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[FAQ] TI’ s solution - UV Sterilization Box

Prodigy 705 points

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TI’ s solution - UV Sterilization Box

UV sterilization box was designed by the principle of using UV rays to kill bacteria. UV LED can produce UV rays of 260nm ~ 280nm which can cut off bacteria DNA / RNA directly and then kill bacteria completely, with a sterilizing rate up to 99%. The LED ultraviolet sterilization technology, first applied to US space water disinfection, now is gradually applied to our daily life. LED strong UV energy can decompose the molecular structure of odor, and effectively remove the musty odor of cosmetics, glasses, watches and other objects, which can be used for sterilization of baby products and everyday objects.

TI provides the system solution of UV sterilization box, and its functional block diagram is as follows.

Figure 1: The system block diagram of UV sterilization box (without battery)

Figure 2: The system block diagram of UV sterilization box (with battery)

Power supply scheme

UCC2891x series is a flyback controller with FM + AM hybrid control, which integrates 700V MOSFET and supports 85-265VAC bus voltage. Among them, UCC28910 can achieve a maximum output power of 9.5W and UCC28911 can achieve a maximum output power of 12W.

It has the following advantages:

1. Low frequency operation at light load to improve efficiency;

2. Valley switching to reduce switching loss;

3. Two output modes: constant voltage(CV) and constant current(CC);

4. 115-kHz Maximum Switching Frequency Design for High-Power Density, and Frequency Dithering to Ease EMI Compliance;

5. Perfect protection features: AC bus protection, output over-voltage protection, over-temperature protection, short circuit protection;

6. The PSR mode is used to reduce optocouplers and TL431, and the V/I regulation precision of ± 5% can be achieved;

7. No external current sense resistor needed;

8. Enables <30mW System Standby Power;

9. No risk of audible noise

 

The UCC28911 design can refer to TIDA-00473 10-W Bias Supply for Brushless DC Applications With >75% Efficiency at Low Load Reference Design.

Figure 3: The system block diagram of TIDA-00473

The TLV760 is an integrated linear-voltage regulator featuring operation from an input as high as 30 V. The TLV760 has a maximum dropout of 1.2 V at the full 100-mA load.. TLV760 is available in 3.3V, 5V, 12V, and 15V versions. SOT-23 packaging allows devices to be used in space-constrained situations. TLV760 withstands a voltage of up to 30V and has reliable internal thermal protection function, which can protect itself from grounding short circuits, ambient temperature rise, high load or high voltage drop events.

Figure 4: Simplified schematic diagram of TLV760

The TLV704 series of low-dropout (LDO) regulators are ultralow quiescent current devices designed for extremely power-sensitive applications. Quiescent current is virtually constant over the complete load current and ambient temperature range. These devices are an ideal power-management attachment to low-power microcontrollers, such as the MSP430.. The TLV704 operates over a wide operating input voltage of 2.5 V to 24 V. Thus, the device is an excellent choice for both battery-powered systems as well as industrial applications that undergo large line transients..

Figure 5: Simplified schematic diagram of TLV704

Charging scheme

BQ25619 is a highly integrated 1.5A battery charging management and system power path management device, which is suitable for the single lithium-ion and lithium polymer battery. Its wide input voltage range of 3.9V to 13.5V makes BQ25619 suitable for a variety of applications. BQ25619 internally integrates input reverse blocking FET (RBFET, Q1), high side switching FET (HSFET, Q2), low side switching FET (LSFET, Q3), battery FET (BATFET, Q4) and bootstrap diode, simplifying the system design. The conduction resistor of BATFET is only 19.5mΩ, and the low-impedance power path management can optimize the operation efficiency, shorten the battery charging time and extend the battery operation time in the discharging stage. At 5V input and 1A charging current, the charging efficiency can reach 94%.. The I2C interface with charging and system settings makes it a truly flexible solution.

Figure 6: Simplified schematic diagram of BQ25619

Compared with BQ25619, BQ25616 is an independent battery charging management device with a maximum charging current of 3A and a faster charging speed.

Figure 7: Simplified schematic diagram of BQ25616

BQ2970 provides protection function for a single-cell Li-Ion/Li-Polymer battery pack, and monitors external power MOSFET to provide protection in case of high charge and discharge current, including overcharge protection, over-discharge protection, overcharge and discharge overcurrent protection, short circuit detection. The current consumed in normal mode operation is only 4µA, reducing battery’s power consumption. The size is only 1.5mm * 1.5mm * 0.75mm, reducing the size of the battery pack.

Figure 8: Simplified schematic diagram of BQ2970

LED drive scheme

High-performance RGB LED driver is essential in smart home and other applications equipped with man-machine interaction. Led animation effects (such as flicking, breathing and chasing) can greatly improve the user experience, and meanwhile, minimizing system noise is also crucial.

LP5012 is a 12 channel constant current sink LED driver. LP5012 includes integrated color mixing and brightness control, and pre-configuration features can simplify the software coding process. The integrated 12 bit, 29kHz PWM generator equipped for each channel can make LED color smooth, vivid and eliminate audible noise. Each LED is controlled independently, which helps to achieve a smooth dimming effect. Independent color mixing and brightness control registers make software coding very simple. When the breathing effect of fade in and fade out type is taken as the goal, global R, G, B control can significantly reduce MCU load. LP5012 can also realize PWM phase-shift function to help reduce input power when multiple LEDs are turned on at the same time. LP5012 can realize automatic energy-saving mode to achieve ultra-low static current. When all channels are turned off for 30ms, the total power consumption of the device will be reduced to 10µA, which makes the LP5012 device become a potential choice for battery-powered terminal equipment.

Figure 9: Simplified schematic diagram of LP5012

TPS61169 is a boost LED Driver with a 40V, 1.8A MOSFET integrated internally, which can drive a single LED or LED string for small or large panel backlighting. The default white LED current is set through the external sensor resistance RSET, and the feedback voltage is stabilized to 204mV. During operation, the LED current can be controlled by a pulse width modulation (PWM) signal applied to the CTRL pin. The duty cycle of the PWM signal determines the feedback reference voltage. TPS61169 will not burst LED current, therefore, it will not generate audible noise on the output capacitor. To provide the optimum protection, the device integrates the LED open circuit protection feature, which will disable TPS61169 in the LED open-circuit state, to prevent the output voltage from exceeding the IC absolute maximum rated voltage.

Figure 10: Simplified schematic diagram of TPS61169

Master control scheme

MSP430FR211x - this ultra-low power, low-cost MCU - has a powerful 16 bit RISC CPU, providing 2KB ~ 4KB of FRAM and 1KB of SRAM. The serial interface includes UART, IrDA or SPI, which integrates 6-bit DAC and 8-Channel 10 bit ADC and has 12 GPIO ports. Its low power consumption and QFN24 (3 * 3mm) packaging is very suitable for portable devices.

Figure 11: Internal resources of MSP430FR211x

Audio scheme

The TPA6203A1 is a 1.25W mono fully differential audio amplifier with a power supply range of 2.5V to 5.5V, which can drive a speaker with at least 8 Ω impedance. The quiescent supply current is only 1.7mA, and the shutdown mode consumes only 10 µA. The 2mm * 2mm tiny packaging and only 5 peripheral devices greatly save the PCB board area.

Figure 12: Reference schematic diagram of TPA6203A1

For the design of TPA6203A1, you may refer toTIDA-01628 Reference Design for Automotive Cluster Driver Notification Functions TIDA-01628 Reference Design for Automotive Cluster Driver Notification Functions.