In many power supply circuits, several power supply systems may be needed to supply power. On the one hand, it ensures the lasting power supply of the circuit, and it also protects components. For example, adapters, UPS power supplies, energy storage devices, etc. These products are very critical for voltage priority selection, and their application circuits have strict regulations on voltage conversion and selection. Voltage priority selection application circuit is a kind of circuit used to select voltage source in circuit design, which plays a key role in many scenarios.

The core principle of voltage priority selection application circuit is to automatically select power supply based on components and chips. When there are multiple voltage sources in the circuit, the circuit will automatically select one of them to supply power. This is usually achieved through specific circuit design and components, such as MOSFET tubes, diodes and other products.

This circuit is widely used in many fields, including adapters, UPS power supplies, energy storage devices and other electronic devices that need multiple voltage sources to supply power. For example, an electronic device may be powered by either a USB interface or a wall adapter. At this time, the voltage priority selection application circuit can ensure that when the wall adapter exists, the adapter is used for power supply first; When the adapter does not exist, it will automatically switch to USB interface for power supply.

For example, this circuit usually includes MOSFET tubes (such as P-channel MOSFET), diodes (such as Schottky diodes) and other elements. The choice of these components depends on the specific requirements of the circuit and the characteristics of the voltage source. When there are two voltage sources (such as VUSB and VBAT) in the circuit, voltage priority can be achieved by a PMOS tube and a diode. When VUSB exists, the PMOS tube is not conductive, and the voltage source VUSB supplies power to the circuit through the diode; When VUSB does not exist, PMOS transistor is turned on and supplied by VBAT.

MOS transistor is often used to control the on-off of current in voltage priority selection circuit. When a voltage source is selected, the corresponding MOSFET tube is turned on, allowing current to pass; When the voltage source is unavailable, the MOS transistor is turned off to prevent the current from passing. In the circuit, a P-channel MOSFET can be used to prevent current from flowing into the USB interface from the wall adapter. When the wall adapter does not exist, the gate of the MOSFET is pulled low and the source and drain are connected, thus allowing the USB interface to supply power to the circuit. Diodes are often used to prevent current backflow and voltage loss in voltage priority selection circuits. For example, Schottky diode can prevent USB interface from consuming energy through resistor, thus improving the energy efficiency of the circuit. When selecting MOS transistor for the circuit, it is necessary to ensure that its maximum working voltage and current capacity can meet the requirements of the circuit. According to the working voltage and current requirements of the circuit, the appropriate MOS transistor is selected to ensure its normal operation without damage, fast switching speed and high efficiency. Heketai's AO3442, IRLML0100 and other products can meet the requirements.

In some cases, more complex circuits can be used to achieve more precise voltage source selection and control. For example, in the system of parallel power supply of super capacitor and lithium ion battery, the intelligent switching and management of the two power supplies can be realized by voltage priority algorithm and corresponding circuit. Switching between battery and external power supply, when the external power supply (such as USB) supplies power, disconnect the battery supply; When the external power supply is disconnected, it is powered by the battery to realize automatic switching. Selection when multiple power supplies exist at the same time: When multiple power supplies exist at the same time, the circuit will select the highest power supply according to the voltage priority. For example, when 5V USB power supply and 4.2V lithium battery coexist, 5V USB power supply has priority.

Voltage priority application circuit is widely used in many fields. Among adapters and UPS power supplies, voltage priority application circuit can ensure that the most suitable power supply can be automatically selected under the condition of multiple power inputs. For example, when the wall adapter and USB interface exist at the same time, the circuit will automatically select the wall adapter as the priority power supply. Moreover, in the battery charging management system, the circuit can intelligently select the charging power source. For example, when the device is connected to the wall adapter and USB interface at the same time, the circuit will automatically select the wall adapter for fast charging, and switch to USB interface for charging when the adapter is unavailable.

In some energy management systems, supercapacitors and lithium-ion batteries may be connected in parallel to supply power to the equipment. At this time, the voltage priority selection application circuit can decide who supplies power to the equipment according to the voltage values of the supercapacitor and the lithium-ion battery. When the voltage of the supercapacitor is high, it will discharge first to supply power to the equipment; When the voltage drops, the lithium-ion battery will take over the power supply task.

For example, in some improved energy management systems, voltage priority selection application circuits may also be designed to charge supercapacitors preferentially. When the voltage of the supercapacitor reaches a certain level, it will start to charge the lithium-ion battery. In the process of discharging, the supercapacitor will discharge first, and when its power is insufficient, the lithium-ion battery will start to discharge to replenish energy.

In embedded system, voltage priority selection application circuit can ensure the stable operation of the system under the condition of multiple power inputs. For example, in some embedded devices that need low power consumption, the circuit can intelligently switch power supply according to the availability of power supply to reduce power consumption. In industrial control system, the application circuit with voltage priority can improve the reliability and stability of the system. For example, in some industrial environments where continuous power supply is needed to ensure uninterrupted production flow, this circuit can ensure quick switching to standby power supply when power supply fails to avoid production interruption. In smart home equipment, voltage priority selection application circuit also plays an important role. For example, in smart plug, intelligent lighting and other devices, the circuit can intelligently switch the power supply according to the user's settings and the availability of power supply to improve the energy efficiency and user experience of the device.

Taking the application circuit scheme of a discrete device product as an example, the circuit uses USB interface and wall adapter at the same time, and the battery is charged through CN3066/CN3066B. When both exist together, the wall adapter has priority. M1 is a P-channel MOSFET, M1 is used to prevent current from flowing into the USB interface from the wall adapter, and Schottky diode D1 can prevent the USB interface from consuming energy through 1K resistor. When the wall adapter does not exist, the G pole of M1 is pulled low and DS is turned on. Voltage priority selection application circuit is widely used. This circuit uses 10MQ100N produced by Heketai, and this diode has good characteristics.

Voltage priority selection application circuit is widely used and requires high safety factor. When selecting electronic components, customers need to consider its characteristics, such as voltage tolerance and current tolerance, to ensure the stability and reliability of the circuit. Reasonable circuit layout and wiring can reduce interference and loss, and improve the efficiency and performance of the circuit. In some cases, the circuit may need additional heat dissipation design to prevent components from overheating and damage.