JPS5960999A - Zero cross detector for dimming discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zero-cross detection device for dimming a discharge lamp.
The phase angle or firing angle of the Xyris is varied to adjust the instantaneous amount of power and thereby the illumination. In other words, dimming control is performed by determining the firing angle with the zero-crossing point as a reference during the half-cycle period of the sine waveform from the power supply, but the detection of the zero-crossing point is due to the collapse of the sine waveform from the power supply or noise. If this cannot be done accurately depending on the components, the reference point for determining the ignition angle will float, causing fluctuations in the instantaneous amount of electric power, which will cause flickering in the illumination of the discharge lamp.

The purpose of the present invention is to eliminate inaccurate detection of zero-crossing points due to distortion of the sine waveform from the power supply or noise contamination, and ultimately to eliminate flickering in the illumination of discharge lamps7. That is, in the storage invention, the sine waveform from the power supply is converted into a P wave, the noise component is removed from the sine wave, and this is shaped, eliminating the possibility of detecting a point other than the zero-crossing point as a zero-crossing point. At the same time, the phase delay caused by Tonami is removed by IT < L/
The zero-crossing point of the shaped sine wave is precisely matched with the zero-crossing point of the sine waveform from the power supply, and the zero-crossing point is detected from this shaped sine wave.

The present invention will be described in detail below with reference to Figure 1.

In FIG. 1, a transformer 4 is connected to the input terminal 2-2, and an adjustment resistor r is connected to the secondary side of the transformer 4.

A first CRP circuit consisting of a fixed resistor R1 and a capacitor C1 is connected. A voltage follower A1 is connected to this first r-wave circuit. A second CRP wave circuit consisting of a fixed resistor R2 and a capacitor C2 is connected to the output of the voltage follower A1.

A non-inverting amplifier A2 for vibration rlJ compensation is connected to this second CRP wave circuit. The gain of this amplifier A2 is determined by the ratio of the transition circuits r1 and r2. A fifth cRP wave circuit consisting of a resistor R3 and a capacitor C3 is connected to the output of the amplifier A2, and a voltage follower A is connected to this p wave circuit.
Finally, a zero cross detection circuit 6 is connected to the output of the voltage follower A3. 8-8 is an output terminal. The zero cross detection circuit converts a sine wave into a rectangular wave and differentiates it to determine the zero cross point, and compares a human signal with zero potential and outputs it for an amplitude larger than zero. There are methods that determine the zero-crossing point from the output waveform.

A human input signal (a sine wave signal containing noise) from the power supply applied to the input terminal 2-2 is made into an appropriate amplitude by the transformer 4, and is applied to the first CRP wave circuit to remove the noise component. A 90 degree phase shift is not possible with a single CR circuit, and a 180 degree phase shift requires at least 6 C11 = "wave circuits. 1st, 2nd, 6th cR-p The wave circuit is designed to remove noise components and shift the phase by 180 degrees.Specifically, the CR value of each p-wave circuit is adjusted appropriately to shift the P-wave by 180 degrees in six stages. The phase is delayed, and in particular, the adjustment resistor r of the first stage p-wave circuit performs offshore adjustment to accurately set the delay to 180 degrees.

The voltage follower A1 between the first and second stage p-wave circuits and the voltage follower A3 between the sixth stage p-wave circuit and zero-cross detection circuit 6 are both in-phase and in-phase. Transmits the human power signal to the output side, but also has a non-circuit 9' inverted 11'' circuit A2 between the second and sixth stage p-wave circuits to compensate for the attenuation.
3, the voltage follower with a very large input impedance is used to ensure isolation or mutual independence between adjacent circuits.

FIG. 2 shows waveforms at each input/output section of the circuit shown in FIG. 1.

FIG. 2(a) shows a sine wave including noise components applied from the power supply to the input terminal 2-2. Figure 2 (b), (c)
.

(d) is a waveform appearing at the output terminal of each p-wave circuit showing how the noise component is removed by the 6-stage 1lFi'lk circuit and the phase shift is delayed by 180 degrees. FIG. 2(e) shows a detection pulse generated by the zero-crossing point detection circuit 6 at the zero-crossing point.

This detection pulse (negative pulse in the figure) exactly coincides with the zero crossing point of the input sine wave, and the phase angle is determined using this as a reference to control the instantaneous power in each half cycle to be constant. and supplies it to the discharge lamp.

[Brief explanation of the drawing]

FIG. 1 shows a circuit of a zero-cross detection device for dimming a discharge lamp according to the present invention. FIG. 2 is a diagram showing waveforms appearing at the input/output terminals of each component circuit of the zero-cross detection device in FIG.
) are the sine wave signals applied from the power supply to the input terminal, Figure 2 <b) (c) <d) are the waveforms appearing at the outputs of the first, second and sixth stage p-wave circuits, respectively, and the second Figure (e) shows the output waveform of the zero-cross detection circuit, and Figure 2 (f)
11. shows a sinusoidal waveform from a regulated power supply with instantaneous power. 2...Input terminal, 4...Transformer, 6...Zero cross detection circuit, 8...Output terminal, C,,C,,,C3
...Capacitor, R,, R2, R3, rl, r2
・・Fixed resistance, r ''Variable resistance., Patent applicant: Toshiba Electric Materials Co., Ltd. Agent: Patent attorney: Tatsuo Ito, Patent attorney: Tetsuya Ito

Claims (1)

[Claims] A discharge lamp '-'j, comprising a series of at least six CT1 Tonami circuits that delay the phase of the input signal by nπ (n is an integer) and a circuit for detecting the zero crossing of the signal delayed by nπ, '+l zero cross detection device,