JP2012019583A - Switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply device that can quickly detect instantaneous interruption of an AC power supply.SOLUTION: The switching power supply device 1A comprises: a main power supply circuit 7; a standby power supply circuit 10A; a main operation control circuit 18 having input terminals 10d and 10e of an main operation control signal Vin that instructs one of main operation mode and standby mode; a primary side rectifying and smoothing circuit 3 that converts AC voltage v1 into primary side DC voltage VC1; an active filter circuit 6 that boosts the primary side DC voltage to predetermined step-up voltage during the main operation mode; an undervoltage detection circuit 13A that compares detection voltage V(+) to reference voltage V(-), the detection voltage V(+) being generated based on DC-converted negative voltage induced on a secondary winding Nb of a standby power supply transformer T2 for the standby power supply circuit, and detects the reduction of the AC voltage by outputting an alarm signal when the detection voltage becomes lower than the reference voltage; and a reference voltage changing circuit 16A, which is connected between the input terminal and the undervoltage detection circuit, for changing the reference voltage according to the instruction of the main operation control signal.

Description

  The present invention relates to a switching power supply device, and in particular, is a dual power supply type switching power supply device including a main power supply circuit that outputs a main power supply voltage and a standby power supply circuit that outputs a standby power supply voltage. The present invention relates to a switching power supply device including a low voltage detection circuit that detects a voltage drop.

2. Description of the Related Art Conventionally, a switching power supply device including a low voltage detection circuit that detects a decrease in AC voltage from an AC power supply is known (see, for example, Patent Document 1).
The low voltage detection circuit (voltage comparison circuit) includes a primary side DC voltage obtained by rectifying and smoothing an AC voltage from an AC power source by a primary side rectification smoothing circuit (input rectification circuit and input smoothing circuit), Compared with the reference voltage, a warning signal is output when the primary side DC voltage becomes smaller than the reference voltage, and a drop in the AC voltage is detected.

  By the way, a switching power supply as shown in the circuit diagram of FIG. 11 is known as an application example in which this low voltage detection circuit is mounted on a dual power supply type switching power supply having a main power supply circuit and a standby power supply circuit. Yes.

  As shown in FIG. 11, the switching power supply device 1Z includes a primary side rectifying / smoothing circuit 3, an active filter circuit 6, a main operation control circuit 18, a main power supply circuit 7, a standby power supply circuit 10Z, a low voltage And a detection circuit 13Z.

  The primary side rectifying / smoothing circuit 3 includes a rectifying unit 4 and a smoothing unit 5, and rectifies and smoothes an AC voltage v <b> 1 from the AC power supply 2 to convert it to a primary DC voltage VC <b> 1. The rectifying unit 4 includes a diode bridge DB. The smoothing unit 5 includes a smoothing capacitor C1.

  The active filter circuit 6 is connected between the rectifying unit 4 and the smoothing unit 5 and includes a coil L1, an active filter switching element (MOSFET) M1, a control IC 1, and a diode D2. The control IC 1 controls the switching operation of the active filter switching element M1 in accordance with a main operation control signal Vin indicating either a main operation mode or a standby mode input to a main operation control circuit 18 described later. In other words, the active filter circuit 6 is inactive in the standby mode and does not boost the primary DC voltage VC1, while it is active in the main operation mode and boosts the primary DC voltage VC1 to a predetermined boost. It is of a boost chopper type that operates to boost the voltage.

  The main operation control circuit 18 is driven by receiving a standby power supply voltage Vs output from a standby power supply circuit 10Z, which will be described later, and receives an input of a main operation control signal Vin indicating either the main operation mode or the standby mode. Terminals 10d and 10e are provided. The main operation control circuit 18 also includes resistors R3 and R4, NPN transistors Q1 and Q2, a photocoupler X1, a drive resistor R1, and a Zener diode D7. When an H level voltage indicating the main operation mode is input as the main operation control signal Vin between the input terminals 10d and 10e, the NPN transistor Q2 is turned on by the voltage divided by the resistors R3 and R4, and the photo The coupler X1 is turned on, the NPN transistor Q1 is turned on by the drive resistor R1, and the stable voltage of the Zener diode D7 is supplied to the control ICs 1 and IC2. Thus, the active filter circuit 6 and a main power supply circuit 7 described later are controlled to be in an operating state by the main operation control circuit 18. On the other hand, when an L level voltage indicating the standby mode is input as the main operation control signal Vin between the input terminals 10d and 10e, the NPN transistor Q2, the photocoupler X1, and the NPN transistor Q1 are turned off, and the control IC 1 IC2 is also turned off. In this way, the active filter circuit 6 and the main power supply circuit 7 described later are controlled to the non-operating state by the main operation control circuit 18.

The main power supply circuit 7 is connected to the subsequent stage of the primary side rectifying and smoothing circuit 3 and includes a main power supply DC-DC converter 8.
The main power supply DC-DC converter 8 includes a main power supply transformer T1 having a primary winding and a secondary winding. One end of the primary winding of the main power transformer T1 is connected to the primary side rectifying / smoothing circuit 3, while the other end of the primary winding of the main power transformer T1 is connected to the main power switching element (MOSFET) M2. It is connected. A control IC 2 is connected to the main power switching element M2. The control IC 2 is driven by the supply of a stable voltage from the Zener diode D7 while the main operation control signal Vin of H level voltage instructing the main operation mode is input between the input terminals 10d and 10e. The switching operation of the main power switching element M2 is controlled. That is, the main power source DC-DC converter 8 is in an operating state in the main mode, and switches the primary side DC voltage VC1 by the main power source switching element M2, and the secondary winding of the main power source transformer T1. The induced switching voltage is rectified and smoothed by the main power supply rectifying / smoothing circuit 9 connected to the secondary winding of the main power supply transformer T1, and converted into a direct current. Vm is output from the output terminals 7a and 7b. Further, the main power DC-DC converter 8 is in a non-operating state in the standby mode.

The standby power supply circuit 10 </ b> Z is connected to the subsequent stage of the primary side rectifying and smoothing circuit 3 independently of the main power supply circuit 7, and includes a standby power supply DC-DC converter 11.
The standby power source DC-DC converter 11 includes a standby power source transformer T2 having a primary winding Na (the number of turns is Na) and a secondary winding Nb (the number of turns is Nb). One end of the primary winding Na of the standby power transformer T2 is connected to the primary side rectifying and smoothing circuit 3, while the other end of the primary winding Na is connected to the standby power switching element (MOSFET) M3. . A control IC 3 is connected to the standby power switching element M3. The control IC 3 is started by supplying the primary side DC voltage VC1 via the start resistor Rin connected to one end of the primary winding Na when the AC power source 2 is turned on, and the standby power source switching element M3. Controls the switching operation. That is, when the AC power supply 2 is turned on, the standby power supply DC-DC converter 11 applies the primary DC voltage VC1 to the standby power supply regardless of the presence or absence of the main operation control signal Vin input to the main operation control circuit 18. Switching element M3, switching voltage Vb = (Nb / Na) × Va proportional to switching voltage Va of primary winding Na is induced in secondary winding Nb, and this induced switching voltage Vb is The standby power supply rectifying and smoothing circuit 12 connected to the secondary winding Nb is rectified and smoothed, and the DC standby power supply voltage Vs is output from the output terminals 10a and 10b. The standby power supply rectifying and smoothing circuit 12 includes a rectifying diode D5 having an anode connected to the negative side of the secondary winding Nb, and a smoothing capacitor C5 connecting the cathode of the diode D5 and the positive side of the secondary winding Nb. It consists of and.

The low voltage detection circuit 13Z is driven by receiving the standby power supply voltage Vs, and is connected to the secondary winding Nb independently of the standby power supply rectifying / smoothing circuit 12; And a comparison circuit 15 connected to the subsequent stage of the negative voltage generating rectifying and smoothing circuit 14.
The negative voltage generating rectifying / smoothing circuit 14 includes a rectifying diode D9 having a cathode connected to the negative side of the secondary winding Nb, and a smoothing capacitor C7 connecting the anode of the diode D9 and the positive side of the secondary winding Nb. It is composed of The negative voltage generating rectifying / smoothing circuit 14 rectifies and smoothes the switching voltage Vb induced in the secondary winding Nb by the standby power supply switching element M3, and converts the switching voltage Vb into a DC negative voltage VC7.
The comparison circuit 15 includes a Zener diode D10, resistors R5 to R8 and R10, and an operational amplifier X2. The anode of the Zener diode D10 is connected to the output terminal 10b and the input terminal 10e of the main operation control circuit 18. On the other hand, the cathode of the Zener diode D10 is connected to the negative voltage generating rectifying / smoothing circuit 14 via the resistors R5 and R10, connected to the output terminal 10b and the input terminal 10e via the resistor R6, and further connected via the resistor R7. It is connected to the operational amplifier X2.
Resistors R7 and R8 are connected to the (+) side input terminal of the operational amplifier X2, and a stable voltage VD10 of the Zener diode D10 as shown in the following equation (1) is divided by the resistors R7 and R8. The reference voltage V (+) is input.

  On the other hand, resistors R5 and R10 are connected to the (−) side input terminal of the operational amplifier X2, and the voltage difference between the negative voltage VC7 and the stable voltage VD10 of the Zener diode D10 as shown in the following equation (2). A detection voltage V (−) obtained by dividing (VD10 − (− VC7)) by the resistors R5 and R10 is input.

The operational amplifier X2 compares the detection voltage V (−) with the reference voltage V (+), and when the detection voltage V (−) becomes smaller than the reference voltage V (+), the output terminal of the operational amplifier X2 While an alarm signal of H level is output from 10c, an alarm signal of L level is output from the output terminal 10c when the detected voltage V (−) becomes equal to or higher than the reference voltage V (+).
The magnitude of the reference voltage V (+) is generally determined such that an H level warning signal is output from the output terminal 10c of the operational amplifier X2 when the primary side DC voltage VC1 becomes a predetermined voltage (for example, 100V). Is done.

  Next, the operation of the switching power supply device 1Z will be described in detail, particularly focusing on the operation of the low voltage detection circuit 13Z.

  FIG. 12 is a graph for explaining the circuit operation of the switching power supply device 1Z in the standby mode (when the main operation control signal Vin is at the L level voltage). FIG. 13 is a diagram for explaining the circuit operation of the switching power supply device 1Z when the standby mode is shifted to the main operation mode (when the main operation control signal Vin is shifted from the L level voltage to the H level voltage). It is a graph.

First, as shown in FIGS. 12A and 12C, after the AC voltage v1 (referred to as AC100V) from the AC power source 2 is turned on (see time t1 in FIG. 12), the diode bridge DB, the coil L1, and the diode The primary side DC voltage VC1 rises to about 125 to 130V via D2 and the smoothing capacitor C1. Then, the control IC 3 is activated via the activation resistor Rin, and the standby power supply voltage Vs voltage-converted by the standby power supply DC-DC converter 11 is output between the output terminals 10a and 10b. Further, as shown in FIG. 12D, a negative voltage VC7 converted into a direct current by the negative voltage generating rectifying / smoothing circuit 14 is output to the anode side of the rectifying diode D9.
Since the main operation control signal Vin is the L level voltage (0 V) after the AC voltage v1 is turned on, the NPN transistor Q2, the photocoupler X1, the NPN transistor Q1, the control ICs 1 and IC2 are turned off, and the active filter circuit 6 and All the main power supply circuits 7 are in a non-operating state.
In addition, after the AC voltage v1 is turned on, as shown in FIG. 12E, the reference voltage V (+) shown in the above equation (1) is input to the (+) side input terminal of the operational amplifier X2. The detection voltage V (−) shown in the above equation (2) is input to the (−) side input terminal of the operational amplifier X2. After the application of the AC voltage v1, the primary side DC voltage VC1 rises to about 125 to 130V, and the detection voltage V (−) falls as the primary side DC voltage VC1 rises. When the detection voltage V (−) becomes smaller than the reference voltage V (+) (see time t2 in FIG. 12), the output terminal 10c of the operational amplifier X2 is switched to H as shown in FIG. A level warning signal is output. Further, when the AC voltage v1 is momentarily cut off (hereinafter referred to as “instantaneous interruption”) (see time t3 in FIG. 12), the primary DC voltage VC1 that has been about 125 to 130 V drops to 0 V. The switching voltage Vb induced in the secondary winding Nb falls to 0V, and the negative voltage VC7 approaches 0V. Then, as shown in FIG. 12E, the detection voltage V (−) increases as the primary DC voltage VC1 decreases, and the detection voltage V (−) becomes equal to or higher than the reference voltage V (+). When this occurs (see time t4 in FIG. 12), as shown in FIG. 12F, an L level warning signal is output from the output terminal 10c of the operational amplifier X2. The detection voltage V (−) eventually rises to the detection voltage V (−) shown in the following equation (3) where VC7 = 0 in the above equation (2).

  As described above, in the low voltage detection circuit 13Z of the switching power supply device 1Z, in the standby mode, an L level warning signal is output after the time ts = (t4−t3) has elapsed since the AC voltage v1 was momentarily interrupted. Is done.

  Next, as shown in FIGS. 13A and 13C, after the AC voltage v1 is input (see time t5 in FIG. 13), the primary DC voltage VC1 rises to about 125 to 130V. The standby power supply voltage Vs is output between the output terminals 10a and 10b. Further, as shown in FIG. 13D, a negative voltage VC7 is output to the anode side of the rectifier diode D9. Further, as shown in FIG. 13E, the reference voltage V (+) shown in the above equation (1) is inputted to the (+) side input terminal of the operational amplifier X2, while the (−) of the operational amplifier X2 is used. The detection voltage V (−) represented by the above equation (2) is input to the side input terminal. At this time, the detection voltage V (−) decreases as the primary DC voltage VC1 increases. Then, when the detection voltage V (−) becomes smaller than the reference voltage V (+) (see time t6 in FIG. 13), as shown in FIG. A level warning signal is output.

  Then, when the AC voltage v1 is turned on and the H level voltage Vin indicating the main operation mode as shown in FIG. 13B is further input between the input terminals 10d and 10e (FIG. 13). At time t7), the NPN transistor Q2, the photocoupler X1 and the NPN transistor Q1 are turned on, the stable voltage of the Zener diode D7 is supplied to the control IC1 and IC2, and both the active filter circuit 6 and the main power supply circuit 7 are operated. It becomes a state. Thus, by the switching operation of the active filter switching element M1, the primary side DC voltage VC1 of about 125 V to 130 V rises to about 390 to 400 V, which is a predetermined boosted voltage (see times t7 to t10 in FIG. 13). The main power supply voltage Vm converted by the main power supply DC-DC converter 8 is output between the output terminals 7a and 7b of the main power supply circuit 7 by the switching operation of the main power supply switching element M2. Further, the standby power supply voltage Vs is output between the output terminals 10a and 10b of the standby power supply circuit 10Z. Furthermore, as shown in FIG. 13D, a negative voltage VC7 having a larger absolute value than that in the standby mode is output to the anode side of the rectifier diode D9 (see times t7 to t10 in FIG. 13).

Finally, when the AC voltage v1 is momentarily interrupted in the main operation mode (see time t10 in FIG. 13), the primary side DC voltage VC1 of about 390 to 400V is lowered to 0V and the secondary winding Nb The switching voltage Vb induced by the voltage drops to 0V, and the negative voltage VC7 approaches 0V (see times t10 to t12 in FIG. 13). Then, as shown in FIG. 13E, the detection voltage V (−) increases as the primary DC voltage VC1 decreases, and the detection voltage V (−) is equal to or higher than the reference voltage V (+). When this occurs (see time t12 in FIG. 13), an L level warning signal is output from the output terminal 10c of the operational amplifier X2, as shown in FIG. 13 (F). The detection voltage V (−) finally rises to the detection voltage V (−) shown in the above equation (3).
As described above, in the low voltage detection circuit 13Z of the switching power supply device 1Z, in the main operation mode, the L level warning signal is output after the time tx = (t12−t10) has elapsed since the AC voltage v1 was momentarily interrupted. Is output.

Japanese Patent Laid-Open No. 5-60804

  However, in this switching power supply apparatus 1Z, as can be seen by comparing the time ts in FIG. 12 and the time tx in FIG. The time until the signal is output (hereinafter referred to as “instantaneous interruption detection time”) is greatly different. That is, in the main operation mode, since the primary side DC voltage VC1 is boosted more greatly by the operation of the active filter circuit than in the standby mode, the instantaneous interruption detection time of the AC power supply becomes longer. For this reason, there has been a problem that it is impossible to quickly detect an instantaneous interruption of the AC power supply in the main operation mode.

  The present invention has been made in view of the above circumstances, and provides a switching power supply device capable of quickly detecting an instantaneous interruption of an AC power supply.

In order to solve the above problems, the present invention provides a main power supply circuit that outputs a main power supply voltage, a standby power supply circuit that outputs a standby power supply voltage, and a main operation control signal that indicates one of a main operation mode and a standby mode. A main operation control circuit for outputting the main power supply voltage from the main power supply circuit when the main operation control signal for instructing the main operation mode is input to the input terminal; and an AC power supply A primary-side rectifying / smoothing circuit that rectifies and smoothes the AC voltage from the output to convert it to a primary-side DC voltage, an active filter circuit that boosts the primary-side DC voltage to a predetermined boosted voltage in the main operation mode, A low voltage detection circuit for detecting a drop in the AC voltage, wherein the main power supply circuit switches the boosted voltage by a main power supply switching element. The switching voltage induced in the secondary winding of the main power transformer is converted into a direct current and output as the main power supply voltage. The standby power supply circuit is activated by the supply of the primary DC voltage. The primary side DC voltage is switched by a standby power source switching element, the switching voltage induced in the secondary winding of the standby power source transformer is converted into a direct current and output as a standby power source voltage, and the low voltage detection circuit is A detection voltage generated based on a negative voltage obtained by converting the switching voltage induced in the secondary winding of the standby power transformer into a direct current is compared with a reference voltage, and the detection voltage becomes smaller than the reference voltage. In a switching power supply device that outputs a warning signal and detects a decrease in the AC voltage when connected, it is connected between the input terminal and the low voltage detection circuit. In accordance with an instruction of the main operation control signal inputted to the input terminal is obtained by a switching power supply device and further comprising a reference voltage changing circuit which changes the reference voltage.
According to this configuration, the reference voltage changing circuit has two types of reference different from each other in both modes as the reference voltage of the low voltage detection circuit according to the main operation control signal instructing either the main operation mode or the standby mode. It is configured to generate a voltage. Accordingly, in each of these modes, as in the conventional switching power supply device, the detection voltage generated based on the negative voltage is compared with only one type of reference voltage in each mode. It is possible to eliminate the difference in the detection time of the AC voltage drop.

In the above configuration, the reference voltage changing circuit changes the reference voltage to the first reference voltage when the main operation control signal instructing the standby mode is input to the input terminal, and sets the main operation mode. When the main operation control signal to be instructed is input to the input terminal, the reference voltage is preferably changed to a second reference voltage smaller than the first reference voltage.
According to this configuration, the reference voltage changing circuit changes the reference voltage of the low voltage detection circuit to the first reference voltage in accordance with the main operation control signal instructing the standby mode, and decreases in accordance with the main operation control signal instructing the main operation mode. The reference voltage of the voltage detection circuit is configured to be changed to a second reference voltage that is smaller than the first reference voltage. Therefore, it is possible to shorten the detection time of the decrease in AC voltage, which is longer due to the boosting operation of the active filter circuit in the main operation mode as in the conventional switching power supply device.

In the above configuration, the reference voltage changing circuit further includes a time constant circuit, and the time constant circuit is configured to pass a predetermined period after the main operation control signal instructing the main operation mode is input to the input terminal. It is preferable that the first reference voltage is changed to the second reference voltage.
According to this configuration, the reference voltage changing circuit changes the reference voltage of the low voltage detection circuit to the first reference voltage in accordance with the main operation control signal instructing the standby mode, and in accordance with the main operation control signal instructing the main operation mode. After the elapse of a predetermined period determined by the time constant circuit, the reference voltage of the low voltage detection circuit is changed to a second reference voltage smaller than the first reference voltage. Therefore, in addition to the above effect, it is useful in that the change timing of the second reference voltage can be controlled by the time constant circuit.

  In the above configuration, the predetermined period is longer than a period from when the main operation control signal instructing the main operation mode is input to the input terminal until the primary side DC voltage is boosted to the boost voltage. Preferably there is.

In order to solve the above problems, the present invention provides a main power supply circuit that outputs a main power supply voltage, a standby power supply circuit that outputs a standby power supply voltage, and a main operation control signal that indicates one of a main operation mode and a standby mode. A main operation control circuit for outputting the main power supply voltage from the main power supply circuit when the main operation control signal for instructing the main operation mode is input to the input terminal; and an AC power supply A primary-side rectifying / smoothing circuit that rectifies and smoothes the AC voltage from the output to convert it to a primary-side DC voltage, an active filter circuit that boosts the primary-side DC voltage to a predetermined boosted voltage in the main operation mode, A low voltage detection circuit for detecting a drop in the AC voltage, wherein the main power supply circuit switches the boosted voltage by a main power supply switching element. The switching voltage induced in the secondary winding of the main power transformer is converted into a direct current and output as the main power supply voltage. The standby power supply circuit is activated by the supply of the primary DC voltage. The primary side DC voltage is switched by a standby power source switching element, the switching voltage induced in the first secondary winding of the standby power source transformer is converted into a direct current and output as a standby power source voltage, and the low voltage detection is performed. The circuit includes a detection voltage generated based on a positive voltage obtained by converting a switching voltage induced in a second secondary winding provided separately from the first secondary winding in the standby power transformer into a direct current. And a reference voltage and a switching power supply device that outputs a warning signal when the detected voltage becomes larger than the reference voltage and detects a decrease in the AC voltage And a reference voltage changing circuit that is connected between the input terminal and the low voltage detection circuit and changes the reference voltage in response to an instruction of the main operation control signal input to the input terminal. A switching power supply device characterized by the above.
According to this configuration, the reference voltage changing circuit has two types of reference different from each other in both modes as the reference voltage of the low voltage detection circuit according to the main operation control signal instructing either the main operation mode or the standby mode. It is configured to generate a voltage. Therefore, in each of these modes, as in a conventional switching power supply device, the detection voltage generated based on the positive voltage is compared with only one type of reference voltage in each mode. It is possible to eliminate the difference in the detection time of the AC voltage drop.

In the above configuration, the reference voltage changing circuit changes the reference voltage to the first reference voltage when the main operation control signal instructing the standby mode is input to the input terminal, and sets the main operation mode. When the main operation control signal to be instructed is input to the input terminal, the reference voltage is preferably changed to a second reference voltage larger than the first reference voltage.
According to this configuration, the reference voltage changing circuit changes the reference voltage of the low voltage detection circuit to the first reference voltage in accordance with the main operation control signal instructing the standby mode, and decreases in accordance with the main operation control signal instructing the main operation mode. The reference voltage of the voltage detection circuit is configured to be changed to a second reference voltage larger than the first reference voltage. Therefore, it is possible to shorten the detection time of the decrease in AC voltage, which is longer due to the boosting operation of the active filter circuit in the main operation mode as in the conventional switching power supply device.

In the above configuration, the reference voltage changing circuit further includes a time constant circuit, and the time constant circuit is configured to pass a predetermined period after the main operation control signal instructing the main operation mode is input to the input terminal. It is preferable that the first reference voltage is changed to the second reference voltage.
According to this configuration, the reference voltage changing circuit changes the reference voltage of the low voltage detection circuit to the first reference voltage in accordance with the main operation control signal instructing the standby mode, and in accordance with the main operation control signal instructing the main operation mode. After a predetermined period determined by the time constant circuit, the reference voltage of the low voltage detection circuit is changed to a second reference voltage larger than the first reference voltage. Therefore, in addition to the above effect, it is useful in that the change timing of the second reference voltage can be controlled by the time constant circuit.

  In the above configuration, the predetermined period is longer than a period from when the main operation control signal instructing the main operation mode is input to the input terminal until the primary side DC voltage is boosted to the boost voltage. Preferably there is.

  ADVANTAGE OF THE INVENTION According to this invention, the switching power supply device which can detect the instantaneous interruption of an alternating current power supply quickly can be provided.

1 is a circuit diagram of a switching power supply device according to a first embodiment of the present invention. 3 is a graph for explaining circuit operation in a standby mode of the switching power supply device of FIG. 1. 2 is a graph for explaining circuit operation when the switching power supply device of FIG. 1 is shifted from a standby mode to a main operation mode. It is a circuit diagram of the switching power supply device by 2nd Example of this invention. 6 is a graph for explaining a circuit operation when the switching power supply device of FIG. 4 shifts from a standby mode to a main operation mode. It is a circuit diagram of the switching power supply device by 3rd Example of this invention. It is a graph for demonstrating the circuit operation | movement at the time of standby mode of the switching power supply device of FIG. 7 is a graph for explaining the circuit operation of the switching power supply device of FIG. 6 when transitioning from a standby mode to a main operation mode. It is a circuit diagram of the switching power supply device by 4th Example of this invention. 10 is a graph for explaining the circuit operation of the switching power supply device of FIG. 9 when transitioning from the standby mode to the main operation mode. It is a circuit diagram of the conventional switching power supply device. 12 is a graph for explaining the circuit operation of the switching power supply device of FIG. 11 in a standby mode. 12 is a graph for explaining the circuit operation of the switching power supply device of FIG. 11 when transitioning from the standby mode to the main operation mode.

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

(First embodiment)
FIG. 1 is a circuit diagram of a switching power supply apparatus according to a first embodiment of the present invention.
As shown in FIG. 1, the switching power supply device 1A includes a primary side rectifying / smoothing circuit 3, an active filter circuit 6, a main operation control circuit 18, a main power supply circuit 7, a standby power supply circuit 10A, a low voltage A detection circuit 13A and a reference voltage changing circuit 16A are provided.

  The primary side rectifying / smoothing circuit 3 includes a rectifying unit 4 and a smoothing unit 5, and rectifies and smoothes an AC voltage v <b> 1 from the AC power supply 2 to convert it to a primary DC voltage VC <b> 1. The rectifying unit 4 includes a diode bridge DB. The smoothing unit 5 includes a smoothing capacitor C1.

  The active filter circuit 6 is connected between the rectifying unit 4 and the smoothing unit 5 and includes a coil L1, an active filter switching element (MOSFET) M1, a control IC 1, and a diode D2. The control IC 1 controls the switching operation of the active filter switching element M1 in accordance with a main operation control signal Vin indicating either a main operation mode or a standby mode input to a main operation control circuit 18 described later. In other words, the active filter circuit 6 is inactive in the standby mode and does not boost the primary DC voltage VC1, while it is active in the main operation mode and boosts the primary DC voltage VC1 to a predetermined boost. It is of a boost chopper type that operates to boost the voltage.

  The main operation control circuit 18 is driven by receiving a standby power supply voltage Vs output from a standby power supply circuit 10A, which will be described later, and receives an input of a main operation control signal Vin indicating either the main operation mode or the standby mode. Terminals 10d and 10e are provided. The main operation control circuit 18 also includes resistors R3 and R4, NPN transistors Q1 and Q2, a photocoupler X1, a drive resistor R1, and a Zener diode D7. When an H level voltage indicating the main operation mode is input as the main operation control signal Vin between the input terminals 10d and 10e, the NPN transistor Q2 is turned on by the voltage divided by the resistors R3 and R4, and the photo The coupler X1 is turned on, the NPN transistor Q1 is turned on by the drive resistor R1, and the stable voltage of the Zener diode D7 is supplied to the control ICs 1 and IC2. Thus, the active filter circuit 6 and a main power supply circuit 7 described later are controlled to be in an operating state by the main operation control circuit 18. On the other hand, when an L level voltage indicating the standby mode is input as the main operation control signal Vin between the input terminals 10d and 10e, the NPN transistor Q2, the photocoupler X1, and the NPN transistor Q1 are turned off, and the control IC 1 IC2 is also turned off. In this way, the active filter circuit 6 and the main power supply circuit 7 described later are controlled to the non-operating state by the main operation control circuit 18.

The main power supply circuit 7 is connected to the subsequent stage of the primary side rectifying and smoothing circuit 3 and includes a main power supply DC-DC converter 8.
The main power supply DC-DC converter 8 includes a main power supply transformer T1 having a primary winding and a secondary winding. One end of the primary winding of the main power transformer T1 is connected to the primary side rectifying / smoothing circuit 3, while the other end of the primary winding of the main power transformer T1 is connected to the main power switching element (MOSFET) M2. It is connected. A control IC 2 is connected to the main power switching element M2. The control IC 2 is driven by the supply of a stable voltage from the Zener diode D7 while the main operation control signal Vin of H level voltage instructing the main operation mode is input between the input terminals 10d and 10e. The switching operation of the main power switching element M2 is controlled. That is, the main power source DC-DC converter 8 is in an operating state in the main mode, and switches the primary side DC voltage VC1 by the main power source switching element M2, and the secondary winding of the main power source transformer T1. The induced switching voltage is rectified and smoothed by the main power supply rectifying and smoothing circuit 9 connected to the secondary winding of the main power supply transformer T1, and the DC main power supply voltage Vm is induced. Are output from the output terminals 7a and 7b. Further, the main power DC-DC converter 8 is in a non-operating state in the standby mode.

The standby power supply circuit 10 </ b> A is connected to the subsequent stage of the primary side rectifying and smoothing circuit 3 independently of the main power supply circuit 7, and includes a standby power supply DC-DC converter 11.
The standby power source DC-DC converter 11 includes a standby power source transformer T2 having a primary winding Na (the number of turns is Na) and a secondary winding Nb (the number of turns is Nb). One end of the primary winding Na of the standby power transformer T2 is connected to the primary side rectifying and smoothing circuit 3, while the other end of the primary winding Na is connected to the standby power switching element (MOSFET) M3. . A control IC 3 is connected to the standby power switching element M3. The control IC 3 is started by supplying the primary side DC voltage VC1 via the start resistor Rin connected to one end of the primary winding Na when the AC power source 2 is turned on, and the standby power source switching element M3. Controls the switching operation. That is, when the AC power supply 2 is turned on, the standby power supply DC-DC converter 11 applies the primary DC voltage VC1 to the standby power supply regardless of the presence or absence of the main operation control signal Vin input to the main operation control circuit 18. Switching element M3, switching voltage Vb = (Nb / Na) × Va proportional to switching voltage Va of primary winding Na is induced in secondary winding Nb, and this induced switching voltage Vb is The standby power supply rectifying and smoothing circuit 12 connected to the secondary winding Nb is rectified and smoothed, and the DC standby power supply voltage Vs is output from the output terminals 10a and 10b. The standby power supply rectifying and smoothing circuit 12 includes a rectifying diode D5 having an anode connected to the negative side of the secondary winding Nb, and a smoothing capacitor C5 connecting the cathode of the diode D5 and the positive side of the secondary winding Nb. It consists of and.

The low voltage detection circuit 13A is driven by receiving the standby power supply voltage Vs, and is connected to the secondary winding Nb independently of the standby power supply rectifying / smoothing circuit 12; And a comparison circuit 15 connected to the subsequent stage of the negative voltage generating rectifying and smoothing circuit 14.
The negative voltage generating rectifying / smoothing circuit 14 includes a rectifying diode D9 having a cathode connected to the negative side of the secondary winding Nb, and a smoothing capacitor C7 connecting the anode of the diode D9 and the positive side of the secondary winding Nb. It is composed of The negative voltage generating rectifying / smoothing circuit 14 rectifies and smoothes the switching voltage Vb induced in the secondary winding Nb by the standby power supply switching element M3, and converts the switching voltage Vb into a DC negative voltage VC7.
The comparison circuit 15 includes a Zener diode D10, resistors R5 to R8 and R10, and an operational amplifier X2. The anode of the Zener diode D10 is connected to the output terminal 10b and the input terminal 10e of the main operation control circuit 18. On the other hand, the cathode of the Zener diode D10 is connected to the negative voltage generating rectifying / smoothing circuit 14 via the resistors R5 and R10, connected to the output terminal 10b and the input terminal 10e via the resistor R6, and further connected via the resistor R7. It is connected to the operational amplifier X2.
Resistors R7, R8, and R9 are connected to the (+) side input terminal of the operational amplifier X2. On the other hand, resistors R5 and R10 are connected to the (−) side input terminal of the operational amplifier X2. The operational amplifier X2 compares the detection voltage V (−) with the reference voltage V (+), and when the detection voltage V (−) becomes smaller than the reference voltage V (+), the output terminal 10c of the operational amplifier X2 H level warning signal is output from the output terminal 10c, while L level warning signal is output from the output terminal 10c when the detected voltage V (-) becomes equal to or higher than the reference voltage V (+). Note that the voltage difference (VD10 − (− VC7)) between the negative voltage VC7 and the stable voltage VD10 of the Zener diode D10 as shown in the above equation (2) is applied to the (−) side input terminal of the operational amplifier X2. The detection voltage V (−) divided by the resistors R5 and R10 is input. Note that a first reference voltage Vα or a second reference voltage Vβ described later is input to the (+) side input terminal of the operational amplifier X2.

The reference voltage changing circuit 16A is connected between the input terminals 10d and 10e and the low voltage detection circuit 13A, and in response to an instruction of the main operation control signal Vin input to the input terminals 10d and 10e, the low voltage detection circuit 13A. The reference voltage is changed.
In this embodiment, the reference voltage changing circuit 16A is composed of resistors R9, R11 to R14 and NPN transistors Q3 to Q5. As described later, the reference voltage changing circuit 16A changes the reference voltage to the first reference voltage Vα when the main operation control signal Vin of L level voltage instructing the standby mode is input between the input terminals 10d and 10e. When the main operation control signal Vin having the H level voltage for instructing the main operation mode is input between the input terminals 10d and 10e, the reference voltage is changed to the second reference voltage Vβ smaller than the first reference voltage Vα. It is supposed to change.

  Next, the operation of the switching power supply device 1A will be described in detail with particular focus on the operations of the low voltage detection circuit 13A and the reference voltage change circuit 16A.

  FIG. 2 is a graph for explaining the circuit operation of the switching power supply apparatus 1A in the standby mode. FIG. 3 is a graph for explaining the circuit operation of the switching power supply device 1A when the standby mode is shifted to the main operation mode.

First, as shown in FIGS. 2A and 2C, after the AC voltage v1 (referred to as AC100V) from the AC power supply 2 is turned on (see time t1 in FIG. 2), the diode bridge DB, the coil L1, and the diode The primary side DC voltage VC1 rises to about 125 to 130V via D2 and the smoothing capacitor C1. Then, the control IC 3 is activated via the activation resistor Rin, and the standby power supply voltage Vs voltage-converted by the standby power supply DC-DC converter 11 is output between the output terminals 10a and 10b. Further, as shown in FIG. 2D, a negative voltage VC7 converted into a direct current by the negative voltage generating rectifying / smoothing circuit 14 is output to the anode side of the rectifying diode D9.
Since the main operation control signal Vin is the L level voltage (0 V) after the AC voltage v1 is turned on, both the active filter circuit 6 and the main power supply circuit 7 are deactivated, and the NPN transistor Q3 is turned off. Since the transistor Q4 is turned on and the NPN transistor Q5 is turned off, both ends of the resistor R9 are not short-circuited. Therefore, at this time, as shown in FIG. 2E, the stable voltage VD10 of the Zener diode D10 as shown in the following equation (4) is applied to the (+) side input terminal of the operational amplifier X2 by the resistor R7, The first reference voltage V (+) = Vα divided by R8 and R9 is input.

  On the other hand, as shown in FIG. 2E, the voltage difference between the negative voltage VC7 and the stable voltage VD10 of the Zener diode D10 as shown in the following equation (5) is applied to the (−) side input terminal of the operational amplifier X2. A detection voltage V (−) obtained by dividing (VD10 − (− VC7)) by the resistors R5 and R10 is input.

  After the application of the AC voltage v1, the primary side DC voltage VC1 rises to about 125 to 130V, and the detection voltage V (−) falls as the primary side DC voltage VC1 rises. When the detection voltage V (−) becomes smaller than the reference voltage V (+) (see time t2 in FIG. 2), as shown in FIG. 2 (F), the output terminal 10c of the operational amplifier X2 outputs H A level warning signal is output. Further, when the AC voltage v1 is momentarily interrupted in the standby mode (see time t3 in FIG. 2), the primary side DC voltage VC1 that has been about 125 to 130 V is lowered to 0 V, and the secondary winding Nb. The switching voltage Vb induced by the voltage drops to 0V, and the negative voltage VC7 approaches 0V. Then, as shown in FIG. 2 (E), the detection voltage V (−) increases as the primary DC voltage VC1 decreases, and the detection voltage V (−) becomes equal to or higher than the reference voltage V (+). 2 (see time t4 in FIG. 2), an L level warning signal is output from the output terminal 10c of the operational amplifier X2, as shown in FIG. 2 (F). The detection voltage V (−) finally rises to the detection voltage V (−) shown in the following equation (6) where VC7 = 0 in the above equation (5).

  As described above, in the low voltage detection circuit 13A of the switching power supply apparatus 1A, in the standby mode, an L level warning signal is output after the time ts = (t4−t3) has elapsed since the AC voltage v1 was momentarily interrupted. Is done.

  Next, as shown in FIGS. 3A and 3C, in the standby mode after the AC voltage v1 is applied (see time t5 in FIG. 3), the primary side DC voltage VC1 is about 125 to 130V. To rise. The standby power supply voltage Vs is output between the output terminals 10a and 10b. Further, as shown in FIG. 3D, a negative voltage VC7 is output to the anode side of the rectifier diode D9. Further, in this standby mode, the main operation control signal Vin is the L level voltage (0 V), so that the active filter circuit 6 and the main power supply circuit 7 are not operated, and the NPN of the reference voltage changing circuit 16A. Since the transistor Q3 is turned off, the NPN transistor Q4 is turned on, and the NPN transistor Q5 is turned off, both ends of the resistor R9 are not short-circuited. Therefore, at this time, as shown in FIG. 3E, the stable voltage VD10 of the Zener diode D10 as shown in the above equation (4) is applied to the (+) side input terminal of the operational amplifier X2. , R8 and R9, the first reference voltage V (+) = Vα is input. On the other hand, the detection voltage V (−) represented by the above equation (5) is input to the (−) side input terminal of the operational amplifier X2. Then, the detection voltage V (−) decreases as the primary side DC voltage VC1 increases. When the detection voltage V (−) becomes smaller than the first reference voltage V (+) = Vα (see time t6 in FIG. 3), as shown in FIG. An H level warning signal is output from the output terminal 10c.

  Then, when the AC voltage v1 is turned on and an H level voltage Vin indicating the main operation mode as shown in FIG. 3B is input between the input terminals 10d and 10e (FIG. 3). At time t7), the NPN transistor Q2, the photocoupler X1 and the NPN transistor Q1 are turned on, the stable voltage of the Zener diode D7 is supplied to the control IC1 and IC2, and both the active filter circuit 6 and the main power supply circuit 7 are operated. It becomes a state. Thus, the switching operation of the active filter switching element M1 increases the primary DC voltage VC1 of about 125V to 130V to the predetermined boosted voltage of about 390 to 400V (see times t7 to t10 in FIG. 3). The main power supply voltage Vm converted by the main power supply DC-DC converter 8 is output between the output terminals 7a and 7b of the main power supply circuit 7 by the switching operation of the main power supply switching element M2. Further, the standby power supply voltage Vs is output between the output terminals 10a and 10b of the standby power supply circuit 10A. Further, as shown in FIG. 3D, a negative voltage VC7 having a larger absolute value than that in the standby mode is output to the anode side of the rectifier diode D9 (see times t7 to t10 in FIG. 3). When the main operation mode is entered, the high-level main operation control signal Vin turns on the NPN transistor Q3 of the reference voltage changing circuit 16A, turns off the NPN transistor Q4, turns on the NPN transistor Q5, and turns on the resistor R9. Are short-circuited (see time t7 in FIG. 3). At this time, as shown in FIG. 3E, a stable voltage VD10 of the Zener diode D10 as shown in the following equation (7) is applied to the (+) side input terminal of the operational amplifier X2 by resistors R7 and R8. The divided second reference voltage V (+) = Vβ is input.

  Therefore, immediately after the main operation control signal Vin instructing the main operation mode is input to the input terminals 10d and 10e, the first reference voltage V (+) = Vα is greater than the first reference voltage V (+) = Vα. Is also changed to a small second reference voltage V (+) = Vβ.

Finally, when the AC voltage v1 is momentarily interrupted in the main operation mode (see time t10 in FIG. 3), the primary side DC voltage VC1 of about 390 to 400V is lowered to 0V and the secondary winding Nb The switching voltage Vb induced by the voltage drops to 0V, and the negative voltage VC7 approaches 0V (see times t10 to t12 in FIG. 3). As shown in FIG. 3E, the detection voltage V (−) increases as the primary side DC voltage VC1 decreases, and the detection voltage V (−) becomes the second reference voltage V (+). = Vβ or more (see time t11 in FIG. 3), as shown in FIG. 3F, an L level warning signal is output from the output terminal 10c of the operational amplifier X2. The detection voltage V (−) eventually rises to the detection voltage V (−) shown in the above equation (6).
As described above, in the low voltage detection circuit 13A of the switching power supply device 1A, in the main operation mode, an L level warning signal is output after the time tx = (t11−t10) has elapsed since the AC voltage v1 was momentarily interrupted. Is output.

  According to this switching power supply device 1A, as apparent from the prior art (FIG. 13C), the instantaneous interruption detection time in the main operation mode: tx can be shortened, and the time ts in FIG. 3 and the time tx in Fig. 3, the instantaneous interruption detection time of the AC voltage v1 can be made substantially the same in the standby mode and the main operation mode. Disconnection can be detected.

(Second embodiment)
By the way, in the switching power supply device 1A according to the first embodiment, as shown in FIGS. 3B, 3E and 3F, the main operation mode is further instructed in the state where the AC voltage v1 is applied. Immediately after the operation control signal Vin is input to the input terminals 10d and 10e (see time t7 in FIG. 3), the first reference voltage V (+) = Vα becomes the first reference voltage V (+) = Vα. Since the second reference voltage V (+) = Vβ, which is smaller than the first reference voltage V (−), is changed to the second reference voltage V (+) = Vβ or more (time t7 to t8 in FIG. 3). The warning signal of L level is output from the output terminal 10c of the operational amplifier X2 for this moment. For this reason, this phenomenon may cause some influence (malfunction) on the operation of the switching power supply. Therefore, the switching power supply device 1B according to the second embodiment has a configuration in which a time constant circuit is further added to the reference voltage changing circuit in order to avoid this phenomenon.
FIG. 4 is a circuit diagram of a switching power supply apparatus according to a second embodiment of the present invention. The switching power supply device 1B of the second embodiment is different from the switching power supply device 1A of the first embodiment in that a time constant circuit 17 is provided. Therefore, only this point will be described.

  As shown in FIG. 4, the time constant circuit 17 includes a first reference voltage Vα after a lapse of a predetermined period after the H-level voltage main operation control signal Vin instructing the main operation mode is input to the input terminals 10d and 10e. Is changed to the second reference voltage Vβ, and includes a resistor R14, a capacitor C6, and a Zener diode D11.

  Next, the operation of the switching power supply device 1B will be described in detail with particular focus on the operations of the low voltage detection circuit 13B and the time constant circuit 17 of the reference voltage changing circuit 16B.

FIG. 5 is a graph for explaining the circuit operation of the switching power supply apparatus 1B when the standby mode is shifted to the main operation mode.
Since the switching power supply device 1B includes the time constant circuit 17, as shown in FIG. 5A, the main operation mode as shown in FIG. When the instructed H level voltage Vin is input between the input terminals 10d and 10e (see time t7 in FIG. 5), the NPN transistor Q3 of the reference voltage changing circuit 16B is turned on and the NPN transistor Q4 is turned off. After the capacitor C6 is charged for a time determined by the resistor R14 of the constant circuit 17 and the time constant τ of the capacitor C6, the NPN transistor Q5 is turned on via the Zener diode D11, and both ends of the resistor R9 are shorted ( (See time t9 in FIG. 5). At this time, as shown in FIG. 5E, the stable voltage VD10 of the Zener diode D10 is applied to the resistors R7 and R8 at the (+) side input terminal of the operational amplifier X2, as shown in the above equation (7). The second reference voltage V (+) = Vβ divided by is input.

That is, after the main operation control signal Vin instructing the main operation mode is input to the input terminals 10d and 10e, the first reference voltage V (+ (+) is passed after a predetermined period determined by the time constant τ of the resistor R14 and the capacitor C6. ) = Vα is changed to a second reference voltage V (+) = Vβ smaller than the first reference voltage V (+) = Vα. Here, during this predetermined period, after the main operation control signal Vin instructing the main operation mode is input to the input terminals 10d and 10e, the primary side DC voltage VC1 is changed to a predetermined boosted voltage (this embodiment) by the active filter circuit 6. In the case of the example, it is preferable that it is not less than the period (t8-t7) until it is boosted to about 390-400V.
Therefore, the time constant circuit 17 can prevent the malfunction of the switching power supply apparatus which is a concern in the switching power supply apparatus 1A according to the first embodiment.

(Third embodiment)
FIG. 6 is a circuit diagram of a switching power supply apparatus according to a third embodiment of the present invention. The switching power supply 1C of the third embodiment is different from the switching power supply 1A of the first embodiment in the configurations of the standby power transformer T2, the low voltage detection circuit 13C, and the reference voltage changing circuit 16C of the standby power supply circuit 10C. . Therefore, only these points will be described.

  As shown in FIG. 6, the switching power supply device 1C includes a standby power supply circuit 10C, a low voltage detection circuit 13C, and a reference voltage changing circuit 16C.

  The standby power supply transformer T2 of the standby power supply circuit 10C has a primary winding Na (the number of turns is Na) and two secondary windings Nb and Nd (the numbers of turns are Nb and Nd, respectively). . When the AC power source 2 is turned on, the standby power source DC-DC converter 11 switches the primary side DC voltage VC1 by the standby power source switching element M3, and the first secondary winding Nb is switched to the primary winding. A switching voltage Vb = (Nb / Na) × Va proportional to the switching voltage Va of Na is induced, and this induced switching voltage Vb is connected to the first secondary winding Nb for a standby power supply rectifying and smoothing circuit The standby power supply voltage Vs that has been rectified and smoothed by 12 and converted into a direct current is output from the output terminals 10a and 10b. At this time, the switching voltage Va of the primary winding Na is applied to the second secondary winding Nd provided separately from the first first secondary winding Nb by switching of the standby power supply switching element M3. A switching voltage Vd = (Nd / Na) × Va is induced in proportion to

The low voltage detection circuit 13C is driven by receiving the standby power supply voltage Vs, and is connected to the second secondary winding Nd. The positive voltage generating rectifying / smoothing circuit 20 and the positive voltage generating rectifying / smoothing circuit 20 are connected to the low voltage detecting circuit 13C. And a comparison circuit 21 connected to the subsequent stage.
The positive voltage generating rectifying / smoothing circuit 20 includes a rectifier diode D9 having an anode connected to the positive side of the second secondary winding Nd, a cathode of the diode D9, and a negative side of the second secondary winding Nd. And a smoothing capacitor C7 to be connected. The positive voltage generating rectifying / smoothing circuit 20 rectifies and smoothes the switching voltage Vd induced in the second secondary winding Nd by the standby power supply switching element M3 and converts the switching voltage Vd into a DC positive voltage VC7. .
The comparison circuit 21 includes a Zener diode D10, resistors R5 to R8 and R10, and an operational amplifier X2. The anode of the Zener diode D10 is connected to the output terminal 10b and the input terminal 10e of the main operation control circuit 18, and is also connected to the positive voltage generating rectifying and smoothing circuit 20. On the other hand, the cathode of the Zener diode D10 is connected to the output terminal 10b and the input terminal 10e via the resistor R6, and further connected to the operational amplifier X2 via the resistor R7.
Resistors R5 and R10 are connected to the (+) side input terminal of the operational amplifier X2, while resistors R7, R8 and R9 are connected to the (−) side input terminal of the operational amplifier X2. In this embodiment, the voltage V (+) input to the (+) side input terminal of the operational amplifier X2 is the detection voltage, and the voltage V (−) input to the (−) side input terminal is the reference voltage. The operational amplifier X2 compares the detection voltage V (+) with the reference voltage V (−), and when the detection voltage V (+) becomes larger than the reference voltage V (−), the output terminal 10c of the operational amplifier X2 H level warning signal is output from the output terminal 10c, and when the detected voltage V (+) becomes equal to or lower than the reference voltage V (−), an L level warning signal is output from the output terminal 10c. The detection voltage V (+) obtained by dividing the positive voltage VC7 by the resistors R5 and R10 as shown in the following equation (8) is input to the (+) side input terminal of the operational amplifier X2.

  Note that a first reference voltage Vα and a second reference voltage Vβ, which will be described later, are input to the (−) side input terminal of the operational amplifier X2.

The reference voltage changing circuit 16C is connected between the input terminals 10d and 10e and the low voltage detection circuit 13C, and in response to an instruction of the main operation control signal Vin input to the input terminals 10d and 10e, the low voltage detection circuit 13C. The reference voltage is changed.
In this embodiment, the reference voltage changing circuit 16C is composed of resistors R9 and R11 to 16 and NPN transistors Q3 to Q6. The reference voltage changing circuit 16C changes the reference voltage to the first reference voltage Vα when the main operation control signal Vin of L level voltage instructing the standby mode is input between the input terminals 10d and 10e, and performs the main operation. When the main operation control signal Vin of H level voltage indicating the mode is input between the input terminals 10d and 10e, the reference voltage is changed to the second reference voltage Vβ larger than the first reference voltage Vα. ing.

  Next, the operation of the switching power supply apparatus 1C will be described in detail with particular focus on the operations of the low voltage detection circuit 13C and the reference voltage change circuit 16C.

  FIG. 7 is a graph for explaining the circuit operation of the switching power supply apparatus 1C in the standby mode. FIG. 8 is a graph for explaining the circuit operation of the switching power supply apparatus 1 </ b> C when the standby mode is shifted to the main operation mode.

First, as shown in FIGS. 7A and 7C, after the AC voltage v1 (AC100V) from the AC power supply 2 is turned on (see time t1 in FIG. 7), the diode bridge DB, the coil L1, and the diode The primary side DC voltage VC1 rises to about 125 to 130V via D2 and the smoothing capacitor C1. Then, the control IC 3 is activated via the activation resistor Rin, and the standby power supply voltage Vs voltage-converted by the standby power supply DC-DC converter 11 is output between the output terminals 10a and 10b. Further, as shown in FIG. 7D, the positive voltage VC7 converted into a direct current by the positive voltage generating rectifying and smoothing circuit 20 is output to the cathode side of the rectifying diode D9.
Since the main operation control signal Vin is the L level voltage (0 V) after the AC voltage v1 is turned on, both the active filter circuit 6 and the main power supply circuit 7 are deactivated, and the NPN transistor Q3 is turned off. Since the transistor Q4 is turned on, the NPN transistor Q5 is turned off, and the NPN transistor Q6 is turned on, both ends of the resistor R9 are short-circuited. Accordingly, at this time, as shown in FIG. 7E, the stable voltage VD10 of the Zener diode D10 as shown in the following equation (9) is applied to the (−) side input terminal of the operational amplifier X2 as a resistor R7 and The first reference voltage V (−) = Vα divided by R8 is input.

On the other hand, as shown in FIG. 7E, the detection voltage V (+) represented by the above equation (8) is input to the (+) side input terminal of the operational amplifier X2. After the application of the AC voltage v1, the primary side DC voltage VC1 rises to about 125 to 130V, and the detection voltage V (+) rises as the primary side DC voltage VC1 rises. When the detection voltage V (+) becomes larger than the reference voltage V (−) (see time t2 in FIG. 7), as shown in FIG. 7 (F), the output terminal 10c of the operational amplifier X2 outputs H A level warning signal is output. Further, when the AC voltage v1 is momentarily interrupted in this standby mode (see time t3 in FIG. 7), the primary side DC voltage VC1 that has been about 125 to 130 V drops to 0 V, and the second secondary voltage The switching voltage Vd induced in the winding Nd drops to 0V, and the positive voltage VC7 approaches 0V. Then, as shown in FIG. 7E, the detection voltage V (+) decreases as the primary side DC voltage VC1 decreases, and the detection voltage V (+) becomes equal to or lower than the reference voltage V (−). When this occurs (see time t4 in FIG. 7), an L level warning signal is output from the output terminal 10c of the operational amplifier X2, as shown in FIG. 7 (F). The detection voltage V (+) is finally lowered to 0 V, where VC7 = 0 in the above equation (8).
As described above, in the low voltage detection circuit 13C of the switching power supply apparatus 1C, in the standby mode, an L level warning signal is output after the time ts = (t4-t3) has elapsed since the AC voltage v1 was momentarily interrupted. Is done.

  Next, as shown in FIGS. 8A and 8C, in the standby mode after the AC voltage v1 is applied (see time t5 in FIG. 8), the primary DC voltage VC1 is about 125 to 130V. To rise. The standby power supply voltage Vs is output between the output terminals 10a and 10b. Further, as shown in FIG. 8D, a positive voltage VC7 is output to the cathode side of the rectifier diode D9. In this standby mode, since the main operation control signal Vin is at the L level voltage (0 V), the active filter circuit 6 and the main power supply circuit 7 are not operated, and the NPN transistor Q3 is turned off. Since the transistor Q4 is turned on, the NPN transistor Q5 is turned off, and the NPN transistor Q6 is turned on, both ends of the resistor R9 are short-circuited. At this time, as shown in FIG. 8 (E), the stable voltage VD10 of the Zener diode D10 as shown in the above equation (9) is applied to the (−) side input terminal of the operational amplifier X2 as resistors R7 and R8. The first reference voltage V (−) = Vα divided by is input. On the other hand, the detection voltage V (+) shown in the above equation (8) is input to the (+) side input terminal of the operational amplifier X2. At this time, the detection voltage V (+) increases as the primary side DC voltage VC1 increases. When the detection voltage V (+) becomes larger than the first reference voltage V (−) = Vα (see time t6 in FIG. 8), as shown in FIG. An H level warning signal is output from the output terminal 10c.

  Then, when the AC voltage v1 is turned on and the H level voltage Vin indicating the main operation mode as shown in FIG. 8B is further input between the input terminals 10d and 10e (FIG. 8). At time t7), the NPN transistor Q2, the photocoupler X1 and the NPN transistor Q1 are turned on, the stable voltage of the Zener diode D7 is supplied to the control IC1 and IC2, and both the active filter circuit 6 and the main power supply circuit 7 are operated. It becomes a state. Thus, by the switching operation of the active filter switching element M1, the primary-side DC voltage VC1 of about 125 V to 130 V rises to about 390 to 400 V, which is a predetermined boosted voltage (see times t7 to t10 in FIG. 8). The main power supply voltage Vm converted by the main power supply DC-DC converter 8 is output between the output terminals 7a and 7b of the main power supply circuit 7 by the switching operation of the main power supply switching element M2. Further, the standby power supply voltage Vs is output between the output terminals 10a and 10b of the standby power supply circuit 10C. Further, as shown in FIG. 8D, a positive voltage VC7 larger than that in the standby mode is output to the cathode side of the rectifier diode D9 (see times t7 to t10 in FIG. 8). When the main operation mode is entered, the NPN transistor Q3 of the reference voltage changing circuit 16C is turned on, the NPN transistor Q4 is turned off, the NPN transistor Q5 is turned on, and the NPN transistor is turned on by the H-level main operation control signal Vin. Q6 is turned off and both ends of the resistor R9 are not short-circuited (see time t7 in FIG. 8). At this time, as shown in FIG. 8E, the stable voltage VD10 of the Zener diode D10 as shown in the following equation (10) is applied to the (+) side input terminal of the operational amplifier X2, and resistors R7, R8 and The second reference voltage V (−) = Vβ divided by R9 is input.

  Therefore, immediately after the main operation control signal Vin instructing the main operation mode is input to the input terminals 10d and 10e, the first reference voltage V (−) = Vα is greater than the first reference voltage V (−) = Vα. Is also changed to a large second reference voltage V (−) = Vβ.

Finally, when the AC voltage v1 is momentarily interrupted in this main operation mode (see time t10 in FIG. 8), the primary side DC voltage VC1 of about 390 to 400V drops to 0V, and the second secondary voltage The switching voltage Vd induced in the winding Nd falls to 0V, and the positive voltage VC7 approaches 0V (see times t10 to t12 in FIG. 8). Then, as shown in FIG. 8E, the detection voltage V (+) decreases as the primary side DC voltage VC1 decreases, and the detection voltage V (+) becomes the second reference voltage V (−). = Vβ or less (see time t11 in FIG. 8), as shown in FIG. 8F, an L level warning signal is output from the output terminal 10c of the operational amplifier X2. The detection voltage V (+) is finally lowered to 0 V, where VC7 = 0 in the above equation (8).
As described above, in the low voltage detection circuit 13C of the switching power supply apparatus 1C, in the main operation mode, an L level warning signal is output after the time tx = (t11−t10) has elapsed since the AC voltage v1 was momentarily interrupted. Is output.

  According to the switching power supply device 1C, as apparent from the comparison with the prior art, the instantaneous interruption detection time: tx in the main operation mode can be shortened. Moreover, as can be seen by comparing the time ts in FIG. 7 and the time tx in FIG. 8, the instantaneous interruption detection time of the AC voltage v1 can be made substantially the same in the standby mode and the main operation mode. For this reason, it is possible to quickly detect an instantaneous interruption of the AC power supply.

(Fourth embodiment)
By the way, in the switching power supply device 1C according to the third embodiment, as shown in FIGS. 8B, 8E and 8F, the main operation mode is further instructed in the state where the AC voltage v1 is applied. Immediately after the operation control signal Vin is input to the input terminals 10d and 10e (see time t7 in FIG. 8), the first reference voltage V (−) = Vα becomes the first reference voltage V (−) = Vα. Larger than the second reference voltage V (−) = Vβ, the time during which the detected voltage V (+) is equal to or lower than the second reference voltage V (−) = Vβ (from time t7 to time t8 in FIG. 8). The warning signal of L level is output from the output terminal 10c of the operational amplifier X2 for this moment. For this reason, this phenomenon may cause some influence (malfunction) on the operation of the switching power supply. Therefore, the switching power supply device 1D according to the fourth embodiment has a configuration in which a time constant circuit is further added to the reference voltage changing circuit in order to avoid this phenomenon.
FIG. 9 is a circuit diagram of a switching power supply apparatus according to a fourth embodiment of the present invention. The switching power supply device 1D of the fourth embodiment is different from the switching power supply device 1C of the third embodiment in that a time constant circuit 17 is provided. Therefore, only this point will be described.

  As shown in FIG. 9, the time constant circuit 17 sets the first reference voltage Vα after a predetermined period has elapsed since the main operation control signal of the H level voltage instructing the main operation mode is input to the input terminals 10d and 10e. This is for changing to the second reference voltage Vβ, and comprises a resistor R14, a capacitor C6, and a Zener diode D11.

  Next, the operation of the switching power supply device 1D will be described in detail with particular focus on the operations of the low voltage detection circuit 13D and the time constant circuit 17 of the reference voltage changing circuit 16D.

FIG. 10 is a graph for explaining the circuit operation of the switching power supply apparatus 1D when the standby mode is shifted to the main operation mode.
Since the switching power supply device 1D includes the time constant circuit 17, as shown in FIG. 10A, the main operation mode as shown in FIG. When the instructed H level voltage Vin is input between the input terminals 10d and 10e (see time t7 in FIG. 10), the NPN transistor Q3 of the reference voltage changing circuit 16D is turned on and the NPN transistor Q4 is turned off. After the capacitor C6 is charged for a time determined by the resistor R14 of the constant circuit 17 and the time constant τ of the capacitor C6, the NPN transistor Q5 is turned on via the Zener diode D11, the NPN transistor Q6 is turned off, and the resistor R9 Are not short-circuited (see time t9 in FIG. 10). At this time, as shown in FIG. 10 (E), the stable voltage VD10 of the Zener diode D10 as shown in the above equation (10) is applied to the (+) side input terminal of the operational amplifier X2 as resistors R7 and R8. And the second reference voltage V (−) = Vβ divided by R9 is input.

That is, after the main operation control signal Vin instructing the main operation mode is input to the input terminals 10d and 10e, the first reference voltage V (− (−) is passed after a predetermined period determined by the time constant τ of the resistor R14 and the capacitor C6. ) = Vα is changed to a second reference voltage V (−) = Vβ that is larger than the first reference voltage V (−) = Vα. Here, during this predetermined period, after the main operation control signal Vin instructing the main operation mode is input to the input terminals 10d and 10e, the primary side DC voltage VC1 is changed to a predetermined boosted voltage (this embodiment) by the active filter circuit 6. In the case of the example, it is preferable that it is not less than the period (t8-t7) until it is boosted to about 390-400V.
Therefore, the time constant circuit 17 can prevent the malfunction of the switching power supply device which is a concern in the switching power supply apparatus 1C according to the third embodiment.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments.

  For example, the reference voltage comparison circuit is not limited to the circuits of the first to fourth embodiments, and may have any circuit configuration as long as the circuit is based on the principle described in this specification.

1A to 1D, 1Z Switching power supply 2 AC power supply 3 Primary side rectifying / smoothing circuit 4 Rectifying unit 5 Smoothing unit 6 Active filter circuit 7 Main power circuit 7a, 7b Output terminal 8 DC-DC converter 9 for main power supply 9 Rectification for main power supply Smoothing circuits 10A to 10D, 11Z Standby power supply circuits 10a to c Output terminal 10d, e Input terminal 11 Standby power supply DC-DC converter 12 Standby power supply rectification smoothing circuits 13A to 13D, 13Z Low voltage detection circuit 14 Negative voltage generation rectification Smoothing circuit 15 Comparison circuits 16A to 16D Reference voltage changing circuit 17 Time constant circuit 18 Main operation control circuit 19 Auxiliary power supply rectification smoothing circuit 20 Positive voltage generating rectification smoothing circuit 21 Comparison circuits C1 to C7 Capacitors D2 to D6, D8, D9 Diodes D7, D10, D11 Zener diodes L1, L4 Coil M1 Active filter switching element M2 Main power source switching element M3 Standby power source switching element R1 to R16 Resistor Rin Starting resistance Q1 to Q6 NPN transistor Na Primary winding Nb Secondary winding (first secondary winding) )
Nd secondary winding (second secondary winding)
T1 Main power transformer T2 Standby power transformer X2 Operational amplifier

Claims (8)

A main power supply circuit that outputs a main power supply voltage;
A standby power supply circuit for outputting a standby power supply voltage;
A main operation control signal for instructing one of a main operation mode and a standby mode; and an input terminal for inputting a main operation control signal for instructing the main operation mode. A main operation control circuit for outputting the main power supply voltage from the circuit;
A primary side rectifying / smoothing circuit that rectifies and smoothes an AC voltage from an AC power source and converts it into a primary side DC voltage;
An active filter circuit that boosts the primary side DC voltage to a predetermined boosted voltage during the main operation mode;
A low voltage detection circuit for detecting a decrease in the AC voltage,
The main power supply circuit switches the boosted voltage by a main power supply switching element, converts the switching voltage induced in the secondary winding of the main power supply transformer into a direct current, and outputs it as the main power supply voltage,
The standby power supply circuit is activated when the primary DC voltage is supplied, and the primary DC voltage is switched by the standby power supply switching element, and is induced in the secondary winding of the standby power supply transformer. Switch the switching voltage to DC and output as standby power supply voltage.
The low voltage detection circuit compares a detection voltage generated based on a negative voltage obtained by converting the switching voltage induced in the secondary winding of the standby power transformer into a direct current with a reference voltage, and detects the detection voltage. In a switching power supply that outputs a warning signal when the voltage becomes lower than the reference voltage and detects a decrease in the AC voltage,
And a reference voltage changing circuit that is connected between the input terminal and the low voltage detection circuit and changes the reference voltage in response to an instruction of the main operation control signal input to the input terminal. Switching power supply.   The reference voltage changing circuit changes the reference voltage to a first reference voltage and instructs the main operation mode when the main operation control signal instructing the standby mode is input to the input terminal. 2. The switching power supply device according to claim 1, wherein, when an operation control signal is input to the input terminal, the reference voltage is changed to a second reference voltage smaller than the first reference voltage. The reference voltage changing circuit further includes a time constant circuit,
The time constant circuit changes the first reference voltage to the second reference voltage after a lapse of a predetermined period after the main operation control signal instructing the main operation mode is input to the input terminal. The switching power supply device according to claim 2.   The predetermined period is longer than a period from when the main operation control signal instructing the main operation mode is input to the input terminal until the primary DC voltage is boosted to the boost voltage. The switching power supply device according to claim 3. A main power supply circuit that outputs a main power supply voltage;
A standby power supply circuit for outputting a standby power supply voltage;
A main operation control signal for instructing one of a main operation mode and a standby mode; and an input terminal for inputting a main operation control signal for instructing the main operation mode. A main operation control circuit for outputting the main power supply voltage from the circuit;
A primary side rectifying / smoothing circuit that rectifies and smoothes an AC voltage from an AC power source and converts it into a primary side DC voltage;
An active filter circuit that boosts the primary side DC voltage to a predetermined boosted voltage during the main operation mode;
A low voltage detection circuit for detecting a decrease in the AC voltage,
The main power supply circuit switches the boosted voltage by a main power supply switching element, converts the switching voltage induced in the secondary winding of the main power supply transformer into a direct current, and outputs it as the main power supply voltage,
The standby power supply circuit is activated by being supplied with the primary side DC voltage, and the primary side DC voltage is switched by a standby power supply switching element to be applied to a first secondary winding of a standby power supply transformer. The induced switching voltage is converted to DC and output as a standby power supply voltage.
The low voltage detection circuit is generated based on a positive voltage obtained by converting a switching voltage induced in a second secondary winding provided separately from the first secondary winding in the standby power transformer into a direct current. In the switching power supply device that compares the detected voltage with a reference voltage and outputs a warning signal when the detected voltage is greater than the reference voltage, and detects a decrease in the AC voltage.
And a reference voltage changing circuit that is connected between the input terminal and the low voltage detection circuit and changes the reference voltage in response to an instruction of the main operation control signal input to the input terminal. Switching power supply.   The reference voltage changing circuit changes the reference voltage to a first reference voltage and instructs the main operation mode when the main operation control signal instructing the standby mode is input to the input terminal. 6. The switching power supply device according to claim 5, wherein, when an operation control signal is input to the input terminal, the reference voltage is changed to a second reference voltage that is higher than the first reference voltage. The reference voltage changing circuit further includes a time constant circuit,
The time constant circuit changes the first reference voltage to the second reference voltage after a lapse of a predetermined period after the main operation control signal instructing the main operation mode is input to the input terminal. The switching power supply device according to claim 6.   The predetermined period is longer than a period from when the main operation control signal instructing the main operation mode is input to the input terminal until the primary DC voltage is boosted to the boost voltage. The switching power supply device according to claim 7.

Images