JPH04351894A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To provide a discharge lamp lighting device with which a circuit constitution is simplified, and of which reliability is improved. CONSTITUTION:A high frequency power is supplied to a discharge lamp FL by switching action of an electric field effect transistor Q11 and a transistor Q12. When the electric field effect transistor Q11 is turned off, an electromagnetic energy accumulated at a choke coil L11 is fed back to a pair of current bleeder capacitors C11, C12, and their outputs are superimposed and boosted. For dimming, or at a life end period of the discharge lamp FL, the electric field effect transistor Q11 is controlled by a separate excitation control circuit 13, and an output of an inverter circuit 12 is reduced and stopped.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device using a half-bridge type inverter circuit.

0003

2. Description of the Related Art Conventionally, a discharge lamp lighting device of this type has a configuration shown in FIG. 2, for example.

The discharge lamp lighting device shown in FIG. 2 has a commercial AC power source E1 connected to four diodes D1, D2, D3,
A full-wave rectifier circuit 1 consisting of D4 is connected. Two diodes D are connected to the output side of this full-wave rectifier circuit 1 via diodes D5, D6 and a choke coil L1.
A half-bridge type inverter circuit 3 consisting of transistors Q1 and Q2 and transistors Q1 and Q2 is connected thereto. Furthermore, voltage dividing capacitors C1 and C2 are connected in parallel to this inverter circuit 3.

Furthermore, these voltage dividing capacitors C1 and C2
Between the inverter circuit 3 and the inverter circuit 3, there are discharge lamps FL1,
A series circuit of the choke coil L2 and the input winding Tr1a of the control transformer Tr1 is connected, and the discharge lamp FL1
A starting capacitor C3 is connected in parallel to the starting capacitor C3.

Further, control circuits 4 and 5 for oscillation control are connected to each transistor Q1 and Q2 of the inverter circuit 3, respectively.

[0007] The control circuit 4 that controls the transistor Q1 has a control winding Tr1b of a control transformer Tr1.
Resistance R1, R2, R3, capacitor C4, diode D
9, D10, a transistor Q3, and a phototransistor PTr1. Similarly, the control circuit 5 that controls the transistor Q2 connects the control winding Tr1c of the control transformer Tr1 to the resistors R4, R5,
R6, capacitor C5, diode D11, D12
, transistor Q4 and phototransistor PTr2
It consists of

[0008] The commercial AC power source E1 is full-wave rectified by the full-wave rectifier circuit 1, and the transistors Q1 and Q2 are alternately turned on and off repeatedly through the control circuits 4 and 5 to discharge high-frequency power. Turn on lamp FL1.

Furthermore, when the discharge lamp FL1 is dimmed or at the end of its life, the phototransistors PTr1,
PTr2 is operated by a photocoupler (not shown),
By controlling transistors Q3 and Q4, transistor Q1
, Q2 by changing the bias current of the inverter circuit 3.
It controls the output of

0010

However, in the case of the configuration shown in FIG. 2, the transistors Q1 and Q2 of the inverter circuit 1 are controlled by separate control circuits 4 and 5, so the circuit configuration is complicated. The number of parts is large,
The switching operation control of the two transistors Q1 and Q2 is poor, which causes heat generation due to switching loss and tends to cause destruction.When the oscillation is stopped, external noise causes abnormal oscillation, which easily causes the destruction of transistors Q1 and Q2. .

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a discharge lamp lighting device that has a simplified circuit configuration and improved reliability.

[Configuration of the invention]

[0013]

[Means for Solving the Problems] The discharge lamp lighting device of the present invention includes a full-wave rectifier circuit connected to an AC power supply, a choke coil connected to the full-wave rectifier circuit, and at least one coil connected to the choke coil. A half-bridge type inverter circuit that has a pair of switching elements and a pair of DC dividing capacitors and lights up a discharge lamp with high-frequency power; The device includes a feedback circuit for feeding back to the pair of DC split capacitors, and a control circuit for separately excitation control of the switching element.

[0014]

[Operation] According to the present invention, high frequency power is supplied to the discharge lamp by the switching operation of the switching element to light the discharge lamp. When one switching element is turned off, the energy stored in the choke coil is fed back to the pair of DC voltage dividing capacitors, and the output is superimposed and boosted. Further, for example, in the event of an abnormality, the control circuit controls the switching elements by separately excitation control to stop the oscillation of the inverter circuit.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the discharge lamp lighting device of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a commercial AC power source E11
A full-wave rectifier circuit 11 for full-wave rectification consisting of a diode bridge is connected to. A half-bridge inverter circuit 12 consisting of two diodes D22 and D23 and a field effect transistor Q11 and a transistor Q12 as switching elements is connected to the output side of the full-wave rectifier circuit 11 via a diode D21 and an inductor L11. has been done. Also, in parallel to this inverter circuit 12, a DC dividing capacitor C1
1 and C12 are connected.

Furthermore, these DC dividing capacitors C11
, C12 and the inverter circuit 12 are connected a series circuit consisting of discharge lamps FL11, FL12, a primary winding Tr11a serving as a choke coil of the transformer Tr11, and an input winding CTa of the current transformer CT serving as a feedback circuit. A starting capacitor C13 is connected in parallel to the lamp FL12, and the discharge lamps FL11,
A capacitor C14 is connected between both ends of FL12,
A transformer Tr11 is installed between the discharge lamps FL11 and FL12.
A secondary winding Tr11b is connected to the secondary winding Tr11b.

Further, the secondary winding Tr11b of the transformer Tr11 and the input winding CTa of the current transformer CT are connected to the gate of the field effect transistor Q11 of the inverter circuit 12, and an astable multivibrator to which the dimming signal is input is connected. Separately excited control circuit 13 having an oscillator such as
is connected. Furthermore, the output winding CTa of the current transformer CT is connected to the base of the transistor Q12 via a resistor R11 and a capacitor C15.

Next, the operation of the above embodiment will be explained.

First, when the commercial AC power source E11 is turned on, the full-wave rectifier circuit 11 performs full-wave rectification, and the choke coil L1
1 and the inverter circuit 12 via the diode D21.

Here, when the field effect transistor Q11 is turned on by the separately excited control circuit 13, the full-wave rectifier circuit 1
A chopping current flows from the positive output terminal of No. 1 to the negative output terminal of No. 1 through the choke coil L11, diode D21, and field effect transistor Q11. As a result, electromagnetic energy is stored in the choke coil L11.

Furthermore, a pair of DC dividing capacitors C11
, C12, a voltage is applied through diodes D21, D23, and the voltage is applied to two DC dividing capacitors C.
11 and C12.

When the field effect transistor Q11 is turned off, the electromagnetic energy stored in the choke coil L11 is transferred to the DC dividing capacitors C11, C12 through the closed circuit of the diode D21, the DC dividing capacitors C11, C12, and the choke coil L11. released.

[0024] As a result, the DC dividing capacitor C11
, C12 is superimposed on the electromagnetic energy from the choke coil L11, and the voltage across the DC dividing capacitors C11, C12 is boosted. That is, choke coil L11, diode D21
A series closed loop circuit consisting of the DC voltage dividing capacitors C11 and C12 functions as a boost chopper circuit.

Next, when the transistor Q12 is turned on, the inverter circuit 12 operates in oscillation using the DC dividing capacitors C11 and C12 as power sources.

When the inverter circuit 12 operates and the field effect transistor Q11 is turned on, the combined current of the chopping current of the full-wave rectifier circuit 11 and the current caused by the inverter operation of the inverter circuit 12 flows into the field effect transistor Q11. flows.

The separately excited control circuit 13 also controls the oscillation frequency of the field effect transistor Q11 according to the dimming signal.

Furthermore, the separately excited control circuit 13 detects the power supply voltage, and when an abnormal surge or the like is detected, performs dimming control to protect the field effect transistor Q11 and the transistor Q12.

Furthermore, the separately excited control circuit 13 detects the output of the secondary winding Tr11b of the transformer Tr11, detects the end of the life of the discharge lamp, and switches the field effect transistor Q.
11 and transistor Q12 to stop oscillation.

In the above embodiment, a field effect transistor is used as the switching element, but similar functions and effects can be obtained by using a bipolar transistor.

[0031]

[Effects of the Invention] According to the discharge lamp lighting device of the present invention,
High frequency power is supplied to the discharge lamp by the switching operation of the switching element to light the discharge lamp. When one switching element is turned off, the energy stored in the choke coil is fed back to the pair of DC voltage dividing capacitors, and the output is superimposed and boosted. In the event of an abnormality or dimming, the control circuit controls the switching elements by separately excitation control to stop the oscillation of the inverter circuit, so reliability can be improved with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting device of the present invention.

FIG. 2 is a circuit diagram showing a conventional discharge lamp lighting device.

[Explanation of symbols]

11 Full-wave rectifier circuit 12 Inverter circuit 13 Separately excited control circuit C11, C12 DC split capacitor CT
Current transformer FL11, FL as a feedback circuit
12 Discharge lamp L11 Choke coil

Claims (1)

[Claims] Claim 1: A full-wave rectifier circuit connected to an AC power supply, a choke coil connected to the full-wave rectifier circuit, at least one pair of switching elements and a pair of DC dividing capacitors connected to the choke coil. a half-bridge inverter circuit that lights a discharge lamp with high-frequency power; a feedback circuit that returns the charge stored in the choke coil to the pair of DC dividing capacitors when the one switching element is off; A discharge lamp lighting device characterized by comprising a control circuit for separately excitation control of a switching element.