CN103414346A - Novel fixed frequency and variable frequency mixed control circuit of LLC resonant converter - Google Patents
Novel fixed frequency and variable frequency mixed control circuit of LLC resonant converter Download PDFInfo
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- CN103414346A CN103414346A CN2013102905742A CN201310290574A CN103414346A CN 103414346 A CN103414346 A CN 103414346A CN 2013102905742 A CN2013102905742 A CN 2013102905742A CN 201310290574 A CN201310290574 A CN 201310290574A CN 103414346 A CN103414346 A CN 103414346A
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Abstract
The invention provides a novel fixed frequency and variable frequency mixed control circuit of an LLC resonant converter. The novel fixed frequency and variable frequency mixed control technology is employed, a fixed frequency and variable frequency mixed controller is formed by an operational amplifier and a transistor, by using the variable resistance characteristic between the emitter and collector of the transistor, the frequency change of a UCC3895 control circuit is realized, and thus the fixed frequency and variable frequency mixed controlling of the whole circuit is realized. The circuit structure is simple, the cost is low, the control is convenient, and the circuit has an important promotion value for the LLC resonant converter. The circuit can be used for replacing the existing LLC resonant converter circuit.
Description
Technical field
The present invention relates to a kind of LLC controlled resonant converter control circuit, relate more specifically to a kind of be applied to controlled resonant converter determine frequency frequency conversion mixing control circuit.
Background technology
The beginning of this century, the LLC controlled resonant converter starts in the aerospace field application, and the traditional control mode of LLC controlled resonant converter has variable frequency control and fixed-frequency control.The advantage of variable frequency control is that efficiency is higher, but aerospace field direct voltage wide input voltage range, and in such cases, switching frequency wider range, make the magnetic element design difficulty large, and volume and weight increases, and is not suitable for aerospace field.Fixed-frequency control magnetic element design difficulty is little, but when input voltage range was wider, the transformer primary secondary turn ratio will reduce, make the rectifier diode voltage stress increase, product efficiency is low, in order to ensure heat radiation, whole small product size and weight increase, and are not suitable for equally aerospace field.
Summary of the invention
For the deficiencies in the prior art, the present invention is applied to the frequency conversion control circuit of controlled resonant converter, what disclose a kind of LLC Resonant Converter determines frequency frequency conversion mixing control circuit, aim to provide a kind of control strategy new under wide input voltage range that solves: when input voltage is low, adopt variable frequency control, the full duty ratio work of converter, carry out regulation output voltage by changing switching frequency; When input voltage is higher, adopt fixed-frequency control, converter is operated in the highest frequency set, and controls output voltage by regulating phase shifting angle.
The present invention adopts following technical scheme:
In the present invention, LLC Resonant Converter determine frequency frequency conversion mixing control circuit, adopt the subtracter and the triode that by operational amplifier, are formed to form fixed frequency frequency conversion mixed-control mode.
In existing fixed-frequency control circuit, the 1st pin EAN of UCC3895 control chip U1 is connected with the 2nd pin EAOUT, and the 3rd pin RAMP and the 7th pin CT meet capacitor C t, and the 8th pin RT connecting resistance Rt forms the Rt loop; Reference voltage Vref 1 connects operational amplifier N1 anode, feedback voltage V o connects operational amplifier N1 negative terminal after resistance R _ f 1 and resistance R _ f 2 dividing potential drops, after resistance R 1 and capacitor C 1 series connection, be connected on negative terminal and the output of operational amplifier N1, with the 20th pin EAP of UCC3895 control chip, be connected after the output parallel voltage-stabilizing diode D1 of operational amplifier N1.
On existing fixed-frequency control circuit base, the present invention is after the output of operational amplifier N1 and between the 8th pin RT of UCC3895 control chip, and access forms the fixed mixture control of frequency conversion frequently by operational amplifier N2 and triode.Corresponding having increased in circuit: operational amplifier N2, triode Q1, voltage stabilizing didoe D2, resistance R 2 and R3, reference voltage Vref 2; Physical circuit is: reference voltage Vref 2 connects operational amplifier N2 anode, after the output parallel voltage-stabilizing diode D2 of operational amplifier N2, be connected with the base stage of triode Q1, the collector electrode of triode Q1 connects the 8th pin RT of UCC3895 control chip, in parallel with voltage stabilizing didoe D2 after the emitter series resistance Rt of triode Q1, parallel resistance R3 between the negative terminal of operational amplifier N2 and output, the output of concatenation operation amplifier N1 after the negative terminal series resistance R2 of operational amplifier N2.
The good effect that the present invention can obtain:
In the present invention, when input voltage is low, adopt variable frequency control, the full duty ratio work of converter, carry out regulation output voltage by changing switching frequency; When input voltage is higher, adopt fixed-frequency control, converter is operated in the highest frequency set, and controls output voltage by regulating phase shifting angle.
Because having adopted novel fixed frequency conversion frequently, the present invention mixes control technology, the subtracter and the triode that operational amplifier, consist of form the fixed mixing of frequency conversion frequently control circuit, utilize the character of changing of resistence between transistor emitter and collector electrode, realized the frequency change of UCC3895 control circuit, thereby realized the mixing of the frequency conversion frequently control surely of whole circuit, be beneficial to the design of whole circuit, can reduce the dependence to heat abstractor, than existing fixed-frequency control circuit or frequency conversion control circuit product, the element that the present invention uses is few, circuit structure is simple, overall weight and the volume of product can be reduced greatly, and with low cost, can extensive use in airplane power source, simultaneously can expand to oil, in the high industry of the reliability requirements such as communication, significant cost advantage is arranged.
The accompanying drawing explanation
Fig. 1 is the existing fixed-frequency control circuit of application UCC3895
Fig. 2 is control circuit line graph of the present invention
In figure, each main symbol description: Vo is feedback voltage, Vref1, Vref2 are reference voltage, U1 is the UCC3895 control chip, D1, D2 are voltage stabilizing didoe, and Q1 is triode, and R1, R2, R3, Rf1, Rf2, Rt are resistance, C1, Ct are electric capacity, N1, N2 are operational amplifier, and VFB means operational amplifier N1 output end voltage, and VC means the output end voltage of operational amplifier N2.
Embodiment
Below, by reference to the accompanying drawings and specific embodiment, invention is further described.
Embodiment 1
As Fig. 1, traditional fixed-frequency control circuit of existing application UCC3895,
Physical circuit is: the 1st pin EAN of UCC3895 control chip U1 is connected with the 2nd pin EAOUT, and external series capacitance Ct after the 3rd pin RAMP and the 7th pin CT short circuit, the 8th pin RT connecting resistance Rt over the ground form the Rt loop.Feedback voltage V o connects operational amplifier N1 negative terminal after resistance R _ f 1 and resistance R _ f 2 dividing potential drops, reference voltage Vref 1 connects operational amplifier N1 anode, after resistance R 1 and capacitor C 1 series connection, be connected in parallel on operational amplifier N1 negative terminal and output, operational amplifier N1 output meets over the ground voltage stabilizing didoe D1 and with control chip U1 the 20th pin EAP, is connected simultaneously.
The 7th, 8 pins of UCC3895 control chip U1 form RC vibration frequently surely.Built-in error amplifier is connected into the form of emitter follower, and the 3rd pin RAMP of UCC3895 control chip U1 connects oscillator output Ct pin, is operated in voltage mode control.Operational amplifier N1 output end voltage is handed over to cut as the sawtooth waveforms of the 3rd pin RAMP generation of modulating wave and UCC3895 control chip U1 and is produced a duty ratio.Phase shifting control output voltage self-regulating process is as follows: and feedback voltage V o increase → operational amplifier N1 negative terminal input voltage Vf reduces → operational amplifier N1 output voltage V FB reduces → control chip U1 duty ratio reduces → and feedback voltage V o reduces.
As Fig. 2, control circuit line graph of the present invention, on existing fixed-frequency control circuit base, triode Q1 connects (1) in the Rt loop; (2) after operational amplifier N1 output, increase by an operational amplifier and form subtracter.
Physical circuit is: reference voltage Vref 2 connects operational amplifier N2 anode, after the output parallel voltage-stabilizing diode D2 of operational amplifier N2, be connected with the base stage of triode Q1, the collector electrode of triode Q1 connects the 8th pin RT of UCC3895 control chip, in parallel with voltage stabilizing didoe D2 after the emitter series resistance Rt of triode Q1, parallel resistance R3 between the negative terminal of operational amplifier N2 and output VC, the output of concatenation operation amplifier N1 after the negative terminal series resistance R2 of operational amplifier N2.
As can be known by the UCC3895 operation principle, the 7th pin CT of UCC3895 control chip U1 and the external timing capacitor Ct of the 8th pin RT and resistance R t, oscillator passes through capacitor charge and discharge work, and charging current is fixed and is directly proportional to the electric current that flows through resistance R t.At resistance R t loop series connection triode Q1, can control VC with the output of operational amplifier N2 and control the Rt both end voltage, thus the control switch frequency.The output end voltage VC of operational amplifier N2 is higher, and the electric current that flows through Rt is larger, and capacitor charging is faster, and switching frequency is larger, and the output end voltage VC of switching frequency and operational amplifier N2 is in direct ratio.Single output voltage reduces with the rising of frequency, therefore, in figure, increases the subtracter that operational amplifier N2 forms, and makes system be in the negative feedback state.The output voltage self-regulating process is as follows: and feedback voltage V o increase → operational amplifier N1 negative terminal input voltage Vf increase → operational amplifier N1 output voltage V FB reduces → and the output end voltage VC increase → switching frequency increase → feedback voltage V o of operational amplifier N2 reduces.
Two kinds of patterns of converter can not be worked simultaneously, and the transient process between two kinds of patterns is as follows:
(1) fixed pattern frequently is to the variable mode transient process: in initial condition, converter is operated in to be determined under the frequency pattern, and switching frequency is maximum setpoint frequency, the output end voltage VC of operational amplifier N2 by the voltage-stabiliser tube clamper under diode breakdown voltage; Along with the increase of operational amplifier N1 output end voltage VFB, the output end voltage VC of operational amplifier N2 reduces gradually until be less than diode breakdown voltage.Now, converter enters variable mode by determining the frequency pattern.
(2) variable mode is to determining frequency mode transition process: in initial condition, converter is operated under variable mode, and now the converter control circuit duty ratio is 1.Along with the rising of the output end voltage VC of operational amplifier N2, operational amplifier N1 output VFB reduces gradually until be not more than the crest voltage of CT oscillator.Now converter exits variable mode, enters and determines the frequency mode of operation.
The foregoing is only better possible embodiments of the present invention, not thereby limit to the scope of the claims of the present invention, therefore the equivalent structure that every utilization specification of the present invention and accompanying drawing content are done changes, all be contained in protection scope of the present invention.
Claims (2)
1. a LLC Resonant Converter determines frequency frequency conversion mixing control circuit, comprise LLC resonant transformation control circuit, UCC3895 control chip the 1st pin EAN is connected with the 2nd pin EAOUT, and the 3rd pin RAMP and the 7th pin CT connect electric capacity (Ct), the 8th pin RT connecting resistance (Rt); Reference voltage (Vref1) connects operational amplifier (N1) anode, feedback voltage (Vo) connects operational amplifier (N1) negative terminal after resistance (Rf1) and resistance (Rf2) dividing potential drop, after resistance (R1) and electric capacity (C1) series connection, be connected on negative terminal and the output of operational amplifier (N1), with the 20th pin EAP of UCC3895 control chip, be connected after the output parallel voltage-stabilizing diode (D1) of operational amplifier (N1); It is characterized in that, after the output of operational amplifier (N1) and between the 8th pin RT of UCC3895 control chip, access is determined frequency frequency conversion mixture control by what operational amplifier (N2) and triode (Q1) formed.
According to claim 1 LLC Resonant Converter determine frequency frequency conversion mixing control circuit, it is characterized in that, the described fixed mixture control of frequency conversion frequently physical circuit is: reference voltage (Vref2) connects operational amplifier (N2) anode, after the output parallel voltage-stabilizing diode (D2) of operational amplifier (N2), be connected with the base stage of triode (Q1), the collector electrode of triode (Q1) connects the 8th pin RT of UCC3895 control chip, in parallel with voltage stabilizing didoe (D2) after the emitter series resistance (Rt) of triode (Q1), parallel resistance (R3) between the negative terminal of operational amplifier (N2) and output, the output of concatenation operation amplifier (N1) after the negative terminal series resistance (R2) of operational amplifier (N2).
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| Application Number | Priority Date | Filing Date | Title |
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| CN2013102905742A CN103414346A (en) | 2013-07-11 | 2013-07-11 | Novel fixed frequency and variable frequency mixed control circuit of LLC resonant converter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2013102905742A CN103414346A (en) | 2013-07-11 | 2013-07-11 | Novel fixed frequency and variable frequency mixed control circuit of LLC resonant converter |
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| CN103414346A true CN103414346A (en) | 2013-11-27 |
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| CN2013102905742A Pending CN103414346A (en) | 2013-07-11 | 2013-07-11 | Novel fixed frequency and variable frequency mixed control circuit of LLC resonant converter |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101800475A (en) * | 2010-03-22 | 2010-08-11 | 艾默生网络能源有限公司 | Link logic control (LLC) resonant converter control method and control device |
| CN102857103A (en) * | 2011-06-30 | 2013-01-02 | 艾默生网络能源系统北美公司 | Three-level LLC (Logical Link Control) direct-current converter and control method thereof |
-
2013
- 2013-07-11 CN CN2013102905742A patent/CN103414346A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101800475A (en) * | 2010-03-22 | 2010-08-11 | 艾默生网络能源有限公司 | Link logic control (LLC) resonant converter control method and control device |
| CN102857103A (en) * | 2011-06-30 | 2013-01-02 | 艾默生网络能源系统北美公司 | Three-level LLC (Logical Link Control) direct-current converter and control method thereof |
Non-Patent Citations (1)
| Title |
|---|
| 李菊等: "全桥LLC谐振变换器的混合式控制策略", 《电工技术学报》 * |
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