JPH03198668A - Inverter device - Google Patents

Abstract

PURPOSE:To simplify a starting circuit by using a signal rectified from an AC power supply voltage as a start signal. CONSTITUTION:An AC power supply 1 is full-wave rectified by a rectifier circuit 3, converted to a smooth DC voltage by a smoothing circuit 4, this DC voltage is converted to a high frequency voltage by an inverter circuit 5, and applied to a load Z. The inverter circuit 5 has transistors Q1, Q2, the transistor Q1 is driven in a self-exciting manner, and the transistor Q2 is driven by a drive control circuit B. A rectified signal A from the power supply 1 is applied to the control circuit B, the transistor Q2 is turned ON after the power source is applied to start an oscillation.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an inverter device for converting direct current voltage to high frequency voltage, and is used, for example, for high frequency lighting of discharge lamps. .

[Prior Art 1] FIG. 11 is a circuit diagram of a conventional inverter device. The circuit configuration will be explained below. The commercial power supply AC is connected to an AC input terminal of a diode bridge DB for full-wave rectification, and a smoothing capacitor C0 and a resistor R6 are connected in parallel to a DC output terminal of the diode bridge DB. A series circuit of transistors Q, Q2, which are main switching elements of the inverter circuit, is connected in parallel to both ends of the capacitor C0. Each transistor Q,...
Diodes D I and D 2 are connected in antiparallel to Q2, respectively. A coupling capacitor C2 for cutting DC components and a current transformer CT for feeding back the load current are connected to both ends of the transistor Q.

A load circuit Z is connected via. Load circuit Z
is constituted by an LC resonant circuit consisting of an inductor L1, a capacitor C3, and a discharge lamp l, and the load current is an oscillating current. This oscillating current is generated by one of the current transformers CT.
It flows through the next winding n1.

Therefore, the secondary winding n2. of the current transformer CT o. n
3, a voltage whose polarity changes according to the oscillating current flowing through the load circuit Z is induced, and this induced voltage is transferred to the transistor Q.
, , Q2 are applied between the bases and emitters of the transistors Q, , Q2 to alternately switch them. Note that resistors R2 and R3 are base resistors of transistor QQ2.

This inverter device includes a startup circuit ST for starting the above-described self-oscillation operation when commercial power supply AC is turned on. In this startup circuit ST, when the power is turned on, the capacitor C5 is charged via the resistor R3, and when the charging voltage reaches the breakover voltage of the two-terminal thyristor Q3, the two-terminal thyristor Q is turned on, and the transistor Q2
A base current is passed through the base of the transistor Q2 through the two-terminal thyristor Q3 to first turn on the transistor Q2 and start the inverter device.

[Problems to be Solved by the Invention] In the above-mentioned conventional example, a starting circuit ST consisting of a two-terminal thyristor Q3, a capacitor CI, a resistor R2, etc. is required to start the inverter device, and when it is mounted on a printed circuit board. However, the drawbacks were that the substrate became thicker and more expensive.

The present invention has been made in view of these points, and its purpose is to realize a starting circuit for an inverter device with a simple circuit configuration.

[Means for Solving the Problems] FIG. 1 is a block circuit diagram showing the basic configuration of the present invention. In this inverter device, an AC power supply 1 is full-wave rectified by a rectifier circuit 3, converted to a smooth DC voltage by a smoothing circuit 4, and this DC voltage is converted to a high-frequency voltage by an inverter circuit 5. It is applied to The inverter circuit 5 includes switching elements such as transistors Q, , Q2. In the circuit shown in FIG. 1, one transistor Q1 is driven by self-excitation, and the other transistor Q2 is driven by a drive/control circuit B. In the circuit shown in FIG. This inverter device is necessary in the startup circuit in order to start the oscillation operation when the power is turned on, but in the present invention, the rectified signal A from the AC power supply 1 is given to the drive control circuit B, and after the power is turned on, the Turn on Q2,
This starts the oscillation operation.

In the present invention, as described above, the rectified signal A from the AC power source 1 is used as the starting signal, so it is possible to realize a starting circuit for an inverter device with a very simple circuit configuration. .

[Example 1] FIG. 2 is a circuit diagram of a first embodiment of the present invention.

In this embodiment, in the conventional example shown in FIG.
The starting circuit ST is omitted, and the commercial power supply 1 is replaced by a diode D. A half-wave rectified voltage (see FIG. 3) is applied to the base of the transistor Q2 from each of the series circuits of the resistor R1 and the resistor R1. Further, a resistor R1 is connected in parallel to both ends of the transistor Q, and a resistor R5 is connected in parallel to both ends of a load ρ consisting of a discharge lamp.

The other configurations are the same as the conventional example shown in FIG.

The operation of this embodiment will be explained below. During the period H when the voltage is at a high level as shown in FIG. It is charged by the current flowing from the capacitor C1. And this capacitor C
During the period when the voltage is at a low level as shown in FIG.
Current transformer CT.

primary winding nl', current-limiting inductance element L1,
It is discharged through the load circuit Z. At this time, the transistor Q, due to the secondary winding n2+n3 of the current transformer CT,
is forward biased, transistor Q2 is reverse biased, transistor Q is on, and transistor Q2 is off. Eventually, when the discharge current from capacitor C2 becomes zero, the voltage induced in the secondary winding of current transformer CT0 is reversed, transistor Q2 is forward biased, transistor Q1 is reverse biased, and transistor Q2 is turned on, and transistor Q1 is turned off. Thereafter, the transistors Q, Q2 are alternately turned on and off by the current transformer CTo, and the self-oscillation operation of the inverter device is continued.

As described above, in this embodiment, since the startup circuit of the inverter device can be easily configured, an inexpensive inverter device can be provided.

[Embodiment 2] FIG. 4 is a block diagram showing a schematic configuration of a second embodiment of the present invention. The power supply device of this embodiment includes a filter circuit 2 connected to a commercial power source 1, a rectifier circuit 3 for full-wave rectification of the commercial power source 1, a smoothing circuit 4 for smoothing the output of the rectifier circuit 3, and a smoothing circuit 4 for smoothing the output of the rectifier circuit 3. The inverter circuit 5 is driven by the output and outputs a high frequency voltage with little low frequency ripple. The smoothing circuit 4 is configured using a smoothing capacitor 41, an inductance element 42, and a switching element 50. The switching element 50 is shared by the rectifier circuit 4 and the inverter circuit 5. This switching element 50 is turned on and off by an inverter starting circuit 6, a control circuit 7, and a drive circuit 8. The inverter starting circuit 6 also serves as an off-detection function for the switching element 50.

FIG. 5 is a specific circuit diagram of this embodiment. The inverter circuit 5 includes a transistor 51 as a main switching element.
and a MOSFET 52. transistor 51
A diode 53 is connected in antiparallel to MO8F.
F, T52 includes a parasitic diode 54 in the opposite direction. A capacitor 58 and one of the transformers 55 are connected to both ends of the transistor 51 via a DC cut capacitor 57.
A series circuit of the next winding 55a is connected. Furthermore, 1
- The secondary winding 55b of the lance 55 is used as a feedback means, and the oscillating current of the inverter circuit 5 is fed back only to the base terminal of the transistor 51, which is one switching element, via the resistor 56.

Next, the smoothing circuit 4 includes an inductance element 42, a MOSFET 52 and a diode 53 of the inverter circuit 5,
It also includes a smoothing capacitor 41. That is, the MOSFET 52 and diode 53 of the inverter circuit 5 are also used as switching means for the chopper of the smoothing circuit 4. The output of the rectifier circuit 3 is applied to the MOSFET 52 via the inductance element 42. When the MOSFET 52 is turned on, electromagnetic energy is accumulated in the inductance element 42, and the MOSFET
When T52 is turned off, the above electromagnetic energy is released to the smoothing capacitor 41 via the diode 53. The DC voltage charged in the smoothing capacitor 41 becomes the input voltage of the inverter circuit 5.

Next, the inverter starting circuit 6 consists of a series circuit of resistors 61 and 62 connected in parallel to both ends of the MOSFET 52 in order to detect whether the transistor 51 is turned off. The rectified output of the rectifier circuit 3 is applied to this series circuit of the resistors 61 and 62 via the inductance element 42, and the rectified signal of the commercial power supply 1 is applied at the time of startup.

Upon receiving the output of this inverter starting circuit 6, the control circuit 7
generates a signal for controlling the on/off of MOSFET 52. The control circuit 7 includes a monostable multi-bi break circuit 73 and a resistor 7 for determining its output pulse width.
1 and a capacitor 72. The monostable multivibrator circuit 73 is made of a general-purpose integrated circuit (for example, μPD4538 manufactured by NEC Corporation), and the falling trigger input terminal B is set from the "Higb'" level to the "Loud" level.
After the level changes, the output terminal Q will be “Hi” for a certain period of time.
gh" level, and the output terminals become "Loud" level. In this embodiment, the output signal of the inverter starting circuit 6 is the trigger signal of the monostable multivibrator circuit 73. The monostable multivibrator circuit 73. The time when the output terminal Q of 73 becomes 'High' level (the time when the output terminal hay becomes IILO, I+ level) is determined by the resistor 71.
and the time constant of the capacitor 72. The output terminal Q is connected to a buffer integrated circuit (for example, NEC μPD40).
MOSFET 5 via a drive circuit 8 configured with
It is connected to the gate terminal of 2. The drive circuit 8 is for amplifying the output current of the output terminal Q of the monostable multivibrator circuit 73. Therefore, the monostable multi-by-break circuit 73 operates as a timer circuit for determining the ON period of the MOSFET 52. Note that a capacitor 21°2 is connected between the commercial power supply 1 and the AC input terminal of the rectifier circuit 3.
4 and a filter circuit 2 including transformers 22 and 23 is inserted. This filter circuit 2 has a low impedance to the commercial AC frequency from the commercial power supply 1,
It is designed to have a high impedance with respect to the switching frequency of the chopper-type smoothing circuit 4, and smoothes the switching current flowing through the smoothing circuit 4 so that the input current has a waveform close to a sine wave.

Hereinafter, the operation of this embodiment will be explained separately during startup of the inverter circuit (before the inverter circuit starts oscillating) and after startup of the inverter circuit (after the inverter circuit starts oscillating).

(a) Operation at startup of inverter circuit First, when the commercial power supply 1 is turned on, the output voltage of the rectifier circuit 3 is applied to both ends of the MO8FET 52 via the inductance element 42. This voltage is applied to the resistor 61.62
Figure 6 (a) shows a voltage waveform diagram divided by . At this time, the voltage V R62 divided by the resistors 61 and 62
The relationship between the threshold voltage value ■th of the trigger input terminal B of the monostable multi-bi break circuit 73 is as follows.
The settings are as shown in Figure (a). Now, the voltage across the resistor 62 ■R6□ is the monostable multi-vibration circuit 7
Threshold voltage value Vth of trigger input terminal B of No. 3
When the state changes from a higher state to a lower state than
As shown in the figure, the level remains "High" for a certain period of time. The time during which this output terminal Q becomes a "High" level is determined by the resistor 71 and capacitor 72. As a result, the MO8FET 52 is turned on, and current flows from the smoothing capacitor 41 through the capacitor 57, the capacitor 58, and the primary winding 55a of the transformer 55, and the capacitor 57 is charged. At this time, the transistor 51 is reverse biased by the secondary winding 55b of the transformer 55, so that it is turned off. Eventually, the output terminal Q of the monostable multivibrator circuit 73 becomes I L oIIlj+ level, and the MO3FET 52 is turned off. At this time, the current flowing through the primary winding 55a of the transformer 55 becomes zero, so an opposite voltage is induced in the secondary winding 55b.
When the transistor 51 turns on and the capacitor 57 starts discharging, and the current becomes zero, the transistor 5
1 is off. When the transistor 51 is turned off, the output voltage of the rectifier circuit 3 is applied again via the inductance element 42, and the MO8FET 52 is turned on again as described above.

As described above, the inverter circuit is activated and eventually shifts to the oscillation mode.

<b) Operation after startup of the inverter circuit FIG. 7 is an operation waveform diagram showing the high frequency operation of this embodiment. Figure 7 (a) shows the voltage VD2 across MO3FET52.
, the same figure (b) shows the voltage across the resistor 62, and the same figure (c) shows the output voltage of the secondary winding 55b of the transformer 55. In addition, Fig. 7 (d) shows the forward current IC of MO3FET52.
2 and reverse current ID2, the same figure (E) shows the transistor 51.
The forward current I C,l and the current D1 flowing through the diode 53 are shown. In FIG. 7, period L2 is a period in which the MO3FET 52 is in the second mode and the transistor 51 is on, and period L2 is a period in which the transistor 51 is off and the MO8FET 52 is on. Here, when an oscillating current flows into the inverter circuit 5 due to the startup operation described in (a) above, the transistor 51 is biased by the secondary winding 55b of the transformer 55, and the transistor 51 uses the accumulated charge of the capacitor 57 as a power source. ■ Current to. 1 flows (see Figure 7 (e)).

At this time, the core of the 1 Herance 55 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 of the transistor 51 becomes infinite. Collector current of transistor 51■. ,
When the current reaches l+fe times the base current, the transistor 5
1 is in an unsaturated state, and each winding 55a of the transformer 55,
551) decreases, the feedback base current also decreases, and the transistor 51 turns off. Even after the transistors 1 to 51 are turned off, the primary winding 5 of the transformer 55
Since the oscillating current flowing through 5a shifts in the same direction, the parasitic diode 54 of the MOSFET 52 becomes conductive, and the current ID2 flows through the load 9 such as a discharge lamp, the capacitor 57,
It flows through capacitor 41.

When the parasitic diode 54 becomes conductive, the drain voltage V,2 of the MOSFET 52 becomes zero, so the falling trigger input terminal B of the monostable multi-bi break circuit 73 changes from the "High" level to the "Low" level.
The output terminal Q of the monostable multi-bi break circuit 73 is "'
Higb" level, and the gate terminal of the MOSFET 52 is forward biased. After the oscillating current ID2 flowing through the parasitic diode 54 of the MOSFET 52 becomes zero,
A composite current (■) of the oscillating current IC2 flowing from the capacitor 41 via the inverter circuit and the current IDC flowing from the rectifier circuit 3 via the inductance element 42. 2 flows.

At this time, electromagnetic energy is accumulated in the inductance element 42 due to the flow of the current IDC.

Eventually, after a predetermined period of time determined by the resistor 71 and capacitor 72 has elapsed, the output terminal Q of the monostable multi-vibration circuit 73 reaches the l L 0uIIT level, and the MOSFET 5
2 is in the off state. The electromagnetic energy stored in the inductance element 42 when the MOSFET 52 is on is released to the smoothing capacitor 41 via the diode 53 and the diode bridge of the rectifier circuit 3 when the MOSFET 52 is off, and the smoothing capacitor 41 is charged. Ru.

In this case, the current ID+ flowing through the diode 53 becomes a composite current of the oscillating current IDI' from the inverter circuit 5 and the output current IDC of the rectifier circuit 3.

FIG. 8 is an operation waveform diagram showing the low frequency operation of this embodiment. Figure 8 (A) shows the power supply voltage VAC of the commercial power supply 1. (B) shows the output current IDC of the rectifier circuit 3. Figure 8 (C) shows the input current from the commercial power supply 1 AC. 41 shows the high frequency voltage VRF output from the inverter circuit 5.

As described above, in this embodiment, a starting circuit inputs the rectified signal of the commercial power supply 1 to the control circuit of one switching element to start the inverter circuit, and detects whether the switching element of the inverter circuit is turned off 5. However, since the circuit for continuing oscillation of the inverter is also used, an inexpensive inverter device can be provided.

[Example 3 FIG. 9 is a circuit diagram of a third embodiment of the present invention.

In this embodiment, in the circuit shown in FIG.
A buffer circuit 63 for waveform shaping is inserted between the falling trigger input terminal B of No. 3. As this buffer circuit Fl@63, a general-purpose integrated circuit (for example, μPD4050 manufactured by NEC Corporation) is used. The other configurations are similar to the circuit shown in FIG.

FIG. 10 is an operational waveform diagram of this embodiment, in which (a) shows the input signal to the buffer circuit 63 for waveform shaping, (b) shows the output signal of the buffer circuit 63, and (c) shows the input signal to the buffer circuit 63 for waveform shaping. is the output signal of the output terminal Q of the monostable multivibrator circuit 73. As shown in the same figure (b), by making the fall of the signal input to the falling trigger input terminal B of the monostable multivibrator circuit 73 steep, the inverter circuit can be activated more reliably. .

[Effects of the Invention] As described above, in the present invention, in an inverter device in which at least one switching element is automatically driven and a starting circuit is required to start the oscillation operation, a signal obtained by rectifying an AC power source is used. Since it is used as a starting signal, it has the effect of realizing a starting circuit for an inverter device with a very simple circuit configuration.

[Brief explanation of drawings]

Figure 1 is a block circuit diagram showing the basic configuration of the present invention, Figure 2 is a block circuit diagram showing the basic configuration of the present invention.
The figure is a circuit diagram of the first embodiment of the present invention, FIG. 3 is an operation waveform diagram of the same as above, FIG. 4 is a block circuit diagram showing a schematic configuration of a second embodiment of the present invention, and FIG. 6 to 8 are operational waveform diagrams of the same as above, FIG. 9 is a circuit diagram of the third embodiment of the present invention, FIG. 10 is an operational waveform diagram of the same as above, and FIG. 11 is a circuit diagram showing the same configuration. is a circuit diagram of a conventional example. 1 is an AC power supply, 3 is a rectifier circuit, 4 is a smoothing circuit, 5 is an inverter circuit, A is a rectification signal, B is a drive/control circuit, and 2 is a load.

Claims (1)

[Claims] (1) A rectifier circuit that rectifies an AC power supply, a smoothing circuit that smoothes the output of the rectifier circuit, and an inverter circuit that converts the output of the smoothing circuit into a high-frequency voltage and supplies it to a load, and the inverter circuit includes at least An inverter device in which one switching element is driven by self-excitation and is provided with a starting circuit for starting an oscillation operation, wherein the starting circuit is a circuit whose starting signal is a signal obtained by rectifying an AC power supply. .