A pure sine wave electronic inverter

Abstract

The utility model discloses a kind of pure sine wave electronic inverters, comprising: boost conversion circuit: for the input DC voltage boost to 220V DC voltage;Voltage stabilizing step-down circuit: for the input DC voltage conversion 5V DC voltage;Signal source module: for generating the square wave signal of frequency 50Hz;Sine wave generating circuit: including series connection's first grade RC integration circuit and second grade RC integration circuit, first grade RC integration circuit is used to carry out preliminary integration to square wave signal, output triangle wave signal, second grade RC integration circuit is used to carry out secondary integration to triangle wave signal, output pure sine wave signal;Opto-coupler isolation driving circuit: for the pure sine wave signal is electrically isolated and converted into high voltage side driving signal;Power output circuit: for periodically turn on and turn off under the control of driving signal, to form and pure sine wave signal synchronous 220V AC voltage in output end.The utility model structure is simple, small in size.

Description

Technical Field

[0001] This utility model relates to the field of power electronic conversion technology, and more specifically to a pure sine wave electronic inverter. Background Technology

[0002] An inverter is a power electronic device that converts direct current (DC) power into alternating current (AC) power. It is widely used in solar power systems, vehicle power supplies, and backup power supplies. In practical applications, AC loads have high requirements for the quality of the output voltage waveform, especially for motors and precision electronic equipment, which typically require a pure sine wave input to ensure stable operation, low noise, and high efficiency.

[0003] Most inverters on the market currently employ topologies based on power frequency transformers or inductor energy storage. Their output waveforms are primarily square waves, modified sine waves (also known as quasi-sine waves), or sine waves generated through pulse width modulation (PWM) technology. Many low-to-mid-range products utilize modified sine wave outputs, typically employing push-pull or full-bridge switching circuits with simple timing control logic to generate stepped AC voltages by periodically switching the polarity of the DC voltage. However, due to the lack of effective waveform shaping circuitry, the output waveform of these inverters is essentially still rectangular or stepped, containing a large number of high-order harmonic components, leading to the following technical problems:

[0004] Severe waveform distortion: The output voltage waveform differs significantly from the standard sine wave, with a high total harmonic distortion (THD), which cannot meet the needs of electrical equipment sensitive to power quality.

[0005] Relying on transformers for electrical isolation and voltage boosting: Traditional solutions generally use large and heavy power frequency transformers, resulting in bulky, inefficient, and costly machines, which is not conducive to miniaturization and portable applications.

[0006] Therefore, there is still a lack of an inverter construction circuit in the existing technology that is simple in structure, does not require complex modulation circuits, and can achieve waveform smoothing and sinusoidal output using only basic passive components. Utility Model Content

[0007] In view of this, the present invention provides a pure sine wave electronic inverter. By setting up a multi-stage integrator circuit composed of resistors and capacitors, the primary switching signal is filtered and shaped step by step to generate a control signal close to a standard sine wave. Combined with optocoupler isolation and power switch structure, it realizes pure sine wave AC output on the high-voltage side. It abandons the traditional transformer-type or complex modulation structure and provides a lightweight, low-harmonic, and highly reliable inverter hardware circuit.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A pure sine wave electronic inverter, comprising:

[0010] Boost converter circuit: Its input terminal is electrically connected to the DC input terminal, and it is used to boost the input DC voltage to 220V DC voltage;

[0011] Voltage regulator / step-down circuit: Its input terminal is electrically connected to the DC input terminal, and it is used to convert the input DC voltage into a 5V DC voltage;

[0012] Signal source module: Its power supply terminal is electrically connected to the output terminal of the voltage regulator and step-down circuit, and it is used to generate a square wave signal with a frequency of 50Hz;

[0013] Sine wave generation circuit: Its input terminal is electrically connected to the square wave signal output terminal of the signal source module. It includes a first-stage RC integrator circuit and a second-stage RC integrator circuit connected in series. The first-stage RC integrator circuit is used to perform preliminary integration of the square wave signal and output a triangular wave signal. The second-stage RC integrator circuit is used to perform secondary integration of the triangular wave signal and output a pure sine wave signal.

[0014] Optocoupler isolation drive circuit: Its input terminal is electrically connected to the output terminal of the sine wave generation circuit, and is used to electrically isolate the pure sine wave signal and convert it into a high-voltage side drive signal;

[0015] Power output circuit: Its control terminal is connected to the output terminal of the optocoupler isolation drive module, and is used to periodically turn on and off under the control of the drive signal, thereby forming a 220V AC voltage synchronized with the pure sine wave signal at the output terminal.

[0016] Preferably, the first-stage RC integrator circuit consists of a resistor R31 and a capacitor C31. One end of the resistor R31 is connected to the square wave signal output terminal, and the other end is connected to the first terminal of the capacitor C31. The second-stage RC integrator circuit consists of a resistor R32 and a capacitor C32. One end of the resistor R32 is connected to the common node of the capacitor C31 and the resistor R31, and the other end is connected to the first terminal of the capacitor C32 and serves as the output terminal of the sine wave generation circuit. The second terminals of both the capacitor C31 and the capacitor C32 are grounded.

[0017] Preferably, the optocoupler isolation drive circuit includes an optocoupler U4, whose input-side light-emitting diode anode is connected to the common node of capacitor C32 and resistor R32, cathode is grounded, output-side phototransistor collector is connected to a high-voltage drive power supply, and emitter is connected to the power output circuit as a drive signal output terminal.

[0018] Preferably, the power output circuit includes a switching transistor Q3 and a current-limiting resistor R33. The gate of the switching transistor Q3 is electrically connected to the emitter of the optocoupler U4 through the resistor R33. The source of the switching transistor Q3 is grounded, and the drain serves as the AC output terminal.

[0019] Preferably, the boost converter circuit adopts a Boost topology, including an inductor L1, a switching transistor Q1, a diode D1, a PWM control chip U1, resistors R4 and R5, a feedback resistor R6 and R7, and an energy storage capacitor C8. One end of the inductor L1 is connected to the DC input terminal, and the other end is connected to the drain of the switching transistor Q1 and the anode of the diode D1. The source of the switching transistor Q1 is grounded through resistor R4, and the gate is connected to the drive output terminal GDRV of the PWM control chip U1 through resistor R3. The cathode of the diode D1 is connected to one end of the energy storage capacitor C8 and one end of the feedback resistor R6. The other end of the energy storage capacitor C8 is grounded. The other end of the feedback resistor R6 is connected to one end of the feedback resistor R7, and both are connected to the feedback input pin FB of the PWM control chip U1. The other end of the feedback resistor R7 is grounded. The current detection terminal ISNS of the PWM control chip U1 is connected to the node between resistor R4 and the source of the switching transistor Q1 through resistor R5.

[0020] Preferably, the voltage regulator / buck circuit includes an integrated buck chip U2, a freewheeling diode D11, an input filter capacitor C12, a power inductor L11, a bootstrap capacitor C15, a feedback voltage divider resistor R12, a feedback voltage divider resistor R14, a compensation capacitor C13, an enable resistor R11, and a resistor R15. The input pin IN of the integrated buck chip U2 is connected to the positive terminal of the DC input. Its switching output pin LK is connected to one end of the power inductor L11 and the cathode of the freewheeling diode D11, forming a switching node. The bootstrap pin BS of the integrated buck chip U2 is connected to the switching node through a series circuit of the bootstrap capacitor C15 and the resistor R15. One end of the power inductor L11 is connected to the 5V DC voltage output terminal. The anode of the freewheeling diode D11 is grounded. One end of the enable resistor R11 is connected to the enable pin EN of the integrated buck chip U2, and the other end is grounded to enable the chip to work. The input filter capacitor C12 is connected between the negative terminal of the DC input terminal and ground. The feedback voltage divider resistors R12 and R14 are connected in series to form a voltage divider network, which is connected between the 5V DC voltage output terminal and ground. Their common voltage divider point is connected to the feedback pin PB of the integrated buck chip U2. The compensation capacitor C13 is connected between the feedback pin PB of the integrated buck chip U2 and ground.

[0021] Preferably, both switch Q1 and switch Q3 are N-channel MOSFETs.

[0022] As can be seen from the above technical solution, compared with the prior art, this utility model discloses a pure sine wave electronic inverter, which has the following effects:

[0023] High waveform quality: Through two-stage RC integration processing, high-order harmonics in the square wave are effectively removed, generating a control signal that is close to an ideal sine wave, which is significantly better than traditional modified sine wave inverters.

[0024] Simple structure: No complex SPWM modulation algorithm or dedicated DDS chip is required. Waveform synthesis can be completed using only basic RC components, reducing design difficulty and cost.

[0025] Electrical isolation safety: Optical couplers are used to isolate the control and power circuits, improving system safety and anti-interference capabilities.

[0026] Highly adaptable: Supports a wide voltage input of 12V-72V, suitable for various DC power supply scenarios.

[0027] Small size and light weight: No power frequency transformer is required, the overall structure is compact, and it is easy to integrate and carry. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0029] Figure 1 The attached figure is a block diagram of a pure sine wave electronic inverter provided by this utility model.

[0030] Figure 2 The attached figure is a detailed circuit diagram of a pure sine wave electronic inverter provided by this utility model. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0032] This utility model discloses a pure sine wave electronic inverter, such as... Figure 1 and Figure 2 As shown, it includes:

[0033] Boost converter circuit: Its input terminal is electrically connected to the DC input terminal, and it is used to boost the input DC voltage (12V-72V) to 220V DC voltage;

[0034] Voltage regulator / step-down circuit: Its input terminal is electrically connected to the DC input terminal, and it is used to convert the input DC voltage into a 5V DC voltage;

[0035] Signal source module: Its power supply terminal is electrically connected to the output terminal of the voltage regulator and step-down circuit, and it is used to generate a square wave signal with a frequency of 50Hz;

[0036] Sine wave generation circuit: Its input terminal is electrically connected to the square wave signal output terminal of the signal source module. It includes a first-stage RC integrator circuit and a second-stage RC integrator circuit connected in series. The first-stage RC integrator circuit is used to perform preliminary integration of the square wave signal and output a triangular wave signal. The second-stage RC integrator circuit is used to perform secondary integration of the triangular wave signal and output a pure sine wave signal.

[0037] Optocoupler isolation drive circuit: Its input terminal is electrically connected to the output terminal of the sine wave generation circuit, and is used to electrically isolate the pure sine wave signal and convert it into a high-voltage side drive signal;

[0038] Power output circuit: Its control terminal is connected to the output terminal of the optocoupler isolation drive module, and is used to periodically turn on and off under the control of the drive signal, thereby forming a 220V AC voltage synchronized with the pure sine wave signal at the output terminal.

[0039] In this embodiment, the boost converter circuit adopts a Boost topology, including an inductor L1, a switching transistor Q1, a diode D1, a PWM control chip U1, resistors R4 and R5, a feedback resistor R6 and R7, and an energy storage capacitor C8. One end of the inductor L1 is connected to the DC input terminal, and the other end is connected to the drain of the switching transistor Q1 and the anode of the diode D1. The source of the switching transistor Q1 is grounded through resistor R4, and the gate is connected to the drive output terminal GDRV of the PWM control chip U1 through resistor R3. The cathode of the diode D1 is connected to one end of the energy storage capacitor C8 and one end of the feedback resistor R6. The other end of the energy storage capacitor C8 is grounded. The other end of the feedback resistor R6 is connected to one end of the feedback resistor R7, and both are connected to the feedback input pin FB of the PWM control chip U1. The other end of the feedback resistor R7 is grounded. The current detection terminal ISNS of the PWM control chip U1 is connected to the node between resistor R4 and the source of the switching transistor Q1 through resistor R5.

[0040] More specifically, the compensation terminal COMP of the PWM control chip U1 is connected to the feedback input pin FB through capacitor C3 and resistor R2; the RC pin of the PWM control chip U1 is connected to the positive terminal of the DC input through resistor R8 and grounded through capacitor C1; the SS pin of the PWM control chip U1 is grounded through resistor R1 and capacitor C2; the FB pin of the PWM control chip U1 is grounded through capacitor C4, and the BP pin is grounded through capacitor C5. The PWM control chip U1 can be selected as UC3843.

[0041] When the switching transistor Q1 is turned on, the inductor L1 stores energy; when the switching transistor Q1 is turned off, the inductor L1 is superimposed with the input voltage, and charges the energy storage C8 through the diode D1. The voltage is sampled by the voltage divider of R6 and R7 and fed back to the FB pin of the PWM control chip U1 to form a closed-loop voltage regulation control, so that the output is stabilized at about 220V DC.

[0042] In this embodiment, the voltage regulator / buck circuit includes an integrated buck chip U2, an MP2307, a freewheeling diode D11, an input filter capacitor C12, a power inductor L11, a bootstrap capacitor C15, a feedback voltage divider resistor R12, a feedback voltage divider resistor R14, a compensation capacitor C13, an enable resistor R11, and a resistor R15. The input pin IN of the integrated buck chip U2 is connected to the positive terminal of the DC input. Its switching output pin LK is connected to one end of the power inductor L11 and the cathode of the freewheeling diode D11, forming a switching node. The bootstrap pin BS of the integrated buck chip U2 is connected to the series circuit of the bootstrap capacitor C15 and the resistor R15. Connected to the switching node, the other end of the power inductor L11 is connected to the 5V DC voltage output terminal. The anode of the freewheeling diode D11 is grounded. One end of the enable resistor R11 is connected to the enable pin EN of the integrated buck chip U2, and the other end is grounded to enable the chip to work. The input filter capacitor C12 is connected between the negative terminal of the DC input terminal and ground. The feedback voltage divider resistors R12 and R14 are connected in series to form a voltage divider network, which is connected between the 5V DC voltage output terminal and ground. Their common voltage divider point is connected to the feedback pin PB of the integrated buck chip U2. The compensation capacitor C13 is connected between the feedback pin PB of the integrated buck chip U2 and ground. Furthermore, the power inductor L11 has an inductance of 4.7μH, the input filter capacitor C12 has a capacitance of 22μF, the diode D11 is an IN5819, used to provide a freewheeling path for the inductor current when the switch is turned off, the bootstrap capacitor C15 has a capacitance of 0.1μF, used to stabilize the output voltage and suppress high-frequency noise, the resistor R11 is an enable control resistor with a resistance of 7MΩ, the feedback voltage divider resistor R12 has a resistance of 33kΩ, the feedback voltage divider resistor R14 has a resistance of 8.7kΩ, the compensation capacitor C13 has a capacitance of 1.47pF, and the resistor R15 has a resistance of 10Ω.

[0043] When the input voltage is connected to the IN pin of the integrated buck converter chip U2, the chip's internal PWM controller drives the internal power switch to periodically turn on and off. During the on-time, the power inductor L11 stores energy; during the off-time, the inductor releases energy and supplies power to the load through D11. The output voltage is fed back to the BS pin by a voltage divider network composed of R12 and R14, adjusting the duty cycle to maintain a constant output of 5V. C12 and C15 act as input / output filters, respectively, reducing voltage fluctuations.

[0044] In this embodiment, the signal source module U3 has a preset 50Hz square wave generation program. It periodically flips the I / O pin level through timer interrupt and outputs a square wave signal with a duty cycle of 50%. This signal serves as the original excitation signal for the sine wave generation circuit. U3 can be an STC89C52.

[0045] In this embodiment, the first-stage RC integrator circuit consists of resistor R31 and capacitor C31. One end of resistor R31 is connected to the square wave signal output terminal, and the other end is connected to the first terminal of capacitor C31. The second-stage RC integrator circuit consists of resistor R32 and capacitor C32. One end of resistor R32 is connected to the common node of capacitor C31 and resistor R31, and the other end is connected to the first terminal of capacitor C32 and serves as the output terminal of the sine wave generation circuit. The second terminals of both capacitor C31 and capacitor C32 are grounded.

[0046] In the first-stage RC integrator circuit, resistor R31 and capacitor C31 form a low-pass filter structure. Its time constant is set to linearly integrate the rising and falling edges of the square wave signal to form a continuous triangular wave voltage signal. In the second-stage RC integrator circuit, resistor R32 and capacitor C32 form a secondary low-pass filter structure. Its time constant is greater than that of the first-stage RC integrator circuit. It is used to perform nonlinear smoothing processing on the triangular wave signal so that the output voltage waveform approximates a standard sine wave.

[0047] In this embodiment, the optocoupler isolation drive circuit includes an optocoupler U4, whose input-side light-emitting diode anode is connected to the common node of capacitor C32 and resistor R32, and the cathode is grounded. The output-side phototransistor collector is connected to the high-voltage drive power supply, i.e., the voltage output by the boost converter circuit. The emitter is connected to the power output circuit as the drive signal output terminal. The optocoupler U4 can be a PC817.

[0048] When the sinusoidal signal voltage increases, the current of the light-emitting diode in optocoupler U4 increases, enhancing its luminous intensity and thus increasing the conduction level of the phototransistor; conversely, the same applies. The emitter output of the phototransistor outputs a drive signal corresponding to the input sinusoidal wave, achieving electrical isolation and signal transmission.

[0049] In this embodiment, the power output circuit includes a switching transistor Q3 and a current-limiting resistor R33. The gate of the switching transistor Q3 is electrically connected to the emitter of the optocoupler U4 through the resistor R33. The source of the switching transistor Q3 is grounded, and the drain serves as the AC output terminal.

[0050] When optocoupler U4 outputs a high level, the gate of switch Q3 is high, and switch Q3 is turned on, allowing current to flow from the 220V high-voltage side to ground, forming the positive half-cycle output. When optocoupler U4 outputs a low level, the gate of switch Q3 is low, and switch Q3 is turned off, allowing current to freewheel through the LC filter, forming the negative half-cycle output. In this way, an approximately pure sine wave AC voltage is generated across the load.

[0051] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0052] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pure sine wave electronic inverter, characterized in that, include: Boost converter circuit: Its input terminal is electrically connected to the DC input terminal, and it is used to boost the input DC voltage to 220V DC voltage; Voltage regulator / step-down circuit: Its input terminal is electrically connected to the DC input terminal, and it is used to convert the input DC voltage into a 5V DC voltage; Signal source module: Its power supply terminal is electrically connected to the output terminal of the voltage regulator and step-down circuit, and it is used to generate a square wave signal with a frequency of 50Hz; Sine wave generation circuit: Its input terminal is electrically connected to the square wave signal output terminal of the signal source module. It includes a first-stage RC integrator circuit and a second-stage RC integrator circuit connected in series. The first-stage RC integrator circuit is used to perform preliminary integration of the square wave signal and output a triangular wave signal. The second-stage RC integrator circuit is used to perform secondary integration of the triangular wave signal and output a pure sine wave signal. Optocoupler isolation drive circuit: Its input terminal is electrically connected to the output terminal of the sine wave generation circuit, and is used to electrically isolate the pure sine wave signal and convert it into a high-voltage side drive signal; Power output circuit: Its control terminal is connected to the output terminal of the optocoupler isolation drive module, and is used to periodically turn on and off under the control of the drive signal, thereby forming a 220V AC voltage synchronized with the pure sine wave signal at the output terminal.

2. The pure sine wave electronic inverter according to claim 1, characterized in that, The first-stage RC integrator circuit consists of resistor R31 and capacitor C31. One end of resistor R31 is connected to the square wave signal output terminal, and the other end is connected to the first terminal of capacitor C31. The second-stage RC integrator circuit consists of resistor R32 and capacitor C32. One end of resistor R32 is connected to the common node of capacitor C31 and resistor R31, and the other end is connected to the first terminal of capacitor C32 and serves as the output terminal of the sine wave generation circuit. The second terminals of both capacitor C31 and capacitor C32 are grounded.

3. A pure sine wave electronic inverter according to claim 2, characterized in that, The optocoupler isolation drive circuit includes optocoupler U4, whose input-side light-emitting diode anode is connected to the common node of capacitor C32 and resistor R32, and cathode is grounded. The output-side phototransistor collector is connected to the high-voltage drive power supply, and the emitter is connected to the power output circuit as the drive signal output terminal.

4. A pure sine wave electronic inverter according to claim 3, characterized in that, The power output circuit includes a switching transistor Q3 and a current-limiting resistor R33. The gate of the switching transistor Q3 is electrically connected to the emitter of the optocoupler U4 through the resistor R33. The source of the switching transistor Q3 is grounded, and the drain is used as the AC output terminal.

5. A pure sine wave electronic inverter according to claim 1, characterized in that, The boost converter circuit adopts a Boost topology and includes an inductor L1, a switching transistor Q1, a diode D1, a PWM control chip U1, resistors R4 and R5, feedback resistors R6 and R7, and an energy storage capacitor C8. One end of the inductor L1 is connected to the DC input terminal, and the other end is connected to the drain of the switching transistor Q1 and the anode of the diode D1. The source of the switching transistor Q1 is grounded through resistor R4, and the gate is connected to the drive output terminal GDRV of the PWM control chip U1 through resistor R3. The cathode of the diode D1 is connected to one end of the energy storage capacitor C8 and one end of the feedback resistor R6. The other end of the energy storage capacitor C8 is grounded. The other end of the feedback resistor R6 is connected to one end of the feedback resistor R7, and together they are connected to the feedback input pin FB of the PWM control chip U1. The other end of the feedback resistor R7 is grounded. The current detection terminal ISNS of the PWM control chip U1 is connected to the node between resistor R4 and the source of the switching transistor Q1 through resistor R5.

6. A pure sine wave electronic inverter according to claim 1, characterized in that, The voltage regulator / buck circuit includes an integrated buck chip U2, a freewheeling diode D11, an input filter capacitor C12, a power inductor L11, a bootstrap capacitor C15, feedback voltage divider resistors R12 and R14, a compensation capacitor C13, an enable resistor R11, and a resistor R15. The input pin IN of the integrated buck chip U2 is connected to the positive terminal of the DC input. Its switching output pin LK is connected to one end of the power inductor L11 and the cathode of the freewheeling diode D11, forming a switching node. The bootstrap pin BS of the integrated buck chip U2 is connected to the switching node through a series circuit of bootstrap capacitor C15 and resistor R15. The other end of the power inductor L11 is connected to the 5V DC voltage output terminal. The anode of the freewheeling diode D11 is grounded. One end of the enable resistor R11 is connected to the enable pin EN of the integrated buck chip U2, and the other end is grounded to enable the chip to work. The input filter capacitor C12 is connected between the negative terminal of the DC input terminal and ground. The feedback voltage divider resistors R12 and R14 are connected in series to form a voltage divider network, which is connected between the 5V DC voltage output terminal and ground. Their common voltage divider point is connected to the feedback pin PB of the integrated buck chip U2. The compensation capacitor C13 is connected between the feedback pin PB of the integrated buck chip U2 and ground.

7. A pure sine wave electronic inverter according to claim 5, characterized in that, Both switching transistors Q1 and Q3 are N-channel MOSFETs.

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