JPS6315674A - Dc/ac converter - Google Patents

Abstract

PURPOSE:To decrease the number of parts, to improve reliability and to reduce power loss, by a method wherein first and second inverters are alternately operated in half-wave period of output AC. CONSTITUTION:First and second inverters 1, 2 are installed, and provided with high-frequency transformes T1, T2 and transistors Q1, Q2 as switching elements. the transistors Q1, Q2 are controlled by output from a control circuit 4, and turned on or off alternately. Thereby current flowing in primary windings P1, P2 of the transformers T1, T2 from a battery EB is interrupted. Outputs of secondary windings S1, S2 of the transformers T1, T2 are combined in reverse polarity to each other, thereby pulsating output having frequency component of the output AC is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for converting direct current power to alternating current power.

[Conventional technology]

When converting DC power into AC power such as a commercial frequency and supplying it to various AC loads, switching type DC-AC inverters using semiconductor switching elements have recently been generally used, but when voltage conversion is required, When insulation between power sources is required, a transformer is added to the DC-AC inverter, and AC power is obtained from the secondary winding of the transformer.

However, if the switching cycle of a DC-AC inverter is set to a commercial frequency, the transformer will be large and it will be difficult to reduce electromagnetic noise. Accordingly, it is a good idea to use a high-frequency transformer to downsize the transformer and reduce electromagnetic noise, and rectify the secondary winding output of the high-frequency transformer. It is common practice to convert the current into direct current and then convert it into alternating current such as a commercial frequency using a DC-AC inverter.

In other words, when converting DC power to AC power at a relatively low frequency such as a commercial frequency, a DC-DC converter that performs switching at a high frequency performs positive conversion, and then switching is performed at a desired frequency.
It is often used to supply AC power to a C-AC inverter and obtain AC power from it.

[Problem that the invention seeks to solve]

However, in the case of using the above-mentioned means, the DC-DC converter and the DC-AC inverter are not connected in cascade, and the switching elements are inserted twice, so the reliability decreases due to the increase in the number of parts, and the power This has led to problems such as increased losses and uneconomic conditions.

[Means for solving problems]

In order to solve the above-mentioned problem, the present invention is constructed by the following means.

That is, it is equipped with a switching element and a transformer for high frequency, and by the switching element of the DC power supply, a high frequency intermittent current is passed to the primary winding of the transformer, rectifying the output of the secondary winding of the transformer and sending out a pulsating current. The first and tg2 inverters are connected with the rectangularity of the pulsating output having opposite polarities, a control circuit drives each switching element of each inverter with high frequency, and the output of this control circuit is connected to each switching element of each inverter. It is equipped with an element and a switch that selectively and repeatedly provides the required output AC according to the half-wave cycle.

[Effect]

Therefore, the first and second inverters each perform a switching operation using a high frequency and operate alternately according to the half-wave period of the output AC, so that the pulsating output of each inverter corresponds to each half of the output AC. Since the pulsating outputs of each inverter are connected to each other with opposite polarities, a pulsating output having frequency components of the output AC is obtained as a combined output.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to figures showing examples.

FIG. 1 is a circuit diagram, and FIG. 2 is a diagram showing waveforms at each part in FIG.
Nv)1.2 are provided, each of which is connected to a high frequency transformer T1. T2 and transistors (hereinafter referred to as TR) Ql and Q2 as switching elements are connected between the collector and emitter of a transformer TI and a T2O primary winding P1. P
By turning on and off TR-Qx and Q2 inserted in series with 2, the current flowing from the battery Ell as a DC power source is intermittent, and high-frequency intermittent current is passed to the primary windings Ps and P2, respectively. .

On the other hand, in order to drive TR-Qz and Q2, the period t.

An oscillator (hereinafter referred to as
osc) 3 is provided, and based on the output (JL) of this, a control circuit (hereinafter referred to as CNT) 4 sends out a drive output (b) with a pulse @t□ and a pulse interval t2, and a switch (hereinafter referred to as CNT)
sw) s to each base of TR-Ql and Qz, and SW5 is the output (a) of 08C3.
It is controlled by the branching output (a) of the branching device (hereinafter referred to as DV) 6, which branches the output AC to the period To that requires the output AC, and
The output (b) is selectively and repeatedly applied to the bases of TR-Ql and Q2 with a period of /2. Therefore, the base current is alternately applied to the bases of TR-Ql and Q2! □(d) and IB□(・) are connected, and accordingly, a high frequency intermittent current is passed to each primary winding Pt, pt, and each secondary winding JS1. Sz has a predetermined effective voltage Vl
, Vz are generated, and if these are rectified by the collectors RECs and RECg, the respective reverse direction components are removed, and the peak value V and the effective voltage V1s, Vl
A pulsatile output (h), (j) with 2 is obtained.

However, these pulse outputs (h) and (j) are connected with opposite polarities and occur alternately every half-wave cycle To/'2 of the output AC, so these pulse outputs (h) and (j) are The combined output of 9 contains the frequency components of the output AC. If the high frequency components are removed through a low-frequency wave filter consisting of a flow wire ring and a capacitor CK, an AC output (k) having a square wave voltage Vo is obtained. is obtained.

Note that the output voltage Vo is given by the following equation.

V6= V X @ 11 @ @ 11
+11t 1+t z Therefore, give an output voltage control signal to CNT4,
If the pulse width tl of the output (b) is made variable, the output voltage Vo can be adjusted or stabilized.

Generally, the frequency of output (b) is selected as 1001G (Z), and the frequency of output (k) is selected as 50 Hz, but it can be determined depending on the conditions, and the oscillation frequency of 08C3 and the branching of DV6 can be adjusted depending on the conditions. Just select the ratio.

However, it is preferable to control sw5 in synchronization with output (b).
, if a pause period is set for the alternate driving of Qz, the output (k)
The waveform can be made to have fewer harmonic components.

That is, as shown in the waveform diagram of FIG. 3, a rest period t is provided for the output (e) of DV6, a multiphase pulse generation circuit, etc. is inserted between sw5, and sw5 is connected from the TR-Ql side to the If it is repeatedly controlled as 7 states - TR - Q2 side - OFF state, an AC output (k) will be obtained, and the waveform will be similar to a sine wave AC.

Note that by varying the pause period ts, the voltage v of the output (k)
It becomes possible to freely control o.

As described above, DC/AC conversion is performed by connecting INVi and 2 in parallel and driving them alternately, eliminating the need for double cascade insertion of switching elements, reducing power loss, and achieving high reliability. INVI,2 operates alternately, cutting operating time in half, extending life and reducing power capacity.

Various types such as center-tap type, half-bridge type, and full-bridge type can be used for INVl and 2 (in addition to TR-Ql and Q2, thyristors, power field-effect transistors, etc.) can be used. Various switching elements can be used, and if a low-frequency P-wave device or smoothing circuit is provided on the load side, the blockage line and capacitor C can be reduced.
Various modifications are possible, such as omitting the above.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a DC/AC converter device with high reliability and low power loss can be obtained, and remarkable effects can be obtained in various applications for obtaining AC power from DC power sources. .

[Brief explanation of drawings]

The figures show an embodiment of the present invention, with FIG. 1 being a circuit diagram, and FIGS. 2 and 3 showing waveforms at various parts in FIG. 1.2...INV (inverter), 3...War/OS
c (oscillator), 4...CNT (control circuit), 5...
-・sw (switch), 6...DV (frequency divider), E
B...Battery, Qs, Qz...TR() transistor), Tz, Tz...Transformer, RECs, R
Fe5 - Rectifier.

Claims (1)

[Claims] A switching element and a high-frequency transformer are provided, and a high-frequency intermittent current is passed to the primary winding of the transformer by the switching element of the DC power supply, rectifying the secondary winding output of the transformer and sending out a pulsating current. and a first and second inverter connected so that the polarities of the pulsating outputs are opposite to each other, a control circuit that drives each of the switching elements of each of the inverters with high frequency, and an output of the control circuit that is connected to each of the inverters. A direct current/alternating current converter comprising: a switch that selectively and repeatedly applies a required half-wave cycle of output alternating current to each switching element.