JPH0346795A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent a switching element from being damaged by a rush current by forming a feedback control circuit in a delay circuit for delaying an ON control timing until voltages at both ends of the switching element are at a low level when the voltages at both ends of the switching element is at a high level in ON of a main switching element. CONSTITUTION:In a predetermined ON control instant, a detection signal VC output from a voltage detection circuit 11 is 'H' in the case where voltages VQ at both ends of a main switching element Q are higher than a reference voltage VS. Consequently, a delayed ripple carry signal RCY' is output when the detection signal VC is 'L'. A pulse signal OUT becomes ''H'' in accordance with the output of the delayed signal RCY', thereby turning on the element Q. Therefore, the element Q is not turned on in case of the high voltages VQ.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a discharge lamp lighting device that lights a discharge lamp at high frequency.8 [Prior Art] Conventionally, a discharge lamp lighting device that lights a discharge lamp at high frequency. As,
As shown in FIG. 12, a DC power rectified by a commercial power supply AC diode bridge DB is applied to the main switching element Q via an LC parallel resonant circuit consisting of a capacitor C1 and an inductance element L1, and the LC parallel resonant circuit is applied to the discharge lamp FL through a current limiting element consisting of an inductance element L2 to form a discharge lamp lighting circuit 10, and the main switching element Q is connected to a pulse generation circuit 9.
There is a single-ended type in which the discharge lamp FL is lit at high frequency by controlling vi with a pulse width modulated pulse signal with a predetermined duty output from C.
0 is a noise prevention capacitor, C2 is a preheating capacitor,
Dl is a diode that prevents reverse voltage from being applied to the main switching element Q.

Now, the main switching element Q is activated by the pulse signal OUT inputted from the pulse generation circuit 9 to the discharge lamp lighting circuit 10.
is controlled on and off, and the LC parallel resonant circuit is operated by turning on and off this main switching element Q, and the resonant circuit voltage is applied to the discharge lamp FL via the inductance element L2, so that the discharge lamp FL is lit at high frequency. By appropriately setting the "H" section (on section) and "L" section (off section) of the pulse width modulated pulse signal, the discharge lamp FL can be dimmed and lit. .

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, when the main switching element Q is turned on at an inappropriate time, a large rush current flows through the main switching element Q, causing the main switching element Q to turn on. There was a problem with it being destroyed. In other words, FIGS. 13 and 14 show the pulse voltage OUT and the voltage across the main switching element Q when the discharge lamp FL is steadily lit, when it is started, or when the load changes (lamp life, persuasion). It shows the relationship between the voltage (collector emitter voltage in the case of a transistor) VQ, and when the discharge lamp FL is in a steady lighting state, the pulse signal OUT becomes "H" as shown in Figure 13. The constants of the LC parallel resonant circuit are set so that the voltage Vo across the main switching element Q when it is turned on becomes O. by the way,
When the discharge lamp FL is started or when the load fluctuates, as shown in Fig. 14, the voltage across the main switching element Q becomes unstable, and the voltage across the main switching element Q 9 is at a high level! The main switching element Q may be turned on at gA (arrow), and at this time, there is a problem in that a large rush current flows through the main switching element Q and destroys the main switching element Q.

The present invention has been made in view of the above points, and its object is to prevent the main switching element from being turned on while the voltage across the main switching element is high.
An object of the present invention is to provide a discharge lamp lighting device that can prevent destruction of a main switching element due to rush current.

[Means for Solving the Problems] The discharge lamp lighting device of the present invention applies DC power to the main switching element via the LC parallel resonant circuit, and
The voltage of the C parallel resonant circuit is applied to the discharge lamp via the current limiting element to form a discharge lamp lighting rgJ path, and the main switching element is connected to the pulse width modulated pulse with a predetermined duty output from the pulse generation circuit. A discharge lamp lighting device that lights a discharge lamp at high frequency by controlling a signal includes a voltage detection circuit that detects the level of the voltage across the main switching element with respect to a reference voltage, and a pulse generation circuit that detects the voltage across the main switching element based on the output of the voltage detection circuit. A feedback control circuit that performs feedback control is provided, and when the voltage across the switching element is at a high level during predetermined ON control of the main switching element,
A feedback control circuit is formed by a delay circuit that delays the ON IIJa1 point until the voltage across the main switching element becomes a low level.

[Function] The present invention is configured as described above, and in a single-ended discharge lamp lighting device similar to the conventional example, the voltage detection circuit detects the level of the voltage across the main switching element with respect to the reference voltage, When the voltage across the switching element is at a high level during a predetermined ON control of the main switching element, a feedback control circuit that performs feedback control of the pulse generation circuit based on the output of the voltage detection circuit is configured such that when the voltage across the switching element is at a high level, the voltage across the main switching element is The main switching element is formed with a delay circuit that delays the voltage until it reaches a low level, so that the main switching element is not turned on when the voltage across the main switching element is high, thereby preventing destruction of the main switching element due to rush current. is now possible.

[Embodiment] Figures 1 to 8 show an embodiment of the present invention, in which a single-ended discharge lamp lighting circuit 10 similar to the conventional example has a voltage vQ across the main switching element Q set to a reference voltage Vs. A voltage detection circuit 11 that detects whether the voltage is higher or lower than the voltage detection circuit 11, and a feedback control circuit 12 that performs feedback control of the pulse generation circuit 9 based on the output of the voltage detection circuit 11 are provided. When the voltage across element Q 9 is at a high level, the on-control point is determined by the voltage across main switching element Q VQ.
The feedback control circuit 12 is formed by a delay circuit that delays the signal until it becomes a low level.

In the embodiment, as shown in FIG. 1, the voltage detection circuit 11 includes a voltage dividing resistor RR2 that divides the voltage V at both ends, and voltage dividing resistors R1 and R4 that divides the circuit power supply to form the reference voltage Vs.
and a comparator CP, and the detection signal Vc becomes "H" when the voltage VQ across the main switching element Q becomes higher than the reference voltage VS. 12 is designed to delay the rising edge (from "L" to "H") of the pulse signal 0UT by feedback control so as not to turn on the main switching element Q when the detection signal Vc is "H" during predetermined ON control. (Detailed operation will be explained later).

By the way, the feedback IIJa1 circuit 12 is provided within the pulse generation circuit 9.
As shown in FIGS. 2 to 8, the pulse signal OUT
a data latch circuit 1 that latches "H" section setting data and "L" section setting data; and a presettable counter circuit 2 that counts a constant cycle clock signal CLK and sets the above two section setting data alternately. , and a toggle flip-flop circuit 3 which uses the ripple carry signal RCY from the counter circuit 2 as a trigger clock. Pulse width modulated pulse signal OU
I'm trying to get a T. In the embodiment, the pulse width control means is formed by a microprocessor, and the "H" section setting data and "L" section setting data output from the microprocessor are input to the input terminal IN of the data latch circuit 1. ~IN, input to □, timing control circuit 4
It is designed to be latched by a timing signal output from.

Here, the data latch circuit 1 is formed of a primary buffer 1a and a secondary buffer 1b, and both buffers la and lb are as follows.
As shown in Figures 2 and 3, the flip-flop and T
It is formed by a buffer. In the primary buffer 1a,
When the section data set signal HL is input, the input terminal IN.

DT and ~DT12 input through ~IN and □ are set to "H" section setting data DA, -DA+z, and "L" section setting data D by latch signals LATCHA and LATCHa.
It is designed to be latched as B l” D B + 2. Also, in the secondary buffer 1b, the latch signal L
Latch data D A of the primary buffer 1a by TCH
+~DA +2, DB +~DB, □ are taken in, and the section setting data DA, ~DA, □ or DB, ~D selected by the enable signals ENA, EN.
B1□. is output as the preset data of the counter circuit 2. Further, the half clock control signal HLF is also latched once and outputted as the signal HALF.

Further, the counter circuit 2 and the toggle flip-flop circuit 3 are integrated as a counter/output circuit 5,
As shown in FIG. 4, a 12-bit counter circuit 2 is formed using three 4-bit presettable counters, and the ripple carry signal RCY of the counter circuit 2 is passed through a feedback control circuit 12 and a half-clock control circuit 6. The clip-flop output of this toggle flip-flop circuit 3 is outputted as a pulse signal OUT via two inverters.
At the same time, preset data is transferred to the data latch circuit 1.
Enable signals EN, , EN, to be read from are output.

Here, when the half clock control signal HALF is "H", the half clock control circuit 6 shifts the rise of the ripple carry signal RCY (the inversion timing of the toggle flip-flop circuit) to the right by half a clock,
With half clock precision (double precision) of clock signal CLK"
It is possible to set an H” section and an "L" section.

Further, the timing control circuit 4 outputs a latch signal LATCH.
, LATCHA, LATCH, , LTCH as shown in FIG. 5, and a clear signal C.
LEAR, 0-code signal LOAD, latch signal LTC
A counter control circuit 4 as shown in FIG. 6 that generates H+
It outputs a predetermined timing signal based on the clock signal CLK, start signal 5TART, and section data set signal HL output from the microprocessor to control the operation timing of each circuit. There is.

Further, in the embodiment, the feedback control circuit 12
As shown in the figure, it is formed using a flip-flop circuit, an inverter circuit, and an OR circuit, and is inserted between the counter circuit 2 and the half-clock control circuit 6.
Ripple carry signal R output from counter circuit 2
By appropriately delaying CY based on the detection signal VC, a corrected ripple carry signal RCY' is output.

In the embodiment, a two-phase lock generation circuit 7 is provided which outputs two-phase lock signals OUT, OLJ T 2 that control a pair of series-connected switching elements of the half-bridge discharge lamp lighting circuit 10. The two-phase lock generation circuit 7 generates two phases based on the pulse signal OUT.
It is designed to generate phase lock signals OUT, , 0UT2. Further, as a switching control signal output from the pulse generation circuit 9, a pulse signal OUT is output, or a two-phase lock signal OUT I, OUT 2 is output.
The output switching circuit 8 selects the pulse signal to be output based on the switching signal SE/HB set by the changeover switch, and is used for single-ended or half-bridge discharge lamp lighting circuits. Ten switching control signals are available.

The operation of the embodiment will be described below. FIG. 9 is a waveform diagram showing the basic operation of the pulse generating circuit 9 of this embodiment (when no feedback control is performed). First, when the start signal 5TART output from the microprocessor rises, a system reset is performed. 0th order, “H”
When the section setting data DA, ~DA, etc. are determined, the section data setting signal HL rises from the microprocessor, one pulse of the latch signal LATCHA is output, and the H section setting data DA is sent to the primary buffer 1a of the data latch circuit 1. , ~DA, the primary where ffi is latched is “L”
When the section setting data DBl to DBI2 are determined, the latch signal LAT is activated at the falling edge of the section data setting signal HL.
CHm outputs one pulse and “L” section setting data D
B, ~DB+2 is the primary buffer 1 of the data latch circuit 1
The 0th order latched in a, the clear signal CLEAR becomes L'
, one pulse of the latch signal LTCH is output, and both section setting data DA, ~D A l 2, DB, ~DB+
z is latched into the secondary buffer 1b. At this time, since the enable signal ENA is at "H", the "H" section setting data DAI to DA are sent from the secondary buffer 1b.

2 is read out and a load signal LOAD for setting preset data in the counter circuit 2 is output, the counter circuit 2 receives "H" interval setting data DA, ~DA +
x is set. In this state, the counter circuit 2 starts counting the clock signal CLK, and when the outputs Q1 to Q+2 of the counter circuit 2 all become "H", the ripple carry signal RCY is output. This ripple carry signal RCY causes the enable signal EN to
Hs, and at the same time, the pulse signal OUT also becomes "H". Then, the section setting data DB, ~DB, 2 is preset in the counter circuit 2, the counting of the clock signal CLK is started, and the ripple carry signal RCY is obtained. Then, the pulse signal OUT becomes "L" and the enable signal ENA becomes "H", and the above-mentioned operation is repeated.Therefore, both section setting data DA, -
Based on D A + 2, DB + to DB12, the “H” section and 'L' section of the pulse signal OUT can be arbitrarily changed (
For example, as shown in FIG. 9, if the frequency of the clock signal CLK is 16 MHz (period: 62°, 5 nsec), and the 'H' interval When setting 191 pulses and 164 pulses for “L” section, set “H” to 191 pulses and “L” interval to 164 pulses
``Set the 8th and 6th bits of the section setting data DA + ~ DA + z to °1'', and set the 8th and 6th bits of the 'L'' section setting data DB, ~DB+2,
It is sufficient to set the second bit and the first bit to n1'.

Next, feedback control when the main switching element Q is turned on will be explained using FIG. 10. Figure 10 (
a) is the voltage V across the main switching element Q, and FIG. 10(b) is the detection signal VC output from the voltage detection circuit 11.
1. FIG. 10(c) shows the pulse signal OUT for controlling the main switching element of the conventional example, and FIG. 10(d) shows the pulse signal OUT of the embodiment. In the figure, the left half shows the steady state, The right half shows an unstable state. Now, in the steady state, when the pulse signal OUT is turned on, it turns on.→
"H") and the off control time ('"H"→"L") are preset times as in the conventional example. On the other hand, in an unstable state, if the voltage VQ across the main switching element Q is higher than the reference voltage Vs at a predetermined ON control point in time (the point in time when the ripple carry signal RCY is output from the counter circuit 2), the voltage is detected. Since the detection signal Vc output from the circuit 11 is "H",
After waiting for this detection signal Vc to become L", a delayed pull-carry signal RCY' is output.

In the embodiment, the clock signal CLK is emitted for a predetermined clock period from the time when the detection signal Vc becomes "L" (in the embodiment, the clock signal CLK
The ripple carry signal R is delayed by 4 clocks)
CY' is output, and by outputting this delayed ripple carry signal RCY°, the pulse signal OUT becomes "H" and the main switching element Q
is turned on. That is, when the voltage VQ across the main switching element Q becomes equal to or lower than the reference voltage Vs, the detection signal V
c becomes "L", but at this point, the voltage at both ends ■9 is not completely 0, so by delaying by a predetermined delay time td (4 clocks), the voltage at both ends ■9 becomes completely O. When this happens, the main switching element Q is turned on.

Therefore, the main switching element Q is not turned on when the voltage V9 across the main switching element Q is at a high level, and the main switching element Q is not destroyed due to a large rush current flowing through the main switching element Q. can be prevented.

[Effects of the Invention] The present invention is configured as described above, and in a single-ended discharge lamp lighting device similar to the conventional example, the voltage detection circuit detects the level of the voltage across the main switching element with respect to the reference voltage. , when the voltage across the switching element is at a high level during a predetermined ON control of the main switching element, the feedback control circuit that performs feedback control of the pulse generation circuit based on the voltage detection circuit output is set to the voltage across the main switching element. The main switching element is not turned on when the voltage across the main switching element is high, which prevents damage to the main switching element due to rush current. It has the effect of being able to

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a block circuit diagram of the same essential parts, FIGS. 3 to 8 are circuit diagrams of essential parts of the same, and FIGS. FIG. 12 is a circuit diagram of a conventional example, and FIGS. 13 and 14 are explanatory diagrams of the same operation. 9 is a pulse generation circuit, 10 is a discharge lamp lighting circuit, 11 is a voltage detection circuit, 12 is a feedback control circuit, and Q is a main switching element.

Claims (1)

[Claims] (1) Apply DC power to the main switching element via the LC parallel resonant circuit, and apply the voltage of the LC parallel resonant circuit to the discharge lamp via the current limiting element to form a discharge lamp lighting circuit. In a discharge lamp lighting device in which the discharge lamp is lit at high frequency by controlling the switching element with a pulse width modulated pulse signal with a predetermined duty output from a pulse generation circuit, the voltage across the main switching element is A voltage detection circuit that detects high and low levels and a feedback control circuit that feedback controls the pulse generation circuit based on the output of the voltage detection circuit are provided, and when the voltage across the switching element is at a high level during predetermined ON control of the main switching element, A discharge lamp lighting device characterized in that a feedback control circuit is formed by a delay circuit that delays the ON control point until the voltage across the main switching element reaches a low level.