JPS63249469A - Switching regulator - Google Patents

Abstract

PURPOSE:To prevent a switching regulator from damaging by controlling the switching time ratio of a switching element correspondingly to the output voltage of a single-phase half-wave voltage rectifier, and stopping the operation when it exceeds a reference value. CONSTITUTION:A series circuit of a switching element 3 and a choke coil L is connected in parallel with an input power source, a single-phase half-wave double voltage rectifier 4 is connected in parallel with the coil L, and the output of the rectifier 4 is fed back through a controller 5 to the element 3. As a result, when a load is short-circuited, the element 3 is turned OFF by the capacitor in the rectifier 4 to stop an excess short-circuiting current, thereby preventing a switching regulator from damaging.

Description

[Detailed Description of the Invention] [Summary] In a switching regulator, a series circuit of a switching element and a choke coil is connected in parallel to a human power source, and a single-phase half-wave voltage doubler rectifier circuit is further connected in parallel to the choke coil.

Then, the output of this rectifier circuit is fed back to the switching element via the control circuit, and the switching element is turned off in the event of a load short circuit, thereby making the switching regulator undamaged.

[Industrial application field]

The present invention relates to improvements in switching regulators.

Generally, there are three basic types of switching regulators. The first type is a step-down type in which the output voltage is lower than the input voltage and has the same polarity, the second type is a step-up type in which the output voltage is higher than the input voltage and has the same polarity, and the third type is in which the output voltage is lower than the input voltage. It is a buck-boost type that goes low or high and has opposite polarity.

Now, when a step-up switching regulator is used to supply a predetermined voltage to a load, it is necessary that the switching regulator not be damaged in the event of a load short circuit.

[Conventional technology]

FIG. 3 shows a circuit diagram of a conventional example. In the figure, the output of control circuit 1 causes switching transistor Q+ (hereinafter +
(abbreviated as Ql) is turned on/off.

When Ol is on, a solid current 1+ flows and energy is stored in the choke coil.

When ql is turned off, a current 12 flows as shown by the dotted line, and the voltage generated in the choke coil is superimposed on the DC input voltage V, . A DC output voltage v0 is applied to the load via.

Here, the relationship between the DC output voltage v0 and the DC input voltage 5 is expressed as V,-(1/(1-D))Vi,.

In addition, D is (to, l/(t,,,+t ott ))
So, ton +L off indicates the on time and off time, so if the denominator is constant, then t of +Ql. , , can keep vo constant.

[Problem that the invention seeks to solve]

Here, the load is directly connected to the power supply via the diode and choke coil L, so if the load is short-circuited, an excessive current will flow through the choke coil and diode, causing damage to the choke coil or diode. be.

[Means for solving problems]

The above problems are solved by the switching regulator shown in FIG. 5 controls the opening/closing time ratio of the switching element 3 in accordance with the output voltage of the single-phase half-wave voltage doubler rectifier circuit 4, and stops the operation of the switching element when the current flowing to the load exceeds a reference value. It is a circuit.

[Effect]

In the present invention, the arrangement of the choke coil L and the switching element 3 is reversed from that of the conventional example, and a single-phase half-wave voltage doubler rectifier circuit is used to provide a connection that can be protected against a load short circuit.

That is, a series circuit of a switching element 3 and a choke coil L is connected in parallel to the input power source, and a single-phase half-wave voltage doubler rectifier circuit 4 is connected in parallel to the choke coil to perform the single-phase half-wave voltage doubler rectifier. The output of the circuit is fed back to the switching element via the control circuit 5.

Therefore, in the event of a load short-circuit, it is possible to block excessive short-circuit current and prevent damage to the switching regulator by using a capacitor in the single-phase half-wave voltage doubler rectifier circuit or by turning off the switching element 3. can.

〔Example〕

FIG. 2 is a circuit diagram of an embodiment of the present invention. Note that the same reference numerals indicate the same objects throughout the figures. Also, transistor Q
2 is a component of the switching element 3, a capacitor C2+
C:l+diode D2. D3 indicates a component of the single-phase half-wave voltage doubler rectifier circuit 4. The operation will be explained below with reference to FIG.

When Q2 is on, a current i flows through the choke coil L as shown by the solid line.
3 flows and energy is stored. 6 when Q2 is off
A current i4 flows as shown by the dotted line and charges the capacitor C2 in the negative direction. When port 2 is turned on again, a charge voltage of (Vi, +Cz) is applied to capacitor C3, resulting in a boosted DC output voltage V. is obtained, but this voltage is Vo=
(1/(1-o)) v , , is expressed by the same formula as in the conventional example.

Here, when the load is short-circuited, the short-circuit current is blocked by the capacitor C2. Further, when the 1 control circuit 5 detects that a current exceeding the reference value has flowed, it turns off +02, so this can also be used as a countermeasure.

〔Effect of the invention〕

As described in detail above, according to the present invention, there is an effect that the switching regulator can be protected in the event of a load short circuit.

[Brief explanation of drawings]

Figure 1 is a block diagram of the principle of the present invention. FIG. 2 is a circuit diagram of an embodiment of the present invention, FIG. 3 shows a circuit diagram of a conventional example. 4 is a single-phase half-wave voltage doubler rectifier circuit, 5 indicates a control circuit. No98〈ofusaαrazoro...11th side Def t’fl

Claims (1)

[Claims] A series circuit of a switching element (3) and a choke coil L is connected in parallel to the input power supply, a single-phase half-wave voltage doubler rectifier circuit (4) is connected in parallel to the choke coil, and the single-phase half-wave voltage doubler rectifier A control circuit (5) that controls the opening/closing time ratio of the switching element (3) in accordance with the output voltage of the circuit (4) and stops the operation of the switching element when the current flowing to the load exceeds a reference value. A switching regulator characterized by having.