SU1658327A1 - Dc voltage converter - Google Patents

Abstract

The invention relates to electrical engineering and can be used in secondary power supply systems. The purpose of the invention is to simplify the design of the converter. The primary winding 9 of the output transformer 8 is connected to the output of the switch on transistors 1 and 2 through the primary winding 6 of the current transformer 3 and the choke 14 of the saturation. The switch output is shunted by capacitor 8 When transistors 1 and 2 are turned off, capacitor 7 is recharged, the voltage on them smoothly increases, which reduces dynamic losses. Losses when turning on the transistors 1 and 2 are reduced due to the limiting of the current of the power circuit by the saturation inductor 14. The switching of transistors 1 and 2 occurs when the output core of the transformer 3 current from the saturation of 2 silt

Description

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The invention relates to electrical engineering and can be used in secondary power supply systems.

The purpose of the invention is to simplify the converter.

Figure 1 shows the diagram of the Converter; Fig. 2 shows timing diagrams explaining its principle of operation.

The converter contains a switch with power transistors 1 and 2, a current transformer 3 with secondary windings 4, 5 and a primary winding 6. Capacitor 7 is connected to the switch output. The output transformer 8 has a primary 9 and a secondary 10 windings. The rectifier 11 and the filter choke 12 connect the winding 10 to the load 13.

A saturated choke 14 is connected between the output of the primary winding 9 of the output transformer and the midpoint of the power supply. The windings 4-6 of the current transformer 3 are turned on in such a way as to ensure positive feedback on the load current. Additional windings (Fig. 1, dash-dotted line) and a resistor are designed to ensure that the converter works only at idle. Additional windings in the nominal operating mode (starting with 0.1 i i Nmax) do not affect the operation of the converter.

The converter operates in self-oscillation mode. In the initial state (up to the moment to) transistor 1 is open, choke 14 is saturated, the voltage on the capacitor 7 and the primary winding 9 is + E / 2, the current in the half-bridge diagonal Iwg is n p, the magnetization current of the switching transformer 3 is

(1n-1v1) “np, where 1n is the load current;

 / Wio - transformation ratio of the power transformer 8,

1b1 - reduced base current.

At the moment to, the transformer 3 is saturated, the transistor 1 is closed, the collector CCs branches into the capacitor 7. With an appropriate choice of the capacitor 7, the voltage on the collector of the transistor during its turn-off does not significantly change, there is no loss in the transistor. In the interval t0-ti, the capacitor 7 is discharged almost constant (since the load current is well smoothed) by the load current Iw9 nl n along the primary winding b circuit - the primary winding 9 of the saturation throttle 14. The current in the half-bore diagonal has the same direction, therefore the choke 14 and transformer 3 remain saturated.

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The base-emitter transitions of transistors 1.2 are closed, the entire load current flows along the winding 9, therefore the operating point of the transformer 3 moves into the region of deep saturation. Consequently. the output of the transformer 3 in the active mode is possible only when Iwg -0 (differential transformer).

At the time ti, when the voltage on the capacitor 7 reaches zero, an emf of self-induction of droplets 12 occurs in polarity. which opens all the rectifier diodes 11. The load current supported by the choke 12 is transferred to the rectifier circuit, mine

15 windings of a transformer 8, the voltages of which are zero. The choke 12, the load 13 and the transformer 8 are short-circuited with a rectifier. The current iwg in the half-bridge diagonal decreases, which leads to

™ exit from saturation of throttles 14 and to the formation of an oscillatory circuit Li-iC. During the oscillatory process, the capacitor 7 is charged with a sinusoidally decreasing current. The polarity of the current iwg remains the same, which ensures that the transformer 3 is saturated.

At time t2, the voltage across the capacitor 7 reaches -E / 2. and the loop current (equal to the current iwg) is zero. Transformer 3 is out of saturation; EMF is formed on its windings. transistor 2 opens. There are no switching losses in the transistor, since, for example, the intake and collector current are close to zero. The oscillatory process in the circuit is disrupted. In the interval, a voltage of –E / 2 is applied to the choke 14; the collector current and the voltage on the windings of the transformer 8 are near p ki. Transistor 2 is open by

energy stored in a transformer 3.

Collector current reaches steady

iHn values at saturation drossel 14.

When the load resistance 45 ki 13 changes, the duration of the intervals to ti-t2 changes, so that by the time the transistor is turned on, the capacitor 7 is always charged to the + E / 2 direction. For example, reducing the load current increases the duration to-ti, since the capacitor 7 discharges more slowly. The trt2 interval also increases in this case, since with a lower load current the saturation inductance 14 of saturation increases. The recharge of capacitor 7, optimal for switching transistors, is carried out in two stages. In the first stage, the capacitor 7 is discharged by the load current, due to the effect of the droplets of the filter 12. In the second stage, the capacitor 7 is charged with a current

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Claims (1)

the loop circuit formed by him and the throttle 14 saturation. When the load changes, the duration of both stages changes first due to the change in the discharge current of the capacitor, the second due to the change in the average inductance of the saturation drops 14 and the frequency of the oscillating circuit. The switching on of the next transistor occurs at the moment when the switching transformer goes into active mode, which corresponds to a complete recharge of the capacitor 7. Claims of the Inverter A DC / DC converter containing a switch with transit The stoppers and output transformer are connected to the output of the switch via serially connected saturation inductor and primary current transformer winding, the secondary output transformer winding is connected to the output terminals through the rectifier and filter choke, and the output of the switch is shunted by a capacitor characterized by that. which, for the sake of simplicity, is made with two secondary windings connected to the control inputs of the switch transistors