SU169662A1 - STATIC CONVERTER - Google Patents

Description

Vehicle power systems and other installations use push-pull transistor static converters of direct current to alternating, operating at an increased frequency.

When switching transistors due to the delay of the transistor closure due to the absorption of excess carriers in its base, a short circuit mode develops in the circuit, resulting in increased dynamic power losses in the transistors. To eliminate this mode, circuits with asymmetrical transistor control are used in which the duration of the opening pulse is shorter than the duration of the closing pulse.

The known schemes of static converters with asymmetrical control use the resorption effect of the carriers of the additional diode. Such schemes are quite complex, uneconomical and the degree of asymmetry is relatively small and practically unregulated.

The proposed converter circuit does not have the indicated disadvantages. According to the invention, the asymmetry of the control pulses is carried out using a saturable transformer with a core made of a material with a rectangular hysteresis loop. The transformer is switched on secondary, shunted

diode winding in series to the base circuit of the transistor, and the primary to the source of control pulses through the limiting resistance. When the opening control pulse arrives for the time of the magnetization reversal of the transformer core, the transistor is actively closed, i.e., its opening is delayed.

The magnitude of this delay time determines the asymmetry of the pulses applied to the input of the transistor, and can be controlled by the choice of transformer parameters.

FIG. 1 shows the proposed control circuit for one of the transistors of the converter; in fig. 2 is a voltage chart at the input of the transistor.

The saturating transformer Tp has two windings and Wa, and the number of turns of the winding W-2 is greater than W. When the polarity of the control signal Uy is for the transistor opening, an emf is induced in the secondary winding Wz. And - the value is more than u. The voltage difference U.-Uy actively closes the transistor. After a certain delay time t.d (see Fig. 2), the transformer core Tr becomes saturated, the voltage (/ o drops almost to zero and the transistor opens under the action of voltage N. After a half period, the polarity of the voltage O y changes to the opposite the transistor is locked

under the action of the locking signal Uy applied to the input of the transistor through a diode shunting the winding Wz- In this case, the core of the transformer is reversal in the other direction. Resistance R is limiting.

The delay time t .ao is determined by the parameters of the transformer and the circuit, and can be chosen any based on the formula:

2B ... 5. IFi

ass -

and R W,

where B and H are the induction of saturation and the coercive force of the core material; 5 and / - the cross section and the length of the magnetic circuit of the core.

The transformer is usually small in size, since the delay time is shorter than the operating period of the converter.

Subject invention

Static DC-to-AC converter made of transistors controlled by asymmetric pulses, characterized in that, in order to reduce dynamic losses, a saturated transformer on a core made of a material with a rectangular hysteresis core is used in transistors; connected in series to the base of the transistor, and the primary winding is connected to the source of control pulses through the limiting resistance.

Figure 1 Closed

Open