JPH0583930A - Power source device - Google Patents

Abstract

PURPOSE:To prevent the generation of inrush currents to the secondary side immediately after the starting of switching operation at the time of starting in a high-frequency chopper type switching regulator. CONSTITUTION:PWM 3 is controlled by an on-start soft start circuit 5, and the duty ratio of switching pulses PSW is increased gradually. Switching operation is started by a transistor Q1 in response to PSW. DC voltage V1 is obtained through a reflux diode D1, a coil L2 and capacitors C1, C2. On resistance is controlled gradually from high resistance immediately after the starting of switching operation to a low resistance state in a transistor Q2. Accordingly, inrush currents immediately after starting to the secondary side can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and particularly to a power supply device having a high frequency switching type switching regulator structure.

[0002]

2. Description of the Related Art Conventionally, a dry battery 1 of, for example, 1.5 [V]
2. Description of the Related Art As a power supply device for obtaining a power supply voltage for an integrated circuit from a book, there is one having a high-frequency boosting chip type switching regulator structure.

That is, as shown in FIG. 4, in this power supply device 1, a primary voltage VIN inputted from a dry battery (not shown) is a switching transistor Q which is a field effect transistor (FET) through a chain yoke coil L1.
1 through the freewheeling diode D1 which is supplied to the drain and connected in the forward direction to the coil L2 and the capacitor C.
1 and C2 are supplied to the smoothing filter 2.

In practice, the source of the transistor Q1 is grounded, and the gate receives the switching pulse PSW generated by the pulse width modulation circuit (PWM) 3, whereby the transistor Q1 performs a switching operation in response to the switching pulse PSW. Then, the booster controller is configured.

As a result, the smoothed voltage V1 after being boosted is output through the smoothing filter 2, and this is supplied to the secondary load 4 composed of the capacitor C3 and the impedance ZL, and is also output as the power supply voltage VOUT when necessary. ..

In this power supply device 1, the smoothed voltage V1 is PWM
The PWM3 generates a switching pulse PSW with a duty ratio that stabilizes the smoothed voltage V1 and thereby obtains a stabilized power supply.

[0007]

By the way, in the power supply device 1 having such a configuration, immediately after the start-up transistor Q1 starts the switching operation in response to the switching pulse PSW, a very large inrush current is applied to the secondary load 4. This may occur and destroy the capacitance C3 and the impedance ZL of the secondary load 4.

In order to solve this problem, this power supply device 1
Is provided with a soft start circuit 5 for controlling the PWM 3 so as to gradually increase the duty ratio of the switching pulse PSW at the time of start-up and performing a so-called soft start.

In such a case, when a very large capacity C3 is present as the secondary side load 4 or a heavy load is present on the secondary side at the time of startup, the operation time of the soft start is set to the secondary side load condition. It has to be set for a very long time.

However, as described above, when the operation time of the soft start is long, there is a problem that the power supply device 1 itself becomes unstable in startup or becomes in an inoperable state. In particular, this problem occurs in the step-up switching type switching regulator, and is more remarkable when the difference between the primary side input voltage and the secondary side output voltage is large.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a power supply device capable of reliably preventing the generation of an inrush current to the secondary side immediately after the start of the switching operation at the time of startup. is there.

[0012]

In order to solve such a problem, in the present invention, a switching regulator of a high frequency chip type is used, which converts a primary voltage VIN into a predetermined voltage and supplies it to a secondary load 4. In the power supply devices 10 and 20,
Between the smoothed voltage V1 after the transformation and the secondary load 4, the on-resistance is gently controlled from the high resistance state immediately after the start of the switching operation to the low resistance state.
20 is provided.

[0013]

The ON resistance of the semiconductor switch means Q2 and Q20 provided between the smoothed voltage V1 after transformation and the secondary load 4 is
The gradual control from the high resistance state immediately after the start of the switching operation to the low resistance state can surely prevent the generation of the inrush current to the secondary side immediately after the start of the switching operation at the time of startup.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.

(1) First Embodiment In FIG. 1 in which parts corresponding to those in FIG. 4 are assigned the same reference numerals, 10 indicates the power supply device according to the present invention as a whole, including a smoothing filter 2 and a secondary load 4 A second switching transistor Q2, which is a field effect transistor (FET), is connected between the two.

With the second transistor Q2 turned on, the smoothed voltage V1 output from the smoothing filter 2 is output as the power supply voltage VOUT to the secondary load 4 from the drain to the source of the transistor Q2.

The gate of the second transistor Q2 is supplied with the gate control signal from the gate voltage control circuit 11, and one end of the second transistor Q2 is commonly connected to the capacitors C1 and C2 of the smoothing filter 2. Capacitor C
The other end of 4 is connected.

In the above configuration, in the case of the power supply device 10, the primary side input voltage VIN is 0.9 [V], the secondary side output voltage VOUT0 is 5 [V], and the switching transistors Q1 and Q.
The gate applied voltage of 2 is set to 10 [V], and the frequency of the switching pulse PSW is selected to be 100 to 200 [kHz].

This secondary side output voltage VOUT0 is determined by the primary side input voltage VIN and the ON / OFF interval of the switching transistor Q1, that is, the duty ratio of the switching pulse PSW, and in the steady state the secondary side output voltage VOUT0 or the smoothing filter. The smoothed voltage V1 output from 2 is fed back to the PWM3 to control the duty ratio of the switching pulse PSW to stabilize the secondary output voltage VOUT0.

Also in this power supply device 10, as shown in FIG. 2, the switching pulse PSW (see FIG. 2 ( The duty ratio of A)) is controlled.

Actually, when the switching operation of the transistor Q1 is started at the timing of time t1 at the time of start-up in this way, the smoothed voltage V1 output from the smoothing filter 2 is generated by the effect of the soft start circuit 5 as shown in FIG. As shown in), it rises moderately.

At time t2 when the smoothed voltage V1 reaches near the steady voltage, the gate voltage control circuit 11 of the transistor Q2 starts to operate, and the gate voltage VG (FIG. 2C) of the transistor Q2 gradually rises. To do.

The gate voltage V of this transistor Q2
G is designed to obtain an accurate gate voltage rising curve by the capacitor C4 connected between the gate and the smoothing filter 2.

The on resistance of the transistor Q2 is
As the gate voltage VG rises, the initial high resistance state gradually changes to the low resistance state, and in the steady state, it is completely turned on.

From the timing of the time point t3 when the on-resistance of the transistor Q2 drops to a predetermined value, the secondary side output voltage VOUT0 gradually rises as shown in FIG. 2 (D), and finally from the timing of the time point t4 to the steady state. become.

In this way, at the time of startup, the secondary side output voltage VOUT0
Gradually rises, so that no rush current due to startup is generated at all in the primary side power supply and the secondary side output voltage VOUT0.

Thus, in the case of this power supply device 10,
The inrush current that occurs when the switching regulator itself starts up and the inrush current that occurs when power is supplied to the secondary load 4 can be independently prevented, so that the inrush current is completely prevented. be able to. As a result, the optimum power supply device 10 can be realized particularly when using a dry battery or the like having a low voltage and a large internal resistance.

According to the above configuration, the smoothed voltage V after transformation
Since the on-resistance of the transistor Q2 provided between the primary and secondary loads 4 is gently controlled from the high resistance state immediately after the start of the switching operation to the low resistance state,
It is possible to realize the power supply device 10 that can reliably prevent the generation of the inrush current to the secondary side immediately after the start of the switching operation at the time of startup.

Further, according to the above-mentioned configuration, if the capacitor C4 connected to the gate of the transistor Q2 is an external component, the capacitor C4 can be used depending on the weight of the secondary load and the size of the secondary capacitance (C3). You can also select the capacity of
Thus, it is possible to realize the power supply device 10 that can significantly improve versatility.

(2) Second Embodiment In FIG. 3 in which parts corresponding to those in FIG. 1 are designated by the same reference numerals, 20 indicates a power supply device as a whole, and field effect transistors (FETs) Q1 and Q2 of the power supply device 10 are shown. Instead, bipolar transistors Q10 and Q20 are used.

Further, in the case of this power supply device 20, a transistor switch Q30 for discharging the base voltage of the transistor Q20 as required is provided, and the power supply device 2 is provided.
When the power supply of 0 is turned off, the discharge signal SH turns on the transistor Q30 to discharge the electric charge of the capacitor C10 and the base voltage of the transistor Q20 rapidly falls to 0 [V].

As a result, even when the power supply device 20 continuously repeats the on / off operation, when the on operation is performed, the on resistance of the transistor Q20 can be controlled to a high resistance, thereby generating the inrush current to the secondary side. It can be prevented.

According to the above configuration, the smoothed voltage V after transformation
The ON resistance of the transistor Q20 provided between the primary and secondary loads 4 is gently controlled from the high resistance state immediately after the start of the switching operation to the low resistance state. It is possible to reliably prevent the generation of the inrush current to the secondary side, and by providing the discharge circuit, even when the on / off operation is continuously repeated, the inrush current to the secondary side immediately after the start of the switching operation can be prevented. It is possible to realize the power supply device 20 that can reliably prevent the occurrence.

(3) Other Embodiments (3-1) In the above embodiment, the field effect transistor (F) is provided between the smoothed voltage V1 after transformation and the secondary load 4.
ET) or a case where a switching transistor having a bipolar transistor configuration is provided, the temperature thermistor or a parallel circuit of a resistor and a thyristor may be used instead.

Incidentally, in the case where the power supply device is continuously controlled to be turned on and off, or when the inrush current is completely prevented, it is better to continuously change the on resistance of the transistor switch as in the above-mentioned embodiment. ..

(3-2) In the above embodiment, as the power supply device of the present invention, the case where the voltage of the dry battery of 1.5 [V] is boosted to obtain the power supply of 5 [V] for driving the integrated circuit is described. However, the present invention is not limited to this, and can be widely applied to a step-down power supply device as long as it has a high-frequency chip type switching regulator configuration.

[0037]

As described above, according to the present invention, the on-resistance of the semiconductor switch provided between the converted smooth voltage and the secondary load is gradually changed from the high resistance state immediately after the start of the switching operation to the low resistance state. By controlling to
It is possible to realize a power supply device capable of reliably preventing generation of an inrush current to the secondary side immediately after the start of the switching operation at the time of startup with a simple configuration.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of a power supply device according to the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation.

FIG. 3 is a connection diagram showing another embodiment of the power supply device according to the present invention.

FIG. 4 is a connection diagram showing a conventional power supply device.

[Explanation of symbols]

1, 10, 20 ... Power supply device, 2 ... Smoothing filter, 3
... PWM, 4 ... secondary load, 5 ... soft start circuit, 11 ... gate voltage control circuit.

Claims (1)

[Claims] 1. A power supply device comprising a high frequency switching type switching regulator for converting a primary voltage into a predetermined voltage and supplying the same to a secondary load, wherein the smoothed voltage after the conversion and the secondary load. In the meantime, the power supply device is provided with a semiconductor switch means in which the on-resistance is gently controlled from a high resistance state immediately after the start of the switching operation to a low resistance state.