JPS6149655A - Power unit - Google Patents

Abstract

PURPOSE:To prevent the abnormal output at main power source energizing and interrupting times by providing means for interrupting a switching pulse supplied to switching means simultaneously at main power source energizing time except power supplying time. CONSTITUTION:In a power source circuit for supplying power generated at the secondary side of a transformer T1 to a load by supplying a switching pulse to switching means Q12 by connecting the switching means Q12 with the primary input side of a switching transformer T1, a shortcircuiting transistor Q10 is connected with the base of a transistor Q11 for supplying a switching pulse to the means Q12, the Q12 is turned ON simultaneously when the main power source is turned ON, and the pulse output from the Q11 is interrupted. A switch S is separately closed at power supply time, the Q10 is turned OFF, and the switching pulse is output from the transistor Q11.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a power supply device, and particularly to a power supply device that uses switching means to intermittent the main power supply to the primary side of a switching transformer to supply power to a load on the secondary side of the transformer. .

[Prior art]

2. Description of the Related Art Conventionally, a power supply device is known in which the primary side of a step-up transformer is switched on and off using a switching means such as a transistor, and the power generated on the secondary side is supplied to another device. Conventionally, this type of device has been used as a high-voltage power supply such as a charger in a copying machine, or as a CR
It is widely used as a power source for generating T deflection voltage.

In this conventional single-layer device, the reswitching pulse generation means malfunctions due to the main power supply rising, a fault occurs when disconnected, or the capacitor in the main power supply circuit discharges, resulting in abnormal high voltage output. There were times when it could be seen. Since this abnormal output occurs even when the power supply control signal is not input to the swinging means, it is likely to cause malfunction of the i-position or damage to the load elements.

〔the purpose〕

The present invention has been made in view of the above-mentioned problems. 1. It prevents violent force when turning on and cutting off the main power. The purpose of the present invention is to provide a power supply device equipped with a mechanism for stopping the power supply.

[Actual implementation]

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 shows a circuit diagram of an embodiment of a power supply device according to the present invention. The configuration shown in Figure 1 basically consists of two switching transformers TI and T2, which are two stages of switching transformers T.
One end of the primary winding 2 is connected to the power supply voltage 1tcc via a resistor 'R42, and the other end is connected to the collector of a transistor Q11 whose emitter is grounded. On the other hand, one end of the secondary side of the switching transformer T2 is grounded, and the other end is connected to the transistor Q12 via a resistor R43.
Not connected to the pace of. The emitter of the transistor Q12 is grounded, and the collector thereof is connected to one end of the primary winding of the switching transformer T1.

There is a transistor between this connection point and ground for protection.

The diode)'D5 and the resonance capacitor CZ force are connected. , = of switching transformer T1.

One end of the next winding is connected to the power supply voltage VCC via a resistor R1.

A diode D is installed in the secondary winding of the switching transformer T1.
6. A rectifier and smoothing circuit consisting of a capacitor C1 and a resistor R3 is connected. The electric power generated in the secondary winding is converted into a DC voltage by this rectifying and smoothing circuit, and is supplied to the load via the spark prevention resistor R2. Further, a resistor R4 for detecting the load current and a resistor C2 for smoothing the detected voltage are connected in series to the secondary winding of the switching transformer T1.

Here, the resistor R5 is a resistor for level shifting the detection voltage.・ ・ The circuit consisting of operational amplifiers Q1 to Q6 is a circuit that amplifies the error between the voltage corresponding to the load current and a predetermined reference voltage, and generates a switching pulse to drive the transistor Q11 according to this error. .

That is, the terminal potential of resistor 1 and 4 is led to the inverting input of operational amplifier Q1 via resistor R6.

At the same time, a DC power supply voltage vCC is applied to this inverting input terminal via a resistor R8. A reference voltage obtained by dividing the power supply voltage VCC by resistors Q9 and Q10 is applied to the non-inverting input terminal of the operational amplifier Q1. Also, the operational amplifier Q1
The inverting input terminal and output terminal of are connected to resistor R7 and capacitor C.
3 is connected □.

The output of operational amplifier Q1 is connected to resistor Q.11. , diode D
1 and the non-inverting input terminal of operational amplifier Q2 via resistor R13. Furthermore, this non-inverting input terminal is connected to resistors R17 and R through resistor R16 and diode D4.
At 18, a voltage obtained by dividing the power supply voltage vCC is applied. On the other hand, the inverting input terminal of operational amplifier Q2 is grounded via capacitor C6. A power supply voltage vCC is applied to the output terminal of the operational amplifier Q2 via a resistor R14, and is further connected to a non-inverting input terminal via a resistor 15 and an inverting input terminal via a resistor R39.

The connection point between the inverting input terminal of the operational amplifier Q2 and the resistor R39 is connected via the resistor R37 to the non-inverting input terminal of a comparator Q3 constituted by an operational amplifier. The inverting input terminal of comparator Q3 is connected to the power supply voltage CC through resistor R3.
5. A reference voltage divided by R36 is applied. The non-inverting input terminal and output terminal of comparator Q6 are resistor R38.
It is connected via. The output terminal of the comparator Q3 is pulled up to the power supply voltage VC'C by a resistor R40, and is further connected to the base of the transistor Q11 via a resistor R41.

The base of this transistor Q11 can be controlled by a transistor Q10, which will be described later.

The circuit consisting of the operational amplifier Q1fF15 and the comparator Q6 whose configuration has been shown above is a circuit that changes one actual pulse width of the switching transistor Qll in accordance with the load current detected via the resistor R4. Below, this operational amplification H
The circuit composed of 3q1 to Q6 is abbreviated as IJW81 (pulse width modulation oscillator).

Here, the outline of the operation of this psw will be described below.

The operational amplifier Q1 outputs an error signal between the voltage corresponding to the load current detected via the resistor R4 and the reference voltage formed by the resistors R9 and rtlo.

This signal is connected to resistor R11, diode D1 and resistor R13.
The signal is input to the operational amplifier Q2 via the input error signal, and the operational amplifier Q2 generates a triangular wave having a different level according to the level of the input error signal using the time constant of the resistor R39 and the capacitor C6. This triangular wave is sent via resistor R37 to comparator Q6, where it is compared with a reference voltage formed by resistor R55 and R36. The level of the triangular wave is adjusted to a predetermined value of the detected load current so that the output of the regulator Q3 changes in pulse 1@ according to the load current. This changes the drive duty ratio of the switching transistor Q11 and controls the load current to be constant.

On the other hand, a circuit is provided between the connection point of the resistor R11, the diode D1, and the base of the transistor Q11 to forcibly control the output when the power is turned on and off.

The switch indicated by the symbol S at the bottom of FIG. 1 is a switch that controls the power output. One end of this switch S is grounded, and the other end is connected to the power supply voltage CC through a resistor Rho and a light emitting diode ZD. There is.

The terminal voltage of switch S is connected to the base of transistor Q7 via resistor R29. transistor Q7
Its base is grounded via a resistor R2B, and its emitter is set to a potential obtained by dividing the power supply voltage vcc by resistors R26 and R27. □The collector of transistor Q7 is the power supply voltage cc~resistance R23
~R25~ C4, which is a series connection of capacitors c4, forms a time constant circuit, and when the switch S is turned on, the PWM
This applies a control voltage that gradually increases.

The potential at this connection point is applied to the transistor Q via the resistor R24.
It is guided by the base of 6. The collector of the transistor Q6 is connected to the power supply voltage cc through a resistor R22.

The emitter of the transistor Q6 is connected to the cathode of a diode D, and the anode of the diode D6 is connected to the base of the transistor Q5. The base of the transistor Q5 is connected via a resistor R19, and the collector is directly connected to the power supply voltage cc. The anode of the diode D2 is connected to the anode of the diode D3, and the resistors R20 and R2 are connected to the cathode of the diode D2.
A divided voltage of the power supply voltage CC by 1 is given. The voltage determined by this resistor R20°R21 provides a control voltage corresponding to the maximum pulse width of PWM according to the maximum load current.

The emitter of transistor Q5 is connected to the base of transistor Q4. transistor. 4 is grounded via a resistor R12, and its emitter is connected to the connection point of the resistor R11 and diode D1.

In addition, for ease of understanding, the circuit configuration on the left side of the switch S is extracted and shown as FIG. 2.

The base of the transistor Q11 that controls the switching transistor T2 is a transistor. 9°Q10 can each control Ff71J.

Transistor Q1o is resistor R30, R31, R36VC
,,l: When a D bias voltage is applied, the switching pulse formed by the PWM described above is prevented from being transmitted to the transistor Q11 when the main power is turned on.

The transistor Q9 has a time constant circuit connected to its base consisting of a resistor R32°R34 and a capacitor c5, and functions to remain conductive for a certain period of time even after the main power supply VCC is cut off.

The connection point between resistors R32 and R54 is connected to the connection point between resistor 1-60 and switch S. .

Next, the operation of the above configuration will be explained in detail. Here, we will first explain the process of turning on the main power and starting the amount of power supplied.

First, turn on the main power of the device and apply the voltage ψCC to each of the above application points.If the switch S is not closed, the resistors R31 and R
The bias is applied through 33 to 9, turning on transistor Q10, which results in the base of transistor Q11 being 0.
Since the potential is set, switching pulses generated due to malfunction of the PWM (indicated by the first block in FIG. 2) are prevented from being applied to the base of the transistor Q11. At this time, the light emitting diode ZD has a resistor R50,
Since it is driven via R31 and R55, it is lit at low brightness in this standby state.

Next, when the switch S is closed, the base of the transistor Q10 is set to 0 potential, and the transistor Q1
0 is high impedance, and pulse application from 9 PWM 1 to the transistor Q11 becomes possible. At this time, the light emitting diode ZD is driven only through the resistor R50, so it emits light with higher brightness than in the standby state.

As described above, operational amplifier Q2 generates a triangular wave from the time the main power is turned on, and a switching pulse obtained by processing this triangular wave by comparator 6 is transmitted to transistor Qll by turning off transistor Q10. As a result, the transistor Q12 is driven by a pulse generated on the secondary side of the transformer T2 according to the turns ratio, and the secondary winding of the switching transformer TI' is switched on and off. In this way, the boosted direct current is supplied to the load on the secondary side of the switching transformer T1. At this time, as mentioned above, the operational amplifier Q
1, the hexagonal wave output level of the operational amplifier Q2 is adjusted according to the load current, and thereby the pulse width of the reswitching pulse is adjusted so as to keep the load current constant.

On the other hand, the circuit of transistors Q7 to Q4 operates as follows. After the main power is turned on, when the switch $ is closed, the core emitter of the transistor Q7 becomes high impedance.The capacitor C4 is charged with electric charge from the power supply voltage VCC through the resistors R25 and R25. is transmitted by transistor Q6.・□ Transistor Q6 is connected to diode D2 and 'D
6 and form a low voltage priority port. That is, the voltage division by resistors R2o and R21 and the transistor Q6
The lower one of the potentials corresponding to the potential of the capacitor C4 at the emitter of the transistor Q5 is applied to the transistor Q5. ” □ 11 In the above manner, the switch S
When starting power supply by closing □, connect capacitor d4.
and the voltage defined by the resistor R25° gradually switches to: G...S width force 8
Expanded, change 1 negative efficiency; gradually raised. After power supply starts, the triangular wave output level of the operational amplifier Q2 is adjusted according to the error voltage output from the operational amplifier Q1, but the low voltage priority circuit consisting of the transistor Q4 and the diode D1 adjusts the level of the triangular wave, that is, the switching pulse. The maximum width is limited to a value determined by resistors R20 and R21, and the maximum value of the load current is controlled.

Next, the operation when the power supply is stopped and the main power supply is cut off will be explained.

To stop power supply to the load, switch S is opened. This applies a bias to transistor Q10, so the base of transistor Q11 is controlled to 0 potential,
Transmission of switching pulses is prevented. If PWM
Even if R4 is malfunctioning, the switching pulse is applied to resistor R4.
1 to ground potential, the power supply operation is immediately stopped. At this time, since the transistor Q7 also becomes conductive due to the opening of the switch S, the control voltage of the PWM4 is set to O by the low voltage priority circuit. Therefore, the output beam of the PWM 4 is controlled so that the duty ratio is approximately zero. Therefore, when the power supply is stopped, the generation and transmission of switching pulses are immediately interrupted, thereby preventing the occurrence of abnormal output.

Furthermore, if you cut off the main power supply and cut off the power supply voltage ■CC,
The output of the transistor Q10 immediately becomes a zero impedance, but the transistor Q9 does not turn off VC for a while. This is because the charge stored in capacitor C5 is discharged through the base-emitter of transistor Q9, and transistor Q9 remains on for a period of time determined by the timing of capacitor C5 and resistor R54. Therefore, l) the operation of the WM 4 is unstable, and even if some pulse is generated, this pulse is not transmitted to the transistor Q11, thereby preventing the generation of an abnormal output.

As shown above, according to the above embodiment, the transmission of the switching pulse is blocked by the transistor Q10 except when the power supply operation is specified by the switch S at the same time as the main power is turned on, and furthermore, the transmission of the switching pulse is prevented by the transistor Q7. ~Q
Since the low voltage priority circuit according to No. 4 also prevents the generation of switching pulses, it is possible to reliably prevent abnormal output during this period.

In addition, capacitor C5 and resistor R5
Since the transmission of the switching pulse is blocked by the transistor Q9 for the period determined by 4, even if a switching pulse is generated due to capacitor discharge in the main power supply circuit, abnormal output due to this pulse is prevented from occurring. be able to.

The above circuit can be widely used as a power source for a charger in a copying machine, a power source device for various electronic devices, or as a pilot lamp.

〔effect〕

As is clear from the above description, according to the present invention, a configuration is adopted in which the transmission of switching pulses is blocked for a period other than when power is being supplied at the same time as the main power is turned on, or for a certain period of time after the main power is turned off. Therefore, we can provide an excellent power supply device that can completely prevent abnormal output when the main power is turned on and off.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a power supply device according to the present invention, and FIG. 2 is a circuit diagram showing a part of the circuit shown in FIG. 1 in detail. Ql, Q2...Operation amplifier Q6...To converter Q4 Qll...Transistors 01 to C7...
Capacitor D1-D6...Diode R1-R41
...Resistors TI, T2...Switching transformer Patent applicant Canon Inc. Figure 1

Claims (4)

[Claims] (1) In a power supply device that uses switching means to intermittent the main power supplied to the primary side of a switching transformer and supplies the power generated on the secondary side to the load, a pulse is generated at the same time as the main power is turned on and during a period other than when power is being supplied. A power supply device comprising: means for cutting off a switching pulse supplied from the means to the switching means. (2) The invention further comprises means for controlling the pulse generating means so as to generate a normal switching pulse at the same time as the power supply starts, and to stop the switching pulse at the same time as the power supply is cut off. The power supply device according to item 1. (3) In a power supply device in which the main power supplied to the primary side of a switching transformer is intermittent by a switching means and the power generated on the secondary side is supplied to a load, the pulse generating means is simultaneously connected to the switching means when the main power is cut off. 1. A power supply device comprising means for blocking switching pulses supplied to the power source for a certain period of time. (4) The invention further comprises means for controlling the pulse generating means so as to generate a normal switching pulse at the same time as the power supply starts, and to stop the switching pulse at the same time as the power supply is cut off. The power supply device according to item 3.