Drive system and AC conversion device

• US 20050105305A1
• Filed: 09/30/2004
• Published: 05/19/2005
• Est. Priority Date: 10/03/2003
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), Sharp Niigata Electronics Corporation (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), Sharp Niigata Electronics Corporation (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Tanaka, Naoki, Ogawa, Takeaki, Sawada, Shinichi
• Granted Patent: US 7,315,464 B2
• Time in Patent Office: Days
• US Class Current: 363/34
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 7/538 in a push-pull configuration H02M7/5375 takes precedence ; with oscillating arrangements H02M7/53832, H02M7/53846
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A drive system with small power loss in power conversion is provided. The drive system has an AC conversion device for converting commercial AC power from a commercial AC power supply and a DC conversion device. An AC power supply path for supplying power to discharge tubes, and a DC power supply path for supplying power to an image processing circuit or the like, are provided independently. The AC conversion device converts commercial AC power into converted AC power and gives the converted AC power to an AC drive device directly. Consequently, it is possible to reduce conversion steps for generating converted AC power and to reduce power loss that occurs in a conversion process. In particular, when power consumption of the discharge tubes is large, it is possible to reduce power loss in an entire liquid crystal display apparatus effectively by providing the AC conversion device.

Claims

1. A drive system that is given AC power from an AC power supply to drive targets to be activated, comprising:

an AC conversion device for acquiring AC power from an AC power supply and converting the supplied AC power into converted AC power having a predetermined frequency and a predetermined voltage;

an AC drive device that is given the converted AC power to be activated;

a DC conversion device for acquiring AC power from an AC power supply and converting the supplied AC power into converted DC power having a predetermined voltage; and

a DC drive device that is given the converted DC power to be activated,

wherein the AC conversion device has a frequency converting unit for converting a frequency of AC power into a predetermined frequency and a voltage converting unit for converting a voltage of AC power into a predetermined voltage, and

the frequency converting unit includes only one pair of a DC power generating circuit for AC conversion and an alternating power generating circuit for AC conversion, in which the DC power generating circuit for AC conversion converts the supplied AC power into DC power, and the alternating power generating circuit for AC conversion converts DC power which is generated by the DC power generating circuit for AC conversion, into AC power of a predetermined frequency.

2. The drive system of claim 1, wherein the voltage converting unit includes:

a first transformer for dropping a voltage of AC power generated by the alternating power generating circuit for AC conversion, and generating power electrically insulated against the AC power supply; and

a second transformer for boosting the voltage of AC power dropped by the first transformer and generating converted AC power, and

wherein the second transformer is directly driven by an alternating voltage outputted from the first transformer.

3. The drive system of claim 1, wherein the voltage converting unit is realized by a single transformer for transforming a voltage of alternating power generated by the alternating power generating circuit for AC conversion and generating converted AC power electrically insulated against an AC power supply.

4. The drive system of claim 1, wherein the DC conversion device includes:

a first DC power generating circuit for DC conversion, for converting the supplied AC power to be given into DC power;

an alternating power generating circuit for DC conversion, for converting the DC power generated by the first DC power generating circuit for DC conversion into AC power of a predetermined frequency;

a transforming circuit for DC conversion, for converting a voltage of the AC power converted by the alternating power generating circuit for DC conversion into a predetermined voltage; and

a second DC power generating circuit for DC conversion, for converting the AC power converted by the transforming circuit for DC conversion into DC power, and

wherein the DC power generating circuit for AC conversion is realized by the same circuit structure as the first DC power generating circuit for DC conversion, and the alternating power generating circuit for AC conversion is realized by the same circuit structure as the alternating power generating circuit for DC conversion.

5. The drive system of claim 1, wherein the DC conversion device includes:

a first DC power generating circuit for DC conversion, for converting the supplied AC power to be given into DC power;

an alternating power generating circuit for DC conversion, for converting the DC power generated by the first DC power generating circuit for DC conversion into AC power of a predetermined frequency;

a transforming circuit for DC conversion, for converting a voltage of the AC power converted by the alternating power generating circuit for DC conversion into a predetermined voltage; and

a second DC power generating circuit for DC conversion, for converting the AC power converted by the transforming circuit for DC conversion into DC power, and

wherein the DC power generating circuit for AC conversion and the first DC power generating circuit for DC conversion are realized by one circuit used as both the circuits.

6. The drive system of claim 1, wherein the voltage converting unit includes:

a transformer for converting a voltage of AC power to be given; and

a capacitor that is connected to a primary winding of the transformer in series.

7. The drive system of claim 1, wherein the voltage converting unit further has a filter circuit part for attenuating a harmonic component of frequency components included in the AC power outputted from the frequency converting unit.

8. The drive system of claim 1, wherein the voltage converting unit includes:

a transformer for converting a voltage of AC power to be given; and

a bypass line for connecting an intermediate part of a coil-like portion of a primary winding of the transformer and one end part of the primary winding, and

wherein an inductor for current superimposition is connected to the bypass line in series.

9. The drive system of claim 1, wherein the frequency converting unit further has a power-factor improving circuit for improving a power factor at the time when the supplied AC power is converted into DC power by the DC power generating circuit for AC conversion.

10. The drive system of claim 1, wherein the drive system is a liquid crystal display apparatus that is given AC power and drives discharge tubes.

11. An AC conversion device provided in the drive system of claim 1.

12. An AC conversion device for acquiring AC power from an AC power supply and converting the supplied AC power into converted AC power having a predetermined frequency and a predetermined voltage, the AC conversion device comprising:

a frequency converting unit for converting a frequency of AC power into a predetermined frequency; and

a voltage converting unit for converting a voltage of AC power into a predetermined voltage,

wherein the frequency converting unit includes only one pair of a DC power generating circuit for AC conversion and an alternating power generating circuit for AC conversion, in which the DC power generating circuit for AC conversion converts the supplied AC power into DC power, and the alternating power generating circuit for AC conversion converts DC power which is generated by the DC power generating circuit for AC conversion, into AC power of a predetermined frequency.