JP2002051542A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device for supplying power conforming to a plurality of standards without changing a configuration. SOLUTION: In the power supply device having a reference voltage generation circuit 30 for generating a reference voltage that becomes the reference of an output voltage, a voltage failure detection circuit 50 for detecting the failure of the output voltage, and a current failure detection circuit 40 for detecting an excessive output current, at least a first switching means 61 for switching the reference voltage generated by the reference voltage generation circuit 30 in two steps or in steps, at least a second switch means 63 for switching a threshold which the voltage failure detection circuit 50 utilizes for detecting voltage failure in two steps or in steps, at least a third switch means 62 for switching a threshold which the current failure detection circuit 40 utilizes for detecting an overcurrent in two steps or in steps, and a synchronization means 60 for turning on or off the second and third switching means simultaneously are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device having a protection circuit against various abnormalities.

[0002]

2. Description of the Related Art For example, in a DC-DC converter used as a part of a power supply device, various abnormalities are protected in order to prevent a failure of the power supply device itself and a failure of a device supplied with power from the power supply. It is necessary to have a circuit. That is, an overvoltage protection circuit for preventing output of an overvoltage larger than a specified value, a low voltage protection circuit for warning about an output of an undervoltage that is smaller than a predetermined value, and limiting an output of an excessive load current. An overcurrent protection circuit and the like are provided.

[0003] The output voltage of the power supply required by the user varies in various ways depending on the application. Therefore, in practice, a large number of power supply devices having different output voltage standards are manufactured for power supply devices having almost the same circuit configuration. Therefore, in the case of the DC-DC converter, the secondary side circuit of the transformer is conventionally unitized as an independent circuit board, and a circuit board conforming to the output voltage standard is selectively mounted, and the standard required by the user is required. It is the fact that the power supply device is configured.

[0004]

In the case of the conventional power supply, it is necessary to prepare an independent circuit board as a secondary circuit of the transformer for each output voltage standard, and it is possible to supply power supplies of various standards. In order to achieve this, a large number of circuit boards had to be manufactured. A power supply device such as a DC-DC converter generally uses a reference voltage generated internally. By changing the reference voltage, it is possible to switch the output voltage of the power supply.

However, when the output voltage of the power supply changes, the standards such as the overvoltage of the overvoltage protection circuit, the undervoltage of the low voltage protection circuit, and the overcurrent of the overcurrent protection circuit also change. It could not be used for power supplies with different standards. An object of the present invention is to provide a power supply device capable of supplying power that conforms to a plurality of standards without changing the configuration.

[0006]

According to a first aspect of the present invention, there is provided a power supply device comprising:
In a power supply device including a reference voltage generation circuit that generates a reference voltage serving as a reference of the output voltage, a voltage abnormality detection circuit that detects an abnormality of the output voltage, and a current abnormality detection circuit that detects an excessive output current, At least one first switch means for switching the reference voltage generated by the voltage generation circuit in a binary or stepwise manner; and a threshold used in the voltage abnormality detection circuit for detecting a voltage abnormality in a binary or stepwise manner. At least one second switch means for switching the threshold value used for detecting an overcurrent by the current abnormality detection circuit in a binary or stepwise manner, and at least one third switch means for switching the threshold value in advance. Synchronous means for simultaneously turning on / off the first switch means, the second switch means, and the third switch means. And butterflies.

In the first aspect, the first switch means, the second switch means, and the third switch means are simultaneously turned on or off by the function of the synchronization means.
The reference voltage generated by the reference voltage generation circuit is switched in a binary manner by turning on / off one of the first switch means. Further, the threshold value used for the voltage abnormality detection by the voltage abnormality detection circuit is binary-switched by turning on / off one second switch means. Further, the threshold value used by the current abnormality detection circuit for detecting the overcurrent is binary-switched by turning on / off one of the third switch means.

Since the first switch means, the second switch means, and the third switch means are simultaneously controlled to be turned on or off, the output voltage of the power supply is switched by switching on / off of the first switch means. At the same time, the threshold of the voltage abnormality detection circuit and the threshold of the current abnormality detection circuit are switched. Therefore, at the same time as the output voltage is switched, the functions (thresholds) of the voltage abnormality detection circuit and the current abnormality detection circuit are switched so as to match the voltage after the switching. Therefore,
Using the same circuit board, it is possible to selectively output voltages respectively conforming to a plurality of types of standards.

The switching of the threshold values in the second switch means and the third switch means can be directly performed by changing the level of a signal input as a reference level to the comparator. When a signal to be monitored is level-converted by a voltage dividing circuit or the like and input to a comparator, the threshold can be indirectly changed by switching the level conversion ratio.

According to a second aspect of the present invention, in the power supply device of the first aspect, a photocoupler is provided for each of the first switch means, the second switch means, and the third switch means. In claim 2, the input circuit and the output circuit are electrically insulated by using a photocoupler, so that the input circuits of the first switch means, the second switch means, and the third switch means are shared. It can be connected to a circuit and controlled on / off simultaneously by the synchronization means.

According to a third aspect of the present invention, in the power supply device of the first aspect, the voltage abnormality detection circuit includes a first comparator for detecting an excessive voltage and a second comparator for detecting an undervoltage. And According to the third aspect, the threshold of the voltage abnormality detection circuit is switched by a single second switch so that the threshold of the first comparator used for detection of the excessive voltage and the second comparison used for detection of the undervoltage. And the threshold of the vessel can be switched simultaneously. Therefore, the circuit configuration of the power supply device can be simplified.

According to a fourth aspect of the present invention, in the power supply device according to the first aspect, the first switch means, the second switch means, and the third switch means are controlled according to the state of a binary signal externally input to the synchronization means. An external signal input circuit for simultaneously controlling on / off is provided. According to the fourth aspect, the first switch means, the second switch means, and the third switch means can be simultaneously turned on / off by a signal applied to an external signal input circuit, so that the output voltage of the power supply device is remotely controlled. You can switch with.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a power supply device according to the present invention will be described with reference to FIGS. This form corresponds to all claims. In this mode, DC-
It is assumed that the present invention is applied to a power supply device having a DC converter. FIG. 1 is a block diagram showing the configuration of the DC-DC converter of this embodiment. FIG. 2 shows the DC of FIG.
FIG. 3 is an electric circuit diagram showing a configuration of a main part of a DC converter.

In this embodiment, the reference voltage generating circuit, the voltage abnormality detecting circuit, the current abnormality detecting circuit, the first switching means, the second switching means, the third switching means and the synchronizing means are each provided with a reference voltage. Voltage generation circuit 30, voltage abnormality detection circuit 50, overcurrent detection circuit 40, photocoupler 6
1, a photocoupler 63, a photocoupler 62, and a characteristic switching circuit 60.

The first comparator and the second comparator in claim 3 correspond to the analog comparator 72 and the analog comparator 73, respectively. The external signal input circuit of claim 4 corresponds to the characteristic switching circuit 60. The DC-DC converter shown in FIG. 1 includes diodes 11, 12, a transformer 13, a rectifier circuit 14, a smoothing circuit 15, a power supply output terminal 16, a voltage detection circuit 17, a voltage comparison circuit 18, a PWM control circuit 19,
A driver circuit 21, a current detector 22, a reference voltage generation circuit 30, an overcurrent detection circuit 40, a voltage abnormality detection circuit 50, and a characteristic switching circuit 60 are provided.

The DC power supplied to the power input terminal 10 is applied to the primary side of the transformer 13 via the diodes 11 and 12. The driver circuit 21 connected to the primary side of the transformer 13 switches the primary side of the transformer 13 according to a pulse signal having a fixed period outputted from the PWM control circuit 19.

Accordingly, AC power flows through the primary winding of the transformer 13, and AC power also appears on the secondary winding of the transformer 13. The AC power appearing on the secondary winding of the transformer 13 is rectified by the rectifier circuit 14 and smoothed by the smoothing circuit 15.
It is output to the power output terminal 16 as a DC voltage. This D
The C-DC converter performs voltage feedback control to stabilize the output voltage. That is, the output voltage appearing at the power output terminal 16 is fed back to one input terminal of the voltage comparison circuit 18 via the voltage detection circuit 17. The reference voltage generated by the reference voltage generation circuit 30 is applied to the other input terminal of the voltage comparison circuit 18.

The voltage comparison circuit 18 includes a reference voltage generation circuit 3
A control signal corresponding to the difference between the reference voltage applied from 0 and the voltage fed back from the power supply output terminal 16 via the voltage detection circuit 17 is output to the PWM control circuit 19. The PWM control circuit 19 controls the pulse width of a pulse for switching the driver circuit 21 according to a control signal input from the voltage comparison circuit 18.

When the switching pulse width of the driver circuit 21 changes, the input power of the primary winding of the transformer 13 changes, and the voltage appearing on the secondary winding of the transformer 13 changes. For this reason, even when the voltage applied to the power input terminal 10 changes or the magnitude of the load connected to the power output terminal 16 changes, the power output terminal 16
Is automatically controlled so as to maintain a predetermined value.

Now, in the DC-DC converter as shown in FIG.
The circuit that supplies power to the
Anomalies may occur on the load side connected to Therefore, the voltage of the power supply output terminal 16 may be out of the range of the predetermined specified value, or the current flowing to the load may exceed the specified value.

In such a case, it is necessary to protect the DC-DC converter itself and the device connected to the power output terminal 16 as a load. DC-DC of FIG.
In the converter, voltage abnormality detection circuit 50 detects an abnormality in the output voltage. That is, the voltage abnormality detection circuit 50
Outputs an overvoltage detection signal (OVA) when the voltage at the power output terminal 16 exceeds a prescribed upper limit, and outputs an undervoltage detection signal (OVA) when the voltage at the power output terminal 16 falls below a prescribed lower limit. UVA) is output.

The overcurrent detection circuit 40 compares the magnitude of the load current detected by the current detector (current transformer) 22 with a predetermined upper limit, and, when the load current exceeds the upper limit, an overcurrent detection signal. (OCA) is output. FIG.
Although the current detector 22 is connected to the secondary side of the transformer 13, the current may be detected by the primary side of the transformer 13.

In this example, the overvoltage detection signal, the undervoltage detection signal and the overcurrent detection signal are applied to the PWM control circuit 19. The PWM control circuit 19 performs a predetermined protection operation according to each of the input overvoltage detection signal, undervoltage detection signal, and overcurrent detection signal. For example, when the excessive voltage detection signal appears and when the undervoltage detection signal appears, the driver circuit 21 is controlled to cut off the supply of power to the power output terminal 16. When an overcurrent detection signal appears, the driver circuit 21 is controlled so as to limit the output current to the power output terminal 16.

The voltage appearing at the power output terminal 16 is controlled so as to conform to a predetermined standard.
In the DC-DC converter, the output voltage can be switched according to a user's request. Therefore, one or more users who need different voltages can be handled by the DC-DC converter having the same configuration. That is, there is no need to prepare a different DC-DC converter for each voltage standard.

However, the standard itself changes when the output voltage is switched, so that the upper limit value and lower limit value of the voltage in the voltage abnormality detection circuit 50 and the upper limit value of the current in the overcurrent detection circuit 40 change. Therefore, in the DC-DC converter of FIG. 1, the characteristic switching circuit 60 automatically changes the threshold value of the overcurrent detection circuit 40 and the threshold value of the voltage abnormality detection circuit 50 in synchronization with the switching of the output voltage.

The characteristic switching circuit 60 shown in FIG. 1 includes photocouplers 61, 62, 63, a transistor 64, resistors 65, 6
8, 69, capacitor 66 and zener diode 67
Is provided. In the characteristic switching circuit 60, the on / off state of the transistor 64 is switched in accordance with the state of a binary signal externally applied to the control input terminal 23. The collector of the transistor 64 has three photocouplers 6
1, 62 and 63 photodiodes are connected in series.

That is, 2 applied to the control input terminal 23
When the transistor 64 is turned on by the value signal,
All the phototransistors of the photocouplers 61, 62 and 63 are turned on. When the transistor 64 is turned off, all the phototransistors of the photocouplers 61, 62, 63 are turned off. The phototransistor of the photocoupler 61 is connected to the reference voltage generating circuit 30, and the phototransistor of the photocoupler 62 is
The phototransistor of the photocoupler 63 is connected to the voltage abnormality detection circuit 50.

Reference voltage generation circuit 30, overcurrent detection circuit 4
The 0 and voltage abnormality detection circuit 50 is configured as shown in FIG. 2 in this example. Referring to FIG. 2, the reference voltage generating circuit 30 includes resistors 31, 33, 34, 37, 38, a variable resistor 32, a terminal 35, an operational amplifier 36, and an output terminal 3.
9 are provided.

Voltage V applied to reference voltage generating circuit 30
1 is a constant voltage. The voltage V1 is applied to the resistor 31, the variable resistor 32, the resistor 3
3. A voltage divided by a voltage dividing circuit constituted by the resistor 34 is applied. At the output terminal 39, a reference voltage equal to the + input terminal of the operational amplifier 36 appears. Photocoupler 61
When the phototransistor is turned off, the terminal 35 is opened, so that the voltage dividing ratio of the voltage dividing circuit is determined by the resistance values of the resistor 31, the variable resistor 32, and the resistor 33.

When the phototransistor of the photocoupler 61 is turned on, the terminal 35 is connected and the resistor 33 and the resistor 34 are connected in parallel. It is determined by the resistance values of the resistor 32 and the resistors 33 and 34. Therefore, the reference voltage generation circuit 30
Is output from the ON / OFF of the photocoupler 61.
Binary switching is performed in response to turning off.

The overcurrent detection circuit 40 includes a resistor 41, a diode 42, a capacitor 43, a resistor 44, and a resistor 4.
5, a terminal 46, an analog comparator 47, an output terminal 48, and an input terminal 49. A constant voltage V2 is constantly applied to the input terminal 49. The current detector 22 outputs a signal corresponding to the magnitude of the load current. This signal is rectified by the diode 42 and the capacitor 43 and the resistor 4
4 and the voltage of the analog comparator 47
Applied to the side input terminal.

When the phototransistor of the photocoupler 62 is off, the terminal 46 is open and the resistor 4
5 is also released. When the phototransistor of the photocoupler 62 is turned on, the terminal 46 is connected and the resistor 4
5 is connected in parallel with the resistor 44. That is, the impedance of the + input terminal of the analog comparator 47 is binary-switched according to the on / off state of the phototransistor of the photocoupler 62. When the impedance changes, the voltage V3 input to the analog comparator 47 changes even if the output level of the current detector 22 is constant. That is, the threshold value of the overcurrent in the overcurrent detection circuit 40 is switched according to ON / OFF of the phototransistor of the photocoupler 62.

The voltage abnormality detection circuit 50 has an input terminal 5
1, resistors 52, 53, 54, 56, 57, 58, 5
9, terminal 55, input terminal 71, analog comparators 72, 7
3. Output terminals 74 and 75 are provided. Input terminal 51
The voltage of the power output terminal 16 of FIG.
7 is input. Further, a constant voltage is constantly applied to the input terminal 71.

The analog comparator 72 determines whether the voltage of the power supply output terminal 16 to be monitored is higher than a predetermined upper limit value by comparing the voltages V5 and V4. The analog comparator 73 determines whether the voltage of the power supply output terminal 16 to be monitored is smaller than a predetermined lower limit value by comparing the voltages V4 and V6. The voltage V5 obtained by dividing the voltage input to the input terminal 51 by the resistors 58 and 59 is applied to the + input terminal of the analog comparator 72. Also, the analog comparator 73
The voltage V6 obtained by dividing the voltage input to the input terminal 51 by the resistors 56 and 57 is applied to the negative input terminal of the input terminal.

The constant voltage applied to the input terminal 71 is
The voltage is divided by a voltage dividing circuit composed of resistors 52, 53, and 54, and is applied as a voltage V4 to the negative input terminal of the analog comparator 72 and the positive input terminal of the analog comparator 73. When the phototransistor of the photocoupler 63 is off, the terminal 55 is opened and the resistor 54 is also opened, so that the voltage dividing ratio of the voltage dividing circuit is determined by the resistance values of the resistors 52 and 53. When the phototransistor of the photocoupler 63 is on, the terminal 55 is connected and the resistor 54 is connected in parallel with the resistor 53, so that the voltage dividing ratio of the voltage dividing circuit is equal to the resistance value of the resistors 52, 53 and 54. Is determined by

That is, the voltage V4 switches in a binary manner according to the on / off state of the phototransistor of the photocoupler 63. The voltage V4 is referred to by the analog comparator 72 as an upper limit value, and is referred to by the analog comparator 73 as a lower limit value. That is, the threshold value for determining the excessive voltage and the threshold value for determining the undervoltage are switched in a binary manner according to ON / OFF of the phototransistor of the photocoupler 63.

In the DC-DC converter shown in FIGS. 1 and 2, since the three photocouplers 61, 62, 63 are simultaneously turned on / off, the reference voltage generated by the reference voltage generating circuit 30 is switched and the power supply output terminal 16 is switched. Is changed, the threshold value used by the overcurrent detection circuit 40 for the determination and the threshold value used by the voltage abnormality detection circuit 50 for the determination are automatically switched so as to conform to the standard.

Therefore, only by switching the state of the binary signal externally applied to the control input terminal 23, the DC-
The characteristics (specified output voltage) of the DC converter can be switched. When the threshold value in the overcurrent detection circuit 40 and the threshold value in the voltage abnormality detection circuit 50 are switched, a level to be referred to as a determination criterion may be switched, or a ratio in level conversion of a signal to be monitored may be switched. Good.

Therefore, for example, instead of the circuit shown in FIG. 2, a modified circuit configuration as shown in FIG. 3 can be used. Referring to FIG. 3, in the overcurrent detection circuit 40, a voltage V <b> 21 generated by dividing a constant voltage V <b> 2 by a resistance voltage dividing circuit is applied to a negative input terminal of an analog comparator 47. Like changing the voltage dividing ratio of this resistor voltage dividing circuit,
The photocoupler 62 is connected.

In the voltage abnormality detection circuit 50 shown in FIG. 3, a photocoupler 63 is connected to a circuit for dividing the voltage to be monitored applied to the input terminal 51. Therefore, the threshold values of the analog comparators 72 and 73 can be switched by the photocoupler 63. Other operations are almost the same as those of the circuit of FIG. In the above-described embodiment, only the case where the characteristics of the DC-DC converter are switched in a binary manner has been described. However, it is also possible to selectively select characteristics from three or more types of characteristics. That is, elements corresponding to each of the photocouplers 61, 62, and 63, and elements that change the threshold value (such as a voltage dividing circuit)
Is provided, the characteristics of each circuit can be switched to three or more types.

[0041]

According to the present invention, it is possible to selectively output electric power conforming to a plurality of standards with one power supply device without replacing an internal circuit board. Moreover, since the thresholds of the voltage abnormality detection circuit and the current abnormality detection circuit are automatically changed so as to match the power actually output, even when the output voltage is switched, the functions of the voltage abnormality detection circuit and the current abnormality detection circuit are changed. Can be maintained normally. Therefore,
There is no need to manufacture a large number of circuit boards in accordance with each standard, and the manufacturing cost of the power supply device can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a DC-DC converter according to an embodiment.

FIG. 2 is an electric circuit diagram showing a configuration of a main part of the DC-DC converter of FIG.

FIG. 3 is an electric circuit diagram showing a configuration of a modification.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Power input terminal 11, 12 Diode 13 Transformer 14 Rectifier circuit 15 Smoothing circuit 16 Power output terminal 17 Voltage detection circuit 18 Voltage comparison circuit 19 PWM control circuit 21 Driver circuit 22 Current detector 23 Control input terminal 30 Reference voltage generation circuit 31, 33, 34, 37, 38 Resistor 32 Variable resistor 35 Terminal 36 Operational amplifier 39 Output terminal 40 Overcurrent detection circuit 41, 44, 45 Resistor 42 Diode 43 Capacitor 46 Terminal 47 Analog comparator 48 Output terminal 49 Input terminal 50 Voltage abnormality detection circuit 51, 71 Input terminal 52, 53, 54, 56, 57, 58, 59 Resistor 55 Terminal 60 Characteristics switching circuit 61, 62, 63 Photocoupler 64 Transistor 65, 68, 69 Resistor 66 Capacitor 67 Zener diode 72 73 Analog comparator 74 and 75 output terminals

Claims (4)

[Claims] 1. A power supply comprising: a reference voltage generation circuit that generates a reference voltage serving as a reference of an output voltage; a voltage abnormality detection circuit that detects an abnormality of an output voltage; and a current abnormality detection circuit that detects an excessive output current. In the apparatus, at least one first switch means for switching the reference voltage generated by the reference voltage generation circuit in a binary or stepwise manner, and a threshold used by the voltage abnormality detection circuit for detecting a voltage abnormality is binary. At least one second switch means for selectively or stepwise switching, and at least one third switch means for binaryly or stepwise switching a threshold value used by the current abnormality detection circuit for detecting an overcurrent. Synchronizing means for simultaneously turning on / off the first switch means, the second switch means, and the third switch means previously associated with each other. Power supply, wherein a provided. 2. The power supply device according to claim 1, wherein
A power supply device, wherein a photocoupler is provided for each of the switch means, the second switch means, and the third switch means. 3. The power supply according to claim 1, wherein the voltage abnormality detection circuit includes a first comparator for detecting an excessive voltage and a second comparator for detecting an undervoltage. apparatus. 4. The power supply device according to claim 1, wherein the first switch means, the second switch means, and the third switch means are simultaneously turned on / off in accordance with a state of a binary signal inputted to the synchronization means from the outside. A power supply device provided with an external signal input circuit for off control.