RU1780180C - Key-pulse generator - Google Patents

Abstract

The invention relates to pulsed technology and is intended for use as key generators, converters in pulsed secondary power supplies and other high-power and medium-power radio devices. The key generator contains a pulse shaper 1, transformer 2, two amplifiers 3, 4, and two key 5. 6 elements, two low-pass filters, two low-frequency diodes, 9.10, and the key and amplifying elements are made of bipolar transistors. Such a combination of blocks and communications provides out-of-phase control of key elements through a single transformer while ensuring a delay of switching on of key elements sufficient to eliminate through currents, with switching edges of no more than 0.1-0.2 microseconds. This made it possible to increase energy efficiency and ensure reliable operation of the key generator. 1 ill. (LsXI00O00o

Description

The invention relates to pulsed technology and is intended for use as key generators, converters in pulsed secondary power supplies and other large and medium power radio devices.

Known key generators containing a pulse shaper and terminal cascades on field-effect transistors, made by push-pull or half-bridge circuits. To eliminate the friction currents flowing through the key elements in known devices, damping chokes are used that are connected between transistors (US Pat. No. 4,626,715), or HC circuits that delay the on-time of transistors. Known technical means allow reliable operation of key generators made by ia field transistors, without a significant increase in power loss. This circumstance is explained by the high speed of field-effect transistors and, in particular, by the small turn-on front even if there is an integrating circuit at their input.

A disadvantage of the known devices is the limited channel power of the key generator on field-effect transistors and insufficient energy efficiency due to the presence of the final resistance of their channel in the open state. So, on domestic field effect transistors, for example, type 2G1 922A, a key generator can be made according to a half-bridge circuit with a maximum output power of up to 300 VA with an efficiency of about 80 ... 85%. Such generators are in the range of operating frequencies up to 200 ... 400.--) They can be used with similar generators made on bipolar transistors. So, for example, a key generator based on 2T 856 A transistors can develop an output power of up to 1 kVA with an efficiency of up to 90 ... 95%. However, such key generators, due to the large inertia of turning off the bipolar transistors and the insufficient steepness of their turning on, require additional measures to eliminate through currents and ensure their reliable and efficient operation.

Key oscillators with terminal stages made on bipolar transistors are known in which the elimination of through currents is achieved by generating separate control signals for each of the key elements with a delay on the switching edge. In this case, the pulsed signals are amplified by separate preamplifiers and require the use of separate links for isolation, which greatly complicates the design of the device. Introduction to

A key generator made on bipolar transistors, damping chokes is associated with significant power losses and an additional surge of voltage on the closed key elements, which leads to a decrease in energy efficiency and affects the reliability of the device. Closest to the proposed one is a key device in which a key element made on a field effect transistor is controlled through an amplifying element also made on a field effect transistor, directly from the secondary winding of the transformer. At

In this case, the inclusion of an amplifying element in the circuit, controlling a powerful key element, ensures the delay of its inclusion required to eliminate through currents.

5 The prototype device contains a pulse shaper, the direct and inverse outputs of which are connected to the primary winding of the transformer, the secondary windings of which are through amplifying elements

0 are connected to the control inputs of the key elements, including sequentially between the busbar power supply.

The prototype device works as follows. Pulse shaper

15 ор Forms a direct 0 and an inverse pulse Hyio sequence such as a meander of a set 1 || 10th frequency and a power level sufficient to switch the key e ;; This pulse sequence is transmitted through a pulse transformer and amplifying elements and is supplied to the key control inputs of the key parts. The corresponding conclusions of the secondary windings of the sub / pole are also to the input m of the control of amplifying elements made on field-effect transistors. Due to the delays in turning on the amplification elements due to the resistance of the MX input circuit and the gate capacitance,

0, a delay of switching on the key elements is formed, which ensures the elimination of through currents in the terminal stage of the key generator. The implementation of key elements on field-effect transistors provides a good front for switching them on (less than 200 ms) after the formation of delays; -1 and thereby reduce dynamic losses in key devices.

The disadvantage of the prototype device is the lack of key power

generator and its relatively low efficiency due to channel resistance of open field-effect transistors. The key generator, made according to the known scheme on field-effect transistors of type 2P 901 in amplifying elements and transistors 2P 922A, used as key elements, provides output power for a matched resonant load of up to 250 W at an efficiency of about 80%. It should be noted that the parallel inclusion of field-effect transistors in key elements to increase the output power of the generator leads to a deterioration in the mass and size characteristics of the device, its cost increase and, ultimately, to a decrease in reliability due to an increase in the number of elements. In the case of the use of bipolar transistor prototype devices (for example, 2T 841A, 2T866A type) in the end cascade, to eliminate through currents, it is necessary to delay their switching on the order of 0.2 ... 0.8 MKS, which leads to an increase in the duration of the switching front and accordingly to increased power losses. Thus, at switching frequencies of the order of 100 ... 200 kHz in the known device with an output power of not more than 500 W, the efficiency does not exceed 75%. The use of field-effect transistors as amplifying elements when using key elements on bipolar transistors prevents the introduction of diode feedback and, accordingly, makes it impossible to provide an unsaturated mode of operation of the terminal stage transistors.

The purpose of the invention is to increase reliability while increasing the output power of a key generator.

The goal is achieved in a device containing a pulse shaper connected by direct and inverse outputs to the primary winding of the transformer, the first and second secondary windings of which are connected by the first leads to the first leads of the first and second key elements, the control inputs of which are connected to the first and second amplifying elements to the second terminals of the first and second secondary windings of the transformer, the first and second key elements being connected in series between the power buses, and the point their mutual connection is an output of the apparatus, by introducing into its structure the first and second low pass filters, first and second diodes, performing amplifying and key elements on the bipolar transistors

and supplying the secondary windings of the transformer with boosting leads, the terminals of which are connected to the inputs of the first and second low-pass filters, the outputs of which are connected to the control inputs of the first and second amplifying elements and are connected through the first and second diodes to the second terminals of the first and second key elements.

The use of a new set of blocks and links in the key generator allows for increasing the power through the use of power bipolar transistors, eliminating through currents and reducing dynamic power losses for switching during antiphase control of key elements. The proposed set of blocks and communications in devices of the class under consideration has not been previously used and is new. Moreover, the distinctive essential features of the claimed technical solution make it possible to improve the basic technical characteristics of the key generator, namely, to increase its reliability while increasing energy efficiency. Thus, the proposed technical solution meets the criterion of significant differences.

The drawing shows a structural diagram of the proposed key generator.

The key generator contains a pulse shaper 1, a transformer 2, amplifying elements 3 and 4, key elements 5 and 6, low-pass filters 7 and 8 and diodes 9 and 10,

Shaper 1 is designed to generate a pulsed meander-type pulse sequence of a given frequency and the required power level sufficient to drive key elements 5, 6 through transformer 2 and amplifying elements 3, 4. Shaper 1 can be made on a master oscillator and push-pull or bridge pre-amplifier.

Transformer 2 is designed for galvanic isolation and matching the output of the driver with the control inputs of key elements 5, 6. Transformer 2 contains two out-of-phase secondary windings equipped with additional raising taps. As a rule, for the effective excitation of key elements 5, 6, made on bipolar transistors, through the bipolar transistors of amplifying elements 3, 4, it is sufficient to have an amplitude of pulses on the main terminals of the secondary windings of the order of ... 5 V. In this case, the maximum

the total current of the secondary windings is determined by the relation

nmax

(1)

Zmgks / JMVIH

where 1imax is the maximum output current

Nmax

key generator;

 -minimum coefficient (n1 percent current-amplification of bipolar transistors of clutch elements 5, 6.

Amplifying elements 3, 4 provide control of the input current of the control and the bipolar transistors of the key elements 5, 6, and also serve to achieve the required delay for their inclusion with a minimum duration of the front of the output pulses of the key generator. The amplifying elements are implemented on bipolar transistors with high pulse characteristics, a large current gain and should be designed to transmit the maximum excitation current of the power bipolar transistors. The adjustment of the excitation current is ensured by the vic use of diode feedback through diodes 9, 10 connected between the inputs of the amplifying elements 3, 4 and the collector terminals of the power bipolar Tpai-i3Hstores of the key elements 5. 6. This potential is based on power transistors in an open state they do not npeBbiujacr collector potential than you provide; their work is in a very valuable mode. Including iine amplifying elements, covered | 1st diode reverse to the input circuit of power transistors; allows the flow of current through the secondary circuit to allow the flow of the formator 2, min and m / s -: s,:, residual for the supply | :; al: v silop TpaH3iC: oors in open state ng-, m at residual voltage i ... 2 V

i. G t 1 .. Ul (2)

- -.-ji

Amplify; 1st elements: 3, t, l, opol; -; only contain diodes included in parallel I. from page 3 and above, as a whole а u ui and e and |; -ovanny locking of power TRZNZ CTopof. npii negative voltage on the secondary windings of the transformer. At switching frequencies up to 100 ... 200 kGi, R r and combining of bipolar transistors of hoisting elements, the use of 2T972A transistors can be recommended. yes, their current gain /) bio is less than 100 and the frequency of the antenna is more than 10 MHz. As the feedback diodes and / iiiOAOB for the forced switching off, the diodes of the 2D212A type can be used in the state of the amplified elements.

Low-pass filters 7, 8 are designed to provide a delay in turning on the transistors of the amplifying elements 3 and 4 and, accordingly, the power transistors of the key elements 5, G, for a time d sufficient to reliably lock the previously conducting power transistor. In this case, after the delay, the fast turn-on of the power transistor and the minimum duration of the front of the output pulse voltage of the key generator should be ensured. Filters 7, 8 are second-order LC filters with a Q factor of about 2 ... 3 and a time constant determined from the required delay value including: and.

/ t:

t /

2 ... 3

(4)

The voltage from the additional taps of the secondary windings of the transformer is supplied to the input of filters 7, 8, the value of which is about 8 ... 10 V (i.e., twice as much as the voltage at the main terminal of the secondary winding). The value of the filter resistors 7, 8 is selected from the condition of ensuring a sufficient value of the input current of the amplifying elements

U2 / N 212max // 4in. (5)

where / jwhh

minimum coefficient pere, p, ach1-1 current transistors of amplifying elements.

Including filters of this type at the input of the amplifier; the bodies of the first elements of the guz allows you to provide the required delay for turning on the s. (Juvenile transistors, depending on their type in the range: - e 0.3 ... 1.5 μs for the front duration VK. Luches TF 0.05 ... 0.3 X:

The key elements 5, 6 are implemented on si; ju bipolar transistors, for example of the type 2T866A, 2T841A, included in the key generator gilloumost circuit, and G1 are medium-sized for key power amplification of the symmetrical pulse sequence. Moreover, in the device according to the invention, the use of power bipolar transistors is ensured in the normal mode while providing arcing; to and and X in the key, than with s-t gaets with | 13, de; the key generator is also effective at output power up to 800 ... 1000 W.

The proposed device operates in an EDU1 .CIM manner.

The pulse shaper 1 generates two antiphase pulse sequences of the meander type arriving at the primary winding of the transformer 2. When