CN115242095A - Bidirectional synchronous rectification control device and method for isolated CLLC converter - Google Patents
Bidirectional synchronous rectification control device and method for isolated CLLC converter Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/01—Resonant DC/DC converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33573—Full-bridge at primary side of an isolation transformer
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33592—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
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Abstract
The invention discloses a bidirectional synchronous rectification control device and method for an isolated CLLC converter, and belongs to the technical field of power electronic converters. The control method is applied to a bidirectional isolation type CLLC converter, and the synchronous rectification conduction time containing the switching frequency and the output equivalent load is calculated in a controller unit by establishing a frequency domain impedance model of the CLLC converter. The on time of the primary side switch tube and the secondary side switch tube of the CLLC converter is the same, and the off time of the synchronous rectifier tube is determined by the calculated synchronous rectifier on time and is equal to the on time plus the calculated on time. The circuit control unit comprises a sampling circuit, a controller unit and an optical coupling isolation driving circuit. The control method realizes accurate control of synchronous rectification time, reduces rectification conduction loss of the circuit, and enables the circuit to have the advantages of high efficiency and high power density.
Description
Technical Field
The invention belongs to the technical field of power electronic converters, and particularly relates to a bidirectional synchronous rectification control device and method for an isolated CLLC converter.
Background
The CLLC resonant converter has a symmetrical structure and a wide ZVS range, so that the CLLC resonant converter is a topological structure which is very suitable for bidirectional application, such as bidirectional electric vehicle chargers or bidirectional energy storage systems. Synchronous rectification is also important for improving efficiency, and the synchronous rectification technology adopts MOSFET to replace diode rectification and has corresponding driving signals. Therefore, there is a need to further improve the accuracy of the synchronous rectified drive signal to optimize CLLC efficiency over a wide load range. In general, CLLC synchronous rectification control can be divided into two types: high frequency signal sensing methods and model-based methods.
Conventional CLLC synchronous rectification schemes typically employ a detection circuit to detect the high frequency voltage or current, or calculate the synchronous rectification duty cycle considering only the switching frequency in the microcontroller unit. Due to the influence of high voltage change rate and large-amplitude change duty ratio, the high voltage change rate and the large-amplitude change duty ratio are difficult to be directly applied in application, and the function of high-voltage synchronous rectification is difficult to realize.
Disclosure of Invention
Aiming at the defects and shortcomings in the prior art, the invention provides a bidirectional synchronous rectification control device and method for an isolated CLLC converter, which can reduce the conduction loss of a synchronous rectifier diode to improve the efficiency of the converter, have high immunity, and can be applied to high-voltage and high-frequency occasions to realize bidirectional energy flow.
In order to solve the technical problem, the invention adopts the following specific technical scheme:
an isolated CLLC converter bidirectional synchronous rectification control device comprises a CLLC converter, a sampling circuit, a controller unit and an optical coupling isolation driving circuit, wherein the CLLC converter comprises a primary side full-bridge conversion circuit, a resonance circuit and a secondary side full-bridge conversion circuit; the primary side full-bridge conversion circuit comprises a first switch tube Q 1 A second switch tube Q 2 A third switching tube Q 3 Fourth switch tube Q 4 (ii) a The resonant circuit comprises a first resonant inductor Lr 1 A second resonant inductor Lr 2 First resonant capacitor Cr 1 A second resonant capacitor Cr 2 And a transformer having an exciting inductance L integrated therein m Said exciting inductance L m The transformer is arranged on the primary side of the transformer; the first switch tube Q 1 And a second switching tube Q 2 And the first resonant inductor Lr 1 Is connected to the third switching tube Q 3 And a fourth switching tube Q 4 The midpoint and the first resonant capacitor Cr 1 Is connected to the first resonant inductor Lr 1 And a first resonant capacitor Cr 1 The other end of the magnetic field is respectively connected with the excitation inductor L m Are connected at both ends; the secondary side full-bridge conversion circuit comprises a fifth switching tube S 1 The sixth switching tube S 2 Seventh switching tube S 3 The eighth switching tube S 4 The fifth switch tube S 1 And a sixth switching tube S 2 And the second resonant inductor Lr 2 Is connected to one end of a seventh switching tube S 3 And an eighth switching tube S 4 And the second resonant capacitor Cr 2 One end is connected; second resonant inductor Lr 2 And a second resonant capacitor Cr 2 The other ends of the two ends are respectively connected with the secondary side of the transformer.
Further, the first to fourth switching tubes Q 1 ～Q 4 Fifth-eighth switching tube S 1 ～S 4 Are both MOSFETs.
The invention also provides a bidirectional synchronous rectification control method of the isolated CLLC converter, which is based on the frequency domain model of the CLLC converter, considers the change of the switching frequency and the output load, and calculates the change of the switching frequency and the output load in the controlSynchronous rectification conduction time; the CLLC converter is provided with a first switching tube Q of the primary side and the secondary side of the converter in a forward operation mode and a reverse operation mode 1 A second switch tube Q 2 A third switching tube Q 3 Fourth switch tube Q 4、 The fifth switch tube S 1 The sixth switching tube S 2 Seventh switching tube S 3 The eighth switching tube S 4 The turn-on time of the synchronous rectification switch is consistent, and the turn-off time is respectively equal to the turn-on time plus the synchronous rectification turn-on time calculated under different modes.
Further, when the CLLC converter works in the forward direction, the method comprises the following steps:
(1) Collecting a forward output direct current voltage signal, and inputting the signal into a controller unit through a sampling circuit; the signal is compared with the reference output voltage in the controller unit to obtain an error signal, and the error signal is calculated by the proportional-integral controller unit to obtain a pulse frequency modulation signal; a pulse frequency modulation signal is input into the optical coupling isolation driving circuit to obtain a primary side first-fourth switching tube Q in the primary side full-bridge conversion circuit 1 ～Q 4 To realize a forward output of a direct current voltage v o Control and adjustment of the operating frequency;
(2) Calculating and outputting an equivalent resistance load by using the output voltage and output current signals obtained by sampling;
calculating the synchronous rectification conduction time of forward operation according to the output equivalent resistance load and the switching frequency;
(3) Fifth-eighth switching tubes S as synchronous rectifiers 1 ～S 4 First-fourth switching tube Q at turn-on time and on primary side 1 ～Q 4 Identical, fifth-eighth switching tube S 1 ～S 4 The turn-off time is determined by the calculated synchronous rectification turn-on time of the forward operation.
Further, when the CLLC converter runs reversely, the method comprises the following steps:
(1) Closed-loop control is adopted for the CLLC converter which runs reversely, reverse output voltage signals are collected and input into the controller unit through the sampling circuit; the signal and controller unitComparing the internal reference output voltage to obtain an error signal, and calculating the error signal by a proportional-integral controller unit to obtain a pulse frequency modulation signal; a pulse frequency modulation signal is input into the optical coupling isolation driving circuit to obtain a fifth-eighth switching tube S of a secondary side in the primary side full-bridge conversion circuit 1 ～S 4 To realize the reverse output voltage v bus Control and adjustment of the operating frequency;
(2) Calculating and outputting an equivalent resistance load by using the input voltage, the input current signal and the reverse output voltage obtained by sampling; calculating synchronous rectification conduction time according to the output equivalent resistance load and the switching frequency;
(3) The CLLC converter with reverse operation has primary and secondary switch tubes with same turn-on time, i.e. the first-fourth switch tubes Q as synchronous rectifier tubes 1 ～Q 4 Fifth-eighth switching tube S for switching-on time and secondary side 1 ～S 4 Identical, first-fourth switching tubes Q 1 ～Q 4 The turn-off time of the transformer is determined by the calculated synchronous rectification turn-on time of the reverse operation.
Further, when the CLLC converter works in the forward direction and works in the reverse direction, the CLLC converter calculates and outputs the equivalent resistive load by using the input voltage, the input current, the output voltage and the output current sampling signals required by closed-loop control.
The invention has the following beneficial effects:
1. the invention reduces the conduction time of the synchronous rectifier diode, obviously reduces the conduction loss of the switching tube and improves the operation efficiency and power density of the converter.
2. The invention can realize synchronous rectification control without detecting any high-frequency signal and has high immunity to switching noise.
3. The invention simplifies the circuit model, can more conveniently calculate each parameter required in the control method by using the simplified equivalent circuit model, simplifies the operation amount and improves the result accuracy.
4. The invention directly uses the current and voltage direct current signals in the closed-loop control to calculate the equivalent output load and the synchronous rectification conduction time without additionally adding a sampling circuit. The circuit design is simple, the reliability is high, the cost is saved, and the realization is easy.
Drawings
FIG. 1 is a forward runtime control block diagram of the present invention.
FIG. 2 is a forward runtime control flow diagram of the present invention.
Fig. 3 is a diagram of the forward operation control waveform of the present invention (less than the resonance point).
Fig. 4 is a diagram of the forward operation control waveform of the present invention (greater than the resonance point).
FIG. 5 is a reverse runtime control block diagram of the present invention.
FIG. 6 is a reverse runtime control flow diagram of the present invention.
The symbols of the components in the drawings illustrate that:
v in1 forward input DC voltage
v in2 Reverse input DC voltage
i in2 Reverse input of direct current
v o Forward output DC voltage
i o Forward output current
v bus Reverse output voltage
Q 1 ，Q 2， A first switch tube, a second switch tube,
Q 3 ，Q 4 third and fourth switching tubes
S 0 ，S 0 A fifth switching tube, a sixth switching tube,
S 3 ，S 4 the seventh switch tube and the eighth switch tube
f r Resonant frequency
Lr 1 ,Lr 2 A first resonant inductor and a second resonant inductor
Cr 1 ,Cr 2 A first resonant capacitor and a second resonant capacitor
L m Excitation magnetFeeling of
i Lr Resonant current
i Lm Excitation current
Transformation ratio of n transformer
i S1 ,i S2 Flows through the first and second switch tubes S 1 ，S 2 Current of
V ref1 ,V ref2 First and second control reference voltages
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings. The specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.
As shown in fig. 1, the isolated CLLC converter bidirectional synchronous rectification control device of the present invention includes a CLLC converter, a sampling circuit, a controller unit, and an optical coupling isolation driving circuit. The CLLC converter comprises a primary side full-bridge conversion circuit, a resonance circuit and a secondary side full-bridge conversion circuit; the primary side full-bridge conversion circuit comprises a first switch tube Q 1 Second switch tube Q 2 Third switch tube Q 3 Fourth switch tube Q 4 (ii) a The resonant circuit comprises a first resonant inductor Lr 1 A second resonant inductor Lr 2 First resonant capacitor Cr 1 A second resonant capacitor Cr 2 And a transformer having an exciting inductance L integrated therein m Said exciting inductance L m The transformer is arranged on the primary side of the transformer; the first switch tube Q 1 And a second switching tube Q 2 The midpoint and the resonant inductance Lr 1 Is connected to the third switching tube Q 3 And a fourth switching tube Q 4 The midpoint and the first resonant capacitor Cr 1 Is connected to the first resonant inductor Lr 1 And a first resonant capacitor Cr 1 The other end of the magnetic field is respectively connected with the excitation inductor L m Are connected at both ends; the secondary side full-bridge conversion circuit comprises a fifth switching tube S 1 The sixth switching tube S 2 Seventh switching tube S 3 The eighth switching tube S 4 The fifth switch tube S 1 And a sixth switching tube S 2 And the second resonant inductor Lr 2 Is connected to a seventh switching tube S 3 And an eighth switching tube S 4 And the second resonant capacitor Cr 2 One end is connected; second resonant inductor Lr 2 And a second resonant capacitor Cr 2 The other ends of the two ends are respectively connected with the secondary side of the transformer; t is t on_Q Is the primary side switching tube on time t on_SR For synchronizing the turn-on time of the rectifier tube, t off_SR The turn-off time of the synchronous rectifier tube. i.e. i S1 ,i S2 For flowing through the fifth and sixth switching tubes S 1 ，S 2 The current of (2).
The apparatus calculates a synchronous rectification on-time in a controller unit, taking into account the variation of the switching frequency and the output load, based on a frequency domain model of the CLLC converter. In the CLLC converter, under the forward operation mode and the reverse operation mode, the switching-on time of the primary and secondary side switching tubes of the converter is set to be consistent, and the switching-off time of the synchronous rectifier tube is respectively equal to the switching-on time plus the synchronous rectifier conducting time calculated under different modes.
The first to fourth switching tubes Q 1 ～Q 4 Fifth-eighth switching tube S 1 ～S 4 Are both MOSFETs.
The invention also provides a bidirectional synchronous rectification control method of the CLLC converter, which is based on the frequency domain model of the CLLC converter, considers the change of the switching frequency and the output load and calculates the synchronous rectification conduction time in the controller unit. In the CLLC converter, under the forward operation mode and the reverse operation mode, the switching-on time of the primary and secondary side switching tubes of the converter is set to be consistent, and the switching-off time of the synchronous rectifier tube is respectively equal to the switching-on time plus the synchronous rectifier conducting time calculated under different modes.
Synchronous rectification conduction time delta t of forward running when CLLC converter runs in forward direction con_f The calculation is as follows:
wherein, f s Is the switching frequency, omega is the switching angular frequency, omega＝2πf s 。
Wherein
The calculations are respectively as follows:
C' r2 ＝n 2 C r2 (6)
R e ＝8n 2 v o /(π 2 i o ) (7)
where n is the transformation ratio. C j Is the equivalent output capacitance of the synchronous rectifier tube.
Wherein, f n Is equal to omega/omega r Is a per unit value of switching frequency, λ is equal to L m /L r1 。
Wherein y is defined as C j /C r1 。
When the CLLC converter operates in reverse, the main difference is the location of the power supply and the load. Synchronous rectification conduction time delta t of reverse operation con_f The calculation is as follows:
△t con_f ＝0.5/f s -θ p /(2πf s ) (18)
wherein f is s Is the switching frequency, omega is the switching angular frequency, f s ＝1/T s ,ω＝2πf s 。θ p ＝θ 2 -θ 1 -θ 3 Wherein θ 1 ，θ 2 ，θ 3 Can be respectively calculated as:
θ 1 ＝arctan(g 1 /h 1 ) (19)
h 1 ＝R b /(R b 2 C j 2 ω 2 +1) (22)
the control circuit adopted by the method comprises a CLLC converter, a sampling circuit, a controller unit and an optical coupling isolation driving circuit, wherein the CLLC converter comprises a primary side full-bridge conversion circuit, a resonance circuit and a secondary side full-bridge conversion circuit.
When the CLLC converter works in the forward direction as shown in FIG. 2, the main control steps are as follows, wherein t on_S For the turn-on time, t, of the secondary side switching tube on_SR For synchronizing the turn-on time, t, of the rectifying tube off_SR The turn-off time of the synchronous rectifier tube.
(1) Collecting forward output DC voltage v o The signal is input into the controller unit through the sampling circuit; the signal is compared with the reference output voltage in the controller unit to obtain an error signal, and the error signal is calculated by the proportional-integral controller unit to obtain a pulse frequency modulation signal; a pulse frequency modulation signal is input into the optical coupling isolation driving circuit to obtain a primary side first-fourth switching tube Q in the primary side full-bridge conversion circuit 1 ～Q 4 To realize a forward output of a direct current voltage v o Control and adjustment of the operating frequency;
(2) Calculating and outputting an equivalent resistance load by using the output voltage and the output current signals obtained by sampling; calculating the synchronous rectification conduction time of forward operation according to the output equivalent resistance load and the switching frequency;
(3) Fifth-eighth switching tube S as synchronous rectifier 1 ～S 4 First-fourth switching tube Q at turn-on time and primary side 1 ～Q 4 Identical, fifth-eighth switching tube S 1 ～S 4 The turn-off time is determined by the calculated synchronous rectification turn-on time.
Since the topology of the CLLC converter is symmetrical, the equivalent circuit and control in forward and reverse modes are similar. When the CLLC converter runs reversely, the main control steps are as follows:
(1) Closed-loop control is also adopted for the CLLC converter which runs in the reverse direction, and reverse output voltage v is acquired bus The signal is input into the controller unit through the sampling circuit; the signal is compared with the reference output voltage in the controller unit to obtain an error signal, and the error signal is calculated by the proportional-integral controller unit to obtain a pulse frequency modulation signal; a pulse frequency modulation signal is input into the optical coupling isolation driving circuit to obtain a fifth-eighth switching tube S of a secondary side in the primary side full-bridge conversion circuit 1 ～S 4 To realize the reverse output voltage v bus Control and adjustment of the operating frequency;
(2) By using sampled reverse input DC voltage v in2 Reverse input of direct current i in2 Signal and inverted output voltage v bus Calculating and outputting an equivalent resistance load; calculating the synchronous rectification conduction time of the reverse operation according to the output equivalent resistance load and the switching frequency;
(3) The primary and secondary side switching tubes of the CLLC converter which runs in reverse are set to be consistent in turn-on time, namely the first switching tube Q and the fourth switching tube Q 1 ～Q 4 Fifth-eighth switching tube S for switching on time and secondary side 1 ～S 4 Identical, first-fourth switching tubes Q 1 ～Q 4 The turn-off time of the synchronous rectifier is determined by the calculated turn-on time of the synchronous rectifier.
When the CLLC converter works in the forward direction and the reverse direction, the CLLC converter calculates and outputs equivalent load by using input direct current voltage, input current, output voltage and output current sampling signals required by closed-loop control.
The isolated CLLC bidirectional synchronous rectification control method of the present invention is further described with reference to fig. 1-6.
When the CLLC converter operates in the forward direction, the closed-loop control of the output voltage is realized by adopting a Pulse Frequency Modulation (PFM) method for control and adjusting the switching frequency of the CLLC converter. Control is shown in fig. 1 and a flow chart is shown in fig. 2.
First, as shown in FIG. 1, a forward output DC voltage v is collected o The signals are input into the controller unit through the sampling circuit; the signal is coupled to a first control reference voltage v in the controller unit ref1 Comparing to obtain an error signal, and comparing the error signal with a triangular carrier to obtain a PFM signal after the error signal is calculated by a PI controller unit; sending the PFM signal into an optical coupling isolation driving circuit to obtain a driving signal t of each switching tube at the primary side of the CLLC converter on_Q Is the primary side switching tube on time t on_SR For synchronizing the turn-on time, t, of the rectifying tube off_SR The turn-off time of the synchronous rectifier tube.
Fig. 3 shows the primary side driving waveform and the secondary side synchronous rectification driving waveform when the switching frequency is higher than the resonance point. According to the graph, under the conditions of heavy load and light load, the provided synchronous rectification control algorithm can well track load change, adjust the conduction duty ratio of synchronous rectification, reduce the conduction loss of diodes of a synchronous rectification tube body and improve the efficiency.
Fig. 4 shows the primary side driving waveform and the secondary side synchronous rectification driving waveform when the switching frequency is lower than the resonance point. According to the graph, under the conditions of heavy load and light load, the provided synchronous rectification control algorithm can well track load change, adjust the conduction duty ratio of synchronous rectification, reduce the conduction loss of diodes of a synchronous rectification tube body and improve the efficiency.
Second, the current i is output in the forward direction according to the sampling o And a forward output DC voltage v o And calculating the output equivalent resistance load, wherein the signal utilizes the existing sampling circuit without adding a new circuit. Using switching frequency obtained by closed loop and equivalent load obtained by samplingAnd calculating the conduction time of the forward-running synchronous rectifier tube.
Thirdly, the turn-on time t of the synchronous rectifier on_SR As on the primary side. Calculating the synchronous rectification conduction time delta t of the forward operation according to the established model con_f At the turn-off time t of the synchronous rectifier off_SR Equal to the turn-on instant plus the calculated turn-on time. And in the controller unit, converting the conduction time of the synchronous rectifier tube to obtain a comparison value of a comparison register, and obtaining a PFM signal. And the optical coupling isolation chip and the driver are utilized to output a driving signal of the synchronous rectifier tube.
When the CLLC converter runs in a reverse direction, the equivalent circuit is similar to that when the CLLC converter runs in a forward direction, so the control mode is also similar, a Pulse Frequency Modulation (PFM) method is adopted for control, and the closed-loop control of the output voltage is realized by adjusting the switching frequency of the CLLC converter. The invention is shown in figure 5 when the CLLC works reversely, and the control flow chart is shown in figure 6. The control method comprises the following steps:
first, collecting the reverse output voltage v bus The signals are input into a controller unit through a sampling circuit; the signal is connected with a second control reference voltage v output in the controller unit ref2 Comparing to obtain an error signal, and comparing the error signal with a triangular carrier to obtain a PFM signal after the error signal is calculated by a PI controller unit; sending the PFM signal into an optical coupling isolation driving circuit to obtain a driving signal t of each switching tube on the secondary side of the CLLC converter on_S For the turn-on time, t, of the secondary side switching tube on_SR For synchronizing the turn-on time, t, of the rectifying tube off_SR The turn-off time of the synchronous rectifier tube.
When the switching frequency is higher than the resonance point or lower than the resonance point, the primary side driving waveform and the secondary side synchronous rectification driving waveform are the same as those of the CLLC converter during forward running.
Second, the DC current i is input in the reverse direction according to the sampling in2 And a reverse input DC voltage v in2 And calculating the output equivalent resistance load, wherein the signal utilizes the existing sampling circuit without adding a new circuit. And calculating the conduction time of the synchronous rectifier tube running reversely by using the switching frequency obtained by the closed loop and the output equivalent resistance load obtained by sampling.
Thirdly, the turn-on time t of the synchronous rectifier on_SR And secondary side turn-on time t on_S The same is true. The synchronous rectification conduction time delta t of the reverse operation calculated according to the established model con_f At the turn-off time t of the synchronous rectifier off_SR Equal to the turn-on instant plus the calculated turn-on time. In the controller unit, the conduction time of the synchronous rectifier tube is converted to obtain a comparison value of a comparison register, and a PFM signal is obtained. And the optical coupling isolation chip and the driver are utilized to output a driving signal of the synchronous rectifier tube.
In summary, the invention considers the change of the switching frequency and the load, can more accurately control the synchronous rectification on-time, reduce the conduction loss of the switching tube, reduce the loss of the converter, and improve the efficiency of the converter, and meanwhile, the circuit is simple, the reliability is high, and the invention has the advantages that the existing control method does not have.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.
Claims (6)
1. The utility model provides a two-way synchronous rectification control device of isolated form CLLC converter, includes CLLC converter, sampling circuit, controller unit and opto-coupler isolation drive circuit, its characterized in that:
the CLLC converter comprises a primary side full-bridge conversion circuit, a resonance circuit and a secondary side full-bridge conversion circuit; the primary side full-bridge conversion circuit comprises a first switch tube Q 1 A second switch tube Q 2 A third switching tube Q 3 Fourth switch tube Q 4 (ii) a The resonant circuit comprises a first resonant inductor Lr 1 A second resonant inductor Lr 2 A first resonant capacitor Cr 1 A second resonant capacitor Cr 2 And a transformer having an exciting inductance L integrated therein m Said exciting inductance L m Is arranged on the primary side of the transformer; the first switch tube Q 1 And a second switching tube Q 2 And the first resonant inductor Lr 1 Is connected to the third switching tube Q, the third switching tube Q 3 And a fourth switching tube Q 4 The midpoint and the first resonant capacitor Cr 1 Is connected to the first resonant inductor Lr 1 And a first resonant capacitor Cr 1 The other end of the magnetic field is respectively connected with the excitation inductor L m Are connected; the secondary side full-bridge conversion circuit comprises a fifth switching tube S 1 The sixth switching tube S 2 Seventh switching tube S 3 The eighth switching tube S 4 The fifth switch tube S 1 And a sixth switching tube S 2 And the second resonant inductor Lr 2 Is connected to one end of a seventh switching tube S 3 And an eighth switching tube S 4 And the second resonant capacitor Cr 2 One end is connected; second resonant inductor Lr 2 And a second resonant capacitor Cr 2 The other ends of the two ends are respectively connected with the secondary side of the transformer.
2. The isolated CLLC converter bidirectional synchronous rectification control device of claim 1, wherein: the first to fourth switching tubes Q 1 ～Q 4 Fifth-eighth switching tube S 1 ～S 4 Are both MOSFETs.
3. A control method of the isolated CLLC converter bidirectional synchronous rectification control device according to claim 1 or 2, characterized in that:
calculating synchronous rectification conducting time in control by considering the change of switching frequency and output load based on a frequency domain model of the CLLC converter; the CLLC converter is provided with a first switching tube Q of the primary side and the secondary side of the converter in a forward operation mode and a reverse operation mode 1 A second switch tube Q 2 A third switching tube Q 3 Fourth switch tube Q 4 The fifth switch tube S 1 The sixth switching tube S 2 Seventh switching tube S 3 The eighth switching tube S 4 The turn-on time of the synchronous rectification switch is consistent, and the turn-off time is respectively equal to the turn-on time plus the synchronous rectification turn-on time calculated under different modes.
4. The control method according to claim 3, characterized in that:
when the CLLC converter works in the forward direction, the method comprises the following steps:
(1) Collecting a forward output direct current voltage signal, and inputting the signal into a controller unit through a sampling circuit; the signal is compared with a first control reference voltage in the controller unit to obtain an error signal, and the error signal is calculated by the proportional-integral controller unit to obtain a pulse frequency modulation signal; a pulse frequency modulation signal is input into the optical coupling isolation driving circuit to obtain a primary side first-fourth switching tube Q in the primary side full-bridge conversion circuit 1 ～Q 4 To realize a forward output of a direct current voltage v o Control and adjustment of the operating frequency;
(2) Calculating and outputting equivalent resistance load by using the forward output direct current voltage and the forward output current signal obtained by sampling; calculating the synchronous rectification conduction time of forward operation according to the output equivalent resistance load and the switching frequency;
(3) Fifth-eighth switching tube S as synchronous rectifier 1 ～S 4 First-fourth switching tube Q at turn-on time and primary side 1 ～Q 4 Identical, fifth-eighth switching tube S 1 ～S 4 The turn-off time is determined by the calculated synchronous rectification turn-on time of the forward operation.
5. The control method according to claim 4, characterized in that:
when the CLLC converter runs reversely, the method comprises the following steps:
(1) Closed-loop control is adopted for the CLLC converter which runs reversely, reverse output voltage signals are collected and input into the controller unit through the sampling circuit; the signal is compared with a second control reference voltage in the controller unit to obtain an error signal, and the error signal is calculated by the proportional-integral controller unit to obtain a pulse frequency modulation signal; a pulse frequency modulation signal is input into the optical coupling isolation driving circuit to obtain a fifth-eighth switching tube S of a secondary side in the primary side full-bridge conversion circuit 1 ～S 4 Drive signal ofThe control of the reverse output voltage and the adjustment of the working frequency are realized;
(2) Calculating and outputting an equivalent resistance load by using the sampled reverse input direct current voltage, the reverse input direct current signal and the reverse output voltage; calculating synchronous rectification conduction time according to the output equivalent resistance load and the switching frequency;
(3) The primary and secondary side switch tubes of the CLLC converter which runs in reverse are set to be consistent in turn-on time, namely, the first to fourth switch tubes Q as synchronous rectifier tubes 1 ～Q 4 Fifth-eighth switching tube S for switching-on time and secondary side 1 ～S 4 Identical, first-fourth switching tubes Q 1 ～Q 4 The off-time of (d) is determined by the calculated synchronous rectification on-time of the reverse operation.
6. The control method according to claim 5, characterized in that:
when the CLLC converter works in the forward direction and the reverse direction, the CLLC converter calculates and outputs equivalent resistive load by using input voltage, input current, output voltage and output current sampling signals required by closed-loop control.
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| CN202210779986.1A CN115242095B (en) | 2022-07-04 | Bidirectional synchronous rectification control device and method for isolated CLLC converter |
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