US 6,664,762 B2 · High voltage battery charger

Abstract

A simple and flexible battery charger for charging high voltage battery strings includes a DC-to-AC converter that drives the primary of a transformer having multiple secondaries. Each secondary winding has a corresponding output stage formed of a rectification circuit, output inductor, and output capacitor. The output terminals of the output stages are connectable either in parallel or series. In either configuration, inductor current and capacitor voltage automatically balance among the output stage circuits. A controller normally regulates output terminal voltage by operating in voltage mode, but limits current by operating in a current mode when the average of inductor currents exceeds a specified limit. Reconfiguration from parallel to series, or vice versa, is obtained physical reconnection of the output stage terminals and adjustment of a single voltage feedback scaling factor. Connecting the output stages in series to produce a high voltage output reduces voltage stresses on the rectification circuits and enables use of Schottky diodes to avoid reverse recovery problems.

Claims57

Dependent claims

A battery charger comprising:

(a) a transformer having at least one primary winding and a plurality of secondary windings;
(b) a buck-based DC-to-AC converter having an arrangement of controllable switching devices, input terminals that may be connected to a DC source, and output terminals connected to the primary winding of the transformer;
(c) a plurality of output stage circuits, an output stage circuit connected to each secondary winding, wherein each output stage circuit has a rectification circuit connected across a secondary winding and connected to a low-pass filter which includes an output to provide filtered DC voltage across output terminals of each output stage circuit;
(d) a positive output terminal and a negative output terminal of the battery charger, the output terminals of the output stage circuits connected across the battery charger output terminals in a series or parallel arrangement;
and
(e) a controller connected to the controllable switching devices to switch them on and off periodically so as to transfer energy from the input terminals of the DC-to-AC converter to the output stage circuits with control of the total voltage and current from the output stage circuits wherein the controller receives a feedback signal proportional to the average of the individual currents in each output inductor of each output stage circuit wherein the controller further receives a feedback signal representing the voltage across the output terminals of the battery charger and controls the switching of the switching devices based on the average current feedback signal and the voltage feedback signal.

3 more elements

A battery charger comprising:

(a) a transformer having at least one primary winding and a plurality of secondary windings;
(b) a DC source comprising a rectifier having input terminals that may be supplied by an AC source and providing rectified DC output voltage;
(c) a buck-based DC-to-AC converter having an arrangement of controllable switching devices, input terminals connected to the DC source to receive the output voltage therefrom, and output terminals connected to the primary winding of the transformer;
(d) a plurality of output stage circuits, an output stage circuit connected to each secondary winding, wherein each output stage circuit has a rectification circuit connected across a secondary winding and connected to a low-pass filter which includes an output inductor and an output capacitor to provide filtered DC voltage across output terminals of each output stage circuit;
(e) a positive output terminal and a negative output terminal of the battery charger, the output terminals of the output stage circuits connected across the battery charger output terminals in a series or parallel arrangement;
and
(f) a controller connected to the controllable switching devices to switch them on and off periodically so as to transfer energy from the input terminals of the DC-to-AC converter to the output stage circuits with control of the total voltage and current from the output stage circuits, wherein the controller receives a feedback signal proportional to the average of the individual currents in each output inductor of each output stage circuit, wherein the controller further receives a feedback signal representing the voltage across the output terminals of the battery charger and controls the switching of the switching devices based on the average current feedback signal and the voltage feedback signal, wherein the controller includes a pulse generator and gate drive circuit to provide pulsed periodic control signals at a selected frequency to the DC-to-AC converter switching devices.

4 more elements

A method of charging a string of series-connected batteries comprising:

(a) connecting a pair of output leads from a battery charger across a string of series-connected batteries to be charged, the battery charger comprising a transformer having at least one primary winding and a plurality of secondary windings;
a buck-based DC-to-AC converter having an arrangement of controllable switching devices, input terminals that may be connected to a DC source, and output terminals connected to the primary winding of the transformer;
a plurality of output stage circuits, an output stage circuit connected to each secondary winding, wherein each output stage circuit has a rectification circuit connected across a secondary winding and connected to a low-pass filter which includes an output inductor and an output capacitor to provide filtered DC voltage across output terminals of each output stage circuit;
a positive output terminal and a negative output terminal of the battery charger, the output terminals of the output stage circuits connected across the battery charger output terminals in a series arrangement;
and a controller connected to the controllable switching devices to switch them on and off periodically so as to transfer energy from the input terminals of the DC-to-AC converter to the output stage circuits with control of the total voltage and current from the output stage circuits;
(b) controlling the controllable switches in the DC-to-AC converter circuit with the controller operating in voltage-mode when a signal proportional to the average of the currents in the output inductors is below a prescribed limit, and controlling the controllable switches in the converter circuit with the controller operating in current-mode when a signal proportional to the average of the currents in the output inductors is above the prescribed limit, by turning the controllable switching devices on and off periodically such that energy transfers to the battery charger output terminals for charging the string of series-connected-batteries.

3 more elements

A method of reconfiguring a high voltage battery charger from charging with a parallel network arrangement of output capacitors to charging with a series network arrangement of output capacitors, the high voltage battery charger having a transformer having a primary winding and a plurality of secondary windings;

a buck-based DC-to-AC converter having an arrangement of controllable switching devices, input terminals that may be connected to a DC source, and output terminals connected to the primary winding of the transformer;
a plurality of output stage circuits, an output stage circuit connected to each secondary winding, wherein each output stage circuit has a rectification circuit connected across a secondary winding and connected to a low-pass filter which includes an output inductor and an output capacitor to provide filtered DC voltage across output terminals of each output stage circuit;
a positive output terminal and a negative output terminal of the battery charger, the output terminals of the output stage circuits connected across the battery charger output terminals in a parallel arrangement;
and a controller connected to the controllable switching devices to switch them on and off periodically so as to transfer energy from the input terminals of the DC-to-AC converter to the output stage circuits with control of the total voltage and current from the output stage circuits, wherein the controller includes an adjustable scaling factor that scales a feedback signal representing the voltage across the battery charger output terminals to form a scaled voltage feedback signal, comprising:
(a) disconnecting all but a first output stage terminal from the positive output terminal of the battery charger;
(b) disconnecting all but a second output stage terminal from the negative output terminal of the battery charger;
(c) connecting the plurality of output stage circuits in series such that the first output stage terminal is at the most positive position in the series string and the second output stage terminal is the most negative position in the series string;
and
(d) adjusting the voltage feedback scaling factor to regulate the battery charger output terminal voltage at a desired value.

6 more elements

A method of reconfiguring a high voltage battery charger from charging with a series network arrangement to charging with a parallel network arrangement, the high voltage battery charger having a transformer having a primary winding and a plurality of secondary windings;

a buck-based DC-to-AC converter having an arrangement of controllable switching devices, input terminals that may be connected to a DC source, and output terminals connected to the primary winding of the transformer;
a plurality of output stage circuits, an output stage circuit connected to each secondary winding, wherein each output stage circuit has a rectification circuit connected across a secondary winding and connected to a low-pass filter which includes an output inductor and an output capacitor to provide filtered DC voltage across output terminals of each output stage circuit;
a positive output terminal and a negative output terminal of the battery charger, the output terminals of the output stage circuits connected across the battery charger output terminals in a series arrangement;
and a controller connected to the controllable switching devices to switch them on and off periodically so as to transfer energy from the input terminals of the DC-to-AC converter to the output stage circuits with control of the total voltage and current from the output stage circuits, wherein the controller includes an adjustable scaling factor that scales a feedback signal representing the voltage across the battery charger output terminals to form a scaled voltage feedback signal, comprising:
(a) disconnecting the output terminals of all output stage circuits from the output terminals of all other output stage circuits, and connecting the positive terminals of all output stage circuits to the positive output terminal of the battery charger;
(b) connecting the negative output terminal of all output stage circuits to the negative output terminal of the battery charger;
and
(c) adjusting the voltage feedback scaling factor to regulate the battery charger output terminal voltage to a desired value.

5 more elements

A control system for controlling the switching of controllable switching devices in a buck-based DC-to-AC converter in a high voltage battery charger connected to a string of series-connected batteries, the high voltage battery charger including a transformer with a primary winding and a plurality of secondary windings, the DC-to-AC converter being connected to the transformer primary winding, an output stage circuit connected to each secondary winding, each output stage circuit having a rectifier and an output inductor and output capacitor and output terminals connectable to a battery to be charged, the output terminals carrying a combination of currents in the output inductors,

wherein the control system includes a current sense means for feeding back a signal proportional to the average current of the output inductors,
wherein the current feedback signal and a feedback signal representing the voltage across the output terminals are provided as inputs to a controller,
a pulse generator and gate drive circuit,
wherein the controller provides an output signal on an output line to the pulse generator and gate drive circuit to provide pulsed periodic control signals at a selected frequency to the controllable switching devices in the DC-to-AC converter.

1 more element

A battery charger comprising:

(a) a full-bridge DC to AC converter having two high-side controllable switching devices, each connectable at a first terminal to a high-side DC source voltage, and two low-side controllable switching devices, each connectable at a first terminal to a low-side DC source voltage, wherein a second terminal of a first high-side controllable switching device is connected to a second terminal of a first low-side controllable switching device, forming a first intermediate junction, and a second terminal of a second high-side controllable switching device is connected to a second terminal of a second low-side controllable switching device forming a second intermediate junction;
(b) a transformer having a primary winding and a plurality of secondary windings having equal members of turns, wherein a first terminal of the primary winding is connected to the first intermediate junction of the full-bridge inverter, and a second terminal of the primary winding is connected through a DC blocking capacitor to the second intermediate junction of the full-bridge inverter;
(c) a plurality of output stage circuits, one output stage circuit connected to each secondary winding, wherein each output stage circuit comprises:
(i) a rectification circuit connected to the secondary winding;
(ii) an output inductor connected to the rectification circuit,
(iii) an output capacitor connected to the output inductor, the output capacitor connected between output terminals of the output stage circuit;
(d) a positive battery charger output terminal and a negative battery charger output terminal, wherein the output terminals of the output stages are connected across the positive and negative battery charger output terminals in a series or parallel arrangement;
(e) a controller connected to the controllable switching devices to switch them on and off periodically so as to transfer energy to the positive and negative output terminals, wherein the controller receives a feedback signal proportional to the average of the individual currents in each output inductor of each output stage, wherein the controller further receives a signal representative of the voltage across the output terminals of the battery charger and controls the switching of the switching devices based on the average current feedback signal and the voltage feedback signal;
and
(f) a DC source connected to the DC-to-AC converter.

7 more elements

Dependencies are inferred from the claim text.

High voltage battery charger

Life of this patent

High voltage battery charger

Life of this patent

Abstract

Claims57