JPH03173362A - Transistor inverter device - Google Patents

Abstract

PURPOSE:To reduce current loss of a base resistor at the time of normal operation by supplying a base current to a current limiting impedance by first/second switching elements capable of being short-circuited/responsive. CONSTITUTION:When capacitors 4, 5 of a smoothing unit 3 are charged through a rectifier 2, an overcurrent is prevented by an impedance 12. First, second transistors 20, 21 of a second switching unit 20 are turned ON. A base current is supplied through a base resistor 25, a transistor inverter 8 is started to energize a load 9. After a power source is turned ON, when certain time is elapsed, a terminal voltage of the impedance 12 for reducing a rush current is reduced, or a first switching unit 13 is closed before it. Accordingly, the unit 20 is opened. Thus, the resistor 25 is electrically disconnected to eliminate power loss of the resistor 25. lts structure is simple.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a transistor inverter device in which power loss due to a starting base resistance is reduced during steady operation.

(Prior Art) Conventionally, this type of device includes a switching element in series with a starting base resistor, and a timer that turns on the switching element for a predetermined time when the power is turned on and turns it off after the elapse of a predetermined time. What has been established is known.

By setting the base resistor and timer, the transistor inverter can be reliably started by supplying sufficient base current at the time of startup, and after the time set in the timer, the switch element is turned off and the base resistor is turned off. It is possible to eliminate power loss.

(Problem to be Solved by the Invention) However, the above-mentioned conventional device does not require a special time constant circuit to configure the timer, and the number of components increases accordingly, making it large and expensive. There was a problem that it became a thing.

The present invention has been made to solve these problems, and it is possible to reduce the power loss due to the base resistance during steady operation, and to minimize the number of parts, thereby increasing the size and price of the device. It is an object of the present invention to provide a transistor inverter device that can avoid this problem.

[Configuration of the Invention] The present invention provides an input power source for a transistor inverter.
When an AC voltage is rectified and this rectified voltage is smoothed, and an impedance for reducing inrush current is inserted in series with the smoothing capacitor, a switching device is provided in parallel with the impedance, and this switching device is This was done by focusing on the fact that a timer is provided to turn it on after a predetermined period of time.

That is, the present invention provides an impedance for reducing inrush current between one end of the smoothing capacitor and the negative output terminal of the rectifier, a first switching device is provided in parallel with the impedance for reducing inrush current, and A second switching device whose conduction is controlled according to the non-power supply side terminal voltage of the impedance for reducing inrush current is provided,
Furthermore, the present invention is characterized in that a base resistor is provided that can supply a base current to the transistor inverter via the second switching device.

(Function) In the present invention, when the power is turned on, current flows through the smoothing capacitor and the inrush current reduction impedance, and in the initial stage, the voltage across the smoothing capacitor is relatively low, and the voltage across the inrush current reduction impedance is relatively low. very high. Then, as time passes, the voltage relationship between the two becomes reversed.

Therefore, at the initial stage, the second switching device is on, and sufficient base resistance is supplied to the transistors of the transistor inverter via the base resistance. Therefore, the transistor inverter will start up reliably.

As described above, as the voltage across the inrush current reducing impedance decreases over time, the first switching device eventually turns off.

Therefore, no base current flows through the base resistor, and no power loss occurs in this base resistor. Note that, after starting, the transistor inverter continues to operate using a feedback circuit for self-oscillation.

Then, after the set time of the timer has elapsed, the inrush current reduction impedance is short-circuited by the first switching device, so the second switching device is no longer turned on, and as in the conventional device, this inrush current reduction impedance is short-circuited. Power loss due to impedance is also eliminated.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. 1 is an AC power source, and 2 is a rectifier that rectifies the output of this AC power source.

3 is a smoothing device, which in this embodiment is a so-called partial smoothing device. That is, it has a series circuit consisting of two capacitors 4.5 and a diode 6, and a diode 7.8 for forming a discharge path for each of the capacitors 4.5. Although such a partial smoothing device is well known,
Briefly, the capacitor is charged during the rainy period when the output voltage value of each cycle (half cycle of AC power supply voltage) of the rectifier 2 is large. Therefore, each capacitor 4.5 is approximately 1 of the peak value of the output voltage of the rectifier 2.
It is charged to a value of /2. During the valley period when the output voltage value of the rectifier 2 is small (approximately less than 1/2 of the peak value), each of the capacitors 4.5 discharges via the diode 7 or 8, respectively.

A transistor inverter 9 is supplied with the output of the rectifying device 2 and the output of the smoothing device 3. That is, as is clear from the above description, a voltage with a waveform in which the valley portion of the full-wave rectified voltage waveform is raised is supplied. This transistor inverter 9 may be of any type, except that it must include a feedback circuit for self-assisted oscillation. The feedback circuit may also be either voltage feedback or current feedback. As the load 10 of this transistor inverter 9,
A discharge lamp, for example a fluorescent lamp, is provided.

Reference numeral 12 denotes an impedance for reducing rush current provided between one end of the smoothing device 3 and the negative output end of the rectifying device 2. Further, 13 is a first switching device connected in parallel to the inrush current reducing impedance, and is made of, for example, an SCR. Furthermore, 14 is a timer, which turns off the first switching device 13 during a predetermined period when the power is turned on, and turns it on after a predetermined period has elapsed. In this embodiment, the midpoint voltage of an inductor 15 inserted between one input terminal of the transistor inverter and the negative output terminal of the rectifier 2 is used as a power source. That is, it consists of a rectifying diode 16 whose anode is connected to the midpoint of the inductor 15, a smoothing capacitor 17, voltage dividing resistors 18 and 19, and the like.

Reference numeral 20 denotes a second switching device whose on/off is controlled according to the terminal voltage on the non-power side of the impedance 12 for reducing the inrush current, and in this embodiment, the base is connected to the inrush current reducing impedance 12. a first transistor 21 connected to the impedance 13 of the first transistor 21; a resistor 22 provided between the collector of the first transistor 21 and the positive output terminal of the rectifier 2;
a second transistor 2 whose base is connected to the collector of
3. The emitter of the second transistor 23 is provided so as to be able to supply a base current to the switching transistor of the transistor inverter.

24 is a base resistor, and the second switching device 20
The rectifying device 2 is provided between the collector of the second transistor 23 and the positive output terminal of the rectifier 2 . Therefore, this base resistor 24 supplies a base current to the switching transistor of the transistor inverter while the second switching device 20 is on.

Next, the operation of this embodiment will be explained. When a power switch (not shown) is turned on, the capacitor 4.5 of the smoothing device 3 is charged via the rectifier 2.

At this time, the impedance 12 for reducing inrush current prevents an excessive charging current from flowing.

Also, at this time, the first transistor 21 of the second switching device 20 is turned on, and the second transistor 23 is turned on. Therefore, since the base current is supplied through the base resistor 25, the transistor inverter 8 is started and outputs high frequency power of, for example, several tens of KHz to energize the load 9.

After a certain period of time has passed after the power is turned on, the terminal voltage of the inrush current reduction impedance 12 decreases as shown in FIG. The second switching device 20 is turned off. Therefore, the base resistor 25 is disconnected from the electrical circuit, and power loss in the base resistor 25 is eliminated.

As already mentioned, the power loss in the impedance 12 for reducing inrush current is reduced in the first switching device 13.

Another embodiment of the present invention will be described with reference to FIG. In this embodiment, the same or corresponding parts as those in FIG. 1 are given the same reference numerals, and their explanation will be omitted. The smoothing device 30 of this embodiment is not a partial smoothing device, but a so-called complete smoothing device, and therefore simply consists of a capacitor.

Although it is a perfect smoothing device, it goes without saying that its smoothness can be changed depending on the capacitance of the capacitor, etc.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be modified in various ways. For example, the switching device can be constructed using elements other than transistors, and even when using transistors, it is possible to have a construction other than the above embodiments. The configuration can be appropriately selected by a person in the relevant technical field.

[Effects of the Invention] As described above, the present invention utilizes a current-limiting impedance for preventing inrush current of a smoothing device and a first switching device capable of short-circuiting the current-limiting impedance, and a first switching device that responds to the voltage of the current-limiting impedance. Since the base current is supplied to the switching transistor of the transistor inverter through the switching device No. 2, power loss in the base resistance during steady operation can be reduced with a simple configuration.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention,
Figure 1 is a circuit diagram, Figure 2 is a voltage waveform diagram explaining the action,
FIG. 3 is a circuit diagram showing another embodiment of the present invention. 2... Rectifier, 3.30... Smoothing device. 9... Transistor inverter, 12... Current limiting impedance, 13... First switching device, 20... Second field switching device, 24... Base resistor.

Claims (1)

[Claims] (1) A rectifier that rectifies an alternating current voltage; A smoothing device that has at least one capacitor and is provided on the output side of the rectifier; A feedback circuit for self-excited oscillation, and the smoothing device and A transistor inverter that is supplied with the output of the rectifier; and a current-limiting impedance provided between the negative output terminal of the rectifier and the capacitor closest to the negative output terminal; a first switching device that can be short-circuited after a predetermined time; a second switching device whose conduction is controlled according to the non-power supply side terminal voltage of the current-limiting impedance; A transistor inverter device comprising: a base resistor capable of supplying a base current to a switching transistor of an inverter;