Document
Vol.02-05-e / June2002
MR1000 Series
Standby-compatible Partial Resonance Power Supply IC Modules
Masaaki Hayashi - Electronic Device Div.Group Advanced Power Products Div. Device Design Dept. Assistant Manager (Joined the company in 1989)
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Introduction
Energy conservation guidelines from the Ministry of Economy, Trade and Industry’s Agency of Natural Resources and Energy place considerable emphasis on reducing standby power consumption of domestic electrical appliances. These guidelines designate domestic electrical appliances as 'special devices', and set target years and criteria for achieving these reductions based on the 'top runner' system. They are characterized by a considerable degree of severity in that, if targets cannot be achieved, manufacturers are legally required to publicly proclaim the fact, and to follow the recommendations of the Agency of Natural Resources and Energy. Domestic electrical appliances employing remote controls are characterized by a standby time which is considerable in proportion to the duration of daily use. While the absolute value of the instantaneous power consumption is low, the proportion of standby power consumption within the total annual power consumption is large, and demands for a reduction in standby power consumption are therefore becoming increasingly vociferous. The MR1000 Series products introduced in this paper are standby-compatible partial resonance power supply IC modules consisting of a multi-chip module (MCM) comprising a control IC and two MOSFET chips. The ability to develop a standby-compatible partial resonance power supply with a minimum of external components facilitates a reduction in design time.
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< Implementation < Use < The < Full
MR1000 Series Features
of a partial resonance power supply with a simple circuit configuration.
of the burst mode allows a reduction in standby power consumption. With a 100V input power supply, input power is approximately 100mW at no-load. module contains a start-up circuit to ensure stable start-up and to reduce start-up resistance. implementation of all protective functions.
These features are described below.
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Basic Operation
Partial resonance power supplies are an effective means of increasing efficiency and reducing noise with a simple circuit configuration. Partial resonance operation requires detection of the secondary zero current (0A) point, and determination of the ON timing for the main switching device. The MR1000 Series incorporates a zero current detection pin (Z/C, pin 1), the negative edge of the voltage in the control coil (wound with opposite polarity to that of the primary coil) being detected in the main transformer and the main switching device switched ON to detect the 0A point of the secondary current. In order to switch the main switching device ON at the VDS resonance trough during partial www.DataSheet4U.com resonance operation it is necessary to delay the ON timing for the primary inductance by 1/2 of the resonance period of the resonance condenser after the secondary current reaches 0A, and simple adjustment of the time constant of the resistor and condenser connected to the IC zero current detect pin (Z/C, pin 1) allows the main switching device to be switched ON at the VDS resonance trough.
0.2V
[Vz/c]
[I D ]
[Secondary rectifying diode current]
[V DS ]
[Control coil voltage] Fig.1 ON Trigger Operation Sequence
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Standby Functions
The MR1000 Series supports a function to reduce power consumption during standby by switching from the normal operation mode to the burst mode using an external signal. The voltage at pin (1) is clamped to a maximum of 2.9V (typ.) with a microcomputer standby signal to switch to the burst mode. Drain current is then limited to I DP (burst) = 425mA (typ.), and intermittent operation begins in which control of the ON width is switched from linear control of the voltage at the F/B pin (pin (2)) to hysteresis operation in which oscillation begins at V F/B > 1.8V and is halted at V F/B < 0.8V.
Drain pin
5 1
F/B pin GND pin Z/C pin
Standby signal (external signal)
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2.9V (typ)
Output voltage error detection feedback signal Fig.2 Standby Mode Selector Circuit
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The burst method reduces switching losses by reducing the number of switching cycles per unit time, and is therefore a very effective method of reducing standby power consumption at very small loads. The MR1000 Series burst mode employs burst operation while controlling output, improving output ripple and transient response. Furthermore, as the IC control current also reduces circuit current wastage at burst oscillation and halt, unnecessary circuit operation is halted, reducing control current durin.