Light emitting power supply circuit

Details Light emitting power supply circuit Light emitting power supply circuit

1991-10-07

1994-06-21

Stephan, Steven L.

Electric power conversion systems

Current conversion

With condition responsive means to control the output...

363 21, 363132, 3151693, 315291, H02M 7523, H05B 3308, G09F 900

Patent

active

053233050

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to a light emitting power supply circuit.


BACKGROUND OF THE INVENTION

There are known systems for operating electro-luminescent (EL) elements, light emitting diodes (LED), and laser diodes (LD) by means of an inverter circuit for inverting DC power into AC power.
For example, systems for operating EL panels are widely used as back light of liquid-crystal panels as found in compact size liquid-crystal television receivers and lap-top computers having a liquid-crystal display built therein.
In the prior art, different EL operating devices are individually designed in accordance with the dimensions (surface area) of EL elements to be operated and lighting luminance. There exists no operating device which can accommodate singly for varying EL area and lighting luminance.
For long life (LL) inverters which are most popular in the prior art, there is used a system for operating an EL panel so as to follow a resonance frequency which is determined by the C value (electrostatic capacity) of the EL and the L value (inductance) of an inductor. The system is designed to compensate for a lowering of the EL luminance by, in response to a lowering of the luminance of EL due to a lowering of the C value thereof, increasing the resonance frequency and increasing the EL operating frequency in a follow-up manner to the resonance frequency.
However, this method has many problems in that the luminance of lighted EL is naturally determined by the resonance frequency of L and C, and it is difficult to fabricate a device for operating an EL panel having a large surface area. For example, the EL surface area corresponding to A-4 size (400 to 600 cm.sup.2) is currently regarded the practically permissible maximum surface area.
Since it is necessary to switch a high current flow for operating EL panels having a large surface area, the switching loss associated therewith invites an increase of power loss and results in substantial heat release. Thus a heat sink is required as a heat dissipating measure, resulting in a larger size of the operating device.
Additionally, the electric charge accumulated in the EL can be coupled with the charge of the counter electrode, resulting in a power loss and a substantial loss of operating efficacy. For instance, even green color EL panels which are regarded best in operating efficacy show a luminous existence of at most about 1 lumen per watt.


SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a light emitting power supply circuit capable of operating many types of loads and having high operating efficacy.
This and other objects are achieved by the present invention defined (1) below.
(1) A light emitting power supply circuit comprising a series coupled component partially including element or EL array having capacitive load characteristic, circuit adapted to supply bidirectional current flows across an LED or LD, or capacitive load characteristic, and said diode circuit, and ends of said load circuit wherein an AC power inverted from a DC power source is supplied to said load circuit to operate at least one member of the EL, EL array, LED and LD, wherein a zero-crossing switch mechanism adapted to automatically close its channel when the current becomes zero, bypass channel having a reverse current bypass diode for bypassing the zero-crossing switch mechanism, load circuit is latched at a secondary zero-crossing phase point which is determined by circuit constants.
The light emitting power supply circuit of the invention is designed such that the surplus power which is accumulated in the load such as an EL panel or passed through the load is recovered as reverse current. From the stand point of energy efficiency, the following four actions take place simultaneously.
(1) The surplus power which is accumulated in the EL panel or load as a surplus charge without being converted into light or which is simply passed through the load is recovered as reverse current, thereby inhibiting recombination of positive and nega

REFERENCES:
patent: 4253097 (1991-02-01), Hochstrate
patent: 4346332 (1982-08-01), Walden
patent: 4833584 (1989-05-01), Divan
patent: 4954726 (1990-09-01), Lipman et al.
patent: 5027040 (1991-06-01), Ikeda et al.
patent: 5063490 (1991-11-01), Maehara et al.
patent: 5066895 (1991-11-01), Alessio

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