Scientific journal
European Journal of Natural History
ISSN 2073-4972

NEW SYSTEM OF SEMI-BRIDGE TRANSISTOR CHOPPER OPERATING

Magazinnik L.T.
Transistor choppers, both single and two cycle, have found a use in different secondary power supply sources [1]. Transistor chopper operating systems are devised on typical microcontroller level [2]. This system is used to operate any two cycle chopper and may differ only by the quantity of output channels (for one bridge- four channels, for semi-bridge- two channels). The operating system generates impulse signals at operating inputs of chopper´s transistors, on-off time of which determines the duration of transistor´s on-mode. In semi-bridge chopper the necessary transistors´ on-mode duration decreases by the stress growth. That means the necessary transistors´ on-mode duration may be much less than the duration of gating impulses from the operating system´s output. That leads to outrageous wastage in transistors.

The suggested operating system of semi-bridge transistor chopper [3] is shown at fig.1 and consists of semi-bridge transistor chopper 1, operating system 2, and automatic regulator 3. The chopper includes two capacitors 4 and 5, successively connected, two transistors 6 and 7, also successively connected, and two bypass diodes 8 and 9, shunting in backward direction transistors 6 and 7. Vertex of capacitors 4 and 5 and transistors 6 and 7 make an alternate current diagonal, which includes load 10.

 

Figure 1

Capacitors´ 4 and 5 and transistor´s 6, 7 exposed ends are combined and respectively connected to direct-current voltage source.

Thus, block 1 represents semi-bridge transistor chopper identical to known prototypes.

Block 2 contains typical operating system of semi-bridge transistor chopper, built on the principle of pulse-width modulation which has two outputs (by the chopper´s transistors). Detailed scheme of block 2 is presented in [1]. Automatic regulator 3 is connected to input of block 2, which is also a typical unit, usually presented as analog comparator. Additional elements of scheme pic.1 are two voltage sensors 11 and 12 and two logical two-input elements "I"13 and 14. Voltage sensors 11 is turned on by input in parallel with capacitor 4, and voltage sensors 12 is turned on by input in parallel with capacitor 11.

Sensor´s 11 output is connected to one of the inputs of logical two-input element "I"13, and voltage sensor´s 12 output is connected to one of the inputs of logical two-input element 14. Exposed inputs of logical two-input element "I" 13 and 14 are connected with respective outputs of operating system 2, and outputs of logical two-input element "I" 13 and 14 are connected with respective inputs of transistors 6 and 7. To simplify, buffer circuit of galvanic separation and formation of signals from the detector element are not shown at pic.1.

As soon as strain at the capacitor, for example 4, reaches 0, "unit´ disappears at output of logical two-input element "I" 13, transistor 6 will close, and accumulated electromagnetic power in load 10 will discharge circuitally: load 10 - diode 9 - capacitor 5 - load 10. Besides, the discharge current will go through energy supply´s output capacity.

Wastage in transistor 6 at this interval is excluded, and accumulated electromagnetic power in the load partially goes to capacitor 5, partially returns to energy supply. Apparently, the efficiency of the suggested mechanism is higher, when load current is more, for example, while using a chopper for power supply through an electric arc´s reducing transformer in a welding set.

Reference

  1. «Invertec V-130-S-Linkoln» - USA, catalogue, 1998-1999.
  2. V.A.Pryanishnikov. "Electronics", Saint Petersburg, 1988, 400 p.
  3. System of semi-bridge transisitor chopper operating. License of Russian Federation # 2311719 from 27.11.2007. Author Magazinnik L.T.

The work is presented for an International Science Conference "Contemporary issues of science and education", Moscow, February 16-18, 2010. Came to the editorial office 1.12.2009.