JPS583353B2 - Control circuit for discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention connects an AC control element S1, such as a triac, to a power supply AC via an inductive reactance L1 and a discharge lamp L having a high vapor pressure during lighting, so that the power supply voltage a A reference voltage generation circuit 2 outputs a rectified voltage of divided voltage b which is more advanced in phase by a certain amount, a detection circuit 1 outputs a rectified and smoothed voltage by dividing the lamp voltage, and the output of the reference voltage generation circuit 2 is the detection circuit 1. This invention relates to a control circuit for a discharge lamp device characterized in that it is provided with a trigger circuit 3 that generates a trigger pulse for an AC control element S1 with a phase smaller than the output, and its purpose is to control induction. An object of the present invention is to provide a control circuit for realizing a compact and lightweight discharge lamp lighting device with small reactance and constant lamp power.

The present invention will be explained in detail by way of examples.

An AC control element S1 is connected to a power source AC via an inductive reactance L1 and a discharge lamp that generates high vapor during lighting, such as a mercury lamp, and a series circuit of a resistor R1 and a capacitor C1, a capacitor C2, and a resistor R3 are connected to the power source AC. The connection point between resistor R1 and capacitor C1 is connected to the base of transistor T1 via resistor R2 and diode D1, and further connected to the base of transistor T2 via resistor R2 and diode D3. connected to the rectifier circuit Re
One of the input terminals of c1 is connected to the connection point between capacitor C2 and resistor R3, and the other end is connected to the collectors of transistors T1 and T2 via diode D2 and diode D4, respectively, and the emitters of transistors T1 and T2 are connected to each other. Connect both to the power supply circuit on the capacitor C1 side,
The reference voltage generation circuit 2 is configured by connecting the positive output end of the rectifier circuit Pec1 to the resistor R6, and the negative output end to the emitters of the transistors T3 and T4, and the voltage b across the resistor R3 is the power supply voltage. Time t1-t2 from a
The phase advances from time t5 to t6, and the voltage C of the capacitor C1 lags in phase from time t2 to t3 and from time t6 to t7.

Voltage b is applied to a series circuit of rectifier circuit Rec1, diode D2, and transistor T1, and a series circuit of rectifier circuit Rec1, diode D4, and transistor T2,
Voltage C is connected to resistor R2, diode D1 and diode D.
3 to the bases of transistor T1 and transistor T2, respectively.

Therefore, from time t2 to t3, voltage b is equal to rectifier circuit R
It is applied via ec1 to a parallel circuit of transistor T1, diode D2, transistor T2, and diode D4.

At this time, the voltage c is a negative voltage, reverse biasing the base end of the transistor T1, and forward biasing the transistor T2.

Here, the voltage b is applied in the forward direction between the collector and emitter of the transistor T1, but since the base end is reverse biased, it is turned off.

Also, voltage c forward biases the base end of transistor T2, while voltage b forward biases the collector end of transistor T2.
Since the emitters are reverse biased, the transistor T
2 is off.

Therefore, since both transistors T1 and T2 are off, no voltage is output to the output terminal of the rectifier circuit Rec1.

Next, at time t3-t5, the voltage C is a positive voltage and forward biases the base end of the transistor T1, and the transistor T
The base end of 2 is reverse biased.

Also, voltage b is applied in the forward direction between the collector and emitter of transistor T1, and the base end is forward biased, so transistor T1 is on, and voltage b is applied to the output end of rectifier circuit Rec1. The voltage becomes d.

Further, the voltage b is applied in the opposite direction between the collector and emitter of the transistor T2, and the transistor T2 is reverse biased, so that it is turned off.

The table below shows the operating status at other times.

The voltage d at the output terminal of the rectifier circuit Rec1 thus formed is supplied to the trigger circuit 3.

The trigger circuit 3 connects a series circuit of a diode D5, a resistor R4, and a capacitor C3 in parallel with a series circuit in which a resistor R5 is connected in series to the collector of a transistor T4, and connects one end of the diode D5 and resistor R5 to the positive output of the rectifier circuit Rec1. The capacitor C3 and the emitters of the transistors T3 and T4 are connected to the rectifier circuit Rec.
1, the base of transistor T3 is connected to the collector of transistor T4, the collector of transistor T3 is connected to the connection point of resistor R4 and capacitor C3 via the input side of transformer Tr1, and One of the output ends of the transformer Tr1 is connected to the gate 4 of the AC control element S1, and the other end is connected to the cathode on the side of the AC control element S1 via a diode D6.

Further, the resistor R6 is connected to the positive output terminal of the rectifier circuit Rec2 via the cathode and anode of the diode D7, the base of the transistor T4 is connected to the negative output terminal, and the resistor R7 is connected to the connection point between the resistor R6 and the diode D7. A capacitor C4 is connected to the positive and negative output terminals of the rectifier circuit Rec2, the other end of the resistor R7 is connected to the negative output terminal, and the input terminal of the rectifier circuit Rec2 is connected to the output terminal of the transformer Tr2. When the input terminal of Tr2 is connected to both ends of the discharge lamp L to form the detection circuit 1, the lamp voltage at the time of lighting is determined by the transformer T.
The voltage is divided by r2, enters the rectifier circuit Rec2, passes through the diode D7, and a rectified and smoothed voltage f appears at both ends of the resistor R7, which is connected to the positive output terminal and negative output terminal of the rectifier circuit Rec2. .

When the voltage f is lower than the voltage d at the output end of the rectifier circuit Rec1 in the phase between time t3 and t4, the current of the rectifier circuit Rec1 flows through the resistor R6, the resistor R7, and the base-emitter of the transistor T4 due to the potential difference.
4 becomes conductive, the transistor T3 becomes cut off, and no pulse voltage is applied to the gate of the AC control element S1, and at time t
When the voltage d becomes lower than the voltage f at step 4, the transistor T4 is reverse biased and shut off, and the transistor T3 becomes conductive.

The conduction of the transistor T3 causes the electric charge of the capacitor C3 to be discharged through the input side of the transformer Tr1 and the transistor T3, and a pulse is applied from the output side of the transformer Tr1 to the gate of the AC control element S1, turning on the switch and turning on the power supply AC. The current flows into the discharge lamp L through the inductive reactance L1.

Transistor T3 continues to conduct from time t4 to t7, and at time t7 to t8, voltage d becomes higher than voltage f, transistor T3 is reverse biased and cut off, and rectifier circuit Rec1
A capacitor C3 is charged from the output side of the capacitor C3 through a circuit including a diode D5, a resistor R4, and a capacitor C3.

At time t3, the voltage d becomes lower than the voltage f, and the transistor T3 becomes conductive again, and the charge on the capacitor C3 is transferred to the transistor T.
The current from the power source AC passes through the inductive reactance L1. The current flows to the discharge lamp L and starts the discharge lamp L, and the transistor T3 continues to be conductive from time t8 to t11.

However, by outputting the voltage d obtained by cutting the first half of each half cycle of the voltage b by turning on and off the transistors T1 and T2, the conduction period of the transistor T3 is reduced to a certain period (approximately 1/4 The reason why the trigger current is set to a value greater than 1.5 cycles is to prevent the period during which the trigger current flows from becoming too short immediately after the discharge lamp starts, and to ensure that the AC control element is conductive.

The above operation is repeated every half cycle, but during the starting process of the discharge lamp L, the lamp impedance is low, so the lamp voltage is also low, so the output voltage f of the detection circuit is also low and becomes almost zero value immediately after starting, and the pulse e occurs at times t5 and t9, and if the AC control element S1 is switched on at rated lighting immediately after startup, the lamp impedance is low and the current flowing through the inductive reactance L1 increases, but the pulse Since the time when e occurs is set later than the time period in which the element S1 should be switched on during rated lighting, the amount of current flowing through the inductive reactance L1 does not increase, and after this, from the start of the discharge lamp L. As the vapor pressure increases, the lighting voltage increases and the output voltage f of the detection circuit 1 also increases, leading to an advance in the phase in which the pulse e is generated.

In this way, during the starting process, the current flowing through the inductive reactance L1 can be suppressed from increasing significantly compared to when the rated lighting is on.

Further, as shown in FIG. 3, when the power supply voltage a' changes from the voltage value a1 to the voltage value a2, the voltage d' from the reference voltage generation circuit 2 also changes from the voltage value d1 to the voltage value d2, while the lamp voltage is approximately Since the voltage f from the detection circuit 1 is constant, it is input to the circuit 3 and compared as a constant voltage, and the pulse e' generated at a phase higher than the voltage d is also the pulse g1 to g.
2 and the time phase can be varied, so the AC control element S1, which is switched on by the pulse e', is configured to always control the current flowing through the inductive reactance L1 to a constant amount of current.

The present invention connects an AC control element to a power supply via an inductive reactance and a discharge lamp that has a high vapor pressure during lighting, and generates a reference voltage that outputs a rectified voltage of a divided voltage that is a certain phase ahead of the power supply voltage. A detection circuit that divides the lamp voltage and outputs a rectified and smoothed voltage, and a trigger circuit that generates a trigger pulse for the AC control element at a phase when the reference voltage generation circuit output is smaller than the detection circuit output. Therefore, the phase of the current flowing through the inductive reactance can be controlled according to the internal impedance of the discharge lamp at the time of starting, and it is therefore possible to limit the current flowing through the inductive reactance and downsize the inductive reactance. It also has the effect of keeping the lamp power approximately constant even when the power supply voltage fluctuates, as it allows a nearly constant current to always flow through the discharge lamp even when the power supply voltage fluctuates. It is something that you have.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram of a discharge lamp lighting device according to the present invention;
FIGS. 2 and 3 are operational waveform diagrams. AC...Power supply, S1...AC control element, L1...Inductive reactance, L...
Discharge lamp, 1...detection circuit, 2...reference voltage generation circuit, 3...trigger circuit.

Claims (1)

[Claims] 1. A reference voltage generation circuit that connects an AC control element to a power supply via an inductive reactance and a discharge lamp that has a high vapor pressure during lighting, and outputs a rectified voltage of a divided voltage that is a certain phase ahead of the power supply voltage; A detection circuit that divides the lamp voltage and outputs a rectified and smoothed voltage, and a trigger circuit that generates a trigger pulse for the AC control element at a phase in which the output of the reference voltage generation circuit is smaller than the output of the detection circuit. A control circuit for a discharge lamp lighting device characterized by: