September 19, 2007

Ideal for LCD TV power supplies
STR-Z2500 Series Power Supply ICs Developed
High efficiency (95%) power supplies readily constructed by using current resonance method

Sanken Electric Co., Ltd. announces the development of the STR-Z2500 Series power supply ICs which employ the current resonance method. The ICs are ideal for the main power supply (such as the power supply for driving CCFL inverters) of LCD televisions and the series features a lineup of five types of ICs, which adopt SIP 24-pin packages and differ according to input voltage and output power. Shipments will be available on October the first, with samples priced at 1,700 to 2,000 yen each. Mass production will be launched in December, starting with 500k units/month, then ramping up to 1,000k units/month from the summer of CY08.

By developing the STR-Z2500 series, Sanken Electric is now capable of providing the total LCT-TV solutions covering from main power supply ICs to control ICs for CCFL inverters, CCFLs, sub-power supply ICs for microcontrollers, ICs for DC/DC converters, etc.
1. Development background and product overview
  Power supply capacities have been increasing along with the recent trend toward larger LCD TVs, leading to demands for control of power consumption.  Additionally, their installation methods are diversifying, so LCD TV displays are progressively becoming thinner and denser, and also countermeasures for heat generation inside the TVs are becoming critical issues.  Especially, much higher efficiency of main power supplies (power supplies for driving CCFL inverters) which accounts for the largest share of power consumption is desired.

There are two methods for configuring high-efficiency power supplies: the current resonance method and its simplified version, the quasi-resonance method.  The current resonance method allows the configuration of power supplies with about 5 to 10 percent higher efficiency compared to the quasi-resonance method, but the number of parts constituting the circuit increases and circuit design becomes more complicated.

Given these facts, Sanken has integrated both a control IC, which is essential for building a current resonance type power supply, and power elements (2 MOSFETs), which are usually applied as discrete parts, into a single package of a proprietary SIP package (SLA type).  By doing this, the part counts as well as man-hours for designing circuits have been reduced.  Thus, Sanken has developed the STR-Z2500 Series power supply ICs that allow ready construction of high efficiency (about 95%) current resonance type power supplies.  These ICs are particularly ideal for power supplies driving CCFL inverters used in high-power-consuming medium- and large-scale LCD TVs (from about 32 inches to 47 inches and beyond).
2. Features
(1) Allows ready construction of high-efficiency (about 95%) power supplies by employing the current resonance method.

(2) Built-in power elements integrated into a single package.

The control IC and power elements (2 MOSFETs) are integrated into a single SIP package (Sanken name: SLA; the resin part dimensions 31 × 16 × 5 mm), which contributes to the reduction of discrete parts and man-hours needed for design.  The package is threadably mounted, allowing ready attachment onto a heat sink.

(3) Built-in function for automatic dead time detection (the industry’s first)

The IC has a built-in function for automatic dead time detection, ensuring that on/off timing is automatically optimized.  This function contributes to higher efficiency of power supplies because this function makes it unnecessary to consider the resonance current variation caused by transformers, etc. in designing, resulting in reduced man-hours for design, and it also controls the reactive currents by the optimal on/off timing of the IC.

(4) Employs a 600 V withstand-voltage BCD process for the control IC.

By making a control IC withstand voltage 600 V, sufficient withstand margin is ensured, even in power supplies with a built-in active filter (the circuit for improving power factors and controlling higher harmonics).

(5) Operating frequency: 300 kHz maximum

Making an operating frequency as high as 300 kHz maximum contributes to downsizing and low-profile of transformers.

(6) Built-in burst mode function

Power loss is controlled by operating the IC at a burst mode (intermittent IC oscillation) at light load.

(7) Built-in startup circuit

A startup circuit is built in for starting the IC during standby. This function allows no need for discrete parts for startup, which allows the component count reduction, resulting in reducing the power consumption during standby.

(8) Built-in versatile protection and other functions

Overcurrent protection, Overvoltage protection, Overload protection, Overheat protection, Resonance deviation detection and protection, Soft-start function, Maximum frequency automatic adjustment function.
3. Product lineup
  Direct current
Output power
active filter
STR-Z2586 ¥1,700 500 0.94 150
STR-Z2587 ¥1,800 500 0.60 200
STR-Z2588 ¥1,900 500 0.38 250
STR-Z2589 ¥2,000 500 0.31 300
STR-Z2519 ¥2,000 250 0.06 300
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