KR940007025Y1 - Over current compensation circuit of electronic stabilizer for discharge lamp - Google Patents

Abstract

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Description

Overcurrent automatic compensation circuit of electronic ballast for discharge lamp

The accompanying drawings are embodiments of the present invention.

* Explanation of symbols for main parts of the drawings

3: load transformer L ₂ : secondary coil

5: rectification part 6: trigger part

7 driver D ₈ , D ₁₅ , -D ₁₉ : diode

ZD: Zener Diodes R ₃ , R ₄ , R _12- R ₁₇ : Resistance

C ₇ -C ₉ : Capacitor TR ₃ : Transistor

SR: SCR

The present invention relates to an overcurrent automatic compensation circuit of an electronic ballast for a discharge lamp, and more particularly, to an overcurrent automatic compensation circuit for preventing damage to an oscillation element by automatically stopping a high frequency oscillation function when an overcurrent flows due to an abnormality in a ballast circuit or a discharge lamp. will be.

Electronic ballasts for discharge lamps, unlike general transformer ballasts, apply high frequency (ultrasound) oscillation. However, such an electronic ballast for the discharge lamp is an abnormal operation of the circuit or when the load, that is, the discharge lamp is broken open to the open state because the oscillator circuit operates abnormally to increase the circuit current rapidly. It has the disadvantage of being broken.

An object of the present invention is to solve the above disadvantages, the overcurrent of the electronic ballast for the discharge lamp to prevent the damage of the oscillation element by stopping the operation of the oscillation circuit automatically when the overcurrent flows to the circuit due to circuit failure or load opening It is to provide an automatic compensation circuit.

In order to achieve the above object, the circuit of the present invention includes a power supply unit for converting an input AC voltage into a DC voltage, an oscillation unit having a high frequency oscillation function by driving the output of the power supply unit, and a load transformer connected between the oscillation unit and a discharge lamp. And a secondary coil installed in the load transformer, a rectifying unit for rectifying and smoothing the voltage induced in the secondary side coil, a trigger unit for operation controlled according to an output voltage level of the rectifying unit, and a trigger unit for outputting a trigger signal. And a driver for driving control by the trigger signal of the trigger unit to stop the operation of the oscillator.

Hereinafter, the specific configuration and operation effects of the present invention circuit will be described in detail by the accompanying drawings.

In an embodiment of the present invention, the rectifier 5 bridge diode (D ₁₆ -D ₁₉ ), the smoothing capacitor (C ₉ ) for rectifying the induced voltage of the secondary side coil (L ₂ ) of the load transformer (3) ) And a resistor (R ₁₇ ), the operation of which is controlled by a voltage applied through the zener diode (ZD ₁ ), which is connected to the output terminal of the rectifier (5), and the zener diode (ZD ₁ ). And a transistor (TR ₃ ), a bias resistor (R ₁₃ -R ₁₆ ) and a capacitor (C ₇ ) (C ₈ ) for outputting a trigger signal through the emitter output terminal.

On the other hand, the driving unit 7 is triggered by the output of the trigger unit 6, SCR (SR), diodes connected to bypass the base voltage of the oscillation transistor TR ₁ in the oscillation unit 2 to ground (D ₈ ) and a resistor (R ₃ ) (R ₄ ).

1 is the power supply, 3 is the load transformer, 4 is the discharge lamp, D ₁ -D ₁₄ . D ₁₉ . D ₂₀ is a die, DAC is a die solution, TR ₂ is a transistor, R ₁ -R ₁₆ , R ₁₈ is a resistor, C ₁ -C ₆ , C ₁₀ -C ₁₃ is a capacitor, CHC is an oscillating coil, TN is a surge protection TNR, FS is a fuse, TH is a thermistor, and FT is a noise filter.

In the present invention configured as described above, the input AC 220V voltage is rectified by the bridge diodes D ₁ -D ₄ in the power supply unit 1 to become a DC voltage, and then supplied to each circuit part. 2) The capacitor C ₆ is charged through the resistor R ₁₁ . The diodes D ₅ -D ₇ and the capacitors C ₂ and C _{3 in the} power supply unit 1 are circuits for improving the power factor when converting AC power to DC.

The voltage charged at both ends of the capacitor C ₆ is supplied to the base of the transistor TR ₂ through the die solution DAC so that the transistor TR ₂ is “turned on”, and thus the transistor TR ₂ The collector current passes through the LC resonance capacitor C ₁₄ , the discharge lamp 4, and the primary coil L ₁ of the load transformer 3, and then again the first coil La of the oscillation coil CHC in the oscillator 2. ), The transistor TR ₂ and the resistor R ₁₀ . The current flowing through the first coil La causes the voltage to be induced to the second coil Lb and the third coil Lc, and the polarity of the induced voltage is based on the base side of the transistor TR ₂ . The second coil Lb becomes the positive electrode and the third coil Lc becomes the negative electrode.

Thus while such conditions as the base voltage of the transistor (TR ₂₎ gradually decreases in the transistor (TR ₂₎ and "turn-off", is the instantaneous current flowing into the base of the transistor (TR ₁₎ and the transistor (TR ₁₎ " Turn on ". Thus, the current flows through the transistor TR ₁ , the resistor R ₇ , the first coil La, the primary coil L ₁ of the load transformer 3, the discharge lamp 4, and the resonant capacitor C _15. In this case, the current flowing through the first coil La causes the voltages of the negative pole and the positive pole to the second coil Lb and the third coil Lc, respectively.

In this state, the transistor TR ₁ is "turned off" by the same circuit operation as described above, while the transistor TR ₂ is "turned on" again, and the oscillation is performed by continuously repeating this circuit operation. The discharge lamp 4 lights up.

On the other hand, if an abnormality occurs in the ballast circuit or the discharge lamp 4 is broken and the load (that is, the discharge lamp) is opened, the oscillation part 2 may have an unbalanced circuit due to entangled circuit balance. As a result, the current rapidly increases.

The rapidly increased current flows through the primary coil L _{1 of} the load transformer 3 to increase the voltage across the coil L ₁ , and accordingly, the secondary coil of the load transformer 3 ( The induced voltage of L ₂ ) is also increased. The voltage across the secondary coil (L ₂₎ is filled there is a diode bridge and then rectified to a DC voltage by (D ₁₅ -D _18), a capacitor (C ₉₎ in the rectifying section (5) of the capacitor (C ₉₎ The charging voltage is about 7 times (about 75V) compared to the normal state (about 11V).

Since the charging voltage of the capacitor C ₉ is higher than the zener voltage of the zener diode ZD in the trigger unit 6 (which is set to about 15V in this embodiment), the resistor R16 is passed through the zener diode ZD. The voltage is applied to both ends of the resistor R ₁₆ except for the zener voltage 15V. Since the voltage across the resistor R ₁₆ is charged to the capacitor C ₈ and applied to the base of the transistor TR ₃ through the resistor R ₁₅ , the transistor TR ₃ is "turned on" so that its collector current is reduced. The capacitor C ₇ is charged.

The charging voltage of the capacitor C ₇ is supplied to the gate of the SCR SR in the driving unit 7 through the resistor R ₁₃ and the diode D ₁₄ to trigger the SCR SR. Since SR is "turned on" and a current flows, a voltage drop occurs across the resistor R ₃ and its anode voltage is zero. Thus, the base voltage of the transistor TR ₁ in the oscillator 2 is bypassed to ground through the resistor R ₄ , the diode D ₈ and the SCR SR, whereby the transistor TR is turned off. The oscillation element is turned off and the oscillation is stopped so that the oscillation current does not flow and maintains the circuit stability. That is, the breakage of the transistors TR ₁ and TR ₂ can be prevented.

On the other hand, when the ballast circuit or the discharge lamp 4 is in a normal state, the current flowing through the primary coil L ₁ of the load transformer 3 is a normal current, not an overcurrent, and at this time, the secondary coil L ₁ Since the voltage charged in the capacitor C ₉ in the rectifying section 5 is about 11V as described above, it is smaller than the Zener voltage (about 15V) of the zener diode ZD in the trigger section 6. ₃ ) becomes the "off" state. Therefore, the trigger signal is not output through the trigger unit 6, and thus the SCR (SR) in the drive unit 7 is also maintained in the "off" state, so that there is no influence on the operation of the transistor TR _{1 in the} oscillation unit 2. Will not give.

As described above, the overcurrent automatic compensation circuit of the present invention does not operate during normal operation of the ballast circuit, and operates only when a sudden overcurrent flows due to abnormality in the ballast circuit or discharge, thereby stopping the high frequency oscillation function to stabilize the ballast circuit. In addition to maintaining the there is an advantage to prevent the damage of the oscillation element.

Claims (4)

A power supply unit 1 for converting an input AC voltage into a DC voltage, an oscillation unit 2 having a high frequency oscillation function using the output of the power supply unit 1 as a driving power source, and connected between the oscillation unit 2 and the discharge lamp 4; In the load transformer 3, the secondary coil L ₂ provided in the load transformer 3, the rectifier 5 for rectifying and smoothing the voltage induced in the secondary coil L ₂ , A trigger part 6 which is operation controlled according to the output voltage level of the rectifier 5 to output a trigger signal, and a drive part which is driven by the trigger signal of the trigger part 6 to stop the operation of the oscillation part 2; (7) The overcurrent automatic compensation circuit of the electronic ballast for discharge lamps, characterized in that consisting of. The bridge diode (D ₁₆ -D ₁₉ ), the smoothing capacitor (C ₉ ) for rectifying the induced voltage of the secondary side coil (L ₂ ) of the load transformer (3), An overcurrent automatic compensation circuit of an electronic ballast for a discharge lamp, characterized in that consisting of a resistor (R ₁₇ ). _2. The emitter output terminal of claim 1, wherein the trigger unit 6 is controlled by a voltage applied through a zener diode ZD ₁ connected to the output terminal of the rectifier 5 and the zener diode ZD ₂ . An overcurrent automatic compensation circuit of an electronic ballast for a discharge lamp comprising a transistor (TR ₃ ), a bias resistor (R ₁₃ -R ₁₈ ), and a capacitor (C ₇ ) (C ₈ ) for outputting a trigger signal. 2. The SCR of claim 1, wherein the driving unit 7 is triggered by the output of the triggering unit 6 to bypass the base voltage of the oscillation transistor TR ₁ in the oscillating unit 2 to ground. An overcurrent automatic compensation circuit of an electronic ballast for a discharge lamp, comprising: SR), a diode (D ₈ ) and a resistor (R ₃ ) (R ₄ ).