JP2000316280A - Power-supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of a power-supply unit by providing a detection means for monitoring the output side of a rectifier means, and a protection means for breaking or reducing the output of the rectifier means when an overvoltage is detected by the detection means. SOLUTION: An overvoltage monitor 20 is provided, a monitor input 20A of the overvoltage monitor 20 is connected to the connection middle point between the + side of a smoothing capacitor 4 and + input 10A of a DC.DC converter 10, and a monitor input 20B of an overvoltage monitor 20 is grounded for taking the output voltage of a rectifier block 3 for applying to filter capacitors 4 and 5 into the overvoltage monitor 20. An output end 20C is provided at the overvoltage monitor 20, and an off control signal is supplied to a protection operation signal input end 8B of a driving circuit 8 from the output end 20C when the overvoltage monitor 20 detects that the output voltage of the rectifier block 3 has been excessive, thus securely preventing an overvoltage from being supplied to a load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to overvoltage protection of a power supply device.

[0002]

2. Description of the Related Art Conventionally, a wide range of voltages of a commercial alternating current (hereinafter referred to as AC) power supply, for example, 100
2. Description of the Related Art There is known a power supply device that can support an AC power supply having a significantly different voltage such as volt AC or 200 volt AC.

In this power supply device, when the AC power supply voltage is in a predetermined voltage range centered on 100 volts AC, the power supply voltage is double-voltage rectified and a direct current voltage in a predetermined voltage range centered on 282 volts DC ( In the following description, this DC voltage is referred to as DC voltage).
When the power supply voltage is in a predetermined voltage range centered on 200 volts AC, the power supply voltage is full-wave rectified to obtain a DC voltage in a predetermined voltage range centered on a 282 volts DC voltage.

In this case, furthermore, a means for detecting the voltage of the AC power supply section is provided in the power supply device, and a rectifier configured to automatically switch between the voltage doubled rectification state and the full-wave rectification state according to the voltage. 2. Description of the Related Art A power supply device having a circuit unit is known.

Therefore, when the place of use of the power supply device is changed, the voltage of the AC power supply unit becomes 100 volts AC and 20 volts.
Even when the voltage is changed between 0 volts AC, by performing such automatic switching, the output DC voltage of the rectification circuit unit can be maintained at 282 volts DC, and DC / When connecting DC conversion means and outputting a DC voltage stabilized to a desired voltage,
The variation range of the input DC voltage required for the DC / DC converter is narrowed to increase the efficiency of the converter.

An example of this conventional power supply device will be described with reference to FIG.

FIG. 6 is a circuit block diagram showing a main part of a conventional power supply device. This power supply device includes a noise filter block 2, a rectifier block 3, a first smoothing capacitor 4, and a second filter.
Capacitor 5, power switch 6, changeover switch 7, first drive circuit section 8, DC / DC converter section 1
0, a second drive circuit section 11, a voltage detection circuit section 12, a rectification / smoothing circuit section 13, a secondary output terminal section 14, and a power control signal input terminal 15. Reference numeral 1 denotes an AC power supply unit.

The rectifier block 3 includes a first rectifier diode 3A, a second rectifier diode 3B, a third rectifier diode 3C, and a fourth rectifier diode 3D, and the cathode side of the first rectifier diode 3A and the second rectifier diode 3A. A first AC power supply input terminal 3E is formed at a connection point on the anode side of the rectifier diode 3B, and a second connection point is formed at the connection point on the cathode side of the third rectifier diode 3C and the anode side of the fourth rectifier diode 3D. Of the AC power supply input terminal 3F.

The second rectifier diode 3B and the fourth rectifier diode 3B
The + DC output terminal 3G is formed at the connection middle point of each rectifier diode 3D on the cathode side, and the first rectifier diode 3A
The -DC output terminal 3H is formed at the connection middle point between the anode and the third rectifier diode 3C. In addition, rectification
The smoothing circuit unit 13 includes a diode 13A and a smoothing capacitor 13B.

One of the AC power supply units 1 is connected to a first AC power supply input terminal 3E through a power supply line 1A and a noise filter block 2, and the other of the AC power supply unit 1 is connected to the power supply line 1A.
B through the noise filter block 2 and to the movable contact 6A side of the power switch 6;
Side is connected to the second AC power input terminal 3F, the + DC output terminal 3G is connected to the + input 10A side of the DC / DC converter unit 10, and the -DC output terminal 3H is connected to the -input of this DC / DC converter unit 10. It is connected to the 10B side.

A connection point between the DC output terminal 3H and the input 10B is connected to a ground point 16, and a first smoothing capacitor 4 and a second smoothing capacitor 5 are connected in series. + Terminal side is + DC output terminal 3G and +
The negative terminal of the second smoothing capacitor 5 is connected to the ground point 16, and the negative terminal of the first smoothing capacitor 4 and the positive terminal of the second smoothing capacitor 5 are connected to the input middle point on the input 10A side.
The connection point 5A on the end side is connected to the fixed contact 7A side of the changeover switch 7.

The movable contact 7B side of the changeover switch 7 is connected to a connection midpoint between the fixed contact 6B side of the power switch 6 and the second AC power input terminal 3F of the rectifier block 3, and this connection midpoint is connected to the voltage detection circuit section. 12, the output terminal 12B of the voltage detection circuit unit 12 is connected to the control signal input terminal 11A of the second drive circuit unit 11, and the power supply control signal input terminal 15 is connected to the first drive circuit It is connected to a power control signal input terminal 8A of the unit 8 and a power control signal input terminal 10C of the DC / DC converter unit 10, respectively.

Each of the + DC voltage output terminal 10D and the −DC voltage output terminal 10E of the DC / DC converter 10 is connected to the secondary side output terminal 14 through the rectifying / smoothing circuit 13.
It is connected to the.

Next, the operation of the power supply device shown in FIG. 6 will be described.

When a power-on signal is supplied from the power control signal input terminal 15, the DC / DC converter section 10 and the first drive circuit section 8 are activated, the power switch 6 is held in the on state, and the AC The power supply voltage of the power supply unit 1 is supplied to a voltage detection terminal 12A of the voltage detection circuit unit 12.

If the power supply voltage is 100 volts AC, a drive signal is supplied from the output terminal 12B to the input terminal 11A of the second drive circuit unit 11 in response to the supply voltage. Switch 7 is held in the ON state, the connection midpoint 5A is connected to the second AC power supply input terminal 3F, and the rectifier block 3, the first smoothing capacitor 4, and the second smoothing capacitor 5 apply a voltage doubler. When the rectifier circuit is configured, DC
The DC voltage boosted to 282 volts DC is supplied between the + input 10A and the − input 10B of the C converter unit 10.

On the other hand, if the power supply voltage is 200 volts AC while the power supply switch 6 is turned on, the output terminal 12B of the voltage detection circuit 12
No drive signal is supplied to the input terminal 11A of the drive circuit unit 11 of FIG. Therefore, the changeover switch 7 is held in the off state, and the state in which the connection midpoint 5A is not connected to the second AC power input terminal 3F is maintained.

Accordingly, a DC voltage of 282 volts DC obtained by full-wave rectifying the power supply voltage of 200 volts AC in the rectifier block 3 is applied to the + input 10 A of the DC / DC converter unit 10.
And-state supplied during input 10B.

However, in the conventional power supply device shown in FIG. 6, when the power supply voltage is 200 volts AC, the rectifier block 3, the first smoothing capacitor 4, and the second smoothing capacitor 5 are used. However, there is an inconvenience that a countermeasure is not taken when the rectifying circuit to be switched from the voltage doubled rectification state to the full-wave rectification state for some reason.

[0020]

In the conventional power supply device, when the power supply voltage is 200 volts AC, the rectifier block 3, the first smoothing capacitor 4, and the second smoothing capacitor 5 are used. The rectifier circuit may not be able to switch to the full-wave rectification state for some reason.

In this case, an overvoltage is applied to the first smoothing capacitor 4, the second smoothing capacitor 5, and the DC / DC converter section 10, so that no problem occurs even in this state. It is necessary to set the withstand voltage value required for the portion, the voltage conversion range of the DC / DC converter section 10 and the like so as not to cause a problem even with this overvoltage. As a result, there is a problem that the cost is increased and the price of the power supply unit is increased.

The present invention has been made in view of the above points,
Between the output side of the rectifier block 3 and the input side of the DC / DC converter section 10, there is provided means for detecting the voltage input to the DC / DC converter section 10, and the detection means detects an abnormal voltage. In this case, it is an object to improve the reliability of the power supply device by operating a protection means for preventing the abnormal voltage from being input to the DC / DC converter section 10 when the power supply device is in the abnormal state.

[0023]

The power supply device according to the present invention is a power supply device having switch means for automatically switching a rectifier between a voltage doubled rectification state and a full-wave rectification state according to the voltage of an AC input unit. Detecting means for monitoring the output side of the rectifying means, and protection means for shutting down or reducing the output of the rectifying means when an overvoltage is detected by the detecting means. In this case, the protection unit is operated so that the abnormal voltage is not input to the DC / DC converter unit 10 when the abnormal voltage is input, thereby improving the reliability of the power supply device.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, in which the same parts as those in FIG.

FIG. 1 is a block diagram showing a main part of a circuit configuration of a power supply device according to the present invention. In the configuration shown in FIG. 1, an overvoltage monitoring unit 20 is provided, and the first monitoring of the overvoltage monitoring unit 20 is performed. The input unit 20A is connected to the +
Side and the positive input 10A of the DC / DC converter section 10 and the second monitoring input section 20B of the overvoltage monitoring section 20 to ground.
The output voltage of the rectifier block 3 applied to the series circuit of FIG.

Further, the output terminal 20 is connected to the overvoltage monitoring unit 20.
C, when the overvoltage monitoring unit 20 detects that the output voltage of the rectifier block 3 is in an overvoltage state, the output terminal 20C is turned off from the output terminal 20C to the protection operation signal input terminal 8B of the first drive circuit unit 8. It is configured to be able to supply signals.

In the configuration shown in FIG. 1, when a power-on signal is supplied from the power control signal input terminal 15, DC / D
The C converter unit 10 and the first drive circuit unit 8 are activated, the power switch 6 is held in the ON state,
The power supply voltage of the C power supply unit 1 is supplied to a voltage detection terminal 12A of the voltage detection circuit unit 12.

In this supply state, when the voltage detection circuit section 12 detects that the power supply voltage of the AC power supply section 1 is 100 volts AC, the second drive circuit is output from the output terminal 12B of the voltage detection circuit section 12. Control signal input terminal 11 of unit 11
A changeover switch-on signal is supplied to A, and the changeover switch 7 is held in the on state from the second drive circuit unit 11.

When the changeover switch 7 is held in the ON state, the rectifier block 3, the first smoothing capacitor 4, and the second smoothing capacitor 5 constitute a voltage doubler rectifier circuit, and a voltage of 282 volts DC is provided. When the voltage is between the + input 10A of the DC / DC converter section 10 and-
It is in a state of being supplied during the input 10B.

On the other hand, in this supply state, the AC power supply unit 1
If the power supply voltage rises to 200 volts AC or a voltage close to 200 volts, this voltage fluctuation is detected by the voltage detection circuit unit 12, and the voltage detection circuit unit 12
A case in which a series of operations for turning off the changeover switch 7 from the above state does not operate for some reason will be described.

In this case, the connection between the rectifier block 3 and the first smoothing capacitor 4 and the second smoothing capacitor 5 is not switched from the double voltage rectification state to the full-wave rectification state. 10 + input 10A
And the voltage supplied between the input 10B rises above this 282 volts DC.

However, in the power supply device shown in FIG. 1, the output voltage of the rectifier block 3 applied to the series circuit of the smoothing capacitors 4 and 5 is supplied to the first monitor input section 20A and the second monitor input section 20B. Thus, the overvoltage monitoring unit 20 can be loaded.

Therefore, this DC / DC converter 1
An abnormal increase in the output voltage supplied between the + input 10A and the − input 10B of 0 is detected by the overvoltage monitoring unit 20, and the output terminal 20C of the overvoltage monitoring unit 20 outputs the first drive circuit unit 8 An OFF control signal is supplied to the protection operation signal input terminal 8B, and the power supply switch 6
Is held in the off state.

Therefore, according to the power supply device shown in FIG. 1, the series circuit of the smoothing capacitors 4 and 5 and the DC
-It is possible to reliably prevent an excessive voltage from being applied to the DC converter unit 10.

Next, the details of the overvoltage monitoring unit 20 will be described with reference to FIGS.

FIG. 2 is a circuit diagram showing a main part of the overvoltage monitoring unit 20, and FIG. 3 is a diagram showing signal waveforms of the overvoltage monitoring unit 20 necessary for explanation. The examples shown in FIGS. 2 and 3 are examples in which the overvoltage protection operation by the overvoltage monitoring unit 20 is provided with a hysteresis characteristic to suppress the overvoltage, and the suppression state is maintained for a predetermined period. This is an example in which it is made possible.

The hysteresis characteristic refers to the first drive circuit unit 8 in FIG. 1 with respect to the output voltage of the rectifier block 3 which serves as a reference for controlling the power switch 6 from the ON state to the OFF state. , The output voltage of the rectifier block 3, which is a reference for controlling the power switch 6 from the off state to the on state, is set to a low voltage.

In FIG. 2, the overvoltage monitoring unit 20 includes a first monitoring input unit 20A, a second monitoring input unit 20B, and an output terminal 20.
C, resistors 23, 24, 25, 26, 27, 28, 29
And 31, a voltage comparator 32, a diode 33, a transistor element 34, and an electrolytic capacitor 35. 36 is a positive power supply terminal, 37 is a ground terminal, 32A
Is an inverting input terminal of the voltage comparator 32, 32C is a non-inverting input terminal of the voltage comparator 32, and 32B is an output terminal of the voltage comparator 32.

It is assumed that a predetermined DC voltage VCC is constantly supplied to the + power supply terminal 36 and the second monitoring input section 20B regardless of whether the DC / DC converter section 10 is in operation. In FIG. 2, Vd is the positive side of the first smoothing capacitor 4 and the DC / DC converter 10.
The voltage at the midpoint of connection of the + input 10A, Vc is the output terminal 2
0C to the protection operation signal input terminal 8B of the first drive circuit unit 8
Of the control signal to be supplied to the power supply.

The first monitoring input section 20A is connected to the second monitoring input section 20B through a series circuit of resistors 23 and 24, and the ground terminal 37 is connected to the second monitoring input section 20B. And 24 are connected to the inverting input terminal 32A of the voltage comparator 32, the + power supply terminal 36 is connected to the emitter of the transistor element 34, and the collector of the transistor element 34 is connected in series with the resistor 31 and the electrolytic capacitor 35. Through the ground terminal 37. In this case, the series circuit is configured with the + side of the electrolytic capacitor 35 connected to the resistor 31.

The connection point of this series circuit is the diode 33
The cathode of the diode 33 is connected to the inverting input terminal 32A of the voltage comparator 32, and the base of the transistor element 34 is connected to the output terminal 32B of the voltage comparator 32 through the resistor 28. The connection point between the output side 32B of the voltage comparator 32 and the + power supply terminal 36 through the resistor 29
, And the output side 32B of the voltage comparator 32 is connected to the + input side 32C of the voltage comparator 32 through the resistor 27.

The output 32 of the voltage comparator 32
The connection midpoint between B and the resistor 27 is connected to the output terminal 20C,
The + power supply terminal 36 is grounded through a series circuit composed of the resistors 25 and 26, and the connection point of the series circuit composed of the resistors 25 and 26 is connected to the non-inverting input terminal 32 C of the voltage comparator 32.

In this overvoltage monitoring section 20, the first monitoring input section 20A is connected between the + side of the first smoothing capacitor 4 and the DC side.
-It is connected to the connection midpoint of the + input 10A of the DC converter section 10, and this voltage Vd is supplied to the first monitoring input section 20A.

The voltage Vd is applied to the resistors 23 and 24.
Is supplied to the inverting input terminal 32A of the voltage comparator 32, and the voltage of the + power supply terminal 36 is
And the voltage divided at 26 (hereinafter, this voltage is referred to as a reference voltage Va) is supplied to a non-inverting input terminal 32C of the voltage comparator 32, and the reference voltage Va and the voltage Vb are supplied to the voltage comparator 32. Make comparisons.

As a result of this comparison, the reference voltage Va is
If b exceeds (Va <Vb), the voltage comparator 32 determines that the voltage Vd is in an overvoltage state, and the reference voltage Va is larger than the voltage Vb (Va).
> Vb), the voltage comparator 32 determines that the voltage Vd is within a normal voltage range.

If the voltage comparator 32 detects that the voltage Vb is going to exceed the reference voltage Va, the output side 32B of the voltage comparator 32
To supply the protection operation signal to the protection operation signal input terminal 8B of the first drive circuit section 8 through the output terminal 20C.

Further, in the overvoltage monitoring section 20 shown in FIG. 2, the resistor 2 is connected between the output side 32B of the voltage comparator 32 and the non-inverting input terminal 32C of the voltage comparator 32.
7, a feedback circuit is formed to provide the hysteresis characteristic between the voltage Vb at which the voltage comparator 32 outputs the protection operation signal and the voltage Vb at which the protection operation signal is stopped.

The waveform change of the voltage Vd when the protection operation of the first drive circuit section 8 is controlled with the hysteresis characteristic as described above will be described with reference to FIG. 3A.

When the voltage Vd reaches the protection voltage indicated by the broken line as Va1 in FIG. 3A, the voltage comparator 32 determines that the voltage Vb exceeds the reference voltage Va, that is, the voltage Vd becomes an overvoltage state. 32 from the output side 32B through the output end 20C.
The protection operation signal supplied to the protection operation signal input terminal 8B of the drive circuit section 8 from the high level state to the low level state,
The power switch 6 is held in the off state from the first drive circuit section 8.

When the power switch 6 is turned off, the voltage Vd decreases with a predetermined gradient, and reaches the signal level indicated by the broken line as the protection release voltage Va2 in FIG. 3A.
When d decreases, the voltage comparator 32 determines that the voltage Vb falls below the reference voltage Va, that is, the voltage Vd falls within the range of the normal voltage state, and the output side of the voltage comparator 32 through the output terminal 20C. The protection operation signal supplied from 32B to the protection operation signal input terminal 8B of the first drive circuit unit 8 is changed from this low level state to a high level state, and the power switch 6 is held in the on state.

Thereafter, the off state and the on state of the power switch 6 are repeated, and the signal Vd shown in FIG. 3A repeats a sawtooth waveform having a predetermined time constant gradient.

In the example shown in FIG.
1, resistor 26 is R2, resistor 27 is R3, resistor 29
Is represented by R4, and the voltage of the + power supply terminal 36 is represented by VCC, and the protection voltage Va1 and the protection release voltage Va2 are represented by the following equations (1), and the protection release voltage Va2 is represented by the following equation (1). It can be represented by 2).

Va1 = R2 · Vcc / ((R1 · R3 · R4 / R1 + R3 + R4) + R2) (1) Va2 = R2 · R3 · Vcc / (R2 · R3 + (R2 + R3) · R1) ···・ ・ ・ ・ ・ ・ ・ ・ （２）

Therefore, according to the power supply device provided with the overvoltage monitoring unit 20 shown in FIG. 2, if the AC voltage of the AC power supply unit 1 temporarily rises for some reason, the first Since the power switch 6 can be temporarily turned off from the drive circuit section 8 and then automatically returned to the on state, the output of the DC / DC converter section 10 can be maintained without interruption. .

For example, if the AC voltage of the AC power supply unit 1 continues to rise for some reason, the first smoothing capacitor 4 and the second smoothing capacitor 5 are connected to the ON / OFF operation of the power switch 6. Since the DC / DC converter 10 can be repeatedly charged and maintained in the operating state, the output of the DC / DC converter 10 can be maintained without interruption even in such a case.

Next, the operation of maintaining the protection state continuously after the change between these voltages Va1 and Va2 is repeated a predetermined number of times as shown in FIG. 3A will be described with reference to FIGS. 2 and 3. It will be described based on.

As shown in FIG. 3A, during the period in which this voltage Vd repeatedly rises and falls between the protection release voltage Va2 and the protection voltage Va2, this voltage Vd drops to the level of the protection release voltage Va2 as shown in FIG. 3B. Every time period b, the transistor element 34 is turned on, the capacitor 35 is charged through the resistor 31, and the voltage charged in the capacitor 35 increases as shown in FIG. 3C according to this repetition.

When a predetermined period indicated by C in FIG. 3C has elapsed, the voltage of the capacitor 35 becomes a voltage level exceeding the reference voltage Va (hereinafter referred to as a latch point). As a result, this capacitor 3
When the voltage of the comparator 5 exceeds the latch point, the operation of the comparator 18 is stopped, the voltage Vc of the output 32B of the comparator 18 is maintained at a low level, and the power switch 6 is turned off. The state is maintained.

That is, by providing these circuits for generating the latch point, the state in which the power switch 6 is repeatedly turned on and off is continuously performed without restriction without any limitation on the first smoothing capacitor 4 and the second smoothing capacitor 5 and the DC / DC converter. DC
An excessive load on the converter unit 10 can be prevented from occurring.

In this embodiment, the power switch 6
In order to maintain the output voltage from the DC / DC converter unit 10 in a steady state in a state where the voltage is alternately switched on and off, or in a state where the voltage doubler circuit and the full-wave rectifier circuit are alternately switched, This voltage Va1 is set such that the charging voltage for the first smoothing capacitor 4 and the second smoothing capacitor is maintained at a value as high as allowable during the period in which the on / off state of the power switch 6 is repeated.

Even if this voltage Va1 is set as described above,
By limiting the number of repetitions, an excessive burden on the first smoothing capacitor 4 and the second smoothing capacitor can be reduced.

Next, another example of the embodiment of the present invention is shown in FIG.
The same parts as those described above are given the same reference numerals, and detailed description is omitted.

In this embodiment, the output voltage of the rectifier block 3 applied to the series circuit of the smoothing capacitors 4 and 5 is taken into the overvoltage monitoring unit 20 and the overvoltage monitoring unit 2
The power switch 6 provided in the configuration shown in FIG. 1 and the first switch thereof can be supplied so that an OFF control signal can be supplied from the output terminal 20C of the second drive circuit unit 11 to the protection operation signal input terminal 11B of the second drive circuit unit 11. This is an example in which the drive circuit unit 8 is omitted.

In the configuration shown in FIG. 4, when a power-on signal is supplied from power-supply control signal input terminal 15, DC / D
C converter unit 10 is turned on.

When the power supply voltage of the AC power supply section 1 is 100 volts AC, this voltage is detected by the voltage detection circuit section 12 and the second drive circuit section 1
The changeover switch 7 is held in the ON state through 1;
The rectifier block 3, the first smoothing capacitor 4, and the second smoothing capacitor 5 constitute a voltage doubler rectifier circuit, and a voltage of 282 volts DC is applied between the + input 10 A and the − input 10 B of the DC / DC converter 10. To be supplied to

On the other hand, in this ON state, the AC power supply 1
Is 200 volts AC, this voltage is detected by the voltage detection circuit 12 and the voltage detection circuit 12
The changeover switch 7 is held in the off state through the second drive circuit section 11 from the rectifier block 3 and the first
The circuit configuration including the smoothing capacitor 4 and the second smoothing capacitor 5 is in a full-wave rectification state,
Is the positive input 10 of the DC / DC converter section 10.
A state is provided between A and -input 10B.

When the power supply voltage of the AC power supply unit 1 is 200 volts AC, the changeover switch 7
Is maintained in the ON state and is not switched to the full-wave rectification state, the + input 1 of the DC / DC
0A and the voltage supplied between the input 10B
Attempts to overvoltage condition exceeding volts DC.

However, in the power supply device shown in FIG. 4, the output voltage of the rectifier block 3 applied to the series circuit of the smoothing capacitors 4 and 5 can be taken into the overvoltage monitoring unit 20 from the first monitoring input unit 20A. With this configuration, the abnormal rise of the output voltage is detected by the overvoltage monitoring unit 20, and the off-control is performed from the output terminal 20 </ b> C of the overvoltage monitoring unit 20 to the protection operation signal input terminal 11 </ b> B of the second drive circuit unit 11. The signal is supplied, and the change-over switch 7 is turned off.

Therefore, according to the power supply device shown in FIG.
And the DC / DC converter unit 1
It is possible to reliably prevent the overvoltage from being applied to 0.

In the example shown in FIG. 4, the overvoltage monitoring section 20 may be constituted by the overvoltage monitoring section 20 described with reference to FIGS.

Next, another example of the embodiment of the present invention is shown in FIG.
The same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description is omitted.

In the example shown in FIG. 5, when a power-on signal is supplied from the power control signal input terminal 15, DC / DC
The converter section 10 is turned on, the power switch 6 is turned on through the first drive circuit section 8, and the changeover switch 7 is switched to the second drive circuit section 11 in which a power-on signal is supplied to the power control input terminal 11. To be turned on. In this state, the power supply voltage of the AC power supply section 1 is detected by the voltage detection circuit section 12, and when the detected value is 200 volts AC, the voltage detection circuit section 12 controls the first drive circuit section 8 Then, the ON state of the changeover switch 6 is held, and the second drive circuit unit 11 is controlled to hold the changeover switch 7 in the OFF state.

In this state, the rectifier block 3, the first smoothing capacitor 4, and the second smoothing capacitor 5
, A full-wave rectifier circuit is formed, and a voltage of 282 volts DC is supplied between the + input 10A and the − input 10B of the DC / DC converter section 10.

On the other hand, in a state where the rectifier block 3, the first smoothing capacitor 4, and the second smoothing capacitor 5 constitute this voltage doubler rectifier circuit,
+ Input 10A and-input 10 of the C / DC converter section 10
If the overvoltage monitoring unit 20 detects that an overvoltage exceeding the reference has occurred during the period B, the overvoltage monitoring unit 20
, A protection operation command is input to the protection operation signal input terminal 8B of the first drive circuit unit 8 from the output terminal 20C, and the power switch 6 is held in the off state through the first drive circuit unit 8.

At the same time, a protection operation command is input from the output terminal 20E of the overvoltage monitoring unit 20 to the protection operation signal input terminal 11B of the second drive circuit unit 11, and the second drive circuit unit 1
Hold the changeover switch 7 in the off state through 1
The first smoothing capacitor 4, the second smoothing capacitor 5, and the DC / DC converter section 10 are protected from this overvoltage state.

In the example shown in FIG. 5, the overvoltage monitoring section 20 is constituted by the overvoltage monitoring section 20 described with reference to FIGS. 2 and 3, and in this overvoltage state, the changeover switch 6 is held in the off state. In the state, the second drive circuit unit 1
Only one side may be controlled as described with reference to FIGS. 2 and 3.

[0077]

According to the present invention, in a power supply device for automatically switching a rectifier between a voltage doubler rectification state and a full-wave rectification state in accordance with the voltage of an AC power supply, a means for monitoring the output side of the rectifier means. Since a protection means is provided to cut off or reduce the output of the rectification means when an overvoltage is detected, for example, when a DC / DC converter is used as a load of the power supply, the rectification is performed according to a change in the voltage of the AC power supply. In a state where the means is automatically switched between the double voltage rectification state and the full-wave rectification state so that a predetermined voltage can always be supplied to the load side, it is possible to reliably prevent an overvoltage from being supplied to the load.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a power supply device of the present invention.

FIG. 2 is a circuit diagram showing details of a part of the configuration of the power supply device of the present invention.

FIG. 3 is a diagram illustrating the operation of the circuit shown in FIG. 2;

FIG. 4 is a block diagram showing a configuration of another power supply device of the present invention.

FIG. 5 is a block diagram showing a configuration of still another power supply device of the present invention.

FIG. 6 is a block diagram showing a configuration of still another power supply device of the present invention.

[Explanation of symbols]

1 AC power supply, 3 rectifier block, 3 G DC output terminal, 3 H DC output terminal, 4 first smoothing capacitor, 5 second smoothing capacitor, 5 A connection Midpoint, 6 power switch, 8 first drive circuit section,
10 DC / DC converter, 10 A + input,
10B ‥‥ -input, 11 ‥‥ second drive circuit section, 14 ‥
{Secondary side output terminal section, 20} Overvoltage monitoring section,

Claims (9)

[Claims] 1. A power supply device having switching means for automatically switching a rectifier between a voltage doubled rectification state and a full-wave rectification state in accordance with a voltage of an AC power supply, a detection means for monitoring an output side of the rectification means, A power supply unit comprising: a protection unit that cuts off or reduces the output of the rectification unit when an overvoltage is detected by the detection unit. 2. The power supply device according to claim 1, wherein a switch is provided between the AC power supply and the rectifier.
A power supply unit, wherein the switch means is cut off by the protection means when an overvoltage is detected by the detection means. 3. The power supply device according to claim 1, wherein said protection means keeps said rectifier in a full-wave rectification state when an overvoltage is detected by said detection means. 4. The power supply device according to claim 1, wherein said detection means monitors a voltage of a smoothing capacitor connected to an output side of said rectification means. 5. The power supply device according to claim 1, wherein a hysteresis characteristic is provided between an overvoltage detection level and a normal voltage detection level of said detection means. 6. The power supply device according to claim 5, wherein an overvoltage detection level of said detection means is set to be lower than an operation guarantee input voltage of said smoothing capacitor. 7. The power supply device according to claim 5, wherein a DCDC converter is provided on an output side of the rectifier. 8. The power supply device according to claim 7, wherein said overvoltage detection level of said detection means is set so as to be equal to or higher than a voltage within a normal operation range of the operation of said DCDC conversion means. . 9. The power supply device according to claim 5, wherein the operation of switching between the overvoltage detection level and the normal voltage detection level of the detection circuit has a time constant.