Circuit for sampling resonant current of LLC resonant converter
By using the first and second samplers and conversion circuits in the LLC resonant converter, the excitation component is eliminated by superimposing the 90° phase difference, the problem of excitation component in resonant current sampling is solved, and more efficient loop compensation and performance optimization is achieved.
Patent Information
- Application Number
- CN202422432177.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-09
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2034-10-09
AI Technical Summary
The existing LLC resonant converters cannot effectively remove the excitation component when sampling the resonant current, resulting in poor loop compensation and limiting the performance of the converter.
The first sampler and the second sampler are used to sample the resonant inductor current and the excitation inductor current respectively, and convert it into a resonant voltage and an excitation voltage through the first conversion circuit and the second conversion circuit. The excitation component is eliminated by superposition of 90° phase difference, and combined with the rectification, filtering and gain amplification circuit, the resonant voltage after the excitation component is output.
Accurate sampling of resonant current is achieved, the impact of excitation components is eliminated, loop stability and bandwidth is improved, and the dynamic response performance of the LLC converter is optimized.
Smart Images
Figure CN223182012U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a circuit for sampling the resonant current of an LLC resonant converter, belonging to the field of LLC resonant converter control. Background Art
[0002] As an excellent DC-DC circuit topology, the LLC resonant converter has a wide range of applications in converting high-voltage DC signals into low-voltage DC signals and in the direction of power transmission. The control of the LLC resonant converter is relatively complex. Nowadays, due to the limitations of analog loop control, digital control has become a research hotspot for loop topologies because of its high flexibility, good stability, and convenient debugging. The loop topologies of LLC include single-voltage-loop control, average-current-mode control, charge-charge control, and other non-linear controls derived therefrom. Among them, the single-voltage-loop control, as the first proposed control topology, no longer meets the requirements of high power density and high dynamic response nowadays. Therefore, the non-linear control of the double-loop feedback control topology based on the resonant cavity current and output voltage control has gradually become the focus of research. In these non-linear controls, the accuracy of sampling the resonant current directly affects the loop. Therefore, an accurate resonant current sampling circuit will greatly improve the stability, bandwidth, and cut-off frequency of the loop.
[0003] Most of the current sampling of double-loop non-linear control LLC resonant converters cannot remove the excitation component of the resonant current, and use irregular current waveforms instead of the average current waveform for loop compensation. As a result, a filter with a very low bandwidth is required to sample the current waveform, which limits the performance of the LLC converter. Moreover, using irregular waveforms for loop compensation conflicts with the control principle of compensating with the average value of sinusoidal current. Although the current signal is made as close as possible to the average value through filtering, it still cannot make excellent compensation for the loop, reducing the performance of the loop. Summary of the Utility Model
[0004] The utility model provides a circuit for sampling the resonant current of an LLC resonant converter, which solves the problems disclosed in the background art.
[0005] According to one aspect of the present disclosure, there is provided a circuit for sampling the resonant current of an LLC resonant converter, including a first sampler, a first conversion circuit, a second sampler, and a second conversion circuit;
[0006] The first sampler samples the resonant inductor current in the LLC resonant converter;
[0007] The first conversion circuit receives the resonant inductor current and converts the resonant inductor current into a resonant voltage;
[0008] The second sampler samples the excitation inductor current in the LLC resonant converter;
[0009] A second conversion circuit receives the exciting inductor current and converts the exciting inductor current into an exciting voltage; receives the resonant voltage, adds the resonant voltage and the exciting voltage, and outputs the resonant voltage after removing the exciting component; wherein, the phase difference between the resonant voltage and the exciting voltage is 90°.
[0010] In some embodiments of the present disclosure, the first sampler is a first sampling coil, and the first sampling coil is coupled with the resonant inductor to form a transformer structure.
[0011] In some embodiments of the present disclosure, the first conversion circuit includes a first resistor and a first capacitor. One end of the first resistor is connected to the same-named end of the first sampling coil. The other end of the first sampling coil is grounded and connected to one end of the first capacitor. One end of the first capacitor is connected to the other end of the first resistor and the second conversion circuit respectively.
[0012] In some embodiments of the present disclosure, the second sampler is a second sampling coil. The second sampling coil is arranged on the secondary side of the LLC resonant converter transformer and serves as the secondary coil of the secondary side. The second sampling coil samples the current of the primary coil in parallel with the exciting inductor, and controls the phase of the sampled current of the second sampling coil by adjusting the winding direction of the second sampling coil.
[0013] In some embodiments of the present disclosure, the second conversion circuit includes a second resistor. The same-named end of the second sampling coil is grounded. The other end of the second sampling coil is connected to one end of the second resistor. The other end of the second resistor is connected to the first conversion circuit and outputs the resonant voltage after removing the exciting component respectively.
[0014] In some embodiments of the present disclosure, a rectifying circuit is further included, and the rectifying circuit rectifies the resonant voltage after removing the exciting component.
[0015] In some embodiments of the present disclosure, a filtering circuit is further included, and the filtering circuit filters the rectified resonant voltage.
[0016] In some embodiments of the present disclosure, a gain amplification circuit is further included, and the gain amplification circuit amplifies the gain of the filtered resonant voltage.
[0017] The beneficial effects achieved by the present utility model: The present utility model samples the resonant inductor current and the exciting inductor current, converts the sampled currents into voltages with a phase difference of 90°, and superimposes the two voltages to obtain the resonant voltage after removing the exciting component for the feedback loop control of the internal current loop of the average current mode control, thereby directly eliminating the influence of the exciting component. Description of the Drawings
[0018] Figure 1 The circuit diagram for sampling the resonant current of the LLC resonant converter;
[0019] Figure 2 is the RC integration circuit diagram;
[0020] Figure 3 is the simulation circuit based on the Half Bridge LLC resonant converter;
[0021] Figure 4 are the waveforms of the rectifier diode current, resonant current, and exciting current of the Half Bridge LLC resonant converter;
[0022] Figure 5 is the waveform with a 90° phase delay of the rectifier diode sampling integration signal of the resonant converter;
[0023] Figure 6 is V sense the signal waveform diagram;
[0024] Figure 7 is the signal waveform diagram before and after rectification;
[0025] Figure 8 are the waveform diagrams of the half-wave signal, the filtered signal, and the gain-amplified signal. Specific Embodiments
[0026] Next, the technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present disclosure.
[0027] Unless otherwise specified, the relative arrangements, numerical expressions, and numerical values of the components and steps described in these embodiments do not limit the scope of the present disclosure.
[0028] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.
[0029] For technologies, methods, and devices known to those of ordinary skill in the relevant fields, detailed discussions may not be made, but where appropriate, the said technologies, methods, and devices should be regarded as part of the specification.
[0030] In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.
[0031] It should be noted that similar symbols and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.
[0032] To solve the problem caused by the inability of existing methods to remove the excitation component of the resonant current, the present disclosure proposes a circuit for sampling the resonant current of an LLC resonant converter.
[0033] Figure 1 A schematic diagram of an embodiment of the circuit for sampling the resonant current of an LLC resonant converter according to the present disclosure includes a first sampler, a first conversion circuit, a second sampler, and a second conversion circuit.
[0034] In the embodiment, the main function of the first sampler is to sample the resonant inductor current in the LLC resonant converter.
[0035] It should be noted that there are many ways of current sampling. The ways of current sampling mainly include resistance detection, current transformer detection, Hall current sensor detection, optocoupler feedback detection, etc. The optimal method here is to sample the resonant inductor current without changing the LLC resonant converter circuit, so as to prevent the sampling circuit from affecting the LLC resonant converter. For example, the current can be sampled by means of coil coupling.
[0036] Therefore, in some embodiments, the first sampler uses a first sampling coil, and the first sampling coil is coupled with the resonant inductor to form a transformer structure.
[0037] In the embodiment, the main function of the first conversion circuit is to receive the resonant inductor current and convert the resonant inductor current into a resonant voltage.
[0038] It should be noted that the ultimate purpose of sampling the resonant current of the LLC resonant converter is for feedback loop control. In practice, a voltage signal is fed back to the loop. Therefore, here it is necessary to further convert the current into a voltage.
[0039] In some embodiments, the first conversion circuit can be converted by an RC integration circuit, which can specifically include a first resistor and a first capacitor. One end of the first resistor is connected to the same-name end of the first sampling coil, and the other end of the first sampling coil is grounded and connected to one end of the first capacitor. One end of the first capacitor is connected to the other end of the first resistor and the second conversion circuit respectively. This conversion circuit has a simple structure and low cost.
[0040] In the embodiment, the main function of the second sampler is to sample the magnetizing inductor current in the LLC resonant converter.
[0041] Similar to collecting the resonant inductor current, in some embodiments, the second sampler is a second sampling coil. The second sampling coil is arranged on the secondary side of the LLC resonant converter transformer and serves as the secondary coil of the secondary side. The second sampling coil samples the current of the primary coil in parallel with the exciting inductor, and controls the phase of the sampled current of the second sampling coil by adjusting the winding direction of the second sampling coil.
[0042] In an embodiment, the second conversion circuit receives the exciting inductor current, converts the exciting inductor current into an exciting voltage; receives the resonant voltage, adds the resonant voltage and the exciting voltage, and outputs the resonant voltage after removing the exciting component; wherein, the phase difference between the resonant voltage and the exciting voltage is 90°.
[0043] It should be noted that since there is an exciting component in the resonant inductor current, the converted voltage must also have an exciting component. In order to eliminate the exciting component, it is necessary to make the phase difference between the resonant voltage and the exciting voltage 90°. Specifically, the phase difference between the two voltages can be made 90° by controlling the direction of the exciting voltage or directly performing a phase transformation. The two voltages are superimposed to cancel the exciting component included in the resonant voltage, that is, a pure resonant voltage is obtained.
[0044] In some embodiments, the second conversion circuit can also adopt an RC integration circuit. However, in order to simplify the circuit, two RC integration circuits can share a capacitor. Therefore, in some embodiments, the second conversion circuit can be simplified to include a second resistor. The same-name terminal of the second sampling coil is grounded, the other end of the second sampling coil is connected to one end of the second resistor, and the other end of the second resistor is respectively connected to the first conversion circuit and outputs the resonant voltage after removing the exciting component.
[0045] It should be noted that in order to make the phase difference 90°, the second sampling coil can be output in reverse, that is, the same-name terminal is grounded, and sampling is performed at the other end of the second sampling coil, while the current sampling signal in the resonant inductor still uses the same-name terminal output. At this time, the phase difference between the two sampling signals reaches 90°.
[0046] It should be noted that the ratio of the currents can be calculated according to the turn ratio of the first sampling coil and the second sampling coil, and the sampling signals under the same ratio can be obtained by adjusting the resistance ratio in the RC integration circuit.
[0047] It should be noted that the first conversion circuit and the second conversion circuit implement two sets of RC integration circuits. The specific calculation principle can be as follows:
[0048] [[ID=2">] ;
[0049] ;
[0050] In the formula, Lr is the value of the resonant inductor, L m is the value of the exciting inductor, T is the period of the switching frequency, U Lr and U Lm are the voltage values across the resonant inductor and the exciting inductor during sampling respectively, I Lr is the current signal obtained by calculating the voltage signal across the resonant inductor through a formula and having the same waveform as the resonant current, I Lm is the current signal obtained by calculating the voltage signal across the exciting inductor through a formula and having the same waveform as the resonant current.
[0051] Assume that the turns ratio of the resonant inductor to the first sampling coil is X, and the turns ratio of the primary coil of the transformer to the second sampling coil is Y. Then the voltage relationship between the primary and secondary is:
[0052] ;
[0053] In the formula, are the sampling voltages of the resonant inductor and the exciting inductor respectively.
[0054] See Figure 2 , the input and output of the RC integrating circuit can be expressed as:
[0055] ;
[0056] In the formula, C is the capacitance value of the RC integrating circuit, R is the resistance value of the RC integrating circuit, V out and V in are the output and input of the RC integrating circuit respectively, , f s is the frequency of the input voltage signal. When SCR is much greater than 1, it can be considered that:
[0057] ;
[0058] Substitute V out and U Lr and U Lm into the formula I Lr and I Lm to obtain:
[0059] ;
[0060] ;
[0061] Wherein, is the voltage signal after the resonant inductor sampling voltage passes through RC integration, that is, the resonant voltage, is the voltage signal after the exciting inductor sampling voltage passes through RC integration, that is, the exciting voltage, C 1. R 1 and R 2 are respectively the capacitance value of the first capacitor, the resistance value of the first resistor, and the resistance value of the second resistor.
[0062] It can be known from the sampling requirements that the proportionality coefficients of these two voltage signals should be the same to ensure that accurate signal waveforms can be obtained by adding or subtracting the two. Therefore:
[0063] ;
[0064] Therefore, the relationship between the first resistor and the second resistor can be obtained as:
[0065] ;
[0066] Wherein, K is the ratio of the exciting inductor to the resonant inductor, from which the following can be further calculated:
[0067] .
[0068] The resonant voltage output by the first conversion circuit is input to the second conversion circuit, combined with the exciting voltage obtained by conversion in the second conversion circuit, and the resonant voltage after removing the exciting component is output.
[0069] In some embodiments, the circuit further includes a rectifying circuit, a filtering circuit, and a gain amplification circuit; the rectifying circuit rectifies the resonant voltage after removing the exciting component, the filtering circuit filters the rectified resonant voltage, and the gain amplification circuit amplifies the filtered resonant voltage, and the amplified signal is used for the feedback loop control of the internal current loop of the average current mode control.
[0070] The above circuit samples the resonant inductor current and the exciting inductor current, converts the sampled current into voltages with a phase difference of 90°, and the two voltages can be superimposed to obtain the resonant voltage after removing the exciting component for the feedback loop control of the internal current loop of the average current mode control, thereby directly eliminating the influence of the exciting component.
[0071] In order to verify the above method and circuit, the following simulations were performed:
[0072] Such asFigure 3 As shown, set X = 6, Y = 16, K = 7, build a simulation circuit of the sampling circuit of the LLC resonant converter. The SIMPLIS circuit simulation software is used to build this simulation circuit. From Figure 4 、 Figure 5 As shown, sample the voltage integration signal of the rectifier diode, after a 90° phase shift, and then superimpose the two signals together to obtain the final sinusoidal sampling signal V sense signal, as Figure 6 shown.
[0073] Such as Figure 4 、 Figure 7 shown, add a voltage-controlled voltage source between the V sense signal and the rectifier circuit, or a voltage follower circuit composed of an operational amplifier. The function of this part of the circuit is to utilize the characteristics of infinite input impedance and almost zero output impedance, so that the subsequent rectifier and filter circuit will not affect the parameter matching of the RC integration circuit. After passing through this circuit, it passes through a half-wave rectifier network. Among them, the driving signal period phase of the switching tube is the same as the input signal period phase of the transformer sampling integration. The driving signal can be output by the chip and sent to the driving chip to provide a driving signal for the rectifier network.
[0074] Such as Figure 4 、 Figure 8 shown, after passing through the rectifier circuit, input the obtained half-wave signal Vsr_half into the filter circuit to obtain the filtered signal. The gain of the operational amplifier can be adjusted according to the resistance value. In this paper, the design adopts an amplification factor of 15 to obtain the final average current sampling signal V ave .
[0075] Through the above simulation analysis, it can be seen that the above circuit can completely remove the exciting current component in the LLC resonant current, obtain a perfect sinusoidal resonant current sampling value, which is used for current loop compensation, making the loop parameters more accurate and optimizing the bandwidth and dynamic characteristics of the loop.
[0076] The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can still be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.
Claims
1. A circuit for sampling the resonant current of an LLC resonant converter, characterized in that, It includes a first sampler, a first conversion circuit, a second sampler, and a second conversion circuit; The first sampler samples the resonant inductor current in the LLC resonant converter; The first conversion circuit receives the resonant inductor current and converts the resonant inductor current into a resonant voltage; The second sampler samples the magnetizing inductor current in the LLC resonant converter; The second conversion circuit receives the magnetizing inductor current and converts the magnetizing inductor current into a magnetizing voltage; Receive the resonant voltage, superimpose the resonant voltage and the magnetizing voltage, and output the resonant voltage after removing the magnetizing component; wherein, the phase difference between the resonant voltage and the magnetizing voltage is 90°.
2. The circuit for sampling the resonant current of the sampling LLC resonant converter according to claim 1, wherein The first sampler is a first sampling coil, and the first sampling coil is coupled with the resonant inductor to form a transformer structure.
3. The circuit for sampling the resonant current of the sampling LLC resonant converter according to claim 2, wherein The first conversion circuit includes a first resistor and a first capacitor. One end of the first resistor is connected to the same-named end of the first sampling coil. The other end of the first sampling coil is grounded and connected to one end of the first capacitor. One end of the first capacitor is respectively connected to the other end of the first resistor and the second conversion circuit.
4. The circuit for sampling the resonant current of the sampling LLC resonant converter according to claim 1, characterized in that, The second sampler is a second sampling coil. The second sampling coil is arranged on the secondary side of the LLC resonant converter transformer and serves as the secondary coil of the secondary side. The second sampling coil samples the current of the primary coil in parallel with the magnetizing inductor, and controls the phase of the sampling current of the second sampling coil by adjusting the winding direction of the second sampling coil.
5. The circuit for sampling the resonant current of the sampling LLC resonant converter according to claim 4, wherein The second conversion circuit includes a second resistor. The same-named end of the second sampling coil is grounded. The other end of the second sampling coil is connected to one end of the second resistor. The other end of the second resistor is respectively connected to the first conversion circuit and outputs the resonant voltage after removing the magnetizing component.
6. The circuit for sampling the resonant current of the sampling LLC resonant converter according to claim 1, wherein It further includes a rectifying circuit, and the rectifying circuit rectifies the resonant voltage after removing the magnetizing component.
7. The circuit for sampling the resonant current of the sampling LLC resonant converter according to claim 6, wherein It further includes a filtering circuit, and the filtering circuit filters the rectified resonant voltage.
8. The circuit for sampling the resonant current of the sampling LLC resonant converter according to claim 7, characterized in that, It further includes a gain amplification circuit, and the gain amplification circuit amplifies the gain of the filtered resonant voltage.