JPH09223591A - Discharge lamp lighting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect an output electric current of a DC power source circuit in a discharge lamp lighting circuit having an electric current detecting resistance to detect its output electric current and a lighting assisting circuit to assist lighting at starting time of a discharge lamp in the rear stage of the DC power source circuit. SOLUTION: A discharge lamp lighting circuit 1 has a DC power source circuit 3 and a DC AC converting circuit 4, and an electric current detecting resistance 6 and a lighting assisting circuit 7 are arranged between these. The lighting assisting circuit 7 is composed of a resistance 9, a capacitor 10 and a switch element 11, and one end of the resistance 9 is connected to a connecting line L(+) between the DC power source circuit 3 and the DC-AC converting circuit 4, and the other end of the resistance 9 is connected to a connecting line L(-) between the DC power source circuit 3 and the DC-AC converting circuit 4 through the capacitor 10. The switch element 11 which is turned off at charging time of the capacitor 10 and is turned on at discharging time of the capacitor 10, is arranged in parallel to the resistance 9, and the electric current detecting resistance 6 is arranged between a connecting point to a line L(+) of the resistance 9 and a connecting point to a line L(+) of the switch element 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting including a current detecting resistor for detecting an output current of a DC power supply circuit and a circuit for assisting lighting of the discharge lamp at the time of starting the discharge lamp. It is about circuits.

[0002]

2. Description of the Related Art Recently, a small discharge lamp (for example, a metal halide lamp) has been attracting attention as a light source which replaces an incandescent light bulb. A device including a power supply, a DC power supply circuit, a DC-AC conversion circuit, a starting circuit, etc. is known.

In the circuit example a shown in FIG. 8, a DC voltage supplied from a DC power supply (not shown) to the DC power supply circuit b is converted into an AC voltage by a DC-AC conversion circuit c provided in a subsequent stage of the DC power supply circuit b. It is configured to be supplied to the discharge lamp after being discharged.

The circuit d provided between the DC power supply circuit b and the DC-AC conversion circuit c is provided to assist the operation delay of the DC power supply circuit b at the moment of breakdown at the time of starting the discharge lamp. Is a circuit including a capacitive load such as a capacitor, and one end of which is a connection line connecting the positive output terminal of the DC power supply circuit b and the input terminal of the DC-AC conversion circuit c (L (+) in the figure). Is connected to the negative side output terminal of the DC power supply circuit b and the DC-AC conversion circuit c.
Is connected to a connection line (indicated by L (-) in the figure) that connects to the input terminal of.

In providing a current detection resistor for detecting the output current of the DC power supply circuit b in this circuit a, for example, when the current detection resistor is arranged on the connection line L (-), the current detection resistor is used. It is conceivable that the resistance e is provided near the DC power supply circuit b, or conversely, the current detection resistance e ′ is provided near the DC-AC conversion circuit c.

[0006]

By the way, in the circuit a as described above, since the charging current and the discharging current in the circuit d flow into the current detecting resistors e and e ', the accuracy of the current detection is improved. There is a problem that it is difficult to meet.

That is, in FIG. 8, when a charging current for the capacitive load in the circuit d (this is referred to as "Ic") flows, this flows through the current detecting resistor e, and also the capacitive load. When the discharge current (for this is referred to as “Id”) flows through the current detection resistor e ′, a pure detection current for the DC power supply circuit b cannot be obtained. .

Therefore, for example, when the electric power of the discharge lamp is controlled based on the detected current related to the output current of the DC power supply circuit b, the electric power supplied to the discharge lamp is insufficient or the detected current is When detecting an abnormality in the discharge lamp or the circuit on the basis of the above, there is a possibility that an inconvenience may occur such that the probability of erroneous detection increases.

An object of the present invention is to accurately detect a current related to an output current of a DC power supply circuit.

[0010]

In order to solve the above-mentioned problems, a discharge lamp lighting circuit according to the present invention is provided with a DC power supply circuit and a DC-circuit.
A lighting auxiliary circuit including a current detection resistor for detecting the output current of the DC power supply circuit and a capacitive load for assisting the lighting of the discharge lamp at the time of starting the discharge lamp, on the connection line connecting to the AC conversion circuit. In order to form a bypass path, the charging current of the capacitive load before starting the discharge lamp and / or the discharging current of the capacitive load during starting the discharge lamp does not flow to the current detection resistor. The switch means is provided.

According to the present invention, the charging current of the capacitive load before starting the discharge lamp and / or the discharging current of the capacitive load at startup of the discharge lamp is detected by the bypass path formed by the switch means. Can be prevented from flowing.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to FIGS.

FIG. 1 shows the configuration of a discharge lamp lighting circuit 1 according to the present invention, which includes a power supply 2, a DC power supply circuit 3, and a DC-
The AC conversion circuit 4, the starting means 5, the current detection resistor 6, and the lighting auxiliary circuit 7 are provided.

The DC power supply circuit 3 is provided for controlling the lighting of the discharge lamp 8 based on the AC or DC power supply voltage supplied from the power supply 2, and its output (DC conversion in the case of an AC power supply). The latter output) is sent to the DC-AC conversion circuit 4 in the subsequent stage and converted into an AC voltage there, and the post discharge lamp 8
Is supplied to.

The starting means 5 is provided to generate a starting signal at the initial stage of lighting the discharge lamp 8 to start the discharge lamp 8.

The current detecting resistor 6 for detecting the output current of the DC power supply circuit 3 is a positive side line (this is L (+) of the connecting lines connecting the DC power supply circuit 3 and the DC-AC conversion circuit 4). On the negative line (this is L (-)
And ) Is provided. The current detected by the current detecting resistor 6 is used as a current corresponding to the tube current of the discharge lamp 8 for controlling the output voltage of the DC power supply circuit 3, or the lighting state of the discharge lamp 8 or the operating state of the circuit is abnormal. It is used as basic information for detecting whether or not the occurrence has occurred.

The auxiliary lighting circuit 7 includes a DC power supply circuit 3 and a DC-
It is provided between the AC conversion circuit 4 and the energy stored in the capacitive load provided in the auxiliary lighting circuit 7 at the moment when the discharge lamp 8 is activated by the activation signal generated by the activation means 5. By supplying to the discharge lamp 8, the glow discharge is assisted so that the arc discharge is surely performed.

FIG. 2 shows an equivalent circuit of the auxiliary lighting circuit 7 and the discharge lamp 8, and shows an example in which the current detecting resistor 6 is provided on the connection line L (+). In the figure, the discharge lamp 8 is represented by a series circuit of a switch SW and a resistor R. Before the discharge lamp 8 is activated, the switch SW is open, and after activation, the switch SW is closed and a current ( IL ”) will flow.

As shown in the figure, the auxiliary lighting circuit 7 includes a resistor 9 indicating a resistive load, a capacitor 10 indicating a capacitive load,
It is composed of switch elements 11 and 11 ', one end of the resistor 9 is connected to the connection line L (+), and the other end is the capacitor 1
It is connected to the connection line L (-) via 0. Then, the switch element 11 ′ includes the current detection resistor 6 and the resistor 9
The switch element 11 is provided in parallel with the resistor 9.

The switch element 11 'is turned on when the capacitor 10 is charged and turned off when the capacitor 10 is discharged, and the switch element 11 is turned off when the capacitor 10 is charged and turned on when the capacitor 10 is discharged. Therefore, the switch elements 11 and 11 'are turned off except when the capacitor 10 is being charged or discharged. For these switch elements, for example, two-terminal unidirectional elements (diodes, thyristors, etc.) and semiconductor switch elements such as transistors are used.

However, in this circuit, the switch SW is open before the discharge lamp 8 is started, and the switch element 11 'is used.
Is turned on and the switch element 11 is turned off, so that the charging current of the capacitor 10 (this is referred to as "Ic") flows through the switch element 11 ', and Ic flows through the current detection resistor 6. There is no. Further, when the discharge lamp 8 is started, the switch SW is closed, the switch element 11 'is turned off, and the switch element 11 is turned on.
The discharge current (referred to as "Id") of 6 flows through the switch element 11 to the discharge lamp 8, and Id does not flow through the current detection resistor 6.

The circuit structure can be simplified by forming the switch means with one switch element as shown in FIGS. 3 and 4 instead of forming the switch means with two switch elements as described above. it can.

3 and 4 show another equivalent circuit for the auxiliary lighting circuit 7 and the discharge lamp 8. FIG. 3 shows an example in which the current detecting resistor 6 is provided on the connection line L (+). 4 shows an example in which the current detection resistor 6 is provided on the connection line L (−).

The auxiliary lighting circuit 7 shown in FIG. 3 comprises a resistor 9 showing a resistive load, a capacitor 10 showing a capacitive load, and a switch element 11, one end of the resistor 9 being a connection line L.
It is connected to (+) and the other end is connected to the connection line L (−) via the capacitor 10. The switch element 11 is provided in parallel with the resistor 9, and the current detection resistor 6 is connected to the connection point L (+) of the resistor 9 and the connection line L (+) of the switch element 11. It is provided between the connection point. The switch element 11 is turned off when the capacitor 10 is charged and turned on when the capacitor 10 is discharged.

In this circuit, however, since the switch SW is open and the switch element 11 is off before the discharge lamp 8 is started, the charging current Ic of the capacitor 10 flows through the resistor 9. , Ic is the current detection resistor 6
Never flows through.

When the discharge lamp 8 is activated, the switch SW
Since the switch element 11 is closed and the switch element 11 is turned on, the discharge current Id of the capacitor 10 flows to the discharge lamp 8 through the switch element 11, and Id does not flow to the current detection resistor 6.

In the auxiliary lighting circuit 7 shown in FIG. 4, one end of the capacitor 10 is connected to the connection line L (+),
The other end is connected to the connection line L (−) via the resistor 9. The switch element 11 is provided in parallel with the resistor 9, and the current detection resistor 6 is connected to the connection point L (−) of the resistor 9 and the connection line L (−) of the switch element 11. It is provided between the connection point.

Therefore, in this circuit, since the switch SW is open and the switch element 11 is off before the discharge lamp 8 is started, the charging current Ic of the capacitor 10 flows through the resistor 9 and Ic becomes It does not flow through the current detection resistor 6. Further, when the discharge lamp 8 is started, the switch SW is closed and the switch element 11 is turned on, so that the capacitor 10
Discharge current Id flows to the discharge lamp 8 through the switch element 11, and Id does not flow to the current detection resistor 6.

As described above, the resistor 9 is replaced by the current detecting resistor 6
Is provided closer to the DC power supply circuit 3, and the switch element 11 is provided closer to the DC-AC conversion circuit 4 than the current detection resistor 6, so that the switch element 11 is turned off when the capacitor 10 is charged, If the switch element 11 is turned on at the time of discharging to form a bypass path for the discharge current to the current detection resistor 6, the occurrence of a detection error due to the charging current and the discharge current related to the capacitor 10 flowing to the current detection resistor 6 occurs. Can be prevented.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 5 to 7 show an example of the implementation of the present invention.

In the lighting circuit 12, a battery 13 corresponding to the power source 2 is connected between the input terminals 14 and 14 ', and lights on one line 15 of the DC power lines 15 and 15' as a manual switch. A switch 16 is provided.

The DC power supply circuit 17 to which the battery voltage is input raises and / or lowers the battery voltage and sends the output to the DC-AC converter circuit 18.
In the present embodiment, a transformer 17a and a semiconductor switch element 17b on the primary side thereof are provided, and a secondary side output of the transformer 17a is configured to be output via a rectifying / smoothing circuit 17c. However, the configuration of the DC power supply circuit 17 does not matter.

The DC-AC conversion circuit 18 for converting the DC output voltage of the DC power supply circuit 17 into an AC voltage is, for example, a bridge type composed of a plurality of pairs of semiconductor switch elements arranged on the power supply path to the discharge lamp 20. A circuit or the like and a drive control circuit thereof may be used, and the DC-AC converting circuit 18 may have any structure for converting a DC voltage into a sine wave voltage, a rectangular wave voltage, or the like. .

The igniter circuit 19 arranged at the subsequent stage of the DC-AC conversion circuit 18 generates an activation signal for the discharge lamp 20 and superimposes it on the output of the DC-AC conversion circuit 18, and then the AC output terminal 21. And 21 ', which is a circuit for applying to the discharge lamp 20 connected between them and corresponds to the above-mentioned starting means 5.

DC power supply circuit 17 and DC-AC conversion circuit 1
The auxiliary lighting circuit 7A provided between the switch 8 and the switch 8 has a configuration in which the diode 22 is used as the switch element 11 in FIG. 3 (the discharge current of the capacitor 10 is in the forward direction of the diode 22). The current detection resistor 6 is arranged on the positive side connection line connecting the DC power supply circuit 17 and the DC-AC conversion circuit 18.

The detection signal from the current detection resistor 6 is sent to the control circuit 23 and the abnormality detection circuit 24.
The output voltage of the DC power supply circuit 17 is detected by the control circuit 23.
And the detection means (voltage dividing resistor, etc.) in the abnormality detection circuit 24.

The control circuit 23 generates a control signal corresponding to the detection signal relating to the output voltage or output current of the DC power supply circuit 17 and sends it to the DC power supply circuit 17 to control the output voltage ( In the example of the figure, switching control of the semiconductor switch element 17b is performed.), Power control according to the state of the discharge lamp 20 at the time of starting, or stable steady lighting is realized. In the control circuit 23, the current detection resistor 6
The detection signal by is used for control for supplying electric power exceeding the rated power at the time of starting the discharge lamp 20 to promote light emission to improve startability, and for constant power control during steady lighting of the discharge lamp 20. , Is used as basic information for determining whether or not the discharge lamp 20 is lit. still,
The control circuit 23 may have a pulse width modulation type configuration or the like, but the configuration does not matter.

The abnormality detection circuit 24 is used for the discharge lamp, the circuit state,
The discharge lamp 20 is provided to detect an abnormality such as a battery voltage value, and when an abnormality is detected based on a detection signal related to the output voltage or output current of the DC power supply circuit 17 or a detection signal of the battery voltage. To stop the power supply to. In the figure, the power supply to the discharge lamp 20 is stopped by stopping the operation of the auxiliary power supply circuit 25 that supplies the power supply voltage (Vcc1) necessary for the control circuit 23, the DC-AC conversion circuit 18, and the like. Stop the power supply from the battery 13 to the DC power supply circuit 17,
Alternatively, a method of stopping the power supply to the discharge lamp by stopping the operation of the DC-AC conversion circuit 18 or the like can be used.

In FIG. 6, the horizontal axis indicates time t, and the vertical axis indicates the output voltage of the DC power supply circuit 17 (this is referred to as "Vdc") and the charging current Ic of the capacitor 10 in the auxiliary lighting circuit 7.
And an example of a temporal change of the discharge current Id, and time t = tb is a time point when the discharge lamp is turned on.

As shown in the figure, before starting the discharge lamp (t <t
The output voltage Vdc is large in b), and the capacitor 10 is slowly charged. During this period, the charging current Ic gradually decreases, but as described above, Ic does not flow to the current detection resistor 6.

When the discharge lamp is activated, the impedance of the discharge lamp is suddenly reduced.
But once it plummeted, it gradually increased. The energy stored in the capacitor 10 before starting the discharge lamp is released from the starting time with a time constant defined by the impedance of the discharge lamp and the capacitance of the capacitor 10, and this is consumed by the discharge lamp, so that the discharge lamp is consumed. The transition from 20 glow discharge to arc discharge is reliably performed. Since the diode 22 is in the conducting state during this period, the discharge current Id
Does not flow through the current detection resistor 6.

The circuit configuration as shown in FIG. 5 is merely an example of the embodiment of the present invention. For example, as shown in FIG. 7, the configuration in which the switch element 11 is replaced by the diode 22 in FIG. 4 (the discharge current of the capacitor 10) is used. Is set to the forward direction of the diode 22.), a configuration in which a resistor 26 is inserted between the capacitor 10 and the connection line L (+), and various other embodiments are possible.

[0043]

As is apparent from what has been described above, according to the invention of claim 1, the charging current of the capacitive load before starting the discharge lamp and / or the capacitive load when starting the discharge lamp. Since the bypass path is formed by the switch means so that the discharge current of (1) does not flow into the current detecting resistor, the output current of the DC power supply circuit can be accurately detected by the current detecting resistor.

According to the second aspect of the invention, the auxiliary lighting circuit is composed of a resistive load, a capacitive load, and one switch element, and the connection relationship among the three parties and the DC power supply circuit and the DC-AC conversion are performed. By defining the arrangement with respect to the circuit, only one switch element needs to be used as the switch means, and the circuit configuration is simplified.

According to the inventions of claims 3 and 4,
When the switch element is a two-terminal unidirectional element, or the resistive load and the capacitive load are a resistive element and a capacitor, respectively, the auxiliary lighting circuit can have a simple structure.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an outline of a configuration of a discharge lamp lighting circuit of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of a lighting auxiliary circuit and a discharge lamp.

FIG. 3 is a diagram showing an equivalent circuit different from that of FIG. 2, in which one of the connection lines connecting the DC power supply circuit and the DC-AC conversion circuit is used for current detection on one connection line L (+). A circuit for arranging resistors is shown.

FIG. 4 is a diagram showing an equivalent circuit different from that of FIG. 2, in which a circuit for arranging a current detection resistor on a connection line L (−) connecting a DC power supply circuit and a DC-AC conversion circuit. Indicates.

5 shows an example of an embodiment of the present invention together with FIGS. 6 and 7, and is a circuit diagram.

FIG. 6 is a graph for explaining the operation of the auxiliary lighting circuit of FIG.

FIG. 7 is a circuit diagram of a main part showing a modified example of a lighting auxiliary circuit.

FIG. 8 is a diagram for explaining a conventional problem.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge lamp lighting circuit, 3 ... DC power supply circuit, 4 ... DC-AC conversion circuit, 5 ... Starting means, 6 ... Current detection resistor, 7 ...
Lighting auxiliary circuit, 7A ... Lighting auxiliary circuit, 8 ... Discharge lamp, 9 ...
Resistive load, 10 ... Capacitive load, 11 ... Switch element,
11, 11 '... switch means, 12 ... discharge lamp lighting circuit,
17 ... DC power supply circuit, 18 ... DC-AC conversion circuit, 19
... igniter circuit (starting means), 20 ... discharge lamp, 22 ...
Diode (2-terminal unidirectional element)

Claims (4)

[Claims] 1. A DC power supply circuit, a DC-AC conversion circuit for converting an output voltage of the DC power supply circuit into an AC voltage and supplying the AC voltage to a discharge lamp, and a starting means for generating a start signal to the discharge lamp. In the discharge lamp lighting circuit, a current detection resistor provided on the connection line that connects the DC power supply circuit and the DC-AC conversion circuit to detect the output current of the DC power supply circuit, and the discharge lamp A lighting auxiliary circuit for assisting lighting is provided, wherein the lighting auxiliary circuit comprises a capacitive load and a charging current of the capacitive load before starting the discharge lamp and / or a discharging current of the capacitive load when starting the discharge lamp. And a switch means for forming a bypass path so that the current does not flow into the current detection resistor. 2. The discharge lamp lighting circuit according to claim 1, wherein the lighting auxiliary circuit has a resistive load, a capacitive load and one switch element, and the resistive load and the switch element are connected in parallel with each other. ,
A capacitive load is connected in series to these, the resistive load is located closer to the DC power supply circuit than the current detection resistor, and the switch element that is turned on when the capacitive load is discharged is the current A discharge lamp lighting circuit, characterized in that it is positioned closer to a DC-AC conversion circuit than a detection resistor. 3. The discharge lamp lighting circuit according to claim 2, wherein a unidirectional element having two terminals is used as a switch element. 4. The discharge lamp lighting circuit according to claim 1, 2 or 3, wherein the auxiliary load circuit has a resistive load as one resistance element and a capacitive load as one capacitor. Discharge lamp lighting circuit characterized in that.