CN117394672B - Soft start control circuit, chip and control method of resonant converter - Google Patents

Soft start control circuit, chip and control method of resonant converter Download PDF

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Publication number
CN117394672B
CN117394672B CN202311689682.7A CN202311689682A CN117394672B CN 117394672 B CN117394672 B CN 117394672B CN 202311689682 A CN202311689682 A CN 202311689682A CN 117394672 B CN117394672 B CN 117394672B
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signal
low
circuit
soft start
value
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CN117394672A (en
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许胜有
施泽群
孙乾坤
王旷
李海松
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Suzhou Poweron IC Design Co Ltd
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Suzhou Poweron IC Design Co Ltd
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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
    • H02M1/36—Means for starting or stopping converters
    • 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
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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
    • 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
    • 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
    • H02M3/33571—Half-bridge at primary side of an isolation transformer
    • 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 present disclosure relates to the field of switching power supply technologies, and in particular, to a soft start control circuit, a chip, and a control method of a resonant converter. The soft start control circuit includes: the first circuit is used for collecting the resonance capacitor voltage of the resonance converter, obtaining a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal; sampling the output voltage of the resonant converter, setting a comparison threshold of the resonant capacitor voltage sampling signal, and outputting a high-side threshold signal and a low-side threshold signal; the second circuit is controlled by the soft start working phase control module and outputs a high-side driving signal and a low-side driving signal according to the resonant capacitor voltage sampling signal, the high-side threshold signal and the low-side threshold signal; and the soft start working stage control module is used for controlling the working of the first circuit and the second circuit and carrying out state detection and mode control on each stage of soft start. The soft start control circuit of the resonant converter has no abrupt signal change in the whole soft start stage of the resonant converter.

Description

Soft start control circuit, chip and control method of resonant converter
Technical Field
The application relates to the technical field of switching power supplies, in particular to a soft start control circuit, a chip and a control method of a resonant converter in a power supply direction.
Background
The resonant converter has the advantages of high switching frequency, small switching loss, high efficiency, light weight, small volume, small electromagnetic interference noise, small switching stress and the like compared with a hard switching PWM (pulse-Width modulation) converter. The zero-voltage switching-on of the primary side power tube and the zero-current switching-off of the secondary side power tube in the full load range can be realized, and the high-efficiency high-frequency high-voltage switching-on power tube has the excellent characteristics of high efficiency, high frequency and the like, and is widely applied to various application occasions.
However, the resonance characteristic of the resonant converter itself causes the resonant converter to have larger voltage-current stress when being started, which has great influence on system application. Soft start technology is the most commonly used method to effectively reduce resonant converter voltage-current stress. The soft start method in the prior art mainly comprises a down-conversion soft start method, a variable duty ratio soft start method and an optimal track soft start method, however, the down-conversion soft start method and the variable duty ratio soft start method both have voltage and current abrupt change conditions, the stability of a circuit is affected, the dead time is long, the optimal track soft start method is complex to control, the calculated amount is large, and the performance requirements of an analog-to-digital converter and a digital microprocessor are high. And the resonant current and the resonant voltage need to be sampled with high frequency and high precision, and are easy to be interfered by external noise.
Therefore, a need exists for a soft start control circuit, chip and method for a resonant converter that avoids abrupt voltage and current changes during start-up without affecting circuit stability.
Disclosure of Invention
In order to solve the defects in the prior art, the purpose of the application is to provide a soft start control circuit, a chip and a method of a resonant converter, which can avoid abrupt change of voltage and current in the starting process and can not influence the stability of the circuit.
To achieve the above object, the present application provides a soft start control circuit of a resonant converter, including:
the first circuit is used for collecting the resonance capacitor voltage of the resonance converter, obtaining a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal; sampling the output voltage of the resonant converter, setting a comparison threshold of the resonant capacitor voltage sampling signal, and outputting a high-side threshold signal and a low-side threshold signal;
the second circuit is controlled by the soft start working phase control module and outputs a high-side driving signal and a low-side driving signal according to the resonant capacitor voltage sampling signal, the high-side threshold signal and the low-side threshold signal;
and the soft start working stage control module is used for controlling the working of the first circuit and the second circuit and carrying out state detection and mode control on each stage of soft start.
Further, the first circuit generates a resonance capacitor voltage comparison signal according to the resonance capacitor voltage sampling signal; and detecting the resonant capacitor voltage comparison signal, and outputting a sign signal and a count value.
Further, the second circuit receives control of a soft start working stage control module, sets a high-side conduction time starting value, a high-side conduction time low-side conduction time maximum value and a high-side conduction time minimum value during soft start, and generates a high-side power tube turn-off signal and a low-side power tube turn-off signal according to the resonance capacitor voltage sampling signal, the high-side threshold signal and the low-side threshold signal; and outputting a high-side driving signal and a low-side driving signal according to the high-side power tube turn-off signal, the low-side power tube turn-off signal, the high-side conduction time starting value, the high-low side conduction time maximum value and the high-low side conduction time minimum value.
Further, the control module of the soft start working phase controls the first circuit to adjust the resonant capacitor voltage sampling signal to a set central value adjusting voltage initial value in a first time period; controlling the first circuit to set and output a high-side threshold signal and a low-side threshold signal in a second time period, and controlling the second circuit to set a high-side conduction time starting value, a high-side and low-side conduction time maximum value and a high-side and low-side conduction time minimum value; controlling the second circuit to increase the high-side on time until a high-side power tube off signal is received in a third time period; to control the first circuit to increase the high side threshold signal and to decrease the low side threshold signal by the same magnitude for a fourth period of time.
Further, the high-side driving signal is used for driving a high-side power tube of the resonant converter; the low-side driving signal is used for driving a low-side power tube of the resonant converter.
Further, the first circuit includes:
the capacitor voltage sampling module is used for collecting the resonance capacitor voltage, generating a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal;
an output sampling and compensating circuit for sampling and compensating the output voltage of the resonant converter to generate an output compensating signal;
the capacitance voltage average value detection and control module generates a resonance capacitance voltage comparison signal according to the resonance capacitance voltage sampling signal;
the capacitor voltage threshold and initial value control operation module is used for setting a comparison threshold of the resonant capacitor voltage sampling signal and outputting a high-side threshold signal and a low-side threshold signal;
the high-low level detection module is used for detecting the high-low level duration of the resonant capacitor voltage comparison signal and outputting a sign signal with equal high-low level duration;
and the edge detection and counting module detects the falling edge of the capacitor voltage comparison signal and outputs a count value.
Further, the first circuit further includes: and the isolation circuit isolates the primary side from the secondary side and transmits the output compensation signal to the primary side to form an output feedback signal.
Further, the capacitance voltage average value detection and control module outputs a current adjusting signal to adjust the center value of the resonance capacitance voltage sampling signal.
Further, the capacitance voltage threshold and initial value control operation module is used for setting a central value to adjust the initial value of the voltage and calculating a voltage threshold difference value according to the feedback signal.
Further, the second circuit includes:
the threshold comparison circuit is used for comparing the resonant capacitor voltage sampling signal, the high-side threshold signal and the low-side threshold signal to generate a high-side power tube turn-off signal and a low-side power tube turn-off signal;
the on-time control and operation module is controlled by the soft start working stage control module, and a soft start high-side on-time starting value, a high-side on-time maximum value and a high-side off-time minimum value are set;
the PWM switch control module receives the high-side power tube turn-off signal, the low-side power tube turn-off signal, a high-side turn-on time starting value, a high-side turn-on time maximum value, a high-side turn-off time minimum value and a high-side turn-on time minimum value, and generates a high-side drive control signal and a low-side drive control signal;
and the driving circuit generates and outputs a high-side driving signal and a low-side driving signal according to the high-side driving control signal and the low-side driving control signal.
Further, the first period is a period from the start of soft start to the end of the first set time; the second time period is a time period when the count value reaches a set value or a second set time is ended after the first time period; the third time period is a time period before the flag signal is valid after the second time period; and the fourth time period is a time period before the difference value of the high-side threshold signal and the low-side threshold signal is larger than the voltage threshold value difference value calculated by the feedback signal after the third time period.
In order to achieve the above object, the present application further provides a soft start control chip of a resonant converter, which includes a soft start control circuit of a resonant converter as described above.
In order to achieve the above object, the present application further provides a soft start control method of a resonant converter, where the soft start control circuit applied to the resonant converter includes:
controlling the first circuit to adjust the resonant capacitor voltage sampling signal to a set central value adjusting voltage initial value;
controlling a first circuit to set and output a high-side threshold signal and a low-side threshold signal, and controlling a second circuit to set a high-side conduction time starting value, a high-side and low-side conduction time maximum value and a high-side and low-side conduction time minimum value;
Controlling the second circuit to increase the high-side on time until receiving a high-side power tube turn-off signal;
the first circuit is controlled to increase the high-side threshold signal and decrease the low-side threshold signal by the same magnitude.
Further, the method further comprises the following steps: and collecting the resonance capacitor voltage of the resonance converter, obtaining a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal.
Controlling the first circuit to adjust the resonant capacitor voltage sampling signal to a set central value adjusting voltage initial value;
controlling a first circuit to set and output a high-side threshold signal and a low-side threshold signal, and controlling a second circuit to set a high-side conduction time starting value, a high-side and low-side conduction time maximum value and a high-side and low-side conduction time minimum value;
controlling the second circuit to increase the high-side on time until receiving a high-side power tube turn-off signal;
the first circuit is controlled to increase the high-side threshold signal and decrease the low-side threshold signal by the same magnitude.
Further, the method further comprises the following steps: and collecting the resonance capacitor voltage of the resonance converter, obtaining a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal.
Still further, the method further comprises: and a step of sampling and compensating the output voltage of the resonant converter to generate an output compensation signal.
Compared with the prior art, the soft start control circuit of the resonant converter has the following beneficial effects:
the voltage and the current are smoothly and stably changed in the soft start full stage, and no abrupt signal change exists;
various starting conditions of the capacitor voltage can be met, the condition that the capacitor voltage has residual voltage at the starting moment is avoided, and the stability of the system is enhanced;
the method can meet various load starting conditions, and the starting time is adjusted by setting the set time length of the first three stages and the threshold value increasing step length of the fourth stage;
zero-voltage conduction of the power tube can be realized in the soft start process, hard switching of the power tube is avoided, and voltage stress is reduced.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.
Drawings
The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate and explain the application and do not limit it. In the drawings:
fig. 1 is a schematic structural diagram of a soft start control circuit of a resonant converter according to embodiment 1 of the present application;
Fig. 2 is a schematic structural diagram of a soft start control circuit of a resonant converter according to embodiment 2 of the present application;
fig. 3 is a schematic structural diagram of a threshold comparison circuit, a capacitor voltage sampling module and a capacitor voltage average value detection and control module according to embodiment 2 of the present application;
FIG. 4 is a schematic diagram of the soft start control and operation waveforms in embodiment 2 of the present application;
FIG. 5 is a schematic diagram of the working waveform when the initial value of the center value adjustment voltage is higher than the steady value;
FIG. 6 is a schematic diagram of an operating waveform when the initial value of the center value adjustment voltage is equal to the steady value;
FIG. 7 is a schematic diagram of the working waveform when the initial value of the center value adjusting voltage is smaller than the steady value.
Detailed Description
Embodiments of the present application will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present application are shown in the drawings, it is to be understood that the present application may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and examples of the present application are for illustrative purposes only and are not intended to limit the scope of the present application.
It should be understood that the various steps recited in the method embodiments of the present application may be performed in a different order and/or performed in parallel. Furthermore, method embodiments may include additional steps and/or omit performing the illustrated steps. The scope of the present application is not limited in this respect.
The term "including" and variations thereof as used herein are intended to be open-ended, i.e., including, but not limited to. The term "based on" is based at least in part on. The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments. Related definitions of other terms will be given in the description below.
It should be noted that references to "one" or "a plurality" in this application are intended to be illustrative rather than limiting, and those of ordinary skill in the art will appreciate that "one or more" is intended to be interpreted as "one or more" unless the context clearly indicates otherwise. "plurality" is understood to mean two or more.
The resonance characteristic of the resonant converter enables the resonant converter to have larger voltage and current stress when being started, and the resonant converter can bring great influence to system application. Therefore, the voltage and current stress of the resonant converter is effectively reduced by using a soft start technology, and the existing soft start technology mainly comprises a frequency-reducing soft start method, a duty ratio-variable soft start method and an optimal track soft start method.
The soft start method is to start at a starting frequency several times higher than the steady-state frequency, and then gradually decrease the frequency to raise the output voltage. However, this method often requires a steady state frequency that is many times greater than the start-up frequency to cause the voltage-current stress to rise slowly at a small value, and when the start-up frequency is low, there is still a large abrupt change in the voltage-current stress. At the end of soft start, voltage and current abrupt changes can be caused by gain changes, and loop stability is affected. And, for a period of time after the soft start, the zero voltage conduction of the power tube may not be realized.
The soft start method with variable duty ratio starts with a smaller duty ratio at the starting moment and then increases continuously, so that the output voltage rises slowly. The method slowly increases the voltage and current stress during starting and has a simple control mode, but the method also has similar problems as the frequency-reducing soft start, such as the zero voltage conduction of the power tube at the beginning can not be realized, the instability of a control loop and the abrupt change of voltage and current peaks are easily caused by the change of control parameters at the end of the soft start. In addition, in the soft start stage, the dead time is longer, and the system is easy to enter a capacitive working area.
The optimal track soft start method is controlled by an optimal state track method, the resonant current and the resonant voltage are expressed in a polar coordinate mode, the working state of the resonant converter can be expressed by a quasi-circular curve, and the track waveforms under different loads can be changed by monitoring the states of the resonant current and the resonant voltage and changing the on time and the dead time of the high side and the low side. The variation of the resonant voltage and the current in one period is controlled by an optimal track method at the starting time, so that the output voltage can be slowly increased, and the voltage and current stress can be avoided. However, the method is complex to control, large in calculation amount and high in performance requirements of the analog-to-digital converter and the digital microprocessor. And the resonant current and the resonant voltage need to be sampled with high frequency and high precision, and are easy to be interfered by external noise.
In summary, in the three soft start methods, the voltage and current abrupt change conditions of the down-conversion soft start method and the variable duty ratio soft start method affect the circuit stability and have long dead time, and the optimal track soft start method has complex control, large calculated amount and higher performance requirements of the analog-to-digital converter and the digital microprocessor. And the resonant current and the resonant voltage need to be sampled with high frequency and high precision, and are easy to be interfered by external noise.
Therefore, the inventor provides a soft start control circuit and a soft start method which can avoid abrupt voltage and current changes in the starting process and cannot influence the stability of the circuit.
Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings.
Example 1
An embodiment of the application provides a soft start control circuit of a resonant converter, which is used for reducing voltage and current stress in the starting process of the resonant converter, enabling output voltage to slowly rise to a reference value, simultaneously realizing cycle-by-cycle zero voltage conduction characteristic of a power tube, avoiding abrupt change of a hard switch and starting end time of the power tube, and improving system stability.
Fig. 1 is a schematic structural diagram of a soft start control circuit of a resonant converter provided in embodiment 1 of the present application, as shown in fig. 1, the soft start control circuit of the resonant converter of the present application includes:
The first circuit 100 is configured to collect a resonant capacitor voltage Vcr of the resonant converter 400, obtain a resonant capacitor voltage sampling signal vcr_sns, and output the resonant capacitor voltage sampling signal vcr_sns; adjusting the central value of the resonance capacitor voltage sampling signal Vcr_sns; sampling and compensating the output voltage Vo of the resonant converter 400; setting and outputting a high-side threshold signal vcr_hs and a low-side threshold signal vcr_ls; comparing and analyzing the resonance capacitor voltage sampling signal Vcr_sns to generate a resonance capacitor voltage comparison signal Vcr_mid_cmp; detecting the high-low level time length of the resonance capacitor voltage comparison signal Vcr_mid_cmp, and outputting a marking signal Vcr_high_low_blc with approximately equal time length capable of reflecting the high-low level time length; the falling edge of the resonance capacitor voltage comparison signal vcr_mid_cmp is detected and a count value ncr_mid_cmp is output.
The first circuit 100 of the present application has a voltage offset function, and can offset the center value of the collected ac voltage to a desired voltage value.
The second circuit 200 is respectively connected with the first circuit 100 and the soft start working phase control module 300, and is controlled by the soft start working phase control module 300, and a high-side conduction time starting value ontime_hs_set, a maximum value ontime_max and a minimum value ontime_min of the high-side and low-side conduction time during soft start are set; comparing the resonance capacitor voltage sampling signal Vcr_sns, the high-side threshold signal Vcr_hs and the low-side threshold signal Vcr_ls to generate a high-side power tube turn-off signal vth_hs_off and a low-side power tube turn-off signal vtl _ls_off respectively; and outputting a high-side driving signal and a low-side driving signal according to the high-side power tube turn-off signal vth_hs_off, the low-side power tube turn-off signal vtl _ls_off, the high-side on time starting value ontime_hs_set, the maximum value ontime_max and the minimum value ontime_min of the high-side on time, wherein the high-side driving signal is used for driving the high-side power tube of the resonant converter 400, and the low-side driving signal is used for driving the low-side power tube of the resonant converter 400.
The soft start working phase control module 300 is respectively connected with the first circuit 100 and the second circuit 200 and is used for controlling the first circuit 100 and the second circuit 200 to control the first circuit 100 to adjust the resonance capacitor voltage sampling signal vcr_sns to a set value in a first time period; to control the first circuit 100 to set and output the high-side threshold signal vcr_hs and the low-side threshold signal vcr_ls during the second period, and to control the second circuit 200 to set the high-side on-time start value ontime_hs_set, the maximum value ontime_max and the minimum value ontime_min of the high-side on-time at the time of soft start; to control the second circuit 200 to increase the high-side on-time start value ontime_hs_set in the third period until receiving the high-side power tube turn-off signal vth_hs_off; to control the first circuit 100 to increase the high-side threshold signal vcr_hs and to decrease the low-side threshold signal vcr_ls by the same magnitude for the fourth period.
Example 2
An embodiment of the application provides a soft start control circuit of a resonant converter, which is used for reducing voltage and current stress in the starting process of the resonant converter, enabling output voltage to slowly rise to a reference value, simultaneously realizing cycle-by-cycle zero voltage conduction characteristic of a power tube, avoiding abrupt change of a hard switch and starting end time of the power tube, and improving system stability.
In the embodiment of the present application, the resonant converter 400 is described by taking an LLC half-bridge resonant converter as an example, and the resonant converter 400 of the soft start control circuit of the resonant converter of the present application is not limited to the LLC half-bridge resonant converter.
Next, a soft start control circuit of a resonant converter of the present application will be described, and fig. 2 is a schematic structural diagram of the soft start control circuit of the resonant converter provided in embodiment 2 of the present application, as shown in fig. 2, where the soft start control circuit of the resonant converter of the present application includes:
the LLC half-bridge resonant converter 400 is composed of an input source Vin, two power transistors Q1 and Q2, a transformer Tr, leakage inductance Lr, an excitation inductance Lm, a resonant capacitor Cr, rectifier diodes Ds1 and Ds2, an output capacitor Co and an output resistor RL. Wherein the leakage inductance Lr and the excitation inductance Lm may be integrated into the transformer Tr. The output of the LLC half-bridge resonant converter 400 of the present application includes a resonant capacitor voltage Vcr and an output voltage Vo.
The first circuit 100 is configured to sample a resonant capacitor voltage of the resonant converter 400 to obtain and output a resonant capacitor voltage sampling signal vcr_sns, adjust a center value of the resonant capacitor voltage sampling signal vcr_sns, and set and output a high-side threshold signal vcr_hs and a low-side threshold signal vcr_ls;
In the present embodiment, the first circuit 100 includes:
the capacitance-voltage sampling module 101 is configured to collect a resonance capacitance voltage Vcr, sample a signal vcr_sns for the resonance capacitance voltage, and output the signal vcr_sns.
Exemplary, specific circuits of the capacitor voltage sampling module 101 are shown in fig. 3, and the capacitor voltage sampling module 101 obtains a resonant capacitor voltage sampling signal vcr_sns after dividing the resonant capacitor voltage Vcr by a capacitor resistor network.
The capacitance-voltage average value detection and control module 102 is configured to compare and analyze the resonance capacitance voltage sampling signal vcr_sns to generate a resonance capacitance voltage comparison signal vcr_mid_cmp; the output current adjustment signal icr_mid_reg adjusts the center value of the resonant capacitor voltage sampling signal vcr_sns, receiving the resonant capacitor voltage center value adjustment signal vcr_mid_reg.
In this embodiment of the present application, the capacitor voltage average value detection and control module 102 has a voltage offset function, and can offset the central value of the collected ac voltage to the required voltage value.
Exemplary, the specific circuit of the capacitor voltage average value detection and control module 102 is shown in fig. 3, and changes the magnitude of the resonant capacitor voltage center value adjustment signal vcr_mid_reg according to the duration of the high-low level of the resonant capacitor voltage comparison signal vcr_mid_cmp, and changes the magnitude of the current adjustment signal icr_mid_reg after being output to the voltage-controlled current source through the DAC. When the high level duration of vcr_mid_cmp is longer than the low level duration, the resonance capacitor voltage center value adjusting signal vcr_mid_reg_dig is reduced, the current adjusting signal icr_mid_reg is reduced, and the capacitor voltage sampling signal vcr_sns is reduced after the current adjusting signal icr_mid_reg is superimposed on the lower end resistor in the capacitor voltage sampling module 101; conversely, when the high level duration is shorter than the low level duration, the resonant capacitor voltage center value adjustment signal vcr_mid_regulation_dig is increased, the current adjustment signal icr_mid_regulation is increased, and the capacitor voltage sampling signal vcr_sns is increased after the current adjustment signal icr_mid_regulation is superimposed on the lower end resistor in the capacitor voltage sampling module 101. Vcr_mid_cmp can be adjusted to the initial set value of the resonant capacitor voltage through repeated adaptive adjustment over multiple cycles. The initial set value of the resonant capacitor voltage can be selected as the initial value vcr_sns_init of the resonant capacitor voltage center value adjustment voltage or the central stable value vcr_mid_stable of the resonant capacitor voltage by the selection signal vcr_sns_init_sel signal.
The high-low level detection module 103 is configured to detect the high-low level duration of the resonant capacitor voltage comparison signal vcr_mid_cmp, compare the two durations, and output a flag signal vcr_high_low_blc that can reflect that the high-low level duration is approximately equal to the soft start working phase control module 300.
The edge detection and counting module 104 is configured to detect a falling edge of the resonant capacitor voltage comparison signal vcr_mid_cmp, and output a count value ncr_mid_cmp to the soft start operation phase control module 300.
An output sampling and compensation circuit 105 for sampling and compensating the output voltage Vo of the resonant converter 400 to generate an output compensation signal vout_comp;
and the isolation circuit 106 is used for isolating the primary side from the secondary side, and receiving the output compensation signal Vout_comp to form an output feedback signal Vfb.
The capacitance voltage threshold and initial value control operation module 107 is configured to set a comparison threshold of the resonant capacitance voltage sampling signal vcr_sns, output a high-side threshold signal vcr_hs and a low-side threshold signal vcr_ls, and set a central value adjustment voltage initial value vcr_sns_init; and receives feedback signal Vfb to calculate a voltage threshold difference.
It will be appreciated that the central value adjusted voltage initial value vcr_sns_init is used to set the stable position of the resonant capacitor voltage sampling signal vcr_sns during the first period of soft start, and of course, this function is effective and needs to be matched with the selection signal vcr_sns_init_sel in the capacitor voltage average detection and control module 102.
It should be noted that the voltage threshold difference is used for closed loop control.
The second circuit 200 is respectively connected with the first circuit 100 and the soft start working phase control module 300, and is controlled by the soft start working phase control module 300, and the high-side conduction time length ontime_hs_set, the maximum value ontime_max and the minimum value ontime_min of the high-side and low-side conduction time during soft start are set; comparing the resonance capacitor voltage sampling signal Vcr_sns, the high-side threshold signal Vcr_hs and the low-side threshold signal Vcr_ls to generate a high-side power tube turn-off signal vth_hs_off and a low-side power tube turn-off signal vtl _ls_off respectively; and outputting a high-side driving signal and a low-side driving signal according to the high-side power tube turn-off signal vth_hs_off, the low-side power tube turn-off signal vtl _ls_off, the high-side on time length ontime_hs_set, the maximum value ontime_max and the minimum value ontime_min of the high-side on time and the low-side on time, wherein the high-side driving signal is used for driving the high-side power tube of the resonant converter 400, and the low-side driving signal is used for driving the low-side power tube of the resonant converter 400.
In the present embodiment, the second circuit 200 includes:
the on-time control and operation module 201 receives the control of the soft start working phase control module 300, and sets the high-side on-time length ontime_hs_set, the maximum value ontime_max and the minimum value ontime_min of the high-side and low-side on-time length on time_hs_set during soft start.
The threshold comparison circuit 202 receives and compares the resonance capacitor voltage sampling signal vcr_sns, the high side threshold signal vcr_hs, and the low side threshold signal vcr_ls, and generates a high side power transistor off signal vth_hs_off and a low side power transistor off signal vtl _ls_off, respectively.
Exemplary, specific circuits of the threshold comparison circuit 202 are shown in fig. 3, the threshold comparison circuit 202 is composed of two comparators, a first comparator for outputting a high-side power-tube off signal vth_hs_off and a second comparator for outputting a low-side power-tube off signal vtl _ls_off. When the resonance capacitor voltage sampling signal Vcr_sns is higher than the high-side threshold signal Vcr_hs, the first comparison outputs a high-level signal, and otherwise, outputs a low-level signal; when the resonance capacitor voltage sampling signal Vcr_sns is lower than the low-side threshold signal Vcr_ls, the second comparison outputs a high-level signal, and otherwise, outputs a low-level signal; the high-level state of the high-side power tube turn-off signal vth_hs_off and the low-side power tube turn-off signal vtl _ls_off can be used for turn-off control of the high-side power tube and the low-side power tube.
The PWM switch control module 203 is configured to receive the high-side power tube turn-off signal vth_hs_off, the low-side power tube turn-off signal vtl _ls_off, the high-side on time start value ontime_hs_set, the high-side on time maximum value ontime_max and the high-side low on time minimum value ontime_min, and generate a high-side drive control signal gatehs_pre and a low-side drive control signal gatehs_pre;
In the present embodiment, the PWM switch control module 203 has a high-low side dead zone setting function inside, or implements adaptive dead zone insertion according to an external zero-voltage on detection function.
In this embodiment, the switching process of the high-low side power transistor is as follows:
the turn-off time of the high-side power tube is controlled by the turn-off signal vth_hs_off of the high-side power tube and the initial value of the high-side turn-on time starting value ontime_hs_set respectively in different stages, and is limited by the minimum value ontime_min and the maximum value ontime_max of the high-side and low-side turn-on time.
The high side turn-off is turned on when the dead time or zero voltage turn-on signal is active.
The turn-off time of the low-side power tube is controlled by the low-side power tube turn-off signal vtl _ls_off, the high-side and low-side turn-on time minimum value ontime_min and the turn-on time maximum value ontime_max.
The low side turn-off is through dead time or the high side power tube is turned on when the zero voltage on signal is active.
The driving circuit 204 is connected to the PWM switch control module 203, and is configured to receive the high-side driving control signal gatehs_pre and the low-side driving control signal gatehs_pre, and output the high-side driving signal gatehs and the low-side driving signal gatehs.
The soft start working phase control module 300 is respectively connected with the first circuit 100 and the second circuit 200, and is used for controlling the first circuit 100 and the second circuit 200 to control the first circuit 100 to adjust the resonance capacitor voltage sampling signal vcr_sns to a set central value adjusting voltage initial value vcr_sns_init in a first time period; to control the first circuit 100 to set and output the high-side threshold signal vcr_hs and the low-side threshold signal vcr_ls during the second period of time, and to control the second circuit 200 to set the start value of the high-side on-time start value ontime_hs_set, the on-time maximum value ontime_max, and the on-time minimum value ontime_min at the time of soft start; to control the second circuit 200 to increase the high-side on-time start value on_hs_set in the third period until receiving the high-side power transistor off signal vth_hs_off; to control the first circuit 100 to increase the high-side threshold signal vcr_hs and to decrease the low-side threshold signal vcr_ls by the same magnitude for the fourth period, the two threshold increases and decreases by exactly the same amount in one cycle. The high-low side power tube is controlled to be turned off by the high-low side power tube turn-off signal vtl_ls_off in the stage.
In the present embodiment, the first period is a period from the start of soft start to the end of the first set time tss_stag1; the second time period is a time period when the count value Ncr_mid_cmpn reaches the set value n or the second set time is finished after the first time period; the third time period is a time period before the flag signal vcr_high_low_blc is valid after the second time period, or a time period until a third set time is over; the fourth period is a period before the difference between the high-side threshold signal vcr_hs and the low-side threshold signal vcr_ls is greater than the voltage threshold difference calculated from the feedback signal Vfb after the third period.
Referring to fig. 4, the working process and working waveforms of the soft start control circuit of the resonant converter of the present application are as follows:
in the first period of time, when the soft start starts, the soft start working phase control module 300 outputs a first control signal ss_stage1_flag, controls the capacitor voltage threshold and initial value control operation module 107 to set a central value adjusting voltage initial value vcr_sns_init, controls the capacitor voltage average value detection and control module 102 to set an initial value of a current adjusting signal icr_mid_regu, and starts to adjust the magnitude of the current adjusting signal icr_mid_regu according to the high and low level duration condition of the resonant capacitor voltage comparison signal vcr_mid_cmp, and adjusts the central value of the resonant capacitor voltage sampling signal vcr_sns to the set central value adjusting voltage initial value vcr_sns_init. When the phase timer is greater than the set first set time tss_stag1, the phase ends and the second period of time is entered.
As shown in fig. 4, the first period, i.e., the capacitor voltage sampling value precharge phase, is a phase in which the soft start signal soft_start is pulled high, the ss_stage1_flag first control signal is pulled high, the resonant capacitor voltage sampling signal vcr_sns is 0, the resonant capacitor voltage comparison signal vcr_mid_cmp is set to 0, icr_mid_regu increases from the beginning, and vcr_sns rises and remains constant when rising to vcr_sns_init. The driving is not started in this stage, and when the time is longer than the first set time tss_stage1, the first period ends.
Referring to fig. 5-7, in the first period of time, the central value adjustment voltage initial value vcr_sns_init may be set according to different situations, where the central value adjustment voltage initial value vcr_sns_init may be higher than, equal to, and smaller than the stable value vcr_mid_init. And in the second time period, smooth transition can be realized, and no abrupt voltage circuit change occurs.
In the second period, the soft start working phase control module 300 outputs a second control signal ss_stage2_flag to control the on-time control and operation module 201, and sets a high-side on-time start value ontime_hs_set, a high-side on-time minimum value ontime_min and a high-side on-time maximum value ontime_max; the control capacitor voltage threshold and initial value control operation module 107 sets the high side threshold signal vcr_hs and the low side threshold signal vcr_ls. In this stage, the PWM switching control module 203 starts generating the high-side driving control signal gatehs_pre and the low-side driving control signal gatehs_pre by receiving the signals.
The turn-off time of the high-side power tube is determined by a high-side turn-on time start value ontime_hs_set, a high-side turn-on time minimum value ontime_min and a high-side turn-on time maximum value ontime_max, and the turn-off time of the low-side power tube is determined by a low-side power tube turn-off signal vtl _hs_off, a high-side turn-on time minimum value ontime_min and a high-side turn-on time maximum value ontime_max. When the soft start operation phase control module 300 detects that the count value ncr_mid_cmpn output by the edge detection and counting module 104 reaches the set value n or when the phase timer is greater than the set second set time tss_stage2, the phase ends and enters the third phase.
As shown in fig. 4, in the second period, i.e. the valley correction phase of the capacitor voltage sampling value, the second control signal ss_stage2_flag is pulled high to drive the start-up signal, the high-side power transistor turn-off time is mainly determined by the high-side turn-on time start value ontime_hs_set, and the low-side turn-off time is controlled by the low-side power transistor turn-off signal vtl _ls_off. The high-side on-time start value ontime_hs_set remains unchanged in this phase. This phase ends when the count value ncr_mid_cmpn is detected to be equal to the set value n or the timer count time is longer than the second set time tss_stage2.
In the third period, the soft start working phase control module 300 outputs a third control signal ss_stage3_flag, controls the on-time control and operation module 201 to increase the high-side on-time starting value on time hs_set, and when the high-side power tube off signal vth_hs_off is increased to reach the high-side on-time setting signal in advance, the high-side power tube is turned off by the high-side power tube off signal vth_hs_off. The low side power tube control logic is unchanged. In this period, whether or not the phase is ended is determined by whether or not the flag signal vcr_high_low_blc output from the high/low level detection block 103 is valid. When the signal is valid or if the timer time is longer than the set time tss_stag3, the phase ends and the fourth phase is entered.
As shown in fig. 4, in the third period, i.e., the central balance phase of the capacitor voltage sampling value, the third control signal ss_stage3_flag is pulled high, and the soft start operation phase control module 300 controls to increase the high-side on-time start value on time hs_set, so that the low-side control logic is unchanged. When the high-side power tube turn-off signal vth_hs_off is detected to arrive earlier than the high-side on-time start value ontime_hs_set, the high-side on-time start value ontime_hs_set stops increasing, and thereafter, the turn-off time of the high-side power tube is controlled by the high-side power tube turn-off signal vth_hs_off. When the detection flag signal vcr_high_low_blc is active, the period ends.
In a fourth period, the soft start working phase control module 300 outputs a fourth control signal ss_stage4_flag, and the control capacitor voltage threshold and initial value control operation module 107 starts to increase the high side threshold signal vcr_hs and decrease the low side threshold signal vcr_ls, wherein the increase and decrease amounts of the two thresholds are identical in one period. The high-low side power tube is controlled to be turned off by the high-low side power tube turn-off signal in the stage. As the difference between the two thresholds increases, the output power increases and the output voltage slowly rises. When the voltage threshold difference value of the high side and the low side is larger than the voltage threshold difference value calculated by the feedback signal VFB, the soft start is finished, the loop starts closed loop control, and the output voltage is stabilized.
As shown in fig. 4, the fourth period of time, i.e., the capacitor voltage threshold increasing phase, the soft start operation phase control module 300 controls to increase the high side threshold vcr_hs and decrease the low side threshold vcr_ls from the central value at the same time, and when the threshold voltage increases to be greater than the voltage threshold difference value calculated by the feedback signal Vfb, the soft start is ended, and thereafter, the control loop takes over, starts the closed loop control, and stabilizes the output voltage.
Example 3
In one embodiment of the present application, a soft start control chip of a resonant converter is provided, including a soft start control circuit of a resonant converter as described above.
The above description is only illustrative of some of the embodiments of the present application and of the principles of the technology employed. It will be appreciated by persons skilled in the art that the scope of the disclosure referred to in this application is not limited to the specific combinations of features described above, but it is intended to cover other embodiments in which any combination of features described above or equivalents thereof is possible without departing from the spirit of the disclosure. Such as the above-described features and technical features having similar functions (but not limited to) disclosed in the present application are replaced with each other.
Moreover, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the present application. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are example forms of implementing the claims.

Claims (11)

1. A soft start control circuit for a resonant converter, comprising:
the first circuit is used for collecting the resonance capacitor voltage of the resonance converter to obtain a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal; adjusting the central value of the resonant capacitor voltage sampling signal; sampling and compensating the output voltage of the resonant converter; setting and outputting a high-side threshold signal and a low-side threshold signal; comparing and analyzing the resonant capacitor voltage sampling signals to generate resonant capacitor voltage comparison signals; detecting the high-low level time length of the resonant capacitor voltage comparison signal, and outputting a mark signal which can reflect that the high-low level time length is approximately equal; detecting the falling edge of the resonant capacitor voltage comparison signal and outputting a count value;
the second circuit is controlled by the control module in the soft start working stage, sets a high-side conduction time starting value, a high-side conduction time and a low-side conduction time maximum value and a high-side conduction time minimum value in soft start, and generates a high-side power tube turn-off signal and a low-side power tube turn-off signal according to the resonant capacitor voltage sampling signal, the high-side threshold signal and the low-side threshold signal; outputting a high-side driving signal and a low-side driving signal according to the high-side power tube turn-off signal, the low-side power tube turn-off signal, the high-side turn-on time starting value, the high-low side turn-on time maximum value and the high-low side turn-on time minimum value;
The soft start working stage control module is used for controlling the first circuit and the second circuit to work, carrying out state detection and mode control on each stage of soft start, and controlling the first circuit to adjust the resonant capacitor voltage sampling signal to a set central value adjusting voltage initial value in a first time period; controlling the first circuit to set and output a high-side threshold signal and a low-side threshold signal in a second time period, and controlling the second circuit to set a high-side conduction time starting value, a high-side and low-side conduction time maximum value and a high-side and low-side conduction time minimum value; controlling the second circuit to increase the high-side on time until a high-side power tube off signal is received in a third time period; to control the first circuit to increase the high side threshold signal and to decrease the low side threshold signal by the same magnitude for a fourth period of time;
the first time period is a time period from the start of soft start to the end of a first set time; the second time period is a time period when the count value reaches a set value or a second set time is ended after the first time period; the third time period is a time period before the flag signal is valid after the second time period; and the fourth time period is a time period before the difference value of the high-side threshold signal and the low-side threshold signal is larger than the voltage threshold value difference value calculated by the feedback signal after the third time period.
2. The soft start control circuit of a resonant converter of claim 1, wherein the high side drive signal is used to drive a high side power tube of the resonant converter; the low-side driving signal is used for driving a low-side power tube of the resonant converter.
3. The soft start control circuit of a resonant converter of claim 1, wherein the first circuit comprises:
the capacitor voltage sampling module is used for collecting the resonance capacitor voltage, generating a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal;
an output sampling and compensating circuit for sampling and compensating the output voltage of the resonant converter to generate an output compensating signal;
the capacitance voltage average value detection and control module generates a resonance capacitance voltage comparison signal according to the resonance capacitance voltage sampling signal;
the capacitor voltage threshold and initial value control operation module is used for setting a comparison threshold of the resonant capacitor voltage sampling signal and outputting a high-side threshold signal and a low-side threshold signal;
the high-low level detection module is used for detecting the high-low level duration of the resonant capacitor voltage comparison signal and outputting a sign signal with equal high-low level duration;
And the edge detection and counting module is used for detecting the falling edge of the resonant capacitor voltage comparison signal and outputting a count value.
4. The soft start control circuit of a resonant converter of claim 1, wherein the first circuit further comprises: and the isolation circuit isolates the primary side from the secondary side and transmits the output compensation signal to the primary side to form an output feedback signal.
5. The soft start control circuit of a resonant converter of claim 1, wherein the capacitance-to-voltage average detection and control module outputs a current adjustment signal that adjusts a center value of the resonant capacitance-to-voltage sampling signal.
6. The soft start control circuit of the resonant converter of claim 4, wherein the capacitor voltage threshold and initial value control operation module sets a central value adjustment voltage initial value and calculates a voltage threshold difference value according to the feedback signal.
7. The soft start control circuit of a resonant converter of claim 1, wherein the second circuit comprises:
the threshold comparison circuit is used for comparing the resonant capacitor voltage sampling signal, the high-side threshold signal and the low-side threshold signal to generate a high-side power tube turn-off signal and a low-side power tube turn-off signal;
The on-time control and operation module is controlled by the soft start working stage control module, and a soft start high-side on-time starting value, a high-side on-time maximum value and a high-side off-time minimum value are set;
the PWM switch control module receives the high-side power tube turn-off signal, the low-side power tube turn-off signal, a high-side turn-on time starting value, a high-side turn-on time maximum value, a high-side turn-off time minimum value and a high-side turn-on time minimum value, and generates a high-side drive control signal and a low-side drive control signal;
and the driving circuit generates and outputs a high-side driving signal and a low-side driving signal according to the high-side driving control signal and the low-side driving control signal.
8. A soft start control chip of a resonant converter, characterized by comprising a soft start control circuit of a resonant converter according to any of claims 1-7.
9. A soft start control method of a resonant converter, the method being applied to the soft start control circuit of a resonant converter of any one of claims 1 to 7, comprising:
controlling the first circuit to adjust the resonant capacitor voltage sampling signal to a set central value adjusting voltage initial value;
controlling a first circuit to set and output a high-side threshold signal and a low-side threshold signal, and controlling a second circuit to set a high-side conduction time starting value, a high-side and low-side conduction time maximum value and a high-side and low-side conduction time minimum value;
Controlling the second circuit to increase the high-side on time until receiving a high-side power tube turn-off signal;
the first circuit is controlled to increase the high-side threshold signal and decrease the low-side threshold signal by the same magnitude.
10. The soft start control method of a resonant converter of claim 9, further comprising: and collecting the resonance capacitor voltage of the resonance converter, obtaining a resonance capacitor voltage sampling signal and outputting the resonance capacitor voltage sampling signal.
11. The soft start control method of a resonant converter of claim 9, further comprising: and a step of sampling and compensating the output voltage of the resonant converter to generate an output compensation signal.
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CN107517006A (en) * 2017-09-25 2017-12-26 安徽工程大学 A kind of LLC resonant converter with mixing control and overcurrent protection measure
CN113098281A (en) * 2021-04-13 2021-07-09 东南大学 Variable duty ratio soft start control system applied to quasi-parallel structure converter
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