JPS63307513A - Power detector for ac phase control power - Google Patents

Abstract

PURPOSE:To avoid the influence of the ambient temperatures that is given to the arithmetic result and also to reduce the error of a power detector, by applying only the digital operations to obtain the effective electric power. CONSTITUTION:An energizing angle computing element 9 detects a time point when the input voltage A1 of an AC phase control power supply is set at zero as well as the energizing time of the output voltage A2 and calculating digitally an energizing angle based on said time point and energizing time. An average current value arithmetic unit 7 detects digitally the average value of the current flowing to a load from the output of a current transformer CT connected to a line A3 led toward the load. Then an effective power arithmetic unit 11 calculates digitally the effective value of the electric power supplied to the load based on the outputs of the element 9 and the unit 7. A ROM of 512k bits is used to both the element 9 and the unit 11 respectively. Thus these calculations receive no influence of temperatures owing to the ROM structure and the calculation speed is satisfactorily high together with an extremely reduced calculation error.

Description

[Detailed Description of the Invention] (Industrial Application Field) - The present invention is useful, for example, when a semiconductor processing device uses an AC phase controlled power supply and a lamp heater to heat a semiconductor substrate at a strictly constant temperature. This invention relates to the configuration of a digital power detector used for precise power detection in a power control system or the like when supplying constant power to a load.

(Prior Art) As mentioned above, power detectors are particularly important when setting a target power value and controlling the output power of an AC phase controlled power supply to match the target value. As shown in Fig. 2, the detection of the power of
A device 31 that detects the effective value of the voltage sent from 0 to the load 34 in an analog manner, a device 32 that detects the effective value of the current by approximately 1 analog, and the outputs of both devices are multiplied in an analog manner to calculate the electric power. Method 7 (Problems to be Solved by the Invention) Method 7 (Problems to be Solved by the Invention) In the above-mentioned analog method for calculating the effective value power, the characteristics of the log amplifier used in the calculation are easily changed depending on the ambient temperature. This has the disadvantage that it fluctuates greatly, causing errors in the calculation results.

Further, since all calculations for determining the effective value of power are performed in an analog manner, errors are accumulated in the calculations until determining the final effective value of power, resulting in a problem that the errors become extremely large.

<Objective of the Invention> The object of the present invention is to provide a power detector that can accurately detect AC phase-controlled power without causing a difference in calculation results depending on the ambient temperature, and with extremely few errors. .

(Means for Solving the Problems) This invention uses a power detector for AC phase controlled power to detect the time of the zero point of the input terminal of the AC phase controlled power source and the conduction time of the output voltage. A device that digitally calculates and outputs the conduction angle, a current average value calculation device that digitally detects and outputs the average value of the current flowing to the load from the output of a current transformer connected to the line toward the load, and both of these devices. The above object is achieved by a power detector equipped with an effective power calculation device that digitally calculates the effective value of the power supplied to the load based on the output of the device.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of a power detector according to an embodiment of the present invention, in which a commercial AC voltage A1 manually applied to an AC phase controlled power source (not shown) such as a thyristor power source is input to a zero point detector 1. Then, at the timing of the zero point of that wave, SET, R
A control pulse for ESET (details of its operation will be described later) is output on line 301.

On the other hand, the output voltage A2 from the AC phase controlled power source is amplified by the waveform amplifier 2, and the detected distribution is manually input to the device 4, where the rise and fall of the wave, that is, the OFF timing and ON timing, are detected. The pulse of O
The allocated amount is output to line 401 and line 402 toward FF counter 5 and ON counter 6.

Counters 5 and 6 are on lines 301, 401.40
The human power pulses from 2 are counted in a minimum time unit of 0.1 ms, and both the OFF time and ON time are converted into 8-bit numbers and output to lines 501 and 601.

Now, in the conduction angle calculator 9, the "conduction angle" calculated in advance from the OFF time and ON time of the phase control for the sine wave is digitized in 8 bits with a minimum angle unit of 0.72°. It is stored in a 512kbit ROM (read-only memory), and the line 501,
The total 16-bit count number 11α input via 601 is used as is as the address of the ROM,
The stored conduction angle is recalled and this 8-bit value is output on line 901.

On the other hand, in the current average value calculator 7, the average value of the current is converted into an analog voltage value (0,0 I
V10.1A) and output to line 701, which is digitized by A/D converter 10 and sent to line 101 as an 8-bit numerical value. 8 uses clocks of 100kHz and 20kHz.

On the other hand, in the power effective value calculator 11, the effective value of power in the case of a resistive load is calculated in advance based on the relationship between the conduction angle and the average value of current, and the result is calculated as a 512 kbit RMS value.
The total 16-bit value stored in the OM and input via lines 901 and 101 is used here as is as an address, and the ROM is accessed to determine the effective value of the power in the minimum unit of 10W. It is output on line 111 as a digital value.

In the data latch 12, the output of this line 111 is held until the next sampling time, and is sent out to the line 121 only after receiving the line 301 pulse.

Reference numeral 13 is a D/A converter, and at the same time as the D/8 conversion is performed, the corrector 14
(for example, when the commercial AC voltage A1 fluctuates, the output value is corrected by product calculation).

The target analog effective value power (-0, OIV/10W) detected by this power detector is output to line 130. However, if digital output is required, D/A conversion is excluded.

As described above, in this embodiment, the effective value power is detected digitally.

Generally, in a digital power detector for AC phase controlled power, calculation of conduction angle and calculation of effective value power are extremely complicated, but in this embodiment, these are completely stored in ROM in advance.
The calculation is not affected by temperature, the calculation speed is sufficiently fast, and the calculation error is extremely small.

Note that it is clear that the above-mentioned ROM can be replaced with an rCPU and a calculation program.

(Effects of the Invention) The present invention has the effect of providing a power detector for AC phase controlled power that does not cause a difference in calculation results depending on the ambient temperature and has extremely small errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a power detector according to an embodiment of the present invention. FIG. 2 is a similar conventional diagram. 1...Zero point detector, 2...Waveform amplifier, 3...Control pulse generator, 4...Detection allocation device, δ... ...OFF counter, 6.
...ON counter, 7...Current average value calculator, 8...Clock, 9...Continuity angle calculator, 10...A /D converter, 11...
...Power effective value calculator, 12...Data latch, 13...D/A converter, 14...
・Corrector.

Claims (1)

[Claims] (1) In a power detector for AC phase control power,
A device that detects the zero point time of the input voltage and the conduction time of the output voltage of the AC phase control power supply and digitally calculates and outputs the conduction angle based on these, and a current transformer connected to the line leading to the load. A current average value calculation device that digitally detects and outputs the average value of the current flowing from the output to the load, and an effective power that digitally calculates the effective value of the power supplied to the load based on the outputs of both devices. A power detector for AC phase controlled power, characterized by comprising a calculation device.