The diode is a common semiconductor device, mainly used for rectification and voltage regulation in the circuit. During operation, due to a specific voltage difference between the on and off state of the diode, a certain conduction loss will be generated.
These losses are usually referred to as forward voltage drop, and the impact of this factor on the energy consumption and stability of the system needs to be considered in actual circuit design. Although the conduction loss of the diode has a certain consumption, it does not mean that we should avoid using this device. On the contrary, correct circuit design and optimization can minimize these losses, thereby obtaining efficient, stable and flexible circuit performance. In actual circuit design, we can take some measures to reduce the conduction loss of the diode.
First, we can choose a diode device with a low voltage drop, which can minimize the power consumption caused by the forward voltage drop. Secondly, we can optimize the stability and response speed of the circuit by selecting appropriate components such as resistors and capacitors, so as to minimize the conduction loss of the diode as much as possible while ensuring performance.
The conduction loss of MOSFET is proportional to RDS(ON), while the conduction loss of diode depends largely on the forward conduction voltage (VF). Diodes usually have greater losses than MOSFETs, and the diode loss is proportional to the forward current, VF and conduction time.Since the diode conducts when the MOSFET is off, the conduction loss of the diode (PCOND(DIODE)) is approximately: PCOND(DIODE) = IDIODE(ON) × VF × (1 - D) Where IDIODE(ON) is the average current during the diode conduction period. As shown in Figure 2, the average current during the diode conduction period is IOUT, so for a buck converter, PCOND(DIODE) can be estimated as follows: PCOND(DIODE) = IOUT × VF × (1 - VOUT/VIN) Unlike the MOSFET power calculation, using the average current can provide a more accurate power calculation result because the diode loss is proportional to I, not I2. Obviously, the longer the MOSFET or diode is on, the greater the conduction loss.
For a buck converter, the lower the output voltage, the greater the power dissipation in the diode because it is in the on state for a longer time.
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