JPH0613391U - Switching regulator - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an efficient switching regulator with no dead loss. [Structure] The primary side of a transformer T ₁ is intermittently connected by a transistor Q ₁ whose base is driven at a full duty by an oscillator CTR, and a transformer T ₂ is connected to this secondary side through a transistor Q ₂ so that a transformer T ₂ The secondary voltage is rectified and smoothed by the rectifier circuit 2 and output to the load RL ₁ . The voltage detection amplifier A ₂ detects that the output voltage V _O1 has _fallen below a predetermined level and _applies it to the base of the transistor Q ₂ . Therefore, the transistor Q ₂ is turned on and the output voltage V _O1 is output only while the pulse voltage V _S3 is present on the secondary side of the transformer T ₁ and the output voltage V _O1 is lower than a predetermined level and the voltage detection amplifier A ₂ outputs. Stabilize.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a switching regulator.

[0002]

[Prior art]

An example of a conventional switching regulator is shown in FIG. In FIG. 3, T ₁ is a transformer connected to the output side of the rectifier 1 via a switching transistor Q ₁ , CTR is a PWM controller for controlling the transistor Q ₁ , and A is a secondary side S of the transformer T _{1. 2} is a main output circuit connected to B, and B is a sub output circuit also connected to the secondary side S ₁ of the transformer T ₁ .

Reference numerals 2 and 3 denote a rectifier circuit that rectifies the voltages on the secondary sides S ₁ and S ₂ of the transformer T. RG ₁ receives a voltage V _OP1 of the rectifier circuit 2 and outputs a stable output voltage V _O1 to a load RL _1. The output 3-terminal regulator, RL ₂ and RD are the main output circuit A load and dummy load, A
_{1, the} controller CT receives the output voltage V _OP2 of the main output circuit A and the reference voltage V _REF1.
It is an output voltage error detection amplifier that controls R 1.

Therefore, when the main and sub output circuits A and B have output voltages V _O2 and V _O1 , the main output circuit A causes an error in the output voltage V _O2 by the error detection amplifier A ₁ depending on the state of the load RL _2. Is detected and the pulse width is controlled by the controller CTR ₁ and the switching transistor Q ₁ to obtain the output voltage V _O2 suitable for the state of the load RL ₂ .

At this time, the on / off times t ₁ and t ₂ of the switching transistor Q ₁ controlled by the PWM pulse width of the controller CTR are, as shown in FIG. 4, generally t ₁ ≈t for all outputs. _2, and a time t 'oN at minimum output. This time t'is determined by the dummy load RD provided so as not to become zero.

[0006] The output voltage V _O1 of the auxiliary output circuit B, for obtaining a constant voltage from the output voltage V _S which changes at time t ₁ '~t ₁ or from the above situation, the output voltage V _OP1 of the rectifier circuit 2 Is

[0007]

[Equation 1]

Therefore, depending on the output status of the main output circuit, a large output voltage fluctuation occurs.

Therefore, generally, the voltage is sliced and used by the three-terminal regulator RG ₁ or the like.

[0010]

[Problems to be solved by the device]

However, the time t ₁ of the PWM control 'when the change width of ~t ₁ is large, the time t _1' when the to ensure the voltage V _O1 even when the smallest, 3 terminal Regulator at the maximum time t ₁ becomes The heat loss due to RG ₁ increases and the efficiency decreases.

In order to prevent the efficiency from being lowered, it may be controlled by a chopper type regulator or the like, but it is wasteful considering the stability of output voltage (noise and ripple level), cost, space and the like.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an efficient switching regulator without dead loss.

[0013]

[Means for Solving the Problems]

 In order to achieve the above object, a switching regulator according to the present invention comprises a first transformer and a first transistor connected in series with the primary side of the transformer and having a full-duty base drive by an oscillator. A switching circuit; a second transformer connected to the secondary side of the first transistor; a second switching circuit including a second transistor connected in series with the primary side of the transformer; The second transformer includes a rectifying circuit having a smoothing circuit connected to the secondary side of the transformer, and a voltage detecting amplifier that detects a decrease in the output voltage of the rectifying circuit and drives the base of the second transistor. .

[0014]

[Action]

 Since the first transistor connected in series with the primary side of the first transformer is turned on / off at full duty by the oscillator, the secondary side voltage of the first transformer is turned on / off at full duty. To do.

This secondary side voltage is applied to the second transformer via the second transistor, and the on / off voltage on the secondary side of the second transformer is rectified and smoothed by the rectifier circuit and output to the load. However, the output voltage increases when the secondary side voltage of the second transformer is on and decreases when it is off.

When the output voltage rises when the secondary side voltage of the second transformer is turned on and exceeds a predetermined level, the output of the voltage detection amplifier is cut off and the second transistor is turned off. Therefore, the secondary side of the second transformer is turned off. The side voltage is turned off.

The output voltage decreases due to the turning off of the secondary side voltage, but since there is no voltage on the secondary side of the first transformer during the off period of the first transistor, even if an output is output from the voltage detection amplifier, The second transistor never turns on. When the first transistor turns on, the output of the voltage detection amplifier turns on the second transistor, so that the output voltage rises. When the output voltage exceeds a predetermined level, the output of the voltage detection amplifier is lost and the second transistor is turned off.

By repeating the above operation, a stable output voltage can be obtained.

[0019]

【Example】

 An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows the circuit of a switching regulator, and FIG. 2 shows the operating time of each switching element. In FIG. 1, the same components as those shown in the conventional FIG.

In FIG. 1, OSC is an oscillator that controls the main switching transistor Q ₁ with full amplitude and full duty, and T ₂ is a transformer connected to the secondary side S ₁ of the transformer T ₁ via a switching transistor Q _2. , T ₃ is also a transformer connected to the secondary side S ₂ of the transformer T ₁ via a switching transistor Q ₃ .

Numerals 2 and 3 are rectifier circuits connected to the secondary sides of the transformers T ₂ and T ₃ , and A ₂ and A ₃ are the reference voltages V _REF1 and V _O2 of the voltages V _O1 and V _O2 of the output circuits B and A, respectively. It is a voltage detection amplifier that drives the bases of the switching transistors Q ₂ and Q ₃ when the output voltages V _O1 and V _O2 are lower than those of _REF2 .

When the main switching transistor Q ₁ is controlled to be turned on and off by the oscillator OSC, the conversion pulse voltage V _{S3 of} full amplitude and full duty is applied to the secondary sides S ₁ and S ₂ of the transformer T ₁ . V _S4 is generated.

The voltages V _S3 and V _S4 are rectified and smoothed by the rectifier circuits 2 and 3, and the voltages V _O1 and V _O2 are output to the loads RL ₁ and RL ₂ . The output voltages V _O1 and V _O2 are smoothed, but since the loads R L ₁ and RL ₂ are connected, they rise when the pulse voltages V _S3 and V _S4 are present and decrease when they disappear.

When a pulse is output from the transformer T _1, since the normal output voltages V _O1 and V _O2 are lower than the reference voltages V _REF1 and V _REF2 , the outputs of the voltage detection amplifiers A ₂ and A ₃ are switching transistors. is input to the base of Q _2, Q _3.

When a pulse is output from the transformer T ₁ , the switching transistors Q ₂ and Q ₃ are turned on and the pulse is input to the transformers T ₂ and T ₃ , so that the output voltages V _O1 and V _{O2 of the} output circuits B and A are output. Rises as shown in FIG.

Output voltage V_O1, V_O2Is the reference voltage V_REF1, V_REF2Voltage detection amplifier A ₂ , A₃Output of the switching transistor Q₂, Q₃Turns off and more pulses than required are in transformer T₂, T₃Block input to.

Therefore, the output voltages V _O1 and V _O2 gradually decrease due to the load currents of the loads RL ₁ and RL ₂ . When the voltages V _O1 and V _O2 decrease to the reference voltages V _REF1 and V _REF2 , the voltage detection amplifiers A ₂ and A ₃ output, but the switching transistors Q ₂ and Q ₃ are output while the main switching transistor Q ₁ is off. Never turns on.

Transformer T₁When the next pulse is output from the switching transistor Q₂, Q ₃ Is turned on, and the output voltage V of the output circuits B and A_O1, V_O2Raise.

As described above, according to this embodiment, the pulse supplied from the transformers T ₁ to T ₂ and T ₃ raises the output voltages V _O1 and V _O2 , and when the output voltage exceeds the reference voltage. The power transistors Q ₂ and Q ₃ can shut off unnecessary pulse inputs to keep the output voltages V _O1 and V _O2 within a certain range.

[0031]

[Effect of device]

 Since the present invention is configured as described above, it has the following effects.

(1) Since dead loss due to a three-terminal regulator or the like is eliminated, the overall efficiency becomes very good.

(2) For the secondary side voltage of the main transformer, the switching transistor on the output circuit side, the transformer, etc., the most efficient voltage for conversion can be selected. It can be composed of a general-purpose power device of about 300V.

(3) It is easy to standardize the preceding stage from the primary side of the output circuit side transformer, and an arbitrary multi-power source can be configured by combining them.

(4) Since primary and secondary insulation feedback control is unnecessary, there are great advantages in cost reduction, design, and adjustment work.

[Brief description of drawings]

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

FIG. 2 is an operation timing chart of the embodiment.

FIG. 3 is a circuit diagram showing a conventional example.

FIG. 4 is a pulse waveform diagram of a main transistor of a conventional example.

[Explanation of symbols]

1,2,3 rectifier circuit _{T 1, T 2, T 3} ... transformer A ... positive output circuit _{A 1, A 2, A 3} ... voltage detecting amplifier _{Q 1, Q 2, Q 3} ... switching transistor

Claims (1)

[Scope of utility model registration request] 1. A first switching circuit comprising a first transformer and a first transistor connected in series with the primary side of the transformer and being base-driven by an oscillator at full duty; A second transformer connected to the secondary side and a second transformer connected in series with the primary side of this transformer.
A second switching circuit including a transistor, a rectifying circuit having a smoothing circuit connected to the secondary side of the second transformer, and a base of the second transistor that detects a decrease in output voltage of the rectifying circuit. A switching regulator characterized in that the output voltage is stabilized by controlling the width of the pulse flowing through the second transformer with the second transistor.