Abstract: 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 t

Abstract: 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 t

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A circuit, for detecting a junction temperature of an insulated gate bipolar transistor (IGBT) which is alternately biased on and off in response to a gate signal, includes a differentiator circuit operable to receive a collector to emitter voltage of the IGBT and produce an output voltage proportional to a rate at which the collector to emitter voltage changes; and a feedback circuit operable to receive the output voltage and alter the gate signal when the output voltage indicates that the rate at which the collector to emitter voltage changes is outside a predetermined limit.

Abstract: A soft start circuit for controlling a rectifier circuit, the rectifier circuit for converting power from an AC source having one or more phases to DC power having an output voltage (Vo) from a Vo+ node to a Vo- node, the rectifier circuit including: (i) at least first and second rectifier legs coupled from the Vo- node to the Vo+ node, each rectifier leg including a diode and a silicon controlled rectifier (SCR), wherein anodes of the diodes are coupled to the Vo- node, cathodes of the diodes are coupled to anodes of the SCRs at AC input nodes, and cathodes of the SCRs are coupled to the Vo+ node; and (ii) a bus capacitor coupled from the Vo+ node to the Vo- node, the soft start circuit operable to control respective firing angles of the SCRs such that: (i) the output voltage substantially linearly ramps from a low initial value to a relatively high final value, and (ii) charge up currents into the bus capacitor are controlled.

Abstract: A soft start bridge rectifier circuit is described for controlling the operation of the bridge rectifier in order to ramp up the DC output upon connection with the AC input in order to limit in-rush current. Additionally, short-circuit/overload protection, temporary line loss protection and undervoltage checking circuitry is provided.

Abstract: 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.

Abstract: The invention relates to a circuit and method for sensing inverter current in a motor drive power train for purposes of detecting overload and fault conditions, based on the use of simple low cost ac current transformers and/or a low cost current-viewing resistor with non-critical inductance characteristics. The invention employs a current-viewing resistor in the negative dc bus of the inverter and a current transformer, connected in series with the current-viewing resistor, which is coupled to detect the current in the smoothing capacitor of the inverter circuit. If a motor braking circuit is included, the voltage developed across the braking resistor is summed with the inverter current signal to obtain a signal indicative of the total current in the inverter circuit. In accordance with another embodiment, a respective current transformer is coupled to each leg of the ac input line and a further current transformer is coupled to sense the filter capacitor current.

Abstract: An isolator surge protector (ISP) is provided which blocks DC current and passes AC current and AC and DC fault currents. The ISP includes a main bypass path, including main bypass path switching devices, that is connected in parallel with a DC blocking capacitor. Primary triggering of the main bypass path switching devices occurs when the voltage across the ISP exceeds a primary voltage trigger level. Repeated triggering of the bypass path switching devices, and high current discharge of the high voltage DC blocking capacitor through the bypass path, under abnormal steady state voltage conditions, is prevented by initiating a secondary triggering period following primary triggering of the bypass path switching devices. During the extended secondary triggering period, triggering of the bypass path switching devices occurs at a low secondary voltage trigger level.

Abstract: A buck regulator circuit provides a low voltage, e.g., about 15 V, power source, directly from a variable high-voltage dc bus voltage that varies from 250 V to about 450 V. A monolithic gate driver circuit is used to drive the switching device, e.g., a MOSgate transistor, which delivers the high voltage dc to the load output node via a charging inductor for controlled time periods. The control principle for controlling the on and off times of the transistor (with the monolithic gate driver circuit) relies on turning on the transistor for fixed time periods that are equal to the intrinsic delay of the gate driver circuit. In contrast, the off period of the switching device is varied to regulate and maintain the output voltage at a constant value, independent of the input dc bus voltage or of the output current.