Hybrid battery charger and control circuit and method thereof
A hybrid battery charger includes a control circuit and a power stage. The control circuit includes an error amplifier to generate a first error signal and a second error signal according to an output voltage and an output current of the hybrid battery charger, a linear controller to generate a first control signal according to the first error signal, a PWM controller to generate a second control signal and a third control signal according to the second error signal, and according to a mode signal, a multiplexer to select the first control signal for the power stage to operate the hybrid battery charger in a linear mode, or the second and third control signals for the power stage to operate the hybrid battery charger in a switching mode.
1. A hybrid battery charger, comprising:
a power input terminal for receiving an input voltage;
a power output terminal for supplying an output voltage and an output current;
an output stage connected to the power input terminal and the power output terminal;
an error amplifier connected to the output stage, operative to generate a first error signal and a second error signal according to the output voltage and the output current;
a linear controller connected to the error amplifier, operative to generate a first control signal according to the first error signal;
a PWM controller connected to the error amplifier, operative to generate a second control signal and a third control signal according to the second error signal; and
a multiplexer connected to the linear controller, the PWM controller, and the output stage, and according to a mode signal, operative to select the first control signal for the output stage to operate the hybrid battery charger in a linear mode or select the second and third control signals for the output stage to operate the hybrid battery charger in a switching mode.
2. The hybrid battery charger of claim 1 , wherein the output stage comprises:
a first transistor connected between the power input terminal and a first node, for being controlled by the first control signal in the linear mode and controlled by the second control signal in the switching mode;
a second transistor connected between the first node and a ground terminal, for being controlled by the third control signal in the switching mode and kept off in the linear mode;
an inductor connected between the first node and a second node; and
a current sense resistor connected between the second node and the power output terminal.
3. The hybrid battery charger of claim 1 , wherein the output stage comprises:
a first transistor connected between the power input terminal and a first node, for being controlled by the second control signal in the switching mode and kept off in the linear mode;
a second transistor connected between the first node and a ground terminal, for being controlled by the third control signal in the switching mode and kept off in the linear mode;
an inductor connected between the first node and a second node;
a third transistor connected between the power input terminal and the second node, for being controlled by the first control signal in the linear mode and kept off in the switching mode; and
a current sense resistor connected between the second node and the power output terminal.
4. The hybrid battery charger of claim 1 , wherein the output stage comprises:
a first transistor connected between the power input terminal and a first node, for being controlled by the second control signal in the switching mode and kept off in the linear mode;
a second transistor connected between the first node and a ground terminal, for being controlled by the third control signal in the switching mode and kept off in the linear mode;
an inductor connected between the first node and a second node;
a current sense resistor connected between the second node and the power output terminal; and
a third transistor connected between the power input terminal and the power output terminal, for being controlled by the first control signal in the linear mode and kept off in the switching mode.
5. A control circuit for a hybrid battery charger, comprising:
an error amplifier operative to generate a first error signal and a second error signal according to an output voltage and an output current of the hybrid battery charger;
a linear controller connected to the error amplifier, operative to generate a first control signal according to the first error signal;
a PWM controller connected to the error amplifier, operative to generate a second control signal and a third control signal according to the second error signal; and
a multiplexer connected to the linear controller and the PWM controller, operative to select the first control signal or the second and third control signals according to a mode signal for the hybrid battery charger.
6. A control method for a hybrid battery charger, comprising the steps of:
generating a first error signal and a second error signal according to an output voltage and an output current of the hybrid battery charger;
generating a first control signal according to the first error signal;
generating a second control signal and a third control signal according to the second error signal; and
according to a mode signal, selecting the first control signal to operate the hybrid battery charger in a linear mode or selecting the second and third control signals to operate the hybrid battery charger in a switching mode.