WO2002075909A1

WO2002075909A1 - Multiple power supply, and method and apparatus for overcurrent protection of multiple power supply

Info

Publication number: WO2002075909A1
Application number: PCT/JP2001/002201
Authority: WO
Inventors: Hiroya Tanaka
Original assignee: Fujitsu Limited; Fujitsu Peripherals Limited
Priority date: 2001-03-19
Filing date: 2001-03-19
Publication date: 2002-09-26

Abstract

A multiple power supply device is provided in which a switching circuit (12) controls input current (I) flowing to the primary of a transformer, and a plurality of output circuits (21-25) provided in the secondary of the transformer produce output. The multiple power supply device comprises a protection circuit (311) for stopping a switching circuit (12) in response to an input current (I) exceeding a maximum input level, a voltage detector circuit (313) for detecting the voltage of at least one output circuit (24) provided on the secondary side, a differentiator circuit connected to the voltage detector circuit (313) to detect the change in the voltage of other output circuits (21-23) provided on the secondary side (315), and a control circuit (312) for operating the protection circuit (311) if the voltage detected by the voltage detector circuit (313) is lower than a threshold.

Description

Description: Overcurrent protection control method and device for multi power supply device and multi power supply device

The present invention relates to a method and a device for controlling overcurrent protection of a multi power supply device and a multi power supply device. In particular, it is used for overcurrent protection of switching type multi power supply devices. Background art

A personal computer and its peripheral devices are equipped with a multi-power supply device for supplying a necessary DC voltage to each part of the device. A multi-power supply device is generally configured so that a switching circuit controls an input current flowing to a primary side of a transformer and extracts output from a plurality of output circuits provided on a secondary side of the transformer. The multi-power supply mounted on the device has three output circuits of 9 volts, 15 volts and 24 volts to supply the control circuits, and 80 volts and 1 volts for driving the brown tube. It has two output circuits of 60 volts.

In such a multi power supply device, an overcurrent protection device for stopping the operation when the output circuit is short-circuited or when the current of the output circuit becomes excessive has been conventionally provided.

Conventional overcurrent protection devices detect the input current on the primary side and stop the switching circuit when the input current exceeds the input upper limit.

However, if an overcurrent occurs in the output circuit on the secondary side, the input current on the primary side is not always increased to the input upper limit. For example, if the output circuit of 80 volts is short-circuited, the power consumed there will be large, and the input current on the primary side will increase significantly and the protection device will operate. However, if the 9 volt output circuit is short-circuited, the power consumed there will be small and the primary side input current will not be as high. It may not increase and the protection device may not operate.

In such a case, if the output circuit continues to be short-circuited, it may also affect other circuits, causing damage to spread and making recovery more difficult.

Therefore, for example, it is conceivable to provide a current detection circuit and a control circuit for operating the overcurrent protection device when an overcurrent is detected for each output circuit. However, in such a case, the circuit becomes complicated and the number of components also increases, resulting in an increase in size and cost. Disclosure of the invention

SUMMARY OF THE INVENTION An object of the present invention is to protect an apparatus by detecting an overcurrent of each of a plurality of output circuits with a simple circuit.

According to one embodiment of the present invention, a multi-power-supply device configured to control an input current flowing to a primary side of a transformer by a switching circuit and extract output from a plurality of output circuits provided on a secondary side of the transformer A protection circuit for stopping the switching circuit when an input current exceeds an input upper limit, and a voltage for detecting a voltage of at least one output circuit provided on the secondary side. A detection circuit, a differentiating circuit connected to the voltage detection circuit for detecting a change in voltage of another output circuit provided on the secondary side, and a voltage detected by the voltage detection circuit. A control circuit for operating the protection circuit when the voltage falls below a threshold value.

Preferably, the switching circuit includes a switching element, and a drive circuit that supplies a pulse signal to the switching element to drive the switching element, wherein the drive circuit has a control input terminal for controlling an ON time of the pulse signal. The control circuit has a control signal that maximizes the ON time of the pulse signal when the voltage detected by the voltage detection circuit drops below a threshold. It is composed of a gate circuit that outputs to BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a circuit diagram of a power supply device 1 showing an embodiment according to the present invention, and FIG. 2 is a power supply device. FIG. 3 is a diagram illustrating a state of a signal of each unit of FIG. BEST MODE FOR CARRYING OUT THE INVENTION

In FIG. 1, a power supply 1 includes a transformer T1, an input circuit 11, a switching circuit 12, five output circuits 21 to 25, and a protection circuit 31. The input circuit 11 includes, for example, a rectifier RC for rectifying 100-volt AC power, a smoothing capacitor C11, and the like.

The switching circuit 12 includes power such as the drive circuit 12 1 and the switching element Q 1. A transistor or FET is used as the switching element Q1.

The drive circuit 1221 drives the switching element Q1 by supplying a pulse signal SD. When the pulse signal SD is on, the switching element Q1 conducts. The drive circuit 122 has a control input terminal FB. The potential VFB of the control input terminal FB is varied according to the resistance value connected between the control input terminal FB and the ground, thereby controlling the on-time (duty ratio) of the pulse signal SD.

That is, for example, when the control input terminal FB is opened and the impedance is increased, the potential VFB of the control input terminal FB becomes the maximum value. The potential VFB at that time is, for example, 5 volts. As a result, the ON time of the pulse signal SD becomes the maximum, and the maximum power is supplied to the primary side of the transformer T1. When the control input terminal FB is grounded, the potential VFB becomes zero, the on-time of the pulse signal SD becomes minimum, and the power supplied to the primary side of the transformer T1 becomes minimum.

Usually, by controlling the impedance connected to the control input terminal FB, the output voltages of the output circuits 21 to 25 are controlled to have a predetermined value. In addition, the drive circuit 122 has a stop terminal HC. When the stop signal SP is input to the stop terminal HC, the drive circuit 122 stops its operation. When the operation of the drive circuit 122 stops, the pulse signal SD is not output, and therefore, the switching element Q1 does not turn on.

Such a drive circuit 122 can be configured using a comparator that compares the voltage of the control input terminal FB with a triangular wave. Drive circuit 1 2 1 It is commercially available as an integrated circuit device (for example, nominal type: UC3842) and is known.

Each of the output circuits 21 to 25 has a rectifying diode, a smoothing capacitor, and the like, and outputs a DC output OUT 1 to 5.

The output voltages of the output circuits 21 to 25 are, for example, 9 volts, 15 volts, 24 volts, 160 volts, and 80 volts.

Each of the output circuits 21 to 23 is provided with a constant voltage circuit 314 and a differentiation circuit 315 described later. The output circuit 24 is provided with a voltage detection circuit 313 described later. The output circuit 25 is provided with a gate circuit 312 described later. The protection circuit 31 is composed of OCP (Over Current Protector) 311, current detection resistor R16, gate circuit 312, voltage detection circuit 313, constant voltage circuit 314, and differentiation. The circuit consists of 3 15. '

The input current I flowing through the input circuit 11 is detected by the resistor R16. The OCP 311 outputs the stop signal SP when the voltage SC generated across the resistor R16 exceeds the input upper limit value th1. The drive circuit 122 stops due to the stop signal SP, and the switching circuit 122 stops.

The input upper limit value t h1 at which 0 C P 311 operates is set, for example, to correspond to about 1.3 to 1.6 times the steady-state current. This protects the power supply 1 from overcurrent. The configuration and action of such OCP311 are known.

The gate circuit 3 1 2 is composed of a photo cover PC 1 and a Shuntregi-Yuraya SR. The gate circuit 312 is connected to the output circuit 25 via a resistor R15, a constant voltage diode D4, a constant voltage circuit, and the like. The rated voltage of the constant voltage diode D4 is, for example, 15 volts. A constant DC voltage is supplied to the gate circuit 312 by the constant voltage circuit.

The shunt-reguler SR is a circuit element that conducts from the cathode to the node when the voltage (gate voltage) VG2 applied to the gate G2 exceeds the threshold th2. For example, the shunt regulée SR is configured using a comparator that compares a voltage equal to the threshold value th2 with a voltage input to the gate G2. When the SR is off, the photo force bra PC 1 is off. Therefore, the potential VFB of the control input terminal FB of the drive circuit 1 2 1 is the maximum value.

When the shunt regulator is turned on, the current supplied from the output circuit 25 flows through the photocoupler PC1 and the shunt regulator SR. As a result, the photo brassier PC 1 is turned on, and the potential V FB of the control input terminal FB becomes zero. In this state, the drive circuit 122 does not output the pulse signal SD.

The on / off signal output from the photocoupler PC1 to the control input terminal FB corresponds to the control signal of the present invention.

The voltage detection circuit 313 includes a resistor R10 and a resistor R11. The voltage detection circuit 3 13 detects the voltage of the output circuit 2 based on the voltage division ratio of the resistor R 10 and the resistor R 11.

Here, as a specific example of numerical values, assuming that the threshold value th2 of the shunt regulator and the threshold value th2 is 2.5 Bonoreto and the output voltage of the output circuit 24 is 160 volts, the voltage detection circuit 3 1 The partial pressure ratio by 3 is 64 times smaller. Therefore, for example, the resistance R 10 may be set to 24.6 kOhm, and the resistance R 11 may be set to 3.9 kOhm. The resistance R12 is of the order of 200 ohms.

By configuring the voltage detection circuit 313 and the gate circuit 312 in this manner, the output voltage of the output circuit 24 is normally maintained at 160 volts, and the other output circuits are also at predetermined levels. Voltage is maintained.

The constant voltage circuit 314 includes resistors R1 to R3 and constant voltage diodes D1 to D3. The rated voltages of the constant voltage diodes Dl, D2, and D3 are, for example, 7 volts, 12 volts, and 20 volts. These are connected to the output circuits 21 to 23, respectively, and remove the pulsating flow of each line to obtain a complete DC voltage.

The differentiating circuit 315 includes capacitors C1 to C3 and resistors R4 to R6. These are connected between the constant voltage circuit 31 and the midpoint of the voltage detection circuit 313. As a result, a change in each voltage when each of the output circuits 21 to 23 is short-circuited is detected as a voltage across the resistor R11.

That is, when any of the output circuits 21 to 23 is short-circuited, the electric charge stored in the capacitors C 1 to C 3 is transferred from the duland side of the resistor R 11 to the resistors R 4 to R 6. Flowing. As a result, a negative voltage is instantaneously generated at both ends of the resistor R11, and the gate voltage VG2 of the shunt regulator SR instantaneously drops below the threshold th2.

Here, as examples of specific numerical values, capacitors C1 to C3 each have a 2-micron farad, resistors R4 to R6 each have a resistance of about 100 kΩ, and resistors R1 to R3 each have a resistance of about 1 kΩ. It is.

Next, the operation of the overcurrent protection of the power supply device 1 configured as described above will be described. In FIG. 2, while the power supply device 1 is operating normally, the gate voltage VG2 rises and falls across the threshold value th2. During this time, the cathodic potential V k of the shunt regley night SR is between the fixed potential V k1 and zero, and the photo power bracket PC 1 repeats on and off. The potential VFB of the control input terminal FB of the drive circuit 121 fluctuates between the maximum voltage and zero, and the duty ratio of the output pulse signal SD varies between large and small. The voltage SC across the resistor R16 is below the input upper limit value th1 and the OCP311 does not output the stop signal SP. Normal voltages are output to the outputs OUT1 to OUT5 of the output circuits 21 to 25.

At time t1, it is assumed that the line of the output circuit 21 is short-circuited. The voltage of the output circuit 21 becomes zero. Then, a negative current flows through the resistor R11 via the capacitor C1 and the resistor R4, and the gate voltage VG2 falls to the threshold value th2 or less. As a result, the potential of the power sword Vk of the shuntle guille night SR rises, and the photo power bra PC 1 is turned off. The potential VFB of the control input terminal FB of the drive circuit 121 becomes the maximum value, and the duty ratio of the pulse signal SD becomes the maximum. As a result, the input current I increases, and the voltage SC across the resistor R16 exceeds the input upper limit value th1. Then, the OCP 311 outputs the stop signal SP, and the operation of the drive circuit 121 stops. As a result, the pulse signal SD disappears, the switching element Q1 turns off, and the input current I becomes zero.

The same applies when the other output circuits 22, 23 are short-circuited.

Further, when the output circuit 24 is short-circuited, the gate voltage VG2 decreases, and 0CP311 operates through the same process as above. When the output circuit 25 is short-circuited, the photo power PC 1 is turned off, and the OCP 311 operates through the same process as above. However, when the output circuits 21 to 25 are short-circuited, the input current I increases by itself, so that the OCP 311 directly performs the overcurrent protection operation without going through the operation of the gate circuit 312. There are cases.

As described above, according to the present embodiment, by adding the constant voltage circuit 314 and the differentiation circuit 315 to the conventional power supply, overcurrent protection due to short-circuiting of the output circuits 21 to 23, etc. Is achieved. That is, the overcurrent of each of the plurality of output circuits 21 to 25 can be detected by a simple circuit to protect the device.

By providing the constant voltage circuit 314, the pulsating flow of each line is completely removed, and the operation of the voltage detection circuit 313 at normal time is not affected.

In the embodiment described above, an example of the power supply device 1 having five output circuits 21 to 25 has been described, but the number of output circuits may be four or less or six or more. The drive circuit 121, 0 CP 311 and the gate circuit 312 can have various circuit configurations or element configurations other than those described above. The configurations and element constants of the voltage detection circuit 3 13, the constant voltage circuit 3 14, and the differentiation circuit 3 15 can be various other than those described above. As a method of connecting the differentiating circuit 315 to the voltage detecting circuit 313, an adding circuit having a diode or a transistor can be used.

In addition, the configuration, circuit, elements used, element constants, number, layout, voltage value, current value, threshold value, set value, and the like of each part or the whole of the power supply device 1 are appropriately changed according to the spirit of the present invention. be able to. Industrial applicability

As described above, the present invention can protect the power supply device by detecting the overcurrent of each of the plurality of output circuits with a simple circuit. It is especially suitable when the voltages of the output circuits differ greatly. The invention is useful in the electronics industry.

Claims

The scope of the claims

1. An overcurrent protection control method for a multi-power supply device configured to control an input current flowing to the primary side of a transformer by a switching circuit and extract output from a plurality of output circuits provided on a secondary side of the transformer. Hot,

A protection circuit for stopping the switching circuit when an input current exceeds an input upper limit value;

A voltage detection circuit that detects a voltage of at least one output circuit provided on the secondary side;

A differential circuit connected to the voltage detection circuit for detecting a change in the voltage of another output circuit provided on the secondary side; and

When the voltage detected by the voltage detection circuit falls below a threshold value, the protection circuit controls the switching circuit to stop.

An overcurrent protection control method for a multi-power-supply device.

2. An overcurrent protection device for a multi-power supply device configured to control an input current flowing to the primary side of a transformer by a switching circuit and extract output from a plurality of output circuits provided on a secondary side of the transformer. hand,

A differentiating circuit connected to the voltage detecting circuit to detect a change in the voltage of another output circuit provided on the secondary side;

A control circuit that operates the protection circuit when a voltage detected by the voltage detection circuit falls below a threshold;

An overcurrent protection device for a multi power supply device, comprising:

3. An overcurrent protection device of a multi-power supply unit configured to control the input current flowing to the primary side of the transformer by the switching circuit and take out the output from the multiple output circuits provided on the secondary side of the transformer. Hot, A protection circuit for stopping the switching circuit when an input current exceeds an input upper limit value;

When the voltage detected by the voltage detection circuit falls below a threshold value, the control circuit controls the input current to exceed the input upper limit value by increasing the ON output of the switching circuit;

An overcurrent protection device for a multi power supply device, comprising:

4. The switching circuit has a switching element, and a drive circuit that supplies a pulse signal to the switching element to drive the switching element.

The drive circuit has a control input terminal for controlling the ON time of the pulse signal,

The control circuit outputs a control signal to the control input terminal to maximize the ON time of the pulse signal when a voltage detected by the voltage detection circuit falls below a threshold value. Gate circuit,

4. The overcurrent protection device for a multi power supply device according to claim 3.

5. The gate circuit operates by a voltage supplied from still another output circuit provided on the secondary side, and when the voltage of the output circuit decreases, the gate circuit operates by the control signal. Output,

The overcurrent protection device for a multi power supply device according to claim 4.

6. The voltage detection circuit includes a resistance element that divides a voltage of the output circuit, and the differentiation circuit includes a capacitor and a resistance element.

7. The differentiating circuit is connected to the output circuit via a constant voltage circuit including a resistance element and a constant voltage element.

An overcurrent protection device for a multi power supply device according to claim 6.

8. The input current flowing to the primary side of the transformer is controlled by the switching circuit, A multi-power-supply device configured to extract output from a plurality of output circuits provided on a secondary side of a lance,

A control circuit for operating the protection circuit when a voltage detected by the voltage detection circuit falls below a threshold value;

A multi-power-supply device comprising: