High-efficiency isolated Cuk converter and electric equipment

Abstract

The invention discloses a high-efficiency isolated Cuk converter and electric equipment. The high-efficiency isolated Cuk converter comprises a magnetic device, a power supply connected to one side of the magnetic device, and an output load connected to the other side of the magnetic device, a driving switch is arranged between the power supply and the magnetic device, and the magnetic device can be matched with the driving switch to generate a boost network so as to boost the voltage of the power supply; a filter capacitor is arranged between the output load and the magnetic device, and the magnetic device can be matched with the filter capacitor to generate a filter network so as to obtain direct current output. Compared with the prior art, the magnetic integrated transformer structure is adopted, and the energy transmission efficiency can be improved under the condition that electrical isolation of one side of the power supply and one side of the output load is achieved.

Description

Technical Field

[0001] The invention relates to the field of Cuk converter design, in particular to a high-efficiency isolated Cuk converter and electrical equipment. Background Art

[0002] The traditional Cuk converter is widely used because it can work efficiently in both boost mode and buck mode. However, in certain safety standards or high voltage difference environments, electrical isolation becomes a necessary requirement.

[0003] Although current isolated DC / DC converters achieve electrical isolation, they often suffer from low efficiency, bulky size or high cost.

[0004] Therefore, how to design a high-efficiency isolated Cuk converter and electrical equipment that can achieve efficient and stable DC voltage conversion under the premise of achieving electrical isolation is a technical problem that the industry urgently needs to solve. Summary of the invention

[0005] In view of the problem in the prior art that the traditional Cuk converter cannot take into account both electrical isolation and DC voltage conversion efficiency, the present invention proposes a high-efficiency isolated Cuk converter and an electrical device.

[0006] The technical solution of the present invention is to propose a high-efficiency isolated Cuk converter, comprising: a magnetic device, a power supply connected to one side of the magnetic device, and an output load connected to the other side of the magnetic device;

[0007] A driving switch is provided between the power supply and the magnetic device, and the magnetic device can cooperate with the driving switch to generate a boost network to raise the voltage of the power supply;

[0008] A filter capacitor is provided between the output load and the magnetic device. The magnetic device can cooperate with the filter capacitor to form a filter network to obtain a DC output.

[0009] Furthermore, the magnetic device is integrated with a transformer and at least two inductors;

[0010] The magnetic device has at least a first inductor and a second inductor. The first inductor cooperates with the drive switch to generate a boost network, and the second inductor cooperates with the filter capacitor to generate a filter network.

[0011] Further, the magnetic device has a rectangular magnetic core, a primary winding is wound on a first side of the rectangular magnetic core, and a secondary winding is wound on a third side opposite to the first side of the rectangular magnetic core;

[0012] The primary winding, the secondary winding, and the rectangular magnetic core cooperate to create the transformer.

[0013] Furthermore, the first inductor is a first winding wound on the second side of the rectangular magnetic core, and the second inductor is a second winding wound on a fourth side of the rectangular magnetic core opposite to the second side.

[0014] Further, it also includes a DSP controller connected between the output load and the driving switch;

[0015] The DSP controller is used for sampling the output signal from the output load and providing a control signal for the driving switch according to the output signal.

[0016] Furthermore, the driving switch adopts an active switch tube, and the first end of the active switch tube is connected between the output side of the first winding and the same-name end of the primary winding, the second end of the active switch tube is connected between the opposite-name end of the primary winding and the negative pole of the power supply, and the third end of the active switch tube is connected to the output end of the DSP controller.

[0017] Furthermore, it also includes a diode connected to the output load, and the diode is used to output a pulsating direct current of the same polarity;

[0018] The anode of the diode is connected between the output end of the second winding and the same-name end of the secondary winding, and the cathode of the diode is connected between the opposite-name end of the secondary winding and the anode of the output load.

[0019] Furthermore, the output voltage of the output load satisfies the calculation model:

[0020]

[0021] Among them, U o is the output voltage of the output load, U i is the input voltage of the power supply, and D is the duty cycle of the drive switch.

[0022] Furthermore, the DSP controller uses a PID control strategy based on a genetic algorithm to control the drive switch.

[0023] The present invention also proposes an electrical device, wherein the electrical device adopts the above-mentioned high-efficiency isolated Cuk converter.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] 1. The present invention introduces a transformer coupling structure, and uses a transformer to replace the front-end and back-end isolation capacitors in the Cuk circuit, which can not only achieve electrical isolation between the primary side and the secondary side, but also improve the energy transmission efficiency;

[0026] 2. The present invention adopts a DSP controller for control, monitors the output voltage of the output load in real time, and adjusts the duty cycle of the drive switch, which can ensure high stability and fast dynamic response of the output voltage;

[0027] 3. The present invention integrates key magnetic components such as transformers and inductors, reduces parasitic parameters, reduces volume, and improves the reliability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 It is a circuit topology diagram of a traditional Cuk circuit;

[0030] Figure 2 Schematic diagram of circuit topology of the Cuk circuit improved by the present invention;

[0031] Figure 3 A schematic diagram of the circuit topology of a Cuk circuit after integration of magnetic devices in the present invention;

[0032] Figure 4 It is a schematic diagram of the integrated design principle of the transformer and inductor in the present invention;

[0033] Figure 5 It is a schematic diagram of the adjustment principle of the DSP controller in the present invention. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects to be solved by 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.

[0035] Thus, a feature indicated in this specification will be used to illustrate one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although some features can be combined together to illustrate possible system designs, these features can also be used in other combinations that are not explicitly described. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

[0036] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0037] See also Figure 1 , which is a circuit topology diagram of an isolated Cuk circuit in the prior art, which has a power supply U i , inductor L1, inductor L2, capacitor C, capacitor C1, output load R, diode D, and drive switch S;

[0038] Its working principle is: the inductor L1 and the switch tube S form a boost network, which is connected to the power supply U i The output side is used to supply power U i Boost the voltage and provide electrical energy to capacitor C1;

[0039] Inductor L2 and capacitor C form an LC filter network, which is used to filter out the AC component in the circuit to obtain a stable DC output;

[0040] The capacitor C1 is an isolation capacitor, which is used to isolate the primary side (i.e., the circuit on the power supply side) from the secondary side (i.e., the circuit on the output load side) to prevent the high-voltage side circuit from damaging the low-voltage side circuit.

[0041] The above Cuk circuit can basically cope with general working environments. However, in some high-safety or high-voltage difference environments, electrical isolation through capacitor C1 cannot meet the requirements. Therefore, the circuit needs to be improved to enhance the electrical isolation capability of the circuit.

[0042] See also Figure 2 , which is a schematic diagram of the circuit topology of the improved Cuk circuit in the present invention, which has a power supply U i , inductor L1, inductor L2, capacitor C, drive switch S, diode D, and output load R;

[0043] In the above circuit, the functions of the inductor L1 and the driving switch S are the same as those in the prior art, and are used to form a boost network, thereby boosting the power supply U i The output voltage is boosted;

[0044] In this implementation, the capacitor C1 in the original Cuk circuit is replaced by a transformer to achieve an isolation effect. The transformer and the diode D together form a forward network for outputting a pulsating DC with the same polarity to the secondary side circuit. Compared with the use of capacitor C1 for electrical isolation, the use of a transformer for electrical isolation can not only avoid the mutual interference between the high voltage and the low voltage between the primary side and the secondary side, but also ensure the energy transmission efficiency.

[0045] The inductor L2 and the capacitor C form a filter network for filtering out the AC component in the same polarity pulsating DC output by the above forward network to obtain a stable same polarity DC output;

[0046] Compared with the traditional circuit topology, this circuit topology is isolated by a transformer, which not only ensures the function of electrical isolation, but also improves the energy transmission efficiency.

[0047] However, the above embodiment still has a large number of magnetic devices, which may cause a problem of large volume. Figure 2 The implementation has been further adjusted to solve the problem of large volume, see Figure 3 In this solution, the inductor L1, the inductor L2 and the transformer are all integrated into the magnetic device in the present invention, thereby further reducing the volume of the entire circuit without affecting the working performance of the circuit.

[0048] Based on the above embodiments, the high-efficiency isolated Cuk converter proposed in the present invention includes: a magnetic device, a power supply connected to one side of the magnetic device, and an output load connected to the other side of the magnetic device;

[0049] Wherein, a driving switch is provided between the power supply and the magnetic device, and the magnetic device can cooperate with the driving switch to generate a boost network to raise the voltage of the power supply;

[0050] A filter capacitor is provided between the output load and the magnetic device. The magnetic device and the filter capacitor can cooperate to form a filter network to obtain a DC output.

[0051] See also Figure 2 and Figure 3 , the magnetic device in the present invention is Figure 2 An integrated device of a transformer, an inductor L1, and an inductor L2;

[0052] Since the magnetic device has an inductor L1, it is connected with the drive switch S to form a circuit as shown below: Figure 2 The boost network shown;

[0053] At the same time, since the magnetic device has an inductor L2, it is connected with the filter capacitor C to form a Figure 2 The filter network shown;

[0054] The magnetic device has a transformer, which replaces the Figure 1 The capacitor C1 in the transformer can achieve the effect of electrical isolation, and at the same time, the energy transmission efficiency of the transformer is higher, thereby achieving the improvement of energy transmission efficiency under the premise of ensuring electrical isolation as mentioned above.

[0055] exist Figure 2 In the improved circuit, the transformer replaces the capacitor C1 to enhance the electrical isolation capability of the Cuk circuit. In the circuit operation, when the drive switch S is turned on, the power supply U i The inductor L1 is charged, and the secondary winding of the transformer and the inductor L2 release energy together to supply power to the output load R;

[0056] When the drive switch S is turned off, the power supply U i Together with the inductor L1, the primary winding of the transformer is charged, while the inductor L2 in the secondary side circuit supplies power to the output load R via the diode D.

[0057] The relationship between the input voltage and the output voltage of this circuit is:

[0058]

[0059] Where D is the duty cycle of the driving switch S; U i is the input voltage of the power supply; U o is the output voltage.

[0060] Although the improved circuit has enhanced its electrical isolation capability, its size will increase, and the traditional control method is no longer applicable to the requirements of current technology.

[0061] In order to further reduce the circuit volume and the parasitic parameters of the magnetic components, the present invention integrates the inductor L1, the inductor L2, and the transformer together, such as Figure 3 As shown, Figure 3 Implementation method compared to Figure 2 In the implementation mode, the inductor L1, the inductor L2, and the transformer are integrated together, which not only reduces the circuit volume and parasitic parameters, but also reduces the influence of the interference generated by the magnetic device on other devices.

[0062] The structure of the magnetic device in the present invention is described below:

[0063] See also Figure 3 and Figure 4 , the magnetic device in the present invention is integrated by a transformer and at least two inductors;

[0064] The magnetic device at least has a first inductor and a second inductor. The first inductor is used to cooperate with the driving switch S to generate a boost network, and the second inductor is used to cooperate with the filtering capacitor C to generate a filtering network.

[0065] It should be noted that the implementation method of the Cuk circuit is not limited to Figure 1 In other implementations, the number of inductors in the Cuk circuit may be far more than two. The circuit obtained based on the optimization of the Cuk circuit of the present invention also needs to be provided with multiple inductors accordingly. Therefore, when the inductor and the transformer are integrated into a magnetic device, there will also be multiple implementations of the inductor in the magnetic device. However, no matter what implementation is used, the Cuk circuit should have at least a first inductor L1 for forming a boost network and a second inductor L2 for forming a filter network, which is the reason why the magnetic device has at least a transformer and at least two inductors, and at least a first inductor L1 and a second inductor L2 in the above solution.

[0066] See also Figure 3 , which is a specific schematic diagram of the magnetic device integration in the present invention. In this integration method, the magnetic device has a rectangular magnetic core, a primary winding is wound on a first side of the rectangular magnetic core, and a secondary winding is wound on a third side opposite to the first side of the rectangular magnetic core;

[0067] The primary winding, the secondary winding, and the rectangular magnetic core cooperate to generate the transformer.

[0068] like Figure 4 As shown, the entire rectangular circle frame is also a rectangular magnetic core, the dotted line portion inside the rectangular magnetic core is the magnetic flux, the left side of the rectangular magnetic core is the first side, and the winding wound on the first side is the primary winding;

[0069] The right side of the rectangular magnetic core is the second side, and the winding wound on the second side is the secondary winding;

[0070] From this Figure 4 It can be clearly found that the turns ratio of the primary winding to the secondary winding is 1:n;

[0071] For a transformer, both sides of the transformer are connected to circuits. In the present invention, the circuit connected to the primary winding is the primary side circuit, that is, Figure 4 A power supply U is provided in i The circuit on one side, the circuit connected to the secondary winding is the secondary side circuit, that is Figure 4 A circuit on one side of the output load R is provided;

[0072] The turns ratio of the primary winding to the secondary winding is used as the step-up coefficient of the transformer. Generally speaking, when the turns ratio of the primary winding to the secondary winding is 1:n, the ratio of the input voltage of the transformer to the primary winding and the output voltage after the secondary winding is also 1:n.

[0073] The present invention can adjust the specific voltage boost ratio of the transformer by setting the turns ratio between the primary winding and the secondary winding.

[0074] For further information, see Figure 4 In the present invention, an inductor L1 and an inductor L2 are also wound on the rectangular magnetic core, where the inductor L1 is the first inductor and the inductor L2 is the second inductor;

[0075] The inductor L1 is a first winding wound on the second side of the rectangular magnetic core, that is, a winding wound on the top of the rectangular magnetic core;

[0076] The inductor L2 is a second winding wound on the fourth side of the rectangular magnetic core, that is, a winding wound below the rectangular magnetic core;

[0077] The above integration method does not change the overall working principle of the circuit, and its specific principle remains the same. Figure 2 As shown, only the inductor L1, the inductor L2, and the transformer are integrated as magnetic devices to reduce the volume of the circuit.

[0078] In addition, traditional control chips, limited by their computing power and logic, can only control circuit outputs step by step, and cannot make intelligent adjustments based on the working environment and load requirements. For this reason, the present invention uses a DSP controller to control the circuit. The DSP controller uses the output signal at the output load, combined with its voltage loop and current loop transfer functions, to perform real-time calculations, and ultimately automatically adjusts the switching frequency and duty cycle of the drive switch S to enhance the circuit's load-carrying and rapid response capabilities.

[0079] See also Figure 3 , the DSP controller is connected between the output load and the driving switch S;

[0080] Its working principle is: it is used to sample the output signal from the output load R, and provide a control signal for the driving switch S according to the output signal.

[0081] Should Figure 3 The DSP in the figure is the above-mentioned DSP controller. It can be seen that one side of the DSP controller is connected to the output load R, and the other side is connected to the third terminal of the driving switch S.

[0082] Therefore, the DSP controller can provide a corresponding control signal for the driving switch S according to the output voltage at the output load R, that is, the output signal;

[0083] As can be seen from the above content, the driving switch S forms a boost network, which can be used to boost the output power supply U i The output voltage is boosted, so after providing a corresponding control signal to the driving switch S in the present invention, the purpose of adjusting the boosting effect can also be achieved.

[0084] That is, by using the above-mentioned DSP controller, the system status can be monitored in real time, and the switching frequency and duty cycle of the driving switch can be automatically adjusted to ensure high stability and fast dynamic response of the output voltage.

[0085] The specific connection method of the driving switch S in the present invention is described below:

[0086] The driving switch S adopts an active switch tube, and the first end of the active switch tube is connected between the output side of the first winding and the same-name end of the primary winding, the second end of the active switch tube is connected between the opposite-name end of the primary winding and the negative pole of the power supply, and the third end of the active switch tube is connected to the output end of the DSP controller.

[0087] In this connection mode, the driving switch S can cooperate with the inductor L1 to form the above-mentioned boost network for boosting the power supply voltage U i of boost.

[0088] The connection method of the diode D in the present invention is described below:

[0089] The anode of the diode D is connected between the output end of the second winding and the same-name end of the secondary winding, and the cathode of the diode D is connected between the opposite-name end of the secondary winding and the positive electrode of the output load.

[0090] In this connection mode, the diode D can cooperate with the transformer to form the above-mentioned forward-excitation network for outputting pulsating direct current of the same polarity.

[0091] Generally speaking, the circuit uses PWM wave for control, but the PWM wave with fixed duty cycle cannot respond when the load changes, so that the output voltage decreases and the load capacity becomes poor. Although the traditional PID adjustment can enhance the load capacity and response speed of the Cuk circuit, when the load changes greatly, the circuit's load capacity will also deteriorate.

[0092] To this end, the DSP controller in the present invention uses a PID control strategy based on a genetic algorithm to control the drive switch.

[0093] See also Figure 5 , which is a schematic diagram of the PID control strategy based on genetic algorithm in the present invention, wherein U is the required output value of the circuit voltage, U o is the real-time circuit voltage output value, U f is the real-time sampling value of the output voltage, e is U and Uf In simple terms, the PID control strategy adjusts the duty cycle D of the PWM wave according to e to achieve timely response of the circuit.

[0094] Genetic Algorithm (GA) is an optimization technique based on natural selection and genetics. It can be used to automatically find the best parameters for PID controllers. Genetic algorithms gradually improve a set of candidate solutions by simulating the selection, crossover (recombination) and mutation in the biological evolution process, and finally find the optimal or near-optimal solution to the problem. The following are the basic steps for adjusting PID parameters using genetic algorithms:

[0095] 1. Initialize the population

[0096] Randomly generate a set of initial PID parameter combinations (k p , k i , k d ), these combinations constitute the first generation population. p is the proportionality coefficient, k i is the integration coefficient, k d is the integration coefficient.

[0097] 2. Define the fitness function

[0098] The fitness function is used to evaluate the performance of each individual on the control task. For PID controllers, the fitness function is usually defined based on the performance indicators of the system.

[0099] In the present invention, the fitness function is as follows:

[0100]

[0101] Where n is a natural number, T is the period, and y is n is the output value of the nth sampling, e n is the deviation of the nth sampling, e n-1 is the n-1th sampling deviation, and y0 is the initial value.

[0102] In the present invention, when the deviation e≤30mV, the PID adjustment is stopped to keep the duty cycle D unchanged. n Converted into the corresponding duty cycle D value to achieve the purpose of adjusting the circuit output.

[0103] 3. Select an action

[0104] According to the fitness value, some individuals are selected from the current population as parents. Usually, individuals with higher fitness are selected.

[0105] 4. Crossover (recombination)

[0106] The selected parents are paired and part of their genes (i.e. part of the PID parameters) are exchanged to produce new offspring.

[0107] 5. Mutation

[0108] Random mutations are performed on the newly generated offspring to change some of their parameter values. This helps maintain population diversity and avoids premature convergence to a local optimal solution.

[0109] 6. Generate a new generation

[0110] Replace some or all of the old generation individuals with the newly generated offspring to form the next generation population. Repeat the selection, crossover and mutation process until the termination condition is met.

[0111] 7. Termination Conditions

[0112] When the preset maximum number of iterations is reached, or when the fitness change of the best individual is less than a certain threshold, the algorithm stops running.

[0113] The optimal individual finally output is the PID parameter (k p , k i , k d ).

[0114] Furthermore, the present invention also proposes an electrical device having the above-mentioned high-efficiency isolated Cuk converter.

[0115] Compared with the prior art, the present invention has at least the following beneficial effects:

[0116] 1. The present invention introduces a transformer coupling structure, and uses a transformer to replace the front-end and back-end isolation capacitors in the Cuk circuit, which can not only achieve electrical isolation between the primary side and the secondary side, but also improve the energy transmission efficiency;

[0117] 2. The present invention adopts a DSP controller for control, monitors the output voltage of the output load in real time, and adjusts the duty cycle of the drive switch, which can ensure high stability and fast dynamic response of the output voltage;

[0118] 3. The present invention integrates key magnetic components such as transformers and inductors, reduces parasitic parameters, reduces volume, and improves the reliability of the entire system.

[0119] 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 high-efficiency isolated Cuk converter, characterized in that: include: A magnetic device, a power supply connected to one side of the magnetic device, and an output load connected to the other side of the magnetic device; A driving switch is provided between the power supply and the magnetic device, and the magnetic device can cooperate with the driving switch to generate a boost network to raise the voltage of the power supply; A filter capacitor is provided between the output load and the magnetic device. The magnetic device can cooperate with the filter capacitor to form a filter network to obtain a DC output.

2. The high-efficiency isolated Cuk converter according to claim 1, characterized in that: The magnetic device is integrated with a transformer and at least two inductors; The magnetic device has at least a first inductor and a second inductor. The first inductor cooperates with the drive switch to generate a boost network, and the second inductor cooperates with the filter capacitor to generate a filter network.

3. The high-efficiency isolated Cuk converter according to claim 2, characterized in that: The magnetic device has a rectangular magnetic core, a primary winding is wound on a first side of the rectangular magnetic core, and a secondary winding is wound on a third side opposite to the first side of the rectangular magnetic core; The primary winding, the secondary winding, and the rectangular magnetic core cooperate to create the transformer.

4. The high-efficiency isolated Cuk converter according to claim 3, characterized in that: The first inductor is a first winding wound on the second side of the rectangular magnetic core, and the second inductor is a second winding wound on a fourth side of the rectangular magnetic core opposite to the second side.

5. The high-efficiency isolated Cuk converter according to claim 4, characterized in that: Also included is a DSP controller connected between the output load and the drive switch; The DSP controller is used for sampling the output signal from the output load and providing a control signal for the driving switch according to the output signal.

6. The high-efficiency isolated Cuk converter according to claim 5, characterized in that: The driving switch adopts an active switch tube, and the first end of the active switch tube is connected between the output side of the first winding and the same-name end of the primary winding, the second end of the active switch tube is connected between the opposite-name end of the primary winding and the negative pole of the power supply, and the third end of the active switch tube is connected to the output end of the DSP controller.

7. The high-efficiency isolated Cuk converter according to claim 4, characterized in that: It also includes a diode connected to the output load, and the diode is used to output a pulsating direct current of the same polarity; The anode of the diode is connected between the output end of the second winding and the same-name end of the secondary winding, and the cathode of the diode is connected between the opposite-name end of the secondary winding and the anode of the output load.

8. The high-efficiency isolated Cuk converter according to claim 5, characterized in that: The output voltage of the output load satisfies the calculation model: Among them, U o is the output voltage of the output load, U i is the input voltage of the power supply, and D is the duty cycle of the drive switch.

9. The high-efficiency isolated Cuk converter according to claim 5, characterized in that: The DSP controller uses a PID control strategy based on a genetic algorithm to control the drive switch.

10. An electrical device, characterized in that: The electrical equipment comprises a high-efficiency isolated Cuk converter as claimed in any one of claims 1 to 9.

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