Direct current (DC)-DC converter operational mode transition with limited voltage undershoot or overshoot
Embodiments of a circuit for a direct current (DC)-DC converter and DC-DC converters are disclosed. In an embodiment, a circuit for a DC-DC converter includes a resistive divider connected to an electrical terminal of the DC-DC converter, an amplifier connected to the resistive divider, a clock synchronization unit connected to a control circuit of the DC-DC converter and configured to generate control signals for the control circuit for switching the DC-DC converter between different operational modes, a first comparator connected to the amplifier and to the control circuit of the DC-DC converter, a second comparator connected to the resistive divider and to the control circuit of the DC-DC converter, and a voltage generator connected to the first comparator and configured to generate a comparator input voltage for the first comparator in response to an output voltage from the amplifier.
1 . A circuit for a direct current (DC)-DC converter, the circuit comprising:
a resistive divider coupled to an electrical terminal of the DC-DC converter;
an amplifier coupled to the resistive divider;
a clock synchronization unit coupled to a control circuit of the DC-DC converter and configured to generate a plurality of control signals for the control circuit for switching the DC-DC converter between different operational modes;
a first comparator having a first input coupled to the amplifier and an output coupled to the control circuit of the DC-DC converter;
a second comparator coupled to the resistive divider and to the control circuit of the DC-DC converter; and
a voltage generator coupled to a second input of the first comparator;
wherein the voltage generator is configured to generate a comparator input voltage for the first comparator in response to an output voltage from the amplifier.
2 . The circuit of claim 1 , wherein the different operational modes comprise a pulse frequency modulation (PFM) operational mode and a pulse width modulation (PWM) operational mode.
3 . The circuit of claim 1 , further comprising a resistor-capacitor (RC) circuit coupled to the amplifier.
4 . The circuit of claim 3 , wherein the RC circuit comprises a resistor and a capacitor.
5 . The circuit of claim 3 , wherein the voltage generator comprises a switch coupled to the RC circuit, a second amplifier coupled to the switch, and a switchable capacitor circuit coupled to the second amplifier.
6 . The circuit of claim 5 , wherein a control signal from the control circuit is applied to the amplifier and to the second amplifier.
7 . The circuit of claim 1 , wherein the amplifier comprises a first input terminal coupled to a first reference voltage and a second input terminal configured to receive an output voltage of the resistive divider.
8 . The circuit of claim 7 , wherein the second comparator is coupled to a second reference voltage.
9 . The circuit of claim 8 , wherein the amplifier comprises an output terminal coupled to an input terminal of the first comparator.
10 . The circuit of claim 9 , wherein the first and second comparators are configured to cause the control circuit of the DC-DC converter to control a high-side (HS) switch and a low-side (LS) switch of the DC-DC converter for switching the DC-DC converter between the different operational modes.
11 . The circuit of claim 10 , wherein at least one of the HS switch and the LS switch comprises a bipolar junction transistor (BJT) or a metal-oxide-semiconductor field-effect transistor (MOSFET).
12 . The circuit of claim 1 , wherein an output inductor and an output capacitor are coupled between two electrical terminals of the DC-DC converter.
13 . The circuit of claim 1 , further comprising the control circuit.
14 . A direct current (DC)-DC converter comprising:
an operational mode transition circuit comprising:
a resistive divider coupled to an electrical terminal of the DC-DC converter;
an amplifier coupled to the resistive divider;
a clock synchronization unit coupled to a control circuit of the DC-DC converter and configured to generate a plurality of control signals for the control circuit for switching the DC-DC converter between different operational modes;
a first comparator coupled to the amplifier and to the control circuit of the DC-DC converter;
a second comparator coupled to the resistive divider and to the control circuit of the DC-DC converter; and
a voltage generator coupled to the first comparator and configured to generate a comparator input voltage for the first comparator in response to an output voltage from the amplifier;
a high-side (HS) driver;
an HS switch coupled to the HS driver;
a low-side (LS) driver;
an LS switch coupled to the LS driver; and
the control circuit coupled to the operational mode transition circuit and configured to control the HS driver, the HS switch, the LS driver, and the LS switch for switching the DC-DC converter between the different operational modes;
wherein the operational mode transition circuit further comprises a resistor-capacitor (RC) circuit;
wherein the RC circuit includes a resistor, a capacitor, and a center-node;
wherein a first end of the resistor is coupled to the amplifier;
wherein a second end of the resistor is coupled to both the capacitor and the center-node; and
wherein the voltage generator is coupled to the center-node.
15 . The DC-DC converter of claim 14 , wherein the different operational modes comprise a low-power operational mode and a high-power operational mode.
16 . The DC-DC converter of claim 15 , wherein the low-power operational mode comprises a pulse frequency modulation (PFM) operational mode, and wherein the high-power operational mode comprises a pulse width modulation (PWM) operational mode.
17 . The DC-DC converter of claim 14 , wherein the voltage generator includes:
a switch coupled to the center-node of the RC circuit,
a second amplifier coupled to the switch, and
a switchable capacitor circuit coupled to the second amplifier.
18 . The DC-DC converter of claim 17 , wherein the control circuit is configured to generate a bias signal for the amplifier and the second amplifier.
19 . An operational mode transition circuit for a direct current (DC)-DC converter, the operational mode transition circuit comprising:
a resistive divider coupled to an electrical terminal of the DC-DC converter;
an amplifier coupled to the resistive divider;
a clock synchronization unit coupled to a control circuit of the DC-DC converter and configured to generate a plurality of control signals for the control circuit for switching the DC-DC converter between a pulse frequency modulation (PFM) operational mode and a pulse width modulation (PWM) operational mode;
a first comparator coupled to the amplifier and to the control circuit of the DC-DC converter;
a second comparator coupled to the resistive divider and to the control circuit of the DC-DC converter;
a resistor-capacitor (RC) circuit coupled to the amplifier, wherein the RC circuit comprises a resistor and a capacitor; and
a voltage generator coupled to the first comparator and the RC circuit and configured to generate a comparator input voltage for the first comparator in response to an output voltage from the amplifier, wherein the voltage generator comprises a switch coupled to the RC circuit, a second amplifier coupled to the switch, and a switchable capacitor circuit coupled to the second amplifier, and wherein a control signal from the control circuit is applied to the amplifier and to the second amplifier.