JP3285280B2 - Buck-boost chopper circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved non-isolated step-up / step-down chopper circuit which steps down when the input voltage is high and boosts when the input voltage is low to stabilize the output voltage.

[0002]

2. Description of the Related Art A step-up / step-down chopper circuit boosts a voltage when an input voltage fluctuates lower than an output voltage, and conversely lowers a voltage when an input voltage fluctuates higher than an output voltage to keep the output voltage constant. It controls and is conventionally known.

The basic circuit of this step-up / step-down chopper circuit is comprised of a step-down switch element 14, a step-up switch element 15, a commutation diode 16, and an output diode 17, as shown in FIG. The chopper circuit is
The step-up and step-down are both performed, but are shared by one inductance element 18. Also, the + input terminal 10
An input-side bypass capacitor 19 is inserted between the positive and negative input terminals 11, and an output-side bypass capacitor 20 is inserted between the positive and negative output terminals 12 and 13.

When the input voltage is lower than the output voltage, the operation as a boost chopper circuit is performed by increasing the time (pulse width of the control signal) in which the step-down switch element 14 and the step-up switch element 15 are simultaneously turned on, as indicated by i1. To excite the inductance element 18 to increase the stored energy.
An output voltage higher than the input voltage is obtained through the output diode 17 via the commutation diode 16.

When the input voltage is higher than the output voltage, the operation as a step-down chopper circuit is performed by shortening the time during which the step-down switch element 14 and the step-up switch element 15 are simultaneously turned on (pulse width of the control signal) as indicated by i1. To excite the inductance element 18 to reduce the stored energy.
The current is commutated by the commutation diode 16 and an output voltage lower than the input voltage is obtained via the output diode 17.

A conventional drive circuit 32 for the step-down switch element 14 and the step-up switch element 15 in the above-described step-up / step-down chopper circuit will be described with reference to FIG. In this circuit, when a control signal corresponding to the fluctuation of the input voltage is input to the PWM IC 21 from the control signal input terminal 23,
ON / OFF of the output transistor 22, that is, the pulse width is controlled. The pulse width control signal controls the opening and closing of the step-down switch element 14 and the step-up switch element 15 via the drive circuit 32. At this time, the step-down switch element 14 includes a reverse bias resistor 24 and a gate current limiting resistor. The boosting switch element 15 is opened and closed via a resistor 29, a diode 31, a resistor 28, a gate current limiting resistor 26, and a reverse bias resistor 27, in particular, via a buffer transistor 30. Controlled.

That is, when the output transistor 22 is turned on, a gate signal is directly sent to the gate of the step-down switch element 14. However, the gate signal amplified by the buffer transistor 30 is sent to the gate of the boost switch element 15.

[0008]

In general, the step-down switch element 14 and the step-up switch element 15 in the step-up / step-down chopper circuit are respectively floating at + of the input power source or grounded at-of the input power source. , P-ch and N-ch MOS-Fs for ease of driving.
ET is used. For this reason, there is a subtle difference in the switching time due to the difference in the gate structure. However, a delay in the timing of turning off the boosting switch element 15 occurs mainly due to the accumulation time of the buffer transistor 30 of the drive circuit 32 in FIG. 8.

By the way, in the conventional circuit shown in FIG.
The timing at which the step-down switch element 14 and the step-up switch element 15 are turned off is not simultaneous, and the step-up switch element 1
When the step-up switch element 15 is delayed, the energy accumulated when the step-down switch element 14 and the step-up switch element 15 are turned on is excited by the inductance element 18 and becomes a loss due to a current flowing as i3 due to the short-circuit of the step-up switch element 15. Would.

More specifically, in FIG. 5, the off timing of the step-up switch element 15 shown in FIG. 5B is later than the off timing of the step-down switch element 14 shown in FIG. Then, during this delay time t, the energy of the inductance element 18 is short-circuited by the boosting switch element 15.

When a timing signal for turning off the step-down switch element 14 and the step-up switch element 15 causes a delay in turning off the step-up switch element 15, the operation as a step-up chopper circuit is performed as shown in FIG. Then, (a)
The current waveform is as in the case of step-up, and in the operation as the step-down chopper circuit, the current waveform is as in (b) step-down.
This is because the energy of the inductance element 18 is transferred to the boost switch element 15 during the short-circuit period of the boost switch element 15.
Are consumed, and the vertices of the ideal triangular waveform shown by the dotted line in FIG. 6 are crushed. Therefore, there is a problem that power conversion cannot be efficiently performed on the output side.

The present invention provides a step-up / step-down chopper circuit that eliminates the time difference between the timings at which the step-down switch element 14 and the step-up switch element 15 are turned off and outputs all the energy stored in the inductance element 18 when the step-up switch element 14 and the step-up switch element 15 are turned on. It is the purpose.

[0013]

According to the present invention, energy is stored in the inductance element 18 when the step-down switch element 14 and the step-up switch element 15 are turned on, and the stored energy is discharged to the output side when the step-down switch element 14 and the step-up switch element 15 are turned off. In the non-insulated step-up / step-down chopper circuit in which the time and the pulse width are controlled by the PWM IC 21 to stabilize the output voltage regardless of the fluctuation of the input voltage, the step-down switch element 1
4 and the drive circuit 32 of the step-up switch element 15 connect the step-down switch element 14 and the step-up switch element 15 directly to the output transistor 22 of the PWM IC 21 or via the buffer transistor 30 of the buffer circuit. These step-down switch elements 14
And a step-up / step-down chopper circuit characterized in that the step-up and step-up switch elements 15 are simultaneously turned on and off.

[0014]

When the output transistor 22 of the PWM IC 21 is turned off, the step-down switch element 14 and the step-up switch element 15 are accurately and synchronously turned off. That is, since a delay due to the accumulation time of the semiconductor element does not occur in the drive signal, there is no delay in turning off the boosting switch element 15. Therefore, a step-up / step-down chopper circuit having little internal loss and high conversion efficiency can be configured.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a drain and a source of a step-down switch element 14, an inductance element 18, and an output diode 17 are inserted in series in a + line between a + input terminal 10 and a + output terminal 12, and a − input terminal 11 -Output terminal 1
3 is directly connected, a commutation diode 16 is connected between the-line and one end of the inductance element 18, and a step-up switch element is connected between the other end of the inductance element 18 and the-line. 15 is connected to the input side bypass capacitor 19 between the + input terminal 10 and the − input terminal 11.
An output-side bypass capacitor 20 is connected between 2 and the −output terminal 13. The above configuration is the basic circuit itself of the step-up / step-down chopper circuit shown in FIG.

In the first embodiment of the present invention shown in FIG. 1, as the drive circuit 32 for the step-down switch element 14 and the step-up switch element 15, the output transistor 22 of the PWM IC 21 is directly used as the step-down switch element 14 and the step-up switch element. The collector of the output transistor 22 is connected to the gate of the step-down switch element 14 via the gate current limiting resistor 25, and the drain and gate of the step-down switch element 14 are used. The emitter of the output transistor 22 is connected to the gate of the boosting switch element 15 via the gate current limiting resistor 26, and the reverse bias resistor 24 is connected between the gate and the source of the booster switch element 15. To the output transistor 2
2 shows a case where on / off is directly controlled.

In such a configuration, the PWM IC 2
When the output transistor 22 is turned on, the + input terminal 1
0, reverse bias resistor 24, gate current limiting resistor 25,
Collector, emitter and gate current limiting resistor 26 of output transistor 22, reverse bias resistor 27, -input terminal 1
1 is formed and turned on, and when the output transistor 22 is turned off, the step-down switch element 14 and the step-up switch element 15 are accurately and synchronously turned off. That is, since a delay due to the accumulation time of the semiconductor element does not occur in the drive signal, there is no delay in turning off the boosting switch element 15.

As described above, since the on / off of the step-down switch element 14 and the step-up switch element 15 are synchronized,
The energy of the inductance element 18 excited at the time of turning on is not lost due to the short circuit of the boosting switch element 15. Therefore, a step-up / step-down chopper circuit having little internal loss and high conversion efficiency can be configured.

In the embodiment shown in FIG.
Although the MOS-FET 4 and the boosting switch element 15 are MOS-FETs, as shown in FIG. 2, similar effects can be obtained by using bipolar transistors.

FIG. 3 shows a second embodiment of the present invention. In this embodiment, a buffer transistor 30 as a buffer circuit is interposed at the collector of the output transistor 22 of the PWM IC 21. In this case, the emitter side of the transistor 30 is connected to the step-down switch element 14 and the collector side is connected to the step-up switch element 15 to indirectly control the on / off operation.
In this circuit, a reverse bias resistor 24, a gate current limiting resistor 25, a gate current limiting resistor 26, and a reverse bias resistor 27 are the same as those in FIG. 1, and a resistor 28 is a reverse bias resistor of the buffer transistor 30. It is.

In such a configuration, the PWM IC 2
When the first output transistor 22 is turned on, first, the buffer transistor 30 is turned on. Then, + input terminal 1
0, reverse bias resistor 24, gate current limiting resistor 25,
A circuit to the emitter, collector, gate current limiting resistor 26, reverse bias resistor 27, and -input terminal 11 of the buffer transistor 30 is formed and turned on, and when the buffer transistor 30 is turned off, the step-down switch element 14 is turned on. And the step-up switch element 15 is accurately and synchronously turned off. That is, even if a delay caused by the accumulation time of the buffer transistor 30 or the like occurs more than the drive signal of the output transistor 22, the step-down switch element 14
And the timing of turning on and off the boosting switch element 15 are performed simultaneously.
There is no delay in 5.

As described above, since the on / off of the step-down switch element 14 and the step-up switch element 15 are synchronized,
The energy of the inductance element 18 excited at the time of turning on is not lost due to the short circuit of the boosting switch element 15. Therefore, a step-up / step-down chopper circuit having little internal loss and high conversion efficiency can be configured.

In the embodiment of FIG. 3, the step-down switch element 1
Although the MOS-FET 4 and the boosting switch element 15 are MOS-FETs, as shown in FIG. 4, similar effects can be obtained by using bipolar transistors.

It is desirable that the step-down switch element 14 and the step-up switch element 15 are turned off at the same time as shown in the first and second embodiments. The same operation and effect can be obtained even if the time is slightly delayed from the time when the switch element 15 is turned off.

[0025]

According to the present invention, the drive circuit 32 has a PWM
The step-down switch element 14 and the step-up switch element 15 are directly driven by the output transistor 22 of the IC 21 for driving, or the drive circuit 32 connects a buffer circuit to the output transistor 22 of the IC 21 for PWM, By indirectly driving by the step 30, there is no delay in turning off the step-up switch element 15 with respect to the step-down switch element 14, and the energy of the inductance element 18 is not wasted. Therefore, a power supply circuit with high power conversion efficiency can be provided.

By using MOS-FETs as the step-down switch element 14 and the step-up switch element 15,
It can be used for a high-frequency switching power supply and can reduce the size of the device.

By amplifying the drive current by the buffer transistor 30 and indirectly driving it, it can be used for a switching power supply having a large capacity.

The drive circuit 32 simply connects the step-down switch element 14 and the step-up switch element 15 directly to the output transistor 22 of the PWM IC 21 or simply connects the output transistor 22 via the buffer transistor 30 of the buffer circuit. Therefore, the circuit configuration is simple.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a first embodiment of a step-up / step-down chopper circuit according to the present invention.

FIG. 2 is a circuit diagram of FIG.
It is an electric circuit diagram in the case of replacing with a transistor.

FIG. 3 is an electric circuit diagram showing a second embodiment of the step-up / step-down chopper circuit according to the present invention.

FIG. 4 is a diagram showing a configuration in which a MOS-FET is replaced with a bipolar transistor in FIG.
It is an electric circuit diagram in the case of replacing with a transistor.

FIG. 5 is a control signal waveform diagram in a case where a delay time is caused in the boosting switch element 15 with respect to the step-down switch element 14.

FIG. 6 is a current waveform diagram of the step-up / step-down chopper circuit when a delay time is generated in the step-up switch element 15 with respect to the step-down switch element 14.

FIG. 7 is a basic electric circuit diagram of a step-up / step-down chopper circuit.

FIG. 8 is an electric circuit diagram of a conventional step-up / step-down chopper circuit.

[Explanation of symbols]

10 ... + input terminal, 11 ...- input terminal, 12 ... + output terminal, 13 ...- output terminal, 14 ... Step-down switch element, 1
5 ... step-up switch element, 16 ... commutation diode, 17
... output diode, 18 ... inductance element, 19 ...
Input-side bypass capacitor, 20: Output-side bypass capacitor, 21: PWM IC, 22: Output transistor, 23: Control signal input terminal, 24: Reverse bias resistor,
25: Gate current limiting resistor, 26: Gate current limiting resistor, 27: Reverse bias resistor, 28: Resistor, 29: Resistor, 30: Buffer transistor, 31: Diode, 32: Drive circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-101373 (JP, A) JP-A-63-157668 (JP, A) JP-A-59-76170 (JP, A) JP-A-4- 156269 (JP, A) JP-A-56-137414 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 3/155

Claims (5)

(57) [Claims] 1. A PWM IC 21 pulsates a time for accumulating energy in an inductance element 18 when a step-down switch element 14 and a step-up switch element 15 are turned on and a time for discharging the stored energy to an output side when turned off. In a non-isolated step-up / step-down chopper circuit in which the output voltage is stabilized irrespective of the fluctuation of the input voltage by controlling the width, the drive circuit 32 of the step-down switch element 14 and the step-up switch element 15 includes the PWM The step-down switch element 14 and the step-up switch element 15 are connected to the collector and the emitter of the output transistor 22 of the IC 21, respectively.
Are connected directly, and these step-down switch elements 14
And a step-up / step-down chopper circuit, wherein the step-up and step-down switch elements 15 are simultaneously turned on and off. 2. A PWM IC 21 pulsates a time for accumulating energy in the inductance element 18 when the step-down switch element 14 and the step-up switch element 15 are turned on and a time for discharging the stored energy to the output side when turned off. In a non-insulated step-up / step-down chopper circuit in which the output voltage is stabilized irrespective of the fluctuation of the input voltage by controlling the width, the step-down switch element 14 and the step-up switch element 15 are composed of MOS-FETs. Drive circuit 32 for step-down switch element 14 and step-up switch element 15
Connects the collector of the output transistor 22 of the PWM IC 21 to the gate of the step-down switch element 14 via a gate current limiting resistor 25, and provides a reverse bias resistor between the drain and the gate of the step-down switch element 14. 2
4 and the emitter of the output transistor 22 is connected to the boost switch element 1 through the gate current limiting resistor 26.
5 and a reverse bias resistor 27 is inserted between the gate and the source of the boosting switch element 15.
5. A step-up / step-down chopper circuit characterized in that the turn-off of step 5 is performed simultaneously. 3. The PWM IC 21 pulsates a time for accumulating energy in the inductance element 18 when the step-down switch element 14 and the step-up switch element 15 are turned on and a time for releasing the stored energy to the output side when turned off. In a non-isolated step-up / step-down chopper circuit in which the output voltage is stabilized irrespective of the fluctuation of the input voltage by controlling the width, the drive circuit 32 of the step-down switch element 14 and the step-up switch element 15 includes the PWM A buffer circuit is connected to the output transistor 22 of the IC 21, and the step-down switch element 14 and the step-up switch element 15 are connected to the collector and the emitter of the buffer transistor 30 of the buffer circuit, respectively. By amplifying the drive current and driving indirectly, A step-up / step-down chopper circuit characterized in that the step-down switch element 14 and the step-up switch element 15 are simultaneously turned on and off. 4. The PWM IC 21 pulsates a time for accumulating energy in the inductance element 18 when the step-down switch element 14 and the step-up switch element 15 are turned on and a time for discharging the stored energy to the output side when turned off. In the non-insulated step-up / step-down chopper circuit in which the output voltage is stabilized irrespective of the fluctuation of the input voltage by controlling the width, the step-down switch element 14 and the step-up switch element 15 are composed of MOS-FETs. Drive circuit 32 for step-down switch element 14 and step-up switch element 15
Connects a buffer circuit to the output transistor 22 of the PWM IC 21, and connects the emitter of the buffer transistor 30 of the buffer circuit to the gate current limiting resistor 25.
, And a reverse bias resistor 24 is inserted between the drain and the gate of the step-down switch element 14, and the collector of the buffer transistor 30 is connected to a gate current limiting resistor 26. , And a reverse bias resistor 27 is inserted between the gate and the source of the boosting switch element 15 to amplify the drive current by the buffer transistor 30 and indirectly amplify the drive current. A step-up / step-down chopper circuit wherein the step-down switch element 14 and the step-up switch element 15 are simultaneously turned on and off by driving. 5. The step-down switch element 14 and the step-up switch element 15 are composed of bipolar transistors.
5. The step-up / step-down chopper circuit according to claim 2, wherein a drain, a gate, and a source in the OS-FET each include a collector, a base, and an emitter.