Mechanism

Device Structure

Material selection

Because the photodiode is sensitive to particular wavelength range, so according to wavelength of light source, the corresponding materials will be chosen to do detection. The materials shown below :

Silicon-based PD : Common sensing wavelength within 400~1100 nm
Compound PD : InGaAs PD, common sensing wavelength within 900~1700nm

Characteristics

Responsivity : The conversion efficiency between radiant optical power and the generated current ; The unit is Ampere/Watt (A/W), which can also be converted to quantum efficiency (%)
Dark current : The internal flowing current in the optical sensing device with no incident light environment ; The unit is nA
Breakdown Voltage : The minimum reverse bias voltage when diode reverse conducting
Responsivity spectrum : The line diagram of photocurrent conversion efficiency over different wavelength of incident light source. The light spectral shown as below :

Mechanism

Main application

In addition to its high voltage withstand capability, VD-MOSFET also possesses fast switching characteristics, enabling efficient power conversion. During switching operations, VD-MOSFET can transit between high-resistance and low-resistance states in a very short time, thereby improving overall system efficiency. Furthermore, VD-MOSFET offers low static power consumption and high reliability, making it suitable for a wide range of applications.

The main applications of VD-MOSFET include power converters, lighting control, DC motor control, electronic locks, chargers, wireless chargers, and power factor correctors. In these applications, VD-MOSFET can provide efficient power conversion and reliability while meeting the requirements for high voltage and low resistance. As a result, it finds widespread use and favor in many high-power applications.

Key parameters for MOSFET application

When using MOSFETs, it is important to consider insulation, heat dissipation, electrostatic protection, and good circuit design. In designing MOSFET circuits, factors such as input power, load, and control circuits need to be considered to ensure the proper functioning of the entire system. Additionally, it is necessary to select and configure other electronic components such as diodes and capacitors appropriately. When using MOSFETs, it is necessary to understand their important parameters, such as：

• Absolute Maximum Ratings :

– BVDSS (Drain-Source Breakdown Voltage) : Maximum breakdown voltage between drain and source.
– VGSS (Gate-Source Voltage) : Maximum driving voltage between gate and source.
– ID(max) (Continuous Drain current (max.) : Maximum continuous drain current.
– PD (Power Dissipation) : Maximum power dissipation of the MOSFET.
– Tj (Operating Junction Temperature) : Maximum operating junction temperature of the MOSFET.

• Electricity Characteristic :

– RDS(on) (Drain to Source on Resistance) : On-resistance of the drain-source channel.
– IDSS (Drain to Source Leakage Current) : Leakage current between drain and source.
– IGSS (Gate to Source Leakage Current) : Leakage current between gate and source.
– Vth (Gate threshold Voltage) : MOSFET turn-on voltage or gate threshold voltage.
– VSD (Diode forward voltage drop) : Parasitic diode forward voltage drop.

• Dynamic Parameters :

– Ciss (Input Capacitance) : Input power capacitance
The total capacitance of Cgs (gate-source capacitance) and Cgd (gate-drain capacitance).
– Coss (Output Capacitance) : Output power capacitance
The total capacitance of Cds (drain-source capacitance) and Cgd (gate-drain capacitance), and it represents all the capacitance on the output power side.
– Crss (Reverse Transfer Capacitance) : Feedback capacitance
Cgd (gate-drain capacitance)

• Transfer Switch Parameters :

– Qg (Total Gate Charge):
The amount of gate charge required for the MOSFET to transit from 0V gate voltage to a certain voltage during operation, which is charged by Ciss (input capacitance).
– Qgs (Gate to Source Charge):
The amount of charge between the gate and source needed for the gate voltage to rise from 0V to a certain voltage, charged by the gate-to-source capacitance.
– Qgd (Gate to Drain Charge):
The amount of charge between the gate and drain needed for the drain-to-source voltage (VDS) to drop from the supply voltage to the on-state voltage, charged by the gate-to-drain capacitance.
– Tr (Rising Time):
The time required for the drain-to-source voltage to decrease from 90% of the setting voltage to 10%.
– Td(on) (Turn On Delay Time):
The time from the gate-to-source voltage drops to 90% of the setting voltage to the drain-to-source voltage rises to 10% of the setting voltage.
– Tf (Falling Time):
The time required for the drain-to-source voltage to rise from 10% to 90% of the setting voltage.
– Td(off) (Turn Off Delay Time):
The time from the gate-to-source voltage drops to 90% of the setting voltage to the drain-to-source voltage rises to 10% of the setting voltage.

Mechanism

General LED Series (TASC)

Chip structure

Parameters Explanation

Dominant wavelength (WLD) : The wavelength which is most closest to vision color of human eye
Peak wavelength (WLP) : The wavelength with highest intensity in light spectrum
Full width at half maximum (FWHM) : The full width of wavelength distance between two points at which the function reaches half its maximum value on spectrum
Radiant Power : The total optical power value per unit time ; The unit is Watt
Luminous Intensity : The illumination of indicated light direction in unit solid angle ; The unit is Candela or cd