An AC-DC converter, power supply board and display apparatus is disclosed. The AC-DC converter comprises: an AC-DC converting circuit; a transformer, whose primary coil has a first terminal coupled to a positive output terminal of the AC-DC converting circuit, and second terminal connected to a load; a voltage monitoring circuit, whose input terminal is coupled to the first terminal of the secondary coil, and second terminal of the secondary coil connected to a ground; and a control circuit, whose input terminal is coupled to an output terminal of the voltage monitoring circuit, and output terminal coupled to the AC-DC converting circuit; wherein the voltage monitoring circuit outputs a control voltage when a voltage outputted by the first terminal of the secondary coil of the transformer exceeds a first threshold; the control circuit controls the AC-DC converting circuit to stop providing power supply when the control voltage exceeds a second threshold.

A power converter for operation from an AC power source may include a bridge rectifier having an input to receive an AC input voltage and an output to provide a DC voltage, the AC input voltage received from the AC power source through a fuse. An AC input overvoltage protection circuit may be configured to cause a short circuit across the AC input voltage in response to the DC voltage output from the bridge rectifier exceeding a predetermined voltage value for a predetermined period of time.

The present disclosure describes aspects of Zener overvoltage protection (OVP) with a thermal trigger for an implant. In some aspects, an apparatus comprises a rectifier disposed in a rectification circuit and configured to rectify alternating current (AC) power received at the rectification circuit to direct current (DC) power. The apparatus also includes a Zener diode and thermistor. The Zener diode is disposed in the rectification circuit between the rectifier and an output terminal, and is configured to clamp the DC power at a predefined voltage. The clamped DC power output at the output terminal is usable by the implant. The thermistor and Zener diode are disposed in temperature-measuring proximity. This enables the thermistor to measure a temperature of the Zener diode, which correlates to voltage at the Zener diode due to clamping. When the measured temperature exceeds a threshold temperature indicative of an OVP condition, remedial OVP actions are initiated.

In an active converter that is connected to an electric machine, in which arresting circuits for activating a voltage arrest beginning at a first point in time are provided, and which is also configured for activating a load shedding reaction only when activation conditions are fulfilled beginning at a second point in time, the activation conditions include determining that the voltage arrest is still activated at the second point in time, that a voltage potential has not yet fallen below the first threshold value, and/or that a value that indicates a current flowing through at least one phase connection is above a third threshold value.

A method for controlling a bridge rectifier which includes active switching elements is provided, in which, during normal operation, at least one of the active switching elements is controlled using a voltage signal, the voltage of which is changed from a first voltage value to a second voltage value within at least one switching time. The at least one switching time is extended by a predefinable time period if load shedding at the bridge rectifier is determined. Also described is a corresponding rectifier system and a computer program product.

A motor vehicle electrical system which includes an electric machine, an active bridge rectifier, and at least one control device, the at least one control device being configured for converting an alternating voltage which is output by the electric machine at a number of phase connections into a direct voltage by controlling active switching elements of the bridge rectifier. An arrangement is provided configured for initiating a short circuit of at least two of the phase connections as soon as a signal characterizing the direct voltage exceeds an upper threshold value, and for deactivating the short circuit as soon as the signal characterizing the direct voltage subsequently falls below a lower threshold value. An evaluation device is provided configured for detecting a value of the direct voltage, for filtering the detected value, and for providing the filtered value as the signal characterizing the direct voltage.

According to some aspects of the present disclosure, isolated power supplies and corresponding control methods are disclosed. Example isolated power supplies include a transformer, at least one power switch coupled to the transformer, a controller, an output terminal, and a feedback circuit coupled to the output terminal to sense the output voltage and compare the sensed output voltage to a voltage reference. The power supplies include a fault detection circuit to sense the output voltage, compare the sensed output voltage to a fault reference, and modify a feedback signal when the sensed output voltage exceeds the fault reference. The power supplies also include a single isolation device coupled between the feedback circuit and the controller. The controller is operable to control the power switch based on the feedback signal and to detect a fault condition when a slew rate of the feedback signal exceeds a fault threshold slew rate value.

A bridge rectifier having AC voltage terminals, two DC voltage terminals, and a number of half-bridges corresponding to the number of AC voltage terminals. Each half-bridge has two activatable switching elements, connected in series between the DC voltage terminals and between which one of the AC voltage terminals is connected in each case. Each half-bridge includes a control circuit configured to detect an output voltage applied between the DC voltage terminals and switch a first switching element of the two switching elements of the particular half-bridge to be conductive by activation using a first control signal until the output voltage falls below a lower threshold value, after it has previously exceeded an upper threshold value, and to activate it in a clocked manner by activation using a second control signal, until the output voltage exceeds the upper threshold value, after it has previously fallen below the lower threshold value.

Disclosed is a short-circuit protection circuit for a voltage sampling resistor of a primary side converter, comprising a high voltage power transistor, a high voltage starting resistor, a first voltage dividing resistor of a port VDD, a second voltage dividing resistor of the port VDD, an NMOS transistor, a diode, a first comparator, a second comparator, a third comparator, a time delay circuit, a filter, a first logic circuit, a second logic circuit, a current supply, a first AND gate and a first inverter. The chip of the present disclosure is capable of correctly and effectively detecting whether the sampling resistor is shorted or not before the chip works normally, thereby avoiding the risk of damaging the chip by large current from the voltage feedback port FB due to turn-on of the switching transistor when the upper voltage sampling resistor is shorted, and greatly reducing the input power.

When switching operations of converter cells are stopped due to temporary voltage reduction in an AC system, a voltage determination unit performs determination regarding a voltage of each DC capacitor after a predetermined period has passed, and a charge control unit transmits a charging gate signal, via a gate control unit, to select a converter cell at a voltage level at which a self-feeding circuit of the converter cell is operable. Thus, a DC capacitor of a converter cell whose voltage is lower than the voltage level at which a self-feeding circuit is operable is charged, thereby enabling switching operations of all the converter cells.