JPH09275677A - Direct-current input and direct-current output converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve response speed and ripple removal rate, lengthen battery service life and reduce size and cost by varying the amplitude of sawtooth voltage according to fluctuation in input direct-current voltage. SOLUTION: An amplified differential voltage Vd between an output direct- current voltage Vout from a power converting section 1 and a reference voltage V0 from a reference voltage section 2, is input to a comparing section 5. Further, a sawtooth voltage S the amplitude of which corresponds to fluctuation in input direct-current voltage Vin, is input from an oscillating section 4 to the comparing section 5. Then the comparing section 5 compares the amplified differential voltage Vd with the sawtooth voltage S, and outputs a control signal C, generated by PWM modulation, to the power converting section 1, which then amplifies the output direct-current voltage Vout according to the control signal C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC input and DC output converter for generating an output DC voltage by removing a ripple of an input DC voltage.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a conventional DC input and DC output converter, and FIG. 8 is a waveform diagram of each signal during operation. This DC input and DC output converter,
As shown in FIG. 7, the power conversion unit 110 and the reference voltage unit 12
0, an error amplifier 130, an oscillator 140, a comparator 150, and a smoothing capacitor 160. This allows
The input DC voltage Vin input from the input terminal 100 is power-converted by the power converter 110, and the output DC voltage Vout is fed back to the error amplifier 130. Then, the error amplification unit 1
30, the output DC voltage Vout and the reference voltage unit 120
The difference from the constant reference voltage is amplified, and the amplified difference voltage Vd 1 as shown by the solid line in FIG. At the same time, a sawtooth wave voltage S1 having a constant amplitude as shown in the figure is output from the oscillating unit 140 to the comparing unit 150 and compared with the amplification difference voltage Vd1. Then, as shown in (b) of FIG. 8, the control signal C1 which becomes the H level and the L level depending on whether or not the sawtooth wave voltage S1 is larger than the amplification difference voltage Vd 1 is transmitted from the comparison unit 150 to the power conversion unit 11
Output to 0. When the input DC voltage Vin is higher than the desired value, the output DC voltage Vout corresponding to the input DC voltage Vin is output from the power conversion unit 110 to the output terminal 101 and fed back to the error amplification unit 130. ) The amplified differential voltage Vd 1 which is lowered as indicated by the two-dot chain line in FIG.
It is output from 30 to the comparison unit 150. As a result, FIG.
(C), the control signal C1 having a long H level and a short L level is transmitted from the comparison unit 150 to the power conversion unit 110.
And the level of the output DC voltage Vout is suppressed. Such an operation is repeated according to the fluctuation of the input DC voltage Vin so that the output DC voltage Vout is converged to a desired value.

[0003]

However, the conventional DC input and DC output converters described above have the following problems. First, the output DC voltage Vout is changed while changing the operating point of the error amplification unit 130 according to the variation of the input DC voltage Vin.
To the desired value, the desired output DC voltage Vout
It takes time to reach. In addition, input DC voltage Vin
If there is a large fluctuation or ripple in the power amplifier 110, it is necessary to set the amplification degree of the error amplification section 130 to be high correspondingly. However, if it is set too high, when the input DC voltage Vin becomes high, the power conversion section 110 As a result, the oscillation degree occurs in the feedback loop including the error amplification unit 130, the comparison unit 150, and the power conversion unit 110. For this reason, the amplification degree of the error amplification unit 130 must be set on the assumption that the input DC voltage Vin is high. Therefore, when the input DC voltage Vin is low, the loop gain is reduced, and the ripple removal rate cannot be sufficiently obtained. Therefore, since the minimum operating voltage must be set higher,
There was a problem that the battery usage time was shortened. In addition, in order to suppress the fluctuation of the input DC voltage Vin itself,
The large-capacity smoothing capacitor 160 is required, and as a result, the converter becomes large and the cost is increased.

The present invention has been made to solve the above-mentioned problems, and by changing the amplitude of the sawtooth wave voltage in response to the fluctuation of the input DC voltage, high-speed response, improvement of the ripple removal rate, and battery It is an object of the present invention to provide a DC input and DC output converter that can extend the usage time, reduce the size, and reduce the cost.

[0005]

In order to solve the above problems, the DC input and DC output converter according to the invention of claim 1 amplifies the input DC voltage by the amplification degree indicated by the control signal to generate the DC voltage. A power converter that outputs, a reference voltage unit that generates a constant reference voltage, an error amplifier that amplifies and outputs a difference voltage between the reference voltage of the reference voltage unit and the output DC voltage of the power converter, and An oscillator that oscillates a sawtooth wave voltage having an amplitude corresponding to the input DC voltage, compares the sawtooth wave voltage from the oscillator and the amplification difference voltage from the error amplifier, and depending on the comparison result, It is configured to include a comparator that generates the control signal for adjusting the amplification degree of the power converter.

According to a second aspect of the present invention, in the DC input and DC output converter according to the first aspect, the error amplification section is
The comparator includes an operational amplifier that amplifies and outputs a difference voltage between the reference voltage from the one input terminal and the output DC voltage from the other input terminal, and the comparison unit includes a sawtooth wave voltage from the oscillator and the operational amplifier. Input the amplification difference voltage of
The power conversion unit includes a comparator that generates the control signal by a WM modulation method, and the power conversion unit smoothes the output voltage from the transistor that changes the duty ratio of the output voltage based on the control signal from the comparator. And a capacitor that outputs the output DC voltage.

According to the first aspect of the invention, when the input DC voltage fluctuates, the amplitude of the sawtooth wave voltage from the oscillating section fluctuates correspondingly. And in the comparison unit,
The sawtooth wave voltage is compared with the amplification difference voltage from the error amplification section, and a control signal is input from the comparison section to the power conversion section according to the comparison result. As a result, in the power conversion unit, the input DC voltage is amplified with the amplification degree indicated by the control signal and output as the output DC voltage. Then, this output DC voltage is fed back to the error amplification section, and a constant amplification difference voltage is output from the error amplification section.

According to the second aspect of the present invention, the amplification difference voltage between the reference voltage and the output DC voltage is input from the operational amplifier to the comparator, and in the comparator, the amplification difference voltage from the pair amplifier and the sawtooth wave voltage from the oscillator. And are compared, and the control signal generated by the PWM modulation method is output to the power conversion unit. As a result, the transistor of the power conversion unit changes the duty ratio of the output voltage based on this control signal, and the output voltage from this transistor is smoothed by the capacitor and output as the output DC voltage.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a DC input and DC output converter according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the DC input and DC output converter of FIG. 1 in detail. As shown in FIG. 1, the direct-current input and direct-current output converter of the present embodiment includes a power conversion section 1, a reference voltage section 2, an error amplification section 3, an oscillation section 4, and a comparison section 5.
Is provided.

The power conversion section 1 is a section for amplifying the input DC voltage Vin with the amplification degree indicated by the control signal C from the comparison section 5 and outputting the output DC voltage Vout. Specifically, as shown in FIG. 2, it has a PNP type bipolar transistor 10. The emitter of the transistor 10 is connected to the input terminal 100 of the input DC voltage Vin via the capacitor 11, the circuit 12 for improving efficiency, and the coil 13. The collector is a diode 14, a coil 15,
Also, it is connected to the output terminal 101 via the smoothing capacitor 16. The base of the transistor 10 is connected to the output terminal of the comparison unit 5. The circuit 12 is
As shown, an NPN type bipolar transistor 12a
And resistors 12b to 12d and capacitors 12e and 12f. As a result, the transistor 10 changes the duty ratio of the output voltage Vout ′ based on the control signal C from the comparison unit 5.

As shown in FIG. 1, the reference voltage section 2 is a section for generating a constant reference voltage V0 and inputting it to the error amplification section 3. Specifically, as shown in FIG. 2, the resistor 20 having one end connected to the input end 100 and the shunt regulator 21 are used to configure the resistor 20 and the shunt regulator 21. The potential at the connection point is input to the error amplification section 3 as the reference voltage V0.

As shown in FIG. 1, the error amplification section 3 amplifies a difference voltage between the reference voltage V0 of the reference voltage section 2 and the output DC voltage Vout fed back from the power conversion section 1, and the amplified difference voltage Vd. Is the part that outputs. Specifically, as shown in FIG. 2, it has an operational amplifier 30. The positive input terminal of the operational amplifier 30 is connected to the reference voltage V0 generating terminal of the reference voltage section 2. Also, the negative input terminal is connected in series with a resistor 3
It is connected to the output end 101 of the power conversion unit 1 via the capacitors 1 and 32 and the capacitor 33. And operational amplifier 3
The output terminal of 0 is connected to the comparison unit 5 and is negatively fed back to the negative input terminal via the capacitor 34 and the resistor 35. As a result, "reference voltage V0-output DC voltage Vout
Is multiplied by a constant, and the amplified difference voltage Vd is generated and output to the comparison unit 5.

On the other hand, the oscillator 4 is a part that oscillates a sawtooth wave voltage S having an amplitude corresponding to the input DC voltage Vin.
Specifically, as shown in FIG. 2, it has circuits 40 and 41 and a comparator 42. The circuits 40 and 41 are circuits for performing constant current charging (circuit 40) or constant current discharging (circuit 41) on the capacitor 45, and perform discharging operation when the output of the inverter 43a is "H". ,
When it is "L", the charging operation is performed. The negative input terminal of the comparator 42 is connected to the constant current charging / discharging circuits of the circuits 40 and 41 via the grounded capacitor 45. A resistor 42a connected to the output end of the coil 13, a resistor 42b, and diodes 42c and 42d are arranged in series on the positive input end side of the comparator 42. But the resistors 42a, 42
It is connected to the connection point of b. The diode 42d
The cathode of is grounded. The inverters 43a and 43b and the diodes 44a and 44b are connected between the output terminal and the positive input terminal of the comparator 42, respectively, and the output terminal of the inverter 43b and the diode 4 are connected.
The cathode of 4b is connected. In such a configuration, the resistor 46 is connected between the output end of the comparator 42 and the inverter 43a, and the output end of the inverter 43a is connected to the connection points of the resistors 40b and 41b of the circuits 40 and 41. The connection point of the capacitor 45 is connected to the comparison unit 5. As a result, the inverter 43
When the output of b is "L", the threshold value of the comparator 42 becomes "2VBE", and when the output of the inverter 43b is "H", the threshold value becomes "R42b. (Vcc-2
VBE) / (R42b + R42a) + 2VBE ". However,
R42a and R42b are resistance values of the resistors 42a and 42b,
VBE is the base-emitter voltage of the transistor, and VBE
cc is the input DC voltage Vin output from the coil 13. If there is no delay in the circuit, the capacitor 45 will oscillate at the voltage of the above threshold difference. As a result, when the input DC voltage Vin output from the coil 13, that is, the input DC voltage Vcc is input to the oscillating unit 4, the sawtooth wave voltage S having an amplitude corresponding to the input DC voltage Vcc is transferred to the capacitor 4
It is input to the comparison unit 5 from five connection points.

As shown in FIG. 1, the comparing section 5 includes an oscillating section 4
From the sawtooth wave voltage S to the amplified difference voltage Vd from the error amplification section 3 and generates a control signal C for determining the duty ratio of the output voltage Vout ′ of the power conversion section 1 according to the comparison result. Then, the power is input to the power conversion unit 1.
Specifically, as shown in FIG. 2, the comparison unit 5 uses the PWM
This is a (Plus Width Modulation) modulation type comparator (hereinafter referred to as "comparator 5"), the negative input end of which is connected to the output end of the operational amplifier 30 of the error amplification unit 3, and the positive input end thereof is connected to the capacitor 4 of the oscillation unit 4.
It is connected to 5 connection points. As a result, the control signal C, which becomes H level when the sawtooth wave voltage S is larger than the amplification difference voltage Vd and becomes L level when it is smaller, is output to the base of the transistor 10 via the circuit 12. Note that FIG.
In the above, reference numerals 6 and 7 are smoothing capacitors and loads.

Next, the operation of the DC input and DC output converter of this embodiment will be described. FIG. 3 is a diagram showing the waveform of each signal during this operation. In FIG.
In a state where the input DC voltage Vin having no ripple is input to the input terminal 100, a constant output DC voltage Vout is output from the output terminal 101 and is also fed back to the negative input terminal of the operational amplifier 30 of the error amplification unit 3. It Then, in the operational amplifier 30, an amplified difference voltage Vd between the output DC voltage Vout and the reference voltage V0 from the reference voltage unit 2 is generated,
It is output to the negative input terminal of the comparator 5. In parallel with this operation, the ripple-free input DC voltage Vcc is input to the oscillator 4. As a result, as shown by the solid line in FIG. 3A, the sawtooth wave voltage S having the desired amplitude is oscillated by the oscillator 4 and input to the positive input terminal of the comparator 5. Then
In the comparator 5, the sawtooth wave voltage S and the amplified difference voltage Vd are compared, and a desired control signal C as shown in FIG. 3B is output from the comparator 5 to the power conversion unit 1. Then, in the transistor 10 of the power conversion unit 1, the voltage of the control signal C is applied to the base, and as shown in FIG. 3C, the output voltage Vout ′ having the opposite polarity to the control signal C is output from the collector of the transistor 10. Is output.
Then, the output voltage Vout ′ is smoothed by the smoothing capacitor 16, is output as the output DC voltage Vout, and is fed back from the output terminal 101 to the operational amplifier 30.

In this state, the voltage of the input DC voltage Vin is a
When the output DC voltage Vout is doubled, the input DC voltage Vcc that is a times the input voltage may be input to the power converter 1 and the amplitude of the output DC voltage Vout may increase a times. In this case, conventionally, the output operating point of the error amplifying section is deviated by the operation of the feedback loop so that the output voltage Vout becomes constant. However, in the DC input and DC output converter of the present embodiment, the amplitude of the output DC voltage Vout is adjusted to a fixed initial value by the following operation. That is, the value of the output DC voltage Vout immediately before the input DC voltage Vin fluctuates is a constant initial value, and a constant amplification difference voltage Vd is input from the operational amplifier 30 to the comparator 5. On the other hand, the oscillating unit 4 receives the a-fold input DC voltage V
Since cc is input, as shown by the chain double-dashed line in (a) of FIG. 3, the oscillator 4 outputs a sawtooth wave voltage S having a fixed trough and an amplitude of a times, which is input to the comparator 5. To be done. Thus, from the comparator 5, the control in which the H level becomes longer and the L level becomes shorter corresponding to the amplitude of the sawtooth wave voltage S as shown in (d) of FIG. 3 regardless of the operation of the feedback loop. The signal C is output. As a result, as shown in FIG. 3E, the output voltage Vout ′ having the opposite polarity to the control signal C is output from the collector of the transistor 10. That is, the duty ratio of the output voltage Vout 'is reduced to 1 / a of the duty ratio of the output voltage Vout before the change. As a result, the variation of the output DC voltage Vout is suppressed without shifting the output operating point of the error amplification unit 3, and the output DC voltage Vout is always constant from the output terminal 101.
Is output. Further, when the input DC voltage Vin becomes a times, the conversion gain of the power conversion section 1 becomes a times, but the output amplitude of the oscillation section 4 also becomes a times, so that the loop characteristic is not related to the input DC voltage Vin. Instead, it is held constant.

Here, the result of the verification test will be described. In this test, each element was set as follows. In the power conversion unit 1, 2SB1211 manufactured by Sanyo Co., Ltd. is used for the transistor 10, and the same diode S is used for the diode 14.
B-05-05 was used. And the capacitors 11, 12
e, 12f, 16 capacitance is 33μF, 82pF, 100
pF and 16.8 μF respectively, and resistors 12b and 1
2c. The resistance value of 12d is set to 33 kΩ, 22 kΩ, and 1 kΩ, respectively, and the coil 15 is 47 μH.
Set to. In the reference voltage section 2, the resistor 20 and the shunt regulator 21 manufactured by TI are selected so that the reference voltage V0 becomes 2.5V. In the error amplification unit 3, one of the general-purpose operational amplifiers, that is, μPC358 manufactured by NEC Corp., which is a general-purpose operational amplifier, is used. The capacitances of the capacitors 33 and 34 are both set to 470 pF, and the resistance values of the resistors 31, 32 and 35 are 47 kΩ and 47 kΩ, respectively.
It was set to kΩ and 10 kΩ, respectively. In the oscillator 4, the transistors 40c and 40d of the circuit 40 are small-signal transistors 2SA1175 made by NEC, and the transistors 41c and 41d of the circuit 41 are small-signal transistors 2SC2785 made by NEC. . Then, the resistors 40a, 40e, 4 of the circuits 40, 41
Set the resistance values of both 1a and 41e to 10 kΩ and set the resistance 4
The resistance values of 0b and 41b were both set to 100 kΩ. As the comparator 42, one of the μPC393 manufactured by NEC Corporation was used. And the diode 42
2SC2785 is used for c, 42d, 44a, and 44b, and inverters 43a and 43b are connected to 7
24HC04 was used, and the resistance values of the resistors 42a and 42b were both set to 10 kΩ. The capacitance of the capacitor 45 was set to 39 pF and the resistance value of the resistor 46 was set to 1 kΩ. In the comparator 5, the μP manufactured by NEC mentioned above is used.
The other comparator of C393 was used. The capacity of the smoothing capacitor 6 was set to 10 μF and the load 7 was set to 18Ω.

When the DC input and DC output converters were operated under the above setting, the following verification results were obtained. FIG. 4 is a diagram showing characteristics of the oscillator 4. In the oscillating unit 4, it is ideal that the amplitude of the sawtooth wave voltage S linearly changes with a predetermined slope with respect to the input DC voltage Vcc, as indicated by the broken line A in FIG. On the other hand, in the DC input and DC output converter of this embodiment, the oscillator 4 generates the sawtooth wave voltage S that changes as shown by the solid line in FIG. 4, and is very close to the ideal straight line A. became. From the linearity of the sawtooth wave voltage S, the feedback loop characteristic (hereinafter, simply referred to as “loop characteristic”) including the error amplification unit 3, the comparison unit 5, and the power conversion unit 1 has the result shown in FIG. 6A shows the gain curve E and the phase curve F when the input DC voltage Vin is 10V, and FIG. 6B shows the gain curve E when the input DC voltage Vin is 6V. And the phase curve F are shown. As is clear from these figures, even if the input DC voltage Vin changes, the gain and phase of the loop characteristic hardly change.
As a result, as shown in FIG. 5, a considerable difference occurs in the ripple removal rate (dVout / dVin) between the conventional DC input / DC output converter and the DC input / DC output converter of the present embodiment. That is, as shown in FIG. 5A, when the input DC voltage Vin is 10 V,
The ripple removal curve D by the DC input and DC output converter of this embodiment is significantly lower than the ripple removal rate curve C by the conventional DC input and DC output converter. Specifically, it was improved by 18.4 dB at 1 kHz. Further, as shown in FIG. 5B, the input DC voltage V
Even when in is 6 V, the ripple removal curve D by the DC input and DC output converter of this embodiment is significantly lower than the ripple removal rate curve C by the conventional DC input and DC output converter, and at 1 kHz. Was improved by 27.1 dB. That is, according to the result of the test using the DC input and DC output converters of the present embodiment, it was verified that the ripple removal rate was improved in the range of 18 dB to 27 dB as compared with the conventional one. This improvement amount can be further increased by driving the characteristics of the oscillator 4 with respect to the input DC voltage Vin.

As described above, according to the DC input and DC output converter of the present embodiment, the desired constant output DC voltage Vout is immediately output from the power converter 1, so that the input DC voltage Vin varies. It has a high-speed response. Further, even if the fluctuation of the input DC voltage Vin is large, it is not necessary to increase the amplification degree of the error amplification unit 130. Further, even when the input DC voltage Vin is low, ripple removal can be sufficiently performed, so that the minimum operating voltage can be set lower, and as a result, the battery usage time can be extended. Further, since it is not necessary to suppress the fluctuation itself of the input DC voltage Vin, the capacity of the smoothing capacitor 6 can be made extremely small, and as a result, the converter can be downsized and the cost can be reduced. Since the loop characteristic is not affected by the input DC voltage Vin, the load fluctuation characteristic at the time of power reduction can be improved.

The present invention is not limited to the above embodiment, but various modifications and changes can be made within the scope of the invention. For example, although a PNP type bipolar transistor is used as the transistor 10,
Of course, ET or the like may be used, or a transformer or the like may be used instead of the coil 15.

[0021]

As described in detail above, according to the DC input and DC output converter of the present invention, the desired output DC voltage is immediately output from the power converter, so that it is possible to cope with fluctuations in the input DC voltage. Can respond quickly. Further, since the amplification degree of the feedback system or the loop gain does not change with respect to the input DC voltage, the loop gain does not decrease even when the input DC voltage is low, and as a result, ripple removal is sufficiently performed. Therefore, the ripple removal rate can be improved. Furthermore, since the minimum operating voltage can be set lower, the battery can be used for a longer time. Further, since it is not necessary to suppress the fluctuation of the input DC voltage itself, the capacity of the capacitor for smoothing the input DC voltage can be made extremely small, and as a result, the converter can be downsized and the cost can be reduced. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a DC input and DC output converter according to an embodiment of the present invention.

2 is a circuit diagram showing in detail the DC input and DC output converter of FIG. 1;

FIG. 3 is a waveform diagram of each signal during operation.

FIG. 4 is a diagram showing characteristics of an oscillation unit.

FIG. 5 is a diagram comparing ripple removal rates.

FIG. 6 is a diagram showing loop characteristics.

FIG. 7 is a block diagram showing a DC input and DC output converter according to a conventional example.

FIG. 8 is a waveform diagram of each signal during operation.

[Explanation of symbols]

1 ... Power conversion unit, 2 ... Reference voltage unit, 3 ...
・ Error amplification section, 4 ... Oscillation section, 5 ... Comparator, 6 ... Smoothing capacitor, C ... Control signal, S ... Sawtooth wave voltage, Vin ... Input DC voltage, Vout. ..Output DC voltage, V0 ... reference voltage, Vd ... amplification differential voltage.

Claims (2)

[Claims] 1. A power converter for amplifying an input DC voltage with a degree of amplification indicated by a control signal to output a DC voltage, a reference voltage unit for generating a constant reference voltage, a reference voltage for the reference voltage unit, and the above An error amplification unit that amplifies and outputs a difference voltage from the output DC voltage of the power conversion unit, an oscillation unit that oscillates a sawtooth wave voltage having an amplitude corresponding to the input DC voltage, and a sawtooth wave voltage from the oscillation unit. A comparison unit that compares the amplification difference voltage from the error amplification unit and generates the control signal for adjusting the amplification degree of the power conversion unit according to the comparison result; DC input and output converter. 2. The DC input and DC output converter according to claim 1, wherein the error amplification section amplifies a difference voltage between the reference voltage from one input end and the output DC voltage from the other input end. The comparator includes a comparator that inputs the sawtooth wave voltage from the oscillator and the amplification difference voltage from the operational amplifier, and generates the control signal by the PWM modulation method. The power conversion unit includes a transistor that changes a duty ratio of an output voltage based on a control signal from the comparator, and a capacitor that smoothes an output voltage from the transistor and outputs the output DC voltage. A DC input and DC output converter characterized by.