CN109120153B - BUCK circuit and switching power supply - Google Patents
BUCK circuit and switching power supply Download PDFInfo
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- CN109120153B CN109120153B CN201811020700.1A CN201811020700A CN109120153B CN 109120153 B CN109120153 B CN 109120153B CN 201811020700 A CN201811020700 A CN 201811020700A CN 109120153 B CN109120153 B CN 109120153B
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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
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Abstract
The invention relates to a BUCK circuit and a switching power supply. The BUCK circuit in the technical scheme of the invention comprises: a first transistor, a drain of which receives an input voltage; a second transistor, a drain of the second transistor being connected to a source of the first transistor; the first end of the inductor is connected with the source electrode of the first transistor, and the second end of the inductor is connected with the output end of the circuit; a ripple generation module adapted to generate a ripple voltage; the driving signal generation module is suitable for generating a driving signal according to a comparison result of the first superposed voltage and the first reference voltage and a comparison result of the second superposed voltage and the second reference voltage; and the switch control module receives the driving signal and generates a first switch signal and a second switch signal according to the driving signal. The technical scheme of the invention can effectively simplify the structure of the BUCK circuit and reduce the circuit cost.
Description
Technical Field
The invention relates to the technical field of switching power supplies, in particular to a BUCK circuit and a switching power supply.
Background
With the development of scientific technology, the functions of electronic equipment become more and more powerful, and higher requirements are also put forward on the used power supply. In general, most electronic devices cannot directly use ac power supplied from a power grid, but require stable dc power. Therefore, the size, weight and performance of the dc power supply directly affect the further development of the electronic device.
The switching power supply has been applied to more and more electronic devices due to its advantages of small size, high efficiency and light weight, and the switching power supply with the BUCK conversion circuit (BUCK circuit for short) can convert an ac power supply into a stable dc power supply to supply power to the electronic devices.
In the prior art, a peak current mode is usually adopted in the BUCK circuit to cooperate with a current loop to stabilize the current supplied to a load in a preset state, but an error amplifier, a compensation circuit and the like are usually required in the BUCK circuit adopting the peak current mode, so that not only is the circuit structure complicated and the cost high, but also the overall response speed of the BUCK circuit is reduced due to the introduction of a large capacitor in the compensation circuit. Especially, when the load suddenly fluctuates, the current regulation capability is weak, the circuit cannot quickly reach a stable state, and even the performance of the electronic device is affected, and the service life of the electronic device is reduced.
Disclosure of Invention
The invention solves the technical problem of how to simplify the structure of the BUCK circuit and reduce the circuit cost.
To solve the above technical problem, an embodiment of the present invention provides a BUCK circuit, including: a first transistor, a drain of which receives an input voltage, and a gate of which receives a first switching signal; a second transistor, wherein a drain of the second transistor is connected to a source of the first transistor, a gate of the second transistor receives a second switching signal, and a source of the second transistor is grounded; the first end of the inductor is connected with the source electrode of the first transistor, the second end of the inductor is connected with the output end of the BUCK circuit, and the output end of the BUCK circuit generates output voltage; the ripple generating module is suitable for generating ripple voltage according to the inductive current flowing through the inductor; the driving signal generating module is suitable for generating a driving signal according to a comparison result of a first superposed voltage and a first reference voltage and a comparison result of a second superposed voltage and a second reference voltage, wherein the first superposed voltage is obtained by superposing a conversion voltage and the ripple voltage, the second superposed voltage is obtained by superposing a related voltage and the ripple voltage, the conversion voltage is obtained by converting the inductance current, and the related voltage changes along with the change of the output voltage; and the switch control module receives the driving signal and generates the first switching signal and the second switching signal according to the driving signal.
Optionally, the BUCK circuit further includes: and a first polar plate of the capacitor is connected with the output end of the BUCK circuit, and a second polar plate of the capacitor is grounded.
Optionally, the BUCK circuit further includes: a conversion module adapted to receive the inductor current and convert the inductor current to the converted voltage.
Optionally, the conversion module includes a transimpedance amplifier, an input end of the transimpedance amplifier receives the inductor current, and an output end of the transimpedance amplifier outputs the conversion voltage.
Optionally, the ripple generating module receives a first voltage at the first end of the inductor, and generates the ripple voltage according to the first voltage.
Optionally, the ripple generating module receives a first voltage at the first end of the inductor and the output voltage, and generates the ripple voltage according to the first voltage and the output voltage.
Optionally, the driving signal generating module includes: a first comparator, a first input terminal of the first comparator receiving the first superimposed voltage, a second input terminal of the first comparator receiving the first reference voltage; a second comparator, a first input terminal of the second comparator receiving the second superimposed voltage, a second input terminal of the second comparator receiving the second reference voltage; and the first input end of the AND gate is connected with the output end of the first comparator, the second input end of the AND gate is connected with the output end of the second comparator, and the output end of the AND gate generates the driving signal.
Optionally, when the load at the output terminal of the BUCK circuit increases, the inductor current increases, the output voltage decreases until the second superimposed voltage is lower than the second reference voltage, the second comparator outputs a high level, so that the driving signal will be controlled by a comparison result of the first superimposed voltage and the first reference voltage, and the first comparator outputs a low level because the first superimposed voltage is higher than the first reference voltage; the AND gate receives the low level output by the first comparator and the high level output by the second comparator, and the driving signal generated by the output end of the AND gate is at the low level; the switch control module receives the driving signal and generates a first switch signal and a second switch signal, the first switch signal controls the first transistor to be turned off, and the second switch signal controls the second transistor to be turned on, so that the inductive current is reduced until the inductive current is reduced to a stable state.
Optionally, the BUCK circuit further includes a timer, the timer is adapted to generate an adjustment signal when the input voltage and/or the output voltage fluctuates, and the first switching signal generated by the switching control module enables the switching frequency of the first transistor to be maintained constant in response to the adjustment signal.
In order to solve the above technical problem, an embodiment of the present invention further provides a switching power supply, where the switching power supply includes the aforementioned BUCK circuit.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
the BUCK circuit of the technical scheme of the invention comprises: a first transistor, a drain of which receives an input voltage, and a gate of which receives a first switching signal; a second transistor, wherein a drain of the second transistor is connected to a source of the first transistor, a gate of the second transistor receives a second switching signal, and a source of the second transistor is grounded; the first end of the inductor is connected with the source electrode of the first transistor, the second end of the inductor is connected with the output end of the BUCK circuit, and the output end of the BUCK circuit generates output voltage; the ripple generating module is suitable for generating ripple voltage according to the inductive current flowing through the inductor; the driving signal generating module is suitable for generating a driving signal according to a comparison result of a first superposed voltage and a first reference voltage and a comparison result of a second superposed voltage and a second reference voltage, wherein the first superposed voltage is obtained by superposing a conversion voltage and the ripple voltage, the second superposed voltage is obtained by superposing a related voltage and the ripple voltage, the conversion voltage is obtained by converting the inductance current, and the related voltage changes along with the change of the output voltage; and the switch control module receives the driving signal and generates the first switching signal and the second switching signal according to the driving signal. Therefore, the inductive current is led into the current feedback loop and the output voltage is led into the voltage feedback loop, so that the output voltage and the current are controlled to be in a stable preset state, the structure of the BUCK circuit is effectively simplified, and the circuit cost is reduced.
Further, the driving signal generating module in the technical solution of the present invention includes: a first comparator, a first input terminal of the first comparator receiving the first superimposed voltage, a second input terminal of the first comparator receiving the first reference voltage; a second comparator, a first input terminal of the second comparator receiving the second superimposed voltage, a second input terminal of the second comparator receiving the second reference voltage; and the first input end of the AND gate is connected with the output end of the first comparator, the second input end of the AND gate is connected with the output end of the second comparator, and the output end of the AND gate generates the driving signal. Therefore, through the cooperation of the first comparator, the second comparator and the AND gate, the switching of the current feedback loop and the voltage feedback loop can be automatically adjusted according to the change of the output voltage and the current signal, so that the load change can be quickly responded, and the fluctuation of the output voltage and the current can be adjusted in time, so that the circuit can quickly enter a stable state.
Further, the conversion module in the technical scheme of the invention comprises a transimpedance amplifier, wherein an input end of the transimpedance amplifier receives the inductive current, and an output end of the transimpedance amplifier outputs the conversion voltage. Therefore, the inductive current is converted into the conversion voltage and then is introduced into the current feedback loop to be compared with the preset value, so that a complex current comparison circuit is saved, and the circuit can be realized by only adopting the voltage comparator with a simple structure, thereby further simplifying the circuit structure and saving the circuit cost.
Further, the BUCK circuit in the technical solution of the present invention further includes a timer, where the timer is adapted to generate an adjustment signal when the input voltage and/or the output voltage fluctuates, and in response to the adjustment signal, the first switching signal generated by the switching control module maintains the switching frequency of the first transistor constant. Therefore, the working frequency of the first transistor is not changed along with the change of the output voltage and/or the output voltage, and the optimal design of the inductance in the BUCK circuit is facilitated.
Drawings
FIG. 1 is a schematic diagram of a BUCK circuit according to an embodiment of the present invention;
FIG. 2 is a simulated waveform diagram of the correlation voltage and the conversion voltage when the BUCK circuit operates according to the embodiment of the invention;
FIG. 3 is a waveform diagram showing the simulation of the first superimposed voltage and the second superimposed voltage of the BUCK circuit after the load is increased according to the embodiment of the invention.
Detailed Description
As can be understood by those skilled in the art, the BUCK circuit in the prior art usually adopts a peak current mode to cooperate with a current loop to stabilize the current supplied to the load in a preset state, but in the BUCK circuit adopting the peak current mode, an error amplifier, a compensation circuit and the like are usually required, which not only has a complicated circuit structure and high cost, but also reduces the overall response speed of the BUCK circuit due to the introduction of a large capacitor in the compensation circuit. Especially, when the load suddenly fluctuates, the current regulation capability is weak, the circuit cannot quickly reach a stable state, and even the performance of the electronic device is affected, and the service life of the electronic device is reduced.
The BUCK circuit in the embodiment of the invention comprises: a first transistor, a drain of which receives an input voltage, and a gate of which receives a first switching signal; a second transistor, wherein a drain of the second transistor is connected to a source of the first transistor, a gate of the second transistor receives a second switching signal, and a source of the second transistor is grounded; the first end of the inductor is connected with the source electrode of the first transistor, the second end of the inductor is connected with the output end of the BUCK circuit, and the output end of the BUCK circuit generates output voltage; the ripple generating module is suitable for generating ripple voltage according to the inductive current flowing through the inductor; the driving signal generating module is suitable for generating a driving signal according to a comparison result of a first superposed voltage and a first reference voltage and a comparison result of a second superposed voltage and a second reference voltage, wherein the first superposed voltage is obtained by superposing a conversion voltage and the ripple voltage, the second superposed voltage is obtained by superposing a related voltage and the ripple voltage, the conversion voltage is obtained by converting the inductance current, and the related voltage changes along with the change of the output voltage; and the switch control module receives the driving signal and generates the first switching signal and the second switching signal according to the driving signal. Therefore, the inductive current is led into the current feedback loop and the output voltage is led into the voltage feedback loop, so that the output voltage and the current are controlled to be in a stable preset state, the structure of the BUCK circuit is effectively simplified, and the circuit cost is reduced.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, belong to the scope of the present invention.
FIG. 1 is a schematic diagram of a BUCK circuit according to an embodiment of the present invention.
The BUCK circuit is a circuit capable of realizing conversion of a high voltage into a low voltage. The inductor and the capacitor in the BUCK circuit form a low-pass filter, so that a direct current component in input voltage can pass through the low-pass filter, harmonic components in the input voltage are restrained from passing through the low-pass filter, and the direct current voltage after voltage reduction can be obtained at the output end of the circuit so as to supply power to a load.
The BUCK circuit in this embodiment may be used alone to design a switching power supply, or may be integrated in other types of integrated circuits, and used as a sub-circuit with a voltage reduction function in cooperation with other sub-circuits.
Referring to fig. 1, the BUCK circuit may include: a first transistor M1, a drain of the first transistor M1 receiving an input voltage Vin, a gate of the first transistor M1 receiving a first switching signal; a second transistor M2, a drain of the second transistor M2 is connected to the source of the first transistor M1, a gate of the second transistor M2 receives a second switching signal, and a source of the second transistor is grounded.
In a specific implementation, when the first transistor M1 is turned on, the BUCK circuit may be allowed to be connected to an input voltage Vin, where the input voltage Vin may be an ac high voltage, for example, the input voltage may be a mains voltage, that is, 220V ac.
Specifically, the first transistor M1 may be a P-type transistor or an N-type transistor. If the first transistor M1 is a P-type transistor, the P-type transistor is turned on when the gate of the P-type transistor receives a low level, and turned off when the gate of the P-type transistor receives a high level.
In specific implementation, the on and off states of the second transistor M2 are opposite to those of the first transistor M1, that is, when the first transistor M1 is turned on, the second transistor M2 is turned off, and after the first transistor M1 is turned off, the second transistor M2 is turned on. The second transistor M2 may play a role of freewheeling in the BUCK circuit, that is, the second transistor M2 may provide a freewheeling path for the current in the BUCK circuit after the first transistor M1 is turned off.
Specifically, the second transistor M2 may be a P-type transistor or an N-type transistor. If the second transistor M2 is a P-type transistor, the P-type transistor is turned on when the gate of the P-type transistor receives a low level, and turned off when the gate of the P-type transistor receives a high level.
It should be noted that, those skilled in the art may adaptively select the types of the first transistor M1 and the second transistor M2 according to their own circuit design habits and specific application of the circuit, and for different types of transistors, only different level signals need to be provided as the on or off signals, and the embodiments of the present invention do not limit the types of the first transistor M1 and the second transistor M2.
The BUCK circuit of this embodiment may further include an inductor L, a first end of the inductor L is connected to the source of the first transistor M1, a second end of the inductor L is connected to the output end of the BUCK circuit, and the output end of the BUCK circuit generates the output voltage Vout. After the first transistor M1 is turned on, the inductor L starts to store energy, and the voltage across the inductor L and the current flowing through the inductor L gradually increase.
In this embodiment, the inductance L with a suitable inductance value may be selected according to the operating frequency of the BUCK circuit required by a specific application. Generally, when the operating frequency of the circuit is lower, the impedance of the inductor L is proportional to the operating frequency of the circuit.
However, at high frequencies, the inductance L may have a distributed capacitance. It can also be said that a higher circuit operating frequency will reduce the impedance of the inductor L, and that the inductor L will exhibit capacitive behavior when the frequency exceeds the self-resonant frequency of the inductor L. Therefore, selecting an inductance L of an appropriate inductance value according to the operating frequency of the circuit is important to the overall operating performance of the BUCK circuit.
Furthermore, the BUCK circuit further comprises a capacitor C, a first pole plate of the capacitor C is connected with the output end of the BUCK circuit, and a second pole plate of the capacitor C is grounded. The capacitor C and the inductor L may form a low-pass filter, so that a dc component in the input voltage Vin passes through, and a harmonic component in the input voltage Vin is suppressed from passing through, so that a stepped-down dc voltage can be obtained at an output terminal of the circuit.
Further, the BUCK circuit may further comprise a ripple generation module 5, the ripple generation module 5 being adapted to generate a ripple voltage V _ Ripp according to the inductor current flowing through the inductor L.
In specific implementation, since the voltage collection is more convenient than the current collection, the ripple generation module 5 may generate the ripple voltage V _ Ripp by receiving the end voltage of the inductor L, where the end voltage of the inductor L may reflect the change condition of the inductor current.
The relationship between the change slope of the inductor current and the end voltage of the inductor L can be expressed as:
K＝(V1-Vout)/L0
wherein, K is the change slope of the inductor current, V1 is the first voltage at the first end of the inductor, the voltage at the output end of the BUCK circuit at Vout is also the voltage at the second end of the inductor, L0Is the inductive reactance value of the inductor. Where V1 is greater than Vout.
In an optional embodiment, the ripple generating module 5 may receive a first voltage V1 at the first end of the inductor L and generate the ripple voltage V _ Ripp according to the first voltage V1.
In another alternative embodiment, the ripple generating module 5 may receive the first voltage V1 at the first end of the inductor L and the output voltage Vout, and generate the ripple voltage V _ Ripp according to the first voltage V1 and the output voltage Vout. Wherein, the output voltage Vout is also the voltage of the second end of the inductor L.
In particular, the ripple generating module 5 may include a low pass filter, which may receive the first voltage V1, or the first voltage V1 and the output voltage Vout, and generate the ripple voltage V _ Ripp. Wherein the ripple voltage V _ Ripp has only a harmonic component and no direct current component (i.e., fundamental component).
Further, the BUCK circuit may further include a driving signal generating module 3 adapted to generate a driving signal according to a comparison result of a first superimposed voltage Ripp _ CC superimposed with the ripple voltage V _ Ripp and a comparison result of a second superimposed voltage Ripp _ CV superimposed with the ripple voltage V _ Ripp, and the comparison result of the first superimposed voltage Ripp _ CC superimposed with the ripple voltage V _ Ripp, the second superimposed voltage Ripp _ CV superimposed with a correlation voltage FB converted from the inductor current, the correlation voltage FB changing with a change of the output voltage Vout; and the switch control module 1 receives the driving signal, and generates the first switch signal and the second switch signal according to the driving signal.
In specific implementation, the inductor current may be converted into the conversion voltage FB _ CC through the conversion module 4.
More specifically, the conversion module 4 may include a transimpedance amplifier, an input end of which receives the inductor current, and an output end of which outputs the conversion voltage FB _ CC.
Further, the driving signal generating module 3 may include: a first comparator 31, a first input terminal of the first comparator 31 receiving the first superimposed voltage Ripp _ CC, a second input terminal of the first comparator 31 receiving the first reference voltage VREF _ CC; a second comparator 32, a first input of the second comparator 32 receiving the second superimposed voltage Ripp _ CV, a second input of the second comparator 32 receiving the second reference voltage VREF _ CV; and an and gate 33, a first input end of the and gate 33 being connected to the output end of the first comparator 31, a second input end of the and gate 33 being connected to the output end of the second comparator 32, and an output end of the and gate 33 generating the driving signal.
Specifically, the first input terminal of the first comparator 31 may be a negative input terminal, and the second input terminal of the first comparator 31 may be a positive input terminal; the first input terminal of the second comparator 32 may be a negative input terminal, and the second input terminal of the second comparator 32 may be a positive input terminal.
More specifically, the first comparator 31 and/or the second comparator 32 may be a hysteresis comparator.
Further, the correlated voltage FB may be obtained by dividing the voltage from the output voltage Vout through a voltage dividing resistor R2. Specifically, the output terminal of the BUCK circuit may be connected to a first terminal of a first resistor R1, a second terminal of the first resistor R1 is connected to a first terminal of a voltage-dividing resistor R2, and a second terminal of the voltage-dividing resistor R2 is grounded. The voltage at the first end of the voltage-dividing resistor R2 is the correlated voltage FB. When the output voltage Vout increases, the correlated voltage FB also increases, and when the output voltage Vout decreases, the correlated voltage FB also decreases.
Specifically, the first resistor R1 and/or the voltage dividing resistor R2 may be a fixed resistor or a variable resistor, so as to meet the requirements of the BUCK circuit operating in various different situations.
Further, the first reference voltage VREF _ CC and the second reference voltage VREF _ CV may be the same or different.
Further, the BUCK circuit may further include a timer 2, the timer 2 is adapted to generate an adjustment signal when the input voltage Vin and/or the output voltage Vout fluctuate, and may send the adjustment signal to the switch control module 1, and the switch control module 1 generates a first switching signal in response to the adjustment signal such that the switching frequency of the first transistor M1 is maintained constant.
The adjustment function of the timer 2 may also be referred to as a pseudo-fixed frequency function. That is, the on-time of the first transistor M1 in each cycle is not constant during the whole operation of the circuit, and the timer 2 can adjust the on-time of the first transistor M1 according to the variation of the input voltage Vin and/or the output voltage Vout, so that the switching frequency of the first transistor M1 is constant.
Specifically, the desired switching frequency value of the first transistor M1 may be set according to (R1+ R2) × C. Wherein R1 is the first resistor, R2 is the second resistor, and C is the capacitor. Due to the influence of external factors of the circuit and the error of various devices, the switching frequency value of the first transistor M1 does not completely match (R1+ R2) × C during the operation of the circuit. However, the closer the operating frequency of the first transistor is to (R1+ R2) × C, the more optimal the entire BUCK circuit can operate.
Further, the signal transmission between the timer 2 and the switch control module 1 may be performed in a wired or wireless manner, which is not limited in this embodiment of the present invention.
In an implementation, an input voltage feedforward loop may be established at the voltage input terminal of the BUCK circuit, and an output voltage feedback loop may be established at the output terminal of the BUCK circuit, and the input voltage feedforward loop and the output voltage feedback loop are utilized to adjust the timing time of the timer 2 (i.e., the on-time of the first transistor), so that the on-time may vary with the variation of the input voltage Vin and/or the output voltage Vout, thereby maintaining the switching frequency of the first transistor M1 constant. The specific circuit structures of the input voltage feedforward loop and the output voltage feedback loop may adopt the circuit structures in the prior art as long as the switching frequency of the first transistor M1 can be maintained constant.
Further, the switch control module 1 may include a logic circuit module 11, a first driving module 12 and a second driving module 13, where the logic circuit module 11 is adapted to receive the driving signal and generate two sub-driving signals, and the two sub-driving signals may be provided to the first transistor M1 and the second transistor M2 through the first driving module 12 and the second driving module 13, respectively, so as to control the first transistor M1 and the second transistor M2 to be turned on and off. The logic circuit module 11, the first driving module 12, and the second driving module 13 may be implemented by using a logic circuit and a driving circuit in the prior art, which is not limited in this embodiment of the present invention.
In one particular application scenario, for example: the BUCK circuit is integrated in an integrated circuit and serves as a sub-circuit which plays a role in voltage reduction in the integrated circuit, and the output end of the BUCK circuit can be connected with a load.
Please refer to fig. 1, fig. 2, and fig. 3. FIG. 2 is a simulated waveform diagram of the correlation voltage and the conversion voltage when the BUCK circuit operates according to the embodiment of the invention; FIG. 3 is a waveform diagram showing the simulation of the first superimposed voltage and the second superimposed voltage of the BUCK circuit after the load is increased according to the embodiment of the invention.
Since the BUCK circuit is used as a sub-circuit of the integrated circuit, when the entire integrated circuit does not start to operate, the first transistor M1 and the second transistor M2 are both in an off state, the first end of the inductor L is in a floating state, the inductor current flowing through the inductor L is 0, and the output voltage Vout of the BUCK circuit is 0.
When the integrated circuit starts to work, the BUCK circuit is also started, the timer 2 sets a fixed on-time for the first transistor M1 according to a preset timing time, the switch control module 1 generates a first switch signal and a second switch signal, the first switch signal controls the first transistor M1 to be turned on through the first driving module 12, the second switch signal controls the second transistor M2 to be maintained in an off state through the second driving module 13, the input voltage Vin is connected to the first end of the inductor L through the turned-on first transistor M1, and is converted into the output voltage Vout through a low-pass filter composed of the inductor L and the capacitor C.
In the time interval 0-t1, the output voltage Vout and the inductor current gradually increase from 0 over time. That is, the correlation voltage FB and the conversion voltage FB _ CC also gradually increase from 0 over time. In the time interval 0-t1, the first superimposed voltage Ripp _ CC is smaller than the first reference voltage VREF _ CC, the second superimposed voltage Ripp _ CV is smaller than the second reference voltage VREF _ CV, the output ends of the first comparator 31 and the second comparator 32 both output high level, and the AND gate 33 outputs high level. At this time, in the time interval 0-t1, the conduction of the first transistor M1 is only controlled by the time set by the timer.
At time t1, the output voltage Vout and inductor current both rise to a steady state, i.e., the correlated voltage FB and the switching voltage FB _ CC also rise to a steady state following the output voltage Vout and inductor current.
In the time interval t1-t2, the correlated voltage FB and the switching voltage FB _ CC are in a steady state. Since the first superimposed voltage Ripp _ CC is less than the first reference voltage VREF _ CC, the first comparator 31 outputs a high level. At this time, although the output terminal of the first comparator 31 is connected to the first input terminal of the and gate 33, the high level signal outputted from the first comparator 31 does not actually affect the output of the and gate 33, so that the driving signal will be controlled by the comparison result of the second superimposed voltage Ripp _ CV and the second reference voltage VREF _ CV, that is, when the second comparator 32 outputs a low level, the and gate 33 outputs a low level, and when the second comparator 32 outputs a high level, the and gate 33 outputs a high level.
Since the ripple voltage V _ Ripp exists in the second superimposed voltage Ripp _ CV, and the ripple voltage V _ Ripp can be regarded as a harmonic voltage with a magnitude that is fluctuating up and down, the second superimposed voltage Ripp _ CV may fluctuate around the second reference voltage VREF _ CV in the time interval t1-t 2. When the second superimposed voltage Ripp _ CV fluctuates and exceeds the second reference voltage VREF _ CV, the second comparator 32 outputs a low level, the and gate 33 outputs a low level, the first transistor M1 is turned off, the second transistor M2 is turned on, at this time, the input voltage Vin does not continue to charge the inductor L, the value of the second superimposed voltage Ripp _ CV tends to decrease, when the second superimposed voltage Ripp _ CV is lower than the second reference voltage VREF _ CV, the second comparator 32 outputs a high level, the first transistor M1 is turned on again, and the second transistor M2 is turned off again. This is repeated so that the second superimposed voltage Ripp _ CV always fluctuates around the second reference voltage VREF _ CV. In the time interval t1-t2, the output voltage Vout can be stably maintained at the predetermined value. In fact, the difference between the output voltage Vout and the preset value is half the amplitude of the ripple voltage V _ Ripp, and the ripple voltage V _ Ripp has a small amplitude and can be ignored in the case of low accuracy requirement, and for the case of high accuracy requirement, the ripple voltage V _ Ripp can be eliminated by connecting a compensation circuit between the output end of the BUCK circuit and the load.
At time t2, the load at the output of the BUCK circuit increases, causing the inductor current to increase and the output voltage Vout to decrease. Because of the current overshoot process in the circuit, the inductor current will maintain a high current for a period of time after increasing, and similarly, the output voltage Vout will maintain a low voltage for a period of time after decreasing. Since the correlated voltage FB varies with the variation of the output voltage Vout and the switching voltage FB _ CC varies with the variation of the inductor current, the switching voltage FB _ CC will maintain a high voltage for a period of time after increasing, and similarly, the correlated voltage FB will maintain a low voltage for a period of time after decreasing.
As the correlation voltage FB decreases, the second superimposed voltage Ripp _ CV also gradually decreases until the second reference voltage VREF _ CV is lower, and the second comparator 32 outputs a high level. At this time, although the output terminal of the second comparator 32 is connected to the second input terminal of the and gate 33, the high level signal outputted by the second comparator 32 does not actually affect the output of the and gate 33, so that the driving signal will be controlled by the comparison result of the first superimposed voltage Ripp _ CC and the first reference voltage VREF _ CC. Since the first superimposed voltage Ripp _ CC is higher than the first reference voltage VREF _ CC, the first comparator 31 outputs a low level; the and gate 33 receives the low level output by the first comparator 31 and the high level output by the second comparator 32, and the driving signal generated at the output end of the and gate 33 is at a low level; the switch control module 1 receives the driving signal and generates a first switch signal and a second switch signal, the first switch signal controls the first transistor M1 to turn off, the second switch signal controls the second transistor M2 to turn on, so that the inductive current is reduced until the inductive current is reduced to a stable state, at this time, the current provided to the load is also reduced to a state capable of maintaining the stable operation of the load, the output voltage Vout gradually increases to the stable state along with the reduction of the load current, the interference of the load fluctuation to the circuit is eliminated, and the circuit returns to the stable operation state again.
Further, the embodiment of the invention also provides a switching power supply, which comprises the aforementioned BUCK circuit. The switching power supply can provide proper working voltage for various electronic devices.
For a detailed description of the process of the BUCK circuit converting the input voltage in the switching power supply, reference may be made to the implementation process of the BUCK circuit in the embodiment shown in fig. 1 to 3, which is not described herein again.
It should be noted that the frequency values of the "high frequency" and the "low frequency" in the embodiment of the present invention are not particularly limited, as long as the frequency value of the high frequency is higher than the frequency value of the low frequency.
In addition, the voltage values of the "high level" and the "low level" in the embodiment of the present invention are not particularly limited, as long as the voltage value of the high level is higher than the voltage value of the low level. For example, a voltage value of a high level can be recognized as a logic 1, and a voltage value of a low level can be recognized as a logic 0.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. A BUCK circuit, comprising:
a first transistor, a drain of which receives an input voltage, and a gate of which receives a first switching signal;
a second transistor, wherein a drain of the second transistor is connected to a source of the first transistor, a gate of the second transistor receives a second switching signal, and a source of the second transistor is grounded;
the first end of the inductor is connected with the source electrode of the first transistor, the second end of the inductor is connected with the output end of the BUCK circuit, and the output end of the BUCK circuit generates output voltage;
the ripple generating module is suitable for generating ripple voltage according to the inductive current flowing through the inductor;
the driving signal generating module is suitable for generating a driving signal according to a comparison result of a first superposed voltage and a first reference voltage and a comparison result of a second superposed voltage and a second reference voltage, wherein the first superposed voltage is obtained by superposing a conversion voltage and the ripple voltage, the second superposed voltage is obtained by superposing a related voltage and the ripple voltage, the conversion voltage is obtained by converting the inductance current, and the related voltage changes along with the change of the output voltage; the driving signal generating module includes: a first comparator, a first input terminal of the first comparator receiving the first superimposed voltage, a second input terminal of the first comparator receiving the first reference voltage; a second comparator, a first input terminal of the second comparator receiving the second superimposed voltage, a second input terminal of the second comparator receiving the second reference voltage; the first input end of the AND gate is connected with the output end of the first comparator, the second input end of the AND gate is connected with the output end of the second comparator, and the output end of the AND gate generates the driving signal;
and the switch control module receives the driving signal and generates the first switching signal and the second switching signal according to the driving signal.
2. The BUCK circuit of claim 1, further comprising:
and a first polar plate of the capacitor is connected with the output end of the BUCK circuit, and a second polar plate of the capacitor is grounded.
3. The BUCK circuit of claim 1, further comprising:
a conversion module adapted to receive the inductor current and convert the inductor current to the converted voltage.
4. The BUCK circuit of claim 3, wherein the conversion module comprises a transimpedance amplifier, an input terminal of the transimpedance amplifier receiving the inductor current, an output terminal of the transimpedance amplifier outputting the converted voltage.
5. The BUCK circuit of claim 1, wherein the ripple generation module receives a first voltage at the first terminal of the inductor and generates the ripple voltage according to the first voltage.
6. The BUCK circuit of claim 1, wherein the ripple generation module receives a first voltage at the first end of the inductor and the output voltage and generates the ripple voltage according to the first voltage and the output voltage.
7. The BUCK circuit of claim 6,
when the load of the output end of the BUCK circuit is increased, the inductive current is increased, the output voltage is reduced until the second superposed voltage is lower than the second reference voltage, the second comparator outputs a high level, so that the driving signal is controlled by the comparison result of the first superposed voltage and the first reference voltage, and the first comparator outputs a low level because the first superposed voltage is higher than the first reference voltage;
the AND gate receives the low level output by the first comparator and the high level output by the second comparator, and the driving signal generated by the output end of the AND gate is at the low level;
the switch control module receives the driving signal and generates a first switch signal and a second switch signal, the first switch signal controls the first transistor to be turned off, and the second switch signal controls the second transistor to be turned on, so that the inductive current is reduced until the inductive current is reduced to a stable state.
8. The BUCK circuit according to claim 1, further comprising a timer adapted to generate an adjustment signal when the input voltage and/or the output voltage fluctuates, the first switching signal generated by the switching control module in response to the adjustment signal causing the switching frequency of the first transistor to be maintained constant.
9. A switching power supply comprising the BUCK circuit according to any one of claims 1 to 8.
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| CN111082644B (en) * | 2019-12-25 | 2021-07-16 | 深圳南云微电子有限公司 | Wide-voltage input buck power converter |
| CN111277140A (en) * | 2019-12-31 | 2020-06-12 | 成都芯源系统有限公司 | Voltage and current control circuit and method and switch converter |
| US11973424B2 (en) | 2020-09-08 | 2024-04-30 | Analog Devices International Unlimited Company | Spur free switching regulator with self-adaptive cancellation of coil current ripple |
| CN112671236B (en) | 2020-12-31 | 2023-05-05 | Tcl华星光电技术有限公司 | Voltage conversion circuit and display device |
| CN113241946B (en) * | 2021-04-21 | 2022-04-15 | 北京大学 | Direct current/direct current conversion circuit and direct current/direct current converter |
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Address after: Room 214, No.1000 Chenhui Road, China (Shanghai) pilot Free Trade Zone, Pudong New Area, Shanghai, 200120 Patentee after: Shanghai Nanxin Semiconductor Technology Co.,Ltd. Address before: Room 2016, No. 2016, No. 81, Xiangyin Road, Shanghai, Shanghai Patentee before: SOUTHCHIP SEMICONDUCTOR TECHNOLOGY (SHANGHAI) Co.,Ltd. |