Disclosed herein is a power supply apparatus for a sub-module controller of a Modular Multilevel Converter (MMC), which supplies driving power to the sub-module controller of an MMC connected to a High Voltage Direct Current (HVDC) system. The power supply apparatus includes a bridge circuit unit including N (N≧2, integer) energy storage units for storing a DC voltage in series-connected sub-modules in the MMC and multiple power semiconductor devices connected in parallel with the N energy storage units in a form of a bridge; and a DC/DC converter for converting a voltage output from output terminals formed between both ends of n (1≦n<N) series-connected energy storage units, among the N energy storage units, into a low voltage and supplying the low voltage to the sub-module controller.

Disclosed herein is a power supply apparatus for a sub-module controller of a Modular Multilevel Converter (MMC), which supplies driving power to the sub-module controller of an MMC connected to a High Voltage Direct Current (HVDC) system. The power supply apparatus includes a bridge circuit unit including N (N≧2, integer) energy storage units for storing a DC voltage in series-connected sub-modules in the MMC and multiple power semiconductor devices connected in parallel with the N energy storage units in a form of a bridge; and a DC/DC converter for converting a voltage output from output terminals formed between both ends of n (1≦n<N) series-connected energy storage units, among the N energy storage units, into a low voltage and supplying the low voltage to the sub-module controller.

An electronic system includes a plurality of switching elements (T) and a plurality of energy storage elements (L; C). The energy storage elements (L; C) are connected to one another by the switching elements (T). The energy storage elements (L; C) can be selectively switched to a first, a second or a third state by switching the switching elements (T). In the first state, the energy storage elements (L; C) are connected in series with one another. In the second state, the energy storage elements (L; C) are connected in parallel with one another. In the third state, the energy storage elements (L; C) are bypassed, wherein two of the energy storage elements (L; C) are each connected by no more than three of the switching elements (T).

A switch mode power supply includes a bootstrap circuit, control circuits, and an auxiliary winding coupled to the bootstrap circuit and configured to supply power to the control circuits after startup of the power supply. The bootstrap circuit is configured to supply power to the control circuits during startup and includes an isolation circuit to limit current flow between the starting capacitor and the control circuits while the starting capacitor is charged to a starting voltage by the high voltage input. During the initial charge of the starting capacitor, the control circuits do not have power to provide the initial functionality of the power supply. Once the starting capacitor is charged to the starting voltage, the isolation circuit is activated to allow current flow that powers the control circuits during the remainder of the startup until the auxiliary winding is able to power the control circuits.

A switch mode power supply includes a bootstrap circuit, control circuits, and an auxiliary winding coupled to the bootstrap circuit and configured to supply power to the control circuits after startup of the power supply. The bootstrap circuit is configured to supply power to the control circuits during startup and includes an isolation circuit to limit current flow between the starting capacitor and the control circuits while the starting capacitor is charged to a starting voltage by the high voltage input. During the initial charge of the starting capacitor, the control circuits do not have power to provide the initial functionality of the power supply. Once the starting capacitor is charged to the starting voltage, the isolation circuit is activated to allow current flow that powers the control circuits during the remainder of the startup until the auxiliary winding is able to power the control circuits.

A microphone system includes: a microphone including a microphone output terminal and a microphone GND terminal, the microphone being configured to output, as an input sound signal, a voltage signal exhibiting a change in voltage between the microphone output terminal and the microphone GND terminal depending on an input sound; an A/D converting unit mounted on a first circuit board and configured to perform digital conversion on the input sound signal that is input; and a power supply circuit mounted on a second circuit board connected to the first circuit board via a pair of power supply lines, and configured to feed DC power to the A/D converting unit via the pair of power supply lines. The microphone outputs the input sound signal to the A/D converting unit via a pair of first signal lines different from the pair of power supply lines.

A microphone system includes: a microphone including a microphone output terminal and a microphone GND terminal, the microphone being configured to output, as an input sound signal, a voltage signal exhibiting a change in voltage between the microphone output terminal and the microphone GND terminal depending on an input sound; an A/D converting unit mounted on a first circuit board and configured to perform digital conversion on the input sound signal that is input; and a power supply circuit mounted on a second circuit board connected to the first circuit board via a pair of power supply lines, and configured to feed DC power to the A/D converting unit via the pair of power supply lines. The microphone outputs the input sound signal to the A/D converting unit via a pair of first signal lines different from the pair of power supply lines.

In described examples, a power management circuit includes a voltage sensor and a differential power converter. The voltage sensor is coupled in series with other voltage sensors between a high voltage bus and a ground bus. The voltage sensor senses a voltage across an impedance and outputs a control signal in response to the sensed voltage. The differential power converter is coupled in series with other differential power converters and in parallel with a load between the high voltage bus and the ground bus. The differential power converter is configured to increase or decrease a supplied current in response to a change in magnitude of the control signal.

In described examples, a power management circuit includes a voltage sensor and a differential power converter. The voltage sensor is coupled in series with other voltage sensors between a high voltage bus and a ground bus. The voltage sensor senses a voltage across an impedance and outputs a control signal in response to the sensed voltage. The differential power converter is coupled in series with other differential power converters and in parallel with a load between the high voltage bus and the ground bus. The differential power converter is configured to increase or decrease a supplied current in response to a change in magnitude of the control signal.

An adjustable power supply suitable for a power switch driver circuit takes an input voltage and generates output voltages at three output terminals. Two of the output terminals provide gate voltage signals to a power switch control device while the third is connected to a reference voltage. The output voltages may be adjusted using a first and second external resistor enabling power requirements for a wide variety of power switch devices to be satisfied.