JPH0793817B2 - Switching power supply circuit - Google Patents

Description

The present invention relates to a switching operation and a DC output voltage using a DC switching synchronizing pulse transmitted from a control unit in which pulse width modulation is applied by a DC output power supply control signal. The present invention relates to a switching power supply circuit that controls

[Conventional technology]

FIG. 3 is a diagram showing a configuration for controlling a plurality of switching power supply circuits by a control unit. In FIG. 3, 1 is a control unit, 2-1 and 2-2 are synchronous pulse transmission lines, 3-1 and 3-2 are voltage adjustment signal transmission lines, and 4-1 and 4-2 are all switching power supply circuits. Common DC output terminal, 5,6 ... n
Are the first power supply unit, the second power supply unit, ... The nth power supply unit, and correspond to switching power supply circuits, respectively. Reference numerals 11 to 22 denote constituent elements of the first power supply unit 5, 11 is a DC power supply, 12 is a switch element, 13 is a transformer, 14 is a rectifying / smoothing circuit, 15 is a resistance element for varying output voltage, and a fixed resistance 15 -1,15
-3 and variable resistance element 15-2. 16 shows a reference voltage source, showing a voltage V _R. Reference numeral 17 is a changeover switch, 18 is a comparison amplifier, 19 is a synchronizing circuit, 20 is a triangular wave oscillation circuit, 21 is a waveform comparator, and 22 is a drive circuit (drive) for the switch element 12.

The second power supply unit 6 ... The nth power supply unit n have the same configuration as that of the first power supply unit 5, and are commonly controlled by the control unit 1 together with the first power supply unit 5. . The control unit 1 was previously proposed by the inventor of the present application, and produces a synchronizing pulse for DC switching in which pulse width modulation is applied by a DC output voltage control signal. The generation / purification synchronization pulse is sent to the first power supply unit 5 and the second power supply unit 5.
Power unit 6, ... Is transmitted to the nth power unit. Thus, each power supply unit 5, 6, ... N controls the switching operation and the DC output voltage by using the transmitted synchronizing pulse.

The output sides of the first, second ... Nth power supply units 5, 6 ... N are all connected in parallel to loads (not shown) connected to the terminals 4-1 and 4-2. . Therefore, a pair of synchronous pulse transmission lines 2-1 and 2-2 and a pair of voltage adjustment signal transmission lines 3-1 and 3-2 are connected from the control unit 1 to the respective power supply units 5, 6 ... There is. The sync pulse is used to synchronously oscillate the triangular wave oscillation circuit 20 of each power supply unit, and the voltage adjustment signal transmission lines 3-1 and 3-2 adjust the output voltage of each power supply unit in order to balance the output voltage. We use to adjust. If there is a deviation in the oscillation frequency between the power supply units, beats may occur in the output voltage and hunting may occur. Therefore, in the power supply unit, the synchronous pulse transmission lines 2-1, 2-2
The pulse taken in through is shaped by the synchronizing circuit 19, and the triangular wave oscillating circuit 20 starts oscillating the triangular wave at the time of rising of the pulse to raise the triangular waveform. The triangular wave falls when the charge storage means such as a capacitor detects that the charge is sufficiently stored. The waveform comparator 21 compares the output of the comparison amplifier 18 and a triangular waveform, which will be described later, for example, the comparison amplifier only for the time until reaching a predetermined value.
The output of 18 is obtained and the drive circuit 22 is driven. The drive circuit
Since the output of 22 is a signal synchronized with the synchronization pulse, when the switch element 12 is repeatedly turned on and off, a predetermined AC voltage is obtained at the output of the transformer 13. The output of the transformer 13 is converted to a direct current by the rectifying and smoothing circuit 14, and the output terminals 4-1 and 4
-2 is reached and the output voltage V ₀ is obtained.

The comparison amplifier 18 is used to keep the output voltage V ₀ constant. That is, a voltage proportional to the output voltage V ₀ is applied to the resistance element.
Removed from 15, usually compares the voltage V _R of the reference voltage source 16. Since the comparison amplifier 18 is connected to a negative feedback (not shown), the output of the amplifier 18 is obtained so that the voltages at the negative terminal and the positive terminal are equalized, and a feedback amplification operation is performed.
The output of the comparison amplifier 18 is applied to the waveform comparator 21 as described above. Therefore, in order to adjust the output voltage intentionally, the voltage value V _R of the voltage source 16 is changed. It is
When the first, second, ... Nth power supply units 5, 6, ... N are commonly controlled, the voltage adjustment signal transmission line 3-from the control unit 1
This is done by applying a predetermined DC voltage via 1, 3-2 and switching the changeover switch 17 to the voltage adjusting line opposite to that shown in the drawing.

[Problems to be Solved by the Invention]

In the configuration of the prior art shown in FIG. 3, when the output voltage is controlled by the control lines 3-1 and 3-2 for voltage adjustment, the changeover switch 17 needs to be changed each time. When the signal transmission is lost due to the disconnection of the signal transmission line, the operation of the power supply units 5, 6, ... N has stopped.

Also, when a signal obtained by modulating the synchronizing pulse is transmitted from the control device, the signal transmission is similarly lost and the operation is stopped. Therefore, the conventional switching power supply circuit has a high failure rate and low reliability.

An object of the present invention is to provide a switching power supply circuit which solves the above-mentioned drawbacks and can continue to operate as a switching power supply circuit even when there is no transmission signal from the control unit.

[Means for Solving the Problems]

The present invention solves the drawbacks of the conventional switching power supply circuit, and provides a switching power supply circuit made to achieve the above-mentioned object. DC switching obtained by applying pulse width modulation with a DC output voltage control signal Detector for detecting the presence or absence of a transmitted pulse signal in a switching power supply circuit for transmitting a synchronizing pulse for control from a control device and controlling a switching operation and a DC output voltage using the synchronizing pulse, and a transmitted pulse A first switch having one end connected to the output side of a reference voltage generation circuit for extracting a DC output voltage control signal from a signal; a second switch having one end connected to the reference voltage source; the first switch and the second switch; An opening / closing control unit for the switch, and applying the output of the pulse detector to the opening / closing control unit to provide the first switch and the second switch. Exclusive control of opening and closing, and by a signal from either the other end or the other end of the second switch of the first switch and performs the switching operation.

In the above switching power supply circuit of the present invention, a plurality of the switching power supply circuits are connected in parallel to the control unit, and a DC output is applied to a common load, or the pulse detector. The output signal of is connected to an opening / closing control unit for the first switch and the second switch via a signal delay circuit.

[Work]

A switching synchronizing pulse and a DC output voltage control signal are transmitted together from the control unit to the switching power supply circuit, and the signals are separated and used separately. At this time, with the first switch closed, by different signals,
The switching power supply circuit operates in the same manner as the conventional one. In the configuration of the present invention, the pulse detector, the opening / closing control unit that exclusively controls the first switch and the second switch, and the first switch and the second switch are provided in the switching power supply circuit. And detecting output when the pulse transmitted by the pulse detector is exhausted. The detection output operates the opening / closing control unit to close the second switch and complements the DC switching operation with the output from the reference voltage source. Therefore, even if there is no pulse transmitted from the external control device,
It does not stop the operation of the switching power supply circuit.

When the pulse transmitted from the control unit is normal, the pulse is applied to the reference voltage generating circuit to generate a DC output voltage control signal. Then, controlling the output voltage is the same as the conventional one.

Further, by providing a plurality of the above switching power supply circuits of the present invention so as to be connected in parallel to the control unit, each switching power supply circuit can operate even when signal transmission from the control unit is lost. Since the operation can be continued, the reliability is high and a large current or power can be supplied to the common load.

Furthermore, since the output signal of the pulse detector is applied to the other end of the first switch and the second switch via the signal delay circuit, the operation to the element for switching the direct current is controlled. Therefore, when the switch is opened / closed, it is effective when switching to the operation by the reference voltage source because the delay circuit is interposed.

〔Example〕

FIG. 1 is a switching power supply circuit diagram showing an embodiment of the present invention, and more specifically, shows a main part of the present invention incorporated in the switching power supply circuit shown in FIG. Therefore, the same reference numerals as those shown in FIG. 3 are used for the switching power supply circuit except for the portions related to the present invention. That is, in FIG. 1, 2-1 and 2-2 are synchronous pulse transmission lines, 1
2 is a switching element, 13 is a transformer, 18 is a comparison amplifier, 1
9 is a synchronizing circuit, 20 is a triangular wave oscillating circuit, 21 is a PWM comparator as a waveform comparator, 23 is a photocoupler, 24 is a reference voltage generating circuit, 25 is an external control device, that is, it is transmitted from the control unit 1 shown in FIG. Pulse detector for detecting the presence or absence of a pulse, 26 is a terminal for voltage V ₁ as a reference voltage, 27 is connected to the built-in reference voltage source at one end, and is connected to terminal 30 for voltage V ₃ at the other end. The first switch 28 is connected to the output side of the reference voltage generating circuit 24 for extracting the DC output voltage control signal from the transmitted pulse signal, and the other end is connected to the terminal 30 for the voltage V ₃ . 2 switches, 29 is voltage V ₂ terminal, 30 is voltage V ₃ terminal, 31 is an inverter, 32
Indicates a NAND gate, and the inverter 31 and the NAND gate 32 form an opening / closing control unit for the first switch 27 and the second switch 28. Reference numeral 33 denotes a signal delay circuit, and the output signal of the pulse detector 25 is applied to the first switch 27 via the signal delay circuit 33 and the NAND gate 32. Further, the output signal of the pulse detector 25 is applied to the signal delay circuit 33, the NAND gate 32, and the inverter 31 forming the opening / closing control unit.

The control output from the opening / closing control unit of the inverter 32 exclusively controls the first switch 27 and the second switch 28. The operation will be described later in the description of FIG.

The voltage V _{3 at the} terminal 30 is fed to the PWM via the comparator amplifier 18.
The PWM comparator 21 is applied to the comparator 21,
The switching of the switching element 12 is controlled by the same operation as the conventional one.

FIG. 2 is a diagram showing an operation waveform diagram based on the switching power supply circuit of the present invention configured as shown in FIG. The pulse width modulated sync pulse is transmitted from the sync pulse transmission lines 2-1 and 2-2 from an external control device, that is, the control unit 1 in FIG. 3, and the first power source is supplied via the photocoupler 23. It is applied to the unit 5, that is, the switching power supply circuit as shown in FIG. 2A. The rising time of the synchronizing pulse is detected by the synchronizing circuit 19, and the triangular wave oscillating circuit 20 oscillates a triangular wave as shown in FIG. 2B. The synchronizing pulse shown in FIG. 2A is applied to the reference voltage generating circuit 24, and a direct current is taken out by a filter or the like in the circuit,
As shown in FIG. 2C, a direct current having a voltage V ₁ is obtained. The time required for the voltage V ₁ to rise from zero is T ₁ . Further, the value of the voltage V ₁ gradually increases as the duty ratio increases and gradually decreases as the duty ratio decreases since the width of the synchronization pulse is modulated. When the voltage V ₁ is available at the terminal 26 and the second switch 28 is on, the voltage V ₃ becomes equal to V ₁ . The first switch 27 is off at this time. If the second switch 28 is turned off, the first switch 27
Turns on. This on / off is based on the operation of the NAND gate 32 and the inverter 31 of the opening / closing control unit described later. When the first switch 27 is turned on, the voltage V _{2 at the} terminal 29 becomes equal to V ₃ . The voltage V ₂ indicates a value obtained by dividing the voltage V _R of the reference voltage source incorporated in the unit by resistors R ₁ and R ₂ (hereinafter, this voltage V ₂ is referred to as an internal reference voltage). The voltage V ₂ is constant as shown in FIG. 2D. The sync pulse from the photocoupler 23 is also checked in the pulse detector 25 only for its presence. Second when the pulse arrives
As shown in FIG. E, a "H" level signal is output as the value. The output of the pulse detector 25 is divided into two, one of which is immediately applied to one terminal IN ₁ of the NAND gate 32, and the other is applied to the other terminal IN ₂ of the NAND gate 32 through the signal delay circuit 33. The input signal to IN ₂ becomes "H" level after a lapse of time T ₂ as shown in FIG. 2F. Therefore, the output level of the NAND gate 32 is changed to "L" level from "H" level when the elapsed time T _2. (See Figure 2G). Therefore, the first switch 27 to which the output of the NAND gate 32 is applied and the second switch 28 to which it is applied via the inverter 31 are turned on and off in mutually opposite phases (see FIG. 2H). .

The voltage V _{3 at the} terminal 30 is then applied to one terminal of the comparison amplifier 18. At the other terminal of the comparison amplifier 18,
As described in FIG. 3, the output voltage V _{0 is set} to the resistances R ₅ and R ₅ .
_The voltage V ₄ divided by ₆ is applied. The comparison amplifier 18
Since the negative feedback connection is made, the amplifier 18 operates so that the voltage V ₃ = V ₄ . At that time, the comparison circuit 21 operating as a comparator is
The duty ratio for switching 12 is determined. The voltage V ₃ was initially V ₂ as shown in FIG. 2I, but when a synchronization pulse arrives and the on / off of the first switch 27 and the second switch 28 is reversed, for example, the voltage V ₁ is slightly changed. Since it is low, the value is low, and the output voltage shown in FIG. 2I is also the same. Next, since V ₁ is included in the synchronization pulse and gradually rises based on the output voltage adjustment signal, as shown in FIG.
V _OUT also rises.

If the synchronization pulse does not arrive in this state, the output of the pulse detector 25 becomes “L” again, the voltage V ₃ becomes the value of V ₂ , that is, (the reference voltage value), and the output voltage becomes It is stabilized at the voltage determined by V ₂ . The operation is not stopped, which leads to improvement in reliability.

It should be noted that the switching power supply circuit of the present invention can have a plurality of them connected in parallel as in the case of FIG. 3 showing the prior art. At that time, the synchronization pulse is transmitted from the external control device to each power supply circuit through a pair of transmission lines, the switching frequencies are synchronized with each other, the output voltages are made equal to each other, and the output voltage is set to another value. It is extremely easy to make changes to And if at equal voltage V _R of the reference voltage source 24 which is incorporated in the power circuits, is not a deactivation system when the synchronization pulse becomes disconnected. Also, the one with increased DC output for the common load can be taken out.

In the switch power supply circuit of the present invention, by connecting the signal delay circuit 33 to the output side of the pulse detector 25, the voltage V ₁ is generated after T _{1 has} elapsed from the operation of the pulse detector 25. , T ₂ and then applied to the terminal IN ₂ of the NAND gate.
27 and the voltage when the second switch 28 is turned on / off
It is executed after V ₁ is sufficiently stable. Therefore, since the changing voltage is not transmitted to the comparison amplifier 18 as the voltage V ₃ ,
Does not significantly change the output voltage V _OUT when the sync pulse arrives.

〔The invention's effect〕

As described above, according to the switching power supply circuit of the present invention, since it is configured as described above, even if there is no DC output control signal from the outside, it is detected and the operation is continued automatically. Reliability is improved because there is no stoppage of operation as seen in the power supply circuit. Further, when a plurality of the switching power supply circuits of the present invention are connected in parallel, when the sync pulse is cut off, the respective switch power supply circuits can continue to operate and bring about an increase in the current or power taken out. Further, by providing a signal delay circuit between the pulse detector and the switch opening / closing control unit, there is an effect that the output voltage can be stabilized when the synchronization pulse arrives.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a switching power supply circuit according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of FIG. 1, and FIG. 3 is a diagram showing a configuration of a conventional switching power supply circuit. 2-1, 2-2 …… Synchronous pulse transmission line 18 …… Comparison amplifier, 24 …… Reference voltage generation circuit 25 …… Pulse detector, 27 …… First switch 28 …… Second switch, 31 …… Inverter 32 …… Nand Gate

Claims (3)

[Claims] 1. A switching power supply circuit for transmitting a synchronizing pulse for DC switching, which is obtained by applying pulse width modulation with a DC output voltage control signal, from a control device and controlling the switching operation and the DC output voltage using the synchronizing pulse. , A pulse detector for detecting the presence or absence of the transmitted pulse signal, a first switch having one end connected to the output side of a reference voltage generation circuit for extracting a DC output voltage control signal from the transmitted pulse signal, and a reference voltage A first switch and an opening / closing control unit for the first switch and the second switch, and an output of the pulse detector is applied to the opening / closing control unit to output the first switch. Exclusive control of opening and closing of the switch and the second switch, and switching by a signal from either the other end of the first switch or the other end of the second switch Switching power supply circuit and performs work. 2. A plurality of the switching power supply circuits according to claim 1 are provided, are connected in parallel to the control unit, and the DC output of each switching power supply circuit is applied to a common load. Switching power supply circuit. 3. The switching power supply circuit according to claim 1, wherein an output signal of the pulse detector is applied to an opening / closing control section for the first switch and the second switch via a signal delay circuit. .