Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
  • H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
  • H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
  • H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
  • H01F38/14—Inductive couplings

Definitions

• This invention relates generally to an inductive power transmitter, particularly, but not exclusively, for an inductive power transfer system and a method of power flow control.
• IPT inductive power transfer
• IPT systems are a well-known area of established technology (for example, wireless charging of electric toothbrushes) and developing technology (for example, wireless charging of handheld devices on a 'charging mat').
• any IPT system some form of power flow control is required for efficient operation and there are tradeoffs as to system complexity and performance.
• reactive power supply in an IPT transmitter has been predetermined by the design of the circuit with a fixed load at the secondary circuit.
• Systems having IPT transmitter side power flow control with no IPT receiver side power flow control may be achieved using a range of approaches including changing the inverter operating frequency, power supply to the inverter or the duty cycle of the switched inverter output waveform based on measured electrical parameters on the transmitter side.
• power flow control on only the IPT transmitter side results in discontinuity of power supply as there is lag in the IPT transmitter side prediction of power demand by the IPT receiver side and power flow control in the IPT transmitter side.
• the invention provides an inductive power transfer system and a method of power flow control that achieves good power flow control utilising a relatively simple design or at least provides the public with a useful choice.
• an inductive power transmitter comprising: a. a controllable DC voltage source; b. a DC-AC converter that receives a DC power supply from the controllable DC voltage source and generates an AC output waveform to drive a transmitter coil of an inductive power transfer system; c. a current sensor for measuring the current supplied by the controllable DC voltage source to the DC-AC converter; and d. a controller that adjusts the output voltage of the DC voltage source based on the current measured by the current sensor.
• an inductive power transmitter supplying power to an inductive power receiver
• the inductive power transmitter includes a DC-AC converter driving a transmitter coil from a controllable DC voltage source and wherein the inductive power receiver has power flow control
• the method including the steps of:
• Figure 1 is a schematic diagram of an inductive power transfer system
• Figure 2 is a circuit diagram including a DC-AC converter design according to one embodiment.
• FIG. 1 a schematic diagram of an inductive power transfer system 1 is shown including an IPT transmitter 2 and an IPT receiver 3.
• the transmitter 2 includes a controllable DC voltage source 5, which in this case is a DC-DC converter receiving a DC input supply 4.
• DC voltage source 5 may be a Buck or Buck-boost converter, however, a Buck-boost converter is preferred as it is able to work over a large input voltage range
• the controllable DC voltage source 5 provides a regulated DC output voltage to DC-AC converter 6 (suitably operating in boost mode) that drives transmitter coil 7.
• the DC-AC converter may incorporate the controllable DC voltage source.
• Controller 8 (a suitable micro-controller) receives this information from sensors 9 and 10 and controls the output voltage of controllable DC voltage source 5 accordingly. Controller 8 also controls the switching of DC-AC converter 6.
• IPT receiver 3 includes a receiver coil 1 1 that supplies power to a rectifier 12 which in turn supplies power to a power flow controller 13 which in this case is in the form of a DC-DC converter.
• Figure 2 shows exemplary circuit components of a push pull implementation of DC-AC converter 6.
• current from DC-DC converter 5 is split between inductors 14 and 15 with each branch connected to one side of a parallel resonant arrangement of transmitter coil 7 and a resonant capacitor 16.
• Switches 17 and 18 are controlled by controller 8 to alternately connect one branch of the parallel resonant circuit to ground. In this embodiment switches 17 and 18 may switch at a constant frequency at or near the resonant frequency of the converter.
• FIG. 2 illustrates a Push Pull converter topology
• other converter types are applicable operating in buck, boost or buck- boost modes with controllable DC to AC conversion.
• Such converter could implement, for example, flyback, full bridge, half bridge, etc. topologies in a manner understood by those skilled in the art.
• Transmitter side power flow control may be performed in a number of ways.
• transmitter side power flow control is effected by controlling the voltage output by controllable DC voltage source 5 based on the current measured by current sensor 9.
• the magnitude of the current that is drawn by the push-pull circuit is indicative of the apparent load (the real load and the coupling coefficient) on the receiver side.
• the DC voltage supplied to the push-pull circuit is regulated (by controlling the DC-DC power converter 5) so that the reactive power in the transmitter coil 7 corresponds approximately (i.e., not too high or not too low) to the power being drawn by the load on the IPT receiver 3. This results in more efficient power transfer by dynamically controlling the reactive power.
• the output voltage of the controllable DC voltage source 5 is adjusted to maintain the output current of the controllable DC voltage source within a prescribed range in accordance with the hysteresis of the output current, preferably within the middle of the range.
• the output power to be supplied by the IPT transmitter is also preferably set to be greater than the power that is required by the IPT receiver by a prescribed margin between about 5% and about 20% to compensate for any lag in transmitter side control. This is possible because the IPT receiver has power flow control. This method has the advantage that only a current sensor is required.
• controller 8 Another way of performing transmitter side power flow control is for the controller 8 to adjust the output voltage of the controllable DC voltage source in accordance with changes in power supplied based on measurements from the voltage sensor 10 and current sensor 9.
• the Push Pull Converter desirably operates in boost mode to compensate for any power shortages that may incur at the IPT receiver side if a load suddenly changes, as the voltage adjustment will not be instantaneous.
• the controller 8 may also be pre-programmed to supply an additional amount of reactive power (preferably between about 5% to about 20%) to help compensate for small or instantaneous load changes.
• This IPT system design and control method allows control of the amount of reactive power needed at the IPT transmitter coil to deliver sufficient power to the IPT receiver regardless of the load. This ensures high efficiency for any load and the ability to satisfy peak load demands to deal with changes in transmitter and receiver coil coupling due to relative coil movement.
• the design is relatively simple and robust and avoids the need for communication between an IPT transmitter and an IPT receiver.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Computer Networks & Wireless Communication (AREA)
• Inverter Devices (AREA)
• Dc-Dc Converters (AREA)
• Current-Collector Devices For Electrically Propelled Vehicles (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (1)

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Citations (2)

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• 2015
  • 2015-12-16 EP EP15870426.2A patent/EP3235106A4/en not_active Withdrawn
  • 2015-12-16 KR KR1020177016911A patent/KR20170095244A/ko not_active Withdrawn
  • 2015-12-16 CN CN201580068915.9A patent/CN107112803A/zh active Pending
  • 2015-12-16 WO PCT/NZ2015/050214 patent/WO2016099295A1/en not_active Ceased
  • 2015-12-16 JP JP2017532695A patent/JP2018501761A/ja not_active Abandoned
  • 2015-12-16 US US15/537,139 patent/US20180219415A1/en not_active Abandoned

Patent Citations (2)

Non-Patent Citations (1)

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