Obviousness

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 5803215

This analysis assesses the obviousness of US Patent 5803215, "Method and apparatus for charging a plurality of electric vehicles," under 35 U.S.C. § 103, considering the state of the art as of the priority date, 1997-01-22. A person having ordinary skill in the art (PHOSITA) at that time would likely be an electrical engineer or technician with expertise in power electronics, battery management systems, and control systems for industrial or automotive applications. The PHOSITA would be familiar with power conversion, battery charging principles (including rapid charging and equalization), and basic thermal management of electrical components.

The following combinations of prior art references are identified as rendering the independent claims of US5803215 obvious:

Claim 1: Electric vehicle charging system with thermal overload capability

Claim 1 describes an electric vehicle charging system for multiple vehicles, featuring a power source converter, a distribution bus, a plurality of vehicle connecting stations (each with a station power converter and controller), and a mechanism to measure the temperature of the power source converter, allowing it to exceed its steady-state rating based on this temperature.

Combination: NL7403570A, US4016474A, and US5640059A.

Reasoning:

• NL7403570A discloses a system with multiple "stations for electric vehicles" that include "common charging and control means". This teaches the foundational concept of a multi-vehicle charging system with a central power source, distribution to multiple stations, and integrated control, encompassing the power source converter, distribution bus, and vehicle connecting stations with couplers and station controllers.
• US4016474A further teaches a "circuit for controlling the charging current supplied to a plurality of battery loads in accordance with a predetermined program". This directly addresses the control of electrical power flow to multiple vehicle batteries, as performed by the station controllers.
• US5640059A explicitly describes a "power supply system including thermal current limiting protection" that permits "thermal overloading of an inverter for a limited duration" based on temperature measurements. The patent itself describes this feature in detail, stating the supervisory controller receives signals indicative of temperature and allows the utility interface station (containing the power source converter) to operate in excess of its steady-state rating for short durations, so long as temperature limits are not exceeded.

Motivation for Combination:
A PHOSITA would be motivated to combine these references to create a more efficient and resilient multi-vehicle charging system. The motivation would be to centralize power and control for multiple EVs (NL7403570A, US4016474A) to reduce infrastructure costs. Additionally, the PHOSITA would seek to optimize the utilization of the central power source by incorporating known thermal management techniques (US5640059A). This allows the system to temporarily supply power exceeding its continuous rating during peak demand periods without damaging components, thereby permitting a smaller and more cost-effective central power converter while still meeting transient high loads.

Claim 14: Method of charging batteries with thermal overload capability

Claim 14 describes a method for charging multiple electric vehicle batteries, including converting electrical power with a power source converter, measuring the converter's temperature, distributing the power to multiple stations, and individually controlling the charge rate as a function of temperature, allowing the converter to exceed its steady-state rating.

Combination: NL7403570A, US4016474A, and US5640059A.

Reasoning:

• As with Claim 1, NL7403570A provides the method steps of converting and distributing power to multiple EV charging stations with common control.
• US4016474A teaches the method of controlling charging current for a plurality of battery loads, which equates to individually controlling the charge rate for each vehicle battery.
• US5640059A teaches the method of measuring temperature in a power supply and allowing it to exceed its steady-state rating based on thermal conditions. Applying this thermal management method to a multi-vehicle charging system's power source converter, and controlling individual charge rates based on this temperature, would be a straightforward engineering application.

Motivation for Combination:
The motivation remains consistent with Claim 1: to develop an efficient, flexible, and economical method for charging multiple electric vehicles. A PHOSITA would apply known thermal overload management (US5640059A) to the shared power infrastructure (NL7403570A) while coordinating individual charging rates (US4016474A) to maximize system utility and respond effectively to varying demands.

Claim 20: EV charging system with mixed coupler types and DC bus

Claim 20 describes an electric vehicle charging system with a power source converter converting to a DC voltage potential on a distribution bus. It includes a first station with an inductive power coupler and a second station that converts the DC bus voltage to AC, rectifies it, and uses a DC power coupler.

Combination: US5548200A, US5594318A, US3940680A, and US5202617A.

Reasoning:

• US5202617A teaches a "Charging station for electric vehicles" connected to a power source. US5548200A further describes a "universal charging station and method for charging electric vehicle batteries". These references establish the concept of a multi-vehicle charging system from a power source.
• The conversion of electrical power to a DC voltage for distribution on a bus is a known power distribution strategy, evidenced by US3940680A, which discloses an "A.C. - D.C. power converter for D.C. load".
• The use of an inductive power coupler for EV charging is directly taught by US5594318A, titled "Traction battery charging with inductive coupling".
• The second station's configuration (DC bus voltage to AC, rectified, then DC power coupler) represents a common power conversion topology. A DC-AC inverter followed by a rectifier to provide DC power is a well-understood method for achieving voltage regulation, isolation, or current shaping. The patent itself mentions the use of "DC conductive coupling" and "Inductive coupling" as existing techniques, further confirming the modularity of these elements.

Motivation for Combination:
A PHOSITA would be motivated to combine these elements to create a versatile multi-vehicle charging system capable of accommodating diverse electric vehicles with different charging interface requirements (e.g., inductive versus conductive, and potentially different voltage or current profiles). By using a common DC distribution bus (known for efficiency) and implementing localized power conversion within stations (US3940680A) to support various couplers (US5594318A for inductive, and known DC conductive coupling), the system achieves the desired flexibility to charge "many types of vehicles having differing levels of priority, different battery voltages, and different states of charge, at the same time," as articulated in the problem statement of US5803215.

Claim 21: Single EV charging system with thermal overload capability

Claim 21 details an electric vehicle charging system for a single vehicle, including a power source converter, a vehicle connecting station, a temperature sensor for the converter, and a controller that uses the temperature signal to control the charge rate and allows the converter to exceed its steady-state rating.

Combination: US5202617A and US5640059A.

Reasoning:

• US5202617A teaches a "Charging station for electric vehicles," which provides the basic structure of a power source converter, a vehicle connecting station, and the function of providing charge to a battery.
• US5640059A explicitly teaches a "power supply system including thermal current limiting protection" that measures temperature and allows the power supply to exceed its steady-state rating for a limited duration based on thermal conditions. This directly covers the temperature sensor, the controller receiving the output signal, and the function of controlling the charge rate while allowing the power source converter to exceed its steady-state rating based on the temperature.

Motivation for Combination:
A PHOSITA would be motivated to integrate the thermal management features of US5640059A into a standard EV charging station (US5202617A). This integration optimizes the power converter's use, allowing it to handle peak power demands for short periods without requiring an oversized and more expensive unit for continuous operation. This is a common engineering practice for improving performance and cost-efficiency in power delivery systems with fluctuating loads.

Claim 22: EV charging system with power source signal control

Claim 22 describes an electric vehicle charging system for a single vehicle battery, including a power source converter, a vehicle connecting station, a signal line from the power source indicating available power, and a controller that receives this signal and controls the power provided by the station.

Combination: US5202617A and general knowledge of power grid management/utility signals.

Reasoning:

• US5202617A establishes the core components of an "Electric vehicle charging system" comprising a "power source converter" and a "vehicle connecting station" that provides "charge to the battery".
• The additional elements—a "signal line from the power source" indicating available power and a "controller receiving the signal and controlling the power provided by the vehicle connecting station as a function of the signal"—represent a well-known concept in utility demand-side management. At the time of the invention, utilities routinely used signals or tariffs to communicate grid load, available power, or pricing to consumers and distributed energy resources to manage overall demand. The patent's detailed description explicitly states that the supervisory controller receives a signal from the power source operator indicative of maximum available power and regulates charging rates accordingly. Applying this established principle to an EV charging station, which can be a significant load, would be an obvious solution for optimizing grid interaction and managing operational costs.

Motivation for Combination:
A PHOSITA would be motivated to integrate utility signals into an EV charging system to manage electrical demand effectively. This allows the charging station to dynamically adjust its power draw based on grid conditions or economic signals (e.g., charging more during off-peak hours), preventing grid overload, reducing operating costs, and ensuring a more stable and reliable charging infrastructure, particularly in public or fleet charging scenarios mentioned by the patent.

Claim 26: Method of charging a battery with power source signal control

Claim 26 describes a method for charging a vehicle battery, including converting power, receiving a signal from the power source indicating power to be converted, distributing the power to a vehicle connecting station, and controlling the power delivered to the battery as a function of the signal.

Combination: US5202617A and general knowledge of power grid management/utility signals.

Reasoning:

• As with Claim 22, US5202617A teaches the fundamental method steps of converting power, distributing it to a vehicle connecting station, and charging a battery.
• The method steps of "receiving a signal from the power source indicative of the power to be converted; and controlling the power delivered to the vehicle battery as a function of the signal" directly align with established demand-side management practices in electrical utility systems. It would be obvious to a PHOSITA to apply this known method of responding to utility signals to the context of EV charging to prevent grid instability or take advantage of favorable pricing.

Motivation for Combination:
The motivation is identical to Claim 22: to enable smart and efficient power management for EV charging. By making the charging process responsive to signals from the power source, the method optimizes for grid stability, cost-efficiency, and available capacity.

Claim 30: EV charging system with DC bus and DC conductive coupler (with internal DC-AC-DC conversion)

Claim 30 describes an electric vehicle charging system that converts power to a DC voltage potential on a distribution bus. A vehicle connecting station comprises a power converter (DC to AC), a rectifier, and a DC power coupler connected to the rectifier and connectable to the battery.

Combination: US5202617A, US3940680A, and general knowledge of power conversion.

Reasoning:

• US5202617A provides the core concept of an EV charging station connected to a power source.
• The conversion to a "DC voltage potential" for a "distribution bus" is a common power distribution strategy, especially where multiple DC loads are served. US3940680A teaches an "A.C. - D.C. power converter for D.C. load", demonstrating knowledge of DC power conversion and distribution.
• The vehicle connecting station's internal configuration (DC-AC-rectifier-DC power coupler) is a well-known power electronics topology. A DC-AC inverter followed by a rectifier to deliver DC power is a standard method to achieve galvanic isolation, precise voltage/current regulation, or convert between different DC voltage levels. The patent's background describes inductive charging involving high-frequency AC power from an off-board charger to an on-board rectifier converting to DC for the battery, illustrating that a DC-AC-rectifier-DC pathway using modular components was known. The implementation of such a conversion chain within a station to deliver controlled DC power to a battery via a DC conductive coupler would be a matter of routine engineering design choice.

Motivation for Combination:
A PHOSITA would be motivated to integrate this DC-AC-DC conversion chain within a vehicle connecting station (US5202617A) fed by a DC bus for several engineering benefits. These include providing galvanic isolation for safety, enabling highly controllable output voltage and current for optimal battery charging using a high-frequency intermediate AC link, and accommodating a wide range of vehicle battery voltages from a single DC distribution bus, addressing the patent's stated need for charging vehicles with "different battery voltages".