SU955461A1 - Two-contact self-excited inverter - Google Patents

Description

(54) TWO-TIME SELF-EXCITING INVERTER

one

The invention relates to electrical engineering and can be used in power supply and electric drive systems for converting DC voltage to AC by means of push-pull inverters.

Push-pull inverters are known which contain main switches, a power magnetic element shunted by a capacitor in order to improve the trajectory of the key switching process and a device for delaying pulses in the key control circuits 1.

Such devices can be made either by means of additional rectifiers and capacitors 2 for the case of an external-excitation circuit, or by means of a trigger and diodes connected to the ends of the power inductive element {3 for the case of a self-excitation circuit.

In this and in another case, the circuit contains a large number of additional elements, which reduces the reliability of the inverter.

Closest to the invention is a push-pull self-initiating insulator containing main keys and a power inductive element included in the output circuit and a bypass capacitor of a lateral compensation switching commutator transformer whose limiting resistor is connected to the primary winding circuit. The IDA diode, the first output of each of which is connected to the corresponding extreme output of the inductive element. The disadvantage of this device is low reliability 3.

The purpose of the invention is to increase power.

The goal is achieved by the fact that an additional key is inserted in the device, the power circuit of which shunts one of the windings of the switching transformer, and the control circuit is connected to the second terminals of these diodes.

The power circuit of the additional key can be connected between one of the input pins of the inverter and the midpoint of the primary winding of the switching transformer or the outermost leads of this winding through the additionally introduced diodes, and can also shunt the output of the additional rectifier whose input is connected to the additional winding of the switching transformer.

FIG. 1-8 show embodiments of the proposed inverter circuit; in fig. 9 - voltage diagrams.

The inverter (Fig. 1) contains a power inductive element 1, shunted by a capacitor 2, the main transistor switches 3 and 4, connecting the element 1 to the input terminals 5 and 6. The inverter has a switching transformer 7 with a resistor 8 - current limiter of its primary winding 9, the extreme terminals of which are connected to the antiphase terminals 10 and 11 of the inductive element 1 via diodes 12 and 13. In the inverter there are also two diodes 14 and 15 connected by their same terminals (cathodes) to the terminals 10 and 11 of the inductive element 1. In addition, the inverter is bzhen normally closed additional key 16 having an input 17 for controlling, connected to the second terminals 18 and 19, diodes 14 and 15, and a power circuit with terminals 20 and 21, one of which

(20) connected to the primary winding 9 of the switching transformer 7, and the second

(21) - with input terminal 6. The secondary winding 22 of the switching transformer 7 is connected via a resistor 23 to the inputs for controlling switches 3 and 4. The inputs for controlling switches 3 and 4 are bridged by diodes 24 and 25 to limit the blocking voltage and resistors 26 and

27 for locking the keys 3 and 4 in the absence of a control signal at their inputs,

FIG. 2 shows an embodiment of a switch 16 with a transistor 28, the base of which is connected to a collector through a resistor 29, designed to provide an unlocking of the transistor 28 in the absence of an external control signal, and a diode 30 connected to the emitter circuit of the transistor 28, designed to ensure the locking of the transistor 28 when presence of an external control signal.

FIG. 3 shows an embodiment of a switch 16 with a transistor 28, the phase of which is connected to the collector via a resistor 29 and a diode 31 with a diode 30 in the emitter circuit and a parametric stabilizer (Zener diode 32 and a resistor 33) for stabilizing the voltage between the base and collector of the transistor 28. In this In the embodiment, the switch 16 in the open state is a voltage stabilizer on the windings of the switching transformer 7.

FIG. 4 shows a variant of the connection of the key 16 with the primary winding 9 of the switching transformer 7 through diodes 34 and 35, and FIG. 5 shows a variant of connecting the primary winding 9 of the switching transformer 7 with the inductive element 1 through two resistors 8 and through parallel resistor-diode circuits 8-12 and 8-13.

FIG. 6 shows a variant of the connection of the primary winding 9 of the commutating

transformer 7 with inductive element 1 through a resistor 8, while the key 16 is connected to the additional commutation winding 36, the transformer 7 via a rectifier 37, which in this case serves as a power source for the key 16. In this embodiment, a key is provided 16 with input and output of the inverter.

FIG. Figure 7 shows an embodiment of the power supply for the key 16 in the form of a rectifier 38 connected to the three leads of the inductive element 1 and to the pin 21 of the key 16. This allows the inverter to be stabilized with the keys not fully open 3 and 4.

FIG. 8 shows the second embodiment of the inverter - half bridge. It uses capacitors 39 and 40 as the power source for the winding circuits of the inductive element 1 and the keys 3 and 4.

In general, inductive element 1 is an arbitrary inductive circuit, for example, an electric motor winding, an output transformer with an arbitrary number of windings, one of which is connected to keys 3 and 4, the second is connected to switching transformer 7, and a third is connected to a capacitor 2.

The diagrams (Fig. 9) include the voltage diagram on the key 3 (a), the voltage diagram on the key 4 (6), the voltage diagram on the windings of the switching transformer 7 (8).

The inverter works as follows.

At the time point corresponding to the reference point, the key 3 (Fig. 1) is open (Fig. 9a) and provides a connection between the output 10 of the inductive element 1 and the cathodes of the diodes 12 and 14, with a negative output of the inverter power circuit 6. Key 4 is closed.

In this case, a voltage is applied to the semi-winding of the inductive element 1, and a current passes through it. Diode 12 is open and, through it and the resistor 8, the primary semi-winding of the switching transformer 7 is connected to the terminals 5 and 6 and a voltage is applied to it (Fig. 9c). On the secondary winding 21 of the switching transformer 7 there is a voltage holding the keys 3 and 4 and in the same state the key 3 is open and the key 4 is closed.

Diode 14 is open and provides locking of key 16. Output potential of inductive element 1, cathodes of diodes 13 and 15, as well as voltage on key 4 are equal to twice the value of the inverter voltage, (Fig. 96). This ensures the locking of the diodes 13 and 15.

Claims (4)

The considered modes of the device elements are maintained during the time interval O ... ti. Time t | corresponds to the saturation of the core of the switching transformer 7. At the same time, the voltage on the secondary winding 22 disappears. Accordingly, the key 3 closes due to resistor 26, and the key 4 remains closed due to resistor 27. However, the potentials of the terminals 10 and 11 of the inductive element 1 remain unchanged due to the voltage the capacitor 2. Thus, the process of locking the key 3 is carried out in the most vulnerable for. conditions, i.e. with a very small value of the voltage on the key 3. After locking the key 3, the current of the inductive element 1 is not interrupted, and an oscillatory process occurs in the circuit formed by the inductance of the inductive element 1 and the capacitance of the capacitor 2. This process continues during the time interval ti ... t4 without the participation of keys 3 and 4 and is as follows: capacitor 2 is discharged and then recharged, as a result of which the voltage on the closed key 3 reaches approximately twice the value of the inverter supply voltage This key 4 is decreasing, tending to zero. In the time interval i, ... t2, the keys 3, 4 and 16 are closed, the voltage on the windings of the switching transformer 7 is zero, and the current of its primary winding is limited by the resistor 5; the voltage on the key 3, the output 10 of the inductive element 1 and the cathodes of the diodes 12 and 14 rises to a value approximately equal to + 2V. At time t, the potential of the cathode of diode 14 reaches a level of + 2 Vm (potential of output 17 of key 16 corresponding to its open state). From this moment, the diode 14 is closed, and the key 16 is open, and through it the primary winding of the switching transformer 7 is connected to pin 6. This eliminates the possibility of switching the switching transformer 7 and affecting keys 3 and 4 in the time interval l2 ... lj. From the moment tj, the current of the primary half-winding of the switching transformer 7 decreases. The current decreases to zero during a negligible time interval, i.e. at time tj, practically the current of the primary semi-winding of the switching transformer is already zero. In the time interval ta -.- tj, the voltage on the key 3 and the potential of the cathodes of the diodes 12 and 14 of the output 10 of the inductive element 1 continues to increase. Keys 3 and 4 and diodes 12, 14, 13 and 15 are closed. Key 16 is open. The voltage on the key 4 and the potential of the output 11 of the inductive element 1 and the cathodes of the diodes 13 and 15 decreases and reaches at time tj a value approximately equal to H-1B. At this point in time, the diode 15 is unlocked, ensuring that the key 16 is locked. Accordingly, the middle terminal of the primary winding 9 of the switching transformer 7 appears connected not only with pin 6, but with pin 5 through a resistor 8. As a result, the diode 13 is biased in the forward direction, opens and connects There is a second output of the primary winding of the switching transformer 7 with the output 11 of the inductive element 1, whose potential is equal to + 1V. This leads to the appearance of voltage on the windings of the switching transformer 7 with polarity inverse to the time interval O ... ti (Fig. 9c). This ensures unlocking of the key 4 and more reliable locking of the key 3. Since by the time ta the voltage on key 4 did not exceed -IV, then when unlocking it, dynamic losses are almost completely excluded. In the time interval tj ... t5, the key 16 is closed: by the signal of the switching transformer 7, the key is kept closed, and the key 4 is open. The time interval 0 ... 14 corresponds to the first half-period of the inverter operation. In the time interval t4 ... t6, which corresponds to the second half-life of the inverter, in the latter processes similar to those considered take place. Further, the processes are repeated. Thus, in the proposed device, as in the prototype, the dynamic losses in the keys are excluded. However, this effect is achieved by simpler means, i.e. using a normally closed key. The embodiments of the device elements shown in FIG. 2-7 further expand its range of application, providing stabilization of the frequency and amplitude of the output voltage, as well as the ability to remotely turn off the inverter. The variant shown in FIG. 4, allows to increase the reliability of the inverter in the case of a slow decrease in the current of the switching transformer. The options shown in FIG. 5 and 6 allow switching transformers with arbitrary winding designs to be used in the inverter. Claim 1. A push-pull self-exciting inverter containing main switches, a power inductive element included in an output circuit shunted by a transverse compensation capacitor, a switching transformer, the limiting resistor included in the primary winding power supply circuit, and two diodes each connected to a first output the corresponding extreme output of the inductive element, characterized in that, in order to increase reliability, an additional key is introduced into it, the power circuit of which is shunt It drives one of the windings of the switching transformer, and the control circuit is connected to the second terminals of these diodes. 2. The inverter according to claim 1, wherein one power output of the additional key is connected to the midpoint of the primary winding of the switching transformer, and the other power output to one of the input leads of the inverter. 3. The inverter according to claim 1, characterized in that one power output of the additional key is connected through two additional the entered diode with the extreme leads of the primary winding of the switching transformer, and the other power lead with one of the input leads of the inverter. 4. Invert |) according to claim 1, characterized in that the power circuit of the auxiliary switch is connected via an inserted rectifier to the extreme terminals of the auxiliary winding of the switching transformer. Information sources, taken into account in the examination 1. Moin V.S. Laptev N.N. Stabilized transistor inverters. M., “Energie, 1972, p. 351, fig. 9-19. 2. USSR author's certificate number 663048, cl. H 02 M 7/537, 1976. 3. USSR author's certificate number 729787, cl. H 02 M 7/537, 1979. s f eight ijizi3 i is is  (rig 9