An active filter device, a power supply and a control method of the active filter device thereof

Abstract

The application discloses an active filtering device, a power supply and a control method of the active filtering device of the power supply. The device comprises a sampling unit, a control unit and an injection unit. The sampling unit samples a noise signal of a noise source to obtain a voltage of the noise source. The control unit determines a voltage opposite to the voltage of the noise source as a pre-output voltage according to the voltage of the noise source, and generates a control signal for controlling the switching unit to be turned on according to the pre-output voltage. The switching unit receives the control signal, and changes from an off state to an on state to inject a voltage equal in size and opposite in direction to the voltage of the noise source into the injection unit through the switching unit. The injection unit injects a voltage equal in size and opposite in direction to the noise signal of the noise source into the noise source to offset the noise signal of the noise source. The scheme can weaken the noise signal and reduce the interference ripple by setting the active filtering device and outputting the reverse voltage to the interference source to suppress the interference source.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power supply, and particularly relates to an active filter device, a power supply and a control method of the active filter device of the power supply, in particular to an active filter circuit, a power supply with the active filter circuit, and a control method of the active filter circuit of the power supply. BACKGROUND

[0002] In typical high-voltage applications, common-mode noise dominates the EMI (i.e. electromagnetic interference) filter size. The common-mode noise is caused by the parasitic capacitance from the switching node to the chassis, which results in the fluctuation of the voltage on the chassis when the switching node of the inverter is working. A passive filter device (such as a passive filter) composed of a power capacitor, a reactor and a resistor is usually used for filtering. The filtering characteristics of the passive filter are greatly affected by system parameters, the filtering range is small, and the performance is single, which is difficult to meet the requirements of power quality in some specific occasions, and there is still a problem of strong noise signal and large interference ripple. For example, the vibration noise of the air conditioner outer casing and various electrical appliances with active switching devices working at high frequency.

[0003] The above content is only used to assist in understanding the technical solutions of the present application, and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0004] The present application aims to provide an active filter device, a power supply and a control method of the active filter device of the power supply, to solve the problem that the filtering characteristics of the passive filter are difficult to meet the requirements of power quality in some specific occasions, and there is still a problem of strong noise signal and large interference ripple, so as to achieve the effect of weakening the noise signal and reducing the interference ripple by setting the active filter device and outputting the reverse voltage to the interference source to suppress the interference source.

[0005] The application provides an active filtering device, comprising a sampling unit, a control unit, a switching unit and an injection unit; the switching unit is arranged between the control unit and the injection unit; the switching unit is in an off state by default; the sampling unit and the injection unit are both connected to a metal shell of a case where a noise source is located; the sampling unit is used to sample a noise signal of the noise source to obtain a voltage of the noise source; the control unit is used to determine a voltage equal in size and opposite in direction to the voltage of the noise source as a pre-output voltage according to the voltage of the noise source, and generate a control signal for controlling the switching unit to be turned on according to the pre-output voltage; the switching unit is used to change the switching unit from the off state to a conductive state when the control signal is received, so that the pre-output voltage is injected into the injection unit through the switching unit when the switching unit is conductive; and the injection unit is used to receive the pre-output voltage and inject the received pre-output voltage into the noise source to offset the noise signal of the noise source by using the injected pre-output voltage.

[0006] In some embodiments, the sampling unit comprises a sampling capacitor and a filtering module; the sampling unit samples the noise signal of the noise source to obtain the voltage of the noise source, which comprises that the sampling capacitor is used to sample the noise signal of the noise source; and the filtering module is used to filter the sampled noise signal of the noise source to obtain a filtered noise signal of the noise source, and the voltage corresponding to the filtered noise signal of the noise source is taken as the voltage of the noise source.

[0007] In some embodiments, the filtering module comprises a filtering capacitor and a filtering resistor; one end of the sampling capacitor is connected to the metal shell of the case where the noise source is located; the other end of the sampling capacitor is connected to a sampling pin of the control unit through the filtering resistor, and is grounded through the filtering capacitor.

[0008] In some embodiments, the active filtering device further comprises a discharge switch tube module; a first connection end of the discharge switch tube module is connected to a sampling pin of the control unit; a second connection end of the discharge switch tube module is grounded; and a control end of the discharge switch tube module is connected to a discharge control pin of the control unit; wherein the control unit is further used to control the discharge switch tube module to be conductive after the active filtering device is powered off or powered on, so that the discharge switch tube module forms a discharge circuit with the sampling capacitor when the discharge switch tube module is conductive, and the sampling capacitor is discharged.

[0009] In some embodiments, the switch unit comprises: a first switch tube module and a second switch tube module, the voltage source of the first switch tube module is a positive voltage source, and the voltage source of the second switch tube module is a negative voltage source; the control unit determines a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage according to the voltage of the noise source, and comprises: determining a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage, and sending an inhibit enable signal to the first switch tube module and the second switch tube module to maintain the first switch tube module and the second switch tube module both off; the control unit generates a control signal for controlling the switch unit to turn on according to the pre-output voltage, and comprises: determining whether the pre-output voltage is greater than 0; if it is determined that the pre-output voltage is greater than 0, generating a control signal for controlling the first switch tube module to turn on according to the pre-output voltage; if it is determined that the pre-output voltage is less than 0, generating a control signal for controlling the second switch tube module to turn on according to the pre-output voltage.

[0010] In some embodiments, each of the first switch tube module and the second switch tube module comprises: a boost chip and a switch tube; the control unit generates a control signal for controlling a corresponding switch tube module among the first switch tube module and the second switch tube module to turn on according to the pre-output voltage, and comprises: determining a duty cycle of an expected SPWM waveform as a control signal for controlling a corresponding switch tube module among the first switch tube module and the second switch tube module to turn on according to the pre-output voltage and the voltage source of the corresponding switch tube module; and sending an enable signal to the corresponding switch tube module and closing the inhibit enable signal of the corresponding switch tube module.

[0011] In some embodiments, the switch unit changes from an off state to a conductive state by itself upon receiving the control signal, and comprises: for a corresponding switch tube module among the first switch tube module and the second switch tube module, the boost chip in the switch tube module increases the amplitude of the duty cycle of the expected SPWM waveform in the control signal to a certain degree to obtain a boost signal upon receiving the control signal and the enable signal and the inhibit enable signal being closed; and the switch tube in the switch tube module changes from an off state to a conductive state by itself based on the boost signal.

[0012] In some embodiments, for a corresponding one of the first switch tube module and the second switch tube module, the switch tube in the switch tube module comprises a triode; the injection unit comprises an injection capacitor; one end of the injection capacitor is connected to a metal shell of a chassis where the noise source is located; the other end of the injection capacitor is connected to an emitter of the switch tube in the corresponding switch tube module; for the first switch tube module, a collector of the switch tube in the first switch tube module is connected to a positive voltage source; a first enable pin of the control unit is connected to an enable pin of a boost chip in the first switch tube module; a first disable enable pin of the control unit is connected to a disable enable pin of the boost chip in the first switch tube module; a control pin of the boost chip in the first switch tube module is connected to a base of the switch tube in the first switch tube module; for the second switch tube module, a collector of the switch tube in the second switch tube module is connected to a negative voltage source; a second enable pin of the control unit is connected to an enable pin of a boost chip in the second switch tube module; a second disable enable pin of the control unit is connected to a disable enable pin of the boost chip in the second switch tube module; a control pin of the boost chip in the second switch tube module is connected to a base of the switch tube in the second switch tube module; wherein the first disable enable pin and the second disable enable pin of the control unit are used to send the disable enable signal; and the first enable pin and the second enable pin of the control unit are used to send the enable signal.

[0013] In order to match the above-mentioned device, the present application further provides a power supply comprising the active filter device.

[0014] In order to match the above-mentioned power supply, the present application further provides a control method of an active filter device of a power supply, comprising: controlling a sampling unit to sample a noise signal of the noise source to obtain a voltage of the noise source; determining a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage according to the voltage of the noise source; and generating a control signal for controlling the switch unit to turn on according to the pre-output voltage; controlling the switch unit to change from an off state to an on state by itself in the case of receiving the control signal, so as to inject the pre-output voltage into the injection unit through the switch unit in the case of the switch unit turning on by itself; and controlling the injection unit to receive the pre-output voltage and inject the received pre-output voltage into the noise source in the case of receiving the pre-output voltage, so as to offset the noise signal of the noise source by the injected pre-output voltage.

[0015] Therefore, the scheme of the present application, by setting the sampling capacitor, the boost chip, the active switch tube and the injection capacitor, using the sampling capacitor to sample the voltage of the noise source, taking the inverse value of the voltage of the noise source as the pre-output voltage, determining the duty cycle signal for controlling the active switch tube according to the pre-output voltage, taking the duty cycle signal as the control signal of the active switch tube after amplitude modulation by the boost chip to control the active switch tube to conduct, injecting the active switch tube with the opposite amount of electricity to the amount of electricity of the noise source under the condition of the active switch tube conducting, to offset the amount of electricity of the noise source, so that by setting the active filter device, by outputting the reverse voltage to the interference source to suppress the interference source, the noise signal can be weakened, and the interference ripple can be reduced.

[0016] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application.

[0017] The technical scheme of the present application will be described in detail below with the help of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The structural schematic diagram of an embodiment of the active filter device of the present application;

[0019] Figure 2 The structural schematic diagram of an embodiment of the active filter circuit of the present application;

[0020] Figure 3 The flowchart of an embodiment of the control method of the active filter device of the present application;

[0021] Figure 4 The control logic diagram of an embodiment of the control method of the active filter circuit of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below with the help of specific embodiments of the present application and corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] According to the embodiments of the present application, an active filter device is provided. Referring to Figure 1A structural schematic diagram of an embodiment of the device of the application is shown. The active filtering device can include a sampling unit, a control unit, a switching unit and an injection unit; the switching unit is arranged between the control unit and the injection unit; the switching unit is in an off state by default; the sampling unit is, for example, a sampling capacitor; the control unit is, for example, an MCU chip; the switching unit is, for example, an active switching tube; and the injection unit is, for example, an injection capacitor. The sampling unit and the injection unit are both connected to the metal shell of the case where the noise source is located.

[0024] The sampling unit is configured to sample a noise signal of the noise source to obtain a voltage of the noise source, for example, a voltage Ui.

[0025] In some embodiments, the sampling unit includes a sampling capacitor and a filtering module. Specifically, Figure 2 A structural schematic diagram of an embodiment of the active filtering circuit of the application is shown. Figure 2 As shown, the sampling capacitor is, for example, a capacitor C2; the filtering module is, for example, an RC filter composed of a capacitor C3 and a resistor R1; and the control unit is, for example, an MCU chip.

[0026] The sampling unit samples a noise signal of the noise source to obtain a voltage of the noise source, for example, a voltage Ui, and includes:

[0027] The sampling capacitor is configured to sample a noise signal of the noise source.

[0028] The filtering module is configured to filter the sampled noise signal of the noise source to obtain a filtered noise signal of the noise source, and take the voltage corresponding to the filtered noise signal of the noise source as the voltage of the noise source, for example, a voltage Ui.

[0029] Preferably, the filtering module includes a filtering capacitor and a filtering resistor, for example, a capacitor C3 and a resistor R1. One end of the sampling capacitor is connected to the metal shell of the case where the noise source is located. The other end of the sampling capacitor is connected to a sampling pin (for example, pin 5 of the MCU chip) of the control unit via the filtering resistor, and is grounded via the filtering capacitor.

[0030] Specifically, Figure 4 A control logic diagram of an embodiment of the control method of the active filtering circuit of the application is shown. Figure 2 and Figure 4 As shown, the voltage value Ui of the noise source is collected by the capacitor C2, the capacitor C3 and the resistor R1 form an RC filter, which is used to reduce the interference of the ground on the sampling signal, and the sampling signal (i.e., the voltage value Ui of the noise source) after filtering interference is input into the MCU chip through the pin 5 of the MCU chip.

[0031] The control unit is configured to determine, according to the voltage of the noise source, a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage, and generate a control signal for controlling the switch unit to turn on according to the pre-output voltage.

[0032] The switch unit is configured to, in a case where the control signal is received, change the switch unit from an off state to an on state, so that the switch unit injects the pre-output voltage into the injection unit through the switch unit in a case where the switch unit is on.

[0033] In some embodiments, the switch unit includes a first switch tube module and a second switch tube module, as shown in Figure 2 The first switch tube module is, for example, a triode Q1, and the second switch tube module is, for example, a triode Q2. The voltage source of the first switch tube module is a positive voltage source (for example, a positive voltage source U2), and the voltage source of the second switch tube module is a negative voltage source (for example, a voltage source U1).

[0034] The control unit is configured to determine, according to the voltage of the noise source, a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage, and generate a control signal for controlling the switch unit to turn on according to the pre-output voltage.

[0035] The control unit is further configured to determine, as the pre-output voltage, a voltage equal in magnitude and opposite in direction to the voltage of the noise source, and send an inhibit enable signal to the first switch tube module and the second switch tube module to maintain the first switch tube module and the second switch tube module both off, as shown in Figure 4 The MCU chip calculates the pre-output voltage Uo such that Uo = -Ui, and the pin 2 and the pin 4 of the MCU chip output a low level to disable the two boost chips (wherein the boost chip S1 and the boost chip S2 are both high to be enabled and effective), so as to prevent other interference from causing the pin 11 of the boost chip S1 and the pin 21 of the boost chip S2 to receive a pulse and the corresponding boost chip to output a control signal to turn on the active switch, i.e., the triode Q1 or the triode Q2.

[0036] The control unit is configured to determine, according to the voltage of the noise source, a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage, and generate a control signal for controlling the switch unit to turn on according to the pre-output voltage.

[0037] The control unit is further configured to determine whether the pre-output voltage is greater than 0.

[0038] The control unit is further configured to, if it is determined that the pre-output voltage is greater than 0, generate a control signal for controlling the first switch tube module to turn on according to the pre-output voltage.

[0039] The control unit is further configured to generate a control signal for controlling the second switch tube module to be turned on according to the pre-output voltage if it is determined that the pre-output voltage is less than 0.

[0040] As shown in Figure 4 The MCU chip microprocessor judges whether the value of the pre-output voltage Uo is positive or negative, i.e., whether the pre-output voltage Uo is greater than 0, through a program, and outputs a SPWM wave through a corresponding pin.

[0041] Preferably, each of the first switch tube module and the second switch tube module comprises a boost chip and a switch tube, as shown in Figure 2 The boost chip in the first switch tube module, such as boost chip S1, and the switch tube, such as triode Q1, and the boost chip in the second switch tube module, such as boost chip S2, and the switch tube, such as triode Q2.

[0042] The control unit generates a control signal for controlling the corresponding switch tube module in the first switch tube module and the second switch tube module to be turned on according to the pre-output voltage, which comprises determining the duty cycle of the expected SPWM waveform as the control signal for controlling the corresponding switch tube module in the first switch tube module and the second switch tube module to be turned on according to the pre-output voltage and the voltage source of the corresponding switch tube module in the first switch tube module and the second switch tube module, sending an enable signal to the corresponding switch tube module in the first switch tube module and the second switch tube module, and closing the disable enable signal of the corresponding switch tube module in the first switch tube module and the second switch tube module.

[0043] As shown in Figure 4 When the pre-output voltage Uo is positive, the duty cycle of the SPWM wave to be output by the MCU chip is calculated by the pre-output voltage Uo and the positive power voltage U2 using the principle of impulse equality, and then the frequency of the modulation waveform is calculated according to the calculated duty cycle of the PWM wave and the carrier frequency of the MCU chip, and the corresponding parameter values in each register of the EPWM module (i.e., the enhanced pulse width modulator) are calculated according to the calculated frequency of the modulation waveform to obtain the expected SPWM waveform. Similarly, when the pre-output voltage Uo is negative, the duty cycle of the SPWM wave to be output by the MCU chip is calculated by the pre-output voltage Uo and the negative power voltage U1, and then the frequency of the modulation waveform is calculated according to the calculated duty cycle and the carrier frequency of the MCU chip, and the corresponding parameter values in each register of the EPWM module are calculated according to the calculated frequency of the modulation waveform to obtain the expected SPWM waveform.

[0044] Correspondingly, the switching unit, in the case of receiving the control signal, changes the switching unit itself from the off state to the on state, which comprises

[0045] For the corresponding switch tube module in the first switch tube module and the second switch tube module, the boost chip in the switch tube module increases the amplitude of the duty cycle of the expected SPWM waveform in the control signal to a certain extent to obtain a boost signal when the control signal and the enable signal are received and the disable enable signal is closed.

[0046] For the corresponding switch tube module in the first switch tube module and the second switch tube module, the switch tube in the switch tube module changes from an off state to an on state based on the boost signal.

[0047] As shown in Figure 4 When the pre-output voltage Uo is positive, the expected SPWM waveform is finally calculated through the pre-output voltage Uo and the positive power voltage U2, so that the expected SPWM waveform is output through the pin 1 of the MCU chip, and a high level signal needs to be output through the pin 2 of the MCU chip to enable the boost chip S1. Similarly, when the pre-output voltage Uo is negative, the expected SPWM waveform is finally calculated through the pre-output voltage Uo and the negative power voltage U1, so that the expected SPWM waveform is output through the pin 3 of the MCU chip, and a high level signal needs to be output through the pin 4 of the MCU chip to enable the boost chip S2.

[0048] The injection unit is configured to receive the pre-output voltage and inject the received pre-output voltage into the noise source to offset the noise signal of the noise source by using the injected pre-output voltage.

[0049] The scheme of the present application provides an effective measure of absorbing harmonics generated by a harmonic source nearby by using a power filter device, suppresses the interference source by outputting a reverse voltage to the interference source to weaken the noise signal and reduce the interference ripple. Moreover, the application of the scheme of the present application can overcome the shortcomings of the harmonic suppression and reactive power compensation method of LC filter, realize dynamic tracking compensation, suppress the noise signal, and reduce the interference ripple.

[0050] Specifically, in the scheme of the present application, the noise voltage signal is first sampled and detected, and then the MCU chip outputs a controllable SPWM waveform through theoretical operation, and the controllable SPWM waveform is used to control the active switch output compensation voltage, solving the problem that the filtering characteristics of the related scheme are greatly affected by system parameters. The filtering characteristics of the passive filter are greatly affected by system parameters, the filtering range is small, the performance is single, it is difficult to meet the requirements of certain specific occasions for power quality, and there is still a problem of strong noise signal and large interference ripple, thereby reducing the noise and the filtering characteristics are less affected by system parameters and have a wide range of applications.

[0051] In some embodiments, for a corresponding one of the first switch tube module and the second switch tube module, the switch tube in the switch tube module comprises a triode, such as Figure 2 triode Q1 and triode Q2 shown.

[0052] The injection unit comprises an injection capacitor, such as Figure 2 capacitor C1 shown. One end of the injection capacitor is connected to the metal shell of the case where the noise source is located. The other end of the injection capacitor is connected to the emitter of the switch tube in the corresponding switch tube module.

[0053] For the first switch tube module, the collector of the switch tube in the first switch tube module (such as the collector of triode Q1) is connected to a positive voltage source (such as voltage source U2). The first enable pin of the control unit (such as pin 1 of the MCU chip) is connected to the enable pin of the boost chip in the first switch tube module (such as pin 11 of boost chip S1). The first disable enable pin of the control unit (such as pin 2 of the MCU chip) is connected to the disable enable pin of the boost chip in the first switch tube module (such as pin 12 of boost chip S1). The control pin of the boost chip in the first switch tube module (such as pin 13 of boost chip S1) is connected to the base of the switch tube in the first switch tube module (such as the base of triode Q1).

[0054] For the second switch tube module, the collector of the switch tube in the second switch tube module (such as the collector of triode Q2) is connected to a negative voltage source (such as voltage source U1). The second enable pin of the control unit (such as pin 3 of the MCU chip) is connected to the enable pin of the boost chip in the second switch tube module (such as pin 21 of boost chip S2). The second disable enable pin of the control unit (such as pin 4 of the MCU chip) is connected to the disable enable pin of the boost chip in the second switch tube module (such as pin 22 of boost chip S2). The control pin of the boost chip in the second switch tube module (such as pin 23 of boost chip S2) is connected to the base of the switch tube in the second switch tube module (such as the base of triode Q2).

[0055] The first disable enable pin and the second disable enable pin of the control unit are used to send the disable enable signal. The first enable pin and the second enable pin of the control unit are used to send the enable signal.

[0056] In some embodiments, the active filter device of the scheme of the present application further comprises a discharge switch tube module, such as Figure 2The MOS tube Q3 is shown. The first connection end of the discharge switch tube module (such as the drain of the MOS tube Q3) is connected to the sampling pin (such as the pin 5 of the MCU chip) of the control unit. The second connection end of the discharge switch tube module (such as the source of the MOS tube Q3) is grounded. The control end of the discharge switch tube module (such as the gate of the MOS tube Q3) is connected to the discharge control pin (such as the pin 6 of the MCU chip) of the control unit.

[0057] The control unit is further configured to control the discharge switch tube module to be turned on after the active filter device is powered off or powered on, so that the discharge switch tube module itself forms a discharge loop with the sampling capacitor in the turned-on state and discharges the sampling capacitor. Figure 4 As shown, when the active filter function is turned off, the MCU chip outputs a signal through the pin 6 to turn on the MOS tube Q3, and discharges the electric quantity in the capacitor C2 to the ground, so as to ensure the safety of the active filter circuit itself.

[0058] Specifically, as shown, Figure 2 The active filter circuit provided by the scheme of the application includes a capacitor C1, a capacitor C2, a capacitor C3, a boost chip S1, a boost chip S2, a triode Q1, a triode Q2, a MOS tube Q3, a resistor R1, and an MCU chip. The pin 1 of the MCU chip is connected to the pin 11 of the boost chip S1, the pin 2 of the MCU chip is connected to the pin 12 of the boost chip S1, the pin 13 of the boost chip S1 is connected to the base of the triode Q1, the collector of the triode Q1 is connected to a positive voltage source U2 (U2 is greater than 0), and the emitter of the triode Q1 is connected to the metal shell (such as the case shell) of a noise source through the capacitor C1. The pin 3 of the MCU chip is connected to the pin 21 of the boost chip S2, the pin 4 of the MCU chip is connected to the pin 22 of the boost chip S2, the pin 23 of the boost chip S2 is connected to the base of the triode Q2, the collector of the triode Q2 is connected to a negative voltage source U1 (U1 is less than 0), and the emitter of the triode Q2 is connected to the emitter of the triode Q1. The pin 5 of the MCU chip is connected to the drain of the MOS tube Q3. The pin 5 of the MCU chip is also connected to the ground GND through the capacitor C3. The pin 5 of the MCU chip is also connected to the metal shell (such as the case shell) of the noise source through the resistor R1 and the capacitor C2. The source of the MOS tube Q3 is connected to the ground GND. The pin 6 of the MCU chip is connected to the control end of the MOS tube Q3.

[0059] As shown, Figure 4As shown, capacitor C1 serves as the injection capacitor. After receiving the control signal (i.e., the SPWM wave) and the enable signal, boost chip S1 outputs a control signal with increased amplitude but unchanged duty cycle through its pin 13 to the gate of an active switch, such as transistor Q1. This drives the active switch to conduct, connecting the positive voltage source U2 to capacitor C1. The charge is then transferred to the noise source through capacitor C1, thus reducing the noise signal. Similarly, after receiving the control signal (i.e., the SPWM wave) and the enable signal, boost chip S2 outputs a control signal with increased amplitude but unchanged duty cycle through its pin 23 to the gate of an active switch, such as transistor Q2. This drives the active switch to conduct, connecting the negative voltage source U1 to capacitor C1. The charge is then transferred to the noise source through capacitor C1, thus reducing the noise signal.

[0060] By employing the technical solution of this invention, a sampling capacitor, a boost chip, an active switching transistor, and an injection capacitor are configured. The sampling capacitor samples the voltage of the noise source, and the inverted value of the noise source voltage is used as a pre-output voltage. Based on this pre-output voltage, a duty cycle signal for controlling the active switching transistor is determined. This duty cycle signal is amplitude-modulated by the boost chip and used as a control signal to control the active switching transistor to turn it on. When the active switching transistor is on, an opposite charge to that of the noise source is injected into the injection capacitor to cancel out the charge of the noise source. Thus, by setting up an active filtering device and outputting a reverse voltage to the interference source to suppress the interference source, the noise signal can be weakened and the interference ripple reduced.

[0061] According to an embodiment of the present invention, a power supply corresponding to an active filter device is also provided. This power supply may include the active filter device described above.

[0062] Since the processing and functions implemented by the power supply in this embodiment are basically the same as those in the embodiments, principles and examples of the device, any details not covered in this embodiment can be found in the relevant descriptions in the foregoing embodiments, and will not be repeated here.

[0063] The technical solution of this invention involves setting up a sampling capacitor, a boost chip, an active switch, and an injection capacitor. The sampling capacitor samples the voltage of the noise source, and the inverted value of the noise source voltage is used as a pre-output voltage. Based on this pre-output voltage, a duty cycle signal for controlling the active switch is determined. This duty cycle signal is amplitude-modulated by the boost chip and used as a control signal to control the active switch to turn it on. When the active switch is on, an opposite charge to that of the noise source is injected into the injection capacitor to cancel out the charge of the noise source. Thus, by outputting a reverse voltage to the interference source, the interference source is suppressed, the noise signal is weakened, and the interference ripple is reduced.

[0064] According to embodiments of the present invention, a control method for an active power filter corresponding to a power supply is also provided, such as...Figure 3 A flowchart of an embodiment of the method of the application is shown. The control method of the active filter device of the power supply can include steps S110 to S140.

[0065] At step S110, a sampling unit is controlled to sample a noise signal of the noise source to obtain a voltage of the noise source, such as voltage Ui.

[0066] At step S120, a voltage equal in magnitude and opposite in direction to the voltage of the noise source is determined as a pre-output voltage according to the voltage of the noise source; and a control signal for controlling the switch unit to turn on is generated according to the pre-output voltage.

[0067] At step S130, the switch unit is controlled to turn from an off state to an on state by itself upon receiving the control signal, so that the pre-output voltage is injected into the injection unit through the switch unit upon the switch unit turning on by itself.

[0068] At step S140, the injection unit is controlled to receive the pre-output voltage and inject the received pre-output voltage into the noise source upon receiving the pre-output voltage, so that the noise signal of the noise source is offset by the injected pre-output voltage.

[0069] Specifically, as Figure 4 shown, the control method of an active filter circuit according to the scheme of the application includes:

[0070] Step 1, the capacitor C2 is used as a sampling capacitor to collect the voltage value Ui of the noise source, and then step 2 is performed. The capacitor C3 behind the capacitor C2 and the resistor R1 form an RC filter, which is used to reduce the interference of the ground on the sampling signal. The filtered sampling signal (i.e. the voltage value Ui of the noise source) is input into the MCU chip through pin 5 of the MCU chip.

[0071] Step 2, the MCU chip calculates the pre-output voltage Uo, such that Uo = -Ui, and the pin 2 and pin 4 of the MCU chip output low level to disable the two boost chips (wherein the boost chip S1 and the boost chip S2 are both high level to enable the effective), so as to prevent other interference from causing the pin 11 of the boost chip S1 and the pin 21 of the boost chip S2 to receive pulses and the corresponding boost chip to output a control signal to turn on the active switch, i.e. the triode Q1 or the triode Q2, and then step 3 is performed.

[0072] Step 3, the MCU chip microprocessor judges the value of the pre-output voltage Uo to be positive or negative, that is, whether the pre-output voltage Uo is greater than 0, so as to output the SPWM wave through the corresponding pin: if yes, step 4 is executed, otherwise step 5 is executed.

[0073] Step 4, when the pre-output voltage Uo is positive, the duty cycle of the SPWM wave to be output by the MCU chip is calculated by using the impulse equal principle of the pre-output voltage Uo and the positive power voltage U2, and then the frequency of the modulation waveform is calculated according to the calculated duty cycle of the PWM wave and the carrier frequency of the MCU chip, the corresponding parameter values in the registers of the EPWM module (i.e. the enhanced pulse width modulator) are calculated according to the calculated frequency of the modulation waveform, the expected SPWM waveform is obtained, and the expected SPWM waveform is output through the pin 1 of the MCU chip, and a high level signal is also output through the pin 2 of the MCU chip to enable the boost chip S1, and then step 6 is executed.

[0074] For example: assuming that the period of the carrier frequency is T, the action time of U2 is t0, and the duty cycle is S; according to the impulse equal principle, U0*T=U2*t0 can be listed; t0=U0*T / U2 can be solved; the duty cycle S=t0 / T=U0 / U2. In the control process, the registers involved in the duty cycle conversion are the comparison register and the period register, and the values stored in the two registers together determine the output duty cycle, that is, changing the value of the register can change the duty cycle S of the output PWM waveform. For example, the calculation is as follows:

[0075] Chip crystal oscillator clock frequency 60Mhz: carrier frequency: 5Khz; period register stores value A1: A1=0.5*60M / 5K=6000; comparison register stores value A2: A2=6000*(1-S). The above calculation is a register configuration value calculation for one period, the value of A1 is always unchanged because it is related to the carrier frequency, and the value of A2 changes according to the duty cycle.

[0076] Step 5, as in step 4, when the pre-output voltage Uo is negative, the duty cycle of the SPWM wave to be output by the MCU chip is calculated by using the pre-output voltage Uo and the negative power voltage U1, and then the frequency of the modulation waveform is calculated according to the calculated duty cycle and the carrier frequency of the MCU chip, the corresponding parameter values in the registers of the EPWM module are calculated according to the calculated frequency of the modulation waveform, the expected SPWM waveform is obtained, and the expected SPWM waveform is output through the pin 3 of the MCU chip, and a high level signal is also output through the pin 4 of the MCU chip to enable the boost chip S2, and then step 6 is executed.

[0077] Step 6, the capacitor C1 as an injection capacitor. After receiving the control signal (i.e. SPWM wave) and the enable signal, the boost chip S1 outputs the control signal with increased amplitude but unchanged duty cycle to the gate of the active switch such as the triode Q1 through the pin 13, drives the active switch to turn on, so that the positive voltage source U2 is connected with the capacitor C1, and the electric quantity is applied to the noise source through the capacitor C1, so that the noise signal is weakened.

[0078] Similarly, after receiving the control signal (i.e. SPWM wave) and the enable signal, the boost chip S2 outputs the control signal with increased amplitude but unchanged duty cycle to the gate of the active switch such as the triode Q2 through the pin 23, drives the active switch to turn on, so that the negative voltage source U1 is connected with the capacitor C1, and the electric quantity is applied to the noise source through the capacitor C1, so that the noise signal is weakened.

[0079] Step 7, when the active filter device is powered off or just powered on, it is necessary to close the active filter function. When the active filter function is closed, the MCU chip outputs a signal through the pin 6, turns on the MOS tube Q3, and discharges the electric quantity in the capacitor C2 to the ground, so as to ensure the safety of the active filter circuit itself.

[0080] The circuit design and control method based on the active input digital filter provided by the scheme are a new active filter circuit and control method, adopt the active filter method, suppress the interference source through the output of the opposite polarity voltage, specifically, the more accurate compensation voltage value is calculated through the operation of the microprocessor, the more accurate compensation voltage injection is carried out through the output of the PWM waveform, the positive or negative voltage signal can be compensated and corrected, and the method is suitable for the case that the voltage fluctuation range is small, so as to reduce the noise signal and reduce the interference ripple, and has the functions of filtering and suppressing interference. Therefore, the problem of cabinet voltage fluctuation caused by frequent switching of the switching node is solved, and the effects of reducing common mode noise and improving user product experience are achieved.

[0081] Since the processing and functions realized by the method of the embodiment are basically corresponding to the foregoing embodiments, principles and examples of the power supply, the description of the embodiment is not described in detail, and the related description in the foregoing embodiments can be referred to, and is not described here.

[0082] According to the technical scheme of the embodiment, the voltage of the noise source is sampled by the sampling capacitor, the inverse value of the voltage of the noise source is taken as the pre-output voltage, the duty cycle signal for controlling the active switch tube is determined according to the pre-output voltage, the duty cycle signal is taken as the control signal of the active switch tube after being amplitude modulated by the boost chip, the active switch tube is controlled to be turned on, the active switch tube injects the electric quantity opposite to that of the noise source into the injection capacitor to offset the electric quantity of the noise source in the case that the active switch tube is turned on, and the noise signal can be reduced and the interference ripple can be reduced in the case that the voltage fluctuation is small.

[0083] In conclusion, those skilled in the art can easily understand that the above-mentioned advantageous modes can be freely combined and superimposed without conflict.

[0084] The above only describes the embodiments of the present application and is not used to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims

1. An active filter device, characterized by The method comprises the following steps: A sampling unit, a control unit, a switching unit and an injection unit; the switching unit is arranged between the control unit and the injection unit; the switching unit is in an off state by default; the sampling unit and the injection unit are both connected to the metal shell of the case where the noise source is located; wherein The sampling unit is configured to sample the noise signal of the noise source to obtain the voltage of the noise source; The control unit is configured to determine, according to the voltage of the noise source, a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage, and generate a control signal for controlling the switching unit to turn on according to the pre-output voltage; The switching unit is configured to, in the case of receiving the control signal, change the state of the switching unit from off to on, so that, in the case of the switching unit being on, the pre-output voltage is injected into the injection unit through the switching unit; The injection unit is configured to receive the pre-output voltage and, in the case of receiving the pre-output voltage, inject the received pre-output voltage into the noise source to offset the noise signal of the noise source by using the injected pre-output voltage; Further comprising: a discharge switch tube module; a first connection end of the discharge switch tube module is connected to a sampling pin of the control unit; a second connection end of the discharge switch tube module is grounded; and a control end of the discharge switch tube module is connected to a discharge control pin of the control unit; The control unit is further configured to control the discharge switch tube module to turn on after the active filter device is powered off or powered on, so that the discharge switch tube module forms a discharge circuit with a sampling capacitor in the sampling unit in the case of the discharge switch tube module being on, and discharges the sampling capacitor.

2. The active filtering device of claim 1, wherein, The sampling unit comprises a sampling capacitor and a filter module; The sampling unit samples the noise signal of the noise source to obtain the voltage of the noise source, which comprises: The sampling capacitor is configured to sample the noise signal of the noise source; The filter module is configured to filter the sampled noise signal of the noise source to obtain a filtered noise signal of the noise source, and take the voltage corresponding to the filtered noise signal of the noise source as the voltage of the noise source.

3. The active filtering device of claim 2, wherein, The filter module comprises a filter capacitor and a filter resistor; wherein One end of the sampling capacitor is connected to the metal shell of the case where the noise source is located; the other end of the sampling capacitor is connected to a sampling pin of the control unit through the filter resistor, and is grounded through the filter capacitor.

4. The active filtering device according to any one of claims 1 to 3, characterized in that, The switching unit comprises a first switch tube module and a second switch tube module; the voltage source of the first switch tube module is a positive voltage source, and the voltage source of the second switch tube module is a negative voltage source; The control unit determines, according to the voltage of the noise source, a voltage equal in magnitude and opposite in direction to the voltage of the noise source as a pre-output voltage, which comprises: The voltage equal to the size of the voltage of the noise source and opposite in direction is taken as a pre-output voltage, and an inhibit enable signal is sent to the first switch tube module and the second switch tube module to maintain the first switch tube module and the second switch tube module both off; The control unit generates a control signal for controlling the switch unit to be turned on according to the pre-output voltage, including: determining whether the pre-output voltage is greater than 0; If it is determined that the pre-output voltage is greater than 0, a control signal for controlling the first switch tube module to be turned on is generated according to the pre-output voltage; If it is determined that the pre-output voltage is less than 0, a control signal for controlling the second switch tube module to be turned on is generated according to the pre-output voltage.

5. The active filtering device of claim 4, wherein, Each of the first switch tube module and the second switch tube module includes a boost chip and a switch tube; The control unit generates a control signal for controlling the corresponding switch tube module in the first switch tube module and the second switch tube module to be turned on according to the pre-output voltage, including: According to the pre-output voltage and the voltage source of the corresponding switch tube module in the first switch tube module and the second switch tube module, the duty cycle of the expected SPWM waveform is determined as the control signal for controlling the corresponding switch tube module in the first switch tube module and the second switch tube module to be turned on; and an enable signal is sent to the corresponding switch tube module in the first switch tube module and the second switch tube module, and the inhibit enable signal of the corresponding switch tube module in the first switch tube module and the second switch tube module is closed.

6. The active filtering device of claim 5, wherein, The switch unit changes from an off state to a conductive state by itself under the condition of receiving the control signal, including: For the corresponding switch tube module in the first switch tube module and the second switch tube module, the boost chip in the switch tube module increases the amplitude of the duty cycle of the expected SPWM waveform in the control signal to a certain degree to obtain a boost signal under the condition of receiving the control signal and the enable signal and the inhibit enable signal being closed; The switch tube in the switch tube module changes from an off state to a conductive state by itself based on the boost signal.

7. The active filtering device of claim 6, wherein, For the corresponding switch tube module in the first switch tube module and the second switch tube module, the switch tube in the switch tube module includes a triode; The injection unit includes an injection capacitor; one end of the injection capacitor is connected to the metal shell of the case where the noise source is located; the other end of the injection capacitor is connected to the emitter of the switch tube in the corresponding switch tube module; For the first switch tube module, the collector of the switch tube in the first switch tube module is connected to a positive voltage source; the first enable pin of the control unit is connected to the enable pin of the boost chip in the first switch tube module; the first inhibit enable pin of the control unit is connected to the inhibit enable pin of the boost chip in the first switch tube module; the control pin of the boost chip in the first switch tube module is connected to the base of the switch tube in the first switch tube module; For the second switch tube module, the collector of the switch tube in the second switch tube module is connected to a negative voltage source; the second enable pin of the control unit is connected to the enable pin of the voltage boosting chip in the second switch tube module; the second disable enable pin of the control unit is connected to the disable enable pin of the voltage boosting chip in the second switch tube module; and the control pin of the voltage boosting chip in the second switch tube module is connected to the base of the switch tube in the second switch tube module. The first disable enable pin and the second disable enable pin of the control unit are used for sending the disable enable signal; and the first enable pin and the second enable pin of the control unit are used for sending the enable signal.

8. A power supply, characterized by, The active filter device comprises: The active filter device according to any one of claims 1 to 7.

9. A method of controlling an active filter device of a power supply as claimed in claim 8, characterized in that, The active filter device comprises: The control sampling unit samples the noise signal of the noise source to obtain the voltage of the noise source; According to the voltage of the noise source, a voltage equal in size and opposite in direction to the voltage of the noise source is determined as a pre-output voltage; and a control signal for controlling the switch unit to be turned on is generated according to the pre-output voltage; The switch unit is controlled to change from an off state to an on state in the case of receiving the control signal, so that the pre-output voltage is injected into the injection unit through the switch unit in the case of the switch unit being on; The injection unit is controlled to receive the pre-output voltage, and inject the received pre-output voltage into the noise source in the case of receiving the pre-output voltage, so that the noise signal of the noise source is offset by the injected pre-output voltage.

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