Control of resonant circuit output characteristics and resonant circuit
[technical field]
The present invention relates to the resonant circuit control technology, specifically relate to a kind of control of resonant circuit output characteristics and resonant circuit.
[background technology]
At present, resonant circuit generally adopts the mode of variable frequency control (PFM), by the switching frequency of regulating circuit work, obtains the output voltage that needs.Fig. 1 is a typical half-bridge LLC series resonant circuit, and this circuit can realize that the no-voltage of main switch S1, S2 is open-minded, eliminates the reverse recovery of output rectifier diode D3, D4, improves the efficient of circuit.When this circuit was adopted PFM control, two complementary symmetries of switching tube S1, S2 drove the switch periods of each conducting 50%.The switching frequency of regulating S1, S2 obtains the output voltage of needs, and the relation of output voltage V o and switching frequency f as shown in Figure 2.
With reference to figure 2, general switching frequency can be chosen in M=Vo/Vin among Fig. 2 and obtain frequency band after the maximum, so the fundamental relation of frequency and voltage is: frequency raises, output voltage decline.But as can be seen from Figure 2, when frequency was elevated to a certain degree, it is very smooth that characteristic curve becomes, even the situation that also may occur going up not down, and makes frequency change become very weak to the regulating power of voltage.Obtain module for needs, influenced the performance of module to a great extent than wide output voltage range.
Be that example has illustrated the defective that the PFM control mode exists with half-bridge LLC series resonant circuit above, same, the phenomenon of full-bridge LLC series resonant circuit and half-bridge LLC series resonance phenomenon are identical.Theoretically, all there is similar problem in the resonant circuit of all PFM control.
[summary of the invention]
The objective of the invention is to remedy the above-mentioned defective that the PFM control mode exists, a kind of control of resonant circuit output characteristics and resonant circuit of expanding the resonant circuit output area is provided.
To achieve these goals, the technical solution used in the present invention is: a kind of control of resonant circuit output characteristics is the variation according to output loading, regulates the electric capacity and/or the inductance parameters of resonant circuit, makes the voltage output range of resonant circuit expand.
Described resonant circuit is preferably the LLC resonant circuit, adopts the effect of said method particularly remarkable in this kind circuit.
The adjusting of electric capacity and/or inductance parameters can be adopted such method: the branch road of regulating in parallel on the electric capacity of described resonant circuit and/or inductance, described adjusting branch road comprises the control capacittance/inductance of series connection and the gate-controlled switch of its break-make of control, obtain the output loading information of resonant circuit by feedback circuit, control circuit receives the break-make of gate-controlled switch that branch road is respectively regulated in this information and control, by inserting or disconnecting electric capacity and/or the inductance parameters that different adjusting branch roads is regulated resonant circuit.
For the LLC resonant circuit, the adjusting of inductance parameters also can be adopted such method: its resonant inductance adopts iron sial or iron powder as core material; Perhaps, its resonant inductance adopts ferrite as magnetic core, has non-homogeneous air gap on the described magnetic core, and the thickness of air gap each several part is variant.
The present invention also provides a kind of resonant circuit that adopts above-mentioned control method, comprise oscillation circuit, regulate branch road, control circuit and feedback circuit, be parallel with at least one on the electric capacity of described oscillation circuit and/or the inductance and regulate branch road, described adjusting branch road comprises the control capacittance/inductance of series connection and the gate-controlled switch of its break-make of control, the control end connection control circuit of described gate-controlled switch; The output of described oscillation circuit is through the feedback circuit connection control circuit, and described control circuit is controlled the break-make of the gate-controlled switch of respectively regulating branch road according to output loading.
And another kind of resonant circuit, described oscillation circuit adopts iron sial or iron powder as core material for series connection oscillation circuit, its resonant inductance.
Above-mentioned resonant circuit is preferably the LLC resonant circuit.
And another resonant circuit, comprising oscillation circuit, its resonant inductance adopts ferrite as magnetic core, and described air gap is heterogeneous, and the thickness of air gap each several part is variant.
Above-mentioned resonant circuit is preferably the LLC resonant circuit, and its oscillation circuit is the series connection oscillation circuit, and described air gap can be wedge shape or step.
Adopt technique scheme, beneficial technical effects of the present invention is:
1) according to the analysis that will in embodiment, be described in detail as can be known, the capacitive/inductive parameter of resonant circuit and the variation tendency of its output characteristic curve are closely related, therefore can come the capacitive/inductive parameter in the regulating circuit according to the loading condition of resonant circuit, make circuit working on the characteristic curve that is fit to.For example: at the seasonal circuit working of high pressure heavy duty in curve with high workload efficient, has the more curve of low-voltage output and work in during the low pressure underloading, just can take into account on both sides, remedy the deficiency of PFM control mode, enlarge the output regulating power of circuit effectively, and don't influence the performance of circuit in the core work district.
2) adopt structure of regulating branch road in parallel to control, accurately reliable; Adopt iron sial core or ferrocart core inductance and employing to have the FERRITE CORE inductance of non-homogeneous air gap, the sensibility reciprocal of the inductance of these types can reduce in adaptive increase with electric current, needn't carry out extra change to circuit and can realize the present invention, simple economy.
The present invention is described in further detail below in conjunction with the drawings and specific embodiments:
[description of drawings]
Fig. 1 is a kind of existing typical half-bridge LLC series resonant circuit schematic diagram.
Fig. 2 is the output characteristic curve figure of circuit among Fig. 1.
Fig. 3 is the asynchronous output characteristic curve comparison diagram of Lm among Fig. 1.
Fig. 4 is the asynchronous output characteristic curve comparison diagram of Ls among Fig. 1.
Fig. 5 (a) and (b) are respectively step air gap and inductance-current relationship figure thereof.
Fig. 6 is the ratio chart of the inductance of iron sial or ferrocart core material inductance value when its inductance value is with respect to 0 electric current under different current condition.
Fig. 7 (a) and (b) are respectively wedged air gap and inductance-current relationship figure thereof.
Fig. 8 is the asynchronous output characteristic curve comparison diagram of Cs among Fig. 1.
Fig. 9 is a kind of resonant circuit schematic diagram that adopts control mode of the present invention.
[embodiment]
Embodiment one, a kind of control of resonant circuit output characteristics are the variations according to output loading, regulate the electric capacity and/or the inductance parameters of resonant circuit, make the voltage output range of resonant circuit expand.
Be example with circuit among Fig. 1 still, when magnetizing inductance Lm changed, the variation of its output characteristic curve as shown in Figure 3.Among Fig. 3
" Lm is big " is that (as the 48V output system, the core work district is that 48V~58V) is the parameter value that optimization aim designs with efficient in the core work district; " Lm is little " is the parameter value that designs for purpose with wide output voltage range under the underloading condition.
Can see that by Fig. 3 the control characteristic curve can change along with the variation of magnetizing inductance Lm, if obtain lower output voltage, can reduce Lm.But reduce Lm merely, though the scope of the output voltage that can extend downwards can make converter can't realize optimal design, transducer effciency significantly descends and reaches 4%, and converter resonant tank device loss is multiplied, the heat radiation difficulty.Therefore regulate Lm according to the variation of output loading, circuit working is in the big curve of Lm when making the heavy duty of output high pressure, and works in little that curve of Lm during the low pressure underloading, just can both take into account on both sides, enlarge the regulating power of output effectively, and don't influence the performance in core work district.
Magnetizing inductance Lm is similar with changing, and other inductance parameters of change series resonant circuit are resonant inductance Ls for example, also can similarly be improved characteristic.Be example with circuit among Fig. 1 still, when magnetizing inductance Lm changed, the variation of its output characteristic curve as shown in Figure 4.Among Fig. 4
" Ls is little " is that (as the 48V output system, the core work district is that 48V~58V) is the parameter value that optimization aim designs with efficient in the core work district; " Ls is big " is the parameter value that designs for purpose with wide output voltage range under the underloading condition.
Can see that by Fig. 4 the control characteristic curve can change along with the variation of resonant inductance Ls, if obtain lower output voltage, can increase Ls.But increase Ls merely, though the scope of the output voltage that can extend downwards can make converter can't realize optimal design.Therefore regulate Ls according to the variation of output loading, circuit working is in the little curve of Ls when making the heavy duty of output high pressure, and works in big that curve of Ls during the low pressure underloading, just can both take into account on both sides, enlarge the regulating power of output effectively, and don't influence the performance in core work district.
The method that inductance can be changed has a lot, can adopt sudden change or gradual change dual mode:
(1) method of sudden change change inductance value has: give controlled inductance the branch road of regulating in parallel, under certain loading condition, open with this branch road incision circuit or from circuit interruption, and the regulating characteristics of change circuit, this structure will be described in detail in the following embodiments; Also can use the inductance of FERRITE CORE, air gap is split into step, shown in Fig. 5 (a), its sensibility reciprocal of the inductance of this structure and electric current have the relation that the sudden change of inductance value when electric current increases to certain value shown in Fig. 5 (b) reduces.
(2) method of gradual change change inductance value has: use magnetic materials such as iron sial, ferrocart core, these properties of materials make inductance to reduce along with the increase inductance value of electric current, as shown in Figure 6 (the current value unit that is marked on each curve is μ A); Also can use the inductance of FERRITE CORE, air gap is split into wedge shape, shown in Fig. 7 (a), the inductance value that its sensibility reciprocal of the inductance of this structure and electric current have shown in Fig. 7 (b) increases the relation that reduces with electric current.
In the engineering practice, Lm big → Lm hour, adopt the adaptive mode effect that gradually changes described in (2) better.
Equally, the capacitance kind parameter of change resonant circuit also has similar effect.Be example with circuit among Fig. 1 still, when capacitance parameter Cs changed, therefore the variation of its output characteristic curve can enlarge the dynamic output area of circuit by the control capacittance parameter as shown in Figure 8 equally.The concrete mode that changes electric capacity can adopt to methods such as controlled electric capacity adjusting in parallel branch roads.
Embodiment two, a kind of resonant circuit as shown in Figure 9, comprise series connection LLC oscillation circuit, regulate branch road, control circuit (not drawing in the drawings) and feedback circuit (not drawing in the drawings).Described series connection LLC oscillation circuit is made of Lm, Ls and Cs series connection, and two complementary symmetries of switching tube S1, S2 drive the switching frequency of control oscillation circuit; Regulate a route and regulate inductance L mt and controllable switch S 3 series connection formations, S3 is controlled conducting, controlled shutoff, and (S3 can be with two controlled conductings, controlled shutoff but can only to block the switching device of unidirectional current synthetic to pushing up can to block bidirectional current when turn-offing, as adopt two metal-oxide-semiconductors synthetic to pushing up), controllable switch S 3 is controlled its turn-on and turn-off by control circuit; Regulating branch road is connected in parallel on the Lm; The output of oscillation circuit is through the feedback circuit connection control circuit, and control circuit is according to the break-make of output loading control controllable switch S 3.
The concrete course of work: feedback circuit sends the load information of output to control circuit, and when the heavy duty of circuit output high pressure, control circuit disconnects S3, makes the curve Lm of circuit working in Fig. 3 big; When the low pressure underloading, control circuit is connected S3, makes the curve Lm of circuit working in Fig. 3 little, has both enlarged the output regulating power of entire circuit effectively, does not influence the performance in core work district again.
The structure of regulating " regulating element+gate-controlled switch " of branch road among Fig. 6 can also be applied in other various resonant circuits, be not limited to above-mentioned form, the object of its adjusting can be that the inductance in the loop also can be an electric capacity, select corresponding regulating element to get final product at controlled plant, even can be that electric capacity and inductance are equipped with the adjusting branch road simultaneously, each is conditioned element and also is not only limited to adjusting branch road of outfit, and precision and actual needs that its number can be regulated are as required determined.