| White LED Driver with Protection |
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White LED Driver with High Temperature Protection
Circuit driving a high-power white LED (WLED), open or short circuit fault occurs when the temperature is too high, and thermistor will turn off the LED. If you work outside the maximum operating temperature range any IC of life will be shortened. When the junction temperature exceeds a certain value, it will be permanently damaged. Philips Lumileds LUXEON high power LED module is manufactured in the thermally enhanced substrate, thus heating will be less. This material improves thermal performance, and allowed to continue working in the high-current, to meet the requirements of high-brightness lighting . However, for applications such as camera flash, is to avoid damage to the device power consumption continue to work, you need to provide additional thermal protection function.
The circuit in Figure 1 include a suitable camera flash applications charge pump regulator (IC1), the device for up to eight white LED (WLED) adjust the current. Paralleling all eight drives as a single 1W LUXEON Star high-output WLED module provides up to 480mA. When the open-drain input EN is pulled to ground, IC1 enters shutdown mode.
Circuit driving a high-power WLED, LED will turn off when the temperature is too high, and the thermistor open or short circuit fault
Can take advantage of the open-drain comparator (IC2), a thermistor and internal reference with a dual space is compact and extremely cost-effective to build a thermal shutdown circuit. VTHERM drops to below 1.2V internal reference voltage, the comparator A EN is pulled low to ground. When the high temperature of the thermistor (R2), will perform the operation. Comparator B is used to provide an open circuit failure protection function, that is, when the thermistor contact is opened, EN is pulled low. Thermistor open circuit failure occurs, VTHERM R1 pulled up, so that the comparator B to pull EN. Resistor divider R3-R4 sets the open threshold voltage, resistors R1 and R2 sets thermistor thermal shutdown threshold.
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3月6日（水）16:34 | トラックバック(0) | コメント(0) | Hobby | 管理
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