JPH07106063B2 - Switching regulator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a switching regulator for synchronously operating a plurality of switching regulator units.

When a large-capacity stabilized DC power supply is configured or a stabilized DC voltage is applied to a load at a distant position, a configuration is adopted in which a plurality of switching regulator units are controlled to operate in synchronization by pulse width control. When a plurality of such switching regulator units are provided, the input DC power supply and the power supply for operating the control circuit are commonly used.

Also, when a plurality of switching regulator units are provided and the oscillator that generates the sawtooth wave signal for controlling the pulse width of the control circuit of each switching regulator unit is operated asynchronously, multiple types of oscillation frequencies and interference of those frequencies are generated. A wave is generated, and this interference wave is also included in the stabilized DC voltage, and the beat phenomenon of the output ripple voltage and the output noise appears. Normally, it is not desirable for the stabilized DC voltage applied to the load to contain a large number of frequency components, so a configuration is adopted in which the oscillators of each control circuit are operated synchronously so that there is only one type of frequency component. There is.

[Conventional technology]

A conventional switching regulator for synchronously operating a plurality of switching regulator units has, for example, the configuration shown in FIG. 6, in which 41 is a transformer and 42 is a field effect transistor or a bipolar transistor connected to the primary winding of the transformer 41. Switching element, 43 is a rectifying / smoothing circuit including a rectifier and a capacitor, 44 is a control circuit for controlling the pulse width of the switching element 42, 45-1 and 45-2 are switching regulator sections, 46 and 47 are capacitors, and 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 between control circuits.

The switching regulator units 45-1 and 45-2 are transformers.
A switching element 42 connected to the primary winding of 41 is a control circuit.
The pulse width is controlled from 44, the voltage induced in the secondary winding of the transformer 41 is rectified and smoothed by the rectifying / smoothing circuit 43, the DC output voltage is supplied to the load, and this DC output voltage is supplied to the control circuit 44. At this time, the ON period of the switching element 42 is controlled so that the DC output voltage becomes a set value as compared with the reference voltage. Further, each switching regulator unit 45 is connected from a battery or a DC power source 49 that rectifies an AC voltage via capacitors 47 and 46 and an inductance 48.
-Switching element on the primary winding of transformer 41 of 1,45-2
Direct current is supplied via 42.

In such a configuration in which the DC outputs of the switching regulator units 45-1 and 45-2 are paralleled to increase the output capacity, or the DC outputs are respectively supplied to the loads at distant positions,
The terminals CT of the control circuit 44 are connected by a control line 50, and the sawtooth wave signal generated in the control circuit 44 of one switching regulator unit 45-1 is supplied to the control circuit 44 of the other switching regulator unit 45-2. It is supplied to and operated synchronously.

FIG. 7 is a block diagram of the control circuit, 51 is an oscillator, 5
2,53 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, 61,62 is an AND circuit, 63,64 is an output transistor, RT
Is a terminal for connecting a resistor R, CT is a terminal for connecting a capacitor C, DT is a dead time control terminal, + IN and −IN are input terminals for applying a rectified and smoothed output voltage, FB is a feedback terminal, OC is an output control terminal, and C1 , C2, E1 and E2 are output terminals.

This control circuit has a configuration applicable to a two-stone type switching regulator, and may include a reference voltage generating circuit (not shown), etc., and is usually a semiconductor integrated circuit.

The oscillator 51 performs constant current charging of the capacitor C connected to the terminal CT, compares the terminal voltage of the capacitor C with a reference voltage, and when the terminal voltage of the capacitor C exceeds the reference voltage, rapidly discharges the capacitor C. By this, a sawtooth wave signal is generated, and a resistor R connected to the terminal RT
Due to [KΩ] and the capacitor C [μF] connected to the terminal CT, the oscillation frequency f of the oscillator 51 becomes f≈1.2 / (RC) [KHz]. In FIG. 6, only this terminal CT is shown, and the control circuit 44 of one switching regulator unit 45-1 connects the above-mentioned capacitor C to the terminal CT and the other switching regulator unit 45-1. The control circuit 44 of 2 is
Without connecting the capacitor C to the terminal CT, the sawtooth wave signal of the one switching regulator section 45-1 is supplied to the other switching regulator section 45-2 for synchronous operation.

Further, the comparator 53 performs a level comparison between the sawtooth wave signal generated at the terminal CT and the output signals of the error amplifiers 54 and 55, and outputs the output transistors 63 and 64 via the OR circuit 57 and the NOR circuits 58 and 59. It controls the ON period. When the output control terminal OC is set to "0", the output transistors 63 and 64 are turned on at the same time.
When the off operation is performed and the output control terminal OC is set to "1", the output transistors 63 and 64 perform the anti-phase operation corresponding to the inversion operation of the flip-flop 56. In the case of a one-stone switching regulator, output transistors 63,6
Either one of the outputs of 4 will be applied to the switching element 42 directly or via a transformer or the like.

FIG. 8 is a block diagram of a main part for the synchronous operation of the conventional example. The terminals CT of the control circuits 81 and 82 of the switching regulator section are connected by the control line 83 as in the case shown in FIG. Further, the terminal G is connected to the earth line 84, the resistor R is connected to the terminal RT of one control circuit 81, and the capacitor C is formed at the terminal CT, and the terminal voltage of this capacitor C becomes a sawtooth wave signal. This sawtooth wave signal is sent to the other control circuit 82 via the control line 83.
Of the same sawtooth wave signal is used in the control circuits 81 and 82 of one side and the other side to perform the synchronous operation.

Further, FIG. 9 shows one control circuit 81 when the control line 83 is extended or when the frequency of the sawtooth wave signal is increased.
The case where the sawtooth wave signal of the terminal CT of is divided by the resistors r1 and r2 and supplied to the terminal CT of the other control circuit 82 is shown.

[Problems to be solved by the invention]

As shown in FIG. 6 and FIG. 8, when one control circuit 81 and the other control circuit 82 are connected between terminals CT by a control line 83 and the same sawtooth wave signal is used, one and the other When the switching regulator section of
Also becomes correspondingly long, and when the frequency of the sawtooth wave signal is increased, 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 is blunted by the resistance component, inductance component, distributed capacitance component, etc. of the control line 83. However, 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, it becomes difficult to perform synchronous operation.

Further, 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 by the resistors r1 and r2, the sawtooth wave applied to the terminal CT of the other control circuit 82 is divided. It is difficult to sufficiently suppress the waveform rounding of the high frequency sawtooth wave signal as the level of the sawtooth wave signal decreases.

When the voltage of the terminal CT in one of the control circuits 81 reaches a certain value when the inductance and the distributed capacitance of the control line 83 can be ignored, the capacitor C connected to the terminal CT is rapidly discharged. The other control circuit 82 is also configured to perform rapid discharge in the same manner, and when the level of rapid discharge is different or noise is controlled due to variations in the comparison voltage or the characteristics of the circuit components in that case. In the case of being superposed on the line 83, the rapid discharge may be performed at the terminal CT of the other control circuit 82 before the rapid discharge at the terminal CT of the one control circuit 81. Control circuit
There is a drawback that the oscillation frequency of the resistor R and the capacitor C in 81 becomes unstable due to the rapid discharge operation of the other control circuit 82.

The present invention is intended to stably and synchronously operate a plurality of switching regulator units.

[Means for Solving the Problems]

The switching regulator of the present invention will be described with reference to FIG. 1. A switching element 2 connected to a primary winding of a transformer 1, a rectifying / smoothing circuit 3 connected to a secondary winding of the transformer 1, and a sawtooth shape. Switching for synchronously operating a plurality of switching regulator units 6 each having a capacitor 4 for generating a wave signal and a control circuit 5 for controlling a pulse width of a switching element 2 using a sawtooth wave signal of a terminal voltage of the capacitor 4. In the regulator, one of the plurality of switching regulator units is a master and the other is a slave, and the level of the sawtooth wave signal in the master switching regulator unit and the reference voltage are compared by the comparator 7, The slave switching regulator is controlled by the output signal of the comparator 7 when the level of the waveform signal exceeds the reference voltage. Forcibly discharge the capacitor 4 of the in sawtooth signal to the master switching regulator section, it is obtained by a structure for generating and in sawtooth signal to the slave switching regulator section in the same phase.

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.

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.

[Action]

The comparator 7 compares the sawtooth wave signal level of the reference control circuit 5 with the reference voltage, and when the sawtooth wave signal level exceeds the reference voltage, sets the output impedance of the comparator 7 to zero and The capacitor 4 of the control circuit 5 is forcibly discharged, and the rising edge of the sawtooth wave signal of the reference control circuit 5 and the rising edge of the sawtooth wave signal of the other control circuit 5 are synchronized to each other. By making the phase and frequency of the sawtooth wave signal of 1 to be the same, each switching regulator unit 6 can be operated in synchronization.

The sawtooth wave signal of the control circuit 5 of the master switching regulator unit can be used as a reference to synchronize the sawtooth wave signal of the control circuit 5 of the slave switching regulator unit.

Further, the capacitor 4 of the control circuit 5 of the master switching regulator unit is also forcibly discharged simultaneously with the capacitor 4 of the control circuit 5 of the slave switching regulator unit, so that the sawtooth wave signal of the control circuit 5 of the slave switching regulator unit is stopped. The period can be zero.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram of the essential parts of one embodiment of the present invention.
The main part of the synchronous operation of the individual switching regulators is shown. In the figure, 11 to 13 are control circuits corresponding to switching regulators, 14 and 15 are comparators, 16 is a ground line, 17 and 18 are control lines, R1 to R7 are resistors, and C1 to C3 are capacitors. .

Each of the control circuits 11 to 13 has resistors R1 to R3 connected to a terminal RT and capacitors C1 to C3 connected to a terminal CT, and has a configuration capable of independently generating a sawtooth wave signal. One of them is used as a master, and the sawtooth wave signal at the terminal CT of the control circuit 11 of the master switching regulator is added to one terminal of the comparators 14 and 15 and the resistors R4 and R
Comparator 1 uses the reference voltage obtained by dividing + V voltage by 5, R6 and R7.
In addition to the +15 terminals of 4,15, the level of the sawtooth signal is compared with the reference voltage. Further, the frequency of the sawtooth wave signal when independently generated by the control circuit 11 of the master switching regulator unit is more than the frequency of the sawtooth wave signal when independently generated by the control circuits 12 and 13 of the slave switching regulator unit. It should be set slightly higher.

Further, the output terminals of the comparators 14 and 15 are connected to the terminals CT of the control circuits 12 and 13 of the slave switching regulator section, and when the + terminal level of the comparators 14 and 15 is higher than the-terminal level, a high impedance output is produced. On the contrary, when the + terminal level is lower than the-terminal level, the output is low impedance.

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 + terminals of the comparators 14 and 15, the output impedance of each becomes zero, so that the terminals of the control circuits 12 and 13 become zero. The capacitors C2 and C3 connected to CT are
It is forcibly discharged by the comparators 14, 15 via the control lines 17, 18. As a result, a sawtooth wave signal is generated at the terminals C of the control circuits 12 and 13 of the slave switching regulator unit in synchronization with the sawtooth wave signal of the control circuit 11 of the master switching regulator unit, and the control circuits 11 to 13 are provided with the sawtooth wave signal. The pulse width control in will be synchronized.

The control lines 17 and 18 in that case do not perform waveform transmission, but only transmit the high-impedance and low-impedance outputs of the comparators 14 and 15, so that the problem of waveform distortion due to inductance and distributed capacitance is reduced. It can be avoided.

FIG. 3 is a diagram for explaining the operation. (A) shows the waveform of the sawtooth wave signal of the control circuit 11 of the master switching regulator section, and the reference voltage in the comparators 14 and 15 is indicated by Vr.
(B) shows the output signals of the comparators 14 and 15, and (c) shows the sawtooth wave signal of the terminal CT of the control circuits 12 and 13 of the slave switching regulator section.

When the sawtooth wave signal of the control circuit 11 of the master switching regulator unit exceeds the reference voltage Vr, the output signals of the comparators 14 and 15 become low impedance as shown in (b),
Slave switching regulator control circuit 12, 13
The capacitors C2 and C3 are forcedly discharged by the comparators 14 and 15.

When the sawtooth wave signal of the control circuit 11 falls, the comparator
Since the output signals of 14 and 15 have high impedance, constant current charging of the capacitors C1 to C3 of the control circuits 11 to 13 is started at the same time. Therefore, the level of the sawtooth wave signal at the terminals CT of the control circuits 12 and 13 rises as shown by the dotted line when it is not forcibly discharged, but it is forcibly discharged and falls, so the solid line in (c) The waveform becomes as shown in.

In this case, the period in which the level of the sawtooth wave signal of the control circuit 11 is higher than the reference voltage Vr is the rest period t _off of the sawtooth wave signal of the other control circuits 12 and 13.

FIG. 4 is a block diagram of essential parts of another embodiment of the present invention.
Similar to the above-described embodiment, a main part in the case of synchronously operating three switching regulator parts will be shown. In the figure, 21
Reference numeral 23 is a control circuit, 24 is a comparator, 25 is a ground line, 26 is a control line, 27 and 28 are npn and pnp bipolar transistors (hereinafter referred to as transistors) that constitute a driver, 29
˜31 are field effect transistors (hereinafter referred to as transistors) as switching elements connected in parallel to the capacitors C11 to C13, 32 is a reference power source, and R11 to R19 are resistors.

Control circuit 21 for 3 switching regulators
The resistors R11 to R13 are connected between the terminal RT of 23 and the ground line 25, and the capacitor C1 is connected between the terminal CT and the ground line 25.
1 to C13 are connected, and each control circuit 21 to 23 has a structure capable of independently generating a sawtooth wave signal. Transistors 29-31 are connected in parallel with capacitors C11-C13,
Terminal of control circuit 21 of master switching regulator
The CT is connected to the minus terminal of the comparator 24, and the reference power source 32 is connected to the plus terminal of the comparator 24. In this case also, the frequency when the sawtooth wave signal is independently generated in the control circuit 21 of the master switching regulator unit is set to the sawtooth wave signal independently in the control circuits 22 and 23 of the slave switching regulator unit. Is set so as to be slightly higher than the frequency at which is generated.

The output signal of the comparator 24 is applied to the bases of the transistors 27 and 28 which form the driver, and the control line 26 is connected to the commonly connected emitters via the resistor R13.
The gates of the transistors 29 to 31 are connected to the transistors via resistors R15, R17, and R19.

The level of the sawtooth signal at the terminal CT of the control circuit 21 is the reference power supply.
When the reference voltage Vr of 32 is not exceeded, the output signal of the comparator 24 is low level, so the transistor 27 is off, the transistor 28 is on, the control line 26 is low level, and the transistors 29 to 31 are off. Become. Therefore, capacitor C11
~ C13 is charged with a constant current, and its terminal voltage rises linearly. When the level of the sawtooth 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 resistance is
The control line 26 connected via R13 becomes high level,
Transistors 29-31 turn on and capacitors C11-C13
Is forcibly discharged. Therefore, the sawtooth signal is forced to fall.

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

Thus, even if the frequency of the sawtooth signal of each control circuit 21-23 is different, by the comparator 24, to compare the reference voltage Vr and the level of the sawtooth signal of the control circuit 21 of the master switching regulator unit, With the output signal of the comparator 24 shown in (b), the transistors 29 to 31 connected in parallel with the capacitors C11 to C13 are turned on to forcibly discharge the capacitors C11 to C13, and (a), (c), As shown in (d), the sawtooth wave signal can be generated in synchronization.

In this case, it is possible to control each of the transistors 29 to 31 at high speed by using the driver composed of the transistors 27 and 28. Further, the idle period t _off is not generated in the sawtooth wave signals of the control circuits 22 and 23 of the slave switching regulator section.

The input power supply voltage of the switching regulator is usually in the range of ± 10 to 20%, but recently, for example, 16 to 20%.
It may be required to operate with an input power supply voltage in the range of about 4 times, such as 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 the peak of the sawtooth wave signal to the vicinity of the zero level. However, when the pause period t _off of the sawtooth wave signal is long, control during that period becomes impossible, so the range in which the output voltage can be stabilized becomes narrow. For such requirements, is In the embodiment described above, the FIG. 5 (a), (c), as can be seen from the waveform of the sawtooth wave signal (d), the rest period t _off is Since there is almost no state, the pulse width control circuit can be widened and a plurality of switching regulator units can be operated synchronously.

The present invention is not limited to the above-described embodiment, but can be variously modified and added, and it is of course possible to use three or more switching regulator sections which operate in synchronization, and FIG. Also in the embodiment shown in FIG. 7, switching elements such as transistors may be connected in parallel to the capacitors C2 and C3 and controlled by the output signals of the comparators 14 and 15. In this case, the switching element can be controlled via the driver. When using a driver, the comparators 14 and 15 can be shared.

〔The invention's effect〕

As described above, the present invention compares the sawtooth wave signal level with the reference voltage by the comparator 7, and forcibly discharges the capacitor 4 for outputting the sawtooth wave signal by the comparison output. Then, the frequencies of the sawtooth wave signals of the control circuits 5 of the plurality of switching regulator units 6 are made the same,
It can be operated synchronously.

In that case, since the control line connecting each control circuit 5 transmits the output signal of the comparator 7 and does not transmit the sawtooth wave signal, the switching regulator units are arranged apart from each other. Even in this case, the waveform of the sawtooth wave signal in each control circuit 5 is not distorted, and the timing of the forced discharge of the capacitor 4 due to noise is not shifted, so that the rising edge of the sawtooth wave signal is synchronized. Therefore, the switching regulator unit 6 can be stably operated in synchronization.

Further, the sawtooth wave signals of the control circuit 5 of the master switching regulator unit are compared by a comparator corresponding to the slave switching regulator unit, and the output signal of the comparator forces the capacitor 4 of the control circuit 5 of the slave switching regulator unit. By discharging, the slave switching regulator unit can be operated in synchronization with the master switching regulator unit as a reference.

Further, the capacitor 4 of the control circuit 5 of the master switching regulator unit is also forcedly discharged at the same time as the capacitor 4 of the control circuit 5 of the slave switching regulator unit, so that the idle period of the sawtooth wave signal can be made zero. Even in the case of synchronous operation, it is not necessary to narrow the pulse width control range, so there is an advantage that stable synchronous operation is possible.

[Brief description of drawings]

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

Claims (3)

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