An auxiliary power supply circuit operating within a wide input voltage range has a voltage follower unit and a voltage comparison unit. The voltage follower unit has an electronic switch, a resistor, and a Zener diode. The electronic switch has a first terminal electrically connected to a voltage input terminal of the working voltage conversion circuit, a second terminal electrically connected to a voltage output terminal of the working voltage conversion circuit, and a control terminal. The resistor is electrically connected between the first terminal and the control terminal of the electronic switch. The Zener diode has a cathode electrically connected to the control terminal of the electronic switch. The voltage comparison unit has a detecting terminal electrically connected to the voltage input terminal of the working voltage conversion circuit, and an output terminal electrically connected to the control terminal of the electronic switch.

A power supply device may include a connector configured to electrically couple the power supply device to a conductor of the underground power lines; a voltage divider configured to receive an input voltage from the conductor, the voltage divider comprising a capacitor and divider voltage control electronics in series with the capacitor; and, a surge resistor in series with the capacitor and configured to provide impulse protection from surge events. The divider voltage control electronics may be configured to regulate an output voltage of the voltage divider to support variable loads on the voltage divider.

A power supply device may include a connector configured to electrically couple the power supply device to a conductor of the underground power lines; a voltage divider configured to receive an input voltage from the conductor, the voltage divider comprising a capacitor and divider voltage control electronics in series with the capacitor; and, a surge resistor in series with the capacitor and configured to provide impulse protection from surge events. The divider voltage control electronics may be configured to regulate an output voltage of the voltage divider to support variable loads on the voltage divider.

A method is for operating an electronic device formed by a low dropout regulator (LDO) having an output coupled to a first conduction terminal of a transistor, with a second conduction terminal of the transistor being coupled to an output node. The electronic device is turned on by turning on the LDO, removing a DC bias from the second conduction terminal of the transistor by opening a first switch that selectively couples the second conduction terminal of the transistor to a supply node through a first diode coupled transistor and by opening a second switch that selectively couples the second conduction terminal of the transistor to a ground node through a second diode coupled transistor, and turning on the transistor. The electronic device is turned off by turning off the transistor, forming the DC bias at the second conduction terminal of the transistor, and turning off the LDO.

A method is for operating an electronic device formed by a low dropout regulator (LDO) having an output coupled to a first conduction terminal of a transistor, with a second conduction terminal of the transistor being coupled to an output node. The electronic device is turned on by turning on the LDO, removing a DC bias from the second conduction terminal of the transistor by opening a first switch that selectively couples the second conduction terminal of the transistor to a supply node through a first diode coupled transistor and by opening a second switch that selectively couples the second conduction terminal of the transistor to a ground node through a second diode coupled transistor, and turning on the transistor. The electronic device is turned off by turning off the transistor, forming the DC bias at the second conduction terminal of the transistor, and turning off the LDO.

A power managing system and method are provided. When an under voltage lockout circuit determines that a common voltage of the power managing system is lower than a first lockout voltage, the under voltage lockout circuit outputs a first under voltage lockout signal for controlling one of a plurality of power converters that supplies a highest output voltage to rapidly reduce its output voltage to a zero value. Then, the under voltage lockout circuit outputs a second under voltage lockout signal for controlling another one of the power converters that supplies a lowest output voltage to gradually reduce its output voltage to the zero value.

A power managing system and method are provided. When an under voltage lockout circuit determines that a common voltage of the power managing system is lower than a first lockout voltage, the under voltage lockout circuit outputs a first under voltage lockout signal for controlling one of a plurality of power converters that supplies a highest output voltage to rapidly reduce its output voltage to a zero value. Then, the under voltage lockout circuit outputs a second under voltage lockout signal for controlling another one of the power converters that supplies a lowest output voltage to gradually reduce its output voltage to the zero value.

An electronic device may include a main circuit including multiple sub-circuits powered by a direct-current (DC) power supply circuit. The main circuit has a main circuit current demand being a time-varying demand for a DC voltage-regulated supply current being a function of a number of the sub-circuits being active. The DC power supply circuit may include multiple DC voltage regulators to provide the main circuit with the supply current and a command decoding and power management circuit to control enablement of the voltage regulators. The command decoding and power management circuit may be configured to detect an instant value of the main circuit current demand and to selectively enable one or more of the voltage regulators based on the detected instant value.

An electronic device may include a main circuit including multiple sub-circuits powered by a direct-current (DC) power supply circuit. The main circuit has a main circuit current demand being a time-varying demand for a DC voltage-regulated supply current being a function of a number of the sub-circuits being active. The DC power supply circuit may include multiple DC voltage regulators to provide the main circuit with the supply current and a command decoding and power management circuit to control enablement of the voltage regulators. The command decoding and power management circuit may be configured to detect an instant value of the main circuit current demand and to selectively enable one or more of the voltage regulators based on the detected instant value.

A power supply control apparatus controls power supply from a DC power source to a load by switching on or off a power supply FET. The current adjustment circuit adjusts the current flowing through the resistor circuit to a value obtained by dividing the voltage between the drain and the source of the power supply FET by the resistance value of the resistor circuit. A drive circuit switches off the power supply FET when a voltage across the detection resistor exceeds a predetermined voltage. The on-resistance value of the power supply FET fluctuates according on the ambient temperature of the power supply FET. The resistance value of the resistor circuit fluctuates in the same direction as the on-resistance value according to the ambient temperature of the power supply FET.