JP2000020143A - Capacitance discharge circuit and slow start circuit provided with this circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance discharge circuit as a means which quickly reduces a voltage at the time of break of voltage supply and a slow start circuit which is provided with this capacitance discharge circuit to prevent the malfunction of an electronic circuit at the time of restart. SOLUTION: A transistor TR Q2 as a switch is connected in parallel to a capacitor C1 connected to the base of a TR Q1. A diode D1, a resistance R2, and a coil L1 as an inductance element are connected in series as a current supply circuit between power lines on the input side of the slow start circuit, and one end on the resistance R2 side of the coil L1 is connected to the gate of the TR Q2. The TR Q2 is turned on in accordance with the voltage generated in the coil L1 to discharge the electric charge stored in the capacitor C1, thus quickly reducing the voltage appearing between terminals 2 and 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for reliably restarting an electronic circuit immediately after stopping it.

[0002]

2. Description of the Related Art In recent years, electronic devices have remarkably become multifunctional, and electronic circuits of respective parts constituting the electronic device have a dense and complicated circuit configuration. Many of these complicated and sophisticated electronic circuits are susceptible to fluctuations in the supply voltage, and specifically, due to factors such as noise entering from the power supply line and abnormal drop in the supply voltage. A malfunction may occur. Therefore, various protection means are provided for these electronic circuits in order to prevent the circuits from malfunctioning. As an example of the protection means, there is a slow start circuit having a configuration as shown in FIG. The slow start circuit shown in FIG. 4 is provided on a high-potential power line from the power supply 1 to the terminal 2a via the power switch S such that the main current path between the collector and the emitter is in series with the external power supply 1. Of the NPN transistor Q1. The capacitor C1 is connected between the base of the transistor Q1 and the low-potential-side power line, that is, the ground, and the resistor R1 is connected between the collector and the base of the transistor Q1. Terminal 2
An electronic circuit (load circuit) that receives a supply of voltage from the power supply 1 via the slow start circuit is connected between a and 2b.

In the circuit having such a configuration, when the power switch S is closed, the capacitor C1 is charged via the resistor R1, and the voltage between its terminals increases according to the time constant of CR. Then, the transistor Q1 conducts between the collector and the emitter, and changes the collector current and the voltage between the collector and the emitter according to the voltage between the terminals of the capacitor C1. As a result, the voltage appearing between the terminals 2a and 2b rises with the passage of time, and as shown in FIG. 5, has the same magnitude as the input voltage supplied from the power supply 1 after a predetermined rise time RT. It will be. As can be seen from the above operation, the slow start circuit of FIG. 4 reduces the rate of rise of the voltage appearing between the terminals 2a and 2b at the time of startup. This prevents noise from occurring in the circuit and reduces voltage stress applied to the load circuit due to the rapidly rising voltage, thereby preventing the load circuit from malfunctioning at startup.

[0004]

Here, consider the case where the power switch S is operated in the circuit shown in FIG. 4 to temporarily stop and restart the electronic circuit on the load side. Immediately after opening the power switch S, a voltage appears between the terminals 2a and 2b due to the charge stored in the capacitor C1. This voltage gradually decreases as the charge stored in the capacitor C1 is consumed in the electronic circuit or the like on the load side. If a sufficient time is left after the power switch S is opened and the power switch S is closed again after the voltage between the terminals 2a and 2b has dropped to zero volt, the voltage between the terminals 2a and 2b will be almost the same as at the time of the first start-up. It will rise on the same trajectory. That is, the solid line (C) in FIG.
As shown in the figure, the voltage becomes the same as the input voltage after the re-startup time RR1 which is almost the same as the initial start-up time RT.
Naturally, the restart of the electronic circuit at this time is performed without any trouble.

However, immediately after the power switch S is opened, if the power switch S is closed again while a voltage of a certain level exists between the terminals 2a and 2b, the voltage between the terminals 2a and 2b becomes the same as the voltage at the time of the first startup. It will rise in a completely different trajectory. Specifically, as shown by a dotted line (D) in FIG.
It is assumed that the voltage between a and 2b starts to rise in the course of falling and becomes the same as the input voltage in the restarting time RR2. In such a case, the situation differs depending on how much the voltage between the terminals 2a and 2b has dropped, but not all parts of the electronic circuit on the load side have completely stopped operating, May be in a semi-operating state. Then, since the voltage starts to rise halfway, each part of the electronic circuit does not start operating in the original order at the time of starting, and as a result, there is a possibility that a malfunction may occur. Therefore, the present invention provides a capacitance discharge circuit as a means for quickly lowering the voltage when the voltage supply is cut off, and a slow start circuit capable of preventing a malfunction of the electronic circuit at the time of restart by including the same. The purpose is to provide.

[0006]

According to the present invention, there is provided a switch connected in parallel to a capacitive element connected to a power line, and a current supply circuit connected between a power line closer to a power supply than the capacitive element. A basic circuit is a capacitive discharge circuit including a series circuit of an inductance element, wherein the switch is turned on in response to a voltage signal generated in the inductance element. Then, a main transistor element installed on one power line connecting the power supply and the load, a first capacitive element connected between the control terminal of the main transistor element and the other power line, A first terminal connected between the current input terminal and the control terminal of the transistor element;
And a capacitive discharge circuit connected to the first capacitive element constitute a slow start circuit. Alternatively, a main transistor element installed on one power line connecting a power supply and a load, a first capacitor connected between a control terminal of the main transistor element and the other power line, and a main transistor element A first current supply circuit connected between the current input terminal of the main transistor element and the control terminal; a second capacitor connected between the current output terminal of the main transistor element and the other power line; A slow start circuit is constituted by the capacitive discharge circuit connected to the capacitive element.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A transistor as a switch is connected in parallel to a capacitor connected to the base of a transistor constituting a slow start circuit or a capacitor connected between power lines on the output side of the slow start circuit. Connect to A series circuit of a current supply circuit and an inductance element is connected between the power lines on the input side of the slow start circuit, and one end of a predetermined winding of the inductance element is connected to a control terminal of the transistor. Here, specifically, a current supply circuit is configured by a series circuit of a diode and a resistor. By turning on the transistor as the switch in accordance with the voltage signal generated in the inductance element, the electric charge stored in the capacitance element is discharged during energization,
The voltage appearing at the output of the slow start circuit is quickly reduced.

[0008]

FIG. 1 shows a first embodiment of a slow start circuit according to the present invention, which is provided with a capacity discharge circuit and in which an electronic circuit hardly malfunctions upon restart. The slow start circuit shown in FIG. 1 includes a collector and a collector on a high-potential-side power line from a power supply 1 to a terminal 2a via a power switch S.
The transistor Q1 is provided so that the main current path between the emitters is in series with the external power supply 1. A capacitor C1 as a first capacitance element is connected between the base of the transistor Q1 and the ground, and a resistor R1 as a first current supply circuit is connected between the collector and the base of the transistor Q1. Between the collector of transistor Q1 and ground,
Diode D1 and resistor R1 as second current supply circuit
And a coil L1 as an inductance element
Are connected in series.

Then, in parallel with the capacitor C1,
A transistor Q2 composed of a P-channel FET as a switch is connected, and the gate of the transistor Q2 is connected to a resistor R
The circuit configuration is connected to the connection point between the coil 2 and the coil L1. Here, the transistor Q2, the diode D1, the resistor R2, and the coil L1 constitute a capacitive discharge circuit 3. The resistor R3 connected between the gate and the source of the transistor Q2 is a protection resistor for preventing the transistor Q2 from being damaged by the voltage generated in the coil L1. The capacity discharging circuit of FIG. 1 having such a configuration and the slow start circuit including the same generally perform the following operations.

When the power switch S is closed, the diode D
1, a current flows through the path of the resistor R2 and the coil L1, and a voltage is generated in the coil L1 such that the terminal on the resistor R2 side has a high potential and the ground side has a low potential. At this time, the voltage appearing in the coil L1 applies a reverse bias between the gate and the source of the transistor Q2, and as a result, the transistor Q2 is turned off. Since the transistor Q2 is off, when the power switch S is closed, the capacitor C1 is charged via the resistor R1, and the voltage between the terminals increases with time at a rate of increase corresponding to the time constant of CR. Go. Then, the transistor Q1 conducts between the collector and the emitter, and changes the collector current and the voltage between the collector and the emitter according to the voltage between the terminals of the capacitor C1. As a result, the voltage appearing between the terminals 2a and 2b rises with the passage of time, and has the same magnitude as the input voltage supplied from the power supply 1 after a predetermined rise time RT.

Next, when the power switch S is opened, the current flowing through the path of the diode D1, the resistor R2 and the coil L1 is cut off inside the capacitive discharge circuit 3, and the resistor R2 is connected to the coil L1. A voltage is generated with the terminal on the low side at a low potential and the ground side at a high potential. At this time, the coil L1
Generates a forward bias between the gate and the source of the transistor Q2.
2 is turned on. When the transistor Q2 is turned on, both ends of the capacitor C1 are short-circuited, and the charge stored in the capacitor C1 is discharged through the main current path of the transistor Q2 and rapidly disappears. As a result, the voltage appearing between the terminals 2a and 2b of the circuit of FIG. 1 is faster than that of the conventional slow start circuit (dotted line (B) in FIG. 2) as shown by the solid line (A) in FIG. Will decrease. Thus, after the power switch S is opened, the terminal 2
By rapidly reducing the voltage appearing between a and 2b, it is possible to prevent malfunction of the electronic circuit when the electronic circuit on the load side is restarted.

FIG. 3 shows a second embodiment of a capacity discharge circuit according to the present invention and a slow start circuit having the same.
The slow start circuit shown in FIG. 3 is used, for example, when an electronic circuit having a relatively large load capacity is connected between the terminals 2a and 2b. The circuit configuration is as follows. A transistor Q1 is provided on a high-potential power line from the power supply 1 to the terminal 2a via the power switch S so that the main current path between the collector and the emitter is in series with the external power supply 1.
A capacitor C1 as a first capacitance element is connected between the base of the transistor Q1 and the ground, and a resistor R1 as a first current supply circuit is connected between the collector and the base of the transistor Q1. A capacitor 2 as a second capacitance element is connected between the emitter of the transistor Q1 and the ground.

A series circuit of a diode D1 and a resistor R1 as a second current supply circuit and a coil L1 as an inductance element are connected in series between the collector of the transistor Q1 and the ground. Then, a transistor Q2 composed of a P-channel FET as a switch is connected in parallel with the capacitor C2, and the gate of the transistor Q2 is connected to a connection point between the resistor R2 and the coil L1. Here, the transistor Q2, the diode D1, the resistor R2 and the coil L1 are connected to the capacitive discharge circuit 3.
Is composed. The resistor R3 connected between the gate and the source of the transistor Q2 is a protection resistor for preventing the transistor Q2 from being damaged by the voltage generated in the coil L1.

In the slow start circuit of FIG. 3 having such a configuration, when the power switch S is opened, the transistor Q2 is turned on to short-circuit both ends of the capacitor C2. As a result, the electric charge stored in the capacitor C2 disappears rapidly, and the voltage between the terminals 2a and 2b drops rapidly. Here, regarding the capacitor C1, the transistor Q
When the transistor 2 is turned on, the transistor Q1 discharges through the current path between the base and the emitter and the transistor Q2. Except for the above points, the circuit of FIG. 3 operates substantially the same as the slow start circuit shown in FIG.

In the circuit of the embodiment of the present invention described above, the single-turn coil (L1) is used for the inductance element constituting the capacitive discharge circuit. However, a transformer may be used instead of the single-turn coil. Absent. Further, in the circuit of the embodiment shown in FIG. 3, a capacitance discharging circuit (3) as shown in FIG. 1 may be further added to the capacitor C1 connected to the base of the transistor Q1. Further, as shown in FIG. 3, in the case where the capacitor discharge circuit 3 is connected to the capacitor C2 provided substantially on the output side of the slow start circuit, the main circuit portion including the transistor Q1 of the slow start circuit is not shown. However, for example, a slow start circuit using a parallel circuit of a resistance element and a thyristor may be used.

[0016]

As described above, the capacitance discharge circuit of the present invention and the slow start circuit provided with the same have a current supply circuit, an inductance element and a switch, and are used when the external voltage supply is cut off. The switch is turned on according to the voltage generated in the inductance element. In addition, the configuration is characterized in that the charge stored in the capacitor provided in the circuit is discharged. With such a configuration, it is possible to reliably discharge the accumulated charge of the capacitance element even though the circuit configuration is simple, and it is possible to rapidly reduce the voltage when the voltage supply is cut off. This makes it possible to prevent the electronic circuit from malfunctioning when the electronic circuit is restarted after being stopped.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of a capacitive discharge circuit according to the present invention and a slow start circuit including the same.

FIG. 2 is a diagram for comparing a change in a voltage appearing between terminals 2a and 2b when the supply of voltage between the present invention and a conventional slow start circuit is cut off.

FIG. 3 is a circuit diagram of a second embodiment of a capacity discharge circuit according to the present invention and a slow start circuit including the same.

FIG. 4 is a diagram showing an example of a conventional slow start circuit.

FIG. 5 shows terminals 2a and 2b of a conventional slow start circuit.
The figure which shows the change of the voltage which appears in between.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 External power supply 2a, 2b Terminal 3 Capacitance discharge circuit S Power switch Q1 Transistor C1 Capacitor R1 as first capacitance R1 Resistance as first current supply circuit D1, R2 Diode and resistance L1 constituting second current supply circuit Coil as inductance element Q2 Transistor as switch

Claims (7)

[Claims] 1. A switch connected in parallel to a capacitance element connected to a power line, and a series circuit of a current supply circuit and an inductance element connected between a power line closer to a power supply than the capacitance element. A capacitive discharge circuit provided with the switch turned on in response to a voltage signal generated in the inductance element. 2. The switch according to claim 1, wherein the switch is a P-channel field-effect type second transistor element, and is turned on by a voltage generated in the inductance element when power supply from the input side is interrupted. Claim 1
The capacity discharge circuit described in the above. 3. A main transistor element provided on one power line connecting a power supply and a load, and a first capacitive element connected between a control terminal of the main transistor element and the other power line. A first current supply circuit connected between a current input terminal and a control terminal of the main transistor element, and a capacitance discharge circuit connected to the first capacitance element. A circuit includes a switch connected in parallel with the first capacitor, a second current supply circuit connected between the current input terminal of the main transistor, and the other power line, and a series connection of an inductance element. Circuit
A slow start circuit, wherein the switch is turned on in response to a voltage signal generated in the inductance element. 4. A main transistor element provided on one power line connecting a power supply and a load, and a first capacitive element connected between a control terminal of the main transistor element and the other power line. A first current supply circuit connected between a current input terminal and a control terminal of the main transistor element, and a capacitive discharge circuit connected to a current output terminal of the main transistor element. A switch connected between the current output terminal of the main transistor element and the other power line; and a second switch connected between the current input terminal of the main transistor element and the other power line. And a series circuit of an inductance element, wherein the switch is turned on in response to a voltage signal generated in the inductance element. 5. The slow start circuit according to claim 4, wherein a second capacitor is connected between the current output terminal of the main transistor element and the other power line. 6. The semiconductor device according to claim 1, wherein the first current supply circuit comprises a first resistance element, and the second current supply circuit comprises a series circuit of a second resistance element and a diode element. The slow start circuit according to claim 3 or 4. 7. The switch comprises a P-channel field effect type second transistor element, and is turned on by a voltage generated in the inductance element when power supply from the input side is interrupted. Claim 3
A slow start circuit according to any one of claims 1 to 6.