CN115622396A - Control circuit for switching converter, switching converter and electronic equipment - Google Patents
Control circuit for switching converter, switching converter and electronic equipment Download PDFInfo
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- CN115622396A CN115622396A CN202211312821.XA CN202211312821A CN115622396A CN 115622396 A CN115622396 A CN 115622396A CN 202211312821 A CN202211312821 A CN 202211312821A CN 115622396 A CN115622396 A CN 115622396A
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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
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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
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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
- H02M3/157—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 with digital control
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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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The application discloses a control circuit for a switching converter, the switching converter and an electronic device. The method comprises the following steps: the ripple voltage sampling module is used for generating a ripple signal with the same frequency and phase as the inductive current of the switch converter; the superposition circuit is used for superposing the ripple signal and a feedback signal representing the output voltage of the switching converter to generate a loop control signal; the hysteresis comparator is used for comparing the loop control signal with a set reference voltage to generate a comparison signal; the logic and driving module is used for generating a switch control signal according to the comparison signal so as to control a power level circuit of the switch converter; and the hysteresis quantity setting module is used for setting the hysteresis voltage of the hysteresis comparator according to the input voltage and the output voltage of the switching converter, and realizing pseudo-fixed frequency by adjusting the hysteresis quantity of the hysteresis comparison, so that a hysteresis control module tending to stabilize frequency is obtained, and the stability of the circuit is improved.
Description
Technical Field
The present invention relates to the field of switching power supplies, and more particularly, to a control circuit for a switching converter, a switching converter and an electronic device.
Background
With the demand of power electronic products and the development of semiconductor technology, power management chips are widely used in portable computers, mobile phones, personal digital assistants, and other portable or non-portable electronic devices. The switching converter adopts a power switch tube to control the transmission of electric energy from an input end to an output end, so that constant output voltage and/or output current can be provided at the output end.
A switching converter generally controls the state of its power stage circuit in three ways, voltage mode, current mode and hysteresis control, so as to generate a stable output voltage. In order to solve subharmonic oscillation output by the switching converter, constant On Time (COT) control based On ripple voltage is widely applied to hysteresis control, and the control mode has the advantages of fast transient response, simple control mode, small tracking error and the like, and can effectively improve the stability of the system. However, the switching frequency is not fixed, the controllability of the switching frequency is poor, and harmonic waves with wide spectrum distribution are generated, so that the design of a post-stage filter is difficult, which is a main reason for limiting the application of hysteresis control.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a control circuit for a switching converter, a switching converter and an electronic device, in which a pseudo-constant frequency is realized by adjusting a hysteresis amount of a hysteresis comparison, so as to obtain a hysteresis control module tending to stabilize a frequency, thereby improving stability of the circuit.
According to a first aspect of embodiments of the present invention, there is provided a control circuit for a switching converter, comprising: the ripple voltage sampling module is used for generating a ripple signal with the same frequency and phase as the inductive current of the switch converter; a superposition circuit for superposing the ripple signal and a feedback signal representing the output voltage of the switching converter to generate a loop control signal; the hysteresis comparator is used for comparing the loop control signal with a set reference voltage to generate a comparison signal; the logic and driving module is used for generating a switch control signal according to the comparison signal so as to control a power level circuit of the switch converter; and the hysteresis quantity setting module is used for setting the hysteresis voltage of the hysteresis comparator according to the input voltage and the output voltage of the switching converter.
Optionally, the ripple voltage sampling module includes: the first resistor and the first capacitor are coupled between two ends of an energy storage element in the power stage circuit; and a second capacitor having a first terminal coupled to the intermediate node of the first resistor and the first capacitor and a second terminal coupled to the feedback signal.
Optionally, the hysteresis setting module includes: a first subtractor configured to perform a difference operation on the input voltage and the output voltage to obtain a first voltage signal; a multiplier configured to multiply the first voltage signal with the output voltage to obtain a second voltage signal; a divider configured to divide the second voltage signal by the input voltage and a coefficient to obtain a first hysteresis voltage of the hysteresis comparator.
Optionally, the coefficient is set according to the first resistor, the first capacitor, and a set switching frequency of the switching converter.
Optionally, the hysteresis comparator includes: a second subtractor configured to perform a difference operation on the reference voltage and a second hysteresis voltage to obtain a first window voltage; an adder configured to sum the reference voltage and a second hysteresis voltage to obtain a second window voltage; a first comparator configured to compare the loop control signal with the first window voltage to obtain a first comparison signal; and a second comparator configured to compare the loop control signal with the second window voltage to obtain a second comparison signal.
Optionally, the second hysteresis voltage is equal to 1/2 of the first hysteresis voltage.
Optionally, the logic and driving module includes: an RS flip-flop configured to perform a set operation according to the first comparison signal and a reset operation according to the second comparison signal to generate the switching control signal; and a driving unit configured to control a switching state of the power stage circuit according to the switching control signal.
According to a second aspect of embodiments of the present invention, there is provided a switching converter comprising: a power stage circuit; and the control circuit described above.
According to a third aspect of embodiments of the present invention, there is provided an electronic apparatus, including: a battery that outputs a battery voltage; a microprocessor; and the switching converter is used for processing the battery voltage and then providing the processed battery voltage to the microprocessor.
In summary, in the embodiments of the present invention, the ripple signal reflecting the energy variation of the energy storage element is obtained by sampling the voltage across the inductor, and is superimposed on the feedback signal to generate the loop control signal, and the power stage circuit is controlled according to the loop control signal and the reference voltage. Because inductive current information is introduced into the control loop in a voltage form, the control circuit in the embodiment does not need to be provided with a current loop to realize the dynamic quick response, so that the current loop can be omitted, and only one voltage loop exists, so that the control circuit can make quick response to the dynamic jump of the load, and the precision of the output voltage of the switching converter can be improved under different applications without an additional compensation circuit.
In addition, the control circuit of the embodiment also realizes the pseudo-fixed frequency by adjusting the hysteresis quantity of the hysteresis comparison, and because the hysteresis quantity contains information such as input voltage, output voltage, set switching frequency and the like, a hysteresis control mode which tends to stabilize the frequency can be obtained, and the stability of the circuit is improved.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1 shows a schematic circuit diagram of a switching converter according to an embodiment of the invention.
Fig. 2 shows a schematic block diagram of an electronic device in which the switching converter of fig. 1 is installed.
Fig. 3 shows a schematic circuit diagram of a ripple voltage sampling module in a switching converter of an embodiment of the present invention.
Fig. 4 shows a schematic block diagram of a hysteresis setting module in a switching converter of an embodiment of the invention.
Fig. 5 shows a schematic block diagram of a hysteresis comparator in a switching converter of an embodiment of the invention.
Fig. 6 shows a schematic operating waveform diagram of a switching converter according to an embodiment of the invention.
Detailed Description
Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the various figures, like elements are identified with the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. In addition, certain well known components may not be shown.
It should be understood that in the following description, a "circuit" refers to a conductive loop formed by at least one element or sub-circuit through an electrical or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.
The present invention may be embodied in various forms, some examples of which are described below.
Fig. 1 shows a schematic circuit diagram of a switching converter 100 according to an embodiment of the present invention, and fig. 2 shows a schematic block diagram of an electronic device 200 in which the switching converter 100 of fig. 1 is installed. As shown in fig. 2, the switching converter of the present embodiment is described by taking a buck converter (buck converter) as an example, and the electronic device 200 is, for example, a notebook personal computer, and includes a battery 210, a microprocessor 220, and the switching converter 100.
The battery 210 is composed of, for example, a plurality of lithium ion battery cells, and outputs a battery voltage Vbat of about 12V. The microprocessor 220 is an LSI (Large Scale Integration) chip that performs various arithmetic processes and integrally controls the entire function block of the electronic device 200, and operates with a power supply voltage of about 1.5V.
The switching converter 100 of the present embodiment steps down the battery voltage Vbat of about 12V and supplies it as a power supply voltage of the microprocessor 220. The microprocessor 220 consumes a large amount of current during the arithmetic processing, and reduces the current consumption in a standby state in which the arithmetic processing is not performed, thereby reducing the power consumption. Therefore, the current Iout flowing from the switching converter 100 to the microprocessor 220 greatly changes depending on the operating state of the microprocessor 220. The switching converter 100 of the present embodiment is suitably used for the following applications: a device operating in a mode in which a consumption current is very small is used as a load to perform voltage conversion efficiently. The structure of the switching converter 100 will be described in detail below with reference to fig. 1.
As shown in fig. 1, a switching converter 100 according to an embodiment of the present invention is illustrated by taking a buck converter (buck converter) topology as an example, and the switching converter 100 includes a power stage circuit 101 and a control circuit 102. The power stage circuit 101 is an output circuit of a general step-down switching regulator of a synchronous rectification system, and steps down an input voltage Vin applied to an input terminal 103 to supply an output voltage Vout from an output terminal 104. The input voltage Vin is, for example, the battery voltage Vbat in fig. 2.
The power stage circuit 101 includes power switches S1 and S2, a first terminal of the power switch S1 receives the input voltage Vin, a second terminal of the power switch S1 is coupled to a first terminal of the power switch S2, and a second terminal of the power switch S2 is coupled to a ground reference of the switching converter. It is understood that in the present embodiment, the power switch S1 is a main power transistor, the power switch S2 is a rectifier, and the power switches S1 and S2 may be any type of field effect transistor, such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), and may be other types of field effect transistors and/or other types of transistors within the scope of the present invention as known to those skilled in the art without departing from the scope of the present invention.
An energy storage element (e.g., an inductance Lx) is provided between the connection points of the power switches S1 and S2. An input capacitance Ci is provided between the input voltage Vin and a reference ground, an output capacitance Co is provided between the output of the switching converter 100 and the reference ground to generate an output voltage Vout across it, and is connected in parallel with a load RL to provide energy storage. The voltage dividing network formed by the resistors R1 and R2 is used for obtaining the feedback signal FB of the output voltage Vout.
In the present embodiment, the voltage at the connection point of the power switches S1 and S2 is referred to as a switching voltage Vsw. The current flowing through the inductor Lx is referred to as an inductor current IL. The inductor current IL defines a direction of flowing to the output capacitor Co as positive, and a current flowing from the output capacitor Co to the load via the output terminal is referred to as an output current Iout.
The control circuit 102 is configured to generate a driving signal applied to the control terminals of the power switches S1 and S2 in a closed-loop control mode according to the output voltage Vout, and control the switching states of the power switches S1 and S2 to supply energy to the load. In the present embodiment, the switching converter 100 performs energy conversion using the inductor Lx by repeatedly turning on/off the power switches S1 and S2 alternately, so that the input voltage Vin is stepped down. The stepped-down voltage is smoothed by the inductor Lx and the output capacitor Co, and is output as an output voltage Vout.
Among them, the control circuit 102 of the switching converter 100 may be an LSI chip integrated on one semiconductor substrate. In the present embodiment, the power switches S1 and S2 may be provided outside the control circuit, but may also be provided inside the control circuit.
In the present embodiment, the control circuit 102 of the switching converter 100 is implemented by adopting a pseudo-fixed-frequency hysteresis control architecture, and includes a ripple voltage sampling module 110, a superposition circuit 120, a hysteresis comparator 130, a hysteresis setting module 140, and a logic and driving module 150. The Ripple voltage sampling module 110 is configured to generate a Ripple signal Ripple having the same frequency and phase as the current IL flowing through the inductor Lx, wherein the variation range of the Ripple signal Ripple is between zero and a preset value, that is, the peak-to-peak value of the Ripple signal Ripple is the preset value, and the preset value is greater than zero. The superimposing circuit 120 superimposes the Ripple signal Ripple in the feedback signal FB to generate the loop control signal Vramp. The positive input terminal of the hysteresis comparator 130 is coupled to the superposition circuit 120, and the negative input terminal is coupled to a set reference voltage Vref, for comparing the loop control signal Vramp with the reference voltage Vref to generate a comparison signal PWM. The hysteresis setting module 140 is configured to collect an input voltage Vin and an output voltage Vout of the switching converter 100, and set a hysteresis voltage in the hysteresis comparator 130 according to the input voltage Vin, the output voltage Vout, and a preset switching frequency. The logic and driving module 150 is configured to implement a logic control function of the system, and is configured to generate a switch control signal according to the comparison signal PWM to control the conducting states of the power switches S1 and S2.
Compared with the prior art, the control circuit in the embodiment of the invention obtains the Ripple signal Ripple reflecting the energy change of the energy storage element Lx by sampling the voltage at the two ends of the inductor Lx, superimposes the Ripple signal Ripple in the feedback signal FB to generate the loop control signal Vramp, and controls the power stage circuit according to the loop control signal Vramp and the reference voltage Vref. Because the inductive current information is introduced into the control loop in the form of voltage, the control circuit in the embodiment does not need to be provided with a current loop to realize the quick response to the dynamic state, so that the current loop can be omitted. In addition, the control circuit of the embodiment also realizes fixed frequency by adjusting hysteresis quantity of hysteresis comparison, and because the hysteresis quantity contains information such as input voltage, output voltage, set switching frequency and the like, a hysteresis control mode which tends to stabilize frequency can be obtained, and the stability of the circuit is improved.
Fig. 3 shows a schematic circuit diagram of a ripple voltage sampling module in a switching converter of an embodiment of the present invention. As shown in fig. 3, the ripple voltage sampling module 110 of the present embodiment includes a resistor R3 and capacitors C1 and C3, the resistor R3 and the capacitor C3 are coupled in series between two ends of the inductor Lx, a first end of the capacitor C1 is coupled to a middle node of the resistor R3 and the capacitor C3, and a second end of the capacitor C1 is coupled to the feedback signal FB. During the operation of the system, the Ripple signal Ripple is generated by sampling the current variation in the inductor Lx through the resistor R3 and the capacitor C3, and the capacitor C1 is used for coupling the Ripple signal Ripple to the feedback signal FB. Since the two ends of the inductor Lx are coupled to the input voltage Vin and the output voltage Vout, respectively, the relationship between the Ripple signal Ripple and the input voltage Vin, the output voltage Vout, and the switching frequency fsw can be obtained as follows:
Ripple＝[(Vin-Vout)×Vout]/[2×(R3×C3)×Vin×fsw] (1)
fig. 4 shows a schematic block diagram of a hysteresis setting module in a switching converter of an embodiment of the invention.
In the present embodiment, during each switching period Tsw, the control circuit 102 alternately and repeatedly executes a first state and a second state, wherein the first state is to turn on the power switch S1 and turn off the power switch S2; the second state turns on the power switch S2 and turns off the power switch S1. Between the first state and the second state, a time (also referred to as a dead time) is provided for rendering neither the power switch S1 nor the power switch S2 conductive.
In the first state, the on-time Ton of the power switch S1 and the input/output voltage have the following relationship:
Ton＝[Vhys×(R3×C3)]/(Vin-Vout) (2)
where Vhys represents a hysteresis amount of the hysteresis comparator 130, and R3 and C3 represent a resistance value of the resistor R3 and a capacitance value of the capacitor C3 in the ripple voltage sampling module 110, respectively.
In the second state, the off-time Toff of the power switch S1 is related to the input/output voltage as follows:
Toff＝[Vhys×(R3×C3)]/Vout (3)
since the switching frequency fsw =1/Tsw = 1/(Ton + Toff), the relationship between the switching frequency and the hysteresis amount of the hysteresis comparator 130 can be obtained as follows:
fsw＝1/(Ton+Toff)＝[(Vin-Vout)×Vout]/[Vhys×(R3×C3)×Vin] (4)
as shown in equation (4), the output frequency of the system can be controlled by adjusting the hysteresis of the hysteresis comparator 130, and then the fixed frequency is realized.
As shown in fig. 4, the hysteresis setting module 140 of the present embodiment includes a subtractor 141, a multiplier 142, and a divider 143. The subtractor 141 is configured to perform a difference operation on the input voltage Vin and the output voltage Vout to obtain a first voltage signal V1, where the first voltage signal V1= Vin-Vout. The multiplier 142 is configured to multiply the first voltage signal V1 with the output voltage Vout to obtain a second voltage signal V2, where the second voltage signal V2= V1 × Vout = (Vin-Vout) × Vout. The divider 143 is configured to divide the second voltage signal V2 by the input voltage Vin and a coefficient α to obtain a hysteresis voltage Vhys1, where the coefficient α = 1/(R3 × C3)/fsw. Therefore, the relationship between the hysteresis voltage Vhys1, the input voltage Vin, the output voltage Vout, and the set switching frequency fsw is:
Vhys1＝[(Vin-Vout)×Vout]/[(R3×C3)×Vin×fsw] (5)
fig. 5 shows a schematic block diagram of a hysteresis comparator in a switching converter of an embodiment of the invention. As shown in fig. 5, the hysteresis comparator 130 of the present embodiment includes a subtractor 131, an adder 132, and comparators 133 and 134. The subtractor 131 is configured to perform a difference operation on the reference voltage Vref and the hysteresis voltage Vhys2 to obtain a first window voltage Vs1, and the adder 132 is configured to perform a sum operation on the reference voltage Vref and the hysteresis voltage Vhys2 to obtain a second window voltage Vs2, where the hysteresis voltage Vhys2= Vhys1/2. The comparator 133 has a positive input receiving the first window voltage Vs1, a negative input coupled to the loop control signal Vramp, and an output outputting the comparison signal PWM1. The comparator 134 has a positive input coupled to the loop control signal Vramp, a negative input for receiving the second window voltage Vs2, and an output for outputting the comparison signal PWM2.
In the present embodiment, the logic and driving module 150 includes an RS flip-flop 151 and a driving unit 152. The RS flip-flop 151 has a set terminal coupled to the comparison signal PWM1 and a reset terminal coupled to the comparison signal PWM2, the RS flip-flop 151 is configured to perform a set operation according to the comparison signal PWM1 and a reset operation according to the comparison signal PWM2, so as to provide switching control signals HSG and LSG at output terminals for controlling the power switches S1 and S2, respectively, and the driving unit 152 is configured to control the switching states of the power switches S1 and S2 according to the switching control signals HSG and LSG.
Fig. 6 shows a schematic operating waveform diagram of a switching converter according to an embodiment of the invention. The switching converter in this embodiment controls the power stage circuit in a ripple controlled hysteretic control mode. As shown in fig. 5, in the switching converter of this embodiment, the feedback signal FB and the Ripple signal Ripple are superimposed to generate the loop control signal Vramp, the hysteresis comparator 130 performs a difference operation on the reference voltage Vref and the hysteresis voltage Vhys2 to obtain a window lower limit reference of the loop control signal Vramp, i.e., vref-Vhys2, and performs a sum operation on the reference voltage Vref and the hysteresis voltage Vhys2 to obtain a window upper limit reference of the loop control signal Vramp, i.e., vref + Vhys2. At time t0, the loop control signal Vramp is equal to the lower limit reference Vref-Vhys2, the control circuit controls the power switch S1 to be turned on, controls the power switch S2 to be turned off, and controls the inductor current to start rising. At time t1, the loop control signal Vramp is equal to the upper and lower references Vref + Vhys2, the control circuit controls the power switch S1 to be turned off, the power switch S2 to be turned on, and the inductor current starts to decrease. At time t2, the loop control signal Vramp is equal to the lower limit reference Vref-Vhys2 again, the power switch S1 is turned on again, the power switch S2 is turned off again, and the switching converter operates in a circulating manner and finally operates in a steady state where the output frequency tends to be stable.
In summary, in the embodiments of the present invention, the ripple signal reflecting the energy change of the energy storage element is obtained by sampling the voltage across the inductor, and the ripple signal is superimposed on the feedback signal to generate the loop control signal, and the power stage circuit is controlled according to the loop control signal and the reference voltage. Because inductive current information is introduced into the control loop in a voltage form, the control circuit in the embodiment does not need to be provided with a current loop to realize the dynamic quick response, so that the current loop can be omitted, and only one voltage loop exists, so that the control circuit can make quick response to the dynamic jump of the load, and the precision of the output voltage of the switching converter can be improved under different applications without an additional compensation circuit.
In addition, the control circuit of the embodiment also realizes the pseudo-fixed frequency by adjusting the hysteresis quantity of the hysteresis comparison, and because the hysteresis quantity contains information such as input voltage, output voltage, set switching frequency and the like, a hysteresis control mode which tends to stabilize the frequency can be obtained, and the stability of the circuit is improved.
In the foregoing embodiment, although the switching converter with the Buck topology is described with reference to fig. 1, it is understood that the control circuit according to the embodiment of the present invention may also be used in switching converters with other topologies, and the structure of the main power circuit includes, but is not limited to, a floating-ground type Buck power circuit, a ground-ground type Buck power circuit, a flyback power circuit, a Buck-Boost type power circuit, and a Boost type power circuit.
In the above description, well-known structural elements and steps are not described in detail. It should be understood by those skilled in the art that the corresponding structural elements and steps may be implemented by various technical means. In addition, in order to form the same structural elements, those skilled in the art can also design a method which is not exactly the same as the method described above. In addition, although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in combination to advantage.
In accordance with the present invention, as set forth above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The scope of the invention should be determined from the following claims.
Claims (9)
1. A control circuit for a switching converter, comprising:
the ripple voltage sampling module is used for generating a ripple signal with the same frequency and phase as the inductive current of the switch converter;
a superposition circuit for superposing the ripple signal and a feedback signal representing the output voltage of the switching converter to generate a loop control signal;
the hysteresis comparator is used for comparing the loop control signal with a set reference voltage to generate a comparison signal;
the logic and driving module is used for generating a switch control signal according to the comparison signal so as to control a power level circuit of the switch converter; and
and the hysteresis quantity setting module is used for setting the hysteresis voltage of the hysteresis comparator according to the input voltage and the output voltage of the switching converter.
2. The control circuit of claim 1, wherein the ripple voltage sampling module comprises:
the first resistor and the first capacitor are coupled between two ends of an energy storage element in the power stage circuit; and
a second capacitor having a first terminal coupled to an intermediate node between the first resistor and the first capacitor and a second terminal coupled to the feedback signal.
3. The control circuit of claim 2, wherein the hysteresis setting module comprises:
a first subtractor configured to perform a difference operation on the input voltage and the output voltage to obtain a first voltage signal;
a multiplier configured to multiply the first voltage signal with the output voltage to obtain a second voltage signal;
a divider configured to divide the second voltage signal by the input voltage and a coefficient to obtain a first hysteresis voltage of the hysteresis comparator.
4. The control circuit of claim 3, wherein the coefficient is set according to the first resistance, the first capacitance, and a set switching frequency of the switching converter.
5. The control circuit of claim 3, wherein the hysteresis comparator comprises:
a second subtractor configured to perform a difference operation on the reference voltage and a second hysteresis voltage to obtain a first window voltage;
an adder configured to sum the reference voltage and a second hysteresis voltage to obtain a second window voltage;
a first comparator configured to compare the loop control signal with the first window voltage to obtain a first comparison signal; and
a second comparator configured to compare the loop control signal with the second window voltage to obtain a second comparison signal.
6. The control circuit of claim 5, wherein the second hysteresis voltage is equal to 1/2 of the first hysteresis voltage.
7. The control circuit of claim 5, wherein the logic and driver module comprises:
an RS flip-flop configured to perform a set operation according to the first comparison signal and a reset operation according to the second comparison signal to generate the switching control signal; and
a driving unit configured to control a switching state of the power stage circuit according to the switching control signal.
8. A switching converter, comprising:
a power stage circuit; and
the control circuit of any of claims 1-7.
9. An electronic device, comprising:
a battery outputting a battery voltage;
a microprocessor; and
the switching converter of claim 8, configured to process the battery voltage and provide the processed battery voltage to the microprocessor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211312821.XA CN115622396A (en) | 2022-10-25 | 2022-10-25 | Control circuit for switching converter, switching converter and electronic equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211312821.XA CN115622396A (en) | 2022-10-25 | 2022-10-25 | Control circuit for switching converter, switching converter and electronic equipment |
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| Publication Number | Publication Date |
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| CN115622396A true CN115622396A (en) | 2023-01-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211312821.XA Pending CN115622396A (en) | 2022-10-25 | 2022-10-25 | Control circuit for switching converter, switching converter and electronic equipment |
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| Country | Link |
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| CN (1) | CN115622396A (en) |
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2022
- 2022-10-25 CN CN202211312821.XA patent/CN115622396A/en active Pending
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