JP2003174773A - Power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply wherein a dead time at optimal off time in accordance with an input voltage range and load conditions is implemented and thus the conversion efficiency is improved, and further regulation is improved without use of a dummy resistor. <P>SOLUTION: The power supply is provided with a PFM/PWM controller. The PFM/PWM controller optimally controls a dead time between ON signals of a pair of transistors according to an input voltage range and the state of an output load, and thereby shifts normal operation by frequency modulation to operation by pulse width modulation in a specific load range. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, particularly D
Half bridge used for C / DC converter etc.
The present invention relates to a converter type power supply device.

[0002]

2. Description of the Related Art As a conventional half bridge converter type power supply device, for example, a practical power supply circuit design handbook (written by Shiro Togawa; CQ Publishing Co., Ltd., 1999)
February 15th, 18th edition), pages 179 to 183
The circuit is described in "How the Half-Bridge Converter Works" on page. The basic configuration of the circuit is shown in FIG. In the figure, a is a half-bridge converter type power supply device, b is a capacitor, c is a main switching FET transistor, d is a main transformer, e is a choke coil, f is a diode, g is a current detection transformer, and h is Is a starter device, i is an auxiliary power supply, j is a FET transistor drive device, k is a control device, m is an overheat protection device for the power supply device, and n is
Is an output ON / OFF control device, o is a feedback control device, and p is an output voltage overvoltage detection device. The feedback control device o includes an output voltage detection device and a feedback device.

[0003]

In the frequency modulation method in the power supply device, the F
The ET transistor has a switching function. Therefore,
When the input voltage range to the power supply device is wide, the off-time is controlled to a constant value, so that the optimum dead time cannot be obtained according to the input voltage. Therefore, there is a problem that the conversion efficiency of the power source is deteriorated. Further, since the output voltage cannot be controlled when there is no load, a dummy resistor q is arranged on the output side to obtain regulation. But,
Dummy resistors are detrimental to the efficiency of the power supply.

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to realize a dead time in an optimum off time according to an input voltage range and a load condition to realize a power supply device. The conversion efficiency can be improved. Another object of the present invention is to provide a power supply device that can obtain improved regulation without using dummy resistors.

[0005]

A power supply device according to a first aspect of the present invention is a normal frequency modulation system in which a dead time between ON signals of a pair of transistors is optimally controlled according to a state of an input power supply range and an output load. It is characterized by including a PFM / PWM controller that operates a device operating in accordance with a pulse width modulation method in a specific load region. In the power supply device according to claim 2, the PFM / PWM controller detects the feedback device, the output voltage detection circuit, the PFM / PWM discrimination device, the off-time variable device, the input voltage detection circuit, and the input voltage to initialize the off-time. An off-time initial setting device for performing the above is provided. Claim 3
According to another aspect of the present invention, the power supply device further includes an overvoltage detection device for an output voltage in parallel with the PFM / PWM controller.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the power supply device according to the present invention will be described below with reference to the drawings. FIG. 2 is a circuit block diagram of a half bridge converter type power supply device. In the figure, reference numeral 1 is a half bridge converter type power supply device,
2 is a capacitor, 3 is a FET transistor that performs a switching action, 4, 5 is a transformer, 6 is a diode, 7 is a choke coil, 8 is a current detection transformer, 9 is a control circuit starter, 10 is an auxiliary power supply, and 11 is a transistor. 3, a drive circuit, 12 a control device, 13 an overheat protection device for the power supply device, 14 an output voltage on / off control device, and 15 a PF
The respective M / PWM controllers are shown. The power supply dividing capacitors 2 (C1, C2) are connected in parallel to the DC voltage source. The input voltage Vin is equal to the two capacitors 2 (C
1, C2), and Vin / 2 is applied to the output transistors 3 (Tr1, Tr2). The two transistors 3 (Tr1, Tr2) are alternately turned on and off repeatedly. Two transistors 3 (Tr
1, Tr2) are driven by the drive circuit 11. The output of the two transistors 3 (Tr1, Tr2) is the transformer 4
, And the midpoint outputs of the two capacitors 2 (C1, C2) are connected to the transformer 5, respectively. Then, a direct current is supplied from the transformer to the load.

FIG. 3 shows a PFM / PWM controller 15
2 is a circuit block diagram of FIG. In the figure, reference numeral 20 is a feedback device, 21 is an output voltage detection circuit, and 22 is P.
FM / PWM discrimination device, 23 is an off-time variable device, 2
Reference numeral 4 is an input voltage detection circuit, and 25 is an off-time initial setting device for detecting an input voltage and performing an off-time initial setting. The off-time initial setting device 25 sets the maximum (A) or the minimum (B) of the off-time according to the input voltage. When the off-time starts from the maximum (A), the output of the feedback device 20 that changes according to the output load condition causes the PFM / PWM discrimination device 22 to output the PFM.
/ PWM is discriminated and the oscillation frequency of the power supply device is fixed. PFM or PWM output is an off-time variable device 2
By 3, the off time is changed from the upper limit (A) to the lower limit (B). The PWM operation is performed between the upper limit (A) and the lower limit (B) of the off time (see FIG. 4). It is output by the controller 12 as frequency modulation or pulse width modulation at Out A and Out B.

As shown in FIG. 5, the off-time can be changed by the controller 12 in the out A and the out B depending on the operating condition. As a result, the arbitrarily set upper limit (A) and lower limit (B) of off-time can be set in the variable region, and the off-time C can be variably controlled like the off-time D. Thus, the duty cycle of the pulse is controlled, and the two transistors 3 (Tr
It is possible to control the optimum dead time between the ON signals of Tr1, Tr2). By linearly varying the dead time according to the range of the input power source and the output load, it is possible to operate the normal frequency modulation system by the pulse width modulation system in the specific load region.

FIG. 6 shows a main part of a circuit block diagram of a power supply device according to another embodiment of the power supply device according to the present invention, which is of a half bridge converter system. In the figure, the difference from FIG. 2 is that the PFM / PWM controller 15
The output voltage overvoltage detecting device 16 is disposed in parallel with. The output voltage overvoltage detection device 16 detects an overvoltage of the output voltage. The output voltage overvoltage detection device 16 is connected to the resonance control device 12. In the conventional power supply device, the control at the time of light load is performed by the dummy resistor q, but by providing the overvoltage detection device 16 of the output voltage, the dummy resistor q becomes unnecessary and the efficiency of the power supply device is improved. You can

[0010]

According to the power supply device of the present invention, the conversion efficiency of the power supply device can be improved by realizing the dead time at the optimum off time according to the input voltage range and the load condition. In addition, improved regulation can be obtained without the use of dummy resistors.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a conventional half bridge converter power supply device.

FIG. 2 is a circuit block diagram showing a power supply device of a half bridge converter system of the present invention.

FIG. 3 is a block diagram showing the PFM / PWM controller of FIG.

FIG. 4 is an explanatory diagram showing a PWM operation.

FIG. 5 is an explanatory diagram showing an off-time operation status.

FIG. 6 is a circuit block diagram of an essential part showing another power supply device of the half bridge converter system of the present invention.

[Explanation of symbols]

1 power supply 2 capacitors 3 Main switch FET transistor 4, 5 Main transformer 7 choke coil 6 diode 8 Current detection transformer 9 Starter 10 Auxiliary power supply 11 FET transistor drive 12 Control device 13 Power supply overheat protection device 14 Output voltage ON / OFF control device 16 Output voltage overvoltage detector 15 PFM / PWM controller 20 Feedback device 21 Output voltage detection circuit 22 PFM / PWM discrimination device 23 Off-time variable device 24 Input voltage detection circuit 25 Off-time initialization device

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Claims (3)

[Claims] 1. A pulse width in a specific load region that operates in a normal frequency modulation system by optimally controlling a dead time between ON signals of a pair of transistors according to an input power supply range and a state of an output load. PF operated by modulation method
A power supply device comprising an M / PWM controller. 2. The PFM / PWM controller includes a feedback device, an output voltage detection circuit, and a PFM / PWM.
3. An off-time variable setting device, an input voltage detection circuit, and an off-time initial setting device for detecting an input voltage and performing an off-time initial setting.
The power supply described. 3. The power supply device according to claim 1, further comprising an output voltage overvoltage detection device in parallel with the PFM / PWM controller.