Abstract: In at least one embodiment, provided is an electric vehicle supply equipment having a line power contactor including a first line power input and a second line power input and a first line power output and a second line power output. It further has a welded contactor detector with a contactor sense circuit, the sense circuit having a first line shunt resistor network connected from the first line power contactor output to ground and a second line shunt resistor network connected from the first line power contactor output to ground. In another embodiment provided is an EVSE including a welded contactor detector with a contactor sense circuit having a bias resistor connected between the hot line relay input and the neutral line relay output.

Abstract: In an embodiment, a missing utility ground detection circuit includes a pair of balanced resistors each connected to receive utility voltage from a different one of a pair of utility power lines, the balanced resistors being connected together at a summing node to be capable of summing the voltages from the pair of utility power lines. It includes an unbalance resistor connected to shunt voltage from one of the utility power lines. It has a summing amplifier with an input coupled to the summing node and to a reference voltage, and an input coupled to a second reference voltage. It has an averaging circuit connected at the output of the summing amplifier. A comparator is provided having an input connected to the averaging circuit an input connected to a threshold voltage.

Abstract: In an embodiment, a missing utility ground detection circuit includes a pair of balanced resistors each connected to receive utility voltage from a different one of a pair of utility power lines, the balanced resistors being connected together at a summing node to be capable of summing the voltages from the pair of utility power lines. It includes an unbalance resistor connected to shunt voltage from one of the utility power lines. It has a summing amplifier with an input coupled to the summing node and to a reference voltage, and an input coupled to a second reference voltage. It has an averaging circuit connected at the output of the summing amplifier. A comparator is provided having an input connected to the averaging circuit an input connected to a threshold voltage.

Abstract: In an embodiment, a missing utility ground detection circuit includes a pair of balanced resistors each connected to receive utility voltage from a different one of a pair of utility power lines, the balanced resistors being connected together at a summing node to be capable of summing the voltages from the pair of utility power lines. It includes an unbalance resistor connected to shunt voltage from one of the utility power lines. It has a summing amplifier with an input coupled to the summing node and to a reference voltage, and an input coupled to a second reference voltage. It has an averaging circuit connected at the output of the summing amplifier. A comparator is provided having an input connected to the averaging circuit an input connected to a threshold voltage.

Abstract: In one possible embodiment, a contactor health monitor circuit is provided having a first operational amplifier connected at a first input to a line one primary side terminal of a contactor and connected at a second input to a line two primary side terminal of the contactor. The circuit also includes a second operational amplifier connected at a first input to a line one secondary side terminal of the contactor and connected at a second input to a line two secondary side terminal of the contactor. A summing amplifier is connected at a first input to an output of the first operational amplifier summed with an output of the second operation amplifier.

Abstract: In one possible implementation, a method is provided for determining contactor health including measuring a differential voltage between a first utility line voltage and a second utility line voltage on a primary side of a contactor and on a secondary side of the contactor. The measuring is performed with both an unloaded current and with a load current. The unloaded and loaded measurements are performed at the primary side and the secondary side, and are made with the contactor closed. It includes determining a difference between a secondary unloaded voltage and a secondary loaded voltage and subtracting a difference between a primary unloaded voltage and a primary loaded voltage to provide a contactor voltage drop. The contactor resistance is determined by dividing the contactor voltage drop by the loaded current.

Abstract: In some embodiments, a pilot signal generation circuit is provided including a buffer and a differential amplifier responsive to an output of the buffer. A first transistor is connected to control a reference voltage at an input of the buffer in response to a pulse width modulated logic signal and a second transistor connected to control a reference voltage at an input of the differential amplifier based on the pulse width modulated logic signal such that the second transistor is connected so as to turn on when the first transistor is turned off and to turn off when the first transistor is turned on. The differential amplifier is configured to provide at an output a pilot signal proportional to a gain of the differential amplifier.

Abstract: In at least one embodiment, provided is an electric vehicle supply equipment having a line power contactor including a first line power input and a second line power input and a first line power output and a second line power output. It further has a welded contactor detector with a contactor sense circuit, the sense circuit having a first line shunt resistor network connected from the first line power contactor output to ground and a second line shunt resistor network connected from the first line power contactor output to ground. In another embodiment provided is an EVSE including a welded contactor detector with a contactor sense circuit having a bias resistor connected between the hot line relay input and the neutral line relay output.

Abstract: In some embodiments, a pilot signal generation circuit is provided including a buffer and a differential amplifier responsive to an output of the buffer. A first transistor is connected to control a reference voltage at an input of the buffer in response to a pulse width modulated logic signal and a second transistor connected to control a reference voltage at an input of the differential amplifier based on the pulse width modulated logic signal such that the second transistor is connected so as to turn on when the first transistor is turned off and to turn off when the first transistor is turned on. The differential amplifier is configured to provide at an output a pilot signal proportional to a gain of the differential amplifier.

Abstract: In various implementations, method is provided for reducing noise in a pilot signal, which may include sampling the pilot signal and creating a first data set comprising the samples of the pilot signal samples. It may also include selecting a first subset from the first data set and averaging the first subset to produce a first tier averaged output of the selected first subset. It may further include creating a second data set of the first tier averaged outputs and selecting a second subset from the second data set and averaging the second subset to produce the pilot signal output. In various embodiments, this method may further include, or separately include generating the pilot signal with a modulation rate within an allowable range and offset from a central modulation rate of the allowable range.

Abstract: In one implementation, a method is provided to detect a ground fault. This includes applying a pulsed test impedance and detecting a utility power voltage with and without the pulsed test impedance applied. It further includes detecting a test current through the pulsed test impedance to ground and determining whether a ground fault exists based on the detected test current and the detected utility power voltage with and without the pulsed test impedance applied.

Abstract: In various embodiments, a pilot signal generation circuit is provided having an operational amplifier buffer connected via a first resistor to receive a source reference voltage. A differential amplifier is connected at a first input to receive the source reference voltage and at a second input to an output of the operational amplifier buffer. A first shunt transistor is connected to shunt the source reference voltage at the operational amplifier buffer in response to pulse width modulated signal. A second shunt transistor is connected to the differential operational amplifier so as to shunt the source reference voltage in response to an output of the first shunt transistor. The output of the differential amplifier provides a pulse width modulated bipolar signal at precision voltage levels in response to the pulse width modulated signal.

Abstract: In one implementation, the method for processor based automated testing of ground fault interrupt circuit for electric vehicle supply equipment is provided. In one implementation the method includes providing a simulated ground fault signal to a ground fault interrupt circuit and detecting at a processor that the ground fault interrupt circuit sensed the simulated ground fault signal. The method further includes commanding from the processor a utility power contactor to close while the ground fault interrupt circuit is disabling closing of the contactor and verifying the utility power contactor is not closed in response to commanding the utility power contactor to close.

Abstract: In various embodiments, a pilot signal generation circuit is provided having an operational amplifier buffer connected via a first resistor to receive a source reference voltage. A differential amplifier is connected at a first input to receive the source reference voltage and at a second input to an output of the operational amplifier buffer. A first shunt transistor is connected to shunt the source reference voltage at the operational amplifier buffer in response to pulse width modulated signal. A second shunt transistor is connected to the differential operational amplifier so as to shunt the source reference voltage in response to an output of the first shunt transistor. The output of the differential amplifier provides a pulse width modulated bipolar signal at precision voltage levels in response to the pulse width modulated signal.

Abstract: In an embodiment, a missing utility ground detection circuit includes a pair of balanced resistors each connected to receive utility voltage from a different one of a pair of utility power lines, the balanced resistors being connected together at a summing node to be capable of summing the voltages from the pair of utility power lines. It includes an unbalance resistor connected to shunt voltage from one of the utility power lines. It has a summing amplifier with an input coupled to the summing node and to a reference voltage, and an input coupled to a second reference voltage. It has an averaging circuit connected at the output of the summing amplifier. A comparator is provided having an input connected to the averaging circuit an input connected to a threshold voltage.

Abstract: In one implementation, a ground fault interrupt circuit is provided for a utility power connection to an electric vehicle charging unit. The ground fault interrupt circuit may include a gain amplifier having an input connected to be capable of receiving a differential current from a current sensing transformer and a comparator having an input connect to a reference voltage. It includes a rectifier circuit connected between the gain amplifier and the comparator with a charge accumulator circuit coupled between the rectifier and the comparator.

Abstract: In one possible implementation, a method is provided for determining contactor health including measuring a differential voltage between a first utility line voltage and a second utility line voltage on a primary side of a contactor and on a secondary side of the contactor. The measuring is performed with both an unloaded current and with a load current. The unloaded and loaded measurements are performed at the primary side and the secondary side, and are made with the contactor closed. It includes determining a difference between a secondary unloaded voltage and a secondary loaded voltage and subtracting a difference between a primary unloaded voltage and a primary loaded voltage to provide a contactor voltage drop. The contactor resistance is determined by dividing the contactor voltage drop by the loaded current.