CN112398335B - Control circuit and control method of switching regulator and switching regulator - Google Patents
Control circuit and control method of switching regulator and switching regulator Download PDFInfo
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- CN112398335B CN112398335B CN201910747577.1A CN201910747577A CN112398335B CN 112398335 B CN112398335 B CN 112398335B CN 201910747577 A CN201910747577 A CN 201910747577A CN 112398335 B CN112398335 B CN 112398335B
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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
Abstract
The application discloses control circuit and control method and switching mode regulator of switching mode regulator for control first switch tube switches on and off, includes: the switching-on circuit comprises a switching-on signal generating circuit, a switching-off time adjusting circuit, a minimum switching-off time circuit and a logic circuit, wherein when the output voltage is greater than a first reference voltage, the switching-off time adjusting circuit controls the switching-off time of a first switching tube to be constant switching-off time, when the output voltage is less than or equal to the first reference voltage, the switching-off time adjusting circuit controls the switching-off time of the first switching tube to be minimum switching-off time, and when the transient change of a load is detected, the energy stored in an inductor can be rapidly increased, large current is provided for an output capacitor, and the rapid transient response to the load change is realized. On the basis of ensuring the better stability of a circuit system, the transient response speed is improved, and the larger fluctuation of the output voltage is avoided.
Description
Technical Field
The present invention relates to the field of switching power supply technologies, and in particular, to a control circuit and a control method for a switching regulator, and a switching regulator.
Background
The switching regulator is used to convert an input voltage into a predetermined output voltage to supply to a load. The existing switching regulator comprises a main switching tube, a synchronous switching tube, an inductor and a control circuit. The control circuit is used for controlling the on-off states of the main switching tube and the synchronous switching tube, so that the inductor alternately stores electric energy and supplies the electric energy, and output voltage and/or output current are/is generated.
And under the constant on-time, comparing the feedback signal with a first reference signal to control the on-time of the main switching tube, and comparing the output voltage with the input voltage to control the off-time of the main switching tube. When the main switching tube is switched on, the synchronous switching tube is switched off, and during the switching-off period of the main switching tube, the synchronous switching tube continues current. In each switching period, the turn-off time of the main switching tube is basically constant, and the turn-on time is variable according to the feedback signal, so that the duty ratio of the switching signal can be adjusted to maintain the output voltage and/or the output current constant.
However, the existing switching regulator has a slow transient response, and when a large voltage drop event occurs at a load end, the voltage of an output end changes, which limits the application of the control model in the field requiring a fast transient response.
Accordingly, it is desirable to improve prior art switching regulators to provide a switching regulator with fast transient response.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a control circuit and a control method of a switching regulator and a switching regulator, which realize a fast transient response to a load change.
According to a first aspect of the embodiments of the present invention, there is provided a control circuit of a switching regulator, for controlling on and off of a first switching tube, including: a conduction signal generating circuit for generating a conduction signal; the turn-off signal generating circuit is used for generating a first control signal according to a switching signal, and the first control signal is used for maintaining the turn-off time of the first switching tube at least at a preset constant turn-off time; the turn-off time adjusting circuit is used for generating an adjusting signal according to the output voltage of the switch-type regulator and a first reference voltage; the minimum turn-off time circuit is used for generating a second control signal according to the switching signal, and the second control signal is used for maintaining the turn-off time of the first switching tube at least at a preset minimum turn-off time; and the logic circuit is used for generating a turn-off signal according to the first control signal, the second control signal and the regulating signal and generating the switching signal according to the turn-on signal and the turn-off signal, wherein when the output voltage is greater than the first reference voltage, the turn-off time regulating circuit controls the turn-off time of the first switching tube to be constant turn-off time, and when the output voltage is less than or equal to the first reference voltage, the turn-off time regulating circuit controls the turn-off time of the first switching tube to be the minimum turn-off time, so that the duty ratio of the switching signal is regulated.
Preferably, when the adjusting signal is in an inactive state, the logic circuit generates the turn-off signal according to the first control signal, and when the adjusting signal is in an active state, the logic circuit generates the turn-off signal according to the second control signal.
Preferably, the logic circuit comprises: the first input end of the AND gate is used for receiving the first control signal, and the second input end of the AND gate is used for receiving the adjusting signal; and the first input end of the OR gate is connected to the output end of the AND gate, the second input end of the OR gate is used for receiving the second control signal, and the output end of the OR gate is used for generating the turn-off signal.
Preferably, the control circuit further comprises a voltage feedback circuit for generating a voltage feedback signal according to the output voltage of the switching regulator.
Preferably, the off-time adjustment circuit includes: a first comparator that compares the voltage feedback signal and the first reference voltage to generate the adjustment signal.
Preferably, the shutdown signal generation circuit includes: the first inverter is used for generating a first trigger signal according to the switching signal; the first charging circuit is used for generating a first voltage signal according to the first trigger signal; and a second comparator for comparing the first voltage signal with a second reference voltage to generate the first control signal.
Preferably, the first charging circuit includes: a first current source and a first capacitor connected in series between a supply voltage and ground; and the first switch is connected in series with two ends of the first capacitor, wherein when the first trigger signal is in an invalid state, the first switch is switched off, the first current source charges the first capacitor, and the voltage at two ends of the first capacitor is used as the first voltage signal.
Preferably, the minimum off-time circuit includes: the second inverter is used for generating a second trigger signal according to the switching signal; the second charging circuit is used for generating a second voltage signal according to the second trigger signal; and a third comparator for generating the second control signal according to the second voltage signal.
Preferably, the second charging circuit includes: a second current source and a second capacitor connected in series between the supply voltage and ground; and the second switch is connected in series with two ends of the second capacitor, wherein when the second trigger signal is in an invalid state, the second switch is switched off, the second current source charges the second capacitor, and the voltage at two ends of the second capacitor is used as the second voltage signal.
Preferably, the control circuit further comprises a current detection circuit for detecting an input voltage of the switching regulator to obtain a current detection signal.
Preferably, the turn-on signal generating circuit includes: a fourth comparator for comparing the voltage feedback signal with a third reference voltage to obtain an output voltage, the third reference voltage being proportional to the first reference voltage; the compensation network is used for obtaining compensation voltage according to the output voltage; and a fifth comparator for comparing the current detection signal with the compensation voltage to obtain the turn-on signal.
Preferably, the first current source generates a first current proportional to an input voltage of the switching regulator.
Preferably, the second reference voltage is proportional to a voltage difference between an input voltage and an output voltage of the switching regulator.
According to a second aspect of embodiments of the present invention. There is provided a switching regulator including: the power stage circuit comprises a first switching tube; and the control circuit generates a switching signal to control the on and off of the first switching tube.
Preferably, the power stage circuit further includes a second switching tube, the first switching tube is connected in series with the second switching tube, and the switching signal is used to control the second switching tube to be turned on and off, so that the first switching tube and the second switching tube are alternately turned on and off.
According to a third aspect of the embodiments of the present invention, there is provided a control method of a switching regulator, including: generating a switching signal; controlling the on and off of the first switching tube according to the switching signal; generating a regulation signal according to the output voltage of the switch-type regulator and a first reference voltage; and controlling the turn-off time of the first switching tube according to the adjusting signal, wherein when the output voltage is greater than the first reference voltage, the turn-off time of the first switching tube is controlled to be constant turn-off time, and when the output voltage is less than or equal to the first reference voltage, the turn-off time of the first switching tube is controlled to be the minimum turn-off time, so that the duty ratio of the switching signal is adjusted.
Preferably, the step of controlling the turn-off time of the first switching tube according to the adjustment signal includes: generating a turn-on signal; generating a first control signal according to a switching signal, wherein the first control signal is used for maintaining the turn-off time of the first switching tube at least at a preset constant turn-off time; generating a second control signal according to the switching signal, wherein the second control signal is used for maintaining the turn-off time of the first switching tube at least at a preset minimum turn-off time; and generating the switching signal according to an on signal and an off signal, wherein the off signal is generated according to the first control signal when the adjusting signal is in an invalid state, and the off signal is generated according to the second control signal when the adjusting signal is in an valid state.
Preferably, the control method further comprises generating a voltage feedback signal according to an output voltage of the switching regulator.
Preferably, the step of generating the regulation signal according to the output voltage of the switching regulator and a first reference voltage comprises: comparing the voltage feedback signal to the first reference voltage to generate the adjustment signal.
Preferably, the step of generating the first control signal according to the switching signal comprises: generating a first trigger signal according to the switching signal; charging a first capacitor according to the first trigger signal to generate a first voltage signal; and comparing the first voltage signal with a second reference voltage to generate the first control signal, wherein the second reference voltage is proportional to a voltage difference between an input voltage and an output voltage of the switching regulator, when the first trigger signal is in an invalid state, the first capacitor is charged by a first current proportional to the input voltage of the switching regulator, and a voltage across the first capacitor is used as the first voltage signal.
Preferably, the generating the second control signal according to the switching signal includes: generating a second trigger signal according to the switching signal; charging a second capacitor according to the second trigger signal to generate a second voltage signal; and generating the second control signal according to the second voltage signal, wherein when the second trigger signal is in an invalid state, the second capacitor is charged by adopting a constant second current, and the voltage at two ends of the second capacitor is used as the second voltage signal.
Preferably, the step of generating the turn-on signal includes: detecting an input voltage of the switching regulator to obtain a current detection signal; comparing the voltage feedback signal to a third reference voltage to obtain an output voltage, the third reference voltage being proportional to the first reference voltage; obtaining a compensation voltage according to the output voltage; and comparing the current detection signal with the compensation voltage to obtain the conducting signal.
Preferably, the control method further includes: and controlling the on and off of the second switching tube by adopting the switching signal, so that the first switching tube and the second switching tube are alternately switched on and off.
The control circuit and the control method of the switch-type regulator and the switch-type regulator of the embodiment of the invention monitor the state of the load in real time, and when the transient change of the load is detected, the energy stored in the inductor can be rapidly increased, and the large current is provided for the output capacitor, so that the rapid transient response to the change of the load is realized. On the basis of ensuring the better stability of a circuit system, the transient response speed is improved, and the larger fluctuation of the output voltage is avoided.
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 circuit schematic of a switching regulator according to an embodiment of the invention;
FIG. 2 shows a circuit schematic of the turn-on signal generating circuit of FIG. 1;
FIG. 3 shows a circuit schematic of the shutdown signal generation circuit of FIG. 1;
FIG. 4 shows a circuit schematic of the off-time adjustment circuit of FIG. 1;
FIG. 5 shows a circuit schematic of the minimum off-time circuit of FIG. 1;
fig. 6 is a diagram showing an operation waveform of a switching regulator according to an embodiment of the present invention;
fig. 7a and 7b are output waveform diagrams of switching regulators of the prior art and the embodiment of the present invention, respectively, when the voltage at the load terminal changes;
fig. 8 shows a flow chart of a control method of the switching regulator in fig. 1.
Detailed Description
Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.
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.
In the present application, the switching transistor is a transistor that operates in a switching mode to provide a current path, and includes one selected from a bipolar transistor or a field effect transistor. The first end and the second end of the switching tube are respectively a high potential end and a low potential end on a current path, and the control end is used for receiving a driving signal to control the switching tube to be switched on and off.
The invention is further illustrated with reference to the following figures and examples.
Fig. 1 shows a circuit schematic of a switching regulator according to an embodiment of the invention. The switching regulator 100 includes a control circuit and a power stage circuit integrated in the same integrated circuit chip. The control circuit includes an on signal generation circuit 120, an off signal generation circuit 140, an off time adjustment circuit 150, a minimum off time circuit 160, a logic circuit, and a PWM control circuit 180. The power stage circuit comprises a first switch tube M1, a second switch tube M2, discrete components such as an inductor Lx and a capacitor Cout, and a load.
The switching regulator 100 is used to provide an output voltage Vout to a load. Referring to fig. 1, the control circuit of the switching regulator 100 further includes a voltage feedback circuit 110, the voltage feedback circuit 110 being configured to provide a voltage feedback signal FB indicative of the output voltage. As an example, the first switch transistor M1 and the second switch transistor M2 of the power stage circuit are connected in series, a first terminal of the first switch transistor M1 is connected to the input voltage terminal for receiving the input voltage Vin, and a second terminal of the second switch transistor M2 is grounded. The second terminal of the first switch transistor M1 and the first terminal of the second switch transistor M2 are commonly connected to the inductor Lx for providing a charging and discharging path to the external inductor Lx.
In the switching regulator 100, the turn-on signal generating circuit 120 is configured to generate the turn-on signal Set according to a voltage feedback signal FB of the output voltage Vout of the switching regulator, a current detection signal Isen of the input voltage Vin of the switching regulator, and a third reference voltage Vref 3. Further, the control circuit of the switching regulator circuit 100 further includes a current detection circuit 130, and the current detection circuit 130 is configured to generate a current detection signal Isen according to the input voltage of the switching regulator 100.
The turn-off signal generating circuit 140 is used for generating a first control signal V1 according to the switching signal SW and a second reference voltage Vref 2. The off-time adjusting circuit 150 is configured to generate a regulating signal Vadj according to the voltage feedback signal FB and the first reference voltage Vref 1. The minimum off-time circuit generates the second control signal V2 according to the switch signal SW.
The logic circuit includes an RS flip-flop 171, an or gate 172, and an and gate 173. Two input terminals of the and gate 173 respectively receive the first control signal V1 and the adjusting signal Vadj, a first input terminal of the or gate 172 is connected to an output terminal of the and gate 173, a second input terminal is used for receiving the second control signal V2, and a shutdown signal Reset is generated according to an output signal of the and gate 173 and the second control signal V2. The Set terminal and the Reset terminal of the RS flip-flop 171 respectively receive the turn-on signal Set and the turn-off signal Reset, and the output terminal provides the switching signal SW. For example, when the adjustment signal Vadj is in an inactive state, the logic circuit generates the shutdown signal Reset according to the first control signal V1; when the adjustment signal Vadj is in an active state, the logic circuit generates the shutdown signal Reset according to a second control signal V2.
The off-signal generating circuit 140 and the minimum off-time circuit 160 are, for example, timing circuits for changing the first control signal V1 and the second control signal V2 from the inactive state to the active state, respectively, and maintaining for a predetermined time when the switching signal SW is changed to the inactive state in the active state. The first control signal V1 is used to maintain the off time of the first switch tube M1 at least at a predetermined constant off time, and the second control signal V2 is used to maintain the off time of the first switch tube M1 at least at a predetermined minimum off time.
The input terminal of the PWM control circuit 180 receives the switch signal SW and provides a first driving signal TG and a second driving signal BG at two output terminals, respectively, for driving the first switch transistor M1 and the second switch transistor M2, respectively.
The first drive signal TG and the second drive signal BG are, for example, an in-phase signal and an inverted signal of the switching signal, respectively. In each switching period, the first switching tube M1 and the second switching tube M2 are alternately turned on and off to charge and discharge the inductor Lx, thereby providing an output voltage to the load. The output voltage is maintained at a constant value by adjusting the duty cycle of the switching signal.
In this embodiment, the off-time adjusting circuit 150 adjusts the off-time of the first switching tube M1 according to the voltage feedback signal FB and the first reference voltage Vref 1. For example, when the voltage feedback signal FB is greater than the first reference voltage Vref1, the off-time adjusting circuit 150 controls the off-time of the first switching tube M1 to be a constant off-time, and when the voltage feedback signal FB is less than/equal to the first reference voltage Vref1, the off-time adjusting circuit 150 controls the off-time of the first switching tube to be a minimum off-time, thereby adjusting the duty ratio of the switching signal.
Therefore, when the voltage of the load end changes, the control circuit conducts and shuts off the first switching tube and the second switching tube in a minimum turn-off time cycle mode, energy stored in the inductor is increased, so that large current is provided for the output capacitor Cout when the load changes, the voltage change of the load end is finally stabilized, and the transient response speed of the load of the switch-type regulator is improved.
Further, the switching regulator 100 further includes a high voltage driving circuit 191 and a low voltage driving circuit 192. The high voltage driving circuit 191 includes a buffer 1911, a capacitor C1 and a diode D1, and the low voltage driving circuit 192 includes a buffer 1912. The switching regulator 100 includes a high-voltage side circuit and a low-voltage side circuit, the low-voltage side circuit can be powered by a direct-current low-voltage power supply, and the high-voltage side circuit needs to be powered by a bootstrap capacitor because the high-voltage side circuit is in a floating state. When the first switch tube M1 of the switching regulator is turned off and the second switch tube M2 is turned on, the power source VCC charges the capacitor C1 through the bootstrap diode D1 and the second switch tube M2; when the first switch M1 is turned on and the second switch M2 is turned off, the bootstrap capacitor supplies power to the high-side circuit.
Fig. 2 shows a circuit schematic diagram of the on signal generating circuit in fig. 1. In the present embodiment, the on-time of the first switch M1 is determined by the loop bandwidth, and the loop bandwidth is determined by the transconductance of the error amplifier and the capacitance of the output terminal of the error amplifier. Referring to fig. 2, the on signal generating circuit 120 includes a comparator 1201, a compensation network 1202, and a comparator 1203.
The comparator 1201 has an inverting input for receiving the voltage feedback signal FB, a non-inverting input for receiving the third reference voltage Vref3, and an output connected to the compensation network 1202. The compensation network 1202 derives a compensation voltage according to the output voltage of the comparator 1201. The comparator 1203 has an inverting input terminal for receiving the current detection signal Isen, a non-inverting input terminal for receiving the compensation voltage, and an output terminal for providing the turn-on signal Set.
Fig. 3 shows a circuit schematic of the shutdown signal generation circuit in fig. 1. Referring to fig. 3, the shutdown signal generation circuit 140 includes an inverter 1401, a current source 1402, a switch 1403, a capacitor C2, and a comparator 1404.
The comparator 1404 has an inverting input for receiving the first voltage signal Vc1, a non-inverting input for receiving the second reference voltage Vref2, and the comparator 1404 for comparing the two to provide the first control signal V1 at the output. The second reference voltage Vref2 is proportional to the voltage difference between the input voltage and the output voltage of the switching regulator. I.e., Vref 2-K2 (Vin-Vout), where K2 is a constant second scaling factor.
The inverter 1401 is used to generate a first trigger signal according to the switch signal SW, and the duration of the active state of the first trigger signal is equal to the turn-off time of the first switch tube M1.
The current source 1402 and the capacitor C2 are connected in series between the power voltage and the ground, and the switch 1403 is connected in parallel to the two ends of the capacitor C2, so that the three constitute a charging circuit. The charging circuit is used for generating the first voltage signal Vc 1. A control terminal of the switch 1403 is connected to the output terminal of the inverter 1401, and when the first trigger signal is in an inactive state, the switch 1403 is turned off, the current source 1402 charges the capacitor C2, and the voltage across the capacitor C2 serves as the first voltage signal Vc 1. The current value I1 of the current source 1402 is proportional to the input voltage Vin of the switching regulator 100, i.e., I1 — K1 Vin, where K1 is a constant first scaling factor.
Fig. 4 shows a circuit schematic of the off-time adjustment circuit of fig. 1. Referring to fig. 4, the off-time adjusting circuit 150 includes a comparator 1501, an inverting input of the comparator 1501 is used for receiving the voltage feedback signal FB, a non-inverting input of the comparator 1501 is used for receiving the first reference voltage Vref1, and the comparator 1501 is used for comparing the voltage feedback signal FB with the first reference voltage Vref1 to generate the adjusting signal Vadj. Wherein the first reference voltage Vref1 is proportional to the third reference voltage Vref 3. For example, Vref 1-98% Vref 3.
Fig. 5 shows a circuit schematic of the minimum off-time circuit of fig. 1. Referring to fig. 5, the minimum off-time circuit 160 includes an inverter 1601, a current source 1602, a switch 1603, a capacitor C3, and a comparator 1604.
The comparator 1604 has an inverting input for receiving the second voltage signal Vc2, a non-inverting input coupled to ground via a power supply, and the comparator 1604 is configured to compare the two signals to provide the second control signal V2 at an output.
The inverter 1601 is used for generating a second trigger signal according to the switch signal SW, and the duration of an active state of the second trigger signal is equal to the turn-off time of the first switch tube M1.
The current source 1602 and the capacitor C3 are connected in series between the power voltage and ground, and the switch 1603 is connected in parallel to two ends of the capacitor C3, so that the three constitute a charging circuit. The charging circuit is used for generating the second voltage signal Vc 2. The control terminal of the switch 1603 is connected to the output terminal of the inverter 1601, and when the second trigger signal is in an inactive state, the switch 1603 is turned off, the current source 1602 charges the capacitor C3, and the voltage across the capacitor C3 is used as the second voltage signal Vc 2. The current value I2 of current source 1602 is a constant current value.
FIG. 6 is a waveform diagram illustrating the operation of a switching regulator according to an embodiment of the present invention, in which the inductor currents I are shown separatelyLxThe first driving signal TG and the second driving signal BG are changed along with time. The first driving signal TG and the second driving signal BG are, for example, an in-phase signal and an anti-phase signal of a switching signal, respectively, for controlling the first switching tube M1 and the second switching tube M2 to be turned on and off. The following description will be made only by taking the operation principle of the first switching tube M1 as an example.
In the switching regulator 100 shown in fig. 1, the on signal generating circuit 110 generates an on signal Set, the off signal generating circuit and the off time adjusting circuit supply the first control signal V1 and the adjustment signal Vadj to the and gate 173, respectively, and the minimum off time circuit supplies the second control signal V2 to the or gate 172, generating an off signal Reset. The set terminal and the reset terminal of the RS flip-flop 171 receive the on signal and the off signal, respectively, and generate the switching signal.
As shown in fig. 6, in one switching cycle, the voltage feedback signal FB and the third reference voltage Vref3 control the on-time of the first switch transistor M1, and the first control signal V1, the second control signal V2, and the adjustment signal Vadj control the off-time of the first switch transistor M1. The on-time Ton of the first switch transistor M1 is the duration of the active state of the switch signal, and the off-time Toff is the duration of the inactive state of the switch signal.
In the period T0, the on signal Set transitions from the inactive state to the active state, and the off signal Reset maintains the inactive state. When the switch signal is changed from the inactive state to the active state, the first switch tube M1 is turned on, the inductor Lx stores energy, and the inductor current ILxAnd gradually increases. When the first switch transistor M1 is turned on, the capacitor C2 and the capacitor C3 in the off-signal generating circuit 140 and the minimum off-time circuit 160 start to charge.
In the time period T1, the voltage feedback signal FB is greater than the first reference voltage Vref1, so the adjustment signal Vadj is in an inactive state, and the logic circuit generates a turn-off signal according to the first control signal V1. When the capacitor C2 in the off signal generating circuit 140 is charged to the second reference voltage Vref2 or higher, the off signal Reset is changed from the inactive state to the active state, and the on signal Set maintains the inactive state. The switching signal is changed into an invalid state from an active state, the first switching tube M1 is turned off for a constant time, the inductor Lx releases energy, and the inductor current ILxGradually decreases.
At time period T2, when the inductor current ILxWhen the current is reduced to be below the preset value again, the on signal Set is changed into an effective state from an ineffective state, and the off signal Reset maintains the ineffective state. The switching signal changes from the inactive state to the active state, and the first switch transistor M1 is turned on again, thereby starting the next switching cycle.
In the switching period, the on-time Ton of the first switching tube M1 is a time period corresponding to T0, and the off-time Toff is a time period corresponding to T1. The capacitor C2 in the turn-off signal generating circuit 140 performs a charging and discharging process according to the switching signal SW, and the charging and discharging process determines the on-time Ton of the first switch tube M1.
During the time period T3, the voltage feedback signalFB is less than/equal to the first reference voltage Vref1, so the adjusting signal Vadj is in an active state, and the logic circuit generates the OFF signal according to the second control signal V2. When the capacitor C3 in the minimum off-time circuit 160 is charged above the positive input voltage of the comparator 1604, the off signal Reset transitions from the inactive state to the active state and the on signal Set remains inactive. The switching signal is changed from an active state to an inactive state, the first switching tube M1 is circularly switched on and off with the minimum switching-off time, the inductor Lx circularly stores and releases energy, and the inductor current ILxAnd is increased.
In the time period T4, the voltage feedback signal FB is again greater than the first reference voltage Vref1, the adjustment signal Vadj is in an inactive state, and the logic circuit generates a turn-off signal according to the first control signal V1. When the capacitor C2 in the off signal generating circuit 140 is charged to the second reference voltage Vref2 or higher, the off signal Reset is changed from the inactive state to the active state, and the on signal Set maintains the inactive state. The switching signal is changed into an invalid state from an active state, the first switching tube M1 is turned off for a constant time, the inductor Lx releases energy, and the inductor current ILxGradually decreases.
In the control strategy of the above embodiment, when the voltage at the load end changes, the control circuit ignores the preset constant turn-off time, and turns on and off the first switching tube and the second switching tube in the minimum turn-off time cycle, so as to increase the energy stored in the inductor, so as to provide a large current to the output capacitor Cout when the load changes, and finally stabilize the voltage change at the load end, thereby improving the load transient response speed of the switching regulator.
Fig. 7a and 7b show output waveform diagrams of switching regulators of the prior art and the embodiment of the present invention, respectively, in which curve 1 shows a variation curve of an output voltage, curve 2 shows a variation curve of an inductor current, and curve 3 shows a variation curve of a load current. Referring to fig. 7a and 7b, when the load current changes by about 5A, the output voltage of the switching regulator according to the embodiment of the present invention changes by about 200mV, whereas the output voltage of the switching regulator according to the related art changes by about 300 mV.
The principle of the implementation of the switching regulator with adaptive off-time control is described in detail above. Similarly, the invention can also be applied to a control mode of self-adaptive turn-off time, monitors the state of the load in real time for the switch-type regulator of the self-adaptive turn-off time control mode, and can quickly increase the energy stored in the inductor and provide large current for the output capacitor when the transient change of the load is detected, thereby realizing the quick transient response to the change of the load. On the basis of ensuring the better stability of a circuit system, the transient response speed is improved, and the larger fluctuation of the output voltage is avoided.
Fig. 8 shows a flowchart of a control method of the switching regulator shown in fig. 1. Referring to fig. 8, the control method of the switching regulator includes steps S01 to S04.
In step S01, a switching signal is generated.
In step S02, the first switch tube is controlled to be turned on and off according to the switch signal.
In step S03, an adjustment signal is generated according to the output voltage of the switching regulator and a first reference voltage.
In step S04, the turn-off time of the first switch tube is controlled according to the adjustment signal. When the output voltage is greater than the first reference voltage, controlling the turn-off time of the first switching tube to be constant turn-off time, and when the output voltage is less than or equal to the first reference voltage, controlling the turn-off time of the first switching tube to be the minimum turn-off time, so as to adjust the duty ratio of the switching signal.
In a preferred embodiment, the step of controlling the turn-off time of the first switching tube according to the adjustment signal includes: generating a turn-on signal; generating a first control signal according to a switching signal, wherein the first control signal is used for maintaining the turn-off time of the first switching tube at least at a preset constant turn-off time; generating a second control signal according to the switching signal, wherein the second control signal is used for maintaining the turn-off time of the first switching tube at least at a preset minimum turn-off time; and generating the switching signal according to an on signal and an off signal, wherein the off signal is generated according to the first control signal when the adjusting signal is in an invalid state, and the off signal is generated according to the second control signal when the adjusting signal is in an valid state.
In a preferred embodiment, the control method further comprises generating a voltage feedback signal based on the output voltage of the switching regulator, and comparing the voltage feedback signal with the first reference voltage to generate the regulation signal.
In a preferred embodiment, the step of generating the first control signal according to the switching signal comprises: generating a first trigger signal according to the switching signal; charging a first capacitor according to the first trigger signal to generate a first voltage signal; and comparing the first voltage signal with a second reference voltage to generate the first control signal, wherein the second reference voltage is proportional to a voltage difference between an input voltage and an output voltage of the switching regulator, when the first trigger signal is in an invalid state, the first capacitor is charged by a first current proportional to the input voltage of the switching regulator, and a voltage across the first capacitor is used as the first voltage signal.
In a preferred embodiment, the generating the second control signal according to the switching signal includes: generating a second trigger signal according to the switching signal; charging a second capacitor according to the second trigger signal to generate a second voltage signal; and generating the second control signal according to the second voltage signal, wherein when the second trigger signal is in an invalid state, the second capacitor is charged by adopting a constant second current, and the voltage at two ends of the second capacitor is used as the second voltage signal.
In a preferred embodiment, the step of generating the turn-on signal comprises: detecting an input voltage of the switching regulator to obtain a current detection signal; comparing the voltage feedback signal to a third reference voltage to obtain an output voltage, the third reference voltage being proportional to the first reference voltage; obtaining a compensation voltage according to the output voltage; and comparing the current detection signal with the compensation voltage to obtain the conducting signal.
In a preferred embodiment, the switching signal is used to control the on and off of the second switching tube, so that the first switching tube and the second switching tube are alternately switched on and off.
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 (21)
1. A control circuit of a switching regulator for controlling the on and off of a first switching tube, comprising:
a conduction signal generating circuit for generating a conduction signal;
the turn-off signal generating circuit is used for generating a first control signal according to a switching signal, and the first control signal is used for maintaining the turn-off time of the first switching tube at least at a preset constant turn-off time;
the turn-off time adjusting circuit is used for generating an adjusting signal according to the output voltage of the switch-type regulator and a first reference voltage;
the minimum turn-off time circuit is used for generating a second control signal according to the switching signal, and the second control signal is used for maintaining the turn-off time of the first switching tube at least at a preset minimum turn-off time; and
a logic circuit for generating an off signal according to the first control signal, the second control signal, and the adjustment signal, and generating the switching signal according to the on signal and the off signal,
when the output voltage is greater than the first reference voltage, the adjusting signal is in an invalid state, the logic circuit generates the turn-off signal according to the first control signal so as to control the turn-off time of the first switching tube to be constant turn-off time, and
when the output voltage is less than or equal to the first reference voltage, the adjusting signal is in an effective state, and the logic circuit generates the turn-off signal according to the second control signal so as to control the turn-off time of the first switching tube to be the minimum turn-off time, so that the duty ratio of the switching signal is adjusted.
2. The control circuit of claim 1, wherein the logic circuit comprises:
the first input end of the AND gate is used for receiving the first control signal, and the second input end of the AND gate is used for receiving the adjusting signal; and
and the first input end of the OR gate is connected to the output end of the AND gate, the second input end of the OR gate is used for receiving the second control signal, and the output end of the OR gate is used for generating the turn-off signal.
3. The control circuit of claim 1, further comprising a voltage feedback circuit for generating a voltage feedback signal based on the output voltage of the switching regulator.
4. The control circuit of claim 3, wherein the off-time adjustment circuit comprises:
a first comparator that compares the voltage feedback signal and the first reference voltage to generate the adjustment signal.
5. The control circuit of claim 1, wherein the shutdown signal generation circuit comprises:
the first inverter is used for generating a first trigger signal according to the switching signal;
the first charging circuit is used for generating a first voltage signal according to the first trigger signal; and
a second comparator for comparing the first voltage signal with a second reference voltage to generate the first control signal.
6. The control circuit of claim 5, wherein the first charging circuit comprises:
a first current source and a first capacitor connected in series between a supply voltage and ground;
a first switch connected in series to both ends of the first capacitor,
when the first trigger signal is in an invalid state, the first switch is turned off, the first current source charges the first capacitor, and the voltage at two ends of the first capacitor is used as the first voltage signal.
7. The control circuit of claim 1, wherein the minimum off-time circuit comprises:
the second inverter is used for generating a second trigger signal according to the switching signal;
the second charging circuit is used for generating a second voltage signal according to the second trigger signal; and
and the third comparator is used for generating the second control signal according to the second voltage signal.
8. The control circuit of claim 7, wherein the second charging circuit comprises:
a second current source and a second capacitor connected in series between the supply voltage and ground;
a second switch connected in series to both ends of the second capacitor,
when the second trigger signal is in an invalid state, the second switch is turned off, the second current source charges the second capacitor, and the voltage at the two ends of the second capacitor is used as the second voltage signal.
9. The control circuit of claim 1, further comprising a current detection circuit for detecting an input voltage of the switching regulator to obtain a current detection signal.
10. The control circuit of claim 9, wherein the turn-on signal generating circuit comprises:
a fourth comparator for comparing a voltage feedback signal with a third reference voltage to obtain an output voltage, the third reference voltage being proportional to the first reference voltage;
the compensation network is used for obtaining compensation voltage according to the output voltage; and
and the fifth comparator is used for comparing the current detection signal with the compensation voltage to obtain the conducting signal.
11. The control circuit of claim 6, wherein the first current source generates a first current proportional to an input voltage of the switching regulator.
12. The control circuit of claim 6, wherein the second reference voltage is proportional to a voltage difference between an input voltage and an output voltage of the switching regulator.
13. A switching regulator, comprising:
the power stage circuit comprises a first switching tube; and
the control circuit of any one of claims 1-12,
the control circuit generates a switching signal to control the on and off of the first switching tube.
14. The switching regulator of claim 13, wherein said power stage circuit further comprises a second switching tube, said first switching tube being connected in series with said second switching tube,
the switching signal is used for controlling the on and off of the second switching tube, so that the first switching tube and the second switching tube are alternately switched on and off.
15. A method of controlling a switching regulator, comprising:
generating a turn-on signal;
generating a switching signal according to the conducting signal and the turn-off signal, wherein the switching signal is used for controlling the conduction and the turn-off of a first switching tube of the switch type regulator;
generating a first control signal according to the switching signal, wherein the first control signal is used for maintaining the turn-off time of the first switching tube at least at a preset constant turn-off time;
generating a second control signal according to the switching signal, wherein the second control signal is used for maintaining the turn-off time of the first switching tube at least at a preset minimum turn-off time;
generating a regulation signal according to the output voltage of the switch-type regulator and a first reference voltage; and
generating the turn-off signal according to the first control signal, the second control signal and an adjustment signal,
wherein when the output voltage is greater than the first reference voltage, the adjustment signal is in an invalid state, the turn-off signal is generated according to the first control signal to control the turn-off time of the first switching tube to be the constant turn-off time, and
when the output voltage is less than or equal to the first reference voltage, the adjusting signal is in an effective state, and the turn-off signal is generated according to the second control signal so as to control the turn-off time of the first switching tube to be the minimum turn-off time, thereby adjusting the duty ratio of the switching signal.
16. The control method of claim 15, further comprising generating a voltage feedback signal based on an output voltage of the switching regulator.
17. The control method of claim 16, wherein the step of generating the regulation signal based on the output voltage of the switching regulator and a first reference voltage comprises:
comparing the voltage feedback signal to the first reference voltage to generate the adjustment signal.
18. The control method of claim 15, wherein the step of generating the first control signal according to the switching signal comprises:
generating a first trigger signal according to the switching signal;
charging a first capacitor according to the first trigger signal to generate a first voltage signal; and
comparing the first voltage signal with a second reference voltage to generate the first control signal, the second reference voltage being proportional to a voltage difference of an input voltage and an output voltage of the switching regulator,
when the first trigger signal is in an invalid state, the first capacitor is charged by adopting a first current which is proportional to the input voltage of the switch-type regulator, and the voltage at two ends of the first capacitor is used as the first voltage signal.
19. The control method of claim 15, wherein generating the second control signal according to the switching signal comprises:
generating a second trigger signal according to the switching signal;
charging a second capacitor according to the second trigger signal to generate a second voltage signal; and
generating the second control signal according to the second voltage signal,
when the second trigger signal is in an invalid state, the second capacitor is charged by adopting a constant second current, and the voltage at two ends of the second capacitor is used as the second voltage signal.
20. The control method of claim 16, wherein the step of generating a turn-on signal comprises:
detecting an input voltage of the switching regulator to obtain a current detection signal;
comparing the voltage feedback signal to a third reference voltage to obtain an output voltage, the third reference voltage being proportional to the first reference voltage;
obtaining a compensation voltage according to the output voltage; and
and comparing the current detection signal with the compensation voltage to obtain the conducting signal.
21. The control method according to claim 15, characterized by further comprising:
and controlling the on and off of the second switching tube by adopting the switching signal, so that the first switching tube and the second switching tube are alternately switched on and off.
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| CN116404869A (en) * | 2021-12-27 | 2023-07-07 | 圣邦微电子（北京）股份有限公司 | Switching power supply and audio noise suppression method thereof |
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| US8493047B2 (en) * | 2011-05-23 | 2013-07-23 | Alpha And Omega Semiconductor Incorporated | Constant on-time switching regulator implementing dual control loops |
| CN202475254U (en) * | 2012-03-27 | 2012-10-03 | 成都芯源系统有限公司 | Switch converter and control circuit thereof |
| CN103023326B (en) * | 2012-12-11 | 2014-11-05 | 矽力杰半导体技术(杭州)有限公司 | Constant time control method, control circuit and switching regulator using same |
| CN104467095A (en) * | 2014-12-09 | 2015-03-25 | 芯荣半导体有限公司 | Constant-current and constant-voltage charger chip based on ACOT framework |
| CN105896942B (en) * | 2016-05-18 | 2018-12-25 | 矽力杰半导体技术(杭州)有限公司 | Control circuit, control method and the switch type regulator of switch type regulator |
| TWI613883B (en) * | 2017-01-06 | 2018-02-01 | 茂達電子股份有限公司 | Constant on-time converter having fast transient response |
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