CN113644814B - Harmonic distortion compensation circuit, related circuit, system and method - Google Patents

Harmonic distortion compensation circuit, related circuit, system and method Download PDF

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Publication number
CN113644814B
CN113644814B CN202010343606.0A CN202010343606A CN113644814B CN 113644814 B CN113644814 B CN 113644814B CN 202010343606 A CN202010343606 A CN 202010343606A CN 113644814 B CN113644814 B CN 113644814B
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time
circuit
switch
signal
inductor
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CN113644814A (en
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赵汗青
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Meixinsheng Technology Beijing Co ltd
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Meixinsheng Technology Beijing Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a harmonic distortion compensation circuit, a related circuit, a system and a method, wherein the harmonic distortion compensation circuit comprises: the device comprises a demagnetization state detection circuit, a time sampling circuit and a time adjusting circuit; the demagnetization state detection circuit is used for detecting the demagnetization state of the inductor in the switching period and outputting an inductor demagnetization ending signal to the time sampling circuit at the inductor demagnetization ending moment; the time sampling circuit is used for sampling the output signal of the pulse width modulator and obtaining time signals representing the switch on time, the inductor demagnetizing time and the switch starting waiting time according to the received inductor demagnetizing end signal, and outputting the time signals to the time adjusting circuit; the time adjusting circuit is used for determining a conduction time control signal according to the time signal and outputting the conduction time control signal to the pulse width modulator so as to control the switch conduction time of the switching power supply system. The THD of the circuit is reduced, and the stability of the switching power supply system for supplying power to the controlled load is improved.

Description

Harmonic distortion compensation circuit, related circuit, system and method
Technical Field
The invention relates to a harmonic distortion compensation circuit, a related circuit, a system and a method.
Background
In the prior art, because of the second harmonic, the third harmonic and the noise test harmonic generated by unavoidable oscillation or other resonance of the circuit are superposed with the actual input signal, the signal output at the output end is not simply the same component as the input signal, but is a signal comprising harmonic components, and the comparison of the redundant harmonic components with the actual input signal is expressed as a percentage and is called total harmonic distortion (Total Harmonic Distortion, THD).
When the input voltage is in the trough section, the peak current of the inductor decreases with the input voltage, resulting in an inductor demagnetization time T dmg The switching period Ts of the switching tube is limited to a minimum value because of the frequency limitation of the switching tube, for example, the frequency of the switching tube is generally between several kilohertz and several hundred kilohertz. The circuit enters a discontinuous conduction mode (Discontinuous Conduction Mode, DCM) from a critical conduction mode (Critical Conduction Mode, CRM) and the current harmonic distortion characteristics change. Currently, the switch is operated at the on time T on The mode of superimposing the input voltage waveform cannot compensate for harmonic distortion due to the change of the circuit conduction mode. Therefore, how to compensate the current harmonic distortion when the circuit enters the DCM mode, and reduce the current harmonic distortion when the circuit enters the DCM mode The lower total harmonic distortion is a problem to be solved by one stamp.
Disclosure of Invention
The embodiment of the invention aims to provide a harmonic distortion compensation circuit, a related circuit, a system and a method capable of reducing total harmonic distortion of a circuit in a DCM mode.
As a first aspect of an embodiment of the present invention, an embodiment of the present invention provides a harmonic distortion compensation circuit including: the device comprises a demagnetization state detection circuit, a time sampling circuit and a time adjusting circuit; the time sampling circuit is respectively connected with the demagnetization state detection circuit and the time adjustment circuit;
the demagnetization state detection circuit is connected with the inductor of the switching power supply system and is used for detecting the demagnetization state of the inductor in a switching period and outputting an inductor demagnetization ending signal to the time sampling circuit at the inductor demagnetization ending moment;
the time sampling circuit is connected with the pulse width modulator of the switching power supply system and is used for sampling an output signal of the pulse width modulator and obtaining a time signal representing the switching-on time, the inductance demagnetization time and the switching-on waiting time according to the received inductance demagnetization ending signal, and outputting the time signal to the time regulating circuit;
The time adjusting circuit is connected with the pulse width modulator, and is used for determining a conduction time control signal according to the time signals representing the switch conduction time, the inductance demagnetizing time and the switch starting waiting time and outputting the conduction time control signal to the pulse width modulator so as to control the switch conduction time of the switch power supply system.
In some optional embodiments, the demagnetization state detection circuit includes a first operational amplifier and an RS flip-flop, an inverting input end of the first operational amplifier is connected to the inductor, a non-inverting input end of the first operational amplifier is grounded, an output end of the first operational amplifier is connected to a reset end of the RS flip-flop, a set end of the RS flip-flop is connected to a reference level, and an output end of the RS flip-flop is connected to the time sampling circuit.
In some alternative embodiments, the time sampling circuit includes a first current source, a time sampling switch, a first capacitor; the first current source is connected with one end of the first capacitor, the other end of the first capacitor is grounded, one end of the time sampling switch is connected with the common end of the first current source and the first capacitor, and the other end of the time sampling switch is grounded; the time sampling switch samples the trigger signal and is conducted, and the first capacitor discharges and outputs a time signal representing the switch conducting time, the inductor demagnetizing time and the switch starting waiting time.
In some alternative embodiments, the output signal of the time sampling switch sampled to the pulse width modulator is a switch on signal and turned on, and the first capacitor discharges and outputs a time signal representing the switch on time;
the time sampling switch samples the output signal of the pulse width modulator as a switch closing signal and is conducted, and the first capacitor discharges and outputs a time signal representing the demagnetizing time of the inductor;
the time sampling switch samples and conducts the inductor demagnetization ending signal, and the first capacitor discharges and outputs a time signal representing the switch starting waiting time.
In some alternative embodiments, the time adjustment circuit includes a logic operation unit and a signal output circuit;
the logic operation unit is configured to obtain a switch on time, an inductance demagnetizing time and a switch start waiting time according to the received time signal, and determine a compensation duty ratio according to the switch on time, the inductance demagnetizing time and the switch start waiting time, where the compensation duty ratio d=t on /(T on +T dmg +K*T wait ) Wherein K is 1 or more, T on Indicating the on time of the switch, T dmg Indicating the inductance demagnetizing time T wait Indicating a switch start wait time;
the signal output circuit comprises a second current source and a third capacitor, wherein the common end of the second current source and the third capacitor is an adjusting signal output end, the second current source determines constant output current according to the compensation duty ratio and preset reference current and charges the third capacitor, so that the signal output end outputs a conduction time control signal corresponding to the constant output current.
In some alternative embodiments, the output end of the adjusting signal is connected with the positive input end of a second operational amplifier in the pulse width modulator, the negative input end of the second operational amplifier is connected with the output end of a feedback detection circuit of the switching power supply system, and the comparing voltage output by the feedback detection circuit is received; the second operational amplifier outputs a driving signal for adjusting the on time according to the on time control signal and the comparison voltage.
As a second aspect of the embodiment of the present invention, the embodiment of the present invention provides a load driving circuit including: the feedback detection circuit, the pulse width modulator, the driver and the harmonic distortion compensation circuit;
the pulse width modulator is respectively connected with the feedback detection circuit and the driver.
In some alternative embodiments, the feedback detection circuit samples a sampled voltage representative of the output current, obtains a comparison voltage from the sampled voltage, and outputs to the pulse width modulator;
the pulse width modulator outputs a driving signal for adjusting the on time according to the comparison voltage and the on time control signal of the harmonic distortion compensation circuit;
And the driver drives a switching tube of the switching power supply system to be conducted according to the driving signal.
In some alternative embodiments, the pulse width modulator comprises a second operational amplifier;
the positive input end of the second operational amplifier is connected with the output end of the time adjusting circuit of the harmonic distortion compensating circuit, the negative input end of the second operational amplifier is connected with the output end of the feedback detecting circuit, and the comparison voltage output by the feedback detecting circuit is received; the second operational amplifier outputs a driving signal for adjusting the on time according to the received comparison voltage of the on time control signal of the harmonic distortion compensation circuit and the feedback detection circuit.
As a third aspect of the embodiment of the present invention, the embodiment of the present invention provides a switching power supply system, including: the rectifier module, the inductor, the switching tube, the sampling resistor and the load driving circuit are connected with the alternating current power supply;
the rectifying module is connected with the input end of the controlled load, the input end of the inductor is connected with the output end of the controlled load, the output end of the inductor is connected with the drain electrode of the switching tube, the source electrode of the switching tube is connected with the sampling resistor, the grid electrode of the switching tube is connected with the output end of the load driving circuit, and the driving signal for adjusting the on time is received; and the output end of the sampling resistor is grounded.
In some optional embodiments, the inductor is a common-mode inductor, two ends of a primary coil of the common-mode inductor are respectively connected with the controlled load and a drain electrode of the switching tube, one end of a secondary coil of the common-mode inductor is connected with the demagnetization state detection circuit, and the other end of the secondary coil of the common-mode inductor is grounded.
As a fourth aspect of the embodiments of the present invention, the embodiments of the present invention provide a harmonic distortion compensation method, including:
detecting an inductance demagnetization state in a switching period, and outputting an inductance demagnetization ending signal to the time sampling circuit at the inductance demagnetization ending time;
sampling an output signal of the pulse width modulator and obtaining a time signal representing the switch on time, the inductor demagnetization time and the switch start waiting time according to the received inductor demagnetization end signal;
and determining a conduction time control signal according to the time signals representing the switch conduction time, the inductance demagnetization time and the switch starting waiting time so as to control the switch conduction time of the switch power supply system.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:
according to the harmonic distortion compensation circuit provided by the embodiment of the invention, the demagnetization state of the inductor of the switching power supply system is detected, so that the detection of the time signals of the inductor demagnetization time and the switch start waiting time in the turn-off time of the switching tube is realized, and the turn-on time control signal is obtained according to the determined switch turn-on time, the determined inductor demagnetization time and the determined switch start waiting time, so that the adjustment of the switch turn-on time is realized. By adjusting the switch on time in the switching period of the switching tube, the current harmonic distortion of the circuit in the CRM mode and the DCM mode is compensated, so that the input current is more similar to an ideal sine half-wave waveform. For a switching power supply system, THD of the circuit is reduced, input current is closer to an ideal sine half-wave waveform, and stability of the switching power supply system for supplying power to a controlled load is improved.
Drawings
Fig. 1 is a schematic diagram of a prior art LED driving circuit;
FIG. 2 is a timing diagram of a switching cycle in the LED driver circuit shown in FIG. 1;
FIG. 3 is a schematic diagram of waveforms and fundamental frequency components of an actual input current and an ideal input current in the LED driving circuit shown in FIG. 1;
fig. 4 is a schematic structural diagram of a switching power supply system according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an inductor L and a demagnetization detecting circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of voltage waveforms at different detection terminals in a switching period according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a time sampling circuit according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a signal output circuit according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of waveforms to be compensated of the input current obtained by performing a difference and a translation between the actual input current and the ideal input current shown in FIG. 3;
FIG. 10 is a schematic diagram illustrating the switch on time adjustment in the switching power supply system shown in FIG. 4;
fig. 11 is a schematic structural diagram of another switching power supply system according to an embodiment of the present invention;
fig. 12 is a schematic diagram of a signal conversion circuit according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
Referring to fig. 1, an LED load driving circuit for realizing constant current driving in the prior art comprises a rectifier 10, an LED load 20 and a regulating circuit, wherein the input of the rectifier 10 is connected with an ac power supply, the output of the rectifier 10 is connected with the LED load 20, the LED load 20 is connected with the drain of a transistor M0, and the source of the transistor M0 is connected with a sampling resistor R cs The regulating circuit comprises a feedback detection circuit 30, a pulse width regulator 40 and a driver U0, wherein the feedback detection circuit 30 has an input and a source of a transistor M0 and a sampling resistor R cs An output of the feedback detection circuit 30 is connected to an input of the pulse width modulator 40, an output of the pulse width modulator 40 is connected to an input of the driver U0, and an output of the driver U0 is connected to a gate of the transistor M0. Specifically, feedback detection circuit 30 samples a sampling resistor R in the circuit that characterizes the input current cs Feedback voltage V on cs The feedback detection circuit 30 feeds back the voltage V cs After processing, the compensation signal V is obtained comp And input to the pulse width modulator 40, the pulse width modulator 40 generates a compensation signal V comp A driving signal for adjusting the output on time is obtained, and the driver U0 is controlled to adjust the on time of the transistor M0 according to the driving signal, thereby realizing constant current driving control. In which the current I is input in And input voltage V in The following relationship is given in equation 1:wherein L represents inductance, T on Indicating the on time of the switching tube, T s Representing the switching period of the switching tube. Referring to FIG. 2, T is shown on 、T off T and T s In (2), wherein T off Indicating the turn-off time of the switch tube, T s For the on time T on And off time T off And (3) summing. Equation 1 can also be expressed as equation 2: />Wherein D is the duty cycle and +.>Referring to fig. 3, a current I is input using the LED load driving circuit shown in fig. 1 in The actual waveform 1 of (2) differs greatly from the ideal sinusoidal waveform of (2), which means that THD in the circuit is large and the power factor is reduced. And during one cycle of the input current the circuit will operate in CRM mode or DCM mode. At present, the on time T of the switching tube is adopted on The mode of superimposing the input voltage waveform cannot compensate for harmonic distortion in DCM. Therefore, how to compensate the voltage output signal of the zero crossing stage in the DCM working mode, so that the input current signal is more approximate to the ideal semicircular waveform is the difficulty solved by the invention. The invention aims to provide a harmonic distortion compensation circuit, so that a switching power supply system can ensure lower THD in any working mode, and the THD compensation circuit is simple and reliable in structure.
In order to solve the problem of harmonic distortion in the prior art, an embodiment of the present invention provides a harmonic distortion compensation circuit, as shown in fig. 4, including: a demagnetization state detection circuit 51, a time sampling circuit 52, and a time adjustment circuit 53; the time sampling circuit 52 is connected with the demagnetization state detection circuit 51 and the time adjustment circuit 53 respectively;
the demagnetization state detection circuit 51 is connected to an inductor L of the switching power supply system, and is configured to detect an inductor demagnetization state in a switching cycle, and output an inductor demagnetization end signal to the time sampling circuit 52 at an inductor demagnetization end time;
the time sampling circuit 52 is connected with the pulse width modulator of the switching power supply system, and is used for sampling the output signal of the pulse width modulator and obtaining a time signal representing the switching-on time, the inductor demagnetization time and the switching start waiting time according to the received inductor demagnetization end signal, and outputting the time signal to the time adjusting circuit 53;
the time adjustment circuit 53 is connected to the pulse width modulator of the switching power supply system, and is configured to determine a conduction time control signal according to a time signal representing the switch on time, the inductor demagnetizing time and the switch start waiting time, and output the conduction time control signal to the pulse width modulator of the switching power supply system to control the switch on time of the switching power supply system.
According to the harmonic distortion compensation circuit provided by the embodiment of the invention, the demagnetization state of the inductor of the switching power supply system is detected, so that the detection of the time signals of the inductor demagnetization time and the switch start waiting time in the turn-off time of the switching tube is realized, and the turn-on time control signal is obtained according to the determined switch turn-on time, the determined inductor demagnetization time and the determined switch start waiting time, so that the adjustment of the switch turn-on time is realized. By adjusting the switch on time in the switching period of the switching tube, the current harmonic distortion of the circuit in the CRM mode and the DCM mode is compensated, so that the input current is more similar to an ideal sine half-wave waveform. For a switching power supply system, THD of the circuit is reduced, input current is closer to an ideal sine half-wave waveform, and stability of the switching power supply system for supplying power to a controlled load is improved.
For more convenience in explaining the specific implementation manner of the embodiment of the present invention, referring to fig. 4, the embodiment of the present invention is described in detail with a switching power supply system including the harmonic distortion compensation circuit. The switching power supply system is used for controlling the working state of a controlled load, and specifically, the controlled load can be the LED load 20 and the regulating circuit. The switching power supply system includes: rectifier module 10 connected with alternating current power supply, inductance L, switching tube M0 and sampling resistor R cs Feedback detection circuit 30, pulse width modulator 40, driver U0, and harmonic distortion compensation circuit 5 described above0; the harmonic distortion compensation circuit 50 includes: a demagnetization state detection circuit 51, a time adjustment circuit 53, and a time sampling circuit 52 connected to the demagnetization state detection circuit 51 and the time adjustment circuit 53, respectively;
the rectification module 10 is connected with the input end of the LED load 20;
the input end of the inductor L is connected with the output end of the LED load 20, and the output end of the inductor L is connected with the drain electrode of the switching tube M0;
the source electrode of the switch tube M0 is connected with a sampling resistor R cs The gate of the switch tube M0 is connected with the output end of the driver U0 and is used for adjusting the on time T on Is a driving signal of (a);
sampling resistor R cs The output end of which is grounded;
the feedback detection circuit 30 is connected to the pulse width modulator 40, the source of the switching tube M0 and the sampling resistor R cs A common terminal therebetween, samples a sampling voltage V representing an output current cs According to the sampling voltage V cs Obtaining a comparison voltage V comp And output to the pulse width modulator 40;
the demagnetization state detection circuit 51 is connected with the inductor L and is used for detecting the demagnetization state of the inductor in the switching period and outputting an inductor demagnetization end signal to the time sampling circuit;
the time sampling circuit 52 is connected to the pwm 40 for sampling the output signal of the pwm 40 and obtaining a time signal V representing the switch on time, the inductor demagnetization time and the switch start waiting time according to the received inductor demagnetization end signal cap And outputs to the time adjustment circuit 53;
the time adjustment circuit 53 is connected to the pulse width modulator 40 for providing a time signal V indicative of the switch on time, the inductor demagnetization time and the switch start wait time cap The on-time control signal SD is determined and output to the pulse width modulator 40;
the pulse width modulator 40 is connected to the driver U0 and receives the comparison voltage V comp And an on-time control signal SD output for adjusting the on-time T on Is set to the drive signal of (2)；
The driver U0 adjusts the on-time T according to the received signal on And the driving signal of the driving circuit drives the switching tube to conduct.
In a specific embodiment, referring to fig. 5, an inductance L of the switching power supply system is a common-mode inductance, two ends of a primary coil of the inductance L are respectively connected to a controlled load 20 and a drain electrode of a switching tube M0, one end of a secondary coil of the inductance L is connected to a demagnetization state detection circuit, and the other end is grounded.
In a specific embodiment, referring to fig. 5, the demagnetization state detection circuit 51 includes a first operational amplifier U1 and an RS flip-flop, where an inverting input terminal of the first operational amplifier U1 is connected to a secondary coil of the inductor L, a forward input terminal of the first operational amplifier is grounded, an output terminal of the first operational amplifier is connected to a reset terminal of the RS flip-flop, and a setting terminal of the RS flip-flop is connected to a reference level The output of the RS flip-flop is connected to a time sampling circuit 52. When the switching tube M0 is switched from on to off, the first operational amplifier U1 detects that the inductor L is discharged and is in an inductor demagnetization state, and at the end of inductor demagnetization, the inverting input terminal of the first operational amplifier U1 detects a level falling edge, and sends a high level signal to the reset terminal of the RS flip-flop, and the output terminal of the RS flip-flop outputs an inductor demagnetization end signal to the time sampling circuit 52 according to the high level signal.
Referring to fig. 6, when the circuit of the switching power supply system operates in DCM, a switching period T of the switching transistor M s Including switch on time T on Inductance demagnetization time T dmg Switch activation wait time T wait . At the switching tube M0 at the switching on time T on In the internal time, the grid voltage V of the switch tube driver For high level signal, when the switch tube M0 is turned off, the gate voltage V of the switch tube driver To switch from a high level signal to a low level signal; conversely, when the switching tube M0 is turned on, the drain voltage V of the switching tube drain Is a low level signal, when the switch tube M0 is turned off, the gate of the switch tubePolar voltage V driver To switch from low level signal to high level signal, the inductor L enters demagnetizing state for the inductor demagnetizing time T dmg And when the inductor demagnetizing time is over, the energy of the inductor L in the circuit is insufficient to compensate more voltage, so the drain voltage V of the switch tube drain The inductor L needs to wait for the switch to start for a waiting time T wait The switching tube is conducted to enter the next switching period to be charged again; for the secondary coil of the inductor L, the voltage waveform and the drain voltage V of the switch tube drain In accordance with the voltage V at the output end by connecting the output end with the common end of the two voltage dividing resistors aux When the falling edge of the first voltage oscillation occurs, the output voltage reaches 0V, so that the reverse input end of the first operational amplifier U1 detects the first level falling edge at the moment when the inductor demagnetization time is finished, the reverse input end of the first operational amplifier U1 detects the level falling edge, a high level signal is sent to the reset end of the RS trigger, and the output end of the RS trigger outputs an inductor demagnetization finishing signal to the time sampling circuit 52 according to the high level signal.
Referring to fig. 7, the time sampling circuit 52 includes a first current source I chg A time sampling switch SN, a first capacitor C1, the first current source I chg One end of the time sampling switch SN is connected with the first current source I chg The other end of the time sampling switch SN is grounded, and a first current source I is connected with the common end of the first capacitor C1 chg The first capacitor C1 can be charged, the time sampling switch SN samples the trigger signal and is conducted, and at the moment, the first capacitor C1 discharges and outputs a time signal V representing the sampling time cap 。
Specifically, the output signal of the pulse width modulator 40 sampled by the time sampling switch SN is a switch on signal and is turned on, the first capacitor C1 discharges, and a time signal V representing the switch on time is output cap1 The method comprises the steps of carrying out a first treatment on the surface of the The output signal of the time sampling switch SN sampled to the pulse width modulator 40 is a switch closing signal and is conducted, the first capacitor discharges, and the characterization inductance is outputTime signal V of magnetic time cap2 The method comprises the steps of carrying out a first treatment on the surface of the The time sampling switch SN samples and conducts the inductor demagnetization end signal, discharges the first capacitor and outputs a time signal V representing the switch starting waiting time cap3 。
In order to make the time sampling circuit 52 not generate signal disturbance when sampling different trigger signals, in the embodiment of the present invention, the time sampling circuit includes 3 groups of circuit structures shown in fig. 7, wherein the trigger signal of the time sampling switch SN of the first group of circuits is the switch on signal of the output signal of the pulse width modulator 40, the trigger signal of the time sampling switch SN of the second group of circuits is the switch off signal of the output signal of the pulse width modulator 40, and the trigger signal of the time sampling switch SN of the third group of circuits is the inductor demagnetization end signal output by the RS trigger of the demagnetization state detection circuit 51.
In the embodiment of the present invention, the time adjustment circuit 53 includes a logic operation unit and a signal output circuit 531;
the logic operation unit of the time adjustment circuit 53 is used for receiving time signals, namely, time signals V representing the on-time of the switch cap1 Time signal V representing the demagnetization time of an inductor cap2 Time signal V characterizing the switch start-up latency cap3 Obtaining the switch on time T on Inductance demagnetization time T dmg Switch activation wait time T wait And according to the switch on time T on Inductance demagnetization time T dmg Switch activation wait time T wait A compensating duty cycle D 'is determined, the compensating duty cycle D' =t on /(T on +T dmg +K*T wait ) Wherein K is 1 or more, T on Indicating the on time of the switch, T dmg Indicating the inductance demagnetizing time T wait Indicating the switch activation latency.
In a specific embodiment, referring to fig. 8, the signal output circuit 531 of the time adjustment circuit 53 includes a second current source I sd And a second capacitor C2, a second current source I sd And the common end of the second capacitor C2 is an adjusting signal output end, and the second current source I sd And determining constant output current according to the compensation duty ratio and a preset reference current, and charging the second capacitor C2 to enable a signal output end to output a conduction time control signal corresponding to the constant output current.
In the embodiment of the present invention, in order to make the compensated waveform more approximate to the ideal waveform, it is necessary to determine the size of the waveform to be compensated first, and when the compensation waveform is actually determined, a difference operation may be performed by using the ideal sinusoidal waveform 2 shown in fig. 3 and the measured actual waveform 1, for example, the obtained ideal sinusoidal waveform 1 and the actual waveform 2 are subjected to a fourier transform algorithm, and the mathematical formula of the actual waveform is subtracted from the mathematical formula of the obtained ideal sinusoidal waveform to obtain the original waveform to be compensated. Because the waveform compensation can only be carried out in the forward direction but not in the reverse direction when the on-off time of the switch is adopted, the conduction T of the switch period is regulated on This corresponds to a reduction in the difference between the input current for the next cycle and the ideal value, and thus a reduction in THD. Therefore, in the embodiment of the present invention, the inventor innovatively adopts the method of translating the original shape to be compensated upwards to obtain the waveform to be compensated shown in fig. 9. According to the waveform to be compensated shown in FIG. 9, in each half-wave period, on both sides of the approximate "W" waveform, the circuit enters DCM mode, the inductor L has insufficient energy at the end of the period and cannot compensate more voltage, at this time, due to the limitation of the frequency of the switching tube M0, when the switching tube M0 is turned off, the inductor demagnetizes for a time T dmg After the end, the switch tube M0 still needs to wait for a certain time to be started again, and the waiting start time of the switch is marked as T wait Then at this time, the switch is turned off for a time T off ＝T dmg +T wait . The actual duty cycle is knownTo realize forward compensation in DCM mode, the switch on time T needs to be changed by controlling the charging time of the second capacitor C2 on . At the switch on time T on Compensating for this, there is a change in the equivalent to the input current. Inventor(s):the charging current of the second capacitor C2 is regulated by the compensation duty ratio D' to further control the charging time of the second capacitor C2, thereby realizing the switch on time T on Is provided. The above-mentioned compensating duty cycle->Wherein K is greater than 1. The value of K in the embodiment of the invention can be selected according to manual experience, or can be obtained through software simulation screening.
The time adjusting circuit 53 is used for controlling the time signal V representing the on-time of the switch according to the time signal V through the logic operation unit cap1 Time signal V representing the demagnetization time of an inductor cap2 Time signal V characterizing the switch start-up latency cap3 Obtaining the switch on time T on Inductance demagnetization time T dmg Switch activation wait time T wait And according to the switch on time T on Inductance demagnetization time T dmg Switch activation wait time T wait A compensating duty cycle D' is determined, followed by a second current source I of the signal output circuit 531 sd Determining a constant output current according to the compensation duty ratio D' and a preset reference current, charging the second capacitor C2, obtaining the voltage on the second capacitor C2, obtaining a time-related voltage parameter U=f (T), and outputting a conduction time control signal SD to the pulse width modulator 40 to realize the adjustment of the T of the next period on 。
Referring to fig. 10, in DCM, when the on-time control signal SD reaches the compensation voltage, the switch on-time reaches a maximum value, and the slope of the on-time control signal SD is controlled to adjust the switch on-time T on . By characterising the on-time T of the current switching cycle on Time of demagnetization T dmg And a switch activation waiting time T wait Time signal detection of (a) to achieve adjustment of T for the next period on This corresponds to a reduction in the difference between the input current for the next cycle and the ideal value, and thus a reduction in THD.
While in CRM mode, the switch waits for a start-up time when the switching tube M0 is turned offT wait 0, inductance demagnetizing time T dmg Equal to the switch off time T off At this time, the compensation duty ratio D' =the actual duty ratio D. Time adjusting circuit 53 adjusts time signal V cap The calculation process is performed to obtain an on-time adjusting signal SD inversely proportional to the duty ratio D, and the on-time adjusting signal SD is outputted to the pulse width modulator 40 to adjust the switch on-time T of the next period on Thereby adjusting the on time T of the switch on Inversely proportional to the duty cycle D, the switch on time T is realized on The product of the duty cycle D is a constant value, so that the input current I in And input voltage V in And in a proportional relation, the switching power supply system can be ensured to have a smaller THD value.
In one particular embodiment, referring to FIG. 8, the pulse width modulator 40 includes a second operational amplifier U2; the positive input end of the second operational amplifier U2 is connected with the output end of the time adjusting circuit 53 of the harmonic distortion compensating circuit 50, the negative input end of the second operational amplifier U2 is connected with the output end of the feedback detecting circuit 30, and the comparison voltage V output by the feedback detecting circuit 30 is received comp The method comprises the steps of carrying out a first treatment on the surface of the The second operational amplifier U2 receives the on-time control signal SD of the harmonic distortion compensation circuit 50 and the comparison voltage V of the feedback detection circuit 30 comp Output for adjusting on-time T on Is provided.
In the embodiment of the present invention, the embodiment shown in fig. 4 is only one specific implementation of the embodiment of the present invention. In the embodiment of the present invention, specific implementation schemes of the rectifying module 10, the switching tube M0, the driver U0 and the feedback detection circuit 30 may refer to the modes described in the prior art, and specific circuit implementation modes thereof are not strictly limited herein in the embodiment of the present invention, so long as the technical purpose of the present invention can be achieved, and in the embodiment of the present invention, details are not repeated.
It should be noted that, although the circuit of the switching power supply system including the harmonic distortion compensation circuit in the above embodiment is a buck type circuit, it is only one specific implementation manner of the embodiment of the present invention, and the harmonic distortion compensation circuit of the embodiment of the present invention may also be applied to a fly-back type circuit or a boost type circuit.
Example two
In a specific implementation manner of the foregoing embodiment, in the time sampling circuit shown in fig. 7, when the first capacitor C1 discharges, the output time signal V cap As a voltage signal, in order to facilitate subsequent signal processing, referring to fig. 11, the harmonic distortion compensation circuit 50 of the switching power supply system in the second embodiment of the present invention further includes a signal conversion circuit 54 disposed between the time sampling circuit 52 and the time adjustment circuit 53, and the signal conversion circuit 54 is configured to convert the voltage signal output from the time sampling circuit 52 into a current signal, and the current signal is input to the time adjustment circuit 53 for signal calculation processing.
In a specific embodiment, referring to fig. 12, the signal conversion circuit 54 includes a current sampling switch SH, a third capacitor C3, a third operational amplifier U3, a conversion transistor M1, and a first resistor R1, and a terminal of the current sampling switch SH receives a time signal V output from the time sampling circuit 52 cap The other end of the current sampling switch SH is connected with the positive input end of the third operational amplifier U3, the other end of the current sampling switch SH is grounded through a third capacitor C3, the output of the third operational amplifier U3 is connected with the grid electrode of the conversion transistor M1, the source electrode of the conversion transistor M1 is grounded through a first resistor R1, the common end of the source electrode of the conversion transistor M1 and the first resistor R1 is connected with the negative input end of the third operational amplifier U3, the drain electrode of the conversion transistor M1 outputs sampling current I representing sampling time out . The signal conversion circuit 54 can input a time signal V in the form of a voltage cap Sampling current I converted into current form out Thereby facilitating signal processing by the subsequent time adjustment circuit 53.
In a specific embodiment, according to the description of the time sampling circuit 52 in the above embodiment, the time sampling circuit 52 includes 3 sets of circuit structures shown in fig. 7, and each outputs the time signal V representing the on time of the switch cap1 Time signal V representing the demagnetization time of an inductor cap2 Time signal V characterizing the switch start-up latency cap3 . Accordingly, the present inventionThe signal conversion circuit 54 in the second embodiment of the invention may also include 3 sets of circuit structures shown in fig. 12 to respectively convert the time signals V representing the on-time of the switch cap1 Time signal V representing the demagnetization time of an inductor cap2 Time signal V characterizing the switch start-up latency cap3 Converted into a corresponding current signal. The signal conversion circuit 54 works well, ensuring the stability of the whole circuit.
The specific circuit implementation and implementation manner of the other components of the circuit in fig. 11 in the embodiment of the present invention have been described in detail in the above embodiment, and will not be described in detail herein.
Example III
Based on the same inventive concept, the embodiment of the present invention also provides a load driving circuit including the feedback detection circuit 30, the pulse width modulator 40, the driver U0, and the harmonic distortion compensation circuit 50 described in the above-described first or second embodiment;
the pulse width modulator 40 is connected to the feedback detection circuit 30 and the driver U0, respectively.
In one particular embodiment, feedback detection circuit 30 samples a sampled voltage V that characterizes the output current cs According to the sampling voltage V cs Obtaining a comparison voltage V comp And output to the pulse width modulator 40;
the pulse width modulator 40 receives the comparison voltage V comp And a turn-on time control signal SD of the harmonic distortion compensation circuit 50 for adjusting the turn-on time T on Is a driving signal of (a);
the driver U0 adjusts the on-time T according to the control signal on The driving signal of the driving circuit drives the switching tube M0 of the switching power supply system to be conducted.
In one embodiment, the pulse width modulator includes a second operational amplifier U2;
the positive input end of the second operational amplifier U2 is connected with the output end of the time adjusting circuit of the harmonic distortion compensating circuit, the negative input end of the second operational amplifier U2 is connected with the output end of the feedback detecting circuit 30Comparison voltage V output by feedback detection circuit 30 comp The method comprises the steps of carrying out a first treatment on the surface of the The second operational amplifier U2 receives the on-time control signal SD of the harmonic distortion compensation circuit and the comparison voltage V of the feedback detection circuit 30 comp Output for adjusting on-time T on Is provided.
The specific structure and implementation manner of the load driving circuit in the embodiment of the present invention may refer to the descriptions of the specific circuit implementation schemes of the switching power supply system in the first embodiment and the second embodiment, and are not repeated herein.
Example IV
Based on the same inventive concept, the embodiment of the invention also provides a harmonic distortion compensation method, which comprises the following steps:
detecting the inductor demagnetizing state in the switching period, and outputting an inductor demagnetizing ending signal at the inductor demagnetizing ending time;
Sampling an output signal of the pulse width modulator and obtaining a time signal representing the switch on time, the inductor demagnetization time and the switch start waiting time according to the received inductor demagnetization end signal;
and determining a conduction time control signal according to the time signals representing the switch conduction time, the inductance demagnetization time and the switch starting waiting time so as to control the switch conduction time of the switch power supply system.
In one embodiment, determining the on-time control signal according to the time signal representing the on-time of the switch, the demagnetizing time of the inductor, and the waiting time of the switch to control the on-time of the switch of the switching power supply system includes:
obtaining the switch on time, the inductor demagnetizing time and the switch starting waiting time according to the time signals representing the switch on time, the inductor demagnetizing time and the switch starting waiting time;
determining a compensating duty cycle based on the switch on time, the inductor demagnetizing time and the switch start waiting time, wherein the compensating duty cycle d=t on /(T on +T dmg +K*T wait ) Wherein K is 1 or more, T on Indicating the on time of the switch, T dmg Indicating the inductance demagnetizing time T wait Indicating a switch start wait time;
And determining a constant output current according to the compensation duty ratio and a preset reference current, so as to output a conduction time control signal corresponding to the constant output current.
The specific implementation manner of the harmonic distortion compensation method provided by the embodiment of the present application may refer to the detailed description of the first embodiment and the second embodiment of the present application. In the embodiments of the present application, details will not be described herein.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any adaptations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It is to be understood that the present disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims (10)

1. A harmonic distortion compensation circuit, comprising: the device comprises a demagnetization state detection circuit, a time sampling circuit and a time adjusting circuit; the time sampling circuit is respectively connected with the demagnetization state detection circuit and the time adjustment circuit;
the demagnetization state detection circuit is connected with the inductor of the switching power supply system and is used for detecting the demagnetization state of the inductor in a switching period and outputting an inductor demagnetization ending signal to the time sampling circuit at the inductor demagnetization ending moment; the demagnetization state detection circuit comprises a first operational amplifier and an RS trigger, wherein the reverse input end of the first operational amplifier is connected with the inductor, the positive input end of the first operational amplifier is grounded, the output end of the first operational amplifier is connected with the reset end of the RS trigger, the setting end of the RS trigger is connected with a reference level, and the output end of the RS trigger is connected with the time sampling circuit;
the time sampling circuit is connected with the pulse width modulator of the switching power supply system and is used for sampling an output signal of the pulse width modulator and obtaining a time signal representing the switching-on time, the inductance demagnetization time and the switching-on waiting time according to the received inductance demagnetization ending signal, and outputting the time signal to the time regulating circuit;
The time adjusting circuit is connected with the pulse width modulator, and is used for determining a conduction time control signal according to the time signals representing the switch conduction time, the inductance demagnetization time and the switch starting waiting time and outputting the conduction time control signal to the pulse width modulator so as to control the switch conduction time of the switch power supply system;
the time adjusting circuit comprises a logic operation unit and a signal output circuit;
the logic operation unit is configured to obtain a switch on time, an inductance demagnetizing time and a switch start waiting time according to the received time signal, and determine a compensation duty ratio according to the switch on time, the inductance demagnetizing time and the switch start waiting time, where the compensation duty ratio d=t on /(T on +T dmg +K*T wait ) Wherein, K is larger than 1, the value of K is selected according to manual experience or obtained by software simulation screening, T on Indicating the on time of the switch, T dmg Indicating the inductance demagnetizing time T wait Indicating a switch start wait time;
the signal output circuit comprises a second current source and a second capacitor, wherein the common end of the second current source and the second capacitor is an adjusting signal output end, the second current source determines constant output current according to the compensation duty ratio and preset reference current and charges the second capacitor, so that the signal output end outputs a conduction time control signal corresponding to the constant output current.
2. The harmonic distortion compensation circuit of claim 1, wherein the time sampling circuit comprises a first current source, a time sampling switch, a first capacitor; the first current source is connected with one end of the first capacitor, the other end of the first capacitor is grounded, one end of the time sampling switch is connected with the common end of the first current source and the first capacitor, and the other end of the time sampling switch is grounded; the time sampling switch samples the trigger signal and is conducted, and the first capacitor discharges and outputs a time signal representing the switch conducting time, the inductor demagnetizing time and the switch starting waiting time.
3. The harmonic distortion compensation circuit of claim 2 wherein the output signal of the time sampling switch sampled to the pulse width modulator is a switch on signal and turned on, the first capacitor discharging and outputting a time signal indicative of the switch on time;
the time sampling switch samples the output signal of the pulse width modulator as a switch closing signal and is conducted, and the first capacitor discharges and outputs a time signal representing the demagnetizing time of the inductor;
the time sampling switch samples and conducts the inductor demagnetization ending signal, and the first capacitor discharges and outputs a time signal representing the switch starting waiting time.
4. The harmonic distortion compensation circuit of claim 1, wherein the adjustment signal output is connected to a positive input of a second operational amplifier in the pulse width modulator, an inverting input of the second operational amplifier is connected to a feedback detection circuit output of the switching power supply system, and a comparison voltage output by the feedback detection circuit is received; the second operational amplifier outputs a driving signal for adjusting the on time according to the on time control signal and the comparison voltage.
5. A load driving circuit, characterized by comprising: a feedback detection circuit, a pulse width modulator, a driver and the harmonic distortion compensation circuit of any one of claims 1-4;
the pulse width modulator is respectively connected with the feedback detection circuit and the driver.
6. The load driving circuit according to claim 5, wherein the feedback detection circuit samples a sampling voltage representing the output current, obtains a comparison voltage from the sampling voltage, and outputs to the pulse width modulator;
the pulse width modulator outputs a driving signal for adjusting the on time according to the comparison voltage and the on time control signal of the harmonic distortion compensation circuit;
And the driver drives a switching tube of the switching power supply system to be conducted according to the driving signal.
7. The load drive circuit of claim 6, wherein the pulse width modulator comprises a second operational amplifier;
the positive input end of the second operational amplifier is connected with the output end of the time adjusting circuit of the harmonic distortion compensating circuit, the negative input end of the second operational amplifier is connected with the output end of the feedback detecting circuit, and the comparison voltage output by the feedback detecting circuit is received; the second operational amplifier outputs a driving signal for adjusting the on time according to the received comparison voltage of the on time control signal of the harmonic distortion compensation circuit and the feedback detection circuit.
8. A switching power supply system, comprising: a rectifying module, an inductor, a switching tube, a sampling resistor and the load driving circuit according to any one of claims 5 to 7 connected to an ac power supply;
the rectifying module is connected with the input end of the controlled load, the input end of the inductor is connected with the output end of the controlled load, the output end of the inductor is connected with the drain electrode of the switching tube, the source electrode of the switching tube is connected with the sampling resistor, the grid electrode of the switching tube is connected with the output end of the load driving circuit, and the driving signal for adjusting the on time is received; and the output end of the sampling resistor is grounded.
9. The switching power supply system according to claim 8, wherein the inductor is a common-mode inductor, two ends of a primary coil of the common-mode inductor are respectively connected to the controlled load and a drain electrode of the switching tube, one end of a secondary coil of the common-mode inductor is connected to the demagnetization state detection circuit, and the other end is grounded.
10. A method of compensating for harmonic distortion, comprising:
detecting an inductance demagnetization state in a switching period, and outputting an inductance demagnetization ending signal to a time sampling circuit at the inductance demagnetization ending time;
sampling an output signal of the pulse width modulator and obtaining a time signal representing the switch on time, the inductor demagnetization time and the switch start waiting time according to the received inductor demagnetization end signal;
determining a conduction time control signal according to the time signals representing the switch conduction time, the inductance demagnetization time and the switch starting waiting time so as to control the switch conduction time of the switch power supply system;
the logic operation unit of the time adjustment circuit is configured to obtain a switch on time, an inductance demagnetizing time and a switch start waiting time according to the received time signal, and determine a compensation duty ratio according to the switch on time, the inductance demagnetizing time and the switch start waiting time, where the compensation duty ratio d=t on /(T on +T dmg +K*T wait ) Wherein, K is larger than 1, the value of K is selected according to manual experience or obtained by software simulation screening, T on Indicating the on time of the switch, T dmg Indicating the inductance demagnetizing time T wait Indicating a switch start wait time;
the signal output circuit of the time adjusting circuit comprises a second current source and a second capacitor, wherein a common end of the second current source and the second capacitor is an adjusting signal output end, the second current source determines constant output current according to the compensation duty ratio and preset reference current and charges the second capacitor, so that the signal output end outputs a conduction time control signal corresponding to the constant output current.
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