A reactive power compensation device is connected with an AC power system via a switch, and includes an arm circuit having a plurality of sub-modules connected in series, and a central control protection device. Each of the sub-modules includes a DC capacitor, and a bridge circuit for switching whether or not to output a voltage held in the DC capacitor. The central control protection device is configured to shift to a standby mode in which all semiconductor switching elements constituting the bridge circuit of each of the sub-modules are set to an opened state, with the switch being set to a closed state, when the AC power system has a power failure during operation of the reactive power compensation device, and to shift from the standby mode to a stop mode in which the switch is set to an opened state.

A reactive power compensation device is connected with an AC power system via a switch, and includes an arm circuit having a plurality of sub-modules connected in series, and a central control protection device. Each of the sub-modules includes a DC capacitor, and a bridge circuit for switching whether or not to output a voltage held in the DC capacitor. The central control protection device is configured to shift to a standby mode in which all semiconductor switching elements constituting the bridge circuit of each of the sub-modules are set to an opened state, with the switch being set to a closed state, when the AC power system has a power failure during operation of the reactive power compensation device, and to shift from the standby mode to a stop mode in which the switch is set to an opened state.

A power supply system includes a wireless power supply end and a wireless receiving end. The wireless receiving end includes a resonant receiving component and a rectifying and voltage-stabilizing component that is connected to the resonant receiving component to output a voltage-stabilized power supply (VCC). A load sudden-change protection circuit includes an overvoltage protection component and an under-voltage protection component that are each respectively connected to the voltage-stabilized power supply and a load. The overvoltage protection component turns on the load when the voltage of the voltage-stabilized power supply is higher than a first preset voltage due to sudden turn-off of the load. The under-voltage protection component turns off the load when the voltage of the voltage-stabilized power supply is lower than a second preset voltage due to sudden turn-on of the load.

Disclosed is a dynamic multi-functional power controller in collocation with a primary side coil, a switching unit, and a current sensing resistor, performing a power control process. An induced current is generated by a secondary side coil coupled with the primary side coil through electromagnetic interaction with a conduction current flowing through the primary side coil, and an output power is generated to supply an external load when the induced current flows through an output rectification unit and an output filter unit. The power control process includes detecting if any abnormal state occurs, sopping a driving signal, waiting for a period of time, and then re-sending the driving signal. Thus, the present invention provides protection for various kinds of peak loading, avoids high power state when abnormal state being not resolved, and further reduces the average output power, thereby implementing power saving.

In an embodiment, a brown-out protection circuit includes: a monitoring terminal; a threshold generator supplying a threshold voltage; a comparator to compare a monitoring voltage at the monitoring terminal and the threshold voltage; and a logic module supplying an enable signal having a brown-in logic value and a brown-out logic value. When the enable signal is at the brown-out logic value, the logic module checks transition conditions, relating to a number of usable transitions of the monitoring voltage from lower to greater than the threshold voltage, and time conditions, relating to permanence of the monitoring voltage above the threshold voltage after a usable transition or in an aggregated manner after a plurality of consecutive usable transitions. The logic module sets the enable signal to the brown-in logic value when the transition conditions or the time conditions are met.

A power tool is provided including a power supply interface having a first node and a second node, a power switch circuit, an input unit actuatable by a user, a controller configured to control the power switch circuit to regulate the supply of electric power, and a driver circuit disposed between the controller and the power switch circuit configured to receive control signals from the controller and drive the power switch circuit according. A no-volt prevention circuit is configured to enable a supply of power to at least one of the driver circuit or the controller when the input unit is actuated after the power supply interface is coupled to the power supply, but not when the input unit is actuated before to the power supply interface is coupled to the power supply.

A power tool is provided including a power supply interface having a first node and a second node, a power switch circuit, an input unit actuatable by a user, a controller configured to control the power switch circuit to regulate the supply of electric power, and a driver circuit disposed between the controller and the power switch circuit configured to receive control signals from the controller and drive the power switch circuit according. A no-volt prevention circuit is configured to enable a supply of power to at least one of the driver circuit or the controller when the input unit is actuated after the power supply interface is coupled to the power supply, but not when the input unit is actuated before to the power supply interface is coupled to the power supply.

Embodiments of the present disclosure provide an over-voltage protection method, an over-voltage protection device and a display device. When the voltage value of the output signal is greater than the first preset voltage threshold, it is determined whether the voltage value of the output signal meets the preset over-voltage protection condition. If the voltage value of the output signal is detected to meet the preset over-voltage protection condition, the first control signal is output to stop output of the output signal or lower the voltage value of the output signal.

A power tool including a power supply interface, a motor control circuit configured to regulate supply of power from the power supply interface to a motor, and an input unit actuatable by a user. A no-volt prevention circuit receives a first voltage signal from the power supply interface and a second voltage signal from the input unit. The no-volt protection circuit includes a main semiconductor switch arranged on a current path from the power supply interface to at least one component of the motor control circuit, and a resistor-capacitor circuit to turn the main semiconductor switch ON when the input unit is actuated after the power supply interface is coupled to the power supply, but not when the input unit is actuated before to the power supply interface is coupled to the power supply.

A power tool including a power supply interface, a motor control circuit configured to regulate supply of power from the power supply interface to a motor, and an input unit actuatable by a user. A no-volt prevention circuit receives a first voltage signal from the power supply interface and a second voltage signal from the input unit. The no-volt protection circuit includes a main semiconductor switch arranged on a current path from the power supply interface to at least one component of the motor control circuit, and a resistor-capacitor circuit to turn the main semiconductor switch ON when the input unit is actuated after the power supply interface is coupled to the power supply, but not when the input unit is actuated before to the power supply interface is coupled to the power supply.