January 21, 2008

STR-H7000 and H3000 Series Developed by Sanken
High-voltage Driver ICs and Control ICs for CCFL Inverters
Direct Inverters with 60% Fewer Component Counts Now Configurable

Sanken Electric Co., Ltd. has developed and started shipping samples of its new STR-H7000 series (package: 14-pin SOP) high-voltage driver ICs and STR-H3000 series (package: 16-pin SOP and 20-pin SOP) ICs.  A combination of these two types of ICs allows easy configuration of a high-efficiency direct inverter for CCFLs used in LCD TV sets.  The tax-excluded sample prices of these ICs are 1,200 yen for the STR-H7000 series and 1,000 yen to 1,500 yen for the STR-H3000 series. 

Shipping of mass-production units is scheduled to start in April, CY2008 with an initial monthly production of 100k units, ramping up to 1 million units by the end of CY2008.
   
1. Development Background and Product Overview
 

Since the larger screens and higher performances of LCD TV sets increase their power consumptions, a higher efficiency is demanded for CCFL inverters, which are responsible for a large portion of the power consumption.  In addition, as the demands for wall-mount TVs have been increasing, the demands for thinner power supply units have also increased.

Conventional power supply systems for lighting CCFLs needs to convert commercial power in three steps: (1) a PFC circuit converts 100 V AC into 380 V DC, (2) a DC/DC converter circuit converts 380 V DC into 24 V DC, and (3) a CCFL inverter circuit that drives MOS FETs converts 24 V DC into 2000 V AC.  (These voltage values are mentioned for reference.)

Compared with these processes, STR-H7000 series high-voltage driver ICs with 600 V withstand voltage, which Sanken Electric has developed, can drive MOS FETs directly in the inverter circuit using the input power supply as is from the PFC circuit.  Mounting this IC eliminates the necessity of a DC/DC converter circuit and reduces power conversions to two steps, namely, (1) conversion by the PFC circuit and (2) conversion by the CCFL inverter circuit, thereby improving the power supply efficiency by about 10%.

On the other hand, half-bridge control has been mainly used for CCFL lighting control. Because of the circuit characteristic, the control system requires plural diodes for circuit protection and these diodes generate a large amount of heat, requiring a thick heat sink and thus constraining realization of thinner power supply units.

The new STR-H7000 series adopts full-bridge control, which does not require diodes for circuit protection. In other words, heat sinks are not necessary because the circuit dissipates less heat, making it possible to achieve an even thinner power supply unit. An efficient inverter reduces the load on the PFC circuit, thus reducing the cost of the PFC circuit.

Additionally, the STR-H3000 series control ICs has been developed as exclusive ICs for controlling STR-H7000 series ICs. Arranging the STR-H7000 series on the primary side and the STR-H3000 series on the secondary side will optimize the inverter system. Furthermore, configuring a direct inverter with full-bridge control allows to decrease the component count by about 60% compared with the conventional half-bridge control, achieving lower inverter prices.

 
2. Features
  STR-H7000 Series High-voltage Driver ICs
 
(1) Built-in high-voltage driver with 600V withstand voltage
The STR-H7000 series incorporates a high-voltage driver with 600 V withstand voltage, allowing direct drive of MOS FETs in the inverter circuit with the input power from the PFC circuit.
(2) Full-bridge control for fewer parts and a thinner power supply unit
Full-bridge control does not require protection diodes needed in half-bridge control.
Compared with half-bridge control, the MOS FETs dissipate less heat and no longer require heat sinks, so MOS FETs can be mounted lying directly onto the printed circuit board to achieve a thinner inverter.
(3) High drive performance (drive voltage: 16 V, max., drive impedance: source side: 12 Ω, sink side 5 Ω)
High drive performance for MOS FETs allows to light multiple CCFLs with only one transformer.
(Example: A single driver for a 57-inch panel can light 26 CCFLs.)
(4) Protection functions
  • · Undervoltage lockout for power supply voltage
  • · Undervoltage lockout on high side (STR-H7224)
  • · Prevention of simultaneous turning on of MOS FETs
  • · Overcurrent protection (STR-H7224)
  • · Thermal protection (STR-H7224)
  STR-H3000 Series Control ICs
 
(1) Various synchronous functions
·  External signal synchronization (STR-H3431S)
Driving in synchronization with an external signal is possible. Destruction in an abnormal state (when double pulses are generated during switchover of a sync signal, or when a sync signal is constantly on or off) can be prevented with no external circuits.
·  Synchronization of plural ICs
Two ICs can be synchronized by merely connecting their oscillator terminals each other, which is useful when high voltages from these two ICs are applied to both ends of a panel.
(2) Dimming function
An oscillator for burst dimming is incorporated.  Burst dimming is accomplished by a DC signal or by a pulse signal.
  • · Positive or negative dimming can be selected. (STR-H3431/STR-H3431S)
  • · Current dimming is also possible. (STR-H3431/STR-H3431S)
(3) Various protection functions
  • · Timer latch protection
  • · Overvoltage protection
  • · Overload detection
  • · Error output (STR-H3431/STR-H3431S)
  • · Undervoltage lockout for power supply voltage (STR-H3431/STR-H3431S)
   
3. Product Lineup
  STR-H7000 Series
 
Part Number Sample Price Package
(Dimensions of
resin part in mm)
Withstand
Voltage
Operation
start voltage
STR-H7224 1,200 yen 14-pin SOP(8.9×4.4×1.5) 600V 9.0V typ
STR-H7214 1,200 yen 7.0V typ
   
  STR-H3000 Series
 
Part Number Sample Price Package
(Dimensions of
resin part in mm)
External Signal
Synchronization
STR-H3431 1,200 yen 20-pin SOP (12.7×5.4×1.8) Not available
STR-H3431S 1,500 yen Available
STR-H3311 1,000 yen 16-pin SOP (10.2×4.4×1.5) Not available
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