JP6479607B2 - DC stabilized power supply - Google Patents

Description

  The present invention rectifies and smoothes the AC power induced in the transformer by the switching of the primary side input circuit in the secondary side output circuit by the flyback method of reverse polarity of the primary and secondary windings to generate the DC output and supplies it to the load DC power supply that generates a feedback signal corresponding to an output voltage in a feedback circuit in a secondary side output circuit and transmits the feedback signal to an output voltage control circuit in a primary side input circuit The present invention relates to an integrated power supply device.

  FIG. 4 is a circuit diagram showing a configuration of a conventional DC stabilized power supply device described in Patent Document 1. In FIG. The main secondary output circuit connecting the secondary winding of the transformer T1 and the load 10 includes a rectifier circuit 1 including a positive half-wave diode D1 and a negative half-wave diode D2, and a smoothing capacitor. A smoothing circuit 2 including C1 and a choke coil L1 is connected. In addition, an auxiliary rectifier circuit 4 including a positive half-wave diode D3 and a negative half-wave diode D4, and an auxiliary smoothing circuit 5 including a smoothing capacitor C2 and a choke coil L1 (shared) are connected. Yes.

  The load 10 is connected to the rectifying circuit 1 and the smoothing circuit 2 via the cable 9, whereas the load 10 is not connected to the auxiliary rectifying circuit 4 and the auxiliary smoothing circuit 5. The rectifier circuit 1 and the smoothing circuit 2 output a DC voltage corresponding to the state change of the load 10, whereas the auxiliary rectifier circuit 4 and the auxiliary smoothing circuit 5 output a constant DC voltage regardless of the state change of the load 10. To do. The difference between the two DC voltages is proportional to the output current of the load 10.

  Therefore, the amplifier circuit 6 takes the difference between the output voltage Va of the smoothing circuit 2 and the DC voltage Vb of the auxiliary smoothing circuit 5, and outputs an amplified voltage Vx obtained by multiplying the difference by the amplification factor A1. The output voltage Va is a voltage immediately before the output terminal and is not subjected to a voltage drop due to the impedance of the cable 9. The adder circuit 32 calculates an added voltage Vy that is the sum of the amplified voltage Vx and the reference voltage Vr, and the differential amplifier 30 subtracts the added voltage Vy from the output voltage Va. The PWM drive circuit 31 drives the switching element Tr with a drive pulse having a pulse width corresponding to the differential voltage Vs.

  As a result, the DC voltage Va appearing at the output terminal is controlled to the reference voltage Vr even when the output current changes. Since the output voltage Va increases in proportion to the output current, the amplification factor of the amplifier circuit 6 is set corresponding to the change of the output current and the voltage drop of the cable 9, thereby increasing the output current. The accompanying line drop is corrected. Since almost no current flows through the auxiliary rectifier circuit 4 and the auxiliary smoothing circuit 5, there is no voltage drop due to resistance, and power loss is small.

JP-A-4-261358

  In the conventional DC stabilized power supply device described above, the auxiliary smoothing circuit 5 is constituted by the smoothing capacitor C2 and the choke coil L1. The choke coil L1 is also used as that of the smoothing circuit 2.

  However, since the choke coil L1 is used as an element, the level of the DC voltage Vb of the auxiliary smoothing circuit 5 is suppressed to a low level. As a result, the level of a signal that can be used for control is limited, and the control system is noisy. It will be easily affected by.

  The present invention was created in view of such circumstances, and an object thereof is to make the control system less susceptible to noise by increasing the signal level for control while reducing power loss.

  The present invention solves the above problems by taking the following measures.

The stabilized DC power supply device according to the present invention is:
A primary side input circuit that induces AC power in the transformer by switching controlled by the output voltage control circuit;
A secondary-side output circuit that rectifies and smoothes the AC power induced in the transformer by a flyback method of reverse polarity of the primary and secondary windings and outputs DC to the load;
A rectifying / smoothing circuit for output current detection for generating and outputting a detection signal corresponding to an output current by rectifying and smoothing a secondary side voltage appearing in the secondary winding of the transformer separately from an output voltage output to the load;
An output voltage correction circuit that corrects the output voltage based on the detection signal so that the output voltage control circuit increases the output voltage in response to an increase in the output current ;
A voltage dividing circuit connected between a hot line and a ground line of the secondary output circuit, generating a feedback signal corresponding to a voltage appearing at the voltage dividing point, and controlling the feedback signal to the output voltage control A feedback circuit for transmitting to the circuit;
The output voltage correction circuit is characterized in that the voltage appearing at the voltage dividing point is lowered in accordance with the increase in the output current .

  In the DC stabilized power supply device of the present invention configured as described above, the rectifying and smoothing circuit for detecting the output current is provided separately from the rectifying and smoothing circuit of the secondary output circuit, and is not directly connected to the load. The circuit does not flow load current. Therefore, power loss due to the load current can be reduced.

  In addition, since the rectifying and smoothing circuit for detecting the output current is connected to the secondary winding of the same transformer to which the secondary side output circuit is connected, the load current increases in the secondary side output circuit. The on-duty of the switching control signal increases.

And the secondary side output circuit rectifies and smoothes the AC power induced in the transformer by the flyback method with the reverse polarity of the primary and secondary windings, and outputs the direct current. Smoothing in a rectifying / smoothing circuit for output current detection using the phenomenon that a surge voltage (a large wave voltage generated momentarily exceeding the steady state) induced in the secondary winding is generated in the voltage control circuit. The capacitor can be peak charged, and the voltage level of the output current detection signal can be increased. As a result, it is possible for the control system to ensure a great resistance to noise and to control the DC stabilized power supply with high accuracy.
In this case, when the output current increases (decreases) in the secondary output circuit, the output voltage correction circuit increases (decreases) the voltage level of the output current detection signal, and the voltage dividing circuit of the voltage dividing circuit works in conjunction therewith. Reduce the voltage appearing at the point. The feedback circuit gives a feedback signal corresponding to the voltage at the voltage dividing point to the output voltage control circuit, and the on-duty of the switching control signal increases (decreases). As a result, the output voltage can be stabilized (suppression of line drop).

In the DC stabilized power supply device of the present invention described above, the output voltage correction circuit includes an inverting amplifier that generates an inverted amplified signal of the level of the detection signal with respect to a reference level, and the inverted amplified signal is output from the inverting amplifier. There is a preferred mode in which the voltage is output to the voltage dividing point.

  According to the present invention, the voltage level of the output current detection signal is increased by performing peak charging to the smoothing capacitor in the rectifying and smoothing circuit for detecting the output current by using the surge voltage generated by switching of the primary side input circuit. Therefore, the noise resistance performance of the control system can be improved, and the components used in the control system circuit can be simplified. The DC stabilized power supply apparatus of the present invention is particularly effective for a power supply that requires high voltage stability accuracy.

The circuit diagram which shows the structure of the direct current | flow stabilized power supply device in the Example of this invention. Characteristic diagram of output current-detection voltage obtained in a DC stabilized power supply device in an embodiment of the present invention Characteristic diagram of output current-output voltage before and after correction by a DC stabilized power supply device in an embodiment of the present invention Circuit diagram showing the configuration of a conventional stabilized DC power supply

  Hereinafter, embodiments of a stabilized DC power supply apparatus according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a circuit diagram showing a configuration of a stabilized DC power supply apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 100 denotes a primary side input circuit, 200 denotes a secondary side output circuit, and 300 denotes a transformer (pulse transformer) that electrically connects the primary side input circuit 100 and the secondary side output circuit 200.

Reference numeral 30 denotes an output voltage control circuit in the primary side input circuit 100. As a component of the secondary side output circuit 200, 60 main rectifying and smoothing circuit, 70 is a feedback circuit 75 is voltage division circuit in the feedback circuit 70, 80 is rectifying and smoothing circuit for detecting the output current, 90 is the output voltage It is a correction circuit.

  One end of the secondary winding N2 of the transformer 300 is connected to the DC output terminal T2p on the high side through a hot line HL in which the main rectifying and smoothing circuit 60 is interposed, and the other end of the secondary winding N2 is connected to the low side. A ground line GL is formed by being connected to the DC output terminal T2n. The primary side input circuit 100 has a function of inducing AC power to the transformer 300 by switching of the switching element Q21 controlled by the output voltage control circuit 30.

  The secondary output circuit 200 rectifies and smoothes the AC power induced in the transformer 300 by a flyback method with reverse polarity of the primary and secondary windings. The high-side DC output terminal T2p and the low-side DC output terminal T2n It has a function of performing DC output to a load (not shown) connected between the two.

  The transformer 300 has a function of propagating the AC power induced in the primary winding N1 to the secondary winding N2 in an electrically insulating manner. The output voltage control circuit 30 has a function of controlling a high-frequency switching operation of a switching element Q21 such as a MOSFET (a field effect transistor made of a metal oxide semiconductor).

  The main rectifying / smoothing circuit 60 includes rectifying diodes D21 and D22 and a smoothing capacitor C21. The main rectifying / smoothing circuit 60 rectifies and smoothes the secondary side voltage appearing in the secondary winding N2 of the transformer 300, and the hot line HL and the ground line GL. And an output voltage with respect to the load.

  The rectifying diodes D21 and D22 are connected in parallel with each other, the anode common connection point is connected to one end of the secondary winding N2, and the cathode common connection point is connected to the DC output terminal T2p. The smoothing capacitor C21 is connected between the hot line HL and the ground line GL.

Voltage dividing circuit 75 in the feedback circuit 70 is constituted by connecting the resistor elements R21, R22 of a pair of resistors divided in series between the hot line HL and a ground line GL. Feedback circuit 70 includes a light emitting element LE such as an LED (light emitting diode) in the voltage dividing circuit 75 and the resistor element R23, R24 and shunt regulator SR21 photocoupler PC.

A series circuit of the resistor element R23, the resistor element R24, and the shunt regulator SR21 is connected between the hot line HL and the ground line GL, and the light emitting element LE is connected between both ends of the resistor element R24. Also connected to the voltage dividing point in the reference terminal voltage dividing circuit 75 of the shunt regulator SR21 (connection node between the resistor R21 the resistance element R22).

  The output current detection rectifying / smoothing circuit 80 includes a rectifying diode D23 and a smoothing capacitor C22, and rectifies and smoothes the secondary side voltage appearing in the secondary winding N2 of the transformer 300 to detect the output current according to the output current. The signal S80 is generated and output. The anode of the rectifying diode D23 is connected to one end of the secondary winding N2, and a smoothing capacitor C22 is connected between the cathode and the ground line GL. The rectifying / smoothing circuit 80 for detecting the output current is not directly connected to the load.

  The output voltage correction circuit 90 includes resistance elements R25, R26, R27, R28, R29, R30, a shunt regulator SR22, and an inverting amplifier OP21 including an operational amplifier. A series circuit of the resistor element R25 and the resistor element R26 is connected between the connection point of the rectifying diode D23 and the smoothing capacitor C22 in the rectifying and smoothing circuit 80 for detecting the output current, and the ground line GL.

The shunt regulator SR22 has an anode connected to the ground line GL, a cathode and a reference terminal connected in common, and the hot line HL and the non-inverting input terminal (+) of the inverting amplifier OP21 via the resistance element R27. It is connected to the. An inverting input terminal (−) of the inverting amplifier OP21 is connected to a connection point between the resistance element R25 and the resistance element R26 via the resistance element R28. The inverting amplifier OP21 of the output terminal is an inverting input via a resistor element R29 for feedback terminal (-) with is connected to, and is connected to the voltage dividing point of the by voltage divider circuit 75 via the resistance element R30 Yes.

  In the output voltage correction circuit 90, the current of the output current detection signal S80 generated by the rectifying / smoothing circuit 80 for detecting the output current flows through the series circuit of the resistor element R25 and the resistor element R26, and is detected between the both ends of the resistor element R26 as the detection voltage V26. Expressed in

Inverting amplifier OP21 is applied to the voltage dividing point of the voltage dividing circuit 75 in the feedback circuit 70 on which inverts and amplifies the difference between the detection voltage V26 with respect to the reference level Vref to output shunt regulator SR22.

Feedback circuit 70, voltage to generate a feedback signal (optical signal) S70 corresponding to the voltage appearing at the voltage dividing point of the divider circuit 75, transmitted to the non-contact the feedback signal S70 to the output voltage control circuit 30 To do. PT is a light receiving element such as a phototransistor in the photocoupler PC.

  Next, the operation of the stabilized DC power supply configured as described above will be described.

  In the primary side input circuit 100, the AC voltage induced in the secondary winding N2 of the transformer 300 by the switching operation of the switching element Q21 by the output voltage control circuit 30 is converted into a DC voltage by the rectifying and smoothing of the main rectifying and smoothing circuit 60. The load is supplied from the high-side output terminal T2p to the load via the hot line HL.

  At this time, in applying feedback control to the output voltage control circuit 30 of the primary side input circuit 100 while monitoring the change in the output current flowing from the high side output terminal T2p to the load, the hot line HL in the secondary side output circuit 200 is applied. The ground line GL is characterized in that no resistance element for detecting the output current is inserted. That is, the output current is detected by the output current detection rectifying and smoothing circuit 80 and the output voltage correction circuit 90.

  In the output voltage correction circuit 90, the voltage of the hot line HL is applied to the reference terminal of the shunt regulator SR22 via the resistance element R27. When the applied voltage exceeds the reference level Vref generated inside the shunt regulator SR22, the current flowing from the cathode to the anode increases. Conversely, when the applied voltage falls below the reference level Vref, the current decreases. The reference level Vref output from the shunt regulator SR22 to the non-inverting input terminal (+) of the inverting amplifier OP21 is kept constant. That is, here, the shunt regulator SR22 is provided to generate a stable reference level Vref.

  When the output current detection rectifying / smoothing circuit 80 outputs the output current detection signal S80 corresponding to the output current to the load to the output voltage correction circuit 90, the detection voltage V26 appearing at both ends of the resistance element R26 in the output voltage correction circuit 90 is It corresponds to the output current. That is, the output current is detected without inserting an output current detection resistance element (shunt resistor) in the hot line HL.

When the output current increases in the secondary output circuit 200, the detection voltage V26 increases accordingly, and the voltage level of the inverted amplification signal S90 (the difference signal of the detection voltage V26 with respect to the reference level Vref) decreases accordingly. The amount of current that draws a part of the current flowing out from the resistance element R21 of the voltage dividing circuit 75 to the resistance element R30 increases.

  As a result, the voltage drop of the resistance element R22 is reduced and the reference terminal voltage of the shunt regulator SR21 in the feedback circuit 70 is reduced, so that the current flowing through the shunt regulator SR21 is reduced. Then, the voltage across the resistance element R24 decreases, and the level of the feedback signal S70 due to the light emission amount of the light emitting element LE in the photocoupler PC decreases.

  As a result, the output voltage control circuit 30 in the primary side input circuit 100 increases the on-duty of the PWM control for the switching element Q21. As a result, the output voltage of the secondary output circuit 200 increases. That is, when the output current of the secondary output circuit 200 increases, the output voltage is increased by the operations of the output current detection rectifying and smoothing circuit 80, the output voltage correction circuit 90, the feedback circuit 70, and the output voltage control circuit 30. Feedback control is performed.

Contrary to the above, when reducing the output current in the secondary side output circuit 200, the detection voltage V26 drops along with it, in conjunction with the voltage level of the inverted amplified signal S90 rises, the the voltage dividing circuit 75 resistance The amount of current that draws a part of the current flowing out from the element R21 to the resistance element R30 decreases. As a result, the voltage drop of the resistance element R22 increases and the reference terminal voltage of the shunt regulator SR21 in the feedback circuit 70 increases, so that the current flowing through the shunt regulator SR21 increases. Then, the voltage between both ends of the resistance element R24 increases, and the level of the feedback signal S70 by the light emitting element LE in the photocoupler PC increases.

  As a result, the output voltage control circuit 30 decreases the on-duty of the PWM control for the switching element Q21. As a result, the output voltage of the secondary output circuit 200 decreases. That is, when the output current of the secondary output circuit 200 decreases, the output voltage is lowered by the operations of the rectifying and smoothing circuit 80 for detecting the output current, the output voltage correction circuit 90, the feedback circuit 70, and the output voltage control circuit 30. Feedback control is performed.

  With the above control operation, the output voltage can be accurately kept at a specified level and stabilized. In this case, the power loss is small because no resistor for detecting the output current is inserted in the hot line HL or the ground line GL.

  FIG. 2 shows the output current-detected voltage characteristics obtained in the DC stabilized power supply device of the embodiment of the present invention. As the output current increases, the detection voltage also increases. In the range where the output current is equal to or greater than a certain value, the detection voltage is substantially proportional to the output current.

  The increase in the detection voltage is caused by a surge voltage generated at the time of switching of the primary side input circuit 100 by the output voltage control circuit 30 being induced in the secondary winding N2 of the transformer 300, and the smoothing capacitor C22 in the rectification smoothing circuit 80 for detecting the output current. In contrast, the peak charge is possible, and the on-duty is widened to stabilize the output voltage by the feedback circuit 70. The increase in the detection voltage due to the output current is used to correct the output voltage.

  FIG. 3 shows the output current-output voltage characteristics before and after correction. A broken line indicates a characteristic curve when a line drop before correction occurs, and a solid line indicates a characteristic curve when line drop is suppressed by correction.

  Before the correction, the maximum value of the output voltage is 24.74 [V], the minimum value is 24.56 [V], and the difference that is a line drop is 0.18 [V]. After correction, the maximum value of the output voltage is 24.80 [V], the minimum value is 24.73 [V], and the difference that is a line drop is 0.07 [V]. By the correction in the embodiment of the present invention, the line drop is suppressed to about 40% from 0.18 [V] to 0.07 [V].

  Since the choke coil inserted in the main circuit in the conventional example does not exist in the embodiment of the present invention, the generation of high frequency components is a concern. However, this high frequency component can be effectively removed by inserting a ceramic capacitor CC or the like between the inverting input terminal (−) of the inverting amplifier OP21 and the ground line GL.

  In the conventional example, each of the rectifier circuit 1 and the auxiliary rectifier circuit 4 requires two diodes for rectification, that is, a positive half-wave diode and a negative half-wave diode. In the embodiment, there is an advantage that only one rectifying diode is required.

  INDUSTRIAL APPLICABILITY The present invention is particularly useful as a technique for improving noise resistance performance of a control system and simplifying parts used in a control system circuit with respect to a direct current stabilized power supply apparatus that requires high voltage stability accuracy.

30 the output voltage control circuit 70 feedback circuit 75 voltage dividing circuit 80 rectifying and smoothing circuit 90 output voltage correcting circuit 100 primary side input circuit 200 secondary output circuit 300 transformer N2 secondary winding HL hotline GL ground for output current detection Line OP21 Inverting amplifier S70 Feedback signal S80 Output current detection signal S90 Inverted amplification signal

Claims (2)

A primary side input circuit that induces AC power in the transformer by switching controlled by the output voltage control circuit;
A secondary-side output circuit that rectifies and smoothes the AC power induced in the transformer by a flyback method of reverse polarity of the primary and secondary windings and outputs DC to the load;
A rectifying / smoothing circuit for output current detection for generating and outputting a detection signal corresponding to an output current by rectifying and smoothing a secondary side voltage appearing in the secondary winding of the transformer separately from an output voltage output to the load;
An output voltage correction circuit that corrects the output voltage based on the detection signal so that the output voltage control circuit increases the output voltage in response to an increase in the output current ;
A voltage dividing circuit connected between a hot line and a ground line of the secondary output circuit, generating a feedback signal corresponding to a voltage appearing at the voltage dividing point, and controlling the feedback signal to the output voltage control A feedback circuit for transmitting to the circuit;
The stabilized direct-current power supply apparatus according to claim 1, wherein the output voltage correction circuit reduces a voltage appearing at the voltage dividing point according to an increase in the output current . The output voltage correction circuit includes an inverting amplifier that generates an inverted amplified signal level of the detection signal relative to a reference level, said inverted amplified signal from said inverting amplifier and said Rukoto is output to the voltage dividing point The direct-current stabilized power supply device according to claim 1.

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