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Moteur de recherche de fiches techniques de composants électroniques |
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TEA1654T Fiches technique(PDF) 6 Page - NXP Semiconductors |
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TEA1654T Fiches technique(HTML) 6 Page - NXP Semiconductors |
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6 / 24 page  2003 May 12 6 Philips Semiconductors Product specification GreenChip ™II SMPS control IC TEA1654 Current mode control Current mode control is used for its good line regulation behaviour. The ‘on-time’ is controlled by the internally inverted control pin voltage, which is compared with the primary current information. The primary current is sensed across an external resistor. The driver output is latched in the logic, preventing multiple switch-on. The internal control voltage is inversely proportional to the external control pin voltage, with an offset of 1.5 V. This means that a voltage range from 1 to 1.5 V on pin CTRL will result in an internal control voltage range from 0.5 to 0 V (a high external control voltage results in a low duty cycle). Oscillator The maximum fixed frequency of the oscillator is set by an internal current source and capacitor. The maximum frequency is reduced once the control voltage enters the VCO control window. Then, the maximum frequency changes linearly with the control voltage until the minimum frequency is reached (see Figs 5 and 6). VCO adjustment The VCOadj pin can be used to set the VCO operation point. As soon as the peak voltage on the sense resistor is controlled below half the voltage on the VCOadj pin (VCO1 level), frequency reduction will start. The actual peak voltage on sense will be somewhat higher due to switch-off delay (see Fig.7). The frequency reduction will stop approximately 25 mV lower (VCO2 level), when the minimum frequency is reached. Cycle skipping At very low power levels, a cycle skipping mode will be activated. A high control voltage will reduce the switching frequency to a minimum of 24 kHz. If the voltage on the control pin has raised even more, switch-on of the external power MOSFET will be inhibited until the voltage on the control pin has dropped to a lower value again (see Fig.7). For system accuracy, it is not the absolute voltage on the control pin that will trigger the cycle skipping mode, but a signal derived from the internal VCO will be used. Remark: If the no-load requirement of the system is such that the output voltage can be regulated to its intended level at a switching frequency of 24 kHz or above, the cycle skipping mode will not be activated. handbook, halfpage VCO fixed quasi resonant P (W) MDB217 f (kHz) 24 65 Fig.4 Multi mode operation. handbook, halfpage VCTRL 1 V (typ) 0.52 V 1.5 V (typ) MGU233 Vsense(max) Fig.5 Vsense(max) as a function of VCTRL. handbook, halfpage Vsense(max) (V) MCE407 f (kHz) 24 65 VCO2 level VCO1 level Fig.6 VCO frequency as a function of Vsense(max). |
Numéro de pièce similaire - TEA1654T |
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Description similaire - TEA1654T |
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