A single-stage series resonant converter

Abstract

A single-stage series resonant converter includes an AC / DC converter circuit and a DC / DC converter circuit. The AC / DC converter circuit rectifies alternating current into direct current and outputs it to the DC / DC converter circuit. The converter also includes a control circuit that integrates a charge control method. The charge control method includes step P1, a voltage control loop, which samples the voltage V of the DC / DC converter circuit. o , and voltage reference value V ref After subtraction, an adjustment operation is performed to obtain the threshold Δv. Cr Step P2 corrects the threshold, K f f is a correction coefficient constant. s V is the switching frequency. in This refers to the voltage value at the input terminal of the DC / DC converter circuit. The input current of the AC / DC converter circuit of this invention linearly follows its input voltage, achieving the optimal power factor.

Description

Technical Field

[0001] This invention belongs to the field of series resonant circuit technology, specifically relating to a method for power factor correction and control of series resonant circuits. Background Technology

[0002] Single-stage series resonant converters eliminate the need for PFC circuits, resulting in higher efficiency and lower circuit costs. Applying series resonant circuits to single-stage series resonant converters is a novel approach; however, the control of series resonant circuits is complex. Among known technologies, there is an input average current control method, which limits the bandwidth of the control loop, making it unsuitable for PFC control. Furthermore, large variations in input voltage make it difficult to design the control parameters for the LLC input current loop. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a charge control method for a series resonant circuit, which can effectively solve the above-mentioned technical difficulties.

[0004] To achieve the above objectives, the present invention mainly adopts the following technical solutions:

[0005] A single-stage series resonant converter includes an AC / DC converter circuit and a DC / DC converter circuit. The AC / DC converter circuit rectifies alternating current into direct current and outputs it to the DC / DC converter circuit. The converter also includes a control circuit that integrates a charge control method. The charge control method includes...

[0006] Step P1: Voltage control loop, sampling the output voltage V of the DC / DC converter circuit. o , and voltage reference value V ref After subtraction, an adjustment operation is performed to obtain the threshold Δv. Cr ;

[0007] Step P2 corrects the threshold.

[0008] K f For the correction coefficient constant,

[0009] f s For switching frequency,

[0010] V in This refers to the voltage value at the input terminal of the DC / DC converter circuit.

[0011] The aforementioned DC / DC converter circuit includes a switching module, a resonant module, and a filtering module. The switching module performs high-frequency chopping on the output of the AC / DC converter circuit. The resonant module receives the output of the switching module and outputs it to the filtering module. The resonant module includes an inductor, a capacitor, and a transformer, which are connected in series. The secondary side of the transformer is connected to the filtering module. The switching module includes a first switch and a second switch, which are connected in series. The input terminal of the resonant module is connected in parallel with the second switch.

[0012] The above-mentioned charge control methods also include,

[0013] Step P3 updates the threshold, upper limit threshold. Lower threshold

[0014] Step P4: Sample the voltage V of the capacitor. cr And compare the capacitor voltage V cr and upper limit threshold V crth_H and lower limit threshold V crth_L Then, a control signal is output, and the voltage V of the capacitor is... cr Less than the threshold V crth_L And until it exceeds the upper limit threshold V crth_H The control signal is low; the voltage V of the capacitor cr Greater than the upper limit threshold V crth_H And until it is less than the lower threshold V crth_L The control signal is at a high level;

[0015] Step P5 generates a drive signal. The drive signal is generated based on the control signal. When the control signal is high, the drive signal drives the first switch to turn off and the second switch to turn on. When the control signal is low, the drive signal drives the first switch to turn on and the second switch to turn off.

[0016] The aforementioned switching frequency f s The acquisition methods include: sampling the input and output voltages of the DC / DC converter circuit, and calculating the switching frequency f based on the gain characteristics of the DC / DC converter circuit. s The switching frequency f is calculated based on the driving signal. s .

[0017] A single-stage series resonant converter includes an AC / DC converter circuit and a DC / DC converter circuit. The AC / DC converter circuit rectifies alternating current into direct current and outputs it to the DC / DC converter circuit. The converter also includes a control circuit that integrates a charge control method. The charge control method includes...

[0018] Step P1: Voltage control loop, sampling the output current I of the DC / DC converter circuit. o , and the current reference value I ref After subtraction, an adjustment operation is performed to obtain the BANG-BANG threshold Δv. Cr ;

[0019] Step P2 corrects the threshold.

[0020] K f For the correction coefficient constant,

[0021] f s For switching frequency,

[0022] V in This refers to the voltage value at the input terminal of the DC / DC converter circuit.

[0023] The aforementioned DC / DC converter circuit includes a switching module, a resonant module, and a filtering module. The switching module performs high-frequency chopping on the output of the AC / DC converter circuit. The resonant module receives the output of the switching module and outputs it to the filtering module. The resonant module includes an inductor, a capacitor, and a transformer, which are connected in series. The secondary side of the transformer is connected to the filtering module. The switching module includes a first switch and a second switch, which are connected in series. The input terminal of the resonant module is connected in parallel with the second switch.

[0024] The above-mentioned charge control methods also include,

[0025] Step P3 updates the threshold, upper limit threshold. Lower threshold

[0026] Step P4: Sample the voltage V of the capacitor. cr And compare the capacitor voltage V cr and upper limit threshold V crth_H and lower limit threshold V crth_L Then, a control signal is output, and the voltage V of the capacitor is... cr Less than the threshold V crth_L And until it exceeds the upper limit threshold V crth_H The control signal is low; the voltage V of the capacitor cr Greater than the upper limit threshold V crth_H And until it is less than the lower threshold V crth_L The control signal is at a high level;

[0027] Step P5 generates a drive signal. The drive signal is generated based on the control signal. When the control signal is high, the drive signal drives the first switch to turn off and the second switch to turn on. When the control signal is low, the drive signal drives the first switch to turn on and the second switch to turn off.

[0028] The aforementioned switching frequency f s The acquisition method includes sampling the input and output voltages of the DC / DC converter circuit and calculating the switching frequency f based on the gain characteristics of the DC / DC converter circuit. s Alternatively, the switching frequency f can be detected based on the drive signal. s .

[0029] The input current of the AC / DC conversion circuit of the present invention linearly follows its input voltage, thereby obtaining the optimal power factor. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings.

[0031] Figure 1 This is a block diagram illustrating the principle of a series resonant circuit and its charge control method in known technologies.

[0032] Figure 2 This is a block diagram illustrating the principle of the first embodiment of the series resonant circuit and its charge control method of the present invention.

[0033] Figure 3 This is a schematic diagram of the second embodiment of the series resonant circuit and its charge control method of the present invention. Detailed Implementation

[0034] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. 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.

[0035] like Figure 1 As shown, the single-stage series resonant converter includes an AC / DC converter module 11 and a DC / DC converter module 12. The AC / DC converter module 11 rectifies the alternating current AC into a voltage V. inThe output is sent to the DC / DC converter module 12. The charge control method P is used to control the DC / DC converter module 22. The charge control method P can be implemented digitally and integrated into a digital controller; or implemented analogally and using analog devices such as comparators and adders; or implemented using a hybrid analog and digital method.

[0036] The charge control method P includes the following steps:

[0037] Step P1: Voltage control loop, sampling voltage V o , and voltage reference value V ref After subtraction, an adjustment operation is performed to obtain the threshold Δv. Cr .

[0038] Step P2 corrects the threshold Δv Cr The corrected threshold is obtained.

[0039] K f This is a correction coefficient constant;

[0040] f s The switching frequency is determined by the voltage V. o and voltage V in Calculated;

[0041] Step P3 updates the upper and lower thresholds, with the upper threshold being... Lower threshold

[0042] Step P4: Sample the voltage V of the capacitor. cr The voltage V of the capacitor cr Less than the threshold V crth_L And until it exceeds the upper limit threshold V crth_H The control signal is low; the voltage V of the capacitor cr Greater than the upper limit threshold V crth_H And until it is less than the lower threshold V crth_L The control signal is at a high level;

[0043] Step P5 generates a drive signal. The drive signal is generated according to the control signal. When the control signal is high, the drive signal drives switch Q1 to turn off and Q2 to turn on; when the control signal is low, the drive signal drives switch Q1 to turn on and Q2 to turn off.

[0044] The voltage V of the capacitor cr Less than the threshold V crth_L And until it exceeds the upper limit threshold V crth_H When switch Q1 is on and Q2 is off, the series resonant module is clamped by the input / output voltage Vin, and the voltage V across the capacitor...cr Less than the threshold V crth_L And until it exceeds the upper limit threshold V crth_H When the control signal is high, switch Q1 is turned off and Q2 is turned on, and the series resonant module begins to resonate.

[0045] like Figure 2 The illustrated embodiment, and Figure 1 The difference is that in this embodiment, the charge control method P uses a current control loop, and step P5 uses a voltage control loop to sample the current I. o , and the current reference value I ref After subtraction, adjustment calculation is performed to obtain Δv Cr .

[0046] like Figure 3 The illustrated embodiment, and Figure 1 The difference is that in this embodiment, the switching frequency f is directly obtained from the drive signal output in step P4. s And used in step P2 to correct the threshold.

[0047] Figures 1-2 In the middle, the input current I in The theoretical formula can be expressed as follows:

[0048] I in =C r f s [v Cr (t Hoff )-v Cr (t Loff )]+2C j f s V in =C r f s Δv cr +2C j f s V in (1)

[0049] I in - Current value at the input terminal of DC / DC converter module 12;

[0050] V in - Voltage value at the input terminal of DC / DC converter module 12;

[0051] C r -Capacitor C r The capacitance value;

[0052] f s - The switching frequency of the main power switch in the DC / DC converter module;

[0053] v cr- The voltage across capacitor Cr;

[0054] t Hoff - The turn-off time of switch Q1;

[0055] t Loff - The turn-off time of switch Q2;

[0056] C j - The junction capacitance values ​​of switches Q1 and Q2.

[0057] Because the junction capacitance C of switches Q1 and Q2 j The capacitance is much smaller than that of capacitor Cr, therefore equation (1) can be simplified to:

[0058] I in =C r f s Δv cr (2)

[0059] I in - Current value at the input terminal of DC / DC converter module 12;

[0060] C r -Capacitor C r The capacitance value;

[0061] f s - Switching frequency of the main power switch in the DC / DC converter module

[0062] Δv Cr -Capacitor C r The voltage BANG-BANG threshold.

[0063] Figure 1 The DC / DC converter module 12 is a series resonant circuit, and there is a gain relationship between its input and output voltages as shown in the following equation:

[0064]

[0065] Considering steady state V o The change is very small; the derivation is done in reverse:

[0066]

[0067] Combining equation (4) and equation (2), we get:

[0068] I in =C r f s (V in )Δv Cr (5)

[0069] When the output voltage control loop reaches steady state, the threshold value Δv for controlling the resonant capacitor voltage is BANG-BANG. Cr As can be seen from equation (5), the current I remains unchanged. in Able to automatically follow voltage V in The changes achieve the effect of PFC control. However, due to V... in When f varies within the power frequency cycle, s With V in The relationship between them is non-linear, which has a certain impact on the effect of the input current following the input voltage, resulting in a certain decrease in the PF value.

[0070] The present invention corrects the threshold through step P2.

[0071]

[0072] K f - is a correction coefficient constant, in which case:

[0073] I in =C r K f V in Δv cr (7)

[0074] In Δv Cr In steady state, I in It can achieve linear following of V in To obtain a better PF value.

[0075] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.

Claims

1. A single-stage series resonant converter, comprising an AC / DC converter circuit and a DC / DC converter circuit, wherein the AC / DC converter circuit rectifies alternating current into direct current and outputs it to the DC / DC converter circuit, characterized in that, It also includes a control circuit, which integrates a charge control method, the charge control method including, Step P1: Voltage control loop, sampling the output voltage of the DC / DC converter circuit. V o , and voltage reference value V ref The threshold is obtained by subtracting and then performing an adjustment operation. ; Step P2 corrects the threshold. The corrected threshold is obtained. , For the correction coefficient constant, f s For switching frequency, V in The voltage value at the input terminal of the DC / DC converter circuit; Step P3 updates the upper and lower thresholds, with the upper threshold being... lower threshold ; Step P4: Sample capacitor voltage V cr And compare capacitor voltages V cr and upper limit threshold V crth_H and lower threshold V crth_L Then, a control signal is output, the capacitor voltage. V cr Less than the lower threshold V crth_L And until it exceeds the upper limit threshold. V crth_H The control signal is low; the capacitor voltage V cr Greater than the upper limit threshold V crth_H And until it is less than the lower threshold. V crth_L The control signal is at a high level; Step P5 generates a drive signal. The drive signal is generated based on the control signal. When the control signal is high, the drive signal drives the first switch to turn off and the second switch to turn on. When the control signal is low, the drive signal drives the first switch to turn on and the second switch to turn off.

2. The single-stage series resonant converter as described in claim 1, characterized in that, The DC / DC converter circuit includes a switching module, a resonant module, and a filtering module. The switching module performs high-frequency chopping on the output of the AC / DC converter circuit. The resonant module receives the output of the switching module and outputs it to the filtering module. The resonant module includes an inductor, a capacitor, and a transformer, which are connected in series. The secondary side of the transformer is connected to the filtering module. The switching module includes a first switch and a second switch, which are connected in series. The input terminal of the resonant module is connected in parallel with the second switch.

3. The single-stage series resonant converter as described in claim 1, characterized in that, The input and output voltages of the DC / DC converter circuit are sampled, and the switching frequency is calculated based on the gain characteristics of the DC / DC converter circuit. f s .

4. The single-stage series resonant converter as described in claim 1, characterized in that, Calculate the switching frequency based on the drive signal. f s .

5. A single-stage series resonant converter, comprising an AC / DC converter circuit and a DC / DC converter circuit, wherein the AC / DC converter circuit rectifies alternating current into direct current and outputs it to the DC / DC converter circuit, characterized in that, It also includes a control circuit, which integrates a charge control method, the charge control method including, Step P1: Voltage control loop, sampling the output current of the DC / DC converter circuit. I o , and current reference value I ref The threshold is obtained by subtracting and then performing an adjustment operation. ; Step P2 corrects the threshold. , For the correction coefficient constant, f s For switching frequency, V in This refers to the voltage value at the input terminal of the DC / DC converter circuit. Step P3 updates the threshold, upper limit threshold. lower threshold ; Step P4: Sample capacitor voltage V cr And compare capacitor voltages V cr and upper limit threshold V crth_H and lower threshold V crth_L Then, a control signal is output, the capacitor voltage. V cr Less than the lower threshold V crth_L And until it exceeds the upper limit threshold. V crth_H The control signal is low; the capacitor voltage V cr Greater than the upper limit threshold V crth_H And until it is less than the lower threshold. V crth_L The control signal is at a high level; Step P5 generates a drive signal. The drive signal is generated based on the control signal. When the control signal is high, the drive signal drives the first switch to turn off and the second switch to turn on. When the control signal is low, the drive signal drives the first switch to turn on and the second switch to turn off.

6. The single-stage series resonant converter as described in claim 5, characterized in that, The DC / DC converter circuit includes a switching module, a resonant module, and a filtering module. The switching module performs high-frequency chopping on the output of the AC / DC converter circuit. The resonant module receives the output of the switching module and outputs it to the filtering module. The resonant module includes an inductor, a capacitor, and a transformer, which are connected in series. The secondary side of the transformer is connected to the filtering module. The switching module includes a first switch and a second switch, which are connected in series. The input terminal of the resonant module is connected in parallel with the second switch.

7. The single-stage series resonant converter as described in claim 5, characterized in that, The input and output voltages of the DC / DC converter circuit are sampled, and the switching frequency is calculated based on the gain characteristics of the DC / DC converter circuit. f s .

8. The single-stage series resonant converter as described in claim 5, characterized in that, Detect the switching frequency based on the drive signal f s .

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