JPH0250514A - Triangular wave generating circuit - Google Patents

Abstract

PURPOSE:To attain high speed and to improve the temperature characteristic by selecting the number of transistors of a diode form at a level shifting circuit so that the voltage between the base and emitter of a transistor cannot be included in the voltage supplied to the resistance to form the base potential and the constant current of a differential transistor with a reference voltage as a starting point. CONSTITUTION:The base and collector voltage of a transistor Q16 of a diode form to constitute a level shifting circuit are supplied to the base of an emitter follower transistor Q9 to supply an action voltage to an oscillation circuit OSC. The voltage of a transistor Q17 is supplied to the base of an emitter follower transistor Q12 to supply an action voltage VC' to a constant current source circuit IG. With a reference voltage as a starting point, the number of transistors of the diode mode at a level shifting circuit is selected so that the voltage between the base and emitter of the transistor cannot be included in the voltage supplied to the resistance to form the base potential and constant current of the differential transistor. Thus, while gaining high speed the temperature characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a triangular wave generation circuit, and relates to a technique that is effective for use in, for example, a switching regulator.

[Conventional technology]

A triangular wave generating circuit is used, for example, in a switching regulator. A switching regulator forms a pulse width modulation signal from a triangular wave and a reference voltage corresponding to the output voltage and performs switching control to obtain a desired output voltage corresponding to the pulse duty of the pulse width modulation signal. It is.

As an example of a triangular wave generation circuit, for example, June 3, 1981
Published on 0th “Integrated Circuit Application Handbook 1 page 150-1
There are 51.

[Problem to be solved by the invention]

In order to obtain a triangular wave generation circuit that achieves high speed (high frequency), an emitter follower output circuit with low output impedance may be used. However, in this case, the temperature characteristics deteriorate due to the temperature dependence of the voltage between the base and emitter of the transistor.

It is an object of the present invention to provide a triangular wave generation circuit that achieves high speed and improved temperature characteristics.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the operating voltage is supplied through the first emitter follower transistor, and the operating voltage is supplied through the oscillation circuit using the emitter follower output circuit and the second emitter follower transistor, and the difference forming the oscillation circuit is A triangular wave generation circuit is composed of a dynamic transistor and a constant current source circuit that forms the operating current of its emitter follower output circuit, and the operating voltage of the oscillation circuit and constant current source circuit is generated by a triangular wave generator whose base is supplied with a predetermined reference voltage. a second transistor in the form of a diode whose emitter is commonly connected to the first transistor;
The transistors connected in series form. The voltage between the base and emitter of the transistor is determined by the voltage supplied to the resistor that forms the base potential of the differential transistor and the constant current, starting from the reference voltage. The number of diode-type transistors in the level shift circuit should be selected so that the level shift circuit does not include

[For production]

According to the above means, speed is increased by using the emitter follower output circuit, and by using the level shift circuit, the voltage between the base and emitter of the transistor is applied to the circuit that determines the threshold voltage and constant current of the oscillation circuit. Since it can be avoided, temperature characteristics can be improved.

〔Example〕

FIG. 1 shows a circuit diagram of an embodiment of a triangular wave generating circuit according to the present invention. Each circuit element in the figure, except for a resistor and a capacitor constituting a time constant circuit, is formed on a single semiconductor substrate such as single-crystal silicon by a known semiconductor integrated circuit manufacturing technique.

In this embodiment, the triangular wave generation circuit includes an oscillation circuit 08C1 a constant current source circuit IG, as shown by a dotted line in the figure.
and a bias circuit BIAS.

The oscillation circuit O8C is composed of the following circuit elements. Differential transistors Q3 and Q4 perform a voltage comparison operation. The common emitter of differential transistors Q3 and Q4 has
A constant current transistor Q7 is provided to flow an operating current.

Load resistors R1 and R2 are provided at the collectors of differential transistors Q3 and Q4, respectively. The collector output voltages of the differential transistors Q3 and Q4 are the same as those of the transistors Q1 and Q2, respectively, which constitute the emitter follower output circuit.
supplied to the base of A constant current transistor Q8 is provided at the emitter of the transistor Q1 via a resistor R3. A constant current source transistor Q6 is provided at the emitter of the transistor Q2 via a resistor R4. To configure the oscillation circuit, the collector output of the differential transistor Q1 is
It is connected to the base of the other differential operation transistor Q4 via the emitter follower output transistor Q1 and emitter resistor R3. A time constant circuit consisting of a charging resistor RT and a capacitor CT is connected to the base of the differential transistor Q1 via an external terminal, and a reset transistor Q5 is connected in parallel to the capacitor CT. is supplied with an output signal from the emitter follower output circuit provided corresponding to the collector output of the other differential transistor Q4.

The above oscillation circuit includes an emitter follower transistor Q9.
An operating voltage VC is applied through the VC.

Constant current source circuit IG is composed of the following circuit elements. The emitter and base of a transistor Qll are coupled to the base and collector of a transistor QIO whose emitter is coupled to the ground potential of the circuit. The above transistor Ql
The collector of l is coupled to the supply voltage V. The collector of the transistor QIO has a resistor R that sets a constant current.
5 is provided. An emitter follower transistor Q12 that supplies an operating voltage is provided at the other end of the resistor R5. The transistor QIO is connected to the constant current transistors Q6 to Q8 in a current mirror configuration, and if the emitter area ratios of the transistor QIO and the transistors Q6 to Q8 are made equal, then assuming that a constant current io flows through the transistor QIO, the current value will be the same. The constant current io thus set also flows through each of the constant current transistors Q6 to Q8.

In the oscillation circuit O3C, when the differential transistor Q4 is on and the differential transistor Q3 is off, the reference voltage VA supplied to the base of the differential transistor Q4 is expressed by the following equation 11>.

VA-VC-VaEQ, -R3・io (1
) where VIIEQI is the base of transistor Q1.

is the emitter voltage. In this way, the differential transistor Q
4 is on, transistor Q5 has VC'A
A voltage of atoz io (R2+R4) is applied to turn it off. Therefore, a charging operation is performed on the capacitor CT via the resistor RT.

When the potential of the capacitor CT reaches the reference voltage VA shown by the formula +11, the differential transistor Q3 is turned on and the differential transistor Q4 is turned off. Depending on the on state of the transistor Q3, the reference voltage VA changes as shown in the following equation (2).

VA-VCVmta+ jO(R1+R3)...
(21) Therefore, in accordance with the off-state of the transistor Q4, its output level increases by the voltage drop of 1o-R2, and the transistor Q5 becomes on-state, performing a discharging operation of the capacitor CT.

When the base potential of the differential transistor Q3 reaches the potential expressed by equation (2) above due to the discharging operation of the capacitor CT,
The differential transistor Q4 is turned on and the differential transistor Q3 is turned off again. An example of the changes in the voltages VA and VB as described above is shown in the waveform diagram of FIG. 2. Hereinafter, the oscillation operation is performed by repeating the same operation, and the voltage VB becomes a triangular wave.

The reference voltage VA supplied to the base of the differential transistor Q4 has a hysteresis characteristic similar to that of VTR and VTL, and includes the voltage VllEQ+ between the base and emitter of the transistor Q1. , has temperature dependence. Further, the constant current to is determined by the following equation (3), assuming that the voltage supplied to the other end of the resistor R5 is ■C'.

io= (VC'-2Vmt)/R5...1312
Vmi is the hemi-emitter voltage of transistors QIO and Qll. Therefore, as is clear from equation (3), the constant current io is also equal to the voltage between the base and emitter of the transistors Q10 and Qll. It has temperature dependence.

In this embodiment, the following bias circuit BTAS is provided in order to improve the temperature dependence as described above.

Power supply voltage V is divided by resistors R6 and R7. The power supply voltage V is formed by a stabilized power supply circuit and has at least no temperature dependence. The above divided voltage V
D is supplied to the base of transistor Q13. A diode-type transistor Q14 having a common emitter with this transistor Q13 is provided. An emitter resistor R9 is provided at the common emitters of the transistors Q13 and Q14.

The diode type transistor Q14 mentioned above also has a diode type! Deactivated transistors Q15 to Q
17 are provided in series and are coupled to the power supply voltage V via a resistor R8.

In this embodiment, the base and collector voltages of a diode-type transistor Q16 constituting the level shift circuit are supplied to the base of an emitter follower transistor Q9 that supplies an operating voltage to the oscillation circuit OSC. Also,
The base and collector voltages of the diode-type transistor Q17 constituting the level shift circuit are constant current source circuit I
It is supplied to the base of an emitter follower transistor Q12 which supplies an operating voltage vC' to C.

The bias circuit BIAS cancels the divided voltage VD with the voltage between the base and emitter of transistors Q13 and Q14, and outputs the divided voltage VD from the transistor Q16 to a level equal to the voltage 2VIE between the base and emitter of transistors Q15 and Q16. Shift ("2 Vmi).

As a result, the operating voltage VC supplied to the oscillation circuit O8C becomes VD+VIE as a result of the voltage CVD+2V□ supplied from the bias circuit BIAS being supplied through the base and emitter of the transistor Q9.

By substituting this operating voltage VC into the above equations (1) and (2), the following equations (4) and (5) are obtained.

VA (VTH) =VD-R3・io −・・1
4) VA (VTL) = VD-to (R1+R3) f
21 By forming the operating voltage VC of the oscillation circuit OSC through the bias circuit BIAS as described above, the temperature dependence in the emitter follower output circuit can be offset.

The bias circuit BIAS' includes the transistor Q1
7, the divided voltage VD is applied to the transistors Q15 to Q17.
Level shift by 3Vst between base and emitter voltage (
+3v□), thereby the constant current source circuit IG
The operating voltage VC' supplied to the bias circuit BI
The voltage (V D + 2 Vat) supplied from AS is supplied through the base and emitter of transistor Q12, resulting in VD + 2 Vgt. By substituting this operating voltage vC' into the above equation (3), the following equation (6) can be obtained.
is obtained.

1o=vD/R5 (6) By forming the operating voltage vc' of the constant current source circuit IG through the bias circuit BIAS as described above, the temperature dependence of the transistor QIO constituting the current mirror circuit is reduced. can be offset. This results in constant current io
can also be made to have no temperature dependence, so Equations (4) and (5)
As is clear from the above, it is possible to obtain a triangular wave generation circuit with improved temperature dependence. Furthermore, since the switching operation of the voltage comparator circuit is performed through the emitter follower output circuit as described above, high-speed operation is possible.

The triangular wave VB is used to form a pulse width modulation signal PV/M by comparing it with a reference voltage VO. For example, in a switching regulator, a switching element is controlled according to the pulse width modulation signal PWM, and the This is to control the output voltage level formed by smoothing the switch output voltage.

The effects obtained from the above examples are as follows. That is, (1) an operating voltage is supplied via the first emitter follower transistor, an oscillation circuit using an emitter follower output circuit, and an operating voltage is supplied via the second emitter follower transistor, and the above oscillation circuit is A triangular wave generation circuit is formed by the constituent differential transistors and a constant current source circuit that forms the operating current of the emitter follower output circuit, and the operating voltage of the oscillation circuit and constant current source circuit is supplied to a predetermined reference voltage or base. a diode-type second transistor whose emitter is commonly connected to the first transistor; and a plurality of diode-type transistors connected in series to the second transistor. The level shift circuit is configured such that the base voltage of the differential transistor and the voltage supplied to the resistor that forms the constant current do not include the voltage between the base and emitter of the transistor, starting from the reference voltage. A circuit that determines the threshold voltage and constant current of the oscillation circuit by selecting the number of diode-type transistors in the oscillator circuit and increasing the speed by using an emitter follower output circuit, and by using the level shift circuit described above. Since the voltage between the transistor 1 and the base and emitter of the transistor can be excluded from the voltage, the temperature characteristics can be improved.

(2) By using the charging resistor and capacitor for obtaining the triangular wave as external components, it is possible to use ones with small temperature dependence and variation, which has the effect of making it possible to obtain a highly accurate triangular wave generation circuit. is obtained.

(3) According to (1) above, a highly accurate triangular wave can be obtained, resulting in the effect that a high-speed and highly accurate switching regulator can be obtained.

Although the invention made by the present inventor has been specifically explained based on Examples above, it goes without saying that the present invention is not limited to the above-mentioned Examples, and can be modified in various ways without departing from the gist thereof. do not have. For example, the emitter follower circuit used in the oscillation circuit may use a Darlington type output transistor. In this case, the operating voltage VC may be obtained from the transistor Q17. The number of diodes that perform the level shift may be determined in accordance with the voltage between the base and emitter of the transistor that determines the threshold voltage of the oscillation circuit. This also applies to constant current source circuits. The capacitor and resistor constituting the time constant circuit may be built into the semiconductor integrated circuit.

It goes without saying that the triangular wave generating circuit according to the present invention can be used not only to form triangular waves in a narrow sense used for pulse width modulation as described above, but also as a highly stable oscillation circuit that is temperature compensated. Probably.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows. That is, the operating voltage is supplied through the first emitter follower transistor, and the operating voltage is supplied through the oscillation circuit using the emitter follower output circuit and the second emitter follower transistor, and the difference forming the oscillation circuit is A triangular wave generation circuit is composed of a dynamic transistor and a constant current source circuit that forms the operating current of its emitter follower output circuit, and the operating voltage of the oscillation circuit and constant current source circuit is generated by a triangular wave generator whose base is supplied with a predetermined reference voltage. 1 transistor, a diode-type second transistor whose emitter is commonly connected to the first transistor, and a plurality of diode-type transistors connected in series to the second transistor. The diode configuration in the level shift circuit is such that the base voltage of the differential transistor and the voltage supplied to the resistor that forms the constant current with the reference voltage as a starting point do not include the voltage between the base and emitter of the transistor. By selecting the number of transistors in the oscillator circuit, the speed can be increased by using an emitter follower output circuit. Since the voltage between the base and the emitter can be eliminated, the temperature characteristics can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining its operation. O20・・Oscillation circuit, IG・・Constant current source circuit, IAS・Bias circuit

Claims (1)

[Claims] 1. A first emitter follower output to which an operating voltage is supplied via the first emitter follower transistor, receives the collector output of one differential transistor, and feeds it back to the base of the other differential transistor. and a second emitter that receives the collector output of the other differential transistor and controls the transistor that resets the capacitor in the time constant circuit that includes a charging resistor and a capacitor provided at the base of the one differential transistor. an oscillation circuit consisting of a follower output circuit; and a constant current source circuit to which an operating voltage is supplied via a second emitter follower transistor and forms an operating current for the differential transistor and the first and second emitter follower output circuits. a first transistor whose base is supplied with a predetermined reference voltage; a second transistor in the form of a diode whose emitter is commonly connected to the first transistor; and a second transistor connected in series to the second transistor. and a level shift circuit consisting of a plurality of diode-type transistors,
The number of diode-type transistors in the level shift circuit is selected so that the base potential of the differential transistor and the voltage supplied to the resistor that forms the constant current starting from the above reference voltage do not include the voltage between the base and emitter of the transistor. A triangular wave generation circuit, wherein a voltage is formed to be supplied to the bases of the first and second emitter follower transistors. 2. The number of diode-type transistors constituting the level shift circuit is three, and the voltage generated by two of them is:
The voltage supplied to the base of the first emitter follower output transistor and formed by three diode-type transistors is supplied to the base of the second emitter follower output transistor. A triangular wave generation circuit according to claim 1. 3. What are the capacitors and resistors that make up the above time constant circuit?
A triangular wave generation circuit characterized in that it is connected via an external terminal.