The THX203H is the switching power controller integrated circuit, providing up to 12W continuous output power in the wide voltage range of 85V-265V, and the peak output power can reach 18W.
THX203H pin map
THX203H pin map
THX203H internal circuit diagram
THX203H pin function
Note: PCBLAYOUT should retain 1 mm or more security distance between PIN6 and PIN7 to avoid discharge.
THX203H pin voltage
1. Start stage: CR closure at power-on; FB pull-up power source is closed; OE inputs the start current to VCC; OB control the base current of the power tube, limits the power tube electrode current (ie THX203H start receiving current), To ensure the safety of the power tube; the VCC voltage rises to 8.8V, the start phase is completed, and the normal phase is entered.
2, the normal stage: VCC voltage should be maintained at 4.8-9.0V, VR output 2.5V benchmark; FB pull-up power source is turned on; the oscillator output OSC1 determines the maximum duty cycle, output OSC2 attempts to trigger the power source into the opening cycle, and shield power Tube opening current peak; if the oscillator cycle between FB is less than 1.8V (about 1.2-1.8V) will increase, the smaller the fb is smaller, the wider the oscillator period is wider until the oscillator stops the vibration (this characteristic has lowered the opening power supply) Standby power); Lower); the opening cycle, OB provides base current, OE pull-down power tube emission to IS, and OB uses ramp current driving (referred to as a function of IS is IS, when IS = 0V Ob current About 40 mA.
Normal phase switching cycle waveform
The OB is then increased with the IS linearity. When IS is increased to 0.6V, the OB is poweredant about 120mA. This characteristic effectively selects the OB output current, reducing the power consumption of THX203H), if IS detects FB specified current, enter Cycle; Off period, OB pull-down, power tube does not judge immediately, but OE clamp 1.5V (the power tube judgment rear bias is reversed, increased pressure); on or off cycle, such as detected power The tube super-upper current current, the upper limit current trigger is prioritized, forced FB to drop, the duty cycle is small, thereby protecting power tubes and transformers; at the beginning of the next level period or fb less than 1.8V, the upper limit current flip flop is reset. Further, the THX203H has a heat protection, and the cycle of the width oscillator is adjusted in the inner temperature than 140 ° C, so that the THX203H temperature does not exceed 150 ° C; the built-in ramp compensation, the THX203H duty cycle or continuous current mode can stably open / off cycle.
3, conversion phase: If VCC drops to 4.3V, the oscillator is turned off, OSC1, OSC2 low, power retention cycle; VCC continues to drop to 3.7V, THX203H re-enters the startup phase.
Global waveform
THX203H Related article: THX203H switch circuit diagram Daquan (five THX203H switch circuits), reading full text, technology area
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