RV converter with current mode and voltage mode switching
View Patent ↗A switched mode converter is disclosed that includes mode logic for switching between voltage mode and current mode. The converter includes sensing circuitry for sensing current on the primary side, load current on the secondary side, and converter output voltage. When load current is less than a predetermined value, the converter operates in voltage mode wherein output voltage of the voltage mode controller is used to control the duty cycle of a PWM controller. When load current is greater than a predetermined value, the converter operates in current mode wherein primary current is used to control the PWM controller. Thus during a light load when the converter is voltage controlled there is no need for a minimum load to stabilize the control loop. In current-mode the control loop will have faster transient response and avoid flux imbalance. Thereby providing advantages of both voltage and current controlled switched mode converters.
1. A switched mode converter for supplying charging current to a battery, the switched mode converter comprising:
a high frequency transformer configured to be selectively coupled to an external power source, said high frequency transformer defining an output and an output signal;
a high frequency switching circuit for selectively connecting said external power source to said high frequency transformer;
current sensing circuit for sensing the charging current applied to said battery;
a pulse width modulator (PWM) for controlling said high frequency switching circuit;
a voltage mode controller for selectively controlling said PWM;
a current mode controller for selectively controlling said PWM; and
a mode switching device for automatically coupling said voltage mode controller to said PWM converter when said charging current is less than a predetermined value defining a voltage mode and automatically coupling said current mode controller to said PWM when said charging current is greater than a predetermined value defining a current mode.
2. The switched mode converter as recited in claim 1 , wherein said current sensing circuit is coupled to said output of said high frequency transformer.
3. The switched mode converter as recited in claim 1 , wherein said external power supply is an AC power supply and said converter further includes a rectifier circuit for rectifying said AC power from said external power supply.
4. The switched mode converter as recited in claim 1 , wherein said external power supply is a DC power supply.
5. The switched mode converter as recited in claim 1 , wherein said voltage mode controller is configured as a feedback loop.
6. The switched mode converter as recited in claim 1 , wherein said current mode controller is configured as a feedback loop.
7. The switched mode converter as recited in claim 1 , wherein said voltage mode controller and said current mode controller are configured as feedback loops.
8. A method for charging a battery coupled to an output of a high frequency transformer from an external power supply, the method comprising the steps of:
(a) selectively connecting said external power supply to said high frequency transformer to produce charging current for charging said battery;
(b) sensing the charging current applied to said battery; and
(c) automatically controlling the connection of said external voltage to said high frequency transformer as a function of voltage in a voltage mode of operation-current in a current mode of operation;
(d) automatically switching between said voltage mode and said current mode as a function of said charging current.
9. The method as recited in claim 8 , wherein step (a) comprises:
(a) selectively coupling an external DC voltage to a high frequency transformer.
10. The method as recited in claim 8 , wherein step (a) comprises:
(a) selectively coupling an external AC voltage to a high frequency transformer; and
(e) rectifying said external AC voltage before it is connected to said high speed transformer.
11. A switched mode converter comprising:
a high frequency transformer configured to be selectively coupled to an external AC power source, said high frequency transformer defining an output and an output signal;
a high frequency switching circuit for selectively connecting said external AC power source to said high frequency transformer;
a rectification circuit coupled to said output of said high frequency transformer for generating a DC current for charging a battery;
a pulse width modulator (PWM) for controlling said high frequency switching circuit;
a voltage mode controller for selectively controlling said PWM;
a current mode controller for selectively controlling said PWM; and
a mode switching device for selectively coupling said voltage mode controller and said current mode controller to said PWM.
12. The switched mode converter recited in claim 11 , further including a current sensing circuit for sensing the current supplied to said battery.
13. The switched mode converter recited in claim 12 , wherein said mode switching device automatically couples said voltage mode controller to said PWM when said current to said battery is less than a predetermined value.
14. The switched mode converter recited in claim 12 , wherein said mode switching device automatically couples said current mode controller to said PWM when said current to said battery is greater than a predetermined value.
15. A switched mode converter comprising:
a high frequency transformer configured to be selectively coupled to an external AC power source, said high frequency transformer defining an output and an output signal;
a high frequency switching circuit for selectively connecting said external AC power source to said high frequency transformer;
a current sensing circuit for sensing the current supplied to said battery;
a pulse width modulator (PWM) for controlling said high frequency switching circuit;
a voltage mode controller for selectively controlling said PWM;
a current mode controller for selectively controlling said PWM; and
a mode switching device for selectively coupling said voltage mode controller and said current mode controller to said PWM as a function of said current supplied to said battery.
16. The switched mode converter recited in claim 15 , wherein said mode switching device automatically couples said voltage mode controller to said PWM when said current to said battery is less than a predetermined value.
17. The switched mode converter recited in claim 15 , wherein said mode switching device automatically couples said current mode controller to said PWM when said current to said battery is greater than a predetermined value.