Matsushita Electric Works, Ltd.

Panasonic Corporation

Haruo Nagase

Toshiaki Nakamura

Takashi Kambara

Yoshitaka Taga

Minoru Maehara

Hiroichi Shinbori

Kiyoaki Uchihashi

Tomoyuki Ono

Masatoshi Ueno

Hisao Kataoka

Masaaki Ichikawa

Hideki Hamada

Nobuo Kato

Noriyuki Satou

Akira Satomi

Shojiro Kido

Yasuhiro Kimura

A light emitting diode drive device includes a drive circuit section that applies a direct-current voltage to a light source including a plurality of light emitting diodes connected in series to allow the light source to light up, a voltage detection circuit section that detects a voltage across the light source, and a malfunction determination circuit section that determines that the light emitting diode is short-circuited when the voltage detection circuit section detects a voltage drop and a potential between the voltage before being dropped and the voltage after being dropped is equal to or more than a predetermined threshold value. Thus, it is possible to detect a fact that a light emitting diode, which lights up, is short-circuited or is not short-circuited, with a simple circuit configuration.

Light emitting diode drive device, illumination device, in-vehicle cabin illumination device, and vehicle illumination device

An LED driver circuit is provided for protecting one (or more) LEDs connected in series from over-current damages which may result from a short circuit condition. The driver circuit includes a current control circuit for receiving an input signal from a power source and providing a current output for powering the LED. A voltage sensor detects a voltage across the LED. An LED current restriction circuit such as a switching element restricts a current flow into the LED. A short circuit response circuit controls the LED current restriction circuit dependent on a comparison between the voltage detected by the voltage sensor and a predetermined threshold value. When the detected voltage is less than or equal to the threshold value, the response circuit determines a short circuit, and a signal is sent to the current restriction circuit to restrict current flow into the one or more LEDs.

LED driver circuit with over-current protection during a short circuit condition

A safety ballast for a discharge lamp capable of interrupting the supply of the electric power upon failure of starting the lamp. The ballast includes a converter providing a DC power voltage from a DC voltage source, a booster providing a boosted DC voltage to a starter which generates, based upon the boosted DC voltage, a starting voltage for starting the lamp, and an inverter receiving the DC power from the converter to provide an AC power for operating the lamp. The booster includes a capacitor which is charged by the DC power and accumulate the boosted voltage. A controller monitors a load condition of the lamp and issues a disable signal when a no-load condition continues over a predetermined starting period. The inverter includes a plurality of switching elements one of which is regulated to be turned on in response to the no-load signal for establishing a supply path of supplying the boosted voltage from the booster's capacitor through the switching element to the starter. The one switching element is also controlled to be turned off in response to the disable signal for interrupting the supply path. Thus, when the no-load condition continues over the predetermined starting period as indicative of the that the lamp has been removed or the lamp reaching its end of life, the booster's capacitor bearing the boosted voltage is disconnected from the starter, applying no voltage to the starter and therefore preventing the starter from being activated to generate unnecessary starting voltage.

Ballast for a discharge lamp

Lamp socket

A power supply apparatus in which a series circuit of first and second switching elements not blocking their reverse-directional currents is connected in parallel to a series circuit of a D.C. power source and a capacitor, a primary winding of a transformer is connected between a junction point of the D.C. power source and capacitor and a junction point of the switching elements, a secondary winding of the transformer is connected to a load circuit, and a controller is provided for controlling ON and OFF operation of the switching elements to cause a switching frequency of the switching elements to be set higher than a resonance frequency of the capacitor and an inductance of the transformer and to cause a voltage across the capacitor to increase.

Power supply apparatus

A power source device includes a voltage converting means to input side of which a DC voltage source is connected and to output side of which a capacitance element and a load circuit are connected, while a control circuit is connected to the voltage converting means and the load circuit, the latter circuit having a load impedance made lower upon starting of a load in the load circuit than that in stable lighting of the load, wherein such control constant as oscillation frequency and duty are made to be substantially constant at the time of the starting and stable lighting of the load, and a switching means in the voltage converting means is turned OFF when the capacitance element has a voltage below a predetermined value.

Power source device

An improved inverter AC power supply includes a chopper providing a DC voltage from an AC source voltage and an inverter providing from the DC voltage a high frequency AC voltage to a load. The chopper incorporates a pair of first and second switching elements operating to turn on and off for obtaining a periodically interrupted AC voltage which is rectified and smoothened to provide the DC voltage to the inverter. The inverter is arranged to share the first and second switching elements in common to the chopper, and operates to drive the same switching elements for switching the DC voltage in order to provide a desired AC voltage to the load. The power supply is provided with an input power sensor monitoring an input power supplied to the chopper and an output power sensor monitoring an output power from the inverter to the load. A power controller is included for varying at least one of a switching frequency and a duty ratio for the first and second switching elements in accordance with the monitored chopper input power and inverter output power for equalizing the input and output powers.

Regulated chopper and inverter with shared switches

A discharge lamp driving circuit includes a chopper with a first switching circuit and an inverter with a second switching circuit. The chopper and inverter are connected to a dc voltage source and controlled to produce a composite lamp driving current composed of a high frequency alternating current interrupted by a dc current in order to keep the discharge lamp free from an acoustic resonance. The chopper and the inverter are arranged to have at least one common switching element in their first and second switching circuits.

Discharge lamp driving circuit

A circuit for operating a discharge lamp at a low frequency AC voltage while repetitively interrupting at a high frequency the voltage component to be applied to the lamp. The circuit includes at least one switching transistor for repetitively interrupting the voltage to be applied to the lamp at the high frequency, for example, 40 KHz so as to allow the use of a light and less bulky inductor as the current limiting conductor to be connected in series with the lamp. A bridge inverter is provided to have at least one pair of switching transistors for alternately reversing a DC voltage to apply the resulting AC voltage to the lamp at the low frequency, for example, 100 Hz low enough to stably operate the lamp without suffering from acoustic resonance. The high frequency component is bypassed through a bypass capacitor connected in parallel with the lamp. By reason of the inverter producing the low frequency AC voltage, the circuit requires all-off period during which the switching transistors of the bridge inverter are simultaneously off for preventing the short circuiting of the power source. An oscillation-inducing inductor is connected in series with the lamp in parallel relation to the bypass capacitor so as to form a series oscillating circuit which causes to flow an alternating oscillating current to the lamp circuit throughout the all-off period. The resulting oscillating lamp current continues for a longer time to thereby retard the deionization of the lamp. Accordingly, the all-off time can be extended to such an extent as to give greater flexibility in designing the circuit which is free from short circuiting of the power source as well as from the increased reignition voltage.

Growing community of inventors

Kitakatsuragi, Japan

Haruo Nagase