DE2412615A1 - CIRCUIT ARRANGEMENT FOR REGULATING THE ELECTRICAL AC POWER SUPPLIED TO A CONSUMER - Google Patents

Description

Circuit arrangement for regulating the one supplied to a consumer AC electrical power

The invention relates to a circuit arrangement for regulating the electrical alternating current power supplied to a consumer with a controlled semiconductor element as the regulating element.

Controlled silicon rectifiers have previously been used to control the electrical power supplied to a consumer. A so-called trigger device was generally required for this, which was connected to an ignition or plias slide circuit at the time when an ignition signal was switched on to the control electrode of the silicon rectifier. The trigger devices contain unijunction transistors, trigger diodes and similar items. One of the advantages of using trigger devices is that with such devices the Control circuit can be operated at low power, since the energy is usually stored in a capacitor and then

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the stored energy is released to ignite the rectifier.

It has been found, however, that when a silicon controlled rectifier is used, there is a considerable impedance between the control electrode and the cathode. However, for a variety of reasons, it is common practice to internally shunt this impedance significantly. There are many silicon controlled rectifiers that do not have such an internal connection. These are, for example, types C107B from General Electric, RCA-107 from RCA and KCR ¹ IOy- ¹ I- from Motorola. It has been shown that this property of a silicon controlled rectifier can be used to advantage in order to implement ignition circuits which operate relatively economically, reliably and precisely.

The object of the invention is therefore to provide a circuit arrangement to propose to regulate the electrical power, which is constructed with relatively few individual parts, at the same time, however, enables relatively precise control of the power.

To solve this problem, a circuit arrangement of the type mentioned is designed according to the invention in such a way that that a semiconductor element with a high resistance between the cathode and control electrode with its anode to one pole of the VJechseIstromquelle, with its cathode connected to a terminal of the Consumer and with its control electrode is connected to the cathode via a capacitor and that in a charging circuit for the capacitor a variable resistor is connected to the control electrode and connected to the connection connected between anode and AC source.

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It can therefore be a relatively high impedance between the cathode and the control electrode is provided a controlled silicon controlled rectifier ¹ which is connected with a load to be powered, and an AC power source in series. The ignition circuit contains a resistor and a capacitor in series and is connected to the controlled silicon rectifier. The connection between these two elements is connected to the control electrode, so that when the capacitor is charged to a sufficiently positive voltage value, a current of such magnitude is supplied to the controlled silicon rectifier that it becomes conductive. The resistance can be changed to regulate the charging speed of the capacitor.

Embodiments of the invention are described below with reference to the figures. Show it:

1 shows a schematic representation of a first exemplary embodiment the invention,

2a shows a representation of voltage forms on the capacitor and on the silicon controlled rectifier;

2b shows a representation of voltage forms on the capacitor and on the silicon rectifier at low current flow angles to show the effect of changing the time constant by a factor of 2,

2c shows a representation of the voltage forms on the capacitor and on the controlled silicon rectifier at high current flow angles,

3 shows a second embodiment of the invention, FIG. 4 shows a third embodiment of the invention, 5 shows a fourth embodiment of the invention,

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FIG. C the circuit implementation of the embodiment shown in FIG. 4,

FIG. 7 shows the circuit implementation of the circuit shown in FIG embodiment shown and

8 shows the arrangement of the circuit according to FIG. 6 in one Power tool that can be controlled as a consumer.

Fig. 1 shows a circuit arrangement according to the invention, which is used to feed a consumer. This 5, st as a series motor shown with a rotor 2 and a field winding 4, it is connected to one pole of an alternating current source a line 5 connected. A line 6 is connected to the other pole of the alternating current source. She leads to a controlled Silicon rectifier 8 via a control switch 10, which switches the arrangement on and off. The rectifier 8 has an anode 12, a cathode 14 and a control electrode 16. A line 17 connects the cathode 14 to the stator winding 4 »A control or ignition circuit is formed by a variable resistor 18, which is connected to a capacitor 20 is connected in series and to the rectifier 8. As can be seen from the figure, the connection point is the Resistor connected to the capacitor directly to the control electrode 16. The cathode 14 is connected to one terminal of the Capacitor 20 and the field winding 4 connected. The anode 12 is connected to a connection of the switch 10 via a line 21 connected.

The illustrated embodiment shows a specific row arrangement the control switch, the load and the. Power source, other arrangements can also be provided. For example the load can be connected between the anode and the switch.

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It should be noted that the silicon controlled rectifier 8 is of the type that has a relatively high resistance between the control electrode and the cathode. These Selection is therefore made in order to enable the capacitor 20 to be charged in the negative direction. When a low resistance were present between the control electrode and the cathode, the negative charge would to a certain extent be above them Resistance is diverted and the ignition delay is reduced. It is also possible to use the "Zener" property of the cathode control electrode path to take advantage of. This means that in such controlled silicon rectifiers, in which no internal shunt connection between cathode and control electrode is provided, the cathode holds a negative voltage until a Zener value is reached. Then the arrangement conductive and the voltage is held at this Zener value. Suitable controlled silicon rectifiers are for example the above types.

If desired, the operating switch 10 can also be arranged at the point 22 as shown in dashed lines, to a to fulfill the purpose yet to be described. The same possibility also arises for the exemplary embodiments shown in FIGS. 3, U and 5.

The operation of the circuit will now be described with reference to FIGS. 2a to 2c. In these figures, the upper curve represents the Voltage curve at the anode 12, while the lower curve applies to the voltage curve across the capacitor 20. Assuming that switch 10 is closed and the rectifier During the positive half cycle of the alternating current on line 6 was conductive, the capacitor has a slight positive Charge that corresponds to the forward voltage between the control electrode

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and the cathode of G Ie; ichrichte rs corresponds. During one negative IIalbv * e] .le on line 6 becomes the capacitor negatively charged. During the following positive wave of calves, the negative charge on the capacitor is zero is reduced, and the capacitor is then charged positively to a value that allows sufficient current to flow in the control electrode allows to control the rectifier conductive. This is through point 24 on the top curve shown in Fig. 2a. Part 26 of the lower curve of this figure shows the value of the small positive charge which is present in the The capacitor remains between the control electrode and cathode of the rectifier due to the forward voltage. It is recognizable, that the charge of the capacitor remains at this small positive value until the next negative half-cycle begins. By Setting the resistor 18, the charge or discharge strength of the capacitor can be changed in order to Determine the point or phase angle of the positive half-wave, in which the rectifier becomes conductive.

Due to the negative charging of the capacitor four of the several Benefits achieved. For example, with a circuit for controlling a specified amount of power, it is possible to use a capacitor with a lower capacitance value, since the negative charge delays the ignition of the rectifier more than it would be without a negative charge. A Another advantage is that a negative charge on the capacitor creates a reverse voltage on the control electrode of the Rectifier generated, which is therefore less due to interference voltages ignites quickly. Another advantage results from Fig. 2a, it consists in the fact that a change in the ignition voltage at the control electrode has only an insignificant influence on the current flow angle due to temperature changes. How out Fig. 2a shows at point 27, the change in the current

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flow angle is very small if one assumes a state at which the voltage on the capacitor 20 has the value zero and due to temperature changes the rectifier at this zero voltage is ignited at the control electrode. This is by the minor Shift of the ignition point between the value Mull and the value 26. This shift is at 29 designated.

A further advantage can be seen on the basis of FIG. 2b. This figure shows with the curve 28 that the voltage across the capacitor is generated by a resistance-capacitance combination with the values R and C, so that a time constant RC is present. if the values of the resistance and the capacitance are changed and this results in the time constant 2RC according to curve 30, so the effect on the delay or the ignition angle is very small. This value is only shifted by the time that is due the vertical lines marked with RC and 2RC are designated. Thus, fine adjustment or adjustment is not required, and arbitrary ones can be selected Resistors and capacitors can be provided which have predetermined values for the circuit design.

Fig. 2c shows the effect of the "Zener" properties of the Control electrode of the silicon rectifier. It is recognizable, that the capacitor is charged negatively until the Zener voltage of the control electrode at 32 is reached. The capacitor voltage remains at this negative value until the positive half-wave begins. Then the capacitor is charged positively to a value which is sufficient to generate a forward voltage at the control electrode, so that the rectifier is conductive will. If the capacitor continued to charge in the negative direction, it would have to be fast during the short part of the positive half-wave before the rectifier becomes conductive. This aspect of the invention also enables the use of capacitors with low operating voltages,

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ORIGiNAL INSPECTeD

and the variable resistor need not have a low resistance for large current flow angles. That is an advantage, since a lower resistance for large flow angles results in a relatively large amount of heat generation would have.

Fig. 1 shows in dashed lines at 22 another Possibility of arranging the operating switch 10. If the Switch is placed at 22 and the circuit is connected to a power source, the ignition circuit is off variable resistor 18 and the capacitor 20 always fed. When the circuit is to be put into operation and switch 22 is closed, the rectifier will not fire until the desired delay point is reached is. If the switch is at point 10, it is possible to apply a single large power pulse to the load to give when the switch is closed. This results from the fact that when the switch 10 is closed, the line 6 is positive can be and the rectifier ignites with a large current conduction angle, since no negative charge ignites the rectifier delayed.

In some cases it can be beneficial to operate the control circuit at a voltage which is lower than the supply voltage For this and for other reasons, the circuits according to FIGS. 3, 5 and 4 can be provided. There are Elements similar to those in FIG. 1 have the same reference numerals Mistake. In the embodiment shown in Fig. 3, the variable resistor 18 'is provided with a fixed voltage divider connected, which ordered from two resistors 34 and 36, which is connected to the feed lines. The voltage at the variable resistor 18 'is slightly less than that Supply voltage, which proves to be beneficial when certain

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Individual parts can be used to extend the service life. For example, you can use changeable resistors with movable ones Obtain a longer service life for grinders by reducing the potential at the grinder. The circuit works otherwise like that shown in FIG.

Fig. 4 shows a circuit in which the "voltage divider a adjustable resistor * 36 'instead of a fixed resistor 36 contains. When operating this circuit, the resistors 18 'and 36' are selected in terms of their relative values so that that the current conduction angle is increased when the resistance value 18 'goes to zero. When the resistance 18 'approaches zero, a transition point is reached at which the capacitor .sator is charged to a maximum negative value, which, however, is below the Zener voltage of the rectifier. Around To further increase the conduction angle, the resistor 36 'is decreased. This not only reduces the time constant, but at the same time also the voltage from the voltage divider with the resistors 34 and 36 '. In practice, the resistances 18 * and 36 'can be coupled to one another, so that only a single actuating element is provided for changing them.

An advantage of this circuit is that the time constant can be reduced to a low value «This means that the current conduction angle can be increased without the resistors 34 and 36 'having to be as low as in the circuit According to FIG. 3, it is also possible to operate this circuit in such a way that the Zener value of the rectifier never reaches will. Thus, cheaper silicon controlled rectifiers be used.

In the embodiment shown in FIG. 5, the resistor is 36 '' shown as a potentiometer, otherwise works

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ORiGfNAL INSPECTED

24126T? ^7th

the circuit like that shown in FIG.

With a power supply of 120 volts and 60 Kz and one Controlled silicon rectifier with a reverse voltage of 250 volts and a control circuit for 0.7 milliamps maximum value results in the following values the remaining elements:

Fig. 1 Fig. 3 Fig. 4 Fig. 5

Resistance 18 or 18 »OHM 160k 40k 27k 27k

up to 15k up to 0 up to 0 up to 0

Resistor 34 OHM 12k 27k 27k

Resistor 36, 36 '

or 36 "OHM 4k 7k 7k

to 500 to

Capacitor micro 0.68 1.5 2.2 2.2

farad

In Fig. 6 and 7 further embodiments of the invention are shown. These figures show in particular the physical arrangement of the individual elements with respect to one another in order to achieve the advantages that can be achieved with the invention. Corresponding reference symbols are used here as in the previous figures. FIG. 1 shows an arrangement which corresponds to the exemplary embodiment according to FIG. Here, the resistance elements 18 ', 34 and 36 ^{f are} printed on an insulating circuit substrate 39, so that the arrangement shown results in which the element 36' consists of two sections 40 and 42 and the element 18 'is aligned with the section 42 . A line 44 is connected to one end of the element 18 ′ and to the connection point of the control electrode 16 with the capacitor 20. A sliding contact in the form of a slider 46 with three contact points 47,

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ORIGINAL INSPECTED

48 land 5 0 with the relative distance shown is provided.

The figure shows three possible positions of the wiper 16. In the first position, which is shown in dashed lines on the left-hand side of the figure and labeled "highly conductive", the contact point 47 is at the connection of the sections 40 and 42, while the contact point 48 is in contact with the other side of section 42. In this position, the section 4 2 is bridged by the position of the wiper between the contact points 47 and 48, so that the resistance value of the resistor 36 'is correspondingly reduced. At the same time, the contact point 50 has no contact with any part of the resistor 18 ', so that its resistance value in the circuit is reduced to Hull. However, the contact point 50 is in contact with the line 44 so that a connection is made from the junction of the sections 40 and 42 to the line 44. If the wiper is arranged as described, the effect is that the resistance value 18 ^f is reduced to zero and the resistance value 36 'is reduced by bridging the section 42. If the wiper is arranged in this way, the time constant of the ignition circuit is significantly reduced, so that the capacitor 20 'charges more quickly and the current conduction angle of the rectifier 8 is increased.

If the current conduction angle is to be reduced, the Grinder 46 is moved to the right to a point labeled "at 18 '* = 0". In this position is the contact point 47 at the connection of the section 42 with the resistor 34. However, the dimensions are chosen such that that the contact point 50 is not yet in contact with one

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Part of the resistor 18 'is so that its value is still Is zero. As can be seen, this is the resistance section 42, however, is no longer bridged by the M-6 grinder, see above that he is in the charging circuit for the capacitor 20 ' and thus increases the time constant of this circuit. As a result, the point in time for the rectifier 8 to become conductive is delayed.

When the wiper 46 is moved further to the right, the contact point 50 begins contact with the resistor 18 ', whereby this resistance within the charging circuit is increased. When the grinder shows the solid line Position reached, the entire resistance is 18 ' in the circuit, and the current conduction angle of the rectifier 8 has its lowest value, which means that the load is fed to a minimum.

In Fig. 8, switch 10 is with a bypass switch 52 mechanically coupled, both are connected to a control button 54, which is in an extreme position by a spring 56 When the button is pressed against the force of the spring 56, the switch 10 is first closed and thus fed the circuit. Further movement of the button 54 causes the grinder 46 to move to the left, so that the speed of a motor in a power tool increases. At the innermost limit of his movement, the Slider 46 is moved the greatest distance to the left and switch 52 is closed, thus bridging of the rectifier 8 takes place and so that the motor works at full speed. Thus causes a running depression of the knob 54 continuously changes the speed of the motor within the range from zero to maximum speed.

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ORIGINAL INSPECTED

In Fig. 7, the embodiment shown in Fig. 5 is shown on an insulating base 58, on which, as before, resistor sections 40 'and 42' are formed, which the resistor element 36 ^l! , form the resistor 34 and zv / ei resistor abs chnxtte 6 0 and 6 2 for the resistor 18 *. In this exemplary embodiment, the wiper 64 need only be provided with two contact points 66 and 68.

When the wiper 64 is in the extreme left position, the dashed line -shown and with "highly conductive" is designated, none of the resistance sections 42 ', 60 or 62 touched by the contact points 66 and 68 of the slider 64 so that this bridges the connection the resistance sections 40 'and 42' to the line 70 which is connected to the junction of the capacitor 20 'and the control electrode 16. Works in this position the circuit so that the capacitor charges the fastest to the point where the rectifier becomes conductive 8 caused. When the wiper is moved to the right, the contact point 66 contacts the resistor section 42 'and reduces the current conduction angle of the rectifier. this continues until a transition point is reached when the slider is in the position indicated by "18 '= 0" is designated. Moving the slider 64 further to the right brings the contact points 66 and 68 into contact with the Resistance sections 60 and 62, whereby the current conduction angle of the rectifier is further changed. This continues until a minimum current conduction angle is reached, if the grinder is in the position shown in solid lines. This embodiment can be provided in a power tool that is controlled by a control button in the is operated in the same manner as shown in FIG. The circuit board, the wiper, the rectifier and the Capacitors can be housed in the handle of such a tool.

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Claims (9)

Patent claims 1. Circuit arrangement for regulating the electrical AC power supplied to a consumer with a controlled semiconductor element as a regulating element, characterized in that a Kalbleiterelement with a high Resistance between cathode and control electrode with its anode to one pole of the alternating current source, with its Cathode is connected to one connection of the consumer and with its control electrode connected to the cathode via a capacitor is and that in a charging circuit for the capacitor, a variable resistor to the control electrode is switched on and connected to the connection between the anode and the alternating current source. 2. Circuit arrangement according to claim 1, characterized in that the variable resistance to the connection point of the Capacitor is connected to the control electrode and to the anode. 3. Circuit arrangement according to claim 1, characterized in that the charging circuit has a resistance voltage divider, which is connected between the anode and the cathode, and that a variable resistor is connected to the tap of the Voltage divider is switched on. 409839/07 8 0 4. Circuit arrangement according to claim 3, characterized in that that a device for adjusting the voltage is provided at the tap of the voltage divider. 5. A circuit arrangement according to claim M, characterized _s that said apparatus is formed to adjust the voltage by a variable resistor connected between the tap and the cathode. 6. Circuit arrangement according to claim 4, characterized in that it is on an electrically insulating circuit carrier is applied that the voltage divider and the variable resistor at a distance from each other on the circuit ^ - carrier are arranged that a movable grinder with a first and a second provided at a distance Contact point is provided, this distance having an effect on the voltage divider or part of the changeable Resistance allows, but is not so great that both contact points on the voltage divider and at the same time the variable resistor act, so that an adjustment of the voltage at the tap of the voltage divider and an adjustment of the variable resistance is possible. 7. Circuit arrangement according to claim 6, characterized in that that the voltage divider cut two separate resistance and that the variable resistor consists of a resistor section, the wiper having a has third contact point, which is one of the other two. Contact points is arranged closer than the other Contact point. 8. Circuit arrangement according to claim 6, characterized in that the voltage divider and the variable resistor each have two separate resistor sections. 409839/0780 9. Use of a circuit arrangement according to one of the claims 1 to 8 for a power tool with drive motor and actuating element, characterized in that the drive motor forms the electrical consumer and that a mechanical connection between the changeable Resistance and the actuator is provided. 409839/0780 Blank page