Rectification control circuit and switching power supply with large current output

Abstract

The application discloses an LLC output large-current rectification control circuit and a switching power supply, and the circuit comprises a first primary side switch module, a second primary side switch module, a transformer, a first secondary side MOS tube, a second secondary side MOS tube, a first inductor, a second inductor and an output capacitor; the output end of the first primary side switch module is connected with the input end of the second primary side switch module and the primary winding of the transformer, and the output end of the second primary side switch module and the primary winding of the transformer are grounded; the first end of the secondary winding of the transformer is connected with the first end of the first inductor and the second secondary side MOS tube, the second end of the secondary winding of the transformer is connected with the first end of the second inductor and the first secondary side MOS tube, the first secondary side MOS tube is connected with the first end of the first inductor, the second secondary side MOS tube is connected with the second inductor, the first secondary side MOS tube and the second secondary side MOS tube are connected with the output capacitor, and the first inductor and the second inductor are connected with the output capacitor. According to the scheme, the current flowing through the output capacitor is always two-way current, and the problem of the ripple current of the output capacitor is improved.

Description

Technical Field

[0001] This invention relates to the field of rectifier circuits, and more specifically to a rectifier control circuit and switching power supply with a large current output from an LLC converter. Background Technology

[0002] LLC is a resonant circuit that contains inductors, capacitors, and resistors. It can achieve a constant output voltage resonance by controlling the switching frequency (frequency regulation). Its advantage is that through soft-switching technology, it can reduce the switching losses of the power supply and improve the efficiency and power density of the power converter.

[0003] Existing LLC topologies are widely used due to their high efficiency in soft-switching operation. However, this topology has a drawback: the output capacitor ripple current ratio is very large, theoretically 0.48 times the output current. When the output current is relatively large, the drawbacks of LLC topologies become more pronounced, and the size, cost, and lifespan of the output capacitor all become disadvantages.

[0004] Therefore, a rectifier control circuit for high current output of LLC is needed.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a rectifier control circuit and switching power supply with large current output of LLC.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention proposes a rectifier control circuit for a large current output of an LLC, comprising a first primary-side switching module, a second primary-side switching module, a transformer, a first secondary-side MOSFET, a second secondary-side MOSFET, a first inductor, a second inductor, and an output capacitor; the input terminal of the first primary-side switching module is connected to a power input, the output terminal of the first primary-side switching module is connected to the input terminal of the second primary-side switching module and the first terminal of the primary winding of the transformer, and the output terminal of the second primary-side switching module and the second terminal of the primary winding of the transformer are grounded;

[0009] The first end of the secondary winding of the transformer is connected to the first end of the first inductor and the gate (G) of the second secondary MOSFET. The second end of the secondary winding of the transformer is connected to the first end of the second inductor and the gate (G) of the first secondary MOSFET. The drain (D) of the first secondary MOSFET is connected to the first end of the first inductor. The drain (D) of the second secondary MOSFET is connected to the first end of the second inductor. The source (S) of the first and second secondary MOSFETs is connected to the negative terminal of the output capacitor. The second ends of the first and second inductors are connected to the positive output terminal of the output capacitor.

[0010] Furthermore, the first primary-side switching module includes a first primary-side MOSFET, a first transistor, a first resistor, a second resistor, and a third resistor; the power input is connected to the drain (D) terminal of the first primary-side MOSFET, the gate (G) terminal of the first primary-side MOSFET is connected to the first terminals of the first and second resistors, the second terminal of the first resistor is connected to the emitter (e) terminal of the first transistor and the first terminal of the third resistor, the base (b) terminal of the first transistor is connected to the second terminal of the third resistor and the first control terminal, and the collector (C) terminal of the first transistor and the second terminal of the second resistor are connected to the first terminal of the primary winding of the transformer.

[0011] Furthermore, the second primary-side switching module includes a second primary-side MOSFET, a second transistor, a fourth resistor, a fifth resistor, and a sixth resistor; the drain (D) of the second primary-side MOSFET is connected to the first terminal of the primary winding of the transformer, the gate (G) of the second primary-side MOSFET is connected to the first terminals of the fourth and fifth resistors, the second terminal of the fourth resistor is connected to the emitter (e) of the second transistor and the first terminal of the sixth resistor, the base (B) of the second transistor is connected to the second terminal of the sixth resistor and the second control terminal, and the collector (C) of the second transistor, the second terminal of the fifth resistor, and the source (S) of the second primary-side MOSFET are grounded.

[0012] Furthermore, it also includes a first secondary capacitor, a seventh resistor, and an eighth resistor. The first terminal of the first secondary capacitor is connected to the second terminal of the secondary winding of the transformer, the second terminal of the first secondary capacitor is connected to the first terminal of the seventh resistor, the second terminals of the seventh resistor and the eighth resistor are connected to the gate (G) terminal of the first secondary MOSFET, and the first terminal of the eighth resistor is connected to the source (S) terminal of the first secondary MOSFET.

[0013] Furthermore, it also includes a second secondary capacitor, a ninth resistor, and a tenth resistor. The first terminal of the second secondary capacitor is connected to the first terminal of the secondary winding of the transformer, the second terminal of the second secondary capacitor is connected to the first terminal of the ninth resistor, the second terminals of the ninth and tenth resistors are connected to the gate (G) terminal of the second secondary MOSFET, and the first terminal of the tenth resistor is connected to the source (S) terminal of the second secondary MOSFET.

[0014] Furthermore, both the first inductor and the second inductor are energy storage inductors.

[0015] Furthermore, it also includes an input capacitor, the positive terminal of which is connected to the input terminal of the first primary-side switching module, and the negative terminal is grounded.

[0016] Furthermore, it also includes a filter capacitor, the first end of which is connected to the second end of the primary winding of the transformer, and the second end of which is grounded.

[0017] Furthermore, the output capacitor is an electrolytic capacitor.

[0018] Secondly, the present invention also proposes a switching power supply, including a rectifier control circuit for a large current output LLC as described in any of the preceding claims.

[0019] The beneficial effects of this invention compared with the prior art are as follows: This invention provides a rectifier control circuit and switching power supply for LLC outputting large current. By alternately turning on the first primary-side switching module and the second primary-side switching module, the first secondary-side MOSFET and the second secondary-side MOSFET of the transformer also alternately and complementaryly turn on, so that the current flowing through the output capacitor is always a dual current, which improves the ripple current problem of the output capacitor, while ensuring the soft-switching characteristics of the LLC.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of the present invention more obvious and understandable, preferred embodiments are described in detail below. Attached Figure Description

[0021] Figure 1 A circuit diagram of a large current rectifier control circuit for LLC output, which is a specific embodiment of the present invention;

[0022] Figure 2 The diagram shows the output current effect of the LLC high-current rectifier control circuit according to a specific embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] 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 some embodiments of the present invention, and not all embodiments. 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.

[0025] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] 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 invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] In this invention, 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 connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical 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 invention according to the specific circumstances.

[0028] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0030] refer to Figure 1-2 This invention proposes a rectifier control circuit for a large current output of an LLC capacitor, comprising a first primary-side switching module 10, a second primary-side switching module 20, a transformer T1, a first secondary-side MOSFET Q3, a second secondary-side MOSFET Q4, a first inductor L1, a second inductor L2, and an output capacitor C4. This scheme achieves this by alternately turning on the first primary-side switching module 10 and the second primary-side switching module 20, and by also alternately and complementaryly turning on the first secondary-side MOSFET Q3 and the second secondary-side MOSFET Q4, ensuring that the current flowing through the output capacitor C4 is always a dual-path current. This improves the ripple current problem of the output capacitor C4 while retaining the soft-switching characteristics of the LLC capacitor.

[0031] In this embodiment, both the first inductor L1 and the second inductor L2 are energy storage inductors. The energy storage inductors utilize the mutual conversion between electromagnetic energies to temporarily store electrical energy.

[0032] In this embodiment, the output capacitor C4 is an electrolytic capacitor. Electrolytic capacitors have a very large capacitance per unit volume, which can effectively store and discharge energy.

[0033] like Figure 1 The input terminal of the first primary-side switch module 10 is connected to the power input, and the output terminal of the first primary-side switch module 10 is connected to the input terminal of the second primary-side switch module 20 and the first terminal of the primary winding Np of the transformer T1. The output terminal of the second primary-side switch module 20 and the second terminal of the primary winding Np of the transformer T1 are grounded. The first primary-side switch module 10, the second primary-side switch module 20 and the primary winding Np of the transformer T1 constitute an LCC resonant half-bridge.

[0034] like Figure 1As shown, the first terminal of the secondary winding Ns of transformer T1 is connected to the first terminal of the first inductor L1 and the gate (G) of the second secondary MOSFET Q4. The second terminal of the secondary winding Ns of transformer T1 is connected to the first terminal of the second inductor L2 and the gate (G) of the first secondary MOSFET Q3. The drain (D) of the first secondary MOSFET Q3 is connected to the first terminal of the first inductor L1. The drain (D) of the second secondary MOSFET Q4 is connected to the first terminal of the second inductor L2. The source (S) of the first secondary MOSFET Q3 and the second secondary MOSFET Q4 are connected to the negative terminal of the output capacitor C4. The second terminals of the first inductor L1 and the second inductor L2 are connected to the positive output terminal of the output capacitor C4. The secondary winding Ns of transformer T1, the first secondary MOSFET Q3, the second secondary MOSFET Q4, the first inductor L1, the second inductor L2, and the output capacitor C4 constitute a current multiplier rectifier circuit.

[0035] refer to Figure 1 The rectifier control circuit for high current output of LLC in this invention also includes a filter capacitor C8. The first end of the filter capacitor C8 is connected to the second end of the primary winding Np of the transformer T1, and the second end of the filter capacitor C8 is grounded. The filter capacitor C8, together with the first primary-side switch module 10, the second primary-side switch module 20, and the primary winding Np of the transformer T1, constitutes an LCC resonant half-bridge.

[0036] refer to Figure 1 The first primary-side switching module 10 includes a first primary-side MOSFET Q1, a first transistor Q5, a first resistor R1, a second resistor R2, and a third resistor R3. The power input is connected to the drain (D) terminal of the first primary-side MOSFET Q1. The gate (G) terminal of the first primary-side MOSFET Q1 is connected to the first terminals of the first resistor R1 and the second resistor R2. The second terminal of the first resistor R1 is connected to the emitter (E) terminal of the first transistor Q5 and the first terminal of the third resistor R3. The base (B) terminal of the first transistor Q5 is connected to the second terminal of the third resistor R3 and the first control terminal. The collector (C) terminal of the first transistor Q5 and the second terminal of the second resistor R2 are connected to the first terminal of the primary winding Np of the transformer T1.

[0037] refer to Figure 1 The second primary-side switching module 20 includes a second primary-side MOSFET Q2, a second transistor Q6, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6. The drain (D) of the second primary-side MOSFET Q2 is connected to the first terminal of the primary winding Np of the transformer T1. The gate (G) of the second primary-side MOSFET Q2 is connected to the first terminals of the fourth resistor R4 and the fifth resistor R5. The second terminal of the fourth resistor R4 is connected to the emitter (e) of the second transistor Q6 and the first terminal of the sixth resistor R6. The base (B) of the second transistor Q6 is connected to the second terminal of the sixth resistor R6 and the second control terminal. The collector (C) of the second transistor Q6, the second terminal of the fifth resistor R5, and the source (S) of the second primary-side MOSFET Q2 are grounded.

[0038] refer to Figure 1The rectifier control circuit for high current output of LLC in this invention also includes a first secondary capacitor C1, a seventh resistor R7 and an eighth resistor R8. The first terminal of the first secondary capacitor C1 is connected to the second terminal of the secondary winding Ns of transformer T1. The second terminal of the first secondary capacitor C1 is connected to the first terminal of the seventh resistor R7. The second terminals of the seventh resistor R7 and the eighth resistor R8 are connected to the gate of the first secondary MOSFET Q3. The first terminal of the eighth resistor R8 is connected to the source of the first secondary MOSFET Q3.

[0039] refer to Figure 1 The rectifier control circuit for high current output of LLC in this invention also includes a second secondary capacitor C2, a ninth resistor R9, and a tenth resistor R10. The first terminal of the second secondary capacitor C2 is connected to the first terminal of the secondary winding Ns of transformer T1, the second terminal of the second secondary capacitor C2 is connected to the first terminal of the ninth resistor R9, the second terminals of the ninth resistor R9 and the tenth resistor R10 are connected to the gate of the second secondary MOSFET Q4, and the first terminal of the tenth resistor R10 is connected to the source of the second secondary MOSFET Q4.

[0040] refer to Figure 1 The rectifier control circuit for high current output of LLC in this invention also includes an input capacitor C6. The positive terminal of the input capacitor C6 is connected to the input terminal of the first primary-side switching module 10, which is also the power input, and the negative terminal is grounded.

[0041] In this embodiment, the primary-side MOSFETs Q1 and Q2, transformer T1, and filter capacitor C8 of the LLC high-current output rectifier control circuit of this scheme constitute an LLC resonant half-bridge; the energy storage inductors L1 and L2, together with the primary-side MOSFETs Q3 and Q4 (self-driven rectifiers), form a current multiplier rectifier circuit. During operation, the primary-side MOSFETs Q1 and Q2, which act as switches, alternately conduct with a complementary duty cycle of 0.5, and the secondary-side MOSFETs Q3 and Q4, which act as rectifiers, also alternately conduct with a complementary duty cycle of 0.5, so that the LLC high-current output rectifier control circuit of this embodiment operates in steady state. The specific working process is as follows:

[0042] a) When Q1 of the primary-side LLC resonant half-bridge is turned on, Q4 of the secondary-side current-doubling rectifier circuit is also turned on, and the current flows into the output capacitor C4 through two current paths.

[0043] Current path 1: Secondary winding Ns --> First inductor L1 charges and stores energy, L1 current increases, output inductor current IL1 --> Output capacitor C4 --> Synchronous rectifier Q4.

[0044] Current path 2: The second inductor L2 discharges, the current of L2 decays, the output inductor current IL2 --> the output capacitor C4 --> the synchronous rectifier Q4.

[0045] 2) When Q2 of the primary-side LLC resonant half-bridge is turned on, and Q3 of the secondary-side current-doubling rectifier circuit is turned on at the same time, the current still flows into the output capacitor C4 through two current paths.

[0046] Current path 1: Secondary winding Ns --> Second inductor L2 charges and stores energy, current increases, output inductor current IL2 --> Output capacitor C4 --> Synchronous rectifier Q3.

[0047] Current path 2: The first inductor L1 discharges, the current of L1 decays, the output inductor current IL1 --> the output capacitor C4 --> the synchronous rectifier Q3.

[0048] Thus, the primary-side LLC resonant half-bridge switches Q1 and Q2 conduct alternately, while the secondary-side rectifiers Q3 and Q4 also conduct alternately. The current flowing through the output capacitor is always two currents (IL1 and IL2), hence the term "current doubler rectification." Figure 2 As shown, the two inductor currents (IL1 and IL2) flow into the output capacitor C4. The output current Iout of the output capacitor C4 is equal to IL1 + IL2, which greatly reduces the ripple current of the output capacitor, thereby reducing the requirements for the capacity and size of the output capacitor, reducing production costs, and extending the service life of the switching power supply.

[0049] It should be understood that the LLC high-current output rectifier control circuit of the present invention can be applied to power supply products that require high current output, such as switching power supplies, adapters, LED display power supplies, and LED centralized power supply drivers, so as to reduce the capacity and size of the output capacitor C4 used in power supply products, thereby reducing production costs and improving the lifespan of power supply products.

[0050] The present invention provides a rectifier control circuit for a large current output of an LLC. By setting the first primary-side switch module 10 and the second primary-side switch module 20 to be alternately turned on, and the first secondary-side MOSFET Q3 and the second secondary-side MOSFET Q4 of the transformer T1 to be alternately and complementaryly turned on, the current flowing through the output capacitor C4 is always a dual current, which improves the ripple current problem flowing through the output capacitor C4, while retaining the soft-switching characteristics of the LLC.

[0051] The present invention also proposes a switching power supply, including a rectifier control circuit for large current output of LLC as described in the above embodiment, in order to improve the ripple current problem of the output current of the switching power supply, while retaining the soft switching characteristics of LLC.

[0052] It should be understood that the switching power supply described in this embodiment can be applied to power supply products that require high current output, such as LED display products or LED centralized power supply products.

[0053] The present invention provides a switching power supply including a rectifier control circuit for a large current output of LLC. By alternately turning on the first primary-side switching module and the second primary-side switching module, the first secondary-side MOSFET and the second secondary-side MOSFET of the transformer also alternately and complementaryly turn on, so that the current flowing through the output capacitor is always a dual current, thereby improving the ripple current problem of the output capacitor and ensuring the soft-switching characteristics of LLC.

[0054] The above examples are merely illustrative of the technical content of the present invention to facilitate easier understanding by the reader, but do not imply that the implementation of the present invention is limited to these examples. Any technical extensions or re-creations made based on the present invention are protected by the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A rectifier control circuit for a large current output of an LLC converter, characterized in that, It includes a first primary-side switching module, a second primary-side switching module, a transformer, a first secondary-side MOSFET, a second secondary-side MOSFET, a first inductor, a second inductor, and an output capacitor; the input terminal of the first primary-side switching module is connected to the power input, the output terminal of the first primary-side switching module is connected to the input terminal of the second primary-side switching module and the first end of the primary winding of the transformer, and the output terminal of the second primary-side switching module and the second end of the primary winding of the transformer are grounded; The first terminal of the secondary winding of the transformer is connected to the first terminal of the first inductor and the gate (G) of the second secondary MOSFET. The second terminal of the secondary winding of the transformer is connected to the first terminal of the second inductor and the gate (G) of the first secondary MOSFET. The drain (D) of the first secondary MOSFET is connected to the first terminal of the first inductor, and the drain (D) of the second secondary MOSFET is connected to the first terminal of the second inductor. The source (S) of the first and second secondary MOSFETs is connected to the negative terminal of the output capacitor. The second terminals of the first and second inductors are connected to the positive output terminal of the output capacitor. The first primary-side switching module and the second primary-side switching module are alternately turned on. The first and second secondary MOSFETs are alternately and complementaryly turned on with a duty cycle of 0.

5. The second secondary MOSFET and the first primary-side switching module are turned on simultaneously, so that the current flowing through the output capacitor is two-way. The rectifier control circuit for the large current output of the LLC also includes: a first secondary capacitor, a seventh resistor, an eighth resistor, a second secondary capacitor, a ninth resistor, and a tenth resistor. The first terminal of the first secondary capacitor is connected to the second terminal of the secondary winding of the transformer, the second terminal of the first secondary capacitor is connected to the first terminal of the seventh resistor, the second terminals of the seventh and eighth resistors are connected to the gate (G) of the first secondary MOSFET, and the first terminal of the eighth resistor is connected to the source (S) of the first secondary MOSFET; the first terminal of the second secondary capacitor is connected to the first terminal of the secondary winding of the transformer, the second terminal of the second secondary capacitor is connected to the first terminal of the ninth resistor, the second terminals of the ninth and tenth resistors are connected to the gate (G) of the second secondary MOSFET, and the first terminal of the tenth resistor is connected to the source (S) of the second secondary MOSFET.

2. The LLC high-current output rectifier control circuit according to claim 1, characterized in that, The first primary-side switching module includes a first primary-side MOSFET, a first transistor, a first resistor, a second resistor, and a third resistor; the power input is connected to the drain (D) terminal of the first primary-side MOSFET, the gate (G) terminal of the first primary-side MOSFET is connected to the first terminals of the first and second resistors, the second terminal of the first resistor is connected to the emitter (e) terminal of the first transistor and the first terminal of the third resistor, the base (b) terminal of the first transistor is connected to the second terminal of the third resistor and the first control terminal, and the collector (C) terminal of the first transistor and the second terminal of the second resistor are connected to the first terminal of the primary winding of the transformer.

3. The LLC high-current output rectifier control circuit according to claim 2, characterized in that, The second primary-side switching module includes a second primary-side MOSFET, a second transistor, a fourth resistor, a fifth resistor, and a sixth resistor. The drain (D) of the second primary-side MOSFET is connected to the first terminal of the primary winding of the transformer. The gate (G) of the second primary-side MOSFET is connected to the first terminals of the fourth and fifth resistors. The second terminal of the fourth resistor is connected to the emitter (e) of the second transistor and the first terminal of the sixth resistor. The base (B) of the second transistor is connected to the second terminal of the sixth resistor and the second control terminal. The collector (C) of the second transistor, the second terminal of the fifth resistor, and the source (S) of the second primary-side MOSFET are grounded.

4. The LLC high-current output rectifier control circuit according to claim 1, characterized in that, Both the first inductor and the second inductor are energy storage inductors.

5. The LLC high-current output rectifier control circuit according to claim 1, characterized in that, It also includes an input capacitor, the positive terminal of which is connected to the input terminal of the first primary-side switching module, and the negative terminal is grounded.

6. The LLC high-current output rectifier control circuit according to claim 1, characterized in that, It also includes a filter capacitor, the first end of which is connected to the second end of the primary winding of the transformer, and the second end of which is grounded.

7. The LLC high-current output rectifier control circuit according to claim 1, characterized in that, The output capacitor is an electrolytic capacitor.

8. A switching power supply, characterized in that, It includes the rectifier control circuit for high-current output of LLC as described in any one of claims 1-7.

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