Control circuit of power electronic converter

Abstract

The invention discloses a control circuit of a power electronic converter, the power electronic converter comprises a DC power supply module, an inverter, a resonant network, a semi-synchronous rectifier, an output filter circuit and a load, the semi-synchronous rectifier comprises a first diode, a second diode, a first switch tube and a second switch tube; the control circuit comprises a synchronizing signal sampling circuit, a synchronizing signal processing circuit, a controller, a rectifier driving module and an inverter driving module. The controller is used for controlling the rectifier driving module to output a first control signal and a second control signal to the first switching tube and the second switching tube respectively according to sampling data. The duty ratio of the first control signal and the duty ratio of the second control signal meet constraint conditions, and meanwhile, the total switching loss of the semi-synchronous rectifier is minimum. Through efficiency optimization control, the loss can be reduced, and the efficiency can be improved.

Description

Technical Field

[0001] The invention belongs to the field of resonant network control, and more specifically, relates to a control circuit of a power electronic converter. Background Art

[0002] Improving the efficiency of power electronic converters has far-reaching background significance for energy conservation and emission reduction, resource utilization, cost reduction, system performance improvement, and technological innovation. Therefore, continuously improving the efficiency of power electronic converters has become one of the important directions for the development of the energy field today.

[0003] A resonant converter is a power electronic converter that uses the characteristics of circuit resonance to achieve energy transmission and conversion by reasonably designing circuit parameters and controlling switching devices. Resonant converters have broad application prospects in energy conversion, wireless transmission, medical treatment, automotive electronics, renewable energy, and communications. They can improve system efficiency and reduce energy loss, and are therefore receiving more and more attention and application in more and more fields.

[0004] A typical resonant converter includes a DC power supply, an inverter, a resonant network, a rectifier filter network, and a load. Due to the presence of the resonant network, the reactive power in the system is significantly reduced, and the resonant converter can achieve zero voltage switching (ZVS) or zero current switching (ZCS), which helps to reduce the loss of switching devices. At this time, the loss of the system is mainly in the rectifier link.

[0005] Traditional rectifiers use bridge rectifier circuits composed of diodes. Since diodes have a high forward voltage drop, the loss of this uncontrolled device is very high. When pursuing high-efficiency applications, a synchronous rectification solution can be used, using a fully controlled device MOS tube to replace the diode, but its control is very complex and costly. It is also prone to control failure in high-frequency applications, which brings safety issues. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides a control circuit of a power electronic converter, which can reduce loss and improve efficiency.

[0007] To achieve the above object, the present invention provides a control circuit of a power electronic converter, wherein the power electronic converter comprises a DC power supply module, an inverter, a resonant network, a semi-synchronous rectifier, an output filter circuit and a load, wherein the semi-synchronous rectifier comprises a first diode, a second diode, a first switch tube and a second switch tube;

[0008] The control circuit includes a synchronous signal sampling circuit, a synchronous signal processing circuit, a controller, a rectifier drive module and an inverter drive module. The synchronous signal sampling circuit is used to sample the high-frequency current signal output by the resonant network. The synchronous signal processing circuit is used to process the sampling data of the synchronous signal sampling circuit and send it to the controller. The controller is used to control the rectifier drive module to output a first control signal and a second control signal to the first switch tube and the second switch tube respectively according to the sampling data. The controller is also used to control the inverter drive module to output an inverter control signal to the inverter.

[0009] The step of outputting the first control signal to the rectifier driving module according to the sampled data and controlling the rectifier driving module to respectively output the first control signal and the second control signal to the first switch tube and the second switch tube according to the sampled data comprises the following steps:

[0010] The peak current of the high-frequency current signal output by the resonant network is recorded as I pk , the average current is recorded as I av , the duty cycle of the first control signal is recorded as d 1 , the duty cycle of the second control signal is recorded as d 2 , d 1 and d 2 While satisfying the constraint condition, the total switching loss of the semi-synchronous rectifier is minimized, so that the constraint condition is:

[0011]

[0012] Where α is the angle of the integration interval.

[0013] Furthermore, the off current of the first switch tube is recorded as I off1 , the off current of the second switch tube is recorded as I off2 ,but

[0014]

[0015] The switching loss of the first switch tube is recorded as P loss1 , the switching loss of the second switch is recorded as P loss2 , the switching loss of the first switch tube and its turn-off current I off1 , Temperature T 1 , voltage U 1 The corresponding relationship is f 1 , the switching loss of the first switch tube and its turn-off current I off2 , Temperature T 2 , voltage U 2 The corresponding relationship is f2 , expressed by the following formula:

[0016]

[0017] The total switching loss of the semi-synchronous rectifier is denoted as P loss ,but

[0018] P loss =P loss1 +P loss2 .

[0019] Further, according to the switching loss P of the first switch tube under the conditions that the junction temperature and voltage are preset voltages, loss1 Its shutdown current I off1 The corresponding relationship between the junction temperature and the switching loss P is determined. loss1 Its shutdown current I off1 , voltage U 1 The corresponding relationship;

[0020] Determine the switching loss P of the first switch tube under the preset turn-off current condition loss1 With temperature T 1 The corresponding relationship;

[0021] According to the switching loss P under the junction temperature condition loss1 Its shutdown current I off1 , voltage U 1 The corresponding relationship between the switching loss P loss1 With its temperature T 1 The corresponding relationship determines f 1 .

[0022] Furthermore, the controller pre-stores Different values ​​of d 1 and d 2 The corresponding relationship between different values ​​is based on The current value of determines the current d 1 and d 2 The current value of .

[0023] Furthermore, the inverter control signal is a fixed duty cycle signal.

[0024] Furthermore, the cathode of the first diode is electrically connected to the cathode of the second diode, forming the positive electrode of the semi-synchronous rectifier after rectification, the source or emitter of the first switching tube is electrically connected to the source or emitter of the second switching tube, forming the negative electrode of the semi-synchronous rectifier after rectification, the anode of the first diode is electrically connected to the drain or collector of the first switching tube, the anode of the second diode is electrically connected to the drain or collector of the second switching tube, forming two input ends of the semi-synchronous rectifier, and the gate or base of the first switching tube and the gate or base of the second switching tube are both electrically connected to the control signal output end of the rectifier drive module.

[0025] Furthermore, the output end of the DC power supply module is electrically connected to the input end of the inverter, the output end of the inverter is electrically connected to the input end of the resonant network, the output end of the resonant network is electrically connected to the input end of the semi-synchronous rectifier, the output end of the semi-synchronous rectifier is electrically connected to the input end of the output filter circuit, and the output end of the output filter circuit is electrically connected to the load.

[0026] In general, the above technical solutions conceived by the present invention have beneficial effects compared with the prior art:

[0027] (1) By adopting the efficiency optimization control method, the loss can be reduced and the efficiency can be improved.

[0028] (2) The present invention optimizes the turn-off current and switching loss of the switch tube, which not only improves the efficiency but also puts the switch tube in a safer operating mode, which is beneficial to improving the system stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of the principle of a power electronic converter according to an embodiment of the present invention;

[0030] Figure 2 It is a schematic diagram of the principle of a double-sided LCC resonant network semi-synchronous rectification circuit according to a specific embodiment of the present invention;

[0031] Figure 3 In the specific embodiment of the present invention, when the output current is 15A, d 1 ′ and d 2 'Relationship;

[0032] Figure 4 In the specific embodiment of the present invention, when the output current is 15A, d 1 ′ and the relationship between the shutdown current;

[0033] Figure 5 In the specific embodiment of the present invention, when the output current is 15A, d 1 ′ and the relationship between turn-off loss;

[0034] Figure 6 When efficiency optimization control is adopted, S 1 and S 2 The driving signal G 1 , G 2 , flows through L f2 The waveform diagram of the current in and the output current;

[0035] Figure 7 It is the output voltage and output current waveform;

[0036] Figure 8 When efficiency optimization control is not adopted, S 1 and S 2 The driving signal G 1 , G 2 , flows through L f2 Waveforms of the current in and the output current. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. "Multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0039] Unless otherwise specified, "plurality" means two or more.

[0040] The terms "including" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or equipment comprising a series of steps or modules is not necessarily limited to those steps or modules clearly listed, but may include other steps or modules not clearly listed or inherent to these processes, methods, products or equipment.

[0041] The naming or numbering of the steps in the embodiments of the present invention does not mean that the steps in the method flow must be executed in the time / logical sequence indicated by the naming or numbering. The execution order of the named or numbered process steps can be changed according to the technical purpose to be achieved, as long as the same or similar technical effects can be achieved.

[0042] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0043] The present invention provides a control circuit of a power electronic converter, wherein the power electronic converter comprises a DC power supply module, an inverter, a resonant network, a semi-synchronous rectifier, an output filter circuit and a load, wherein the semi-synchronous rectifier comprises a first diode, a second diode, a first switch tube and a second switch tube.

[0044] The control circuit includes a synchronous signal sampling circuit, a synchronous signal processing circuit, a controller (DSP / MCU), a rectifier drive module and an inverter drive module. The synchronous signal sampling circuit is used to sample the high-frequency current signal output by the resonant network. The synchronous signal processing circuit is used to process the sampling data of the synchronous signal sampling circuit and send it to the controller. The controller is used to control the rectifier drive module to output the first control signal and the second control signal to the first switch tube and the second switch tube respectively according to the sampling data. The controller is also used to control the inverter drive module to output an inverter control signal to the inverter.

[0045] The DC power supply is connected to the inverter input, the inverter output is connected to the inductor-capacitor resonant network input, the inductor-capacitor resonant network output is connected to the semi-synchronous rectifier input, the synchronous signal sampling circuit samples the high-frequency current signal output by the inductor-capacitor resonant network, the synchronous signal processing circuit converts the high-frequency current signal into a high-frequency voltage signal, and the synchronous signal processing circuit filters and amplifies the high-frequency voltage signal and sends it to the DSP / MCU to transmit the PWM signal to the rectifier driver, the rectifier driver is connected to the semi-synchronous rectifier, and the semi-synchronous rectifier turns on the switch tube for rectification after receiving the drive signal, the output end of the semi-synchronous rectifier is connected to the input end of the output filter circuit, and the output end of the output filter circuit is connected to the load.

[0046] The semi-synchronous rectifier consists of a diode D 1 and D 2 , and MOS tube S1 and S 2 Composition, MOS tube S 1 and S 2 The gate connection of the rectifier driver.

[0047] The control principle of the controller is described in detail below.

[0048] Assume that the flow through i Lf2 The peak current is I pk , the average output current is I av , MOS tube S 1 and S 2 The gate drive signal G 1 and G 2 The duty cycle is d 1 and d 2 , that is, the duty ratios of the first control signal and the second control signal are d 1 and d 2 .make

[0049]

[0050] Then we can get the flow through i Lf2 The peak current is I pk And the average output current I av satisfy

[0051]

[0052] Where α is the angle of the integral interval. According to formula (2), we can get

[0053]

[0054] Formula (3) is monotonically increasing in the interval [0, π], so we can get:

[0055]

[0056] Formula (4) gives d 1 ′ and d 2 'The constraints that should be met in the asymmetric control circuit of the resonant network semi-synchronous rectifier are The value of is recorded as C. Different output current values ​​correspond to different C; for a certain C value, there are multiple d 1 ′ and d 2 ’ combination method.

[0057] Assume that for a certain C value, MOS tube S 1 and S 2 The currents when turned off are I off1 and I off2 ,but

[0058]

[0059] Since the semi-synchronous rectifier works in the zero voltage switching state, the turn-on loss is almost zero. 1 and S 2 , at different temperatures (T 1 and T 2 ), voltage condition (U 1 and U 2 ),the switching loss (P loss1 and P loss2 ) has a corresponding relationship with the shutdown current and can be expressed by the following formula:

[0060]

[0061] Total switching loss P loss It can be expressed as:

[0062] P loss =P loss1 +P loss2 (7)

[0063] When equation (7) takes the minimum value, the system switching loss is minimized, improving the system efficiency.

[0064] According to the above analysis, for a certain C value, under the constraint of formula (4), from multiple d 1 ′ and d 2 ′, find the combination with the minimum total switching loss d 1 ′ and d 2 ' combination, to achieve P in formula (7) loss Minimize the system efficiency.

[0065] The efficiency optimization control method can be implemented by making a table through offline calculation and looking up the table online, thereby reducing the real-time calculation amount of the online system. That is, different values ​​of C and d are pre-stored in the controller. 1 and d 2 The corresponding relationship between different values, the current d is determined according to the current value of C 1 and d 2 The current value of

[0066] The resonant network takes the bilateral LCC compensation network as an example and is simulated using the LTspice software. The simulation schematic is shown in the figure below: Figure 2 , schematic diagram of asymmetric control circuit based on bilateral LCC resonant network semi-synchronous rectifier, where U DC 600V DC power supply, MOS tube S p1 , S p2 , S p3 and Sp4 To form a full-bridge inverter, the series resonant inductor L f1 , parallel resonant capacitor C f1 , series resonant capacitor C 1 The transmitting side LCC resonant network is formed, the transmitting coil is L1 and the receiving coil is L 2 , energy in L 1 and L 2 Through resonant transmission, the series resonant inductor L f2 , parallel resonant capacitor C f2 , series resonant capacitor C 2 The semi-synchronous rectifier consists of a diode D 1 and D 2 、MOS tube S 1 and S 2 Composition, among which S 1 and S 2 The driving signals are G 1 and G 2 The inductor Lo and the capacitor Co form an output filter circuit. L The load is 40 ohms. The series resonant inductor L f2 Coupled inductor L C Collect current i Lf2 The collected information is processed by the synchronous signal processing circuit and then transmitted to the MCU or DSP. Lf2 When the value changes from negative to zero, at zero point, the MCU or DSP turns on G 2 ; When i is detected Lf2 When the positive value changes to zero, the MCU turns on G 1 The full-bridge inverter drive uses a fixed duty cycle close to 50% with a certain dead time.

[0067] f 1 The determination includes the following steps:

[0068] According to the switching loss P of the first switch tube under the conditions that the junction temperature and voltage are the preset voltage loss1 Its shutdown current I off1 The corresponding relationship between the junction temperature and the switching loss P is determined. loss1 Its shutdown current I off1 , voltage U 1 The corresponding relationship;

[0069] Determine the switching loss P of the first switch tube under the preset turn-off current condition loss1 With temperature T 1 The corresponding relationship;

[0070] According to the switching loss P under the junction temperature condition loss1 Its shutdown current Ioff1 , voltage U 1 The corresponding relationship between the switching loss P loss1 With its temperature T 1 The corresponding relationship determines f 1 .

[0071] The specific implementation method of the present invention is described below using the power device IMZ120R045M1 of Infineon as an example. According to the data sheet, the relationship between the turn-off loss and the turn-off current under the conditions of a junction temperature of 175°C and a DC voltage of 800V is as follows:

[0072]

[0073] The turn-off loss of a power device is approximately proportional to the turn-off voltage. Therefore, the relationship between the turn-off loss and the turn-off current under different voltage conditions is as follows:

[0074]

[0075] According to the relationship between the turn-off loss and the junction temperature when the turn-off current is 20A, the relationship between the turn-off loss and the temperature under different temperature conditions is as follows:

[0076]

[0077] The above formula is normalized according to the turn-off loss when the junction temperature is 175℃ and the turn-off current is 20A, and we can get

[0078]

[0079] Therefore, the switching losses are related to temperature, voltage and off-state current:

[0080]

[0081] After the parameters are determined, L f2 The peak current in has been determined. f2 The current peak value Ipk = 52A, the output Iav = 15A, then according to formula (2) we can get:

[0082]

[0083] Therefore, the key to optimizing efficiency is to determine d under the constraints of (13) 1 ′ and d 2 ′, according to equations (5) and (12), the value of (7) is minimized.

[0084] From formula 13, we can get:

[0085] cos(πd 1 ′)+cos(πd 2′)=0.18754 (14)

[0086] According to formula (14), we can get d 1 When ' changes, d 1 ′ and d 2 ′, such as Figure 3 According to formula (5), we can get d 1 When ' changes, d 1 The relationship between ′ and the turn-off current is as follows: Figure 4 According to formula (13), under the conditions of DC voltage 600V and junction temperature 125℃, d 1 When ' changes, d 1 The relationship between ′ and turn-off loss is as follows: Figure 5 As shown. Figure 5 The minimum turn-off loss is 117.66uJ. 1 ′=0.04,d 2 ′=0.7976.

[0087] f 2 With f 1 The same method is used to determine, which will not be repeated here.

[0088] By analogy, we can get the minimum turn-off loss d under different output current conditions. 1 ′ and d 2 ’ are listed in a table for DSP / MCU online lookup.

[0089] The LTspice simulation waveform after efficiency optimization is as follows Figure 6 and Figure 7 As shown. Figure 6 For S 1 and S 2 The driving signal G 1 , G 2 , flows through L f2 The waveform of the current in and the output current. Figure 7 is the output voltage and output current waveform. 1 and S 2 The switching frequency is 83kHz, and the total turn-off loss is 9.77W.

[0090] Figure 8 For Figure 7 LTspice simulation waveform without efficiency optimization under the same output voltage and current conditions. 1 ′=0.1,d 2 ′=0.6, the total turn-off loss is 17.126 W. It can be seen that the efficiency optimization control algorithm can greatly reduce the turn-off loss, that is, the total switching loss.

[0091] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control circuit for a power electronic converter, characterized in that: The power electronic converter comprises a DC power supply module, an inverter, a resonant network, a semi-synchronous rectifier, an output filter circuit and a load, wherein the semi-synchronous rectifier comprises a first diode, a second diode, a first switch tube and a second switch tube; The control circuit includes a synchronous signal sampling circuit, a synchronous signal processing circuit, a controller, a rectifier drive module and an inverter drive module. The synchronous signal sampling circuit is used to sample the high-frequency current signal output by the resonant network. The synchronous signal processing circuit is used to process the sampling data of the synchronous signal sampling circuit and send it to the controller. The controller is used to control the rectifier drive module to output a first control signal and a second control signal to the first switch tube and the second switch tube respectively according to the sampling data. The controller is also used to control the inverter drive module to output an inverter control signal to the inverter. The step of outputting the first control signal to the rectifier driving module according to the sampled data and controlling the rectifier driving module to respectively output the first control signal and the second control signal to the first switch tube and the second switch tube according to the sampled data comprises the following steps: The peak current of the high-frequency current signal output by the resonant network is recorded as I pk , the average current is recorded as I av , the duty cycle of the first control signal is recorded as d1, and the duty cycle of the second control signal is recorded as d2, d1 and d2 satisfy the constraint condition while minimizing the total switching loss of the semi-synchronous rectifier, so that the constraint condition is: Where α is the angle of the integration interval.

2. A control circuit for a power electronic converter as claimed in claim 1, characterized in that: The off current of the first switch tube is recorded as I off1 , the off current of the second switch tube is recorded as I off2 ,but The switching loss of the first switch tube is recorded as P loss1 , the switching loss of the second switch is recorded as P loss2 , the switching loss of the first switch tube and its turn-off current I off1 , temperature T1, and voltage U1 correspond to each other as f1. The switching loss of the first switch tube and its turn-off current I off2 The corresponding relationship between temperature T2 and voltage U2 is f2, which can be expressed by the following formula: The total switching loss of the semi-synchronous rectifier is denoted as P loss ,but P loss =P loss1 +P loss2 。 3. A control circuit for a power electronic converter as claimed in claim 2, characterized in that: According to the switching loss P of the first switch tube under the conditions that the junction temperature and voltage are the preset voltage loss1 Its shutdown current I off1 The corresponding relationship is used to determine the switching loss P under the junction temperature condition. loss1 Its shutdown current I off1 , the corresponding relationship of voltage U1; Determine the switching loss P of the first switch tube under the preset turn-off current condition loss1 Corresponding relationship with temperature T1; According to the switching loss P under the junction temperature condition loss1 Its shutdown current I off1 , the corresponding relationship between voltage U1 and switching loss P loss1 f1 is determined in correspondence with its temperature T1.

4. A control circuit for a power electronic converter as claimed in claim 1, characterized in that: The controller pre-stores The corresponding relationship between different values ​​of and different values ​​of d1 and d2 is as follows: The current value of determines the current values ​​of d1 and d2.

5. A control circuit for a power electronic converter as claimed in claim 1, characterized in that: The inverter control signal is a fixed duty cycle signal.

6. A control circuit for a power electronic converter as claimed in claim 1, characterized in that: The cathode of the first diode is electrically connected to the cathode of the second diode, forming the positive electrode of the semi-synchronous rectifier after rectification; the source or emitter of the first switching tube is electrically connected to the source or emitter of the second switching tube, forming the negative electrode of the semi-synchronous rectifier after rectification; the anode of the first diode is electrically connected to the drain or collector of the first switching tube; the anode of the second diode is electrically connected to the drain or collector of the second switching tube, forming two input ends of the semi-synchronous rectifier; the gate or base of the first switching tube and the gate or base of the second switching tube are both electrically connected to the control signal output end of the rectifier drive module.

7. A control circuit for a power electronic converter as claimed in claim 1, characterized in that: The output end of the DC power supply module is electrically connected to the input end of the inverter, the output end of the inverter is electrically connected to the input end of the resonant network, the output end of the resonant network is electrically connected to the input end of the semi-synchronous rectifier, the output end of the semi-synchronous rectifier is electrically connected to the input end of the output filter circuit, and the output end of the output filter circuit is electrically connected to the load.

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