JPS5814706Y2 - DC-DC converter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a DC-DC converter, and in particular, by adding a return winding to a DC-DC converter using a conventionally known Royer oscillation circuit, significant drooping characteristics can be achieved over the entire load range. The present invention relates to a DC-DC converter having output voltage and current characteristics exhibiting the following characteristics.

Figure 1 shows a DC using a conventionally known Royer oscillation circuit.
- A circuit diagram showing an example of a DC converter (however, the rectifier circuit connected to the output winding is omitted), in which the positive voltage of the power supply 7 is applied to the center tap of the primary winding 1.1' of the transformer 10. Therefore, current flows through one of the primary windings depending on which of the transistors 3 and 3' is conductive.

Now, assuming that transistor 3 is conducting, -
The next current is power supply 7 - primary winding 1 - transistor 3 - power supply 7
circuit, and this induces a voltage in the secondary windings 2, 2'.

The voltage induced in the secondary winding 2 supplies a forward base current to the transistor 3, so that the primary current increases, thereby making the base current even larger.

Due to this so-called positive feedback effect, the transistor 3 rapidly approaches saturation.

In this way, the iron core is excited by the current flowing through the primary winding, and eventually the magnetic flux of the iron core becomes saturated.

During this time, a reverse bias is applied to the base of the transistor 3' due to the voltage induced in the secondary winding 2'.
Transistor 3' is kept in the cut-off state and output winding 6
produces a voltage that depends on changes in the primary current.

When the iron core is saturated as described above, the voltage induced in the secondary winding 2 disappears, and the base current of the transistor 3 becomes 0.
, and transistor 3 enters the cut-off state.

- Since the magnetic flux of the iron core begins to decrease by interrupting the current flowing through the secondary winding 1, a voltage of opposite polarity is induced in the secondary winding 2.2', and this causes the transistor 3
' becomes a forward bias state, and a negative current flows through the circuit of power supply 7, primary winding 1', transistor 3', and power supply 7.

Due to the same positive feedback effect as described above, the transistor 3' becomes saturated, and excitation is performed so as to saturate the magnetic flux of the iron core in the opposite direction.

As a result, a voltage of opposite polarity to that in the previous cycle is induced in the output winding 6.

When the iron core is saturated, the induced voltage in the secondary winding 2', and therefore the base current of the transistor 3', becomes O, transistor 3' becomes cut off, and the other transistor 3 becomes conductive in the same manner as described above. becomes.

In the above manner, the two transistors 3 and 3' are alternately made conductive, and the output winding 6 is supplied with a period t as shown in FIG. 3A.
.

generates a square wave.

As is well known, a spike occurs at the rising point of the output rectangular wave, and due to the distributed capacitance or inductance component of the output winding 6, the high voltage value obtained from a constant DC power supply voltage - that is, the step-up ratio has a certain value. There were drawbacks such as limitations.

In DC-DC converters using conventional Royer oscillation circuits, improvements have been made to reduce drooping characteristics and bring them closer to constant voltage characteristics, and constant voltage control circuits have been added. is the current situation.

The present invention aims to improve the above-mentioned drawbacks and, contrary to the conventional art, to provide voltage-current characteristics that emphasize the drooping characteristics over the entire load region, and will be described in detail below with reference to the drawings.

FIG. 2 is a circuit diagram of one embodiment of the present invention.

As is clear from a comparison with FIG. 1, this device differs from the conventional device in that the transformer 10 is provided with a feedback winding 8, and its output voltage is directly connected in series with the DC power source 7.

According to this embodiment, AC return is performed to the DC power supply 7.

As a result, as shown in FIG. 3B, an output voltage with a small duty ratio and an unbalanced waveform can be obtained.

This duty ratio changes depending on the size of the load.

Figure 4 shows the output voltage and current characteristics of the DC-DC converter according to the present invention.Compared to the characteristics (dotted line) of the conventional device without feedback, the DC-DC converter according to the present invention A significant drooping characteristic is obtained which is accentuated over the entire length.

Although the reason for this is not clear, it is presumed that the internal impedance of the DC-DC converter changes depending on the load current due to the feedback effect.

Therefore, the converter of the present invention is a strobe discharge device,
It is suitable as a power source for discharge devices such as internal combustion engine ignition systems, and eliminates the need for magnetic leakage transformers and stabilizing resistors (high series resistance), which were conventionally considered essential for discharge circuits, reducing power loss and improving power supply efficiency. Improvement is expected.

In particular, the DC-DC converter of the present invention is extremely suitable as an auxiliary DC power source for coil-task charge type internal combustion engine ignition systems that use various DC auxiliary power sources that have been proposed in the past.

This is because, when a normal DC-DC converter without a feedback winding is used as the auxiliary power source, it exhibits characteristics close to constant voltage characteristics, as shown by the dotted line in FIG.

Therefore, after a discharge is generated in the ignition plug due to the superposition of the secondary output voltage of the ignition coil and the auxiliary DC power supply voltage, even if the discharge is tried to be extinguished by the back electromotive force of the ignition coil at the end of discharge, the auxiliary DC power supply The voltage causes the spark plug to continue discharging, causing a strong spark discharge in the high-voltage power distribution section of the distributor, damaging this section, and in severe cases, there is a risk that the power distribution section will catch fire and burn out.

On the other hand, the DC-DC converter of the present invention has a significant drooping characteristic as shown by the solid line in FIG.

Then, at the end of the discharge, when the discharge is about to be extinguished by the back electromotive force of the ignition coil, charging of the DC output side capacitor of the DC-DC converter starts, so its output load current increases, and the output The voltage has dropped significantly.

Therefore, the discharge at the ignition plug is reliably extinguished, and undesirable spark discharge, flaming, and burnout phenomena in the high-voltage power distribution section can be completely suppressed.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional DC-DC converter, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is an output voltage waveform diagram obtained by the DC-DC converter of Figs. 1 and 2, FIG. 4 is a diagram similarly showing the output voltage and current characteristics. 1.1'...-Next winding, 2,2'...
Secondary winding, 3, 3'...transistor, 6...
...Output winding, 8...Feedback winding, 10...
····Trance.

Claims (1)

[Scope of utility model registration request] A transformer having a primary winding, a secondary winding, and an output winding, each with its collector connected to the terminal of the primary winding, its base connected to the terminal of the secondary winding, and its emitter commonly connected to a DC power source. a pair of transistors each connected to a pole;
In a Royer oscillation circuit comprising means for connecting a common connection point of emitters to a center tap of a secondary winding, the transformer is provided with a return winding, and the voltage generated in the return winding is transferred to the secondary winding. A DC-DC converter characterized in that the intermediate tap and the other pole of the DC power supply are directly connected in series and overlapped.