JP2801068B2 - Lamp voltage detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lamp voltage detecting device for detecting a lamp voltage of a discharge lamp for controlling a discharge lamp such as a metal halide lamp or the like using an inverter circuit. It is about.

2. Description of the Related Art For example, a series inverter as shown in FIG. 9 is known as a lighting device for lighting a discharge lamp using an inverter circuit. In FIG. 9, clocks E ₁ , E ₂ for inverting the phases of drive transistors Q ₂₁ and Q ₂₂ connected to the primary winding of the drive transformer DT ′ are opposite to each other.
And the switching transistors Q ₂₃ and Q ₂₄ connected to the secondary winding are turned on and off alternately, and connected to the connection point between the switching transistors Q ₂₃ and Q ₂₄ via the capacitor C and the choke coil L. The discharge lamp HL is turned on by passing a current that is alternately inverted. At this time, if it is desired to detect the lamp voltage of the discharge lamp HL in order to control the lighting operation, a voltage detection terminal VL may be connected to a terminal of the discharge lamp HL opposite to the ground.

Problems to be Solved by the Invention In the series inverter having the above configuration, the earth line A of the discharge lamp is directly connected to the ground GND,
Since it is configured not to float above the ground GND, it can be easily detected by converting the voltage taken out from the voltage detection terminal VL into a DC voltage using a rectifier. However, if the inverter circuit is configured as a bridge inverter or a half-bridge inverter, the ground line of the inverter circuit, which is one end of the discharge lamp HL, has a configuration floating above the ground GND. Voltage cannot be taken out only from the voltage detection terminal VL.

The present invention solves such a problem, and extracts a signal common to the ground line of the inverter circuit from a differential voltage generated at both ends of, for example, a capacitor voltage dividing circuit provided in parallel with the discharge lamp, and converts this signal into a bridge inverter or It is an object of the present invention to provide a lamp voltage detecting device used for controlling an inverter circuit such as a half-bridge inverter.

Means for Solving the Problems In order to solve the above problems, a lamp voltage detection device of the present invention includes a lamp voltage detection circuit that detects a differential voltage generated across a discharge lamp driven by an inverter circuit, It comprises a differential amplifier for differentially amplifying the differential voltage detected by the ramp voltage detection circuit, and a DC voltage detection circuit comprising a rectifier for rectifying the output to obtain a DC voltage.

Further, the present invention provides the lamp voltage detecting circuit, wherein the differential voltage detected by the lamp voltage detecting circuit is input to the collector and the emitter of the first transistor via a diode, and the gate of the first transistor is connected to the gate. And a current mirror circuit for obtaining a DC current corresponding to the current flowing through the first transistor from the second transistor to which the differential voltage is connected, and obtaining a control DC voltage from the DC current. Things.

Further, according to the present invention, the lamp voltage detecting circuit and the differential voltage detected by the lamp voltage detecting circuit are input to the collector and the emitter of the first transistor via the diode bridge, and are connected to the gate of the first transistor. A current mirror circuit that obtains a DC current corresponding to a current flowing through the first transistor from the second transistor to which the gate is connected by the differential voltage, and obtains a control DC voltage from the DC current. It was done.

Further, according to the present invention, the lamp voltage detecting circuit and the differential voltage detected by the lamp voltage detecting circuit are respectively input to the emitter and the gate via the diode, and flow from the collector through the emitter and the gate by the differential voltage. A transistor for obtaining a DC current corresponding to the current, and a DC voltage for control is obtained from the DC current.

Operation With the above configuration, the lamp voltage detection circuit detects the differential voltage generated at both ends of the discharge lamp and converts the differential voltage into a DC voltage by the DC voltage detection circuit, so that the earth line of the inverter circuit floats above the ground. Even with the above configuration, a DC voltage can be extracted as a signal common to the ground line of the inverter circuit, and the inverter circuit can be reliably operated by the DC voltage.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a basic configuration of a discharge lamp lighting device to which a lamp voltage detecting device according to one embodiment of the present invention is applied. In FIG. 1, reference numeral 1 denotes a DC power supply, and an inverter circuit 2 is driven by the DC power supply 1 and oscillates a clock signal having a predetermined frequency. The inverter circuit 2 includes, as load circuits, a resonance circuit composed of a series circuit of a choke coil 3 and a resonance capacitor 4, and a discharge lamp 5 such as a metal halide lamp connected to a connection point between the choke coil 3 and the capacitor 4. Have.
Reference numeral 6 denotes a lamp voltage detection circuit provided in parallel with the discharge lamp 5 to detect the lamp voltage of the discharge lamp 5,
It is constituted by a capacitor having a larger capacity than the capacity of the resonance capacitor 4. Reference numeral 7 denotes a lamp current detection circuit provided in series with the discharge lamp 5 for detecting the lamp current of the discharge lamp 5. This lamp voltage detection circuit 6
The output signal of the lamp current detection circuit 7 is input to the lighting control circuit 8, which changes the oscillation frequency of the inverter circuit 2 or its duty ratio based on these and controls the lighting operation of the discharge lamp 5. .

Next, an operation example according to the above configuration will be described. DC power supply 1
Is turned on, the inverter circuit 2 first oscillates at a low frequency of about 2 KHz, and applies this low frequency voltage to the resonance circuit of the choke coil 3 and the capacitor 4.
At this time, a high-frequency resonance voltage generated by the resonance circuit is superimposed on the low-frequency voltage. The lamp voltage detection circuit 6 connected to the resonance circuit detects the resonance voltage, and the lighting control circuit 8 detects this voltage. Then, the oscillation frequency of the inverter circuit 2 is changed to a high frequency, and a high resonance voltage is generated in the capacitor 4 at a high frequency of, for example, about 100 KHz by the resonance circuit. At this time, the discharge lamp 5 is started by the high resonance voltage generated in the capacitor 4, and a large amount of current flows through the discharge lamp 5. Therefore, the lamp voltage detecting circuit 6 detects that the discharge lamp 5 has started by detecting that the current flowing through the capacitor 4 has sharply decreased by the voltage drop in the lamp voltage detecting circuit 6, and the lighting control circuit 8 By detecting the lowered voltage of the lamp voltage detecting circuit 6 and controlling the oscillation frequency of the inverter circuit 2 to be a low frequency of about 10 KHz, when the lamp voltage is low, the oscillation frequency of the inverter circuit 2 is lowered and the choke is performed. The current flowing through the discharge lamp 5 through the coil 3 is increased, and when the lamp voltage is high, the oscillation frequency of the inverter circuit 2 is increased, and the current flowing through the choke coil 3 through the discharge lamp 5 is reduced. Control to turn on.

FIG. 2 is a circuit diagram showing main parts of the inverter circuit 2 and the lamp voltage detection circuit 6. In FIG. 2, the inverter circuit 2 has a configuration of a bridge inverter composed of _four switching transistors Q ₁ , Q ₂ , Q ₃ and Q ₄ for driving a load circuit 11 composed of a choke coil 3, a capacitor 4 and a discharge lamp 5. . 12 is a drive circuit for driving the bridge inverter, across the primary winding of the drive transformer DT is the ground GND through the drive transistor Q _5, Q _6, to the gate of the drive transistor Q _5, Q ₆ is Clocks E ₁ and E ₂ having an oscillation frequency of about 2 KHz and having phases inverted to each other are input, and a drive voltage VD is applied to a middle point of the primary winding. On the secondary side of the drive transformer DT, four secondary windings are provided. One end of each of the secondary windings is connected to a resistor R ₁₃ , R ₁₅ , R ₁₇ , R ₁₉ and diodes D ₃ , D connected in parallel to the resistor R ₁₃ , R ₁₅ , R ₁₇ , R _{19. 4,} D _5, D ₆ and resistors _{R 12, R 14, R 16} , R
It is connected to the gates of _four switching transistors Q ₁ , Q ₂ , Q ₃ , Q ₄ constituting a bridge inverter via ₁₇ series circuits. In addition, the switching transistor Q ₁
The series circuit and the series circuit of the switching transistor Q ₃ and Q ₄ Q ₂ 'is interposed between the earth line A of the DC power supply voltage VDD and the inverter circuit, the switching transistor Q ₁
The load circuit 11 during the connection point and the connection point of the switching transistor Q ₃ and Q ₄ Q ₂ is interposed a. The other end of the secondary winding is connected to the connection point of the transistors Q ₁ and Q ₂ , and the other end of the secondary winding connected to the gate of the switching transistor Q ₃ is connected to the connection point of the transistors Q ₃ and Q ₄ The other ends of the secondary windings connected to the respective gates of the switching transistors Q ₂ and Q ₄ are connected to the ground line A of the bridge and float above the ground GND. As a result, the pair of switching transistors Q ₁ and Q ₄ and the switching transistors Q ₂ and Q _{3 that} are obliquely opposed to each other are such that when one Q ₁ and Q ₄ are simultaneously turned on, the other Q ₂ and Q ₃ are sometimes turned off. It is configured.

C ₂ is a voltage detection capacitor constituting the lamp voltage detection circuit 6 and has a larger capacitance than the capacitance of the resonance capacitor, and is connected between the capacitor 4 and the connection point of the switching transistors Q ₃ and Q _4. is connected between the differential voltage across the capacitor C ₂ is detected as the lamp voltage of the discharge lamp 5. That is, a series circuit of the capacitor C ₃ and the resistors R ₂ and R ₃ is connected between the input side of the voltage detecting capacitor C ₂ and the ground GND, and the capacitor C ₃ is connected between the output side and the ground GND.
₄ , a resistor R ₄ , and a series circuit of a variable resistor R ₅ are connected, and resistors R ₂ and R ₃
The voltage detection terminals VL ₁ and VL ₂ are respectively taken out from the connection point of the resistor R ₄ and the connection point of the variable resistor R ₅ , and the differential voltage is detected by the voltage detection capacitor C ₂ as shown in FIG. It is input to the lighting control circuit 8.

The other ends of the switching transistors Q ₂ and Q ₄ are connected to the ground line A of the bridge, further connected to the ground GND via the resistor R ₇ , and connected to the current detection terminal IDC via the resistor R _6. The resistors R ₆ and R ₇ constitute a lamp current detection circuit 7 together with a capacitor C ₅ interposed between the current detection terminal IDC and the ground GND.

FIG. 3 is a circuit diagram showing one embodiment of the lamp voltage detecting device of the present invention. In FIG. 3, the lamp voltage detecting device comprises a lamp voltage detecting circuit 6 shown in FIG. ₂ and a DC voltage detecting circuit 9 connected to the voltage detecting terminals VL ₁ and VL ₂ and incorporated in the lighting control circuit 8. The differential voltage at both ends of the discharge lamp 5 detected by the lamp voltage detection circuit 6 is input to the DC voltage detection circuit 9 in the lighting control circuit 8 and becomes a DC voltage V ₀ that can control the inverter circuit 2. Is converted.

2 and 3, clocks E ₁ and E ₂ having an oscillation frequency of about ₂ KHz whose phases are inverted to each other are applied to the primary winding of the drive transformer DT. For example, the switching transistors Q ₁ and Q ₄ are simultaneously driven. When turned on, load circuit 11
When the switching transistors Q ₂ and Q ₃ are simultaneously turned on when the next clock is inverted, a current in the direction (b) flows through the resonance circuit of the load circuit 11. At this time, a high-frequency resonance voltage is superimposed on a low-frequency voltage of about 2 KHz, and the voltage detection capacitor C ₂ detects a differential voltage generated on both sides of the discharge lamp 5 at this time as a lamp voltage. dynamic voltage is converted to a DC voltage V ₀ by the DC voltage detection circuit 9, the lighting control circuit 8 of FIG. 1 is based on this direct-current voltage V _0, the inverter circuit 2
The discharge lamp is started by generating a high resonance voltage in the capacitor 4 at a high frequency of, for example, about 100 KHz, and a large amount of current flows through the discharge lamp 5. Therefore, the differential voltage between the voltage detection terminals VL ₁ and VL ₂ drops sharply, thereby detecting the start of the discharge lamp 5. This decrease in the differential voltage is detected through the lamp voltage detection circuit 6 and the DC voltage detection circuit 9, and the lighting control circuit 8 controls the oscillation frequency of the inverter circuit 2 to be a low frequency of about 10 KHz. Lights up rated.

In the present embodiment, the configuration of the bridge inverter is described, but the present invention can be similarly applied to a half-bridge inverter having a configuration in which the switching transistors Q ₃ and Q ₄ are replaced with capacitors.

FIG. 4 is a circuit diagram showing another embodiment of the lamp voltage detecting device of the present invention. 4, in the lamp voltage detecting device of the present embodiment, the voltage detecting terminals VL ₁ ′ and VL ₂ ′ are directly drawn from the input side and the output side of the lamp voltage detecting circuit 6. _A DC voltage detecting circuit 9 'is connected to ₁ ' and VL ₂ '. A differential voltage across the discharge lamp 5 detected by the lamp voltage detecting circuit 6 is applied to a DC voltage detecting circuit 9' in the lighting control circuit 8. The DC voltage V _{0 which} can be directly input to the inverter circuit 2 and can control the inverter circuit 2 as in FIG.
Is converted to

FIG. 5 is a circuit diagram showing a specific example of a DC voltage detection circuit 9 constituting a part of the lamp voltage detection device in FIG. In Figure 5, the DC voltage detecting circuit 9 comprises a differential amplifier 13 and the rectifier 14, the voltage taken out from the voltage detection terminal VL _1, VL ₂ is a positive input terminal of the operational amplifier OP ₁ of the differential amplifier 13 - Input The differential voltage input to the terminals and generated at the voltage detection terminals VL ₁ and VL ₂ is differentially amplified by the differential amplifier 13.
This output is input to the − input terminal of the operational amplifier OP whose + input terminal of the rectifier 14 is grounded, and the output is
It is taken out as a DC voltage V ₀ to a capacitor C ₀ of the output terminal via the _11.

FIG. 6 is a circuit diagram showing a specific example of a DC voltage detection circuit 9 'constituting a part of the lamp voltage detection device in FIG. In the sixth figure, the DC voltage detecting circuit 9 'comprises a current mirror circuit 15 constituted by transistors Q _11, Q _12, the voltage detection terminal VL _1' is connected to the emitter of the transistor Q _11, the voltage detecting terminal VL ₂ 'it is connected to the collector of the transistor Q ₁₁ via the reverse direction of the diode D _12,
The gate of the transistor Q ₁₁ is connected to the gate of the collector of the transistor Q ₁₂ of the transistor Q _11. The emitter of the transistor Q ₁₂ is connected to the voltage detection terminal VL ₁ ', the collector via a forward diode D ₁₃ resistance
Are connected to a series circuit of R _21, R _22, connection point of the resistors R _21, R ₂₂ is connected to the output terminal.

Therefore, the voltage detecting terminal VL ₁ ', VL _2' emitter of the transistor Q ₁₁ by a differential voltage generated in - the corresponding current transistors of the current flowing through the collector Q ₁₂
Flows from the collector through the diode D _13, the series circuit R
DC voltage V _{0 from the} voltage dividing point of R ₂₁ and R ₂₂ to the capacitor C ₀ at the output end.
Is taken out as

FIG. 7 is a circuit diagram showing another specific example of the DC voltage detection circuit 9 'constituting a part of the lamp voltage detection device in FIG. In Figure 7, the DC voltage detecting circuit 9 'is the transistor Q _13, Q ₁₄ current mirror circuit 16 constituted by
Made, the voltage detecting terminal VL ₁ ', VL _2' both output ends of the connected diode bridge DB is connected to the emitter and collector of the transistor Q _13, the collector of the transistor Q of the gate of the transistor Q ₁₃ is the transistor Q ₁₃ Connected to ₁₄ gates. The emitter of the transistor Q ₁₄ is connected to the output terminal of the diode bridge DB having an emitter connected transistors Q _13, the collector is connected to the series circuit of a resistor R _23, R ₂₄ through forward diode D ₁₄ ,
Connection point of the resistors R _23, R ₂₄ is connected to the output terminal.

Therefore, the voltage detecting terminal VL ₁ ', VL _2' emitter of the transistor Q ₁₃ by a differential voltage generated in the - current corresponding to the current flowing through the collector transistor Q ₁₄
Flows from the collector through the diode D _14, the series circuit R
DC voltage V _{0 from the} voltage dividing point of ₂₃ and R ₂₄ to the capacitor C ₀ at the output end.
Is taken out as

FIG. 8 is a circuit diagram showing still another specific example of the DC voltage detection circuit 9 'forming a part of the lamp voltage detection device in FIG. In Figure 8, the DC voltage detecting circuit 9 'comprises a transistor Q _15, the voltage detecting terminal VL _1' is connected to the emitter of the transistor Q ₁₅ via the forward diode D _15, a voltage detection terminal VL ₂ 'is is connected to the gate of the transistor Q ₁₅ via the reverse direction of the diode D _16,
Transistor collector of Q ₁₅ is connected to the series circuit of a resistor R _25, R ₂₆ through forward diode D _17, resistors R _25, R ₂₆
Is connected to the output terminal.

Therefore, the voltage detecting terminal VL ₂ ', VL _1' by the differential voltage generated in the emitter of the transistor Q ₁₅ - current corresponding to the current flowing through the gate transistor Q ₁₅
Flows from the collector through the diode D _17, the series circuit R
DC voltage V _{0 from the} voltage dividing point of ₂₅ and R ₂₆ to the capacitor C ₀ at the output end.
Is taken out as

In the Figure 6-Figure 8, a capacitor as shown in FIG. 3 C _3, C _4, a resistor R ₂ to R ₅ is not required, the circuit can be simplified.

As described above, according to the present invention, the differential voltage across the discharge lamp detected by the lamp voltage detection circuit is converted to a DC voltage by the DC voltage detection circuit and used as a control voltage for the inverter circuit. Therefore, even if the ground line of the inverter circuit is raised above the ground, a DC voltage can be used as a signal common to the ground line of the inverter circuit, and the inverter circuit can be reliably operated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a discharge lamp lighting device to which a lamp voltage detection device according to one embodiment of the present invention is applied, and FIG. 2 is an inverter circuit and a lamp voltage detection device in the discharge lamp lighting device. Circuit diagram showing the main part of the part,
3 and 4 are main circuit diagrams of a lamp voltage detecting device showing an embodiment of the present invention, respectively. FIGS. 5 to 8 show specific examples of DC voltage detecting circuits of the lamp voltage detecting device, respectively. FIG. 9 is a circuit diagram illustrating the configuration of the series inverter. 1 DC power supply 2 Inverter circuit 3 Choke coil 4 Resonant capacitor 5 Discharge lamp
6 ... Lamp voltage detection circuit, 7 ... Lamp current detection circuit, 8 ... Lighting control circuit, 9,9 '... DC voltage detection circuit, 11 ... Load circuit, 12 ... Drive circuit, 13 ... Difference Dynamic amplifier, 14 rectifier, 15, 16 current mirror circuit.

Continued on the front page (72) Inventor Koji Miyazaki 1006 Kadoma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Takuyuki Kamiya 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Masayoshi Ten 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Takeshi Saito 1006 Kadoma Odoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (JP, A) JP-A-2-172192 (JP, A) JP-A-2-162696 (JP, A) JP-A-2-273497 (JP, A) (58) Fields investigated (Int. Cl. ⁶⁾ , DB name) H05B 41/14-41/29 H02M 7/48 G01R 19/165

Claims (4)

(57) [Claims] 1. A lamp voltage detecting circuit for detecting a differential voltage generated between both ends of a discharge lamp driven by an inverter circuit, and a differential amplifier for differentially amplifying the differential voltage detected by the lamp voltage detecting circuit. And a DC voltage detecting circuit comprising a rectifying unit for rectifying an output of the lamp voltage to obtain a DC voltage. 2. A lamp voltage detecting circuit for detecting a differential voltage generated between both ends of a discharge lamp driven by an inverter circuit, and a differential voltage detected by the lamp voltage detecting circuit is connected to a first diode via a diode. A current mirror circuit for obtaining a DC current corresponding to a current flowing through the first transistor by the differential voltage from the second transistor which is input to the collector and the emitter of the transistor and whose gate is connected to the gate of the first transistor; A lamp voltage detecting device comprising: 3. A lamp voltage detecting circuit for detecting a differential voltage generated between both ends of a discharge lamp driven by an inverter circuit, and a differential voltage detected by the lamp voltage detecting circuit is supplied to a first terminal via a diode bridge. Current mirror circuit that obtains a DC current corresponding to a current flowing through the first transistor by the differential voltage from the second transistor which is input to the collector and the emitter of the first transistor and whose gate is connected to the gate of the first transistor A lamp voltage detecting device comprising: 4. A lamp voltage detecting circuit for detecting a differential voltage generated between both ends of a discharge lamp driven by an inverter circuit, and the differential voltages detected by the lamp voltage detecting circuit are respectively connected to an emitter and a diode via diodes. A lamp voltage detecting device comprising: a transistor that is input to a gate and obtains a DC current corresponding to a current flowing through the emitter and the gate from the collector by the differential voltage from the collector.