JPS631588Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a starting circuit for a switching regulator, which uses an N-gate thyristor, has low power loss, can be easily configured, and has good regulation characteristics. The purpose is to provide a starting circuit.

FIG. 1 shows a circuit diagram of an example of a conventional switching regulator. At startup, when a DC power supply voltage is applied to terminal 1, the startup transistor Q ₄ is turned on and the pulse width modulator IC ₁ is connected via resistors R ₁₉ and R ₂₀ .
Power supply voltage is applied to. As a result, a rectangular wave pulse with a certain pulse width is extracted from the pulse width modulator IC ₁ , and at the same time as the transistor Q ₆ is switched, the rectangular wave pulse is applied to the switching transistor Q ₅ via the drive transformer T ₄ . , transistor _Q5 is switched. Due to the operation of the transistor _Q5 , the output coil _L1 provided on the secondary side of the switching transformer _T3 ,
Electromotive force is generated in the drive transistor power supply coil L ₂ and the pulse width modulator power supply coil L ₃ .

Turning on transistor Q ₄ causes resistor R ₁₃ and resistor
The potential at the dividing point g with R ₁₅ is the Zener diode D _Z
When the Zener voltage is exceeded, transistor Q ₃ is turned on and transistor Q ₄ is turned off.
Thereafter, the transistor _Q6 uses the potential at point f, which is obtained by rectifying and smoothing the electromotive force generated in the coil _L2 , and the pulse width modulator _IC1 uses the potential at point e, which is obtained by rectifying and smoothing the electromotive force generated in the coil _L3 , as a power source. It is operated as.

The output detection voltage (potential at point d) is the pulse width modulator
The voltage applied to IC ₁ is compared with a reference voltage in error amplifier 2a to generate an error voltage, and the pulse width modulator 2c, which is supplied with the signal from oscillator 2b, generates a rectangular wave pulse according to the magnitude of the error voltage. It is taken out. The opening and closing periods of the transistors Q ₆ and Q ₅ are controlled in accordance with the H level period and the L level period of this rectangular wave pulse, and the output terminals 3 a and 3 are controlled by the operation of a well-known switching regulator.
The output voltage taken out from b is controlled to be constant.

However, according to this conventional circuit, the secondary coil of the switching transformer T ₃ is the output coil L ₁
In order to insulate the power supply coils L ₂ and L ₃ from each other, the transformer T ₃ is made large, and the power supply coils L 2 and L ₃ are each made up of separate coils. Since it takes a certain amount of time, power loss occurs in the transistor _Q4 , and there are also disadvantages such as a large number of parts.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to FIG. 2.

2 and 3 respectively show a circuit diagram and a schematic circuit system diagram of an embodiment of the switching regulator starting circuit according to the present invention, and in each figure, the same components are denoted by the same numbers and symbols. Attach. In the figure, 4 is an N-gate thyristor (programmable/UJT)
Its anode A is connected to the connection point between resistor R ₁ and capacitor C ₁ , its gate G is connected to the connection point between resistor R ₂ and resistor R ₃ , and its cathode K is connected to the drive transformer.
Starting coil on the primary side of T ₂ (about a few turns) L ₄
are connected to each other. The collector of the switching transistor Q ₁ is connected to the anode A of the thyristor 4 and the primary side of the switching transformer T _{1 via the cathode and anode of the diode D 1 ,} and its base is connected to the primary side of the switching transformer T 1 via the drive transformer T ₂ . is connected to coil L ₄ . The secondary side of the switching transformer T ₁ is an output coil L ₅ and an IC ₁ power supply coil L ₆ , which are connected to the output terminal 5 . Output terminal 5 is a pulse width modulator
Transformer via input terminal 2d of IC ₁ and resistor _R5
Connected to the secondary side of T ₂ .

At startup, when DC power voltage is applied to terminal 1,
The capacitor C 1 is charged with a charging time constant (set to be sufficiently larger than the discharging time constant described later) by the resistors R ₄ , R ₁ and _{the capacitor C 1 ,} and this charging causes the anode potential of the thyristor 4 to rise. When the potential becomes higher than the gate potential, the thyristor 4 is turned on. When the thyristor 4 is turned on, the electric charge of the capacitor C ₁ is supplied to the starting coil L 4 of the drive transformer T ₂ and the transistor Q ₁ via the anode and cathode of the thyristor ₄ (coil L ₄
(A voltage is induced in the drive coil of the transistor Q ₁ (the other coil other than the coil L ₄ of the drive transformer T ₂ ) by the current flowing through the transistor Q 1), the transistor Q ₁ is turned on, and its charge is discharged. Ru.

When the transistor _Q1 is turned on, the anode potential of the thyristor 4 becomes lower than the gate potential, and the thyristor 4 is turned off.Then, the charge in the capacitor _C1 is discharged through the diode _D1 and the transistor _Q1, and the switching transformer is turned on. Contributes to power supply to T ₁ . By turning on the transistor _Q1 , an electromotive force is generated on the secondary side of the transformer _T1 .

This electromotive force is applied as a power supply voltage to the pulse width modulator IC ₁ and the transistor Q ₂ via the rectifying and smoothing circuit 6 to put them into operation. error amplifier 2a
The output voltage that has entered the input terminal 2d is compared with the reference voltage, and an error voltage is extracted.
A rectangular wave pulse with a pulse width corresponding to the error voltage is extracted from the pulse width modulation section 2c and is applied to the transistor.
Supplied on the base of Q ₂ . Transistor _Q2 is switched by this rectangular wave pulse, transistor _Q1 is also switched, and the output voltage taken out from output terminal 5 is controlled to be constant by a well-known switching regulator operation.
In this case, after transistor Q ₁ starts up, capacitor C ₁ is not charged. This is because the switching period of transistor _Q1 is set much smaller than the charging time constant of resistor _R1 and capacitor _C1 , and capacitor _C1 is bypassed with diode _D1 . For this reason, capacitor C ₁
It can be assumed that there is no power consumption.

As mentioned above, the starting circuit of the switching regulator according to the present invention includes a charging circuit that increases the potential when the power is turned on at startup, and an N circuit that is turned on for a period when the anode potential is higher than the gate potential due to charging of this charging circuit. When the gate thyristor and the thyristor are turned on, the switching element is put into operation, and the charge in the charging circuit is partially discharged through the thyristor and the switching element, and after the thyristor is turned off, it is charged through the diode and the switching element without going through the thyristor. , a charging circuit with a time constant sufficiently smaller than the time constant of the charging time constant circuit, a transformer through which an intermittent current of the power supply flows by turning on and off the switching element, and a voltage difference between the output voltage of this transformer and the reference voltage. Since it consists of a circuit that generates a pulse with a pulse width to control the switching element on and off, it is possible to
It does not require a power supply transistor (starting transistor Q ₄ in Figure 1) for the drive transistor that operates the switching element, so there is no power loss, and the drive transistor that operates the switching element and voltage stabilization operation are not required. Since the output voltage can be used directly as a power source for the circuit to be used, the regulation characteristics of the output voltage are improved.Moreover, unlike conventional switching transformers, the secondary coil of the switching transformer can be divided into two parts: the output coil and the power supply coil. There is no need to insulate and separate the transformer into different types, the transformer can be made compact, the number of parts is small, the circuit can be easily constructed, and since an N-gate thyristor is used, the amount of trigger energy and rise It has features such as high speed and high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an example of a conventional circuit, and FIGS. 2 and 3 are a circuit diagram of an embodiment of the circuit of the present invention and a schematic circuit system diagram thereof, respectively. 1...Power supply voltage terminal, 4...N gate thyristor, 5...Output terminal, IC ₁ ...Pulse width modulator,
_R1 to _R4 ...Resistor, _C1 ...Capacitor, _Q1 ...Switching transistor, _Q2 ...Drive transistor, _T1 ...Switching transformer, _T2 ...
...Drive transformer, L ₄ ...Starting coil, L ₅
...Output coil, L ₆ ...IC ₁ power supply coil,
_D1 ...diode.

Claims (1)

[Claims for Utility Model Registration] A charging circuit whose potential increases when the power is turned on at startup, and an N gate whose anode is connected to the charging circuit and whose anode potential is turned on for a period of time when the charging circuit is charged so that the anode potential is higher than the gate potential. It includes a thyristor, a switching element that performs a voltage stabilizing operation, and a diode provided between the charging circuit and the switching element, and when the N-gate thyristor is turned on, the switching element is activated and the charge in the charging circuit is reduced. is partially discharged through the N-gate thyristor and the switching element, and after the N-gate thyristor is turned off, the N-gate thyristor is turned off.
A discharging circuit having a time constant sufficiently smaller than the time constant of the charging circuit, which discharges the charge of the charging circuit through the diode and the switching element without going through the gate thyristor; Activation of a switching regulator consisting of a transformer through which an intermittent current flows and a circuit that generates a pulse with a pulse width corresponding to the error voltage between the output voltage of the transformer and a reference voltage to control the switching element on and off. circuit.