Pulse width modulation soft start circuit

Abstract

The utility model relates to a modulation pulse width soft start circuit, which belongs to the technical field of circuits and comprises a power supply circuit, a synchronous pulse sampling circuit, a voltage stabilizing circuit, a synchronous pulse detection circuit, a soft start and soft stop switching circuit and a follower circuit, wherein the power supply circuit is electrically connected with the synchronous pulse sampling circuit, the synchronous pulse sampling circuit is electrically connected with the voltage stabilizing circuit, the synchronous pulse detection circuit, the soft start and soft stop switching circuit and the follower circuit, and the soft start and soft stop switching circuit is electrically connected with the follower circuit; the synchronous pulse sampling circuit comprises a pulse generator and an mos tube. The modulation pulse width soft start effect can be improved.

Description

Technical Field

[0001] The present application belongs to the field of circuit technology, and specifically relates to a pulse width modulation soft start circuit. Background Art

[0002] At present, some high-power single-phase electric tools have a very large starting current when they are started, which makes the electric tools reach full speed within milliseconds, which brings certain harm to the users and even causes injuries. In response to this, high-power electric tools usually use soft start to improve the safety of electric tools.

[0003] In practice, it is found that most soft starters currently use thyristors as the main control switch devices. Thyristors are semi-controlled devices that can be controlled to turn on in the DC state, but cannot be controlled to turn off. In addition, thyristor voltage regulation will generate a large amount of harmonic currents. These harmonic currents cannot bring active power, but can only form vibrations in the motor and release heat on the motor windings, thereby affecting the waveform of the circuit. In addition, due to the large number of harmonics and low-frequency components, it is not easy to filter. In addition, under the condition of "deep control", the power factor will become lower. When the voltage regulator needs to be used for a long time or is used more in deep control, appropriate compensation measures need to be taken. It can be seen that the current soft start method has the problem of poor starting effect.

[0004] To address the above-mentioned problems, no effective solution has been proposed yet. Summary of the invention

[0005] To this end, the present application provides a modulated pulse width soft start circuit, which can improve the modulated pulse width soft start effect.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] The present application provides a modulated pulse width soft start circuit, comprising: a power supply circuit, a synchronous pulse sampling circuit, a voltage stabilizing circuit, a synchronous pulse detection circuit, a soft start and soft stop switch circuit, and a follower circuit; wherein the power supply circuit is electrically connected to the synchronous pulse sampling circuit, the synchronous pulse sampling circuit is electrically connected to the voltage stabilizing circuit, the synchronous pulse detection circuit, the soft start and soft stop switch circuit, and the follower circuit respectively, and the soft start and soft stop switch circuit is electrically connected to the follower circuit; wherein the synchronous pulse sampling circuit includes a pulse generator and a MOS tube.

[0008] Furthermore, the main control chip of the pulse generator adopts chip SG3525.

[0009] Furthermore, the 11th and 14th pins of the chip SG3525 output positive and negative pulses to the diode D1 and the diode D3 respectively, and output them to the transistor Q1 and the transistor Q2 through the diode D1 and the diode D3 to form the base of the totem pole circuit; the 11th and 14th pins of the chip SG3525 output the added pulses to the MOSFET Q5 and the MOSFET Q6, so that the MOSFET Q5 and the MOSFET Q6 are turned on at the corresponding voltage value and current value; wherein the synchronous pulse sampling circuit also includes the diode D1, the diode D3, the transistor Q1, and the transistor Q2.

[0010] Furthermore, the synchronization pulse detection circuit is electrically connected to the power supply circuit; wherein, the synchronization pulse detection circuit includes an integrated circuit U2 and an integrated circuit U3; the LED power supply pin 4 of the integrated circuit U2 and the integrated circuit U3 outputs pulses and synchronization signals to the pin 10 of the chip SG3525 through the diode D2.

[0011] Furthermore, the soft start and soft stop switch circuit includes a switch K1, a variable resistor RW1, and a capacitor C9; wherein, after the switch K1 is turned on, the voltage charges the capacitor C9 through the variable resistor RW1.

[0012] Furthermore, the follower circuit includes an operational amplifier U6C, a resistor R13, a resistor R1, a resistor R2, a transistor Q3, and a capacitor C1; wherein the follower circuit is used to adjust the pulse width of pins 11 and 14 of the chip SG3525 in the synchronous pulse sampling circuit to change the AC voltage.

[0013] Furthermore, the voltage stabilizing circuit uses TT7550 as a voltage stabilizing chip.

[0014] This application adopts the above technical solution, which has at least the following beneficial effects:

[0015] Through the solution of the present application, the use of MOS tubes as switching devices reduces the defects of using thyristors as switching devices and can improve the soft-start effect of modulated pulse width.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a structural schematic diagram of a modulated pulse width soft start circuit according to an exemplary embodiment;

[0019] Figure 2 is an internal schematic diagram of SG3525 according to an exemplary embodiment;

[0020] Figure 3 is a structural schematic diagram of a synchronous pulse sampling circuit according to an exemplary embodiment;

[0021] Figure 4 is a pulse waveform schematic diagram according to an exemplary embodiment;

[0022] Figure 5 is a structural schematic diagram of a synchronization pulse detection circuit according to an exemplary embodiment;

[0023] Figure 6 is a schematic diagram of a sine wave output synchronization pulse according to an exemplary embodiment;

[0024] Figure 7 is a structural schematic diagram of a soft start and soft stop switch circuit according to an exemplary embodiment;

[0025] Figure 8 is a structural schematic diagram of a follower circuit according to an exemplary embodiment;

[0026] Fig. 9 is a structural schematic diagram of a 99% pulse voltage detection direct-through circuit according to an exemplary embodiment;

[0027] Fig.10 is a structural schematic diagram of a TT7550 5V+ voltage stabilizing circuit according to an exemplary embodiment;

[0028] Fig.11 is an internal block diagram of a TT7550 according to an exemplary embodiment;

[0029] Fig.12 The figure is a schematic diagram of the structure of a 12V auxiliary power supply according to an exemplary embodiment. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other implementation methods obtained by ordinary technicians in the field without creative work belong to the scope of protection of the present application.

[0031] See also Figure 1 , Figure 1 It is a structural schematic diagram of a modulated pulse width soft start circuit according to an exemplary embodiment, which includes a power supply circuit, a synchronous pulse sampling circuit, a voltage stabilizing circuit, a synchronous pulse detection circuit, a soft start and soft stop switch circuit, and a follower circuit; wherein the power supply circuit is electrically connected to the synchronous pulse sampling circuit, and the synchronous pulse sampling circuit is electrically connected to the voltage stabilizing circuit, the synchronous pulse detection circuit, the soft start and soft stop switch circuit, and the follower circuit respectively, and the soft start and soft stop switch circuit is electrically connected to the follower circuit; wherein the synchronous pulse sampling circuit includes a pulse generator and a MOS tube.

[0032] in, Figure 1 The upper right position is the synchronous pulse sampling circuit and voltage stabilization circuit; Figure 1 The upper left position is the 12V auxiliary power supply; Figure 1 The lower left position is the synchronization pulse detection circuit; Figure 1 The lower right position is the soft start and soft stop switch circuit and the follower circuit.

[0033] At present, some high-power single-phase electric tools have a very large starting current when they are started, which makes the electric tools reach full speed within milliseconds. This brings certain harm to users and even injuries. Therefore, electric tools with higher power use soft start. At present, most soft starters use thyristors as the main control switch devices to change the duty cycle and chop the 50HZ sine wave to obtain the voltage and current when the motor starts. Thyristors are semi-controlled devices. They can be controlled to turn on in the DC state, but cannot be controlled to turn off. IGBT, mosfet, etc. are fully controlled devices, and the switches are all controllable. This makes it difficult to solve the power factor harmonics and other aspects of the converter made of thyristors. Thyristor voltage regulation will form a large amount of harmonic currents. These harmonic currents cannot bring active power, but can only form vibrations in the motor and release heat on the motor windings. The loss is not necessarily very large. But the waveform is very bad, there are many harmonics and the low-frequency components are too large, which is not easy to filter. It will affect the waveform of the circuit, and the thyristor voltage regulation will generate a lot of heat. The influence of power factor will cause the factor to decrease, especially in the case of "deep control", the power factor will become lower. When the voltage regulator needs to be used for a long time or used more in deep control, appropriate compensation measures need to be taken. In this regard, the present application proposes a modulated pulse width soft start circuit, which can use MOS tubes as switching devices to reduce the defects of using thyristors as switching devices.

[0034] Furthermore, the main control chip of the pulse generator adopts chip SG3525.

[0035] See also Figure 2 , Figure 2This is an internal schematic diagram of SG3525 according to an exemplary embodiment. The accuracy of the +5.1V reference voltage inside the chip is ±1%. Since the reference voltage value is within the input common mode range of the error amplifier, no external resistor is required. SG3525 can work in master-slave mode or synchronize with an external clock. The dead time can be adjusted by the resistor between CT and the discharge terminal. Other functional circuits inside the chip also include: soft start circuit, shutdown circuit, and undervoltage circuit. The output stage of the SG3525 control chip is a high-power totem pole output, and its source current and sink current exceed 150mA. The logic level it gives is "NOR" logic, and it is low level when in the "off" state. Working voltage range 8~35V; 5.1V reference voltage, accuracy ±1%; oscillation frequency range 100Hz~500KHz; oscillator synchronization signal input terminal; adjustable dead time; built-in soft start circuit; gradual pulse shutdown; input undervoltage lockout with hysteresis voltage; PWM lock function, prohibiting multiple pulses. Among them, G3525 constitutes a pulse generator that can output pulses with a duty cycle of 1-99%. R3 and C3 determine the oscillation frequency parameter value. U4SG352511 and pin 14 output positive and negative pulses, which are then fed to Q1 and Q2 through diodes D1 and D3 to form the base of the totem pole circuit. The emitter outputs the pulse added by the output of U4SG352511 and pin 14. Q5 / Q6 is turned on according to this pulse width, and the voltage and current of 50HZ also change with this pulse. L1, L2, C5, and C11 filter out high-frequency pulses, leaving only 50Hz sine waves.

[0036] Furthermore, the 11th and 14th pins of the chip SG3525 output positive and negative pulses to the diode D1 and the diode D3 respectively, and output them to the transistor Q1 and the transistor Q2 through the diode D1 and the diode D3 to form the base of the totem pole circuit; the 11th and 14th pins of the chip SG3525 output the added pulses to the MOSFET Q5 and the MOSFET Q6, so that the MOSFET Q5 and the MOSFET Q6 are turned on at the corresponding voltage value and current value; wherein the synchronous pulse sampling circuit also includes the diode D1, the diode D3, the transistor Q1, and the transistor Q2.

[0037] Furthermore, the synchronization pulse detection circuit is electrically connected to the power supply circuit; wherein, the synchronization pulse detection circuit includes an integrated circuit U2 and an integrated circuit U3; the LED power supply pin 4 of the integrated circuit U2 and the integrated circuit U3 outputs pulses and synchronization signals to the pin 10 of the chip SG3525 through the diode D2.

[0038] See also Figure 3 , Figure 3This is a schematic diagram of a synchronous pulse sampling circuit according to an exemplary embodiment. The 220VAC 50HZ power supply connected to AC1 and AC2 is limited by R7 and R10 to power the LEDs inside the 1st and 2nd pins of U2 and U3. The 4th pin outputs two zero-crossing narrow pulses in a complete cycle through D2 to point A to the 10th pin of U4, adding a synchronous signal to the pulse output inside U4.

[0039] See also Figure 4 , Figure 4 is a pulse waveform schematic diagram according to an exemplary embodiment. Figure 4 As shown, Figure 4 The left side is a pulse waveform with a duty cycle of 1%. Figure 4 The right side is a pulse waveform diagram with a duty cycle of 99.6%.

[0040] See also Figure 5 , Figure 5 It is a structural diagram of a synchronous pulse detection circuit according to an exemplary embodiment. The 220VAC 50HZ power supply connected to AC1 AC2 forms a current limiter through R7 and R10 to power the LED inside U2, U31, and 2 feet. The 4th foot outputs two zero-crossing narrow pulses in a complete cycle through D2 to reach point A to U410 foot, and a synchronization signal is added to the pulse output inside U4.

[0041] Furthermore, the soft start and soft stop switch circuit includes a switch K1, a variable resistor RW1, and a capacitor C9; wherein, after the switch K1 is turned on, the voltage charges the capacitor C9 through the variable resistor RW1.

[0042] Furthermore, the follower circuit includes an operational amplifier U6C, a resistor R13, a resistor R1, a resistor R2, a transistor Q3, and a capacitor C1; wherein the follower circuit is used to adjust the pulse width of pins 11 and 14 of the chip SG3525 in the synchronous pulse sampling circuit to change the AC voltage.

[0043] See also Figure 6 , Figure 6 is a schematic diagram of a sine wave output synchronization pulse according to an exemplary embodiment. Figure 6 The figure shows a 50Hz sine wave output synchronization pulse. Figure 6 The waveform above is a 50Hz sine wave, that is, Figure 5 The waveforms of AC1 and AC2 are: Figure 6 The waveform below is the zero-crossing detection pulse, that is, Figure 5 The waveform output at point A. It can be seen that the waveform amplitude increases with the increase of time.

[0044] See also Figure 7 , Figure 7 It is a structural schematic diagram of a soft start and soft stop switch circuit according to an exemplary embodiment. When the switch K1 is turned on, the 5V+ voltage charges the capacitor C9 through the RW1 variable resistor. The voltage at point C9B increases and the voltage at C9B decreases when K1 is turned off.

[0045] See also Figure 8 , Figure 8 This is a structural diagram of a follower circuit according to an exemplary embodiment. The soft start and soft stop voltage follower circuit is composed of U6C, R13, R1, R2, and Q3C1. It can follow the voltage at point B to increase or decrease. The voltage at point A3 is sent to pin U4 and 9 to adjust the pulse width of pins U4 and 11 and 14 to change the output AC voltage. Please refer to Fig. 9 , Fig. 9 It is a structural schematic diagram of a 99% pulse voltage detection direct circuit according to an exemplary embodiment. When the voltage at the output terminals AC2 and AC3 reaches 99% of the input, the 99% pulse voltage detection direct circuit 00'U6B, 6 feet have R4 and R14 voltage division to form 3.25V. When the voltage at point A3 rises to 0→0.885V, the output duty cycle is 0.5%, →3.25V or above, that is, the pulse width duty cycle of the pulse output added by U4SG352511 and 14 feet output is 99.6%. K1 is closed to soft stop C9, and the voltage reduction process at point B is inverted. R45 is used to eliminate the jitter of the output voltage at the critical point of U6B conversion.

[0046] Furthermore, the voltage stabilizing circuit uses TT7550 as a voltage stabilizing chip.

[0047] See also Fig.10 , Fig.10 is a schematic diagram of a TT7550 5V+ voltage regulator circuit according to an exemplary embodiment. Fig.11 , Fig.11This is a TT7550 internal block diagram according to an exemplary embodiment. The TT75XX series is a low-power high-voltage regulator manufactured using CMOS technology. The maximum input voltage can reach 18V and the output voltage range is 2.0V to 5.0V. It has the characteristics of high-precision output voltage, extremely low supply current, and extremely low dropout voltage. TT7550 has the following characteristics: low power consumption: ≤3μA; low dropout voltage: typical value 0.1V; low temperature drift: typical value 50 ppm / ℃; high input voltage: up to 18V; high-precision output voltage: tolerance is +3%; packaging form: TO-92, SOT89-3, SOT23-3; TT7550 has the following product uses: power supply equipment such as batteries; various communication equipment; audio / video equipment; security monitoring equipment. Among them, the buck switch provides 12V0.4A working power supply to the internal circuit to power all internal circuits. This power supply uses an AP3968 using the primary feedback voltage regulation mode. Not only does it save a photocoupler and a reference voltage regulator IC, but the circuit is also simplified.

[0048] See also Fig.12 , Fig.12 The figure is a schematic diagram of a 12V auxiliary power supply according to an exemplary embodiment.

[0049] This application adopts the above technical solution, which has at least the following beneficial effects:

[0050] Through the solution of the present application, the use of MOS tubes as switching devices reduces the defects of using thyristors as switching devices and can improve the soft-start effect of modulated pulse width.

[0051] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0052] It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" and "multiple" refers to at least two.

[0053] It should be understood that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may be an intermediate element at the same time; when an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. In addition, the "connection" used here may include wireless connection; the wording "and / or" used includes any unit and all combinations of one or more associated listed items.

[0054] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0055] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0056] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0057] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0058] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A pulse width modulation soft start circuit, characterized in that: include: A power supply circuit, a synchronous pulse sampling circuit, a voltage stabilizing circuit, a synchronous pulse detection circuit, a soft start and soft stop switch circuit and a follower circuit; wherein the power supply circuit is electrically connected to the synchronous pulse sampling circuit, the synchronous pulse sampling circuit is electrically connected to the voltage stabilizing circuit, the synchronous pulse detection circuit, the soft start and soft stop switch circuit and the follower circuit respectively, and the soft start and soft stop switch circuit is electrically connected to the follower circuit; wherein the synchronous pulse sampling circuit includes a pulse generator and a MOS tube.

2. The pulse width modulation soft start circuit according to claim 1, characterized in that: The main control chip of the pulse generator adopts chip SG3525.

3. The pulse width modulation soft start circuit according to claim 2, characterized in that: Pins 11 and 14 of the chip SG3525 output positive and negative pulses to diode D1 and diode D3 respectively, and output them to transistors Q1 and Q2 through the diodes D1 and D3 to form the base of the totem pole circuit; pins 11 and 14 of the chip SG3525 output added pulses to MOSFET Q5 and MOSFET Q6 to make MOSFET Q5 and MOSFET Q6 conduct corresponding voltage and current values; wherein the synchronous pulse sampling circuit also includes the diode D1, the diode D3, the transistor Q1, and the transistor Q2.

4. The pulse width modulation soft start circuit according to claim 3, characterized in that: The synchronization pulse detection circuit is electrically connected to the power supply circuit; wherein, the synchronization pulse detection circuit includes an integrated circuit U2 and an integrated circuit U3; the LED power supply pin 4 of the integrated circuit U2 and the integrated circuit U3 outputs pulses and synchronization signals to the pin 10 of the chip SG3525 through the diode D2.

5. The pulse width modulation soft start circuit according to claim 1, characterized in that: The soft start and soft stop switch circuit includes a switch K1, a variable resistor RW1, and a capacitor C9; wherein, when the switch K1 is turned on, the voltage charges the capacitor C9 through the variable resistor RW1.

6. The pulse width modulation soft start circuit according to claim 1, characterized in that: The follower circuit includes an operational amplifier U6C, a resistor R13, a resistor R1, a resistor R2, a transistor Q3, and a capacitor C1; wherein the follower circuit is used to adjust the pulse width of pins 11 and 14 of the chip SG3525 in the synchronous pulse sampling circuit to change the AC voltage.

7. The pulse width modulation soft start circuit according to claim 1, characterized in that: The voltage stabilizing circuit adopts TT7550 as the voltage stabilizing chip.

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