CN109001523B - Wave trough detection device of alternating current-direct current converter - Google Patents
Wave trough detection device of alternating current-direct current converter Download PDFInfo
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Abstract
The application discloses a trough detection device of an AC-DC converter. The device includes: the device comprises an excitation end detector, a resonance zero-crossing detector, a cosine wave quarter period detector and a trough predictor, wherein the excitation end detector and the resonance zero-crossing detector are respectively connected with the cosine wave quarter period detector, and the cosine wave quarter period detector is connected with the trough predictor. The detection sensitivity of the device is obviously superior to that of the existing excitation end detection circuit, the time for the excitation sampling signal to oscillate from the highest point to the zero crossing point can be more accurately obtained, and the time point of the arrival of the wave trough is obtained based on the time, so that the wave trough time point is subsequently utilized to control the subsequent equipment, such as the starting of equipment, such as a switch, a controller, a transistor and the like, and therefore the switching loss can be reduced, and the utilization rate of a power supply is improved.
Description
Technical Field
The present application relates to the field of analog integrated circuits, and more particularly, to a valley detection apparatus for an ac-dc converter.
Background
With the popularization of electronic products, the electronic products are ubiquitous, and as long as the electronic products need power supplies, in order to reduce pollution and save resources, the purpose of saving power can be achieved only by saving power for any power supply, namely, by achieving high efficiency. To improve efficiency, it is necessary to solve the problem from the power supply system. The conventional alternating current to direct current (AC/DC) converter does not detect whether the turn-on time occurs in the trough of resonance, but turns on immediately as long as the turn-on time controlled by the internal oscillator is reached. This causes the controller to be turned on at a time when the oscillation waveform is still high, which increases the switching loss at the time of turning on. The existing wave trough detection device can detect the resonance waveform after the power switch is turned off, and when the resonance waveform passes through zero, the power tube is controlled to be turned on. This technique cannot turn on the power transistor at the trough of the resonance, but only at the time when the oscillating waveform resonates to the power supply voltage, and although the switching loss is reduced, it is still not turned on at the trough of the resonance waveform, and therefore, there is room for further reduction of the switching loss.
Disclosure of Invention
It is an object of the present application to overcome the above problems or to at least partially solve or mitigate the above problems.
According to an aspect of the present application, there is provided a valley detection apparatus of an ac-dc converter. The device includes: the device comprises an excitation end detector, a resonance zero-crossing detector, a cosine wave quarter period detector and a trough predictor, wherein the excitation end detector and the resonance zero-crossing detector are respectively connected with the cosine wave quarter period detector, and the cosine wave quarter period detector is connected with the trough predictor;
the input of the excitation end detector is an excitation sampling signal of a winding of an alternating current-direct current converter, the moment of excitation end is judged through the detected slope mutation of the excitation sampling signal, an excitation end detection signal is output, and the excitation end detection signal is sent to the cosine wave quarter-cycle detector;
the input of the resonance zero-crossing detector is an excitation sampling signal of a winding of the alternating current-direct current converter, a zero-crossing detection signal is output by comparing the excitation sampling signal with a reference voltage, and the zero-crossing detection signal is sent to the cosine wave quarter-cycle detector;
the cosine wave quarter-cycle detector is used for obtaining a signal representing the time taken by a quarter cycle of the resonance waveform based on the excitation end detection signal and the zero crossing detection signal and sending the signal representing the time taken by the quarter cycle of the resonance waveform to the trough predictor; and
the wave trough predictor is used for obtaining a signal representing the required time for the cosine wave of the excitation sampling signal to oscillate to the wave trough based on the signal representing the time used by the quarter period of the resonance waveform, and sending the signal representing the required time for the cosine wave of the excitation sampling signal to oscillate to the wave trough to the start judger.
The detection sensitivity of the device is obviously superior to that of the existing excitation end detection circuit, the time for the excitation sampling signal to oscillate from the highest point to the zero crossing point can be more accurately obtained, and the time point of the arrival of the wave trough is obtained based on the time, so that the wave trough time point is subsequently utilized to control the subsequent equipment, such as the starting of equipment, such as a switch, a controller, a transistor and the like, and therefore the switching loss can be reduced, and the utilization rate of a power supply is improved.
Optionally, the apparatus further comprises an on-determiner connected to the trough predictor, the on-determiner configured to generate an on-signal based on a clock on-signal and the signal characterizing a time required for a cosine wave of the excitation sampling signal to oscillate to a trough.
The device converts the trough detection result into the turn-on signal, and this signal can be used for controlling other devices, for example, the opening of devices such as controller, switch, transistor to can reduce switching loss, improve the utilization ratio of power.
Optionally, the end of excitation detector comprises a first operational amplifier, a first resistor, a second resistor, a first current source, a second current source, a first capacitor, and a first comparator, wherein,
the input of the non-inverting input end of the first operational amplifier is an excitation sampling signal of a winding of an alternating current-direct current converter, the inverting input end of the first operational amplifier is connected with the positive electrode of the first capacitor, and the output end of the first operational amplifier is connected with one end of the first resistor;
the anode of the first capacitor is connected with the other end of the first resistor, and the cathode of the first capacitor is grounded;
the anode of the first current source is connected with a power supply, and the cathode of the first current source is connected with the anode of the first capacitor;
one end of the second resistor is connected with the cathode of the first current source, and the other end of the second resistor is connected with the anode of the second current source and the non-inverting input end of the first comparator;
the negative electrode of the second current source is grounded; and
and the inverting input end of the first comparator is connected with the output end of the first operational amplifier, and the output end of the first comparator outputs an excitation end detection signal.
The excitation end detector can accurately judge the position of signal mutation according to the slope of the signal, thereby accurately detecting the excitation end time, and the sensitivity of the excitation end detector is obviously superior to that of the traditional excitation end detection circuit.
Optionally, the end of excitation detector comprises a first operational amplifier, a first resistor, a second resistor, a first current source, a second current source, a first capacitor, and a first comparator, wherein:
the input of the non-inverting input end of the first operational amplifier is an excitation sampling signal of a winding of an alternating current-direct current converter, the inverting input end of the first operational amplifier is connected with the positive electrode of the first capacitor, and the output end of the first operational amplifier is connected with one end of the first resistor;
the anode of the first capacitor is connected with the other end of the first resistor, and the cathode of the first capacitor is grounded;
the anode of the first current source is connected with a power supply, and the cathode of the first current source is connected with the anode of the first capacitor;
one end of the second resistor is connected with the cathode of the first current source, and the other end of the second resistor is connected with the anode of the second current source and the inverting input end of the first comparator;
the negative electrode of the second current source is grounded; and
and the non-inverting input end of the first comparator is connected with the output end of the first operational amplifier, and the output end of the first comparator outputs an excitation end detection signal.
Optionally, the resonant zero-crossing detector includes a second comparator, a non-inverting input of the second comparator is connected to the reference voltage, an inverting input of the second comparator is connected to the excitation sampling signal, and an output of the second comparator outputs a zero-crossing detection signal.
The resonance zero-crossing detector can detect a signal of a zero-crossing point, so that the detection result of the excitation end detector is verified, and the accuracy of waveform zero-point detection is ensured.
Optionally, the resonant zero-crossing detector includes a second comparator, an inverting input of the second comparator is connected to the reference voltage, a non-inverting input of the second comparator is connected to the excitation sampling signal, and an output of the second comparator outputs a zero-crossing detection signal.
Optionally, the cosine wave quarter-cycle detector comprises a first nor gate, a second nor gate, a third nor gate, a fourth nor gate, a first nand gate, a first inverter, a second inverter, a third inverter, and a fourth inverter, wherein,
one input end of the first NOR gate is connected with an excitation end detection signal output by the excitation end detector, and the other input end of the first NOR gate is connected with the output end of the second NOR gate;
one input end of the second NOR gate is connected with a pulse width modulation signal, and the other input end of the second NOR gate is connected with the output end of the first NOR gate;
the input end of the first inverter is connected with the output end of the first NOR gate;
the input end of the second inverter is connected with the output end of the first inverter;
one input end of the first NAND gate is connected with the zero-crossing detection signal output by the resonance zero-crossing detector, and the other input end of the first NAND gate is connected with the output end of the first inverter;
the input end of the third inverter is connected with the output end of the first NAND gate;
one input end of the third NOR gate is connected with the output end of the second inverter, and the other input end of the third NOR gate is connected with the output end of the fourth NOR gate;
one input end of the fourth NOR gate is connected with the output end of the third NOR gate, and the other input end of the fourth NOR gate is connected with the output end of the third inverter; and
the input end of the fourth inverter is connected with the output end of the third NOR gate, and the output end of the fourth inverter outputs a signal representing the time taken by one-quarter period of the resonance waveform.
The detector can accurately obtain the time of one quarter of a cosine wave period in each period according to the results of the excitation end detector and the resonance zero-crossing detector, and the calculation is simple and quick.
Optionally, the trough predictor comprises: a first field effect transistor, a second field effect transistor, a third field effect transistor, a fourth field effect transistor, a first switch, a second switch, a third switch, a fourth switch, a third current source, a fourth current source, a fifth current source, a sixth current source, a second capacitor and a third capacitor,
the anode of the third current source is connected with the power supply;
one end of the first switch is connected with the negative electrode of a third current source, and the other end of the first switch is connected with the drain electrode and the grid electrode of the first field effect transistor;
the drain electrode and the grid electrode of the third field effect transistor are respectively connected with the source electrode of the first field effect transistor;
one end of the second switch is connected with the source level of the third field effect transistor, and the other end of the second switch is grounded;
the anode of the second capacitor is connected with the grid of the first field effect transistor, and the cathode of the second capacitor is grounded;
one end of the third resistor is connected with the power supply, and the other end of the third resistor is connected with the drain of the second field effect transistor;
the grid electrode of the second field effect transistor is connected with the grid electrode of the first field effect transistor, and the source electrode of the second field effect transistor is connected with the positive electrode of the fourth current source;
the negative electrode of the fourth current source is grounded;
one end of the third switch is connected with the source level of the second field effect transistor, and the other end of the third switch is respectively connected with one end of the fourth switch and the anode of the third capacitor;
the other end of the fourth switch is connected with the anode of the fifth current source, and the cathode of the fifth current source is grounded;
the negative electrode of the third capacitor is grounded;
the positive electrode of the sixth current source is connected with the power supply;
and the drain electrode of the fourth field effect transistor is connected with the negative electrode of the sixth current source, the grid electrode of the fourth field effect transistor is connected with the positive electrode of the third capacitor, the source stage of the fourth field effect transistor is grounded, and the drain electrode outputs a signal representing the required time for the cosine wave of the excitation sampling signal to oscillate to the wave trough.
The predictor can predict the time of the trough according to the time from the peak to the zero, the design is ingenious, and the calculation result is accurate.
Optionally, the start determiner includes a second nand gate, one input of the second nand gate is connected to the signal representing the time required for the cosine wave of the excitation sampling signal to oscillate to the trough, which is output by the trough predictor, the other input of the second nand gate is connected to a clock start signal, and the output of the second nand gate outputs the start signal.
The on-determiner can generate a control signal according to the valley time so as to control the operation of a subsequent device or component.
Optionally, the first current source is configured to output a constant current, and the second current source is configured to sink the constant current.
The above and other objects, advantages and features of the present application will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Some specific embodiments of the present application will be described in detail hereinafter by way of illustration and not limitation with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:
FIG. 1 is a schematic block diagram of one embodiment of a valley detection apparatus according to the present application;
fig. 2 is a schematic waveform diagram of a conventional excitation end detection signal;
fig. 3 is a schematic waveform diagram of an excitation end detection signal of the present application;
FIG. 4 is a diagram of a system application of a conventional AC/DC converter;
FIG. 5 is a schematic block diagram of another embodiment of a trough detection apparatus according to the present application;
FIG. 6 is a schematic circuit diagram of one embodiment of an end of excitation detector according to the prior art;
FIG. 7 is a schematic circuit diagram of one embodiment of an end of excitation detector according to the present application;
FIG. 8 is a schematic circuit diagram of one embodiment of a resonant zero-crossing detector according to the present application;
FIG. 9 is a schematic circuit diagram of one embodiment of a cosine wave quarter-cycle detector according to the present application;
FIG. 10 is a schematic circuit diagram of one embodiment of a valley predictor according to the present application;
FIG. 11 is a schematic circuit diagram of one embodiment of a turn-on determiner according to the present application;
fig. 12 is a schematic waveform diagram of a signal of a trough detecting device according to the present application.
Detailed Description
The above and other objects, advantages and features of the present application will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Embodiments of the present application provide a valley detection apparatus of an ac-dc converter. FIG. 1 is a schematic block diagram of one embodiment of a trough detection apparatus according to the present application. The apparatus may include: the device comprises an excitation end detector 10, a resonance zero-crossing detector 20, a cosine wave quarter-cycle detector 30 and a trough predictor 40, wherein the excitation end detector and the resonance zero-crossing detector are respectively connected with the cosine wave quarter-cycle detector, and the cosine wave quarter-cycle detector is connected with the trough predictor.
The input of the excitation end detector is an excitation sampling signal of a winding of the alternating current-direct current converter, the moment of excitation end is judged through the detected slope mutation of the excitation sampling signal, the excitation end detection signal is output, and the excitation end detection signal is sent to the cosine wave quarter-cycle detector.
The input of the resonance zero-crossing detector is an excitation sampling signal of a winding of the alternating current-direct current converter, a zero-crossing detection signal is output by comparing the excitation sampling signal with a reference voltage, and the zero-crossing detection signal is sent to the cosine wave quarter-cycle detector.
The cosine wave quarter period detector is used for obtaining a signal representing the time used by the quarter period of the resonance waveform based on the excitation end detection signal and the zero crossing detection signal and sending the signal representing the time used by the quarter period of the resonance waveform to the trough predictor.
The wave trough predictor is used for obtaining a signal representing the required time for the cosine wave of the excitation sampling signal to oscillate to the wave trough based on the signal representing the time used by the quarter period of the resonance waveform, and sending the signal representing the required time for the cosine wave of the excitation sampling signal to oscillate to the wave trough to the start judger.
The detection sensitivity of the device is obviously superior to that of the existing excitation end detection circuit, the time for the excitation sampling signal to oscillate from the highest point to the zero crossing point can be more accurately obtained, and the time point of the arrival of the wave trough is obtained based on the time, so that the wave trough time point is subsequently utilized to control the subsequent equipment, such as the starting of equipment, such as a switch, a controller, a transistor and the like, and therefore the switching loss can be reduced, and the utilization rate of a power supply is improved.
After the power device is turned off, the mathematical expression of an oscillating waveform formed by the primary side main inductor and the parasitic capacitance of the power switch to the ground is as follows:
VDS(t)≈Vin+VR·e-α·t·cos(2·π·fr·t)
wherein:
α is an attenuation factor, frIs the resonant frequency, RpIs the equivalent resistance of the resonant tank, LpIs the equivalent capacitance of the resonant tank, CdParasitic capacitance, V, being power field effect transistor (MOS) and main inductanceinIs a direct current component of an oscillating waveform, VRIs the ac component of the oscillating waveform.
Waveforms obtained by filtering direct-current components from the oscillation waveforms by using the existing trough detection device and the trough detection device of the present application are respectively shown in fig. 2 and 3. According to the conventional valley conduction technique, as long as the zero crossing point of the resonant waveform is detected, the power device is turned on, that is, the conventional valley detection device generally detects points a1, a2, A3 and the like shown in fig. 1, and these points are not valley signals, but can reduce conduction loss compared with the conventional hard switch, but cannot achieve the best effect. These points are therefore not true troughs, and switching losses can only be maximally reduced by turning on the power device at the true trough times B1, B2, B3.
As can be seen from the figure, the oscillating waveform is at line voltage VlineIs a cosine waveform of a zero crossing point, and oscillates from the highest point to the zero crossing point if the zero crossing point is taken as a boundary pointTime t taken for spot1And the time t taken for oscillation from the zero crossing to the trough2Are equal. As described above, since the time taken for the oscillation waveform to oscillate from the highest point to the zero-crossing point is equal to the time taken for the oscillation waveform to oscillate from the zero-crossing point to the trough, it is only necessary to detect t1Then t is2Can be derived by operation, and t2That is the moment at which the trough of the resonant waveform is located. Thus, the time when the valley comes can be determined without directly detecting the valley of the resonance waveform. t is t2Is heavily dependent on t1Only t is1Detected to be accurate t2Accuracy is possible.
On the one hand, due to the manufacturing process of the chip itself, if the oscillating voltage of the main inductor (drain of the power MOS) is directly detected, the voltage is high, and may reach several hundred volts at most, which may damage the chip. Therefore, the voltage of the main inductor is not directly detected, but the voltage of the auxiliary winding, the oscillating voltage waveform of which is completely coupled with the oscillating voltage waveform of the main inductor and is proportional to the turn ratio of the auxiliary coil and the main coil in the amplitude of the voltage, is detected. Because the auxiliary winding provides power supply for the chip, the oscillation voltage of the auxiliary winding can be ensured not to be higher than the withstand voltage of the chip as long as a proper primary and auxiliary turn ratio is set during the design of a power supply system. FIG. 4 is a diagram of a system application of a conventional AC/DC converter if a conventional valley detecting device is used to detect t2In the meantime, since an electrostatic discharge (ESD) protection circuit exists in a chip of the conventional valley detection device, when a negative voltage appears at a pin for detecting resonance, a diode in the ESD protection circuit is turned on in a forward direction to clamp a voltage near-0.7V, and a valley signal is shielded, so that a conventional voltage detection circuit cannot detect a valley. Waveform information below ground potential cannot be transferred into the chip, so it is desirable to detect the time t taken for oscillation from the zero crossing to the trough by oscillating the waveform2And obtaining valley information is not feasible.
On the other hand, if the existing valley detecting means is used to detect t1Time, since the device detects the auxiliary winding VAUXPartial pressure V ofAUX_dIf V is changedAUX_dThe variation range is V1For example, 100mV to 200mV, the excitation of the secondary winding is considered to be finished, the moment is taken as the starting point of resonance, the zero-crossing moment of resonance is measured, and the two points are taken as t1Since the calculation places the start of resonance at VAUX_dAfter a change of 100mV to 200mV, t is therefore1Is not accurate and thus may lead to t2Is not accurate enough. Therefore, t is detected by the conventional valley detecting device1A large deviation is introduced and the time of arrival of the trough is therefore calculated to be inaccurate.
The device of the invention estimates the time required by the arrival of the wave trough by detecting the time from the wave crest to the zero point, thus being not influenced by the ESD device. The method has the advantages of judging the accurate time when the wave trough arrives, and conducting the wave trough in the true sense.
FIG. 5 is a schematic block diagram of another embodiment of a trough detection apparatus according to the present application. Optionally, the apparatus may further include an on determiner 50 connected to the valley predictor, the on determiner configured to generate an on signal based on a clock on signal and the signal representing a required time for the cosine wave of the excitation sampling signal to oscillate to the valley.
The device converts the trough detection result into the turn-on signal, and this signal can be used for controlling other devices, for example, the opening of devices such as controller, switch, transistor to can reduce switching loss, improve the utilization ratio of power.
Fig. 6 is a schematic circuit diagram according to an embodiment of a conventional end-of-excitation detector. The traditional excitation end detector is realized by adopting a simple comparator COMP, a capacitor Ca, a capacitor Cb and a switch Ksamp, namely a resonance signal V of an excitation sampling signaldemAnd comparing the voltage with a reference voltage (usually, a voltage offset which is 100mV to 200mV lower than the excitation sampling signal is selected as the reference voltage), namely, if the excitation signal changes to 100mV to 200mV, the excitation is considered to be finished, and the output signal is dem _ over 1. In fact, the actual end of excitation occurs at the inflection point of the excitation signal, i.e. at the point of inflectionThe slope abruptly changes the moment, so that the traditional detection circuit obviously has an error on the end of excitation.
Fig. 7 is a schematic circuit diagram of one embodiment of an end of excitation detector according to the present application. Optionally, in an embodiment, the excitation end detector may include a first operational amplifier OPA _1, a first resistor R1, a second resistor R2, a first current source I1, a second current source I2, a first capacitor C1, and a first comparator COMP _1, where an input of a non-inverting input terminal of the first operational amplifier OPA _1 is an excitation sampling signal of a winding of an ac-dc converter, an inverting input terminal of the first capacitor is connected to an anode of the first capacitor, and an output terminal of the first operational amplifier OPA _1 is connected to one end of the first resistor; the anode of the first capacitor C1 is connected with the other end of the first resistor, and the cathode is grounded; the anode of the first current source I1 is connected with a power supply, and the cathode of the first current source I1 is connected with the anode of the first capacitor; one end of the second resistor R2 is connected with the cathode of the first current source, and the other end is connected with the anode of the second current source and the non-inverting input end of the first comparator; the negative pole of the second current source I2 is grounded; and the inverting input end of the first comparator is connected with the output end of the first operational amplifier, and the output end outputs an excitation end detection signal.
Alternatively, in another embodiment, the end-of-excitation detector may include a first operational amplifier, a first resistor, a second resistor, a first current source, a second current source, a first capacitor, and a first comparator, wherein: the input of the non-inverting input end of the first operational amplifier is an excitation sampling signal of a winding of an alternating current-direct current converter, the inverting input end of the first operational amplifier is connected with the positive electrode of the first capacitor, and the output end of the first operational amplifier is connected with one end of the first resistor; the anode of the first capacitor is connected with the other end of the first resistor, and the cathode of the first capacitor is grounded; the anode of the first current source is connected with a power supply, and the cathode of the first current source is connected with the anode of the first capacitor; one end of the second resistor is connected with the cathode of the first current source, and the other end of the second resistor is connected with the anode of the second current source and the inverting input end of the first comparator; the negative electrode of the second current source is grounded; and the non-inverting input end of the first comparator is connected with the output end of the first operational amplifier, and the output end outputs an excitation end detection signal.
In the present application, the excitation end signal is detected by the change rate, i.e., the slope, of the excitation signal. When the slope of the excitation signal is zero, the excitation is not finished; if the excitation signal has abrupt change, namely the slope is not zero, namely the excitation is finished, namely the starting point of the resonance is started, then the V of the power MOSDSThe slope is suddenly changed when the resonance waveform begins to fall, that is, the inflection point of the resonance waveform comes, and the excitation end detector is used for detecting the sudden change of the slope, so that the output signal dem _ over2 is inverted once the slope is suddenly changed, which means that the excitation is ended. Therefore, the excitation end detector can accurately judge the position of the signal mutation according to the slope of the signal, so that the excitation end time can be accurately detected, and the sensitivity of the excitation end detector is obviously superior to that of a traditional excitation end detection circuit.
Optionally, the first current source I1 is configured to output a constant current, and the second current source I2 is configured to sink a constant current.
FIG. 8 is a schematic circuit diagram of one embodiment of a resonant zero-crossing detector according to the present application. Optionally, in one embodiment, the resonant zero-crossing detector may include a second comparator COMP _2, a non-inverting input of which is connected to the reference voltage VrefThe inverting input end of the second comparator is connected with an excitation sampling signal VdemAnd an output terminal outputs a zero-crossing detection signal zcd.
The resonance zero-crossing detector can detect a signal of a zero-crossing point, so that the detection result of the excitation end detector is verified, and the accuracy of waveform zero-point detection is ensured.
Alternatively, in another embodiment, the resonant zero-crossing detector may include a second comparator, an inverting input of the second comparator is connected to the reference voltage, a non-inverting input of the second comparator is connected to the excitation sampling signal, and an output thereof outputs a zero-crossing detection signal.
FIG. 9 is a schematic circuit diagram of one embodiment of a cosine wave quarter-cycle detector according to the present application. Optionally, the cosine wave quarter-cycle detector may include a first nor gate nor1, a second nor gate nor2, a third nor gate nor3, a fourth nor gate nor4, a first nand gate nand1, a first inverter inv1, a second inverter inv2, a third inverter inv3 and a fourth inverter inv4, wherein one input of the first nor gate nor1 is connected to the excitation end detection signal dem _ over2 output by the excitation end detector, and the other input is connected to the output of the second nor gate; one input end of the second NOR gate nor2 is connected with a pulse width modulation signal pwm, and the other input end is connected with the output end of the first NOR gate; the input end of the first inverter inv1 is connected with the output end of the first NOR gate; the input end of the second inverter inv2 is connected with the output end of the first inverter; one input of the first nand gate nand1 is connected to the zero-crossing detection signal zcd output by the resonant zero-crossing detector, and the other input of the first nand gate is connected to the output end of the first inverter; the input end of the third inverter inv3 is connected with the output end of the first NAND gate; one input end of the third nor gate nor3 is connected with the output end of the second inverter, and the other input end of the third nor gate nor3 is connected with the output end of the fourth nor gate; one input end of the fourth NOR gate nor4 is connected with the output end of the third NOR gate, and the other input end of the fourth NOR gate nor4 is connected with the output end of the third inverter; and the input of the fourth inverter inv4 is connected to the output of the third nor gate, and the output outputs a signal representing the time taken for a quarter of a cycle of the resonant waveform.
The detector can accurately obtain the time of one quarter of a cosine wave period in each period according to the results of the excitation end detector and the resonance zero-crossing detector, and the calculation is simple and quick.
The output of the fourth inverter inv4 is a K1 signal, the signal between the second inverter inv2 and the third nor gate nor3 is a K2 signal, the signal between the first nand gate nand1 and the third inverter inv3 is a K3 signal, and the signal between the third inverter inv3 and the fourth nor gate nor4 is a K4 signal.
The detector can provide switching value control for the next circuit through the signal value of each node, so that each device of the trough predictor can work conveniently, and the trough prediction function is realized.
FIG. 10 is a schematic circuit diagram of one embodiment of a valley predictor according to the present application. Optionally, the trough predictor may include: a first field effect transistor NM1, a second field effect transistor NM2, a third field effect transistor NM3, a fourth field effect transistor NM4, a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a third current source I3, a fourth current source I4, a fifth current source I5, a sixth current source I6, a second capacitor C2 and a third capacitor C3, wherein the positive electrode of the third current source I3 is connected with the power supply; one end of the first switch K1 is connected with the cathode of a third current source I3, and the other end is connected with the drain and the grid of the first field effect transistor; the drain and the gate of the third field effect transistor NM3 are respectively connected with the source of the first field effect transistor NM 1; one end of the second switch K2 is connected to the source of the third fet NM3, and the other end is grounded; the anode of the second capacitor C2 is connected with the gate of the first field effect transistor, and the cathode of the second capacitor C2 is grounded; one end of the third resistor R3 is connected with the power supply, and the other end is connected with the drain of the second field effect transistor NM 2; the grid electrode of the second field effect transistor NM2 is connected with the grid electrode of the first field effect transistor, and the source electrode is connected with the positive electrode of the fourth current source; the negative pole of the fourth current source I4 is grounded; one end of the third switch K3 is connected with the source of the second field effect transistor, and the other end is respectively connected with one end of the fourth switch K4 and the anode of the third capacitor C3; the other end of the fourth switch K4 is connected with the anode of the fifth current source I5, and the cathode of the fifth current source I5 is grounded; the negative electrode of the third capacitor C3 is grounded; the anode of the sixth current source I6 is connected with the power supply; the drain of the fourth field effect transistor NM4 is connected to the negative electrode of the sixth current source I6, the gate is connected to the positive electrode of the third capacitor, the source is grounded, and the drain outputs a signal Valley _ on representing the time required for the cosine wave of the excitation sampling signal to oscillate to the trough.
The predictor can predict the time of the trough according to the time from the peak to the zero, the design is ingenious, and the calculation result is accurate.
Optionally, the signals K1 to K4 in the cosine wave quarter-cycle detector control the opening and closing of the first switch K1 to the fourth switch K4 in the valley predictor, respectively.
Fig. 11 is a schematic circuit diagram of one embodiment of a turn-on determiner according to the present application. Alternatively, the on-determiner may include a second nand gate, one input of which is connected to the signal Valley _ on representing the time required for the cosine wave of the excitation sampling signal to oscillate to the trough output by the trough predictor, the other input of which is connected to a clock on-signal clk _ rise, and the output of which outputs the on-signal gate _ on.
The on-determiner can generate a control signal according to the valley time so as to control the operation of a subsequent device or component.
Fig. 12 is a schematic waveform diagram of a signal of a trough detecting device according to the present application. It can be seen from the figure that the device of the application can well obtain the time starting point and the time ending point from the wave crest to the zero crossing point in each period of the waveform, and further obtain t1At a time and according to t1Time of day prediction t2Time and control the operation of subsequent devices or components, e.g., opening or closing.
This application has solved two technical accuracy problems of traditional trough sampling.
First, the present application is able to detect true resonance troughs. Conventional valley detection techniques simply detect the quarter time of the valley resonance period. The starting point of the resonance waveform is to perform attenuation oscillation according to a cosine law by taking a direct current ground (a sampling auxiliary winding, and an oscillation waveform takes a zero level as a symmetrical axis) as a symmetrical axis from a wave crest. The negative voltage cannot be detected due to the negative effects of the ESD protection mechanism of the integrated circuit, so that the zero level is considered as a valley. The method avoids the phenomenon of harmonic information distortion caused by ESD protection of an integrated circuit, does not detect the resonance voltage of a resonance waveform to judge the trough, but detects whether excitation is finished or not, then detects the time required from the excitation finishing moment to the resonance waveform zero crossing moment, wherein the time is a quarter period of the resonance waveform, and then calculates the time of the trough according to the detected quarter period of the resonance waveform by using a related circuit, namely the trough detection technology.
Second, since the present application needs to use the excitation end time as a reference time point, the detection of the excitation end time is also the inventive content of the present application. The traditional excitation end detection is only used for judging by detecting the voltage variation of the resonance voltage in the excitation time period, and the application name is that the judgment is carried out by the slope variation of the resonance, so that the sensitivity and the precision are improved.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, 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 an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (16)
1. A valley detection apparatus of an AC-DC converter, comprising: the device comprises an excitation end detector, a resonance zero-crossing detector, a cosine wave quarter period detector and a trough predictor, wherein the excitation end detector and the resonance zero-crossing detector are respectively connected with the cosine wave quarter period detector, and the cosine wave quarter period detector is connected with the trough predictor;
the input of the excitation end detector is an excitation sampling signal of a winding of an alternating current-direct current converter, the moment of excitation end is judged through the detected slope mutation of the excitation sampling signal, an excitation end detection signal is output, and the excitation end detection signal is sent to the cosine wave quarter-cycle detector;
the input of the resonance zero-crossing detector is an excitation sampling signal of a winding of the alternating current-direct current converter, a zero-crossing detection signal is output by comparing the excitation sampling signal with a reference voltage, and the zero-crossing detection signal is sent to the cosine wave quarter-cycle detector;
the cosine wave quarter-cycle detector is used for obtaining a signal representing the time taken by a quarter cycle of the resonance waveform based on the excitation end detection signal and the zero crossing detection signal and sending the signal representing the time taken by the quarter cycle of the resonance waveform to the trough predictor; and
the wave trough predictor is used for obtaining a signal representing the time required for the cosine wave of the excitation sampling signal to oscillate to the wave trough based on the signal representing the time used by the quarter period of the resonance waveform, and sending the signal representing the time required for the cosine wave of the excitation sampling signal to oscillate to the wave trough to an opening judger;
the excitation end detector includes a first operational amplifier, a first resistor, a second resistor, a first current source, a second current source, a first capacitor, and a first comparator,
the input of the non-inverting input end of the first operational amplifier is an excitation sampling signal of a winding of an alternating current-direct current converter, the inverting input end of the first operational amplifier is connected with the positive electrode of the first capacitor, and the output end of the first operational amplifier is connected with one end of the first resistor;
the anode of the first capacitor is connected with the other end of the first resistor, and the cathode of the first capacitor is grounded;
the anode of the first current source is connected with a power supply, and the cathode of the first current source is connected with the anode of the first capacitor;
one end of the second resistor is connected with the cathode of the first current source, and the other end of the second resistor is connected with the anode of the second current source and the non-inverting input end of the first comparator;
the negative electrode of the second current source is grounded; and
and the inverting input end of the first comparator is connected with the output end of the first operational amplifier, and the output end of the first comparator outputs an excitation end detection signal.
2. The apparatus of claim 1, further comprising an on-determiner connected to the valley predictor, the on-determiner configured to generate an on-signal based on a clock on-signal and the signal indicative of a time required for a cosine wave of the excitation sampling signal to oscillate to a valley.
3. The apparatus of claim 1, wherein the resonant zero-crossing detector comprises a second comparator, a non-inverting input of the second comparator is connected to the reference voltage, an inverting input of the second comparator is connected to the excitation sampling signal, and an output of the second comparator outputs a zero-crossing detection signal.
4. The apparatus of claim 1, wherein the resonant zero-crossing detector comprises a second comparator, an inverting input of the second comparator is connected to the reference voltage, a non-inverting input of the second comparator is connected to the excitation sampling signal, and an output of the second comparator outputs a zero-crossing detection signal.
5. The apparatus of claim 1, wherein the cosine wave quarter-cycle detector comprises a first NOR gate, a second NOR gate, a third NOR gate, a fourth NOR gate, a first NAND gate, a first inverter, a second inverter, a third inverter, and a fourth inverter, wherein,
one input end of the first NOR gate is connected with an excitation end detection signal output by the excitation end detector, and the other input end of the first NOR gate is connected with the output end of the second NOR gate;
one input end of the second NOR gate is connected with a pulse width modulation signal, and the other input end of the second NOR gate is connected with the output end of the first NOR gate;
the input end of the first inverter is connected with the output end of the first NOR gate;
the input end of the second inverter is connected with the output end of the first inverter;
one input end of the first NAND gate is connected with the zero-crossing detection signal output by the resonance zero-crossing detector, and the other input end of the first NAND gate is connected with the output end of the first inverter;
the input end of the third inverter is connected with the output end of the first NAND gate;
one input end of the third NOR gate is connected with the output end of the second inverter, and the other input end of the third NOR gate is connected with the output end of the fourth NOR gate;
one input end of the fourth NOR gate is connected with the output end of the third NOR gate, and the other input end of the fourth NOR gate is connected with the output end of the third inverter; and
the input end of the fourth inverter is connected with the output end of the third NOR gate, and the output end of the fourth inverter outputs a signal representing the time taken by one-quarter period of the resonance waveform.
6. The apparatus of claim 1, wherein the valley predictor comprises: a first field effect transistor, a second field effect transistor, a third field effect transistor, a fourth field effect transistor, a first switch, a second switch, a third switch, a fourth switch, a third current source, a fourth current source, a fifth current source, a sixth current source, a second capacitor and a third capacitor,
the anode of the third current source is connected with the power supply;
one end of the first switch is connected with the negative electrode of a third current source, and the other end of the first switch is connected with the drain electrode and the grid electrode of the first field effect transistor;
the drain electrode and the grid electrode of the third field effect transistor are respectively connected with the source electrode of the first field effect transistor;
one end of the second switch is connected with the source level of the third field effect transistor, and the other end of the second switch is grounded;
the anode of the second capacitor is connected with the grid of the first field effect transistor, and the cathode of the second capacitor is grounded;
one end of the third resistor is connected with the power supply, and the other end of the third resistor is connected with the drain of the second field effect transistor;
the grid electrode of the second field effect transistor is connected with the grid electrode of the first field effect transistor, and the source electrode of the second field effect transistor is connected with the positive electrode of the fourth current source;
the negative electrode of the fourth current source is grounded;
one end of the third switch is connected with the source level of the second field effect transistor, and the other end of the third switch is respectively connected with one end of the fourth switch and the anode of the third capacitor;
the other end of the fourth switch is connected with the anode of the fifth current source, and the cathode of the fifth current source is grounded;
the negative electrode of the third capacitor is grounded;
the positive electrode of the sixth current source is connected with the power supply;
and the drain electrode of the fourth field effect transistor is connected with the negative electrode of the sixth current source, the grid electrode of the fourth field effect transistor is connected with the positive electrode of the third capacitor, the source stage of the fourth field effect transistor is grounded, and the drain electrode outputs a signal representing the required time for the cosine wave of the excitation sampling signal to oscillate to the wave trough.
7. The apparatus of any one of claims 1 to 6, wherein the turn-on determiner comprises a second NAND gate, one input of the second NAND gate is connected to the signal representing the time required for the cosine wave of the excitation sampling signal to oscillate to the trough, which is output by the trough predictor, the other input of the second NAND gate is connected to a clock turn-on signal, and an output of the second NAND gate outputs the turn-on signal.
8. The apparatus of claim 1, wherein the first current source is configured to output a constant current and the second current source is configured to sink a constant current.
9. A valley detection apparatus of an AC-DC converter, comprising: the device comprises an excitation end detector, a resonance zero-crossing detector, a cosine wave quarter period detector and a trough predictor, wherein the excitation end detector and the resonance zero-crossing detector are respectively connected with the cosine wave quarter period detector, and the cosine wave quarter period detector is connected with the trough predictor;
the input of the excitation end detector is an excitation sampling signal of a winding of an alternating current-direct current converter, the moment of excitation end is judged through the detected slope mutation of the excitation sampling signal, an excitation end detection signal is output, and the excitation end detection signal is sent to the cosine wave quarter-cycle detector;
the input of the resonance zero-crossing detector is an excitation sampling signal of a winding of the alternating current-direct current converter, a zero-crossing detection signal is output by comparing the excitation sampling signal with a reference voltage, and the zero-crossing detection signal is sent to the cosine wave quarter-cycle detector;
the cosine wave quarter-cycle detector is used for obtaining a signal representing the time taken by a quarter cycle of the resonance waveform based on the excitation end detection signal and the zero crossing detection signal and sending the signal representing the time taken by the quarter cycle of the resonance waveform to the trough predictor; and
the wave trough predictor is used for obtaining a signal representing the time required for the cosine wave of the excitation sampling signal to oscillate to the wave trough based on the signal representing the time used by the quarter period of the resonance waveform, and sending the signal representing the time required for the cosine wave of the excitation sampling signal to oscillate to the wave trough to an opening judger;
the excitation end detector includes a first operational amplifier, a first resistor, a second resistor, a first current source, a second current source, a first capacitor, and a first comparator, wherein:
the input of the non-inverting input end of the first operational amplifier is an excitation sampling signal of a winding of an alternating current-direct current converter, the inverting input end of the first operational amplifier is connected with the positive electrode of the first capacitor, and the output end of the first operational amplifier is connected with one end of the first resistor;
the anode of the first capacitor is connected with the other end of the first resistor, and the cathode of the first capacitor is grounded;
the anode of the first current source is connected with a power supply, and the cathode of the first current source is connected with the anode of the first capacitor;
one end of the second resistor is connected with the cathode of the first current source, and the other end of the second resistor is connected with the anode of the second current source and the inverting input end of the first comparator;
the negative electrode of the second current source is grounded; and
and the non-inverting input end of the first comparator is connected with the output end of the first operational amplifier, and the output end of the first comparator outputs an excitation end detection signal.
10. The apparatus of claim 9, further comprising an on-determiner connected to the valley predictor, the on-determiner configured to generate an on-signal based on a clock on-signal and the signal indicative of a time required for a cosine wave of the excitation sampling signal to oscillate to a valley.
11. The apparatus of claim 9, wherein the resonant zero-crossing detector comprises a second comparator, a non-inverting input of the second comparator is connected to the reference voltage, an inverting input of the second comparator is connected to the excitation sampling signal, and an output of the second comparator outputs a zero-crossing detection signal.
12. The apparatus of claim 9, wherein the resonant zero-crossing detector comprises a second comparator, an inverting input of the second comparator is connected to the reference voltage, a non-inverting input of the second comparator is connected to the excitation sampling signal, and an output of the second comparator outputs a zero-crossing detection signal.
13. The apparatus of claim 9, wherein the cosine wave quarter-cycle detector comprises a first NOR gate, a second NOR gate, a third NOR gate, a fourth NOR gate, a first NAND gate, a first inverter, a second inverter, a third inverter, and a fourth inverter, wherein,
one input end of the first NOR gate is connected with an excitation end detection signal output by the excitation end detector, and the other input end of the first NOR gate is connected with the output end of the second NOR gate;
one input end of the second NOR gate is connected with a pulse width modulation signal, and the other input end of the second NOR gate is connected with the output end of the first NOR gate;
the input end of the first inverter is connected with the output end of the first NOR gate;
the input end of the second inverter is connected with the output end of the first inverter;
one input end of the first NAND gate is connected with the zero-crossing detection signal output by the resonance zero-crossing detector, and the other input end of the first NAND gate is connected with the output end of the first inverter;
the input end of the third inverter is connected with the output end of the first NAND gate;
one input end of the third NOR gate is connected with the output end of the second inverter, and the other input end of the third NOR gate is connected with the output end of the fourth NOR gate;
one input end of the fourth NOR gate is connected with the output end of the third NOR gate, and the other input end of the fourth NOR gate is connected with the output end of the third inverter; and
the input end of the fourth inverter is connected with the output end of the third NOR gate, and the output end of the fourth inverter outputs a signal representing the time taken by one-quarter period of the resonance waveform.
14. The apparatus of claim 9, wherein the valley predictor comprises: a first field effect transistor, a second field effect transistor, a third field effect transistor, a fourth field effect transistor, a first switch, a second switch, a third switch, a fourth switch, a third current source, a fourth current source, a fifth current source, a sixth current source, a second capacitor and a third capacitor,
the anode of the third current source is connected with the power supply;
one end of the first switch is connected with the negative electrode of a third current source, and the other end of the first switch is connected with the drain electrode and the grid electrode of the first field effect transistor;
the drain electrode and the grid electrode of the third field effect transistor are respectively connected with the source electrode of the first field effect transistor;
one end of the second switch is connected with the source level of the third field effect transistor, and the other end of the second switch is grounded;
the anode of the second capacitor is connected with the grid of the first field effect transistor, and the cathode of the second capacitor is grounded;
one end of the third resistor is connected with the power supply, and the other end of the third resistor is connected with the drain of the second field effect transistor;
the grid electrode of the second field effect transistor is connected with the grid electrode of the first field effect transistor, and the source electrode of the second field effect transistor is connected with the positive electrode of the fourth current source;
the negative electrode of the fourth current source is grounded;
one end of the third switch is connected with the source level of the second field effect transistor, and the other end of the third switch is respectively connected with one end of the fourth switch and the anode of the third capacitor;
the other end of the fourth switch is connected with the anode of the fifth current source, and the cathode of the fifth current source is grounded;
the negative electrode of the third capacitor is grounded;
the positive electrode of the sixth current source is connected with the power supply;
and the drain electrode of the fourth field effect transistor is connected with the negative electrode of the sixth current source, the grid electrode of the fourth field effect transistor is connected with the positive electrode of the third capacitor, the source stage of the fourth field effect transistor is grounded, and the drain electrode outputs a signal representing the required time for the cosine wave of the excitation sampling signal to oscillate to the wave trough.
15. The apparatus of any one of claims 9 to 14, wherein the turn-on determiner comprises a second nand gate, one input of the second nand gate is connected to the signal representing the time required for the cosine wave of the excitation sampling signal to oscillate to the trough output by the trough predictor, the other input of the second nand gate is connected to a clock turn-on signal, and an output of the second nand gate outputs the turn-on signal.
16. The apparatus of claim 9, wherein the first current source is configured to output a constant current and the second current source is configured to sink a constant current.
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| TW200822514A (en) * | 2006-11-03 | 2008-05-16 | Richtek Techohnology Corp | Circuit and method to detect the wave trough of switching device |
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