JPH0386081A - Inverter device - Google Patents

Abstract

PURPOSE:To improve starting performance by providing a pair of switching elements serially connected between both ends of a DC power source and alternately turned ON and OFF, and providing the ON period of the switching element to a specific value of an intrinsic vibration period of a load circuit at the time of starting. CONSTITUTION:The ON period of a transistor Q2 is controlled by the oscillation output of a starter 1 immediately after a power source E1 is turned ON, and the pulse width of the output signal of the starter 1 is set to a specific value of the intrinsic vibration period of a load circuit Z. The residual energy of an inductance L1 when the transistor Q2 is turned OFF becomes maximum, a transistor Q1 is easily turned ON and an inverter device is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter device that converts a DC voltage of a DC power supply into an AC voltage using a switching element to supply power to a load.

[Prior art] Fig. 7 shows a conventional inverter device (Japanese patent application No. 63-2'97).
276) is a circuit diagram. The circuit configuration will be explained below. A power switch S is installed at both ends of the DC power supply E1.
Transistor Q, which is the main switching element, is connected via W.
Q2 are connected in series, and a diode DD2 is connected in antiparallel to each transistor Q, , Q, respectively. A load circuit 2 is connected to both ends of the transistor Q via a coupling capacitor C0 for cutting DC components.

The load circuit Z is constituted by an LC resonant circuit including an inductor 3, a capacitor C1, and a discharge lamp 2, and the load current is an oscillating current. This oscillating current flows through the inductor L,
flows through the primary winding n1 of.

Therefore, a voltage whose polarity changes according to the oscillating current flowing through the load circuit 2 is induced in the secondary winding n of the inductor L1, and this induced voltage is applied between the base and emitter of the transistor Q1 via the resistor R1. The voltage is applied to control the on/off of the transistor Q.

The other transistor Q2 is a monostable multivibrator M
It is on/off controlled by VI.

The monostable multivibrator MVI is made of a general-purpose integrated circuit (for example, μPD4538 manufactured by NEC Corporation), and the falling trigger input terminal B changes from the “High” level to the “L” level.
After changing to "ow" level, output terminal Q is at "High" level and output terminal q is at "Low" level for a certain period of time. It is detected by dividing the voltage in a series circuit of R, and is used as a trigger signal for the monostable multivibrator MV1. is determined by the time constant of resistor R9 and capacitor C4.The output terminal Q is connected to resistor R
+4 to the base of the driving transistor Q4, and the output terminal Q is connected to the base of the driving transistor Q through a resistor RIS. transistor Q
The collector of 4 is connected to the positive terminal of the DC power supply E2, and the transistor Q
The emitters of s are connected to the negative electrode of the DC power source E2, and the emitter of the transistor Q4 and the collector of the transistor Q are connected to the base of the transistor Q2 via a resistor R2. Therefore, the monostable multivibrator MVI operates as a timer circuit for determining the on period τ1 of the transistor Q2. By changing the value of the time constant setting resistor R of the monostable multivibrator MVI, it is possible to continuously adjust the output, and when the load l is a discharge lamp, continuous dimming is possible.

This inverter device includes a starting circuit ST for starting the above-described self-oscillation operation when the DC power source E is turned on. In this startup circuit ST, when the power is turned on, the capacitor C2 is charged via the resistor R5, and when the charging voltage reaches the breakover voltage of the two-terminal thyristor Q4, the two-terminal thyristor Q is turned on, and the two terminals are connected to the base of the transistor Q2. A base current is caused to flow through the thyristor Q to first turn on the transistor Q2, thereby activating the inverter device. When the inverter device starts operating, the charge in the capacitor C2 is discharged via the diode D1 and the transistor Q2 every time the transistor Q2 is turned on, so that no starting pulse is generated. This starting circuit is known from Japanese Patent Application Laid-Open No. 58-192296 and Japanese Patent Application No. 6
It is also disclosed in No. 1-241839.

FIG. 8 is an operating waveform diagram when the load circuit Z of the inverter device is inductive. The same figure (A) is the inductor L.
, shows the load current I flowing through . I+IQ1 is the collector current flowing through transistors Q, Q2, IOI+
ID2 indicates the current flowing through the diodes D, D2. In addition, the same figure (b) shows the collector of transistor Q.
The emitter voltage V,..., the same figure (c) is the transistor Q2
The collector-emitter voltage vQ2 of the transistor Q is the collector-emitter voltage vQ2, the figure (d) is the base-emitter voltage V of the transistor Q, . The output signals are shown respectively.

The operation of the inverter device will be described below with reference to the operation waveform diagram of FIG. 8. When the power switch SW is turned on, the transistor Q is turned on by the startup circuit ST, and the voltage VQ2 across it (FIG. 8 (c)) becomes "L".
os” level, so monostable multivibrator M
■Trigger input terminal B of 1 goes from “High” level to “
The level changes to "Los" level.

As a result, the monostable multivibrator MVI is triggered, and its output terminal Q becomes the "High" level and the output terminal Q becomes the "Los" level (FIG. 8 (E)).

(to)), Therefore, the driving transistor Q4 is turned on and the transistor Q is turned off, and the DC power supply E2 is connected to the transistor Q2 through the transistor Q1 and the resistor R2.
A base current is supplied to the transistor Q2, and the on state of the transistor Q2 is maintained. When transistor Q2 turns on, diode D becomes conductive and capacitor C2 is no longer charged, so starting circuit ST stops. At this time, the secondary winding n2 of the inductor is connected to the base of the transistor Q1.
The transistor Q1 is wound with a polarity such that a reverse bias voltage is applied between the emitters, and the transistor Q1 remains in an off state.

Next, after a predetermined time t determined by the resistor R and capacitor C4 has elapsed, the output terminal Q of the monostable multivibrator MV1 becomes "Low" level, the output terminal q becomes "High" level, the transistor Q4 is turned off, and the transistor Q
, is turned on. Therefore, transistor Q2 is turned off. Transistor Q2 at point A shown in FIG. 8(a)
is turned off, the collector current IQ2 of transistor Q2
As a result, the residual inductance of the inductor Ll generates an opposite induced voltage, and the oscillating currents flowing through the inductors L and 2 tend to flow in the same direction, so the diode DI becomes conductive and a current IO+ flows. In addition, as the secondary winding lin+ of the inductor L1 generates an opposite induced voltage, the transistor Q1
is forward biased, and transistor Q is turned on. When the current In of the diode D1 becomes zero, the transistor Q1 is powered by the accumulated HI charge of the capacitor C0.
Current IQI flows through.

At this time, the core of inductor L+ is linearly magnetized toward the saturation magnetic flux. Eventually, when the core reaches saturation magnetic flux, the inductance rapidly goes toward zero, and as a result, the amount of time change in the collector current IQ+ of transistor Q becomes infinite. When the collector current IQI of the transistor Q1 reaches hfe times the base current, the transistor Q becomes unsaturated and the induced voltage in each winding of the inductor L decreases, so the base current fed back also decreases and the transistor Q1 is turned off. Even after the transistor Q1 is turned off, the oscillating current I flowing through the inductor L+ tends to flow in the same direction, so the diode D2 becomes conductive and the current ID2 flows through the path of the load circuit Z, the capacitor C0, and the DC power supply E. When the diode D2 becomes conductive, the voltage VQ2 of the transistor Q2 becomes zero, so the falling trigger input terminal B of the monostable multivibrator MV1 changes from the "High" level to the "Los" level, and the voltage of the monostable multivibrator MVI changes from the "High" level to the "Los" level. The output terminal Q becomes High" level, the driving transistor Q is turned on, and the transistor Q2 is forward biased. After the oscillating current ID2 flowing through the diode D becomes zero, the DC power supply E1 Collector current IQ2 flows through the path of capacitor C0, load circuit 2, and transistor Q2.

Thereafter, by repeating the above-described operation, the oscillation operation of the inverter is continued.

[Problems to be Solved by the Invention] In the above-mentioned inverter device, one transistor Q1 is controlled on and off by the feedback winding n2 according to the oscillating current of the load circuit Z, and the other transistor Q2 is monostable. Since the on/off control is controlled by the multivibrator MVI, there is no need to use a current transformer with a pair of feedback windings or drive windings, and oscillation can be performed with a very simple configuration.Moreover, it is a monostable multivibrator. MV
Since the on-period of the transistor Q2 can be changed according to the time constant of I, the output of the inverter device can be adjusted. However, this conventional example has a problem in that the startup performance is not necessarily good.

In the above conventional example, the on-period of the transistor Q2 by the starting circuit ST is caused by the accumulated charge in the capacitor C2 and the two-terminal thyristor Q, which is the discharge path thereof.

It is determined by the impedance of the transistor Q2, and the on-voltage of the transistor Q2. Also, the interval between the starting pulse and the next starting pulse is determined by the voltage of the DC power supply EI and the resistance R9.
and the time constant of capacitor C2. However, since the DC power source E1 is generally obtained by rectifying and smoothing the commercial AC voltage, the voltage of the DC power source E gradually increases when the power is turned on.For example, E,! -1150V, Rs=270Ω
, C2 = 0.15 μF, the 2-terminal thyristor Q is N413 (M) manufactured by NEC Corporation, and the transistor Q2 is FK1050 (manufactured by Sanken Electric Co., Ltd.).
When using , the on period of transistor Q2 is approximately 2QA
It was zsec. The operating waveforms observed in this experiment are shown in FIG. 9. FIG. 9(a) shows the drain-source voltage VDs2 of the transistor Q2, and FIG. 9(b) shows the train current IDI of the transistor Q2.

Transistor Q2 is turned off after an on period of approximately 20 μSee. At this time, since the oscillating current is near zero and the transistor Q2 is off, the energy stored in the inductor L1 to turn on the transistor Q1 is small, and the electromotive force induced in the secondary winding n2 is also small. There is a problem that Q1 cannot be easily turned on.

The present invention has been made in view of these points, and its purpose is to improve the starting performance in an inverter device that controls on/off of at least one switching element by feedback of load current. It's about improving.

[Means for Solving the Problems] In order to solve the above problems, in the inverter device according to the present invention, as shown in FIG. A pair of transistors Q, , Q connected in series and turned on and off alternately, and a capacitor C connected to at least one of the transistors Q, , Q.
A load circuit 2 including a series circuit of an inductor Ll and a load L is connected in parallel through a transistor Q1, and an oscillating current flowing through the load circuit 2 is fed back to the control end of at least one transistor Q1, and a predetermined amount determined by the oscillating current is In an inverter device equipped with a feedback winding 1int that periodically controls on/off the transistor Q, the transistor Q is turned on and off at startup.
The present invention is characterized in that a starting means 1 is provided for setting the ON period of the load circuit 2 to around 1/4 or 5/4 times the natural vibration period of the load circuit 2.

Note that in the control means A shown in FIG.
It is determined whether or not the oscillation of the inverter device has started. If the oscillation of the inverter device has not started, the starting means 1 operates, and if the oscillation of the inverter device has started, the trigger circuit 3 activates the transistor. The timer circuit 4 is triggered when Q is turned off, and the timer output of the timer circuit 4 turns on the transistor Q2 for a certain period of time. In this circuit, the switching frequency is set higher than the natural vibration frequency of the load circuit Z.

[Operation] In the circuit shown in FIG. 1, when an ON signal as shown in FIG. 2 (a) is applied to the base of the transistor Q2,
An oscillating current as shown in FIG. 2(b) flows through the switching element consisting of the transistor Q2 and the diode D2. This oscillating current gradually attenuates.If this oscillating current is represented by The stored energy increases. Therefore, if the transistor Q2 is turned off at time 1+ (or tz) when the current flowing through the transistor Q2 reaches its peak, the residual energy in the inductor L increases,
This makes it easier for transistor Q to turn on, improving startup performance. When the transistor Q2 is turned off at this time 1+ (or tz), the on period of the transistor Q2 is equal to the natural vibration period of the load circuit 2 [. 1/4 times (or 5/4 times)

Also, this time h (or tz) is dI/dt with I>O
There are also cases where =O.

Note that if n is an integer greater than or equal to 1, then -m is the on-period of the transistor Q2, which is (4) of the natural vibration period t0 of the load circuit Z.
If it is set to n-3>/4 times, dI/dt will be obtained when I>0, but the amplitude of the oscillating current ■ will gradually attenuate over time, so in practical terms it will be It is appropriate to set the on period to about /4 times (or 5/4 times).

When the discharge lamp 1 is used as a load, since the discharge lamp 1 is in a high impedance state at startup, the natural oscillation period of the load circuit 2! , tto=:2r(L+C1Cz/(C+
+Cz))"2. Therefore, transistor Q2
The on period of t1=(π/2 HL +C1C2/
(CI+ 02))”2 or h=(5r/2)
(L+C1C1/(C++C2))'/" may be used.

FIG. 3 is a waveform diagram of the ON signal of transistor Q2.

At startup, the pulse width of the on signal of transistor Q2 is set to t.
If oscillation is not started within a predetermined time T, the pulse width is set to 1. Gives an on signal. Once oscillation is started, the timer circuit 4 determines the pulse width of the ON signal of the transistor Q2.

Note that the transistors Q, Q2 may be other switching elements (for example, electrostatic induction thyristors, GTOs, etc.).

[Example 1] FIG. 4 is a circuit diagram of a first embodiment of the present invention.

In this embodiment, the AC power supply Vs is full-wave rectified by a diode bridge DB, and the rectified output is connected to a capacitor C.
By smoothing by 1, the DC power source for the inverter circuit is obtained. The m precepts of the inverter circuit are the same as those of the conventional example shown in FIG. However, since power MO8FETs are used as the transistors Q, , Q, resistors R, , R, are connected in parallel between their gates and sources.

The configuration of the control circuit will be explained below. The voltage across transistor Q2 is divided by resistors Ri, R,
The signal is input as a trigger signal to the timer circuit 4 via the buffer BF. This resistance Ra, R? and buffer BF constitute a trigger circuit 3. As with the conventional example shown in FIG. 7, the timer circuit 4 includes a monostable multivibrator made of general-purpose integrated circuits 1 (for example, μPD4538 manufactured by NEC Corporation), and its time constant is determined by a resistor R9 and a capacitor C4. The timer output of the timer circuit 4 is connected to one input in the AND circuit.The output of the detection circuit 2 is connected to the other input in the AND circuit. is connected to one input of the AND circuit G2 via the NOT circuit G3.The output of the startup circuit 1 is connected to the other input of the AND circuit G2.The output of the AND circuit and G4 is ORed. It is connected to the bases of driving transistors Q6 and Q7 via a circuit Gl and a resistor R8.

Transistor Qi.

The respective collectors of Q are connected to the positive and negative electrodes of the control power supply Vl)D, respectively, and the emitters are connected to the gate of the transistor Q2. Thereby, transistor Q6 constitutes a totem pole circuit.

The starting circuit 1 includes an astable multivibrator made of a general-purpose integrated circuit IC (for example, μPC1555 manufactured by NEC Corporation). The oscillation period and output pulse width are determined by the resistor R1.
°, determined by R11 and capacitor C5.

The operation of this embodiment will be explained below. First, the detection circuit 2 detects, for example, the level of the oscillating current flowing through the inverter device, counts the number of pulses of the rectangular wave voltage appearing across the transistor Q2, or detects the voltage across the resonance capacitor CI. It detects whether the inverter device has started oscillation by
Immediately after the power is turned on, the inverter device has not started oscillating, so the output of the detection circuit 2 is “high” level.
Therefore, the output of the timer circuit 4 is blocked within the AND circuit, so it is not input to the OR circuit G1, and the output within the NOT circuit is "Hi" level.
gh' level, the output of the starting circuit I is input to the OR circuit G via the AND circuit G2. Therefore, immediately after the power is turned on, the on period of the transistor Q2 is controlled by the oscillation output of the startup circuit 1. The pulse width of the signal output from this starting circuit 1 is the natural vibration period t0 of the load circuit.
It is set to about 1/4 times (or 415 times) that of Therefore, when transistor Q2 is turned off, the residual energy in inductor L is maximized, and transistor Q1 is easily turned on. As a result, the inverter device is activated. Even if startup fails, in this embodiment, since an astable multivibrator is used as the startup circuit 1, a startup pulse will be given again within a certain period of time, and eventually the inverter device will start oscillating. Then, the output of the detection circuit 2 changes to "High" level. As a result, the output of the NOT @ circuit G becomes "Low" level, so the output of the starting circuit 1 is blocked by the AND circuit G2 and is not input to the OR circuit G1.On the other hand, the output of the timer circuit 4 is It is input to the OR circuit G1 via the circuit G4. Therefore, after the inverter device starts oscillating, the on-period of the transistor Q2 is controlled by the output of the timer circuit 4.

[Example 2] FIG. 5 is a circuit diagram of another embodiment of the present invention.

In this embodiment, a half bridge circuit is used as the inverter circuit. In other words, a series circuit of capacitors Cot and CO2 is connected in parallel to both ends of the DC power supply E, and a load circuit is connected between the connection point of the capacitor Co + + C112 and the connection point of the transistors Q,,Q,. It is. Further, the secondary winding of the inductor Ll is omitted, and a current transformer T exclusively for current feedback is provided, and its primary winding is connected in series with the inductor. The current transformer T is provided with two secondary windings, one of which is connected between the base and emitter of the transistor Q1 via a resistor R7, and the other secondary winding is connected to a resistor R2. It is connected between the base and emitter of transistor Q2 via. Note that resistors Rl 2 and R13 for overcurrent prevention are connected in series to the emitters of the transistors Q, , Q, respectively. The oscillating current flowing in the load circuit is
The current is fed back to the base of the transistors Q, ,Q, via the current transformer T, which causes the transistors Q, ,Q,
is turned on and off alternately, and the inverter device performs self-excited oscillation operation.

When transistor Q is on and transistor Q2 is off, current flows from capacitor C to the load circuit via transistor Q1, and when transistor Q1 is off,
When transistor Q2 is on, transistor Q2
Current flows from the capacitor C02 to the load circuit via the capacitor C02, thereby supplying alternating current to the load circuit.

Next, the configuration of the starting circuit 1 used in this embodiment will be explained. Startup diagram! 1 is equipped with an astable multivibrator made of a general-purpose j[circuit IC (for example, μPCl555 manufactured by NEC Corporation), and is operated by a control power supply voltage VDD.

As is well known, this integrated circuit C1 has one trigger terminal (
When the voltage (No. 2 pin) becomes below (1/3) Voo, it is triggered and the output terminal (No. 3 bin) goes to "High" level, and the discharge terminal (No. 7 bin) becomes high impedance.

Also, the threshold terminal (bin 6) is (2/3) Vo
When it reaches o, the output terminal (bin 3) goes to "Low" level, and the discharge terminal (bin No. 7) also goes to "Low" level. The power supply terminal (No. 8 pin) is connected to the control power supply voltage VOO, and the earth terminal (No. 1 pin) is grounded. Also, the reset terminal (bin 4) is the power terminal (bin 8).
The frequency control terminal (Pin 5) is connected to the resistor R that constitutes the 0 time constant circuit, which is connected to the ground terminal (Pin 1) via the decoupling capacitor C6.
, , A control power supply voltage VOO is applied to the series circuit of the R-th capacitor and the capacitor Cs. The connection point of resistors R1° and R11 is connected to the discharge terminal (bin 7), and the resistor R1+
The connection point between capacitor C7 and capacitor C7 is connected to the threshold terminal (bin 6) and the trigger terminal (pin 2).

As a result, the capacitor C2 is charged to (2/3) Voo via the resistors R+o, R, , and discharged to (1/3) Voo via the resistor R11. Therefore, this circuit operates as an astable multivibrator. The rectangular wave oscillation signal is obtained from the output terminal (bin 3). This signal is N.

Inverted by T circuit G, diode D4 and resistor R4
It is supplied to the base of transistor Q through.

A series circuit of resistors Rs and Ry is connected to both ends of the transistor Q2. Resistance Rs, R? The voltage obtained at the connection point of is passed through the buffer circuit consisting of the NOT circuit s and G t and the resistor R+7 to the transistor Q,
is supplied to the base. This transistor Q.

are connected in parallel across the capacitor C7.

When the inverter device is not started, no voltage is applied across the transistor Q2, so the transistor Q is in the off state, and the astable multivibrator of the startup circuit 1 performs oscillation, and its output terminal (No. 3 A voltage obtained by inverting the rectangular wave signal obtained at the input terminal (bin) by the NOT circuit is applied to the transistor Q2 as a starting pulse. When the inverter device is thereby activated and starts an oscillation operation, the voltage across the transistor Q2 increases periodically, so the transistor Q8 is periodically turned on and the charge in the capacitor C9 is discharged. Therefore, the trigger terminal (pin 2) of the astable multivibrator is always below (1/3) Voo, and the output terminal (bin 3) is always at "High" level.

Therefore, the output of the NOT circuit is always at a "Low" level, and the supply of the activation pulse to the transistor Q2 is stopped.

FIG. 6 is an operational waveform diagram of this embodiment. Same figure (A is NO
Wave of starting pulse output from T circuit Gs> In the figure, tl is the pulse width of the starting pulse, which is determined by t + # 0, 693 R+ + Cs. In addition, T is the interval between starting pulses, and at least T>
The values of the resistor R1 and capacitor C1 are set so that the voltage becomes 4tl. Pulse 41 of the starting pulse! t + is the natural vibration period t of the load circuit. When set to around 1/4 times (or 5/4 times), the residual energy of the inductor L1 becomes maximum when the on period of the transistor Q2 due to the activation pulse has elapsed and the transistor Q2 is turned off. Therefore, the inverter device starts up easily.

Figures 6 (B) and (C) show the operating waveforms when the inverter device is started with the first starting pulse, and Figures 6 (2) and (E) show the operation waveforms when the inverter device is started with the first starting pulse. This shows the operating waveforms when the device is not activated. Here, FIGS. The positive direction is the current of the transistor Q, and the negative direction is the current of the diode D1.Furthermore, FIGS. In the figure, the positive direction is the current of the transistor Q2, and the negative direction is the current of the diode D2.

As shown in Figures 6(d) and (e), if the inverter device is not started by the first starting pulse, diodes D, D2 are turned on and off alternately, causing an oscillating current to flow. , this oscillating current gradually attenuates. In this case, since the voltage across transistor Q2 does not rise, transistor Q remains in the off state, and the astable multivibrator of starting circuit 1 continues to oscillate. And the sixth
As shown by the broken line in Figure (A), the next activation pulse is applied and continues until activation is successful.

[Effects of the Invention] According to the present invention, in an inverter device that controls on/off of a switching element by feeding back an oscillating current flowing into a load circuit, the on-period of the switching element at startup is set to 174 times the natural vibration period of the load circuit. Since the starting means is provided to set the value to about double or 5/4 times, the residual energy in the inductor of the load circuit becomes maximum at the moment the switching element is turned off, and therefore the starting performance is improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the basic configuration of the present invention, FIGS. 2 and 3 are operational waveform diagrams of the same as above, FIG. 4 is a circuit diagram of the first embodiment of the present invention, and FIG. 5 is a circuit diagram of the first embodiment of the present invention. Circuit diagram of the second embodiment, No. 6
The figure is the same operating waveform diagram as above, Figure 7 is the circuit diagram of the conventional example, and Figure 8 is the circuit diagram of the conventional example.
FIG. 9 and FIG. 9 are operation waveform diagrams of the same as above. E is a DC power supply, Q and Q2 are transistors, co. CI is a capacitor, Ll is an inductor, l is a discharge lamp, n
2 is a feedback winding, 1 is a starting circuit, A is a control means, and Z is a load circuit.

Claims (1)

[Claims] (1) A DC power supply, a pair of switching elements connected in series between both ends of the DC power supply and turned on and off alternately, and an inductor and an inductor connected in parallel to at least one of the switching elements via a capacitor. In an inverter device comprising a load circuit including a series circuit of loads, and feedback means for returning an oscillating current flowing through the load circuit to the control terminal of at least one switching element to control on/off of the switching element, the The on-period of the switching element is set to 1/4 of the natural vibration period of the load circuit.
An inverter device characterized in that it is provided with a starting means for setting around twice or 5/4 times.