JP3189458B2 - Phase control circuit of electric water heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase control circuit for an electric water heater.

[0002]

2. Description of the Related Art The structure of an electric water heater is shown in FIG. In the figure, a heater 4 and a thermistor 5 are provided in a tank 3 provided between a water supply port 1 and a shower head 2. Then, while detecting the hot water temperature with the thermistor 5, the amount of electricity supplied to the heater 4 is phase-controlled by the controller 7 so that the flowing water is heated so as to reach the temperature set by the volume 6, and the hot water is discharged from the shower head 2. . Next, a conventional phase control circuit for controlling the electric water heater will be described with reference to FIGS.

A power supply circuit 11 generates a DC voltage Vcc from an AC power supply 10 and supplies it to each circuit. Pulse generation circuit 12
Generates a zero-cross pulse synchronized with the AC power supply 10 to drive the discharge unit 14 of the CR charge / discharge circuit 13. During periods other than the zero-cross pulse generation period, since the transistor 15 of the discharging unit 14 is off, the capacitor 17 of the charging unit 16 is charged and the non-inverting input terminal (+) of the comparator 18 which is the output Vs of the CR charging / discharging circuit 13 Potential Vs rises. Then, during the zero-cross pulse generation period, the transistor 15 is turned on, the charge of the capacitor 17 is rapidly discharged, and the potential Vs of the non-inverting input terminal (+) of the comparator 18 becomes almost the emitter potential of the transistor 15. Therefore, the voltage Vs of the non-inverting input terminal (+) of the comparator 18 has a saw-like waveform as shown in FIG.

On the other hand, a DC voltage Vt obtained by amplifying a potential difference between a temperature detecting circuit 19 and a temperature setting circuit 20 by an amplifier circuit 21 is input to an inverting input terminal (−) of the comparator 18. The voltage Vt of the inverting input terminal (-) of the comparator 18 becomes lower as the temperature rises. For example, when the resistance value of the potentiometer 22 is reduced and set to the high temperature side, the voltage Vt of the inverting input terminal (-) of the comparator 18 decreases and approaches 100% conduction. The comparator 18 outputs the output Vs of the CR charge / discharge circuit 13 and the amplifier circuit 2
The output Vt is compared with the output Vt, and when the potential relationship of Vs> Vt is established, Hi is output, the trigger circuit 23 is driven, the triac 24 is turned on, the heater 25 is energized, and the flowing water is heated.
Then, the thermistor 26 of the temperature detection circuit 19 detects a change in the hot water temperature due to a change in the incoming water temperature or the flow rate, and controls the ON phase of the triac 24 to determine the amount of power to the heater 25.
The temperature is controlled to the temperature set by the temperature setting circuit 20.

The diode 27 has an output voltage Vt of the amplifier circuit.
However, in order to make sure that there is a place higher than the output voltage Vs of the CR charge / discharge circuit 13, without the diode 27,
In the zero-cross pulse generation period, Vs is the sum of the VCE (sat) voltage of the transistor 15 and the voltage generated at the resistor 28, and is generated at about 0.3 V. However, since Vt is an operational amplifier output, it falls to the minimum Vcc, and Vt is always Vs
And the output of the comparator 18 becomes Lo, and the triac 2 is required even though 100% current is required.
4 turns off. The diode 27 prevents the triac 24 from being turned off on the 100% conducting side.

[0006]

However, in the configuration described above, the relationship between the output Vs of the CR charge / discharge circuit 13 and the output Vt of the amplifier circuit 21 on the 100% energized side is not shown when the AC power supply 10 is rated. 7, the phase Ta at which the output Vs and the output Vt intersect is close to 0 V of the AC power supply 10, and the heater 25 is almost 100% energized. However, when the AC power supply 10 drops and the power supply circuit 11 does not stabilize, as shown in FIG.
Is a constant voltage element, the voltage Va from the negative DC voltage Vcc is the same as at the rated value of the AC power supply 10, and the output V of the CR charge / discharge circuit 13
s, the output waveform Vs and the output Vt
Becomes significantly distant from 0 V of the AC power supply 10, so that a 100% energized state cannot be obtained.
The predetermined hot water temperature is lost. Of course, if the resistance 29 of the power supply circuit 11 is set to such a small value that stabilization can be obtained even if the AC power supply 10 is lowered, the above-mentioned problem does not occur, but the power consumption of the resistance 29 is reduced this time. In particular, the voltage of the AC power supply 10 in Malaysia or the like becomes 24
In a country where the resistance is as high as 0 V, the power consumption of the resistor 29 becomes extremely large. If the power consumption of the resistor 29 becomes large, the shape of the resistor 29 must be increased, and a heat radiation space is required. It was necessary and costly, and it was very difficult to realize.

The present invention solves the above-mentioned conventional problem. Even if the mounting capacity is small and the AC power supply is reduced, the present invention is not limited to this.
It is an object of the present invention to provide a phase control circuit of an electric water heater that can obtain a sufficient hot water temperature by obtaining a power supply state of 00%.

[0008]

To solve the above-mentioned problems, a phase control circuit of an electric water heater according to the present invention comprises a first power supply circuit for generating a negative DC voltage from an AC power supply, and a first power supply circuit for generating a negative DC voltage. A second power supply circuit for generating a DC voltage by dividing the voltage is constituted, a power supply of the comparator and a discharging unit of the CR charging / discharging circuit are connected to the first power supply circuit, and a charging unit of the amplifying circuit and the CR charging / discharging circuit are connected. Is a phase control circuit connected to the second power supply circuit.

[0009]

According to the present invention, even if the first power supply circuit and the second power supply circuit that generate a negative DC voltage when the AC power supply drops are not stabilized, the minimum charge / discharge circuit of the CR charge / discharge circuit is provided. The voltage difference between the voltage and the lowest value of the output voltage of the amplifier circuit is determined by the voltage generated by the voltage dividing resistor constituting the second power supply circuit, and the voltage generated by the voltage dividing resistor is the load current of the second power supply circuit. Depends on Therefore, when the AC power supply is reduced and the first power supply circuit and the second power supply circuit are not stabilized and are reduced, the load current of the second power supply circuit is reduced and the voltage division constituting the second power supply circuit is reduced. The voltage generated by the resistor also drops. That is, the voltage difference between the lowest voltage of the CR charge / discharge circuit and the lowest value of the output voltage of the amplifier circuit becomes smaller as the AC power supply decreases, and the phase at which the output of the CR charge / discharge circuit and the output of the amplifier circuit intersect is 0 V of the AC power supply. The phase is approached, and therefore, a 100% energized state of the heater can be ensured.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a phase control circuit diagram of an electric water heater.
Is a power supply circuit, 31 is a first power supply circuit, rectified by a diode 32, stepped down by a resistor 33, stabilized by a Zener diode 34, smoothed by a capacitor 35 and output a negative DC voltage Vcc. Numeral 36 denotes a second power supply circuit which reduces the DC voltage Vcc of the first power supply circuit 31 by a voltage dividing resistor 37, stabilizes it by a Zener diode 38, smoothes it by a capacitor 39, and outputs a DC voltage Vdd. Reference numeral 40 denotes a pulse generating circuit which is an AC power source 3
A zero-cross pulse synchronized with 0 is generated. 41 is CR
The charging / discharging circuit is driven by the pulse generating circuit 40, the charging unit 44 is constituted by the resistor 42 and the capacitor 43, and the discharging unit 46 is constituted by the transistor 45, and outputs a voltage Vs having a sawtooth waveform.
A temperature detecting circuit 47 detects the temperature of the hot water with a thermistor 48 and outputs a divided voltage with the resistor 49. Reference numeral 50 denotes a temperature setting circuit for setting the temperature of the hot water with the volume 51 and outputting a divided voltage with the resistor 52. 53, an operational amplifier 54 for performing impedance conversion by an amplifier circuit, an operational amplifier 55 for amplifying, and a resistor 5
6, a resistor 57 and a resistor 58 to amplify the output voltage difference between the temperature detection circuit 47 and the temperature setting circuit 50 to increase the DC voltage Vt.
Is output. A comparator 59 compares the output Vs of the CR charge / discharge circuit 41 with the output Vt of the amplifier circuit 53 and outputs Hi if Vs> Vt. Reference numeral 60 denotes a trigger circuit which outputs a trigger pulse at a phase when the output of the comparator 59 becomes Hi. 6
Reference numeral 1 denotes a triac which is driven by a trigger pulse of the trigger circuit 60. Reference numeral 62 denotes a heater. When the triac 61 is turned on, the AC power supply 30 is supplied to heat the flowing water. And
The power supply of the comparator 59 and the discharging unit 46 of the CR charging / discharging circuit 41 are connected to the first power supply circuit 31, and the amplifying circuit 53 and the charging unit 44 of the CR charging / discharging circuit 41 are connected to the second power supply circuit 36. I have.

The above configuration will be described with reference to the operation explanatory diagram of FIG. The output Vz of the pulse generation circuit 40 that generates a zero-cross pulse synchronized with the AC power supply 30 is
It becomes Hi at 0 V of 0, and drives the discharge unit 46 of the CR charge / discharge circuit 41. The output V of this pulse generation circuit 40
During the period when z is Lo, the capacitor 43 of the charging unit 44 of the CR charge / discharge circuit 41 is charged by a time constant determined by the resistor 42. Then, during the period when the output Vz of the pulse generation circuit 40 is Hi, the transistor 45 is turned on to rapidly discharge the charge of the capacitor 43 through the voltage dividing resistor 37 of the second power supply circuit 36, and the voltage of the output Vs Is output as the sawtooth wave output Vs as the negative DC voltage Vcc potential of the first power supply circuit 31. The amplification circuit 53 amplifies the output voltage difference between the temperature detection circuit 47 and the temperature setting circuit 50 and outputs a DC voltage Vt.
Becomes lower as the resistance value of the second power supply circuit 36 decreases, and the lowest value is the potential of the DC voltage Vdd which is the output of the second power supply circuit 36. Further, even if the resistance value of the volume 51 is constant and the flow rate increases, or the resistance value of the thermistor 48 increases due to a decrease in the incoming water temperature, the DC voltage Vt decreases and the minimum value is the output of the second power supply circuit 36. , Which is the DC voltage Vdd potential.

The comparator 59 outputs the output Vs and the output Vt.
Are compared, and when Vs> Vt, the comparator 59 becomes Hi.
To drive the trigger circuit 60 to output a trigger pulse, and turn on the triac 61 to energize the heater 62. The time when the comparator 59 outputs Hi, that is, the phase is advanced as the output Vt of the amplifier circuit 53 is lower, and the energization amount of the heater 62 is increased to the 100% side. If the amount of electricity supplied to the heater 62 increases, the ability to heat the flowing water increases, and the temperature of the hot water that flows out increases. The maximum energization amount of the heater 62 depends on the minimum value of the output Vs and the minimum value of the output Vt at the time of 0 V of the AC power supply 30, that is, the first power supply circuit 3
1 and the potential difference Vb between the output Vdd of the second power supply circuit 36 and the smaller the potential difference Vb, the greater the maximum energization amount.

Next, a first power supply circuit 31 for generating a negative DC voltage Vcc and a second power supply circuit for generating a negative DC voltage Vdd when the AC power supply 30 drops as shown in FIG. 36 is no longer stabilized, the lowest voltage of the output Vs of the CR charge / discharge circuit 41 and the output Vt of the amplifier 53
Is determined by the voltage generated at the voltage dividing resistor 37 constituting the second power supply circuit 36, and the voltage dividing resistor 37
Is determined by the load current of the second power supply circuit 36. Therefore, when the AC power supply 30 decreases and the first power supply circuit 31 and the second power supply circuit 36 become unstable and decrease, the load current of the second power supply circuit 36 decreases and the second power supply circuit 36 decreases. , The voltage generated by the voltage dividing resistor 37 is also reduced. That is, the voltage difference Vc between the lowest voltage of the output Vs of the CR charge / discharge circuit 41 and the lowest value of the output voltage Vt of the amplifier circuit 53 decreases as the AC power supply 30 decreases, and the phase Tc at which the output Vs and the output Vt intersect is , Near the 0V of the AC power supply 30.

[0014]

As described above, the present invention provides a first power supply circuit for generating a negative DC voltage from an AC power supply and a second power supply circuit for generating a DC voltage by dividing the voltage from the first power supply circuit. The power supply of the comparator and the discharging part of the CR charging / discharging circuit are connected to the first power supply circuit, and the charging part of the amplifying circuit and the CR charging / discharging circuit are connected to the second power supply circuit. Is reduced, the output V of the CR charge / discharge circuit is reduced without reducing the value of the step-down resistor of the first power supply circuit.
The phase at which the minimum value of s and the minimum value of the output Vt of the amplifier circuit has the potential relationship of Vs> Vt can be brought close to the 0 V phase of the AC power supply, the 100% energized state of the heater can be reliably ensured, and sufficient hot water temperature can be obtained. As a result, the power consumption of the resistor that steps down the AC power supply of the first power supply circuit is suppressed, and therefore, the shape of the step-down resistor of the first power supply circuit and the heat radiation space are also reduced, and the mounting capacity is reduced. In addition, it is possible to provide a phase control circuit of an electric water heater that is inexpensive.

[Brief description of the drawings]

FIG. 1 is a phase control circuit diagram of an electric water heater according to one embodiment of the present invention.

FIG. 2 is a first operation explanatory diagram of the circuit.

FIG. 3 is a diagram illustrating a second operation of the circuit.

FIG. 4 is a configuration diagram of an electric water heater.

FIG. 5 is a phase control circuit diagram of a conventional electric water heater.

FIG. 6 is a first operation explanatory diagram of the circuit.

FIG. 7 is a diagram illustrating a second operation of the circuit.

FIG. 8 is a diagram illustrating a third operation of the circuit.

[Explanation of symbols]

 Reference Signs List 30 AC power supply 31 First power supply circuit 36 Second power supply circuit 40 Pulse generation circuit 41 CR charge / discharge circuit 44 Charging unit 46 Discharging unit 47 Temperature detection circuit 50 Temperature setting circuit 53 Amplification circuit 59 Comparator 60 Trigger circuit 61 Triac 62 heater

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 3/00 F24H 1/20 G05D 23/00

Claims (1)

(57) [Claims] 1. A heater for heating water, a triac for supplying AC power to the heater, a first power supply circuit for generating a negative DC voltage from the AC power supply, and a voltage divider for dividing the voltage from the first power supply circuit. A second power supply circuit that generates a DC voltage, a pulse generation circuit that generates a zero cross pulse synchronized with the AC power supply, a charging unit that charges a capacitor when the zero cross pulse is not generated, and the zero cross pulse is generated. A CR charging / discharging circuit that outputs a sawtooth wave, comprising a discharging unit that discharges electric charge to a capacitor when performing
A temperature detection circuit for detecting the temperature of the water heated by the heater; a temperature setting circuit for setting the temperature of the water to be heated by the heater; and an amplifier for amplifying a voltage difference between the temperature detection circuit and the temperature setting circuit. A comparator for comparing outputs of the CR charge / discharge circuit and the amplifier circuit; and a trigger circuit driven by an output from the comparator to output the triac trigger signal, and a power supply for the comparator. And the C
A phase control circuit for an electric water heater, wherein a discharging unit of the R charging / discharging circuit is connected to a first power supply circuit, and a charging unit of the amplification circuit and the CR charging / discharging circuit is connected to the second power supply circuit.