Contactless battery system utilizing a bidirectional power converter
A bidirectional power converter circuit is controlled via a hysteresis loop such that the bidirectional power converter circuit can compensate for variations and even changes in transmit and receive coil locations without damaging components of the system. Because the bidirectional power converter is capable of both transmitting and receiving power (at different times), one circuit and board may be used as the main component in multiple wireless power converter designs. A first bidirectional power converter is employed in a sealed battery unit having no external electrical contacts. A second bidirectional power converter is employed in a corresponding cart bidirectional power converter assembly. The battery unit and the cart bidirectional power converter assembly cooperate to wirelessly transmit power from the battery unit to a load of the cart bidirectional power converter assembly and from a power source to the battery unit via the cart bidirectional power converter assembly.
1. A battery unit comprising:
a sealed housing with no external electrical contacts;
a battery enclosed by the sealed housing, wherein the battery is configured to selectively store direct current (DC) power and selectively provide DC power;
a coil enclosed by the sealed housing;
a bidirectional power converter having an alternating current (AC) terminal connected to the coil, a DC input terminal, a DC output terminal, a direction control, and a transmission enable input, wherein the bidirectional power converter has a transmit mode operable to provide AC output power to the coil from the battery and a receive mode operable to receive AC power via the coil and provide a DC output to the DC output terminal;
a battery management system connected to the battery, the DC input terminal, and the DC output terminal, wherein the battery management system is responsive to a charge signal to selectively provide DC power to the battery for storage from the DC output of the bidirectional power converter and to provide DC power received from the battery to the DC input of the bidirectional power converter;
a digital hall effect sensor configured to sense proximity of a permanent magnet of a cart bidirectional power converter assembly and provide a binary presence signal indicative of the proximity of the permanent magnet; and
a microprocessor connected to the direction control of the bidirectional power converter, the transmission enable input of the bidirectional power converter, the digital hall effect sensor, and the battery management system, wherein the microprocessor is configured to determine a mode of the bidirectional power converter from the cart bidirectional power converter assembly, and in the transmit mode:
set the battery management system to provide DC power from the battery to the DC input of the bidirectional power converter by providing the charge signal;
set the bidirectional power converter to the transmit mode via the direction control input; and
provide a transmit enable signal to the transmission enable input of the bidirectional power converter in response to receiving the binary presence signal from the digital hall effect sensor indicating the presence of the permanent magnet of the cart bidirectional power converter assembly; and, in the receive mode:
set the battery management system to provide DC power to the battery for storage from the DC output of the bidirectional power converter via the charge signal; and
set the bidirectional power converter to the receive mode via the direction control input.
2. The battery unit of claim 1 , wherein the microprocessor of the battery unit is operable to communicate with a microprocessor of the cart bidirectional power converter assembly via Bluetooth to determine in which mode to set the bidirectional power converter of the battery unit.
3. The battery unit of claim 1 , wherein the bidirectional power converter comprises a control logic configured to receive a temperature sensing signal and the transmission enable signal and provide a modulator enable signal as a function of the temperature sensing signal and the transmission enable signal.
4. The battery unit of claim 1 , wherein the bidirectional power converter is operable to provide alternating current (AC) power at an AC terminal of the bidirectional power converter in the transmit mode of the bidirectional power converter and provide direct current (DC) power at the DC output terminal of the bidirectional power converter in the receive mode, said bidirectional power converter comprising:
an oscillator configured to provide a drive signal at a base frequency when the bidirectional power converter is operating in the transmit mode;
an amplifier configured to receive power from a power source via the DC input terminal of the bidirectional power converter and provide an AC output signal to the AC terminal of the bidirectional power converter in response to receiving the drive signal when the bidirectional power converter is operating in the transmit mode;
a modulator configured to selectively provide the drive signal from the oscillator to the amplifier as a function of a hysteretic control signal when the bidirectional power converter is operating in the transmit mode;
a hysteretic receiver circuit configured to receive a transmitted control signal at the bidirectional power converter and provide the hysteretic control signal to the modulator as a function of the received, transmitted control signal when the bidirectional power converter is operating in the transmit mode;
a transmit relay configured to electrically connect the amplifier to the AC terminal of the bidirectional power converter when the bidirectional power converter is operating in the transmit mode and electrically disconnect the amplifier from the AC terminal of the bidirectional power converter when the bidirectional power converter is operating in the receive mode;
a rectifier configured to receive an alternating current power signal from the AC terminal of the bidirectional power converter and provide the DC output to the DC output terminal of the bidirectional power converter when the bidirectional power converter is operating in the receive mode;
a receive relay configured to enable the rectifier to provide the DC output to the DC output terminal of the bidirectional power converter when the bidirectional power converter is operating in the receive mode and prevent the rectifier from providing the DC output to the DC output terminal when the bidirectional power converter is operating in the transmit mode; and
a hysteretic control circuit configured to monitor the DC output and transmit a control signal as a function of the monitored DC output when the bidirectional power converter is operating in the receive mode.
5. The battery unit of claim 4 , wherein the hysteretic control circuit comprises:
a hysteretic controller configured to provide a logic signal, wherein the logic signal is a first binary value when a voltage of the direct current (DC) output is less than a predetermined threshold and the logic signal is a second binary value when the voltage of the DC output is more than the predetermined threshold and wherein the first binary value is different than the second binary value; and
a coil pulse driver configured to receive the logic signal and generate a magnetic field via the magnetic coupling coil, wherein the generated magnetic field is indicative of the logic signal; and
the hysteretic receiver circuit comprises a magnetic sensor configured to receive a magnetic field and provide the hysteretic control signal to the modulator as a function of the received magnetic field.
6. The battery unit of claim 4 , wherein the modulator is an amplitude shift keyed modulator.
7. The battery unit of claim 4 , wherein the amplifier is a full bridge amplifier.
8. The battery unit of claim 4 , wherein the rectifier is a full wave rectifier.
9. A cart bidirectional power converter assembly comprising:
a cradle configured to receive a battery unit;
a permanent magnet configured to be in proximity with a digital hall effect sensor of the battery unit when the battery unit is in the cradle;
a coil configured to be aligned with a coil of the battery unit when the battery unit is in the cradle;
a bidirectional power converter connected to the coil and configured to receive power from the battery unit via the coil when the battery unit is in the cradle, a bidirectional power converter of the battery unit is in a transmit mode, and the bidirectional power converter is in a receive mode; and to provide power from a direct current (DC) input of the bidirectional power converter to the coil when the bidirectional power converter is in a transmit mode;
a power distribution assembly configured to:
provide power from a DC output of the bidirectional power converter to a load of the cart bidirectional power converter when the power distribution assembly is not connected to a power source;
provide power from the power source to the DC input of the bidirectional power converter and to the load when the power distribution assembly is connected to the power source; and
provide a mode signal as a function of whether the power distribution assembly is receiving power from the power source; and
a microprocessor connected to a directional control of the bidirectional power converter and to the power distribution assembly, wherein the microprocessor is responsive to the mode signal from the power distribution assembly to set a mode of the bidirectional power converter to a transmit mode when the power distribution assembly is receiving power from the power source and set the bidirectional power converter to a receive mode when the bidirectional power converter is not receiving power from the power source, and wherein the microprocessor is configured to communicate with a microprocessor of the battery unit to set a mode of the bidirectional power converter of the battery unit to a transmit mode when the power distribution assembly is not receiving power from the power source and to set the mode of the bidirectional power converter of the battery unit to a receive mode when the power distribution assembly is receiving power from the power source.
10. The cart bidirectional power converter assembly of claim 9 , wherein the bidirectional power converter is operable to provide alternating current (AC) power at an AC terminal of the bidirectional power converter in a transmit mode of the bidirectional power converter and provide direct current (DC) power at the DC output terminal of the bidirectional power converter in a receive mode, said bidirectional power converter comprising:
an oscillator configured to provide a drive signal at a base frequency when the bidirectional power converter is operating in the transmit mode;
an amplifier configured to receive power from a power source via the DC input terminal of the bidirectional power converter and provide an AC output signal to the AC terminal of the bidirectional power converter in response to receiving the drive signal when the bidirectional power converter is operating in the transmit mode;
a modulator configured to selectively provide the drive signal from the oscillator to the amplifier as a function of a hysteretic control signal when the bidirectional power converter is operating in the transmit mode;
a hysteretic receiver circuit configured to receive a transmitted control signal at the bidirectional power converter and provide the hysteretic control signal to the modulator as a function of the received, transmitted control signal when the bidirectional power converter is operating in the transmit mode;
a transmit relay configured to electrically connect the amplifier to the AC terminal of the bidirectional power converter when the bidirectional power converter is operating in the transmit mode and electrically disconnect the amplifier from the AC terminal of the bidirectional power converter when the bidirectional power converter is operating in the receive mode;
a rectifier configured to receive an alternating current power signal from the AC terminal of the bidirectional power converter and provide a DC output to the DC output terminal of the bidirectional power converter when the bidirectional power converter is operating in the receive mode;
a receive relay configured to enable the rectifier to provide the DC output to the DC output terminal of the bidirectional power converter when the bidirectional power converter is operating in the receive mode and prevent the rectifier from providing the DC output to the DC output terminal when the bidirectional power converter is operating in the transmit mode; and
a hysteretic control circuit configured to monitor the DC output and transmit a control signal as a function of the monitored DC output when the bidirectional power converter is operating in the receive mode.
11. The cart bidirectional power converter assembly of claim 10 , wherein the hysteretic control circuit comprises:
a hysteretic controller configured to provide a logic signal, wherein the logic signal is a first binary value when a voltage of the direct current (DC) output is less than a predetermined threshold and the logic signal is a second binary value when the voltage of the DC output is more than the predetermined threshold and wherein the first binary value is different than the second binary value; and
a coil pulse driver configured to receive the logic signal and generate a magnetic field via the magnetic coupling coil, wherein the generated magnetic field is indicative of the logic signal; and
the hysteretic receiver circuit comprises a magnetic sensor configured to receive a magnetic field and provide the hysteretic control signal to the modulator as a function of the received magnetic field.
12. The cart bidirectional power converter assembly of claim 10 , wherein the modulator is an amplitude shift keyed modulator.
13. The cart bidirectional power converter assembly of claim 10 , wherein the amplifier is a full bridge amplifier.
14. The cart bidirectional power converter assembly of claim 10 , wherein the rectifier is a full wave rectifier.