阅读说明：本技术 一种利用数波法调节输出功率的软开关电路及方法 (Soft switching circuit and method for adjusting output power by using digital wave method ) 是由 易智勇 王德斌 于 2019-09-28 设计创作，主要内容包括：本发明公开了一种利用数波法调节输出功率的软开关电路及方法,属于电力电子技术领域。该方法充分利用了交流电的能量传输特点,在交流电压过零检测电路中,控制电路中的单片机或DSP判断出单相交流电的过零时刻,控制开关器件每次都在交流电电压过零瞬间进行通断操作,不仅保证了开关器件的完美零电压通断,而且对供电电网几乎是零谐波污染。单片机或DSP根据所要求输出功率与额定功率的百分比,按照相关比例从电网中提取能量：以单相电电压的一个周期作为最小单位,按同样比例通断MOS管。如果负载是需要保持稳定运转的电动机,可以把这连续通断的若干单位时间重新组合,使得每次通断的时间尽可能地短,以确保电动机稳定运转。(The invention discloses a soft switching circuit and a method for adjusting output power by using a digital wave method, and belongs to the technical field of power electronics. The method fully utilizes the energy transmission characteristics of the alternating current, in the alternating voltage zero-crossing detection circuit, a singlechip or a DSP in a control circuit judges the zero-crossing moment of the single-phase alternating current, and controls a switching device to be switched on and off at the moment of the zero-crossing of the alternating voltage each time, so that the perfect zero-voltage switching-on and switching-off of the switching device are ensured, and the zero-harmonic pollution to a power supply grid is almost realized. The single chip microcomputer or the DSP extracts energy from the power grid according to the percentage of the required output power and the rated power and the relevant proportion: and taking one period of single-phase electric voltage as a minimum unit, and switching on and off the MOS tube according to the same proportion. If the load is a motor that needs to maintain stable operation, the number of units of this successive switching can be recombined so that the time per switching is as short as possible to ensure stable operation of the motor.)

1. A soft switch circuit for regulating output power by using digital wave method is characterized by that said circuit is formed from two portions of AC voltage zero-crossing detection control circuit and related main circuit. The on-off of a full-control device in the main circuit is controlled by a zero-crossing detection circuit and a related control system. Therefore, the switching device is switched on and off at the zero crossing of the alternating voltage, and the output power is adjusted by adjusting the percentage of the wave number of the passing sine wave in each 100 alternating current periods.

2. The main circuit according to claim 1, characterized in that it comprises MOS transistors Q1, Q2, free-wheeling CBB capacitance Cx, load RL. A pin D of the MOS tube Q1 is connected with a live wire (or a zero wire) of single-phase electricity, a reverse parallel diode D1 for follow current is arranged inside the MOS tube Q1, and a pin S of the MOS tube Q1 is connected with one end of a capacitor Cx and one end of a load RL; the other ends of the capacitor Cx and the load RL are connected with an S pin of the MOS transistor Q2; the D pin of the MOS transistor Q2 is connected to the neutral line (or the live line) of the single-phase power, and an anti-parallel diode D2. for freewheeling is provided inside the MOS transistor Q2.

3. The soft switching circuit and method for regulating output power by digital wave method as claimed in claim 2, characterized in that it comprises the following steps:

in the alternating voltage zero-crossing detection circuit, a singlechip in the control circuit can judge the zero-crossing time of single-phase alternating current, so that the on-off time of an MOS (metal oxide semiconductor) tube can be driven to accurately coincide with the zero-crossing time of the alternating voltage. Further, the MOS tube works in a zero-voltage pure soft switch working state, and harmonic pollution to a power grid cannot be generated. After receiving the power regulation instruction, the single chip microcomputer extracts energy from the power grid according to the percentage q% (0< q < 100) of the required output power and the rated output power according to the relevant proportion: taking one period of single-phase electric voltage as a minimum unit, in 100 unit time, conducting the MOS tube in q unit time, and in the rest 100-q unit time, turning off the MOS tube.

Technical Field

The invention relates to the technical field of power electronics, in particular to a soft switching circuit and a method for adjusting output power by using a digital wave method.

Background

In various household or industrial electrical appliances using resistance wires or motors as loads, how to guarantee continuous adjustability of output power at low cost is always a technical problem in the industry. The most common adjustment mode is grade adjustment, which cannot achieve continuous adjustment, and only in a relatively high-grade motor speed adjustment system, an expensive frequency converter is used for speed and power adjustment, and the frequency converter is used in a circuit for controlling the motor, so that not only is the system cost increased, but also the power factor of the system is low, the efficiency is reduced, and meanwhile, the harmonic pollution to a power grid is increased.

The invention patent with application number 201610021738.5 and named as motor wave-dropping soft start control method and device proposes a solution for performing motor soft start by using a half-wave-shaping method, but the method has a fatal defect that the actual effect is to provide a direct current for an alternating current motor if half sine waves taken each time are in the same direction when the motor is started, so that the alternating current motor works abnormally, because the half-wave-shaping method does not take the whole sine wave as the minimum unit of energy but takes the half sine wave as the minimum unit of energy when the motor is started. Moreover, half-wave is taken out from the power grid every time, and the normal operation of the power grid is also not influenced.

An effective solution to the problems in the related art has not been proposed yet.

Disclosure of Invention

In view of the problems in the related art, the present invention provides a soft switching circuit and method for adjusting output power by using a digital wave method. Because the alternating current is generally used for supplying power to the electric appliance at the present stage, the method fully utilizes the energy transmission characteristic of the alternating current, controls the switching device to carry out on-off operation at the moment of zero-crossing of the alternating current voltage every time, not only ensures the perfect zero-voltage on-off of the switching device, but also has almost zero harmonic pollution to a power supply grid, and can not impact the grid when being applied to the starting of the electric appliance with the high-power motor.

The technical scheme of the invention is realized as follows:

according to one aspect of the invention, an alternating voltage zero-crossing detection control circuit and an associated main circuit are utilized.

Further, the main circuit comprises MOS transistors Q1 and Q2, a follow current CBB capacitor Cx and a load RL. A pin D of the MOS tube Q1 is connected with a live wire (or a zero wire) of single-phase electricity, a reverse parallel diode D1 for follow current is arranged inside the MOS tube Q1, and a pin S of the MOS tube Q1 is connected with one end of a capacitor Cx and one end of a load RL; the other ends of the capacitor Cx and the load RL are connected with an S pin of the MOS transistor Q2; the pin D of the MOS transistor Q2 is connected with the neutral wire (or the live wire) of single-phase electricity, and an anti-parallel diode D2 for follow current is arranged inside the MOS transistor Q2.

According to another aspect of the present invention, there is provided a soft switching circuit or method for regulating output power by using a digital wave method, which includes the following steps:

in the alternating voltage zero-crossing detection circuit, a singlechip in the control circuit can judge the zero-crossing time of single-phase alternating current, so that the on-off time of an MOS (metal oxide semiconductor) tube can be driven to accurately coincide with the zero-crossing time of the alternating voltage. Further, the MOS tube works in a zero-voltage pure soft switch working state, and harmonic pollution to a power grid cannot be generated.

After receiving the power regulation instruction, the single chip microcomputer extracts energy from the power grid according to the percentage q% (0< q < 100) of the required output power and the rated output power according to the relevant proportion: taking one period of single-phase electric voltage as a minimum unit, in 100 unit time, the MOS tube is turned on in q unit time, and in the remaining 100-q unit time, the MOS tube is turned off.

The above is a specific implementation method for adjusting the output power by the digital wave method. In practical applications, if the load is not a pure resistive load, but a motor that needs to maintain stable operation, the 100 unit times of the continuous on-off can be recombined to make the time of each on-off as short as possible to ensure stable operation of the motor. Such as: when the output power is 60 percent of the rated power, if the load is a pure resistance type load, the load can be continuously switched on for 60 cycles and switched off for 40 cycles in every 100 cycles; if the motor which needs to keep stable operation is used as a load, the motor can be closed for 2 periods every time the motor is switched on for 3 periods: that is, "on (1T) off (1T)", and then, optimization is performed again, and the following changes are made: "on (1T) off (1T) on (1T) off (1T)", and other values of the output power percentage can be similarly optimized.

The invention has the beneficial effects that:

the invention utilizes the characteristic of alternating current energy transmission to make the switching device be switched on and off every time when the alternating current voltage is over zero, so that the switching loss of the switching tube is almost equal to zero, and the harmonic pollution of related loads to a power grid during working is also almost zero. The power regulation mode is convenient and flexible, and is cheap and reliable. The regulation mode can be used not only on single-phase alternating current, but also on three-phase alternating current. Therefore, the application field of the invention is extremely wide.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a diagram of a main circuit provided according to the present invention. In the figure, the switching transistors Q1 and Q2 are MOS transistors, and may be other fully-controlled switching devices including IGBTs. Cx in the figure is a high-voltage high-frequency capacitor with a medium-small capacity and is used as a freewheeling current in an inductive load.

Detailed Description

The present invention will be further illustrated with reference to the following specific examples.