Parallel high side switches for a buck converter

A DC-to-DC voltage converter comprising:

• a supply voltage input;
• a high-side n-channel transistor including a source terminal, a drain terminal and a gate terminal, the drain terminal being coupled to the voltage input and the source terminal being coupled to a first node;
• a high-side p-channel transistor including a source terminal, a drain terminal and a gate terminal, the source terminal being coupled to the voltage input and the drain terminal being coupled to the first node;
• a low-side n-channel transistor including a source terminal, a drain terminal and a gate terminal, the drain terminal being coupled to the first node and the source terminal being coupled to ground;
• an inductor coupled between the first node and a converter output;
• a capacitor coupled between the converter output and ground;
• and
• control circuitry operable to receive information regarding a supply voltage coupled to the voltage input:
• if the supply voltage is below a predetermined threshold value, the control circuitry is operable to cause the high-side n-channel transistor to serve as the active high-side transistor of the DC-to-DC converter, while deactivating the high-side p-channel transistor by providing a constant voltage that is substantially equal to the supply voltage to the gate of the high-side p-channel transistor, and
• if the supply voltage is above the predetermined threshold value, the control circuitry is operable to cause the high-side p-channel transistor to serve as the active high-side transistor of the DC-to-DC converter by regulating the duty cycle of a gate driver signal provided to the gate of the high-side p-channel transistor in order to regulate an output voltage of the DC-to-DC converter, while deactivating the high-side n-channel transistor.

A method of operating a power stage of a DC-to-DC converter, comprising:

• providing a high-side n-channel transistor including a source terminal, a drain terminal and a gate terminal, the drain terminal being coupled to a power supply voltage input, and the source terminal being coupled to a first node that is coupled to an output of the DC-to-DC converter;
• providing a high-side p-channel transistor including a source terminal, a drain terminal and a gate terminal, the source terminal being coupled to the voltage input and the drain terminal being coupled to the first node;
• comparing the power supply voltage to a threshold voltage level;
• if the power supply voltage is less than the threshold voltage level, causing the high-side n-channel transistor to serve as the active high-side transistor of the DC-to-DC converter, and deactivating the high-side p-channel transistor by providing a constant voltage that is substantially equal to the supply voltage to the gate of the high-side p-channel transistor;
• and
• if the power supply voltage is greater than the threshold voltage level, causing the high-side p-channel transistor to serve as the active high-side transistor of the DC-to-DC converter by regulating the duty cycle of a gate driver signal provided to the gate of the high-side p-channel transistor in order to regulate an output voltage of the DC-to-DC converter, and deactivating the high-side n-channel transistor.