JPH0516271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single-stone resonant self-excited inverter device mainly composed of a transformer, a resonant capacitor, a transistor, a saturable inductor, and a starting circuit. The purpose of this invention is to provide an efficient inverter device.

The circuit configuration of a conventional single-stone resonant inverter device is as shown in FIG. In the figure, the transformer T has primary, secondary, and tertiary windings 11 and 1.
2, 13, the primary winding 11 is the capacitor 10
This parallel circuit is connected to the DC power supply 1 through a transistor 7 and a diode 9 in series. The base of the transistor 7 is connected to the negative side of the power supply 1 through a parallel circuit of a diode 5 and a capacitor 3, a resistor 2 and a tertiary winding 13 in series, and a junction between this parallel circuit of a diode 5 and a capacitor 3 and the resistor 2. A saturable inductor 4 is connected between the point and the negative side of the power supply 1 in a bypass manner. The base of the transistor 7 is connected to the positive side of the power supply 1 via the starting resistor 6, and a reverse current bypass diode 8 is connected in parallel with the series circuit of the collector circuit of the transistor 7 and the diode 9. Secondary winding 12 is connected to the AC output terminal of the device.

In the time curve diagram shown in FIG. 2 for explaining the operation of the above device, curve A is the collector-emitter voltage V _ce of the transistor 7, curve B is the voltage V _t3 of the tertiary winding 13, and curve C is the voltage V t3 of the resistor 2. The current I _r2 , the curve D represents the current I _l4 of the saturable inductor 4, the curve E represents the base current I _b of the transistor 7, and the curve F represents the collector current I _c of the transistor 7. When the power supply is established at time _t0 , a starting current is supplied to the transistor 7 through the resistor 6, thereby reducing the collector-emitter voltage of the transistor 7.
The voltage of the power supply 1 is applied to the primary winding 11 of the transformer T. At the same time, an in-phase voltage is induced in the tertiary winding 13 as well, and is positively fed back to the base of the transistor 7 through the parallel circuit of the resistor 2, capacitor 3, and diode 5. In this way, transistor 7 is instantly turned on.

When a power supply voltage is applied to the primary winding 11, its excitation current increases linearly with time. This current becomes the collector current of transistor 7, which is shown by curve F. On the other hand, in the circuit of the tertiary winding 13, the diode 5 and the base of the transistor 7
The sum of the forward voltages between the emitters and across the diode 9 is applied to the saturable inductor 4, and its magnetic flux density increases with time. Since the inductor 4 exhibits a high impedance until this magnetic flux density reaches saturation, almost all of the current flowing through the resistor 2 becomes the base current of the transistor 7, which maintains an on state.

When the magnetic flux density of the inductor 4 reaches saturation at time _t1 , its impedance drops sharply and the series circuit including the base circuit of the transistor 7 is short-circuited. The base current is applied, and therefore the base current is withdrawn, and the transistor 7 is abruptly turned off. Then, the inductance of the primary winding 11 and the capacitor 10 start to freely oscillate due to the energy stored during the on-period of the transistor 7, and the tertiary winding 13 has the primary winding as seen from time t ₁ to _{t 2} of curve B. A voltage in phase with 11 is induced.

Then, after time _t2 has elapsed slightly, the voltage on curve B becomes slightly positive and the base circuit of transistor 7 is energized, and at the same time its collector-emitter voltage is still sufficiently positive as seen in curve A.
At this point, transistor 7 is suddenly turned on and its collector current rises steeply as shown by curve F.
This current charges the capacitor 10 to near the voltage of the power source 1 and returns to zero, but at this time the current in the primary winding 11 is still a negative value, that is, in the direction from bottom to top in Figure 1, so this current Current is capacitor 1
0 continues to be charged, and its voltage gradually increases. When this voltage reaches the voltage of the power supply 1, the collector circuit of the transistor 7 loses voltage so that it is turned off. Therefore, the voltage of the capacitor 10 tries to continue to rise further, but when it slightly exceeds the voltage of the power supply 1, the diode 8 starts to conduct current, so the voltage of the capacitor 10 is kept constant from then on, and the primary winding The current at 11 continues to decrease at a rate proportional to this voltage. This situation is shown in FIG. 2 after time _t3 . Thereafter, the collector current of transistor 7 starts at time _t4 , ends at time _t5 , and further thereafter, at time _t6 to t7, the same phenomenon as at time _t2 to _t3 described above occurs, and the collector current of transistor 7 starts to increase _. rises steeply and then falls again. Thereafter, the same process is repeated, and thus self-oscillation is performed. The voltage with the same waveform as the primary winding 11 is applied to the secondary winding 1.
Generated at output terminal 2.

A disadvantage of the above conventional device is that the switching loss when transistor 7 is turned on is large, which deteriorates the efficiency of the inverter. That is _, in curve F _{of FIG .}
As shown in the figure, when the voltage of the primary winding 11, that is, the voltage of the capacitor 10 is near zero, the transistor
This is because the charging current to the capacitor 10 flows to the transistor 7 because the capacitor 10 is turned on.

The present invention is intended to improve the drawbacks of the above-mentioned conventional devices, and one embodiment thereof is shown in FIG. The configuration shown in the third figure is mostly the same as that shown in the first figure, but the important difference is that the resistor 2 is replaced with an inductor 14. This substitution results in significant differences in the operation of the device. In FIG. 4 for explaining the operation of the device shown in FIG.
~F represent the voltage or current at the same location as in FIG. 2, respectively.

When the power is turned on at time t ₀ , a starting current is supplied to the transistor 7 through the resistor 6, which turns this transistor on, through which the capacitor 10 is instantly charged to the voltage close to the voltage of the power supply 1, and at the same time the voltage of the transformer T is The primary winding 11 is also applied with the same voltage, and the tertiary winding 13 is also applied with an in-phase proportional voltage. Due to this voltage, the current in the circuit of the tertiary winding 13 increases linearly as seen in curve C due to the presence of the inductor 14, and this current is mostly at the base of the transistor 7 since the saturable inductor 4 is not yet saturated. At the same time as flowing into the circuit and self-maintaining its on state, capacitor 3 is charged relatively quickly to the forward voltage of diode 5. Further, the excitation current of the primary winding 11 increases linearly at a rate proportional to the voltage of the capacitor 10, which is shown by the curve F as the collector current of the transistor 7.

At time _t1 , when the saturable inductor 4 is saturated, its impedance drops sharply and short-circuits the circuit parallel to it, so that the transistor 7 is turned off and from this point on, the capacitor 10 and the primary winding 11 begin to freely oscillate. However, the voltage waveform is the same as that of curve B after time _t1 . This tertiary winding 13
The current flowing through the inductor 14 due to the voltage V _t3
As shown in curve C, I ₁₄ has a waveform that lags behind the waveform of voltage V _t3 by approximately 90°, that is, when voltage V _t3 reaches zero from negative at time t ₂ , it is still near the maximum negative value. In Figure 2 above, at this time t ₂ , curve A
As shown in Fig. 4, when the voltage V _ce is sufficiently large, the base current I _b starts to flow as shown in curve E, so a sudden current flows in transistor 7 as shown in curve E, but in Fig. 4, at time t Curve A between ₂ and _t3
As shown in , the voltage V _ce is a positive value, but in the meantime, as shown in curves C and D, both currents I ₁₄ and I _l4 are near their negative maximum values, and as shown in curve E, the base current is zero. Transistor 7 continues to be off.
In addition, as shown in curve C during time t ₁ to _{t 2} , the current
The period in which I ₁₄ remains close to zero value for a certain period of time represents the period until the saturable inductor 14 finishes positive saturation, passes through an unsaturated state, and then transitions to negative saturation.

After time _t2 , the charging current entering the capacitor 10 from the primary winding 11 decreases but continues, so the voltage of the primary winding 11 increases as seen in curve B, but at time _t3 , the voltage value is When the voltage of the power supply 1 is exceeded, and it is slightly exceeded, the diode 8 begins to conduct, after which the current in the primary winding 11 flows back through the power supply 1 and through the diode 8.

At time _t4 , the current in the primary winding 11 passes through zero and reverses, and the capacitor 10 begins to discharge. Then, the reverse current to the power supply 1 disappears, and a positive voltage starts to be applied to the collector circuit of the transistor 7 after a short time. On the other hand, almost simultaneously, a current I ₁₄ in the inductor 14 which is approximately in phase with the current in the primary winding 11
also changes from negative to positive, and the saturable inductor 4 immediately before it is in the unsaturated state, so the positive current
I ₁₄ flows into the base circuit of transistor 7 after a short time. Therefore, the transistor 7 starts to conduct current, and at this time, as described above, the voltage of the collector circuit is extremely low, so the current is very small. Thereafter, the primary winding 11 receives a constant voltage from the power supply 1, and increases with a constant slope as shown by curve F.

At time t ₅ , the saturable inductor 4 curve D
As shown in FIG. 2, the transistor 7 enters a positive saturation state, so the base circuit of the transistor 7 is short-circuited and loses current, becoming an OFF state, and the collector current suddenly disappears. The state at this time is the same as at time _t1 , and the same process is repeated thereafter. That is, the same energization occurs again from time t ₆ to _{t 7} , and energy is supplied from the power source 1 to the vibration circuit. A voltage of the same shape as curve B is developed in the secondary winding 12, which becomes the output voltage at its terminals. Note that this output is AC, but
A DC output can also be obtained by connecting a rectifying and smoothing circuit to the secondary winding 12.

In the third illustrated embodiment, the capacitor 10 is connected in parallel with the primary winding 11, but as a modification, its position can be changed and it can be placed in parallel with the diode 8. That is, in either case, considering the equivalent circuit, since the power source has low impedance at high frequencies, the resonant circuits for both when the transistor 7 is off are exactly the same. The only difference is that in this modified circuit, the power supply 1 is included in the resonant circuit of the winding 11 and the capacitor 10, so that it is easily affected by the impedance of the power supply.

As mentioned above, in the device shown in the third diagram, the switching loss when the transistor 7 is turned on is greatly reduced compared to the device shown in the first diagram, and therefore the resonance is generally said to have less switching loss and less noise. The characteristics of the mold can be fully demonstrated. In summary, according to the present invention, it is possible to construct a highly reliable single-stone resonant inverter device with a small number of parts, low switching loss, and low interference noise.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional device, FIG. 2 is an explanatory diagram of its operation, and FIG. 3 is a circuit diagram of a device according to the present invention.
FIG. 4 is an explanatory diagram of its operation. 1: DC power supply, 2: Resistor, 4: Saturable inductor, 7: Transistor, 8: Reverse current bypass diode, 10: Capacitor, 11: Primary winding,
12: Secondary winding, 13: Tertiary winding, 14: Series inductor.

Claims (1)

[Claims] 1 Connect the primary winding of the transformer T and the transistor in series to a DC power supply, connect a capacitor in parallel to one of these two, connect a reverse current bypass diode in parallel with the transistor, A parallel circuit consisting of a capacitor and a diode is connected to the base of the transistor, a saturable inductor is connected in series to the parallel circuit, the other end of the saturable inductor is connected to the emitter of the transistor, and the saturable inductor is connected to the base of the transistor. A one-stone type system in which an inductor and a series circuit of a tertiary winding of a transformer T are connected in parallel, and the DC power supply and the base of the transistor are connected through a resistor to obtain an AC output to the secondary winding of the transformer T. Resonant self-excited inverter device.