CN111509978A - DC-DC conversion device and power management system - Google Patents
DC-DC conversion device and power management system Download PDFInfo
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- CN111509978A CN111509978A CN202010470722.9A CN202010470722A CN111509978A CN 111509978 A CN111509978 A CN 111509978A CN 202010470722 A CN202010470722 A CN 202010470722A CN 111509978 A CN111509978 A CN 111509978A
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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
- H02M3/158—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 including plural semiconductor devices as final control devices for a single load
- H02M3/1584—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 including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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Abstract
The present application relates to a DC-DC conversion apparatus and a power management system. The device includes: the device comprises an error amplification module, a PWM control module, a PFM control module, a mode selection module, a power conversion module and a load module; the mode selection module is used for obtaining output current, comparing the output current with a preset current critical value to obtain a comparison result, and selecting the PWM control module or the PFM control module to output a corresponding control signal to the power conversion module according to the comparison result so as to control the power conversion module to carry out voltage conversion. According to the device, the output current of the power conversion module is obtained through the mode selection mode, the output current is compared with the preset current critical value to obtain a comparison result, and the PWM control module or the PFM control module is determined and selected according to the comparison result to control the power conversion module to carry out voltage conversion, so that the DC-DC conversion device can adopt different control modules to control the power conversion module to carry out voltage conversion, and the purpose of improving the voltage conversion efficiency is achieved.
Description
Technical Field
The present disclosure relates to power management systems, and particularly to a DC-DC converter and a power management system.
Background
Currently, power management systems have been applied in a variety of different mobile electronic devices, the power management system being composed of multiple parts, and among them the most critical is the DC-DC converter. Most of the traditional DC-DC converters adopt a PWM control mode or a PFM control module, the PWM control mode works under fixed frequency, high-stability and low-ripple voltage can be obtained under the condition of heavy load, and higher conversion efficiency can be obtained; the switching frequency of the PFM control mode is changed along with the load change, and higher conversion efficiency can be obtained under the condition of light load.
However, when the PWM control mode is adopted, if the load current is reduced, the conversion efficiency will be reduced, and when the PFM control mode is under heavy load, the conversion efficiency will be low, so that many power management systems have the problem of low efficiency no matter whether the PWM control mode or the PFM control mode is adopted.
Disclosure of Invention
In view of the above, it is necessary to provide a DC-DC conversion device and a power management system capable of improving efficiency in response to a problem of low voltage conversion efficiency.
A DC-DC conversion apparatus comprising: the device comprises an error amplification module, a PWM control module, a PFM control module, a mode selection module, a power conversion module and a load module; the error amplification module is connected with the PWM control module, the PFM control module and the load module; the PWM control module is connected with the mode selection module and the power conversion module; the PFM control module is connected with the mode selection module and the power conversion module; the power conversion module is connected with the mode selection module and the load module and is also used for connecting an input power supply; the mode selection module is used for obtaining the output current of the power conversion module, comparing the output current with a preset current critical value to obtain a comparison result, selecting the PWM control module or the PFM control module according to the comparison result, and outputting a corresponding control signal to the power conversion module to control the power conversion module to carry out voltage conversion according to the output error of the error amplification module.
According to the DC-DC conversion device, the output current of the power conversion module is obtained through the mode selection mode, the output current is compared with the preset current critical value to obtain the comparison result, and the PWM control module or the PFM control module is determined and selected according to the comparison result to control the power conversion module to carry out voltage conversion, so that the DC-DC conversion device can control the power conversion module to carry out voltage conversion by adopting different control modules, and the purpose of improving the voltage conversion efficiency is achieved.
In one embodiment, the error amplification module comprises an amplifier and a reference voltage source, an inverting input terminal of the amplifier is connected with the reference voltage source, a non-inverting input terminal of the amplifier is connected with the load module, and an output terminal of the amplifier is respectively connected with the PWM control module and the PFM control module.
In one embodiment, the DC-DC conversion apparatus further includes a soft start module, and the soft start module is connected to the start terminal of the amplifier.
In one embodiment, the power conversion module includes a first switch tube and a second switch tube, an input end of the first switch tube is used for connecting an input power supply, a control end of the first switch tube is respectively connected with the PWM control module and the PFM control module, an output end of the first switch tube is connected with an input end of the second switch tube and the load module, a control end of the second switch tube is respectively connected with the PWM control module and the PFM control module, and an output end of the second switch tube is grounded.
In one embodiment, the load module comprises an inductance assembly, an energy storage charging assembly and a voltage dividing resistance assembly, one end of the inductance assembly is connected with the output end of the first switch tube, the other end of the inductance assembly is connected with one end of the energy storage charging assembly and the input end of the voltage dividing resistance assembly, the other end of the energy storage charging assembly is connected with the output end of the second switch tube, the output end of the voltage dividing resistance assembly is connected with the output end of the second switch tube, and the feedback end of the voltage dividing resistance assembly is connected with the error amplification module.
In one embodiment, the first switching tube component and the second switching tube component are both field effect transistors.
In one embodiment, the PFM control module includes a PFM controller and an oscillator, the oscillator is connected to the PFM controller, the PFM controller is connected to the error amplification module, the mode selection module and the power conversion module, and the PFM controller outputs a corresponding control signal to the power conversion module according to an oscillation signal of the oscillator and an output error of the error amplification module to control the power conversion module to perform voltage conversion.
In one embodiment, the PWM control module includes a comparator, a positive input terminal of the comparator is connected to the error amplifying module, a negative input terminal of the comparator is used for accessing a voltage signal with a preset waveform, an output terminal of the comparator is connected to the power converting module, a control terminal of the comparator is connected to the mode selecting module, and the comparator is used for outputting a corresponding control signal to the converting mode according to the voltage signal with the preset waveform and an output error of the error amplifying module to control the power converting module to perform voltage conversion.
A power management system comprises the DC-DC conversion device.
In one embodiment, the power management system further comprises a wireless transceiver, a microcontroller and a sensor, wherein the wireless transceiver, the microcontroller and the sensor are all connected with the DC-DC conversion device.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings needed to be used in the description of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without any creative work;
FIG. 1 is a schematic diagram of a system framework of a DC-DC converter in one embodiment;
FIG. 2 is a schematic diagram of a specific structure of a DC-DC converter according to an embodiment;
FIG. 3 is a schematic diagram of a specific structure of a DC-DC converter according to an embodiment;
FIG. 4 is a schematic diagram of an embodiment of a PFM control module;
fig. 5 is a schematic structural diagram of a PWM control module according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In one embodiment, as shown in fig. 1, there is provided a DC-DC conversion apparatus including an error amplification module 100, a PWM control module 200, a PFM control module 300, a mode selection module 400, a power conversion module 500, and a load module 600; the error amplification module 100 is connected with the PWM control module 200, the PFM control module 300 and the load module 600; the PWM control module 200 is connected to the mode selection module 400 and the power conversion module 500; the PFM control module 300 is connected to the mode selection module 400 and the power conversion module 500; the power conversion module 500 is connected to the mode selection module 400 and the load module 600, and the power conversion module 500 is further used for connecting to an input power source. The mode selection module 400 is configured to obtain an output current of the power conversion module 500, compare the output current with a preset current threshold to obtain a comparison result, and select the PWM control module 200 or the PFM control module 300 according to the comparison result, and output a corresponding control signal to the power conversion module 500 to control the power conversion module 500 to perform voltage conversion according to an output error of the error amplification module 100.
Specifically, the DC-DC conversion refers to DC-DC conversion, when the DC-DC conversion device performs DC-DC conversion, the current output by the input power is converted, that is, the power conversion module 500 implements a process of DC-DC conversion on the current input by the input power, and then the power conversion module 500 outputs the converted current to the load module 600, and the power conversion module 500 is controlled by the PFM control module 300 or the PWM control module 200 in the whole process of DC-DC conversion on the current output by the input power, that is, the PFM control module 300 or the PWM control module 200 outputs a corresponding control signal to the power conversion module 500, so as to control the power conversion module 500 to convert the current input by the input power, and finally output the current from the load module 600.
Further, how to determine that the PFM control module 300 or the PWM control module 200 controls the power conversion module 500 is determined by the mode selection module 400 obtaining the output current of the power conversion module 500 for determination, for example, when the output current of the power conversion module 500 is greater than or equal to a preset current threshold, the PWM control module 200 is selected to control the power conversion module 500, that is, the PFM control module 300 does not work, the PWM control module 200 outputs a corresponding control signal to the power conversion module 500, and controls the power conversion module 500 to perform dc-dc conversion, and when the output current is less than the preset current threshold, the PWM control module 200 does not work, the PFM control module 300 outputs a corresponding control signal to the power conversion module 500, and controls the power conversion module 500 to perform dc-dc conversion. Other ways to determine whether the PFM control module 300 or the PWM control module 200 controls the power conversion module 500 may also be used, for example, obtaining the output voltage of the power conversion module 500 and comparing the output voltage with a preset voltage threshold to obtain a comparison result, i.e., determining whether the PFM control module 300 or the PWM control module 200 controls the power conversion module 500 according to the magnitude of the output voltage and the preset voltage threshold, and so on.
It should be noted that the control signal output from the PFM control module 300 or the PWM control module 200 to the power conversion module 500 is generated according to the output error of the error amplification module 100, that is, the error amplification module 100 outputs the error to the PFM control module 300 or the PWM control module 200, and then the PFM control module 300 or the PWM control module 200 generates the corresponding control signal according to the output error. Further, in an embodiment, the output error of the error amplification module 100 may be a square wave signal, for example, the error amplification module 100 collects a feedback voltage of the load module 600, and then compares the feedback voltage with a preset reference voltage in the error amplification module 100, so as to obtain the square wave signal as the output error, and provide the square wave signal to the PWM control module 200 or the PFM control module 300, and then the PWM control module 200 or the PFM control module 300 generates a corresponding control signal according to the square wave signal to control the power conversion module 500 to perform dc-dc conversion. It will be appreciated that the output error may also be a level signal of other waveforms, such as a sawtooth signal or the like.
It should be noted that, in the present application, reference may be made to the conventional technology for the functions of the PFM control module 300 and the PWM control module 200, for example, the PFM control module 300 adjusts and controls the output voltage of the power conversion module 500 by fixing the on-time or off-time of the MOS transistor and changing the switching frequency, the switching loss of the PFM control module 300 is proportional to the output current of the load module 600, the loss increases with the increase of the output current of the load module 600, and the PFM control module 300 is used to control the power conversion module 500, so that a higher conversion efficiency can be obtained when the load module 600 is in a light load condition. The switching frequency of the PWM control module 200 is constant, and when the load current of the load module 600 changes, the switching loss remains unchanged, and the conduction loss increases with the increase of the load current, so that the PWM control module 200 can have higher conversion efficiency when the load module 600 is heavily loaded. It should be noted that, in order to obtain higher conversion efficiency under different loads, the present application adopts a control manner in which the PWM control module 200 and the PFM control module 300 are mixed, that is, the PWM control module 200 is selected under any load condition, and the PFM control module 300 is selected under any load condition to control the power conversion module 500, so as to finally achieve the purpose of improving the conversion efficiency, and the PWM control module 200 and the PFM control module 300 may adopt the conventional technology, so the specific operation principle of the PWM control module 200 and the PFM control module 300 is not described in detail herein.
In one embodiment, as shown in fig. 2, the error amplifying module 100 includes an amplifier and a reference voltage source, an inverting input terminal of the amplifier is connected to the reference voltage source, a non-inverting input terminal of the amplifier is connected to the load module 600, and output terminals of the amplifier are respectively connected to the PWM control module 200 and the PFM control module 300.
Specifically, the reference voltage source is configured to provide a reference voltage to the amplifier, the load module 600 outputs a feedback voltage to the amplifier, and the amplifier compares the reference voltage with the feedback voltage to generate an output error (for example, the output error may be a square wave signal), and outputs the output error to the PWM control module 200 or the PFM control module 300, so that the PWM control module 200 or the PFM control module 300 generates a corresponding control signal to the power conversion module 500 according to the output error, and controls the power conversion module 500 to perform voltage conversion.
It should be noted that, the reference voltage source multiplies two voltages with opposite temperature coefficients by a certain coefficient and adds the two voltages to obtain a reference voltage with zero temperature coefficient, which is provided to the amplifier, and the reference voltage is obtained by the following formula:
VREF＝α1V1+α2V2
in the above formula, VREFAs reference voltage, α1And α2Respectively the weight of the positive temperature coefficient voltage and the weight of the negative temperature coefficient voltage, V1And V2The reference voltage with zero temperature coefficient can be obtained by selecting proper weight according to actual needs.
In an embodiment, as shown in fig. 2, the DC-DC conversion apparatus further includes a soft start module, the soft start module is connected to the start end of the amplifier, wherein the soft start module is used to implement soft start of the DC-DC conversion apparatus, it can be understood that the DC-DC conversion apparatus can perform DC-DC conversion only after start is required, by setting the soft start module, the DC-DC conversion apparatus can be started without occurrence of phenomena of excessive surge current and overshoot of output voltage, so as to protect circuit elements in the whole DC-DC conversion apparatus and improve service life, it should be noted that the soft start technology is a technology that by controlling an input voltage and the like, an input voltage can be increased, so as to achieve the purpose of soft start, and a specific working principle of soft start can refer to an existing conventional soft start technology, and thus will not be described in detail herein.
In one embodiment, as shown in fig. 2, the power conversion module 500 includes a first switching tube assembly (e.g., a switching tube Q1) and a second switching tube assembly (e.g., a switching tube Q2), wherein an input terminal of the first switching tube assembly is used for connecting an input power source, a control terminal of the first switching tube assembly is connected to the PWM control module 200 and the PFM control module 300, respectively, an output terminal of the first switching tube assembly is connected to an input terminal of the second switching tube assembly and the load module 600, a control terminal of the second switching tube assembly is connected to the PWM control module 200 and the PFM control module 300, respectively, and an output terminal of the second switching tube assembly is grounded.
Specifically, the PWM control module 200 and the PFM control module 300 may not generate control signals simultaneously, when the PWM control module 200 generates the control signals during operation, the control signals are output to the control terminal of the first switch tube assembly and the control terminal of the second switch tube assembly, so as to control the on/off of the first switch tube assembly and the second switch tube assembly, the PWM control module 200 keeps the switching frequency constant, and adjusts the on-time of the switch tube, so as to improve the conversion efficiency when the load module 600 is under heavy load, and the PFM control module 300 keeps the on-time or the off-time of the switch tube, and adjusts the switching frequency of the switch tube, so as to improve the conversion efficiency when the load module 600 is under light load, by outputting the control signals to the control terminal of the first switch tube assembly and the control terminal of the second switch tube assembly.
Further, in one embodiment, the first switching tube element and the second switching tube element are both field effect transistors (i.e., power MOSFET tubes), and by using the field effect tubes, the tube voltage drop can be smaller, the power can be lower, and the conversion efficiency of the DC-DC conversion device can be improved.
In one embodiment, as shown in fig. 3, the load module 600 includes an inductance component 601, an energy storage charging component 602, and a voltage dividing resistance component 603, one end of the inductor component 601 is connected to an output end of the first switching tube component (for example, the switching tube Q1), the other end of the inductor component 601 is connected to one end of the energy storage charging component 602 and an input end of the voltage dividing resistor component 603, the other end of the energy storage charging component 602 is connected to an output end of the second switching tube component (for example, the switching tube Q2), an output end of the voltage dividing resistor component 603 is connected to an output end of the second switching tube component, and a feedback end of the voltage dividing resistor component 603 is connected to the error amplification module 100. Specifically, the load module 600 further includes a positive input terminal and a negative input terminal for connecting to a load (such as a heavy load or a light load), and the output voltage of the load module 600 is VoutThe energy storage charging component 602 can provide power to the load when the first switch tube component and the second switch tube component are disconnected, the voltage dividing resistor component 603 can perform the voltage dividing function, and obtain the feedback voltage VFBAnd outputs to the error amplification block 100.
In one embodiment, as shown in fig. 3, the mode selection module 400 includes a load detection unit for acquiring the output current I of the power conversion module 500 and a PWM/PFM control mode switching unitoAnd will output a current IoAnd comparing the comparison result with a preset current threshold value to obtain a comparison result, so that the PWM/PFM control mode switching unit switches the PWM control module 200 and the PFM control module 300 according to the comparison result. Specifically, the preset current threshold value may adopt the following calculation formula:
calculated to obtain in the above formula, IomIs a predetermined current threshold value, VinFor inputting the voltage of the power supply, IPFMFor the current limit of the PFM control module 300, L is the inductance of the inductor component, VoutFor the output voltage, T is the clock signal period outputted by the oscillator in the PFM control module 300, and it should be noted that the PFM control module 300 includes the oscillator and the PFM controller, as will be described in detail later.
In one embodiment, as shown in fig. 3, control logic and a driving circuit may be disposed between the PWM control module 200 and the PFM control module 300 and the power conversion module 500, and the PWM control module 200 and the PFM control module 300 are connected to the mode selection module 400 through the control logic. Specifically, the control logic may be a switch, for example, when the mode selection module 400 determines that the PWM control module 200 is selected to output a corresponding control signal to the power conversion module 500, the switch may be switched to conduct between the PWM control module 200 and the power conversion module 500, and when the mode selection module 400 determines that the PFM control module 300 is selected to output a corresponding control signal to the power conversion module 500, the switch may be switched to conduct between the PFM control module 300 and the power conversion module 500. Further, the driving circuit may be composed of a rectifying filter circuit, a voltage stabilizing circuit, and the like, so that the control signal output to the power conversion module 500 is stable.
In one embodiment, as shown in fig. 4, the PFM control module 300 includes a PFM controller and an oscillator, the oscillator is connected to the PFM controller, the PFM controller is connected to the error amplifying module, the mode selecting module and the power converting module, and the PFM controller outputs a corresponding control signal to the power converting module according to an oscillation signal of the oscillator and an output error of the error amplifying module to control the power converting module to perform voltage conversion.
Specifically, the mode selection module can also output an enable signal to the PFM controller, for example, after the mode selection module compares the output current with a preset current threshold value to obtain a comparison result, it is determined that the PFM control module 300 outputs a corresponding control signal to the power conversion module, and then the mode selection module outputs the enable signal to the PFM controller, so that the PFM controller starts to operate, an output error of the oscillation signal of the oscillator and the error amplification module is used as its own input, and then the control signal is obtained according to the oscillation signal and the output error and output to the power conversion module to perform dc-dc conversion.
It should be noted that the PFM control module 300 changes the switching frequency by fixing the on-time or off-time of the power conversion module, so as to adjust and control the output voltage of the power conversion module, that is, the power conversion module performs voltage conversion on the input power to obtain the output voltage and outputs the output voltage to the load module, the load module is connected to the error amplification module, outputs the feedback voltage to the error amplification module, and compares the feedback voltage with the reference voltage through the error amplification module to generate an output error (the output error is, for example, a square wave signal), and the low level signal of the square wave signal and the high level signal generated by the oscillator are used together as a control signal to control the on-time or off-time of the power conversion module, so as to control the power conversion module. It can be understood that, when the power conversion module outputs to different load modules, the output voltage falls for different time periods, so that the time of the low level of the control signal is different, and the PFM control module performs the cycle control on the power conversion module.
In one embodiment, as shown in fig. 5, the PWM control module 200 includes a comparator, a positive input terminal of the comparator is connected to the error amplifying module, a negative input terminal of the comparator is used for receiving a voltage signal with a preset waveform, an output terminal of the comparator is connected to the power converting module, a control terminal of the comparator is connected to the mode selecting module, and the comparator is used for outputting a corresponding control signal to the converting mode according to the voltage signal with the preset waveform and the output error of the error amplifying module to control the power converting module to perform voltage conversion.
Specifically, the positive input end of the comparator receives the output error of the error amplification module, the error amplification module amplifies the voltage difference between the feedback voltage of the load module and the reference voltage, the amplified voltage difference is used as the output error and is output to the positive input end of the comparator, the negative input end of the comparator is connected with a voltage signal (taking a sawtooth wave voltage signal as an example) with a preset waveform, and the comparator compares the sawtooth wave voltage signal with the amplified voltage difference to obtain a corresponding control signal (such as a square wave signal) and outputs the control signal to the power conversion module to control the power conversion module to perform dc-dc conversion. It can be understood that the feedback voltages fed back to the error amplification module by different load modules are different, and when the load modules are in heavy load, the feedback voltages can be increased, so that the amplified voltage difference value is increased, the duty ratio of the square wave signals obtained by the comparator is increased, the output voltage ripple is low, and the PWM control module is used for controlling the power conversion module to perform high-efficiency voltage conversion when the load modules are in heavy load.
In an embodiment, in order to fully disclose the present application, the present embodiment will be described in detail with reference to fig. 1 to 5, and first the present embodiment includes the following six steps:
the method comprises the following steps that firstly, a DC-DC conversion device is subjected to soft start through a soft start module, and the phenomena of surge current and output overvoltage of the DC-DC converter in the power-on process are eliminated;
providing a reference value for a feedback voltage output from a feedback end of a voltage division resistor assembly of the load module to the error amplification module through a reference voltage source, and ensuring normal use of other circuit modules;
thirdly, carrying out load detection to obtain the output current I of the power conversion moduleoAccording to the output current IoDetermining that the load connected to the load module is light load or heavy load, and comparing the light load or heavy load with a preset current critical value, thereby determining to select a PFM control module or a PWM control module;
step four, when the load connected to the load module is light load, namely current I is outputoWhen the current is smaller than the preset current critical value, the PFM control module is started, and the PFM control module outputs a control signal to the power conversion module through corresponding control logic so as to carry out voltage conversion;
step five, when the load connected to the load module is heavy load, namely the current I is outputoWhen the current is larger than or equal to the preset current critical value, the PWM control module is started, and the PWM control module outputs a control signal to the power conversion module through corresponding control logic so as to carry out voltage conversion;
and step six, improving the dynamic response performance by adopting a voltage feedforward technology.
In the first step, when the DC-DC converter is started, the phenomena of excessive surge current and output voltage overshoot are likely to occur, and the excessive surge current may damage circuit elements such as inductors, thereby reducing the service life of the DC-DC converter. Therefore, for the safety of the DC-DC conversion device, the circuit needs to be started by soft start.
In step two, the reference voltage provided by the reference voltage source is:
VREF＝α1V1+α2V2(2)
in the above formula, VREFAs reference voltage, α1And α2Respectively the weight of the positive temperature coefficient voltage and the weight of the negative temperature coefficient voltage, V1And V2Positive temperature voltage and negative temperature voltage, respectively. By choosing appropriate weights, a reference voltage with zero temperature coefficient can be obtained.
In step three, the calculation formula of the preset current threshold value is as follows:
in the above formula, IomIs a predetermined current threshold value, VinFor inputting the voltage of the power supply, IPFMFor the current limit of the PFM control module, L is the inductance of the inductive component, VoutFor output voltage, T is the clock signal period output by the oscillator in the PFM control module when the load current Io≤IomWhen the voltage is converted, the PFM control module is selected to control the power conversion module to carry out voltage conversion; when the load current Io>IomAnd when the voltage is converted, the PWM control module is selected to control the power conversion module to convert the voltage.
In the fourth step, the PFM control module changes the switching frequency by fixing the on-time of the first switching tube assembly and the second switching tube assembly, thereby implementing the adjustment and control of the output voltage. Output voltage VoutGenerating a feedback voltage V through a voltage dividing resistor assemblyFBAnd the comparison between the feedback voltage and the reference voltage is realized through an error amplification module to generate a square wave signal. Low level signal of square wave signal and high power generated by oscillator in PFM control moduleThe level signal is used as a driving signal to control the working states of the first switch tube component and the second switch tube component; the output voltage falling time and the output voltage rising time are different for different loads (such as heavy load or light load), so that the low level time of the driving signal is different, and the voltage conversion control of the PFM control module to the power conversion module under the condition of light load is realized.
In the fourth step, the PFM control module uses the hysteresis comparator as the amplifier of the error amplifying module to implement the oscillator OSC, thereby implementing the switching between the light load operating state and the sleep state. When the feedback voltage rises to a high value of the hysteresis comparator, an output signal of the hysteresis comparator is inverted, most modules in the power tube and the DC-DC conversion device are closed, and the power tube and the DC-DC conversion device enter a sleep mode. In the sleep mode, the load current continues current through the energy storage charging assembly, the output voltage is reduced, the loss is reduced accordingly, and the power consumption is low. When the feedback voltage drops to the low value of the hysteresis comparator, the DC-DC conversion device enters a light load working state.
In the fifth step, the PWM control module adopts pulse width modulation, and the constant voltage value is ensured to be output by keeping the switching frequency constant and adjusting the conduction time of the first switching tube component or the second switching tube component. Output voltage VoutGenerating a feedback voltage V through a voltage dividing resistor assemblyFBThe comparison between the feedback voltage and the reference voltage is realized through an error amplification module, the difference value is amplified and output to the positive end of a comparator, the negative end of the comparator generates a periodic sawtooth wave voltage signal, and the sawtooth wave voltage is compared with the output voltage V of the error amplifierCThereby obtaining the driving signal. When the load is heavy, the output voltage of the error amplification module is increased, the duty ratio of the square wave signal output by the comparator is increased, the output voltage ripple is low, and the heavy-load high conversion efficiency is realized.
In the sixth step, in order to improve the input transient response performance of the DC-DC conversion device, a voltage feedforward technique is adopted to suppress small signal disturbance generated by the input voltage, and a linear adjustment rate is improved, where the linear adjustment rate is defined as follows:
in the above formula,. DELTA.VoutFor the variation of the output voltage, Δ VinIs the variation of the input voltage.
By adopting the DC-DC conversion device, the conversion efficiency of the power management system can be improved, wherein the conversion efficiency formula is as follows:
in the above formula, η is conversion efficiency, VinFor an input voltage, IinFor input of current, VoutTo output a voltage, IoutTo output a current, PoConsuming energy for the load, PfAnd losses of the DC-DC converter include switching losses, conduction losses, external losses, and the like.
In one embodiment, a power management system is provided, which includes the above DC-DC conversion apparatus.
In one embodiment, the power management system further comprises a wireless transceiver, a microcontroller and a sensor, the transceiver, the microcontroller and the sensor being connected to the DC-DC conversion device. The wireless transceiver, the microcontroller and the sensor are powered through the DC-DC conversion device, and the normal work of the wireless transceiver, the microcontroller and the sensor is guaranteed.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.
Claims (10)
1. A DC-DC conversion apparatus, comprising: the device comprises an error amplification module, a PWM control module, a PFM control module, a mode selection module, a power conversion module and a load module;
the error amplification module is connected with the PWM control module, the PFM control module and the load module;
the PWM control module is connected with the mode selection module and the power conversion module; the PFM control module is connected with the mode selection module and the power conversion module;
the power conversion module is connected with the mode selection module and the load module, and is also used for connecting an input power supply;
the mode selection module is used for obtaining the output current of the power conversion module, comparing the output current with a preset current critical value to obtain a comparison result, and selecting the PWM control module or the PFM control module according to the comparison result to output a corresponding control signal to the power conversion module to control the power conversion module to carry out voltage conversion according to the output error of the error amplification module.
2. The DC-DC conversion apparatus of claim 1, wherein the error amplifying module comprises an amplifier and a reference voltage source, an inverting input terminal of the amplifier is connected to the reference voltage source, a non-inverting input terminal of the amplifier is connected to the load module, and an output terminal of the amplifier is connected to the PWM control module and the PFM control module, respectively.
3. The DC-DC conversion apparatus according to claim 2, further comprising a soft start module connected to the start terminal of the amplifier.
4. The DC-DC conversion apparatus according to claim 1, wherein the power conversion module comprises a first switching tube assembly and a second switching tube assembly, an input terminal of the first switching tube assembly is used for connecting the input power source, a control terminal of the first switching tube assembly is respectively connected to the PWM control module and the PFM control module, an output terminal of the first switching tube assembly is connected to an input terminal of the second switching tube assembly and the load module, a control terminal of the second switching tube assembly is respectively connected to the PWM control module and the PFM control module, and an output terminal of the second switching tube assembly is grounded.
5. The DC-DC conversion device according to claim 4, wherein the load module comprises an inductance component, an energy storage and charging component, and a voltage dividing resistance component, one end of the inductance component is connected to the output end of the first switch tube component, the other end of the inductance component is connected to one end of the energy storage and charging component and the input end of the voltage dividing resistance component, the other end of the energy storage and charging component is connected to the output end of the second switch tube component, the output end of the voltage dividing resistance component is connected to the output end of the second switch tube component, and the feedback end of the voltage dividing resistance component is connected to the error amplification module.
6. The DC-DC conversion device according to claim 5, wherein the first switching tube component and the second switching tube component are both field effect transistors.
7. The DC-DC conversion apparatus according to claim 1, wherein the PFM control module comprises a PFM controller and an oscillator, the oscillator is connected to the PFM controller, the PFM controller is connected to the error amplifying module, the mode selecting module and the power converting module, and the PFM controller outputs a corresponding control signal to the power converting module according to an oscillation signal of the oscillator and an output error of the error amplifying module to control the power converting module to perform voltage conversion.
8. The DC-DC conversion apparatus according to claim 1, wherein the PWM control module comprises a comparator, a positive input terminal of the comparator is connected to the error amplifying module, a negative input terminal of the comparator is configured to receive a voltage signal with a preset waveform, an output terminal of the comparator is connected to the power conversion module, a control terminal of the comparator is connected to the mode selection module, and the comparator is configured to output a corresponding control signal to the conversion mode according to the voltage signal with the preset waveform and an output error of the error amplifying module to control the power conversion module to perform voltage conversion.
9. A power management system, characterized in that the power management system comprises a DC-DC conversion device according to any one of claims 1 to 8.
10. The power management system of claim 9, further comprising a wireless transceiver, a microcontroller, and a sensor, the transceiver, microcontroller, and sensor each coupled to the DC-DC conversion device.
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