JPS6018186B2 - DC stabilized power supply - Google Patents

Description

[Detailed description of the invention] The present invention relates to a DC stabilized power supply circuit.

Conventionally, two types of circuit systems have been put into practical use in DC stabilized power supply circuits: a series regulator system and a switching regulator system.

In the series regulator method, a transistor is connected in series between the input and output in order to stabilize the output voltage, and by controlling the transistor, the voltage difference between the input and output is generated as a voltage drop between the collector and emitter of the transistor. By doing so, the output voltage was controlled to be constant. Therefore, as the output current increases or the voltage difference between input and output increases, the amount of heat generated by transistors increases, and to cope with this, it is necessary to use transistors with large heat capacity and large heat sinks with low thermal resistance. Therefore, the disadvantage was that the circuit efficiency was low. On the other hand, the switching regulator method controls the output voltage to a constant value by switching transistors connected in series between input and output and controlling the duty cycle of the transistor drive signal. The heat generated by the transistor, which is a problem with this method, is small;
Therefore, although the circuit efficiency is high, there are drawbacks such as generation of spike noise due to the switching operation and increase in ripple voltage due to the characteristics of the output smoothing circuit.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional technology, and therefore, an object of the present invention is to change the control transistor connected in series between input and output to a series regulator type control mode as the output current increases. By shifting from the switching regulator control mode to the switching regulator type control mode, we have developed a new system that makes it possible to improve circuit efficiency by reducing spike noise and ripples during output current and reducing heat generated during high output current. Our mission is to provide DC stabilized power supply circuits.

In order to achieve the above object, the present invention explores the following configuration.

That is, a transistor connected in series between input and output, a choke input type smoothing circuit including a commutating diode, a comparator with hysteresis characteristics that outputs a control signal depending on the output current value, and an oscillation circuit that generates a triangular wave output based on the control signal. and an integrating circuit, a reference voltage source on which the triangular wave can be superimposed, and an error amplification circuit that amplifies the difference between the reference voltage source and the output voltage and controls the transistor. With this configuration, when the output current value of the stabilized power supply circuit is less than a preset value, the circuit operates as a series regulator to suppress noise generation, while when the output current value is higher than the preset value, the circuit operates as a switching regulator. The circuit operates according to the method and increases the circuit efficiency. Therefore, when the output current is below a certain value, the disadvantages of a switching regulator can be eliminated, and when the output current is above a certain value, the disadvantages of a series regulator can be eliminated. Next, a preferred embodiment of the present invention will be explained in detail with reference to FIG.

One embodiment of the present invention includes a series bus transistor 2 for controlling the output, a diode 3 for commutating the energy stored in the inductor during switching mode, a choke input type smoothing circuit 4 composed of a choke coil and a capacitor, A flow sense circuit that senses the output current and generates a voltage proportional to it, compares the output of this current sense circuit 5 and the reference voltage 8, and generates an "ON/OFF" signal according to the output of the current sense circuit 5. A hysteresis comparator 7 with hysteresis characteristics is output, and the oscillation is turned on by the output of this hysteresis comparator 7.
A rectangular wave oscillation circuit 9 that can be turned OFF or OFF, integrates the oscillation output of this rectangular wave oscillation circuit 9, and outputs a triangular wave by integrating the voltage at the reference voltage source and output terminal 6 of integrating circuits 10 and 11 constituted by resistors and capacitors. and an error amplification circuit 12 for comparing and controlling the transistor 2.

The operation of each part according to the output current at the output terminal 6 will be explained below.

When the output current at the output terminal 6 is small, the output voltage of the current sense circuit 5 is lower than the reference voltage 8, and the output of the hysteresis comparator 7 is "OFF".

Therefore, the oscillation circuit 9 stops oscillating, and the integration circuit 10 does not output a triangular wave. The output of the integrating circuit 10 is the reference voltage 1
However, since the triangular wave is not superimposed from the integrating circuit 10, a constant DC voltage is input to the error amplifier circuit 12, and the signal of the difference between this voltage and the voltage at the output terminal 6 is output from the error amplifier circuit 12. The output of the error amplification circuit 12 controls the control transistor 2 so that negative feedback is applied to the control transistor 2, and controls the voltage at the output terminal 6 to be kept constant. At this time, the diode 3 becomes a reverse voltage and does not function. Further, the choke input type smoothing circuit 4 operates as a filter. On the other hand, when the output current at the output terminal 6 is large, the output voltage of the current sense circuit 5 is higher than the reference voltage 8, and the output of the hysteresis comparator 7 is "
OW, the oscillation circuit 9 oscillates, a triangular wave is generated at the output of the integrating circuit 10, this triangular wave output is superimposed on the output of the reference voltage 11, and the reference voltage containing this triangular wave component and the voltage at the output terminal 6 are The output of the error amplification circuit 12 is
When the voltage peak value of the triangular wave component is higher than the voltage at the output terminal 6, it becomes an "ON" rectangular wave output, and when it is lower than the voltage at the output terminal 6, it becomes an "OFF" rectangular wave output, causing the control transistor 2 to perform a switching operation.

This switching output is fed to a choke input type flat wire circuit 4, and a DC output is outputted to an output terminal 6. At this time, the diode 3 commutates the energy accumulated in the choke coil included in the smoothing circuit 4 when the control transistor 2 is "OFF", increasing smoothing efficiency. The hysteresis characteristic of the hysteresis comparator 7 is provided to stabilize the operation when the output current value is near the boundary value of the comparator. As explained above, the present invention operates in two modes, a series regulator type operation mode and a switching regulator type operation mode, by sensing the output current. When the output current is high, it operates as a series regulator, reducing noise troubles and S/N ratio declines caused by spikes and noise, and when the current exceeds a certain set value, it operates as a switching regulator. Since the power supply circuit operates as a power supply circuit and efficiently supplies output current, it has the effect of making it possible to downsize the power supply circuit section and save power.

Although the present invention has been described above with respect to one preferred embodiment thereof, this is merely an illustrative example, and it goes without saying that the present invention is not limited only to the embodiment described herein.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1...Input terminal, 2...Transistor, 3...Diode, 4...Choke input type smoothing circuit, 5...Current sense circuit, 6...
...Output terminal, 7...Hysteresis comparator, 8...Reference voltage, 9...Oscillation circuit, 10...Integrator circuit, 11... -Reference voltage, 12...Error amplification circuit. Leopard figure

Claims (1)

[Claims] 1. A series-connected transistor that controls the output voltage, a chiyoke input smoothing circuit that includes a commutating diode that smoothes the output controlled by this transistor, and a circuit that detects the output current of this smoothing circuit and detects the current value above a certain value. a comparator circuit that sometimes outputs a control signal and has a hysteresis characteristic; an oscillation circuit and an integration circuit that generate a triangular wave output according to the control signal output from the comparator circuit;
A direct current comprising: a reference voltage source having means for superimposing the triangular wave output; and an error amplification circuit that amplifies the difference voltage between the output voltage of the reference voltage source and the output voltage to control the output control transistor. Stabilized power supply circuit.