WS21351

WS21351 Half-bridge power IC for CFL lamps FEATURES ■ Integrated 600V half-bridge gate driver ■ Lower power level-shifting circuit ■ Adjustable oscillator frequency and preheat time ■ Maximum voltage of 600 V ■ Internal clamping zener diode ■ Soft start functionality Product Summary VOFFSET Duty Cycle Tr/Tp 600V Max. 50% 80/40ns 15.6V typ. 2μs Vclamp Deadtime (typ.) GERNERAL DESCRIPTION The WS21351 is a high-voltage monolithic integrated circuit which is designed for driving Compact Fluorescent Lamps (CFL) in a half-bridge configuration.WS21351 features a soft start function, an adjustable oscillator and an internal drive function with a high-voltage level shifter for driving the half bridge. Packages 8 Lead PDIP TYPICAL APPLICATION Rev. A Mar.2010 Copyright@W ins emi Microelectronics Co., Ltd., All right reserved. T11-1 WS21351 GENERAL INFORMATION Pin Configuration WS21351 TERMINAL ASSIGNMENTS Pin # 1 2 3 4 5 6 7 8 Name PGND OUT VDC VB VDD GND RMIN CPH Power ground Half bridge output High-voltage supply High-side floating supply Supply voltage Signal ground Oscillator frequency set resistor Preheating time set capacitor Description BLOCK DIAGRAM WS21351 2/7 Steady, Steady, keep you advance WS21351 ABSOLUTE MAXIMUM RATINGS Symbol VB VOUT VIN ICL dVOUT/dt TA TSTG TL Parameter High-side floating supply Half bridge output RMIN, CPH pins input voltage Clamping current level Allowable offset voltage slew rate Operating temperature range Storage temperature range Lead temperature (soldering,10 seconds) Min. -0.3 -0.3 -0.3 -25 -50 -25 -65 Typ. Max. 600 575 7 25 50 125 150 300 Unit V mA V/ns °C Note: more than the limit specified in the table parameters will result in permanent damage to the device. The device is not recommended in these extreme conditions of work, working conditions in the limit above which may affect device reliability. Electrical Characteristics (VBIAS(VDD, VB-Vout)=14.0V, TA=25°C, unless otherwise specified.) Symbol Parameter Condition Min. Typ. Max. Unit Supply characteristics VDDTH(ST+) VDDTH(ST-) VDDHY(ST) VCL IST IDD VDD UVLO positive going threshold VDD UVLO negative going threshold VDD-side UVLO hysteresis Supply clamping voltage Start-up supply current Dynamic operating supply current IDD =20mA VDD = 10V Running freq=85KHZ 14．4 VDD rising from 0V VDD decreasing 11.2 9 12.8 10 2．8 15．6 50 4．5 80 μA mA 14 11 V Floating supply characteristics (VB-VOUT) VHSTH(ST+) VHSTH(ST-) VHSHY(ST) IHST High-side UVLO positive going threshold High-side UVLO negative going threshold High-side UVLO hysteresis High-side quiescent supply current VB –VOUT = 14V VB –VOUT increasing VB –VOUT decreasing 7．5 7．8 9 8 1 60 uA 10．5 9．2 V Oscillator characteristics fPRE fOSC Duty DT VCPH Preheating frequency Running frequency Oscillator duty cycle Output dead time Maximum CPH voltage RMIN = 82kΩ, VCPH =0V RMIN = 82kΩ, VCPH =6V 66 29 86 34 50 2．0 6 96 39 kHz kHz % Us V MOSFET characteristics ILKMOS RON MOSFET leakage current On resistance (dynamic) VGS = 12V, ID = 500mA 10 VDS = 500V VGS = 12V, ID = 100mA 8 Ω 10 μA 3/7 Steady, Steady, keep you advance WS21351 OPERATION DESCRIPTION Under-Voltage Lockout (UVLO)Function The WS21351 has UVLO circuits for both high-side and low-side circuits. When VDD reaches VDDTH+, UVLO is released and the WS21351 operates normally. Under UVLO condition,WS21351 consumes little current, typically 50uA. After UVLO is released,WS21351 operates normally until VDD goes below VDDTH-, the UVLO has hysteresis which typically is 2.8V . At UVLO condition, all latches that determine the status of the IC are reset. WS21351 has a high-side gate driver circuit. The supply for the high-side driver is applied between VB and VOUT. To protect from malfunction of the driver at low supply voltage between VB and VOUT,WS21351 provides an additional UVLO circuit between this supply rails. If VB-VOUT is under VHSTH+, the driver holds low state to turn off the high-side switch, when VB-VOUT is higher than VHSTH– after VB-VOUT exceeds VHSTH+, operation of the driver continues. ignition and improve lamp life longevity.Accordingly, the oscillation frequency is changed in the following sequence: Preheating freq > Ignition freq > running freq. WS21351 Oscillator Operation The ballast circuit for a fluorescent lamp is based on the LCC resonant tank and a half-bridge inverter circuit, as shown in Fig4 . To accomplish Zero-Voltage Switching (ZVS) of the half-bridge inverter circuit, the LCC must be driven at a higher frequency than its resonant Frequency, which is determined by L, CS, CP, and RL; where RL is the equivalent lamp's impedance. The transfer function of LCC resonant tank is heavily dependent on the lamp impedance, RL, as illustrated in Figure 4. The oscillator inWS21351 generates effective driving frequencies to assist lamp Preheating and ignition Mode When VDD exceeds VDDTH+ threshold, theWS21351 enters preheating mode. An internal current source charges the external capacitor on pin CPH, and the voltage on pin CPH starts ramping up linearly. The frequency ramps down towards the resonance frequency of the high-Q ballast output stage causing the lamp voltage and load current to Increase. The voltage on pin CPH continues to increase and the frequency keeps decreasing until the lamp ignites. If the 4/7 Steady, Steady, keep you advance WS21351 Lamp ignites successfully, the voltage on pin CPH continues to increase until it internally limits at 6V (VCPH_MAX). The frequency stops decreasing when VCPH reach 5V and stays at the minimum frequency as programmed by an external resistor, on pin RMIN (as show in Fig 4). The minimum frequency should be set below the High-Q resonance frequency of the ballast output stage to ensure that the frequency ramps through resonance for lamp Ignition .The desired preheat time can be set by adjusting the slope of the VCPH ramp with the external capacitor on pin CPH. The relation of LCC tank frequency and Pin CPH voltage VCPH as show in Fig5. Run Mode TheWS21351 enters RUN mode when the voltage on pin CPH exceeds 5V . The lamp has ignited and the ballast output stage becomes a low-Q, series-L, parallel-RC circuit. The voltage on the CPH pin continues to increase but the frequency don't change as the minimum frequency is reached. The resonant inductor, resonant capacitor, DC bus voltage and minimum frequency determine the running lamp power. The relation of minimum run frequency and the setting resistor RRMIN as show in Fig 6. The IC stays at this minimum frequency unless VDD decreases below the VDDTH– threshold 5/7 Steady, Steady, keep you advance WS21351 WS21351 for 18W CFL Application 6/7 Steady, Steady, keep you advance WS21351 DIP-8 Package Dimension 7/7 Steady, Steady, keep you advance