JPH048919B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device using an inverter, and provides a configuration that achieves reduction in power loss.

FIG. 1 shows an example of a conventional discharge lamp lighting device, in which the AC side ends of a rectifier circuit 1b are connected to both ends of an AC power source 1a such as a commercial power source to form a DC power source 1, and an inverter is connected to both ends of the AC power source 1a. In addition, a fluorescent lamp 4 serving as a load discharge lamp is connected to the output end of a leakage type oscillation transformer 3 of the inverter 2. The inverter 2 is a well-known two-stone push-pull type, and one of the oscillation transformers 3 has a constant current inductor L connected in series.
A resonance capacitor 5 is connected in parallel with the next winding 3a, two oscillation transistors 6 and 7 are connected in a push-pull manner to both ends of the resonance capacitor 5, and both ends of the feedback winding 3b of the oscillation transformer 3 are oscillated. The bases of transistors 6 and 7 are connected to each other. The oscillation transformer 3 is provided with a drive winding 8 for base drive, the AC side ends of the rectifier circuit 9 are connected to both ends of the drive winding 8, and the smoothing capacitor 10 is connected to the DC side end of the rectifier circuit 9. , a series circuit between the base resistor 12 and the base and emitter of the oscillation transistor 6 is connected to both ends of the smoothing capacitor 10 via the collector and emitter of an NPN type synchronizing transistor 11 that turns on and off in synchronization with the AC power supply voltage. The base resistor 13 and the series circuit between the base and emitter of the other oscillation transistor 7 are connected in parallel. The base of the synchronizing transistor 11 is connected to the positive electrode of the DC power supply 1 via the starting resistor 14 .

The operation of such a discharge lamp lighting device will be explained below. When the AC power supply 1a is turned on, the constant current inductor L, the starting resistor 14 and the synchronizing transistor 1
A base current is supplied to the oscillation transistors 6 and 7 through the base and emitter of the inverter 2, one of the oscillation transistors is turned on, and the inverter 2 starts oscillating. When the inverter 2 starts oscillating, an oscillator output is induced in the drive winding 8,
This output is smoothed into DC by a smoothing capacitor 10, and thereafter this smoothed output is used by a synchronizing transistor 11.
The inverter 2 continues to oscillate by serving as a collector current source for the oscillating transistors 6 and 7, that is, as a base current source for the oscillating transistors 6 and 7.

In this way, the starting resistor 14 serves to supply the base current of the oscillation transistors 6 and 7 only when oscillation starts when the inverter 2 is powered on, and once the oscillation starts, the smoothing capacitor 10 starts the oscillation. Since the starting resistor 14 serves as a base current source for the synchronizing transistors 6 and 7, the resistance value of the starting resistor 14 may be large enough to drive the synchronizing transistor 11. However, when the load is heavy, for example, when a fluorescent lamp 4 with a preheating filament is used as the load, as in the case shown in FIG. If the value is too large, the smoothing capacitor 10
Since no voltage has been generated yet and the base current of the oscillation transistors 6 and 7 is supplied from the DC power supply 1 side through the starting resistor 14, the oscillation transistors 6 and 7 cannot obtain sufficient base current. Therefore, there is a risk that the inverter 2 will not be able to start oscillation.

Therefore, the resistance value of the starting resistor 14 cannot be made very large, and the power loss generated in the starting resistor 14 during operation of the inverter 2 cannot be sufficiently reduced.

Note that the synchronizing transistor 11 is configured to supply base current to the oscillation transistors 6 and 7 in synchronization with the AC power supply voltage of the AC power supply supplied to the inverter 2, that is, in accordance with this voltage level. This prevents abnormal oscillations and the like of No. 2 and contributes to stabilizing the operation.

On the other hand, in the case of FIG. 1, as shown in FIG. 2, depending on the voltage level of the pulsating output voltage V1 of the DC power supply 1, the oscillating transistor 6 . , 7, stable oscillation is achieved with respect to the pulsating output voltage V1 of the DC power supply 1, but the pulsating output voltage V
In the low voltage section of 1, inverter 2 has an oscillation output V2
However, the oscillation output near the zero point of the pulsating voltage does not contribute to the lighting of the fluorescent lamp 4, and the period T1 until the fluorescent lamp 4 is re-ignited at the beginning of each half cycle of the pulsating current is simply nothing. Oscillation is only performed in a loaded state, and the oscillation in this section T1 is one of the causes of power loss in the entire device.

The present invention has been made in view of the drawbacks of the conventional example, and provides a discharge lamp lighting device that achieves low power consumption by suppressing power loss in the starting resistor portion and power loss in the no-load oscillation section. The purpose is to The present invention will be described below based on embodiments shown in the drawings.

FIG. 3 shows an embodiment of the present invention, in which the starting resistor 14 is a series connection of two first resistors 14a and a second resistor 14b, and the second resistor 14 is connected in series.
The configuration differs from that shown in FIG. 1 in that a bypass capacitor 16 is connected in parallel with the circuit 16b to form a bypass circuit 15. The terminal voltage Vc of the capacitor 16 maintains a value larger than the output voltage V1 only in an interval T3 that includes an interval T1 from the zero point of the pulsating output V1 of the DC power supply 1 to a predetermined phase.
3, the capacitor 16 performs the switch-off function, and the collector-emitter voltage VCE of the oscillation transistors 6 and 7, the lamp voltage V2, and the lamp current 12 are in a state where oscillation is stopped during the period T3, as shown in FIG. 4. Therefore, sufficient optical output can be obtained while suppressing power loss. Here, the current flowing through the series circuit of the first resistor 14a and the second resistor 14b having high resistance is set so that the inverter 2 does not oscillate.
The base current of the synchronizing transistor 11 flowing through the series circuit of the inverter a and the bypass capacitor 16 is set to be sufficiently large to cause the inverter 2 to oscillate.

Therefore, originally, if the smoothing capacitor 10 is not sufficiently initially charged and sufficient voltage is not generated when the AC power is turned on, there is no base current source and the oscillation transistors 6 and 7 should be driven. However, since the bypass capacitor 16 is configured as described above, even if the smoothing capacitor 10 is not sufficiently initially charged and sufficient voltage is not generated, the capacitor 16
The current flowing through the oscillation transistors 6 and 7
As a result, the base current becomes sufficient for the inverter 2, and the oscillation of the inverter 2 can be started much more easily than in the conventional case.

After the inverter 2 starts oscillating, the drive winding 8
Smoothing capacitor 1 due to the oscillation output induced by
0 maintains a sufficient terminal voltage, and from then on, the terminal voltage Vc of the capacitor 16 becomes the pulsating output V1 of the DC power supply 1.
Since the output voltage maintains a value larger than V1 only in the interval T3 including the interval T1 from the zero point of , to the predetermined phase,
The inverter 2 is in a state in which oscillation is stopped for this period T3, and the inverter 2 as a whole continues to be in an intermittent oscillation state.

Further, the first resistor 14a, which is a high resistance, and the second resistor 14a have a high resistance.
By using a variable resistor for the resistor 14b or changing the value of the capacitor 16 with a switch, it is possible to stop the oscillation output by an arbitrary width including the zero point of the pulsating output voltage V1. The lamp can be dimmed while eliminating the no-load oscillation portion during each cycle of V1, and an efficient dimming device can be obtained.

In the above embodiment, a drive winding for detecting the output corresponding to the AC output of the oscillation transformer 3 was provided in the oscillation transformer 3, but it may be provided in each collector circuit of the oscillation transistors 6 and 7, or in a constant current inductor. Of course, it may be provided on the secondary side of L.

As described above, the present invention provides a DC power supply that rectifies an AC power supply to obtain a pulsating output voltage, an oscillation transistor that switches this pulsating output voltage, and an AC output that is generated by switching the oscillation transistor. a discharge lamp connected to the output side of the oscillation transformer, a feedback winding provided in the oscillation transformer to control the oscillation transistor, a drive winding to detect an output corresponding to the above AC output, and a drive A rectifier circuit connected to the output end of the winding, a smoothing capacitor connected to the DC side end of the rectifier circuit and supplying base current to the oscillation transistor, and a connection between the smoothing capacitor and the base-emitter of the oscillation transistor. a synchronizing transistor connected to the positive pole side of the DC power supply through a series circuit of a first resistor and a second resistor inserted between the bases of which cannot drive the oscillation transistor, and the second resistor. a bypass capacitor that is connected in parallel to form a series circuit with a first low resistor to sufficiently drive the oscillation transistor; Since the AC output is generated only in the high section, a simple starting circuit is constructed in which the pulsating output voltage is divided and a capacitor is connected in parallel to one side of the divided voltage, so the power at the starting resistor is reduced. This has the remarkable effect that it is possible to improve the efficiency of the circuit by suppressing loss and power loss in the no-load oscillation section, and it is also possible to easily start oscillation of the inverter when the AC power is turned on.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a waveform diagram for explaining the same, FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG. 4 is a waveform diagram for explaining the same. . DESCRIPTION OF SYMBOLS 1... DC power supply, 2... Inverter, 3... Oscillation transformer, 4... Discharge lamp, 6, 7... Oscillation transistor, 8... Drive winding, 10... Smoothing capacitor, 11... Synchronization transistor, 15... Bypass circuit, S...Switch.

Claims (1)

[Claims] 1. A DC power supply that rectifies an AC power supply to obtain a pulsating output voltage, an oscillation transistor that switches this pulsating output voltage, an oscillation transformer that generates an AC output as the oscillation transistor switches, and an oscillation transformer. a discharge lamp connected to the output side of the oscillator, a feedback winding provided in the oscillation transformer to control the oscillation transistor, a drive winding that detects the output corresponding to the above AC output, and a discharge lamp connected to the output end of the drive winding. A smoothing capacitor connected to the DC side end of the rectifier circuit to supply base current to the oscillation transistor, and a smoothing capacitor inserted between the base and emitter of the oscillation transistor to cause the base to oscillate. A synchronizing transistor connected to the positive electrode side of the DC power supply through a series circuit of a first resistor and a second resistor that cannot drive the synchronizing transistor, and a first resistor connected in parallel to the second resistor. and a bypass capacitor capable of sufficiently driving the oscillation transistor by forming a series circuit with the bypass capacitor, and generates the AC output only in an area where the pulsating output voltage is higher than the voltage of the bypass capacitor. A discharge lamp lighting device characterized in that: