FI116493B - Control circuit and method for switching on load - Google Patents

Description

'116493

CONTROL CIRCUIT AND METHOD FOR SWITCHING THE LOAD

This invention relates to a control circuit as defined in the preamble of claim 1 and to a method of load switching as defined in claim 5 of claim 5.

Many electrical equipment used in homes and workplaces, when operating and / or turning it off and on, causes voltage and current peaks and other disturbances in the mains supplying them. Often, the effect of these interferences is most pronounced on nearby electrical equipment in the network, particularly on electrical equipment connected to the same line and the interfering device itself.

15 A good example for everyone to know about the damage to the device itself when switching on the device is the destruction of the filament of a standard filament when the lights are turned on. Usually, the bulb is damaged just when the lights are turned on, and not by 20 when all the light is on. If the lamp is damaged while the light is on, this is usually due to a malfunction in the mains. Such a disturbance is, for example, the current peak resulting from the burning of fuse f :. For example, the functions of conventional ** fuse panels are mechanical.

25 Fuses allow current to pass through as and when; the current exceeds the fuse rating. Too much current in the fuse causes the fuse resistor wire to overheat and thereby melt the wire, resulting in a break in current flow. Most conventional electrical mains consuming devices connected to the mains are typically switched on such that the mechanical switch directly directs the mains voltage to the actuator. In this case, the switching can occur at any point of the phase, and the voltage rises in a leap compared to conventional alternating current voltage variation.

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Pressing the mechanical switch will cause switch vibrations, resulting in sparking and arcing phenomena that will appear as a malfunction in the rest of the system. The resulting spikes cause a shortening of the service life of some household appliances, for example. In addition, sparking increases the risk of fire.

Because of the high throughput and sparking, the switch has to be designed in massive and spark-proof materials, which causes moderate costs for the switches and their enclosure 10 or other appropriate location or structural protection.

Switching off the actuator by means of a mechanical switch will again cause switch vibrations. Coupling can also occur at any point during the phase. If the load is inductive in nature, intermittent oscillating disconnection will cause voltage peaks of up to several hundred volts when the inductance is discharged. These peaks also appear as EMC faults, 20 and shorten the life of devices on the same input * ·

In light bulbs and some other devices, the load is almost short-circuited when switched on, which causes a sharp high current peak, which is often seen in other actuators as a voltage drop.

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To overcome the above problems and the '.' to provide a better on and off of the electrical equipment 30, the invention provides a control circuit and a method. As to the features characterizing the invention, reference is made to the claims.

The basic idea of the invention is to control the change of current in the case of switching the devices on and off so that not very sharp changes occur. The sharp changes are avoided by adjusting the switching moment to or near the AC voltage and limiting the rate of change of current.

The control circuit implementing the invention has a switch coupled to a low current control circuit, whereby the switch may be small and inexpensive since the operating current does not pass through the switch. The control circuit also includes a switching circuit which ensures that the switching of the output stage is carried out at the beginning of 10 steps with a voltage of zero, whereby the output stage is softly switched on as well as the actuator switches softly. In addition, for example, the lamp suit load is gradually switched on so that the lamp is gradually energized, thereby warming the lamp and increasing its resistance. Disconnection is also handled gently so that the voltage applied to the load is gradually released by inducing the energy of the inductance in a controlled manner to prevent the resulting peak. Likewise, final power-down disconnection is performed at the zero point of the phase. Thus, the load is engaged unconditionally at the zero point of the phase and controlled to the load; the voltage gradually increasing as the current in the actuator increases; evenly controlled, that is, the current cannot grow by flapping the ground.

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The invention is suitable for use with most AC devices. Suitable locations in the house's electrical network or electrical equipment include: safety boards, mains cable, for example, when integrated into a junction box, switches and plugs. Advantageously, the control circuit has an adjustable current limit, whereby at least the power in the device-specific control circuits can be set per actuator. A preferred embodiment of the control circuit is one where the control circuit shuts off the load when the current limit is exceeded. This is how the control circuit functions like a fuse.

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By treating the disconnection of the alternating current devices at the zero point of the phase, no matter where the switch is turned off, this prevents a voltage surge that can damage other 5 devices.

The invention provides, in a simple manner, rapid detection of overloads and disconnection of the actuator, whereby no sparking or fire risk occurs. The control circuit has no switch oscillations on and off, so there is no EMC interference caused by them.

The invention reduces the "wear" of the device to be connected and also saves other actuators in the power grid.

The invention will now be described in more detail by way of non-limiting embodiments of the invention and with reference to the accompanying drawings, in which: Figure 1 illustrates a control circuit implementing the invention.

Figure 25 illustrates a control circuit applying the invention.

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The control circuit is coupled with a pair of power supplies, either FET or transistor, T1 and T2, to supply a load connected to the control circuit, which switches and adjusts the power supply according to the control of the control circuit. The control circuit i · · · 30 has a switch connected to a low current control circuit, whereby the switch may be small and inexpensive. The workflow »i * does not pass through the switch but through the output stage. The control circuit also includes a switching circuit which ensures that the switching of the power stage is carried out at the beginning of step 35 with a voltage of zero, whereby the drive stage is smoothly switched on as well as the actuator 5 116493 switches smoothly. In addition, for example, the lamp load is gradually switched on so that the lamp is gradually energized, thereby heating the lamp and increasing its resistance. Disconnection is also handled gently so that the voltage applied to the load is gradually discharged by releasing the energy stored in the load, for example the load inductance, in a controlled manner to prevent the resulting peak. Similarly, the final power-off is performed at step zero-10.

The fact that the connection is made at or near the voltage zero protects the control circuit and the load to be connected. When switching from zero, for example, in a load short-circuit situation, a pair of terminals may be switched off before the power loss becomes too high and destroys overloaded components or motors. 1

The operation of the control circuit can be described as follows.

The operating voltage VCC required for the operation of the control member is generated by charging capacitor Cl with resistor R1 and | via diode D1. The Zener diode D2 limits the voltage to an appropriate level. Cl keeps the voltage relatively constant.

: 25 Dl prevents capacitor discharge when changing:; : voltage potential changes.

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Initial resetting of the control circuit occurs when the voltage is applied.

: The flip-flop circuit IC-2 is reset when the voltages are applied to the system by applying a positive pulse to its reset input. As the VCC voltage rises, the • · »

Vref voltage (where vref is in circuit) slowly *! ' rise as capacitor C5 charges via R11 and R12 to a voltage division ratio of * ... · 35 formed by resistors R11, R12 and R13. The output of comparator A2 controls T3 nmos,

which controls the reset on IC-2. With the switch SI

6 116493 is pressed via resistor R3 to the voltage input of the voltage flip-flop circuit IC-1. The next time the mains voltage goes positive, the Al output goes up to the VCC voltage, whereby the rising edge of the clock input of the IC-2 transfers the state of the 5 d input (either OV or VCC) to the Q output.

The IC output of the IC-1 controls the clock input CLK of the IC-2, whereby the reset Q output of IC-2 is 0 and the XQ output is VCC. Since the XQ output is coupled to the IC input of the IC-2, the rising edge of the IC-2 clock input (CLK) switches the D input status to the Q output.

As the Q-output of IC-2 increases with the VCC voltage, the bases of the capacitor components T1 and T2 according to the capacitance time constant (T = R14 * Cpp) begin to charge through resistor R14, whereby the base voltage T1 and T2 begin to rise T2) conductive through a branch formed by resistor R14 and a pair of terminals, whereby the terminating stage is gradually activated.

The resistor R15 and the capacitor C6 form a time constant, after which time the 20 currents over the fetuses begin to be monitored.

· Comparator A4 measures during the positive semiconductor:: current and comparator A3 measures the current during the negative semiconductor.

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After a time constant based on resistor R15 and capacitor C6, the output of comparator A2 drops to zero, whereby nmos T3 is opened. If the comparators of A4 and A3 | currents below the set limit remain at T3 D-point VCC-; **. 30, so that the reset input of the IC-2 is at the VCC voltage, and the control remains on.

T If a short-circuit or overcurrent occurs during the positive half-cycle, the A4 output will reset to zero, with T3 35 open to IC-2 reset input 0V, which will reset the IC-2 Q output lowers to 1 116493 and then the base voltage of the power components T1 and T2 drops to zero via diode D5.

In order to reconnect the power stage, it is required that the 5 switches SI have to be turned off and on again before the control re-activates. Thus, load switching can only be done when the voltage is at zero, and after switching on the load begins to steadily increase current. In this case, changes are par-10 poorly controlled for load life.

By always adjusting the switching to start from zero voltage, the current peak of the lamp-type loads is prevented by first allowing the lamp to warm up so that its resistance 15 begins to increase as it heats up.

Similarly, the power-off is normally done at zero voltage. When the switch S1 is turned off, the D-input tila 'state of IC-1 will be clocked at Q output 20 as the Vac voltage passes zero and rises to positive. The output of Al then rises and the 0-state of the D-input shifts to the Q-output, and further the Q-output of IC-2 is reset by lowering the Vgs voltage through diode D6. Comparators A4 and A2 measure over Fetti: 25 currents, examining the internal resistance of T1 and T2; ; current supply voltage. When A4 output exceeds vref. _. voltage, there is an overcurrent situation where the output of A2 or t A4 (depending on the current direction) rises to Ί ': resetting the IC-2 and then the IC-2 Q output is reset and the 30 Vgs voltage is discharged, and the power pair (or transistors) T1 and T2 are switched off.

• ► · 1 t '1 I * FETs receive a common VGS voltage, both of which are in the conductive state when the control is on. Only when:: 35 The SI switch is turned off and on, can the Fets be switched on again.

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In the event of an AC voltage zero crossing, the circuit operates as follows. As the AC voltage VAC rises from the negative side above zero, the output of comparator AI rises up, clocking the Q-output of the data at IC input D-2.

If necessary, the overcurrent limit set on the control circuit can be changed by changing the value of resistor R9. When the 10 resistors R9 are reduced, the current limit rises. In some applications, it is preferable to use a resistor R9 as a resistor.

Advantageously, the control circuit has a status indication indicating the output state. Illustrative indication is necessary especially if the actuator or other load on the control circuit does not otherwise indicate. The operation of the control circuit can be indicated, for example, as follows. The green LED LD2 when illuminated 20 indicates that the voltages are connected to the load and the red LED LD1 respectively indicates that the voltages are not connected. Resistors R21 and R23 limit: Current to LD2 and LD1.

: 25; ; It will be apparent to one skilled in the art that the various embodiments of the invention are not limited to the examples above, but may vary; within the scope of the following claims.

The control circuit may have components, for example resistors, not mentioned in the foregoing description, to accommodate voltages, currents, or the mutual operation of the various control circuit components.

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Claims (7)

1. A control circuit located between a load and an AC power network for switching on and / or pointing a voltage off / to the load, which pointing on the load has been controlled in the control circuit to start and / or fringed coupling of the load has been controlled in the control circuit to terminate at the zero point of the voltage or in the vicinity of the zero point, characterized in that a rate of change of the current to be measured for the load is limited and that the control circuit has a current limit, in excess of which the control circuit disconnects the load from the AC voltage network. Control circuit according to claim 1, characterized in that the rate of change of current has been limited according to time constant formed by resistance of a resistor R14 and capacitance of a final stage. Control circuit according to claim 1, characterized in that the control circuit feeds the load through end-stage pairs (T1, T2) and parts (T1, T2) of end-stage pairs are coupled and they operate with the same control. Control circuit according to any of the preceding claims, characterized in that the current limit for both steps is regulated by changing the value of a resistor R9. 5. A method for pointing load to the AC network and / or fringing from the AC using a control circuit, in which method pointing the load to the network and / or fringing from the network is controlled to bend / terminate at the zero point of the voltage, or near the zero point. characterized in that the rate of change of the alternating current to be measured to the load is limited and that the control circuit has a current limit, in excess of which the load is disconnected from the AC voltage network. Method according to claim 5, characterized in that when the load is switched on, the change of the current to be measured to the load is prevented faster than the set current change rate. Method according to claim 5, characterized in that when the load is switched off the change of the current to be measured to the load is prevented faster than the set current change rate.