JP2003015748A - Regulated voltage circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new regulated voltage circuit capable of preventing any output which is lower than a set voltage, and realizing hysteresis at the time of start and at the time of stop. SOLUTION: The regulated voltage circuit is provided with a turn-on control circuit 11 having a start voltage threshold setting part for setting the threshold of a start voltage according to an input voltage and an operation stopping part for stopping the operation when an output voltage reaches a specific value, a current limiting circuit 12 having an output voltage generating part to be started according to a start voltage outputted by the start voltage threshold setting part for generating an output voltage and an output current control part for controlling the output current, a voltage stabilization control circuit 13 having an output voltage setting part for setting an output voltage based on the output of the current limiting circuit 12 and a negative feedback circuit for stabilizing the output voltage including the output of the current control circuit 12, and a low voltage interrupting circuit 14 having a stop voltage threshold detecting part for detecting that the output voltage decreases and reaches the threshold of a stop voltage and for stopping the output voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant voltage circuit for stabilizing and outputting an unstable input voltage, and more particularly to a constant voltage circuit characterized by having the following additional functions.

1. Function that can be automatically started and stopped with a specific input voltage value 2. 2. A function that does not output voltage below a specific input voltage value. Function that can limit the output current 4. Function that start voltage and stop voltage have hysteresis

SUMMARY OF THE INVENTION FIG. 1 shows a constant voltage circuit according to the present invention.

The constant voltage circuit according to the present invention comprises a turn-on control circuit 11, a current limiting circuit 12, and a voltage stabilization control circuit 1.
3. It is composed of a low voltage cutoff circuit 14.

The resistor R3 determines the threshold value (Von) of the starting voltage.

The output voltage (Vout) is set by the resistor R13. The resistor R9 determines the threshold value (Vlv) of the stop voltage.

The resistor R1 determines the output voltage (Voff) at which the turn-on control circuit 11 stops its operation. The current limit value (Iim) is set by the resistor R5.

The voltage regulated by the above resistor is Vlv <Voff <Von <Vout Is set.

FIG. 2 shows the operating characteristics of the constant voltage circuit according to the present invention set as described above.

By setting the respective voltages as shown in FIG. 2, it is possible to eliminate unnecessary voltages below the required voltage as in the conventional type. Further, since the start voltage and the stop voltage can be set respectively, it is possible to easily add hysteresis to the circuit, and it is possible to easily prevent the circuit from malfunctioning due to noise in the input voltage.

[0010]

2. Description of the Related Art In a conventional constant voltage circuit, a voltage until an input voltage is applied and stabilized in operating characteristics is also output. In this case, depending on the circuit connected to the load, there may occur a problem such as malfunction at a circuit operating voltage or less. In addition, output of the voltage until stabilization is wasteful of power loss during that time.

In order to solve such a conventional problem, a switching power supply device disclosed in Japanese Patent Laid-Open No. 3-18273, a power supply control circuit disclosed in Japanese Patent Laid-Open No. 5-328717, and Japanese Patent Laid-Open No. 2000-156932. The power supply device disclosed in the publication and the power supply device disclosed in JP-A-2000-341935 are proposed.

[0012]

However, in each of the above-mentioned prior arts, as the start / stop control circuit of the DC-DC converter, by detecting the input DC voltage and setting the start voltage value and the stop voltage value, There is hysteresis, D
The present invention is the same in that the purpose is to prevent malfunction of the C-DC converter, but a stable power supply voltage cannot be supplied to the PWM control circuit of the DC-DC converter.

Further, in each of the above prior arts, the start / stop of the DC-DC converter is controlled by the H / L signal of the voltage detection circuit, and the DC-DC converter is controlled by the constant voltage circuit including the voltage detection circuit. The start / stop of the DC converter is controlled by directly “ON / OFF” the power supply voltage of the PWM control circuit of the DC-DC converter, and has a circuit that supplies a stable voltage as the power supply voltage to the PWM control circuit. There is also no overcurrent protection circuit to prevent overcurrent at startup.

Therefore, in the prior art, the start / stop control of the DC-DC converter, the control of the supply voltage of the PWM control circuit, and the overcurrent protection at the start can be performed at the same time.
It was also impossible to improve the malfunction of the M control circuit.

The present invention has been made in view of the above-mentioned conventional circumstances. Therefore, the object of the present invention is to eliminate the above-mentioned drawbacks inherent in the conventional technology and to eliminate the output below a set voltage.
Another object of the present invention is to provide a new constant voltage circuit capable of having a hysteresis when starting and stopping.

[0016]

In order to achieve the above object, a constant voltage circuit according to the present invention has a starting voltage threshold setting means for setting a threshold of a starting voltage by an input voltage and an output voltage of a specific value. A turn-on control circuit having an operation stopping means for stopping the operation when the output voltage is generated, an output voltage generating means for generating an output voltage by being activated by a starting voltage output from the starting voltage threshold setting means, and an output for controlling an output current A current limiting circuit having current control means, output voltage setting means for setting an output voltage based on the output of the current limiting circuit, and negative feedback means for stabilizing the output voltage including the output of the current limiting circuit. A voltage stabilization control circuit having
And a low voltage cutoff circuit having a stop voltage threshold detection means for stopping the output voltage by detecting that the output voltage has dropped and reached the threshold of the stop voltage. It is characterized by giving the circuit hysteresis characteristics by setting them independently.

The start-up voltage threshold setting means includes a first resistor connected to the input voltage and an "O" by the first resistor.
The operation stopping means includes a second transistor connected to the output voltage and an ON / OFF controlled first transistor including an N / OFF "controlled first transistor. A second transistor that controls the first transistor.

The output current control means includes a third resistor connected to the input voltage, and the output voltage generation means includes a third transistor controlled by the first transistor.

The output voltage setting means includes a fourth resistance connected to the output of the third transistor, and the negative feedback means includes a fourth transistor connected to the fourth resistance and the fourth transistor. It includes a fifth transistor controlled by the output of the fourth transistor and a third transistor controlled by the output of the fifth transistor.

The stop voltage threshold detecting means includes a fifth resistor connected to the output voltage and a sixth transistor controlled by the fifth resistor.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block circuit diagram showing an embodiment according to the present invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a constant voltage circuit according to the present invention comprises a turn-on control circuit 11, a current limiting circuit 12, a voltage stabilization control circuit 13, and a low voltage cutoff circuit 14.

The threshold value (Von) of the starting voltage is determined by the resistor R3.

The output voltage (Vout) is set by the resistor R13. The resistor R9 determines the threshold value (Vlv) of the stop voltage.

The resistor R1 determines the output voltage (Voff) at which the turn-on control circuit 11 stops its operation. The current limit value (Iim) is set by the resistor R5.

The voltage adjusted by the above-mentioned resistor is Vlv <Voff <Von <Vout Is set.

FIG. 2 shows the operating characteristics of the constant voltage circuit according to the present invention set as described above.

As shown in FIG. 2, by setting the respective voltages, it is possible to eliminate the unnecessary voltage below the required voltage as in the conventional type. Further, since the start voltage and the stop voltage can be set respectively, it is possible to easily add hysteresis to the circuit, and it is possible to easily prevent the circuit from malfunctioning due to noise in the input voltage.

An example of one embodiment according to the present invention will be described with reference to FIGS. 1 and 3.

One embodiment of the form of one embodiment according to the present invention is to implement the present invention by PWM (Pulse) of a switching power supply.
This is an example of using the Width Modulation) as a starting circuit for moving the control circuit.

The constant voltage circuit according to one embodiment of the present invention supplies a constant power supply voltage to the PWM control circuit from an unstable input voltage. The PWM control circuit turns “ON / OFF” only in the constant voltage circuit of the present invention. It turns “ON” when the input voltage is above a certain voltage and turns “OFF” when it is below a certain voltage. Further, since the current flowing in the PWM control circuit can be provided with the current limiting means, the reliability of the power supply system can be improved.

The threshold value of the starting voltage is set by the resistor R3 of the turn-on control circuit 11. With this threshold, the constant voltage circuit of the present invention is activated to supply a constant voltage to the PWM control circuit,
The switching power supply starts operating.

The resistance R13 of the voltage stabilization control circuit 13 is P
Set the stable voltage supplied to the WM control circuit.

The threshold value of the stop voltage is set by the resistor R9 of the low voltage cutoff circuit 14. At this threshold, the constant voltage circuit of the present invention stops, and the voltage supply to the PWM control circuit stops, so the switching power supply stops.

The resistor R1 of the turn-on control circuit 11 is for stopping the operation of the turn-on control circuit 11 when the output voltage reaches a specific value, and when the output voltage rises to some extent, the voltage stabilization control circuit 13 outputs it. A negative feedback control is applied to the voltage, and a stable output can be obtained.

[0037]

Operation of the Embodiment Next, the operation of one embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 4 is a view similar to FIG. 1 shown to make the circuit shown in FIG. 1 easier to see.

When the input voltage Vin is applied, the resistance R3,
A current flows through R4. Due to the resistance ratio of the resistors R3 and R4, a potential difference is generated at both ends of the resistors R3 and R4. When the potential difference of the resistor R4 becomes larger than the sum of the Zener voltage of the Zener diode ZD1 and the base-emitter Vbe voltage of the transistor TR4, the transistor TR
4, a base current flows through the resistor R3, and the transistor TR4 is turned on. Input voltage Vi at that time
The resistor R3 is set so that n becomes the starting voltage.

When the base current flows through the transistor TR4, a collector current flows through the transistor TR4 via the resistor R6. When the collector current flows through the transistor TR4, the base current of the transistor TR3 flows through the resistor R5, and the transistor TR3 is turned on.
When the transistor TR3 turns “ON” and the collector current flows, a voltage is generated in the output voltage Vout.

The collector current of the transistor TR3 is supplied to the load connected to the output voltage Vout, and
Flowing through the resistors R1, R2, R9, R10, R13, R14, a potential difference is generated at both ends of each resistor.

The potential difference of the resistor R14 is the Zener diode Z.
When it becomes larger than the sum of the Zener voltage of D3 and the base-emitter Vbe voltage of the transistor TR7, a base current flows through the transistor TR7 via the resistor R13, and the transistor TR7 is turned on. The resistor R13 is set so that the output voltage Vout at that time becomes the supply voltage of the PWM control circuit. Transistor TR7
When a base current flows through the transistor TR7, a collector current flows through the transistor TR7 via the resistor R11.

The potential difference of the resistor R10 depends on the Zener voltage of the Zener diode ZD2 and the V of the transistor TR6.
When it becomes larger than the added value of the be voltage, the base current flows through the transistor TR6 through the resistor R9, and the transistor TR6 is turned on. Transistor T
When R6 is in the "ON" state, a base current flows through the transistor TR5 via the resistor R11,
5 is in the "ON" state.

Transistor TR5 and transistor TR
When the base current flows through the transistor 6, the collector current flows through the transistor R5 and the transistor TR6 through the resistor R7. When this collector current flows, the transistor TR3
A base current flows through the resistor R5 to maintain the “ON” state of the transistor TR3.

While the transistor TR3 remains in the "ON" state, the output voltage Vout can obtain a stable output voltage by the negative feedback loop.

When the potential difference of the resistor R2 becomes larger than the added value of the forward voltage of the diode D1 and the Vbe voltage of the transistor TR1, a base current flows through the transistor TR1 through the resistor R1 and the transistor TR1.
1 is in the "ON" state. The resistance R is set so that the output voltage Vout at that time becomes the stop voltage of the turn-on control circuit 11.
Set 1. When the base current flows through the transistor TR1, the collector current flows through the transistor TR1 through the resistor R3.

When the transistor TR1 is in the "ON" state, the current flowing through the resistor R4 decreases, and the potential difference across the resistor R4 is the collector-emitter V of the transistor TR1.
ce becomes equal to the added value of the forward voltage of the diode D1 and becomes smaller than the added value of the Vbe voltage of the transistor TR4 and the Zener voltage of the Zener diode ZD1. Therefore, the base current of the transistor TR4 stops flowing, and the transistor TR4 is in the "OFF" state. As a result, the turn-on control circuit 11 is stopped.

As the input voltage Vin decreases, the resistance R
When the voltage value becomes equal to or lower than the voltage value set in 13, the output voltage Vout
Leaves the negative feedback loop. Furthermore,
As the input voltage Vin decreases, the output voltage Vout decreases following the decrease in the input voltage Vin. When the output voltage Vout decreases, the resistors R9, R11, R13,
The current flowing through R1 is reduced.

When the current flowing through the resistor R10 via the resistor R9 decreases, the potential difference across the resistor R10 decreases.

The potential difference of the resistor R10 is the transistor T.
When the base-emitter Vbe voltage of R6 and the Zener voltage of the Zener diode ZD2 become smaller than the added value, the base current of the transistor TR6 stops flowing,
The transistor TR6 is in the "OFF" state. The resistor R9 is set so that the input voltage Vin at this time becomes the stop voltage. When the transistor TR6 is in the "OFF" state,
Since the collector current does not flow, the base current of the transistor TR3 flowing through the resistor R5 stops flowing.
Therefore, the transistor TR3 is in the "OFF" state,
The output voltage Vout becomes 0V, and this circuit is stopped.

The resistor R5 is a resistor for detecting the current, and the resistor R5 is caused by the current flowing through the resistor R5 from the input voltage Vin.
A potential difference occurs at both ends of the. When the potential difference across the resistor R5 becomes equal to or higher than the Vbe voltage of the transistor TR2, a base current flows through the transistor TR2, and the transistor TR2 is turned on. When the transistor TR2 is in the "ON" state, the Vbe voltage of the transistor TR3 is controlled, so that the collector current of the transistor TR3 is controlled. The collector current of the transistor TR3 is limited to the current value determined by the Vbe voltage of the resistor R5 and the transistor TR2. Therefore, the current flowing through the output voltage Vout is current limited.

[0051]

Other Embodiments Next, another embodiment of the present invention will be described in detail with reference to FIG.

FIG. 5 shows a circuit in which the polarities of components are replaced when the constant voltage circuit of the present invention is used with a negative input / output voltage.

The description of the operation is the same as that of the above-described embodiment of the present invention, except that the direction of the current flow and the polarity of the generated voltage are opposite.

Regarding the operating characteristics, the output voltage Vo shown in FIG.
ut and the polarity of the input voltage Vin are replaced by minus. Therefore, the constant voltage circuit of the present invention can be realized even with a negative input / output voltage.

[0055]

The present invention is constructed and operates as described above, and according to the present invention, the following effects can be obtained.

As shown in FIG. 2, a stable output voltage (Vo
ut) is automatically output at a constant input voltage (Vin2) or higher, and is automatically stopped at a constant input voltage (Vin3) or lower, so that a voltage lower than a constant voltage value (Vout) is not output. A constant voltage circuit is possible.

In the conventional constant voltage circuit, since the voltage is output even before it is stabilized, it may cause a malfunction depending on the circuit connected to the load. Also, by shifting the set values of the start voltage and the stop voltage, it is possible to easily add hysteresis, so that there is an advantage that the malfunction area of this circuit can be eliminated even if the input voltage contains noise. .

Further, since the current limiting circuit is added, the overcurrent protection of the load circuit is possible, and the operation is automatically stopped at the time of overload. This is because the circuit shown in FIG. 1 has a turn-on control circuit, a current limiting circuit, a voltage stabilization control circuit, and a low-voltage cutoff circuit, and the voltage and current can be set in each circuit. is there.

[Brief description of drawings]

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

FIG. 2 is a diagram showing characteristics of the present invention in comparison with a conventional example.

FIG. 3 is a block diagram showing an example of use of the present invention.

FIG. 4 is a view similar to FIG. 1 shown to make the circuit shown in FIG. 1 easier to see.

FIG. 5 is a circuit configuration diagram showing another embodiment according to the present invention.

[Explanation of symbols]

11 ... Turn-on control circuit 12 ... Current limiting circuit 13 ... Voltage stabilization control circuit 14 ... Low voltage cutoff circuit

Continued front page    F-term (reference) 5H410 BB02 BB04 CC02 EA10 EA11                       EB37 FF03 FF25 KK01 KK05                       LL12 LL20                 5H430 BB01 BB09 BB11 EE02 FF02                       FF12 FF13 GG02 KK01 KK11                 5H730 AS01 BB23 BB57 DD04 FD03                       FD13 FG05 FG26 XC02 XC12                       XX02 XX15 XX22 XX33

Claims (5)

[Claims] 1. A turn-on control circuit having start-up voltage threshold setting means for setting a start-up voltage threshold value by an input voltage and operation stopping means for stopping operation when an output voltage of a specific value is reached, and the start-up voltage. A current limiting circuit having an output voltage generating unit that is activated by an activation voltage output from the threshold setting unit to generate an output voltage and an output current control unit that controls the output current, and outputs based on the output of the current limiting circuit. A voltage stabilization control circuit having an output voltage setting means for setting a voltage and a negative feedback means for stabilizing the output voltage including the output of the current limiting circuit; and the output voltage decreasing to reach the threshold value of the stop voltage. A low voltage cutoff circuit having stop voltage threshold detection means for detecting that the output voltage is stopped and setting the start voltage and the stop voltage independently. A constant voltage circuit characterized by giving the circuit hysteresis characteristics. 2. The starting voltage threshold value setting means includes a first resistor connected to the input voltage and a first transistor which is “ON / OFF” controlled by the first resistor, and the operation is stopped. The means further comprises a second resistor connected to the output voltage and a second transistor "ON / OFF" controlled by the second resistor to control the first transistor by its output. The constant voltage circuit according to claim 1, which is characterized in that. 3. The output current control means includes a third resistor connected to the input voltage, and the output voltage generation means includes a third transistor controlled by the first transistor. The constant voltage circuit according to claim 2, which is further characterized. 4. The output voltage setting means includes a fourth resistor connected to the output of the third transistor, and the negative feedback means includes a fourth transistor connected to the fourth resistor. The constant voltage according to claim 3, further comprising: a fifth transistor controlled by the output of the fourth transistor, and a third transistor controlled by the output of the fifth transistor. circuit. 5. The stop voltage threshold detection means further includes a fifth resistor connected to the output voltage, and a sixth transistor controlled by the fifth resistor. The constant voltage circuit according to item 4.