JPS626873Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an inverter for a switching regulator.

The inverter of a switching regulator has conventionally been constructed as shown in FIG. 1, for example.

The figure shows a half-bridge type having four power transistors Q1 to Q4, and a constant DC voltage V _I is supplied between input terminals 1A and 1B from a chopper type constant voltage circuit to perform square wave oscillation.
A square wave voltage υ _p is taken out between the output terminals 2A and 2B.

T1 is a drive transformer, and T2 is an output transformer. Primary and secondary output transformer T2
The following circuit insulation and voltage conversion are performed. The drive transformer T1 includes transistors Q1 and Q2.
base winding NB1 and transistors Q3 and Q4
base winding NB2 and current feedback winding N6
A winding N1 for voltage feedback is provided. T
3 is a current feedback transformer, whose primary winding N4 is connected to the primary winding N3 of the output transformer T2, and whose secondary winding N5 is connected to the winding of the drive transformer T1. It is connected to N6 to form a current feedback loop. Also, winding N2 is connected to transformer T2.
is provided, and this winding N2 is connected to the winding N1 of the transformer T1 via a resistor R1 to form a voltage feedback loop.

First, the starting circuit 3 generates a pulse in the winding N1. This pulse turns on transistors Q1 and Q2, for example, and turns on transistors Q3 and Q4.
Occurs in the direction of turning off. Therefore, transistors Q1 and Q2 are turned on, and transistor Q
3. Q4 turns off. When transistors Q1 and Q2 are turned on, input terminal 1A → transistors Q1 and Q
2 → Winding N3 → Winding N4 → Capacitor C2 → Resistor R2 → Input terminal 1B. At this time, a current proportional to the current flowing through the winding N3 flows through the winding N6 via the transformer T3, and this flows into the base winding.
This is fed back to NB1 and generates an electromotive voltage that further turns on transistors Q1 and Q2. At the same time, a voltage is generated in the winding N2, which is applied to the winding N1 via the resistor R1 and fed back to the base winding NB1, producing an electromotive voltage that also turns on the transistors Q1 and Q2.

In this way, due to the two types of feedback, current and voltage, transistors Q1 and Q2 are sufficiently saturated, and the transformer T
However, the transformer T1 eventually becomes saturated and cannot generate the voltage that turns on the transistors Q1 and Q2. At that moment, transistors Q1 and Q2 are turned off, and a voltage of opposite polarity is generated in winding N2. This voltage is the transformer T
1 is increased in the opposite direction, a voltage is generated in the base winding NB2 that turns on the transistors Q3 and Q4, and the transistors Q3 and Q4 are turned on. When transistors Q3 and Q4 turn on,
Input terminal 1A → Capacitor C1 → Winding N4 → Winding N
3→transistors Q3, Q4→resistance R2→input terminal 1B, a current flows. At this time, as in the previous half cycle, the base winding is
An electromotive voltage is generated in NB2 that further turns on transistors Q3 and Q4.

Thereafter, the same operation as described above is repeated, self-oscillation due to positive feedback continues, and a square wave voltage υ _p is obtained between the output terminals 2A and 2B.

By the way, in the case of this circuit, the current in the winding N6 is such that in one half cycle, the front part becomes sharp, and in the next half cycle, the previous part becomes rounded. become. This is transistor Q1, Q2 and transistor Q
3. Unbalance of Q4 characteristics and capacitor C1
This is because the duty ratio of the transistors is not completely 1:1 due to the unbalance of the capacitor C2 and the like, and the transistor on one side may turn on before the transistor on the other side turns off.

Since the current with a sharp waveform turns on the transistor on one side, and the current with a round waveform turns on the transistor on the other side, an imbalance occurs in the operation of transistors Q1 and Q2 and transistors Q3 and Q4. The balance acts to further emphasize this asymmetry of the current waveform. Since the operations of the transistors Q1 and Q2 and the transistors Q3 and Q4 become unbalanced in this way, there are disadvantages in that the switching characteristics deteriorate and the efficiency deteriorates.

In consideration of this point, this invention makes the feedback current waveform vertically symmetrical and stable, thereby balancing the operation of the transistor, improving switching characteristics and increasing efficiency.

Fig. 3 shows an example of the inverter of this invention, in which a coil _LX constituting an integrating circuit or a low-pass filter is inserted in series with a current feedback winding N6, or a capacitor _Cx constituting an integrating circuit may be inserted in parallel with the winding N6 as shown in Fig. 4.

In any case, by inserting the integrator circuit L _{X or} C . Therefore, the operations of transistors Q1 and Q2 and transistors Q3 and Q4 are balanced, and switching characteristics and efficiency are improved.

As shown in Fig. 5, a coil _LX forming an integrating circuit is inserted in series with the voltage feedback winding N1, or a capacitor C forming an integrating circuit is inserted in parallel with the winding N1 as shown in Fig. 6. _X may also be inserted, and in this case as well, it is equivalent to inserting an integrating circuit into the current feedback loop.

As described above, according to this invention, by inserting an integrating circuit into the current or voltage feedback loop, the operations of the upper and lower transistors are balanced, and the switching characteristics and efficiency are improved.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram of an example of a conventional inverter, Fig. 2 is a waveform diagram for explaining this invention, and Figs.
FIG. 6 is a connection diagram of the whole or essential parts of an example of the inverter of this invention. T1 is a drive transformer, T2 is an output transformer, N6 is a current feedback winding, N1 is a voltage feedback winding, L _X is a coil forming an integrating circuit, C _X
is a capacitor that constitutes an integrating circuit.

Claims (1)

[Claims for Utility Model Registration] A series circuit of a pair of capacitors and a series circuit of a pair of switching elements are respectively connected between a pair of power input terminals, and the pair of capacitors and the pair of switching elements are connected between the pair of power input terminals. A half-bridge inverter in which the primary winding of an output transformer is connected between the connection midpoints of the switching elements, and the pair of switching elements are alternately connected and disconnected by a drive signal from the drive transformer. In the above, the current in the primary winding of the output transformer is supplied to one winding of the drive transformer to form a current return loop, and the other winding of the output transformer is supplied to the other winding of the drive transformer. A voltage feedback loop is formed by connecting to the winding of Inverter removed.