Active switch large-proportion boost circuit and voltage converter

Abstract

The invention relates to the technical field of voltage conversion, and discloses an active switch large-proportion boost circuit and a voltage converter, the active switch large-proportion boost circuit comprises a first winding, a second winding, an active switch, a first capacitor and a second capacitor, a synonym terminal of the first winding is connected with a voltage anode input end, and a dotted terminal of the first winding is connected with an output end of the active switch; the enabling end of the active switch is connected with a driving signal source, the input end of the active switch is connected with a grounding end, the second winding and the first winding are arranged in a matched mode so that the second winding can generate induction voltage based on magnetic flux change generated by the first winding, and the dotted terminal of the second winding is connected with the voltage positive electrode output end and one end of the first capacitor. The other end of the first capacitor is connected with the synonym end of the second winding, the output end of the active switch and one end of the second capacitor, the other end of the second capacitor is connected with the grounding end, and large-proportion high-gain boosting can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage conversion, and in particular to an active switch large-ratio boost circuit and a voltage converter. Background Art

[0002] At present, the existing non-isolated boost circuits mostly use Boost boost circuits, buck-boost boost-boost circuits, etc. Among them, the Boost boost circuit and the buck-boost boost-boost circuit both achieve boost by controlling the on and off of the MOSFET. When the MOSFET is turned on, the energy storage inductor stores energy. When the MOSFET is turned off, the energy storage inductor releases energy through the freewheeling diode to achieve boost.

[0003] Since the existing boost circuit discharges only through one energy storage inductor when releasing energy, the boost gain is low and cannot meet the large-proportion high-gain boost demand. Summary of the invention

[0004] In view of this, the present invention provides an active switch large-ratio boost circuit and a voltage converter to solve or partially solve the technical problem of low boost gain in the prior art.

[0005] The technical solution proposed by the present invention is as follows: In a first aspect, the present invention provides an active switch large-proportion boost circuit, comprising a first winding, a second winding, an active switch, a first capacitor and a second capacitor, wherein the opposite-name end of the first winding is connected to a voltage positive input end, the same-name end of the first winding is connected to an output end of the active switch, an enable end of the active switch is connected to a drive signal source, the input end of the active switch is connected to a ground end, the second winding and the first winding are cooperatively arranged so that the second winding generates an induced voltage based on a change in magnetic flux generated by the first winding, the same-name end of the second winding is respectively connected to a voltage positive output end and one end of the first capacitor, the other end of the first capacitor is respectively connected to the opposite-name end of the second winding, the output end of the active switch and one end of the second capacitor, the other end of the second capacitor is connected to a ground end, and the active switch large-proportion boost circuit further comprises a first polarity capacitor, the positive electrode of the first polarity capacitor is connected to the voltage positive input end, and the negative electrode of the first polarity capacitor is connected to the ground end.

[0006] An active switch large-proportion boost circuit of the present invention outputs a drive signal through a drive signal source to control the on and off of the active switch. When the active switch is on, the second winding is cut off and energy is accumulated through the first winding. When the active switch is off, energy is released through the first winding and the second winding, and the output voltage is the sum of the voltage across the first capacitor and the voltage across the second capacitor. A boost effect with a gain greater than 50 can be achieved, realizing a large-proportion high-gain boost.

[0007] At the same time, a first polarity capacitor is added. The addition of the first polarity capacitor helps to stabilize the input voltage and reduce voltage fluctuations, thereby improving the stability and reliability of the circuit.

[0008] Furthermore, the active switch large-ratio boost circuit also includes a first diode, the anode of the first diode is connected to the same-name end of the second winding, and the cathode of the first diode is respectively connected to the voltage positive output end and one end of the first capacitor.

[0009] In this manner, by adding the first diode, current is prevented from flowing from the first capacitor to the second winding, thereby improving circuit stability.

[0010] Furthermore, the active switch large-ratio boost circuit also includes a second diode, the anode of the second diode is connected to the same-name end of the first winding, and the cathode of the second diode is connected to the connection node between the first capacitor and the second capacitor.

[0011] In this manner, by adding the second diode, current is prevented from flowing from the second capacitor to the first winding, thereby improving circuit stability.

[0012] Furthermore, the active switch is a MOS tube, a gate of the MOS tube is connected to a driving signal source, a source of the MOS tube is connected to a ground terminal, and a drain of the MOS tube is connected to a same-name terminal of the first winding.

[0013] In this way, using MOS tubes as active switches can provide fast switching control, reduce switching losses, and improve circuit efficiency and response speed.

[0014] Furthermore, the MOS tube is an N-channel MOS tube.

[0015] In this method, high-level conduction is achieved by using an N-channel MOS tube as an active switch.

[0016] Furthermore, the driving signal source is a pulse width modulation signal source for outputting a pulse width modulation signal.

[0017] In this manner, the use of a pulse width modulation signal can accurately control the switching of the MOS tube, thereby accurately controlling the output voltage.

[0018] Furthermore, the calculation formula for the number of turns of the first winding is: Np=Lp×Ip÷Ae÷△B; Ip=Vinmin×Dmax÷Lp÷fs; Lp=(Vinmin×Dmax)²÷2÷Pin÷fs; Among them, Np is the number of turns of the first winding, Lp is the inductance of the first winding, Ip is the current flowing through the first winding, Ae is the cross-sectional area of ​​the magnetic circuit of the first winding core, △B is the change in the magnetic flux density of the first winding core, Vinmin is the minimum value of the voltage input to the positive voltage input terminal, Dmax is the maximum value of the duty cycle of the active switch, fs is the set switching frequency, and Pin is the estimated input power.

[0019] In this way, the number of turns of the first winding is calculated by the minimum input voltage, the maximum duty cycle, the switching frequency and the estimated input power, so as to ensure that the energy stored in the inductor during the switch-on period matches the required output voltage and achieve efficient voltage conversion.

[0020] In a second aspect, the present invention provides a voltage converter, comprising an active switch large-ratio boost circuit as described in any one of the first aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly express the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 is a circuit block diagram of an active switch large-ratio boost circuit according to an embodiment of the present invention; Figure 2 Schematic diagram of waveforms of various voltages and currents in an embodiment of the present invention; Description of reference numerals: D1, first diode; D2, second diode; C1, first capacitor; C2, second capacitor; Q1, active switch; CE1, first polarity capacitor; CE2, second polarity capacitor; Vin+, positive voltage input terminal; Vo+, positive voltage output terminal; GND- ground terminal. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two elements, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] At present, the existing non-isolated boost circuit has a low boost gain because it only discharges through one energy storage inductor and cannot meet the needs of large-proportion high-gain boost. In addition, the energy storage inductor has leakage inductance, and the leakage inductance energy will oscillate with the parasitic capacitance of the transformer and the parasitic capacitance of the active switch, generating voltage spikes and increasing the voltage stress of the active switch. An active switch that can withstand larger voltage stress is required to meet the circuit requirements.

[0028] In view of this, an embodiment of the present invention provides an active switch large-proportion boost circuit, which can achieve large-proportion high-gain boost while effectively utilizing leakage inductance energy. The voltage stress of the active switch will not be affected by the leakage inductance peak voltage, and the selection cost is low.

[0029] like Figure 1 As shown, the active switch large-proportion boost circuit of the embodiment of the present invention includes: a first winding, a second winding, an active switch Q1, a first capacitor C1 and a second capacitor C2, the opposite-name end of the first winding is connected to the voltage positive input terminal Vin+, the same-name end of the first winding is connected to the output end of the active switch Q1, the enable end of the active switch Q1 is connected to the drive signal source, the input end of the active switch Q1 is connected to the ground terminal GND, the second winding and the first winding are arranged in cooperation so that the second winding generates an induced voltage based on the change of magnetic flux generated by the first winding, the same-name end of the second winding is respectively connected to the voltage positive output terminal Vo+ and one end of the first capacitor C1, the other end of the first capacitor C1 is respectively connected to the opposite-name end of the second winding, the output end of the active switch Q1 and one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the ground terminal GND.

[0030] Specifically, the voltage positive input terminal Vin+ is used to provide an input voltage Vin, and the input voltage Vin is used to provide initial power to the active switch large-ratio boost circuit.

[0031] The first winding and the second winding are the primary winding and the secondary winding of a transformer. The first winding and the second winding act as energy storage inductors in the circuit, and using the principle of electromagnetic induction, the change in the magnetic flux of the first winding will cause the second winding to generate a corresponding induced voltage.

[0032] The same-named ends of the first winding and the same-named ends of the second winding are Figure 1 The end with a dot in the middle. The opposite end is the heteronymous end.

[0033] The number of turns of the first winding is Np, the number of turns of the second winding is Ns, and Ns:Np=n.

[0034] The active switch Q1 can be a semiconductor switch such as a MOS tube or a triode, and the enable terminal is connected to a driving signal source, and the driving signal source outputs a control signal to control the active switch Q1 to be turned on and off.

[0035] Specifically, the driving signal source is a pulse width modulation signal source for outputting a pulse width modulation signal (PWM). By using the pulse width modulation signal, the on and off time of the active switch Q1 can be precisely controlled.

[0036] The first capacitor C1 and the second capacitor C2 mainly play the role of energy storage. The output voltage Vo of the active switch large-ratio boost circuit is the sum of the voltage Vc1 across the first capacitor C1 and the voltage Vc2 across the second capacitor C2, that is, Vo=Vc1+Vc2.

[0037] The active switch large-proportion boost circuit of the embodiment of the present invention combines the converter boost and the flyback converter, shares the energy storage links of the two converters, and connects the energy release links in series, thereby achieving a large-proportion voltage boost and effectively utilizing the leakage inductance of the first winding, thereby improving the conversion efficiency compared with flyback, because the leakage inductance energy is utilized and will not oscillate with the parasitic capacitance of the transformer and the parasitic capacitance of the active switch Q1, so there is no voltage spike caused by oscillation, thereby reducing the voltage stress of the active switch Q1.

[0038] The working process of the active switch large-ratio boost circuit of the embodiment of the present invention is as follows: First, the turns ratio of the first winding and the second winding is n=Np÷Ns, and the voltage Vc1 across the first capacitor C1 is coupled to the voltage of the first winding through the transformer and recorded as the reflected voltage Vor, where Vor=Vc1×n.

[0039] In the active switch large-proportion boost circuit of the embodiment of the present invention, according to its connection relationship, the output voltage Vo=Vc1+Vc2, under the output steady-state condition, the output rated load, because Vc1 is completely working in the flyback state, the input voltage Vin is defined to take the minimum value, that is, when the input voltage is Vinmin, the converter works in a critical state.

[0040] The on time of the active switch Q1 is Ton, and the off time is Toff, Ton+Toff=T, T is the period corresponding to the fixed switching frequency. The duty cycle D of the active switch Q1=Ton÷T. When the active switch large-ratio boost circuit of the embodiment of the present invention works in a steady state, Vinmin×Ton=Vor×Toff can be obtained from the volt-second balance of the first winding.

[0041] After sorting, we can get the duty cycle D=Vor÷(Vinmin+Vor), where D is less than 0.5 and is a custom parameter. The formula is converted to Vor=Vinmin×D÷(1-D), and then the gain of Vc1 is obtained, Vc1÷Vinmin=D÷(1-D)×n. At this time, Vc2=Vc1×n+Vinmin+(Lk×Ip÷dt). Among them, Lk×Ip÷dt is the voltage generated by the leakage inductance energy, Lp is the inductance of the first winding, Ip is the current flowing through the first winding, and Lk is the leakage inductance of the inductance Lp of the first winding.

[0042] The above analysis fully demonstrates the characteristics of the active switch large-ratio boost circuit of the embodiment of the present invention that utilizes leakage inductance energy. However, when actually discussing the output voltage gain, the gain generated by the leakage inductance is very small and is ignored in the calculation. That is, Vc2≈Vc1×n+Vinmin. The gain of Vc2 Vc2÷Vinmin=Vc1×n÷Vinmin+1. Since the output voltage Vo=Vc1+Vc2, the active switch large-ratio boost circuit of the embodiment of the present invention can achieve a large-ratio high-gain boost.

[0043] An active switch large-proportion boost circuit of the present invention outputs a drive signal through a drive signal source to control the on and off of an active switch Q1. When the active switch Q1 is on, the second winding is cut off and energy is accumulated through the first winding. When the active switch Q1 is off, energy is released through the first winding and the second winding. The output voltage is the sum of the voltage across the first capacitor C1 and the voltage across the second capacitor C2. A boost effect with a gain greater than 50 can be achieved, thereby realizing a large-proportion high-gain boost.

[0044] In addition, the leakage inductance of the first winding is effectively utilized through the second capacitor C2 and the first capacitor C1, thereby improving the conversion efficiency. Because the leakage inductance energy is utilized, it will not oscillate with the parasitic capacitance of the transformer and the parasitic capacitance of the active switch Q1, so there is no voltage spike caused by oscillation, thereby reducing the voltage stress of the active switch Q1. The voltage stress of the active switch Q1 will not be affected by the leakage inductance spike voltage, and the selection cost is low.

[0045] In some embodiments, the active switch large-proportional boost circuit also includes a first polarity capacitor CE1, the positive electrode of the first polarity capacitor CE1 is connected to the voltage positive input terminal Vin+, and the negative electrode of the first polarity capacitor CE1 is connected to the ground terminal GND. The addition of the first polarity capacitor CE1 helps to stabilize the input voltage and reduce voltage fluctuations. In the circuit, the input voltage may fluctuate due to power supply fluctuations or load changes. The first polarity capacitor CE1 can absorb these fluctuations and provide a more stable voltage input. In addition, in the circuit, voltage spikes may occur due to various reasons (such as power switching, etc.). The first polarity capacitor CE1 can absorb these spikes to protect sensitive components in the circuit from damage.

[0046] In this manner, a first polarity capacitor CE1 is added. The addition of the first polarity capacitor CE1 helps to stabilize the input voltage and reduce voltage fluctuations, thereby improving the stability and reliability of the circuit.

[0047] Furthermore, the output end of the active switch large-ratio boost circuit is connected to the second polarity capacitor CE2, and the second polarity capacitor CE2 is used as a load.

[0048] In some embodiments, the active switch large-ratio boost circuit further includes a first diode D1, the anode of the first diode D1 is connected to the same-name end of the second winding, and the cathode of the first diode D1 is respectively connected to the voltage positive output terminal Vo+ and one end of the first capacitor C1.

[0049] Specifically, when the active switch Q1 is turned on, the first diode D1 is turned off, the second winding does not store energy, and energy is stored through the first winding. When the active switch Q1 is turned off, the first diode D1 is turned on, and energy can be released through the second winding and the first diode D1.

[0050] The addition of the first diode D1 ensures that when the active switch Q1 is turned on, the current does not flow from the first capacitor C1 to the second winding, but accumulates energy through the first winding. This design prevents ineffective energy backflow and improves the efficiency of the circuit.

[0051] In addition, the design of the first diode D1 enables the circuit to adapt to different load conditions. Whether the load is light or heavy, the first diode D1 can ensure the stable operation of the circuit, which is particularly important for a power supply system that needs to work stably under different conditions.

[0052] In this manner, by adding the first diode D1 , current is prevented from flowing from the first capacitor C1 to the second winding, thereby improving circuit stability.

[0053] Furthermore, the active switch large-ratio boost circuit further includes a second diode D2, the anode of the second diode D2 is connected to the same-name end of the first winding, and the cathode of the second diode D2 is connected to the connection node between the first capacitor C1 and the second capacitor C2.

[0054] Specifically, when the active switch Q1 is turned on, the second diode D2 is turned off, and energy is stored through the first winding. When the active switch Q1 is turned off, the second diode D2 is turned on, and energy can be released through the first winding and the second diode D2, and at the same time, energy is also released through the second winding and the first diode D1.

[0055] The addition of the second diode D2 ensures that when the active switch Q1 is turned on, the current does not flow from the second capacitor C2 to the first winding, but accumulates energy through the first winding. This design prevents ineffective energy backflow and improves the efficiency of the circuit.

[0056] In addition, the design of the second diode D2 enables the circuit to adapt to different load conditions. Whether the load is light or heavy, the second diode D2 can ensure the stable operation of the circuit, which is particularly important for power supply systems that need to work stably under different conditions.

[0057] In this manner, by adding the second diode D2, current is prevented from flowing from the second capacitor C2 to the first winding, thereby improving circuit stability.

[0058] In some embodiments, the active switch Q1 is a MOS tube, a gate of the MOS tube is connected to a driving signal source, a source of the MOS tube is connected to a ground terminal GND, and a drain of the MOS tube is connected to a same-name terminal of the first winding.

[0059] By using a MOS tube as the active switch Q1, fast switching control can be provided, switching losses can be reduced, and the efficiency and response speed of the circuit can be improved.

[0060] Furthermore, the MOS transistor is an N-channel MOS transistor. By using the N-channel MOS transistor as the active switch Q1, high-level conduction is achieved.

[0061] In some embodiments, the number of turns of the first winding is calculated as: Np=Lp×Ip÷Ae÷△B; Ip=Vinmin×Dmax÷Lp÷fs; Lp=(Vinmin×Dmax)²÷2÷Pin÷fs; Among them, Np is the number of turns of the first winding, Lp is the inductance of the first winding, Ip is the current flowing through the first winding, Ae is the cross-sectional area of ​​the magnetic path of the first winding core, △B is the change in the magnetic flux density of the first winding core, Vinmin is the minimum value of the voltage input to the positive voltage input terminal Vin+, Dmax is the maximum value of the duty cycle of the active switch Q1, fs is the set switching frequency, and Pin is the estimated input power.

[0062] Specifically, the driving signal is a pulse width modulation signal. In one example, its waveform is as follows: Figure 2 As shown in waveform 1, the duty cycle is D. Correspondingly, waveform 2 is the voltage waveform of the active switch Q1, waveform 3 is the current waveform of the first winding, waveform 4 is the voltage waveform of the first diode D1, waveform 5 is the current waveform of the first diode D1, waveform 6 is the voltage waveform of the second diode D2, and waveform 7 is the current waveform of the second diode D2.

[0063] When Vinmin, the active switch large-proportion boost circuit works in the critical mode, and Vinmin=Lp×Ip÷ton, ton=fs÷Dmax can be obtained, which can be simplified as follows: Ip=Vinmin×Dmax÷Lp÷fs (Formula 1); From the critical mode, we can also get: Pin=Lp×Ip²×fs÷2 (Formula 2); Substituting (Formula 1) into (Formula 2) and simplifying it, we can get: Lp = (Vinmin × Dmax)² ÷ 2 ÷ Pin ÷ fs (Formula 3); Where Vinmin and Pin are known parameters before design, Dmax and fs are self-set parameters, and Lp can be calculated by substituting all parameters into (Formula 3).

[0064] The peak current calculation formula of the first winding is: Ip=Vinmin×Dmax÷Lp÷fs, all parameters are known quantities, and Ip can be calculated by substituting them in. The number of primary turns Np, after selecting a transformer, Np=Lp×Ip÷Ae÷△B. Lp and Ip are known quantities, Ae is the inherent parameter of the transformer, △B is the set parameter, and Np can be calculated.

[0065] In this way, the number of turns of the first winding is calculated by the minimum input voltage, the maximum duty cycle, the switching frequency and the estimated input power, so as to ensure that the energy stored in the inductor during the switch-on period matches the required output voltage and achieve efficient voltage conversion.

[0066] In the active switch large-proportion boost circuit of the embodiment of the present invention, when the active switch Q1 is turned on, the second winding is turned off, and energy is accumulated through the first winding. When the active switch Q1 is turned off, energy is released through the first winding and the second winding, and the output voltage is the sum of the voltage across the first capacitor C1 and the voltage across the second capacitor C2. A boosting effect with a gain greater than 50 can be achieved, and a large-proportion high-gain boost can be realized. The battery voltage can be boosted to a peak voltage covering the voltage of the power grids in most countries and regions.

[0067] And the conversion efficiency is high, the stress of the active switch Q1 is well controlled, the selection cost of the active switch Q1 is reduced, and a lower-cost P-channel MOS tube can be used as the active switch Q1 to reduce the circuit cost.

[0068] The present invention further provides a voltage converter, comprising the active switch large-ratio boost circuit as in any of the above embodiments.

[0069] Although example embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions and modifications to these embodiments without departing from the spirit and defined scope of the present invention, and such modifications and variations are all within the defined scope.

Claims

1. An active switch large-ratio boost circuit, characterized in that: The invention comprises a first winding, a second winding, an active switch, a first capacitor and a second capacitor, wherein the opposite-name end of the first winding is connected to the positive voltage input end, the same-name end of the first winding is connected to the output end of the active switch, the enable end of the active switch is connected to the driving signal source, the input end of the active switch is connected to the ground end, the second winding and the first winding are arranged in cooperation so that the second winding generates an induced voltage based on the change of magnetic flux generated by the first winding, the same-name end of the second winding is respectively connected to the positive voltage output end and one end of the first capacitor, the other end of the first capacitor is respectively connected to the opposite-name end of the second winding, the output end of the active switch and one end of the second capacitor, and the other end of the second capacitor is connected to the ground end. The active switch large-proportion boost circuit also comprises a first polarity capacitor, the positive electrode of the first polarity capacitor is connected to the positive voltage input end, and the negative electrode of the first polarity capacitor is connected to the ground end.

2. The active switch large ratio boost circuit according to claim 1, characterized in that: The active switch large-ratio boost circuit also includes a first diode, the anode of the first diode is connected to the same-name end of the second winding, and the cathode of the first diode is respectively connected to the voltage positive output end and one end of the first capacitor.

3. The active switch large ratio boost circuit according to claim 1, characterized in that: The active switch large-ratio boost circuit also includes a second diode, the anode of the second diode is connected to the same-name end of the first winding, and the cathode of the second diode is connected to the connection node between the first capacitor and the second capacitor.

4. The active switch large ratio boost circuit according to claim 1, characterized in that: The active switch is a MOS tube, a gate of the MOS tube is connected to a driving signal source, a source of the MOS tube is connected to a ground terminal, and a drain of the MOS tube is connected to a same-name terminal of the first winding.

5. The active switch large ratio boost circuit according to claim 4, characterized in that: The MOS tube is an N-channel MOS tube.

6. The active switch large ratio boost circuit according to claim 1, characterized in that: The driving signal source is a pulse width modulation signal source, which is used to output a pulse width modulation signal.

7. The active switch large ratio boost circuit according to claim 1, characterized in that: The calculation formula for the number of turns of the first winding is: Np=Lp×Ip÷Ae÷△B; Ip=Vinmin×Dmax÷Lp÷fs; Lp=(Vinmin×Dmax)²÷2÷Pin÷fs; Among them, Np is the number of turns of the first winding, Lp is the inductance of the first winding, Ip is the current flowing through the first winding, Ae is the cross-sectional area of ​​the magnetic circuit of the first winding core, △B is the change in the magnetic flux density of the first winding core, Vinmin is the minimum value of the voltage input to the positive voltage input terminal, Dmax is the maximum value of the duty cycle of the active switch, fs is the set switching frequency, and Pin is the estimated input power.

8. A voltage converter, characterized in that: The invention comprises the active switch large ratio boost circuit as claimed in any one of claims 1 to 7.

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