CN106655747B - Power supply circuit, switching power supply system and power supply method thereof - Google Patents
Power supply circuit, switching power supply system and power supply method thereof Download PDFInfo
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- CN106655747B CN106655747B CN201611032143.6A CN201611032143A CN106655747B CN 106655747 B CN106655747 B CN 106655747B CN 201611032143 A CN201611032143 A CN 201611032143A CN 106655747 B CN106655747 B CN 106655747B
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- 238000000034 method Methods 0.000 title claims abstract description 15
- 239000003990 capacitor Substances 0.000 claims description 54
- 238000001514 detection method Methods 0.000 claims description 38
- 238000005070 sampling Methods 0.000 claims description 18
- 230000005347 demagnetization Effects 0.000 claims description 8
- 230000001502 supplementing effect Effects 0.000 claims description 6
- 239000013589 supplement Substances 0.000 claims description 5
- 230000005611 electricity Effects 0.000 claims 2
- 230000007547 defect Effects 0.000 abstract description 6
- 238000005516 engineering process Methods 0.000 abstract description 6
- 238000010586 diagram Methods 0.000 description 6
- 101100464782 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) CMP2 gene Proteins 0.000 description 5
- 101100464779 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) CNA1 gene Proteins 0.000 description 5
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Classifications
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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
- H02M1/32—Means for protecting converters other than automatic disconnection
- H02M1/34—Snubber circuits
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal 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
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal 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
-
- 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
- H02M1/0048—Circuits or arrangements for reducing losses
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a power supply circuit, a switching power supply system and a power supply method thereof, which adopt a self-powered and high-voltage power supply combined mode and are suitable for a switching power supply system and an LED driver for driving a power triode; the power supply system overcomes the defects of the prior power supply technology, realizes that the output voltage is not limited by the working voltage of the controller, improves the efficiency and the EMI characteristics of the switching power supply system and the LED driver, and expands the application range, in particular the range of the output voltage.
Description
Technical Field
The present invention relates to the field of switching power supply control, and in particular, to a power supply circuit, a switching power supply system, and a power supply method thereof, which are suitable for an AC-DC switching power supply driving a power transistor.
Background
The high-side buck/buck-boost (buck-boost) AC-DC switching power supply is widely applied to fields such as home appliances and electric meters, and with the progress of technology, the industry has higher requirements on the performance of products, and needs higher efficiency, lower standby power consumption, better EMI performance, better use flexibility and lower cost.
The power consumption during standby is divided into: dummy load consumption, controller consumption, starting circuit consumption and the like, wherein the controller consumption is determined by an internal circuit of the controller and a power supply voltage of the controller, so that standby power consumption can be effectively reduced by reducing the power supply voltage of the controller. The power triode is superior to the power MOS tube in cost, EMI characteristics and the like, and can be well applied to a switching power supply system. In the existing AC-DC switching power supply based on a driving power triode, most of power supply modes of a controller are output power supply.
Referring to fig. 1, Q1 is a power transistor in a high-side buck structure of the prior art. The power supply mode of the output power supply has the following defects: the output voltage cannot be lower than the operating voltage of the controller, so the range of the output voltage is limited (i.e., the output voltage must meet the operating voltage range of the controller), resulting in limited control of the controller application.
Therefore, it is needed to provide a new power supply mode for a controller of a switching power supply system, so as to realize that the output voltage is not limited by the working voltage of the controller, and meanwhile, low power consumption and high efficiency can be realized.
Disclosure of Invention
The invention aims to provide a power supply circuit, a switching power supply system and a power supply method thereof, which overcome the defects of the prior power supply technology by adopting a mode of combining self-power supply and high-voltage power supply, realize that the output voltage is not limited by the working voltage of a controller, and simultaneously realize low power consumption and high efficiency.
In order to achieve the above object, the present invention provides a power supply circuit suitable for a switching power supply system, the power supply circuit comprising: the device comprises a high-voltage power supply unit, a self-powered unit, a control unit and a charging capacitor; the high-voltage power supply unit is respectively and electrically connected with the direct-current voltage input end of the switching power supply system and the VCC voltage input end of the switching power supply system; the self-powered unit is electrically connected with the direct-current voltage input end, the VCC voltage input end and the load end of the switching power supply system respectively; the control unit is respectively coupled with the VCC voltage input end, the self-powered unit and the high-voltage power supply unit and is used for generating a control signal for driving the high-voltage power supply unit to be turned on or off and/or generating a control signal for driving the self-powered unit to be turned on or off; one end of the charging capacitor is electrically connected with the VCC voltage input end, and the other end of the charging capacitor is electrically connected with the load end; when the high-voltage power supply unit is conducted, the high-voltage power supply unit charges a charging capacitor; when the high-voltage power supply unit is turned off, the self-power supply unit supplies power to the load end when the self-power supply unit is turned on, and when the self-power supply unit receives the turn-off control signal output by the control unit, the self-power supply unit completely turns off the charging capacitor after supplying power for one supplying time.
In order to achieve the above purpose, the invention also provides a control chip of the switching power supply, wherein the control chip is internally provided with the power supply circuit.
In order to achieve the above object, the present invention further provides a switching power supply system, including an ac voltage source, a rectifying circuit electrically connected to the ac voltage source, a bus capacitor electrically connected to the rectifying circuit, a dc voltage input terminal electrically connected to the bus capacitor and a common terminal of the rectifying circuit, and a load terminal, the system further includes the power supply circuit of the present invention; when the high-voltage power supply unit is conducted, the high-voltage power supply unit charges a charging capacitor; when the high-voltage power supply unit is turned off, the self-power supply unit supplies power to the load end when the self-power supply unit is turned on, and when the self-power supply unit receives the turn-off control signal output by the control unit, the self-power supply unit completely turns off the charging capacitor after supplying power for one supplying time.
In order to achieve the above purpose, the present invention also provides a power supply method for a switching power supply system, which comprises the following steps: (1) When the switching power supply system works normally, the control unit generates a control signal for driving the self-powered unit to be conducted to control the self-powered unit to be conducted, and the self-powered unit supplies power to a load end; (2) The control unit generates a control signal for driving the self-powered unit to be turned off so as to control the self-powered unit to completely turn off after supplying power to the charging capacitor for one power supplying time.
The invention has the advantages that the self-powered and high-voltage power supply combined mode is adopted, and the self-powered and high-voltage power supply combined LED driver is suitable for a switching power supply system and an LED driver for driving a power triode. The power supply system overcomes the defects of the prior power supply technology, realizes that the output voltage is not limited by the working voltage (namely VCC voltage) of the controller, improves the efficiency and the EMI characteristics of a switching power supply system and an LED driver, expands the application range, particularly the range of the output voltage, and simultaneously can realize low power consumption and high efficiency.
Drawings
FIG. 1 shows a high-side buck structure of a prior art output power supply;
FIG. 2 is a schematic diagram of a switching power supply system according to the present invention;
FIG. 3 is a schematic diagram of an embodiment of a switching power supply system according to the present invention;
FIG. 4 is a waveform diagram of each key node in the embodiment shown in FIG. 3.
Detailed Description
The power supply circuit, the switching power supply system and the power supply method thereof provided by the invention are described in detail below with reference to the accompanying drawings.
Referring to fig. 2, a schematic diagram of a switching power supply system according to the present invention is shown; the switching power supply system includes: the power supply circuit comprises an alternating voltage source Vin, a rectifying circuit 21 electrically connected with the alternating voltage source Vin, a bus capacitor Cin electrically connected with the rectifying circuit 21, a direct voltage input end Mdc electrically connected with the bus capacitor Cin and a common end of the rectifying circuit 21, a load end 29 and a power supply circuit 22. The power supply circuit 22 includes: a high voltage power supply unit 221, a self-power supply unit 222, a control unit 223, and a charging capacitor Cvcc.
The high voltage power supply unit 221 is electrically connected to the dc voltage input terminal Mdc of the switching power supply system and the VCC voltage input terminal Mvcc of the switching power supply system, respectively. The self-powered unit 222 is electrically connected to the dc voltage input terminal Mdc, the VCC voltage input terminal Mvcc, and the load terminal 29 of the switching power supply system, respectively. The control unit 223 is coupled to the VCC voltage input terminal Mvcc, the self-powered unit 222, and the high-voltage power supply unit 221, respectively, and is configured to generate a control signal for driving the high-voltage power supply unit 221 to turn on or off, and/or generate a control signal for driving the self-powered unit 222 to turn on or off. The charging capacitor Cvcc has one end electrically connected to the VCC voltage input terminal Mvcc and the other end electrically connected to the load terminal 29. When the high voltage power supply unit 221 is turned on, the high voltage power supply unit 221 charges the charging capacitor Cvcc. When the high voltage power supply unit 221 is turned off, the self power supply unit 222 supplies power to the load terminal 29 when the self power supply unit 222 is turned on; when the self-power supply unit 222 receives the turn-off control signal output by the control unit 223, the self-power supply unit 222 completely turns off after supplying the charging capacitor Cvcc with the power for a power-supplying time Tch.
Specifically, the high-voltage power supply unit 221 is turned on after receiving the on control signal output by the control unit 223; the dc voltage of the switching power supply system is input to the high voltage power supply unit 221 through the dc voltage input terminal Mdc and is output to the charging capacitor Cvcc through the VCC voltage input terminal Mvcc, so that the switching power supply system charges the charging capacitor Cvcc through the high voltage power supply unit 221. After the high voltage power supply unit 221 receives the off control signal output from the control unit 223, the high voltage power supply unit 221 is turned off.
Specifically, after the self-powered unit 222 receives the on control signal output by the control unit 223, the self-powered unit 222 is turned on; the dc voltage of the switching power supply system is input to the self-powered unit 222 through the dc voltage input terminal Mdc and output to the load terminal 29 through the self-powered unit 222, so that the switching power supply system supplies power to the load terminal 29 through the self-powered unit 222. After the self-power supply unit 222 receives the turn-off control signal output by the control unit 223, the self-power supply unit 222 completely turns off after supplying power to the charging capacitor Cvcc for a power-supplying time Tch.
Preferably, the power supply circuit 22 further includes a VCC detecting unit 224; the VCC detecting unit 224 is configured to detect a VCC voltage on the charging capacitor Cvcc (i.e., a VCC voltage output by a VCC voltage input terminal Mvcc), and output a first detection signal to the control unit 223 when the VCC voltage is greater than or equal to a first reference voltage VCC-TH1 after comparing the VCC voltage with the first reference voltage VCC-TH 1; the control unit 223 generates a control signal for driving the high voltage power supply unit 221 to turn off according to the first detection signal. Specifically, when the switching power supply system is started, the VCC voltage on the charging capacitor Cvcc is initially zero, and the switching power supply system charges the charging capacitor Cvcc through the high-voltage power supply unit 221, so that the VCC voltage gradually increases. When the VCC voltage is equal to or greater than the first reference voltage vcc_th1, the VCC detecting unit 224 outputs a first detection signal to the control unit 223, the control unit 223 outputs a control signal for driving the high voltage power supply unit 221 to turn off, and the high voltage power supply unit 221 is controlled to turn on or off, so that the system startup is completed.
Preferably, the power supply circuit 22 further includes a VCC detecting unit 224; the VCC detecting unit 224 is configured to detect a VCC voltage on the charging capacitor Cvcc (i.e., a VCC voltage output by the VCC voltage input terminal Mvcc), and output a second detection signal to the control unit 223 when the VCC voltage is less than the second reference voltage VCC-TH 2; the control unit 223 is further configured to generate a control signal for driving the high-voltage power supply unit 221 to be turned on according to the second detection signal after the self-power supply unit 222 receives the turn-off control signal outputted by the control unit 223 and is completely turned off.
In some cases, the self-powered unit 222 is only used for self-powering, and there is still a power shortage condition, for example, when the operating frequency is particularly low, because the self-powered unit 222 is powered once in each period, the duty cycle of the power supply is very small, which easily results in the power shortage, and thus the control unit is restarted repeatedly, and the normal operation of the system is affected. Therefore, when the switching power supply system is operating normally, the high voltage power supply unit 221 needs to be supplied with power in time when the power supply of the self-power supply unit 222 is insufficient, so as to prevent the control unit 223 from restarting repeatedly. When the VCC voltage is detected to be lower than the second reference voltage vcc_th2, the VCC detecting unit 224 outputs a second detection signal to the control unit 223, and the control unit 223 generates a control signal for driving the high voltage power supply unit 221 to be turned on according to the second detection signal, so as to control the high voltage power supply unit 221 to be turned on; the high voltage power supply unit 221 starts charging the charging capacitor Cvcc until the VCC voltage is higher than the first reference voltage vcc_th1, and the high voltage power supply unit 221 stops charging. The second reference voltage vcc_th2 is smaller than the first reference voltage vcc_th1.
Preferably, the power supply circuit 20 further includes a demagnetization detecting unit 225; the demagnetization detecting unit 225 is configured to detect a demagnetization point, and feed back a detected demagnetization signal to the control unit 223; the control unit 223 further generates a control signal for driving the self-powered unit 222 to be turned on according to the demagnetizing signal. Once the demagnetizing point is detected, the control unit 223 outputs a turn-on control signal to control the self-powered unit 222 to turn on.
Preferably, the power supply circuit 20 further includes a CS detection unit 226; the CS detection unit 226 is configured to detect a current sampling voltage Vcs of the load terminal 29, and provide a CS detection signal to the control unit 223 when the current sampling voltage Vcs is greater than a preset voltage threshold; the control unit 223 further generates a control signal for driving the self-powered unit 222 to turn off according to the CS detection signal.
The invention adopts a mode of combining self-power supply and high-voltage power supply, and is suitable for a switching power supply system and an LED driver for driving a power triode. The invention overcomes the defects of the prior power supply technology, and the output voltage is not limited by the power supply voltage (namely the VCC voltage) of the control unit because the VCC is not required to be supplied from the output, thereby improving the efficiency and the EMI characteristics of the switching power supply system and the LED driver, expanding the application range, and particularly expanding the range of the output voltage.
The invention also provides a switching power supply control chip, and the power supply circuit is arranged in the control chip. One or more of the self-powered unit 222, the high-voltage power supply unit 221, the control unit 223, the VCC detection unit 224, the demagnetization detection unit 225, and the CS detection unit 226 are integrated in the same control chip, thereby forming a switching power supply control chip.
Referring to fig. 3-4, fig. 3 is a schematic diagram of an embodiment of a switching power supply system according to the present invention; FIG. 4 is a waveform diagram of each key node in the embodiment shown in FIG. 3. Fig. 3 shows a typical application of the present invention in a high-side buck topology, and it should be noted that the present invention is not limited to use in a high-side buck topology, but can be used in switching power supply systems and LED drivers in other topologies.
The ac input Vin is input to the bus capacitor Cin through the rectifier circuit 21 to obtain a dc voltage Vindc, and the dc voltage Vindc is input to the dc voltage input terminal Mdc. The load terminal 29 includes a sampling resistor Rcs, an inductance L0, a capacitance C0, a freewheeling diode D0, and a load 291. One end of the sampling resistor Rcs is electrically connected with the charging capacitor Cvcc and is electrically connected with the inductor L0, and the other end of the sampling resistor Rcs is electrically connected with the output end of the power supply circuit 20; the other end of the inductor L0 is electrically connected with the load 291, and the other end of the load 291 is grounded; the capacitor C0 is connected in parallel to two ends of the load 291; the cathode of the freewheeling diode D0 is electrically connected to the output terminal of the power supply circuit 20, and the anode is grounded.
In the present embodiment, the high voltage power supply unit 221 includes a high voltage power supply element HD1 and a second switch S2; the input end of the high-voltage power supply element HD1 is electrically connected to the dc voltage input end Mdc, and the output end is electrically connected to the first access point of the second switch S2; the second switch S2, the second access point is electrically connected to the VCC voltage input terminal Mvcc (i.e. electrically connected to the upper plate of the charging capacitor Cvcc), and the control terminal is electrically connected to the second output terminal OUT2 of the control unit 223. The second switch S2 is turned on or off according to a control signal generated by the control unit 223; when the second switch S2 is turned on, the high-voltage power supply element HD1 charges the charging capacitor Cvcc. The high-voltage power supply element HD1 is typically a high-voltage JFET or a Depletion MOS (Depletion MOS). The second switch S2 is implemented by a switching transistor, which may be a MOS transistor or a transistor such as a diode or a triode.
In this embodiment, the self-powered unit 222 includes a power transistor Q1, a diode D1, and a first switch S1. The collector of the power transistor Q1 is electrically connected to the dc voltage input terminal Mdc, the base is coupled to the third output terminal OUT3 of the control unit 223, and the emitter is electrically connected to the first access point of the first switch S1 and is electrically connected to the anode of the diode D1; the first switch S1, the second access point is electrically connected to the load terminal 29 (specifically, electrically connected to the sampling resistor Rcs), and the control terminal is electrically connected to the first output terminal OUT1 of the control unit 223; the cathode of the diode D1 is electrically connected with the VCC voltage input end Mvcc. The first switch S1 and the power transistor Q1 are turned on or off according to the control signal generated by the control unit 223; when the first switch S1 is turned off according to the turn-off control signal output by the first output terminal OUT1 of the control unit 223, when the voltage Vce of the emitter of the power transistor Q1 is greater than the sum of the VCC voltage VCC of the VCC voltage input terminal and the forward voltage drop VD1 of the diode D1, that is, vce > (vcc+vd1), the current in the power transistor Q1 supplements the charge capacitor Cvcc through the diode D1. When the power triode Q1 is charged for a certain time, the base electrode of the power triode Q1 is pulled down, the diode D1 is turned off, and the power triode Q1 is thoroughly turned off. The first switch S1 is implemented by a switching tube, which may be a transistor such as a MOS tube or a diode, a triode, or the like. The power transistor Q1 and the first switch S1 are turned off in the same period.
In the present embodiment, the power supply circuit 20 further includes a driving unit 227; the driving unit 227 has one end electrically connected to the base of the power transistor Q1, and the other end electrically connected to the third output terminal OUT3 of the control unit 223, and is configured to output a power transistor control signal to provide a base current for the power transistor Q1 according to the logic control signal provided by the control unit 223.
In this embodiment, the VCC detecting unit 224 includes a first comparator CMP1. One input end of the first comparator CMP1 is electrically connected with the VCC voltage input end and is used for receiving VCC voltage, and the other input end is used for receiving the first reference voltage VCC_TH1; the output terminal is electrically connected to the control unit 223. When VCC voltage is higher than vcc_th1, CMP1 outputs a high level to the control unit 223, and the second output terminal OUT2 of the control unit 223 outputs a turn-off control signal to control the switching tube S2 to turn off, and the high voltage power supply element HD1 stops supplying power.
In this embodiment, the VCC detecting unit 224 further includes a second comparator CMP2. One input end of the second comparator CMP2 is electrically connected with the VCC voltage input end and is used for receiving VCC voltage, and the other input end is used for receiving the second reference voltage VCC_TH2; the output terminal is electrically connected to the control unit 223, wherein vcc_th2 is smaller than vcc_th1. When the VCC voltage is lower than vcc_th2, CMP2 outputs a low level to the control unit 223, and the second output terminal OUT2 of the control unit 223 outputs a turn-on control signal to control the switching tube S2 to be turned on; the switching power supply system charges the charging capacitor Cvcc through the high voltage power supply element HD1 until the VCC voltage rises again to vcc_th1; at this time, CMP1 outputs a high level to the control unit 223, and the second output terminal OUT2 of the control unit 223 outputs an off control signal to control the switching tube S2 to be turned off, so that the high voltage power supply element HD1 stops supplying power.
In this embodiment, the demagnetizing detection unit 225 has an input end electrically connected to the base of the power triode Q1 and an output end electrically connected to the control unit 223, and is configured to detect a demagnetizing point and feed back a detected demagnetizing signal to the control unit 223; the control unit 223 further generates a turn-on control signal to turn on the power transistor Q1 according to the demagnetizing signal. That is, once the demagnetization detecting unit 225 detects the demagnetization point, the control unit 223 outputs the turn-on control signal to control the power transistor Q1 to turn on.
In this embodiment, the input end of the CS detection unit 226 is electrically connected to one end of the sampling resistor Rcs, and the output end of the CS detection unit is electrically connected to the control unit 223, and is configured to detect a current sampling voltage Vcs (i.e. a current flowing from the Q1 emitter) on the sampling resistor Rcs, and provide a CS detection signal to the control unit 223 when the current sampling voltage Vcs is greater than a preset voltage threshold; the control unit 223 further generates a control signal for driving the self-powered unit 222 to turn off according to the CS detection signal. In the on time of the power triode Q1, the current flowing through the Q1 is gradually increased, and the voltage Vcs on the Rcs is gradually increased because the current flowing through the Q1 also flows through the sampling resistor Rcs; when Vcs is higher than a certain preset voltage threshold value set inside the CS detection unit 226, the CS detection unit 226 outputs a high level, and the control unit 223 outputs a turn-off control signal to Q1 and S1, and stops supplying current to the base of Q1, so that the base of Q1 floats.
The working principle of the embodiment of the present invention will be described with reference to fig. 3.
When the switching power supply system is started, the VCC voltage is initially zero, the second comparator CMP2 outputs a low level to the control unit 223, the second output terminal OUT2 of the control unit 223 outputs a turn-on control signal to control the second switch S2 to be turned on, and the system charges the charging capacitor Cvcc through the high-voltage power supply element HD1, so that the VCC voltage gradually rises. During this time, the power transistor Q1 is always in an off state. When the VCC voltage is equal to or greater than the first reference voltage vcc_th1, the first comparator CMP1 outputs a high level, and the second output terminal OUT2 of the control unit 223 outputs a turn-off control signal to control the turn-off of S2, and the start is completed.
After the start, the switching power supply system starts to enter a normal switching working stage. Before the triode Q1 of the power tube is conducted, the collector electrode of the Q1 is high-voltage relative to the ground of the chip; when Q1 is conducted, Q1 and the first switch S1 are simultaneously opened, the current of the inductor L0 starts to increase, and energy is transmitted from the input Vindc to the output VOUT; the input Vindc is connected together through the conducting Q1 and the chip ground, and the collector to chip ground voltage difference of Q1 is small.
During the on time of Q1, the current flowing through Q1 gradually increases; since the current flowing through Q1 also flows through the sampling resistor Rcs, the voltage Vcs on Rcs also gradually increases, and when Vcs is higher than a certain preset voltage threshold value set inside the CS detection unit 226, the CS detection unit 226 outputs a high level, the control unit 223 outputs an off control signal to Q1 and S1, and the control unit 223 stops supplying current to the base of Q1, so that the base of Q1 floats. Because of the stored charge in Q1, Q1 still maintains the on state in a short time, and the voltages of the emitter and the base of Q1 start to rise; when the Q1 emitter voltage rises to vcc+vd1 (VD 1 is the diode forward voltage drop of about 0.7V), the current in Q1 begins to recharge charge capacitor Cvcc through diode D1 and the inductor L0 current continues to increase. At this time, the voltage difference between Vindc and ground is VCC+VD1+Vce, because Q1 is still in the saturation region, vce voltage drop is very low, and at this time, the switching power supply system supplies power for low voltage, and power consumption is low and efficiency is high. When the power supply of the Q1 exceeds the maximum power supply time threshold Tch_max or the VCC voltage is larger than or equal to VCC_TH1, the base electrode of the Q1 is pulled down, the D1 is turned off, the Q1 is completely turned off, the current of the inductor L0 starts to be reduced, and the freewheeling diode D0 is turned on.
High voltage and power transistor combination power supply principle: self-powered by the power transistor alone can still have the condition of insufficient power supply under certain conditions; for example, when the working frequency is particularly low, because the triode is powered once in each period, the duty ratio of the power supply is very small, and the power supply is insufficient easily, so that the control circuit is restarted repeatedly, and the normal operation of the system is affected. When the power supply is insufficient, the high-voltage power supply unit is required to supplement power in time so as to prevent the control circuit from restarting repeatedly. Therefore, when it is detected that the VCC voltage is lower than the second reference voltage vcc_th2, the second comparator CMP2 outputs a low level, the control unit 223 controls S2 to be turned on, the high-voltage power supply element HD1 starts charging the charging capacitor Cvcc until the VCC voltage rises again to the first reference voltage vcc_th1, and the high-voltage power supply element HD1 stops charging.
Tbase in fig. 3 is the time to supply current to the base of Q1; tch_max is Q1 self-powered for the longest time; toff is the Q1 off time; tch_hv is the high voltage supply time. As can be seen from fig. 3, in the time (Tbase) when the base current is provided to Q1, VCC drops faster because the base current is provided by VCC, which consumes more power; after the CS detection unit 226 outputs the high level, OUT1 and OUT3 jump to low, the driving unit 227 stops providing the base current to Q1, Q1 starts to supplement the charge capacitor Cvcc with power, and VCC voltage rises; however, for some reasons (such as too low frequency or other reasons), even if the Q1 self-power time reaches the set maximum time tch_max, the VCC voltage is still lower than vcc_th2, at this time, the high-voltage power supply element HD1 starts to be supplied with power, and the VCC voltage continues to rise; when the VCC voltage rises to vcc_th1, the high-voltage power supply element HD1 stops supplying power. Note that the high-voltage power supply element HD1 supplies power only for the Toff period.
The invention adopts a mode of combining self-power supply and high-voltage power supply of the power triode, and is suitable for a switching power supply system and an LED driver for driving the power triode. The advantages of the power triode are fully exerted, the self-power period of the power triode belongs to low-voltage power supply, and the charging capacitor is charged when the voltage drop of the power triode Vce is relatively low, so that low power consumption and high efficiency are ensured; when the self-power of the power triode is insufficient, the high-voltage power supply unit supplements power in time, so that the system is prevented from being restarted repeatedly. The defects of the prior power supply technology are overcome, the output voltage is not limited by the VCC voltage, the efficiency and the EMI characteristics of the switching power supply system and the LED driver are improved, and the application range, particularly the range of the output voltage, is expanded.
The invention also provides a power supply method of the switching power supply system, and the switching power supply system is adopted; the power supply method comprises the following steps: when the switching power supply system works normally, the control unit generates a control signal for driving the self-powered unit to be conducted to control the self-powered unit to be conducted, and the self-powered unit supplies power to a load end; the control unit generates a control signal for driving the self-powered unit to be turned off so as to control the self-powered unit to completely turn off after supplying power to the charging capacitor for one power supplying time.
Before the normal operation of the switching power supply system, the starting operation of the switching power supply system is further carried out: the control unit generates a control signal for driving the high-voltage power supply unit to be conducted to control the high-voltage power supply unit to be conducted, and the high-voltage power supply unit charges the charging capacitor; and the control unit generates a control signal for driving the high-voltage power supply unit to be turned off to control the high-voltage power supply unit to be turned off, and the starting of the switching power supply system is completed.
The control unit generating a control signal that drives the self-powered unit to turn off further comprises: the power supply circuit receives feedback sampling voltage of the load end, and when the feedback sampling voltage is larger than a preset voltage threshold, the control unit generates a control signal for driving the self-powered unit to be turned off.
The control unit generates a control signal for driving the self-powered unit to turn off and controls the self-powered unit to completely turn off after supplying power to the charging capacitor for one power supplying time further comprises: after the self-powered unit receives the turn-off control signal output by the control unit, the self-powered unit is thoroughly turned off when the power supplementing time is greater than a maximum power supplementing time threshold or the VCC voltage is greater than or equal to a first reference voltage.
After the self-powered unit receives the turn-off control signal output by the control unit and is completely turned off, the method further comprises the following steps: when the VCC voltage of the VCC voltage input end is smaller than the second reference voltage, the control unit further generates a control signal for driving the high-voltage power supply unit to be conducted.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (15)
1. A power supply circuit adapted for use in a switching power supply system, the power supply circuit comprising: the device comprises a high-voltage power supply unit, a self-powered unit, a control unit and a charging capacitor;
the high-voltage power supply unit is respectively and electrically connected with the direct-current voltage input end of the switching power supply system and the VCC voltage input end of the switching power supply system;
the self-powered unit is electrically connected with the direct-current voltage input end, the VCC voltage input end and the load end of the switching power supply system respectively;
the control unit is respectively coupled with the VCC voltage input end, the self-powered unit and the high-voltage power supply unit and is used for generating a control signal for driving the high-voltage power supply unit to be turned on or off and/or generating a control signal for driving the self-powered unit to be turned on or off;
one end of the charging capacitor is electrically connected with the VCC voltage input end, and the other end of the charging capacitor is electrically connected with the load end;
when the high-voltage power supply unit is conducted, the high-voltage power supply unit charges a charging capacitor; when the high-voltage power supply unit is turned off, the self-power supply unit supplies power to the load end when the self-power supply unit is turned on, and when the self-power supply unit receives a turn-off control signal output by the control unit, the self-power supply unit completely turns off the charging capacitor after supplying power for one power supplying time;
the power supply circuit further includes a VCC detection unit; the VCC detection unit is used for detecting VCC voltage on the charging capacitor and outputting a second detection signal to the control unit when the VCC voltage is smaller than a second reference voltage;
the control unit is further used for generating a control signal for driving the high-voltage power supply unit to be conducted according to the second detection signal after the self-powered unit receives the turn-off control signal output by the control unit and is thoroughly turned off.
2. The power supply circuit of claim 1, wherein the high voltage power supply unit comprises a high voltage power supply element and a second switch;
the input end of the high-voltage power supply element is electrically connected with the direct-current voltage input end, and the output end of the high-voltage power supply element is electrically connected with the first access point of the second switch;
the second switch, the second access point is connected with the VCC voltage input end, the control end is connected with the control unit;
and the second switch is turned on or off according to a control signal generated by the control unit, and when the second switch is turned on, the high-voltage power supply element charges the charging capacitor.
3. The power supply circuit of claim 1, wherein the self-powered unit comprises a power transistor, a diode, and a first switch;
the collector electrode of the power triode is electrically connected with the direct-current voltage input end, the base electrode of the power triode is coupled to the control unit, the emitter electrode of the power triode is electrically connected with the first access point of the first switch, and meanwhile, the power triode is electrically connected with the anode of the diode;
the first switch, the second access point is electrically connected to the load end, and the control end is electrically connected with the control unit;
the cathode of the diode is electrically connected with the VCC voltage input end;
when the first switch is turned off according to a turn-off control signal output by the control unit, when the voltage of the emitter of the power triode is larger than the sum of the VCC voltage input end and the forward voltage drop of the diode, the current in the power triode supplements electricity for the charging capacitor through the diode.
4. A power supply circuit according to claim 3, characterized in that the power supply circuit further comprises a drive unit; and one end of the driving unit is electrically connected with the base electrode of the power triode, and the other end of the driving unit is electrically connected with the control unit and is used for outputting a power tube control signal to provide base electrode current for the power triode according to the logic control signal provided by the control unit.
5. A power supply circuit according to claim 3, wherein the turning off of the power transistor and the first switch is done in the same cycle.
6. The power supply circuit according to claim 1, further comprising a VCC detection unit; the VCC detection unit is used for detecting the VCC voltage on the charging capacitor and outputting a first detection signal to the control unit when the VCC voltage is greater than or equal to a first reference voltage;
the control unit is further used for generating a control signal for driving the high-voltage power supply unit to be turned off according to the first detection signal.
7. The power supply circuit according to claim 1, characterized in that the power supply circuit further comprises a demagnetization detection unit; the demagnetizing detection unit is used for detecting demagnetizing points and feeding back detected demagnetizing signals to the control unit;
the control unit further generates a control signal for driving the self-powered unit to conduct according to the demagnetizing signal.
8. The power supply circuit according to claim 1, further comprising a CS detection unit;
the CS detection unit is used for detecting the current sampling voltage of the load end and providing a CS detection signal to the control unit when the current sampling voltage is greater than a preset voltage threshold;
the control unit further generates a control signal for driving the self-powered unit to be turned off according to the CS detection signal.
9. A switching power supply control chip, characterized in that the control chip is provided with the power supply circuit according to any one of claims 1-8.
10. A switching power supply system comprising an ac voltage source, a rectifier circuit electrically connected to the ac voltage source, a bus capacitor electrically connected to the rectifier circuit, a dc voltage input electrically connected to the bus capacitor and a common terminal of the rectifier circuit, and a load terminal, the system further comprising the power supply circuit of any one of claims 1-8;
when the high-voltage power supply unit is conducted, the high-voltage power supply unit charges a charging capacitor; when the high-voltage power supply unit is turned off, the self-power supply unit supplies power to the load end when the self-power supply unit is turned on, and when the self-power supply unit receives a turn-off control signal output by the control unit, the self-power supply unit completely turns off the charging capacitor after supplying power for one power supplying time;
after the self-powered unit receives the turn-off control signal output by the control unit and is completely turned off, when the VCC voltage at the VCC voltage input end is smaller than the second reference voltage, the control unit further generates a control signal for driving the high-voltage power supply unit to be turned on.
11. The system of claim 10, wherein the self-powered unit is completely turned off when the power-up time is greater than a maximum power-up time threshold or the VCC voltage is greater than or equal to a first reference voltage after the self-powered unit receives the off control signal output from the control unit.
12. A method for supplying power to a switching power supply system, using the switching power supply system according to claim 10, comprising the steps of:
(1) When the switching power supply system works normally, the control unit generates a control signal for driving the self-powered unit to be conducted to control the self-powered unit to be conducted, and the self-powered unit supplies power to a load end;
(2) The control unit generates a control signal for driving the self-powered unit to be turned off to control the self-powered unit to completely turn off after supplementing electricity to the charging capacitor for one power supplementing time;
(3) After the self-powered unit receives the turn-off control signal output by the control unit and is completely turned off, the method further comprises the following steps: when the VCC voltage of the VCC voltage input end is smaller than the second reference voltage, the control unit further generates a control signal for driving the high-voltage power supply unit to be conducted.
13. The method of claim 12, wherein prior to step (1) further comprises:
(10) The control unit generates a control signal for driving the high-voltage power supply unit to be conducted to control the high-voltage power supply unit to be conducted, and the high-voltage power supply unit charges the charging capacitor;
(11) And the control unit generates a control signal for driving the high-voltage power supply unit to be turned off to control the high-voltage power supply unit to be turned off, and the starting of the switching power supply system is completed.
14. The method of claim 12, wherein the control unit generating a control signal to drive the self-powered unit off in step (2) further comprises:
the power supply circuit receives current sampling voltage of a load end, and when the current sampling voltage is larger than a preset voltage threshold value, the control unit generates a control signal for driving the self-powered unit to be turned off.
15. The method of claim 12, wherein step (2) further comprises:
after the self-powered unit receives the turn-off control signal output by the control unit, the self-powered unit is thoroughly turned off when the power supplementing time is greater than a maximum power supplementing time threshold or the VCC voltage is greater than or equal to a first reference voltage.
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| CN108712062B (en) * | 2018-05-10 | 2020-04-10 | 深圳市芯茂微电子有限公司 | Switch control circuit, chip, adapter and switch control method |
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| CN109510484B (en) * | 2018-09-30 | 2021-11-30 | 昂宝电子（上海）有限公司 | High-voltage power supply control system and method for chip |
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| CN112152429A (en) * | 2019-09-30 | 2020-12-29 | 深圳市芯茂微电子有限公司 | Switching power supply device and power supply driver suitable for same |
| CN111555643B (en) * | 2020-06-05 | 2024-02-27 | 上海晶丰明源半导体股份有限公司 | Switching power supply controller, switching power supply system and switching power supply system power supply method |
| CN112018860B (en) * | 2020-08-13 | 2023-02-10 | 成都芯源系统有限公司 | Circuit and method for setting a supply voltage in a power supply system |
| CN114050711B (en) * | 2021-11-16 | 2022-09-13 | 东科半导体(安徽)股份有限公司 | Self-powered method for detecting current of built-in high-voltage power tube |
| CN114499188B (en) * | 2022-01-26 | 2022-11-11 | 上海南麟集成电路有限公司 | DC-DC voltage reduction circuit |
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