JPS5832345Y2 - pulse width converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse width converter using an astable multi-vibrator.

Pulse width converters that convert the amplitude of a continuous signal into a pulse width signal are used in a variety of ways in a variety of electronic devices.

There are various ways to configure a pulse width converter, but an unstable multi-channel converter is a simple one that functions as both an oscillator and a modulator.
There is a pulse width converter that uses a vibrator.

A conventional example of a pulse width converter using an astable multi-vibrator is shown in Figure 1, in which a continuous signal to be converted is applied to the base of transistor Q3, and the pulse width is converted from the collector of transistor Q1 or Q2. I'm trying to get the signal out.

Since the conductivity of transistor Q3 changes depending on the continuous signal applied to its base, the charging/discharging time constant of the capacitor changes, thus transistor Q1. The on/off duty ratio of Q2 changes.

In such a pulse width converter, changing the duty ratio also changes the oscillation frequency, which may be inconvenient depending on the application.

Conventional examples of pulse width converters that do not change frequency include:
Some devices consist of a fixed frequency oscillation circuit and a pulse width conversion circuit whose timing is regulated by the output signal of this oscillation circuit, but such devices have a large number of component parts, so It is not suitable as a low-cost pulse width converter.

An object of the present invention is to provide a constant frequency pulse width converter using an astable multi-pie break.

In the present invention, two voltages, at least one of which is a signal to be converted, are applied to the collector-emitter circuits of l pairs of transistors in an unstable multi-pie break, and the voltage obtained by linear combination of these voltages is applied to the collector-emitter circuits of l pairs of transistors in an unstable multi-pie break. This is the base bias voltage.

The present invention will be explained below with reference to the drawings.

FIG. 2 is a diagram showing the basic configuration of the present invention.

In FIG. 2, Ql and Q2 are transistors whose bases are coupled to the collectors of the other side through capacitors C1 and C2, respectively, and the collectors are connected to resistors R,
, R2 are applied with voltages ■□ and V2, respectively, and a bias voltage ■□ and V2 are applied to the base through resistors R3 and R4.
is given.

Voltage■1. (2) At least one of transistors Q1 and 2 is a continuous signal to be converted. Q2 operates using these voltages as power supply voltages.

Bias voltage V3 is voltage ■1. ■It is given as a linear combination of two.

In the circuit configured in this way, the bias voltage (3) is set to the voltage (1). (2) It is similar to a well-known non-stable multi-vibrator except that it is provided as a linear combination of transistors Q1. Q2 alternately repeats on/off operations in a certain period.

Transistor Q1. Q2 on duration time T1. T2 is substantially expressed by the following equations.

Therefore, the period of oscillation is: If it is possible to do so, the period of oscillation can be made constant while the value of equation (4) remains constant.

Voltage v3 is a linear combination of voltage v1 and ■2, but (5
) can be determined to satisfy the equation.

An example of linear combination is shown in FIG.

In Figure 3, voltages □ and V2 are applied to the bases of both transistors through resistors R1 and R2, respectively, and voltages to the collectors are applied to β1 and R2, respectively.
The partial pressure is given as follows.

In such a circuit, the equivalent resistance that determines the charging and discharging time constants of the capacitors C1 and C2 is the parallel resistance of R1 and R2.

This parallel resistance corresponds to resistor R3 or R4 in FIG.

That is, R3=~=Kl/R2(6) becomes.

Therefore, the voltage applied to such circuits ■3
is expressed by the following formula.

By substituting the relationships in equations (6) and (7) into equations (1) and (2), the following equations are obtained, respectively.

That is, the duration time T1 of the transistor Q2 is in the on state. Since T2 changes depending on the values of the voltages ■□ and V2, the voltage V1 or ■2 can be converted into a pulse width signal.

However, the conversion characteristics become non-linear.

Here, if the circuit constants are determined so that β1RIC1-β2R2C2, then the oscillation period becomes constant.

That is, a pulse width converter with a constant frequency can be realized by a simple circuit using an astable multi-vibrator.

An application example of such a pulse width converter is shown in FIG.

FIG. 4 shows the use of the pulse width converter of the present invention in a drive circuit for an on-off type switching regulator.

In FIG. 4, REG is a switching regulator, CNv is a pulse width converter, and A is an error amplifier for feedback control.

The switching regulator REG uses the transistor Q□ of the pulse width converter CNV as a switching element, and stores electromagnetic energy in the transformer T when the transistor Q1 is on, and releases it to the secondary circuit when the transistor Q1 is off. It has become.

Output voltage E. is adjusted by the on/off duty ratio of transistor Q1.

Error amplifier A outputs voltage E.

A feedback control voltage is generated by amplifying the deviation between the reference voltage Vref and the reference voltage Vref, and this is applied to the pulse width converter CNV as a voltage .

The primary side voltage E+ of the switching regulator REG is applied to the pulse width converter CNV as a voltage 2.

When the on/off duty ratio of the transistor Q is represented by X, the voltage conversion characteristic of the switching regulator REG is expressed by the following equation.

However, the turns ratio of the transformer T is assumed to be 1.

That is, the voltage conversion characteristics of this switching regulator are nonlinear with respect to the duty ratio X.

It is generally difficult to stabilize the output voltage of a switching regulator with such nonlinear conversion characteristics through feedback control because the gain of the -circuit loop changes; converter CN
As described below, the conversion characteristics of V have a nonlinearity that is an inverse function to that of the switching regulator REG, so the two cancel each other out and feedback control can be performed with the gain of some loops constant. .

That is, when the function f (X) is given by equation (15), its inverse function is given by V as the independent variable, and the duty ratio of the on/off operation of transistor Q1 is (9), (13 ), however, K = R2/R1-1/Ei.

Since this equation is the same as equation (16), the conversion characteristics of the pulse width converter CNV are as follows:
It is an inverse function of the conversion characteristics of EG.

i.e. x = f-(KVI) It is.

Therefore, control proportional to the feedback control signal (1) of the error amplifier A can be performed.

Also, substituting equation (19) into equation (22) yields,
Output voltage E.

is unrelated to fluctuations in the primary side voltage E1.

FIG. 5 shows a modification of a part of the device shown in FIG. 4, in which a transistor Q3 is provided as a switching element and is driven by a transistor Q1 of a pulse width converter via a transistor T2.

As described above, the present invention applies two voltages, at least one of which is a signal to be converted, to the collector-emitter circuit of a pair of transistors of an astable multivibrator, and obtains a signal by linearly combining these voltages. The voltage was used as the base bias voltage for both transistors.

Therefore, a pulse width converter with a constant frequency and a simple structure using an unstable multi-vibrator can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an electrical connection diagram of the conventional example, Fig. 2 is a basic configuration diagram of the present invention, Fig. 3 is an electrical connection diagram of the embodiment of the present invention, and Fig. 4 is an electrical connection diagram of the conventional example.
The figure is an electrical connection diagram of an applied example of the present invention, and FIG. 5 is a partial modification of the device shown in FIG. 3. Qo, Q2...Transistor, C, C2...
...Condenser, R1-R4...Resistor,
REG・・・Switching regulator, CNv
...Pulse width converter, A...Error amplifier.

Claims (1)

[Scope of utility model registration request] One of the two voltages, at least one of which is a signal to be converted, ■1, is applied to a first voltage divider circuit with a voltage dividing ratio of β1; the other of the two voltages, at least one of which is a signal to be converted, ■2. a second voltage divider circuit with a given voltage division ratio of R2; a first transistor Q1 and a second transistor Q2; A first capacitor C1 connects the voltage dividing point of the voltage dividing circuit to the base of the second transistor Q2, and connects the voltage dividing point of the second voltage dividing circuit to the base of the second transistor Q2.
a second capacitor C2 connected to the base of the transistor Q1, two first resistors R1 that lead one of the two voltages to the base of the first transistor Q1 and the second transistor Q2, respectively; , the other of the two voltages 2 is connected to the base of the first transistor and the second
The two second
A pulse width converter comprising a resistor R2 and whose circuit constants satisfy the relationship β, R, C = β2 R2C2.