International Rectifier Corporation

Dairyland Electrical Industries, Inc.

Other

Brian R Pelly

Henry N Tachick

Toshio Takahashi

Ajit Dubhashi

Jun Honda

Peter R Ewer

Stefano Clemente

Yi Zhang

Rutton Ruttonsha

An active filter for reducing the common mode current in a pulse width modulated drive circuit driving a load, said drive circuit comprising an a-c source, a rectifier connected to said a-c source and producing a rectified output voltage connected to a positive d-c bus and a negative d-c bus, a PWM inverter having input terminals coupled to said positive d-c bus and negative d-c bus and having a controlled a-c output, a load driven by said a-c output of said PWM inverter, a ground wire extending from said load, and a current sensor for measuring the common mode current in said drive circuit, said current sensor producing an output current related to said common mode current; said active filter comprising a first and second transistor, each having first and second main electrodes and a control electrode, and an amplifier circuit driving said transistors; said first electrode of said first and second transistor coupled to a common node, said second electrodes of said first and second transistors being coupled to said positive d-c bus and said negative d-c respectively; said amplifier circuit having an input coupled to said output of said current sensor and having an output connected to said control electrodes; and a d-c isolating capacitor connecting said common node of said first electrode of said first and second transistors to said ground wire; and wherein said current sensor is a current transformer having a primary winding connected in series with said ground wire and a secondary winding connected as the signal input to the amplifier circuit.

Active filter for reduction of common mode current

An active filter for reducing the common mode current in a pulse width modulated drive circuit driving a load said drive circuit comprising an a-c source, a rectifier connected to said a-c source and producing a rectified output voltage connected to a positive d-c bus and a negative d-c bus, a PWM inverter having input terminals coupled to said positive d-c bus and negative d-c bus and having a controlled a-c output, a load driven by said a-c output of said PWM inverter, a ground wire extending from said load, and a current sensor for measuring the common mode current in said drive circuit, said current sensor producing an output current related to said common mode current; said active filter comprising a first and second transistor, each having first and second main electrodes and a control electrode, and an amplifier circuit driving said transistors; said first electrode of said first and second transistor coupled to a common node, said second electrodes of said first and second transistors being coupled to said positive d-c bus and said negative d-c respectively; said amplifier circuit having an input coupled to said output of said current sensor and having an output connected to said control electrodes; and a d-c isolating capacitor connecting said common node of said first electrode of said first and second transistors to said ground wire; and wherein said current sensor is a current transformer having a primary winding connected in series with said ground wire and a secondary winding connected as the signal input to the amplifier circuit.

An active filter for reducing the common mode current in a pulse width modulated drive circuit driving a load, said drive circuit comprising an a-c source, a rectifier connected to said a-c source and producing a rectified output voltage connected to a positive d-c bus and a negative d-c bus, a PWM inverter having input terminals coupled to said positive d-c bus and negative d-c bus and having a controlled a-c output, a load driven by said a-c output of said PWM inverter, a ground wire extending from said load, and a current sensor for measuring the common mode current in said drive circuit in said ground wire, said current sensor producing an output current related to said common mode current, said active filter comprising a first and second MOSFET transistor, each having first and second main electrodes and a control electrode, and an amplifier driving a respective one of the transistors; said first electrode of said first and second transistor coupled to a common node, said second electrodes of said first and second transistors being coupled to said positive d-c bus and said negative d-c respectively; each of said amplifiers having an input coupled to said output of said current sensor and each having an output connected to a respective one of said control electrodes; and a d-c isolating capacitor connecting said common node of said first electrode of said first and second transistors to said ground wire.

An active EMI filter for reducing common mode noise current in a circuits, comprising: a transistor stage having two transistors coupled in series, a current sensor for sensing the common mode noise current, the current sensor having an output driving the transistor stage, whereby each of the transistors is driven in response to the common mode noise current, a capacitor coupling the transistor stage and the ground return line, the capacitor providing a cancellation current to cancel the common mode noise current, the current sensor comprising a current transformer having a primary coupled with the circuit having the common mode noise. The current sensor and the transistor stage may be coupled in a feed forward arrangement wherein the transistor stage and the current sensor have an amplitude gain of approximately unity; or in a feedback arrangement wherein the transistor stage and current sensor provide high gain.

Active common mode EMI filters

An active EMI filter for reducing common mode current in a circuit comprising a rectifier coupled to an AC network, the rectifier supplying DC power to a DC bus, the DC bus feeding an inverter stage for providing AC power to a load, the load having a ground return line to a ground connection of the AC network, the active filter comprising: a transistor switching stage coupled across the DC bus, a current sensor coupled to the DC bus for sensing the common mode current flowing in the DC bus and proportional to the common mode current flowing in the ground return line from or to the load, the current sensor having inputs coupled to respective legs of the DC bus and an output driving the transistor switching stage, the transistor switching stage comprising two transistors driven by said output of the current sensor whereby one of said transistors is turned on by said current sensor output depending on the direction of common mode current in said DC bus, a capacitor coupling said transistor switching stage and said ground return line and wherein said current sensor and said switching stage are coupled in a feed forward arrangement whereby the switching stage is coupled across said DC bus between said rectifier and said current sensor, said capacitor providing a cancellation current to said ground return line from said transistor switching stage to substantially cancel the common mode current in said ground return line, said transistor switching stage and said current sensor having an amplitude gain of approximately unity, said current sensor comprising a current transformer having a primary connected in series with a respective leg of said DC bus, said two transistors of said transistor switching stage comprising two complementary type transistors coupled such that a corresponding main electrode of each transistor are coupled together in a common connection, another corresponding main electrode of each transistor being coupled to a respective secondary of each of said current transformer and wherein the control electrodes of said transistors are coupled to respective legs of said DC bus.

Active EMI filter with feed forward cancellation

An electromagnetic interference filter for filtering common mode current in an inverter device, the filter comprising: an inductor coupled in a least one power supply line to the inverter device; the inverter device having a ground return line, a capacitor coupled between the inductor and the ground return line; and a controlled switch coupled in series with the capacitor between the inductor and ground return line, and a control unit controlled in accordance with commutations in said inverter device whereby said switch is turned on when common mode current is drawn by said inverter device and turned off when common mode current ceases substantially to be drawn by said inverter device.

Passive common mode filter and method for operating a passive common mode filter

An active EMI filter for reducing common mode noise current in a circuit, comprising: at least one transistor stage, each having two transistors, a current sensor coupled to the circuit and an output driving the transistor stage, a capacitor coupling the transistor stage and the ground return line, providing a cancellation current to cancel the common mode current in the ground return line. In a feed forward arrangement the transistor stage is coupled between the rectifier and the current sensor, which provide an amplitude gain of approximately unity. The transistor stage may have a local power source and a drive transistor.

Active common mode EMI filter, including series cascaded filter with reduced power dissipation and transistor voltage rating

An active filter for reducing common mode current in a pulse width modulating driving circuit for driving a load from a-c lines of an a-c source, wherein the driving circuit includes a rectifier connectable to the a-c lines and producing a rectified output voltage connected to a d-c bus, a PWM inverter having input terminals connected to the d-c bus and having a controlled a-c output for driving the load, the active filter comprising a current sensor for sensing the common mode current in the driving circuit, an active filter circuit comprising first and second transistors, each having first and second main electrodes and a control electrode, the transistors being coupled in a series circuit to feed an output node, the transistors being controlled such that they are alternately switched between a non-conducting state and a conducting state in a linear region by control of their control electrodes, their control electrodes being connected to an output from the current sensor, a output node between the transistors being coupled to an isolating capacitor, the isolating capacitor being coupled to a ground line coupled to the load, the two transistors providing alternate paths for current in the ground line to flow to respective ones of the a-c lines of the a-c source thereby to reduce the ground current flowing in the ground line by providing a circulating path for the current in the ground line, the active filter circuit being connected in the a-c lines coupled to the pulse width modulated driving circuit.

Active common mode filter connected in A-C line

An active filter reduces the common mode current in the ground wire of a PWM controlled motor drive circuit. The active filter is, in part, integrated into an integrated circuit chip and contains a buffer amplifier which drives two junction type or MOSFET transistors linearly to divert common mode current from a ground wire and through the transistors. The transistors are connected between positive and negative d-c busses which supply d-c power to a PWM inventor which drives an a-c motor, producing the common mode ground current in its grounded frame. A current transformer monitors the common mode current and its output is coupled to the input of the buffer amplifier to control the transistors. An internal power supply for the amplifiers is formed at the nodes between two current sources and two zener diodes which are connected between the d-c bus conductors. Headroom control circuits are disclosed to insure sufficient headroom voltage for each of the transistors under all input a-c voltage conditions.

A combined filter inductor and Hall current sensor for a double inverter motor drive is formed on a unitary magnetic core. The magnetic core has a suitable winding and air gap to comprise an inductor. The Hall effect sensor is situated in the airgap to detect a Hall effect voltage created by the magnetic flux in the air gap.

Combined filter inductor and hall current sensor

A combination of an IGBT and an antiparallel-connected freewheeling diode in which the IGBT die size is greater than about twice the diode die size. Preferably the diode die size is about 10%-25% of that of the IGBT. The respective die sizes of an IGBT and an antiparallel connected freewheeling diode may be adjusted by the steps of: determining respective initial die sizes for the IGBT and the diode; increasing the IGBT die size from the initial value; and reducing said diode die size from the initial value. The IGBT die size is increased sufficiently to reduce current density, conduction losses and switching losses in the IGBT. The diode die size is reduced sufficiently to reduce the reverse recovery charge of the diode so as to further reduce switching losses in the IGBT, to a minimum size which is sufficient to carry the antiparallel current without substantial overheating. The adjustment of the diode die size is advantageous either independently of, or in combination with, the adjustment of the IGBT die size. These adjustments are capable of reducing the switching energy of the IGBT and diode by about 30%-40% below that of a conventional IGBT-diode combination.

IGBT and free-wheeling diode combination

A circuit for synchronous rectification including two power MOSFET transistor switches in which the bottom switch is a P channel MOSFET, rather than an N channel MOSFET. The circuit of the present invention uses a single channel driver, rather than a dual driver and eliminates the deadtime associated with conventional circuits, thus minimizing reverse recovery losses. In an alternative arrangement, the position of the output filter is switched so that the N channel MOSFET conducts during the freewheeling time and the P channel MOSFET (with a larger RDSON) conducts during the conductor charge cycle.

Circuit for synchronous rectification with minimal reverse recovery losses

A massive heat slug in thermally coupled to the top of an IGBT to act as a local thermal inertia element to absorb and store heat from the die during peak temperature rise and to return heat to the die at reduced die temperature, thereby reducing the ratio of die peak temperature to die average temperature. The device is useful in applications in which the IGBT is called upon to carry current at a range of frequencies which includes very low (eg 3 Hz) frequencies as in a motor control circuit.

Top heatsink for IGBT

A simple, off-chip circuit and method for endowing high efficiency IGBTs with short-circuit capability, that is essentially transparent to the user. The invention involves adding an external common emitter resistor to reduce the effective gain of an IGBT under short circuit. Under normal operating conditions, the voltage across the resistor is small, such that the modifying effect on the normal operating gate-emitter voltage is almost negligible.

Growing community of inventors

Palos Verdes Estates, CA, United States of America

Brian R Pelly