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AN11012 Datasheet(PDF) 6 Page - NXP Semiconductors |
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AN11012 Datasheet(HTML) 6 Page - NXP Semiconductors |
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6 / 36 page  AN11012 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved. Application note Rev. 1 — 30 March 2011 6 of 36 NXP Semiconductors AN11012 Using the TEA1703 to reduce standby power 6. TEA1703 description and calculation This section describes the TEA1703 functions and operation in a typical application. 6.1 General description The TEA1703 is a standby controller IC that reduces the standby power of a switched mode power supply. Standby mode operation information is obtained by sensing the output voltage and the output power of the SMPS. The output voltage is measured at pin VSENSE of the TEA1703 via the resistor divider R4 and R5 as shown in Figure 1. The output power is measured at the flyback winding of the transformer via D2 and a low-pass filter made by R2, R3 and C4 as shown in Figure 1. The principle of output power measuring is based on SMPS converters where the output power at low load increases with frequency, e.g. in a discontinuous conduction mode flyback converter which has a fixed primary peak current during low load operation. The block diagram (Figure 2) shows the VSENSE and PSENSE inputs and the corresponding comparators. A SWDET input is added to disable Standby mode detection e.g. when a latched protection is active. When pins VSENSE, PSENSE and SWDET have the correct levels, the 28 kHz oscillator is enabled. The oscillator drives the MOSFET at the OPTO pin with an on-time of 1.4 μS (4 % duty cycle). Pin OPTO drives the optocoupler via a coil and disables the SMPS. 6.2 Standby mode operation The Standby mode operation signals are shown in Figure 3. In Standby mode the optocoupler pulses generated by the TEA1703 disable the SMPS and consequently the output voltage drops. When the voltage at pin VSENSE reaches 1.22 V, the 0.9 μA current source is switched off and VSENSE drops below 1.22 V. The small hysteresis prevents fast on/off switching of the VSENSE comparator. Fig 2. Block diagram 019aab498 VCC 1 GND 2 OPTO 3 n.c. 4 8 VSENSE 7 PSENSE 6 SWDET 0.5 V 5 n.c. REFERENCE AND SUPPLY OSCILLATOR VOLTAGE SENSE POWER SENSE SWITCH DETECT 0.9 μA 1.2 μA 1.22 V |
Similar Part No. - AN11012_15 |
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Similar Description - AN11012_15 |
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