JPS5879307A - Power supply circuit for amplifier - Google Patents

Abstract

PURPOSE:To impove the power conversion efficiency of a titled amplifier, by using a capacitor charged with a control switch and an inductor and supplying a plurality of voltages to an output transistor (TR) with a single power supply. CONSTITUTION:An input signal Vi is applied to a load as an output voltage V0 via output TRs Q1, Q1' and a preamplifier 1. A comparator 32 compares a voltage Vc of a capacitor C1 with a voltage V0+Es shifting the output voltage V0 by the voltage Es and turns on a switch 31 at V0+Es>=Vc. In this case, a power supply +B charges the C1 via an inductance L1 and the charging voltage of a capacitor C2 is added to the voltage and applied to the output TRQ1. With the switch 31 turned off at V0+Es<Vc, the magnetic energy of the L1 due to the charging current of the C1 is charged in the C2 as charges and the Vc is applied to the TRQ1. The load circuit operates similarly as mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit for an amplifier, and in particular to a power supply circuit for a power amplification element of a power amplifier. The power consumed by a pair of complementary transistors, which are power amplification elements, is instantaneously expressed as PC=IC''VCE.Io is the collector current of the transistor, and ■
oE tri collector-emitter voltage. Only this power PC is consumed inside the amplifier, causing a decrease in efficiency. For example, the efficiency is theoretically 78.5% at maximum amplitude, but it decreases further when the signal is small. In order to improve this power conversion efficiency, the human input signal or output signal level is detected and the level A method is adopted in which one of the outputs of a plurality of power supplies having different output voltage levels is selected depending on the output voltage level and supplied as the voltage source of the power amplification element. However, there are drawbacks such as the need for multiple power supplies, which is undesirable, and the fact that if the maximum amplitude is set to 1,000, a power supply with a higher voltage level is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply circuit that can improve power efficiency using a single power supply and can generate a larger voltage than the single power supply.

A power supply circuit for an amplifier according to the present invention includes first and second capacitance elements, a switching element for supplying a power supply voltage as a charging voltage to the first capacitance element via an inductance element, and The electromagnetic energy stored in the inductance element during the charging period of the element is transferred to the second one during the non-conducting period of the switching element.
The switching circuit is made conductive when the absolute value of the difference between the voltage corresponding to the amplifier output and the charging voltage of the first capacitance element becomes less than or equal to a certain value. It is characterized in that the stored voltage of the second capacitance element is superimposed on the circuit power supply and is supplied to the power supply terminal of the amplifier, and when it is not conductive, the stored voltage of the first capacitance element is supplied.

The present invention will be explained below using the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention, in which human input signals ■,
is amplified by the voltage amplification stage IK, and supplied to the power amplification stage 2 consisting of mutually complementary output transistors Ql + Q'1. Common emitter output V for both transistors Ql lQ/. powers the load.

In order to supply power to the collectors which are power supply ends of these output transistors Ql*Q'l, power supply circuits indicated by 3 and 3' are provided, respectively.

The positive side power supply circuit 3 includes an inverted Darlington-connected transistor Q2. A switching circuit 31 consisting of Q, a first capacitance element CI supplied with the circuit power supply 1B as a charging voltage via an inductance element L1 when the switching circuit 31 is turned on;
Furthermore, there is an inductance element.

a second capacitance element C connected equi-parsimoniously in parallel with
2. The charging voltage VC of the first capacitor (sitance element CI) is supplied to the collector terminal of the transistor Q1 via the diode D. is provided, and when there is no charging charge in this element C2, the circuit power supply 1B is applied via the diode D2, and when there is charge, a voltage obtained by superimposing the charging voltage of this capacitance element C2 on the circuit power supply 1B is provided. are respectively supplied as the collector terminal voltage va of the transistor Q1.

Switching transistor Q2. For the control of Q,
A level comparator 32 is installed. This is the charging voltage V of the first capacitance element C1. and the amplifier circuit output voltage■. Voltage ■ whose level is shifted to a higher level by a constant value E5. It is compared with 10E5. And v
When o1a, ≧■o, that is, ■. −■c≧E
s and the difference between the circuit output and the charging voltage exceeds a certain value E, the comparator 32 generates a control output,
It is applied to the base of the transistor Q2, and controls the switching circuit 31 to be turned on.

Therefore, when V, -V, < E, the switching circuit 31 is off.0 The negative side circuit 3' has a complementary configuration with the positive side circuit 3, and the switching circuit 31 is turned off when V, -V, < E. are all indicated with a ''].

The operation of the positive side circuit having such a configuration will be explained using the waveforms shown in FIG. In the explanation, we will use the forward voltage drop of each diode, the BE (pace-emitter voltage) of each transistor, and the switching transistor VCE.
(Collector-emitter-lid voltage) are all zero.

Furthermore, in the system of the comparator 32 and the switching circuit 31,
For example, the transition from on to off of the switching circuit 31 may have a slight time delay with respect to the control signal from the comparator 32, or the comparator 32 may have hysteresis characteristics with respect to the detected voltage. O When the power is turned on at time t0, the human power signal ■
, assuming that there is no output ■. is zero port. At this point, since there is no charge accumulation in both capacitance elements C1 and C2, the capacitance element C1 output (■).

is initially zero port, and ■. 10E, :E,
Therefore, the output of the level comparator 32 is the transistor Q
2. A control signal is generated to turn on Q. Therefore, the circuit power source 1B directly becomes the collector potential of the transistor Q via the transistor QsI diode D2, and the capacitance element C1 is charged via the inductance element.

Therefore, the charging curve becomes as shown by the dotted line in the figure. At this time, since va>■o, the diode D1 is cut off, and discharge from the capacitance element CI to the transistor Q is prevented.

When charging of the capacitance element C1 progresses and vc>Es (time tt), the output state of the comparator 32 is reversed and the switching circuit 31 is turned off. Therefore, evening.

Iode D is on, 9, cano (sitance element CI)
The output voltage V. becomes the collector voltage of the transistor Q1, and charging of the element C1 also ends. At this time, if the idle current of transistor Q is ignored, the voltage of element C1 becomes ■. is maintained approximately constant for transistor Q.

On the other hand, the electromagnetic energy stored in the inductance element L1 during the charging period of the capacitance element CI becomes an electromotive force in the polar direction shown in Fig. 1, so the switching circuit 31
is off and charging is stopped, this electromotive force causes a current to flow in the direction of the arrow in the figure through the on-state diode D1, charging the second capacitance element C2, and converting the electromagnetic energy into electrostatic energy. will be converted. This situation is shown in FIG. 2 (waveform Bl), where vb is the voltage across the second capacitance element C2.

At time t2, human input signal ■2 arrives and the output is V. When swings to the positive side as shown in Figure 2 (2), the capacitance element C
The charge on diode D1. The voltage V discharges through the transistor Q and the load. begins to fall. ■ At time t. When +E5≧vc, the comparator 32 is inverted and turns on the switching circuit 31. Therefore, the collector voltage of the transistor Q1 becomes a superimposed voltage of the charging voltage vh of the second capacitance element C2 and the circuit power source. At this time, since the diode D2 is off, the circuit power supply 1B is not directly applied to the collector of the transistor Q. Therefore, at this time, a voltage higher than the circuit power source by V6 is applied to the collector of the transistor Q1, and the output level can be increased accordingly. However, this voltage Vb is due to the electric charge of the capacitance element C2, and is discharged by the transistor Q and the load and gradually drops. During this time, the first capacitance element CI has an inductance element.

Charging is carried out via the terminal voltage V. increases along the charging curve, during which electromagnetic energy is stored again in the inductance element L1.

As the output signal level decreases, ■O+E at time t4,
<V. Then, the switching circuit 31 is turned off,
The collector voltage of the transistor Q1 is supplied from the first capacitance element CI. At this time too, due to the electromotive force of the inductance element L1,! the second via the iode D,
It is clear that exactly the same operation is performed for the zero negative side circuit in which the capacitance element C2 is charged and replenishes the energy lost due to the previous discharge.

FIG. 3 is a partial circuit diagram of another embodiment of the present invention;
Parts equivalent to those in the figures are designated by the same reference numerals. Although only the positive side circuit is shown in this example, the negative side circuit also has a complementary circuit configuration. As the switching circuit 31, a transistor Q! + is provided, and this transistor Q4 is driven by the transistor Q2, and the second
When the capacitance element C2 has no charge, the collector voltage of the transistor Q is directly supplied from the circuit power supply 1B via the transistor Q4 and the diode D2. As the level comparator 32, transistors Q, , Q are used.

and current source I. The control signal for the switching circuit 31 is derived from the collector load resistance R of the transistor Q. The circuit operation in this example is also performed with the same waveform as shown in FIG.

As shown above, when the output signal level is low, power is supplied from the capacitance element that has been charged in advance, so power consumption is reduced and efficiency is increased. Furthermore, since a peak output higher than the maximum output determined by the circuit power supply ±8 is instantaneously extracted, it is possible to output a higher level of output.

Although the circuit output is used as the single input of the comparator 32, any signal may be used as long as it has a level corresponding to this.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram of the operation of each part of the circuit of FIG. 1, and FIG. 3 is a partial circuit diagram of another embodiment of the present invention. Explanation of symbols of main parts 31.31'...Switching circuit 32, 32'...Level comparison circuit QI I Q'l...Amplification transistor C,, C-
...First capacitance element C2, C'2...Second capacitance element...Inductance element Figure 1I

Claims (1)

[Claims] A first capacitance element and an inductance element forming a charging path for the first capacitance element are electrically connected by a predetermined control signal to supply a circuit power supply as a voltage for charging the first capacitance element through the charging path. a second capacitance element that converts and stores electromagnetic energy stored in the inductance element into electrostatic energy during a non-conducting period of the switching element; generating the predetermined control signal when the absolute value of the difference between the output voltage of the first capacitance element and the voltage corresponding to the amplifier output voltage is less than or equal to a predetermined value; Voltage and storage of the second capacitance element 1! A power supply circuit configured to supply a voltage superimposed on the voltage and a voltage stored in the first capacitance element when non-conducting to a power supply terminal of an amplifier, respectively.