Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
  • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
  • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
  • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
  • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
  • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration

Definitions

• the invention relates to a DC-fed circuit for generating voltages and / or currents of different curve shape and / or different frequency and / or different polarity with at least one load.
• the invention has now set itself the task, starting from a DC voltage supply, of developing a circuit with which the solution to this problem is possible.
• the invention is now characterized by a choke coil connected in series with this load and at least two controlled semiconductor switches which are each connected in series with respect to the load and the choke coil, but are in different conduction paths, and these conduction paths have different potentials Supply voltage are connected, with one switch being open during operation, while the other switch is open and closed in an alternating sequence and actuating the previously alternating sequence (clock frequency) after an adjustable or controllable period of time Switch kept open is consequently open and closed and this sequence of switch actuation (pole reversal frequency) is repeated continuously.
• a particularly simple circuit of this type is characterized according to a feature according to the invention in that the line path comprising the load and choke in series connection is connected to an average value of the supply voltage.
• a further circuit of this type is characterized according to a further feature of the invention in that the line path comprising the load and the choke in series connection via at least two capacitors, each with respect to the load and the choke coil ⁇ because it is connected in series, but in different conduction paths, to different potentials of the supply voltage, the capacitors being connected to the same potentials of the supply voltage as the controlled semiconductor switches.
• Another circuit which meets the highest requirements in terms of performance and possible variations, is characterized according to a further feature of the invention. is characterized in that the line path containing the load and choke in a series circuit is connected to different potentials of the supply voltage via at least two further controllable semiconductor switches which are connected in series but with different line paths with respect to the load and the choke coil, these semiconductor switches are opened or closed in the period of the pole reversal frequency of the other semiconductor switches and thus each form a closed circuit in connection with the load and choke coil, in which the direction of the current flow changes in accordance with the pole reversal frequency.
• the size of the ratio of the pole reversal frequency to the clock frequency determines the control quality of the circuit; the greater this ratio, the smaller the throttle can be made. It is therefore expedient to set this ratio at about 1: 1000, preferably even higher.
• FIG. 1 to 3 show three different circuits; Figures 4 and 5 voltage and current waveform diagrams.
• Fig. 6 a . 7 shows a detail from the current flow diagram according to Tig. 5 on a considerably enlarged scale.
• a battery B with a center tap and with the terminal voltage U is used as the voltage source.
• the line branch 3 which has the choke D and the load L in series connection, is connected on the one hand to the center tap of the battery B, and on the other hand between the two controlled semiconductor switches T, and T «, each of which is individually connected to a terminal of the battery B, so that each is connected in series with the inductor D and the load L.
• the control of the semiconductors is explained in detail below. First of all, it should be noted here that during a first period of time the semiconductor switch T, is opened and closed in a clockwise manner (clock frequency) and during this period the other semiconductor switch T_ is open.
• Load current now depends on the one hand on the inductance of the choke and the clock frequency of the switches T and T_; the time duration of the current flow in one direction from the pole reversal frequency.
• Both the clock frequency and the polarity reversal frequency can be controlled by different variables, which will be discussed in the following.
• FIG. 2 A further circuit with which particularly low-frequency voltages or currents can be obtained starting from a DC voltage is shown in FIG. 2.
• the voltage U is at the terminals XY of the circuit, parallel to the semiconductor switches T. and T ", free-wheeling diodes D. and D" are provided.
• a capacitor C is arranged in different circuits, so that the load and inductor in series connection includes a line path via two capacitors, each of which is connected in series with respect to the load and the inductor , but are in different line paths, is connected to different potentials of the supply voltage, the capacitors C being connected to the same potentials of the supply voltage U as the controlled semiconductor switches T. and T_.
• the controlled semiconductor switches T 1 and T 1 are in the sense of the above-mentioned clock frequency or polarity reversal frequency. operated.
• the frequency of the voltage applied to the load is u. a. depending on the capacitance and the time constant of the capacitors.
• This DC-powered circuit is designed as a bridge circuit.
• a transistor T. to T. is arranged in each outer branch of this bridge circuit.
• Two of these transistors, namely the transistors T, and T " " which lie between the connection points X and Y for the supply voltage U, have freewheeling diodes D. and D ⁇ connected in parallel.
• the other two transistors T and T. Diodes D and D. are connected in parallel for protection purposes.
• the bases B. to B ⁇ of the transistors T 1 to T. are connected, for example, to integrated circuits, which are not shown here, however.
• the load L is connected to terminals A and E in the diagonal branch of the bridge circuit.
• ohmic, inductive and capacitive resistances can be considered as loads, but also those that have a complex resistance behavior.
• the choke D is connected between the terminal A and the connection point F between the two transistors T. and T 1 serving as semiconductor switches.
• a capacitor C is provided here in parallel with the load. Instead of this capacitor, which is parallel to the load L, another capacitor C can be provided, one electrode of which lies between the load L and the inductor D and the other electrode of which is at the connection point Y for the supply voltage U which has the lower potential. This is indicated in Fig. 3 with a dashed line.
• the transistors T 1 and T 1 serving as semiconductor switches are actuated in the sense of the clock frequency and polarity reversal frequency described above. In contrast, the transistors T and T serving as semiconductor switches are only switched over according to the polarity reversal frequency.
• 6 illustrates a pulse sequence with which the bases of the transistors T, and T_ can be controlled.
• PD means the period; ED the duty cycle (pulse length) and TL the key gap.
• the ratio between duty cycle ED and period duration PD is referred to as the duty cycle. This duty cycle is adjustable and changeable on the integrated circuit, not shown, mentioned as an example.
• the circuit of FIG. 3 explained above in its basic structure is now to be used to operate a DC-powered gas discharge lamp, which is symbolized by the load L in FIG. 3.
• the operation of a gas discharge lamp with direct voltage is preferable to that with alternating voltage, since in this case the gas discharge lamp flickers less and shows a higher luminous efficacy.
• the only disadvantage is that during continuous operation with direct voltage, deposits accumulate in the electrode area of the gas discharge lamp, caused by the ion flow which always flows in the same direction. In order to avoid these deposits, the lamp is therefore reversed in polarity, for which mechanical switches have hitherto been used. Using the circuit described, this is now done electronically as follows:
• the direct voltage U present at the terminals X, Y can either be taken directly from a direct voltage network, but it can also be provided via a converter (alternating current / direct current).
• the transistors T. to T. serve as electronic switches and their bases are controlled by the size of the operating current via pulse trains according to FIG. 6.
• the transistors T, and T. closed, the transistors T "and T, however, open.
• the transistor T. or its base B is driven by a pulse sequence shown in FIG. 6.
• the duty cycle ED of a pulse the transistor T is closed and direct current flows from the terminal X via the transistor T., the inductor D and the lamp L via the transistor T., which is always closed during this operating phase, to the terminal Y.
• the nominal Size of the lamp operating current is reached, that is - in terms of time - at the end of the duty cycle ED des
• Control pulse the transistor T. opens, the current flow from the network is interrupted and the magnetic energy built up in the inductor D by the current flow is now converted into electrical energy and supplies a counter voltage, which lasts until the switch-on time of the next control pulse, i.e. during the key gap TL, the current flow through the lamp L is maintained in the same direction, the energy stored in the choke being reduced.
• the next following control pulse is applied to the base B. of the transistor T, which in turn is switched on, that is to say closed, and as a result energy and current from the network are again supplied to the circuit in the manner described, until shortly before the nominal value of the lamp operating current is reached again. whereupon the aforementioned switching process is initiated and carried out again.
• the lamp L is always let through by the current in the same direction.
• the described control processes are very short and take place in fractions of a second.
• the transistor T. is always closed.
• the lamp L is now reversed after some time. This now happens because the
• Transistors T. and T. are opened, the transistor T, is closed and the transistor T "is actuated in cycles in its manner via its base B., as has been described in connection with the transistor T. The current flow in the lamp is reversed.
• the capacitor C can be dispensed with in the operating mode described here.
• the polarity reversal frequency can be derived and controlled, for example, from the mains frequency if the direct voltage at the connection terminals X, Y of the circuit is via an alternating current, not shown here - DC converter is obtained. Other control frequencies for polarity reversal can also be used successfully.
• the period of the polarity reversal is always greater than the period of the control pulses (clock frequency).
• the diodes D. and D_ connected in parallel with the transistors T, and T_ serve as freewheeling diodes which maintain the current flow. when the transistors T and T open and close in a pulse-controlled manner, the diodes D and D have a protective function in parallel with the transistors T and T.
• the current profile through the gas discharge lamp L after the circuit according to FIG. 3 and the operating mode described above is shown schematically in FIG. 5.
• it is a trapezoidal course with a changing sign.
• the period P of this sequence depends on the polarity reversal. If the current curve shown in the diagram with a straight line is shown enlarged, so to speak, the result is a line which is shown in FIG. 7 and which represents the section G encircled in FIG. 5, so to speak, on an enlarged scale.
• This line is jagged, its rise or fall is determined by the resistance behavior of inductor D and load L, their reversal points are dependent on the clock frequency and their smoothness (hatched areas) is determined by the smoothing capacitors C after the circuit in FIG. 3.
• a voltage profile as shown in FIG. 4 can also be forced, for example.
• Circuit-inherent electrical quantities can be used to control the clock frequency or the polarity reversal, that is, quantities that can be measured, for example, at the load L, such as voltage, voltage increase, current, current increase, active or apparent load.
• the load current was used to control the clock frequency for the semiconductor switches T. and T. That is, the semiconductor switches T. and T. were opened in cycles before the load current reached the nominal lamp current and switched on again as soon as it had dropped somewhat.
• the current values at which the device has been switched on or off are designated I. or I. in the diagram according to FIG. 7.
• the polarity reversal frequency (P - Fig. 5) was derived from the frequency of a conventional AC power supply network with 50 Hertz. Control from or via a formwork-independent variable, such as the network frequency of an AC power supply network, is referred to as external excitation.
• the polarity reversal frequency can be controlled by the voltage rise at the capacitors C (natural frequency). Further control possibilities for the clock frequency result from the choice of the ratio of the on-time ED to the off-time TL or by changing the pulse duration PD (pulse width modulation).
• programmable processors are expediently used, with which control curves and control curves of any shape can be achieved. If the operation of a gas discharge lamp L has been explained in more detail above with reference to FIG. 3, it should be mentioned here that other devices or apparatuses can also be used as the load. For example, an AC motor, to which an AC voltage that can be changed with regard to its frequency and size can be supplied in order to regulate the speed and torque within wide limits.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Circuit Arrangements For Discharge Lamps (AREA)
• Electronic Switches (AREA)
• Inverter Devices (AREA)

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• 1985
  • 1985-02-04 AT AT304/85A patent/AT392384B/de not_active IP Right Cessation
• 1986
  • 1986-01-30 EP EP86901064A patent/EP0210242A1/de not_active Ceased
  • 1986-01-30 AU AU53957/86A patent/AU588282B2/en not_active Ceased
  • 1986-01-30 US US06/928,285 patent/US4725762A/en not_active Expired - Fee Related
  • 1986-01-30 WO PCT/EP1986/000042 patent/WO1986004752A1/de not_active Application Discontinuation
  • 1986-02-04 ZA ZA86799A patent/ZA86799B/xx unknown
  • 1986-02-04 ES ES551643A patent/ES8800564A1/es not_active Expired

Non-Patent Citations (1)

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