JPH03212160A - Switching regulator - Google Patents

Abstract

PURPOSE:To operate a plurality of switching regulators synchronously and stably by comparing a saw-tooth signal level with a reference level through a comparator and discharging a capacitor forcibly. CONSTITUTION:A switching regulator section 6 comprises a transformer 1, a switching element 2, a rectifying/smoothing circuit 3, a capacitor 4 and a control circuit 5. The control circuit 5 for a plurality of switching regulator sections 6 is connected with a comparator 7. The level of a saw-tooth signal from the control circuit 5 is compared through the comparator 7 with a reference voltage. When the saw-tooth signal level exceeds the reference voltage, the capacitor 4 in the switching regulator section 6 is discharged forcibly thus generating respective saw-tooth signals inphase.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching regulator that operates a plurality of switching regulator sections synchronously.

When configuring a large-capacity stabilized DC power supply or when applying a stabilized DC voltage to a load at a remote location, a configuration in which multiple switching regulator sections are operated synchronously by pulse width control is adopted. When a plurality of such switching regulator sections are provided, it is common to use a common input DC power source and an operating power source for the control circuit.

Furthermore, if multiple switching regulator sections are provided and the oscillators that generate sawtooth wave signals for controlling the pulse width of the control circuit of each switching regulator section are operated asynchronously, multiple types of oscillation frequencies and interference between those frequencies will be generated. This interference wave is also included in the stabilized DC voltage, resulting in output ripple voltage and output noise beat phenomena. Normally, it is undesirable for the stabilized DC voltage applied to the load to contain many frequency components.
A configuration is adopted in which the oscillators of each control circuit are operated synchronously so that only one type of frequency component is generated.

[Conventional technology]

A conventional switching regulator that operates a plurality of switching regulator sections in synchronization has, for example, the configuration shown in FIG. 6, where 41 is a transformer, 42 is a transformer 41
A switching element such as a field effect transistor or a bipolar transistor connected to the primary winding, 43 a rectifying and smoothing circuit including a rectifier, a capacitor, etc., 44 a control circuit controlling the pulse width of the switching element 42, 45-, 45-
2 is a switching regulator section, 46 and 47 are capacitors, 48 is an inductance, 49 is a DC power source such as a battery or a rectified output power source, and 50 is a control line connecting the control circuits.

The switching regulator sections 45 - and 45 - 2 control the pulse width of the switching element 42 connected to the primary winding of the transformer 41 from the control circuit 44, and the voltage induced in the secondary winding of the transformer 41 is controlled by the rectifying and smoothing circuit 43. rectifying and smoothing, supplying the DC output voltage to the load, and comparing this DC output voltage with a reference voltage in the control circuit 44,
It has a configuration in which the on-period of the switching element 42 is controlled so that the DC output voltage becomes a set value. Further, a direct current is supplied from a battery or a direct current power source 49 which is a rectified alternating current voltage to the primary winding of the transformer 41 of each switching regulator section 45-, 45-2 via a switching element 42 via a capacitor 47, 46 and an inductance 48. supply

Such switching regulator sections 45-, 45-
In a configuration in which two DC outputs are connected in parallel to increase the output capacity or to supply DC outputs to loads at separate locations, terminals CT of the control circuit 44 are connected with a control line 50,
A sawtooth wave signal generated in the control circuit 44 of one switching regulator section 45-1 is supplied to the control circuit 44 of the other switching regulator section 45-2 for synchronous operation.

FIG. 7 is a block diagram of the control circuit, where 51 is an oscillator;
52.53 is a comparator, 54.55 is an error amplifier, 56 is a flip-flop, 57 is an OR circuit, 58.59 is a NOR circuit, 60 is an inverter, 6 and 62 are AND circuits, 63
．． 64 is an output transistor, RT is a terminal to which a resistor R is connected, CT is a terminal to which a capacitor C is connected, DT is a dead time control terminal, +IN, -IN are input terminals to which a rectified and smoothed output voltage is applied, FB is a feedback terminal, OC is an output control terminal, and CI, C2, El, and E2 are output terminals.

This control circuit has a configuration that can be applied to a two-stone switching regulator, and may also include a reference voltage generation circuit (not shown), and is usually a semiconductor integrated circuit.

The oscillator 51 charges the capacitor C connected to the terminal CT with a constant current, compares the terminal voltage of the capacitor C with a reference voltage, and rapidly discharges the capacitor C when the terminal voltage of the capacitor C exceeds the reference voltage. This generates a sawtooth wave signal, and the resistor R (KΩ) connected to the terminal RT and the capacitor C [μF] connected to the terminal CT
], the oscillation frequency f of the oscillator 51 becomes fL:, 2/(R-C) (KHz). 6th
In the figure, only this terminal CT is shown, and the control circuit 44 of one switching regulator section 45-1 is shown.
connects the aforementioned capacitor C to the terminal CT, and the control circuit 44 of the other switching regulator section 45-2,
Without connecting the capacitor C to the terminal CT, the sawtooth wave signal of one switching regulator section 45-1 is supplied to the other switching regulator section 45-2 to perform synchronous operation.

Further, the comparator 53 compares the level of the sawtooth wave signal generated at the terminal CT with the output signal of the error amplifier 54.55, and outputs the OR circuit 57. The ON period of the output transistor 3.64 is controlled via the NOR circuits 58 and 59.

Also, when the output control terminal OC is set to "0", the output transistor transistor 3.64 turns on and off at the same time, and when the output control terminal OC is set to "1", the output turns on and off in response to the inversion operation of the flip-flop 56. The quadrant distal 3.64 performs anti-phase operation.In the case of a single-stone switching regulator, the output of one of the quadrant distals 3.64 is sent to the switching element 42 directly or via a transformer, etc. I will add it.

FIG. 8 is a block diagram of main parts for conventional synchronous operation, in which terminals CT of the control circuits 8 and 82 of the switching regulator section are connected by a control line 83, as in the case shown in FIG. , the terminal G is connected to the ground line 84, the resistor R is connected to the terminal RT of one control circuit 81, and the terminal C
A capacitor C is connected to T, and the terminal voltage of this capacitor C becomes a sawtooth wave signal.This sawtooth wave signal is supplied to the terminal CT of the other control circuit 82 via the control line 83, and one and the other control circuit 8,
By using the same sawtooth signal at 82,
It performs synchronous operation.

Further, FIG. 9 is used when the control line 83 is extended or when the frequency of the sawtooth wave signal is increased.

A case is shown in which the sawtooth wave signal at the terminal CT of one control circuit 81 is voltage-divided by resistors rl and r2 and is supplied to the terminal CT of the other control circuit 82.

[Problem that the invention seeks to solve]

As shown in FIGS. 6 and 8, when the terminals CT of one control circuit 81 and the other control circuit 82 are connected by a control line 83 and the same sawtooth wave signal is used, If the switching regulator parts are placed apart from each other,
The length of the control line 83 also increases correspondingly, and when the sawtooth wave signal is made to have a high frequency, the impedance of the control line 83 cannot be ignored. That is, even if the sawtooth wave signal in one control circuit 81 has a desired waveform, the waveform of the sawtooth wave signal may become dull due to the resistance, inductance, distributed capacitance, etc. of the control line 83. Since the waveforms of the sawtooth wave signal in one control circuit 81 and the sawtooth wave signal in the other control circuit 82 are different, synchronous operation becomes difficult.

Furthermore, as shown in FIG. 9, even if an attempt is made to reduce the influence of the distributed capacitance of the control line 83 by dividing the sawtooth wave signal using resistors r and r2, the sawtooth wave signal applied to the terminal CT of the other control circuit 82 is As the level of the sawtooth wave signal decreases, it becomes difficult to sufficiently suppress waveform rounding of the high frequency sawtooth wave signal.

In addition, when the inductance and distributed capacitance of the control line 83 can be ignored, when the voltage at the terminal CT in one control circuit 81 reaches a certain value, the capacitor C connected to that terminal CT is rapidly discharged. The other control circuit 82 has a similar configuration for rapid discharge, and the level of rapid discharge may differ depending on the comparison voltage and variations in the characteristics of circuit components, or noise may be caused by noise on the control line. 83, a rapid discharge may occur at the terminal CT of the other control circuit 82 before rapid discharge occurs at the terminal CT of one control circuit 81, and one control There is a drawback that the oscillation frequency caused by the resistor R and capacitor C in the circuit 81 becomes unstable due to the rapid discharging operation of the other control circuit 82.

An object of the present invention is to operate a plurality of switching regulator sections stably and synchronously.

[Means to solve the problem]

The switching regulator of the present invention will be described with reference to FIG. Switching that synchronizes operation of a plurality of switching regulator units 6 having a capacitor 4 for generating a wave signal and a control circuit 5 controlling the pulse width of the switching element 2 using the sawtooth wave signal of the terminal voltage of the capacitor 4. In the regulator, one of the plurality of switching regulator sections is designated as the master, and the others are designated as slaves, and the level of the sawtooth wave signal in the master switching regulator section is compared with the reference voltage by the comparator 7, and the sawtooth wave signal is When the level of the wave signal exceeds the reference voltage, the output signal of the comparator 7 forcibly discharges the capacitor 4 of the slave switching regulator, and the sawtooth wave signal in the master switching regulator and the slave switching The configuration is such that the sawtooth wave signal in the regulator section is generated in the same phase.

Further, the capacitor 4 of the master switching regulator section is forcibly discharged at the same time as the capacitor 4 of the slave switching regulator section by the output signal of the comparator 7.

Further, a switching element is connected in parallel to the capacitor 4, and this switching element is operated by the output signal of the comparator 7 via a driver to forcibly discharge the capacitor 4.

(Function) The comparator 7 compares the sawtooth wave signal level of the control circuit 5 and the reference voltage, and when the sawtooth wave signal level exceeds the reference voltage, the output impedance of the comparator 7 is set to zero. As a result, the capacitors 4 of the other control circuits 5 are forcibly discharged, and the rise of the sawtooth wave signal of the reference control circuit 5 is synchronized with the rise of the sawtooth wave signal of the other control circuits 5. By making the sawtooth wave signals of the control circuit 5 the same in phase and frequency, each switching regulator section 6 can be operated synchronously.

Further, the sawtooth wave signal of the control circuit 5 of the slave switching regulator section can be synchronized with the sawtooth wave signal of the control circuit 5 of the master switching regulator section as a reference.

In addition, by forcibly discharging the capacitor 4 of the control circuit 5 of the master switching regulator section at the same time as the capacitor 4 of the control circuit 5 of the slave switching regulator section, the sawtooth wave signal of the control circuit 5 of the slave switching regulator section is stopped. It is possible to set the period to zero.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of main parts of an embodiment of the present invention, and 3
This figure shows the main parts when operating two switching regulator sections synchronously. In the figure, 11 to 13 are control circuits corresponding to the switching regulator section, 14 and 15 are comparators,
16 is the ground line, 17.18 is the control line, R1-R7
is a resistor, and 01 to C3 are capacitors.

Each of the control circuits 11 to 13 has resistors R1 to R3 connected to the terminal RT.
Capacitors 01 to C3 are connected to the terminal CT, each having a configuration capable of independently generating a sawtooth wave signal, and one of the plurality of switching regulator sections is used as a master,
Control circuit 11 of the master switching regulator section
The sawtooth signal at terminal CT of is applied to one terminal of comparator 14.15 and +
A reference voltage obtained by dividing the voltage of V is applied to the child terminals of comparators 14 and 15, and the level of the sawtooth wave signal is compared with the reference voltage. Also, the control circuit 1 of the master switching regulator section
The frequency of the sawtooth wave signal when generated independently is determined by the control circuit 12 of the slave switching regulator section.
．． The frequency of the sawtooth wave signal is set slightly higher than the frequency of the sawtooth wave signal when the signals are generated independently.

The output terminal of the comparator 14.15 is connected to the terminal CT of the control circuit 12.13 of the slave switching regulator section, and when the + terminal level of the comparator 14.15 is higher than the 1-terminal level, a high impedance output is output. On the other hand, when the ten-terminal level is lower than the one-terminal level, a low impedance output is obtained.

Therefore, when the level of the sawtooth wave signal at the terminal CT of the control circuit 11 exceeds the reference voltage applied to the ten terminals of the comparator 14.15, the respective output impedances become zero, so that the terminals of the control circuit 12.13 Capacitors C2, C3 connected to CT are connected to comparator 1 via control lines 17.18.
4.15 forcibly discharges. As a result, a sawtooth wave signal is generated at the terminal CT of the control circuit 12, 13 of the slave switching regulator section in synchronization with the sawtooth wave signal of the control circuit 11 of the master switching regulator section, and a sawtooth wave signal is generated at the terminal CT of the control circuit 12, 13 of the slave switching regulator section. The pulse width control at the time will be synchronized.

In that case, the control lines 17 and 18 do not transmit waveforms, but only transmit the high impedance and low impedance outputs of the comparators 14 and 15, so there is a problem of waveform distortion due to inductance and distributed capacitance. can be avoided.

FIG. 3 is an explanatory diagram of the operation, in which (a) shows the waveform of the sawtooth wave signal of the control circuit 11 of the master switching regulator section, and the reference voltage at the comparator 14.15 is indicated by Vr. (C) is the output signal of the comparator 14.15, and (C) is the control circuit 12.13 of the slave switching regulator section.
shows a sawtooth signal at terminal CT of .

When the sawtooth wave signal of the control circuit 11 of the master switching regulator section exceeds the reference voltage Vr, the comparator 14.1
The output signal of 5 becomes a low impedance as shown in (b), and the capacitors C2 and C3 of the control circuit 12.13 of the slave switching regulator section are connected to the comparator 14.1.
5 forcibly discharges.

Then, when the sawtooth wave signal of the control circuit 11 falls, the output signals of the comparators 14 and 15 become high impedance, so that constant current charging of the capacitors 01 to C3 of the control circuits 11 to 13 is simultaneously started.

Therefore, if the sawtooth wave signal at the terminal CT of the control circuit 12.13 is not forcibly discharged, the level will rise as shown by the dotted line, but since it is forcibly discharged and falls, (C
) is the waveform shown by the solid line.

In this case, the period during which the level of the sawtooth wave signal of the control circuit 11 is higher than the reference voltage Vr becomes the rest period toff of the sawtooth wave signals of the other control circuits 12.13.

FIG. 4 is a block diagram of main parts of another embodiment of the present invention,
The main parts of the case where three switching regulator sections are operated synchronously in the same manner as in the above-mentioned embodiment are shown. In the same figure, 2
1 to 23 are control circuits, 24 is a comparator, 25 is a ground line, 26 is a control line, and 27.28 is a driver.
pn and pnp bipolar transistors (hereinafter referred to as transistors), 29-31 are capacitors C1l-C
13 is a field effect transistor (hereinafter referred to as a transistor) as a switching element connected in parallel, 32 is a reference power supply, and R11 to R19 are resistors.

Control circuit 21 compatible with three switching regulator sections
A resistor R1 is connected between the terminal RT of ~23 and the ground line 25.
1 to R13 are connected, and capacitors CI1 to C13 are connected between the terminal CT and the ground line 25, and each control circuit 21 to 23 has a configuration that can independently generate a sawtooth wave signal. Further, transistors 29 to 31 are connected in parallel to the capacitors C11 to C13, and the terminal CT of the control circuit of the master switching regulator section 21 is connected to one terminal of the comparator 24, and the reference power supply 32 is connected to the + terminal of the comparator 24. It is connected. Also in this case, the frequency at which the sawtooth wave signal is generated independently in the control circuit 21 of the master switching regulator section is changed to the frequency at which the sawtooth wave signal is generated independently in the control circuit 22 and 23 of the slave switching regulator section. The frequency is set to be slightly higher than the frequency at which the signal is generated.

The output signal of the comparator 24 is applied to the bases of transistors 27 and 28 constituting the driver, and the commonly connected emitters are connected to a control line 26 via a resistor R13. The gates of transistors 29-31 are connected via R19.

When the level of the sawtooth wave signal at the terminal CT of the control circuit 21 does not exceed the reference voltage Vr of the reference power supply 32, the comparator 24
Since the output signal of transistor 27 is low level,
is off, transistor 28 is on, control line 26 is at low level, and transistors 29 to 31 are off.

Therefore, the capacitors C11 to C13 are charged with a constant current, and the voltage at their terminals increases linearly. When the level of this sawtooth wave signal exceeds the reference voltage Vr, the output signal of the comparator 24 becomes high level, the transistor 27 is turned on, the transistor 28 is turned off, and the control line 26 connected through the resistor R13 is turned on. becomes high level, transistors 29 to 31 are turned on, and capacitors C11 to Cl3 are forcibly discharged.

Therefore, the sawtooth signal is forced to fall.

FIG. 5 is an explanatory diagram of the operation, (a) is a sawtooth wave signal of the control circuit 21 of the master switching regulator section, (b)
) shows the output signal of the comparator 24, (C) and (d) show the sawtooth wave signals of the control circuits 22 and 23 of the slave switching regulator section, and in the control circuit 21 of the master switching regulator section, the reference voltage By comparing it with VR, the internal oscillator outputs a sawtooth wave signal with the dotted line waveform shown in (a), and in the control circuits 22 and 23 of the slave switching regulator section, for example, (C) .

As shown in (d), this is the falling edge of the dotted line waveform.

In this way, even if the frequencies of the sawtooth wave signals of the respective control circuits 21 to 23 are different, the comparator 24 adjusts the reference voltage V
r and the control circuit 21 of the master switching regulator section
Comparator 2 compares the level of the sawtooth signal with the level of the sawtooth signal and indicates the occurrence of Φ.
4, the transistors 29 to 31 connected in parallel with the capacitors CIl to C13 are turned on, and the capacitors 011 to C13 are forcibly discharged. (a)
As shown in (C) and (d), sawtooth waveform signals can be generated synchronously.

In this case, by using a driver consisting of transistors 27 and 28, each transistor 29 to 31 can be controlled at high speed. Further, the sawtooth wave signals of the control circuits 22 and 23 of the slave switching regulator section do not have an idle period L off.

The input power supply voltage of the switching regulator section is usually in the range of ±lθ to 20%, but recently, for example,
It may be required to operate with approximately four times the range of human power supply voltages, such as 16-63V. In such a case, it is necessary to have a wide pulse width control range. That is, it is necessary to control the on-width of the switching element in the range from near the peak of the sawtooth wave signal to near the zero level.

However, if the f-watering period t0 of the sawtooth wave signal is long, control during that period becomes impossible, and the range in which the output voltage can be stabilized becomes narrow. In response to such a request, in the above-mentioned embodiment, the steps (a) and (C) in FIG.

As can be seen from the waveform of the sawtooth wave signal in (d), there is almost no rest period Loff, so the pulse width control range can be widened and multiple switching regulator sections can be operated synchronously.

The present invention is not limited only to the above-mentioned embodiments (
, various additions and changes can be made, and it is of course possible to have three or more switching regulator sections operating synchronously, and also in the embodiment shown in FIG. It is possible to connect a switching element such as a transistor and to control the output signal of the comparator 14, 15. In that case, a configuration may be adopted in which the switching element is controlled via a driver. Also, when using a driver, comparators 14 and 15
can be shared.

〔Effect of the invention〕

As explained above, the present invention compares the sawtooth wave signal level and the reference voltage using the comparator 7, and uses the comparison output to forcibly discharge the capacitor 4 for outputting the sawtooth wave signal. Then, the frequencies of the sawtooth wave signals of the control circuits 5 of the plurality of switching regulator sections 6 are made the same,
Can be operated synchronously.

In that case, the control lines connecting each control circuit 5 are for transmitting the output signal of the comparator 7, and not for transmitting the sawtooth wave signal, so each switching regulator section is arranged separately. Even in such a case, the waveform of the sawtooth wave signal in each control circuit 5 will not be distorted, and the timing of the forced discharge of the capacitor 4 will not be shifted due to noise, so the rise of the sawtooth wave signal can be synchronized. , and the switching regulator section 6 can be operated stably and synchronously.

Also, the sawtooth wave signals of the control circuit 5 of the master switching regulator section are compared by comparators corresponding to the slave switching regulator sections, and the output signals of the comparators forcefully close the capacitor 4 of the control circuit 5 of the slave switching regulator section. By discharging, the slave switching regulator section can be operated synchronously with respect to the master switching regulator section.

Furthermore, by forcibly discharging the capacitor 4 of the control circuit 5 of the master switching regulator section at the same time as the capacitor 4 of the control circuit 5 of the slave switching regulator section, the pause period of the sawtooth wave signal can be made zero. Even in the case of synchronous operation, there is no need to narrow the pulse width control range, so there is an advantage that stable synchronous operation is possible.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention, FIG. 2 is a block diagram of essential parts of an embodiment of the present invention, FIG. 3 is an explanatory diagram of the operation of an embodiment of the present invention, and FIG. FIG. 5 is an explanatory diagram of the operation of another embodiment of the present invention. FIG. 6 is a block diagram of the main part of the conventional example. FIG. 7 is a block diagram of the control circuit. and FIG. 9 is a block diagram of essential parts for conventional synchronous operation. 1 is a transformer, 2 is a switching element, 3 is a rectifying and smoothing circuit, 4 is a capacitor, 5 is a control circuit, 6 is a switching regulator section, and 7 is a comparator.

Claims (3)

[Claims] (1), a switching element (2) connected to the primary winding of the transformer (1), a rectifying and smoothing circuit (3) connected to the secondary winding of the transformer (1), and generating a sawtooth wave signal. and a capacitor (4) for switching the switching element (2) using the sawtooth wave signal of the terminal voltage of the capacitor (4).
) and a control circuit (5) for controlling the pulse width of a switching regulator, in which one of the plurality of switching regulator sections (6) is operated as a master, the other is a switching regulator that operates synchronously. is a slave, the level of the sawtooth wave signal in the master switching regulator section is compared with a reference voltage by a comparator (7), and when the level of the sawtooth wave signal exceeds the reference voltage, Comparator (
By the output signal of 7), the capacitor (4) of the slave switching regulator section is forcibly discharged,
A switching regulator characterized in that a sawtooth wave signal in the master switching regulator section and a sawtooth wave signal in the slave switching regulator section are generated in the same phase. (2) The output signal of the comparator (7) causes the capacitor (4) of the master switching regulator section to
2. The switching regulator according to claim 1, wherein the switching regulator is configured to be forcibly discharged at the same time as the capacitor (4) of the slave switching regulator section. (3), connecting a switching element in parallel to the capacitors (4) of the plurality of switching regulator sections;
The switching element is connected to the comparator (7) via a driver.
) The capacitor (4) is forcibly discharged by operating the capacitor (4) with an output signal.
The switching regulator described.