JP2526108B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a circuit for stopping generation of a start pulse when a discharge lamp in a discharge lamp lighting device does not start and light.

[Prior Art] The circuit of FIG. 2 has been conventionally known as a discharge lamp lighting device.

In FIG. 2, the AC power source 10 is connected to the high frequency oscillation circuit section 14 via the AC / DC converter 12, and the high frequency oscillation circuit section 14 is connected.
A discharge lamp 16 is connected from the secondary side of 14 through a series circuit of a phase advancing capacitor C ₁ and a choke coil L ₁ . Further, a starting pulse generating circuit section 18 is connected in parallel to the discharge lamp 16, and the starting pulse generating circuit section 18 is a bidirectional two-terminal thyristor at a predetermined location and one end (on the side of the discharge lamp 16) of the choke coil L _1. A series circuit of sidac S _D and capacitor C _S is connected in parallel. Further, a series circuit of a diode D _S and a resistor R _{S1 in} the reverse direction (cathode on the Sidac side) is connected to the connection point between the sidac S _D and the capacitor C _S for generating the starting pulse.

To explain the operation of such a circuit, first, the AC power supply
The AC / DC converter 12 converts DC into DC, and the high frequency oscillation circuit unit 14 oscillates at a predetermined frequency. So in the first half-wave, through the resistor R _S1 and the diode D _S , the capacitor C
While charging _S , the phase advancing capacitor C ₁ is charged via the choke coil L ₁ . In the next half wave in the opposite direction, the electric charge charged in the phase advancing capacitor C ₁ cannot be discharged and the circuit state does not change. While repeating these steps, when the charging voltage of the capacitor C _S rises and reaches the breakover voltage of the sidac S _D , the capacitor C _S is discharged and the starting pulse voltage is applied to the discharge lamp 16 via the sidac S _D and the choke coil L _1. It is applied and turned on.

The discharge lamp device as described above is generally used because the circuit is simple and inexpensive, and as a method of preventing the rectification phenomenon of the lamp at the end of the lamp life, the current control circuit on the secondary side of the high frequency oscillation circuit is connected in series with LC. This is because the shape is preferable.

[Problems to be Solved by the Invention] By the way, as a method of increasing the terminal voltage of a capacitor for starting pulse generation in order to apply a sufficiently high voltage pulse to the discharge lamp 16, a resistor for current control is used in the starting pulse generation circuit section. It is conceivable to connect the lamps to the discharge lamp in parallel. According to this method, the terminal voltage of the capacitor for generating the start pulse can be increased to ensure the start lighting of the discharge lamp to some extent.

Here, when the discharge lamp 16 is turned on, the terminal voltage of the capacitor for generating the start pulse drops, and the pulse generation stops, but when the discharge lamp does not light due to a defective discharge lamp or the like, the pulse continues to be emitted. There are problems that the life of the starting pulse generating circuit is shortened and that high voltage pulses are generated when the discharge lamp is replaced, which is dangerous.

Therefore, the present invention has been made in view of the above problems, and if the discharge lamp does not start and light up within a certain period of time, the resistance connected by the resistance of the discharge lamp in parallel generates heat with time. It is an object of the present invention to provide a discharge lamp lighting device that stops charging a capacitor for generating a starting pulse when heat is generated above a predetermined value and starts charging the capacitor when cooled to below a predetermined value.

[Means for Solving the Problem] In order to solve the above-mentioned problems, the discharge lamp lighting device of the present invention generates heat when the resistance for current control generates heat above a predetermined value without the start of lighting of the discharge lamp. The focus is on detecting and stopping the charging of the capacitor for generating the starting pulse.

That is, the present invention includes an AC / DC converter, a high frequency oscillation circuit section, a series circuit of a phase advancing capacitor and a choke coil, a starting pulse generating circuit section including a starting pulse generating capacitor, and a discharge lamp. The starting pulse generating circuit section is provided with a current control resistor for discharging the charge of the phase advancing capacitor in parallel with the discharge lamp, and is connected to the starting pulse generating capacitor charging circuit. It has a reset type thermal protector close to the.

[Operation] In the discharge lamp lighting device of the present invention, the current control resistor is provided in parallel with the discharge lamp in the starting pulse generating circuit section including the capacitor for generating the starting pulse. As a result, the first half wave of the output to the high-frequency oscillation circuit section is charged into the phase advancing capacitor via the starting pulse generating capacitor of the starting pulse generating circuit section and the choke coil. In the next half-wave, the charging charge of the phase advancing capacitor is discharged through the choke coil and the current controlling resistor of the starting pulse generating circuit. By repeating this, the capacitor for generating the starting pulse is gradually charged and the terminal voltage rises.
Then, when the terminal voltage of the capacitor for generating the starting pulse reaches a predetermined value, the starting pulse is applied to the discharge lamp via a part of the choke coil to start lighting.

Further, the starting pulse generating circuit is provided with a reset type thermal protector which is connected to a charging circuit for a capacitor for generating the starting pulse and which is brought close to the current controlling resistor. As a result, when the discharge lamp does not illuminate at the start and the resistance heats up to a predetermined value or more, the thermal protector detects this and shuts off the charging circuit for the capacitor for generating the start pulse, and the high frequency oscillation circuit section 14 Since the resistor continues to generate heat during the operation of, the charging circuit continues to be cut off. On the other hand, when the high-frequency oscillator circuit section 14 stops operating due to turning off the power, etc., and the resistance cools below a predetermined value, the thermal protector recovers and allows the capacitor for starting pulse generation to be charged again. is there.

This makes it possible to prevent the resistance for current control from being damaged by heat generation even if the discharge lamp remains unlit.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a discharge lamp lighting device of the present invention. In FIG. 1, an AC power supply 110 is connected to an AC / DC converter 112.
Is connected to the discharge lamp 116 from the secondary side of the high frequency oscillation circuit section 114 via the series circuit of the phase advancing capacitor C ₁ and the choke coil L ₁ . Then, the starting pulse generating circuit unit 118 is connected to the discharge lamp 116 in parallel.

Here, in the starting pulse generating circuit unit 118, a current control resistor R _S2 is connected in parallel with the discharge lamp 116. In addition, the choke coil L _{1 has} a predetermined position and one end (the discharge lamp 116
Side) is a bi-directional two-terminal thyristor Sidac _SD
And a series circuit of a capacitor C _S for generating a starting pulse is connected in parallel, and a diode D _S in the reverse direction (cathode on the side of the sidac) is connected to the connection point between the sidac S _D and the capacitor C _S.
The charging circuit of the resistor R _S1 and the series circuit of the resettable thermal protector 120 in which the heat-sensitive portion is located close to the resistor R _S2 are connected.

Next, the operation of the above circuit will be described. First, AC power supply 11
0 is converted into direct current by the AC / DC converter 112 and input to the primary side of the high frequency oscillation circuit unit 114. High frequency oscillation circuit section 114
Is, for example, an inverter circuit using two transistors oscillates at a desired frequency (e.g., an audible frequency 20 kHz _Z or higher), and is outputted from the secondary side.

First, the thermal protector 12 which is conducting in the first half wave
The capacitor C _S for generating the starting pulse is charged through 0, the resistor R _S1 and the diode D _S , and the choke coil is also charged.
The phase advancing capacitor C ₁ is charged via L ₁ . In the next half-wave in the opposite direction, the charge of the phase advancing capacitor C ₁ is discharged via the choke coil L ₁ and the resistor R _S2 . This time,
Since the capacitor C _S is a diode D _S , the charge is not discharged and is maintained. Further, in the next half wave, the phase advancing capacitor C ₁ is charged again in the direction of the thermal protector 120, the resistor R _S1 , the diode D _S and the capacitor C _S , and the capacitor C _S is also charged again. The terminal voltage rises compared to the previous charge.

By repeating these cycles, capacitor C _S
The terminal voltage of is gradually increased, and the bidirectional two-terminal thyristor Sidac S _D is increased to the breakover voltage.
Then, when the sidac S _D breaks over, the charge stored in the capacitor C _S is charged to the sidac S _D and the choke coil.
The discharge is performed through a part of L ₁ , a start pulse is applied to the discharge lamp 116, and this is repeated to start and light the discharge lamp 116.

Here, the resistance R _S2 for current control is such that when the discharge lamp 116 is lit, its terminal voltage drops to the lamp voltage and heat generation hardly occurs, but during the starting operation of the discharge lamp 116, the secondary voltage of the high frequency oscillation circuit unit 114 Acts and heats up over time. Therefore, during the start cycle, if the discharge lamp 116 does not start lighting and continues for a certain period of time, the resistance R _S2 generates heat and the temperature gradually rises,
This is detected by the thermal protector 120 and the contact is turned off. When the contact of the thermal protector 120 is turned off, no current flows through the capacitor C _S for generating the start pulse and charging is stopped. Further, the resistor R _S2 is the high frequency oscillation circuit unit 1
Since the secondary voltage of 14 continues to act, the starting pulse generating circuit section 118 that is once in the off state is stopped until the power supply of this device is turned off and the secondary voltage of the high frequency oscillation circuit section 114 is in the off state. Keep doing

Next, when the secondary voltage of the high-frequency oscillation circuit unit 114 is turned off and the resistor R _S2 is cooled, the thermal protector 120 is restored and becomes conductive. And the starting pulse generation circuit section 11
8 becomes operable again, and when the power is turned on, the starting pulse is applied to the discharge lamp 116 by the above cycle. On the other hand, when the discharge lamp 116 is not lit, the above operation is repeated.

Then, when the discharge lamp 116 is turned on, the resistance R _S2 does not rise to the operating temperature of the thermal protector 120, so the thermal protector 120 does not operate and the start pulse stops in normal operation.

[Effects of the Invention] As is apparent from the above-described embodiments, according to the present invention, a resistor for current control is provided in parallel with the discharge lamp in the starting pulse generating circuit section, and a charging circuit for charging a capacitor for starting pulse generation. By providing a reset type thermal protector that is connected to the resistor and is close to the resistor, the thermal protector detects the temperature rise due to the heat generation of the resistor for current control that occurs when the discharge lamp is not lit and the start pulse generation circuit It is possible to stop the operation of the section, thereby shortening the life of the starting pulse generating circuit section and preventing the problem that a high voltage pulse is generated when the discharge lamp is replaced and is dangerous.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a discharge lamp lighting device of the present invention, and FIG.
FIG. 1 is a circuit diagram showing a conventional discharge lamp lighting device. 112 …… AC / DC converter 114 …… High-frequency oscillation circuit section 116 …… Discharge lamp 118 …… Starting pulse generation circuit section 120 …… Thermal protector R _S2 …… Resistance for current control

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-117690 (JP, A) JP-A-59-160998 (JP, A) JP-A-62-26790 (JP, A) JP-B-50- 22829 (JP, B2)

Claims (1)

(57) [Claims] 1. An AC / DC converter connected to an AC power source, and the A
A high-frequency oscillation circuit section for oscillating the output of the C / DC converter, a series circuit of a phase advancing capacitor and a choke coil connected to the secondary side of the high-frequency oscillation circuit section, and a part of the choke coil of the series circuit In a discharge lamp lighting device comprising a starting pulse generating circuit section including a starting pulse generating capacitor and a discharge lamp, a current for causing the starting pulse generating circuit section to discharge the charging charge of the phase advancing capacitor. Discharge lamp lighting characterized in that a resistance for control is provided in parallel with the discharge lamp, and a reset type thermal protector is provided which is connected to a charging circuit for the capacitor for generating the starting pulse and is close to the resistance. apparatus.