JP2007049833A - Input voltage detection circuit and power supply unit therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a commercial power supply voltage at low cost without using a transformer. <P>SOLUTION: A flyback voltage is peak-charged using a diode and a capacitor, and resistance synthesis is made with a DC output voltage of a switching power to generate a voltage corresponding to the commercial power supply voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit configuration for detecting a commercial power supply voltage, and in particular, a high voltage DC voltage obtained by rectifying and smoothing a commercial power supply voltage is a low voltage of several V to several tens of V required by an apparatus. The present invention relates to an input voltage detection method and a circuit system when performing peak charge mainly using a flyback voltage in a switching power supply for converting to a direct current voltage.

In general, as a circuit example for detecting a commercial power supply voltage, a specific circuit example is described in Japanese Patent Registration No. 03240591, the commercial power supply voltage of the previous stage that is smoothed and rectified by a diode bridge and a capacitor is directly used as the primary side of a commercial frequency transformer. In general, the commercial power supply voltage is detected by performing peak charging from the secondary side of the arranged transformer using a diode and a capacitor.
Japanese Patent Registration No. 03240591

  However, in the commercial power supply voltage detection circuit specifically described in the above special registration 03240591, a transformer is used for insulation between the primary side which is the commercial power supply voltage side and the secondary side which is the DC output voltage side. Therefore, there is a problem that the device itself becomes large due to the mounting area of the component to be mounted with the input voltage detection circuit. Further, since a transformer is arranged for detecting the commercial power supply voltage, there is a problem that the number of parts increases and it is difficult to reduce the cost.

  This will be described in detail below using a circuit example.

(Basic operation of switching power supply unit)
A conventional switching power supply device will be described with a self-excited flyback converter (RCC: ringing choke converter) shown in FIG. 2 as a basic circuit. The insulating transformer T21 includes an input-side primary winding Np, an output-side secondary winding Ns, and a primary-side auxiliary winding Nb. The auxiliary winding Nb is a driving winding for the switching element Q22 that performs on / off control of the control terminal of the main switching element Q21. The commercial power supply voltage is rectified by the bridge diode D23 and rectified and smoothed to the DC input voltage E by the aluminum electric field capacitor C25. The DC input voltage E is applied between one end of the primary winding Np and the current outflow terminal of the main switching element Q21. The (+) side of the input voltage is one end of the primary winding Np and the (−) side of the input voltage. Is connected to the current outflow terminal of the main switching element Q21. The auxiliary winding Nb is connected to the same polarity as the primary winding Np, and the secondary winding Ns is connected to a different polarity. A starting resistor R201 is connected between the (+) side of the input voltage and the control terminal of the main switching element Q21. Further, a resistor R202 is connected between the control terminal of the main switching element Q21 and the (−) side of the DC voltage E, and the main switching element Q21 is turned on by dividing the starting resistor R201 and the DC input voltage E. Sufficient voltage is generated. A capacitor C21 and resistors R203 and R204 are connected between the control terminal of the main switching element Q21 and the same polarity side of the primary winding of the auxiliary winding Nb. A diode D21 with the auxiliary winding Nb facing the cathode is connected to both ends of the resistor R204 to adjust the turn-on and turn-off speed of the main switching element Q21. The switching element Q22 is provided for controlling on / off of the main switching element Q21. The current inflow terminal is connected to the control terminal of the main switching element Q21, and the current outflow terminal is connected to the (−) side of the DC voltage E. A capacitor C22 is connected between the control terminal and the current outflow terminal. A resistor R205 is connected between the auxiliary winding Nb and the control terminal of the switching element Q22, and a time constant circuit is configured with the capacitor C22. A resistor R202 is connected between the primary current inflow terminal of the optocoupler IC21 and the control terminal of the main switching element Q21 to limit the current flowing through the optocoupler IC21. The current outflow terminal of the phototransistor of the optocoupler IC21 is connected to the control terminal of the switching element Q22. The anode side of the rectifying diode D22 is connected to the side opposite to the primary winding of the secondary winding Ns of the insulating transformer T21, and is the same as the cathode side of the diode D22 and the primary winding of the secondary winding Ns. An electric field capacitor C23 is connected between the pole side and the alternating voltage rectified by the diode D22 is smoothed. The output voltage Vo is divided by the resistors R207 and R208, the divided voltage is connected to the inverting input terminal of the differential amplifier IC22, and the reference voltage generated by the Zener diode ZD21 and the resistor R209 is the voltage of the differential amplifier IC22. The differential amplifier IC22 is input to the non-inverting input terminal, and the voltage at the output terminal is changed by comparing the input voltage at the inverting input terminal with the reference voltage. Is controlling. A resistor R211 and a capacitor C24 connected between the inverting input terminal and the output terminal of the differential amplifier IC22 are for adjusting the gain and phase of the closed loop.

  The main switching element Q21 becomes conductive when a voltage is applied to the control terminal by the starting resistor R201 and the resistor R202. When the main switching element Q21 becomes conductive, the input voltage E is applied to the primary winding Np, and a voltage having a positive polarity on the same polarity side as the primary winding is induced in the auxiliary winding Nb. At this time, a voltage is also induced in the secondary winding Ns. However, since the voltage is negative on the anode side of the rectifier diode D22, the voltage is not transmitted to the secondary side. Accordingly, the current flowing through the primary winding Np is only the exciting current of the insulating transformer T21, and energy proportional to the square of the exciting current is accumulated in the insulating transformer T21. This exciting current increases in proportion to time. The control terminal of the main switching element Q21 is charged through the capacitor C21 and the resistors R203 and R204 by the voltage induced in the auxiliary winding Nb, and the conduction state is continued. The resistor R205 and the capacitor C22 constituting the time constant circuit are charged from the auxiliary winding Nb. When the voltage across the capacitor C22 becomes higher than the threshold value of the switching element Q22, the switching element Q22 becomes conductive, and the main switching The main switching element Q21 becomes non-conductive because the control terminal voltage of the element Q21 decreases. At this time, a voltage having a polarity opposite to that at the time of starting is generated in each winding of the insulating transformer T21, and a voltage having a positive polarity on the anode side of the rectifier diode D22 is generated in the secondary winding. Therefore, the voltage is accumulated in the insulating transformer T21. Energy is rectified and smoothed and transmitted to the secondary side. When the energy stored in the insulating transformer T21 is all transmitted to the secondary side, the main switching element Q21 becomes conductive again. This is because a voltage corresponding to the winding ratio of the voltage between the current inflow and current outflow terminals of the switching element Q21 is generated in the auxiliary winding Nb, but the control terminal is negative immediately after the main switching element Q21 is turned off. However, since the negative bias gradually decreases when the transmission of energy to the secondary side is completed, the control terminal of the main switching element Q21 is again biased in the positive direction from the C-coupled capacitor C21. Because. Since a large amount of current flows from the photocoupler IC21 when the output voltage Vo is high, the current is supplied to the capacitor C22, thereby shortening the charging time. This indicates that the conduction time of the main switching element Q21 is shortened. As a result, the energy stored in the insulating transformer T21 is reduced, whereby the output voltage Vo is lowered and the constant voltage operation is performed. The operation is reversed when the output voltage is low.

  FIG. 3 shows the waveform of each part in the RCC method. Vgs is a control terminal voltage of the main switching element Q21, Vds is a voltage between the current inflow terminal and the current outflow terminal of the main switching element Q21, Id is a current flowing through the main switching element Q21, and VNs is generated in the secondary winding Ns. , Is is a current flowing through the secondary side rectifier diode D22, and VNb is a voltage generated in the auxiliary winding Nb. First, the ON period of the main switching element Q21 will be described. When the voltage is applied to the control terminal by the starting resistor and the potential of Vgs rises, the main switching element Q21 becomes conductive, and Id increases linearly with a positive slope with time, and energy is stored in the insulating transformer T21. The At this time, since the main switching element Q21 is in a conducting state, Vds has a potential of almost zero, and VNs is applied to the secondary side rectifier diode and is reverse-biased, so Is does not flow. At this time, VNb indicates the voltage of the auxiliary winding Nb. When the capacitor is charged and the transistor becomes conductive, the control terminal voltage Vgs of the main switching element Q21 becomes zero and the main switching element Q21 becomes nonconductive, so that Id becomes zero and Vds is equal to the DC input voltage E. A voltage that is twice the winding ratio of the output voltage on the secondary side and a surge voltage are superimposed. At this time, the rectifier diode on the secondary side becomes conductive, and the energy stored in the insulating transformer T21 is transmitted to the secondary side. Is decreases linearly with a negative slope. At this time, a negative voltage is generated in the auxiliary winding, but the main switching element becomes conductive again due to the subsequent decrease in the negative voltage, and the oscillation operation is continued.

  By the above operation, when the device is operating and the load is large, control is performed so as to output a constant voltage with respect to the load fluctuation. At that time, the mode selection terminal provided in the microcontroller IC23 sets the control terminal of the switching element Q23 to LOW. As a result, the switching element Q23 does not become conductive, and the main switching element Q21 is not forced to stop oscillating. On the other hand, when the load is reduced when the device is at rest, the mode selection terminal applies a pulse signal that repeats HI / LOW to the control terminal of the switching element Q23. (Hereinafter referred to as a pulse mode.) During the period when the control terminal of the switching element Q23 is HI, the light-emitting diode on the secondary side of the optocoupler IC21 has a current limited by the resistor R212 regardless of the output of the differential amplifier IC22. Flows. This current is sufficiently larger than that during the operation of the device. When the current is transmitted to the phototransistor on the primary side of the optocoupler IC21, the voltage of the capacitor C22 is instantaneously increased to bring the switching element Q22 into a conductive state, and the main switching element Q21. Is turned off. If this state continues for about 2 to 20 times the oscillation frequency of the self-excited switching power supply, for example, the energy of the insulating transformer T21 is completely released, and the primary side of the self-excited switching power supply is in the same state as before the start-up. Since the load on the secondary side of the switching power supply in this state is small, the output voltage can be maintained almost as it is. When the control terminal of the switching element Q23 returns from HI to LOW, the current of the light emitting diode on the secondary side of the optocoupler IC21 is also almost restored to the previous state. When the voltage drop due to the current of the phototransistor of the optocoupler IC21 due to the resistor R205 is set to be larger than the threshold voltage of the switching element Q22, the switching element Q32 continues to be in a conductive state, and all the current from the starting resistor R201 flows to the switching element Q22. Flows in. Therefore, since the main switching element Q21 cannot be turned on, the self-excited switching power supply continues to be in an oscillation stopped state. As the time passes, as the charge accumulated in the capacitor C23 is consumed by the load, the output voltage on the secondary side also decreases. Along with this, the output voltage of the differential amplifier circuit also rises and the current flowing to the phototransistor side of the optocoupler IC21 decreases. Therefore, when the voltage drop due to the resistor R205 becomes smaller than the threshold voltage of the switching element Q22, the capacitor C21 is activated by the starting resistor R201. Is charged and the main switching element Q21 is turned on, so that the self-excited switching power supply starts to oscillate again. As described above, by repeatedly inputting the HI / LOW signal to the control terminal of the switching element Q23, the number of oscillations per unit time of the self-excited switching power supply can be reduced. Loss can be reduced and higher efficiency can be achieved.

(Operation of input voltage detection circuit)
However, since a time difference occurs in the start-up time from R201 due to fluctuations in the smoothed rectified DC input voltage E input to the switching power supply, a difference occurs in efficiency at light load. Therefore, in order to improve the efficiency, information on the commercial power supply voltage is necessary. Therefore, the commercial power supply voltage is applied by applying the commercial power supply voltage before the diode bridge D23 and the smoothing capacitor C25 to the primary side input terminal of the transformer T22, and performing the peak charge on the secondary side output by the diode D34 and the capacitor C26. A DC output voltage proportional to is generated and input to the microcontroller IC23. The resistor R214 is a discharging resistor with a peak charge voltage. With this circuit, the microcontroller IC 23 can obtain information on the commercial power supply voltage, and can arbitrarily change the oscillation state in accordance with the commercial power supply voltage. In this case, the oscillation state can be changed by increasing the oscillation frequency when the commercial power supply voltage is high, or by increasing the conduction time of the transistor Q23, so that the number of oscillations can be increased compared to when the commercial power supply voltage is low. By reducing the switching loss, the switching loss can be reduced and the efficiency can be improved.

  In order to achieve the above object, according to a first aspect of the present invention, a flyback voltage is peak-charged using a diode and a capacitor, and a voltage corresponding to a commercial power supply voltage is obtained by combining a resistance with a DC output voltage of a switching power supply. Is to provide a circuit for generating

  The second invention according to the present application provides a method for improving the power supply efficiency by using the information on the commercial power supply voltage generated by using the first invention.

  The input voltage detection circuit in the conventional example uses a transformer for commercial power supply voltage detection because it requires electrical insulation. However, as described above, according to the present invention, a transformer for commercial power supply voltage detection is used. Without using it, the input voltage detection circuit can be configured using the output of the transformer used in the switching power supply. Further, the efficiency of the switching power supply device can be improved with an inexpensive configuration by using information from the input voltage detection circuit.

  FIG. 1 is a circuit diagram showing a configuration of a self-excited switching power supply according to the present embodiment. Parts having the same functions as those of the conventional example are given the same sign, and the explanation of the operation is omitted. The difference between this embodiment and the conventional example is in the method of detecting the commercial power supply voltage.

  The operation of the input voltage detection circuit will be described below.

  Although the voltage VNs generated in the secondary winding Ns of the transformer T21 is also described in FIG. 3, when the switching element Q21 is turned on, a voltage of VNs = −E × Ns / Np is generated with respect to the DC input voltage E, and switching is performed. A voltage of Vo is generated when the element Q21 is turned off. Therefore, the cathode terminal of the diode D11 is connected to the beginning of the secondary winding of the transformer T21, the anode terminal is connected to the cathode side of the capacitor C11, and the anode terminal of the capacitor is connected to the reference voltage side of the DC output voltage. As a result, a voltage V1 peak-charged to −E × Ns / Np is generated in the capacitor C11. The voltage V2 = (V1 × R102 + V2 × R101) / (R101 + R102) is synthesized by synthesizing this V1 and Vo, which is the DC output voltage of the switching power supply, with resistors R101 and R102. As a result of this synthesis, information on the commercial power supply voltage converted to a voltage level that can be input is input to P2 of the microcontroller IC23. Further, by appropriately selecting R101 and R102, it becomes possible to arbitrarily adjust the input voltage to the microcontroller IC23.

  In this embodiment, the microcomputer is taken as an example. However, it is not limited to the microcontroller as long as the mode can be selected and the oscillation state of the pulse mode can be changed by detecting the voltage level. Please specify. Further, as a circuit example showing the configuration of the self-excited switching power supply, the MOSFET is used as the main switching element. However, the configuration can be appropriately changed as in the case where the main switching element Q21 is configured from a bipolar transistor, for example. is there. In the embodiment, the reference power source is created by a Zener diode. However, the present invention does not limit the creation method of the reference voltage to this means.

  In addition, information on the commercial power supply voltage is very meaningful in operating the switching power supply more efficiently, but the information on the commercial power supply voltage is not limited to the switching power supply apparatus. For example, in Japanese Patent Registration No. 03240591, information on input voltage is utilized for driving control of a magnetron of an electromagnetic cooker, and it should be noted that the applicable range of the present invention is a wide range of products using a switching power supply.

It is a circuit diagram which shows the structure of the input voltage detection circuit and self-excited switching power supply which concern on the Example of this invention. It is a circuit diagram which shows the structure of the input voltage detection circuit and self-excitation switching power supply which concern on the prior art Example of this invention. It is each part waveform at the time of operation | movement of the self-excited switching power supply which concerns on the prior art and Example of this invention.

Explanation of symbols

D11 Diode constituting the peak charge circuit C11 Capacitor constituting the peak charge circuit R101, R102 Resistors for voltage synthesis

Claims (4)

  A transformer having a primary winding, an auxiliary winding, and a secondary winding, one end of the primary winding of the transformer, and a high potential side of a DC power source generated from a commercial power source are connected, and the primary winding of the transformer Winding current control means for controlling the current flowing in the primary winding of the transformer and smoothing the alternating voltage generated in the secondary winding. A smoothing rectifying means for rectifying, an error detecting means for comparing a DC output voltage of the smoothing rectifying means with a reference voltage, and outputting a voltage corresponding to the difference, a primary side portion and a secondary side portion, and the error detection Transmission means for transmitting the output of the means to the primary side, and control means for controlling conduction interruption of the current flowing through the winding current control means by a feedback signal from the transmission means and a feedback signal from the auxiliary winding. In the input voltage detection circuit of the power supply In addition to the smoothing rectification means, the secondary side has input voltage detection means for generating a negative voltage corresponding to the commercial power supply voltage, and a direct current output voltage from the smoothing rectification means and a direct current output voltage from the input voltage detection means An input voltage detection circuit characterized in that a DC voltage that can be detected by a control circuit on the load side is generated by resistance synthesis.   A transformer having a primary winding, an auxiliary winding, and a secondary winding, one end of the primary winding of the transformer, and a high potential side of a DC power source generated from a commercial power source are connected, and the primary winding of the transformer Winding current control means for controlling the current flowing in the primary winding of the transformer and smoothing the alternating voltage generated in the secondary winding. A smoothing rectifying means for rectifying, an error detecting means for comparing a DC output voltage of the smoothing rectifying means with a reference voltage, and outputting a voltage corresponding to the difference, a primary side portion and a secondary side portion, and the error detection Transmission means for transmitting the output of the means to the primary side, and control means for controlling conduction interruption of the current flowing through the winding current control means by a feedback signal from the transmission means and a feedback signal from the auxiliary winding. In the power supply device to And an input voltage detecting means for generating a negative voltage corresponding to the commercial power supply voltage on the secondary side, and combining the resistance of the DC output voltage from the smoothing rectifying means and the DC output voltage from the input voltage detecting means. A power supply apparatus comprising an input voltage detection circuit, wherein a DC voltage that can be detected by a load-side control circuit is generated. A transformer having a primary winding, an auxiliary winding, and a secondary winding, one end of the primary winding of the transformer, and a high potential side of a DC power source generated from a commercial power source are connected, and the primary winding of the transformer Winding current control means for controlling the current flowing in the primary winding of the transformer and smoothing the alternating voltage generated in the secondary winding. A smoothing rectifying means for rectifying, an error detecting means for comparing a DC output voltage of the smoothing rectifying means with a reference voltage, and outputting a voltage corresponding to the difference, a primary side portion and a secondary side portion, and the error detection Transmission means for transmitting the output of the means to the primary side, control means for controlling conduction interruption of the current flowing through the winding current control means by a feedback signal from the transmission means and a feedback signal from the auxiliary winding, and Separately from the smooth rectification means, the commercial power supply on the secondary side An input voltage detecting means for generating a negative voltage corresponding to the voltage, and a DC output voltage from the smoothing rectifying means and a DC output voltage from the input voltage detecting means are combined by resistance and detected by a control circuit on the load side In a power supply device equipped with an input voltage detection circuit characterized by generating a possible DC voltage,
In the power supply apparatus having the oscillation means for forcibly reducing the output of the error detection means for a time sufficient for the winding current control means to stop, the operation of the oscillation means according to the output from the input voltage detection means A power supply device characterized by changing a state. A transformer having a primary winding, an auxiliary winding, and a secondary winding, one end of the primary winding of the transformer, and a high potential side of a DC power source generated from a commercial power source are connected, and the primary winding of the transformer Winding current control means for controlling the current flowing in the primary winding of the transformer and smoothing the alternating voltage generated in the secondary winding. A smoothing rectifying means for rectifying, an error detecting means for comparing a DC output voltage of the smoothing rectifying means with a reference voltage, and outputting a voltage corresponding to the difference, a primary side portion and a secondary side portion, and the error detection Transmission means for transmitting the output of the means to the primary side, control means for controlling conduction interruption of the current flowing through the winding current control means by a feedback signal from the transmission means and a feedback signal from the auxiliary winding, and Separately from the smooth rectification means, the commercial power supply on the secondary side An input voltage detecting means for generating a negative voltage corresponding to the voltage, and a DC output voltage from the smoothing rectifying means and a DC output voltage from the input voltage detecting means are combined by resistance and detected by a control circuit on the load side In a control method of a power supply device equipped with an input voltage detection circuit, characterized by generating a possible DC voltage,
In the power supply apparatus having the oscillation means for forcibly reducing the output of the error detection means for a time sufficient for the winding current control means to stop, the operation of the oscillation means according to the output from the input voltage detection means A control method of a power supply device, characterized by changing a state.

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