SU913533A1 - Semibridge inverter - Google Patents

Description

The invention relates to electrical engineering and can be used to power radio equipment and communications.

A half-bridge inverter is known, containing two series-connected transistors, a capacitive voltage divider, a switching and an output transformer, an additional voltage divider, the primary one being. the coil of the switching transformer is connected between the common point of the transistors and the middle point of the additional voltage divider (1).

The disadvantage of this device is low efficiency due to power losses in the saturating transformer and resistive voltage divider, the impossibility of correcting the duration of half periods with significant variations in the parameters of transistors.

Closest to the proposed technical solution is a half-bridge inverter containing two po2

hence the connected transistor, capacitive voltage divider, transformer, the primary winding of which is included. between the midpoint of a capacitive divider and the connection point of transistors, and the windings of positive feedback through current-carrying circuits containing ballast resistors are connected to control transitions, shunted circuits of reverse conduction of the corresponding transistors, and balancing elements of the correction unit (2}.

The disadvantage of this device is the complexity and impossibility of automatic. balancing the saturating transformer.

The purpose of the invention is to simplify and extend the functionality of the converter.

To achieve staged sang

in the famous half bridge inverter,

specified current limiting circuits

supplied with capacitors included

3

in series with the specified ballast resistors, and the indicated balancing elements of the correction unit are connected in parallel to the capacitors.

Moreover, these elements balancing node correction made in the form of resistors, and at least one of them is adjustable.

In addition, the adjustable resistor is made in the form of an additional transistor connected by a control input through an amplifier cascade with an output of an input differential amplifier, the inputs of which are connected to the outputs of the first and second resistive voltage dividers, and the extreme terminals of the first divider are connected to the extreme terminals of the indicated capacitive divider, and the conclusions of the second divider are between the middle point and the negative terminal of the capacitive divider.

FIG. 1 is a schematic diagram of a half bridge inverter; in fig. 2 is a schematic diagram of a half-bridge inverter with automatic balancing of the half-periods of operation of a power transformer.

A half-bridge inverter containing two series-connected transistors 1 and 2, a capacitive divider 3 and 4 voltages, a transformer 5, the primary winding 6 of which is connected between the midpoint of the capacitive divider and the junction point of the transistors, and the positive feedback winding 7 and 8 through the current limiting circuits containing the ballast resistors 9 and 10 are connected to the control transitions, shunted by the reverse conduction circuits 11 and 12 of the respective transistors, and the balancing elements, made in the form of adjustable transistors 13 and 14 are provided with capacitors 15 and 16 connected in series with said ballast resistors, and said elements of balancing the capacitors are connected in parallel.

In addition, the specified adjustable resistor is made in the form of an additional transistor 17 connected by a control input through an amplifier cascade 18 with an output of an inputted differential amplifier 19, the inputs of which are connected to the outputs of the first 20 and 21 and second 22 and 23 resistive voltage dividers connected to

 extreme findings of the indicated capacitive

1.3533 4

divider 3 or 4, and the extreme conclusions of the second divider - between the midpoint and the negative terminal of the capacitive divider.

5 Half-bridge inverter operates as follows.

Consider its work in the absence of a correction node.

One half open one of

Yu transistors, such as transistor 1.

In this case, the positive feedback winding 7 maintains it in the open state, ensuring the flow of the base current through the circuit: winding 7, resistor 9, charging capacitor 15, emitter-base transition of transistor 1.

The transistor 2 is closed by means of a shunt circuit of reverse conduction 12, and the capacitor 16 is charged

20 to the positive side winding voltage with polarity indicated without brackets.

As the capacitor 15 charges (the polarity indicated without parentheses) the base

25, the current of transistor 1 decreases, which leads to the output of transistor 1 from saturation. This increases the resistance of its collector circuit, decreases the collector current and at

30 reaching the magnetizing current of the transformer 5, the polarity of the voltage on its windings changes.

When the polarity of the voltage on the windings of the transformer 5 changes, a blocking voltage equal to the sum of the voltages on the winding 7 and the capacitor 15 (the polarity indicated without brackets) is applied to the emitter – ter-base transition of the transistor 1, which leads to the accelerated dosing of transistor 1. When This through the emitter-base transition of the transistor 2 begins to flow the base current, determined by the sum of the voltage on the winding 8 and the capacitor

4 $ 16 (polarity indicated without brackets)

and the resistance of the ballast resistor 10, causing the forced unlocking of the transistor 2. As the capacitor 16 overcharges, the voltage on it changes polarity (in brackets), the base current of the transistor 2 decreases, which leads to an increase in the resistance of the collector circuit of transistor 2 and a decrease in the collector current, as a result which causes a change in the polarity of the voltages on the windings of 6 8 transformer 5. At the same time, similarly to the considered, there is a forced dozing of the transistor 2

5 913533 6

and the forced unlocking of the transistor 1. The pattern operation nikl is repeated.

When connecting adjustable resistors 13 and 14, the base current of transistors 1 and 2 will increase by the amount of 5 current flowing through the corresponding resistors 14 and 13, with a small change in the additional current through resistor 14 leads to a significant change in the duration of the open 10 of that state of transistor 2, t. e. the duration of the half period of the output voltage.

Balancing the operation of power transformer 5 according to the scheme (see Fig. 2) '5

carried out automatically.

The parameters of the resistive-capacitive circuits 9 - 15 and 10-16 are selected in such a way that, in all, the range of variation of the input voltage and. load current 20 when the auxiliary transistor 17 is disconnected; the duration of the open state of the transistor 1 unit is longer than the duration of the open state of transistor 2.. 25

As follows from the above, the duration of the open state of the transistor 2 depends on the additional current through the additional transistor 17 of the amplifier stage 18, which in turn depends on the state of the differential amplifier 19 and, therefore, on the ratios of the voltages at its inputs. The division coefficients of the resistive dividers of the first 20 - 21 and 35

the second 22 and 23 are chosen so that at equal voltage on the capacitors 3 and 4, the additional current through the transistor 17 ensures the duration of the open state of the transistor 40 of the torus 2 is the same as the transistor 1.

If the duration of the open state of transistor 2 becomes less than the duration of the open state of transistor 1, then due to the different, $ 4

In each half cycle, the voltage on capacitor 3 will become less, and on capacitor 4, more than half of the input voltage. This will lead to a redistribution of the voltages at the inputs of the differential amplifier 19 and the differential amplifier 19 acts on the amplifier stage 18 in such a way that the current through the transistor 17 increases. This will increase the base current of the transistor 2 and, as a consequence, the duration of the open state of the transistor 2 will increase so that

becomes equal to the duration of the open state of the transistor 1. ·

If the duration of the open state of transistor 2 becomes longer than the duration of the open state of transistor 1, then the voltage on the capacitor 3 will become greater, and on the capacitor 4 less than half of the input voltage. This will reduce the current through the transistor 17 and reduce the duration of the open state of transistor 2 so that it becomes equal to the duration of the open state of the transistor.

Thus, the invention makes it possible to completely correct the duration of the half-cycles of the output voltage, and, if necessary, to perform automatic balancing during the operation of the inverter. In addition, the automatic balancing mode expands the functionality of the inverter, which allows you to maintain the voltage on the capacitors of the voltage divider, equal to half of the input voltage and does not allow it to exceed.

Simplification of the inverter settings allows you to increase productivity in the process of its operation.

Claims (3)

Claim 1. A half-bridge inverter containing two series-connected transistors, a capacitive voltage divider, a transformer whose primary winding is connected between the midpoint of a capacitive divider and a junction point of transistors, and positive feedback windings through current-limiting circuits containing ballast resistors are connected to control transitions , shunted backward conduction circuits of the respective transistors, and balancing elements of the correction node, characterized in that, in order to simplify The connections, the indicated current-limiting circuits are supplied with capacitors connected in series with the indicated ballast resistors, and the indicated balancing elements of the correction unit are connected in parallel with the capacitors. 2. The inverter according to claim. ^ Characterized in that the specified element! balancing the correction node is made in the form of resistors, and at less than 7. 9: at least one of them is adjustable. 3. Inverter on the PP. 1 and 2, that is, in order to expand the functionality, the adjustable resistor is made in the form of an additional transistor connected by a control input through an amplifier cascade to the output of an input differential amplifier whose inputs are connected to the outputs of the first and the second resistive divider tension 33 8 the extreme terminals of the first divider are connected to the extreme leads of the indicated capacitive divider, and the extreme leads of the second divider are between the 'midpoint and the negative lead of the capacitive divider.