JPH0531322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amplifier circuit that amplifies an AC voltage that is in phase with an AC power supply voltage.

[Prior art]

In a semiconductor characteristic measuring device (curve tracer) that measures the characteristics of a transistor or the like, an AC power supply voltage is used with appropriate amplitude control as the voltage supplied to the collector of the transistor to be measured. Also,
In waveform measurement devices such as oscilloscopes, line
In trigger mode, the AC power supply voltage is used as the trigger signal. In these measuring devices, it is necessary to amplify the amplitude-adjusted AC voltage, that is, the AC voltage that is in phase with the AC power supply voltage.

By the way, in order for the output voltage of the amplifier to follow the input voltage, the drive voltage of the amplifier must be higher than the maximum values of the input and output voltages. In a semiconductor characteristic measuring device, the amplitude of the AC voltage supplied to the collector is variable from several volts to several tens of volts or more, so the driving voltage of the amplifier that amplifies this AC voltage must also be several tens of volts or more. Therefore, when amplifying an alternating current voltage of several volts, the power consumption of the amplifier becomes extremely large.

As one of the prior art, Japanese Unexamined Patent Publication No. 129411/1989 discloses an amplifier circuit that causes the drive voltage of an amplifier to follow the input voltage. In this amplifier circuit, a drive voltage that changes in accordance with the input voltage is generated by a drive voltage supply circuit and is supplied to the amplifier. Furthermore, Japanese Patent Application Laid-Open No. 50-45552 discloses an amplifier circuit in which a plurality of amplifiers with different drive voltages are provided and these amplifiers are selectively used depending on the input voltage.

[Problem that the invention seeks to solve]

In the amplifier circuit disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 56-129411, the driving voltage of the amplifier changes depending on the input voltage, so that the power loss of the amplifier itself is reduced. However, the drive voltage supply circuit must be supplied with a voltage that is higher than the maximum value of the input/output voltage of the amplifier, and the power loss of this drive voltage supply circuit becomes large. Therefore, this conventional amplifier circuit cannot reduce power loss as a whole. Rather, this conventional amplifier circuit is intended to extend the dynamic range of the amplifier.

On the other hand, JP-A-50-45552 can reduce power loss, but it requires multiple amplifiers with different drive voltages, and these amplifiers must be switched for use, resulting in a complicated configuration. It becomes expensive.

[Means for solving problems]

In the amplifier circuit of the present invention, the push-pull amplifier 24 amplifies the AC input voltage that is in phase with the AC power supply voltage.
, a transformer 12 whose primary winding receives an AC power supply voltage, floating first rectifying and smoothing means 60 and 62 connected to both ends of the first secondary winding 58 of the transformer, and Floating second rectifying and smoothing means 66 and 68 connected to both ends of the second secondary winding 64, a third secondary winding 70 of the transformer receiving a reference voltage at one end, and a first rectifying and smoothing means a first diode 72 whose cathode and anode are respectively connected between the low voltage side output terminal of the second rectifying and smoothing means and the intermediate tap of the third secondary winding; A second diode 74 whose anode and cathode are respectively connected between the intermediate taps of the secondary winding, a switch element 78 whose one end is connected to the other end of the third secondary winding, and a low voltage diode of the first rectifying and smoothing means. A third diode 82 having a cathode and an anode connected between the voltage side output terminal and the other end of the switch element, respectively, and a third diode 82 having an anode and a cathode connected between the high voltage side output terminal of the second rectifying and smoothing means and the other end of the switch element, respectively. A connected fourth diode 84, detection means 100 to 104 for detecting a voltage corresponding to the maximum value of the output voltage of the push-pull amplifier, and an output voltage of the detection means are compared with a reference voltage V _REF to determine the output of the detection means. a comparator 106 for controlling the switch element to turn on when the voltage exceeds the reference voltage;
The voltage from the high voltage side output terminal of the rectifying and smoothing means is supplied as a positive driving voltage to the push-pull amplifier, and the voltage from the low voltage side output terminal of the second rectifying and smoothing means is supplied as a negative driving voltage to the push-pull amplifier. There is.

Note that in this specification, positive and negative refer to the reference voltage of the amplifier circuit, and generally refer to the ground voltage, but in a floating amplifier circuit, It is.

[Effect]

In the present invention, the AC input voltage is in phase with the AC power supply voltage. When the AC input voltage is in a positive half cycle, a positive half cycle portion of the AC power supply voltage or a voltage proportional thereto is supplied as a positive drive voltage to a push-pull amplifier (hereinafter sometimes simply referred to as an amplifier). During this time, no negative drive voltage is supplied to the amplifier. Therefore, only the positive signal amplifying half of this amplifier is active. Further, when the AC input voltage is in a negative half cycle, the negative half cycle portion of the AC power supply voltage or a voltage proportional thereto is supplied to the amplifier as a negative drive voltage. During this time, no positive drive voltage is supplied to the amplifier.
Therefore, only the negative signal amplifying half of this amplifier is active. Furthermore, the drive voltage of the amplifier varies depending on the AC input voltage. Therefore, the power loss of the amplifier can be significantly reduced.

Further, since the drive voltage for the amplifier can be generated by a transformer and a rectifier, power loss in these means is very small. Therefore, the power loss of the amplifier circuit as a whole can be significantly reduced.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In FIG. 1, an external commercial AC power supply voltage is supplied to a primary winding 14 of a transformer 12 via a switch 10. In FIG. Timing circuit 16 generates various timing pulses synchronized to the AC power supply voltage through a phase lock loop. A sine wave generator 20 generates a sine wave voltage A of variable amplitude using these timing pulses. Note that the reason why the AC voltage from the secondary winding of the transformer 12 is not directly utilized is because the distortion of the AC power supply voltage waveform is large and an ideal sine wave cannot be obtained. A sinusoidal voltage (alternating current input voltage) A is supplied via an input resistor 22 to an input end 26 of a push-pull amplifier 24 . Between the input end 26 and the output end 28 of this amplifier 24,
Connect the feedback resistor 30. This amplifier 24 is
A common base type NPN transistor 32 and a PNP transistor 34 each having an emitter connected to the input terminal 26, and a common emitter type PNP transistor 3 having a base connected to the collector of the transistor 32.
6, and a common emitter type NPN transistor 38 whose base is connected to the collector of the transistor 34. A predetermined bias voltage divided by resistors 40 and 42 is supplied to the base of the transistor 32, and a predetermined bias voltage divided by resistors 44 and 46 is supplied to the base of the transistor 34. The collector of transistor 32 is connected to a positive drive voltage supply 50 through a resistor 48, and the collector of transistor 34 is connected to a negative drive voltage supply 54 through a resistor 52. Further, the emitters of transistors 36 and 38 are connected to driving voltage supply terminals 50 and 54, respectively, and the collectors of these transistors are connected to output terminal 28.
The signal from the output 28 of the amplifier 24 is transferred to the transformer 5
It is used in the next stage circuit etc. via 6. This push-pull amplifier 24 includes transistors 32 and 36.
The portion of transistors 34 and 38 amplifies the negative portion of the input voltage, and the gain is determined by input resistor 22 and feedback resistor 3.
It is determined by the ratio of 0.

The small amplitude AC voltage from the secondary winding 58 of the transformer 12 is rectified by a full wave rectifier 60 and smoothed by a capacitor 62 to provide a low voltage, for example 20 volts, DC voltage at both outputs. Similarly, the small amplitude AC voltage from the secondary winding 64 of the transformer 12 is rectified by a full wave rectifier 66 and smoothed by a capacitor 68 to provide a 20 volt DC voltage at both outputs. Therefore, the full-wave rectifier 60 and the capacitor 62 constitute the first rectifying and smoothing means, and the full-wave rectifier 6
6 and a capacitor 68 constitute a second rectifying and smoothing means. Note that the full-wave rectifiers 60 and 66 are floating, and the voltage at the upper output end of each rectifier is higher than the lower output end. The upper end of the secondary winding 70 of the transformer 12 is grounded,
The intermediate tap is connected to the anode of a semiconductor diode (hereinafter simply referred to as a diode) 72 and the cathode of a diode 74, which are rectifiers. Also 2
The lower end of the next winding 70 is connected to the anode of a diode 82 and the cathode of a diode 84 via a light receiving switch element 78 of an optical relay 76. AC voltages of, for example, 30 volts and 60 volts are generated at the middle tap and lower end of the secondary winding 70, respectively. Note that in the optical relay 76, the light receiving switch element 78 is turned on only when the generating element 80 emits light. The anodes of diode 74 and diode 84 are connected to the upper output end of full-wave rectifier 66 , and the cathodes of diodes 72 and 82 are connected to the lower output end of full-wave rectifier 60 . A series circuit of protection diodes 86 and 88 is connected between the upper output terminal of full-wave rectifier 66 and the lower output terminal of full-wave rectifier 60, and the common connection point of these diodes is grounded. Full wave rectifier 6
The upper output terminal of 0 is connected to the noise removal capacitor 9.
0 to ground, and also connected to the positive drive voltage supply end 50 of the amplifier 24. Similarly, the lower output end of the full-wave rectifier 66 is grounded via a noise removal capacitor 92 and connected to the negative drive voltage supply end 54 of the amplifier 24 .

The output terminal 28 of the amplifier 24 is connected to a capacitor 94,
Ground through resistors 96 and 98. Further, the common connection point of these resistors 96 and 98 is a diode 100, a capacitor 102, and a resistor 10.
Grounded through 4 parallel circuits. Resistors 96 and 98 divide the AC voltage at output 28 of amplifier 24, and elements 100-104 detect the maximum value of this divided AC voltage. Note that these elements 100
to 104 constitute a detection means. Comparator 106
compares this maximum value with the reference voltage V _REF , and when the maximum value exceeds the reference voltage V _REF , causes the light emitting element 80 of the optical relay 76 to emit light. Note that the base bias voltage of the transistors 32 and 34 of the amplifier 24 is supplied from a DC stabilizing circuit (not shown).

Next, the operation shown in FIG. 1 will be further explained with reference to FIG. Note that the AC output voltage A of the sine wave generator 20
is a sine wave that is in phase with the AC power supply voltage. When this AC voltage has a small amplitude, the light emitting element 8 of the optical relay 76
0 does not emit light, and the light receiving switch element 78 is off. Therefore, of the AC voltage from the intermediate tap of the secondary winding 70 of the transformer 12, the positive half cycle is supplied to the lower end of the capacitor 62 via the diode 72, and the negative half cycle is supplied via the diode 74 to the lower end of the capacitor 62. Supplied to the top of capacitor 68. Diode 88 controls the voltage at the lower end of capacitor 62 so that it does not become negative, and diode 86 controls capacitor 6
The voltage at the upper end of 8 is controlled so that it does not become positive.
Further, no voltage is applied to the optical relay 76 side of the diodes 82 and 84. Therefore, as shown by the solid line in FIG. The result is a superposition of half cycles. Also,
The voltage C at the lower end of the capacitor 68 is connected to the full-wave rectifier 66 and the capacitor 6
The negative half cycle of the alternating current voltage from the middle tap of the secondary winding 70 is superimposed on the negative direct current component caused by 8. These voltages B and C are applied to drive voltage supplies 50 and 54 of amplifier 24.

During the half-cycle period when the AC voltage A is positive, the amplifier 24
The voltage B at the drive voltage supply terminal 50 is an AC voltage that is higher than the AC voltage A and changes in the same way as the AC voltage A. During this period, the voltage C at the drive voltage supply end 54 of the amplifier 24 is a constant low negative DC voltage. Therefore, transistor 32 of amplifier 24
The upper portions such as and 36 amplify the input signal A, while the lower portions such as transistors 34 and 38 do not. Since voltage B changes in the same way as AC voltage A, transistors 32 and 36
There is also little power loss in the upper part of the device. Furthermore, since the lower portions of transistors 34, 36, etc. do not perform amplification, no power is lost.

During the negative half-cycle period of AC voltage A, voltage C is lower than AC voltage A and is an AC voltage that changes in the same way as AC voltage A. Further, voltage B is a constant low positive DC voltage. Therefore, the lower portions such as transistors 34 and 38 amplify the input signal A, but the power loss is small. Further, since the upper portions of transistors 32, 36, etc. do not perform amplification, no power is lost. The above relationship is as shown in FIG. 2D, where the shaded area represents power loss. The reason why the DC component is superimposed on voltages B and C is to reliably amplify the part where AC voltage A changes from a positive half cycle to a negative half cycle and from a negative half cycle to a positive half cycle. This is to do so. Furthermore, the circuit that supplies the drive voltage is a passive element such as a diode, and power loss is extremely small.

As the amplitude of AC voltage A increases and approaches voltages B and C, the voltage across capacitor 102 reaches reference voltage V _REF
(as the circuit is set up), the comparator 106 causes the light emitting element 80 of the optical relay 76 to emit light. Then, the light receiving switch 78 is turned on, and an AC voltage higher than the AC voltage from the intermediate tap of the secondary winding 70 of the transformer 12 is applied from the lower end of the secondary winding 70 to the diodes 82 and 84 via the light receiving switch 78. join. Thus, a positive half cycle of AC voltage greater than the voltage from diode 72 is applied to the bottom of capacitor 62 through diode 82, turning diode 72 off. Meanwhile, a negative half cycle of AC voltage greater than the voltage from diode 74 is applied to the top of capacitor 68 through diode 84, turning diode 74 off. Therefore, voltages B and C are as shown in FIG.
As shown in FIG.
can be definitely amplified. Note that the secondary winding 70 and the diodes 72 and 82 are the first means for extracting a voltage proportional to the positive half cycle of the AC power supply voltage,
Secondary winding 70, diodes 74 and 84 are a second means for extracting a voltage proportional to the negative half cycle of the AC supply voltage.

Although the above is a description of preferred embodiments of the present invention, various changes and modifications can be made without departing from the gist of the present invention. For example, the positive and negative half cycles may be taken directly from the AC power supply voltage. Further, the number of intermediate taps of the secondary winding 70 may be increased, and the number of comparators may also be increased. In this case, each of these comparators compares the voltage at the output of the amplifier with a different reference voltage and selects the intermediate tap of the secondary winding 70 depending on the amplitude of its output voltage. The positive and negative half cycles of the AC voltage from the selected intermediate tap may then be used as the drive voltage for the amplifier. Additionally, the comparator may compare the AC input voltage to a reference voltage. Also, each ground in the circuit of FIG. 1 may be floated. Furthermore, as the amplifier, push-pull amplifiers with various configurations can be used. Alternatively, the AC input voltage may be obtained directly from the AC power supply voltage.

〔Effect of the invention〕

As described above, according to the present invention, power loss can be significantly reduced when the push-pull amplifier amplifies an AC input voltage that is in phase with the AC power supply voltage. Furthermore, the means for generating positive and negative drive voltages for the push-pull amplifier can be constructed of a transformer, rectifying means, diodes, etc., so the construction is simple and the power loss therein is very small. Furthermore, the third 2
Since the AC voltage obtained from the next winding is selected depending on whether the maximum value of the output voltage of the push-pull amplifier is lower or higher than the reference voltage, the amplifier can reliably amplify the AC voltage with increased amplitude.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a preferred embodiment of the present invention, and FIG. 2 is a waveform diagram illustrating the operation of the circuit shown in FIG. In the figure, 24 is a push-pull amplifier, 12
is a transformer, 14 is a primary winding, 58 is a first secondary winding, 64 is a second secondary winding, 70 is a third secondary winding, 60 and 62 are first rectifying and smoothing means. , 66 and 68 are second rectifying and smoothing means, 72 is a first diode, 74 is a second diode, 78 is a switch element, 82 is a third diode, 84 is a fourth diode, 100 to 104 are detection means, and 106 is a comparison It is a vessel.

Claims (1)

[Scope of Claims] 1. A push-pull amplifier that amplifies an AC input voltage that is in phase with an AC power supply voltage, comprising: a transformer whose primary winding receives the AC power supply voltage; and a first secondary winding of the transformer. a first rectifying and smoothing means connected to both ends and floating; a second rectifying and smoothing means connected to both ends of the second secondary winding of the transformer and floating; 3rd 2
a first diode having a cathode and an anode connected between the low voltage side output terminal of the first rectifying and smoothing means and the intermediate tap of the third secondary winding; and the second rectifying and smoothing means. a second diode having an anode and a cathode respectively connected between the high voltage side output terminal of the output terminal and an intermediate tap of the third secondary winding; and one end connected to the other end of the third secondary winding. a switch element; a third diode having a cathode and an anode connected between the low-voltage output terminal of the first rectifying and smoothing means and the other end of the switching element; and a high-voltage output terminal of the second rectifying and smoothing means. and a fourth diode having an anode and a cathode respectively connected between the other ends of the switch element, a detection means for detecting a voltage corresponding to the maximum value of the output voltage of the push-pull amplifier, and a reference to the output voltage of the detection means. a comparator that compares the output voltage of the detection means with the voltage and turns on the switch element when the output voltage of the detection means exceeds the reference voltage, and the voltage from the high voltage side output terminal of the first rectification and smoothing means is adjusted to be An amplifier circuit characterized in that: a voltage from the low voltage side output terminal of the second rectifying and smoothing means is supplied to the push-pull amplifier as a negative drive voltage;