JPS6322039B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a constant input current for a discharge lamp that can control the input current of the discharge lamp to be below the input current at the rated time from immediately after the discharge lamp starts to when the discharge lamp shifts to the rated lighting state. It relates to a lighting device.

In recent years, in order to meet the demand for compact, lightweight, and power-saving lighting devices, AC control elements are connected in series with the discharge lamps, even in the lighting circuits of high-pressure vapor pressure discharge lamps such as mercury lamps and high-pressure sodium lamps. A so-called phase control method, which reduces current-limiting impedance by controlling the conduction phase angle of an AC control element, has been researched and has been put into practical use in some cases. Figure 1 is a diagram showing the principle circuit, in which 1 is a commercial power supply, 2 is a current-limiting impedance element, 3 is a discharge lamp,
4 is an AC control element, and 5 is a current limiting element that compensates for the current limiting impedance element 2 when the AC control element 4 is off. Figure 2 a and b show the lamp current of discharge lamp 3.
The phase relationship between I _la and the power supply voltage Vs is shown. Figure a shows the state immediately after starting, and figure b shows the state at the rated time.

Generally, immediately after starting a high-pressure discharge lamp, the lamp conductance is much larger than at the rated time, so it is necessary to appropriately delay the conduction phase θ of the AC control element 4 compared to the rated time, as shown in FIG. If such phase control is performed, the input current can be suppressed to less than the input current at the rated value during the period until the transition to the rated value (hereinafter referred to as the starting period), and constant input starting is possible. First, connect the AC control element 4, current limiting impedance element 2, and discharge lamp 3 in series to the commercial power supply 1, and set the commercial power supply voltage.
A lamp having a control circuit that controls the conduction phase θ of the AC control element 4 every half cycle of the commercial power supply in accordance with the lamp current commutation phase angle T from the zero cross phase of Vs to the commutation of the lamp current Ila. In a lamp constant input lighting device, corresponding to the lamp current commutation phase angle Ti _-1 immediately before the current half cycle to be controlled,
The application has been filed for a constant input lighting device for a discharge lamp characterized in that it is equipped with a control circuit that controls the conduction phase θi of the AC control element 4 during the current half cycle. Although the problem of positive and negative asymmetry of the waveform has been improved,
The sudden increase in lamp current Ila during glow discharge has not been improved.

To explain this rapid increase in lamp current Ila, in Fig. 3, (i+2) of power supply voltage Vs
A large current flows during a half cycle, and the condition for this phenomenon is half-wave lighting. During glow discharge, there is naturally half-wave lighting because the discharge breakdown inside the lamp is incomplete. Figure 3 shows what happens when this situation occurs in (i+1) half cycles. That is,
In the i half cycle, the lamp current commutation phase Ti
Suppose that there is a large delay. In this case, a large current flows through the lamp during the (i-1) half cycle. Then, since the lamp current commutation phase angle Ti _-1 in the (i-1) half cycle is small, the off period ΔTi of the AC control element 4 in the i half cycle also becomes small.
Therefore, the conduction phase θi (=Ti+△
Ti) is delayed, so from i half cycle to (i+1)
The lamp current Ila over a half cycle is small.
If half-wave lighting is performed for (i+1) half cycles, Ti+1 becomes smaller and ΔTi+1 becomes larger. At this time, the lamp current is
Ila is small, and a large current flows in (i+2) half cycles.

In this way, the constant input control condition Ti _-1 −△Ti has the effect of converging the conduction phase θ of the AC control element 4, but if it continues as it is, the conduction phase θ will abnormally advance during the glow discharge period. This cannot be prevented and reduces the reliability of the AC control element 4 for several seconds during the glow discharge period.

The present invention has been made in view of the above, and its purpose is to improve the reliability of the AC control element by preventing the conduction phase of the AC control element from abnormally advancing during glow discharge. It is in.

In the case of high-pressure sodium lamps, a sufficient heater current must flow through the heater resistor immediately after the power is turned on, so the off-period △Ti of the AC control element 4 needs to be much smaller than the off-period △Ti that should be controlled immediately after the lamp starts. There is. In addition, immediately after the power is turned on, the lamp current commutation phase Ti _-1 advances much earlier than immediately after the lamp is started, because the heater has a high resistance. This situation is shown in Figure 4, where point A indicates the preheating current sufficient to generally start a high-pressure sodium lamp.
The phase conditions for obtaining 0.8A are shown. This heater current phase becomes a steady phase determined only by the inductance of the main choke coil 2 and the heater resistance shown in FIG. 5, and is constant during heater preheating. Therefore, during the heater preheating period, the preset upper limit of the conduction phase of the AC control element 4 is fixed at point A without exceeding one and a half cycles. Then, when the heater switch is opened and the lamp starts to start and enters a glow discharge, the lamp current commutation phase T is disturbed and may exceed the upper limit of the conduction phase. In the present invention, when this upper limit phase is exceeded, the upper limit phase is made the conduction phase of the AC control element.

FIG. 6 is a block diagram showing the function of a circuit implementing the present invention, and FIG. 7 is a timing chart of each part of the same. The lamp current commutation phase Ti _-1 immediately before the current half cycle in FIG.
It is detected during the addition count period of 0, and the off period ΔTi of the AC control element 4 in the current half cycle is calculated by subtracting the same number of clock pulses from the second clock 11 as the number of addition counts from the first clock 10. The content is the lamp current commutation phase of the current half cycle.
The period is defined as the period after Ti until it becomes zero.
Note that the initial value _N0 of the addition counter 13 is △ in FIG.
This is the second clock count corresponding to _T0 .

Next, the operation will be explained. When the power supply voltage zero cross detection circuit 14 detects the zero cross phase of the power supply voltage Vs, the contents of the addition counter 13 are preset to the initial value _N0 during the period _T0 in FIG. Then, after the time _T0 has elapsed, the addition counter adds and counts the first clock pulse and continues counting until the lamp current Ila commutates. On the other hand, the subtraction counter 12 presets the output of the delay circuit 15 (latch circuit) from after the zero crossing of the power supply voltage Vs is detected until the lamp current Ila commutates. At the same time as the lamp current Ila commutates and the contents of the addition counter 12 are input to the delay circuit 15, the subtraction counter 12 starts subtracting the clock pulses of the second clock 11. Therefore, the subtraction counter 12 calculates the commutation phase angle of the lamp current Ila in the previous half cycle.
The number of first clock pulses corresponding to Ti _-1 will be subtracted. Then, the zero comparator circuit 16 outputs a pulse shown at C in FIG. 7 at the time when the content of the subtraction counter 12 becomes zero. This pulse C is generated at the conduction phase angle θ of the AC control element 4 determined by the constant input starting control condition Ti ₋₁ −ΔTi. 7b is a reference pulse generated by the reference pulse generation circuit 17, and the positive period is the prohibited phase of the conduction phase θ of the AC control element 4.

Therefore, reference pulse b and flip-flop 1
Output e via AND gate 19 with output d of 8
occurs when the pulse C output from the zero comparison circuit 16 enters the positive interval of the reference pulse b. In other words, the time when the positive pulse e is generated is the time when the phase limit of the AC control element 4 is exceeded, and
The AC control element 4 is triggered by a positive pulse of the output f via the OR gate 20 of the outputs e and c.
In addition, in FIG. 6, 21 is a lamp current commutation phase detection circuit, and the symbols a to f in the figure are the seventh
The signal outputs a to f in the figure are shown.

In this way, if the conduction phase is prevented from being abnormally delayed, the (i+2) half-cycle phenomenon in Figure 3 will not occur, and the convergence effect due to the control condition of Ti _-1 -△Ti will cause conduction. The phase will converge.

Therefore, since the conduction phase of the AC control element is not forcibly fixed by a timer after the power is turned on as in the past, high-pressure sodium lamps can be started reliably, and moreover, the conduction phase lags behind the upper limit phase during glow discharge. Since there is no noise, the inrush current to the AC control element can be suppressed, improving the reliability of the element, and even if noise enters the power supply circuit during preheating, the conduction phase will not be fixed due to it, making it more reliable. It is now possible to start.

[Brief explanation of drawings]

Fig. 1 is a principle circuit diagram of a discharge lamp constant input lighting device, Fig. 2 a and b are waveform diagrams of the lamp current and power supply voltage of the same discharge lamp, and a shows the state immediately after starting.
b indicates the rated state. Fig. 3 is a waveform diagram of the conventional lamp current and power supply voltage during glow discharge, Fig. 4 is an explanatory diagram showing the control conditions necessary for starting the high-pressure sodium lamp according to the present invention, and Fig. 5 is the principle of the present invention. FIG. 6 is a block diagram showing the function of the control circuit of the present invention, and FIG. 7 is a time chart of each part of the same.

Claims (1)

[Claims] 1. An AC control element, a current limiting impedance element, and a discharge lamp are connected in series to a commercial power supply, and the AC control element In a discharge lamp constant input lighting device having a control circuit that controls the conduction phase of the current half cycle for each half cycle of the commercial power supply, the current half cycle A control circuit for controlling the conduction phase of the AC control element is provided, and when the conduction phase lags behind a constant phase for each half cycle, the constant phase is set as the conduction phase of the AC control element. Electric light constant input lighting device.