CN217010699U - Bridgeless ac/dc converter adopting peak current control - Google Patents
Bridgeless ac/dc converter adopting peak current control Download PDFInfo
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- CN217010699U CN217010699U CN202123048184.3U CN202123048184U CN217010699U CN 217010699 U CN217010699 U CN 217010699U CN 202123048184 U CN202123048184 U CN 202123048184U CN 217010699 U CN217010699 U CN 217010699U
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Abstract
The utility model discloses a bridgeless ac/dc converter controlled by peak current, which comprises a bridgeless PFC main circuit, a switching tube logic control circuit, an input rectification filter circuit, an auxiliary source circuit, a control loop and an output overvoltage protection circuit, wherein the input end of the bridgeless PFC main circuit is connected with alternating current of 220V of mains supply, and the switching tube logic control circuit is connected between the bridgeless PFC main circuit and the control loop; the control loop carries out operation processing by using sampling values of input voltage and output voltage of the bridgeless PFC main circuit, and then generates PWM control signals for controlling a switching tube logic control circuit by using the operation values and the input current through a third comparator; the switching tube logic control circuit is used for operating the PWM control signal and generating a control signal for controlling the main circuit of the bridgeless PFC, so that the peak current control of the bridgeless PFC is realized. The converter of the utility model uses a logic gate circuit to convert a PWM0 control signal output by a control loop into 4 paths of new PWM control signals, and finally, the circuit has accurate voltage output and higher power factor under closed-loop control.
Description
Technical Field
The utility model relates to the technical field of power factor correction of a power supply, in particular to a bridgeless ac/dc converter controlled by peak current.
Background
With the rapid development of power electronic technology in recent years, the wide application of the technology brings the change of covering the earth to human life, and simultaneously causes certain difficulty to the harmonic treatment of the power grid. PFC (power factor correction) is a method for effectively solving the problem of power grid pollution caused by a conventional AC (alternating current) rectification circuit; the rectifier bridge of the conventional rectifier filter circuit is conducted only when the input sine wave voltage reaches a certain value, so that the input current is distorted, and a large amount of harmonic current components are generated in the input.
The PFC circuit enables the input current and the input voltage to become sine waves with the same frequency and the same phase by shaping the input AC current, so that the purpose of greatly reducing harmonic wave input is achieved. For a common PFC converter, a two-stage structure is generally required, however, the conventional pre-stage PFC converter has low efficiency and a complex structure at low-voltage input, and has high cost.
In order to improve the power factor and reduce the harmonic content of the input current, most of the high-power switching power supplies adopt an active power factor correction system for adjustment. Compared with the traditional active power factor correction system, the bridgeless PFC system has more advantages and wider application in a high-power switching power supply. At present, the difficulty of the control scheme of the bridgeless PFC converter is the design of a control loop, and no complete control scheme of the bridgeless PFC converter is available in the market.
In order to solve the above problems, there is a scheme to realize the control of the bridgeless PFC circuit through a DSP controller. (such as a digital bridgeless PFC control circuit, application number: CN201621445281.2), the scheme respectively samples an alternating current input voltage and an input current, and utilizes a DSP chip TMS32010 to process the sampled signals, so that a PWM (pulse width modulation) control signal is obtained. The control signal is utilized to adjust the conduction state of the bridgeless PFC switch tube, so that the input current effectively follows the input voltage, and the aim of correcting the power factor is fulfilled.
The scheme well solves the control problem of the bridgeless PFC, but has low applicability in certain occasions, for example, when the circuit works in a high-power state, a DSP chip in the scheme is easy to influence the normal work of the circuit due to electromagnetic interference; on the other hand, the scheme is mainly constructed by adopting a digital circuit, the DSP is used as a main control chip, the circuit design is complex, a large amount of control programs need to be compiled, and the realization is troublesome.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a bridgeless ac/dc converter adopting peak current control, which uses a logic gate circuit to convert a PWM0 control signal output by a control loop into 4 paths of new PWM control signals, respectively correspondingly controls 4 switching tubes of a main circuit of a bridgeless PFC, and finally enables the circuit to have accurate voltage output and higher power factor under closed-loop control.
The purpose of the utility model can be realized by the following technical scheme:
a bridgeless ac/dc converter adopting peak current control comprises a bridgeless PFC main circuit, a switching tube logic control circuit, an input rectification filter circuit, an auxiliary source circuit, a control loop and an output overvoltage protection circuit, wherein the input end of the bridgeless PFC main circuit is connected with 220V alternating current of mains supply, and the switching tube logic control circuit is connected between the bridgeless PFC main circuit and the control loop.
The input rectification filter circuit and the auxiliary source circuit are used for converting 220V alternating current into 5V and 12V direct current and simultaneously used for providing the direct current for circuits such as a control loop, a switch tube logic control circuit and output voltage protection.
The input end of the control loop is connected with the output end of the bridgeless PFC main circuit, and the output end of the control loop is connected with the input end of the switch tube logic control circuit.
And the output end of the switch tube logic control circuit is connected with the control end of the bridgeless PFC main circuit.
The control loop is used for carrying out operation processing on sampling values of input voltage, input current and output voltage of the bridgeless PFC main circuit to generate a PWM control signal for controlling the switch tube logic control circuit.
And the switching tube logic control circuit is used for operating the PWM control signal and generating a control signal for controlling the bridgeless PFC main circuit.
Further, the switching tube logic control circuit comprises a first comparator, a first and gate, a second and gate, a third and gate, a fourth and gate, a first or gate, a second or gate, a first not gate, a second not gate and a third not gate.
The alternating current sampling value of the commercial power 220V is input from the positive phase input end of the first comparator, the negative phase input end of the first comparator is grounded, the positive power supply end is connected with the voltage of 5V, and the negative power supply end is grounded.
The input end of the first NOT gate is connected with the output end of the first comparator, and the output end of the first NOT gate is connected with the first input end of the first AND gate; the second input end of the first AND gate is connected with the first input end of the fourth AND gate, and the output end of the first AND gate is connected with the first input end of the first OR gate; and the second input end of the fourth AND gate is connected with the output end of the first comparator, and the output end of the fourth AND gate is connected with the second input end of the second OR gate.
The first input end of the second AND gate is connected with the second input end of the fourth AND gate, and the second input end of the second AND gate is connected with the output end of the third NOT gate; the input end of the third NOT gate is connected with the output end of the second OR gate; the first input end of the second OR gate is connected with the output end of the third AND gate.
The second input end of the first OR gate is connected with the output end of the third AND gate, and the output end of the first OR gate is connected with the input end of the second NOT gate; the first input end of the third AND gate is connected with the first input end of the first AND gate, and the output end of the third AND gate is connected with the output end of the second NOT gate.
The bridgeless PFC main circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor and a first inductor.
The grid electrode of the first switching tube is connected with the output end of the first OR gate, the source electrode of the first switching tube is connected with the drain electrode of the second switching tube, and the drain electrode of the first switching tube is connected with the drain electrode of the third switching tube; the grid electrode of the second switching tube is connected with the output end of the second OR gate, and the source electrode of the second switching tube is grounded; the grid electrode of the third switch tube is connected with the first input end of the first AND gate, and the source electrode of the third switch tube is connected with the drain electrode of the fourth switch tube; the grid electrode of the second switch tube is connected with the output end of the second OR gate, and the source electrode is grounded.
The second resistor and the third resistor are connected in series, and a series circuit of the second resistor and the third resistor is connected in parallel at two ends of alternating current of 220V mains supply; one end of the first resistor is connected with the positive pole of the commercial power 220V alternating current, the other end of the first resistor is connected with one end of a first inductor, and the other end of the first inductor is connected with the source electrode of the first switching tube; the negative electrode of alternating current of 220V mains supply is connected with the drain electrode of the fourth switching tube; the fourth resistor and the fifth resistor are connected in series, and a series circuit of the fourth resistor and the fifth resistor is connected in parallel to the first capacitor; the positive electrode of the first capacitor is connected to the drain electrode of the third switching tube, and the negative electrode of the first capacitor is grounded.
Further, the control loop comprises an adder, a PI regulator, a multiplier, a third comparator and an RS trigger.
One input end of the adder is connected between the fourth resistor and the fifth resistor and used for inputting a sampling value of the output voltage of the bridgeless PFC main circuit, the other input end of the adder is provided with a reference voltage, and the output end of the adder is connected with the input end of the PI regulator.
The output end of the PI regulator is connected with one input end of the multiplier, the other input end of the multiplier is connected between the second resistor and the third resistor, and the PI regulator is used for inputting a sampling value of the input voltage of the bridgeless PFC main circuit.
The output end of the multiplier is connected with one input end of a third comparator, the other input end of the third comparator is connected with the anode of alternating current of 220V mains supply and is used for inputting a sampling value of input current of the bridgeless PFC main circuit, the output end of the third comparator is connected with the input end of an RS trigger, and the output end of the RS trigger is connected with the second input end of the first AND gate.
Furthermore, the input rectifying and filtering circuit comprises a first transformer, a second capacitor, a third capacitor and a bridge circuit consisting of a first diode, a second diode, a third diode and a fourth diode.
The input end of the first transformer is connected with 220V alternating current of commercial power in parallel, the output end of the first transformer is connected with the alternating current input end of the bridge circuit in parallel, the second capacitor is connected with the direct current output end of the bridge circuit in parallel, the anode of the second capacitor is connected with the three-terminal linear voltage stabilizer, one end of the third capacitor is connected with the cathode of the second capacitor, and the other end of the third capacitor is connected with the output end of the three-terminal linear voltage stabilizer.
Further, the auxiliary source circuit comprises a three-coil transformer, a fifth switching tube, a fifth diode, a sixth resistor, a seventh resistor, a fourth capacitor, a fifth capacitor, a sixth capacitor and a seventh capacitor.
And the positive electrode of the primary coil of the three-coil transformer is connected with the positive electrode of the third capacitor, and the negative electrode of the primary coil of the three-coil transformer is connected with the drain electrode of the fifth switching tube.
And the source electrode of the fifth switching tube is connected to the anode of the third capacitor.
And the anode of the secondary coil of the three-coil transformer is connected with the anode of the fifth diode, and the cathode of the secondary coil of the three-coil transformer is grounded.
And the cathode of the secondary side coil of the three-coil transformer is grounded, and the anode of the secondary side coil of the three-coil transformer is connected with the anode of a sixth diode.
And the sixth capacitor and the seventh resistor are connected in series, and a series circuit of the sixth capacitor and the seventh resistor is connected in parallel at two ends of the sixth diode.
And the anode of the fifth capacitor is connected to the cathode of the fifth diode, and the cathode of the fifth capacitor is grounded.
And the anode of the seventh capacitor is connected to the cathode of the sixth diode, and the cathode of the seventh capacitor is grounded.
The positive electrode of the fifth capacitor outputs 12V direct current, and the positive electrode of the seventh capacitor outputs 5V direct current.
The utility model has the beneficial effects that:
1. the converter firstly samples the input voltage, the input current and the output voltage of the bridgeless PFC main circuit, and then a control loop carries out operation processing on the sampled values, so that the circuit achieves the purpose that the input current waveform follows the input voltage waveform; finally, a PWM control signal which is turned off at regular time is output by an output end Q of an RS trigger in a control loop, the control signal is operated by a switch tube logic control circuit to generate four paths of new PWM control signals of PWM 1-PWM 4 and is correspondingly connected to the grids of switch tubes Q1-Q4, and finally, the switch tubes in the bridgeless PFC main topology realize the functions of rectification, boosting and power factor correction under the control of 4 paths of PWM signals;
2. the bridgeless PFC main circuit of the converter utilizes the switching tube to replace a bridge arm diode, reduces the loss of a switching device of a conduction path, and improves the efficiency;
3. the control scheme adopted by the circuit of the converter is peak value flow control, an additional absolute value circuit does not need to be designed, and the converter has an overcurrent protection function, so that the circuit is simpler, more convenient and safer.
Drawings
The utility model will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of the overall architecture of the converter of the present invention;
fig. 2 is a schematic diagram of the main circuit topology of the bridgeless PFC of the present invention;
FIG. 3 is a schematic diagram of an input rectifying filter circuit of the present invention;
FIG. 4 is a schematic diagram of an auxiliary source circuit of the present invention;
FIG. 5 is a schematic diagram of the switching tube logic control circuit of the present invention;
fig. 6 is a schematic diagram of the output overvoltage protection circuit of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A bridgeless ac/dc converter adopting peak current control comprises a bridgeless PFC main circuit, a switching tube logic control circuit, an input rectification filter circuit, an auxiliary source circuit, a control loop and an output overvoltage protection circuit.
The input end of the bridgeless PFC main circuit is connected with alternating current of 220V of mains supply, the input voltage of the bridgeless PFC main circuit is recorded as VI N, the output voltage is recorded as Vo, and the switching tube logic control circuit is connected between the bridgeless PFC main circuit and the control loop.
The input rectification filter circuit and the auxiliary source circuit are used for converting 220V alternating current into 5V and 12V direct current and simultaneously used for providing the direct current for circuits such as a control loop, a switch tube logic control circuit and output voltage protection.
The input end of the control loop is connected with the output end of the bridgeless PFC main circuit, and the output end of the control loop is connected with the input end of the switch tube logic control circuit; the output end of the switch tube logic control circuit is connected with the control end of the bridgeless PFC main circuit.
The control loop utilizes the sampling values of the input voltage and the output voltage of the bridgeless PFC main circuit to carry out operation processing, and then the operation value and the input current are used for generating a PWM control signal for controlling the switch tube logic control circuit through a third comparator.
The switching tube logic control circuit is used for operating the PWM control signal to generate a control signal for controlling the main circuit of the bridgeless PFC, so that the peak value flow control of the bridgeless PFC is realized.
The circuit structure of the switch tube logic control circuit is shown in fig. 5, and the switch tube logic control circuit comprises a first comparator U1AFirst AND gate AND1AND gate AND2AND the third AND gate AND3Fourth AND gate AND4First OR gate OR1A second OR gate OR2First NOT gate ONT1Second NOT gate ONT2And a third not gate ONT3。
AC sampling value of commercial power 220V is from first comparator U1AA positive phase input terminal of the first comparator U1AThe inverting input end of the transformer is grounded, the positive power supply end is connected with 5V voltage, and the negative power supply end is grounded.
First NOT gate ONT1Is connected with a first comparator U1AThe output end of the first AND gate AND is connected with the output end of the first AND gate AND1A first input terminal of; first AND gate AND1Is connected with a fourth AND gate AND4Has a first input terminal and an output terminal connected with a first OR gate1A first input terminal of; fourth AND gate AND4Second input terminal of the first comparator U is connected with the first comparator U1AOutput terminal of the first OR gate is connected to the second OR gate2To the second input terminal of (a).
Second AND gate AND2Is connected with the fourth AND gate AND4The second input end is connected with the third NOT gate ONT3An output terminal of (a); third NOT gate ONT3Is connected to the second OR gate OR2An output terminal of (a); second OR gate OR2Is connected with a third AND gate AND3To the output terminal of (a).
First OR gate OR1Is connected with a third AND gate AND3The output end of the first NOT gate is connected with the first NOT gate ONT2An input terminal of (1); third AND gate AND3Is connected with a first AND gate AND1The output end of the first input end is connected with the second NOT gate ONT2To the output terminal of (a).
The main topology structure of the bridgeless PFC main circuit is shown in FIG. 2, and the bridgeless PFC main circuit comprises a first switching tube Q1A second switch tube Q2And a third switching tube Q3And a fourth switching tube Q4A first resistor R1A second resistor R2A third resistor R3A fourth resistor R4A fifth resistor R5A first capacitor C1And a first inductance L1。
First switch tube Q1Is connected to the first OR gate OR1Output terminal, source electrode and second switch tube Q2Is connected with the drain electrode of the third switching tube Q3The drain electrodes of the two electrodes are connected; second switch tube Q2Second OR gate OR of the gate2The output ends of the two-way transistor are connected, and the source electrode is grounded; third switch tube Q3With the first AND gate AND1The first input end of the first switch tube is connected with the source electrode of the fourth switch tube Q4The drain electrodes of the two electrodes are connected; second switch tube Q2Second OR gate OR of the gate2The output terminals of the first and second transistors are connected, and the source electrodes are grounded.
A second resistor R2And a third resistor R3The series circuit is connected in parallel at two ends of the alternating current of the commercial power 220V; a first resistor R1One end of the first inductor is connected with the positive pole of the alternating current of 220V of the mains supply, and the other end of the first inductor is connected with the first inductor L1One end of (1), a first inductance L1Is connected to the first switch tube Q1A source electrode of (a); the negative pole of the alternating current of the commercial power 220V is connected with a fourth switch tube Q4A drain electrode of (1); a fourth resistor R4And a fifth resistor R5Are connected in series, the series circuit of which is connected in parallel to the first capacitor C1The above step (1); a first capacitor C1Is connected to the third switch tube Q3And the cathode of the drain is grounded.
The control loop comprises an adder, a PI regulator, a multiplier, a third comparator and an RS trigger.
An input end of the adder is connected with the fourth resistor R4And a fifth resistor R5The other input end of the adder is connected with the input end of the PI regulator, the output end of the PI regulator is connected with one input end of the multiplier, and the other input end of the multiplier is connected with the input end of the second resistor R2And a third resistor R3The sampling value of the input voltage of the bridgeless PFC main circuit is input;
the output end of the multiplier is connected with one input end of a comparator, the other input end of the comparator is connected with the positive pole of alternating current of 220V mains supply AND is used for inputting a sampling value of input current of the bridgeless PFC main circuit, the output end of the comparator is connected with the input end of an RS trigger, AND the output end of the RS trigger is connected with a first AND gate AND1To the second input terminal.
The input rectifying filter circuit comprises a first transformer T1A second capacitor C2And a third capacitance C3And a first diode D1A second diode D2A third diode D3The fourth diodeD4Forming a bridge circuit, a first transformer T1The input end of the first capacitor C is connected with the alternating current of the commercial power 220V in parallel, the output end of the first capacitor C is connected with the alternating current input end of the bridge circuit in parallel, and the second capacitor C2A second capacitor C connected in parallel with the DC output end of the bridge circuit2The anode of the three-terminal linear voltage stabilizer is connected with a third capacitor C3Is connected to the second capacitor C2The other end of the negative electrode is connected with the output end of the three-terminal linear voltage stabilizer and a second capacitor C2The positive and negative voltages are Vbus + and Vbus-, respectively.
The auxiliary source circuit comprises a three-coil transformer T2The fifth switch tube Q5A fifth diode D5A sixth diode D6A sixth resistor R6A seventh resistor R7A fourth capacitor C4A fifth capacitor C5And a sixth capacitor C6And a seventh capacitance C7。
Three-coil transformer T2The positive electrode of the primary coil is connected with a third capacitor C3The anode and the cathode of the first switch tube are connected with a fifth switch tube Q5A drain electrode of (1); fifth switch tube Q5Is connected to the third capacitor C3The positive electrode of (1); three-coil transformer T2The anode of the secondary coil is connected with a fifth diode D5The anode and the cathode of the battery are grounded; three-coil transformer T2The negative pole of the secondary side coil is grounded, and the positive pole is connected with a sixth diode D6The positive electrode of (1).
Fourth capacitor C4And a sixth capacitance C6Are connected in series, and the series circuit thereof is connected in parallel with the fifth switch tube Q5Both ends of (a); sixth capacitor C6And a seventh resistor R7Are connected in series, the series circuit of which is connected in parallel to the sixth diode D6Both ends of (a); fifth capacitor C5Is connected to the fifth diode D5The negative electrode of (2) is grounded; seventh capacitance C7Is connected to the sixth diode D6Negative electrode of (2), negative electrode is grounded, and fifth capacitor C5The positive pole of the capacitor outputs 12V direct current, and a seventh capacitor C7The positive electrode of (2) outputs 5V direct current.
The output overvoltage protection circuit includes a second comparisonDevice U1BAn eighth resistor R8A ninth resistor R9A tenth resistor R10An eleventh resistor R11And a twelfth resistor R12Triode Q6The seventh diode D7And a relay RY1The tenth resistor R10One end of the first comparator is connected with 12V direct current, and the other end of the first comparator is connected with a second comparator U1BThe inverting input terminal of (1); eleventh resistor R11One end of the first comparator is connected with a second comparator U1BThe other end of the inverting input end of the first capacitor is grounded; eighth resistor R8One end of the second comparator is connected with the output end of the bridgeless PFC main circuit, and the other end of the second comparator is connected with the second comparator U1BThe output voltage of the bridgeless PFC main circuit is Vo; ninth resistor R9One end of the first comparator is connected with a second comparator U1BAnd the other end of the non-inverting input terminal of (a) is grounded.
Second comparator U1BThe positive power supply end of the resistor is connected with 5V direct current, the negative power supply end of the resistor is grounded, and a twelfth resistor R12One end of the first comparator is connected with a second comparator U1BThe other end of the output end of the transistor is connected with a triode Q6An emitter of (1); triode Q6Base of (D) is grounded, and a seventh diode D7The anode of the transistor is connected with a triode Q6The negative pole of the collector of (1) is connected with a 5V direct current, and a relay RY1Is connected in parallel to a seventh diode D7Two ends of relay RY1One end of the output end of the voltage sampling circuit is connected with the output voltage sampling end of the bridgeless PFC main circuit, and the other end of the output end of the voltage sampling circuit is connected with 5V direct current.
When the bridge-free PFC main circuit is used, firstly, the input voltage, the input current and the output voltage of the bridge-free PFC main circuit are sampled, the control loop carries out operation processing on the sampled values to finally obtain a control signal PWM0, and the signal generates 4 paths of new PWM control signals after passing through the logic control circuit and realizes the control action on the first switching tube Q1 to the fourth switching tube Q4;
in the topology of the bridgeless PFC main circuit, diodes of a rectifier bridge are correspondingly replaced by Mos tubes, an inductor is added at the input side, and the functions of rectification, boosting and power factor correction are realized by controlling 4 Mos tubes.
The input rectifying and filtering circuit is used for transforming, rectifying and filtering the alternating current of 220V of the mains supply and providing direct current input for a subsequent auxiliary source circuit so as to generate an auxiliary voltage source and provide stable power supply voltage for each chip and other circuits.
The auxiliary source circuit provides stable 5V and 12V supply voltage for each logic gate, AD8277 dual-channel differential amplifier and other circuits in the control loop, so that the whole circuit can work stably.
The switching tube logic control circuit is used for generating 4 paths of new control signals, namely a first pulse width modulation signal PWM (pulse width modulation) after the PWM0 control signal output by the control loop passes through the logic control circuit1Second pulse width modulation signal PWM2Third pulse width modulation signal PWM3And a fourth pulse width modulation signal PWM4The 4 paths of control signals respectively and correspondingly control a first switch tube Q in the bridgeless PFC main topology circuit1-fourth switching tube Q4The conduction states of the 4 switching tubes finally enable the circuit to achieve the purposes of voltage stable output and power factor correction.
The overvoltage output protection circuit is connected to the second comparator U after dividing the output voltage of the bridgeless PFC main circuit through the resistor 1B12V is connected to a second comparator U via a reference voltage VP generated by resistive voltage division1BThe inverting input terminal of (1); when the output voltage is too large, the voltage of the same-phase input end is larger than the voltage VP of the reverse-phase input end, the second comparator U1BIs at a high level, when the triode Q is at the time6Conducting normally open relay RY1And attracting, pulling up the output sampling voltage, and accelerating the loop regulation to reduce the output voltage.
The specific treatment process is as follows: firstly, a reference voltage and an output voltage sample are operated by an adder, an output result is subjected to PI regulation and then is multiplied by an input voltage sample by a multiplier, an output result of the multiplier is compared with an input current sample by a comparator, and an output result of the comparator is subjected to PWM (pulse-width modulation) which is output to an output end Q of an RS (remote sensing) trigger and is turned off at fixed time0A control signal;
the control signal passes through a switchAfter the operation of the tube logic control circuit, a first pulse width modulation signal PWM is generated1Fourth pulse width modulation signal PWM4Four paths of new PWM control signals are correspondingly connected to the first switch tube Q1-fourth switching tube Q4A gate electrode of (2). Finally, the switching tube in the bridgeless PFC main topology realizes the functions of rectification, boosting and power factor correction under the control of 4 paths of PWM signals.
First comparator U1AOutputting a group of fourth pulse width modulation signals PWM with the same frequency as the input voltage of the bridgeless PFC main circuit and the duty ratio of 50 percent according to the change of the input alternating voltage4Control signals respectively connected to the fourth switching tubes Q4Gate of (D), second AND gate AND2Fourth AND gate AND4An input terminal of (1);
and then the fourth PWM signal4The control signal passes through the first NOT gate ONT1Then generates a and a fourth pulse width modulation signal PWM4Third PWM signal with completely opposite level3The third pulse width modulation signal PWM3Are respectively connected to the third switching tubes Q4Gate of (1), first AND gate AND1AND gate, AND gate3The circuit can make the fourth switch tube Q through the logic operation circuit after working normally4Conducting only in the first half period, and a third switching tube Q3Conducting only in the last half cycle.
When the input ac voltage is in the first half cycle: third pulse width modulation signal PWM3The output is a low level fourth pulse width modulation signal PWM4The output is high level, AND gate1AND third AND gate AND3Are all low.
At this time, the second pulse width modulation signal PWM2Independent of the first pulse width modulation signal PWM1And the first pulse width modulation signal PWM1Is completely influenced by the second pulse width modulation signal PWM2And the first pulse width modulation signal PWM1And a second pulse width modulation signal PWM2The level states are completely opposite.
When the input alternating voltage is in the second half period: third pulse width modulation signal PWM3The output is high level and the fourth pulse width modulation signal PWM4Output is low level, second AND gate AND2AND fourth AND gate AND4The outputs of (a) are all low levels; at this time, the first pulse width modulation signal PWM1Independent of the second pulse width modulation signal PWM2And the second pulse width modulation signal PWM2Is completely influenced by the first pulse width modulation signal PWM1And the first pulse width modulation signal PWM1And a second pulse width modulation signal PWM2The level states are still completely opposite.
Under control of the logic circuit: first pulse width modulation signal PWM1And a second pulse width modulation signal PWM2Completely opposite and corresponding to the AC input, the second PWM signal in the first half period2Control the first pulse width modulation signal PWM1Level change of (2), second half period: first pulse width modulation signal PWM1Control the second pulse width modulation signal PWM2The level of (2) is changed.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing shows and describes the general principles, essential features, and advantages of the utility model. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the utility model as claimed.
Claims (7)
1. A bridgeless ac/dc converter controlled by peak current is characterized by comprising a bridgeless PFC main circuit, a switching tube logic control circuit, an input rectification filter circuit, an auxiliary source circuit, a control loop and an output overvoltage protection circuit, wherein the input end of the bridgeless PFC main circuit is connected with 220V alternating current of mains supply, and the switching tube logic control circuit is connected between the bridgeless PFC main circuit and the control loop;
the input rectifying filter circuit and the auxiliary source circuit are used for converting 220V alternating current into 5V and 12V direct current and simultaneously providing the direct current for circuits such as a control loop, a switch tube logic control circuit and output voltage protection;
the input end of the control loop is connected with the input end and the output end of the bridgeless PFC main circuit, and the output end of the control loop is connected with the input end of the switch tube logic control circuit;
the output end of the switch tube logic control circuit is connected with the control end of the bridgeless PFC main circuit;
the control loop is used for carrying out operation processing on sampling values of input voltage, input current and output voltage of the bridgeless PFC main circuit and generating a PWM control signal for controlling the switch tube logic control circuit;
and the switching tube logic control circuit is used for operating the PWM control signal and generating a control signal for controlling the bridgeless PFC main circuit.
2. A bridgeless ac/dc converter with peak current control according to claim 1, characterized in that the switching tube logic control circuit comprises a first comparator (U)1A) First AND gate (AND)1) AND a second AND gate (AND)2) AND a third AND gate (AND)3) Fourth AND gate (AND)4) First OR gate (OR)1) Second OR gate (OR)2) First NOT gate (ONT)1) And a second not gate (ONT)2) And a third not gate (ONT)3)；
The AC sampling value of the commercial power 220V is obtained from a first comparator (U)1A) Is inputted to the non-inverting input terminal of the first comparator (U)1A) The inverting input end of the transformer is grounded, the positive power supply end is connected with 5V voltage, and the negative power supply end is grounded;
the first not gate (ONT)1) Is connected to a first comparator (U)1A) The output terminal of the first AND gate (AND) is connected to the output terminal of the first AND gate1) A first input terminal of; first AND gate (AND)1) Is connected with a fourth AND gate (AND)4) Has a first input terminal and an output terminal connected to a first OR gate (OR)1) A first input terminal of; fourth AND gate (AND)4) Is connected to a first comparator (U)1A) Is connected to a second OR gate (OR)2) A second input terminal of;
said second AND gate (AND)2) Is connected with a fourth AND gate (AND)4) Second input terminal connected to a third not gate (ONT)3) An output terminal of (a); third not gate (ONT)3) Is connected to a second OR gate (OR)2) An output terminal of (a); second OR gate (OR)2) Is connected to a third AND-gate (AND)3) An output terminal of (a);
the first OR gate (OR)1) Is connected to a third AND gate (AND)3) The output end of the first NOT gate is connected with a first NOT gate (ONT)2) An input terminal of (1); third AND gate (AND)3) Is connected to a first AND gate (AND)1) Has a first input end and an output end connected with a second NOT gate (ONT)2) To the output terminal of (a).
3. The bridgeless ac/dc converter with peak current control according to claim 2, characterized in that the bridgeless PFC main circuit comprises a first switching tube (Q)1) A second switch tube (Q)2) And a third switching tube (Q)3) And a fourth switching tube (Q)4) A first resistor (R)1) A second resistor (R)2) A third resistor (R)3) A fourth resistor (R)4) Fifth resistance (c)R5) A first capacitor (C)1) And a first inductance (L)1)；
The first switch tube (Q)1) Is connected to a first OR gate (OR)1) Output terminal, source and second switching tube (Q)2) Is connected with the drain electrode of the third switching tube (Q)3) The drain electrodes of the two electrodes are connected; second switch tube (Q)2) Second OR gate (OR) of the gate2) The output ends of the two-way transistor are connected, and the source electrode is grounded; three-switch tube (Q)3) With a first AND gate (AND)1) Is connected with the first input end of the fourth switch tube (Q)4) The drain electrodes of the two electrodes are connected; second switch tube (Q)2) Second OR gate (OR) of the gate2) The output ends of the two transistors are connected, and the source electrode is grounded;
the second resistor (R)2) And a third resistor (R)3) The series circuit is connected in parallel at two ends of the alternating current of the commercial power 220V; a first resistance (R)1) One end of the first inductor is connected with the positive pole of the 220V alternating current of the mains supply, and the other end of the first inductor is connected with the first inductor (L)1) One terminal of (1), the first inductance (L)1) Is connected to the first switching tube (Q)1) A source electrode of (a); the negative pole of the alternating current of the commercial power 220V is connected with a fourth switching tube (Q)4) A drain electrode of (1); fourth resistance (R)4) And a fifth resistor (R)5) Are connected in series, the series circuit of which is connected in parallel to the first capacitor (C)1) The above step (1); a first capacitor (C)1) Is connected to the third switching tube (Q)3) And the cathode of the drain is grounded.
4. A bridgeless ac/dc converter with peak current control according to claim 3, wherein the control loop comprises an adder, a PI regulator, a multiplier, a third comparator and an RS flip-flop;
one input end of the adder is connected with a fourth resistor (R)4) And a fifth resistor (R)5) The other input end of the bridge-free PFC main circuit is provided with a reference voltage, and the output end of the adder is connected with the input end of the PI regulator;
the output end of the PI regulator is connected with multiplicationOne input terminal of the multiplier and the other input terminal of the multiplier are connected to a second resistor (R)2) And a third resistor (R)3) The sampling value of the input voltage of the bridgeless PFC main circuit is input;
the output end of the multiplier is connected with one input end of a third comparator, the other input end of the third comparator is connected with the anode of alternating current of 220V mains supply AND is used for inputting a sampling value of input current of the bridgeless PFC main circuit, the output end of the third comparator is connected with the input end of an RS trigger, AND the output end of the RS trigger is connected with a first AND gate (AND gate)1) To the second input terminal.
5. A bridgeless ac/dc converter with peak current control according to claim 1, characterized in that the input rectifying filter circuit comprises a first transformer (T)1) A second capacitor (C)2) And a third capacitance (C)3) And a first diode (D)1) A second diode (D)2) A third diode (D)3) A fourth diode (D)4) A bridge circuit is formed;
the first transformer (T)1) The input end of the first capacitor (C) is connected with the alternating current of the commercial power 220V in parallel, the output end of the first capacitor (C) is connected with the alternating current input end of the bridge circuit in parallel, and the second capacitor (C) is connected with the alternating current input end of the bridge circuit in parallel2) A second capacitor (C) connected in parallel with the DC output end of the bridge circuit2) The anode of the three-terminal linear voltage stabilizer is connected with a third capacitor (C)3) Is connected to the second capacitor (C)2) The other end of the negative electrode is connected with the output end of the three-terminal linear voltage stabilizer.
6. A bridgeless ac/dc converter with peak current control according to claim 5, characterized in that the auxiliary source circuit comprises a three-coil transformer (T)2) And a fifth switching tube (Q)5) A fifth diode (D)5) And a sixth diode (D)6) A sixth resistor (R)6) A seventh resistor (R)7) A fourth capacitor (C)4) A fifth capacitor (C)5) A sixth capacitor (C)6) And a seventh capacitance (C)7)；
The three-coil transformer (T)2) The positive pole of the primary coil is connected with a third capacitor (C)3) The anode and the cathode of the second switch are connected with a fifth switch tube (Q)5) A drain electrode of (1);
the fifth switch tube (Q)5) Is connected to the third capacitance (C)3) The positive electrode of (1);
the three-coil transformer (T)2) The anode of the secondary winding of the transformer is connected with a fifth diode (D)5) The anode and the cathode of the battery are grounded;
the three-coil transformer (T)2) The negative pole of the secondary winding of the transformer is grounded, and the positive pole of the secondary winding of the transformer is connected with a sixth diode (D)6) The positive electrode of (1);
the sixth capacitance (C)6) And a seventh resistor (R)7) Are connected in series, the series circuit of which is connected in parallel to the sixth diode (D)6) Both ends of (a);
the fifth capacitor (C)5) Is connected to the fifth diode (D)5) The negative electrode of (2) is grounded; the seventh capacitance (C)7) Is connected to the sixth diode (D)6) The negative electrode of (2) is grounded;
the fifth capacitor (C)5) The positive pole of the capacitor (C) outputs 12V direct current, and a seventh capacitor (C)7) The positive electrode of (2) outputs 5V direct current.
7. A bridgeless ac/dc converter with peak current control according to claim 6, characterized in that the output overvoltage protection circuit comprises a second comparator (U)1B) Eighth resistor (R)8) And a ninth resistor (R)9) Tenth resistor (R)10) Eleventh resistor (R)11) Twelfth resistor (R)12) Triode (Q)6) A seventh diode (D)7) And Relay (RY)1)；
The tenth resistor (R)10) One end of the first comparator is connected with the 12V direct current, and the other end is connected with a second comparator (U)1B) The inverting input terminal of (1);
the eleventh resistance (R)11) Is connected to a second comparator (U)1B) The other end of the inverting input end of the first capacitor is grounded;
the eighth resistor (R)8) One end of the second comparator is connected with the output end of the bridgeless PFC main circuit, and the other end is connected with the second comparator (U)1B) A positive phase input terminal of;
the ninth resistor (R)9) Is connected to a second comparator (U)1B) The other end of the positive phase input end of the transformer is grounded;
the second comparator (U)1B) The positive power supply end of the transformer is connected with 5V direct current, and the negative power supply end of the transformer is grounded;
the twelfth resistor (R)12) Is connected to a second comparator (U)1B) The other end of the output end of the transistor (Q) is connected with a triode6) An emitter of (a);
the triode (Q)6) The base of (D) is grounded, and a seventh diode (D)7) Is connected with a triode (Q)6) The negative electrode of the collector is connected with 5V direct current;
the Relay (RY)1) The input end is connected in parallel with a seventh diode (D)7) One end of the output end of the two ends of the bridge-free PFC main circuit is connected with the output voltage sampling end of the bridge-free PFC main circuit, and the other end of the output end of the bridge-free PFC main circuit is connected with 5V direct current.
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