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Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
General Description
The AP3703 is a high performance AC/DC power supply controller for battery charger and adapter applications. The device uses Pulse Frequency Modulation (PFM) method to build discontinuous conduction mode (DCM) flyback power supplies. The AP3703 provides accurate constant voltage, constant current (CV/CC) regulation while removing the opto-coupler and secondary control circuitry. It also eliminates the need of loop compensation circuitry while maintaining stability. The AP3703 achieves excellent regulation and high average efficiency, yet meets the requirement for no-load consumption less than 100mW. The AP3703 is available in SOT-23-5 package.
Features
* * * * * * * * * * Primary Side Control for Rectangular Constant Current and Constant Voltage Output Secondary CV/CC Control Circuitry Eliminating Opto-Coupler No Need for Control Loop Compensation Circuitry Flyback Topology in DCM Operation Random Frequency Modulation to Reduce System EMI Built-in Soft Start Open Feedback Protection Over Voltage Protection Short Circuit Protection Small SOT-23-5 package to achieve compact size and less component
Applications
* * * Adapters/Chargers for Cell/Cordless Phones, PDAs, MP3 and Other Portable Apparatus Standby and Auxiliary Power Supplies LED Driver
SOT-23-5
Figure 1. Package Type of AP3703
Feb. 2009 Rev. 1.0 1
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Pin Configuration
K Package (SOT-23-5)
OUT GND VCC
1 2 3
5
FB
4
CS
Figure 2. Pin Configuration of AP3703 (Top View)
Pin Description
Pin Number 1 2 3 4 5 Pin Name OUT GND VCC CS FB Ground Supply voltage The primary current sense The voltage feedback from the auxiliary winding Function This pin drives the base of external power NPN switch
Feb. 2009 Rev. 1.0 2
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Functional Block Diagram
VCC
3
UVLO
FB
5
OVP & OCkP
pro
0.1V COMP pfm Tonsec Detector Tons
Regulator & Bias
UVLO
EA 4.0V Tons V+ S&H
Vea V+ COMP pfm_d Vea R S Q CV_ctrl pfm
1
Driver
OUT
4
CS
0.5V
t COMP
pfm
LEB Delay 430ns
pfm_d
COMP 0.46V I VDD
Tons
3.75V
COMP
R
Q
CC_ctrl
2
GND
S 0.75*I
Figure 3. Functional Block Diagram of AP3703
Feb. 2009 Rev. 1.0 3
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Ordering Information
AP3703 Circuit Type Package K: SOT-23-5
Package SOT-23-5 Temperature Range -40 to 85oC Part Number AP3703KTR-G1 GAT
-
G1: Green TR: Tape and Reel
Marking ID
Packing Type Tape & Reel
BCD Semiconductor's products, as designated with "G1" suffix in the part number, are RoHS compliant and Green.
Absolute Maximum Ratings (Note 1)
Parameter Supply Voltage VCC Voltage at CS, OUT to GND FB input (Pin 5) Output Current at OUT Operating Junction Temperature Storage Temperature Lead Temperature (Soldering, 10s) Thermal Resistance Junction-to-Ambient ESD (Machine Model) ESD (Human Body Model) Value -0.3 to 30 -0.3 to 7 -40 to 10 Internally limited 150 -65 to 150 300 250 200 2000
o
Unit V V V A
oC oC o
C
C/W V V
Note 1: Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "Recommended Operating Conditions" is not implied. Exposure to "Absolute Maximum Ratings" for extended periods may affect device reliability.
Feb. 2009 Rev. 1.0 4
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Electrical Characteristics
(VCC=15V, TA=25oC, unless otherwise specified.)
Parameter UVLO SECTION Start-up Threshold Minimal Operating Voltage STANDBY CURRENT SECTION Start-up Current Operating Current DRIVE OUTPUT SECTION OUT Maximum Current Sink Source IOUT 50 24 30 36 mA IST ICC(OPR) VCC = VTH (ST)-0.5V, Before start-up Static 45 240 60 300 A A VTH (ST) VOPR(min) 16.5 6.5 19.5 8 22.5 9.5 V V Symbol Conditions Min Typ Max Unit
CURRENT SENSE SECTION Current Sense Threshold Pre-Current Sense Leading Edge Blanking FEEDBACK INPUT SECTION Feedback Current Pin Input Leakage IFB VFB VFB(EN) VFB(OVP) VFB=4V 2.3 3.65 -2.0 6.4 2.7 3.95 -1.5 8 3.1 4.25 -1.0 9.6 A V V V VCS VCS(PRE) 450 350 485 395 430 530 440 mV mV ns
Feedback Threshold Enable Turn-on Voltage Over Voltage Protection
Feb. 2009 Rev. 1.0 5
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Typical Performance Characteristics
21
100
20
80
Start-up Voltage (V)
19
Start-up Current (A)
60
18
40
17
20
16
15 -40
-20
0
20
40
60
o
80
100
120
0 -40
-20
0
20
40
60
o
80
100
120
Ambient Temperature ( C)
Ambient Temperature ( C)
Figure 4. Start-up Voltage vs. Ambient Temperature
Figure 5. Start-up Current vs. Ambient Temperature
400
350
Operating Current (A)
300
250
200
150
100 -40
-20
0
20
40
60
o
80
100
120
Ambient Temperature ( C)
Figure 6. Operating Current vs. Ambient Temperature
Feb. 2009 Rev. 1.0 6
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Operation Description
Bridge VIN Vg + C1 LM NP VS NS D1 IS + CO VO IO
Q1
OUT
VAUX NAUX IP
AP3703
FB GND CS
RCS
Figure 7. Simplified Flyback Converter Controlled by AP3703
Figure 7 illustrates a simplified flyback converter controlled by AP3703. Constant Primary Peak Current The primary current ip(t) is sensed by a current sense resistor RCS as shown in Figure 7. The current rises up linearly at a rate of:
dip (t ) vg (t ) = dt LM
The energy stored in the magnetizing inductance LM each cycle is therefore:
1 Eg = x LM Ipk 2 2
......(3)
So the power transferring from the input to the output is given by:
......(1)
1 P = x LM x Ipk2 x f SW 2
......(4)
See equation 2
Where the fsw is the switching frequency. When the peak current Ipk is constant, the output power depends on the switching frequency fsw. Constant Voltage Operation The AP3703 captures the auxiliary winding feedback voltage at FB pin and operates in constant-voltage (CV) mode to regulate the output voltage. Assuming the secondary winding is master, the auxiliary winding is slave during the D1 on-time and the auxiliary voltage is given by:
V AUX = N AUX x (Vo + Vd ) NS
Ip 0A
Figure 8. Primary Current Waveform
As illustrated in Figure 8, when the current ip(t) rises up to Ipk, the switch Q1 turns off. The constant peak current is given by:
Vcs Ipk = Rcs
......(2)
......(5)
Feb. 2009 Rev. 1.0 7
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Operation Description (Continued)
where the Vd is the diode forward drop voltage.
See equation 5
The relationship between the output constant-current and secondary peak current Ipks is given by:
1 Tons Iout = x Ipksx 2 Tons + Toffs
......(7)
0V 2/3 Tons Tons
At the instant of D1 turn-on, the primary current transfers to the secondary at an amplitude of:
Ipks = NP x Ipk NS
......(8)
Figure 9. Auxiliary Voltage Waveform
Thus the output constant-current is given by:
1N Tons 2N Iout = x P x Ipk x = x P x Ipk 2 NS Tons + Toffs 7 N S
The output voltage is different from the secondary voltage in a diode forward drop voltage that depends on the current. If the secondary voltage is always detected at a fixed secondary current, the difference between the output voltage and the secondary voltage will be a fixed Vd. For AP3703, the voltage detection point is at two-thirds of the D1 on-time, which means the the secondary voltage is detected at a fixed secondary current of one-third of Ipks. The CV loop control function of AP3703 then generates a D1 offtime to regulate the output voltage. Constant Current Operation Figure 10 shows the secondary current waveforms.
See equation 8
......(9)
Leading Edge Blanking When the power switch is turned on, a turn-on spike will occur on the sense-resistor. To avoid falsetermination of the switching pulse, a 430ns leadingedge blanking is built in. During this blanking period, the current sense comparator is disabled and the gate driver can not be switched off. CCM Protection The AP3703 is designed to operate in discontinuous conduction mode (DCM) in both CV and CC modes. To avoid operating in continuous conduction mode (CCM), the AP3703 detects the falling edge of the FB input voltage on each cycle. If a 0.1V falling edge of FB is not detected, the AP3703 will stop switching. OVP & OCkP The AP3703 includes output over-voltage protection (OVP) and open circuit protection (OCkP) circuitry as shown in Figure 11. If the voltage at FB pin exceeds 8V, 100% above the normal detection voltage, or the -1.5V falling edge of the FB input can not be monitored, the AP3703 will immediately shut off and enters hiccup mode. The AP3703 sends out a fault detection pulse every 24ms in hiccup mode until the fault has been removed.
Is
0A Tons Toffs
Iout
Figure 10. Secondary Current Waveform
In CC operation, the CC loop control function of AP3703 will keep a fixed proportion between D1 ontime Tons and D1 off-time Toffs by discharging or charging a capacitor embedded in the IC. The fixed proportion is:
Tons 4 = Toffs 3
......(6)
Feb. 2009 Rev. 1.0 8
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Operation Description (Continued)
FB COMP 8V R Q pro
S COMP -1.5V Timer_24ms
UVLO
Figure 11. OVP and OCkP Function Block
Typical Application
T1 + R5 C2 D1 D3 C3 Np Ns
D2
VO+ C4 +
C1
R1
+ R2
VO-
VCC
R3
OUT
Q1
Nfb R6
AP3703
CS
R4
FB GND
R7
Rs
Figure 12. 5V/500mA Output for Battery Charger of Mobile Phone
Feb. 2009 Rev. 1.0 9
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet
LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER AP3703
Mechanical Dimensions SOT-23-5 Unit: mm(inch)
2.820(0.111) 3.020(0.119)
0.100(0.004) 0.200(0.008)
2.650(0.104)
2.950(0.116)
1.500(0.059) 1.700(0.067)
0.200(0.008)
0.300(0.012) 0.600(0.024)
0.700(0.028) REF
0.950(0.037) TYP
0.300(0.012) 0.400(0.016) 1.800(0.071) 2.000(0.079)
0 8
1.050(0.041)
1.250(0.049)
0.000(0.000) 0.100(0.004)
1.050(0.041) 1.150(0.045)
Feb. 2009 Rev. 1.0 10
BCD Semiconductor Manufacturing Limited
BCD Semiconductor Manufacturing Limited
http://www.bcdsemi.com
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