JPH067747B2 - Control circuit for positive / negative output switching power supply - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a control circuit for a positive / negative output switching power supply,
In particular, it relates to improvement of a circuit for controlling output stabilization on the secondary side of a transformer by using a magnetic amplifier.

2. Description of the Related Art A switching power supply using a magnetic amplifier is known from, for example, Japanese Patent Laid-Open No. 60-160372. Such a magnetic amplifier is a multi-output power supply that outputs voltages such as +5, +12, and -5 Volt. For example, +12 Volt is the main output and is stabilized by using a PWM control IC, and the other outputs are secondary outputs. It is used for applications such as stabilization by a magnetic amplifier. FIG. 4 is a block diagram of the configuration when the magnetic amplifier is used as a positive / negative output switching power supply. In the figure, a DC voltage Vin is connected to the primary winding n1 of the transformer and is turned on / off by a switching element such as a transistor Tr1. The signal supplied to the base terminal of the transistor Tr1 is supplied by the switching control circuit 10. For example, an IC for PWM (pulse width modulation) control is adopted to stabilize the voltage at the main output so as to be equal to the reference voltage Vref1. ing. The secondary winding n2 of the transformer generates a positive voltage + E0. The switching signal generated on the secondary side is fed to the diode D
It is rectified by 1, D2, smoothed by choke coil L1 and capacitor C1, and outputs a DC voltage. The error signal output means 20 compares the output voltage + E0 with a predetermined reference voltage Vref2 and outputs an error signal e ₀₁ . The mag-amplifier control unit 30 supplies the control signal e _M1 obtained by amplifying the error signal e ₀₁ to the saturable reactor SR1 via the diode D3 and outputs a sub output + E.
0 is stabilized. The secondary winding n3 of the transformer generates a negative voltage -E0, and the switching signal generated on the secondary side is fed to the diode D.
It is rectified by 4, D5, smoothed by choke coil L2 and capacitor C2, and outputs a DC voltage. The error signal output means 40 sets the output voltage −E0 to the same reference voltage Vref3 as the positive voltage.
And outputs an error signal e ₀₂ . The mag-amplifier control unit 50 supplies the control signal e _M2 obtained by amplifying the error signal e ₀₂ to the saturable reactor SR2 via the diode D6 to stabilize the sub output -E0. In order to make the circuits of the error signal output means 20, 40 and the mag-amplifier control units 30, 50 similar to each other, the positive and negative voltages are made equal. Then, the reference voltages Vref2 and 3 become the same, and at the positive voltage, the reference voltage is used as the common line and the power required for the operation is supplied from the positive voltage + E0. As for the negative voltage, the reference voltage is set to the negative voltage −E0 and the power required for operation is supplied from the common line.

[Problems to be Solved by the Invention]

However, the conventional device has the following problems. With a positive voltage, the reference voltage is the common line, so the transient response is straightforward and stabilizes quickly. Since the reference voltage of the negative voltage is a negative voltage line, the fluctuation is larger than that of the common line and the transient response characteristic is deteriorated. Therefore, there is a problem in that the degree of stabilization differs depending on whether the voltage is positive or negative, and the dynamic characteristics of stabilization differ when the output stabilization circuit is commonly used. In addition, if the dynamic characteristics are made to coincide with each other, there is a problem that the phase compensating circuits are different between the two and common parts cannot be achieved. The present invention solves such a problem, and an object of the present invention is to provide a control circuit for a positive / negative output switching power supply, which has a stabilizing circuit for positive / negative voltage outputs in common and has substantially the same dynamic characteristics.

[Means for Solving the Problems]

The present invention that achieves such an object turns on / off the DC voltage input to the primary winding of the transformer by a switching element, and rectifies and smoothes the switching signals appearing in the first and second secondary windings. A positive / negative output switching power supply that outputs the same positive / negative DC voltage has the following configuration. That is, in order to stabilize the output voltage of the positive output, a means (20) for comparing the difference voltage between the common line and the positive output voltage with a reference voltage with the common line as a reference and outputting an error signal (e01), A mag-amplifier control unit (30) which receives this error signal, receives electric power required for operation from the positive output voltage, and sends a control signal to a saturable reactor (SR1) connected to the first secondary winding. It is equipped with. Further, in order to stabilize the output voltage of the negative output, a means (40) for comparing the difference voltage between the negative output voltage and the common line with a reference voltage based on the negative output voltage and outputting an error signal (e03). ), A level shift circuit (60) for subtracting a voltage corresponding to a negative output voltage from the error signal, and an error signal (e04) shifted by the level shift circuit are input to supply power necessary for operation from the common line. In response to this, a mag-amplifier control section (50) which sends a control signal to the saturable reactor (SR2) connected to the second secondary winding.
It is equipped with. The error signal output means and the mag-amplifier control section are shared by the positive and negative output circuits. When the absolute values of the positive output voltage and the negative output voltage are not equal, it is preferable to provide a voltage dividing means for unifying the levels.

[Action]

Each component of the present invention has the following action. Since the error signal output means and the mag-amplifier control section are shared by the positive and negative output circuits, parts can be commonly used and mass productivity is improved. In addition, a level shift circuit is mounted to stabilize the negative output voltage, and the dynamic characteristics in stabilizing the positive and negative outputs are made substantially the same.

【Example】

The present invention will be described below with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of the present invention. Incidentally, in FIG. 1, those having the same functions as those in FIG. In the figure, the level shifting means 60 outputs a shift error signal e ₀₄ subtracts the negative output voltage -E0 from the error signal e ₀₃ output by the error signal output means 40, for example, zener diode zener voltage E0 using Error signal e ₀₃ on the cathode side
Enter. The shift error signal e ₀₄ is supplied to the mag amplifier control unit 5
0 is supplied as a control input signal. The operation of the apparatus thus configured will be described below. Second
The figure is an illustration of the signal level of the error signal. A ground GND exists as a common line in the center, a positive output voltage + E0 and error signals e ₀₁ and e ₀₃ exist on the upper side, and a negative output voltage −E0 and error signal e ₀₄ exist on the lower side. The input signal of the mag-amplifier control unit 30 is the error signal e ₀₁ , and the output signal is the control signal e _M1 . On the other hand, the input signal of the mag amp control unit 50 is the error signal e ₀₄ having the same level as the error signal e _{02 of} FIG. 4, and the output signal is the control signal e _M2 . Unlike the error signal e ₀₄ , the potential of the error signal e ₀₃ is equal to that of the error signal e _{01 by} the action of the level shift means 60. Therefore, the potential of the control signal e _M2 is negative voltage −E0 in consideration of the action of the level shift means 60.
It is given by the following formula as a standard. e _M2 − (− E0) (1) As a result, the level of the control signal e _M1,2 sent to the saturable reactors SR1,2 by the mag amp control units 30,50 becomes the same as the conventional value as a steady value, and it is the reference for the positive and negative power supplies. The difference in voltage is determined by the error signal output means 20, 40 and the level shift means 60.
And the dynamic characteristics are almost the same. FIG. 3 is a circuit diagram showing a specific embodiment of the present invention. In the figure, the error signal output means 20 comprises a voltage dividing circuit 21, a differential amplifier 22, and an error amplifier 23. The voltage dividing circuit 21 is composed of, for example, a pair of resistors R21, R22, R23, and applies a voltage proportional to the potential difference between the common line and the positive voltage to the resistor R2.
It occurs in 2. The differential amplifier 22 differentially configures the OP amplifiers U21 and U22 to take out the voltage generated in the resistor R22, and the OP amplifier U23 amplifies the voltage at a ratio determined by the ratio of the resistors U24 and R25. This amplification factor K is given by the following equation. K = − (R25 / R24) × {(R22) / (R21 + R22 + R23)} (2) The error amplifier 23 constitutes a reference voltage source by the variable shunt regulator U24. The differential voltage signal output from the OP amplifier U23 is divided by the resistor and applied as e ₀₅ to the variable shunt regulator U24. Resistors R26 and R27 are connected to the variable shunt regulator U24, and the sink current on the cathode side is controlled so that the voltage e ₀₅ is constant, thereby generating an error signal between the difference voltage signal and the reference voltage. There is. The OP amplifier U25 constitutes an integrator having a predetermined time constant determined by the capacitor and the resistance, amplifies this error signal, and outputs the error signal e ₀₁ via the filter circuit. The magamplifier control unit 30 inputs the error signal e ₀₁ to the base terminal and turns on / off the transistor Tr31, and the collector terminal voltage of the transistor Tr31 is used as the control input to utilize the output voltage as the control signal e _M1 to the saturable reactor SR1.
And a large current transistor Tr32 for transmitting a current. Next, the negative voltage side will be described. Error signal output means 4
0 is composed of a voltage dividing circuit 41, a differential amplifier 42, and an error amplifier 23. When the positive and negative output voltages are the same,
It has the same configuration as the error signal output means 20. When the positive and negative output voltages differ, the level conversion rate of the voltage dividing circuit 41 is set to be the same as the voltage in the voltage dividing circuit 21, and the differential amplifier 42 and the error amplifier 43 output the error signal. It can be the same as the means 20. The error signal e ₀₃ output from the error amplifier 43 becomes the level-converted error signal e ₀₄ via the level shift means 60, and the saturable reactor SR via the transistors Tr51 and 52.
Control signal e _M2 is sent to ₂ . In the device thus configured, the differential amplifiers 22,4
Since the signal related to the output voltage is obtained in a differential form by using 2, the control reference potential independent of the common line of the power supply output can be determined, and the degree of freedom in combination is increased. Therefore, the reference potentials of the error amplifiers 23 and 43 are made equal,
It is adjusted to the positive voltage side. However, on the negative voltage side, it is necessary to operate the magamplifier control unit 50 with the reference potential as a negative output voltage, so the level shift means 60 changes the reference potential.

【The invention's effect】

As described above, according to the present invention, since the output voltage is stabilized by using the level shift means 60 in the negative power source,
Even if the error signal output means 20 and 21 and the mag-amplifier control units 30 and 31 that are common to the positive power supply are used, the dynamic characteristics are substantially equal, and the output voltage is well stabilized, which is a practical effect.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of the present invention, and FIG.
FIG. 4 is an explanatory diagram of the signal level of the error signal, FIG. 3 is a circuit diagram showing a specific embodiment of the present invention, and FIG. 4 is a block diagram of a configuration when the magnetic amplifier is used as a positive / negative output switching power supply. 20,40 ... Error signal output means, 30,50 ... Magnamp control unit,
60 ... Level shift means, SR1, SR2 ... Saturable reactor.

Claims (2)

[Claims] 1. A switching device which turns on and off a direct current input voltage (Vin) input to a primary winding (n1) of a transformer, and which appears in a first and a second secondary winding (n2, n3). In a positive / negative output switching power supply that rectifies and smoothes the signal and outputs the same positive / negative DC voltage, compares the difference voltage between the common line and the positive output voltage with the reference voltage with the common line as the reference, and outputs the error signal (e01). Outputting means (20) receives the error signal, receives the power required for operation from the positive output voltage, and outputs a control signal to the saturable reactor (SR1) connected to the first secondary winding. A mag-amp control unit (30) for sending is provided to stabilize the output voltage of the positive output and compare the difference voltage between the negative output voltage and the common line with a reference voltage based on the negative output voltage as an error signal ( e03 (40), a level shift circuit (60) for subtracting a voltage corresponding to a negative output voltage from the error signal, and an error signal (e04) shifted by the level shift circuit are input to operate from the common line. Mag amplifier control section (50) for supplying a control signal to a saturable reactor (SR2) connected to the second secondary winding by receiving the supply of power necessary for the
A control circuit for a positive / negative output switching power supply, characterized in that the output voltage of a negative output is stabilized and the error signal output means and the mag-amplifier control section are shared by a positive / negative output circuit. 2. Switching which appears in the first and second secondary windings (n2, n3) by turning on and off a DC input voltage (Vin) input to the primary winding (n1) of the transformer by a switching element. In a positive / negative output switching power supply that rectifies and smoothes a signal and outputs a positive / negative DC voltage, a means (21) for dividing a voltage difference between a common line and the positive output voltage, and using the divided signal as a reference with respect to the common line. Means (22, 23) for comparing with a reference voltage to output an error signal (e01), and receiving the power required for operation from the positive output voltage by inputting the error signal, and the first secondary winding. It is equipped with a mag-amplifier control unit (30) that sends a control signal to the saturable reactor (SR1) connected to the output terminal, stabilizes the output voltage of the positive output, and outputs the difference voltage between the negative output voltage and the common line to the positive output. Partial pressure of Means (41) for dividing the divided voltage into a voltage equal to the voltage divided by the stage, comparing the divided differential voltage with the negative output voltage as a reference, and comparing the value with the same reference voltage as the positive output side. Means (42, 4) for outputting the error signal (e03)
3), a level shift circuit (60) for subtracting a voltage corresponding to a negative output voltage from this error signal, and an error signal (e04) shifted by this level shift circuit are input and the power required for operation is supplied from the common line. A magamplifier control unit (50) that receives a supply and sends a control signal to a saturable reactor (SR2) connected to the second secondary winding is provided to stabilize the negative output voltage, and A control circuit for a positive / negative output switching power supply, wherein a part of the error signal output means excluding the voltage dividing means and a mag-amplifier control section are common to the positive / negative output circuits.