Resonance circuit with fixed-frequency variable gain output and control method

Abstract

The invention discloses a resonant circuit with fixed-frequency variable gain output and a control method, and the resonant circuit is composed of a first inverter circuit, a resonant network, a second inverter circuit and a resonant control module which are connected in sequence. The resonant network is composed of a resonant capacitor, a resonant inductor, a first relay, a second relay, a resistor, a transformer, at least one additional relay and at least one additional resonant capacitor. The resonant inductor and the resistor are respectively connected with one end connected with the first inverter circuit through a second relay contact, and the transformer excitation inductor is connected with the primary winding in parallel; each additional relay contact is connected with an additional harmonic capacitor in series to form an additional module, and all the additional modules and the resonant capacitor are connected to the two ends of a series branch formed by the resistor and the first relay contact in parallel. The problem that the voltage gain adjusting range is narrow when the resonant circuit is controlled is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of resonant frequency control, and more particularly, to a resonant circuit with fixed frequency and variable gain output and a control method. BACKGROUND

[0002] Currently, in DC-DC power supply products, resonant circuit topologies are increasingly used in consideration of cost and efficiency. Resonant circuit topologies can derive half-bridge LLC topology, full-bridge LLC topology, bidirectional full-bridge CLLLC topology, and the like according to power levels and use scenarios.

[0003] The mainstream method for ensuring that the resonant circuit works inductively at present is to write an algorithm through software, sample the voltages at the input and output ends through a hardware circuit, adjust the output frequency of the drive duty cycle, thereby adjusting the operating frequency of the entire circuit, adjusting the impedance of the overall circuit, and ensuring that the entire circuit works inductively. However, the above frequency conversion control has the following problems: 1. The software algorithm is complex and requires a higher level of software development personnel. 2. When a large load switch occurs at the output end, the software algorithm takes a long time to calculate, and the operating frequency may be too low or too high in a short period of time, resulting in a problem of temporary capacitive or over-resonance of the overall circuit. 3. Since the inductance and capacitance parameters of the resonant circuit are fixed, the voltage gain adjustment range is narrow, which limits its applicability. 4. After the resonant circuit stops working, the inductance and capacitor devices have not completely released energy, and when the next stage circuit is connected to the circuit for work, the problem of current backflow may occur.

[0004] CN116566210A proposes a bidirectional LLC conversion circuit, which includes a main circuit, the main circuit includes an input battery pack, an input power device, an input resonant cavity adjustment unit, an output resonant cavity adjustment unit, an output power device, and an output battery pack; an input detection unit for detecting the input parameters of the input battery pack; an output detection unit for detecting the output parameters of the output battery pack; a control unit for controlling the switching state of the input power device and the output power device according to the input parameters and the output parameters, and controlling the input resonant cavity parameters and the output resonant cavity parameters. However, in addition to controlling the capacitance of the total resonant capacitor, this patent also needs to control the inductance of the resonant inductor. However, in fact, the inductance of the resonant inductor includes not only the inductance itself, but also the PCB parasitic inductance and transformer leakage inductance. In a resonant circuit with medium and high power, the inductance of the resonant inductor is generally small, and modifying the resonant parameters can easily increase the influence of parasitic parameters on the resonant circuit, which can easily cause a resonant current spike when starting.

[0005] At the same time, this circuit does not have a discharge circuit, and directly switches the resonant capacitor or resonant inductor, which can cause individual devices to not be completely discharged, thereby affecting the current change of the entire resonant circuit.

[0006] CN109831114A discloses a LLC type bidirectional active bridge inverter resonance parameter design method, and the resonance circuit of the LLC type bidirectional active bridge inverter is composed of a resonance inductance Lr of a primary side of a transformer, a resonance capacitance Cr and an excitation inductance Lm. The resonance parameter deviation of the bidirectional active bridge inverter caused by environmental factors will cause the change of voltage transmission gain, and the mutual interference of the output impedance of the cascade system and the input impedance of the load converter will cause the cascade instability problem. However, the circuit cannot automatically calculate and adjust the resonance parameters by using the main control module. If the resonance parameters are adjusted, the devices need to be manually replaced, and when the parameters need to be adjusted, the calculation process is extremely tedious. SUMMARY

[0007] To solve the problems in the prior art, the present application provides a resonant circuit with fixed frequency and variable gain output and a control method.

[0008] The first aspect of the present application provides a resonant circuit with fixed frequency and variable gain output, which comprises a first inverter circuit, a resonant network, a second inverter circuit and a resonant control module connected in sequence, comprising:

[0009] The resonant network is composed of a resonant capacitance, a resonant inductance, a first relay contact, a second relay contact, a resistor, a transformer, at least one additional relay contact and at least one additional resonant capacitance;

[0010] One bridge arm midpoint of the first inverter circuit is connected to one end of the primary winding of the transformer through the resonant inductance; the other bridge arm midpoint of the first inverter circuit is connected to the other end of the primary winding of the transformer through the resistor and the first relay contact in sequence; the end of the resonant inductance connected to the first inverter circuit and the end of the resistor connected to the first inverter circuit are connected through the second relay contact, and the excitation inductance of the transformer is connected in parallel with the primary winding;

[0011] Each additional relay contact is connected in series with one additional harmonic capacitance to form an additional module, and all additional modules are connected in parallel with the resonant capacitance at both ends of the series branch composed of the resistor and the first relay contact;

[0012] The resonant control module is used to control the conduction or turn-off of the first and second relay contacts and each additional relay contact of the resonant network, and drive the switching tubes of the first inverter circuit and the second inverter circuit, so as to adjust the voltage gain range of the resonant circuit.

[0013] Preferably, the resonant circuit further comprises a first filter capacitance and a second filter capacitance, the first filter capacitance is connected between the high-voltage side bus and the low-voltage side bus of the first inverter circuit, and the second filter capacitance is connected between the high-voltage side bus and the low-voltage side bus of the second inverter circuit.

[0014] Preferably, the resonance control module comprises a first relay control circuit, a second relay control circuit, a resonance capacitor voltage sampling circuit, a master control module, a communication circuit, a rear-stage communication circuit and a rear-stage master control module, in particular:

[0015] The first relay control circuit is used for controlling the first and second relay contacts to be turned on or turned off, the second relay control circuit is used for controlling each additional relay contact to be turned on or turned off, the resonance capacitor voltage sampling circuit is used for collecting the voltage across the resonance capacitor, and the master control module is used for calculating the voltage gain value and controlling the first and second relay control circuits and driving the switching tubes of the first and second inverter circuits.

[0016] The master control module and the rear-stage master control module communicate data through the communication circuit and the rear-stage communication circuit, and the rear-stage master control module is used for obtaining the output power of the resonance circuit and the working voltage of the rear-stage circuit thereof.

[0017] Preferably, the capacitance values of the resonance capacitor and the additional resonance capacitors are equal, and the sum of the number of the resonance capacitor and all the additional resonance capacitors is equal to the total resonance capacitance value corresponding to the set maximum gain divided by the capacitance value of a single additional resonance capacitor.

[0018] The second aspect of the present application proposes a control method based on the circuit of the first aspect of the present application, comprising:

[0019] The first relay contact and the second relay contact are turned off, all the additional relay contacts are closed, the output power of the resonance circuit and the working voltage of the rear-stage circuit thereof are obtained, the normalized impedance of the rear-stage circuit of the resonance circuit is calculated, the quality factor of the resonance circuit is calculated according to the normalized impedance, and the voltage gain of the resonance circuit is calculated according to the quality factor of the resonance circuit; if the calculated voltage gain value M meets the output voltage requirement, the master control module controls the switching tubes through proportional integral control to adjust the voltage and current output by the harmonic circuit to the expected values of the voltage and current of the rear-stage circuit.

[0020] On the contrary, the master control module stops sending driving signals to the switching tubes of each resonance circuit, controls the first relay contact and the second relay contact to be closed at the same time, and discharges the resonance circuit; when the voltage across the resonance capacitor is 0, the current resonance circuit voltage gain is obtained, and the total resonance capacitance value of the resonance circuit corresponding to the current resonance circuit voltage gain is calculated when the quality factor of the resonance circuit is still the quality factor before discharge; if the capacitance difference between the calculated total resonance capacitance value and the current total resonance capacitance value is greater than the set difference threshold value, the additional relay contacts are turned off one by one until the capacitance difference between the calculated total resonance capacitance value and the current total resonance capacitance value is less than or equal to the set difference threshold value, and the master control module controls the switching tubes through proportional integral control to adjust the voltage and current output by the harmonic circuit to the expected values of the voltage and current of the rear-stage circuit.

[0021] Preferably, the resonant circuit voltage gain is calculated, in particular:

[0022]

[0023] wherein: M is the resonant circuit voltage gain; R ac is the normalized impedance of the resonant circuit; U bus is the operating voltage of the subsequent circuit; P rms is the output power of the resonant circuit; n is the transformer ratio; L r1 is the resonant inductance; m is the ratio of the resonant inductance to the inductance of the primary winding of the transformer; f sn is the normalized frequency of the resonant circuit; f sw is the operating frequency of the harmonic circuit; Q L is the quality factor of the harmonic circuit; C r is the total resonant capacitance of the resonant circuit.

[0024] Preferably, the voltage gain value M meets the output voltage requirement, in particular:

[0025] If the voltage gain value M is less than or equal to the set maximum gain and greater than or equal to the set minimum gain, the output voltage requirement is met.

[0026] The maximum gain is equal to the set maximum output voltage multiplied by the transformer ratio and divided by the set minimum input voltage.

[0027] The minimum gain is equal to the set minimum output voltage multiplied by the transformer ratio and divided by the set maximum input voltage.

[0028] Preferably, the set difference threshold is ±10% of the calculated total resonant capacitance.

[0029] A third aspect of the present application provides a device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the steps of the control method according to the second aspect of the present application.

[0030] A fourth aspect of the present application provides a computer readable storage medium storing a computer program, wherein the computer program is executable by a processor to perform the steps of the control method according to the second aspect of the present application.

[0031] The application adopts the technical scheme as follows. The application has the beneficial effects that, compared with the prior art, the application solves the problem of narrow voltage gain adjustment range of the resonant circuit when the resonant circuit is controlled at a fixed frequency. The main control module of the application controls the switching tubes by proportional integral control to adjust the voltage and current output by the harmonic circuit to the desired values of the voltage and current of the subsequent circuit, thereby preventing the problem of current backflow when the resonant circuit is connected to the subsequent circuit. When the difference between the calculated total resonant capacitance value and the current total resonant capacitance value is greater than the set difference threshold, the additional relay contacts are disconnected one by one, thereby solving the problem of transient capacitive or over-resonance when the load is switched during frequency conversion control. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The figure is a circuit structure diagram of the resonant circuit of the application. DETAILED DESCRIPTION

[0033] To make the purpose, technical scheme and advantages of the application clearer, the technical scheme of the application will be described clearly and completely below in combination with the drawings in the embodiments of the application. The embodiments described in the application are only a part of the embodiments of the application, rather than all the embodiments. All other embodiments obtained by those skilled in the art without creative labor based on the spirit of the application are within the protection scope of the application.

[0034] As shown in FIG. 1, the embodiment 1 of the application proposes a resonant circuit with fixed frequency and variable gain output, which is composed of a first inverter circuit, a resonant network, a second inverter circuit and a resonant control module in sequence, specifically: Figure 1 The resonant network includes a resonant capacitance Cr1, a resonant inductance Lr1, a first relay contact SW1, a second relay contact SW2, a resistor R1, a transformer T, at least one additional relay contact (one additional relay contact SW3 in this embodiment), and at least one additional resonant capacitance (one additional resonant capacitance Cr2 in this embodiment).

[0035] One bridge arm midpoint of the first inverter circuit is connected to one end of the primary winding of the transformer T through the resonant inductance Lr1; the other bridge arm midpoint of the first inverter circuit is connected to the other end of the primary winding of the transformer T through the resistor R1 and the first relay contact SW1 in sequence; one end of the resonant inductance Lr1 and the resistor R1 connected to the first inverter circuit is connected through the second relay contact SW2, and the transformer excitation inductance Lm is connected in parallel with the primary winding.

[0036]

[0037] ​An additional relay contact SW3 and an additional harmonic capacitor Cr2 are connected in series to form an additional module, and all the additional modules are connected in parallel between the series branch formed by the resistor R1 and the first relay contact SW1 and the second relay contact SW2.

[0038] The resonance control module is used for controlling the turn-on or turn-off of the first relay contact SW1, the second relay contact SW2 and each additional relay contact, and driving the switch tubes of the first inverter circuit and the second inverter circuit, and adjusting the voltage gain range of the resonance circuit.

[0039] It should be noted that the first inverter circuit includes switch tubes S1, S2, S3 and S4, and the second inverter circuit includes switch tubes S5, S6, S7 and S8.

[0040] Preferably, the resonance circuit further includes a first filter capacitor C1 and a second filter capacitor C2, the first filter capacitor C1 is connected between the high-voltage side bus and the low-voltage side bus of the first inverter circuit, and the second filter capacitor C2 is connected between the high-voltage side bus and the low-voltage side bus of the second inverter circuit.

[0041] Preferably, the resonance control module includes a first relay control circuit 3, a second relay control circuit 4, a resonance capacitor voltage sampling circuit 5, a master control module 6, a communication circuit 7, a rear-stage communication circuit 8 and a rear-stage master control module 9, and specifically:

[0042] The first relay control circuit 3 is used for controlling the turn-on or turn-off of the first and second relay contacts, the second relay control circuit 4 is used for controlling the turn-on or turn-off of each additional relay contact, the resonance capacitor voltage sampling circuit 5 is used for collecting the voltage across the resonance capacitor, and the master control module 6 is used for calculating the voltage gain value and controlling the first and second relay control circuits 4 and the switch tubes of the first inverter circuit and the second inverter circuit.

[0043] The master control module 6 and the rear-stage master control module 9 perform data communication through the communication circuit 7 and the rear-stage communication circuit 8, and the rear-stage master control module 9 is used for obtaining the output power of the resonance circuit and the operating voltage of the rear-stage circuit thereof.

[0044] Preferably, the capacitance values of the resonance capacitor and the additional resonance capacitors are equal, and the sum of the number of the resonance capacitor and all the additional resonance capacitors is equal to the total resonance capacitance value corresponding to the maximum gain divided by the capacitance value of a single additional resonance capacitor.

[0045] Embodiment 2 of the present application proposes a control method based on the circuit described in Embodiment 1 of the present application, which includes:

[0046] The first relay contact and the second relay contact are disconnected, all the additional relay contacts are closed, the output power of the resonant circuit and the working voltage of the subsequent circuit are obtained, the normalized impedance of the resonant circuit subsequent circuit is calculated, the quality factor of the resonant circuit is calculated according to the normalized impedance, and the voltage gain of the resonant circuit is calculated according to the quality factor of the resonant circuit; if the calculated voltage gain value M meets the output voltage requirement, the main control module 6 controls the switch tubes through proportional integral control to adjust the voltage and current output by the harmonic circuit to the expected value of the voltage and current of the subsequent circuit;

[0047] On the contrary, the main control module 6 stops sending driving signals to the switch tubes of each resonant circuit, controls the first relay contact and the second relay contact to be closed at the same time, and performs discharge on the resonant circuit. When the voltage across the resonant capacitor is 0, the current resonant circuit voltage gain is obtained, and the total resonant capacitance value of the resonant circuit corresponding to the current resonant circuit voltage gain is calculated when the quality factor of the resonant circuit is still the quality factor before discharge. If the capacitance difference between the calculated total resonant capacitance value and the current total resonant capacitance value is greater than the set difference threshold value, the additional relay contacts are disconnected one by one until the capacitance difference between the calculated total resonant capacitance value and the current total resonant capacitance value is less than or equal to the set difference threshold value. The main control module 6 controls the switch tubes through proportional integral control to adjust the voltage and current output by the harmonic circuit to the expected value of the voltage and current of the subsequent circuit.

[0048] Preferably in the embodiment, the resonant circuit voltage gain is calculated, in particular:

[0049]

[0050] In the formula, M is the resonant circuit voltage gain; R ac is the normalized impedance of the resonant circuit; U bus is the working voltage of the subsequent circuit; P rms is the output power of the resonant circuit; n is the transformer ratio; L r1 is the resonant inductance value; m is the ratio of the resonant inductance value to the inductance value of the primary winding of the transformer; f sn is the resonant circuit normalized frequency; f sw is the working frequency of the harmonic circuit; Q L is the quality factor of the harmonic circuit; C r is the total resonant capacitance value of the current resonant circuit.

[0051] Preferably in the embodiment, the voltage gain value M meets the output voltage requirement, in particular:

[0052] If the voltage gain value M is less than or equal to the set maximum gain and greater than or equal to the set minimum gain, it meets the output voltage requirement;

[0053] The maximum gain is equal to the set maximum output voltage multiplied by the transformer turns ratio divided by the set minimum input voltage.

[0054] The minimum gain is equal to the set minimum output voltage multiplied by the transformer turns ratio divided by the set maximum input voltage.

[0055] Preferably, the set difference threshold is ±10% of the calculated total resonant capacitance value.

[0056] Embodiment 3 of the present application proposes a device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor performing the steps of the control method according to Embodiment 2 of the present application.

[0057] Embodiment 4 of the present application proposes a computer-readable storage medium storing a computer program, the computer program being executable by a processor to perform the steps of the control method according to Embodiment 2 of the present application.

[0058] The present disclosure can be a system, a method, and / or a computer program product. The computer program product can include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure.

[0059] It should be noted that the above-mentioned embodiments are only used to illustrate but not to limit the technical solutions of the present application. Although the present application is described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. A resonant circuit with a fixed frequency and variable gain output, the resonant circuit comprising a first inverter circuit, a resonant network, a second inverter circuit, and a resonant control module connected in sequence, characterized in that: The resonant network is composed of a resonant capacitor, a resonant inductor, a first relay contact, a second relay contact, a resistor, a transformer, at least one additional relay contact and at least one additional resonant capacitor; The midpoint of one bridge arm of the first inverter circuit is connected to one end of the primary winding of the transformer via a resonant inductor; the midpoint of the other bridge arm of the first inverter circuit is connected to the other end of the primary winding of the transformer via a resistor and a first relay contact in sequence; one end of the resonant inductor connected to the first inverter circuit and one end of the resistor connected to the first inverter circuit are connected via a second relay contact, and the transformer excitation inductor is connected in parallel with the primary winding; Each additional relay contact is connected in series with an additional harmonic capacitor to form an additional module, and all additional modules and the resonant capacitor are connected in parallel at both ends of a series branch formed by a resistor and the first relay contact; The resonance control module is used to control the on / off of the first and second relay contacts and each additional relay contact of the resonant network and drive the switch tubes of the first inverter circuit and the second inverter circuit to adjust the voltage gain range of the resonant circuit.

2. The resonant circuit with fixed frequency and variable gain output according to claim 1, characterized in that: The resonant circuit also includes a first filter capacitor and a second filter capacitor. The first filter capacitor is connected between the high-voltage side bus and the low-voltage side bus of the first inverter circuit, and the second filter capacitor is connected between the high-voltage side bus and the low-voltage side bus of the second inverter circuit.

3. The resonant circuit with fixed frequency and variable gain output according to claim 1, characterized in that: The resonance control module includes a first relay control circuit, a second relay control circuit, a resonant capacitor voltage sampling circuit, a main control module, a communication circuit, a subsequent communication circuit, and a subsequent main control module. Specifically, the first relay control circuit is used to control the first and second relay contacts to be turned on or off, and the second relay control circuit is used to control the additional relay contacts to be turned on or off; the resonant capacitor voltage sampling circuit is used to collect the voltage across the resonant capacitor; the main control module is used to calculate the voltage gain value, and control the first and second relay control circuits and drive the switch tubes of the first inverter circuit and the second inverter circuit; The main control module and the subsequent main control module perform data communication via the communication circuit and the subsequent communication circuit; the subsequent main control module is used to obtain the output power of the resonant circuit and the operating voltage of its subsequent circuit.

4. The resonant circuit with fixed frequency and variable gain output according to claim 1, characterized in that: The capacitance values ​​of the resonant capacitor and the additional resonant capacitor are equal, and the sum of the resonant capacitor and all the additional resonant capacitors is equal to the total resonant capacitance value corresponding to the set maximum gain divided by the capacitance value of a single additional resonant capacitor.

5. A control method based on the circuit according to any one of claims 1 to 4, characterized in that: include: The first relay contact and the second relay contact are disconnected, and all additional relay contacts are closed. The output power of the resonant circuit and the operating voltage of its subsequent circuit are obtained, the normalized impedance of the subsequent circuit of the resonant circuit is calculated, and the quality factor of the resonant circuit is calculated based on the normalized impedance. The voltage gain of the resonant circuit is calculated based on the quality factor of the resonant circuit. If the calculated voltage gain value M meets the output voltage requirement, the main control module controls each switching tube through the proportional product to adjust the voltage and current output by the harmonic circuit to the desired values ​​of the voltage and current of the subsequent circuit. On the contrary, the main control module stops sending driving signals to each switch tube of each resonant circuit, controls the first relay contact and the second relay contact to close at the same time, and discharges the resonant circuit. When the voltage across the resonant capacitor is 0, the current resonant circuit voltage gain is obtained, and the total resonant capacitance value of the resonant circuit corresponding to the current resonant circuit voltage gain is calculated when the quality factor of the resonant circuit is still the quality factor before discharge. If the capacitance difference between the calculated total resonant capacitance value and the current total resonant capacitance value is greater than the set difference threshold, the additional relay contacts are disconnected one by one until the capacitance difference between the calculated total resonant capacitance value and the current total resonant capacitance value is less than or equal to the set difference threshold. The main control module controls each switch tube through the proportional product to adjust the voltage and current output of the harmonic circuit to the expected values ​​of the voltage and current of the subsequent circuit.

6. The control method according to claim 5, characterized in that: The calculation of the resonant circuit voltage gain is specifically as follows: Where: M is the voltage gain of the resonant circuit; R ac is the normalized impedance of the resonant circuit; U bus is the operating voltage of the subsequent circuit; P rms is the output power of the resonant circuit; n is the transformer ratio; L r1 is the resonant inductance value; m is the ratio of the resonant inductance value to the inductance value of the primary winding of the transformer; f sn is the normalized frequency of the resonant circuit; f sw is the operating frequency of the harmonic circuit; Q L is the quality factor of the harmonic circuit; C r ' is the total resonant capacitance value of the current resonant circuit.

7. The control method according to claim 5, characterized in that: The voltage gain value M meets the output voltage requirement, specifically: If the voltage gain value M is less than or equal to the set maximum gain and greater than or equal to the set minimum gain, the output voltage requirement is met; The maximum gain is equal to the set maximum output voltage multiplied by the transformer ratio divided by the set minimum input voltage; The minimum gain is equal to the set minimum output voltage multiplied by the transformer ratio and then divided by the set maximum input voltage.

8. The control method according to claim 5, characterized in that: The set difference threshold is ±10% of the calculated total resonant capacitance value.

9. A device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the steps of the control method according to any one of claims 5 to 8. 10 . A computer-readable storage medium storing a computer program, wherein the computer program performs the steps of the control method according to claim 5 when executed by a processor.

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