JPH0127651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage control circuit for a load such as a DC motor, and particularly when the rated value of the commercial power supply voltage differs depending on the region, such as 100V and 200V.
When 200V is input, the voltage is automatically switched from full wave to half wave, so that the average voltage applied to the load is almost the same as when 100V is input, and 100V/200V is applied. The purpose is to enable shared use.

Hereinafter, one embodiment of the present invention will be described based on the drawings. In Figure 1, B is 3 of D ₁ , D ₂ , D ₃
A bridge circuit consisting of two diodes and a switching element SCR1 having a control pole, _C1 is connected to the switching element by a diode _D4 .
The capacitor S that is charged during the cycle of the power supply to which SCR1 is reverse biased is a switching circuit, and this switching circuit S consists of a series circuit of resistors R ₃ and R ₄ , and a control pole of the resistors R ₃ and R ₄ . It consists of a parallel circuit of a switching element SCR2 connected to the connection point via a Zener diode _D5 , which is connected in parallel with a diode _D4 . When the capacitor _C1 is discharged in the reverse power supply cycle described above, a switch operation is performed when the discharge current of the capacitor _C1 reaches a predetermined value. Also, the output terminal of the switching circuit (in Figure 1, the connection point between switching element SCR2 and capacitor _C1 )
The switching element SCR1 is connected via the resistor _R1 .
control poles are connected. L is a load connected to the output terminal of the bridge circuit B, and in this embodiment, it is composed of a smoothing resistor R ₂ , a capacitor C ₂ and a motor M.
It is not limited to. Note that a commercial power source (not shown) is connected between terminals a and b.

In FIG. 2, A represents the relationship between the voltage waveform V _ab applied between terminals a and b in FIG. 1, the current waveform I _c flowing through capacitor _C1 , and the voltage waveform across switching element SCR2. B is the switching element
Voltage waveform V _SCR during full-wave operation of SCR2 and resistance R ₄
The voltage waveform across V _R4 and the Zener diode D ₅
The relationship between the breakdown voltage V _S and the voltage V _R4 ″ across the resistor R ₄ when this device is in half-wave operation
This represents the relationship between V and _S.

In the above configuration, the operation of the automatic full-wave and half-wave switching circuit for commercial power supply according to the present invention will be explained. When the rated value of the commercial power supply voltage is low, such as 100 VAC, the rated voltage V _ab between the terminals a and b is low, as shown in Figure 2 (b), so the voltage across the resistor R ₄ increases. V _R4 does not reach the breakdown voltage V _S of the Zener diode D ₅ and therefore the switching element SCR
2 does not fire. The switching element SCR1 is fired by the current _Ic of the capacitor _C1 , and a full-wave rectified voltage is applied to the load L. In other words, in a power cycle when terminal b is positive, current flows from diode D ₄ to capacitor C ₁ , and
Diode D ₂ for load L → load L → diode
D ₃ and current flows. On the other hand, in a power cycle when terminal a is positive, current flows through capacitor C ₁ → resistor R ₃ → resistor R ₄ and capacitor C ₁ → resistor R ₁ → control pole of switching element SCR1.
turns on (zero voltage switching due to phase-advanced current). Therefore, in the load L, the diode D ₁ →L→
Current flows through SCR1.

Next, if the rated value of the commercial power supply voltage is high, such as 200V AC, the rated voltage V _ab between terminals a and b
is high, the voltage V _R4 across the resistor R ₄ reaches the breakdown voltage V _S of the Zener diode D ₅ as shown in V _R4 ′ in FIG. The current then flows through the Zener diode _D5 and into the gate of the switching element SCR2. This allows the switching element to
SCR2 is ignited, and the voltage across it becomes almost zero (Figure 2C shows that the voltage across resistor _R4 at this time _V
waveform).

Then, the current _Ic flowing through the capacitor _C1 flows through the switching element SCR2, and the current Ic flows through the switching element SCR2.
It does not flow to the control pole of SCR1, and as a result, switching element SCR1 does not fire. Therefore,
No current flows through the load L during a current cycle when the terminal a is positive, whereas current flows through the load L only when the terminal b is a positive power cycle, and a half-wave rectified voltage is applied.

As described above, in this embodiment, the bridge circuit B is composed of three diodes D ₁ , D ₂ , D ₃ and the switching element SCR1 having a control pole;
Capacitor charged on one cycle of power supply
C ₁ and inserted into the discharge path of this capacitor C ₁ ,
and a switching circuit S that performs a switching operation when the discharge current of this capacitor C ₁ reaches a predetermined value in the other cycle, and when the rated value of the commercial power supply voltage is different, for example in an AC 100V area and AC 200V area. When the power supply voltage has a high rated value, it automatically switches from full wave to half wave so that the average voltage supplied to the load L is equal to the voltage with a low rated value.

In the embodiment of the present invention, a thyristor is used as the switching element SCR1, but a triax may also be used. In addition, the switching circuit S
may be any other switching circuit.

As described above, according to the present invention, for example, 200V
Even if the rated value of the commercial power supply voltage is different, such as 100V, if the supplied commercial power is 200V,
Since the voltage applied to the load is automatically switched to half wave, almost the same voltage (on average) as in the case of 100V is applied to the load.
It becomes possible to share 100V/200V commercial power supply.
Furthermore, since it is possible to switch between full-wave and half-wave using capacitors, switching elements, and capacitors commonly used in circuits, the circuit configuration can be made compact and a practical circuit can be provided. Moreover,
Since a bridge circuit is necessary for loads such as DC motors that are converted to direct current, there are few additional parts, and the switching element SCR1 that makes up the bridge is replaced by a capacitor _C1.
Since the switching element SCR1 is triggered by a phase-advanced current, the switching element SCR1 is turned on at the zero phase of the power supply voltage, and as a result, less noise is generated.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram of a full-wave and half-wave automatic switching circuit for a commercial power source showing an embodiment of the present invention, and FIG. 2 is a signal waveform diagram of the main parts of the circuit. B...Bridge circuit, _C1 ...Capacitor, _D1 ,
D ₂ , D ₃ , D ₄ ...diode, SCR1 ... switching element.

Claims (1)

[Claims] 1. A bridge circuit connected to a commercial power source and consisting of three diodes and a first switching element having a control pole, and a bridge circuit connected to the commercial power source to be charged in one cycle of the commercial power source. A series circuit of a diode and a capacitor, and a Zener diode connected in parallel with the diode and causing a second switching element to switch when the discharge current of the capacitor reaches a predetermined value during the other cycle of the commercial power supply. full-wave half-wave automatic switching of a commercial power supply, comprising a switching circuit having a switching circuit and a switching circuit configured to cause the discharge current of the capacitor to flow into the control pole side of the first switching element when the second switching element of the switching circuit is turned off. circuit.