JPH11167422A - Three-terminal regulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-terminal regulator capable of reducing power consumption, stabilizing output and preventing the occurrence of overheat destruction. SOLUTION: A MOSFET of an output stage circuit is replaced by the MOSFET(PM4) with back gate in a conventional circuit constituted of an output stage circut 1, a feedback resistor circuit 2, a differential circut 3 and a constant bias circuit 4. Then, a circuit constituted of a feedback impedance switch circuit 5, a load detection circuit 6, an output cut-off circuit 7, a bias circuit 4a to be added to the constant current bias circut 4 and an output stabilizer capacitor C3 connected to the output circuit 1 is added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-terminal regulator (also referred to as a series regulator) used for a power supply of a cellular phone or the like.

[0002]

2. Description of the Related Art There is a strong demand for a three-terminal regulator used for a power supply used in a cellular phone or the like to reduce power consumption during standby and during use. Further, it is desired that the output voltage be stable regardless of the load state of the load. FIG.
Is a circuit diagram of a conventional three-terminal regulator. This conventional three-terminal regulator circuit includes a constant current bias circuit 4,
The output stage circuit 1 includes a differential circuit 3, an output drive circuit 1a, a feedback resistor circuit 2, and an output capacitor C2. The constant current bias circuit 4 functions to make the current I3 of the differential circuit 3 and the output drive circuit 1a constant. The differential circuit is
The bias voltage Vbias is compared with the feedback voltage from the feedback resistor circuit 2 to provide a gate signal for keeping the load current constant to the output drive circuit. The output drive circuit 1a functions to determine the gate voltage of the p-channel MOSFET PM4a (no back gate) of the output stage circuit 1. The output stage circuit 1 functions to determine the magnitude of the load current based on the magnitude of the gate voltage of the PM 4a. Feedback resistor circuit 2
Functions to feed back the change in the output voltage to the differential circuit.

The output voltage VOUT is an arbitrarily fixed voltage between the power supply voltage VCC and the ground voltage (GND voltage), and the output current has a value of several mA to several tens mA.
The output voltage is the bias voltage Vbias of the constant current bias circuit 4.
By changing the setting of (reference voltage), it is possible to set the voltage arbitrarily fixed. The bias voltage Vbias determines the magnitude of the constant current of the differential circuit 3 and the output drive circuit 1a. An output capacitor C2 connected to the output and a phase compensation capacitor C1 connected between the drain and source of the NM3 which is an n-channel MOSFET constituting the output drive circuit 1a prevent the output voltage VOUT and the output current from oscillating. Work.

[0004]

In the conventional circuit shown in FIG. 7, when a portable telephone is used, the power supply voltage VCC may decrease due to the consumption of battery power. On the other hand, since the three-terminal regulator maintains the set voltage, the terminal voltage of the output capacitor C2 becomes the output voltage VOUT. In such a case, the power supply voltage VCC falls below the output voltage VOUT, and reverse currents I1 and I2 flow on the power supply side via the parasitic diodes of PM3 and PM4a, and control circuit components (not shown) constituting a three-terminal regulator. May be destroyed.

Further, the resistances R1 and R2 are set to relatively small resistance values (several k) in accordance with the load condition when the mobile phone is used.
Ω) and a large output current is obtained, so that large bias currents I3 and I4 flow even during standby, resulting in an increase in power consumption of the three-terminal regulator. Since the protection against overcurrent when the load is short-circuited is not always sufficient, the output stage circuit constituting the three-terminal regulator may be broken.

When a large load current flows, the output voltage may decrease or the output voltage may oscillate. In order to reduce the size of the circuit, the output capacitor C2
Is reduced, the current absorption capability is reduced, and the output voltage oscillates. When the phase compensation capacitor C1 connected between the drain and the gate of the NM3 to suppress the oscillation of the output voltage under a small load, the oscillation of the output voltage may be increased when the load is large.

As described above, the conventional circuit has many problems. SUMMARY OF THE INVENTION It is an object of the present invention to provide a three-terminal regulator capable of solving the above-mentioned problems and achieving power saving, output stabilization, and prevention of destruction due to reverse current or overcurrent.

[0008]

In order to achieve the above object, in a three-terminal regulator having a drain of an output MOSFET in an output stage and an output capacitor, the output MOSFET has a back gate and the power supply voltage is equal to the power supply voltage. When the terminal voltage becomes lower than the terminal voltage of the output capacitor, the terminal voltage of the output capacitor can be applied to the back gate of the output MOSFET.

It is preferable that the apparatus further comprises a selection means for selecting either the power supply voltage or the voltage of the terminal of the output capacitor and applying the selected voltage to the back gate of the output MOSFET. In a three-terminal regulator having a drain of an output MOSFET as an output and having a feedback resistor circuit in an output stage,
The feedback resistance circuit is switchable between a high impedance state and a low impedance state, and includes a load state detection unit that detects a load state. The output of the load state detection unit changes the resistance value of the feedback resistance circuit. It is good to be able to switch.

It is preferable that a bias circuit capable of switching a bias current is provided, and a bias current value of the bias circuit is switched by an output of the load state detecting means. A current detecting means for detecting that the output current has become excessive; and a cutoff means for cutting off the gate voltage of the output MOSFET, wherein when the current detection means detects an excessive current, the cutoff means It is preferable that the gate voltage of the MOSFET be cut off.

In a three-terminal regulator having a drain of an output MOSFET as an output and having a feedback resistor circuit in an output stage, a stabilizing capacitor is provided between an output point of the three-terminal regulator and a feedback resistor circuit feedback point. It is good to A configuration including a plurality of the above configurations is preferable.

[0012]

FIG. 1 is a main part circuit diagram of an output stage according to a first embodiment of the present invention. In the following description, PM is a p-channel MOSFET, NM is an n-channel MOSFET, IN
V represents an inverter circuit. In the following description of the embodiments, it is assumed that a three-terminal regulator is applied to a mobile phone.

This circuit is different from the conventional circuit in that INV3, PM
A circuit composed of 15, PM12, PM7 and PM11 is added, and like PM4 (output MOSFET), PM7 and PM11 are also back-gate MOSFETs to prevent reverse current. This is to prevent a reverse current from flowing through PM3. In addition, a MOSFET with a back gate refers to a four-terminal MOSFET in which a source electrode does not contact a semiconductor substrate and has a back gate in contact with a semiconductor substrate in addition to an original insulated gate.

When VOUT (output voltage) becomes higher than VCC (power supply voltage), VCNT (control signal voltage) is set to L level by another control circuit (not shown). VCNT
Is set to L level, the output of INV3 becomes H level, PM15 is turned off, and PM12 is turned on.
The voltage of the back gate of PM4 becomes VOUT, and PM4 is turned off. Further, since the back gate of PM4 becomes VOUT, the voltage between the anode and the cathode (the drain and backgate of PM4) of the parasitic diode of PM4 becomes zero and the PM4 is turned off. Therefore, the reverse currents I1 and I2 do not flow through the parasitic diode of the PM 4a shown in FIG. 7, and the destruction of the three-terminal regulator can be prevented. Of course, when VOUT is normal lower than VCC, the back gate voltage of PM4 becomes VCC, and the same operation as PM4a used in FIG. 7 of the conventional circuit is performed.

FIG. 2 is a circuit diagram of a main part of an output stage according to a second embodiment of the present invention. In this circuit, the resistors R1 and R2 constituting a part of the feedback resistor circuit 2 of the output stage circuit 1 are connected to R1
R1 and R10 are replaced with R1 and R1 in FIG.
A low resistance (for example, several kΩ) having a resistance value corresponding to R2 is set. In the standby state, a small current flows through R1 and R2, and in the use state (during a call), a large current flows through R11 and R10. R11, R10, PM13, NM7, NM are added to the conventional circuit shown in FIG.
9, a feedback impedance switching circuit 5 including NM10, INV1, and INV2, and a load detection circuit 6 including R7, PM9, and R8 are added. Also P
M4a (Normal p-channel MOSF without back gate)
The gate of ET) is connected to the drain of PM3 (not shown). Next, the operation of this circuit will be described. In the use state, the gate voltage of the PM 4a is reduced in order to flow a large load current. The decrease in the gate voltage of PM4a is because the drain voltage of PM7 (not shown) decreases with a large load current. When the gate voltage of the PM 4a decreases, the PM 4a can flow a large load current. Further, the gate voltage of PM9 connected to the drain of PM7 also decreases, and R7, PM9,
The current flowing through R8 increases. Then, R8
, The output of INV1 goes low and the output of INV2 goes high. As a result, P
M13 and NM7 turn on, and PM4a, R11, R10
, A large load current flows. On the other hand, in the standby state, PM13 and NM7 are turned off.
a, a small load current flows through R1, R2, and the current consumption of the three-terminal regulator can be reduced.

Note that R1 and R2 are one feedback resistor, and R1
0 and R11 are another feedback resistor. In FIG. 2, 2
One feedback resistor forms a feedback resistor circuit. FIG. 3 is a circuit diagram of a main part around a constant current bias circuit according to a third embodiment of the present invention. This circuit corresponds to PM1, NM4, R in FIG.
R3 and NM5 are connected to a constant current bias circuit composed of R4, and a load detection circuit 6 composed of R7, PM9, and R8.
Is connected to the gate of NM5. The operation of this circuit will be described. When the load increases, the potential at the upper end of R8 increases, and NM5 turns on. When NM5 turns on,
A large bias current flows through the relatively small resistor R3. By increasing the bias current, a large current also flows through PM1, PM2, and PM3 (not shown) to stabilize the gate voltage of PM4,
Suppresses output voltage oscillation. If the load is small,
Since the NM5 is turned off and the bias circuit 4a is disconnected from the constant current bias circuit 4, the bias current flows via the relatively large resistor R4, and the power consumption is reduced.

FIG. 4 is a circuit diagram of a main part around an output cutoff circuit according to a fourth embodiment of the present invention. The output cutoff circuit 7 is connected between the overload detection circuit 9 and the differential circuit 3. Specifically, the drain of NM6 is connected to the connection point between NM2 and PM6, and this connection point is also connected to the gate of NM3. The gate of NM6 is connected to the upper end of R6. When the load becomes excessively large or when the load is short-circuited, the gate voltage of the PM8 connected to the PM4a decreases, and the R5-PM
The current flowing in the route of 8-R6 increases, and the potential at the upper end of R6 increases. When the potential at the upper end of R6 rises, N
M6 turns on, PM3 turns on, and NM3 turns off. PM
When 3 is turned on and NM3 is turned off, PM4a (or PM4) of the output stage circuit 1 (not shown) is turned off and the output is cut off. This output cut-off prevents the three-terminal regulator from being overheated.

FIG. 5 is a main part circuit diagram around an output stage circuit according to a fifth embodiment of the present invention. In this circuit, even if the output capacitor C2 is reduced, the phase compensation capacitor C1 attached to the NM3 of the conventional circuit is removed so that the output does not oscillate, and an output stabilizing capacitor C3 for preventing oscillation is provided at both ends of R1. Connected. Thereby, high frequency vibration is suppressed.

As a result of the experiment, the output drive circuit 1b
A charging current I5 flowing through the constant current source 10 and PM7;
By adjusting the ratio of NM3 to the discharge current I6 flowing through the constant current source 11 to be 1: 3, it was found that high-frequency vibration was reliably suppressed. FIG. 6 is a circuit diagram of a three-terminal regulator according to a sixth embodiment of the present invention. This circuit includes the back gated MOSFET PM4 of the first embodiment, and includes all of the second to fifth embodiments. The drawings include the circuits of FIGS. 3 to 8 of each embodiment. Of course, any of these embodiments may be employed depending on the application and cost.

This circuit is different from a conventional circuit comprising an output stage circuit 1, a feedback resistor circuit 2, a differential circuit 3 and a constant current bias circuit 4 shown in FIG. Output stage circuit 1 having gated MOSFET PM4, feedback impedance switching circuit 5, load detection circuit 6, output cutoff circuit 7, constant current bias circuit 4
And a circuit including an output stabilizing capacitor C3 connected to the output stage circuit 1 and the like. Further, the constant current source 1 of the output drive circuit 1b
PM which is MOSFET with back gate instead of 0
7, the ratio of the charging current I5 to the discharging current I6 of FIG. 5 is controlled to 1: 3. It should be noted that IV1 and IV2 in FIG.
NV1 and INV2.

[0021]

According to the present invention, for example, in a three-terminal regulator used in a mobile phone, a MOSFET with a back gate is used, and when the output voltage becomes the power supply voltage, the back gate voltage is switched to the output voltage, and By stopping the reverse current flowing through the diode and blocking the reverse current flowing into the power supply side, it is possible to prevent the control circuit components constituting the three-terminal regulator from being destroyed. Power consumption can be reduced by switching the feedback resistor circuit to a high impedance circuit during standby. Further, the power consumption can be reduced by switching the constant current bias circuit to a small current circuit during standby. By providing the output cutoff circuit, it is possible to prevent the output stage circuit constituting the three-terminal regulator from being destroyed when an excessive current flows or the output is short-circuited. By eliminating the phase compensation capacitor and providing the output stabilizing capacitor between the output point and the feedback point, the output can be prevented from oscillating under heavy load, and the output can be stabilized.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram of an output stage according to a first embodiment of the present invention;

FIG. 2 is a main part circuit diagram of an output stage according to a second embodiment of the present invention;

FIG. 3 is a main part circuit diagram of a constant current bias circuit according to a third embodiment of the present invention;

FIG. 4 is a main part circuit diagram of an output cutoff circuit according to a fourth embodiment of the present invention;

FIG. 5 is a main part circuit diagram of an output stage in a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram of a three-terminal regulator according to a sixth embodiment of the present invention.

FIG. 7 is a circuit diagram of a conventional three-terminal regulator.

[Explanation of symbols]

PM1 p-channel MOSFET (constituting constant current bias circuit) PM2 p-channel MOSFET (constituting differential circuit) PM3 p-channel MOSFET (constituting output drive circuit / feedback impedance circuit) PM4 p-channel MOSFET with back gate
(Construction of output stage circuit) PM4a p-channel MOSFET (construction of output stage circuit) PM5 p-channel MOSFET (construction of differential circuit) PM6 p-channel MOSFET (construction of differential circuit) PM7 p-channel MOSFET with back gate PM8 p-channel MOSFET (configures an overload detection circuit) PM9 p-channel MOSFET (configures a load detection circuit) PM11 p-channel MOSFET with a back gate PM12 p-channel MOSFET (configures an inverter circuit) PM13 p-channel MOSFET (configures a feedback impedance circuit) PM14 p Channel MOSFET (constituting inverter circuit) PM15 p-channel MOSFET (constituting inverter circuit) NM1 n-channel MOSFET (constituting differential circuit) NM2 n-channel MOS ET (configures a differential circuit) NM3 n-channel MOSFET (configures an output drive circuit) NM4 n-channel MOSFET (configures a constant current bias circuit) NM5 n-channel MOSFET (configures a bias circuit) NM6 n-channel MOSFET (configures an output cutoff circuit) Configuration) NM7 n-channel MOSFET (configures a feedback impedance circuit) NM8 n-channel MOSFET (configures an inverter circuit) NM9 n-channel MOSFET (configures a feedback impedance circuit) NM10 n-channel MOSFET (configures a feedback impedance circuit) R1 resistance (return resistance) R2 resistance (feedback resistance) R3 resistance (configures a bias circuit) R4 resistance (configures a constant current bias circuit) R5 resistance (configures an overload state detection circuit) R6 resistance (configures an overload state detection circuit) R Resistance (constituting load detection circuit) R8 Resistance (constituting load detection circuit) R10 Resistance (constituting feedback impedance circuit) R11 Resistance (constituting feedback impedance circuit) C1 Phase compensation capacitor C2 output capacitor C3 output stabilization capacitor VCC power supply voltage (High potential side of power supply) VOUT Output voltage (output) VCNT Control voltage Vbias Bias voltage VIN Input power supply voltage (High potential side of input power supply) GND Ground potential (earth) INV1 Inverter circuit (constitutes feedback impedance circuit) INV2 Inverter circuit (Construction of feedback impedance circuit) INV3 Inverter circuit I1 Leakage current I2 Leakage current I3 Bias current I4 Bias current I5 Charge current I6 Discharge current 1 Output stage circuit 1a Output drive circuit 1b Output drive circuit 2 Feedback resistance circuit (Invention circuit / Conventional circuit) Differential circuit 4 constant current bias circuit 4a bias circuit 5 feedback impedance switching circuit 6 the load detecting circuit 7 output cutoff circuit 9 excessive load detecting circuit 10 a constant current source 11 a constant current source

Claims (6)

[Claims] 1. A three-terminal regulator having a drain of an output MOSFET at an output stage and having an output capacitor, wherein the output MOSFET has a back gate, and when a power supply voltage becomes lower than a terminal voltage of the output capacitor, the output MOSFET is output. A three-terminal regulator for applying a terminal voltage of the output capacitor to a back gate of the MOSFET. 2. The three-terminal regulator according to claim 1, further comprising selection means for selecting one of a power supply voltage and a voltage of a terminal of said output capacitor and applying the selected voltage to a back gate of said output MOSFET. Features a three-terminal regulator. 3. A three-terminal regulator having a drain of an output MOSFET as an output and having a feedback resistor circuit in an output stage, wherein the feedback resistor circuit is switchable between a high impedance state and a low impedance state. A three-terminal regulator comprising a load state detecting means for detecting a state, wherein a resistance value of the feedback resistor circuit is switched by an output of the load state detecting means. 4. The three-terminal regulator according to claim 3, further comprising a bias circuit capable of switching a bias current, wherein a bias current value of said bias circuit is switched by an output of said load state detecting means. Terminal regulator. 5. The three-terminal regulator according to claim 3, further comprising current detection means for detecting that the output current has become excessive, and interruption means for interrupting the gate voltage of the output MOSFET. Wherein the shut-off means cuts off the gate voltage of the output MOSFET when an excessive current is detected. 6. A three-terminal regulator having a drain of an output MOSFET as an output and having a feedback resistor circuit at an output stage, comprising a stabilizing capacitor between an output point of the three-terminal regulator and a feedback resistor circuit feedback point. A three-terminal regulator.