A step-down DC converter

Abstract

The present invention relates to the field of integrated circuit technology, and in particular to a step-down DC converter, comprising: an output module; a current sensing module, generating a current control signal according to a peak current and a first feedback voltage; a delay unit, generating a delay control signal according to the peak current; a voltage sensing module, obtaining a second feedback voltage, and generating a voltage control signal according to the second feedback voltage; the output module takes power from a power supply circuit according to the control of the current control signal, the delay control signal and the voltage control signal, and outputs an output current to a load circuit. The beneficial effect of the present invention is that by setting a delay unit in the current sensing module to replace the zero-crossing comparator in the prior art, the discharge of the output module can be achieved by controlling the generation of the delay control signal under relatively stable output conditions, thereby avoiding the problem of false triggering due to grounding jitter in the prior art by grounding and sensing the peak current of the inductor, and achieving a relatively stable output effect.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a step-down direct current converter. Background Art

[0002] A step-down DC converter is a DC-DC converter. The characteristic of this circuit is that a DC voltage is converted into a high-frequency power supply through an oscillation circuit, and then the required DC voltage is output through a pulse transformer, a rectifier filter circuit, etc., so that the output voltage is lower in amplitude than the input voltage, and the ripple is reduced, thereby outputting a relatively stable DC voltage. It is widely used in a variety of electronic circuits.

[0003] In the prior art, there are many technical solutions for step-down DC converters. For example, Chinese patent 201210027568.3 discloses a step-down converter. The solution provides a step-down conversion circuit based on PFM control, including a zero-crossing comparator for detecting the zero-crossing point of the inductor current, a current comparator for detecting the peak value of the inductor current, and a voltage comparator for detecting the output voltage. The PFM control module controls the on and off of the switch tube according to the detection result, thereby realizing the step-down DC output.

[0004] However, during the implementation process, the inventors found that in the implementation process of the above technical solution, since the zero-crossing comparator is connected to the inductor front stage through the positive input terminal and the reverse input terminal is grounded to realize the zero-crossing time judgment of the inductor current. However, due to the grounding design of the integrated circuit and other reasons, the grounding terminal sometimes jitters, which in turn causes the comparator to be falsely triggered, thereby affecting the conversion efficiency of the overall conversion circuit. Summary of the invention

[0005] In view of the above problems existing in the prior art, a step-down DC converter is now provided.

[0006] The specific technical solutions are as follows:

[0007] A step-down DC converter, comprising:

[0008] An output module, wherein an input end of the output module is connected to a power supply circuit, and an output end of the output module is connected to a load circuit;

[0009] a current sensing module, wherein an input end of the current sensing module is connected to a current feedback end and a first voltage feedback end of the output module, an output end of the current sensing module is connected to a control end of the output module, the current sensing module obtains a peak current and a first feedback voltage from the output module, and generates a current control signal according to the peak current and the first feedback voltage;

[0010] The current sensing module is further provided with a delay unit, and the delay unit generates a delay control signal according to the peak current;

[0011] a voltage sensing module, wherein an input end of the voltage sensing module is connected to a second voltage feedback end of the output module, an output end of the voltage sensing module is connected to a control end of the output module, the voltage sensing module obtains a second feedback voltage from the output module, and generates a voltage control signal according to the second feedback voltage;

[0012] The output module obtains power from the power supply circuit according to the control of the current control signal, the delay control signal and the voltage control signal, and outputs an output current to the load circuit.

[0013] Preferably, the output module comprises:

[0014] A control unit, wherein a power input terminal of the control unit is an input terminal of the output module, a signal input terminal of the control unit is a control terminal of the output module, and the control unit receives the current control signal, the voltage control signal and the delay control signal respectively;

[0015] an inductor, wherein a first end of the inductor is connected to an output end of the control unit, and a second end of the inductor is an output end of the output module;

[0016] an output capacitor, wherein a first end of the output capacitor is connected to the second end of the inductor, and a second end of the output capacitor is grounded;

[0017] The first end of the inductor is a first voltage feedback end of the output module, and the second end of the inductor is a second voltage feedback end of the output module.

[0018] Preferably, the control unit comprises:

[0019] A logic controller, wherein the logic controller receives the current control signal, the voltage control signal and the delay control signal respectively;

[0020] A first switch tube, wherein an input end of the first switch tube is connected to the power supply circuit, and an output end of the first switch tube is an output end of the output module;

[0021] A second switch tube, wherein an input end of the second switch tube is connected to an output end of the first switch tube, and an output end of the second switch tube is grounded;

[0022] The first control terminal of the logic controller is connected to the gate of the first switch tube, and the second control terminal of the control unit is connected to the gate of the second switch tube;

[0023] The logic controller controls the first switch tube and the second switch tube respectively according to the current control signal, the voltage control signal and the delay control signal.

[0024] Preferably, the current sensing module comprises:

[0025] a current sensor, the current sensor acquiring a peak current on the inductor and generating a peak voltage output according to the peak current;

[0026] A first comparator, wherein a non-inverting input terminal of the first comparator is connected to an input terminal of the current sensing module, a reverse input terminal of the first comparator is connected to a first output terminal of the current sensor, and an output terminal of the first comparator is connected to the output module to send the current control signal;

[0027] The first input end of the delay unit is connected to the output end of the first comparator, the second input end of the delay unit is connected to the second output end of the current sensor, and the output end of the delay unit is connected to the output module to send the delay control signal.

[0028] Preferably, the delay unit comprises:

[0029] A constant current source, wherein an output end of the constant current source is connected to a first end of a delay capacitor, and a second end of the delay capacitor is grounded;

[0030] A second comparator, wherein a non-inverting input terminal of the second comparator is connected to the first terminal of the delay capacitor, and a reverse input terminal of the second comparator is connected to the output terminal of the current sensor;

[0031] A D-type flip-flop, wherein the clock input end of the D-type flip-flop is connected to the output end of the first comparator, the data input end of the D-type flip-flop is at a high level, and the output end of the D-type flip-flop is connected to the output module to send the delay control signal;

[0032] A feedback switch tube, wherein the input end of the feedback switch tube is connected to the non-inverting input end of the second comparator, the output end of the feedback switch tube is grounded, and the gate of the feedback switch tube is connected to the output end of the D-type trigger.

[0033] Preferably, the second output terminal of the current sensor is grounded via a pull-down resistor.

[0034] Preferably, the voltage sensing module comprises:

[0035] Reference voltage source;

[0036] A third comparator, wherein the non-inverting input terminal of the third comparator is connected to the output terminal of the reference voltage source, and the inverting input terminal of the third comparator is connected to the input terminal of the voltage sensing module.

[0037] Preferably, the logic controller operates in PFM mode.

[0038] The above technical solution has the following advantages or beneficial effects: by setting a delay unit in the current sensing module to replace the zero-crossing comparator in the prior art, the discharge of the output module can be achieved by controlling the generation of the delay control signal under relatively stable output conditions, thereby avoiding the problem of false triggering due to grounding jitter in the prior art by grounding and sensing the peak current of the inductor, thereby achieving a relatively stable output effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The embodiments of the present invention will be described more fully with reference to the attached drawings, which are provided for illustration and description only and are not intended to limit the scope of the present invention.

[0040] Figure 1 is a schematic diagram of an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of a delay unit in an embodiment of the present invention;

[0042] Figure 3 FIG. 4 is a working timing diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0045] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0046] The present invention comprises:

[0047] A step-down DC converter, such as Figure 1 As shown, including:

[0048] Output module 1, the input end of the output module 1 is connected to the power supply circuit VIN, and the output end of the output module 1 is connected to the load circuit OUT;

[0049] A current sensing module 2, wherein the input end of the current sensing module 2 is connected to the current feedback end and the first voltage feedback end of the output module, the output end of the current sensing module 2 is connected to the control end of the output module 1, the current sensing module 2 obtains the peak current and the first feedback voltage from the output module 1, and generates a current control signal according to the peak current and the first feedback voltage;

[0050] The current sensing module 2 is also provided with a delay unit 21, and the delay unit 21 generates a delay control signal according to the peak current;

[0051] A voltage sensing module 3, wherein the input end of the voltage sensing module 3 is connected to the second voltage feedback end of the output module 1, the output end of the voltage sensing module 3 is connected to the control end of the output module 1, the voltage sensing module 3 obtains the second feedback voltage from the output module 1, and generates a voltage control signal according to the second feedback voltage;

[0052] The output module 1 obtains power from the power supply circuit according to the control of the current control signal, the delay control signal and the voltage control signal, and outputs the output current to the load circuit OUT.

[0053] Specifically, for the DC converter in the prior art, it is necessary to detect the zero-crossing time of the inductor L1 based on the ground terminal, which may cause the comparator to be falsely triggered due to the jitter of the ground terminal. In this embodiment, the output module 1 is adjusted so that the output module 1 can output according to the current control signal, the delay control signal and the voltage control signal, and a delay control signal with a relatively stable period is used to replace the zero-crossing signal of the inductor L1 in the prior art, thereby improving the stability of the circuit control and avoiding the problem of false triggering due to the jitter of the ground terminal.

[0054] In a preferred embodiment, the output module 1 includes:

[0055] A control unit 11, wherein the power input terminal of the control unit 11 is the input terminal of the output module 1, the signal input terminal of the control unit 11 is the control terminal of the output module 1, and the control unit 11 receives a current control signal, a voltage control signal and a delay control signal respectively;

[0056] An inductor L1, wherein a first end of the inductor L1 is connected to an output end of the control unit 11, and a second end of the inductor L1 is an output end of the output module 1;

[0057] An output capacitor C1, wherein a first end of the output capacitor C1 is connected to a second end of the inductor L1, and a second end of the output capacitor C1 is grounded;

[0058] The first end of the inductor L1 is a current feedback end of the output module 1 , and the second end of the inductor L1 is a voltage feedback end of the output module 1 .

[0059] Specifically, in order to achieve a better control effect, in this embodiment, a control unit 11 is set so that the control unit 11 can control the current output according to the received current control signal, voltage control signal and delay control signal, so that the resonant circuit composed of the inductor L1 and the output capacitor C1 oscillates periodically and outputs a specific DC signal to the load circuit OUT.

[0060] In a preferred embodiment, the control unit 11 includes:

[0061] The logic controller U1 receives a current control signal, a voltage control signal and a delay control signal respectively;

[0062] A first switch tube Q1, where the input end of the first switch tube Q1 is connected to the power supply circuit Vin, and the output end of the first switch tube Q1 is the output end of the output module 1;

[0063] A second switch tube Q2, where the input end of the second switch tube Q2 is connected to the output end of the first switch tube Q1, and the output end of the second switch tube Q2 is grounded;

[0064] The first control terminal of the logic controller U1 is connected to the gate of the first switch tube Q1, and the second control terminal of the control unit 11 is connected to the gate of the second switch tube Q2;

[0065] The logic controller U1 controls the first switch tube Q1 and the second switch tube Q2 respectively according to the current control signal, the voltage control signal and the delay control signal.

[0066] Specifically, in order to achieve a better control effect, in this embodiment, a logic controller U1 is set to drive the half-bridge output circuit composed of the first switch tube Q1 and the second switch tube Q2 based on the PFM mode according to the current control signal, the voltage control signal and the delay control signal to output a voltage to the rear inductor L1, thereby achieving a better step-down output effect by controlling the charging and discharging of the resonant circuit.

[0067] During implementation, the first switch tube Q1 and the second switch tube Q2 can be implemented by MOS tubes or other forms of power devices, such as IGBT devices. In this embodiment, the first switch tube Q1 is set to a PMOS tube, whose source is connected to the power supply circuit Vin as the output end, and the drain is the output end; the second switch tube Q2 is an NMOS tube, whose drain is the input end, and the source is the output end. However, in other embodiments, the first switch tube Q1 can be set to an NMOS tube or other devices according to actual needs, and the second switch tube Q2 can be set to a PMOS tube or other devices, and the input and output ends thereof can be adaptively adjusted, which is not limited here.

[0068] In a preferred embodiment, the current sensing module 2 includes:

[0069] A current sensor Isense, wherein the current sensor Isense obtains a peak current on the inductor L1 and generates a peak voltage output according to the peak current;

[0070] A first comparator CMP1, wherein a non-inverting input terminal of the first comparator CMP1 is connected to an input terminal of the current sensing module 2, a reverse input terminal of the first comparator CMP1 is connected to a first output terminal of the current sensor Isense, and an output terminal of the first comparator CMP1 is connected to the output module 1 to send a current control signal;

[0071] The delay unit 21 has a first input connected to the output of the first comparator CMP1, a second input connected to the second output of the current sensor Isense, and an output connected to the output module 1 to send a delay control signal.

[0072] Specifically, for the step-down DC converter in the prior art, which relies on the zero-crossing signal of the inductor L1 for control, the comparator may be falsely triggered due to the jitter of the ground terminal, thereby affecting the output efficiency of the converter. In this embodiment, a delay unit 21 is set to generate a delay control signal according to the peak voltage output by the current sensor Isense. The delay control signal is only related to the peak current of the inductor L1, thereby avoiding the problem of false triggering of the comparator caused by the jitter of the ground terminal, thereby achieving a more stable control effect of the output module 1.

[0073] During the implementation process, the non-inverting input terminal of the first comparator CMP1 is connected to the first end of the inductor L1 to receive the current output by the control unit 11 through the half-bridge, that is, the charging current of the inductor L1; the reverse input terminal of the first comparator CMP1 is connected to the output current of the current sensor Isense, and the current sensor Isense detects the peak current on the inductor L1 through the sensing coil, and converts it into a peak voltage through a resistor and inputs it into the reverse input terminal of the first comparator CMP1.

[0074] In a preferred embodiment, Figure 2 As shown, the delay unit 21 includes:

[0075] A constant current source I0, wherein an output end of the constant current source I0 is connected to a first end of a delay capacitor C1, and a second end of the delay capacitor C1 is grounded;

[0076] A second comparator CMP2, wherein a non-inverting input terminal of the second comparator CMP2 is connected to a first terminal of the delay capacitor C1, and a reverse input terminal of the second comparator CMP2 is connected to an output terminal of the current sensor 2;

[0077] A D-type flip-flop DFF, a clock input terminal of the D-type flip-flop DFF is connected to the output terminal of the first comparator CMP1, a data input terminal of the D-type flip-flop DFF is at a high level, and an output terminal of the D-type flip-flop DFF is connected to the output module 1 to send a delay control signal;

[0078] Feedback switch tube Q3, the input end of the feedback switch tube Q3 is connected to the non-inverting input end of the second comparator CMP2, the output end of the feedback switch tube Q3 is grounded, and the gate of the feedback switch tube Q3 is connected to the output end of the D-type trigger DFF.

[0079] Specifically, in order to generate a relatively stable delay control signal, in this embodiment, the delay capacitor C1 is charged by setting a constant current source I0. After the delay capacitor C1 is charged, the non-inverting input terminal of the second comparator CMP2 turns to a high level, and the level is higher than the inductor peak current input by the current sensor Isense. At this time, the second comparator CMP2 outputs a high level to cause the D-type trigger DFF to flip, and causes the feedback switch tube Q3 to turn on and discharge, completing a delay signal generation process.

[0080] In a preferred embodiment, the second output terminal of the current sensor Isense is grounded via a pull-down resistor R1 .

[0081] Based on the above process, a delay control signal is generated to control the converter circuit. The time for the inductor L1 to discharge to zero is only related to the peak current:

[0082] Wherein, U is the voltage at the end of charging of the delay capacitor C1, L is the inductance value of the inductor L1, t is the time for the inductor L1 to discharge to zero, which is equivalent to the zero-crossing time of the inductor current collected in the prior art, I max is the peak current of inductor L1.

[0083] At the same time, in the above process, the discharge time of the feedback switch tube depends on the charging time of the delay capacitor C1, so:

[0084] Among them, t dly is the discharge time of the feedback switch tube Q3, C is the capacitance value of the delay capacitor C1, R is the resistance value of the pull-down resistor R1, I0 is the output current of the constant current source I0, I max is the peak current of inductor L1.

[0085] In order to make the above discharge process consistent with the time for the inductor L1 to discharge to zero, the capacitance of the delay capacitor C2 can be adjusted, including:

[0086]

[0087] Where C is the capacitance of the delay capacitor C2, R is the resistance of the pull-down resistor R1, I0 is the output current of the constant current source, I max is the peak current of inductor L1.

[0088] In a preferred embodiment, the voltage sensing module 3 includes:

[0089] Reference voltage source Vref;

[0090] The third comparator CMP3 has a non-inverting input terminal connected to the output terminal of the reference voltage source Vref, and a reverse input terminal connected to the input terminal of the voltage sensing module 3 .

[0091] In a preferred embodiment, the logic controller operates in PFM mode.

[0092] Figure 3 This is a voltage timing diagram of the present invention. It can be seen from the diagram that a better output effect can be achieved by sending a current control signal, a delay control signal and a voltage control signal in sequence.

[0093] The beneficial effect of the present invention is that by setting a delay unit in the current sensing module to replace the zero-crossing comparator in the prior art, the discharge of the output module can be achieved under relatively stable output conditions by controlling the generation of a delay control signal, thereby avoiding the problem of false triggering due to grounding jitter in the prior art by grounding and sensing the peak current of the inductor, thereby achieving a relatively stable output effect.

[0094] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A step-down DC converter, characterized in that: include: An output module, wherein an input end of the output module is connected to a power supply circuit, and an output end of the output module is connected to a load circuit; a current sensing module, wherein an input end of the current sensing module is connected to a current feedback end and a first voltage feedback end of the output module, an output end of the current sensing module is connected to a control end of the output module, the current sensing module obtains a peak current and a first feedback voltage from the output module, and generates a current control signal according to the peak current and the first feedback voltage; The current sensing module is further provided with a delay unit, and the delay unit generates a delay control signal according to the peak current; a voltage sensing module, wherein an input end of the voltage sensing module is connected to a second voltage feedback end of the output module, an output end of the voltage sensing module is connected to a control end of the output module, the voltage sensing module obtains a second feedback voltage from the output module, and generates a voltage control signal according to the second feedback voltage; The output module takes power from the power supply circuit according to the control of the current control signal, the delay control signal and the voltage control signal, and outputs an output current to the load circuit; The output module comprises: A control unit, wherein a power input terminal of the control unit is an input terminal of the output module, a signal input terminal of the control unit is a control terminal of the output module, and the control unit receives the current control signal, the voltage control signal and the delay control signal respectively; an inductor, wherein a first end of the inductor is connected to an output end of the control unit, and a second end of the inductor is an output end of the output module; an output capacitor, wherein a first end of the output capacitor is connected to the second end of the inductor, and a second end of the output capacitor is grounded; The first end of the inductor is the first voltage feedback end of the output module, and the second end of the inductor is the second voltage feedback end of the output module; The control unit comprises: A logic controller, wherein the logic controller receives the current control signal, the voltage control signal and the delay control signal respectively; A first switch tube, wherein an input end of the first switch tube is connected to the power supply circuit, and an output end of the first switch tube is an output end of the output module; A second switch tube, wherein an input end of the second switch tube is connected to an output end of the first switch tube, and an output end of the second switch tube is grounded; The first control terminal of the logic controller is connected to the gate of the first switch tube, and the second control terminal of the control unit is connected to the gate of the second switch tube; The logic controller controls the first switch tube and the second switch tube respectively according to the current control signal, the voltage control signal and the delay control signal.

2. The step-down DC converter according to claim 1, characterized in that: The current sensing module comprises: a current sensor, the current sensor acquiring a peak current on the inductor and generating a peak voltage output according to the peak current; A first comparator, wherein a non-inverting input terminal of the first comparator is connected to an input terminal of the current sensing module, a reverse input terminal of the first comparator is connected to a first output terminal of the current sensor, and an output terminal of the first comparator is connected to the output module to send the current control signal; The first input end of the delay unit is connected to the output end of the first comparator, the second input end of the delay unit is connected to the second output end of the current sensor, and the output end of the delay unit is connected to the output module to send the delay control signal.

3. The step-down DC converter according to claim 2, characterized in that: The delay unit comprises: A constant current source, wherein an output end of the constant current source is connected to a first end of a delay capacitor, and a second end of the delay capacitor is grounded; A second comparator, wherein a non-inverting input terminal of the second comparator is connected to the first terminal of the delay capacitor, and a reverse input terminal of the second comparator is connected to the output terminal of the current sensor; A D-type flip-flop, wherein the clock input end of the D-type flip-flop is connected to the output end of the first comparator, the data input end of the D-type flip-flop is at a high level, and the output end of the D-type flip-flop is connected to the output module to send the delay control signal; A feedback switch tube, wherein the input end of the feedback switch tube is connected to the non-inverting input end of the second comparator, the output end of the feedback switch tube is grounded, and the gate of the feedback switch tube is connected to the output end of the D-type trigger.

4. The step-down DC converter according to claim 2, characterized in that: The second output terminal of the current sensor is grounded through a pull-down resistor.

5. The step-down DC converter according to claim 1, characterized in that: The voltage sensing module comprises: Reference voltage source; A third comparator, wherein the non-inverting input terminal of the third comparator is connected to the output terminal of the reference voltage source, and the inverting input terminal of the third comparator is connected to the input terminal of the voltage sensing module.

6. The step-down DC converter according to claim 1, characterized in that: The logic controller operates in PFM mode.

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