JPH059185U - AC power supply controller - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an AC power supply control device in which radio noise is not generated by eliminating a rising step of a voltage applied to a load. [Structure] A continuous triangular wave signal having a constant frequency and amplitude is generated, and the electric potential of the triangular wave signal is compared with an appropriately adjustable comparison reference electric potential, and during the period of one state of the large or small discrimination signal. The load is energized every time the AC power supply voltage becomes zero. [Effect] Since the waveform of the voltage applied to the load is a combination of the waveforms from the zero potential point to the next zero potential point of the waveform of the AC power supply voltage, no step is generated in the waveform and radio noise is eliminated.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an AC power supply control device for controlling the voltage of an AC power supply used for a heater or the like.

[0002]

[Prior Art]

 An AC power supply control device used for a heater or the like is shown in FIG.

In the figure, 1 is an AC power source, 2 is a load consisting of a heater, 3 is a triac for controlling the phase of the voltage applied to the load 2, and 4 is an SBS for controlling the firing of the triac 3. The variable resistor 5, the fixed resistor 6, and the capacitor 7 form an ignition control circuit, and the charging time constant of the capacitor 7 is adjusted by adjusting the variable resistor 5, and the discharge time by each breakover of SB S4. To the next breakover voltage is adjusted, so that the phase control by the triac 3 is performed. The resistor 8 and the capacitor 9 are elements constituting the snubber circuit, and the diodes 10 and 11 and the resistor 12 are the hysteresis when the ignition phase adjusted by the variable resistor 5 is advanced or delayed. This is a hysteresis reduction circuit for reducing the noise.

[0004]

[Problems to be solved by the device]

 However, in the AC power supply control device described above, there is a problem that radio noise increases because the rising step of the voltage becomes large especially when the phase is delayed.

An object of the present invention is to provide an AC power supply control device which eliminates the rising step of the voltage applied to the load and prevents radio noise from occurring.

[0006]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention appropriately adjusts a triangular wave generator that continuously generates triangular wave signals of constant frequency and amplitude and a comparison reference potential for comparing with the electric potential of the triangular wave signal. And a comparison reference potential generation circuit capable of generating, a discrimination circuit for comparing the value of the triangular wave signal with the comparison reference potential and outputting a discrimination signal of the magnitude thereof, and opening / closing control of the AC power supply with respect to the load. An AC power supply control device is provided which includes a zero voltage switching circuit which is a circuit and conducts to a load each time the AC power supply voltage becomes zero over a period in which the determination signal is one of large and small.

[0007]

[Action]

 According to the present invention, when the comparison reference potential is adjusted, the proportion of each period of the discrimination signal in which the potential of the triangular wave signal is larger than the comparison reference potential and the discrimination signal in which the comparison signal is smaller than the comparison reference potential changes according to the adjustment. The ratio of the period during which the zero-voltage switching circuit is enabled to conduct and the period during which it is inactive changes, and thus the effective voltage applied to the load is controlled. Then, every time the AC power supply voltage becomes zero during the conduction operable period, the AC power supply becomes conductive with respect to the load.

[0008]

【Example】

 FIG. 1 is a circuit diagram of an AC power supply controller showing an embodiment of the present invention.

In the figure, V is an AC power source consisting of a commercial power source, T is an insulating transformer, S is a full-wave rectifier circuit, C1 is a smoothing capacitor, R1 is a current limiting resistor, and ZD is a control DC voltage E. Zener diode for adjusting the voltage, W is a triangular wave generating circuit that receives the voltage E to generate a triangular wave signal Vb, and X is a comparative reference potential generation that generates a comparative reference potential Vre ₂ for comparing the potential of the triangular wave signal Vb. A circuit, Y is a discrimination circuit which compares the value of the triangular wave signal Vb with the comparison reference potential Vre ₂ and outputs the discrimination signal Vc of the magnitude. Z is a zero voltage switching circuit, which controls the opening and closing of the AC power supply V with respect to the load L for each zero voltage based on the discrimination signal Vc. D is a drive circuit for controlling the on / off drive of the zero voltage switching circuit Z according to the discrimination signal Vc.

The triangular wave generation circuit W includes a square wave generation circuit having an operational amplifier A as a main body and an integrating circuit having an operation amplifier B as a main body and integrating the square wave. The potential Vre _{1 obtained} by dividing the voltage E by the resistors R2 and R3 is applied to the inverting input terminal (−) of the operational amplifier A and the non-inverting input terminal (+) of the operational amplifier B, and the potential Vre ₁ is square wave. As the inversion level of the generation circuit, the operational amplifier B outputs a triangular wave signal Vb having a cycle and amplitude determined by the resistors R4, R5, R6 and the capacitor C2. The frequency of the triangular wave signal Vb is set to be significantly smaller than the frequency of the AC power supply V.

The comparison reference potential generation circuit X generates a comparison reference potential Vre _{2 obtained} by dividing the voltage E by the combination of the resistor R7 and the variable resistor VR and the resistor R8, and generates the comparison reference potential Vre ₂ by the variable resistor VR. Adjustment is possible over a range including the amplitude of the triangular wave signal Vb.

The discriminator circuit Y is mainly composed of a comparator C, receives a comparison reference potential Vre ₂ at a non-inverting input terminal (+), and receives a triangular wave signal Vb at an inverting input terminal (−). The output terminal of the determination signal Vc is connected to the voltage E point via the pull-up resistor R9 and to the zero potential point via the pull-down resistor R10. Therefore V b <discrimination signal Vc is high level when the Vre _2, to a low level when the reverse.

The zero-voltage switching circuit Z receives the output voltage of the rectifier circuit S on the (+) side of the control input terminal via the current limiting resistor R11, and the (-) side is connected to the drive circuit D. The AC power supply V is controlled to be conductive with respect to the load L every time the voltage of the AC power supply V becomes zero during the period in which the circuit D energizes the terminals.

The drive circuit D receives the discrimination signal Vc at the base of the transistor TR via the resistor R12, and the zero voltage switching circuit Z can be turned on (ON when the discrimination signal Vc is at a high level). ), And disable (OFF) during low levels.

Next, the control operation with the above configuration will be described. FIG. 3 is a timing chart showing the control operation.

When the AC power supply V is turned on, the triangular wave signal Vb is continuously input to the inverting input terminal (−) of the comparator C. Then, the discrimination signal Vc is kept at a high level for a period in which the potential of the triangular wave signal Vb is lower than the comparison reference potential Vre ₂ adjusted by the variable resistor VR, and the transistor TR is turned on. And make this non-conductive. Therefore, the zero voltage switching circuit Z is ON / OFF drive controlled according to each level (ON) and (OFF) shown together with the discrimination signal Vc in FIG. For example, when the discrimination signal Vc becomes high level at the time t1, the zero voltage switching circuit Z is turned on at t2 and t3 when the AC power supply voltage V becomes 0 during the high level, and the subsequent half cycle is turned on. Become. When the discrimination signal Vc becomes low level at the time point t4, the zero voltage switching circuit Z is turned off at t5, t6, t7, and t8 when the AC power supply voltage V becomes 0 during the low level, and after that, Half cycle is off. Then, t9, t10, ... Are similarly repeated. The effective voltage of the voltage V _L with respect to the load L is determined by the ratio of the ON period and the OFF period.

Here, when the variable resistance VR is adjusted and its resistance value is increased, the comparison reference potential V re ₂ is lowered and the ON period ratio of the zero-voltage switching circuit Z is reduced, so that the effective voltage V _L is reduced. The voltage decreases. When the comparison reference potential Vre ₂ deviates from the triangular wave due to the increase in the resistance value, the effective voltage of the voltage V _L becomes 0. Further, in the opposite operation, the effective voltage of the voltage V _L gradually increases until it reaches the power supply voltage V. The waveform of the voltage V _L is a combination of the waveforms from the zero potential point to the next zero potential point of the waveform of the AC power supply voltage V, so that there is no step in the waveform and radio noise is eliminated.

[0018]

[Effect of the device]

 As described above, according to the present invention, the potential of a continuous triangular wave signal whose frequency and amplitude are constant is compared with an appropriately adjusted comparison reference potential, and the period of one state of the large or small discrimination signal is compared. Since the load is energized every time the AC power supply voltage becomes zero over the period, the ratio of the large and small periods of the determination signal changes according to the adjustment, and the voltage applied to the load is controlled. The voltage waveform is a combination of waveforms from the zero potential point to the next zero potential point of the waveform of the AC power supply voltage, so that there is no step in the waveform and radio noise is eliminated.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an AC power supply controller showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional AC power supply control device.

3 is a timing chart showing a control operation of the AC power supply control device of FIG.

[Explanation of symbols]

V ... AC power supply, W ... Triangular wave generation circuit, X ... Comparison reference potential generation circuit, Y ... Discrimination circuit, D ... Driving circuit, Z ... Zero voltage switching circuit, L ... Load.

Claims (1)

[Claims for utility model registration] 1. A triangular wave generator for continuously generating a triangular wave signal having a constant frequency and amplitude, and a comparison reference potential for comparing with the potential of the triangular wave signal are appropriately adjusted. A comparison reference potential generation circuit that is capable of generating, a determination circuit that compares the value of the triangular wave signal with a comparison reference potential and outputs a determination signal of the magnitude, and a circuit that controls the opening and closing of the AC power supply with respect to the load. An AC power supply control device, comprising: a zero voltage switching circuit that conducts to a load each time the AC power supply voltage becomes zero over a period in which the determination signal is one of large and small.