JP2831057B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention includes a pair of switching elements, controls ON / OFF of one of the switching elements in a separately excited manner, and turns on the other switching element in a self-excited manner. , An inverter device that performs off control.

[Prior Art] A conventional inverter device is shown in FIG. In FIG. 6, an inverter device is used as a discharge lamp lighting device having a discharge lamp 1 as a load, and a self-excited half-bridge inverter device is used as the inverter device. In this discharge lamp lighting device, transistors Q ₁ and Q ₂ having diodes D ₁ and D ₂ connected in anti-parallel to both ends of a DC power supply E are connected in series, and a commutation capacitor C ₀ is connected to both ends of the transistor Q _1. through the discharge lamp la, choke coil L _1, and the drive transformer
Be connected to one primary winding of T _1, to apply a voltage are respectively induced in the two secondary windings of the driver transformer T ₁ to the base of the transistor Q _1, Q _2, the transistor Q _1, Q ₂ The DC power supplied from the DC power supply E is alternately turned on and off to be converted into high-frequency power and supplied to the discharge lamp la. In addition,
Capacitor C connected in parallel to the non-power supply side of discharge lamp la
_1, together with preheating of the filaments of the discharge lamp la, and constitutes a series resonant circuit together with the choke coil L _1. Moreover, commutation capacitor C ₀ is larger capacity than the capacitor C _1, it does not contribute to the resonance. The start of the inverter device of the discharge lamp lighting device is performed by an SBS (Silicon Birateral Switch).
h) Startup circuit 2 consisting of Q ₃ , capacitor C ₂ and resistor R ₁ . That is charged in the capacitor C ₃ when the power source is turned on,
When the charging electric charge of the capacitor C ₂ reaches the breakover voltage of SBSQ _3, SBSQ ₃ conducts. Thus, the base current of the transistor Q ₂ is supplied, the transistor Q ₂
Is turned on, the inverter device is started.
In this way, when the inverter is started, the transistors Q ₁ and Q ₂ are alternately turned on and off by the action of the drive transformer T ₁ , and the inverter starts oscillating.

Here, in this way, the discharge lamp la
In the current is supplied, the preheating current flows through the capacitor C ₁ to the filament of the discharge lamp la. When the starting voltage of the discharge lamp la thermionic This preheating is released is reduced, the capacitor due to the resonance between the capacitor C ₁ and the choke coil L ₁
Voltage generated in the C ₂ discharge lamp la is illuminated. FIG. 7 shows the switching states of the transistors Q ₁ and Q ₂ of the discharge lamp lighting device and the resonance current indicated by I in FIG.

However, in this discharge lamp lighting device, transistors Q ₁ and Q _1
2 Transistor due to variation in h _FE (DC amplification factor)
Since the conduction periods of Q ₁ and Q ₂ change, there is a problem that the entire oscillation frequency changes greatly and the load current greatly varies.
In addition, since the oscillation frequency is affected by variations in the constants of the circuit components, there is a problem that it is difficult to control the oscillation frequency.

To solve the above problem, a discharge lamp lighting device shown in FIG. 8 is provided. In the case of the discharge lamp lighting apparatus, the on transistor Q _1, and approximately the same as the case described above the off FIG. 6 controls the self-excited, on the FETs Q ₂ 'used as the other switching elements, The off is controlled separately. The FET Q ₂ ′ is on / off controlled by the astable multivibrator 3.

Also in this inverter device, although the on / off control method of each switching element is different, the transistors Q ₁ and FET Q ₂ ′ are alternately turned on and off in the same manner as in the circuit of FIG.
Turn off.

By the way, this inverter device has a transistor Q ₁
And in order to prevent the simultaneous ON of FETs Q ₂ ', resistors R _2, R _3,
A simultaneous ON prevention circuit 4 including an inverter gate G ₁ and an AND gate G ₂ is provided. Inverter That is, in the simultaneous ON prevention circuit 4, when the transistor Q ₁ is the voltage of the turned-on the DC power source E is applied between the gate and source of the FETs Q ₂ ', the divided voltage of the resistors R _2, R ₃ close the aND gate G ₂ by inverting at gate G _1, the transistor
During the ON period of Q _1, the astable multivibrator 3 switches the FET Q ₂
Block the output of the signal to turn on the transistor Q ₁ , FET
Q ₂ ′ is prevented from turning on at the same time. Note that when off FETs Q ₂ 'in this inverter device, a voltage that turns on the transistor Q ₂ in the secondary winding by the energy accumulated in the primary winding of the driving transformer T ₁ until it is induced, thereby the transistor Q ₁ is turned on to flow a current in a direction to discharge the charged electric charge stored in the capacitor C _0. And
When the resonance current is saturated, the transistor Q ₁ is reverse biased by the action of drive transformer T _1, turned off, then FE
TQ ₂ ′ is turned on and the above operation is repeated thereafter.
The inverter device oscillates. FIG. 9 shows an operation waveform diagram of each part of the circuit of FIG.

In this inverter device, the oscillation frequency can be made to coincide with the oscillation frequency of the astable multivibrator 3. Therefore, by changing the oscillation frequency of the astable multivibrator 3, the oscillation frequency of the inverter device is changed to control the load current. it can. Moreover, in this inverter device, since the FET Q ₂ ′, which is the main switching element, is separately controlled by switching, it is not affected by variations in the DC amplification factor as in the case of controlling both switching elements by self-excitation.

[Problems to be Solved by the Invention] However, the circuit shown in FIG. 8 has the following problems. In other words, in this discharge lamp lighting device, the capacitor
When the voltage at both ends of the series circuit of C ₀ and C ₁ is charged up to the voltage of the DC power supply E, an instantaneous power failure or instantaneous voltage drop occurs in the commercial power supply, and when the transistor Q ₁ turns off, the FET Q ₂ turns on and off. even after repeated drive since no current flows in the primary winding of the transformer T _1, holding the state of the transistor Q ₁ is turned off, the oscillation operation will be stopped in this order inverter device. Therefore, in this case, the power must be turned on again to restart the inverter device.

The present invention has been made in view of the above points, and a purpose thereof is to provide a pair of switching elements,
In an inverter device that controls the ON / OFF of one switching element in a separately excited manner and controls the other switching element ON / OFF in a self-excited manner, the operation of the inverter device is stopped due to an instantaneous power failure or an instantaneous voltage drop. The goal is not to be.

Means for Solving the Problems In order to achieve the above object, the present invention connects a capacitor for commutation and an impedance element for discharging a charge of a capacitor constituting a resonance circuit to each of the capacitors. A detection circuit for detecting a state in which the switching element holds the off state is provided in the control circuit, and when the first switching element holds the off state, the control is performed when the charged charges of the two capacitors are sufficiently discharged. The circuit stops the operation of turning on and off the second switching element.

[Operation] The present invention is configured as described above, and when the oscillation of the inverter is stopped due to an instantaneous power failure or the like, the control circuit stops turning on and off the second switching element, and the commutation capacitor and By waiting for the charge of the capacitor of the resonance circuit to be discharged, and then operating the control circuit, the inverter device can be automatically restarted.

Embodiment 1 FIGS. 1 and 2 show an embodiment of the present invention. In this embodiment, as shown in FIG. 1, FETs Q ₂ 'ON, off controlled by astable multivibrator 3 which is a timer IC (555), the transistor Q _1, FETs Q _2' turned on simultaneously with the A simultaneous ON prevention circuit 4 for preventing the ON state is provided. In the case of this embodiment, a certain time from power-on (e.g., about 1 second) switching frequency and is to ensure that the discharge lamp preheating of filaments la is carried out, the transistor Q _1, FETs Q ₂ ' , The applied voltage to the discharge lamp la is reduced, and after the elapse of the preheating time, the switching frequency is reduced to increase the applied voltage to the discharge lamp la, thereby lighting the discharge lamp la. For this purpose, in the present embodiment, the timer circuit 5 for measuring the preheating time and the voltage of the 5th terminal of the astable multivibrator 3 are gradually increased to increase the discharge lamp la.
And a frequency control circuit 6 for lowering the frequency of the output of the astable multivibrator 3 until the frequency at which the multi-vibrator 3 starts.
Then, the state in this embodiment the transistor Q ₁ is holding the OFF state, that is, detects the oscillation stop of the inverter, at the time of oscillation stop stops on, off control of the FETs Q ₂ 'for a fixed time astable multivibrator 3 The diode D _{3 for} detecting the oscillation stop state of the inverter device from the output of the simultaneous ON prevention circuit 4 for this purpose,
Capacitor C _3, the detection circuit 7 composed of the inverter gate G _3, and resistor R _4, a certain time from the point at which the oscillation stop of the inverter device is detected by the detection circuit 7, no by AND gate G ₂ of the simultaneous ON prevention circuit 4 Stable multivibrator 3
Monostable multivibrator (CMOSIC45
28) 8 is provided. Also, if in the case of the embodiment in which transistor Q ₁ is longer on, the capacitor C _0, C
Discharge resistors R ₅ and R ₆ are connected in parallel to capacitors C ₀ and C ₁ , respectively, in order to quickly discharge ₁ .

Hereinafter, the operations of the detection circuit 7 and the monostable multivibrator 8 will be described. At the time of steady oscillation in which the transistor Q ₁ and the FET Q ₂ ′ are alternately turned on and off, the simultaneous ON prevention circuit 4
The output of repeats a high level and a low level, charges of the capacitor C ₃ does not reach the threshold value of the inverter gate G _3, the output of the monostable multivibrator 8 is at a high level. For this reason, FETQ ₂ ′ is shown in FIG.
On / off control is performed by the output of the astable multivibrator 3 as shown in FIG.

Now, in a state in which the charges of the capacitor C _0, C ₁ is charged to the voltage of the DC power source E, a momentary power failure or the like occurs, thereby when the transistor Q ₁ is turned off, the transistor Q ₁ is turned off as described above And the oscillation operation stops.
At this time, since the output of the simultaneous ON prevention circuit 4 becomes a high level, the discharge of the charges of the capacitor C ₃ is stopped, thereby the voltage across the capacitor C ₃ exceeds the threshold value of the inverter gate G ₃ (the 2 Figure (c) shows an inverter gate G ₃ outputs). Therefore, as shown in FIG. 2 (d), the output of the monostable multivibrator 8 is at a low level, and while the output of the monostable multivibrator 8 is at a low level, the output of the astable multivibrator 3 is AND gated. It is prevented by G _2. Therefore, FETQ ₂ ′
Is off while the output of the monostable multivibrator 8 is at a low level. Here, while the output of the monostable multivibrator 8 is at a low level, the capacitors C ₀ and C _0
The period is set so that the charge of ₁ is sufficiently discharged.
Therefore, the output of the monostable multivibrator 8 becomes high level, and the output of the astable multivibrator 3
When Q ₂ ′ is turned on, a current flows through the primary winding of the driving transformer T ₁ and the transistor Q ₁ turns on. As described above, according to the present embodiment, the oscillation operation of the inverter device can be automatically restarted without restarting the power supply or the like.

Embodiment 2 FIGS. 3 and 4 show another embodiment of the present invention. In the present embodiment, the monostable multivibrator 8 of the first embodiment is used.
4B, an astable multivibrator 9 having a longer on-duty than the astable multivibrator 3 is used as shown in FIG. 4 (b), and the output control of the astable multivibrators 3, 9 is controlled by a detection circuit 7. which was to perform, aND gate which receives the outputs of the astable multivibrator third inverter gate G ₃ of the detection circuit 7
And G _4, AND gate G ₅ which receives the outputs of the astable multivibrator 9 impervious to inverter gate G ₃ of the detection circuit 7, and inputs the output of each AND gate G _4, G ₅ and a gate G _6.

In this embodiment, when the oscillation of the inverter device stops, the FET Q ₂ ′ is turned on and off by the output of the astable multivibrator 9. In this case, while the output of the astable multivibrator 9 is at a low level, the capacitors C ₀ , C
_{Since the} period in which _one charge is sufficiently discharged is reached, the oscillation operation of the inverter device can be automatically started in the same manner as in the above-described embodiment.

Third Embodiment FIG. 5 shows still another embodiment of the present invention. The detection circuit 7 which was constructed integrally with astable multivibrator 10 in the present embodiment, turning on transistor Q ₄ when oscillation stop the output of the astable multivibrator 10 of the inverter device, and off control, the transistor Q ₄ Is turned on, the output of the astable multivibrator 3 is lowered to a low level. The on-duty of the astable multivibrator 10 is the same as that of the astable multivibrator 3.
Longer and the output is at low level
This is a period during which the charged charges of C ₀ and C ₁ are sufficiently discharged.
Therefore, also in this embodiment, the oscillation operation of the inverter device can be automatically started.

[Effects of the Invention] As described above, in the present invention, a commutation capacitor and an impedance element that discharges a charge of a capacitor constituting a resonance circuit are connected to the respective capacitors, and the first switching element maintains an off state. The control circuit is provided with a detection circuit for detecting the state of the second switching element until the charge of the two capacitors is sufficiently discharged when the first switching element holds the OFF state. Is turned off, the control circuit turns on and off the second switching element when the first switching element holds the off state and the oscillation of the inverter device stops due to an instantaneous power failure or the like. And wait for the charge of the commutation capacitor and the capacitor of the resonance circuit to discharge, and then operate the control circuit. Therefore, the inverter device can be automatically re-oscillated.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is an operation explanatory diagram of the above embodiment, FIG. 3 is a circuit diagram of another embodiment, FIG. 4 is an operation explanatory diagram of the above embodiment, and FIG. FIG. 6 is a circuit diagram of a conventional example, FIG. 7 is an operation explanatory diagram of the above example, FIG. 8 is a circuit diagram of another conventional example, and FIG. 9 is an operation explanatory diagram of the above example. It is. 3, 9, 10 are astable multivibrators, 7 is a detection circuit, Q ₁
Is a transistor, Q ₂ ′ is a FET, la is a discharge lamp, E is a DC power supply, T ₁ is a driving transformer, C ₀ and C ₁ are capacitors, and R ₅ and R ₆ are resistors.

Claims (1)

(57) [Claims] A first switching element connected in series to both ends of a DC power supply and a load circuit comprising a load and a resonance circuit connected to both ends of the first switching element via a commutation capacitor; And a control circuit for controlling the on / off of the second switching element, and the first switching element by the voltage induced in the secondary winding of the drive transformer. An inverter device for turning on / off and alternately turning on / off the first and second switching elements to convert DC power supplied from a DC power supply into AC power and to supply the load to a load, A capacitor and an impedance element for discharging a charge of the capacitor constituting the resonance circuit are connected to the respective capacitors, and the first switching element holds the off state A detecting circuit for detecting the state of the second switching element is provided in the control circuit until the charge of the two capacitors is sufficiently discharged when the first switching element holds the off state. Inverter device that stops the operation of turning on and off.