JP7027989B2 - Zero cross point detection method for AC commercial voltage in power supply units, power supply systems, and power supply units - Google Patents

Description

The present invention relates to a power supply unit, a power supply system, and a method for detecting a zero cross point of an AC commercial voltage in a power supply unit.

The power supply device and AC control board of the image forming device are equipped with an AC commercial voltage detection circuit and a zero cross point detection circuit to convey the voltage value and phase of the AC commercial power supply to the system control unit as information necessary for heater fixing control. is doing.

In a substrate for a power supply device for a general image forming apparatus, there is a technique of mounting a detection board of a dedicated circuit for AC commercial voltage detection and zero cross point detection, respectively.

For example, Patent Document 1 discloses a technique of using a photocoupler as an insulating element to secure insulation from an AC commercial power supply and detecting a zero cross point of the AC commercial power supply.

Further, Patent Document 2 discloses a technique of detecting a voltage value of an AC commercial voltage by using a low frequency transformer as an insulating element for ensuring insulation from an AC commercial power supply.

However, in the configuration of Patent Document 1, the accuracy of detecting the zero cross point is poor due to the characteristics of the photocoupler, and even if the specifications of the photocoupler are used properly according to the commercial voltage used, the zero cross point is detected due to the temperature change used. The variation has occurred.

Further, in the AC commercial voltage detection circuit of Patent Document 2, since the transformer used for ensuring insulation is for a large low frequency, the circuit mounting area becomes large.

Therefore, in view of the above circumstances, it is an object of the present invention to provide a power supply device capable of accurately detecting a zero crossing point while downsizing the circuit.

In order to solve the above problems, in one aspect of the present invention,
An isolated flyback AC / DC converter equipped with an active PFC function that converts the AC voltage of the AC commercial power supply to a DC voltage.
An AC coupling section or offset section that extracts a ripple voltage waveform from the DC voltage of the output of the AC / DC converter, and
A half-wave rectifier circuit that is connected to the rear stage of the AC coupling section or offset section to make the ripple voltage waveform half-wave, and a half-wave rectifier circuit that is connected to the rear stage of the half-wave rectifier circuit to generate a binary signal based on the half-wave. With a zero cross point detector with a Schmitt trigger circuit to output ,
In the DC voltage output from the AC / DC converter, a ripple voltage with a frequency twice that of the AC commercial power supply appears as a frequency feature.
The zero cross point detection unit is located at a point that substantially coincides with the zero cross point of the AC voltage of the AC commercial power supply and intersects 0 from the top to the bottom of the phase of the ripple voltage waveform taken out by the AC coupling unit or the offset unit. Based on this, the zero cross point of the AC voltage of the AC commercial power supply is detected.
Provides a power supply.

According to one aspect, in the power supply device, the zero cross point can be detected with high accuracy while miniaturizing the circuit.

The schematic diagram about the structure of the power supply device which concerns on embodiment of this invention. The block diagram of the power supply device which concerns on a comparative example. Explanatory drawing about detection of zero crossing point of AC commercial voltage using the photocoupler of the comparative example. A table showing variations in photocouplers of AC commercial power supply 100V and 200V. The graph which shows the variation in the photocoupler of the AC commercial power supply 100V, 200V corresponding to FIG. The figure explaining the ripple voltage waveform and AC commercial voltage used for the zero crossing point detection of this invention. The figure explaining the detection procedure by the waveform processing of the zero cross point detection of this invention. The figure explaining the time difference between the ripple voltage waveform and AC commercial voltage waveform in zero crossing point detection of this invention. The figure explaining the accuracy of zero crossing point detection of this invention. The figure explaining the peak-to-peak voltage of the ripple voltage included in the DC voltage of the power supply output used for AC commercial voltage detection of this invention. The figure explaining the identification method by the voltage region of AC commercial voltage detection of this invention. The figure explaining the detection procedure by the waveform processing of AC commercial voltage detection of this invention. The circuit diagram which shows the detailed configuration example of the waveform processing circuit of the power supply device of FIG. 1 of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following drawings, the same components may be designated by the same reference numerals and duplicate explanations may be omitted.

<Power supply unit of the present invention>
FIG. 1 is a schematic diagram of a configuration of a power supply device according to an embodiment of the present invention.

In the power supply device 1, AC (Alternating Current) commercial voltage (alternating current) VAC is supplied from the _AC commercial power supply 10, converted into direct current voltage, and DC (Direct Current) voltage (direct current voltage) is supplied to the system control unit 30. Supply. The power supply device 1 and the system control unit 30 function as the power supply system 100.

The power supply device 1 includes a power supply unit 2, an AC coupling unit or an offset unit 3, a zero cross point detection unit 4, and a bipolar peak detection circuit 7. The power supply unit 2 is an isolated flyback converter equipped with an active PFC.

The zero cross point detection unit 4 is composed of a half-wave rectifier circuit 5 and a Schmitt trigger circuit 6. The ambipolar peak detection circuit 7 functions as an AC commercial voltage detection unit.

The AC coupling unit or offset unit 3, the half-wave rectifier circuit 5, the Schmitt trigger circuit 6, and the bipolar peak detection circuit 7 are waveform processing circuits for the power supply unit 2.

The power supply unit (voltage conversion unit) 2 inputs the _AC commercial voltage VAC from the AC commercial power supply 10 to the power supply unit 2, converts it into a DC voltage, and outputs it. The power supply unit 2 is an AC-DC converter, and is provided with a diode bridge 21, an electrolytic capacitor 22, a high frequency transformer 23, a rectifier diode 24, a control IC (Integrated Circuit) 25, and a coil 26. The power supply unit 2 is isolated from the AC commercial voltage by the high frequency transformer 23.

The control IC 25 has a function of generating a switch signal for controlling ON / OFF to the high frequency transformer 23 and a monitoring function for active PFC (Power Factor Correction: power factor improvement circuit).

In the power supply unit 2, the negative side of the input AC commercial voltage waveform is inverted and output to the positive side by the diode bridge 21 in which four diodes are combined, and the entire waveform becomes the voltage on the positive side.

The electrolytic capacitor 22, the high frequency transformer 23, and the rectifier diode 24 in the subsequent stage of the diode bridge 21 of the power supply unit 2 are flyback type DC-DC converters, which are ON / OFF controlled. In the flyback type DC-DC converter, the primary winding and the secondary winding of the high frequency transformer 23 are connected in opposite polarities. In the flyback type DC-DC converter, the input (switch signal) from the control IC 25 stores energy in the primary side of the high frequency transformer 23 during the ON period, and the energy released from the secondary winding during the OFF period of the input. It is rectified by the electrolytic capacitor 22 and the rectifying diode 24 to convert it to direct current.

Further, in the active PFC section composed of the control IC 25 and the coil 26, instead of the normal pulse-shaped current pattern (harmonics) generated only in the peak portion of the AC voltage, the coil 26 is powered during periods other than the peak portion. By accumulating, the current waveform is controlled to be a sine wave. As a result, the generated current waveform (output current) is corrected so as to be in phase and similar to the voltage waveform so as not to include harmonics.

In the power supply unit 2, the DC voltage converted from AC to DC remains ripple (ripple) even if it is smoothed by the electrolytic capacitor 22, and the ripple voltage, which is its amplitude, changes depending on the capacity and load of the electrolytic capacitor 22. do.

The direct current voltage ( _DC voltage) VDC of the output of the power supply unit 2 including the ripple voltage is input to the AC coupling unit or the offset unit 3.

One of the outputs of the AC coupling unit or the offset unit 3 is connected to the bipolar peak detection circuit 7 that detects the bipolar peak.

The ambipolar peak detection circuit 7 is an AC commercial voltage detection unit, which generates an AC commercial voltage signal and outputs it to the system control unit 30.

The other of the outputs of the AC coupling unit or the offset unit 3 is connected to the zero cross point detection unit 4 including the half-wave rectifier circuit 5 and the Schmitt trigger circuit 6. The zero cross point detection unit 4 generates a zero cross point signal using the ripple voltage waveform V _RIP and outputs it to the system control unit 30.

The system control unit 30 includes a power input terminal 31, an AC commercial voltage detection terminal 32, and a zero cross point detection terminal 33. The DC voltage _VDC from the power supply unit 2 is input to the power supply input terminal 31.

The AC commercial voltage detection terminal 32 of the system control unit 3 detects an accurate voltage value of the AC commercial voltage by the AC commercial voltage signal from the ambipolar peak detection circuit 7.

The zero cross point detection terminal 33 detects the phase of the AC commercial voltage by the zero cross point signal from the zero cross point detection unit 4.

<Comparison example>
Here, for comparison with the conventional case, the zero crossing point of the AC commercial power supply and the AC commercial voltage detection in the comparative example will be described with reference to FIGS. 2 to 5.

FIG. 2 is a configuration diagram of a power supply device according to a comparative example. The power supply device 1X of the comparative example shown in FIG. 2 includes a power supply unit 2X, a relay 8 as a waveform processing circuit of the power supply unit 2X, a zero cross point detection unit 4X, and an AC commercial voltage detection unit 9.

The relay 8 receives electric power from the relay power supply 34 of the system control unit 30X, and is controlled by the relay ON / OFF control unit 35 to be turned ON / OFF.

The zero cross point detection unit 4X includes a diode bridge 41, a photocoupler 42, and a synchronous pulse circuit 43.

The AC commercial voltage detection unit 9 includes a low frequency transformer 91, a diode bridge 92, and a detection circuit 93.

In the power supply device 1X of the comparative example, one of the _AC commercial voltage VAC from the AC commercial power supply 10 is connected to the zero cross point detection unit 4X by connecting via the relay 8.

When the _AC commercial voltage VAC is input to the zero cross point detection unit 4X, the voltage is rectified by the diode bridge 41, the voltage is applied to the photocoupler 42, and the photocoupler 42 operates. Then, a zero cross signal is generated by operating the synchronous pulse circuit 43 connected to the secondary side of the photocoupler 42 with a current according to the CTR (Current Transfer Ratio) of the photocoupler 42.

In this comparative example, the AC commercial voltage before the input of the power supply unit 2X is drawn into the zero cross point detection unit 4X. Therefore, a photocoupler 42 is required for insulation of the zero cross point detection unit 4X from the AC commercial power supply 10, and the circuit scale of the zero cross point detection unit 4X becomes large.

Further, in the power supply device 1X, another _AC commercial voltage VAC from the AC commercial power supply 10 is input to the AC commercial voltage detection unit 9 by connecting via the relay 8.

In the AC commercial voltage detection unit 9, the input _AC commercial voltage VAC is stepped down by the low frequency transformer 91. The stepped-down voltage is rectified by the diode bridge 92 and converted into a DC voltage signal by the detection circuit 93. The DC converted signal is converted by the system control unit to calculate the voltage value of the AC commercial voltage.

In the power supply voltage detection method by the AC commercial voltage detection unit 9 of FIG. 2, since the AC commercial voltage is converted into a DC voltage signal for measurement, a transformer 91, a diode bridge 92, and a detection circuit 93 are required. In this comparative example, the AC commercial voltage detection unit 9 is isolated from the AC commercial voltage by the low frequency transformer 91, so that the circuit scale becomes large.

Here, the characteristics of the photocoupler will be described with reference to FIGS. 3 to 5.

FIG. 3 is a diagram illustrating detection of a zero cross point of an AC commercial voltage using a photocoupler.

When the photocoupler detects the zero cross point, the detection circuit including the photocoupler (for example, the zero cross point detection unit 4X) is set so that the zero cross point of the AC commercial voltage is within the low potential holding period as shown in FIG. , A square wave (binary signal) is generated to detect a zero crossing point.

At this time, the detection circuit including the photocoupler has a predetermined time (front time) from the low potential start point (falling time) at which the potential starts in the entire width of the low potential holding period which is the downwardly convex portion of the square wave. The elapsed time is the zero crossing point where the AC commercial voltage actually crosses 0V.

Therefore, the time difference (front) between the low potential start time, which is the falling timing of the square wave, and the zero crossing point where the AC commercial voltage actually crosses 0V becomes the time difference at the zero crossing point at the time of measurement, and the AC commercial voltage. Zero cross will be detected earlier by the amount of the front.

Further, in a normal photocoupler, the CTR (current transmission rate) is distributed from 50% to 600% even in the same component. Therefore, the CTR is specified as follows, for example, depending on the destination (country or region) where the AC commercial power source is different.
100V system: 80% -160%
200V system: 200% -400%

Therefore, in a general power supply configuration that uses a photocoupler for zero cross point detection, in order to reduce fluctuations due to AC commercial voltage VAC and CTR fluctuations due to environmental temperature, photos are taken according to the destination (AC commercial power supply 100V system 200V system). CTR is specified as the characteristic value of the coupler parts and used properly.

Here, the zero cross point in the power supply device of the comparative example shown in FIG. 2 was measured. The zero crossing point detection in the power supply device of the comparative example shown in FIG. 2 will be described with reference to FIGS. 4 and 5.

FIG. 4 is a table showing the variation of the photocoupler. In FIG. 4, (a) shows the variation of the photocoupler of AC commercial power supply 100V, and (b) shows the variation of the photocoupler of AC commercial power supply 200V.

In FIG. 4, the front shows the time difference from the low potential start time to the zero crossing point of the AC commercial voltage, and the total width shows the low potential holding period in the rectangular wave shown in FIG. 3 (b). The unit of the numerical value of the front and the full width is ms. The CTR column in the left column shows the CTR value at room temperature (25 ° C.).

In order to make the distribution of the table easier to understand, Fig. 5 shows an example of comparing the front values on the vertical axis and the _AC commercial voltage VAC (83V, 138V) on the horizontal axis for each variable factor (frequency, environmental temperature, CTR). (A) is shown in FIG. 5 (b). 5 (a) shows a comparison of the front variation of the AC commercial power supply 100 V photocoupler in the table of FIG. 4 (a), and FIG. 5 (b) shows the comparison of the front variation of the AC commercial power supply 200 V photocoupler in the table of FIG. 4 (b). The comparison of the variation of the front of is shown.

From FIGS. 5 (a) and 5 (b), it can be seen that the front surface varies within the range of the thick arrow depending on the temperature.
100V system: 0.077ms ~ 1.13ms
200V system: 0.253ms ~ 1.794ms
In the entire voltage range, 0.077ms to 1.794ms (0.08ms to 1.80ms)

In this way, even if the products are sorted according to the destination (AC commercial power supply 100V system 200V system), as shown in FIGS. 4 and 5, the time difference from the start of the low potential holding period to the zero cross point is the time difference of the front. Time fluctuates greatly.

That is, when a photocoupler is used for zero crossing point detection as in the comparative example, the component characteristics (CTR) change greatly depending on the environmental temperature, and the current flowing through the photocoupler also changes depending on the AC commercial voltage, so that the zero crossing point detection fluctuates greatly. do.

On the other hand, in the present invention, the photocoupler is not used for detecting the zero cross point. The details of the zero cross point of the present invention will be described below.

<Waveform processing of the present invention: AC component of ripple voltage>
FIG. 6 is a diagram illustrating a ripple voltage waveform and an AC commercial voltage used in the zero cross point detection of the present invention.

In the configuration of FIG. 1, the zero cross detection is calculated from the waveform characteristics of the output voltage of the isolated flyback converter 2 equipped with the active PFC.

Since the isolated flyback converter 2 equipped with the active PFC constituting the power supply unit 2 has a small capacity of the electrolytic capacitor 22 and is a flyback type converter, the frequency characteristic of the AC commercial power supply is the direct current output from the power supply unit 2. In the voltage _VDC , it appears as a ripple voltage as it is.

This ripple voltage is used in zero cross point detection. Specifically, in the DC voltage _VDC of the output of the power supply unit 2, a ripple voltage having a frequency twice the frequency (50Hz, 60Hz) of the AC commercial power supply appears as a frequency feature.

Then, when the AC coupling unit or the offset unit 3 performs AC coupling (or DC component offset) from the DC voltage _VDC of the power supply output and extracts only the AC component waveform (ripple voltage), the phase is as shown in FIG. Ripple voltage waveform V _RIP almost coincides with the point where the AC commercial power supply frequency crosses zero at the point where it intersects 0V from top to bottom. This makes it possible to accurately detect the zero crossing point even if the AC commercial voltage or frequency fluctuates.

<Zero cross point detection>
FIG. 7 is a diagram illustrating a detection procedure by waveform processing for zero cross point detection of the present invention.

As a detection procedure, as shown in the figure, the zero cross point is detected in the order of output of power supply unit 2 ⇒ AC coupling (or DC offset) circuit ⇒ half-wave rectifier circuit 5 ⇒ Schmitt trigger circuit 6. The figure on the right shows how to shape the waveform in each circuit.

S1: The power supply unit 2 outputs a _DC voltage waveform VDC including ripples. A ripple voltage, which is an AC component, is superimposed on this DC voltage waveform.

S2: In the AC coupling unit 3, the DC signal component is removed from the _DC voltage waveform VDC containing both the AC (alternating current) component (ripple component) and the DC (direct current) component output from the power supply unit 2 to obtain the AC. Take out the component (ripple voltage V _RIP ). DC voltage waveform of power supply output The _DC component of VDC becomes a voltage offset, and by removing the offset, the resolution of the subsequent measurement can be improved.

S3: In the half-wave rectifier circuit 5, the ripple voltage waveform V _RIP , which is an AC component extracted from the DC voltage waveform V _DC ripple voltage of the power supply output, is cut every half cycle so that the current flows only half a cycle. Ripple.

S4: The Schmitt trigger circuit 6 has two threshold values for the input signal, outputs the potential of logic H when the potential of the input signal exceeds the high threshold value, and conversely, when the potential of the input signal falls below the low threshold value. The potential of logic L is output to. When the input signal is between the low threshold and the high threshold, the immediately preceding output potential is retained. The waveform output by the Schmitt trigger circuit 6 becomes a binary signal (rectangular wave), and the timing of zero cross is detected at the falling portion.

Next, the AC voltage waveform (AC commercial voltage waveform) of the AC commercial power supply and the ripple voltage waveform V _RIP , which is an AC component extracted from the ripple voltage of the _DC voltage waveform VDC of the power supply output, are compared. FIG. 8 is a diagram illustrating a time difference between a ripple voltage waveform and an AC commercial voltage waveform in the zero cross point detection of the present invention.

Specifically, FIG. 8A is a diagram showing a ripple voltage waveform V _RIP and an AC commercial voltage waveform. FIG. 8B is an enlarged view of the ripple voltage waveform V _RIP and the AC commercial voltage waveform near the zero crossing point when the AC commercial power supply 10 is at a low voltage (83V). FIG. 8C is an enlarged view of the ripple voltage waveform V _RIP and the AC commercial voltage waveform near the zero cross point when the AC commercial power supply 10 has a high voltage (276V).

Referring to FIG. 8A, the zero crossing point of the AC commercial voltage waveform almost coincides at the point where the ripple voltage waveform V _RIP intersects 0V from top to bottom.

However, when the time difference is confirmed by the enlarged waveform, the ripple voltage waveform V _RIP is obtained at the low voltage (83V) of the AC commercial power supply shown in FIG. 8 (b) and the high voltage (276V) shown in FIG. 8 (c). There is a time lag in the AC commercial voltage waveform. Comparing FIG. 8 (b) and FIG. 8 (c), the higher the voltage, the larger the time difference.

In the example of FIG. 8, the time difference between the ripple voltage waveform V _RIP and the zero crossing point of the AC commercial voltage is a minimum difference of 0.25 ms (at 83 V) and a maximum difference of 0.63 ms (276 V).

Further, from FIGS. 8 (b) and 8 (c), it can be seen that a time difference occurs so that the zero cross point of the ripple voltage waveform V _RIP is earlier than the zero cross point of the AC commercial voltage waveform.

Next, the zero crossing point detection error of the present invention caused by the above zero crossing point detecting procedure will be described. FIG. 9 is a diagram illustrating the accuracy of zero cross point detection of the present invention.

First, as (1), as shown in FIG. 6, the ripple voltage waveform V _RIP , which is an AC component extracted from the ripple voltage of the _DC voltage waveform VDC of the power supply output, is the original zero crossing point of the AC commercial voltage waveform. Therefore, a time difference occurs in the direction of 0.25ms to 0.63ms earlier.

In addition, (2) due to the characteristics of the threshold value of the Schmitt trigger circuit 6 after half-wave rectification, the time is delayed by 0.2 ms from the zero cross point of the ripple voltage waveform V _RIP which is the input value of the Schmitt trigger circuit 6. This delay time has a small variation in the AC commercial voltage and the environmental temperature, and is a fixed value.

Then, when the system control unit 30 corrects so as to subtract the fixed value (0.2 ms) of (2) from the time difference (error) of (1), an error of (3) difference of 0.05 ms to 0.43 ms occurs.

Here, when the error of the present invention is compared with the error of zero cross point detection using a photocoupler that fluctuates depending on the AC commercial voltage and the ambient temperature, the error of the zero cross point detection of the present invention is smaller than 0.08 ms to 1.80 ms. It turns out that the accuracy is good.

<Detection of AC commercial voltage>
The method of AC commercial voltage detection of the present invention will be described with reference to FIGS. 10 to 12.

FIG. 10 is a diagram illustrating a peak-to-peak voltage of a ripple voltage included in a DC voltage of a power supply output used for AC commercial voltage detection of the present invention.

In the configuration of FIG. 1, AC commercial voltage detection is also calculated from the waveform characteristics of the output voltage of the isolated flyback converter 2 equipped with the active PFC.

In the AC commercial voltage detection unit including the bipolar peak detection circuit 7, the peak toe is the difference (= ripple width) between the maximum value and the minimum value of the ripple voltage included in the DC voltage waveform including the ripple voltage of the power supply unit 2. Use the peak voltage value.

FIG. 11 is a diagram illustrating a method for identifying an AC commercial voltage detection according to the voltage region of the present invention.

As an AC commercial voltage detection method, the output voltage of the isolated flyback converter equipped with an active PFC varies in peak-to-peak voltage value as shown in FIG. 11 according to the voltage region of the AC commercial voltage.

Since the peak-to-peak voltage value is not linear as shown in FIG. 11, the peak-to-peak voltage value is set in advance by the system control unit 30 as to whether to use the 100V system voltage region or the 200V system voltage region of the AC commercial power supply. The AC commercial voltage is identified from the peak voltage detection value.

FIG. 12 is a diagram illustrating a detection procedure by waveform processing for AC commercial voltage detection according to the present invention.

As a detection procedure, from the power supply output in S11 to the AC coupling (or DC component offset) in S12 is the same as the zero cross point detection shown in FIG. 7, but in the AC commercial voltage detection, the AC coupling (offset) is used. Later, the peak-to-peak voltage value is taken out by the bipolar peak detection circuit 7 (S13).

The figure on the right shows how to shape the waveform in each circuit. In FIG. 11, S11 and S12 are common to S1 and S2 in FIG. 7.

S13: The ambipolar peak detection circuit 7 outputs a stable DC voltage value from which the ripple voltage is removed by taking out the peak-to-peak voltage value. For example, the ambipolar peak detection circuit 7 is stable by holding the peak values on the plus side and the minus side of the ripple voltage, calculating the median value, and offsetting the DC component offset in S12 so as to return to the base. Output the DC voltage value.

<Waveform processing circuit of power supply unit>
FIG. 13 is a circuit diagram showing a detailed configuration example of the waveform processing circuit of the power supply device of FIG. 1 of the present invention. The circuit configuration shown in FIG. 13 is an example, and other circuit configurations may be used as long as the waveform processing shown in FIGS. 6 to 11 described above can be achieved for each part.

The AC coupling portion 3 is composed of a capacitor C0 connected in series with respect to the signal.

The half-wave rectifier circuit 5 includes an operational amplifier O1, two diodes D1 and D2, and a resistor R1. A half wave is generated by outputting Vout = 0 when Vin <0 by the operational amplifier O1.

The Schmitt trigger circuit 6 includes two NPN transistors T1, T2 and five resistors R2 to R6. The Schmitt trigger circuit 6 has a history system characteristic when T1 and T2 are turned on and off with respect to the threshold value, respectively.

The ambipolar peak detector consists of four operational amplifiers O2 to O5, two diodes D3 and D4, four capacitors C1 to C4, two switches S1 and S2, and one variable resistance connected operational amplifier O6. The resistors R7 to R16 are provided.

The two operational amplifiers O2 and O3 in the upper stage of the ambipolar peak detection circuit 7, the diode D3, the two capacitors C1 and C2, the switch S1, and the four resistors R7 to R10 are peak hold circuits. Similarly, the lower two operational amplifiers O4 and O5, the diode D4, the two capacitors C3 and C4, the switch S2, and the four resistors R11 to R14 are peak hold circuits.

The variable resistance operational amplifier O6 and the resistance R15 adjust the input offset voltage.

As shown in FIG. 1, the power supply unit 2 has an insulating function by a high-frequency transformer smaller than the low-frequency transformer. As for AC commercial voltage detection, since AC commercial voltage can be detected from the ripple voltage waveform appearing at the output of the power supply device, a low frequency transformer dedicated to AC commercial voltage detection becomes unnecessary, and the waveform is as shown in FIG. A large element is not required in the processing circuit. Therefore, in the present invention, the power supply device including the waveform processing circuit can be miniaturized.

Further, as shown in FIG. 9, in the zero cross point detection of the present invention, an active PFC-equipped isolated flyback converter type power supply device having the frequency and voltage characteristics of an AC commercial power supply can be used without using a photocoupler. By attaching a waveform processing circuit and using the ripple voltage of the DC voltage waveform of the power supply output, the zero cross point can be detected with high accuracy.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and is within the scope of the gist of the embodiment of the present invention described in the claims. Various modifications and changes are possible.

10 AC commercial power supply 1 Power supply unit 2 Power supply unit (insulated flyback converter with active PFC)
3 AC coupling or offset circuit 4 Zero cross point detector 5 Half-wave rectifier circuit 6 Schmitt trigger 7 Bipolar peak detection circuit (AC commercial voltage detector)
30 System power supply 1 Power supply 10 AC commercial power supply 100 Power supply system V _AC AC commercial voltage (AC voltage)
DC voltage (DC voltage) of V _DC power supply output
V _RIP ripple voltage waveform

Japanese Unexamined Patent Publication No. 06-110141 Japanese Unexamined Patent Publication No. 2008-052045

Claims (5)

An isolated flyback AC / DC converter equipped with an active PFC function that converts the AC voltage of the AC commercial power supply to a DC voltage.
An AC coupling section or offset section that extracts a ripple voltage waveform from the DC voltage of the output of the AC / DC converter, and
A half-wave rectifier circuit that is connected to the rear stage of the AC coupling section or offset section to make the ripple voltage waveform half-wave, and a half-wave rectifier circuit that is connected to the rear stage of the half-wave rectifier circuit to generate a binary signal based on the half-wave. With a zero cross point detector with a Schmitt trigger circuit to output ,
In the DC voltage output from the AC / DC converter, a ripple voltage with a frequency twice that of the AC commercial power supply appears as a frequency feature.
The zero cross point detection unit is located at a point that substantially coincides with the zero cross point of the AC voltage of the AC commercial power supply and intersects 0 from the top to the bottom of the phase of the ripple voltage waveform taken out by the AC coupling unit or the offset unit. Based on this, the zero cross point of the AC voltage of the AC commercial power supply is detected.
Power supply. The power supply device according to claim 1, further comprising an AC commercial voltage detection unit that detects the peak-to-peak voltage of the ripple voltage waveform in the subsequent stage of the AC coupling unit or the offset unit. The AC / DC converter is
An isolated flyback AC / DC converter with a diode bridge, capacitor, high frequency transformer, and rectifying diode,
The power supply device according to claim 1 or 2, comprising an active PFC unit including a coil and a control IC. The power supply device according to any one of claims 1 to 3.
A system control unit connected to the power supply device is provided.
In the system control unit, the point where the phase of the ripple voltage waveform taken out by the AC coupling unit or the offset unit intersects 0 from top to bottom is earlier than the original zero crossing point of the AC voltage of the AC commercial power supply. The time difference is corrected by subtracting the fixed value of the delay due to the characteristic of the threshold of the Schmitt trigger circuit.
Power system. A method for detecting the zero crossing point of AC commercial voltage in a power supply unit.
A step of converting the AC voltage of an AC commercial power supply into a DC voltage while insulating it with an isolated flyback AC / DC converter equipped with an active PFC function.
A step of extracting a ripple voltage waveform from the DC voltage of the output of the AC / DC converter by the AC coupling unit or the offset unit.
The step of making the ripple voltage waveform half-wave by the half-wave rectifier circuit,
It has a step of detecting a zero crossing point by outputting a binary signal based on the half wave by a Schmitt trigger circuit.
In the DC voltage output in the step of converting to the DC voltage, a ripple voltage having a frequency twice that of the AC commercial power supply appears as a frequency feature.
In the step of detecting the zero cross point, 0 intersects from the top to the bottom of the phase of the ripple voltage waveform taken out by the AC coupling portion or the offset portion, which substantially matches the zero cross point of the AC voltage of the AC commercial power supply. Based on the point, the zero cross point of the AC voltage of the AC commercial power supply is detected.
Zero cross point detection method for AC commercial voltage in a power supply.

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