Conduction mode control

Abstract

The invention relates to conduction mode control. A circuit includes an input terminal (VFB), a reference voltage circuit (202), a comparator (204), a delay circuit (206), a conduction mode control circuit (208), and a switching converter controller. The input terminal (VFB) is configured to receive a converter output voltage. The reference voltage circuit (202) has an output. The comparator (204) has a first input coupled to the input terminal (VFB), a second input coupled to the output of the reference voltage circuit (202), and an overvoltage output. The delay circuit (206) has an input coupled to the overvoltage output, and a delayed overvoltage output. The conductive mode control circuit (208) has a first input coupled to the overvoltage output, a second input coupled to the delayed overvoltage output, and a mode output. The switching converter controller has a continuous conduction mode input coupled to the mode output.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 559,496, filed on February 29, 2024, entitled “Method for Reducing Nuisance Tripping of Voltage Monitors for DC / DC Converters in Discontinuous Conduction Mode (DCM)” which is hereby incorporated by reference. Technical Field

[0003] This application relates generally to semiconductors, and in particular, to conduction mode control. Background Art

[0004] A switching-mode converter is an electronic circuit that converts an input direct current (DC) voltage into one or more DC output voltages that are higher or lower in magnitude than the input DC voltage. A switching-mode converter that produces an output voltage lower than the input voltage is called a buck or step-down converter. A switching-mode converter that produces an output voltage higher than the input voltage is called a boost or step-up converter.

[0005] Some switched-mode converter topologies include a drive / power switch coupled to an energy storage inductor / transformer at the switch terminals. By alternately opening and closing the switch in response to a switching signal, electrical energy is transferred to a load through the energy storage inductor / transformer. The amount of electrical energy transferred to the load depends on the on / off duty cycle of the switch and the frequency of the switching signal. Switched-mode converters are widely used in electronic devices, particularly battery-powered devices such as portable cellular phones, laptop computers, and other electronic systems where efficient use of power is required. Summary of the Invention

[0006] In one example, a circuit includes an input terminal, a reference voltage circuit, a comparator, a delay circuit, a conduction mode control circuit, and a switching converter controller. The input terminal is configured to receive a converter output voltage. The reference voltage circuit has an output. The comparator has a first input coupled to the input terminal, a second input coupled to the output of the reference voltage circuit, and an overvoltage output. The delay circuit has an input coupled to the overvoltage output and a delayed overvoltage output. The conduction mode control circuit has a first input coupled to the overvoltage output, a second input coupled to the delayed overvoltage output, and a mode output. The switching converter controller has a continuous conduction mode (CCM) input coupled to the mode output.

[0007] In another example, a circuit includes a switching converter controller, a comparator, a delay circuit, and a conduction mode control circuit. The switching converter controller is configured to control switching of the switching mode converter circuit. The comparator is configured to compare the switching mode converter output voltage with an overvoltage threshold voltage and provide an overvoltage signal indicating that the switching mode converter output voltage is greater than the overvoltage threshold voltage. The delay circuit is coupled to the comparator. The delay circuit is configured to delay the overvoltage signal and provide a delayed overvoltage signal. The conduction mode control circuit has inputs coupled to the comparator and the delay circuit, and a mode output coupled to an input of the switching converter controller. The conduction mode control circuit is configured to provide a CCM control signal based on the overvoltage signal and the delayed overvoltage signal. The switching converter controller is configured to transition from operating in discontinuous conduction mode to operating in continuous conduction mode in response to the CCM control signal.

[0008] In another example, a system includes a power supply, a switching-mode converter circuit, and an advanced driver assistance system. The power supply has an output. The switching-mode converter circuit has an input coupled to the output of the power supply. The advanced driver assistance system has an input coupled to the output of the switching-mode converter circuit. The switching-mode converter circuit includes a reference voltage circuit, a comparator, a delay circuit, a conduction mode control circuit, and a switching converter controller. The reference voltage circuit has an output. The comparator has a first input coupled to the output of the switching-mode converter circuit, a second input coupled to the output of the reference voltage circuit, and an overvoltage output. The delay circuit has an input coupled to the overvoltage output and a delayed overvoltage output. The conduction mode control circuit has a first input coupled to the overvoltage output, a second input coupled to the delayed overvoltage output, and a mode output. The switching converter controller has a continuous conduction mode (CCM) input coupled to the mode output. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a block diagram of an example switching-mode converter including conduction-mode control based on the converter output voltage.

[0010] Figure 2 Suitable for Figure 1 Block diagram of an example conduction-mode control circuit in a switching-mode converter.

[0011] Figure 3 and 4 for Figure 2 Figure 2 is a graph of example signals in a conduction mode control circuit.

[0012] Figure 5 To include Figure 1 A block diagram of an example system of a switching-mode converter. DETAILED DESCRIPTION

[0013] Figure 1 FIG. 1 is a block diagram of an example switching mode converter 100 including conduction mode control based on the converter output voltage. Figure 1 1 is a buck converter and includes a high-side switching transistor 102, a low-side switching transistor 104, an inductor 106, a voltage divider 108, an output capacitor 110, a switching converter controller 112, and a mode control circuit 114. The high-side switching transistor 102 is coupled between a voltage input terminal and a switching terminal, and the low-side switching transistor 104 is coupled between the switching terminal and a reference terminal (e.g., ground). The switching mode converter 100 supplies power to a load 111.

[0014] Switching converter controller 112 controls high-side switching transistor 102 and low-side switching transistor 104 to charge and discharge inductor 106. When high-side switching transistor 102 is on and low-side switching transistor 104 is off, current flows through high-side switching transistor 102 to charge inductor 106. When low-side switching transistor 104 is on and high-side switching transistor 102 is off, current flows through low-side switching transistor 104 as inductor 106 discharges. The current flowing from inductor 106 charges output capacitor 110 and powers load 111.

[0015] A voltage divider 108 is coupled to an output terminal 100A of the switching-mode converter 100. The voltage divider 108 divides the output voltage (Vout) of the switching-mode converter 100 to generate a feedback voltage (VFB) that is proportional to Vout. A switching converter controller 112 compares VFB with a reference voltage to generate an error signal for controlling switching of the high-side switching transistor 102 and the low-side switching transistor 104, thereby generating a desired value for the output voltage Vout.

[0016] The high-side switching transistor 102 and the low-side switching transistor 104 form the power stage of the switching mode converter 100. The switching of the switching converter controller 112 can control the high-side switching transistor 102 and the low-side switching transistor 104 to provide an operation in a continuous conduction mode (CCM) or a discontinuous conduction mode (DCM). In CCM, the current flowing through the inductor 106 is continuous, wherein the current increases or decreases in the switching cycle. In DCM, the power stage can be in a high impedance state, wherein the high-side switching transistor 102 and the low-side switching transistor 104 both do not conduct current. If the current drawn by the load 111 is very low, the switching converter controller 112 can provide DCM operation. The reduced switching of the DCM operation can improve the efficiency of the switching mode converter 100 under small load currents. However, when operating in DCM, the switching mode converter 100 can supply current to the inductor 106, but may not absorb current from the inductor 106. Without the ability to sink current, Vout may increase if the current drawn by load 111 suddenly drops while operating in DCM. For example, Vout may increase to a voltage greater than the safe operating voltage of load 111. Some systems may include circuitry that monitors Vout and, if Vout exceeds the safe operating voltage of load 111, disconnects switching-mode converter 100 or disconnects switching-mode converter 100 from load 111, which may cause load 111 to disconnect or malfunction.

[0017] Mode control circuit 114 is coupled between output terminal 100A and switching converter controller 112 to detect an increase in Vout that may be caused by a decrease in load current when operating in DCM. If such an increase in Vout is detected, mode control circuit 114 may cause switching converter controller 112 to revert to operating in CCM. When operating in CCM, switching mode converter 100 may supply current to inductor 106 and may sink current from inductor 106. Therefore, if Vout increases due to a decrease in load current when switching mode converter 100 is operating in DCM, mode control circuit 114 may cause switching mode converter 100 to reduce Vout by reverting to CCM operation in a short period of time. After Vout has decreased to less than a threshold voltage (e.g., less than a selected overvoltage threshold), mode control circuit 114 may allow switching mode converter 100 to return to DCM operation.

[0018] Mode control circuit 114 has an input coupled to output terminal 100A (via voltage divider 108) for receiving a representation of Vout. Mode control circuit 114 has an output coupled to a conduction mode input of switching converter controller 112. Mode control circuit 114 provides a CCM control signal (CCM CONTROL) at the output of mode control circuit 114 to cause switching converter controller 112 to switch from DCM to CCM operation if Vout exceeds an overvoltage threshold.

[0019] Although the switching-mode converter 100 is illustrated as a buck converter, embodiments of the mode control circuit 114 may be employed in a boost converter, a buck-boost converter, or other types of single-phase or multi-phase switching-mode converters. Embodiments of the switching-mode converter 100 may be employed in a wide variety of applications that benefit from accurate current sensing. For example, the switching-mode converter 100 may be employed in various applications that may benefit from or require compliance with functional safety standards.

[0020] Figure 2 FIG2 is a block diagram of an exemplary mode control circuit 114 suitable for use in the switching mode converter 100. The mode control circuit 114 includes a reference voltage circuit 202, a comparator 204, a delay circuit 206, and a conduction mode control circuit 208. The reference voltage circuit 202 generates a reference voltage VREF that defines an overvoltage threshold.

[0021] Comparator 204 has a first input coupled to the output of reference voltage circuit 202 for receiving an overvoltage threshold voltage, and a second input coupled to output terminal 100A via voltage divider 108 for receiving VFB. Comparator 204 compares VFB (which represents Vout) provided by voltage divider 108 with an overvoltage threshold provided by reference voltage circuit 202. An output signal OV provided at the output of comparator 204 indicates whether Vout is greater than the overvoltage threshold. Comparator 204 provides a first state (e.g., a logic high, or overvoltage state) of OV indicating that Vout is greater than the overvoltage threshold, and provides a second state (e.g., a logic low) of OV indicating that Vout is not greater than the overvoltage threshold.

[0022] The input of delay circuit 206 is coupled to the output of comparator 204. Delay circuit 206 has an output at which a delayed overvoltage signal (DOV) is provided. If OV has a first state within a selected delay time, delay circuit 206 can provide DOV in a first state (e.g., a logic high, or overvoltage state). For example, if OV maintains the first state for a selected delay time (e.g., a selected transient suppression time), delay circuit 206 can cause DOV to transition from a second state (e.g., a logic low) to a first state (e.g., a logic high). In one example, delay circuit 206 can be implemented as a timer that, in some examples, increments when OV has a first state and DOV has a second state and resets when OV is in the second state. In other examples, other implementations of delay circuit 206 can be implemented using different circuitry (e.g., charging a capacitor to a threshold). In some examples, the delay time provided by delay circuit 206 can be greater than 100 microseconds.

[0023] Conduction mode control circuit 208 has a first input coupled to the output of comparator 204 for receiving OV, and a second input coupled to the output of delay circuit 206 for receiving DOV. Conduction mode control circuit 208 generates a CCM CONTROL signal based on OV and DOV. The output of conduction mode control circuit 208 is coupled to an input of switching converter controller 112. Conduction mode control circuit 208 may generate CCM CONTROL as shown in Table 1.

[0024] Table 1

[0025] OV DOV CCM CONTROL 0 0 0 0 1 0 1 0 1 1 1 0

[0026] Thus, if OV has a first state (indicating that Vout has exceeded the overvoltage threshold) and DOV has a second state (indicating that the delay time from asserting OV has not expired), conduction mode control circuit 208 sets CCM CONTROL to the first state (e.g., logic 1, or CCM state). Conduction mode control circuit 208 sets CCM CONTROL to the second state (e.g., logic 0, or DCM state) in all other state combinations of OV and DOV. Switching converter controller 112 operates in CCM in response to CCM CONTROL having the first state. For example, if switching converter controller 112 is operating in DCM and switching converter controller 112 provides CCM CONTROL in the first state, switching converter controller 112 may transition from operating in DCM to operating in CCM in an attempt to pull down (reduce) Vout. If conduction mode control circuit 208 provides CCM CONTROL in the second state, switching converter controller 112 may operate in DCM as appropriate based on the load current.

[0027] Figure 3 and 4 is a graph of example signals in switching converter controller 112 . Figure 3 and 4 The signals VREF, VFB, OV, DOV and CCM CONTROL are shown in Figure 3 , VFB is a scaled representation of Vout. Vout and VFB increase at time 302, and VFB exceeds VREF, indicating that Vout exceeds the overvoltage threshold. The switching mode converter 100 operates in DCM at time 302. At time 304, the comparator 204 sets OV to logic high. The timing of the transition of OV from logic low to logic high may be delayed due to the hysteresis applied in the comparator 204 (e.g., Figure 3 ). At time 304, conduction mode control circuit 208 sets CCM CONTROL to logic high (as shown in Table 1) based on the states of OV and DOV. In interval 306, between the transition of OV to logic high and the transition of DOV to logic high, switching converter controller 112 causes switching mode converter 100 to operate in CCM, which allows switching mode converter 100 to draw current from output terminal 100A. Figure 3 In CCM operation, Vout is not reduced, and VFB does not drop below VREF. For example, in Figure 3In this case, the reduction in current drawn by load 111 does not cause an increase in Vout. At time 308, delay circuit 206 sets DOV to logic high, and conduction mode control circuit 208, in response, sets CCM CONTROL to logic low. With CCM CONTROL set to logic low, switching converter controller 112 may revert to DCM.

[0028] exist Figure 4 , VFB is a scaled representation of Vout. Vout and VFB increase at time 402, and VFB exceeds VREF, indicating that Vout exceeds the overvoltage threshold. The switching mode converter 100 operates in DCM at time 402. At time 404, the comparator 204 sets OV to logic high. The timing of the transition of OV from logic low to logic high may be delayed due to the hysteresis applied in the comparator 204 (e.g., Figure 4 ). At time 404, conduction mode control circuit 208 sets CCM CONTROL to logic high based on the states of OV and DOV (as shown in Table 1). In interval 406, while CCM CONTROL has a logic high state, switching converter controller 112 causes switching mode converter 100 to operate in CCM, which allows switching mode converter 100 to draw current from output terminal 100A. Figure 4 In the CCM operation, Vout is reduced, and at time 408, VFB decreases below VREF. At time 410, the comparator 204 sets OV to a logic low state in response to the decrease in Vout and VFB. The timing of the transition of OV from logic high to logic low may be delayed due to the hysteresis applied in the comparator 204 (e.g., Figure 4 ). At time 410, conduction mode control circuit 208 restores CCM CONTROL to a logic low state, and in response, switching converter controller 112 may resume DCM operation. At time 412, the selected delay time expires (relative to time 404), and DOV remains in a logic low state.

[0029] Figure 5is a block diagram of an example system 500 including a switching-mode converter 100. System 500 also includes a power supply 502 and an advanced driver assistance system (ADAS) 504. Power supply 502 may be a battery pack, such as a battery pack that powers a vehicle's electrical / electronic systems. Power supply 502 provides a voltage Vin at an output of power supply 502. The output of power supply 502 is coupled to an input of switching-mode converter 100. Switching-mode converter 100 generates Vout from Vin. The output of switching-mode converter 100 (e.g., output terminal 100A) is coupled to an input of ADAS 504. ADAS 504 may apply Vout to power electronic circuits of ADAS 504 (e.g., a processor, memory, sensor, display, etc.). Other embodiments of system 500 may include different circuit systems in place of ADAS 504 (e.g., an infotainment system, an instrument cluster system, an industrial control system, etc.).

[0030] Because the switching-mode converter 100 includes the mode control circuit 114, the switching-mode converter 100 can reduce the occurrence of interruptions in Vout provided to the ADAS 504, which results in a reduction in the current drawn by the ADAS 504 when the switching-mode converter 100 operates in DCM. Therefore, the operation of the system 500 can be more reliable than the operation of a similar system lacking the switching-mode converter 100.

[0031] In this description, the term "coupled" may encompass any connection, communication, or signal path that enables a functional relationship consistent with this description. For example, if device A generates a signal to control device B to perform an action, then: (a) in a first example, device A is coupled to device B via a direct connection; or (b) in a second example, device A is coupled to device B via an intermediate component C, provided that the intermediate component C does not alter the functional relationship between devices A and B such that device B is controlled by device A via the control signal generated by device A.

[0032] As used herein, the terms "terminal," "node," "interconnect," "pin," and "lead" are used interchangeably. Unless specifically stated to the contrary, these terms are generally used to refer to an interconnection between or terminations of a device element, circuit element, integrated circuit, device, or other electronic or semiconductor component.

[0033] A circuit or device described herein as including certain components may actually be adapted to be coupled to those components to form the described circuit system or device. For example, a structure described as including one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., resistors, capacitors, and / or inductors), and / or one or more sources (e.g., voltage and / or current sources) may actually include only semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package), and may be adapted to be coupled to at least some of the passive elements and / or sources during or after manufacture, for example, by an end user and / or a third party, to form the described structure.

[0034] Although the use of specific transistors is described herein, other transistors (or equivalent devices) may be used instead with little or no change to the remaining circuitry. For example, field effect transistors ("FETs") (e.g., n-channel FETs (NFETs) (n-type transistors) or p-channel FETs (PFETs) (p-type transistors)), bipolar junction transistors (BJTs, e.g., NPN transistors or PNP transistors), insulated gate bipolar transistors (IGBTs), and / or junction field effect transistors (JFETs) may be used in place of or in combination with the devices described herein. The transistors may be depletion mode devices, drain extended devices, enhancement mode devices, native transistors, or other types of device structure transistors. Furthermore, the devices may be implemented in / on silicon substrates (Si), silicon carbide substrates (SiC), gallium nitride substrates (GaN), or gallium arsenide substrates (GaAs).

[0035] In the claims, reference may be made to the control input of a transistor and its current terminals. In the case of a FET, the control input (or transistor control terminal) is the gate, and the current terminals are the drain and source. In the context of a BJT, the control input is the base, and the current terminals are the collector and emitter.

[0036] Reference herein to a FET being "on" means that a conduction channel exists for the FET and drain current can flow through the FET. Reference herein to a FET being "off" means that a conduction channel does not exist, and therefore drain current does not flow through the FET. However, an "off" FET can have current flowing through the body diode of the transistor.

[0037] The circuits described herein can be reconfigured to include additional or different components to provide functionality that is at least partially similar to the functionality available before the components were replaced. Unless otherwise specified, components shown as resistors generally represent any one or more elements coupled in series and / or in parallel to provide the amount of impedance represented by the resistor shown. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in parallel between the same terminals. For example, a resistor or capacitor shown and described herein as a single component may actually be multiple resistors or capacitors, respectively, coupled in series between the same two terminals as a single resistor or capacitor.

[0038] While some elements of the described examples are included in the integrated circuit and other elements are external to the integrated circuit, in other example embodiments, additional or fewer features may be incorporated into the integrated circuit. Furthermore, some or all of the features described as external to the integrated circuit may be included in the integrated circuit, and / or some features described as internal to the integrated circuit may be incorporated externally. As used herein, the term "integrated circuit" refers to one or more circuits that: (i) are incorporated in / on a semiconductor substrate; (ii) are incorporated in a single semiconductor package; (iii) are incorporated in the same module; and / or (iv) are incorporated in / on the same printed circuit board.

[0039] The use of the phrase "ground" in the foregoing description includes chassis ground, ground line ground, floating ground, virtual ground, digital ground, universal ground, and / or any other form of ground connection that is applicable or suitable for the teachings of this specification. In this specification, unless otherwise specified, the word "about," "substantially," or "substantially" preceding a parameter means within + / - 10% of the parameter, or if the parameter is zero, within a reasonable range of values ​​about zero.

[0040] Modifications are possible in the described embodiments, and other embodiments are possible within the scope of the claims.

Claims

1. A circuit comprising: an input terminal configured to receive a converter output voltage; a reference voltage circuit having an output; a comparator having a first input coupled to the input terminal, a second input coupled to the output of the reference voltage circuit, and an overvoltage output; a delay circuit having an input coupled to the overvoltage output and delaying the overvoltage output; a conduction mode control circuit having a first input coupled to the overvoltage output, a second input coupled to the delayed overvoltage output, and a mode output; and A switching converter controller has a conduction mode input coupled to the conduction mode output.

2. The circuit according to claim 1, wherein: The conduction mode control circuit is configured to provide a CCM control signal at the mode output; and the conduction mode control circuit is configured to set the CCM control signal to a first state in response to an overvoltage signal at the overvoltage output having the first state; and The switching converter controller is configured to operate in continuous conduction mode in response to the CCM control signal in the first state.

3. The circuit of claim 2, wherein: The conduction mode control circuit is configured to change the CCM control signal from the first state to the second state in response to the overvoltage signal changing from the first state to the second state; and The switching converter controller is configured to operate in discontinuous conduction mode in response to the CCM control signal in the second state.

4. The circuit of claim 2, wherein: the conduction mode control circuit being configured to change the CCM control signal from the first state to a second state in response to the overvoltage signal having the first state and the delayed overvoltage signal at the delayed overvoltage output having the first state; and The switching converter controller is configured to operate in discontinuous conduction mode in response to the CCM control signal in the second state.

5. The circuit of claim 4 , wherein: The comparator is configured to compare the converter output voltage with an overvoltage threshold voltage; and The overvoltage signal having the first state indicates that the converter output voltage is greater than the overvoltage threshold voltage. 6 . The circuit of claim 5 , wherein the delay circuit is configured to set the delayed overvoltage signal to an overvoltage state in response to the overvoltage signal indicating that the converter output voltage is greater than the overvoltage threshold voltage within a selected transient suppression time.

7. The circuit of claim 2 , further comprising a transistor having a first terminal coupled to a switch-mode converter output, a second terminal coupled to a reference terminal, and a control terminal coupled to an output of the switching converter controller; wherein the switching converter controller is configured to cause the transistor to conduct current from the switch-mode converter output in response to the CCM control signal having the first state.

8. A circuit comprising: a switching converter controller configured to control switching of the switch-mode converter circuit; a comparator configured to compare a switch-mode converter output voltage with an overvoltage threshold voltage and provide an overvoltage signal indicating that the switch-mode converter output voltage is greater than the overvoltage threshold voltage; a delay circuit coupled to the comparator, the delay circuit configured to delay the overvoltage signal and provide a delayed overvoltage signal; as well as a conduction mode control circuit having inputs coupled to the comparator and the delay circuit, and a mode output coupled to the switching converter controller, the conduction mode control circuit configured to cause the switching converter controller to transition from operating in a discontinuous conduction mode to a continuous conduction mode in response to the overvoltage signal and the delayed overvoltage signal.

9. The circuit of claim 8, wherein: The conduction mode control circuit is configured to provide a CCM control signal at the mode output; and the conduction mode control circuit is configured to set the CCM control signal to a CCM state in response to the overvoltage signal indicating that the switching mode converter output voltage is greater than the overvoltage threshold voltage; and The switching converter controller is configured to operate in a continuous conduction mode in response to the CCM control signal in the CCM state.

10. The circuit of claim 9, wherein: The conduction mode control circuit is configured to change the CCM control signal from the CCM state to the DCM state in response to the overvoltage signal indicating that the switching mode converter output voltage is not greater than the overvoltage threshold voltage; and The switching converter controller is configured to operate in a discontinuous conduction mode in response to the CCM control signal in the DCM state.

11. The circuit of claim 9, wherein the conduction mode control circuit being configured to change the CCM control signal from the CCM state to the DCM state in response to the overvoltage signal indicating that the switching-mode converter output voltage is greater than the overvoltage threshold voltage and the delayed overvoltage signal indicating that an overvoltage exists after a delay time; and The switching converter controller is configured to operate in a discontinuous conduction mode in response to the CCM control signal in the DCM state.

12. The circuit of claim 8, wherein the delay circuit is configured to set the delayed overvoltage signal to an overvoltage state in response to the overvoltage signal indicating that the switch-mode converter output voltage is greater than the overvoltage threshold voltage within a selected transient suppression time.

13. The circuit of claim 9 , further comprising a power stage having an output coupled to the input of the comparator and an input coupled to the output of the switching converter controller, the switching converter controller configured to cause the power stage to sink current through the output in response to the CCM control signal having the CCM state.

14. A system comprising: a power supply having an output; a switching mode converter circuit having an input coupled to the output of the power supply; and an advanced driver assistance system having an input coupled to the output of the switching-mode converter circuit, the switching-mode converter circuit comprising: a reference voltage circuit having an output; a comparator having a first input coupled to the output of the switch-mode converter circuit, a second input coupled to the output of the reference voltage circuit, and an overvoltage output; a delay circuit having an input coupled to the overvoltage output and delaying the overvoltage output; a conduction mode control circuit having a first input coupled to the overvoltage output, a second input coupled to the delayed overvoltage output, and a mode output; and A switching converter controller has a continuous conduction mode (CCM) input coupled to the mode output.

15. The system of claim 14, wherein the conduction mode control circuit is configured to cause the switching converter controller to operate in the CCM in response to an overvoltage signal provided at the overvoltage output and a delayed overvoltage signal provided at the delayed overvoltage output.

16. The system of claim 14, wherein: The conduction mode control circuit is configured to provide a CCM control signal at the mode output; and the conduction mode control circuit is configured to set the CCM control signal to the first state in response to the overvoltage signal at the overvoltage output having a first state and the delayed overvoltage signal at the delayed overvoltage output having a second state; and The switching converter controller is configured to operate in CCM in response to the CCM control signal in the first state.

17. The system of claim 16, wherein: The conduction mode control circuit is configured to change the CCM control signal from the first state to the second state in response to the overvoltage signal changing from the first state to the second state; and The switching converter controller is configured to operate in discontinuous conduction mode in response to the CCM control signal in the second state.

18. The system of claim 16, wherein: the conduction mode control circuit being configured to change the CCM control signal from the first state to a second state in response to the overvoltage signal having the first state and the delayed overvoltage signal having the first state; and The switching converter controller is configured to operate in discontinuous conduction mode in response to the CCM control signal in the second state.

19. The system of claim 16, wherein: the comparator being configured to compare a representation of a converter output voltage provided at the output of the switching-mode converter circuit with an overvoltage threshold voltage; and The overvoltage signal having the first state indicates that the representation of the converter output voltage is greater than the overvoltage threshold voltage.

20. The system of claim 16, wherein the delay circuit is configured to set the delayed overvoltage signal to indicate an overvoltage in response to the overvoltage signal having the first state within a selected transient suppression time.

Images