JP3525611B2 - Constant voltage circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a constant voltage circuit,
In particular, it relates to a constant voltage circuit that supplies a reference voltage to an amplifier or the like by using a Zener diode or the like.

[0002]

2. Description of the Related Art In a semiconductor device, a reference voltage is generated and the generated reference voltage is used as a reference level of an amplifier. FIG. 3 shows a circuit configuration diagram of an example of a conventional reference voltage circuit.

The conventional reference voltage circuit 1 has a power supply voltage V_CCOr
Constant current I₁Constant current source 2 to generate
Constant current I₁Depending on the reference voltage V_REF0To generate
Zener diode D_Z1It is composed of The constant current source 2 is
Power supply voltage V at one end_CCConnected to the other end of the Zener
Mode D _Z1It is connected to the. Zener diode D_Z1Is
The cathode is connected to the other end of the constant current source 2 and the anode is connected.
Grounded, power supply voltage V_CCConnected in the opposite direction to
It

The Zener diode D _Z1 generates a Zener voltage at a connection point a between the constant current source 2 and the cathode of the Zener diode D _Z1 by the current supplied from the constant current source 2. This Zener voltage is used as the reference voltage V _REF0 . The connection point a between the constant current source 2 and the cathode of the Zener diode D _Z1 is connected to the reference voltage output terminal T _VREF1 .

The reference voltage output terminal T _VREF1 is connected to an amplifier or the like, and supplies the reference voltage V _REF0 to the amplifier or the like. In such a reference voltage circuit 1, the constant current source 2, the Zener diode D _Z , and the output resistance R ₁ are mounted in one semiconductor chip to supply a reference voltage for an amplifier or the like in the semiconductor chip.

[0006]

[SUMMARY OF THE INVENTION] However, in the conventional reference voltage circuit, because it was fed the Zener voltage V _Z which is generated by the Zener diode D _Z as the reference voltage V _REF0 such as direct amplifier, the Zener diode D _Z Due to the generated thermal noise (white noise), the reference voltage fluctuates, the reference voltage supplied to the amplifier fluctuates, and the effect of noise is amplified and output to the output of the amplifier. there were.

The present invention has been made in view of the above points, and an object of the present invention is to provide a constant voltage circuit which is less affected by thermal noise and has a good response to the application of the power supply voltage V _CC .

[0008]

[Means for Solving the Problems] Claim 1 of the present invention provides P
In a constant voltage circuit for generating a constant voltage by supplying a current to an N junction, a noise removing capacitor connected between the constant voltage generated at the PN junction and ground ,
When the output constant voltage is below a predetermined level, the capacitor
Supply a current to the output constant voltage to the reference voltage.
And a current supply unit that cuts off the current when there is a failure .

According to the first aspect, by providing the noise removing capacitor, the noise removing capacitor absorbs the thermal noise generated in the constant voltage, and the constant voltage reference voltage with less noise can be generated . Charging current supplier
Depending on the stage, the output voltage when the power supply voltage is turned on, etc. has a predetermined level
Supply the charging current to the capacitor and
The capacitor is charged rapidly by
The delay time due to electricity can be shortened. Claim 2 is the charging
Switching the current supply means according to the output voltage
Control means for generating a control signal, the power supply voltage and the
It is connected between the constant voltage output terminal and the charging control means.
Switching according to the generated switching control signal
Charging current to supply charging current to the constant voltage output terminal
It is composed of a supply transistor.

[0010]

[0011] wherein, according to claim 2, raw form a switching control signal in accordance with the output voltage by the charging control means, the power supply by switching the charging current supply transistor by the switching control signal generated by the charging control means The charging speed of the capacitor can be shortened when the capacitor is charged at the time of turning on.

According to a third aspect of the present invention, the charge control means is connected between a constant current source for generating a constant current according to the power supply voltage, and the constant current source and the reference voltage output terminal, and the constant voltage output is provided. A switching voltage generating element that generates a switching voltage according to the voltage of the terminal, and the switching voltage generated by the switching voltage generating element is connected between the constant current source and the constant voltage output terminal. And a switching signal generating means for generating a switching control signal for switching the charging current supply transistor according to the switching voltage.

According to the third aspect of the present invention, the voltage at the constant voltage output terminal is detected by the switching voltage generating element, a switching voltage according to the detected voltage is generated and supplied to the switching signal generating means, and according to the switching voltage. Supplying the charging current to the capacitor when charging the capacitor such as when the power is turned on by controlling the supply of the charging current to the capacitor by generating the switching signal by the switching signal generating means and controlling the switching of the charging current supply transistor. Therefore, the charging speed of the capacitor can be shortened.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a circuit configuration diagram of an embodiment of the present invention. In this embodiment, a reference voltage circuit will be described as a constant voltage circuit. The reference voltage circuit 11 of this embodiment is
_Charging of the reference voltage generating circuit section 12 for generating the reference voltage, the noise removing capacitor C ₁₁ for absorbing the fluctuation of the output reference voltage V _REF11 generated by the reference voltage generating circuit section 12, and the noise removing capacitor C ₁₁ is assisted. It is composed of the charging current supply circuit unit 13.

The reference voltage circuit 11 includes a semiconductor chip 1 having a reference voltage generation circuit section 12 and a charging current supply circuit section 13 as one.
7, the semiconductor chip 17 is provided with an external reference voltage output terminal T _VREF11 , and the external reference voltage output terminal T _VREF11 is provided.
_{The configuration is such} that the noise removing capacitor C ₁₁ is connected to _{VREF 11} as an external element.

The reference voltage generating circuit section 12 has a power supply voltage V _CC.
Constant current source 14 for generating a constant current I ₁₁ from the constant current source 14
Zener diode D _Z11, the output resistance R ₁₁ for outputting a reference voltage V _Ref10 generated by the Zener diode D _Z11, capacitor for removing noise which generates a reference voltage V _Ref10 depending on a constant current I ₁₁ which is generated in It is composed of C ₁₁ .

The constant current source 14 has one end connected to the power supply voltage V _CC and the other end connected to the Zener diode D _Z11 . The Zener diode D _Z11 has a cathode connected to the other end of the constant current source 14, an anode grounded, and a polarity connected in the opposite direction to the power supply voltage V _CC .

The zener diode D _Z11 corresponds to the PN junction in claim 1 and applies a zener voltage to the connection point a between the constant current source 14 and the cathode of the zener diode D _Z11 by the current supplied from the constant current source 14. Occur. This Zener voltage is used as the reference voltage V _REF10 .

Constant current source 14 and Zener diode D _Z11
The connection point a with the cathode of is connected to the reference voltage output terminal T _VREF11 via the output resistor R ₁₁ . One end of the output resistor R ₁₁ is connected to the connection point a between the constant current source 14 and the cathode of the Zener diode D _Z11 , and the other end is the reference voltage output terminal T.
_Connected to _VREF11 to limit output current.

The reference voltage output terminal T _VREF11 is connected to an amplifier or the like and supplies the reference voltage V _REF11 to the amplifier or the like.
A noise removing capacitor C ₁₁ is connected to the reference voltage output terminal T _VREF11 . The capacitor C ₁₁ has one end connected to the reference voltage output terminal T _VREF11 , the other end grounded, and the reference voltage V generated at the reference voltage output terminal T _{VREF11.
It absorbs} fluctuations in _REF11 and stabilizes the reference voltage V _REF11 .

The charging current supply circuit section 13 corresponds to the charging current supply means in claim 2. Charging current supply circuit unit 13
, The charge control circuit 1 for controlling switching of the charging current supply transistor Q ₁₂ and the charging current supply transistor Q ₁₂ for supplying a charging current to the noise removing capacitor C ₁₁
It is composed of 5.

The charging current supply transistor Q ₁₂ is an NP
The switching control signal is _composed of an N-transistor, the power supply voltage V _CC is supplied to the collector, the emitter is connected to the reference voltage output terminal T _VREF11 , the base is connected to the charge control circuit unit 15, and the charge control circuit unit 15 is supplied. The power supply voltage V _CC and the reference voltage output terminal T _VREF11 are connected to each other at the time of turning on and supplied to the noise removing capacitor C ₁₁ to assist charging.

The charge control circuit section 15 corresponds to the charge control means in claim 2, and includes a constant current source 16 for generating a constant current I ₁₂ from the power supply voltage V _CC , a constant current source 14 and a zener diode D _{Z1 1} . Resistors R ₁₂ and R ₁₃ that are connected in series between the connection point with the output resistor R ₁₁ and the constant current source 16 and that generate a switching control signal that controls the switching of the charging current supply transistor Q ₁₂ , and the constant current source 14 And Zener diode D
Connected between _Z11 and the connection point and the constant current source 16 and the output resistor R _11, the resistor in accordance with the output voltage of the reference voltage output terminal T _{VREF 11} R _12, a switching voltage for controlling the switching voltage to be applied to R ₁₃ It is composed of a generation transistor Q ₁₁ .

The constant current source 16 corresponds to the constant current source in claim 3, the power supply voltage V _CC is applied to one end, and the resistor R is applied to the other end.
One end of ₁₂ and switching voltage generating transistor Q ₁₁
It is connected to the emitter, and generates a constant current I _12, resistor R ₁₂
And to the emitter of the switching voltage generating transistor Q ₁₁ .

The resistors R ₁₂ and R ₁₃ are connected in series, one end of the resistor R ₁₂ is connected to the constant current source 16, the other end is connected to one end of the resistor R ₁₃ , and one end of the resistor R ₁₃ is connected. Is connected to the other end of the resistor R _{12, and} the other end is connected to the connection point of the constant current source 14, the Zener diode D _Z11 and the output resistor R ₁₁ . The connection point between the resistors R ₁₂ and R ₁₃ is connected to the base of the charging current supply transistor Q ₁₂ .

Resistance R₁₂And resistance R₁₃Divides the applied voltage
The charging current supply transistor Q₁₂The sui
Generate a switching control signal to control
Current supply transistor Q₁₂Supply to the base of. Sui
Transistor Q for generating voltage₁₁Is in claim 3
It corresponds to a voltage detection element. Switching voltage generation tiger
Register Q₁₁Is a PNP transistor,
The constant current source 16 and the resistor R₁₂Connected to the connection point with
The collector is grounded and the base is the constant current source 14 and the Zener.
Iodo D_Z11And output resistance R₁₁Is connected to the connection point with
It Switching voltage generation transistor Q₁₁Is the constant current
Constant current I supplied from the source 16₁₂From Base-Emi
Voltage V_BE1Occurs, resistance R ₁₂, R₁₃Apply to.

In the charging current supply circuit unit 13, when the noise removing capacitor C ₁₁ is not charged and the output voltage of the reference voltage output terminal T _VREF11 is 0, the base-emitter of the switching voltage generating transistor Q ₁₁ is discharged. Voltage V
A switching control signal obtained by dividing _BE1 by resistors R ₁₂ and R ₁₃ is supplied to the base of the charging current supply transistor Q ₁₂ . At this time, since the output voltage of the reference voltage output terminal T _{VREF 11} is zero, the base of the charging current supply transistor Q ₁₂ - emitter voltage V _BE2 is turned on voltage, therefore, the transistor Q ₁₂ is turned on for the charging current supply The charging current I ₁₄ is supplied to the reference voltage output terminal T _{VREF 11} .

The reference voltage output terminal T _VREF11 is connected to the reference voltage generating circuit section 12, and the current I ₁₃ supplied from the reference voltage generating circuit section 12 is also supplied. Therefore, the noise removing capacitor C ₁₁ is charged by the current I ₁₃ supplied from the reference voltage generation circuit unit 12 and the current I ₁₄ supplied from the charging current supply circuit unit 13, and is charged at high speed.

When the noise removing capacitor C ₁₁ is charged, the output voltage of the reference voltage output terminal T _{VREF 11} becomes the reference voltage V _REF11 . When the output voltage of the reference voltage output terminal T _VREF11 becomes the reference voltage V _REF11 , the emitter voltage of the charging current supply transistor Q ₁₂ rises and the base-emitter voltage V _BE2 becomes the off voltage.

Therefore, therefore, the transformer for supplying the charging current is
Dista Q₁₂Turns off and the charging current I ₁₄Becomes 0, and Neu
Chip removal capacitor C₁₁Charging is stopped. Book in Figure 2
The operation | movement waveform diagram of one Example of invention is shown. In FIG. 2, time t_Tenso
Power supply voltage V_CCIs turned on, the power supply voltage V_ccBy
Constant current source 14₁₁Is generated. Constant current source 1
Current I generated in 4₁₁Constant current source 14 and Zener
Diode D_ZAt the connection point a with the cathode of the reference voltage V
_REF10Occurs.

Constant current source 14 and Zener diode D_Zof
Reference voltage V at the connection point a with the cathode _REF10Occurs
And the reference voltage V_REF10Is the output resistance R₁₁Through the reference voltage
Output terminal T_VREF11Is supplied to. On the other hand, time t_TenPower on
Voltage V_CCIs turned on, the power supply voltage V_CCBy constant current source
Constant current I at 16₁₂Is generated. Generated by constant current source 16
Constant current I₁₂For switching voltage generation
Star Q₁₁Voltage between the base and emitter of_BEOccurs.

Power supply voltage V_CCWhen the
Removal capacitor C₁₁Is not charged, the reference voltage
Output terminal T_VREF11Has an output voltage of zero. At this time,
Transistor Q for supplying electric current₁₂Switchon at the base of
Voltage generation transistor Q ₁₁Base-emitter voltage
Pressure V_BE1Resistance R₁₂, R₁₃Level switch divided by
Control signal is provided.

At this time, the charging current supply transistor Q
₁₂ , the output voltage V _REF11 of the reference voltage output terminal T _VREF11 is V _REF11 = V _Z − {R ₁₂ / (R ₁₂ + R ₁₃ )} V _F (V _F ; forward voltage between the base and emitter of the transistor Q ₁₂ ) (V _Z : output reference voltage), and the charging current is supplied to the noise removing capacitor C ₁₁ .

Immediately after the power source voltage V _{CC is} applied and the capacitor C ₁₁ is not charged, the output voltage of the reference voltage output terminal T _VREF11 is 0 and the base-emitter voltage V _BE2 of the charging current supply transistor Q ₁₂ is It becomes maximum, and the charging current supply transistor Q ₁₂ is turned on.

Charging current supply transistor Q₁₂Turns on
The reference voltage output terminal T _VREF11Current I₁₄But
Supplied. At this time, the reference voltage output terminal T_VREF11In
The current I also flows from the reference voltage generation circuit section 12.₁₃Has been supplied
Therefore, the noise removing capacitor C₁₁Is the reference voltage generation frequency
Current I supplied from the road portion 12₁₃And charging current supply circuit
Current I supplied from the part 13₁₄Is charged by. Obey
And noise removal capacitor C₁₁Is the reference voltage generator
Current I supplied from 12₁₃And charging current supply circuit unit 1
Current I supplied from 3₁₄Is charged rapidly by
₁₁To complete charging.

When the charging is completed at time t ₁₁ , the output voltage of the reference voltage output terminal T _VREF11 becomes the reference voltage V _REF11 . When the output voltage of the reference voltage output terminal T _{VREF 11} becomes the reference voltage V _{RE F11,} the base of the charging current supply transistor Q ₁₂ - emitter voltage V _{BE 2} decreases, 0, and therefore, the charging current supply transistor Q ₁₂ Turns off. By turning off the charging current supply transistor Q ₁₂ ,
The supply of the current I ₁₄ to the reference voltage output terminal T _{VREF 11} is interrupted.

When the supply of the current I ₁₄ to the reference voltage output terminal T _VREF11 is interrupted, the noise removing capacitor C ₁₁ charges and discharges according to the fluctuation of the reference voltage V _{REF11 at} the reference voltage output terminal T _VREF11 . It absorbs fluctuations in the reference voltage V _REF11 . Therefore, = power supply voltage V _CC reference from time t ₁₀ is turned voltage V _ref11 is the reference voltage output time t ₁₁ until the output from the terminal T _{VREF 11} the delay time between T ₁₀ (t ₁₁ -
t ₁₀ ) can be shortened. Since the delay time can be shortened, the reference voltage V _REF11 can be supplied to the amplifier quickly, and the amplifier can be started up at high speed.

[0038] According to this embodiment, as described above, thermal noise is generated in the Zener diode D _Z, also Zener voltage V _Ref10 generated by the Zener diode D _Z is varied, the noise removing capacitor C ₁₁ since the voltage variation due to thermal noise is absorbed, it is unnecessary to provide a variation of the reference voltage to the amplifier or the like using the Zener voltage V _Z which is generated by the Zener diode D _Z as the reference voltage. Therefore, the influence of thermal noise is not amplified and output from the amplifier, and stable operation without noise can be realized.

Further, according to the present embodiment, when the noise removing capacitor C ₁₁ is not charged such as when the power supply voltage V _CC is turned on, the charging current supply circuit section 13 operates and is supplied from the reference voltage generation circuit section 12. In addition to the current I ₁₃ , which is supplied from the charging current supply circuit unit 13, the noise removal capacitor C ₁₁ is charged by the current I _14, so that the charging time of the noise removal capacitor C ₁₁ can be shortened.

Further, a noise removing capacitor C₁₁Charge of
When the charging is completed, the charging current supply circuit unit 13 is turned off.
And current I₁₄Supply is stopped and the noise removal capacitor
SA C ₁₁Is the reference voltage output terminal T_VREF11Reference voltage V_REF11
The reference voltage V_REF11Fluctuation of
Can be absorbed and a normal noise removal operation can be executed.

In the present embodiment, the example applied to the reference voltage circuit has been described, but the present invention is not limited to the reference voltage circuit, and any other circuit can be used as long as the output terminal is connected to a noise removing capacitor. Can also be applied to.

[0042]

As described above, according to the first aspect of the present invention, by providing the noise removing capacitor, the noise removing capacitor absorbs the thermal noise generated in the constant voltage, so that the noise is constant. Can generate a voltage reference voltage ,
In addition, the current supply means provides output power when the power supply voltage is applied.
When the pressure is below a certain level, the capacitor is supplied with current.
By quickly charging the charging capacitor,
With features such as Ru can reduce the delay time due to the charging of the capacitor.

[0043]

[0044] According to claim 2, raw form a switching control signal in accordance with the output voltage by the charging control means, by switching the charging current supply transistor by the switching control signal generated by the charging control unit of the power supply It has the feature that the charging speed of the capacitor can be shortened when charging the capacitor at the time of turning on.

According to the third aspect of the present invention , the voltage at the reference voltage output terminal is detected by the switching voltage generating element, a switching voltage corresponding to the detected voltage is generated and supplied to the switching signal generating means, and according to the switching voltage. Supplying the charging current to the capacitor when charging the capacitor such as when the power is turned on by controlling the supply of the charging current to the capacitor by generating the switching signal by the switching signal generating means and controlling the switching of the charging current supply transistor. As a result, the charging speed of the capacitor can be shortened.

[Brief description of drawings]

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

FIG. 2 is an operation waveform diagram of an embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a conventional example.

[Explanation of symbols]

11 Reference Voltage Circuit 12 Reference Voltage Generation Circuit Section 13 Charging Current Supply Circuit Section 14, 16 Constant Current Source 15 Bias Circuit 17 Bias Voltage Generation Circuit C ₁₁ Noise Removing Capacitor T _VREF11 Reference Voltage Output Terminal D _Z11 Zener Diode Q ₁₁ Bias Voltage control transistor Q ₁₂ charging current supply transistor R _11, R ₁₂ resistors R ₁₃ output resistance V _REF10, V _rEF11 reference voltage

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G05F 3/20 H02J 1/00

Claims (3)

(57) [Claims] 1. A constant voltage circuit for generating a constant voltage by supplying a current to a PN junction, wherein a noise removing capacitor connected between the constant voltage generated at the PN junction and ground, and the output constant. When the voltage is below a predetermined level, the
The current is supplied to the capacitor, and the output constant voltage is the reference voltage.
A constant voltage circuit for cutting off the current when the voltage reaches a constant level. 2. The current supply means is responsive to the output voltage.
Charging control means for generating a switching control signal by means of, is connected between the power supply voltage and the constant voltage output terminal,
The switching control signal generated by the charging control means
Switching according to the charging current to the constant voltage output terminal
And a transistor for supplying charging current
The constant voltage circuit according to claim 1. 3. The charging control means responds to the power supply voltage.
A constant current source that generates a constant current, and is connected between the constant current source and the constant voltage output terminal,
A switching voltage is set according to the voltage of the constant voltage output terminal.
The switching voltage generating element that is generated is connected between the constant current source and the reference voltage output terminal.
The switching voltage generating element
Switching voltage is supplied to the switching voltage
Switching the charging current supply transistor accordingly
Switching signal to generate switching control signal
3. The constant voltage circuit according to claim 2, further comprising a generating unit .