LLC resonant converter with high conversion efficiency

Abstract

The present invention mainly provides a high-efficiency LLC resonant converter. According to the design of the present invention, an error amplification unit generates an adjustment voltage signal based on a voltage difference detected from two ends of a detection unit, and transmits it to a first control unit, so that the first control unit can know a current load rate based on the adjustment voltage signal. Continuing, a second control unit receives a first adjustment signal transmitted by the first control unit through a first isolation feedback unit, thereby generating a switch component control signal and transmitting it to a switch component in a direct current supply unit to control the switch component and adjust an output voltage of the direct current supply unit, so that the LLC resonant converter can maintain a conversion efficiency greater than or equal to 98% under any load condition.

Description

Technical Field

[0001] The present invention relates to the technical field of switching-mode power supply (SMPS), and in particular to an LLC resonant converter with high conversion efficiency. Background Art

[0002] The technology of switching-mode power supply (SMPS) has been widely used in the production of power supplies for various motor devices and electronic products. In addition, as electronic products are developing towards being thinner and smaller, the power density of the switching power converter must be increased by increasing the switching frequency in order to effectively reduce the size of the switching power converter. Therefore, the LLC resonant converter (LLC resonant converter) with the characteristics of zero voltage switching (ZVS) and zero current switching (ZCS) was proposed.

[0003] Figure 1 The circuit structure diagram of an existing LLC series resonant converter is shown. Figure 1 As shown, the existing LLC series resonant converter 2' includes: a full-bridge rectifier 21' coupled to the mains, a power factor correction unit 22' having a first switch component SQ1', a bridge switch unit 23' including a second switch component SQ2' and a third switch component SQ3', a resonant unit 24', a transformer unit 25', an output rectifier unit 26', a current detection resistor RS', a voltage detection unit including a first voltage-dividing resistor RV1' and a second voltage-dividing resistor RV2', an error amplification unit 27', an isolation feedback unit 28', and a control unit 29'. The resonant unit 24' includes a resonant inductor Lr' and a resonant capacitor Cr'. In addition, an excitation inductor Lm' of the transformer unit 25', the resonant inductor Lr' and the resonant capacitor Cr' together form an LLC resonant tank.

[0004] Under normal working conditions, the switching frequency (Switching frequency, fS) of the second switch component SQ2' and the third switch component SQ3' can change the gain value (gain) of the LLC series resonant converter 2' to achieve the adjustment of the output voltage. In other words, relative to the wide range of output voltage, the switching frequency must also be widened. In this way, the wider the range of output voltage modulation, the wider the operating frequency, and thus the hardware specifications of the LLC resonant tank must be relatively improved so that the ratio of the switching frequency to a resonant frequency (Resonant frequency, fr) of the LLC resonant tank can be controlled as close to 1 as possible, that is, fS = fr.

[0005] However, from a practical perspective, after the hardware specifications of the LLC resonant tank are designed and manufactured to adjust the range of the output voltage, the resonant frequency is fixed. In other words, the resonant frequency cannot be adjusted online in real time according to the current load rate of the circuit. In this case, the switching frequency can only be adjusted by the control unit 29'. For example, when the load device 3' switches from no load or light load to full load, the switching frequency must be adjusted quickly and significantly so that the output voltage range can be stabilized within the specification. Therefore, in practical operation, when the load rate changes rapidly, the switching frequency cannot be directly adjusted to be equal to or close to the resonant frequency, resulting in a significant decrease in the conversion efficiency of the LLC series resonant converter 2'.

[0006] like Figure 1 As shown, the prior art uses the method of adjusting the compensation parameters of the control unit 29' to achieve the effect of quickly adjusting the switching frequency. However, practical experience shows that this method will cause unstable fluctuations in the output voltage. Figure 1 As shown, the addition of the power factor correction unit 22' can reduce the harmonic components of a pulsating DC signal output by the full-bridge rectifier 21' and make the input current and the input voltage in phase, thereby improving the power factor. After the first switch component SQ1' is controlled by a switching signal, the output voltage of the power factor correction unit 22' can be adjusted to achieve the effect of assisting in stabilizing the output voltage.

[0007] Figure 2 A graph showing the load factor versus conversion efficiency of a conventional LLC series resonant converter 2' having the power factor correction unit 22' is shown. Figure 2In the figure, curve A is measured when the mains provides 115Vac AC power, while curve B is measured when the mains provides 230Vac AC power. The measured data show that the power factor correction unit 22' does help to improve the conversion efficiency of the existing LLC series resonant converter 2', and the maximum value of the conversion efficiency is about 95%, when the load rate of the LLC series resonant converter 2' is about 50%. It is worth noting that when the LLC series resonant converter 2' is operated under light load or heavy load, the conversion efficiency will still drop significantly.

[0008] From the above description, it can be seen that the existing LLC series resonant converter with a power factor correction unit still has room for further improvement. In view of this, the inventor of this case has made great efforts to study and invent, and finally developed a high conversion efficiency LLC resonant converter of the present invention. Summary of the invention

[0009] The main purpose of the present invention is to provide an LLC resonant converter with high conversion efficiency, which includes: a DC power supply unit, a bridge switch unit, a resonant unit, a transformer unit, an output rectifier unit, a detection unit, a first control unit, an error amplifier unit, a first isolation feedback unit, and a second control unit. According to the design of the present invention, the error amplifier unit generates an adjustment voltage signal based on a voltage difference detected from both ends of the detection unit and transmits it to the first control unit, so that the first control unit can know a current load rate of the LLC resonant converter based on the adjustment voltage signal, and then generate a first adjustment signal based on the current load rate. Continuing, the second control unit receives the first adjustment signal through the first isolation feedback unit, and generates a switch component control signal based on the first adjustment signal and transmits it to a switch component in the DC power supply unit, so that the switch component is periodically turned on / off to adjust an output voltage of the DC power supply unit, so that the LLC resonant converter can maintain a conversion efficiency greater than or equal to 98% under any load condition.

[0010] To achieve the above object, the present invention proposes a first embodiment of the LLC resonant converter, which includes:

[0011] A DC power supply unit has at least one first switch component and is used to receive a power source, thereby outputting a first voltage signal after performing a power conversion process on the power source;

[0012] a bridge switch unit, coupled to the DC power providing unit to receive the first voltage signal;

[0013] a resonant unit, coupled to the bridge switch unit to receive a second voltage signal transmitted from the bridge switch unit, and comprising a resonant inductor and a resonant capacitor;

[0014] A transformer unit, comprising a primary winding, an exciting inductor connected in parallel with the primary winding, and a secondary winding having a first electrical end, a second electrical end and a third electrical end, wherein the primary winding is coupled to the resonant unit so that the exciting inductor, the resonant inductor and the resonant capacitor together form an LLC resonant tank;

[0015] an output rectifying unit, coupled to the first electrical end and the third electrical end of the secondary winding, for rectifying a third voltage signal received from the secondary winding, thereby providing an output voltage to at least one load device;

[0016] A detection unit coupled to the second electrical end of the secondary winding;

[0017] a first control unit, coupled to the output rectifying unit;

[0018] an error amplifying unit coupled to two ends of the detecting unit and the first control unit, so as to generate an adjustment voltage signal according to a voltage difference between the two ends of the detecting unit and transmit the adjustment voltage signal to the first control unit, so that the first control unit can learn a current load rate of the LLC resonant converter according to the adjustment voltage signal, and then generate a first adjustment signal based on the current load rate;

[0019] a first isolation feedback unit, coupled to the first control unit; and

[0020] A second control unit is coupled to the first isolation feedback unit to receive the first adjustment signal through the first isolation feedback unit, and generates a first switch component control signal according to the first adjustment signal and transmits it to a control signal receiving end of the first switch component, thereby controlling the first switch component to periodically turn on / off to adjust the first voltage signal corresponding to the current load rate, thereby maintaining a conversion efficiency of the LLC resonant converter.

[0021] To achieve the above object, the present invention proposes a second embodiment of the LLC resonant converter, which includes:

[0022] A DC power supply unit has at least one first switch component and is used to receive a power source, thereby outputting a first voltage signal after performing a power conversion process on the power source;

[0023] a bridge switch unit, coupled to the DC power providing unit to receive the first voltage signal;

[0024] a resonant unit, coupled to the bridge switch unit to receive a second voltage signal transmitted from the bridge switch unit, and comprising a resonant inductor and a resonant capacitor;

[0025] A transformer unit, comprising a primary winding, an exciting inductor connected in parallel with the primary winding, and a secondary winding having a first electrical end, a second electrical end and a third electrical end, wherein the primary winding is coupled to the resonant unit so that the exciting inductor, the resonant inductor and the resonant capacitor together form an LLC resonant tank;

[0026] an output rectifying unit, coupled to the first electrical end and the third electrical end of the secondary winding, for rectifying a third voltage signal received from the secondary winding, thereby providing an output voltage to at least one load device;

[0027] A detection unit coupled to the second electrical end of the secondary winding;

[0028] a first control unit, coupled to the output rectifying unit;

[0029] an error amplifying unit coupled to two ends of the detecting unit, so as to generate an adjusting voltage signal according to a voltage difference between the two ends of the detecting unit;

[0030] a first isolation feedback unit, coupled to the error amplification unit; and

[0031] A second control unit is coupled to the first isolation feedback unit to receive the adjustment voltage signal through the first isolation feedback unit, so that the second control unit can learn a current load rate of the LLC resonant converter according to the adjustment voltage signal, and then generate a first switch component control signal based on the current load rate and transmit it to a control signal receiving end of the first switch component, so as to control the first switch component to periodically turn on / off to adjust the first voltage signal corresponding to the current load rate, thereby maintaining a conversion efficiency of the LLC resonant converter.

[0032] In the first embodiment and the second embodiment of the LLC resonant converter of the present invention, the DC power providing unit is an AC-DC converter or a DC-DC converter.

[0033] Furthermore, in a feasible embodiment, the DC power providing unit is a boost AC-DC converter, and includes:

[0034] a full-bridge rectifier unit coupled to the power source and configured to convert an alternating current signal transmitted from the power source into a pulsating direct current voltage signal; and

[0035] A power factor correction unit includes the at least one first switch component.

[0036] In the first and second embodiments of the LLC resonant converter of the present invention, the power factor correction unit is a semi-bridgeless PFC, an interleaving PFC, a totem pole PFC, or a conventional PFC.

[0037] In the first embodiment and the second embodiment of the LLC resonant converter of the present invention, the bridge switch unit is a half-bridge switch unit or a full-bridge switch unit.

[0038] Furthermore, in a feasible embodiment, the bridge switch unit is a half-bridge switch unit, and includes:

[0039] a second switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the power factor correction unit and the resonance unit of the direct current providing unit;

[0040] A third switch component has a first electrical end, a second electrical end and a control signal receiving end, and is respectively coupled to the power factor correction unit and the resonance unit of the direct current providing unit through the second electrical end and the first electrical end.

[0041] In the first and second embodiments of the LLC resonant converter of the present invention, the output rectifier unit is a synchronous rectifier unit and includes:

[0042] a fourth switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the first electrical end and the third electrical end of the secondary winding; and

[0043] a fifth switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the third electrical end of the secondary winding and the load device;

[0044] The first control unit is coupled to the control signal receiving end of the fourth switch component and the control signal receiving end of the fifth switch component.

[0045] In the first and second embodiments of the LLC resonant converter of the present invention, the first switch component, the second switch component, the third switch component, the fourth switch component, and the fifth switch component are all a power metal oxide semiconductor field effect transistor, a gallium nitride power metal oxide semiconductor field effect transistor, or an insulated gate bipolar transistor (IGBT).

[0046] In the first embodiment of the LLC resonant converter of the present invention, the first control unit comprises:

[0047] a conversion unit, configured to perform a conversion process on the adjustment voltage signal to obtain the current load rate; and

[0048] A microprocessing unit generates the first adjustment signal according to the current load rate.

[0049] Furthermore, the first embodiment of the LLC resonant converter of the present invention further includes:

[0050] a voltage detection unit, coupled to the second electrical end of the secondary winding; and

[0051] a second isolation feedback unit coupled to the first control unit and simultaneously coupled to the control signal receiving end of the second switch component and the control signal receiving end of the third switch component;

[0052] The first control unit obtains a sampled output voltage through the voltage detection unit, and then generates a second adjustment signal according to the sampled output voltage, and the second isolation feedback unit transmits a second switch component control signal and a third switch component control signal to the second switch component and the third switch component respectively after receiving the second adjustment signal.

[0053] In the second embodiment of the LLC resonant converter of the present invention, the second control unit comprises:

[0054] a conversion unit, configured to perform a conversion process on the adjustment voltage signal to obtain the current load rate; and

[0055] A microprocessing unit generates the first switch component control signal according to the current load rate.

[0056] Furthermore, the second embodiment of the LLC resonant converter of the present invention further includes:

[0057] a voltage detection unit, coupled to the second electrical end of the secondary winding; and

[0058] a second isolation feedback unit coupled to the first control unit and simultaneously coupled to the control signal receiving end of the second switch component and the control signal receiving end of the third switch component;

[0059] The first control unit obtains a sampled output voltage through the voltage detection unit, and then generates an adjustment signal according to the sampled output voltage, and the second isolation feedback unit transmits a second switch component control signal and a third switch component control signal to the second switch component and the third switch component respectively after receiving the adjustment signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A circuit architecture diagram of an existing LLC series resonant converter;

[0061] Figure 2 is a graph showing load rate versus conversion efficiency of a conventional LLC series resonant converter having a power factor correction unit;

[0062] Figure 3 A circuit architecture diagram of a high conversion efficiency LLC resonant converter of the present invention;

[0063] Figure 4 is a circuit topology diagram of a power factor correction unit;

[0064] Figure 5 is a data curve diagram of load rate relative to output voltage of the power factor correction unit;

[0065] Figure 6 A graph showing the load rate versus conversion efficiency of the high conversion efficiency LLC resonant converter of the present invention; and

[0066] Figure 7 This is a circuit architecture diagram of a high conversion efficiency LLC resonant converter of the present invention. Explanation of the main symbols in the figure:

[0067] 1: LLC resonant converter

[0068] 10: DC power supply unit

[0069] 11: Full-bridge rectifier unit

[0070] 12: Power factor correction unit

[0071] 13: Bridge switch unit

[0072] 14: Resonance unit

[0073] 15: Transformer unit

[0074] 16: Output rectifier unit

[0075] 17: First control unit

[0076] 171: Microprocessing unit

[0077] 172:Conversion unit

[0078] 18a: First isolation feedback unit

[0079] 18b: Second isolation feedback unit

[0080] 19: Second control unit

[0081] 191: Microprocessing Unit

[0082] 192:Conversion unit

[0083] 1E: Error amplifier unit

[0084] SQ1: First switch component

[0085] SQ2: Second switch assembly

[0086] SQ3: Third switch assembly

[0087] SQ4: Fourth switch component

[0088] SQ5: Fifth switch assembly

[0089] RV1: The first voltage divider resistor

[0090] RV2: The second voltage divider resistor

[0091] RS: Checkout unit

[0092] Co: output capacitance

[0093] Cr: resonant capacitor

[0094] Lr: resonant inductor

[0095] Lm: Magnetizing inductance

[0096] 3: Load device

[0097] 2': LLC series resonant converter

[0098] 21': Full Bridge Rectifier

[0099] 22': Power factor correction unit

[0100] 23': Bridge switch unit

[0101] 24': Resonance unit

[0102] 25': Transformer unit

[0103] 26': Output rectifier unit

[0104] 27': Error amplification unit

[0105] 28': Isolation feedback unit

[0106] 29': Control unit

[0107] SQ1': First switch component

[0108] SQ2': Second switch component

[0109] SQ3': The third switch component

[0110] RV1': The first voltage divider resistor

[0111] RV2': The second voltage divider resistor

[0112] RS': Current detection resistance

[0113] Cr': resonant capacitance

[0114] Lr': resonant inductance

[0115] Lm': Magnetizing inductance

[0116] 3': Loading device DETAILED DESCRIPTION

[0117] In order to more clearly describe the LLC resonant converter with high conversion efficiency proposed by the present invention, the preferred embodiments of the present invention will be described in detail below with reference to the drawings.

[0118] First embodiment

[0119] See also Figure 3 , which shows a circuit architecture diagram of a high conversion efficiency LLC resonant converter of the present invention. Figure 3 As shown, the LLC resonant converter with high conversion efficiency of the present invention (hereinafter referred to as "LLC resonant converter 1") mainly includes: a DC power supply unit 10, a bridge switch unit 13, a resonant unit 14, a transformer unit 15, an output rectifier unit 16, a detection unit R S , a first control unit 17, an error amplifying unit 1E, a first isolation feedback unit 18a, and a second control unit 19. The DC power providing unit 10 has at least one first switch element SQ1, and is used to receive a power source, so as to perform a power conversion process on the power source and then output a first voltage signal V1. In a feasible embodiment, the DC power providing unit 10 can be an AC-DC converter or a DC-DC converter.

[0120] Continue to read Figure 3 , and please also refer to Figure 4 A circuit topology of the power factor correction unit 12 is shown. Figure 4 The DC power supply unit 10 is exemplarily a boost AC-DC converter, and includes a full-bridge rectifier unit 11 and a power factor correction unit 12 including the at least one first switch element SQ1. In more detail, the full-bridge rectifier unit 11 is coupled to the power source to convert an AC signal AC transmitted from the power source into a pulsating DC voltage signal V IN Furthermore, the power factor correction unit 12 is coupled to the full-bridge rectifier unit 11 to receive the pulsating DC voltage signal V IN , thereby outputting the first voltage signal V1. In other words, the pulsating DC voltage signal VIN serves as an input voltage signal of the power factor correction unit 12, and the first voltage signal V1 serves as an output voltage signal of the power factor correction unit 12.

[0121] Here, it must be emphasized that the present invention does not particularly limit the implementation of the power factor correction unit 12. Therefore, in a feasible embodiment, the power factor correction unit 12 can be a semi-bridgeless power factor corrector (semi-bridgeless PFC), an interleaving power factor corrector (interleaving PFC), a totem pole power factor corrector (totem pole PFC), or an existing conventional power factor corrector. Further, Figure 3 and Figure 4 The bridge switch unit 13 is shown coupled to the DC power providing unit 10 to receive the first voltage signal V1 .

[0122] The present invention also does not particularly limit the implementation of the bridge switch unit 13. Therefore, in a feasible embodiment, the bridge switch unit 13 can be a half-bridge switch unit or a full-bridge switch unit. Figure 4 The bridge switch unit 13 is shown as a half-bridge switch unit, and includes a second switch component SQ2 and a third switch component SQ3. In more detail, the second switch component SQ2 has a first electrical end, a second electrical end, and a control signal receiving end, and is coupled to the power factor correction unit 12 and the resonance unit 14 of the DC power providing unit 10 at the first electrical end and the second electrical end, respectively. On the other hand, the third switch component SQ3 has a first electrical end, a second electrical end, and a control signal receiving end, and is coupled to the power factor correction unit 12 and the resonance unit 14 of the DC power providing unit 10 at the second electrical end and the first electrical end, respectively.

[0123] The resonant unit 14 is coupled to the bridge switch unit 13 to receive a second voltage signal V2 transmitted from the bridge switch unit 13, and includes a resonant inductor Lr and a resonant capacitor Cr. A first end of the resonant inductor Lr is coupled to a common point between the second electrical end of the second switch component SQ2 and the first electrical end of the third switch component SQ3, and a first end of the resonant capacitor Cr is coupled to the second electrical end of the third switch component SQ3. Figure 3 and Figure 4 As shown, the transformer unit 15 includes a primary winding, an excitation inductor Lm connected in parallel with the primary winding, and a secondary winding having a first electrical end, a second electrical end and a third electrical end, and the primary winding is coupled to the resonant unit 14 so that the excitation inductor Lm, the resonant inductor Lr and the resonant capacitor Cr together form an LLC resonant tank.

[0124] Continue to read Figure 3 and Figure 4 The output rectifier unit 16 is coupled to the first electrical terminal and the third electrical terminal of the secondary winding, and is used to perform a rectification process on a third voltage signal V3 received from the secondary winding, thereby O And provide an output voltage to at least one load device 3. In an exemplary embodiment, the output rectifier unit 16 is a synchronous rectifier unit, and it includes a fourth switch component SQ4 and a fifth switch component SQ5. Among them, the fourth switch component SQ4 has a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the first electrical end and the third electrical end of the secondary winding. And, the fifth switch component SQ5 has a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the third electrical end of the secondary winding and the load device 3. In terms of circuit function, the transformer unit 15 receives the second voltage signal V2 transmitted by the bridge switch unit 13 through the resonant unit 14, thereby converting the second voltage signal V2 into a third voltage signal V3. Furthermore, the output rectifying unit 16 performs a rectification process on a third voltage signal V3 received from the secondary winding, thereby outputting the output voltage.

[0125] Depend on Figure 3 and Figure 4 It can be known that the detection unit RS is a detection resistor coupled to the second electrical end of the secondary winding, and the first control unit 17 is coupled to the output rectifier unit 16. On the other hand, the error amplification unit 1E is coupled to the first control unit 17 and the detection unit RS. S The two ends of the detection unit R SA voltage difference between the two ends of the M The voltage signal S is transmitted to the first control unit 17 so that the first control unit 17 can adjust the voltage signal S according to the voltage signal S M The current load rate of the LLC resonant converter 1 is obtained, and then a first adjustment signal Smd1 is generated based on the current load rate. In more detail, the first isolation feedback unit 18a is coupled to the first control unit 17, and the second control unit 19 is coupled to the first isolation feedback unit 18a to receive the first adjustment signal Smd1 through the first isolation feedback unit 18a.

[0126] According to the design of the present invention, the second control unit 19 generates a first switch component control signal S1 according to the first adjustment signal Smd1 and transmits it to a control signal receiving end of the first switch component SQ1, thereby controlling the first switch component Q1 to periodically turn on / off to adjust the first voltage signal V1 corresponding to the current load rate. When the first voltage signal V1 (i.e., the output voltage of the power factor correction unit 12 of the DC power supply unit 10) is correspondingly modulated according to the current load rate of the LLC resonant converter 1, the first control unit 17 can be used to control the switching frequency (Switching frequency, f) of the second switch component SQ2 and the third switch component SQ3. S ), so that the switching frequency is consistent with the resonant frequency of the LLC resonant tank (Resonant frequency, f r ) can be controlled as close to 1 as possible, so that the LLC resonant converter 1 can maintain high conversion efficiency under any load condition.

[0127] like Figure 3 and Figure 4 As shown, the first control unit 17 includes a conversion unit 172 and a microprocessing unit 171. The conversion unit 172 is used to adjust the voltage signal S M A conversion process is performed to obtain the current load rate, so that the microprocessing unit 171 generates the first adjustment signal Smd1 according to the current load rate. In a feasible embodiment, the conversion unit 172 can be an algorithm for adjusting the voltage signal Smd1 based on the error amplifier unit 1E. M An immediate load rate of the LLC resonant converter 1 is calculated.

[0128] In another feasible embodiment, the conversion unit 172 may be a look-up table (LUT), and it includes the adjustment voltage signal S MIt should be noted that since the first control unit 17 is a microprocessor, the upper limit of its acceptable input voltage is 3.3V. For this reason, the adjustment voltage signal S sent by the error amplification unit 1E must be M The voltage value (level) of is limited to within 3.3V. Therefore, the adjustment voltage signal S M The voltage value of the adjustment voltage signal S is between 0V and 3.3V. M The voltage value of is between 0V and 2.0V, where 0V corresponds to a load rate of 0%, and 2V corresponds to a load rate of 100%. It should be understood that the design (2-0)N can determine the monitoring resolution of the load rate. In other words, the larger the value of N, the higher the monitoring resolution for the load rate. For example, the lookup table (i.e., the conversion unit 172) includes the adjustment voltage signal S M The multiple voltage values ​​are 0V, 0.02V, ..., 1V, 1.02V, ..., 1.98V, 2V. Correspondingly, the multiple load rates corresponding to the multiple voltage values ​​included in the lookup table are 1%, 2%, ..., 50%, 51%, ..., 99%, 100%.

[0129] In other words, the micro-processing unit 171 receives the adjustment voltage signal S transmitted from the error amplifying unit 1E. M , so as to adjust the voltage signal S M A current voltage value is used to find a corresponding load rate from the lookup table 172, and then a corresponding adjustment parameter is found according to the load rate, so as to generate the first adjustment signal Smd1 according to the adjustment parameter. Finally, the second control unit 19 receives the first adjustment signal Smd1 through the first isolation feedback unit 18a, and generates a first switch component control signal S1 according to the first adjustment signal Smd1 and transmits it to the control signal receiving end of the first switch component SQ1, so as to control the first switch component SQ1 to periodically turn on / off to adjust the first voltage signal V1 corresponding to the current load rate, so as to maintain a conversion efficiency of the LLC resonant converter 1.

[0130] Figure 5 A data curve diagram showing the load rate relative to the output voltage (ie, the first voltage signal V1) of the power factor correction unit 12, and Figure 6 The load ratio curve of the high conversion efficiency LLC series resonant converter 1 of the present invention is shown relative to the conversion efficiency. Figure 3 and Figure 5 As shown, the first control unit 17 adjusts the voltage signal S according to the error amplification unit 1E. MA first adjustment signal Smd1 is generated, and the second control unit 19 receives the first adjustment signal Smd1 through the first isolation feedback unit 18a, thereby generating a first switch component control signal S1 according to the first adjustment signal Smd1 and transmitting it to the control signal receiving end of the first switch component SQ1, thereby controlling the first switch component SQ1 to periodically turn on / off to adjust the first voltage signal V1 (that is, the output voltage of the power factor correction unit 12) corresponding to the current load rate.

[0131] Furthermore, if Figure 6 As shown, when the output voltage of the power factor correction unit 12 is adjusted according to the current load rate, the LLC resonant converter 1 can maintain a conversion efficiency greater than or equal to 98% under any load condition. Figure 6 Curve C in FIG. 1 is measured from the LLC resonant converter 1 of the present invention when the mains provides 230Vac AC power, while curve B is measured from the existing LLC resonant converter when the mains provides 230Vac AC power. In addition, Figure 6 The experimental data also show that the conversion efficiency of the LLC resonant converter 1 of the present invention is significantly greater than the conversion efficiency of the conventional LLC resonant converter regardless of operating at light load, medium load or heavy load.

[0132] It is additionally noted that if Figure 3 and Figure 4 As shown, the LLC resonant converter 1 of the present invention further includes a voltage detection unit and a second isolation feedback unit 18b. The voltage detection unit is coupled to the second electrical end of the secondary winding. And, Figure 3 and Figure 4 The voltage detection unit is shown to include a first voltage dividing resistor R V1 and a second voltage dividing resistor R V2 A voltage divider unit. Further, the second isolation feedback unit 18b is coupled to the first control unit 17, and is also coupled to the control signal receiving end of the second switch component SQ2 and the control signal receiving end of the third switch component SQ3. With such a configuration, the first control unit 17 obtains a sampled output voltage through the voltage detection unit, and then generates a second adjustment signal Smd2 according to the sampled output voltage, and the second isolation feedback unit 18b transmits a second switch component control signal S2 and a third switch component control signal S3 to the second switch component SQ2 and the third switch component SQ3 respectively after receiving the second adjustment signal Smd2.

[0133] Second embodiment

[0134] See also Figure 7 , which shows a circuit architecture diagram of a high conversion efficiency LLC resonant converter of the present invention. Figure 7 As shown, the second embodiment of the LLC resonant converter with high conversion efficiency (hereinafter referred to as "LLC resonant converter 1") of the present invention mainly includes: a DC power supply unit 10, a bridge switch unit 13, a resonant unit 14, a transformer unit 15, an output rectifier unit 16, a detection unit R S , a first control unit 17 , an error amplifying unit 1E, a first isolation feedback unit 18 a , and a second control unit 19 .

[0135] In the second embodiment, the DC power supply unit 10 has at least one first switch component Q1, and is used to receive a power source, so as to output a first voltage signal V1 after performing a power conversion process on the power source. In addition, the bridge switch unit 13 is coupled to the DC power supply unit 10 to receive the first voltage signal V1, and the resonance unit 14 is coupled to the bridge switch unit 13 to receive a second voltage signal V2 transmitted from the bridge switch unit 13, and includes a resonant inductor Lr and a resonant capacitor Cr. In more detail, the transformer unit 15 includes a primary winding, an excitation inductor Lm connected in parallel with the primary winding, and a secondary winding having a first electrical end, a second electrical end and a third electrical end, and the primary winding is coupled to the resonance unit 14, so that the excitation inductor Lm, the resonant inductor Lr and the resonant capacitor Cr together form an LLC resonant tank. The output rectifier unit 16 is coupled to the first electrical terminal and the third electrical terminal of the secondary winding to perform a rectification process on a third voltage signal V3 received from the secondary winding, thereby providing an output voltage to at least one load device 3. S The second electrical end is coupled to the secondary winding.

[0136] Differently, in the second embodiment, the first control unit 17 is coupled to the output rectifier unit 16, and the error amplification unit 1E is coupled to the detection unit R S The two ends of the detection unit R S A voltage difference between the two ends of the M .like Figure 7 As shown, the first isolation feedback unit 18a is coupled to the error amplifying unit 1E, and the second control unit 19 is coupled to the first isolation feedback unit 18a, so as to receive the adjustment voltage signal S through the first isolation feedback unit 18a. M , so that the second control unit 19 adjusts the voltage signal S MA current load rate of the LLC resonant converter 1 is obtained, and then a first switch component control signal S1 is generated based on the current load rate and transmitted to a control signal receiving end of the first switch component Q1, so as to control the first switch component Q1 to be periodically turned on / off to adjust the first voltage signal V1 corresponding to the current load rate, thereby maintaining a conversion efficiency of the LLC resonant converter 1.

[0137] In the second embodiment, the second control unit 19 includes a conversion unit 192 and a processing unit 191. The conversion unit 192 is used to adjust the voltage signal S M A conversion process is performed to obtain the current load rate, and the microprocessor unit 191 generates the first switch component control signal S1 according to the current load rate. In a feasible embodiment, the conversion unit 192 of the second control unit 19 can be an algorithm for adjusting the voltage signal S1 based on the error amplification unit 1E. M A current load rate of the LLC resonant converter 1 is calculated.

[0138] In another feasible embodiment, the conversion unit 192 of the second control unit 19 can be a look-up table (LUT), and it includes the adjustment voltage signal S M For example, the adjustment voltage signal S M The voltage value of is between 0V and 2.0V, so that 0V corresponds to a load rate of 0% and 2V corresponds to a load rate of 100%. In this way, the lookup table (ie, the conversion unit 192) includes the adjustment voltage signal S M The multiple voltage values ​​are 0V, 0.02V, ..., 1V, 1.02V, ..., 1.98V, 2V. Correspondingly, the multiple load rates corresponding to the multiple voltage values ​​included in the lookup table are 1%, 2%, ..., 50%, 51%, ..., 99%, 100%.

[0139] In other words, Figure 3 In the first embodiment shown in the figure, a conversion unit 172 is provided in the first control unit 17 for converting an adjustment voltage signal S transmitted from the error amplifying unit 1E into MThe data and / or signal used to represent the current load rate of the LLC resonant converter 1 is converted so that the microprocessor unit 171 of the first control unit 17 can generate the first switch component control signal S1 according to the current load rate and transmit it to the first switch component SQ1 included in the power factor correction unit 12 of the DC power providing unit 10 to adjust the first voltage signal V1 output by the DC power providing unit 10. On the other hand, Figure 7 In the second embodiment shown, a conversion unit 192 is provided in the second control unit 19 to convert an adjustment voltage signal S transmitted from the error amplifying unit 1E into M The data and / or signal used to represent the current load rate of the LLC resonant converter 1 are converted so that the microprocessor unit 191 of the first control unit 19 can generate the first switch component control signal S1 according to the current load rate and transmit it to the first switch component SQ1 included in the power factor correction unit 12 of the DC power providing unit 10 to adjust the first voltage signal V1 output by the DC power providing unit 10.

[0140] It is additionally noted that if Figure 7 The second embodiment of the LLC resonant converter 1 of the present invention further comprises a voltage detection unit and a second isolation feedback unit 18b. The voltage detection unit is coupled to the second electrical end of the secondary winding. And, Figure 7 The voltage detection unit is shown to include a first voltage dividing resistor R V1 and a second voltage dividing resistor R V2 A voltage divider unit. Further, the second isolation feedback unit 18b is coupled to the first control unit 17, and is also coupled to the control signal receiving end of the second switch component SQ2 and the control signal receiving end of the third switch component SQ3. With such a configuration, the first control unit 17 obtains a sampled output voltage through the voltage detection unit, and then generates an adjustment signal Smd according to the sampled output voltage, and the second isolation feedback unit 18b transmits a second switch component control signal S2 and a third switch component control signal S3 to the second switch component SQ2 and the third switch component SQ3 respectively after receiving the adjustment signal Smd.

[0141] Thus, all embodiments of the LLC resonant converter with high conversion efficiency provided by the present invention have been fully and clearly described above. It must be emphasized that the above detailed description is a specific description of the feasible embodiments of the present invention, and the embodiments are not used to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the technical spirit of the present invention should be included in the patent scope of this case.

Claims

1. An LLC resonant converter, comprising: A DC power supply unit has at least one first switch component and is used to receive a power source, thereby outputting a first voltage signal after performing a power conversion process on the power source; a bridge switch unit, coupled to the DC power providing unit to receive the first voltage signal; a resonant unit, coupled to the bridge switch unit to receive a second voltage signal transmitted from the bridge switch unit, and comprising a resonant inductor and a resonant capacitor; A transformer unit, comprising a primary winding, an exciting inductor connected in parallel with the primary winding, and a secondary winding having a first electrical end, a second electrical end and a third electrical end, wherein the primary winding is coupled to the resonant unit so that the exciting inductor, the resonant inductor and the resonant capacitor together form an LLC resonant tank; an output rectifying unit, coupled to the first electrical end and the third electrical end of the secondary winding, for rectifying a third voltage signal received from the secondary winding, thereby providing an output voltage to at least one load device; a current detection resistor, one end of which is coupled to the second electrical end of the secondary winding, and the other end of which is coupled to the load device; a first control unit, coupled to the output rectifying unit; an error amplifying unit, coupled to both ends of the current detection resistor and the first control unit, so as to generate an adjustment voltage signal according to a voltage difference between both ends of the current detection resistor and transmit it to the first control unit, so that the first control unit can know a current load rate of the LLC resonant converter according to the adjustment voltage signal, and then generate a first adjustment signal based on the current load rate; a first isolation feedback unit, coupled to the first control unit; as well as A second control unit is coupled to the first isolation feedback unit to receive the first adjustment signal through the first isolation feedback unit, and generates a first switch component control signal according to the first adjustment signal and transmits it to a control signal receiving end of the first switch component, thereby controlling the first switch component to periodically turn on / off to adjust the first voltage signal corresponding to the current load rate, thereby maintaining a conversion efficiency of the LLC resonant converter.

2. The LLC resonant converter according to claim 1, characterized in that: The DC power supply unit is an AC-DC converter or a DC-DC converter.

3. The LLC resonant converter according to claim 1, characterized in that: The DC power supply unit is a boost AC-DC converter and includes: a full-bridge rectifier unit coupled to the power source and configured to convert an alternating current signal transmitted from the power source into a pulsating direct current voltage signal; and A power factor correction unit includes the at least one first switch component.

4. The LLC resonant converter according to claim 3, characterized in that: The power factor correction unit is any one of the following: a semi-bridgeless power factor corrector, an interleaved power factor corrector, or a totem pole power factor corrector.

5. The LLC resonant converter according to claim 1, characterized in that: The bridge switch unit is any one of the following: a half-bridge switch unit or a full-bridge switch unit.

6. The LLC resonant converter according to claim 3, characterized in that: The bridge switch unit is a half-bridge switch unit and comprises: a second switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the power factor correction unit and the resonance unit of the direct current providing unit; A third switch component has a first electrical end, a second electrical end and a control signal receiving end, and is respectively coupled to the power factor correction unit and the resonance unit of the direct current providing unit through the second electrical end and the first electrical end.

7. The LLC resonant converter according to claim 6, characterized in that: Also includes: A voltage detection unit coupled to the second electrical end of the secondary winding; as well as a second isolation feedback unit coupled to the first control unit and simultaneously coupled to the control signal receiving end of the second switch component and the control signal receiving end of the third switch component; The first control unit obtains a sampled output voltage through the voltage detection unit, and then generates a second adjustment signal according to the sampled output voltage, and the second isolation feedback unit transmits a second switch component control signal and a third switch component control signal to the second switch component and the third switch component respectively after receiving the second adjustment signal.

8. The LLC resonant converter according to claim 6, characterized in that: The output rectifier unit is a synchronous rectifier unit and includes: a fourth switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the first electrical end of the secondary winding and the load device; and a fifth switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the third electrical end of the secondary winding and the load device; The first control unit is coupled to the control signal receiving end of the fourth switch component and the control signal receiving end of the fifth switch component.

9. The LLC resonant converter according to claim 8, characterized in that: The first switch component, the second switch component, the third switch component, the fourth switch component, and the fifth switch component are all selected from any one of the group consisting of power metal oxide semiconductor field effect transistors and insulated gate bipolar transistors.

10. The LLC resonant converter according to claim 1, characterized in that: The first control unit comprises: a conversion unit, configured to perform a conversion process on the adjustment voltage signal to obtain the current load rate; and A microprocessing unit generates the first adjustment signal according to the current load rate.

11. An LLC resonant converter, comprising: A DC power supply unit has at least one first switch component and is used to receive a power source, thereby outputting a first voltage signal after performing a power conversion process on the power source; a bridge switch unit, coupled to the DC power providing unit to receive the first voltage signal; a resonant unit, coupled to the bridge switch unit to receive a second voltage signal transmitted from the bridge switch unit, and comprising a resonant inductor and a resonant capacitor; A transformer unit, comprising a primary winding, an exciting inductor connected in parallel with the primary winding, and a secondary winding having a first electrical end, a second electrical end and a third electrical end, wherein the primary winding is coupled to the resonant unit so that the exciting inductor, the resonant inductor and the resonant capacitor together form an LLC resonant tank; an output rectifying unit, coupled to the first electrical end and the third electrical end of the secondary winding, for rectifying a third voltage signal received from the secondary winding, thereby providing an output voltage to at least one load device; a current detection resistor, one end of which is coupled to the second electrical end of the secondary winding, and the other end of which is coupled to the load device; a first control unit, coupled to the output rectifying unit; an error amplifying unit coupled to both ends of the current detecting resistor, so as to generate an adjustment voltage signal according to a voltage difference between the two ends of the current detecting resistor; a first isolation feedback unit, coupled to the error amplification unit; as well as A second control unit is coupled to the first isolation feedback unit to receive the adjustment voltage signal through the first isolation feedback unit, so that the second control unit can learn a current load rate of the LLC resonant converter according to the adjustment voltage signal, and then generate a first switch component control signal based on the current load rate and transmit it to a control signal receiving end of the first switch component, so as to control the first switch component to periodically turn on / off to adjust the first voltage signal corresponding to the current load rate, thereby maintaining a conversion efficiency of the LLC resonant converter.

12. The LLC resonant converter according to claim 11, characterized in that: The DC power supply unit is an AC-DC converter or a DC-DC converter.

13. The LLC resonant converter according to claim 11, characterized in that: The DC power supply unit is a boost AC-DC converter and includes: a full-bridge rectifier unit coupled to the power source and configured to convert an alternating current signal transmitted from the power source into a pulsating direct current voltage signal; and A power factor correction unit includes the at least one first switch component.

14. The LLC resonant converter according to claim 13, characterized in that: The power factor correction unit is any one of the following: a semi-bridgeless power factor corrector, an interleaved power factor corrector, or a totem pole power factor corrector.

15. The LLC resonant converter according to claim 11, characterized in that: The bridge switch unit is any one of the following: a half-bridge switch unit or a full-bridge switch unit.

16. The LLC resonant converter according to claim 13, characterized in that: The bridge switch unit is a half-bridge switch unit and comprises: a second switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the power factor correction unit and the resonance unit of the direct current providing unit; A third switch component has a first electrical end, a second electrical end and a control signal receiving end, and is respectively coupled to the power factor correction unit and the resonance unit of the direct current providing unit through the second electrical end and the first electrical end.

17. The LLC resonant converter according to claim 16, characterized in that: Also includes: A voltage detection unit coupled to the second electrical end of the secondary winding; as well as a second isolation feedback unit coupled to the first control unit and simultaneously coupled to the control signal receiving end of the second switch component and the control signal receiving end of the third switch component; The first control unit obtains a sampled output voltage through the voltage detection unit, and then generates an adjustment signal according to the sampled output voltage, and the second isolation feedback unit transmits a second switch component control signal and a third switch component control signal to the second switch component and the third switch component respectively after receiving the adjustment signal.

18. The LLC resonant converter according to claim 16, characterized in that: The output rectifier unit is a synchronous rectifier unit and includes: a fourth switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the first electrical end of the secondary winding and the load device; and a fifth switch component having a first electrical end, a second electrical end and a control signal receiving end, and the first electrical end and the second electrical end are respectively coupled to the third electrical end of the secondary winding and the load device; The first control unit is coupled to the control signal receiving end of the fourth switch component and the control signal receiving end of the fifth switch component.

19. The LLC resonant converter according to claim 18, characterized in that: The first switch component, the second switch component, the third switch component, the fourth switch component, and the fifth switch component are all selected from any one of the group consisting of power metal oxide semiconductor field effect transistors and insulated gate bipolar transistors.

20. The LLC resonant converter according to claim 11, characterized in that: The second control unit comprises: a conversion unit, configured to perform a conversion process on the adjustment voltage signal to obtain the current load rate; and A microprocessing unit generates the first switch component control signal according to the current load rate.

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