CN112803763B - Control circuit, voltage conversion system and control method thereof - Google Patents
Control circuit, voltage conversion system and control method thereof Download PDFInfo
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- CN112803763B CN112803763B CN202110166136.XA CN202110166136A CN112803763B CN 112803763 B CN112803763 B CN 112803763B CN 202110166136 A CN202110166136 A CN 202110166136A CN 112803763 B CN112803763 B CN 112803763B
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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
- H02M1/36—Means for starting or stopping converters
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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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Abstract
The invention provides a control circuit, a voltage conversion system and a control method thereof. A control circuit for controlling a voltage conversion circuit is provided with a multiplexing terminal, the multiplexing terminal is coupled with an output terminal of the voltage conversion circuit and a second transistor, the terminal voltage of the multiplexing terminal is used for providing a feedback signal and a power supply for the control circuit, when the terminal voltage is smaller than a reference threshold value, the second transistor is conducted, when the terminal voltage is larger than the reference threshold value, the second transistor is turned off, and the reference threshold value is adjustable according to different states. The control circuit, the voltage conversion system and the control method thereof can select different multiplexing end voltage reference thresholds according to the condition of the voltage conversion system, so that the voltage conversion system can be quickly started and fully powered, can reliably provide feedback signals and reduce standby power consumption.
Description
Technical Field
The present invention relates to the field of electronics, and more particularly, but not exclusively, to a control circuit, a voltage conversion system thereof, and a control method thereof.
Background
The voltage conversion system is used for converting an input voltage into an output voltage suitable for driving a load. In electrical appliances such as household electrical appliances or small household electrical appliances, it is often necessary to supply power to high-power loads such as motors and also to supply power to low-power loads such as processing voltage conversion systems, and the input power supply of the electrical appliances needs to adopt commercial power alternating current. When a low-power load is supplied, the required output voltage is low during driving. Fig. 1 shows a voltage conversion system for an electrical appliance such as a household electrical appliance, which provides a lower output voltage Vout through a voltage conversion circuit based on a dc input voltage Vin obtained by rectifying a commercial ac. The voltage conversion system has simple structure and low standby power consumption, and is very suitable for providing power for low-voltage loads in household appliances. In order to reduce the complexity of the voltage conversion system as much as possible, the control circuit 10 in the voltage conversion system supplies power to the control circuit 10 by using the feedback voltage Vout through the multiplexing pin FB/VDD. The control circuit 10 provides a supply voltage through the current source when starting, and shuts down the current source to supply power through the output voltage Vout when the output voltage reaches a certain threshold value, so as to further reduce the power consumption of the voltage conversion system. However, when the output voltage Vout is low, for example, the output voltage Vout is below 5 volts, the higher threshold will cause the terminal voltage generated by the current source to occasionally interfere with the sampling of the feedback signal when the output voltage Vout is low, such as in a standby state. When a lower threshold is adopted, the main transistor Q1 may be insufficiently turned on, and enter a saturation state, thereby reducing the efficiency of the voltage conversion system.
In view of the above, there is a need to provide a new structure or control method to solve at least some of the above problems.
Disclosure of Invention
The invention provides a control circuit with adjustable voltage reference threshold at a multiplexing terminal, a voltage conversion system and a control method thereof, aiming at one or more problems in the prior art.
According to an aspect of the present invention, a voltage converting system includes a voltage converting circuit and a control circuit controlling the voltage converting circuit, wherein the control circuit has a multiplexing terminal, wherein the multiplexing terminal is coupled to an output terminal of the voltage converting circuit and a second transistor, and a terminal voltage of the multiplexing terminal is used for providing a feedback signal and a power supply for the control circuit, wherein: when the terminal voltage is smaller than the reference threshold value, the second transistor is conducted; when the terminal voltage is larger than a reference threshold value, the second transistor is turned off; and the reference threshold is adjustable according to different conditions.
In one embodiment, the reference threshold is lowered when the voltage conversion system enters closed-loop control from the startup state.
In one embodiment, the control circuit includes: a state signal generating circuit for providing at least one state signal according to different states; a threshold selection circuit that selects one of a plurality of thresholds as a reference threshold according to the at least one status signal; and the comparison circuit is used for comparing the reference threshold value and the terminal voltage, and the output end of the comparison circuit is coupled with the control end of the second transistor.
In one embodiment, the status signal generating circuit includes a second comparing circuit that compares the terminal voltage with a second threshold value, the status signal being in a first state when the terminal voltage is less than the second threshold value, the threshold selecting circuit selects a first reference threshold value as the reference threshold value, the status signal being in a second state when the terminal voltage is greater than the second threshold value, the threshold selecting circuit selects a second reference threshold value as the reference threshold value, wherein the first reference threshold value is higher than the second reference threshold value.
In one embodiment, the state signal generating circuit provides the state signal according to a feedback sampling mode of the voltage conversion system, the threshold selecting circuit selects a third reference threshold when the sampling mode of the feedback signal is single-point sampling, and selects a fourth reference threshold when the sampling mode of the feedback signal is global sampling, wherein the third reference threshold is higher than the fourth reference threshold.
In one embodiment, the second transistor has a control terminal, a first terminal and a second terminal, wherein the first terminal of the second transistor is coupled to the high voltage source, and the second terminal of the second transistor is coupled to the multiplexing terminal.
In one embodiment, a diode is coupled between the multiplexing terminal and the output terminal of the voltage converting circuit, wherein an anode of the diode is coupled to the output terminal of the voltage converting circuit, and a cathode of the diode is coupled to the multiplexing terminal.
In one embodiment, the multiplexing terminal is further coupled to a capacitor. In one embodiment, the control circuit further has a control terminal coupled to a control terminal of a main transistor of the voltage conversion circuit, wherein a first terminal of the main transistor is coupled to the high voltage source, and a second terminal of the main transistor is coupled to the other terminal of the capacitor and a ground terminal of the control circuit.
In one embodiment, the control circuit includes a second transistor that is a junction field effect transistor.
In one embodiment, the voltage conversion circuit includes a Buck circuit.
According to another aspect of the present invention, a voltage conversion system includes the control circuit and the voltage conversion circuit described in any of the above embodiments.
According to still another aspect of the present invention, a control method for a voltage conversion system includes: simultaneously providing a power supply and a feedback signal for the control circuit through one multiplexing end of the control circuit; when the terminal voltage of the multiplexing terminal is lower than a reference threshold value, the second transistor is conducted and a first current path is established to provide a power supply for the control circuit; when the voltage of the end is higher than the reference threshold value, the second transistor is switched off and a feedback signal and a power supply are provided through the output end of the voltage conversion circuit; and adjusting the reference threshold according to the state of the voltage conversion system; the voltage conversion system comprises a voltage conversion circuit and a control circuit for controlling the voltage conversion circuit.
In one embodiment, the control method is used for a Buck circuit, the second transistor is conducted when the terminal voltage is lower than a reference threshold value, and the first current path comprises flowing from the drain of a main transistor of the Buck circuit to the multiplexing terminal through the second transistor.
In one embodiment, the control method comprises the steps of comparing the terminal voltage with a second threshold value after the voltage transformation system is started or restarted, setting the reference threshold value as a first reference threshold value when the terminal voltage is smaller than the second threshold value, and setting the reference threshold value as a second reference threshold value by single triggering when the terminal voltage is larger than the second threshold value, wherein the first reference threshold value is larger than the second reference threshold value.
In one embodiment, the control method comprises setting the reference threshold to a third reference threshold when the voltage transformation system selects single-point sampling of the feedback signal, and setting the reference threshold to a fourth reference threshold when the voltage transformation system selects global sampling of the feedback signal, wherein the third reference threshold is greater than the fourth reference threshold.
In one embodiment, the control method includes decreasing the reference threshold when the voltage conversion system enters closed-loop control from the startup state.
According to the control circuit, the voltage conversion system and the control method thereof, the multiplexing terminal is adopted to provide the power supply and the feedback signal for the control circuit at the same time, and different multiplexing terminal voltage reference thresholds can be selected according to the condition of the voltage conversion system, so that the voltage conversion system can be started and supplied with power fully and can provide the feedback signal reliably, and the standby power consumption is reduced.
Drawings
Fig. 1 shows a voltage conversion system for use in an appliance such as a household appliance;
FIG. 2 shows a schematic diagram of a voltage conversion system according to an embodiment of the invention;
FIG. 3 shows a schematic diagram of a power supply control circuit according to an embodiment of the invention;
FIG. 4 shows a schematic diagram of a power supply control circuit according to another embodiment of the invention;
FIG. 5 shows a schematic diagram of a status signal generating circuit according to an embodiment of the invention;
FIG. 6 is a flow chart illustrating a control method for a voltage conversion system according to an embodiment of the present invention;
fig. 7A and 7B are diagrams illustrating waveforms when different reference thresholds are selected according to an embodiment of the present invention.
The same reference numbers in different drawings identify the same or similar elements or components.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
The description in this section is for several exemplary embodiments only and the invention is not to be limited in scope by the embodiments described. Combinations of different embodiments, and substitutions of features from different embodiments, or similar prior art means may be substituted for or substituted for features of the embodiments shown and described.
The term "coupled" or "connected" in this specification includes both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a conductor, wherein the electrically conductive medium may contain parasitic inductance or parasitic capacitance, or through an intermediate circuit or component as described in the embodiments in the specification; indirect connections may also include connections through other active or passive devices that perform the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, and so on. "plurality" or "plurality" means two or more.
Fig. 2 shows a schematic diagram of a voltage conversion system according to an embodiment of the invention. The voltage conversion system is used for converting an input voltage source Vin into an output voltage Vout suitable for driving a load. Wherein the voltage conversion system comprises a voltage conversion circuit. In the illustrated embodiment, the voltage conversion circuit is a Buck circuit (voltage reduction circuit) for converting a higher dc input voltage Vin to a dc output voltage Vout lower than Vin. The Buck circuit comprises a main transistor Q1, a rectifier tube D1 and an inductor L, wherein a first terminal of the main transistor Q1 is coupled to a high voltage source Vin, a second terminal of the main transistor Q1 is coupled to a first terminal of the inductor L and a rectifier tube D1, a control terminal of the main transistor Q1 is coupled to a control terminal CT of the control circuit 20, and the control circuit 20 controls the main transistor Q1 to be turned on and off. The second terminal of the inductor L is coupled to the output terminal of the voltage conversion system for providing the output voltage Vout. Preferably, the high voltage source Vin is a dc bus voltage signal obtained by rectifying ac power of a mains supply through a bridge rectifier circuit. Thus, a low output voltage alternating current-direct current (AC-DC) conversion can be achieved by the rectifier circuit and the Buck circuit shown in the figure. Of course, the input voltage Vin may be other types of input power sources. By controlling the on and off of the main transistor Q1, the output of the Buck circuit provides the output voltage Vout, where Vout — D Vin, where D is the duty cycle of the main transistor Q1, which is the ratio of the on duration to the cycle duration of the main transistor Q1. The rectifier D1 may be a diode or a synchronous rectifier. In the illustrated embodiment, the rectifier tube D1 is a diode, and has an anode grounded and a cathode coupled to the first end of the inductor L. The second terminal of the inductor L provides the output voltage. In further embodiments, the voltage conversion circuit may also have other types of topologies, such as a Buck-Boost circuit (Buck-Boost circuit). Preferably, the main transistor Q1 includes a Metal Oxide Semiconductor Field Effect Transistor (MOSFET).
The voltage conversion system further includes a control circuit 20 for driving the main transistor Q1 to be turned on and off. The control circuit 20 includes a switch control circuit 21, a power supply control circuit 22, and a second transistor Q2. The control circuit 20 has a multiplexing terminal FB/VDD for simultaneously providing the control circuit 20 with the power supply VDD and the feedback signal FB. The power supply VDD and the feedback signal FB are provided by the terminal voltage of the multiplexing terminal FB/VDD. Wherein the switch control circuit 21 is coupled to the multiplexing terminal FB/VDD for receiving the feedback signal FB, and the switch control circuit 21 at least performs duty cycle adjustment and control on the main transistor Q1 based on the feedback signal FB. The power supply control circuit 22 is coupled to the multiplexing terminal FB/VDD for receiving the terminal voltage VDD, and controls the second transistor Q2 based on the terminal voltage VDD. Preferably, the second transistor Q2 comprises a Junction Field Effect Transistor (JFET). The second transistor may also be another type of transistor, such as a MOSFET. The second transistor Q2 has a control terminal, a first terminal and a second terminal, wherein the first terminal of the second transistor Q2 is coupled to the high voltage source HV, and the second terminal of the second transistor Q2 is coupled to the multiplexing terminal FB/VDD. In a preferred embodiment, the high voltage source HV is an input voltage Vin of a voltage conversion circuit, which may be a rectified voltage of a mains alternating current. Thus, when the second transistor Q2 is turned on, current flows from the input terminal Vin of the voltage conversion circuit to the multiplexing terminal FB/VDD through the second transistor Q2. The high voltage source may also originate from other supply voltage conversion systems. The first terminal of the second transistor Q2 may also be coupled to other types of power supplies that are not classified as high voltage supplies. The voltage transformation system may further include a one-way pass device D2 and a capacitor C1, the one-way pass device D2 is coupled between the multiplexing terminal FB/VDD and the output terminal of the voltage transformation circuit for feeding back the output voltage Vout to the multiplexing terminal FB/VDD. In the illustrated embodiment, the one-way conduction device D2 is a diode D2, wherein an anode of the diode D2 is coupled to the output terminal of the voltage transformation circuit, and a cathode of the diode D2 is coupled to the multiplexing terminal FB/VDD. In other embodiments, diode D2 may be replaced by other types of unidirectional devices, such as a controlled switch. The capacitor C1 is coupled to the multiplexing terminal FB/VDD for stabilizing the terminal voltage. When the second transistor Q2 is turned on, current flows from the input terminal Vin of the voltage conversion circuit to the multiplexing terminal FB/VDD through the second transistor Q2 to charge the capacitor C1, thereby increasing the supply voltage VDD of the control circuit 20. In the illustrated embodiment, the control circuit 20 includes a second transistor Q2. In further embodiments, the capacitor C1 may be omitted. In another embodiment, the second transistor Q2 may also be located outside the control circuit 20 as a discrete device. Preferably, the second terminal of the main transistor Q1 is further coupled to the other terminal of the capacitor C1 and the ground terminal GND of the control circuit 20, so that the ground reference of the control circuit 20 is the second terminal of the main transistor Q1, and is controlled by floating.
The multiplexing terminal FB/VDD is coupled to the output terminal of the voltage converting circuit for receiving a feedback signal FB indicative of the output voltage Vout and supplying power to the control circuit 20 through the feedback signal when the voltage converting system is operating normally. When the terminal voltage at the multiplexing terminal FB/VDD is smaller than the reference threshold Vref, the second transistor Q2 is turned on to supply power to the control circuit 20 through or mainly through the second transistor Q2, and when the terminal voltage is larger than the reference threshold Vref, the second transistor Q2 is turned off to supply power to the control circuit 20 through the output voltage Vout of the voltage conversion circuit.
In the application of the low output voltage Vout, in order to enable the output voltage to be accurately fed back to the multiplexing terminal without being affected by the feedback signal caused by the conduction of the second transistor Q2 during normal operation, the reference threshold Vref is set to be low. Therefore, the terminal voltage VDD is also low. And terminal voltage VDD is the maximum voltage that can be applied to the gate of the main transistor MOSFET. To reduce the MOSFET turn-on gate voltage, a thin gate oxide application may be selected, i.e., process optimization is used to allow the MOSFET to be fully turned on at a lower gate supply voltage. But based on this choice, risks include whether MOSFET saturation is sufficiently uncontrollable unless redundancy is designed to avoid MOSFET saturated areas.
When the voltage conversion system is restarted, the voltage conversion system usually works in a deep Continuous Current Mode (CCM), and at the moment, if the reference threshold value Vref is lower, the terminal voltage VDD is lower, so that the danger that the MOSFET enters a saturation state is increased, the power consumption is increased, the control is unreliable, and the like.
In order to improve the operational reliability of the voltage conversion system, the reference threshold Vref is adjusted according to different states of the voltage conversion system. In one embodiment, the reference threshold is lowered when the voltage conversion system enters closed-loop control from a startup state. The starting state can be represented by a state signal when the voltage conversion system is started or restarted, and the closed-loop control can be represented by detecting the voltage VDD of the end or other signals for representing that the voltage conversion system can enter the closed-loop control.
In one embodiment, the control circuit 20 is fabricated in a semiconductor package and the multiplexing terminal FB/VDD is formed as a pin of the semiconductor package. In another embodiment, the control circuit 20 is fabricated on a semiconductor chip, and the multiplexing terminal FB/VDD is formed as a pin of the control circuit 20 chip, which can be embodied as a metal wire, a pad, or the like. In one embodiment, the main transistor Q1 is fabricated on another semiconductor chip, the control circuit 20 and the main transistor Q1 are packaged in the same package, and the multiplexing terminal FB/VDD is formed as a pin of the chip inside the package and as a pin of the package outside the package.
Fig. 3 shows a schematic diagram of a power supply control circuit according to an embodiment of the invention. Wherein a control terminal of the second transistor Q2 is coupled to the output terminal of the power supply control circuit. The power supply control circuit includes a state signal generation circuit 31, a threshold selection circuit 32, and a comparison circuit 33. The status signal generating circuit 31 is adapted to provide at least one status signal CV depending on the different states. For example, during the period when the voltage conversion system is in a power-on state or a restart state suitable for a saturation depth CCM (continuous current mode) operation, the state signal CV is set to the first state for increasing the reference threshold value and preventing the main transistor Q1 from operating in a saturation state due to insufficient supply voltage, and when the main transistor Q1 operates normally and the voltage conversion system enters a closed-loop operation, the state signal CV is set to the second state for decreasing the reference threshold value Vref so as to prevent the second transistor Q2 from being turned on and causing interference to the feedback signal in a subsequent standby state. Or when the switch control circuit controls the duty ratio of the main transistor based on single-point sampling of the feedback signal, the reference threshold Vref may be appropriately increased, and when the switch control circuit controls the duty ratio of the main transistor based on the global sampling value of the feedback signal, the reference threshold Vref needs to be decreased to avoid interference caused by the conduction of the second transistor Q2 on the feedback signal in a subsequent standby state. The number of the state signals CV may be one or more. In another embodiment, the control circuit may not include the state signal generating circuit 31, and the state signal is directly set through an external pin of the control circuit. An input terminal of the threshold selection circuit 32 is coupled to the output terminal of the state signal generation circuit 31 for receiving the at least one state signal CV, and the threshold selection circuit 32 selects one of a plurality of thresholds Vreg1, Vreg2, etc. as a reference threshold according to a state value of the state signal CV. In the embodiment shown in fig. 2, the threshold selection circuit 32 has two threshold signals Vreg1 and Vreg 2. The threshold selection circuit 32 selects the first reference threshold Vreg1 as the reference threshold signal Vref when the state signal CV is in a first state, such as high, and the threshold selection circuit 32 selects the second reference threshold Vreg2 as the reference threshold signal Vref when the state signal CV is in a second state, such as low. Thus, under different conditions or conditions, the reference threshold Vref will be varied or adjusted accordingly. The non-inverting input and the inverting input of the comparison circuit 33 receive the reference threshold signal Vref and the supply signal VDD, respectively. The comparison circuit 33 may also adopt other types of circuits having a comparison function. The power supply signal VDD may be directly the terminal voltage of the terminal FB/VDD in fig. 2, or reflect the terminal voltage. The comparison circuit 33 compares the reference threshold Vref with the terminal voltage VDD, and an output terminal of the comparison circuit 33 is coupled to a control terminal of the second transistor Q2. By such control, when in some states, such as the voltage conversion system working enters the closed-loop control or the voltage conversion system selects to globally sample the feedback signal, the state signal CV is the first state, the voltage conversion system selects a lower reference threshold as the condition for turning on the second transistor Q2, and the second transistor Q2 is turned on only at a lower terminal voltage VDD, so that when the output voltage is lower, the feedback signal sampling is not affected by the second transistor Q2, the accuracy of the feedback control is ensured, and simultaneously, the power consumption of the voltage conversion system, especially the power consumption in the standby state, is effectively reduced. When the voltage conversion system is in saturation restart or the voltage conversion system selects to perform single-point sampling on the feedback signal, the state signal CV is in a second state, the voltage conversion system selects a higher reference threshold as a condition for conducting the second transistor Q2, and the second transistor Q2 is conducted at a higher terminal voltage VDD, so that the voltage conversion system can be used for providing sufficient electric energy for the voltage conversion system under the condition that the saturation restart and the like do not need the feedback signal but have a large power supply requirement or under the condition that the sampling of the feedback signal is not easy to generate interference.
Fig. 4 shows a schematic diagram of a power supply control circuit according to another embodiment of the invention. Wherein the state signal generating circuit generates a plurality of state signals C1 and C2 for selecting one of a plurality of threshold signals Vreg1, Vreg2, Vreg3 and Vreg4 as a reference threshold according to different states characterized by the state signals C1 and C2. For example, the reference threshold is set to four steps according to whether the voltage conversion system works in a closed loop state or not and whether global sampling is adopted or not.
FIG. 5 shows a schematic diagram of a status signal generation circuit according to an embodiment of the invention. The state signal generating circuit includes a second comparing circuit 51 and a one-shot circuit 52. The non-inverting input terminal of the second comparing circuit 51 is coupled to the multiplexing terminal for receiving the terminal voltage VDD, and the inverting input terminal of the second comparing circuit 51 receives the second threshold signal Vref 2. The second comparison circuit 51 compares the terminal voltage VDD with a second threshold value Vref2, when the terminal voltage VDD is smaller than the second threshold value Vref2, the second comparison circuit 51 outputs a low level state, the state signal CV is in a first state (for example, a high level), the threshold selection circuit 32 shown in fig. 3 selects a higher first reference threshold value Vreg1 as the reference threshold value Vref, when the terminal voltage VDD is larger than the second threshold value Vref2, the comparison circuit outputs a high level, the one-shot circuit 52 detects a change of the signal, the trigger state signal CV is switched from the first state to the second state (for example, a low level), and the threshold selection circuit selects a second reference threshold value Vreg2 as the reference threshold value Vref, wherein the first reference threshold value Vreg1 is higher than the second reference threshold value Vreg 2. The one-shot circuit 52 triggers only once, after which the state signal CV remains unchanged so that the reference threshold is kept at a lower value so that the sampling of the feedback signal by the voltage transformation system is not disturbed by the conduction of the second transistor. When the voltage conversion system is restarted, the voltage conversion system does not enter closed-loop control yet at the starting stage, the output voltage of the output end does not need to be fed back to a multiplexing end VDD/FB, the second transistor is conducted, the end voltage VDD rises, when the end voltage VDD is smaller than Vref2, the voltage conversion system is in a first state, the threshold selection circuit 32 selects a higher first reference threshold Vreg1 as a threshold signal, the power supply of the voltage conversion system is fully ensured when the restarting stage meets the deep continuous current mode, and the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) serving as a main transistor in the section is prevented from entering saturation risk. When the VDD voltage is high enough, for example, VDD is greater than Vref2, the state signal is switched to the second state, the voltage transformation system enters a feedback control stage, and the threshold selection circuit selects a smaller second reference threshold Vreg2 as the reference threshold Vref, so that the feedback signal sampling of the output voltage at the multiplexing terminal is not affected by the conduction of the second transistor, the voltage transformation system can feed back a lower output voltage, and the standby power consumption of the voltage transformation system is lower.
In one embodiment, the state signal generating circuit provides the state signal according to a feedback sampling mode of the voltage conversion system, the threshold selecting circuit selects a third reference threshold Vreg3 when the sampling mode of the feedback signal is single-point sampling, and selects a fourth reference threshold Vreg4 when the sampling mode of the feedback signal is global sampling, wherein the third reference threshold Vreg3 is higher than the fourth reference threshold Vreg4, so that when the sampling mode is global sampling, the requirement for accuracy of the feedback signal is higher, and the reference threshold for turning on the second transistor Q2 can be set lower.
Fig. 6 is a flowchart illustrating a control method for a voltage conversion system according to an embodiment of the present invention. The control method includes, at step 601: the control circuit is used for controlling the switching state of a main transistor of the voltage conversion circuit to generate output voltage at the output end of the voltage conversion circuit, and the feedback signal is a signal representing the output voltage. In one embodiment, the feedback signal is proportional to the output voltage. The control method includes, at step 602: the terminal voltage VDD is compared with a reference threshold. In step 603: if the terminal voltage VDD of the multiplexing terminal is lower than the reference threshold Vref, the second transistor Q2 is turned on and a first current path is established to provide the power supply for the control circuit. Referring to fig. 2 and 3, the voltage conversion circuit includes a Buck circuit, when the multiplexing terminal voltage VDD is less than the reference threshold Vref, the second transistor Q coupled between the input voltage terminal Vin and the multiplexing terminal FB/VDD is turned on, the control circuit 20 is powered through the multiplexing terminal FB/VDD, and the first current path includes flowing from the drain of the Buck circuit main transistor Q1 to the multiplexing terminal FB/VDD through the second transistor Q2. Preferably, the main transistor of the Buck circuit is a MOSFET tube, and the second transistor is a JFET tube. In step 604, when the terminal voltage VDD is higher than the reference threshold Vref, the second transistor JFET is turned off and provides a feedback signal FB and power supply for the control circuit through the output terminal Vout of the voltage conversion circuit. The control method includes adjusting the reference threshold according to the state in step 604, so that the terminal voltage can meet the power supply requirement of the voltage conversion system, and the normal operation is not interfered, so that the voltage conversion system has better standby performance.
In one embodiment, the method further comprises comparing the terminal voltage VDD and the second threshold Vref2 after the voltage transformation system is powered on or restarted, setting the reference threshold Vref to the first reference threshold Vreg1 when the terminal voltage VDD is smaller than the second threshold Vref2, and setting the reference threshold Vref to the second reference threshold Vreg2 in a single trigger when the terminal voltage VDD is larger than the second threshold Vref2, wherein the first reference threshold Vreg1 is larger than the second reference threshold Vreg 2. Therefore, the power supply in the deep continuous current mode can be fully satisfied in the restart stage of the voltage conversion system, when the restart stage of the voltage conversion system is finished and enters the normal working mode,
in another embodiment, the reference threshold Vref is set to a third reference threshold Vreg3 when the voltage transformation system selects single-point sampling of the feedback signal, and the reference threshold Vref is set to a fourth reference threshold Vreg4 when the voltage transformation system selects global sampling control of the feedback signal, wherein the third reference threshold Vreg3 is greater than the fourth reference threshold Vreg 4.
In one embodiment, when the voltage transformation system is in a power-on or restart state, the reference threshold Vref is set as a first reference threshold Vreg1, and when the voltage transformation system enters a closed-loop control state, for example, the terminal voltage VDD is greater than a preset reference signal Vref2 or other signals indicating that the voltage transformation system enters the closed-loop control state are active, the reference threshold Vref is lowered to a second reference threshold Vreg2, wherein the first reference threshold Vreg1 is greater than the second reference threshold Vreg 2. The method is used for enabling the terminal voltage VDD to reflect the output voltage Vout in a large range, feeding back the output voltage Vout in a low range and realizing reliable closed-loop control.
Fig. 7A and 7B are schematic diagrams illustrating waveforms when different reference thresholds are selected according to an embodiment of the present invention. Referring to fig. 7A, the top-down signals represent the terminal voltage VDD, the main transistor Q1 turn-ON signal Q1 ON, and the second transistor Q2 turn-ON signal, respectively. In fig. 7A, when the reference threshold Vref is set to the higher first reference threshold Vreg1, the terminal voltage VDD cannot reflect the lower output voltage, the second transistor Q2 is turned on for a longer time, and the Q2 generates a larger power consumption, which can provide more energy for the voltage conversion system. In fig. 7B, when the reference threshold Vref is set to the lower second reference threshold Vref2, the terminal voltage VDD may reflect a lower output voltage, the second transistor Q2 is turned on for a shorter time or may not be turned on, the power consumption generated on Q2 is lower, the second transistor Q2 may not be involved when the voltage converting system is idle, and the standby power consumption of the voltage converting system is lower.
Those skilled in the art should understand that the logic controls such as "high" and "low", "set" and "reset", "and gate" and "or gate", "non-inverting input" and "inverting input" in the logic controls referred to in the specification or the drawings may be exchanged or changed, and the subsequent logic controls may be adjusted to achieve the same functions or purposes as the above-mentioned embodiments.
The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. The descriptions related to the effects or advantages in the specification may not be reflected in practical experimental examples due to uncertainty of specific condition parameters or influence of other factors, and the descriptions related to the effects or advantages are not used for limiting the scope of the invention. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.
Claims (16)
1. A control circuit for a voltage converting system, the voltage converting system comprising a voltage converting circuit and a control circuit for controlling the voltage converting circuit, wherein the control circuit has a multiplexing terminal, wherein the multiplexing terminal is coupled to an output terminal of the voltage converting circuit and a second transistor, a terminal voltage of the multiplexing terminal is used for providing a feedback signal and a power supply for the control circuit, the second transistor has a control terminal, a first terminal and a second terminal, wherein the first terminal of the second transistor is coupled to a high voltage source, and the second terminal of the second transistor is coupled to the multiplexing terminal, wherein:
when the terminal voltage is smaller than a reference threshold value, the second transistor is conducted;
when the terminal voltage is greater than the reference threshold, the second transistor is turned off;
and the reference threshold is adjustable according to different states.
2. The control circuit of claim 1, wherein the reference threshold is lowered when the voltage conversion system enters closed-loop control from a startup state.
3. The control circuit of claim 1, wherein the control circuit comprises:
a status signal generating circuit providing at least one status signal according to different statuses;
a threshold selection circuit that selects one of a plurality of thresholds as the reference threshold according to the at least one status signal; and
and the comparison circuit is used for comparing the reference threshold value with the terminal voltage, and the output end of the comparison circuit is coupled with the control end of the second transistor.
4. The control circuit of claim 3, wherein said status signal generating circuit includes a second comparing circuit for comparing said terminal voltage with a second threshold value, said status signal being in a first state when said terminal voltage is less than said second threshold value, said threshold value selecting circuit selecting a first reference threshold value as said reference threshold value, said status signal being in a second state when said terminal voltage is greater than said second threshold value, said threshold value selecting circuit selecting a second reference threshold value as said reference threshold value, wherein said first reference threshold value is higher than said second reference threshold value.
5. The control circuit of claim 3, wherein the status signal generation circuit provides the status signal according to a feedback sampling mode of the voltage conversion system, the threshold selection circuit selects a third reference threshold when the sampling mode of the feedback signal is single-point sampling, and selects a fourth reference threshold when the sampling mode of the feedback signal is global sampling, wherein the third reference threshold is higher than the fourth reference threshold.
6. The control circuit of claim 1, wherein a diode is coupled between the multiplexing terminal and the output terminal of the voltage converting circuit, an anode of the diode is coupled to the output terminal of the voltage converting circuit, and a cathode of the diode is coupled to the multiplexing terminal.
7. The control circuit of claim 1, wherein the multiplexing terminal is further coupled to a capacitor.
8. The control circuit of claim 7, wherein the control circuit further has a control terminal, wherein the control terminal is coupled to a control terminal of a main transistor of the voltage converting circuit, wherein a first terminal of the main transistor is coupled to a high voltage source, and a second terminal of the main transistor is coupled to the other terminal of the capacitor and a ground terminal of the control circuit.
9. The control circuit of claim 1, wherein the control circuit comprises the second transistor, the second transistor being a junction field effect transistor.
10. The control circuit of claim 1, wherein the voltage conversion circuit comprises a Buck circuit.
11. A voltage conversion system comprising the control circuit of any one of claims 1 to 10 and the voltage conversion circuit.
12. A control method for a voltage conversion system including a voltage conversion circuit and a control circuit that controls the voltage conversion circuit, characterized by comprising:
simultaneously providing a power supply and a feedback signal for the control circuit through one multiplexing end of the control circuit;
when the terminal voltage of the multiplexing terminal is lower than a reference threshold value, a second transistor is conducted and a first current path is established to provide a power supply for the control circuit;
when the end voltage is higher than the reference threshold value, the second transistor is turned off, and a feedback signal and a power supply are provided through the output end of the voltage conversion circuit; and
the reference threshold is adjusted according to the state of the voltage conversion system.
13. The control method according to claim 12, wherein the control method is for a Buck circuit, the second transistor is turned on when the terminal voltage is lower than the reference threshold, and the first current path includes flowing from a drain of a main transistor of the Buck circuit to the multiplexing terminal through the second transistor.
14. The control method according to claim 12, wherein the control method includes comparing the terminal voltage with a second threshold value after the voltage conversion system is turned on or restarted, setting the reference threshold value as a first reference threshold value when the terminal voltage is smaller than the second threshold value, and setting the reference threshold value as a second reference threshold value with a single trigger when the terminal voltage is larger than the second threshold value, wherein the first reference threshold value is larger than the second reference threshold value.
15. The control method of claim 12, comprising setting the reference threshold to a third reference threshold when the voltage transformation system selects single-point sampling of the feedback signal, and setting the reference threshold to a fourth reference threshold when the voltage transformation system selects global sampling of the feedback signal, wherein the third reference threshold is greater than the fourth reference threshold.
16. The control method of claim 12, comprising decreasing the reference threshold when the voltage conversion system enters closed-loop control from a startup state.
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