CN115085550A - A step-down DC converter - Google Patents

Abstract

The invention relates to the technical field of integrated circuits, in particular to a buck direct current converter, which comprises: an output module; the current sensing module generates a current control signal according to the peak current and the first feedback voltage; the delay unit generates a delay control signal according to the peak current; the voltage sensing module acquires a second feedback voltage and generates a voltage control signal according to the second feedback voltage; the output module controls the self-powered circuit to get electricity according to the current control signal, the delay control signal and the voltage control signal, and outputs output current to the load circuit. The invention has the beneficial effects that: the current sensing module is provided with the delay unit to replace a zero crossing point comparator in the prior art, and the output module can be discharged by controlling the generation of the delay control signal under the relatively stable output condition, so that the problem that the peak current of the inductor is mistakenly triggered due to the shaking of the grounding end by grounding and sensing in the prior art is solved, and the relatively stable output effect is realized.

Description

A step-down DC converter

technical field

The invention relates to the technical field of integrated circuits, in particular to a step-down DC converter.

Background technique

The step-down DC converter is a DC-DC converter. The characteristic of this circuit is to convert the DC voltage into a high-frequency power supply through an oscillating circuit, and then output the required DC voltage through a pulse transformer, a rectifier filter circuit, etc. As a result, the amplitude of the output voltage is reduced relative to the input voltage, and the ripple is reduced, thereby outputting a relatively stable DC voltage, which is widely used in various electronic circuits.

In the prior art, there are many technical solutions of step-down DC converters. For example, Chinese Patent 201210027568.3 discloses a buck converter. The scheme 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.

However, during the implementation process, the inventor found that, in the implementation process of the above technical solution, since the zero-crossing comparator is connected to the front stage of the inductor through the forward 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 may sometimes vibrate, thereby causing false triggering of the comparator, thereby affecting the conversion efficiency of the overall conversion circuit.

SUMMARY OF THE INVENTION

Aiming at the above problems existing in the prior art, a step-down DC converter is now provided.

The specific technical solutions are as follows:

A step-down DC converter, comprising:

an output module, the input end of the output module is connected to the power supply circuit, and the output end of the output module is connected to the load circuit;

a current sensing module, the input terminal of the current sensing module is connected to the current feedback terminal and the first voltage feedback terminal of the output module, the output terminal of the current sensing module is connected to the control terminal of the output module, the The current sensing module obtains the peak current and the 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, the input end of the voltage sensing module is connected to the second voltage feedback end of the output module, the output end of the voltage sensing module is connected to the control end of the output module, the voltage sensing module Obtain a second feedback voltage from the output module, and generate 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.

Preferably, the output module includes:

a control unit, the power input end of the control unit is the input end of the output module, the signal input end of the control unit is the control end of the output module, the control unit receives the current control signal, the the voltage control signal and the delay control signal;

an inductor, the first end of the inductor is connected to the output end of the control unit, and the second end of the inductor is the output end of the output module;

an output capacitor, the first end of the output capacitor is connected to the second end of the inductor, and the second end of the output capacitor is grounded;

The first end of the inductance is the first voltage feedback end of the output module, and the second end of the inductance is the second voltage feedback end of the output module.

Preferably, the control unit includes:

a logic controller, which respectively receives the current control signal, the voltage control signal and the delay control signal;

a first switch tube, the input end of the first switch tube is connected to the power supply circuit, and the output end of the first switch tube is the output end of the output module;

a second switch tube, the input end of the second switch tube is connected to the output end of the first switch tube, and the 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.

Preferably, the current sensing module includes:

a current sensor, the current sensor obtains a peak current on the inductor, and generates a peak voltage output according to the peak current;

a first comparator, the non-inverting input terminal of the first comparator is connected to the input terminal of the current sensing module, and the inverting input terminal of the first comparator is connected to the first output terminal of the current sensor , the output end 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 second input end of the delay unit is connected to the second output end of the current sensor. The output terminal is connected to the output module to send the delay control signal.

Preferably, the delay unit includes:

a constant current source, the output end of the constant current source is connected to the first end of the delay capacitor, and the second end of the delay capacitor is grounded;

a second comparator, the non-inverting input terminal of the second comparator is connected to the first terminal of the delay capacitor, and the inverting input terminal of the second comparator is connected to the output terminal of the current sensor;

D-type flip-flop, the clock input terminal of the D-type flip-flop is connected to the output terminal of the first comparator, the data input terminal of the D-type flip-flop is at a high level, and the output terminal of the D-type flip-flop is at a high level. connecting the output module to send the delay control signal;

a feedback switch tube, 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 D-type flip-flop 's output.

Preferably, the second output terminal of the current sensor is grounded through a pull-down resistor.

Preferably, the voltage sensing module includes:

reference voltage source;

The third comparator, 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.

Preferably, the logic controller operates in a PFM mode.

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 point comparator in the prior art, it can be realized by controlling the generation of a delay control signal under relatively stable output conditions The discharge of the output module avoids the problem of false triggering caused by the jittering of the ground terminal through grounding and sensing the peak current of the inductor in the prior art, and achieves a relatively stable output effect.

Description of drawings

Embodiments of the present invention are described more fully with reference to the accompanying drawings. However, the accompanying drawings are for illustration and illustration only, and are not intended to limit the scope of the present invention.

1 is a schematic diagram of an embodiment of the present invention;

2 is a schematic diagram of a delay unit in an embodiment of the present invention;

FIG. 3 is a working sequence diagram of an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but it is not intended to limit the present invention.

The present invention includes:

A step-down DC converter, as shown in Figure 1, includes:

The 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;

The current sensing module 2, the input terminal of the current sensing module 2 is connected to the current feedback terminal and the first voltage feedback terminal of the output module, the output terminal of the current sensing module 2 is connected to the control terminal of the output module 1, and the current sensing module 2 is automatically The output module 1 obtains the peak current and the first feedback voltage, and generates a current control signal according to the peak current and the first feedback voltage;

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

The voltage sensing module 3, the input terminal of the voltage sensing module 3 is connected to the second voltage feedback terminal of the output module 1, the output terminal of the voltage sensing module 3 is connected to the control terminal of the output module 1, and the voltage sensing module 3 is connected from the output module 1 acquiring a second feedback voltage, and generating a voltage control signal according to the second feedback voltage;

The output module 1 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 OUT.

Specifically, for the DC converter in the prior art, it is necessary to detect the zero-crossing time of the inductance L1 according to the ground terminal, which leads to the problem of false triggering of the comparator due to the jitter of the ground terminal. Adjustment, so that the output module 1 can output according to the current control signal, the delay control signal and the voltage control signal, and the delay control signal with a relatively stable period is used to replace the zero-crossing signal of the inductor L1 in the prior art, which improves the circuit control. The stability of the device avoids the problem of false triggering caused by the jitter of the ground terminal.

In a preferred embodiment, the output module 1 includes:

The control unit 11, the power input end of the control unit 11 is the input end of the output module 1, the signal input end of the control unit 11 is the control end of the output module 1, the control unit 11 respectively receives the current control signal, the voltage control signal and the delay control Signal;

Inductor L1, the first end of the inductance L1 is connected to the output end of the control unit 11, and the second end of the inductance L1 is the output end of the output module 1;

output capacitor C1, the first end of the output capacitor C1 is connected to the second end of the inductor L1, and the second end of the output capacitor C1 is grounded;

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

Specifically, in order to achieve a better control effect, in this embodiment, by setting the control unit 11, 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 inductance The resonant circuit composed of L1 and the output capacitor C1 oscillates periodically, and outputs a specific DC signal to the load circuit OUT.

In a preferred embodiment, the control unit 11 includes:

The logic controller U1, the logic controller U1 respectively receives the current control signal, the voltage control signal and the delay control signal;

The first switch tube Q1, 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;

The second switch tube Q2, 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;

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;

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

Specifically, in order to achieve a better control effect, in this embodiment, the logic controller U1 is set to drive the first switch transistor Q1 and the second switch transistor Q2 based on the PFM mode according to the current control signal, the voltage control signal and the delay control signal. The formed half-bridge output circuit outputs the voltage to the rear inductor L1, and then achieves a better step-down output effect by controlling the charge and discharge of the resonant circuit.

In the implementation process, the first switch transistor Q1 and the second switch transistor Q2 may be implemented by using MOS transistors or other forms of power devices, such as IGBT devices. In this embodiment, the first switch tube Q1 is set as a PMOS tube, its source is used as an output terminal to connect to the power supply circuit Vin, and its drain is used as an output terminal; the second switch tube Q2 is an NMOS tube, and its drain is used as an input terminal, source as the output. However, in other embodiments, the first switch transistor Q1 can be set as an NMOS transistor or other device according to actual needs, and the second switch transistor Q2 can be set as a PMOS transistor or other device, and the input end and output end of the switch tube Q2 can be set as a PMOS transistor or other device. Adaptive adjustment is not limited here.

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

a current sensor Isense, the current sensor Isense obtains the peak current on the inductor L1, and generates a peak voltage output according to the peak current;

The first comparator CMP1, the non-inverting input end of the first comparator CMP1 is connected to the input end of the current sensing module 2, the inverting input end of the first comparator CMP1 is connected to the first output end of the current sensor Isense, the first The output end of the comparator CMP1 is connected to the output module 1 to send the current control signal;

The delay unit 21, the first input end of the delay unit 21 is connected to the output end of the first comparator CMP1, the second input end of the delay unit 21 is connected to the second output end of the current sensor Isense, the delay unit 21 The output terminal is connected to the output module 1 to send the delay control signal.

Specifically, for the step-down DC converter in the prior art, which relies on the zero-crossing signal of the inductance L1 for control, the comparator may be mis-triggered due to the jitter of the ground terminal, thereby affecting the output efficiency of the converter. This embodiment , by setting the delay unit 21 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, thus avoiding the comparator error caused by the jitter of the ground terminal. Therefore, a relatively stable control effect of the output module 1 is realized.

In the implementation process, the non-inverting input terminal of the first comparator CMP1 is connected to the first terminal of the inductor L1, so as to receive the current output by the control unit 11 through the half-bridge, that is, the charging current of the inductor L1; the first comparator The reverse input terminal of CMP1 is connected to the output current of the current sensor Isense, the current sensor Isense realizes the detection of the peak current on the inductor L1 through the sensing coil, and converts it into a peak voltage through the resistance and inputs it to the first comparator CMP1 in the reverse input of .

In a preferred embodiment, as shown in FIG. 2 , the delay unit 21 includes:

The constant current source I0, the output end of the constant current source I0 is connected to the first end of the delay capacitor C1, and the second end of the delay capacitor C1 is grounded;

The second comparator CMP2, the non-inverting input end of the second comparator CMP2 is connected to the first end of the delay capacitor C1, and the inverting input end of the second comparator CMP2 is connected to the output end of the current sensor 2;

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

Feedback switch Q3, the input terminal of the feedback switch Q3 is connected to the non-inverting input terminal of the second comparator CMP2, the output terminal of the feedback switch Q3 is grounded, and the gate of the feedback switch Q3 is connected to the output terminal of the D-type flip-flop DFF.

Specifically, in order to generate a relatively stable delay control signal, in this embodiment, a constant current source I0 is set to charge the delay capacitor C1. After the delay capacitor C1 is charged, the same-direction input of the second comparator CMP2 The terminal turns to high level, and the level is higher than the peak current of the inductor input by the current sensor Isense. At this time, the second comparator CMP2 outputs a high level to make the D-type flip-flop DFF flip, and make the feedback switch Q3 Turn on and discharge to complete the generation process of a delay signal.

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

Based on the above process to generate a delay control signal to control the converter circuit, the time for the inductor L1 to discharge to zero is only related to its peak current:

Among them, U is the voltage at the end of the 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, and _Imax is Peak current of inductor L1.

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, as follows:

Among them, t _dly is the discharge time of the feedback switch Q3, C is the capacitance value of the delay capacitor C1, R is the resistance value of the pull-down resistor R1, I ₀ is the output current of the constant current source I0, and I _max is the peak value of the inductor L1 current.

In order to keep the above discharge process consistent with the time when the inductor L1 discharges to zero, it can be achieved by adjusting the capacitance of the delay capacitor C2, including:

Among them, C is the capacitance value of the delay capacitor C2, R is the resistance value of the pull-down resistor R1, I ₀ is the output current of the constant current source, and I _max is the peak current of the inductor L1.

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

reference voltage source Vref;

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

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

3 is a voltage timing diagram of the present invention, according to which it can be seen that a better output effect can be achieved by sequentially sending the current control signal, the delay control signal and the voltage control signal.

The beneficial effect of the present invention is that: by setting the delay unit in the current sensing module to replace the zero-crossing point comparator in the prior art, under relatively stable output conditions, the output module can be controlled by controlling the generation of the delay control signal. It avoids the problem of false triggering due to the jitter of the ground terminal caused by grounding and sensing the peak current of the inductor in the prior art, and achieves a relatively stable output effect.

The above are only preferred embodiments of the present invention, and are not intended to limit the embodiments and protection scope of the present invention. For those skilled in the art, they should be aware of the equivalent replacement and Solutions obtained by obvious changes shall all be included in the protection scope of the present invention.

Claims (8)

1. a step-down DC converter, is characterized in that, comprises: an output module, the input end of the output module is connected to the power supply circuit, and the output end of the output module is connected to the load circuit; a current sensing module, the input terminal of the current sensing module is connected to the current feedback terminal and the first voltage feedback terminal of the output module, the output terminal of the current sensing module is connected to the control terminal of the output module, the The current sensing module obtains the peak current and the 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, the input end of the voltage sensing module is connected to the second voltage feedback end of the output module, the output end of the voltage sensing module is connected to the control end of the output module, the voltage sensing module Obtain a second feedback voltage from the output module, and generate 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. 2. The step-down DC converter according to claim 1, wherein the output module comprises: a control unit, the power input end of the control unit is the input end of the output module, the signal input end of the control unit is the control end of the output module, the control unit receives the current control signal, the the voltage control signal and the delay control signal; an inductor, the first end of the inductor is connected to the output end of the control unit, and the second end of the inductor is the output end of the output module; an output capacitor, the first end of the output capacitor is connected to the second end of the inductor, and the second end of the output capacitor is grounded; The first end of the inductance is the first voltage feedback end of the output module, and the second end of the inductance is the second voltage feedback end of the output module. 3. The step-down DC converter according to claim 2, wherein the control unit comprises: a logic controller, which respectively receives the current control signal, the voltage control signal and the delay control signal; a first switch tube, the input end of the first switch tube is connected to the power supply circuit, and the output end of the first switch tube is the output end of the output module; a second switch tube, the input end of the second switch tube is connected to the output end of the first switch tube, and the 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. 4. The step-down DC converter according to claim 2, wherein the current sensing module comprises: a current sensor, the current sensor obtains a peak current on the inductor, and generates a peak voltage output according to the peak current; a first comparator, the non-inverting input terminal of the first comparator is connected to the input terminal of the current sensing module, and the inverting input terminal of the first comparator is connected to the first output terminal of the current sensor , the output end 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 second input end of the delay unit is connected to the second output end of the current sensor. The output terminal is connected to the output module to send the delay control signal. 5. The step-down DC converter according to claim 1, wherein the delay unit comprises: a constant current source, the output end of the constant current source is connected to the first end of the delay capacitor, and the second end of the delay capacitor is grounded; a second comparator, the non-inverting input terminal of the second comparator is connected to the first terminal of the delay capacitor, and the inverting input terminal of the second comparator is connected to the output terminal of the current sensor; D-type flip-flop, the clock input terminal of the D-type flip-flop is connected to the output terminal of the first comparator, the data input terminal of the D-type flip-flop is at a high level, and the output terminal of the D-type flip-flop is at a high level. connecting the output module to send the delay control signal; a feedback switch tube, 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 D-type flip-flop 's output. 6 . The step-down DC converter according to claim 4 , wherein the second output terminal of the current sensor is grounded through a pull-down resistor. 7 . 7. The step-down DC converter according to claim 1, wherein the voltage sensing module comprises: reference voltage source; The third comparator, 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. 8 . The step-down DC converter according to claim 3 , wherein the logic controller operates in a PFM mode. 9 .

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