JPH03218217A - Power supply circuit with inrush current prevention circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply circuit with an inrush current prevention circuit used in a switching power supply or the like.

[Prior art 1] Fig. 2 shows a conventional power supply circuit with an inrush current prevention circuit of this type.As shown in the figure, the inrush current prevention circuit 400 has a triac 401 and a resistor 402 connected in parallel, and a diode bridge. A rectifier circuit inserted in series between the rectifier circuit 200 and the AC power supply 1 is often used.

The gate signal of the triac 401 is generated by providing a transformer winding 506 in the first lance 501 of the DC-DC converter 500 and connecting it to the diode 40 of the inrush current prevention circuit 400.
4. It is configured to rectify and smooth the signal using a capacitor 405 and the like.

The DC output of the rectifier circuit 200 is directly connected to the smoothing capacitor 2, and this output supplies power to the DC-DC converter 500.

The DC-DC converter 500 includes a transformer 501, a switching element 502, a gate circuit 503, and a diode 5.
04, a capacitor 505, etc.

Note that 100 is a noise prevention choke coil, 403 is a resistor, L is a load, and SW is a power switch.The inrush current prevention function of this circuit is as follows.

Since the gate trigger signal of the triac 401 is generated only when the DC-DC converter 500 is in oscillation operation, the triac 401 is off immediately after the AC power supply 1 is turned on to this power supply device. Therefore, smoothing capacitor 2 is gradually charged through resistor 4o2 and rectifier 200. Assuming that the resistance value of the resistor 402 is R+ and the voltage of the AC power supply 1 is ■Ac, the peak value of the AC power supply current Ip is suppressed to the following. When the charging voltage of the smoothing capacitor 2 reaches a predetermined voltage, the DC-DC converter 500 starts oscillating, and a high frequency voltage is generated in the transformer winding 506, which is rectified and smoothed to trigger the triac 401. Triac 401 turns on and the charging current that was previously flowing through resistor 402 flows through triac 401. This operation will continue from then on. The on-voltage of the triac 401 is normally 1.
Since 5V is less than 5V, the loss due to constant current supply can be kept small.

[Problems to be Solved by the Invention] Since the conventional power supply circuit with an inrush current prevention circuit is configured and operates as described above, it has the following problems.

1) As the frequency increases to improve the performance of the power supply, the gate trigger sensitivity of the triac 401 decreases as the pulse width becomes narrower, so the gate drive current must be increased.
The loss of the gate drive circuit increases (approximately IW is consumed when the switching frequency of the DC-DC converter 500 is 300 KHz).

2) The inrush current limiting resistor 402 needs to withstand a large instantaneous power loss, so a relatively large cement resistor is used, but this is expensive because it has a built-in fuse function.

3) DC-DC converter 500 such as instantaneous interruption of AC power supply 1
If the power is turned on again before the circuit stops, a charging current flows to the smoothing capacitor 2 through the triac 401. At this time, the inrush current prevention function does not work, so the rectifier circuit 200, triac 401, and power switch SW must be large and have strong surge current resistance.

4) When constructing a multi-output power supply by modularizing the DC-DC converter 500, it is necessary to provide an output terminal for driving the triac from the DC-DC converter module, which poses problems in miniaturization and economy.

5) DC-DC ml :/The transformer 501 of the converter 5oO requires a transformer winding 506 for the triact trigger, which is expensive.

Note that a thyristor-type inrush current prevention circuit is also used in which a thyristor is used instead of the triac 401 and connected in series with the smoothing capacitor 2 on the DC output side of the rectifier circuit 200, but it is similar to the triac type described above. has the disadvantages of

This invention was made to solve the above-mentioned problems, and has a small control power loss even when used at high frequencies, a small size, and an inrush current prevention circuit that responds well to momentary power interruptions. The purpose is to obtain a power supply circuit.

[Means for Solving the Problems] The present invention uses an insulated gate type 8 Ybora transistor as an inrush current prevention circuit, and connects a series connection body of the collector/emitter of the insulated gate type bipolar transistor and a current detection resistor to the main current. The circuit consists of a gate voltage suppression circuit that detects the main current flowing through the current detection resistor and suppresses the gate voltage of the insulated gate bipolar transistor when the main current exceeds a predetermined value, and a gate voltage suppression circuit that separates the output voltage of the rectifier circuit. The device is equipped with a voltage dividing circuit that applies a voltage to the gate of an insulated gate type bipolar transistor.

[Operation] In the present invention, when an output is output from the rectifier circuit by turning on the AC power, the gate voltage of the IGBT increases, turns on, and starts charging the smoothing capacitor. This charging current generates a voltage drop across the current detection resistor, which is used by the gate voltage suppression circuit to control the IGBT to operate at a constant current, so that the inrush current is also clipped.

[Example] Hereinafter, an example of the present invention will be described based on FIG. 1.

In FIG. 1, 300 is an inrush current prevention circuit, and the main current circuit is connected in series with the smoothing capacitor 2 between the DC output terminals of the rectifier circuit 200. This main current circuit is IGBT
Between collector and emitter of 301 and current detection resistor 302
It consists of a series circuit. The gate of the IGBT 301 is supplied with power from the positive output terminal of the rectifier circuit 200 via a voltage dividing circuit consisting of a resistor 308 and a constant voltage diode 307. Further, resistors 303 and 30 are connected between the base and emitter of the npn transistor 305 at both ends of the current detection resistor 302.
Connected via 4. The collector of the npn transistor 305 is connected to the gate of the IGBT 301, and a gate voltage suppression circuit 306 is configured. The other parts are similar to the conventional circuit, but in this embodiment, the DC-DC converter 5 is connected to both ends of the smoothing capacitor 2.
Inrush current control power is not obtained from the transformer winding 00. Note that 309 is a diode.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

When the AC power supply 1 is turned on, a rectified voltage is generated across the rectifier circuit 200. This voltage is applied through resistor 308 to I
Increase the gate voltage of GBT301. IGBT3
When the threshold voltage of 01 is exceeded, IGBT301 turns on, and IGBT301 and current sensing resistor 302
Charging of the smoothing capacitor 2 begins through this. At this time, the charging current generates a voltage drop across the current detection resistor 302, and when the voltage divided by the resistors 303 and 304 exceeds the base-emitter barrier potential of the NPN transistor 305, a collector current flows and the gate voltage of the IGBT 301 works to lower the As a result, the IGBT 301 exhibits constant current operation, and the rush current is clipped at .

Since the IGBT 301 operates as an active part, an instantaneous power of a maximum of VAcX5xIcp is applied when an inrush current is applied, but the application time of this power is usually within Sms, and considering that the power is turned on from a low temperature state, IGBT3
It is relatively easy to design the device so that it falls within the safe operation area of 01.

As the charging of the smoothing capacitor 2 progresses, the charging current decreases, and when it becomes less than the constant current setting value I cp, ■GBT30
1 is gate biased by the clamp voltage of the constant voltage diode 307 and is completely turned on. Therefore, the on-voltage in a steady state is as small as about 1.5V, and the loss can be reduced to the same level as a conventional circuit using a triac.

A specific example of the circuit constants of the main parts is as follows.

IGBT (301) = CT20TM-8R (3021
=0. 1 2Ω R(3031=560Ω R(3041=560Ω T r (305) = 2 3 C 2 6 0 3
DZ (3071 = 20V R (3081 = 47KΩ VAC = 1 0 0 V r m s] 2) = 370
μF D (309) = SR I FM-8 Since the IGBT 301 is a voltage-driven device and does not require a current to flow to maintain the on state, the gate bias resistance can be designed to be high.

Therefore, the loss of the control circuit is small (approximately 0.0 with the above constant.
4W). Similar circuit configurations include bibolar Tr and MOSFE.
Although it is possible to achieve this with a bibolar transistor, the bias resistance must be selected to a low value, resulting in a large drive circuit loss, which poses a problem in practicality. Furthermore, MOSFETs have problems such as high on-state voltage, large on-state loss during steady operation, and too much cost to reduce loss.

In this respect, the circuit of this embodiment to which the IGBT 301 is applied can be said to be the most practical.

In the embodiment shown in FIG. 1, the constant voltage diode 30
7 can be replaced with a resistor. Furthermore, the diode 309 is connected to prevent reverse voltage from being applied when the IGBT 301 is off due to the reverse recovery current and junction capacitance of the rectifier circuit 200, but it is possible to perform the same operation without it. .

[Effects of the Invention] As explained above, the present invention uses an insulated gate type bipolar transistor as an inrush current prevention circuit, and connects the collector/emitter of this insulated gate type bipolar transistor in series with a current detection resistor. The main current circuit consists of a gate voltage suppression circuit that detects the main current flowing through the current detection resistor and suppresses the gate voltage of the insulated gate bipolar transistor when a main current exceeding a predetermined value flows, and a rectifier. Since the present invention includes a voltage dividing circuit that divides the output voltage of the circuit using a resistor and a constant voltage diode and applies the divided voltage to the gate of the insulated gate bipolar transistor, the following effects can be obtained.

■ The power consumption of the device can be reduced and it is easy to support higher frequencies.

■ Inrush prevention works even when the power is turned on again due to a momentary power interruption, etc., so protection is complete, and rectifier circuits and power switches can be made small and inexpensive with low surge current resistance, making it possible to use smoothing capacitors. You can use one with low ripple resistance.

(2) Since the DC-DC converter and the inrush current prevention circuit are independent, it is easy to accommodate multiple outputs by modularizing the DC-DC converter, and the transformer also reduces the number of windings, making it cheaper.

■ Since a large amount of power is not applied to the current detection resistor even at the time of rush, a small one can be used, making it possible to downsize the set.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a power supply circuit with an inrush current prevention circuit according to the present invention, and FIG. 2 is a diagram showing a conventional power supply circuit with an inrush current prevention circuit. In the figure, 1 is an AC power supply, 2 is a smoothing capacitor, and 10
0 is a choke coil for noise prevention, 200 is a rectifier circuit, 3
00 is inrush current prevention circuit, 301 is IGBT, 302
is a current detection resistor, 306 is a gate voltage suppression circuit, 30
7 is a constant voltage diode, 308 is a resistor, 500 is DC
- It is a DC converter. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A rectifier circuit using a diode bridge connected to an AC power source, a series connection body of a smoothing capacitor and an inrush current prevention circuit connected to the DC output side of the rectifier circuit, and an inverter connected in parallel to both ends of the smoothing capacitor. In a power supply circuit that includes a circuit and supplies power to a load, an insulated gate bipolar transistor is used as the inrush current prevention circuit, and the main current a gate voltage suppression circuit that detects a main current flowing through the current detection resistor and suppresses a gate voltage of the insulated gate bipolar transistor when a main current exceeding a predetermined value flows; and an output of the rectifier circuit. A power supply circuit with an inrush current prevention circuit, comprising a voltage dividing circuit that divides a voltage and applies the divided voltage to the gate of the insulated gate bipolar transistor.