JPH05146145A - Control circuit for switching regulator - Google Patents

Abstract

PURPOSE:To provide a control circuit for a switching regulator in which fluctuation due to noise, temperature change, aging change is small and a stable output is obtained. CONSTITUTION:A control circuit for a switching regulator comprises an A/D converter 11 for converting an input voltage into a digital signal, an error amplifier 15 for calculating a difference between an output signal of the converter 11 and target data externally input to multiply it by a coefficient, and a Shanon rack type D/A converter 14 for converting the output signal of the amplifier 15 into a pulse width. The amplifier 15 has a constant adder 12 and a constant multiplier 13, and calculates base on the constants inputted and set from the exteriors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator control circuit, and more particularly to a switching regulator control circuit using a PWM control method.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional switching regulator control circuit includes an error amplifier 31, a reference voltage generator 32, a triangular wave generator 35, and a PWM comparator 3.
4 and an external resistor 33 for gain setting. For example, when controlling the output of the DC-DC converter, the output voltage of the DC-DC converter is the error amplifier 31.
The difference between this input signal and the reference voltage generated by the reference voltage generator 32 is detected and further multiplied by a coefficient.
This coefficient is determined by the external resistance 33.

The error signal multiplied by the coefficient is input to the PWM comparator 34, and the voltage is compared with the triangular wave generated by the triangular wave generator 35. Then, the control pulse width is determined based on this result. That is, the width of the control pulse is narrowed when a positive error occurs, and the width of the control pulse is widened when a negative error occurs. This control pulse is input to the switching transistor in the DC-DC comparator, and the output voltage of the switching regulator is controlled by turning this switching transistor on and off.

[0004]

Since the control circuit of the conventional switching regulator as described above uses the reference voltage generator as a target value for its control, the fluctuation of the reference voltage generated by the reference voltage generator is caused. However, there is a problem that the output voltage of the switching regulator fluctuates as it is, and the output voltage easily fluctuates. Moreover, since the control system itself is an analog circuit, it is susceptible to noise, and temperature changes and aging changes are large. Therefore, due to these disturbances, the value of the reference voltage output from the reference voltage generator, the external resistance that determines the amplification factor, the oscillation frequency of the triangular wave generator, and the like fluctuates, and the characteristics of the switching regulator deteriorate. there were.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a control circuit for a switching regulator which can obtain stable output with little fluctuation due to noise, temperature change, and secular change.

[0006]

A control circuit for a switching regulator according to the present invention includes an A / D converter for converting an input voltage into a digital signal, an output signal of the A / D converter and a target externally input. Since the error amplifier for calculating the difference from the data and multiplying by the coefficient and the Shannon rack type D / A converter for converting the output signal of the error amplifier into the pulse width are provided, the above-mentioned problems are caused. Settled.

The error amplifier comprises a constant adder and a constant multiplier, and the constant adder calculates the difference between the output signal of the A / D converter and the target data input from the outside, and the constant multiplier. Can multiply the output of the constant adder by a constant input from the outside and output the result to the D / A converter.

The error amplifier is composed of a constant adder and a constant multiplier, and the constant multiplier multiplies the output signal of the A / D converter by a constant set externally. The difference between the output of the constant multiplier and the target data input from the outside may be calculated, and the result may be output to the D / A converter.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. The control circuit of this embodiment includes an A / D converter 11, a digital error amplifier 15 that receives the output of the A / D converter 11, and a Shannon rack type D / A converter 14 that receives the output of the digital error amplifier 15. It consists of and. Digital error amplifier 15
Is composed of a constant adder 12 that receives the output of the A / D converter 11, and a constant multiplier 13 that receives the output of the constant adder 12. The constant adder 12 and the constant multiplier 13 have data setting terminals data1 and data1.
The constants can be set by inputting the respective predetermined constants from 2.

In the control circuit having the above structure, for example, DC
The input signal input from the DC converter to the input terminal Vin is A / D converted in the A / D converter 11 and then input to the digital error amplifier 15. The digitally converted input signal is compared by the constant adder 12 with the constant input / set from the data setting terminal data1, and the difference is calculated. The result is further multiplied by a constant multiplier 13 with a constant input / set from the data setting terminal data2. This result is input to the final stage Shannon rack type D / A converter 14 as the output of the digital error amplifier 15,
The control pulse width is determined based on this.

Now, the data setting terminals data1 and da
When Vref and Av are set as constants in ta2, respectively, the output Vamp of the digital error amplifier 15 is Vamp = adc (Av · (Vin−Vref)). However, Vin represents an input signal and adc (x) represents a digital code of x.

As described above, since the setting data (data1, data2) of the digital error amplifier 15 is externally given as an electric signal, it is irrelevant to noise, temperature change, and secular change. Therefore, it can be seen that it is extremely strong against these disturbances.

Next, the output fluctuations of the control circuit of this embodiment and the conventional switching regulator will be compared.
In the control circuit of the conventional switching regulator of FIG. 3, fluctuations including the noise and the secular change in the outputs of the error amplifier 31 and the reference voltage generator 32 are respectively changed by δc1 and δ.
c2, the PWM comparator 34 and the triangular wave generator 35
Letting δc3 be a variation including a conversion error of the PWM converter configured by, the output Voc of this control circuit is Voc = Kp · Av (1 + δc1) {Vin−Vr (1 + δc2)} + δc3 (a1). However, Kp is the conversion coefficient of the PWM converter, A
v is the gain of the error amplifier, Vr is the reference voltage, and Vin
Is the input voltage. Now, in the formula (a1), Vin =
When Vr is set, the variation Δc of this control circuit can be calculated by the following equation. Here, for simplicity, Kp = 1. | Δc | = Av · Vr · δc2 + Av · Vr · δc1 · δc2 + δc3 (a2)

Next, in the embodiment of the present invention shown in FIG.
If the fluctuations including the conversion error of the / D and D / A converters are set as δn1 and δn2, respectively, the output Vo of this control circuit is
n is Von = Kd · Av {Vin (1 + δn1) −Vr} + δn2 (a3). Where Kd is the conversion coefficient of the D / A converter, A
v is gain data of the amplifier, Vr is reference voltage data, and Vin is an input voltage. If Vin = Vr is set in the equation (a3), the variation Δn of this control circuit can be calculated by the following equation. Here, for simplicity, Kd = 1. | Δn | = Av · Vin · δn1 + δn2 (a4)

Here, if all the fluctuations are δ and the difference from the fluctuation | Δc | of the conventional control circuit is taken, then | Δc | − | Δn | = Av · Vr · δ ² (a5) It can be seen that the control circuit of the embodiment is more resistant to fluctuations due to noise, aging, etc. than the conventional control circuit.

FIG. 2 is a block diagram showing another embodiment of the present invention. The configuration of this embodiment is almost the same as that of the embodiment of FIG. 1, but the configuration of the digital error amplifier 25 is slightly different. That is, the digital error amplifier 25 is
A constant multiplier 22 having the output of the / D converter 11 as an input
And a constant adder 23 whose input is the output of the constant multiplier 22
And a constant multiplier 22 and a constant adder 23.
Can be set by inputting a predetermined constant from each of the data setting terminals data1 and data2.

Now, Av is set to the data setting terminal data1.
When Av · Vref is set to the data setting terminal data2, the output voltage Vam of the digital error amplifier 25
p becomes Vamp = adc (Av · Vin−Av · Vref) = adc (Av · (Vin−Vref)), and the operation is exactly the same as in the first embodiment.

[0018]

As described above, according to the present invention, since the A / D converter, the Shannon rack type D / A converter and the digital error amplifier whose data can be set externally are used, the output thereof is noisy. It has the effect of being robust against changes over time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a control circuit of a conventional switching regulator.

[Explanation of symbols]

 11, 21 A / D converter 12, 23 Constant adder 13, 22 Constant multiplier 14, 24 D / A converter 15, 25 Error amplifier

Claims (3)

[Claims] 1. An A / D converter for converting an input voltage into a digital signal, and an error amplifier for calculating a difference between an output signal of the A / D converter and target data input from the outside and multiplying it by a coefficient. And a Shannon rack D / A converter for converting an output signal of the error amplifier into a pulse width, a control circuit for a switching regulator. 2. The error amplifier comprises a constant adder and a constant multiplier, and the constant adder calculates a difference between an output signal of the A / D converter and target data input from the outside, and performs constant multiplication. The control circuit of the switching regulator according to claim 1, wherein the converter multiplies the output of the constant adder by a constant input from the outside and outputs the result to the D / A converter. 3. The error amplifier comprises a constant adder and a constant multiplier, and the constant multiplier multiplies the output signal of the A / D converter by a constant set externally,
The control circuit of the switching regulator according to claim 1, wherein the constant adder calculates a difference between the output of the constant multiplier and target data input from the outside and outputs the result to the D / A converter. ..