JPH0965645A - Power source protective circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To break an abrupt large current during the startup time of a power source by providing an on-timer which adjusts and sets protection starting time in corresponding to the rise completing time of the output voltage of the power source and is connected to an LVP and another LVP which outputs a power source cutting-off signal upon detecting a voltage which is lower than a detecting level. SOLUTION: A remote-on signal 21 and other control signals 22 are connected to a DC-DC switching regulator 20, with the remote-on signal being connected as a control signal also. An OCP 30 the output of which is connected to the regulator 20 for monitoring protects a power source by dropping the voltage of the power source with an inverted-L shaped characteristic which makes a large current to flow. When the output voltage of the power source drops from a specific monitoring voltage, and LVP 40 is actuated and cuts off the power source. In a power source protective circuit constituted in such a way, the remote-on signal 21 which can set different output voltage monitoring starting time depending upon the load of an electric device and an on-timer 60 connected to the LVP 40 are provided. In addition, at least another LVP 50 which monitors the abnormality of the output voltage of the power source during the startup time and is actuated depending upon a detecting level 2 is 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 protection circuit for a switching regulator which supplies power to a semiconductor test device and other electric devices (hereinafter referred to as electric devices).

[0002]

2. Description of the Related Art Each electric device is a commercial power source such as AC20.
The voltage suitable for each electric device is output from 0V or AC100V. There are many circuit systems for each power supply, and among them, many power supply devices use switching regulators, but the power supply used differs depending on each electric device. When an abnormality occurs in the load circuit that supplies power, stopping the power supply device protects the entire electric device, and therefore, many power supply devices have a protection circuit.

An example block diagram of a power supply protection circuit is shown in FIG. In the block diagram of FIG. 5A, for example, commercial power supply AC2
00V is input to the AC-DC power supply 10 and converted into a DC voltage, and the DC-DC switching regulator 2 in the next stage is converted.
It is a power source that can input a stable DC output voltage of 5 V and a rated output current of 150 A from the DC output side by inputting 0. D
The C-DC switching regulator 20 has a signal circuit for inputting a remote-on signal 21 and other control signals 22 as control signals. As a power supply protection circuit for the DC-DC switching regulator 20, OCP30 (Over Current P) having an inverted L-shaped characteristic and a foldback characteristic
LVP40 (Low Voltage Protecti) that operates according to the protection level and detection level 1.
on).

FIG. 5B shows the relationship between the monitor voltage and the monitor current of the OCP 30 of the power supply protection circuit. It is a circuit of OCP30 having an inverted L-shaped characteristic. For example, when the supplied power is designed to have a rated output voltage of 5V and a rated output current of 150A, if the overcurrent exceeds 150A, the reverse L
When the output voltage is lowered by 5V and falls below the detection level 1 due to the voltage characteristic, the LVP 40 of the power supply protection circuit is activated to cut off the DC output voltage, and the electric device connected thereto is protected.

FIG. 6A shows the relationship between the monitor current and time of the LVP 40 of the power protection circuit and the relationship between the monitor voltage and time.
It shows in (B). FIG. 6A shows an LVP40 of the power supply protection circuit.
The relationship between the monitor current and the monitor current is shown as follows. When the time when the current starts to flow is t0 and the end time of the initial state is represented by t1, when the electric power starts to be supplied to the electric device, the current is temporarily charged with initial charge or the like. Therefore, it is indicated that the overcurrent results in reaching the end of the initial state when supplied until t1.

FIG. 6B shows the relationship between the monitor voltage of the LVP40 of the power supply protection circuit and the time. It also shows that the rising of the voltage also reaches the end of the initial state at t1 corresponding to the current. If an abnormally large current flows suddenly after passing, the reverse L-shaped characteristic of OCP 30 will act and the output voltage will drop, and LVP 40 that operates at detection level 1 will operate and if it exceeds the voltage monitoring region below, it is judged that the load is abnormal. Then, the output voltage is cut off.

It is desired that the larger the power supplied from the power source to the electric device, the shorter the time t1 as much as possible in order to ensure the safety of the electric device. However, the time t0 to t1 supplied from the power source causes the capacitor of the circuit to operate. There are charges etc.
It is inevitable that overcurrent will flow for 0 to t1 hours. t
For safety monitoring after entering the stable region for more than 1 hour, the LVP 40 operates in addition to the OCP 30 of the power supply protection circuit to shut off the power supply device and safely protect the electric device.

Normally, when a large load is connected when the DC-DC switching regulator 20 is turned on,
If the supply voltage may not reach the end of the initial state even if t1 is exceeded, it is determined that the LVP 40 operating at the detection level 1 is activated and the load circuit has entered a region other than the safe region.
Since the DC output of the DC switching regulator 20 is cut off, the electric device cannot be started.

[0009]

Even if the load of the electric device is normal, if the supply voltage does not reach the detection level 1 by t1, the power supply device is shut off and the electric device does not start, so monitoring is started. If the time until is set to be long and tn is set, the electric device is activated. If an abnormal situation such as an output short circuit exists within t0 to tn, a large current will flow from that time to t
There was a problem that the DC output was not cut off even if it flowed until it reached n.

Even if a load such as a DC-DC switching regulator 20 of a DC power supply which has a large initial current at power-on and requires a long time to reach the initial state end region is connected, the output is shut off by the LVP. To provide a power supply protection circuit for a power supply device that can start an electric device without any trouble and avoid an abnormal situation by performing a cutoff operation of the power supply protection circuit even if a load has an abnormal situation within t0 to tn and a large current flows. To aim.

[0011]

In order to achieve the above object, the power supply protection circuit of the power supply device of the present invention can freely adjust the start time of monitoring of the electric device, and the set time can be changed from t0 depending on the load. If set within tn hours, t0 to t
Even if an abnormal situation exists within n and a large current flows, a detection level 2 for protecting the power supply is provided, and a means for shutting off the power by newly providing an LVP operating at the detection level 2 is provided. It was The LVP that operates at the detection level 1 that monitors the area after the end of the initial state after the power is turned on that exists in the past exists and is monitored as it is.

In the conventional LVP, for example, assuming that the rated output voltage is 100%, it monitors the abnormality after the power source is turned on. Therefore, the detection level 1 is monitored at the point of 65%, and the detection level 1 is detected. As the voltage fluctuates further downward, the LVP operates and protects the safety of the power supply. If a large current suddenly flows in the stable region after the power is turned on, the reverse L of OCP
The output voltage drops due to the letter-shaped characteristic, and when the detection level 1 is divided downward, the LVP is immediately activated to shut off the power source and the safety of the entire device is maintained.

The load of the electric device is various, and the time in the region of overcurrent and low voltage from the start of power supply to the start of the power supply is different, so that the power supply rises at tn.
The conventional LVP can be set freely by installing an on-timer up to
, And separately from this, there is provided an LVP that performs a protection operation by detection level 2. For example, assuming that the rated output voltage is 100%, the output voltage during power-up is 40%.
Immediately below 30% below 30% and LV
This is a power supply protection circuit that operates P to shut off the power supply.

[0014]

An embodiment will be described with reference to the drawings. FIG. 1 is a block diagram of a power protection circuit. An AC-DC power supply 10 for converting a commercial power supply into a DC voltage and a DC-DC switching regulator 20 for inputting the DC output thereof output a specified DC voltage. DC-DC switching
The regulator 20 is connected with the remote-on signal 21 and the other control signal 22 as control signals, and the output DC voltage is monitored in the next part. The OCP 30 connected for output has a reverse L when a large current flows. In the power supply protection circuit that protects the power supply by dropping the voltage with a linear characteristic and shuts down the power supply by operating the LVP40 when the output voltage drops below the specified monitoring voltage, the output voltage monitoring start time that differs depending on the load of the electric device An on-timer 60 connected to the settable remote-on signal 21 and the LVP 40 is provided, and at least an LVP 50 that monitors a voltage abnormality during power-on and operates at a detection level 2 is provided.
The OCPs 30, LVPs 40, 50 of the power supply protection circuit have a function of immediately feeding back to the DC-DC switching regulator 20 when an abnormality is detected to ensure the safety of the power supply.

FIG. 4A shows the relationship between current and time.
The relationship between voltage and time is shown in (B). In FIG. 4A, time is taken on the X-axis and output current is taken on the Y-axis, and current is supplied to an electric device, that is, a load. When the start time is t0 and the overcurrent is t
It flows to the load up to 1 and becomes stable at tn. For example, the DC output voltage is 5 V and the rated output current is 150 A, the voltage drop point due to overcurrent is 180 A, and t1 time is about 1 second, and the current capacity used is 1/2 of the power supply current capacity. However, it shows that the current capacity has a sufficient margin. Furthermore, if the time from t0 to tn is 1.2 seconds, it indicates that the stable region after the end of the initial state is sufficiently entered.

In FIG. 4B, time is taken on the X axis and voltage is taken on the Y axis to supply power to the load of the electric device. A low voltage is shown while the start time is t0 and the overcurrent is flowing through the load until t1, and when the initial current supply state ends, the voltage becomes the rated output voltage. Conventionally, the output voltage that has entered the region after the end of the initial state at t1 time is provided with the detection level 1 and the voltage is monitored by the LVP. However, a new LVP that operates at the detection level 2 is newly provided to detect the time from t0 to tn. The level 2 voltage is monitored. By the time the initial current supply state ends,
That is, when there is an abnormality from the start time t0 to the time tn, and when a large current flows below the newly established voltage detection level 2, the voltage is monitored by the operating LVP, and when an abnormality is detected, DC- The DC switching regulator 20 is fed back to shut off the power source to ensure the safety of the power source.

(Embodiment 2) FIG. 2 is a block diagram of a power supply protection circuit. AC-DC that converts commercial power to DC voltage
The DC-DC switching regulator 20 which inputs the power supply 10 and its DC output outputs a specified DC voltage.
The DC-DC switching regulator 20 is connected with the remote-on signal 21 and the other control signal 22 as control signals, and the output DC voltage is monitored in the next part. The output connected for monitoring OCP 30 has a large current. When a current flows, the voltage drops with an inverted L-shaped characteristic to protect the power supply. When the voltage drops below a specified monitoring voltage, the LVP40 that operates at detection level 1 operates to shut off the power supply. There is provided a remote-on signal 21 capable of setting a power supply monitoring start time which differs depending on the load of No. 1 and an on-timer 60 connected to the LVP 40. The LVP50 which operates by the detection level 2 becomes unnecessary when the power supply rise time for monitoring the voltage abnormality during the power supply rise and the area after the end of the initial state has passed, so it is possible to turn it off after the time tn. A timer 70 was provided connected to the LVP 50. An on-timer 60, which is turned on almost at the same time as the LVP 50 is turned off, monitors the area after the end of the initial state at the detection level 1
Perform at P40. Power protection circuit OCP30, LVP4
Immediately after detecting an abnormality, 0 and 50 feed back to the DC-DC switching regulator 20 to ensure the safety of the power supply.

Although the on-timer 60 and the off-timer 70 are connected to the LVPs 40 and 50, respectively, an on-off timer 80 may be provided to interlock the operation.

(Embodiment 3) FIG. 3 shows a block diagram of a power supply protection circuit in which a plurality of LVPs are not provided. The difference from FIG. 1 as the third embodiment is that the LVP4 among the plurality of LVPs 40 and 50 is different.
This is a power supply protection circuit in which only one 0 is used, the on-timer 60 is not used, and the timer 90 is connected to the LVP 40. The DC-DC switching regulator 20 has a remote-on signal 21 and other control signals 2 as control signals.
2 is connected and the output DC voltage is monitored in the next part. The output monitoring OCP30 drops the voltage with an inverted L-shaped characteristic when a large current flows and protects the power supply. Below the specified monitoring voltage. When the voltage drops to the low level, the LVP 40 that operates according to the detection level operates and shuts off the power supply. LV
A plurality of internal reference voltages of P40 are set, the set point is provided as a detection level, and a timer 90 having a function of controlling time according to the detection level is connected and provided. For example, the timer 90 controls the internal reference voltage of the LVP 40 by setting the detection level 2 in the region up to the end of the initial state and the detection level 1 in the region higher than that, and controlling the use of each detection level by time.

The power protection circuit OCP30 and LVP40,
Since the monitor control circuit of 50 requires a small amount of power consumption, it can be finished as a hybrid IC or a one-chip IC and applied to various power supplies of different systems, which is useful for improving the safety and miniaturization of various power supplies.

[0021]

Since the present invention is constructed as described above, it has the following effects.

Although the rise time of the power supply varies depending on the electric device serving as the load, the output voltage monitoring start time is conventionally short, and it may be difficult to start the electric device serving as the load even if there is no abnormality in the load. However, by freely setting the output voltage monitoring timing at the start-up of the power supply with a timer and designing it, it became possible to start the electric device with a load without abnormality.

Switching to detection levels 1 and 2 can be performed by an on-timer or an off-timer.

The monitor control circuits of OCP and LVP can be used for various power supplies of different systems by finishing them into a hybrid IC or a one-chip IC, which is useful for improving the safety of power supplies and downsizing.

The power supply protection circuit is effective in safety management because it operates even against a sudden large current within the rise time of the power supply.

[Brief description of drawings]

FIG. 1 is a block diagram of a power supply protection circuit of the present invention.

FIG. 2 is a block diagram of a power supply protection circuit (second embodiment) of the present invention.

FIG. 3 is a block diagram of a power supply protection circuit (third embodiment) of the present invention.

FIG. 4A is a relationship diagram of current and time of a power supply protection circuit, and FIG. 4B is a relationship diagram of voltage and time of a power supply protection circuit and a monitoring area.

5A is a block diagram of a power supply protection circuit according to a conventional technique, and FIG. 5B is a diagram of an inverse L-shaped characteristic of voltage and current.

FIG. 6A is a relationship diagram of current and time of a power supply protection circuit according to the related art, and FIG. 6B is a relationship diagram of voltage, time and a monitoring region of the power supply protection circuit according to the related art.

[Explanation of symbols]

10 AC-DC power supply 20 DC-DC switching regulator 21 Remote ON signal 22 Other control signal 30 OCP (Over Current Prote)
40, 50 LVP (Low Voltage Pro)
60) ON timer 70 OFF timer 80 ON / OFF timer 90 timer

Claims (4)

[Claims] 1. A DC voltage / current output from a DC-DC switching regulator (20) is monitored,
OCP (3 with overcurrent protection even if a large current suddenly flows
0) actuates to drop the output voltage and monitors the stable region after the power supply rises. The LVP (40) shuts off the power supply when it detects an output voltage below the detection level 1 in the power protection circuit. Since the rise time of the power supply output voltage varies depending on the electric device of the above, the LVP is set to the ON timer (60) for adjusting the protection start time according to the rise end time.
A power supply protection circuit, which is provided with being connected to (40), further has an LVP (50) for detecting a voltage below detection level 2 and outputting a power supply cutoff signal, and having the above configuration. 2. In addition to the power protection circuit according to claim 1, an off timer (70) that can be set by adjusting the operation end time of the LVP (50) that operates when the detection level 2 is exceeded downward after power is turned on. ) Is connected and provided with the above-mentioned structure. 3. In addition to the power supply protection circuit according to claim 1, an on / off timer (80) that operates in conjunction with the LVP (40, 50) after power is turned on is provided, and the above configuration is provided. Power protection circuit characterized by. 4. In addition to the power protection circuit according to claim 1, a timer (90) for controlling the use of each detection level by time is connected to the LVP (40) in which the internal reference voltage is set as a plurality of detection levels. A power supply protection circuit having the above configuration.