A non-isolated hybrid single-phase ac-dc conversion circuit and a control method thereof

Abstract

The application discloses a non-isolated hybrid single-phase AC-DC conversion circuit and a control method thereof, which comprises an input AC source, an input filter unit, an AC rectification unit, a switching conversion unit, an output filter unit and a control unit. The input end of the input filter unit is connected with the input AC source, and the output end of the input filter unit is connected with the AC input end of the AC rectification unit. The rectification output end of the AC rectification unit is connected with the input end of the switching conversion unit, and the output end of the switching conversion unit is connected with the output filter unit to realize DC output. The application can realize wider range of voltage increase and greater voltage decrease duty ratio, thereby better meeting the use of small and medium power electronic products in a full voltage range and obtaining better cost performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a switching power supply, in particular to a non-isolated hybrid single-phase AC-DC conversion circuit and a control method thereof. BACKGROUND

[0002] With the development of electronic information, more and more devices need to be powered by DC, among which the popularity of IT devices and the wide application of lighting in various places require small and medium power electronic converters to complete the conversion from AC to DC. However, these application fields have high requirements for the size, weight and portability of the power supply (such as adapters, electronic ballasts, etc.), so the power density of the power supply needs to be further improved. At the same time, in order to reduce the harmonic pollution of the power supply converter to the power grid, there are many relevant international standards, such as IEC61000-3-2, etc., therefore, the power supply not only needs to meet the explicit requirements of the customers (size, weight, appearance, etc.), but also needs to meet the legal requirements of the relevant countries. For the power supply, the most important factor limiting the improvement of its power density is its efficiency (or loss), if the overall conversion efficiency of the power supply is low, its loss will be large (the heat generation will be large), and it is difficult to reduce the size of the power supply, otherwise the heat will be difficult to dissipate; on the contrary, if the efficiency is high, the loss is small (the heat generation is small), and the required heat dissipation space is small. In order to achieve the purpose of improving the power density of the power supply, everyone is trying to improve its efficiency, such as optimizing the core power components (replacing the conventional silicon components with new low-loss silicon carbide components, etc.) and heat dissipation to achieve the purpose of reducing the size. In addition, the application scenarios of the aforementioned adapters and other AC-DC converters usually require the power supply to have the ability of wide range input, therefore, the Buck type power factor correction (PFC) circuit is gradually introduced instead of the traditional Boost type power factor correction (PFC) circuit, so as to obtain more size, efficiency and cost, etc. SUMMARY

[0003] The present application relates to a switching power supply, in particular to a non-isolated hybrid single-phase AC-DC conversion circuit and a control method thereof.

[0004] Technical solution: A non-isolated hybrid single-phase AC-DC conversion circuit, comprising an input AC source, an input filter unit, an AC rectifier unit, a switching conversion unit, an output filter unit, and a control unit, the input end of the input filter unit being connected to the input AC source, the output end of the input filter unit being connected to the AC input end of the AC rectifier unit, the rectification output end of the AC rectifier unit being connected to the input end of the switching conversion unit, the output end of the switching conversion unit being connected to the output filter unit to perform DC output.

[0005] Further, the switching conversion unit comprises a first switch tube Q1, a second switch tube Q2, a first diode D1, a second diode D2, a third diode D3, an inductor L1, the inductor L1 comprising two coupled windings L1-1 and L1-2, a first filter capacitor C1, and a second filter capacitor C2; one end of the first filter capacitor C1 is connected to the positive end of the AC rectifier unit, and the other end is connected to the negative end of the AC rectifier unit; the first switch tube Q1 is placed in series in the rectification power supply positive end loop, the source thereof is connected to the positive end of the AC rectifier unit, and the drain thereof is connected to the cathode of the first diode D1 and one end of the first winding L1-1 of the inductor L1; the source of the second switch tube Q2 is connected to the anode of the second diode D2 and the same-named end of the first winding L1-1 of the inductor L1, and the drain of the second switch tube Q2 is connected to the cathode of the third diode D3 and the negative end of the AC rectifier unit; the cathode of the second diode D2 is connected to the positive end of the second filter capacitor C2, which is also the output positive end of the switching conversion unit, the anode of the third diode D3 is connected to the same-named end of the second winding L1-2 of the inductor L1, and the other end of the second winding L1-2 of the inductor L1 is connected to the negative end of the second filter capacitor C2, which is also the output negative end of the switching conversion unit.

[0006] Further, the first switch tube Q1 in the switching conversion unit can also be placed in series in the rectification power supply negative end loop, the source thereof is connected to the negative end of the AC rectifier unit and the negative end of the first filter capacitor C1, and the drain thereof is connected to the drain of the second switch tube Q2 and the cathode of the third diode D3.

[0007] Further, the first filter capacitor C1 and the second filter capacitor C2 in the switching conversion unit are small-capacity high-frequency non-polarity capacitors.

[0008] Further, the inductor L1 in the switching conversion unit has two coupled windings L1-1 and L1-2 or is equivalent to two coupled windings L1-1 and L1-2, the two windings are highly tightly coupled, have the same number of turns, and have consistent inductance.

[0009] The same-named end of the coupled inductor is only used to facilitate the determination of the connection order of the two inductor windings in the loop, and in the case of not changing the consistency of the series direction of the two coupled inductors, the other end can also be taken as the same-named end at the same time or the same-named end can be marked on the other end.

[0010] Further, the first switch tube Q1 and the second switch tube Q2 are switch tubes with reverse-parallel diodes that can be opened and closed at high frequency, and the reverse-parallel diodes can be integrated or parasitic diodes, or can be separate diodes.

[0011] Further, the input filter unit is a conventional non-polarity capacitor filter or a π-type filter with common-mode inductance, and the output filter unit is a conventional energy storage capacitor filter or a π-type filter with differential-mode inductance.

[0012] A control method of a non-isolated hybrid single-phase AC-DC conversion circuit, comprising the following steps:

[0013] (1) The control unit processes a voltage signal or an external communication command;

[0014] (2) The control unit determines whether the circuit needs to work in a soft-start mode, a boost mode or a buck mode;

[0015] (3) After determining the mode, the control unit applies corresponding driving control signals to the first switch tube Q1 and the second switch tube Q2, and the switching conversion unit works according to the mode.

[0016] Further, when Q1 and Q2 work in the boost mode, Q1 is applied with a driving signal to be fully on all the time, and Q2 is applied with a PWM driving signal to boost; when Q1 and Q2 work in the buck mode, Q1 is applied with a PWM driving signal, and Q2 is not applied with a PWM driving signal or is applied with a closed signal to make Q1 work in the buck mode.

[0017] In the boost mode, the two coupled windings are coupled through the energy storage of the inductors, and when the energy is released, the two inductor windings form a series relationship in the circuit, so as to improve the boost ratio; in the buck mode, the two coupled windings are coupled through the energy storage of the inductors, and when the energy is released, the two inductor windings can form a parallel relationship in the circuit, so as to reduce the buck attenuation ratio, thereby effectively expanding the boost ratio or the buck ratio in a wide range, thereby avoiding the limitation of the maximum duty cycle in the boost mode or the buck mode compared with the traditional buck-type PFC, and effectively changing the loss in the two modes, achieving efficiency improvement and energy saving.

[0018] Further, the control unit comprises an operation processing unit, a signal sampling unit, an auxiliary power supply and a driving unit.

[0019] Beneficial effects: compared with the prior art, the beneficial effects of the present application are that: (1) by changing the switching conversion unit and controlling the switching conversion unit, the voltage stabilizing circuit realizes a wider range of voltage boosting (larger gain) to output stable voltage; (2) by changing the switching conversion unit and controlling the switching conversion unit, the voltage stabilizing circuit realizes a smaller voltage reduction (attenuation ratio), so that a larger duty cycle conduction can be realized, thereby reducing the inductive freewheeling ripple current, reducing the freewheeling loss, and realizing high efficiency; (3) by using the wide range of operation of the switching conversion unit, the conversion circuit is smaller in size and higher in cost performance compared with the traditional two-stage voltage stabilizer. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural block diagram of the present application;

[0021] Figure 2 is Figure 1 a circuit schematic diagram of the switching conversion unit in the middle;

[0022] Figure 3 is Figure 1 a structural block diagram of the control unit;

[0023] Figure 4 is a known schematic diagram of a traditional series hybrid PFC;

[0024] Figure 5 is a schematic diagram of interval division of a mixed operation mode;

[0025] Figure 6 is Figure 2 a schematic diagram of the conversion unit of the voltage reduction mode of operation;

[0026] Figure 7 is Figure 2 a schematic diagram of the conversion unit of the voltage reduction mode of operation. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be further introduced below in combination with specific embodiments and the drawings of the specification.

[0028] As shown in Figure 1 , the present application comprises a single-phase AC source, an input filter unit, an AC rectifier unit, a switching conversion unit, an output filter unit, and a control unit. The input end of the input filter unit is connected to the input AC source, the output end of the input filter unit is connected to the AC input end of the AC rectifier unit, the rectification output end of the AC rectifier unit is connected to the input end of the switching conversion unit, and the output end of the switching conversion unit is connected to the output filter capacitor and the load or equivalent load converter.

[0029] As shown in Figure 2As shown, the switching conversion unit includes the first to second switching transistors (Q1 to Q2), the first to third diodes (D1 to D3), the inductor L1 with two coupling windings (L1-1, L1-2), and the first to second filter capacitors (C1 to C2). One end of the first filter capacitor C1 is connected to the positive terminal of the AC rectifier unit, and the other end is connected to the negative terminal of the AC rectifier unit; the source of the first switch Q1 is connected to the positive terminal of the AC rectifier unit, and the drain of the first switch Q1 is connected to the cathode of the first diode D1 and one end of the first winding (L1-1) of the inductor L1; the source of the second switch Q2 is connected to the anode of the second diode D2 and the same-name terminal of the first winding (L1-1) of the inductor L1, and the drain of the second switch Q2 is connected to the cathode of the third diode D3 and the negative terminal of the AC rectifier unit; the cathode of the second diode D2 is connected to the positive terminal of the second filter capacitor C2, which is also the positive output terminal of the switching conversion unit; the anode of the third diode D3 is connected to the same-name terminal of the second winding (L1-2) of the inductor L1, and the other end of the second winding (L1-2) of the inductor L1 is connected to the negative terminal of the second filter capacitor C2, which is also the negative output terminal of the switching conversion unit.

[0030] like Figure 2 As shown, the first and second filter capacitors in the switching converter unit are small-capacity, high-frequency, non-polar capacitors; the two coupled windings (L1-1, L1-2) of inductor L1 are highly tightly coupled, with the same number of turns and similar inductance. The first and second switching transistors are MOS, IGBT, or other switching transistors with anti-parallel diodes that can be turned on and off at high frequencies. The anti-parallel diode of the switching transistor can be an integrated or parasitic diode, or an externally added separate diode.

[0031] like Figure 3 As shown, the control unit includes a processing unit, a signal sampling unit, an auxiliary power supply, and a drive unit. The control unit may also include a communication unit for external communication.

[0032] Figure 4 A schematic diagram of a known traditional series-type hybrid PFC;

[0033] This invention also includes a control method for a non-isolated single-phase AC voltage regulator converter, comprising the following steps:

[0034] 1) The control unit processes voltage signals or external communication commands;

[0035] 2) The control unit determines whether the converter needs to operate in soft-start mode, boost mode, or buck mode; such as... Figure 5The shown is a mixed mode working interval diagram. When the half-wave rectified output voltage is greater than the set output voltage reference, it needs to work in buck mode; when the half-wave rectified output voltage is less than the set output voltage reference, it needs to work in boost mode; when the output voltage is zero or much lower than the half-wave rectified output voltage at the moment of starting, it must perform soft start mode to gradually raise the output voltage to the normal output voltage.

[0036] 3) The control unit controls the first switch tube Q1 and the second switch tube Q2 in the switching conversion unit to work in a mode. That is, the control unit applies a driving control signal to the first switch Q1 and the second switch Q2 of the switching conversion unit, so that the switching conversion unit works in an equivalent boost circuit mode or an equivalent buck circuit mode.

[0037] When it is determined to be in the boost interval, Q1 and Q2 work in the boost mode, that is, Q1 is applied with a driving signal to be fully on all the time, and Q2 is applied with a PWM driving signal to make Q2 boost;

[0038] When it is determined to be in the buck interval, Q1 and Q2 work in the buck mode, that is, Q1 is applied with a PWM driving signal, and Q2 is not applied with a PWM driving signal or is applied with a closed signal to make Q1 buck;

[0039] In the boost mode, the two coupled windings are coupled through the energy storage of the inductor, and in the energy release, the two inductor windings form a series relationship in the circuit, so as to improve the boost ratio. In the buck mode, the two coupled windings are coupled through the energy storage of the inductor, and in the energy release, the two inductor windings can form a parallel relationship in the circuit, so as to reduce the buck ratio, thereby effectively expanding the boost ratio or the buck ratio in a wide range, thereby avoiding the limitation of the maximum duty cycle in the boost mode or the buck mode compared with the traditional buck PFC, and effectively changing the loss in the two modes, realizing the efficiency improvement and energy saving.

[0040] The following takes the circuit of example one as an example to further illustrate the above control method:

[0041] The control unit obtains the voltage signal sampled by the sampling circuit or the command obtained from the external communication through the program operation in the operation processor unit. When the reference Figure 5 is determined to work in the buck mode according to the basic principle, as Figure 6(a), the second switch Q2 is a freewheeling function, can be regarded as a freewheeling diode without the need to apply a drive signal, or in its anti-parallel diode conduction time to apply a drive signal to do synchronous rectification work; the first switch Q1 is a step-down switch, need to apply a PWM signal, so that it works as a step-down conversion. At this time, according to the foregoing about the characteristics of L1 inductance can be set L1-1 and L1-2 equal, inductance L, rectified input voltage is higher than the conversion output part of the then respectively in L1-1 and L1-2 step-down energy storage, electromotive force direction as shown in Figure 6 (a), the current from the rectifier positive terminal through Q1, L1-1, D2, output equivalent load back to L1-2, D3, and then back to the rectifier negative terminal. When the drive signal of Q1 is off, the original connection of Q1 is disconnected, due to the effect of inductance L1, the current cannot be reversed, then through the available channel freewheeling, so D1, biased by L1-1 and conductive freewheeling, D3, Q2, biased by L1-2 and conductive freewheeling, instead of rectifier power end and then form a complete freewheeling channel; the related circuit as shown in Figure 6 (b). Assuming that the load is sufficient to make the inductance current continuous or critical, from the above analysis, when energy storage, duty cycle D, Vl1-1+Vl 1-2 = Vin-Vo = 2Vl, when the freewheeling energy release, duty cycle 1-D, Vl1 -1 = Vl 1-2 = Vo, according to the principle of volt-second balance (Vin-Vo) * DT / 2 = Vo * (1-D) * T, so Vo = Vin * D / (2-D), since 1 > D > 0, according to which D / (2-D) < D, so in step-down mode, compared with the traditional circuit, it needs a larger duty cycle to obtain the same voltage, that is, the step-down attenuation coefficient is smaller, effectively increasing the duty cycle, reducing the freewheeling time, while also helps to reduce the current ripple.

[0042] When the basic principles of reference Figure 5 determine that the circuit needs to work in boost mode, as shown in Figure 7 (a), the first switch Q1 must be a constant conduction, at this time to apply a direct signal, can be regarded as a wire; the second switch Q2 is a boost switch, need to apply a PWM signal, so that it works as a boost conversion. At this time, according to the foregoing about the characteristics of L1 inductance can be set L1-1 and L1-2 equal, inductance L, rectified input voltage is directly added to L1-1 (can be regarded as L1) to store energy, electromotive force direction as shown in Figure 7As shown in (a), the current flows from the positive terminal of the rectifier through Q1, L1-1, Q2, and then back to the negative terminal. When the drive signal of Q2 is turned off, the original connection of Q2 is disconnected. Due to the effect of inductor L1, the current cannot suddenly reverse. However, L1-1 and L1-2 are tightly coupled, so both L1-1 and L1-2 have a back electromotive force. Therefore, D2 and D3 are biased by the common bias voltage of L1-1 and L1-2 and conduct freewheeling current. The current flows from the positive terminal of the rectifier through Q1, L1-1, D2, and the output equivalent load returns to L1-2, D3, and then back to the negative terminal of the rectifier. The relevant energy release freewheeling circuit is as follows: Figure 7 As shown in (b). Assuming the load is sufficient to make the inductor current continuous or critical, it can be seen from the above analysis that during energy storage, the duty cycle is D, and Vl 1-1 =Vin=Vl, when the freewheeling energy is released, the duty cycle is 1-D, Vin+(Vl1-1+Vl1-2)=Vo, Vl1-1=Vl1-2. According to the volt-second balance theorem, Vin*DT=(Vo-Vin)*(1-D)*T / 2, so Vo=Vin*(1+D) / (1-D). Since 1>D>0, it can be known that (1+D) / (1-D)>1 / (1-D). Therefore, in boost mode, compared with the traditional circuit, only a slightly smaller duty cycle is needed to obtain the same voltage, that is, effectively increasing the boost ratio, reducing the energy storage time, and also expanding the boost range.

[0043] Therefore, as Figure 5 As shown, based on the operating mode range and the aforementioned working principle, the controller modulates the duty cycle to make the current and voltage in phase, thereby achieving power factor correction (PFC). It then continuously controls and operates according to the voltage's operating frequency. The effect of this control method is consistent with the well-known series hybrid PFC circuit, thus achieving in-phase buck conversion of the AC input voltage.

[0044] If the output voltage is zero or significantly lower than the half-wave rectified output voltage at power-on, a gradual soft start must be performed to gradually raise the output voltage to the normal output voltage. Its specific working principle is the same as the single-phase version described above. It simply compares the instantaneous output voltage with the input rectified half-wave voltage; if it's higher, it operates in boost mode; if it's lower, it operates in buck mode. Therefore... Figure 6 , Figure 7 The specific working principles will not be explained in detail here.

[0045] In summary, the control unit of the application controls the switch tube of the switch conversion unit to turn on and turn off according to the pre-setting or the judgment of other voltage and current signals outside, and the AC circuit can work in three working modes of step-up, step-down or soft start of starting, which can meet the use of small and medium power electronic products in full voltage range and obtain better cost performance.

[0046] The preferred embodiments of the application have been described above with the preferred embodiments, but not for limiting the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A non-isolated hybrid single-phase AC / DC converter circuit, characterized in that: It includes an input AC source, an input filter unit, an AC rectification unit, a switching conversion unit, an output filter unit, and a control unit. The input terminal of the input filter unit is connected to the input AC source, the output terminal of the input filter unit is connected to the AC input terminal of the AC rectification unit, the rectified output terminal of the AC rectification unit is connected to the input terminal of the switching conversion unit, and the output terminal of the switching conversion unit is connected to the output filter unit to output DC. The switching conversion unit includes a first switching transistor Q1, a second switching transistor Q2, a first diode D1, a second diode D2, a third diode D3, an inductor L1, a first filter capacitor C1, and a second filter capacitor C2. The inductor L1 includes two coupled windings L1-1 and L1-2. One end of the first filter capacitor C1 is connected to the positive terminal of the AC rectifier unit, and the other end is connected to the negative terminal of the AC rectifier unit. The first switching transistor Q1 is connected in series in the positive terminal circuit of the rectifier power supply, with its drain connected to the positive terminal of the AC rectifier unit and its source connected to the cathode of the first diode D1 and the opposite-named terminal of the first winding L1-1 of the inductor L1. The anode of the first diode D1 is connected to the opposite-named terminal of the second winding L1-2. The drain of the second switching transistor Q2 is connected to the anode of the second diode D2 and the same-name terminal of the first winding L1-1 of the inductor L1. The source of the second switching transistor Q2 is connected to the cathode of the third diode D3 and the negative terminal of the AC rectifier unit. The cathode of the second diode D2 is connected to the positive terminal of the second filter capacitor C2, which is also the positive output terminal of the switching conversion unit. The anode of the third diode D3 is connected to the same-name terminal of the second winding L1-2 of the inductor L1. The opposite-name terminal of the second winding L1-2 of the inductor L1 is connected to the negative terminal of the second filter capacitor C2, which is also the negative output terminal of the switching conversion unit.

2. The non-isolated hybrid single-phase AC / DC converter circuit according to claim 1, characterized in that: The first switching transistor Q1 in the switching conversion unit can also be placed in series in the negative terminal circuit of the rectifier power supply, with its source connected to the negative terminal of the AC rectifier unit and the negative terminal of the first filter capacitor C1, and its drain connected to the source of the second switching transistor Q2 and the cathode of the third diode D3.

3. The non-isolated hybrid single-phase AC / DC converter circuit according to claim 1, characterized in that: The first filter capacitor C1 and the second filter capacitor C2 in the switching conversion unit are small-capacity, high-frequency, non-polarized capacitors.

4. The non-isolated hybrid single-phase AC / DC converter circuit according to claim 1, characterized in that: The inductor L1 in the switching conversion unit has two coupled windings L1-1 and L1-2, or equivalently, two coupled windings L1-1 and L1-2. These two windings are highly tightly coupled and have the same number of turns.

5. The non-isolated hybrid single-phase AC / DC converter circuit according to claim 1, characterized in that: The first switch Q1 and the second switch Q2 are high-frequency switching transistors with anti-parallel diodes. The anti-parallel diodes can be integrated or parasitic diodes, or they can be external separate diodes.

6. The non-isolated hybrid single-phase AC / DC converter circuit according to claim 1, characterized in that: The input filtering unit is a conventional non-polarized capacitor filter or a π-type filter with a common-mode inductor, and the output filtering unit is a conventional energy storage capacitor filter or a π-type filter with a differential-mode inductor.

7. A control method for a non-isolated hybrid single-phase AC / DC converter circuit according to claim 1, characterized in that, Includes the following steps: (1) The control unit processes voltage signals or external communication commands; (2) The control unit determines whether the circuit needs to operate in soft-start mode, boost mode or buck mode; (3) After determining the mode, the control unit applies the corresponding drive control signal to the first switch Q1 and the second switch Q2, and the switching unit works according to the mode.

8. A control method for a non-isolated hybrid single-phase AC / DC converter circuit according to claim 7, characterized in that, When Q1 and Q2 are operating in boost mode, Q1 is always fully turned on by the applied drive signal, and Q2 is driven by the applied PWM drive signal to boost the voltage of Q2. When Q1 and Q2 are operating in buck mode, Q1 is given a PWM drive signal, while Q2 is not given a PWM drive signal or is given a turn-off signal, so that Q1 performs buck operation.

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