rectifier bridge 1 via discharge diode 7. Due to the isolation effect of discharge diode 7, the rectifier bridge 1... The high output voltage at the terminal cannot directly charge the valley filler capacitor 6. Therefore, when the rectified input voltage is higher than the voltage on the valley filler capacitor 6, the rectifier bridge 1 will directly power the subsequent conversion circuit. When the input unidirectional sinusoidal pulsating voltage crosses the peak and begins to drop until it is lower than the voltage on the valley filler capacitor 6, the electrical energy stored on the valley filler capacitor 6 will begin to power the subsequent conversion circuit through the discharge diode 7. Since the valley filler capacitor 6 has a large capacitance and the voltage drops slowly, it provides continuous power to the input terminal of the conversion circuit before / after the zero crossing of the input AC current, so that the input energy is not interrupted and the converter maintains continuous output. This effectively reduces the pulsation of the output DC current and reduces the output ripple.

[0029] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," 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, an electrical connection, or a communication 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. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] In this invention, unless otherwise expressly specified and limited, the first feature "on" or "below" the second feature may be in direct contact with the first and second features, or indirect contact through an intermediate medium. In the description of this specification, references to terms such as "a solution," "some solutions," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that solution or example is included in at least one solution or example of this invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same solution or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more solutions or examples.

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