JPS6027273B2 - inverter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter circuit including a pair of transistors that are alternately conductive, and the efficiency of the inverter circuit is improved by reducing switching loss.

For example, a parallel resonant push-pull inverter, as shown in FIG. and the same winding N
Each terminal of P is connected to the negative terminal P2 of the DC power supply E via the collector/emitter of transistors TR, TR2, respectively.
The intermediate tap of the feedback winding NB of the transformer T is connected to P via the bias resistor R, and each terminal of the feedback winding NB is connected to the transistor TR.
, , is connected to the base of TR2, and constitutes a base drive circuit A.

The primary winding NP has both self-inductance and stray capacitance, and the voltage generated in the primary winding NP becomes an oscillating voltage due to its self-inductance and stray capacitance, and due to the vibration, the feedback winding NB also increases. vibrates,
Due to the reversal of these voltages, the transistors TR, TR2 repeat mutually opposite on/off operations, thereby causing the 2
An AC voltage is supplied to a load L connected between both terminals of the next winding NS. And each transistor TR,
, TR2 has a characteristic that even if this base current becomes 0, the collector current does not immediately become 0, but becomes 0 after a short delay, and both transistors TR, , TR2 are turned on simultaneously for a short time, but at this time, the inductance Element CH acts to prevent a sudden increase in current to transistors TR, TR2, thereby increasing the efficiency of this inverter. However, if the period during which the transistors TR, TR2 are simultaneously turned on is long, the efficiency of the inverter still decreases, and the efficiency has not been significantly improved. Therefore, immediately after the base current becomes 0, transistors TR, . T
All you have to do is turn off R2. To do this, reduce the base current and turn off the transistors TR, ,T.
If R2 does not completely enter the saturated region and is operated in the unsaturated region, it can be immediately shifted to the off state. However, reducing the base current in this way requires a large on-voltage (collector-emitter voltage), especially when transistors TR, TR2 transition from on to off, resulting in large power loss during this period. becomes.
Therefore, the efficiency of the inverter cannot be improved with this method. The present invention has been made in view of the above points, and is characterized by connecting one end of the DC power supply E to both ends of the primary winding NP of the oscillation transformer T with a pair of transistors TR.
, , TR2, and the other end of the DC power source E is connected to the center tap of the primary winding NP, and the pair of transistors TR, , TR2 are connected alternately from the base winding NB of the oscillation transformer T. In an inverter circuit, a base drive circuit A is provided to cause a base current to flow through the transistors TR, TR2 so that the base drive circuit A is adapted to conduct In addition to the feedback winding NB, there is also a winding NB provided in the oscillation transformer T, and the current flowing through the winding NB is connected to the feedback winding N.
The winding N is arranged so that the phase is approximately 90 degrees ahead of the current flowing through B.
In the first half of the conduction period of transistors TR, TR2, the current is controlled by the capacitor C connected to B and the current flowing through the winding NB, and the current is alternately increased with respect to the base current from the base winding NB. It is equipped with a pair of transistors TR, , TR2 that are turned on and off at different times.

Hereinafter, the present invention will be explained according to the illustrated embodiments.
The figure shows an embodiment of the present invention, in which the base drive circuit A includes a feedback winding NB, a winding NB connected to a capacitor C, and a winding connected to resistors R4 and R3, respectively. The transistors TR, TR2 are controlled by the current flowing through the winding NB, and the transistors TR, TR2 are controlled by the current flowing through the winding NB2, N&.
, TR2 is constructed so that a large base current flows in the first half of the conduction period, and a small current flows in the latter half.

That is, as shown in Fig. 3, the current flowing through the windings NB, NB2, and NB3 has an AC waveform 'A', and the current flowing through the winding NB has an AC waveform 'A' because the capacitor C is connected to the winding NB. It becomes an AC waveform 'o-' whose phase is 90 degrees ahead of that of t, and for example, during a period of time ~t, each winding NP, N
The polarities of B, NB, NB2, and N& are as shown in FIG.

Therefore, during the period shown by waveform 1, ie, the period from time t to t2, the base drive current flows through the resistor R to the transistor TR, and the transistor Tr is turned on. Further, during the period shown by waveform 8, the transistor Tr is turned on,
In the first half of the waveform (period (time to to t) indicated by the waveform), that is, the period indicated by the waveform, both transistors Tr, Tr, are turned on, so during this period, there is also no power from the power supply E through the resistor R2. A base current flows through the transistor TRR. Therefore, as shown by the waveform, a current flows through the resistor R in the first half of the conduction period ~t2, that is, during the period ~t. A large base current flows in which the current flowing through the resistor R2 is superimposed on the current flowing through the resistor R2, and at the same time, in the latter half, that is, during the period of time ~t2, a small base current flows, which is only the current flowing through the resistor R. As shown in the waveform 'T), the transistor TR2 has a waveform in the first half of its conduction period (time to).
A large base current, which is a superimposition of the current flowing through resistor R and the current flowing through resistor R2, flows through
In the latter half (from time to), a small base current flows through the resistor R. Therefore, before the base current of transistors TR, TR2 becomes 0, the base current decreases, so at that time transistors TR, TR2 do not completely enter the saturated region and can be operated in the unsaturated region. , after the base current becomes 0, it can be turned off immediately, and both transistors T
The period during which R, , TR2 are simultaneously on can be almost eliminated.

Moreover, since a large base current flows when the transistors TR, TR2 move from OFF to ON, their ON voltage (collector-emitter voltage) can be kept low, and this large power loss will not occur. FIG. 4 shows another embodiment, in which the transistor Tr and the diode D are turned on during the first half of the conduction period of the transistor TR, and the voltage generated in the winding NB via the resistor R2 causes the transistor TR to be turned on. At the same time as the base drive current flows, the transistor T
r2 and diode ○2 are turned on, and the base drive current flows through the transistor TR2 via the resistor R2, and the base drive circuit A supplies the conductor to the transistors TR, TR2, as in the case of Fig. 2. A large base drive current can flow in the first half of the period, and a small drive current can flow in the second half.

In the above embodiment, the electric wire E or the winding N is used as a power source for the current that flows through the transistors TR, TR2 through the resistor R during the first half of their conductive period.
B is used, but instead of these, a choke CH may be used as a power source, or a new winding may be provided in the pace transformer T, and this winding may be used as a power source.

Further, in the embodiment described above, a capacitor C is connected to the winding NB to cause a leading current to flow, but a choke may be connected in place of the capacitor C to reverse the polarity of the winding NB. , an inverter drive circuit A that operates similarly can be constructed. In the inverter circuit according to the present invention, in addition to the feedback winding NB, the base drive circuit A has a winding NB provided in the oscillation transformer T, and a current flowing through the winding NB has a phase approximately smaller than that of a current flowing through the feedback winding NB. 90
A capacitor C is connected to the winding NB so as to move forward, and a transistor TR is controlled by the current flowing through the winding NB.
, TR2, which are turned on and off alternately so as to superimpose the current on the base current from the base winding NB during the first half of the conduction period of the feedback winding NB. By connecting the current capacitor C flowing to NB', the current is advanced approximately 90o relative to the feedback winding NB,
Making good use of this phase difference, transistors TR, ,TR
It is possible to reliably turn on and off the transistors Tr, , T, etc. at approximately the midpoint of the conduction period of 2, and no matter what shape the waveform from the base current from the feedback winding NB is, By turning on and off the transistors Tr, Tr2, it is possible to superimpose a current only in the first half of the conductive period of the transistors TR, TR2, thereby ensuring that each transistor TR, TR2 has a current in the first half of its conductive period. A large base current can flow in the front half, and a small base current can flow in the front half. Before the base current becomes 0, each of the transistors TR, TR2 is operated in the unsaturated region, and after the base drive current becomes 0,
It can be turned off immediately, almost eliminating the period during which both transistors are on at the same time, and when each transistor TR, TR2 transitions from off to on, a large base current flows, and the on-voltage at this time is It is low cost and does not cause power loss. Therefore, the switching loss of the inverter circuit can be minimized and its efficiency can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a circuit diagram showing one embodiment of the present invention, FIG. 3 is a waveform diagram for explanation, and FIG. 4 is a circuit diagram showing another embodiment. TR,, TR2...Transistor, A...Base drive circuit. Figure 1 Figure 4 Figure 2 Figure 3

Claims (1)

[Claims] 1 Connect one end of the DC power supply E to the primary winding N of the oscillation transformer T.
The other end of the DC power source E is connected to the middle tap of the primary winding NP, and the pair of Transistor TR_1, TR
The transistors TR_1, TR_2 are alternately made conductive.
A base drive circuit A is provided to flow a base current to TR_2,
In an inverter circuit configured to take out an alternating current voltage to a secondary winding Ns of an oscillation transformer T, the base drive circuit A
In addition to the feedback winding NB, a winding NB provided in the oscillation transformer T is connected to the winding NB so that the current flowing through the winding NB is approximately 90 degrees ahead of the current flowing through the feedback winding NB in phase. A pair of capacitors C and a pair of capacitors that are turned on and off alternately so as to superimpose the current on the base current from the base winding NB during the first half of the conduction period of the transistors TR_1 and TR_2 controlled by the current flowing through the winding NB. An inverter circuit comprising transistors TR_1 and TR_2.