A constant power protection circuit includes a voltage conversion circuit, a current detection circuit, a voltage detection circuit, a power setting circuit, a voltage feedback circuit, an addition circuit, a current feedback circuit, and a signal isolation unit. When an output voltage of the voltage conversion circuit is larger than a voltage of the voltage detection circuit and an output current of the voltage conversion circuit is larger than a current of the current detection circuit, the power setting circuit provides a comparison signal to the current feedback circuit, the current feedback circuit outputs a feedback signal to the signal isolation unit. According to a signal outputted from the signal isolation unit, the voltage conversion circuit enables a constant power mode.

An electrical current flowing in a selected one of a plurality of electric motors (51, 52, 53) connected to and supplied from a power supply, wherein a current measuring device (46) is arranged in a connection between the power supply and the plurality of electric motors, is determined. Non-selected electric motors are controlled to be temporarily disconnected from the power supply, and then a current measurement is performed by the current measuring device, while the non-selected electric motors are temporarily disconnected from the power supply. Thus, this current measurement is indicative of the electrical current flowing in the selected electric motor. When the current measurement has been performed, the non-selected electric motors are again controlled to be reconnected to the power supply. In this way, the current drawn by individual motors can be determined with the use of only one current measuring device, so that additional costs can be avoided.

A circuit for detecting failure of a device includes a plurality of monitoring modules. Each respective monitoring module of the plurality of monitoring modules is configured to generate a monitoring value at an output of the respective monitoring module based on a signal received at an input of the respective monitoring module. The circuit further includes a data selector module configured to couple, for each step of a switching cycle, the input of each of the plurality of monitoring modules to one of a plurality of function modules such that each of the plurality of monitoring modules generates the monitoring value for each of the plurality of function modules to generate monitoring information and evaluation logic configured to determine whether a failure has occurred at the plurality of function modules based on the monitoring information.

A system characterizes and identifies one of a plurality of different operating modes of a number of electric loads. The system includes a processor; a voltage sensor providing a voltage signal for one of the electric loads to the processor; a current sensor providing a current signal for the one electric load to the processor; and a routine executed by the processor and structured to characterize the different operating modes using steady state and voltage-current trajectory features determined from the voltage and current signals, and to identify a particular one of the different operating modes based on a plurality of operating mode membership functions of the steady state and voltage-current trajectory features.

In a configuration for measuring a signal voltage by a voltage measuring unit through a multiplexer to which signals are inputted from a plurality of sensors including a thermistor, a series circuit which includes the thermistor, a driving resistor and a level shift resistor is connected between a power supply and the ground. A common connection point between the driving resistor and the level shift resistor is connected to an input terminal of the multiplexer.

A driver circuit arrangement for driving a transistor bridge, which includes at least a first half-bridge composed of a low-side transistor and a high-side transistor, is described herein. In accordance with one example of the description, the circuit includes a current source and a detection circuit. The current source is operably coupled to the high-side transistor of the first half-bridge and configured to supply a test current to the first half bridge. The detection circuit is configured to compare a voltage sense signal, which represents the voltage across the high-side transistor of the first half-bridge, with at least one first threshold to detect, dependent on the result of this comparison, whether a short-circuit is present in the first half-bridge.

In an overcurrent detection circuit for switches parallely connected to each other, sense detectors are respectively provided for the switches. Each of the sense detectors detects a sense voltage of the corresponding one of the switches. The sense voltage of each of the switches is based on a sense current associated with a current flowing through the corresponding one of the switches. A parameter calculator calculates, based on the sense voltages calculated by the respective sense detectors, a determination parameter that is less subject to imbalance between currents flowing through the respective switches. A determiner determines whether a value of the determination parameter is higher than an overcurrent threshold, and determines that there is an overcurrent flowing through at least one of the switches upon determining that the value of the determination parameter is higher than the overcurrent threshold.

Disclosed in the present invention are a control method and device for a power factor correction circuit. The method comprises: obtaining voltage information of the power factor correction circuit; determining whether the voltage information meets a set switching condition; if the set switching condition is met, switching a control mode of the power factor correction circuit to a continuous conduction mode; and if the set switching condition is not met, switching the control mode of the power factor correction circuit to a triangular wave current mode or a critical conduction mode. Compared with the prior art, the control mode of the power factor correction circuit can be different according to the voltage information in the embodiment of the present invention, instead of remaining unchanged at all times, without increasing the withstand voltage level of the bus capacitor, thereby reducing the cost of implementation. Moreover, it is not necessary to forcibly change a given value of the current peak, thereby improving the total harmonic distortion of the input current.

In a state that a first voltage is applied to a charging member so as to form a surface potential on a region of an image bearing member and a second voltage the same in polarity as the first voltage is applied to a transfer ember, a detection unit detects a transfer current in the region of the image bearing member during one rotation of the image hearing member after the region passes through a charging portion, when an absolute value of the surface potential formed on the region immediately before entry into the charging portion is larger than an absolute value of the surface potential formed on the region when it is positioned upstream of a transfer portion and downstream of the charging portion in a rotational direction of the image bearing member.

A switched-mode power supply includes a transformer, a switching element, a switching controller, a voltage generator circuit, an overvoltage protection circuit, and a load increase circuit. The overvoltage protection circuit is configured to, when a first DC voltage outputted from the voltage generator circuit is below a predetermined voltage, apply a first drive voltage to an input terminal of the switching controller, and to, when the first DC voltage exceeds the predetermined voltage, apply a second drive voltage, which is different from the first drive voltage, to the input terminal, whereby the switching controller stops controlling switching operation. The load increase circuit is configured to, when the output voltage exceeds a threshold voltage, flow a current from the secondary side, thereby increasing a load applied to the secondary side. The threshold voltage is less than a rated voltage of the transformer and greater than the target voltage.