CN115483823B - Switching power factor corrector and AC/DC converter - Google Patents
Switching power factor corrector and AC/DC converter Download PDFInfo
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- CN115483823B CN115483823B CN202211150839.4A CN202211150839A CN115483823B CN 115483823 B CN115483823 B CN 115483823B CN 202211150839 A CN202211150839 A CN 202211150839A CN 115483823 B CN115483823 B CN 115483823B
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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
- H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
- H02M1/4208—Arrangements for improving power factor of AC input
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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
- H02M1/0048—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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Abstract
The present disclosure provides a switching power factor corrector and an AC/DC converter, wherein the switching power factor corrector comprises a first boost circuit connected between a first AC input terminal and a first DC output terminal, and a second boost circuit connected between a second AC input terminal and the first DC output terminal, wherein the switching power factor corrector operates and the second boost circuit is turned off during a positive half cycle of an AC input voltage received between the first AC input terminal and the second AC input terminal; in the negative half cycle of the ac input voltage, the second boost circuit operates and the first boost circuit is turned off to provide a stable dc output voltage between the first dc output and ground. Therefore, the power factor correction without a rectifier bridge can be realized, the power loss of an alternating current rectifier bridge is saved, the power factor is improved, the design difficulty of a control chip is reduced, the integration level of the whole system is improved, and the cost is effectively reduced.
Description
Technical Field
The disclosure relates to the technical field of switching power supplies, in particular to a switching power factor corrector and an AC/DC converter.
Background
In power electronics, AC/DC is referred to as rectification, DC/AC is referred to as inversion, AC/AC is referred to as alternating current variable frequency transformation, and DC/DC is referred to as direct current/direct current conversion. It is important to note that in most consumer applications, the power source is directly from the AC grid, but almost all circuits need to be powered using DC, so the AC/DC converter described above becomes an essential part of many electronic products. In order to achieve the purpose of converting alternating current into direct current, various conversion methods are designed, wherein a bridge rectifier circuit is the simplest and commonly used, and is widely applied to various switching power supplies.
The 220V AC power grid is supplied with DC power after being input, rectified and filtered, which is a basic rectification technology widely applied in power electronics technology and electronic instruments. The conventional AC/DC converter is composed of a diode bridge rectifying and electrolytic capacitor filtering circuit as shown in fig. 1. The AC mains supply is rectified by a diode and filtered by a large capacitor to obtain smoother DC voltage, and then DC/DC conversion is carried out by a DC converter to obtain the required output voltage. The rectifier-capacitor filter circuit is a combination of a nonlinear element and an energy storage element. The large capacity capacitor is used for reducing output voltage ripple and providing necessary energy storage for a load when the system is powered down. However, since the input rectified voltage charges the capacitor only at an instant higher than the capacitor voltage, the input current is spike-like and there are a large number of harmonics as shown in fig. 2. A large amount of current harmonic components flow back into the power grid to cause harmonic pollution to the power grid, and as a result, accidents such as noise, misoperation, overheating and even burning of electric equipment are caused; and meanwhile, the loss of the wires and transformers of the power distribution system is increased, and the normal operation of various radio communication and radar equipment is seriously interfered. On the other hand, a "secondary effect" is generated, i.e. the current flows through the line impedance to cause a harmonic voltage drop, which in turn causes distortion to the grid.
Two main methods for solving harmonic pollution are: the harmonic compensation device is adopted to compensate harmonic, and a Power Factor Correction (PFC) circuit is introduced into the power electronic circuit. The adoption of PFC technology is an active method, and can fundamentally eliminate a harmonic source.
Conventional single-phase active power factor correction circuits (APFCs) employ a silicon rectifier bridge as a front-end AC/DC converter circuit. The conduction loss of the system comprises the conduction loss caused by two rectifier diodes. In high power low voltage PFC applications, the on-state loss of the full bridge directly affects the operating efficiency of the whole machine. In order to further improve the performance of the original PFC rectifier, more and more researchers begin to study PFC circuit topologies without rectifier bridges. Compared with the traditional silicon rectifier bridge single-phase APFC, the main circuit without the rectifier bridge topology only needs two power semiconductor devices to form a current circuit at any time, so that the conduction loss can be reduced, and the efficiency is further improved. In particular, under the condition of low voltage and high current, the bridgeless circuit has higher efficiency and better development prospect.
As shown in fig. 3a to 3c, several main techniques of the modern rectification technique without rectifier bridge are respectively: 1) A conventional bridge-free BOOST power factor correction circuit (shown in fig. 3 a); 2) A common drain bi-directional switching rectifier bridge free power factor correction circuit (shown in fig. 3 b); 3) Totem pole non-rectifier bridge power factor correction circuits (shown in fig. 3 c), etc., and the main drawbacks of these circuits are: (1) Only operating in Discontinuous Current Mode (DCM) switching power is limited; (2) common mode and differential mode interference is large; (3) low conversion efficiency; (4) complex control and difficult sampling; (5) The circuit is complex, the number of used components is too large, and (6) the manufacturing cost is high. Therefore, there is a need for intensive research and improvement of the new method.
Disclosure of Invention
In order to solve the technical problems, the present disclosure provides a switching power factor corrector and an AC/DC converter, which can save power loss of an AC rectifier bridge, improve power factor, not only reduce design difficulty of a control chip, but also improve integration level of an overall system, and effectively reduce cost thereof.
In one aspect the present disclosure provides a switching power factor corrector comprising:
the first boost circuit is connected between the first alternating current input end and the first direct current output end; and
a second boost circuit connected between the second AC input terminal and the first DC output terminal,
wherein the switching power factor corrector receives an ac input voltage between a first ac input terminal and a second ac input terminal, provides a dc output voltage between a first dc output terminal and ground,
in the positive half cycle of the ac input voltage, the first boost circuit is operated and the second boost circuit is turned off,
in the negative half cycle of the ac input voltage, the second boost circuit operates and the first boost circuit is turned off.
Preferably, the aforementioned first booster circuit includes:
the first inductor and the first diode are connected in series between the first alternating current input end and the first direct current output end, and the second end of the first inductor is connected with the anode of the first diode;
a first switching tube connected between the second end of the first inductor and ground, and a second switching tube connected between the second ac input end and ground.
Preferably, the aforementioned second booster circuit includes:
the second inductor and the second diode are connected in series between the second alternating current input end and the first direct current output end, and the second end of the second inductor is connected with the anode of the second diode;
a third switching tube connected between the second end of the second inductor and the ground, and a fourth switching tube connected between the first ac input end and the ground.
Preferably, the first switch tube is grounded via a first detection resistor, and the first detection resistor provides a first inductor current signal flowing through the first inductor when the first boost circuit is operated.
Preferably, the third switching transistor is grounded via a second detection resistor, and the second detection resistor provides a second inductor current signal flowing through the second inductor when the second boost circuit is operated.
Preferably, the first switching tube and the third switching tube are grounded via a common detection resistor, the detection resistor provides a first inductor current signal flowing through the first inductor when the first boost circuit is operated, and provides a second inductor current signal flowing through the second inductor when the second boost circuit is operated.
Preferably, the aforementioned switching power factor corrector further comprises:
an input capacitor connected between the first ac input terminal and the second ac input terminal and configured to high-frequency filter the ac input voltage;
and the output capacitor is connected between the first direct current output end and ground.
Preferably, the aforementioned switching power factor corrector further comprises:
a control circuit configured to generate a switching control signal based on the detection signal, the first/second inductor current signal, and a feedback voltage for sampling the dc output voltage, and generate a first control signal, a second control signal, a third control signal, and a fourth control signal by processing the switching control signal to correspond to control terminals sequentially provided to the first switching transistor, the second switching transistor, the third switching transistor, and the fourth switching transistor,
the detection signal is used for representing the positive and negative half-period states of the alternating input voltage operation.
Preferably, the aforementioned control circuit includes:
the detection unit is coupled with the first alternating current input end and the second alternating current input end and outputs the detection signal;
an output feedback unit configured to sample the dc output voltage and generate the feedback voltage by dividing the dc output voltage;
the positive input end of the operational amplifier is connected with a preset reference voltage, the negative input end of the operational amplifier is connected with the output feedback unit, the operational amplifier is connected with the feedback voltage, and the output end of the operational amplifier provides a first voltage signal;
the non-inverting input end of the first comparator is connected with the first voltage signal, the inverting input end of the first comparator is connected to the ground through the detection resistor so as to obtain the current sensing signal, and the output end of the first comparator provides a second voltage signal;
a logic control unit configured to generate the switch control signal based on the detection signal and the second voltage signal;
and a driver configured to generate the first control signal, the second control signal, the third control signal, and the fourth control signal, respectively, according to processing of the switch control signal.
Preferably, the aforementioned detection unit includes a first resistor, a second resistor, and a third resistor connected to each other, and a second comparator,
the first end of the first resistor is connected to the second alternating current input end, the second end of the first resistor is connected to the non-inverting input end of the second comparator through the third resistor, the first end of the second resistor is connected to the first alternating current input end, the second end of the second resistor and the second end of the first resistor are connected to the first end of the third resistor together, the inverting input end of the second comparator is grounded, and the output end of the second comparator is used for providing the detection signal.
Preferably, the output feedback unit includes a fourth resistor, a fifth resistor, and a sixth resistor connected in series between the first dc output terminal and ground, and a connection node of the fifth resistor and the sixth resistor is used for providing the feedback voltage.
Preferably, the aforementioned control circuit further includes:
a high pass filter including a seventh resistor and a first capacitor connected in series between the output of the operational amplifier and ground.
Preferably, the second control signal and the fourth control signal are a pair of complementary signals, and a high level of the second control signal is used for maintaining an on state of the second switching tube and an off state of the fourth switching tube, and a low level of the second control signal is used for maintaining the off state of the second switching tube and the on state of the fourth switching tube.
Preferably, the ac input voltage operates in a positive half cycle, the second control signal maintains a high level state, and the first switching tube is turned on and off at a high frequency during the period to supply electric energy to the first dc output terminal through the first inductor;
the alternating current input voltage works in a negative half cycle, the fourth control signal maintains a high level state, and the third switching tube is turned on and off at high frequency in the period so as to provide electric energy for the first direct current output end through the second inductor.
Preferably, any one of the first switching tube, the second switching tube, the third switching tube and the fourth switching tube is an N-channel metal oxide semiconductor field effect transistor.
In another aspect, the present disclosure provides an AC/DC converter comprising: a switching power factor corrector as hereinbefore described.
The beneficial effects of the present disclosure are: the present disclosure provides a switching power factor corrector and an AC/DC converter, wherein the switching power factor corrector comprises a first boost circuit connected between a first AC input terminal and a first DC output terminal, and a second boost circuit connected between a second AC input terminal and a first DC output terminal, wherein the switching power factor corrector receives an AC input voltage between the first AC input terminal and the second AC input terminal, provides a DC output voltage between the first DC output terminal and ground, and in a positive half cycle of the AC input voltage, the first boost circuit operates and the second boost circuit is turned off; in the negative half cycle of the ac input voltage, the second boost circuit operates and the first boost circuit is turned off. The switching power factor corrector provided by the disclosure utilizes the alternate work of the two boost circuits according to the positive half cycle and the negative half cycle of the alternating current input voltage to provide electric energy for the output end, the mutual noninterference and the working mode are completely the same, the problem of inductance current diversion is perfectly solved, the circuit structure of power factor correction without a rectifier bridge is realized, the power loss of the alternating current rectifier bridge is saved, the power factor is improved, the design difficulty of a control chip is reduced, the integration level of the whole system is improved, and the cost is effectively reduced.
Drawings
The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of the embodiments of the present disclosure with reference to the accompanying drawings.
Fig. 1 shows a circuit schematic of a conventional AC/DC converter with a bridge rectifier circuit;
FIG. 2 is a schematic diagram showing waveforms of an input voltage and an input current of the conventional AC/DC converter shown in FIG. 1;
fig. 3a to 3c are schematic diagrams showing the structures of several power factor correction circuits without rectifier bridges in the prior art;
fig. 4 is a schematic diagram of a switching power factor corrector without a rectifier bridge and a control circuit thereof according to an embodiment of the present disclosure;
FIG. 5 shows a schematic diagram of the control circuit shown in FIG. 4;
FIG. 6 shows a schematic circuit diagram of a detection unit in the control circuit shown in FIG. 5;
FIG. 7 shows a timing diagram of the operation of the signals in the switching power factor corrector of FIG. 4;
FIG. 8 shows a schematic diagram of the current path of the switching power factor corrector of FIG. 4 when the AC input voltage is operating in the positive half cycle;
fig. 9a and 9b are schematic diagrams of current paths of the switching power factor corrector in fig. 4 when the third switching tube Q3 is turned on and off when the ac input voltage is operated in a negative half cycle.
Detailed Description
In order that the disclosure may be understood, a more complete description of the disclosure will be rendered by reference to the appended drawings. Preferred embodiments of the present disclosure are shown in the drawings. This disclosure may, however, be embodied in different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description of the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure.
The present disclosure is described in detail below with reference to the accompanying drawings.
Fig. 4 is a schematic diagram of a switching power factor corrector without a rectifier bridge and a control circuit thereof according to an embodiment of the present disclosure, fig. 5 is a schematic diagram of a structure of the control circuit shown in fig. 4, and fig. 6 is a schematic diagram of a detection unit in the control circuit shown in fig. 5.
On the one hand, the embodiment of the disclosure provides a switching power factor corrector, which can be applied to an alternating current-to-direct current switching power supply system, and adopts two boost circuits to be connected in parallel and work alternately to replace a traditional alternating current rectifier bridge, so that the power factor active correction without the alternating current rectifier bridge is realized, and the switching power factor corrector is simple to control, low in loss and low in cost.
Specifically, referring to fig. 4, the switching power factor corrector 200 includes: an ac input circuit 201, an input capacitor Cin, a first boost circuit connected between a first ac input terminal a and a first dc output terminal c, and a second boost circuit connected between a second ac input terminal b and a first dc output terminal c,
the ac input circuit 201 is configured to provide the ac input voltage V AC The method comprises the steps of carrying out a first treatment on the surface of the The input capacitor Cin is connected in parallel between the first and second ac input terminals a and b of the ac input circuit 201 and is configured to supply an ac input voltage V AC Performing high-frequency filtering; the first boost circuit comprises a first inductor L1, a first switching tube Q1, a first diode D1 and a second switching tube Q2; the second boost circuit comprises a second inductor L2, a third switching tube Q3, a second diode D2 and a fourth switching tube Q4,
wherein the switching power factor corrector 200 receives an ac input voltage V between a first ac input terminal a and a second ac input terminal b AC A DC output voltage Vo is provided between the first DC output terminal c and Ground (GND), at which an AC input voltage V AC In the positive half period of (2), the first voltage boosting circuit works and the second voltage boosting circuit is turned off; at the AC input voltage V AC The second boost circuit is operated and the first boost circuit is turned off.
Specifically, in the first boost circuit of the present embodiment, the first inductor L1 and the first diode D1 are connected in series between the first ac input terminal a and the first dc output terminal b, the second terminal of the first inductor L1 is connected to the anode of the first diode D1, the first switching tube Q1 is connected between the second terminal of the first inductor L1 and the ground, and the second switching tube Q2 is connected between the second ac input terminal b and the ground.
In the second boost circuit of this embodiment, the second inductor L2 and the second diode D2 are connected in series between the second ac input terminal b and the first dc output terminal c, the second terminal of the second inductor L2 is connected to the anode of the second diode D2, the third switching tube Q3 is connected between the second terminal of the second inductor L2 and ground, and the fourth switching tube Q4 is connected between the first ac input terminal a and ground.
In this embodiment, the first switching tube Q1 and the third switching tube Q3 are grounded via a common detection resistor Rcs, and the detection resistor Rcs provides a first inductor current signal Vcs1 flowing through the first inductor L1 when the first boost circuit is operated; when the aforementioned second boost circuit is operated, the detection resistor Rcs provides the second inductor current signal Vcs2 flowing through the second inductor L2.
In the present embodiment, the input capacitor Cin, the output capacitor Co, and the detection resistor Rcs are common to two booster circuits.
It should be noted that, in an alternative embodiment, the first switching tube Q1 and the third switching tube Q3 are respectively connected to the ground via respective independent detection resistors, for example, the first switching tube Q1 is grounded via a first detection resistor, and the first detection resistor provides the first inductor current signal Vcs1 flowing through the first inductor L1 when the first boost circuit is operated; the third switching tube Q3 is grounded via a second detection resistor, which provides a second inductor current signal Vcs1 flowing through the second inductor L2 when the second boost circuit is in operation, which is not limited herein.
Referring to fig. 4 and 5, in the present embodiment, the switching power factor corrector further includes a control circuit 210, the control circuit 210 is configured to generate a switching control signal PWM based on a detection signal V2, an inductor current signal Vcs (the inductor current signal Vcs is the first inductor current signal Vcs1 when the first boost circuit is operated, the inductor current signal Vcs2 when the second boost circuit is operated, hereinafter collectively shown as the inductor current signal Vcs), and a feedback voltage Vfb of the sampled dc output voltage Vo, and generate first to fourth control signals (S1 to S4) by processing the switching control signal PWM to correspond to control terminals provided to the first to fourth switching tubes (Q1 to Q4), wherein the detection signal V2 is used to characterize the ac input voltage V AC Positive and negative half-cycle states of operation.
Further, referring to fig. 5, the aforementioned control circuit 210 includes: a driver 211, a logic control unit 212, a detection unit 213, a first comparator 214, an operational amplifier 215, and an output feedback unit 216, wherein,
the detecting unit 213 is coupled to the first ac input terminal a and the second ac input terminal b, and outputs a detecting signal V2, wherein the detecting signal V2 is used for representing the ac input voltage V AC Positive and negative half-cycle states of operation;
the output feedback unit 216 is configured to sample the dc output voltage Vo, and generate a feedback voltage Vfb by dividing the voltage;
the positive input end of the operational amplifier 215 is connected to a preset reference voltage Vref, the negative input end is connected to the output feedback unit 216, the positive input end is connected to the feedback voltage Vfb, and the output end provides a first voltage signal Vc;
the non-inverting input end of the first comparator 214 is connected to the first voltage signal Vc, the inverting input end is connected to the detection resistor Rcs to obtain a current sensing signal Vcs, and the output end provides the second voltage signal V1;
the logic control unit 212 is configured to generate the switch control signal PWM according to the detection signal V2 and the second voltage signal V1;
the driver 211 is configured to generate the first control signal S1, the second control signal S2, the third control signal S3, and the fourth control signal S4, respectively, according to processing the switch control signal PWM.
Further, referring to fig. 6, the aforementioned detecting unit 213 includes a first resistor R1, a second resistor R2, and a third resistor R3 connected to each other, and a second comparator 2131, wherein,
the first end of the first resistor R1 is connected to the second ac input terminal b, the second end is connected to the non-inverting input terminal of the second comparator 2131 through the third resistor R3, the first end of the second resistor R2 is connected to the first ac input terminal a, the second end and the second end of the first resistor R1 are commonly connected to the first end of the third resistor R3, the inverting input terminal of the second comparator 2131 is grounded, and the output terminal of the second comparator 2131 is used for providing the detection signal V2.
It will be appreciated that the ac input voltage V in the above embodiment and shown in fig. 6 AC Is only an exemplary schematic configuration and in other alternative embodiments may be other circuit configurations aimed at obtaining a signal characteristic of the ac input voltage V AC The detection signal V2 operating in the positive and negative half periods is not limited herein. In the above embodiment, the ac input voltage V AC After passing through the first resistor R1, the second resistor R2 (as a starting resistor), and the third resistor R3 (as a current limiting resistor), the non-inverting input terminal of the second comparator 2131 still obtains an ac waveform completely synchronized with the input (in practical applications, for example, a voltage clamping circuit may be added, for example, 2 diodes are connected in parallel positively and negatively to ensure the safety of the second comparator 2131), and the ac waveform is compared with the ground signal of the inverting input terminal, when the voltage is high, the ac input voltage V AC Operating in a positive half period and outputting a high-level detection signal V2; at low time ac input voltage V AC Operating in the negative half cycle, the detection signal V2 of low level is output.
Further, the output feedback unit 216 includes a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6 connected in series between the first dc output terminal c and the ground, and a connection node of the fifth resistor R5 and the sixth resistor R6 is used for providing the feedback voltage Vfb.
Further, the aforementioned control circuit 210 further includes a high-pass filter 217, and the high-pass filter 217 includes a seventh resistor R7 and a first capacitor C1 connected in series between the output terminal of the operational amplifier 215 and ground.
Further, any one of the first switching transistor Q1, the second switching transistor Q2, the third switching transistor Q3 and the fourth switching transistor Q4 is an N-channel metal oxide semiconductor field effect transistor (Metal Oxide Semiconductor Field Effect Transistor, MOSFET, which may also be simply referred to as MOS transistor).
In the above embodiment, MOSFETs are used as the boosting switching elements Q1 to Q4, but in other alternative examples, switching elements such as IGBTs and bipolar transistors may be used, and the present invention is not limited thereto.
Fig. 7 shows an operation timing diagram of signals in the switching power factor corrector shown in fig. 4, fig. 8 shows a schematic current path diagram of the switching power factor corrector shown in fig. 4 when the ac input voltage is operated in a positive half cycle, and fig. 9a and 9b show a schematic current path diagram of the switching power factor corrector shown in fig. 4 when the third switching tube Q3 is turned on and off when the ac input voltage is operated in a negative half cycle, respectively.
Further, referring to fig. 7, the second control signal S2 and the fourth control signal S4 are a pair of complementary signals, and the high level of the second control signal S2 is used for maintaining the on state of the second switching tube Q2 and the off state of the fourth switching tube Q4, and the low level of the second control signal S2 is used for maintaining the off state of the second switching tube Q2 and the on state of the fourth switching tube Q4.
Further, the AC input voltage V AC Operating in a positive half cycle, the second control signal S2 maintains a high level state, and the first switching tube Q1 is turned on and off at a high frequency during this period, so as to provide electric energy to the aforementioned first dc output terminal c through the first inductor L1;
and the AC input voltage V AC The fourth control signal S4 maintains a high state during the negative half cycle, and the third switching tube Q3 is turned on and off at a high frequency during the negative half cycle, so as to supply the electric energy to the first dc output terminal c through the second inductor L2.
In the power supply starting stage, when the output voltage Vo does not reach the potential of the feedback voltage Vfb (namely, the preset reference voltage Vref) during starting, a starting circuit arranged in the power supply chip acts until the output voltage Vo reaches the potential of the feedback voltage Vfb, at the moment, the operational amplifier 215 can adjust the output voltage Vo to be reduced, so that the peak current of the main switching tube (Q1 or Q3) is reduced (or the switching frequency is reduced, and the switching frequency is related to a feedback control method selected by the chip), and the duty ratio is reduced, so that the stability of output is maintained; when the output voltage Vo is low, the operational amplifier 215 adjusts the output voltage Vo to rise, causing the peak current of the main switch to increase (or rise the switching frequency, associated with the feedback control method of chip selection), the duty cycle to increase, thereby maintaining the stability of the output.
Specifically, in the normal operating state of the ac input voltage VAC in this embodiment, when the ac input voltage VAC is in the positive half cycle, the first boost circuit is operated, the second boost circuit is turned off, that is, the third switch Q3 and the fourth switch Q4 are both in the off state, and the second switch Q2 is in the on state all the time during this period, when the first switch Q1 is turned on, the current flows through the first inductor L1 from the first ac input terminal a, the first switch Q1, the detection resistor Rcs and the second switch Q2, and returns to the second ac input terminal b, and the energy is stored in the first inductor L1, the first switch Q1, the detection resistor Rcs, and the second switch Q2 form a current energy storage loop, as shown in line2 in fig. 8, and at this time, the output capacitor Co of the dc output terminal supplies power to the load through the isolation of the first diode D1. When the first switching tube Q1 is turned off, the first inductor L1 generates an induced voltage, and the energy stored in the first inductor L1 discharges to the output terminal through the first diode D1 and charges the output capacitor Co, so that the first inductor L1, the first diode D1, the output capacitor Co, and the second switching tube Q2 form a current energy release loop, as shown in fig. 8, line1.
When the ac input voltage VAC is in the negative half cycle, the second boost circuit is operated, the first boost circuit is turned off completely, that is, the first switching tube Q1 and the second switching tube Q2 are both in the off state, and the fourth switching tube Q4 is in the on state all the time during this period, when the third switching tube Q3 is turned on, the current flows through the second inductor L2 from the first ac input terminal a, the third switching tube Q3, the detection resistor Rcs and the fourth switching tube Q4, and returns to the second ac input terminal b, the energy is stored in the second inductor L2, and the second inductor L2, the third switching tube Q3, the detection resistor Rcs and the fourth switching tube Q4 form a current energy storage loop, as shown in fig. 9a, line3, and at this time, the output capacitor Co at the dc side output terminal supplies power to the load through the isolation of the second diode D2. When the third switching tube Q3 is turned off, the second inductor L2 generates an induced voltage, and the energy stored in the second inductor L2 discharges to the output terminal through the second diode D2 and charges the output capacitor Co, so that the second inductor L2, the second diode D2, the output capacitor Co, and the fourth switching tube Q4 form a current energy release loop, as shown in line4 in fig. 9 b.
The two booster circuits are operated according to the input AC input voltage V AC The positive half period and the negative half period of the transformer work alternately, do not interfere with each other, and have the same working mode, so that the problem of inductance current shunt is perfectly solved. The input capacitor Cin, the output capacitor Co and the current detection resistor Rcs are common devices of two boost circuits, and during the alternating operation of the two boost circuits, continuous current pulses are generated on the input capacitor Cin, the output capacitor Co and the current detection resistor Rcs, which are different from the common boost circuits. Thus, the two boost circuits can operate in Continuous Current Mode (CCM), discontinuous Current Mode (DCM) and critical continuous mode (CRM), respectively.
The switching power factor corrector 200 provided by the embodiment of the disclosure realizes active correction of the power factor without a rectifier bridge, saves the power loss of an alternating current rectifier bridge, improves the power factor, reduces the pollution of a power supply system to a power grid, and makes a contribution to energy and environmental protection.
In another aspect the present disclosure provides an AC/DC converter that may include a switching power factor corrector 200 as described in the above embodiments.
The AC/DC converter may operate in Continuous Current Mode (CCM), discontinuous Current Mode (DCM) and critical continuous mode (CRM).
For the power supply system (AC/DC converter) with the switching power factor corrector 200, the efficiency can be effectively improved, favorable conditions are created for high frequency and high density power of the power supply, the design difficulty of a control chip is reduced, the integration level of the whole system is improved, the application circuit is simplified, and the difficulty of mass production is reduced.
In summary, the embodiment of the disclosure provides the switching power factor corrector 200 and the AC/DC converter, wherein the switching power factor corrector 200 includes a first boost circuit connected between the first AC input terminal a and the first DC output terminal c, and a second boost circuit connected between the second AC input terminal b and the first DC output terminalc, the switching power factor corrector 200 receiving an ac input voltage V between a first ac input terminal a and a second ac input terminal b AC A DC output voltage Vo is provided between the first DC output terminal c and ground, at which AC input voltage V AC The first boost circuit is operated and the second boost circuit is turned off in the positive half cycle; at the AC input voltage V AC The second boost circuit is operated and the first boost circuit is turned off. The switching power factor corrector 200 provided by the present disclosure uses two boost circuits (a first boost circuit and a second boost circuit) according to an ac input voltage V AC The alternating work of positive and negative half cycle is in order to provide the electric energy to first direct current output terminal c, and mutually noninterfere and the operational mode is the same, perfectly solves inductance current reposition of redundant personnel problem, has realized the circuit structure of the power factor correction of no rectifier bridge, has saved the power loss of alternating current rectifier bridge, has improved power factor, has not only reduced the design degree of difficulty of control chip, has improved the integrated level of whole system moreover, effectively reduces its cost simultaneously.
It should be noted that in the description of the present disclosure, it should be understood that the terms "upper," "lower," "inner," and the like indicate an orientation or a positional relationship, and are merely for convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present disclosure.
Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Finally, it should be noted that: it is apparent that the above examples are merely illustrative of the present disclosure and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present disclosure.
Claims (14)
1. A switching power factor corrector, characterized by: comprising the following steps: the first boost circuit is connected between the first alternating current input end and the first direct current output end; and a second boost circuit connected between a second ac input terminal and the first dc output terminal, wherein the switching power factor corrector receives an ac input voltage between the first ac input terminal and the second ac input terminal, provides a dc output voltage between the first dc output terminal and ground, and the first boost circuit is operated in a positive half cycle of the ac input voltage, the second boost circuit is turned off, and the second boost circuit is operated in a negative half cycle of the ac input voltage, and the first boost circuit is turned off;
the first booster circuit includes: the first inductor and the first diode are connected in series between the first alternating current input end and the first direct current output end, and the second end of the first inductor is connected with the anode of the first diode; the first switching tube is connected between the second end of the first inductor and the ground, and the second switching tube is connected between the second alternating current input end and the ground;
the second booster circuit includes: a second inductor and a second diode connected in series between the second ac input terminal and the first dc output terminal, the second terminal of the second inductor being connected to the anode of the second diode; and the third switching tube is connected between the second end of the second inductor and the ground, and the fourth switching tube is connected between the first alternating current input end and the ground.
2. The switching power factor corrector as set forth in claim 1, wherein: the first switch tube is grounded through a first detection resistor, and when the first boost circuit works, the first detection resistor provides a first inductance current signal flowing through the first inductance.
3. The switching power factor corrector as set forth in claim 1, wherein: the third switch tube is grounded through a second detection resistor, and when the second boost circuit works, the second detection resistor provides a second inductance current signal flowing through the second inductance.
4. The switching power factor corrector as set forth in claim 1, wherein: the first switch tube and the third switch tube are grounded through a common detection resistor, when the first boost circuit works, the detection resistor provides a first inductance current signal flowing through the first inductor, and when the second boost circuit works, the detection resistor provides a second inductance current signal flowing through the second inductor.
5. The switching power factor corrector of claim 4, wherein: further comprises: an input capacitance connected between the first ac input terminal and the second ac input terminal, configured to high-frequency filter the ac input voltage; and the output capacitor is connected between the first direct current output end and the ground.
6. The switching power factor corrector of claim 5, wherein: further comprises: the control circuit is configured to generate a switch control signal according to a detection signal, the first/second inductance current signal and a feedback voltage for sampling the direct current output voltage, and generate a first control signal, a second control signal, a third control signal and a fourth control signal through processing the switch control signal so as to be correspondingly and sequentially provided to control ends of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, wherein the detection signal is used for representing positive and negative half-period states of the alternating current input voltage operation.
7. The switching power factor corrector of claim 6, wherein: the control circuit includes: the detection unit is coupled with the first alternating current input end and the second alternating current input end and outputs the detection signal; an output feedback unit configured to sample the dc output voltage, the feedback voltage being generated by dividing the voltage; the positive input end of the operational amplifier is connected with a preset reference voltage, the negative input end of the operational amplifier is connected with the output feedback unit, the operational amplifier is connected with the feedback voltage, and the output end of the operational amplifier provides a first voltage signal; the non-inverting input end of the first comparator is connected with the first voltage signal, the inverting input end of the first comparator is connected to the ground through the detection resistor so as to obtain the first/second current sensing signal, and the output end of the first comparator provides a second voltage signal; a logic control unit configured to generate the switch control signal according to the detection signal and the second voltage signal; and a driver configured to generate the first control signal, the second control signal, the third control signal, and the fourth control signal, respectively, according to processing of the switch control signal.
8. The switching power factor corrector of claim 7, wherein: the detection unit comprises a first resistor, a second resistor and a third resistor which are connected with each other, and a second comparator, wherein the first end of the first resistor is connected to the second alternating current input end, the second end of the first resistor is connected to the non-inverting input end of the second comparator through the third resistor, the first end of the second resistor is connected to the first alternating current input end, the second end of the second resistor and the second end of the first resistor are connected to the first end of the third resistor together, the inverting input end of the second comparator is grounded, and the output end of the second comparator is used for providing the detection signal.
9. The switching power factor corrector of claim 8, wherein: the output feedback unit comprises a fourth resistor, a fifth resistor and a sixth resistor which are connected in series between the first direct current output end and ground, and a connection node of the fifth resistor and the sixth resistor is used for providing the feedback voltage.
10. The switching power factor corrector of claim 9, wherein: the control circuit further includes: a high pass filter comprising a seventh resistor and a first capacitor connected in series between the output of the operational amplifier and ground.
11. The switching power factor corrector of claim 7, wherein: the second control signal and the fourth control signal are a pair of complementary signals, the high level of the second control signal is used for maintaining the on state of the second switching tube and the off state of the fourth switching tube, and the low level of the second control signal is used for maintaining the off state of the second switching tube and the on state of the fourth switching tube.
12. The switching power factor corrector of claim 11, wherein: the alternating current input voltage works in a positive half cycle, the second control signal maintains a high level state, and the first switch tube is turned on and off in a high frequency mode during the period so as to provide electric energy for the first direct current output end through the first inductor; the alternating current input voltage works in a negative half cycle, the fourth control signal maintains a high level state, and the third switching tube is turned on and off at high frequency in the period so as to provide electric energy for the first direct current output end through the second inductor.
13. The switching power factor corrector as set forth in claim 1, wherein: any one of the first switching tube, the second switching tube, the third switching tube and the fourth switching tube is an N-channel metal oxide semiconductor field effect transistor.
14. An AC/DC switching converter, characterized by: comprising the following steps: a switching power factor corrector as claimed in any of claims 1 to 13.
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