CN115733336A - Method for designing critical value of input capacitance of Buck converter of wireless charging system - Google Patents
Method for designing critical value of input capacitance of Buck converter of wireless charging system Download PDFInfo
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- CN115733336A CN115733336A CN202211464094.9A CN202211464094A CN115733336A CN 115733336 A CN115733336 A CN 115733336A CN 202211464094 A CN202211464094 A CN 202211464094A CN 115733336 A CN115733336 A CN 115733336A
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Abstract
The invention provides a design method of a Buck converter input capacitance critical value of a wireless charging system. According to the method, the capacitance critical values in different time periods are determined by switching on and off the switching tube S in different time periods, so that the minimum critical capacitance value is obtained according to the capacitance critical values in different time periods. The method can inhibit the adverse effect caused by the existence of the right half plane zero point, realizes the improvement of the overall performance, and has important significance for the reasonable design of the wireless charging system.
Description
Technical Field
The invention belongs to the technical field of parameter optimization of wireless power transmission systems, and particularly relates to a design method of a Buck converter input capacitance critical value of a wireless charging system.
Background
A magnetic coupling resonant wireless power transmission system in the prior art is shown in fig. 1, and the magnetic coupling resonant wireless power transmission system mainly comprises a transmitting end inversion source, a primary coil, a secondary coil, a resonant network, a receiving end converter and a load. The receiving end converter plays an important role in adjusting output voltage and maintaining system output stability. When the front-stage resonant network has the property of a constant current source, a right half-plane zero point appears in a control-output transfer function of the Buck converter at the receiving end, and the steady-state and dynamic performances of the wireless charging system are deteriorated under the influence of the right half-plane zero point. The invention provides an input capacitance parameter design method, so that adverse effects caused by the existence of a right half-plane zero point are inhibited, the overall performance is improved, and the method is of great significance to the reasonable design of a wireless charging system.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a method for designing a critical value of an input capacitor of a Buck converter of a wireless charging system.
The invention is realized by the following technical scheme, and provides a method for designing a critical value of an input capacitance of a Buck converter of a wireless charging system, which specifically comprises the following steps:
performing signal modeling on the wireless charging system to obtain a control-output transfer function:
in the formula, D is the duty ratio of Buck;
from (1), there exists a right half-plane zero point in the transfer function, whose position is:
determining the input capacitance C of the DC side dc The minimum critical capacitance value ofThe method for determining the value specifically comprises the following steps:
the sinusoidal current at the receiving end is assumed to be:
i Ls (t)＝I Ls sin(ωt) (3)
where ω is the resonance angular frequency, ω =2 π f; the rectified current is then:
i r (t)＝I Ls |sin(ωt)| (4)
the time interval of the switch tube S is 0-DT b Switching on, rectifying the current i r (t) and an input capacitance C dc Jointly charging the inductors; c dc The charge quantity is continuously reduced, the voltage is reduced, and the inductive current is increased; at this stage, C dc Average value of discharge current I dc1 Expressed as:
in the formula T b For switching period, T, of Buck circuit b ＝1/f b (ii) a Switching frequency of f b (ii) a The circuit operates in CCM, L is sufficiently large that the inductor current is considered constant during this period, i.e. I L ＝I o ＝U/R；
When i is r (t) when it is in the minimum value interval, C dc The average discharge current is maximum, and the following conditions are met:
capacitance charge equation Q = C · Δ U = i · T, at which stage the minimum capacitance value C dc-min1 The requirements are as follows:
when the capacitance is a critical value:
simultaneous (6) - (8) to obtain:
switching tube S in time interval DT b ～T b Turn off, rectify current i r (t) supplying a capacitance C dc Charging, C dc The charge is continuously accumulated, the voltage rises, the inductor L freewheels along the diode D, the current decreases, and at this stage C dc Average value of charging current I dc2 Expressed as:
when i is r (t) when it is in the maximum value range, C dc The average charging current is maximum and meets the following requirements:
at this stage, the minimum capacitance C dc-min2 The requirements are as follows:
combined (11), (12) to obtain:
from (9) and (13), the minimum critical capacitance value C is obtained dc-min ：
C dc-min ＝max{C dc-min1 ,C dc-min2 } (14)。
Furthermore, the Buck converter of the wireless charging system consists of a switching tube S, a diode D, an inductor L and an output filter capacitor C o And (4) forming.
Further, the receiving end circuit of the wireless charging system comprises L s And C s Formed series resonant circuit, D 1 -D 4 Formed uncontrolled rectifier bridge and DC link capacitor C dc A Buck converter and a load R.
The beneficial effects of the invention are as follows:
the invention provides a design method of a critical value of an input capacitor of a Buck converter of a wireless charging system, which can inhibit adverse effects caused by the existence of a right half-plane zero point, realize the improvement of overall performance and has important significance for the reasonable design of the wireless charging system.
Drawings
Fig. 1 is a block diagram of a magnetic coupling resonant wireless power transmission system in the prior art;
fig. 2 is an equivalent circuit diagram of a receiving end of a wireless charging system with a constant current input characteristic;
FIG. 3 is a timing diagram of operation;
FIG. 4 is a graph of simulation verification results;
FIG. 5 is a diagram showing a comparison of the system waveforms when the normal capacity value and the critical capacity value are obtained, wherein (a) the capacity value is normal C dc =3 μ F, (b) volume critical C dc ＝1.8μF。
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention adopts a parameter design method to design the input capacitance parameters of the BUCK converter at the receiving end. The method for determining the optimal value of the capacitor is given by taking the system circuit diagram given in fig. 2 as an example. To suppress the adverse effects of the right half-plane zero point.
FIG. 2 is a diagram of an exemplary series compensated wireless charging system receive side circuit, where L s And C s Form a series connectionA resonant circuit having a resonant frequency f s ；D 1 -D 4 Forming an uncontrolled rectifier bridge; c dc A dc link capacitor (also referred to as a Buck converter input capacitor); switch tube S, diode D, inductor L and output filter capacitor C o Forming a Buck converter with a switching frequency f b (ii) a R is a load. In the figure i Ls ，i dc ，i L Respectively, the input current of the rectifier bridge flows through the input capacitor C dc Current and inductor current. u. of dc Is C dc The voltage across the terminals.
The invention provides a method for designing a critical value of an input capacitance of a Buck converter of a wireless charging system, which specifically comprises the following steps:
performing signal modeling on the wireless charging system to obtain a control-output transfer function:
in the formula, D is the duty ratio of Buck;
from (1), there exists a right half-plane zero point in the transfer function, whose position is:
in a visible, C dc The smaller the position of the right half-plane zero point is located further away from the imaginary axis, the less it will have an adverse effect on the system. However, the DC side input capacitance C dc The functions of circuit follow current and providing buffer energy need to be satisfied, the capacity value cannot be too small, and a minimum critical value exists. Determining the input capacitance C of the DC side dc The method for determining the minimum critical capacitance value specifically includes:
the sinusoidal current at the receiving end is assumed to be:
i Ls (t)＝I Ls sin(ωt) (3)
where ω is the resonance angular frequency, ω =2 π f; the rectified current is then:
i r (t)＝I Ls |sin(ωt)| (4)
the switch tube S is between 0 and DT b Opening, rectifying the current i r (t) and an input capacitance C dc Jointly charging the inductors; c dc The charge quantity is continuously reduced, the voltage is reduced, and the inductive current is increased; as shown in fig. 3. At this stage, C dc Average value of discharge current I dc1 Expressed as:
in the formula T b For switching periods of Buck circuits, T b ＝1/f b (ii) a Switching frequency of f b (ii) a The circuit operates in CCM, L is sufficiently large that the inductor current is considered constant during this period, i.e. I L ＝I o ＝U/R；
When i is r (t) in the minimum value interval, as shown in FIG. 3, C dc The average discharge current is maximum, and the following conditions are met:
capacitance charge equation Q = C · Δ U = i · T, at which stage the minimum capacitance value C dc-min1 The requirements are as follows:
when the capacitance is a critical value:
simultaneous (6) to (8):
switch tube S is inSection DT b ～T b Turn off, rectify current i r (t) supplying a capacitance C dc Charging, C dc The amount of charge accumulates and the voltage rises and the inductor L freewheels along the diode D and the current decreases as shown in fig. 3. At this stage, C dc Average value of charging current I dc2 Expressed as:
when i is r (t) is in the maximum value range, as shown in FIG. 3. C dc The average charging current is maximum and meets the following requirements:
at this stage, the minimum capacitance C dc-min2 The requirements are as follows:
combined (11), (12) to obtain:
from (9) and (13), the minimum critical capacitance value C is obtained dc-min ：
C dc-min ＝max{C dc-min1 ,C dc-min2 } (14)。
The effect of the method is verified in a simulation mode, as shown in fig. 4, when the given control quantity changes (from 16V to 14V), the adjusting speed is gradually increased along with the gradual reduction of the capacitance value of the capacitor, the negative overshoot is also gradually reduced, and the performance of the system is improved. When the input DC side voltage is 35V, f b At =40kHz, C dc-min At 1.8. Mu.F. As shown in FIG. 5, when C dc =3 μ F: normal capacity value, small voltage fluctuation and energy requirementAnd (4) buffering requirements. C dc =1.8 μ F: the capacitance value is critical, and the capacitance just can meet the energy buffering requirement.
The method for designing the critical value of the input capacitance of the Buck converter of the wireless charging system, which is provided by the invention, is described in detail above, and the principle and the implementation mode of the invention are explained in the text by applying specific examples, and the description of the above examples is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (3)
1. The method for designing the critical value of the input capacitance of the Buck converter of the wireless charging system is characterized by comprising the following steps: the method specifically comprises the following steps:
performing signal modeling on the wireless charging system to obtain a control-output transfer function:
in the formula, D is the duty ratio of Buck;
from (1), there exists a right half-plane zero point in the transfer function, whose position is:
determining the input capacitance C of the DC side dc The method for determining the minimum critical capacitance value specifically includes:
the sinusoidal current at the receiving end is assumed to be:
i Ls (t)＝I Ls sin(ωt) (3)
where ω is the resonance angular frequency, ω =2 π f; the rectified current is then:
i r (t)＝I Ls |sin(ωt)| (4)
the time interval of the switch tube S is 0-DT b Switching on, rectifying the current i r (t) and an input capacitance C dc Jointly charging the inductors; c dc The charge quantity is continuously reduced, the voltage is reduced, and the inductive current is increased; at this stage, C dc Average value of discharge current I dc1 Expressed as:
in the formula T b For switching periods of Buck circuits, T b ＝1/f b (ii) a Switching frequency of f b (ii) a The circuit operates in CCM, L is sufficiently large that the inductor current is considered constant during this period, i.e. I L ＝I o ＝U/R；
When i is r (t) when it is in the minimum value interval, C dc The average discharge current is maximum, and the following conditions are met:
capacitance charge equation Q = C · Δ U = i · T, at which stage the minimum capacitance value C dc-min1 The requirements are as follows:
when the capacitance is a critical value:
simultaneous (6) to (8):
switch tube S in time interval DT b ～T b Turn off, rectify current i r (t) supplying a capacitance C dc Charging, C dc The charge is continuously accumulated, the voltage rises, the inductor L freewheels along the diode D, the current decreases, and at this stage C dc Average value of charging current I dc2 Expressed as:
when i is r (t) when it is in the maximum value range, C dc The average charging current is maximum and meets the following requirements:
at this stage, the minimum capacitance C dc-min2 The requirements are as follows:
the following components are obtained in a combined manner (11) and (12):
from (9) and (13), the minimum critical capacitance value C is obtained dc-min ：
C dc-min ＝max{C dc-min1 ,C dc-min2 } (14)。
2. The method of claim 1, wherein the Buck converter of the wireless charging system is composed of a switch tube S, a diode D, an inductor L and an output filter capacitor C o And (4) forming.
3. The method of claim 1, wherein said absence isThe receiving end circuit of the line charging system comprises L s And C s Formed series resonant circuit, D 1 -D 4 Formed uncontrolled rectifier bridge and DC link capacitor C dc A Buck converter and a load R.
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| RU2007100796A (en) * | 2007-01-09 | 2008-07-20 | Государственное образовательное учреждение высшего профессионального образования Воронежское высшее военное авиационное инженерное училище (военный институт) (RU) | ACTIVE FOUR FOUR FOUR ORDER WITH ZERO TRANSMISSION |
| CN103401416A (en) * | 2013-07-31 | 2013-11-20 | 西安交通大学 | Main circuit structure eliminating right half plane zeros of boost DC-DC (Direct Current - Direct Current) converter and method for determining parameters thereof |
| CN103856046A (en) * | 2012-11-30 | 2014-06-11 | 杰力科技股份有限公司 | Voltage-reducing type voltage conversion device |
| CN104753346A (en) * | 2013-12-30 | 2015-07-01 | 展讯通信（上海）有限公司 | Technology for improving efficiency of BUCK circuit |
| US20200091821A1 (en) * | 2018-09-17 | 2020-03-19 | Hamilton Sundstrand Corporation | Controller for buck dc/dc converter with effective decoupling |
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- 2022-11-22 CN CN202211464094.9A patent/CN115733336B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| RU2007100796A (en) * | 2007-01-09 | 2008-07-20 | Государственное образовательное учреждение высшего профессионального образования Воронежское высшее военное авиационное инженерное училище (военный институт) (RU) | ACTIVE FOUR FOUR FOUR ORDER WITH ZERO TRANSMISSION |
| CN103856046A (en) * | 2012-11-30 | 2014-06-11 | 杰力科技股份有限公司 | Voltage-reducing type voltage conversion device |
| CN103401416A (en) * | 2013-07-31 | 2013-11-20 | 西安交通大学 | Main circuit structure eliminating right half plane zeros of boost DC-DC (Direct Current - Direct Current) converter and method for determining parameters thereof |
| CN104753346A (en) * | 2013-12-30 | 2015-07-01 | 展讯通信（上海）有限公司 | Technology for improving efficiency of BUCK circuit |
| US20200091821A1 (en) * | 2018-09-17 | 2020-03-19 | Hamilton Sundstrand Corporation | Controller for buck dc/dc converter with effective decoupling |
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