Control circuit and method of single-stage resonance type AC / DC conversion circuit
By introducing a charge control method, the inner current loop of the single-stage resonant AC/DC converter circuit is eliminated, thereby improving the dynamic response speed and reducing the cost. This simplifies the control circuit design and is suitable for single-loop control of single-stage resonant AC/DC converter circuits.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2026-03-13
AI Technical Summary
Existing single-stage resonant AC/DC converter circuits have slow dynamic response speeds when the load changes, dual-loop control is complex and costly, and the simulated ramp method requires additional circuitry and parameter modification is inconvenient.
By employing a charge control method, the inner current loop is eliminated. The charge integral control threshold is generated by sampling the input voltage, resonant current, and ramp compensation voltage, and the drive signal for the switch is generated, simplifying the control to a single loop.
It significantly improves the dynamic response speed of the conversion circuit, reduces costs, simplifies compensator design, and has good versatility and dynamic performance.
Smart Images
Figure CN121664005A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power conversion technology, and in particular to a control circuit and method for a single-stage resonant AC / DC converter circuit. Background Technology
[0002] Currently, single-stage resonant AC / DC converter circuits typically employ an average current control method, using an outer voltage loop and an inner current loop to stabilize the output DC voltage at the reference voltage, ensuring that the input current has good tracking performance for the sinusoidal input voltage.
[0003] However, single-stage resonant AC / DC converter circuits using the average current control method have the following problems: by directly changing the switching frequency f s Controlling the resonant cavity impedance to adjust the resonant cavity gain results in a slow dynamic response of the converter when the load changes; it requires dual-loop control with an outer voltage loop and an inner current loop, making the compensator design complex and requiring sampling of the input current, which increases costs; using the analog ramp method requires additional circuitry and makes parameter modification inconvenient. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a control circuit and method for a single-stage resonant AC / DC converter circuit, which, based on a charge control method, eliminates the current inner loop and improves dynamic response speed.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows:
[0006] A control method for a single-stage resonant AC / DC converter circuit, used to control a single-stage resonant AC / DC converter circuit, including,
[0007] Step S1, sample the input voltage and multiply it by the scaling factor K m Then take the absolute value to get the first parameter;
[0008] Step S2: Sample the resonant current and compare it with the slope compensation voltage V. bias After integration, a charge integral sample value v is generated. sum ;
[0009] Step S3, set the output voltage reference value v ref Subtract the output voltage v o The voltage v obtained afterwards e The adjusted value is multiplied by the first parameter to obtain the input current reference value; the input current reference value is then multiplied by the proportional coefficient A. x In addition to the bias coefficient B x Obtain the control quantity v c , where the proportionality coefficient A x 1 / 2C ramp Ks F r Bias coefficient B x For I ramp / 2C ramp F r C ramp To generate the slope compensation voltage V bias The equivalent charge / discharge capacitance, I ramp For the equivalent charge / discharge capacitance C ramp The equivalent charging current, K s F is the sampling coefficient of the resonant current. r This is the resonant frequency of a single-stage resonant AC / DC converter circuit.
[0010] Step S4, control quantity v c Multiply by the frequency capture value f n Obtain the charge integral control threshold v comp Based on the charge integral sampling value v sum With charge integral control threshold v comp The comparison results generate the drive signal for the switch in the single-stage resonant AC / DC converter circuit.
[0011] This invention also provides a control circuit for a single-stage resonant AC / DC converter circuit. The control method for this single-stage resonant AC / DC converter circuit includes a voltage control unit, a charge control unit, a sampling unit, and a digital controller. The sampling unit samples the AC voltage, takes its absolute value, and inputs it to the voltage control unit. The voltage control unit samples the output voltage of the single-stage resonant AC / DC converter circuit, processes it, and outputs a control quantity v. c To the charge control unit; the charge control unit based on the sampled resonant current and the control quantity v c Output signal v after calculation single The digital controller generates drive signals for the switches in the single-stage resonant AC / DC converter circuit.
[0012] In one specific embodiment, the sampling unit includes a first proportional calculator and an absolute value calculator, and the sampled value of the input voltage is input to the voltage control unit through the first proportional calculator and the absolute value calculator.
[0013] In one specific embodiment, the voltage control unit includes a regulator, a multiplier, and a second proportional amplifier. The voltage obtained by subtracting the output voltage from the output voltage reference value is input to the multiplier after passing through the regulator. The sampled value of the input voltage is input to the multiplier after passing through the first proportional amplifier and the absolute value amplifier. The output of the multiplier is the input current reference value. The input current reference value is then added to the bias coefficient B by the second proportional amplifier. xObtain the control quantity v c The input is given to the charge control unit, wherein the scaling factor of the second scaling unit is A. x .
[0014] In one specific embodiment, the charge control unit includes a slope compensator, an integrator, a third proportional amplifier, and a first comparator, wherein the slope compensator generates a slope compensation voltage V. bias The integrator samples the resonant current of the single-stage resonant AC / DC converter circuit, integrates it with the slope compensation voltage, and obtains the charge integral sample value v. sum The control quantity output by the voltage control unit is used by the third proportional arithmetic unit to obtain the charge integral control threshold v. comp The charge integral sampling value v sum Connect the positive input terminal of the first comparator, the charge integration control threshold v comp Connect the negative input terminal of the first comparator, and the output terminal of the first comparator outputs a signal v. single To the digital controller, wherein the scaling factor of the third proportional arithmetic unit is the frequency capture value f. n The expression is f s / F r f n f is the normalized switching frequency. s This represents the switching frequency.
[0015] In one specific embodiment, the above-mentioned slope compensator is implemented using digital slope compensation, which multiplies the on-time of the previous switching cycle by the slope compensation coefficient to obtain the corresponding slope compensation voltage V. bias Wherein, the slope compensation coefficient is the offset coefficient B. x .
[0016] In one specific embodiment, the integrator includes a current transformer, a first resistor, a second resistor, a third resistor, a first amplifier, a second amplifier, a fourth resistor, a first capacitor, and a first switch. The two ends of the first winding of the current transformer are connected to the resonant cavity of a single-stage resonant AC / DC converter circuit. The two ends of the second winding of the current transformer are connected in parallel to the first and second ends of the first resistor. The first end of the first resistor is connected to the first end of the second resistor. The second end of the second resistor is connected to the negative input terminal of the first amplifier. The positive input terminal of the first amplifier is grounded. The negative input terminal of the first amplifier is connected to the first end of the third resistor. The second end of the third resistor is connected to the output terminal of the first amplifier. The output terminal of the first amplifier is connected to the first end of the fourth resistor. The second end of the fourth resistor is connected to the negative input terminal of the second amplifier. The positive input terminal of the second amplifier is connected to the slope compensation voltage V. biasThe first terminal of the first capacitor is connected to the negative input terminal of the second amplifier, and the second terminal of the first capacitor is connected to the output terminal of the second amplifier. The first terminal of the first switch is connected to the first terminal of the first capacitor, and the second terminal of the first switch is connected to the second terminal of the first capacitor. The control terminal of the first switch is connected to a reset signal. The output terminal of the second amplifier outputs the charge integral sample value v. sum .
[0017] In one specific embodiment, the single-stage resonant AC / DC converter circuit includes an AC-side switching unit, a resonant unit, and a DC-side switching unit, wherein the AC voltage, the AC-side switching unit, the resonant unit, the DC-side switching unit, and the DC voltage are connected in sequence.
[0018] Beneficial effects: The present invention provides a control circuit and method for a single-stage resonant AC / DC converter circuit, which introduces a charge control method into the single-phase single-stage resonant AC / DC converter circuit, effectively improving the model of the converter circuit and significantly enhancing the dynamic response speed of the converter circuit; it is simple and reliable to apply, low in cost, and has strong versatility.
[0019] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description
[0020] Figure 1 This is a circuit diagram of the control circuit for a single-stage resonant AC / DC converter circuit according to the present invention.
[0021] Figure 2 This is the logic diagram of the drive signal for a single-stage resonant AC / DC converter circuit.
[0022] Figure 3 This is a circuit diagram of an integrator in a specific embodiment.
[0023] Figure 4 This is a key waveform diagram of a single-stage resonant AC / DC converter circuit within one cycle.
[0024] Figure 5 For the output voltage v o Higher than the output voltage reference value v ref This is a schematic diagram of the adjustment process of the control circuit of the present invention.
[0025] Figure 6 For the output voltage v o Below the output voltage reference value v ref This is a schematic diagram of the adjustment process of the control circuit of the present invention.
[0026] Figure 7This is a flowchart of a control method for a single-stage resonant AC / DC converter circuit according to the present invention.
[0027] Figure 8 The simulation waveforms of a single-stage resonant AC / DC converter circuit under half-load conditions are shown.
[0028] Figure 9 The simulation waveforms of a single-stage resonant AC / DC converter circuit under full load are shown.
[0029] Figure 10 The waveform diagram is shown in the load switching experiment of a single-stage resonant AC / DC converter circuit. Detailed Implementation
[0030] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0031] Figure 1 This is a circuit diagram of the control circuit for a single-stage resonant AC / DC converter circuit according to the present invention. Figure 1 As shown, the control circuit 1 of the single-stage resonant AC / DC converter circuit of the present invention is used to control the single-stage resonant AC / DC converter circuit 2.
[0032] exist Figure 1 In a specific embodiment, the single-stage resonant AC / DC converter circuit 2 includes an AC-side switching unit 21, a resonant unit 22, and a DC-side switching unit 23, with AC voltage u AC AC side switching unit 21, resonant unit 22, DC side switching unit 23, DC voltage V o Connect them sequentially.
[0033] More specifically, the AC side switching unit 21 includes switch S 1u Switch S 1d Switch S 2u Switch S 2d Capacitors C1 and C2, switch S 1u and switch S 1d After being connected in reverse series, it is connected in series with capacitor C1, and switch S 2u and switch S 2d After being connected in reverse series, it is connected in series with capacitor C2, and switch S 1u Switch S 1d The series branch of capacitor C1 and switch S 2u Switch S2d The AC voltage u is connected in parallel with the series branch of capacitor C2. AC The first end is connected to switch S 1d The AC voltage u between capacitor C1 and capacitor C1 AC The second end is connected to switch S 2d Between and capacitor C2.
[0034] More specifically, the resonant unit 22 includes a transformer T1 and an inductor L. r With capacitor C r The first terminal of the primary winding of transformer T1 is connected to inductor L. r The first terminal is connected to the capacitor C at the second terminal of the primary winding of transformer T1. r The first terminal, inductor L r The second terminal and capacitor C r The second terminal is connected to switch S 2u Switch S 2d The magnetizing inductance L is connected in parallel with the series branch of capacitor C2. m It is connected in parallel across the primary winding of transformer T1.
[0035] More specifically, the DC-side switching unit 23 includes switch SR1 and switch SR2. The first terminal of switch SR1 is connected to the first terminal of the first secondary winding of transformer T1, and the second terminal of switch SR1 is connected to capacitor C. o The first terminal, capacitor C o The second terminal of SR1 is connected to the second terminal of the first secondary winding of transformer T1, and the second terminal of the first secondary winding of transformer T1 is connected to the first terminal of the second secondary winding of transformer T1. The first terminal of switch SR2 is connected to the second terminal of the second secondary winding of transformer T1, and the second terminal of switch SR2 is connected to the second terminal of switch SR1. Capacitor C o Parallel load R at both ends o Load R o The two ends are DC voltage V o .
[0036] The drive signal logic of the single-stage resonant AC / DC converter circuit 2 is as follows: Figure 2 As shown, i inave For the input current, u o DC voltage V o Instantaneous value, u S1d_gs For switch S 1d The driving voltage, u S2u_gs For switch S 2u The driving voltage, u S1u_gs For switch S 1u The driving voltage, u S2d_gs For switch S 2d The driving voltage, when the AC voltage u ACWhen >0, switch S 1u and switch S 2d Normally open, switch S 1d and switch S 2u Operating in high-frequency switching mode; when AC voltage u AC When <0, switch S 1d and switch S 2u Normally open, switch S 1u and switch S 2d It operates in a high-frequency switching state.
[0037] The control circuit 1 of the single-stage resonant AC / DC converter circuit of the present invention includes a voltage control unit 11, a charge control unit 12, a sampling unit 13, and a digital controller (DSP) 14. The sampling unit 13 samples the AC voltage u. AC The absolute value is then input to the voltage control unit 11; the voltage control unit 11 samples the output voltage v of the single-stage resonant AC / DC converter circuit 2. o The processed output control quantity v c To charge control unit 12; charge control unit 12 based on the sampled resonant current and control quantity v c Output signal v after calculation single To digital controller 14; digital controller 14 generates switch S 1u drive signal G 1u Switch S 1d drive signal G 1d Switch S 2u drive signal G 2u Switch S 2d drive signal G 2d .
[0038] Furthermore, the sampling unit 13 includes a first proportional arithmetic unit 131 and an absolute value arithmetic unit 132, with input voltage u. AC The sampled values are input to the voltage control unit 11 after passing through the first proportional arithmetic unit 131 and the absolute value arithmetic unit 132. The proportionality coefficient K of the first proportional arithmetic unit 131 is... m 1 / U rms 2 .
[0039] Furthermore, the voltage control unit 11 includes a regulator 111, a multiplier 112, and a second proportional arithmetic unit 113, and outputs a voltage reference value v. ref Subtract the output voltage v o The voltage v obtained afterwards e The input voltage u is fed to multiplier 112 after passing through regulator 111. ACThe sampled value is fed into multiplier 112 after passing through the first proportional arithmetic unit 131 and the absolute value arithmetic unit 132. The output of multiplier 112 is the input current reference value I. m |sin(ωt)|, input current reference value I m |sin(ωt)| is processed by the second proportional operator 113 and then added with the bias coefficient B. x Obtain the control quantity v c The input is sent to the charge control unit 12. The proportional coefficient A of the second proportional calculator 113 is also included. x 1 / 2C ramp K s F r Bias coefficient B x For I ramp / 2C ramp F r Among them, C ramp To generate the slope compensation voltage V bias Equivalent charge / discharge capacitance; I ramp For the equivalent charge / discharge capacitance C ramp The equivalent current of charging; K s F is the sampling coefficient of the resonant current; r This is the resonant frequency of the single-stage resonant AC / DC converter circuit 2.
[0040] In one specific embodiment, regulator 111 is specifically a PI regulator.
[0041] More specifically, the control variable v c The expression is as follows:
[0042]
[0043] Among them, the input current reference value I m |sin(ωt)| is derived from power and input voltage u AC The input voltage u is determined jointly. AC The expression is U m |sin(ωt)|, input current reference value I m The expression for |sin(ωt)| is I m |sin(ωt)|=U m |sin(ωt)|·PI out / U rms 2 P represents the output power of the single-stage resonant AC / DC converter circuit 2, and I represents... out This is the output current of the single-stage resonant AC / DC converter circuit 2;
[0044] Furthermore, the charge control unit 12 includes a slope compensator 121, an integrator 122, a third proportional arithmetic unit 123, and a first comparator 124. The slope compensator 121 generates a slope compensation voltage V. bias The sample is fed to integrator 122; integrator 122 samples the resonant current of the single-stage resonant AC / DC converter circuit 2, and the slope compensation voltage V. bias After integration, the charge integral sample value v is obtained. sum The control quantity v output by the voltage control unit 11 c The charge integral control threshold v is obtained after the third proportional arithmetic unit 123. comp Charge integral sampling value v sum Connect the positive input terminal of the first comparator 124, and the charge integration controls the threshold v. comp Connect the negative input terminal of the first comparator 124, and the output terminal of the first comparator 124 outputs a signal v. single To the digital controller 14. The proportional coefficient of the third proportional arithmetic unit 123 is the frequency capture value f. n The expression is f s / F r f n f is the normalized switching frequency. s This represents the switching frequency.
[0045] Because analog slope compensation has drawbacks such as inconvenient parameter modification and the need for additional circuitry, in a specific embodiment of the present invention, the slope compensator 121 is implemented using digital slope compensation. The frequency acquisition module of the digital controller 14 samples the drive signal in real time to obtain the value of the previous switching cycle. The on-time of the previous switching cycle is multiplied by the slope compensation coefficient to obtain the corresponding slope compensation voltage V. bias Wherein, the slope compensation coefficient is the offset coefficient B. x .
[0046] Figure 3 A circuit diagram of integrator 122 in a specific embodiment is shown, as follows: Figure 3 As shown, the integrator 122 includes a current transformer CT1 and a resistor R. s Resistor R1, Resistor R2, Amplifier OP1, Amplifier OP2, Resistor R i Capacitor C i With switch SW1, the two ends of the first winding of current transformer CT1 are connected to the resonant cavity of single-stage resonant AC / DC converter circuit 2, and a resistor R is connected in parallel across the two ends of the second winding of current transformer CT1. s The first and second terminals, resistor R s The second terminal is grounded, and the resistor R sThe first terminal of the amplifier is connected to the first terminal of resistor R1. The second terminal of resistor R1 is connected to the negative input terminal of amplifier OP1. The positive input terminal of amplifier OP1 is grounded. The negative input terminal of amplifier OP1 is connected to the first terminal of resistor R2. The second terminal of resistor R2 is connected to the output terminal of amplifier OP1. The output terminal of amplifier OP1 is connected to resistor R... i The first terminal, resistor R i The second terminal is connected to the negative input terminal of amplifier OP2, and the positive input terminal of amplifier OP2 is connected to the ramp compensation voltage V. bias Capacitor C i The first terminal is connected to the negative input terminal of amplifier OP2, and capacitor C... i The second terminal is connected to the output terminal of amplifier OP2, and the first terminal of switch SW1 is connected to capacitor C. i The first terminal of switch SW1 is connected to capacitor C. i At the second terminal, the control terminal of switch SW1 is connected to the reset signal res, and the output terminal of amplifier OP2 outputs the charge integral sample value v. sum The turns ratio of the first winding to the second winding of the current transformer CT1 is 1:N.
[0047] More specifically, the resonant current signal sampled by current transformer CT1 passes through resistor R. s Converted to voltage v s The voltage v is then amplified by amplifier OP1. r The sampling coefficient K of the resonant current s The expression is as follows:
[0048]
[0049] Among them, the slope compensation voltage V bias DC bias voltage, slope compensation voltage V bias In resistor R i A constant current I will be generated on it. ramp Current I ramp In capacitor C i Integrating the result on the surface produces a periodic sawtooth wave, and the integral result is the voltage v. ramp Meanwhile, the slope compensation voltage V bias A DC bias voltage is also provided to prevent the negative voltage of charge integration from damaging the ADC pins of the digital controller. For amplifier OP2, when only charge integration is considered, the positive input terminal of amplifier OP2 can be grounded, and the integration current is V. r / R i The integral current in capacitor C i The result of the upper integration is the voltage v th According to the superposition theorem, the sampled value of charge integral v sum =Vbias +v ramp +v th The expression is:
[0050]
[0051] Among them, i inave This is the input current.
[0052] In addition, by selecting Figure 3 With appropriate parameters for the components, it is also possible to ensure that the voltage input to the digital controller does not exceed the power supply voltage.
[0053] Figure 4 The key waveforms of a single-stage resonant AC / DC converter circuit 2 within one cycle are shown, where V gs1 V is the drive voltage for one of the high-frequency switching switches. gs2 For the drive voltage of another high-frequency switching switch, v i The integral current in capacitor C i The instantaneous voltage value generated by the upper integration, i r For the resonant current, i m This is the excitation current. Within one switching cycle, the adjustment process of the single-stage resonant AC / DC converter circuit 2 is divided into the following three stages.
[0054] Stage 1, t = [t1, t3]: At time t1, the resonant current begins to flow through capacitor C. i Up-integration, charge integral sample value v sum With charge integral control threshold v comp When comparing, the charge integral sample value v sum Reaching the charge integral control threshold v comp When the value is reached, the output signal is sent to the digital controller 14 to cause the drive to flip.
[0055] Stage 2, t = [t3, t4]: At time t3, the reset signal res is enabled, and the voltage v ramp The voltage v drops, and at the same time i =0, after the dead time, at time t4, another high-frequency switching switch is turned on.
[0056] Stage 3, t = [t4, t5]: Voltage v ramp The voltage decreases until time t5, at which point the voltage v drops. ramp When the value drops to 0, the output signal to the digital controller 14 causes the drive to flip again; in this case, the second half of the switching cycle and the positive half of the switching cycle remain strictly symmetrical.
[0057] According to the charge control principle, under the same input voltage, the charge integral sample value v sum With the average value of input current Iinave There is a corresponding relationship; however, the correspondence between the two also includes the switching frequency f. s The effects are not one-to-one; to eliminate the switching frequency f s Due to the influence of this, the present invention samples the switching frequency of the drive signal, so that the control quantity v c With input current i inave One-to-one correspondence, the control quantity v after introducing frequency compensation c The expression is:
[0058]
[0059] Ignoring the parasitic capacitance of the switch, the capacitor C is set to... i The equivalent charge / discharge capacitance C of the ramp compensator 121 is equal to ramp Then the input current i in one switching cycle inave for:
[0060]
[0061] In the above formula, the input current i inave Only with control quantity v c Related to, control quantity v c It can monitor power conditions, facilitating the implementation of light-load intermittent operation and power factor correction functions. In this invention, charge control can be achieved by changing the control quantity v. c To control the input current i cycle by cycle inave Make the input current i inave It follows the sinusoidal variation of the input voltage. Input current i inave The reference value is I m If |sin(ωt)|, then it is related to the control variable v. c The following relationship exists:
[0062] Im|sin(ωt)|=2CrampKsFrvc(t)-KsIramp.
[0063] Traditional average current control directly changes the switching frequency f. s The resonant cavity gain is adjusted by controlling the resonant cavity impedance. In contrast, in the charge control of this invention, the resonant cavity charge becomes a directly controllable quantity, and the switching frequency f... s As a passive control variable, it is automatically adjusted to a value that matches the controlled charge. The charge control of this invention introduces resonant cavity current information into the control loop, which can reduce the model order of the resonant converter in the low-frequency range, eliminate the resonance peak caused by the beat frequency double pole in the lower resonance region, and avoid the compensator design difficulties caused by the rapid phase drop.
[0064] The adjustment process of the control circuit of this invention is as follows: Figure 5 and Figure 6 As shown.
[0065] like Figure 5 As shown, when the output voltage v o Higher than the output voltage reference value v ref At that time, the control quantity v c Decrease, charge integral sampling value v sum The decrease in frequency leads to a decrease in the charge entering the resonant cavity, and thus a decrease in the switching frequency f. s Increase, switching period T s As the resonant cavity gain decreases, the energy E flowing into the resonant cavity from the input terminal also decreases. LLC Decrease, output voltage v o The corresponding decrease.
[0066] like Figure 6 As shown, when the output voltage v o Below the output voltage reference value v ref At that time, the control quantity v c Increase the charge integral sampling value v sum Increase the switching frequency f s The energy E flowing into the resonant cavity decreases. LLC Increase, output voltage v o It will increase accordingly.
[0067] Furthermore, in a single-stage resonant AC / DC converter circuit with no current inner loop charge control, only a voltage loop needs to be designed, making the design of the compensator easier. It also eliminates the need for input current sampling, thus reducing costs.
[0068] like Figure 7 As shown, the present invention also provides a control method for a single-stage resonant AC / DC converter circuit, comprising the following steps.
[0069] Step S1, sample the input voltage and multiply it by the scaling factor K m Then take the absolute value to get the first parameter.
[0070] Step S2: Sample the resonant current and compare it with the slope compensation voltage V. bias After integration, a charge integral sample value v is generated. sum .
[0071] Step S3, set the output voltage reference value v ref Subtract the output voltage v o The voltage v obtained afterwards e The adjusted value is multiplied by the first parameter to obtain the input current reference value; the input current reference value is then multiplied by the proportional coefficient A. x In addition to the bias coefficient B x Obtain the control quantity v c , where the proportionality coefficient A x1 / 2C ramp K s F r Bias coefficient B x For I ramp / 2C ramp F r C ramp To generate the slope compensation voltage V bias The equivalent charge / discharge capacitance, I ramp For the equivalent charge / discharge capacitance C ramp The equivalent current of charging; K s F is the sampling coefficient of the resonant current. r This is the resonant frequency of a single-stage resonant AC / DC converter circuit.
[0072] Step S4, control quantity v c Multiply by the frequency capture value f n Obtain the charge integral control threshold v comp Based on the charge integral sampling value v sum With charge integral control threshold v comp The comparison results generate the drive signal for the switch in the single-stage resonant AC / DC converter circuit.
[0073] Figure 8 The simulation waveforms of a single-stage resonant AC / DC converter circuit under half-load conditions are shown. Figure 9 The simulation waveform of the single-stage resonant AC / DC converter circuit under full load is shown. It can be seen that the output voltage is stably controlled at the rated voltage, the input current is in phase with the input voltage, and it has good tracking capability for the input voltage. The power factor is 0.99, the total harmonic distortion (THD) is 1.85% under half load, and 3.42% under full load.
[0074] Figure 10 The waveform of the load switching experiment of the single-stage resonant AC / DC converter circuit is shown. The output current switches between half load (6.25A) and full load (12.5A). When switching from half load to full load, the output voltage undershoots by about 5.4V and the recovery time is about 20ms. The input current reacts instantly to the load switching, so the adjustment speed is fast, which verifies the good dynamic performance.
[0075] It should be noted that the control circuit and control method of the present invention are applicable to both the primary resonant cavity resonant current detection method and the secondary rectified current detection method.
[0076] It should be noted that the control circuit and control method of the present invention can be used in bidirectional AC / DC converters. For bidirectional AC / DC converters, resonant cavity current rectification can be used to make the two directions equivalent.
[0077] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.
Claims
1. A control method for a single-stage resonant AC / DC converter circuit, used to control a single-stage resonant AC / DC converter circuit, characterized in that, include, Step S1, sample the input voltage and multiply it by the scaling factor K m Then take the absolute value to get the first parameter; Step S2: Sample the resonant current and compare it with the slope compensation voltage V. bias After integration, a charge integral sample value v is generated. sum ; Step S3, set the output voltage reference value v ref Subtract the output voltage v o The voltage v obtained afterwards e The adjusted value is multiplied by the first parameter to obtain the input current reference value; Multiply the input current reference value by the scaling factor A. x In addition to the bias coefficient B x Obtain the control quantity v c , where the proportionality coefficient A x 1 / 2C ramp K s F r Bias coefficient B x For I ramp / 2C ramp F r C ramp To generate the slope compensation voltage V bias The equivalent charge / discharge capacitance, I ramp For the equivalent charge / discharge capacitance C ramp The equivalent charging current, K s F is the sampling coefficient of the resonant current. r This is the resonant frequency of a single-stage resonant AC / DC converter circuit. Step S4, control quantity v c Multiply by the frequency capture value f n Obtain the charge integral control threshold v comp Based on the charge integral sampling value v sum With charge integral control threshold v comp The comparison results generate the drive signal for the switch in the single-stage resonant AC / DC converter circuit.
2. A control circuit for a single-stage resonant AC / DC converter circuit, characterized in that, The control method for a single-stage resonant AC / DC converter circuit as described in claim 1 includes a voltage control unit, a charge control unit, a sampling unit, and a digital controller. The sampling unit samples the AC voltage, takes its absolute value, and inputs it to the voltage control unit. The voltage control unit samples the output voltage of the single-stage resonant AC / DC converter circuit, processes it, and outputs a control quantity v. c To the charge control unit; the charge control unit based on the sampled resonant current and the control quantity v c Output signal v after calculation single The digital controller generates drive signals for the switches in the single-stage resonant AC / DC converter circuit.
3. The control circuit of the single-stage resonant AC / DC converter circuit as described in claim 2, characterized in that, The sampling unit includes a first proportional calculator and an absolute calculator. The sampled value of the input voltage is input to the voltage control unit through the first proportional calculator and the absolute calculator.
4. The control circuit of the single-stage resonant AC / DC converter circuit as described in claim 3, characterized in that, The voltage control unit includes a regulator, a multiplier, and a second proportional amplifier. The voltage obtained by subtracting the output voltage from the output voltage reference value is input to the multiplier after passing through the regulator. The sampled value of the input voltage is input to the multiplier after passing through the first proportional amplifier and the absolute value amplifier. The output of the multiplier is the input current reference value. The input current reference value is then processed by the second proportional amplifier and a bias coefficient B is added. x Obtain the control quantity v c The input is given to the charge control unit, wherein the scaling factor of the second scaling unit is A. x .
5. The control circuit of the single-stage resonant AC / DC converter circuit as described in claim 4, characterized in that, The charge control unit includes a ramp compensator, an integrator, a third proportional amplifier, and a first comparator. The ramp compensator generates a ramp compensation voltage V. bias The integrator samples the resonant current of the single-stage resonant AC / DC converter circuit, integrates it with the slope compensation voltage, and obtains the charge integral sample value v. sum The control quantity output by the voltage control unit is used by the third proportional arithmetic unit to obtain the charge integral control threshold v. comp The charge integral sampling value v sum Connect the positive input terminal of the first comparator, the charge integration control threshold v comp Connect the negative input terminal of the first comparator, and the output terminal of the first comparator outputs a signal v. single To the digital controller, wherein the scaling factor of the third proportional arithmetic unit is the frequency capture value f. n The expression is f s / F r f n f is the normalized switching frequency. s This refers to the switching frequency.
6. The control circuit of the single-stage resonant AC / DC converter circuit as described in claim 5, characterized in that, The slope compensator employs digital slope compensation, which multiplies the on-time of the previous switching cycle by the slope compensation coefficient to obtain the corresponding slope compensation voltage V. bias Wherein, the slope compensation coefficient is the offset coefficient B. x .
7. The control circuit of the single-stage resonant AC / DC converter circuit as described in claim 5, characterized in that, The integrator includes a current transformer, a first resistor, a second resistor, a third resistor, a first amplifier, a second amplifier, a fourth resistor, a first capacitor, and a first switch. The two ends of the first winding of the current transformer are connected to the resonant cavity of a single-stage resonant AC / DC converter circuit. The two ends of the second winding of the current transformer are connected in parallel to the first and second ends of the first resistor. The first end of the first resistor is connected to the first end of the second resistor. The second end of the second resistor is connected to the negative input terminal of the first amplifier. The positive input terminal of the first amplifier is grounded. The negative input terminal of the first amplifier is connected to the first end of the third resistor. The second end of the third resistor is connected to the output terminal of the first amplifier. The output terminal of the first amplifier is connected to the first end of the fourth resistor. The second end of the fourth resistor is connected to the negative input terminal of the second amplifier. The positive input terminal of the second amplifier is connected to the slope compensation voltage V. bias The first terminal of the first capacitor is connected to the negative input terminal of the second amplifier, and the second terminal of the first capacitor is connected to the output terminal of the second amplifier. The first terminal of the first switch is connected to the first terminal of the first capacitor, and the second terminal of the first switch is connected to the second terminal of the first capacitor. The control terminal of the first switch is connected to a reset signal. The output terminal of the second amplifier outputs the charge integral sample value v. sum .
8. The control circuit of the single-stage resonant AC / DC converter circuit as described in claim 2, characterized in that, A single-stage resonant AC / DC converter circuit includes an AC-side switching unit, a resonant unit, and a DC-side switching unit, with the AC voltage, the AC-side switching unit, the resonant unit, the DC-side switching unit, and the DC voltage connected in sequence.