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 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.

A portable electrical energy power node is provided. The power node includes first and second input power terminals and first and second output power terminals. The input power terminals are adapted for receiving a source of electrical power and the output terminals are adopted for connecting to a load. A first power line connects the first input terminal to the first output terminal, a second power line connects the second input terminal to the input side of a circuit interrupter and a third power line connects the output side of the circuit interrupter to the second output terminal. The circuit interrupter selectively interrupts the connection between the second input terminal and the second output terminal in accordance with a fault sensor and a control unit.

A resonant converter includes a first switch on the primary side and a second switch coupled to the first switch, a synchronization rectification switch on a secondary side configured to conduct during a conduction period in response to a switching operation of the first switch, and a switch control circuit configured to determine an operating region of the resonant converter to be below resonance based on a result of a comparison between the conduction period and an on period of the first switch.

A resonant converter includes a first switch on the primary side and a second switch coupled to the first switch, a synchronization rectification switch on a secondary side configured to conduct during a conduction period in response to a switching operation of the first switch, and a switch control circuit configured to determine an operating region of the resonant converter to be below resonance based on a result of a comparison between the conduction period and an on period of the first switch.

The object of the present application is to ensure the security of a device when a precharging relay is not closed and a load current passes through a precharging resistor, so as to ensure the customer's security. Provided is a security control method for a system with a precharging circuit, comprising: giving out an error alarm and stopping operating the system when the number of times of undervoltage of a precharging circuit achieves m times and the duration between the first undervoltage and the mth undervoltage is less than or equal to seconds, where m and are positive integers. Compared with the previous method, the present invention has the following advantages of no danger of combustion and high reliability; and cost saving and no need of adding additional hardware.

The object of the present application is to ensure the security of a device when a precharging relay is not closed and a load current passes through a precharging resistor, so as to ensure the customer's security. Provided is a security control method for a system with a precharging circuit, comprising: giving out an error alarm and stopping operating the system when the number of times of undervoltage of a precharging circuit achieves m times and the duration between the first undervoltage and the mth undervoltage is less than or equal to seconds, where m and are positive integers. Compared with the previous method, the present invention has the following advantages of no danger of combustion and high reliability; and cost saving and no need of adding additional hardware.

An integrated processing unit is supplied by a power supply voltage present at the terminals of a capacitor configured to supply a maximum permissible voltage drop. A periodic pulse signal is generated having a period that is less than or equal to a current period determined from the maximum permissible voltage drop and a current consumption of the processing unit. The power supply voltage is compared with a threshold voltage at the pulse rate of the periodic pulse signal. A control signal generated from that comparison is delivered to the processing unit and has a first value when the power supply voltage is greater than or equal to the threshold voltage and a second value when the power supply voltage is less than the threshold voltage.

A system includes a circuit breaker and a delay circuit. The circuit breaker has a coil to enable control of a contact to selectively couple a load to a power source responsive to a coil voltage signal applied to the coil. The delay circuit has a depletion mode MOSFET and an energy storage circuit. The depletion mode MOSFET is controlled as an active current sink to provide the coil voltage signal based on a DC voltage signal. The energy storage circuit has an input coupled to a drain of the depletion mode MOSFET, a capacitor, and an output coupled to the drain of the depletion mode MOSFET, the energy storage circuit charges the capacitor from the DC voltage signal and delivers current to the depletion mode MOSFET to delay discontinuation of the coil voltage signal responsive to a drop or discontinuation of the DC voltage signal.