JP3019472B2 - 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 obtaining a stabilized DC output from a commercial power supply, and more particularly to a power supply using a resonance circuit.

[0002]

2. Description of the Related Art FIG. 3 shows an embodiment according to the prior art. 1
Is an unstable input power obtained by rectifying commercial power, 2 is primary and 2
This is a transformer with a secondary coil. A control circuit 3 compares the output 4 with a reference value and feeds back an error signal to the primary side. In the figure, L is the coil, C ₁ to accumulate electromagnetic energy is a capacitor constituting a resonant circuit and the exciting coil or leakage inductance of the transformer 2. D
₁ and C ₂ are a diode and a capacitor for smoothing the output of the secondary winding of the transformer 2. TR1 is a switching transistor.

FIG. 4 shows operation waveforms of various parts in FIG.
(A) is a diagram showing the maximum conduction time of the transistor Tr1 in a constant cycle. (B) shows that the transistor Tr1 has the output 4
FIG. 4 is a diagram showing that the conduction time is modulated by the state of FIG. (C) is the current i ₁ flowing through the coil L, and (d) is the current i ₂ flowing through the capacitor C ₁ (the primary winding of the transformer 2).

The current i ₂ flows sinusoidally (as a negative current in the figure) when the transistor Tr1 is conducting.
This part is the resonance current. (E) shows the transistor Tr
1 shows the voltage waveform of one collector (or drain), and shows that a large spike occurs.

[0005] to use such a resonant circuit is for the voltage applied to Daiodo D ₁ prevents short end by a storage effect of the occurrence of interruption in the manner not abruptly. Therefore,
On the output side V, the occurrence of ringing is small and the electromagnetic radiation is also small. However, when the load is small, the current i ₂ becomes small or is cut off in the middle of the sine feb.
_The voltage applied to ₁ becomes sharp, and ringing occurs.

On the primary side, when the transistor Tr1 is cut off, a large spike due to a sudden change in both the currents i ₁ and i ₂ , ringing due to stray inductance on the line is large, and electromagnetic radiation is large.

The above is the power supply device according to the prior art.

[0008]

However, although the circuit is simple in the above-mentioned prior art, a large spike and ringing due to a sudden change in current occur on the primary side of the transformer regardless of the load on the primary side of the transformer, and on the secondary side, There is a problem in that electromagnetic radiation cannot be reduced due to ringing generated by the load.

Therefore, the power supply device of the present invention solves the above-mentioned problems, and an object of the present invention is to use a half bridge to drive a resonance circuit including an output transformer, and at least a half of the drive cycle is abrupt. An object of the present invention is to provide a power supply device in which electromagnetic radiation is reduced by eliminating current interruption.

[0010]

According to the present invention, there is provided a power supply apparatus for obtaining a stabilized DC output from an AC input, comprising a half bridge driving means, a resonance circuit of an output transformer inductance or an additional inductance, and Output means for obtaining an output Vo from a secondary coil of the output transformer, error detection means for comparing the output Vo of the output means with a reference value and feeding back an error signal to the primary, and the half bridge driving means substantially Driving at a constant cycle, one of the switch means conducts for a substantially constant time, and the other switch means comprises a drive circuit for modulating the conduction time by the error signal. It is characterized in that electromagnetic radiation is reduced.

[0011]

FIG. 1 is a diagram showing a specific configuration circuit in an embodiment of the present invention. In the figure, 10 is AC input (commercial power)
Terminal, 11 is a bridge rectifier, 24 is a safety device and rectifier 1
To prevent rush of sudden large current to the capacitor C ₃ to smooth the 1 pulsating. Reference numeral 12 denotes an auxiliary power supply having outputs of AX1 for the primary side and AX2 for the secondary side. Transistor Tr2
When Tr3, constitute a half-bridge driving means Daiodo D ₂ and D _3. Reference numeral 13 denotes a drive transformer which alternately drives the transistors Tr2 and Tr3 of the half bridge driving means in a substantially predetermined cycle. 14 constitutes a resonant circuit with capacitor C ₄ in the output transformer. Output transformer 14
It is discharged from the secondary winding of the output while charging the capacitor C ₄ When the transistor Tr2 is turned on. Transistor Tr3 to be the discharging while the output transformer 14 from 2 then releasing the energy stored in the capacitor C ₄ conductive.

[0012] 15 to obtain an output Vo of the smoothing direct current by the capacitor C ₅ with bridge rectifier. It is a feature of the present invention to obtain a stabilized DC output by reducing electromagnetic radiation from the unstable DC voltage V ₁ N of the capacitor C ₃ through a resonance circuit. Reference numeral 23 denotes a terminal for the output Vo.

Reference numeral 16 denotes a comparator which outputs the output Vo to the resistors R ₁ and R _2.
Then, a zener diode 20 for generating a reference value is connected to the + -phase input terminal and the zener diode 20 for generating the reference value is connected to the --phase input terminal to detect an error signal and to blink the light emitting diode of the photocoupler 17. The reason for using the photocoupler 17 is to separate the primary and secondary sides.

The output of the photocoupler 17 is guided to a control circuit 18. This control circuit emits a signal having a short width when the output Vo is higher than the reference value, and supplies the signal to the AND gate 19.

Reference numeral 21 denotes an oscillator, and reference numeral 22 denotes a trigger flip
The flop (T-FF). The Q output of the T-FF 22 causes the transistor Tr2 to conduct for half a cycle via the drive circuit 20 and the drive transformer 13. The Q output of the T-FF 22 limits the control circuit 18 and the AND gate 19 to the time width of the next half cycle. The signal of the AND gate 19 turns on the transistor Tr3 via the drive circuit 20 and the drive transformer 13.

Although the auxiliary power supply 12 is not shown, AX
1 is a primary side oscillator, T-FF22, AND gate 1
9. To the control circuit 18, the AX2 supplies small power to the comparator 16 and Zena diode ZD, respectively.

The above is the control loop of the present invention for obtaining an output Vo in which the unstable DC voltage V ₁ N having the power supply is stabilized.

Next, the operation will be described with reference to FIG. FIGS. 2 (a) represents a half cycle transistor Tr2 is conductive in the Q output of the T-FF 22, the capacitor C ₄ is the charging direction.
FIG. 2B shows the conductive state of the transistor Tr3 in the next half cycle. This shows that the conduction width of the transistor Tr3 is modulated by the state of the output Vo or the load condition.

The energization widths are determined the frequency of the oscillator 21 so as to complete the discharge of the capacitor C ₄ at maximum.

FIG. 2D shows the charging / discharging current of the capacitor C ₄ . At full load, high-frequency components are small due to sinusoidal currents in both directions, and electromagnetic radiation can be reduced. However, the current rate of change since the discharge current of the load is small capacitor C ₄ is cut off in the middle is large. Even in this case, the electromagnetic radiation is reduced since it is much smaller than in the prior art FIG. The energy stored in the transformer 14 at the time of cutoff is the capacitor C ₄ → transformer 14 → diode D ₂ → capacitor C ₃ →
Since it recovered in the capacitor C ₃ in the loop of the capacitor C ₄ efficiency increases.

[0021] Since the discharge time of the capacitor C ₄ is left charge and shortens the charging current of the next half-cycle is also reduced gradually. The output transformer 14 also emits less energy, and the output Vo is stabilized.

In FIGS. 2A and 2B, a delay is provided so that the transistors Tr2 and Tr3 do not conduct simultaneously. Further, the operating frequency of the present invention is 30 KHz to several MH.
z. In Matazu 1 shows a resonant circuit with the excitation Indakudansu and capacitor C ₄ of the output transformer 14, may be added to another inductance.

[0023]

According to the configuration of the present invention described above, the occurrence of spikes and ringing can be suppressed small with a simple configuration only for controlling the discharge current of the capacitor of the resonance circuit. The effect of providing the power supply is significant.

[Brief description of the drawings]

FIG. 1 is a diagram showing a specific circuit configuration in an embodiment of the present invention.

FIG. 2 is a diagram showing operation waveforms of FIG.

FIG. 3 is a diagram showing an embodiment according to the prior art.

FIG. 4 is a diagram showing operation waveforms of FIG. 3;

Claims (1)

(57) [Claims] In a power supply device for obtaining a stabilized DC output from an AC input, a half bridge driving means, a resonance circuit of an inductance or an additional inductance of an output transformer, and a secondary coil of the output transformer are provided. Output V
o, an error detecting means for comparing the output Vo of the output means with a reference value and feeding back an error signal to the first order,
The half-bridge drive means is driven at a substantially constant cycle, one switch means is made conductive for a substantially fixed time, and the other switch means comprises a drive circuit for modulating the conductive time by the error signal. A power supply device that performs modulation.