JPS6139860A - One-transistor inverter - Google Patents

Abstract

PURPOSE:To reduce a pulsating surge voltage by using an inductor for forming part of a series resonator as a saturable inductor. CONSTITUTION:A discharge firing device using a base feedback type one-transistor inverter is composed by connecting a full-wave rectifier 2 with an AC power source 1, connecting one-transistor blocking oscillation transistor inverter 3 between the output terminals (a) and (b) of the rectifier 2, and connecting a discharge lamp 4 of a load with the secondary winding 31S of the output transistor 31. In this case, an inductor connected with the base of a main transistor 32 is formed of a saturable inductor 39. Thus, when a series resonator of the capacitor 36 and the inductor 39 drives a transistor 32 in a positive current and turns OFF the transistor 32 in a negative current at inverting time, a large voltage is not generated at the inductor 39 to reduce the pulsating voltage applied to a protecting diode 34.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a one-right type inverter used, for example, in a discharge lamp lighting device.

[Prior Art] FIG. 2 shows a circuit configuration of a discharge lamp lighting device using a conventional base feedback type single-stone inverter. In the same figure, 1
is an AC power source such as a commercial power source, and a rectifier M is connected to this AC power source 1.
A full-wave rectifier circuit 2 is connected to the chest, a single-stone blocking oscillation type transistor inverter 3 is connected to the rectifier output terminals a and bii of the rectifier circuit 2, and a secondary winding of the output transformer 31 of this inverter 3 is connected. A discharge lamp (lamp) 4 as a load is connected to the line 31s. 5 is a high frequency bypass capacitor, which may also be used as a smoothing capacitor in a capacitor input type rectifier circuit. Reference numeral 6 denotes a constant current inductor, which together with the capacitor 5 constitutes a high frequency blocking filter.

The inverter 3 includes an output transformer 31, a main transistor 32, and the like, and is connected between the positive output terminal a of the rectifier circuit 2 and the collector of the transistor 32.
While connecting the secondary winding 31p - this primary winding 31p
A resonance capacitor 33 is connected in parallel with . The emitter of the transistor 32 is connected to the rectifier circuit 2 via a diode 34.
Furthermore, one end of the base feedback winding 31f of the output transformer 31 is connected to the negative output terminal b of the rectifier circuit 2, and its intermediate tap is connected to the capacitor 36 and the inductor 31. LC consisting of etc.
It is connected to the base of transistor 32 via a series resonant circuit. A resistor 394 is connected to the other end of the base feedback winding 31f.
The base of a transistor 391 is connected through a diode 393, and the collector and emitter of this transistor 391 are connected to a capacitor 36 through a resistor 392.

Note that the diode 34 protects the transistor 32 from reverse voltage between the base and emitter, and supplies base extraction current in excess or deficiency.

Next, the operation of the discharge lamp lighting device constructed as above will be described.

When AC power supply 1 is turned on, full-wave rectifier circuit 2 generates a full-wave rectified output (pulsating output), which is applied to inverter 3 . As a result, in the inverter 3, the rectified output is applied as a base current to the transistor 32 via the bias resistor 38, and the transistor 32 is turned on. The transistor 32 is driven via a collector-base positive feedback loop consisting of the primary winding 31p of the output transformer 31 connected to the collector, the base feedback winding 31f, the capacitor 36, the inductor 37, and the base of the transistor 32. Current flows until it is saturated. When it is saturated and there is no change in current, no voltage is generated in the base feedback winding, and the positive feedback loop is opened and the transistor 32 is turned off. Then, the resonant circuit consisting of the inductance of the primary winding 31p and the capacitor 33 oscillates, and the output transformer 31
A high frequency output is generated in each of the windings 31p, 31s, and 31f. The lamp 4 is supplied with this high frequency output via the secondary winding 31s of the output transformer 31 and is turned on.

By the way, in this inverter 3, the capacitor 36
By supplying base current to the transistor 32 through the series circuit of the inductor 31 and the inductor 31, the high frequency switching characteristics are improved. That is, the capacitor 36 and the inductor 31 form a series resonant circuit, and the positive direction current provides sufficient drive to the main transistor 32, and the negative direction current extracts a large base charge, quickly and clearly turning the transistor 32 into the off state. to migrate. Also, during operation of the inverter 3, when the voltage of the base feedback winding 31f becomes negative and the transistor 32 turns off, the negative voltage of the base feedback winding @31f turns off the transistor 391.
is turned on, and as a result, when the transistor 32 is turned on, the charge in the capacitor 36 charged by the base current to the transistor 32 is discharged, that is, reset. As a result, the capacitor 36 is then connected to the base feedback winding 31f.
When the voltage of the transistor 32 rotates in the normal direction, the base current can be supplied to the transistor 32.

[Problems to be Solved by the Invention] The diode 34 protects the transistor 32 from reverse voltage between the base and emitter, and also contributes to the base charge drawing action by the series resonant circuit of the capacitor 36 and the inductor 37. When the series resonant circuit drives transistor 32 with a positive current, then reverses and draws a large base charge with a negative current to turn off transistor 32, a large voltage is instantaneously generated in inductor 37. The withstand voltage of the diode 34 must be selected in consideration of this voltage, but the abnormal surge voltage is 200V for the rated AC power supply voltage of 100V, and as much as 220V for 110% of the rated voltage. If this surge voltage is reduced, the withstand voltage rank of the J diode 34 will be reduced, and an inexpensive diode can be selected.

The purpose of the present invention is to reduce the surge voltage generated when the base current of the main transistor is extracted in a single-stone blocking oscillation inverter circuit, thereby lowering the withstand voltage rank of a protective diode, thereby making it possible to select an inexpensive diode. be.

[Means and effects for solving the problems] According to the present invention, the inductor connected to the base of the main transistor forming part of the series resonant circuit is a saturable inductor. This makes it possible to reduce the pulse-like surge voltage that occurs across the inductor at the moment when the base current is drawn out and turned off, and it is possible to select protective diodes from those with lower breakdown voltage ranks.

[Description of Examples] FIG. 1 shows an example of the present invention. The only difference from the conventional circuit of FIG. 2 is that the inductor connected to the base of the main transistor 32 is a saturable inductor 39 in the embodiment of the present invention.
That is to say.

The configuration and operation of the embodiment shown in FIG. 1 are the same as those already described for the circuit shown in FIG. 2, and therefore will not be described here. However, the difference in operation due to the use of a saturable inductor is that the series resonant circuit of the capacitor 36 and the saturable inductor 39 drives the transistor 32 with a positive current;
When the circuit is then reversed and a large base charge is extracted with a negative direction current to turn off the transistor 32, no large voltage is generated in the saturable inductor 39, so that the pulsed voltage applied to the protection diode 34 is reduced.

[Effects of the Invention] The observed waveforms in FIG. 3 show how the voltage 2 across the protective diode is controlled by the short pulse-like voltage applied to the voltage across the inductor according to the configuration of the present invention.

In Figure 3, the waveform on the left is the voltage across the protective diode [the upper part is near the rated voltage (iooy), the lower part is the rated voltage (iooy)]
110%)], and the right-hand waveform shows the voltage across the inductor [the upper part is around the rated voltage (100V), the lower part is around (110%) of the rated voltage].

As shown in the figure, a short pulse-like voltage is generated up to the level of the arrow, but its magnitude is 170% compared to the rated voltage.
V, 150V for 110% of the rated voltage, both of which are substantially reduced compared to the conventional circuit [200V for the rated voltage, 220V for 110% of the rated voltage] .

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a discharge lamp lighting device using a conventional single-block blocking oscillation inverter circuit. FIG. 3 shows a waveform diagram of voltages applied to a protection diode and a saturable inductor of an inverter circuit according to an embodiment of the present invention. In the figure, 1... commercial frequency AC power supply, 2... full wave rectifier circuit, 3... - Stone type blocking oscillation type transistor inverter 1. 4... Discharge lamp, 5... Capacitor for high frequency bypass, 6... Constant current inductor, 31... Output transformer, 31p... Primary winding of output transformer, 31 "...
・Base feedback winding of output transformer, 31s... 2nd winding of output transformer, 32... Transistor 33... Resonance capacitor, 34... Protection diode, 36.
... Capacitor, 31 ... Inductor, 38, 392
, 394...Resistor, 39...Saturable inductor 391...Transistor, 393...Diode.

Claims (1)

[Scope of Claims] An output transformer having a primary winding and a feedback winding, and a main transistor that energizes the primary winding. A base feedback single-stone blocking inverter for driving the base of the main transistor, characterized in that a saturable inductor is used as an inductor constituting the LC series resonant circuit.