Supertex inc. HV9931DB2 LED Driver Demoboard Input 230VAC // Output 350mA, 40V (14W) General Description The HV9931 LED driver is primarily targeted at low to featured are output current soft start and protections from medium power LED lighting applications where galvanic line overvoltage, load overvoltage and open circuit. The isolation of the LED string is not an essential requirement. driver is inherently short circuit proof by virtue of the peak The driver provides near unity power factor and constant current regulation method. current regulation using a two stage topology driven by a single MOSFET and control IC. Triac dimming of this Specifications design is possible with the addition of some components for Input voltage: 200V to 265V , 50Hz RMS RMS preloading and inrush current shaping. Output voltage: 0 to 40V The DB1 and DB2 Demoboards were designed for a fixed Output current: 350mA +/-5% string current of 350mA and a string voltage of 40V for a load Output power: 14W power of about 14W. The boards will regulate current for an output voltage down to 0V. Power factor 98% Total harmonic distortion EN61000-3-2 Class C Nominal input voltage for the DB1 is 120VAC, for the DB2 EMI limits CISPR 15 (see text) 230VAC. Design for universal input (85 to 265VAC) is by all means possible but does increase cost and size while Efficiency 83% lowering efficiency. Output current ripple 30% PP The input EMI filter was designed to suppress the differential Input overvoltage protection 265V , Non-Latching RMS mode switching noise to meet CISPR15 requirements. Output overvoltage protection 46V, Latching No specific components were added to suppress currents Switching frequency 80kHz of common mode nature. Common mode current can be NOM controlled in many ways to satisfy CISPR 15 requirements. Dimensions: 3.5 x 3.0 x 1.25 The board is fitted with a number of optional circuits a schematic of a simplified driver is given as well. The circuits Board Layout and Connections A V V A Doc. DSDB-HV9931DB2 Supertex inc. A062513 www.supertex.comHV9931DB2 Special Note: Warning The electrolytic capacitor carries a hazardous voltage for an Working with this board can cause serious bodily harm or extended time after the board is disconnected. The board death. Connecting the board to a source of line voltage will includes a 1M resistor placed across the electrolytic ca- result in the presence of hazardous voltage throughout the pacitor which will slowly discharge the capacitor after dis- system including the LED load. connection from line voltage. The voltage will fall more or The board should only be handled by persons well aware of less exponentially to zero with a time constant of about 100 the dangers involved with working on live electrical equip- seconds. Check the capacitor voltage before handling the ment. Extreme care should be taken to protect against elec- board. tric shock. Disconnect the board before attempting to make any changes to the system configuration. Always work with another person nearby who can offer assistance in case of an emergency. Wear safety glasses for eye protection. Connection Instructions Step 1. voltage and LED string voltage are more or less constant Carefully inspect the board for shipping damage, loose as well. Duty cycle and bus voltage do adjust in response to components, etc, before making connections. changes in line or load voltage but are otherwise constant over the course of a line cycle. With the HV9931, OFF time is Step 2. fixed by design, being programmed by an external resistor, Attach the board to the line and load as shown in the diagram. whereas ON time adjusts to a more or less constant value, Be sure to check for correct polarity when connecting the being under control of the HV9931 peak current regulator. LED string to avoid damage to the string. The board is short circuit and open circuit proof. The LED string voltage can The input or buck-boost stage is designed for operation be anything between zero and 40V, though performance will in discontinuous conduction mode (DCM) throughout the suffer when the string voltage is substantially lower than the range of line and load voltage anticipated. This can be target of 40V. See the typical performance graphs. accomplished by making the input inductor sufficiently small. A well known property of the DCM buck-boost stage, when Step 3. operated with constant ON time and constant OFF time, is Energize the mains supply. The board can be connected to that input current is proportional to input voltage, whether mains directly. Alternatively voltage can be raised gradually in peak value or average value. This results in sinusoidal from zero to full line voltage with the aid of an adjustable AC input current when the input voltage is sinusoidal, thereby supply such as a Variac or a programmable AC source. giving unity power factor operation when operating from the Principles of Operation rectified AC line voltage. The HV9931 topology can be viewed as a series connection When operated in the anticipated range of line and load of two basic power supply topologies, (1) a buck-boost voltage, the MOSFET ON time will be under control of the stage as first or input stage, for purpose of converting AC output stage current controller, which turns the MOSFET line power into a source of DC power, commonly known as off when sensing that the output inductor current has the DC bus, having sufficient capacitive energy storage to reached the desired peak current level as programmed by maintain the bus voltage more or less constant throughout a resistive divider at the CS2 pin. Under certain abnormal the AC line cycle, and (2) a buck stage as second or output circumstances such as initial run-up and line undervoltage, stage for powering the LED string, stepping down the DC which both could lead to the draw of abnormally high line bus voltage to the LED string voltage in order to produce a current, ON time is further curtailed by the action of the CS1 steady LED string current. comparator, which monitors the input stage inductor current The output or buck stage is designed for operation in against a threshold. This threshold can be a simple DC level continuous conduction mode (CCM), operating with about 20 or be shaped in time as is performed on the Demoboard. In to 30% inductor current ripple. This amount of ripple serves particular, when shaping the CS1 threshold with the shape of the needs of the HV9931 peak current controller which relies the rectified AC line input voltage waveform, the line current on a sloping inductor current for setting ON time, and is of an will be bounded by a more or less sinusoidal line current acceptable level to high brightness LEDs. Duty cycle is more envelope which results in sinusoidal input current for low line or less constant throughout the line cycle as the DC bus and other abnormal conditions. Doc. DSDB-HV9931DB2 Supertex inc. A062513 2 www.supertex.com