JPS5832415B2 - power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device for a complementary amplifier with two positive and negative power supply systems, which is optimal for low frequencies, particularly audio frequencies of about several tens of Hz to 20 Hz.

Generally, the unstable power supply output is switched at high frequency by a power switch element, and the on-off ratio is controlled.
The so-called switching regulator, which stabilizes the output by doing so, is known as a low-loss power supply system.

For example, FIG. 1 shows an example of a power supply device configured to control power on the primary side of an isolation transformer using the switching regulator as a power supply for a power amplifier or the like.

That is, in the figure, AC is an alternating current power supply, and R8 is an alternating current power supply AC.
A rectifying and smoothing circuit that rectifies and smoothes the AC input from the rectifying and smoothing circuit R8, SC is a switching circuit that switches according to the large input, and T1 is an output isolation transformer provided on the output side of the switching circuit SC. RF is a rectifier circuit that rectifies the output of the output isolation transformer T1, L
F is a low-pass filter that averages the output of the rectifier circuit RF to obtain a DC output, OD is an output error detection circuit that detects the output voltage of the low-pass filter LF and obtains a detection signal according to the error voltage with respect to the set voltage, and PM is the output Error detection circuit O
D is a pulse width modulator whose output pulse width increases or decreases according to the detection signal; T2 is an insulated transformer for transmitting the output of the pulse width modulator PM to the switching circuit SC as a switching control signal; and OT is the low-pass Filter L
This is an output terminal that outputs a DC stabilized output E obtained through F.

In this case, the output voltage of the low-pass filter LF is detected by the output error detection circuit OD, this is given to the pulse width modulator PM as a signal corresponding to the error with respect to the set voltage, and the output is sent to the switching circuit SC via the transformer T2. By inputting it as a switching system signal, a feedback control □□ loop is formed, and the output voltage E.

The structure is designed to stabilize the

By the way, for example, in low-frequency power amplifiers for audio, etc., complementary output amplifiers are widely used, which operate independent amplification sections on the positive and negative sides using a positive and negative dual power supply system using a positive power supply and a negative power supply. When attempting to construct a power supply device for such an amplifier with two positive and negative power supplies, if the above configuration is used as is, the configuration shown in Figure 1 will be required for each of the positive and negative pots, making the configuration complex and expensive. Become.

In addition, in this case, especially when an extremely low frequency, large amplitude signal such as a loud extremely low frequency signal is input, only the positive side amplifier operates during the positive half wave period, so only the positive side power supply receives the load current. is supplied, and the negative side power supply is almost in a no-load state.

Furthermore, since only the negative side amplifier section operates during the negative half wave period, only the negative side power supply supplies the load current.

Therefore, two positive and negative power supply units are required, each having an instantaneous current capacity corresponding to the maximum output dark current required by the amplifier (twice the instantaneous current capacity corresponding to the average current).
It is uneconomical.

In contrast, as shown in Figure 2, a square wave inverter using self-oscillation is used on the primary side of the isolation transformer, and after rectification is performed on the secondary side, stabilization is achieved using chopper circuits for each positive and negative side. I can think of things.

That is, in the figure, the same parts as in Figure 1 are indicated with the same symbols, SI is a self-excited square wave inverter, T is an isolation transformer, and DFLS is a rectifier for the secondary output of the isolation transformer T. CHl is a rectifying and smoothing circuit with two positive and negative outputs using a center tap bridge circuit etc. to smooth and obtain positive and negative DC voltages.
and CH2 respectively switch the positive and negative side outputs of the positive and negative two-output rectifier and smoothing circuit DR8 at timings according to the control signal.The positive and negative side choppers, LP, and LP2 remove ripples from the outputs of the choppers CH1 and CH2, respectively. The low-pass filters OD1 and OD2 detect the output voltages of the low-pass filters LF1 and LP2, respectively, and obtain a control signal according to the error with respect to the set value for each positive and negative voltage, and feed it back to the choppers CH1 and CH2. output error detection circuit, OTl and OT
2 are positive and negative side output terminals that output positive and negative output voltages +Eo and -Eo obtained from the low-pass filters LP and LP2, respectively, and ET is a ground terminal.

In this case, the DC unstable input from the rectifier and smoothing circuits R and S is switched by the self-excited square wave inverter SI,
On the secondary side of the isolation transformer T, the positive and negative 2-output rectifying and smoothing circuit DR8 rectifies and smooths the positive and negative output voltages +Eo and -E.
A voltage close to o is obtained, and choppers CH1 and CH2 are used to stabilize each positive and negative output.

In this way, a self-excited square wave inverter SI is provided on the primary side of the isolation transformer T, and is used commonly on both the positive and negative sides, so that the output voltage ±
Obtaining a voltage close to Eo can be said to be an economical method with a simple circuit configuration for this part only, but the output capacitance of choppers CH1 and CH2 has exactly the same drawbacks as mentioned above. Furthermore, since there are three power switching sections including the square wave inverter SI and the choppers CH1 and CH2, switching loss becomes large and conversion efficiency becomes low.

Therefore, if one control section on the primary side of the isolation transformer is used in common to control the positive and negative side outputs, the configuration can be simplified.

In this case, since there is only one control section, it may be possible to stabilize the system by feeding back either the positive or negative output, for example, the positive output, to the control section as shown in FIG.

That is, in FIG. 3, the same parts as in FIGS. 1 and 2 are shown with the same reference numerals, and CB rectifies the output of the switching circuit SC obtained through the isolation transformer T1 to convert the positive and negative With a center tap bridge rectifier circuit that obtains side output,
The positive and negative rectified outputs of this center tap bridge rectifier circuit CB are output from positive and negative side output terminals OT1 and OT2 via low pass filters LF1 and LP2, respectively.

Further, the output error detection circuit OD detects the output voltage +Eo of the positive side low-pass filter LP, and feeds it back to the switching circuit SC via the pulse width modulator PM1 and transformer T2 as a signal corresponding to the error with respect to the set voltage. There is.

On the other hand, the positive and negative side output terminals OT and OT2 and the ground terminal ET are connected to the positive and negative power input terminals T1, ■ of the audio amplifier AA as the load of this power supply device, for example.
It is connected to T2 as well as the power input ground terminal IE.

In this case, the audio amplifier AA is a complementary amplifier composed of a preamplifier PA and a complementary output circuit CO consisting of, for example, transistors Q, 1, Q2, and transistors Q1. Signal output terminal L derived from the connection point of both emitters of Q2 and the ground point.
A signal load LD such as a speaker is connected between O□ and LO2, and an audio signal is input between signal input terminals A11 and Al1 derived from the input terminal of the preamplifier section and the ground point.

The voltages +Eo and -Eo applied to the negative power supply input terminals T1 and T2 are respectively supplied to the positive and negative amplifier sections of the complementary output circuit CO.

Similarly, positive and negative voltages are supplied to the preamplifier PA.

The waveforms of various parts in this case are shown in FIG.

That is, ■□ shown in Fig. 4a is the signal output terminal L of the audio amplifier AA which receives this power supply and performs power amplification.
Dt, the output current from L D2, this amplifier output current ■□ at an extremely low frequency and +■Lm as shown.

■Assuming a sine wave with a maximum amplitude of Lm, in the illustrated period a = b, the power supply regulation (voltage drop of the smoothing part of the rectifier and smoothing circuit R8, transformer, filter, etc.) is corrected according to the load current of the positive side output. Therefore, as shown in the figure, the pulse width of the output PWM wave Pw of the pulse width modulator PM widens (the on-duty increases), and the detection side, that is, the positive side output voltage +E.

is stabilized as shown in Figure C.

On the other hand, the non-detection side, that is, the negative side output -Eo shown in Figure d is not loaded, and in common with the positive side, the pulse width of the PWM wave Pw is widened, so that It increases and decreases.

However, in this section, the negative side width section of the audio amplifier AA is not operating and almost no load current flows through the negative side amplifier section, so there is no loss in the corresponding amplification element of the amplifier AA, for example, the transistor Q2.

By the way, IL shown in figure a is an output low-pass filter L.
F1.

This is the amplifier output current waveform when the charging/discharging time constant of L12 is relatively small with respect to the signal frequency, and approximately corresponds to the non-detection side output voltage -Eo slope (rough) shown in d of the same figure.

However, the low pass filter LF1. If the time constant of L12 is designed to be large (due to the relationship with output ripple, etc.), the amplifier output current ■L will look like the broken line shown in figure a, and the amplifier output current ■L and negative side output -EOC will become as shown in figure d. ] A phase difference of θ1 is generated between the ripple of the output voltage, but if this is not too large, the effect on the output voltage will not be large.

In addition, during the period b - c, the positive side output terminal E Pw has a very narrow pulse width and the negative side output voltage -E.

is about to decline.

In addition, since the load current of the negative side amplifier increases, the non-detection side output voltage -E.

causes a significant voltage drop.

The magnitude of this voltage drop becomes larger as the value of the filter capacitor for the positive and negative side outputs becomes smaller.

This is because, under the output current ■L with a constant repetition frequency, the time constant of the positive output low-pass filter LF1 is small during the illustrated period b - c, so the rising speed of the capacitor voltage in the filter becomes faster, and the PWM This is because the pulse width of the wave Pw suddenly becomes narrower, and when the negative side load current increases, the output voltage decreases in a short time if the discharge time constant of the filter is small.

If the time constant is large, the slope of the voltage drop will be gradual, and once the peak of current -IL passes, recovery will begin immediately, so the dip will not be too large. However, if the absolute value of the load current is still large, then This results in a significant voltage drop, resulting in a drop in the output level of the amplifier and generation of large distortion.

If you try to obtain two positive and negative outputs from a power supply with only one control unit as shown in Figure 3 and supply them to a complementary amplifier, the output voltage on the feedback side, that is, on the detection side, will be stabilized and can always be constant. On the other side, where feedback is not performed, that is, on the non-detection side, a large ripple is generated, resulting in an output range and distortion when an audio amplifier serving as a power supply load has a large input.

The present invention has been made based on the above considerations, and provides a power supply device in which multiple power outputs, which are selectively consumed, are controlled by a single electricity rate unit. By automatically detecting the output voltage on the side where load current is being consumed and feeding it back to the power control unit, the output voltage of the output under load can be stabilized with a simple configuration, making it inexpensive and highly efficient. The purpose is to provide power supplies for

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 5, the same parts as in FIGS. 1 to 3 are given the same reference numerals, and detailed explanation thereof will be omitted.

In the figure, A variable resistor that divides the voltage into rl and r2,
■R2 is the negative side output voltage -E.

+Es and Es are positive and negative reference voltage power supplies, respectively, A1 and A2 are positive and negative comparison amplifiers, respectively, Si1 and Si2 are diodes, and R is a resistor.

Moreover, AMP has positive and negative side outputs +EO and -E.

a power amplifier that amplifies the signal power S to which each is supplied;
RL is the load of the power amplifier AMP.

In the above configuration, first, the reference voltage +Es is input to the 1 inverting input of the positive comparison amplifier A1, and the positive output voltage +Eo divided by the variable resistor VRi is input to the non-inverting input.
Part of the information has been entered.

On the other hand, in the negative side comparison amplifier A2, the reference voltage Es is input to the non-inverting input, and a part of the negative side output voltage -Eo divided by the variable resistor R2 is input to the inverting input.

Now, let us set the amplification degrees of comparison amplifiers A1 and A2 to Aυ1, respectively.
, Aυ2, the output voltage of the comparison amplifier A1 is 1 ((+Eo)X()-(+Es))xAυ1-,-(1
)1+r2 Similarly, the output voltage of comparison amplifier A2 is 3 ((Eo)X()(-ES))XAυ2...(2)1
+r4, l +E01=l-Eol, l+Es
1=-Esl, the comparison amplifier A1. The output of A2 becomes a positive voltage at the same level.

Furthermore, if the voltage drop across the diode Si1°S+2 is made zero, the output voltages of the comparator amplifiers A f and A2 appear simultaneously at the common connection point of these diodes Si1 and S+2.

By the way, in period a=b in FIG. 6 a to d shown corresponding to a=d in FIG. 4, the positive output side causes current to flow through the load amplifier AMP, and the low-pass filter LF or the center tap bridge rectifier circuit CB. The output type E+Eo drops by one moment corresponding to the voltage drop across the diode, etc.

Then, the output voltage of the comparison amplifier A0 becomes the output voltage of the comparison amplifier A2.
Therefore, the positive output terminal 0
From T1 (voltage +Eo) to resistor R and diode Si.

The current 11 flowing through the diode Sil,
The output of the comparator amplifier A1 is connected to the common connection point of Si2.

This voltage signal is fed back via the pulse width modulator PM to lengthen the on-period of the switch due to the PWM wave Pw shown in FIG. The preset reference voltage +Es throughout the period a = b when the AMP output current ■L is positive
It will be a constant value depending on.

Also, the period b during which the output current ■L of the amplifier AMP is negative
= c, the output voltage of the comparator amplifier A2 is lower than the output voltage of the comparator/spanner A1, so the output voltage of the comparator amplifier A
The output voltage of 2 is fed back, and the negative output voltage -Eo is stabilized through the period b=c as shown in FIG. 6d.

In addition, as shown in Fig. 6 cyd, the positive and negative side outputs +Eo, -
E.

In both cases, there is a slight voltage rise when there is no power supply load, but this is a period in which almost no load current flows through the positive and negative amplification sections of the amplifier AMP, and there is no effect on the operation of the amplifier AMP.

The above explanation is for the case where the frequency of the amplifier output current ■L is low, but on the contrary, when the frequency of ■L is high, the phase difference θ2 shown in FIG. 6a [FIG. The phase difference generated in the same way as θ1 shown in a) becomes large.

However, in this case, the positive and negative side outputs +Eo t Eo
The voltage amplitude that increases during the period in which the amplifier output current IL is not flowing is determined by the low-pass filters LF1 and L, respectively.
From the relationship between the charging time constant of F2 and the period of the amplifier output current z0, it decreases as the frequency increases. Therefore, this voltage amplitude becomes a negligible value at very high frequencies, and the output voltage is close to the stabilizing voltage. Therefore, the phase difference θ
The influence of 2 is not very large.

As mentioned above, by obtaining the error voltage on the side where the power supply voltage has decreased according to the consumption of the load current corresponding to the output current IL of the amplifier AMP as a load of the power supply, and feeding it back to the electric power rate section, The power supply output voltage is controlled to be stabilized according to the load consumption, and the output of the amplifier AMP is compensated for fluctuations in the AC power supply AC and load fluctuations of the amplifier AMP, thereby preventing deterioration of sound quality, etc. can.

Further, since positive and negative output voltages can be stabilized with a simple configuration having only one power switching section, the power supply device can be made smaller and lighter, and moreover, economical efficiency can be improved.

As described above, according to the present invention, multiple power supply outputs that are selectively consumed are controlled by one power control section.
In a power supply device, the output voltage of each power supply output on the side where the load current is consumed is automatically detected and fed back to the power control unit, thereby stabilizing the output voltage of the output under load with a simple configuration. It is possible to provide an inexpensive and highly efficient power supply device.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without changing the gist thereof.

For example, a circuit as shown in FIG. 7 may be inserted between the variable resistor VR1 and the non-inverting input of the comparator amplifier A1 and between the variable resistor R2 and the inverting input of the comparator amplifier A2.

That is, in the figure, CP is a voltage comparator as a polarity discriminator, R1 to R6 are resistors, and DI and D2 are diodes, which are assumed to be R1-R2.

In this case, as described above, when the non-inverting input voltage of comparison amplifier A1 decreases, the feedback system acts to increase the positive output voltage +Eo, and when the inverting input voltage of comparison amplifier A-2 decreases, the feedback system acts to increase the positive output voltage +Eo. acts to increase the negative side output voltage -Eo.

Therefore, if the positive side output +Eo is consumed,
If the potentials of the points are respectively Ed and Ee, then E d >
E becomes e.

Then, the output of the voltage comparator CP becomes a sufficiently higher positive voltage than the divided voltage output of the variable resistor VR1, and the diode D1 is reverse biased and turned off, and the divided voltage output is used as the detection voltage to the non-inverting input of the comparator amplifier A1. The diode D2 becomes forward biased and becomes conductive, and the positive output voltage of the voltage comparator CP is applied to the comparison amplifier A as the detection voltage.
applied to the inverting input of 2.

As a result, an output voltage with a smaller absolute value is detected, feedback is performed accordingly, and the output voltage is stabilized.

In addition, in the above actual case, we have explained the case where a comparator amplifier and a diode are used as a means to detect two positive and negative power supply output voltages, and as a means to select the voltage with the lower absolute value among them. There are many known means for realizing this function, and any of these well-known means may be used.

Further, as the electric power braking section, a device using a thyristor, a mag-amp, or the like may be used.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing the configuration of an example of a conventional power supply device, and FIG. Figure 3 is another possible example of an output stabilization method when there are two positive and negative power outputs. ) A waveform diagram of each part showing the amplifier output current, b pulse width modulator output PWM wave, C positive side output voltage, and d negative side output voltage, respectively, Fig. 5 is a block circuit diagram showing the configuration of an embodiment of the present invention, Figures 6a to 6d are waveform diagrams of each part showing a amplifier output current, b pulse width modulator output PWM wave, C positive side output voltage, and d negative side output voltage in the same embodiment, and Figure 7 shows the present invention. FIG. 3 is a circuit diagram showing the main parts of another actual case used. AC: AC power supply, R8: Rectifier and smoothing circuit, T1. T2...Isolation transformer, SC...
...Switching circuit, CB... Center tap bridge rectifier circuit, LF, , LF2...
Low-pass filter, PM...Pulse width modulator,
■R1, ■R2...Variable resistor, +Es, -E
s...Reference power supply, A1. A2... Comparison amplifier, S 11 j S 12 HDl 2
D2...Diode, OTl, OT2...
...Positive and negative power output terminals, ET...Ground terminal, AMP...Amplifier, RL...Amplifier load, S...Amplifier signal input, R1-R6・
...Resistance, CP...Voltage comparator.

Claims (1)

[Claims] 1 In a switching regulator type power supply device in which one power control section controls a pair of positive and negative power supply outputs that are supplied to a complementary power amplifier in a two-power supply system, each output voltage of the pair of positive and negative power supply outputs is detected. means for selecting the lower absolute value of each output voltage (7'+) detected by this means, and feeding back the output voltage selected by this means to the power control section in order to stabilize the output. A power supply device characterized by comprising means for.