JP2013034354A - Input voltage correction method of output current in isolated constant current power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an isolated transformer type constant current power supply device which is a power supply device capable of adjusting an output current with a phase control type input voltage converter and which has an error amplifier for detecting an output current on the secondary side and controls an oscillation frequency or duty on the primary control section because the power device of this type has a problem that an output current varies when a commercial input voltage varies, with the input voltage converter provided at the pre-stage.SOLUTION: An input voltage correction circuit which operates only when an input voltage converter is used is provided and, in use of the input voltage converter, is configured so that an output current is not changed by applying secondary reference voltage correction to an output current variation due to a variation in an input voltage. In addition, an input voltage is monitored in a pseudo manner with a secondary voltage of an isolated transformer.

Description

  The present invention makes it possible to suppress fluctuations in the output current when the commercial input voltage fluctuates only when the phase control type input voltage conversion device for adjusting the output current is used. The present invention relates to an insulation transformer type constant current power supply device having an error amplifier for detecting the above.

  When a phase control type input voltage converter intended to adjust the output current is not used, it has an error amplifier that detects the output current on the secondary side, and the oscillation frequency or duty is controlled by the primary side control unit. In the insulated transformer type constant current power source, even if there is a commercial input voltage fluctuation, since the secondary side current is detected and controlled, there is no change in the output current.

  However, a phase control type input voltage conversion device intended to adjust the output current is used, and the output current adjustment method detects the conduction width or conduction duty on the primary side, and a reference corresponding to them. When the voltage is determined on the secondary side and the input voltage conversion device is inserted into the input stage of the power supply device and used, there is a problem that the output current changes with the fluctuation of the commercial input voltage. It is considered that the commercial input voltage frequently varies between 110 and 70 V depending on the environment in which it is used.

  The reason is that the conduction width or conduction duty fluctuates (point A in FIG. 1) and the threshold conduction detection point fluctuates (point B in FIG. 1) due to the characteristics of the phase control type input voltage conversion device with commercial input voltage fluctuation. For this reason, the secondary side reference voltage fluctuates as the primary side conduction detection width fluctuates. The conduction width of the phase control type input voltage conversion device is generally that the gate of a triac or the like is set with a CR time constant, so that the fluctuation of the commercial input voltage becomes the fluctuation of the conduction width. Also in the phase control type input voltage conversion device controlled by the microcomputer, the reference phase position is detected by monitoring the commercial input voltage value, and the reference phase position fluctuates when the commercial input voltage fluctuates. Thus, the conduction width or the conduction duty varies.

  Even if the output current adjustment method is based on the average value or effective value of the input voltage, the commercial input voltage fluctuation becomes the output current fluctuation and the same can be said.

  In a circuit in which the output current is controlled on the primary side, the input voltage correction of the output current can be easily achieved on the primary side and is generally used. However, in this case, since there is no feedback system from the secondary side, there is a drawback that it does not operate stably against commercial input voltage fluctuations and load fluctuations when the input voltage converter is not used.

  The problem to be solved is that when a phase control type input voltage converter intended to adjust the output current is used, a commercial input voltage fluctuation occurs in an isolated transformer type constant current power supply having a secondary side error amplifier. This is the point where the output current fluctuates.

Only when the input voltage conversion device is used, the secondary side reference voltage varies due to fluctuations in conduction width or conduction duty and fluctuations in conduction detection threshold so that there is no fluctuation in secondary side reference voltage with respect to fluctuations in commercial input voltage. Correction is made according to the commercial input voltage value so as to cancel the fluctuation (the secondary side reference voltage is fluctuated). (FIG. 2) This can solve the problem.
The function of changing the secondary side reference voltage according to the commercial input voltage value is a function of changing the output current according to the commercial input voltage fluctuation. When the input voltage converter is not used, the conduction width or the conduction duty does not fluctuate, so that the output current fluctuates according to the correction. When it is assumed that the input voltage converter is not used, it is necessary to eliminate or reduce the influence of the function of correcting according to the commercial input voltage value.

When an insulation transformer is used, the method of changing the secondary side reference voltage according to the commercial input voltage value is a method in which the commercial input voltage is artificially monitored from the winding of the secondary side of the insulation transformer. It becomes.
In that case, it is necessary to monitor the secondary winding voltage of the insulating transformer when the main switching (generally, a transistor or a MOSFET) is conducting.

  When correction is performed by the primary side conduction width detection unit, a circuit that once converts information such as conduction width into DC voltage, converts it to AC again, and transmits it to the secondary side is prepared and correction is performed in the process. There is a need. In that case, the circuit becomes complicated and expensive.

  In the power supply device of the present invention, only when the input voltage conversion device is used, the conduction width or conduction duty varies and the conduction detection threshold fluctuation varies so that there is no fluctuation in the secondary-side reference voltage with respect to fluctuations in the commercial input voltage. Is corrected according to the commercial input voltage value so as to cancel the fluctuation of the secondary side reference voltage. Therefore, when the input voltage converter is not used, the output current does not fluctuate with respect to the commercial input voltage fluctuation, and even when the input voltage converter is used, the input voltage correction circuit operates. There is an advantage that a state in which the output current does not fluctuate with respect to fluctuations in the commercial input voltage can be realized.

  In addition, if the method of monitoring the commercial input voltage from the secondary winding of the isolation transformer is used to vary the secondary reference voltage according to the commercial input voltage value, the correction is made on the primary side. There is an advantage that it can be achieved at a lower cost than that of the above.

It is explanatory drawing explaining the problem at the time of using the said input voltage converter. It is explanatory drawing explaining the problem-solving method. It is a block diagram explaining the implementation circuit. Example 1 It is a circuit diagram explaining the implementation circuit. (Example 2) It is a circuit diagram explaining the implementation circuit. (Example 3) It is a circuit diagram explaining the implementation circuit. Example 4

  A specific circuit configuration will be described below.

  FIG. 3 is a block diagram showing an embodiment of the electrical configuration of the present invention.

  A phase control type input voltage conversion device 2 is provided at a subsequent stage of the commercial input 1, a power supply device 13 as an object of the present invention is provided at the subsequent stage, and a load 14 is connected at the final stage. The power supply device can be used without the input voltage conversion device 2. The load 14 may be any type, but is described here as a diode.

  The power supply device 13 includes a rectifier diode bridge 3, a smoothing capacitor 4, a control unit 5, a switching element 6, an insulating transformer 7, a feedback photocoupler 8, a secondary rectifier diode 9, a secondary smoothing capacitor 10, Basically, an output current detection resistor 11, a secondary side error amplifier 12, a conduction width detection unit 15, a conduction width transmission photocoupler 16, an input voltage correction unit 17, a secondary side reference voltage capacitor 18, and a secondary side control unit 19 It is composed.

  This configuration is a flyback power supply device that employs a general feedback system. Even if the feedback method is not adopted, it is sufficient that the current can be set to a predetermined current by detecting the current on the secondary side and comparing it with the secondary side reference voltage. Further, although the circuit diagram of the flyback type power supply device is shown, a forward type power supply device may be used.

  The input voltage correction unit 17 is a main part of the present invention. When the commercial input voltage 1 fluctuates, the secondary side reference voltage fluctuates due to a change in conduction width. The input voltage correction unit 17 operates so that the secondary side reference voltage fluctuates in reverse, and finally, correction is performed so that the secondary side reference voltage does not fluctuate. For example, when the commercial input voltage 1 fluctuates in the decreasing direction, the secondary side reference voltage decreases, so correction is applied so that the secondary side reference voltage increases. Conversely, when the commercial input voltage 1 increases, the secondary side reference voltage increases. Since the voltage increases, correction is applied so that the voltage decreases accordingly. As a result, even if the commercial input voltage varies, the secondary-side reference voltage does not vary and the output current does not vary. The fluctuation of the commercial input voltage is assumed to be + 10% -30%, and if it is 100V commercial, it is desirable to correct between 70V and 110V.

  The power supply device is assumed to be used even when the input voltage conversion device 2 is not provided. When the input voltage conversion device 2 is not used, the variation in the conduction width of the conduction width detector (A in FIG. 1). If there is no influence of the input voltage correction unit, output current fluctuations will occur.

  4 and 5 describe a specific circuit configuration of the input voltage correction unit.

  In FIG. 4, the switching element 6, the insulating transformer 7, the secondary side reference voltage capacitor 18, and the secondary side control unit 19 are a part of the basic circuit of the power supply device 13. The input voltage correction unit includes a pseudo input voltage rectifying diode 20, a noise absorbing resistor 21, a pseudo input voltage charging capacitor 22, and a correction adjusting resistor 23.

  The pseudo input voltage rectifying diode 20 is inserted in a direction to extract a voltage generated when the switching element 6 is turned on. The secondary side voltage corresponding to the turn ratio of the primary side voltage of the insulating transformer 7 when the switching element 6 is conducting is monitored. (The primary voltage peak value of the insulation transformer 7 corresponds to the peak value of the input voltage of the power supply device 13.) The secondary winding of the insulation transformer 7 to be monitored is assumed to be the main winding leading to the output. However, a secondary auxiliary winding may be provided separately.

  When the commercial input voltage 1 fluctuates and decreases, the primary voltage of the insulating transformer 7 decreases, and the secondary voltage of the insulating transformer 7 decreases (the voltage of the pseudo input voltage charging capacitor 22 decreases). As a result, the bias that is biased in the direction of lowering the secondary side reference voltage is weakened, and the secondary side reference voltage is increased. Now, the commercial input voltage fluctuates and the secondary side reference voltage decreases, and the total secondary side reference voltage does not fluctuate. The correction adjusting resistor 23 is used for adjusting the secondary side reference voltage. An amplifier or the like may be used instead of the correction adjustment resistor 23.

  FIG. 5 shows a circuit configuration in the case of the forward method. Compared to FIG. 4 of the flyback method, the insulating transformer 7 is changed to the insulating transformer 24 and the pseudo input voltage rectifying diode 20 is changed to the pseudo input voltage rectifying diode 25. When the voltage generated when the switching element 6 is turned on is inserted in the direction of taking out the voltage, the direction of the diode is reversed like the pseudo input voltage rectifying diode 25. Other operations are the same as those in FIG. Here, an amplifier 26 is used in place of the correction adjustment resistor 23.

  Since the method of providing the input voltage correction unit on the secondary side is inexpensive, the embodiment has been described with reference to FIGS. 4 and 5. However, there is also a method of providing correction on the primary side and transmitting it to the secondary side. However, in the case of detecting the conduction width or conduction duty, since the secondary side transmission cannot be performed unless the signal is once converted to DC and then AC again, there are disadvantages such as an increase in the number of parts.

  FIG. 6 shows a specific circuit configuration that does not affect the input voltage correction unit when the input voltage converter 2 is not used.

  6, the output current detection resistor 11, the secondary side error amplifier 12, the secondary side reference voltage capacitor 18, the secondary side control unit 19, and the input voltage correction unit 17 are the same as those in FIG. The internal configuration circuit of the secondary side control unit 19 is specifically described.

  The internal circuit of the secondary side control unit 19 includes an amplifier 27 (AMP2), an amplifier 28 (AMP3), a diode 29, a resistor 30, and a DC power source 31.

  When the input voltage converter 2 is used, the amplifier 27 (AMP2) is operating when the conduction width is narrow, but the amplifier 28 (AMP3) is operated when the conduction width becomes wide. 31 is set, and even if the conduction width is further widened, the input voltage of the secondary error amplifier 12 does not increase due to the influence of the amplifier 28 (AMP3), and the output current is fixed. When the input voltage conversion device 2 is not used, the conduction width MAX and the amplifier 28 (AMP3) are in operation. As a result, there is no influence of the amplifier 27 (AMP2), so there is no influence of the input voltage correction unit.

For lighting, a phase control type input voltage converter may be used. In that case, fluctuations in output current due to fluctuations in commercial input voltage can be suppressed, and a flicker-free system can be constructed.
In addition, the same effect can be expected for a device in which it is beneficial to adjust the output current.

DESCRIPTION OF SYMBOLS 1 Commercial input 2 Input voltage converter 3 Rectifier diode bridge 4 Smoothing capacitor 5 Control part 6 Switching element 7 Insulation transformer 8 Feedback photocoupler 9 Secondary side rectifier diode 10 Secondary side smoothing capacitor 11 Output current detection resistor 12 2 Secondary side error amplifier 13 Power supply device 14 Load 15 Conduction width detection unit 16 Conduction width transmission photocoupler 17 Input voltage correction unit 18 Secondary side reference voltage capacitor 19 Secondary side control unit 20 Pseudo input voltage rectifier diode 21 Noise absorption Resistor 22 pseudo input voltage charging capacitor 23 correction adjusting resistor 24 insulation transformer 25 pseudo input voltage rectifier diode 26 amplifier 27 amplifier 28 amplifier 29 diode 30 resistor 31 DC power supply

Claims (3)

  Insulation transformer that can adjust the output current with a phase control type input voltage converter, has an error amplifier that detects the output current on the secondary side, and controls the oscillation frequency or duty, etc., on the primary side control unit Type constant current power supply device is equipped with an input voltage correction circuit for correcting fluctuations in output current due to fluctuations in commercial input voltage, and the input voltage correction circuit corrects the secondary side reference voltage. .   2. The power supply apparatus according to claim 1, wherein the input voltage correction circuit operates only when the input voltage converter is used.   2. The power supply apparatus according to claim 1, wherein the input voltage correction is performed by artificially detecting an input voltage value with a transformer secondary winding and adding the input voltage correction to the secondary reference voltage.

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