TWM454670U - DC-DC converter - Google Patents

Abstract

The invention discloses a DC-DC converter. The DC-DC converter includes an output stage, a current sensing unit, an error amplifier, a compensating signal processing unit, and a pulse width modulation controller. The output stage is used to provide an output current. The current sensing unit generates a compensating current signal varied with the output current according to the output current. The error amplifier receives a reference voltage and a feedback voltage and provides an error signal. The feedback voltage is related to an output voltage of the DC-DC converter. The compensating signal processing unit receives the error signal and the compensating current signal to provide a compensated comparison signal varied with the output current. The pulse width modulation controller receives the compensated comparison signal and a triangle wave signal to provide a pulse width modulation signal to the output stage.

Description

DC to DC converter

This creation is related to power converters, especially with regard to a DC to DC converter.

In recent years, various types of DC-DC converters have been widely used in different electronic devices. For example, a regulator with a constant on-time (COT) is a DC-to-DC converter. When the feedback voltage is less than the reference voltage, the constant on-time voltage regulator can turn on a main switch in a fixed period, and can adjust the off-time of the main switch to provide a relatively stable output voltage.

However, for a conventional step-down DC-to-DC converter, when the equivalent resistance above the load capacitor is too small, the output ripple is too small and the output chopping and the inductor current are not in phase, resulting in system output. When the voltage is oscillating, it seriously affects the stability of the system.

One of the scope of this creation is to propose a DC-to-DC converter. In one embodiment, the DC-to-DC converter includes an output stage, a current sensing unit, an error amplifier, a compensation signal processing unit, and a pulse width modulation controller. The compensation signal processing unit is coupled to the current sensing unit and the error amplifier. The pulse width modulation controller is coupled to the compensation signal processing unit. The output stage is used to provide an output current. Current The sensing unit generates a compensation current signal that varies with the output current according to the output current. The error amplifier receives the reference voltage and the feedback voltage and provides an error signal. The feedback voltage is related to the output voltage of the DC to DC converter. The compensation signal processing unit receives the error signal and the compensation current signal to provide a compensation control signal that varies with the output current. The pulse width modulation controller receives the compensation control signal and the triangular wave signal to provide a pulse width modulation signal to the output stage.

In one embodiment, the pulse width modulation signal has a fixed on time.

In an embodiment, the DC-DC converter further includes a compensation unit for compensating for the error signal output by the error amplifier. The compensation unit includes a compensation resistor and a compensation capacitor. The compensation resistor is coupled between the error amplifier and the compensation signal processing unit. The compensation capacitor is coupled between the compensation resistor and the ground.

In one embodiment, the pulse width modulation controller includes a triangular wave generator, a comparator, and a pulse width modulation generator. A triangular wave generator is used to generate a triangular wave signal. The comparator is coupled to the compensation signal processing unit and the triangular wave generator, and receives the compensation control signal and the triangular wave signal to provide the trigger signal. The pulse width modulation generator is coupled to the comparator and the output stage, and receives the trigger signal.

In an embodiment, the compensation signal processing unit includes a first current source, a second current source, and a resistor. The first current source is controlled by a current sensing unit. The second current source is coupled to the ground. The second current source is controlled by the current sensing unit. The resistor is coupled between the first current source and the second current source. The error amplifier is coupled between the first current source and the resistor. The comparator is coupled between the resistor and the second current source.

In one embodiment, the compensation signal processing unit includes a resistor, a switch, and a current source. The switches are respectively coupled to the error amplifier, the operating voltage, and the resistor. The current sources are respectively coupled to the resistor, the ground, and the current sensing unit. The current source is controlled by a current sensing unit. The comparator is coupled between the resistor and the current source.

Compared with the prior art, the DC-to-DC converter disclosed in the present invention generates a compensation current signal that varies with the output current according to the output current of the output stage to the inductor through its current sensing unit to the output of the error amplifier. Since the error signal is the reverse amplification signal of the feedback voltage, it is equivalent to amplifying the output voltage chopping on the system, thereby improving the output chopping too small and the output chopping and inductor current caused by the equivalent resistance above the load capacitance being too small. The phenomenon of different phases enables the system to stably output voltage without oscillating, so it can effectively improve the stability of the system.

The advantages and spirit of this creation can be further understood by the following detailed description of the creation and the drawings.

A preferred embodiment of the present invention is a DC to DC converter. Please refer to FIG. 1. FIG. 1 is a schematic circuit diagram of a DC-DC converter according to the embodiment.

As shown in FIG. 1, the DC-to-DC converter 1 is used to convert the input voltage V _IN into an output voltage V _OUT . The DC-to-DC converter 1 includes an output stage 10, a current sensing unit 11, an error amplifier 12, a compensation signal processing unit 13, a pulse width modulation controller 14, a compensation unit 15, an input node N0, an output node N1, and an output inductor L. . The input node N0 is for receiving the input voltage V _IN ; the output node N1 is for providing the output voltage V _OUT to the load LD.

The output stage 10 is coupled between the input node N0 and the ground, and the output stage 10 is coupled to the pulse width modulation controller 14, the current sensing unit 11 and the output inductor L respectively; one end of the current sensing unit 11 is coupled to The output stage 10 is coupled to the compensation signal processing unit 13; the error amplifier 12 is coupled to the compensation signal processing unit 13, the reference voltage V _REF , and the voltage division between the first voltage dividing resistor R1 and the second voltage dividing resistor R2. The node N2; the compensation signal processing unit 13 is coupled to the error amplifier 12, the current sensing unit 11, and the pulse width modulation controller 14, respectively; the pulse width modulation controller 14 is coupled to the compensation signal processing unit 13 and the output stage 10, respectively; One end of the unit 15 is coupled between the error amplifier 12 and the compensation signal processing unit 13 and the other end is coupled to the ground. The output inductor L is coupled between the output stage 10 and the output node N1.

In addition, the output resistor R0 and the output capacitor C0 connected in series are coupled between the output inductor L and the load LD and the ground end; the first voltage dividing resistor R1 and the second voltage dividing resistor R2 connected in series are coupled to the output inductor. L and load LD and ground. As shown in FIG. 1, the feedback voltage V _FB of the voltage dividing node N2 between the first voltage dividing resistor R1 and the second voltage dividing resistor R2 is the output voltage V _OUT through the first voltage dividing resistor R1 and the second voltage dividing resistor. The divided voltage is obtained by dividing R2, so the feedback voltage V _{FB is} related to the output voltage V _OUT .

The output stage 10 includes a first switch M1, a second switch M2, a driver DR, and a node N3. The first switch M1 is coupled to the input node N0; the second switch M2 is coupled between the first switch M1 and the ground; the driver DR is coupled to the pulse width modulation controller 14, the first switch M1, and the second switch M2, respectively. . The driver DR is configured to receive the pulse width modulation signal PWM having a fixed on-time, and accordingly control the opening or closing of the first switch M1 and the second switch M2. The node N3 is disposed between the first switch M1 and the second switch M2. The output inductor L is coupled to the node N3 and the output current I _OUT outputted by the node N3 of the output stage 10 flows through the output inductor L.

The output of current sensing means 11 sensing the output stage 10 of the node N3 sensing the output current I _OUT, and generates a compensation current signal with the change of the output current I I _{COMP OUT} compensation signal to the processing unit 13 according to the output current I _OUT.

The error amplifier 12 has a positive input terminal +, a negative input terminal - and an output terminal K. The error amplifier 12 receives the reference voltage V _REF through the positive input terminal +. The error amplifier 12 transmits a feedback voltage V _FB related to the output voltage V _{OUT from the} voltage dividing node N2 between the first voltage dividing resistor R1 and the second voltage dividing resistor R2 through the negative input terminal. The error amplifier 12 with a reference voltage V _REF to generate the feedback voltage V _FB error signal S _ERR after subtraction, and outputs an error signal S _ERR K through the output terminal.

It should be noted that since the feedback voltage V _{FB is} input to the negative input terminal of the error amplifier 12 instead of the positive input terminal +, the error signal S _ERR is the reverse amplification signal of the feedback voltage V _FB . That is to say, if the error signal S _ERR becomes smaller, it is equal to the increase of the feedback voltage V _FB .

In addition, the compensation unit 15 coupled to the output terminal K of the error amplifier 12 is used to compensate the error signal S _ERR outputted by the output terminal K of the error amplifier 12 . In this embodiment, the compensation unit 15 includes a compensation resistor R _COMP and a compensation capacitor C _COMP . The compensation resistor R _{COMP is} coupled between the error amplifier 12 and the compensation signal processing unit 13; the compensation capacitor C _{COMP is} coupled between the compensation resistor R _COMP and the ground.

The compensation signal processing unit 13 receives the error signal S _ERR from the error amplifier 12 and the compensation current signal I _COMP from the current sensing unit 11, and generates a compensation control signal S _NCOMP according to the error signal S _ERR and the compensation current signal I _COMP . Since the compensation current signal I _COMP varies with the output current I _OUT , the compensation control signal S _NCOMP generated according to the compensation current signal I _COMP also changes with the output current I _OUT . Next, the compensation signal processing unit 13 outputs the compensation control signal S _NCOMP that varies with the output current I _OUT to the pulse width modulation controller 14.

The pulse width modulation controller 14 includes a triangular wave generator 140, a comparator 142, and a pulse width modulation generator 144. The triangular wave generator 140 is used to generate a triangular wave signal S _RAMP . The positive input terminal of the comparator 142 is coupled to the compensation signal processing unit 13, the negative input terminal thereof is coupled to the triangular wave generator 140, and the output terminal J thereof is coupled to the pulse width modulation generator 144.

The comparator 142 receives the compensation control signal S _NCOMP as a function of the output current I _OUT and the triangular input signal S _RAMP from the triangular wave generator 140 through the positive input terminal + from the compensation signal processing unit 13 and receives the triangular wave signal S _RAMP from the triangular wave generator 140, and according to the compensation control signal S The comparison between the _NCOMP and the triangular wave signal S _RAMP produces a trigger signal S _TR . Next, the comparator 142 outputs the trigger signal S _TR to the pulse width modulation generator 144 through the output terminal J.

The pulse width modulation generator 144 is coupled to the comparator 142 and the driver DR of the output stage 10 for receiving the trigger signal S _TR from the comparator 142 and providing a pulse width modulation signal PWM with a fixed on time to the driver of the output stage 10. The DR causes the driver DR to control the opening or closing of the first switch M1 and the second switch M2 according to the pulse width modulation signal PWM having a fixed on-time.

In practical applications, the compensation signal processing unit 13 of the DC-to-DC converter 1 of the present invention can have different types of circuit architectures according to actual needs.

Referring to FIG. 2, FIG. 2 illustrates an embodiment of a circuit architecture of the compensation signal processing unit 13 in the DC-to-DC converter 1. As shown in FIG. 2, the compensation signal processing unit 13 includes a first current source 131, a second current source 132, and a resistor R3. The resistor R3 and the compensation resistor R _{COMP of the} compensation unit 15 are connected in parallel with each other. The second current source 132 is coupled to the ground. The resistor R3 is coupled between the first current source 131 and the second current source 132. The first current source 131 and the second current source 132 are respectively controlled by the compensation current signal I _COMP generated by the current sensing unit 11 as a function of the output current I _OUT .

The output terminal K of the error amplifier 12 is coupled between the first current source 131 and the resistor R3, and the output terminal K of the error amplifier 12 outputs the error signal S _ERR to between the first current source 131 and the resistor R3. The positive input terminal + of the comparator 142 is coupled between the resistor R3 and the second current source 132, and the positive input terminal of the comparator 142 receives the compensation control signal S _NCOMP from the resistor R3 and the second current source 132.

That is, in this embodiment, the resistor R3 that is connected in parallel with the compensation resistor R _{COMP of the} compensation unit 15 is connected, and the compensation current signal I _COMP generated by the current sensing unit 11 that varies with the output current I _OUT is The current sinking and current drawing operations are performed from the top to the bottom, so that the current signal passes through the resistor R3 to generate a compensation control signal S _NCOMP which varies with the output current I _OUT and is input to the comparator through the positive input terminal of the comparator 142. The 142 is compared with the triangular wave signal S _RAMP . This action will not affect the current output from the original error amplifier 12, so the original compensation characteristics can be preserved.

Referring to FIG. 3, FIG. 3 illustrates another embodiment of the circuit architecture of the compensation signal processing unit 13 in the DC-to-DC converter 1. As shown in FIG. 3, the compensation signal processing unit 13 includes a resistor R4, a switch M3, and a current source 133. The switch M3 is coupled to the error amplifier 12, the operating voltage V _dd and the resistor R4, respectively. The current source 133 is coupled to the resistor R4, the ground terminal, and the current sensing unit 11, respectively. The current source 133 is controlled by the compensation current signal I _COMP generated by the current sensing unit 11 as a function of the output current I _OUT . The output K of the error amplifier 12 is coupled to the gate of the switch M3. The positive input terminal + of the comparator 142 is coupled between the resistor R4 and the current source 133, and receives the compensation control signal S _NCOMP from the resistor R4 and the current source 133.

That is to say, in this embodiment, the compensation current signal I _COMP generated by the current sensing unit 11 as a function of the output current I _OUT passes through the source follower and the resistor R4, and can generate a change with the output current I _OUT . The compensation control signal S _NCOMP is input to the comparator 142 through the positive input terminal + of the comparator 142 for comparison with the triangular wave signal S _RAMP . Since the current signal is provided by the source follower, it is independent of the original compensation unit 15, so the current output from the original error amplifier 12 is not affected, and the original compensation characteristic can be retained.

It should be noted that FIG. 2 and FIG. 3 only show two possible embodiments of the circuit architecture of the compensation signal processing unit 13, respectively, in fact, as long as the output current I _OUT generated by the current sensing unit 11 can be changed. The compensation current signal I _COMP generates a compensation control signal S _{NCOMP which} changes with the output current I _OUT via the current as an input of the comparator 142, so as to meet the requirements of the compensation signal processing unit 13 in the DC-to-DC converter 1 of the present _invention . Therefore, it is not limited to the above embodiment.

Please refer to FIG. 4. FIG. 4 is a diagram showing a waveform of a signal in the DC-DC converter 1 of FIG. As shown in FIG. 4, the DC-DC converter 1 compares the compensation control signal S _NCOMP and the triangular wave signal S _RAMP which are varied with the output current I _OUT through the comparator 142, and adjusts the pulse width modulation generator 144 according to the comparison result. The duty cycle of the pulse width modulated signal PWM is generated. At time t1, the angle θ between the compensation control signal S _NCOMP and the triangular wave signal S _RAMP is large enough to avoid noise interference, so that the signal-to-noise ratio (SNR) can be effectively improved.

Please refer to FIG. 5. FIG. 5 is a diagram showing another signal waveform in the DC-DC converter 1 of FIG. As can be seen from FIG. 1 and FIG. 5, the period T _H in FIG. 5 represents that the load LD in FIG. 1 has a higher load amount, and the period T _L in FIG. 5 represents that the load LD in FIG. 1 has a lower load. the amount. At time t2, the load LD will change from a lower load to a higher load; at time t3, the load LD will change from a higher load to a lower load. When the load of the load LD changes, the comparator 142 compares the compensation control signal S _NCOMP and the triangular wave signal S _RAMP which vary with the output current I _OUT , and adjusts the output trigger signal S _TR to the pulse width adjustment according to the comparison result. The point in time at which the generator 144 is changed. Therefore, the DC-to-DC converter 1 of the present invention can immediately provide a suitable output voltage V _OUT according to the load amount of the load LD, thereby improving the stability of the system.

Compared with the prior art, the DC-to-DC converter disclosed in the present invention generates a compensation current signal that varies with the output current according to the output current of the output stage to the inductor through its current sensing unit to the output of the error amplifier. Since the error signal is the reverse amplification signal of the feedback voltage, it is equivalent to amplifying the output voltage chopping on the system, thereby improving the output chopping too small and the output chopping and inductor current caused by the equivalent resistance above the load capacitance being too small. The phenomenon of different phases enables the system to stably output voltage without oscillating, so it can effectively improve the stability of the system.

The features and spirit of the present invention are more clearly described in the above detailed description of the preferred embodiments, and are not intended to limit the scope of the present invention. On the contrary, it is intended to cover all kinds of changes and equivalences within the scope of the patent application to which the present invention is intended.

1‧‧‧DC to DC converter

10‧‧‧Output level

11‧‧‧ Current sensing unit

12‧‧‧Error amplifier

13‧‧‧Compensation signal processing unit

14‧‧‧ Pulse width modulation controller

15‧‧‧Compensation unit

N0‧‧‧ input node

N1‧‧‧ output node

L‧‧‧Output inductor

V _IN ‧‧‧ input voltage

V _OUT ‧‧‧ output voltage

LD‧‧‧ load

V _REF ‧‧‧reference voltage

R1‧‧‧ first voltage divider resistor

R2‧‧‧Second voltage divider resistor

N2‧‧‧ partial pressure node

R0‧‧‧ output resistance

C0‧‧‧ output capacitor

V _FB ‧‧‧ feedback voltage

M1‧‧‧ first switch

M2‧‧‧ second switch

DR‧‧‧ drive

N3‧‧‧ node

PWM‧‧‧ pulse width modulation signal

I _OUT ‧‧‧Output current

I _COMP ‧‧‧Compensated current signal

+‧‧‧正Input

-‧‧‧negative input

J, K‧‧‧ output

S _ERR ‧‧‧Error signal

R _COMP ‧‧‧compensation resistor

C _COMP ‧‧‧compensating capacitor

S _{NCOMP ‧‧‧Compensation} Control Signal

140‧‧‧ Triangle Wave Generator

142‧‧‧ Comparator

144‧‧‧ Pulse width modulation generator

S _RAMP ‧‧‧ triangle wave signal

S _TR ‧‧‧trigger signal

131‧‧‧First current source

132‧‧‧second current source

R3, R4‧‧‧ resistance

M3‧‧‧ switch

133‧‧‧current source

V _dd ‧‧‧ working voltage

T _H , T _L ‧‧ cycle

θ‧‧‧An angle between the compensation control signal and the triangular wave signal

1 is a circuit diagram of a DC-to-DC converter according to a preferred embodiment of the present invention.

2 illustrates an embodiment of a circuit architecture of a compensation signal processing unit in a DC to DC converter.

FIG. 3 illustrates another embodiment of a circuit architecture of a compensation signal processing unit in a DC to DC converter.

FIG. 4 is a diagram showing a waveform of a signal in the DC-to-DC converter of FIG. 1.

FIG. 5 is a diagram showing another signal waveform in the DC-to-DC converter of FIG. 1.

1‧‧‧DC to DC converter

10‧‧‧Output level

11‧‧‧ Current sensing unit

12‧‧‧Error amplifier

13‧‧‧Compensation signal processing unit

14‧‧‧ Pulse width modulation controller

15‧‧‧Compensation unit

N0‧‧‧ input node

N1‧‧‧ output node

L‧‧‧Output inductor

V _IN ‧‧‧ input voltage

V _OUT ‧‧‧ output voltage

LD‧‧‧ load

V _REF ‧‧‧reference voltage

R1‧‧‧ first voltage divider resistor

R2‧‧‧Second voltage divider resistor

N2‧‧‧ partial pressure node

R0‧‧‧ output resistance

C0‧‧‧ output capacitor

V _FB ‧‧‧ feedback voltage

M1‧‧‧ first switch

M2‧‧‧ second switch

DR‧‧‧ drive

N3‧‧‧ node

PWM‧‧‧ pulse width modulation signal

I _OUT ‧‧‧Output current

I _COMP ‧‧‧Compensated current signal

+‧‧‧正Input

-‧‧‧negative input

J, K‧‧‧ output

S _ERR ‧‧‧Error signal

R _COMP ‧‧‧compensation resistor

C _COMP ‧‧‧compensating capacitor

S _{NCOMP ‧‧‧Compensation} Control Signal

140‧‧‧ Triangle Wave Generator

142‧‧‧ Comparator

144‧‧‧ Pulse width modulation generator

S _RAMP ‧‧‧ triangle wave signal

S _TR ‧‧‧trigger signal

Claims (6)

A DC-to-DC converter includes: an output stage for providing an output current; a current sensing unit for generating a current signal according to the output current to compensate for a current signal; and an error amplifier for receiving a The reference voltage and a feedback voltage provide an error signal, wherein the feedback voltage is related to an output voltage of the DC-to-DC converter; a compensation signal processing unit coupled to the current sensing unit and the error amplifier, and receiving the An error signal and the compensation current signal for providing a compensation control signal with the output current change; and a pulse width modulation controller coupled to the compensation signal processing unit and receiving the compensation control signal and a triangular wave signal to A pulse width modulation signal is provided to the output stage. The DC-to-DC converter of claim 1, wherein the pulse width modulation signal has a fixed on-time. The DC-to-DC converter of claim 1, further comprising: a compensation unit for compensating the error signal output by the error amplifier, the compensation unit comprising: a compensation resistor coupled to Between the error amplifier and the compensation signal processing unit; and a compensation capacitor coupled between the compensation resistor and the ground. The DC-to-DC converter of claim 1, wherein the pulse width modulation controller comprises: a triangular wave generator for generating the triangular wave signal; a comparator coupled to the compensation signal processing unit and The triangular wave generator receives the compensation control signal and the triangular wave signal to provide a trigger signal; and a pulse width modulation generator coupled to the comparator and the output stage and receives the trigger signal. The DC-to-DC converter of claim 4, wherein the compensation signal processing unit comprises: a first current source controlled by the current sensing unit; and a second current source coupled to the ground. The second current source is controlled by the current sensing unit; and a resistor coupled between the first current source and the second current source; wherein the error amplifier is coupled to the first current source and the resistor The comparator is coupled between the resistor and the second current source. The DC-to-DC converter of claim 4, wherein the compensation signal processing unit comprises: a resistor; a switch coupled to the error amplifier, an operating voltage and the resistor; and a current source coupled The current source and the current sensing unit are controlled by the current sensing unit; wherein the comparator is coupled between the resistor and the current source.