Three-phase resonant converter and control method thereof

Abstract

A three-phase resonant converter comprises a three-phase transformer, an input bridge arm group, an output bridge arm group and a control unit. The three-phase transformer is provided with three groups of primary side windings and three groups of secondary side windings. The input bridge arm group comprises three input switch bridge arms which are respectively coupled with the three groups of primary side windings, and each input switch bridge arm comprises an upper switch and a lower switch. The output bridge arm group comprises three output synchronous rectification switch bridge arms which are respectively coupled with the three groups of secondary side windings, each output synchronous rectification switch bridge arm comprises an upper rectification switch and a lower rectification switch, and the control of each output synchronous rectification switch bridge arm corresponds to the control of each input switch bridge arm. The control unit controls the upper rectification switch or the lower rectification switch to conduct a corresponding phase angle of the upper switch or the lower switch in advance so as to maintain the output voltage of the resonant converter to be higher than a voltage threshold value.

Description

Technical Field

[0001] The present invention relates to a resonant converter and a control method thereof, and in particular to a three-phase resonant converter and a control method thereof. Background Art

[0002] Due to its soft-cut characteristics, the resonant converter has better efficiency than the traditional DC / DC converter. Therefore, it has been widely used in various power products in recent years, among which the LLC structure is more common. However, the resonant converter has the characteristic that high gain and high efficiency cannot be satisfied at the same time: if the characteristic curve is optimized for high efficiency, the gain capability will be sacrificed, resulting in the inability to meet the current market demand for the hold-up time of the power converter when the input power is lost, and the output voltage must be maintained at a certain output level (hereinafter referred to as the voltage threshold); if the high gain curve is optimized, the efficiency must be sacrificed to increase energy consumption.

[0003] The current control strategy has been successful in the application of single-phase resonant converters. However, as power products gradually develop towards higher output power, the application of single-phase resonant converters has begun to appear insufficient. In order to achieve three-phase current balance, the common method of three-phase resonant converters in the past was to independently adjust the duty cycle of the three phases, but this method cannot operate the three-phase duty cycle at the optimal point, thereby affecting efficiency. Another common method is to adjust the relative angle of the three-phase duty cycle so that the three phases are not fixed at a difference of 120 degrees from each other, thereby achieving current balance, but the control difficulty of this method is relatively high.

[0004] Therefore, how to design a three-phase resonant converter and a control method thereof to solve the problems and technical bottlenecks existing in the prior art is an important topic studied by the inventor of this case. Summary of the invention

[0005] An object of the present invention is to provide a three-phase resonant converter. The three-phase resonant converter includes a three-phase transformer, an input bridge arm group, an output bridge arm group and a control unit. The three-phase transformer has three groups of primary side windings and three groups of secondary side windings. The input bridge arm group includes three input switch bridge arms, which are respectively coupled to the three groups of primary side windings, wherein each input switch bridge arm includes an upper switch and a lower switch. The output bridge arm group includes three output synchronous rectification switch bridge arms, which are respectively coupled to the three groups of secondary side windings, wherein each output synchronous rectification switch bridge arm includes an upper rectification switch and a lower rectification switch, and the control of each output synchronous rectification switch bridge arm corresponds to the control of each input switch bridge arm. The control unit controls the upper rectification switch or the lower rectification switch to be turned on ahead of the corresponding upper switch or the lower switch by a phase angle to maintain the output voltage of the resonant converter above the voltage threshold.

[0006] Thus, the three-phase resonant converter proposed in the present invention has the following features and advantages: 1. The three-phase resonant converter and its control method can have high gain and high efficiency characteristics at the same time, and can be applied to higher output power designs. 2. By controlling the unbalanced input current and adjusting the phase angle difference of the first phase angle, the second phase angle and the third phase angle, the optimal leading conduction phase angle control can be achieved, and the three-phase current balance can be achieved. 3. The three groups of primary windings and the three groups of secondary windings of the three-phase transformer can be implemented in a star connection (Y connection) or a triangle connection (Δ connection), which increases the flexibility and convenience of circuit design.

[0007] Another object of the present invention is to provide a three-phase resonant converter control method. The control method includes the steps of: providing a three-phase resonant converter including a three-phase transformer, an input bridge arm group and an output bridge arm group; wherein the input bridge arm group includes three input switch bridge arms, and each input switch bridge arm includes an upper switch and a lower switch; wherein the output bridge arm group includes three output synchronous rectification switch bridge arms, and each output synchronous rectification switch bridge arm includes an upper rectification switch and a lower rectification switch. Control each output synchronous rectification switch bridge arm and each corresponding input switch bridge arm. Control the upper rectification switch or the lower rectification switch to be turned on ahead of the corresponding upper switch or the lower switch by a phase angle to maintain the output voltage of the resonant converter above the voltage threshold.

[0008] Thus, the three-phase resonant converter control method proposed in the present invention has the following features and advantages: 1. The three-phase resonant converter and its control method can have high gain and high efficiency characteristics at the same time, and can be applied to higher output power designs. 2. For the unbalanced input current, the phase angle difference between the first phase angle, the second phase angle and the third phase angle is adjusted to achieve the best leading conduction phase angle control and achieve three-phase current balance. 3. The three groups of primary windings and the three groups of secondary windings of the three-phase transformer can be implemented in a star connection (Y connection) or a triangle connection (Δ connection), which increases the flexibility and convenience of circuit design.

[0009] In order to further understand the technology, means and effects adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, characteristics and features of the present invention can be understood in depth and in detail. However, the drawings are only provided for reference and explanation and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 : is a circuit block diagram of the three-phase resonant converter of the present invention.

[0011] Figure 2A : This is a schematic diagram of the switching signal waveform when the existing three-phase resonant converter operates at a frequency less than the frequency threshold.

[0012] Figure 2B : This is a schematic diagram of the switching signal waveform when the existing three-phase resonant converter operates at a frequency greater than the frequency threshold.

[0013] Figure 3A : is a schematic diagram of the switching signal waveform when the three-phase resonant converter of the present invention operates at a frequency less than the frequency threshold.

[0014] Figure 3B : is a schematic diagram of the switching signal waveform when the three-phase resonant converter of the present invention operates at a frequency greater than the frequency threshold.

[0015] Figure 4 : is a block diagram of the current balancing controller of the present invention.

[0016] Figure 5A : is a waveform diagram of the unbalanced input current of the three-phase resonant converter of the present invention.

[0017] Figure 5B : is a waveform diagram of the input current balance of the three-phase resonant converter of the present invention.

[0018] Figure 6A to Figure 6H : It is a circuit diagram of different implementation modes of three groups of primary side windings of the three-phase transformer of the present invention.

[0019] Fig. 7A , Figure 7B : is a circuit diagram of different implementation modes of three groups of secondary side windings of the three-phase transformer of the present invention.

[0020] Figure 8 : is a flow chart of the three-phase resonant converter control method of the present invention.

[0021] The reference numerals are described as follows:

[0022] 11: Three-phase transformer

[0023] 12: Input bridge arm group

[0024] 13: Output bridge arm group

[0025] 10: Control unit

[0026] 101: Current balancing controller

[0027] 121, 122, 123: Input switch bridge arm

[0028] 131, 132, 133: Output synchronous rectification switch bridge arm

[0029] Q1, Q3, Q5: upper switch

[0030] Q2, Q4, Q6: Lower switch

[0031] SR1, SR3, SR5: upper rectifier switch

[0032] SR2, SR4, SR6: Lower rectifier switch

[0033] N A :First contact

[0034] N B :Second contact

[0035] N C :The third contact

[0036] f R : Resonant frequency

[0037] Vdc: input voltage

[0038] Vout: output voltage

[0039] S Q1 ~S Q6 : Input bridge arm switch signal

[0040] S SR1 ~S SR6 : Output bridge arm switch signal

[0041] ФL1: First phase angle

[0042] ФL2: Second phase angle

[0043] ФL3: The third phase angle

[0044] ΔФL12: First phase angle difference

[0045] ΔФL13: Second phase angle difference

[0046] Ir1: First current

[0047] Ir2: Second current

[0048] Ir3: The third current

[0049] t0~t0"', t1~t1"', t2~t2': time points

[0050] Cr1~Cr3: resonant capacitor

[0051] Lr1~Lr3: resonant inductor

[0052] Tr1~Tr3: Transformer

[0053] S10~S30: Steps DETAILED DESCRIPTION

[0054] The technical content and detailed description of the present invention are described as follows with reference to the accompanying drawings.

[0055] See also Figure 1 , which is a circuit block diagram of the three-phase resonant converter of the present invention. The three-phase resonant converter includes a three-phase transformer 11, an input bridge arm group 12, an output bridge arm group 13 and a control unit 10. The three-phase transformer 11 includes a resonant circuit (including resonant capacitors Cr1 to Cr3 and resonant inductors Lr1 to Lr3), and has three sets of primary windings and three sets of secondary windings. The control strategy proposed in the present invention can be applied to various three-phase resonant converter architectures, and can be used in conjunction with the control strategy of FIG. Figure 6A to Figure 6H As shown, the three sets of primary windings of the three-phase transformer 11 are implemented in a star connection (Y connection) or a triangle connection (Δ connection); Fig. 7A , Figure 7B As shown, the three sets of secondary windings of the three-phase transformer 11 are implemented in a star connection (Y connection) or a triangle connection (Δ connection).

[0056] The input bridge arm group 12 includes three input switch bridge arms 121, 122, and 123, namely, a first input switch bridge arm 121, a second input switch bridge arm 122, and a third input switch bridge arm 123, which are respectively coupled to one of the three primary side windings. Each input switch bridge arm 121, 122, and 123 includes an upper switch Q1, Q3, and Q5 and a lower switch Q2, Q4, and Q6, namely, the first input switch bridge arm 121 includes a first upper switch Q1 and a first lower switch Q2, and the first upper switch Q1 and the first lower switch Q2 are connected to a first contact N. A The second input switch bridge arm 122 includes a second upper switch Q3 and a second lower switch Q4, and the second upper switch Q3 and the second lower switch Q4 are connected to the second contact point N B The third input switch bridge arm 123 includes a third upper switch Q5 and a third lower switch Q6, and the third upper switch Q5 and the third lower switch Q6 are connected to the third contact point N C .

[0057] The output bridge arm group includes three output synchronous rectification switch bridge arms 131, 132, 133, namely, the first output synchronous rectification switch bridge arm 131, the second output synchronous rectification switch bridge arm 132, and the third output synchronous rectification switch bridge arm 133, which are respectively coupled to one of the three sets of secondary side windings. Each output synchronous rectification switch bridge arm 131, 132, 133 includes an upper rectification switch SR1, SR3, SR5 and a lower rectification switch SR2, SR4, SR6, namely, the first output synchronous rectification switch bridge arm 131 includes a first upper rectification switch SR1 and a first lower rectification switch SR2; the second output synchronous rectification switch bridge arm 132 includes a second upper rectification switch SR3 and a second lower rectification switch SR4; the third output synchronous rectification switch bridge arm 133 includes a third upper rectification switch SR5 and a third lower rectification switch SR6.

[0058] It is worth mentioning that the control of each output synchronous rectification switch bridge arm 131, 132, 133 corresponds to the control of each input switch bridge arm 121, 122, 123. Specifically, the control of the first upper rectification switch SR1 and the first lower rectification switch SR2 of the first output synchronous rectification switch bridge arm 131 corresponds to the control of the first upper switch Q1 and the first lower switch Q2 of the first input switch bridge arm 121; the control of the second upper rectification switch SR3 and the second lower rectification switch SR4 of the second output synchronous rectification switch bridge arm 132 corresponds to the control of the second upper switch Q3 and the second lower switch Q4 of the second input switch bridge arm 122; the control of the third upper rectification switch SR5 and the third lower rectification switch SR6 of the third output synchronous rectification switch bridge arm 133 corresponds to the control of the third upper switch Q5 and the third lower switch Q6 of the third input switch bridge arm 123.

[0059] In different embodiments, the control unit 10 can receive the input voltage Vdc of the three-phase resonant converter, or receive the output voltage Vout, which means that any state that can directly or indirectly know the size of the output voltage Vout can become a source of voltage information. Figure 1 Taking the embodiment of receiving the output voltage Vout as an example, the control unit 10 provides an input bridge arm switch signal S according to the output voltage Vout. Q1 ~S Q6 They respectively control the upper switches Q1, Q3, Q5 and the lower switches Q2, Q4, Q6, and provide the output bridge arm switch signal S SR1 ~S SR6The upper rectifier switches SR1, SR3, SR5 and the lower rectifier switches SR2, SR4, SR6 are controlled respectively, so that the upper rectifier switches SR1, SR3, SR5 or the lower rectifier switches SR2, SR4, SR6 are turned on first by a phase angle corresponding to the upper switches Q1, Q3, Q5 or the lower switches Q2, Q4, Q6, so as to maintain the output voltage Vout of the three-phase resonant converter higher than the voltage threshold, so that when the three-phase resonant converter is shut down or the input power is cut off, the output voltage can be maintained at the output level for a longer time. The detailed operation and principle will be described later.

[0060] See also Figure 2A and Figure 2B , which are schematic diagrams of the switching signal waveforms of the existing three-phase resonant converter when the frequency is less than the threshold and when the frequency is greater than the threshold. Figure 2A As shown, when the resonant converter operates at a frequency lower than the frequency threshold (the resonant frequency is the best frequency threshold in this case, and the resonant frequency is used as an example for explanation below), in order to avoid the switch switching of the synchronous rectification switch on the output side from entering hard switching, which leads to an increase in switching loss, the conduction time is shortened. For example, the conduction period of the third lower rectification switch SR6 shown in the figure is 1 / f of the resonant period. R However, this will cause the power supply to maintain the output voltage at the output level when the power supply is turned off or the input power is cut off. Compared with the situation where the resonant converter operates at a frequency lower than the resonant frequency, the resonant converter operates at a frequency higher than the resonant frequency (such as Figure 2B This situation is less likely to occur.

[0061] Therefore, in order to solve the aforementioned problem that the switching mode and the holding time cannot be taken into account at the same time, the present invention designs a three-phase resonant converter and a control method thereof to solve the problems and technical bottlenecks existing in the prior art.

[0062] See also Figure 3A , which is a schematic diagram of the switching signal waveform when the three-phase resonant converter of the present invention operates at a frequency less than the frequency threshold. The control unit 10 obtains the operating frequency command according to the output voltage Vout of the three-phase resonant converter. Based on the operating frequency command being less than the frequency threshold of the resonant converter (for example, the resonant frequency f R), the upper rectifier switches SR1, SR3, SR5 or the lower rectifier switches SR2, SR4, SR6 are turned on in advance by a phase angle corresponding to the upper switches Q1, Q3, Q5 or the lower switches Q2, Q4, Q6. That is, the first upper rectifier switch SR1 is turned on in advance by a first phase angle ΦL1 of the first upper switch Q1 (or the first lower rectifier switch SR2 is turned on in advance by the first phase angle ΦL1 of the first lower switch Q2). Similarly, the second upper rectifier switch SR3 is turned on in advance by a second phase angle ΦL2 of the second upper switch Q3 (or the second lower rectifier switch SR4 is turned on in advance by the second phase angle ΦL2 of the second lower switch Q4). Similarly, the third upper rectifier switch SR5 is turned on in advance by a third phase angle ΦL3 of the third upper switch Q5 (or the third lower rectifier switch SR6 is turned on in advance by the third phase angle ΦL3 of the third lower switch Q6).

[0063] In this operation, the conduction period of the upper rectifier switches SR1, SR3, SR5 or the lower rectifier switches SR2, SR4, SR6 is designed to lead the phase angle, so compared with Figure 2A (The conduction period of the rectifier switch SR6 is the resonant period 1 / f R ) is greater than the resonant period 1 / f R , where the resonant period is 1 / f R is the resonant frequency f R The reciprocal of .

[0064] Furthermore, if Figure 3A As shown, the time point when the upper rectifier switch SR1, SR3, SR5 or the lower rectifier switch SR2, SR4, SR6 is turned on is earlier than the time point when the corresponding upper switch Q1, Q3, Q5 or the lower switch Q2, Q4, Q6 is turned on. The time point when the upper rectifier switch SR1, SR3, SR5 or the lower rectifier switch SR2, SR4, SR6 is turned off is earlier than the time point when the corresponding upper switch Q1, Q3, Q5 or the lower switch Q2, Q4, Q6 is turned off, and the conduction period of the upper rectifier switch SR1, SR3, SR5 or the lower rectifier switch SR2, SR4, SR6 in different switching cycles gradually increases with time. Specifically, taking the third lower rectifier switch SR6 and the third lower switch Q6 as an example: the time point when the third lower rectifier switch SR6 is turned on (at time t0") is earlier than the time point when the third lower switch Q6 is turned on (at time t0), and the time point when the third lower rectifier switch SR6 is turned off (at time t0') is earlier than the time point when the third lower switch Q6 is turned off (at time t2). Similarly, the same is true for other upper and lower rectifier switches and corresponding upper and lower switches.

[0065] See also Figure 3B, which is a schematic diagram of the switching signal waveform when the three-phase resonant converter of the present invention operates at a frequency greater than the frequency threshold. The control unit 10 obtains the operating frequency command according to the output voltage Vout of the three-phase resonant converter. Based on the operating frequency command being greater than the frequency threshold of the resonant converter (for example, the resonant frequency f R ), the upper rectifier switches SR1, SR3, SR5 or the lower rectifier switches SR2, SR4, SR6 are turned on first by a phase angle corresponding to the upper switches Q1, Q3, Q5 or the lower switches Q2, Q4, Q6. That is, the first upper rectifier switch SR1 is turned on first by a first phase angle ΦL1 (or the first lower rectifier switch SR2 is turned on first by a first phase angle ΦL1). Similarly, the same is true for the other upper and lower rectifier switches and the corresponding upper and lower switches.

[0066] Furthermore, if Figure 3B As shown, the time point when the upper rectifier switch SR1, SR3, SR5 or the lower rectifier switch SR2, SR4, SR6 is turned on is earlier than the time point when the corresponding upper switch Q1, Q3, Q5 or the lower switch Q2, Q4, Q6 is turned on. The conduction period of the upper rectifier switch SR1, SR3, SR5 or the lower rectifier switch SR2, SR4, SR6 is equal to the conduction period of the corresponding upper switch Q1, Q3, Q5 or the lower switch Q2, Q4, Q6. Specifically, taking the third lower rectifier switch SR6 and the third lower switch Q6 as an example: the time point when the third lower rectifier switch SR6 is turned on (at time t0") is earlier than the time point when the third lower switch Q6 is turned on (at time t0), and the conduction period of the third lower rectifier switch SR6 (time t0" to t0"') is equal to the conduction period of the third lower switch Q6 (time t0 to t2). Similarly, the same is true for other upper and lower rectifier switches and corresponding upper and lower switches.

[0067] In one operating scenario, when the three input currents flowing into the three primary windings are the same, that is, when the currents of the three-phase resonant converter are balanced (see Figure 5B ), the phase angles of the upper switches Q1, Q3, Q5 or lower switches Q2, Q4, Q6 corresponding to the upper rectifier switches SR1, SR3, SR5 or lower rectifier switches SR2, SR4, SR6 being turned on first are equal. In another operating scenario, when the three input currents flowing into the three sets of primary windings are different, that is, when the current of the three-phase resonant converter is unbalanced (see Figure 5A ), the phase angles of the upper switches Q1, Q3, Q5 or the lower switches Q2, Q4, Q6 corresponding to the upper rectifier switches SR1, SR3, SR5 or the lower rectifier switches SR2, SR4, SR6 being turned on first are different. The above two operation scenarios are specifically described as follows.

[0068] See also Figure 3A and Figure 3BAs shown, the first upper rectifier switch SR1 and the first lower rectifier switch SR2 respectively lead the first upper switch Q1 and the first lower switch Q2 by a first phase angle ΦL1. The second upper rectifier switch SR3 and the second lower rectifier switch SR4 respectively lead the second upper switch Q3 and the second lower switch Q4 by a second phase angle ΦL2. The third upper rectifier switch SR5 and the third lower rectifier switch SR6 respectively lead the third upper switch Q5 and the third lower switch Q6 by a third phase angle ΦL3. The relationship among the first phase angle ΦL1, the second phase angle ΦL2 and the third phase angle ΦL3 is:

[0069] The second phase angle ΦL2 is equal to the first phase angle ΦL1 plus the first phase angle difference ΔΦL12, that is, ΦL2=ΦL1+ΔΦL12.

[0070] The third phase angle ΦL3 is equal to the first phase angle ΦL1 plus the second phase angle difference ΔΦL13, that is, ΦL3=ΦL1+ΔΦL13.

[0071] For the current balanced operation of the three-phase resonant converter, the first phase angle difference ΔΦL12 and the second phase angle difference ΔΦL13 are zero, so the first phase angle ΦL1, the second phase angle ΦL2 and the third phase angle ΦL3 are equal.

[0072] For the operation scenario of the three-phase resonant converter with unbalanced current, the first phase angle difference ΔΦL12 and the second phase angle difference ΔΦL13 are not zero, so the first phase angle ΦL1, the second phase angle ΦL2 and the third phase angle ΦL3 are not equal.

[0073] Further, the first phase angle difference ΔФL12 is determined according to the first current Ir1 and the second current Ir2; the second phase angle difference ΔФL13 is determined according to the first current Ir1 and the third current Ir3. The first current Ir1 is the common point (i.e., the first point N A ) flows into the three-phase transformer 11. The second current Ir2 is the current flowing from the common point of the second upper switch Q3 and the second lower switch Q4 (ie, the second point N B ) flows into the three-phase transformer 11. The third current Ir3 is the current flowing from the common point of the third upper switch Q5 and the third lower switch Q6 (ie, the third point N C )The current flowing into the three-phase transformer 11.

[0074] When the second current Ir2 is greater than the first current Ir1, the first phase angle difference ΔФL12 is a negative value; when the second current Ir2 is less than the first current Ir1, the first phase angle difference ΔФL12 is a positive value. Furthermore, the greater the absolute value of the difference between the second current Ir2 and the first current Ir1, the greater the absolute value of the first phase angle difference ΔФL12. That is, when the second current Ir2 is greater than the first current Ir1, the first phase angle difference ΔФL12 is a smaller negative value; when the second current Ir2 is less than the first current Ir1, the first phase angle difference ΔФL12 is a larger positive value.

[0075] Similarly, when the third current Ir3 is greater than the first current Ir1, the second phase angle difference ΔФL13 is a negative value; when the third current Ir3 is less than the first current Ir1, the second phase angle difference ΔФL13 is a positive value. Furthermore, the greater the absolute value of the difference between the third current Ir3 and the first current Ir1, the greater the absolute value of the second phase angle difference ΔФL13. That is, when the third current Ir2 is greater than the first current Ir1, the second phase angle difference ΔФL13 is a smaller negative value; when the second current Ir2 is less than the first current Ir1, the first phase angle difference ΔФL12 is a larger positive value.

[0076] See also Figure 4 , which is a block diagram of the current balance controller of the present invention. The three-phase resonant converter further includes a current balance controller 101. The current balance controller 101 receives a first current Ir1, a second current Ir2, and a third current Ir3, and calculates a first phase angle difference ΔФL12 and a second phase angle difference ΔФL13 according to a peak value, an average value, or a root-mean-square value of the first current Ir1, the second current Ir2, and the third current Ir3.

[0077] In this way, the current balancing controller 101 controls the unbalanced input current and adjusts the phase angle difference between the first phase angle ΦL1 , the second phase angle ΦL2 , and the third phase angle ΦL3 , thereby achieving optimal control of the leading conduction phase angle.

[0078] See also Figure 8As shown, it is a flow chart of the control method of the three-phase resonant converter of the present invention. In conjunction with the complete description and diagram of the above-mentioned three-phase resonant converter, the control method of the resonant converter of the present invention includes the following steps: First, a three-phase resonant converter including a three-phase transformer, an input bridge arm group and an output bridge arm group is provided (step S10). The input bridge arm group includes three input switch bridge arms 121, 122, 123, and each input switch bridge arm includes an upper switch Q1, Q3, Q5 and a lower switch Q2, Q4, Q6. The output bridge arm group includes three output synchronous rectification switch bridge arms 131, 132, 133, and each output synchronous rectification switch bridge arm includes an upper rectification switch SR1, SR3, SR5 and a lower rectification switch SR2, SR4, SR6. Then, each output synchronous rectification switch bridge arm and the corresponding input switch bridge arm are controlled (step S20). Finally, the upper or lower switch phase angle corresponding to the upper or lower rectification switch being turned on in advance is controlled to maintain the output voltage of the resonant converter higher than the voltage threshold (step S30). As for the more complete circuit architecture and control method of the three-phase resonant converter, please refer to the above content and will not be elaborated here.

[0079] In summary, the present invention has the following features and advantages:

[0080] 1. The three-phase resonant converter and its control method can have high gain and high efficiency characteristics at the same time, and can be applied to higher output power design.

[0081] 2. Control the unbalanced input current and adjust the phase angle difference of the first phase angle, the second phase angle and the third phase angle to achieve the best leading conduction phase angle control and achieve three-phase current balance.

[0082] 3. The three sets of primary windings and the three sets of secondary windings of the three-phase transformer can be implemented in a star connection (Y connection) or a triangle connection (Δ connection), which increases the flexibility and convenience of circuit design.

[0083] The above description is only a detailed description and drawings of the preferred specific embodiments of the present invention, but the features of the present invention are not limited thereto and are not intended to limit the present invention. The entire scope of the present invention shall be subject to the following claims. All embodiments that conform to the spirit of the claims of the present invention and similar variations thereof shall be included in the scope of the present invention. Any changes or modifications that can be easily conceived by a person familiar with the art within the field of the present invention shall be covered by the following patent scope of this case.

Claims

1. A three-phase resonant converter, comprising: A three-phase transformer having three sets of primary windings and three sets of secondary windings; An input bridge arm group, including three input switch bridge arms, respectively coupled to the three groups of primary side windings, wherein each of the input switch bridge arms includes an upper switch and a lower switch; an output bridge arm group, comprising three output synchronous rectification switch bridge arms, respectively coupled to the three sets of secondary windings, wherein each of the output synchronous rectification switch bridge arms comprises an upper rectification switch and a lower rectification switch, and the control of each of the output synchronous rectification switch bridge arms corresponds to the control of each of the input switch bridge arms; as well as A control unit controls the upper rectifier switch or the lower rectifier switch to be turned on in advance by a phase angle of the upper switch or the lower switch corresponding to the upper switch or the lower switch, so as to maintain an output voltage of the resonant converter higher than a voltage threshold.

2. The three-phase resonant converter as claimed in claim 1, wherein the control unit obtains an operating frequency command according to the output voltage; in, When the operating frequency command is less than a frequency threshold of the resonant converter, the upper rectifier switch or the lower rectifier switch is turned on first at the phase angle of the upper switch or the lower switch corresponding to the phase angle; The conduction period of the upper rectifying switch or the lower rectifying switch is greater than a cycle, wherein the cycle is the inverse of the frequency threshold.

3. The three-phase resonant converter as claimed in claim 2, wherein the time point at which the upper rectifier switch or the lower rectifier switch is turned on is earlier than the time point at which the corresponding upper switch or the lower switch is turned on; the time point at which the upper rectifier switch or the lower rectifier switch is turned off is earlier than the time point at which the corresponding upper switch or the lower switch is turned off, and the conduction period of the upper rectifier switch or the lower rectifier switch in different switching cycles gradually increases with time.

4. The three-phase resonant converter as claimed in claim 1, wherein the control unit obtains an operating frequency command according to the output voltage; in, Based on the fact that the operating frequency command is greater than a frequency threshold of the resonant converter, the upper rectifier switch or the lower rectifier switch is turned on ahead of the corresponding upper switch or the lower switch by the phase angle; wherein the time point at which the upper rectifier switch or the lower rectifier switch is turned on is earlier than the time point at which the corresponding upper switch or the lower switch is turned on; the turn-on period of the upper rectifier switch or the lower rectifier switch is equal to the turn-on period of the corresponding upper switch or the lower switch. 5 . The three-phase resonant converter as claimed in claim 2 , wherein the frequency threshold is a resonant frequency of the three-phase resonant converter.

6. The three-phase resonant converter as claimed in claim 1, wherein when the three input currents flowing into the three groups of primary windings are the same, the phase angles of the upper switch or the lower switch corresponding to the leading conduction of the upper rectifier switch or the lower rectifier switch are equal.

7. The three-phase resonant converter as claimed in claim 6, wherein the upper switch comprises a first upper switch, a second upper switch and a third upper switch, the lower switch comprises a first lower switch, a second lower switch and a third lower switch; the upper rectifier switch comprises a first upper rectifier switch, a second upper rectifier switch and a third upper rectifier switch, the lower rectifier switch comprises a first lower rectifier switch, a second lower rectifier switch and a third lower rectifier switch; wherein the first upper rectifier switch and the first lower rectifier switch respectively lead the first upper switch and the first lower switch to be turned on by a first phase angle; the second upper rectifier switch and the second lower rectifier switch respectively lead the second upper switch and the second lower switch to be turned on by a second phase angle; the third upper rectifier switch and the third lower rectifier switch respectively lead the third upper switch and the third lower switch to be turned on by a third phase angle; The relationship among the first phase angle, the second phase angle and the third phase angle is: The second phase angle is equal to the first phase angle plus a first phase angle difference; The third phase angle is equal to the first phase angle plus a second phase angle difference; in, The first phase angle difference and the second phase angle difference are zero, so the first phase angle, the second phase angle and the third phase angle are equal.

8. The three-phase resonant converter as claimed in claim 1, wherein when the three input currents flowing into the three groups of primary windings are different, the phase angle of the upper switch or the lower switch corresponding to the leading conduction of the upper rectifier switch or the lower rectifier switch is different.

9. The three-phase resonant converter as claimed in claim 8, wherein the upper switch comprises a first upper switch, a second upper switch and a third upper switch, the lower switch comprises a first lower switch, a second lower switch and a third lower switch; the upper rectifier switch comprises a first upper rectifier switch, a second upper rectifier switch and a third upper rectifier switch, the lower rectifier switch comprises a first lower rectifier switch, a second lower rectifier switch and a third lower rectifier switch; wherein the first upper rectifier switch and the first lower rectifier switch respectively lead the first upper switch and the first lower switch to be turned on by a first phase angle; the second upper rectifier switch and the second lower rectifier switch respectively lead the second upper switch and the second lower switch to be turned on by a second phase angle; the third upper rectifier switch and the third lower rectifier switch respectively lead the third upper switch and the third lower switch to be turned on by a third phase angle; The relationship among the first phase angle, the second phase angle and the third phase angle is: The second phase angle is equal to the first phase angle plus a first phase angle difference; The third phase angle is equal to the first phase angle plus a second phase angle difference; in, The first phase angle difference and the second phase angle difference are not zero, so the first phase angle, the second phase angle and the third phase angle are not equal.

10. The three-phase resonant converter as claimed in claim 9, wherein the first phase angle difference is determined according to a first current and a second current; the second phase angle difference is determined according to the first current and a third current; wherein the first current is a current flowing into the three-phase transformer from a common point of the first upper switch and the first lower switch; the second current is a current flowing into the three-phase transformer from a common point of the second upper switch and the second lower switch; the third current is a current flowing into the three-phase transformer from a common point of the third upper switch and the third lower switch; When the second current is greater than the first current, the first phase angle difference is a negative value; when the second current is less than the first current, the first phase angle difference is a positive value; when the absolute value of the difference between the second current and the first current is greater, the absolute value of the first phase angle difference is greater; When the third current is greater than the first current, the second phase angle difference is a negative value; when the third current is less than the first current, the second phase angle difference is a positive value; and when the absolute value of the difference between the third current and the first current is greater, the absolute value of the second phase angle difference is greater.

11. The three-phase resonant converter according to claim 7 or claim 9, wherein the three-phase resonant converter further comprises: a current balancing controller receiving a first current, a second current and a third current, and calculating the first phase angle difference and the second phase angle difference according to peak values, average values ​​or root mean square values ​​of the first current, the second current and the third current; The first current is the current flowing into the three-phase transformer from a common point of the first upper switch and the first lower switch; the second current is the current flowing into the three-phase transformer from a common point of the second upper switch and the second lower switch; and the third current is the current flowing into the three-phase transformer from a common point of the third upper switch and the third lower switch.

12. The three-phase resonant converter as claimed in claim 1, wherein the three sets of primary windings of the three-phase transformer are star-connected or delta-connected; the three sets of secondary windings of the three-phase transformer are star-connected or delta-connected.

13. A three-phase resonant converter control method, comprising: A three-phase resonant converter is provided, comprising a three-phase transformer, an input bridge arm group and an output bridge arm group; wherein the input bridge arm group comprises three input switch bridge arms, and each of the input switch bridge arms comprises an upper switch and a lower switch; wherein the output bridge arm group comprises three output synchronous rectification switch bridge arms, and each of the output synchronous rectification switch bridge arms comprises an upper rectification switch and a lower rectification switch; Controlling each of the output synchronous rectification switch bridge arms and each of the corresponding input switch bridge arms; as well as The upper rectifier switch or the lower rectifier switch is controlled to be turned on ahead of the corresponding upper switch or the lower switch by a phase angle, so as to maintain an output voltage of the resonant converter higher than a voltage threshold.

14. The three-phase resonant converter control method as claimed in claim 13, wherein an operating frequency command is obtained according to the output voltage; in, When the operating frequency command is less than a frequency threshold of the resonant converter, the upper rectifier switch or the lower rectifier switch is turned on first at the phase angle of the upper switch or the lower switch corresponding to the phase angle; The conduction period of the upper rectifying switch or the lower rectifying switch is greater than a cycle, wherein the cycle is the inverse of the frequency threshold.

15. The three-phase resonant converter control method as claimed in claim 14, wherein the time point at which the upper rectifier switch or the lower rectifier switch is turned on is earlier than the time point at which the corresponding upper switch or the lower switch is turned on, and the turn-on period of the upper rectifier switch or the lower rectifier switch in different switching cycles gradually increases with time.

16. The three-phase resonant converter control method as claimed in claim 13, wherein an operating frequency command is obtained according to the output voltage; in, When the operating frequency command is greater than a frequency threshold of the resonant converter, the time point when the upper rectifier switch or the lower rectifier switch is turned on is earlier than the time point when the corresponding upper switch or the lower switch is turned on; the turn-on period of the upper rectifier switch or the lower rectifier switch is equal to the turn-on period of the corresponding upper switch or the lower switch. 17 . The three-phase resonant converter control method as claimed in claim 14 , wherein the frequency threshold is a resonant frequency of the three-phase resonant converter.

18. The three-phase resonant converter control method as claimed in claim 13, wherein when the three input currents flowing into the three groups of primary windings of the three-phase transformer are different, the phase angle of the upper switch or the lower switch corresponding to the leading conduction of the upper rectifier switch or the lower rectifier switch is different.

19. The three-phase resonant converter control method as claimed in claim 18, wherein the upper switch comprises a first upper switch, a second upper switch and a third upper switch, the lower switch comprises a first lower switch, a second lower switch and a third lower switch; the upper rectifier switch comprises a first upper rectifier switch, a second upper rectifier switch and a third upper rectifier switch, the lower rectifier switch comprises a first lower rectifier switch, a second lower rectifier switch and a third lower rectifier switch; wherein the first upper rectifier switch and the first lower rectifier switch respectively lead the first upper switch and the first lower switch to be turned on by a first phase angle; the second upper rectifier switch and the second lower rectifier switch respectively lead the second upper switch and the second lower switch to be turned on by a second phase angle; the third upper rectifier switch and the third lower rectifier switch respectively lead the third upper switch and the third lower switch to be turned on by a third phase angle; The relationship among the first phase angle, the second phase angle and the third phase angle is: The second phase angle is equal to the first phase angle plus a first phase angle difference; The third phase angle is equal to the first phase angle plus a second phase angle difference; in, The first phase angle difference and the second phase angle difference are not zero, so the first phase angle, the second phase angle and the third phase angle are not equal.

20. The three-phase resonant converter control method as claimed in claim 19, wherein the first phase angle difference is determined according to a first current and a second current; the second phase angle difference is determined according to the first current and a third current; wherein the first current is a current flowing into the three-phase transformer from a common point of the first upper switch and the first lower switch; the second current is a current flowing into the three-phase transformer from a common point of the second upper switch and the second lower switch; the third current is a current flowing into the three-phase transformer from a common point of the third upper switch and the third lower switch; When the second current is greater than the first current, the first phase angle difference is a negative value; when the second current is less than the first current, the first phase angle difference is a positive value; when the absolute value of the difference between the second current and the first current is greater, the absolute value of the first phase angle difference is greater; When the third current is greater than the first current, the second phase angle difference is a negative value; when the third current is less than the first current, the second phase angle difference is a positive value; and when the absolute value of the difference between the third current and the first current is greater, the absolute value of the second phase angle difference is greater.

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