BL8896 High-performance current mode PWM Controller GENERAL DESCRIPTION FEATURES BL8896 is a high-performance current mode PWM control IC designed for AC/DC convertor, which built-in high-voltage power switch tube and supplies continuous output power of 10W within the range of wide-voltage between 85V and 300V, the output power of peak value can be up to 12W.The combination of optimized reasonable circuit design and bipolar facture technology with high performance and price ratio economizes the whole cost ultimately. The power controller can be applied to the typical flyback circuit topology so as to form a simple AC/DC transformer. IC circuit can use the power switch tube itself within a larger version of startup, greatly reduces the power loss of starting resistance .IC built-in PFM function that when the output power increases then the working frequency increases, thus reducing switching loss and achieving high efficiency when the power output decreases. The PFM function combination of patent drive circuit that can easily meet "of energy Star 2.0" strict requirements. When VCC reaches 12V, the chip internal over voltage protection activates and limits the output voltage rising. That can prevent the too high output voltage because the light coupling or the feedback circuit damaged. The circuit built-in the input voltage compensation function, which realizes the constant output power limiting in the whole power grid conditions. In the IC internal that provides the overload and the perfect saturation function. It can real time control van overload, transformer saturation, output short circuit in abnormal condition, so improving the reliability of power supply. IC has integrated the internal temperature protection function, when the system is overheating, the output power will be lower, or shuts down the output. We can provide meeting ROHS and green environmental protection requirements of DIP-8 standard. ■ Meeting AC85-300V input voltage range of the design requirements ■ Low starting current and working current ■ The standby power consumption can be as low as 0.15W ■ Improve driving circuit efficiency 2-3% ■ Meeting the requirements of energy efficiency energy star 2.0 ■ With temperature compensation function accurate current control ■ Wide voltage continuous output power can be up to 10W, the peak output power can be up to 12W ■ AC line compensation ■ With functions of thermal protection (OTP) ■ With functions of over voltage protection (OVP) ■ Can be realized without Y capacitor system design ■ Less peripheral components, and the overall scheme of low cost www.belling.com.cn APPLICATIONS ■ The charger ■ DVD/DVB power ■ Small appliances (such as: induction cooker) ■ PC&LCD TV standby power supply ■ The power adapter (such as communications terminal products) 1 V1.0 BL8896 High-performance current mode PWM Controller TYPICAL APPLICATION Figure 1 Typical application diagram www.belling.com.cn 2 V1.0 BL8896 High-performance current mode PWM Controller GENERALINFORMATION Pin Configuration The pin map is shown as below for DIP-8 Absolute Maximum Ratings Power supply voltage VCC 18V Pins input voltage VCC+0.3V Endurance voltage of OC collector -0.3-750V VIN OC Switching current of peak value 1000mA VCC OC Total dissipation power 1500mW IS Operating temperature range -20 to +125℃ Deposit temperature range -55 to +150℃ GND BL8896 FB NC Welding temperature +260℃,10S TERMINAL ASSIGNMENTS Pin Num. Pin Name I/O Description 1 VIN I Circuit input compensation and high voltage current source to trigger feet, external compensation resistance 2 VCC P Power Supply 3 GND P Ground 4 NC 5 FB I Feedback pins 6 IS I Switching current sampling and limit enactment, sampling resistance of external current 7/8 OC O Output pins, meet switching transformer No Connection Recommended operating conditions PARAMETER MIN Power supply voltage VCC 5 Pins input voltage -0.3 Peak inverse voltage - Switching current of peak value Operating temperature www.belling.com.cn TYP MAX UNIT 10 V - Vcc V - 650 V - 800 -10 100 mA ℃ 3 V1.0 BL8896 High-performance current mode PWM Controller BLOCK DIAGRAM Figure 2 schematic diagram www.belling.com.cn 4 V1.0 BL8896 High-performance current mode PWM Controller ELECTRICAL CHARACTERISTICS (Ta=25℃, VCC=5.5-7.5V, RS=1Ω, if not otherwise noted) Parameter Symbol Test Conditions Min I_OC=10mA 750 Typ Max Unit Output Section Max withstanding voltage of the switching tube Saturation voltage Output Rise time Output Fall time Vsat TR TF V I_OC=500mA CL=1nF CL=1nF 0.8 75 75 V ns ns Current Sampling Section Current sampling threshold The maximum current Transmission delay Oscillator Section Oscillating Frequency Voltage stability Temperature stability RS=1Ω 0.63 0.65 V 0.61 - 0.63 150 0.65 250 A ns KHz % % ns F_OSC 65 VCC=5-10V Ta=0-85℃ Leading edge blanking time Feedback Section FB Input impedance 0.61 Pull up Current Pull down Resistor - 500 1 1 - - 550 40 - uA KΩ 55 - 60 1.5 65 - % % 15 2.0 1.0 8.9 2.5 12 50 - uA mA mA V V V PWM Section Maximum Duty Ratio Minimum Duty Ratio D_max D_min VFB=2.5V VFB=0V Power Supply Current Section Initiation Static Current Static Current High voltage current source IQ VCC=8.0V Startup voltage Oscillator turn off voltage Over Voltage limiting Threshold www.belling.com.cn - Vac>80V 11 5 13 V1.0 BL8896 High-performance current mode PWM Controller OPERATION DESCRIPTION ●Start control: During start-up phase, the internal ●Standby benchmark, and In standby mode, when the output voltage protection circuit is stopped working, the small increases, then the FB voltages lower. If the FB current of 50uA on the starting resistance is input voltage is less than 1.8V (about between from VIN to the base of the Power Transistor, the 1.2-1.8V) then the oscillator cycle will increase, amplifying current from Emitter through current the smaller FB, the wider oscillator cycle. This oscillators, driving circuit limiting circuit outflows to VCC, more than 50uA feature frequency reduction control circuit: is to reduce the standby power current part charge to parallel capacitor of VCC, consumption and prevent the occurrence of audio when VCC voltage rises to 8.9 V, entering a state interference at the same time. of PWM control chip. ●Efficient ●PWM makes the switch tube in critical saturation driving control: The voltage of FB pins through the driving circuit: The efficient driving circuit partial pressure resistance exports to the PWM state, improving the frequency of the triode, comparator as the peak switching current effectively reference, the FB signal determines the size of the improving the work efficiency of the whole system, switch tube peak current, through the FB to realize greatly reducing the fever of the chip at the same the control of the PWM control. At the same time time. That makes the system more reliable. the Output pulse duty ratio is limited by maximum ●AC duty cycle, the FB is controlled by internal and the voltage size and real-time compensate the external feedback circuit. maximum output power; this makes the maximum ●External limiting power constant. When high and low ac is feedback circuit: After amplification the reducing the triode switch loss, line compensation: The chip from VIN detects system output error adjusting signal is converted input. into current signal that can adjust the voltage of FB ●Thermal by isolation transmission of the optocoupler. The temperature is higher than 140℃, then making the heavier load, the smaller optocoupler current, the internal FB voltage reducing and the oscillator higher FB voltage, the greater duty ratio of PWM cycle widening, reducing or closing the power signal, the output power increases, and vice versa, output, so the BL8896 temperature does not the load is light, the feedback current is added, the exceed 150℃ in order to achieve protection. protection function: When the internal FB voltage decreases, the duty ratio decreases, and the output decreases, so as to realize the adjustment of the output voltage. ●VCC overvoltage protection circuit: if the peripheral feedback makes the VCC increasing that is more than 12V, then the internal feedback circuit makes the FB voltage reducing and reducing the output power, it makes the VCC voltage keeping in 12V, this feature can prevent the output voltage increasing because the optocoupler or feedback is damaged. Thus the secondary circuit and its output load will not damage. www.belling.com.cn 6 V1.0 BL8896 High-performance current mode PWM Controller Electric Parameter Definitions Application information ●Start-up static current: The minimum current sourcing current which can enable VCC surging when VCC is connected to a filter capacitor and an adjustable current sourcing. ●Start-up voltage: The maximum of VCC above. ●Restart-up voltage: The minimum of VCC above. ●Oscillator shut-down voltage: The Negative edge of VCC above; the value of VCC which can stop the oscillator. ●Static current: The VCC power supply current in normal period when FB is connected to the ground by a 1.0KΩ resistance. ●FB pull up current: which occurs in normal period, when FB=2.5V, and IS=0A. ●FB upper current protection: The pull down current of FB when FB=2.0V and IS=0.3A in normal period. ● FB feedback and control In normal working state, the FB voltage will determine the maximum switching current value, the higher the voltage, the bigger switch current (only limited to peak current limit). The FB pin internal pull-up 550uA current source, pull-down about 40KΩ resistor (approximate equivalent), An external resistor reduces the depth of the feedback, the size of the external resistance will not affect the maximum peak current, it is recommended to use 7.5K to 10K resistor, an external resistor can improve reaction speed of the system with overload and the input voltage jumping. It is advantageous to the short circuit protection. Moreover the FB voltage below 1.8V, will make the period of oscillation widening, the switch frequency falling, It is lower than 1.8V, the frequency will be lower. FB converter capacitance will affect feedback bandwidth, thus influence some external parameters, such as transient characteristics. ●The VCC voltage limit: The value of VCC when there is no feedback circuit of BL8896 in normal period. ●OC upper limit current: If FB=2.0V, the minimum OC current when there is pull down current in FB. Figure 3. FB feedback and control www.belling.com.cn 7 V1.0 BL8896 High-performance current mode PWM Controller Typical applications for CFB capacitance value, can be between 10-100nF selection based on the frequency characteristics of the feedback loop, General application can use the 100nF. ● Over temperature protection IC has built-in precision over temperature protection function. In the chip internal when the temperature reaches 140 ℃ , the thermal protection circuit pulls down the clock signal, and the switch frequency is reduced in order to reduce the power consumption. The Switching frequency decreases with the rise of the temperature, and until the oscillation shuts down. As shown in the figure below Figure 4.Over temperature protection ●Power tube driving characteristics and high pressure offset technology In the IC internal, it has an unique offset technology, at the time of power tube shutting off, the base output of Power Transistor drops down to the ground instantly, at the same time the offset output voltage of emitter is greater than the base. Launching E junction reverse, it accelerates the IC current rate of descent and expands the effective security work area, The CB of the switch tube is in the reverse voltage that achieves greater than 750V voltage. About more details of the switch tube please refer to the relevant technical data compression characteristics. www.belling.com.cn 8 Figure5 The collector emitter clamping voltage Offset waveform as shown in the figure below: Figure 6 Vbe driving voltage waveform ●Over voltage and under-voltage protection IC has with hysteresis under voltage protection function. When the VCC voltage achieves to 8.9 V the IC will start, the initial voltage is provided by a driving resistor, the input of high voltage through the driving resistor enters to B injection of the switch tube, the amplifying IC current through current limiting circuit outflows to VCC capacitor Thus forming the driving voltage. The VCC voltage should be maintained in between 5-10V (including full load) in the normal working, if the VCC voltage pulls down to 2.5V the oscillator will enter closed state. V1.0 BL8896 High-performance current mode PWM Controller In IC internal, the VCC has an upper limit voltage comparator control, if the VCC is more than 12V the comparator actions, the FB will be drop-down, locking the VCC in 12V, achieving over-voltage limit function. Use this function, it can easily achieve front end voltage feedback function; also can avoid the output voltage rising significantly in the open loop, guaranteeing the safety of the load. Therefore, the VCC should keep in a suitable range and avoid the VCC rising too high with large output loads, leading to the output voltage dropping because the IC overvoltage limitation. ●Coil larges current programming and driving current compensation circuit Figure 7 Coil larges current programming and driving current compensation circuit www.belling.com.cn 9 The IC has a current limiting function. Each switching cycle detects the switching current, when it achieves the setting current of the FB or the upper limit of the current, then entering the closed cycle, the current detection has the functions of real-time leading edge blanking, shielding switching peak, avoiding error detection of the switching current. The reasonable temperature compensation eliminates the influence of the temperature, relative to conventional transistor, the switching current in a wide range can be very accurate, this don't have too big margin when designing scheme, then can satisfy work in big temperature range, improving the use safety of the circuit. Inside the IS chip connects a resistor R1 to the ground, using to compensate the influence of the internal drive current to the coil current. Its corresponding relationship is I drive*R1=0.7V, the biggest coil current is calculated according to the volume of power, this can be made of the external resistance R2 programming, its relationship is: Iwinding(Max)=0.7/R2. As a result of the existence of the internal resistor R1. When calculating the R2 value will not consider the influence of the internal drive current to the coil current. V1.0 BL8896 High-performance current mode PWM Controller ● The heat dissipation requirements ● VCC design points As a result of the drive technology breakthrough, When the VCC voltage rises to 8.9V, the IC will the chip internal loss (fever) 40% less than the PIN start, the VCC capacitor will store enough power TO PIN the other products, but for a typical power for IC before entering normal working until switch, cooling establishing normal output voltage; So the VCC measures, in order to avoid high temperature lead capacitor is not too small, and the reasonable VCC to thermal protection. In the IC internal, this main capacitor is 22uF. should use the necessary heating is the generated by the switching loss, so the appropriate cooling position is the IC Pin7-8 feet, an easy to use method is laid a certain area of PCB copper foil in Pin7-8 feet, especially it will increase thermal capacity on copper foil tinning, For a 85-265V input, typical application of 10W output, 200mm ² is the size of copper foil is necessary. Figure 8 Heat dissipation map www.belling.com.cn 10 V1.0 BL8896 High-performance current mode PWM Controller Package size Symbol Dimensions In Inches Min Max Min Max A 3.710 4.310 0.146 0.170 A1 0.510 0.020 - A2 3.200 3.600 0.126 0.142 B 0.380 0.570 0.015 0.020 B1 1.524(BSC) 0.060(BSC) C 0.204 0.360 0.008 0.014 D 9.000 9.400 0.354 0.370 E 6.200 6.600 0.244 0.260 E1 7.320 7.920 0.288 0.312 e www.belling.com.cn Dimensions In Millimeters 2.540(BSC) 0.100(BSC) L 3.00 3.60 0.118 0.142 E2 8.400 9.000 0.331 0.354 11 V1.0 BL8896 High-performance current mode PWM Controller IC reference junction temperature and thermal resistance IC reference junction temperature and thermal resistance DIP8 encapsulating junction temperature data (θJC)1 …………………………………………………………………25℃/W (θJA)2 …………………………………………………………………70℃/W Note: 1. The test points to Pin7, 8 close to encapsulate the position. 2. Pin7, 8 are connected in a 2 oz copper area of not less than 200mm². www.belling.com.cn 12 V1.0