JP3239338B2 - Ripple noise voltage measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a ripple noise voltage superimposed on an output voltage of a switching power supply.

[0002]

2. Description of the Related Art In general, a switching power supply device used as a DC power supply for various electronic devices drives and controls a switching element by an oscillation pulse of a pulse oscillator built in the power supply. The switching noise and the ripple voltage of the switching frequency are superimposed. Such amounts of switching noise and ripple voltage are important factors for indicating the performance of the switching power supply device, and accurate measurement thereof is indispensable.

FIG. 3 shows a waveform of an AC component included in an output voltage of the switching power supply. The period T1 of the switching fundamental wave is equal to the switching frequency of the switching element in the power supply, and the voltage VRN from the uppermost end to the lowermost end of the waveform is called a ripple noise voltage. The voltage VR is called a ripple voltage. Among them, a ripple voltage measuring device for measuring a ripple voltage VR is disclosed in Japanese Patent Application Laid-Open No. 61-22166.
It is disclosed in Japanese Patent Publication No. 2 and the like. This measuring device
An integrator composed of an operational amplifier, an integrating circuit of a resistor and a capacitor, and a voltage comparator for comparing an output voltage of the integrator with a measured input voltage, and appropriately adjusting a time constant of the resistor and the capacitor. By doing
When the output voltage of the integrator is lower than the input voltage to be measured, a negative current flows into the input terminal of the operational amplifier, and when the output voltage of the integrator is higher than the input voltage to be measured, the input terminal of the operational amplifier A positive current flows into the switching fundamental wave, and the integral output voltage value from the integrator is proportional to the duration of the negative current and the positive current. The ripple voltage VR having the peak at the intersection A is measured.

[0004]

The measuring device of the prior art can measure the ripple voltage VR contained in the output voltage of the switching power supply almost accurately, but as shown in FIG. When measuring VRN, the period T of the spike pulse to be measured
2 is much shorter than the period T1 of the switching fundamental wave, and the period T2 of this spike-shaped pulse is greatly different depending on each switching power supply. Therefore, the time constant of the fixed resistor and capacitor is: The period T2 within a range where the ripple noise voltage VRN can be accurately measured is limited, and there has been a problem that the reliability of the measurement is extremely poor.

On the other hand, for example, Japanese Patent Laid-Open No. 58-171676
The gazette states that power or impulse voltage in signal transmission circuits
As a device for measuring the amplitude of
The impulse voltage is extracted from the
To compare with the reference voltage,
Store in the memory circuit and display the state of the memory circuit Show
An impulse voltage measuring device to output to a circuit is disclosed
I have. Here, the impulse voltage is repeatedly input.
The reference voltage, for example,
By using a method such as viewing the output of the display circuit,
It is also disclosed that the impulse voltage amplitude can be measured.
You.

However, in such a configuration, the input voltage
Timing when included impulse voltage exceeds reference voltage
To detect the presence of a pulse immediately.
To the switching fundamental of the switching power supply
Measuring the spike-like ripple noise voltage
Considers a pulse that is sporadically mixed as a ripple noise voltage.
There is a risk of malfunction due to interruption. In addition, the input voltage
If the period of the pulse mixed into the
Cannot be measured accurately, which reduces the reliability of the device.
There is a fear.

Therefore, the present invention solves the above-mentioned problems and enables accurate measurement without being affected by the period of the spike-like pulse of the input voltage to be measured.
It is an object of the present invention to provide a ripple noise voltage measuring device which does not malfunction even when a pulse is output spontaneously .

[0008]

SUMMARY OF THE INVENTION The present invention provides a switching power supply.
Spikes synchronized with the switching fundamental of the
Ripple noise voltage measurement device for measuring ripple noise voltage
In location, a reference voltage generating circuit for outputting a different level of the reference voltage, the reference voltage is the ripple noise voltage
When the peak value becomes lower than the
A voltage output that outputs a pulse-like detection signal for each period of the fundamental wave
Comparator and the detection signal of this voltage comparator
Switch the voltage level of the divided signal when the number of pulses is output
And the voltage level of the divided signal is switched.
Until the above, the voltage level of the reference voltage is sequentially changed every predetermined time.
Outputting a control signal to be changed to the reference voltage generation circuit,
When the voltage level of the divided signal is switched, the reference voltage
And the voltage level of the ripple noise voltage
And a control circuit for reading the data.

[0009]

According to the above configuration, the power of the frequency- divided signal from the frequency divider is transmitted.
Until the voltage level is switched, the control circuit outputs a control signal to the reference voltage generating circuit so that the voltage level of the reference voltage sequentially changes at predetermined time intervals. Be compared .
At this time, when the reference voltage reaches the peak value of the input voltage to be measured , a pulse-like detection signal is repeatedly output for each cycle of the switching fundamental wave.
For the first time when the detection signal of the
Switch the voltage level of the divided signal and the voltage level of the reference voltage
Is read as the voltage level of the ripple noise voltage. This
Thus, ripple noise synchronized with the switching fundamental
Uses voltage to divide signals that are slower than the operating speed of the control circuit.
Signal, the lip included in the measured input voltage is
Calculates peak value of noise voltage accurately and with high reliability
Process, and a single pulse is generated from the detection signal.
The control circuit does not malfunction even if it is input.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a switching power supply having a built-in pulse oscillator.
More predetermined DC voltage is output. Reference numerals 3 and 3A denote input terminals connected to the output terminals 2 and 2A of the switching power supply 1, and a positive input terminal 3 is connected to a voltage comparator 5 serving as a voltage comparator through a filter circuit 4 that cuts off a DC component.
And the non-inverting input terminal of the voltage comparator 5A, while the negative input terminal 3A is grounded. The reference voltages VSTEP1 and VSTEP2 from the reference voltage generation circuit 6 are supplied to the non-inverting input terminal of the voltage comparator 5 and the inverting input terminal of the voltage comparator 5A, respectively. The reference voltage generating circuit 6 is composed of a DA converter, an operational amplifier, etc., converts the control signal VS from the control circuit 7 into an analog signal, and based on the analog signal, changes the reference voltage of a different level at predetermined time intervals. VSTEP1,
VSTEP2 is output. At this time, the reference voltage V
STEP1 and reference voltage VSTEP2 are inverted and output.

Between the output terminals of the voltage comparators 5 and 5A and the control circuit 7, flip-flops 8 and 9 having a frequency dividing function and flip-flops having an output holding function are provided.
The frequency dividing circuits 11 constituted by 10 are connected respectively.
The frequency divider 11 connects the output terminals of the voltage comparators 5 and 5A to the input terminal CK of the flip-flop 8, and connects the input terminal D and the output terminal 12 of the flip-flop 8 to the input terminal CK of the flip-flop 9. In addition, the input terminal D and the output terminal 13 of the flip-flop 9 are connected to the input terminal CK of the flip-flop 10, and a predetermined operating voltage VCC is supplied to the input terminal D of the flip-flop 10. Then, the voltage comparators 5 and 5A compare the reference voltages VSTEP1 and VSTEP2 with the measured input voltage VIN applied through the filter circuit 4, and detect signals VD1 and VD2 based on the comparison result. , The frequency-divided signals VB1 and VB2 are output from the output terminal 14 of the flip-flop 10 to the control circuit 7. The control circuit 7 is composed of well-known elements such as a ROM, a RAM, and a CPU, and has reference voltages VSTEP1, VSS according to a predetermined program.
A control signal VS for switching the level of TEP2 at predetermined time intervals is output to the reference voltage generating circuit 6, and the detection signal VD is output by the frequency-divided signals VB1 and VB2 output from the frequency-divider circuit 11.
It is determined whether or not VD2 has been output for a predetermined number of pulses, and the value of the ripple noise voltage VRN included in the measured input voltage VIN is displayed on the display circuit 15 based on the determination result. The operating speed of each element in this device is 6 nSec at maximum for the voltage comparators 5 and 5A, 5 nSec at maximum for the frequency dividing circuit 11, and the CPU included in the control circuit 7.
Is 25 nSec, the oscillation frequency of the switching power supply 1 is 100 MHz at the maximum, and the cycle T1 of the switching fundamental wave is 10 nSec at the minimum.

Next, the operation of the above configuration will be described.

When the switching power supply 1 is started and a DC voltage is output from the output terminals 2 and 2A to the input terminals 3 and 3A, the DC component is cut off by the filter circuit 4, and as shown in FIG. Input voltage under measurement VIN of AC component including ripple noise voltage VRN and ripple voltage VR
Is applied to the inverting input terminal of the voltage comparator 5 and the non-inverting input terminal of the voltage comparator 5A. On the other hand, the reference voltages VSTEP1 and VSTEP2 are output from the reference voltage generating circuit 6 while switching their voltage levels at predetermined time intervals based on the control signal VS of the control circuit 7, and the voltage comparators 5 and 5A output the measured input voltage VIN Is compared.

FIG. 2 shows operation waveforms of various parts on the voltage comparator 5 side. The control circuit 7 is always a frequency dividing circuit
11 divided signals VB1 and VB2 are read. When these divided signals VB1 and VB2 are at the H level, the reference voltage VSTEP1
Is output to the reference voltage generation circuit 6 so that the voltage level of the control signal Vs gradually decreases every TS = 3 mSec. When the voltage level of the reference voltage VSTEP1 drops and becomes lower than the voltage of the measured input voltage VIN, the detection signal VD1 from the output terminal of the voltage comparator 5 goes low. At this time, the reference voltage VSTEP1 is changed to the measured input voltage VIN.
Is lower than the peak value of the ripple noise voltage VRN, the state where the detection signal VD1 becomes L level in the cycle T1 of the next switching fundamental wave is reproduced, and the detection signal VD1
Is 10nSec, which is the period T1 of the switching fundamental wave.
Each time, an L level pulse wave is repeatedly output.

On the other hand, in the frequency dividing circuit 11, every time the detection signal VD1 falls from the H level to the L level, the flip-flop 8 switches the voltage level of the output signal VE from the output terminal 12 and switches the output signal VE. Each time VE rises from the L level to the H level, the flip-flop 9 switches the voltage level of the output signal VF from the output terminal 13, and when the output signal VF rises from the L level to the H level. Since the input terminal D of the signal 10 is always at the H level, the frequency-divided signal VB1 from the output terminal 14 switches from the H level, and is thereafter held at the L level. That is, the pulse of the detection signal VD1 in a state where the ripple noise voltage VRN of the input voltage under measurement VIN is detected is much shorter than 25 nSec, which is the operation speed of the control circuit 7, and the control circuit 7 converts each pulse of the detection signal VD1 individually. , The frequency of the detection signal V
D1 is divided by 4 into a period slower than the operation speed of the control circuit 7,
Only when four pulses of this detection signal VD1 are output, the frequency-divided signal VB1 is switched from H level to L level and supplied to the control circuit 7. When the control circuit 7 detects that the voltage level of the frequency-divided signal VB1 has changed, it immediately sends the reference voltage VSTEP to the reference voltage generation circuit 6.
In addition to outputting the control signal VS for stopping the switching of the voltage level of 1, the voltage level of the reference voltage VSTEP1 at this time is read as the voltage level at the upper end of the ripple noise voltage VRN included in the measured input voltage VIN. By the same control, the voltage level of the reference voltage VS TE P2 is sequentially increased at predetermined time intervals, and the voltage level at the lower end of the ripple noise voltage VRN is read on the voltage comparator 5A side, and the upper end of the ripple noise voltage VRN is read. By calculating the difference between the voltage level at the lower end and the control circuit 7, the measured value of the ripple noise voltage VRN of the switching power supply 1 can be displayed on the display circuit 15.

As described above, in the above embodiment, the measured input voltage VIN is simply compared with the reference voltages VSTEP1 and VSTEP2 by the voltage comparators 5 and 5A, and the pulse signals of the detection signals VD1 and VD2 output based on the comparison result. Is divided by the frequency dividing circuit 11 so that the control circuit 7 can determine it. Therefore, even when different types of switching power supply devices 1 are measured, the period T2 of the spike-like pulse included in the input voltage VIN to be measured is The control circuit 7 can accurately and highly reliably calculate the peak value of the ripple noise voltage VRN included in the measured input voltage VIN without being influenced by the influence.

Moreover, the control circuit 7 detects the detection signals VD1, VD2
When four pulses are output, the measured input voltage V
In order to read the voltage level of the ripple noise voltage VRN included in IN, for example, even if noise is mixed in the input voltage to be measured VIN and a pulse is output sporadically from the detection signals VD1 and VD2, the control circuit 7 operates. No malfunction occurs, and the reliability of the device can be significantly improved.

[0018] That is, the frequency division signal VB1 from the frequency division circuit 11 is
Until the voltage level is switched, the control circuit 7 outputs the reference voltage V
STEP1 so that the voltage level changes sequentially every predetermined time
When the control signal VS is output to the reference voltage generation circuit 6,
The reference voltage VSTEP1 and the measured input voltage VIN
The comparison is performed by the comparator 5. At this time,
When the voltage VSTEP1 reaches the peak value of the measured input voltage VIN
A pulse-like detection signal VD1 for each period of the switching fundamental wave
Are output repeatedly, and this voltage comparator
When the detection signal VD1 of the data 5 is output for a predetermined number of pulses,
For the first time, the voltage level of the frequency-divided signal VB1 is switched and the reference voltage V
Change the voltage level of STEP1 to the ripple noise voltage VRN.
Read as bell. Thus, the switching fundamental wave
Control circuit using synchronized ripple noise voltage VRN
7 to supply a frequency-divided signal VB1 slower than the operation speed
And the ripple noise voltage included in the measured input voltage VIN
VRN peak value can be calculated accurately and with high reliability
And a single pulse is output from the detection signal VD1.
In this case, the control circuit 7 does not malfunction.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. For example, in order to improve the stability of the device, the number of pulses of the detection signal determined by the control circuit may be further increased. In order to measure the value of the ripple noise voltage more accurately, the switching of the reference voltage value may be further finely controlled by a control signal from the control circuit. It can also be used to measure periodic noise voltage.

[0020]

According to the present invention, the switching power supply device
Spike-like ripple noise power synchronized with the fundamental
In a ripple noise voltage measuring device for measuring pressure, a reference voltage generating circuit for outputting reference voltages of different levels,
The reference voltage is higher than the peak value of the ripple noise voltage.
Also becomes lower, every cycle of the switching fundamental wave
A voltage comparator that outputs a pulse-like detection signal to the
The detection signal of this voltage comparator outputs a predetermined number of pulses.
Frequency divider for switching the voltage level of the divided signal when it is
Until the voltage level of the frequency-divided signal is switched.
A system for sequentially changing the voltage level of the reference voltage every predetermined time
Output the control signal to the reference voltage generating circuit, and
Is switched, the voltage level of the reference voltage
Is read as the voltage level of the ripple noise voltage.
Is obtained by and a control circuit, without being influenced by the period of the spike pulse of the measured input voltage, it is possible to make accurate measurements, moreover sporadically out pulse
It is possible to provide a ripple noise voltage measuring device which does not cause a malfunction even when it is input .

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart of each part of the above.

FIG. 3 is a waveform diagram showing an output voltage of a switching power supply.

FIG. 4 is a partially enlarged waveform diagram of FIG. 3;

[Explanation of symbols]

 4,5 Voltage comparator 6 Reference voltage generation circuit 7 Control circuit 11 Divider circuit

Continuation of the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 19/00-19/32 G01R 29/00 G01R 31/00

Claims (1)

(57) [Claims] 1. A switching base of a switching power supply device.
Measures spike-shaped ripple noise voltage synchronized with the main wave
In Ripple noise voltage measuring device for a reference voltage generating circuit for outputting a different level of the reference voltage, the reference
Voltage is lower than the peak value of the ripple noise voltage.
In this case, a pulse is generated every period of the switching fundamental wave.
A voltage comparator that outputs a detection signal
When a predetermined number of pulses are output from the comparator detection signal
A frequency divider for switching the voltage level of the frequency-divided signal;
Until the voltage level of the frequency signal changes, the reference voltage
A control signal for sequentially changing the voltage level every predetermined time
Output to the reference voltage generation circuit, and outputs the voltage level of the divided signal.
Is switched, the voltage level of the reference voltage is reset to the reset level.
A ripple noise voltage measuring device, comprising: a control circuit for reading as a voltage level of a pull noise voltage.