JPS6120999B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device that lights a discharge lamp by turning on a switch element of a main circuit for a certain period of time during each half cycle of an AC power supply. An object of the present invention is to provide a compact, lightweight, and inexpensive discharge lamp lighting device.

Conventionally, this type of discharge lamp lighting device, as shown in Fig. 1, connects a DC power supply V _S with a voltage approximately equal to the rated voltage of the discharge lamp L _A , a current limiting inductance L ₁ , and a discharge lamp L _{A .}
are connected in series to form the main circuit, and the discharge lamp L _A
A transistor Tr as a switch element is connected in parallel to the bridge rectifier circuit BD, and the output voltage of a secondary winding _L2 is obtained by winding the power supply of the transistor Tr and the control circuit A of the transistor Tr around a current limiting inductance _L1. is rectified by rectifier diode _D1 ,
It was obtained by smoothing with a smoothing capacitor C.

Now, when the power switch SW is turned on, the current limiting inductance L ₁ , the discharge lamp L _A , and the bridge rectifier circuit BD
Transistors used as switch elements through
A double-wave rectified power supply voltage appears at the collector of Tr ₁ . This voltage charges the smoothing capacitor C used for the DC power supply of the control circuit A via the resistor R. At this time, the discharge lamp _LA is not lit and the transistor Tr ₁ is not conductive, so no current flows through the main circuit consisting of the power supply V _S , the current limiting inductance L ₁ and the discharge lamp _LA . Now, the charge accumulated in the smoothing capacitor C is released to the control circuit A, but since transistors Tr ₂ to _{Tr 4} are in a cut-off state, all the released charge is transferred to the control circuit A.
This becomes the base current of Tr ₁ , and transistor Tr ₁ becomes conductive. For this reason, a bridge rectifier circuit is installed in the main circuit.
Current flows through BD and transistor Tr ₁ , and this current generates a voltage across current-limiting inductance L ₁ . The generated voltage is transmitted to the secondary winding L ₂ of the current limiting inductance L ₁ according to its turns ratio by the transformer effect. After this is double-wave rectified, it is smoothed by a smoothing capacitor C to become a direct current, and the control circuit A starts operating.

Next, the operation of control circuit A will be explained. Discharge lamp L
The waveform appearing at the collector of transistor Tr ₁ when _A is not lit is a waveform obtained by full-wave rectification of alternating current, as shown in Figure 2, and this waveform is the same as that of resistor R ₁ ,
The voltage is divided by R ₂ and applied to the base of transistor Tr ₂ . Therefore, the collector voltage of the transistor Tr ₂ rapidly rises to the DC power supply voltage because the transistor Tr ₂ is cut off at the time when the collector voltage of the transistor Tr ₁ becomes zero. This change is expressed as a capacitor.
It is converted into a positive pulse by a differentiating circuit consisting of C ₁ and resistor R ₃ , and then passed through diode Dz to transistor Tr ₃ ~
Add to the base of transistor Tr ₃ of the monostable multivibrator consisting of Tr ₄ . Normally, transistor Tr ₄ is in a conducting state, so transistor Tr ₁
The base potential of is zero, so the transistor
Tr ₁ is blocked. However, the transistor
The positive pulse applied to the base of Tr ₃ quickly turns off transistor Tr ₄ , so that a DC voltage is applied to the base of transistor Tr ₁ , making it conductive. The time during which the transistor Tr ₁ is conductive is determined by the capacitance of the capacitor C ₀ and the resistor R ₇ in the monostable multivibrator, and at the same time as the transistor Tr ₄ becomes conductive after a certain period of time, the transistor Tr ₁ is cut off. A current flows from the main circuit to the bridge rectifier circuit BD until the transistor Tr ₁ is cut off, but this current causes energy to be stored in the current limiting inductance L ₁ and the transistor
At the same time as Tr ₁ is cut off, the stored energy generates a high pulse voltage in the current limiting inductance L ₁ . This high-voltage pulse starts and keeps the discharge lamp L _A lit.

When the discharge lamp _LA is lit, the lamp voltage has a waveform as shown in FIG. 3, and the waveform obtained by full-wave rectification of FIG. 3 appears at the collector of the transistor _Tr1 . Therefore, the conduction and cutoff of the transistor Tr ₂ are not instantaneous, but the cutoff state continues for the operating time of the monostable multivibrator. When the transistor Tr ₂ changes from a conductive state to a cut-off state, a positive pulse is generated in the differentiating circuit made up of the capacitor C ₁ and a resistor R ₃ , but when the transistor Tr 2 changes from a cut-off state to a conductive state, a negative pulse is generated. Diode _D2 is inserted to suppress this negative pulse.

In this case, the amount of energy stored in the smoothing capacitor C is sufficient to operate the entire circuit when the DC current amplification factor h _FE of transistor Tr ₁ is large, but when h _FE is small and the energy is completely If a large current is required, such as when a considerable base current needs to flow to turn on transistor Tr 1, the amount of energy stored in smoothing capacitor C will be released while it is still small, making it impossible to turn on transistor Tr ₁ . . It is possible to drive a circuit that requires a large current by reducing the value of the charging resistor R, but this increases the loss due to the resistor R, causing problems such as increasing the size of the resistor R and reducing the efficiency of the entire circuit. It had drawbacks.

The present invention has been made in view of this point, and will be explained in detail below with reference to Examples.

In Fig. 4, V _S is an AC power supply, L ₁ is a current limiting inductance, and L _A is a discharge lamp. These form a main circuit, and a transistor Tr as a switch element is connected to this main circuit via a bridge rectifier circuit BD. Connect ₁ . Current limiting inductance L ₁ and secondary winding L ₂
is wound, rectified by a rectifier diode _D1 , smoothed by a smoothing capacitor C, and a resistor R for charging the smoothing capacitor C is connected between the smoothing capacitor C and the transistor _Tr1 . S is a switch element connected between the smoothing capacitor C and the control circuit A.

Now, when the power switch SW is turned on, the smoothing capacitor C is charged in the same way as the circuit shown in Fig. 1, but since the control circuit A is separated by the switch element S, the smoothing capacitor C is charged. This eliminates the inconvenience that the stored energy is released while it is still at a low level, resulting in insufficient current flowing to operate circuits that require large currents, and the terminal voltage of the smoothing capacitor C is raised to allow sufficient energy to be stored. be able to. After that, switch element S
, the control circuit A can flow a very large current due to the charge in the smoothing capacitor C, and the circuit can be sufficiently activated even if h _FE of the transistor Tr ₁ is small. Once the circuit starts up and current flows through the current limiting inductance _L1 , power is supplied to the control circuit A through the secondary winding _L2 of the current limiting inductance _L1 , and from then on, the circuit operates similarly to the circuit in Figure 1. Operate.

Figure 5 shows a transistor as a switch element S.
A Tr is used to double as a DC stabilizing transistor. A resistor _R10 and a switch Sa connected in series are connected between the collector and base of the transistor Tr, and a constant voltage diode ZD is connected to the base of the transistor Tr. I'll keep it.

Now, when the power switch SW is turned on, the smoothing capacitor C is charged in the same way as the circuit shown in Figure 1.
Since the collector and base of the transistor Tr are separated by the switch Sa,
No base current flows through the Tr, and it is turned off.
After sufficient energy has been stored in the smoothing capacitor C, when the switch Sa is closed, the transistor Tr is turned on, the smoothing capacitor C and the control circuit A are connected, and the circuit operates in the same manner as the circuit shown in FIG. At this time,
A constant voltage diode is used at the base of the transistor Tr.
Since ZD is connected, the transistor Tr also operates as a DC voltage stabilizing circuit.

FIG. 6 is a specific circuit diagram of the switch element shown in FIG. 5, in which a PUT element _Q1 is used in place of the switch Sa. When the power switch SW is turned on, the terminal voltage of the smoothing capacitor C increases as described above, but immediately after the power is turned on, the terminal voltage of the smoothing capacitor C is lower than the operating voltage of the voltage regulator diode ZD ₁ , so the voltage at the voltage regulator diode ZD ₁ increases. remains off and the resistor
No current flows through R ₁₁ and R ₁₂ , and no voltage is applied to the gate of PUT element Q ₁ . Therefore, PUT element Q ₁
is off, which is the same as the state in which switch Sa is off in FIG. When the terminal voltage of the smoothing capacitor C exceeds the operating voltage of the constant voltage diode ZD ₁ , the constant voltage diode ZD ₁ is turned on, and the terminal voltage of the smoothing capacitor C is connected to the gate of the PUT element Q ₁ through the resistors R ₁₁ , R ₁₂ and the constant voltage diode ZD 1 . A voltage divided by voltage diode ZD ₁ is applied,
PUT element _Q1 turns on. Therefore, the state is the same as when switch Sa in Fig. 5 is closed, transistor Tr is turned on, and current flows through the circuit.
It operates similarly to the circuit of FIG. Thereafter, the transistor Tr operates as a DC voltage stabilizing circuit using the constant voltage diode ZD. Also, once the circuit operates, the voltage between a and b becomes equal to the constant voltage diode ZD ₁
Even if the voltage regulator diode ZD ₁ turns off when the voltage drops below the operating voltage, due to the self-holding function of PUT element Q ₁ , PUT element Q ₁ remains off unless the current flowing through PUT element Q ₁ falls below the holding current. DC power can be supplied as is. Next, when the power switch SW is turned off, the voltage between a and b decreases.
When the current flowing through PUT element Q ₁ becomes equal to or less than the holding current, PUT element Q ₁ is turned off and returns to its original state.

As described above, the present invention forms a main circuit by a series circuit of an AC power source, a current limiting inductance, and a discharge lamp, connects a switch element in parallel with the discharge lamp of the main circuit, and limits the current during the conduction period of the switch element. The energy stored in the inductance is released when the switch element is cut off to apply high voltage pulses for starting and maintaining lighting to the discharge lamp, and a DC power source for a control circuit for driving the switch element is wound around the current limiting inductance. In a discharge lamp lighting device formed by a smoothing capacitor charged by the rectified voltage of the output voltage of the secondary winding and the voltage across the switch element, the lamp turns on when the terminal voltage of the smoothing capacitor exceeds a predetermined voltage. Since the switch element is connected between the smoothing capacitor and the control circuit, the transformer for the DC power supply can be omitted, making the device smaller, lighter, and less expensive, and can be used not only for small signal circuits but also for circuits that require large currents. In addition, since a transistor is used as a switch element and also serves as a DC stabilizing transistor, it has the effect of reducing the number of parts, being inexpensive, and improving reliability. be.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional discharge lamp lighting device, Figure 2 is a circuit diagram of a conventional discharge lamp lighting device.
The figure is a voltage waveform diagram of the switch element same as above, FIG. 3 is a voltage waveform diagram of a discharge lamp same as above, FIG. 4 is a circuit diagram of one embodiment of the present invention, and FIG. 5 is a circuit diagram of another embodiment same as above. , FIG. 6 is a specific circuit diagram of the switch element described above. V _S ... AC power supply, L ₁ ... Current limiting inductance, L _A ... Discharge lamp, Tr ₁ ... Transistor as a switch element, A ... Control circuit, L ₂ ... 2
Next winding, C: smoothing capacitor, R: charging resistor, S: switch element, Tr: transistor.

Claims (1)

[Scope of Claims] 1. A main circuit is formed by a series circuit of a DC power source, a current limiting inductance, and a discharge lamp, and a switch element is connected in parallel with the discharge lamp in the main circuit, and the current limiting inductance is connected during the conduction period of the switch element. The energy accumulated in the switch element is released when the switch element is cut off to apply high voltage pulses for starting and maintaining lighting to the discharge lamp, and the DC power source of the control circuit for driving the switch element is wound around the current limiting inductance. In a discharge lamp lighting device formed by a smoothing capacitor charged by the rectified voltage of the output voltage of the next winding and the voltage across the switch element, a switch is turned on when the terminal voltage of the smoothing capacitor exceeds a predetermined voltage. A discharge lamp lighting device characterized in that an element is connected between a smoothing capacitor and a control circuit. 2 Using a transistor as a switch element,
2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is configured to also serve as a DC voltage stabilizing transistor.