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CN114499179A - Variable output power DC-DC power supply framework and control method thereof - Google Patents

Variable output power DC-DC power supply framework and control method thereof Download PDF

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Publication number
CN114499179A
CN114499179A CN202210272835.7A CN202210272835A CN114499179A CN 114499179 A CN114499179 A CN 114499179A CN 202210272835 A CN202210272835 A CN 202210272835A CN 114499179 A CN114499179 A CN 114499179A
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reference voltage
comparator
feedback
module
output
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Inventor
郭昌澎
薛若男
夏勤
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Shaanxi Reactor Microelectronics Co ltd
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Shaanxi Reactor Microelectronics Co ltd
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Priority to CN202210272835.7A priority Critical patent/CN114499179A/en
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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
    • H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
    • H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
    • H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC 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
    • H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC 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
    • H02M3/156—Conversion of DC power input into DC power output without intermediate conversion into AC 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 with automatic control of output voltage or current, e.g. switching regulators
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

A variable output power DC-DC power supply framework and a control method thereof comprise a driving module, a switch module, an LC module, a sampling module and a feedback control module. When the output voltage needs to be adjusted to change the power supply of the power supply to the load RL, the corresponding output voltage is adjusted by adjusting the resistance value of the feedback resistor; the first comparator, the second comparator and the third comparator of the feedback control module respectively compare the feedback voltage with the first reference voltage, the second reference voltage and the third reference voltage, output corresponding control signals, control the driving module to open the NMOS power tube in the switch module, accelerate the adjustment of the output voltage and help the power supply framework loop to be quickly reestablished. The invention solves the technical problems of circuit board or integrated chip area waste, high design complexity of the comparator and poor loop stability of the existing DC-DC power supply frame structure, and has the advantages of less DAC number of digital-to-analog conversion units, simple design of the comparator and good loop stability.

Description

Variable output power DC-DC power supply framework and control method thereof
Technical Field
The present invention relates to a DC-DC power architecture and a control method thereof, and more particularly, to a DC-DC power architecture with variable output power and a control method thereof.
Background
Modern electronic industry, especially power electronic products, have wider and wider application scenes based on the DC-DC power supply, and have more severe efficiency requirements on the system level besides the requirement on the efficiency of the DC-DC power supply. For example, for the same electronic product, for different application scenarios and working modes, if the DC-DC power supply can dynamically provide power output of a corresponding level according to actual needs, the power utilization rate of the system can be greatly improved. In a dynamic power supply system, a traditional DC-DC power supply is required to be capable of switching the amplitude of output voltage at any time through a central control unit, and when the system needs high-power output, the DC-DC power supply outputs high voltage; when the system has no strict requirement on the output power, the DC-DC power supply outputs low voltage, thereby achieving the purpose of saving energy of the whole system.
Referring to fig. 1, taking a Buck circuit (Buck converter circuit) as an example, a digital-to-analog conversion unit (DAC), i.e., a first DAC1 in fig. 1, is added on the basis of an ordinary DC-DC power architecture, so that when a system detects that an output voltage Vout needs to be adjusted to change power supply of a power supply to a load RL in a certain mode, a central control unit can issue an instruction through a digital interface to modify a DAC codeword stored in a register, thereby modifying a reference voltage Vref1 at an input end of a first comparator Comp1, and then a loop achieves the purpose of changing the output voltage under the action of negative feedback adjustment.
In order to simplify the circuit, a peripheral auxiliary circuit is omitted in fig. 1, and a first Logic control unit Logic adopts control circuits such as PWM, PFM or COT; the error amplifier EA is used for increasing the loop gain; the first comparator Comp1 is the main loop comparator, completing the negative feedback loop adjustment function; when the load is light, the Buck circuit efficiency is reduced, the output voltage Vout ripple is increased, and the feedback voltage Vfb fluctuation is also increased. To improve efficiency, a second comparator Comp2 is added, whose input reference voltage is set to the second reference voltage Vref2, requiring the second reference voltage Vref2 > the first reference voltage Vref 1. When the feedback voltage Vfb > the second reference voltage Vref2, the first logic control unit is controlled by the comparison result to close the other power consuming part circuits in the loop except the second comparator Comp 2. When the output voltage decreases causing the feedback voltage Vfb to drop below the second reference voltage Vref2, the system loop is again established. Through the dynamic adjustment, the purpose of improving the system efficiency under the condition of light load is achieved, and then the Low-power mode (Low-Iq mode) is adopted, the Driver output of the driving unit is driven under the mode, and the output of the MOS power tube is maintained in a floating state.
However, when the digital-to-analog conversion unit is added on the basis of the ordinary DC-DC power architecture to realize the low power consumption mode, in order to improve the efficiency in the light load state with different output voltages, the second reference voltage Vref2 needs to be changed in the same direction as the first reference voltage Vref1, and the second digital-to-analog conversion unit DAC2 needs to be additionally added, thereby causing the waste of the area of the circuit board or the integrated chip. This disadvantage is more serious when the number of bits of the digital-to-analog conversion unit is larger.
In addition, the DC-DC power architecture has a disadvantage to be overcome: because the loop of the Buck circuit is complex, the output voltage Vout can change in a relatively wide range when the DC-DC power supply architecture performs dynamic output switching. This requires the DAC of the DAC unit to control the corresponding reference voltage to vary within a relatively wide range, which may increase the design complexity of the comparator to a certain extent, for example, the requirement for the input common-mode voltage range is more strict; the drift of the static working point can also influence the loop stability of the power supply system under different output conditions; a series of negative effects are brought on design simulation.
Disclosure of Invention
The invention aims to provide a variable output power DC-DC power supply framework and a control method thereof, which solve the technical problems that the traditional DC-DC power supply framework causes the waste of the area of a circuit board or an integrated chip, the design complexity of a comparator is high, and the loop stability is poor, and have the advantages of small DAC number of digital-to-analog conversion units, simple design of the comparator and good loop stability.
The technical solution of the invention is as follows:
the first variable output power DC-DC power supply framework comprises a driving module Driver, a switch module, an LC module, a sampling module and a feedback control module which are sequentially connected and form a loop; the switch module comprises a PMOS power tube and an NMOS power tube which are connected in sequence; the sampling module comprises a feedback resistor Rf and a gain resistor Rg which are connected in series; the feedback control module comprises a first comparison unit, a second comparison unit and a first Logic control unit Logic; the input ends of the first comparing unit and the second comparing unit are both connected with the feedback voltage Vfb1, and the output ends of the first comparing unit and the second comparing unit are respectively connected with the corresponding input ends of the first logic control unit; the output end of the first Logic control unit Logic is connected with the input end of a Driver of a driving module; the second comparing unit comprises a second comparator comp 2; the first comparison unit comprises an error amplifier EA and a first comparator comp1 which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, and the negative input end of the second comparator comp2 is connected with a second reference voltage Vref 2; the sampling module is characterized by also comprising a digital-to-analog conversion unit DAC; the feedback resistance Rf2 is a digital adjustable resistor; the first reference voltage Vref1 is a fixed value, the second reference voltage Vref2 is a fixed value, and the second reference voltage Vref2 > the first reference voltage Vref 1.
The control method of the first variable output power DC-DC power supply architecture comprises the following steps:
the driving module controls the on-off of the switch module, and the output voltage provides an output voltage Vout1 to the load RL after passing through the LC module;
when the output voltage Vout1 needs to be adjusted to change the power supply of the power supply to the load RL, the central control unit adjusts the resistance value of the feedback resistor Rf in the sampling module through the digital-to-analog conversion unit DAC, and accordingly adjusts the magnitude of the output voltage Vout 1; the first comparator Comp1 of the feedback control module compares the feedback voltage Vfb1 with a first reference voltage Vref1, and the second comparator Comp2 compares the feedback voltage Vfb1 with a second reference voltage Vref 2;
when the feedback voltage Vfb1 is greater than the first reference voltage Vref1 and less than the second reference voltage Vref2, the first comparator comp1 outputs a corresponding negative feedback control signal, and the driving module drives the loop to adjust the output voltage Vout2 under the action of the negative feedback control signal;
when the feedback voltage Vfb1 is greater than the second reference voltage Vref2, the first comparator comp1 outputs a low level; the second comparator Comp2 outputs a low power consumption mode enable signal, and the driving module turns off other power consuming circuits in the power architecture loop except the second comparator under the action of the low power consumption mode enable signal;
when the output voltage drops causing the feedback voltage Vfb1 to drop below the second reference voltage Vref2, the power architecture loop is again established.
The second variable output power DC-DC power supply framework comprises a driving module Driver, a switch module, an LC module, a sampling module and a feedback control module which are sequentially connected and form a loop; the switch module comprises a PMOS power tube and an NMOS power tube which are connected in sequence; the sampling module comprises a feedback resistor Rf and a gain resistor Rg which are connected in series; the feedback control module comprises a first comparison unit, a second comparison unit, a third comparison unit and a first Logic control unit Logic; the input ends of the first comparing unit and the second comparing unit are both connected with the feedback voltage Vfb2, and the output ends of the first comparing unit and the second comparing unit are respectively connected with the corresponding input ends of the first logic control unit; the output end of the first Logic control unit Logic is connected with the input end of a Driver of a driving module; the second comparing unit comprises a second comparator comp 2; the first comparison unit comprises an error amplifier EA and a first comparator comp1 which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, and the negative input end of the second comparator comp2 is connected with a second reference voltage Vref 2; the third comparing unit comprises a third comparator comp3 and a second Logic control unit Logic _2 which are connected in sequence; the positive input end of the third comparator comp3 is connected to the feedback voltage Vfb2, and the negative input end thereof is connected to the third reference voltage Vref 3; the sampling module also comprises a digital-to-analog conversion unit DAC; the feedback resistance Rf is a digital adjustable resistor; the first reference voltage Vref1 is a fixed value, the second reference voltage Vref2 is a fixed value, the third reference voltage Vref3 is a fixed value, and the third reference voltage Vref3 > the peak value of the feedback voltage Vfb2 > the second reference voltage Vref2 > the first reference voltage Vref 1; and an output end Npd of the second Logic control unit Logic _2 is connected with the other input end of the driving module and is used for turning on an NMOS power tube of the switch module.
The second Logic control unit Logic _2 comprises a timing and zero setting circuit Vrcg which are connected in sequence and form a loopen, a fourth comparator comp4, an inverter and a delay circuit Td; wherein, the positive input end of the fourth comparator comp4 is connected with the feedback voltage Vfb2, and the negative input end thereof is connected with the output signal V of the timing and zero setting circuit VrcgenRCThe output end of the delay circuit Td is connected with a zero setting end Vpd of the timing and zero setting circuit Vrcgen; the inverter output signal Npd is connected with the input end of the driving module.
The second control method for the variable output power DC-DC power supply architecture is characterized by comprising the following steps:
the driving module controls the on-off of the switch module;
the driving module controls the on-off of the switch module, and the output voltage provides an output voltage Vout2 to the load RL after passing through the LC module;
when the output voltage Vout2 needs to be adjusted to change the power supply of the power supply to the load RL, the central control unit adjusts the resistance value of the feedback resistor Rf in the sampling module through the digital-to-analog conversion unit DAC, and adjusts the size of the corresponding output voltage Vout 2;
the first comparator Comp1, the second comparator Comp2 and the third comparator Comp3 of the feedback control module compare the feedback voltage Vfb2 with the first reference voltage Vref1, the second reference voltage Vref2 and the third reference voltage Vref3 respectively and output corresponding control signals;
wherein:
when the feedback voltage Vfb2 is greater than the first reference voltage Vref1 and less than the second reference voltage Vref2, the first comparator comp1 outputs a corresponding negative feedback control signal, and the driving module drives the loop to adjust the output voltage Vout2 under the action of the negative feedback control signal;
when the feedback voltage Vfb2 is greater than the second reference voltage Vref2 and less than the third reference voltage Vref3, the first comparator comp1 outputs a low level; the second comparator Comp2 outputs a low power mode enable signal, and the driving module turns off other power consuming circuits in the power architecture loop except for the second comparator and the third comparator Comp3 under the action of the low power mode enable signal;
when the feedback voltage Vfb2 is greater than the third reference voltage Vref3, both the first comparator Comp1 and the second comparator Comp2 output a low level; the output signal of the third comparator Comp3 controls the driving module to turn on the NMOS power transistor in the switch module through the logic circuit, so as to speed up the adjustment of the output voltage Vout2 and help the power supply architecture loop to be quickly reestablished.
The invention has the following beneficial effects:
the power architecture of the invention can give consideration to both the two purposes of dynamic change of output voltage and low power consumption mode tracking and discrimination by only needing one digital-to-analog conversion unit DAC, and simultaneously simplifies the circuit structure, reduces the chip area and reduces the chip power consumption.
The input reference voltage of the comparator in the power supply framework is a fixed value, so that the power consumption can be effectively reduced, the output voltage precision is increased, the design difficulty of the comparator is simplified, and the risk of static operating point drift is reduced.
The second DC-DC power supply framework can remarkably reduce the setup time of the output voltage Vout2 when jumping down, and is beneficial to the stability of the system.
The invention has universality and is suitable for various DC-DC power supply architectures.
The invention solves the technical problems that the prior DC-DC power supply framework causes the waste of the area of a circuit board or an integrated chip, the design complexity of the comparator is high, and the loop stability is poor, and has the advantages of less DAC (digital-to-analog conversion) units, simple design of the comparator and good loop stability.
Drawings
FIG. 1 is a schematic diagram of a conventional variable output DC-DC power supply architecture;
FIG. 2 is a schematic diagram of a first variable output DC-DC power supply architecture according to the present invention;
FIG. 3 is a schematic diagram of a second variable output DC-DC power supply architecture according to the present invention;
FIG. 4 is a schematic diagram illustrating the relationship between the active phases and the reference voltages of each comparator in a second variable output DC-DC power supply architecture according to the present invention;
FIG. 5 is a schematic diagram of a second method for controlling successive turn-on of an NMOS power transistor switch in a DC-DC power architecture with variable output power according to the present invention when Vfb2 > Vref 3;
FIG. 6 is a schematic block diagram of a second logic control unit in a second variable output power DC-DC power architecture according to the present invention;
FIG. 7 is a diagram illustrating a comparison of waveforms of key nodes in a first power architecture and a second power architecture according to the present invention.
Detailed Description
The first variable output power DC-DC power supply architecture, see fig. 2, is substantially the same as the conventional variable output power DC-DC power supply architecture except that the first power supply architecture of the present invention places the digital-to-analog conversion unit DAC that adjusts the output voltage Vout1 on the output feedback resistor Rf.
The invention relates to a variable output power DC-DC power supply framework, which comprises a driving module Driver, a switch module, an LC module, a sampling module and a feedback control module which are sequentially connected and form a loop; the switch module comprises a PMOS power tube and an NMOS power tube which are connected in sequence; the sampling module comprises a feedback resistor Rf and a gain resistor Rg which are connected in series; the feedback control module comprises a first comparison unit, a second comparison unit and a first Logic control unit Logic; the first comparison unit and the second comparison unit are connected in parallel, and output ends of the first comparison unit and the second comparison unit are connected with corresponding input ends of the first logic control unit; the output end of the first Logic control unit Logic is connected with the input end of a Driver of a driving module; the second comparing unit comprises a second comparator comp 2; the first comparison unit comprises an error amplifier EA and a first comparator comp1 which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, and the negative input end of the second comparator comp2 is connected with a second reference voltage Vref 2; the sampling module is characterized by also comprising a digital-to-analog conversion unit DAC; the feedback resistor Rf is a digital adjustable resistor, the resistance value control end of the feedback resistor Rf is connected with a digital decoder, and a digital signal is used as a control signal to adjust the resistance value of the feedback resistor Rf; the first reference voltage Vref1 is a fixed value, the second reference voltage Vref2 is a fixed value, and the second reference voltage Vref2 > the first reference voltage Vref 1.
Wherein, the first comparing unit may further adopt the following alternative structure: the device comprises an error amplifier EA, a first comparator comp1 and an inverter which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, the positive input end of the second comparator comp2 is connected with a second reference voltage Vref2, and the output end of the second comparator comp2 is connected with the input end of the inverter.
The invention also provides a control method of the first variable output power DC-DC power supply architecture, which comprises the following steps:
the driving module controls the on-off of the switch module;
the switch module controls the power supply to provide the output voltage Vout2 to the load RL in one half cycle, and the capacitor Cs in the LC module provides the output voltage Vout2 to the load RL in the other half cycle;
when the output voltage Vout1 needs to be adjusted to change the power supply of the power supply to the load RL, the central control unit adjusts the resistance value of the feedback resistor Rf in the sampling module through the digital-to-analog conversion unit DAC, and accordingly adjusts the magnitude of the output voltage Vout 1; the first comparator Comp1 of the feedback control module compares the feedback voltage Vfb1 with the first reference voltage Vref1, and the second comparator Comp2 compares the feedback voltage Vfb with the second reference voltage Vref 2;
when the feedback voltage Vfb is greater than the first reference voltage Vref1, the first comparator comp1 outputs a corresponding negative feedback control signal, and the driving module drives the loop to adjust the output voltage Vout1 under the action of the negative feedback control signal;
when the feedback voltage Vfb1 is greater than the second reference voltage Vref2, the second comparator Comp2 outputs a low power consumption mode enable signal, and the driving module turns off other power consuming circuits in the power architecture loop except the second comparator under the action of the low power consumption mode enable signal;
when the output voltage drops causing the feedback voltage Vfb to drop below the second reference voltage Vref2, the power architecture loop is again established.
The first power architecture of the present invention has the following two advantages: 1) the power supply architecture only needs one digital-to-analog conversion unit DAC to achieve two purposes of dynamic change of output voltage and low power consumption mode tracking judgment; 2) the input reference voltage of the comparator is a fixed value, so that the design difficulty of the comparator can be reduced, the power consumption of a system can be effectively reduced, and the precision of the output voltage can be increased.
However, the power supply architecture has a disadvantage: when the resistance of the feedback resistor Rf is changed from large to small by the DAC code word, due to the slow change rate of the output voltage Vout1, at the instant of DAC state switching of the digital-to-analog conversion unit, a transient current larger than a current flowing through the gain resistor Rg is generated at both ends of the feedback resistor Rf, so that a node voltage of the feedback voltage Vfb1 has a large overshoot. This node is a high-impedance node, which causes the node voltage recovery process of the feedback voltage Vfb1 to be too long, resulting in a longer settling time when the output voltage Vout1 switches from high to low. Since such overshoot of the feedback voltage Vfb1 tends to be larger than the second reference voltage Vref2, which triggers the low power consumption mode, i.e., the loop regulation mode is actively turned off, so that the loop loses the NMOS power transistor pull-down regulation capability, and the settling time during the switching of the output voltage Vout1 is deteriorated to an unacceptable level.
When the output voltage Vout1 switches to a high voltage, the system will not go into a low power mode at all. Although the feedback voltage Vfb1 is still a high-resistance node, the system settling time is rather short under the action of the loop negative feedback. Therefore, only the digital-to-analog conversion unit DAC needs to be considered to control the output voltage down-jump process, in the process, how to eliminate or reduce the influence caused by the deficiency does not hinder the normal entering of the low power consumption mode in the light load state, and the establishment time of the system power down-jump can meet the performance requirement, so that the problem to be solved by the framework is solved.
In order to overcome the above disadvantages, a second variable output power DC-DC power architecture is provided, which includes a Driver, a switch module, an LC module, a sampling module and a feedback control module, which are connected in sequence and form a loop, as shown in fig. 3; the switch module comprises a PMOS power tube and an NMOS power tube which are connected in sequence; the sampling module comprises a feedback resistor Rf and a gain resistor Rg which are connected in series; the feedback control module is characterized by comprising a first comparison unit, a second comparison unit, a third comparison unit and a first Logic control unit Logic; the first comparison unit and the second comparison unit are connected in parallel, and output ends of the first comparison unit and the second comparison unit are connected with corresponding input ends of the first logic control unit; the output end of the first Logic control unit Logic is connected with the input end of a Driver of a driving module; the second comparing unit comprises a second comparator comp 2; the first comparison unit comprises an error amplifier EA and a first comparator comp1 which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, and the negative input end of the second comparator comp2 is connected with a second reference voltage Vref 2; the third comparing unit comprises a third comparator comp3 and a second Logic control unit Logic _2 which are connected in sequence; the positive input end of the third comparator comp3 is connected to the feedback voltage Vfb2, and the negative input end thereof is connected to the third reference voltage Vref 3; or, the third comparing unit comprises a third comparator comp3, a second Logic control unit Logic _2 and an inverter which are connected in sequence; the negative input end of the third comparator comp3 is connected with the feedback voltage Vfb, the positive input end thereof is connected with the third reference voltage Vref3, and the output end thereof is connected with the input end of the inverter; the sampling module also comprises a digital-to-analog conversion unit DAC; the feedback resistor Rf is a digital adjustable resistor, the resistance value control end of the feedback resistor Rf is connected with a digital decoder, and a digital signal is used as a control signal to adjust the resistance value of the feedback resistor Rf; the first reference voltage Vref1 is a fixed value, the second reference voltage Vref2 is a fixed value, the third reference voltage Vref3 is a fixed value, and the third reference voltage Vref3 > the peak value of the feedback voltage Vfb2 > the second reference voltage Vref2 > the first reference voltage Vref 1; and the output end of the second Logic control unit Logic _2 is connected with the input end of the driving module and is used for turning on an NMOS power tube of the switch module.
Wherein, the first comparing unit may further adopt the following alternative structure: the device comprises an error amplifier EA, a first comparator comp1 and an inverter which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, the positive input end of a second comparator comp2 is connected with a second reference voltage Vref2, and the output end of the second comparator comp2 is connected with the input end of the inverter;
the second Logic control unit Logic _2 specifically comprises a timing and zero setting circuit Vrcgen, a fourth comparator comp4 and a delay circuit, which are connected in sequence and form a loop; the negative input end of the fourth comparator comp4 is connected with the sampling voltage of the output voltage Vout2, and the positive input end thereof is connected with the output signal Vrc of the timing and zero setting circuit Vrcgen; or, the second Logic control unit Logic _2 includes a timing and zero setting circuit Vrcgen, a fourth comparator comp4, an inverter and a delay circuit, which are connected in sequence and form a loop; the positive input end of the fourth comparator comp4 is connected with the sampling voltage of the output voltage Vout2, and the negative input end thereof is connected with the output signal Vrc of the timing and zero setting circuit Vrcgen; the inverter output signal Npd is connected with the input end of the driving module.
The invention also provides a control method of the second variable output power DC-DC power supply architecture, which comprises the following steps:
the driving module controls the on-off of the switch module;
the switch module controls the power supply to provide the output voltage Vout2 to the load RL in one half cycle, and the capacitor Cs in the LC module provides the output voltage Vout2 to the load RL in the other half cycle;
when the output voltage Vout2 needs to be adjusted to change the power supply of the power supply to the load RL, the central control unit adjusts the resistance value of the feedback resistor Rf in the sampling module through the digital-to-analog conversion unit DAC, and adjusts the size of the corresponding output voltage Vout 2;
the first comparator Comp1, the second comparator Comp2 and the third comparator Comp3 of the feedback control module compare the feedback voltage Vfb2 with the first reference voltage Vref1, the second reference voltage Vref2 and the third reference voltage Vref3 respectively and output corresponding control signals;
wherein:
when the feedback voltage Vfb2 is greater than the first reference voltage Vref1, the first comparator comp1 outputs a corresponding negative feedback control signal, and the driving module drives the loop to adjust the output voltage Vout2 under the action of the negative feedback control signal;
when the feedback voltage Vfb2 is greater than the second reference voltage Vref2 and less than the third reference voltage Vref3, the second comparator Comp2 outputs a low power consumption mode enable signal, and the driving module turns off other power consuming circuits in the power architecture loop except for the second comparator and the third comparator Comp3 under the action of the low power consumption mode enable signal;
when the feedback voltage Vfb2 is greater than the third reference voltage Vref3, the output signal of the third comparator Comp3 controls the driving module to turn on the NMOS power transistor in the switch module through the logic circuit, so as to speed up the adjustment of the output voltage Vout2 and help the power supply architecture loop to be quickly reestablished.
The second variable output power DC-DC power supply architecture is capable of distinguishing "the feedback voltage Vfb2 is too high due to too large ripple in the low power consumption mode" and "the feedback voltage Vfb2 overshoot phenomenon caused by the output voltage Vout2 regulated by the digital-to-analog conversion unit DAC", and introduces a new third reference voltage Vref3 for secondary threshold judgment. Fig. 4 shows that in order to ensure that no erroneous determination occurs under any conditions, it is necessary to obtain the peak value of the feedback Voltage Vfb2 corresponding to the maximum ripple in the low power consumption mode through simulation in the range of full PVT (Process, Voltage, Temperature), and then to set the third reference Voltage Vref3 > the peak value of the feedback Voltage Vfb2 > the second reference Voltage Vref 2.
With the above arrangement, when the feedback voltage Vfb2 > the third reference voltage Vref3, the comparator turns on the NMOS power transistor through the control logic, and pulls the output voltage of Vout2 low, so that the sampled voltage at the feedback node of Vfb2 drops below Vref2 quickly, and the adjustment of the output voltage of Vout2 can be accelerated by using the negative feedback characteristic of the loop.
The third comparator Comp3 determines that the NMOS power transistor is not turned on directly to pull down the output voltage Vout 2. Due to the limitation of the loop bandwidth and the excessive driving capability of the NMOS power transistor, the output voltage Vout2 is pulled to be extremely low in a short time due to the continuous strong pull-down, so that the feedback voltage Vfb2 has a large variation range, which affects the loop stability. The solution is to reasonably set up a second Logic control unit Logic _2, and make the second Logic control unit Logic _2 into a successive pull-down form, i.e. the output voltage Vout2 is gradually reduced through a Logic circuit, so as to ensure the smooth change rate of the charging and discharging current at the node of the feedback voltage Vfb2 and the stability of the system. Referring to fig. 5, a second Logic control unit Logic _2 circuit structure corresponding to a Logic output waveform of a second variable output power DC-DC power architecture according to the present invention is shown in fig. 6.
In fig. 6, Vfb2 is a sampled voltage obtained by dividing the output voltage Vout2, VRCIs a ramp voltage obtained by charging a capacitor with a fixed current, and the charging time is TRCA pull-down period equal to about TRC+ Td, where Td is the high pulse width of the control signal Ndrv for the NMOS power transistor in fig. 5. After the second Logic control unit Logic _2 adopts the control circuit shown in fig. 6, the voltage changes of the key nodes such as the system output voltage Vout2 and the feedback voltage Vfb2 are shown in fig. 7. As can be seen from fig. 7, the second variable output power DC-DC power architecture of the present invention can well reduce the settling time of the output voltage Vout2 when it jumps down, and the improvement effect will be different according to different circuit parameter settings. Through actual circuit simulation, the establishment time after the voltage jump can be reduced from about 400us to 60us, the establishment time when the output voltage Vout2 jumps can be obviously reduced, the stability of a system is facilitated, the technical problems that the area of a circuit board or an integrated chip constructed by the conventional DC-DC power supply frame is wasted, the design complexity of a comparator is high, and the stability of a loop is poor can be effectively solved, and the digital-to-analog conversion circuit has the advantages of small DAC number of digital-to-analog conversion units, simple design of the comparator and good stability of the loop.
In addition, in the first power architecture, the first comparing unit may also adopt another implementation manner: the device comprises an error amplifier EA, a first comparator comp1 and an inverter which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, the positive input end of the second comparator comp2 is connected with a second reference voltage Vref2, and the output end of the second comparator comp2 is connected with the input end of the inverter.
In a second power architecture, the first comparing unit and the third comparing unit may also adopt another implementation manner: the first comparison unit comprises an error amplifier EA, a first comparator comp1 and an inverter which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, the positive input end of a second comparator comp2 is connected with a second reference voltage Vref2, and the output end of the second comparator comp2 is connected with the input end of the inverter; the third comparing unit comprises a third comparator comp3, a second Logic control unit Logic _2 and an inverter which are connected in sequence; the negative input of the third comparator comp3 is connected to the feedback voltage Vfb2, the positive input thereof is connected to the third reference voltage Vref3, and the output thereof is connected to the inverter input.

Claims (5)

1. A variable output power DC-DC power supply framework comprises a Driver module, a switch module, an LC module, a sampling module and a feedback control module which are sequentially connected and form a loop;
the switch module comprises a PMOS power tube and an NMOS power tube which are connected in sequence;
the sampling module comprises a feedback resistor Rf and a gain resistor Rg which are connected in series;
the feedback control module comprises a first comparison unit, a second comparison unit and a first Logic control unit Logic;
the input ends of the first comparing unit and the second comparing unit are both connected with the feedback voltage Vfb1, and the output ends of the first comparing unit and the second comparing unit are respectively connected with the corresponding input ends of the first logic control unit;
the output end of the first Logic control unit Logic is connected with the input end of a Driver of a driving module;
the second comparing unit comprises a second comparator comp 2;
the first comparison unit comprises an error amplifier EA and a first comparator comp1 which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, and the negative input end of the second comparator comp2 is connected with a second reference voltage Vref 2;
the method is characterized in that:
the sampling module also comprises a digital-to-analog conversion unit DAC;
the feedback resistance Rf2 is a digital adjustable resistor;
the first reference voltage Vref1 is a fixed value, the second reference voltage Vref2 is a fixed value, and the second reference voltage Vref2 > the first reference voltage Vref 1.
2. A control method of a variable output power DC-DC power supply architecture is characterized by comprising the following steps:
the driving module controls the on-off of the switch module, and the output voltage provides an output voltage Vout1 to the load RL after passing through the LC module;
when the output voltage Vout1 needs to be adjusted to change the power supply of the power supply to the load RL, the central control unit adjusts the resistance value of the feedback resistor Rf in the sampling module through the digital-to-analog conversion unit DAC, and accordingly adjusts the magnitude of the output voltage Vout 1; the first comparator Comp1 of the feedback control module compares the feedback voltage Vfb1 with a first reference voltage Vref1, and the second comparator Comp2 compares the feedback voltage Vfb1 with a second reference voltage Vref 2;
when the feedback voltage Vfb1 is greater than the first reference voltage Vref1 and less than the second reference voltage Vref2, the first comparator comp1 outputs a corresponding negative feedback control signal, and the driving module drives the loop to adjust the output voltage Vout2 under the action of the negative feedback control signal;
when the feedback voltage Vfb1 is greater than the second reference voltage Vref2, the first comparator comp1 outputs a low level; the second comparator Comp2 outputs a low power consumption mode enable signal, and the driving module turns off other power consuming circuits in the power architecture loop except the second comparator under the action of the low power consumption mode enable signal;
when the output voltage drops causing the feedback voltage Vfb1 to drop below the second reference voltage Vref2, the power architecture loop is again established.
3. A variable output power DC-DC power supply framework comprises a driving module Driver, a switch module, an LC module, a sampling module and a feedback control module which are sequentially connected and form a loop;
the switch module comprises a PMOS power tube and an NMOS power tube which are connected in sequence;
the sampling module comprises a feedback resistor Rf and a gain resistor Rg which are connected in series;
the method is characterized in that:
the feedback control module comprises a first comparison unit, a second comparison unit, a third comparison unit and a first Logic control unit Logic; the input ends of the first comparison unit and the second comparison unit are both connected with the feedback voltage Vfb2, and the output ends of the first comparison unit and the second comparison unit are respectively connected with the corresponding input ends of the first logic control unit; the output end of the first Logic control unit Logic is connected with the input end of a Driver of a driving module;
the second comparing unit comprises a second comparator comp 2;
the first comparison unit comprises an error amplifier EA and a first comparator comp1 which are connected in sequence; the positive input end of the error amplifier EA is connected with a first reference voltage Vref1, and the negative input end of the second comparator comp2 is connected with a second reference voltage Vref 2;
the third comparing unit comprises a third comparator comp3 and a second Logic control unit Logic _2 which are connected in sequence; the positive input end of the third comparator comp3 is connected to the feedback voltage Vfb2, and the negative input end thereof is connected to the third reference voltage Vref 3;
the sampling module also comprises a digital-to-analog conversion unit DAC;
the feedback resistance Rf is a digital adjustable resistor;
the first reference voltage Vref1 is a fixed value, the second reference voltage Vref2 is a fixed value, the third reference voltage Vref3 is a fixed value, and the third reference voltage Vref3 > the peak value of the feedback voltage Vfb2 > the second reference voltage Vref2 > the first reference voltage Vref 1;
and an output end Npd of the second Logic control unit Logic _2 is connected with the other input end of the driving module and is used for turning on an NMOS power tube of the switch module.
4. The variable output power DC-DC power supply architecture of claim 3, wherein:
the second Logic control unit Logic _2 comprises a timing and zero setting circuit Vrcgen, a fourth comparator comp4, an inverter and a delay circuit Td which are connected in sequence and form a loop; wherein, the positive input end of the fourth comparator comp4 is connected with the feedback voltage Vfb2, and the negative input end thereof is connected with the output signal V of the timing and zero setting circuit VrcgenRCThe output end of the delay circuit Td is connected with a zero setting end Vpd of the timing and zero setting circuit Vrcgen;
the inverter output signal Npd is connected with the input end of the driving module.
5. A control method of a variable output power DC-DC power supply architecture is characterized by comprising the following steps:
the driving module controls the on-off of the switch module;
the driving module controls the on-off of the switch module, and the output voltage provides an output voltage Vout2 to the load RL after passing through the LC module;
when the output voltage Vout2 needs to be adjusted to change the power supply of the power supply to the load RL, the central control unit adjusts the resistance value of the feedback resistor Rf in the sampling module through the digital-to-analog conversion unit DAC, and adjusts the size of the corresponding output voltage Vout 2;
the first comparator Comp1, the second comparator Comp2 and the third comparator Comp3 of the feedback control module compare the feedback voltage Vfb2 with the first reference voltage Vref1, the second reference voltage Vref2 and the third reference voltage Vref3 respectively and output corresponding control signals;
wherein:
when the feedback voltage Vfb2 is greater than the first reference voltage Vref1 and less than the second reference voltage Vref2, the first comparator comp1 outputs a corresponding negative feedback control signal, and the driving module drives the loop to adjust the output voltage Vout2 under the action of the negative feedback control signal;
when the feedback voltage Vfb2 is greater than the second reference voltage Vref2 and less than the third reference voltage Vref3, the first comparator comp1 outputs a low level; the second comparator Comp2 outputs a low power mode enable signal, and the driving module turns off other power consuming circuits in the power architecture loop except for the second comparator and the third comparator Comp3 under the action of the low power mode enable signal;
when the feedback voltage Vfb2 is greater than the third reference voltage Vref3, both the first comparator Comp1 and the second comparator Comp2 output a low level; the output signal of the third comparator Comp3 controls the driving module to turn on the NMOS power transistor in the switch module through the logic circuit, so as to speed up the adjustment of the output voltage Vout2 and help the power supply architecture loop to be quickly reestablished.
CN202210272835.7A 2022-03-18 2022-03-18 Variable output power DC-DC power supply framework and control method thereof Pending CN114499179A (en)

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