JPH0797909B2 - Discharge lamp lighting device - Google Patents

Description

TECHNICAL FIELD The present invention has a function of supplying a DC power source obtained by rectifying and smoothing an AC power source to an inverter circuit and stopping the oscillation of the inverter circuit when the discharge lamp is removed. The present invention relates to a discharge lamp lighting device.

BACKGROUND ART Conventionally, in this type of discharge lamp lighting device, an AC power source is input to a rectifier circuit via a power switch, the rectifier circuit output is smoothed by a smoothing capacitor, and a DC power source is supplied to an inverter circuit. Some have a function of stopping the oscillation of the inverter circuit when there is no load. However, this does not apply to the circuit configuration in which the inverter circuit itself cannot oscillate when the discharge lamp is removed.

However, in the discharge lamp lighting device described above, the oscillation operation of the inverter circuit is stopped because the oscillation stop circuit that stops the operation of the inverter circuit is provided when the load is removed, that is, in the no-load state. Since the smoothing capacitor is charged by the output of the rectifying circuit, even when the supply of the AC power is cut off by the power switch, the smoothed capacitor is in a state where the charged charge is accumulated. For this reason, ordinary people think that it is safe because they cut off the power supply and tend not to consider the residual charge of the capacitor, and there is a sufficient risk of electric shock even if they call their attention. For example, as an example, when inspecting the operating state of the device, or during repair or adjustment, mistakes such as accidental touching of the output of the inverter circuit to which a high voltage is applied are likely to occur. Moreover, since it is a direct current electric shock, it is extremely dangerous and may cause a life-threatening accident. In order to prevent such accidents, regulations (regardless of 30VDC or less within one minute after the power switch is cut off) are set and regulated by the Electrical Appliance and Material Control Law. Therefore, in general, a parallel resistance is connected to a smoothing capacitor, and a resistance value is set so that the above-mentioned rule can be activated to enhance safety.

However, in this case, it is necessary to reduce the resistance value in order to discharge quickly.If the resistance value is reduced in this way, the loss increases, the component size increases, and the cost increases. was there.

As another method, for example, a normally closed contact of a relay that operates by opening a power switch is used, and a series circuit of a resistor having a low resistance value and a relay contact is connected to both ends of a smoothing capacitor so that the power switch is A method is conceivable in which the relay contacts are closed when the relay is open, and the relay contacts are closed, and the charge accumulated in the smoothing capacitor is discharged by the smoothing capacitor, relay contact, and resistor closed circuit. However, there is no problem in terms of component size and cost.

[Object of the Invention] The present invention has been made in view of the above points, and an object of the present invention is to provide an oscillation stop circuit for stopping the operation of an inverter circuit in a no-load state, in which no load is applied. It is another object of the present invention to provide a highly safe discharge lamp lighting device capable of preventing electric shock by instantaneously discharging the electric charge accumulated in the smoothing capacitor when the AC power supply is cut off by the power switch.

DISCLOSURE OF THE INVENTION (Example 1) FIG. 1 is a diagram showing a schematic configuration of an example of the present invention.
An AC power supply AC is connected to a DC power supply unit 1 via a power switch SW, and this DC power supply unit 1 is composed of a rectifier circuit Rec and a smoothing capacitor C _0. The DC power source generated by rectifying and smoothing the is supplied to the inverter circuit 2. A discharge lamp 3 is connected to the output of the inverter circuit 2. This discharge lamp lighting device includes a no-load detection unit 4 for detecting a state in which the discharge lamp 3 is removed, that is, a no-load state, and the oscillation stop control unit 5 outputs an inverter circuit by the output of the no-load detection unit 4. 2 Oscillation operation is stopped. In the present embodiment, the oscillation stop circuit described in the conventional example is used as the no-load detector 4 and the oscillation stop controller 5.
It is composed of. The above is a description of the circuit configuration that is the premise of the present invention. Next, the configuration that characterizes the present invention will be described. In this embodiment, the power switch SW
When the input power stop detection unit 6 detects the open / closed state of the AC power supply, that is, the supply state of the AC power supply AC to the DC power supply unit 1, and the input power supply stop detection unit 6 detects that the power switch SW is opened. And an oscillation stop cancellation control section 7 for reactivating the inverter circuit 2 to discharge the electric charge charged in the smoothing capacitor C ₀ .

The operation will be described below. First, when the power switch SW is closed while the discharge lamp 3 is connected to the inverter circuit 2, the rectifier circuit Rec of the DC power supply unit 1 rectifies the AC power supply AC and the smoothing capacitor C _0. Is smoothed and converted to DC power. This DC power supply is converted into a high-frequency AC power supply by the inverter circuit 2, and the discharge lamp 3 is started and lit. At this time, of course, neither the no-load detector 4 nor the oscillation stop controller 5 operates, and the inverter circuit 2 supplies a normal output to the discharge lamp 3. Now, assuming that the discharge lamp 3 is removed and becomes in a no-load state, the no-load detecting section 4 detects the no-load state, and the oscillation stop control section 5 is operated by the output of the no-load detecting section 4. The oscillation operation of the inverter circuit 2 is stopped. At this time, power is stored in the smoothing capacitor C ₀ by the AC power supply AC. When the power switch SW is opened, the input power stop detection unit 6 detects the open state of the power switch SW, and the oscillation stop cancellation control unit 7 operates at the output of this input power stop detection unit 6 to perform the oscillation stop control. By canceling the oscillation stop operation of the inverter circuit 2 of the section 5,
The inverter circuit 2 operates by using the charging charge of the smoothing capacitor C ₀ of the DC power supply unit 1 as a power source, and the smoothing capacitor
The inverter circuit 2 operates until the charged electric charge of C ₀ is discharged. At this time it is unloaded condition, intended for the inverter circuit 2 is relatively heavy load to no-load oscillation for the charging energy of the smoothing capacitor C _0, the charge of the smoothing capacitor C ₀ is to be discharged instantaneously Is.

FIG. 2 is a diagram showing a specific circuit of the circuit shown in FIG.
The left side of FIG. 2 shows a case where the AC power supply AC is connected to the rectifier circuit Rec via the power switch SW, and the DC power supply obtained by rectifying the AC power supply AC and the normal DC power supply E are used.
In either case, the inverter circuit 2 is connected via the smoothing capacitor C ₀ . When the DC power source E is used, the smoothing capacitor C ₀ also serves to lower the internal impedance. Here, the inverter circuit 2 is composed of transistors Q ₁ and Q ₂ , a drive transformer T ₁ having two secondary windings n ₂ and n ₃ , a thyristor Q ₃ and a starting circuit 8 including a capacitor C _{3 and the} like. ing. Furthermore, the load circuit includes capacitors C ₁ and C ₂ , discharge lamp l, and choke coil L.
_{Consists of 1} . Here, the capacitor C ₁ has a capacity sufficiently larger than that of the capacitor C ₂ . In this concrete circuit, a series circuit of transistors Q ₁ and Q ₂ is connected to both ends of a smoothing capacitor C ₀ , and a discharge lamp 3 and a drive transformer are connected in parallel with the transistor Q _1.
A series circuit of the primary winding n ₁ of T ₁ is connected, and the load current flowing in the discharge lamp 3 causes the secondary currents of both transistors Q ₁ and Q ₂ to pass through the secondary windings n ₂ and n ₃ of the drive transformer T ₁ . The current is fed back to the base to oscillate the transistors Q ₁ and Q ₂ , and the detailed operation is omitted. The activation circuit 8 when power is supplied, is charged capacitor C _3, is intended for activating the inverter circuit 2 by turning on the transistor Q ₂ to ignite the thyristor Q ₃ at the charging voltage. In this concrete circuit, the inverter circuit 2 has a function of stopping the oscillation operation when there is no load, and the no-load detection unit 4 is composed of the diode D ₄ and the resistors R ₄ and R ₅ , and the oscillation stop control unit 5 is It is composed of transistors Q ₄ and Q ₅ and resistors R ₆ and R ₇ .

The operation of stopping the oscillation of the inverter circuit 2 when there is no load will be schematically described. First, in a state where the discharge lamp 3 is connected, a predetermined voltage is applied to both ends of the no-load detection unit 4, and the resistance is
Since the voltage across R ₅ is applied to the base of the transistor Q _5, the transistor Q ₅ is turned on, the transistor Q ₄ is turned off. Therefore, the oscillation stop control unit 5 becomes inoperative, and the inverter circuit 2 performs normal oscillation operation. When the discharge lamp 3 is now removed and is in a no-load state, a charging circuit for the capacitor C ₁ , the diode D ₄ , and the resistors R ₄ , R ₅ is constructed. And the capacitor C ₀ is charged and the capacitor
The voltage across C ₁ rises to the output voltage of DC power supply 1.
Therefore, no voltage is generated across the resistor R ₅ , and the transistor Q ₅ is turned off. Thus the base of the transistor Q ₄ are a base current flows through the resistor R _6, transistor Q ₄ is turned on, the voltage induced in the secondary winding n ₃ of the driving transformer T _1, the base of the transistor Q ₂ Since it is bypassed by the transistor Q ₄ without being applied to the transistor Q ₂ , the transistor Q ₂ is turned off and the inverter circuit 2 becomes inoperative. At this time, since the power switch SW is closed, the smoothing capacitor C ₀ is charged by the output of the rectifier circuit Rec or the DC power source E.

Further, in the present embodiment, when the DC power source E is used, the input power stop detection unit 6 is composed of voltage dividing resistors r ₁ and r ₂ ,
When AC power supply AC is used, resistors r ₁ and r ₂ , capacitor C
₄ , the diode D ₇ , and the oscillation stop cancellation control unit 7 is composed of the gate G, the resistor r ₃ , and the diode D ₆ . And, when both the DC power supply E and the AC power supply AC are used,
The input power stop detection unit 6 is connected to both ends via the power switch SW, and the oscillation stop release control unit 7 outputs the oscillation stop control unit 5
It is connected to the base of the transistor Q _5. Here, the diode D ₅ for isolation between the positive terminal of the power switch SW and the smoothing capacitor C ₀ so as not to cause malfunction due to voltage of the smoothing capacitor C ₀ in the case of using the DC power source E Insert. Further, when the AC power supply AC is used, the diode D ₇ of the input power supply stop detection unit 6 is a diode for preventing backflow, and the capacitor C ₄ smoothes the AC power supply AC and prevents malfunctions during an instantaneous power failure. It is connected across the resistor r ₂ .

The operations of the input power stop detection unit 6 and the oscillation stop cancellation detection unit 7 will be described. Now, when the power switch SW is closed, a voltage is generated across the resistor r ₂ , and this voltage is inverted by the gate G which is an inverter. Therefore, the output of the oscillation stop release control unit 7 becomes low level, and the base of the transistor Q ₅ of the oscillation stop control unit 5 is not affected at all. Now, assuming that the power switch SW is opened, the DC power E is no longer applied to the input power stop detection unit 6,
The voltage across the resistor r ₂ becomes zero. Therefore, the output of the gate G becomes high level, and the transistor Q ₅ is turned on and the transistor Q ₄ is turned off in the same manner as described in the operation of the oscillation stop control unit 5 described above. Therefore, when the oscillation stop control unit 5 operates in the no load detection unit 4 and the operation of the inverter circuit 2 is stopped in the no load state, the inverter circuit 2 operates again by the output of the oscillation stop release control unit 7. State,
The inverter circuit 2 oscillates with the electric charge charged in the smoothing capacitor C ₀ . However, since this operation of the inverter circuit 2 is unloaded oscillation, the inverter circuit 2 as a load of the smoothing capacitor C ₀ becomes heavier, the electric charge charged in the smoothing capacitor C ₀ to be discharged quickly Therefore, the oscillation operation of the inverter circuit 2 is naturally stopped by the discharging of the smoothing capacitor C ₀ .

(Embodiment 2) FIG. 3 is a diagram showing another embodiment of the present invention. In this embodiment, a discharge lamp 3 is used, and the above-mentioned first embodiment is a self-excited inverter circuit 2. However, in this embodiment, the transistor Q is generated by the oscillation of the astable multi-mibrator AM _1.
A separately excited inverter circuit 2'which turns on and off ₇ and alternately switches the transistors Q ₁ and Q ₂ by the voltage induced in the secondary windings n ₂ and n ₃ of the drive transformer T ₁ is used. . Further, the no-load detector 4 is composed of a transistor Q ₆ , diodes D ₈ and D ₉ , a choke coil L ₀ , and a capacitor C ₅ ,
The oscillation stop control unit 5 is composed of a diode D ₁₀ , a capacitor C ₆ , a differentiating circuit 9 including a resistor r ₄ , a monostable multi-mibrator MM, and a transistor Q ₈ . Further, the input power supply stop detection unit 6 is a current transformer CT, a diode
Oscillation stop release control unit 7 composed of D ₁₁ and capacitor C ₇ .
Is a monostable multi-mibrator AM ₂ and transistor Q ₉ . The no-load detection unit 4 of the present embodiment detects the no-load state by the current flowing in the discharge lamp 3. Therefore, even when the filament of the discharge lamp 1 is cut, Capacitors C ₀₁ and C ₀₂ are connected to both ends of the filament so that a current flows through the filament 3.

The operation of this embodiment will be described below. First, the operation of the no-load detector 4 will be described. When the discharge lamp 1 is normally lit, the current i is changed as shown in FIG. 4 (b).
Is set so that the choke coil L ₁ and the capacitor C ₂ are delayed with respect to the phase of the voltage e. By setting the delay phase in this way, almost no recovery current flows through the feedback diodes D ₁ and D ₂ . However, when the phase advances, a large recovery current flows through the feedback diodes D ₁ and D ₂ , and this current flows from the feedback diode D ₁ through the transistor Q ₂ to the DC power source E (smoothed when viewed from the inverter circuit 2 ′). Capacitor C ₀ output) or from the transistor Q ₁ to the DC power source E via the feedback diode D ₂ , and at this moment, the DC power source E is fed back to the feedback diode D ₁ , transistor Q ₂ or transistor Q ₁ , feedback. A steep current flows as if it were apparently short-circuited in the diode D ₂ . Therefore, in order to detect the state in which the discharge lamp 3 is removed by the no-load detector 4, the capacitors C ₀₁ and C ₀₂ are selected so that the current i has a phase advance. FIG. 4 (a) shows the current i ₀ flowing through the feedback diodes D ₁ and D ₂ when the current i has advanced. When the current i is advanced by removing the discharge lamp 3 as described above,
A large recovery current flows through the feedback diodes D ₁ and D ₂ ,
At this time, a voltage proportional to this current change is generated in the choke coil L ₀ . The voltage of the choke coil L ₀ charges the capacitor C ₅ via the diode D ₉ . The change in the potential of the capacitor C ₅ is shown in FIG. Thus when the capacitor C ₅ is charged, the base current flows through the transistor Q _6, the transistor Q ₆ is turned on. When the transistor Q ₆ is turned on, the differentiation circuit 9 of the oscillation stop control unit 5
Is differentiated by applying a voltage to the trigger pulse shown in FIG. 5 (c) that triggers the monostable multi-mibrator MM. This trigger pulse causes the output of the monostable multi-mibrator MM to go high, turning on the transistor Q _{8 as} shown in FIG. Therefore, the output of the astable multi-mibrator AM ₁ is bypassed by the transistor Q ₈ , the transistor Q ₇ is turned off, and the base currents of the transistors Q ₁ and Q ₂ are not supplied, as shown in FIG. Both transistors Q ₁ and Q ₂ are turned off. Here, the metastable period of the monostable multi-mibrator MM is set as long as possible.After the monostable multi-mibrator MM returns to the stable state, the transistor Q ₈ turns off and the transistor Q ₇ turns on the astable multi-mybrator. It is switched by the blazer AM ₁ output,
The transistors Q ₁ and Q ₂ start oscillating operation again, but the capacitor C ₅ is instantly charged in the same manner as described above, so that the oscillation of the inverter circuit 2 is further stopped and the above operation is repeated. It is a thing. Incidentally, FIG. 5 (g) is a diagram showing the voltage across the open end when the discharge lamp 3 is removed, and FIG. 6 is an enlarged view of this waveform. The oscillation period is made longer so that the oscillation state can be understood in both FIG. 5 (g) and FIG. 6, but actually, as described above, the metastable state of the monostable multi-mibrator MM is made as long as possible. Therefore, the oscillation period is extremely short, and is less than several pulses. Therefore, apparently the inverter circuit 2 '
Seems to stop oscillating. Further, when the discharge lamp 3 is connected and the discharge lamp 3 is normally turned on, the rising of the current i ₀ flowing through the feedback diodes D ₁ and D ₂ is negative di ₀ as shown in FIG. 4 (b). / dt with a capacitor C ₀
Is not charged. In the state described above, the full load seen from the DC power source E is light because the discharge lamp 3 is removed,
The smoothing capacitor C ₀ is fully charged.

The case where the power switch SW is opened in this state will be described. First, in the normal state, that is, in the state where the power switch SW is closed and opened, the voltage induced on the secondary side of the current transformer CT is rectified by the diode D _{11 and} smoothed by the capacitor C ₇ , and the transistor Q _{Applied to} the base of ₉ . Therefore, the transistor Q ₉ maintains the ON state in the normal state, and the output of the astable multimibrator AM ₂ is not supplied to the transistor Q ₇ . Now, assuming that the power switch SW is opened, the current transformer
No voltage is induced on the secondary side of CT. This causes the transistor Q ₉ to turn off and the astable multi-mybrator AM ₂
Output is supplied to the transistor Q _7, are unloaded oscillating charges inverter circuit 2 at the transistor Q ₇ 'has been charged in the smoothing capacitor C ₀ as the power source. Therefore, the electric charge of the smoothing capacitor C ₀ is rapidly discharged, and when the electric charge of the smoothing capacitor C ₀ is discharged, the oscillation of the inverter circuit 2'is naturally stopped. When it is necessary to further shorten the discharging time of the smoothing capacitor C ₀ , if the oscillation frequency of the astable multi-mybrator AM ₂ is made higher than the oscillation frequency of the astable multi-mybrator AM ₁ , the inverter circuit 2 ′ will be used. The flowing current increases, and the discharging time of the smoothing capacitor C ₀ can be positively shortened.

Summarizing the above into the generalized constraint conditions, when the phase mode of the inverter circuit 2 ′ in the no-load state is SW “closed”, it switches to SW “open” Condition Slow phase fy ₁ Slow phase fy ₂ fy ₁ > fy ₂ Leading phase fx ₁ Leading phase fx ₂ fx ₁ <fx ₂ and the astable multi-mybrator AM ₂ so that the frequencies fx ₂ and fy ₂ approach the natural resonance frequency of the inverter circuit 2 ′.
By previously setting the oscillation frequency of, the same effect as described above can be obtained. The natural resonance frequency is 2
In the case where there are more than one inverter circuits 2 ', it is sufficient to approach any one of the natural resonance frequencies. However, in practice, when the rated performance of the semiconductor element and the mounting condition are constrained, the economically advantageous natural resonance frequency is obtained. You just have to take the approach. Further, in the above-described embodiment, the frequency of the inverter circuit 2'is controlled to achieve the intended purpose, but it is easily conceivable that the duty ratio may be controlled. Further, in the present embodiment, the case where the oscillation operation of the inverter circuit 2'apparently stops has been described, but it is needless to say that the present invention can be applied to the case where the oscillation of the inverter circuit 2'is completely stopped as in the first embodiment. Further, the input power stop detection unit 6 may detect the open / closed state of the power switch SW by detecting the charging current of the smoothing capacitor C ₀ as shown in FIG.

[Advantages of the Invention] As described above, the present invention has a rectifier circuit connected to an AC power source via a power switch, a smoothing capacitor connected to the output of the rectifier circuit, and a high-frequency voltage connected to both ends of the smoothing capacitor. An inverter circuit that outputs the output, a discharge lamp connected to the output of the inverter circuit, an oscillation stop circuit that stops the oscillation of the inverter circuit when the discharge lamp is removed, and a detection that the power switch is opened. The input power supply stop detection unit and the oscillation stop circuit stop the oscillation of the inverter circuit, and when the input power supply stop detection unit detects the stop of the input power supply, the charge charged in the smoothing capacitor is Since there is an oscillation stop release control unit that releases the oscillation stop state of the oscillation stop circuit in order to discharge by the oscillation of the inverter circuit, When the input power supply stop detection unit detects that the power supply switch is opened, the inverter circuit whose oscillation operation has been stopped is restarted by the output of the oscillation stop release control unit and the inverter circuit It is possible to instantly discharge the electric charge charged in the smoothing capacitor by load oscillation, eliminating the risk of electric shock due to the misunderstanding that there is no electricity when the power switch is turned off, improving safety and equipping it in advance. Using an inverter circuit,
Since only the input power supply stop detection unit and the oscillation stop release detection unit, which require a relatively simple circuit configuration, are added, there is an effect that an inexpensive device can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention,
FIG. 2 is a specific circuit diagram of the above, FIG. 3 is a circuit configuration diagram showing another embodiment of the present invention, FIGS. 4 to 7 are operation explanatory diagrams of the same as above, and FIG. 8 is another of the present invention. It is a circuit diagram showing an input power stop detection unit. 1 is a DC power supply unit, 2 and 2'is an inverter circuit, 3 is a discharge lamp, 4 is a no-load detection unit, 5 is an oscillation stop control unit, 6 is an input power supply stop detection unit, 7 is an oscillation stop release control unit, and AC. Is an AC power supply, E is a DC power supply, SW is a power switch, and C ₀ is a smoothing capacitor.

Claims (1)

[Claims] 1. A rectifier circuit connected to an AC power source via a power switch, a smoothing capacitor connected to the output of the rectifier circuit, an inverter circuit connected to both ends of the smoothing capacitor to output a high frequency voltage, and an inverter. A discharge lamp connected to the output of the circuit, an oscillation stop circuit for stopping the oscillation of the inverter circuit when the discharge lamp is removed, an input power stop detection unit for detecting that the power switch is opened, When the oscillation of the inverter circuit is stopped by the oscillation stop circuit and the input power stop detection unit detects the stop of the input power, the charge stored in the smoothing capacitor is discharged by the oscillation of the inverter circuit. 2. A discharge lamp lighting device, further comprising: an oscillation stop cancellation control unit that cancels the oscillation stopped state of the oscillation stop circuit.