LLC topology circuit with high reliability

Abstract

The utility model discloses an LLC topology circuit with high reliability, comprising a switch unit, a resonance unit, a rectification unit, an auxiliary power supply, an input capacitor Cin and an output capacitor Cout, a first end of the input capacitor Cin is connected with a first end of the switch unit, a second end of the switch unit is connected with a first end of the resonance unit, and a second end of the resonance unit is connected with a second end of the rectification unit. The second end of the resonance unit is connected with the first end of the rectification unit, the second end of the rectification unit is connected with the first end of the output capacitor Cout and the auxiliary power supply, and the second end of the input capacitor Cin, the third end of the switch unit, the third end of the resonance unit and the second end of the output capacitor Cout are grounded. The auxiliary power supply is utilized to provide energy for the output capacitor Cout of the LLC before the LLC circuit is started, so that the output capacitor of the LLC has a certain voltage before the LLC circuit is started, the impact current when the LLC circuit is started is reduced, and the reliability of the LLC circuit is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of LLC circuits, and in particular to an LLC topology circuit with high reliability. Background Art

[0002] Currently, LLC topology circuits are frequently used in the power supply industry. LLC resonant converters feature excellent soft-switching characteristics and high efficiency, making them widely used. With the continuous advancement of power electronics technology, high frequency, low cost, and high efficiency have become its ongoing development direction. Currently, LLCs are started directly when there is no voltage on the LLC's output capacitor. During LLC startup, the lower the voltage on the output capacitor and the larger the output capacitance, the greater the inrush current that will flow through the LLC's MOSFET during startup, and the longer the duration. Existing LLCs start directly when there is no voltage on the output capacitor, causing the LLC's MOSFET to continuously flow a large inrush current during startup. The greater this inrush current, the greater the probability of failure of the LLC's MOSFET.

[0003] Based on this, a new solution is needed. Utility Model Content

[0004] The main purpose of the utility model is to provide an LLC topology circuit with high reliability, which uses an auxiliary power supply in the power supply to first charge the output capacitor of the LLC, so as to reduce the impact on the MOS tube when starting the LLC circuit and improve the reliability of the LLC during startup.

[0005] To achieve the above-mentioned objectives, the present invention provides an LLC topology circuit with high reliability, including a switching unit, a resonant unit, a rectifier unit, an auxiliary power supply, an input capacitor C_in and an output capacitor C_out, wherein the first end of the input capacitor C_in is connected to the first end of the switching unit, the second end of the switching unit is connected to the first end of the resonant unit, the second end of the resonant unit is connected to the first end of the rectifier unit, the second end of the rectifier unit is connected to the first end of the output capacitor C_out and the auxiliary power supply, and the second end of the input capacitor C_in, the third end of the switching unit, the third end of the resonant unit and the second end of the output capacitor C_out are grounded.

[0006] In the LLC topology circuit with high reliability provided by the present utility model, the auxiliary power supply includes a current limiting resistor R1, a third diode D3, a fourth diode D4, and a second transformer T2. The second end of the current limiting resistor R1 is connected to the first end of the output capacitor C_out, the first end of the current limiting resistor R1 is connected to the cathode of the third diode D3, the anode of the third diode D3 is connected to the same-name end of the first secondary winding of the second transformer T2, the same-name end of the second secondary winding of the second transformer T2 is connected to the anode of the fourth diode D4, the cathode of the fourth diode D4 serves as the auxiliary power supply output end, the opposite-name end of the first secondary winding of the second transformer T2 and the opposite-name end of the second secondary winding of the second transformer T2 are grounded, and the primary winding of the second transformer T2 is connected to the power supply voltage.

[0007] In the LLC topology circuit with high reliability provided by the present invention, the switching unit includes a first switching tube Q1 and a second switching tube Q2, the drain of the first switching tube Q1 is connected to the first end of the input capacitor C_in, the source of the first switching tube Q1 is connected to the drain of the second switching tube Q2, the source of the second switching tube Q2 is connected to the second end of the input capacitor C_in, and the gate of the first switching tube Q1 and the gate of the second switching tube Q2 are connected to the input square wave.

[0008] In the LLC topology circuit with high reliability provided by the present utility model, the resonant unit includes a resonant inductor Lr, a resonant transformer T1 and a resonant capacitor C1. The first end of the resonant inductor Lr is connected to the source of the first switch tube Q1, the second end of the resonant inductor Lr is connected to the same-name end of the primary coil of the resonant transformer T1, the first end of the resonant capacitor C1 is connected to the opposite-name end of the primary coil of the resonant transformer T1, the second end of the resonant capacitor C1 is connected to the second end of the input capacitor C_in, and the same-name end of the first secondary coil of the resonant transformer T1 and the opposite-name end of the second secondary coil of the resonant transformer T1 are grounded.

[0009] In the LLC topology circuit with high reliability provided by the present invention, the rectifier unit includes a first rectifier diode D1 and a second rectifier diode D2, the anode of the first rectifier diode D1 is connected to the opposite-name end of the first secondary winding of the resonant transformer T1, the anode of the second rectifier diode D2 is connected to the same-name end of the second secondary winding of the resonant transformer T1, and the cathode of the first rectifier diode D1 and the cathode of the second rectifier diode D2 are connected to the first end of the output capacitor C_out.

[0010] The LLC topology circuit with high reliability provided by the utility model has the following beneficial effects: the LLC topology circuit with high reliability provided by the utility model utilizes an auxiliary power supply to provide energy to the LLC output capacitor C_out before the LLC circuit is started, so that a certain voltage exists on the LLC output capacitor before starting, thereby reducing the inrush current during LLC startup and improving the reliability of the LLC circuit; by utilizing the auxiliary power supply that must be included in the power supply to pre-charge the LLC output capacitor in advance, the inrush current during LLC startup is reduced, and the reliability of the power supply can be improved without substantially increasing the cost of the power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only embodiments of the present invention. Those skilled in the art can obtain other drawings based on the provided drawings without inventive work.

[0012] Figure 1 FIG2 is a circuit diagram of an LLC topology circuit with high reliability provided by an embodiment of the present utility model;

[0013] Figure 2 and Figure 3 The figure shows the current value flowing through the MOS tube when the voltage on the LLC output capacitor is 60V and the LLC is started;

[0014] Figure 4 and Figure 5 The figure shows the current value flowing through the MOS tube when the LLC is started when the voltage on the output capacitor is 0V. DETAILED DESCRIPTION

[0015] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be provided below with reference to the accompanying drawings. The drawings illustrate exemplary embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0017] Figure 1 The figure shows a schematic diagram of an LLC topology circuit with high reliability provided by an embodiment of the present invention. Figure 1 As shown, the LLC topology circuit with high reliability provided by the present invention includes a switch unit 100, a resonant unit 200, a rectifier unit 300, an auxiliary power supply 400, an input capacitor C_in, and an output capacitor C_out. The first end of the input capacitor C_in is connected to the first end of the switch unit 100, the second end of the switch unit 100 is connected to the first end of the resonant unit 200, the second end of the resonant unit 200 is connected to the first end of the rectifier unit 300, the second end of the rectifier unit 300 is connected to the first end of the output capacitor C_out and the auxiliary power supply 400, and the second end of the input capacitor C_in, the third end of the switch unit 100, the third end of the resonant unit 200, and the second end of the output capacitor C_out are grounded. When in use, the auxiliary power supply is turned on after the power supply is powered on to supply power to the working control circuit within the power supply, while also allowing the auxiliary power supply to charge the LLC output capacitor. Therefore, the auxiliary power supply 400 is used to provide a certain amount of energy to the LLC output capacitor C_out before the LLC circuit is started, so that a certain voltage exists on the LLC output capacitor before starting, thereby reducing the inrush current during LLC startup and improving the reliability of the LLC circuit.

[0018] Specifically, in one embodiment of the present invention, the auxiliary power supply 400 includes a current-limiting resistor R1, a third diode D3, a fourth diode D4, and a second transformer T2. The second end of the current-limiting resistor R1 is connected to the first end of the output capacitor C_out, the first end of the current-limiting resistor R1 is connected to the cathode of the third diode D3, the anode of the third diode D3 is connected to the same-name terminal of the first secondary winding of the second transformer T2, the same-name terminal of the second secondary winding of the second transformer T2 is connected to the anode of the fourth diode D4, and the cathode of the fourth diode D4 serves as the auxiliary power supply output terminal. The opposite-name terminal of the first secondary winding of the second transformer T2 and the opposite-name terminal of the second secondary winding of the second transformer T2 are grounded, and the primary winding of the second transformer T2 is connected to the power supply voltage. In this embodiment, after the power supply is powered on, the flyback auxiliary power supply is first turned on, so that VCC_aux reaches a set value to provide energy for the operation of the internal circuit of the power supply. While providing energy to VCC_aux, the flyback auxiliary power supply also connects the two ends of the first secondary winding of the transformer T2 (i.e., Figure 1 The windings at pins 3 and 5 in the circuit generate an induced electromotive force, which is then transferred to the LLC output capacitor C_out through the third diode D3 and the current-limiting resistor R1, causing the voltage of the LLC output capacitor C_out to increase. At this time, turning on the LLC circuit can reduce the inrush current on the LLC MOS tube and improve LLC reliability.

[0019] Specifically, in one embodiment of the present invention, the switching unit 100 includes a first switching tube Q1 and a second switching tube Q2, the resonant unit 200 includes a resonant inductor Lr, a resonant transformer T1 and a resonant capacitor C1, and the rectifier unit 300 includes a first rectifier diode D1 and a second rectifier diode D2. The drain of the first switching tube Q1 is connected to the first end of the input capacitor C_in, the source of the first switching tube Q1 is connected to the drain of the second switching tube Q2, the source of the second switching tube Q2 is connected to the second end of the input capacitor C_in, and the gate of the first switching tube Q1 and the gate of the second switching tube Q2 are connected to the input square wave; the first end of the resonant inductor Lr is connected to the source of the first switching tube Q1, the second end of the resonant inductor Lr is connected to the same-name terminal of the primary coil of the resonant transformer T1, and the first end of the resonant capacitor C1 is connected to the resonant transformer T1. The opposite-name end of the primary coil of the resonant transformer T1 is connected to the opposite-name end of the primary coil, the second end of the resonant capacitor C1 is connected to the second end of the input capacitor C_in, the same-name end of the first secondary coil of the resonant transformer T1 and the opposite-name end of the second secondary coil of the resonant transformer T1 are grounded; the anode of the first rectifier diode D1 is connected to the opposite-name end of the first secondary coil of the resonant transformer T1, the anode of the second rectifier diode D2 is connected to the same-name end of the second secondary coil of the resonant transformer T1, and the cathode of the first rectifier diode D1 and the cathode of the second rectifier diode D2 are connected to the first end of the output capacitor C_out. During use, the first switch tube Q1 and the second switch tube Q2 are alternately turned on under the control of the input square wave. When the first switch tube Q1 is turned on, the input capacitor C_in is charged through the resonant inductor and the resonant transformer, and energy is injected into the secondary coil of the resonant transformer. After rectification by the rectifier unit, it is transferred to the output capacitor C_out; when the second switch tube Q2 is turned on, the input capacitor C_in is discharged through the resonant inductor and the resonant transformer, and energy is injected into the secondary coil of the resonant transformer. After rectification by the rectifier unit, it is transferred to the output capacitor C_out.

[0020] Figure 2 and Figure 3 The figure shows the current value flowing through the MOS tube when the voltage on the LLC output capacitor is 60V. Figure 4 and Figure 5 The figure shows the current flowing through the MOS transistor when the LLC is started with the voltage on the output capacitor at 0V. The waveform shows that when the LLC is started with the output capacitor voltage at 0V, the inrush current peaks at 23.7A, while when the output capacitor voltage is at 60V, the inrush current is only 11.7A. This data comparison shows that when the LLC is started, the higher the voltage on the output capacitor, the smaller the inrush current flowing through the MOS transistor, significantly improving the reliability of the LLC circuit.

[0021] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0022] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various invention aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the claims below, invention aspects lie in less than all of the features of the individual embodiments disclosed above. Accordingly, the claims that follow the detailed description are hereby expressly incorporated into this detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0023] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of the present invention and to form different embodiments. For example, in the claims below, any of the claimed embodiments may be used in any combination.

[0024] It should be noted that the above embodiments illustrate rather than limit the present invention, and that a person skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbols placed between brackets should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

Claims

1. An LLC topology circuit with high reliability, characterized in that: The invention comprises a switch unit (100), a resonance unit (200), a rectification unit (300), an auxiliary power supply (400), an input capacitor C_in and an output capacitor C_out, wherein the first end of the input capacitor C_in is connected to the first end of the switch unit (100), the second end of the switch unit (100) is connected to the first end of the resonance unit (200), the second end of the resonance unit (200) is connected to the first end of the rectification unit (300), the second end of the rectification unit (300) is connected to the first end of the output capacitor C_out and the auxiliary power supply (400), and the second end of the input capacitor C_in, the third end of the switch unit (100), the third end of the resonance unit (200) and the second end of the output capacitor C_out are grounded.

2. The LLC topology circuit with high reliability according to claim 1, characterized in that: The auxiliary power supply (400) comprises a current limiting resistor R1, a third diode D3, a fourth diode D4, and a second transformer T2, wherein the second end of the current limiting resistor R1 is connected to the first end of the output capacitor C_out, the first end of the current limiting resistor R1 is connected to the cathode of the third diode D3, the anode of the third diode D3 is connected to the same-name end of the first secondary winding of the second transformer T2, the same-name end of the second secondary winding of the second transformer T2 is connected to the anode of the fourth diode D4, the cathode of the fourth diode D4 serves as the auxiliary power output end, the opposite-name end of the first secondary winding of the second transformer T2 and the opposite-name end of the second secondary winding of the second transformer T2 are grounded, and the primary winding of the second transformer T2 is connected to the power supply voltage.

3. The LLC topology circuit with high reliability according to claim 1, wherein: The switch unit (100) comprises a first switch tube Q1 and a second switch tube Q2, wherein the drain of the first switch tube Q1 is connected to the first end of the input capacitor C_in, the source of the first switch tube Q1 is connected to the drain of the second switch tube Q2, the source of the second switch tube Q2 is connected to the second end of the input capacitor C_in, and the gates of the first switch tube Q1 and the second switch tube Q2 are connected to an input square wave.

4. The LLC topology circuit with high reliability as claimed in claim 3, characterized in that: The resonant unit (200) comprises a resonant inductor Lr, a resonant transformer T1 and a resonant capacitor C1, wherein the first end of the resonant inductor Lr is connected to the source of the first switch tube Q1, the second end of the resonant inductor Lr is connected to the same-name end of the primary coil of the resonant transformer T1, the first end of the resonant capacitor C1 is connected to the opposite-name end of the primary coil of the resonant transformer T1, the second end of the resonant capacitor C1 is connected to the second end of the input capacitor C_in, and the same-name end of the first secondary coil of the resonant transformer T1 and the opposite-name end of the second secondary coil of the resonant transformer T1 are grounded.

5. The LLC topology circuit with high reliability as claimed in claim 4, characterized in that: The rectifier unit (300) includes a first rectifier diode D1 and a second rectifier diode D2, wherein the anode of the first rectifier diode D1 is connected to the opposite-name end of the first secondary winding of the resonant transformer T1, the anode of the second rectifier diode D2 is connected to the same-name end of the second secondary winding of the resonant transformer T1, and the cathode of the first rectifier diode D1 and the cathode of the second rectifier diode D2 are connected to the first end of the output capacitor C_out.

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