SU754659A1 - Saw-tooth current generator - Google Patents

Description

The invention relates to communication technology and can be used, for example, in scanning devices of transmitting television cameras. five

Known generator sawtooth current, which contains the master oscillator, pre-output amplifier, output push-pull stage, the output of which is connected to an inductive load with condenser-10 reverse gear and a semiconductor switching device built into the output push-pull stage [1]. 9

A disadvantage of the known device 15 is the impossibility of implementing in it the economic mode of operation (class B), i.e. the inevitability of nonlinear distortion during the forward stroke sweep. 20

Known generator sawtooth current with a separate semiconductor switching device in the form of PA ·· parallel connection of the diode to the transistor, a controlled input of which 25 is connected to a source of triggering pulses [2].

The sawtooth current generator contains the master oscillator, power> power with push-pull output-ka

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A unit whose output is connected to an inductive load with a return capacitor and a semiconductor switching device made in parallel with a return capacitor of a diode and a transistor, the controlled input of which is connected to a source of trigger pulses using an additional inductive element (transformer). This generator has a relatively higher efficiency with a short return period.

The disadvantages of the known sawtooth generator are the non-linearity of the sawtooth current caused by a two-contact output stage operating in class B mode, as well as in nonlinearity caused by a semiconductor switching device. The first drawback is caused by non-simultaneous switching of the output push-pull cascade transistors and eliminated by creating an AV push-switch by the inclusion of additional diodes between the bases of the transistors of the output stage. In this case, the circuit becomes less economical, and its DC mode is unstable. Vtoz 754659

: the swarm lack is connected with the non-simultaneous-> 'of switching the Transistor and the diode in a semiconductor switching device. In addition, an additional inductive element is required to control the switching device (the tr & nSformator, which is also a drawback.

The purpose of the invention is to reduce the nonlinearity of the output pulses.

This goal is achieved by the fact that in a sawtooth current generator containing a master oscillator, a preamplifier, connected in series, and an output stage on transistors of opposite conductivity type, the collectors of which are connected to buses 15 of the positive and negative power supplies, the base of the pnpn transistor output cascade connected to the output of the preamplifier, inductive load, a capacitor, a switching transistor, 20 the base of which is connected to the input bus, a diode, the cathode of which is connected to the collector switch a switching transistor, and the first resistor connected between the zero potential bus and the second preamplifier inlet, a second resistor and an additional diode and a third resistor connected in parallel, the anode of the additional diode connected to the collector of the switching transistor and the pn-transistor base the output stage, the emitter of which is connected to the cathode of the additional diode through a capacitor - with a zero potential bus and through an inductive load - with the second input pre-amped -'- * tel, the emitter of a pnp transistor output This stage is connected to the diode anode, and the pnp transistor of the output stage is connected via a second resistor to the emitter of the switching trans-40 nsistor.

FIG. 1 shows a block diagram of a sawtooth current generator; in fig. 2 - time diagrams of currents and voltages of the sawtooth generator.

The sawtooth current generator contains the master oscillator 1, the output of which is connected to the input of the preamplifier 2, the output of which is connected to the base of the pn-transistor 3 of the output stage. ^υ Capacitor 4, reverse and inductive load 5 are connected to the output of this stage through a switching device containing a diode b and switching transistor 7, the base of which is connected to the input of the master oscillator ¹ . The first resistor 8 podklyu- ^; There is a diode-resistance circuit between the base and the emitter of the pnp transistor 10 of the output stage, consisting of an additional diode 11 and the third resistor 12. The negative voltage source 13 is connected to the second through a resistor

the output of the switching transistor 7,

The generator also has an input bus 15.

The sawtooth generator operates as follows. · ·

In the intervals between the trigger pulses (the forward sweep stroke), the sawtooth voltage from the output of the master oscillator 1 (Fig. 2a) is fed through the preamplifier 2 to the input of the pnpn transistor 3 of the output stage, pnpn and pnp The p-transistors of the 3.1b output stage, as well as the diode of the bth switching transistor 7, are unlocked, while the additional diode 11 remains locked. The current through the pnp transistor 10 increases sharply, and then begins to gradually decrease, since the pnp transistor 10 closes the current of inductive load 5 flowing in the direction from the zero potential bus 9 through the first resistor 8, inductive load 5 and ppn transistor 10 to a source of negative 13 voltage, and also partially through the third resistor 12 switching transistor 7 and the second resistor 14 to the same negative voltage source 13 (Fig 2, b 1; 2, in 1) . Current pnp transistor 3 and diode

6 also closes through the switching transistor 7 (FIG. 2, 2), therefore the current of the switching transistor

7 is equal to the sum of the currents flowing through the third resistor 12 and the pnp transistor 3 (diode 6) and is maintained almost constant in magnitude, only slightly increasing in accordance with the control voltage at the input of the transistor (see Fig. 2.6 2). By the end of the first half of the forward stroke of the current pn-transistor 10 is reduced to zero. In the absence of a diode-resistive circuit 11, 12 in the switching device, the cessation of current through the pp-p-transistor 10 would lead to the cut-off of the current of the inductive load 5. The presence of the diode-resistive circuit ensures the flow of the current of the inductive load 5 -p-transistor .10, in the direction from the third resistor 12 through the switching transistor 7, the second resistor 14 to the negative voltage source 13 (Fig. 2, in 1; 2, in 3), due to this, the current cut-off is eliminated. During the second half of the forward stroke, the pnp transistor 10 is locked, and the additional diode 11 of the diode-resistive circuit is unlocked, and the current through the npn transistor 3, diode 6 and the diode-resistive circuit 11, 12 begins to increase (figure 2, in 1; 2, in 3). In this case, a sharp change in current does not occur. Inductive Load Current

5 is closed through the pnp transistor

3, diode 6, diode-resistive circuit

11, 12, load 5 and first resistor

8, increasing in accordance with up5

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equal voltage (figa) to the end of the forward stroke (figure 2, 3).

Upon receipt at the input 15 of the device trigger pulses (reverse sweep) at the output of the master oscillator 1, there is a sharp voltage drop 5 (Fig.2a), which through the preamplifier 2 is transmitted to the input pnp-transistor 3, and it is locked. Under the action of the trigger pulse at the input 15, the switching transistor 7 is locked (Fig 2.6 2). The voltage on the inductive load 5 increases to a value greater than the voltage of the power source. As a consequence, the additional diode 11 is locked, providing the disconnection of the pnp transistor 3 and diode 6 from the inductive load 5, which prevents the oscillating circuit formed by the inductive load 5 and the capacitor 4 from shunting 20 is locked, and an oscillatory process begins in the oscillating circuit 4.5. The current in the inductive load 5 (figure 2, 3} first decreases to zero, and then, changing the direction to 25 the opposite, begins to increase.

The presence in the switching device of a diode-resistive circuit 11, 12, the findings of which are connected to the base and the emitter of the pnp-transistor 10 output 30 of the switching transistor 7 connected by the emitter through the second resistor 14 to the source 13 of the negative voltage and diode 6 connected to the conclusion pnp-transistor 3 35

output stage, allows you to eliminate the current cut-off. Inductive load 5, since the diode b and the switching transistor 7 during the forward stroke is constantly open, and the diode-resistive circuit 11, 12 does not make the cut-off, although it is nonlinear. The nonlinearity of the circuit 11, 12 is corrected by the feedback circuit. FIG. 2, 3 shows the curve of the inductive load current without taking into account feedback, but in the presence of feedback, the changes in the current of the inductive load are linear. The sawtooth generator, when used in low-power sweepers (for transmitting television tubes), has

efficiency and stability is almost the same as that of the most advanced non-known generators operating in class B mode, provides a higher linearity of the electron beam deflection.

Claims (1)

Claim A sawtooth current generator containing a master oscillator, a preamplifier connected in series, and an output stage on transistors of the opposite conductivity type, whose collectors are connected by buses from positive and negative power sources, the base of the output transistor cascade is connected to the preamplifier output , inductive load, a capacitor, a switching transistor, the base of which is connected to the input bus, a diode, the cathode of which is connected to the collector of the switching transistor, and the first resistor on The connection between the zero potential bus and the second preamplifier input is characterized in that, in order to reduce the nonlinearity of the output pulses, a second resistor and an additional diode and a third resistor connected in parallel are inserted, the anode of the additional diode connected to the collector of the switching transistor and the base p- p-transistor of the output stage, the emitter of which is connected to the cathode of an additional diode, through a capacitor - with a zero-potential bus and through an inductive load - to the second preamplifier input, e The output stage miter transistor is connected to the diode anode, and the output stage p-p transistor collector is connected via a second resistor to the emitter of the switching transistor.