JP2579142Y2 - Power supply - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for electric equipment, and more particularly to a power supply in which load characteristics are not relatively important, such as a power supply for driving an actuator of a printer of an electronic computer.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of the configuration of a power supply device of a conventional printer. The commercial AC voltage input from the power plug CN ₁₁ is connected to the fuse F ₁₁ and the switch S
Is input to the transformer T ₁₁ through W _11, is transformed to the desired voltage. In general, a printer uses a power supply device having an output of two systems of 5 V supplied to a control circuit, 24 to 40 V supplied to an actuator such as a print head drive mechanism or a paper feed mechanism, or more. , FIG.
Has two outputs of 5V and 38V. AC voltage transformed by the transformer T _11, the diode D ₂₁ to D
₂₄ , D _{25 to} D ₂₈ are rectified and smoothed by capacitors C ₁₁ and C ₁₂ to be DC. The output voltage of the 5 V system is stabilized and supplied by the regulator IC ₁₁ , and the output of the 38 V system is the switching control circuit 11, the transistor T
The power is stabilized and supplied by a switching power supply circuit including r ₁₁ , a diode D ₂₉ , a choke coil L ₁₁ and a capacitor C ₁₃ . Since the output of the 5V system is supplied to the control circuit of the printer, it must be kept constant regardless of the load current. However, the output of the 38 V system is generally simplified since it is sufficient that the output is equal to or higher than the minimum operating voltage at which the actuator can operate at the maximum load current.

FIG. 4 is a graph showing a load characteristic of a 38V output of the circuit example of FIG. Due to the use of transformer T _11, but have different output voltage at the maximum load current by an AC input voltage, is designed such that a minimum operating voltage higher than the maximum load current during the rated minimum voltage input is output I have. Generally, when the load current is large, the switching operation of the switching power supply stabilizing circuit is stopped and the transformer T ₁₁
The load characteristics that make the trajectory due to the load characteristics of the transformer appear to be low are to reduce the cost and weight of the transformer by reducing the size of the transformer and to reduce the cost of the switching power supply stabilization circuit. is there. This is because the maximum load current of the 38V system output is as large as several to several tens of amperes (A), and a complete power supply would result in a large-scale power supply circuit.

[0004]

However, since the power supply uses a transformer for commercial frequency, there is a problem that the power supply becomes large and heavy.

There is also known a power supply device which rectifies a commercial power supply called a switching power supply, converts it into a high frequency, and steps down and rectifies it with a small high-frequency transformer. However, the circuit is large and expensive. Also, the load characteristics of the switching power supply are very good. However, when used as a power supply for the actuator system of a printer, the load characteristics may be poor. Even when the performance of the load characteristics of a switching power supply is minimized, the price is hardly changed, and cost reduction is expected. Absent. Furthermore, ordinary switching power supplies generate a lot of electrical noise and are relatively efficient, but they also generate heat due to switching loss and other losses, so that they are also large in size. There is a problem that the size cannot be reduced significantly.

[0006] Further, a resonance type switching power supply is also known. In this resonance type switching power supply, the timing when the switching element is turned off is a point where the current is zero. Therefore, the generation of noise is small, the efficiency is high,
There is an advantage that the size can be reduced. However, since the characteristics are determined by its own resonance, there is a problem that it is difficult to control such as voltage control.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned problems, and has as its object to provide an inexpensive power supply device which is small in size, has a necessary and sufficient load characteristic, generates little noise, and has a low noise level. .

[0008]

A power supply device according to the present invention includes a self-excited resonance type switching power supply circuit which is started by input of a start-up pulse, a rectification of a commercial AC power supply, and a pulsating current flowing through the resonance type switching power supply circuit. A rectifier circuit that outputs a signal, and outputs a start pulse to the resonance-type switching power supply circuit to start oscillation, detects an output voltage of the resonance-type switching power supply circuit, and sets a phase of the start-up pulse according to the output voltage. And a control circuit for controlling in synchronization with the frequency of the commercial AC power supply.

[0009]

In the present invention, the rectifier circuit rectifies the commercial AC power supply and supplies a pulsating current to the resonance type switching power supply circuit, and the control circuit outputs a starting pulse to the resonance type switching power supply circuit to start oscillation. At the same time, the output voltage of the resonance type switching power supply circuit is detected, and the phase of the starting pulse is controlled in synchronization with the frequency of the commercial AC power supply in accordance with the output voltage.
The output voltage can be easily controlled.

[0010]

DETAILED DESCRIPTION FIG. 1 is a circuit block diagram showing an embodiment of the present invention, D ₁ to D ₄ in the rectifier, the commercial power source is inputted through the fuse F _1, the power switch SW ₁ and the power supply plug CN ₁ You. The output terminals of the rectifiers D _{1 to} D ₄ are connected to a series circuit of capacitors C ₁ and C ₂ . T ₁ is the primary winding turns are the same two in trans L _1, L ₂ and 3
It has secondary windings L ₃ and L ₄ for the 8 V system and the 5 V system. The primary winding L ₁ and L ₂ of the transformer T ₁ are respectively transistors Tr ₁ and Tr ₂ are connected in series as shown, it is connected to the output terminal of the rectifier D ₁ to D _4.
Note that diodes D ₆ and D ₇ are connected in anti-parallel between the collector and the emitter of the transistors Tr ₁ and Tr ₂ , respectively. The center tap of the capacitors C ₁ and C ₂ is connected to the primary center tap of the transformer T ₁ through the primary winding of the transformer T _2, 2 winding of the transformer T ₂ are through respective resistors R ₁ and R _2, Transistor T
It is connected to the bases of r ₁ and Tr ₂ .

The capacitors C ₁ and C ₂ are diodes D ₆
And through D _7, to form the primary winding and the resonant circuit of the transformer T _1. The resonance current flowing through the capacitors C ₁ and C ₂ and the primary winding of the transformer T ₁ is detected by the transformer T ₂ and switches the transistors Tr ₁ and Tr ₂ alternately. Then, a rectifier circuit and a smoothing circuit connected to the secondary winding of the transformer T ₁ of the later also included, to form a resonance type switching power source P ₁ of the self-excited.

On the secondary side of the transformer T ₁ , rectifiers D ₈ and D ₉ , a choke coil CH ₁ , and a smoothing capacitor C ₄ are connected to the 38 V system winding, and the rectifier D is connected to the 5 V system winding.
₁₀ and D ₁₁ , choke coil CH ₂ , smoothing capacitor C
₅ is connected, and further connected to the regulator IC ₁ 'on the output side of the capacitor C _5. CN ₂ is a DC output terminal. 38V system output has Zener diode D ₁₂ ,
The resistor R ₄ and the light emitting diode of the photocoupler PC ₁ are connected in series.

The control circuit 1 is, for example, a microcomputer, and outputs a start pulse of a resonant type switching power supply P ₁ to the transistor Tr _2. The input port of the control circuit 1, the output signal of the phototransistor of the photocoupler PC ₁ is input, also to the other input port,
Because of the commercial AC power supply of the phase detection is input is clipped by a rectifier D ₁ pulsating current resistance R ₃ of the output to D ₄ and the Zener diode D _13. The operation power supply of the control circuit 1, the pulsating flow rectifier D ₅ and a smoothing capacitor C
_The DC power is supplied by ₃ .

FIG. 2 is a waveform diagram showing operation waveforms of the circuit of FIG. 1, showing waveforms at points A to D in the circuit diagram of FIG. The waveform A is the power supply voltage input to the resonant switching power supply,
Waveform phase detection signals produced by the resistor R ₃ and the Zener diode D _13, C waveform is a pulse output waveform to start the oscillation of the resonant switching power supply, D is an output waveform of the transformer T ₁ of the resonant switching power supply.

Next, the operation will be described. Power switch SW
_{When 1} is turned on, the pulsating current represented by the waveform A output from the rectifiers D _{1 to} D ₄ is applied to the capacitors C ₁ and C ₂ . Further, the power supply voltage is applied to the control circuit 1, and outputs a start pulse to the transistor Tr _2, resonant switching power supply circuit P ₁ is operated. The resonance current flowing through the capacitors C ₁ and C ₂ and the primary windings L ₁ and L ₂ of the transformer T ₁ is detected by the transformer T _2, and switches the transistors Tr ₁ and Tr ₂ alternately. Converted to high frequency alternating current. Here, the transistors Tr ₁ and Tr ₂ are not biased, and do not start oscillating unless a start pulse is input. Further, since the waveform A has a pulsating flow, the voltage becomes zero one cycle later, and the oscillation stops at this point. Then, since much higher in oscillation frequency than the commercial AC frequency, as the output waveform D waveform of the transformer T _1, a waveform obtained by an envelope the ripple indicated by A waveform.

The voltage converted into a high frequency alternating current is stepped down to a desired voltage by the transformer T _1, diode D ₈ to D
_{The current is} rectified by ₁₁ and smoothed by the choke coils CH ₁ , CH ₂ and the capacitors C ₄ , C ₅ to be DC. Since the 5V power supply is supplied to the control circuit of the printer, the direct current is further input to the regulator IC ₁ and output after being stabilized.

The 38V system power source becomes equal to or larger than a desired voltage, the zener diode current flows through the D ₁₂ and the resistor R ₄ to the light emitting diode of the photocoupler PC _1, when a current of the phototransistor of the light receiving increases, the overvoltage Is transmitted to the control circuit 1. The control circuit 1 generates a pulse to start the oscillation of the aforementioned resonant switching power supply P _1, but the load advances the heavy desired when it is voltage following phase of the start pulse across all cycles as oscillation continues Let When the load is light and becomes equal to or higher than the desired voltage, the phase of the starting pulse is delayed to shorten the oscillation period. This is shown in FIG. This operation is performed in real time based on a preset program, and FIG. 2 shows a state where the output is balanced with the load.

As described above, the power supply of the present invention does not smooth the voltage rectified by the rectifiers D _{1 to} D ₄ , but inputs the pulsating current represented by the waveform A to the resonance type switching power supply, and outputs the pulsating current by phase control. The feature is that the voltage is controlled. Therefore, it is possible to easily control the output voltage by taking advantage of the advantage of the resonance type switching power supply that noise generation is small, the efficiency is high, and the size can be reduced. Incidentally, 5V system power supply also, the output voltage of the secondary winding L ₄ are, varies due to the phase control, since the stabilized by the regulator IC _1, the output voltage becomes constant at the DC output terminal CN _2.

In addition, according to the present invention, a large-capacity smoothing capacitor on the primary side can be omitted. Although a conventional large-capacity smoothing capacitor is required on the secondary side, this is absolutely necessary even if the present method is not used. In a printer, it is necessary to instantaneously extract a pulse-like load current that far exceeds the power supply circuit. It is. Also, the control circuit 1
Requires a DC power supply and pressure, which is the rectifier D ₅
And it is smoothed produced by the capacitor C _3. Because the current consumption of the control circuit 1 is small, C ₃ may be a small-capacity capacitor.

Further, since the control is a phase control of a low frequency of 100 to 120 Hz, even a one-chip microcontroller (one-chip microcomputer) having a built-in control program (firmware) has a sufficient control speed.
This can be used, and furthermore, the circuit can be simplified, the price can be reduced, and software control is used. Therefore, it is possible to flexibly respond without changing the circuit according to the load condition of the printer using the power supply. And a power supply device that can perform the operation.

The above description has been given of the case where the present invention is applied to the power supply of the printer. However, the present invention can be applied to devices other than the printer if the load characteristics are not important.

[0022]

As described in detail above, according to the present invention, the rectifier circuit rectifies the commercial AC power to supply a pulsating current to the resonant switching power supply circuit, and the control circuit controls the resonant switching power supply. A starting pulse is output to the circuit to start oscillation, the output voltage of the resonant switching power supply circuit is detected, and the phase of the starting pulse is controlled in synchronization with the frequency of the commercial AC power supply according to the output voltage. Therefore, there is an effect that a power supply device that generates less noise, is efficient, can be reduced in size and weight, and can easily control the output voltage can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart showing operation waveforms of the circuit of FIG.

FIG. 3 is a circuit block diagram of a conventional power supply device.

FIG. 4 is an output load characteristic diagram of a conventional power supply device.

[Explanation of symbols]

First control circuit C ₃ capacitor D ₁ to D _4, D ₅ rectifier D _12, D ₁₃ Zener diode R _3, R ₄ resistors P ₁ resonant switching power supply circuit PC ₁ photocoupler

Claims (1)

(57) [Scope of request for utility model registration] 1. A self-excited resonance type switching power supply circuit activated by input of a start-up pulse, a rectification circuit for rectifying a commercial AC power supply and outputting a pulsating current to the resonance type switching power supply circuit, Outputting the starting pulse to the power supply circuit to start the oscillation, detecting the output voltage of the resonant switching power supply circuit, and synchronizing the phase of the starting pulse with the frequency of the commercial AC power supply according to the output voltage. And a control circuit for controlling the power supply.