Method and Device for D.C. Voltage Regulation Across Load

The invention will be more clearly understood from the following detailed description of a preferred embodiment thereof when read with reference to the accompanying drawing which is a circuit diagram of a preferred embodiment of a device for regulating D.C. voltage across a load.

A device for regulating D.C. voltage across a load disclosed herein is supplied from a supply source I and comprises a master oscillator 2 with a transformer 3, a main transistor inverter circuit 4 and auxiliary transistor inverter circuits 5, 6 and 7, a first, a second, and a third circuit respectively. All the transistor inverter circuits have transformers.

A transformer of the main transistor inverter circuit 4 has primary windings 4.sub.1 and 4.sub.2, an output winding 4.sub.3, and measuring windings 4.sub.4 and 4.sub.5.

A transformer of the first additional transistor inverter circuit 5 has primary windings 5.sub.1 and 5.sub.2, an output winding 5.sub.3, and measuring windings 5.sub.4 and 5.sub.5.

A transformer of the second additional transistor inverter circuit 6 has primary windings 6.sub.1, 6.sub.2, an output winding 6.sub.3, and measuring windings 6.sub.4 and 6.sub.5. A transformer of the third additional transistor inverter circuit 7 has three windings: two primary windings 7.sub.1 and 7.sub.2, and an output winding 7.sub.3. The master oscillator 2 generates square-wave voltage in the form of alternating square pulses which control the transistor inverter circuits 4, 5, 6 and 7. The transformer 3 of the master oscillator 2 has nine windings: a primary winding 3.sub.1 and eight secondary windings 3.sub.2 - 3.sub.9.

The device of the invention also includes a reference voltage source 8, diodes 9, 9'; 10, 10', and 11, 11', switching elements 12, 13, 14 of the first additional transistor inverter circuit 5, of the second circuit 6, and of the third circuit 7, respectively. In a preferred embodiment of the device, the switching elements are transistors which in further text will be called control transistors 12, 13 and 14, respectively.

The drawing also shows back diodes 15, 16, 17, 18, 19 and 20, a rectifier 21, a load 22, a capacitor 23, transistors 24, 25, 26, 27, 28, 29, 30 and 31, resistors 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, and diodes 46 and 47.

The reference voltage source 8; the measuring windings 4.sub.4 and 4.sub.5 of the main transistor inverter circuit 4; the measuring windings 5.sub.4 and 5.sub.5 of the first additional transistor inverter circuit 5; the measuring windings 6.sub.4 and 6.sub.5 of the second additional transistor inverter circuit 6; and also the diodes 9 and 9', 10 and 10', and 11 and 11' make up a logical unit.

In the logical unit, the measuring winding 4.sub.4 of the transformer of the main transistor inverter circuit 4 connected in series with the diode 9 (and also the measuring winding 4.sub.5 of the main transistor inverter circuit 4 connected in series with the diode 9' to achieve full-wave rectification) are provided between the reference voltage source 8 and the first output of the logical unit corresponding to the control transistor 12 (switching element) of the first additional transistor inverter circuit 5; the measuring winding 4.sub.4 of the transformer of the main transistor inverter circuit 4 connected in series with the measuring winding 5.sub.4 of the transformer of the first additional transistor inverter circuit 5 and the diode 10 (and also the measuring winding 4.sub.5 of the transformer of the main transistor inverter circuit 4 connected in series with the measuring winding 5.sub.5 of the transformer of the first additional transistor inverter circuit 5 and the diode 10 to achieve full-wave rectification) are provided between the reference voltage source 8 and the second output of the logical unit corresponding to the control transistor 13 (switching element) of the second additional transistor inverter circuit 6; and the measuring winding 4.sub.4 of the transformer of the main transistor inverter circuit 4 connected in series with the measuring widing 5.sub.4 of the transformer of the first additional transistor inverter circuit 5, the measuring winding 6.sub.4 of the transformer of the second additional transistor inverter circuit 6 and the diode II (and also the measuring winding 4.sub.5 of the transformer of the main transistor inverter circuit 4 connected in series with the measuring winding 5.sub.5 of the transformer of the first additional transistor inverter circuit 4, the measuring winding 6.sub.5 of the transformer of the second additional transistor inverter circuit 6, and the diode II' to achieve full-wave rectification) are provided between the reference voltage source 8 and the third output of the logical unit corresponding to the control transistor 14 (switching element) of the third additional transistor inverter circuit 7.

The diodes 46 and 47 serve to bias the transistors 26-31 of the additional inverter circuits 5, 6 and 7 beyond the cut-off level, with the control transistor 12, 13 and 14, respectively, in a non-conducting state.

For normal operation of the device, the absolute value of the output voltage of the main transistor inverter circuit must be larger than the output voltage of any additional transistor inverter circuit.

Assuming for the sake of simplicity, that all the elements of the circuitry have ideal characteristics, consider operation of the circuitry when regulating the output voltage of a prefered embodiment of the device at certain relative level 1.00 with the supply voltage varying within 0.80-1.20, for instance, for the following relation of the transformation ratios of the main and additional inverter circuits:

K.sub.O : K.sub.1 : K.sub.2 : K.sub.3 = 1:0.143:0.071:0.036 /K is the ratio of the number of turns in the output winding of the transformer of a circuit to the number of turns in its primary winding.

Under the assumptions made the regulation process has characteristics shown in the table below:

Regardless of the voltage output of the supply source 1, the master oscillator 2 with the transformer 3 (primary winding 3.sub.1, secondary windings 3.sub.2-3.sub.9) connected to the source 1 generates symmetrical alternating square pulses to be used for controlling both the main inverter circuit 4 and the additional inverter circuits 5-7.

At a minimum supply voltage equal to 0.80 in relative units, the total voltages of the reference source 8 and corresponding measuring windings 4.sub.4, 4.sub.5, 5.sub.4, 5.sub.5 and 6.sub.4, 6.sub.5 are such that back voltages are applied to the diodes 9, 9', 10, 10' and 11, 11' , the diodes are cut off and, consequently, currents from the windings 3.sub.2 and 3.sub.3 of the master oscillator and from the windings 3.sub.4 - 3.sub.9 of the master oscillator are delivered, respectively, to the bases of the control transistors 12-14 and to the bases of the switching transistors of all the additional inverter circuits so that the voltage outputs of these circuits vary in phase with the voltage output of the main circuit. No current flows through any of the back diodes 15-20 and the output voltage of the converter is the arithmetic sum of the voltage outputs of all the inverter circuits.

If the voltage supply level is 0.85, the states of the diodes 9, 9', 10, 10' and, consequently, those of the additional inverter circuits 5, 6 remain unchanged, whereas currents passing alternately through the diodes 11, 11' drive the control transistor 14 and the switching transistors of the additional transistor inverter circuit 7 into a cut-off state, and the inverter circuit starts acting as a rectifier to recuperate power from the external circuit through the back diodes 19.20 into the power supply source.

In this case, the output voltage of the circuit varies out of phase with the output voltages of the remaining circuits and, consequently, is subtracted from the sum of these voltages (see the table).

With a further increase of the supply voltage, depending on the states of the diodes 9, 9', 10, 10', 11 and 11' each of the additional inverter circuits may produce a positive or a negative component of the output voltage of the preferred embodiment, the sign of the component being automatically determined by the relation between the reference source voltage and the sum of the voltages of the corresponding measuring windings, so that the output voltage of the device of the invention is maintained stable within preset limits.

The table above shows that at selected transformation ratios relative stability of the converter output voltage is not worse than .+-.3.6% in a preset supply voltage range.

As the rise time of square-wave voltage pulses at the circuit transformer windings in other than zero, the switching capacitor 23 of rather low capacitance is coupled to the load 22 connected via the rectifier 21 with a view to avoiding voltage surges as the circuits are turned on or off.

It is obvious that due to a filter being practically absent and to a small total power of the additional inverter circuits (in our example it is approximately 20% of the total power of the device), the circuitry operates at a high efficiency close to the efficiency of a non-stabilized device for controlling D.C. voltage across a load.

Various embodiments of the device can be provided. Thus, the reference voltage source 8 may be a Zener diode fed through an auxiliary resistor and an auxiliary fullwave rectifier from the additional windings of the master oscillator transformer or the transformer in the main inverter circuit.

The master oscillator can be connected through its supply circuit to the windings of the main inverter circuit transformer or to the output of the device for D.C. voltage regulation. The main inverter circuit operating in a continuous generation mode makes redundant the use of a master oscillator, therefore, the transistors of the additional inverter circuits may be controlled directly from the winding of the main circuit transformer.

To ensure reliable operation of the switching transistors as gates, it is advisable that composite transistors, relay elements of the Schmitt trigger type, etc. be used as switching elements in the input circuits of the additional inverter circuits.

For raising the stability of the output voltage, another additional low-power inverter circuit may be connected in series with the load, with the output winding of its transformer connected in series with the output windings of the transformers of all other circuits, so that the operation of the inverter circuit is directly affected by the voltage difference across the load and at a certain additional reference voltage source. If the supply voltage of such a circuit is continuously variable under the effect of variations in said voltage difference, the inverter circuit provides automatically additional continuous regulation of D.C. output voltage at a preset stabilization level.

One of the most important applications of the device of this invention may be its use for producing regulated D.C. voltage from non-regulated commercial-frequency three-phase mains.

In this case, as follows from the above described operating principle of the device, the supply source 1 may be three-phase mains with a bridge rectifier connected to its output without any additional filter necessary.

Due to common electrodes of the transistors, the regulator can be easily minituarized by employing an integrated control circuit.

For regulating the output voltage of the device, it is required to vary voltage at the reference voltage source 8.