LLC rectifying circuit capable of effectively reducing current stress
By introducing zero voltage and zero current switching technology into the LLC circuit, combined with full wave and full bridge rectifier circuit, the problem of excessive current stress in the secondary rectifier circuit of the LLC circuit is solved, and the effective reduction of current stress and the improvement of power conversion efficiency is achieved.
Patent Information
- Application Number
- CN202422156995.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-04
- Publication Date
- 2025-07-11
- Estimated Expiration
- 2034-09-04
AI Technical Summary
When the switching unit of the secondary rectifier circuit of the LLC circuit is operated at low frequency, the output side either operates in the full wave rectifier mode or in the full bridge rectifier mode, resulting in excessive current stress.
By designing an LLC rectifier circuit including input module, resonance module, switching module and output module, the inductor L and capacitor C of the resonant circuit form a zero voltage switch and a zero current switch, and combining a full-wave rectifier circuit and a full-bridge rectifier circuit to reduce current stress.
It significantly reduces the current stress of the switch tube and diode, reduces switching losses and common mode current of the transformer, and improves the power conversion efficiency.
Smart Images
Figure CN223093658U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of LLC circuits, and specifically, to an LLC rectifier circuit that can effectively reduce current stress. Background Art
[0002] The LLC circuit, that is, the resonant circuit, is a circuit structure that uses the resonant characteristics of inductance and capacitance elements to achieve power conversion. It can generate a situation where the port voltage and current waveforms are in the same phase at a specific operating frequency, thereby achieving efficient power conversion. The LLC secondary rectifier circuit is an efficient power conversion circuit and is widely used in the secondary side of transformers. It realizes the conversion from alternating current to direct current by utilizing the characteristics of the LLC resonant circuit and rectifier diodes, while reducing energy loss.
[0003] Currently, the switching unit of the LLC circuit secondary rectifier circuit only operates at low frequencies. The output side either operates in the full-wave rectification mode or the full-bridge rectification mode, and the switching unit needs to bear the full current, resulting in a large current stress. Therefore, we propose an LLC rectifier circuit that can effectively reduce current stress. Summary of the Utility Model
[0004] The purpose of the present utility model is to provide an LLC rectifier circuit that can effectively reduce current stress to solve the problems raised in the above background art.
[0005] To achieve the above purpose, the present utility model provides an LLC rectifier circuit that can effectively reduce current stress, including an input module, a resonant module, a switching module, and an output module. The resonant module includes a switch control circuit and a resonant circuit. The switching module includes a full-wave rectifier circuit, a full-bridge rectifier circuit, a switching transistor QH1, a switching transistor QH2, and a frequency control unit. The switch control circuit is connected to the resonant circuit, and the resonant circuit is connected to the switching module;
[0006] The current at the input end is controlled by the switch control circuit to reach the resonant circuit. After being filtered by the resonant circuit, the frequency control unit and the output voltage control the opening and closing of the switching transistors QH1 and QH2, switching the secondary circuit to the full-wave rectifier circuit or the full-bridge rectifier circuit, reducing the output current to half of the input current, and reducing the current stress.
[0007] As a further improvement of this technical solution, the resonant circuit includes a capacitor C, an inductor L, and a transformer T, where:
[0008] One end of the capacitor C is connected to one end of the inductor L. The other end of the inductor L is connected to one end of the primary winding of the transformer T. The other end of the capacitor C is connected to the source-drain of the CMOS transistor V1 and the drain-source of the CMOS transistor V2. The source-drain of the CMOS transistor V2 is connected to the other end of the primary winding of the transformer T.
[0009] As a further improvement of this technical solution, the switch control circuit includes a COMS transistor V1, a COMS transistor V2, a diode D6, and a diode D7, where:
[0010] The source of the COMS transistor V1 is connected in parallel with the negative electrode of the diode D6, the drain of the COMS transistor V1 is connected in parallel with the positive electrode of the diode D6, the source of the COMS transistor V2 is connected in parallel with the negative electrode of the diode D7, the drain of the COMS transistor V2 is connected in parallel with the positive electrode of the diode D7, and the source of the COMS transistor V1 is connected to the drain of the COMS transistor V2.
[0011] As a further improvement of this technical solution, the full-wave rectifier circuit includes a transformer T and diodes D1, D2, and D5, where:
[0012] The main winding of the transformer T is connected to the resonant circuit, the secondary winding of the transformer T is connected to the negative electrodes of the diode D1 and the diode D2, the positive electrodes of the diode D1 and the diode D2 are connected to the output terminal, the positive electrode of the diode D5 is connected to the center tap of the secondary winding of the transformer T, and the negative electrode of the diode D5 is connected to the output terminal. When the transformer T is wound, the number of turns of the 4-5 winding in the secondary winding of the transformer T is the same as that of the 3-6 winding.
[0013] As a further improvement of this technical solution, the full-bridge rectifier circuit includes a transformer T and diodes D1, D2, D3, D4, and D5, where:
[0014] The main winding of the transformer T is connected to the resonant circuit, one end of the secondary winding of the transformer T is connected to the negative electrode of the diode D1 and the positive electrode of the diode D3, the other end of the secondary winding of the transformer T is connected to the negative electrode of the diode D2 and the positive electrode of the diode D4, the positive electrodes of the diode D1 and the diode D2 are connected for output filtering, the negative electrodes of the diode D3 and the diode D4 are connected in parallel with the negative electrode of the diode D5 for output filtering, and the positive electrode of the diode D5 is connected to the center tap of the secondary winding of the transformer T.
[0015] As a further improvement of this technical solution, the switching transistors QH1 and QH2 can use relays, MOS transistors, IGBTs, etc. as switching units.
[0016] Compared with the prior art, the beneficial effects of the present utility model:
[0017] 1. The LLC rectifier circuit that effectively reduces current stress forms zero-voltage switches and zero-current switches through the inductor L, capacitor C of the resonant circuit, and CMOS transistors V1 and V2, thereby reducing the voltage and current stress of the switching transistors. In the zero-voltage state, the voltage of the CMOS transistor drops to zero before conduction and remains zero when turned off; while in the zero-current state, the current remains zero during conduction and drops to zero before turning off, which significantly reduces the switching losses and improves the efficiency.
[0018] 2. The secondary winding of the full-wave rectifier circuit transformer T is doubled, and the anode of the diode D5 is connected from the center tap, reducing the common-mode current of the transformer T, thereby reducing the current stress of the transformer T.
[0019] 3. The current of each diode in the full-bridge rectifier circuit is always half of the input current, thereby greatly reducing the current stress of the diodes. Brief Description of the Drawings
[0020] Figure 1 It is a schematic diagram of the overall process of the first utility model;
[0021] Figure 2 It is a schematic diagram of the overall circuit of the first utility model;
[0022] Figure 3 It is a schematic diagram of the full-wave rectifier circuit of the first utility model;
[0023] Figure 4 It is a schematic diagram of the full-bridge rectifier circuit of the first utility model;
[0024] Figure 5 It is the overall circuit diagram of the second embodiment in the first utility model. Detailed Embodiments
[0025] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.
[0026] Embodiment 1
[0027] The LLC circuit, namely the resonant circuit, is a circuit structure that utilizes the resonant characteristics of inductance and capacitance elements to achieve power conversion. It can generate a situation where the port voltage and current waveforms are in the same phase at a specific operating frequency, thereby achieving efficient power conversion. The LLC secondary rectifier circuit is an efficient power conversion circuit and is widely used on the secondary side of transformers. It realizes the conversion from alternating current to direct current by utilizing the characteristics of the LLC resonant circuit and rectifier diodes, while reducing energy loss. Please refer to Figures 1-4 As shown in the figure, the present invention provides an LLC rectifier circuit that effectively reduces current stress, including an input module, a resonant module, a switching module, and an output module. The resonant module includes a switch control circuit and a resonant circuit. The switching module includes a full-wave rectifier circuit, a full-bridge rectifier circuit, a switching transistor QH1, a switching transistor QH2, and a frequency control unit. The switch control circuit is connected to the resonant circuit, and the resonant circuit is connected to the switching module;
[0028] The current at the input end is controlled by the switch control circuit to reach the resonant circuit, filtered by the resonant circuit, and the disconnection and closure of the switching transistors QH1 and QH2 are controlled through the frequency control unit and the output voltage, switching the secondary circuit to a full-wave rectifier circuit or a full-bridge rectifier circuit, reducing the output current to half of the input current, and reducing the current stress.
[0029] Principle: When the current enters from the input end, a zero-voltage switch and a zero-current switch are formed by the inductor L, capacitor C of the resonant circuit and the CMOS transistors V1 and V2, thereby reducing the voltage and current stress of the switching transistors. When the secondary circuit is switched to the full-wave rectifier circuit, the secondary winding of the transformer T of the full-wave rectifier circuit is doubled and connected to the positive pole of the diode D5 from the center tap, reducing the common-mode current of the transformer T, thereby reducing the current stress of the transformer T. When the secondary circuit is switched to the full-bridge rectifier circuit, the current of each diode of the full-bridge rectifier circuit is always half of the input current, thereby greatly reducing the current stress of the diodes, and further reducing the current stress of the entire circuit.
[0030] In order to form a zero-voltage switch and a zero-current switch by the resonant circuit and the CMOS transistors V1 and V2, among them, the resonant circuit includes a capacitor C, an inductor L, and a transformer T, where:
[0031] One end of the capacitor C is connected to one end of the inductor L. The other end of the inductor L is connected to one end of the primary winding of the transformer T. The other end of the capacitor C is connected to the source of the CMOS transistor V1 and the drain of the CMOS transistor V2. The source of the CMOS transistor V2 is connected to the other end of the primary winding of the transformer T.
[0032] In this circuit, the resonance of the inductor L and the capacitor C controls the turn-on and turn-off of the zero-voltage switch and the zero-current switch. The zero-voltage switch technology realizes the minimization of the voltage and current overlap during the switching process by turning on the switching device at a voltage close to zero, thereby reducing the switching loss.
[0033] In order to reduce the current and loss of the CMOS transistors V1 and V2, the switching control circuit includes the CMOS transistors V1, V2, the diode D6, and the diode D7, where:
[0034] The source of the CMOS transistor V1 is connected to the negative electrode of the diode D6, the drain of the CMOS transistor V1 is connected to the positive electrode of the diode D6, the source of the CMOS transistor V2 is connected to the negative electrode of the diode D7, the drain of the CMOS transistor V2 is connected to the positive electrode of the diode D7, and the source of the CMOS transistor V1 is connected to the drain of the CMOS transistor V2.
[0035] In this circuit, the diodes D6 and D7 are in parallel with the CMOS transistors V1 and V2. When the CMOS transistors are turned off, the inductor L in the circuit will generate a back electromotive force. The parallel diodes D6 and D7 provide a current path for it, so that the energy in the inductor L can be released, protecting the CMOS transistors from the damage of the back electromotive force and reducing the current of the CMOS transistors V1 and V2.
[0036] In order to reduce the common-mode current of the transformer T in the full-wave rectifier circuit, the full-wave rectifier circuit includes the transformer T and the diodes D1, D2, and D5, where:
[0037] The primary winding of the transformer T is connected to the resonant circuit. The secondary winding of the transformer T is connected to the negative electrodes of the diodes D1 and D2. The positive electrodes of the diodes D1 and D2 are connected to the output terminal. The positive electrode of the diode D5 is connected to the center tap of the secondary winding of the transformer T, and the negative electrode of the diode D5 is connected to the output terminal. When the transformer T is wound, the number of turns of the 4-5 winding in the secondary winding of the transformer T is the same as that of the 3-6 winding.
[0038] In this circuit, by connecting the center tap of the secondary winding of the transformer T to the positive electrode of the diode D5, the common-mode current in the transformer T is conducted out, thereby reducing the current in the transformer T and reducing its current stress.
[0039] In order to reduce the current passing through the diodes D1, D2, D3, and D4, the full-bridge rectifier circuit includes the transformer T and the diodes D1, D2, D3, D4, and D5, where:
[0040] The main winding of transformer T is connected to the resonant circuit. One end of the secondary winding of transformer T is connected to the negative electrode of diode D1 and the positive electrode of diode D3, and the other end of the secondary winding of transformer T is connected to the negative electrode of diode D2 and the positive electrode of diode D4. The positive electrodes of diode D1 and diode D2 are connected for output filtering. The negative electrodes of diode D3 and diode D4 are connected in parallel to the negative electrode of diode D5 for output filtering, and the positive electrode of diode D5 is connected to the center tap of the secondary winding of transformer T.
[0041] In this circuit, diodes D1, D2, D3, and D4 form a simple full-bridge rectifier bridge. During the positive half-cycle of the alternating current, that is, when the voltage of the alternating current starts to rise from zero, diodes D1 and D4 conduct due to the forward voltage, and the current reaches the output terminal through diodes D1 and D4. At this time, diodes D2 and D3 are reverse-biased and cut off, preventing the current from passing through. During the negative half-cycle of the alternating current, that is, when the voltage of the alternating current starts to drop from the peak value, diodes D2 and D3 conduct due to the forward voltage, and the current reaches the output terminal through diodes D2 and D3. At this time, diodes D1 and D4 are reverse-biased and cut off, preventing the current from passing through. This ensures that the current flowing through the diodes is always half of the input current, thus greatly reducing the current stress on the diodes.
[0042] To increase the practicality of this module, among them, switch tubes QH1 and QH2 can use relays, MOS tubes, IGBTs, etc. as switching units, and a variety of switching units can meet the use in different occasions.
[0043] Embodiment 2
[0044] As Figure 5 shown, the switching control circuit on the primary side of the LLC rectifier circuit that effectively reduces current stress can be replaced by a full-bridge switching control circuit. Among them, the switching control circuit includes COMS tubes V1, V2, V3, V4, diodes D6, D7, D8, and diode D9, where:
[0045] The source of COMS tube V1 is connected in parallel to the negative electrode of diode D6, and the drain of COMS tube V1 is connected in parallel to the positive electrode of diode D6. The source of COMS tube V2 is connected in parallel to the negative electrode of diode D7, and the drain of COMS tube V2 is connected in parallel to the positive electrode of diode D7. The source of COMS tube V3 is connected in parallel to the negative electrode of diode D8, and the drain of COMS tube V3 is connected in parallel to the positive electrode of diode D8. The source of COMS tube V4 is connected in parallel to the negative electrode of diode D9, and the drain of COMS tube V4 is connected in parallel to the positive electrode of diode D9. The source of COMS tube V1 is connected to the drain of COMS tube V2 and then to capacitor C. The source of COMS tube V3 is connected to the drain of COMS tube V4 and then to inductor L.
[0046] In this circuit, the CMOS transistors V1, V2, V3, and V4 form a simple full-bridge switching control circuit, which can not only reduce conduction losses and improve system efficiency, but also achieve fast switching. Among them, the diodes D6 and D7 are connected in parallel with the CMOS transistors V1 and V2, and the diodes D8 and D9 are connected in parallel with the CMOS transistors V3 and V4. When the CMOS transistors are turned off, the inductor L in the circuit will generate a back electromotive force. The parallel-connected diodes D6, D7, D8, and D9 provide a current path for it, releasing the energy in the inductor L, protecting the CMOS transistors from the damage of the back electromotive force, and reducing the current of the CMOS transistors V1, V2, V3, and V4.
[0047] When the current enters from the input terminal, the inductor L, capacitor C of the resonant circuit, and the CMOS transistors V1, V2, V3, and V4 form a zero-voltage switch and a zero-current switch, thereby reducing the voltage and current stress of the switching transistors. In the zero-voltage state, the voltage of the CMOS transistor drops to zero before conduction and remains zero when turned off; while in the zero-current state, the current remains zero during conduction and drops to zero before turning off, which significantly reduces the switching losses and improves the efficiency. When the secondary circuit switches to the full-wave rectifier circuit, the secondary winding of the full-wave rectifier circuit transformer T is doubled and connected to the positive pole of the diode D5 from the center tap, reducing the common-mode current of the transformer T, thereby reducing the current stress of the transformer T. When the secondary circuit switches to the full-bridge rectifier circuit, the diodes D1, D2, D3, and D4 form a simple full-bridge rectifier bridge. During the positive half-cycle of the alternating current, that is, when the voltage of the alternating current starts to rise from zero, the diodes D1 and D4 conduct due to the forward voltage, and the current reaches the output terminal through the diodes D1 and D4. At this time, the diodes D2 and D3 are reverse-biased and cut off, preventing the current from passing through. During the negative half-cycle of the alternating current, that is, when the voltage of the alternating current starts to drop from the peak value, the diodes D2 and D3 conduct due to the forward voltage, and the current reaches the output terminal through the diodes D2 and D3. At this time, the diodes D1 and D4 are reverse-biased and cut off, preventing the current from passing through, thus ensuring that the current flowing through the diodes always remains half of the input current, greatly reducing the current stress of the diodes, and further reducing the current stress of the entire circuit.
[0048] The above has shown and described the basic principles, main features and advantages of the present utility model. Those skilled in the art should understand that the present utility model is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present utility model and are not used to limit the present utility model. Without departing from the spirit and scope of the present utility model, the present utility model will have various changes and improvements, and these changes and improvements all fall within the scope of the present utility model claimed. The scope of protection claimed by the present utility model is defined by the appended claims and their equivalents.
Claims
1. An LLC rectifier circuit that effectively reduces current stress, characterized in that: It includes an input module, a resonance module, a switching module and an output module. The resonance module includes a switch control circuit and a resonance circuit. The switching module includes a full-wave rectifier circuit, a full-bridge rectifier circuit, a switching transistor QH1, a switching transistor QH2 and a frequency control unit. The switch control circuit is connected to the resonance circuit, and the resonance circuit is connected to the switching module; The current at the input end is controlled by the switch control circuit to reach the resonance circuit, filtered by the resonance circuit, and the disconnection and closing of the switching transistors QH1 and QH2 are controlled through the frequency control unit and the output voltage, switching the secondary circuit to a full-wave rectifier circuit or a full-bridge rectifier circuit, reducing the output current to one-half of the input current and reducing the current stress.
2. The LLC rectifier circuit for effectively reducing current stress according to claim 1, wherein: The resonance circuit includes a capacitor C, an inductor L and a transformer T, where: One end of the capacitor C is connected to one end of the inductor L. The other end of the inductor L is connected to one end of the primary winding of the transformer T. The other end of the capacitor C is connected to the source of the CMOS transistor V1 and the drain of the CMOS transistor V2. The source of the CMOS transistor V2 is connected to the other end of the primary winding of the transformer T.
3. The LLC rectifier circuit for effectively reducing current stress according to claim 1, wherein: The switch control circuit includes a CMOS transistor V1, a CMOS transistor V2, a diode D6 and a diode D7, where: The source of the CMOS transistor V1 is connected in parallel to the negative pole of the diode D6, the drain of the CMOS transistor V1 is connected in parallel to the positive pole of the diode D6, the source of the CMOS transistor V2 is connected in parallel to the negative pole of the diode D7, the drain of the CMOS transistor V2 is connected in parallel to the positive pole of the diode D7, and the source of the CMOS transistor V1 is connected to the drain of the CMOS transistor V2.
4. The LLC rectifier circuit for effectively reducing current stress according to claim 1, characterized in that: The full-wave rectifier circuit includes a transformer T and diodes D1, D2, D5, where: The primary winding of the transformer T is connected to the resonance circuit. The secondary winding of the transformer T is connected to the negative poles of the diode D1 and the diode D2. The positive poles of the diode D1 and the diode D2 are connected to the output end. The positive pole of the diode D5 is connected to the center tap of the secondary winding of the transformer T. The negative pole of the diode D5 is connected to the output end. When the transformer T is wound, the number of turns of the 4-5 winding in the secondary winding of the transformer T is the same as that of the 3-6 winding.
5. The LLC rectifier circuit for effectively reducing current stress according to claim 1, characterized in that: The full-bridge rectifier circuit includes a transformer T and diodes D1, D2, D3, D4, D5, where: The primary winding of the transformer T is connected to the resonance circuit. One end of the secondary winding of the transformer T is connected to the negative pole of the diode D1 and the positive pole of the diode D3. The other end of the secondary winding of the transformer T is connected to the negative pole of the diode D2 and the positive pole of the diode D4. The positive poles of the diode D1 and the diode D2 are connected to the output filter. The negative poles of the diode D3 and the diode D4 are connected in parallel to the negative pole of the diode D5 and connected to the output filter. The positive pole of the diode D5 is connected to the center tap of the secondary winding of the transformer T.
6. The LLC rectifier circuit for effectively reducing current stress according to claim 1, wherein: The switching transistors QH1 and QH2 use a relay, a MOS transistor, an IGBT as the switching unit.