JP3224427B2 - Static AC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static AC power supply for converting DC power into AC and supplying it to a load, and more particularly to a power supply in which the switching loss of an electronic switch element in a static inverter circuit is reduced to a minimum. About.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6, a bridge circuit is constituted by switching transistors T4 to T9 used as electronic switch elements for a DC power supply 1, and three transistor pairs (T4, T5, T6) of the bridge circuit are formed.
And a filter circuit 3 including a reactor and a capacitor (L and C) at a connection point of T7 and T8 and T9, respectively.
There is known a static AC power supply for three-phase AC, which is configured to be connected to a load 4 such as an AC electric device via the AC power supply.
Switching transistor T4 of the above bridge circuit
T9 is controlled by an electronic control circuit (not shown) so as to perform a switch operation at a high repetition frequency of several KHz to several tens KHz. For example, the transistors T4 and T5 are alternately turned ON and OFF at a predetermined timing, and the voltage Va between the connection point of the transistors T4 and T5 and the negative input terminal of the bridge circuit has a voltage waveform as shown in FIG. . When the transistor T4 is OFF and the transistor T5 is ON, the voltage Va becomes zero volt. Transistors T4 and T5 are ON
The time ratio, that is, the duty ratio is continuously changed as shown in FIG. 7, that is, a square wave voltage which is pulse width modulated and repeats a gradual increase and decrease is output.
Similarly to the transistor pairs T4 and T5, the above-described electronic control circuit controls the other transistor pairs T6 and T7 and T8 and T9 so that they are repeatedly turned on and off.

As described above, a square-wave voltage pulse-modulated as described above is output between the three connection points of the transistor pairs T4 and T5, T6 and T7, and T8 and T9 in the bridge circuit, that is, between the output terminals of each phase. Is done. The high-frequency pulse train of each phase subjected to pulse width modulation has its harmonic components removed by the filter circuit 3, and a sine-wave AC voltage having a predetermined frequency is applied to the load 4. The bridge circuit whose switch operation is controlled by the electronic control circuit in this manner is referred to as an inverter circuit 2 in the following description. Note that feedback diode elements D are connected in anti-parallel to the collectors and emitters of the transistors T4 to T9 of the inverter circuit 2, respectively. These feedback diode elements D
Is the reactive power of the AC output of the inverter circuit 2
It is a well-known thing which performs the effect | action which returns to.

As described above, the DC power from the DC power supply 1 is converted into the inverter circuit 2 by the conventional AC power supply device.
Sine wave AC having a desired frequency can be sufficiently obtained. However, in the above-mentioned conventional power supply device, since each electronic switch element of the inverter circuit performs a switching operation at a considerably high frequency, there is a serious disadvantage that the switching loss is large and the efficiency is low.

For example, as shown in FIG. 7, when the transistor T4 changes from the OFF state to the ON state at time t1, the conduction current of the transistor T4 rapidly changes from zero to a large value. Loss, so-called turn-on loss, occurs. Similarly, at time t2, when the transistor T4 changes from the ON state to the OFF state, the transistor T4
The conduction current of the transistor rapidly decreases from a relatively large value to zero, and a large turn-off loss occurs at this moment. Such switching loss occurs in all the switching elements T4 to T9, and since switching is performed at a high repetition frequency of several KHz to several tens KHz, the total switching loss is very large, and not only the efficiency is lowered but also This causes overheating of the electronic switch element, and the operation stability is still unsatisfactory.

[0006]

SUMMARY OF THE INVENTION The present invention provides:
The purpose of the present invention is to completely overcome the disadvantages of the conventional device described above. An auxiliary electric circuit is provided between the DC power supply and the inverter circuit, and the auxiliary electric circuit synchronizes with the turn-on or turn-off of all the electronic switch elements in the inverter circuit. During this time, the voltage applied to the electronic switching elements is reduced to zero volts, so-called zero volt switching (ZVS) is performed, thereby eliminating the switching loss of all the electronic switching elements, achieving extremely high efficiency and without overheating of the switching elements. An object of the present invention is to provide a stable static AC power supply.

In order to achieve the above object, the present invention provides a method for controlling a voltage between input terminals between a DC power supply and an inverter circuit during a period commensurate with the commutation time of each electronic switch element in the inverter circuit. Is provided with an auxiliary electric circuit which makes zero.

The present invention will be described below with reference to the accompanying drawings showing preferred embodiments.

[0009]

FIG. 1 shows an embodiment of the present invention.
The same reference numerals are given to the components equivalent to the components in the conventional static AC power supply device shown in FIG.

As shown in FIG. 1, main components of the present invention are provided between a DC power supply 1 having an output voltage E and positive and negative input terminals 21 and 22 of a bridge type three-phase AC inverter circuit 2. The auxiliary electric circuit 10. This auxiliary electric circuit 1
At 0, an electronic switch element (hereinafter simply referred to as a transistor) T1 using a switching transistor is connected in series with the intermediate tap 11 of the DC power supply 1, and a semiconductor diode D1 is connected in anti-parallel to the emitter-collector of the transistor T1. One end of the choke coil L1 is connected in series with the collector of the transistor T1 and the anode of the diode D1, and the other end is connected to the positive input terminal 21 of the inverter circuit 2. Between the positive terminal 12 of the DC power supply 1 and the other end of the choke coil L1, that is, between the positive input terminal 21 of the inverter circuit 2, an electronic switch element (hereinafter simply referred to as a transistor) T2 using a switching transistor and a transistor T2. A first parallel circuit 23 composed of three elements of a semiconductor diode D2 and a capacitor C1 connected in anti-parallel to the collector-emitter is connected, while the negative terminal 13 of the DC power supply 1 and the negative input of the inverter circuit 2 are connected. An electronic switch element (hereinafter simply referred to as a transistor) T3 using a switching transistor between the terminals 22 and a semiconductor diode D3 connected in anti-parallel to the emitter-collector of the transistor T3
And a second parallel circuit 24 composed of three elements, a capacitor C2. The ON / OFF switch operation of each of the transistors T1, T2 and T3 in the auxiliary electric circuit 10 is performed by the electronic switch element T4 of the inverter circuit 2.
An electronic control circuit (not shown) that controls the switch operations of T9 to T9 controls the operation in the operation modes a to i according to a time schedule described later in detail. The electronic control circuit can be configured using, for example, a microcomputer.

The operation of the embodiment of FIG. 1 is based on the current IL flowing through the choke coil L1 in each of the operation modes a to i of FIG.
1 and the positive and negative input terminals 21 and 2 of the inverter circuit 2
The operation curve showing the voltage VO between the two with the same time axis and the circuit operation explanatory diagrams of FIGS. 3A to 3I will be described.

Mode a: A state in which none of the electronic switching elements in the inverter circuit 2, ie, the switching transistors T4 to T9 (hereinafter simply referred to as transistors) is performing a commutation operation , that is, the auxiliary electricity The transistor T2 of the circuit 10 is turned on and the transistor T3 is turned off. As shown in FIG. 3A, DC power is supplied from the DC power supply 1 to the inverter circuit 2 via the transistor T2 with the voltage E (FIG. 2). Of FIG. 6), and the same operation state as in the conventional device of FIG. this
In the state, immediately before any of the transistors T4 to T9 in the inverter circuit 2 starts the commutation operation,
The transistor T1 is turned on, and the mode shifts to mode b.

Mode b: As shown in FIG. 3B, current flows from the positive terminal 12 of the DC power supply 1 to the transistor T2, the transistor T1, and the intermediate tap 11, and the voltage (1/2) E is applied to the choke coil L1. Is applied, and the accumulated current IL1 of the choke coil L1 gradually increases in the negative direction (see the current curve IL1 in FIG. 2). On the other hand, DC power supply 1
Is supplied to the inverter circuit 2 via the transistor T2 with the voltage E (the voltage curve V in FIG. 2).
O). At this time, since the conduction current of the transistor T1 is gradually increased from zero after being turned on, the switching of the transistor T is so-called zero current turn-on, and no switching loss occurs. Thereafter, the mode shifts to the mode c when the transistor T2 is turned off.

Mode c: When the transistor T2 is turned off, a charging current flows from the positive terminal 12 of the DC power supply 1 to the capacitor C1 and a discharging current flows from the capacitor C2 charged with the voltage E, as shown in FIG. Flows. DC power is supplied to the inverter circuit 2 with the charging current of the capacitor C1 and the discharging current of the capacitor C2. At the same time, capacitors C1 and C2
, A current flows through the choke coil L1 and the transistor T1. Until the voltage between the electrodes of the capacitors C1 and C2 both becomes (1/2) E, the current flowing through the choke coil L1 gradually increases in the negative direction as shown by the current curve IL1 in FIG. Further, the discharge of the capacitor C2 is completed, that is, the choke coil L1 is removed from the capacitor C2 until the voltage between the electrodes becomes zero.
Then, a discharge current flows through the transistor T1, and the flowing current IL1 of the choke coil L1 gradually decreases from a negative maximum value as shown in a current curve of FIG. The turn-off of the transistor T2 is performed before the charging of the capacitor C1 is started, that is, the turn-off is zero volt, and no switching loss occurs. When the discharge of the capacitor C2 is completed, the mode shifts to the mode d.

Mode d: As shown in FIG. 3D, a flyback current flows from a choke coil (not shown) in the inverter circuit 2 to the positive input terminal 21 through the negative input terminal 22 and the diode D3. The charge stored in the choke coil L1, that is, the flyback current, is returned to the intermediate tap 11 of the DC power supply 1 via the transistor T1. As shown in FIG. 2, the current IL1 flowing through the choke coil L1 gradually becomes zero while the inverter circuit 2
The voltage VO between the positive and negative input terminals 21 and 22 is maintained at zero. When the current IL1 flowing through the choke coil L1 becomes zero, the mode shifts to mode e.

Mode e: At the start of the mode e, that is, when the flowing current IL1 of the choke coil L1 is zero, and thus the conduction current of the transistor T1 becomes zero, the transistor T1 is turned off, that is, zero current is turned off. You. At this time, FIG.
As shown in (1), a voltage (1/2) is applied from the intermediate tap 11 of the DC power supply 1 to the choke coil L1 via the diode D1.
DC power is supplied with E and the choke coil L1
2 gradually increases in the positive direction as shown by the current curve in FIG. On the other hand, a flyback current from a not-shown choke coil in the inverter circuit 2 flows from the negative input terminal 22 to the positive input terminal 21 via the diode D3 in the same manner as in the mode d described above. Thus, the inverter circuit 2 is connected to the diode D3.
The transistor T3 is turned on while the flyback current is flowing back. At this time, as shown by the voltage curve in FIG. 2, the voltage VO between the positive and negative input terminals 21 and 22 of the inverter circuit 2, and therefore the collector of the transistor T3.
The emitter-to-emitter voltage is zero, so the transistor T3 turns on zero volts and no switching losses occur. Thereafter, the flowing current IL of the choke coil L1
When 1 becomes larger than the circulating current from the inside of the inverter circuit 2, that is, the current flowing through the diode D3, the mode shifts to the mode f.

Mode f: As shown in FIG. 3 (f), DC power is supplied from the intermediate tap 11 of the DC power supply 1 to the inverter circuit 2 via the diode D1 and the choke coil L1, and the inverter circuit 2 of the current IL1 Current that exceeds the input current to the transistor flows through transistor T3. Thereafter, the mode shifts to the mode g when the transistor T3 is turned off.

While the transistor T3 is on from mode e to mode f, the inverter circuit 2
Of the transistors T4 to T9. At this time, the transistor T3 is turned on, so that the voltage V between the positive and negative input terminals 21 and 22 of the inverter circuit 2 is set.
O is zero volt, so that the transistors T4 to T9 in the inverter circuit 2 perform zero volt switching (Z
VS), and no switching loss occurs. Also,
The transistor T3 is turned off when its collector-emitter voltage is zero, so that it turns off zero volts, and no switching loss occurs.

Mode g: As shown in FIG. 3 (g), the part of the flowing current IL1 of the choke coil L1 that exceeds the input current to the inverter circuit 2 is the capacitor C1, the positive terminal 12 of the DC power source 1, and the DC power source. 1 through the middle tap 11 and the diode D1, that is, the capacitor C1 discharges and flows through the capacitor C2, the negative terminal 13 of the DC power supply 1, the middle tap 11 of the DC power supply 1 and the diode D1, ie, the capacitor C2.
Is charged. At this time, the voltage between the electrodes of the capacitor C2, and thus the positive and negative input terminals 2 of the inverter circuit 2
When the voltage VO between 1 and 22 rises to (1/2) E, the flowing current IL1 of the choke coil L1 becomes the maximum value in the positive direction, and thereafter, the charging of the capacitor C2 further proceeds, and the electrode of the capacitor C2 As the voltage between the terminals, that is, the voltage VO between the input terminals of the inverter circuit 2 gradually increases to the voltage E, the flowing current IL1 of the choke coil L1
Decreases gradually as shown by the current curve in FIG. When the discharging of the capacitor C1 and the charging of the capacitor C2 are completed, the mode shifts to the mode h.

Mode h: As shown in FIG. 3 (h), the portion of the outflow current IL1 from the choke coil L1 that exceeds the input current to the inverter circuit 2 is the diode D2, the positive terminal 12 of the DC power supply 1, and the intermediate tap. 11 and the diode D1. The reverse voltage (1/2) E is applied to the choke coil L1 from the DC power supply 1, and therefore, the outflow current IL1 of the choke coil L1 gradually decreases as shown by the current curve in FIG. Thereafter, the transistor T2 is turned on, at which time the diode D2 is conducting, as described above, and the voltage between the collector and the emitter of the transistor T2 is zero volt, so that the transistor T2 is turned on zero volts, and no switching loss occurs. When the transistor T2 is turned on, the mode shifts to the mode i.

Mode i As shown in FIG. 3 (i), DC power is supplied from the positive terminal 12 of the DC power supply 1 to the inverter circuit 2 via the transistor T2 with the voltage E, and the outflow current IL1 of the choke coil L1 is reduced. It becomes zero as shown in the current curve of FIG. At this time, the state becomes the same as the state of the mode a described above.
Completes one cycle operation composed of modes a to i.

The one-cycle operation is performed by the inverter circuit 2
Each of the electronic switch elements T4 to T9 is several KHz to several tens KH.
It is performed every time the switch operation is performed with the repetition frequency of z. For example, each time the transistor T4 in the inverter circuit 2 is turned on at the time t1 and turned off at the time t2 as shown in FIG. 7, the transistor T4 is synchronized with the switch operation as shown in FIGS. 4 and 5, respectively. Electronic switch elements T1 to T3 in auxiliary electric circuit 10
Are turned ON and OFF, and the above-described series of operation modes a to i
Execute

In the above description of the operation, only the state in which the power supply device is performing a power running operation has been described in detail. Similarly, the regenerative operation of the power supply device, that is, each electronic switch element T4 in the inverter circuit 2 is performed. ~ T9
In the operation of returning the reactive power in the inverter circuit 2 to the DC power supply 1 via the diodes connected in anti-parallel to the respective electronic switch elements T1 of the auxiliary electric circuit 10,
T3 can perform zero volt switching.

The present invention is not limited to an inverter circuit using a power switching transistor as an electronic switch element.
For example, it is needless to say that the present invention can also be applied to an inverter circuit using a thyristor element. Also,
The present invention is not limited to the three-phase AC type inverter circuit as in the above embodiment, but can be applied to a single-phase AC type inverter circuit.

[0025]

As described above, according to the present invention, an auxiliary electric circuit including an electronic switch element controlled in synchronization with a switching operation of the inverter circuit is provided between the DC power supply and the input terminal of the inverter circuit. During the period commensurate with the commutation time of the electronic switch elements in the inverter circuit by the auxiliary electric circuit, the voltage between the input terminals is set to zero during the period commensurate with the commutation time, and all the electronic switch elements in the inverter circuit are switched to zero volts ( ZVS), the switching loss caused by the electronic switching elements that are generally switched at a repetition frequency of several KHz to several tens KHz is substantially zero, and therefore, overheating of each electronic switching element is reliably avoided. It has good efficiency and stability, and can have very high practical value.

[Brief description of the drawings]

FIG. 1 is a schematic electric circuit diagram of a static AC power supply device according to an embodiment of the present invention.

FIG. 2 is an operation characteristic graph showing a current curve and a voltage curve in a main part for explaining the operation of the power supply device of FIG. 1 on the same time axis.

3 is a simplified circuit diagram partially illustrating the operation of the power supply device of FIG. 1, in which (a) to (i) show flows of operation currents in operation modes a to i, respectively. It is.

FIG. 4 is a diagram showing a voltage waveform at the output end of the auxiliary electric circuit in accordance with the rising axis of the voltage pulse appearing between the collector and the emitter of the transistor T5 in the inverter circuit during operation of the power supply device of FIG. It is a curve figure.

5 shows the voltage waveform at the output end of the auxiliary electric circuit at the falling part of the voltage pulse appearing between the collector and the emitter of the transistor T5 in the inverter circuit during operation of the power supply device of FIG. It is a voltage curve figure.

FIG. 6 is an electric circuit diagram of a conventional static AC power supply device.

FIG. 7 shows a voltage pulse train appearing between the collector and the emitter of the transistor T5 in the inverter circuit during operation of the conventional power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter circuit 3 Filter circuit 4 Load 10 Auxiliary electric circuit 11 Intermediate tap 12 Positive terminal of DC power supply 13 Negative terminal of DC power supply 21 Positive input terminal of inverter circuit 22 Negative input terminal of inverter circuit 23 First parallel circuit 24 Second parallel circuit

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuya Hirachi 6-6 Josaicho, Takatsuki-shi, Osaka Yuasa Battery Co., Ltd. (56) References JP-A-4-88876 (JP, A) (58) Investigated Field (Int.Cl. ⁷ , DB name) H02M 7/48

Claims (2)

(57) [Claims] An inverter circuit (2) comprising a plurality of electronic switch elements is connected to a DC power supply (1), and each electronic switch element of the inverter circuit (2) is repeatedly switched to perform a DC power supply. A static AC power supply that converts DC power from AC power into AC power and outputs the AC power, the DC power supply (1) is provided with an intermediate tap (11), and the first electronic switch element ( T
1) and a choke coil (L1), and a diode element (D
1), a second electronic switch element (T2), a capacitor (C1), and a feedback diode element (D2) between the other end of the choke coil (L1) and the positive terminal (12) of the DC power supply (1). A first parallel circuit (23) in which the three circuit elements described above are connected in parallel to each other is inserted, and a third electron is connected between the other end of the choke coil (L1) and the negative terminal (13) of the DC power supply (1). A second parallel circuit (24) in which three circuit elements of a switch element (T3), a capacitor (C2), and a feedback diode element (D3) are connected in parallel to each other is inserted, and a positive input terminal ( 21)
To the other end of the choke coil (L1) and its negative input terminal (22) to the negative terminal (13) of the DC power supply (1).
And an auxiliary electric circuit (10) configured to be connected to the first, second and third auxiliary electric circuits (10) .
Each switch operation of electronic switch element (T1, T2, T3)
The operation is performed by each electronic switch element of the inverter circuit (2).
And switching operation control in sync with the (T4~T9), the
Choke coil (L1) and capacitors (C1, C2)
Based on resonance action of, during the commutation operation period of each electronic switching device (T4～T9) of the inverter circuit (2), it
To substantially reduce the voltage between the input terminals of the inverter circuit (2).
And the above electronic switch element (T4 to
A static AC power supply, wherein the commutation operation of T9) is completed . 2. The static AC power supply according to claim 1, wherein the first, second and third electronic switching elements in the auxiliary electric circuit (10) are both power switching transistors.