A DC / DC converter and a communication power supply

Abstract

The present application discloses a DC / DC converter and a communication power supply. The converter includes: a primary winding, a secondary winding, a resonant inductor, a resonant capacitor, and a noise suppression network; the primary winding and the secondary winding form a transformer; the noise suppression network is connected between the primary static point and the secondary static point; the primary static point is the DC stable potential point at the input end of the DC / DC converter, and the secondary static point is the DC stable potential point at the output end of the DC / DC converter; the first parasitic capacitance of the first end of the primary winding relative to the secondary static point is equal to the second parasitic capacitance of the second end of the primary winding relative to the secondary static point; the noise suppression network generates a suppression current, the direction of which is opposite to the direction of the total noise current generated by the resonant inductor and the resonant capacitor, so as to suppress the total noise current. The voltage of the noise suppression network changes with the load size, realizing common-mode noise suppression in the full load range, and effectively reducing the common-mode noise formed between the primary winding and the secondary winding.

Description

[0001] This application is a divisional application of a Chinese patent application with the application number 202010930447.4, the application date of September 7, 2020, and the invention title of "A DC / DC Converter and Communication Power Supply". Technical Field

[0002] This application relates to the field of power electronics technology, and particularly to a DC / DC converter and a communication power supply. Background Art

[0003] Currently, switching power converters are widely used in communication power supplies due to their advantages such as high efficiency and small size. As the load capacity of the power consumption continues to expand, the requirement for the power density of the power module is getting higher and higher. However, the volume ratio of magnetic devices in current switching power converters is relatively large.

[0004] In order to reduce the volume occupied by magnetic devices, their operating frequency can be increased. For example, the operating frequency of the switching power supply can be increased from 200 kHz to 1 M - 10 MHz. However, increasing the switching frequency increases the switching noise (the bare noise increases by 20 dB+), which brings great pressure to the front-end filtering circuit. Therefore, how to reduce the noise of the switching power supply and the cost of the front-end filtering circuit has become an important research direction.

[0005] Currently, the main problem faced by switching power supplies is common-mode interference, and a common-mode inductor can be used for filtering. Refer to Figure 1 , which is a schematic diagram of suppressing common-mode interference provided by the prior art.

[0006] Figure 1 In

[0007]

[0008]

[0009] Summary of the Invention

[0010] To solve the above technical problems, this application provides a DC / DC converter and a communication power supply, which can suppress common-mode noise and is beneficial to the miniaturization of the switching power supply.

[0010] An embodiment of the present application provides a DC / DC converter, which is an LLC resonant DC / DC converter, which can be a full-bridge LLC resonant DC / DC converter or a half-bridge LLC resonant DC / DC converter. The working principle is to convert the input DC power into AC power, which is transmitted to the rectifier circuit at the output end through a transformer. The rectifier circuit rectifies the DC power and then outputs it. Since it is isolated by the transformer, it can play a role in isolating interference signals, and the interference signal of the primary winding of the transformer will not be transmitted to the secondary winding of the transformer.

[0011] The DC / DC converter includes: a primary winding, a secondary winding, a resonant inductor, a resonant capacitor and a noise suppression network; the primary winding, the resonant inductor and the resonant capacitor are connected in series to a first node and a second node; the secondary winding is connected to a third node and a fourth node; the primary winding and the secondary winding form a transformer; the noise suppression network is connected between the primary static point and the secondary static point of the transformer; the primary static point is a DC stable potential point at the input end of the DC / DC converter, and the secondary static point is a DC stable potential point at the output end of the DC / DC converter; the first parasitic capacitance of the first end of the primary winding relative to the secondary static point is equal to the second parasitic capacitance of the second end of the primary winding relative to the secondary static point; the noise suppression network is used to generate a suppression current, the direction of the total noise current generated by the resonant inductor and the resonant capacitor is opposite to the direction of the suppression current, the suppression current is used to suppress the total noise current, and the voltage of the noise suppression network changes with the change of load size.

[0012] Since it is difficult to achieve complete symmetry in actual design, the first parasitic capacitor C AD ≠The second parasitic capacitance C BD Therefore, a common-mode noise channel is formed between the primary winding and the secondary winding of the transformer. However, by adding a balancing capacitor, C AD =C BD On the basis of transformer symmetry, the common-mode noise source signal can be balanced to achieve common-mode noise cancellation. At the same time, the common-mode noise generated by the transformer leakage inductance can also be cancelled on the symmetrical transformer. The balancing capacitor can be added between point A and point D, or between point B and point D. The specific analysis requires C AD and C BD After adding the balancing capacitor, C AD =C BD That's it. The static point means that the DC potential of the static point is stable relative to GND. The static point exists on the primary side of the transformer and also on the secondary side of the transformer. As the name suggests, the potential of the moving point fluctuates relative to the static point.

[0013] On the basis that the technical solution includes a balancing capacitor in a DC / DC converter, a noise suppression network is added. The noise suppression network can generate a suppression current, and the direction of the suppression current is opposite to the direction of the total noise current generated by the resonant inductor and the resonant capacitor. Therefore, the total noise current generated by the resonant inductor and the resonant capacitor can be suppressed. The current source of the noise suppression network can be additionally added or can be sourced from the energy within the DC / DC converter. The noise suppression network is connected between the primary static point and the secondary static point of the transformer, thereby effectively reducing the common-mode noise formed on the parasitic capacitance between the primary winding and the secondary winding of the transformer in the resonant circuit. Moreover, the voltage of the noise suppression network changes with the load size. Therefore, it can be applied to the common-mode noise suppression in the full load range. Since the current changes when the load changes, and the voltage amplitude on the inductor (resonant inductor Lr and leakage inductor Lk) is proportional to the current, the voltage amplitudes on Lk, Lr, and the resonant capacitor Cr will all change with the load change. The voltage of the noise suppression network provided in this embodiment changes with the load size. Therefore, the common-mode noise suppression in the full load range can be achieved. Thus, regardless of the load size, the noise suppression network can automatically adjust its output according to the load size, and therefore can cancel the common-mode noise in the full load range.

[0014] Preferably, the noise suppression network includes: a signal source and an impedance network; the impedance network is for adjusting the magnitude of the voltage injected by the signal source between the primary static point and the secondary static point. The signal source is connected between the primary static point and the secondary static point in series with the impedance network.

[0015] Among them, the signal source can have multiple implementation manners. A signal source can be additionally added, or energy can be directly coupled from the converter to form a signal source. For example, energy can be coupled from the resonant inductor, or energy can be coupled from the resonant capacitor.

[0016] For example, the signal source couples energy from the resonant inductor; the voltage amplitude of the signal source is proportional to the voltage amplitude of the resonant inductor. That is, when the voltage on the resonant inductor increases, the voltage of the signal source also increases.

[0017] Specifically, to couple energy from the resonant inductor, the inductor can couple energy from the resonant inductor through a magnetic field, that is, the signal source includes a canceling inductor; the canceling inductor is used to couple energy from the resonant inductor, and the canceling inductor is connected between the primary static point and the secondary static point in series with the impedance network.

[0018] In specific implementation, for the convenience of winding and to save the magnetic core, the canceling inductor and the resonant inductor are wound around the same magnetic core.

[0019] In addition to using the above-mentioned canceling inductor to couple energy from the resonant inductor, energy can also be coupled from the resonant inductor through a capacitor. That is, the signal source includes: a first capacitor coupling circuit; the first capacitor coupling circuit is used to couple energy from the resonant inductor, and the first capacitor coupling circuit is connected between the primary static point and the secondary static point in series with the impedance network.

[0020] The signal source couples energy from the resonant capacitor; the voltage amplitude of the signal source is proportional to the voltage amplitude of the resonant capacitor. That is, when the voltage on the resonant capacitor increases, the voltage of the signal source also increases.

[0021] The above introduced is that the signal source couples energy from the resonant inductor. Next, the signal source coupling energy from the resonant capacitor will be introduced. Coupling energy from the resonant capacitor can be achieved in various ways. For example, energy can be coupled from the resonant capacitor through a capacitor coupling circuit, or energy can be coupled from the resonant capacitor through a coupling transformer. The following will be introduced separately.

[0022] That is, the signal source includes: a second capacitor coupling circuit; the second capacitor coupling capacitor is used to couple energy from the resonant capacitor, and the second capacitor coupling circuit is connected between the primary static point and the secondary static point in series with the impedance network.

[0023] That is, the signal source includes: a signal coupling transformer; the primary winding of the signal coupling transformer is used to couple energy from the resonant capacitor, and the secondary winding of the signal coupling transformer is connected between the primary static point and the secondary static point in series with the impedance network.

[0024] To achieve a better noise reduction effect, the sum of the total noise current generated by the resonant inductor and the resonant capacitor on the parasitic capacitance and the current of the canceling impedance is zero; the parasitic capacitance is the parasitic capacitance between the primary winding and the secondary winding.

[0025] That is, the expression is as follows:

[0026] V C / Z1 + V L / Z2 + V / Z = 0;

[0027] Where, V C represents the voltage across the resonant capacitor, V L represents the inductance across the resonant inductor, Z1 represents the impedance presented by C AD , Z2 represents the impedance presented by C BD .

[0028] Preferably, the DC / DC converter includes at least one of the following: a full-bridge LLC resonant DC / DC converter and a half-bridge LLC resonant DC / DC converter.

[0029] Preferably, it further includes: a full-wave rectifier circuit; the secondary winding includes: a first secondary winding and a second secondary winding; the first secondary winding is connected between the third node and the fifth node, and the second secondary winding is connected between the fifth node and the fourth node; the third node and the fourth node are connected to the full-wave rectifier circuit; the output end of the full-wave rectifier circuit is the output end of the DC / DC converter.

[0030] The signal source couples energy from the resonant inductor, without the need to additionally increase a signal source, which is simple and easy to implement. By winding a canceling inductor on the magnetic core of the resonant inductor, energy can be coupled from the resonant inductor. The amplitude of the injected signal can be adjusted through the impedance network Z connected in series with the canceling inductor. Since the currents through Cr and Lr will both change when the load varies, therefore, as the current changes, the amplitude of the voltage coupled by the canceling inductor also changes accordingly. Thus, this solution is applicable to noise suppression within the full load range.

[0031] Preferably, it further includes: a full-bridge rectifier circuit; the secondary winding is one; the third node and the fourth node are respectively the positive and negative poles of the input end of the full-bridge rectifier circuit; the output end of the full-bridge rectifier circuit is the output end of the DC / DC converter.

[0032] In addition, the impedance network includes at least one of the following: a resistor, a capacitor, and an inductor, that is, it includes at least one or more of the above three items. For example, the impedance network can include one, two, or three of the above items.

[0033] The embodiment of the present application further provides a communication power supply, which includes the DC / DC converter introduced above, and further includes: a rectifier circuit; the first end of the rectifier circuit is used to connect to an AC power supply; the rectifier circuit is used to convert the alternating current of the AC power supply into direct current; the second end of the rectifier circuit is used to connect to the first end of the DC / DC converter; the second end of the DC / DC converter is used to supply power to a load; the DC / DC converter is used to convert the direct current and provide it to the load.

[0034] The load can be any electrical device. Specifically, according to the different loads, the voltage output by the DC / DC converter 200 is different. For example, it can output voltages such as 48V, 12V, 5V, 3.3V, etc.

[0035] The communication power supply provided by the embodiment of the present application, due to the addition of a noise suppression network in the DC / DC converter therein, this noise suppression network can generate a suppression current, and the direction of the suppression current is opposite to the current directions of the resonant inductor and the resonant capacitor. Therefore, the total noise current generated by the resonant inductor and the resonant capacitor can be suppressed. The current source of this noise suppression network can be additionally added or can be sourced from the energy inside the DC / DC converter. The noise suppression network is connected between the primary static point and the secondary static point of the transformer, thereby effectively reducing the common-mode noise formed on the parasitic capacitance between the primary winding and the secondary winding of the transformer. Moreover, the voltage of this noise suppression network changes with the load size. Therefore, it can be applied to the common-mode noise suppression in the full load range. Therefore, the communication power supply with this DC / DC converter can achieve a better common-mode noise suppression effect, thereby providing a higher-quality power supply for the load.

[0036] Compared with the prior art, the technical solution provided by the embodiment of the present application has the following advantages:

[0037] The DC / DC converter provided by this technical solution is an LLC resonant DC / DC converter, including a transformer and a resonant circuit. The resonant circuit is connected in series with the primary winding of the transformer. The resonant circuit includes a series-connected resonant inductor and a resonant capacitor. Due to the leakage inductance of the transformer, when the load size is different, the magnitude of the current flowing through the leakage inductance is also different. Furthermore, the influence of different current magnitudes on the leakage inductance is different. When the inductance of the leakage inductance through which the current flows is larger, the influence of the leakage inductance as a noise source is greater and thus cannot be ignored. Therefore, in order to suppress the influence of common-mode noise in the full load range, on the premise that the first parasitic capacitance of the first end of the primary winding of the transformer relative to the secondary static point is equal to the second parasitic capacitance of the second end of the primary winding relative to the secondary static point, a noise suppression network is added in the DC / DC converter. This noise suppression network can generate a suppression current, and the direction of the suppression current is opposite to the direction of the total noise current generated by the resonant inductor and the resonant capacitor. Therefore, the total noise current generated by the resonant inductor and the resonant capacitor can be suppressed. The current source of this noise suppression network can be additionally added or can be sourced from the energy inside the DC / DC converter. The noise suppression network is connected between the primary static point and the secondary static point of the transformer, thereby effectively reducing the common-mode noise formed on the parasitic capacitance between the primary winding and the secondary winding of the transformer. Moreover, the voltage of this noise suppression network changes with the load size. Therefore, it can be applied to the common-mode noise suppression in the full load range. Description of the Drawings

[0038] Figure 1 It is a schematic diagram for suppressing common-mode interference provided by the prior art;

[0039] Figure 2Schematic diagram of a full-bridge LLC resonant DC / DC converter provided by an embodiment of the present application;

[0040] Figure 3 Schematic diagram of a half-bridge LLC resonant DC / DC converter provided by an embodiment of the present application;

[0041] Figure 4 Schematic diagram of another half-bridge LLC resonant DC / DC converter provided by an embodiment of the present application;

[0042] Figure 5 Schematic diagram of another full-bridge LLC resonant DC / DC converter provided by an embodiment of the present application;

[0043] Figure 6 Schematic diagram of a DC / DC converter provided by an embodiment of the present application;

[0044] Figure 7 Schematic diagram of a DC / DC converter in which a signal source couples energy from a resonant inductor provided by an embodiment of the present application;

[0045] Figure 8 Schematic diagram of another DC / DC converter in which a signal source couples energy from a resonant inductor provided by an embodiment of the present application;

[0046] Figure 9A Provided by an embodiment of the present application and Figure 7 and Figure 8 Corresponding small-signal model schematic diagram;

[0047] Figure 9B Schematic diagram of a capacitive coupling circuit coupling energy from a resonant inductor provided by an embodiment of the present application;

[0048] Figure 10 Schematic diagram of a DC / DC converter in which a signal source couples energy from a resonant capacitor provided by an embodiment of the present application;

[0049] Figure 11A Schematic diagram of another DC / DC converter in which a signal source couples energy from a resonant capacitor provided by an embodiment of the present application;

[0050] Figure 11B Schematic diagram of a signal coupling transformer coupling energy from a resonant capacitor provided by an embodiment of the present application;

[0051] Figure 12 Equivalent schematic diagram of a full-bridge LLC resonant DC / DC converter provided by an embodiment of the present application;

[0052] Figure 13 Equivalent schematic diagram of a half-bridge LLC resonant DC / DC converter provided by an embodiment of the present application;

[0053] Figure 14 Schematic diagram of a communication power supply provided by an embodiment of the present application. Specific embodiments

[0054] To enable those skilled in the art to better understand the technical solutions provided by the embodiments of the present application, the working principle of the DC / DC converter will be introduced first.

[0055] The DC / DC converter provided in the embodiments of the present application is an isolated switching power supply. Taking the LLC resonant DC / DC converter as an example, it can be a full-bridge LLC resonant DC / DC converter or a half-bridge LLC resonant DC / DC converter according to the circuit topology connected to the primary side of the transformer. The form of the rectifier circuit connected to the secondary winding of the transformer is not limited.

[0056] As Figure 2 shown, it is a schematic diagram of a full-bridge LLC resonant DC / DC converter provided by an embodiment of the present application.

[0057] The working principle of the LLC resonant DC / DC converter is to convert the input direct current into alternating current, which is transmitted to the rectifier circuit at the output end through the transformer. The rectifier circuit rectifies it into direct current and then outputs it. Since it passes through the transformer isolation, it can play the role of isolating interference signals, and the interference signals of the primary winding of the transformer will not be transmitted to the secondary winding of the transformer.

[0058] Figure 2 The primary winding of the transformer in [[ ]] includes the exciting winding Lm. In addition, the leakage inductances Lk of the primary winding and the secondary winding of the transformer are also drawn at the position of the primary winding of the transformer.

[0059] The resonant inductor Lr and the resonant capacitor Cr are connected in series with the primary winding of the transformer to form LLC resonance.

[0060] Figure 2 Taking the connection of the secondary winding of the transformer to the full-wave rectifier circuit as an example for illustration in [[ ]].

[0061] The primary winding of the transformer, Lr and Cr are connected in series between the first node and the second node. As shown in the figure, the first node is the midpoint V1N of the first bridge arm of the full bridge, and the second node is the midpoint V2N of the second bridge arm of the full bridge.

[0062] The secondary winding of the transformer is connected between the third node C and the fourth node E. When the rectifier circuit at the output end of the DC / DC converter is a full-wave rectifier circuit, the secondary winding of the transformer also includes a center tap, that is, the point D is the lead-out end of the center tap of the secondary winding. Figure 2 In [[ ]], the points D and G are respectively the positive and negative poles of the output end of the DC / DC converter, and the negative pole is grounded.

[0063] The static point of the primary side of the transformer is the positive pole (point M) or the negative pole (point N) of the input end of the DC / DC converter, and the static point of the secondary side of the transformer is the positive pole (i.e., point D) or the ground of the output end of the DC / DC converter;

[0064] The static point in the embodiment of the present application refers to a static point for AC small signals, that is, for the ground potential GND, the potential of the static point is a DC stable potential point, that is, relative to GND, the DC potential of the static point is stable. As the name implies, relative to the static point, the potential of the moving point is fluctuating. For example, for the transformer, the potentials of points C and E are fluctuating and belong to AC potentials. Therefore, points C and E are the moving points on the secondary side of the transformer, while points A and B are the moving points on the primary side of the transformer.

[0065] The above describes the structure of the full-bridge LLC resonant DC / DC converter. Next, the structures of two half-bridge LLC resonant DC / DC converters will be introduced.

[0066] As Figure 3 shown, it is a schematic diagram of a half-bridge LLC resonant DC / DC converter provided by an embodiment of the present application.

[0067] Figure 3 For the half-bridge LLC resonant DC / DC converter shown, there is only one bridge arm in the conversion circuit connected to the primary side of the transformer. One end of the primary winding of the transformer is connected to the midpoint V1N of the bridge arm, and the other end of the primary winding of the transformer is connected to the common end V2N of capacitors C1 and C2.

[0068] The other connection relationships are the same as those in Figure 2 and will not be elaborated here.

[0069] As Figure 4 shown, it is a schematic diagram of another half-bridge LLC resonant DC / DC converter provided by an embodiment of the present application.

[0070] Figure 4 The difference between the half-bridge LLC resonant DC / DC converter shown and Figure 3 is that both ends of the primary winding are connected to the same bridge arm. One end of the primary winding is connected to the midpoint V1N of the bridge arm, and the other end of the primary winding is connected to the other output end V2N of the bridge arm.

[0071] Figure 3 And Figure 4 are respectively two topological forms of the half-bridge LLC resonant DC / DC converter in which the primary winding is connected, Figure 4 And Figure 3 only differ in the connection position of V2N.

[0072] As Figure 5As shown, it is a schematic diagram of another full-bridge LLC resonant DC / DC converter provided by an embodiment of the present application.

[0073] Figures 2 - 4 The rectifier circuits connected to the secondary windings shown are all full-wave rectifier circuits. Figure 5 The rectifier circuit shown is a full-bridge rectifier circuit.

[0074] The first end C of the secondary winding is connected to the first input terminal of the full-bridge rectifier circuit, and the second end E of the secondary winding is connected to the second input terminal of the full-bridge rectifier circuit. The positive pole of the output terminal of the full-bridge rectifier circuit is point D, and the negative pole of the output terminal of the full-bridge rectifier circuit is point G, that is, the ground.

[0075] Points D and G can be connected to a load, that is, an electrical device.

[0076] For the DC / DC converters of the above several topologies, due to the presence of switching tubes, resonant inductors, resonant capacitors, and transformer leakage inductance, these are all sources of common-mode noise. The transformer transfers this common-mode noise from the primary winding to the secondary winding during the energy transfer process, serving as a transmission path for interference.

[0077] Therefore, the technical solution provided by the embodiment of the present application is that on the premise that the first parasitic capacitance C between the first end of the primary winding of the transformer and the static point of the secondary side is equal to the second parasitic capacitance C between the second end of the primary winding and the static point of the secondary winding, that is, C AD = C BD When they are equal, the two moving points A and B of the primary winding of the transformer are symmetric with respect to the static point D of the secondary winding. Then, by adding a signal source, the common-mode interference in the DC / DC converter is canceled within the full load range. The following will be introduced in detail with reference to the accompanying drawings. It should be noted that the technical solutions provided by all embodiments of the present application are applicable to AD = C BD any DC / DC converter of a topological form. Figures 2 - 5

[0078] DC / DC converter Embodiment 1:

[0079] Figure 6 Refer to Figure 6 , this figure is a schematic diagram of a DC / DC converter provided by an embodiment of the present application.

[0080] In this embodiment, a full-bridge LLC resonant DC / DC converter is taken as an example, and the rectifier circuit connected to the secondary winding is a full-wave rectifier circuit for introduction.

[0081] The DC / DC converter provided by this embodiment includes: a primary winding, a secondary winding, a resonant inductor Lr, a resonant capacitor Cr, and a noise suppression network;

[0082] For the convenience of analyzing its working principle, an example is introduced where the noise suppression network may include a signal source V and an impedance network Z; the signal source V is used to generate voltage and current signals, and the impedance network Z is used to match the suppression current output by the noise suppression network.

[0083] The primary winding, the resonant inductor Lr, and the resonant capacitor Cr are connected in series between the first node V1N and the second node V2N;

[0084] The secondary winding is connected between the third node D and the fourth node E;

[0085] The primary winding and the secondary winding form a transformer;

[0086] The signal source V is connected between the primary static point and the secondary static point of the transformer; the primary static point is the DC stable potential point at the input end of the DC / DC converter, and the secondary static point is the DC stable potential point at the output end of the DC / DC converter. For example, the primary static point is the positive pole M or the negative pole N at the input end of the DC / DC converter, and the secondary static point is the positive pole D or the ground G at the output end of the DC / DC converter;

[0087] The first parasitic capacitance of the first end of the primary winding relative to the secondary static point is equal to the second parasitic capacitance of the second end of the primary winding relative to the secondary static point;

[0088] The noise suppression network is used to generate a suppression current, and the direction of the suppression current is opposite to the direction of the total noise current generated by the resonant inductor and the resonant capacitor, and is used to suppress the total noise current generated by the resonant inductor and the resonant capacitor. The voltage of the noise suppression network changes with the load size.

[0089] Figure 6 In the example, the signal source V is introduced with it connected between the primary static point N and the secondary static point D. Additionally, the signal source V can also be connected between the primary static point M and the secondary static point G.

[0090] In practical applications, there is a parasitic capacitance between the primary winding and the secondary winding of the transformer. For the convenience of introduction, the parasitic capacitance is equivalent to Figure 6 the first parasitic capacitance C of point A at the first end of the primary winding relative to the secondary static point D as shown in AD and the second parasitic capacitance C of point B at the second end of the primary winding relative to the secondary static point D, BD that is, the parasitic capacitance is equivalent between point A and point B of the primary winding of the transformer and point D of the secondary winding. In reality, the parasitic capacitance may be evenly distributed between the primary winding and the secondary winding.

[0091] Due to the fact that in actual design, it is difficult to achieve complete symmetry, thus the first parasitic capacitance CAD ≠The second parasitic capacitance C BD Therefore, a common-mode noise channel is formed between the primary winding and the secondary winding of the transformer. However, by adding a balancing capacitor, C AD =C BD On the basis of transformer symmetry, the common-mode noise source signal can be balanced to achieve common-mode noise cancellation. At the same time, the common-mode noise generated by the transformer leakage inductance can also be cancelled on the symmetrical transformer. The balancing capacitor can be added between point A and point D, or between point B and point D. The specific analysis requires C AD and C BD After adding the balancing capacitor, C AD =C BD That's it.

[0092] When the LLC resonant DC / DC converter works in the resonant state, the total noise of Lk+Lr is equal to the total noise of Cr in amplitude, but in opposite phases, VLr+VCr+VLk=0; in fact, Lk is evenly distributed in the transformer, and Lk cannot be ignored, so the noise amplitudes of Lr and Cr are not equal and cannot be offset, VLr+VCr≠0, and the amplitude of the current component on Lk varies with the size of the load, and is not a fixed value, that is, the load size will affect the current component on Lk, thereby affecting the amplitude of VLr+VCr. When the current flowing through Lk is larger, the proportion of Lk in (Lk+Lr) is larger, and the influence of Lk as a noise source cannot be ignored.

[0093] The technical solution includes a balancing capacitor in the DC / DC converter, and adds a noise suppression network. The noise suppression network can generate a suppression current, and the direction of the suppression current is opposite to the direction of the total noise current generated by the resonant inductor and the resonant capacitor, so the total noise current generated by the resonant inductor and the resonant capacitor can be suppressed. The current source of the noise suppression network can be additionally added, or it can be derived from the energy inside the DC / DC converter. The noise suppression network is connected between the primary side static point and the secondary side static point of the transformer, so that the common mode noise formed by the resonant circuit on the parasitic capacitance between the primary winding and the secondary winding of the transformer can be effectively reduced. In addition, the voltage of the noise suppression network changes with the load size, so it can be applied to common mode noise suppression in the full load range.

[0094] When the load changes, the current will change. Since the voltage amplitude across the inductors (Lr and Lk) is proportional to the current, the voltage amplitudes across Lk, Lr, and Cr will all change as the load changes. The voltage of the noise suppression network provided in this embodiment changes with the load size, so common-mode noise suppression can be achieved within the full load range. Thus, regardless of the load size, the noise suppression network can automatically adjust its output according to the load size, and therefore can cancel the common-mode noise within the full load range.

[0095] The following describes the implementation method of the signal source coupling energy from inside the DC / DC converter. Energy can be coupled from the resonant inductor or from the resonant capacitor. The following will be described in detail with reference to the accompanying drawings respectively.

[0096] DC / DC Converter Embodiment 2:

[0097] In this embodiment, the case where the signal source couples energy from the resonant inductor is taken as an example for introduction.

[0098] See Figure 7 , which is a schematic diagram of the DC / DC converter in which the signal source couples energy from the resonant inductor provided by the embodiment of the present application.

[0099] The signal source provided in this embodiment includes an impedance network Z and a cancellation inductor; as shown in the figure, the inductance coupled on the cancellation inductor is V.

[0100] The cancellation inductor can be a winding. The cancellation inductor couples energy from the resonant inductor Lr. Specifically, in implementation, it can be wound on the same magnetic core as Lr, that is, share the same magnetic core with Lr.

[0101] The cancellation inductor is connected between the primary static point N and the secondary static point D in series with the impedance network Z. Figure 7 In Figure 8 , the signal source is connected between N and D. Additionally, as shown in

[0102] , the signal source can also be connected between the primary static point M and the secondary static point G.

[0103] The impedance network Z is used to adjust the magnitude of the voltage injected by the signal source between the primary static point and the secondary static point.

[0104] In this embodiment, the specific implementation manner of the impedance network Z is not specifically limited. The impedance network Z is a two-port network and can be connected in series with the cancellation inductor. For example, the impedance network Z can at least include any one of the following: resistor, inductor, and capacitor. That is, it can be at least one, two, or three of the above three. For example, Z can include an inductor, or can include an inductor and a resistor, or can include a capacitor and a resistor, or can include an inductor and a capacitor, or can simultaneously include an inductor, a resistor, and a capacitor.

[0105] Figure 7 As can be seen, the voltage V coupled by the cancellation inductor from Lr is opposite to the voltage across Lr. The same-name terminal of the cancellation inductor is connected to the primary static point M, and the opposite-name terminal of the cancellation inductor is connected to the secondary static point G through the impedance network Z. That is, the same-name terminal of the cancellation inductor is close to the primary static point, and the opposite-name terminal of the cancellation inductor is close to the secondary static point.

[0106] Figure 7 The LISN in it is grounded, indicating that the line impedance stabilization network (LISN) in the electromagnetic compatibility (EMC) test is grounded.

[0107] See Figure 9A This figure is a schematic diagram of the small-signal model corresponding to Figure 7 and Figure 8

[0108] Next, analyze in combination with Figure 9A the small-signal model shown. Figure 9A Short-circuiting V1N and V2N together in the small-signal model shown does not affect the calculation of V.

[0109] First, since the signal amplitudes at the two points V1N and V2N are equal and the phases are opposite, when C AD = C BD the noise generated by V1N and V2N cancels each other out.

[0110] Second, since Lk is uniformly distributed inside the transformer and the parasitic capacitances at both ends of the transformer are balanced, that is, when C AD = C BD the noise generated by Lk cancels out.

[0111] Third, in order to achieve a better noise reduction effect, the sum of the total noise current generated by the resonant inductor and the resonant capacitor on the parasitic capacitance and the current of the cancellation impedance is zero; where the parasitic capacitance refers to the parasitic capacitance between the primary winding and the secondary winding, that is, the expression is as follows:

[0112] V C / Z1 + V L / Z2 + V / Z = 0;

[0113] Wherein, V C represents the voltage across the resonant capacitor, V L represents the inductance across the resonant inductor, Z1 represents the impedance presented by C AD and Z2 represents the impedance presented by C BD .

[0114] Since the canceling inductor is reversely coupled with the resonant inductor Lr, thus, V = -n1V L .

[0115] Wherein, n1 represents the turns ratio of the canceling inductor to the resonant inductor Lr

[0116] In actual operation, when the DC / DC converter operates at the resonant frequency point, the voltage V of the resonant inductor L , the voltage V of the resonant capacitor C and the voltage V of the leakage inductance of the transformer satisfy the following relationship: V Lk + V L - V Lk - V C = 0

[0117] It should be noted that during actual operation, the DC / DC converter does not necessarily operate exactly at the resonant frequency point; it is sufficient to operate approximately at the resonant frequency point. For example, V L + V Lk - V C is approximately equal to 0

[0118] Since the leakage inductance Lk of the transformer is in series with the resonant inductor Lr, thus, V C = V L + V Lk = (1 + n)V L .

[0119] Wherein, n = V Lk / V L .

[0120] Also, since C AD = C BD , thus, Z = [n1 / (n + 2)]Z1

[0121] Therefore, by using the above formula, the impedance value presented by the impedance network can be obtained

[0122] In the technical solution provided in this embodiment, the signal source couples energy from the resonant inductor. There is no need to additionally increase the signal source, which is simple and easy to implement. By winding a canceling inductor on the magnetic core of the resonant inductor, energy can be coupled from the resonant inductor. The amplitude of the injected signal can be adjusted through the impedance network Z connected in series with the canceling inductor. Since the currents passing through Cr and Lr will both change when the load changes, therefore, as the current changes, the amplitude of the voltage coupled by the canceling inductor also changes accordingly. Therefore, this solution is applicable to noise suppression within the full load range.

[0123] The comparison table of the technical solution provided in this embodiment with respect to the case where no signal source is set for canceling and reducing noise is as follows.

[0124] Table 1

[0125]

[0126] Analyzing the data in Table 1, it can be seen that when using the signal source provided in the embodiment of the present application for canceling and reducing noise, the area of the circuit board occupied by the filter circuit is reduced to nearly one-third of the previous value, that is, the area is reduced by 2 / 3. That is, while this solution suppresses the common-mode noise, it reduces the area of the circuit board, and the effect is remarkable, which is beneficial to the miniaturization of the DC / DC converter and also beneficial to the miniaturization of the entire communication power supply.

[0127] In the above embodiment, energy is coupled from the resonant inductor through the canceling inductor. Additionally, energy can also be coupled from the resonant inductor through a capacitive coupling circuit.

[0128] See Figure 9B , this figure is a schematic diagram of the capacitive coupling capacitor coupling energy from the resonant inductor provided in the embodiment of the present application.

[0129] For the DC / DC converter provided in this embodiment, the signal source may include: a first capacitive coupling circuit Z2;

[0130] The first capacitive coupling circuit Z2 couples energy from the resonant inductor Lr, and after the first capacitive coupling circuit Z2 is connected in series with the impedance network Z, it is connected between the primary static point N and the secondary static point D. Additionally, after Z2 and Z are connected in series, they can also be coupled between other primary static points and other secondary static points, not limited to the Figure 9B shown connection method.

[0131] The above introduction is about coupling energy from the resonant point inductor. Next, coupling energy from the resonant capacitor will be introduced.

[0132] DC / DC Converter Embodiment Three:

[0133] See Figure 10, this figure is a schematic diagram of a DC / DC converter in which a signal source couples energy from a resonant capacitor provided by an embodiment of the present application.

[0134] This embodiment describes that the signal source couples energy from the resonant capacitor Cr; the voltage amplitude V of the signal source is proportional to the voltage amplitude of the resonant capacitor Cr.

[0135] When the signal source couples energy from the resonant capacitor Cr, the signal source may include: a second capacitor coupling circuit Z3;

[0136] The second capacitor coupling circuit Z3 couples energy from the resonant capacitor Cr. Specifically, both ends of the second capacitor coupling circuit Z3 are respectively connected to both ends of Cr, and after Z3 and the impedance network Z are connected in series, they are connected between the primary static point and the secondary static point.

[0137] Figure 10 Taking the example where Z3 and Z are connected in series and then connected to the primary static point M and the secondary static point G, in addition, after Z3 and Z are connected in series, they can also be connected to the primary static point N and the secondary static point D as shown in Figure 11A See Figure 11A , this figure is a schematic diagram of another DC / DC converter in which a signal source couples energy from a resonant capacitor provided by an embodiment of the present application.

[0138] The following analyzes the specific working principle.

[0139] First, since the signal amplitudes at points V1N and V2N are equal and the phases are opposite, when C AD = C BD , the noises generated at V1N and V2N cancel each other out.

[0140] Second, since Lk is evenly distributed inside the transformer and the parasitic capacitances at both ends of the transformer are balanced, that is, when C AD = C BD , the noise generated by Lk is cancelled.

[0141] Third, in order to achieve a better noise reduction effect, the sum of the total noise current generated by the resonant inductor and the resonant capacitor on the parasitic capacitance and the current of the cancellation impedance is zero; where the parasitic capacitance refers to the parasitic capacitance between the primary winding and the secondary winding, that is, the expression is as follows:

[0142] V C / Z1 + V L / Z2 + V / Z = 0;

[0143] Among them, V C represents the voltage across the resonant capacitor, V L represents the inductance across the resonant inductor, Z1 represents the impedance presented by C AD , and Z2 represents the impedance presented by C BD .

[0144] Since the cancellation impedance is reversely coupled with the resonant capacitor Cr, V = -n2V C .

[0145] where n2 represents the ratio of the coupled voltage of the cancellation impedance to the voltage across Cr.

[0146] In actual operation, when the DC / DC converter operates at the resonant frequency point, V L +V Lk -V C = 0.

[0147] Since the leakage inductance Lk of the transformer is in series with the resonant inductance Lr, V C = V L +V Lk = (1 + n)V L .

[0148] where n = V Lk / V L .

[0149] Also, since C AD = C BD , Z = [n2(n + 1) / (n + 2)]Z1.

[0150] The impedance magnitude presented by the impedance network can be obtained from the above formula.

[0151] The implementation method introduced above couples energy from the resonant capacitor through a capacitive coupling capacitor. Additionally, energy can also be coupled from the resonant capacitor through a transformer. For details, see Figure 11B , which is a schematic diagram of the signal coupling transformer coupling energy from the resonant capacitor provided in the embodiment of the present application.

[0152] The signal source includes: a signal coupling transformer T;

[0153] The primary winding of the signal coupling transformer T couples energy from the resonant capacitor Cr, and the secondary winding of the signal coupling transformer T is connected between the primary static point and the secondary static point in series with the impedance network Z.

[0154] Figure 11B Taking the secondary winding of T connected in series with the impedance network Z and connected between the primary static point M and the secondary static point D in

[0155] For the technical solution provided in this embodiment, the signal source couples energy from the resonant capacitor, without the need to additionally increase the signal source, which is simple and easy to implement. By connecting a cancellation impedance in parallel at both ends of the resonant capacitor, energy can be coupled from the resonant capacitor. The amplitude of the injected signal can be adjusted through the impedance network Z connected in series with the cancellation impedance. Since the currents passing through Cr and Lr will both change when the load changes, therefore, as the current changes, the amplitude of the voltage coupled by the cancellation impedance also changes accordingly. Thus, this solution is applicable to noise suppression within the full load range.

[0156] The above introduced the working principle by taking the secondary winding of the transformer connected to a full-wave rectifier circuit as an example. When the secondary winding of the transformer is connected to a full-bridge rectifier circuit, the equivalent forms of the parasitic capacitance between the primary winding and the secondary winding of the transformer are as Figure 12 and Figure 13 shown, where Figure 12 is that the primary winding of the transformer is connected to a full-bridge LLC resonant circuit, Figure 13 is that the primary winding of the transformer is connected to a half-bridge LLC resonant circuit.

[0157] Figure 12 and Figure 13 both include two parasitic capacitances, which are C AC and C BC respectively, that is, the parasitic capacitance C AC is between the first end of the primary winding and the first end of the secondary winding, and the parasitic capacitance C BC is between the second end of the primary winding and the first end of the secondary winding.

[0158] Similar to Figure 6 , for the topologies shown in Figure 12 and Figure 13 , on the premise of the symmetry of the transformer, the first parasitic capacitance of the first end of the primary winding relative to the static point of the secondary winding is equal to the second parasitic capacitance of the second end of the primary winding relative to the static point of the secondary winding, that is, C AC = C BC . The equality of C AC = C BC can be achieved by adding a balancing capacitance, that is, adding a balancing capacitance between A and C, or between B and C. When C AC = C BCBased on this, in the embodiments of the present application, by adding a noise suppression network on the basis of including a balancing capacitor, this noise suppression network can generate a suppression current, and the direction of the suppression current is opposite to the direction of the total noise current generated by the resonant inductor and the resonant capacitor. Therefore, the total noise current generated by the resonant inductor and the resonant capacitor can be suppressed. The current source of this noise suppression network can be additionally added or can come from the energy inside the DC / DC converter. The noise suppression network is connected between the primary static point and the secondary static point of the transformer, thereby effectively reducing the common-mode noise formed on the parasitic capacitance between the primary winding and the secondary winding of the transformer. Moreover, the voltage of this noise suppression network changes with the load size. Therefore, it can be applied to the common-mode noise suppression in the full load range.

[0159] For the technical solutions of the above various embodiments, if they are not implemented in parallel, they can be used interchangeably without specific limitations.

[0160] Embodiment of communication power supply

[0161] Based on a DC / DC converter provided by the above embodiments, the embodiments of the present application also provide a communication power supply, which will be introduced in detail below with reference to the accompanying drawings.

[0162] See Figure 14 , this figure is a schematic diagram of a communication power supply provided by the embodiments of the present application.

[0163] The communication power supply provided by this embodiment includes the DC / DC converter 200 introduced in any one of the above embodiments, and further includes: a rectification circuit 300;

[0164] The first end of the rectification circuit 300 is used to connect to the AC power supply AC, and the rectification circuit 300 is used to convert the alternating current of the AC power supply AC into direct current;

[0165] The second end of the rectification circuit 300 is used to connect to the first end of the DC / DC converter 200; the second end of the DC / DC converter 200 is used to supply power to the load;

[0166] The DC / DC converter 200 is used to convert the direct current and provide it to the load.

[0167] The load can be any electrical device. Specifically, depending on the different loads, the voltage output by the DC / DC converter 200 is different. For example, it can output voltages such as 48V, 12V, 5V, 3.3V, etc.

[0168] The communication power supply provided by the embodiment of the present application, because a noise suppression network is added to the DC / DC converter therein, the noise suppression network can generate a suppression current, and the direction of the suppression current is opposite to the current directions of the resonant inductor and the resonant capacitor. Therefore, the total noise current generated by the resonant inductor and the resonant capacitor can be suppressed. The current source of the noise suppression network can be additionally added, or can be sourced from the energy inside the DC / DC converter. The noise suppression network is connected between the primary static point and the secondary static point of the transformer, so that the common-mode noise formed on the parasitic capacitance between the primary winding and the secondary winding of the transformer in the resonant circuit can be effectively reduced. Moreover, the voltage of the noise suppression network changes with the load size. Therefore, it can be applied to the common-mode noise suppression in the full load range. Therefore, the communication power supply with this DC / DC converter can achieve a better effect of common-mode noise suppression, thereby providing a higher-quality power supply for the load.

[0169] It should be understood that in the present application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Among them, A and B can be singular or plural. The character " / " generally means that the associated objects before and after are in an "or" relationship. "At least one (one) of the following" or its similar expression refers to any combination of these items, including any combination of single item (one) or plural items (ones). For example, at least one (one) of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0170] As described above, it is only a preferred embodiment of the present application and does not impose any formal limitation on the present application. Although the present application has been disclosed above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present application, or modify it into an equivalent embodiment with equivalent changes, without departing from the scope of the technical solution of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application still fall within the scope of protection of the technical solution of the present application.

Claims

1. A DC / DC converter, characterized in that, Comprising: A primary winding, a secondary winding, a resonant inductor, a resonant capacitor, and a noise suppression network; The primary winding and the secondary winding form a transformer; The noise suppression network is connected between the primary static point and the secondary static point of the transformer; the primary static point is the DC stable potential point at the input end of the DC / DC converter, and the secondary static point is the DC stable potential point at the output end of the DC / DC converter; The first parasitic capacitance of the first end of the primary winding relative to the secondary static point is equal to the second parasitic capacitance of the second end of the primary winding relative to the secondary static point; The noise suppression network is used to generate a suppression current, and the direction of the suppression current is opposite to the direction of the total noise current generated by the resonant inductor and the resonant capacitor; The noise suppression network includes: a signal source and an impedance network; the signal source couples energy from the resonant inductor or the resonant capacitor; the signal source is connected between the primary static point and the secondary static point in series with the impedance network.

2. The DC / DC converter according to claim 1, wherein The signal source couples energy from the resonant inductor; The voltage amplitude of the signal source is proportional to the voltage amplitude of the resonant inductor.

3. The DC / DC converter according to claim 2, wherein, The signal source includes a canceling inductor; The canceling inductor is used to couple energy from the resonant inductor, and the canceling inductor is connected between the primary static point and the secondary static point in series with the impedance network.

4. The DC / DC converter according to claim 3, characterized in that, The canceling inductor and the resonant inductor are wound around a common magnetic core.

5. The DC / DC converter according to claim 2, characterized in that, The signal source includes: a first capacitor coupling circuit; The first capacitor coupling circuit is used to couple energy from the resonant inductor, and the first capacitor coupling circuit is connected between the primary static point and the secondary static point in series with the impedance network.

6. The DC / DC converter according to claim 1, characterized in that, The signal source couples energy from the resonant capacitor; The voltage amplitude of the signal source is proportional to the voltage amplitude of the resonant capacitor.

7. The DC / DC converter according to claim 6, characterized in that, The signal source includes: a second capacitor coupling circuit; The second capacitor coupling circuit is used to couple energy from the resonant capacitor, and the second capacitor coupling circuit and the impedance network are connected between the primary static point and the secondary static point in series.

8. The DC / DC converter according to claim 6, characterized in that, The signal source includes: a signal coupling transformer; The primary winding of the signal coupling transformer is used to couple energy from the resonant capacitor, and the secondary winding of the signal coupling transformer is connected between the primary static point and the secondary static point in series with the impedance network.

9. The DC / DC converter according to any one of claims 2-6, characterized in that, The sum of the total noise current generated by the resonant inductor and the resonant capacitor on the parasitic capacitance and the current of the canceling impedance is zero; The canceling impedance is the impedance of the impedance network; The parasitic capacitance is the parasitic capacitance between the primary winding and the secondary winding; 10. The DC / DC converter according to claim 9, wherein The DC / DC converter includes at least one of the following: a full-bridge LLC resonant DC / DC converter and a half-bridge LLC resonant DC / DC converter.

11. The DC / DC converter according to claim 1, characterized in that, The impedance network includes at least one of the following: a resistor, a capacitor, and an inductor.

12. A communication power supply, characterized in that, Comprising the DC / DC converter according to any one of claims 1-11, further comprising: a rectifier circuit; The first end of the rectifier circuit is used to connect to an AC power source; The rectifier circuit is used to convert the alternating current of the AC power source into direct current; The second end of the rectifier circuit is used to connect to the first end of the DC / DC converter; The second end of the DC / DC converter is used to supply power to the load; The DC / DC converter is used to convert the direct current and supply it to the load.

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