JPS626422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transformer-coupled single-stone converter.

FIG. 1 shows a conventional step-up single-stone converter.
For boost converters, where the output voltage is relatively high and the forward voltage of the output rectifier diode can be ignored, the first priority is to downsize the main transformer and design it withstand voltage.
As shown in the figure, a circuit that performs full-wave rectification with one output winding is used.

The operation in FIG. 1 will be explained with reference to the operation waveforms of each part in FIG. 2. Now, when the main transistor Q ₁ turns on at t=0, the output rectifier diodes D ₁ and D ₂ turn on, and an exciting current flows into Q ₁ , and immediately before Q ₁ turns on, it flows into the output winding of the main transformer T ₁ . The current for making the current continuous and the current corresponding to the load current are summed and flow as a collector current. Now, t
When _Q1 is cut off at = t ₁ , diode D5 is turned on by the flyback voltage due to the excitation energy stored in the main transformer T ₁ during the period from t = 0 to t ₁ , and most of the excitation energy is transferred to the power supply E ₁ side. be returned. At this time, rectifier diodes D3, D4
is turned on and releases a part of the excitation energy of T1 to the output side. When the excitation energy disappears at t= _t2 and the diode D5 is cut off, the output current continues to flow along the path L1→R→D4→winding _n3 →D3 so as to make the current flowing through the output smoothing yoke L1 continuous. .

Here, the output voltage V ₀ is expressed by the following equation.

V ₀ ≒E ₁ n ₃ /n ₁・t ₁ +t ₂ /T In Figure 1, when Q1 is cut off, the emitter
Depending on the voltage applied between the collectors (≒E ₁ n ₁ /n ₂ )
The number of turns of winding n ₂ of T ₁ is limited and the transformer
Since most of the excitation energy of T ₁ is returned to the input power supply side, the only way to obtain high voltage output is to increase the turns ratio (n ₃ /n ₁ ). As a result, the conventional circuit has the disadvantage that it is difficult to downsize the main transformer _T1 and to design the voltage resistance.

The present invention provides a circuit that eliminates the drawbacks of such conventional circuits.

FIG. 3 shows the circuit of the present invention. In this circuit, the main transformer has only two windings, input and output.The anode side of diode D1 and the cathode side of diode D2 are connected to one end of the output winding, and the anode side of the capacitor and diode D3 are connected to the other end of the output winding. , the anode side of the diode D2 and the cathode side of the diode D4 are connected to the other end of the capacitor, the cathode side of the diode D3 is connected to the output smoothing circuit, and the anode side of the diode D4 is connected to one end of the output smoothing capacitor.

The operation of this circuit will be explained with reference to the operation waveforms of each part shown in FIG.

Now, when the transistor _Q1 is cut off at t= _t1 , the flyback voltage due to the excitation energy accumulated in the transformer _T1 during the period from t=0 to _t1 turns on the diode D2, and the capacitor C2 starts charging. Charging is performed until all of the excitation energy (1/2L _s i ² ) of T ₁ is transferred to the capacitor C2 as electrostatic energy (1/2C ₂ ▽ ₂ ² ). (Here L _s
is the primary inductance of the main transformer, and i is the exciting current). At this time, the output current changes from L1 → R ₁ → D4 → D2 → winding n ₂ → D so that the current that was flowing when Q ₁ was on is made continuous in the smoothing yoke L1.
It flows through 3 routes.

Next, when the transistor Q ₁ turns on at t=T, the diode D1 turns on, and the output current flows through the winding n ₂
→ D1 → L1 → R ₁ → D4 → G2 → Winding n ₂ It flows through the path. At this time, since the capacitor C2 is connected in series with the load _R1 , the electrostatic energy stored in the capacitor C2 while the transistor Q1 is cut off is released to the output. Therefore, in the circuit of the present invention, the step-up ratio (n ₂ /n ₁ ) of T ₁ is increased to increase the input/output power transfer efficiency compared to the conventional circuit that returns the excitation energy of the transformer T 1 to the input power supply side. It can be made smaller by that amount. As a result, the size of the transformer can be reduced, and at the same time, it is advantageous in terms of voltage resistance design.

As explained above, the present invention allows one winding of the main transformer to be removed by simply adding one capacitor to the output, and moreover, the excitation energy accumulated in the main transformer can be efficiently transferred to the output side without returning it to the input side. It is characterized by the fact that it can be released into the air.

[Brief explanation of the drawing]

FIG. 1 shows a conventional circuit, FIG. 2 shows operating waveforms of each part of the conventional circuit, FIG. 3 shows a circuit of an embodiment of the present invention, and FIG. 4 shows operating waveforms of each part of FIG. show. E ₁ ... Input power supply, T1 ... Main transformer, n ₁ ...
...Primary winding, _Q1 ...Main transistor, _L1 ...Chiyork, _n2 ...Output winding, D1-D4...Diode.

Claims (1)

[Claims] 1. In a single-stone converter circuit having an input circuit in which an input power source, the primary winding of the main transformer, and the main transistor are connected in series, and a smoothing circuit of a choke input at the output part, one end of the output winding of the main transformer the anode side of the first diode and the cathode side of the second diode to the other end of the output winding, one end of the capacitor and the anode side of the third diode to the other end of the output winding, and the second diode to the other end of the capacitor. the anode side of the first diode and the cathode side of the fourth diode at one end of the smoothing circuit, the cathode side of the first diode and the cathode side of the third diode at one end of the smoothing circuit, and the fourth diode at the other end of the smoothing circuit. A single-stone converter characterized in that the anode sides of the two are connected to each other.