Fading on and fading off electronic switch

Abstract: The present invention provides a fading on and off electronic switch suitable for fading on/off control of electrical equipments like lamp and motor. The main circuit comprises a rectifier bridge circuit (D1-D4) and a thyristor (T R ). Control circuit includes a fast discharging synchronic integrator and a trigger pulse integrator (R1,D5,D6,C2), the former acts as a pulse phase shifter for triggering branch so as to provide a self-adapting magnitude variable sawtooth waveform, while the latter acts as a dynamic phase variation memory so as to provide varible reference for comparison. Trigger pulses, after being voltage feed back via main branch causes the synchronic integrator to fast discharge. If the discharging circuit of the trigger pulse integrator (R1,D5,D6,C2) is closed, the voltage on the integral capacitor (C2) decreases gradually, and trigger angle also decrease gradually. This is fading on process, and in fading off process, the conditions are just opposite. Fading on/off time can be independently set.

Description: The present invention relates to a fading on and fading off electronic switch suitable for natural light - simulated control of illumination and fading on and off reduced voltage on/off control of electrical heaters. The fading process of the switch goes on automatically after on/off guiding operation. In the prior art, electrical devices like illumination apparatus, motor, and electrical heater are all turned on and off suddenly at the whole voltage, and their transition processes are determined by the physical inertia parameters of the devices themselves and can not be controlled or adjusted. In many cases, it can not meet the demand of the people, or even cause damage to users. If some large or special equipments need reduction start or reduction shut down, an equipment which can adjust a series-connected adjustable resistance apparatus is often used to control the on/off transition process. In some more critical applications, analog computing apparatus comprising the combination of open loop or close loop propotional integral, differential or inertia stages or even digital program-controlled apparatus or a special industry-control computer are used to automatically control various transition processes including start and shut down. However, these apparatuses or computers are very expensive, and go beyond the category of fading on/off switch. As to illumination control, specially designed fading on/off illumination control equipments including a manually operated brine knife switch, a voltage regulator and a transistor continuous light regulator are used in some high-grade theatres. The operating process of these equipments all belong to man-machine closed-loop realtime operation and must be carried out in coordination with the on/off operations of switches. Among the continuous light regulated apparatus for home use, a single point touch switch is developed recently. This switch detects the touch operation by using body induction signal, and control the trigger of a thyristor by phase regulation performed by built-in IC circuits. Trigger angle will be hold when people stop touch the apparatus, and instantaneous touch will use the on/off states to exchange. Apparently , this also belongs to man-machine closed-loop real-time operation. Up to now, commercially avaliable light-adjustable lamps are also products of this category. US-A-4 360 743 discloses a solid state control device for gradually controlling the turn on and turn off of a light bulb. The device includes a full-wave rectifier, a SCR and a charging capacitor connected parallel to a control branch consisting of a resistor and a switch connected in series. The gate leakage current of the SCR is used to charge the charging capacitor. OBJECT OF THE INVENTION The object of the present invention is to provide a convenient and cheap fading on and off switch for controlling the illumination so as to simulate the fading on/off transition characteristics of the nature sunlight, and for controlling equipments like motor and electrical appliances so as to provide fading on/off reduction start and shut down functions, wherein the fading process go on automatically after on/off guiding operation. SUMMARY OF THE INVENTION The fading on and off electronic switch according to the present invention is defined in Claim 1. The electronic switch thus comprises a main branch including a bridge rectifier and a thyristor, and a triggering branch which has a trigger pulse integrator including a series connection branch of a diode and a capacitor. Said trigger pulse integrator is connected between the anode and control terminal of the thyristor. A discharge control branch comprising operational connection points of an one-blade-two-throw switch (of hole type or non hold type) and a parallel network series-connected with each other is connected parallel between the two sides of the integral capacity. The parallel network consists a resistor and a capacity connected in parallel. When the switch according to the present invention is used, the two AC lines are connected to two AC input of the bridge rectifier, respectively. The on and off processes are completed automatically after the operational connection points are operated. When this switch is turned off, the integral capacity of the trigger pulse integrator is charged to a maximum voltage value, and the diode in the branch is turned off because of reverse biasing. As a result, the thyristor is kept in cut-off state because no trigger current flows. Once the normally open connection points are closed, the integral capacity begins to discharge via a discharging resistor and its voltage decreases gradually. In each period of 10 ms (reciprocal of the base frequency of 100 Hz outputted by the bridge rectifier), the diode is biased forwardly and is conductive so as to produce a current pulse to trigger the thyristor when the difference between the instantaneous pulse voltage and the voltage of the integral capacity is positive. After the thyristor is triggered, the anode-cathode voltage drop of the thyristor is reduced to saturation voltage and the diode resumes reverse biasing immediately. As the capacity discharges gradually, the time at which the difference between the instantaneous pulse voltage and the voltage of the integral capacity becomes positive preacts step by step, and the average current flowing in the main branch becomes larger and larger until a maximum value is reached. This is the fading on process. When the normally open connection points are opened, discharge branch of the integral capacity is disconnected, the integral capacity is charged by a trigger pulse every 10 ms. As contrasted with the switch in fading process, the voltage of the integral capacity increases gradually, and the time at which the difference between the instantaneous pulse voltage and that of the integral capacity becomes positive lags gradually, and the trigger angle also increases gradually. As a result, the average current flowing in the main branch decreases gradually. When the voltage of the integral capacity reaches its maximum value, the diode is reversely biased and the thyristor is also cut off. This is the fading off process. After the fading on/off processes are completed, the switch enters a on or off stationary state determined by the states of the operational connection points. The holding of these stationary states is the same to that of the an ordinary switch. The speed of the fading on process is determined by RC discharging constant and is inversely proportional to that constant. On the other hand, the speed of switch off fading process is determined by the integral capacitance and charge quantity of the integral pulse, and is proportional to the former, and inversely proportion to the latter. The branch comprising normally closed connection points and the resistor is connected between the control and cathode terminal of the thyristor, and this branch has two functions; one is to reduce and normalize the trigger sensitivity of the thyristor so that the manufacture technique and components can be standardized in mass production and capacitors of large capacitance can be choosen as integral capacity to ensure the range of time constant of fading on process so that a resistor having the resistance beyond the normal series can be avoided, the other to eliminate the unfavourable effects on the fading off time by variation of trigger sensitivity of the thyristor due to the change of ambient temperature and load. By using the combination of single-blade-two-throw, the potential sensitivity can be fully used and the angle of flow in on stationary state can also be reduced. Actually, the fading on and off functions provided by the present invention is needed in many application fields. When the present invention is used in illumination control, the controlled illuminating apparatus can be provided with nature sunlight simulated fading on and off transition characters which is adaptative to adjustment mechanism of human eyes and make people feel comfortable. Therefore, the present invention can protect human sight and prolong the life span of the illumination equipments. Once the present invention is used in fading on and off reduction on/off control of electrical motor, start current and impulse torque can be reduced, which is helpful to the stabilization of the power network parameters and safety of the equipments. The present invention can also be used in fading on and off reduction on/off control of the electrical heating equipments. By using the present invention, the cold state impulse current and thermal stress can be reduced so that the length of life of the equipments can also be prolonged. Since the fading on/off process is automatically controlled and carried out after the on/off guiding operation in the present invention, the complicated on/off transition process adjustment/control apparatus can be partly replaced. Therefore, the cost of some integrated equipments can be reduced. The cost of the present invention is relatively low due to the simple design while the ratio of performance to cost is higher than any substitutive products. Advantageous effects will be obtained when the present invention is widely used. When the operation button of non hold type is choosen as the operational connection points in the present invention, the present invention will become a new type of fading on and off delay switch which can be used in public area like stairs and corridors. Satisfactory results will be obtained when the fading on time and fading off time is set to about 2s and 2min, respectively. The lamp controlled by the present invention has the functions of fading on and off, roughly controlling the turn on time and displaying turn off time. Advantageous effects like comfortable and convenient to user, energy saving and prolonging the life of lamp can be achieved when the present application is promoted to be widely used. The dependent Claims set out preferred embodiments of the invention. The further improvements of the present invention are as follows: a fast discharging synchronic integrator is connected between the anode and cathode of the thyristor, said fast-discharging synchronic integrator consists of a resistor sample circuit, a resistor-capacitor integral circuit and a multiple-transistor fast discharging circuit controlled by the sample circuit. The branch of trigger pulse integrator is connected between the positive side of the integral capacitor of the synchronic integrator and the control terminal of the thyristor. In this improvement, the fast-discharging sychronic integrator, acting as the pulse rifter for the trigger branch, provides self adapting magnitude variable sawtooth waveform while the trigger pulse integrator, acting as a dynamic phase variation memory, provides variable trigger reference signal. After being voltage fedback via main branch, the trigger pulse causes the synchronic integrator to fast discharge. Thus, the magnititude envelope of the sawtooth waveform produced by the fast discharging synchronic integrator, in turn, changes monotonously according to the changes of trigger angle, and forms a self adapting magnitude varible signal of sawtooth waveform. When the connection points are closed, the discharge circuit of the trigger pulse integrator is closed, and voltage of the integral capacity decreases gradually. As a result, the instantaneous value of the sawtooth voltage necessary to forwardly bias the diode in trigger pulse integrator branch decreases accordingly, and the integral time of the fast discharging integrator shortens gradually, and its trigger angle decreases gradually. This is fading-on process. When the connection points are opened, the discharge circuit of the trigger pulse integrator is opened, too. The continuous flow of trigger pulse causes the voltage of integral capacity to increases gradually, and the instantaneous value of the sawtooth voltage necessary to forwardly bias the diode in trigger pulse integrator branch also increase gradually. As a result, the integral time of the fast-discharging is prolonged gradually and trigger angle also increases accordingly. This improvement can enlarge the dynamic range of trigger angle. When the integral time constant of the fast discharging synchronic integrator is set to about 30 ms, the upper limit of the dynamic range of the trigger angle reaches nearly 180°. Therefore, the lower limit of the fading dynamic range of voltage and current in main branch decreases to nearly zero and an excellent controlled characteristics can be realized. The solutions used to narrow down the angle of flow in on stationary state as follows: a voltage-regulator diode or light emitting diode branch is added to the fast discharging synchronic integrator, this diode branch is connected between the negative side of the integral capacitor of the fast discharging synchronic integrator and the cathode of the thyristor. The nonlinear characteristic of the voltage-regulator diode or LED inactivates the fast discharging synchronic integrator in on stationary state. Therefore, the synchronic integrator will not exert any shunting effects on trigger current branch. As a result, the instantaneous value of sawtooth wave voltage necessary to forwardly bias the diode in the trigger pulse integrator branch can be reduced, and the angle of triggering can also be reduced. The feature plays a very important role in eliminating electro-magnetic "pollution" and reducing the potential drop across the switch. BRIEF DESCRIPTION OF THE DRAWING One preferred embodiment is disclosed in accordance with the drawing wherein, Fig. 1 is a circuit diagram illustrating a embodiment according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, a preferred embodiment will be described by reference to the accompanying Fig. 1. Refer to Fig. 1 , diodes D1-D4 form a full-wave bridge circuit. The main current flowing in this bridge circuit is controlled by a thyristor TR. Resistor R1, diodes D5, D6 and capacitor C2 form a trigger pulse integrator which, acting as a dynamic phase variation memory, provides a variable triggering reference signal. Resistors R1 and R2 form a voltage divider sampling circuit, and multiple transistors are provided with a fast discharging synchronic control signal by resistor R2 so as to make the integral capacitor C1 to discharge in time once an operation cycle. The multiple transistors are a controllable fast discharging branch of the integral capacitor C1, while R1, D6, C1 and voltage-regulator diode W1 form an integral circuit. Said voltage divider sampling circuit, said fast discharging branch and said integral circuit form a fast discharging synchronic integrator. In on/off transient process, the integrator produces a self-adapting magnitude-variable sawtooth wave which has a gradually increasing, decreasing envelope. The peak-to-peak voltage of the sawtooth wave is higher than the voltage on the integral capacitor C2. Therefore, diode D5 is biased forwardly, and a pulse flows to trigger the thyristor. After the thyristor is triggered, the voltage across sample resistor R2 decreases to zero, and capacitor Cl is fast discharged, which is the preparation for the next period. The integral time of the fast-discharging synchronic integrator in each period depends on the voltage value on its integral capacitor. The higher the voltage, the longer the integral time, and therefore, the larger the trigger angle, and the smaller the average current of the main branch over one period. Operational connection points are a single-blade-two-throw switch KS. When the discharging circuit of C2 is closed by KS, the voltage on C2 decreases gradually, trigger angle also decreases gradually. As a result, the average current flowing in the main branch over one period increases gradually until full-open is reached. On the other hand, when the discharging circuit of C2 is opened by switch KS, the voltage on capacitor C2 rise up as pulse charges accumulates on the capacitor, and trigger angle also increases gradually. As a result, the average current flowing in the main branch over one period decreases gradually until full-close is reached. The function of R4 is to reduce and normalize the trigger sensitivity of the thyristor during a transition process so as to increase the capacitance of C2 and to reduce the resistance of resistor R3. The function of capacitor C3 is to make the voltage on capacitor C2 to generate a negative step at the time the switch is just closed, in order to provide the lamp with a practical initial brightness. In on stationary state, the fast discharging synchronic integrator is cut-off by voltage-regulator diode W1, and the R4 branch is opened by switch KS. This will substantially reduce the on state trigger angle. As a result, the requirements on electric-magnetic compatibility can be met. The fading on and off switch according to the present invention is particularly suitable for the fading on and off control of a bedroom lamp, which makes the lamp to have fading on and off light intensity simulating the nature sunlight. Therefore, human sight can be protected, and ambient comfortability can be improved. In the present preferred embodiment, the time constant for charging the fast-discharging synchronic integrator ( R₁. C₁) is preferably set to about 30 ms, and the time constant for discharging ( R₂. C₁ / , wherein is current amplification ratio of the multiple-transistors) is preferably set to O.1 ms; and the time constant for charging the trigger pulse integrator is preferably set to 2O,000 periods (1O ms per period), and the time constant for discharging ( (C₂ + C₃) . (R₃ + R₄) ) is preferably set to about 3Os. The present invention can be improved by adjusting the above-mentioned parameters according to the specific application and changing or simplifying some additional circuit so as to develop fading on and off switch of different type, like bedroom type, delay type, start type and thermo-stress eliminating type to be used in nature sunlight-simulated light control in bedrooms, delay-off lamp control in public area, reduction on/off control of motors and thermo-stress eliminating control of electrical heaters, respectively.

Claims: A fading on and fading off electronic switch, comprising: a main circuit including a rectifying bridge circuit and a thyristor (TR) controlling the main current flow in the rectifying bridge circuit; a thyristor triggering circuit having a trigger pulse integrator which includes a series branch of a diode (D5) and an integral capacitor(C2), said trigger pulse integrator being connected between the anode and the control terminal of the thyristor; and a control branch formed by operational connection points of a switch (KS), a resistor (R4) and a parallel network connected serially, wherein said parallel network consists of a resistor (R3) and a capacitor (C3) connected in parallel, said control branch being connected parallel to the integral capacitor (C2), wherein one side of the integral capacitor (C2) of the trigger pulse integrator is connected to the control terminal of the thyristor, and wherein the operational connection points are two groups of contacts of an one-blade-two-throw switch, one group of contacts being normally open contacts connected in series with the parallel network (R3, C3), and the other group of contacts being normally closed contacts connected to the cathode of the thyristor, on the one hand, and, after being serially connected with the resistor R4, to the control terminal of the thyristor, on the other hand. A fading on and off electronic switch according to claim 1, further comprising a fast-discharging synchronic integrator connected between the anode and cathode of the thyristor and comprising a sample circuit formed by resistors (R1 and R2), an integrating circuit consisting of a resistor (R1), a diode (D6), and a capacitor (C1), and a fast-discharging circuit formed by multiple transistors, the series branch of the trigger pulse integrator being connected between the positive side of the integral capacitor (C1) of the synchronic integrator and the control terminal of the thyristor. A fading on and off electronic switch according to claim 2, wherein a voltage-regulator diode (W1) or a LED branch is added to said fast-discharging synchronic integrator, and said voltage-regulator diode or LED branch is connected serially between the negative side of the integral capacitor (C1) of the synchronic integrator and the cathode of the thyristor. A fading on and off electronic switch according to claim 1, wherein said operational connection points are an operation switch or button of hold type or non-hold type.

Inventors: JIANG ZIGANG, JIANG, ZIGANG
Applicants: JIANG ZIGANG, JIANG, ZIGANG
Application year: 1992
Main classification: H03K17
IPC codes: H05B39, H03K17