CN115425851B - Control method of LLC resonant converter - Google Patents
Control method of LLC resonant converter Download PDFInfo
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- CN115425851B CN115425851B CN202211365480.2A CN202211365480A CN115425851B CN 115425851 B CN115425851 B CN 115425851B CN 202211365480 A CN202211365480 A CN 202211365480A CN 115425851 B CN115425851 B CN 115425851B
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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
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
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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
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
- H02M1/38—Means for preventing simultaneous conduction of switches
- H02M1/385—Means for preventing simultaneous conduction of switches with means for correcting output voltage deviations introduced by the dead time
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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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- 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)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a control method of an LLC resonant converter, which comprises the following steps: 101 Sampling the input voltage, the output current and the output voltage of the LLC resonant converter in real time, dividing the working condition of the LLC resonant converter into a small gain working state and a normal gain working state according to a sampling value, and selecting corresponding loop control according to the working state; 102 In a low-gain working state, the LLC loop control adds set dead time into a real-time driving signal obtained by calculating a feedback loop, so that the driving duty ratio is reduced, and the system gain is reduced; 103 High gain loop control, in a normal gain operating state, the LLC loop control removes dead time added by the low gain loop control, causing the drive duty cycle to return to normal, and the system gain to return. The invention can effectively avoid the problem of overlarge output voltage ripple caused by the fact that light load enters a high-frequency intermittent mode, and the output voltage ripple is small.
Description
Technical Field
The invention relates to a communication power supply, in particular to a control method of an LLC resonant converter.
Background
In recent years, with the improvement of living standard and the increasing demand for living matter conditions, the development of communication technology brings great convenience to daily travel of people. With the further improvement of the requirements of communication technology in the aspects of operation reliability, comfort, energy conservation, noise reduction, maintainability and the like, the requirements of people on the indexes of efficiency, power density, noise vibration and the like of a communication power supply are stricter, the requirements on an input voltage range and an output voltage range are wider and wider, and the requirements on output voltage ripple are stricter. LLC resonant converters have gained much attention in recent years because they can meet the trend of high switching frequency, high power density and conversion efficiency of switching power supplies. The LLC resonant converter can realize zero voltage switching-on in a full load range, and the secondary side rectifier diode can realize zero current switching-off. Meanwhile, magnetic elements in a main circuit of the converter are easy to integrate, and leakage inductance of a transformer is utilized to the limited extent, so that the LLC resonant converter is widely applied to the communication power supply industry.
In the conventional analog LLC resonant converter and the conventional digital LLC resonant converter, the system gain is already fixed under the condition that the resonant cavity parameters are determined. When the input voltage range and the output voltage range of the power supply are both enlarged, the adjustment range of the switching frequency is enlarged, the high-voltage input which may occur at the time can cause the influence of overhigh switching frequency, the parasitic parameters of an exciting circuit and the like on a system, and in addition, the output voltage ripple and the signal-to-noise ratio are difficult to meet the requirements.
Disclosure of Invention
The invention aims to provide a control method of an LLC resonant converter with small output voltage ripple under the conditions of wide input voltage range and wide output voltage range.
In order to solve the technical problem, the invention adopts the technical scheme that the control method of the LLC resonant converter comprises the following steps:
101 Sampling input voltage, output current and output voltage of the LLC resonant converter in real time, dividing the working condition of the LLC resonant converter into a small-gain working state and a normal-gain working state according to the sampling values of the input voltage, the output current and the output voltage, and selecting corresponding loop control according to the working state;
102 In a low-gain working state, the LLC loop control adds a set dead time to a real-time driving signal obtained by calculating a feedback loop, so that the driving duty ratio is reduced, and the system gain is reduced;
103 High gain loop control, in a normal gain operating state, the LLC loop control removes dead time added by the low gain loop control, causing the drive duty cycle to return to normal, and the system gain to return.
In the control method, the low-gain working state includes a high-voltage input high-voltage output light-load working state, a high-voltage input low-voltage output heavy-load working state and a non-high-voltage input low-voltage output light-load working state; the normal gain working state comprises a high-voltage input and high-voltage output heavy-load working state, a non-high-voltage input and high-voltage output light-load working state, a non-high-voltage input and high-voltage output heavy-load working state and a non-high-voltage input and low-voltage output heavy-load working state.
In the control method, in step 102, the set dead time is added to limit the duty ratio of the driving signal to be not more than 30%.
According to the control method, the voltage value of the DC bus is adjusted at a matched speed by adding or subtracting the driving dead time when the loop is switched: the dead time is increased, the driving duty ratio is reduced, and the DC bus voltage is increased; the dead time is reduced, the driving duty ratio is increased, and the DC bus voltage is reduced; to keep the smooth rising and falling of the working frequency of the system and achieve the effect of stable transition
The control method can effectively avoid the problem of overlarge output voltage ripple caused by the fact that light load enters a high-frequency intermittent mode, and the output voltage ripple is small.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a flow chart of a control method of an LLC resonant converter in an embodiment of the invention.
FIG. 2 is a list of the input and output specifications of the 6KW 5G power supply of the embodiment of the invention.
Detailed Description
The implementation manner of the control method of the LLC resonant converter in the embodiment of the invention is as follows:
the whole LLC resonant converter working condition can be divided into 8 states, and the eight states are distinguished by input voltage detection, output current detection and voltage detection:
(1) high-voltage input and high-voltage output light load;
(2) high-voltage input and high-voltage output heavy load;
(3) high-voltage input and low-voltage output light load;
(4) high-voltage input and low-voltage output heavy load;
(5) inputting high voltage and outputting light load under non-high voltage;
(6) non-high voltage input and high voltage output heavy load;
(7) inputting non-high voltage and outputting low voltage and light load;
(8) and (4) inputting non-high voltage and outputting low voltage for heavy load.
These eight states are actually working on the double loop of the LLC:
first loop (low gain loop, including states (1) (3) (4) (7)): in this state, the LLC loop control adds the set dead time to the real-time drive signal calculated by the feedback loop, so that the drive duty ratio is reduced, the system gain is reduced, and the system exits the high-frequency discontinuous mode as early as possible and enters the low-frequency continuous mode. The problem that output ripples are overlarge due to a high-frequency intermittent mode when light loads occur can be effectively solved.
Second loop (high gain loop, including states (2) (5) (6) (8)): in this state, the LLC loop control removes the dead time added by the first loop state, at which time the drive duty cycle is normal and the system gain is restored.
Because the addition and subtraction of the driving dead time are involved in the loop switching caused by the state change, and the oscillation of an LLC resonant cavity is caused by the instantaneous change, so that the output voltage ripple is unstable, the addition and subtraction of the driving dead time should be slowly changed when the loop is switched, and the voltage value of a DC bus is adjusted at a matched speed: the dead time increases and the drive duty decreases. In order to keep the current output stable, the DC bus voltage should be increased; on the contrary, the dead time is reduced, the driving duty ratio is increased, and in order to keep the current output stable, the DC bus voltage is reduced. The size of the control dead zone and the addition and subtraction of the DC bus should find a proper adjusting rate, and the adjusting rate is required to be slowly debugged, wherein the characteristics of each system are different and the adjusting rate is different according to the condition of the system. The purpose is to keep the smooth rising and falling of the working frequency of the system as much as possible when adjusting the driving dead zone and the DC bus so as to achieve the effect of stable transition.
The low-gain loop limits the duty ratio of the driving signal to be 30% by adding a certain dead time into the driving signal, so that the system gain can be effectively reduced. The high-gain loop is normal loop control, dead time does not need to be added into the driving signal, and the duty ratio of the driving signal is about 45%. Because the high gain loop calculates a higher drive duty cycle than the low gain loop at the same frequency, the system operating in the high gain loop has a higher gain than the low gain loop under the same conditions.
According to the ripple control method under the double-gain LLC loop, the working state of the power supply is divided according to the real-time input voltage, output current and voltage sampling results, and then the corresponding loop is selected according to the working state. After the corresponding loop is selected, the gain of the system is adjusted by changing the frequency and the duty ratio of the real-time driving signal in a loop control mode (PI, 2P2Z or other high-order negative feedback control modes) of the system. When the frequency and the duty ratio of the driving signal are operated, the frequency and the duty ratio of the driving signal are slowly and transitionally changed according to a fixed step (nanosecond plus-minus), and the voltage value of the DC bus is adjusted at a matched speed (the DC bus is added or subtracted by taking 1V or 2V as the step), and the action of adding or subtracting the voltage of the DC bus is opposite to the action of adding or subtracting the duty ratio so as to achieve the effect of stable transition. Therefore, the output voltage ripple and the signal-to-noise ratio in the full voltage range and the full load range reach the standard of the communication power supply industry.
The ripple control principle in the double-gain LLC loop is shown in fig. 1, and the details are described here by taking the 6kw 5G communication power supply as an example, and the basic specifications of the communication power supply are shown in fig. 2.
And starting module sampling, wherein the module sampling of the power supply comprises input voltage sampling, output current sampling and output voltage sampling, and sampling results of the input voltage sampling, the output current sampling and the output voltage sampling are combined into a basis for selecting a loop.
The transformer turn ratio of the communication power supply is 10:3, the lowest voltage of the DC bus is limited to 380V in order to meet the condition of 264V input of high voltage. When the input voltage is 230V and the output voltage is 42V and no load exists, the theoretical value of the most set DC bus is 280V according to the ratio, but the actual DC bus is 380V, and the actual value is far higher than the theoretical value. In this case, to stabilize the output 42V, the conventional loop would drive the frequency high, even into discontinuous mode, which makes the output ripple difficult to control. And the double-gain LLC loop selects a non-high-voltage input and low-voltage output light-load mode according to the current input and output states, and uses small-gain loop control to reduce the system gain, quit a high-frequency discontinuous mode as early as possible and enter a low-frequency continuous mode. The problem of overlarge output ripple caused by a high-frequency intermittent mode of light load can be effectively avoided.
The above embodiment of the present invention changes the state of the output voltage 42V no-load from the above input 230V to the state of the output voltage 58V full-load through voltage-regulating loading, and during this change, the loop switches from low gain to high gain, and this switching process is controlled by the sampling result. According to the transformation ratio, when the output 58V is unloaded, the theoretical value of the DC bus is 386V, and 30V is added on the basis under the condition of full load, namely the theoretical value of the full load is about 416V. In the case where the actual value is greater than the lowest point of the DC bus voltage, it is necessary to remove the dead time previously added to the driving signal to make the loop gain as large as possible, and then to control the DC bus voltage by the loop to make the system stably operate near the resonant frequency. The loop with large gain in the double-gain LLC loop is substantially the same as the normal LLC loop control, except for the switching of the loop. The loop switching involves the addition and subtraction of the driving dead time, and the instantaneous change causes the oscillation of an LLC resonant cavity, so that the output voltage ripple is unstable, the addition and subtraction of the driving dead time should be changed slowly when the loop is switched, and meanwhile, the voltage value of a DC bus is adjusted, so that the working frequency of the system cannot fluctuate greatly, and the effect of stable transition is achieved. The step diameter of the driving dead time plus-minus of the above embodiment of the invention is 10ns, and the step diameter of the DC bus voltage adjustment is 1V.
Claims (3)
1. A method of controlling an LLC resonant converter, characterized by the steps of:
101 Sampling input voltage, output current and output voltage of the LLC resonant converter in real time, dividing the working condition of the LLC resonant converter into a small-gain working state and a normal-gain working state according to the sampling values of the input voltage, the output current and the output voltage, and selecting corresponding loop control according to the working state;
102 In a low-gain working state, the LLC loop control adds a set dead time to a real-time driving signal obtained by calculating a feedback loop, so that the driving duty ratio is reduced, and the system gain is reduced;
103 In a normal gain working state, the LLC loop control removes dead time added by the low gain loop control, so that the drive duty cycle is restored to normal, and the system gain is restored;
the low-gain working state comprises a high-voltage input high-voltage output light-load working state, a high-voltage input low-voltage output heavy-load working state and a non-high-voltage input low-voltage output light-load working state; the normal gain working state comprises a high-voltage input and high-voltage output heavy-load working state, a non-high-voltage input and high-voltage output light-load working state, a non-high-voltage input and high-voltage output heavy-load working state and a non-high-voltage input and low-voltage output heavy-load working state.
2. The control method of claim 1, wherein in step 102, a set dead time is added to limit the duty cycle of the drive signal to no more than 30%.
3. The control method of claim 1, wherein the driving dead time plus or minus when switching the loop adjusts the DC bus voltage value at a matched rate: the dead time is increased, the driving duty ratio is reduced, and the DC bus voltage is increased; the dead time is reduced, the driving duty ratio is increased, and the DC bus voltage is reduced; so as to keep the smooth rising and falling of the working frequency of the system and achieve the effect of stable transition.
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| CN113472199A (en) * | 2021-06-30 | 2021-10-01 | 易事特集团股份有限公司 | Mode smooth switching method and system of Buck-Boost circuit |
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| CN114726223A (en) * | 2022-04-19 | 2022-07-08 | 西北工业大学 | Control method and device of LLC resonant converter and LLC resonant conversion system |
| CN115224916A (en) * | 2022-05-24 | 2022-10-21 | 青岛海尔智慧厨房电器有限公司 | Alternating current-direct current power supply circuit and range hood |
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