JPS5934075B2 - transistor inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transistor inverter used in a discharge lamp lighting power source and the like.

A discharge lamp lighting circuit using a conventional transistor inverter is shown in FIG.

That is, in this circuit, the lamps FL, FL! are connected independently, and the commercial power supply E is full-wave rectified by a rectifier DB and connected to the common connection points P and P' of the primary winding of the oscillation transformer OT (7) via the choke coil L, and the primary side The collectors of push-pull transistors Tr, Tr2 are connected to both ends of the winding, and their emitters are connected to the power supply side. Further, the output side of the choke coil L3 is connected to the bases of the transistors Tr3 and Tr2 via resistors R1 to R3, and a positive feedback winding No provided in the oscillation transformer OT is connected between the base terminals. Cl is a capacitor, and L, ~L are inductance elements. In this circuit, a commercial power source E is full-wave rectified by a rectifier DB, and a voltage is applied between the collectors and emitters of transistors Tr and Tr2 through a choke coil L and primary windings A and B.

At the same time, transistors Tr3 and T are connected through resistors R and ~R3.
A base current is applied to r2. As a result, one of the transistors Tr, Tr2 starts to conduct first. Now, if the transistor Trl becomes conductive first, a collector current flows through the windings N2 and Ni' of the primary windings A and B, and a voltage is induced in the feedback winding N2 in a direction that further conducts the transistor Tr. . Then the transistor Tr
Due to the regeneration effect in which the base current of Tr increases and the collector current increases, the transistor Tr suddenly reaches saturation.
When saturation is reached, the collector current no longer increases, so no voltage is induced in the feedback winding N3, and as a result, the transistor Tr2 becomes forward biased and the base current begins to flow, causing it to conduct, and now to the transistor Tr. Since the feedback winding N3 is in the positive feedback direction, the base current further increases and the collector current increases, reaching saturation at once.
Note that during this time, the transistor Tr is reverse biased by the feedback winding N3, and rapidly turns off from when the transistor Tr2 begins to conduct. The operation of 2 is repeated in these transistors T, T continues oscillation, and the secondary windings A' and B' each have a turns ratio (N4+N2+No.
) two (N2+N2) and (N!+N', +N'6):
A secondary voltage is induced at (Ni+N',), and the lamp FLI
, FL! lights up. However, in such a circuit configuration, due to fluctuations in the oscillation transformer OT, a loop current ILoop is generated between the windings N2, N,' of the primary windings A and B and between the windings N2 and N, as shown in FIG. ,IZoop
For example, if a large current flows through the winding N2 and a current flows through the winding N2', an unbalance in the winding current will occur (the collector currents of both transistors Tr, Tr, and Tr are the same). ). As a result, due to such a phenomenon, the temperature rise of the oscillation transformer 0T may significantly increase due to the variation), which is very inconvenient. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a transistor inverter in which temperature rise in the windings due to variations in the oscillation transformer is reduced.

FIG. 3 shows a discharge lamp lighting circuit to which an embodiment of the present invention is applied. That is, in this circuit, diodes D are connected between the chiyoke coil L1, which is the power supply side for the oscillation transformer 0T, and the common connection points (intermediate points) P and P' on the primary side.
1 and D2 are additionally connected in the forward direction, and the common connection points P and P'' are connected in series with opposite polarity, and the other configuration is the same as that in Fig. 1. ), the loop current 1L00P, /00p due to the variation of the oscillation transformer 0T shown in FIG.
Therefore, temperature rise in the winding due to variations can be suppressed.

Other circuit operations are similar to those in FIG. As described above, in the transistor inverter of the present invention, a diode is inserted in the oscillation transformer in which two primary windings are connected in parallel to suppress the generation of loop current due to variations in the oscillation transformer, thereby reducing the temperature rise of the winding. This has the effect of reducing the

[Brief explanation of the drawing]

FIG. 1 is a discharge lamp lighting circuit diagram to which a conventional transistor inverter is applied, FIG. 2 is a circuit diagram of a main part thereof, and FIG. 3 is a discharge lamp lighting circuit diagram to which an embodiment of the present invention is applied. 0T...Oscillation transformer, A, B...Primary winding, D,
, D2... Diode, Tr,, Tr,... Transistor, E... Commercial power supply, DB... Rectifier.

Claims (1)

[Claims] 1. An oscillation transformer that has a primary side with two primary windings connected in parallel, and a pair that is push-pull connected to both ends of the primary side of this oscillation transformer and whose common connection point is connected to one pole of the power supply. and a pair of backflow blocking diodes each having one end connected in a forward direction to each intermediate point of the two primary windings and each other end connected to the other pole of a power supply.