A power supply device including: a transformer generating, from an input voltage, low output voltage and high output voltage; an upper limiter circuit receiving the high output voltage and controlling the high output voltage not to exceed a maximum; a power controller performing feedback control on the input voltage so that the low output voltage matches a target voltage; an operation mode acquirer configured to acquire an operation mode of an image forming device; and a target value controller configured to change the target voltage depending upon the acquired operation mode. The target voltage when consumption amount of current with the high output voltage is relatively great ensures that the high output voltage does not fall below a minimum of a rated voltage range of the high output voltage, and is higher than the target voltage when consumption amount of current with the high output voltage is relatively small.

A power supply device including: a transformer generating, from an input voltage, low output voltage and high output voltage; an upper limiter circuit receiving the high output voltage and controlling the high output voltage not to exceed a maximum; a power controller performing feedback control on the input voltage so that the low output voltage matches a target voltage; an operation mode acquirer configured to acquire an operation mode of an image forming device; and a target value controller configured to change the target voltage depending upon the acquired operation mode. The target voltage when consumption amount of current with the high output voltage is relatively great ensures that the high output voltage does not fall below a minimum of a rated voltage range of the high output voltage, and is higher than the target voltage when consumption amount of current with the high output voltage is relatively small.

The present invention relates in a first aspect to a galvanically isolated power converter assembly comprising a first set of electrically interconnected resonant power inverters configured for generating respective output voltages and output currents. The galvanically isolated power converter assembly further a first positive summing node and a first negative summing node configured to combining the output voltages and output currents of the first set of resonant power inverters and a first common load circuit comprising a positive load input and a negative load input. A galvanic isolation barrier comprises first and second common isolation capacitors electrically insulating the common load circuit. Each of the first and second common isolation capacitors possesses an official safety rating.

The invention provides a driver circuit for driving an LED arrangement which uses a switch mode power converter, for example a flyback ringing choke converter, which comprises a main switch (e.g. bipolar transistor) and a sub-circuit for generating a current for the control terminal of the main switch. The sub-circuit in some examples makes use of an auxiliary winding as a voltage supply, and further comprises a ramp circuit for generating a ramp voltage from the voltage supply and a voltage follower, such as a control transistor, connected between the voltage supply and the control input of the main switch. By ramping up the current of the main switch, the losses arising as a result of the current flowing to the control input of the main switch are reduced. One set of examples makes use of a flyback ringing choke converter, which enables low cost implementation and good efficiency. The driver is able to receive a wide range of input voltages, by ensuring that the power loss is kept low. In particular, by ramping up the control current of the main switch, the losses arising as a result of the current flowing are reduced.

A current limit peak regulation circuit, a current limit circuit and a power converter including the current limit peak regulation circuit. The current limit peak regulation circuit provides a current limit threshold to limit a maximum allowable peak current value of a current flowing through a main switch of the power converter and adjusts the current limit threshold to decrease with decrease in a switching frequency of the power converter when the power converter is in a constant voltage mode so as to reduce power dissipation of the power converter in standby mode.

A current limit peak regulation circuit, a current limit circuit and a power converter including the current limit peak regulation circuit. The current limit peak regulation circuit provides a current limit threshold to limit a maximum allowable peak current value of a current flowing through a main switch of the power converter and adjusts the current limit threshold to decrease with decrease in a switching frequency of the power converter when the power converter is in a constant voltage mode so as to reduce power dissipation of the power converter in standby mode.

A circuit including over-current protection includes a voltage input, first and second switching transistors that are complementarily switched and that receive current from the voltage input, a first resistor, a first diode including a first anode and a first cathode, and a second diode including a second anode and a second cathode. The first anode and the second anode are connected to each other and are connected to the voltage input via the first resistor. The first cathode is connected to the first switching transistor and the second cathode is connected to the second switching transistor such that the connection of the first and second anodes provides an over-current signal that is related to the current in the first and second switching transistors.

The present invention relates to a resonant DC-DC power converter comprising an input side circuit comprising a positive and a negative input terminal for receipt of an input voltage or current and an output side circuit comprising positive and negative output terminals for supply of a converter output voltage and connection to a converter load. The resonant DC-DC power converter further comprises a rectification circuit connected between an output of a resonant network and the output side circuit. The resonant network is configured for alternatingly being charged from the input voltage or current and discharged through the rectification circuit by a first controllable switch arrangement in accordance with a first switch control signal. A second controllable switch arrangement of the resonant DC-DC power converter is configured to select a first impedance characteristic of the resonant network in a first switch state and select a second impedance characteristic of the resonant network in a second switch state. An output voltage or current control circuit is configured to adjust the converter output voltage and/or current by activating and interrupting the first switch control signal in accordance with the switch state of the second controllable switch arrangement.

The present invention relates to a resonant DC-DC power converter comprising an input side circuit comprising a positive and a negative input terminal for receipt of an input voltage or current and an output side circuit comprising positive and negative output terminals for supply of a converter output voltage and connection to a converter load. The resonant DC-DC power converter further comprises a rectification circuit connected between an output of a resonant network and the output side circuit. The resonant network is configured for alternatingly being charged from the input voltage or current and discharged through the rectification circuit by a first controllable switch arrangement in accordance with a first switch control signal. A second controllable switch arrangement of the resonant DC-DC power converter is configured to select a first impedance characteristic of the resonant network in a first switch state and select a second impedance characteristic of the resonant network in a second switch state. An output voltage or current control circuit is configured to adjust the converter output voltage and/or current by activating and interrupting the first switch control signal in accordance with the switch state of the second controllable switch arrangement.

Disclosed are advances in the arts with novel and useful current mode regulators. Circuits, systems, and methods for current mode regulation include a primary side for receiving an input signal and a secondary for outputting an output signal. A regulator spans the primary and secondary sides in a configuration by which the input signal may be rectified and thereafter provided to the output node as an output signal. A current monitor is provided at the output node for comparing the output signal to a reference. A communication link is included for providing feedback to the primary side of the regulator for use in regulating the signal.