JP3185632B2 - Output protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output protection circuit that detects an overload state of an output circuit, cuts off power supply to the output circuit, and protects the output circuit.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a configuration of a conventional output protection circuit C. An output driver protection circuit 5 is provided in a control signal generation circuit 1 for outputting a control signal for output circuit protection.
The output driver of the output driver protection circuit 5 is connected to an output driver 3 for supplying power to the output circuit. The output terminal of the output driver 3 is connected to the output terminal t0. Is connected to an output circuit to be subjected to an overload protection operation. Output driver 3
Is connected to a current detection resistor 25 for detecting an overcurrent of the output circuit, and a detection terminal t1 of the current detection resistor 25 is connected to an overcurrent detection terminal t2 of the output driver protection circuit 5.

In the conventional output protection circuit C having such a configuration, when an overcurrent flows in the output circuit, an abnormal current flows in the current detection resistor 25 in response to the overcurrent, and the current detection resistor 25
Changes at the detection terminal t1, and the detection signal is input to the overcurrent detection terminal t2 of the output driver protection circuit 5. By the input of the detection signal to the overcurrent detection terminal t2, a stop signal is input from the output driver protection circuit 5 to the output driver 3, and the stop signal causes the output driver 3 to stop supplying power to the output circuit. The output circuit is protected from overload conditions.

[0004]

In the conventional output protection circuit described above, the current flowing through the output circuit is reduced because the current detection resistor 25 is inserted and connected, and the output driver 3 compensates for the large power. Supply is required and the capacity of the device needs to be increased. Further, when the output current is large, the power loss in the current detection resistor 25 increases, and a current detection resistor having a large allowable power is required, and the mounting area of the output protection circuit C is increased.

The present invention has been made in view of the above-mentioned current situation of an output protection circuit of the type described above, and an object of the invention is to provide an output protection circuit capable of reducing the loss of output current and the mounting area. Is to provide.

[0006]

In order to achieve the above object, the present invention is directed to a method for connecting an output terminal to an output terminal.
Output driver for outputting force, and output of the output driver
An output control driver for performing control and the output control driver
An output driver protection circuit for outputting a drive signal to the
Control signal generation circuit that supplies control signals to force control driver
Wherein the output driver protection circuit includes the output driver.
Output terminal connected to the
Connected between the output terminals and the output connected to the output driver.
If the output terminal voltage is normal, the output control driver
A drive signal for controlling the operation of the output driver
From the output terminal connected to the output driver.
When the pressure is equal to or lower than the allowable level, a drive signal for causing the output control driver to perform control for stopping the operation of the output driver is output . With this configuration, the output circuit
Is protected from overload, reducing output current loss,
With the mounting area of the output driver protection circuit reduced,
It is possible to protect the power circuit from overload.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a circuit diagram showing a configuration of the present embodiment,
FIG. 2 is a block diagram showing a schematic configuration of the present embodiment.

In this embodiment, as shown in FIG. 2, a control signal generating circuit 1 for outputting a control signal of an output protection circuit CA is provided.
An output control driver 2 for controlling the output driver is connected to the output control driver 2. An output terminal of the output control driver 2 is connected to an output driver 3 for supplying power to an output circuit. The output driver 3 is connected to an output terminal t0. An output circuit to be overloaded is connected to the output terminal t0. The output driver protection control circuit 5 detects an overload state of the output circuit between the input terminal and the output terminal t0 of the output control driver 2 and inputs a drive signal to the output control driver 2.
A is connected.

In the actual circuit of this embodiment, as shown in FIG. 1, the output terminal of the control signal generating circuit 1 is connected to the base of an output control transistor 8 via a resistor 6, and A connection point with the base of the transistor 8;
The resistor 7 is connected between the grounds, and the emitter of the output control transistor 8 is grounded. The collector of the output control transistor 8 is connected to the output transistor 1 via the resistor 9.
1 and a resistor 9 and an output transistor 11
A resistor 10 is connected between a connection point with the base and the bias terminal, a collector of the output transistor 11 is connected to the output terminal t0, and an output circuit (not shown) is connected to the output terminal t0.

On the other hand, the collector of the output transistor 11 is connected to the base of the transistor 16 via a series connection circuit of the diode 13 and the resistor 14, the emitter of the transistor 16 is grounded, and the output of the transistor 14 is connected to the base of the transistor 16. Resistor 15 between the connection point and ground
Is connected. The collector of the transistor 16 is connected to the base of the transistor 20, the emitter of the transistor 20 is grounded, and the collector of the transistor 20 is connected to the base of the output control transistor 8.

A resistor 17 is connected between a connection point between the base of the transistor 20 and the output terminal of the control signal generating circuit 1, and a capacitor 18 is connected between the connection point between the resistor 17 and the transistor 20 and the ground. The resistor 19 is connected in parallel with each other.

In this embodiment having such a configuration, during normal operation, a control signal is output from the control signal generation circuit 1, and when the control signal is at the H level, the output control transistor 8 is turned on, and A predetermined bias is applied to the base of the output transistor 11 by a current flowing through the output transistor 10, the output transistor 11 is turned on, the voltage of the output terminal t0 becomes H level, and a predetermined current is supplied to the output circuit. At this time, the transistor 16 is ON
In this state, the voltage of the base of the transistor 20 decreases, and the transistor 20 is turned off. Therefore, the output control transistor 8 maintains the on state, and power supply to the output circuit is continued.

When the control signal is not output from the control signal generation circuit 1 and the control signal goes low, the output control transistor 8 is turned off and the output transistor 11 is also turned off.
Since the state is the FF state, the voltage of the output terminal t0 becomes L level, and power is not supplied to the output circuit. At this time,
Since the transistor 16 is turned off and the transistor 20 is turned on, the output control transistor 8 maintains the off state, and the power supply to the output circuit is stopped.

In this embodiment, if a short circuit or the like occurs in the output circuit and an overcurrent flows while the control signal is at the H level, the voltage at the output terminal t0 goes to the L level, and the transistor 16 is turned on in the 0N state. To OFF state,
The transistor 20 shifts from the OFF state to the ON state, the output control transistor 8 shifts to the 0FF state, the output transistor 11 changes to the OFF state, and power supply to the output circuit is stopped.

If a short circuit or the like occurs in the output circuit and an overcurrent flows while the control signal is at the L level, the voltage at the output terminal t0 is at the L level and the transistor 16 is turned off. Keep transistor 20
Maintains the ON state, and the output control transistor 8
In order to maintain the state and keep the output transistor 11 in the OFF state, power supply to the output circuit is stably maintained in the stopped state.

Further, in the present embodiment, after the overload state of the output circuit is detected and the power supply to the output circuit is cut off by the output transistor 11, the control signal generation circuit 1 is reset to output the control signal. When the L level is set to the L level, the transistor 20 is set to the OFF state. Therefore, the output protection circuit CA is initialized, and when the overload state of the output circuit is restored to the normal load state, the output protection circuit CA returns to the normal control state. Return to.

As described above, according to the present embodiment, when the output circuit is overloaded due to a short circuit accident or the like and the voltage of the output terminal t0 goes low, the transistor 16 is turned off and the transistor 20 is turned on. In this state, the output transistor 8 is turned off, so that the output transistor 11 is turned off and power supply to the output circuit is stopped. However, since no current is detected by the resistance element, the output transistor 8 is turned off. No loss of flowing current,
The mounting area of the output protection circuit can be significantly reduced.

[0019]

According to the present invention, the control signal from the control signal generation circuit is supplied to the output control driver, and the output driver controlled by the output control driver supplies power to the output circuit connected to the output terminal. When the voltage of the output terminal falls below the allowable level, a drive signal is input to the output control driver by the output driver protection circuit,
The output control driver controls the output driver to stop supplying power to the output circuit, and the output circuit is protected from overload, so the output current loss is reduced and the mounting area of the output driver protection circuit is reduced. In this state, the output circuit can be protected from overload.

Further, an initialization means for initializing the output protection circuit after the operation of the output driver is stopped due to the detection of the overload state is provided. Are initialized and can be operated immediately after returning to the normal load state.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of the embodiment;

FIG. 3 is a block diagram showing a schematic configuration of a conventional output protection circuit.

[Explanation of symbols]

 Reference Signs List 1 control signal generation circuit 2 output control driver 3 output driver 5A output driver protection circuit 8 output control transistor 11 output transistor 16 transistor 20 transistor

Claims (2)

(57) [Claims] An output terminal connected to the output terminal;
Output driver for outputting force, and output of the output driver
An output control driver for performing control and the output control driver
An output driver protection circuit for outputting a drive signal to the
Control signal generation circuit that supplies control signals to force control driver
Wherein the output driver protection circuit includes the output driver.
Output terminal connected to the
Connected between the output terminals and the output connected to the output driver.
If the voltage of the output terminal is normal, the output control driver
A driving signal for controlling the operation of the output driver.
Output terminal, and an output terminal connected to the output driver.
If the voltage is below acceptable levels, the output protection circuit and outputting a driving signal for causing the control to stop the operation of the output driver to the output control driver. 2. The output driver protection circuit according to claim 1 , wherein
When the voltage of the output terminal connected to the driver is normal
Turns on and the output terminal connected to the output driver
When the voltage of the child is below the allowable level, it turns off.
A first transistor and the first transistor are in an ON state
In the case of the status, the output driver is operated by the output control driver.
Output a drive signal for controlling the operation of the first
When the transistor is in the OFF state, the output control driver
To control the operation of the output driver to stop.
And a second transistor that outputs a motion signal.
The output control driver outputs from the second transistor.
The operation of the output driver is controlled by the input drive signal.
Characterized by comprising an output control transistor
2. The output protection circuit according to claim 1, wherein: