A DCDC converter overshoot fast response circuit and method thereof

Abstract

The present invention discloses an overshoot fast response circuit of a DCDC converter and a method thereof, comprising a DCDC topology, an output voltage detection circuit, a zero current detection circuit, a control logic circuit, a load detection and mode switching circuit, wherein the control logic circuit generates a control signal to control the DCDC topology to generate a constant output voltage, the load detection machine mode switching circuit detects the load state and the control circuit performs mode switching, the output voltage detection circuit determines whether to turn off the zero current detection circuit and whether to enable the mode switching circuit to perform mode switching by detecting the output voltage, and the zero current detection circuit generates a ZCD signal after detecting the zero inductance current and sends it to the control logic circuit. The present invention adds an output voltage detection circuit to the traditional current mode controlled DCDC converter to determine whether an overshoot is generated and controls the zero current detection circuit and the load detection and mode switching circuit, thereby achieving rapid recovery of overshoot and improving the transient characteristics of the DCDC converter.

Description

Technical Field

[0001] The invention relates to the technical field of power management, and in particular to an overshoot fast response circuit of a DCDC converter. Background Art

[0002] DCDC converter chips have the advantages of high integration, high efficiency, and large drive current. DCDC converters are a very important module in power management chips. With the widespread application of portable electronic devices, new requirements have been put forward for the performance of DCDC converters, namely higher efficiency, better transient characteristics, and larger output current.

[0003] The traditional current-mode controlled dual-mode BUCK type DCDC converter will have extremely high overshoot when the load switches from heavy load to light load, and the process of the output voltage recovering to the normal set value is very slow. This is mainly because when the load switches from heavy load to light load, a large amount of charge flows into the capacitor CL, the output voltage rises and produces an overshoot voltage. At this time, the capacitor charge discharge path is only the load current ILOAD. When the load is light, ILOAD is small, resulting in slow output voltage recovery and poor transient characteristics of the DCDC converter.

[0004] The deterioration of transient characteristics is fatal to some application scenarios of DCDC converters. Therefore, it is urgent to propose a method to improve the transient characteristics of a current-mode controlled dual-mode BUCK DCDC converter. Summary of the invention

[0005] In view of this, an object of the present invention is to provide an overshoot fast response circuit of a DCDC converter and a method thereof.

[0006] In a first aspect, the present invention provides an overshoot fast response circuit of a DCDC converter, which adopts the following technical solution, including:

[0007] DCDC topology, output voltage detection circuit, zero current detection circuit, control logic circuit, load detection and mode switching circuit, the DCDC topology is connected with the output voltage detection circuit, the zero current detection circuit and the control logic circuit in sequence, the load detection and mode switching circuit is connected with the DCDC topology, the output voltage detection circuit and the control logic circuit, the load detection and mode switching circuit includes a load current sampling circuit, a comparator circuit and a mode switching circuit; wherein,

[0008] The control logic circuit generates a control signal to control the DCDC topology to generate a constant output voltage;

[0009] The output voltage detection circuit determines whether to turn off the zero current detection circuit and whether to enable the mode switching circuit to perform mode switching by detecting the output voltage;

[0010] After detecting the zero inductor current, the zero current detection circuit generates a ZCD signal and sends it to the control logic circuit to avoid reverse current.

[0011] The load detection and mode switching circuit detects the state of the load and controls the circuit to perform mode switching.

[0012] Preferably, the load current sampling circuit is connected to the DCDC topology and the in-phase input terminal of the comparator circuit to convert the load current signal into a voltage signal;

[0013] The comparator circuit compares the voltage signal with a reference voltage signal generated by a reference to determine whether the load condition of the DCDC topology is switched from heavy load to light load, and generates an enable signal to enable the output voltage detection circuit;

[0014] The mode switching circuit is controlled by the output voltage detection circuit, generates a mode switching signal and sends it to the control logic circuit for mode switching.

[0015] In a second aspect, the present invention provides a method for fast overshoot response of a DCDC converter, which adopts the following technical solution:

[0016] When the load detection and mode switching circuit detects that the load condition of the DCDC topology switches from heavy load to light load, the output voltage detection circuit starts to work;

[0017] (1) If the output voltage generated by the DCDC topology exceeds the upper threshold voltage of the output voltage detection circuit, the output voltage detection circuit will generate a shutdown signal to shut down the zero current detection circuit and allow the DCDC topology to quickly discharge the overshoot voltage through reverse current. At this time, the output voltage detection circuit will not enable the mode switching circuit, that is, the mode switching circuit is not allowed to switch modes;

[0018] When the output voltage generated by the DCDC topology drops to the lower threshold voltage of the output voltage detection circuit, the output voltage detection circuit will generate a start signal to turn on the zero current detection circuit and enable the mode switching circuit to switch the mode. At this time, the DCDC topology enters a normal working state under light load;

[0019] (2) If the output voltage generated by the DCDC topology does not exceed the upper threshold voltage of the output voltage detection circuit, the output voltage detection circuit will not control the zero current detection circuit, and will directly enable the mode switching circuit to switch the mode. At this time, the DCDC topology enters the normal working state under light load.

[0020] Aiming at the overshoot problem of a current-mode controlled dual-mode BUCK-type DCDC converter during load switching, the present application proposes an overshoot fast response circuit and method thereof, which achieves fast recovery of overshoot and improves the transient characteristics of the DCDC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0022] Figure 1 A fast overshoot response circuit of a DCDC converter according to an embodiment of the present invention is schematically shown;

[0023] Figure 2 The circuit block diagram of the conventional current mode controlled dual mode BUCK type DCDC converter is shown;

[0024] Figure 3 The working waveforms of the inductor current and output voltage of the conventional current mode controlled dual mode BUCK type DCDC converter during load switching are shown;

[0025] Figure 4 The figure shows the simulated waveforms of the inductor current and output voltage of the conventional current mode controlled dual mode BUCK type DCDC converter during load switching;

[0026] Figure 5 A circuit block diagram of a current-mode controlled dual-mode BUCK type DCDC converter using the DCDC overshoot fast response circuit and method of the present invention is shown;

[0027] Figure 6 The working waveform diagram of the inductor current and the output voltage of the current-mode controlled dual-mode BUCK type DCDC converter using the DCDC overshoot fast response circuit and method of the present invention during load switching is shown;

[0028] Figure 7 The diagram shows the simulated waveforms of the inductor current and the output voltage of the current-mode controlled dual-mode BUCK-type DCDC converter during load switching using the DCDC overshoot fast response circuit and method of the present invention. DETAILED DESCRIPTION

[0029] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0030] Specific details are set forth below, such as specific embodiments or examples for purposes of explanation and not limitation. Those skilled in the art will recognize that, in addition to these specific details, other examples may be used. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted to avoid obscuring the description with unnecessary details. It should be noted that "enable" appearing below may be understood to mean that the condition is established and executable.

[0031] Figure 1 A fast overshoot response circuit of a DCDC converter according to an embodiment of the present invention is schematically shown. The circuit includes a DCDC topology 1, an output voltage detection circuit 2, a zero current detection circuit 3, a control logic circuit 4, and a load detection and mode switching circuit 5. The DCDC topology 1 is connected to the output voltage detection circuit 2, the zero current detection circuit 3, and the control logic circuit 4 in sequence. The load detection and mode switching circuit 5 is connected to the DCDC topology 1, the output voltage detection circuit 2, and the control logic circuit 4. The load detection and mode switching circuit 5 includes a load current sampling circuit 501, a comparator circuit COMP502, and a mode switching circuit 503.

[0032] Among them, the control logic circuit 4 generates a control signal CTRL to control the DCDC topology 1 to generate a constant output voltage VOUT; the output voltage detection circuit 2 determines whether to turn off the zero current detection circuit 3 and whether to enable the mode switching circuit 503 to switch the mode by detecting the output voltage VOUT; the zero current detection circuit 3 will generate a ZCD signal (zero crossing detection signal) after detecting the zero inductor current and send it to the control logic circuit 4 to avoid reverse current.

[0033] In addition, the load detection and mode switching circuit 5 is mainly used to detect the load state of the DCDC topology 1 and enable the output voltage detection circuit when it is determined that the load is switched to a light load, and perform logic control of the mode switching.

[0034] Specifically, in the load detection and mode switching circuit 5: the load current sampling circuit 501 is connected to the DCDC topology 1 and the comparator circuit COMP502 in phase input terminal to convert the load current signal ILOAD into a voltage signal V SENCE The comparator circuit COMP502 converts this voltage signal V SENCE The reference voltage signal V REF The comparison is performed to determine whether the load condition of the DCDC topology 1 is switched from heavy load to light load, and an enable signal EN is generated to enable the output voltage detection circuit 2; the mode switching circuit 503 is controlled by the EN_V generated by the output voltage detection circuit 2. SWC Signal control, generating mode switching signal V SWC The control logic circuit 4 performs mode switching.

[0035] The specific working principle of the above overshoot fast response circuit is as follows:

[0036] First, the comparator circuit COMP502 in the load detection and mode switching circuit 5 detects the load condition of the DCDC topology 1. When it is determined that the load condition of the DCDC topology 1 is switched from heavy load to light load, the output voltage detection circuit 2 starts to work, and then there will be two working conditions.

[0037] Case 1: If the output voltage VOUT generated by DCDC topology 1 exceeds the upper threshold voltage VH of output voltage detection circuit 2, then output voltage detection circuit 2 will generate a shutdown signal OFF_ZCD to shut down zero current detection circuit 3 and allow DCDC topology 1 to quickly discharge the overshoot voltage through reverse current. It is worth noting that at this time, output voltage detection circuit 2 will not generate EN_V SWC The signal enables the mode switching circuit 503 to perform mode switching, that is, the mode switching circuit 503 is not allowed to perform mode switching.

[0038] When the output voltage VOUT generated by the DCDC topology 1 drops to the lower threshold voltage VL of the output voltage detection circuit 2, the output voltage detection circuit 2 will generate an enable signal to turn on the zero current detection circuit 3 and pass EN_V SWC The signal enables the mode switching circuit 503 in the load detection and mode switching circuit 5 to perform mode switching. At this time, the DCDC topology 1 enters a normal working state under light load.

[0039] Case 2: If the output voltage VOUT generated by the DCDC topology 1 does not exceed the upper threshold voltage VH of the output voltage detection circuit 2, the output voltage detection circuit 2 does not control the zero current detection circuit 3, that is, it directly generates EN_V SWC The signal enables the mode switching circuit 503 to switch modes, and the DCDC topology 1 enters a normal working state under light load.

[0040] The following examples will illustrate the effects of the present invention:

[0041] Figure 2 The circuit block diagram of the conventional current mode controlled dual-mode BUCK type DCDC converter is shown, and it can be seen that it is not optimized accordingly for the output overshoot problem.

[0042] Figure 3The working waveforms of the inductor current and output voltage of the dual-mode BUCK type DCDC converter with traditional current mode control during load switching are shown. It can be seen from the figure that when the load switches from heavy load to light load, the mode switching circuit has switched the DCDC converter to the normal working mode of PWM / Sleep mixed at light load. At this time, the output overshoot can only be discharged through the load current ILOAD, and the recovery is slow.

[0043] Figure 4 The figure shows the simulated waveforms of the inductor current and output voltage of the dual-mode BUCK DCDC converter with traditional current mode control during load switching. It can be seen from the simulation results that at 500μs, the load switches from heavy load to light load, and the DCDC converter working mode also switches from PWM mode to PWM / Sleep mixed mode. By observing the waveform of the output voltage VOUT, it can be seen that the output overshoot occurs at 502μs and does not return to the normal set value of 1.8V until 860μs. The recovery process is only discharged through load current, and the transient response is extremely poor.

[0044] Figure 5 The circuit block diagram of a current-mode controlled dual-mode BUCK-type DCDC converter using the DCDC overshoot fast response circuit and method of the present invention is shown, and an output voltage detection circuit is added to determine whether overshoot occurs and to control the zero current detection circuit (ZCD) and the load detection and mode switching circuit.

[0045] Figure 6 The working waveforms of the inductor current and the output voltage of the current-mode controlled dual-mode BUCK type DCDC converter applying the DCDC overshoot fast response circuit and method of the present invention during load switching are shown.

[0046] Figure 7 The present invention shows a simulation waveform diagram of the inductor current and output voltage of a dual-mode BUCK-type DCDC converter using the overshoot fast response circuit and method of DCDC of the present invention during load switching. It can be seen from the simulation results that at 500 μs, the load is switched from heavy load to light load. At this time, the output voltage detection circuit detects that the output voltage VOUT overshoots higher than its upper threshold voltage VH, and turns off the zero current detection circuit. The overshoot is quickly discharged through the reverse inductor current. At 509 μs, the output voltage drops to the lower threshold voltage VL of the output voltage detection circuit, the overshoot has recovered, the mode switching circuit is enabled, and the circuit enters the PWM / Sleep mixed mode under light load to work.

[0047] By comparison, it can be found that compared with the traditional DCDC converter that does not use the overshoot fast response circuit and method of the present invention, the overshoot recovery time of the present invention is shortened by 349μs. It can be seen that the fast overshoot response circuit and method proposed in the present invention can quickly reduce the overshoot voltage and greatly improve the transient characteristics of the DCDC converter.

[0048] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A DCDC converter overshoot fast response circuit, characterized in that: It includes a DCDC topology, an output voltage detection circuit, a zero current detection circuit, a control logic circuit, a load detection and mode switching circuit, wherein the DCDC topology is connected to the output voltage detection circuit, the zero current detection circuit, and the control logic circuit in sequence, and the load detection and mode switching circuit is connected to the DCDC topology, the output voltage detection circuit, and the control logic circuit, and the load detection and mode switching circuit includes a load current sampling circuit, a comparator circuit, and a mode switching circuit; wherein, The control logic circuit generates a control signal to control the DCDC topology to generate a constant output voltage; The output voltage detection circuit determines whether to turn off the zero current detection circuit and whether to enable the mode switching circuit to perform mode switching by detecting the output voltage; After detecting the zero inductor current, the zero current detection circuit generates a ZCD signal and sends it to the control logic circuit to avoid reverse current. The load detection and mode switching circuit detects the state of the load and controls the circuit to perform mode switching; The overshoot fast response method of the overshoot fast response circuit comprises the following steps: When the load detection and mode switching circuit detects that the load condition of the DCDC topology switches from heavy load to light load, the output voltage detection circuit starts to work; (1) If the output voltage generated by the DCDC topology exceeds the upper threshold voltage of the output voltage detection circuit, the output voltage detection circuit will generate a shutdown signal to shut down the zero current detection circuit and allow the DCDC topology to quickly discharge the overshoot voltage through reverse current. At this time, the output voltage detection circuit will not enable the mode switching circuit, that is, the mode switching circuit is not allowed to switch modes; When the output voltage generated by the DCDC topology drops to the lower threshold voltage of the output voltage detection circuit, the output voltage detection circuit will generate a start signal to turn on the zero current detection circuit and enable the mode switching circuit to switch the mode. At this time, the DCDC topology enters a normal working state under light load; (2) If the output voltage generated by the DCDC topology does not exceed the upper threshold voltage of the output voltage detection circuit, the output voltage detection circuit will not control the zero current detection circuit, and will directly enable the mode switching circuit to switch the mode. At this time, the DCDC topology enters the normal working state under light load.

2. The overshoot fast response circuit of a DCDC converter according to claim 1, characterized in that: The load current sampling circuit is connected to the DCDC topology and the in-phase input terminal of the comparator circuit to convert the load current signal into a voltage signal; The comparator circuit compares the voltage signal with a reference voltage signal generated by a reference to determine whether the load condition of the DCDC topology is switched from heavy load to light load, and generates an enable signal to enable the output voltage detection circuit; The mode switching circuit is controlled by the output voltage detection circuit, generates a mode switching signal and sends it to the control logic circuit for mode switching.

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